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Sample records for lateral diffusion electrodes

  1. Lateral Diffusion in an Archipelago

    PubMed Central

    Saxton, Michael J.

    1982-01-01

    Lateral diffusion of molecules in lipid bilayer membranes can be hindered by the presence of impermeable domains of gel-phase lipid or of proteins. Effective-medium theory and percolation theory are used to evaluate the effective lateral diffusion constant as a function of the area fraction of fluid-phase lipid and the permeability of the obstructions to the diffusing species. Applications include the estimation of the minimum fraction of fluid lipid needed for bacterial growth, and the enhancement of diffusion-controlled reactions by the channeling effect of solid patches of lipid. PMID:7052153

  2. Diffusion induced stresses in buckling battery electrodes

    NASA Astrophysics Data System (ADS)

    Bhandakkar, Tanmay K.; Johnson, Harley T.

    2012-06-01

    Highly networked nanostructured battery electrode materials offer the possibility of achieving both rapid battery charge-discharge rates and high storage capacity. Recently, lithium ion battery (LIB) electrodes based on a 2-D honeycomb architecture were shown to undergo remarkable and reversible morphological changes during the lithiation process. Charge-discharge rates in 3-D composite electrode have also been shown to benefit from sandwiching the electrolytically active material between highly conductive ion and electron transport pathways to reduce electrical resistance and solid-state diffusion lengths. In the present work we simulate and analyze the observed morphological changes in honeycomb electrodes, with and without the presence of conductive pathways, during the lithiation-delithiation process. Diffusion induced stresses are analyzed for such structures undergoing elastic-plastic deformation during cycling. The results show that such a periodic, nanostructured electrode geometry allows for the presence of buckling-like deformation modes, which effectively reduce the resulting mechanical stresses that lead to electrode failure.

  3. The structure of hydrophobic gas diffusion electrodes.

    NASA Technical Reports Server (NTRS)

    Giner, J.

    1972-01-01

    The 'flooded agglomerate' model of the Teflon-bonded gas diffusion electrode is discussed. A mathematical treatment of the 'flooded agglomerate' model is given; it can be used to predict the performance of the electrode as a function of measurable physical parameters.

  4. Attractive membrane domains control lateral diffusion.

    PubMed

    Forstner, Martin B; Martin, Douglas S; Rückerl, Florian; Käs, Josef A; Selle, Carsten

    2008-05-01

    Lipid membranes play a fundamental role in vital cellular functions such as signal transduction. Many of these processes rely on lateral diffusion within the membrane, generally a complex fluid containing ordered microdomains. However, little attention has been paid to the alterations in transport dynamics of a diffusing species caused by long-range interactions with membrane domains. In this paper, we address the effect of such interactions on diffusive transport by studying lateral diffusion in a phase-separated Langmuir phospholipid monolayer via single-particle tracking. We find that attractive dipole-dipole interactions between condensed phase domains and diffusing probe beads lead to transient confinement at the phase boundaries, causing a transition from two- to one-dimensional diffusion. Using Brownian dynamics simulations, the long-term diffusion constant for such a system is found to have a sensitive, Boltzmann-like, dependence on the interaction strength. In addition, this interaction strength is shown to be a strong function of the ratio of domain to particle size. As similar interactions are expected in biological membranes, the modulation of diffusive transport dynamics by varying interaction strength and/or domain size may offer cells selective spatial and temporal control over signaling processes. PMID:18643101

  5. Lateral drug diffusion in human nails.

    PubMed

    Palliyil, Biji B; Li, Cong; Owaisat, Suzan; Lebo, David B

    2014-12-01

    The main objective of the current work is to demonstrate the process of passive lateral diffusion in the human nail plate and its effect on the passive transungual permeation of antifungal drug ciclopirox olamine (CPO). A water soluble dye, methyl red sodium salt (MR) was used to visualize the process of lateral diffusion using a novel suspended nail experiment. The decline in concentration of CPO correlates with that of concentration of MR from the proximal to the distal end of the nail in suspended nail study. Three toenails each were trimmed to 5 mm × 5 mm (25 mm(2)), 7 mm × 7 mm (49 mm(2)), and 9 mm × 9 mm (81 mm(2)) to study the extent and effect of lateral diffusion of the CPO on its in vitro transungual permeation. The permeation flux of CPO decreased as the surface area of the toenail increased. There was a positive correlation between the concentrations of CPO and MR in the area of application and in the peripheral area of the toenails of the three surface areas, confirming the findings in the suspended nail experiment. Profound lateral diffusion of CPO was demonstrated and shown to reduce the in vitro passive transungual drug permeation and prolong the lag-time in human toenails. The study data implies that during passive in vitro transungual permeation experiments, the peripheral nail around the area of drug application has to be kept to a minimum, in order to get reliable data which mimics the in vivo situation. PMID:24970585

  6. Vapor diffusion electrode improves fuel cell operation

    NASA Technical Reports Server (NTRS)

    Smith, J. O.

    1966-01-01

    Vapor diffusion type fuel cell electrode presents a nonwetting barrier to the liquid feedstocks so they may contact the electrolyte only in the vapor state. Thus, it effects feedstock mixing with the electrolyte at the electrolyte/catalyst interface but prevents feedstock decomposition and catalyst poisoning from liquid mingling.

  7. Diffusion in biofilms respiring on electrodes

    SciTech Connect

    Renslow, Ryan S.; Babauta, Jerome T.; Majors, Paul D.; Beyenal, Haluk

    2012-11-15

    The goal of this study was to measure spatially and temporally resolved effective diffusion coefficients (De) in biofilms respiring on electrodes. Two model electrochemically active biofilms, Geobacter sulfurreducens PCA and Shewanella oneidensis MR-1, were investigated. A novel nuclear magnetic resonance microimaging perfusion probe capable of simultaneous electrochemical and pulsed-field gradient nuclear magnetic resonance (PFG-NMR) techniques was used. PFG-NMR allowed for noninvasive, nondestructive, high spatial resolution in situ De measurements in living biofilms respiring on electrodes. The electrodes were polarized so that they would act as the sole terminal electron acceptor for microbial metabolism. We present our results as both two-dimensional De heat maps and surface-averaged relative effective diffusion coefficient (Drs) depth profiles. We found that (1) Drs decreases with depth in G. sulfurreducens biofilms, following a sigmoid shape; (2) Drs at a given location decreases with G. sulfurreducens biofilm age; (3) average De and Drs profiles in G. sulfurreducens biofilms are lower than those in S. oneidensis biofilms—the G. sulfurreducens biofilms studied here were on average 10 times denser than the S. oneidensis biofilms; and (4) halting the respiration of a G. sulfurreducens biofilm decreases the De values. Density, reflected by De, plays a major role in the extracellular electron transfer strategies of electrochemically active biofilms.

  8. DIFFUSION IN BIOFILMS RESPIRING ON ELECTRODES.

    PubMed

    Renslow, Rs; Babauta, Jt; Majors, Pd; Beyenal, H

    2013-01-01

    The goal of this study was to measure spatially and temporally resolved effective diffusion coefficients (D(e)) in biofilms respiring on electrodes. Two model electrochemically active biofilms, Geobacter sulfurreducens PCA and Shewanella oneidensis MR-1, were investigated. A novel nuclear magnetic resonance microimaging perfusion probe capable of simultaneous electrochemical and pulsed-field gradient nuclear magnetic resonance (PFG-NMR) techniques was used. PFG-NMR allowed noninvasive, nondestructive, high spatial resolution in situ D(e) measurements in living biofilms respiring on electrodes. The electrodes were polarized so that they would act as the sole terminal electron acceptor for microbial metabolism. We present our results as both two-dimensional D(e) heat maps and surface-averaged relative effective diffusion coefficient (D(rs)) depth profiles. We found that 1) D(rs) decreases with depth in G. sulfurreducens biofilms, following a sigmoid shape; 2) D(rs) at a given location decreases with G. sulfurreducens biofilm age; 3) average D(e) and D(rs) profiles in G. sulfurreducens biofilms are lower than those in S. oneidensis biofilms-the G. sulfurreducens biofilms studied here were on average 10 times denser than the S. oneidensis biofilms; and 4) halting the respiration of a G. sulfurreducens biofilm decreases the D(e) values. Density, reflected by D(e), plays a major role in the extracellular electron transfer strategies of electrochemically active biofilms. PMID:23420623

  9. DIFFUSION IN BIOFILMS RESPIRING ON ELECTRODES

    PubMed Central

    Renslow, RS; Babauta, JT; Majors, PD; Beyenal, H

    2013-01-01

    The goal of this study was to measure spatially and temporally resolved effective diffusion coefficients (De) in biofilms respiring on electrodes. Two model electrochemically active biofilms, Geobacter sulfurreducens PCA and Shewanella oneidensis MR-1, were investigated. A novel nuclear magnetic resonance microimaging perfusion probe capable of simultaneous electrochemical and pulsed-field gradient nuclear magnetic resonance (PFG-NMR) techniques was used. PFG-NMR allowed noninvasive, nondestructive, high spatial resolution in situ De measurements in living biofilms respiring on electrodes. The electrodes were polarized so that they would act as the sole terminal electron acceptor for microbial metabolism. We present our results as both two-dimensional De heat maps and surface-averaged relative effective diffusion coefficient (Drs) depth profiles. We found that 1) Drs decreases with depth in G. sulfurreducens biofilms, following a sigmoid shape; 2) Drs at a given location decreases with G. sulfurreducens biofilm age; 3) average De and Drs profiles in G. sulfurreducens biofilms are lower than those in S. oneidensis biofilms—the G. sulfurreducens biofilms studied here were on average 10 times denser than the S. oneidensis biofilms; and 4) halting the respiration of a G. sulfurreducens biofilm decreases the De values. Density, reflected by De, plays a major role in the extracellular electron transfer strategies of electrochemically active biofilms. PMID:23420623

  10. Characterization and optimization of liquid electrodes for lateral dielectrophoresis.

    PubMed

    Demierre, Nicolas; Braschler, Thomas; Linderholm, Pontus; Seger, Urban; van Lintel, Harald; Renaud, Philippe

    2007-03-01

    Using the concept of insulator-based "electrodeless" dielectrophoresis, we present a novel geometry for shaping electric fields to achieve lateral deviation of particles in liquid flows. The field is generated by lateral planar metal electrodes and is guided along access channels to the active area in the main channel. The equipotential surfaces at the apertures of the access channels behave as vertical "liquid" electrodes injecting the current into the main channel. The field between a pair of adjacent liquid electrodes generates the lateral dielectrophoretic force necessary for particle manipulation. We use this force for high-speed deviation of particles. By adding a second pair of liquid electrodes, we focus a particle stream. The position of the focused stream can be swept across the channel by adjusting the ratio of the voltages applied to the two pairs. Based on conformal mapping, we provide an analytical model for estimating the potential at the liquid electrodes and the field distribution in the main channel. We show that the simulated particle trajectories agree with observations. Finally, we show that the model can be used to optimize the device geometry in different applications. PMID:17330167

  11. Rapid Lateral Diffusion of Phospholipids in Rabbit Sarcoplasmic Reticulum

    PubMed Central

    Scandella, Carl J.; Devaux, Philippe; McConnell, Harden M.

    1972-01-01

    Phospholipid spin labels incorporated in the sarcoplasmic reticulum from rabbit-skeletal muscle undergo rapid lateral diffusion within the plane of the membrane. The diffusion constant, D, is 6×10-8 cm2/sec at 37°. With this diffusion constant, a phospholipid molecule can diffuse a distance of the order of 5000 nm in 1 sec. PMID:4506073

  12. Rapid prototyping of electrochemical lateral flow devices: stencilled electrodes.

    PubMed

    Aller Pellitero, Miguel; Kitsara, Maria; Eibensteiner, Friedrich; del Campo, F Javier

    2016-04-21

    A straightforward and very cost effective method is proposed to prototype electrodes using pressure sensitive adhesives (PSA) and a simple cutting technique. Two cutting methods, namely blade cutting and CO2 laser ablation, are compared and their respective merits are discussed. The proposed method consists of turning the protective liner on the adhesive into a stencil to apply screen-printing pastes. After the electrodes have been printed, the liner is removed and the PSA can be used as a backing material for standard lateral flow membranes. We present the fabrication of band electrodes down to 250 μm wide, and their characterization using microscopy techniques and cyclic voltammetry. The prototyping approach presented here facilitates the development of new electrochemical devices even if very limited fabrication resources are available. Here we demonstrate the fabrication of a simple lateral-flow device capable of determining glucose in blood. The prototyping approach presented here is highly suitable for the development of novel electroanalytical tools. PMID:26998899

  13. Lateral diffusion and percolation in membranes.

    PubMed

    Sung, Bong June; Yethiraj, Arun

    2006-06-01

    An algorithm based on Voronoi tessellation and percolation theory is presented to study the diffusion of model membrane components (solutes) in the plasma membrane. The membrane is modeled as a two-dimensional space with integral membrane proteins as static obstacles. The Voronoi diagram consists of vertices, which are equidistant from three matrix obstacles, joined by edges. An edge between two vertices is said to be connected if solute particles can pass directly between the two regions. The percolation threshold, pc, determined using this passage criterion is pc approximately equal to 0.53. This is smaller than if the connectivity of edges were assigned randomly, in which case the percolation threshold pr=2/3, where p is the fraction of connected edges. Molecular dynamics simulations show that diffusion is determined by percolation of clusters of edges. PMID:16803348

  14. Tunable diffusive lateral inhibition in chemical cells⋆

    PubMed Central

    Li, Ning; Tompkins, Nathan; Gonzalez-Ochoa, Hector; Fraden, Seth

    2015-01-01

    The Belousov-Zhabotinsky (BZ) reaction has become the prototype of nonlinear chemical dynamics. Microfluidic techniques provide a convenient method for emulsifying BZ solutions into monodispersed drops with diameters of tens to hundreds of microns, providing a unique system in which reaction-diffusion theory can be quantitatively tested. In this work, we investigate monolayers of microfluidically generated BZ drops confined in close-packed two-dimensional (2D) arrays through experiments and finite element simulations. We describe the transition from oscillatory to stationary chemical states with increasing coupling strength, controlled by independently varying the reaction chemistry within a drop and diffusive flux between drops. For stationary drops, we studied how the ratio of stationary oxidized to stationary reduced drops varies with coupling strength. In addition, using simulation, we quantified the chemical heterogeneity sufficient to induce mixed stationary and oscillatory patterns. PMID:25795263

  15. Lateral PNP bipolar transistor with aiding field diffusions

    NASA Technical Reports Server (NTRS)

    Gallagher, R. C.; Mc Cann, D. H.

    1969-01-01

    Fabrication technique produces field aided lateral PNP transistors compatible with micropower switching circuits. The sub-collector diffusion is performed with phosphorus as the dopant and the epitaxy is grown using the higher temperature silicon tetrachloride process.

  16. Characterization of gas diffusion electrodes for metal-air batteries

    NASA Astrophysics Data System (ADS)

    Danner, Timo; Eswara, Santhana; Schulz, Volker P.; Latz, Arnulf

    2016-08-01

    Gas diffusion electrodes are commonly used in high energy density metal-air batteries for the supply of oxygen. Hydrophobic binder materials ensure the coexistence of gas and liquid phase in the pore network. The phase distribution has a strong influence on transport processes and electrochemical reactions. In this article we present 2D and 3D Rothman-Keller type multiphase Lattice-Boltzmann models which take into account the heterogeneous wetting behavior of gas diffusion electrodes. The simulations are performed on FIB-SEM 3D reconstructions of an Ag model electrode for predefined saturation of the pore space with the liquid phase. The resulting pressure-saturation characteristics and transport correlations are important input parameters for modeling approaches on the continuum scale and allow for an efficient development of improved gas diffusion electrodes.

  17. Lateral diffusion of proteins in the periplasm of Escherichia coli.

    PubMed Central

    Brass, J M; Higgins, C F; Foley, M; Rugman, P A; Birmingham, J; Garland, P B

    1986-01-01

    We have introduced biologically active, fluorescently labeled maltose-binding protein into the periplasmic space of Escherichia coli and measured its lateral diffusion coefficient by the fluorescence photobleaching recovery method. Diffusion of this protein in the periplasm was found to be surprisingly low (lateral diffusion coefficient, 0.9 X 10(-10) cm2 s-1), about 1,000-fold lower than would be expected for diffusion in aqueous medium and almost 100-fold lower than for an equivalent-size protein in the cytoplasm. Galactose-binding protein, myoglobin, and cytochrome c were also introduced into the periplasm and had diffusion coefficients identical to that determined for the maltose-binding protein. For all proteins nearly 100% recovery of fluorescence was obtained after photobleaching, indicating that the periplasm is a single contiguous compartment surrounding the cell. These data have considerable implications for periplasmic structure and for the role of periplasmic proteins in transport and chemotaxis. Images PMID:3005237

  18. Numerical Evaluation of Lateral Diffusion Inside Diffusive Gradients in Thin Films Samplers

    PubMed Central

    2015-01-01

    Using numerical simulation of diffusion inside diffusive gradients in thin films (DGT) samplers, we show that the effect of lateral diffusion inside the sampler on the solute flux into the sampler is a nonlinear function of the diffusion layer thickness and the physical sampling window size. In contrast, earlier work concluded that this effect was constant irrespective of parameters of the sampler geometry. The flux increase caused by lateral diffusion inside the sampler was determined to be ∼8.8% for standard samplers, which is considerably lower than the previous estimate of ∼20%. Lateral diffusion is also propagated to the diffusive boundary layer (DBL), where it leads to a slightly stronger decrease in the mass uptake than suggested by the common 1D diffusion model that is applied for evaluating DGT results. We introduce a simple correction procedure for lateral diffusion and demonstrate how the effect of lateral diffusion on diffusion in the DBL can be accounted for. These corrections often result in better estimates of the DBL thickness (δ) and the DGT-measured concentration than earlier approaches and will contribute to more accurate concentration measurements in solute monitoring in waters. PMID:25877251

  19. Lateral Membrane Diffusion Modulated by a Minimal Actin Cortex

    PubMed Central

    Heinemann, Fabian; Vogel, Sven K.; Schwille, Petra

    2013-01-01

    Diffusion of lipids and proteins within the cell membrane is essential for numerous membrane-dependent processes including signaling and molecular interactions. It is assumed that the membrane-associated cytoskeleton modulates lateral diffusion. Here, we use a minimal actin cortex to directly study proposed effects of an actin meshwork on the diffusion in a well-defined system. The lateral diffusion of a lipid and a protein probe at varying densities of membrane-bound actin was characterized by fluorescence correlation spectroscopy (FCS). A clear correlation of actin density and reduction in mobility was observed for both the lipid and the protein probe. At high actin densities, the effect on the protein probe was ∼3.5-fold stronger compared to the lipid. Moreover, addition of myosin filaments, which contract the actin mesh, allowed switching between fast and slow diffusion in the minimal system. Spot variation FCS was in accordance with a model of fast microscopic diffusion and slower macroscopic diffusion. Complementing Monte Carlo simulations support the analysis of the experimental FCS data. Our results suggest a stronger interaction of the actin mesh with the larger protein probe compared to the lipid. This might point toward a mechanism where cortical actin controls membrane diffusion in a strong size-dependent manner. PMID:23561523

  20. Diffusion-bonded electrodes for chronic neural stimulation.

    PubMed

    Shah, Kedar G; Lee, Kye Young; Tolosa, Vanessa; Tooker, Angela; Felix, Sarah; Pannu, Satinderpall

    2014-01-01

    We report a novel method to fabricate chronic neural interfaces with the intent to combine the reliability and lifetime of bulk metal electrodes, with the miniaturization and mechanical flexibility of thin-film polymer microelectrode arrays. 10 μm thick platinum discs were laser cut from a foil into the shape of individual electrodes, and coated with gold on the backside. The discs were bonded to a microelectrode array with gold bond pads via gold-gold inter-diffusion using a flipchip bonder. Electrode bonding and adhesion was characterized using mechanical shear testing and electrical testing. Electrode performance was characterized in vitro using electrochemical impedance spectroscopy and cyclic voltammetry. Biphasic electrical pulsing experiments were conducted on the bonded electrodes to study degradation of the electrode; the preliminary results show that the electrodes can withstand at least 4,900 million pulses with no adverse electrochemical or visual degradation. Overall, this is a promising new method for fabricating chronic neural electrodes for stimulation or recording that combines the reliability of commercial bulk electrodes with the miniaturization and versatility of microfabricated technologies. PMID:25569992

  1. Lateral diffusion of cytochrome P-450 in phospholipid bilayers.

    PubMed

    Wu, E S; Yang, C S

    1984-01-01

    The lateral diffusion coefficient (D) of cytochrome P-450 (P-450) has been measured in lipid multibilayers with the method of fluorescence recovery after photobleaching. In the liquid-crystal phase of egg phosphatidylcholine (EPC) and dimyristoylphosphatidylcholine (DMPC), the diffusion of P-450 is fast with D about 2 X 10(-8) cm2/s. In DMPC multibilayers, P-450 diffusion dropped by a factor of 20 near the liquid crystal to gel phase transition region, and D is about 5 X 10(-10) cm2/s in the gel phase. A value of 50 mol % of cholesterol reduced the diffusion of P-450 in the liquid-crystal phase only slightly but enhanced the diffusion of P-450 in the gel phase significantly. In EPC membranes, P-450 diffusion underwent a stepwise drop as the cholesterol contents increased from 20 to 30 mol %. With the assumption of a lateral diffusion mediated electron transfer between P-450 and NADPH-P-450 reductase and with D = 2.5 X 10(-8) cm2/s for both enzymes, the reduction rate for P-450 in liposomes was calculated and compared with the reported experimental value. PMID:6691964

  2. Lateral diffusivity of lipid analogue excimeric probes in dimyristoylphosphatidylcholine bilayers.

    PubMed Central

    Sassaroli, M; Vauhkonen, M; Perry, D; Eisinger, J

    1990-01-01

    The lateral mobility of pyrenyl phospholipid probes in dimyristoylphosphatidylcholine (DMPC) vesicles was determined from the dependence of the pyrene monomeric and excimeric fluorescence yields on the molar probe ratio. The analysis of the experimental data makes use of the milling crowd model for two-dimensional diffusivity and the computer simulated random walks of probes in an array of lipids. The fluorescence yields for 1-palmitoyl-2-(1'-pyrenedecanoyl)phosphatidylcholine (py10PC) in DMPC bilayers are well fitted by the model both below and above the fluid-gel phase transition temperature (Tc) and permit the evaluation of the probe diffusion rate (f), which is the frequency with which probes take random steps of length L, the host membrane lipid-lipid spacing. The lateral diffusion coefficient is then obtained from the relationship D = fL2/4. In passing through the fluid-gel phase transition of DMPC (Tc = 24 degrees C), the lateral mobility of py10PC determined in this way decrease only moderately, while D measured by fluorescence photobleaching recovery (FPR) experiments is lowered by two or more orders of magnitude in gel phase. This difference in gel phase diffusivities is discussed and considered to be related either to (a) the diffusion length in FPR experiments being about a micrometer or over 100 times greater than that of excimeric probes (approximately 1 nm), or (b) to nonrandomicity in the distribution of the pyrenyl probes in gel phase DMPC. At 35 degrees C, in fluid DMPC vesicles, the diffusion rate is f = 1.8 x 10(8) s-1, corresponding to D = 29 microns2 s-1, which is about three times larger than the value obtained in FPR experiments. The activation energy for lateral diffusion in fluid DMPC was determined to be 8.0 kcal/mol. PMID:2317550

  3. Lateral Diffusion of Nutrients by Mammalian Herbivores in Terrestrial Ecosystems

    PubMed Central

    Wolf, Adam; Doughty, Christopher E.; Malhi, Yadvinder

    2013-01-01

    Animals translocate nutrients by consuming nutrients at one point and excreting them or dying at another location. Such lateral fluxes may be an important mechanism of nutrient supply in many ecosystems, but lack quantification and a systematic theoretical framework for their evaluation. This paper presents a mathematical framework for quantifying such fluxes in the context of mammalian herbivores. We develop an expression for lateral diffusion of a nutrient, where the diffusivity is a biologically determined parameter depending on the characteristics of mammals occupying the domain, including size-dependent phenomena such as day range, metabolic demand, food passage time, and population size. Three findings stand out: (a) Scaling law-derived estimates of diffusion parameters are comparable to estimates calculated from estimates of each coefficient gathered from primary literature. (b) The diffusion term due to transport of nutrients in dung is orders of magnitude large than the coefficient representing nutrients in bodymass. (c) The scaling coefficients show that large herbivores make a disproportionate contribution to lateral nutrient transfer. We apply the diffusion equation to a case study of Kruger National Park to estimate the conditions under which mammal-driven nutrient transport is comparable in magnitude to other (abiotic) nutrient fluxes (inputs and losses). Finally, a global analysis of mammalian herbivore transport is presented, using a comprehensive database of contemporary animal distributions. We show that continents vary greatly in terms of the importance of animal-driven nutrient fluxes, and also that perturbations to nutrient cycles are potentially quite large if threatened large herbivores are driven to extinction. PMID:23951141

  4. High Speed, Low Cost Fabrication of Gas Diffusion Electrodes for Membrane Electrode Assemblies

    SciTech Connect

    DeCastro, Emory S.; Tsou, Yu-Min; Liu, Zhenyu

    2013-09-20

    Fabrication of membrane electrode assemblies (MEAs) depends on creating inks or pastes of catalyst and binder, and applying this suspension to either the membrane (catalyst coated membrane) or gas diffusion media (gas diffusion electrode) and respectively laminating either gas diffusion media or gas diffusion electrodes (GDEs) to the membrane. One barrier to cost effective fabrication for either of these approaches is the development of stable and consistent suspensions. This program investigated the fundamental forces that destabilize the suspensions and developed innovative approaches to create new, highly stable formulations. These more concentrated formulations needed fewer application passes, could be coated over longer and wider substrates, and resulted in significantly lower coating defects. In March of 2012 BASF Fuel Cell released a new high temperature product based on these advances, whereby our customers received higher performing, more uniform MEAs resulting in higher stack build yields. Furthermore, these new materials resulted in an “instant” increase in capacity due to higher product yields and material throughput. Although not part of the original scope of this program, these new formulations have also led us to materials that demonstrate equivalent performance with 30% less precious metal in the anode. This program has achieved two key milestones in DOE’s Manufacturing R&D program: demonstration of processes for direct coating of electrodes and continuous in-line measurement for component fabrication.

  5. Diffusion in multilayer media: Transient behavior of the lateral diffusion coefficient

    NASA Astrophysics Data System (ADS)

    Berezhkovskii, Alexander M.; Weiss, George H.

    2006-04-01

    A general formalism for treating lateral diffusion in a multilayer medium is developed. The formalism is based on the relation between the lateral diffusion and the distribution of the cumulative residence time, which the diffusing particle spends in different layers. We exploit this fact to derive general expressions which give the global and local time-dependent diffusion coefficients in terms of the average cumulative times spent by the particle in different layers and the probabilities of finding the particle in different layers, respectively. These expressions are used to generalize two recently obtained results: (a) A solution for the short-time behavior of the lateral diffusion coefficient in two layers separated by a permeable membrane obtained by a perturbation theory is extended to the entire range of time. (b) A solution for the time-dependent diffusion coefficient of a ligand, which repeatedly dissociates and rebinds to sites on a planar surface, obtained under the assumption that the medium above the surface is infinite, is generalized to allow for the medium layer of finite thickness. For the latter problem we derive an expression for the Fourier-Laplace transform of the propagator in terms of the double Laplace transform of the probability density of the cumulative residence time spent by the ligand in the medium layer.

  6. Hybrid Tunnel Junction-Graphene Transparent Conductive Electrodes for Nitride Lateral Light Emitting Diodes.

    PubMed

    Wang, Liancheng; Cheng, Yan; Liu, Zhiqiang; Yi, Xiaoyan; Zhu, Hongwei; Wang, Guohong

    2016-01-20

    Graphene transparent conductive electrode (TCE) applications in nitride light emitting diodes (LEDs) are still limited by the large contact resistance and interface barrier between graphene and p-GaN. We propose a hybrid tunnel junction (TJ)-graphene TCE approach for nitride lateral LEDs theoretically and experimentally. Through simulation using commercial advanced physical models of semiconductor devices (APSYS), we found that low tunnel resistance can be achieved in the n(+)-GaN/u-InGaN/p(+)-GaN TJ, which has a lower tunneling barrier and an enhanced electric field due to the polarization effect. Graphene TCEs and hybrid graphene-TJ TCEs are then modeled. The designed hybrid TJ-graphene TCEs show sufficient current diffusion length (Ls), low introduced series resistance, and high transmittance. The assembled TJ LED with the triple-layer graphene (TLG) TCEs show comparable optoelectrical performance (3.99 V@20 mA, LOP = 10.8 mW) with the reference LED with ITO TCEs (3.36 V@20 mA, LOP = 12.6 mW). The experimental results further prove that the TJ-graphene structure can be successfully incorporated as TCEs for lateral nitride LEDs. PMID:26699194

  7. Lateral Diffusion of Bedload Transport under Laminar Flow

    NASA Astrophysics Data System (ADS)

    Ortiz, C. P.; Houssais, M.; Purohit, P. K.; Durian, D. J.; Jerolmack, D. J.

    2014-12-01

    Lateral sediment transport is a key momentum-exchange mechanism to model equilibrium channel geometry and channel bar evolution. We study sediment transport from a statistical mechanical point of view akin to Furbish et al. 2012. This approach holds promise for linking grain-scale motion to macroscopic transport, but there are few data to definitively develop and test such models. We study an experimental model river, composed of monodisperse acrylic spheres dispersed in silicon oil, driven by a layer of fluid under steady shear. We choose to drive fluid flow in the laminar regime (Re < 1) to suppress fluid turbulence and isolate granular and bed structure controls. We use a refractive-index-matched laser scanning technique to observe the motion of particles at the surface of the bed as well as the particle dynamics below the surface. We study how the probability distribution of displacements varies as a function of distance from the bed surface and as a function of distance to the channel center. In the streamwise direction, in agreement with Furbish et al. 2012, we find that the dynamics can be decomposed into an advection and a diffusion term. In the lateral direction, we find a competition between diffusion and an elastic-like interaction with the bed. We study this lateral stochastic process and find a need to introduce two parameters to quantify this competition. The first parameter describes the tendency for particles to reside near the center of the channel and the second parameter describes the kinetic energy distribution of the particles. We study how the requisite averaging scales and ensemble sizes to achieve statistically convergent parameters, and we explore how these parameters depend on the driving rate.

  8. Quantitative diffusion tensor imaging in amyotrophic lateral sclerosis: revisited.

    PubMed

    Sage, Caroline A; Van Hecke, Wim; Peeters, Ronald; Sijbers, Jan; Robberecht, Wim; Parizel, Paul; Marchal, Guy; Leemans, Alexander; Sunaert, Stefan

    2009-11-01

    Voxel-based analyses (VBA) are increasingly being used to detect white matter abnormalities with diffusion tensor imaging (DTI) in different types of pathologies. However, the validity, specificity, and sensitivity of statistical inferences of group differences to a large extent depend on the quality of the spatial normalization of the DTI images. Using high-dimensional nonrigid coregistration techniques that are able to align both the spatial and orientational diffusion information and incorporate appropriate templates that contain this complete DT information may improve this quality. Alternatively, a hybrid technique such as tract-based spatial statistics (TBSS) may improve the reliability of the statistical results by generating voxel-wise statistics without the need for perfect image alignment and spatial smoothing. In this study, we have used (1) a coregistration algorithm that was optimized for coregistration of DTI data and (2) a population-based DTI atlas to reanalyze our previously published VBA, which compared the fractional anisotropy and mean diffusivity maps of patients with amyotrophic lateral sclerosis (ALS) with those of healthy controls. Additionally, we performed a complementary TBSS analysis to improve our understanding and interpretation of the VBA results. We demonstrate that, as the overall variance of the diffusion properties is lowered after normalizing the DTI data with such recently developed techniques (VBA using our own optimized high-dimensional nonrigid coregistration and TBSS), more reliable voxel-wise statistical results can be obtained than had previously been possible, with our VBA and TBSS yielding very similar results. This study provides support for the view of ALS as a multisystem disease, in which the entire frontotemporal lobe is implicated. PMID:19404990

  9. Lateral actuation of an organic droplet on conjugated polymer electrodes via imbalanced interfacial tensions.

    PubMed

    Xu, Wei; Xu, Jian; Li, Xin; Tian, Ye; Choi, Chang-Hwan; Yang, Eui-Hyeok

    2016-08-17

    This paper presents a new mechanism for the controlled lateral actuation of organic droplets on dodecylbenzenesulfonate-doped polypyrrole (PPy(DBS)) electrodes at low voltages (∼0.9 V) in an aqueous environment. The droplet actuation is based on the tunable surface wetting properties of the polymer electrodes induced by electrochemical redox reactions. The contact angle of a dichloromethane (DCM) droplet on the PPy(DBS) surface switches between ∼119° upon oxidation (0.6 V) and ∼150° upon reduction (-0.9 V) in 0.1 M NaNO3 solution. The droplet placed across the reduced and oxidized PPy(DBS) electrodes experiences imbalanced interfacial tensions, which prompt the actuation of the droplet from the reduced electrode to the oxidized electrode. The lateral actuation of DCM droplets on two PPy(DBS) electrodes is demonstrated, and the actuation process is studied. The driving force due to the imbalanced interfacial tensions is estimated to be approximately 10(-7) N for a 6 μL droplet. PMID:27426489

  10. Simultaneous Characterization of Lateral Lipid and Prothrombin Diffusion Coefficients by Z-Scan Fluorescence Correlation Spectroscopy

    PubMed Central

    Štefl, Martin; Kułakowska, Anna; Hof, Martin

    2009-01-01

    Abstract A new (to our knowledge) robust approach for the determination of lateral diffusion coefficients of weakly bound proteins is applied for the phosphatidylserine specific membrane interaction of bovine prothrombin. It is shown that z-scan fluorescence correlation spectroscopy in combination with pulsed interleaved dual excitation allows simultaneous monitoring of the lateral diffusion of labeled protein and phospholipids. Moreover, from the dependencies of the particle numbers on the axial sample positions at different protein concentrations phosphatidylserine-dependent equilibrium dissociation constants are derived confirming literature values. Increasing the amount of membrane-bound prothrombin retards the lateral protein and lipid diffusion, indicating coupling of both processes. The lateral diffusion coefficients of labeled lipids are considerably larger than the simultaneously determined lateral diffusion coefficients of prothrombin, which contradicts findings reported for the isolated N-terminus of prothrombin. PMID:19651025

  11. Lateral spin valves with two-different Heusler-alloy electrodes on the same platform

    SciTech Connect

    Oki, S.; Yamada, S.; Tanikawa, K.; Yamasaki, K.; Miyao, M.; Hamaya, K.

    2013-11-18

    Using room-temperature molecular beam epitaxy on Si(111), we demonstrate Heusler-alloy bilayers consisting of L2{sub 1}-Co{sub 2}FeSi (CFS) and D0{sub 3}-Fe{sub 3}Si (FS). By fabricating lateral spin valves with L2{sub 1}-CFS and D0{sub 3}-FS electrodes, we can see ideal spin signals even though we use one L2{sub 1}-CFS as a spin injector and another D0{sub 3}-FS as a spin detector. The difference in the spin absorption between L2{sub 1}-CFS and D0{sub 3}-FS can also be examined, and we find that the spin resistance of D0{sub 3}-FS is larger than that of L2{sub 1}-CFS. This work will be useful for understanding spin transport in lateral spin-valve devices with different Heusler-alloy electrodes.

  12. Lateral diffusion in model membranes is independent of the size of the hydrophobic region of molecules.

    PubMed Central

    Balcom, B J; Petersen, N O

    1993-01-01

    We have systematically investigated the probe size and shape dependence of lateral diffusion in model dimyristoyl phosphatidylcholine membranes. Linear hydrophobic polymers, which differ in length by an order of magnitude, were used to explore the effect on the lateral diffusion coefficient of hydrodynamic restrictions in the bilayer interior. The polymers employed are isoprenoid alcohols--citronellol, solanesol, and dolichol. Tracer lateral diffusion coefficients were measured by fluorescence photobleaching recovery. Despite the large difference in lengths, the nitrobenzoxadiazole labelled alcohols all diffuse at the rate of lipid self-diffusion (5.0 x 10(-12) m2 s-1, 29 degrees C) in the liquid crystal phase. Companion measurements in isotropic polymer solution, in gel phase lipid membranes and with nonpolar fluorescent polyaromatic hydrocarbons, show a marked dependence of the lateral diffusion coefficient on the probe molecule size. Our results in the liquid crystal phase are in accord with free area theory which asserts that lateral diffusion in the membrane is restricted by the surface-free area. Probe molecules which are significantly longer than the host phospholipid, seven times longer in the case of dolichol, are still restricted in their lateral motion by the surface properties of the bilayer in the liquid crystal phase. Fluorescence quenching experiments indicate that the nitrobenzoxadiazole label does not reside at the aqueous interface, although it must reside in close proximity according to the diffusion measurements. PMID:8218892

  13. Quantitating Changes in Jitter and Spike Number Using Concentric Needle Electrodes in Amyotrophic Lateral Sclerosis Patients

    PubMed Central

    Liu, Ming-Sheng; Niu, Jing-Wen; Li, Yi; Guan, Yu-Zhou; Cui, Li-Ying

    2016-01-01

    Background: Single-fiber electromyography (SFEMG) has been suggested as a quantitative method for supporting chronic partial denervation in amyotrophic lateral sclerosis (ALS) by the revised EI Escorial criteria. Although concentric needle (CN) electrodes have been used to assess jitter in myasthenia gravis patients and healthy controls, there are few reports using CN electrodes to assess motor unit instability and denervation in neurogenic diseases. The aim of this study was to determine whether quantitative changes in jitter and spike number using CN electrodes could be used for ALS studies. Methods: Twenty-seven healthy controls and 23 ALS patients were studied using both CN and single-fiber needle (SFN) electrodes on the extensor digitorum communis muscle with an SFEMG program. The SFN-jitter and SFN-fiber density data were measured using SFN electrodes. The CN-jitter and spike number were measured using CN electrodes. Results: The mean CN-jitter was significantly increased in ALS patients (47.3 ± 17.0 μs) than in healthy controls (27.4 ± 3.3 μs) (P < 0.001). Besides, the mean spike number was significantly increased in ALS patients (2.5 ± 0.5) than in healthy controls (1.7 ± 0.3) (P < 0.001). The sensitivity and specificity in the diagnosis of ALS were 82.6% and 92.6% for CN-jitter (cut-off value: 32 μs), and 91.3% and 96.3% for the spike number (cut-off value: 2.0), respectively. There was no significant difference between the SFN-jitter and CN-jitter in ALS patients; meanwhile, there was no significant difference between the SFN-jitter and CN-jitter in healthy controls. Conclusion: CN-jitter and spike number could be used to quantitatively evaluate changes due to denervation-reinnervation in ALS. PMID:27098787

  14. Diffusion welded nonconsumable electrode assembly and use thereof for electrolytic production of metals and silicon

    DOEpatents

    Byrne, Stephen C.; Vasudevan, Asuri K.

    1984-01-01

    A nonconsumable electrode assembly suitable for use in the production of metal by electrolytic reduction of a metal compound dissolved in a molten salt, the assembly comprising a metal conductor diffusion welded to a portion of a ceramic electrode body having a level of free metal or metal alloy sufficient to effect a metal bond.

  15. Lateral diffusion of small compounds in human stratum corneum and model lipid bilayer systems.

    PubMed Central

    Johnson, M E; Berk, D A; Blankschtein, D; Golan, D E; Jain, R K; Langer, R S

    1996-01-01

    An image-based technique of fluorescence recovery after photobleaching (video-FRAP) was used to measure the lateral diffusion coefficients of a series of nine fluorescent probes in two model lipid bilayer systems, dimyristoylphosphatidylcholine (DMPC) and DMPC/cholesterol (40 mol%), as well as in human stratum corneum-extracted lipids. The probes were all lipophilic, varied in molecular weight from 223 to 854 Da, and were chosen to characterize the lateral diffusion of small compounds in these bilayer systems. A clear molecular weight dependence of the lateral diffusion coefficients in DMPC bilayers was observed. Values ranged from 6.72 x 10(-8) to 16.2 x 10(-8) cm2/s, with the smaller probes diffusing faster than the larger ones. Measurements in DMPC/cholesterol bilayers, which represent the most thorough characterization of small-solute diffusion in this system, exhibited a similar molecular weight dependence, although the diffusion coefficients were lower, ranging from 1.62 x 10(-8) to 5.60 x 10(-8) cm2/s. Lateral diffusion measurements in stratum corneum-extracted lipids, which represent a novel examination of diffusion in this unique lipid system, also exhibited a molecular weight dependence, with values ranging from 0.306 x 10(-8) to 2.34 x 10(-8) cm2/s. Literature data showed that these strong molecular weight dependencies extend to even smaller compounds than those examined in this study. A two-parameter empirical expression is presented that describes the lateral diffusion coefficient in terms of the solute's molecular weight and captures the size dependence over the range examined. This study illustrates the degree to which small-molecule lateral diffusion in stratum corneum-extracted lipids can be represented by diffusion in DMPC and DMPC/cholesterol bilayer systems, and may lead to a better understanding of small-solute transport across human stratum corneum. PMID:8913603

  16. Time of Flight Electrochemistry: Diffusion Coefficient Measurements Using Interdigitated Array (IDA) Electrodes

    SciTech Connect

    Liu, Fei; Kolesov, Grigory; Parkinson, Bruce A.

    2014-09-26

    A simple and straightforward method for measuring diffusion coefficients using interdigitated array (IDA) electrodes is reported. The method does not require that the exact electrode area be known but depends only the size of the gap between the IDA electrode pairs. Electroactive molecules produced at the generator electrode of the IDA by a voltage step or scan can diffuse to the collector electrode and the time delay before the current for the reverse electrochemical reaction is detected at the collector is used to calculate the diffusion coefficient. The measurement of the diffusion rate of Ru(NH3)6+2 in aqueous solution has been used as an example measuring diffusion coefficients using this method. Additionally, a digital simulation of the electrochemical response of the IDA electrodes was used to simulate the entire current/voltage/time behavior of the system and verify the experimentally measured diffusion coefficients. This work was supported as part of the Center for Molecular Electrocatalysis, an Energy Frontier Research Center funded by the Department of Energy, Office of Science, Office of Basic Energy Sciences.

  17. Exploratory laboratory study of lateral turbulent diffusion at the surface of an alluvial channel

    USGS Publications Warehouse

    Sayre, William W.; Chamberlain, A.R.

    1964-01-01

    In natural streams turbulent diffusion is one of the principal mechanisms by which liquid and suspended-particulate contaminants are dispersed in the flow. A knowledge of turbulence characteristics is therefore essential in predicting the dispersal rates of contaminants in streams. In this study the theory of diffusion by continuous movements for homogeneous turbulence is applied to lateral diffusion at the surface of an open channel in which there is uniform flow. An exploratory-laboratory investigation was conducted in which the lateral dispersion at the water surface of a sand-Led flume was studied by measuring the lateral spread from a point source of small floating polyethylene articles. The experiment was restricted to a single set of low and channel geometry conditions. The results of the study indicate that with certain restrictions lateral dispersion in alluvial channels may be successfully described by the theory of diffusion by continuous movements. The experiment demonstrates a means for evaluating the lateral diffusion coefficient and also methods for quantitatively estimating fundamental turbulence properties, such as the intensity and the Lagrangian integral scale of turbulence in an alluvial channel. The experimental results show that with increasing distance from the source the coefficient of lateral turbulent diffusion increases initially but tends toward a constant limiting value. This result is in accordance with turbulent diffusion theory. Indications are that the distance downstream from the source required for the diffusion coefficient to reach its limiting value is actually very small when compared to the length scale of most diffusion phenomena in natural streams which are of practical interest.

  18. Static and Dynamic Effects of Lateral Carrier Diffusion in Semiconductor Lasers

    NASA Technical Reports Server (NTRS)

    Li, Jian-Zhong; Cheung, Samson H.; Ning, C. Z.; Biegel, Bryan A. (Technical Monitor)

    2002-01-01

    Electron and hole diffusions in the plane of semiconductor quantum wells play an important part in the static and dynamic operations of semiconductor lasers. It is well known that the value of diffusion coefficients affects the threshold pumping current of a semiconductor laser. At the same time, the strength of carrier diffusion process is expected to affect the modulation bandwidth of an AC-modulated laser. It is important not only to investigate the combined DC and AC effects due to carrier diffusion, but also to separate the AC effects from that of the combined effects in order to provide design insights for high speed modulation. In this presentation, we apply a hydrodynamic model developed by the present authors recently from the semiconductor Bloch equations. The model allows microscopic calculation of the lateral carrier diffusion coefficient, which is a nonlinear function of the carrier density and plasma temperature. We first studied combined AC and DC effects of lateral carrier diffusion by studying the bandwidth dependence on diffusion coefficient at a given DC current under small signal modulation. The results show an increase of modulation bandwidth with decrease in the diffusion coefficient. We simultaneously studied the effects of nonlinearity in the diffusion coefficient. To clearly identify how much of the bandwidth increase is a result of decrease in the threshold pumping current for smaller diffusion coefficient, thus an effective increase of DC pumping, we study the bandwidth dependence on diffusion coefficient at a given relative pumping. A detailed comparison of the two cases will be presented.

  19. Diffusion-Mediated Synthesis of MoS2/WS2 Lateral Heterostructures.

    PubMed

    Bogaert, Kevin; Liu, Song; Chesin, Jordan; Titow, Denis; Gradečak, Silvija; Garaj, Slaven

    2016-08-10

    Controlled growth of two-dimensional transition metal dichalcogenide (TMD) lateral heterostructures would enable on-demand tuning of electronic and optoelectronic properties in this new class of materials. Prior to this work, compositional modulations in lateral TMD heterostructures have been considered to depend solely on the growth chronology. We show that in-plane diffusion can play a significant role in the chemical vapor deposition of MoS2/WS2 lateral heterostructures leading to a variety of nontrivial structures whose composition does not necessarily follow the growth order. Optical, structural, and compositional studies of TMD crystals captured at different growth temperatures and in different diffusion stages suggest that compositional mixing versus segregation are favored at high and low growth temperatures, respectively. The observed diffusion mechanism will expand the realm of possible lateral heterostructures, particularly ones that cannot be synthesized using traditional methods. PMID:27438807

  20. Application of gas diffusion electrodes in bioelectrochemical syntheses and energy conversion.

    PubMed

    Horst, Angelika E W; Mangold, Klaus-Michael; Holtmann, Dirk

    2016-02-01

    Combining the advantages of biological components (e.g., reaction specificity, self-replication) and electrochemical techniques in bioelectrochemical systems offers the opportunity to develop novel efficient and sustainable processes for the production of a number of valuable products. The choice of electrode material has a great impact on the performance of bioelectrochemical systems. In addition to the redox process at the electrodes, interactions of biocatalysts with electrodes (e.g., enzyme denaturation or biofouling) need to be considered. In recent years, gas diffusion electrodes (GDEs) have proved to be very attractive electrodes for bioelectrochemical purposes. GDEs are porous electrodes, that posses a large three-phase boundary surface. At this interface, a solid catalyst supports the electrochemical reaction between gaseous and liquid phase. This mini-review discusses the application of GDEs in microbial and enzymatic fuel cells, for microbial electrolysis, in biosensors and for electroenzymatic synthesis reactions. PMID:26152235

  1. Lateral Diffusion of CO2 in Leaves Is Not Sufficient to Support Photosynthesis[w

    PubMed Central

    Morison, James I.L.; Gallouët, Emily; Lawson, Tracy; Cornic, Gabriel; Herbin, Raphaèle; Baker, Neil R.

    2005-01-01

    Lateral diffusion of CO2 was investigated in photosynthesizing leaves with different anatomy by gas exchange and chlorophyll a fluorescence imaging using grease to block stomata. When one-half of the leaf surface of the heterobaric species Helianthus annuus was covered by 4-mm-diameter patches of grease, the response of net CO2 assimilation rate (A) to intercellular CO2 concentration (Ci) indicated that higher ambient CO2 concentrations (Ca) caused only limited lateral diffusion into the greased areas. When single 4-mm patches were applied to leaves of heterobaric Phaseolus vulgaris and homobaric Commelina communis, chlorophyll a fluorescence images showed dramatic declines in the quantum efficiency of photosystem II electron transport (measured as Fq′/Fm′) across the patch, demonstrating that lateral CO2 diffusion could not support A. The Fq′/Fm′ values were used to compute images of Ci across patches, and their dependence on Ca was assessed. At high Ca, the patch effect was less in C. communis than P. vulgaris. A finite-volume porous-medium model for assimilation rate and lateral CO2 diffusion was developed to analyze the patch images. The model estimated that the effective lateral CO2 diffusion coefficients inside C. communis and P. vulgaris leaves were 22% and 12% of that for free air, respectively. We conclude that, in the light, lateral CO2 diffusion cannot support appreciable photosynthesis over distances of more than approximately 0.3 mm in normal leaves, irrespective of the presence or absence of bundle sheath extensions, because of the CO2 assimilation by cells along the diffusion pathway. PMID:16113223

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

    PubMed Central

    Liu, Xiaoping; Zweier, Jay L.

    2012-01-01

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

  3. Lateral diffusion of specific antibodies bound to lipid monolayers on alkylated substrates.

    PubMed Central

    Subramaniam, S; Seul, M; McConnell, H M

    1986-01-01

    We have measured the lateral mobility of fluoresceinated monoclonal IgG antibodies bound specifically to a spin label lipid hapten in phospholipid monolayers supported on alkylated silicon oxide surfaces. Dimyristoyl phosphatidylcholine and dipalmitoyl phosphatidylcholine monolayers containing 5 mol% of the lipid hapten were transferred by conventional Langmuir-Blodgett techniques onto substrates alkylated with hydrocarbon chains containing 10, 16, and 18 carbon atoms. We show that the diffusion of the bound antibodies depends on their lateral density, the composition of the lipid monolayer, and the nature of lipid coupling to hydrocarbon chains on the alkylated substrate. Antibody diffusion coefficients at low antibody densities are within a factor of 2 of those displayed by the lipid hapten in the absence of the bound antibody. High antibody densities result in reduced antibody mobility, but the lateral diffusion of unbound lipids is unaffected. Images PMID:3006037

  4. Dynamics of the atmospheric pressure diffuse dielectric barrier discharge between cylindrical electrodes in roll-to-roll PECVD reactor

    NASA Astrophysics Data System (ADS)

    Starostin, Sergey A.; Welzel, Stefan; Liu, Yaoge; van der Velden-Schuermans, Bernadette; Bouwstra, Jan B.; van de Sanden, Mauritius C. M.; de Vries, Hindrik W.

    2015-07-01

    The high current diffuse dielectric barrier discharge (DBD) was operated in a bi-axial cylindrical electrode configuration using nitrogen, oxygen and argon gas flow with the addition of tetraethyl orthosilicate as precursor for silica-like film deposition. The behaviour of the transient plasma was visualized by means of fast imaging from two orthogonal directions. The formation and propagation (~3 × 104 m s-1) of lateral ionization waves with the transverse light emission structure similar to the low pressure glow discharge was observed at time scales below 1 µs. Despite plasma non-uniformity at nanosecond time scale the deposition process on the web-rolled polymer results in smooth well adherent films with good film uniformity and excellent gas diffusion barrier properties. Contribution to the topical issue "The 14th International Symposium on High Pressure Low Temperature Plasma Chemistry (HAKONE XIV)", edited by Nicolas Gherardi, Ronny Brandenburg and Lars Stollenwark

  5. Multiplicity of equilibrium states in laterally heated thermosolutal systems with equal diffusivity coefficients

    NASA Astrophysics Data System (ADS)

    Tsitverblit, N.

    1999-09-01

    This work uncovers the instabilities arising in laterally heated stably stratified systems when the diffusivities of the two involved components are equal. These instabilities are demonstrated to be the result of the differential diffusion caused by the unequal lateral diffusion gradients of the components. Such gradients form in the perturbed state due to the different side-wall boundary conditions. Examination of the bifurcation phenomena in the finite enclosures with equal diffusivities exhibited most qualitative features established by Tsitverblit and Kit [Phys. Fluids A 5, 1062 (1993)] and Tsitverblit [Phys. Fluids 7, 718 (1995)] for such phenomena in the heat-salt problem. In the behavior of singularities and steady flows, a number of the regularities that are not distinct in the heat-salt case were distinguished. Additional results obtained with the solute sidewall boundary conditions being of the same (fixed-value) type as the temperature conditions were also discussed.

  6. Thermal imaging measurement of lateral diffusivity and non-invasive material defect detection

    DOEpatents

    Sun, Jiangang; Deemer, Chris

    2003-01-01

    A system and method for determining lateral thermal diffusivity of a material sample using a heat pulse; a sample oriented within an orthogonal coordinate system; an infrared camera; and a computer that has a digital frame grabber, and data acquisition and processing software. The mathematical model used within the data processing software is capable of determining the lateral thermal diffusivity of a sample of finite boundaries. The system and method may also be used as a nondestructive method for detecting and locating cracks within the material sample.

  7. A quantitative radioluminographic imaging method for evaluating lateral diffusion rates in skin.

    PubMed

    Rush, Allison K; Miller, Matthew A; Smith, Edward D; Kasting, Gerald B

    2015-10-28

    A method is presented for measuring the lateral diffusion coefficients of exogenously applied compounds on excised skin. The method involves sequential high resolution imaging of the spatial distribution of β-radiation associated with [(14)C]-labeled compounds to monitor the development of the concentration profile on the skin surface. It is exemplified by measurements made on three radiolabeled test compounds--caffeine, testosterone, and zinc pyrithione (ZnPT)--administered as solutions. Lateral diffusivity is expected to be an important determinant of the topical bioavailability of ZnPT, which is characteristically administered as a fine suspension and must reach microorganisms in molecular form to exert biocidal activity. Application of the test compounds at levels below and above their estimated saturation doses in the upper stratum corneum allows one to distinguish between diffusion-limited and dissolution rate-limited kinetics. The effective lateral diffusivities of the two chemically stable reference compounds, caffeine and testosterone, were (1-4) × 10(-9) cm(2)/s and (3-9) × 10(-9) cm(2)/s, respectively. Lateral transport of [(14)C] associated with ZnPT was formulation-dependent, with effective diffusivities of (1-2) × 10(-9) cm(2)/s in water and (3-9) × 10(-9) cm(2)/s in a 1% body wash solution. These differences are thought to be related to molecular speciation and/or the presence of a residual surfactant phase on the skin surface. All values were greater than those estimated for the transverse diffusivities of these compounds in stratum corneum by factors ranging from 250 to over 2000. Facile lateral transport on skin, combined with a low transdermal permeation rate, may thus be seen to be a key factor in the safe and effective use of ZnPT as a topical antimicrobial agent. PMID:26241749

  8. Strong influence of periodic boundary conditions on lateral diffusion in lipid bilayer membranes.

    PubMed

    Camley, Brian A; Lerner, Michael G; Pastor, Richard W; Brown, Frank L H

    2015-12-28

    The Saffman-Delbrück hydrodynamic model for lipid-bilayer membranes is modified to account for the periodic boundary conditions commonly imposed in molecular simulations. Predicted lateral diffusion coefficients for membrane-embedded solid bodies are sensitive to box shape and converge slowly to the limit of infinite box size, raising serious doubts for the prospects of using detailed simulations to accurately predict membrane-protein diffusivities and related transport properties. Estimates for the relative error associated with periodic boundary artifacts are 50% and higher for fully atomistic models in currently feasible simulation boxes. MARTINI simulations of LacY membrane protein diffusion and LacY dimer diffusion in DPPC membranes and lipid diffusion in pure DPPC bilayers support the underlying hydrodynamic model. PMID:26723598

  9. Strong influence of periodic boundary conditions on lateral diffusion in lipid bilayer membranes

    SciTech Connect

    Camley, Brian A.; Lerner, Michael G.; Pastor, Richard W.; Brown, Frank L. H.

    2015-12-28

    The Saffman-Delbrück hydrodynamic model for lipid-bilayer membranes is modified to account for the periodic boundary conditions commonly imposed in molecular simulations. Predicted lateral diffusion coefficients for membrane-embedded solid bodies are sensitive to box shape and converge slowly to the limit of infinite box size, raising serious doubts for the prospects of using detailed simulations to accurately predict membrane-protein diffusivities and related transport properties. Estimates for the relative error associated with periodic boundary artifacts are 50% and higher for fully atomistic models in currently feasible simulation boxes. MARTINI simulations of LacY membrane protein diffusion and LacY dimer diffusion in DPPC membranes and lipid diffusion in pure DPPC bilayers support the underlying hydrodynamic model.

  10. Strong influence of periodic boundary conditions on lateral diffusion in lipid bilayer membranes

    NASA Astrophysics Data System (ADS)

    Camley, Brian A.; Lerner, Michael G.; Pastor, Richard W.; Brown, Frank L. H.

    2015-12-01

    The Saffman-Delbrück hydrodynamic model for lipid-bilayer membranes is modified to account for the periodic boundary conditions commonly imposed in molecular simulations. Predicted lateral diffusion coefficients for membrane-embedded solid bodies are sensitive to box shape and converge slowly to the limit of infinite box size, raising serious doubts for the prospects of using detailed simulations to accurately predict membrane-protein diffusivities and related transport properties. Estimates for the relative error associated with periodic boundary artifacts are 50% and higher for fully atomistic models in currently feasible simulation boxes. MARTINI simulations of LacY membrane protein diffusion and LacY dimer diffusion in DPPC membranes and lipid diffusion in pure DPPC bilayers support the underlying hydrodynamic model.

  11. Microprobe PIXE study of Ni-Ge interactions in lateral diffusion couples

    NASA Astrophysics Data System (ADS)

    Chilukusha, D.; Pineda-Vargas, C. A.; Nemutudi, R.; Habanyama, A.; Comrie, C. M.

    2015-11-01

    Rutherford backscattering spectrometry on the nuclear microprobe (μRBS) is often used in studies of lateral diffusion couples. RBS requires that the positions of the interacting species on the periodic table are not too close in terms of atomic number and therefore do not produce excessive RBS peak overlap. In order to satisfactorily characterize systems that have atomic numbers which are close, it is necessary to find techniques which can complement μRBS. The aim of this study was to determine the extent to which particle induced X-ray emission (PIXE) could be applied in the lateral diffusion couple study of a system with relatively close atomic numbers. This was with a view that it may eventually be adopted to study systems where the atomic numbers are too close for RBS analysis. The system studied here was the Ni-Ge binary system. Since RBS is an established technique for studying lateral diffusion couples, we used it as a standard for comparison. The PIXE results showed a maximum error of 12% with reference to the RBS standard. In order to achieve the most effective use of PIXE in lateral diffusion couple studies we recommend the use of the technique in such a way as to obtain depth information and the use of relatively thick sample layers.

  12. Thermal imaging measurement of lateral thermal diffusivity in continuous fiber ceramic composites

    SciTech Connect

    Sun, J. G.; Deemer, C.; Ellingson, W. A.

    2000-02-18

    Infrared thermal imaging has become a common technique for nondestructive evaluation and measurement of thermal properties in ceramic specimens. Flash thermal imaging can be used to determine two-dimensional through-thickness thermal diffusivity in a planar specimen. In this study, the authors extended the method to determine lateral, or transverse, thermal diffusivity in the specimen. During the flash thermal imaging test, pulsed heat energy is applied to a specimen's back surface, which is partially shielded, and the change of temperature distribution on the front surface is monitored by an infrared thermal imaging system. The temperature distribution represents the effect of both the normal heat transfer through the specimen's thickness and the lateral heat transfer through the interface between the shielded and unshielded back-surface regions. Those temperature distributions are then fitted with a theoretical solution of the heat transfer process to determine the lateral thermal diffusivity at the interface. This technique has been applied to measure lateral thermal diffusivity in a steel plate and a continuous fiber ceramic composite specimen.

  13. Vanadium diaphragm electrode serves as hydrogen diffuser in lithium hydride cell

    NASA Technical Reports Server (NTRS)

    Crouthamel, C. E.; Heinrich, R. R.; Johnson, C. E.

    1967-01-01

    Lithium hydride cell uses vanadium diaphragm electrode as a hydrogen diffuser. Vanadium is high in hydrogen gas solubility and permeability, is least sensitive to adverse surface effects, maintains good mechanical strength in hydrogen atmospheres, and appears to be compatible with all alkali-halide electrolytes and lithium metals.

  14. (abstract) Alkali Metal Diffusion Through Porous Metal Electrodes in AMTEC Cells

    NASA Technical Reports Server (NTRS)

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

    1993-01-01

    The mechanisms of mass transport of an alkali metal through porous metal electrodes in alkali metal thermal-to-electric converter AMTEC cells is important in optimizing these high current density devices, but also affords the opportunity to investigate a variety of simple mass transport modes at high temperatures via electrochemical techniques. We have previously reported evidence of ionic, free molecular flow, and surface transport of sodium in several types of AMTEC electrodes. Quantitative investigations of Na transport through WPt(sub 3.5) via surface or grain boundary diffusion, and K transport through porous Mo electrodes by free molecular flow, over large ranges of temperature have been performed. WPt(sub 3.5) has especially low transport impedance over the 950 to 1200K temperature range. New results are the Na through porous WPt(sub 3.5) and K through porous Mo diffusion rates and mechanisms.

  15. On the meaning of the diffusion layer thickness for slow electrode reactions.

    PubMed

    Molina, A; González, J; Laborda, E; Compton, R G

    2013-02-21

    A key concept underpinning electrochemical science is that of the diffusion layer - the zone of depletion around an electrode accompanying electrolysis. The size of this zone can be found either from the simulated or measured concentration profiles (yielding the 'true' diffusion layer thickness) or, in the case of the Nernst ('linear') diffusion layer by extrapolating the concentration gradient at the electrode surface to the distance at which the concentration takes its bulk value. The latter concept is very well developed in the case of fast (so-called reversible) electrode processes, however the study of the linear diffusion layer has received scant attention in the case of slow charge transfer processes, despite its study being of great interest in the analysis of the influence of different experimental variables which determine the electrochemical response. Analytical explicit solutions for the concentration profiles, surface concentrations and real and linear diffusion layers corresponding to the application of a potential step to a slow charge transfer process are presented. From these expressions the dependence of the diffusion layer thickness on the potential, pulse time, heterogeneous rate constant and ratio of bulk concentrations of electroactive species and of diffusion coefficients is quantified. A profound influence of the reversibility degree of the charge transfer on the diffusion layer thickness is clear, showing that for non-reversible processes the real and linear diffusion layers reveal a minimum thickness which coincides with the equilibrium potential of the redox couple in the former case and with the reversible half-wave potential in the latter one. PMID:23301247

  16. FTIR microscopy and confocal Raman microscopy for studying lateral drug diffusion from a semisolid formulation.

    PubMed

    Gotter, B; Faubel, W; Neubert, R H H

    2010-01-01

    Fourier transform infrared (FTIR) microscopy was applied to obtain information on lateral drug diffusion of dithranol in artificial acceptor membranes. Lateral (2D) drug distribution into an artificial membrane was investigated on an area of 300microm x 1000microm with a lateral resolution of 25microm x 25microm by integrating a specific IR band located at 1430cm(-1). The concentration profiles show a heterogeneous distribution of dithranol particles resulting in non-uniform drug diffusion. Use of the FTIR microscope either in the transmission or in the reflection mode was restricted to a thickness of the DDC membrane <15microm. The third dimension (depth profile) was analysed by means of confocal Raman microscopy (CRM). In an artificial membrane, the depth range from a minimum of 1.5microm up to a maximum of 49microm was analysed for dithranol distribution. PMID:19615444

  17. Effect of binders on natural graphite powder-based gas diffusion electrode for Mg-air cell

    NASA Astrophysics Data System (ADS)

    Arinton, Ghenadi; Rianto, Anton; Faizal, Ferry; Hidayat, Darmawan; Hidayat, Sahrul; Panatarani, Camellia; Joni, I. Made

    2016-03-01

    This paper mainly discussed the electrical performance of gas diffusion electrode of Mg-Air Cell. The gas diffusion electrodes (GDE) use a natural graphite powder as catalyst material. The effect of additional binders to the GDE have been investigated to improve electrode performances. Several types of GDE have been developed using binder materials such as epoxy resin, natural clay, carboxymethyl cellulose (CMC) and urea-formaldehyde (UF). By using discharge performance measurement, the characteristics of the as-prepared GDEs are reported.

  18. LATERAL HEAT FLOW INFRARED THERMOGRAPHY FOR THICKNESS INDEPENDENT DETERMINATION OF THERMAL DIFFUSIVITY IN CFRP

    SciTech Connect

    Tralshawala, Nilesh; Howard, Don; Knight, Bryon; Plotnikov, Yuri; Ringermacher, Harry

    2008-02-28

    In conventional infrared thermography, determination of thermal diffusivity requires thickness information. Recently GE has been experimenting with the use of lateral heat flow to determine thermal diffusivity without thickness information. This work builds on previous work at NASA Langley and Wayne State University but we incorporate thermal time of flight (tof) analysis rather than curve fitting to obtain quantitative information. We have developed appropriate theoretical models and a tof based data analysis framework to experimentally determine all components of thermal diffusivity from the time-temperature measurements. Initial validation was carried out using finite difference simulations. Experimental validation was done using anisotropic carbon fiber reinforced polymer (CFRP) composites. We found that in the CFRP samples used, the in-plane component of diffusivity is about eight times larger than the through-thickness component.

  19. Lateral Heat Flow Infrared Thermography for Thickness Independent Determination of Thermal Diffusivity in CFRP

    NASA Astrophysics Data System (ADS)

    Tralshawala, Nilesh; Howard, Don; Knight, Bryon; Plotnikov, Yuri; Ringermacher, Harry

    2008-02-01

    In conventional infrared thermography, determination of thermal diffusivity requires thickness information. Recently GE has been experimenting with the use of lateral heat flow to determine thermal diffusivity without thickness information. This work builds on previous work at NASA Langley and Wayne State University but we incorporate thermal time of flight (tof) analysis rather than curve fitting to obtain quantitative information. We have developed appropriate theoretical models and a tof based data analysis framework to experimentally determine all components of thermal diffusivity from the time-temperature measurements. Initial validation was carried out using finite difference simulations. Experimental validation was done using anisotropic carbon fiber reinforced polymer (CFRP) composites. We found that in the CFRP samples used, the in-plane component of diffusivity is about eight times larger than the through-thickness component.

  20. Variations of boundary reaction rate and particle size on the diffusion-induced stress in a phase separating electrode

    SciTech Connect

    Zhang, Lei; He, Linghui; Ni, Yong; Song, Yicheng

    2014-10-14

    In contrast to the case of single-phase delithiation wherein faster discharging leads to higher diffusion-induced stress (DIS), this paper reports nonmonotonous dependency of the boundary reaction rate on the DIS in nanosized spherical electrode accompanying phase separation. It is attributed to a transition from two-phase to single-phase delithiation driven by increase of the boundary reaction rate leading to narrowing and vanishing of the miscibility gap in a range of the particle size. The profiles of lithium concentration and the DIS are identified during the transition based on a continuum model. The resultant maximum DIS first decreases in the region of two-phase delithiation and later returns to increase in the region of single-phase delithiation with the increase of the boundary reaction rate. A map for the failure behavior in the spherical electrode particle is constructed based on the Tresca failure criterion. These results indicate that the failure caused by the DIS can be avoided by appropriate selection of the said parameters in such electrodes.

  1. Electrochemical characterization of binderless, recompressed exfoliated graphite electrodes: electron-transfer kinetics and diffusion characteristics.

    PubMed

    Ramesh, P; Sampath, S

    2003-12-15

    Exfoliated graphite (EG) is prepared by the thermal exfoliation of graphite intercalation compounds at different temperatures. Surface and bulk physicochemical properties of EG are followed by spectroscopic and analytical methods and are observed to be a function of exfoliation temperature. EG particles can be recompressed without any binder and used as surface-renewable electrodes. Surface preparation is accomplished by either polishing or roughening the electrode surface using emery sheets. Effects of exfoliation temperature and the surface preparation on the electron-transfer kinetics and on the diffusion characteristics have been followed by electrochemical methods using several benchmark redox systems. It is found that the electron-transfer kinetics and the diffusion of K(4)[Fe(CN)(6)] are affected by the nature of the EG surface while that of iron(II)(1,10-phenanthroline)(3) and cobalt(II)(1,10-phenanthroline)(3) are not affected by the surface preparation. The redox systems are classified into different groups according to their kinetic sensitivity. Diffusion of electroactive species toward the EG electrodes is found to nonlinear. Current-time plots suggest that the recompressed EG electrodes can be modeled as fractals. PMID:14670057

  2. Measurement of lateral charge diffusion in thick, fully depleted, back-illuminated CCDs

    SciTech Connect

    Karcher, Armin; Bebek, Christopher J.; Kolbe, William F.; Maurath, Dominic; Prasad, Valmiki; Uslenghi, Michela; Wagner, Martin

    2004-06-30

    Lateral charge diffusion in back-illuminated CCDs directly affects the point spread function (PSF) and spatial resolution of an imaging device. This can be of particular concern in thick, back-illuminated CCDs. We describe a technique of measuring this diffusion and present PSF measurements for an 800 x 1100, 15 mu m pixel, 280 mu m thick, back-illuminated, p-channel CCD that can be over-depleted. The PSF is measured over a wavelength range of 450 nm to 650 nm and at substrate bias voltages between 6 V and 80 V.

  3. Influence of impeller and diffuser geometries on the lateral fluid forces of whirling centrifugal impeller

    NASA Technical Reports Server (NTRS)

    Ohashi, Hideo; Sakurai, Akira; Nishihama, Jiro

    1989-01-01

    Lateral fluid forces on two-dimensional centrifugal impellers, which whirl on a circular orbit in a vaneless diffuser, were reported. Experiments were further conducted for the cases in which a three-dimensional centrifugal impeller, a model of the boiler feed pump, whirls in vaneless and vaned diffusers. The influence of the clearance configuration between the casing and front shroud of the impeller was also investigated. The result indicated that the fluid dynamic interaction between the impeller and the guide vanes induces quite strong fluctuating fluid forces to the impeller, but nevertheless its influence on radial and tangential force components averaged over a whirling orbit is relatively small.

  4. Improved chemically amplified photoresist characterization using interdigitated electrode sensors: photoacid diffusivity measurements

    NASA Astrophysics Data System (ADS)

    Berger, Cody M.; Henderson, Clifford L.

    2004-05-01

    The ability of interdigitated electrodes to serve as novel chemically amplified resist characterization tools has recently been demonstrated through their ability to measure the Dill C kinetic rate constant for photoacid generation. The work presented in this paper attempts to further extend the capabilities of the interdigitated electrode (IDE) sensors by investigating their potential use as a measurement tool for photoacid diffusion coefficients. Impedance spectroscopy of chemically amplified photoresist coated interdigitated electrodes is used to calculate the bulk ionic conductivity of the resist film. The ionic conductivity is subsequently utilized in the Nernst-Einstein equation to calculate the diffusion coefficient of the photoacid, assuming that it is the major charge carrying species in the film. A detailed description of the measurement and data analysis processes required to calculate the diffusion coefficient of triphenylsulfonium triflate in poly(p-hydroxystyrene) is provided. In addition, the effect of varying the relative humidity of the measurement environment upon the impedance data collected has been examined. It has been observed that the presence of water within the resist film, typically as a result of absorption of water from the humid ambient environment, dramatically changes the conductivity of the resist coated IDE. This change is apparently the result of changes in the proton conduction mechanism within the resist as a function of film water content. A discussion of several possible causes of this phenomena and its impact on the interpretation of the electrical data and the calculation and meaning of an acid diffusion coefficient are presented.

  5. Applicability of a diffusion model to lateral transport in the terrestrial and lunar exospheres.

    NASA Technical Reports Server (NTRS)

    Hodges, R. R., Jr.

    1972-01-01

    Kinetic theory is used to determine a series expansion of the vertical flux of particles in an exosphere in terms of time and space derivatives of particle concentration, exobase velocity, and temperature. For sufficiently large scale variations of these parameters in time and space, the series can be truncated to a form that is similar to a diffusion equation. Owing to this analogy, it is possible to unite the mathematical description of molecular diffusion, which governs thermospheric flow, and the corresponding exospheric equation by using effective transport coefficients which change smoothly with altitude through the transition from thermosphere to exosphere. A new definition of the exobase for lateral flow emerges from the analogy of exospheric and thermospheric diffusion, as the altitude where the horizontal mean free path length equals the mean horizontal extent of ballistic trajectories of the transported gas, as opposed to the scale height of the dominant gas which determines the exobase for escape. It is shown that the approximation of exospheric lateral flow as a diffusion process is applicable to global scale problems concerning terrestrial helium and heavier gases, and lunar gases heavier than helium.

  6. A lateral field excited (yxl)88° LiTaO3 bulk acoustic wave sensor with interdigital electrodes.

    PubMed

    Ma, Tingfeng; Wang, Ji; Du, Jianke; Yuan, Lili; Qian, Zhenghua; Zhang, Zhitian; Zhang, Chao

    2013-03-01

    In this work, to improve the sensitivity of lateral field excited (LFE) sensors to changes of liquid conductivity, LFE bulk acoustic wave sensors with interdigital electrodes are investigated. LFE bulk acoustic wave on thickness-shear mode is excited successfully by interdigital electrodes on (yxl)88° LiTaO(3) and applied in liquid-phase sensor. The electric field direction of LFE (yxl)88° LiTaO(3) plates is determined. Based on this, several LFE bulk acoustic wave sensors with interdigital electrodes are designed and fabricated to increase the sensitivity of LiTaO(3) LFE sensors. The results show that the (yxl)88° LiTaO(3) LFE sensor with interdigital electrodes is 10.9 times and 2.1 times more sensitive to changes in liquid conductivity compared to traditional LFE devices with single gap circular electrodes and Archimedes spiral electrodes, respectively. The results are important for investigating high-sensitivity LFE bulk acoustic wave sensors by using LiTaO(3) crystal. PMID:23339996

  7. Paper electrode integrated lateral flow immunosensor for quantitative analysis of oxidative stress induced DNA damage

    PubMed Central

    Zhu, Xuena; Shah, Pratikkumar; Stoff, Susan; Liu, Hongyun; Li, Chen-zhong

    2014-01-01

    A novel device combining electrochemical and colorimetric detection is developed for the rapid measurement of 8-hydroxy-2′-deoxyguanosine (8-OHdG), a DNA oxidative damage biomarker. The device takes advantage of the speed and low cost of the conventional strip test as well as the high reliability and accuracy of electrochemical assay. Competitive immunoreactions were performed on the lateral flow strip, and the captured 8-OHdG on the control line was determined by chronoamperometric measurement with carbon nanotubes paper as the working electrode. At the same time, the color intensity of the test line was measured by a scanner and analyzed by the ImageJ software. The device was able to detect 8-OHdG concentrations in PBS as low as 2.07 ng mL−1 by the colorimetric method and 3.11 ng mL−1 by the electrochemical method. Furthermore, the device was successfully utilized to detect 8-OHdG in urine with a detection limit of 5.76 ng mL−1 (colorimetric method) and 8.85 ng mL−1 (electrochemical method), respectively. In conclusion, the integrated device with dual detections can provide a rapid, visual, quantitative and feasible detection method for 8-OHdG. The integration of these two methods holds two major advantages over tests based on single method. Firstly, it can provide double confidence on the same assay. Secondly, by involving two methods that differ in principle, the integration could potentially avoid false results coming from one method. In addition, these methods do not require expensive equipment or trained personnel, deeming it suitable for use as a simple, economical, portable field kit for on-site monitoring of 8-OHdG in a variety of clinical settings. PMID:24733353

  8. Multiscale Structured and Functionally Graded Gas Diffusion Electrodes for PEM-Fuel Cells and Electrodialysis

    NASA Astrophysics Data System (ADS)

    Wolf, H.; Franz, M.; Bienhüls, C.; Willert-Porada, M.

    2008-02-01

    In the presented work, different methods of preparation of functionally graded gas diffusion electrodes (GDE) for fuel cell and electrodialysis application were investigated. High electrochemical performance with a low platinum catalyst content of only 0.1 mg/cm2 was achieved. The new GDEs are superior to commercial ones with five times higher platinum content, due to their optimized pore structure and improved distribution of catalyst and ion conductive polymer.

  9. Amperometric Determination of Sulfite by Gas Diffusion-Sequential Injection with Boron-Doped Diamond Electrode

    PubMed Central

    Chinvongamorn, Chakorn; Pinwattana, Kulwadee; Praphairaksit, Narong; Imato, Toshihiko; Chailapakul, Orawon

    2008-01-01

    A gas diffusion sequential injection system with amperometric detection using a boron-doped diamond electrode was developed for the determination of sulfite. A gas diffusion unit (GDU) was used to prevent interference from sample matrices for the electrochemical measurement. The sample was mixed with an acid solution to generate gaseous sulfur dioxide prior to its passage through the donor channel of the GDU. The sulfur dioxide diffused through the PTFE hydrophobic membrane into a carrier solution of 0.1M phosphate buffer (pH 8)/0.1% sodium dodecyl sulfate in the acceptor channel of the GDU and turned to sulfite. Then the sulfite was carried to the electrochemical flow cell and detected directly by amperometry using the boron-doped diamond electrode at 0.95 V (versus Ag/AgCl). Sodium dodecyl sulfate was added to the carrier solution to prevent electrode fouling. This method was applicable in the concentration range of 0.2-20 mg SO32−/L and a detection limit (S/N = 3) of 0.05 mg SO32−/L was achieved. This method was successfully applied to the determination of sulfite in wines and the analytical results agreed well with those obtained by iodimetric titration. The relative standard deviations for the analysis of sulfite in wines were in the range of 1.0-4.1 %. The sampling frequency was 65 h−1.

  10. Lateral diffusivity coefficients from the dynamics of a SF6 patch in a coastal environment

    NASA Astrophysics Data System (ADS)

    Kersalé, M.; Petrenko, A. A.; Doglioli, A. M.; Nencioli, F.; Bouffard, J.; Blain, S.; Diaz, F.; Labasque, T.; Quéguiner, B.; Dekeyser, I.

    2016-01-01

    The dispersion of a patch of the tracer sulfur hexafluoride (SF6) is used to assess the lateral diffusivity in the coastal waters of the western part of the Gulf of Lion (GoL), northwestern Mediterranean Sea, during the Latex10 experiment (September 2010). Immediately after the release, the spreading of the patch is associated with a strong decrease of the SF6 concentrations due to the gas exchange from the ocean to the atmosphere. This has been accurately quantified, evidencing the impact of the strong wind conditions during the first days of this campaign. Few days after the release, as the atmospheric loss of SF6 decreased, lateral diffusivity coefficient at spatial scales of 10 km has been computed using two approaches. First, the evolution of the patch with time was combined with a diffusion-strain model to obtain estimates of the strain rate (γ = 2.5 10- 6 s- 1) and of the lateral diffusivity coefficient (Kh = 23.2 m2 s- 1). Second, a steady state model was applied, showing Kh values similar to the previous method after a period of adjustment between 2 and 4.5 days. This implies that after such period, our computation of Kh becomes insensitive to the inclusion of further straining of the patch. Analysis of sea surface temperature satellite imagery shows the presence of a strong front in the study area. The front clearly affected the dynamics within the region and thus the temporal evolution of the patch. Our results are consistent with previous studies in open ocean and demonstrate the success and feasibility of those methods also under small-scale, rapidly-evolving dynamics typical of coastal environments.

  11. Interplay of electron hopping and bounded diffusion during charge transport in redox polymer electrodes.

    PubMed

    Akhoury, Abhinav; Bromberg, Lev; Hatton, T Alan

    2013-01-10

    Redox polymer electrodes (RPEs) have been prepared both by attachment of random copolymers of hydroxybutyl methacrylate and vinylferrocene (poly(HBMA-co-VF)) to carbon substrates by grafting either "to" or "from" the substrate surfaces, and by impregnation of porous carbon substrates with redox polymer gels of similar composition. An observed linear dependence of peak current on the square root of the applied voltage scan rate in cyclic voltammetry (CV) led to the conclusion that the rate controlling step in the redox process was the diffusive transfer of electrons through the redox polymer layer. The variation in the peak current with increasing concentration of the redox species in the polymer indicated that the electron transport transitioned from bounded diffusion to electron hopping. A modified form of the Blauch-Saveant equation for apparent diffusivity of electrons through a polymer film indicated that bounded diffusion was the dominant mechanism of electron transport in RPEs with un-cross-linked polymer chains at low concentrations of the redox species, but, as the concentration of the redox species increased, electron hopping became more dominant, and was the primary mode of electron diffusion above a certain concentration level of redox species. In the cross-linked polymer gels, bounded diffusion was limited because of the restricted mobility of the polymer chains. Electron hopping was the primary mode of electron diffusion in such systems at all concentrations of the redox species. PMID:23137318

  12. Examination of methods to determine free-ion diffusivity and number density from analysis of electrode polarization.

    PubMed

    Wang, Yangyang; Sun, Che-Nan; Fan, Fei; Sangoro, Joshua R; Berman, Marc B; Greenbaum, Steve G; Zawodzinski, Thomas A; Sokolov, Alexei P

    2013-04-01

    Electrode polarization analysis is frequently used to determine free-ion diffusivity and number density in ionic conductors. In the present study, this approach is critically examined in a wide variety of electrolytes, including aqueous and nonaqueous solutions, polymer electrolytes, and ionic liquids. It is shown that the electrode polarization analysis based on the Macdonald-Trukhan model [J. Chem. Phys. 124, 144903 (2006); J. Non-Cryst. Solids 357, 3064 (2011)] progressively fails to give reasonable values of free-ion diffusivity and number density with increasing salt concentration. This should be expected because the original model of electrode polarization is designed for dilute electrolytes. An empirical correction method which yields ion diffusivities in reasonable agreement with pulsed-field gradient nuclear magnetic resonance measurements is proposed. However, the analysis of free-ion diffusivity and number density from electrode polarization should still be exercised with great caution because there is no solid theoretical justification for the proposed corrections. PMID:23679415

  13. Examination of methods to determine free-ion diffusivity and number density from analysis of electrode polarization

    SciTech Connect

    Wang, Yangyang; Sun, Che-Nan; Fan, Fei; Sangoro, Joshua R; Berman, Marc; Greenbaum, Steve; Zawodzinski, Thomas; Sokolov, Alexei P

    2013-01-01

    Electrode polarization analysis is frequently used to determine free-ion diffusivity and number density in ionic conductors. In the present study, this approach is critically examined in a wide variety of electrolytes, including aqueous and nonaqueous solutions, polymer electrolytes, and ionic liquids. It is shown that the electrode polarization analysis based on theMacdonald-Trukhan model [J. Chem. Phys. 124, 144903 (2006); J. Non-Cryst. Solids 357, 3064 (2011)] progressively fails to give reasonable values of free-ion diffusivity and number density with increasing salt concentration. This should be expected because the original model of electrode polarization is designed for dilute electrolytes. An empirical correction method which yields ion diffusivities in reasonable agreement with pulsed-field gradient nuclear magnetic resonance measurements is proposed. However, the analysis of free-ion diffusivity and number density from electrode polarization should still be exercised with great caution because there is no solid theoretical justification for the proposed corrections.

  14. Polymerized lipid bilayers on a solid substrate: morphologies and obstruction of lateral diffusion.

    PubMed

    Okazaki, Takashi; Inaba, Takehiko; Tatsu, Yoshiro; Tero, Ryugo; Urisu, Tsuneo; Morigaki, Kenichi

    2009-01-01

    Substrate supported planar lipid bilayers (SPBs) are versatile models of the biological membrane in biophysical studies and biomedical applications. We previously developed a methodology for generating SPBs composed of polymeric and fluid phospholipid bilayers by using a photopolymerizable diacetylene phospholipid (DiynePC). Polymeric bilayers could be generated with micropatterns by conventional photolithography, and the degree of polymerization could be controlled by modulating UV irradiation doses. After removing nonreacted monomers, fluid lipid membranes could be integrated with polymeric bilayers. Herein, we report on a quantitative study of the morphology of polymeric bilayer domains and their obstruction toward lateral diffusion of membrane-associated molecules. Atomic force microscopy (AFM) observations revealed that polymerized DiynePC bilayers were formed as nanometer-sized domains. The ratio of polymeric and fluid bilayers could be modulated quantitatively by changing the UV irradiation dose for photopolymerization. Lateral diffusion coefficients of lipid molecules in fluid bilayers were measured by fluorescence recovery after photobleaching (FRAP) and correlated with the amount of polymeric bilayer domains on the substrate. Controlled domain structures, lipid compositions, and lateral mobility in the model membranes should allow us to fabricate model membranes that mimic complex features of biological membranes with well-defined structures and physicochemical properties. PMID:19067577

  15. Modulation of lateral transport of membrane components by spatial variations in diffusivity and solubility.

    PubMed Central

    de Beus, A; Eisinger, J

    1992-01-01

    The effect of spatially varying diffusivity and solubility on the efficiency of intramembrane transport is investigated by obtaining solutions to the generalized lateral diffusion equation in which both the diffusion coefficient, D(r), and the partition coefficient, K(r), are functions of position. The mean-time-to-capture by a sink, tc, of particles diffusing in a plane is obtained analytically for the case of a sink surrounded by gradients in D(r) and K(r) with radially symmetrical geometry. It is shown that for particles originating at random locations, tc is shortened dramatically, if in an annular region around the sink, D and K are significantly greater than in the remainder of the plane. Similarly, a viscous boundary layer surrounding a sink is demonstrated to represent a significant barrier for diffusing particles. To investigate more complex geometries, a finite difference numerical integration method is used and is shown to provide comparable results for tc with modest computational power. The same method is used to calculate the tc for particles originating at a source that is joined to the sink by a channel. The increase in the rate with which particles travel from a source to a sink when they are joined by a high diffusivity and/or solubility channel is illustrated by several numerical examples and by graphical representations that show the equilibrium particle density (and hence the effective particle flow) in the presence of different sink, source, and channel combinations. These results are discussed in terms of fluidity domains and other membrane heterogeneities. Images FIGURE 1 FIGURE 2 FIGURE 4 PMID:1420902

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

    SciTech Connect

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

    2014-07-15

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

  17. Generating diffuse discharge via repetitive nanosecond pulses and line-line electrodes in atmospheric air.

    PubMed

    Li, Lee; Liu, Yun-Long; Ge, Ya-Feng; Bin, Yu; Huang, Jia-Jia; Lin, Fo-Chan

    2013-10-01

    Diffuse discharge in atmospheric air can generate extremely high power density and large-scale non-thermal plasma. An achievable method of generating diffuse discharge is reported in this paper. Based on the resonance theory, a compact high-voltage repetitive nanosecond pulse generator (HRNPG) has been developed as discharge excitation source. The HRNPG mainly consists of repetitive charging circuit, Tesla transformer and sharpening switch. With the voltage lower than 1.0 kV, the primary repetitive charging circuit comprises two fast thyristors as low-voltage switches. A spiral Tesla transformer is designed to provide a peak transformation ratio of more than 100. The HRNPG prototype is capable of generating a pulse with over 100 kV peak voltage and ~30 ns rise-time at the repetition frequency of 500 Hz. Using the copper line electrodes with a diameter of 0.4 mm, the gaps with highly non-uniform electric field are structured. With the suitable gap spacing and applied pulse, the glow-like diffuse discharge has been generated in line-type and ring-type electrode pairs. Some typical images are presented. PMID:24182161

  18. Generating diffuse discharge via repetitive nanosecond pulses and line-line electrodes in atmospheric air

    NASA Astrophysics Data System (ADS)

    Li, Lee; Liu, Yun-Long; Ge, Ya-Feng; Bin, Yu; Huang, Jia-Jia; Lin, Fo-Chan

    2013-10-01

    Diffuse discharge in atmospheric air can generate extremely high power density and large-scale non-thermal plasma. An achievable method of generating diffuse discharge is reported in this paper. Based on the resonance theory, a compact high-voltage repetitive nanosecond pulse generator (HRNPG) has been developed as discharge excitation source. The HRNPG mainly consists of repetitive charging circuit, Tesla transformer and sharpening switch. With the voltage lower than 1.0 kV, the primary repetitive charging circuit comprises two fast thyristors as low-voltage switches. A spiral Tesla transformer is designed to provide a peak transformation ratio of more than 100. The HRNPG prototype is capable of generating a pulse with over 100 kV peak voltage and ˜30 ns rise-time at the repetition frequency of 500 Hz. Using the copper line electrodes with a diameter of 0.4 mm, the gaps with highly non-uniform electric field are structured. With the suitable gap spacing and applied pulse, the glow-like diffuse discharge has been generated in line-type and ring-type electrode pairs. Some typical images are presented.

  19. Gas diffusion electrode setup for catalyst testing in concentrated phosphoric acid at elevated temperatures

    SciTech Connect

    Wiberg, Gustav K. H. E-mail: m.arenz@chem.ku.dk; Fleige, Michael; Arenz, Matthias E-mail: m.arenz@chem.ku.dk

    2015-02-15

    We present a detailed description of the construction and testing of an electrochemical cell setup allowing the investigation of a gas diffusion electrode containing carbon supported high surface area catalysts. The setup is designed for measurements in concentrated phosphoric acid at elevated temperature, i.e., very close to the actual conditions in high temperature proton exchange membrane fuel cells (HT-PEMFCs). The cell consists of a stainless steel flow field and a PEEK plastic cell body comprising the electrochemical cell, which exhibits a three electrode configuration. The cell body and flow field are braced using a KF-25 vacuum flange clamp, which allows an easy assembly of the setup. As demonstrated, the setup can be used to investigate temperature dependent electrochemical processes on high surface area type electrocatalysts, but it also enables quick screening tests of HT-PEMFC catalysts under realistic conditions.

  20. An electrocorticographic electrode array for simultaneous recording from medial, lateral, and intrasulcal surface of the cortex in macaque monkeys

    PubMed Central

    Fukushima, Makoto; Saunders, Richard C.; Mullarkey, Matthew; Doyle, Alexandra M.; Mishkin, Mortimer; Fujii, Naotaka

    2014-01-01

    Background Electrocorticography (ECoG) permits recording electrical field potentials with high spatiotemporal resolution over a large part of the cerebral cortex. Application of chronically implanted ECoG arrays in animal models provides an opportunity to investigate global spatiotemporal neural patterns and functional connectivity systematically under various experimental conditions. Although ECoG is conventionally used to cover the gyral cortical surface, recent studies have shown the feasibility of intrasulcal ECoG recordings in macaque monkeys. New Method Here we developed a new ECoG array to record neural activity simultaneously from much of the medial and lateral cortical surface of a single hemisphere, together with the supratemporal plane (STP) of the lateral sulcus in macaque monkeys. The ECoG array consisted of 256 electrodes for bipolar recording at 128 sites. Results We successfully implanted the ECoG array in the left hemisphere of three rhesus monkeys. The electrodes in the auditory and visual cortex detected robust event related potentials to auditory and visual stimuli, respectively. Bipolar recording from adjacent electrode pairs effectively eliminated chewing artifacts evident in monopolar recording, demonstrating the advantage of using the ECoG array under conditions that generate significant movement artifacts. Comparison with Existing Methods Compared with bipolar ECoG arrays previously developed for macaque monkeys, this array significantly expands the number of cortical target areas in gyral and intralsulcal cortex. Conclusions This new ECoG array provides an opportunity to investigate global network interactions among gyral and intrasulcal cortical areas. PMID:24972186

  1. Lateral diffusion of PEG-Lipid in magnetically aligned bicelles measured using stimulated echo pulsed field gradient 1H NMR.

    PubMed

    Soong, Ronald; Macdonald, Peter M

    2005-01-01

    Lateral diffusion measurements of PEG-lipid incorporated into magnetically aligned bicelles are demonstrated using stimulated echo (STE) pulsed field gradient (PFG) proton (1H) nuclear magnetic resonance (NMR) spectroscopy. Bicelles were composed of dimyristoyl phosphatidylcholine (DMPC) plus dihexanoyl phosphatidylcholine (DHPC) (q = DMPC/DHPC molar ratio = 4.5) plus 1 mol % (relative to DMPC) dimyristoyl phosphatidylethanolamine-N-[methoxy(polyethylene glycol)-2000] (DMPE-PEG 2000) at 25 wt % lipid. 1H NMR STE spectra of perpendicular aligned bicelles contained only resonances assigned to residual HDO and to overlapping contributions from a DMPE-PEG 2000 ethoxy headgroup plus DHPC choline methyl protons. Decay of the latter's STE intensity in the STE PFG 1H NMR experiment (g(z) = 244 G cm(-1)) yielded a DMPE-PEG 2000 (1 mol %, 35 degrees C) lateral diffusion coefficient D = 1.35 x 10(-11) m2 s(-1). Hence, below the "mushroom-to-brush" transition, DMPE-PEG 2000 lateral diffusion is dictated by its DMPE hydrophobic anchor. D was independent of the diffusion time, indicating unrestricted lateral diffusion over root mean-square diffusion distances of microns, supporting the "perforated lamellae" model of bicelle structure under these conditions. Overall, the results demonstrate the feasibility of lateral diffusion measurements in magnetically aligned bicelles using the STE PFG NMR technique. PMID:15475584

  2. Lateral Diffusion of Membrane Proteins: Consequences of Hydrophobic Mismatch and Lipid Composition

    PubMed Central

    Ramadurai, Sivaramakrishnan; Duurkens, Ria; Krasnikov, Victor V.; Poolman, Bert

    2010-01-01

    Biological membranes are composed of a large number lipid species differing in hydrophobic length, degree of saturation, and charge and size of the headgroup. We now present data on the effect of hydrocarbon chain length of the lipids and headgroup composition on the lateral mobility of the proteins in model membranes. The trimeric glutamate transporter (GltT) and the monomeric lactose transporter (LacY) were reconstituted in giant unilamellar vesicles composed of unsaturated phosphocholine lipids of varying acyl chain length (14–22 carbon atoms) and various ratios of DOPE/DOPG/DOPC lipids. The lateral mobility of the proteins and of a fluorescent lipid analog was determined as a function of the hydrophobic thickness of the bilayer (h) and lipid composition, using fluorescence correlation spectroscopy. The diffusion coefficient of LacY decreased with increasing thickness of the bilayer, in accordance with the continuum hydrodynamic model of Saffman-Delbrück. For GltT, the mobility had its maximum at diC18:1 PC, which is close to the hydrophobic thickness of the bilayer in vivo. The lateral mobility decreased linearly with the concentration of DOPE but was not affected by the fraction of anionic lipids from DOPG. The addition of DOPG and DOPE did not affect the activity of GltT. We conclude that the hydrophobic thickness of the bilayer is a major determinant of molecule diffusion in membranes, but protein-specific properties may lead to deviations from the Saffman-Delbrück model. PMID:20816060

  3. Limiting diffusion current at rotating disk electrode with dense particle layer

    NASA Astrophysics Data System (ADS)

    Weroński, P.; Nosek, M.; Batys, P.

    2013-09-01

    Exploiting the concept of diffusion permeability of multilayer gel membrane and porous multilayer we have derived a simple analytical equation for the limiting diffusion current at rotating disk electrode (RDE) covered by a thin layer with variable tortuosity and porosity, under the assumption of negligible convection in the porous film. The variation of limiting diffusion current with the porosity and tortuosity of the film can be described in terms of the equivalent thickness of stagnant solution layer, i.e., the average ratio of squared tortuosity to porosity. In case of monolayer of monodisperse spherical particles, the equivalent layer thickness is an algebraic function of the surface coverage. Thus, by means of cyclic voltammetry of RDE with a deposited particle monolayer we can determine the monolayer surface coverage. The effect of particle layer adsorbed on the surface of RDE increases non-linearly with surface coverage. We have tested our theoretical results experimentally by means of cyclic voltammetry measurements of limiting diffusion current at the glassy carbon RDE covered with a monolayer of 3 μm silica particles. The theoretical and experimental results are in a good agreement at the surface coverage higher than 0.7. This result suggests that convection in a monolayer of 3 μm monodisperse spherical particles is negligibly small, in the context of the coverage determination, in the range of very dense particle layers.

  4. Structural and diffusion imaging versus clinical assessment to monitor amyotrophic lateral sclerosis.

    PubMed

    Cardenas-Blanco, Arturo; Machts, Judith; Acosta-Cabronero, Julio; Kaufmann, Joern; Abdulla, Susanne; Kollewe, Katja; Petri, Susanne; Schreiber, Stefanie; Heinze, Hans-Jochen; Dengler, Reinhard; Vielhaber, Stefan; Nestor, Peter J

    2016-01-01

    Amyotrophic lateral sclerosis is a progressive neurodegenerative disease that affects upper and lower motor neurons. Observational and intervention studies can be tracked using clinical measures such as the revised Amyotrophic Lateral Sclerosis Functional Rating Scale (ALSFRS-R) but for a complete understanding of disease progression, objective in vivo biomarkers of both central and peripheral motor pathway pathology are highly desirable. The aim of this study was to determine the utility of structural and diffusion imaging as central nervous system biomarkers compared to the standard clinical measure, ALSFRS-R, to track longitudinal evolution using three time-point measurements. N = 34 patients with ALS were scanned and clinically assessed three times at a mean of three month time intervals. The MRI biomarkers were structural T1-weighted volumes for cortical thickness measurement as well as deep grey matter volumetry, voxel-based morphometry and diffusion tensor imaging (DTI). Cortical thickness focused specifically on the precentral gyrus while quantitative DTI biomarkers focused on the corticospinal tracts. The evolution of imaging biomarkers and ALSFRS-R scores over time were analysed using a mixed effects model that accounted for the scanning interval as a fixed effect variable, and, the initial measurements and time from onset as random variables. The mixed effects model showed a significant decrease in the ALSFRS-R score, (p < 0.0001, and an annual rate of change (AROC) of - 7.3 points). Similarly, fractional anisotropy of the corticospinal tract showed a significant decrease (p = 0.009, AROC = - 0.0066) that, in turn, was driven by a significant increase in radial diffusivity combined with a trend to decrease in axial diffusivity. No significant change in cortical thickness of the precentral gyrus was found (p > 0.5). In addition, deep grey matter volumetry and voxel-based morphometry also identified no significant changes. Furthermore, the

  5. Structural and diffusion imaging versus clinical assessment to monitor amyotrophic lateral sclerosis

    PubMed Central

    Cardenas-Blanco, Arturo; Machts, Judith; Acosta-Cabronero, Julio; Kaufmann, Joern; Abdulla, Susanne; Kollewe, Katja; Petri, Susanne; Schreiber, Stefanie; Heinze, Hans-Jochen; Dengler, Reinhard; Vielhaber, Stefan; Nestor, Peter J.

    2016-01-01

    Amyotrophic lateral sclerosis is a progressive neurodegenerative disease that affects upper and lower motor neurons. Observational and intervention studies can be tracked using clinical measures such as the revised Amyotrophic Lateral Sclerosis Functional Rating Scale (ALSFRS-R) but for a complete understanding of disease progression, objective in vivo biomarkers of both central and peripheral motor pathway pathology are highly desirable. The aim of this study was to determine the utility of structural and diffusion imaging as central nervous system biomarkers compared to the standard clinical measure, ALSFRS-R, to track longitudinal evolution using three time-point measurements. N = 34 patients with ALS were scanned and clinically assessed three times at a mean of three month time intervals. The MRI biomarkers were structural T1-weighted volumes for cortical thickness measurement as well as deep grey matter volumetry, voxel-based morphometry and diffusion tensor imaging (DTI). Cortical thickness focused specifically on the precentral gyrus while quantitative DTI biomarkers focused on the corticospinal tracts. The evolution of imaging biomarkers and ALSFRS-R scores over time were analysed using a mixed effects model that accounted for the scanning interval as a fixed effect variable, and, the initial measurements and time from onset as random variables. The mixed effects model showed a significant decrease in the ALSFRS-R score, (p < 0.0001, and an annual rate of change (AROC) of − 7.3 points). Similarly, fractional anisotropy of the corticospinal tract showed a significant decrease (p = 0.009, AROC = − 0.0066) that, in turn, was driven by a significant increase in radial diffusivity combined with a trend to decrease in axial diffusivity. No significant change in cortical thickness of the precentral gyrus was found (p > 0.5). In addition, deep grey matter volumetry and voxel-based morphometry also identified no significant changes. Furthermore, the

  6. CAD/CAM-designed 3D-printed electroanalytical cell for the evaluation of nanostructured gas-diffusion electrodes.

    PubMed

    Chervin, Christopher N; Parker, Joseph F; Nelson, Eric S; Rolison, Debra R; Long, Jeffrey W

    2016-04-29

    The ability to effectively screen and validate gas-diffusion electrodes is critical to the development of next-generation metal-air batteries and regenerative fuel cells. The limiting electrode in a classic two-terminal device such as a battery or fuel cell is difficult to discern without an internal reference electrode, but the flooded electrolyte characteristic of three-electrode electroanalytical cells negates the prime function of an air electrode-a void volume freely accessible to gases. The nanostructured catalysts that drive the energy-conversion reactions (e.g., oxygen reduction and evolution in the air electrode of metal-air batteries) are best evaluated in the electrode structure as-used in the practical device. We have designed, 3D-printed, and characterized an air-breathing, thermodynamically referenced electroanalytical cell that allows us to mimic the Janus arrangement of the gas-diffusion electrode in a metal-air cell: one face freely exposed to gases, the other wetted by electrolyte. PMID:26987282

  7. The structure of (linearly) stable double diffusive flow patterns in a laterally heated stratified liquid

    NASA Astrophysics Data System (ADS)

    Kranenborg, E. Jurjen; Dijkstra, Henk A.

    1995-03-01

    Layered double diffusive flow patterns in a laterally heated stably stratified liquid are considered in a configuration which allows for steady states to exist. For the heat/salt system, these flows are characterized by the thermal and solutal Rayleigh numbers RaT and RaS, or equivalently by RaT and the buoyancy ratio Rρ. The bifurcation structure of steady patterns with respect to RaT is computed for two cases: fixed RaS and fixed Rρ. For the first case, results in N. Tsitverblit and E. Kit [Phys. Fluids A 5, 1062 (1993)], are computed and extended, and it is shown that many of the previously found flow patterns are unstable; only in a small interval of RaT, multiple (linearly) stable steady states exist. For the second case, the physical relevance of the unstable steady states with respect to the evolution of the flow toward a stable steady state is demonstrated.

  8. Design issues for lateral double-diffused metal-oxide-semiconductor with higher breakdown voltage.

    PubMed

    Sung, Kunsik; Won, Taeyoung

    2013-05-01

    In this paper, we discuss a new High-Side nLDMOSFET whose breakdown voltage is over 100 V while meeting the thermal budget for the conventional process. The proposed n-channel lateral double-diffused metal-oxide-semiconductor field-effect transistor (LDMOSFET) has a feature in that the structure comprises a gap of 5 microm between the DEEP N-WELL and the center of the source, the surface of which is implanted by the NADJUST-layer for high breakdown voltage and simultaneously the low specific on-resistance. The computer simulation of the proposed High-Side nLDMOS exhibits BVdss of 126 V and R(ON,sp) of as low as 2.50 m(omega) x cm2. The NBL, which plays a significant role as a blocking layer against the punch-through seems to function as a hurdle for increasing the breakdown voltage. PMID:23858840

  9. Effect of diffusion from a lateral surface on the rate of GaN nanowire growth

    SciTech Connect

    Sibirev, N. V. Tchernycheva, M.; Cirlin, G. E.; Patriarche, G.; Harmand, J. C.; Dubrovskii, V. G.

    2012-06-15

    The kinetics of the growth of GaN crystalline nanowires on a Si (111) surface with no catalyst is studied experimentally and theoretically. Noncatalytic GaN nanowires were grown by molecular-beam epitaxy with AlN inserts, which makes it possible to determine the rate of the vertical growth of nanowires. A model for the formation of GaN nanowires is developed, and an expression for their rate of growth is derived. It is shown that, in the general case, the dependence of the rate of growth on the nanowire diameter has a minimum. The diameter corresponding to the experimentally observed minimum of the rate of growth steadily increases with increasing diffusion flux from the lateral surface.

  10. Effects of concentration-dependent elastic modulus on Li-ions diffusion and diffusion-induced stresses in spherical composition-gradient electrodes

    SciTech Connect

    Zhang, Kai; Li, Yong; Zheng, Bailin

    2015-09-14

    The composition-gradient electrode material is considered as one of the most promising materials for lithium-ion batteries because of its excellent electrochemical performance and thermal stability. In this work, the effects of concentration-dependent elastic modulus on Li-ions diffusion and diffusion-induce stress in the composition-gradient electrodes were studied. The coupling equations of elasticity and diffusion under both potentiostatic charging and galvanostatic charging were developed to obtain the distributions of both the Li-ions concentration and the stress. The results indicated that the effects of the concentration-dependent elastic modulus on the Li-ions diffusion and the diffusion-induce stresses are controlled by the lithiation induced stiffening factor in the composition-gradient electrodes: a low stiffening factor at the center and a high stiffening factor at the surface lead to a significant effect, whereas a high stiffening factor at the center and a low stiffening factor at the surface result in a minimal effect. The results in this work provide guidance for the selection of electrode materials.

  11. Effects of concentration-dependent elastic modulus on Li-ions diffusion and diffusion-induced stresses in spherical composition-gradient electrodes

    NASA Astrophysics Data System (ADS)

    Zhang, Kai; Li, Yong; Zheng, Bailin

    2015-09-01

    The composition-gradient electrode material is considered as one of the most promising materials for lithium-ion batteries because of its excellent electrochemical performance and thermal stability. In this work, the effects of concentration-dependent elastic modulus on Li-ions diffusion and diffusion-induce stress in the composition-gradient electrodes were studied. The coupling equations of elasticity and diffusion under both potentiostatic charging and galvanostatic charging were developed to obtain the distributions of both the Li-ions concentration and the stress. The results indicated that the effects of the concentration-dependent elastic modulus on the Li-ions diffusion and the diffusion-induce stresses are controlled by the lithiation induced stiffening factor in the composition-gradient electrodes: a low stiffening factor at the center and a high stiffening factor at the surface lead to a significant effect, whereas a high stiffening factor at the center and a low stiffening factor at the surface result in a minimal effect. The results in this work provide guidance for the selection of electrode materials.

  12. Nano-fabricated perpendicular magnetic anisotropy electrodes for lateral spin valves and observation of Nernst-Ettingshausen related signals

    SciTech Connect

    Chejanovsky, N.; Sharoni, A.

    2014-08-21

    Lateral spin valves (LSVs) are efficient structures for characterizing spin currents in spintronics devices. Most LSVs are based on ferromagnetic (FM) electrodes for spin-injection and detection. While there are advantages for using perpendicular magnetic anisotropy (PMA) FM, e.g., stability to nano-scaling, these have almost not been studied. This is mainly due to difficulties in fabricating PMA FMs in a lateral geometry. We present here an efficient method, based on ion-milling through an AlN mask, for fabrication of LSVs with multi-layered PMA FMs such as Co/Pd and Co/Ni. We demonstrate, using standard permalloy FMs, that the method enables efficient spin injection. We show the multi-layer electrodes retain their PMA properties as well as spin injection and detection in PMA LSVs. In addition, we find a large asymmetric voltage signal which increases with current. We attribute this to a Nernst-Ettingshausen effect caused by local Joule heating and the perpendicular magnetic easy axis.

  13. Nano-fabricated perpendicular magnetic anisotropy electrodes for lateral spin valves and observation of Nernst-Ettingshausen related signals

    NASA Astrophysics Data System (ADS)

    Chejanovsky, N.; Sharoni, A.

    2014-08-01

    Lateral spin valves (LSVs) are efficient structures for characterizing spin currents in spintronics devices. Most LSVs are based on ferromagnetic (FM) electrodes for spin-injection and detection. While there are advantages for using perpendicular magnetic anisotropy (PMA) FM, e.g., stability to nano-scaling, these have almost not been studied. This is mainly due to difficulties in fabricating PMA FMs in a lateral geometry. We present here an efficient method, based on ion-milling through an AlN mask, for fabrication of LSVs with multi-layered PMA FMs such as Co/Pd and Co/Ni. We demonstrate, using standard permalloy FMs, that the method enables efficient spin injection. We show the multi-layer electrodes retain their PMA properties as well as spin injection and detection in PMA LSVs. In addition, we find a large asymmetric voltage signal which increases with current. We attribute this to a Nernst-Ettingshausen effect caused by local Joule heating and the perpendicular magnetic easy axis.

  14. Diffusion Tensor Imaging of Basal Ganglia and Thalamus in Amyotrophic Lateral Sclerosis

    PubMed Central

    Sharma, Khema R.; Sheriff, Sulaiman; Maudsley, Andrew; Govind, Varan

    2016-01-01

    Purpose To assess the involvement of basal ganglia and thalamus in patients with amyotrophic lateral sclerosis (ALS) using diffusion tensor imaging (DTI) method. Methods Fourteen definite-ALS patients and 12 age-matched controls underwent whole brain DTI on a 3T scanner. Mean-diffusivity (MD) and fractional anisotropy (FA) were obtained bilaterally from the basal ganglia and thalamus in the regions-of-interest (ROI). Results The MD was significantly higher (p < 0.02) in basal ganglia and thalamus in patients with ALS compared with controls. Correspondingly, the FA was significantly lower (p < 0.02) in these structures, except in caudate (p =0.04) and putamen (p = 0.06) in patients compared with controls. There were mild to strong correlations (r: 0.3 – 0.7) between the DTI measures of basal ganglia and finger–tap, foot-tap, and lip-and-tongue-movement-rate. Conclusions The increased MD in basal ganglia and thalamus, and decreased FA in globus pallidus and thalamus are indicative of neuronal loss or dysfunction in these structures. PMID:22273090

  15. CAD/CAM-designed 3D-printed electroanalytical cell for the evaluation of nanostructured gas-diffusion electrodes

    NASA Astrophysics Data System (ADS)

    Chervin, Christopher N.; Parker, Joseph F.; Nelson, Eric S.; Rolison, Debra R.; Long, Jeffrey W.

    2016-04-01

    The ability to effectively screen and validate gas-diffusion electrodes is critical to the development of next-generation metal-air batteries and regenerative fuel cells. The limiting electrode in a classic two-terminal device such as a battery or fuel cell is difficult to discern without an internal reference electrode, but the flooded electrolyte characteristic of three-electrode electroanalytical cells negates the prime function of an air electrode—a void volume freely accessible to gases. The nanostructured catalysts that drive the energy-conversion reactions (e.g., oxygen reduction and evolution in the air electrode of metal-air batteries) are best evaluated in the electrode structure as-used in the practical device. We have designed, 3D-printed, and characterized an air-breathing, thermodynamically referenced electroanalytical cell that allows us to mimic the Janus arrangement of the gas-diffusion electrode in a metal-air cell: one face freely exposed to gases, the other wetted by electrolyte.

  16. Enhancement of Lateral Diffusion in Catanionic Vesicles during Multilamellar-to-Unilamellar Transition.

    PubMed

    Mitra, S; Sharma, V K; Garcia-Sakai, V; Orecchini, A; Seydel, T; Johnson, M; Mukhopadhyay, R

    2016-04-21

    Catanionic vesicles are formed spontaneously by mixing cationic and anionic dispersions in aqueous solution in suitable conditions. Because of spontaneity in formation, long-term stability, and easy modulation of size and charge, they have numerous advantages over conventional lipid-based vesicles. The dynamics of such vesicles is of interest in the field of biomedicine, as they can be used to deliver drug molecules into the cell membrane. Dynamics of catanionic vesicles based on sodium dodecyl sulfate (SDS) and cetyltrimethylammonium bromide (CTAB) have been studied using incoherent elastic and quasielastic neutron scattering (QENS) techniques. Neutron scattering experiments have been carried out on two backscattering spectrometers, IRIS and IN16B, which have different energy resolutions and energy transfer windows. An elastic fixed-window scan carried out using IN16B shows a phase transition at ∼307 K during the heating cycle, whereas on cooling the transition occurred at ∼294 K. DSC results are found to be in close agreement with the elastic scan data. This transition is ascribed to a structural rearrangement from a multilamellar to a unilamellar phase [ Andreozzi J. Phys. Chem. B 2010 , 114 , 8056 - 8060 ]. It is found that a model in which the surfactant molecules undergo both lateral and internal motions can describe the QENS data quite well. While the data from IRIS have contributions from both dynamical processes, the data from IN16B probe only lateral motions, as the internal motions are too fast for the energy window of the spectrometer. It is found that, through the transition, the fraction of surfactant molecules undergoing lateral motion increases of a factor of 2 from the multilamellar to the unilamellar phase, indicating an enhanced fluidity of the latter. The lateral motion is found to be Fickian in nature, while the internal motion has been described by a localized translational diffusion model. The results reported here could have direct

  17. Notch-mediated lateral inhibition regulates proneural wave propagation when combined with EGF-mediated reaction diffusion.

    PubMed

    Sato, Makoto; Yasugi, Tetsuo; Minami, Yoshiaki; Miura, Takashi; Nagayama, Masaharu

    2016-08-30

    Notch-mediated lateral inhibition regulates binary cell fate choice, resulting in salt and pepper patterns during various developmental processes. However, how Notch signaling behaves in combination with other signaling systems remains elusive. The wave of differentiation in the Drosophila visual center or "proneural wave" accompanies Notch activity that is propagated without the formation of a salt and pepper pattern, implying that Notch does not form a feedback loop of lateral inhibition during this process. However, mathematical modeling and genetic analysis clearly showed that Notch-mediated lateral inhibition is implemented within the proneural wave. Because partial reduction in EGF signaling causes the formation of the salt and pepper pattern, it is most likely that EGF diffusion cancels salt and pepper pattern formation in silico and in vivo. Moreover, the combination of Notch-mediated lateral inhibition and EGF-mediated reaction diffusion enables a function of Notch signaling that regulates propagation of the wave of differentiation. PMID:27535937

  18. Magnetically Diffused Radial Electric-Arc Air Heater Employing Water-Cooled Copper Electrodes

    NASA Technical Reports Server (NTRS)

    Mayo, R. F.; Davis, D. D., Jr.

    1962-01-01

    A magnetically rotated electric-arc air heater has been developed that is novel in that an intense magnetic field of the order of 10,000 to 25,000 gauss is employed. This field is supplied by a coil that is connected in series with the arc. Experimentation with this heater has shown that the presence of an intense magnetic field transverse to the arc results in diffusion of the arc and that the arc has a positive effective resistance. With the field coil in series with the arc, highly stable arc operation is obtained from a battery power supply. External ballast is not required to stabilize the arc when it is operating at maximum power level. The electrode erosion rate is so low that the airstream contamination is no more than 0.07 percent and may be substantially less.

  19. Protein Crowding in Lipid Bilayers Gives Rise to Non-Gaussian Anomalous Lateral Diffusion of Phospholipids and Proteins

    NASA Astrophysics Data System (ADS)

    Jeon, Jae-Hyung; Javanainen, Matti; Martinez-Seara, Hector; Metzler, Ralf; Vattulainen, Ilpo

    2016-04-01

    Biomembranes are exceptionally crowded with proteins with typical protein-to-lipid ratios being around 1 ∶50 -1 ∶100 . Protein crowding has a decisive role in lateral membrane dynamics as shown by recent experimental and computational studies that have reported anomalous lateral diffusion of phospholipids and membrane proteins in crowded lipid membranes. Based on extensive simulations and stochastic modeling of the simulated trajectories, we here investigate in detail how increasing crowding by membrane proteins reshapes the stochastic characteristics of the anomalous lateral diffusion in lipid membranes. We observe that correlated Gaussian processes of the fractional Langevin equation type, identified as the stochastic mechanism behind lipid motion in noncrowded bilayer, no longer adequately describe the lipid and protein motion in crowded but otherwise identical membranes. It turns out that protein crowding gives rise to a multifractal, non-Gaussian, and spatiotemporally heterogeneous anomalous lateral diffusion on time scales from nanoseconds to, at least, tens of microseconds. Our investigation strongly suggests that the macromolecular complexity and spatiotemporal membrane heterogeneity in cellular membranes play critical roles in determining the stochastic nature of the lateral diffusion and, consequently, the associated dynamic phenomena within membranes. Clarifying the exact stochastic mechanism for various kinds of biological membranes is an important step towards a quantitative understanding of numerous intramembrane dynamic phenomena.

  20. Reducing diffusion induced stress in planar electrodes by plastic shakedown and cyclic plasticity of current collector

    NASA Astrophysics Data System (ADS)

    Song, Yicheng; Li, Zongzan; Zhang, Junqian

    2014-10-01

    This paper proposes a strategy to reduce the diffusion induced stress and enhance the capacity of a layered electrode by allowing the plastic deformation of current collector. Based on analytical formulations of the stress in whole electrode, three types of elastoplastic behaviors of current collector, i.e. pure elastic deformation, plastic shakedown and cyclic plasticity, are identified. Criterions separating the three cases are proposed. It is found applying a thin current collector and allowing it to plastically yield in the charge/discharge cycles is beneficial not only to capacity as more space can be provided for active materials but also to electrochemical stability because the stress in active layer is significantly reduced. Structural design corresponding to plastic shakedown shows good balance between the said improvements and structural safety, whereas the case of cyclic plasticity further enhances the improvements. Therefore, structural designing scheme is provided for the former case according to the criterion of plastic shakedown but for the latter one based on the Coffin-Manson relation with expected cycle life.

  1. Effect of cation on diffusion coefficient of ionic liquids at onion-like carbon electrodes.

    PubMed

    Van Aken, Katherine L; McDonough, John K; Li, Song; Feng, Guang; Chathoth, Suresh M; Mamontov, Eugene; Fulvio, Pasquale F; Cummings, Peter T; Dai, Sheng; Gogotsi, Yury

    2014-07-16

    While most supercapacitors are limited in their performance by the stability of the electrolyte, using neat ionic liquids (ILs) as the electrolyte can expand the voltage window and temperature range of operation. In this study, ILs with bis(trifluoromethylsulfonyl)imide (Tf2N) as the anion were investigated as the electrolyte in onion-like carbon-based electrochemical capacitors. To probe the influence of cations on the electrochemical performance of supercapacitors, three different cations were used: 1-ethyl-3-methylimidazolium, 1-hexyl-3-methylimidazolium and 1,6-bis(3-methylimidazolium-1-yl). A series of electrochemical characterization tests was performed using cyclic voltammetry (CV), galvanostatic cycling and electrochemical impedance spectroscopy (EIS). Diffusion coefficients were measured using EIS and correlated with quasielastic neutron scattering and molecular dynamics simulation. These three techniques were used in parallel to confirm a consistent trend between the three ILs. It was found that the IL with the smaller sized cation had a larger diffusion coefficient, leading to a higher capacitance at faster charge-discharge rates. Furthermore, the IL electrolyte performance was correlated with increasing temperature, which limited the voltage stability window and led to the formation of a solid electrolyte interphase on the carbon electrode surface, evident in both the CV and EIS experiments. PMID:24920163

  2. Lateral carrier diffusion and current gain in terahertz InGaAs/InP double-heterojunction bipolar transistors

    SciTech Connect

    Chiang, Han-Wei; Rode, Johann C.; Choudhary, Prateek; Rodwell, Mark J. W.

    2014-01-21

    The DC current gain in In{sub 0.53}Ga{sub 0.47}As/InP double-heterojunction bipolar transistors is computed based on a drift-diffusion model, and is compared with experimental data. Even in the absence of other scaling effects, lateral diffusion of electrons to the base Ohmic contacts causes a rapid reduction in DC current gain as the emitter junction width and emitter-base contact spacing are reduced. The simulation and experimental data are compared in order to examine the effect of carrier lateral diffusion on current gain. The impact on current gain due to device scaling and approaches to increase current gain are discussed.

  3. Lateral ventricular cerebrospinal fluid diffusivity as a potential neuroimaging marker of brain temperature in multiple sclerosis: a hypothesis and implications.

    PubMed

    Hasan, Khader M; Lincoln, John A; Nelson, Flavia M; Wolinsky, Jerry S; Narayana, Ponnada A

    2015-04-01

    In this retrospective study we tested the hypothesis that the net effect of impaired electrical conduction and therefore increased heat dissipation in multiple sclerosis (MS) results in elevated lateral ventricular (LV) cerebrospinal fluid (CSF) diffusivity as a measure of brain temperature estimated in vivo using diffusion tensor imaging (DTI). We used validated DTI-based segmentation methods to obtain normalized LV-CSF volume and its corresponding CSF diffusivity in 108 MS patients and 103 healthy controls in the age range of 21-63 years. The LV CSF diffusivity was ~2% higher in MS compared to controls that correspond to a temperature rise of ~1°C that could not be explained by changes in the CSF viscosity due to altered CSF protein content in MS. The LV diffusivity decreased with age in healthy controls (r=-0.29; p=0.003), but not in MS (r=0.15; p=0.11), possibly related to MS pathology. Age-adjusted LV diffusivity increased with lesion load (r=0.518; p=1×10(-8)). Our data suggest that the total brain lesion load is the primary contributor to the increase in LV CSF diffusivity in MS. These findings suggest that LV diffusivity is a potential in vivo biomarker of the mismatch between heat generation and dissipation in MS. We also discuss limitations and possible confounders. PMID:25485790

  4. Delineation of Early and Later Adult Onset Depression by Diffusion Tensor Imaging

    PubMed Central

    Yu, Hongjun; Nie, Binbin; Li, Na; Luo, Chunrong; Li, Haijun; Liu, Fang; Bai, Yan; Shan, Baoci; Xu, Lin; Xu, Xiufeng

    2014-01-01

    Background Due to a lack of evidence, there is no consistent age of onset to define early onset (EO) versus later onset (LO) major depressive disorder (MDD). Fractional anisotropy (FA), derived from diffusion tensor imaging (DTI), has been widely used to study neuropsychiatric disorders by providing information about the brain circuitry, abnormalities of which might facilitate the delineation of EO versus LO MDD. Method In this study, 61 pairs of untreated, non-elderly, first-episode MDD patients and healthy controls (HCs) aged 18–45 years old received DTI scans. The voxel-based analysis method (VBM), classification analysis, using the Statistical Package for the Social Sciences (SPSS), and regression analyses were used to determine abnormal FA clusters and their correlations with age of onset and clinical symptoms. Results Classification analysis suggested in the best model that there were two subgroups of MDD patients, delineated by an age of onset of 30 years old, by which MDD patients could be divided into EO (18–29 years old) and LO (30–45 years old) groups. LO MDD was characterized by decreased FA, especially in the white matter (WM) of the fronto-occipital fasciculus and posterior limb of internal capsule, with a negative correlation with the severity of depressive symptoms; in marked contrast, EO MDD showed increased FA, especially in the WM of the corpus callosum, corticospinal midbrain and inferior fronto-occipital fasciculus, while FA of the WM near the midbrain had a positive correlation with the severity of depressive symptoms. Conclusion Specific abnormalities of the brain circuitry in EO vs. LO MDD were delineated by an age of onset of 30 years old, as demonstrated by distinct abnormal FA clusters with opposite correlations with clinical symptoms. This DTI study supported the evidence of an exact age for the delineation of MDD, which could have broad multidisciplinary importance. Trial Registration ClinicalTrials.gov NCT00703742 PMID:25393297

  5. Effect of local velocity on diffusion-induced stress in large-deformation electrodes of lithium-ion batteries

    NASA Astrophysics Data System (ADS)

    Li, Yong; Zhang, Kai; Zheng, Bailin; Yang, Fuqian

    2016-07-01

    In this work, the contribution of local velocity to the resultant flux of lithium in lithium-ion battery is introduced into the diffusion equation to describe the migration of lithium in the active material of electrodes. The effect of the local velocity on the stress evolution in a spherical electrode made of silicon is analyzed, using the derived diffusion equation and nonlinear theory of elasticity. Two boundary conditions at the surface of the electrode, which represent two extreme conditions of real electrode materials, are used in the stress analysis: one is stress-free, and the other is immobile. The numerical results with the stress-free boundary condition suggest that the effect of the local velocity on the distribution of radial stress and hoop stress increases with the increase of time and the effect of the local velocity on the distribution of lithium is relatively small. In comparison with the results without the effect of the local velocity, the effect of the local velocity is negligible for the immobile boundary condition. The numerical result shows that the use of the immobile boundary condition leads to the decrease of von-Mises stress, which likely will retard the mechanical degradation of electrode and improve the electrochemical performance of lithium-ion battery.

  6. Solid-state linear sweep voltammetry. A probe of diffusion in thin films of polymer ion conductors on microdisk electrodes

    SciTech Connect

    Geng, L.; Reed, R.A.; Longmire, M.; Murray, R.W.

    1987-05-21

    Pt microdisk electrodes of diameter 10-70 ..mu..m sealed in glass, lying in the same plane with Ag pseudoreference and Pt auxiliary disk electrodes, and coated with a few micrometers of ionically conducting polymer film containing electroactive solutes provide a convenient experimental microcell format for solid-state linear sweep and cyclic voltammetry of the electroactive solutes. Transport rates of the solutes in the polymer depend on composition of the bathing (plasticizing) gas around the microcell, the temperature (polymer fluidity), and solute charge, size, and physical diffusion vs. electron self-exchange rates. Investigation of such transport phenomena requires theoretical analysis of the transport geometry of the microcell, which is the main subject of this paper. The preferred situations for measurements of transport rate are (i) polymer films thick in comparison to electrode diameter and transport rate, so that semi-infinite transport applies, and (ii) films thin in the same respects, so that currents are a summation of thin layer cell and microcylindrical geometries. Measured diffusion constants are confirmed with data from a four-electrode interdigitated array electrode experiment.

  7. Lateral diffusion of CO2 in leaves of the crassulacean acid metabolism plant Kalanchoe daigremontiana Hamet et Perrier.

    PubMed

    Duarte, Heitor M; Jakovljevic, Ivona; Kaiser, Friedemann; Lüttge, Ulrich

    2005-04-01

    Dynamic patchiness of photosystem II (PSII) activity in leaves of the crassulacean acid metabolism (CAM) plant Kalanchoe daigremontiana Hamet et Perrier, which was independent of stomatal control and was observed during both the day/night cycle and circadian endogenous oscillations of CAM, was previously explained by lateral CO2 diffusion and CO2 signalling in the leaves [Rascher et al. (2001) Proc Natl Acad Sci USA 98:11801-11805; Rascher and Luttge (2002) Plant Biol 4:671-681]. The aim here was to actually demonstrate the importance of lateral CO2 diffusion and its effects on localized PSII activity. Covering small sections of entire leaves with silicone grease was used for local exclusion of a contribution of atmospheric CO2 to internal CO2 via transport through stomata. A setup for combined measurement of gas exchange and chlorophyll fluorescence imaging was used for recording photosynthetic activity with a spatiotemporal resolution. When remobilization of malic acid from vacuolar storage and its decarboxylation in the CAM cycle caused increasing internal CO2 concentrations sustaining high PSII activity behind closed stomata, PSII activity was also increased in adjacent leaf sections where vacuolar malic acid accumulation was minimal as a result of preventing external CO2 supply due to leaf-surface greasing, and where therefore CO2 could only be supplied by diffusion from the neighbouring malic acid-remobilizing leaf tissue. This demonstrates lateral CO2 diffusion and its effect on local photosynthetic activity. PMID:15843962

  8. Lateral diffusion contributes to FRET from lanthanide-tagged membrane proteins

    SciTech Connect

    Lan, Tien-Hung; Wu, Guangyu; Lambert, Nevin A.

    2015-08-14

    Diffusion can enhance Förster resonance energy transfer (FRET) when donors or acceptors diffuse distances that are similar to the distances separating them during the donor's excited state lifetime. Lanthanide donors remain in the excited state for milliseconds, which makes them useful for time-resolved FRET applications but also allows time for diffusion to enhance energy transfer. Here we show that diffusion dramatically enhances FRET between membrane proteins labeled with lanthanide donors. This phenomenon complicates interpretation of experiments that use long-lived donors to infer association or proximity of mobile membrane proteins, but also offers a method of monitoring diffusion in membrane domains in real time in living cells. - Highlights: • Diffusion enhances TR-FRET from membrane proteins labeled with lanthanide donors. • Diffusion-dependent FRET can overshadow FRET due to oligomerization or clustering. • FRET studies using lanthanide-tagged membrane proteins should consider diffusion. • FRET from lanthanide donors can be used to monitor membrane protein diffusion.

  9. Lateral diffusion of lipid probes in the surface membrane of human platelets. An electron-electron double resonance (ELDOR) study.

    PubMed Central

    Lai, C S; Wirt, M D; Yin, J J; Froncisz, W; Feix, J B; Kunicki, T J; Hyde, J S

    1986-01-01

    Electron-electron double resonance (ELDOR) techniques employing [14N], [15N] 16-Doxylstearate spin-label pairs have been used to measure the lateral diffusion constant, D, of lipids in the surface membrane of intact human blood platelets. For freshly prepared platelets, D is 1.0 X 10(-8) cm2/s at 37 degrees C and for platelets stored for 3 d at room temperature under accepted routine blood bank conditions, D is 2.6 X 10(-8) cm2/s at 37 degrees C. This is the first time that D in the surface membrane of platelets is reported. The marked increase in D for stored platelets may be attributed at least partly to loss of cholesterol during storage, suggesting a correlation between lipid lateral diffusion and cholesterol levels in cell membranes. PMID:3019445

  10. Isotopic evidence for lateral flow and diffusive transport, but not sublimation, in a sloped seasonal snowpack, Idaho, USA

    NASA Astrophysics Data System (ADS)

    Evans, Samantha L.; Flores, Alejandro N.; Heilig, Achim; Kohn, Matthew J.; Marshall, Hans-Peter; McNamara, James P.

    2016-04-01

    Oxygen and hydrogen isotopes in snow were measured in weekly profiles during the growth and decline of a sloped subalpine snowpack, southern Idaho, 2011-2012. Isotopic steps (10‰, δ18O; 80‰, δD) were preserved relative to physical markers throughout the season, albeit with some diffusive smoothing. Melting stripped off upper layers without shifting isotopes within the snowpack. Meltwater is in isotopic equilibrium with snow at the top but not with snow at each respective collection height. Transport of meltwater occurred primarily along pipes and lateral flow paths allowing the snowpack to melt initially in reverse stratigraphic order. Isotope diffusivities are ~2 orders of magnitude faster than estimated from experiments but can be explained by higher temperature and porosity. A better understanding of how snowmelt isotopes change during meltout improves hydrograph separation methods, whereas constraints on isotope diffusivities under warm conditions improve models of ice core records in low-latitude settings.

  11. Nonlinearity Effects of Lateral Density Diffusion Coefficient on Gain-Guided VCSEL Performance

    NASA Technical Reports Server (NTRS)

    Li, Jian-Zhong; Cheung, Samson H.; Ning, C. Z.; Biegel, Bryan (Technical Monitor)

    2001-01-01

    Electron and hole diffusions in the plane of semiconductor quantum wells play an important part in the static and dynamic operations of semiconductor lasers. In this paper, we apply a hydrodynamic model developed from the semiconductor Bloch equations to numerically study the effects of nonlinearity in the diffusion coefficient on single mode operation and direct modulation of a gain-guided InGaAs/GaAs multiple quantum well laser, operating not too far from threshold. We found that a small diffusion coefficient is advantageous for lowering the threshold current and increasing the modulation bandwidth. Most importantly, the effects of nonlinearity in the coefficient can be approximately reproduced by replacing the coefficient with an effective constant diffusion coefficient, which corresponds roughly to the half height density of the density distribution.

  12. Cell wall constrains lateral diffusion of plant plasma-membrane proteins

    PubMed Central

    Martinière, Alexandre; Lavagi, Irene; Nageswaran, Gayathri; Rolfe, Daniel J.; Maneta-Peyret, Lilly; Luu, Doan-Trung; Botchway, Stanley W.; Webb, Stephen E. D.; Mongrand, Sebastien; Maurel, Christophe; Martin-Fernandez, Marisa L.; Kleine-Vehn, Jürgen; Friml, Jirí; Moreau, Patrick; Runions, John

    2012-01-01

    A cell membrane can be considered a liquid-phase plane in which lipids and proteins theoretically are free to diffuse. Numerous reports, however, describe retarded diffusion of membrane proteins in animal cells. This anomalous diffusion results from a combination of structuring factors including protein–protein interactions, cytoskeleton corralling, and lipid organization into microdomains. In plant cells, plasma-membrane (PM) proteins have been described as relatively immobile, but the control mechanisms that structure the PM have not been studied. Here, we use fluorescence recovery after photobleaching to estimate mobility of a set of minimal PM proteins. These proteins consist only of a PM-anchoring domain fused to a fluorescent protein, but their mobilities remained limited, as is the case for many full-length proteins. Neither the cytoskeleton nor membrane microdomain structure was involved in constraining the diffusion of these proteins. The cell wall, however, was shown to have a crucial role in immobilizing PM proteins. In addition, by single-molecule fluorescence imaging we confirmed that the pattern of cellulose deposition in the cell wall affects the trajectory and speed of PM protein diffusion. Regulation of PM protein dynamics by the plant cell wall can be interpreted as a mechanism for regulating protein interactions in processes such as trafficking and signal transduction. PMID:22689944

  13. Generation of large-scale, barrier-free diffuse plasmas in air at atmospheric pressure using array wire electrodes and nanosecond high-voltage pulses

    SciTech Connect

    Teng, Yun; Li, Lee Liu, Yun-Long; Liu, Lun; Liu, Minghai

    2014-10-15

    This paper introduces a method to generate large-scale diffuse plasmas by using a repetition nanosecond pulse generator and a parallel array wire-electrode configuration. We investigated barrier-free diffuse plasmas produced in the open air in parallel and cross-parallel array line-line electrode configurations. We found that, when the distance between the wire-electrode pair is small, the discharges were almost extinguished. Also, glow-like diffuse plasmas with little discharge weakening were obtained in an appropriate range of line-line distances and with a cathode-grounding cross-electrode configuration. As an example, we produced a large-scale, stable diffuse plasma with volumes as large as 18 × 15 × 15 cm{sup 3}, and this discharge region can be further expanded. Additionally, using optical and electrical measurements, we showed that the electron temperature was higher than the gas temperature, which was almost the same as room temperature. Also, an array of electrode configuration with more wire electrodes had helped to prevent the transition from diffuse discharge to arc discharge. Comparing the current waveforms of configurations with 1 cell and 9 cells, we found that adding cells significantly increased the conduction current and the electrical energy delivered in the electrode gaps.

  14. Generation of large-scale, barrier-free diffuse plasmas in air at atmospheric pressure using array wire electrodes and nanosecond high-voltage pulses

    NASA Astrophysics Data System (ADS)

    Teng, Yun; Li, Lee; Liu, Yun-Long; Liu, Lun; Liu, Minghai

    2014-10-01

    This paper introduces a method to generate large-scale diffuse plasmas by using a repetition nanosecond pulse generator and a parallel array wire-electrode configuration. We investigated barrier-free diffuse plasmas produced in the open air in parallel and cross-parallel array line-line electrode configurations. We found that, when the distance between the wire-electrode pair is small, the discharges were almost extinguished. Also, glow-like diffuse plasmas with little discharge weakening were obtained in an appropriate range of line-line distances and with a cathode-grounding cross-electrode configuration. As an example, we produced a large-scale, stable diffuse plasma with volumes as large as 18 × 15 × 15 cm3, and this discharge region can be further expanded. Additionally, using optical and electrical measurements, we showed that the electron temperature was higher than the gas temperature, which was almost the same as room temperature. Also, an array of electrode configuration with more wire electrodes had helped to prevent the transition from diffuse discharge to arc discharge. Comparing the current waveforms of configurations with 1 cell and 9 cells, we found that adding cells significantly increased the conduction current and the electrical energy delivered in the electrode gaps.

  15. Water at hydrophobic interfaces delays proton surface-to-bulk transfer and provides a pathway for lateral proton diffusion.

    PubMed

    Zhang, Chao; Knyazev, Denis G; Vereshaga, Yana A; Ippoliti, Emiliano; Nguyen, Trung Hai; Carloni, Paolo; Pohl, Peter

    2012-06-19

    Fast lateral proton migration along membranes is of vital importance for cellular energy homeostasis and various proton-coupled transport processes. It can only occur if attractive forces keep the proton at the interface. How to reconcile this high affinity to the membrane surface with high proton mobility is unclear. Here, we tested whether a minimalistic model interface between an apolar hydrophobic phase (n-decane) and an aqueous phase mimics the biological pathway for lateral proton migration. The observed diffusion span, on the order of tens of micrometers, and the high proton mobility were both similar to the values previously reported for lipid bilayers. Extensive ab initio simulations on the same water/n-decane interface reproduced the experimentally derived free energy barrier for the excess proton. The free energy profile G(H(+)) adopts the shape of a well at the interface, having a width of two water molecules and a depth of 6 ± 2RT. The hydroniums in direct contact with n-decane have a reduced mobility. However, the hydroniums in the second layer of water molecules are mobile. Their in silico diffusion coefficient matches that derived from our in vitro experiments, (5.7 ± 0.7) 10(-5) cm(2) s(-1). Conceivably, these are the protons that allow for fast diffusion along biological membranes. PMID:22675120

  16. Water at hydrophobic interfaces delays proton surface-to-bulk transfer and provides a pathway for lateral proton diffusion

    PubMed Central

    Zhang, Chao; Knyazev, Denis G.; Vereshaga, Yana A.; Ippoliti, Emiliano; Nguyen, Trung Hai; Carloni, Paolo; Pohl, Peter

    2012-01-01

    Fast lateral proton migration along membranes is of vital importance for cellular energy homeostasis and various proton-coupled transport processes. It can only occur if attractive forces keep the proton at the interface. How to reconcile this high affinity to the membrane surface with high proton mobility is unclear. Here, we tested whether a minimalistic model interface between an apolar hydrophobic phase (n-decane) and an aqueous phase mimics the biological pathway for lateral proton migration. The observed diffusion span, on the order of tens of micrometers, and the high proton mobility were both similar to the values previously reported for lipid bilayers. Extensive ab initio simulations on the same water/n-decane interface reproduced the experimentally derived free energy barrier for the excess proton. The free energy profile GH+ adopts the shape of a well at the interface, having a width of two water molecules and a depth of 6 ± 2RT. The hydroniums in direct contact with n-decane have a reduced mobility. However, the hydroniums in the second layer of water molecules are mobile. Their in silico diffusion coefficient matches that derived from our in vitro experiments, (5.7 ± 0.7) × 10-5 cm2 s-1. Conceivably, these are the protons that allow for fast diffusion along biological membranes. PMID:22675120

  17. Electrochemical reduction of CO₂ to organic acids by a Pd-MWNTs gas-diffusion electrode in aqueous medium.

    PubMed

    Lu, Guang; Wang, Hui; Bian, Zhaoyong; Liu, Xin

    2013-01-01

    Pd-multiwalled carbon nanotubes (Pd-MWNTs) catalysts for the conversion of CO₂ to organic acids were prepared by the ethylene glycol reduction and fully characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), transmission electron microscope (TEM), X-ray photoelectron spectroscopy (XPS), and cyclic voltammetry (CV) technologies. The amorphous Pd particles with an average size of 5.7 nm were highly dispersed on the surface of carbon nanotubes. Functional groups of the MWNTs played a key role in the palladium deposition. The results indicated that Pd-MWNTs could transform CO₂ into organic acid with high catalytic activity and CO₂ could take part in the reduction reaction directly. Additionally, the electrochemical reduction of CO₂ was investigated by a diaphragm electrolysis device, using a Pd-MWNTs gas-diffusion electrode as a cathode and a Ti/RuO₂ net as an anode. The main products in present system were formic acid and acetic acid identified by ion chromatograph. The selectivity of the products could be achieved by reaction conditions changing. The optimum faraday efficiencies of formic and acetic acids formed on the Pd-MWNTs gas-diffusion electrode at 4₂V electrode voltages under 1 atm CO₂ were 34.5% and 52.3%, respectively. PMID:24453849

  18. Electrochemical Reduction of CO2 to Organic Acids by a Pd-MWNTs Gas-Diffusion Electrode in Aqueous Medium

    PubMed Central

    Lu, Guang; Bian, Zhaoyong; Liu, Xin

    2013-01-01

    Pd-multiwalled carbon nanotubes (Pd-MWNTs) catalysts for the conversion of CO2 to organic acids were prepared by the ethylene glycol reduction and fully characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), transmission electron microscope (TEM), X-ray photoelectron spectroscopy (XPS), and cyclic voltammetry (CV) technologies. The amorphous Pd particles with an average size of 5.7 nm were highly dispersed on the surface of carbon nanotubes. Functional groups of the MWNTs played a key role in the palladium deposition. The results indicated that Pd-MWNTs could transform CO2 into organic acid with high catalytic activity and CO2 could take part in the reduction reaction directly. Additionally, the electrochemical reduction of CO2 was investigated by a diaphragm electrolysis device, using a Pd-MWNTs gas-diffusion electrode as a cathode and a Ti/RuO2 net as an anode. The main products in present system were formic acid and acetic acid identified by ion chromatograph. The selectivity of the products could be achieved by reaction conditions changing. The optimum faraday efficiencies of formic and acetic acids formed on the Pd-MWNTs gas-diffusion electrode at 4 V electrode voltages under 1 atm CO2 were 34.5% and 52.3%, respectively. PMID:24453849

  19. A historical perspective on the lateral diffusion model of GTPase activation and related coupling of membrane signaling proteins

    PubMed Central

    Liebman, Paul A

    2014-01-01

    Aspects of our discovery of lateral diffusion of the G protein coupled receptor (GPCR) rhodopsin and that a single activated rhodopsin can non-covalently catalyze GTP binding to thousands of GTPases per second on rod disk membranes via this diffusion are summarized herein. Rapid GTPase coupling to membrane-bound phosphodiesterase (PDE) further amplifies the signal via cGMP hydrolysis, essential to visual transduction. Important generalizations from this work are that biomembranes can uniquely concentrate, orient for reaction and provide a solvent appropriate to rapid, powerful and appropriately controlled sequential interaction of signaling proteins. Of equal importance to function is timely control and termination of such powerful amplification via receptor phosphorylation (quenching) and arrestin binding. Downstream kinetic modulation by GTPase activating proteins (GAPs) and regulators of G protein signaling (RGS) and related mechanisms as well as limitations set by membrane domain fencing, structural protein binding etc. can be essential in relevant systems. PMID:25279248

  20. Effects of reversible chemical reaction on Li diffusion and stresses in spherical composition-gradient electrodes

    SciTech Connect

    Li, Yong; Zhang, Kai; Zheng, Bailin Zhang, Xiaoqian; Wang, Qi

    2015-06-28

    Composition-gradient electrode materials have been proven to be one of the most promising materials in lithium-ion battery. To study the mechanism of mechanical degradation in spherical composition-gradient electrodes, the finite deformation theory and reversible chemical theory are adopted. In homogeneous electrodes, reversible electrochemical reaction may increase the magnitudes of stresses. However, reversible electrochemical reaction has different influences on stresses in composition-gradient electrodes, resulting from three main inhomogeneous factors—forward reaction rate, backward reaction rate, and reaction partial molar volume. The decreasing transition form of forward reaction rate, increasing transition form of backward reaction rate, and increasing transition form of reaction partial molar volume can reduce the magnitudes of stresses. As a result, capacity fading and mechanical degradation are reduced by taking advantage of the effects of inhomogeneous factors.

  1. Fast spatiotemporal correlation spectroscopy to determine protein lateral diffusion laws in live cell membranes.

    PubMed

    Di Rienzo, Carmine; Gratton, Enrico; Beltram, Fabio; Cardarelli, Francesco

    2013-07-23

    Spatial distribution and dynamics of plasma-membrane proteins are thought to be modulated by lipid composition and by the underlying cytoskeleton, which forms transient barriers to diffusion. So far this idea was probed by single-particle tracking of membrane components in which gold particles or antibodies were used to individually monitor the molecules of interest. Unfortunately, the relatively large particles needed for single-particle tracking can in principle alter the very dynamics under study. Here, we use a method that makes it possible to investigate plasma-membrane proteins by means of small molecular labels, specifically single GFP constructs. First, fast imaging of the region of interest on the membrane is performed. For each time delay in the resulting stack of images the average spatial correlation function is calculated. We show that by fitting the series of correlation functions, the actual protein "diffusion law" can be obtained directly from imaging, in the form of a mean-square displacement vs. time-delay plot, with no need for interpretative models. This approach is tested with several simulated 2D diffusion conditions and in live Chinese hamster ovary cells with a GFP-tagged transmembrane transferrin receptor, a well-known benchmark of membrane-skeleton-dependent transiently confined diffusion. This approach does not require extraction of the individual trajectories and can be used also with dim and dense molecules. We argue that it represents a powerful tool for the determination of kinetic and thermodynamic parameters over very wide spatial and temporal scales. PMID:23836651

  2. Determination of the thermal diffusivity of bulk and layered samples by time domain thermoreflectance: Interest of lateral heat diffusion investigation in nanoscale time range

    SciTech Connect

    Belliard, L. Charron, E.; Vincent, S.; Perrin, B.; Fournier, D.; Frétigny, C.

    2015-02-14

    We report on thermal investigations performed in a time resolved experimental scheme. The time domain thermoreflectance (TDTR) is applied in an unusual geometry where the pump and probe beams are not superimposed but focused and shifted. In this way, the determination of the in-plane thermal diffusivity is achieved from temperature snapshots at different time delays. In the first part, taking into account the specific generation process and the detection inherent to the time domain thermoreflectance approach, an analytical solution for the temperature field is obtained for bulk samples, and compared to experimental data. A comparison with the frequency domain thermoreflectance microscopy is also outlined. In Part II section, the lateral heat diffusion in a layered structure is investigated. The comparison of the heat diffusion spreading in case of a highly conductive layer deposited on an insulator substrate and the reverse situation are carefully studied. Finally, we show how the time dependence is efficient to probe and identify material thermal properties or thermal interfacial resistance.

  3. Molecular Mechanism for Lateral Lipid Diffusion between the Outer Membrane External Leaflet and a β-Barrel Hydrocarbon Ruler†

    PubMed Central

    Khan, M. Adil; Bishop, Russell E.

    2016-01-01

    Membrane-intrinsic enzymes are embedded in lipids, yet how such enzymes interrogate lipid substrates remains a largely unexplored fundamental question. The outer membrane phospholipid:lipid A palmitoyltransferase PagP combats host immune defenses during infection and selects a palmitate chain using its β-barrel interior hydrocarbon ruler. Both a molecular embrasure and crenel in Escherichia coli PagP display weakened transmembrane β-strand hydrogen bonding to provide potential lateral routes for diffusion of the palmitoyl group between the hydrocarbon ruler and outer membrane external leaflet. Prolines in strands A and B lie beneath the dynamic L1 surface loop flanking the embrasure, whereas the crenel is flanked by prolines in strands F and G. Reversibly barricading the embrasure prevents lipid A palmitoylation without affecting the slower phospholipase reaction. Lys42Ala PagP is also a dedicated phospholipase, implicating this disordered L1 loop residue in lipid A recognition. The embrasure barricade additionally prevents palmitoylation of nonspecific fatty alcohols, but not miscible alcohols. Irreversibly barricading the crenel inhibits both lipid A palmitoylation and phospholipase reactions without compromising PagP structure. These findings indicate lateral palmitoyl group diffusion within the PagP hydrocarbon ruler is likely gated during phospholipid entry via the crenel and during lipid A egress via the embrasure. PMID:19769329

  4. Lateral fluid forces acting on a whirling centrifugal impeller in vaneless and vaned diffuser

    NASA Technical Reports Server (NTRS)

    Ohashi, H.; Shoji, H.

    1984-01-01

    Fluid forces on a rotating centrifugal impeller in whirling motion were studied. A two dimensional impeller installed in a parallel-walled vaneless and vaned diffuser whirled on a circular orbit with various positive and negative angular velocities. It is shown that the fluid forces exert a damping effect on the rotor in most operating conditions, but become excitatory when the impeller operates at very low partial discharge while rotating far faster than the whirl speed. The fluid forces were expressed in terms of mass, damping and stiffness matrices. Impellers with the same geometry and whirl condition are calculated. Quantitative agreement is obtained especially in positive whirl.

  5. Spin diffusion and non-local spin-valve effect in an exfoliated multilayer graphene with a Co electrode.

    PubMed

    Li, Lijun; Lee, Inyeal; Lim, Dongsuk; Rathi, Servin; Kang, Moonshik; Uemura, Tetsuya; Kim, Gil-Ho

    2016-08-19

    We fabricated a non-local spin valve with a thin layer of graphite with Co transparent electrodes. The spin-valve effect and spin precession were observed at room temperature. The magnitude of the mangetoresistance increases when temperature decreases. The spin-relaxation time, [Formula: see text], obtained from the fitting of the Hanle curves increases with decreasing temperature with a weak dependence [Formula: see text] while the spin-diffusion constant D decreases. At room temperature, [Formula: see text] exceeds 100 ps and the spin-diffusion length, [Formula: see text], is ∼2 μm. The temperature dependence of [Formula: see text] is not monotonic, and it has the largest value at room temperature. Our results show that multilayer graphene is a suitable material for spintronic devices. PMID:27378597

  6. Spin diffusion and non-local spin-valve effect in an exfoliated multilayer graphene with a Co electrode

    NASA Astrophysics Data System (ADS)

    Li, Lijun; Lee, Inyeal; Lim, Dongsuk; Rathi, Servin; Kang, Moonshik; Uemura, Tetsuya; Kim, Gil-Ho

    2016-08-01

    We fabricated a non-local spin valve with a thin layer of graphite with Co transparent electrodes. The spin-valve effect and spin precession were observed at room temperature. The magnitude of the mangetoresistance increases when temperature decreases. The spin-relaxation time, {τ }s, obtained from the fitting of the Hanle curves increases with decreasing temperature with a weak dependence ∼ {T}-0.065 while the spin-diffusion constant D decreases. At room temperature, {τ }s exceeds 100 ps and the spin-diffusion length, {λ }s, is ∼2 μm. The temperature dependence of {λ }s is not monotonic, and it has the largest value at room temperature. Our results show that multilayer graphene is a suitable material for spintronic devices.

  7. The neuronal K-Cl cotransporter KCC2 influences postsynaptic AMPA receptor content and lateral diffusion in dendritic spines

    PubMed Central

    Gauvain, Grégory; Chamma, Ingrid; Chevy, Quentin; Cabezas, Carolina; Irinopoulou, Theano; Bodrug, Natalia; Carnaud, Michèle; Lévi, Sabine; Poncer, Jean Christophe

    2011-01-01

    The K-Cl cotransporter KCC2 plays an essential role in neuronal chloride homeostasis, and thereby influences the efficacy and polarity of GABA signaling. Although KCC2 is expressed throughout the somatodendritic membrane, it is remarkably enriched in dendritic spines, which host most glutamatergic synapses in cortical neurons. KCC2 has been shown to influence spine morphogenesis and functional maturation in developing neurons, but its function in mature dendritic spines remains unknown. Here, we report that suppressing KCC2 expression decreases the efficacy of excitatory synapses in mature hippocampal neurons. This effect correlates with a reduced postsynaptic aggregation of GluR1-containing AMPA receptors and is mimicked by a dominant negative mutant of KCC2 interaction with cytoskeleton but not by pharmacological suppression of KCC2 function. Single-particle tracking experiments reveal that suppressing KCC2 increases lateral diffusion of the mobile fraction of AMPA receptor subunit GluR1 in spines but not in adjacent dendritic shafts. Increased diffusion was also observed for transmembrane but not membrane-anchored recombinant neuronal cell adhesion molecules. We suggest that KCC2, likely through interactions with the actin cytoskeleton, hinders transmembrane protein diffusion, and thereby contributes to their confinement within dendritic spines. PMID:21878564

  8. Effect of lithium-ion diffusibility on interfacial resistance of LiCoO2 thin film electrode modified with lithium tungsten oxides

    NASA Astrophysics Data System (ADS)

    Hayashi, Tetsutaro; Miyazaki, Takamichi; Matsuda, Yasutaka; Kuwata, Naoaki; Saruwatari, Motoaki; Furuichi, Yuki; Kurihara, Koji; Kuzuo, Ryuichi; Kawamura, Junichi

    2016-02-01

    To investigate the contribution of lithium-ion diffusibility of lithium tungsten oxides (LWOs) to low interfacial resistance, we fabricate thin-film electrodes of 6Li-enriched LiCoO2 (6LCO) modified with various structure-types of 6Li-enriched LWOs by pulsed laser deposition. The electrodes are subjected to X-ray diffraction (XRD), electrochemical impedance spectroscopy (EIS), and secondary-ion mass spectrometry (SIMS) analyses. XRD reveals that the LWO layers have Li2WO4 structure with rhombohedral and tetragonal symmetries and amorphous states. EIS shows that the lowest interfacial resistance of the positive electrodes is given by the amorphous state, followed in order by the tetragonal and the rhombohedral symmetry, and that the diffusion coefficients of lithium-ions in the electrodes increase in the same order. SIMS demonstrates that the fastest lithium-ion self-diffusibility into the LWOs is found in the amorphous state, followed in order by tetragonal and rhombohedral symmetry. Furthermore, the amorphous state LWO modification shows smooth lithium-ion diffusion between the LWO and LCO layers after the electrochemical test. Conversely, the rhombohedral LWO modification demonstrates congested lithium-ion diffusion between the LWO and LCO layers after the test. Thus, fast lithium-ion self-diffusibility into the LWO-modified LCO contributes to enhancing the diffusion of lithium-ions, resulting in the reduction of interfacial resistance.

  9. Investigation of the Gas-Diffusion-Electrode Used as Lithium/Air Cathode in Non-aqueous Electrolyte and the Importance of Carbon Material Porosity

    SciTech Connect

    Qu, D.; Yang, X.; Tran, C.

    2010-04-02

    The gas-diffusion-electrode used in a Li-air cell has been studied in a unique homemade electrochemical cell. Three major obstacles for the development of a feasible Li-air system were discussed with a focus on the development of a functional gas-diffusion-electrode in non-aqueous electrolytes and the way of avoiding the passivation of gas-diffusion-electrodes caused by the deposition of the reduction products. It is the first time that the importance of establishing the 3-phase electrochemical interface in non-aqueous electrolyte is demonstrated by creating air-diffusion paths and an air saturated portion for an air cathode. A model mechanism of electrode passivation by the reaction products was also proposed. Lithium oxides formed during O{sub 2} reduction tend to block small pores, preventing them from further utilization in the electrochemical reaction. On the other hand, lithium oxides would accumulate inside the large pores during the reduction until the density of oxides becomes high enough to choke-off the mass transfer. Carbon materials with a high surface area associated with larger pores should be selected to make the gas-diffusion-electrode for Li-air battery. For the first time, a near linear relationship between the capacity of GDE in a non-aqueous electrolyte and the average pore diameter was demonstrated, which could be used to estimate the capacity of the GDE quantitatively.

  10. Bifurcation phenomena in confined thermosolutal convection with lateral heating: Commencement of the double-diffusive region

    NASA Astrophysics Data System (ADS)

    Tsitverblit, N.

    1995-04-01

    As has recently been reported by Tsitverblit and Kit [Phys. Fluids A 5, 1062 (1993)], a vertical rectangular enclosure containing stably stratified brine and differentially heated from its side walls is characterized by complex steady bifurcation phenomena. In the present work, the structure of steady solutions in the enclosure has been studied in detail for several values of the salinity Rayleigh number, RaS, fixed near the commencement of the double-diffusive region. It was found that when the thermal Rayleigh number, RaT, is either very small or sufficiently large, the steady solution is unique while in an intermediate region of this parameter, there exists a great variety of the multiple steady flows, being the result of nondegenerate hysteresis points and isolas of asymmetric solutions forming as RaS is increased. In particular, at the maximal value of RaS considered there have been observed symmetric and asymmetric one-, two-, three-, four-, and five-cell flows. Despite the multiplicity of the flow patterns, a critical interval of the buoyancy ratio has been distinguished, above and below which the generic characteristics of the steady solutions were found to resemble the respective features of the ``successive'' and ``simultaneous'' regimes of layer formation whose existence was established in previous studies. Although the set of the steady solutions has been found to contain no linearly stable multicell flows, the perturbation was so long retained in the close proximity of the unstable steady solutions that such flows could be easily observable in the experiment. In spite of the appreciably different range of the Rayleigh numbers, the physically meaningful parameters suggested in previous studies were found to be represented in the present results.

  11. Spin-related thermoelectric conversion in lateral spin-valve devices with single-crystalline Co2FeSi electrodes

    NASA Astrophysics Data System (ADS)

    Yamasaki, Kento; Oki, Soichiro; Yamada, Shinya; Kanashima, Takeshi; Hamaya, Kohei

    2015-04-01

    We demonstrate the conversion between a heat current and a spin current in Cu-based lateral spin valves (LSVs) with single-crystalline Co2FeSi (CFS) electrodes. We can observe the thermally induced spin injection from CFS into Cu resulting from the spin-dependent Seebeck effect, and the heat current generated by the spin-dependent Peltier effect can be detected even in the LSV structures. This study is an important step toward understanding heat-spin conversion in single-crystalline materials with various electronic band structures.

  12. An Integrated Field-Effect Microdevice for Monitoring Membrane Transport in Xenopus laevis Oocytes via Lateral Proton Diffusion

    PubMed Central

    Schaffhauser, Daniel Felix; Patti, Monica; Goda, Tatsuro; Miyahara, Yuji; Forster, Ian Cameron; Dittrich, Petra Stephanie

    2012-01-01

    An integrated microdevice for measuring proton-dependent membrane activity at the surface of Xenopus laevis oocytes is presented. By establishing a stable contact between the oocyte vitelline membrane and an ion-sensitive field-effect (ISFET) sensor inside a microperfusion channel, changes in surface pH that are hypothesized to result from facilitated proton lateral diffusion along the membrane were detected. The solute diffusion barrier created between the sensor and the active membrane area allowed detection of surface proton concentration free from interference of solutes in bulk solution. The proposed sensor mechanism was verified by heterologously expressing membrane transport proteins and recording changes in surface pH during application of the specific substrates. Experiments conducted on two families of phosphate-sodium cotransporters (SLC20 & SLC34) demonstrated that it is possible to detect phosphate transport for both electrogenic and electroneutral isoforms and distinguish between transport of different phosphate species. Furthermore, the transport activity of the proton/amino acid cotransporter PAT1 assayed using conventional whole cell electrophysiology correlated well with changes in surface pH, confirming the ability of the system to detect activity proportional to expression level. PMID:22792166

  13. Manipulating the Lateral Diffusion of Surface-Anchored EGF Demonstrates that Receptor Clustering Modulates its Phosphorylation Levels

    SciTech Connect

    Stabley, Daniel; Retterer, Scott T; Marshal, Stephen; Salaita, Khalid

    2013-01-01

    Upon activation, the epidermal growth factor (EGF) receptor becomes phosphorylated and triggers a vast signaling network that has profound effects on cell growth. The EGF receptor is observed to assemble into clusters after ligand binding and tyrosine kinase autophosphorylation, but the role of these assemblies in the receptor signaling pathway remains unclear. To address this question, we measured the phosphorylation of EGFR when the EGF ligand was anchored onto laterally mobile and immobile surfaces. We found that cells generated clusters of ligand-receptor complex on mobile EGF surfaces, and generated a lower ratio of phosphorylated EGFR to EGF than when compared to immobilized EGF that is unable to cluster. This result was verified by tuning the lateral assembly of ligand-receptor complexes on the surface of living cells using patterned supported lipid bilayers. Nanoscale metal lines fabricated into the supported membrane constrained lipid diffusion and EGF receptor assembly into micron and sub-micron scale corrals. Single cell analysis indicated that clustering impacts EGF receptor activation, and larger clusters (> 1 m2) of ligand-receptor complex generated lower EGF receptor phosphorylation per ligand than smaller assemblies (< 1 m2) in HCC1143 cells that were engaged to ligand-functionalized surfaces. We investigated EGFR clustering by treating cells with compounds that disrupt the cytoskeleton (Latrunculin-B), clathrin-mediated endocytosis (Pitstop2), and inhibit EGFR activation (Gefitinib). These results help elucidate the nature of large-scale EGFR clustering, thus underscoring the general significance of receptor spatial organization in tuning function.

  14. The removal of low levels of organics from aqueous solutions using Fe(II) and hydrogen peroxide formed in situ at gas diffusion electrodes

    SciTech Connect

    Harrington, T.; Pletcher, D.

    1999-08-01

    The removal of several organics (phenol, aniline, acetic acid, formaldehyde, and three azo dyes) from aqueous solutions (pH 2) containing Fe(II) and using hydrogen peroxide produced by the reduction of oxygen at a gas-diffusion electrode is demonstrated. It is shown that chemical oxygen demand of solutions containing such organics may be reduced by >90% with a current efficiency >50%, leading to acceptable energy consumptions. The approach also clearly has considerable generality. The voltammetry of the gas diffusion electrodes, fabricated by screen printing an XC72-R carbon powder/polytetrafluorene active layer on a carbon fiber paper support is also reported and discussed.

  15. GRAPHITE ELECTRODE FOR THE MEASUREMENT OF REDOX POTENTIAL AND OXYGEN DIFFUSION RATE IN SOIL

    EPA Science Inventory

    The objective of the project was to evaluate control measurements that might be made at land treatment sites to determine the effectiveness of operation in the management of hazardous wastes. Initial studies were on measurement of oxygen concentration and oxygen diffusion rate (O...

  16. Lateral diffusion of inositol 1,4,5-trisphosphate receptor type 1 is regulated by actin filaments and 4.1N in neuronal dendrites.

    PubMed

    Fukatsu, Kazumi; Bannai, Hiroko; Zhang, Songbai; Nakamura, Hideki; Inoue, Takafumi; Mikoshiba, Katsuhiko

    2004-11-19

    Inositol 1,4,5-trisphosphate receptor type1 (IP3R1) plays an important role in neuronal functions; however, the lateral diffusion of IP3R1 on the endoplasmic reticulum membrane and its regulation in the living neurons remain unknown. We expressed green fluorescent protein-tagged IP3R1 in cultured rat hippocampal neurons and observed the lateral diffusion by the fluorescence recovery after photobleaching technique. IP3R1 showed lateral diffusion with an effective diffusion constant of approximately 0.3 microm2/s. Depletion of actin filaments increased the diffusion constant of IP3R1, suggesting that the diffusion of IP3R1 is regulated negatively through actin filaments. We also found that protein 4.1N, which binds to IP3R1 and contains an actin-spectrin-binding region, was responsible for this actin regulation of the IP3R1 diffusion constant. Overexpression of dominant-negative 4.1N and blockade of 4.1N binding to IP3R1 increased the IP3R1 diffusion constant. The diffusion of IP3R type 3 (IP3R3), one of the isoforms of IP3Rs lacking the binding ability to 4.1N, was not dependent on actin filaments but became dependent on actin filaments after the addition of a 4.1N-binding sequence. These data suggest that 4.1N serves as a linker protein between IP3R1 and actin filaments. This actin filament-dependent regulation of IP3R1 diffusion may be important for the spatiotemporal regulation of intracellular Ca2+ signaling. PMID:15364918

  17. Narrow groove welding gas diffuser assembly and welding torch

    SciTech Connect

    Rooney, Stephen J.

    2000-02-04

    A diffuser assembly is provided for narrow groove welding using an automatic gas tungsten arc welding torch. The diffuser assembly includes manifold adapted for adjustable mounting on the welding torch which is received in a central opening in the manifold. Laterally extending manifold sections communicate with a shield gas inlet such that shield gas supplied to the inlet passes to gas passages of the manifold sections. First and second tapered diffusers are respectively connected to the manifold sections in fluid communication with the gas passages thereof. The diffusers extend downwardly along the torch electrode on opposite sides thereof so as to release shield gas along the length of the electrode and at the distal tip of the electrode. The diffusers are of a transverse width which is on the order of the thickness of the electrode so that the diffusers can, in use, be inserted into a narrow welding groove before and after the electrode in the direction of the weld operation.

  18. Narrow groove welding gas diffuser assembly and welding torch

    DOEpatents

    Rooney, Stephen J.

    2001-01-01

    A diffuser assembly is provided for narrow groove welding using an automatic gas tungsten arc welding torch. The diffuser assembly includes a manifold adapted for adjustable mounting on the welding torch which is received in a central opening in the manifold. Laterally extending manifold sections communicate with a shield gas inlet such that shield gas supplied to the inlet passes to gas passages of the manifold sections. First and second tapered diffusers are respectively connected to the manifold sections in fluid communication with the gas passages thereof. The diffusers extend downwardly along the torch electrode on opposite sides thereof so as to release shield gas along the length of the electrode and at the distal tip of the electrode. The diffusers are of a transverse width which is on the order of the thickness of the electrode so that the diffusers can, in use, be inserted into a narrow welding groove before and after the electrode in the direction of the weld operation.

  19. Silver nanoparticle-decorated carbon nanotubes as bifunctional gas-diffusion electrodes for zinc-air batteries

    NASA Astrophysics Data System (ADS)

    Wang, T.; Kaempgen, M.; Nopphawan, P.; Wee, G.; Mhaisalkar, S.; Srinivasan, M.

    Thin, lightweight, and flexible gas-diffusion electrodes (GDEs) based on freestanding entangled networks of single-walled carbon nanotubes (SWNTs) decorated with Ag nanoparticles (AgNPs) are tested as the air-breathing cathode in a zinc-air battery. The SWNT networks provide a highly porous surface for active oxygen absorption and diffusion. The high conductivity of SWNTs coupled with the catalytic activity of AgNPs for oxygen reduction leads to an improvement in the performance of the zinc-air cell. By modulating the pH value and the reaction time, different sizes of AgNPs are decorated uniformly on the SWNTs, as revealed by transmission electron microscopy and powder X-ray diffraction. AgNPs with sizes of 3-5 nm double the capacity and specific energy of a zinc-air battery as compared with bare SWNTs. The simplified, lightweight architecture shows significant advantages over conventional carbon-based GDEs in terms of weight, thickness and conductivity, and hence may be useful for mobile and portable applications.

  20. Enhanced performance of gas diffusion electrode for electrochemical reduction of carbon dioxide to formate by adding polytetrafluoroethylene into catalyst layer

    NASA Astrophysics Data System (ADS)

    Wang, Qinian; Dong, Heng; Yu, Han; Yu, Hongbing

    2015-04-01

    Gas diffusion electrode (GDE) with Nafion bonded catalyst layer (CL) for electrochemical reduction of CO2 to formate (ERCF) suffers from CO2 mass transfer limitation. In this work, polytetrafluoroethylene (PTFE) with contents of 5.9 wt%, 7.7 wt%, 11.1 wt% and 20 wt% are added into the CL of the GDE with Sn catalyst (P-SGDE) for ERCF. The morphologies and porous structures of the P-SGDEs are examined by scanning electron microscope and mercury intrusion measurement, respectively. The electrochemical performances of the P-SGDEs are investigated by linear sweep voltammetry, electrochemical impedance spectroscopy and constant potential electrolysis. The results show that the Faraday efficiency (86.75 ± 2.89%) and current density (21.67 ± 1.29 mA cm-2) for ERCF were improved by 25.4% and 25.8% respectively when the content of PTFE is 11.1 wt%, probably owing to the enhancement in the catalyst active surface area and CO2 diffusion. This Faraday efficiency is the highest one found for ERCF with Sn GDE under similar conductions.

  1. High-frequency performances of superjunction laterally diffused metal-oxide-semiconductor transistors for RF power applications

    NASA Astrophysics Data System (ADS)

    Chen, Bo-Yuan; Chen, Kun-Ming; Chiu, Chia-Sung; Huang, Guo-Wei; Chang, Edward Yi

    2016-04-01

    This paper presents the dc and high-frequency performances of laterally diffused metal-oxide-semiconductor (LDMOS) transistors with superjunction (SJ) structures. The SJ-LDMOS transistors were fabricated using a 0.5-µm CMOS process. By utilizing a modified SJ/RESURF layout (Type I) or a tapered SJ layout (Type II) in our devices, better high-frequency performances and higher breakdown voltages are achieved compared with conventional SJ counterpart, owing to the suppression of the substrate-assisted depletion effect and the reduction of the drain resistance. For Type I device with an optimal SJ layout dimension, the cutoff frequency and the breakdown voltage are 3.7 GHz and 68 V, respectively. For Type II device with a smallest p-pillar width near the drain, they can be enhanced further and reach to 4.9 GHz and 83 V. These experimental results suggest that the SJ-LDMOS can be used in the RF power amplifiers.

  2. Interlayer molecular diffusion and thermodynamic equilibrium in organic heterostructures on a metal electrode

    NASA Astrophysics Data System (ADS)

    Amsalem, P.; Wilke, A.; Frisch, J.; Niederhausen, J.; Vollmer, A.; Rieger, R.; Müllen, K.; Rabe, J. P.; Koch, N.

    2011-12-01

    In this paper, we investigate by photoemission the electronic properties of an organic/organic interface consisting in a strong electron acceptor hexaazatriphenylene-hexacarbonitrile (HATCN) deposited on a physisorbed N,N'-bis(1-naphthyl)-N,N'-diphenyl-1,1'-biphenyl-4,4'-diamine (α-NPD) monolayer on Ag(111). At the first HATCN deposition steps (˜1 monolayer), the sample work function increases by 1.05 eV and the hole injection barrier (HIB) in the pre-adsorbed α-NPD monolayer is lowered by 0.65 eV. This results from HATCN diffusion to the silver surface through the α-NPD monolayer. Furthermore, this HATCN monolayer is proposed to form a compact chemisorbed monolayer, with a different structural arrangement than that observed on pristine Ag(111). In a second step, the additional deposited HATCN start growing on top of the α-NPD layer, and Fermi-level pinning, associated with the formation of HATCN negative polarons, is identified at the HATCN/α-NPD interface. Finally, HATCN is deposited on a α-NPD multilayer film. In this case, HATCN is also found to diffuse to the silver surface giving a similar HIB value in the α-NPD multilayer. This work demonstrates the importance of studying in detail the formation of organic heterostructures to understand the interplay between growth mode and electronic properties.

  3. Oxidation resistance of tantalum-ruthenium dioxide diffusion barrier for memory capacitor bottom electrodes

    NASA Astrophysics Data System (ADS)

    Yoon, Dong-Soo; Baik, Hong Koo; Lee, Sung-Man; Park, Chang-Soo; Lee, Sang-In

    1998-07-01

    The effect of the RuO2 addition into a Ta film on the oxidation resistance of a diffusion barrier for the Ta+RuO2/Si system was investigated. The Ta+RuO2/Si system was sustained up to 800 °C without an increase in resistivity, while the Ta/Si structure completely degraded after annealing at 450 °C. The Ta+RuO2 diffusion barrier showed an amorphous microstructure for an as-deposited state and formed a conductive RuO2 phase after annealing. Ta was sufficiently bound to oxygen of RuO2 for an as-deposited state, but RuO2 was divided into Ru and Ru-O binding states. Ta-O bonds showed a little change compared to the as-deposited state with increasing annealing temperature, whereas Ru-O bonds significantly increased. Therefore, the Ta layer deposited by the RuO2 addition effectively prevented the indiffusion of oxygen up to 800 °C and its oxidation resistance was superior to those of polycrystalline nitride (TiN, TaN) and ternary amorphous (TaSiN) barriers reported by others.

  4. Ab initio diffuse-interface model for lithiated electrode interface evolution

    NASA Astrophysics Data System (ADS)

    Stournara, Maria E.; Kumar, Ravi; Qi, Yue; Sheldon, Brian W.

    2016-07-01

    The study of chemical segregation at interfaces, and in particular the ability to predict the thickness of segregated layers via analytical expressions or computational modeling, is a fundamentally challenging topic in the design of novel heterostructured materials. This issue is particularly relevant for the phase-field (PF) methodology, which has become a prominent tool for describing phase transitions. These models rely on phenomenological parameters that pertain to the interfacial energy and thickness, quantities that cannot be experimentally measured. Instead of back-calculating these parameters from experimental data, here we combine a set of analytical expressions based on the Cahn-Hilliard approach with ab initio calculations to compute the gradient energy parameter κ and the thickness λ of the segregated Li layer at the LixSi-Cu interface. With this bottom-up approach we calculate the thickness λ of the Li diffuse interface to be on the order of a few nm, in agreement with prior experimental secondary ion mass spectrometry observations. Our analysis indicates that Li segregation is primarily driven by solution thermodynamics, while the strain contribution in this system is relatively small. This combined scheme provides an essential first step in the systematic evaluation of the thermodynamic parameters of the PF methodology, and we believe that it can serve as a framework for the development of quantitative interface models in the field of Li-ion batteries.

  5. Ab initio diffuse-interface model for lithiated electrode interface evolution.

    PubMed

    Stournara, Maria E; Kumar, Ravi; Qi, Yue; Sheldon, Brian W

    2016-07-01

    The study of chemical segregation at interfaces, and in particular the ability to predict the thickness of segregated layers via analytical expressions or computational modeling, is a fundamentally challenging topic in the design of novel heterostructured materials. This issue is particularly relevant for the phase-field (PF) methodology, which has become a prominent tool for describing phase transitions. These models rely on phenomenological parameters that pertain to the interfacial energy and thickness, quantities that cannot be experimentally measured. Instead of back-calculating these parameters from experimental data, here we combine a set of analytical expressions based on the Cahn-Hilliard approach with ab initio calculations to compute the gradient energy parameter κ and the thickness λ of the segregated Li layer at the Li_{x}Si-Cu interface. With this bottom-up approach we calculate the thickness λ of the Li diffuse interface to be on the order of a few nm, in agreement with prior experimental secondary ion mass spectrometry observations. Our analysis indicates that Li segregation is primarily driven by solution thermodynamics, while the strain contribution in this system is relatively small. This combined scheme provides an essential first step in the systematic evaluation of the thermodynamic parameters of the PF methodology, and we believe that it can serve as a framework for the development of quantitative interface models in the field of Li-ion batteries. PMID:27575197

  6. Comparison of Diffusion MRI Acquisition Protocols for the In Vivo Characterization of the Mouse Spinal Cord: Variability Analysis and Application to an Amyotrophic Lateral Sclerosis Model.

    PubMed

    Figini, Matteo; Scotti, Alessandro; Marcuzzo, Stefania; Bonanno, Silvia; Padelli, Francesco; Moreno-Manzano, Victoria; García-Verdugo, José Manuel; Bernasconi, Pia; Mantegazza, Renato; Bruzzone, Maria Grazia; Zucca, Ileana

    2016-01-01

    Diffusion-weighted Magnetic Resonance Imaging (dMRI) has relevant applications in the microstructural characterization of the spinal cord, especially in neurodegenerative diseases. Animal models have a pivotal role in the study of such diseases; however, in vivo spinal dMRI of small animals entails additional challenges that require a systematical investigation of acquisition parameters. The purpose of this study is to compare three acquisition protocols and identify the scanning parameters allowing a robust estimation of the main diffusion quantities and a good sensitivity to neurodegeneration in the mouse spinal cord. For all the protocols, the signal-to-noise and contrast-to noise ratios and the mean value and variability of Diffusion Tensor metrics were evaluated in healthy controls. For the estimation of fractional anisotropy less variability was provided by protocols with more diffusion directions, for the estimation of mean, axial and radial diffusivity by protocols with fewer diffusion directions and higher diffusion weighting. Intermediate features (12 directions, b = 1200 s/mm2) provided the overall minimum inter- and intra-subject variability in most cases. In order to test the diagnostic sensitivity of the protocols, 7 G93A-SOD1 mice (model of amyotrophic lateral sclerosis) at 10 and 17 weeks of age were scanned and the derived diffusion parameters compared with those estimated in age-matched healthy animals. The protocols with an intermediate or high number of diffusion directions provided the best differentiation between the two groups at week 17, whereas only few local significant differences were highlighted at week 10. According to our results, a dMRI protocol with an intermediate number of diffusion gradient directions and a relatively high diffusion weighting is optimal for spinal cord imaging. Further work is needed to confirm these results and for a finer tuning of acquisition parameters. Nevertheless, our findings could be important for the

  7. Comparison of Diffusion MRI Acquisition Protocols for the In Vivo Characterization of the Mouse Spinal Cord: Variability Analysis and Application to an Amyotrophic Lateral Sclerosis Model

    PubMed Central

    Marcuzzo, Stefania; Bonanno, Silvia; Padelli, Francesco; Moreno-Manzano, Victoria; García-Verdugo, José Manuel; Bernasconi, Pia; Mantegazza, Renato; Bruzzone, Maria Grazia; Zucca, Ileana

    2016-01-01

    Diffusion-weighted Magnetic Resonance Imaging (dMRI) has relevant applications in the microstructural characterization of the spinal cord, especially in neurodegenerative diseases. Animal models have a pivotal role in the study of such diseases; however, in vivo spinal dMRI of small animals entails additional challenges that require a systematical investigation of acquisition parameters. The purpose of this study is to compare three acquisition protocols and identify the scanning parameters allowing a robust estimation of the main diffusion quantities and a good sensitivity to neurodegeneration in the mouse spinal cord. For all the protocols, the signal-to-noise and contrast-to noise ratios and the mean value and variability of Diffusion Tensor metrics were evaluated in healthy controls. For the estimation of fractional anisotropy less variability was provided by protocols with more diffusion directions, for the estimation of mean, axial and radial diffusivity by protocols with fewer diffusion directions and higher diffusion weighting. Intermediate features (12 directions, b = 1200 s/mm2) provided the overall minimum inter- and intra-subject variability in most cases. In order to test the diagnostic sensitivity of the protocols, 7 G93A-SOD1 mice (model of amyotrophic lateral sclerosis) at 10 and 17 weeks of age were scanned and the derived diffusion parameters compared with those estimated in age-matched healthy animals. The protocols with an intermediate or high number of diffusion directions provided the best differentiation between the two groups at week 17, whereas only few local significant differences were highlighted at week 10. According to our results, a dMRI protocol with an intermediate number of diffusion gradient directions and a relatively high diffusion weighting is optimal for spinal cord imaging. Further work is needed to confirm these results and for a finer tuning of acquisition parameters. Nevertheless, our findings could be important for the

  8. Measuring localization and diffusion coefficients of basolateral proteins in lateral versus basal membranes using functionalized substrates and kICS analysis.

    PubMed

    Marlar, Saw; Arnspang, Eva C; Pedersen, Gitte A; Koffman, Jennifer S; Nejsum, Lene N

    2014-10-01

    Micropatterning enabled semiquantitation of basolateral proteins in lateral and basal membranes of the same cell. Lateral diffusion coefficients of basolateral aquaporin-3 (AQP3-EGFP) and EGFP-AQP4 were extracted from "lateral" and "basal" membranes using identical live-cell imaging and k-space Image Correlation Spectroscopy (kICS). To simultaneously image proteins in "lateral" and "basal" membranes, micropatterning with the extracellular domain of E-cadherin and collagen, to mimic cell-cell and cell-extracellular matrix (ECM) adhesion, respectively, was used. In kidney collecting duct principal cells AQP3 localizes lateral and basal whereas AQP4 localizes mainly basal. On alternating stripes of E-cadherin and collagen, AQP3-EGFP was predominantly localized to "lateral" compared to "basal" membranes, whereas Orange-AQP4 was evenly distributed. Average diffusion coefficients were extracted via kICS analysis of rapid time-lapse sequences of AQP3-EGFP and EGFP-AQP4 on uniform substrates of either E-cadherin or collagen. AQP3-EGFP was measured to 0.022±0.010μm(2)/s on E-cadherin and 0.019±0.004μm(2)/s on collagen, whereas EGFP-AQP4 was measured to 0.044±0.009μm(2)/s on E-cadherin and 0.037±0.009μm(2)/s on collagen, thus, diffusion did not differ between substrates. Cholesterol depletion by methyl-beta-cyclodextrin (MBCD) reduced the AQP3-EGFP diffusion coefficient by 43% from 0.024±0.007μm(2)/s (water) to 0.014±0.003μm(2)/s (MBCD) (p<0.05) on collagen surfaces, and by 41% from 0.023±0.011μm(2)/s (water) to 0.014±0.005μm(2)/s (MBCD) (p<0.05) on E-cadherin surfaces. Thus, protein patterning enables the semiquantitation of protein distribution between the "lateral" and "basal" membranes as well as measurements of lateral diffusion coefficients. PMID:24950246

  9. Results of pulsed radiofrequency technique with two laterally placed electrodes in the annulus in patients with chronic lumbar discogenic pain.

    PubMed

    Fukui, Sei; Rohof, Olav

    2012-08-01

    Discogenic pain is an important cause of low back pain (LBP). We have developed a pulsed radiofrequency (P-RF) technique, using two electrodes placed bilaterally in the annulus, for applying radiofrequency current in the disc (bi-annular P-RF disc method). The purpose of this study was to investigate the effect of the bi-annular P-RF disc method, using Diskit needles (Neurotherm, Middleton, MA, USA) in patients with discogenic LBP. The subjects were 15 patients with a mean age of 37.3 ± 8.63 years with chronic discogenic lower back pain that was not responsive to aggressive nonoperative care. Two Diskit II needles (15-cm length, 20G needles with a 20-mm active tip) were placed bilaterally in the annulus in the disc. Pulsed radiofrequency was applied for 12 min at a setting of 5 × 50 ms/s and 60 V. The pain intensity scores on a 0-10 numeric rating scale (NRS) and the Roland-Morris Disability Questionnaire (RMDQ) were measured pretreatment, and at 1 week and 1, 3, and 6 months post-treatment. The mean pain severity score (NRS) improved from 7.27 ± 0.58 pretreatment to 2.5 ± 0.94 at the 6-month follow-up (p < 0.01). The RMDQ showed significant (p < 0.01) improvement, from 10.70 ± 2.35 pretreatment to 2.10 ± 1.85 at the 6-month follow up (p < 0.01). The bi-annular P-RF disc method with consecutive P-RF 5/5/60 V, 12-min (with Diskit needle), appears to be a safe, minimally invasive treatment option for patients with chronic discogenic LBP. PMID:22476553

  10. A finite element simulation on transient large deformation and mass diffusion in electrodes for lithium ion batteries

    NASA Astrophysics Data System (ADS)

    An, Yonghao; Jiang, Hanqing

    2013-10-01

    Lithium-ion batteries have attracted great deal of attention recently. Silicon is one of the most promising anode materials for high-performance lithium-ion batteries, due to its highest theoretical specific capacity. However, the short lifetime confined by mechanical failure in the silicon anode is now considered to be the biggest challenge in desired applications. High stress induced by the huge volume change due to lithium insertion/extraction is the main reason underlying this problem. Some theoretical models have been developed to address this issue. In order to properly implement these models, we develop a finite element based numerical method using a commercial software package, ABAQUS, as a platform at the continuum level to study fully coupled large deformation and mass diffusion problem. Using this method, large deformation, elasticity-plasticity of the electrodes, various spatial and temporal conditions, arbitrary geometry and dimension could be fulfilled. The interaction between anode and other components of the lithium ion batteries can also be studied as an integrated system. Several specific examples are presented to demonstrate the capability of this numerical platform.

  11. Computationally efficient approach for solving time dependent diffusion equation with discrete temporal convolution applied to granular particles of battery electrodes

    NASA Astrophysics Data System (ADS)

    Senegačnik, Jure; Tavčar, Gregor; Katrašnik, Tomaž

    2015-03-01

    The paper presents a computationally efficient method for solving the time dependent diffusion equation in a granule of the Li-ion battery's granular solid electrode. The method, called Discrete Temporal Convolution method (DTC), is based on a discrete temporal convolution of the analytical solution of the step function boundary value problem. This approach enables modelling concentration distribution in the granular particles for arbitrary time dependent exchange fluxes that do not need to be known a priori. It is demonstrated in the paper that the proposed method features faster computational times than finite volume/difference methods and Padé approximation at the same accuracy of the results. It is also demonstrated that all three addressed methods feature higher accuracy compared to the quasi-steady polynomial approaches when applied to simulate the current densities variations typical for mobile/automotive applications. The proposed approach can thus be considered as one of the key innovative methods enabling real-time capability of the multi particle electrochemical battery models featuring spatial and temporal resolved particle concentration profiles.

  12. Tubular carbon nanotube-based gas diffusion electrode removes persistent organic pollutants by a cyclic adsorption - Electro-Fenton process.

    PubMed

    Roth, Hannah; Gendel, Youri; Buzatu, Pompilia; David, Oana; Wessling, Matthias

    2016-04-15

    We report a novel tubular electrochemical cell which is operated in a cyclic adsorption - electro-Fenton process and by this means overcomes the drawbacks of the traditional electro-Fenton process. A microtube made only of multi-walled carbon nanotubes (MWCNT) functions as a gas diffusion electrode (GDE) and highly porous adsorber. In the process, the pollutants were first removed electroless from the wastewater by adsorption on the MWCNT-GDE. Subsequently, the pollutants are electrochemically degraded in a defined volume of electrolyte solution using the electro-Fenton process. Oxygen was supplied into the lumen of the saturated microtubular GDE which was surrounded by a cylindrical anode made of Ti-felt coated with Pt/IrO2 catalysts. For the proof of concept the model pollutant Acid Red 14 (AR14), an azo dye, was used. The decomposition of AR14 was studied at different applied current densities and initial concentrations of ferrous iron in the electrolyte solution. At optimal conditions, complete regeneration of the adsorption capacity of the MWCNT-GDE, complete decolorization and TOC and COD removal rates of 50% and 70% were achieved, respectively. The MWCNT-GDE is regenerated and again available for adsorption. This approach allows water treatment independent of its composition, thus does not require any addition of chemicals to the wastewater. PMID:26775104

  13. Development of rolling tin gas diffusion electrode for carbon dioxide electrochemical reduction to produce formate in aqueous electrolyte

    NASA Astrophysics Data System (ADS)

    Wang, Qinian; Dong, Heng; Yu, Hongbing

    2014-12-01

    Carbon dioxide electrochemical reduction to produce formate (CERPF) basing on gas diffusion electrode (GDE) is a promising carbon cycle technology. However, its performance is still restrained by formate accumulation and catalyst loss in the catalyst layer (CL). In this study, a novel rolling Sn-loading GDE (SGDE) without porous hydrophilic CL is developed. The electrochemical behavior of CERPF on the SGDE is investigated by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The electrochemical performance of the SGDE for CERPF is assessed by constant potential electrolysis. The results show that the CERPF process basing on the SGDE performs a double charge transfer and is dominated by the electron transfer rate. The highest partial current density for CERPF (17.43 ± 2.60 mA cm-2) and corresponding Faraday efficiency (78.60 ± 0.11%) are obtained under the applied potential of -1.8 V vs Ag/AgCl in 0.5 M KHCO3 solution. The produced formate is allowed to be released into the electrolyte easily and the catalyst holds steady during the CERPF process. Since its excellent electrochemical performance and low fabrication cost (ca. 30 m-2), bright prospect for SGDE application in CERPF can be convinced.

  14. Multi-electrode laterally coupled distributed feedback InGaAsP/InP lasers: a prescription for longitudinal mode control

    NASA Astrophysics Data System (ADS)

    Benhsaien, Abdessamad; Dridi, Kais; Zhang, Jessica; Hall, Trevor J.

    2013-10-01

    Photonic Integrated Circuits (PICs) enable photons as data carriers at a very high speed. PIC market opportunities call for reduced wafer dimensions, power consumption and cost as well as enhanced reliability. The PIC technology development must cater for the latter relentless traits. In particular, monolithic PICs are sought as they can integrate hundreds of components and functions onto a single chip. InGaAsP/InP laterally-coupled distributed feedback (LC-DFB) lasers stand as key enablers in the PIC technology thanks to the compelling advantages their embedded high-order surface-gratings have. The patterning of the spatial corrugation along the sidewalls of the LC-DFB ridge, has been established to make the epitaxial overgrowth unnecessary thereby reducing the cost and time of manufacturing, and ultimately increasing the yield. LC-DFBs boast a small footprint synonymous of enhanced monolithic integrate-ability. Nonetheless, LC-DFBs suffer from the adverse longitudinal spatial hole burning (LSHB) effects materialized by typically quite high threshold current levels. Indeed, the carrier density longitudinal gradient- responsible for modes contending for the available material gain in the cavity- may be alleviated somewhat by segmenting the LC-DFB electrode into two or three reasonably interspaced longitudinal sections. In this work we report on the realization and performance of various electrode partition configurations. At room temperature, the experimental characterization of many as-cleaved LC-DFB devices provides ample evidence of superior performance such as a narrow linewidth (less than 400 kHz), a wide wavelength tune-ability (over 4 nm) and a hop-free single mode emission (side mode suppression ratio (SMSR) exceeding 54dB).

  15. Language Laterality in Autism Spectrum Disorder and Typical Controls: A Functional, Volumetric, and Diffusion Tensor MRI Study

    PubMed Central

    Knaus, Tracey A.; Silver, Andrew M.; Kennedy, Meaghan; Lindgren, Kristen A.; Dominick, Kelli C.; Siegel, Jeremy; Tager-Flusberg, Helen

    2010-01-01

    Language and communication deficits are among the core features of autism spectrum disorder (ASD). Reduced or reversed asymmetry of language has been found in a number of disorders, including ASD. Studies of healthy adults have found an association between language laterality and anatomical measures but this has not been systematically investigated in ASD. The goal of this study was to examine differences in gray matter volume of perisylvian language regions, connections between language regions, and language abilities in individuals with typical left lateralized language compared to those with atypical (bilateral or right) asymmetry of language functions. 14 adolescent boys with ASD and 20 typically developing adolescent boys participated, including equal numbers of left- and right-handed individuals in each group. Participants with typical left lateralized language activation had smaller frontal language region volume and higher fractional anisotropy of the arcuate fasciculus compared to the group with atypical language laterality, across both ASD and control participants. The group with typical language asymmetry included the most right-handed controls and fewest left-handers with ASD. Atypical language laterality was more prevalent in the ASD than control group. These findings support an association between laterality of language function and language region anatomy. They also suggest anatomical differences may be more associated with variation in language laterality than specifically with ASD. Language laterality therefore may provide a novel way of subdividing samples, resulting in more homogenous groups for research into genetic and neurocognitive foundations of developmental disorders. PMID:20031197

  16. Efficient degradation of rhodamine B using modified graphite felt gas diffusion electrode by electro-Fenton process.

    PubMed

    Tian, Jiangnan; Olajuyin, Ayobami Matthew; Mu, Tingzhen; Yang, Maohua; Xing, Jianmin

    2016-06-01

    The electro-Fenton (EF) process treatment of 0.1-M (rhodamine B) RhB solution was studied with different graphite cathode materials, and graphite felt (GF) was selected as a promising material in further investigation. Then, the degradation performances of gas diffusion electrode (GDE) and graphite felt (GF) were compared, and GDE was confirmed to be more efficient in RhB removal. The operational parameters such as Fe(2+) dosage and current density were optimized, and comparison among different modified methods-polytetrafluoroethylene-carbon black (PTFE-CB), polytetrafluoroethylene-carbon nanotube (PTFE-CNT), electrodeposition-CB, and electrodeposition-CNT-showed 98.49 % RhB removal by PTFE-CB-modified cathode in 0.05 M Na2SO4 at a current density of 50 A/m(2) and an air flow rate of 1 L/min after 20 min. Meanwhile, after cathode modified by PTFE-CB, the mineralization efficiency and mineralization current efficiency performed absolutely better than the pristine one. Cyclic voltammograms, SEM images, contact angles, and BET surface area were carried out to demonstrate stronger current responses and higher hydrophilicity of GF after modified. The value of biochemical oxygen demand/chemical oxygen demand (BOD5/COD) increased from 0.049 to 0.331 after 90-min treatment, suggesting the solution was biodegradable, and the modified cathode was confirmed to be stable after ten circle runs. Finally, a proposed degradation pathway of RhB was put forward. PMID:26931661

  17. Symptoms of degeneration of the pyramidal tracts in conventional magnetic resonance imaging and diffusion tensor imaging in a young woman with primary lateral sclerosis

    PubMed Central

    Budrewicz, S; Szewczyk, P; Slotwinski, K; Koszewicz, M

    2015-01-01

    Primary lateral sclerosis (PLS) is one of the forms of motor neuron disease (MND), affecting only upper motor neurons. The diagnosis of PLS should be made on different diagnostic criteria, for example, Pringle or Gordon, but it is usually a diagnosis of exclusion. There are no characteristic findings in standard laboratory and electrophysiological assessment. We present details of a 31-year-old woman who had suffered from progressive paraparesis with right-side predominance. Conventional MRI of brain and spinal cord and diffusion tensor imaging (DTI) studies showed Hyperintense lesions in the upper part of the cervical spinal cord at the level C1 in lateral funicules, in the medulla oblongata at the pyramidal decussation and in the midbrain. Brain DTI revealed changes along the corticospinal tracts on fractional anisotropy (FA) maps. MRI of the thoracic spinal cord showed in T2-weighted images hyperintensive regions in the course of the lateral corticospinal tracts. This aided in PLS recognition. PMID:26119443

  18. Continuous fluorescence microphotolysis of anthracene-labeled phospholipids in membranes. Theoretical approach of the simultaneous determination of their photodimerization and lateral diffusion rates.

    PubMed Central

    Ferrières, X; Lopez, A; Altibelli, A; Dupou-Cezanne, L; Lagouanelle, J L; Tocanne, J F

    1989-01-01

    Anthracene is a fluorescent and photoactivatable (dimerization) group which can be used for investigating the lateral distribution and dynamics of lipids in membranes. In fluorescence recovery after photobleaching or in microphotolysis experiments, and when using this fluorophore, the bleaching (or microphotolysis) step in the illuminated part of the membrane is in fact the sum of two antagonistic processes: fluorescence decay, which is due to dimerization of anthracene residues, and fluorescence recovery, which is due to a diffusion mediated exchange of bleached and unbleached particles between the illuminated and diffusion area in the membrane. Here, we propose a new mathematical algorithm that enables such a second-order reaction-diffusion process to be analyzed. After coupling a fluorescence recovery step to a microphotolysis step, this algorithm allows us to calculate the lateral diffusion coefficient D and the photodimerization constant K of anthracene-labeled lipids in membranes, two parameters which contribute to the understanding of the fluidity of the lipid phase in membranes. This algorithm also provides us with a complete description of the anthracene-labeled molecules distribution in the illuminated and diffusion area, at any time of the experiment. The fluorescence recovery after microphotolysis procedure we propose was tested with an anthracene-labeled phosphatidylcholine inserted in egg-phosphatidylcholine multilayers, in monolayers adsorbed onto alkylated glass surfaces and in the plasma membrane of Chinese hamster ovary cells. It is shown that this procedure can also be used to evaluate the important parameters of probe mobile fraction and to determine the relative size of the illuminated and diffusion areas. This will enable membranes to be explored in terms of microdomains and/or macrodomains. PMID:2765646

  19. Effects of carbon on oxygen reduction and evolution reactions of gas-diffusion air electrodes based on perovskite-type oxides

    NASA Astrophysics Data System (ADS)

    Nishio, Koji; Molla, Sergio; Okugaki, Tomohiko; Nakanishi, Shinji; Nitta, Iwao; Kotani, Yukinari

    2015-12-01

    Electrochemical properties of three perovskite oxides with different B-site elements, LaMnO3, La0.6Sr0.4FeO3 and LaNiO3, are examined with and without carbon using gas-diffusion electrodes, in comparison with our previous results on La0.5Sr0.5CoO3. Cyclic voltammetry studies reveal very low oxygen reduction current density of carbon-free perovskite oxides, indicating their poor catalytic activity on oxygen reduction reactions. By mixing carbon with perovskite oxides, the oxygen reduction current density is increased by about two orders. The results are consistent with the peroxide pathway mechanism in which the perovskite oxide is highly active on either electrochemical reduction or chemical decomposition. Electrochemical properties of a three-layered gas diffusion electrode demonstrate the peroxide pathway mechanism works even the perovskite oxide and the carbon exist in separate layers. Oxygen evolution reactions are prominently dependent on the oxide species and also on an addition of carbon. The electrode based on carbon-free LaNiO3 or La0.5Sr0.5CoO3 show moderate oxygen evolution activity, and the activity is further enhanced by an addition of carbon, while LaMnO3 and La0.6Sr0.4FeO3 show poor activity even with an addition of carbon.

  20. The effect of electrolyte composition on the electroreduction of CO2 to CO on Ag based gas diffusion electrodes.

    PubMed

    Verma, Sumit; Lu, Xun; Ma, Sichao; Masel, Richard I; Kenis, Paul J A

    2016-03-14

    The electroreduction of CO2 to C1-C2 chemicals can be a potential strategy for utilizing CO2 as a carbon feedstock. In this work, we investigate the effect of electrolytes on the electroreduction of CO2 to CO on Ag based gas diffusion electrodes. Electrolyte concentration was found to play a major role in the process for the electrolytes (KOH, KCl, and KHCO3) studied here. Several fold improvements in partial current densities of CO (jCO) were observed on moving from 0.5 M to 3.0 M electrolyte solution independent of the nature of the anion. jCO values as high as 440 mA cm(-2) with an energy efficiency (EE) of ≈ 42% and 230 mA cm(-2) with EE ≈ 54% were observed when using 3.0 M KOH. Electrochemical impedance spectroscopy showed that both the charge transfer resistance (Rct) and the cell resistance (Rcell) decreased on moving from a 0.5 M to a 3.0 M KOH electrolyte. Anions were found to play an important role with respect to reducing the onset potential of CO in the order OH(-) (-0.13 V vs. RHE) < HCO3(-) (-0.46 V vs. RHE) < Cl(-) (-0.60 V vs. RHE). A decrease in Rct upon increasing electrolyte concentration and the effect of anions on the cathode can be explained by an interplay of different interactions in the electrical double layer that can either stabilize or destabilize the rate limiting CO2˙(-) radical. EMIM based ionic liquids and 1 : 2 choline Cl urea based deep eutectic solvents (DESs) have been used for CO2 capture but exhibit low conductivity. Here, we investigate if the addition of KCl to such solutions can improve conductivity and hence jCO. Electrolytes containing KCl in combination with EMIM Cl, choline Cl, or DESs showed a two to three fold improvement in jCO in comparison to those without KCl. Using such mixtures can be a strategy for integrating the process of CO2 capture with CO2 conversion. PMID:26661416

  1. Effects of lateral diffusion on morphology and dynamics of a microscopic lattice-gas model of pulsed electrodeposition

    NASA Astrophysics Data System (ADS)

    Frank, Stefan; Roberts, Daniel E.; Rikvold, Per Arne

    2005-02-01

    The influence of nearest-neighbor diffusion on the decay of a metastable low-coverage phase (monolayer adsorption) in a square lattice-gas model of electrochemical metal deposition is investigated by kinetic Monte Carlo simulations. The phase-transformation dynamics are compared to the well-established Kolmogorov-Johnson-Mehl-Avrami theory. The phase transformation is accelerated by diffusion, but remains in accord with the theory for continuous nucleation up to moderate diffusion rates. At very high diffusion rates the phase-transformation kinetic shows a crossover to instantaneous nucleation. Then, the probability of medium-sized clusters is reduced in favor of large clusters. Upon reversal of the supersaturation, the adsorbate desorbs, but large clusters still tend to grow during the initial stages of desorption. Calculation of the free energy of subcritical clusters by enumeration of lattice animals yields a quasiequilibrium distribution which is in reasonable agreement with the simulation results. This is an improvement relative to classical droplet theory, which fails to describe the distributions, since the macroscopic surface tension is a bad approximation for small clusters.

  2. Reaction and transport in Ag/Ag2O gas diffusion electrodes of aqueous Li-O2 batteries: Experiments and modeling

    NASA Astrophysics Data System (ADS)

    Danner, Timo; Horstmann, Birger; Wittmaier, Dennis; Wagner, Norbert; Bessler, Wolfgang G.

    2014-10-01

    Aqueous lithium-oxygen batteries are promising candidates for electric energy storage. In this paper we present and discuss a multiphase continuum model of an aqueous lithium-oxygen single cell including reactions and transport in a porous gas diffusion electrode (GDE). The model is parameterized using in-house half-cell experiments and available literature data on aqueous electrolytes. We validate our transport model with cyclic voltammetry and electrochemical impedance spectroscopy measurements over a wide range of temperatures (25, 40, 55 °C) and electrolyte concentrations (0.1-2 M). We observe very good agreement between simulations and measurements during oxygen reduction conditions. A sensitivity analysis of the validated model demonstrates the influence of the porous structure on GDE performance and gives directions for the future development of electrodes.

  3. Language Laterality in Autism Spectrum Disorder and Typical Controls: A Functional, Volumetric, and Diffusion Tensor MRI Study

    ERIC Educational Resources Information Center

    Knaus, Tracey A.; Silver, Andrew M.; Kennedy, Meaghan; Lindgren, Kristen A.; Dominick, Kelli C.; Siegel, Jeremy; Tager-Flusberg, Helen

    2010-01-01

    Language and communication deficits are among the core features of autism spectrum disorder (ASD). Reduced or reversed asymmetry of language has been found in a number of disorders, including ASD. Studies of healthy adults have found an association between language laterality and anatomical measures but this has not been systematically…

  4. Comparison of the simplified laterally uniform and geometrically realistic optical fiber probe-tissue interface in terms of Monte Carlo simulated diffuse reflectance

    NASA Astrophysics Data System (ADS)

    Naglič, Peter; Pernuš, Franjo; Likar, Boštjan; Bürmen, Miran

    2015-07-01

    Diffuse reflectance spectroscopy utilizing optical fiber probes is a useful and simple method for non-invasive determination of biological tissue optical properties. In order to extract the optical properties from the acquired diffuse reflectance spectra, an accurate light propagation model, such as Monte Carlo, is required. The results obtained by the model can significantly depend on the description of the tissue and optical fiber probe geometry. Optical fiber probes commonly comprise fibers arranged into a desired source-detector layout enclosed in a stainless steel ferrule. By using Monte Carlo simulations, we investigate the impact of the stainless steel optical fiber probe-tissue interface on the diffuse reflectance spectra. For this purpose, a commonly used simple laterally uniform optical probe-tissue interface with mismatched refractive indices was compared to the improved optical probe-tissue interface taking into account the fiber layout and the specular reflections from the stainless steel probe tip. The results show that the error introduced into the simulated diffuse reflectance by the simplified probe-tissue interface can easily exceed 5%.

  5. Anomalous output characteristic shift for the n-type lateral diffused metal-oxide-semiconductor transistor with floating P-top layer

    SciTech Connect

    Liu, Siyang; Zhang, Chunwei; Sun, Weifeng; Su, Wei; Wang, Shaorong; Ma, Shulang; Huang, Yu

    2014-04-14

    Anomalous output characteristic shift of the n-type lateral diffused metal-oxide-semiconductor transistor with floating P-top layer is investigated. It shows that the linear drain current has obvious decrease when the output characteristic of fresh device is measured for two consecutive times. The charge pumping experiments demonstrate that the decrease is not from hot-carrier degradation. The reduction of cross section area for the current flowing, which results from the squeezing of the depletion region surrounding the P-top layer, is responsible for the shift. Consequently, the current capability of this special device should be evaluated by the second measured output characteristic.

  6. The lateral diffusion and fibrinogen induced clustering of platelet integrin αIIbβ3 reconstituted into physiologically mimetic GUVs.

    PubMed

    Gaul, Vinnie; Lopez, Sergio G; Lentz, Barry R; Moran, Niamh; Forster, Robert J; Keyes, Tia E

    2015-04-01

    Platelet integrin αIIbβ3 is a key mediator of platelet activation and thrombosis. Upon activation αIIbβ3 undergoes significant conformational rearrangement, inducing complex bidirectional signalling and protein recruitment leading to platelet activation. Reconstituted lipid models of the integrin can enhance our understanding of the structural and mechanistic details of αIIbβ3 behaviour away from the complexity of the platelet machinery. Here, a novel method of αIIbβ3 insertion into Giant Unilamellar Vesicles (GUVs) is described that allows for effective integrin reconstitution unrestricted by lipid composition. αIIbβ3 was inserted into two GUV lipid compositions that seek to better mimic the platelet membrane. First, "nature's own", comprising 32% DOPC, 25% DOPE, 20% CH, 15% SM and 8% DOPS, intended to mimic the platelet cell membrane. Fluorescence Lifetime Correlation Spectroscopy (FLCS) reveals that exposure of the integrin to the activators Mn(2+) or DTT does not influence the diffusion coefficient of αIIbβ3. Similarly, exposure to αIIbβ3's primary ligand fibrinogen (Fg) alone does not affect αIIbβ3's diffusion coefficient. However, addition of Fg with either activator reduces the integrin diffusion coefficient from 2.52 ± 0.29 to μm(2) s(-1) to 1.56 ± 0.26 (Mn(2+)) or 1.49 ± 0.41 μm(2) s(-1) (DTT) which is consistent with aggregation of activated αIIbβ3 induced by fibrinogen binding. The Multichannel Scaler (MCS) trace shows that the integrin-Fg complex diffuses through the confocal volume in clusters. Using the Saffman-Delbrück model as a first approximation, the diffusion coefficient of the complex suggests at least a 20-fold increase in the radius of membrane bound protein, consistent with integrin clustering. Second, αIIbβ3 was also reconstituted into a "raft forming" GUV with well defined liquid disordered (Ld) and liquid ordered (Lo) phases. Using confocal microscopy and lipid partitioning dyes, αIIbβ3 showed an affinity for

  7. Impact of Cu Electrode on Switching Behavior in a Cu/HfO2/Pt Structure and Resultant Cu Ion Diffusion

    NASA Astrophysics Data System (ADS)

    Haemori, Masamitsu; Nagata, Takahiro; Chikyow, Toyohiro

    2009-06-01

    In a newly proposed switching device using polycrystalline HfO2 thin film with ion diffusion path, we have found that a Cu electrode could contribute to improved switching performance. Current-voltage measurements at room temperature revealed clear resistive switching, not accompanied by a forming process, in our Cu/HfO2/Pt structure. The current step difference from one state to the other one was in the order of 103-104, giving a sufficient on/off ratio. Voltage sweep polarity suggested that filamentary Cu paths were formed due to Cu ion diffusion and annihilated at the HfO2/Pt interface at reversed bias. This filament path formation and annihilation was the origin of the switching device performance.

  8. Highly efficient electro-generation of hydrogen peroxide using NCNT/NF/CNT air diffusion electrode for electro-Fenton degradation of p-nitrophenol.

    PubMed

    Tang, Q; Wang, D; Yao, D M; Yang, C W; Sun, Y C

    2016-01-01

    To promote the in situ generation of hydrogen peroxide (H2O2) in electro-Fenton system, a new air diffusion electrode (ADE) was put forward in the present work using N-doped multi-walled carbon nanotubes (NCNT) as the catalyst layer, multi-walled carbon nanotubes (CNT) as the diffusion layer, and nickel foam (NF) as the supporting material, respectively. The catalyst layer in ADE was characterized by transmission electron microscopy and X-ray photoelectron spectroscopy. Then the performances of H2O2 accumulation and p-nitrophenol (p-NP) degradation with the electrode (NCNT/NF/CNT ADE) were investigated. The experimental results showed that H2O2 accumulation on the NCNT/NF/CNT ADE was greatly improved by the presence of N doping, and H2O2 accumulation concentration could reach 307 mg L(-1) after 120 min at the current intensity of 100 mA. Moreover, the NCNT/NF/CNT ADE presented more effective performance on p-NP degradation than the CNT/NF/CNT ADE or the NF ADE. p-NP of initial 50 mg L(-1) could be almost completely removed after 30 min, and the total organic carbon removal efficiency reached 62.61% after 120 min when 0.4 mM Fe(2+) was added into the system. The repeatability test suggested that the stability of the NCNT/NF/CNT ADE was very good. PMID:27054737

  9. Atmospheric air diffuse array-needles dielectric barrier discharge excited by positive, negative, and bipolar nanosecond pulses in large electrode gap

    NASA Astrophysics Data System (ADS)

    Zhang, Li; Yang, De-zheng; Wang, Wen-chun; Liu, Zhi-jie; Wang, Sen; Jiang, Peng-chao; Zhang, Shuai

    2014-09-01

    In this paper, positive, negative, and bipolar nanosecond pulses are employed to generate stable and diffuse discharge plasma using array needles-plate electrode configuration at atmospheric pressure. A comparison study of discharge images, electrical characteristics, optical emission spectra, and plasma vibrational temperature and rotational temperatures in three pulsed polarity discharges is carried on under different discharge conditions. It is found that bipolar pulse is beneficial to the excitation of diffuse dielectric barrier discharge, which can generate a room temperature plasma with more homogeneous and higher discharge intensity compared with unipolar discharges. Under the condition of 6 mm electrode gap distance, 26 kV pulse peak voltage, and 150 Hz pulse repetition rate, the emission intensity of N2 (C3Πu → B3Πg) of the bipolar pulsed discharge is 4 times higher than the unipolar discharge (both positive and negative), while the plasma gas temperature is kept at 300 K, which is about 10-20 K lower than the unipolar discharge plasma.

  10. Lateral Diffusion of Proteins on Supported Lipid Bilayers: Additive Friction of Synaptotagmin 7 C2A–C2B Tandem Domains

    PubMed Central

    2015-01-01

    The synaptotagmin (Syt) family of proteins contains tandem C2 domains, C2A and C2B, which bind membranes in the presence of Ca2+ to trigger vesicle fusion during exocytosis. Despite recent progress, the role and extent of interdomain interactions between C2A and C2B in membrane binding remain unclear. To test whether the two domains interact on a planar lipid bilayer (i.e., experience thermodynamic interdomain contacts), diffusion of fluorescent-tagged C2A, C2B, and C2AB domains from human Syt7 was measured using total internal reflection fluorescence microscopy with single-particle tracking. The C2AB tandem exhibits a lateral diffusion constant approximately half the value of the isolated single domains and does not change when additional residues are engineered into the C2A–C2B linker. This is the expected result if C2A and C2B are separated when membrane-bound; theory predicts that C2AB diffusion would be faster if the two domains were close enough together to have interdomain contact. Stopped-flow measurements of membrane dissociation kinetics further support an absence of interdomain interactions, as dissociation kinetics of the C2AB tandem remain unchanged when rigid or flexible linker extensions are included. Together, the results suggest that the two C2 domains of Syt7 bind independently to planar membranes, in contrast to reported interdomain cooperativity in Syt1. PMID:25437758

  11. Design and Analysis of Power Low-Temperature Polysilicon Lateral Double-Diffusion Metal Oxide Semiconductor Field Effect Transistors with Shielding-Trench Structure

    NASA Astrophysics Data System (ADS)

    Lin, Jyh-Ling; Lin, Cang-Ting

    2013-08-01

    A new polycrystalline silicon (poly-Si) lateral double-diffusion metal oxide semiconductor field-effect transistor power device combining super-lateral-growth technology and shielding-trench oxide structures (STO-LDMOSFET) is introduced. The trench oxide offers a platform for amorphous silicon lateral growth through excimer laser annealing; this not only enables stable control of the crystallization of poly-Si but also promotes the blocking ability of devices. The breakdown voltages of the manufactured devices with and without trench oxide are 460 and 387 V, respectively, increasing by approximately 73 V. The characteristics of poly-Si treated with an excimer laser were obtained by low-temperature poly-Si LDMOSFET (LTPS-LDMOSFET) measurement and simulation. Then, STO-LDMOSFETs were studied by simulation. The results showed that the STO-LDMOSFET with a 150 cm2 V-1 s-1 mobility had a breakdown voltage and a specific on-resistance of approximately 450 V and 16 Ω cm2, respectively, at a 40 µm drift region length.

  12. Shrinkage Behavior and Diffusion in Ni-based Internal Electrodes with Additional Amount and Particle Size of BaTiO3 Additive

    NASA Astrophysics Data System (ADS)

    Kang, Ji-Hun; Joo, Dongwon; Jung, Yeon-Gil; Paik, Ungyu

    2008-02-01

    The effect of additional amount and particle size of BaTiO3 additive on shrinkage behavior and inter-diffusion in Ni-based internal electrodes has been investigated, in order to reduce the large shrinkage mismatch between the internal electrode and the dielectric layer and to control the thermal and/or residual stresses in multilayer ceramic capacitors (MLCCs). Ni powder of 100-500 nm and two kinds of BaTiO3 powders of 100 and 200 nm were used as matrix and additive, respectively. The Ni and BaTiO3 powders were mixed with volume ratios of 95:5, 90:10, 85:15, respectively, and then cold-isostatic pressed. The shrinkage of starting materials and each composite was measured in a range of 700-1300 °C with 150 °C interval in H2/Ar atmosphere, using ASTM standard method. Diffusion phenomena at interface of Ni/BaTiO3 composites with 85:15 and 90:10 volume ratios were investigated using SEM, EDX, and TEM. The particle size affects the shrinkage behavior in relatively low temperatures below 1000 °C, showing a turning point at that temperature. The final shrinkage of composites is matched with that of bulk BaTiO3 of smaller particle size, independent of additional amount of BaTiO3 additive. A reaction layer of about 1000 nm wide is observed at the interface between the Ni and BaTiO3 powders in the composite of 85:15 volume ratio. The quantitative amount of elemental Ni diffused into the BaTiO3 is about 9.7 mass% in the composite of 90:10 volume ratio, without another phase seen in the Ni.

  13. Barriers for lateral diffusion of transferrin receptor in the plasma membrane as characterized by receptor dragging by laser tweezers: fence versus tether

    PubMed Central

    1995-01-01

    Our previous results indicated that the plasma membrane of cultured normal rat kidney fibroblastic cell is compartmentalized for diffusion of receptor molecules, and that long-range diffusion is the result of successive intercompartmental jumps (Sako, Y. and Kusumi, A. 1994. J. Cell Biol. 125:1251-1264). In the present study, we characterized the properties of intercompartmental boundaries by tagging transferrin receptor (TR) with either 210-nm-phi latex or 40-nm-phi colloidal gold particles, and by dragging the particle-TR complexes laterally along the plasma membrane using laser tweezers. Approximately 90% of the TR- particle complexes showed confined-type diffusion with a microscopic diffusion coefficient (Dmicro) of approximately 10(-9) cm2/s and could be dragged past the intercompartmental boundaries in their path by laser tweezers at a trapping force of 0.25 pN for gold-tagged TR and 0.8 pN for latex-tagged TR. At lower dragging forces between 0.05 and 0.1 pN, particle-TR complexes tended to escape from the laser trap at the boundaries, and such escape occurred in both the forward and backward directions of dragging. The average distance dragged was half of the confined distance of TR, which further indicates that particle- TR complexes escape at the compartment boundaries. Since variation in the particle size (40 and 210 nm, the particles are on the extracellular surface of the plasma membrane) hardly affects the diffusion rate and behavior of the particle-TR complexes at the compartment boundaries, and since treatment with cytochalasin D or vinblastin affects the movements of TR (Sako and Kusumi as cited above), argument has been advanced that the boundaries are present in the cytoplasmic domain. Rebound of the particle-TR complexes when they escape from the laser tweezers at the compartment boundaries suggests that the boundaries are elastic structures. These results are consistent with the proposal that the compartment boundaries consist of membrane

  14. Reduced Integrity of Right Lateralized White Matter in Patients with Primary Insomnia: A Diffusion-Tensor Imaging Study.

    PubMed

    Li, Shumei; Tian, Junzhang; Bauer, Andreas; Huang, Ruiwang; Wen, Hua; Li, Meng; Wang, Tianyue; Xia, Likun; Jiang, Guihua

    2016-08-01

    Purpose To analyze the integrity of white matter (WM) tracts in primary insomnia patients and provide better characterization of abnormal WM integrity and its relationship with disease duration and clinical features of primary insomnia. Materials and Methods This prospective study was approved by the ethics committee of the Guangdong No. 2 Provincial People's Hospital. Tract-based spatial statistics were used to compare changes in diffusion parameters of WM tracts from 23 primary insomnia patients and 30 healthy control (HC) participants, and the accuracy of these changes in distinguishing insomnia patients from HC participants was evaluated. Voxel-wise statistics across subjects was performed by using a 5000-permutation set with family-wise error correction (family-wise error, P < .05). Multiple regressions were used to analyze the associations between the abnormal fractional anisotropy (FA) in WM with disease duration, Pittsburgh Sleep Quality Index, insomnia severity index, self-rating anxiety scale, and the self-rating depression scale in primary insomnia. Characteristics for abnormal WM were also investigated in tract-level analyses. Results Primary insomnia patients had lower FA values mainly in the right anterior limb of the internal capsule, right posterior limb of the internal capsule, right anterior corona radiata, right superior corona radiata, right superior longitudinal fasciculus, body of the corpus callosum, and right thalamus (P < .05, family-wise error correction). The receiver operating characteristic areas for the seven regions were acceptable (range, 0.60-0.74; 60%-74%). Multiple regression models showed abnormal FA values in the thalamus and body corpus callosum were associated with the disease duration, self-rating depression scale, and Pittsburgh Sleep Quality Index scores. Tract-level analysis suggested that the reduced FA values might be related to greater radial diffusivity. Conclusion This study showed that WM tracts related to regulation

  15. Bifunctional catalytic electrode

    NASA Technical Reports Server (NTRS)

    Cisar, Alan (Inventor); Murphy, Oliver J. (Inventor); Clarke, Eric (Inventor)

    2005-01-01

    The present invention relates to an oxygen electrode for a unitized regenerative hydrogen-oxygen fuel cell and the unitized regenerative fuel cell having the oxygen electrode. The oxygen electrode contains components electrocatalytically active for the evolution of oxygen from water and the reduction of oxygen to water, and has a structure that supports the flow of both water and gases between the catalytically active surface and a flow field or electrode chamber for bulk flow of the fluids. The electrode has an electrocatalyst layer and a diffusion backing layer interspersed with hydrophilic and hydrophobic regions. The diffusion backing layer consists of a metal core having gas diffusion structures bonded to the metal core.

  16. Diagnosis of lateral pelvic lymph node metastasis of T1 lower rectal cancer using diffusion-weighted magnetic resonance imaging: A case report with lateral pelvic lymph node dissection of lower rectal cancer

    PubMed Central

    OGAWA, SHIMPEI; ITABASHI, MICHIO; HIROSAWA, TOMOICHIRO; HASHIMOTO, TAKUZO; BAMBA, YOSHIKO; OKAMOTO, TAKAHIRO

    2016-01-01

    The present study presented a 35-year-old female patient in whom fecal occult blood was detected in a medical check-up. Colonoscopy revealed a superficial elevated-type tumor with central depression in the lower rectum. The tumor was diagnosed as T1 deep invasive cancer. No swollen lymph nodes or distant metastasis were found on computed tomography or [18F]-fluorodeoxyglucose-positron emission tomography with computed tomography. However, a swollen right lateral pelvic lymph node (LPLN; short axis 4 mm) was revealed on magnetic resonance imaging (MRI). This lymph node exhibited high intensity on diffusion-weighted imaging (DWI), suggesting metastasis. Low anterior resection, regional lymph node dissection and right LPLN dissection (LPLD) were performed. Histological analysis revealed metastasis in the right LPLN, as suggested by the high DWI intensity. The indication for LPLD in the current Japanese guidelines is based on the tumor location and depth of invasion (≥T3), however, not on the status of LPLN metastasis in pre-operative evaluation. The present case was cT1, which is not included in this indication. DWI is sensitive for the diagnosis of lymph node metastasis of colorectal cancer, although inflammation-induced swelling of lymph nodes in advanced rectal cancer may cause a false-positive result, which is uncommon in T1 cases. Therefore, an LPLN with a high intensity DWI signal in T1 cases is likely to be metastasis-positive. Pre-operative DWI-MRI may be useful for identifying LPLN metastasis when planning the treatment strategy in these cases. The present study suggested reinvestigation of the indication for LPLD with inclusion of LPLN status on pre-operative imaging. PMID:27123286

  17. Boron diffusion in magnetic tunnel junctions with MgO (001) barriers and CoFeB electrodes

    SciTech Connect

    Kurt, H.; Rode, K.; Oguz, K.; Coey, J. M. D.; Boese, M.; Faulkner, C. C.

    2010-06-28

    Boron diffusion out of the CoFeB layers in model systems with thick CoFeB and MgO layers grown by radiofrequency sputtering or electron-beam evaporation and in MgO-based magnetic tunnel junctions (MTJs) is probed after annealing by x-ray photoemission spectroscopy (XPS) and electron energy loss spectroscopy. Successive interfaces are exposed by ion milling the stacks, layer by layer, in the XPS system. Despite the presence of thick CoFeB and a high annealing temperature of 400 deg. C, we found no boron in the MgO or at the MgO/CoFe interfaces. Similar results are also obtained in the MTJs.

  18. Enhanced thermal stability of a sputtered titanium-nitride film as a diffusion barrier for capacitor-bottom electrodes

    NASA Astrophysics Data System (ADS)

    Yoon, Dong-Soo; Roh, Jae Sung; Lee, Sung-Man; Baik, Hong Koo

    2003-08-01

    The effect of a thin RuOx layer formed on the Ru/TiN/doped poly-Si/Si stack structure was compared with that on the RuOx/TiN/doped poly-Si/Si stack structure over the post-deposition annealing temperature ranges of 450-600°C. The Ru/TiN/poly-Si/Si contact system exhibited linear behavior at forward bias with a small increase in the total resistance up to 600°C. The RuOx/TiN/poly-Si/Si contact system exhibited nonlinear characteristics under forward bias at 450°C, which is attributed to no formation of a thin RuOx layer at the RuOx surface and porous-amorphous microstructure. In the former case, the addition of oxygen at the surface layer of the Ru film by pre-annealing leads to the formation of a thin RuOx layer and chemically strong Ru-O bonds. This results from the retardation of oxygen diffusion caused by the discontinuity of diffusion paths. In particular, the RuOx layer in a nonstoichiometric state is changed to the RuO2-crystalline phase in a stoichiometric state after post-deposition annealing; this phase can act as an oxygen-capture layer. Therefore, it appears that the electrical properties of the Ru/TiN/poly-Si/Si contact system are better than those of the RuOx/TiN/poly-Si/Si contact system.

  19. Fundamental principals of battery design: Porous electrodes

    NASA Astrophysics Data System (ADS)

    Qu, Deyang

    2014-06-01

    The fundamental aspects of a porous electrode from electrochemistry and material chemistry standpoints are discussed in the light of battery engineering designs. For example, the ionic diffusion, the electrode-electrolyte interface, interfacial charge transfer and electrode catalytic processes are discussed. The discussion of such fundamental electrochemical aspects is in conjunction with the design of batteries, e.g. the electrochemical assessable surface area for porous electrode, electrode catalytic reactions. The porous electrodes used as a gas diffusion electrode and the electrode in a supercapacitor are discussed to demonstrate the application of electrochemical principals in battery design.

  20. The back-diffusion effect of air on the discharge characteristics of atmospheric-pressure radio-frequency glow discharges using bare metal electrodes

    NASA Astrophysics Data System (ADS)

    Sun, Wen-Ting; Liang, Tian-Ran; Wang, Hua-Bo; Li, He-Ping; Bao, Cheng-Yu

    2007-05-01

    Radio-frequency (RF), atmospheric-pressure glow discharge (APGD) plasmas using bare metal electrodes have promising prospects in the fields of plasma-aided etching, deposition, surface treatment, disinfection, sterilization, etc. In this paper, the discharge characteristics, including the breakdown voltage and the discharge voltage for sustaining a stable and uniform α mode discharge of the RF APGD plasmas are presented. The experiments are conducted by placing the home-made planar-type plasma generator in ambient and in a vacuum chamber, respectively, with helium as the primary plasma-forming gas. When the discharge processes occur in ambient, particularly for the lower plasma-working gas flow rates, the experimental measurements show that it is the back-diffusion effect of air in atmosphere, instead of the flow rate of the gas, that results in the obvious decrease in the breakdown voltage with increasing plasma-working gas flow rate. Further studies on the discharge characteristics, e.g. the luminous structures, the concentrations and distributions of chemically active species in plasmas, with different plasma-working gases or gas mixtures need to be conducted in future work.

  1. Electrodes for microfluidic applications

    DOEpatents

    Crocker, Robert W.; Harnett, Cindy K.; Rognlien, Judith L.

    2006-08-22

    An electrode device for high pressure applications. These electrodes, designed to withstand pressure of greater than 10,000 psi, are adapted for use in microfluidic devices that employ electrokinetic or electrophoretic flow. The electrode is composed, generally, of an outer electrically insulating tubular body having a porous ceramic frit material disposed in one end of the outer body. The pores of the porous ceramic material are filled with an ion conductive polymer resin. A conductive material situated on the upper surface of the porous ceramic frit material and, thus isolated from direct contact with the electrolyte, forms a gas diffusion electrode. A metal current collector, in contact with the gas diffusion electrode, provides connection to a voltage source.

  2. Positive electrodes of nickel-cadmium batteries

    NASA Technical Reports Server (NTRS)

    Wabner, D. W.; Kandler, L.; Krienke, W.

    1985-01-01

    Ni hydroxide sintered electrodes which are filled electrochemically are superior to chemically treated electrodes. In the electrochemical process, the hydroxide grows on the Ni grains and possesses a well-defined porous structure. Diffusion and conducting mechanisms are therefore facilitated.

  3. Multifunctional reference electrode

    DOEpatents

    Redey, L.; Vissers, D.R.

    1981-12-30

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

  4. Multifunctional reference electrode

    DOEpatents

    Redey, Laszlo; Vissers, Donald R.

    1983-01-01

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

  5. Atomic Insight into the Lithium Storage and Diffusion Mechanism of SiO2/Al2O3 Electrodes of Lithium Ion Batteries: ReaxFF Reactive Force Field Modeling.

    PubMed

    Ostadhossein, Alireza; Kim, Sung-Yup; Cubuk, Ekin D; Qi, Yue; van Duin, Adri C T

    2016-04-01

    Atomically deposited layers of SiO2 and Al2O3 have been recognized as promising coating materials to buffer the volumetric expansion and capacity retention upon the chemo-mechanical cycling of the nanostructured silicon- (Si-) based electrodes. Furthermore, silica (SiO2) is known as a promising candidate for the anode of next-generation lithium ion batteries (LIBs) due to its superior specific charge capacity and low discharge potential similar to Si anodes. In order to describe Li-transport in mixed silica/alumina/silicon systems we developed a ReaxFF potential for Li-Si-O-Al interactions. Using this potential, a series of hybrid grand canonical Monte Carlo (GCMC) and molecular dynamic (MD) simulations were carried out to probe the lithiation behavior of silica structures. The Li transport through both crystalline and amorphous silica was evaluated using the newly optimized force field. The anisotropic diffusivity of Li in crystalline silica cases is demonstrated. The ReaxFF diffusion study also verifies the transferability of the new force field from crystalline to amorphous phases. Our simulation results indicates the capability of the developed force field to examine the energetics and kinetics of lithiation as well as Li transportation within the crystalline/amorphous silica and alumina phases and provide a fundamental understanding on the lithiation reactions involved in the Si electrodes covered by silica/alumina coating layers. PMID:26978039

  6. Hydrogen nanobubble at normal hydrogen electrode

    NASA Astrophysics Data System (ADS)

    Nakabayashi, S.; Shinozaki, R.; Senda, Y.; Yoshikawa, H. Y.

    2013-05-01

    Electrochemically formed hydrogen nanobubbles at a platinum rotating disk electrode (RDE) were detected by re-oxidation charge. The dissolution time course of the hydrogen nanobubbles was measured by AFM tapping topography under open-circuit conditions at stationary platinum and gold single-crystal electrodes. The bubble dissolution at platinum was much faster than that at gold because two types of diffusion, bulk and surface diffusion, proceeded at the platinum surface, whereas surface diffusion was prohibited at the gold electrode. These findings indicated that the electrochemical reaction of normal hydrogen electrode partly proceeded heterogeneously on the three-phase boundary around the hydrogen nanobubble.

  7. Origin, Diffusion, and Differentiation of Y-Chromosome Haplogroups E and J: Inferences on the Neolithization of Europe and Later Migratory Events in the Mediterranean Area

    PubMed Central

    Semino, Ornella; Magri, Chiara; Benuzzi, Giorgia; Lin, Alice A.; Al-Zahery, Nadia; Battaglia, Vincenza; Maccioni, Liliana; Triantaphyllidis, Costas; Shen, Peidong; Oefner, Peter J.; Zhivotovsky, Lev A.; King, Roy; Torroni, Antonio; Cavalli-Sforza, L. Luca; Underhill, Peter A.; Santachiara-Benerecetti, A. Silvana

    2004-01-01

    The phylogeography of Y-chromosome haplogroups E (Hg E) and J (Hg J) was investigated in >2,400 subjects from 29 populations, mainly from Europe and the Mediterranean area but also from Africa and Asia. The observed 501 Hg E and 445 Hg J samples were subtyped using 36 binary markers and eight microsatellite loci. Spatial patterns reveal that (1) the two sister clades, J-M267 and J-M172, are distributed differentially within the Near East, North Africa, and Europe; (2) J-M267 was spread by two temporally distinct migratory episodes, the most recent one probably associated with the diffusion of Arab people; (3) E-M81 is typical of Berbers, and its presence in Iberia and Sicily is due to recent gene flow from North Africa; (4) J-M172(xM12) distribution is consistent with a Levantine/Anatolian dispersal route to southeastern Europe and may reflect the spread of Anatolian farmers; and (5) E-M78 (for which microsatellite data suggest an eastern African origin) and, to a lesser extent, J-M12(M102) lineages would trace the subsequent diffusion of people from the southern Balkans to the west. A 7%–22% contribution of Y chromosomes from Greece to southern Italy was estimated by admixture analysis. PMID:15069642

  8. Physical description of the impregnation mechanism of dye molecules in contact with porous electrodes

    NASA Astrophysics Data System (ADS)

    Shahzad, N.; Alexe-Ionescu, A. L.; Tresso, E.; Barbero, G.

    2013-05-01

    We propose and discuss two models that take into account the decreasing of the bulk density of dyes molecules in contact with a porous electrode. We show that the models based on the standard adsorption phenomenon have to be considered just as fitting models, of limited physical significance. A more physical model has to take into account the diffusion of dye molecules into the channels present in the porous electrode and also the adsorption of dye molecules on the lateral surfaces of these channels. The agreement between the theoretical prediction of such a model and the experimental data is reasonably good.

  9. Electrode compositions

    DOEpatents

    Block, Jacob; Fan, Xiyun

    1998-01-01

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

  10. Electrode compositions

    DOEpatents

    Block, J.; Fan, X.

    1998-10-27

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

  11. Magnetohydrodynamic electrode

    DOEpatents

    Boquist, Carl W.; Marchant, David D.

    1978-01-01

    A ceramic-metal composite suitable for use in a high-temperature environment consists of a refractory ceramic matrix containing 10 to 50 volume percent of a continuous high-temperature metal reinforcement. In a specific application of the composite, as an electrode in a magnetohydrodynamic generator, the one surface of the electrode which contacts the MHD fluid may have a layer of varying thickness of nonreinforced refractory ceramic for electrode temperature control. The side walls of the electrode may be coated with a refractory ceramic insulator. Also described is an electrode-insulator system for a MHD channel.

  12. Working Electrodes

    NASA Astrophysics Data System (ADS)

    Komorsky-Lovrić, Šebojka

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

  13. High temperature behavior of multi-region direct current current-voltage spectroscopy and relationship with shallow-trench-isolation-based high-voltage laterally diffused metal-oxide-semiconductor field-effect-transistors reliability

    NASA Astrophysics Data System (ADS)

    He, Yandong; Zhang, Ganggang; Zhang, Xing

    2014-01-01

    With the process compatibility with the mainstream standard complementary metal-oxide-semiconductor (CMOS), shallow trench isolation (STI) based laterally diffused metal-oxide-semiconductor (LDMOS) devices have become popular for its better tradeoff between breakdown voltage and performance, especially for smart power applications. A multi-region direct current current-voltage (MR-DCIV) technique with spectroscopic features was demonstrated to map the interface state generation in the channel, accumulation and STI drift regions. High temperature behavior of MR-DCIV spectroscopy was analyzed and a physical model was verified. Degradation of STI-based LDMOS transistors under high temperature reverse bias (HTRB) stress is experimentally studied by MR-DCIV spectroscopy. The impact of interface state location on device electrical characteristics was investigated. Our results show that the major contribution to HTRB degradation, in term of the on-resistance degradation, was attributed to interface state generation under STI drift region.

  14. Diffusion barriers

    NASA Technical Reports Server (NTRS)

    Nicolet, M. A.

    1983-01-01

    The choice of the metallic film for the contact to a semiconductor device is discussed. One way to try to stabilize a contact is by interposing a thin film of a material that has low diffusivity for the atoms in question. This thin film application is known as a diffusion barrier. Three types of barriers can be distinguished. The stuffed barrier derives its low atomic diffusivity to impurities that concentrate along the extended defects of a polycrystalline layer. Sacrificial barriers exploit the fact that some (elemental) thin films react in a laterally uniform and reproducible fashion. Sacrificial barriers have the advantage that the point of their failure is predictable. Passive barriers are those most closely approximating an ideal barrier. The most-studied case is that of sputtered TiN films. Stuffed barriers may be viewed as passive barriers whose low diffusivity material extends along the defects of the polycrystalline host.

  15. Measurement of the lateral diffusion of dipalmitoylphosphatidylcholine adsorbed on silica beads in the absence and presence of melittin: a 31P two-dimensional exchange solid-state NMR study.

    PubMed Central

    Picard, F; Paquet, M J; Dufourc, E J; Auger, M

    1998-01-01

    31P two-dimensional exchange solid-state NMR spectroscopy was used to measure the lateral diffusion, D(L), in the fluid phase of dipalmitoylphosphatidylcholine (DPPC) in the presence and absence of melittin. The use of a spherical solid support with a radius of 320 +/- 20 nm, on which lipids and peptides are adsorbed together, and a novel way of analyzing the two-dimensional exchange patterns afforded a narrow distribution of D(L) centered at a value of (8.8 +/- 0.5) x 10(-8) cm2/s for the pure lipid system and a large distribution of D(L) spanning 1 x 10(-8) to 10 x 10(-8) cm2/s for the lipids in the presence of melittin. In addition, the determination of D(L) for nonsupported DPPC multilamellar vesicles (MLVs) suggests that the support does not slow down the lipid diffusion and that the radii of the bilayers vary from 300 to 800 nm. Finally, the DPPC-melittin complex is stabilized at the surface of the silica beads in the gel phase, opening the way to further study of the interaction between melittin and DPPC. PMID:9533697

  16. Liquid electrode

    DOEpatents

    Ekechukwu, Amy A.

    1994-01-01

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

  17. Lifetimes of Electrodes for AMTEC Cells

    NASA Technical Reports Server (NTRS)

    Ryan, M. A.; Kisor, A.; Williams, R F.; Jeffries-Nakamura, B.; O'Connor, D.

    1994-01-01

    The lifetime of an AMTEC electrode depends on the rate of grain growth, which in turn depends on the surface self-diffusion coefficient of the electrode material under AMTEC operating conditions. Grain growth rates for molybdenum and platinum-tungsten alloy electrodes have been determined, and have been used to predict operating lifetimes of AMTEC electrodes. For lifetimes of 10 years of more, Mo may be used in AMTEC cells only at operating temperatures under 1100 K. Pt(sub 2.5)W electrodes may be used at much higher temperatures, up to 1300 K.

  18. Morphology Effect of Vertical Graphene on the High Performance of Supercapacitor Electrode.

    PubMed

    Zhang, Yu; Zou, Qionghui; Hsu, Hua Shao; Raina, Supil; Xu, Yuxi; Kang, Joyce B; Chen, Jun; Deng, Shaozhi; Xu, Ningsheng; Kang, Weng P

    2016-03-23

    Graphene and its composites are widely investigated as supercapacitor electrodes due to their large specific surface area. However, the severe aggregation and disordered alignment of graphene sheets hamper the maximum utilization of its surface area. Here we report an optimized structure for supercapacitor electrode, i.e., the vertical graphene sheets, which have a vertical structure and open architecture for ion transport pathway. The effect of morphology and orientation of vertical graphene on the performance of supercapacitor is examined using a combination of model calculation and experimental study. Both results consistently demonstrate that the vertical graphene electrode has a much superior performance than that of lateral graphene electrode. Typically, the areal capacitances of a vertical graphene electrode reach 8.4 mF/cm(2) at scan rate of 100 mV/s; this is about 38% higher than that of a lateral graphene electrode and about 6 times higher than that of graphite paper. To further improve its performance, a MnO2 nanoflake layer is coated on the surface of graphene to provide a high pseudocapacitive contribution to the overall areal capacitance which increases to 500 mF/cm(2) at scan rate of 5 mV/s. The reasons for these significant improvements are studied in detail and are attributed to the fast ion diffusion and enhanced charge storage capacity. The microscopic manipulation of graphene electrode configuration could greatly improve its specific capacitance, and furthermore, boost the energy density of supercapacitor. Our results demonstrate that the vertical graphene electrode is more efficient and practical for the high performance energy storage device with high power and energy densities. PMID:26927820

  19. Liquid electrode

    DOEpatents

    Ekechukwu, A.A.

    1994-07-05

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

  20. Graphene based nanocomposite hybrid electrodes for supercapacitors

    NASA Astrophysics Data System (ADS)

    Aphale, Ashish N.

    There is an unmet need to develop high performance energy storage systems (ESS), capable of storing energy from both renewable and non-renewable sources to meet the current energy crisis and depletion of non-renewable sources. Amongst many available ESS, supercapacitors (ECs) are the most promising because they exhibit a high charge/discharge rate and power density, along with a long cycle life. The possibility of exploring the use of atomically thin carbon allotropes like graphene, carbon nanotubes (CNTs) and electrically conducting polymers (ECPs) such as polypyrrole (PPy) has been studied as a high performance conducting electrodes in supercapacitor application. A novel templated sustainable nanocomposite electrode has been fabricated using cellulose extracted from Cladophora c. aegagropila algae as component of the assembled supercapacitor device which later has been transitioned to a unique template-less freestanding nanocomposite supercapacitor electrode. The specific capacitance of polypyrrole-graphene-cellulose nanocomposite as calculated from cyclic voltammetry curve is 91.5 F g -1 at the scan rate 50 m Vs-1 in the presence of 1M NaCl electrolyte. The open circuit voltage of the device with polypyrrole -graphene-cellulose electrode was found to be around 225 m V and that of the polypyrrole -cellulose device is only 53 m V without the presence of graphene in the nanocomposite electrode. Understanding the fundamentals by fabricating template nanocomposite electrode, it led to fabricate a unique nanocomposite template-less freestanding film which comprises of polypyrrole-graphene-CNT hybrid. Various experiments have been performed using different electrolytes such ascorbic acid, sodium sulfate and sulfuric acid in different scan rates. The specific capacitance of polypyrrole-graphene-CNT nanocomposite with 0.1 wt% of graphene-CNT, as calculated from cyclic voltammetry curve is 450 F g-1 at the scan rate 5 m V s-1. For the first time a nanofibrous membrane has

  1. Hot-carrier-induced linear drain current and threshold voltage degradation for thin layer silicon-on-insulator field P-channel lateral double-diffused metal-oxide-semiconductor

    SciTech Connect

    Zhou, Xin; Qiao, Ming; He, Yitao; Li, Zhaoji; Zhang, Bo

    2015-11-16

    Hot-carrier-induced linear drain current (I{sub dlin}) and threshold voltage (V{sub th}) degradations for the thin layer SOI field p-channel lateral double-diffused MOS (pLDMOS) are investigated. Two competition degradation mechanisms are revealed and the hot-carrier conductance modulation model is proposed. In the channel, hot-hole injection induced positive oxide trapped charge and interface trap gives rise to the V{sub th} increasing and the channel conductance (G{sub ch}) decreasing, then reduces I{sub dlin}. In the p-drift region, hot-electron injection induced negative oxide trapped charge enhances the conductance of drift doping resistance (G{sub d}), and then increases I{sub dlin}. Consequently, the eventual I{sub dlin} degradation is controlled by the competition of the two mechanisms due to conductance modulation in the both regions. Based on the model, it is explained that the measured I{sub dlin} anomalously increases while the V{sub th} is increasing with power law. The thin layer field pLDMOS exhibits more severe V{sub th} instability compared with thick SOI layer structure; as a result, it should be seriously evaluated in actual application in switching circuit.

  2. Modeling of a triple reduced surface field silicon-on-insulator lateral double-diffused metal-oxide-semiconductor field-effect transistor with low on-state resistance

    NASA Astrophysics Data System (ADS)

    Yu-Ru, Wang; Yi-He, Liu; Zhao-Jiang, Lin; Dong, Fang; Cheng-Zhou, Li; Ming, Qiao; Bo, Zhang

    2016-02-01

    An analytical model for a novel triple reduced surface field (RESURF) silicon-on-insulator (SOI) lateral double-diffused metal-oxide-semiconductor (LDMOS) field effect transistor with n-type top (N-top) layer, which can obtain a low on-state resistance, is proposed in this paper. The analytical model for surface potential and electric field distributions of the novel triple RESURF SOI LDMOS is presented by solving the two-dimensional (2D) Poisson’s equation, which can also be applied to single, double and conventional triple RESURF SOI structures. The breakdown voltage (BV) is formulized to quantify the breakdown characteristic. Besides, the optimal integrated charge of N-top layer (Qntop) is derived, which can give guidance for doping the N-top layer. All the analytical results are well verified by numerical simulation results, showing the validity of the presented model. Hence, the proposed model can be a good tool for the device designers to provide accurate first-order design schemes and physical insights into the high voltage triple RESURF SOI device with N-top layer. Project supported by the National Natural Science Foundation of China (Grant No. 61376080), the Natural Science Foundation of Guangdong Province, China (Grant No. 2014A030313736), and the Fundamental Research Funds for the Central Universities, China (Grant No. ZYGX2013J030).

  3. Investigation of Hot Carrier Degradation in Shallow-Trench-Isolation-Based High-Voltage Laterally Diffused Metal-Oxide-Semiconductor Field-Effect Transistors by a Novel Direct Current Current-Voltage Technique

    NASA Astrophysics Data System (ADS)

    He, Yandong; Zhang, Ganggang

    2012-04-01

    Shallow trench isolation (STI) based laterally diffused metal-oxide-semiconductor (LDMOS) devices have become popular with its better tradeoff between breakdown voltage and on-resistance and its compatibility with the standard complementary metal-oxide-semiconductor (CMOS) process. A novel direct current current-voltage (DCIV) technique demonstrated with multiple sharp peak signals is proposed to characterize interface state generation in the channel and in the STI drift regions separately. Degradation of STI-based LDMOS transistors in various hot-carrier stress modes is investigated experimentally by proposed technique. A two-dimensional numerical device simulation is performed to obtain insight into the proposed technique and device degradation characteristics under hot-carrier stress conditions. The impact of interface state location on device electrical characteristics is analyzed from measurement and simulation. Our results show that the maximum Isub stress becomes the worst hot-carrier degradation mode in term of the on-resistance degradation, which is attributed to interface state generation under STI drift region.

  4. Lateral conduction infrared photodetector

    DOEpatents

    Kim, Jin K.; Carroll, Malcolm S.

    2011-09-20

    A photodetector for detecting infrared light in a wavelength range of 3-25 .mu.m is disclosed. The photodetector has a mesa structure formed from semiconductor layers which include a type-II superlattice formed of alternating layers of InAs and In.sub.xGa.sub.1-xSb with 0.ltoreq.x.ltoreq.0.5. Impurity doped regions are formed on sidewalls of the mesa structure to provide for a lateral conduction of photo-generated carriers which can provide an increased carrier mobility and a reduced surface recombination. An optional bias electrode can be used in the photodetector to control and vary a cut-off wavelength or a depletion width therein. The photodetector can be formed as a single-color or multi-color device, and can also be used to form a focal plane array which is compatible with conventional read-out integrated circuits.

  5. Cermet electrode

    DOEpatents

    Maskalick, Nicholas J.

    1988-08-30

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

  6. Magnetohydrodynamic electrode

    DOEpatents

    Marchant, David D.; Killpatrick, Don H.

    1978-01-01

    An electrode capable of withstanding high temperatures and suitable for use as a current collector in the channel of a magnetohydrodynamic (MHD) generator consists of a sintered powdered metal base portion, the upper surface of the base being coated with a first layer of nickel aluminide, an intermediate layer of a mixture of nickel aluminide - refractory ceramic on the first layer and a third or outer layer of a refractory ceramic material on the intermediate layer. The sintered powdered metal base resists spalling by the ceramic coatings and permits greater electrode compliance to thermal shock. The density of the powdered metal base can be varied to allow optimization of the thermal conductivity of the electrode and prevent excess heat loss from the channel.

  7. Photoelectrochemical electrodes

    NASA Technical Reports Server (NTRS)

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

    1983-01-01

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

  8. Graphene-based battery electrodes having continuous flow paths

    DOEpatents

    Zhang, Jiguang; Xiao, Jie; Liu, Jun; Xu, Wu; Li, Xiaolin; Wang, Deyu

    2014-05-24

    Some batteries can exhibit greatly improved performance by utilizing electrodes having randomly arranged graphene nanosheets forming a network of channels defining continuous flow paths through the electrode. The network of channels can provide a diffusion pathway for the liquid electrolyte and/or for reactant gases. Metal-air batteries can benefit from such electrodes. In particular Li-air batteries show extremely high capacities, wherein the network of channels allow oxygen to diffuse through the electrode and mesopores in the electrode can store discharge products.

  9. Impedance spectroscopy of bacterial membranes: Co-enzyme Q diffusion in a finite diffusion layer

    PubMed Central

    Jeuken, Lars J.C.; Weiss, Sophie A; Henderson, Peter J.F.; Evans, Stephen D.; Bushby, Richard J.

    2013-01-01

    The inner membrane of Escherichia coli, over-expressing an ubiquinol oxidase, cytochrome bo3 (cbo3), was tethered in a planar configuration to a gold electrode. Electron transfer to cbo3 was achieved via native ubiquinol-8 or added ubiquinol-10 and impedance spectroscopy was used to characterise the diffusion properties of the ubiquinol/ubiquinone in the tethered membrane system. Spectra were obtained at varying DC potentials covering the potential window in which the voltammetric catalytic wave of cbo3 is visible. These spectra were compared to those obtained after addition of a potent inhibitor of cbo3, cyanide, and the difference in impedance was analysed using a derived equivalent circuit, which is similar to that of Open Finite-Length Diffusion (OFLD) or the finite Warburg circuit, but with the boundary conditions modified to account for the fact that ubiquinol reoxidation is limited by enzyme activity. Analysis of the impedance spectra of the tethered membrane system gave kinetic parameters that are consistent with values obtained using cyclic voltammetry. Importantly, the diffusion rate of ubiquinone (10−13 - 10−12 cm2/s) was found to be orders of magnitude lower than accepted values for lateral diffusion (10−8 - 10−7 cm2/s). It is hypothesised that this result represent perpendicular diffusion of quinone across the membrane, corresponding to a ‘flip’ time between 0.05 and 1 s. PMID:19551979

  10. Carbon nanotube macrofilm-based nanocomposite electrodes for energy applications

    NASA Astrophysics Data System (ADS)

    Cao, Zeyuan

    , Ni)) with CNT macofilms as high performance anodes for rechargeable lithium-ion batteries and as catalysts for oxygen reduction/evolution (ORR/OER). All MxOy-CNT macrofilm nanocomposites inherit the high specific capacity and cycling stability for lithium-ion batteries. NiO/SWNT and Co3O4/SWNT (200 °C) have their specialized high catalytic activities for ORR and OER in alkaline solutions, respectively. NiO/SWNT also exhibits an excellent electrochemical performance in asymmetric supercapacitors with a high power and energy density. Experimental measurements on electrochemical kinetics such as potentiostatic/galvanostatic intermittent titration techniques (PITT/GITT) are depended to understand the underlying improved Li+ diffusion behavior of nanocomposites. Critical effects of the film thickness have been identified. The CNT macrofilm with a thickness that is comparable to the characteristic diffusion length of 300~500 nm enables the nanocomposite with the highest Li+ chemical diffusion coefficient and thus an optimal electrochemical performance. The adhesive characteristic of CNT macrofilms is noticed for the first time after fragmentation by ultrasound that origins from irregular structures of laterally 2-D distributed CNT segments. The fragmented CNT macrofilms (FCNT) as "bifunctional" adhesive conductors promote a general approach to construct nanocomposite electrodes with both cathode and anode materials for lithium-ion batteries. An in-situ tribology method combining the wear track imaging and force measurement is employed to evaluate the adhesion strength of the adhesive FCNT conductors. The results show that the FCNT macrofilms have a higher adhesion strength than the conventional polymer binder polyvinylidene fluoride (PVDF). It is confirmed that the fabricated nanocomposite electrodes exhibit high rate and retention capabilities, superior to the electrodes using PVDF and carbon black. Thus, FCNT is recognized to be a competent substitute for polymer

  11. Solid Electrolyte Interphase Growth and Capacity Loss in Silicon Electrodes.

    PubMed

    Michan, Alison L; Divitini, Giorgio; Pell, Andrew J; Leskes, Michal; Ducati, Caterina; Grey, Clare P

    2016-06-29

    The solid electrolyte interphase (SEI) of the high capacity anode material Si is monitored over multiple electrochemical cycles by (7)Li, (19)F, and (13)C solid-state nuclear magnetic resonance spectroscopies, with the organics dominating the SEI. Homonuclear correlation experiments are used to identify the organic fragments -OCH2CH2O-, -OCH2CH2-, -OCH2CH3, and -CH2CH3 contained in both oligomeric species and lithium semicarbonates ROCO2Li, RCO2Li. The SEI growth is correlated with increasing electrode tortuosity by using focused ion beam and scanning electron microscopy. A two-stage model for lithiation capacity loss is developed: initially, the lithiation capacity steadily decreases, Li(+) is irreversibly consumed at a steady rate, and pronounced SEI growth is seen. Later, below 50% of the initial lithiation capacity, less Si is (de)lithiated resulting in less volume expansion and contraction; the rate of Li(+) being irreversibly consumed declines, and the Si SEI thickness stabilizes. The decreasing lithiation capacity is primarily attributed to kinetics, the increased electrode tortuousity severely limiting Li(+) ion diffusion through the bulk of the electrode. The resulting changes in the lithiation processes seen in the electrochemical capacity curves are ascribed to non-uniform lithiation, the reaction commencing near the separator/on the surface of the particles. PMID:27232540

  12. Multiscale porous fuel cell electrodes

    NASA Astrophysics Data System (ADS)

    Wen, Hao

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

  13. Submersed sensing electrode used in fuel-cell type hydrogen detector

    NASA Technical Reports Server (NTRS)

    Niedrach, L. W.; Rudek, F. P.; Rutkoneski, M. D.

    1971-01-01

    Electrode has silicone rubber diffusion barrier with fixed permeation constant for hydrogen. Barrier controls flow of hydrogen to anode and Faraday relationship establishes upper limit for current through cell. Electrode fabrication is described.

  14. sensor electrodes

    NASA Astrophysics Data System (ADS)

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

    2014-11-01

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

  15. Iron serves as diffusion barrier in thermally regenerative galvanic cell

    NASA Technical Reports Server (NTRS)

    Crouthamel, C. E.

    1967-01-01

    Pure iron or iron-coated diaphragm provides a hydrogen diffusion electrode for a thermally regenerative galvanic cell. It allows the gas to diffuse through its interatomic spaces and resists the corrosive action of the cell environment.

  16. Lateral orientation (image)

    MedlinePlus

    A lateral orientation is a position away from the midline of the body. For instance, the arms are lateral to the ... ears are lateral to the head. A medial orientation is a position toward the midline of the ...

  17. Subcutaneous electrode structure

    NASA Technical Reports Server (NTRS)

    Lund, G. F. (Inventor)

    1980-01-01

    A subcutaneous electrode structure suitable for a chronic implant and for taking a low noise electrocardiogram of an active animal, comprises a thin inflexible, smooth disc of stainless steel having a diameter as of 5 to 30 mm, which is sutured in place to the animal being monitored. The disc electrode includes a radially directed slot extending in from the periphery of the disc for approximately 1/3 of the diameter. Electrical connection is made to the disc by means of a flexible lead wire that extends longitudinally of the slot and is woven through apertures in the disc and held at the terminal end by means of a spot welded tab. Within the slot, an electrically insulative sleeve, such as silicone rubber, is placed over the wire. The wire with the sleeve mounted thereon is captured in the plane of the disc and within the slot by means of crimping tabs extending laterally of the slot and over the insulative wire. The marginal lip of the slot area is apertured and an electrically insulative potting material such as silicone rubber, is potted in place overlaying the wire slot region and through the apertures.

  18. resterilizable electrode for electrosurgery

    NASA Technical Reports Server (NTRS)

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

    1979-01-01

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

  19. Voltammetric behavior of gold nanotrench electrodes.

    PubMed

    Guerrette, Joshua P; Percival, Stephen J; Zhang, Bo

    2011-10-01

    We report the fabrication and electrochemical response of a gold nanoband electrode located at the bottom of a glass/epoxy nanotrench, hereafter referred to as a gold nanotrench electrode. Gold nanotrench electrodes of 12.5 and 40 nm in width with various depths from a few tens of nanometers to approximately 4 μm are fabricated and further characterized by cyclic voltammetry. The fabrication of a Au nanotrench electrode follows a simple electrochemical etching process in which a small AC signal is applied to an inlaid Au nanoband electrode submersed in a NaCl solution. The voltammetric behavior of a Au nanotrench electrode is characterized by a quasi-steady-state response at lower scan rates (e.g., <1 V/s for a 12.5-nm-wide electrode). We present an analytical expression for the quasi-steady-state diffusion-limited current of the nanotrench electrode based upon the analysis of the mass-transport resistance. Finite-element simulation of steady-state and transient voltammetric responses of the nanotrench electrodes provides additional insights for the analytical model. Peak-shaped transient voltammetric responses were observed at scan rates as low as 5 V/s for both inlaid and nanotrench electrodes. This result may suggest that the exposed area of the nanoband electrode is much greater than that expected from the fabrication of the inlaid bands. However, the extent to which this is seen is greatly decreased in the nanotrench electrode by a smoothing effect during etching. Our results confirm previous reports of excess overhanging metal and delamination crack contributing significantly to the shape and magnitude of the voltammetric response. PMID:21866978

  20. Nanoband array electrode as a platform for high sensitivity enzyme-based glucose biosensing.

    PubMed

    Falk, Magnus; Sultana, Reshma; Swann, Marcus J; Mount, Andrew R; Freeman, Neville J

    2016-12-01

    We describe a novel glucose biosensor based on a nanoband array electrode design, manufactured using standard semiconductor processing techniques, and bio-modified with glucose oxidase immobilized at the nanoband electrode surface. The nanoband array architecture allows for efficient diffusion of glucose and oxygen to the electrode, resulting in a thousand-fold improvement in sensitivity and wide linear range compared to a conventional electrode. The electrode constitutes a robust and manufacturable sensing platform. PMID:27118384

  1. The study of piezoelectric lateral-electric-field-excited resonator.

    PubMed

    Zaitsev, Boris; Kuznetsova, Iren; Shikhabudinov, Alexander; Teplykh, Andrey; Borodina, Irina

    2014-01-01

    The piezoelectric lateral-electric-field-excited resonator based on an X-cut lithium niobate plate has been investigated. Two rectangular electrodes were applied on one side of the plate so that the lateral electric field components were parallel to the crystallographic Y-axis and excited the longitudinal wave in the gap between the electrodes. The region around the electrodes was covered with a special absorbing varnish to suppress the spurious oscillations. The effect of the absorbing coating width on the resonant frequency and Q-factor of the lateral field-excited resonator was studied in detail with the series and parallel resonances for different width of the gap between the electrodes. As a result, we found experimentally the parameter regions of pure resonances and the boundaries of value variation for resonance frequency, Q-factor, and effective electromechanical coupling coefficient. PMID:24402903

  2. Modified electrodes based on lipidic cubic phases.

    PubMed

    Bilewicz, Renata; Rowiński, Paweł; Rogalska, Ewa

    2005-04-01

    The lipidic cubic phase can be characterized as a curved bilayer forming a three-dimensional, crystallographical, well-ordered structure that is interwoven by aqueous channels. It provides a stable, well-organized environment in which diffusion of both water-soluble and lipid-soluble compounds can take place. Cubic phases based on monoacylglycerols form readily and attract our interest due to their ability to incorporate and stabilize proteins. Their lyotropic and thermotropic phase behaviour has been thoroughly investigated. At hydration over 20%, lipidic cubic phases Ia3d and Pn3m are formed. The latter is stable in the presence of excess water, which is important when the cubic phase is considered as an electrode-modifying material. Due to high viscosity, the cubic phases can be simply smeared over solid substrates such as electrodes and used to host enzymes and synthetic catalysts, leading to new types of catalytically active modified electrodes as shown for the determination of cholesterol, CO(2), or oxygen. The efficiency of transport of small hydrophilic molecules within the film can be determined by voltametry using two types of electrodes: a normal-size electrode working in the linear diffusion regime, and an ultramicroelectrode working under spherical diffusion conditions. This allows determining both the concentration and diffusion coefficient of the electrochemically active probe in the cubic phase. The monoolein-based cubic phase matrices are useful for immobilizing enzymes on the electrode surface (e.g., laccases from Trametes sp. and Rhus vernicifera were employed for monitoring dioxygen). The electronic contact between the electrode and the enzyme was maintained using suitable electroactive probes. PMID:15833697

  3. Bioanalysis with Potentiometric Membrane Electrodes.

    ERIC Educational Resources Information Center

    Rechnitz, G. A.

    1982-01-01

    Discusses major themes and interrelationships common to bioselective potentiometric membrane electrodes including the nature of bioselective electrodes, applications, and future prospects. Includes tables on traditional ion-selective membrane electrodes, nontraditional electrodes, and typical biocatalytic potentiometric electrodes. (Author/JN)

  4. Ion-Selective Electrodes.

    ERIC Educational Resources Information Center

    Arnold, Mark A.; Meyerhoff, Mark E.

    1984-01-01

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

  5. Fundamental electrode kinetics

    NASA Technical Reports Server (NTRS)

    Elder, J. P.

    1968-01-01

    Report presents the fundamentals of electrode kinetics and the methods used in evaluating the characteristic parameters of rapid-charge transfer processes at electrode-electrolyte interfaces. The concept of electrode kinetics is outlined, followed by the principles underlying the experimental techniques for the investigation of electrode kinetics.

  6. Electrochemistry of Prussian blue films on metal and semiconductor electrodes

    SciTech Connect

    Viehbeck, A.; DeBerry, D.W.

    1985-06-01

    The electrochemical properties of Prussian blue films on Pt and spark anodized n-type TiO/sub 2/ electrodes were investigated. Evidence for four redox states for Prussian blue was obtained. While the oxidation of Everitt's salt to Prussian blue involves the high spin iron atoms, the oxidation of Prussian blue to Berlin green and Berlin green to Prussian yellow involves the low spin hexacyanoferrate groups. The Prussian blue/Everitt's salt redox system (E/sub 0/ = +0.2V vs. SCE) is the most stable and reversible couple. The diffusion coefficients for reduction and oxidation of this redox couple are 5.0 x 10/sup -9/ and 2.7 x 10/sup -9/ cm/sup 2//S, respectively. The photoelectrochromic behavior of Prussian blue on semiconductor TiO/sub 2/ electrodes is discussed. The films deposited on TiO/sub 2/ have short-circuit memory, and lateral color spreading through the film is slow. A light addressable electrochromic display is described.

  7. Variability of electrode positions using electrode caps.

    PubMed

    Atcherson, Samuel R; Gould, Herbert Jay; Pousson, Monique A; Prout, Tina M

    2007-01-01

    We investigated the variability of electrode positions for a multi-channel, custom electrode cap placed onto participants' heads without taking scalp measurements. The electrode positions were digitized in a three-dimensional space for 10 young adult participants on three separate occasions. Positional variability was determined for 15 selected electrodes within the three-dimensional preauricular-nasion (PAN) coordinate system and from this system, angular coordinate variability was also determined. The standard deviations of the 15 selected electrodes ranged from 3.0 to 12.7 mm in the PAN system. These data resulted in a variability of 2.0 degrees to 10.4 degrees among the angular coordinates. The measurements indicated slightly greater variability of electrode positions compared to studies when electrodes were placed using scalp measurements. The implication of this study is that the use of electrode caps may not be appropriate when electroencephalographic (EEG) or evoked potential (EP) techniques depend on accurate electrode placement. Additionally, if a longitudinal study is performed, electrode locations should be checked to ensure that they conform with previous sessions. PMID:17929157

  8. HSPES membrane electrode assembly

    NASA Technical Reports Server (NTRS)

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

    2000-01-01

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

  9. Controlled porosity in electrodes

    SciTech Connect

    Chiang, Yet-Ming; Bae, Chang-Jun; Halloran, John William; Fu, Qiang; Tomsia, Antoni P.; Erdonmez, Can K.

    2015-06-23

    Porous electrodes in which the porosity has a low tortuosity are generally provided. In some embodiments, the porous electrodes can be designed to be filled with electrolyte and used in batteries, and can include low tortuosity in the primary direction of ion transport during charge and discharge of the battery. In some embodiments, the electrodes can have a high volume fraction of electrode active material (i.e., low porosity). The attributes outlined above can allow the electrodes to be fabricated with a higher energy density, higher capacity per unit area of electrode (mAh/cm.sup.2), and greater thickness than comparable electrodes while still providing high utilization of the active material in the battery during use. Accordingly, the electrodes can be used to produce batteries with high energy densities, high power, or both compared to batteries using electrodes of conventional design with relatively highly tortuous pores.

  10. Flexible retinal electrode array

    DOEpatents

    Okandan, Murat; Wessendorf, Kurt O.; Christenson, Todd R.

    2006-10-24

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

  11. Micromachined electrode array

    DOEpatents

    Okandan, Murat; Wessendorf, Kurt O.

    2007-12-11

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

  12. High frequency reference electrode

    DOEpatents

    Kronberg, J.W.

    1994-05-31

    A high frequency reference electrode for electrochemical experiments comprises a mercury-calomel or silver-silver chloride reference electrode with a layer of platinum around it and a layer of a chemically and electrically resistant material such as TEFLON around the platinum covering all but a small ring or halo' at the tip of the reference electrode, adjacent to the active portion of the reference electrode. The voltage output of the platinum layer, which serves as a redox electrode, and that of the reference electrode are coupled by a capacitor or a set of capacitors and the coupled output transmitted to a standard laboratory potentiostat. The platinum may be applied by thermal decomposition to the surface of the reference electrode. The electrode provides superior high-frequency response over conventional electrodes. 4 figs.

  13. High frequency reference electrode

    DOEpatents

    Kronberg, James W.

    1994-01-01

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

  14. Amyotrophic lateral sclerosis

    MedlinePlus

    ... this page: //medlineplus.gov/ency/article/000688.htm Amyotrophic lateral sclerosis To use the sharing features on this page, please enable JavaScript. Amyotrophic lateral sclerosis, or ALS, is a disease of the nerve ...

  15. Accessory lateral discoid meniscus.

    PubMed

    Saygi, Baransel; Yildirim, Yakup; Senturk, Salih; Sezgin Ramadan, Saime; Gundes, Hakan

    2006-12-01

    The lateral meniscus tends to have more developmental variation than the medial counterpart. This is a report of an accessory discoid layer of lateral meniscus. All arthroscopic, magnetic resonance imaging and histopathological views are presented. PMID:16710729

  16. Method of making an electrode

    DOEpatents

    Isenberg, Arnold O.

    1986-01-01

    Disclosed is a method of coating an electrode on a solid oxygen conductive oxide layer. A coating of particles of an electronic conductor is formed on one surface of the oxide layer and a source of oxygen is applied to the opposite surface of the oxide layer. A metal halide vapor is applied over the electronic conductor and the oxide layer is heated to a temperature sufficient to induce oxygen to diffuse through the oxide layer and react with the metal halide vapor. This results in the growing of a metal oxide coating on the particles of electronic conductor, thereby binding them to the oxide layer.

  17. High performance cermet electrodes

    DOEpatents

    Isenberg, Arnold O.; Zymboly, Gregory E.

    1986-01-01

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

  18. P-Channel Lateral Double-Diffused Metal-Oxide-Semiconductor Field-Effect Transistor with Split N-Type Buried Layer for High Breakdown Voltage and Low Specific On-Resistance

    NASA Astrophysics Data System (ADS)

    Liaw, Chorng-Wei; Chang, Ching-Hung; Lin, Ming-Jang; King, Ya-Ching; Hsu, Charles Ching-Hsiang; Lin, Chrong Jung

    2007-07-01

    Many high voltage complementary metal-oxide-semiconductor (HV-CMOS) processes are modified from a standard 5 V CMOS process by adding an N-type heavily doped layer under the P-well of a HV-PMOS drain terminal to isolate a high voltage P-well from a grounded P-substrate. The limitation of breakdown voltage is dominated by P-well concentration and junction depth. For designing a certain breakdown voltage (\\mathit{BV}dss) for a HV-PMOS, the original 5 V CMOS P-well concentration should be decreased, which could degrade 5 V CMOS characteristics, such as NMOS punch through and latch-up immunity. In this study, we demonstrate a novel HV-PMOS based on a split N-type buried layer (NBL), which provides a high \\mathit{BV}dss in a HV-CMOS process. The newly proposed device with NBL split under the P-well of a drain electrode increases \\mathit{BV}dss without degrading specific on-resistance (Ron,sp) and any added process complexity. From this result, P-well concentration could be increased to improve both 5 V NMOS characteristics and HV-PMOS Ron,sp.

  19. Lateral flow strip assay

    SciTech Connect

    Miles, Robin R.; Benett, William J.; Coleman, Matthew A.; Pearson, Francesca S.; Nasarabadi, Shanavaz L.

    2011-03-08

    A lateral flow strip assay apparatus comprising a housing; a lateral flow strip in the housing, the lateral flow strip having a receiving portion; a sample collection unit; and a reagent reservoir. Saliva and/or buccal cells are collected from an individual using the sample collection unit. The sample collection unit is immersed in the reagent reservoir. The tip of the lateral flow strip is immersed in the reservoir and the reagent/sample mixture wicks up into the lateral flow strip to perform the assay.

  20. Improved biomedical electrode

    NASA Technical Reports Server (NTRS)

    Frost, J. D., Jr.

    1972-01-01

    Newly designed electrode is prefilled, disposable, electrolyte-saturated spong. New design permits longe periods of storage without deterioration, and readiness in matter of seconds. Electrodes supply signals for electroencephalogram, electro-oculogram, and electrocardiogram.

  1. Corneal-shaping electrode

    DOEpatents

    Doss, James D.; Hutson, Richard L.

    1982-01-01

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

  2. Lateral Programmable Metallization Cell Devices And Applications

    NASA Astrophysics Data System (ADS)

    Ren, Minghan

    2011-12-01

    Programmable Metallization Cell (PMC) is a technology platform which utilizes mass transport in solid or liquid electrolyte coupled with electrochemical (redox) reactions to form or remove nanoscale metallic electrodeposits on or in the electrolyte. The ability to redistribute metal mass and form metallic nanostructure in or on a structure in situ, via the application of a bias on laterally placed electrodes, creates a large number of promising applications. A novel PMC-based lateral microwave switch was fabricated and characterized for use in microwave systems. It has demonstrated low insertion loss, high isolation, low voltage operation, low power and low energy consumption, and excellent linearity. Due to its non-volatile nature the switch operates with fewer biases and its simple planar geometry makes possible innovative device structures which can be potentially integrated into microwave power distribution circuits. PMC technology is also used to develop lateral dendritic metal electrodes. A lateral metallic dendritic network can be grown in a solid electrolyte (GeSe) or electrodeposited on SiO2 or Si using a water-mediated method. These dendritic electrodes grown in a solid electrolyte (GeSe) can be used to lower resistances for applications like self-healing interconnects despite its relatively low light transparency; while the dendritic electrodes grown using water-mediated method can be potentially integrated into solar cell applications, like replacing conventional Ag screen-printed top electrodes as they not only reduce resistances but also are highly transparent. This research effort also laid a solid foundation for developing dendritic plasmonic structures. A PMC-based lateral dendritic plasmonic structure is a device that has metallic dendritic networks grown electrochemically on SiO2 with a thin layer of surface metal nanoparticles in liquid electrolyte. These structures increase the distribution of particle sizes by connecting pre-deposited Ag

  3. Compartmented electrode structure

    DOEpatents

    Vissers, Donald R.; Shimotake, Hiroshi; Gay, Eddie C.; Martino, Fredric J.

    1977-06-14

    Electrodes for secondary electrochemical cells are provided with compartments for containing particles of the electrode reactant. The compartments are defined by partitions that are generally impenetrable to the particles of reactant and, in some instances, to the liquid electrolyte used in the cell. During cycling of the cell, reactant material initially loaded into a particular compartment is prevented from migrating and concentrating within the lower portion of the electrode or those portions of the electrode that exhibit reduced electrical resistance.

  4. Engineering interface-type resistive switching in BiFeO3 thin film switches by Ti implantation of bottom electrodes

    PubMed Central

    You, Tiangui; Ou, Xin; Niu, Gang; Bärwolf, Florian; Li, Guodong; Du, Nan; Bürger, Danilo; Skorupa, Ilona; Jia, Qi; Yu, Wenjie; Wang, Xi; Schmidt, Oliver G.; Schmidt, Heidemarie

    2015-01-01

    BiFeO3 based MIM structures with Ti-implanted Pt bottom electrodes and Au top electrodes have been fabricated on Sapphire substrates. The resulting metal-insulator-metal (MIM) structures show bipolar resistive switching without an electroforming process. It is evidenced that during the BiFeO3 thin film growth Ti diffuses into the BiFeO3 layer. The diffused Ti effectively traps and releases oxygen vacancies and consequently stabilizes the resistive switching in BiFeO3 MIM structures. Therefore, using Ti implantation of the bottom electrode, the retention performance can be greatly improved with increasing Ti fluence. For the used raster-scanned Ti implantation the lateral Ti distribution is not homogeneous enough and endurance slightly degrades with Ti fluence. The local resistive switching investigated by current sensing atomic force microscopy suggests the capability of down-scaling the resistive switching cell to one BiFeO3 grain size by local Ti implantation of the bottom electrode. PMID:26692104

  5. Engineering interface-type resistive switching in BiFeO3 thin film switches by Ti implantation of bottom electrodes.

    PubMed

    You, Tiangui; Ou, Xin; Niu, Gang; Bärwolf, Florian; Li, Guodong; Du, Nan; Bürger, Danilo; Skorupa, Ilona; Jia, Qi; Yu, Wenjie; Wang, Xi; Schmidt, Oliver G; Schmidt, Heidemarie

    2015-01-01

    BiFeO3 based MIM structures with Ti-implanted Pt bottom electrodes and Au top electrodes have been fabricated on Sapphire substrates. The resulting metal-insulator-metal (MIM) structures show bipolar resistive switching without an electroforming process. It is evidenced that during the BiFeO3 thin film growth Ti diffuses into the BiFeO3 layer. The diffused Ti effectively traps and releases oxygen vacancies and consequently stabilizes the resistive switching in BiFeO3 MIM structures. Therefore, using Ti implantation of the bottom electrode, the retention performance can be greatly improved with increasing Ti fluence. For the used raster-scanned Ti implantation the lateral Ti distribution is not homogeneous enough and endurance slightly degrades with Ti fluence. The local resistive switching investigated by current sensing atomic force microscopy suggests the capability of down-scaling the resistive switching cell to one BiFeO3 grain size by local Ti implantation of the bottom electrode. PMID:26692104

  6. Electrically conductive diamond electrodes

    DOEpatents

    Swain, Greg; Fischer, Anne ,; Bennett, Jason; Lowe, Michael

    2009-05-19

    An electrically conductive diamond electrode and process for preparation thereof is described. The electrode comprises diamond particles coated with electrically conductive doped diamond preferably by chemical vapor deposition which are held together with a binder. The electrodes are useful for oxidation reduction in gas, such as hydrogen generation by electrolysis.

  7. Insulated ECG electrodes

    NASA Technical Reports Server (NTRS)

    Portnoy, W. M.; David, R. M.

    1973-01-01

    Insulated, capacitively coupled electrode does not require electrolyte paste for attachment. Other features of electrode include wide range of nontoxic material that may be employed for dielectric because of sputtering technique used. Also, electrode size is reduced because there is no need for external compensating networks with FET operational amplifier.

  8. Longitudinal discharge laser electrodes

    DOEpatents

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

    1994-08-23

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

  9. Longitudinal discharge laser electrodes

    DOEpatents

    Warner, Bruce E.; Miller, John L.; Ault, Earl R.

    1994-01-01

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

  10. A Simple Hydrogen Electrode

    ERIC Educational Resources Information Center

    Eggen, Per-Odd

    2009-01-01

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