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Sample records for ac impedance resistance

  1. Microfabricated AC impedance sensor

    DOEpatents

    Krulevitch, Peter; Ackler, Harold D.; Becker, Frederick; Boser, Bernhard E.; Eldredge, Adam B.; Fuller, Christopher K.; Gascoyne, Peter R. C.; Hamilton, Julie K.; Swierkowski, Stefan P.; Wang, Xiao-Bo

    2002-01-01

    A microfabricated instrument for detecting and identifying cells and other particles based on alternating current (AC) impedance measurements. The microfabricated AC impedance sensor includes two critical elements: 1) a microfluidic chip, preferably of glass substrates, having at least one microchannel therein and with electrodes patterned on both substrates, and 2) electrical circuits that connect to the electrodes on the microfluidic chip and detect signals associated with particles traveling down the microchannels. These circuits enable multiple AC impedance measurements of individual particles at high throughput rates with sufficient resolution to identify different particle and cell types as appropriate for environmental detection and clinical diagnostic applications.

  2. AC impedance analysis of polypyrrole thin films

    NASA Technical Reports Server (NTRS)

    Penner, Reginald M.; Martin, Charles R.

    1987-01-01

    The AC impedance spectra of thin polypyrrole films were obtained at open circuit potentials from -0.4 to 0.4 V vs SCE. Two limiting cases are discussed for which simplified equivalent circuits are applicable. At very positive potentials, the predominantly nonfaradaic AC impedance of polypyrrole is very similar to that observed previously for finite porous metallic films. Modeling of the data with the appropriate equivalent circuit permits effective pore diameter and pore number densities of the oxidized film to be estimated. At potentials from -0.4 to -0.3 V, the polypyrrole film is essentially nonelectronically conductive and diffusion of polymer oxidized sites with their associated counterions can be assumed to be linear from the film/substrate electrode interface. The equivalent circuit for the polypyrrole film at these potentials is that previously described for metal oxide, lithium intercalation thin films. Using this model, counterion diffusion coefficients are determined for both semi-infinite and finite diffusion domains. In addition, the limiting low frequency resistance and capacitance of the polypyrrole thin fims was determined and compared to that obtained previously for thicker films of the polymer. The origin of the observed potential dependence of these low frequency circuit components is discussed.

  3. Impedance, AC conductivity and dielectric behavior Adeninium Trichloromercurate (II)

    NASA Astrophysics Data System (ADS)

    Fersi, M. Amine; Chaabane, I.; Gargouri, M.

    2016-09-01

    In this work, we report the measurements impedance spectroscopy technique for the organic-inorganic hybrid compound (C5H6N5) HgCl3, 11/2H2O measured in the 209 Hz-5 MHz frequency range from 378 to 428 K. Besides, the Cole-Cole (Z″ versus Z‧) plots were well fitted to an equivalent circuit built up by a parallel combination of resistance (R), fractal capacitance (CPE) and capacitance (C). Furthermore, the AC conductivity was investigated as a function of temperature and frequency in the same range. The experiment results indicated that AC conductivity (σac) was proportional to σdc + A ωS . The obtained results are discussed in terms of the correlated barrier hopping (CBH) model. An agreement between the experimental and theoretical results suggests that the AC conductivity behavior of Adeninium Trichloromercurate (II) can be successfully explained by CBH model. The contribution of single polaron hopping to AC conductivity in a present alloy was also studied.

  4. AC resistance measuring instrument

    DOEpatents

    Hof, P.J.

    1983-10-04

    An auto-ranging AC resistance measuring instrument for remote measurement of the resistance of an electrical device or circuit connected to the instrument includes a signal generator which generates an AC excitation signal for application to a load, including the device and the transmission line, a monitoring circuit which provides a digitally encoded signal representing the voltage across the load, and a microprocessor which operates under program control to provide an auto-ranging function by which range resistance is connected in circuit with the load to limit the load voltage to an acceptable range for the instrument, and an auto-compensating function by which compensating capacitance is connected in shunt with the range resistance to compensate for the effects of line capacitance. After the auto-ranging and auto-compensation functions are complete, the microprocessor calculates the resistance of the load from the selected range resistance, the excitation signal, and the load voltage signal, and displays of the measured resistance on a digital display of the instrument. 8 figs.

  5. AC Resistance measuring instrument

    DOEpatents

    Hof, Peter J.

    1983-01-01

    An auto-ranging AC resistance measuring instrument for remote measurement of the resistance of an electrical device or circuit connected to the instrument includes a signal generator which generates an AC excitation signal for application to a load, including the device and the transmission line, a monitoring circuit which provides a digitally encoded signal representing the voltage across the load, and a microprocessor which operates under program control to provide an auto-ranging function by which range resistance is connected in circuit with the load to limit the load voltage to an acceptable range for the instrument, and an auto-compensating function by which compensating capacitance is connected in shunt with the range resistance to compensate for the effects of line capacitance. After the auto-ranging and auto-compensation functions are complete, the microprocessor calculates the resistance of the load from the selected range resistance, the excitation signal, and the load voltage signal, and displays of the measured resistance on a digital display of the instrument.

  6. Equivalent Circuits For AC-Impedance Analysis Of Corrosion

    NASA Technical Reports Server (NTRS)

    Danford, M. D.

    1992-01-01

    Report presents investigation of equivalent circuits for ac-impedance analysis of corrosion. Impedance between specimen and electrolyte measured as function of frequency. Data used to characterize corrosion electrochemical system in terms of equivalent circuit. Eleven resistor/capacitor equivalent-circuit models were analyzed.

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

    NASA Technical Reports Server (NTRS)

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

    1987-01-01

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

  8. Single grain boundary characterization of Nb-doped SrTiO{sub 3} bicrystals using ac four-point impedance spectroscopy

    SciTech Connect

    Hwang, Jin-Ha; Johnson, Kevin D.; Mason, Thomas O.; Dravid, Vinayak P.

    2000-05-01

    AC four-point impedance spectroscopy has been applied to Nb-doped SrTiO{sub 3} bicrystals. Due to the simplified geometry and highly conductive bulk of the bicrystal, the reference impedance of the electrode was significantly reduced, validating the applicability of ac four-point impedance spectroscopy for electroceramics. DC current-voltage characteristics without any interference due to electrodes confirmed these ac measurements. Using ac four-point impedance spectroscopy, grain boundary contributions are isolated and the corresponding grain boundary thickness and resistivity are estimated. (c) 2000 American Institute of Physics.

  9. ac-resistance-measuring instrument

    SciTech Connect

    Hof, P.J.

    1981-04-22

    An auto-ranging ac resistance measuring instrument for remote measurement of the resistance of an electrical device or circuit connected to the instrument includes a signal generator which generates an ac excitation signal for application to a load, including the device and the transmission line, a monitoring circuit which provides a digitally encoded signal representing the voltage across the load, and a microprocessor which operates under program control to provide an auto-ranging function by which range resistance is connected in circuit with the load to limit the load voltage to an acceptable range for the instrument, and an auto-compensating function by which compensating capacitance is connected in shunt with the range resistance to compensate for the effects of line capacitance.

  10. Study of metal corrosion using ac impedance techniques in the STS launch environment

    NASA Technical Reports Server (NTRS)

    Calle, Luz M.

    1989-01-01

    AC impedance measurements were performed to investigate the corrosion resistance of 19 alloys under conditions similar to the STS launch environment. The alloys were: Zirconium 702, Hastelloy C-22, Inconel 625, Hastelloy C-276, Hastelloy C-4, Inconel 600, 7Mo + N, Ferralium 255, Inco Alloy G-3, 20Cb-3, SS 904L, Inconel 825, SS 304LN, SS 316L, SS 317L, ES 2205, SS 304L, Hastelloy B-2, and Monel 400. AC impedance data were gathered for each alloy after one hour immersion time in each of the following three electrolyte solutions: 3.55 percent NaCl, 3.55 percent NaCl-0.1N HCl, and 3.55 percent NaCl-1.0N HCl. The data were analyzed qualitatively using the Nyquist plot and quantitatively using the Bode plot. Polarization resistance, Rp, values were obtained using the Bode plot. Zirconium 702 was the most corrosion resistant alloy in the three electrolytes. The ordering of the other alloys according the their resistance to corrosion varied as the concentration of hydrochloric acid in the electrolyte increased. The corrosion resistance of Zirconium 702 and Ferralium 255 increased as the concentration of hydrochloric acid in the electrolyte increased. The corrosion resistance of the other 17 alloys decreased as the concentration of the hyrdochloric acid in the electrolyte increased.

  11. HVDC-AC system interaction from AC harmonics. Volume 1. Harmonic impedance calculations. Final report

    SciTech Connect

    Breuer, G D; Chow, J H; Lindh, C B; Miller, N W; Numrich, F H; Price, W W; Turner, A E; Whitney, R R

    1982-09-01

    Improved methods are needed to characterize ac system harmonic behavior for ac filter design for HVDC systems. The purpose of this General Electric Company RP1138 research is to evaluate the present filter design practice and to investigate methods for calculating system harmonic impedances. An overview of ac filter design for HVDC systems and a survey of literature related to filter design have been performed. Two methods for calculating system harmonic impedances have been investigated. In the measurement method, an instrumentation system for measuring system voltage and current has been assembled. Different schemes of using the measurements to calculate system harmonic impedances have been studied. In the analytical method, a procedure to include various operating conditions has been proposed. Computer programs for both methods have been prepared, and the results of the measurement and analytical methods analyzed. A conclusion of the project is that the measurement and analytical methods both provided reasonable results. There are correlations between the measured and analytical results for most harmonics, although there are discrepancies between the assumptions used in the two methods. A sensitivity approach has been proposed to further correlate the results. From the results of the analysis, it is recommended that both methods should be tested further. For the measurement method, more testing should be done to cover different system operating conditions. In the analytical method, more detailed models for representing system components should be studied. In addition, alternative statistical and sensitivity approaches should be attempted.

  12. Development of AC impedance methods for evaluating corroding metal surfaces and coatings

    NASA Technical Reports Server (NTRS)

    Knockemus, Ward

    1986-01-01

    In an effort to investigate metal surface corrosion and the breakdown of metal protective coatings the AC Impedance Method was applied to zinc chromate primer coated 2219-T87 aluminum. The model 368-1 AC Impedance Measurement System recently acquired by the MSFC Corrosion Research Branch was used to monitor changing properties of coated aluminum disks immersed in 3.5% NaCl buffered at ph 5.5 over three to four weeks. The DC polarization resistance runs were performed on the same samples. The corrosion system can be represented by an electronic analog called an equivalent circuit that consists of transistors and capacitors in specific arrangements. This equivalent circuit parallels the impedance behavior of the corrosion system during a frequency scan. Values for resistances and capacities that can be assigned in the equivalent circuit following a least squares analysis of the data describe changes that occur on the corroding metal surface and in the protective coating. A suitable equivalent circuit was determined that predicts the correct Bode phase and magnitude for the experimental sample. The DC corrosion current density data are related to equivalent circuit element parameters.

  13. High Impedance Comparator for Monitoring Water Resistivity.

    ERIC Educational Resources Information Center

    Holewinski, Paul K.

    1984-01-01

    A high-impedance comparator suitable for monitoring the resistivity of a deionized or distilled water line supplying water in the 50 Kohm/cm-2 Mohm/cm range is described. Includes information on required circuits (with diagrams), sensor probe assembly, and calibration techniques. (JN)

  14. AC impedance electrochemical modeling of lithium-ion positive electrodes.

    SciTech Connect

    Dees, D.; Gunen, E.; Abraham, D.; Jansen, A.; Prakash, J.; Chemical Engineering; IIT

    2004-01-01

    Under Department of Energy's Advanced Technology Development Program,various analytical diagnostic studies are being carried out to examine the lithium-ion battery technology for hybrid electric vehicle applications, and a series of electrochemical studies are being conducted to examine the performance of these batteries. An electrochemical model was developed to associate changes that were observed in the post-test analytical diagnostic studies with the electrochemical performance loss during testing of lithium ion batteries. While both electrodes in the lithium-ion cell have been studied using a similar electrochemical model, the discussion here is limited to modeling of the positive electrode. The positive electrode under study has a composite structure made of a layered nickel oxide (LiNi{sub 0.8}Co{sub 0.15}Al{sub 0.05}O{sub 2}) active material, a carbon black and graphite additive for distributing current, and a PVDF binder all on an aluminum current collector. The electrolyte is 1.2M LiPF{sub 6} dissolved in a mixture of EC and EMC and a Celgard micro-porous membrane is used as the separator. Planar test cells (positive/separator/negative) were constructed with a special fixture and two separator membranes that allowed the placement of a micro-reference electrode between the separator membranes [1]. Electrochemical studies including AC impedance spectroscopy were then conducted on the individual electrodes to examine the performance and ageing effects in the cell. The model was developed by following the work of Professor Newman at Berkeley [2]. The solid electrolyte interface (SEI) region, based on post-test analytical results, was assumed to be a film on the oxide and an oxide layer at the surface of the oxide. A double layer capacity was added in parallel with the Butler-Volmer kinetic expression. The pertinent reaction, thermodynamic, and transport equations were linearized for a small sinusoidal perturbation [3]. The resulting system of differential

  15. Module Twelve: Series AC Resistive-Reactive Circuits; Basic Electricity and Electronics Individualized Learning System.

    ERIC Educational Resources Information Center

    Bureau of Naval Personnel, Washington, DC.

    The module covers series circuits which contain both resistive and reactive components and methods of solving these circuits for current, voltage, impedance, and phase angle. The module is divided into six lessons: voltage and impedance in AC (alternating current) series circuits, vector computations, rectangular and polar notation, variational…

  16. An AC impedance study of steel in concrete

    NASA Astrophysics Data System (ADS)

    Lay, P.; Lawrence, P. F.; Wilkins, N. J. M.; Williams, D. E.

    1984-01-01

    Impedance measurements executed between both steel and platinum electrodes embedded in both porous and non-porous concretes were used to explore the physical characteristics of the system. A simple method is described for measuring high impedances (up to 500 M) in which the unknown impedance is compared with the imput impedance of the measuring instrument, previously calibrated. Impedance measurements on concrete immersed in an electrolyte were used to quantify concrete quality, and the dynamics of wetting, drying and electrolyte exchange were explored: the dynamics of such processes are considered to be among the factors determining the rate of corrosion of steel reinforcement under some conditions, since intermittent wetting is an efficient method for transporting oxygen and salt into the concrete. The existence of cracks along the electrode-concrete interface was inferred. Impedance changes consequent on the initiation of corrosion of steel electrodes were noted, but the changes were small and not clear-cut.

  17. An electrochemical study of corrosion protection by primer-topcoat systems on 4130 steel with ac impedance and dc methods

    NASA Technical Reports Server (NTRS)

    Mendrek, M. J.; Higgins, R. H.; Danford, M. D.

    1988-01-01

    To investigate metal surface corrosion and the breakdown of metal protective coatings, the ac impedance method is applied to six systems of primer coated and primer topcoated 4130 steel. Two primers were used: a zinc-rich epoxy primer and a red lead oxide epoxy primer. The epoxy-polyamine topcoat was used in four of the systems. The EG and G-PARC Model 368 ac impedance measurement system, along with dc measurements with the same system using the polarization resistance method, were used to monitor changing properties of coated 4230 steel disks immersed in 3.5 percent NaCl solutions buffered at pH 5.4 over periods of 40 to 60 days. The corrosion system can be represented by an electronic analog called an equivalent circuit consisting of resistors and capacitors in specific arrangements. This equivalent circuit parallels the impedance behavior of the corrosion system during a frequency scan. Values for the resistors and capacitors, that can be assigned in the equivalent circuit following a least-squares analysis of the data, describe changes that occur on the corroding metal surface and in the protective coatings. Two equivalent circuits have been determined that predict the correct Bode phase and magnitude of the experimental sample at different immersion times. The dc corrosion current density data are related to equivalent circuit element parameters. Methods for determining corrosion rate with ac impedance parameters are verified by the dc method.

  18. AC impedance spectroscopy and conductivity studies of Dy doped Bi4V2O11 ceramics

    NASA Astrophysics Data System (ADS)

    Bag, Sasmitarani; Das, Parthasarathi; Behera, Banarji

    2017-03-01

    The ac impedance and conductivity properties of Dy doped Bi4V2 - x Dy x O11 (x = 0.05, 0.10, 0.15 and 0.20) ceramics prepared by solid-state reaction technique, in a wide frequency range at different temperatures have been studied. All the samples exhibited β-type phase orthorhombic structure at room temperature. The Nyquist plot confirmed the presence of both grain and grain boundary effects for all Dy doped samples. Double relaxation behavior was also observed. The grain and grain boundary resistance decreases with rise in temperature for all the concentration and exhibits a typical negative temperature co-efficient of resistance (NTCR) behavior. An analysis of the electric modulus suggests the possible hopping mechanism for electrical transport processes of all the materials. The ac conductivity spectrum obeys Jonscher's universal power law. DC conductivity of the materials were also studied and values of the activation energy found to be 0.40, 0.49, 0.73 and 0.78 eV for the compositions x = 0.05, 0.10, 0.15 and 0.20, respectively, at different temperatures (150-375 °C).

  19. Investigation of water and ice by ac impedance using electrochemical properties cup.

    PubMed

    Chin, K B; Buehler, M G; Seshadri, S; Keymeulen, D; Anderson, R C; Dutz, S; Narayanan, S R

    2007-01-01

    Water and ice were investigated by ac impedance with the electrochemical properties cup in an effort to develop an in situ instrument for water characterization. In liquid water, the impedance modulus decreased with the increase in charge carriers. In the ice, the impedance measurements were characterized by the dielectric relaxation and its corresponding activation energy. The activation energy of 0.400 eV was determined for pure ice. With ice containing Cl(-) anions, the activation energy was 0.24 eV. H(+) and OH(-) doped ice has the lowest activation energy for dielectric relaxation. Results from previous works are similar to the results reported in this study.

  20. AC Impedance Studies on Metal/Nanoporous Silicon/ p-Silicon Structures

    NASA Astrophysics Data System (ADS)

    Mabrook, M. F.; Ray, A. K.

    2017-04-01

    Alternating current (AC) impedance measurements have been performed on 10- to 15- μm thick porous silicon layers on a (100) p-type silicon ( p(+)Si) substrate with the aluminium (Al) top electrode in a sandwich configuration in the range of 20 Hz-1 MHz and in the temperature ranging between 152 K and 292 K. The ac conductivity σ ac was found to increase with frequency f according to the universal power law: σ_{{ac}} = Afs where the exponent s is a frequency and temperature-dependent quantity. A hopping process is found to be dominant at low temperatures and high frequencies, while a thermally activated free band process is responsible for conduction at higher temperatures. Capacitance is found to decrease with frequency but increase with temperature. Frequency dependence of the loss tangent is observed with a temperature-dependent minimum value.

  1. AC Impedance Studies on Metal/Nanoporous Silicon/p-Silicon Structures

    NASA Astrophysics Data System (ADS)

    Mabrook, M. F.; Ray, A. K.

    2016-11-01

    Alternating current (AC) impedance measurements have been performed on 10- to 15-μm thick porous silicon layers on a (100) p-type silicon (p(+)Si) substrate with the aluminium (Al) top electrode in a sandwich configuration in the range of 20 Hz-1 MHz and in the temperature ranging between 152 K and 292 K. The ac conductivity σ ac was found to increase with frequency f according to the universal power law: σ_{ac} = Afs where the exponent s is a frequency and temperature-dependent quantity. A hopping process is found to be dominant at low temperatures and high frequencies, while a thermally activated free band process is responsible for conduction at higher temperatures. Capacitance is found to decrease with frequency but increase with temperature. Frequency dependence of the loss tangent is observed with a temperature-dependent minimum value.

  2. Laser Raman and ac impedance spectroscopic studies of PVA: NH 4NO 3 polymer electrolyte

    NASA Astrophysics Data System (ADS)

    Hema, M.; Selvasekarapandian, S.; Hirankumar, G.; Sakunthala, A.; Arunkumar, D.; Nithya, H.

    2010-01-01

    Ion conducting polymer electrolyte PVA:NH 4NO 3 has been prepared by solution casting technique and characterized using XRD, Raman and ac impedance spectroscopic analyses. The amorphous nature of the polymer films has been confirmed by XRD and Raman spectroscopy. An insight into the deconvoluted Raman peaks of υ1 vibration of NO 3- anion for the polymer electrolyte reveals the dominancy of ion aggregates at higher NH 4NO 3 concentration. From the ac impedance studies, the highest ion conductivity at 303 K has been found to be 7.5 × 10 -3 S cm -1 for 80PVA:20NH 4NO 3. The conductivity of the polymer electrolytes has been found to depend on the degree of dissociation of the salt in the host polymer matrix. The combination of the above-mentioned analyses has proven worth while and in fact necessary in order to achieve better understanding of these complex systems.

  3. Analytical evaluations of coupling impedances of resistive and magnetic bellows

    NASA Astrophysics Data System (ADS)

    Shobuda, Yoshihiro

    2014-03-01

    A theory is developed to calculate both the longitudinal and transverse impedances of magnetic as well as resistive bellows with cylindrical symmetry that is sandwiched between chambers with perfectly conductive metal fittings. Analytical estimations of the impedances are necessary because the skin depth is too small to make sufficiently tiny mesh sizes in current numerical codes. The impedances of bellows made of materials having both large conductivity and permeability are drastically increased owing to magnetic effects, compared with those of bellows made of perfectly conductive materials.

  4. AC impedance modelling study on porous electrodes of proton exchange membrane fuel cells using an agglomerate model

    NASA Astrophysics Data System (ADS)

    Gerteisen, Dietmar; Hakenjos, Alex; Schumacher, Jürgen O.

    A one-dimensional model of the PEM fuel cell cathode is developed to analyse ac impedance spectra and polarisation curves. The porous gas diffusion electrode is assumed to consist of a network of dispersed catalyst (Pt/C) forming spherically shaped agglomerated zones that are filled with electrolyte. The coupled differential equation system describes: ternary gas diffusion in the backing (O2 , N2 , water vapour), Fickian diffusion and Tafel kinetics for the oxygen reduction reaction (ORR) inside the agglomerates, proton migration with ohmic losses and double-layer charging in the electrode. Measurements are made of a temperature-controlled fuel cell with a geometric area of 1.4 cm × 1.4 cm. Lateral homogeneity is ensured by using a high stoichiometry of λmin . The model predicts the behaviour of measured polarisation curves and impedance spectra. It is found that a better humidification of the electrode leads to a higher volumetric double-layer capacity. The catalyst layer resistance shows the same behaviour depending on the humidification as the membrane resistance. Model parameters, e.g. Tafel slope, ionic resistance and agglomerate radius are varied. A sensitivity analysis of the model parameters is conducted.

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

    NASA Technical Reports Server (NTRS)

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

    1992-01-01

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

  6. Effect of nonsymmetrical flow resistance upon orifice impedance resistance

    NASA Technical Reports Server (NTRS)

    Posey, J. W.; Compton, K. J.

    1974-01-01

    A nonreactive orifice in an infinite baffle is analyzed. The pressure difference delta across the orifice varies sinusoidally with amplitude 1.0 and average value -P. The orifice resistance, delta p is discontinuous at zero velocity and exhibits the constant values R sub + and R sub - for u 0 and u 0, respectively. The resultant velocity has power in all harmonics of the excitation frequency. A quasi-linear resistance is defined and found to be relatively insensitive to the presence or absence of a resonant backing cavity; however, it does vary from 1.33 R sub + to 0.67 R sub + for a resistance ratio R sub +/R sub - between 0.5 and 2.0.

  7. AC impedance spectroscopy studies on solid-state sintered zinc aluminum oxide (ZnAl2O4) ceramics

    NASA Astrophysics Data System (ADS)

    Kumar, B. Rajesh; Rao, T. Subba

    2012-07-01

    In the present investigation Zinc Aluminum Oxide (ZnAl2O4) is prepared by solid-state reaction technique. Dielectric constant (ɛ'), dielectric loss(tan δ), ac conductivity (σac) as a function of temperature are studied by varying frequencies from 100 Hz to 1MHz using an impedance analyzer. The dielectric constant and dielectric loss increases gradually with an increase of temperature, but it decreases with increase of frequency. The ac conductivity (σac) also increases with increases of frequency. The transition peaks for ZnAl2O4 are observed at 490°C, 510°C, 520°C for the frequencies 1 KHz, 10 KHz and 100 KHz. No transition peaks are found for the frequency 100 Hz and 1 MHz because of high conductive loss.

  8. Failure of thin organic films by a combination of shearography and electrochemical impedance spectroscopy: the new concept of resistivity

    NASA Astrophysics Data System (ADS)

    Habib, Khaled

    2012-04-01

    A critical (steady state) value of the resistivity of different organic coatings was determined by a combination of optical shearography and electrochemical impedance spectroscopy (EIS). The behavior of organic coatings, i.e., ACE premiumgray enamel, white enamel, beige enamel (spray coatings), a yellow acrylic lacquer, and a gold nail polish on a metallic alloy, i.e., a carbon steel, was investigated over a temperature range of 20-60 °C. The value of the resistivity of coatings was determined by correlating the in-plan displacement of the coating (by shearography over a temperature range of 20- 60 °C) and the value of the alternating current (A.C) impedance of the coating by EIS in 3% NaCl solution. The integrity of the coatings with respect to time was assessed by comparison the measured value of resistivity to the critical (steady state) or asymptotic value of resistivity. In other words, by shearography, measurement of coating properties could be performed independent of parameters such as UV exposure, humidity, presence of chemical species, and other parameters which may normally interfere with conventional methods of the assessing of the integrity of coatings. Therefore, one may measure the resistivity of coatings, regardless of the history of the coating, in order to assess the integrity of coatings. Also, the obtained shearography data were found to be in a reasonable trend with the data of electrochemical impedance spectroscopy (EIS) in 3%NaCl solution.

  9. Phonon impedance matching: minimizing interfacial thermal resistance of thin films

    NASA Astrophysics Data System (ADS)

    Polanco, Carlos; Zhang, Jingjie; Ghosh, Avik

    2014-03-01

    The challenge to minimize interfacial thermal resistance is to allow a broad band spectrum of phonons, with non-linear dispersion and well defined translational and rotational symmetries, to cross the interface. We explain how to minimize this resistance using a frequency dependent broadening matrix that generalizes the notion of acoustic impedance to the whole phonon spectrum including symmetries. We show how to ``match'' two given materials by joining them with a single atomic layer, with a multilayer material and with a graded superlattice. Atomic layer ``matching'' requires a layer with a mass close to the arithmetic mean (or spring constant close to the harmonic mean) to favor high frequency phonon transmission. For multilayer ``matching,'' we want a material with a broadening close to the geometric mean to maximize transmission peaks. For graded superlattices, a continuous sequence of geometric means translates to an exponentially varying broadening that generates a wide-band antireflection coating for both the coherent and incoherent limits. Our results are supported by ``first principles'' calculations of thermal conductance for GaAs / Gax Al1 - x As / AlAs thin films using the Non-Equilibrium Greens Function formalism coupled with Density Functional Perturbation Theory. NSF-CAREER (QMHP 1028883), NSF-IDR (CBET 1134311), XSEDE.

  10. Synthesis and characterization of cancrinite-type zeolite, and its ionic conductivity study by AC impedance analysis

    NASA Astrophysics Data System (ADS)

    Kriaa, A.; Ben Saad, K.; Hamzaoui, A. H.

    2012-12-01

    The synthesis of cancrinite in the system NaOH-SiO2-Al2O3-NaHCO3-H2O was performed, according to methods described in the literature, in an autoclave under hydrothermal conditions at T = 473 K. The electrical properties of cancrinite-type zeolite pellets were investigated by complex impedance spectroscopy in the temperature range 465-800°C. The effect of temperature on impedance parameters was studied using an impedance analyzer in a wide frequency range (1 Hz to 13 MHz). The real and imaginary parts of complex impedance trace semicircles in the complex plane are plotted. The bulk resistance of the material decreases with rise in temperature. This exhibits a typical negative temperature coefficient of resistance (NTCR) behavior of the material. The results of bulk electrical conductivity and its activation energy are presented. The modulus analysis suggests that the electrical transport processes in the material are very likely to be of electronic nature. Relaxation frequencies follow an Arrhenius behavior with activation energy values not comparable to those found for the electrical conductivity.

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

    SciTech Connect

    Ouyang, Jianyong

    2013-12-02

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

  12. Gas hydrate saturation from acoustic impedance and resistivity logs in the shenhu area, south china sea

    USGS Publications Warehouse

    Wang, X.; Wu, S.; Lee, M.; Guo, Y.; Yang, S.; Liang, J.

    2011-01-01

    During the China's first gas hydrate drilling expedition -1 (GMGS-1), gas hydrate was discovered in layers ranging from 10 to 25 m above the base of gas hydrate stability zone in the Shenhu area, South China Sea. Water chemistry, electrical resistivity logs, and acoustic impedance were used to estimate gas hydrate saturations. Gas hydrate saturations estimated from the chloride concentrations range from 0 to 43% of the pore space. The higher gas hydrate saturations were present in the depth from 152 to 177 m at site SH7 and from 190 to 225 m at site SH2, respectively. Gas hydrate saturations estimated from the resistivity using Archie equation have similar trends to those from chloride concentrations. To examine the variability of gas hydrate saturations away from the wells, acoustic impedances calculated from the 3 D seismic data using constrained sparse inversion method were used. Well logs acquired at site SH7 were incorporated into the inversion by establishing a relation between the water-filled porosity, calculated using gas hydrate saturations estimated from the resistivity logs, and the acoustic impedance, calculated from density and velocity logs. Gas hydrate saturations estimated from acoustic impedance of seismic data are ???10-23% of the pore space and are comparable to those estimated from the well logs. The uncertainties in estimated gas hydrate saturations from seismic acoustic impedances were mainly from uncertainties associated with inverted acoustic impedance, the empirical relation between the water-filled porosities and acoustic impedances, and assumed background resistivity. ?? 2011 Elsevier Ltd.

  13. Enhanced absorption performance of carbon nanostructure based metamaterials and tuning impedance matching behavior by an external AC electric field.

    PubMed

    Gholipur, Reza; Khorshidi, Zahra; Bahari, Ali

    2017-03-27

    Metamaterials have surprisingly broadened the range of available practical applications in new devices such as shielding, microwave absorbing, and novel antenna. More researches are related to the tuning DNG frequency bands of ordered or disordered metamaterials, and far less research has focused on the importance of impedance matching behavior, and is not effort and attention in adjusting the magnitude of negative permittivity values. This is particularly important if devices deal with low amplitude signals such as radio or TV antenna. The carbon/hafnium nickel oxide (C/Hf0.9Ni0.1Oy) nanocomposites with simultaneously negative permittivity and negative permeability, excellent metamaterial performance and good impedance matching could become an efficient alternative for the ordered metamaterials in wave-transparent, microwave absorbing, and solar energy harvesting fields. In this study, we prepared C/Hf0.9Ni0.1Oy nanocomposites by solvothermal method, and we clarified how the impedance matching and double negative (DNG) behaviors of C/Hf0.9Ni0.1Oy can be tuned by an external AC electric field created by electric quadrupole system. External electric field allows for the alignment of the well-dispersed nanoparticles of carbon with long-range orientations order. We believe that this finding broadens our understanding of moderate conductive material-based random metamaterials (MCMRMs), and provides a novel strategy for replacing high loss ordered or disordered metamaterials with MCMRMs.

  14. AC/RF Superconductivity

    SciTech Connect

    Ciovati, Gianluigi

    2015-02-01

    This contribution provides a brief introduction to AC/RF superconductivity, with an emphasis on application to accelerators. The topics covered include the surface impedance of normal conductors and superconductors, the residual resistance, the field dependence of the surface resistance, and the superheating field.

  15. AC impedance analysis of ionic and electronic conductivities in electrode mixture layers for an all-solid-state lithium-ion battery

    NASA Astrophysics Data System (ADS)

    Siroma, Zyun; Sato, Tomohiro; Takeuchi, Tomonari; Nagai, Ryo; Ota, Akira; Ioroi, Tsutomu

    2016-06-01

    The ionic and electronic effective conductivities of an electrode mixture layers for all-solid-state lithium-ion batteries containing Li2Ssbnd P2S5 as a solid electrolyte were investigated by AC impedance measurements and analysis using a transmission-line model (TLM). Samples containing graphite (graphite electrodes) or LiNi0.5Co0.2Mn0.3O2 (NCM electrodes) as the active material were measured under a "substrate | sample | bulk electrolyte | sample | substrate" configuration (ion-electron connection) and a "substrate | sample | substrate" configuration (electron-electron connection). Theoretically, if the electronic resistance is negligibly small, which is the case with our graphite electrodes, measurement with the ion-electron connection should be effective for evaluating ionic conductivity. However, if the electronic resistance is comparable to the ionic resistance, which is the case with our NCM electrodes, the results with the ion-electron connection may contain some inherent inaccuracy. In this report, we theoretically and practically demonstrate the advantage of analyzing the results with the electron-electron connection, which gives both the ionic and electronic conductivities. The similarity of the behavior of ionic conductivity with the graphite and NCM electrodes confirms the reliability of this analysis.

  16. AC-impedance measurements during thermal runaway process in several lithium/polymer batteries

    NASA Astrophysics Data System (ADS)

    Uchida, I.; Ishikawa, H.; Mohamedi, M.; Umeda, M.

    In this work, we present a set of thermal characterization experiments of charged prismatic polymer lithium-ion battery (PLB) comparatively with those of a lithium-ion battery (LIB). These cells at different state of charge (SOC) were tested inside an accelerated rate calorimeter (ARC) to determine the onset-of-thermal runaway (OTR) temperatures. In addition, the thermally activated components of these cells were followed by monitoring the impedance (at 1 kHz) and the open-circuit voltage (OCV) as a function of temperature. An increase in the impedance was observed at around 133 °C corresponding to the polyethylene separator shutdown. Above 140 °C, the OCV dropped to zero indicating an internal short-circuit due the separator meltdown suggesting that the pinholes created in the separator at meltdown are large enough to create an internal short-circuit.

  17. Evaluation of the electrode performance for PAFC by using acid absorption, acceleration and ac-impedance measurement

    SciTech Connect

    Kim, Chang-Soo; Song, Rak-Hyun; Choi, Byung-Woo

    1996-12-31

    In PAFC, the degradation on cathode electrode caused by carbon corrosion, platinum dissolution and growth is especially severe. An acceleration test is a good technique for evaluating the degradation of electrode performance, because it does not need long time. Coleman et al used thermal cycling and on-off cycling as an acceleration test. Song et al showed that hydrogen shortage decreased the electrode performance more rapidly than that of air shortage in gas shortage test. Honji et al reported that the rate of coarsening of Pt particle is rapid in open circuit potential and this is one of major causes on the performance degradation of electrode. The cathode performance has been studied by using acid absorption, acceleration and ac-impedance measurements as functions of the polytetrafluoroethylene (PTFE) contents and sintering temperatures of the electrode.

  18. System and method for determining stator winding resistance in an AC motor using motor drives

    DOEpatents

    Lu, Bin; Habetler, Thomas G; Zhang, Pinjia

    2013-02-26

    A system and method for determining the stator winding resistance of AC motors is provided. The system includes an AC motor drive having an input connectable to an AC source and an output connectable to an input terminal of an AC motor, a pulse width modulation (PWM) converter having switches therein to control current flow and terminal voltages in the AC motor, and a control system connected to the PWM converter. The control system generates a command signal to cause the PWM converter to control an output of the AC motor drive corresponding to an input to the AC motor, selectively generates a modified command signal to cause the PWM converter to inject a DC signal into the output of the AC motor drive, and determines a stator winding resistance of the AC motor based on the DC signal of at least one of the voltage and current.

  19. AC losses in multifilamentary Bi(2223) tapes with an interfilamentary resistive carbonate barrier

    NASA Astrophysics Data System (ADS)

    Eckelmann, H.; Quilitz, M.; Oomen, M.; Leghissa, M.; Goldacker, W.

    1998-12-01

    For the most common AC application frequencies, the main component of the AC losses in multifilamentary Bi(2223) tapes are caused by hysteresis- and coupling losses. These losses can be reduced enhancing the matrix resistivity and applying a twist to the filaments. We report on the AC loss properties of 37-filament tapes with AgAu (8 wt.%) matrix, and novel 19-filament tapes with SrCO 3 barriers between the filaments. We performed transport AC loss and magnetic AC loss measurements in parallel and perpendicular magnetic fields. Both kinds of tapes were also prepared with filament twists below a twist pitch of 20 mm. The influence of the different tape modifications on the AC loss behaviour is presented and compared with theoretical models to understand the effect of the resistive matrix. In the case of magnetic AC loss measurements, reduced AC losses due to decoupled filaments were observed for the twisted tapes with a resistive matrix in low parallel fields.

  20. New Resistance Mechanism in Helicoverpa armigera Threatens Transgenic Crops Expressing Bacillus thuringiensis Cry1Ac Toxin

    PubMed Central

    Gunning, Robin V.; Dang, Ho T.; Kemp, Fred C.; Nicholson, Ian C.; Moores, Graham D.

    2005-01-01

    In Australia, the cotton bollworm, Helicoverpa armigera, has a long history of resistance to conventional insecticides. Transgenic cotton (expressing the Bacillus thuringiensis toxin Cry1Ac) has been grown for H. armigera control since 1996. It is demonstrated here that a population of Australian H. armigera has developed resistance to Cry1Ac toxin (275-fold). Some 70% of resistant H. armigera larvae were able to survive on Cry1Ac transgenic cotton (Ingard) The resistance phenotype is inherited as an autosomal semidominant trait. Resistance was associated with elevated esterase levels, which cosegregated with resistance. In vitro studies employing surface plasmon resonance technology and other biochemical techniques demonstrated that resistant strain esterase could bind to Cry1Ac protoxin and activated toxin. In vivo studies showed that Cry1Ac-resistant larvae fed Cy1Ac transgenic cotton or Cry1Ac-treated artificial diet had lower esterase activity than non-Cry1Ac-fed larvae. A resistance mechanism in which esterase sequesters Cry1Ac is proposed. PMID:15870346

  1. New resistance mechanism in Helicoverpa armigera threatens transgenic crops expressing Bacillus thuringiensis Cry1Ac toxin.

    PubMed

    Gunning, Robin V; Dang, Ho T; Kemp, Fred C; Nicholson, Ian C; Moores, Graham D

    2005-05-01

    In Australia, the cotton bollworm, Helicoverpa armigera, has a long history of resistance to conventional insecticides. Transgenic cotton (expressing the Bacillus thuringiensis toxin Cry1Ac) has been grown for H. armigera control since 1996. It is demonstrated here that a population of Australian H. armigera has developed resistance to Cry1Ac toxin (275-fold). Some 70% of resistant H. armigera larvae were able to survive on Cry1Ac transgenic cotton (Ingard) The resistance phenotype is inherited as an autosomal semidominant trait. Resistance was associated with elevated esterase levels, which cosegregated with resistance. In vitro studies employing surface plasmon resonance technology and other biochemical techniques demonstrated that resistant strain esterase could bind to Cry1Ac protoxin and activated toxin. In vivo studies showed that Cry1Ac-resistant larvae fed Cy1Ac transgenic cotton or Cry1Ac-treated artificial diet had lower esterase activity than non-Cry1Ac-fed larvae. A resistance mechanism in which esterase sequesters Cry1Ac is proposed.

  2. Effect of nonsymmetrical flow resistance upon orifice impedance

    NASA Technical Reports Server (NTRS)

    Posey, J. W.; Compton, K. J.

    1974-01-01

    Previous laboratory work has indicated that an orifice in a thin sheet behaves in a quasisteady manner under acoustical excitation. Also, it has been found that the steady flow resistance of an orifice may be dependent upon the direction of flow, especially in the presence of a crossflow on one side of the hole. An analytical study is presented which assumes a nonreactive orifice in an infinite baffle. The pressure difference across the orifice varies sinusoidally with amplitude 1.0 and average value -P. The orifice resistance is discontinuous at zero velocity and exhibits the constant values when the velocity is nonzero. The resultant velocity has power in all harmonics of the excitation frequency, providing an explanation of the even harmonic excitation observed by other investigators, but not predicted by symmetric nonlinearity. A quasilinear resistance is defined and found to be relatively insensitive to the presence or absence of a resonant backing cavity.

  3. Impedance and AC conductivity study of nano crystalline, fine grained multiferroic bismuth ferrite (BiFeO3), synthesized by microwave sintering

    NASA Astrophysics Data System (ADS)

    Kolte, Jayant; Salame, Paresh H.; Daryapurkar, A. S.; Gopalan, P.

    2015-09-01

    In this paper, major reduction in sintering time,temperautre and significant improvement over final density of sitnered sample is reported for the microwave sintered nanocrystalline BiFeO3 (BFO) ceramic. Also, different sintering time and temperatures have been used to tailor the grain size and the final density of the resulting BFO ceramics synthesized from phase pure BFO nanoparticles ( d ¯ ≈ 10 n m ). Microwave sintering resulted in reducing the sintering time substantially (by 1h), and has resulted in submicron sized grains and high resistivity ˜1.8 GΩ-cm. The AC conductivity is seen to follow the Jonscher's power law behavior, suggesting correlated barrier hopping (CBH) mechanism in the sample. The role of oxygen vacancies at high temperature, due to volatility of bismuth, in dielectric and conductivity behavior is also discussed. Further, the sample displayed dielectric anomaly near magnetic transition temperature (˜180 °C) indicating bearing of magnetic moments on the dielectric properties. Using Impedance Spectroscopy (IS) we have established, the electrical heterogeneity of the ceramic BFO reavealing semiconducting nature of grains and insulating nature of grain boundary. This, formation of network of insulating grain boundaries and semiconducting grains could lead to formation of internal barrier layer capacitance (IBLC) leading to high dielectric constant in microwave sintered BFO.

  4. Influence of Dopants on Electrical Properties of ZnO-V2O5 Varistors Deduced from AC Impedance and Variable-Temperature Dielectric Spectroscopy

    NASA Astrophysics Data System (ADS)

    Wu, Jun; Li, Taotao; Qi, Ting; Qin, Qingwei; Li, Guangqiang; Zhu, Bailin; Wu, Run; Xie, Changsheng

    2012-07-01

    The influence of MnO2, PbO, and a mixture of MnO2, PbO, and B2O3 on the electrical and dielectric properties of ZnO-V2O5 ceramics was studied by alternating-current (AC) impedance and variable-temperature dielectric spectroscopy. The results show that, compared with the resistivity of the intervening layer at the grain boundary, the Schottky barrier present at the grain boundary is much more important for varistor performance, which can be significantly improved by using a mixture of MnO2, PbO, and B2O3. Consequently, better varistor performance is achieved for 94.5 mol.% ZnO + 0.5 mol.% V2O5 + 1.0 mol.% MnO2 + 2.0 mol.% PbO + 2.0 mol.% B2O3 (ZVMPB), i.e., nonlinear coefficient α = 35.3 and leakage current density I l = 2.72 μA/cm2. The activation energy for the characteristic dielectric relaxation process is in the range of 0.339 eV to 0.365 eV, indicating that it is only associated with oxygen vacancy V{O/·}.

  5. A novel two-terminal-pair pulse-driven Josephson impedance bridge linking a 10 nF capacitance standard to the quantized Hall resistance

    NASA Astrophysics Data System (ADS)

    Bauer, S.; Behr, R.; Hagen, T.; Kieler, O.; Lee, J.; Palafox, L.; Schurr, J.

    2017-04-01

    In this paper the realization of a two-terminal-pair impedance bridge based on pulse-driven Josephson arrays will be presented. This bridge was used to link a 10 nF capacitance standard to the quantized Hall resistance at 1233 Hz. With pulse-driven Josephson arrays the setup for a quadrature bridge can be reduced dramatically. For the combination of the AC quantum Hall resistance and a 10 nF capacitance standard, most of the uncertainties caused by contact resistances in a two-terminal-pair definition were circumvented by a triple-series connection of the AC quantum Hall resistance. The capacitance value obtained by the new Josephson impedance bridge was compared to the results from a transformer-based ratio bridge and agrees within 1.3 parts in 108. Sources of systematic uncertainties were investigated and the combined relative uncertainty of the bridge was determined to be less than 1× {{10}-8} (k  =  1) and 13.9 nF F‑1 (k  =  1) for the link of the 10 nF capacitance standard.

  6. Note: Direct sensor resistance-to-frequency conversion with generalized impedance converter.

    PubMed

    Ramírez Muñoz, D; Sánchez Moreno, J; Casans Berga, S; Navarro Antón, A E

    2010-12-01

    In this note a squared output signal is generated from an astable circuit. Its frequency has a linear dependence on the resistance value of a resistive temperature sensor. The main circuit to obtain this direct relationship is the generalized impedance converter configured as a capacitor controlled by a sensor resistance. The proposed measurement method allows a direct analog-to-digital interface of information involved in resistive sensors. The converter finds applications in portable low voltage and low power design of instrumentation electronic systems.

  7. Oxygen diffusion in niobia-doped zirconia as surrogate for oxide film on Zr-Nb alloy: AC impedance analysis

    NASA Astrophysics Data System (ADS)

    Yamana, Teppei; Arima, Tatsumi; Yoshihara, Takatoshi; Inagaki, Yaohiro; Idemitsu, Kazuya

    2013-11-01

    The oxygen conductivities and crystallographic properties of niobia-doped yttria-stabilized tetragonal zirconia with 0.0-2.6 wt% Nb2O5 were evaluated by the AC impedance analysis and the X-ray diffraction measurement, respectively. The tetragonality of zirconia increased with niobia content and approached ˜1.017 while the tetragonal-to-monoclinic phase transition occurred above ca. 1 wt% Nb2O5. On the other hand, oxygen conductivities of bulk and grain-boundary (GB) decreased with increasing niobia content. The bulk conductivity controlled the total ionic conductivity at high temperatures, and its activation energy had smaller dependence on temperature than that of GB. In addition to the effect of [VO] depletion by niobia addition, the behaviors of bulk and GB conductivities might be explained by the decrease of mobility of oxygen ion due to Coulomb repulsion between Nb5+ and VO and by no segregation of Nb ions in the space-charge layers, respectively.

  8. Characterisation of a Selection of AC and DC Resistance Bridges for Standard Platinum Resistance Thermometry

    NASA Astrophysics Data System (ADS)

    Pearce, J. V.; Gray, J.; Veltcheva, R. I.

    2016-11-01

    Accurate resistance bridges are used to measure the ratio between the resistance of standard platinum resistance thermometers and a reference (standard) resistor at the level of microkelvin in temperature terms and as such play a critical role in the realisation and dissemination of the ITS-90. For AC bridges, the ratio test unit has been available for some time, and for both AC and DC bridges, the increasing availability of resistance bridge calibrators based on combinatorial calibration has increased the ease with which the accuracy and linearity of resistance bridges may be determined, under conditions which provide a realistic representation of the actual measurement set-up. In this study, the performance of 14 resistance bridges, which were available for testing at NPL, consisting of a range of manufacturers and types, has been evaluated and expressed in terms of the standard deviation of the bridge errors over a given range of ratios, namely s. In general, the bridges are found to comply with the manufacturers' specifications. The uncertainty of s has also been determined using Monte Carlo techniques and is found to be of the order of 10 % of s for most bridge types.

  9. Production and characterization of Bacillus thuringiensis Cry1Ac-resistant cotton bollworm Helicoverpa zea (Boddie).

    PubMed

    Anilkumar, Konasale J; Rodrigo-Simón, Ana; Ferré, Juan; Pusztai-Carey, Marianne; Sivasupramaniam, Sakuntala; Moar, William J

    2008-01-01

    Laboratory-selected Bacillus thuringiensis-resistant colonies are important tools for elucidating B. thuringiensis resistance mechanisms. However, cotton bollworm, Helicoverpa zea, a target pest of transgenic corn and cotton expressing B. thuringiensis Cry1Ac (Bt corn and cotton), has proven difficult to select for stable resistance. Two populations of H. zea (AR and MR), resistant to the B. thuringiensis protein found in all commercial Bt cotton varieties (Cry1Ac), were established by selection with Cry1Ac activated toxin (AR) or MVP II (MR). Cry1Ac toxin reflects the form ingested by H. zea when feeding on Bt cotton, whereas MVP II is a Cry1Ac formulation used for resistance selection and monitoring. The resistance ratio (RR) for AR exceeded 100-fold after 11 generations and has been maintained at this level for nine generations. This is the first report of stable Cry1Ac resistance in H. zea. MR crashed after 11 generations, reaching only an RR of 12. AR was only partially cross-resistant to MVP II, suggesting that MVP II does not have the same Cry1Ac selection pressure as Cry1Ac toxin against H. zea and that proteases may be involved with resistance. AR was highly cross-resistant to Cry1Ab toxin but only slightly cross-resistant to Cry1Ab expressing corn leaf powder. AR was not cross-resistant to Cry2Aa2, Cry2Ab2-expressing corn leaf powder, Vip3A, and cypermethrin. Toxin-binding assays showed no significant differences, indicating that resistance was not linked to a reduction in binding. These results aid in understanding why this pest has not evolved B. thuringiensis resistance, and highlight the need to choose carefully the form of B. thuringiensis protein used in experiments.

  10. Screening of the resistive-wall impedance by a cylindrical electron plasma

    NASA Astrophysics Data System (ADS)

    Al-Khateeb, A.; Hasse, R. W.; Boine-Frankenheim, O.; Hofmann, I.

    2008-08-01

    The effect of an electron cloud on the longitudinal coupling impedance is studied by idealizing it as a cold and uniformly distributed non-neutral plasma of electrons. The beam pipe is assumed to be of circular cross section with a thick resistive wall and the beam charge is idealized as a uniform disk. The electron contribution to the charge and current densities is obtained from the collective electron response to the beam passage through the pipe. In the presence of the electron background, a general closed formula for the longitudinal coupling impedance is obtained. The screening of the coupling impedance with the density of the electron plasma is studied and discussed for typical parameters in an accelerator beam pipe for the under-dense and the over-dense plasma regions.

  11. Laser Raman, XRD, DSC and Ac-Impedance Analysis of Polymer Blend Electrolyte Based on Eco-Friendly Pva-Pvp Blend with NH4NO3

    NASA Astrophysics Data System (ADS)

    Rajeswari, N.; Selvasekarapandian, S.; Prabaharan, S. R. S.; Kawamura, J.; Iwai, Y.; Karthikeyan, S.

    2013-07-01

    Proton conducting polymer blend electrolytes have attractive interest because of their advantages such as processability, flexibility, electrochemical stability, easy handling and their applications to a variety of electrochemical devices such as fuel cells, chemical sensor and electrochemical displays. In the present work, the films of 50PVA-50PVP blend with different MWt% concentrations of NH4NO3 have been prepared by solution casting techniques using distilled water as a solvent. The prepared films have been investigated by different techniques such as XRD, DSC, Laser Raman and AC Impedance spectroscopy. XRD studies reveal the amorphous nature of the polymer blend-salt complexes. The glass transition temperature has been calculated from the DSC analysis. From the AC Impedance spectroscopy, the high conductivity of the 30MWt% of NH4NO3 doped 50PVA-50PVP polymer complex has been found to be the order of 1.41 × 10-3S cm-1 at room temperature.

  12. System and method for determining stator winding resistance in an AC motor

    DOEpatents

    Lu, Bin; Habetler, Thomas G.; Zhang, Pinjia; Theisen, Peter J.

    2011-05-31

    A system and method for determining stator winding resistance in an AC motor is disclosed. The system includes a circuit having an input connectable to an AC source and an output connectable to an input terminal of an AC motor. The circuit includes at least one contactor and at least one switch to control current flow and terminal voltages in the AC motor. The system also includes a controller connected to the circuit and configured to modify a switching time of the at least one switch to create a DC component in an output of the system corresponding to an input to the AC motor and determine a stator winding resistance of the AC motor based on the injected DC component of the voltage and current.

  13. Intra-wire resistance and AC loss in multi-filamentary MgB2 wires

    NASA Astrophysics Data System (ADS)

    Zhou, C.; Offringa, W.; Bergen, A.; Wessel, W. A. J.; Krooshoop, H. J. G.; Dhallé, M.; Sumption, M. D.; Collings, E. W.; Rindfleisch, M.; Tomsic, M.; ten Kate, H. H. J.; Nijhuis, A.

    2013-02-01

    Intra-wire resistance and AC loss of various multi-filamentary MgB2 wires with filaments surrounded by Nb barriers have been measured and analyzed. The intra-wire resistance is measured with a direct four-probe voltage-current method at various temperatures. The AC loss is acquired by both vibrating sample magnetometer (VSM) and magnetization measurements at 4.2 K. With the aid of finite element method simulations, the filament-to-matrix contact resistance and effective transverse resistivity are derived from direct intra-wire resistance measurements. The effective transverse resistivity values are in good agreement with those analytically derived from the AC coupling loss measurements. Surprisingly, very high values of filament-to-matrix contact resistivity are found, being 2 or 3 orders higher than commonly found for NbTi or Nb3Sn wires.

  14. Synergistic interactions between Cry1Ac and natural cotton defenses limit survival of Cry1Ac-resistant Helicoverpa zea (Lepidoptera: Noctuidae) on Bt cotton.

    PubMed

    Anilkumar, Konasale J; Sivasupramaniam, Sakuntala; Head, Graham; Orth, Robert; Van Santen, Edzard; Moar, William J

    2009-07-01

    Larvae of the bollworm Helicoverpa zea (Boddie) show some tolerance to Bacillus thuringiensis (Bt) Cry1Ac, and can survive on Cry1Ac-expressing Bt cotton, which should increase resistance development concerns. However, field-evolved resistance has not yet been observed. In a previous study, a population of H. zea was selected for stable resistance to Cry1Ac toxin. In the present study, we determined in laboratory bioassays if larvae of the Cry1Ac toxin-resistant H. zea population show higher survival rates on field-cultivated Bt cotton squares (= flower buds) collected prebloom-bloom than susceptible H. zea. Our results show that Cry1Ac toxin-resistant H. zea cannot complete larval development on Cry1Ac-expressing Bt cotton, despite being more than 150-fold resistant to Cry1Ac toxin and able to survive until pupation on Cry1Ac toxin concentrations greater than present in Bt cotton squares. Since mortality observed for Cry1Ac-resistant H. zea on Bt cotton was higher than expected, we investigated whether Cry1Ac interacts with gossypol and or other compounds offered with cotton powder in artificial diet. Diet incorporation bioassays were conducted with Cry1Ac toxin alone, and with gossypol and 4% cotton powder in the presence and absence of Cry1Ac. Cry1Ac toxin was significantly more lethal to susceptible H. zea than to resistant H. zea, but no difference in susceptibility to gossypol was observed between strains. However, combinations of Cry1Ac with gossypol or cotton powder were synergistic against resistant, but not against susceptible H. zea. Gossypol concentrations in individual larvae showed no significant differences between insect strains, or between larvae fed gossypol alone vs. those fed gossypol plus Cry1Ac. These results may help explain the inability of Cry1Ac-resistant H. zea to complete development on Bt cotton, and the absence of field-evolved resistance to Bt cotton by this pest.

  15. Non-invasive determination of absolute lung resistivity in adults using electrical impedance tomography.

    PubMed

    Zhang, Jie; Patterson, Robert

    2010-08-01

    Lung resistivity is a physiological parameter that describes the electrical characteristics of the lungs. Lung composition changes due to changes in the lung tissues, fluid and air volume. Various diseases that can cause a change in lung composition may be monitored by measuring lung resistivity. Currently, there is no accepted non-invasive method to measure lung resistivity. In this study, we presented a method and framework to non-invasively determine lung resistivity using electrical impedance tomography (EIT). By comparing actual measurements from subjects with data from a 3D human thorax model, an EIT image can be reconstructed to show a resistivity difference between the model and the subject. By adjusting the lung resistivity in the model, the resistivity difference in the lung regions can be reduced to near zero. This resistivity value then is the estimation of the lung resistivity of the subject. Using the proposed method, the lung resistivities of four normal adult males (43 +/- 13 years, 78 +/- 10 kg) in the supine position at air volumes starting at functional residual capacity (FRC--end expiration) and increasing in 0.5 l steps to 1.5 l were studied. The averaged lung resistivity changes 12.59%, from 1406 Omega cm to 1583 Omega cm, following the inspiration of 1.5 l air from FRC. The coefficients of variation (CV) of precision for the four subjects are less than 10%. The experiment was repeated five times at each air volume on a subject to test the reproducibility. The CVs are less than 3%. The results show that it is feasible to determine absolute lung resistivity using an EIT-based method.

  16. Cytoplasm resistivity of mammalian atrial myocardium determined by dielectrophoresis and impedance methods.

    PubMed

    Fry, Christopher H; Salvage, Samantha C; Manazza, Alessandra; Dupont, Emmanuel; Labeed, Fatima H; Hughes, Michael P; Jabr, Rita I

    2012-12-05

    Many cardiac arrhythmias are caused by slowed conduction of action potentials, which in turn can be due to an abnormal increase of intracellular myocardial resistance. Intracellular resistivity is a linear sum of that offered by gap junctions between contiguous cells and the cytoplasm of the myocytes themselves. However, the relative contribution of the two components is unclear, especially in atrial myocardium, as there are no precise measurements of cytoplasmic resistivity, R(c). In this study, R(c) was measured in atrial tissue using several methods: a dielectrophoresis technique with isolated cells and impedance measurements with both isolated cells and multicellular preparations. All methods yielded similar values for R(c), with a mean of 138 ± 5 Ω·cm at 23°C, and a Q(10) value of 1.20. This value is about half that of total intracellular resistivity and thus will be a significant determinant of the actual value of action potential conduction velocity. The dielectrophoresis experiments demonstrated the importance of including divalent cations (Ca(2+) and Mg(2+)) in the suspension medium, as their omission reduced cell integrity by lowering membrane resistivity and increasing cytoplasm resistivity. Accurate measurement of R(c) is essential to develop quantitative computational models that determine the key factors contributing to the development of cardiac arrhythmias.

  17. High Resistivity Lipid Bilayers Assembled on Polyelectrolyte Multilayer Cushions: An Impedance Study.

    PubMed

    Diamanti, Eleftheria; Gregurec, Danijela; Rodríguez-Presa, María José; Gervasi, Claudio A; Azzaroni, Omar; Moya, Sergio E

    2016-06-28

    Supported membranes on top of polymer cushions are interesting models of biomembranes as cell membranes are supported on a polymer network of proteins and sugars. In this work lipid vesicles formed by a mixture of 30% 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) and 70% 1,2-dioleoyl-sn-glycero-3-phospho-l-serine (DOPS) are assembled on top of a polyelectrolyte multilayer (PEM) cushion of poly(allylamine hydrochloride) (PAH) and poly(styrene sodium sulfonate) (PSS). The assembly results in the formation of a bilayer on top of the PEM as proven by means of the quartz crystal microbalance with dissipation technique (QCM-D) and by cryo-transmission electron microscopy (cryo-TEM). The electrical properties of the bilayer are studied by electrochemical impedance spectroscopy (EIS). The bilayer supported on the PEMs shows a high resistance, on the order of 10(7) Ω cm(2), which is indicative of a continuous, dense bilayer. Such resistance is comparable with the resistance of black lipid membranes. This is the first time that such values are obtained for lipid bilayers supported on PEMs. The assembly of polyelectrolytes on top of a lipid bilayer decreases the resistance of the bilayer up to 2 orders of magnitude. The assembly of the polyelectrolytes on the lipids induces defects or pores in the bilayer which in turn prompts a decrease in the measured resistance.

  18. Effects of Operating Conditions on Internal Resistances in Enzyme Fuel Cells Studied via Electrochemical Impedance Spectroscopy

    SciTech Connect

    Aaron, D; Borole, Abhijeet P; Yiacoumi, Sotira; Tsouris, Costas

    2012-01-01

    Enzyme fuel cells (EFCs) offer some advantages over traditional precious-metal-catalyzed fuel cells, such as polymer electrolyte membrane fuel cells (PEMFCs). However, EFCs exhibit far less power output than PEMFCs and have relatively short life spans before materials must be replaced. In this work, electrochemical impedance spectroscopy (EIS) is used to analyze the internal resistances throughout the EFC at a variety of operating conditions. EIS analysis is focused primarily on the resistances of the anode, solution/membrane, and cathode. Increased enzyme loading results in improved power output and reductions in internal resistance. Conditions are identified for which enzyme loading does not limit the EFC performance. EIS experiments are also reported for EFCs operated continuously for 2 days; power output declines sharply over time, while all internal resistances increase. Drying of the cathode and enzyme/mediator degradation are believed to have contributed to this behavior. Finally, experiments are performed at varying air-humidification temperatures. Little effect on internal resistances or power output is observed. However, it is anticipated that increased air humidification can improve longevity by delivering more water to the cathode. Improvements to the enzymatic cathode are needed for EFC development. These improvements need to focus on improving transport rather than increasing enzyme loading.

  19. rf resistance and inductance of massively parallel single walled carbon nanotubes: Direct, broadband measurements and near perfect 50 Ω impedance matching

    NASA Astrophysics Data System (ADS)

    Rutherglen, Chris; Jain, Dheeraj; Burke, Peter

    2008-08-01

    We report using dielectrophoresis to accumulate hundred to thousands of solubilized single walled carbon nanotubes in parallel to achieve impedance values very close to 50Ω. This allows us to clearly measure the real (resistive) and imaginary (inductive) impedance over a broad frequency range. We find a negligible to mild frequency dependent resistance for the devices and an imaginary impedance that is significantly smaller then the resistance over the range of dc to 20GHz. This clearly and unambiguously demonstrates that kinetic inductance is not the major issue facing nanotube array interconnects, when compared to the real impedance (the resistance).

  20. An MRI-Compatible High Frequency AC Resistive Heating System for Homeothermic Maintenance in Small Animals

    PubMed Central

    Gomes, Ana L.; Kinchesh, Paul; Kersemans, Veerle; Allen, Philip D.; Smart, Sean C.

    2016-01-01

    Purpose To develop an MRI-compatible resistive heater, using high frequency alternating current (AC), for temperature maintenance of anaesthetised animals. Materials and Methods An MRI-compatible resistive electrical heater was formed from narrow gauge wire connected to a high frequency (10–100 kHz) AC power source. Multiple gradient echo images covering a range of echo times, and pulse-acquire spectra were acquired with the wire heater powered using high frequency AC or DC power sources and without any current flowing in order to assess the sensitivity of the MRI acquisitions to the presence of current flow through the heater wire. The efficacy of temperature maintenance using the AC heater was assessed by measuring rectal temperature immediately following induction of general anaesthesia for a period of 30 minutes in three different mice. Results Images and spectra acquired in the presence and absence of 50–100 kHz AC through the wire heater were indistinguishable, whereas DC power created field shifts and lineshape distortions. Temperature lost during induction of anaesthesia was recovered within approximately 20 minutes and a stable temperature was reached as the mouse’s temperature approached the set target. Conclusion The AC-powered wire heater maintains adequate heat input to the animal to maintain body temperature, and does not compromise image quality. PMID:27806062

  1. Lamin A/C deficiency reduces circulating tumor cell resistance to fluid shear stress

    PubMed Central

    Denais, Celine; Chan, Maxine F.; Wang, Zhexiao; Lammerding, Jan

    2015-01-01

    Metastasis contributes to over 90% of cancer-related deaths and is initiated when cancer cells detach from the primary tumor, invade the basement membrane, and enter the circulation as circulating tumor cells (CTCs). While metastasis is viewed as an inefficient process with most CTCs dying within the bloodstream, it is evident that some CTCs are capable of resisting hemodynamic shear forces to form secondary tumors in distant tissues. We hypothesized that nuclear lamins A and C (A/C) act as key structural components within CTCs necessary to resist destruction from elevated shear forces of the bloodstream. Herein, we show that, compared with nonmalignant epithelial cells, tumor cells are resistant to elevated fluid shear forces in vitro that mimic those within the bloodstream, as evidenced by significant decreases in cellular apoptosis and necrosis. Knockdown of lamin A/C significantly reduced tumor cell resistance to fluid shear stress, with significantly increased cell death compared with parental tumor cell and nontargeting controls. Interestingly, lamin A/C knockdown increased shear stress-induced tumor cell apoptosis, but did not significantly affect cellular necrosis. These data demonstrate that lamin A/C is an important structural component that enables tumor cell resistance to fluid shear stress-mediated death in the bloodstream, and may thus facilitate survival and hematogenous metastasis of CTCs. PMID:26447202

  2. Static resistivity image of a cubic saline phantom in magnetic resonance electrical impedance tomography (MREIT).

    PubMed

    Lee, Byung Il; Oh, Suk Hoon; Woo, Eung Je; Lee, Soo Yeol; Cho, Min Hyeong; Kwon, Ohin; Seo, Jin Keun; Baek, Woon Sik

    2003-05-01

    In magnetic resonance electrical impedance tomography (MREIT) we inject currents through electrodes placed on the surface of a subject and try to reconstruct cross-sectional resistivity (or conductivity) images using internal magnetic flux density as well as boundary voltage measurements. In this paper we present a static resistivity image of a cubic saline phantom (50 x 50 x 50 mm3) containing a cylindrical sausage object with an average resistivity value of 123.7 ohms cm. Our current MREIT system is based on an experimental 0.3 T MRI scanner and a current injection apparatus. We captured MR phase images of the phantom while injecting currents of 28 mA through two pairs of surface electrodes. We computed current density images from magnetic flux density images that are proportional to the MR phase images. From the current density images and boundary voltage data we reconstructed a cross-sectional resistivity image within a central region of 38.5 x 38.5 mm2 at the middle of the phantom using the J-substitution algorithm. The spatial resolution of the reconstructed image was 64 x 64 and the reconstructed average resistivity of the sausage was 117.7 ohms cm. Even though the error in the reconstructed average resistivity value was small, the relative L2-error of the reconstructed image was 25.5% due to the noise in measured MR phase images. We expect improvements in the accuracy by utilizing an MRI scanner with higher SNR and increasing the size of voxels scarifying the spatial resolution.

  3. Power-law resistivity, magnetic relaxation and ac susceptibility

    SciTech Connect

    Gilchrist, J.; van der Beek, C.J.

    1994-07-01

    The nonlinear diffusion of magnetic flux into a superconducting sample can be studied by measuring the relaxation of the magnetisation after application of a step field or by measuring the ac susceptibility, {chi}{sub 1} and its third harmonic, {chi}{sub 3}, or preferably both methods covering different time scales. Each has been analysed recently for a field-cooled sample of a material whose creep activation energy depends logarithmically on current density, J corresponding to a power-law relation between electric field, E and J. Here, results are compared, using a universal scaling depth. Maximum {chi}{sub 1}{double_prime} {vert_bar}{chi}{sub 3}{vert_bar} and values occur, and also the magnetisation has relaxed to half its initial value when the scaling depth is comparable to the sample half-thickness.

  4. Beam heat load due to geometrical and resistive wall impedance in COLDDIAG

    NASA Astrophysics Data System (ADS)

    Casalbuoni, S.; Migliorati, M.; Mostacci, A.; Palumbo, L.; Spataro, B.

    2012-11-01

    One of the still open issues for the development of superconductive insertion devices is the understanding of the heat intake from the electron beam. With the aim of measuring the beam heat load to a cold bore and the hope to gain a deeper understanding in the underlying mechanisms, a cold vacuum chamber for diagnostics (COLDDIAG) was built. It is equipped with the following instrumentation: retarding field analyzers to measure the electron flux, temperature sensors to measure the beam heat load, pressure gauges, and mass spectrometers to measure the gas content. Possible beam heat load sources are: synchrotron radiation, wakefield effects due to geometrical and resistive wall impedance and electron/ion bombardment. The flexibility of the engineering design will allow the installation of the cryostat in different synchrotron light sources. COLDDIAG was first installed in the Diamond Light Source (DLS) in 2011. Due to a mechanical failure of the thermal transition of the cold liner, the cryostat had to be removed after one week of operation. After having implemented design changes in the thermal liner transition, COLDDIAG has been reinstalled in the DLS at the end of August 2012. In order to understand the beam heat load mechanism it is important to compare the measured COLDDIAG parameters with theoretical expectations. In this paper we report on the analytical and numerical computation of the COLDDIAG beam heat load due to coupling impedances deriving from unavoidable step transitions, ports used for pumping and diagnostics, surface roughness, and resistive wall. The results might have an important impact on future technological solutions to be applied to cold bore devices.

  5. Acquired immunity and stochasticity in epidemic intervals impede the evolution of host disease resistance.

    PubMed

    Harding, Karin C; Hansen, B Johan L; Goodman, Simon J

    2005-12-01

    Disease can generate intense selection pressure on host populations, but here we show that acquired immunity in a population subject to repeated disease outbreaks can impede the evolution of genetic disease resistance by maintaining susceptible genotypes in the population. Interference between the life-history schedule of a species and periodicity of the disease has unintuitive effects on selection intensity, and stochasticity in outbreak period further reduces the rate of spread of disease-resistance alleles. A general age-structured population genetic model was developed and parameterized using empirical data for phocine distemper virus (PDV) epizootics in harbor seals. Scenarios with acquired immunity had lower levels of epizootic mortality compared with scenarios without acquired immunity for the first PDV outbreaks, but this pattern was reversed after about five disease cycles. Without acquired immunity, evolution of disease resistance was more rapid, and long-term population size variation is efficiently dampened. Acquired immunity has the potential to significantly influence rapid evolutionary dynamics of a host population in response to age-structured disease selection and to alter predicted selection intensities compared with epidemiological models that do not consider such feedback. This may have important implications for evolutionary population dynamics in a range of human, agricultural, and wildlife disease settings.

  6. Effects of grazing flow on the steady-state flow resistance and acoustic impedance of thin porous-faced liners

    NASA Technical Reports Server (NTRS)

    Hersh, A. S.; Walker, B.

    1978-01-01

    The effects of grazing flow on the steady state flow resistance and acoustic impedance of seven Feltmetal and three Rigimesh thin porous faced liners were studied. The steady-state flow resistance of the ten specimens was measured using standard fluid mechanical experimental techniques. The acoustic impedance was measured using the two microphone method. The principal findings of the study are that the effects of grazing flow were measured and found to be small; small differences were measured between steady-state and acoustic resistance, and a semi-empirical model was derived that correlated the steady-state resistance data of the seven Feltmetal liners and the face sheet reactance of both the Feltmetal and Rigimesh liners.

  7. Cross-resistance and interactions between Bt toxins Cry1Ac and Cry2Ab against the cotton bollworm.

    PubMed

    Wei, Jizhen; Guo, Yuyuan; Liang, Gemei; Wu, Kongming; Zhang, Jie; Tabashnik, Bruce E; Li, Xianchun

    2015-01-14

    To delay evolution of pest resistance to transgenic crops producing insecticidal proteins from Bacillus thuringiensis (Bt), the "pyramid" strategy uses plants that produce two or more toxins that kill the same pest. We conducted laboratory diet experiments with the cotton bollworm, Helicoverpa armigera, to evaluate cross-resistance and interactions between two toxins in pyramided Bt cotton (Cry1Ac and Cry2Ab). Selection with Cry1Ac for 125 generations produced 1000-fold resistance to Cry1Ac and 6.8-fold cross-resistance to Cry2Ab. Selection with Cry2Ab for 29 generations caused 5.6-fold resistance to Cry2Ab and 61-fold cross-resistance to Cry1Ac. Without exposure to Bt toxins, resistance to both toxins decreased. For each of the four resistant strains examined, 67 to 100% of the combinations of Cry1Ac and Cry2Ab tested yielded higher than expected mortality, reflecting synergism between these two toxins. Results showing minor cross-resistance to Cry2Ab caused by selection with Cry1Ac and synergism between these two toxins against resistant insects suggest that plants producing both toxins could prolong the efficacy of Bt cotton against this pest in China. Including toxins against which no cross-resistance occurs and integrating Bt cotton with other control tactics could also increase the sustainability of management strategies.

  8. Cross-resistance and interactions between Bt toxins Cry1Ac and Cry2Ab against the cotton bollworm

    PubMed Central

    Wei, Jizhen; Guo, Yuyuan; Liang, Gemei; Wu, Kongming; Zhang, Jie; Tabashnik, Bruce E.; Li, Xianchun

    2015-01-01

    To delay evolution of pest resistance to transgenic crops producing insecticidal proteins from Bacillus thuringiensis (Bt), the "pyramid" strategy uses plants that produce two or more toxins that kill the same pest. We conducted laboratory diet experiments with the cotton bollworm, Helicoverpa armigera, to evaluate cross-resistance and interactions between two toxins in pyramided Bt cotton (Cry1Ac and Cry2Ab). Selection with Cry1Ac for 125 generations produced 1000-fold resistance to Cry1Ac and 6.8-fold cross-resistance to Cry2Ab. Selection with Cry2Ab for 29 generations caused 5.6-fold resistance to Cry2Ab and 61-fold cross-resistance to Cry1Ac. Without exposure to Bt toxins, resistance to both toxins decreased. For each of the four resistant strains examined, 67 to 100% of the combinations of Cry1Ac and Cry2Ab tested yielded higher than expected mortality, reflecting synergism between these two toxins. Results showing minor cross-resistance to Cry2Ab caused by selection with Cry1Ac and synergism between these two toxins against resistant insects suggest that plants producing both toxins could prolong the efficacy of Bt cotton against this pest in China. Including toxins against which no cross-resistance occurs and integrating Bt cotton with other control tactics could also increase the sustainability of management strategies. PMID:25586723

  9. ADVANCES IN IMPEDANCE THEORY

    SciTech Connect

    Stupakov, G.; /SLAC

    2009-06-05

    We review recent progress in the following areas of the impedance theory: calculation of impedance of tapers and small angle collimators; optical approximation and parabolic equation for the high-frequency impedance; impedance due to resistive inserts in a perfectly conducting pipe.

  10. Impedance of the grape berry cuticle as a novel phenotypic trait to estimate resistance to Botrytis cinerea.

    PubMed

    Herzog, Katja; Wind, Rolf; Töpfer, Reinhard

    2015-05-27

    Warm and moist weather conditions during berry ripening provoke Botrytis cinerea (B. cinerea) causing notable bunch rot on susceptible grapevines with the effect of reduced yield and wine quality. Resistance donors of genetic loci to increase B. cinerea resistance are widely unknown. Promising traits of resistance are represented by physical features like the thickness and permeability of the grape berry cuticle. Sensor-based phenotyping methods or genetic markers are rare for such traits. In the present study, the simple-to-handle I-sensor was developed. The sensor enables the fast and reliable measurement of electrical impedance of the grape berry cuticles and its epicuticular waxes (CW). Statistical experiments revealed highly significant correlations between relative impedance of CW and the resistance of grapevines to B. cinerea. Thus, the relative impedance Zrel of CW was identified as the most important phenotypic factor with regard to the prediction of grapevine resistance to B. cinerea. An ordinal logistic regression analysis revealed a R2McFadden of 0.37 and confirmed the application of Zrel of CW for the prediction of bunch infection and in this way as novel phenotyping trait. Applying the I-sensor, a preliminary QTL region was identified indicating that the novel phenotypic trait is as well a valuable tool for genetic analyses.

  11. Impedance of the Grape Berry Cuticle as a Novel Phenotypic Trait to Estimate Resistance to Botrytis Cinerea

    PubMed Central

    Herzog, Katja; Wind, Rolf; Töpfer, Reinhard

    2015-01-01

    Warm and moist weather conditions during berry ripening provoke Botrytis cinerea (B. cinerea) causing notable bunch rot on susceptible grapevines with the effect of reduced yield and wine quality. Resistance donors of genetic loci to increase B. cinerea resistance are widely unknown. Promising traits of resistance are represented by physical features like the thickness and permeability of the grape berry cuticle. Sensor-based phenotyping methods or genetic markers are rare for such traits. In the present study, the simple-to-handle I-sensor was developed. The sensor enables the fast and reliable measurement of electrical impedance of the grape berry cuticles and its epicuticular waxes (CW). Statistical experiments revealed highly significant correlations between relative impedance of CW and the resistance of grapevines to B. cinerea. Thus, the relative impedance Zrel of CW was identified as the most important phenotypic factor with regard to the prediction of grapevine resistance to B. cinerea. An ordinal logistic regression analysis revealed a R2McFadden of 0.37 and confirmed the application of Zrel of CW for the prediction of bunch infection and in this way as novel phenotyping trait. Applying the I-sensor, a preliminary QTL region was identified indicating that the novel phenotypic trait is as well a valuable tool for genetic analyses. PMID:26024417

  12. AC losses and transverse resistivity in filamentary MgB 2 tape with Ti barriers

    NASA Astrophysics Data System (ADS)

    Polák, M.; Demenčík, E.; Hušek, I.; Kopera, L.; Kováč, P.; Mozola, P.; Takács, S.

    2011-07-01

    We measured and analyzed AC losses of MgB 2 tape with 19 filaments surrounded by Ti barriers and embedded in copper stabilization, exposed to external magnetic field with frequencies from 30 mHz up to 1.4 Hz and amplitudes up to 0.8 T at 4.2 K. Using the measured frequency dependence of the total AC losses we determined the contribution of hysteresis and coupling losses. The transverse resistivity determined from the coupling losses is considerably higher than that corresponding to the resistivity of copper stabilization before the tape processing due to diffusion of Ti. From the measured penetration field critical current densities were determined using results of theories for circular as well as rectangular filaments.

  13. Analysis of resistance to Cry1Ac in field-collected pink bollworm, Pectinophora gossypiella (Lepidoptera:Gelechiidae), populations.

    PubMed

    Ojha, Abhishek; Sree, K Sowjanya; Sachdev, Bindiya; Rashmi, M A; Ravi, K C; Suresh, P J; Mohan, Komarlingam S; Bhatnagar, Raj K

    2014-01-01

    High survivorship of pink bollworrm, Pectinophora gossypiella in bolls of Bollgard® cotton hybrids and resistance to Cry1Ac protein, expressed in Bollgard cotton were reported in field-populations collected from the state of Gujarat (western India) in 2010. We have found Cry1Ac-resistance in pink bollworm populations sourced from Bollgard and non-Bt cotton fields in the adjoining states of Maharashtra and Madhya Pradesh in Central India. Further, we observed reduced binding of labeled Cry1Ac protein to receptors localized on the brush-border membrane of pink bollworm larval strains with high tolerance to Cry1Ac. These strains were sourced from Bollgard and conventional cotton fields. A pooled Cry1Ac-resistant strain, further selected on Cry1Ac diet also showed significantly reduced binding to Cry1Ac protein. The reduced binding of Cry1Ac to receptors could be an underlying mechanism for the observed resistance in pink bollworm populations feeding on Bollgard hybrids.

  14. Electrical resistivity and AC-calorimetric measurements of PrRu 4P 12 under pressure

    NASA Astrophysics Data System (ADS)

    Miyake, A.; Holmes, A. T.; Kagayama, T.; Shimizu, K.; Sekine, C.; Shirotani, I.; Kikuchi, D.; Sugawara, H.; Sato, H.

    2008-04-01

    We have studied the effect of pressure in the filled skutterudite PrRu 4P 12, which shows a metal-insulator (MI) transition at TMI=63 K, via simultaneous measurements of electrical resistivity ( ρ) and AC-calorimetry ( CAC). Schottky-like anomalies in CAC disappear under pressure, suggesting a change of the ground state. The resistivity below TMI is strongly suppressed with increasing pressure, in contrast to the weak pressure dependence of TMI. Above 10 GPa, ρ(T) shows metallic behavior with small anomalies at TMI. We discuss the likely change of ground state in PrRu 4P 12 with pressure from triplet to singlet.

  15. Asymmetrical cross-resistance between Bacillus thuringiensis toxins Cry1Ac and Cry2Ab in pink bollworm.

    PubMed

    Tabashnik, Bruce E; Unnithan, Gopalan C; Masson, Luke; Crowder, David W; Li, Xianchun; Carrière, Yves

    2009-07-21

    Transgenic crops producing Bacillus thuringiensis (Bt) toxins kill some key insect pests and can reduce reliance on insecticide sprays. Sustainable use of such crops requires methods for delaying evolution of resistance by pests. To thwart pest resistance, some transgenic crops produce 2 different Bt toxins targeting the same pest. This "pyramid" strategy is expected to work best when selection for resistance to 1 toxin does not cause cross-resistance to the other toxin. The most widely used pyramid is transgenic cotton producing Bt toxins Cry1Ac and Cry2Ab. Cross-resistance between these toxins was presumed unlikely because they bind to different larval midgut target sites. Previous results showed that laboratory selection with Cry1Ac caused little or no cross-resistance to Cry2A toxins in pink bollworm (Pectinophora gossypiella), a major cotton pest. We show here, however, that laboratory selection of pink bollworm with Cry2Ab caused up to 420-fold cross-resistance to Cry1Ac as well as 240-fold resistance to Cry2Ab. Inheritance of resistance to high concentrations of Cry2Ab was recessive. Larvae from a laboratory strain resistant to Cry1Ac and Cry2Ab in diet bioassays survived on cotton bolls producing only Cry1Ac, but not on cotton bolls producing both toxins. Thus, the asymmetrical cross-resistance seen here does not threaten the efficacy of pyramided Bt cotton against pink bollworm. Nonetheless, the results here and previous evidence indicate that cross-resistance occurs between Cry1Ac and Cry2Ab in some key cotton pests. Incorporating the potential effects of such cross-resistance in resistance management plans may help to sustain the efficacy of pyramided Bt crops.

  16. Common, but complex, mode of resistance of Plutella xylostella to Bacillus thuringiensis toxins Cry1Ab and Cry1Ac.

    PubMed

    Sayyed, Ali H; Gatsi, Roxani; Ibiza-Palacios, M Sales; Escriche, Baltasar; Wright, Denis J; Crickmore, Neil

    2005-11-01

    A field collected population of Plutella xylostella (SERD4) was selected in the laboratory with Bacillus thuringiensis endotoxins Cry1Ac (Cry1Ac-SEL) and Cry1Ab (Cry1Ab-SEL). Both subpopulations showed similar phenotypes: high resistance to the Cry1A toxins and little cross-resistance to Cry1Ca or Cry1D. A previous analysis of the Cry1Ac-SEL showed incompletely dominant resistance to Cry1Ac with more than one factor, at least one of which was sex influenced. In the present study reciprocal mass crosses between Cry1Ab-SEL and a laboratory susceptible population (ROTH) provided evidence that Cry1Ab resistance was also inherited as incompletely dominant trait with more than one factor, and at least one of the factors was sex influenced. Analysis of single pair mating indicated that Cry1Ab-SEL was still heterogeneous for Cry1Ab resistance genes, showing genes with different degrees of dominance. Binding studies showed a large reduction of specific binding of Cry1Ab and Cry1Ac to midgut membrane vesicles of the Cry1Ab-SEL subpopulation. Cry1Ab-SEL was found to be more susceptible to trypsin-activated Cry1Ab toxin than protoxin, although no defect in toxin activation was found. Present and previous results indicate a common basis of resistance to both Cry1Ab and Cry1Ac in selected subpopulations and suggest that a similar set of resistance genes are responsible for resistance to Cry1Ab and Cry1Ac and are selected whichever toxin was used. The possibility of an incompletely dominant trait of resistant to these toxins should be taken into account when considering refuge resistance management strategies.

  17. Resistivity and AC calorimetry measurements on CeNiGe2 under pressure

    NASA Astrophysics Data System (ADS)

    Holmes, A. T.; Muramatsu, T.; Miyake, A.; Kaczorowski, D.; Bukowski, Z.; Kagayama, T.; Shimizu, K.

    2007-03-01

    We present resistivity and AC calorimetry measurements of single crystalline CeNiGe2 under high pressure and low temperature in a diamond anvil cell. CeNiGe2 is a highly anisotropic, antiferromagnetic Kondo system at ambient pressure, located close to the boundary with non-magnetic systems. It has two ordering temperatures, T=3.9 K and T=3.2 K, which are suppressed under pressure. Between 0.7 and 1.4 GPa only a single transition was identified, with TN reaching 1.9 K by 1.4 GPa. At 1.9 GPa two transitions could again be seen by AC calorimetry at 2.0 and 1.3 K, accompanied by a qualitative change in the behaviour of the resistivity. The Sommerfeld coefficient showed a maximum of 755 mJ mol-1 K-2 at 1.4 GPa, up from 448 mJ mol-1 K-2 at close to ambient pressure. The residual resistivity was found to decrease sharply above 1.4 GPa after an initial increase with pressure.

  18. Binding of Bacillus thuringiensis Cry1Ac Toxin to Aminopeptidase in Susceptible and Resistant Diamondback Moths (Plutella xylostella)

    PubMed Central

    Luo, K.; Tabashnik, B. E.; Adang, M. J.

    1997-01-01

    Bacillus thuringiensis Cry1Ac toxin bound to a 120-kDa protein isolated from the brush border membranes of both susceptible and resistant larvae of Plutella xylostella, the diamondback moth. The 120-kDa protein was purified by Cry1Ac toxin affinity chromatography. Like Cry1Ac-binding aminopeptidase N (EC 3.4.11.2) from other insects, this protein was eluted from the affinity column with 200 mM N-acetylgalactosamine. The purified protein had aminopeptidase activity and bound Cry1Ac toxin on ligand blots. Purified aminopeptidase was recognized by antibodies to the cross-reacting determinant found on phosphatidylinositol-specific phospholipase C-solubilized proteins. The results show that the presence of Cry1Ac-binding aminopeptidase in the brush border membrane is not sufficient to confer susceptibility to Cry1Ac. Furthermore, the results do not support the hypothesis that resistance to Cry1Ac was caused by lack of a Cry1Ac-binding aminopeptidase. PMID:16535536

  19. An intelligent control framework for robot-aided resistance training using hybrid system modeling and impedance estimation.

    PubMed

    Xu, Guozheng; Guo, Xiaobo; Zhai, Yan; Li, Huijun

    2015-08-01

    This study presents a novel therapy control method for robot-assisted resistance training using the hybrid system modeling technology and the estimated patient's bio-impedance changes. A new intelligent control framework based on hybrid system theory is developed, to automatically generate the desired resistive force and to make accommodating emergency behavior, when monitoring the changes of the impaired limb's muscle strength or the unpredictable safety-related occurrences during the execution of the training task. The impaired limb's muscle strength progress is online evaluated using its bio-damping and bio-stiffness estimation results. The proposed method is verified with a custom constructed therapeutic robot system featuring a Barrett WAM™ compliant manipulator. A typical inpatient stroke subject was recruited and enrolled in a ten-week resistance training program. Preliminary results show that the proposed therapeutic strategy can enhance the impaired limb's muscle strength and has practicability for robot-aided rehabilitation training.

  20. Inheritance patterns, dominance and cross-resistance of Cry1Ab- and Cry1Ac-selected Ostrinia furnacalis (Guenée).

    PubMed

    Zhang, Tiantao; He, Mingxia; Gatehouse, Angharad M R; Wang, Zhenying; Edwards, Martin G; Li, Qing; He, Kanglai

    2014-09-11

    Two colonies of Asian corn borer, Ostrinia furnacalis (Guenée), artificially selected from a Bt-susceptible colony (ACB-BtS) for resistance to Cry1Ab (ACB-AbR) and Cry1Ac (ACB-AcR) toxins, were used to analyze inheritance patterns of resistance to Cry1 toxins. ACB-AbR and ACB-AcR evolved significant levels of resistance, with resistance ratios (RR) of 39-fold and 78.8-fold to Cry1Ab and Cry1Ac, respectively. The susceptibility of ACB-AbR larvae to Cry1Ac and Cry1F toxins, which had not previously been exposed, were significantly reduced, being >113-fold and 48-fold, respectively. Similarly, susceptibility of ACB-AcR larvae to Cry1Ab and Cry1F were also significantly reduced (RR > nine-fold, RR > 18-fold, respectively), indicating cross-resistance among Cry1Ab, Cry1Ac, and Cry1F toxins. However, ACB-AbR and ACB-AcR larvae were equally susceptible to Cry1Ie as were ACB-BtS larvae, indicating no cross-resistance between Cry1Ie and Cry1Ab or Cry1Ac toxins; this may provide considerable benefits in preventing or delaying the evolution of resistance in ACB to Cry1Ab and Cry1Ac toxins. Backcrossing studies indicated that resistance to Cry1Ab toxin was polygenic in ACB-AbR, but monogenic in ACB-AcR, whilst resistance to Cry1Ac toxin was primarily monogenic in both ACB-AbR and ACB-AcR, but polygenic as resistance increased.

  1. Targeting ACLY sensitizes castration-resistant prostate cancer cells to AR antagonism by impinging on an ACLY-AMPK-AR feedback mechanism.

    PubMed

    Shah, Supriya; Carriveau, Whitney J; Li, Jinyang; Campbell, Sydney L; Kopinski, Piotr K; Lim, Hee-Woong; Daurio, Natalie; Trefely, Sophie; Won, Kyoung-Jae; Wallace, Douglas C; Koumenis, Constantinos; Mancuso, Anthony; Wellen, Kathryn E

    2016-07-12

    The androgen receptor (AR) plays a central role in prostate tumor growth. Inappropriate reactivation of the AR after androgen deprivation therapy promotes development of incurable castration-resistant prostate cancer (CRPC). In this study, we provide evidence that metabolic features of prostate cancer cells can be exploited to sensitize CRPC cells to AR antagonism. We identify a feedback loop between ATP-citrate lyase (ACLY)-dependent fatty acid synthesis, AMPK, and the AR in prostate cancer cells that could contribute to therapeutic resistance by maintaining AR levels. When combined with an AR antagonist, ACLY inhibition in CRPC cells promotes energetic stress and AMPK activation, resulting in further suppression of AR levels and target gene expression, inhibition of proliferation, and apoptosis. Supplying exogenous fatty acids can restore energetic homeostasis; however, this rescue does not occur through increased β-oxidation to support mitochondrial ATP production. Instead, concurrent inhibition of ACLY and AR may drive excess ATP consumption as cells attempt to cope with endoplasmic reticulum (ER) stress, which is prevented by fatty acid supplementation. Thus, fatty acid metabolism plays a key role in coordinating ER and energetic homeostasis in CRPC cells, thereby sustaining AR action and promoting proliferation. Consistent with a role for fatty acid metabolism in sustaining AR levels in prostate cancer in vivo, AR mRNA levels in human prostate tumors correlate positively with expression of ACLY and other fatty acid synthesis genes. The ACLY-AMPK-AR network can be exploited to sensitize CRPC cells to AR antagonism, suggesting novel therapeutic opportunities for prostate cancer.

  2. Cell-surface galectin-3 confers resistance to TRAIL by impeding trafficking of death receptors in metastatic colon adenocarcinoma cells.

    PubMed

    Mazurek, N; Byrd, J C; Sun, Y; Hafley, M; Ramirez, K; Burks, J; Bresalier, R S

    2012-03-01

    Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) induces apoptosis and preferentially kills tumor cells by engaging specific glycosylated death receptors, resulting in the internalization of ligand/receptor complexes and recruitment of the initiator caspase-8 to an activation platform known as the death-inducing signaling complex (DISC). However, emergence of TRAIL-resistant sub-populations may contribute to therapeutic failure. To investigate resistance mechanisms, we isolated a stable TRAIL-resistant sub-population of the metastatic colon cancer cell line LS-LIM6, designated LIM6-TR. LIM6-TR cells are impaired in endocytosis of TRAIL/death receptors complexes and failed to recruit/activate caspase-8 to the DISC upon TRAIL stimulation. Differential activation of Wnt and JNK pathways is not responsible for acquisition of TRAIL resistance. LIM6-TR cells display a marked increase in cell-surface expression of galectin-3, an endogenous lectin, which co-localizes with and binds death receptors. Silencing of galectin-3 restores TRAIL sensitivity and promotes TRAIL-mediated endocytosis of TRAIL/death receptors complexes. Inhibitors of galectin-3 and glycosylation also re-sensitize LIM6-TR to TRAIL and restore internalization of ligand/receptors complexes. These studies identify a novel TRAIL-resistance mechanism in which galectin-3 impedes trafficking of death receptor by anchoring them in glycan nano-clusters, blocking the execution of the apoptosis signal.

  3. Transgenic Sugarcane with a cry1Ac Gene Exhibited Better Phenotypic Traits and Enhanced Resistance against Sugarcane Borer

    PubMed Central

    Gao, Shiwu; Yang, Yingying; Wang, Chunfeng; Guo, Jinlong; Zhou, Dinggang; Wu, Qibin; Su, Yachun; Xu, Liping

    2016-01-01

    We developed sugarcane plants with improved resistance to the sugarcane borer, Diatraea saccharalis (F). An expression vector pGcry1Ac0229, harboring the cry1Ac gene and the selectable marker gene, bar, was constructed. This construct was introduced into the sugarcane cultivar FN15 by particle bombardment. Transformed plantlets were identified after selection with Phosphinothricin (PPT) and Basta. Plantlets were then screened by PCR based on the presence of cry1Ac and 14 cry1Ac positive plantlets were identified. Real-time quantitative PCR (RT-qPCR) revealed that the copy number of cry1Ac gene in the transgenic lines varied from 1 to 148. ELISA analysis showed that Cry1Ac protein levels in 7 transgenic lines ranged from 0.85 μg/FWg to 70.92 μg/FWg in leaves and 0.04 μg/FWg to 7.22 μg/FWg in stems, and negatively correlated to the rate of insect damage that ranged from 36.67% to 13.33%, respectively. Agronomic traits of six transgenic sugarcane lines with medium copy numbers were similar to the non-transgenic parental line. However, phenotype was poor in lines with high or low copy numbers. Compared to the non-transgenic control plants, all transgenic lines with medium copy numbers had relatively equal or lower sucrose yield and significantly improved sugarcane borer resistance, which lowered susceptibility to damage by insects. This suggests that the transgenic sugarcane lines harboring medium copy numbers of the cry1Ac gene may have significantly higher resistance to sugarcane borer but the sugarcane yield in these lines is similar to the non-transgenic control thus making them superior to the control lines. PMID:27093437

  4. Transgenic Sugarcane with a cry1Ac Gene Exhibited Better Phenotypic Traits and Enhanced Resistance against Sugarcane Borer.

    PubMed

    Gao, Shiwu; Yang, Yingying; Wang, Chunfeng; Guo, Jinlong; Zhou, Dinggang; Wu, Qibin; Su, Yachun; Xu, Liping; Que, Youxiong

    2016-01-01

    We developed sugarcane plants with improved resistance to the sugarcane borer, Diatraea saccharalis (F). An expression vector pGcry1Ac0229, harboring the cry1Ac gene and the selectable marker gene, bar, was constructed. This construct was introduced into the sugarcane cultivar FN15 by particle bombardment. Transformed plantlets were identified after selection with Phosphinothricin (PPT) and Basta. Plantlets were then screened by PCR based on the presence of cry1Ac and 14 cry1Ac positive plantlets were identified. Real-time quantitative PCR (RT-qPCR) revealed that the copy number of cry1Ac gene in the transgenic lines varied from 1 to 148. ELISA analysis showed that Cry1Ac protein levels in 7 transgenic lines ranged from 0.85 μg/FWg to 70.92 μg/FWg in leaves and 0.04 μg/FWg to 7.22 μg/FWg in stems, and negatively correlated to the rate of insect damage that ranged from 36.67% to 13.33%, respectively. Agronomic traits of six transgenic sugarcane lines with medium copy numbers were similar to the non-transgenic parental line. However, phenotype was poor in lines with high or low copy numbers. Compared to the non-transgenic control plants, all transgenic lines with medium copy numbers had relatively equal or lower sucrose yield and significantly improved sugarcane borer resistance, which lowered susceptibility to damage by insects. This suggests that the transgenic sugarcane lines harboring medium copy numbers of the cry1Ac gene may have significantly higher resistance to sugarcane borer but the sugarcane yield in these lines is similar to the non-transgenic control thus making them superior to the control lines.

  5. Broadband 120 MHz Impedance Quartz Crystal Microbalance (QCM) with Calibrated Resistance and Quantitative Dissipation for Biosensing Measurements at Higher Harmonic Frequencies.

    PubMed

    Kasper, Manuel; Traxler, Lukas; Salopek, Jasmina; Grabmayr, Herwig; Ebner, Andreas; Kienberger, Ferry

    2016-05-25

    We developed an impedance quartz crystal microbalance (QCM) approach with the ability to simultaneously record mass changes and calibrated energy dissipation with high sensitivity using an impedance analyzer. This impedance QCM measures frequency shifts and resistance changes of sensing quartz crystals very stable, accurately, and calibrated, thus yielding quantitative information on mass changes and dissipation. Resistance changes below 0.3 Ω were measured with corresponding dissipation values of 0.01 µU (micro dissipation units). The broadband impedance capabilities allow measurements between 20 Hz and 120 MHz including higher harmonic modes of up to 11th order for a 10 MHz fundamental resonance frequency quartz crystal. We demonstrate the adsorbed mass, calibrated resistance, and quantitative dissipation measurements on two biological systems including the high affinity based avidin-biotin interaction and nano-assemblies of polyelectrolyte layers. The binding affinity of a protein-antibody interaction was determined. The impedance QCM is a versatile and simple method for accurate and calibrated resistance and dissipation measurements with broadband measurement capabilities for higher harmonics measurements.

  6. Broadband 120 MHz Impedance Quartz Crystal Microbalance (QCM) with Calibrated Resistance and Quantitative Dissipation for Biosensing Measurements at Higher Harmonic Frequencies

    PubMed Central

    Kasper, Manuel; Traxler, Lukas; Salopek, Jasmina; Grabmayr, Herwig; Ebner, Andreas; Kienberger, Ferry

    2016-01-01

    We developed an impedance quartz crystal microbalance (QCM) approach with the ability to simultaneously record mass changes and calibrated energy dissipation with high sensitivity using an impedance analyzer. This impedance QCM measures frequency shifts and resistance changes of sensing quartz crystals very stable, accurately, and calibrated, thus yielding quantitative information on mass changes and dissipation. Resistance changes below 0.3 Ω were measured with corresponding dissipation values of 0.01 µU (micro dissipation units). The broadband impedance capabilities allow measurements between 20 Hz and 120 MHz including higher harmonic modes of up to 11th order for a 10 MHz fundamental resonance frequency quartz crystal. We demonstrate the adsorbed mass, calibrated resistance, and quantitative dissipation measurements on two biological systems including the high affinity based avidin-biotin interaction and nano-assemblies of polyelectrolyte layers. The binding affinity of a protein-antibody interaction was determined. The impedance QCM is a versatile and simple method for accurate and calibrated resistance and dissipation measurements with broadband measurement capabilities for higher harmonics measurements. PMID:27231946

  7. CRISPR/Cas9-mediated phage resistance is not impeded by the DNA modifications of phage T4.

    PubMed

    Yaung, Stephanie J; Esvelt, Kevin M; Church, George M

    2014-01-01

    Bacteria rely on two known DNA-level defenses against their bacteriophage predators: restriction-modification and Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR)-CRISPR-associated (Cas) systems. Certain phages have evolved countermeasures that are known to block endonucleases. For example, phage T4 not only adds hydroxymethyl groups to all of its cytosines, but also glucosylates them, a strategy that defeats almost all restriction enzymes. We sought to determine whether these DNA modifications can similarly impede CRISPR-based defenses. In a bioinformatics search, we found naturally occurring CRISPR spacers that potentially target phages known to modify their DNA. Experimentally, we show that the Cas9 nuclease from the Type II CRISPR system of Streptococcus pyogenes can overcome a variety of DNA modifications in Escherichia coli. The levels of Cas9-mediated phage resistance to bacteriophage T4 and the mutant phage T4 gt, which contains hydroxymethylated but not glucosylated cytosines, were comparable to phages with unmodified cytosines, T7 and the T4-like phage RB49. Our results demonstrate that Cas9 is not impeded by N6-methyladenine, 5-methylcytosine, 5-hydroxymethylated cytosine, or glucosylated 5-hydroxymethylated cytosine.

  8. Introducing AC inductive reactance with a power tool

    NASA Astrophysics Data System (ADS)

    Bryant, Wesley; Baker, Blane

    2016-09-01

    The concept of reactance in AC electrical circuits is often non-intuitive and difficult for students to grasp. In order to address this lack of conceptual understanding, classroom exercises compare the predicted resistance of a power tool, based on electrical specifications, to measured resistance. Once students discover that measured resistance is smaller than expected, they are asked to explain these observations using previously studied principles of magnetic induction. Exercises also introduce the notion of inductive reactance and impedance in AC circuits and, ultimately, determine self-inductance of the motor windings within the power tool.

  9. The investigation of dielectric properties and ac conductivity of new ceramic diphosphate Ag0.6Na0.4FeP2O7 using impedance spectroscopy method

    NASA Astrophysics Data System (ADS)

    Nasri, S.; Megdiche, M.; Gargouri, M.

    2016-10-01

    In this paper, Ag0.6Na0.4FeP2O7 has been synthesized by solid state reaction method. The ceramic compound was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), vibrational spectroscopy and impedance measurements. In fact, the investigated sample has shown single phase type monoclinic structure with P21/C space group. The frequency-dependent electrical data are analyzed in the frame-work of conductivity and electric modulus formalisms. The real and imaginary parts of complex impedance are well fitted to equivalent circuit model based on the Z-View-software. Besides, the observed frequency dependence of conductivity is found to obey Jonscher's universal law. The temperature dependence of both ac conductivity and the parameter s is reasonably well interpreted by the correlated barrier hopping (CBH). The theoretical fitting between the proposed model and the experimental data showed good agreement. The contribution of single polaron and bipolaron hopping to a.c. conductivity in present compound is also studied. The ionic conductivity is discussed on the basis of the structural characteristics of the sample.

  10. Towards a graphene-based quantum impedance standard

    SciTech Connect

    Kalmbach, C.-C.; Schurr, J. Ahlers, F. J.; Müller, A.; Novikov, S.; Lebedeva, N.; Satrapinski, A.

    2014-08-18

    Precision measurements of the quantum Hall resistance with alternating current (ac) in the kHz range were performed on epitaxial graphene in order to assess its suitability as a quantum standard of impedance. The quantum Hall plateaus measured with alternating current were found to be flat within one part in 10{sup 7}. This is much better than for plain GaAs quantum Hall devices and shows that the magnetic-flux-dependent capacitive ac losses of the graphene device are less critical. The observed frequency dependence of about −8 × 10{sup −8}/kHz is comparable in absolute value to the positive frequency dependence of plain GaAs devices, but the negative sign is attributed to stray capacitances which we believe can be minimized by a careful design of the graphene device. Further improvements thus may lead to a simpler and more user-friendly quantum standard for both resistance and impedance.

  11. Nontoxic colloidal particles impede antibiotic resistance of swarming bacteria by disrupting collective motion and speed.

    PubMed

    Lu, Shengtao; Liu, Fang; Xing, Bengang; Yeow, Edwin K L

    2015-12-01

    A monolayer of swarming B. subtilis on semisolid agar is shown to display enhanced resistance against antibacterial drugs due to their collective behavior and motility. The dynamics of swarming motion, visualized in real time using time-lapse microscopy, prevents the bacteria from prolonged exposure to lethal drug concentrations. The elevated drug resistance is significantly reduced when the collective motion of bacteria is judiciously disrupted using nontoxic polystyrene colloidal particles immobilized on the agar surface. The colloidal particles block and hinder the motion of the cells, and force large swarming rafts to break up into smaller packs in order to maneuver across narrow spaces between densely packed particles. In this manner, cohesive rafts rapidly lose their collectivity, speed, and group dynamics, and the cells become vulnerable to the drugs. The antibiotic resistance capability of swarming B. subtilis is experimentally observed to be negatively correlated with the number density of colloidal particles on the engineered surface. This relationship is further tested using an improved self-propelled particle model that takes into account interparticle alignment and hard-core repulsion. This work has pertinent implications on the design of optimal methods to treat drug resistant bacteria commonly found in swarming colonies.

  12. Nontoxic colloidal particles impede antibiotic resistance of swarming bacteria by disrupting collective motion and speed

    NASA Astrophysics Data System (ADS)

    Lu, Shengtao; Liu, Fang; Xing, Bengang; Yeow, Edwin K. L.

    2015-12-01

    A monolayer of swarming B. subtilis on semisolid agar is shown to display enhanced resistance against antibacterial drugs due to their collective behavior and motility. The dynamics of swarming motion, visualized in real time using time-lapse microscopy, prevents the bacteria from prolonged exposure to lethal drug concentrations. The elevated drug resistance is significantly reduced when the collective motion of bacteria is judiciously disrupted using nontoxic polystyrene colloidal particles immobilized on the agar surface. The colloidal particles block and hinder the motion of the cells, and force large swarming rafts to break up into smaller packs in order to maneuver across narrow spaces between densely packed particles. In this manner, cohesive rafts rapidly lose their collectivity, speed, and group dynamics, and the cells become vulnerable to the drugs. The antibiotic resistance capability of swarming B. subtilis is experimentally observed to be negatively correlated with the number density of colloidal particles on the engineered surface. This relationship is further tested using an improved self-propelled particle model that takes into account interparticle alignment and hard-core repulsion. This work has pertinent implications on the design of optimal methods to treat drug resistant bacteria commonly found in swarming colonies.

  13. High Susceptibility to Cry1Ac and Low Resistance Allele Frequency Reduce the Risk of Resistance of Helicoverpa armigera to Bt Soybean in Brazil

    PubMed Central

    Bacalhau, Fabiana B.; Amado, Douglas; Carvalho, Renato A.; Martinelli, Samuel; Head, Graham P.; Omoto, Celso

    2016-01-01

    The Old World bollworm, Helicoverpa armigera (Hübner), was recently introduced into Brazil, where it has caused extensive damage to cotton and soybean crops. MON 87701 × MON 89788 soybean, which expresses the Bt protein Cry1Ac, was recently deployed in Brazil, providing high levels of control against H. armigera. To assess the risk of resistance to the Cry1Ac protein expressed by MON 87701 × MON 89788 soybean in Brazil, we conducted studies to evaluate the baseline susceptibility of H. armigera to Cry1Ac, in planta efficacy including the assessment of the high-dose criterion, and the initial resistance allele frequency based on an F2 screen. The mean Cry1Ac lethal concentration (LC50) ranged from 0.11 to 1.82 μg·mL−1 of diet among all H. armigera field populations collected from crop seasons 2013/14 to 2014/15, which indicated about 16.5-fold variation. MON 87701 × MON 89788 soybean exhibited a high level of efficacy against H. armigera and most likely met the high dose criterion against this target species in leaf tissue dilution bioassays up to 50 times. A total of 212 F2 family lines of H. armigera were established from field collections sampled from seven locations across Brazil and were screened for the presence of MON 87701 × MON 89788 soybean resistance alleles. None of the 212 families survived on MON 87701 × MON 89788 soybean leaf tissue (estimated allele frequency = 0.0011). The responses of H. armigera to Cry1Ac protein, high susceptibility to MON 87701 × MON 89788 soybean, and low frequency of resistance alleles across the main soybean-producing regions support the assumptions of a high-dose/refuge strategy. However, maintenance of reasonable compliance with the refuge recommendation will be essential to delay the evolution of resistance in H. armigera to MON 87701 × MON 89788 soybean in Brazil. PMID:27532632

  14. High Susceptibility to Cry1Ac and Low Resistance Allele Frequency Reduce the Risk of Resistance of Helicoverpa armigers to Bt Soybean in Brazil.

    PubMed

    Dourado, Patrick M; Bacalhau, Fabiana B; Amado, Douglas; Carvalho, Renato A; Martinelli, Samuel; Head, Graham P; Omoto, Celso

    2016-01-01

    The Old World bollworm, Helicoverpa armigera (Hübner), was recently introduced into Brazil, where it has caused extensive damage to cotton and soybean crops. MON 87701 × MON 89788 soybean, which expresses the Bt protein Cry1Ac, was recently deployed in Brazil, providing high levels of control against H. armigera. To assess the risk of resistance to the Cry1Ac protein expressed by MON 87701 × MON 89788 soybean in Brazil, we conducted studies to evaluate the baseline susceptibility of H. armigera to Cry1Ac, in planta efficacy including the assessment of the high-dose criterion, and the initial resistance allele frequency based on an F2 screen. The mean Cry1Ac lethal concentration (LC50) ranged from 0.11 to 1.82 μg·mL-1 of diet among all H. armigera field populations collected from crop seasons 2013/14 to 2014/15, which indicated about 16.5-fold variation. MON 87701 × MON 89788 soybean exhibited a high level of efficacy against H. armigera and most likely met the high dose criterion against this target species in leaf tissue dilution bioassays up to 50 times. A total of 212 F2 family lines of H. armigera were established from field collections sampled from seven locations across Brazil and were screened for the presence of MON 87701 × MON 89788 soybean resistance alleles. None of the 212 families survived on MON 87701 × MON 89788 soybean leaf tissue (estimated allele frequency = 0.0011). The responses of H. armigera to Cry1Ac protein, high susceptibility to MON 87701 × MON 89788 soybean, and low frequency of resistance alleles across the main soybean-producing regions support the assumptions of a high-dose/refuge strategy. However, maintenance of reasonable compliance with the refuge recommendation will be essential to delay the evolution of resistance in H. armigera to MON 87701 × MON 89788 soybean in Brazil.

  15. A new monitoring method for electrochemical aggregates by impedance spectroscopy

    NASA Astrophysics Data System (ADS)

    Kurzweil, P.; Fischle, H.-J.

    A variant of ac impedance spectroscopy is applied to monitor and control electrochemical cells and appliances without need for reference values and knowledge of control points in advance. Electrolyzers, fuels cells, energy stores, sensors and electrochemical reactors are steered to an optimum operating state by continuous evaluation of capacitance and the derivatives thereof. Dry and humid electrode-electrolyte interfaces are distinguished with the aid of the low-frequency impedance. The problem is solved in order to determine electrolyte concentrations unambiguously from electrolyte resistance, although the conductivity of the solution has a maximum and changes nonlinearly with the concentration.

  16. Similar genetic basis of resistance to Bt toxin Cry1Ac in Boll-selected and diet-selected strains of pink bollworm.

    PubMed

    Fabrick, Jeffrey A; Tabashnik, Bruce E

    2012-01-01

    Genetically engineered cotton and corn plants producing insecticidal Bacillus thuringiensis (Bt) toxins kill some key insect pests. Yet, evolution of resistance by pests threatens long-term insect control by these transgenic Bt crops. We compared the genetic basis of resistance to Bt toxin Cry1Ac in two independently derived, laboratory-selected strains of a major cotton pest, the pink bollworm (Pectinophora gossypiella [Saunders]). The Arizona pooled resistant strain (AZP-R) was started with pink bollworm from 10 field populations and selected with Cry1Ac in diet. The Bt4R resistant strain was started with a long-term susceptible laboratory strain and selected first with Bt cotton bolls and later with Cry1Ac in diet. Previous work showed that AZP-R had three recessive mutations (r1, r2, and r3) in the pink bollworm cadherin gene (PgCad1) linked with resistance to Cry1Ac and Bt cotton producing Cry1Ac. Here we report that inheritance of resistance to a diagnostic concentration of Cry1Ac was recessive in Bt4R. In interstrain complementation tests for allelism, F(1) progeny from crosses between AZP-R and Bt4R were resistant to Cry1Ac, indicating a shared resistance locus in the two strains. Molecular analysis of the Bt4R cadherin gene identified a novel 15-bp deletion (r4) predicted to cause the loss of five amino acids upstream of the Cry1Ac-binding region of the cadherin protein. Four recessive mutations in PgCad1 are now implicated in resistance in five different strains, showing that mutations in cadherin are the primary mechanism of resistance to Cry1Ac in laboratory-selected strains of pink bollworm from Arizona.

  17. Calculation of the ac to dc resistance ratio of conductive nonmagnetic straight conductors by applying FEM simulations

    NASA Astrophysics Data System (ADS)

    Riba, Jordi-Roger

    2015-09-01

    This paper analyzes the skin and proximity effects in different conductive nonmagnetic straight conductor configurations subjected to applied alternating currents and voltages. These effects have important consequences, including a rise of the ac resistance, which in turn increases power loss, thus limiting the rating for the conductor. Alternating current (ac) resistance is important in power conductors and bus bars for line frequency applications, as well as in smaller conductors for high frequency applications. Despite the importance of this topic, it is not usually analyzed in detail in undergraduate and even in graduate studies. To address this, this paper compares the results provided by available exact formulas for simple geometries with those obtained by means of two-dimensional finite element method (FEM) simulations and experimental results. The paper also shows that FEM results are very accurate and more general than those provided by the formulas, since FEM models can be applied in a wide range of electrical frequencies and configurations.

  18. Frequency of alleles conferring resistance to the Bt toxins Cry1Ac and Cry2Ab in Australian populations of Helicoverpa armigera (Lepidoptera: Noctuidae).

    PubMed

    Mahon, R J; Olsen, K M; Downes, S; Addison, S

    2007-12-01

    Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae) is an important lepidopteran pest of cotton (Gossypium spp.) in Australia and the Old World. From 2002, F2 screens were used to examine the frequency of resistance alleles in Australian populations of H. armigera to Bacillus thuringiensis (Bt) CrylAc and Cry2Ab, the two insecticidal proteins present in the transgenic cotton Bollgard II. At that time, Ingard (expressing Cry1Ac) cotton had been grown in Australia for seven seasons, and Bollgard II was about to be commercially released. The principal objective of our study was to determine whether sustained exposure caused an elevated frequency of alleles conferring resistance to Cry1Ac in a species with a track record of evolving resistance to conventional insecticides. No major alleles conferring resistance to Cry1Ac were found. The frequency of resistance alleles for Cry1Ac was <0.0003, with a 95% credibility interval between 0 and 0.0009. In contrast, alleles conferring resistance to Cry2Ab were found at a frequency of 0.0033 (0.0017, 0.0055). The first isolation of this allele was found before the widespread deployment of Bollgard II. For both toxins the experiment-wise detection probability was 94.4%. Our results suggest that alleles conferring resistance to Cry1Ac are rare and that a relatively high baseline frequency of alleles conferring resistance to Cry2Ab existed before the introduction of Bt cotton containing this toxin.

  19. Structural elucidation and evaluation of multidrug-resistance modulatory capability of amarissinins A-C, diterpenes derived from Salvia amarissima.

    PubMed

    Bautista, Elihú; Fragoso-Serrano, Mabel; Ortiz-Pastrana, Naytzé; Toscano, Rubén A; Ortega, Alfredo

    2016-10-01

    Three new diterpenes (amarissinins A-C, 1-3) containing several oxygenated functionalities were isolated from the leaves and flowers of Salvia amarissima. The structures of these compounds were established through the analysis of their NMR spectroscopy and mass spectrometry data. The structures of compounds 1 and 2 were confirmed by single crystal X-ray diffraction. Compound 2 was identified as a C-10 epimer of dugesin F (5). The cytotoxic activity of these compounds against five human cancer cell lines was determined. Additionally, the capability to modulate the multidrug resistance (MDR) in the MCF-7 cancer cell line resistant to vinblastine was tested.

  20. AC losses in perpendicular external magnetic fields in ring bundle barrier multifilamentary BSCCO(2223) tapes with a central resistive barrier

    NASA Astrophysics Data System (ADS)

    Eckelmann, H.; Krelaus, J.; Nast, R.; Goldacker, W.

    2001-06-01

    For the most common AC frequencies, the main components of the AC losses in multifilamentary Bi(2223) tapes are caused by both hysteresis and coupling losses. These losses can be reduced by increasing the matrix resistivity, applying a twist to the filaments and by the use of a conductor design optimised for a practical application. In the ring bundle barrier (RBB) conductor design we have bundles of filaments which are twisted around a central resistive core. The RBB structure was prepared via the powder in tube assemble and react (PITAR) route . In these tapes six bundles of seven filaments are twisted around a resistive layer of a mixture of 50% SrCO 3 and 50% SrZrO 3 in the centre of the tape. A series of tapes with twist lengths down to 3.4 mm was prepared. We present the measured AC losses of these tapes in external perpendicular magnetic fields. By using existing models, a description of the losses in the low Ḃ range was possible, leading to a separation into hysteresis, eddy current and coupling current losses. The frequency dependent loss contribution is dominated by the coupling current losses, from which the coupling current decay time constant, the effective permeability, the matrix resistivity and the critical Ḃc for filament coupling were extracted. In tapes with a twist length below 5 mm the typical loss behaviour for decoupled filaments is observed at frequencies up to 500 Hz. Compared to the untwisted tapes, a loss reduction of up to 70% for low field amplitudes (below 10 mT) was achieved.

  1. Efficacy of Genetically Modified Bt Toxins Alone and in Combinations Against Pink Bollworm Resistant to Cry1Ac and Cry2Ab

    PubMed Central

    Tabashnik, Bruce E.; Fabrick, Jeffrey A.; Unnithan, Gopalan C.; Yelich, Alex J.; Masson, Luke; Zhang, Jie; Bravo, Alejandra; Soberón, Mario

    2013-01-01

    Evolution of resistance in pests threatens the long-term efficacy of insecticidal proteins from Bacillus thuringiensis (Bt) used in sprays and transgenic crops. Previous work showed that genetically modified Bt toxins Cry1AbMod and Cry1AcMod effectively countered resistance to native Bt toxins Cry1Ab and Cry1Ac in some pests, including pink bollworm (Pectinophora gossypiella). Here we report that Cry1AbMod and Cry1AcMod were also effective against a laboratory-selected strain of pink bollworm resistant to Cry2Ab as well as to Cry1Ab and Cry1Ac. Resistance ratios based on the concentration of toxin killing 50% of larvae for the resistant strain relative to a susceptible strain were 210 for Cry2Ab, 270 for Cry1Ab, and 310 for Cry1Ac, but only 1.6 for Cry1AbMod and 2.1 for Cry1AcMod. To evaluate the interactions among toxins, we tested combinations of Cry1AbMod, Cry1Ac, and Cry2Ab. For both the resistant and susceptible strains, the net results across all concentrations tested showed slight but significant synergism between Cry1AbMod and Cry2Ab, whereas the other combinations of toxins did not show consistent synergism or antagonism. The results suggest that the modified toxins might be useful for controlling populations of pink bollworm resistant to Cry1Ac, Cry2Ab, or both. PMID:24244692

  2. Local impedance measurement of an electrode/single-pentacene-grain interface by frequency-modulation scanning impedance microscopy

    SciTech Connect

    Kimura, Tomoharu; Yamada, Hirofumi; Kobayashi, Kei

    2015-08-07

    The device performances of organic thin film transistors are often limited by the metal–organic interface because of the disordered molecular layers at the interface and the energy barriers against the carrier injection. It is important to study the local impedance at the interface without being affected by the interface morphology. We combined frequency modulation atomic force microscopy with scanning impedance microscopy (SIM) to sensitively measure the ac responses of the interface to an ac voltage applied across the interface and the dc potential drop at the interface. By using the frequency-modulation SIM (FM-SIM) technique, we characterized the interface impedance of a Pt electrode and a single pentacene grain as a parallel circuit of a contact resistance and a capacitance. We found that the reduction of the contact resistance was caused by the reduction of the energy level mismatch at the interface by the FM-SIM measurements, demonstrating the usefulness of the FM-SIM technique for investigation of the local interface impedance without being affected by its morphology.

  3. Study of Influence of Electrode Geometry on Impedance Spectroscopy

    SciTech Connect

    Ahmed, Riaz; Reifsnider, Kenneth L

    2011-01-01

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

  4. Structural and complex AC impedance spectroscopic studies of A 2CoNbO 6 (A = Sr, Ba) ordered double perovskites

    NASA Astrophysics Data System (ADS)

    Bashir, J.; Shaheen, R.

    2011-05-01

    Powder X-ray diffraction has been employed to study the crystal structures of Sr 2CoNbO 6 ( SCNO) and Ba 2CoNbO 6 ( BCNO) double perovskites. Rietveld fit to the X-ray diffraction data showed that Ba 2CoNbO 6 perovskites was monoclinic with space group P2 1/ n whereas Sr 2CoNbO 6 was found to be tetragonal with space group I4/ m. Like other cobalt based perovskites, both materials exhibit high values of dielectric constant at room temperature and low frequencies. Room temperature impedance and modulus spectra, measured over the 1 Hz to 10 MHz, reveal two relaxation processes with different relaxation times which were attributed to the grain and grain boundaries.

  5. Microfabricated multi-frequency particle impedance characterization system

    SciTech Connect

    Fuller, C K; Hamilton, J; Ackler, H; Krulevitch, P; Boser, B; Eldredge, A; Becker, F; Yang, J; Gascoyne, P

    2000-03-01

    We have developed a microfabricated flow-through impedance characterization system capable of performing AC, multi-frequency measurements on cells and other particles. The sensor measures both the resistive and reactive impedance of passing particles, at rates of up to 100 particles per second. Its operational bandwidth approaches 10 MHz with a signal-to-noise ratio of approximately 40 dB. Particle impedance is measured at three or more frequencies simultaneously, enabling the derivation of multiple particle parameters. This constitutes an improvement to the well-established technique of DC particle sizing via the Coulter Principle. Human peripheral blood granulocyte radius, membrane capacitance, and cytoplasmic conductivity were measured (r = 4.1 {micro}m, C{sub mem} = 0.9 {micro}F/cm{sup 2}, {sigma}{sub int} = 0.66 S/m) and were found to be consistent with published values.

  6. Electrochemical Performance and Stability of the Cathode for Solid Oxide Fuel Cells. I. Cross Validation of Polarization Measurements by Impedance Spectroscopy and Current-Potential Sweep

    SciTech Connect

    Zhou, Xiao Dong; Pederson, Larry R.; Templeton, Jared W.; Stevenson, Jeffry W.

    2009-12-09

    The aim of this paper is to address three issues in solid oxide fuel cells: (1) cross-validation of the polarization of a single cell measured using both dc and ac approaches, (2) the precise determination of the total areal specific resistance (ASR), and (3) understanding cathode polarization with LSCF cathodes. The ASR of a solid oxide fuel cell is a dynamic property, meaning that it changes with current density. The ASR measured using ac impedance spectroscopy (low frequency interception with real Z´ axis of ac impedance spectrum) matches with that measured from a dc IV sweep (the tangent of dc i-V curve). Due to the dynamic nature of ASR, we found that an ac impedance spectrum measured under open circuit voltage or on a half cell may not represent cathode performance under real operating conditions, particularly at high current density. In this work, the electrode polarization was governed by the cathode activation polarization; the anode contribution was negligible.

  7. NEW APPROACHES: Investigating power, work and effective values in an AC resistive circuit through a microcomputer-based laboratory

    NASA Astrophysics Data System (ADS)

    Trumper, Ricardo; Gelbman, Moshe

    1997-11-01

    Microcomputer-based laboratory (MBL) tools have been developed which interface with a great variety of computers. Students use these tools to collect physical data in real time which can later be manipulated and analysed. This new investigative method together with a high standard of precision enables students to investigate many principles of physics that have not previously been feasible. In this article we describe some examples of experiments designed for high-school students with the help of the MBL Explorer. We mainly analyse power, work and effective (RMS) values in an AC resistive circuit.

  8. Resistance of Trichoplusia ni to Bacillus thuringiensis toxin Cry1Ac is independent of alteration of the cadherin-like receptor for Cry toxins.

    PubMed

    Zhang, Xin; Tiewsiri, Kasorn; Kain, Wendy; Huang, Lihua; Wang, Ping

    2012-01-01

    Alteration of binding sites for Bacillus thuringiensis (Bt) toxins in insect midgut is the major mechanism of high-level resistance to Bt toxins in insects. The midgut cadherin is known to be a major binding protein for Bt Cry1A toxins and linkage of Bt-resistance to cadherin gene mutations has been identified in lepidopterans. The resistance to Bt toxin Cry1Ac evolved in greenhouse populations of Trichoplusia ni has been identified to be associated with the down-regulation of an aminopeptidase N (APN1) gene by a trans-regulatory mechanism and the resistance gene has been mapped to the locus of an ABC transporter (ABCC2) gene. However, whether cadherin is also involved with Cry1Ac-resistance in T. ni requires to be understood. Here we report that the Cry1Ac-resistance in T. ni is independent of alteration of the cadherin. The T. ni cadherin cDNA was cloned and the cadherin sequence showed characteristic features known to cadherins from Lepidoptera. Various T. ni cadherin gene alleles were identified and genetic linkage analysis of the cadherin alleles with Cry1Ac-resistance showed no association of the cadherin gene with the Cry1Ac-resistance in T. ni. Analysis of cadherin transcripts showed no quantitative difference between the susceptible and Cry1Ac-resistant T. ni larvae. Quantitative proteomic analysis of midgut BBMV proteins by iTRAQ-2D-LC-MS/MS determined that there was no quantitative difference in cadherin content between the susceptible and the resistant larvae and the cadherin only accounted for 0.0014% (mol%) of the midgut BBMV proteins, which is 1/300 of APN1 in molar ratio. The cadherin from both the susceptible and resistant larvae showed as a 200-kDa Cry1Ac-binding protein by toxin overlay binding analysis, and nano-LC-MS/MS analysis of the 200-kDa cadherin determined that there is no quantitative difference between the susceptible and resistant larvae. Results from this study indicate that the Cry1Ac-resistance in T. ni is independent of cadherin

  9. Down-regulation of a novel ABC transporter gene (Pxwhite) is associated with Cry1Ac resistance in the diamondback moth, Plutella xylostella (L.).

    PubMed

    Guo, Zhaojiang; Kang, Shi; Zhu, Xun; Xia, Jixing; Wu, Qingjun; Wang, Shaoli; Xie, Wen; Zhang, Youjun

    2015-04-01

    Biopesticides or transgenic crops based on Cry toxins from the soil bacterium Bacillus thuringiensis (Bt) effectively control agricultural insect pests. The sustainable use of Bt biopesticides and Bt crops is threatened, however, by the development of Cry resistance in the target pests. The diamondback moth, Plutella xylostella (L.), is the first pest that developed resistance to a Bt biopesticide in the field, and a recent study has shown that the resistance of P. xylostella to Cry1Ac is caused by a mutation in an ATP-binding cassette (ABC) transporter gene (ABCC2). In this study, we report that down-regulation of a novel ABC transporter gene from ABCG subfamily (Pxwhite) is associated with Cry1Ac resistance in P. xylostella. The full-length cDNA sequence of Pxwhite was cloned and analyzed. Spatial-temporal expression detection revealed that Pxwhite was expressed in all tissues and developmental stages, and highest expressed in Malpighian tubule tissue and in egg stage. Sequence variation analysis of Pxwhite indicated the absence of constant non-synonymous mutations between susceptible and resistant strains, whereas midgut transcript analysis showed that Pxwhite was remarkably reduced in all resistant strains and further reduced when larvae of the moderately resistant SZ-R strain were subjected to selection with Cry1Ac toxin. Furthermore, RNA interference (RNAi)-mediated suppression of Pxwhite gene expression significantly reduced larval susceptibility to Cry1Ac toxin, and genetic linkage analysis confirmed that down-regulation of Pxwhite gene is tightly linked to Cry1Ac resistance in P. xylostella. To our knowledge, this is the first report indicating that Pxwhite gene is involved in Cry1Ac resistance in P. xylostella.

  10. Electron Impedances

    SciTech Connect

    P Cameron

    2011-12-31

    It is only recently, and particularly with the quantum Hall effect and the development of nanoelectronics, that impedances on the scale of molecules, atoms and single electrons have gained attention. In what follows the possibility that characteristic impedances might be defined for the photon and the single free electron is explored is some detail, the premise being that the concepts of electrical and mechanical impedances are relevant to the elementary particle. The scale invariant quantum Hall impedance is pivotal in this exploration, as is the two body problem and Mach's principle.

  11. Electrical Effect in Silver-Point Realization Due to Cell Structure and Bias Voltage Based on Resistance Measurement Using AC and DC Bridges

    NASA Astrophysics Data System (ADS)

    Widiatmo, J. V.; Harada, K.; Yamazawa, K.; Tamba, J.; Arai, M.

    2015-08-01

    Electrical effects related to insulating leakage represent one of the major factors contributing to uncertainties in measurements using high-temperature standard platinum resistance thermometers (HTSPRTs), especially during the realization of the silver freezing point (). This work is focused on the evaluation of the differences in resistance measurements observed when using AC resistance bridges and DC resistance bridges, hereafter, termed the AC-DC differences, as the result of various electrical effects. The magnitude of the AC-DC difference in several silver-point cells is demonstrated with several HTSPRTs. The effect of the cell structure on the AC-DC difference is evaluated by exchanging some components, part by part, within a silver-point cell. Then, the effect of the bias voltage applied to the heat pipe within the silver-point furnace is evaluated. Through the analysis of the experimental results and comparison with the reports in the literature, the importance of evaluating the AC-DC difference as a means to characterize the underlying electrical effects is discussed, considering that applying a negative bias condition to the furnace with respect to the high-temperature SPRT can minimize the AC-DC difference. Concluding recommendations are proposed on the components used in silver-point cells and the application of a bias voltage to the measurement circuit to minimize the effects of the electrical leakage.

  12. Efficacy of genetically modified Bt toxins alone and in combinations against pink bollworm resistant to Cry1Ac and Cry2Ab

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Evolution of resistance in pests threatens the long-term success of transgenic crops that produce insecticidal proteins from Bacillus thuringiensis (Bt). Previous work showed that genetically modified Bt toxins Cry1AbMod and Cry1AcMod effectively countered resistance to native Bt toxins Cry1Ab and ...

  13. MAPK signaling pathway alters expression of midgut ALP and ABCC genes and causes resistance to Bacillus thuringiensis Cry1Ac toxin in diamondback moth.

    PubMed

    Guo, Zhaojiang; Kang, Shi; Chen, Defeng; Wu, Qingjun; Wang, Shaoli; Xie, Wen; Zhu, Xun; Baxter, Simon W; Zhou, Xuguo; Jurat-Fuentes, Juan Luis; Zhang, Youjun

    2015-04-01

    Insecticidal crystal toxins derived from the soil bacterium Bacillus thuringiensis (Bt) are widely used as biopesticide sprays or expressed in transgenic crops to control insect pests. However, large-scale use of Bt has led to field-evolved resistance in several lepidopteran pests. Resistance to Bt Cry1Ac toxin in the diamondback moth, Plutella xylostella (L.), was previously mapped to a multigenic resistance locus (BtR-1). Here, we assembled the 3.15 Mb BtR-1 locus and found high-level resistance to Cry1Ac and Bt biopesticide in four independent P. xylostella strains were all associated with differential expression of a midgut membrane-bound alkaline phosphatase (ALP) outside this locus and a suite of ATP-binding cassette transporter subfamily C (ABCC) genes inside this locus. The interplay between these resistance genes is controlled by a previously uncharacterized trans-regulatory mechanism via the mitogen-activated protein kinase (MAPK) signaling pathway. Molecular, biochemical, and functional analyses have established ALP as a functional Cry1Ac receptor. Phenotypic association experiments revealed that the recessive Cry1Ac resistance was tightly linked to down-regulation of ALP, ABCC2 and ABCC3, whereas it was not linked to up-regulation of ABCC1. Silencing of ABCC2 and ABCC3 in susceptible larvae reduced their susceptibility to Cry1Ac but did not affect the expression of ALP, whereas suppression of MAP4K4, a constitutively transcriptionally-activated MAPK upstream gene within the BtR-1 locus, led to a transient recovery of gene expression thereby restoring the susceptibility in resistant larvae. These results highlight a crucial role for ALP and ABCC genes in field-evolved resistance to Cry1Ac and reveal a novel trans-regulatory signaling mechanism responsible for modulating the expression of these pivotal genes in P. xylostella.

  14. Concentration dependence of nanochannel impedance and the determination of surface charge

    NASA Astrophysics Data System (ADS)

    Schiffbauer, Jarrod; Liel, Uri; Yossifon, Gilad

    2014-03-01

    In this paper, we demonstrate the variation of nanochannel impedance with bulk (reservoir) electrolyte concentration. The impedance of a nanochannel is shown to correspond to a characteristic deformed semicircular arc. The degree of deformation decreases with increasing concentration, and at a sufficiently low concentration the complex impedance saturates, becoming essentially independent of the reservoir concentration. This behavior is indicative of a surface-conduction dominant regime. Here we demonstrate that this effect extends beyond dc conductance and affects the ac response of the system as well, including both phase relationship and magnitude. The nanochannel resistance, obtained from low-voltage ac measurements, is then used to extract the nanochannel surface charge density. This is found to increase in magnitude with increasing electrolyte concentration.

  15. Module Fourteen: Parallel AC Resistive-Reactive Circuits; Basic Electricity and Electronics Individualized Learning System.

    ERIC Educational Resources Information Center

    Bureau of Naval Personnel, Washington, DC.

    In this module the student will learn about parallel RL (resistive-inductance), RC (resistive-capacitive), and RCL (resistive-capacitive-inductance) circuits and the conditions that exist at resonance. The module is divided into six lessons: solving for quantities in RL parallel circuits; variational analysis of RL parallel circuits; parallel RC…

  16. Overview Of Impedance Sensors

    NASA Astrophysics Data System (ADS)

    Abele, John E.

    1989-08-01

    Electrical impedance has been one of the many "tools of great promise" that physicians have employed in their quest to measure and/or monitor body function or physiologic events. So far, the expectations for its success have always exceeded its performance. In simplistic terms, physiologic impedance is a measure of the resistance in the volume between electrodes which changes as a function of changes in that volume, the relative impedance of that volume, or a combination of these two. The history and principles of electrical impedance are very nicely reviewed by Geddes and Baker in their textbook "Principles of Applied Biomedical Instrumentation". It is humbling, however, to note that Cremer recorded variations in electrical impedance in frog hearts as early as 1907. The list of potential applications includes the measurement of thyroid function, estrogen activity, galvanic skin reflex, respiration, blood flow by conductivity dilution, nervous activity and eye movement. Commercial devices employing impedance have been and are being used to measure respiration (pneumographs and apneamonitors), pulse volume (impedance phlebographs) and even noninvasive cardiac output.

  17. Effect of antimony on the semiconducting properties of the anodic plumbous oxide film formed in sulfuric acid solution I. Studies with alternating-current (a.c.) impedance

    NASA Astrophysics Data System (ADS)

    He, Zhuo-Li; Pu, Cong; Zhou, Wei-Fang

    The semiconducting properties of the anodic plumbous oxide films formed on lead and leadantimony alloys in 4.5 M H 2SO 4 (20 °C) at 0.9 V (versus Hg/Hg 2SO 4) for 2 h have been studied using the a.c. method. From the Mott-Schottky plots, the films are demonstrated to be n-type semiconductors. The flat-band potentials of the films on Pb, Pb—1at.%Sb, Pb—3at.%Sb and Pb—9at.%Sb are -0.95, -1.0, -0.69 and -0.70 V (versus Hg/Hg 2SO 4), respectively; while the corresponding donor densities are 0.82×10 16, 1.2×10 17, 5.5×10 17 and 6.3×10 17 cm -3. The shift of the flat-band potential to more positive values with increase in the antimony content is probably due to the occlusion of a Sb 2O 3 phase in the film. The effect of antimony on the donor density and the lattice-defect density of the n-type semiconductor oxide both conform to the Hauffe Rules.

  18. Input Impedance of the Microstrip SQUID Amplifier

    NASA Astrophysics Data System (ADS)

    Kinion, Darin; Clarke, John

    2008-03-01

    We present measurements of the complex scattering parameters of microstrip SQUID amplifiers (MSA) cooled to 4.2 K. The input of the MSA is a microstrip transmission line in the shape of a square spiral coil surrounding the hole in the SQUID washer that serves as the ground plane. The input impedance is found by measuring the reverse scattering parameter (S11) and is described well by a low-loss transmission line model. We map the low-loss transmission line model into an equivalent parallel RLC circuit in which a resistance R, inductance L, and capacitance C are calculated from the resonant frequency, characteristic impedance and attenuation factor. Using this equivalent RLC circuit, we model the MSA and input network with a lumped circuit model that accurately predicts the observed gain given by the forward scattering parameter (S21). We will summarize results for different coil geometries and terminations as well as SQUID bias conditions. A portion of this work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory in part under Contract W-7405-Eng-48 and in part under Contract DE-AC52-07NA27344 and by Lawrence Berkeley National Laboratory under Contract No. DE-AC02-05CH11231.

  19. Microstructure, AC impedance and DC electrical conductivity characteristics of NiFe2-xGdxO4 (x = 0, 0.05 and 0.075)

    NASA Astrophysics Data System (ADS)

    Kamala Bharathi, K.; Markandeyulu, G.; Ramana, C. V.

    2012-03-01

    The structure and electrical characteristics of Gd doped Ni ferrite materials, namely NiFe1.95Gd0.05O4 and NiFe1.925Gd0.075O4, are reported to demonstrate their improved electrical properties compared to that of pure NiFe2O4. NiFe1.95Gd0.05O4 and NiFe1.925Gd0.075O4 compounds crystallize in the cubic inverse spinel phase with a very small amount of GdFeO3 additional phase while pure NiFe2O4 crystallize in inverse spinel phase without any impurity phase. The back scattered electron imaging analysis indicate the primary and secondary formation in NiFe1.95Gd0.05O4 and NiFe1.925Gd0.075O4 compounds. Atomic force microscopy measurements indicate that the bulk grains are ˜2-5 micron size while the grain boundaries are thin compared to bulk grains. Impedance spectroscopic analysis at different temperature indicates the different relaxation mechanisms and their variation with temperature, bulk grain and grain-boundary contributions to the electrical conductivity (Rg) and capacitance (Cg) of these materials. The conductivity in pure NiFeO4 is found to be predominantly due to intrinsic bulk contribution (Rg=213 kΩ and Cg=4.5 x 10-8 F). In the case of NiFe1.95Gd0.05O4 and NiFe1.925Gd0.075O4 compounds, grain and grain-boundary contributions to the conductivity are clearly observed. The DC conductivity values (at 300 K) of NiFe2O4, NiFe1.95Gd0.05O4 and NiFe1.925Gd0.075O4 compounds are found to be 1.06 x 10-7 Ω-1 cm-1, 5.73 x 10-8 Ω-1 cm-1 and 1.28 x 10-8 Ω-1 cm-1 respectively.

  20. Electrical transport properties of Mn-Ni-Zn ferrite using complex impedance spectroscopy

    NASA Astrophysics Data System (ADS)

    Azizar Rahman, M.; Hossain, A. K. M. Akther

    2014-02-01

    Polycrystalline Mn0.45Ni0.05Zn0.50Fe2O4 was prepared by a standard solid state reaction technique. We report the electrical properties of this ferrite using ac impedance spectroscopy as a function of frequency (20 Hz-10 MHz) at different temperatures (50-350 °C). X-ray diffraction patterns reveal the formation of cubic spinel structure. Complex impedance analysis has been used to separate the grain and grain boundary resistance of this ferrite. The variation of grain and grain boundary conductivities with temperature confirms semiconducting behavior. The dielectric permittivity shows dielectric dispersion at lower frequency and reveals that it has almost the same value on the high-frequency side. The non-coincidence of peaks corresponding to modulus and impedance indicates deviation from Debye-type relaxation. A similar value of activation energy is obtained from impedance and modulus spectra, indicating that charge carriers overcome the same energy barrier during relaxation. Electron hopping is responsible for ac conduction in this ferrite. The electron hopping shifts toward higher frequency with increasing temperature, below which the conductivity is frequency independent. The frequency-independent ac conductivity has been observed at and above 300 °C in the frequency range 20 Hz-1 MHz. This frequency-independent ac conductivity is due to the long-range movement of the mobile charge carriers.

  1. Resistance of Trichoplusia ni Populations Selected by Bacillus thuringiensis Sprays to Cotton Plants Expressing Pyramided Bacillus thuringiensis Toxins Cry1Ac and Cry2Ab

    PubMed Central

    Kain, Wendy; Song, Xiaozhao; Janmaat, Alida F.; Zhao, Jian-Zhou; Myers, Judith; Shelton, Anthony M.

    2014-01-01

    Two populations of Trichoplusia ni that had developed resistance to Bacillus thuringiensis sprays (Bt sprays) in commercial greenhouse vegetable production were tested for resistance to Bt cotton (BollGard II) plants expressing pyramided Cry1Ac and Cry2Ab. The T. ni colonies resistant to Bacillus thuringiensis serovar kurstaki formulations were not only resistant to the Bt toxin Cry1Ac, as previously reported, but also had a high frequency of Cry2Ab-resistant alleles, exhibiting ca. 20% survival on BollGard II foliage. BollGard II-resistant T. ni strains were established by selection with BollGard II foliage to further remove Cry2Ab-sensitive alleles in the T. ni populations. The BollGard II-resistant strains showed incomplete resistance to BollGard II, with adjusted survival values of 0.50 to 0.78 after 7 days. The resistance to the dual-toxin cotton plants was conferred by two genetically independent resistance mechanisms: one to Cry1Ac and one to Cry2Ab. The 50% lethal concentration of Cry2Ab for the resistant strain was at least 1,467-fold that for the susceptible T. ni strain. The resistance to Cry2Ab in resistant T. ni was an autosomally inherited, incompletely recessive monogenic trait. Results from this study indicate that insect populations under selection by Bt sprays in agriculture can be resistant to multiple Bt toxins and may potentially confer resistance to multitoxin Bt crops. PMID:25480752

  2. Reactanceless synthesized impedance bandpass amplifier

    NASA Technical Reports Server (NTRS)

    Kleinberg, L. L. (Inventor)

    1985-01-01

    An active R bandpass filter network is formed by four operational amplifier stages interconnected by discrete resistances. One pair of stages synthesize an equivalent input impedance of an inductance (L sub eq) in parallel with a discrete resistance (R sub o) while the second pair of stages synthesizes an equivalent input impedance of a capacitance (C sub eq) serially coupled to another discrete resistance (R sub i) coupled in parallel with the first two stages. The equivalent input impedances aggregately define a tuned resonant bandpass filter in the roll-off regions of the operational amplifiers.

  3. Effects of defoliating insect resistance QTLs and a cry1Ac transgene in soybean near-isogenic lines.

    PubMed

    Zhu, S; Walker, D R; Boerma, H R; All, J N; Parrott, W A

    2008-02-01

    The crystal proteins coded by transgenes from Bacillus thuringiensis (Bt) have shown considerable value in providing effective insect resistance in a number of crop species, including soybean, Glycine max (L.) Merr. Additional sources of soybean insect resistance would be desirable to manage the development of tolerance/resistance to crystal proteins by defoliating insects and to sustain the deployment of Bt crops. The objective of this study was to evaluate the effects and interactions of three insect resistance quantitative trait loci (QTLs; QTL-M, QTL-H, and QTL-G) originating from Japanese soybean PI 229358 and a cry1Ac gene in a "Benning" genetic background. A set of 16 BC(6)F(2)-derived near isogenic lines (NILs) was developed using marker-assisted backcrosses and evaluated for resistance to soybean looper [SBL, Pseudoplusia includens (Walker)] and corn earworm [CEW, Helicoverpa zea (Boddie)] in field cage, greenhouse, and detached leaf assays. Both Bt and QTL-M had significantly reduced defoliation by both SBL and CEW and reduced larval weight of CEW. The antibiosis QTL-G had a significant effect on reducing CEW larval weight and also a significant effect on reducing defoliation by SBL and CEW in some assays. The antixenosis QTL-H had no main effect, but it appeared to function through interaction with QTL-M and QTL-G. Adding QTL-H and QTL-G further enhanced the resistance of the Bt and QTL-M combination to CEW in the field cage assay. These results should help guide the development of strategies for effective management of insect pests and for sustainable deployment of Bt genes.

  4. Antimicrobial Peptide P60.4Ac-Containing Creams and Gel for Eradication of Methicillin-Resistant Staphylococcus aureus from Cultured Skin and Airway Epithelial Surfaces

    PubMed Central

    Haisma, Elisabeth M.; Göblyös, Anikó; Ravensbergen, Bep; Adriaans, Alwin E.; Cordfunke, Robert A.; Schrumpf, Jasmijn; Limpens, Ronald W. A. L.; Schimmel, Kirsten J. M.; den Hartigh, Jan; Hiemstra, Pieter S.; Drijfhout, Jan Wouter; El Ghalbzouri, Abdoelwaheb

    2016-01-01

    We previously found the LL-37-derived peptide P60.4Ac to be effective against methicillin-resistant Staphylococcus aureus (MRSA) on human epidermal models (EMs). The goal of this study was to identify the preferred carrier for this peptide for topical application on skin and mucosal surfaces. We prepared P60.4Ac in three formulations, i.e., a water-in-oil cream with lanolin (Softisan 649), an oil-in-water cream with polyethylene glycol hexadecyl ether (Cetomacrogol), and a hydroxypropyl methylcellulose (hypromellose) 4000 gel. We tested the antimicrobial efficacy of the peptide in these formulations against mupirocin-resistant and -sensitive MRSA strains on EMs and bronchial epithelial models (BEMs). The cytotoxic effects of formulated P60.4Ac on these models were determined using histology and WST-1 and lactate dehydrogenase assays. Moreover, we assessed the stability of the peptide in these formulations with storage for up to 3 months. Killing of MRSA by P60.4Ac in the two creams was less effective than that by P60.4Ac in the hypromellose gel. In agreement with those findings, P60.4Ac in the hypromellose gel was highly effective in eradicating the two MRSA strains from EMs. We found that even 0.1% (wt/wt) P60.4Ac in the hypromellose gel killed >99% of the viable planktonic bacteria and >85% of the biofilm-associated bacteria on EMs. Hypromellose gels containing 0.1% and 0.5% (wt/wt) P60.4Ac effectively reduced the numbers of viable MRSA cells from BEMs by >90%. No cytotoxic effects of P60.4Ac in the hypromellose gel with up to 2% (wt/wt) P60.4Ac on keratinocytes in EMs and in the hypromellose gel with up to 0.5% (wt/wt) P60.4Ac on epithelial cells in BEMs were observed. High-performance liquid chromatography analysis showed that P60.4Ac was stable in the Softisan cream and the hypromellose gel but not in the Cetomacrogol cream. We conclude that P60.4Ac formulated in hypromellose gel is both stable and highly effective in eradicating MRSA from colonized EMs and

  5. Effect of crop plants on fitness costs associated with resistance to Bacillus thuringiensis toxins Cry1Ac and Cry2Ab in cabbage loopers.

    PubMed

    Wang, Ran; Tetreau, Guillaume; Wang, Ping

    2016-02-12

    Fitness costs associated with resistance to Bacillus thuringiensis (Bt) toxins critically impact the development of resistance in insect populations. In this study, the fitness costs in Trichoplusia ni strains associated with two genetically independent resistance mechanisms to Bt toxins Cry1Ac and Cry2Ab, individually and in combination, on four crop plants (cabbage, cotton, tobacco and tomato) were analyzed, in comparison with their near-isogenic susceptible strain. The net reproductive rate (R0) and intrinsic rate of increase (r) of the T. ni strains, regardless of their resistance traits, were strongly affected by the host plants. The ABCC2 gene-linked mechanism of Cry1Ac resistance was associated with relatively low fitness costs, while the Cry2Ab resistance mechanism was associated with higher fitness costs. The fitness costs in the presence of both resistance mechanisms in T. ni appeared to be non-additive. The relative fitness of Bt-resistant T. ni depended on the specific resistance mechanisms as well as host plants. In addition to difference in survivorship and fecundity, an asynchrony of adult emergence was observed among T. ni with different resistance mechanisms and on different host plants. Therefore, mechanisms of resistance and host plants available in the field are both important factors affecting development of Bt resistance in insects.

  6. Effect of crop plants on fitness costs associated with resistance to Bacillus thuringiensis toxins Cry1Ac and Cry2Ab in cabbage loopers

    PubMed Central

    Wang, Ran; Tetreau, Guillaume; Wang, Ping

    2016-01-01

    Fitness costs associated with resistance to Bacillus thuringiensis (Bt) toxins critically impact the development of resistance in insect populations. In this study, the fitness costs in Trichoplusia ni strains associated with two genetically independent resistance mechanisms to Bt toxins Cry1Ac and Cry2Ab, individually and in combination, on four crop plants (cabbage, cotton, tobacco and tomato) were analyzed, in comparison with their near-isogenic susceptible strain. The net reproductive rate (R0) and intrinsic rate of increase (r) of the T. ni strains, regardless of their resistance traits, were strongly affected by the host plants. The ABCC2 gene-linked mechanism of Cry1Ac resistance was associated with relatively low fitness costs, while the Cry2Ab resistance mechanism was associated with higher fitness costs. The fitness costs in the presence of both resistance mechanisms in T. ni appeared to be non-additive. The relative fitness of Bt-resistant T. ni depended on the specific resistance mechanisms as well as host plants. In addition to difference in survivorship and fecundity, an asynchrony of adult emergence was observed among T. ni with different resistance mechanisms and on different host plants. Therefore, mechanisms of resistance and host plants available in the field are both important factors affecting development of Bt resistance in insects. PMID:26868936

  7. Electrochemical impedance spectroscopy of metal alloys in the space transportation system launch environment

    NASA Technical Reports Server (NTRS)

    Calle, Luz

    1990-01-01

    AC impedance measurements were performed to investigate the corrosion resistance of 18 alloys under conditions similar to the Space Transportation System (STS) launch environment. The alloys were: (1) zirconium 702; (2) Hastelloy C-22, C-276, C-4, and B-2; (3) Inconel 600 and 825; (4) Ferralium 255; (5) Inco Alloy G-3; (6) 20Cb-3; (7) SS 904L, 304LN, 316L, 317L, and 304L; (8) ES 2205; and (9) Monel 400. AC impedance data were gathered for each alloy at various immersion times in 3.55 percent NaCl-0.1N HCl. Polarization resistance values were obtained for the Nyguist plots at each immersion time using the EQUIVALENT CIRCUIT software package available with the 388 electrochemical impedance software. Hastelloy C-22 showed the highest overall values for polarization resistance while Monel 400 and Inconel 600 had the lowest overall values. There was good general correlation between the corrosion performance of the alloys at the beach corrosion testing site, and the expected rate of corrosion as predicted based on the polarization resistance values obtained. The data indicate that electrochemical impedance spectroscopy can be used to predict the corrosion performance of metal alloys.

  8. Cross-resistance responses of CrylAc-selected Heliothis virescens (Lepidoptera: Noctuidae) to the Bacillus thuringiensis protein vip3A.

    PubMed

    Jackson, R E; Marcus, M A; Gould, F; Bradley, J R; Van Duyn, J W

    2007-02-01

    One susceptible and three Cry1Ac-resistant strains of tobacco budworm, Heliothis virescens (F.) (Lepidoptera: Noctuidae), were used in laboratory studies to determine the level of cross-resistance between the Bacillus thuringiensis (Berliner) toxins Cry1Ac and Vip3A by using concentration-mortality and leaf tissue experiments. Concentration-mortality data demonstrated that the three Cry1Ac-resistant H. virescens strains, YHD2, KCBhyb, and CxC, were at least 215- to 316-fold resistant to Cry1Ac compared with the susceptible strain, YDK. Results from Vip3A concentration-mortality tests indicated that mortality was similar among all four H. virescens strains. Relative larval growth on Cry1Ac reflected concentration-mortality test results, because YHD2 larval growth was mostly unaffected by the Cry1Ac concentrations tested. Growth ratios for KCBhyb and CXC indicated that they had a more moderate level of resistance to Cry1Ac than did YHD2. Relative larval growth on Vip3A was highly variable at lower concentrations, but it was more consistent on concentrations of Vip3A above 25 microg/ml. Differences in larval growth among strains on Vip3A were not as pronounced as seen in Cry1Ac experiments. Mortality and larval growth also was assessed in leaf tissue bioassays in which YDK, CxC, and KCBhyb neonates were placed onto leaf disks from non-Bt and Bt cotton, Gossypium hirsutum L., for 5 d. Three Bt lines were used in an initial bioassay and consisted of two Vip3A-containing lines, COT203 and COT102, and a Cry1Ac-producing line. Mortality of KCBhyb and CXC was lower than that of YDK larvae in the presence of leaf tissue from the Cry1Ac-producing line. Additionally, increased larval growth and leaf tissue consumption on Cry1Ac-containing leaf disks was observed for KCBhyb and CXC. Mortality and larval weights were similar among strains when larvae were fed leaf tissue of either non-Bt, COT203, or COT102. A subsequent leaf tissue bioassay was conducted that evaluated four

  9. Successive superconducting transitions in Ta2S2C studied by electrical resistivity and nonlinear ac magnetic susceptibility

    NASA Astrophysics Data System (ADS)

    Suzuki, Masatsugu; Suzuki, Itsuko S.; Noji, Takashi; Koike, Yoji; Walter, Jürgen

    2007-05-01

    Ta2S2C compound undergoes superconducting transitions at Tcl=3.60±0.02K and Tcu=9.0±0.2K . The nature of successive superconducting transitions has been studied from electrical resistivity and linear and nonlinear ac magnetic susceptibilities. The resistivity ρ at H=0 shows a local maximum near Tcu , a kinklike behavior around Tcl , and reduces to zero at below T0=2.1K . The lnT dependence of ρ is observed at H=50kOe at low temperatures, which is due to a two-dimensional weak-localization effect. Below Tcu , a two-dimensional superconducting phase occurs in each TaC layer. The linear and nonlinear susceptibilities χ1″ , χ3' , χ5' , and χ7' as well as the difference δχ (=χFC-χZFC) between the field-cooled (FC) and zero-field-cooled (ZFC) susceptibilities start to appear below 6.0K , the onset temperature of irreversibility. A drastic growth of the in-plane superconducting coherence length below 6.0K gives rise to a three-dimensional superconducting phase below Tcl through interplanar Josephson couplings between adjacent TaC layers. The oscillatory behavior of χ3″ , χ5″ , and χ7″ below Tcl is related to the nonlinear behavior arising from the thermally activated flux flow.

  10. The frequency dependent impedance of an HVdc converter

    SciTech Connect

    Wood, A.R.; Arrillaga, J.

    1995-07-01

    A linear and direct method of determining the frequency dependent impedance of a 12 pulse HVdc converter is presented. Terms are developed for both the dc and ac side impedances of the converter, including the effect of the firing angle control system, the commutation period, and the variability of the commutation period. The impedance predictions are verified by dynamic simulation.

  11. Intrawire resistance, AC loss and strain dependence of critical current in MgB2 wires with and without cold high-pressure densification

    NASA Astrophysics Data System (ADS)

    Zhou, C.; Gao, P.; Krooshoop, H. J. G.; Dhallé, M.; Sumption, M. D.; Rindfleisch, M.; Tomsic, M.; Kulich, M.; Senatore, C.; Nijhuis, A.

    2014-07-01

    The intrawire resistance and alternating current (AC) loss of two MgB2 wires with filaments surrounded by Nb barriers have been measured and analyzed. Relatively high values of filament-to-matrix contact resistivity are found in the MgB2 wires; the values are two or three orders higher than those commonly found in NbTi or Nb3Sn wires. Considering the high porosity of the MgB2 filaments, cold high-pressure densification has been applied on the two MgB2 wires to investigate its impact on intrawire resistance and AC loss. The intrawire resistance is measured with a direct four-probe voltage-current method at various temperatures. The AC loss is measured by vibrating sample magnetometer measurements at 4.2 K. In addition to the intrawire resistance measurements, the critical current of MgB2 wires before and after densification is measured with a U-shaped bending spring at 4.2 K as function of axial strain. The critical current in densified MgB2 wires is found to be higher than that in the same wire without densification; it is also less sensitive to the applied axial strain.

  12. Dielectric and impedance spectroscopic studies of neodymium gallate

    NASA Astrophysics Data System (ADS)

    Sakhya, Anup Pradhan; Dutta, Alo; Sinha, T. P.

    2016-05-01

    The AC electrical properties of a polycrystalline neodymium gallate, NdGaO3 (NGO), synthesized by the sol-gel method have been investigated by employing impedance spectroscopy in the frequency range from 42 Hz to 5 MHz and in the temperature range from 323 K to 593 K. The X-ray diffraction analysis shows that the compound crystallizes in the orthorhombic phase with Pbnm space group at room temperature. Two relaxation processes with different relaxation times are observed from the impedance as well as modulus spectroscopic measurements, which have been attributed to the grain and the grain boundary effects at different temperatures in NGO. The complex impedance data are analyzed by an electrical equivalent circuit consisting of a resistance and a constant phase element in parallel. It has been observed that the value of the capacitance and the resistance associated with the grain boundary is higher than those associated with the grain. The temperature dependent electrical conductivity shows the negative temperature coefficient of resistance. The frequency dependent conductivity spectra are found to follow the power law.

  13. A Monte Carlo simulation of range for an invasive impedance respiration monitor.

    PubMed

    Valenta, H L; Fischer, S K

    1990-01-01

    One method of rate responsive pacing utilizes an analog of minute ventilation as the input to the rate control algorithm. A measure of the intravenous impedance along the pacing catheter is a convenient means of determining minute ventilation. Design of the impedance converter requires a knowledge of the range of DC and AC impedance signals. During normal and deep breathing, 116 AC measurements were taken from 34 Electrophysiology (EP) patients and 31 DC measurements were taken from 13 EP patients. The patient data produced skewed distributions with a normal AC mean of 0.45 +/- 0.40 ohms p-p, a deep AC mean of 2.0 +/- 1.6 ohms and a DC mean of 44 +/- 13 ohms. An eight variable static model was derived from prior work. Five of the physiological variables were chosen from established clinical ranges, one geometrical variable was chosen from prior work and two were selected by matching the statistics of a Monte Carlo analysis of the model with the statistics of the patient data. The blood resistivity was obtained from prior work. A simulation of 1000 measurements produced a normal breathing range of 0 to 2.24 ohms, a deep breathing range of 0 to 9.6 ohms and a DC range of 19 to 100 ohms.

  14. Chromium-modified a-C films with advanced structural, mechanical and corrosive-resistant characteristics

    NASA Astrophysics Data System (ADS)

    Ming, Miao Yi; Jiang, Xiaohong; Piliptsou, D. G.; Zhuang, Yuzhao; Rogachev, A. V.; Rudenkov, A. S.; Balmakou, A.

    2016-08-01

    To improve structural, mechanical and chemical properties of diamond-like carbon films, we developed amorphous carbon chromium-modified composite films fabricated by means of cathode magnetic filtered arc deposition. The properties were analyzed by Raman spectroscopy, X-ray photoelectron spectroscopy and atomic force microscopy for the purpose of the structure characterization, elemental analysis and topology examination. Moreover, we also assessed residual stress, the coefficient of friction, hardness, the elastic modulus and corrosion parameters through X-ray double-crystal surface profilometry, tribo-testing, nanoindenter-testing, as well as contact angle measurements and potentiodynamic polarization analysis. As a result of a comparative analysis, we revealed a substantial improvement in the characteristics of developed composite films in comparison with amorphous carbon films. For example, Cr-modification is resulted, in greater integrated performance, toughness and corrosion resistance; the residual stress was reduced substantially.

  15. The expression patterns of bromelain and AcCYS1 correlate with blackheart resistance in pineapple fruits submitted to postharvest chilling stress.

    PubMed

    Raimbault, Astrid-Kim; Zuily-Fodil, Yasmine; Soler, Alain; Mora, Phillipe; Cruz de Carvalho, Maria H

    2013-11-01

    Blackheart is a physiological disorder induced by postharvest chilling storage during pineapple fruit export shipping. The aim of this study was to check the involvement of bromelain, the cysteine protease protein family abundantly present in pineapple fruits, and AcCYS1, an endogenous inhibitor of bromelain, in the development of blackheart. For this we checked the response to postharvest chilling treatment of two pineapple varieties (MD2 and Smooth Cayenne) differing in their resistance to blackheart. Quantitative RT-PCR analyses showed that postharvest chilling treatment induced a down-regulation of bromelain transcript accumulation in both varieties with the most dramatic drop in the resistant variety. Regarding AcCYS1 transcript accumulation, the varieties showed opposite trends with an up-regulation in the case of the resistant variety and a down-regulation in the susceptible one. Taken together our results suggest that the control of bromelain and AcCYS1 expression levels directly correlates to the resistance to blackheart development in pineapple fruits.

  16. On the Loss of Protective Scale Formation in Creep-Resistant, Alumina-Forming Austenitic Stainless Steels at 900?aC in Air

    SciTech Connect

    Brady, Michael P; Yamamoto, Yukinori; Pint, Bruce A; Santella, Michael L; Maziasz, Philip J; Walker, Larry R

    2008-01-01

    A family of creep-resistant, Al2O3-forming austenitic (AFA) stainless steels was recently developed. The alloys exhibit excellent oxidation resistance up to 800 aC, but are susceptible to internal attack of Al at higher temperatures. In the present work, higher levels of Ni, Cr, Al, and Nb additions were found to correlate with improved oxidation behavior at 900 aC in air. The alloys generally appeared to be initially capable of external Al2O3 scale formation, with a subsequent transition to internal attack of Al (internal oxidation and internal nitridation) that is dependent on alloy composition. Compositional profiles at the alloy/scale interface suggest that the transition to internal oxidation is preceded by subsurface depletion of Al. Alloy design directions to increase the upper-temperature limit of protective Al2O3 scale formation in these alloys are discussed

  17. Bioelectrical impedance analysis as a laboratory activity: At the interface of physics and the body

    NASA Astrophysics Data System (ADS)

    Mylott, Elliot; Kutschera, Ellynne; Widenhorn, Ralf

    2014-05-01

    We present a novel laboratory activity on RC circuits aimed at introductory physics students in life-science majors. The activity teaches principles of RC circuits by connecting ac-circuit concepts to bioelectrical impedance analysis (BIA) using a custom-designed educational BIA device. The activity shows how a BIA device works and how current, voltage, and impedance measurements relate to bioelectrical characteristics of the human body. From this, useful observations can be made including body water, fat-free mass, and body fat percentage. The laboratory is engaging to pre-health and life-science students, as well as engineering students who are given the opportunity to observe electrical components and construction of a commonly used biomedical device. Electrical concepts investigated include alternating current, electrical potential, resistance, capacitance, impedance, frequency, phase shift, device design, and the use of such topics in biomedical analysis.

  18. Aegle marmelos (L.) Corr. impedes onset of Insulin resistance syndrome in rats provided with drinking fructose from weaning to adulthood stages of development: A mechanistic study.

    PubMed

    Mathur, Rajani; Sehgal, Ratika; Rajora, Preeti; Sharma, Shveta; Kumar, Rajesh; Mathur, Sandeep

    2016-12-17

    To explore the effect of aqueous extract of leaves of Aegle marmelos (AM) on hepatic carbohydrate metabolism and insulin downstream signalling in rats provided with drinking fructose (15%) from weaning to adulthood. Wistar albino rats (4week) were randomly divided into Normal Control (NC), Fructose Control (FC) and treatment (AMT) groups and provided over 8 weeks, chow + water, chow + fructose (15%) and chow + fructose (15%) + AM (500 mg/kg/d, p.o.), respectively. Significantly (p<0.05) raised levels of Fasting Blood Glucose, lipid, visceral weight, plasma insulin and leptin, glycogen, gluconeogenesis enzyme levels but decreased glycolytic enzyme activity was recorded in FC as compared to NC. Raised levels of glucose transporter (GLUT 2) protein but decreased activity of phosphatidylinositol-3-kinase (PI3K/AkT) and Janus Kinase -Signal Transducer And Activator of Transcription-3 (JAK-STAT3) in hepatic tissue, indicate a state of insulin and leptin resistance in FC. AMT recorded significant (p<0.05) lowering of physical, and glycemic parameters, reinforcement of hepatic glycolytic over gluconeogenic pathway and upregulated PI3K/AkT and JAK-STAT3 pathways, as compared to FC. For the first time, the mechanism underlying development of Insulin Resistance Syndrome (IRS) is delineated here, along with the potential of Aegle marmelos in impeding the same.

  19. Copper Phthalocyanine Thin Film Morphology Impact on Impedance Spectrum

    NASA Astrophysics Data System (ADS)

    Robinson, Kyle; Gredig, Thomas

    2012-11-01

    Copper phthlacyanine thin films play an important role as the active layer in gas sensors, organic solar cells, and organic field-effect transistors. The surface morphology of such thin films can be controlled via modification of thermal deposition parameters. Thin films were deposited onto platinum interdigitated electrodes for impedance measurements to study the effect of structure on charge transport. The average grain size increases and changes from α- and β-phase for samples deposited in the temperature range of 295-534 K. AC measurements in the temperature range of 295-385 K reveal relaxation peaks in the impedance spectra. From this spectrum, essential properties are retrieved, such as relaxation times and effective capacities, and correlated with the film morphology. Subject to both photo- and 5-day-dark current trials, photodecay rates are extracted via effective impedance circuit analysis using a phenomenological model that includes contributions from the grain boundary and the bulk part of the grain. Results indicate that the resistance contribution of low frequency relaxation peaks decrease while approaching the phase transition temperature, and vice versa for capacitance. We attribute the low-frequency peaks to grain boundaries, which are reduced in high temperature deposited samples. Hyper β-phase deposition temperatures show a sudden rise in resistance and lower capacitance due to increased roughness of samples.

  20. Impedance Analysis of Surface-Bound Biomembranes

    DTIC Science & Technology

    1990-06-08

    and identify by block numb (i FIELD GROUP SUB-GROLm--- AC Impedance, Biomembranes, Lipid, Electrod\\) ’CBiosensor - O ( S. &-’te ,,• J ABSTRACT...Instit-ute 57 Union St., Worcester, MA 01608 ABSTRACTElcchria isThe impedance of different electrode substratesElcharacteriz l biomemance atnactuses fomed ...T10 2), indium/tin oxide (ITO) and platinum electrodes that have been "primed" by covalent attachment of long-chained alkyl groups . The electroes were

  1. Ionic conductivity and electrical relaxation of nanocrystalline scandia-stabilized c-zirconia using complex impedance analysis

    NASA Astrophysics Data System (ADS)

    Kumar, Ashok; Manna, I.

    2008-07-01

    A solid solution of 8 mol% of scandia-stabilized cubic-zirconia (8ScSZ) has been prepared by co-precipitation technique. The synthesized powder has an average crystallite size ∼40 nm, surface area of 8.49 m 2/g, and agglomerated particle size of 150 nm. The activation energy of 8ScSZ has been calculated from impedance loss spectra; electrical modulus spectra are in the range of 0.90-1.30 eV. The frequency and temperature-dependent conductivities and impedance were measured in range of 50 Hz-1 MHz and 300-900 K, respectively. Complex impedance spectra, complex modulus formalism and complex conductivity spectra have been carefully analyzed in order to separate the grain, grain boundary and electrode-electrolyte effects. Analysis of ac impedance data using complex impedance indicates a typical negative temperature coefficient of resistance (NTCR) behavior of the materials. The intrinsic conductivity is mainly due to hopping of mobile ions among the available localized site. Relaxation time obtained from complex conductivity spectra are matched well with the impedance loss and modulus loss spectra. Impedance analysis suggests the presence of temperature-dependent electrical relaxation process in the material.

  2. Impedance spectroscopic analysis of nanoparticle functionalized graphene/p-Si Schottky diode sensors

    NASA Astrophysics Data System (ADS)

    Uddin, Md Ahsan; Singh, Amol; Daniels, Kevin; Vogt, Thomas; Chandrashekhar, M. V. S.; Koley, Goutam

    2016-11-01

    Metallic nanoparticle (NP) functionalized graphene/p-Si Schottky diode (chemidiode) sensors have been investigated through dc amperometric and ac impedance spectroscopic (IS) measurements. Four fold sensitivity enhancement for NH3 is demonstrated after Pt nanoparticle functionalization of graphene/p-Si Schottky diode sensor, and the response is also orders of magnitude higher compared to functionalized graphene chemiresistor. Experimentally obtained impedance spectra were modeled utilizing an equivalent circuit for both sensor types, and the junction resistance and capacitance were extracted for various gaseous analytes exposure. Variations in junction resistance, capacitance and 3-dB cut-off frequency plotted in three-dimensional (3D) enables extraction of unique signatures for various analyte gases.

  3. Electrical test methods for on-line fuel cell ohmic resistance measurement

    NASA Astrophysics Data System (ADS)

    Cooper, K. R.; Smith, M.

    The principles and trade-offs of four electrical test methods suitable for on-line measurement of the ohmic resistance (R Ω) of fuel cells is presented: current interrupt, AC resistance, high frequency resistance (HFR), and electrochemical impedance spectroscopy (EIS). The internal resistance of a proton exchange membrane (PEM) fuel cell determined with the current interrupt, HFR and EIS techniques is compared. The influence of the AC amplitude and frequency of the HFR measurement on the observed ohmic resistance is examined, as is the ohmic resistance extracted from the EIS data by modeling the spectra with a transmission line model for porous electrodes. The ohmic resistance of a H 2/O 2 PEM fuel cell determined via the three methods was within 10-30% of each other. The current interrupt technique consistently produced measured cell resistances that exceeded those of the other two techniques. For the HFR technique, the frequency at which the measurement was conducted influenced the measured resistance (i.e., higher frequency providing smaller R Ω), whereas the AC amplitude did not effect the observed value. The difference in measured ohmic resistance between these techniques exceeds that reasonably accounted for by measurement error. The source of the discrepancy between current interrupt and impedance-based methods is attributed to the difference in the response of a non-uniformly polarized electrode, such as a porous electrode with non-negligible ohmic resistance, to a large perturbation (current interrupt event) as compared to a small perturbation (impedance measurement).

  4. Correlation between AC and DC transport properties of Mn substituted cobalt ferrite

    NASA Astrophysics Data System (ADS)

    Supriya, Sweety; Kumar, Sunil; Kar, Manoranjan

    2016-12-01

    The CoFe2-xMnxO4 compound is prepared by following the sol gel technique. The structural analysis through XRD and Rietveld has been confirmed for the single cubic phase having F d 3 ¯ m space group for CoFe2-xMnxO4 and also verified it through Raman spectroscopy measurements. The tetrahedral site observed to be red shifted with increase in Mn concentration in cobalt ferrite. All the XRD patterns have been analyzed by employing the Rietveld refinement technique. The particle size was found to be in the range of 30-40 nm. The electrical properties of polycrystalline CoFe2-xMnxO4 for x = 0.00, 0.10, 0.15, and 0.2, spinel ferrite was investigated by impedance spectroscopy. The influence of doping, frequency and temperature on the electrical transport properties of the CoFe2-xMnxO4 for x = 0.00, 0.10, 0.15, and 0.20 were investigated. The magnitude of Z' and Z″ decreases with increase in temperature. Only one semicircle is observed in each Cole Cole plot which reveals that ac conductivity is dominated by grains. The grain resistance and grain boundary resistance both were found to decrease as a function of temperature. Temperature variation of DC electrical conductivity follows the Arrhenius relationship. A detailed analysis of electrical parameters provides assistance in connecting information regarding the conduction mechanism as well as determination of both dielectric and magnetic transition temperatures in the substituted cobalt ferrite. Detailed analysis of ac impedance and DC resistivity measurement reveals that, the magnetic ordering temperature in the Mn substituted cobalt ferrite does not respond to the frequency of ac electrical signal; however, it responds to the DC resistivity. The correlation between ac impedance and DC resistivity has been established.

  5. Impedance analysis of BaMo1-xWxO4 ceramics

    NASA Astrophysics Data System (ADS)

    Bouzidi, C.; Sdiri, N.; Boukhachem, A.; Elhouichet, H.; Férid, M.

    2015-06-01

    The materials BaMo1-xWxO4 (x = 0.00, 0.05, 0.10, 0.15 and 0.20) were prepared by solid state reaction method. XRD analysis showed that the prepared samples crystallize in tetragonal structure with a preferred orientation of the crystallites along (1 1 2) direction. The values of optical band gap and Urbach energy are in the ranges 2.21-2.44 eV and 77.82-151.51 meV, respectively. Their impedance analysis have been determined in frequency and temperature range of (40-106 Hz) and (30-800 °C) respectively. The Nyquist diagrams were investigated in terms of equivalent circuits due to resistors and constant phase elements (CPE). Complex impedance analysis showed the behavior of a dielectric relaxation non-Debye type. We found that resistance of the compounds decreases with temperature, which is related to the electrical conductivity improvement. Conductivity measurements using σac were performed on compact pellets of these materials. The ac conductivity versus frequency shows Jonscher's universal power law. In order to study the activation energy versus temperature, we have chosen the small polaron hopping (SPH) model. The obtained activation energy values ranges from 0.29 to 1.08 eV. The dielectric constant (ε) and dielectric loss (tan δ) decreased with frequency, however the ac conductivity (σac) increased.

  6. [Relationship of Zn content and Na/K ratio to the resistance to pathogen invasion in antisense ACS transgenic tomato fruit and normal tomato].

    PubMed

    Fan, Bei; Shen, Lin; Liu, Can; Tian, Shi-Ping; Sheng, Ji-Ping

    2009-02-01

    In the present work, inductively coupled plasma atomic emission spectrometry (ICP-AES) was used to determine the content of Zn, Na and K and the ratio of Na/K in antisense ACS transgenic tomato fruit (in which the antisense ACC synthase gene construct was inserted) and in normal tomato fruit of the same variety (Lycopersicon esculentum cv. Lichun). The difference in mineral elements content between the two tomatoes and the involvement of Zn content and Na/K ratio in the disease resistance of postharvest tomato fruit were discussed. The results showed that the ethylene biosynthesis is limited in antisense ACS transgenic tomato fruit. Meanwhile, the resistance to Rhizopus nigricans invasion of this transgenic tomato was higher, the disease incidence and lesion area in transgenic tomato fruit were 20.0% and 33.3% lower than those in control fruit, respectively. In addition, the content of Zn in transgenic tomato fruit was 0.322 microg x g(-1) and was 1.5 times higher than that in Lichun tomato fruit. There was no significant difference in K content between transgenic tomato fruit and Lichun fruit, but the content of Na in transgenic tomato fruit was significant higher than that in Lichun fruit and the Na/K ratio in transgenic tomato fruit was 2.0 times higher than that in Lichun fruit. It is suggested that the content of Zn and the Na/K ratio may be involved in the resistance response to pathogen invasion and the development of antisense ACS transgenic tomato fruit.

  7. FDTD modeling of thin impedance sheets

    NASA Technical Reports Server (NTRS)

    Luebbers, Raymond J.; Kunz, Karl S.

    1991-01-01

    Thin sheets of resistive or dielectric material are commonly encountered in radar cross section calculations. Analysis of such sheets is simplified by using sheet impedances. In this paper it is shown that sheet impedances can be modeled easily and accurately using Finite Difference Time Domain (FDTD) methods.

  8. Effects of four entomopathogenic nematode species on fitness costs of pink bollworm resistance to Bacillus thuringiensis toxin Cry1Ac

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Evolution of resistance by pests can reduce the efficacy of transgenic crops that produce insecticidal toxins from the bacterium Bacillus thuringiensis (Bt). However, fitness costs can slow the evolution of resistance. We tested whether four species of entomopathogenic nematodes (Steinernematidae ...

  9. Impedance Measurement for the Analysis of Corrosion Induced Failures.

    DTIC Science & Technology

    1982-02-01

    for a C-Mn Steel (C1117) in 1 M Na3PO4 , pH=4, T-21 C and in 1.0 M NaHCO3/0.1 M Na CO, T=70 C at controlled potentials with continuous recording of the...Impedance Parameters for C1117 Steel in 1 N Na3PO4 , pH = 4.............................................. 25 IV A.C. Impedance Parameters for Al 7075...CERT with continuous recording of the ac impedance.........................5 2 Anodic potentiodynamic polarization curves for 1008 steel in 1N Na3PO4

  10. Calibration of electrical impedance tomography

    SciTech Connect

    Daily, W; Ramirez, A

    2000-05-01

    Over the past 10 years we have developed methods for imaging the electrical resistivity of soil and rock formations. These technologies have been called electrical resistance tomography of ERT (e.g. Daily and Owen, 1991). Recently we have been striving to extend this capability to include images of electric impedance--with a new nomenclature of electrical impedance tomography or EIT (Ramirez et al., 1999). Electrical impedance is simply a generalization of resistance. Whereas resistance is the zero frequency ratio of voltage and current, impedance includes both the magnitude and phase relationship between voltage and current at frequency. This phase and its frequency behavior is closely related to what in geophysics is called induced polarization or (Sumner, 1976). Why is this phase or IP important? IP is known to be related to many physical phenomena of importance so that image of IP will be maps of such things as mineralization and cation exchange IP (Marshall and Madden, 1959). Also, it is likely that IP, used in conjunction with resistivity, will yield information about the subsurface that can not be obtained by either piece of information separately. In order to define the accuracy of our technologies to image impedance we have constructed a physical model of known impedance that can be used as a calibration standard. It consists of 616 resistors, along with some capacitors to provide the reactive response, arranged in a three dimensional structure as in figure 1. Figure 2 shows the construction of the network and defines the coordinate system used to describe it. This network of components is a bounded and discrete version of the unbounded and continuous medium with which we normally work (the subsurface). The network has several desirable qualities: (1) The impedance values are known (to the accuracy of the component values). (2) The component values and their 3D distribution is easily controlled. (3) Error associated with electrode noise is eliminated. (4

  11. Effects of entomopathogenic nematodes on the evolution of pink bollworm resistance to Bt toxin Cry1Ac.

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The evolution of resistance by pests can reduce the efficacy of transgenic crops that produce insecticidal toxins from the bacterium Bacillus thuringiensis (Bt). Conversely, fitness costs may act to delay pest resistance to Bt. The entomopathogenic nematode Steinernema riobrave (Rhabditida: Steinern...

  12. Effects of four nematodes species on fitness costs of pink bollworm resistance to Bacillus thuringiensis toxin Cry1Ac

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Evolution of resistance by pests can reduce efficacy of transgenic crops that produce insecticidal toxins from the bacterium Bacillus thuringiensis (Bt). In conjunction with refuges of non-Bt host plants, fitness costs can delay the evolution of resistance. Furthermore, fitness costs often vary wit...

  13. Effects of Defoliating Insect Resistance QTLs and a crylAc Transgene in Soybean Near-Isogenic Lines

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Additional sources of resistance would be desirable to manage defoliating insect resistance to crystal proteins coded by transgenes from Bacillus thuringiensis (Bt) and to sustain the deployment of Bt crops. The objective of this study was to evaluate the effects and interactions of three soybean (G...

  14. Plasmonic-Based Electrochemical Impedance Spectroscopy: Application to Molecular Binding

    PubMed Central

    Lu, Jin; Wang, Wei; Wang, Shaopeng; Shan, Xiaonan; Li, Jinghong; Tao, Nongjian

    2012-01-01

    Plasmonic-based electrochemical impedance spectroscopy (P-EIS) is developed to investigate molecular binding on surfaces. Its basic principle relies on the sensitive dependence of surface plasmon resonance (SPR) signal on surface charge density, which is modulated by applying an AC potential to a SPR chip surface. The AC component of the SPR response gives the electrochemical impedance, and the DC component provides the conventional SPR detection. The plasmonic-based impedance measured over a range of frequency is in quantitative agreement with the conventional electrochemical impedance. Compared to the conventional SPR detection, P-EIS is sensitive to molecular binding taking place on the chip surface, and less sensitive to bulk refractive index changes or non-specific binding. Moreover, this new approach allows for simultaneous SPR and surface impedance analysis of molecular binding processes. PMID:22122514

  15. [Comparison between transgenic insect-resistant cotton expressing Cry1Ac protein and its parental variety in rhizospheric fungal diversity].

    PubMed

    Pan, Jian-Gang; Jiao, Hai-Hua; Bai, Zhi-Hui; Qi, Hong-Yan; Ma, An-Zhou; Zhuang, Guo-qiang; Zhang, Hong-xun

    2014-11-01

    The dynamics of rhizospheric fungal diversity and biomass at different sampling stages associated with two transgenic insectresistant cottons expressing Cry1Ac protein and their control varieties were studied under greenhouse conditions, followed by PCR-denaturing gradient gel electrophoresis (PCR-DGGE) and quantitative real-time polymerase chain reaction (Q-PCR), in order to evaluate the ecological security of planting transgenic cotton expressing Cry1Ac protein. The results indicated that the fungal superior bands in rhizosphere of transgenic Bt cotton were similar with that of control cotton at four sampling stages, the more obvious difference in the blurred bands among transgenic Bt cotton, JM20 and SHIYUAN321 was detected. The rhizospheric fungal biomass of transgenic Bt cotton SGK321 was significantly lower than that of its parental control cotton at seedling stage, while the slight decrease in fungal biomass of transgenic Bt cotton XP188 was detected at boll forming stage, the ill-defined decrease, even growing tendency in two transgenic Bt cottons was detected at other stages. However, the difference of rhizospheric fungal community compositions and biomass was not only existed between transgenic cotton and its control, but also between SHIYUAN321 and JM20, and the same phenomenon was also detected between transgenic Bt cotton SGK321 and XP188. Hence, Bt protein is not the only incentive resulting in the difference in fungal community composition and diversity, the decrease in biomass between transgenic cotton and untransgenic cotton, different cotton varieties has an effect on them.

  16. Production of marker-free transgenic Jatropha curcas expressing hybrid Bacillus thuringiensis δ-endotoxin Cry1Ab/1Ac for resistance to larvae of tortrix moth (Archips micaceanus)

    PubMed Central

    2014-01-01

    Background The potential biofuel plant Jatropha curcas L. is affected by larvae of Archips micaceanus (Walker), a moth of the family Tortricidae. The hybrid Bacillus thuringiensis (Bt) δ-endotoxin protein Cry1Ab/1Ac confers resistance to lepidopteran insects in transgenic rice. Results Here, we report the production of a marker-free transgenic line of J. curcas (L10) expressing Cry1Ab/1Ac using Agrobacterium-mediated transformation and a chemically regulated, Cre/loxP-mediated DNA recombination system. L10 carries a single copy of marker-free T-DNA that contains the Cry1Ab/1Ac gene under the control of a maize phosphoenolpyruvate carboxylase gene promoter (P Pepc :Cry1Ab/1Ac:T Nos ). The P Pepc :Cry1Ab/1Ac:T Nos gene was highly expressed in leaves of L10 plants. Insecticidal bioassays using leaf explants of L10 resulted in 80-100% mortality of larvae of A. micaceanus at 4 days after infestation. Conclusion The results demonstrate that the hybrid Bt δ-endotoxin protein Cry1Ab/1Ac expressed in Jatropha curcas displays strong insecticidal activity to A. micaceanus. The marker-free transgenic J. curcas line L10 can be used for breeding of insect resistance to A. micaceanus. PMID:24808924

  17. Superconducting fault current-limiter with variable shunt impedance

    DOEpatents

    Llambes, Juan Carlos H; Xiong, Xuming

    2013-11-19

    A superconducting fault current-limiter is provided, including a superconducting element configured to resistively or inductively limit a fault current, and one or more variable-impedance shunts electrically coupled in parallel with the superconducting element. The variable-impedance shunt(s) is configured to present a first impedance during a superconducting state of the superconducting element and a second impedance during a normal resistive state of the superconducting element. The superconducting element transitions from the superconducting state to the normal resistive state responsive to the fault current, and responsive thereto, the variable-impedance shunt(s) transitions from the first to the second impedance. The second impedance of the variable-impedance shunt(s) is a lower impedance than the first impedance, which facilitates current flow through the variable-impedance shunt(s) during a recovery transition of the superconducting element from the normal resistive state to the superconducting state, and thus, facilitates recovery of the superconducting element under load.

  18. Impedance spectroscopic analysis of composite electrode from activated carbon/conductive materials/ruthenium oxide for supercapacitor applications

    SciTech Connect

    Taer, E.; Awitdrus,; Farma, R.; Deraman, M. Talib, I. A.; Ishak, M. M.; Omar, R.; Dolah, B. N. M.; Basri, N. H.; Othman, M. A. R.; Kanwal, S.

    2015-04-16

    Activated carbon powders (ACP) were produced from the KOH treated pre-carbonized rubber wood sawdust. Different conductive materials (graphite, carbon black and carbon nanotubes (CNTs)) were added with a binder (polivinylidene fluoride (PVDF)) into ACP to improve the supercapacitive performance of the activated carbon (AC) electrodes. Symmetric supercapacitor cells, fabricated using these AC electrodes and 1 molar H{sub 2}SO{sub 4} electrolyte, were analyzed using a standard electrochemical impedance spectroscopy technique. The addition of graphite, carbon black and CNTs was found effective in reducing the cell resistance from 165 to 68, 23 and 49 Ohm respectively, and increasing the specific capacitance of the AC electrodes from 3 to 7, 17, 32 F g{sup −1} respectively. Since the addition of CNTs can produce the highest specific capacitance, CNTs were chosen as a conductive material to produce AC composite electrodes that were added with 2.5 %, 5 % and 10 % (by weight) electro-active material namely ruthenium oxide; PVDF binder and CNTs contents were kept at 5 % by weight in each AC composite produced. The highest specific capacitance of the cells obtained in this study was 86 F g{sup −1}, i.e. for the cell with the resistance of 15 Ohm and composite electrode consists of 5 % ruthenium oxide.

  19. Dielectric, Impedance and Conduction Behavior of Double Perovskite Pr2CuTiO6 Ceramics

    NASA Astrophysics Data System (ADS)

    Mahato, Dev K.; Sinha, T. P.

    2017-01-01

    Polycrystalline Pr2CuTiO6 (PCT) ceramics exhibits dielectric, impedance and modulus characteristics as a possible material for microelectronic devices. PCT was synthesized through the standard solid-state reaction method. The dielectric permittivity, impedance and electric modulus of PCT have been studied in a wide frequency (100 Hz-1 MHz) and temperature (303-593 K) range. Structural analysis of the compound revealed a monoclinic phase at room temperature. Complex impedance Cole-Cole plots are used to interpret the relaxation mechanism, and grain boundary contributions towards conductivity have been estimated. From electrical modulus formalism polarization and conductivity relaxation behavior in PCT have been discussed. Normalization of the imaginary part of impedance ( Z″) and the normalized imaginary part of modulus ( M″) indicates contributions from both long-range and localized relaxation effects. The grain boundary resistance along with their relaxation frequencies are plotted in the form of an Arrhenius plot with activation energy 0.45 eV and 0.46 eV, respectively. The ac conductivity mechanism has been discussed.

  20. Frequency of alleles conferring resistance to the Bacillus thuringiensis toxins Cry1Ac and Cry2Ab in Australian populations of Helicoverpa punctigera (Lepidoptera: Noctuidae) from 2002 to 2006.

    PubMed

    Downes, S; Parker, T L; Mahon, R J

    2009-04-01

    Helicoverpa punctigera and Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae) are important pests of field and horticultural crops in Australia. The former is endemic to the continent, whereas the latter is also distributed in Africa and Asia. Although H. armigera rapidly developed resistance to virtually every group of insecticide used against it, there is only one report of resistance to an insecticide in H. punctigera. In 1996 the Australian cotton industry adopted Ingard, which expresses the Bacillus thuringiensis (Bt) toxin gene cry1Ac. In 2004/2005, Bollgard II (which expresses Cry1Ac and Cry2Ab) replaced Ingard and has subsequently been grown on 80% of the area planted to cotton, Gossypium hirsutum L. From 2002/2003 to 2006/2007, F2 screens were used to detect resistance to Cry1Ac or Cry2Ab. We detected no alleles conferring resistance to Cry1Ac; the frequency was < 0.0005 (n = 2,180 alleles), with a 95% credibility interval between 0 and 0.0014. However, during the same period, we detected alleles that confer resistance to Cry2Ab at a frequency of 0.0018 (n = 2,192 alleles), with a 95% credibility interval between 0.0005 and 0.0040. For both toxins, the experiment-wise detection probability was 94%, i.e., if there actually was a resistance allele in any tested lines, we would have detected it 94% of the time. The first isolation of Cry2Ab resistance in H. punctigera was before the widespread deployment of Bollgard II. This finding supports our published notion for H. armigera that alleles conferring resistance to Cry2Ab may be present at detectable frequencies in populations before selection by transgenic crops.

  1. Novel Pink Bollworm Resistance to the Bt Toxin:Cryl Ac: Effects on Mating, Oviposition, Larval Development, and Survival.

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Bt cotton plants are genetically engineered to produce insecticidal toxins from the Bacillus thuringiensis (Bt) bacterium and target key lepidopteran pests. At least four strains of pink bollworm, Pectinophora gossypiella (Saunders), have been selected in the laboratory for resistance to insecticid...

  2. Altered binding of the Cry1Ac toxin to larval membranes but not to the toxin-binding protein in Plodia interpunctella selected for resistance to different Bacillus thuringiensis isolates.

    PubMed Central

    Mohammed, S I; Johnson, D E; Aronson, A I

    1996-01-01

    Immunoblotting and cytochemical procedures were used to determine whether toxin binding was altered in strains of the Indianmeal moth, Plodia interpunctella, selected for resistance to various strains of Bacillus thuringiensis. Each of these B. thuringiensis subspecies produces a mixture of protoxins, primarily Cry1 types, and the greatest insect resistance is to the Cry1A protoxins. In several cases, however, there was also resistance to toxins not present in the B. thuringiensis strains used for selection. The Cry1Ab and Cry1Ac toxins bound equally well over a range of toxin concentrations and times of incubation to a single protein of ca. 80-kDa in immunoblots of larval membrane extracts from all of the colonies. This binding protein is essential for toxicity since a mutant Cry1Ac toxin known to be defective in binding and thus less toxic bound poorly to the 80-kDa protein. This binding protein differed in size from the major aminopeptidase N antigens implicated in toxin binding in other insects. Binding of fluorescently labeled Cry1Ac or Cry1Ab toxin to larval sections was found at the tips of the brush border membrane prepared from the susceptible but not from any of the resistant P. interpunctella. Accessibility of a major Cry1A-binding protein appears to be altered in resistant larvae and could account for their broad resistance to several B. thuringiensis toxins. PMID:8900008

  3. FDTD modeling of thin impedance sheets

    NASA Technical Reports Server (NTRS)

    Luebbers, Raymond; Kunz, Karl

    1991-01-01

    Thin sheets of resistive or dielectric material are commonly encountered in radar cross section calculations. Analysis of such sheets is simplified by using sheet impedances. It is shown that sheet impedances can be modeled easily and accurately using Finite Difference Time Domain (FDTD) methods. These sheets are characterized by a discontinuity in the tangential magnetic field on either side of the sheet but no discontinuity in tangential electric field. This continuity, or single valued behavior of the electric field, allows the sheet current to be expressed in terms of an impedance multiplying this electric field.

  4. RHIC ABORT KICKER WITH REDUCED COUPLING IMPEDANCE.

    SciTech Connect

    HAHN,H.; DAVINO,D.

    2002-06-02

    Kicker magnets typically represent the most important contributors to the transverse impedance budget of accelerators and storage rings. Methods of reducing the impedance value of the SNS extraction kicker presently under construction and, in view of a future performance upgrade, that of the RHIC abort kicker have been thoroughly studied at this laboratory. In this paper, the investigation of a potential improvement from using ferrite different from the BNL standard CMD5005 is reported. Permeability measurements of several ferrite types have been performed. Measurements on two kicker magnets using CMD5005 and C2050 suggest that the impedance of a magnet without external resistive damping, such as the RHIC abort kicker, would benefit.

  5. AC Impedance Behavior of LaNi3.55Mn0.4Al0.3Co0.6Fe0.15 Hydrogen-Storage Alloy: Effect of Surface Area

    NASA Astrophysics Data System (ADS)

    Tliha, M.; Khaldi, C.; Lamloumi, J.

    2016-04-01

    The decrease of Cobalt content in alloy is very beneficial to reduce the production cost of the alloy, whereas the effect of Co on cycle life of the AB5-type hydrogen-storage alloys is extremely important. Therefore, it is interesting to investigate low-Co and/or Co-free AB5-type alloys in which Co was substituted by other elements. Iron is a key element in the development of low-Co AB5-type alloys. The aim of this work is to systematically investigate the effect of the real surface area on the all kinetic properties of a low-Co LaNi3.55Mn0.4Al0.3Co0.6Fe0.15 alloy under cycling using electrochemical impedance spectroscopy (EIS) technique. All kinetic properties of the electrode, such as exchange density, limiting current density, high-rate charge/discharge ability, cycle life time, electrocatalytic activity, and diffusion rate are related to the real surface area. During the EIS analysis, interestingly, we found that with increasing number of charge/discharge cycles, the metal hydride alloy powders undergo micro-cracking into smaller particles, and thus the real surface area of the alloy increases, which then influences the kinetic properties of the electrode reactions.

  6. Dielectric and Impedance Spectroscopy of Barium Bismuth Vanadate Ferroelectrics

    NASA Astrophysics Data System (ADS)

    Sutar, B. C.; Choudhary, R. N. P.; Das, Piyush R.

    2014-07-01

    Structural, micro-structural and electrical properties of barium bismuth vanadate Ba(Bi0.5V0.5)O3 ceramics were investigated. X-ray diffraction (XRD) analysis of the prepared material confirmed the formation of the compound with monoclinic crystal system. Scanning electron microscopy (SEM) of the compound exhibits well-defined grains that are uniformly distributed throughout the surface of the sample. Dielectric properties of the compound were studied as a function of temperature at different frequencies. An observation of dielectric anomaly at 295 °C is due to ferroelectric phase transition that was later confirmed by the appearance of hysteresis loop. Detailed studies of complex impedance spectroscopy have provided a better understanding of the relaxation process and correlations between the microstructure-electrical properties of the materials. The nature of frequency dependence of ac conductivity obeys the Debye power law. The dc conductivity, calculated from the ac conductivity spectrum, shows the negative temperature coefficient of resistance behavior similar to that of a semiconductor.

  7. Knockout of the alpha 1A/C-adrenergic receptor subtype: the alpha 1A/C is expressed in resistance arteries and is required to maintain arterial blood pressure.

    PubMed

    Rokosh, D Gregg; Simpson, Paul C

    2002-07-09

    alpha 1-adrenergic receptors (ARs) play a major role in blood pressure regulation. The three alpha 1-AR subtypes (A/C, B, and D) stimulate contraction of isolated arteries, but it is uncertain how different subtypes contribute to blood pressure regulation in the intact animal. We studied the role of the alpha 1A/C subtype by using gene knockout. alpha 1A/C knockout (KO) mice were viable and overtly normal. The LacZ reporter gene replaced alpha 1A/C coding sequence in the KO, and beta-galactosidase staining was present in resistance arteries and arterioles, but not in the thoracic aorta or its main branches. By tail cuff manometer and arterial catheter in conscious mice, alpha 1A/C KO mice were hypotensive at rest, with an 8-12% reduction of blood pressure dependent on alpha 1A/C gene copy number. A61603, an alpha 1A/C-selective agonist, caused a pressor response that was lost in the KO and reduced but significant in heterozygous mice with a single copy of the alpha 1A/C. A subtype-nonselective agonist [phenylephrine (PE)] caused a pressor response in KO mice, but the final arterial pressure was only 85% of wild type. The baroreflex was reset in the KO, and heart rate variability was decreased. After baroreflex blockade with atropine, PE increased blood pressure but did not change heart rate. Cardiac and vascular responses to the beta-AR agonist isoproterenol were unchanged, and the arterial lumen area was not altered. We conclude that the alpha 1A/C-AR subtype is a vasopressor expressed in resistance arteries and is required for normal arterial blood pressure regulation. alpha 1A/C-selective antagonists might be desirable antihypertensive agents.

  8. Anisotropic Artificial Impedance Surfaces

    NASA Astrophysics Data System (ADS)

    Quarfoth, Ryan Gordon

    Anisotropic artificial impedance surfaces are a group of planar materials that can be modeled by the tensor impedance boundary condition. This boundary condition relates the electric and magnetic field components on a surface using a 2x2 tensor. The advantage of using the tensor impedance boundary condition, and by extension anisotropic artificial impedance surfaces, is that the method allows large and complex structures to be modeled quickly and accurately using a planar boundary condition. This thesis presents the theory of anisotropic impedance surfaces and multiple applications. Anisotropic impedance surfaces are a generalization of scalar impedance surfaces. Unlike the scalar version, anisotropic impedance surfaces have material properties that are dependent on the polarization and wave vector of electromagnetic radiation that interacts with the surface. This allows anisotropic impedance surfaces to be used for applications that scalar surfaces cannot achieve. Three of these applications are presented in this thesis. The first is an anisotropic surface wave waveguide which allows propagation in one direction, but passes radiation in the orthogonal direction without reflection. The second application is a surface wave beam shifter which splits a surface wave beam in two directions and reduces the scattering from an object placed on the surface. The third application is a patterned surface which can alter the scattered radiation pattern of a rectangular shape. For each application, anisotropic impedance surfaces are constructed using periodic unit cells. These unit cells are designed to give the desired surface impedance characteristics by modifying a patterned metallic patch on a grounded dielectric substrate. Multiple unit cell geometries are analyzed in order to find the setup with the best performance in terms of impedance characteristics and frequency bandwidth.

  9. Specific heat, resistivity, and AC susceptibility of the cubic PrX 2 compounds (X = Pt, Ru, Ir, Rh)

    NASA Astrophysics Data System (ADS)

    Greidanus, F. J. A. M.; Nieuwenhuys, G. J.; de Jongh, L. J.; Huiskamp, W. J.; Capel, H. W.; Buschow, K. H. J.

    1983-04-01

    Specific-heat, differential-susceptibility and electrical-resistivity measurements on PrX 2 (X = Ir, Pt, Rh, Ru) compounds reveal phase transitions at Tc = 11.2±0.5 K, 7.7±0.5 K, 7.9±0.5 Kand 33.9±0.5 K for X = Ir, Pt, Rh, and Ru, respective ly. From earlier neutron inelastic scattering experiments, the crystalline electric field levels of these compounds have been determined. The specific-heat results are compared with the results of a mean-field calculation, assuming bilinear exchange interactions. The presence of broad secondary maxima in the temperature dependence of the specific heat of PrRh 2, PrRu 2 and especially PrIr 2 can qualitatively be explained by the presence of biquadratic (quadrupolar) interactions. The behaviour of the susceptibility is in agreement with ferromagnetic ordering. The electrical resistivity drops markedly below Tc, and the dϱ/d T versus T curve is similar to that of the specific heat.

  10. Electrical transport properties of CoMn0.2-xGaxFe1.8O4 ferrites using complex impedance spectroscopy

    NASA Astrophysics Data System (ADS)

    Tsay, Chien-Yie; Lin, Yi-Hsiang; Wang, Yao-Ming; Chang, Horng-Yi; Lei, Chien-Ming; Jen, Shien-Uang

    2016-05-01

    In this study, we report the influence of Ga content on the microstructural, magnetic, and AC impedance properties of Co-based ferrites with compositions of CoMn0.2-xGaxFe1.8O4 (x=0, 0.1, and 0.2) prepared by the solid-state reaction method. Experimental results showed that the as-prepared Co-based ferrites had a single-phase spinel structure; the Curie temperature of Co-based ferrites decreased with increasing Ga content. All ferrite samples exhibited a typical hysteresis behavior with good values of saturation magnetization at room temperature. The electrical properties of Co-based ferrites were investigated using complex impedance spectroscopy analysis in the frequency range of 100 kHz-50 MHz at temperatures of 150 to 250 oC. The impedance analysis revealed that the magnitudes of the real part (Z') and the imaginary part (Z") of complex impedance decreased with increasing temperature. Only one semicircle was observed in each complex impedance plane plot, which revealed that the contribution to conductivity was from the grain boundaries. It was found that the relaxation time for the grain boundary (τgb) also decreased with increasing temperature. The values of resistance for the grain boundary (Rgb) significantly increased with increasing Ga content, which indicated that the incorporation of Ga into Co-based ferrites enhanced the electrical resistivity.

  11. Impedance matching between ventricle and load.

    PubMed

    Piene, H

    1984-01-01

    Impedance matching in the cardiovascular system is discussed in light of two models of ventricle and load: a Thevenin equivalent consisting of a hydromotive pressure source and an internal, source resistance and compliance in parallel; and a time-varying compliance filled from a constant pressure source and ejecting into a load of three components, a central resistor, a compliance, and a peripheral resistance. According to the Thevenin analog, the energy source and the load are matched when the load resistance is T/t times the internal source resistance (T is total cycle length, t is systolic time interval). Both from this model and from the variable compliance model it appears that optimum matching between source and load depends on the compliance of the Windkessel, as low compliance shifts the matching load resistance to a low value. Animal experiments (isolated cat hearts) indicated that both left and right ventricles at normal loads work close to their maxima of output hydraulic power, and, according to experiments in the right ventricle, maximum power output is related to load resistance and compliance as predicted by the above models. From an experimentally determined relationship among instantaneous ventricular pressure and volume (right ventricle of isolated cat hearts), an optimum load impedance was calculated on the basis of the assumption that the ratio between stroke work and static, potential energy developed in the ventricular cavity is maximum. The optimum load impedance found by this procedure closely resembles the normal input impedance of the cat lung vessel bed.

  12. High frequency AC response, DC resistivity and magnetic studies of holmium substituted Ni-ferrite: A novel electromagnetic material

    NASA Astrophysics Data System (ADS)

    Pervaiz, Erum; Gul, I. H.

    2014-01-01

    Nanoparticles of holmium substituted nickel ferrites (NiHoxFe2-xO4) with x ranging from 0.0 to 0.15 have been prepared by the sol-gel auto-combustion method. Structural and morphology studies have been performed by X-ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM). XRD patterns revealed the formation of pure spinel phase ferrites without any impurity phase. Lattice parameter increases along with a decrease in crystallite size with increasing the concentration of Ho3+ in the parent nickel ferrite due to large ionic radius of Ho3+ (0.901 Å) as compared to Fe3+ (0.67 Å). SEM shows the spherical, uniformly distributed homogenous nanoparticles grown by controlled reaction parameters of the sol-gel method. Complex permittivity (ɛ*) and complex electric modulus (M*) have been studied for the present nanoferrites in the frequency ranges of 1 MHz-1 GHz. Frequency dependent dielectric parameters (relative permittivity (ɛ'), dielectric loss (ɛ″), dielectric loss tangent (tan δ)) decreases due to holmium substitution in nickel ferrites, showing the electrical conduction is decreasing in the nickel holmium ferrites with increase in the concentration of holmium. Complex modulus plots shows the poorly resolved semi circles and relaxation of nanoferrite is studied in the high frequency region. Also the relaxation time increases due to increase in x (0.0-0.15). DC electrical resistivity increases (107 Ω-cm-1010 Ω-cm) due to holmium ions substitution in nickel ferrites. Magnetic behavior was also characterized using a Vibrating Sample Magnetometer (VSM) under an applied magnetic field of 10 kOe and shows that magnetization decreases with increase in composition of holmium in nickel ferrites. High frequency behavior, low losses and very high DC electrical resistivity made the material a novel one for electromagnetic devices.

  13. Voltammetric and impedance behaviours of surface-treated nano-crystalline diamond film electrodes

    SciTech Connect

    Liu, F. B.; Jing, B.; Cui, Y.; Di, J. J.; Qu, M.

    2015-04-15

    The electrochemical performances of hydrogen- and oxygen-terminated nano-crystalline diamond film electrodes were investigated by cyclic voltammetry and AC impedance spectroscopy. In addition, the surface morphologies, phase structures, and chemical states of the two diamond films were analysed by scanning probe microscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy, respectively. The results indicated that the potential window is narrower for the hydrogen-terminated nano-crystalline diamond film than for the oxygen-terminated one. The diamond film resistance and capacitance of oxygen-terminated diamond film are much larger than those of the hydrogen-terminated diamond film, and the polarization resistances and double-layer capacitance corresponding to oxygen-terminated diamond film are both one order of magnitude larger than those corresponding to the hydrogen-terminated diamond film. The electrochemical behaviours of the two diamond film electrodes are discussed.

  14. Elite Indica transgenic rice plants expressing modified Cry1Ac endotoxin of Bacillus thuringiensis show enhanced resistance to yellow stem borer (Scirpophaga incertulas).

    PubMed

    Khanna, H K; Raina, S K

    2002-08-01

    Bt-transgenics of elite indica rice breeding lines (IR-64, Pusa Basmati-1 and Karnal Local) were generated through biolistic or Agrobacterium-mediated approaches. A synthetic cry1Ac gene, codon optimised for rice and driven by the maize ubiquitin-1 promoter, was used. Over 200 putative transformants of IR-64 and Pusa Basmati-1 and 26 of the Karnal Local were regenerated following use of the hpt (hygromycin phosphotransferase) selection system. Initial transformation frequency was in the range of 1 to 2% for particle bombardment while it was comparatively higher (approximately 9%) for Agrobacterium. An improved selection procedure, involving longer selection on the antibiotic-supplemented medium, enhanced the frequency of Bt-transformants and reduced the number of escapes. Molecular evaluation revealed multiple transgene insertions in transformants, whether generated through biolistic or Agrobacterium. In the latter case, it was also observed that all genes on the T-DNA do not necessarily get transferred as an intact insert. Selected Bt-lines of IR-64 and Pusa Basmati-1, having Bt-titers of 0.1% (of total soluble protein) and above were evaluated for resistance against manual infestation of freshly hatched neonate larvae of yellow stem borers collected from a hot spot stem borer infested area in northern India. Several Bt-lines were identified showing 100% mortality of larvae, within 4-days of infestation, in cut-stem as well as vegetative stage whole plant assays. However, there was an occasional white head even among such plants when assayed at the reproductive stage. Results are discussed in the light of resistance management strategies for deployment of Bt-rice.

  15. ac and dc percolative conductivity of magnetite-cellulose acetate composites

    SciTech Connect

    Chiteme, C.; McLachlan, D. S.; Sauti, G.

    2007-03-01

    ac and dc conductivity results for a percolating system, which consists of a conducting powder (magnetite) combined with an 'insulating' powder (cellulose acetate), are presented. Impedance and modulus spectra are obtained in a percolation system. The temperature dependence of the resistivity of the cellulose acetate is such that at 170 deg. C, it is essentially a conductor at frequencies below 0.059{+-}0.002 Hz, and a dielectric above. The percolation parameters, from the dc conductivity measured at 25 and 170 deg. C, are determined and discussed in relation to the ac results. The experimental results scale as a function of composition, temperature, and frequency. An interesting result is the correlation observed between the scaling parameter (f{sub ce}), obtained from a scaling of the ac measurements, and the peak frequency (f{sub cp}) of the arcs, obtained from impedance spectra, above the critical volume fraction. Scaling at 170 deg. C is not as good as at 25 deg. C, probably indicating a breakdown in scaling at the higher temperature. The modulus plots show the presence of two materials: a conducting phase dominated by the cellulose acetate and the isolated conducting clusters below the critical volume fraction {phi}{sub c}, as well as the interconnected conducting clusters above {phi}{sub c}. These results are confirmed by computer simulations using the two exponent phenomenological percolation equation. These results emphasize the need to analyze ac conductivity results in terms of both impedance and modulus spectra in order to get more insight into the behavior of composite materials.

  16. Impedance Noise Identification for State-of-Health Prognostics

    SciTech Connect

    Jon P. Christophersen; Chester G. Motloch; John L. Morrison; Ian B. Donnellan; William H. Morrison

    2008-07-01

    Impedance Noise Identification is an in-situ method of measuring battery impedance as a function of frequency using a random small signal noise excitation source. Through a series of auto- and cross-correlations and Fast Fourier Transforms, the battery complex impedance as a function of frequency can be determined. The results are similar to those measured under a lab-scale electrochemical impedance spectroscopy measurement. The lab-scale measurements have been shown to correlate well with resistance and power data that are typically used to ascertain the remaining life of a battery. To this end, the Impedance Noise Identification system is designed to acquire the same type of data as an on-board tool. A prototype system is now under development, and results are being compared to standardized measurement techniques such as electrochemical impedance spectroscopy. A brief description of the Impedance Noise Identification hardware system and representative test results are presented.

  17. Surface resistivity/conductivity of different organic-thin films by shearography

    NASA Astrophysics Data System (ADS)

    Habib, Khaled

    2011-08-01

    Optical shearography techniques were used for the first time to measure the surface resistivity/conductivity of different organic-thin films. Different organic coatings i.e., ACE Premium- gray, white, and beige Enamels (spray coatings), on a metallic alloy, i.e., a carbon steel, were investigated at a temperature range simulating the severe weather temperatures in Kuwait, especially between the daylight and the night time temperatures, 20-60 °C. The investigation focused on determining the in-plane displacement of the coatings, which amounts to the thermal deformation (strain) with respect to the applied temperature range. Then, the alternating current (AC) impedance (resistance) of the coated samples was determined by the technique of electrochemical impedance spectroscopy (EIS) in 3.5 % NaCl solution at room temperature. In addition, a mathematical model was derived in order to correlate between the AC impedance (resistance) and to the surface (in-plane) displacement of the samples in solutions. In other words, a proportionality constant (surface resistivity or conductivity=1/ surface resistivity) between the determined AC impedance (by EIS technique) and the in-plane displacement (by the optical interferometry techniques) was obtained. Consequently the surface resistivity (ρ) and conductivity (σ) of the coated samples in solutions were obtained. Also, electrical resistivity values (ρ) from other source were used for comparison with the calculated values of this investigation. This study revealed that the measured values of the resistivity for the ACE Premium - gray, white, and beige coatings were carried out for the first time. No data on the values of (ρ) were found in literature for the same coatings, using direct current (DC) methods. However, the value range of (ρ) of all investigated coatings, 0.25×108 - 0.27×1010 Ω-cm was found in the insulator range.

  18. Impedance spectroscopy of thin-film CdTe/CdS solar cells under varied illumination

    NASA Astrophysics Data System (ADS)

    Proskuryakov, Y. Y.; Durose, K.; Al Turkestani, M. K.; Mora-Seró, I.; Garcia-Belmonte, G.; Fabregat-Santiago, F.; Bisquert, J.; Barrioz, V.; Lamb, D.; Irvine, S. J. C.; Jones, E. W.

    2009-08-01

    The electrical properties of CdTe/CdS solar cells grown by metal organic chemical vapor deposition were investigated by a technique of impedance measurements under varied intensity of AM1.5 illumination. A generalized impedance model was developed and applied to a series of CdTe/CdS cells with variations in structure and doping. The light measurements were compared to the conventional ac measurements in dark under varied dc bias, using the same methodology for equivalent circuit analysis in both cases. Detailed information on the properties of the device structure was obtained, including the properties of the main p-n junction under light, minority carrier lifetime, back contact, as well as the effect of the blocking ZnO layer incorporated between the transparent conductor and CdS layers. In particular, the comparison between samples with different chemical concentrations of As has shown that the total device impedance and the series resistance are strongly increased at lower As densities, resulting in the lower collection current and efficiencies. At the same time the minority carrier lifetime was found to be one order of magnitude larger for the lowest value of As density, when compared to the optimized devices.

  19. Creating dynamic equivalent PV circuit models with impedance spectroscopy for arc-fault modeling.

    SciTech Connect

    Johnson, Jay Dean; Kuszmaul, Scott S.; Strauch, Jason E.; Schoenwald, David Alan

    2011-06-01

    Article 690.11 in the 2011 National Electrical Code{reg_sign} (NEC{reg_sign}) requires new photovoltaic (PV) systems on or penetrating a building to include a listed arc fault protection device. Currently there is little experimental or empirical research into the behavior of the arcing frequencies through PV components despite the potential for modules and other PV components to filter or attenuate arcing signatures that could render the arc detector ineffective. To model AC arcing signal propagation along PV strings, the well-studied DC diode models were found to inadequately capture the behavior of high frequency arcing signals. Instead dynamic equivalent circuit models of PV modules were required to describe the impedance for alternating currents in modules. The nonlinearities present in PV cells resulting from irradiance, temperature, frequency, and bias voltage variations make modeling these systems challenging. Linearized dynamic equivalent circuits were created for multiple PV module manufacturers and module technologies. The equivalent resistances and capacitances for the modules were determined using impedance spectroscopy with no bias voltage and no irradiance. The equivalent circuit model was employed to evaluate modules having irradiance conditions that could not be measured directly with the instrumentation. Although there was a wide range of circuit component values, the complex impedance model does not predict filtering of arc fault frequencies in PV strings for any irradiance level. Experimental results with no irradiance agree with the model and show nearly no attenuation for 1 Hz to 100 kHz input frequencies.

  20. Measuring plasma potential with an impedance probe in low density plasma

    NASA Astrophysics Data System (ADS)

    Walker, David; Blackwell, David; Fernsler, Richard; Amatucci, William

    2012-10-01

    A recent rf technique for determining plasma potential, φp , using an impedance probe was shown to be independent of probe geometry, magnetic field, and orientation. However, a problem which arises in low density plasma concerns a magnitude mismatch between typical network analyzer input impedance (Z0 = 50 φ) and the large value of ac resistance (Rac) which is inversely proportional to ne. The method relies on finding a minimum in Re(Zac)footnotetextPhys. Plasmas 17, 113503 (2010).^,footnotetextNRL Memorandum Report 6750-12-9413 (2012). which is difficult if Rac is much larger than Z0. For low density space plasmas (10^4 -10^5 cm-3) values of Rac range to kφ levels. We have developed numerical simulations based on solving the Boltzmann equation in spherical geometry for a given sheath size. These simulations include a presheath and predict values for Zac which are then used to estimate the error as a function of input impedance based on the error associated with a 50 φ load.

  1. Current density distribution in cylindrical Li-Ion cells during impedance measurements

    NASA Astrophysics Data System (ADS)

    Osswald, P. J.; Erhard, S. V.; Noel, A.; Keil, P.; Kindermann, F. M.; Hoster, H.; Jossen, A.

    2016-05-01

    In this work, modified commercial cylindrical lithium-ion cells with multiple separate current tabs are used to analyze the influence of tab pattern, frequency and temperature on electrochemical impedance spectroscopy. In a first step, the effect of different current tab arrangements on the impedance spectra is analyzed and possible electrochemical causes are discussed. In a second step, one terminal is used to apply a sinusoidal current while the other terminals are used to monitor the local potential distribution at different positions along the electrodes of the cell. It is observed that the characteristic decay of the voltage amplitude along the electrode changes non-linearly with frequency, where high-frequent currents experience a stronger attenuation along the current collector than low-frequent currents. In further experiments, the decay characteristic is controlled by the cell temperature, driven by the increasing resistance of the current collector and the enhanced kinetic and transport properties of the active material and electrolyte. Measurements indicate that the ac current distribution depends strongly on the frequency and the temperature. In this context, the challenges for electrochemical impedance spectroscopy as cell diagnostic technique for commercial cells are discussed.

  2. Method and apparatus for identifying conductive objects by monitoring the true resistive component of impedance change in a coil system caused by the object

    DOEpatents

    Gregory, William D.; Capots, Larry H.; George, James P.; Janik, Richard

    1981-01-01

    The type of conductor, its property, and if a metal, its type and cross-sectional area can be obtained from measurements made at different frequencies for the amount of unbalance created in a previously balanced stable coil detection system. The true resistive component is accurately measured and thus reflects only the voltage loss attributable to eddy currents caused by introduction of the test sample to the coil system. This voltage divided by corresponding applied frequency gives a curve which peaks at a frequency dependent upon type of conductor. For a metal this peak frequency is proportional to the samples resistivity divided by its cross-sectional area.

  3. Constant current load matches impedances of electronic components

    NASA Technical Reports Server (NTRS)

    Alexander, R. M.

    1970-01-01

    Constant current load with negative resistance characteristics actively compensates for impedance variations in circuit components. Through a current-voltage balancing operation the internal impedance of the diodes is maintained at a constant value. This constant current load circuit can be used in simple telemetry systems.

  4. Antenna impedance matching with neural networks.

    PubMed

    Hemminger, Thomas L

    2005-10-01

    Impedance matching between transmission lines and antennas is an important and fundamental concept in electromagnetic theory. One definition of antenna impedance is the resistance and reactance seen at the antenna terminals or the ratio of electric to magnetic fields at the input. The primary intent of this paper is real-time compensation for changes in the driving point impedance of an antenna due to frequency deviations. In general, the driving point impedance of an antenna or antenna array is computed by numerical methods such as the method of moments or similar techniques. Some configurations do lend themselves to analytical solutions, which will be the primary focus of this work. This paper employs a neural control system to match antenna feed lines to two common antennas during frequency sweeps. In practice, impedance matching is performed off-line with Smith charts or relatively complex formulas but they rarely perform optimally over a large bandwidth. There have been very few attempts to compensate for matching errors while the transmission system is in operation and most techniques have been targeted to a relatively small range of frequencies. The approach proposed here employs three small neural networks to perform real-time impedance matching over a broad range of frequencies during transmitter operation. Double stub tuners are being explored in this paper but the approach can certainly be applied to other methodologies. The ultimate purpose of this work is the development of an inexpensive microcontroller-based system.

  5. Microwave impedance imaging on semiconductor memory devices

    NASA Astrophysics Data System (ADS)

    Kundhikanjana, Worasom; Lai, Keji; Yang, Yongliang; Kelly, Michael; Shen, Zhi-Xun

    2011-03-01

    Microwave impedance microscopy (MIM) maps out the real and imaginary components of the tip-sample impedance, from which the local conductivity and dielectric constant distribution can be derived. The stray field contribution is minimized in our shielded cantilever design, enabling quantitative analysis of nano-materials and device structures. We demonstrate here that the MIM can spatially resolve the conductivity variation in a dynamic random access memory (DRAM) sample. With DC or low-frequency AC bias applied to the tip, contrast between n-doped and p-doped regions in the dC/dV images is observed, and p-n junctions are highlighted in the dR/dV images. The results can be directly compared with data taken by scanning capacitance microscope (SCM), which uses unshielded cantilevers and resonant electronics, and the MIM reveals more information of the local dopant concentration than SCM.

  6. Determination of reaction resistances for metal-hydride electrodes during anodic polarization

    NASA Astrophysics Data System (ADS)

    Wang, Chunsheng; Soriaga, Manuel P.; Srinivasan, Supramaniam

    The anodic polarization process in metal-hydride electrodes occurs via the following consecutive steps: (i) diffusion of absorbed hydrogen from the bulk to the surface of the electrode, (ii) hydrogen transfer from absorbed state to adsorbed state at the electrode surface, and (iii) electrochemical oxidation of the adsorbed hydrogen on the electrode surface. A theoretical treatment is presented to account for the dependencies on these three consecutive steps, of the reaction resistances, anodic limiting current, cathodic limiting current, and exchange current. The theoretical analysis predicts that the total resistances measured from linear micropolarization is the sum of the charge-transfer, hydrogen-transfer, and hydrogen-diffusion resistances, which is in contradiction with the generally accepted idea that the resistance measured from linear micropolarization is only the charge-transfer resistance. For a metal-hydride electrode with a flat pressure plateau at a low state of discharge (SOD), the resistance measured from linear micropolarization is approximately equal to the sum of three resistances measured from AC impedance, namely, charge-transfer, hydrogen-transfer and hydrogen-diffusion resistances; however, when the SOD is high, the resistance measured from linear micropolarization is higher than total resistances measured from AC impedance.

  7. Electrochemical Impedance Spectroscopy Of Metal Alloys

    NASA Technical Reports Server (NTRS)

    Macdowell, L. G.; Calle, L. M.

    1993-01-01

    Report describes use of electrochemical impedance spectroscopy (EIS) to investigate resistances of 19 alloys to corrosion under conditions similar to those of corrosive, chloride-laden seaside environment of Space Transportation System launch site. Alloys investigated: Hastelloy C-4, C-22, C-276, and B-2; Inconel(R) 600, 625, and 825; Inco(R) G-3; Monel 400; Zirconium 702; Stainless Steel 304L, 304LN, 316L, 317L, and 904L; 20Cb-3; 7Mo+N; ES2205; and Ferralium 255. Results suggest electrochemical impedance spectroscopy used to predict corrosion performances of metal alloys.

  8. Impeded Dark Matter

    NASA Astrophysics Data System (ADS)

    Kopp, Joachim; Liu, Jia; Slatyer, Tracy R.; Wang, Xiao-Ping; Xue, Wei

    2016-12-01

    We consider dark matter models in which the mass splitting between the dark matter particles and their annihilation products is tiny. Compared to the previously proposed Forbidden Dark Matter scenario, the mass splittings we consider are much smaller, and are allowed to be either positive or negative. To emphasize this modification, we dub our scenario "Impeded Dark Matter". We demonstrate that Impeded Dark Matter can be easily realized without requiring tuning of model parameters. For negative mass splitting, we demonstrate that the annihilation cross-section for Impeded Dark Matter depends linearly on the dark matter velocity or may even be kinematically forbidden, making this scenario almost insensitive to constraints from the cosmic microwave background and from observations of dwarf galaxies. Accordingly, it may be possible for Impeded Dark Matter to yield observable signals in clusters or the Galactic center, with no corresponding signal in dwarfs. For positive mass splitting, we show that the annihilation cross-section is suppressed by the small mass splitting, which helps light dark matter to survive increasingly stringent constraints from indirect searches. As specific realizations for Impeded Dark Matter, we introduce a model of vector dark matter from a hidden SU(2) sector, and a composite dark matter scenario based on a QCD-like dark sector.

  9. Impedance matching based stability criteria for ac microgrids

    NASA Astrophysics Data System (ADS)

    Mendoza-Araya, Patricio A.

    Well logs, measured in depth, must be tied to seismograms, processed in time, using a time-depth function. Well ties are commonly computed using manual techniques, and are therefore prone to human error. I first introduce an automatic single-well tie method that uses smooth dynamic time warping to compute time shifts that align a synthetic seismogram with a seismic trace. These time shifts are constrained to be smoothly varying. I also show that these well ties, in my example, are insensitive to the complexity of my synthetic seismogram modeling. Tying multiple wells compounds errors in single well ties, and maintaining consistency among multiple single well ties is difficult. I introduce an automatic approach to tying multiple wells that improves consistency among well ties. I first model synthetic seismograms for each well. I then create a synthetic image by interpolating the synthetic seismograms between the wells and along seismic image structure. I use smooth dynamic image warping to align the synthetic image to the seismic image and compute updated time-depth functions for each well. I then interpolate the updated time-depth functions between the wells, and map the time-migrated seismic image to depth.

  10. AC Impedance Analysis of Corrosion Fatigue in Naval Aircraft Alloys.

    DTIC Science & Technology

    1987-05-01

    bridge. 2.3 Inhibitor Systems A saturated xylene solution of tri-alkyl (C8-CI0) ammonium complexes of the inhibiting anions borate, molybdate, dichromate ...dedThs the electrochemical rate of oxidation in hite crack tip by a factor of 100. The role of aqueous and organic phase dichrom &’e, nitrite, borate and...UNCLASSIFIED NADC 87183-60 SI 4NITY CLASSIFICATI ON 0 THIS PACE 𔃺.01 M borate reduces the cathodically aerated CF. The molybdate and dichromate inhibitors at

  11. Superconducting active impedance converter

    DOEpatents

    Ginley, David S.; Hietala, Vincent M.; Martens, Jon S.

    1993-01-01

    A transimpedance amplifier for use with high temperature superconducting, other superconducting, and conventional semiconductor allows for appropriate signal amplification and impedance matching to processing electronics. The amplifier incorporates the superconducting flux flow transistor into a differential amplifier configuration which allows for operation over a wide temperature range, and is characterized by high gain, relatively low noise, and response times less than 200 picoseconds over at least a 10-80 K. temperature range. The invention is particularly useful when a signal derived from either far-IR focal plane detectors or from Josephson junctions is to be processed by higher signal/higher impedance electronics, such as conventional semiconductor technology.

  12. Superconducting active impedance converter

    DOEpatents

    Ginley, D.S.; Hietala, V.M.; Martens, J.S.

    1993-11-16

    A transimpedance amplifier for use with high temperature superconducting, other superconducting, and conventional semiconductors allows for appropriate signal amplification and impedance matching to processing electronics. The amplifier incorporates the superconducting flux flow transistor into a differential amplifier configuration which allows for operation over a wide temperature range, and is characterized by high gain, relatively low noise, and response times less than 200 picoseconds over at least a 10-80 K. temperature range. The invention is particularly useful when a signal derived from either far-IR focal plane detectors or from Josephson junctions is to be processed by higher signal/higher impedance electronics, such as conventional semiconductor technology. 12 figures.

  13. AC0010, an Irreversible EGFR Inhibitor Selectively Targeting Mutated EGFR and Overcoming T790M-Induced Resistance in Animal Models and Lung Cancer Patients.

    PubMed

    Xu, Xiao; Mao, Long; Xu, Wanhong; Tang, Wei; Zhang, Xiaoying; Xi, Biao; Xu, Rongda; Fang, Xin; Liu, Jia; Fang, Ce; Zhao, Li; Wang, Xiaobo; Jiang, Ji; Hu, Pei; Zhao, Hongyun; Zhang, Li

    2016-11-01

    AC0010 is a pyrrolopyrimidine-based irreversible EGFR inhibitor, structurally distinct from previously reported pyrimidine-based irreversible EGFR inhibitors, such as osimertinib and rociletinib. AC0010 selectively inhibits EGFR-active and T790M mutations with up to 298-fold increase in potency compared with wild-type EGFR. In a xenograft model, oral administration of AC0010 at a daily dose of 500 mg/kg resulted in complete remission of tumors with EGFR-active and T790M mutations for over 143 days with no weight loss. Three major metabolites of AC0010 were tested and showed no wild-type EGFR inhibition or off-target effects, such as inhibition of IGF-1R. AC0010 is safe in non-small cell lung cancer (NSCLC) patients at a dose range between 50 and 550 mg once per day, and no hyperglycemia or other severe adverse effects were detected, such as grade 3 QT prolongation. The objective responses were observed in NSCLC patients with EGFR T790M mutation. Mol Cancer Ther; 15(11); 2586-97. ©2016 AACR.

  14. Impedance spectroscopy for the detection and identification of unknown toxins

    NASA Astrophysics Data System (ADS)

    Riggs, B. C.; Plopper, G. E.; Paluh, J. L.; Phamduy, T. B.; Corr, D. T.; Chrisey, D. B.

    2012-06-01

    Advancements in biological and chemical warfare has allowed for the creation of novel toxins necessitating a universal, real-time sensor. We have used a function-based biosensor employing impedance spectroscopy using a low current density AC signal over a range of frequencies (62.5 Hz-64 kHz) to measure the electrical impedance of a confluent epithelial cell monolayer at 120 sec intervals. Madin Darby canine kidney (MDCK) epithelial cells were grown to confluence on thin film interdigitated gold electrodes. A stable impedance measurement of 2200 Ω was found after 24 hrs of growth. After exposure to cytotoxins anthrax lethal toxin and etoposide, the impedance decreased in a linear fashion resulting in a 50% drop in impedance over 50hrs showing significant difference from the control sample (~20% decrease). Immunofluorescent imaging showed that apoptosis was induced through the addition of toxins. Similarities of the impedance signal shows that the mechanism of cellular death was the same between ALT and etoposide. A revised equivalent circuit model was employed in order to quantify morphological changes in the cell monolayer such as tight junction integrity and cell surface area coverage. This model showed a faster response to cytotoxin (2 hrs) compared to raw measurements (20 hrs). We demonstrate that herein that impedance spectroscopy of epithelial monolayers serves as a real-time non-destructive sensor for unknown pathogens.

  15. Longitudinal impedance of RHIC

    SciTech Connect

    Blaskiewicz, M.; Brennan, J. M.; Mernick, K.

    2015-05-03

    The longitudinal impedance of the two RHIC rings has been measured using the effect of potential well distortion on longitudinal Schottky measurements. For the blue RHIC ring Im(Z/n) = 1.5±0.2Ω. For the yellow ring Im(Z/n) = 5.4±1Ω.

  16. Characterization of the corrosion resistance of biologically active solutions: The effects of anodizing and welding

    NASA Technical Reports Server (NTRS)

    Walsh, Daniel W.

    1991-01-01

    An understanding of fabrication processes, metallurgy, electrochemistry, and microbiology is crucial to the resolution of microbiologically influenced corrosion (MIC) problems. The object of this effort was to use AC impedance spectroscopy to characterize the corrosion resistance of Type II anodized aluminum alloy 2219-T87 in sterile and biologically active media and to examine the corrosion resistance of 316L, alloy 2219-T87, and titanium alloy 6-4 in the welded and unwelded conditions. The latter materials were immersed in sterile and biologically active media and corrosion currents were measured using the polarization resistance (DC) technique.

  17. Recycler short kicker beam impedance

    SciTech Connect

    Crisp, Jim; Fellenz, Brian; /Fermilab

    2009-07-01

    Measured longitudinal and calculated transverse beam impedance is presented for the short kicker magnets being installed in the Fermilab Recycler. Fermi drawing number ME-457159. The longitudinal impedance was measured with a stretched wire and the Panofsky equation was used to estimate the transverse impedance. The impedance of 3319 meters (the Recycler circumference) of stainless vacuum pipe is provided for comparison. Although measurements where done to 3GHz, impedance was negligible above 30MHz. The beam power lost to the kicker impedance is shown for a range of bunch lengths. The measurements are for one kicker assuming a rotation frequency of 90KHz. Seven of these kickers are being installed.

  18. Electrochemical impedance measurement of a carbon nanotube probe electrode

    NASA Astrophysics Data System (ADS)

    Inaba, Akira; Takei, Yusuke; Kan, Tetsuo; Matsumoto, Kiyoshi; Shimoyama, Isao

    2012-12-01

    We measured and analyzed the electrochemical impedance of carbon nanotube (CNT) probe electrodes fabricated through the physical separation of insulated CNT bridges. The fabricated CNT electrodes were free-standing CNTs that were completely covered with an insulator, except for their tips. Typical dimensions of the nanoelectrodes were 1-10 nm in CNT diameter, 80-300 nm in insulator diameter, 0.5-4 μm in exposed CNT length and 1-10 μm in probe length. The electrochemical impedance at frequencies ranging from 40 Hz to 1 MHz was measured in physiological saline. The measured impedance of the CNT electrode was constant at 32 MΩ at frequencies below 1 kHz and was inversely proportional to frequency at frequencies above 10 kHz. By means of comparison with the parasitic capacitive impedance of the insulator membrane, we confirmed that the electrode was sufficiently insulated such that the measured constant impedance was given by the exposed CNT tip. Consequently, we can use the CNT electrode for highly localized electrochemical impedance measurements below 1 kHz. Considering an equivalent circuit and the nanoscopic dimensions of the CNT electrode, we demonstrated that the constant impedance was governed by diffusion impedance, whereas the solution resistance, charge-transfer resistance and double-layer capacitance were negligible.

  19. A two electrode apparatus for electrical impedance measurements

    NASA Astrophysics Data System (ADS)

    Merriam, J. B.

    2009-12-01

    A two electrode cell for complex impedance measurements on core samples in the range 1 mHz - 0.3 kHz is described. Two electrode cells are more convenient than four electrode cells but some restrictions need to be observed. I will show that the contact impedance between the electrodes and the sample can be controlled and reduced to less than fifty ohms in most cases. The contact impedance is repeatable, with a peak phase near 10 Hz of less than one degree and a maximum change in impedance magnitude of less than fifty ohm. A model for the contact impedance is used to correct impedance measurements, leaving an un-modeled contact impedance of a few ohms. There is typically a drift of about 100 ohm during a measurement sequence due to diffusion between the ceramic frits at the ends of the sample. This is corrected by repeat measurements at 100 Hz. Un-modeled impedance changes due to drift are about ten ohm. The un-modeled impedance changes mean that the relative error on conductive samples is greater than on resistive samples. Repeat measurements on a sandstone sample with conductive pore water (0.14 S/m) yield a mean of 492 ohms with a standard deviation of 20 ohm, or about five percent. Measurements on mineralized core and on cells constructed from mixtures of silica sand and polarizable minerals demonstrate that the two electrode set up can be used even on heavily mineralized samples.

  20. Cry1Ac and Vip3Aa proteins from Bacillus thuringiensis targeting Cry toxin resistance in Diatraea flavipennella and Elasmopalpus lignosellus from sugarcane

    PubMed Central

    2017-01-01

    The biological potential of Vip and Cry proteins from Bacillus is well known and widely established. Thus, it is important to look for new genes showing different modes of action, selecting those with differentiated entomotoxic activity against Diatraea flavipennella and Elasmopalpus lignosellus, which are secondary pests of sugarcane. Therefore, Cry1 and Vip3 proteins were expressed in Escherichia coli, and their toxicities were evaluated based on bioassays using neonate larvae. Of those, the most toxic were Cry1Ac and Vip3Aa considering the LC50 values. Toxins from E. coli were purified, solubilized, trypsinized, and biotinylated. Brush Border Membrane Vesicles (BBMVs) were prepared from intestines of the two species to perform homologous and heterologous competition assays. The binding assays demonstrated interactions between Cry1Aa, Cry1Ac, and Vip3Aa toxins and proteins from the BBMV of D. flavipennella and E. lignosellus. Homologous competition assays demonstrated that binding to one of the BBMV proteins was specific for each toxin. Heterologous competition assays indicated that Vip3Aa was unable to compete for Cry1Ac toxin binding. Our results suggest that Cry1Ac and Vip3Aa may have potential in future production of transgenic sugarcane for control of D. flavipennella and E. lignosellus, but more research is needed on the potential antagonism or synergism of the toxins in these pests. PMID:28123906

  1. Cry1Ac and Vip3Aa proteins from Bacillus thuringiensis targeting Cry toxin resistance in Diatraea flavipennella and Elasmopalpus lignosellus from sugarcane.

    PubMed

    Lemes, Ana Rita Nunes; Figueiredo, Camila Soares; Sebastião, Isis; Marques da Silva, Liliane; da Costa Alves, Rebeka; de Siqueira, Herbert Álvaro Abreu; Lemos, Manoel Victor Franco; Fernandes, Odair Aparecido; Desidério, Janete Apparecida

    2017-01-01

    The biological potential of Vip and Cry proteins from Bacillus is well known and widely established. Thus, it is important to look for new genes showing different modes of action, selecting those with differentiated entomotoxic activity against Diatraea flavipennella and Elasmopalpus lignosellus, which are secondary pests of sugarcane. Therefore, Cry1 and Vip3 proteins were expressed in Escherichia coli, and their toxicities were evaluated based on bioassays using neonate larvae. Of those, the most toxic were Cry1Ac and Vip3Aa considering the LC50 values. Toxins from E. coli were purified, solubilized, trypsinized, and biotinylated. Brush Border Membrane Vesicles (BBMVs) were prepared from intestines of the two species to perform homologous and heterologous competition assays. The binding assays demonstrated interactions between Cry1Aa, Cry1Ac, and Vip3Aa toxins and proteins from the BBMV of D. flavipennella and E. lignosellus. Homologous competition assays demonstrated that binding to one of the BBMV proteins was specific for each toxin. Heterologous competition assays indicated that Vip3Aa was unable to compete for Cry1Ac toxin binding. Our results suggest that Cry1Ac and Vip3Aa may have potential in future production of transgenic sugarcane for control of D. flavipennella and E. lignosellus, but more research is needed on the potential antagonism or synergism of the toxins in these pests.

  2. The Influence of Segmental Impedance Analysis in Predicting Validity of Consumer Grade Bioelectrical Impedance Analysis Devices

    NASA Astrophysics Data System (ADS)

    Sharp, Andy; Heath, Jennifer; Peterson, Janet

    2008-05-01

    Consumer grade bioelectric impedance analysis (BIA) instruments measure the body's impedance at 50 kHz, and yield a quick estimate of percent body fat. The frequency dependence of the impedance gives more information about the current pathway and the response of different tissues. This study explores the impedance response of human tissue at a range of frequencies from 0.2 - 102 kHz using a four probe method and probe locations standard for segmental BIA research of the arm. The data at 50 kHz, for a 21 year old healthy Caucasian male (resistance of 180φ±10 and reactance of 33φ±2) is in agreement with previously reported values [1]. The frequency dependence is not consistent with simple circuit models commonly used in evaluating BIA data, and repeatability of measurements is problematic. This research will contribute to a better understanding of the inherent difficulties in estimating body fat using consumer grade BIA devices. [1] Chumlea, William C., Richard N. Baumgartner, and Alex F. Roche. ``Specific resistivity used to estimate fat-free mass from segmental body measures of bioelectrical impedance.'' Am J Clin Nutr 48 (1998): 7-15.

  3. Impedance calculation for ferrite inserts

    SciTech Connect

    Breitzmann, S.C.; Lee, S.Y.; Ng, K.Y.; /Fermilab

    2005-01-01

    Passive ferrite inserts were used to compensate the space charge impedance in high intensity space charge dominated accelerators. They study the narrowband longitudinal impedance of these ferrite inserts. they find that the shunt impedance and the quality factor for ferrite inserts are inversely proportional to the imaginary part of the permeability of ferrite materials. They also provide a recipe for attaining a truly passive space charge impedance compensation and avoiding narrowband microwave instabilities.

  4. Superconducting surface impedance under radiofrequency field

    DOE PAGES

    Xiao, Binping P.; Reece, Charles E.; Kelley, Michael J.

    2013-04-26

    Based on BCS theory with moving Cooper pairs, the electron states distribution at 0K and the probability of electron occupation with finite temperature have been derived and applied to anomalous skin effect theory to obtain the surface impedance of a superconductor under radiofrequency (RF) field. We present the numerical results for Nb and compare these with representative RF field-dependent effective surface resistance measurements from a 1.5 GHz resonant structure.

  5. Impedance Measurement Box

    ScienceCinema

    Christophersen, Jon

    2016-07-12

    Energy storage devices, primarily batteries, are now more important to consumers, industries and the military. With increasing technical complexity and higher user expectations, there is also a demand for highly accurate state-of-health battery assessment techniques. IMB incorporates patented, proprietary, and tested capabilities using control software and hardware that can be part of an embedded monitoring system. IMB directly measures the wideband impedance spectrum in seconds during battery operation with no significant impact on service life. It also can be applied to batteries prior to installation, confirming health before entering active service, as well as during regular maintenance. For more information about this project, visit http://www.inl.gov/rd100/2011/impedance-measurement-box/

  6. Impedance Measurement Box

    SciTech Connect

    Morrison, William

    2014-11-20

    The IMB 50V software provides functionality for design of impedance measurement tests or sequences of tests, execution of these tests or sequences, processing measured responses and displaying and saving of the results. The software consists of a Graphical User Interface that allows configuration of measurement parameters and test sequencing, a core engine that controls test sequencing, execution of measurements, processing and storage of results and a hardware/software data acquisition interface with the IMB hardware system.

  7. High input impedance amplifier

    NASA Technical Reports Server (NTRS)

    Kleinberg, Leonard L.

    1995-01-01

    High input impedance amplifiers are provided which reduce the input impedance solely to a capacitive reactance, or, in a somewhat more complex design, provide an extremely high essentially infinite, capacitive reactance. In one embodiment, where the input impedance is reduced in essence, to solely a capacitive reactance, an operational amplifier in a follower configuration is driven at its non-inverting input and a resistor with a predetermined magnitude is connected between the inverting and non-inverting inputs. A second embodiment eliminates the capacitance from the input by adding a second stage to the first embodiment. The second stage is a second operational amplifier in a non-inverting gain-stage configuration where the output of the first follower stage drives the non-inverting input of the second stage and the output of the second stage is fed back to the non-inverting input of the first stage through a capacitor of a predetermined magnitude. These amplifiers, while generally useful, are very useful as sensor buffer amplifiers that may eliminate significant sources of error.

  8. Gynecologic electrical impedance tomograph

    NASA Astrophysics Data System (ADS)

    Korjenevsky, A.; Cherepenin, V.; Trokhanova, O.; Tuykin, T.

    2010-04-01

    Electrical impedance tomography extends to the new and new areas of the medical diagnostics: lungs, breast, prostate, etc. The feedback from the doctors who use our breast EIT diagnostic system has induced us to develop the 3D electrical impedance imaging device for diagnostics of the cervix of the uterus - gynecologic impedance tomograph (GIT). The device uses the same measuring approach as the breast imaging system: 2D flat array of the electrodes arranged on the probe with handle is placed against the body. Each of the 32 electrodes of the array is connected in turn to the current source while the rest electrodes acquire the potentials on the surface. The current flows through the electrode of the array and returns through the remote electrode placed on the patient's limb. The voltages are measured relative to another remote electrode. The 3D backprojection along equipotential surfaces is used to reconstruct conductivity distribution up to approximately 1 cm in depth. Small number of electrodes enables us to implement real time imaging with a few frames per sec. rate. The device is under initial testing and evaluation of the imaging capabilities and suitability of usage.

  9. Modification of Relaxor and Impedance Spectroscopy Properties of Lead Magnesium Niobate by Bismuth Ferrite

    NASA Astrophysics Data System (ADS)

    Das, S. N.; Pradhan, S.; Bhuyan, S.; Choudhary, R. N. P.; Das, P.

    2017-03-01

    The relaxor and impedance characteristics of classic or traditional lead magnesium niobate (PbMg1/3Nb2/3O3; PMN) ferroelectric relaxor material have been modified by chemically synthesizing with multiferroic bismuth ferrite (BiFeO3; BFO). Detailed studies of structural, morphological and electrical properties of PMN-BFO-prepared solid solutions [((Pb1- x Bi x ) (Mg0.33(1- x)Nb0.66(1- x)Fe x ) O3) with x = 0.1, 0.2, 0.3 and 0.4] reveal some interesting findings on structure-properties relationships. The formation of single phase material of each compound in orthorhombic crystal system is identified from x-ray diffraction. The microstructure analyses reveal that the grain size of PMN-BFO increases for increasing BFO weight percent with PMN. The increase of BFO concentration not only improves the dielectric response of PMN-BFO but also modifies the nature of attained phase transition from a typical relaxor to a normal ferroelectric. The impedance spectroscopy studies exhibit the presence of grain and grain boundary effects, and the existence of a positive temperature coefficient of resistance (PTCR) in the material. The ac conductivity increases with the increase in frequency in the low-temperature region for larger content of BFO in the solid solutions. It is observed that the prepared electronic materials obey the non-Debye-type of conductivity relaxation behavior.

  10. Electrical-Impedance Tomography for Measuring Material Distributions of Multiphase Flows in Conducting Vessels

    NASA Astrophysics Data System (ADS)

    Liter, S. G.; Torczynski, J. R.; Shollenberger, K. A.; Ceccio, S. L.

    2001-11-01

    An implementation of resistive electrical-impedance tomography (EIT) for measuring material distributions of two-phase flows in vessels with electrically conducting walls is presented. A thin nonconducting rod, with N-1 ring electrodes wrapped around its exterior at equally-spaced axial positions, is inserted into the vessel (i.e., into the interior of the flow). The vessel wall is grounded and serves as the N-th electrode. Current is injected from a ring electrode and exits to the vessel wall, and the resulting voltages at all ring electrodes are recorded. Each ring electrode is used in turn for current injection, and the collection of all measured voltages comprises a data set. Multiple data sets are used to numerically reconstruct the time-averaged impedance distribution within the vessel, from which the material distribution is inferred. Design issues, including the size, spacing, and number of the ring electrodes, are considered. An experiment in which the rod is inserted coaxially into a vertical pipe is presented, and bubble-column applications are discussed. *Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy under Contract DE-AC04-94AL85000.

  11. Impedance spectroscopy on ceramic materials at high temperatures, considering stray fields and electromagnetic noise.

    PubMed

    Müller, T M; Meinhardt, J; Raether, F

    2013-01-01

    Impedance spectroscopy of many ceramics is a challenge due to their high electrical resistance. Small disturbances can significantly alter the measuring results. In the present paper, it is shown how impedance measurements can be performed in an electromagnetically noisy ac furnace, using consequent Faraday shielding of the sample and the electrical connections. As example, the conductivity data of alumina was measured between room temperature and 1000 °C and compared to literature data. In addition, a correction method for the calculation of permittivity was developed to consider the stray fields in the sample-electrode setup. The distribution of the electrical field was simulated by finite element (FE) methods for different sample geometries and electrode arrangements. The deviations from the behavior of an ideal plate capacitor follow a linear trend and are in the order of 5% to 20% for an experimentally reasonable range of sample thicknesses. To check the theoretical results experimentally, alumina samples of varying thickness were measured. The customary calculation of permittivity leads to a clear trend with sample thickness, whereas the correction from the FE-simulation produces almost constant values of the relative permittivity.

  12. Development on electromagnetic impedance function modeling and its estimation

    SciTech Connect

    Sutarno, D.

    2015-09-30

    Today the Electromagnetic methods such as magnetotellurics (MT) and controlled sources audio MT (CSAMT) is used in a broad variety of applications. Its usefulness in poor seismic areas and its negligible environmental impact are integral parts of effective exploration at minimum cost. As exploration was forced into more difficult areas, the importance of MT and CSAMT, in conjunction with other techniques, has tended to grow continuously. However, there are obviously important and difficult problems remaining to be solved concerning our ability to collect process and interpret MT as well as CSAMT in complex 3D structural environments. This talk aim at reviewing and discussing the recent development on MT as well as CSAMT impedance functions modeling, and also some improvements on estimation procedures for the corresponding impedance functions. In MT impedance modeling, research efforts focus on developing numerical method for computing the impedance functions of three dimensionally (3-D) earth resistivity models. On that reason, 3-D finite elements numerical modeling for the impedances is developed based on edge element method. Whereas, in the CSAMT case, the efforts were focused to accomplish the non-plane wave problem in the corresponding impedance functions. Concerning estimation of MT and CSAMT impedance functions, researches were focused on improving quality of the estimates. On that objective, non-linear regression approach based on the robust M-estimators and the Hilbert transform operating on the causal transfer functions, were used to dealing with outliers (abnormal data) which are frequently superimposed on a normal ambient MT as well as CSAMT noise fields. As validated, the proposed MT impedance modeling method gives acceptable results for standard three dimensional resistivity models. Whilst, the full solution based modeling that accommodate the non-plane wave effect for CSAMT impedances is applied for all measurement zones, including near-, transition

  13. Modifying the acoustic impedance of polyurea-based composites

    NASA Astrophysics Data System (ADS)

    Nantasetphong, Wiroj; Amirkhizi, Alireza V.; Jia, Zhanzhan; Nemat-Nasser, Sia

    2013-04-01

    Acoustic impedance is a material property that depends on mass density and acoustic wave speed. An impedance mismatch between two media leads to the partial reflection of an acoustic wave sent from one medium to another. Active sonar is one example of a useful application of this phenomenon, where reflected and scattered acoustic waves enable the detection of objects. If the impedance of an object is matched to that of the surrounding medium, however, the object may be hidden from observation (at least directly) by sonar. In this study, polyurea composites are developed to facilitate such impedance matching. Polyurea is used due to its excellent blast-mitigating properties, easy casting, corrosion protection, abrasion resistance, and various uses in current military technology. Since pure polyurea has impedance higher than that of water (the current medium of interest), low mass density phenolic microballoon particles are added to create composite materials with reduced effective impedances. The volume fraction of particles is varied to study the effect of filler quantity on the acoustic impedance of the resulting composite. The composites are experimentally characterized via ultrasonic measurements. Computational models based on the method of dilute-randomly-distributed inclusions are developed and compared with the experimental results. These experiments and models will facilitate the design of new elastomeric composites with desirable acoustic impedances.

  14. Effect of randomly varying impedance on the interference of the direct and ground-reflected waves.

    PubMed

    Ostashev, Vladimir E; Wilson, D Keith; Vecherin, Sergey N

    2011-10-01

    A randomly varying ground impedance is introduced into the solution for the sound field produced by a point source in a homogeneous atmosphere above a flat ground. The results show that in general the ground with a random impedance cannot be represented by an effective, non-random impedance. The behavior of the solution is studied with a relaxation model for the impedance in which porosity and the static flow resistivity are random variables. Mean values and standard deviations are adopted from measurements of two types of ground surfaces. For both surfaces, the mean intensity of the sound field above a random-impedance ground deviates only slightly from the intensity above a non-random impedance. The normalized standard deviation of intensity fluctuations can, however, be greater than one, thus indicating that for a particular realization of the random impedance, the sound intensity might significantly deviate from the intensity for a non-random impedance.

  15. Positive impedance humidity sensors via single-component materials

    PubMed Central

    Qian, Jingwen; Peng, Zhijian; Shen, Zhenguang; Zhao, Zengying; Zhang, Guoliang; Fu, Xiuli

    2016-01-01

    Resistivity-type humidity sensors have been investigated with great interest due to the increasing demands in industry, agriculture and daily life. To date, most of the available humidity sensors have been fabricated based on negative humidity impedance, in which the electrical resistance decreases as the humidity increases, and only several carbon composites have been reported to present positive humidity impedance. However, here we fabricate positive impedance humidity sensors only via single-component WO3−x crystals. The resistance of WO3−x crystal sensors in response to relative humidity could be tuned from a negative to positive one by increasing the compositional x. And it was revealed that the positive humidity impedance was driven by the defects of oxygen vacancy. This result will extend the application field of humidity sensors, because the positive humidity impedance sensors would be more energy-efficient, easier to be miniaturized and electrically safer than their negative counterparts for their lower operation voltages. And we believe that constructing vacancies in semiconducting materials is a universal way to fabricate positive impedance humidity sensors. PMID:27150936

  16. Influences of internal resistance and specific surface area of electrode materials on characteristics of electric double layer capacitors

    NASA Astrophysics Data System (ADS)

    Suda, Yoshiyuki; Mizutani, Akitaka; Harigai, Toru; Takikawa, Hirofumi; Ue, Hitoshi; Umeda, Yoshito

    2017-01-01

    We fabricated electric double layer capacitors (EDLCs) using particulate and fibrous types of carbon nanomaterials with a wide range of specific surface areas and resistivity as an active material. The carbon nanomaterials used in this study are carbon nanoballoons (CNBs), onion-like carbon (OLC), and carbon nanocoils (CNCs). A commercially used activated carbon (AC) combined with a conductive agent was used as a comparison. We compared the EDLC performance using cyclic voltammetry (CV), galvanostatic charge/discharge testing, and electrochemical impedance spectroscopy (EIS). OLC showed a poor EDLC performance, although it has the lowest resistivity among the carbon nanomaterials. CNB, which has a 1/16 lower specific surface area than AC but higher specific surface area than CNC and OLC, had a higher specific capacitance than CNC and OLC. Moreover, at current densities of 1.5 Ag-1 and larger, the specific capacitance of the EDLC using CNB was almost the same as that using AC. Electrochemical impedance spectroscopy of the EDLCs revealed that the CNB and CNC electrodes had a much lower internal resistance than the AC electrode, which correlated with a low capacitance maintenance factor as the current density increased.

  17. Dissection of the Mechanical Impedance Components of the Outer Hair Cell Using a Chloride-Channel Blocker

    NASA Astrophysics Data System (ADS)

    Harasztosi, Csaba; Gummer, Anthony W.

    2011-11-01

    The voltage-dependent chloride-channel blocker anthracene-9-carboxylic acid (9AC) has been found to reduce the imaginary but not the real part of the mechanical impedance of the organ of Corti, suggesting that the effective stiffness of outer hair cells (OHCs) is reduced by 9AC. To examine whether 9AC interacts directly with the motor protein prestin to reduce the membrane component of the impedance, the patch-clamp technique in whole-cell configuration was used to measure the nonlinear capacitance (NLC) of isolated OHCs and, as control, prestin-transfected human embryonic kidney 293 (HEK293) cells. Extracellular application of 9AC significantly reduced the NLC of both OHCs and HEK293 cells. Intracellular 9AC did not influence the blocking effect of the extracellular applied drug. These results suggest that 9AC interacts directly with prestin, reducing the effective stiffness of the motor, and that the interaction is extracellular.

  18. Development of a Triple Gene Cry1Ac-Cry2Ab-EPSPS Construct and Its Expression in Nicotiana benthamiana for Insect Resistance and Herbicide Tolerance in Plants.

    PubMed

    Naqvi, Rubab Z; Asif, Muhammad; Saeed, Muhammad; Asad, Shaheen; Khatoon, Asia; Amin, Imran; Mukhtar, Zahid; Bashir, Aftab; Mansoor, Shahid

    2017-01-01

    Insect pest complex, cotton leaf curl disease and weeds pose major threat to crop production worldwide, including Pakistan. To address these problems, in the present study a triple gene construct harboring Cry1Ac, Cry2Ab, and EPSPS cassettes has been developed for plant specifically in cotton transformation against lepidopteron insect-pests and weeds. Nicotiana benthamiana (tobacco) was used as a model system for characterization of this triple gene construct. The construct has been assembled in plant expression vector and transformed in N. benthamiana. In six transgenic tobacco lines the integration of Cry1Ac-Cry2Ab-EPSPS in tobacco genome was checked by PCR, while successful protein expression of all the three genes was confirmed through immunostrip assay. Efficacy of Cry1Ac and Cry2Ab was evaluated through insect bioassay using armyworm (Spodoptera littoralis). These transgenic tobacco plants showed significant insect mortality as compared to control plants during insect bioassay. Three out of six tested transgenic lines L3, L5, and L9 exhibited 100% mortality of armyworm, while three other lines L1, L10, and L7 showed 86, 80, and 40% mortality, respectively. This construct can readily be used with confidence to transform cotton and other crops for the development of insect resistant and herbicide tolerant transgenic plants. The transgenic crop plants developed using this triple gene construct will provide an excellent germplasm resource for the breeders to improve their efficiency in developing stable homozygous lines as all the three genes being in a single T-DNA border will inherit together.

  19. Development of a Triple Gene Cry1Ac-Cry2Ab-EPSPS Construct and Its Expression in Nicotiana benthamiana for Insect Resistance and Herbicide Tolerance in Plants

    PubMed Central

    Naqvi, Rubab Z.; Asif, Muhammad; Saeed, Muhammad; Asad, Shaheen; Khatoon, Asia; Amin, Imran; Mukhtar, Zahid; Bashir, Aftab; Mansoor, Shahid

    2017-01-01

    Insect pest complex, cotton leaf curl disease and weeds pose major threat to crop production worldwide, including Pakistan. To address these problems, in the present study a triple gene construct harboring Cry1Ac, Cry2Ab, and EPSPS cassettes has been developed for plant specifically in cotton transformation against lepidopteron insect-pests and weeds. Nicotiana benthamiana (tobacco) was used as a model system for characterization of this triple gene construct. The construct has been assembled in plant expression vector and transformed in N. benthamiana. In six transgenic tobacco lines the integration of Cry1Ac-Cry2Ab-EPSPS in tobacco genome was checked by PCR, while successful protein expression of all the three genes was confirmed through immunostrip assay. Efficacy of Cry1Ac and Cry2Ab was evaluated through insect bioassay using armyworm (Spodoptera littoralis). These transgenic tobacco plants showed significant insect mortality as compared to control plants during insect bioassay. Three out of six tested transgenic lines L3, L5, and L9 exhibited 100% mortality of armyworm, while three other lines L1, L10, and L7 showed 86, 80, and 40% mortality, respectively. This construct can readily be used with confidence to transform cotton and other crops for the development of insect resistant and herbicide tolerant transgenic plants. The transgenic crop plants developed using this triple gene construct will provide an excellent germplasm resource for the breeders to improve their efficiency in developing stable homozygous lines as all the three genes being in a single T-DNA border will inherit together. PMID:28174591

  20. Aortic Input Impedance during Nitroprusside Infusion

    PubMed Central

    Pepine, Carl J.; Nichols, W. W.; Curry, R. C.; Conti, C. Richard

    1979-01-01

    Beneficial effects of nitroprusside infusion in heart failure are purportedly a result of decreased afterload through “impedance” reduction. To study the effect of nitroprusside on vascular factors that determine the total load opposing left ventricular ejection, the total aortic input impedance spectrum was examined in 12 patients with heart failure (cardiac index <2.0 liters/min per m2 and left ventricular end diastolic pressure >20 mm Hg). This input impedance spectrum expresses both mean flow (resistance) and pulsatile flow (compliance and wave reflections) components of vascular load. Aortic root blood flow velocity and pressure were recorded continuously with a catheter-tip electromagnetic velocity probe in addition to left ventricular pressure. Small doses of nitroprusside (9-19 μg/min) altered the total aortic input impedance spectrum as significant (P < 0.05) reductions in both mean and pulsatile components were observed within 60-90 s. With these acute changes in vascular load, left ventricular end diastolic pressure declined (44%) and stroke volume increased (20%, both P < 0.05). Larger nitroprusside doses (20-38 μg/min) caused additional alteration in the aortic input impedance spectrum with further reduction in left ventricular end diastolic pressure and increase in stroke volume but no additional changes in the impedance spectrum or stroke volume occurred with 39-77 μg/min. Improved ventricular function persisted when aortic pressure was restored to control values with simultaneous phenylephrine infusion in three patients. These data indicate that nitroprusside acutely alters both the mean and pulsatile components of vascular load to effect improvement in ventricular function in patients with heart failure. The evidence presented suggests that it may be possible to reduce vascular load and improve ventricular function independent of aortic pressure reduction. PMID:457874

  1. Scheme for rapid adjustment of network impedance

    DOEpatents

    Vithayathil, John J.

    1991-01-01

    A static controlled reactance device is inserted in series with an AC electric power transmission line to adjust its transfer impedance. An inductor (reactor) is serially connected with two back-to-back connected thyristors which control the conduction period and hence the effective reactance of the inductor. Additional reactive elements are provided in parallel with the thyristor controlled reactor to filter harmonics and to obtain required range of variable reactance. Alternatively, the static controlled reactance device discussed above may be connected to the secondary winding of a series transformer having its primary winding connected in series to the transmission line. In a three phase transmission system, the controlled reactance device may be connected in delta configuration on the secondary side of the series transformer to eliminate triplen harmonics.

  2. Ionospheric effects to antenna impedance

    NASA Technical Reports Server (NTRS)

    Bethke, K. H.

    1986-01-01

    The reciprocity between high power satellite antennas and the surrounding plasma are examined. The relevant plasma states for antenna impedance calculations are presented and plasma models, and hydrodynamic and kinetic theory, are discussed. A theory from which a variation in antenna impedance with regard to the radiated power can be calculated for a frequency range well above the plasma resonance frequency is give. The theory can include photo and secondary emission effects in antenna impedance calculations.

  3. Using FOCUS to determine the radiation impedance for square transducers

    NASA Astrophysics Data System (ADS)

    Jennings, Matthew R.; McGough, Robert J.

    2012-10-01

    The power radiated by an ultrasound transducer is calculated with the radiation resistance, which is the real part of the radiation impedance. For circular transducers, an analytical solution for the radiation impedance is known, but an analytical expression for the radiation impedance is not available for rectangular or square transducers. To determine the radiation resistance in FOCUS, the pressure on the surface of a square transducer is computed with the fast nearfield method, and then the force on the transducer face is computed by integrating the pressure. Results using this approach are numerically evaluated for a range of ka values from 0.1 to 16. The pressure on the transducer face is also computed with the Rayleigh-Sommerfeld integral, and the results are compared. The numerical value of the radiation resistance computed with FOCUS and with the Rayleigh-Sommerfeld integral converge to the same value, although FOCUS calculates the same result in about one-quarter of the time.

  4. Optically stimulated differential impedance spectroscopy

    SciTech Connect

    Maxey, Lonnie C; Parks, II, James E; Lewis, Sr., Samuel A; Partridge, Jr., William P

    2014-02-18

    Methods and apparatuses for evaluating a material are described. Embodiments typically involve use of an impedance measurement sensor to measure the impedance of a sample of the material under at least two different states of illumination. The states of illumination may include (a) substantially no optical stimulation, (b) substantial optical stimulation, (c) optical stimulation at a first wavelength of light, (d) optical stimulation at a second wavelength of light, (e) a first level of light intensity, and (f) a second level of light intensity. Typically a difference in impedance between the impedance of the sample at the two states of illumination is measured to determine a characteristic of the material.

  5. Application of plant impedance for diagnosing plant disease

    NASA Astrophysics Data System (ADS)

    Xu, Huirong; Jiang, Xuesong; Zhu, Shengpan; Ying, Yibin

    2006-10-01

    Biological cells have components acting as electrical elements that maintain the health of the cell by regulation of the electrical charge content. Plant impedance is decided by the state of plant physiology and pathology. Plant physiology and pathology can be studies by measuring plant impedance. The effect of Cucumber Mosaic Virus red bean isolate (CMV-RB) on electrical resistance of tomato leaves was studied by the method of impedance measurement. It was found that the value of resistance of tomato leaves infected with CMV-RB was smaller than that in sound plant leaves. This decrease of impedances in leaf tissue was occurred with increased severity of disease. The decrease of resistance of tomato leaves infected with CMV-RB could be detected by electrical resistance detecting within 4 days after inoculation even though significant visible differences between the control and the infected plants were not noted, so that the technique for measurement of tomato leaf tissue impedance is a rapid, clever, simple method on diagnosis of plant disease.

  6. Comparison of Several Methods for Determining the Internal Resistance of Lithium Ion Cells

    PubMed Central

    Schweiger, Hans-Georg; Obeidi, Ossama; Komesker, Oliver; Raschke, André; Schiemann, Michael; Zehner, Christian; Gehnen, Markus; Keller, Michael; Birke, Peter

    2010-01-01

    The internal resistance is the key parameter for determining power, energy efficiency and lost heat of a lithium ion cell. Precise knowledge of this value is vital for designing battery systems for automotive applications. Internal resistance of a cell was determined by current step methods, AC (alternating current) methods, electrochemical impedance spectroscopy and thermal loss methods. The outcomes of these measurements have been compared with each other. If charge or discharge of the cell is limited, current step methods provide the same results as energy loss methods. PMID:22219678

  7. AC conductivity and relaxation mechanism in (Nd1/2Li1/2)(Fe1/2V1/2)O3 ceramics

    NASA Astrophysics Data System (ADS)

    Nath, Susmita; Barik, Subrat Kumar; Choudhary, R. N. P.

    2016-05-01

    In the present study we have synthesized polycrystalline sample of (Nd1/2Li1/2)(Fe1/2V1/2)O3 ceramic by a standard high-temperature solid-state reaction technique. Studies of dielectric and electrical properties of the compound have been carried out in a wide range of temperature (RT - 400 °C) and frequency (1kHz - 1MHz) using complex impedance spectroscopic technique. The imaginary vs. real component of the complex impedance plot (Nyquist plot) of the prepared sample exhibits the existence of grain, grain boundary contributions in the complex electrical parameters and negative temperature coefficient of resistance (NTCR) type behavior like semiconductor. Details study of ac conductivity plot reveals that the material obeys universal Jonscher's power law.

  8. The Influence of Uncompensated Solution Resistance on the Determination and Standard Electrochemical Rate Constants Using Cyclic Voltammetry, and Some Comparisons with AC Voltammetry.

    DTIC Science & Technology

    1987-09-25

    constants, k2ob, using cyclic voltammetry . The results are expressed in terms of systematic deviations of ’apparent measured’ rate constants, k2ob...Keywords: Digital simulation analysis, Uncompensated solution resistance, Electrochemical rate constants, Cyclic voltammetry .

  9. Temperature dependent dielectric and conductivity studies of polyvinyl alcohol-ZnO nanocomposite films by impedance spectroscopy

    NASA Astrophysics Data System (ADS)

    Hemalatha, K. S.; Sriprakash, G.; Ambika Prasad, M. V. N.; Damle, R.; Rukmani, K.

    2015-10-01

    Dielectric and conductivity behaviors of nano ZnO doped polyvinyl alcohol (PVA) composites for various concentrations of dopant were investigated using impedance spectroscopy for a wide range of temperatures (303 K-423 K) and frequencies (5 Hz-30 MHZ). The dielectric properties of host polymer matrix have been improved by the addition of nano ZnO and are found to be highly temperature dependent. Anomalous dielectric behavior was observed in the frequency range of 2.5 MHz-5 MHz. Increase in dielectric permittivity and dielectric loss was observed with respect to temperature. The Cole-Cole plot could be modeled by low resistance regions in a high resistance matrix and the lowest resistance was observed for the 10 mol. % films. The imaginary part of the electric modulus showed asymmetric peaks with the relaxation following Debye nature below and non-Debye nature above the peaks. The ac conductivity is found to obey Jonscher's power law, whereas the variation of dc conductivity with temperature was found to follow Arrhenius behavior. Two different activation energy values were obtained from Arrhenius plot indicating that two conduction mechanisms are involved in the composite films. Fitting the ac conductivity data to Jonscher's law indicates that large polaron assisted tunneling is the most likely conduction mechanism in the composites. Maximum conductivity is observed at 423 K for all the samples and it is optimum for 10 mol. % ZnO doped PVA composite film. Significant increase in dc and ac conductivities in these composite films makes them a potential candidate for application in electronic devices.

  10. Temperature dependent dielectric and conductivity studies of polyvinyl alcohol-ZnO nanocomposite films by impedance spectroscopy

    SciTech Connect

    Hemalatha, K. S.; Damle, R.; Rukmani, K.; Sriprakash, G.; Ambika Prasad, M. V. N.

    2015-10-21

    Dielectric and conductivity behaviors of nano ZnO doped polyvinyl alcohol (PVA) composites for various concentrations of dopant were investigated using impedance spectroscopy for a wide range of temperatures (303 K–423 K) and frequencies (5 Hz–30 MHZ). The dielectric properties of host polymer matrix have been improved by the addition of nano ZnO and are found to be highly temperature dependent. Anomalous dielectric behavior was observed in the frequency range of 2.5 MHz–5 MHz. Increase in dielectric permittivity and dielectric loss was observed with respect to temperature. The Cole-Cole plot could be modeled by low resistance regions in a high resistance matrix and the lowest resistance was observed for the 10 mol. % films. The imaginary part of the electric modulus showed asymmetric peaks with the relaxation following Debye nature below and non-Debye nature above the peaks. The ac conductivity is found to obey Jonscher's power law, whereas the variation of dc conductivity with temperature was found to follow Arrhenius behavior. Two different activation energy values were obtained from Arrhenius plot indicating that two conduction mechanisms are involved in the composite films. Fitting the ac conductivity data to Jonscher's law indicates that large polaron assisted tunneling is the most likely conduction mechanism in the composites. Maximum conductivity is observed at 423 K for all the samples and it is optimum for 10 mol. % ZnO doped PVA composite film. Significant increase in dc and ac conductivities in these composite films makes them a potential candidate for application in electronic devices.

  11. Monolithically compatible impedance measurement

    DOEpatents

    Ericson, Milton Nance; Holcomb, David Eugene

    2002-01-01

    A monolithic sensor includes a reference channel and at least one sensing channel. Each sensing channel has an oscillator and a counter driven by the oscillator. The reference channel and the at least one sensing channel being formed integrally with a substrate and intimately nested with one another on the substrate. Thus, the oscillator and the counter have matched component values and temperature coefficients. A frequency determining component of the sensing oscillator is formed integrally with the substrate and has an impedance parameter which varies with an environmental parameter to be measured by the sensor. A gating control is responsive to an output signal generated by the reference channel, for terminating counting in the at least one sensing channel at an output count, whereby the output count is indicative of the environmental parameter, and successive ones of the output counts are indicative of changes in the environmental parameter.

  12. Correcting electrode impedance effects in broadband SIP measurements

    NASA Astrophysics Data System (ADS)

    Huisman, Johan Alexander; Zimmermann, Egon; Esser, Odilia; Haegel, Franz-Hubert; Vereecken, Harry

    2016-04-01

    Broadband spectral induced polarization (SIP) measurements of the complex electrical resistivity can be affected by the contact impedance of the potential electrodes above 100 Hz. In this study, we present a correction procedure to remove electrode impedance effects from SIP measurements. The first step in this correction procedure is to estimate the electrode impedance using a measurement with reversed current and potential electrodes. In a second step, this estimated electrode impedance is used to correct SIP measurements based on a simplified electrical model of the SIP measurement system. We evaluated this new correction procedure using SIP measurements on water because of the well-defined dielectric properties. It was found that the difference between the corrected and expected phase of the complex electrical resistivity of water was below 0.1 mrad at 1 kHz for a wide range of electrode impedances. In addition, SIP measurements on a saturated unconsolidated sediment sample with two types of potential electrodes showed that the measured phase of the electrical resistivity was very similar (difference <0.2 mrad) up to a frequency of 10 kHz after the effect of the different electrode impedances was removed. Finally, SIP measurements on variably saturated unconsolidated sand were made. Here, the plausibility of the phase of the electrical resistivity was improved for frequencies up to 1 kHz, but errors remained for higher frequencies due to the approximate nature of the electrode impedance estimates and some remaining unknown parasitic capacitances that led to current leakage. It was concluded that the proposed correction procedure for SIP measurements improved the accuracy of the phase measurements by an order of magnitude in the kHz frequency range. Further improvement of this accuracy requires a method to accurately estimate parasitic capacitances in situ.

  13. Impedance in School Screening Programs.

    ERIC Educational Resources Information Center

    Robarts, John T.

    1985-01-01

    This paper examines the controversy over use of impedance screening in public schools to identify students with hearing problems, including otitis media, a common ear condition in infants and young children. It cites research that questions the value of pure tone screening as a single test and raises critics' objections to the use of impedance,…

  14. Ultra-wideband impedance sensor

    DOEpatents

    McEwan, Thomas E.

    1999-01-01

    The ultra-wideband impedance sensor (UWBZ sensor, or Z-sensor) is implemented in differential and single-ended configurations. The differential UWBZ sensor employs a sub-nanosecond impulse to determine the balance of an impedance bridge. The bridge is configured as a differential sample-and-hold circuit that has a reference impedance side and an unknown impedance side. The unknown impedance side includes a short transmission line whose impedance is a function of the near proximity of objects. The single-ended UWBZ sensor eliminates the reference side of the bridge and is formed of a sample and hold circuit having a transmission line whose impedance is a function of the near proximity of objects. The sensing range of the transmission line is bounded by the two-way travel time of the impulse, thereby eliminating spurious Doppler modes from large distant objects that would occur in a microwave CW impedance bridge. Thus, the UWBZ sensor is a range-gated proximity sensor. The Z-sensor senses the near proximity of various materials such as metal, plastic, wood, petroleum products, and living tissue. It is much like a capacitance sensor, yet it is impervious to moisture. One broad application area is the general replacement of magnetic sensors, particularly where nonferrous materials need to be sensed. Another broad application area is sensing full/empty levels in tanks, vats and silos, e.g., a full/empty switch in water or petroleum tanks.

  15. Ultra-wideband impedance sensor

    DOEpatents

    McEwan, T.E.

    1999-03-16

    The ultra-wideband impedance sensor (UWBZ sensor, or Z-sensor) is implemented in differential and single-ended configurations. The differential UWBZ sensor employs a sub-nanosecond impulse to determine the balance of an impedance bridge. The bridge is configured as a differential sample-and-hold circuit that has a reference impedance side and an unknown impedance side. The unknown impedance side includes a short transmission line whose impedance is a function of the near proximity of objects. The single-ended UWBZ sensor eliminates the reference side of the bridge and is formed of a sample and hold circuit having a transmission line whose impedance is a function of the near proximity of objects. The sensing range of the transmission line is bounded by the two-way travel time of the impulse, thereby eliminating spurious Doppler modes from large distant objects that would occur in a microwave CW impedance bridge. Thus, the UWBZ sensor is a range-gated proximity sensor. The Z-sensor senses the near proximity of various materials such as metal, plastic, wood, petroleum products, and living tissue. It is much like a capacitance sensor, yet it is impervious to moisture. One broad application area is the general replacement of magnetic sensors, particularly where nonferrous materials need to be sensed. Another broad application area is sensing full/empty levels in tanks, vats and silos, e.g., a full/empty switch in water or petroleum tanks. 2 figs.

  16. [Experimental study on electrical impedance properties of human hepatoma cells].

    PubMed

    Fang, Yun; Tang, Zhiyuan; Zhang, Qian; Zhao, Xin; Ma, Qing

    2014-10-01

    The AC impedance of human hepatoma SMMC-7721 cells were measured in our laboratory by Agilent 4294A impedance analyzer in the frequency range of 0.01-100 MHz. And then the effect of hematocrit on electrical impedance characteristics of hepatoma cells was observed by electrical impedance spectroscopy, Bode diagram, Nyquist diagram and Nichols diagram. The results showed that firstly, there is a frequency dependence, i.e., the increment of real part and the imaginary part of complex electrical impedance (δZ', δZ"), the increment of the amplitude modulus of complex electrical impedance (δ[Z *]) and phase angle (δθ) were all changed with the increasing frequency. Secondly, it showed cell volume fraction (CVF) dependence, i. e. , the increment of low-frequency limit (δZ'0, δ[Z*] 0), peak (δZ"(p), δθ(p)), area and radius (Nyquist diagram, Nichols diagram) were all increased along with the electric field frequency. Thirdly, there was the presence of two characteristic frequencies: the first characteristic frequency (f(c1)) and the second characteristic frequency (f(c2)), which were originated respectively in the polarization effects of two interfaces that the cell membrane and extracellular fluid, cell membrane and cytoplasm. A conclusion can be drawn that the electrical impedance spectroscopy is able to be used to observe the electrical characteristics of human hepatoma cells, and therefore this method can be used to investigate the electrophysiological mechanisms of liver cancer cells, and provide research tools and observation parameters, and it also has important theoretical value and potential applications for screening anticancer drugs.

  17. Experimental verification of the feasibility of the cardiovascular impedance simulator.

    PubMed

    Gwak, Kwan-Woong; Paden, Brad E; Antaki, James F; Ahn, Ihn-Seok

    2010-05-01

    Mock circulatory systems (MCS) are often used for the development of cardiovascular devices and for the study of the dynamics of blood flow through the cardiovascular system. However, conventional MCS suffer from the repeatability, flexibility, and precision problems because they are typically built up with passive and linear fluidic elements such as compliance chamber, manual valve, and tube. To solve these limitations, we have developed an impedance simulator, comprised of a feedback-controlled positive displacement pump that is capable of generating analogous dynamic characteristics as the conventional fluidic elements would generate, thereby replacing the conventional passive fluidic elements that often cause problems. The impedance simulator is experimentally proven to reproduce the impedance of the various discrete elements, such as resistance and compliance of the cardiovascular system model, as well as the combined impedances of them.

  18. Electromagnetic scattering by impedance structures

    NASA Technical Reports Server (NTRS)

    Balanis, Constantine A.; Griesser, Timothy

    1987-01-01

    The scattering of electromagnetic waves from impedance structures is investigated, and current work on antenna pattern calculation is presented. A general algorithm for determining radiation patterns from antennas mounted near or on polygonal plates is presented. These plates are assumed to be of a material which satisfies the Leontovich (or surface impedance) boundary condition. Calculated patterns including reflection and diffraction terms are presented for numerious geometries, and refinements are included for antennas mounted directly on impedance surfaces. For the case of a monopole mounted on a surface impedance ground plane, computed patterns are compared with experimental measurements. This work in antenna pattern prediction forms the basis of understanding of the complex scattering mechanisms from impedance surfaces. It provides the foundation for the analysis of backscattering patterns which, in general, are more problematic than calculation of antenna patterns. Further proposed study of related topics, including surface waves, corner diffractions, and multiple diffractions, is outlined.

  19. Frequency-dependent impedance spectroscopy on the 0.925(Bi0.5Na0.40K0.10)TiO3-0.075(Ba0.70Sr0.30)TiO3 ceramic

    NASA Astrophysics Data System (ADS)

    Ullah, Amir; Rahman, Muneeb-ur; Iqbal, Muhammad Javid; Ahn, Chang Won; Kim, Ill Won; Ullah, Aman

    2016-06-01

    The electrical properties of the 0.925(Bi0.5(Na0.40K0.10)TiO3-0.075(Ba0.70Sr0.30)TiO3 (0.925BNKT-0.075BST) ceramic were investigated by using AC impedance spectroscopy over a wide range of frequencies (10 -2 ~ 105 Hz). The X-ray diffraction patterns confirmed the formation of a single-phase compound. A single semicircular arc in the impedance spectrum indicates that the main contribution of the bulk resistance ( R b ) were due to grain effects, with Rb decreasing with increasing temperature. The conductivity of the ceramics increased with increasing temperature, and the activation energy resulting from the DC conductivity was 0.86 eV. The ceramic displayed a typical negative temperature coefficient of resistance (NTCR) behavior, like that of a semiconductor.

  20. Application of impedance spectroscopy to SOFC research

    SciTech Connect

    Hsieh, G.; Mason, T.O.; Pederson, L.R.

    1996-12-31

    With the resurgence of interest in solid oxide fuel cells and other solid state electrochemical devices, techniques originally developed for characterizing aqueous systems are being adapted and applied to solid state systems. One of these techniques, three-electrode impedance spectroscopy, is particularly powerful as it allows characterization of subcomponent and interfacial properties. Obtaining accurate impedance spectra, however, is difficult as reference electrode impedance is usually non-negligible and solid electrolytes typically have much lower conductance than aqueous solutions. Faidi et al and Chechirlian et al have both identified problems associated with low conductivity media. Other sources of error are still being uncovered. Ford et al identified resistive contacts with large time constants as a possibility, while Me et al showed that the small contact capacitance of the reference electrode was at fault. Still others show that instrument limitations play a role. Using the voltage divider concept, a simplified model that demonstrates the interplay of these various factors, predicts the form of possible distortions, and offers means to minimize errors is presented.

  1. How the Inductive Voltage Adder (IVA) output impedance affects impedance dynamics of a Self-Magnetic Pinch (SMP) diode

    NASA Astrophysics Data System (ADS)

    Renk, Timothy; Simpson, Sean; Webb, Timothy; Mazarakis, Michael; Kiefer, Mark

    2016-10-01

    The SMP diode, fielded on the RITS-6 (3.5-8.5 MV) IVA accelerator at Sandia National Laboratories, produces a focused electron beam (<3mm diameter) onto a high Z metal converter for flash x-ray applications. Experiments have been undertaken with two different magnetically insulated transmission line (MITL) center conductors, of 40 and 80 ohms flow impedance. We have operated in-situ heating and discharge-cleaning hardware in the load region, in order to address the tendency of some shots to undergo premature impedance (Z) collapse, defined as a fall in impedance beyond that due to normal movement of electrode plasmas that reduces the effective A-K gap. The goal of heating/cleaning was to reduce the volume of evolving gases near the A-K gap. Despite clear evidence that the cleaning techniques removed the proton portion of beam current, we observed no consistent increase in diode impedance (ZDIODE). This forced an examination of the role that the IVA flow impedance has on ZDIODE. A preliminary conclusion is that ZDIODE should be at least 1.5 times the flow impedance before ZDIODE is a parameter independent of flow impedance. This has implications for SMP as a load for a IVA, since ZDIODE >100 ohms has not been consistently demonstrated. Data analysis is ongoing, and latest results will be reported. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

  2. Military Curricula for Vocational & Technical Education. Basic Electricity and Electronics Individualized Learning System. CANTRAC A-100-0010. Module Twelve: Series AC Resistive-Reactive Circuits. Study Booklet.

    ERIC Educational Resources Information Center

    Chief of Naval Education and Training Support, Pensacola, FL.

    This individualized learning module on series alternating current resistive-reactive circuits is one in a series of modules for a course in basic electricity and electronics. The course is one of a number of military-developed curriculum packages selected for adaptation to vocational instructional and curriculum development in a civilian setting.…

  3. Military Curricula for Vocational & Technical Education. Basic Electricity and Electronics Individualized Learning System. CANTRAC A-100-0010. Module Fourteen: Parallel AC Resistive-Reactive Circuits. Study Booklet.

    ERIC Educational Resources Information Center

    Chief of Naval Education and Training Support, Pensacola, FL.

    This individualized learning module on parallel alternating current resistive-reaction circuits is one in a series of modules for a course in basic electricity and electronics. The course is one of a number of military-developed curriculum packages selected for adaptation to vocational instructional and curriculum development in a civilian…

  4. Acoustic impedance testing for aeroacoustic applications

    NASA Astrophysics Data System (ADS)

    Schultz, Todd

    Accurate acoustic propagation models are required to characterize and subsequently reduce aircraft engine noise. These models ultimately rely on acoustic impedance measurements of candidate materials used in sound-absorbing liners. The standard two-microphone method (TMM) is widely used to estimate acoustic impedance but is limited in frequency range and does not provide uncertainty estimates, which are essential for data quality assessment and model validation. This dissertation presents a systematic framework to estimate uncertainty and extend the frequency range of acoustic impedance testing. Uncertainty estimation for acoustic impedance data using the TMM is made via two methods. The first employs a standard analytical technique based on linear perturbations and provides useful scaling information. The second uses a Monte Carlo technique that permits the propagation of arbitrarily large uncertainties. Both methods are applied to the TMM for simulated data representative of sound-hard and sound-soft acoustic materials. The results indicate that the analytical technique can lead to false conclusions about the magnitude and importance of specific error sources. Furthermore, the uncertainty in acoustic impedance is strongly dependent on the frequency and the uncertainty in the microphone locations. Next, an increased frequency range of acoustic impedance testing is investigated via two methods. The first method reduces the size of the test specimen (from 25.4 mm square to 8.5 mm square) and uses the standard TMM. This method has issues concerning specimen nonuniformity because the small specimens may not be representative of the material. The second method increases the duct cross section and, hence, the required complexity of the sound field propagation model. A comparison among all three methods is conducted for each of the three specimens: two different ceramic tubular specimens and a single degree-of-freedom liner. The results show good agreement between the

  5. Impedance Spectroscopy of Potential Sulphide Ion Conductors: Instability of Impedance Arcs

    NASA Astrophysics Data System (ADS)

    Johnson, V. S.; Hellgardt, K.; Dann, S. E.; Whiter, R.

    Very few studies are available which deal with sulphide systems while a large number of different types of oxide ion conducting ceramics are described in the open literature. The research here has focused on oxide ion conducting analogues. Solid solutions of CaNd2S3 and Nd2S3 were characterized using Impedance Spectroscopy (IS), temperature programmed oxidation (TPO) and temperature programmed reduction (TPR). The materials resist oxidation up to a temperature of approximately 680°C and reduction up to 750°C. Instability of impedance arcs at elevated temperatures have been reported previously and are explained in terms of three phase boundary area (TPB). Examples include CaS using gold electrodes and Yttria-Stabilized-Zirconia (YSZ) with platinum electrodes. Only a single impedance arc is observed for the undoped CaNd2S4. Two arcs are observed for the doped material indicating ionic mobility. At low frequencies significant instability is observed as a function of temperature (change of decreasing real component of impedance to increasing real component at approximately 250°C for the undoped and 200°C for the doped material). This may be explained by the formation and subsequent decomposition of Au2S forming at the interface of electrolyte and electrode.

  6. Impedance-estimation methods, modeling methods, articles of manufacture, impedance-modeling devices, and estimated-impedance monitoring systems

    SciTech Connect

    Richardson, John G.

    2009-11-17

    An impedance estimation method includes measuring three or more impedances of an object having a periphery using three or more probes coupled to the periphery. The three or more impedance measurements are made at a first frequency. Three or more additional impedance measurements of the object are made using the three or more probes. The three or more additional impedance measurements are made at a second frequency different from the first frequency. An impedance of the object at a point within the periphery is estimated based on the impedance measurements and the additional impedance measurements.

  7. I/O impedance controller

    DOEpatents

    Ruesch, Rodney; Jenkins, Philip N.; Ma, Nan

    2004-03-09

    There is disclosed apparatus and apparatus for impedance control to provide for controlling the impedance of a communication circuit using an all-digital impedance control circuit wherein one or more control bits are used to tune the output impedance. In one example embodiment, the impedance control circuit is fabricated using circuit components found in a standard macro library of a computer aided design system. According to another example embodiment, there is provided a control for an output driver on an integrated circuit ("IC") device to provide for forming a resistor divider network with the output driver and a resistor off the IC device so that the divider network produces an output voltage, comparing the output voltage of the divider network with a reference voltage, and adjusting the output impedance of the output driver to attempt to match the output voltage of the divider network and the reference voltage. Also disclosed is over-sampling the divider network voltage, storing the results of the over sampling, repeating the over-sampling and storing, averaging the results of multiple over sampling operations, controlling the impedance with a plurality of bits forming a word, and updating the value of the word by only one least significant bit at a time.

  8. Dielectric relaxation in AC powder electroluminescent devices

    NASA Astrophysics Data System (ADS)

    Zhang, Shuai; Su, Haibin; Tan, Chuan Seng; Wong, Terence Kin Shun; Teo, Ronnie Jin Wah

    2017-01-01

    The dielectric properties of AC powder electroluminescent devices were measured and analyzed using complex impedance spectroscopy to determine the relaxation processes occurring within the devices. The relaxation processes identified were ascribed to the electrode polarization caused by ion accumulation at the electrode/resin interfaces, the Maxwell-Wagner-Sillars effects at the (ZnS or BaTiO3) particle/resin interfaces, and the dipolar reorientation of polymer chains in the resin matrix. Each relaxation process was represented by its corresponding equivalent circuit component. Space charge polarization at the electrodes were represented by a Warburg element, a resistor, and a constant phase element. The resin matrix, ZnS/resin and BaTiO3/resin interfaces could each be modeled by a resistor and a capacitor in parallel. The simulated equivalent circuits for three different printed structures showed good fitting with their experimental impedance results.

  9. Impedances and collective instabilities of the Tevatron at Run II

    SciTech Connect

    Ng, King-Yuen, FERMI

    1998-09-01

    The longitudinal and transverse coupling impedances of the Tevatron vacuum chamber are estimated and summed up. The resistive-wall impedances of the beam pipe and the laminations in the Lambertson magnets dominate below {approximately} 50 MHz. Then come the inductive parts of the bellows and BPM`s. The longitudinal and transverse collective instabilities, for both single bunch and multi bunches, are studied using Run II parameters. As expected the transverse coupled-bunch instability driven by the resistive-wall impedance is the most severe collective instability. However, it can be damped by a transverse damper designed for the correction of injection offsets. The power of such a damper has been studied.

  10. GB-R impedances: new approach to impedance simulation

    NASA Astrophysics Data System (ADS)

    Serrano, L.; Carlosena, A.

    1995-04-01

    A new design procedure is presented for obtaining simulated inductors and large capacitors from classical opamp circuits. Such impedances exploit almost all of the available bandwidth of the operational amplifier.

  11. Analyses of temperature-dependent interface states, series resistances, and AC electrical conductivities of Al/p—Si and Al/Bi4Ti3O12/p—Si structures by using the admittance spectroscopy method

    NASA Astrophysics Data System (ADS)

    Mert, Yıldırım; Perihan, Durmuş; Şemsettin, Altındal

    2013-10-01

    In this study, Al/p—Si and Al/Bi4Ti3O12/p—Si structures are fabricated and their interface states (Nss), the values of series resistance (Rs), and AC electrical conductivity (σac) are obtained each as a function of temperature using admittance spectroscopy method which includes capacitance—voltage (C—V) and conductance—voltage (G—V) measurements. In addition, the effect of interfacial Bi4Ti3O12 (BTO) layer on the performance of the structure is investigated. The voltage-dependent profiles of Nss and Rs are obtained from the high-low frequency capacitance method and the Nicollian method, respectively. Experimental results show that Nss and Rs, as strong functions of temperature and applied bias voltage, each exhibit a peak, whose position shifts towards the reverse bias region, in the depletion region. Such a peak behavior is attributed to the particular distribution of Nss and the reordering and restructuring of Nss under the effect of temperature. The values of activation energy (Ea), obtained from the slope of the Arrhenius plot, of both structures are obtained to be bias voltage-independent, and the Ea of the metal-ferroelectric-semiconductor (MFS) structure is found to be half that of the metal—semiconductor (MS) structure. Furthermore, other main electrical parameters, such as carrier concentration of acceptor atoms (NA), built-in potential (Vbi), Fermi energy (EF), image force barrier lowering (Δ Φb), and barrier height (Φb), are extracted using reverse bias C-2—V characteristics as a function of temperature.

  12. [Input impedance for studying hydraulic parameters of the vessel system].

    PubMed

    Naumov, A Iu; Sheptutsolov, K V; Balashov, S A; Mel'kumiants, A M

    2001-03-01

    Vascular input impedance can be used as an effective tool in estimating hydraulic parameters of arterial bed. These parameters may be interpreted as hydraulic resistance, elastance and inertance of particular sites of the arterial system. There is no significant difference between these parameters and those obtained through a direct measurement.

  13. High Efficiency Si Solar Cells Characterization Using Impedance Spectroscopy Analysis

    NASA Astrophysics Data System (ADS)

    Braña, A. F.; Forniés, E.; López, N.; García, B. J.

    2015-10-01

    Impedance Spectroscopy has been used to analyse commercial Si photovoltaic solar cells, to obtain information about minority carrier lifetimes, series and parallel resistances, and acceptor impurity densities. Silicon solar cells efficiencies ranging between 17 and 18% from different manufacturers have been analysed obtaining differences mainly in the electron lifetimes and doping densities. Relations between these parameters and DC curves are discussed.

  14. ACS: ALMA Common Software

    NASA Astrophysics Data System (ADS)

    Chiozzi, Gianluca; Šekoranja, Matej

    2013-02-01

    ALMA Common Software (ACS) provides a software infrastructure common to all ALMA partners and consists of a documented collection of common patterns and components which implement those patterns. The heart of ACS is based on a distributed Component-Container model, with ACS Components implemented as CORBA objects in any of the supported programming languages. ACS provides common CORBA-based services such as logging, error and alarm management, configuration database and lifecycle management. Although designed for ALMA, ACS can and is being used in other control systems and distributed software projects, since it implements proven design patterns using state of the art, reliable technology. It also allows, through the use of well-known standard constructs and components, that other team members whom are not authors of ACS easily understand the architecture of software modules, making maintenance affordable even on a very large project.

  15. Studies of Resistive Wall Heating at JLAB FEL

    SciTech Connect

    Li, Rui; Benson, Stephen V.

    2013-06-01

    When the JLAB FEL is under CW operation, it had been observed that temperature rises over the wiggler vacuum chamber, presumably as the result of the power deposition on the resistive wall of the wiggler chamber. Previous analyses have been done on the resistive wall impedance for various cases, such as DC, AC, and anomalous skin effects*. Here we report an investigation on the beam kinetic energy losses for each of these cases. This study includes the non-ultrarelativistic effect on resistive wall loss, for both round pipe and parallel plates. We will present the comparison of our results with the measured data obtained during CW operation of the JLAB FEL. Other possible factors contributing to the measured heating will also be discussed.

  16. Dielectric properties and study of AC electrical conduction mechanisms by non-overlapping small polaron tunneling model in Bis(4-acetylanilinium) tetrachlorocuprate(II) compound

    NASA Astrophysics Data System (ADS)

    Abkari, A.; Chaabane, I.; Guidara, K.

    2016-09-01

    In the present work, the synthesis and characterization of the Bis(4-acetylanilinium) tetrachlorocuprate(II) compound are presented. The structure of this compound is analyzed by X-ray diffraction which confirms the formation of single phase and is in good agreement the literature. Indeed, the Thermo gravimetric Analysis (TGA) shows that the decomposition of the compound is observed in the range of 420-520 K. However, the differential thermal analysis (DTA) indicates the presence of a phase transition at T=363 k. Furthermore, the dielectric properties and AC conductivity were studied over a temperature range (338-413 K) and frequency range (200 Hz-5 MHz) using complex impedance spectroscopy. Dielectric measurements confirmed such thermal analyses by exhibiting the presence of an anomaly in the temperature range of 358-373 K. The complex impedance plots are analyzed by an electrical equivalent circuit consisting of resistance, constant phase element (CPE) and capacitance. The activation energy values of two distinct regions are obtained from log σT vs 1000/T plot and are found to be E=1.27 eV (T<363 K) and E=1.09 eV (363 Kac conductivity, σac, has been analyzed by Jonscher's universal power law σ(ω)=σdc+Aωs. The value of s is to be temperature-dependent, which has a tendency to increase with temperature and the non-overlapping small polaron tunneling (NSPT) model is the most applicable conduction mechanism in the title compound. Complex impedance spectra of [C8H10NO]2CuCl4 at different temperatures.

  17. An impedance study on admiralty brass dezincification originated by microbiologically influenced corrosion.

    PubMed

    Ibars, J R; Polo, J L; Moreno, D A; Ranninger, C; Bastidas, J M

    2004-09-30

    In this article we describe a field study of biofouling and microbiologically influenced corrosion (MIC) of admiralty brass heat exchanger tubes in contact with running fresh water on the river Tagus close to Almaraz nuclear power plant in Spain. Dezincification originated by biofouling and MIC was studied using impedance, polarization resistance, gravimetric, scanning electron microscopy (SEM), and X-ray diffraction (XRD) measurements. Close correlation was observed between the biofilms formed and the corrosion process (dezincification) using the different experimental techniques. Impedance data showed a capacitive behavior including two time constants. Kramers-Kronig (KK) transforms were used to validate impedance data. The admiralty tubes' impedance data satisfied the KK relations.

  18. Investigation of microflow reversal by ac electrokinetics in orthogonal electrodes for micropump design.

    PubMed

    Yang, Kai; Wu, Jie

    2008-04-04

    Orthogonal electrodes have been reported to produce high velocity microflows when excited by ac signals, showing potential for micropumping applications. This paper investigates the microflow reversal phenomena in such orthogonal electrode micropumps. Three types of microflow fields were observed by changing the applied electric signals. Three ac electrokinetic processes, capacitive electrode polarization, Faradaic polarization, and the ac electrothermal effect, are proposed to explain the different flow patterns, respectively. The hypotheses were corroborated by impedance analysis, numerical simulations, and velocity measurements. The investigation of microflow reversal can improve the understanding of ac electrokinetics and hence effectively manipulate fluids.

  19. Impedance and instabilities in the NLC damping rings

    SciTech Connect

    Corlett,J.; Li, D.; Pivi, M.; Rimmer, R.; DeSantis, S.; Wolski, A.; Novokhatski,A.; Ng, C.

    2001-06-12

    We report on impedance calculations and single-bunch and multi-bunch instabilities in the NLC damping rings. Preliminary designs of vacuum chambers and major components have addressed beam impedance issues, with the desire to increase instability current thresholds and reducing growth rates. MAFIA calculations of short-range and long-range wakefields have allowed computations of growth rates and thresholds, which are presented here. Resistive wall instability dominates long-range effects, and requires a broadband feedback system to control coupled-bunch motion. Growth rates are within the range addressable by current feedback system technologies. Single-bunch instability thresholds are safely above nominal operating current.

  20. Bunch Length and Impedance Measurements at SPEAR3

    SciTech Connect

    Corbett, W.J.; Cheng, W.X.; Fisher, A.S.; Huang, X.; /SLAC

    2011-11-02

    Streak camera measurements were made at SPEAR3 to characterize longitudinal coupling impedance. For the nominal optics, data was taken at three rf voltages and a single-bunch current range of 0-20mA. Both bunchcentroid phase shift and bunch lengthening were recorded to extract values for resistive and reactive impedance. An (R+L) and a Q=1 model were then back-substituted into the Haissinski equation and compared with raw profile data. In the short bunch (low-{alpha}) mode, distribution 'bursting' was observed.

  1. IMPEDANCE AND INSTABILITIES IN THE NLC DAMPING RINGS

    SciTech Connect

    Novokhatski, Alexander

    2002-08-20

    We report on impedance calculations and single-bunch and multi-bunch instabilities in the NLC damping rings. Preliminary designs of vacuum chambers and major components have addressed beam impedance issues, with the desire to increase instability current thresholds and reducing growth rates. MAFIA calculations of short-range and long-range wakefields have allowed computations of growth rates and thresholds, which are presented here. Resistive wall instability dominates long-range effects, and requires a broadband feedback system to control coupled-bunch motion. Growth rates are within the range addressable by current feedback system technologies. Single-bunch instability thresholds are safely above nominal operating current.

  2. [Monitoring cervical dilatation by impedance].

    PubMed

    Salvat, J; Lassen, M; Sauze, C; Baud, S; Salvat, F

    1992-01-01

    Several different physics procedures have been tried to mechanize the recording of partograms. Can a measure of impedance of tissue Z using potential difference V, according to Ohm's law V = Z1, and 1 is a constant, be correlated with a measure of cervical dilatation using vaginal examination? This was our hypothesis. The tissue impedance meter was made to our design and applied according to a bipolar procedure. Our work was carried out on 28 patients. 10 patients were registered before labour started in order to test the apparatus and to record the impedance variations without labour taking place, and 18 patients were registered in labour to see whether there was any correlation. The level of impedance in the cervix without labour was 302.7 Ohms with a deviation of 8.2. Using student's t tests it was found that there was a significant correlation (p less than 0.001) in four measurements between the impedance measure and measures obtained by extrapolating the degrees of dilatation calculated from vaginal examination. This is a preliminary study in which we have defined the conditions that are necessary to confirm these first results and to further develop the method.

  3. Hemodynamics Associated with Breathing Through an Inspiratory Impedance Threshold Device in Human Volunteers

    DTIC Science & Technology

    2004-01-01

    Hemodynamics associated with breathing through an inspiratory impedance threshold device in human volunteers Victor A. Convertino, PhD; Duane A...and animals (6–13). Building on this concept, an inspiratory impedance threshold de- vice (ITD) was designed to create a vac- uum within the chest each...associ- ated with the elevated blood pressure during inspiratory resistance (16). How- ever, stroke volume during resistance breathing with an ITD set at

  4. AC and Phase Sensing of Nanowires for Biosensing

    PubMed Central

    Crescentini, Marco; Rossi, Michele; Ashburn, Peter; Lombardini, Marta; Sangiorgi, Enrico; Morgan, Hywel; Tartagni, Marco

    2016-01-01

    Silicon nanowires are label-free sensors that allow real-time measurements. They are economical and pave the road for point-of-care applications but require complex readout and skilled personnel. We propose a new model and technique for sensing nanowire sensors using alternating currents (AC) to capture both magnitude and phase information from the sensor. This approach combines the advantages of complex impedance spectroscopy with the noise reduction performances of lock-in techniques. Experimental results show how modifications of the sensors with different surface chemistries lead to the same direct-current (DC) response but can be discerned using the AC approach. PMID:27104577

  5. Study of AC/RF properties of SRF ingot niobium

    SciTech Connect

    Dhakal, Pashupati; Tsindlekht, Menachem I; Genkin, Valery M; Ciovati, Gianluigi; Myneni, Ganapati Rao

    2013-09-01

    In an attempt to correlate the performance of superconducting radiofrequency cavities made of niobium with the superconducting properties, we present the results of the magnetization and ac susceptibility of the niobium used in the superconducting radiofrequency cavity fabrication. The samples were subjected to buffer chemical polishing (BCP) surface and high temperature heat treatments, typically applied to the cavities fabrications. The analysis of the results show the different surface and bulk ac conductivity for the samples subjected to BCP and heat treatment. Furthermore, the RF surface impedance is measured on the sample using a TE011 microwave cavity for a comparison to the low frequency measurements.

  6. Uncertainties in Transfer Impedance Calculations

    NASA Astrophysics Data System (ADS)

    Schippers, H.; Verpoorte, J.

    2016-05-01

    The shielding effectiveness of metal braids of cables is governed by the geometry and the materials of the braid. The shielding effectiveness can be characterised by the transfer impedance of the metal braid. Analytical models for the transfer impedance contain in general two components, one representing diffusion of electromagnetic energy through the metal braid, and a second part representing leakage of magnetic fields through the braid. Possible sources of uncertainties in the modelling are inaccurate input data (for instance, the exact size of the braid diameter or wire diameter are not known) and imperfections in the computational model. The aim of the present paper is to estimate effects of variations of input data on the calculated transfer impedance.

  7. All electronic approach for high-throughput cell trapping and lysis with electrical impedance monitoring.

    PubMed

    Ameri, Shideh Kabiri; Singh, Pramod K; Dokmeci, Mehmet R; Khademhosseini, Ali; Xu, Qiaobing; Sonkusale, Sameer R

    2014-04-15

    We present a portable lab-on-chip device for high-throughput trapping and lysis of single cells with in-situ impedance monitoring in an all-electronic approach. The lab-on-chip device consists of microwell arrays between transparent conducting electrodes within a microfluidic channel to deliver and extract cells using alternating current (AC) dielectrophoresis. Cells are lysed with high efficiency using direct current (DC) electric fields between the electrodes. Results are presented for trapping and lysis of human red blood cells. Impedance spectroscopy is used to estimate the percentage of filled wells with cells and to monitor lysis. The results show impedance between electrodes decreases with increase in the percentage of filled wells with cells and drops to a minimum after lysis. Impedance monitoring provides a reasonably accurate measurement of cell trapping and lysis. Utilizing an all-electronic approach eliminates the need for bulky optical components and cameras for monitoring.

  8. Effect of amino acid immobilization on the impedance of graphene oxide

    NASA Astrophysics Data System (ADS)

    Tran, Minh-Hai; Han, Jinwoo; Min, Byeong June; Lee, ChangWoo; Jang, Sei-Heon; Jeong, Hae Kyung

    2015-05-01

    A single residue, dipeptide, or tripeptide of alanine or histidine is covalently attached to graphene oxide (GO), and the effect of the amino acid immobilization on the impedance of GO is investigated using the impedance spectroscopy. The histidine of a tripeptide exhibits the lowest resistance compared to the single or dipeptide histidine in the KCl electrolyte, and the single alanine residue shows the lowest resistance in an acidic electrolyte compared to the dipeptide or tripeptide alanine. The peculiar behavior of the impedance could be explained by different net charges of the amino acids, chain length, and π-π stacking interaction.

  9. REDUCING BEAM COUPLING IMPEDANCES IN SNS RING EXTRACTION KICKERS

    SciTech Connect

    S.S. KURENNOY; D. DAVINO; Y. LEE

    2001-06-01

    The Spallation Neutron Source (SNS) Accumulator ring extraction system [1] includes 14 modules of window-frame ferrite pulsing kicker magnets with the rise time of about 200 ns. Their contribution to the beam coupling impedances is a serious concern. The kicker impedances, as well as its deflecting magnetic field versus time, are studied using detailed 3-D MAFIA modeling. Various design options, external circuit resistances, and a range of ferrite permeabilities are explored. A kicker module with wide conductor windings around the ferrite behind the kicker current sheet suggests a significant reduction of the kicker transverse and longitudinal coupling impedances. This design provides a good extraction field performance, as demonstrated by electromagnetic simulations. Results of measurements for a small model are also presented.

  10. REDUCING BEAM COUPLING IMPEDANCES IN SNS RING EXTRACTION KICKERS

    SciTech Connect

    Kurennoy, S.; Davino, D.; Lee, Y. Y.

    2001-01-01

    The Spallation Neutron Source (SNS) Accumulator ring extraction system includes 14 modules of windowframe ferrite pulsing kicker magnets with the rise time of about 200 ns. Their contribution to the beam coupling impedances is a serious concern. The kicker impedances, as well as its deflecting magnetic field versus time, are studied using detailed 3-D MAFIA modeling. Various design options, external circuit resistances, and a range of ferrite permeabilities are explored. A kicker module with wide conductor windings around the ferrite behind the kicker current sheet suggests a significant reduction of the kicker transverse and longitudinal coupling impedances. This design provides a good extraction field performance, as demonstrated by electromagnetic simulations. Results of measurements for a small model are also presented.

  11. Investigation of an Anomaly Observed in Impedance Eduction Techniques

    NASA Technical Reports Server (NTRS)

    Watson, W. R.; Jones, M. G.; Parrott, T. L.

    2008-01-01

    An intensive investigation into the cause of anomalous behavior commonly observed in impedance eduction techniques is performed. The investigation consists of grid refinement studies, detailed evaluation of results at and near anti-resonance frequencies, comparisons of different model results with synthesized and measured data, assessment or optimization techniques, and evaluation or boundary condition effects. Results show that the root cause of the anomalous behavior is the sensitivity of the educed impedance to small errors in the measured termination resistance at frequencies near anti-resonance or cut-on of a higher-order mode. Evidence is presented to show that the common usage of an anechoic, plane wave termination boundary condition in ducts where the "true" termination is reflective may act as a trigger for these anomalies. Replacing the exit impedance boundary condition by an exit pressure condition is shown to reduce the anomalous results.

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

    NASA Astrophysics Data System (ADS)

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

    2015-08-01

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

  13. AC losses in a HTS coil carrying DC current in AC external magnetic field

    NASA Astrophysics Data System (ADS)

    Ogawa, J.; Zushi, Y.; Fukushima, M.; Tsukamoto, O.; Suzuki, E.; Hirakawa, M.; Kikukawa, K.

    2003-10-01

    We electrically measured AC losses in a Bi2223/Ag-sheathed pancake coil excited by a DC current in AC external magnetic field. Losses in the coil contain two kinds of loss components that are the magnetization losses and dynamic resistance losses. In the measurement, current leads to supply a current to the coil were specially arranged to suppress electromagnetic coupling between the coil current and the AC external magnetic field. A double pick-up coils method was used to suppress a large inductive voltage component contained in voltage signal for measuring the magnetization losses. It was observed that the magnetization losses were dependent on the coil current and that a peak of a curve of the loss factor vs. amplitude of the AC external magnetic field shifted to lower amplitude of the AC magnetic field as the coil current increased. This result suggests the full penetration magnetic field of the coil tape decreases as the coil current increases. The dynamic resistance losses were measured by measuring a DC voltage appearing between the coil terminals. It was observed that the DC voltage appearing in the coil subject to the AC external magnetic field was much larger than that in the coil subject to DC magnetic field.

  14. Bench-Top Impedance Measurements for a Rotatable Copper Collimator for the LHC Phase II Collimation Upgrade

    SciTech Connect

    Smith, Jeffrey Claiborne; Bane, Karl; Doyle, Eric; Keller, Lew; Lundgren, Steve; Markiewicz, Tom; Ng, Cho-Kuen; Xiao, Liling; /SLAC

    2010-08-26

    Simulations have been performed in Omega3P to study both trapped modes and impedance contributions of a rotatable collimator for the LHC phase II collimation upgrade. Bench-top stretched coil probe impedance methods are also being implemented for measurements on prototype components to directly measure the low frequency impedance contributions. The collimator design also calls for a RF contact interface at both jaw ends with contact resistance much less than a milliohm in order to limit transverse impedance. DC resistance measurements in a custom built test chamber have been performed to test the performance of this interface.

  15. Electrical impedance imaging of water distribution in the root zone

    NASA Astrophysics Data System (ADS)

    Newill, P.; Karadaglić, D.; Podd, F.; Grieve, B. D.; York, T. A.

    2014-05-01

    The paper describes a technique that is proposed for imaging water transport in and around the root zone of plants using distributed measurements of electrical impedance. The technique has the potential to analyse sub-surface phenotypes, for instance drought tolerance traits in crop breeding programmes. The technical aim is to implement an automated, low cost, instrument for high-throughput screening. Ultimately the technique is targeted at in-field, on-line, measurements. For demonstration purposes the present work considers measurements on laboratory scale rhizotrons housing growing maize plants. Each rhizotron is fitted with 60 electrodes in a rectangular array. To reduce electrochemical effects the capacitively coupled contactless conductivity (C4D) electrodes have an insulating layer on the surface and the resistance of the bulk material is deduced from spectroscopic considerations. Electrical impedance is measured between pairs of electrodes to build up a two-dimensional map. A modified electrical model of such electrodes is proposed which includes the resistive and reactive components of both the insulating layer and the bulk material. Measurements taken on a parallel-plate test cell containing water confirm that the C4D technique is able to measure electrical impedance. The test cell has been used to explore the effects of water content, compaction and temperature on measurements in soil. Results confirm that electrical impedance measurements are very sensitive to moisture content. Impedance fraction changes up to 20% are observed due to compaction up to a pressure of 0.21 kg cm-2 and a temperature fraction sensitivity of about 2%/°C. The effects of compaction and temperature are most significant under dry conditions. Measurements on growing maize reveal the changes in impedance across the rhizotron over a period of several weeks. Results are compared to a control vessel housing only soil.

  16. The A to Z of A/C plasmids.

    PubMed

    Harmer, Christopher J; Hall, Ruth M

    2015-07-01

    Plasmids belonging to incompatibility groups A and C (now A/C) were among the earliest to be associated with antibiotic resistance in Gram-negative bacteria. A/C plasmids are large, conjugative plasmids with a broad host range. The prevalence of A/C plasmids in collections of clinical isolates has revealed their importance in the dissemination of extended-spectrum β-lactamases and carbapenemases. They also mobilize SGI1-type resistance islands. Revived interest in the family has yielded many complete A/C plasmid sequences, revealing that RA1, designated A/C1, is different from the remainder, designated A/C2. There are two distinct A/C2 lineages. Backbones of 128-130 kb include over 120 genes or ORFs encoding proteins of at least 100 amino acids, but very few have been characterized. Genes potentially required for replication, stability and transfer have been identified, but only the replication system of RA1 and the regulation of transfer have been studied. There is enormous variety in the antibiotic resistance genes carried by A/C2 plasmids but they are usually clustered in larger regions at various locations in the backbone. The ARI-A and ARI-B resistance islands are always at a specific location but have variable content. ARI-A is only found in type 1 A/C2 plasmids, which disseminate blaCMY-2 and blaNDM-1 genes, whereas ARI-B, carrying the sul2 gene, is found in both type 1 and type 2. This review summarizes current knowledge of A/C plasmids, and highlights areas of research to be considered in the future.

  17. In situ impedance measurement of microwave atmospheric pressure plasma

    NASA Astrophysics Data System (ADS)

    Lee, S. T.; Nam, W. J.; Lee, J. K.; Yun, G. S.

    2017-04-01

    The impedance of atmospheric pressure argon plasma jets driven by microwave frequency is determined in situ by a novel ‘two frequency method’. In the conventional method of reflection coefficient ({{S}}11) measurement, the frequency of the driving microwave power is scanned, which inevitably affects the plasma characters and leads to uncertainty in the estimated plasma impedance. In our proposed method, the frequency-scanning signal additional to the driving power is used to measure {{S}}11 over a wide frequency range, which enables accurate determination of the plasma impedance based on an equivalent circuit model. The measured resistance and reactance of the plasma increase with the driving power in agreement with the transmission line theory. Based on this in situ measurement of the plasma impedance, the net power coupled to the plasma has been determined. The overall power efficiency remains approximately unchanged around 45% for different input power levels owing to the competing effects between the impedance mismatch and the volume change of the plasma.

  18. Maximizing switching current of superconductor nanowires via improved impedance matching

    NASA Astrophysics Data System (ADS)

    Zhang, Labao; Yan, Xiachao; Jia, Xiaoqing; Chen, Jian; Kang, Lin; Wu, Peiheng

    2017-02-01

    The temporary resistance triggered by phase slips will result in the switching of a superconductor nanowire to a permanent normal state, decreasing the switching current. In this letter, we propose an improved impedance matching circuit that releases the transition triggered by phase slips to the load resistor through the radio frequency (RF) port of a bias tee. The transportation properties with different load resistors indicate that the switching current decreases due to the reflection caused by impedance mismatching, and it is maximized by optimized impedance matching. Compared to the same setup without the impedance matching circuit, the switching current was increased from 8.0 μA to 12.2 μA in a niobium nitride nanowire after releasing the temporary transition triggered by phase slips. The leakage process with impedance matching outputs a voltage pulse, which enables the user to directly register the transition triggered by phase slips. The technique for maximizing the switching current has a potential practical application in superconductor devices, and the technique for counting phase slips may be applied to explore the behavior of phase slips.

  19. Bioelectrical impedance analysis. What does it measure?

    NASA Technical Reports Server (NTRS)

    Schoeller, D. A.

    2000-01-01

    Bioelectrical impedance analysis (BIA) has been proposed for measuring fat-free mass, total body water, percent fat, body cell mass, intracellular water, and extracellular water: a veritable laboratory in a box. Although it is unlikely that BIA is quite this versatile, correlations have been demonstrated between BIA and all of these body compartments. At the same time, it is known that all of the compartments are correlated among themselves. Because of this, it is difficult to determine whether BIA is specific for any or all of these compartments. To investigate this question, we induced acute changes in total body water and its compartments over a 3-h period. Using this approach, we demonstrated that multifrequency BIA, using the Cole-Cole model to calculate the zero frequency and infinite frequency resistance, measures extracellular and intracellular water.

  20. Wave guide impedance matching method and apparatus

    DOEpatents

    Kronberg, James W.

    1990-01-01

    A technique for modifying the end portion of a wave guide, whether hollow or solid, carrying electromagnetic, acoustic or optical energy, to produce a gradual impedance change over the length of the end portion, comprising the cutting of longitudinal, V-shaped grooves that increase in width and depth from beginning of the end portion of the wave guide to the end of the guide so that, at the end of the guide, no guide material remains and no surfaces of the guide as modified are perpendicular to the direction of energy flow. For hollow guides, the grooves are cut beginning on the interior surface; for solid guides, the grooves are cut beginning on the exterior surface. One or more resistive, partially conductive or nonconductive sleeves can be placed over the exterior of the guide and through which the grooves are cut to smooth the transition to free space.

  1. Characteristic impedance of microstrip lines

    NASA Technical Reports Server (NTRS)

    Bailey, M. C.; Deshpande, M. D.

    1989-01-01

    The dyadic Green's function for a current embedded in a grounded dielectric slab is used to analyze microstrip lines at millimeter wave frequencies. The dyadic Green's function accounts accurately for fringing fields and dielectric cover over the microstrip line. Using Rumsey's reaction concept, an expression for the characteristic impedance is obtained. The numerical results are compared with other reported results.

  2. Acoustic Ground-Impedance Meter

    NASA Technical Reports Server (NTRS)

    Zuckerwar, A. J.

    1983-01-01

    Helmoltz resonator used in compact, portable meter measures acoustic impedance of ground or other surfaces. Earth's surface is subject of increasing acoustical investigations because of its importance in aircraft noise prediction and measurment. Meter offers several advantages. Is compact and portable and set up at any test site, irrespective of landscape features, weather or other environmental condition.

  3. The Aberdeen Impedance Imaging System.

    PubMed

    Kulkarni, V; Hutchison, J M; Mallard, J R

    1989-01-01

    The Aberdeen Impedance Imaging System is designed to reconstruct 2 dimensional images of the average distribution of the amplitude and phase of the complex impedance within a 3 dimensional region. The system uses the four electrode technique in a 16 electrode split-array. The system hardware consists of task-orientated electronic modules for: driving a constant current, multiplexing the current drive, demultiplexing peripheral voltages, differential amplification, phase sensitive detection and low-pass filtration, digitisation with a 14 bit analog to digital converter (ADC), and -control logic for the ADC and multiplexors. A BBC microprocessor (Master series), initiates a controlled sequence for the collection of a number of data sets which are averaged and stored on disk. Image reconstruction is by a process of convolution-backprojection similar to the fan-beam reconstruction of computerised tomography and is also known as Equipotential Backprojection. In imaging impedance changes associated with fracture healing the changes may be large enough to allow retrieval of both the amplitude and phase of the complex impedance. Sequential imaging of these changes would necessitate monitoring electronic and electrode drift by imaging an equivalent region of the contralateral limb. Differential images could be retrieved when the image of the normal limb is the image template. Better characterisation of tissues would necessitate a cleaner retrieval of the quadrature signal.

  4. High Dynamic Range Complex Impedance Measurement System for Petrophysical Usage

    NASA Astrophysics Data System (ADS)

    Chen, R.; He, X.; Yao, H.; Tan, S.; Shi, H.; Shen, R.; Yan, C.; Zeng, P.; He, L.; Qiao, N.; Xi, F.; Zhang, H.; Xie, J.

    2015-12-01

    Spectral induced polarization method (SIP) or complex resistivity method is increasing its application in metalliferous ore exploration, hydrocarbon exploration, underground water exploration, monitoring of environment pollution, and the evaluation of environment remediation. And the measurement of complex resistivity or complex impedance of rock/ore sample and polluted water plays a fundamental role in improving the application effect of SIP and the application scope of SIP. However, current instruments can't guaranty the accuracy of measurement when the resistance of sample is less than 10Ω or great than 100kΩ. A lot of samples, such as liquid, polluted sea water, igneous rock, limestone, and sandstone, can't be measured with reliable complex resistivity result. Therefore, this problem projects a shadow in the basic research and application research of SIP. We design a high precision measurement system from the study of measurement principle, sample holder, and measurement instrument. We design input buffers in a single board. We adopt operation amplifier AD549 in this system because of its ultra-high input impedance and ultra-low current noise. This buffer is good in acquiring potential signal across high impedance sample. By analyzing the sources of measurement error and errors generated by the measurement system, we propose a correction method to remove the error in order to achieve high quality complex impedance measurement for rock and ore samples. This measurement system can improve the measurement range of the complex impedance to 0.1 Ω ~ 10 GΩ with amplitude error less than 0.1% and phase error less than 0.1mrad when frequency ranges as 0.01 Hz ~ 1 kHz. We tested our system on resistors with resistance as 0.1Ω ~ 10 GΩ in frequency range as 1 Hz ~ 1000 Hz, and the measurement error is less than 0.1 mrad. We also compared the result with LCR bridge and SCIP, we can find that the bridge's measuring range only reaches 100 MΩ, SCIP's measuring range

  5. AC magnetohydrodynamic microfluidic switch

    SciTech Connect

    Lemoff, A V; Lee, A P

    2000-03-02

    A microfluidic switch has been demonstrated using an AC Magnetohydrodynamic (MHD) pumping mechanism in which the Lorentz force is used to pump an electrolytic solution. By integrating two AC MHD pumps into different arms of a Y-shaped fluidic circuit, flow can be switched between the two arms. This type of switch can be used to produce complex fluidic routing, which may have multiple applications in {micro}TAS.

  6. Organic electrochemical transistors for cell-based impedance sensing

    SciTech Connect

    Rivnay, Jonathan E-mail: owens@emse.fr; Ramuz, Marc; Hama, Adel; Huerta, Miriam; Owens, Roisin M. E-mail: owens@emse.fr; Leleux, Pierre

    2015-01-26

    Electrical impedance sensing of biological systems, especially cultured epithelial cell layers, is now a common technique to monitor cell motion, morphology, and cell layer/tissue integrity for high throughput toxicology screening. Existing methods to measure electrical impedance most often rely on a two electrode configuration, where low frequency signals are challenging to obtain for small devices and for tissues with high resistance, due to low current. Organic electrochemical transistors (OECTs) are conducting polymer-based devices, which have been shown to efficiently transduce and amplify low-level ionic fluxes in biological systems into electronic output signals. In this work, we combine OECT-based drain current measurements with simultaneous measurement of more traditional impedance sensing using the gate current to produce complex impedance traces, which show low error at both low and high frequencies. We apply this technique in vitro to a model epithelial tissue layer and show that the data can be fit to an equivalent circuit model yielding trans-epithelial resistance and cell layer capacitance values in agreement with literature. Importantly, the combined measurement allows for low biases across the cell layer, while still maintaining good broadband signal.

  7. Organic electrochemical transistors for cell-based impedance sensing

    NASA Astrophysics Data System (ADS)

    Rivnay, Jonathan; Ramuz, Marc; Leleux, Pierre; Hama, Adel; Huerta, Miriam; Owens, Roisin M.

    2015-01-01

    Electrical impedance sensing of biological systems, especially cultured epithelial cell layers, is now a common technique to monitor cell motion, morphology, and cell layer/tissue integrity for high throughput toxicology screening. Existing methods to measure electrical impedance most often rely on a two electrode configuration, where low frequency signals are challenging to obtain for small devices and for tissues with high resistance, due to low current. Organic electrochemical transistors (OECTs) are conducting polymer-based devices, which have been shown to efficiently transduce and amplify low-level ionic fluxes in biological systems into electronic output signals. In this work, we combine OECT-based drain current measurements with simultaneous measurement of more traditional impedance sensing using the gate current to produce complex impedance traces, which show low error at both low and high frequencies. We apply this technique in vitro to a model epithelial tissue layer and show that the data can be fit to an equivalent circuit model yielding trans-epithelial resistance and cell layer capacitance values in agreement with literature. Importantly, the combined measurement allows for low biases across the cell layer, while still maintaining good broadband signal.

  8. Analysis and design of triple-band high-impedance surface absorber with periodic diversified impedance

    NASA Astrophysics Data System (ADS)

    Rui Zhang, Guo; Heng Zhou, Pei; Bin Zhang, Hui; Bo Zhang, Lin; Liang Xie, Jian; Jiang Deng, Long

    2013-10-01

    In this paper, a triple-band planar absorber with high-impedance surface (HIS) is designed and fabricated. The absorber structure is composed of polyurethane foam sandwiched between a lossy sheet of frequency selective surfaces (FSS) and a perfect electric conductor. The lossy FSS possesses different resistances in a periodic composite unit as compared with typical HIS absorber. Losses in the FSS are introduced by printing the periodic composite square ring pattern on blank stickers using various resistive inks. Physical mechanism of the HIS absorbers is analyzed by equivalent circuit model and electric field distribution studies. The proposed absorber with periodic composite units offers superimposed triple-band absorption as compared with that of the single units having single- or dual-band absorption characteristics. The reflection loss measurements show that the 90% absorption bandwidth of the HIS absorber is increased by 42% by the proposed composite periodic units.

  9. Uncertainty and Sensitivity Analyses of a Two-Parameter Impedance Prediction Model

    NASA Technical Reports Server (NTRS)

    Jones, M. G.; Parrott, T. L.; Watson, W. R.

    2008-01-01

    This paper presents comparisons of predicted impedance uncertainty limits derived from Monte-Carlo-type simulations with a Two-Parameter (TP) impedance prediction model and measured impedance uncertainty limits based on multiple tests acquired in NASA Langley test rigs. These predicted and measured impedance uncertainty limits are used to evaluate the effects of simultaneous randomization of each input parameter for the impedance prediction and measurement processes. A sensitivity analysis is then used to further evaluate the TP prediction model by varying its input parameters on an individual basis. The variation imposed on the input parameters is based on measurements conducted with multiple tests in the NASA Langley normal incidence and grazing incidence impedance tubes; thus, the input parameters are assigned uncertainties commensurate with those of the measured data. These same measured data are used with the NASA Langley impedance measurement (eduction) processes to determine the corresponding measured impedance uncertainty limits, such that the predicted and measured impedance uncertainty limits (95% confidence intervals) can be compared. The measured reactance 95% confidence intervals encompass the corresponding predicted reactance confidence intervals over the frequency range of interest. The same is true for the confidence intervals of the measured and predicted resistance at near-resonance frequencies, but the predicted resistance confidence intervals are lower than the measured resistance confidence intervals (no overlap) at frequencies away from resonance. A sensitivity analysis indicates the discharge coefficient uncertainty is the major contributor to uncertainty in the predicted impedances for the perforate-over-honeycomb liner used in this study. This insight regarding the relative importance of each input parameter will be used to guide the design of experiments with test rigs currently being brought on-line at NASA Langley.

  10. Comparison of impedance measurements near the skin of newborns and adults.

    PubMed

    Amm, Bruce; Kao, Tzu-Jen; Newell, Jonathan; Isaacson, David; Saulnier, Gary; Shoudy, David; Boverman, Greg; Sahni, Rakesh; Weindler, Marilyn; Chong, David; DiBardino, David; Davenport, David; Ashe, Jeffrey

    2016-06-01

    Electrical impedance tomography (EIT) is a non-invasive imaging technology that has been extensively studied for monitoring lung function of neonatal and adult subjects, especially in neonatal intensive care unit (NICU) and intensive care unit (ICU) environments. The sources of the total impedance in these applications include internal organs, near-boundary tissues, electrode-skin impedance, electrodes and conducting wires. This total impedance must be considered for system design and setting voltage gain since it will contribute to the measured voltage. To adapt a single instrument for use on infants and adults, we studied the difference between the impedance near the skin in both classes of patients. We used a simultaneous multi-source EIT (SMS-EIT) system to make impedance measurements. Characteristic resistance was calculated for two different current patterns: one that is more sensitive to boundary region impedance and another that is more sensitive to interior changes. We present ratios of these resistances to assess the relative contribution of near-skin effects to the overall impedance. Twenty adult ICU subjects (10 male, 10 female, age: 49.05  ±  16.32 years (mean  ±  standard deviation)) and 45 neonates (23 male, 22 female, gestational age: 37.67  ±  2.11 weeks, postnatal age, 2.56  ±  2.67 d) were studied at Columbia University Medical Center. Impedance measurements at 10 kHz were collected for approximately one hour from each subject. The characteristic resistance ratio for each subject was computed and analyzed. The result shows the impedance at or near the skin of newborns is significantly higher than in adult subjects.

  11. Experimental Impedance of Single Liner Elements with Bias Flow

    NASA Technical Reports Server (NTRS)

    Follet, J. I.; Betts, J. F.; Kelly, Jeffrey J.; Thomas, Russell H.

    2000-01-01

    An experimental investigation was conducted to generate a high quality database, from which the effects of a mean bias flow on the acoustic impedance of lumped-element single-degree-of-freedom liners was determined. Acoustic impedance measurements were made using the standard two-microphone method in the NASA Langley Normal Incidence Tube. Each liner consisted of a perforated sheet with a constant-area cavity. Liner resistance was shown to increase and to become less frequency and sound pressure level dependent as the bias flow was increased. The resistance was also consistently lower for a negative bias flow (suction) than for a positive bias flow (blowing) of equal magnitude. The slope of the liner reactance decreased with increased flow.

  12. Nuclear radiation-warning detector that measures impedance

    DOEpatents

    Savignac, Noel Felix; Gomez, Leo S; Yelton, William Graham; Robinson, Alex; Limmer, Steven

    2013-06-04

    This invention is a nuclear radiation-warning detector that measures impedance of silver-silver halide on an interdigitated electrode to detect light or radiation comprised of alpha particles, beta particles, gamma rays, X rays, and/or neutrons. The detector is comprised of an interdigitated electrode covered by a layer of silver halide. After exposure to alpha particles, beta particles, X rays, gamma rays, neutron radiation, or light, the silver halide is reduced to silver in the presence of a reducing solution. The change from the high electrical resistance (impedance) of silver halide to the low resistance of silver provides the radiation warning that detected radiation levels exceed a predetermined radiation dose threshold.

  13. AC Losses of Prototype HTS Transmission Cables

    SciTech Connect

    Demko, J.A.; Dresner, L.; Hughey, R.L.; Lue, J.W.; Olsen, S.K.; Sinha, U.; Tolbert, J.C.

    1998-09-13

    Since 1995 Southwire Company and Oak Ridge National Laboratory (ORNL) have jointly designed, built, and tested nine, l-m long, high temperature superconducting (HTS) transmission cable prototypes. This paper summarizes the AC loss measurements of five of the cables not reported elsewhere, and compares the losses with each other and with theory developed by Dresner. Losses were measured with both a calorimetric and an electrical technique. Because of the broad resistive transition of the HTS tapes, the cables can be operated stably beyond their critical currents. The AC losses were measured in this region as well as below critical currents. Dresner's theory takes into account the broad resistive transition of the HTS tapes and calculates the AC losses both below and above the critical current. The two sets of AC 10SS data agree with each other and with the theory quite welL In particular, at low currents of incomplete penetration, the loss data agree with the theoretical prediction of hysteresis loss based on only the outer two Iayers carrying the total current.

  14. Superconducting shielded core reactor with reduced AC losses

    DOEpatents

    Cha, Yung S.; Hull, John R.

    2006-04-04

    A superconducting shielded core reactor (SSCR) operates as a passive device for limiting excessive AC current in a circuit operating at a high power level under a fault condition such as shorting. The SSCR includes a ferromagnetic core which may be either closed or open (with an air gap) and extends into and through a superconducting tube or superconducting rings arranged in a stacked array. First and second series connected copper coils each disposed about a portion of the iron core are connected to the circuit to be protected and are respectively wound inside and outside of the superconducting tube or rings. A large impedance is inserted into the circuit by the core when the shielding capability of the superconducting arrangement is exceeded by the applied magnetic field generated by the two coils under a fault condition to limit the AC current in the circuit. The proposed SSCR also affords reduced AC loss compared to conventional SSCRs under continuous normal operation.

  15. Studies on Electrical behavior of Glucose using Impedance Spectroscopy

    NASA Astrophysics Data System (ADS)

    Juansah, Jajang; Yulianti, Wina

    2016-01-01

    In this work we report the electrical characteristics of glucose at different frequencies. We show the correlation between electrical properties (impedance, reactance, resistance and conductance) of glucose and glucose concentration. Electrical property measurements on glucose solution were performed in order to formulate the correlation. The measurements were conducted for frequencies between 50 Hz and 1 MHz. From the measurements, we developed a single-pole Cole-Cole graph as a function of glucose concentration.

  16. 21 CFR 870.2750 - Impedance phlebograph.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Impedance phlebograph. 870.2750 Section 870.2750...) MEDICAL DEVICES CARDIOVASCULAR DEVICES Cardiovascular Monitoring Devices § 870.2750 Impedance phlebograph. (a) Identification. An impedance phlebograph is a device used to provide a visual display of...

  17. 21 CFR 870.2770 - Impedance plethysmograph.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Impedance plethysmograph. 870.2770 Section 870...) MEDICAL DEVICES CARDIOVASCULAR DEVICES Cardiovascular Monitoring Devices § 870.2770 Impedance plethysmograph. (a) Identification. An impedance plethysmograph is a device used to estimate peripheral...

  18. 21 CFR 870.2750 - Impedance phlebograph.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Impedance phlebograph. 870.2750 Section 870.2750...) MEDICAL DEVICES CARDIOVASCULAR DEVICES Cardiovascular Monitoring Devices § 870.2750 Impedance phlebograph. (a) Identification. An impedance phlebograph is a device used to provide a visual display of...

  19. 21 CFR 870.2770 - Impedance plethysmograph.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Impedance plethysmograph. 870.2770 Section 870...) MEDICAL DEVICES CARDIOVASCULAR DEVICES Cardiovascular Monitoring Devices § 870.2770 Impedance plethysmograph. (a) Identification. An impedance plethysmograph is a device used to estimate peripheral...

  20. 21 CFR 870.2750 - Impedance phlebograph.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Impedance phlebograph. 870.2750 Section 870.2750...) MEDICAL DEVICES CARDIOVASCULAR DEVICES Cardiovascular Monitoring Devices § 870.2750 Impedance phlebograph. (a) Identification. An impedance phlebograph is a device used to provide a visual display of...

  1. 21 CFR 870.2770 - Impedance plethysmograph.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Impedance plethysmograph. 870.2770 Section 870...) MEDICAL DEVICES CARDIOVASCULAR DEVICES Cardiovascular Monitoring Devices § 870.2770 Impedance plethysmograph. (a) Identification. An impedance plethysmograph is a device used to estimate peripheral...

  2. 21 CFR 870.2770 - Impedance plethysmograph.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Impedance plethysmograph. 870.2770 Section 870...) MEDICAL DEVICES CARDIOVASCULAR DEVICES Cardiovascular Monitoring Devices § 870.2770 Impedance plethysmograph. (a) Identification. An impedance plethysmograph is a device used to estimate peripheral...

  3. 21 CFR 870.2750 - Impedance phlebograph.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Impedance phlebograph. 870.2750 Section 870.2750...) MEDICAL DEVICES CARDIOVASCULAR DEVICES Cardiovascular Monitoring Devices § 870.2750 Impedance phlebograph. (a) Identification. An impedance phlebograph is a device used to provide a visual display of...

  4. 21 CFR 870.2750 - Impedance phlebograph.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Impedance phlebograph. 870.2750 Section 870.2750...) MEDICAL DEVICES CARDIOVASCULAR DEVICES Cardiovascular Monitoring Devices § 870.2750 Impedance phlebograph. (a) Identification. An impedance phlebograph is a device used to provide a visual display of...

  5. 21 CFR 870.2770 - Impedance plethysmograph.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Impedance plethysmograph. 870.2770 Section 870...) MEDICAL DEVICES CARDIOVASCULAR DEVICES Cardiovascular Monitoring Devices § 870.2770 Impedance plethysmograph. (a) Identification. An impedance plethysmograph is a device used to estimate peripheral...

  6. Impedance analysis of acupuncture points and pathways

    NASA Astrophysics Data System (ADS)

    Teplan, Michal; Kukučka, Marek; Ondrejkovičová, Alena

    2011-12-01

    Investigation of impedance characteristics of acupuncture points from acoustic to radio frequency range is addressed. Discernment and localization of acupuncture points in initial single subject study was unsuccessfully attempted by impedance map technique. Vector impedance analyses determined possible resonant zones in MHz region.

  7. Tapping mode microwave impedance microscopy

    SciTech Connect

    Lai, K.

    2010-02-24

    We report tapping mode microwave impedance imaging based on atomic force microscope platforms. The shielded cantilever probe is critical to localize the tip-sample interaction near the tip apex. The modulated tip-sample impedance can be accurately simulated by the finite-element analysis and the result agrees quantitatively to the experimental data on a series of thin-film dielectric samples. The tapping mode microwave imaging is also superior to the contact mode in that the thermal drift in a long time scale is totally eliminated and an absolute measurement on the dielectric properties is possible. We demonstrated tapping images on working nanodevices, and the data are consistent with the transport results.

  8. Tevatron AC dipole system

    SciTech Connect

    Miyamoto, R.; Kopp, S.E.; Jansson, A.; Syphers, M.J.; /Fermilab

    2007-06-01

    The AC dipole is an oscillating dipole magnet which can induce large amplitude oscillations without the emittance growth and decoherence. These properties make it a good tool to measure optics of a hadron synchrotron. The vertical AC dipole for the Tevatron is powered by an inexpensive high power audio amplifier since its operating frequency is approximately 20 kHz. The magnet is incorporated into a parallel resonant system to maximize the current. The use of a vertical pinger magnet which has been installed in the Tevatron made the cost relatively inexpensive. Recently, the initial system was upgraded with a more powerful amplifier and oscillation amplitudes up to 2-3{sigma} were achieved with the 980 GeV proton beam. This paper discusses details of the Tevatron AC dipole system and also shows its test results.

  9. Introducing AC Inductive Reactance with a Power Tool

    ERIC Educational Resources Information Center

    Bryant, Wesley; Baker, Blane

    2016-01-01

    The concept of reactance in AC electrical circuits is often non-intuitive and difficult for students to grasp. In order to address this lack of conceptual understanding, classroom exercises compare the predicted resistance of a power tool, based on electrical specifications, to measured resistance. Once students discover that measured resistance…

  10. Impedance microflow cytometry for viability studies of microorganisms

    NASA Astrophysics Data System (ADS)

    Di Berardino, Marco; Hebeisen, Monika; Hessler, Thomas; Ziswiler, Adrian; Largiadèr, Stephanie; Schade, Grit

    2011-02-01

    Impedance-based Coulter counters and its derivatives are widely used cell analysis tools in many laboratories and use normally DC or low frequency AC to perform these electrical analyses. The emergence of micro-fabrication technologies in the last decade, however, provides a new means of measuring electrical properties of cells. Microfluidic approaches combined with impedance spectroscopy measurements in the radio frequency (RF) range increase sensitivity and information content and thus push single cell analyses beyond simple cell counting and sizing applications towards multiparametric cell characterization. Promising results have been shown already in the fields of cell differentiation and blood analysis. Here we emphasize the potential of this technology by presenting new data obtained from viability studies on microorganisms. Impedance measurements of several yeast and bacteria strains performed at frequencies around 10 MHz enable an easy discrimination between dead and viable cells. Moreover, cytotoxic effects of antibiotics and other reagents, as well as cell starvation can also be monitored easily. Control analyses performed with conventional flow cytometers using various fluorescent dyes (propidium iodide, oxonol) indicate a good correlation and further highlight the capability of this device. The label-free approach makes on the one hand the use of usually expensive fluorochromes obsolete, on the other hand practically eliminates laborious sample preparation procedures. Until now, online cell monitoring was limited to the determination of viable biomass, which provides rather poor information of a cell culture. Impedance microflow cytometry, besides other aspects, proposes a simple solution to these limitations and might become an important tool for bioprocess monitoring applications in the biotech industry.

  11. Electron density dependence of impedance probe plasma potential measurements

    SciTech Connect

    Walker, D. N.; Blackwell, D. D.; Amatucci, W. E.

    2015-08-15

    In earlier works, we used spheres of various sizes as impedance probes in demonstrating a method of determining plasma potential, φ{sub p}, when the probe radius is much larger than the Debye length, λ{sub D}. The basis of the method in those works [Walker et al., Phys. Plasmas 13, 032108 (2006); ibid. 15, 123506 (2008); ibid. 17, 113503 (2010)] relies on applying a small amplitude signal of fixed frequency to a probe in a plasma and, through network analyzer-based measurements, determining the complex reflection coefficient, Γ, for varying probe bias, V{sub b}. The frequency range of the applied signal is restricted to avoid sheath resonant effects and ion contributions such that ω{sub pi} ≪ ω ≪ ω{sub pe}, where ω{sub pi} is the ion plasma frequency and ω{sub pe} is the electron plasma frequency. For a given frequency and applied bias, both Re(Z{sub ac}) and Im(Z{sub ac}) are available from Γ. When Re(Z{sub ac}) is plotted versus V{sub b}, a minimum predicted by theory occurs at φ{sub p} [Walker et al., Phys. Plasmas 17, 113503 (2010)]. In addition, Im(Z{sub ac}) appears at, or very near, a maximum at φ{sub p}. As n{sub e} decreases and the sheath expands, the minimum becomes harder to discern. The purpose of this work is to demonstrate that when using network analyzer-based measurements, Γ itself and Im(Z{sub ac}) and their derivatives are useful as accompanying indicators to Re(Z{sub ac}) in these difficult cases. We note the difficulties encountered by the most commonly used plasma diagnostic, the Langmuir probe. Spherical probe data is mainly used in this work, although we present limited data for a cylinder and a disk. To demonstrate the effect of lowered density as a function of probe geometry, we compare the cylinder and disk using only the indicator Re(Z{sub ac})

  12. Constant current loop impedance measuring system that is immune to the effects of parasitic impedances

    NASA Technical Reports Server (NTRS)

    Anderson, Karl F. (Inventor)

    1994-01-01

    A constant current loop measuring system is provided for measuring a characteristic of an environment. The system comprises a first impedance positionable in the environment, a second impedance coupled in series with said first impedance and a parasitic impedance electrically coupled to the first and second impedances. A current generating device, electrically coupled in series with the first and second impedances, provides a constant current through the first and second impedances to produce first and second voltages across the first and second impedances, respectively, and a parasitic voltage across the parasitic impedance. A high impedance voltage measuring device measures a voltage difference between the first and second voltages independent of the parasitic voltage to produce a characteristic voltage representative of the characteristic of the environment.

  13. ACS CCDs daily monitor

    NASA Astrophysics Data System (ADS)

    Sirianni, Marco

    2006-07-01

    This program consists of a set of basic tests to monitor, the read noise, thedevelopment of hot pixels and test for any source of noise in ACS CCDdetectors. The files, biases and dark will be used to create referencefiles for science calibration. This programme will be for the entire lifetime of ACS.For cycle 15 the program will cover 18 months 12.1.06->05.31.08and it has been divied into three different proposal each covering six months.The three poroposal are 11041-11042-11043.

  14. ac bidirectional motor controller

    NASA Technical Reports Server (NTRS)

    Schreiner, K.

    1988-01-01

    Test data are presented and the design of a high-efficiency motor/generator controller at NASA-Lewis for use with the Space Station power system testbed is described. The bidirectional motor driver is a 20 kHz to variable frequency three-phase ac converter that operates from the high-frequency ac bus being designed for the Space Station. A zero-voltage-switching pulse-density-modulation technique is used in the converter to shape the low-frequency output waveform.

  15. Simple method of determining plasma impedance of streamer discharge in atmospheric air.

    PubMed

    Okano, Daisuke

    2011-12-01

    For atmospheric streamer discharges using a lightning impulse generator, we demonstrate a method of determining the plasma impedance in a streamer region by analyzing the periodic attenuated discharge waveforms having high-frequency components. When the streamer region in the plasma can be treated as an equivalent series circuit model including resistance and inductance elements, the regression waveforms obtained by reducing and smoothing the discharge waveforms are analyzed in the equivalent circuit. We found that the streamer resistance increased exponentially with time after the discharge, whereas the streamer inductance and series impedance were constant at 4.0 Ω for longer than the first period of the discharge waveforms. Moreover, the slope of the regression curve increases more rapidly for the positive streamer resistance than for the negative resistance. Finally, the absolute values of the streamer impedance versus time were 3.3-19 Ω and 3.5-9.0 Ω for positive and negative discharges, respectively.

  16. Impedance study of membrane dehydration and compression in proton exchange membrane fuel cells

    NASA Astrophysics Data System (ADS)

    Le Canut, Jean-Marc; Latham, Ruth; Mérida, Walter; Harrington, David A.

    Electrochemical impedance spectroscopy (EIS) is used to measure drying and rehydration in proton exchange membrane fuel cells running under load. The hysteresis between forward and backward acquisition of polarization curves is shown to be largely due to changes in the membrane resistance. Drying tests are carried out with hydrogen and simulated reformate (hydrogen and carbon dioxide), and quasi-periodic drying and rehydration conditions are studied. The membrane hydration state is clearly linked to the high-frequency arc in the impedance spectrum, which increases in size for dry conditions indicating an increase in membrane resistance. Changes in impedance spectra as external compression is applied to the cell assembly show that EIS can separate membrane and interfacial effects, and that changes in membrane resistance dominate. Reasons for the presence of a capacitance in parallel with the membrane resistance are discussed.

  17. Impedance Spectroscopy as a Tool for the Electrochemical Study of Mixed Conducting Ceria

    NASA Astrophysics Data System (ADS)

    Lai, Wei

    2007-10-01

    The A.C. impedance response of mixed ionic and electronic conductors (MIECs) is derived from first principles and quantitatively compared with experimental data of three model systems: pO2 |Pt|Sm0.15Ce0.85O2--delta(1350°C)|Pt| pO2 (system I), pO2 |Pt|Sm0.15Ce0.85O2--delta(1550°C|Pt| pO2 (system II), and pO2 (c)|Ba0.5Sr0.5Co0.8Fe 0.2O3--delta|Sm0.15Ce0.85O 2--delta(1350°C)|Pt| pO2 (a) (system III). For the equilibrium systems I and II, which differ in terms of the preparation of the electrolyte, a broad spectrum of electrical and thermodynamic properties is extracted solely from the measurement of impedance spectra over wide oxygen partial pressure (10--31--0.21 atm) and temperature ranges (500 to 650°C). Electrolyte parameters derived from quantitative fitting of the impedance spectra include the concentration of free electron carriers, the mobilities for both ion and electron transport, the entropy and enthalpy of reduction of Ce4+ to Ce3+, and, for system II, the space charge potential characterizing the grain boundary behavior. In addition, the electrochemical behavior of O2 and H2 at the Pt|ceria interface has been characterized from these measurements. Under oxidizing conditions, the data suggest an oxygen electro-reduction reaction that is rate limited by the dissociated adsorption/discussion of oxygen species on the Pt electrode, similar to Pt|zirconia. Under reducing conditions, the inverse of the electrode polarization resistivity obeys a p-1/4O2 dependence, with an activation energy that is similar to that measured for the electronic conductivity. These results suggest that ceria is electrochemically active for hydrogen electro-oxidation and that the reaction is limited by the rate of removal of electrons from the ceria surface. For the nonequilibrium system III, examined from 550 to 650°C, the cathode oxygen partial pressure was fixed at 0.21 atm and the anode H2 was varied from 0.2 to 1 atm. The combination of Open Circuit Voltage (OCV) measurement

  18. Local impedance imaging of boron-doped polycrystalline diamond thin films

    SciTech Connect

    Zieliński, A.; Ryl, J.; Burczyk, L.; Darowicki, K.

    2014-09-29

    Local impedance imaging (LII) was used to visualise surficial deviations of AC impedances in polycrystalline boron-doped diamond (BDD). The BDD thin film electrodes were deposited onto the highly doped silicon substrates via microwave plasma-enhanced CVD. The studied boron dopant concentrations, controlled by the [B]/[C] ratio in plasma, ranged from 1 × 10{sup 16} to 2 × 10{sup 21} atoms cm{sup −3}. The BDD films displayed microcrystalline structure, while the average size of crystallites decreased from 1 to 0.7 μm with increasing [B]/[C] ratios. The application of LII enabled a direct and high-resolution investigation of local distribution of impedance characteristics within the individual grains of BDD. Such an approach resulted in greater understanding of the microstructural control of properties at the grain level. We propose that the obtained surficial variation of impedance is correlated to the areas of high conductance which have been observed at the grain boundaries by using LII. We also postulate that the origin of high conductivity is due to either preferential boron accumulation, the presence of defects, or sp{sup 2} regions in the intragrain regions. The impedance modulus recorded by LII was in full agreement with the bulk impedance measurements. Both variables showed a decreasing trend with increasing [B]/[C] ratios, which is consistent with higher boron incorporation into BDD film.

  19. Multiple piezo-patch energy harvesters integrated to a thin plate with AC-DC conversion: analytical modeling and numerical validation

    NASA Astrophysics Data System (ADS)

    Aghakhani, Amirreza; Basdogan, Ipek; Erturk, Alper

    2016-04-01

    Plate-like components are widely used in numerous automotive, marine, and aerospace applications where they can be employed as host structures for vibration based energy harvesting. Piezoelectric patch harvesters can be easily attached to these structures to convert the vibrational energy to the electrical energy. Power output investigations of these harvesters require accurate models for energy harvesting performance evaluation and optimization. Equivalent circuit modeling of the cantilever-based vibration energy harvesters for estimation of electrical response has been proposed in recent years. However, equivalent circuit formulation and analytical modeling of multiple piezo-patch energy harvesters integrated to thin plates including nonlinear circuits has not been studied. In this study, equivalent circuit model of multiple parallel piezoelectric patch harvesters together with a resistive load is built in electronic circuit simulation software SPICE and voltage frequency response functions (FRFs) are validated using the analytical distributedparameter model. Analytical formulation of the piezoelectric patches in parallel configuration for the DC voltage output is derived while the patches are connected to a standard AC-DC circuit. The analytic model is based on the equivalent load impedance approach for piezoelectric capacitance and AC-DC circuit elements. The analytic results are validated numerically via SPICE simulations. Finally, DC power outputs of the harvesters are computed and compared with the peak power amplitudes in the AC output case.

  20. Effect of AC Electrostatic Precipitator on Removal Diesel Exhaust Particles

    NASA Astrophysics Data System (ADS)

    Kawakami, Hitomi; Zukeran, Akinori; Yasumoto, Koji; Kubojima, Masaki; Ehara, Yoshiyasu; Yamamoto, Toshiaki

    Collection of low resistive particulate matter (PM) generated from automobile and marine diesel engines or diesel generators have been known to be difficult by the conventional electrostatic precipitators (ESP). The collection efficiency for two types ESPs such as conventional DC energized ESP (DC ESP) and rectangular-AC-waveform energized ESP (AC ESP) were investigated. The low resistive PMs agglomerate like a pearl-chain on the collection plate in DC ESP, so that these are detached from the collection plate by electrostatic repulsion force and wind force. The pearl-chain particles are changed the shape, which is such a spherical, by AC ESP. Therefore, the particle re-entrainment is suppressed by AC ESP.

  1. Determination of Complex Microcalorimeter Parameters with Impedance Measurements

    NASA Technical Reports Server (NTRS)

    Saab, T.; Bandler, S. R.; Chervenak, J.; Figueroa-Feliciano, E.; Finkbeiner, F.; Iyomoto, N.; Kelley, R.; Kilbourne, C. A.; Lindeman, M. A.; Porter, F. S.; Sadleir, J.

    2005-01-01

    The proper understanding and modeling of a microcalorimeter s response requires the accurate knowledge of a handful of parameters, such as C, G, alpha, . . . . While a few of these, such 8s the normal state resistance and the total thermal conductance to the heat bath (G) are directly determined from the DC IV characteristics, some others, notoriously the heat capacity (C) and alpha, appear in degenerate combinations in most measurable quantities. The case of a complex microcalorimeter, i.e. one in which the absorber s heat capacity is connected by a finite thermal impedance to the sensor, and subsequently by another thermal impedance to the heat bath, results in an added ambiguity in the determination of the individual C's and G's. In general, the dependence of the microcalorimeter s complex impedance on these parameters varies with frequency. This variation allows us to determine the individual parameters by fitting the prediction of the microcalorimeter model to the impedance data. We describe in this paper our efforts at characterizing the Goddard X-ray microcalorimeters. Using the parameters determined with this method we them compare the pulse shape and noise spectra predicted by the microcalorimeter model to data taken with the same devices.

  2. Tunable nanogap devices for ultra-sensitive electrochemical impedance biosensing.

    PubMed

    Lu, Yong; Guo, Zheng; Song, Jing-Jing; Huang, Qin-An; Zhu, Si-Wei; Huang, Xing-Jiu; Wei, Yan

    2016-01-28

    A wealth of research has been available discussing nanogap devices for detecting very small quantities of biomolecules by observing their electrical behavior generally performed in dry conditions. We report that a gold nanogapped electrode with tunable gap length for ultra-sensitive detection of streptavidin based on electrochemical impedance technique. The gold nanogap is fabricated using simple monolayer film deposition and in-situ growth of gold nanoparticles in a traditional interdigitated array (IDA) microelectrode. The electrochemical impedance biosensor with a 25-nm nanogap is found to be ultra-sensitive to the specific binding of streptavidin to biotin. The binding of the streptavidin hinder the electron transfer between two electrodes, resulting in a large increase in electron-transfer resistance (Ret) for operating the impedance. A linear relation between the relative Ret and the logarithmic value of streptavidin concentration is observed in the concentration range from 1 pM (picomolar) to 100 nM (nanomolar). The lowest detectable concentration actually measured reaches 1 pM. We believe that such an electrochemical impedance nanogap biosensor provides a useful approach towards biomolecular detection that could be extended to a number of other systems.

  3. Monitoring solid phase synthesis reactions with electrochemical impedance spectroscopy (EIS).

    PubMed

    Hutton, Roger S; Adams, Joseph P; Trivedi, Harish S

    2003-01-01

    This work describes the use of electrochemical impedance spectroscopy (EIS) as a means to monitor solid phase synthesis on resin beads. EIS was used to track changes during the swelling of beads in various solvents, during three typical reactions and throughout cleavage of the final product from the bead. The impedance response was investigated in a chemical reactor and was found to be faintly sensitive to the resin swelling and solvent flow. The position of the electrode within the reactor was found to be critical as polystyrene based beads float or sink dependent upon the solvent used. However, by choosing electrode position it was possible to monitor reaction progress on beads or within the bulk reactant/product mixture. Of the three typical chemical reactions studied impedance spectroscopy successfully followed two. Fitting of the impedance data to an equivalent electrical circuit provided an estimate as to the relative contribution of capacitive and resistive components to the overall response. Kinetic data from two reactions were also modelled, in both cases complex kinetics was observed, in close agreement with other studies.

  4. Three-dimensional electrical impedance tomography: a topology optimization approach.

    PubMed

    Mello, Luís Augusto Motta; de Lima, Cícero Ribeiro; Amato, Marcelo Britto Passos; Lima, Raul Gonzalez; Silva, Emílio Carlos Nelli

    2008-02-01

    Electrical impedance tomography is a technique to estimate the impedance distribution within a domain, based on measurements on its boundary. In other words, given the mathematical model of the domain, its geometry and boundary conditions, a nonlinear inverse problem of estimating the electric impedance distribution can be solved. Several impedance estimation algorithms have been proposed to solve this problem. In this paper, we present a three-dimensional algorithm, based on the topology optimization method, as an alternative. A sequence of linear programming problems, allowing for constraints, is solved utilizing this method. In each iteration, the finite element method provides the electric potential field within the model of the domain. An electrode model is also proposed (thus, increasing the accuracy of the finite element results). The algorithm is tested using numerically simulated data and also experimental data, and absolute resistivity values are obtained. These results, corresponding to phantoms with two different conductive materials, exhibit relatively well-defined boundaries between them, and show that this is a practical and potentially useful technique to be applied to monitor lung aeration, including the possibility of imaging a pneumothorax.

  5. AC/DC converter

    NASA Astrophysics Data System (ADS)

    Jain, Praveen K.

    1992-08-01

    In a system such as a 20 kHz space station primary electrical power distribution system, power conversion from AC to DC is required. Some of the basic requirements for this conversion are high efficiency, light weight and small volume, regulated output voltage, close to unity input power factor, distortionless input current, soft-starting, low electromagnetic interference, and high reliability. An AC-to-DC converter is disclosed which satisfies the main design objectives of such converters for use in space. The converter of the invention comprises an input transformer, a resonant network, a current controller, a diode rectifier, and an output filter. The input transformer is for connection to a single phase, high frequency, sinusoidal waveform AC voltage source and provides a matching voltage isolating from the AC source. The resonant network converts this voltage to a sinusoidal, high frequency bidirectional current output, which is received by the current controller to provide the desired output current. The diode rectifier is connected in parallel with the current controller to convert the bidirectional current into a unidirectional current output. The output filter is connected to the rectifier to provide an essentially ripple-free, substantially constant voltage DC output.

  6. Potentiodynamic electrochemical impedance spectroscopy of silver on platinum in underpotential and overpotential deposition

    NASA Astrophysics Data System (ADS)

    Ragoisha, Genady A.; Bondarenko, Alexander S.

    2004-09-01

    Simultaneous monitoring of ac and dc responses of the electrode-electrolyte interface with potentiodynamic electrochemical impedance spectroscopy (PDEIS) in silver underpotential and overpotential deposition on platinum has confirmed the role of intrinsic Pt surface changes in the irreversibility of Ag underpotential deposition and disclosed exceptionally high stability of Ag monolayer on Pt. PDEIS has been demonstrated to be a convenient means for wet surface chemistry monitoring.

  7. In situ measurement of tissue impedance using an inductive coupling interface circuit.

    PubMed

    Chiu, Hung-Wei; Chuang, Jia-min; Lu, Chien-Chi; Lin, Wei-Tso; Lin, Chii-Wann; Lin, Mu-Lien

    2013-06-01

    In this work, a method of an inductive coupling impedance measurement (ICIM) is proposed for measuring the nerve impedance of a dorsal root ganglion (DRG) under PRF stimulation. ICIM provides a contactless interface for measuring the reflected impedance by an impedance analyzer with a low excitation voltage of 7 mV. The paper develops a calibration procedure involving a 50-Ω reference resistor to calibrate the reflected resistance for measuring resistance of the nerve in the test. A de-embedding technique to build the equivalent transformer circuit model for the ICIM circuit is also presented. A batteryless PRF stimulator with ICIM circuit demonstrated good accuracy for the acute measurement of DRG impedance both in situ and in vivo. Besides, an in vivo animal experiment was conducted to show that the effectiveness of pulsed radiofrequency (PRF) stimulation in relieving pain gradually declined as the impedance of the stimulated nerve increased. The experiment also revealed that the excitation voltage for measuring impedance below 25 mV can prevent the excitation of a nonlinear response of DRG.

  8. Skin-electrode impedance measurement during ECG acquisition: method’s validation

    NASA Astrophysics Data System (ADS)

    Casal, Leonardo; La Mura, Guillermo

    2016-04-01

    Skm-electrode impedance measurement can provide valuable information prior. dunng and post electrocardiographic (ECG) or electroencephalographs (EEG) acquisitions. In this work we validate a method for skm-electrode impedance measurement using test circuits with known resistance and capacitor values, at different frequencies for injected excitation current. Finally the method is successfully used for impedance measurement during ECG acquisition on a subject usmg 125 Hz and 6 nA square wave excitation signal at instrumentation amplifier mput. The method can be used for many electrodes configuration.

  9. Broadband impedance calculations and single bunch instabilities estimations of of the HLS-II storage ring

    NASA Astrophysics Data System (ADS)

    Zhang, Qing-Kun; Wang, Lin; Li, Wei-Min; Gao, Wei-Wei

    2015-12-01

    The upgrade project of the Hefei Light Source storage ring is under way. In this paper, the broadband impedances of resistive wall and coated ceramic vacuum chamber are calculated using the analytic formula, and the wake fields and impedances of other designed vacuum chambers are simulated by CST code, and then a broadband impedance model is obtained. Using the theoretical formula, longitudinal and transverse single bunch instabilities are discussed. With the carefully-designed vacuum chamber, we find that the thresholds of the beam instabilities are higher than the beam current goal. Supported by Natural Science Foundation of China (11175182, 11175180)

  10. Input impedance matching of acoustic transducers operating at off-resonant frequencies.

    PubMed

    Son, Kyu Tak; Lee, Chin C

    2010-12-01

    The input impedance matching technique of acoustic transducers at off-resonant frequencies is reported. It uses an inherent impedance property of transducers and thus does not need an external electric matching circuit or extra acoustic matching section. The input electrical equivalent circuit includes a radiation component and a dielectric capacitor. The radiation component consists of a radiation resistance and a radiation reactance. The total reactance is the sum of the radiation reactance and the dielectric capacitive reactance. This reactance becomes zero at two frequencies where the impedance is real. The transducer size can be properly chosen so that the impedance at one of the zero-crossing frequencies is close to 50 Ω, the output impedance of signal generators. At this off-resonant operating frequency, the reflection coefficient of the transducer is minimized without using any matching circuit. Other than the size, the impedance can also be fine tuned by adjusting the thickness of material that bonds the transducer plate to the substrates. The acoustic impedance of the substrate and that of the bonding material can also be used as design elements in the transducer structure to achieve better transducer matching. Lead titanate piezoelectric plates were bonded on Lucite, liquid crystal polymer (LCP), and bismuth (Bi) substrates to produce various transducer structures. Their input impedance was simulated using a transducer model and compared with measured values to illustrate the matching principle.

  11. Influence of sodium chloride content in electrolyte solution on electrochemical impedance measurements of human dentin

    PubMed Central

    Eldarrat, Aziza; High, Alec; Kale, Girish

    2017-01-01

    Background: The aim of this study was to investigate the influence of sodium chloride (NaCl) content in electrolyte solution on electrochemical impedance measurements of human dentin by employing electrochemical impedance spectroscopy. Materials and Methods: Dentin samples were prepared from extracted molars. Electrochemical impedance measurements were carried out over a wide frequency range (0.01Hz-10MHz). After measurements, samples were characterized using scanning electron microscopy. Results: Electrochemical impedance measurements showed that the mean values of dentin electrical resistance were 4284, 2062, 1336, 53 and 48kΩ at different NaCl contents in electrolyte solution. One-way ANOVA test of mean values of dentin electrical resistance revealed a significant difference (P < 0.0001) as a function of NaCl content in electrolyte solution. Comparing electrical resistance values of dentin samples at 0.05% w/v and 0.9% w/v concentrations were found to be significantly different (P < 0.05 at 95% confidence level). Scanning electron microscopy revealed structure of dentin sample with intertubular dentin matrix and distribution of patent dentinal tubules. Conclusion: This in vitro study indicated, through electrochemical impedance spectroscopy measurements, that electrical resistance of dentin was affected by the concentration of NaCl in electrolyte solution. It is clear from the current study that NaCl concentration in electrolyte solution has a marked influence on dentin electrical resistance. Therefore, this baseline data need to be considered in any future study on dental samples. PMID:28348614

  12. Impedance spectroscopy of food mycotoxins

    NASA Astrophysics Data System (ADS)

    Bilyy, Oleksandr I.; Yaremyk, Roman Ya.; Kotsyumbas, Ihor Ya.; Kotsyumbas, Halyna I.

    2012-01-01

    A new analytical method of high-selective detection of mycotoxins in food and feed are considered. A method is based on optical registration the changes of conduct of the electric polarized bacterial agents in solution at the action of the external gradient electric fields. Measuring are conducted in integrated electrode-optical cuvette of the special construction, which provides the photometric analysis of forward motion of the objects registration in liquid solution under act of the enclosed electric field and simultaneous registration of kinetics of change of electrical impedance parameters solution and electrode system.

  13. Bilateral Impedance Control For Telemanipulators

    NASA Technical Reports Server (NTRS)

    Moore, Christopher L.

    1993-01-01

    Telemanipulator system includes master robot manipulated by human operator, and slave robot performing tasks at remote location. Two robots electronically coupled so slave robot moves in response to commands from master robot. Teleoperation greatly enhanced if forces acting on slave robot fed back to operator, giving operator feeling he or she manipulates remote environment directly. Main advantage of bilateral impedance control: enables arbitrary specification of desired performance characteristics for telemanipulator system. Relationship between force and position modulated at both ends of system to suit requirements of task.

  14. DIFFERENTIAL SOIL IMPEDANCE OBSTACLE DETECTION

    SciTech Connect

    Maximillian J. Kieba; Christopher J. Ziolkowski

    2005-01-17

    This project aimed at developing a new and unique obstacle detection sensor for horizontal directional drilling (HDD) equipment. The development of this new technology will greatly improve the reliability and safety of natural gas HDD construction practices. This sensor utilizes a differential soil impedance measurement technique that will be sensitive to the presence of plastic and ceramic, as well as metallic obstacles. The use of HDD equipment has risen significantly in the gas industry because HDD provides a much more cost-effective and less disruptive method for gas pipe installation than older, trenching methods. However, there have been isolated strikes of underground utilities by HDD equipment, which may have been avoided if methods were available to detect other underground obstacles when using HDD systems. GTI advisors from the gas industry ranked the value of solving the obstacle detection problem as the most important research and development project for GTI to pursue using Federal Energy Regulatory Commission (FERC) funds available through its industry partner, GTI. GTI proposed to develop a prototype down-hole sensor system that is simple and compact. The sensor utilizes an impedance measurement technique that is sensitive to the presence of metallic or non-metallic objects in the proximity of the HDD head. The system will use a simple sensor incorporated into the drill head. The impedance of the soil will be measured with a low frequency signal injected through the drill head itself. A pair of bridge type impedance sensors, mounted orthogonal to one another, is coupled to the soil. Inclusions in the soil will cause changes to the sensor balance distinguishable from homogeneous soil. The sensor will provide range and direction data for obstacles near the HDD head. The goal is to provide a simple, robust system that provides the information required to avoid obstacles. This must be done within the size and ruggedness constraints of the HDD equipment

  15. DIFFERENTIAL SOIL IMPEDANCE OBSTACLE DETECTION

    SciTech Connect

    Maximillian J. Kieba

    2002-08-30

    This project develops a new and unique obstacle detection sensor for horizontal directional drilling (HDD) equipment. The development of this new technology will greatly improve the reliability and safety of natural gas HDD construction practices. This sensor utilizes a differential soil impedance measurement technique that will be sensitive to the presence of plastic and ceramic, as well as metallic obstacles. The use of HDD equipment has risen significantly in the gas industry because HDD provides a much more cost-effective and less disruptive method for gas pipe installation than older, trenching methods. However, there have been isolated strikes of underground utilities by HDD equipment, which may have been avoided if methods were available to detect other underground obstacles when using HDD systems. GTI advisors from the gas industry have ranked the value of solving the obstacle detection problem as the most important research and development project for GTI to pursue using Federal Energy Regulatory Commission (FERC) funds available through its industry partner, GRI. GTI proposes to develop a prototype down-hole sensor system that is simple and compact. The sensor utilizes an impedance measurement technique that is sensitive to the presence of metallic or nonmetallic objects in the proximity of the HDD head. The system will use a thin film sensor conformal with the drill head. The impedance of the soil will be measured with a low frequency signal injected through the drill head itself. A pair of bridge type impedance sensors, mounted orthogonal to one another, is capacitively coupled to the soil. Inclusions in the soil will cause changes to the sensor balance distinguishable from homogeneous soil. The sensor will provide range and direction data for obstacles near the HDD head. The goal is to provide a simple, robust system that provides the information required to avoid obstacles. This must be done within the size and ruggedness constraints of the HDD

  16. DIFFERENTIAL SOIL IMPEDANCE OBSTACLE DETECTION

    SciTech Connect

    Maximillian J. Kieba

    2003-10-01

    This project develops a new and unique obstacle detection sensor for horizontal directional drilling (HDD) equipment. The development of this new technology will greatly improve the reliability and safety of natural gas HDD construction practices. This sensor utilizes a differential soil impedance measurement technique that will be sensitive to the presence of plastic and ceramic, as well as metallic obstacles. The use of HDD equipment has risen significantly in the gas industry because HDD provides a much more cost-effective and less disruptive method for gas pipe installation than older, trenching methods. However, there have been isolated strikes of underground utilities by HDD equipment, which may have been avoided if methods were available to detect other underground obstacles when using HDD systems. GTI advisors from the gas industry have ranked the value of solving the obstacle detection problem as the most important research and development project for GTI to pursue using Federal Energy Regulatory Commission (FERC) funds available through its industry partner, GRI. GTI proposes to develop a prototype down-hole sensor system that is simple and compact. The sensor utilizes an impedance measurement technique that is sensitive to the presence of metallic or nonmetallic objects in the proximity of the HDD head. The system will use a simple sensor incorporated into the drill head. The impedance of the soil will be measured with a low frequency signal injected through the drill head itself. A pair of bridge type impedance sensors, mounted orthogonal to one another, is coupled to the soil. Inclusions in the soil will cause changes to the sensor balance distinguishable from homogeneous soil. The sensor will provide range and direction data for obstacles near the HDD head. The goal is to provide a simple, robust system that provides the information required to avoid obstacles. This must be done within the size and ruggedness constraints of the HDD equipment. Imaging

  17. DIFFERENTIAL SOIL IMPEDANCE OBSTACLE DETECTION

    SciTech Connect

    Maximillian J. Kieba

    2004-02-01

    This project develops a new and unique obstacle detection sensor for horizontal directional drilling (HDD) equipment. The development of this new technology will greatly improve the reliability and safety of natural gas HDD construction practices. This sensor utilizes a differential soil impedance measurement technique that will be sensitive to the presence of plastic and ceramic, as well as metallic obstacles. The use of HDD equipment has risen significantly in the gas industry because HDD provides a much more cost-effective and less disruptive method for gas pipe installation than older, trenching methods. However, there have been isolated strikes of underground utilities by HDD equipment, which may have been avoided if methods were available to detect other underground obstacles when using HDD systems. GTI advisors from the gas industry have ranked the value of solving the obstacle detection problem as the most important research and development project for GTI to pursue using Federal Energy Regulatory Commission (FERC) funds available through its industry partner, GRI. GTI proposes to develop a prototype down-hole sensor system that is simple and compact. The sensor utilizes an impedance measurement technique that is sensitive to the presence of metallic or nonmetallic objects in the proximity of the HDD head. The system will use a simple sensor incorporated into the drill head. The impedance of the soil will be measured with a low frequency signal injected through the drill head itself. A pair of bridge type impedance sensors, mounted orthogonal to one another, is coupled to the soil. Inclusions in the soil will cause changes to the sensor balance distinguishable from homogeneous soil. The sensor will provide range and direction data for obstacles near the HDD head. The goal is to provide a simple, robust system that provides the information required to avoid obstacles. This must be done within the size and ruggedness constraints of the HDD equipment. Imaging

  18. DIFFERENTIAL SOIL IMPEDANCE OBSTACLE DETECTION

    SciTech Connect

    Maximillian J. Kieba; Christopher J. Ziolkowski

    2004-06-30

    This project develops a new and unique obstacle detection sensor for horizontal directional drilling (HDD) equipment. The development of this new technology will greatly improve the reliability and safety of natural gas HDD construction practices. This sensor utilizes a differential soil impedance measurement technique that will be sensitive to the presence of plastic and ceramic, as well as metallic obstacles. The use of HDD equipment has risen significantly in the gas industry because HDD provides a much more cost-effective and less disruptive method for gas pipe installation than older, trenching methods. However, there have been isolated strikes of underground utilities by HDD equipment, which may have been avoided if methods were available to detect other underground obstacles when using HDD systems. GTI advisors from the gas industry have ranked the value of solving the obstacle detection problem as the most important research and development project for GTI to pursue using Federal Energy Regulatory Commission (FERC) funds available through its industry partner, GRI. GTI proposes to develop a prototype down-hole sensor system that is simple and compact. The sensor utilizes an impedance measurement technique that is sensitive to the presence of metallic or nonmetallic objects in the proximity of the HDD head. The system will use a simple sensor incorporated into the drill head. The impedance of the soil will be measured with a low frequency signal injected through the drill head itself. A pair of bridge type impedance sensors, mounted orthogonal to one another, is coupled to the soil. Inclusions in the soil will cause changes to the sensor balance distinguishable from homogeneous soil. The sensor will provide range and direction data for obstacles near the HDD head. The goal is to provide a simple, robust system that provides the information required to avoid obstacles. This must be done within the size and ruggedness constraints of the HDD equipment. Imaging

  19. Impedance Spectroscopic Studies of BiFeO3-Pb(ZrTi)O3 Nanocomposites

    NASA Astrophysics Data System (ADS)

    Choudhary, R. N. P.; Barik, Subrat K.; Katiyar, R. S.

    BiFeO3-Pb(ZrTi)O3 [i.e., (Bi1-xPbx)(Fe1-xZr0.6xTi0.4x)O3 (x = 0.15, 0.25, 0.40, 0.50)] nanocomposites were synthesized using mechanical activation followed by a solid-state reaction technique. The dielectric parameters (capacitance, dissipation factor D, impedance Z and phase angle Φ) of all the samples were measured in a wide range of frequencies (1 kHz-1 MHz) and temperatures (300-630 K) in air atmosphere using an impedance analyzer with low signal amplitude of 500 mV. Electrical properties of the compounds were studied using a complex impedance spectroscopy (CIS) technique. The frequency dependence of electrical data was analyzed in the framework of conductivity and modulus formalisms. AC conductivity spectrum obeys Jonscher's universal power law.

  20. A comprehensive impedance journey to continuous microbial fuel cells.

    PubMed

    Sevda, Surajbhan; Chayambuka, Kudakwashe; Sreekrishnan, T R; Pant, Deepak; Dominguez-Benetton, Xochitl

    2015-12-01

    The aim of the present work was to characterize the impedance response of an air-cathode MFC operating in a continuous mode and to determine intrinsic properties that define its performance which are crucial to be controlled for scalability purposes. The limiting step on electricity generation is the anodic electrochemically-active biofilm, independently of the external resistance, Rext, utilized. However, for Rext below 3 kΩ the internal impedance of the bioanode remained invariable, in good correspondence to the power density profile. The hydraulic retention time (HRT) had an effect on the impedance of both the bioanode and the air-cathode and especially on the overall MFC. The lowest HRT at which the MFC was operable was 3h. Yet, the variation on the HRT did not have a significant impact on power generation. A two constant phase element-model was associated with the EIS response of both bioanode and air-cathode, respectively. Consistency was found between the CPE behaviour and the normal power-law distribution of local resistivity with a uniform dielectric constant, which represented consistent values with the electrical double layer, the Nernst diffusion layer and presumably the biofilm thickness. These results have future implications on MFC monitoring and control, as well as in providing critical parameters for scale-up.

  1. Impedance spectroscopic characterization of gadolinium substituted cobalt ferrite ceramics

    SciTech Connect

    Rahman, Md. T. Ramana, C. V.

    2014-10-28

    Gadolinium (Gd) substituted cobalt ferrites (CoFe{sub 2−x}Gd{sub x}O{sub 4}, referred to CFGO) with variable Gd content (x = 0.0–0.4) have been synthesized by solid state ceramic method. The crystal structure and impedance properties of CFGO compounds have been evaluated. X-ray diffraction measurements indicate that CFGO crystallize in the inverse spinel phase. The CFGO compounds exhibit lattice expansion due to substitution of larger Gd ions into the crystal lattice. Impedance spectroscopy analysis was performed under a wide range of frequency (f = 20 Hz–1 MHz) and temperature (T = 303–573 K). Electrical properties of Gd incorporated Co ferrite ceramics are enhanced compared to pure CoFe{sub 2}O{sub 4} due to the lattice distortion. Impedance spectroscopic analysis illustrates the variation of bulk grain and grain-boundary contributions towards the electrical resistance and capacitance of CFGO materials with temperature. A two-layer heterogeneous model consisting of moderately conducting grain interior (ferrite-phase) regions separated by insulating grain boundaries (resistive-phase) accurately account for the observed temperature and frequency dependent electrical characteristic of CFGO ceramics.

  2. AC Zeeman potentials for atom chip-based ultracold atoms

    NASA Astrophysics Data System (ADS)

    Fancher, Charles; Pyle, Andrew; Ziltz, Austin; Aubin, Seth

    2015-05-01

    We present experimental and theoretical progress on using the AC Zeeman force produced by microwave magnetic near-fields from an atom chip to manipulate and eventually trap ultracold atoms. These AC Zeeman potentials are inherently spin-dependent and can be used to apply qualitatively different potentials to different spin states simultaneously. Furthermore, AC Zeeman traps are compatible with the large DC magnetic fields necessary for accessing Feshbach resonances. Applications include spin-dependent trapped atom interferometry and experiments in 1D many-body physics. Initial experiments and results are geared towards observing the bipolar detuning-dependent nature of the AC Zeeman force at 6.8 GHz with ultracold 87Rb atoms trapped in the vicinity of an atom chip. Experimental work is also underway towards working with potassium isotopes at frequencies of 1 GHz and below. Theoretical work is focused on atom chip designs for AC Zeeman traps produced by magnetic near-fields, while also incorporating the effect of the related electric near-fields. Electromagnetic simulations of atom chip circuits are used for mapping microwave propagation in on-chip transmission line structures, accounting for the skin effect, and guiding impedance matching.

  3. Evaluation of a novel correction procedure to remove electrode impedance effects from broadband SIP measurements

    NASA Astrophysics Data System (ADS)

    Huisman, Johan Alexander; Zimmermann, Egon; Esser, Odilia; Haegel, Franz-Hubert; Treichel, Andrea; Vereecken, Harry

    2016-12-01

    Broadband spectral induced polarization (SIP) measurements of the complex electrical resistivity can be affected by the contact impedance of the potential electrodes above 100 Hz. In this study, we present a correction procedure to remove electrode impedance effects from SIP measurements to improve the accuracy of broadband complex electrical resistivity measurements. The first step in this correction procedure is to estimate the electrode impedance using a measurement with reversed current and potential electrodes. In a second step, this estimated electrode impedance is used to correct SIP measurements based on a simplified electrical model of the SIP measurement system. We evaluated this new correction procedure using SIP measurements on water because of the well-defined dielectric properties. It was found that the difference between the corrected and expected phase of the complex electrical resistivity of water was below 0.1 mrad at 1 kHz for a wide range of electrode impedances. In addition, SIP measurements on a saturated unconsolidated sediment sample with two types of potential electrodes showed that the measured phase of the electrical resistivity was very similar (difference < 0.2 mrad) up to a frequency of 10 kHz after the effect of the different electrode impedances was removed. Finally, SIP measurements on variably saturated unconsolidated sand were made. Here, the plausibility of the phase of the electrical resistivity was improved for frequencies up to 1 kHz, but errors remained for higher frequencies due to the approximate nature of the electrode impedance estimates and some remaining unknown parasitic capacitances that led to current leakage. It was concluded that the proposed correction procedure for SIP measurements improved the accuracy of the phase measurements by an order of magnitude in the kHz frequency range. Further improvement of this accuracy requires a method to accurately estimate parasitic capacitances in situ.

  4. Nested Sphere Model for SQUID-based Impedance Magnetocardiography

    NASA Astrophysics Data System (ADS)

    Vajrala, Vijayanand; Nawarathna, Dharmakeerthi; Claycomb, James; Miller, John

    2004-03-01

    An axisymmetric FEM model is used to predict the SQUID response to changes in tissue conductivity and blood volume during the cardiac cycle. The heart is modeled as a nested sphere inside a cylindrical conducting thorax. The current density and resulting magnetic field is calculated during end systolic, end diastolic and diastolic phases. Modeling results are compared to Impedance Magnetocardiography (IMCG) measurements made using a High-Tc SQUID magnetometer in an unshielded environment .In this measurements, a low amplitude ac current is passed through the body through outer electrodes. Variations in blood flow during the cardiac cycle perturb currents that give rise to time varying magnetic fields amplitudes. Applications to inductive IMCG will be discussed.

  5. Analysis of bio-anode performance through electrochemical impedance spectroscopy.

    PubMed

    ter Heijne, Annemiek; Schaetzle, Olivier; Gimenez, Sixto; Navarro, Lucia; Hamelers, Bert; Fabregat-Santiago, Francisco

    2015-12-01

    In this paper we studied the performance of bioanodes under different experimental conditions using polarization curves and impedance spectroscopy. We have identified that the large capacitances of up to 1 mF·cm(-2) for graphite anodes have their origin in the nature of the carbonaceous electrode, rather than the microbial culture. In some cases, the separate contributions of charge transfer and diffusion resistance were clearly visible, while in other cases their contribution was masked by the high capacitance of 1 mF·cm(-2). The impedance data were analyzed using the basic Randles model to analyze ohmic, charge transfer and diffusion resistances. Increasing buffer concentration from 0 to 50mM and increasing pH from 6 to 8 resulted in decreased charge transfer and diffusion resistances; lowest values being 144 Ω·cm(2) and 34 Ω·cm(2), respectively. At acetate concentrations below 1 mM, current generation was limited by acetate. We show a linear relationship between inverse charge transfer resistance at potentials close to open circuit and saturation (maximum) current, associated to the Butler-Volmer relationship that needs further exploration.

  6. Detection of Chlamydia trachomatis by electrochemical impedance spectroscopy

    NASA Astrophysics Data System (ADS)

    Zheng, Linan

    Chlamydia trachomatis is detected by electrochemical impedance spectroscopy using a mouse monoclonal IgG2a anti-MOMP antibody immobilized onto a Si electrode. Two types of electrochemical cells are used in this study, one with the electrode at the bottom and the other will the electrode on the side. Control experiments with Escherichia coli demonstrate this biosensor is not selective to Chlamydia trachomatis. Another control experiment with Chlamydia trachomatis immobilized onto mouse monoclonal IgG2a isotype antibody coated electrode obtains an increased charge transfer resistance (Rct) which is inversely proportional to the rate of electron transfer. These results demonstrate further investigations are needed to develop the Chlamydia trachomatis impedance biosensor.

  7. Evaluation of non toxic alkyd primers by electrochemical impedance spectroscopy

    SciTech Connect

    Hernandez, L.S.; Garcia, G. |; Lopez, C.

    1998-12-31

    The purpose of this work was to compare the protective capacity of several alkyd primers pigmented with 12.1 volume percent either of calcium phosphate or micronized zinc phosphate as anticorrosive pigments. A paint containing zinc chromate was used as reference. The performance of these paints on steel was assessed through Electrochemical Impedance Spectroscopy (EIS) using a 3% NaCl solution. After 576 hr immersion, the paint with calcium phosphate and specially that with micronized zinc phosphate, showed a better behavior than paint with zinc chromate. Paint rating, using impedance parameters (ionic resistance and capacitance of the paint film, and breakpoint frequency), was in agreement with the visible paint deterioration and corrosion, In addition, there was a good correlation between these parameter and the open circuit corrosion potential of the metallic substrate.

  8. Study of complex impedance spectroscopic properties of Na{sub 2}Pb{sub 2}Pr{sub 2}W{sub 2}Ti{sub 4}Nb{sub 4}O{sub 30} Ceramic

    SciTech Connect

    Biswal, L.; Das, Piyush R.; Behera, Banarji

    2012-07-23

    The polycrystalline sample of Na{sub 2}Pb{sub 2}Pr{sub 2}W{sub 2}Ti{sub 4}Nb{sub 4}O{sub 30} was prepared by high temperature solid state reaction technique. The formation of compounds with an orthorhombic structure was confirmed by X-ray diffraction technique. Surface morphology study showed homogenous distribution of plate and rod like grains over the entire surface with less porosity. The study of effect of temperature on impedance parameters in the frequency range 10{sup 2}-10{sup 6} Hz and temperature range 30-500 Degree-Sign C revealed the presence of both bulk and grain boundary effects above 275 Degree-Sign C. The bulk resistance of the material decreased with rise in temperature exhibiting a typical negative temperature coefficient of resistance (NTCR) behavior like a semiconductor. Both the complex impedance and modulus studies suggested the presence of non-Debye type of relaxation in the materials. The ac conductivity spectrum obeys Johnsche's universal power law.

  9. Effect of Ca2+ substitution on impedance and electrical conduction mechanism of Ba1-xCaxZr0.1Ti0.9O3 (0.00≤x≤0.20) ceramics

    NASA Astrophysics Data System (ADS)

    Mondal, Tanusree; Das, Sayantani; Badapanda, T.; Sinha, T. P.; Sarun, P. M.

    2017-03-01

    The Ca modified Ba1-xCaxZr0.1Ti0.9O3 (BCZT) system for x=0.00-0.20 is synthesized by the high-temperature conventional solid state reaction method. The morphotropic phase boundary (MPB) between the tetragonal and cubic structure is obtained at room temperature for the composition x=0.15. The doping of Ca facilitates the enhancement of the homogeneity of microstructure and growth of the grain size. The phase transition is also confirmed by Raman spectroscopy. In order to explore the effect of Ca concentration variation on the conduction mechanism of BaZr0.1Ti0.9O3 (BZT) ceramic, the frequency dependent ac impedance spectroscopy technique is used at various temperatures. The effect of Ca doping on the electrical properties of BZT is clearly noticeable. The resistance of the grain (bulk) and the grain boundary is increased as a consequence of the increase in the activation energy of Ca substituted BZT samples. The enhanced resistivity of the Ca substituted BZT ceramics is explained in terms of the decrease in the mobility of the charge carriers associated with the lattice distortion. The electric modulus analysis reveals the enhanced capacitance of BCZT ceramics which is in good agreement with the results obtained from complex impedance analysis.

  10. A New Design Method of AC Filter for Static Var Compensator

    NASA Astrophysics Data System (ADS)

    Tamura, Yuji; Irokawa, Shoichi; Takeda, Hideo; Takagi, Kikuo; Noro, Yasuhiro; Ametani, Akihiro

    A new approach of the AC filter design for the SVC (Static Var Compensator) is proposed in this paper. When the SVC consists of TCR(s) (Thyristor Controlled Reactor(s)) or TCT(s) (Thyristor Controlled Transformer(s)) and the AC filter(s), it is required to design AC filter(s) carefully to meet regulation level of harmonic voltage and current at the connection point of the SVC. In general, the AC filter design may require many iterative calculations of the harmonic performance by changing electrical parameters of the AC filter until all the harmonic voltage and current performances at the connection point of the SVC meet the regulation level on various conditions in terms of the filter de-tuning cases and the AC power system conditions. In this respect a new AC filter design approach is proposed, which is innovative on evaluation method of the performance to predetermine the permissible range of the AC filter harmonic impedance on the complex plane. By using this method, the iterations of the calculation can be reduced and it enables more efficient process of the design providing clear accountability of the decision of AC filter parameters.

  11. Electrical Impedance Tomography of Breast Cancer

    DTIC Science & Technology

    2005-06-01

    SUBJECT TERMS Diagnosis of Metastatic Cancer, Magnetic Resonance Imaging, Electrical Impedance Imaging, Electrical Impedance Scanning, MRI current...1) To develop and optimize the necessary hardware and software for Magnetic Resonance Electrical Impedance Tomography (MREIT) and interface it with...of Magnetic Resonance in Medicine (ISMRM) conference and included in the appendix for reference. 2.2.2. Second Year: A series of new phantom studies

  12. [A study of coordinates transform iterative fitting method to extract bio-impedance model parameters bio-impedance model parameters].

    PubMed

    Zhou, Liming; Yang, Yuxing; Yuan, Shiying

    2006-02-01

    A new algorithm, the coordinates transform iterative optimizing method based on the least square curve fitting model, is presented. This arithmetic is used for extracting the bio-impedance model parameters. It is superior to other methods, for example, its speed of the convergence is quicker, and its calculating precision is higher. The objective to extract the model parameters, such as Ri, Re, Cm and alpha, has been realized rapidly and accurately. With the aim at lowering the power consumption, decreasing the price and improving the price-to-performance ratio, a practical bio-impedance measure system with double CPUs has been built. It can be drawn from the preliminary results that the intracellular resistance Ri increased largely with an increase in working load during sitting, which reflects the ischemic change of lower limbs.

  13. Impedance Spectroscopy of Human Blood

    NASA Astrophysics Data System (ADS)

    Mesa, Francisco; Bernal, José J.; Sosa, Modesto A.; Villagómez, Julio C.; Palomares, Pascual

    2004-09-01

    The blood is one of the corporal fluids more used with analytical purposes. When the blood is extracted, immediately it is affected by agents that act on it, producing transformations in its elements. Among the effects of these transformations the hemolysis phenomenon stands out, which consists of the membrane rupture and possible death of the red blood cells. The main purpose of this investigation was the quantification of this phenomenon. A Solartron SI-1260 Impedance Spectrometer was used, which covers a frequency range of work from 1 μHz to 10 MHz, and its accuracy has been tested in the accomplishment of several applications. Measurements were performed on 3 mL human blood samples, from healthy donors. Reactive strips for sugar test of 2 μL, from Bayer, were used as electrodes, which allow gathering a portion of the sample, to be analyzed by the spectrometer. Preliminary results of these measurements are presented.

  14. On Impedance Spectroscopy of Supercapacitors

    NASA Astrophysics Data System (ADS)

    Uchaikin, V. V.; Sibatov, R. T.; Ambrozevich, A. S.

    2016-10-01

    Supercapacitors are often characterized by responses measured by methods of impedance spectroscopy. In the frequency domain these responses have the form of power-law functions or their linear combinations. The inverse Fourier transform leads to relaxation equations with integro-differential operators of fractional order under assumption that the frequency response is independent of the working voltage. To compare long-term relaxation kinetics predicted by these equations with the observed one, charging-discharging of supercapacitors (with nominal capacitances of 0.22, 0.47, and 1.0 F) have been studied by means of registration of the current response to a step voltage signal. It is established that the reaction of devices under study to variations of the charging regime disagrees with the model of a homogeneous linear response. It is demonstrated that relaxation is well described by a fractional stretched exponent.

  15. Electrical impedance tomography of electrolysis.

    PubMed

    Meir, Arie; Rubinsky, Boris

    2015-01-01

    The primary goal of this study is to explore the hypothesis that changes in pH during electrolysis can be detected with Electrical Impedance Tomography (EIT). The study has relevance to real time control of minimally invasive surgery with electrolytic ablation. To investigate the hypothesis, we compare EIT reconstructed images to optical images acquired using pH-sensitive dyes embedded in a physiological saline agar gel phantom treated with electrolysis. We further demonstrate the biological relevance of our work using a bacterial E.Coli model, grown on the phantom. The results demonstrate the ability of EIT to image pH changes in a physiological saline phantom and show that these changes correlate with cell death in the E.coli model. The results are promising, and invite further experimental explorations.

  16. Assessment of cytotoxicity by emerging impedance spectroscopy

    SciTech Connect

    Xiao Caide; Luong, John H.T. . E-mail: john.luong@cnrc-nrc.gc.ca

    2005-08-07

    An on-line and continuous technique based on electric cell substrate impedance sensing (ECIS) was developed for measuring the concentration and time response function of fibroblastic V79 cells exposed to toxicants. Mercury chloride (HgCl{sub 2}), cadmium chloride (CdCl{sub 2}), benzalkonium chloride (BAK), sodium arsenate (Na{sub 2}HAsO{sub 4}), and trinitrobenzene (TNB) were used as five test models. The first four chemicals serve as a model for acute toxicants, and TNB represents a model for long-term cytotoxicity effects. Adhesion, spreading, and proliferation of V79 fibroblastic cells cultured on a microarray of small gold electrodes precoated with fibronectin were detected as resistance changes. The response function was derived to reflect the resistance change as a result of cell attachment, spreading, mitosis and cytotoxicity effect. Exposure of V79 cells to toxicants led to alterations in cell behavior, and therefore, chemical cytotoxicity was easily screened by measuring the response function of the attached and spread cells in the presence of inhibitor. The half inhibition concentration, the required concentration to achieve 50% inhibition, was obtained from the response function to provide dynamic information about cytotoxicity during the course of the assay. A simple mathematical model was developed to describe the responses of ECIS that were related to the adhesion, spreading, and proliferation of V79 fibroblastic cells. The novel results of this paper are mainly characterized by the systematic study of several parameters including the cell number, detection limit, sensor sensitivity, and cytotoxicity, and they may motivate further research and study of ECIS sensors.

  17. Studies of deionization and impedance spectroscopy for blood analyzer

    NASA Astrophysics Data System (ADS)

    Kwong, Charlotte C.; Li, Nan; Ho, Chih-Ming

    2005-11-01

    Blood analysis provides vital information for health conditions. For instance, typical infection response is correlated to an elevated White Blood Cell (WBC) count, while low Red Blood Cell (RBC) count, hemoglobin and hematocrit are caused by anemia or internal bleeding. We are developing two essential modules, deionization (DI) chip and microfluidic cytometer with impedance spectroscopy flow, for enabling the realization of a single platform miniaturized blood analyzer. In the proposed analyzer, blood cells are preliminarily sorted by Dielectrophoretic (DEP) means into sub-groups, differentiated and counted by impedance spectroscopy in a flow cytometer. DEP techniques have been demonstrated to stretch DNA, align Carbon Nanotubes (CNT) and trap cells successfully. However, DEP manipulation does not function in biological media with high conductivity. The DI module is designed to account for this challenge. H Filter will serve as an ion extraction platform in a microchamber. Sample and buffer do not mix well in micro scale allowing the ions being extracted by diffusion without increasing the volume. This can keep the downstream processing time short. Micro scale hydrodynamic focusing is employed to place single cell passing along the central plane of the flow cytometer module. By applying an AC electrical field, suspended cells are polarized, membrane capacitance C m, cytoplasm conductivity σ c, and cytoplasm permittivity ɛ c will vary as functions of frequency. Tracing back the monitored current, the numbers of individual cell species can be evaluated.

  18. Dielectric and impedance behavior of neodymium substituted strontium hexaferrite

    NASA Astrophysics Data System (ADS)

    Bhat, Bilal Hamid; Samad, Rubiya; Want, Basharat

    2016-09-01

    In this study, dielectric behavior and complex impedance of neodymium (Nd) substituted strontium hexaferrite system: Sr1- x Nd x Fe12O19 ( x = 0.0, 0.05, 0.1, 0.15, 0. 20), synthesized by citrate precursor technique, have been evaluated as a function of applied frequency and temperature. Variation of dielectric constant and dielectric loss with frequency shows the identical behavior for all the compositions. The value of dielectric constant increases with Nd doping. Relaxation process is observed in the composition x = 0.20, and the peaks in this composition shift toward the higher-frequency region as the temperature increases. The dielectric constants show temperature-independent behavior at low temperature, whereas at higher temperatures it increases for all the frequencies. The AC conductivity follows Jonscher's power law, showing that conduction mechanism is due to polaron hopping. Complex impedance as a function of composition and temperature is used to examine the role of grain and grain boundary in the prepared material. Cole-cole plot shows only one semicircle up to x = 0.15, while as for x = 0.20 two semicircles are observed. The conduction mechanism is explained on the basis of both grain and grain boundary.

  19. On the Use of Experimental Methods to Improve Confidence in Educed Impedance

    NASA Technical Reports Server (NTRS)

    Jones, Michael G.; Watson, Willie R.

    2011-01-01

    Results from impedance eduction methods developed by NASA Langley Research Center are used throughout the acoustic liner community. In spite of recent enhancements, occasional anomalies persist with these methods, generally at frequencies where the liner produces minimal attenuation. This investigation demonstrates an experimental approach to educe impedance with increased confidence over a desired frequency range, by combining results from successive tests with different cavity depths. A series of tests is conducted with three wire-mesh facesheets, for which the results should be weakly dependent on source sound pressure level and mean grazing flow speed. First, a raylometer is used to measure the DC flow resistance of each facesheet. These facesheets are then mounted onto a frame and a normal incidence tube is used to determine their respective acoustic impedance spectra. A comparison of the acoustic resistance component with the DC flow resistance for each facesheet is used to validate the measurement process. Next, each facesheet is successively mounted onto three frames with different cavity depths, and a grazing flow impedance tube is used to educe their respective acoustic impedance spectra with and without mean flow. The no-flow results are compared with those measured in the normal incidence tube to validate the impedance eduction method. Since the anti-resonance frequency varies with cavity depth, each sample provides robust results over a different frequency range. Hence, a combination of results can be used to determine the facesheet acoustic resistance. When combined with the acoustic reactance, observed to be weakly dependent on the source sound pressure level and grazing flow Mach number, the acoustic impedance can be educed with increased confidence. Representative results of these tests are discussed, and the complete database is available in electronic format upon request.

  20. An impedance matching of femoral-popliteal arterial grafts: a theoretical study.

    PubMed

    Hirayama, H; Nishimura, T; Fukuyama, Y

    1997-05-01

    We have proposed a mathematical method to investigate the matching conditions for an arterial graft in the femoral-popliteal region from a mechanical stand-point. Pulsatory blood flow, arterial wall motions, and conservation law are expressed by linear dynamical equations based on strict mechanical and constitutional considerations. To express the physiological blood flow in an actual arterial system, the tethering effects from the surrounding tissue and wall tensions were incorporated. The physiological parameters of arterial wall and tethering were utilized from reported experimental data. By complex analysis, mathematical expressions for the local impedance and reflection coefficient were obtained. They include not only blood properties such as viscosity and density, but also arterial properties including elastic modulus, radius, Poisson ratio, wall thickness, wall tension, frequency, and tethering effects from surrounding tissue. A matching condition was defined for minimizing the local impedance and reflection coefficient. The biophysical background was to reduce any mechanical mismatches, thus minimizing the disturbance of the flow velocity profile and shear stress distribution within the artery. Impedance matching in turn diminishes the negative factors for graft substitution represented by intimal hyperplasia and thrombosis. The calculated impedance and reflection coefficient inversed parabolically to functions of the resistance of the host artery, and there was one host arterial resistance that minimized the impedance and reflection coefficient. The present analysis revealed that for matching host artery with an elevated resistance, the dynamic elastic modulus of the wall of the graft that minimizes the impedance and reflection coefficient was increased. This indicates that for a host artery with a high resistance, an impedance matched stiff wall graft is preferable. For a large radius and a compliant host artery on the other hand, a large compliant graft

  1. Structural and impedance properties of KBa{sub 2}V{sub 5}O{sub 15} ceramics

    SciTech Connect

    Behera, Banarji; Nayak, P.; Choudhary, R.N.P.

    2008-02-05

    The polycrystalline sample of KBa{sub 2}V{sub 5}O{sub 15} ceramics was prepared by a mixed oxide method at low temperature (i.e., at 560 deg. C). The formation of the compound was confirmed using an X-ray diffraction technique at room temperature. Scanning electron micrograph of the material showed uniform grain distribution on the surface of the sample. Detailed studies of dielectric properties of the compound as a function of temperature at different frequencies suggest that the compound has a dielectric anomaly of ferroelectric to paraelectric type at 323 deg. C, and exhibits diffuse phase transition. Electrical properties of the material were analyzed using a complex impedance technique. The Nyquists plot showed the presence of both grain (>10{sup 3} Hz) and the grain boundary (<10{sup 3} Hz) effects in the material. Studies of electrical conductivity over a wide temperature range suggest that the compound exhibits the negative temperature coefficient of resistance behavior. The ac conductivity spectrum was found to obey Jonscher's universal power law.

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

    NASA Technical Reports Server (NTRS)

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

    1988-01-01

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

  3. Impedance spectra of hot, dry silicate minerals and rocks: qualitative interpretation of spectra

    USGS Publications Warehouse

    Huebner, J.S.; Dillenburg, R.G.

    1995-01-01

    Impedance spectroscopy helps distinguish the contributions that grain interiors and grain boundaries make to electrical resistance of silicate minerals and rocks. Olivine, orthopyroxene, clinopyroxenes, and both natural and synthetic clinopyroxenite were measured. A network of electrical elements is presented for use in interpreting impedance spectra and conductive paths in hot or cold, wet or dry, minerals and rocks at any pressure. In dry rocks, a series network path predominates; in wet rocks, aqueous pore fluid and crystals both conduct. Finite resistance across the sample-electrode interface is evidence that electronic charge carriers are present at the surface, and presumably within, the silicate minerals and rocks measured. -from Authors

  4. Fluid mechanical model of the acoustic impedance of small orifices

    NASA Technical Reports Server (NTRS)

    Hersh, A. S.; Rogers, T.

    1976-01-01

    A fluid mechanical model of the acoustic behavior of small orifices is presented which predicts orifice resistance and reactance as a function of incident sound pressure level, frequency, and orifice geometry. Agreement between predicted and measured values is excellent. The model shows the following: (1) The acoustic flow in immediate neighborhood of the orifice can be modeled as a locally spherical flow. Within this near field, the flow is, to a first approximation, unsteady and incompressible. (2) At very low sound pressure levels, the orifice viscous resistance is directly related to the effect of boundary-layer displacement along the walls containing the orifice, and the orifice reactance is directly related to the inertia of the oscillating flow in the neighborhood of the orifice. (3) For large values of the incident acoustic pressure, the impedance is dominated by nonlinear jet-like effects. (4) For low values of the pressure, the resistance and reactance are roughly equal.

  5. Impedance adaptation methods of the piezoelectric energy harvesting

    NASA Astrophysics Data System (ADS)

    Kim, Hyeoungwoo

    In this study, the important issues of energy recovery were addressed and a comprehensive investigation was performed on harvesting electrical power from an ambient mechanical vibration source. Also discussed are the impedance matching methods used to increase the efficiency of energy transfer from the environment to the application. Initially, the mechanical impedance matching method was investigated to increase mechanical energy transferred to the transducer from the environment. This was done by reducing the mechanical impedance such as damping factor and energy reflection ratio. The vibration source and the transducer were modeled by a two-degree-of-freedom dynamic system with mass, spring constant, and damper. The transmissibility employed to show how much mechanical energy that was transferred in this system was affected by the damping ratio and the stiffness of elastic materials. The mechanical impedance of the system was described by electrical system using analogy between the two systems in order to simply the total mechanical impedance. Secondly, the transduction rate of mechanical energy to electrical energy was improved by using a PZT material which has a high figure of merit and a high electromechanical coupling factor for electrical power generation, and a piezoelectric transducer which has a high transduction rate was designed and fabricated. The high g material (g33 = 40 [10-3Vm/N]) was developed to improve the figure of merit of the PZT ceramics. The cymbal composite transducer has been found as a promising structure for piezoelectric energy harvesting under high force at cyclic conditions (10--200 Hz), because it has almost 40 times higher effective strain coefficient than PZT ceramics. The endcap of cymbal also enhances the endurance of the ceramic to sustain ac load along with stress amplification. In addition, a macro fiber composite (MFC) was employed as a strain component because of its flexibility and the high electromechanical coupling

  6. Acoustic input impedance of the avian inner ear measured in ostrich (Struthio camelus).

    PubMed

    Muyshondt, Pieter G G; Aerts, Peter; Dirckx, Joris J J

    2016-09-01

    In both mammals and birds, the mechanical behavior of the middle ear structures is affected by the mechanical impedance of the inner ear. In this study, the aim was to quantify the acoustic impedance of the avian inner ear in the ostrich, which allows us to determine the effect on columellar vibrations and middle ear power flow in future studies. To determine the inner ear impedance, vibrations of the columella were measured for both the quasi-static and acoustic stimulus frequencies. In the frequency range of 0.3-4 kHz, we used electromagnetic stimulation of the ossicle and a laser Doppler vibrometer to measure the vibration response. At low frequencies, harmonic displacements were imposed on the columella using piezo stimulation and the resulting force response was measured with a force sensor. From these measurement data, the acoustic impedance of the inner ear could be determined. A simple RLC model in series of the impedance measurements resulted in a stiffness reactance of KIE = 0.20·10(12) Pa/m³, an inertial impedance of MIE = 0.652·10(6) Pa s(2)/m³, and a resistance of RIE = 1.57·10(9) Pa s/m. We found that values of the inner ear impedance in the ostrich are one to two orders in magnitude smaller than what is found in mammal ears.

  7. Behind the (impedance) baseline in children.

    PubMed

    Salvatore, S; Salvatoni, A; Van Steen, K; Ummarino, D; Hauser, B; Vandenplas, Y

    2014-01-01

    Impedance baseline is a new parameter recently related to esophageal integrity. The aim of this study was to assess the effect of different factors on impedance baseline in pediatric patients. We analyzed the impedance baseline of 800 children with symptoms of gastroesophageal reflux. Mean impedance baseline was automatically calculated throughout 24-hour tracings. The presence of different age groups and of esophagitis was evaluated. Unpaired t-test, Spearman rank correlation, polynomial, and regression plot were used for statistical analysis. Age-related percentile curves were created. We considered a P-value<0.05 as statistically significant. Impedance baseline was significantly (P<0.001) lower in younger compared to older children up to 48 months. The mean increase of baseline per month was much higher in the first 36 months of life (47.5 vs. 2.9 Ohm in Channel 1 and 29.9 vs. 2.3 Ohm in Channel 6, respectively) than in older ages. Patients with esophagitis showed significantly decreased impedance baseline (P<0.05). Infants (especially in the first months of life) and young children present a significantly lower impedance baseline compared to older children both in proximal and distal esophagus. The presence of esophagitis may also determine a decreased impedance baseline regardless of the age of the patients.

  8. Active impedance matching of complex structural systems

    NASA Technical Reports Server (NTRS)

    Macmartin, Douglas G.; Miller, David W.; Hall, Steven R.

    1991-01-01

    Viewgraphs on active impedance matching of complex structural systems are presented. Topics covered include: traveling wave model; dereverberated mobility model; computation of dereverberated mobility; control problem: optimal impedance matching; H2 optimal solution; statistical energy analysis (SEA) solution; experimental transfer functions; interferometer actuator and sensor locations; active strut configurations; power dual variables; dereverberation of complex structure; dereverberated transfer function; compensators; and relative power flow.

  9. Beam impedance of a split cylinder

    SciTech Connect

    Lambertson, G.

    1990-04-01

    A common geometry for position electrodes at moderately low frequencies is the capacitive pickup consisting of a diagonally- divided cylinder that encloses the beam trajectory. For the simplified system here, a relatively direct approach will given the longitudinal and transverse beam impedances (Z{parallel}and Z{perpendicular}) at low frequencies. This paper discusses the determination of this impedance.

  10. Transverse impedance localization using intensity dependent optics

    SciTech Connect

    Calaga,R.; Arduini, G.; Metral, E.; Papotti, G.; Quatraro, D.; Rumolo, G.; Salvant, B.; Tomas, R.

    2009-05-04

    Measurements of transverse impedance in the SPS to track the evolution over the last few years show discrepancies compared to the analytical estimates of the major contributors. Recent measurements to localize the major sources of the transverse impedance using intensity dependent optics are presented. Some simulations using HEADTAIL to understand the limitations of the reconstruction and related numerical aspects are also discussed.

  11. Possibilities of electrical impedance tomography in gynecology

    NASA Astrophysics Data System (ADS)

    V, Trokhanova O.; A, Chijova Y.; B, Okhapkin M.; V, Korjenevsky A.; S, Tuykin T.

    2013-04-01

    The paper describes results of comprehensive EIT diagnostics of mammary glands and cervix. The data were obtained from examinations of 170 patients by EIT system MEM (multi-frequency electrical impedance mammograph) and EIT system GIT (gynecological impedance tomograph). Mutual dependence is discussed.

  12. LHC Kicker Beam-Impedance Calculation

    SciTech Connect

    Lambertson, G.R.

    1998-10-01

    Longitudinal and transverse beam impedances are calculated for the injection kickers designed for use in the CERN large hadron col- Iider. These combine the contributions of a ceramic beam tube with conducting stripes and a traveling-wave kicker magnet. The results show peak impedances of 1300 ohm longitudinal and 8 Mfl/m trans- verse for four units per ring.

  13. Effect of 60Co gamma irradiation on dielectric and complex impedance properties of Dy3+ substituted Ni-Zn nanoferrites

    NASA Astrophysics Data System (ADS)

    Veena, M.; Somashekarappa, A.; Shankaramurthy, G. J.; Jayanna, H. S.; Somashekarappa, H. M.

    2016-12-01

    Nanocrystalline Ni1-xZnxFe2-yDyyO4 (x=0.0, 0.2, 0.4, 0.6, 0.8, 1.0; y=0.0 and 0.1) ferrites were synthesized by combustion method. Ni-Zn-Dy nanoferrites were investigated by X-ray diffraction, scanning electron microscopy, dielectric and impedance properties, before and after γ-irradiation process by 60Co γ-radiation with a dose rate of 310 kGy. The lattice parameter of irradiated samples increased attributed to the conversion of smaller size Fe3+ ions to larger size Fe2+ ions on ionizing effect of gamma radiation. Experimental results reveal that reduction in dielectric constant (ε‧), loss tangent (tan δ), real (Z‧) and imaginary (Z‧‧) impedance and increase in ac conductivity (σac) have been increased with increasing in frequency. It was found that ε‧, tan δ, σac increase, Z‧‧ and Z‧‧ reach a maximum value and thereafter decrease with further Zn ion substitution. The values of ε‧, tan δ and σac decrease with Dy3+ substitution and enhanced after irradiation. The complex impedance analysis suggesting predominant contribution to conduction was through the grain boundary.

  14. Rapid Impedance Spectrum Measurements for Onboard State-of-Health Applications

    SciTech Connect

    Jon P. Christophersen; John L. Morrison; Chinh D. Ho

    2012-06-01

    Rapid impedance measurements can provide a useful online tool for improved state-of-health estimation. A validation study has been initiated at the Idaho National Laboratory for a rapid impedance technique known as Harmonic Compensated Synchronous Detection. This technique enables capturing the impedance spectra over a broad frequency range within about ten seconds. Commercially available lithium-ion cells are being calendar-life aged at 50°C with reference performance tests at 30°C every 32.5 days to gauge degradation The cells have completed the first set of reference performance tests and preliminary results are presented. The spectra change as a function of temperature and depth-of-discharge condition, as expected. The data indicate that the rapid impedance measurement technique is a benign measurement tool that can be successfully used to gauge changes in the corresponding pulse resistance.

  15. In vivo impedance measurements on nerves and surrounding skeletal muscles in rats and human body.

    PubMed

    Prokhorov, E; Llamas, F; Morales-Sánchez, E; González-Hernández, J; Prokhorov, A

    2002-05-01

    The aim of the work was to use impedance measurements to find the location of nerves under the human skin. In vivo impedance measurements were performed on exposed nervous and muscular tissues of rats. Similarly, the impedance measurements were also performed on the skin of six men, over the median nerve at the wrist, as well as 4-5 mm away from this location. Results obtained with rats have shown that the relative permittivity and conductivity of nerves are larger (by almost two orders of magnitude) than those observed for the muscular tissues surrounding the nerve. The results obtained on human skin in the frequency range of 20-200 kHz, when the electrodes were placed over the nerve, show lower resistance and higher capacitance than in the other areas measured. These preliminary results indicate that it may be possible to use impedance measurements to find the location of exposed nerves and also nerves under the skin.

  16. Structural health monitoring using piezoelectric impedance measurements.

    PubMed

    Park, Gyuhae; Inman, Daniel J

    2007-02-15

    This paper presents an overview and recent advances in impedance-based structural health monitoring. The basic principle behind this technique is to apply high-frequency structural excitations (typically greater than 30kHz) through surface-bonded piezoelectric transducers, and measure the impedance of structures by monitoring the current and voltage applied to the piezoelectric transducers. Changes in impedance indicate changes in the structure, which in turn can indicate that damage has occurred. An experimental study is presented to demonstrate how this technique can be used to detect structural damage in real time. Signal processing methods that address damage classifications and data compression issues associated with the use of the impedance methods are also summarized. Finally, a modified frequency-domain autoregressive model with exogenous inputs (ARX) is described. The frequency-domain ARX model, constructed by measured impedance data, is used to diagnose structural damage with levels of statistical confidence.

  17. AC Optimal Power Flow

    SciTech Connect

    2016-10-04

    In this work, we have implemented and developed the simulation software to implement the mathematical model of an AC Optimal Power Flow (OPF) problem. The objective function is to minimize the total cost of generation subject to constraints of node power balance (both real and reactive) and line power flow limits (MW, MVAr, and MVA). We have currently implemented the polar coordinate version of the problem. In the present work, we have used the optimization solver, Knitro (proprietary and not included in this software) to solve the problem and we have kept option for both the native numerical derivative evaluation (working satisfactorily now) as well as for analytical formulas corresponding to the derivatives being provided to Knitro (currently, in the debugging stage). Since the AC OPF is a highly non-convex optimization problem, we have also kept the option for a multistart solution. All of these can be decided by the user during run-time in an interactive manner. The software has been developed in C++ programming language, running with GCC compiler on a Linux machine. We have tested for satisfactory results against Matpower for the IEEE 14 bus system.

  18. Electrical impedance characterization of cell growth on interdigitated microelectrode array.

    PubMed

    Lee, Gi Hyun; Pyun, Jae-Chul; Cho, Sungbo

    2014-11-01

    Electrical cell-substrate impedance sensing is a method for label-free and real-time monitoring of biological cells, which has been increasingly employed in the diagnostic and pharmaceutical industries. In this study, we fabricated an interdigitated electrode (IDE) array, which consists of 10 fingers, with a length of 1.2 mm, width of 50 μm, spacing of 50 μm, and thickness of 75 nm. The impedance spectra of the fabricated IDE were measured without or with cells in the frequency range of 100 Hz to 100 kHz using a lock-in amplifier based system and characterized by equivalent circuit modelling. Regarding the total impedance as a series resistance (R) and capacitance (C) model, R and C parameters were traced at a selected frequency during cell growth. It was able to monitor cell adherence and proliferation dependent on the behaviours and characteristics of cells on the fabricated IDE array by monitoring RC parameters. The degree of changes in RC value during cell growth was dependent on the type of cells used.

  19. Surface characterization of nanostructured 'black silicon' using impedance spectroscopy

    NASA Astrophysics Data System (ADS)

    Duan, Wenqi; Toor, Fatima

    2016-09-01

    In this work, we utilize electrochemical impedance spectroscopy (EIS) to study the electronic characteristics of nanostructured silicon (Si) fabricated using the metal-assisted chemical etched (MACE) process. The nanostructured Si fabricated using the MACE process results in a density graded surface that reduces the broadband surface reflection of Si making it appear almost black, which coins it the name `black Si' (bSi). We study two bSi samples prepared using varying MACE times (20s and 40s) and a reference bare silicon sample using EIS between 1 MHz and 1 Hz frequencies. At an illumination intensity created with the use of a tungsten lamp source calibrated to output an intensity of 1-Sun (1000 W/m2), the impedance behavior at bias potentials in both the forward and reverse bias ranging between -1 V and 1 V are studied. We also study the effect of illumination wavelength by using bandpass filters at 400 nm and 800 nm. The results indicate that the charge transfer resistance (Rct) decreases as the surface roughness of the electrodes increases and as the illumination wavelength increases. We also find that the constant phase element (CPE) impedance of the electrodes increases with increasing surface roughness. These results will guide our future work on high efficiency bSi solar cells.

  20. Identification of /sup 233/Ac

    SciTech Connect

    Chu, Y.Y.; Zhou, M.L.

    1983-09-01

    We report in this paper identification of the new isotope /sup 233/Ac. Uranium targets were irradiated with 28 GeV protons; after rapid retrieval of the target and separation of actinium from thorium, /sup 233/Ac was allowed to decay into the known /sup 233/Th daughter. Exhaustive chemical purification was employed to permit the identification of /sup 233/Th via its characteristic ..gamma.. radiations. The half-life derived for /sup 233/Ac from several experiments is 2.3 +- 0.3 min. The production cross section for /sup 233/Ac is 100 ..mu..b.

  1. Method to detect the end-point for PCR DNA amplification using an ionically labeled probe and measuring impedance change

    DOEpatents

    Miles, Robin R.; Belgrader, Phillip; Fuller, Christopher D.

    2007-01-02

    Impedance measurements are used to detect the end-point for PCR DNA amplification. A pair of spaced electrodes are located on a surface of a microfluidic channel and an AC or DC voltage is applied across the electrodes to produce an electric field. An ionically labeled probe will attach to a complementary DNA segment, and a polymerase enzyme will release the ionic label. This causes the conductivity of the solution in the area of the electrode to change. This change in conductivity is measured as a change in the impedance been the two electrodes.

  2. Impedance matching at arterial bifurcations.

    PubMed

    Brown, N

    1993-01-01

    Reflections of pulse waves will occur in arterial bifurcations unless the impedance is matched continuously through changing geometric and elastic properties. A theoretical model is presented which minimizes pulse wave reflection through bifurcations. The model accounts for the observed linear changes in area within the bifurcation, generalizes the theory to asymmetrical bifurcations, characterizes changes in elastic properties from parent to daughter arteries, and assesses the effect of branch angle on the mechanical properties of daughter vessels. In contradistinction to previous models, reflections cannot be minimized without changes in elastic properties through bifurcations. The theoretical model predicts that in bifurcations with area ratios (beta) less than 1.0 Young's moduli of daughter vessels may be less than that in the parent vessel if the Womersley parameter alpha in the parent vessel is less than 5. Larger area ratios in bifurcations are accompanied by greater increases in Young's moduli of branches. For an idealized symmetric aortic bifurcation (alpha = 10) with branching angles theta = 30 degrees (opening angle 60 degrees) Young's modulus of common iliac arteries relative to that of the distal abdominal aorta has an increase of 1.05, 1.68 and 2.25 for area ratio of 0.8, 1.0 and 1.15, respectively. These predictions are consistent with the observed increases in Young's moduli of peripheral vessels.(ABSTRACT TRUNCATED AT 250 WORDS)

  3. Interdigitated microelectrode-based microchip for electrical impedance spectroscopic study of oral cancer cells.

    PubMed

    Mamouni, Jaouad; Yang, Liju

    2011-12-01

    In this study, electric/electrochemical impedance spectroscopy and cyclic voltammetry were used to study the cellular activities of oral cancer cell line CAL 27, including the kinetics of cell adhesion, spreading, and cell proliferation on interdigitated microelectrodes (IMEs). Impedance spectra of CAL 27 cells on IMEs electrodes were obtained in cell growth medium and in 0.1 M PBS with 50 mM [Fe(CN)₆]³⁻/⁴⁻ as redox probe. Equivalent circuits were used to model both cases. In cell growth medium, impedance spectra allowed us to analyze the changes in capacitance and resistance due to cell attachment on the IMEs over the entire experiment period. It was found that cell spreading caused the most significant decrease in capacitance component and slight increase in resistance component. Impedance change at given frequencies (between 10 kHz to 100 kHz) was found to be linearly increased with increasing cell number of CAL 27 on the IMEs. In comparison with non-cancer oral epithelial cells (Het-1A), at equal cell number, cancer cells always generated impedance several folds higher than that of non-cancer cells. In the presence of [Fe(CN)₆]³⁻/⁴⁻, impedance spectra allowed us to analyze the change in electron transfer resistance of IMEs due to cell attachment, in which an increase trend was observed at 24 h with increasing cell number from 2500 cells to 10,000 cells on IMEs. Double layer capacitance was also affected by cell attachment, and a decrease in double layer capacitance was observed with increasing cell number on the electrodes. Cyclic voltammetric measurements correlated well with the impedance results. The results of this study demonstrated the use of electrochemical approaches to obtain and understand cellular behaviors/activities of oral cancer cells, potentially providing useful tools for cancer cell research.

  4. Effect of Resonator Axis Skew on Normal Incidence Impedance

    NASA Technical Reports Server (NTRS)

    Parrott, Tony L.; Jones, Michael G.; Homeijer, Brian

    2003-01-01

    in the nature of a progress report and is limited to examining the implications of resonator axis skew on the composite normal incidence impedance of an array of resonator channels. Specifically, experimental results are compared with a modified impedance prediction model for highaspect- ratio, rectangular, resonator channels with varying amounts of skew relative to the incident particle velocity. It is shown that for resonator channel widths of 1 to 2 mm, aspect ratios of 25 to 50, and skew angles of zero to sixty degrees, the surface impedance of test models can be predicted with good accuracy. Predicted resistances and reactances are particularly well correlated through the first resonance and first anti-resonance for all six test models investigated. Beyond the first anti-resonance, the impedance prediction model loses the ability to predict details of resistance and reactance but still predicts the mean trends very well.

  5. Unfolding plasma density from cylindrical monopole impedance measurements in ionosphere

    NASA Astrophysics Data System (ADS)

    Kiraga, A.

    2003-04-01

    Several common problems occur in measurement techniques and interpretation of plasma natural emissions and impedance data. Antenna characteristics are of prime importance in equivalent circuit analysis. Spacecraft - plasma interaction contributes to variability of equivalent circuit impedances and e.m.f. components and imposes constrains on usefulness of experimental data. In order to have independent, built in estimate of local plasma frequency and to get deeper insight into properties of equivalent circuit for wave diagnostics, impedance measurement was integrated with radio receivers on the ACTIVE, APEX and CORONAS satellites. Impedance measurements of 7.5m long monopole were performed in frequency range .1-10MHz with the frequency step of 50kHz, in voltage divider configuration. Due to high inclination of 82.5deg and altitude range of 500-3000km, data from very different plasmas were collected. Data can be split into quasi normal, disturbed and very disturbed measurements. Equivalent circuit structure evolved in attempt to match even very disturbed measurements. For quasi normal measurements, satisfactory matching is obtained with computed gyrofrequency fc and fitted plasma frequency fn, stray capacitance Cs and capacitance Cv of phenomenological vacuum sheath. With formulas for monopole impedance in cold magnetoplasma, two basic pectral structures are explained. For sufficiently magnetized plasma (roughly fn/fc<2 if Cs=20pF), circuit parallel resonance frequency Fr falls into upper hybrid band (max(fn,fc),fu), resonance amplitude is reduced by high antenna resistance and horn like absolute maximum points fu. For values of fn/fc ratio, greater then critical, Fr is less than fn and broad absolute maximum at Fr follows from low antenna resistance. Further increase of fn/fc results in increasing lag of Fr behind fn. Critical ratio fn/fc increases with decreasing stray capacitance Cs. It follows from data analysis that stray capacitance may change in flight, at

  6. Anisotropy of human muscle via non invasive impedance measurements. Frequency dependence of the impedance changes during isometric contractions

    NASA Astrophysics Data System (ADS)

    Kashuri, Hektor

    In this thesis we present non invasive muscle impedance measurements using rotatable probes extending the work done by Aaron et al. (1997) by measuring not only the real part of the impedance but the imaginary part as well. The results reveal orientations of underlying muscle fibers via minima in resistance and reactance versus angle curves, suggesting this method as potentially useful for studying muscle properties in clinical and physiological research. Calculations of the current distribution for a slab of material with anisotropic conductivity show that the current distribution depends strongly on the separation of two current electrodes and as well as on its conducting anisotropy. Forearm muscle impedance measurements at 50 kHz done by Shiffman et al. (2003) had shown that both resistance (R) and reactance (X) increase during isometric contraction. We have extended these measurements in the 3 to 100 kHz range and we found that resistance (R) and reactance (X) both increase and their changes increased or decreased at frequency dependent rates. Analysis based on circuit models of changes in R and X during the short contraction pulses showed that the extra cellular fluid resistance increased by 3.9 +/- 1.4 %, while the capacitance increased by 5.6 +/- 2 %. For long contraction pulses at very low frequencies: (1) there was practically no change in R during contraction, which implies that these changes are due to cellular membrane or intracellular effects with the extra cellular water component not participating, and (2) in post contraction stage there were no morphological changes which means that drifts in R can only be due to physiological changes. Following Shiffman et al. (2003) we measured impedance changes of R and X during a triangular shaped pulse of force generated via isometric forearm muscle contraction at 50 kHz. We measured these changes in 3-100 kHz frequency range for a stair case pulse of forces and the results showed that they are frequency

  7. Estimates of Acausal Joint Impedance Models

    PubMed Central

    Perreault, Eric J.

    2013-01-01

    Estimates of joint or limb impedance are commonly used in the study of how the nervous system controls posture and movement, and how that control is altered by injury to the neural or musculoskeletal systems. Impedance characterizes the dynamic relationship between an imposed perturbation of joint position and the torques generated in response. While there are many practical reasons for estimating impedance rather than its inverse, admittance, it is an acausal representation of the limb mechanics that can lead to difficulties in interpretation or use. The purpose of this study was to explore the acausal nature of nonparametric estimates of joint impedance representations to determine how they are influenced by common experimental and computational choices. This was accomplished by deriving discrete-time realizations of first-and second-order derivatives to illustrate two key difficulties in the physical interpretation of impedance impulse response functions. These illustrations were provided using both simulated and experimental data. It was found that the shape of the impedance impulse response depends critically on the selected sampling rate, and on the bandwidth and noise characteristics of the position perturbation used during the estimation process. These results provide important guidelines for designing experiments in which nonparametric estimates of impedance will be obtained, especially when those estimates are to be used in a multistep identification process. PMID:22907963

  8. Tracking of electrochemical impedance of batteries

    NASA Astrophysics Data System (ADS)

    Piret, H.; Granjon, P.; Guillet, N.; Cattin, V.

    2016-04-01

    This paper presents an evolutionary battery impedance estimation method, which can be easily embedded in vehicles or nomad devices. The proposed method not only allows an accurate frequency impedance estimation, but also a tracking of its temporal evolution contrary to classical electrochemical impedance spectroscopy methods. Taking into account constraints of cost and complexity, we propose to use the existing electronics of current control to perform a frequency evolutionary estimation of the electrochemical impedance. The developed method uses a simple wideband input signal, and relies on a recursive local average of Fourier transforms. The averaging is controlled by a single parameter, managing a trade-off between tracking and estimation performance. This normalized parameter allows to correctly adapt the behavior of the proposed estimator to the variations of the impedance. The advantage of the proposed method is twofold: the method is easy to embed into a simple electronic circuit, and the battery impedance estimator is evolutionary. The ability of the method to monitor the impedance over time is demonstrated on a simulator, and on a real Lithium ion battery, on which a repeatability study is carried out. The experiments reveal good tracking results, and estimation performance as accurate as the usual laboratory approaches.

  9. Measurement of the Impedance of Frog Skeletal Muscle Fibers

    PubMed Central

    Valdiosera, R.; Clausen, C.; Eisenberg, R. S.

    1974-01-01

    Impedance measurements are necessary to determine the passive electrical properties of cells including the equivalent circuits of the several pathways for current flow. Such measurements are usually made with microelectrodes of high impedance (some 15 MΩ) over a wide frequency range (1-10,000 Hz) and so are subject to many errors. An input amplifier has been developed which has negligible phase shift in this frequency range because it uses negative feedback to keep tiny the voltage on top of the microelectrode. An important source of artifact is the extracellular potential produced by capacitive current flow through the wall of the microelectrodes and the effective resistance of the bathing solution. This artifact is reduced some 10 times by shielding the current microelectrode with a conductive paint. The residual artifact is analyzed, measured, and subtracted from our results. The interelectrode coupling capacitance is reduced below 2 × 10-17 F and can be neglected. Phase and amplitude measurements are made with phase-sensitive detectors insensitive to noise. The entire apparatus is calibrated at different signal to noise ratios and the nature of the extracellular potential is investigated. The phase shift in the last 5-20 μm of the microelectrode tip is shown to be small and quite independent of frequency under several conditions. Experimental measurements of the phase characteristic of muscle fibers in normal Ringer are presented. The improvements in apparatus and the physiological significance of impedance measurements are discussed. It is suggested that the interpretation of impedance measurements is sensitive to small errors and so it is necessary to present objective evidence of the reliability of one's apparatus and measurements. PMID:4857358

  10. Application of stochastic Galerkin FEM to the complete electrode model of electrical impedance tomography

    SciTech Connect

    Leinonen, Matti Hakula, Harri Hyvönen, Nuutti

    2014-07-15

    The aim of electrical impedance tomography is to determine the internal conductivity distribution of some physical body from boundary measurements of current and voltage. The most accurate forward model for impedance tomography is the complete electrode model, which consists of the conductivity equation coupled with boundary conditions that take into account the electrode shapes and the contact resistances at the corresponding interfaces. If the reconstruction task of impedance tomography is recast as a Bayesian inference problem, it is essential to be able to solve the complete electrode model forward problem with the conductivity and the contact resistances treated as a random field and random variables, respectively. In this work, we apply a stochastic Galerkin finite element method to the ensuing elliptic stochastic boundary value problem and compare the results with Monte Carlo simulations.

  11. Modeling the impedance response of mixed-conducting thin film electrodes.

    PubMed

    Chen, Chi; Chen, Dengjie; Chueh, William C; Ciucci, Francesco

    2014-06-21

    In this paper a novel numerical impedance model is developed for mixed-conducting thin films working as electrodes for solid oxide fuel cells. The relative importance of interfaces is considered by incorporating double layer contributions at the film/gas boundary. Simulations are performed on a model system, namely doped ceria, in a symmetric cell configuration using geometrically well-defined patterned metal current collectors. Results reveal that experimentally consistent bulk impedances and surface capacitances can be extracted using the model. The impedance response depends strongly on the pattern spacing of the current collector, and is attributed to the electronic in-plane drift-diffusion as well as to the interplay between the surface reaction resistance and the electronic/ionic bulk drift-diffusion resistance.

  12. A Review of Electrical Impedance Spectrometry Methods for Parametric Estimation of Physiologic Fluid Volumes

    NASA Technical Reports Server (NTRS)

    Dewberry, B.

    2000-01-01

    Electrical impedance spectrometry involves measurement of the complex resistance of a load at multiple frequencies. With this information in the form of impedance magnitude and phase, or resistance and reactance, basic structure or function of the load can be estimated. The "load" targeted for measurement and estimation in this study consisted of the water-bearing tissues of the human calf. It was proposed and verified that by measuring the electrical impedance of the human calf and fitting this data to a model of fluid compartments, the lumped-model volume of intracellular and extracellular spaces could be estimated, By performing this estimation over time, the volume dynamics during application of stimuli which affect the direction of gravity can be viewed. The resulting data can form a basis for further modeling and verification of cardiovascular and compartmental modeling of fluid reactions to microgravity as well as countermeasures to the headward shift of fluid during head-down tilt or spaceflight.

  13. Channel model for AC electric arc

    NASA Astrophysics Data System (ADS)

    Larsen, H. L.

    1993-06-01

    This report contains the results from calculations of free-burning AC electric arcs in argon. In order to calculate the arc current and arc voltage, the external electric circuit must be taken into consideration. The external circuit is modeled by an equivalent circuit consisting of an ideal AC voltage source, a loss resistance, and an inductance. The qualitative behavior of the current-voltage characteristic is in agreement with observed characteristics, but experimental data are necessary in order to check whether the calculated power loss is reasonable. Non-symmetry was modeled by introducing different anode and cathode falls in the two half periods. An attempt at taking into account different cathode current densities in the two half periods, depending on whether the electrode or silicon melt is cathode, did not give satisfactory results. Thermionic emission was assumed in both half periods, but this may not be the right mechanism when the silicon melt is cathode. The time delay of the AC arc compared to the DC case is modeled by a time constant. It was shown that this preset time constant must be in agreement with the mean 'mechanical' relaxation time in the arc in order to fulfill the energy balance. By updating the time constant until this is achieved, the time constant is eliminated as a parameter that must be chosen a priori.

  14. Synthesis, dielectric behavior and impedance measurement studies of Cr-substituted Zn-Mn ferrites

    SciTech Connect

    Hankare, P.P.; Patil, R.P.; Garadkar, K.M.; Sasikala, R.; Chougule, B.K.

    2011-03-15

    Graphical abstract: Variation of dielectric constant with frequency. Research highlights: {yields} Sol-gel route synthesized spherical crystalline nanoparticles of ZnMn{sub 1-x}Cr{sub x}FeO{sub 4}. {yields} XRD, DTA, FTIR, SEM, dielectric and impedance study. {yields} The ferrites show concentration dependence of ac electrical conductivity. {yields} Impedance response is dominated by grain boundary behavior. -- Abstract: Nanocrystalline ZnMn{sub 1-x}Cr{sub x}FeO{sub 4} (1.0 {>=} x {>=} 0) ferrites were synthesized by sol-gel technique. X-ray diffraction (XRD) confirmed the formation of single phasic cubic spinel lattice for all the compositions studied. Lattice parameter shows a decreasing trend with an increase in Cr content in the compositions. Formation of spherical nanoparticles was revealed by scanning electron microscopy (SEM) analysis. Infrared spectroscopic studies revealed two main absorption bands in the range 400-800 cm{sup -1} arising due to tetrahedral (A) and octahedral (B) site vibrations. Dielectric constant, dielectric loss tangent, ac conductivity and complex impedance were measured as a function of frequency in the range 20 Hz to 1 MHz. Frequency dependence of dielectric constant shows dielectric dispersion due to the Maxwell-Wagner type of interfacial polarization. The role of chromium in modifying structural and dielectric properties of these ferrites has been explained.

  15. Electric-Field Instrument With Ac-Biased Corona Point

    NASA Technical Reports Server (NTRS)

    Markson, R.; Anderson, B.; Govaert, J.

    1993-01-01

    Measurements indicative of incipient lightning yield additional information. New instrument gives reliable readings. High-voltage ac bias applied to needle point through high-resistance capacitance network provides corona discharge at all times, enabling more-slowly-varying component of electrostatic potential of needle to come to equilibrium with surrounding air. High resistance of high-voltage coupling makes instrument insensitive to wind. Improved corona-point instrument expected to yield additional information assisting in safety-oriented forecasting of lighting.

  16. Impedance match for Stirling type cryocoolers

    NASA Astrophysics Data System (ADS)

    Dai, Wei; Luo, Ercang; Wang, Xiaotao; Wu, Zhanghua

    Impedance match in Stirling type cryocoolers is important for the compressor efficiency and available acoustic power. This paper generalizes the basic principles concerning the efficiency and acoustic power output of the linear compressor. Starting from basic governing equations and mainly from the viewpoint of energy balance, the physical mechanisms behind the principles are clearly shown. Specially, this paper focuses on the impedance match for an existing compressor, where the current limit and displacement limit should also be taken into consideration when selecting a suitable impedance. Some case studies based on a commercial compressor are also provided for a deep understanding.

  17. Linearly tapered slot antenna impedance characteristics

    NASA Technical Reports Server (NTRS)

    Simons, Rainee N.; Lee, Richard Q.

    1995-01-01

    The paper presents for the first time an experimental technique to de-embed the input impedance of a LTSA from the measured reflection coefficient. The results show that the input impedance is dependent on the semi-flare angle and the length of the LTSA. The Re(Z(sub in)) is large when the electrical length of the LTSA is small and is on the order of few thousand ohms. However for an electrically large LTSA the Re(Z(sub in)) is in the range of 55 to 130 ohms. These results have potential applications in the design of broad band impedance matching networks for LTSA.

  18. Wearable impedance monitoring system for dialysis patients.

    PubMed

    Bonnet, S; Bourgerette, A; Gharbi, S; Rubeck, C; Arkouche, W; Massot, B; McAdams, E; Montalibet, A; Jallon, P

    2016-08-01

    This paper describes the development and the validation of a prototype wearable miniaturized impedance monitoring system for remote monitoring in home-based dialysis patients. This device is intended to assess the hydration status of dialysis patients using calf impedance measurements. The system is based on the low-power AD8302 component. The impedance calibration procedure is described together with the Cole parameter estimation and the hydric volume estimation. Results are given on a test cell to validate the design and on preliminary calf measurements showing Cole parameter variations during hemodialysis.

  19. Digital ac monitor

    DOEpatents

    Hart, George W.; Kern, Jr., Edward C.

    1987-06-09

    An apparatus and method is provided for monitoring a plurality of analog ac circuits by sampling the voltage and current waveform in each circuit at predetermined intervals, converting the analog current and voltage samples to digital format, storing the digitized current and voltage samples and using the stored digitized current and voltage samples to calculate a variety of electrical parameters; some of which are derived from the stored samples. The non-derived quantities are repeatedly calculated and stored over many separate cycles then averaged. The derived quantities are then calculated at the end of an averaging period. This produces a more accurate reading, especially when averaging over a period in which the power varies over a wide dynamic range. Frequency is measured by timing three cycles of the voltage waveform using the upward zero crossover point as a starting point for a digital timer.

  20. Digital ac monitor

    DOEpatents

    Hart, G.W.; Kern, E.C. Jr.

    1987-06-09

    An apparatus and method is provided for monitoring a plurality of analog ac circuits by sampling the voltage and current waveform in each circuit at predetermined intervals, converting the analog current and voltage samples to digital format, storing the digitized current and voltage samples and using the stored digitized current and voltage samples to calculate a variety of electrical parameters; some of which are derived from the stored samples. The non-derived quantities are repeatedly calculated and stored over many separate cycles then averaged. The derived quantities are then calculated at the end of an averaging period. This produces a more accurate reading, especially when averaging over a period in which the power varies over a wide dynamic range. Frequency is measured by timing three cycles of the voltage waveform using the upward zero crossover point as a starting point for a digital timer. 24 figs.

  1. Cooling Floor AC Systems

    NASA Astrophysics Data System (ADS)

    Jun, Lu; Hao, Ding; Hong, Zhang; Ce, Gao Dian

    The present HVAC equipments for the residential buildings in the Hot-summer-and-Cold-winter climate region are still at a high energy consuming level. So that the high efficiency HVAC system is an urgently need for achieving the preset government energy saving goal. With its advantage of highly sanitary, highly comfortable and uniform of temperature field, the hot-water resource floor radiation heating system has been widely accepted. This paper has put forward a new way in air-conditioning, which combines the fresh-air supply unit and such floor radiation system for the dehumidification and cooling in summer or heating in winter. By analyze its advantages and limitations, we found that this so called Cooling/ Heating Floor AC System can improve the IAQ of residential building while keep high efficiency quality. We also recommend a methodology for the HVAC system designing, which will ensure the reduction of energy cost of users.

  2. A.c. conductivity and dielectric properties of LiNi 3/5Cu 2/5VO 4 ceramics

    NASA Astrophysics Data System (ADS)

    Ram, Moti

    2010-03-01

    The LiNi 3/5Cu 2/5VO 4 was synthesized using solution-based chemical method whose dielectric and a.c. conductivity properties were investigated using complex impedance spectroscopy (CIS) technique. Variation of dielectric constant ( εr) as a function of frequency at different temperatures indicates low frequency dispersion. A.c conductivity analysis indicates that electrical conduction in the material is a thermally activated process. Frequency dependence of a.c. conductivity at different temperatures obeys Jonscher's universal law: σ ac= σ dc+ A( ω) n.

  3. Synthesis, crystal structure, NMR study and AC conductivity of [(C3H7)4N]2Cd2ClF5 compound

    NASA Astrophysics Data System (ADS)

    Hajji, Rachid; Oueslati, Abderrazak; Body, Monique; Hlel, Faouzi

    2015-08-01

    The [(C3H7)4N]2Cd2ClF5 compound was crystallized in the triclinic system with space group P1. The crystal structure consists of organic-inorganic layers, stacked along direction. The organic part consists of two cations types. The inorganic layer is made up of Cd2ClF5 dimmers composed of two in-equivalent irregular tetrahedra sharing one edge (Cl-F). The MAS NMR spectra showed two, three and five isotropic resonances relative to 111Cd, 13C and 19F nuclei, respectively. DSC measurement disclosed a phase transition at around 380 K. The impedance spectroscopy and AC electrical conductivity measurements of our compound were taken from 209 Hz to 5 MHz over the temperature range of 350-381 K. Nyquist plots ( Z″ vs Z') show semicircle arcs at different temperatures, and an electrical equivalent circuit has been proposed to explain the impedance results. The circuits consist of the parallel combination of bulk resistance ( R), capacitance ( C) and fractal capacitance (CPE). The conductivity σ p follows the Arrhenius relation. The near value of activation energies obtained from the conductivity data and circuit equivalent confirms that the transport is through hopping mechanism. The analysis of the experimental data shows that the reorientation motion of [N(C3H7)4]+ cations and/or [Cd2ClF5]2- anions is probably responsible for the observed conductivity.

  4. Automated ac galvanomagnetic measurement system

    NASA Technical Reports Server (NTRS)

    Szofran, F. R.; Espy, P. N.

    1985-01-01

    An automated, ac galvanomagnetic measurement system is described. Hall or van der Pauw measurements in the temperature range 10-300 K can be made at a preselected magnetic field without operator attendance. Procedures to validate sample installation and correct operation of other system functions, such as magnetic field and thermometry, are included. Advantages of ac measurements are discussed.

  5. Impedance Analysis of 7YSZ Thermal Barrier Coatings During High-Temperature Oxidation

    NASA Astrophysics Data System (ADS)

    Chen, Wen-Long; Liu, Min; Zhang, Ji-Fu

    2016-12-01

    ZrO2-7 wt.%Y2O3 (7YSZ) thermal barrier coatings (TBCs) were prepared by atmospheric plasma spraying. High-temperature oxidation of 7YSZ TBCs was accomplished at 950 °C and characterized by impedance spectroscopy and scanning electron microscopy with energy-dispersive spectrometry. The results indicated that the thermally grown oxide (TGO) mainly contained alumina. The increase of the thickness of the TGO layer appeared to follow a parabolic law. Impedance analysis demonstrated that the resistance of the TGO increased with increasing oxidation time, also following a parabolic law, and that characterization of the TGO thickness based on fitting an equivalent circuit to its measured resistance is feasible. The YSZ grain-boundary resistance increased due to increasing cracks within the coating for oxidation time less than 50 h. However, beyond 150 h, the YSZ grain-boundary resistance slightly decreased, mainly due to sintering of the coating during the oxidation process.

  6. AC plasma anemometer—characteristics and design

    NASA Astrophysics Data System (ADS)

    Marshall, Curtis; Matlis, Eric; Corke, Thomas; Gogineni, Sivaram

    2015-08-01

    The characteristics and design of a high-bandwidth flow sensor that uses an AC glow discharge (plasma) as the sensing element is presented. The plasma forms in the air gap between two protruding low profile electrodes attached to a probe body. The output from the anemometer is an amplitude modulated version of the AC voltage input that contains information about the mean and fluctuating velocity components. The anemometer circuitry includes resistance and capacitance elements that simulate a dielectric-barrier to maintain a diffuse plasma, and a constant-current feedback control that maintains operation within the desired glow discharge regime over an extended range of air velocities. Mean velocity calibrations are demonstrated over a range from 0 to 140 m s-1. Over this velocity range, the mean output voltage varied linearly with air velocity, providing a constant static sensitivity. The effect of the electrode gap and input AC carrier frequency on the anemometer static sensitivity and dynamic response are investigated. Experiments are performed to compare measurements obtained with a plasma sensor operating at two AC carrier frequencies against that of a constant-temperature hot-wire. All three sensors were calibrated against the same known velocity reference. An uncertainty based on the standard deviation of the velocity calibration fit was applied to the mean and fluctuating velocity measurements of the three sensors. The motivation is not to replace hot-wires as a general measurement tool, but rather as an alternative to hot-wires in harsh environments or at high Mach numbers where they either have difficulty in surviving or lack the necessary frequency response.

  7. Effect of borehole design on electrical impedance tomography measurements

    NASA Astrophysics Data System (ADS)

    Mozaffari, Amirpasha; Huisman, Johan Alexander; Treichel, Andrea; Zimmermann, Egon; Kelter, Matthias; Vereecken, Harry

    2015-04-01

    Electrical Impedance Tomography (EIT) is a sophisticated non-invasive tool to investigate the subsurface in engineering and environmental studies. To increase the depth of investigation, EIT measurements can be made in boreholes. However, the presence of the borehole may affect EIT measurements. Here, we aim to investigate the effect of different borehole components on EIT measurements using 2,5-D and 3D finite element modeling and unstructured meshes. To investigate the effect of different borehole components on EIT measurements, a variety of scenarios were designed. In particular, the effect of the water-filled borehole, the PVC casing, and the gravel filter were investigated relative to complex resistivity simulations for a homogenous medium with chain and electrode modules. It was found that the results of the complex resistivity simulations were best understood using the sensitivity distribution of the electrode configuration under consideration. In all simulations, the sensitivity in the vicinity of the borehole was predominantly negative. Therefore, the introduction of the water-filled borehole caused an increase in the real part of the impedance, and a decrease (more negative) in the imaginary part of the simulated impedance. The PVC casing mostly enhanced the effect of the water-filled borehole described above, although this effect was less clear for some electrode configuration. The effect of the gravel filter mostly reduced the effect of the water-filled borehole with PVC casing. For EIT measurements in a single borehole, the highest simulated phase error was 12% for a Wenner configuration with electrode spacing of 0.33 m. This error decreased with increasing electrode spacing. In the case of cross-well configurations, the error in the phase shit was as high as 6%. Here, it was found that the highest errors occur when both current electrodes are located in the same borehole. These results indicated that cross-well measurements are less affected by the

  8. A phase field model of electrochemical impedance spectroscopy

    NASA Astrophysics Data System (ADS)

    Gathright, William

    One of the fundamental tenets of Material Science is the link between microstructure and material properties. As such, there is a need for a microstructure-sensitive model of electrochemistry. Phase field models have been designed to simulate systems with complex and evolving microstructures such as eutectic solidification and dendrite growth. The goal of this work is to extend phase field models into electrochemistry: with a chemical reaction model and a method of simulating electro-chemical impedance spectroscopy (EIS). The model given in the present work also forms the foundation for a microstructure-sensitive model of electrochemistry. EIS is a widely-used and powerful diagnostic technique in which the frequency-dependant impedance is measured. Though popular, data from EIS can be notoriously difficult to interpret. The present work also presents simulated EIS data, as well as explanations into the origins of common Nyquist plot features. At high-frequency, an analytic expression for the resistances is derived by analogy to Ohm's law. At low-frequency, the value for the resistance can be predicted by a simulated DC experiment. High- frequency capacitance originates in a difference in the current between the electrode and electrolyte. Low-frequency capacitance is defined by an “effective" surface charge, calculated by integrating the current over time rather than the charge density over distance. Depressed semicircle constant-phase element (CPE) behavior is also observed in the simulated data. Simulations with fast reaction kinetics exhibit power-law CPE impedance behavior, while simulations with a slow or no reaction are best explained by a combination of finite-length diffusion and electromigration. The model developed in this work is a tool to simulate, study, and interpret EIS data. Ultimately, it will serve as the foundation for a microstructure-sensitive model of electrochemistry.

  9. Transverse impedances of cavities and collimators

    SciTech Connect

    Kheifets, S.A.; Bane, K.L.F.; Bizek, H.

    1987-03-01

    Field matching has been used to compute the transverse impedance of simple, cylindrically symmetric, perfectly conducting structures, the subregions of which are separated by radial cuts. The method is briefly described, and some early results are presented. (LEW)

  10. Surface impedance of transversely moving microwave ferrite

    NASA Astrophysics Data System (ADS)

    Mueller, R. S.

    1990-01-01

    A theoretical study was made of the surface impedance Z for an electromagnetic transverse magnetic wave from free space on a magnetized ferrite surface moving normal to the plane of incidence. It was found convenient to decompose the surface impedance into two transfer impedances, Z1 and Z2, which relate the hybrid reflected amplitudes to the amplitude of the incident wave. The surface impedance does not vary much with respect to the angle of incidence, so only the case of normal incidence (θi = 0°) was evaluated. Resonant poles at ƒc, [ƒc(ƒc + ƒm)]1/2, and ƒc + ƒm dominate the frequency characteristics of Z1 and Z2. The frequencies ƒc andƒm are the precessional frequency and magnetization frequency, respectively.

  11. Antenna pattern control using impedance surfaces

    NASA Technical Reports Server (NTRS)

    Balanis, Constantine A.; Liu, Kefeng; Tirkas, Panayiotis A.

    1993-01-01

    During the period of this research project, a comprehensive study of pyramidal horn antennas was conducted. Full-wave analytical and numerical techniques were developed to analyze horn antennas with or without impedance surfaces. Based on these full-wave analytic techniques, research was conducted on the use of impedance surfaces on the walls of the horn antennas to control the antenna radiation patterns without a substantial loss of antenna gain. It was found that the use of impedance surfaces could modify the antenna radiation patterns. In addition to the analytical and numerical models, experimental models were also constructed and they were used to validate the predictions. Excellent agreement between theoretical predictions and the measured data was obtained for pyramidal horns with perfectly conducting surfaces. Very good comparisons between numerical and experimental models were also obtained for horns with impedance surfaces.

  12. Adaptive impedance control of redundant manipulators

    NASA Technical Reports Server (NTRS)

    Colbaugh, R.; Glass, K.; Seraji, H.

    1990-01-01

    A scheme for controlling the mechanical impedance of the end-effector of a kinematically redundant manipulator is presented. The proposed control system consists of two subsystems: an adaptive impedance controller which generates the Cartesian-space control input F (is a member of Rm) required to provide the desired end-effector impedance characteristics, and an algorithm that maps this control input to the joint torque T (is a member of Rn). The F to T map is constructed so that the robot redundancy is utilized to improve either the kinematic or dynamic performance of the robot. The impedance controller does not require knowledge of the complex robot dynamic model or parameter values for the robot, the payload, or the environment, and is implemented without calculation of the robot inverse kinematic transformation. As a result, the scheme is very general and is computationally efficient for on-line implementation.

  13. Quantitative assessment of impedance tomography for temperature measurements in hyperthermia.

    PubMed

    Blad, B; Persson, B; Lindström, K

    1992-01-01

    The objective of this study is a non-invasive assessment of the thermal dose in hyperthermia. Electrical impedance tomography (EIT) has previously been given a first trial as a temperature monitoring method together with microwave-induced hyperthermia treatment, but it has not been thoroughly investigated. In the present work we have examined this method in order to investigate the correlation in vitro between the true spatial temperature distribution and the corresponding measured relative resistivity changes. Different hyperthermia techniques, such as interstitial water tubings, microwave-induced, laser-induced and ferromagnetic seeds have been used. The results show that it is possible to find a correlation between the measured temperature values and the tomographically measured relative resistivity changes in tissue-equivalent phantoms. But the uncertainty of the temperature coefficients, which has been observed, shows that the method has to be improved before it can be applied to clinical in vivo applications.

  14. Easy method for measurement of environmental impedance and superconducting phase fluctuations in one-dimensional arrays of Josephson junctions

    NASA Astrophysics Data System (ADS)

    Chien, Wei-Chen; Lin, Kuan-Yu; Liou, Saxon; Ho, I.-Lin; Kuo, Watson

    2017-04-01

    We conduct microwave impedance measurements on a one-dimensional (1D) array of Josephson junctions to experimentally determine the Josephson inductance and shunt resistance of the constituent junctions. The effective Josephson energy provides an estimate of the environmental impedance, which is greatly increased due to phase fluctuations in the neighboring junctions. This enhancement is attributed to the charge solitons in the 1D system. In general, the environmental impedance is dominated by the junction’s normal resistance in the superconducting phase coherent regime, but overwhelmed by zero-bias resistance and differential resistance, respectively, in the Coulomb blockaded regime and in the phase fluctuating regime. The change in phase fluctuations owing to a dc bias agrees with the finite temperature phase diffusion model.

  15. Inversion of elastic impedance for unconsolidated sediments

    USGS Publications Warehouse

    Lee, Myung W.

    2006-01-01

    Elastic properties of gas-hydrate-bearing sediments are important for quantifying gas hydrate amounts as well as discriminating the gas hydrate effect on velocity from free gas or pore pressure. This paper presents an elastic inversion method for estimating elastic properties of gas-hydrate-bearing sediments from angle stacks using sequential inversion of P-wave impedance from the zero-offset stack and S-wave impedance from the far-offset stack without assuming velocity ratio.

  16. CSR Impedance for Non-Ultrarelativistic Beams

    SciTech Connect

    Li, Rui; Tsai, Cheng Y.

    2015-09-01

    For the analysis of the coherent synchrotron radiation (CSR)-induced microbunching gain in the low energy regime, such as when a high-brightness electron beam is transported through a low-energy merger in an energy-recovery linac (ERL) design, it is necessary to extend the CSR impedance expression in the ultrarelativistic limit to the non-ultrarelativistic regime. This paper presents our analysis of CSR impedance for general beam energies.

  17. Acoustic impedance measurements of pulse tube refrigerators

    NASA Astrophysics Data System (ADS)

    Iwase, Takashi; Biwa, Tetsushi; Yazaki, Taichi

    2010-02-01

    Complex acoustic impedance is determined in a prototype refrigerator that can mimic orifice-type, inertance-type, and double inlet-type pulse tube refrigerators from simultaneous measurements of pressure and velocity oscillations at the cold end. The impedance measurements revealed the means by which the oscillatory flow condition in the basic pulse tube refrigerator is improved by additional components such as a valve and a tank. The working mechanism of pulse tube refrigerators is explained based on an electrical circuit analogy.

  18. Acoustic Impedance Measurement for Underground Surfaces.

    NASA Astrophysics Data System (ADS)

    Cockcroft, Paul William

    Available from UMI in association with The British Library. Requires signed TDF. This thesis investigates the measurement of acoustic impedance for surfaces likely to be found in underground coal mines. By introducing the concepts of industrial noise, the effects of noise on the ear and relevant legislation the need for the protection of workers can be appreciated. Representative acoustic impedance values are vital as input for existing computer models that predict sound levels in various underground environments. These enable the mining engineer to predict the noise level at any point within a mine in the vicinity of noisy machinery. The concepts of acoustic intensity and acoustic impedance are investigated and different acoustic impedance measurement techniques are detailed. The possible use of either an impedance tube or an intensity meter for these kinds of measurements are suggested. The problems with acoustic intensity and acoustic impedance measurements are discussed with reference to the restraints that an underground environment imposes on any measurement technique. The impedance tube method for work in an acoustics laboratory is shown and the theory explained, accompanied by a few representative results. The use of a Metravib intensity meter in a soundproof chamber to gain impedance values is explained in detail. The accompanying software for the analysis of the two measured pressure signals is shown as well as the actual results for a variety of test surfaces. The use of a Nagra IV-SJ tape recorder is investigated to determine the effect of recording on the measurement and subsequent analysis of the input signals, particularly with reference to the phase difference introduced between the two simultaneous pressure signals. The subsequent use of a Norwegian Electronic intensity meter, including a proposal for underground work, is shown along with results for tests completed with this piece of equipment. Finally, recommendations are made on how to link up

  19. Electrical Impedance Tomography of Breast Cancer

    DTIC Science & Technology

    2004-06-01

    Resonance Research Systems, Guildford, UK) that has broadband RF transmit and receive channels. A 16 leg, quadrature, high-pass birdcage coil with 10...metastatic cancer, magnetic resonance imaging, 43 electrical impedance imaging, electrical impedance scanning, MRI 16. PRICE CODE current density imaging...tissue with high spatial resolution, by using it in conjunction with Magnetic Resonance Imaging (MRI) to improve diagnostic accuracy of screening. For

  20. Effect of shear on duct wall impedance.

    NASA Technical Reports Server (NTRS)

    Goldstein, M.; Rice, E.

    1973-01-01

    The solution to the equation governing the propagation of sound in a uniform shear layer is expressed in terms of parabolic cylinder functions. This result is used to develop a closed-form solution for acoustic wall impedance which accounts for both the duct liner and the presence of a boundary layer in the duct. The effective wall impedance can then be used as the boundary condition for the much simpler problem of sound propagation in uniform flow.

  1. Non-invasive measurement of micro-area skin impedance in vivo

    NASA Astrophysics Data System (ADS)

    Li, Dachao; Liang, Wenshuai; Liu, Tongkun; Yu, Haixia; Xu, Kexin

    2011-12-01

    Volume measurement of interstitial fluid transdermally extracted is important in continuous glucose monitoring instrument. The volume of transdermally extracted interstitial fluid could be determined by a skin permeability coefficient. If the skin impedance which is the indicator of skin permeability coefficient can be accurately measured, the volume of interstitial fluid can be calculated based on the relationship between the indicator and the skin permeability coefficient. The possibility of using the skin impedance to indicate the skin permeability coefficient is investigated. A correlation model between the skin impedance and the skin permeability coefficient is developed. A novel non-invasive method for in vivo, real-time, and accurate measurement of skin impedance within a micro skin area is brought forward. The proposed measurement method is based on the theory that organisms saliva and interstitial fluid are equipotential. An electrode is put on the surface of a micro skin area and another one is put in the mouth to be fully contacted with saliva of an animal in the experiments. The electrode in mouth is used to replace the implantable subcutaneous electrode for non-invasive measurement of skin impedance in vivo. A biologically compatible AC current with amplitude of 100mv and frequency of 10Hz is applied to stimulate the micro skin area by the two electrodes. And then the voltage and current between the two electrodes are measured to calculate the skin impedance within a micro skin area. The measurement results by electrode in mouth are compared with the results by subcutaneous electrode in animal experiments and they are consistent so the proposed measurement method is verified well. The effect of moisture and pressure for the measurement is also studied in the paper.

  2. Optimally tuned resonant negative capacitance for piezoelectric shunt damping based on measured electromechanical impedance

    NASA Astrophysics Data System (ADS)

    Salloum, Rogério; Heuss, Oliver; Götz, Benedict; Mayer, Dirk

    2015-04-01

    In this paper, a new tuning method for shunt damping with a series resistance, inductance and negative capacitance is proposed and its validity is investigated. It is based on the measured electromechanical impedance of a piezoelectric system, which is represented through an equivalent electrical circuit that takes into account the characteristics of the piezoelectric transducer and the host structure. Afterwards, an additional circuit representing the shunt is connected and the Norton equivalent impedance is obtained at the terminals that represent the mechanical mode of interest. During the tuning process, the optimal shunt parameters are found by minimizing the maximum absolute value of the Norton equivalent impedance over a defined frequency range through a numerical optimization. Taking benefit from the analogy between electrical impedance and mechanical admittance, the minimization of different mechanical responses (displacement, velocity or acceleration) is also proposed and the different optimum shunt parameters obtained are compared. In view of real technical applications, this method allows the integration of a real negative capacitance circuit, i.e., a negative impedance converter, rather than an ideal component. It is thus possible to use the impedance of this circuit and optimize the individual component values. Since this method is based on one simple measurement, it can be applied to arbitrary structures without the need of complex dynamic tests or expensive finite elements calculations. Finally, an experimental analysis is carried out in order to compare the damping performance of the proposed method and the conventional analytical method that minimizes a mechanical frequency response function.

  3. Electrical Impedance Spectroscopy for Electro-Mechanical Characterization of Conductive Fabrics

    PubMed Central

    Bera, Tushar Kanti; Mohamadou, Youssoufa; Lee, Kyounghun; Wi, Hun; Oh, Tong In; Woo, Eung Je; Soleimani, Manuchehr; Seo, Jin Keun

    2014-01-01

    When we use a conductive fabric as a pressure sensor, it is necessary to quantitatively understand its electromechanical property related with the applied pressure. We investigated electromechanical properties of three different conductive fabrics using the electrical impedance spectroscopy (EIS). We found that their electrical impedance spectra depend not only on the electrical properties of the conductive yarns, but also on their weaving structures. When we apply a mechanical tension or compression, there occur structural deformations in the conductive fabrics altering their apparent electrical impedance spectra. For a stretchable conductive fabric, the impedance magnitude increased or decreased under tension or compression, respectively. For an almost non-stretchable conductive fabric, both tension and compression resulted in decreased impedance values since the applied tension failed to elongate the fabric. To measure both tension and compression separately, it is desirable to use a stretchable conductive fabric. For any conductive fabric chosen as a pressure-sensing material, its resistivity under no loading conditions must be carefully chosen since it determines a measurable range of the impedance values subject to different amounts of loadings. We suggest the EIS method to characterize the electromechanical property of a conductive fabric in designing a thin and flexible fabric pressure sensor. PMID:24892493

  4. Investigating the low-temperature impedance increase of lithium-ion cells.

    SciTech Connect

    Abraham, D. P.; Heaton, J. R.; Kang, S.-H.; Dees, D. W.; Jansen, A. N.; Chemical Engineering

    2008-01-01

    Low-temperature performance loss is a significant barrier to commercialization of lithium-ion cells in hybrid electric vehicles. Increased impedance, especially at temperatures below 0 C, reduces the cell pulse power performance required for cold engine starts, quick acceleration, or regenerative braking. Here we detail electrochemical impedance spectroscopy data on binder- and carbon-free layered-oxide and spinel-oxide electrodes, obtained over the +30 to ?30 C temperature range, in coin cells containing a lithium-preloaded Li{sub 4/3}Ti{sub 5/3}O{sub 4} composite (LTOc) counter electrode and a LiPF{sub 6}-bearing ethylene carbonate/ethyl methyl carbonate electrolyte. For all electrodes studied, the impedance increased with decreasing cell temperature; the increases observed in the midfrequency arc dwarfed the increases in ohmic resistance and diffusional impedance. Our data suggest that the movement of lithium ions across the electrochemical interface on the active material may have been increasingly hindered at lower temperatures, especially below 0 C. Low-temperature performance may be improved by modifying the electrolyte-active material interface (for example, through electrolyte composition changes). Increasing surface area of active particles (for example, through nanoparticle use) can lower the initial electrode impedance and lead to lower cell impedances at -30 C.

  5. Ultrahigh impedance method to assess electrostatic accelerator performance

    NASA Astrophysics Data System (ADS)

    Lobanov, Nikolai R.; Linardakis, Peter; Tsifakis, Dimitrios

    2015-06-01

    This paper describes an investigation of problem-solving procedures to troubleshoot electrostatic accelerators. A novel technique to diagnose issues with high-voltage components is described. The main application of this technique is noninvasive testing of electrostatic accelerator high-voltage grading systems, measuring insulation resistance, or determining the volume and surface resistivity of insulation materials used in column posts and acceleration tubes. In addition, this technique allows verification of the continuity of the resistive divider assembly as a complete circuit, revealing if an electrical path exists between equipotential rings, resistors, tube electrodes, and column post-to-tube conductors. It is capable of identifying and locating a "microbreak" in a resistor and the experimental validation of the transfer function of the high impedance energy control element. A simple and practical fault-finding procedure has been developed based on fundamental principles. The experimental distributions of relative resistance deviations (Δ R /R ) for both accelerating tubes and posts were collected during five scheduled accelerator maintenance tank openings during 2013 and 2014. Components with measured Δ R /R >±2.5 % were considered faulty and put through a detailed examination, with faults categorized. In total, thirty four unique fault categories were identified and most would not be identifiable without the new technique described. The most common failure mode was permanent and irreversible insulator current leakage that developed after being exposed to the ambient environment. As a result of efficient in situ troubleshooting and fault-elimination techniques, the maximum values of |Δ R /R | are kept below 2.5% at the conclusion of maintenance procedures. The acceptance margin could be narrowed even further by a factor of 2.5 by increasing the test voltage from 40 V up to 100 V. Based on experience over the last two years, resistor and insulator

  6. Rapid Impedance Spectrum Measurements for State-of-Health Assessment of Energy Storage Devices

    SciTech Connect

    Jon P. Christophersen; John L. Morrison; Chester G. Motloch; William H. Morrison

    2012-04-01

    Harmonic compensated synchronous detection (HCSD) is a technique that can be used to measure wideband impedance spectra within seconds based on an input sum-of-sines signal having a frequency spread separated by harmonics. The battery (or other energy storage device) is excited with a sum-of-sines current signal that has a duration of at least one period of the lowest frequency. The voltage response is then captured and synchronously detected at each frequency of interest to determine the impedance spectra. This technique was successfully simulated using a simplified battery model and then verified with commercially available Sanyo lithium-ion cells. Simulations revealed the presence of a start-up transient effect when only one period of the lowest frequency is included in the excitation signal. This transient effect appears to only influence the low-frequency impedance measurements and can be reduced when a longer input signal is used. Furthermore, lithium-ion cell testing has indicated that the transient effect does not seem to impact the charge transfer resistance in the mid-frequency region. The degradation rates for the charge transfer resistance measured from the HCSD technique were very similar to the changes observed from standardized impedance spectroscopy methods. Results from these studies, therefore, indicate that HCSD is a viable, rapid alternative approach to acquiring impedance spectra.

  7. New equivalent-electrical circuit model and a practical measurement method for human body impedance.

    PubMed

    Chinen, Koyu; Kinjo, Ichiko; Zamami, Aki; Irei, Kotoyo; Nagayama, Kanako

    2015-01-01

    Human body impedance analysis is an effective tool to extract electrical information from tissues in the human body. This paper presents a new measurement method of impedance using armpit electrode and a new equivalent circuit model for the human body. The lowest impedance was measured by using an LCR meter and six electrodes including armpit electrodes. The electrical equivalent circuit model for the cell consists of resistance R and capacitance C. The R represents electrical resistance of the liquid of the inside and outside of the cell, and the C represents high frequency conductance of the cell membrane. We propose an equivalent circuit model which consists of five parallel high frequency-passing CR circuits. The proposed equivalent circuit represents alpha distribution in the impedance measured at a lower frequency range due to ion current of the outside of the cell, and beta distribution at a high frequency range due to the cell membrane and the liquid inside cell. The calculated values by using the proposed equivalent circuit model were consistent with the measured values for the human body impedance.

  8. Changes in biphasic electrode impedance with protein adsorption and cell growth

    PubMed Central

    Newbold, Carrie; Richardson, Rachael; Millard, Rodney; Huang, Christie; Milojevic, Dusan; Shepherd, Robert; Cowan, Robert

    2012-01-01

    This study was undertaken to assess the contribution of protein adsorption and cell growth to increases in electrode impedance that occur immediately following implantation of cochlear implant electrodes and other neural stimulation devices. An in vitro model of the electrode-tissue interface was used. Radiolabelled albumin in phosphate buffered saline was added to planar gold electrodes and electrode impedance measured using a charge-balanced biphasic current pulse. The polarisation impedance component increased with protein adsorption, while no change to access resistance was observed. The maximum level of protein adsorbed was measured at 0.5 μg/cm2, indicating a tightly packed monolayer of albumin molecules on the gold electrode and resin substrate. Three cell types were grown over the electrodes, macrophage cell line J774, dissociated fibroblasts and epithelial cell line MDCK, all of which created a significant increase in electrode impedance. As cell cover over electrodes increased, there was a corresponding increase in the initial rise in voltage, suggesting cell cover mainly contributes to the access resistance of the electrodes. Only a small increase in the polarisation component of impedance was seen with cell cover. PMID:20841637

  9. Impedance Biosensing to detect food allergens, endocrine disrupting chemicals, and food pathogens

    NASA Astrophysics Data System (ADS)

    Radhakrishnan, Rajeswaran

    Electrochemical impedance biosensors can be viewed as an AC electroanalytical method for the analyte detection in the fields of biomedicine, environmental monitoring, and food and agriculture, amongst others. The most common format for AC impedance biosensing involves surface immobilization of an antibody, receptor protein, DNA strand, or other species capable of bio-recognition, and AC impedance detection of the binding event. Technological application of AC impedance biosensors has been hindered by several obstacles, including the more complex circuitry required for AC relative to DC electrochemistry, chemical and physical interference arising from non-specific adsorption, and the stability and reproducibility of protein immobilization. One focus of these PhD studies is on methods to reduce or compensate for non-specific adsorption, including sample dilution, site blocking with BSA, and the use of control electrodes onto which reference antibodies are immobilized. Examples that will be presented include impedance detection of food pathogens, such as Listeria monocytogenes, using a mouse monoclonal antibody immobilized onto an Au electrode. This yields detection limits of 5 CFU/ml and 4 CFU/ml for ideal solutions and filtered tomato extract, respectively. Control experiments with an Au electrode onto which a mouse monoclonal antibody to GAPDH is immobilized demonstrate that non-specific adsorption is insignificant for the system and methodology studied here. Control experiments with Salmonella enterica demonstrate no cross-reactivity to this food pathogen. In addition, Detection of two endocrine-disrupting chemicals (EDC), norfluoxetine and BDE-47, is reported here by impedance biosensing, with a detection limit of 8.5 and 1.3 ng/ml for norfluoxetine and BDE-47, respectively. Additional research has focused on alternative substrates and linker chemistries for protein immobilization, including the use of degenerate (highly doped) Si and bidendate thiol monolayer

  10. Stability Analysis of a Constant Power Load Serviced by a Buck Converter as the Source Impedance Varies

    DTIC Science & Technology

    2012-09-01

    electric ships, being aware of the stability issues associated with direct current (DC)-DC and DC-alternating current (AC) power converters and...problem here is that in MVDC shipboard power systems, the DC-DC converters are used to supply constant power to electrical loads, and these loads have...OF A CONSTANT POWER LOAD SERVICED BY A BUCK CONVERTER AS THE SOURCE IMPEDANCE VARIES by George J. Roth September 2012 Thesis Advisor

  11. Method and device for bio-impedance measurement with hard-tissue applications.

    PubMed

    Guimerà, A; Calderón, E; Los, P; Christie, A M

    2008-06-01

    Bio-impedance measurements can be used to detect and monitor several properties of living hard-tissues, some of which include bone mineral density, bone fracture healing or dental caries detection. In this paper a simple method and hardware architecture for hard tissue bio-impedance measurement is proposed. The key design aspects of such architecture are discussed and a commercial handheld ac impedance device is presented that is fully certified to international medical standards. It includes a 4-channel multiplexer and is capable of measuring impedances from 10 kOmega to 10 MOmega across a frequency range of 100 Hz to 100 kHz with a maximum error of 5%. The device incorporates several user interface methods and a Bluetooth link for bi-directional wireless data transfer. Low-power design techniques have been implemented, ensuring the device exceeds 8 h of continuous use. Finally, bench test results using dummy cells consisting of parallel connected resistors and capacitors, from 10 kOmega to 10 MOmega and from 20 pF to 100 pF, are discussed.

  12. Phase-sensitive detection of both inductive and non-inductive ac voltages in ferromagnetic resonance

    NASA Astrophysics Data System (ADS)

    Weiler, Mathias; Shaw, Justin M.; Nembach, Hans T.; Schoen, Martin A.; Boone, Carl T.; Silva, Thomas J.

    2014-03-01

    Spin pumping causes significant damping in ultrathin ferromagnetic/normal metal (NM) multilayers via spin-current generation of both dc and ac character in the NM system. While the nonlinear dc component has been investigated in detail by utilization of the inverse spin Hall effect (iSHE) in NMs, much less is known about the linear ac component that is presumably much larger in the small-excitation limit. We measured generated ac voltages in a wide variety of Permalloy/NM multilayers via vector-network-analyzer ferromagnetic resonance. We employ a custom, impedance-matched, broadband microwave coupler that features a ferromagnetic thin film reference resonator to accurately compare ac voltage amplitudes and phases between varieties of multilayers. By use of the fact that inductive and ac iSHE signals are phase-shifted by π/2, we find that inductive signals are major contributors in all investigated samples. It is only by comparison of the phase and amplitude of the recorded ac voltages between multiple samples that we can extract the non-inductive contributions due to spin-currents. Voltages due to the ac iSHE in Permalloy(10nm)/platinum(5nm) bilayers are weaker than inductive signals, in agreement with calculations based upon recent theoretical predictions. M.W. acknowledges financial support by the German Academic Exchange service (DAAD).

  13. Comparison of segmental with whole-body impedance measurements in peritoneal dialysis patients.

    PubMed

    Nescolarde, Lexa; Doñate, Teresa; Piccoli, Antonio; Rosell, Javier

    2008-09-01

    Segmental impedance measurements were obtained using nine electrode configurations in 21 male patients undergoing peritoneal dialysis PD before and after the fluid drainage. For each segment we analyzed the impedance Z and the impedance divided by the height H of the patient Z/H. Our objective was to compare different segmental measurements with whole-body measurements in peritoneal dialysis. The Wilcoxon test was used to analyze the change in impedance produced by a PD session. Pearson or Spearman correlation coefficients were used for continuous or discrete variables, respectively. Statistical significance was set at P<0.05. Similar results were obtained for Z and Z/H. The correlation coefficients between the real R and imaginary X(c) parts of segmental impedances after drainage were within the expected range for healthy population (0.46-0.70), but not before drainage for the abdomen (0.34) and the upper part of the leg (0.24). The correlation between the real part of whole-body and the real part of longitudinal segments in the limbs was high (r=0.807-0.879). Furthermore, the imaginary part of whole-body showed a high correlation with the imaginary part of all longitudinal segments (r=0.856-0.931). The high contribution of arm and leg impedances in the whole-body impedance produced high correlation between whole-body and segmental measurements in legs and arms. In agreement with other previous studies, a significant increase of the arm resistance was detected after fluid drainage. The drainage of fluids in PD patients produced significant changes in the measured real parts of impedance in all measured segments, but only the measurement in the abdomen showed a significant positive correlation (r=0.533) with the extracted fluid volume. This low correlation indicates that the individual assessment of fluid volumes using segmental measurements will be highly inaccurate.

  14. Modeling the longitudinal wall impedance instability in heavy ion beams using an R-Z PIC code

    SciTech Connect

    Callahan, D.A.; Langdon, A.B.; Friedman, A.; Grote, D.P. ); Haber, I. )

    1991-02-22

    The effects of the longitudinal wall impedance instability in a heavy ion beam are of great interest for heavy ion fusion drivers. We are studying this instability using the R-Z thread of the WARP PIC code. We describe the code and our model of the impedance due to the accelerating modules of the induction LINAC as a resistive wall. We present computer simulations which illustrate this instability. 2 refs., 2 figs., 1 tab.

  15. Layoff Handling Still Lags ACS Standards.

    ERIC Educational Resources Information Center

    Chemical and Engineering News, 1981

    1981-01-01

    Reviews termination procedures of professional chemists and the compliance of these terminations to the American Chemical Society's (ACS's) Professional Employment Guidelines. Provides the ACS guidelines. (DS)

  16. Utilizing CMP-Sialic Acid Analogs to Unravel Neisseria gonorrhoeae Lipooligosaccharide-Mediated Complement Resistance and Design Novel Therapeutics.

    PubMed

    Gulati, Sunita; Schoenhofen, Ian C; Whitfield, Dennis M; Cox, Andrew D; Li, Jianjun; St Michael, Frank; Vinogradov, Evgeny V; Stupak, Jacek; Zheng, Bo; Ohnishi, Makoto; Unemo, Magnus; Lewis, Lisa A; Taylor, Rachel E; Landig, Corinna S; Diaz, Sandra; Reed, George W; Varki, Ajit; Rice, Peter A; Ram, Sanjay

    2015-12-01

    Neisseria gonorrhoeae deploys a novel immune evasion strategy wherein the lacto-N-neotetraose (LNnT) structure of lipooligosaccharide (LOS) is capped by the bacterial sialyltransferase, using host cytidine-5'-monophosphate (CMP)-activated forms of the nine-carbon nonulosonate (NulO) sugar N-acetyl-neuraminic acid (Neu5Ac), a sialic acid (Sia) abundant in humans. This allows evasion of complement-mediated killing by recruiting factor H (FH), an inhibitor of the alternative complement pathway, and by limiting classical pathway activation ("serum-resistance"). We utilized CMP salts of six additional natural or synthetic NulOs, Neu5Gc, Neu5Gc8Me, Neu5Ac9Ac, Neu5Ac9Az, legionaminic acid (Leg5Ac7Ac) and pseudaminic acid (Pse5Ac7Ac), to define structural requirements of Sia-mediated serum-resistance. While all NulOs except Pse5Ac7Ac were incorporated into the LNnT-LOS, only Neu5Gc incorporation yielded high-level serum-resistance and FH binding that was comparable to Neu5Ac, whereas Neu5Ac9Az and Leg5Ac7Ac incorporation left bacteria fully serum-sensitive and did not enhance FH binding. Neu5Ac9Ac and Neu5Gc8Me rendered bacteria resistant only to low serum concentrations. While serum-resistance mediated by Neu5Ac was associated with classical pathway inhibition (decreased IgG binding and C4 deposition), Leg5Ac7Ac and Neu5Ac9Az incorporation did not inhibit the classical pathway. Remarkably, CMP-Neu5Ac9Az and CMP-Leg5Ac7Ac each prevented serum-resistance despite a 100-fold molar excess of CMP-Neu5Ac in growth media. The concomitant presence of Leg5Ac7Ac and Neu5Ac on LOS resulted in uninhibited classical pathway activation. Surprisingly, despite near-maximal FH binding in this instance, the alternative pathway was not regulated and factor Bb remained associated with bacteria. Intravaginal administration of CMP-Leg5Ac7Ac to BALB/c mice infected with gonorrhea (including a multidrug-resistant isolate) reduced clearance times and infection burden. Bacteria recovered from CMP

  17. Moderately nonlinear diffuse-charge dynamics under an ac voltage

    NASA Astrophysics Data System (ADS)

    Stout, Robert F.; Khair, Aditya S.

    2015-09-01

    The response of a symmetric binary electrolyte between two parallel, blocking electrodes to a moderate amplitude ac voltage is quantified. The diffuse charge dynamics are modeled via the Poisson-Nernst-Planck equations for a dilute solution of point-like ions. The solution to these equations is expressed as a Fourier series with a voltage perturbation expansion for arbitrary Debye layer thickness and ac frequency. Here, the perturbation expansion in voltage proceeds in powers of Vo/(kBT /e ) , where Vo is the amplitude of the driving voltage and kBT /e is the thermal voltage with kB as Boltzmann's constant, T as the temperature, and e as the fundamental charge. We show that the response of the electrolyte remains essentially linear in voltage amplitude at frequencies greater than the RC frequency of Debye layer charging, D /λDL , where D is the ion diffusivity, λD is the Debye layer thickness, and L is half the cell width. In contrast, nonlinear response is predicted at frequencies below the RC frequency. We find that the ion densities exhibit symmetric deviations from the (uniform) equilibrium density at even orders of the voltage amplitude. This leads to the voltage dependence of the current in the external circuit arising from the odd orders of voltage. For instance, the first nonlinear contribution to the current is O (Vo3) which contains the expected third harmonic but also a component oscillating at the applied frequency. We use this to compute a generalized impedance for moderate voltages, the first nonlinear contribution to which is quadratic in Vo. This contribution predicts a decrease in the imaginary part of the impedance at low frequency, which is due to the increase in Debye layer capacitance with increasing Vo. In contrast, the real part of the impedance increases at low frequency, due to adsorption of neutral salt from the bulk to the Debye layer.

  18. Resistive Wall Growth Rate Measurements in the Fermilab Recycler

    SciTech Connect

    Ainsworth, R.; Adamson, P.; Burov, A.; Kourbanis, I.

    2016-10-05

    Impedance could represent a limitation of running high intensity beams in the Fermilab recycler. With high intensity upgrades foreseen, it is important to quantify the impedance. To do this,studies have been performed measuring the growth rate of presumably the resistive wall instability. The growth rates at varying intensities and chromaticities are shown. The measured growth rates are compared to ones calculated with the resistive wall impedance.

  19. Obtaining DC and AC isothermal electrical characteristics for RF MOSFET

    NASA Astrophysics Data System (ADS)

    Sahoo, A. K.; Fregonese, S.; Scheer, P.; Celi, D.; Juge, A.; Zimmer, T.

    2015-04-01

    In this paper we demonstrate a new and simple approach to obtain isothermal electrical characteristics of metal oxide field effect transistor (MOSFET) from conventional non-isothermal measurements. DC and continuous wave (CW) S-parameter measurements are performed at different chuck temperatures (Tchuck). Knowing the thermal resistance (RTH) of the device the variation of DC and AC characteristic due to self-heating can be de-embedded and all the isothermal DC data and AC data above isothermal frequency can be determined. The method is validated by comparing the results with pulsed DC and pulsed RF measurements and found to be in good agreements.

  20. Electromagnetic model for near-field microwave microscope with atomic resolution: Determination of tunnel junction impedance

    SciTech Connect

    Reznik, Alexander N.

    2014-08-25

    An electrodynamic model is proposed for the tunneling microwave microscope with subnanometer space resolution as developed by Lee et al. [Appl. Phys. Lett. 97, 183111 (2010)]. Tip-sample impedance Z{sub a} was introduced and studied in the tunneling and non-tunneling regimes. At tunneling breakdown, the microwave current between probe and sample flows along two parallel channels characterized by impedances Z{sub p} and Z{sub t} that add up to form overall impedance Z{sub a}. Quantity Z{sub p} is the capacitive impedance determined by the near field of the probe and Z{sub t} is the impedance of the tunnel junction. By taking into account the distance dependences of effective tip radius r{sub 0}(z) and tunnel resistance R{sub t}(z) = Re[Z{sub t}(z)], we were able to explain the experimentally observed dependences of resonance frequency f{sub r}(z) and quality factor Q{sub L}(z) of the microscope. The obtained microwave resistance R{sub t}(z) and direct current tunnel resistance R{sub t}{sup dc}(z) exhibit qualitatively similar behavior, although being largely different in both magnitude and the characteristic scale of height dependence. Interpretation of the microwave images of the atomic structure of test samples proved possible by taking into account the inductive component of tunnel impedance ImZ{sub t} = ωL{sub t}. Relation ωL{sub t}/R{sub t} ≈ 0.235 was obtained.

  1. Discerning Apical and Basolateral Properties of HT-29/B6 and IPEC-J2 Cell Layers by Impedance Spectroscopy, Mathematical Modeling and Machine Learning

    PubMed Central

    Schmid, Thomas; Bogdan, Martin; Günzel, Dorothee

    2013-01-01

    Quantifying changes in partial resistances of epithelial barriers in vitro is a challenging and time-consuming task in physiology and pathophysiology. Here, we demonstrate that electrical properties of epithelial barriers can be estimated reliably by combining impedance spectroscopy measurements, mathematical modeling and machine learning algorithms. Conventional impedance spectroscopy is often used to estimate epithelial capacitance as well as epithelial and subepithelial resistance. Based on this, the more refined two-path impedance spectroscopy makes it possible to further distinguish transcellular and paracellular resistances. In a next step, transcellular properties may be further divided into their apical and basolateral components. The accuracy of these derived values, however, strongly depends on the accuracy of the initial estimates. To obtain adequate accuracy in estimating subepithelial and epithelial resistance, artificial neural networks were trained to estimate these parameters from model impedance spectra. Spectra that reflect behavior of either HT-29/B6 or IPEC-J2 cells as well as the data scatter intrinsic to the used experimental setup were created computationally. To prove the proposed approach, reliability of the estimations was assessed with both modeled and measured impedance spectra. Transcellular and paracellular resistances obtained by such neural network-enhanced two-path impedance spectroscopy are shown to be sufficiently reliable to derive the underlying apical and basolateral resistances and capacitances. As an exemplary perturbation of pathophysiological importance, the effect of forskolin on the apical resistance of HT-29/B6 cells was quantified. PMID:23840862

  2. AC photovoltaic module magnetic fields

    SciTech Connect

    Jennings, C.; Chang, G.J.; Reyes, A.B.; Whitaker, C.M.

    1997-12-31

    Implementation of alternating current (AC) photovoltaic (PV) modules, particularly for distributed applications such as PV rooftops and facades, may be slowed by public concern about electric and magnetic fields (EMF). This paper documents magnetic field measurements on an AC PV module, complementing EMF research on direct-current PV modules conducted by PG and E in 1993. Although not comprehensive, the PV EMF data indicate that 60 Hz magnetic fields (the EMF type of greatest public concern) from PV modules are comparable to, or significantly less than, those from household appliances. Given the present EMF research knowledge, AC PV module EMF may not merit considerable concern.

  3. Crosstalk Compensation for a Rapid, Higher Resolution Impedance Spectrum Measurement

    SciTech Connect

    Jon P. Christophersen; John L. Morrison; David M. Rose; William H. Morrison; Chester G. Motloch

    2012-03-01

    Batteries and other energy storage devices are playing larger roles in various industries (e.g., military, automotive, electric utilities, etc.) as the U.S. seeks to reduce its dependence on foreign energy resources. As such, there exists a significant need for accurate, robust state-of-health assessment techniques. Present techniques tend to focus on simple, passive monitoring of voltage and current at a given ambient temperature. However, this approach has the disadvantage of ignoring key elements of health, that is, changes in resistance growth and power fade. Impedance spectroscopy is considered a useful laboratory tool in gauging changes in the resistance and power performance, but it has not been widely considered as an onboard diagnostic tool due to the length of time required to complete the measurement. Cross-Talk Compensation (CTC) is a novel approach that enables rapid, high resolution impedance spectra measurements using a hardware platform that could be designed as an embedded system. This input signal consists of a sum-of-sines excitation current that has a known frequency spread and a duration of one period of the lowest frequency. The voltage response is then captured at a sufficiently fast sample rate. Previously developed rapid impedance spectrum measurement techniques either required a longer excitation signal or a sum-of-sines signal that was separated by harmonic frequencies to reduce or eliminate, respectively, the cross-talk interference in the calculated results. The distinct advantage of CTC, however, is that non-harmonic frequencies can now be included within the excitation signal while still keeping the signal duration at one period of the lowest frequency. Since the frequency spread of the input signal is known, the crosstalk interference between sinusoidal signals within the sum-of-sines at a given frequency of interest can be pre-determined and assigned to an error matrix. Consequently, the real and imaginary components of the

  4. Investigation of low frequency electrolytic solution behavior with an accurate electrical impedance method

    NASA Astrophysics Data System (ADS)

    Ho, Kung-Chu; Su, Vin-Cent; Huang, Da-Yo; Lee, Ming-Lun; Chou, Nai-Kuan; Kuan, Chieh-Hsiung

    2017-01-01

    This paper reports the investigation of strong electrolytic solutions operated in low frequency regime through an accurate electrical impedance method realized with a specific microfluidic device and high resolution instruments. Experimental results show the better repeatability and accuracy of the proposed impedance method. Moreover, all electrolytic solutions appear the so-called relaxation frequency at each peak value of dielectric loss due to relaxing total polarization inside the device. The relaxation frequency of concentrated electrolytes becomes higher owing to the stronger total polarization behavior coming from the higher conductivity as well as the lower resistance in the electrolytic solutions.

  5. Vertical impedance measurements on concrete bridge decks for assessing susceptibility of reinforcing steel to corrosion.

    PubMed

    Bartholomew, Paul D; Guthrie, W Spencer; Mazzeo, Brian A

    2012-08-01

    Corrosion is a pressing problem for aging concrete infrastructure, especially bridge decks. Because of its sensitivity to factors that affect corrosion of reinforcing steel in concrete, resistivity is an important structural health indicator for reinforced concrete structures. In this research, an instrument was developed to measure vertical impedance on concrete bridge decks. Measurements of vertical impedance on slabs prepared in the laboratory, on slabs removed from decommissioned bridge decks, and on an in-service bridge deck in the field demonstrate the utility of the new apparatus.

  6. Vertical impedance measurements on concrete bridge decks for assessing susceptibility of reinforcing steel to corrosion

    NASA Astrophysics Data System (ADS)

    Bartholomew, Paul D.; Guthrie, W. Spencer; Mazzeo, Brian A.

    2012-08-01

    Corrosion is a pressing problem for aging concrete infrastructure, especially bridge decks. Because of its sensitivity to factors that affect corrosion of reinforcing steel in concrete, resistivity is an important structural health indicator for reinforced concrete structures. In this research, an instrument was developed to measure vertical impedance on concrete bridge decks. Measurements of vertical impedance on slabs prepared in the laboratory, on slabs removed from decommissioned bridge decks, and on an in-service bridge deck in the field demonstrate the utility of the new apparatus.

  7. Influences of Cry1Ac broccoli on larval survival and oviposition of diamondback moth.

    PubMed

    Yi, Dengxia; Cui, Shusong; Yang, Limei; Fang, Zhiyuan; Liu, Yumei; Zhuang, Mu; Zhang, Yangyong

    2015-01-01

    Larval survival and oviposition behavior of three genotypes of diamondback moth, Plutella xylostella L. (Lepidoptera: Plutellidae), (homozygous Cry1Ac-susceptibile, Cry1Ac-resistant, and their F1 hybrids), on transgenic Bacillus thuringiensis (Bt) broccoli expressing different levels of Cry1Ac protein were evaluated in laboratory. These Bt broccoli lines were designated as relative low, medium, and high, respectively, according to the Cry1Ac content. Untransformed brocccoli plants were used as control. Larval survival of diamondback moth on non-Bt leaves was not significantly different among the three genotypes. The Cry1Ac-resistant larvae could survive on the low level of Bt broccoli plants, while Cry1Ac-susceptible and F1 larvae could not survive on them. The three genotypes of P. xylostella larvae could not survive on medium and high levels of Bt broccoli. In oviposition choice tests, there was no significant difference in the number of eggs laid by the three P. xylostella genotypes among different Bt broccoli plants. The development of Cry1Ac-susceptible and Cry1Ac-resistant P. xylostella on intact Bt plants was also tested in greenhouse. All susceptible P. xylostella larvae died on all Bt plants, while resistant larvae could survive on broccoli, which expresses low Cry1Ac protein under greenhouse conditions. The results of the greenhouse trials were similar to that of laboratory tests. This study indicated that high dose of Bt toxins in broccoli cultivars or germplasm lines is required for effective resistance management.

  8. Effects of Liner Geometry on Acoustic Impedance

    NASA Technical Reports Server (NTRS)

    Jones, Michael G.; Tracy, Maureen B.; Watson, Willie R.; Parrott, Tony L.

    2002-01-01

    Current aircraft engine nacelles typically contain acoustic liners consisting of perforated sheets bonded onto honeycomb cavities. Numerous models have been developed to predict the acoustic impedance of these liners in the presence of grazing flow, and to use that information with aeroacoustic propagation codes to assess nacelle liner noise suppression. Recent efforts have provided advances in impedance education methodologies that offer more accurate determinations of acoustic liner properties in the presence of grazing flow. The current report provides the results of a parametric study, in which a finite element method was used to assess the effects of variations of the following geometric parameters on liner impedance, with and without the presence of grazing flow: percent open area, sheet thickness, sheet thickness-to-hole diameter ratio and cavity depth. Normal incidence acoustic impedances were determined for eight acoustic liners, consisting of punched aluminum facesheets bonded to hexcell honeycomb cavities. Similar liners were tested in the NASA Langley Research Center grazing incidence tube to determine their response in the presence of grazing flow. The resultant data provide a quantitative assessment of the effects of these perforate, single-layer liner parameters on the acoustic impedance of the liner.

  9. Utilizing CMP-Sialic Acid Analogs to Unravel Neisseria gonorrhoeae Lipooligosaccharide-Mediated Complement Resistance and Design Novel Therapeutics

    PubMed Central

    Gulati, Sunita; Schoenhofen, Ian C.; Whitfield, Dennis M.; Cox, Andrew D.; Li, Jianjun; St. Michael, Frank; Vinogradov, Evgeny V.; Stupak, Jacek; Zheng, Bo; Ohnishi, Makoto; Unemo, Magnus; Lewis, Lisa A.; Taylor, Rachel E.; Landig, Corinna S.; Diaz, Sandra; Reed, George W.; Varki, Ajit; Rice, Peter A.; Ram, Sanjay

    2015-01-01

    Neisseria gonorrhoeae deploys a novel immune evasion strategy wherein the lacto-N-neotetraose (LNnT) structure of lipooligosaccharide (LOS) is capped by the bacterial sialyltransferase, using host cytidine-5’-monophosphate (CMP)-activated forms of the nine-carbon nonulosonate (NulO) sugar N-acetyl-neuraminic acid (Neu5Ac), a sialic acid (Sia) abundant in humans. This allows evasion of complement-mediated killing by recruiting factor H (FH), an inhibitor of the alternative complement pathway, and by limiting classical pathway activation (“serum-resistance”). We utilized CMP salts of six additional natural or synthetic NulOs, Neu5Gc, Neu5Gc8Me, Neu5Ac9Ac, Neu5Ac9Az, legionaminic acid (Leg5Ac7Ac) and pseudaminic acid (Pse5Ac7Ac), to define structural requirements of Sia-mediated serum-resistance. While all NulOs except Pse5Ac7Ac were incorporated into the LNnT-LOS, only Neu5Gc incorporation yielded high-level serum-resistance and FH binding that was comparable to Neu5Ac, whereas Neu5Ac9Az and Leg5Ac7Ac incorporation left bacteria fully serum-sensitive and did not enhance FH binding. Neu5Ac9Ac and Neu5Gc8Me rendered bacteria resistant only to low serum concentrations. While serum-resistance mediated by Neu5Ac was associated with classical pathway inhibition (decreased IgG binding and C4 deposition), Leg5Ac7Ac and Neu5Ac9Az incorporation did not inhibit the classical pathway. Remarkably, CMP-Neu5Ac9Az and CMP-Leg5Ac7Ac each prevented serum-resistance despite a 100-fold molar excess of CMP-Neu5Ac in growth media. The concomitant presence of Leg5Ac7Ac and Neu5Ac on LOS resulted in uninhibited classical pathway activation. Surprisingly, despite near-maximal FH binding in this instance, the alternative pathway was not regulated and factor Bb remained associated with bacteria. Intravaginal administration of CMP-Leg5Ac7Ac to BALB/c mice infected with gonorrhea (including a multidrug-resistant isolate) reduced clearance times and infection burden. Bacteria recovered from

  10. Changes in impedance of Ni/Cd cells with voltage and cycle life

    NASA Astrophysics Data System (ADS)

    Reid, Margaret A.

    1992-07-01

    Impedances of aerospace design Super Ni/Cd cells are being measured as functions of voltage and number of cycles. The cells have been cycled over 4400 cycles to date. Analysis of the impedance data has been made using a number of equivalent circuits. The model giving the best fit over the whole range of voltage has a parallel circuit of a kinetic resistance and a constant phase element in series with the ohmic resistance. The values for the circuit elements have been treated as empirical parameters, and no attempt has been made as yet to correlate them with physical and chemical changes in the electrode. No significant changes have been seen as yet with the exception of a decrease in kinetic resistance at low states of charge in the first 500 cycles.

  11. Changes in impedance of Ni/Cd cells with voltage and cycle life

    NASA Technical Reports Server (NTRS)

    Reid, Margaret A.

    1992-01-01

    Impedances of aerospace design Super Ni/Cd cells are being measured as functions of voltage and number of cycles. The cells have been cycled over 4400 cycles to date. Analysis of the impedance data has been made using a number of equivalent circuits. The model giving the best fit over the whole range of voltage has a parallel circuit of a kinetic resistance and a constant phase element in series with the ohmic resistance. The values for the circuit elements have been treated as empirical parameters, and no attempt has been made as yet to correlate them with physical and chemical changes in the electrode. No significant changes have been seen as yet with the exception of a decrease in kinetic resistance at low states of charge in the first 500 cycles.

  12. Tunable microwave impedance matching to a high impedance source using a Josephson metamaterial

    SciTech Connect

    Altimiras, Carles Parlavecchio, Olivier; Joyez, Philippe; Vion, Denis; Roche, Patrice; Esteve, Daniel; Portier, Fabien

    2013-11-18

    We report the efficient coupling of a 50  Ω microwave circuit to a high impedance conductor. We use an impedance transformer consisting of a λ/4 co-planar resonator whose inner conductor contains an array of superconducting quantum interference devices (SQUIDs), providing it with a tunable lineic inductance L∼80 μ{sub 0}, resulting in a characteristic impedance Z{sub C}∼1 kΩ. The impedance matching efficiency is characterized by measuring the shot noise power emitted by a dc biased tunnel junction connected to the resonator. We demonstrate matching to impedances in the 15 to 35 kΩ range with bandwidths above 100 MHz around a resonant frequency tunable between 4 and 6 GHz.

  13. In vivo non-thermal irreversible electroporation impact on rat liver galvanic apparent internal resistance

    NASA Astrophysics Data System (ADS)

    Golberg, A.; Laufer, S.; Rabinowitch, H. D.; Rubinsky, B.

    2011-02-01

    Non-thermal irreversible electroporation (NTIRE) is a biophysical phenomenon which involves application of electric field pulses to cells or tissues, causing certain rearrangements in the membrane structure leading to cell death. The treated tissue ac impedance changes induced by electroporation were shown to be the indicators for NTIRE efficiency. In a previous study we characterized in vitro tissue galvanic apparent internal resistance (GAIR) changes due to NTIRE. Here we describe an in vivo study in which we monitored the GAIR changes of a rat liver treated by NTIRE. Electrical pulses were delivered through the same Zn/Cu electrodes by which GAIR was measured. GAIR was measured before and for 3 h after the treatment at 15 min intervals. The results were compared to the established ac bioimpedance measurement method. A decrease of 33% was measured immediately after the NTIRE treatment and a 40% decrease was measured after 3 h in GAIR values; in the same time 40% and 47% decrease respectively were measured by ac bioimpedance analyses. The temperature increase due to the NTIRE was only 0.5 °C. The results open the way for an inexpensive, self-powered in vivo real-time NTIRE effectiveness measurement.

  14. Controlling the electrical impedance of nanomechanical oscillators by electromigration

    NASA Astrophysics Data System (ADS)

    Sun, Fengpei; Zou, Jie; Chan, Ho Bun

    2015-03-01

    Detection of nanomechanical motion is of fundamental and practical interests. For doubly clamped nanobeams, a common method is the magnetomotive reflection technique. However, this technique usually suffers from large signal background due to the mismatch of the electrical resistance (Re) of the oscillators to the impedance (50ohm usually) of the cables for detection. The large signal background precludes the possibility of driving the device into self-sustaining oscillations using a phase-locked loop. We develop a reproducible method of minimizing the signal background in the magnetomotive reflection technique. A gold nanowire with a junction in the middle is fabricated on the top of a doubly-clamped SixNy nanobeam via e-beam lithography. By passing a large direct current through the nanowire, migration of the gold atoms around the junction is activated due to the heat dissipated. An analog feedback loop is designed to maintain a stable process of electromigration until the target Re is reached. Initially Re is smaller than 50ohm. The motional impedance of the nanowire shifts the total impedance closer to 50ohm so that the resonance of the nanobeam appears as a dip on a large background in the amplitude spectrum. As Re is increased to near 50ohm, the background reaches a minimum, and the resonance of the nanobeam turns into a peak. Self-sustaining oscillations of the nanobeam are successfully achieved via a phase-locked loop in this case. As Re is further increased, the background becomes higher again. The dependence of the background signal on Re agrees with calculations.

  15. Direct adaptive impedance control of manipulators

    NASA Technical Reports Server (NTRS)

    Colbaugh, R.; Seraji, H.; Glass, K.

    1991-01-01

    An adaptive scheme for controlling the end-effector impedance of robot manipulators is presented. The proposed control system consists of three subsystems: a simple filter which characterizes the desired dynamic relationship between the end-effector position error and the end-effector/environment contact force, an adaptive controller which produces the Cartesian-space control input required to provide this desired dynamic relationship, and an algorithm for mapping the Cartesian-space control input to a physically realizable joint-space control torque. The controller does not require knowledge of either the structure or the parameter values of the robot dynamics, and it is implemented without calculation of the robot inverse kinematic transformation. As a result, the scheme represents a very general and computationally efficient approach to controlling the impedance of both nonredundant and redundant manipulators. Furthermore, the method can be applied directly to trajectory tracking in free-space motion by removing the impedance filter.

  16. Propagation of waves along an impedance boundary

    NASA Technical Reports Server (NTRS)

    Wenzel, A. R.

    1974-01-01

    A theoretical analysis of the scalar wave field due to a point source above a plane impedance boundary is presented. A surface wave is found to be an essential component of the total wave field. It is shown that, as a result of ducting of energy by the surface wave, the amplitude of the total wave near the boundary can be greater than it would be if the boundary were perfectly reflecting. Asymptotic results, valid near the boundary, are obtained both for the case of finite impedance (the soft-boundary case) and for the limiting case in which the impedance becomes infinite (the hard-boundary case). In the latter, the wave amplitude in the farfield decreases essentially inversely as the horizontal propagation distance; in the former (if the surface-wave term is neglected), it decreases inversely as the square of the horizontal propagation distance.

  17. Wavelet analysis of the impedance cardiogram waveforms

    NASA Astrophysics Data System (ADS)

    Podtaev, S.; Stepanov, R.; Dumler, A.; Chugainov, S.; Tziberkin, K.

    2012-12-01

    Impedance cardiography has been used for diagnosing atrial and ventricular dysfunctions, valve disorders, aortic stenosis, and vascular diseases. Almost all the applications of impedance cardiography require determination of some of the characteristic points of the ICG waveform. The ICG waveform has a set of characteristic points known as A, B, E ((dZ/dt)max) X, Y, O and Z. These points are related to distinct physiological events in the cardiac cycle. Objective of this work is an approbation of a new method of processing and interpretation of the impedance cardiogram waveforms using wavelet analysis. A method of computer thoracic tetrapolar polyrheocardiography is used for hemodynamic registrations. Use of original wavelet differentiation algorithm allows combining filtration and calculation of the derivatives of rheocardiogram. The proposed approach can be used in clinical practice for early diagnostics of cardiovascular system remodelling in the course of different pathologies.

  18. Impedance properties of circular microstrip antenna

    NASA Technical Reports Server (NTRS)

    Deshpande, M. D.; Bailey, M. C.

    1983-01-01

    A moment method solution to the input impedance of a circular microstrip antenna excited by either a microstrip feed or a coaxial probe is presented. Using the exact dyadic Green's function and the Fourier transform the problem is formulated in terms of Richmond's reaction integral equation from which the unknown patch current can be solved for. The patch current is expanded in terms of regular surface patch modes and an attachment mode (for probe excited case) which insures continuity of the current at probe/patch junction, proper polarization and p-dependance of patch current in the vicinity of the probe. The input impedance of a circular microstrip antenna is computed and compared with earlier results. Effect of attachment mode on the input impedance is also discussed.

  19. Impedance characteristics of nanoparticle-LiCoO{sub 2}+PVDF

    SciTech Connect

    Panjaitan, Elman Kartini, Evvy Honggowiranto, Wagiyo

    2016-02-08

    The impendance of np-LiCoO{sub 2}+xPVDF, as a cathode material candidate for lithium-ion battery (LIB), has been characterized using impedance spectroscopy for x = 0, 5, 10, 15 and 20 volume percentage (%v/v) and for frequencies in the 42 Hz to 5 MHz range. Both real and imaginary components of the impedance were found to be frequency dependent, and both tend to increase for increasing PVDF (polyvinyilidene fluoride) concentration, except that for 10% PVDF both real and imaginary components of impedance are smaller than for 5%. The mechanism for relaxation time for each addition of PVDF was analyzed using Cole-Cole plots. The analysis showed that the relaxation times of the nanostructured LiCoO{sub 2} with PVDF additive is relatively constant. Further, PVDF addition increases the bulk resistance and decreases the bulk capacitance of the nanostructured LiCoO{sub 2}.

  20. Temperature-stable parallel-plate dielectric cell for broadband liquid impedance measurements

    NASA Astrophysics Data System (ADS)

    Mazzeo, Brian A.; Chandra, Satyan; Mellor, Brett L.; Arellano, Jesus

    2010-12-01

    A liquid impedance cell for broadband impedance measurements up to 110 MHz is presented. The design incorporates temperature control and minimizes parasitic capacitance and inductance. The cell is simple to fabricate and uses chemically resistant materials, stainless steel, and Teflon. This dielectric cell can be used in a variety of liquid measurements, particularly those related to impedance measurements of biological objects in solution. Temperature control is illustrated in measurements of the permittivity of deionized water from 5 to 55 °C. Numerical fitting procedures employed on the relaxation curves indicate good agreement with previous studies on beta-lactoglobulin and hen lysozyme. Titration capability is demonstrated through dielectric titration of hen lysozyme and beta-lactoglobulin.

  1. The influence of nanopore dimensions on the electrochemical properties of nanopore arrays studied by impedance spectroscopy.

    PubMed

    Kant, Krishna; Priest, Craig; Shapter, Joe G; Losic, Dusan

    2014-11-11

    The understanding of the electrochemical properties of nanopores is the key factor for better understanding their performance and applications for nanopore-based sensing devices. In this study, the influence of pore dimensions of nanoporous alumina (NPA) membranes prepared by an anodization process and their electrochemical properties as a sensing platform using impedance spectroscopy was explored. NPA with four different pore diameters (25 nm, 45 nm and 65 nm) and lengths (5 μm to 20 μm) was used and their electrochemical properties were explored using different concentration of electrolyte solution (NaCl) ranging from 1 to 100 μM. Our results show that the impedance and resistance of nanopores are influenced by the concentration and ion species of electrolytes, while the capacitance is independent of them. It was found that nanopore diameters also have a significant influence on impedance due to changes in the thickness of the double layer inside the pores.

  2. Sustainable AC/AC hybrid electrochemical capacitors in aqueous electrolyte approaching the performance of organic systems

    NASA Astrophysics Data System (ADS)

    Abbas, Qamar; Babuchowska, Paulina; Frąckowiak, Elżbieta; Béguin, François

    2016-09-01

    A high energy hybrid AC/AC electrochemical capacitor has been realized in aqueous Li2SO4+KI electrolyte mixture. Owing to the redox processes associated with the 2I-/I2 system, the positive electrode operates in narrow potential range and displays high capacity. During prolonged potentiostatic floating at 1.6 V, the hybrid cell demonstrates remarkably stable capacitance and resistance. Analyses by temperature programmed desorption after floating at 1.6 V proved that oxidation of the positive AC electrode is prevented by the use of Li2SO4+KI, which enables the maximum potential of this electrode to be shifted below the water oxidation potential. When charged at 0.2 A g-1 up to U = 1.6 V, the hybrid cell displays a high capacitance of 75 F g-1 (300 F g-1 per mass of one electrode) compared to 47 F g-1 (188 F g-1 per mass of one electrode) for a symmetric cell in Li2SO4. At 0.2 A g-1 up to 1.6 V, the hybrid capacitor in Li2SO4+KI displays an energy density of 26 Wh kg-1 which approaches the energy density of 30.9 Wh kg-1 measured when the same carbon is implemented in a capacitor using TEABF4/ACN electrolyte and charged up to 2.5 V.

  3. Impedance Scaling for Small Angle Transitions

    SciTech Connect

    Stupakov, G.; Bane, Karl; Zagorodnov, I.; /DESY

    2010-10-27

    Based on the parabolic equation approach to Maxwell's equations we have derived scaling properties of the high frequency impedance/short bunch wakefields of structures. For the special case of small angle transitions we have shown the scaling properties are valid for all frequencies. Using these scaling properties one can greatly reduce the calculation time of the wakefield/impedance of long, small angle, beam pipe transitions, like one often finds in insertion regions of storage rings. We have tested the scaling with wakefield simulations of 2D and 3D models of such transitions, and found that the scaling works well. In modern ring-based light sources one often finds insertion devices having extremely small vertical apertures (on the order of millimeters) to allow for maximal undulator fields reaching the beam. Such insertion devices require that there be beam pipe transitions from these small apertures to the larger cross-sections (normally on the order of centimeters) found in the rest of the ring. The fact that there may be many such transitions, and that these transitions introduce beam pipe discontinuities very close to the beam path, means that their impedance will be large and, in fact, may dominate the impedance budget of the entire ring. To reduce their impact on impedance, the transitions are normally tapered gradually over a long distance. The accurate calculation of the impedance or wakefield of these long transitions, which are typically 3D objects (i.e. they do not have cylindrical symmetry), can be quite a challenging numerical task. In this report we present a method of obtaining the impedance of a long, small angle transition from the calculation of a scaled, shorter one. Normally, the actual calculation is obtained from a time domain simulation of the wakefield in the structure, where the impedance can be obtained by performing a Fourier transform. We shall see that the scaled calculation reduces the computer time and memory requirements

  4. Protein Aggregation Measurement through Electrical Impedance Spectroscopy

    NASA Astrophysics Data System (ADS)

    Affanni, A.; Corazza, A.; Esposito, G.; Fogolari, F.; Polano, M.

    2013-09-01

    The paper presents a novel methodology to measure the fibril formation in protein solutions. We designed a bench consisting of a sensor having interdigitated electrodes, a PDMS hermetic reservoir and an impedance meter automatically driven by calculator. The impedance data are interpolated with a lumped elements model and their change over time can provide information on the aggregation process. Encouraging results have been obtained by testing the methodology on K-casein, a protein of milk, with and without the addition of a drug inhibiting the aggregation. The amount of sample needed to perform this measurement is by far lower than the amount needed by fluorescence analysis.

  5. Hole-Impeded-Doping-Superlattice LWIR Detectors

    NASA Technical Reports Server (NTRS)

    Maserjian, Joseph

    1991-01-01

    Hole-Impeded-Doping-Superlattice (HIDS) InAs devices proposed for use as photoconductive or photovoltaic detectors of radiation in long-wavelength infrared (LWIR) range of 8 to 17 micrometers. Array of HIDS devices fabricated on substrates GaAs or Si. Radiation incident on black surface, metal contacts for picture elements serve as reactors, effectively doubling optical path and thereby increasing absorption of photons. Photoconductive detector offers advantages of high gain and high impedance; photovoltaic detector offers lower noise and better interface to multiplexer readouts.

  6. System and method for monitoring and controlling stator winding temperature in a de-energized AC motor

    DOEpatents

    Lu, Bin [Kenosha, WI; Luebke, Charles John [Sussex, WI; Habetler, Thomas G [Snellville, GA; Zhang, Pinjia [Atlanta, GA; Becker, Scott K [Oak Creek, WI

    2011-12-27

    A system and method for measuring and controlling stator winding temperature in an AC motor while idling is disclosed. The system includes a circuit having an input connectable to an AC source and an output connectable to an input terminal of a multi-phase AC motor. The circuit further includes a plurality of switching devices to control current flow and terminal voltages in the multi-phase AC motor and a controller connected to the circuit. The controller is configured to activate the plurality of switching devices to create a DC signal in an output of the motor control device corresponding to an input to the multi-phase AC motor, determine or estimate a stator winding resistance of the multi-phase AC motor based on the DC signal, and estimate a stator temperature from the stator winding resistance. Temperature can then be controlled and regulated by DC injection into the stator windings.

  7. A multichannel continuously selectable multifrequency electrical impedance spectroscopy measurement system.

    PubMed

    Hartov, A; Mazzarese, R A; Reiss, F R; Kerner, T E; Osterman, K S; Williams, D B; Paulsen, K D

    2000-01-01

    There is increasing evidence that alterations in the electrical property spectrum of tissues below 10 MHz is diagnostic for tissue pathology and/or pathophysiology. Yet, the complexity associated with constructing a high-fidelity multichannel, multifrequency data acquisition instrument has limited widespread development of spectroscopic electrical impedance imaging concepts. To contribute to the relatively sparse experience with multichannel spectroscopy systems this paper reports on the design, realization and evaluation of a prototype 32-channel instrument. The salient features of the system include a continuously selectable driving frequency up to 1 MHz, either voltage or current source modes of operation and simultaneous measurement of both voltage and current on each channel in either of these driving configurations. Comparisons of performance with recently reported fixed-frequency systems is favorable. Volts dc (VDC) signal-to-noise ratios of 75-80 dB are achieved and the noise floor for ac signals is near 100 dB below the signal strength of interest at 10 kHz and 60 dB down at 1 MHz. The added benefit of being able to record multispectral information on source and sense signal amplitudes and phases has also been realized. Phase-sensitive detection schemes and multiperiod undersampling techniques have been deployed to ensure measurement fidelity over the full bandwidth of system operation.

  8. Impedance and modulus spectroscopic study of nano hydroxyapatite

    NASA Astrophysics Data System (ADS)

    Jogiya, B. V.; Jethava, H. O.; Tank, K. P.; Raviya, V. R.; Joshi, M. J.

    2016-05-01

    Hydroxyapatite (Ca10 (PO4)6 (OH)2, HAP) is the main inorganic component of the hard tissues in bones and also important material for orthopedic and dental implant applications. Nano HAP is of great interest due to its various bio-medical applications. In the present work the nano HAP was synthesized by using surfactant mediated approach. Structure and morphology of the synthesized nano HAP was examined by the Powder XRD and TEM. Impedance study was carried out on pelletized sample in a frequency range of 100Hz to 20MHz at room temperature. The variation of dielectric constant, dielectric loss, and a.c. conductivity with frequency of applied field was studied. The Nyquist plot as well as modulus plot was drawn. The Nyquist plot showed two semicircle arcs, which indicated the presence of grain and grain boundary effect in the sample. The typical behavior of the Nyquist plot was represented by equivalent circuit having two parallel RC combinations in series.

  9. Methods for Specific Electrode Resistance Measurement during Transcranial Direct Current Stimulation

    PubMed Central

    Khadka, Niranjan; Rahman, Asif; Sarantos, Chris; Truong, Dennis Q.; Bikson, Marom

    2014-01-01

    test signal does not itself confound electrode stability or sensation. DC-resistance to AC-impedance ratio was ~1:08, averaged across frequencies. Conclusion Using the methods developed here, a test signal can predict DC electrode resistance. Since unique test frequencies can be used at each tDCS electrode, specific electrode resistance can be resolved for any number of stimulating channels – a process made still more robust by the use of a sentinel electrode. These findings provide the first method for monitoring individual electrode resistance during tDCS that integrated into devices may minimize irritation at electrodes. PMID:25456981

  10. Compressible turbulent channel flow with impedance boundary conditions

    NASA Astrophysics Data System (ADS)

    Scalo, Carlo; Bodart, Julien; Lele, Sanjiva

    2014-11-01

    We have performed large-eddy simulations of compressible turbulent channel flow at one bulk Reynolds number, Reb = 6900, for bulk Mach numbers Mb = 0.05, 0.2, 0.5, with linear acoustic impedance boundary conditions (IBCs). The IBCs are formulated in the time domain following Fung and Ju (2004) and coupled with a Navier-Stokes solver. The impedance model adopted is a three-parameter Helmholtz oscillator with resonant frequency tuned to the outer layer eddies. The IBC's resistance, R, has been varied in the range, R = 0.01, 0.10, 1.00. Tuned IBCs result in a noticeable drag increase for sufficiently high Mb and/or low R, exceeding 300% for Mb = 0.5 and R = 0.01, and thus represents a promising passive control technique for delaying boundary layer separation and/or enhancing wall heat transfer. Alterations to the turbulent flow structure are confined to the first 15% of the boundary layer thickness where the classical buffer-layer coherent vortical structures are replaced by an array of Kelvin-Helmholtz-like rollers. The non-zero asymptotic value of the Reynolds shear stress gradient at the wall results in the disappearance of the viscous sublayer and very early departure of the mean velocity profiles from the law of the wall.

  11. Uterine artery impedance during the first eight postpartum weeks

    PubMed Central

    Guedes-Martins, L.; Gaio, A. R.; Saraiva, J.; Cunha, A.; Macedo, F.; Almeida, H.

    2015-01-01

    The aim of this study was to construct reference ranges for the uterine artery (UtA) mean pulsatility (PI) and resistance (RI) indices from 1–8 weeks postpartum. A prospective, cross-sectional, and observational study was performed with 320 healthy women from week 1 through week 8 postpartum. UtAs were examined transvaginally using colour and pulsed Doppler imaging, and the means of the right and left values of the PI and RI, as well as the presence or absence of a bilateral protodiastolic notch, were recorded. The 5th, 50th and 95th reference percentile curves for the UtA-PI and UtA-RI were derived using regression models. The adjusted reference intervals uncovered a convergence trend at the week 8 time-point, although impedance was lower at the week 1 time-point in multiparous women compared with primiparous women. The notching prevalence was 22.5% (9/40) at week 1 and 95.0% (38/40) at week 8. The study revealed consistent evidence of a progressive increase of postpartum uterine impedance and provided new average UtA-PI and UtA-RI reference charts for weeks 1 through 8. Multiparity does not change the trend but does impart a lower rate of increase, likely as a consequence of previous vascular structural and functional differences. PMID:25739463

  12. Mungbean yellow mosaic virus (MYMV) AC4 suppresses post-transcriptional gene silencing and an AC4 hairpin RNA gene reduces MYMV DNA accumulation in transgenic tobacco.

    PubMed

    Sunitha, Sukumaran; Shanmugapriya, Gnanasekaran; Balamani, Veluthambi; Veluthambi, Karuppannan

    2013-06-01

    Mungbean yellow mosaic virus (MYMV) is a legume-infecting geminivirus that causes yellow mosaic disease in blackgram, mungbean, soybean, Frenchbean and mothbean. AC4/C4, which is nested completely within the Rep gene, is less conserved among geminiviruses. Much less is known about its role in viral pathogenesis other than its known role in the suppression of host-mediated gene silencing. Transient expression of MYMV AC4 by agroinfiltration suppressed post-transcriptional gene silencing in Nicotiana benthamiana 16c expressing green fluorescence protein, at a level comparable to MYMV TrAP expression. AC4 full-length gene and an inverted repeat of AC4 (comprising the full-length AC4 sequence in sense and antisense orientations with an intervening intron) which makes a hairpin RNA (hpRNA) upon transcription were introduced into tobacco by Agrobacterium-mediated leaf disc transformation. Leaf discs of the transgenic plants were agroinoculated with partial dimers of MYMV and used to study the effect of the AC4-sense and AC4 hpRNA genes on MYMV DNA accumulation. Leaf discs of two transgenic plants that express the AC4-sense gene displayed an increase in MYMV DNA accumulation. Leaf discs of six transgenic plants containing the AC4 hpRNA gene accumulated small-interfering RNAs (siRNAs) specific to AC4, and upon agroinoculation with MYMV they exhibited a severe reduction in the accumulation of MYMV DNA. Thus, the MYMV AC4 hpRNA gene has emerged as a good candidate to engineer resistance against MYMV in susceptible plants.

  13. Uniformly Porous Nanocrystalline CaMgFe1.33Ti3O12 Ceramic Derived Electro-Ceramic Nanocomposite for Impedance Type Humidity Sensor

    PubMed Central

    Tripathy, Ashis; Pramanik, Sumit; Manna, Ayan; Shasmin, Hanie Nadia; Radzi, Zamri; Abu Osman, Noor Azuan

    2016-01-01

    Since humidity sensors have been widely used in many sectors, a suitable humidity sensing material with improved sensitivity, faster response and recovery times, better stability and low hysteresis is necessary to be developed. Here, we fabricate a uniformly porous humidity sensor using Ca, Ti substituted Mg ferrites with chemical formula of CaMgFe1.33Ti3O12 as humidity sensing materials by solid-sate step-sintering technique. This synthesis technique is useful to control the grain size with increased porosity to enhance the hydrophilic characteristics of the CaMgFe1.33Ti3O12 nanoceramic based sintered electro-ceramic nanocomposites. The highest porosity, lowest density and excellent surface-hydrophilicity properties were obtained at 1050 °C sintered ceramic. The performance of this impedance type humidity sensor was evaluated by electrical characterizations using alternating current (AC) in the 33%–95% relative humidity (RH) range at 25 °C. Compared with existing conventional resistive humidity sensors, the present sintered electro-ceramic nanocomposite based humidity sensor showed faster response time (20 s) and recovery time (40 s). This newly developed sensor showed extremely high sensitivity (%S) and small hysteresis of <3.4%. Long-term stability of the sensor had been determined by testing for 30 consecutive days. Therefore, the high performance sensing behavior of the present electro-ceramic nanocomposites would be suitable for a potential use in advanced humidity sensors. PMID:27916913

  14. A hybrid mock circulatory system: development and testing of an electro-hydraulic impedance simulator.

    PubMed

    Kozarski, M; Ferrari, G; Clemente, F; Górczyńska, K; De Lazzari, C; Darowski, M; Mimmo, R; Tosti, G; Guaragno, M

    2003-01-01

    Mock circulatory systems are used to test mechanical assist devices and for training and research purposes; when compared to numerical models, however, they are not flexible enough and rather expensive. The concept of merging numerical and physical models, resulting in a hybrid one, is applied here to represent the input impedance of the systemic arterial tree, by a conventional windkessel model built out of an electro-hydraulic (E-H) impedance simulator added to a hydraulic section. This model is inserted into an open loop circuit, completed by another hybrid model representing the ventricular function. The E-H impedance simulator is essentially an electrically controlled flow source (a gear pump). Referring to the windkessel model, it is used to simulate the peripheral resistance and the hydraulic compliance, creating the desired input impedance. The data reported describe the characterisation of the E-H impedance simulator and demonstrate its behaviour when it is connected to a hybrid ventricular model. Experiments were performed under different hemodynamic conditions, including the presence of a left ventricular assist device (LVAD).

  15. Studies of longitudinal profile of electron bunches and impedance measurements at Indus-2 synchrotron radiation source

    NASA Astrophysics Data System (ADS)

    Garg, Akash Deep; Yadav, S.; Kumar, Mukesh; Shrivastava, B. B.; Karnewar, A. K.; Ojha, A.; Puntambekar, T. A.

    2016-04-01

    Indus-2 is a 3rd generation synchrotron radiation source at the Raja Ramanna Centre for Advanced Technology (RRCAT) in India. We study the longitudinal profile of electrons in Indus-2 by using dual sweep synchroscan streak camera at visible diagnostic beamline. In this paper, the longitudinal profiles of electron bunch are analyzed by filling beam current in a single bunch mode. These studies are carried at injection energy (550 MeV) and at ramped beam energy (2.5 GeV). The effects of the wakefield generated interactions between the circulating electrons and the surrounding vacuum chamber are analyzed in terms of measured effects on longitudinal beam distribution. The impedance of the storage ring is obtained by fitting the solutions of Haissinski equation to the measured bunch lengthening with different impedance models. The impedance of storage ring obtained by a series R+L impedance model indicates a resistance (R) of 1350±125 Ω, an inductance (L) of 180±25 nH and broadband impedance of 2.69 Ω. These results are also compared with the values obtained from measured synchronous phase advancing and scaling laws. These studies are very useful in better understanding and control of the electromagnetic interactions.

  16. LDV measurement of bird ear vibrations to determine inner ear impedance and middle ear power flow

    NASA Astrophysics Data System (ADS)

    Muyshondt, Pieter G. G.; Pires, Felipe; Dirckx, Joris J. J.

    2016-06-01

    The mechanical behavior of the middle ear structures in birds and mammals is affected by the fluids in the inner ear (IE) that are present behind the oval window. In this study, the aim was to gather knowledge of the acoustic impedance of the IE in the ostrich, to be able to determine the effect on vibrations and power flow in the single-ossicle bird middle ear for future studies. To determine the IE impedance, vibrations of the ossicle were measured for both the quasi-static and acoustic stimulus frequencies. In the acoustic regime, vibrations were measured with a laser Doppler vibrometer and electromagnetic stimulation of the ossicle. The impedance of the inner ear could be determined by means of a simple RLC model in series, which resulted in a stiffness reactance of KIE = 0.20.1012 Pa/m3, an inertial impedance of MIE = 0.652.106 Pa s2/m3, and a resistance of RIE = 1.57.109 Pa s/m. The measured impedance is found to be considerably smaller than what is found for the human IE.

  17. Chronic impedance spectroscopy of an endovascular stent-electrode array

    NASA Astrophysics Data System (ADS)

    Opie, Nicholas L.; John, Sam E.; Rind, Gil S.; Ronayne, Stephen M.; Grayden, David B.; Burkitt, Anthony N.; May, Clive N.; O'Brien, Terence J.; Oxley, Thomas J.

    2016-08-01

    Objective. Recently, we reported a minimally invasive stent-electrode array capable of recording neural signals from within a blood vessel. We now investigate the use of electrochemical impedance spectroscopy (EIS) measurements to infer changes occurring to the electrode-tissue interface from devices implanted in a cohort of sheep for up to 190 days. Approach. In a cohort of 15 sheep, endovascular stent-electrode arrays were implanted in the superior sagittal sinus overlying the motor cortex for up to 190 days. EIS was performed routinely to quantify viable electrodes for up to 91 days. An equivalent circuit model (ECM) was developed from the in vivo measurements to characterize the electrode-tissue interface changes occurring to the electrodes chronically implanted within a blood vessel. Post-mortem histological assessment of stent and electrode incorporation into the wall of the cortical vessels was compared to the electrical impedance measurements. Main results. EIS could be used to infer electrode viability and was consistent with x-ray analysis performed in vivo, and post-mortem evaluation. Viable electrodes exhibited consistent 1 kHz impedances across the 91 day measurement period, with the peak resistance frequency for the acquired data also stable over time. There was a significant change in 100 Hz phase angles, increasing from -67.8° ± 8.8° at day 0 to -43.8° ± 0.8° at day 91, which was observed to stabilize after eight days. ECM’s modeled to the data suggested this change was due to an increase in the capacitance of the electrode-tissue interface. This was supported by histological assessment with >85% of the implanted stent struts covered with neointima and incorporated into the blood vessel within two weeks. Conclusion. This work demonstrated that EIS could be used to determine the viability of electrode implanted chronically within a blood vessel. Impedance measurements alone were not observed to be a useful predictor of alterations occurring

  18. NONLINEAR DIAGNOSTICS USING AC DIPOLES.

    SciTech Connect

    PEGGS,S.

    1999-03-29

    There are three goals in the accurate nonlinear diagnosis of a storage ring. First, the beam must be moved to amplitudes many times the natural beam size. Second, strong and long lasting signals must be generated. Third, the measurement technique should be non-destructive. Conventionally, a single turn kick moves the beam to large amplitudes, and turn-by-turn data are recorded from multiple beam position monitors (BPMs) [1-6]. Unfortunately, tune spread across the beam causes the center of charge beam signal to ''decohere'' on a time scale often less than 100 turns. Filamentation also permanently destroys the beam emittance (in a hadron ring). Thus, the ''strong single turn kick'' technique successfully achieves only one out of the three goals. AC dipole techniques can achieve all three. Adiabatically excited AC dipoles slowly move the beam out to large amplitudes. The coherent signals then recorded last arbitrarily long. The beam maintains its original emittance if the AC dipoles are also turned off adiabatically, ready for further use. The AGS already uses an RF dipole to accelerate polarized proton beams through depolarizing resonances with minimal polarization loss [7]. Similar AC dipoles will be installed in the horizontal and vertical planes of both rings in RHIC [8]. The RHIC AC dipoles will also be used as spin flippers, and to measure linear optical functions [9].

  19. Bioelectrical Impedance Vector Analysis and Muscular Fitness in Healthy Men

    PubMed Central

    Rodríguez-Rodríguez, Fernando; Cristi-Montero, Carlos; González-Ruíz, Katherine; Correa-Bautista, Jorge Enrique; Ramírez-Vélez, Robinson

    2016-01-01

    Muscle strength can define the general muscular fitness (MF) measurable through hand-grip strength (HG), which is a factor that relates to the health of people of different ages. In this study we evaluated the muscle strength together with a bioimpedance electric analysis in 223 healthy Colombian adult subjects. The bioelectrical impedance vector analysis (BIVA) was conducted to determine the resistance (R), reactance (Xc) and phase angle (PhA). We classified the subjects into three groups (for tertiles), obtaining lower values of R and Xc in subjects with lower HG, plus a high correlation between PhA and HG. An increase in the level of PhA is associated with a high level of MF in a sample of healthy Latin American adult men. The BIVA’s parameters and PhA are a potentially effective preventive measure to be integrated into routine screening in the clinical setting. PMID:27384579

  20. Piston-cylinder apparatus for high-pressure impedance spectroscopy

    NASA Astrophysics Data System (ADS)

    Hinrichs, R.; da Jornada, J. A. H.

    1997-01-01

    A simple piston-cylinder apparatus was developed for impedance spectroscopy at pressures up to 3 GPa and temperatures up to 500 °C. The apparatus is of the compound cylinder type, with the innermost cylinder made of a commercially available low-cost alumina-based ceramic, with pistons of hard metal that allow electric connections. Cell electrical resistance was higher than 1 MΩ at T<300 °C and higher than 100 kΩ at 400 °C. The inductivity in the wires and pistons was about 2 μH. The sample was enclosed in a h-BN capsule, which insured a good hydrostaticity without disturbing the measurement. The equipment proved to be very useful in determining the activation volume of the conduction process in several ionic conductors.

  1. Using electrical impedance tomography to map subsurface hydraulic conductivity

    DOEpatents

    Berryman, James G.; Daily, William D.; Ramirez, Abelardo L.; Roberts, Jeffery J.

    2000-01-01

    The use of Electrical Impedance Tomography (EIT) to map subsurface hydraulic conductivity. EIT can be used to map hydraulic conductivity in the subsurface where measurements of both amplitude and phase are made. Hydraulic conductivity depends on at least two parameters: porosity and a length scale parameter. Electrical Resistance Tomography (ERT) measures and maps electrical conductivity (which can be related to porosity) in three dimensions. By introducing phase measurements along with amplitude, the desired additional measurement of a pertinent length scale can be achieved. Hydraulic conductivity controls the ability to flush unwanted fluid contaminants from the surface. Thus inexpensive maps of hydraulic conductivity would improve planning strategies for subsequent remediation efforts. Fluid permeability is also of importance for oil field exploitation and thus detailed knowledge of fluid permeability distribution in three-dimension (3-D) would be a great boon to petroleum reservoir analysts.

  2. Electrical Impedance Tomography Technology (EITT) Project

    NASA Technical Reports Server (NTRS)

    Oliva-Buisson, Yvette J.

    2014-01-01

    Development of a portable, lightweight device providing two-dimensional tomographic imaging of the human body using impedance mapping. This technology can be developed to evaluate health risks and provide appropriate medical care on the ISS, during space travel and on the ground.

  3. Impedance-matched drilling telemetry system

    DOEpatents

    Normann, Randy A.; Mansure, Arthur J.

    2008-04-22

    A downhole telemetry system that uses inductance or capacitance as a mode through which signal is communicated across joints between assembled lengths of pipe wherein efficiency of signal propagation through a drill string, for example, over multiple successive pipe segments is enhanced through matching impedances associated with the various telemetry system components.

  4. Energy-storage of a prescribed impedance

    NASA Technical Reports Server (NTRS)

    Smith, W. E.

    1969-01-01

    General mathematical expression found for energy storage shows that for linear, passive networks there is a minimum possible energy storage corresponding to a prescribed impedance. The electromagnetic energy storage is determined at different excitation frequencies through analysis of the networks terminal and reactance characteristics.

  5. Bioelectrical Impedance and Body Composition Assessment

    ERIC Educational Resources Information Center

    Martino, Mike

    2006-01-01

    This article discusses field tests that can be used in physical education programs. The most common field tests are anthropometric measurements, which include body mass index (BMI), girth measurements, and skinfold testing. Another field test that is gaining popularity is bioelectrical impedance analysis (BIA). Each method has particular strengths…

  6. Electrical impedance spectroscopy and diagnosis of tendinitis.

    PubMed

    Yoon, Kisung; Lee, Kyeong Woo; Kim, Sang Beom; Han, Tai Ryoon; Jung, Dong Keun; Roh, Mee Sook; Lee, Jong Hwa

    2010-02-01

    There have been a number of studies that investigate the usefulness of bioelectric signals in diagnoses and treatment in the medical field. Tendinitis is a musculoskeletal disorder with a very high rate of occurrence. This study attempts to examine whether electrical impedance spectroscopy (EIS) can detect pathological changes in a tendon and find the exact location of the lesion. Experimental tendinitis was induced by injecting collagenase into one side of the patellar tendons in rabbits, while the other side was used as the control. After measuring the impedance in the tendinitis and intact tendon tissue, the dissipation factor was computed. The real component of impedance and the dissipation factor turned out to be lower in tendinitis than in intact tissues. Moreover, the tendinitis dissipation factor spectrum showed a clear difference from that of the intact tendon, indicating its usefulness as a tool for detecting the location of the lesion. Pathologic findings from the tissues that were obtained after measuring the impedance confirmed the presence of characteristics of tendinitis. In conclusion, EIS is a useful method for diagnosing tendinitis and detecting the lesion location in invasive treatment.

  7. Explicit expressions of impedances and wake functions

    SciTech Connect

    Ng, K.Y.; Bane, K,; /SLAC

    2010-10-01

    Sections 3.2.4 and 3.2.5 of the Handbook of Accelerator Physics and Engineering on Landau damping are combined and updated. The new addition includes impedances and wakes for multi-layer beam pipe, optical model, diffraction model, and cross-sectional transition.

  8. Explicit Expressions of Impedances and Wake Functions

    SciTech Connect

    Ng, K.Y.; Bane, K,; /SLAC

    2012-06-11

    Sections 3.2.4 and 3.2.5 of the Handbook of Accelerator Physics and Engineering on Landau damping are combined and updated. The new addition includes impedances and wakes for multi-layer beam pipe, optical model, diffraction model, and cross-sectional transition.

  9. Landau damping with high frequency impedance

    SciTech Connect

    Blaskiewicz,M.

    2009-05-04

    Coupled bunch longitudinal stability in the presence of high frequency impedances is considered. A frequency domain technique is developed and compared with simulations. The frequency domain technique allows for absolute stability tests and is applied to the problem of longitudinal stability in RHIC with the new 56 MHz RF system.

  10. Evaluation of Parallel-Element, Variable-Impedance, Broadband Acoustic Liner Concepts

    NASA Technical Reports Server (NTRS)

    Jones, Michael G.; Howerton, Brian M.; Ayle, Earl

    2012-01-01

    Recent trends in aircraft engine design have highlighted the need for acoustic liners that provide broadband sound absorption with reduced liner thickness. Three such liner concepts are evaluated using the NASA normal incidence tube. Two concepts employ additive manufacturing techniques to fabricate liners with variable chamber depths. The first relies on scrubbing losses within narrow chambers to provide acoustic resistance necessary for sound absorption. The second employs wide chambers that provide minimal resistance, and relies on a perforated sheet to provide acoustic resistance. The variable-depth chambers used in both concepts result in reactance spectra near zero. The third liner concept employs mesh-caps (resistive sheets) embedded at variable depths within adjacent honeycomb chambers to achieve a desired impedance spectrum. Each of these liner concepts is suitable for use as a broadband sound absorber design, and a transmission line model is presented that provides good comparison with their respective acoustic impedance spectra. This model can therefore be used to design acoustic liners to accurately achieve selected impedance spectra. Finally, the effects of increasing the perforated facesheet thickness are demonstrated, and the validity of prediction models based on lumped element and wave propagation approaches is investigated. The lumped element model compares favorably with measured results for liners with thin facesheets, but the wave propagation model provides good comparisons for a wide range of facesheet thicknesses.

  11. Measurement of respiratory impedance by impulse oscillometry--effects of endotracheal tubes.

    PubMed

    Kuhnle, G E; Brandt, T; Roth, U; Goetz, A E; Smith, H J; Peter, K

    2000-12-01

    Impulse Oscillometry is a new, noninvasive method to measure respiratory impedance, i.e. airway resistance and reactance at different oscillation frequencies. These parameters are potentially useful for the monitoring of respiratory mechanics in the critically ill patent with respiratory dysfunction. The endotracheal tube, used to mechanically ventilate these patients, however, represents an additional nonlinear impedance that introduces artifacts into the measurements. The objective of this work was therefore to investigate the effects of clinically available endotracheal tubes on resistance and reactance of an in vitro analogue of the respiratory system. Additionally, the effects of decreasing the compressible gas volume in this experimental model, as a simulation of decreased lung capacity and compliance, was investigated. Impulse oscillometric measurements of the test analogue gave highly reproducible results with and without an endotracheal tube. The tubes had significant influence on the measurement of the test object at all frequencies investigated. Changes of low frequent reactance were negligible - at least if repetitive measurements of the same system are performed - for realistic measurement of airway resistance, a correction of the tube impedance or measurement of the pressure distal of the tube is required. Resistance increased and low frequent reactance decreased significantly with decreasing gas volume. These changes were of magnitudes higher than the variations due to the introduction of the endotracheal tubes. Our results suggest that changes of respiratory reactance measured with impulse oscillometry may be used as a monitoring parameter in intubated patients.

  12. One-chip electronic detection of DNA hybridization using precision impedance-based CMOS array sensor.

    PubMed

    Lee, Kang-Ho; Lee, Jeong-Oen; Sohn, Mi-Jin; Lee, Byunghun; Choi, Suk-Hwan; Kim, Sang Kyu; Yoon, Jun-Bo; Cho, Gyu-Hyeong

    2010-12-15

    This paper describes a label-free and fully electronic detection method of DNA hybridization, which is achieved through the use of a 16×8 microarray sensor in conjunction with a new type of impedance spectroscopy constructed with standard complementary metal-oxide-semiconductor (CMOS) technology. The impedance-based method is based on changes in the reactive capacitance and the charge-transfer resistance after hybridization with complementary DNA targets. In previously published label-free techniques, the measured capacitance presented unstable capacitive properties due to the parallel resistance that is not infinite and can cause a leakage by discharging the charge on the capacitor. This paper presents an impedance extraction method that uses excitation by triangular wave voltage, which enables a reliable measurement of both C and R producing a highly sensitive sensor with a stable operation independent of external variables. The system was fabricated in an industrial 0.35-μm 4-metal 2-poly CMOS process, integrating working electrodes and readout electronics into one chip. The integrated readout, which uses a parasitic insensitive integrator, achieves an enlarged detection range and improved noise performance. The maximum average relative variations of C and R are 31.5% and 68.6%, respectively, after hybridization with a 1 μM target DNA. The proposed sensor allows quantitative evaluation of the molecule densities on the chip with distinguishable variation in the impedance. This fully electronic microsystem has great potential for use with bioanalytical tools and point-of-care diagnosis.

  13. Graphene/Silicon heterojunction Schottky diode for vapors sensing using impedance spectroscopy.

    PubMed

    Fattah, Ali; Khatami, Saeid; Mayorga-Martinez, Carmen C; Medina-Sánchez, Mariana; Baptista-Pires, Luis; Merkoçi, Arben

    2014-10-29

    A graphene(G)/Silicon(Si) heterojunction Schottky diode and a simple method that evaluates its electrical response to different chemical vapors using electrochemical impedance spectroscopy (EIS) are implemented. To study the impedance response of the device of a given vapor, relative impedance change (RIC) as a function of the frequency is evaluated. The minimum value of RIC for different vapors corresponds to different frequency values (18.7, 12.9 and 10.7 KHz for chloroform, phenol, and methanol vapors respectively). The impedance responses to phenol, beside other gases used as model analytes for different vapor concentrations are studied. The equivalent circuit of the device is obtained and simplified, using data fitting from the extracted values of resistances and capacitances. The resistance corresponding to interphase G/Si is used as a parameter to compare the performance of this device upon different phenol concentrations and a high reproducibility with a 4.4% relative standard deviation is obtained. The efficiency of the device fabrication, its selectivity, reproducibility and easy measurement mode using EIS makes the developed system an interesting alternative for gases detection for environmental monitoring and other industrial applications.

  14. Synthesis and electrical properties of BaBiO 3 and high resistivity BaTiO 3 –BaBiO 3 ceramics

    SciTech Connect

    Kumar, Nitish; Golledge, Stephen L.; Cann, David P.

    2016-12-01

    Ceramics of the composition BaBiO3 (BB) were sintered in oxygen to obtain a single phase with monoclinic II2/mm symmetry as suggested by high-resolution X-ray diffraction. X-ray photoelectron spectroscopy confirmed the presence of bismuth in two valence states - 3+ and 5+. Optical spectroscopy showed presence of a direct bandgap at ~ 2.2eV and a possible indirect bandgap at ~ 0.9eV. This combined with determination of the activation energy for conduction of 0.25eV, as obtained from ac impedance spectroscopy, suggested that a polaron-mediated conduction mechanism was prevalent in BB. The BB ceramics were crushed, mixed with BaTiO3 (BT), and sintered to obtain BT–BB solid solutions. All the ceramics had tetragonal symmetry and exhibited a normal ferroelectric-like dielectric response. Using ac impedance and optical spectroscopy, it was shown that resistivity values of BT–BB were orders of magnitude higher than BT or BB alone, indicating a change in the fundamental defect equilibrium conditions. A shift in the site occupancy of Bi to the A-site is proposed to be the mechanism for the increased electrical resistivity.

  15. Generalized wave envelope analysis of sound propagation in ducts with stepped noise source profiles and variable axial impedance

    NASA Technical Reports Server (NTRS)

    Baumeister, K. J.

    1975-01-01

    A finite difference formulation is presented for sound propagation in a rectangular two-dimensional duct without steady flow. Before the difference equations are formulated, the governing Helmholtz equation is first transformed to a form whose solution tends not to oscillate along the length of the duct. This transformation reduces the required number of grid points by an order of magnitude. Example solutions indicate that stepped noise source profiles have much higher attenuation than plane waves in a uniform impedance liner. Also, multiple stepped impedance liners are shown to have higher attenuation than uniform ducts if the impedances are chosen properly. For optimum noise reduction with axial variations in impedance, the numerical analysis indicates that for a plane wave input the resistance should be near zero at the entrance of a suppressor duct, while the reactance should be near the optimum value associated with the least-attenuated mode in a uniform duct.

  16. Imaging and characterizing root systems using electrical impedance tomography

    NASA Astrophysics Data System (ADS)

    Kemna, A.; Weigand, M.; Kelter, M.; Pfeifer, J.; Zimmermann, E.; Walter, A.

    2011-12-01

    Root architecture, growth, and activity play an essential role regarding the nutrient uptake of roots in soils. While in recent years advances could be achieved concerning the modeling of root systems, measurement methods capable of imaging, characterizing, and monitoring root structure and dynamics in a non-destructive manner are still lacking, in particular at the field scale. We here propose electrical impedance tomography (EIT) for the imaging of root systems. The approach takes advantage of the low-frequency capacitive electrical properties of the soil-root interface and the root tissue. These properties are based on the induced migration of ions in an externally applied electric field and give rise to characteristic impedance spectra which can be measured by means of electrical impedance spectroscopy. The latter technique was already successfully applied in the 10 Hz to 1 MHz range by Ozier-Lafontaine and Bajazet (2005) to monitor root growth of tomato. We here apply the method in the 1 mHz to 45 kHz range, requiring four-electrode measurements, and demonstrate its implementation and potential in an imaging framework. Images of real and imaginary components of complex electrical conductivity are computed using a finite-element based inversion algorithm with smoothness-constraint regularization. Results from laboratory measurements on rhizotrons with different root systems (barley, rape) show that images of imaginary conductivity delineate the spatial extent of the root system under investigation, while images of real conductivity show a less clear response. As confirmed by numerical simulations, the latter could be explained by the partly compensating electrical conduction properties of epidermis (resistive) and inner root cells (conductive), indicating the limitations of conventional electrical resistivity tomography. The captured spectral behavior exhibits two distinct relaxation processes with Cole-Cole type signatures, which we interpret as the responses

  17. Compressible turbulent channel flow with impedance boundary conditions

    NASA Astrophysics Data System (ADS)

    Scalo, Carlo; Bodart, Julien; Lele, Sanjiva K.

    2015-03-01

    We have performed large-eddy simulations of isothermal-wall compressible turbulent channel flow with linear acoustic impedance boundary conditions (IBCs) for the wall-normal velocity component and no-slip conditions for the tangential velocity components. Three bulk Mach numbers, Mb = 0.05, 0.2, 0.5, with a fixed bulk Reynolds number, Reb = 6900, have been investigated. For each Mb, nine different combinations of IBC settings were tested, in addition to a reference case with impermeable walls, resulting in a total of 30 simulations. The adopted numerical coupling strategy allows for a spatially and temporally consistent imposition of physically realizable IBCs in a fully explicit compressible Navier-Stokes solver. The IBCs are formulated in the time domain according to Fung and Ju ["Time-domain impedance boundary conditions for computational acoustics and aeroacoustics," Int. J. Comput. Fluid Dyn. 18(6), 503-511 (2004)]. The impedance adopted is a three-parameter damped Helmholtz oscillator with resonant angular frequency, ωr, tuned to the characteristic time scale of the large energy-containing eddies. The tuning condition, which reads ωr = 2πMb (normalized with the speed of sound and channel half-width), reduces the IBCs' free parameters to two: the damping ratio, ζ, and the resistance, R, which have been varied independently with values, ζ = 0.5, 0.7, 0.9, and R = 0.01, 0.10, 1.00, for each Mb. The application of the tuned IBCs results in a drag increase up to 300% for Mb = 0.5 and R = 0.01. It is shown that for tuned IBCs, the resistance, R, acts as the inverse of the wall-permeability and that varying the damping ratio, ζ, has a secondary effect on the flow response. Typical buffer-layer turbulent structures are completely suppressed by the application of tuned IBCs. A new resonance buffer layer is established characterized by large spanwise-coherent Kelvin-Helmholtz rollers, with a well-defined streamwise wavelength λx, traveling downstream with

  18. Intravascular electric impedance spectroscopy of atherosclerotic lesions using a new impedance catheter system.

    PubMed

    Süselbeck, T; Thielecke, H; Köchlin, J; Cho, S; Weinschenk, I; Metz, J; Borggrefe, M; Haase, K K

    2005-09-01

    Newer techniques are required to identify atherosclerotic lesions that are prone to rupture. Electric impedance spectroscopy (EIS) can characterize biological tissues by measuring the electrical impedance over a frequency range. We tested a newly designed intravascular impedance catheter (IC) by measuring the impedance of different stages of atherosclerosis induced in an animal rabbit model. Six female New Zealand White rabbits were fed for 17 weeks with a 5% cholesterol-enriched diet to induce early forms of atherosclerotic plaques. All aortas were prepared from the aortic arch to the renal arteries and segments of 5-10 mm were marked by ink spots. A balloon catheter system with an integrated polyimide-based microelectrode structure was introduced into the aorta and the impedance was measured at each spot by using an impedance analyzer. The impedance was measured at frequencies of 1 kHz and 10 kHz and compared with the corresponding histomorphometric data of each aortic segment.Forty-four aortic segments without plaques and 48 segments with evolving atherosclerotic lesions could be exactly matched by the histomorphometric analysis. In normal aortic segments (P0) the change of the magnitude of impedance at 1 kHz and at 10 kHz (|Z|(1 kHz) - |Z|(10 kHz), = ICF) was 208.5 +/- 357.6 Omega. In the area of aortic segments with a plaque smaller than that of the aortic wall diameter (PI), the ICF was 137.7 +/- 192.8 Omega. (P 0 vs. P I; p = 0.52), whereas in aortic segments with plaque formations larger than the aortic wall (PII) the ICF was significantly lower -22.2 +/- 259.9 Omega. (P0 vs. PII; p = 0.002). Intravascular EIS could be successfully performed by using a newly designed microelectrode integrated onto a conventional coronary balloon catheter. In this experimental animal model atherosclerotic aortic lesions showed significantly higher ICF in comparison to the normal aortic tissue.

  19. A compact wideband precision impedance measurement system based on digital auto-balancing bridge

    NASA Astrophysics Data System (ADS)

    Hu, Binxin; Wang, Jinyu; Song, Guangdong; Zhang, Faxiang

    2016-05-01

    The ac impedance spectroscopy measurements are predominantly taken by using impedance analyzers based on analog auto-balancing bridge. However, those bench-top analyzers are generally complicated, bulky and expensive, thus limiting their usage in industrial field applications. This paper presents the development of a compact wideband precision measurement system based on digital auto-balancing bridge. The methods of digital auto-balancing bridge and digital lock-in amplifier are analyzed theoretically. The overall design and several key sections including null detector, direct digital synthesizer-based sampling clock, and digital control unit are introduced in detail. The results show that the system achieves a basic measurement accuracy of 0.05% with a frequency range of 20 Hz-2 MHz. The advantages of versatile measurement capacity, fast measurement speed, small size and low cost make it quite suitable for industrial field applications. It is demonstrated that this system is practical and effective by applying in determining the impedance-temperature characteristic of a motor starter PTC thermistor.

  20. THE ELECTRICAL IMPEDANCE OF MUSCLE DURING THE ACTION OF NARCOTICS AND OTHER AGENTS.

    PubMed

    Guttman, R

    1939-05-20

    1. The effect of certain inorganic cations upon the electrical impedance of the sartorius muscle of the frog was investigated. While Na, K, and Mg have little effect upon the resistance of muscle, Ba and Ca cause it to fall. The use of physiologically "unbalanced" salt solution does not in itself seem to affect muscle impedance. 2. The time course of the effect upon muscle impedance of the penetration of substances into the intercellular spaces was studied by treating the muscle with sugar solutions. Half of the effect is over in three-quarters of a minute when the sugar solution is permitted to circulate past both sides of the muscle. This sets an upper limit for the time necessary for inorganic cations and organic narcotics to reach the cell surfaces. The action of inorganic cations and organic narcotics upon muscle is slow compared to the time necessary for them to reach the scene of action. The penetration of the sugar solutions into the intercellular spaces of muscle was found to follow the well known diffusion law, the amount diffusing in being proportional to the square root of the time. Average values of 77.7 per cent for rho, the volume concentration of fibers; 231 ohms specific resistance for r(2), the resistance of the interior of the fibers; and 71.0 degrees for theta, the phase angle of the impedance locus, were obtained for the muscle in Ringer's solution. How these values change when the muscle is placed in various concentrations of sugar was also studied. 3. The action of a number of organic narcotics upon muscle was studied. All decrease 1000 cycle resistance if the concentration is sufficiently high. A detailed analysis of the action of the narcotic, iso-amyl carbamate, was made, and it was noted that low concentrations increase resistance while higher concentrations decrease it. By investigating the effect of narcotics upon muscle impedance over a wide frequency range, it was found that during narcosis the resistance of the fiber membranes first