Science.gov

Sample records for avec capacites calorifiques

  1. Capacitive Extensometer

    NASA Technical Reports Server (NTRS)

    Perusek, Gail P. (Inventor)

    2003-01-01

    The present invention provides for measurements of the principal strain magnitudes and directions, and maximum shear strain that occurs in a porous specimen, such as plastic, ceramic or porous metal, when it is loaded (or subjected to a load). In one embodiment the invention includes a capacitive delta extensometer arranged with six sensors in a three piece configuration, with each sensor of each pair spaced apart from each other by a predetermined angle, such as 120 degrees.

  2. Variable Synthetic Capacitance

    NASA Technical Reports Server (NTRS)

    Kleinberg, L. L.

    1986-01-01

    Feedback amplifier circuit synthesizes electronically variable capacitance. Variable Synthetic Capacitor is amplifier circuit with follower/feedback configuration. Effective input capacitance depends on input set current. If synthetic capacitor is connected across resonant element of oscillator, oscillator frequency controlled via input set current. Circuit especially suitable for fine frequency adjustments of piezoelectric-crystal or inductor/capacitor resonant oscillators.

  3. Capacitance measuring device

    DOEpatents

    Andrews, W.H. Jr.

    1984-08-01

    A capacitance measuring circuit is provided in which an unknown capacitance is measured by comparing the charge stored in the unknown capacitor with that stored in a known capacitance. Equal and opposite voltages are repetitively simultaneously switched onto the capacitors through an electronic switch driven by a pulse generator to charge the capacitors during the ''on'' portion of the cycle. The stored charge is compared by summing discharge currents flowing through matched resistors at the input of a current sensor during the ''off'' portion of the switching cycle. The net current measured is thus proportional to the difference in value of the two capacitances. The circuit is capable of providing much needed accuracy and stability to a great variety of capacitance-based measurement devices at a relatively low cost.

  4. Capacitance pressure sensor

    DOEpatents

    Eaton, William P.; Staple, Bevan D.; Smith, James H.

    2000-01-01

    A microelectromechanical (MEM) capacitance pressure sensor integrated with electronic circuitry on a common substrate and a method for forming such a device are disclosed. The MEM capacitance pressure sensor includes a capacitance pressure sensor formed at least partially in a cavity etched below the surface of a silicon substrate and adjacent circuitry (CMOS, BiCMOS, or bipolar circuitry) formed on the substrate. By forming the capacitance pressure sensor in the cavity, the substrate can be planarized (e.g. by chemical-mechanical polishing) so that a standard set of integrated circuit processing steps can be used to form the electronic circuitry (e.g. using an aluminum or aluminum-alloy interconnect metallization).

  5. Capacitive chemical sensor

    DOEpatents

    Manginell, Ronald P; Moorman, Matthew W; Wheeler, David R

    2014-05-27

    A microfabricated capacitive chemical sensor can be used as an autonomous chemical sensor or as an analyte-sensitive chemical preconcentrator in a larger microanalytical system. The capacitive chemical sensor detects changes in sensing film dielectric properties, such as the dielectric constant, conductivity, or dimensionality. These changes result from the interaction of a target analyte with the sensing film. This capability provides a low-power, self-heating chemical sensor suitable for remote and unattended sensing applications. The capacitive chemical sensor also enables a smart, analyte-sensitive chemical preconcentrator. After sorption of the sample by the sensing film, the film can be rapidly heated to release the sample for further analysis. Therefore, the capacitive chemical sensor can optimize the sample collection time prior to release to enable the rapid and accurate analysis of analytes by a microanalytical system.

  6. System for Measuring Capacitance

    NASA Technical Reports Server (NTRS)

    McNichol, Randal S. (Inventor)

    2001-01-01

    A system has been developed for detecting the level of a liquid in a tank wherein a capacitor positioned in the tank has spaced plates which are positioned such that the dielectric between the plates will be either air or the liquid, depending on the depth of the liquid in the tank. An oscillator supplies a sine wave current to the capacitor and a coaxial cable connects the capacitor to a measuring circuit outside the tank. If the cable is very long or the capacitance to be measured is low, the capacitance inherent in the coaxial cable will prevent an accurate reading. To avoid this problem, an inductor is connected across the cable to form with the capacitance of the cable a parallel resonant circuit. The impedance of the parallel resonant circuit is infinite, so that attenuation of the measurement signal by the stray cable capacitance is avoided.

  7. Online capacitive densitometer

    DOEpatents

    Porges, Karl G.

    1990-01-01

    This invention is an apparatus for measuring fluid density of mixed phase fluid flow. The apparatus employs capacitive sensing of the mixed phased flow combined with means for uniformizing the electric field between the capacitor plates to account for flow line geometry. From measurement of fluid density, the solids feedrate can be ascertained.

  8. Steerable Capacitive Proximity Sensor

    NASA Technical Reports Server (NTRS)

    Jenstrom, Del T.; Mcconnell, Robert L.

    1994-01-01

    Steerable capacitive proximity sensor of "capaciflector" type based partly on sensing units described in GSC-13377 and GSC-13475. Position of maximum sensitivity adjusted without moving sensor. Voltage of each driven shield adjusted separately to concentrate sensing electric field more toward one side or other.

  9. Digital capacitance measuring system

    NASA Technical Reports Server (NTRS)

    1973-01-01

    The hardware phase of a digital capacitance measuring system is presented with the major emphasis placed on the electrical design and operation. Test results are included of the three units fabricated. The system's interface is applicable to existing requirements for the space shuttle vehicle.

  10. Online capacitive densitometer

    DOEpatents

    Porges, K.G.

    1988-01-21

    This invention is an apparatus for measuring fluid density of mixed phase fluid flow. The apparatus employs capacitive sensing of the mixed phased flow combined with means for uniformizing the electric field between the capacitor plates to account for flow line geometry. From measurement of fluid density, the solids feedrate can be ascertained. 7 figs.

  11. Capacitive deionization of seawater

    SciTech Connect

    Farmer, J.C.; Fix, D.V.; Mack, G.V.

    1995-10-01

    Capacitive deionization with carbon aerogel electrodes is an efficient and economical new process for removing salt and impurities from water. Carbon aerogel is a material that enables the successful purification of water because of its high surface area, optimum pore size, and low electrical resistivity. The electrodes are maintained at a potential difference of about one volt; ions are removed from the water by the imposed electrostatic field and retained on the electrode surface until the polarity is reversed. The capacitive deionization of water with a stack of carbon aerogel electrodes has been successfully demonstrated. The overall process offers advantages when compared to conventional water-purification methods, requiring neither pumps, membranes, distillation columns, nor thermal heaters. Consequently, the overall process is both robust and energy efficient. The current state of technology development, commercialization, and potential applications of this process are reviewed.

  12. Capacitive skin characterization

    NASA Technical Reports Server (NTRS)

    Mcconnell, Robert; Manzo, Michael

    1992-01-01

    NASA is currently involved in research that utilizes a capacitive sensor that is used for proximity detection of objects. This sensor is sensitive to conductive and dielectric materials including metal objects and humans. The range of the sensor has been found to be about twelve inches. It is the goal of this research project to further characterize the sensor so that it can be tailored to specific requirements. The characterization of the sensor should be with respect to shield size, sensor size, object size, and object distance. The method of finite elements to calculate the capacitance of the sensor while varying different parameters was used. Each of the parameters was varied in turn, often by selecting data points from different runs. The plotted results are shown and an apparent functionality developed for each.

  13. Electrical capacitance clearanceometer

    NASA Technical Reports Server (NTRS)

    Hester, Norbert J. (Inventor); Hornbeck, Charles E. (Inventor); Young, Joseph C. (Inventor)

    1992-01-01

    A hot gas turbine engine capacitive probe clearanceometer is employed to measure the clearance gap or distance between blade tips on a rotor wheel and its confining casing under operating conditions. A braze sealed tip of the probe carries a capacitor electrode which is electrically connected to an electrical inductor within the probe which is inserted into a turbine casing to position its electrode at the inner surface of the casing. Electrical power is supplied through a voltage controlled variable frequency oscillator having a tuned circuit in which the probe is a component. The oscillator signal is modulated by a change in electrical capacitance between the probe electrode and a passing blade tip surface while an automatic feedback correction circuit corrects oscillator signal drift. A change in distance between a blade tip and the probe electrode is a change in capacitance therebetween which frequency modulates the oscillator signal. The modulated oscillator signal which is then processed through a phase detector and related circuitry to provide an electrical signal is proportional to the clearance gap.

  14. Capacitive label reader

    DOEpatents

    Arlowe, H. Duane

    1985-01-01

    A capacitive label reader includes an outer ring transmitting portion, an inner ring transmitting portion, and a plurality of insulated receiving portions. A label is the mirror-image of the reader except that identifying portions corresponding to the receiving portions are insulated from only one of two coupling elements. Positive and negative pulses applied, respectively, to the two transmitting rings biased a CMOS shift register positively to either a 1 or 0 condition. The output of the CMOS may be read as an indication of the label.

  15. Capacitive label reader

    DOEpatents

    Arlowe, H.D.

    1985-11-12

    A capacitive label reader includes an outer ring transmitting portion, an inner ring transmitting portion, and a plurality of insulated receiving portions. A label is the mirror-image of the reader except that identifying portions corresponding to the receiving portions are insulated from only one of two coupling elements. Positive and negative pulses applied, respectively, to the two transmitting rings biased a CMOS shift register positively to either a 1 or 0 condition. The output of the CMOS may be read as an indication of the label. 5 figs.

  16. Improved Capacitive Liquid Sensor

    NASA Technical Reports Server (NTRS)

    Waldman, Francis A.

    1992-01-01

    Improved capacitive sensor used to detect presence and/or measure thickness of layer of liquid. Electrical impedance or admittance of sensor measured at prescribed frequency, and thickness of liquid inferred from predetermined theoretical or experimental relationship between impedance and thickness. Sensor is basically a three-terminal device. Features interdigitated driving and sensing electrodes and peripheral coplanar ground electrode that reduces parasitic effects. Patent-pending because first to utilize ground plane as "shunting" electrode. System less expensive than infrared, microwave, or refractive-index systems. Sensor successfully evaluated in commercial production plants to characterize emulsions, slurries, and solutions.

  17. Capacitive label reader

    DOEpatents

    Arlowe, H.D.

    1983-07-15

    A capacitive label reader includes an outer ring transmitting portion, an inner ring transmitting portion, and a plurality of insulated receiving portions. A label is the mirror-image of the reader except that identifying portions corresponding to the receiving portions are insulated from only one of two coupling elements. Positive and negative pulses applied, respectively, to the two transmitting rings biased a CMOS shift register positively to either a 1 or 0 condition. The output of the CMOS may be read as an indication of the label.

  18. Programmable electronic synthesized capacitance

    NASA Technical Reports Server (NTRS)

    Kleinberg, Leonard L. (Inventor)

    1987-01-01

    A predetermined and variable synthesized capacitance which may be incorporated into the resonant portion of an electronic oscillator for the purpose of tuning the oscillator comprises a programmable operational amplifier circuit. The operational amplifier circuit has its output connected to its inverting input, in a follower configuration, by a network which is low impedance at the operational frequency of the circuit. The output of the operational amplifier is also connected to the noninverting input by a capacitor. The noninverting input appears as a synthesized capacitance which may be varied with a variation in gain-bandwidth product of the operational amplifier circuit. The gain-bandwidth product may, in turn, be varied with a variation in input set current with a digital to analog converter whose output is varied with a command word. The output impedance of the circuit may also be varied by the output set current. This circuit may provide very small ranges in oscillator frequency with relatively large control voltages unaffected by noise.

  19. Capacitively-coupled inductive sensor

    DOEpatents

    Ekdahl, Carl A.

    1984-01-01

    A capacitively coupled inductive shunt current sensor which utilizes capacitive coupling between flanges having an annular inductive channel formed therein. A voltage dividing capacitor is connected between the coupling capacitor and ground to provide immediate capacitive division of the output signal so as to provide a high frequency response of the current pulse to be detected. The present invention can be used in any desired outer conductor such as the outer conductor of a coaxial transmission line, the outer conductor of an electron beam transmission line, etc.

  20. Capacitive deionization system

    SciTech Connect

    Richardson, J. H., LLNL

    1996-10-01

    The new capacitive deionization system (CDI) removes ions, contaminants impurities from water and other aqueous process streams, and further selectively places the removed ions back into solution during regeneration. It provides a separation process that does not utilize chemical regeneration processes, and thus significantly reduces or completely eliminates secondary wastes associated with the operation of ion exchange resins. In the CDI, electrolyte flows in open channels formed between adjacent electrodes, and consequently the pressure drop is much lower than conventional separation processes. The fluid flow can be gravity fed through these open channels, and does not require membranes. This feature represents a significant advantage over the conventional reverse osmosis systems which include water permeable cellulose acetate membranes, and over the electrodialysis systems which require expensive and exotic ion exchange membranes. The CDI is adaptable for use in a wide variety of commercial applications, including domestic water softening, industrial water softening, waste water purification, sea water desalination, treatment of nuclear and aqueous wastes, treatment of boiler water in nuclear and fossil power plants, production of high-purity water for semiconductor processing, and removal of salt from water for agricultural irrigation. CDI accomplishes this removal of impurities by a variety of mechanisms, but predominantly by electrostatic removal of organic and inorganic ions from water or any other dielectric solvent.

  1. Shielded capacitive electrode

    SciTech Connect

    Kireeff Covo, Michel

    2013-07-09

    A device is described, which is sensitive to electric fields, but is insensitive to stray electrons/ions and unlike a bare, exposed conductor, it measures capacitively coupled current while rejecting currents due to charged particle collected or emitted. A charged particle beam establishes an electric field inside the beam pipe. A grounded metallic box with an aperture is placed in a drift region near the beam tube radius. The produced electric field that crosses the aperture generates a fringe field that terminates in the back surface of the front of the box and induces an image charge. An electrode is placed inside the grounded box and near the aperture, where the fringe fields terminate, in order to couple with the beam. The electrode is negatively biased to suppress collection of electrons and is protected behind the front of the box, so the beam halo cannot directly hit the electrode and produce electrons. The measured signal shows the net potential (positive ion beam plus negative electrons) variation with time, as it shall be observed from the beam pipe wall.

  2. Oscillation of Capacitance inside Nanopores

    SciTech Connect

    Jiang, De-en; Jin, Zhehui; Wu, Jianzhong

    2011-10-26

    Porous carbons of high surface area are promising as cost-effective electrode materials for supercapacitors. Although great attention has been given to the anomalous increase of the capacitance as the pore size approaches the ionic dimensions, there remains a lack of full comprehension of the size dependence of the capacitance in nanopores. Here we predict from a classical density functional theory that the capacitance of an ionic-liquid electrolyte inside a nanopore oscillates with a decaying envelope as the pore size increases. The oscillatory behavior can be attributed to the interference of the overlapping electric double layers (EDLs); namely, the maxima in capacitance appear when superposition of the two EDLs is most constructive. The theoretical prediction agrees well with the experiment when the pore size is less than twice the ionic diameter. Confirmation of the entire oscillatory spectrum invites future experiments with a precise control of the pore size from micro- to mesoscales.

  3. Oscillation of Capacitance inside Nanopores

    SciTech Connect

    Jiang, Deen; Wu, Jianzhong; Jin, Zhehui

    2011-01-01

    materials for supercapacitors. Although great attention has been given to the anomalous increase of the capacitance as the pore size approaches the ionic dimensions, there remains a lack of full comprehension of the size dependence of the capacitance in nanopores. Here we predict from a classical density functional theory that the capacitance of an ionic-liquid electrolyte inside a nanopore oscillates with a decaying envelope as the pore size increases. The oscillatory behavior can be attributed to the interference of the overlapping electric double layers (EDLs); namely, the maxima in capacitance appear when superposition of the two EDLs is most constructive. The theoretical prediction agreeswell with the experiment when the pore size is less than twice the ionic diameter.Confirmation of the entire oscillatory spectruminvites future experiments with a precise control of the pore size from micro- to mesoscales.

  4. Capacitive Position Sensor For Accelerometer

    NASA Technical Reports Server (NTRS)

    Vanzandt, Thomas R.; Kaiser, William J.; Kenny, Thomas W.

    1995-01-01

    Capacitive position sensor measures displacement of proof mass in prototype accelerometer described in "Single-Crystal Springs for Accelerometers" (NPO-18795). Sensor is ultrasensitive, miniature device operating at ultra-high frequency and described in more detail in "Ultra-High-Frequency Capacitive Displacement Sensor," (NPO-18675). Advances in design and fabrication of prototype accelerometer also applicable to magnetometers and other sensors in which sensed quantities measured in terms of deflections of small springs.

  5. The Capacitive Magnetic Field Sensor

    NASA Astrophysics Data System (ADS)

    Zyatkov, D. O.; Yurchenko, A. V.; Balashov, V. B.; Yurchenko, V. I.

    2016-01-01

    The results of a study of sensitive element magnetic field sensor are represented in this paper. The sensor is based on the change of the capacitance with an active dielectric (ferrofluid) due to the magnitude of magnetic field. To prepare the ferrofluid magnetic particles are used, which have a followingdispersion equal to 50 < Ø < 56, 45 < Ø < 50, 40 < Ø < 45 and Ø < 40micron of nanocrystalline alloy of brand 5BDSR. The dependence of the sensitivity of the capacitive element from the ferrofluid with different dispersion of magnetic particles is considered. The threshold of sensitivity and sensitivity of a measuring cell with ferrofluid by a magnetic field was determined. The experimental graphs of capacitance change of the magnitude of magnetic field are presented.

  6. Label free redox capacitive biosensing.

    PubMed

    Fernandes, Flávio C Bedatty; Góes, Márcio S; Davis, Jason J; Bueno, Paulo R

    2013-12-15

    A surface confined redox group contributes to an interfacial charging (quantifiable by redox capacitance) that can be sensitively probed by impedance derived capacitance spectroscopy. In generating mixed molecular films comprising such redox groups, together with specific recognition elements (here antibodies), this charging signal is able to sensitively transduce the recognition and binding of specific analytes. This novel transduction method, exemplified here with C-reactive protein, an important biomarker of cardiac status and general trauma, is equally applicable to any suitably prepared interfacial combination of redox reporter and receptor. The assays are label free, ultrasensitive, highly specific and accompanied by a good linear range. PMID:23896524

  7. Defect Location Using Capacitative Imaging

    NASA Astrophysics Data System (ADS)

    Diamond, G. G.; Hutchins, D. A.; Gan, T. H.

    2008-02-01

    Further details of a novel capacitance sensing technique are presented, which is capable of imaging defects within a range of materials, including insulators, conductors and fibre reinforced composites. Representative results from each of these separate classes of material are presented here as are the results of real-life field trials in the inspection of civil structures.

  8. Driven shielding capacitive proximity sensor

    NASA Technical Reports Server (NTRS)

    Vranish, John M. (Inventor); McConnell, Robert L. (Inventor)

    2000-01-01

    A capacitive proximity sensing element, backed by a reflector driven at the same voltage as and in phase with the sensor, is used to reflect the field lines away from a grounded robot arm towards an intruding object, thus dramatically increasing the sensor's range and sensitivity.

  9. Capacitive Proximity Sensor Has Longer Range

    NASA Technical Reports Server (NTRS)

    Vranish, John M.

    1992-01-01

    Capacitive proximity sensor on robot arm detects nearby object via capacitive effect of object on frequency of oscillator. Sensing element part of oscillator circuit operating at about 20 kHz. Total capacitance between sensing element and ground constitutes tuning capacitance of oscillator. Sensor circuit includes shield driven by replica of alternating voltage applied to sensing element. Driven shield concentrates sensing electrostatic field in exterior region to enhance sensitivity to object. Sensitivity and dynamic range has corresponding 12-to-1 improvement.

  10. Active Targets For Capacitive Proximity Sensors

    NASA Technical Reports Server (NTRS)

    Jenstrom, Del T.; Mcconnell, Robert L.

    1994-01-01

    Lightweight, low-power active targets devised for use with improved capacitive proximity sensors described in "Capacitive Proximity Sensor Has Longer Range" (GSC-13377), and "Capacitive Proximity Sensors With Additional Driven Shields" (GSC-13475). Active targets are short-distance electrostatic beacons; they generate known alternating electro-static fields used for alignment and/or to measure distances.

  11. Triboelectricity in capacitive biopotential measurements.

    PubMed

    Wartzek, Tobias; Lammersen, Thomas; Eilebrecht, Benjamin; Walter, Marian; Leonhardt, Steffen

    2011-05-01

    Capacitive biopotential measurements suffer from strong motion artifacts, which may result in long time periods during which a reliable measurement is not possible. This study examines contact electrification and triboelectricity as possible reasons for these artifacts and discusses local triboelectric effects on the electrode-body interface as well as global electrostatic effects as common-mode interferences. It will be shown that most probably the triboelectric effects on the electrode-body interface are the main reason for artifacts, and a reduction of artifacts can only be achieved with a proper design of the electrode-body interface. For a deeper understanding of the observed effects, a mathematical model for triboelectric effects in highly isolated capacitive biopotential measurements is presented and verified with experiments. Based on these analyses of the triboelectric effects on the electrode-body interface, different electrode designs are developed and analyzed in order to minimize artifacts due to triboelectricity on the electrode-body interface. PMID:21177156

  12. Quantum Capacitance in Topological Insulators

    PubMed Central

    Xiu, Faxian; Meyer, Nicholas; Kou, Xufeng; He, Liang; Lang, Murong; Wang, Yong; Yu, Xinxin; Fedorov, Alexei V.; Zou, Jin; Wang, Kang L.

    2012-01-01

    Topological insulators show unique properties resulting from massless, Dirac-like surface states that are protected by time-reversal symmetry. Theory predicts that the surface states exhibit a quantum spin Hall effect with counter-propagating electrons carrying opposite spins in the absence of an external magnetic field. However, to date, the revelation of these states through conventional transport measurements remains a significant challenge owing to the predominance of bulk carriers. Here, we report on an experimental observation of Shubnikov-de Haas oscillations in quantum capacitance measurements, which originate from topological helical states. Unlike the traditional transport approach, the quantum capacitance measurements are remarkably alleviated from bulk interference at high excitation frequencies, thus enabling a distinction between the surface and bulk. We also demonstrate easy access to the surface states at relatively high temperatures up to 60 K. Our approach may eventually facilitate an exciting exploration of exotic topological properties at room temperature. PMID:22993694

  13. Flexible Framework for Capacitive Sensing

    NASA Technical Reports Server (NTRS)

    Woodard, Stanley E. (Inventor); Taylor, Bryant D. (Inventor)

    2006-01-01

    A flexible framework supports electrically-conductive elements in a capacitive sensing arrangement. Identical frames are arranged end-to-end with adjacent frames being capable of rotational movement there between. Each frame has first and second passages extending therethrough and parallel to one another. Each of the first and second passages is adapted to receive an electrically-conductive element therethrough. Each frame further has a hollowed-out portion for the passage of a fluent material therethrough. The hollowed-out portion is sized and shaped to provide for capacitive sensing along a defined region between the electrically-conductive element in the first passage and the electrically-conductive element in the second passage.

  14. Full-bridge capacitive extensometer

    NASA Astrophysics Data System (ADS)

    Peters, Randall D.

    1993-08-01

    Capacitive transducers have proven to be very effective sensors of small displacements, because of inherent stability and noninvasive high resolution. The most versatile ones have been those of a differential type, in which two elements are altered in opposite directions in response to change of the system parameter being monitored. Oftentimes, this differential pair has been incorporated into a bridge circuit, which is a useful means for employing synchronous detection to improve signal to noise ratios. Unlike previous differential capacitive dilatometers which used only two active capacitors, the present sensor is a full-bridge type, which is well suited to measuring low-level thermal expansions. This analog sensor is capable of 0.1 μm resolution anywhere within a range of several centimeters, with a linearity of 0.1%. Its user friendly output can be put on a strip chart recorder or directed to a computer for sophisticated data analysis.

  15. Capacitive de-ionization electrode

    SciTech Connect

    Daily, III, William D.

    2013-03-19

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

  16. Capacitively-Heated Fluidized Bed

    NASA Technical Reports Server (NTRS)

    Mchale, E. J.

    1982-01-01

    Fluidized-bed chamber in which particles in bed are capacitively heated produces high yields of polycrystalline silicon for semiconductor devices. Deposition of unrecoverable silicon on chamber wall is reduced, and amount of recoverable silicon depositing on seed particles in bed is increased. Particles also have a size and density suitable for direct handling without consolidation, unlike silicon dust produced in heated-wall chambers.

  17. Redox regulation of mammalian sperm capacitation

    PubMed Central

    O’Flaherty, Cristian

    2015-01-01

    Capacitation is a series of morphological and metabolic changes necessary for the spermatozoon to achieve fertilizing ability. One of the earlier happenings during mammalian sperm capacitation is the production of reactive oxygen species (ROS) that will trigger and regulate a series of events including protein phosphorylation, in a time-dependent fashion. The identity of the sperm oxidase responsible for the production of ROS involved in capacitation is still elusive, and several candidates are discussed in this review. Interestingly, ROS-induced ROS formation has been described during human sperm capacitation. Redox signaling during capacitation is associated with changes in thiol groups of proteins located on the plasma membrane and subcellular compartments of the spermatozoon. Both, oxidation of thiols forming disulfide bridges and the increase on thiol content are necessary to regulate different sperm proteins associated with capacitation. Reducing equivalents such as NADH and NADPH are necessary to support capacitation in many species including humans. Lactate dehydrogenase, glucose-6-phospohate dehydrogenase, and isocitrate dehydrogenase are responsible in supplying NAD (P) H for sperm capacitation. Peroxiredoxins (PRDXs) are newly described enzymes with antioxidant properties that can protect mammalian spermatozoa; however, they are also candidates for assuring the regulation of redox signaling required for sperm capacitation. The dysregulation of PRDXs and of enzymes needed for their reactivation such as thioredoxin/thioredoxin reductase system and glutathione-S-transferases impairs sperm motility, capacitation, and promotes DNA damage in spermatozoa leading to male infertility. PMID:25926608

  18. An approach to evaluate capacitance, capacitive reactance and resistance of pivoted pads of a thrust bearing

    NASA Astrophysics Data System (ADS)

    Prashad, Har

    1992-07-01

    A theoretical approach is developed for determining the capacitance and active resistance between the interacting surfaces of pivoted pads and thrust collar, under different conditions of operation. It is shown that resistance and capacitive reactance of a thrust bearing decrease with the number of pads times the values of these parameters for an individual pad, and that capacitance increases with the number of pads times the capacitance of an individual pad. The analysis presented has a potential to diagnose the behavior of pivoted pad thrust bearings with the angle of tilt and the ratio of film thickness at the leading to trailing edge, by determining the variation of capacitance, resistance, and capacitive reactance.

  19. Capacitance enhancement via electrode patterning

    NASA Astrophysics Data System (ADS)

    Ho, Tuan A.; Striolo, Alberto

    2013-11-01

    The necessity of increasing the energy density in electric double layer capacitors to meet current demand is fueling fundamental and applied research alike. We report here molecular dynamics simulation results for aqueous electrolytes near model electrodes. Particular focus is on the effect of electrode patterning on the structure of interfacial electrolytes, and on the potential drop between the solid electrodes and the bulk electrolytes. The latter is estimated by numerically integrating the Poisson equation using the charge densities due to water and ions accumulated near the interface as input. We considered uniform and patterned electrodes, both positively and negatively charged. The uniformly charged electrodes are modeled as graphite. The patterned ones are obtained by removing carbon atoms from the top-most graphene layer, yielding nanoscopic squares and stripes patterns. For simplicity, the patterned electrodes are effectively simulated as insulators (the charge remains localized on the top-most layer of carbon atoms). Our simulations show that the patterns alter the structure of water and the accumulation of ions at the liquid-solid interfaces. Using aqueous NaCl solutions, we found that while the capacitance calculated for three positively charged electrodes did not change much, that calculated for the negatively charged electrodes significantly increased upon patterning. We find that both water structure and orientation, as well as ion accumulation affect the capacitance. As electrode patterning affects differently water structure and ion accumulation, it might be possible to observe ion-specific effects. These results could be useful for advancing our understanding of electric double layer capacitors, capacitive desalination processes, as well as of fundamental interfacial electrolytes properties.

  20. Dual Cryogenic Capacitive Density Sensor

    NASA Technical Reports Server (NTRS)

    Youngquist, Robert; Mata, Carlos; Vokrot, Peter; Cox, Robert

    2009-01-01

    A dual cryogenic capacitive density sensor has been developed. The device contains capacitive sensors that monitor two-phase cryogenic flow density to within 1% accuracy, which, if temperature were known, could be used to determine the ratio of liquid to gas in the line. Two of these density sensors, located a known distance apart, comprise the sensor, providing some information on the velocity of the flow. This sensor was constructed as a proposed mass flowmeter with high data acquisition rates. Without moving parts, this device is capable of detecting the density change within a two-phase cryogenic flow more than 100 times a second. Detection is enabled by a series of two sets of five parallel plates with stainless steel, cryogenically rated tubing. The parallel plates form the two capacitive sensors, which are measured by electrically isolated digital electronics. These capacitors monitor the dielectric of the flow essentially the density of the flow and can be used to determine (along with temperature) the ratio of cryogenic liquid to gas. Combining this information with the velocity of the flow can, with care, be used to approximate the total two-phase mass flow. The sensor can be operated at moderately high pressures and can be lowered into a cryogenic bath. The electronics have been substantially improved over the older sensors, incorporating a better microprocessor, elaborate ground loop protection and noise limiting circuitry, and reduced temperature sensitivity. At the time of this writing, this design has been bench tested at room temperature, but actual cryogenic tests are pending

  1. Capacitance enhancement via electrode patterning.

    PubMed

    Ho, Tuan A; Striolo, Alberto

    2013-11-28

    The necessity of increasing the energy density in electric double layer capacitors to meet current demand is fueling fundamental and applied research alike. We report here molecular dynamics simulation results for aqueous electrolytes near model electrodes. Particular focus is on the effect of electrode patterning on the structure of interfacial electrolytes, and on the potential drop between the solid electrodes and the bulk electrolytes. The latter is estimated by numerically integrating the Poisson equation using the charge densities due to water and ions accumulated near the interface as input. We considered uniform and patterned electrodes, both positively and negatively charged. The uniformly charged electrodes are modeled as graphite. The patterned ones are obtained by removing carbon atoms from the top-most graphene layer, yielding nanoscopic squares and stripes patterns. For simplicity, the patterned electrodes are effectively simulated as insulators (the charge remains localized on the top-most layer of carbon atoms). Our simulations show that the patterns alter the structure of water and the accumulation of ions at the liquid-solid interfaces. Using aqueous NaCl solutions, we found that while the capacitance calculated for three positively charged electrodes did not change much, that calculated for the negatively charged electrodes significantly increased upon patterning. We find that both water structure and orientation, as well as ion accumulation affect the capacitance. As electrode patterning affects differently water structure and ion accumulation, it might be possible to observe ion-specific effects. These results could be useful for advancing our understanding of electric double layer capacitors, capacitive desalination processes, as well as of fundamental interfacial electrolytes properties. PMID:24289370

  2. Capacitance enhancement via electrode patterning

    SciTech Connect

    Ho, Tuan A.; Striolo, Alberto

    2013-11-28

    The necessity of increasing the energy density in electric double layer capacitors to meet current demand is fueling fundamental and applied research alike. We report here molecular dynamics simulation results for aqueous electrolytes near model electrodes. Particular focus is on the effect of electrode patterning on the structure of interfacial electrolytes, and on the potential drop between the solid electrodes and the bulk electrolytes. The latter is estimated by numerically integrating the Poisson equation using the charge densities due to water and ions accumulated near the interface as input. We considered uniform and patterned electrodes, both positively and negatively charged. The uniformly charged electrodes are modeled as graphite. The patterned ones are obtained by removing carbon atoms from the top-most graphene layer, yielding nanoscopic squares and stripes patterns. For simplicity, the patterned electrodes are effectively simulated as insulators (the charge remains localized on the top-most layer of carbon atoms). Our simulations show that the patterns alter the structure of water and the accumulation of ions at the liquid-solid interfaces. Using aqueous NaCl solutions, we found that while the capacitance calculated for three positively charged electrodes did not change much, that calculated for the negatively charged electrodes significantly increased upon patterning. We find that both water structure and orientation, as well as ion accumulation affect the capacitance. As electrode patterning affects differently water structure and ion accumulation, it might be possible to observe ion-specific effects. These results could be useful for advancing our understanding of electric double layer capacitors, capacitive desalination processes, as well as of fundamental interfacial electrolytes properties.

  3. Compact monolithic capacitive discharge unit

    DOEpatents

    Roesler, Alexander W.; Vernon, George E.; Hoke, Darren A.; De Marquis, Virginia K.; Harris, Steven M.

    2007-06-26

    A compact monolithic capacitive discharge unit (CDU) is disclosed in which a thyristor switch and a flyback charging circuit are both sandwiched about a ceramic energy storage capacitor. The result is a compact rugged assembly which provides a low-inductance current discharge path. The flyback charging circuit preferably includes a low-temperature co-fired ceramic transformer. The CDU can further include one or more ceramic substrates for enclosing the thyristor switch and for holding various passive components used in the flyback charging circuit. A load such as a detonator can also be attached directly to the CDU.

  4. Non- contacting capacitive diagnostic device

    DOEpatents

    Ellison, Timothy

    2005-07-12

    A non-contacting capacitive diagnostic device includes a pulsed light source for producing an electric field in a semiconductor or photovoltaic device or material to be evaluated and a circuit responsive to the electric field. The circuit is not in physical contact with the device or material being evaluated and produces an electrical signal characteristic of the electric field produced in the device or material. The diagnostic device permits quality control and evaluation of semiconductor or photovoltaic device properties in continuous manufacturing processes.

  5. Detection of Telomerase Activity Using Capacitance Measurements

    NASA Astrophysics Data System (ADS)

    Kang, Bong Keun; Lee, Ri Mi; Choi, Ahmi; Jung, Hyo-Il; Yoo, Kyung-Hwa

    2007-03-01

    Telomerase activity has been found in about 85% cancer cells, while no activity observed in normal cells, so that telomerase has been proposed as a marker for cancer detection. Here, we describe electrical detection of telomerase activity using capacitance measurements. We have investigated the length dependence of capacitance on DNA solutions and found that the capacitance of DNA solutions were dependent on the DNA length. In addition, upon adding telomerase into the solution of telomeric substrate primer, the capacitance was observed to change as a function of time due to the telomeric elongation. These results suggest that this novel nanosensor may be used for rapid detection of telomerase activity.

  6. Module Eleven: Capacitance; 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 another circuit quantity, capacitance, and discover the effects of this component on circuit current, voltage, and power. The module is divided into seven lessons: the capacitor, theory of capacitance, total capacitance, RC (resistive-capacitive circuit) time constant, capacitive reactance, phase and…

  7. Capacitance Measurement with a Sigma Delta Converter for 3D Electrical Capacitance Tomography

    NASA Technical Reports Server (NTRS)

    Nurge, Mark

    2005-01-01

    This paper will explore suitability of a newly available capacitance to digital converter for use in a 3D Electrical Capacitance Tomography system. A switch design is presented along with circuitry needed to extend the range of the capacitance to digital converter. Results are then discussed for a 15+ hour drift and noise test.

  8. Ultrahigh Temperature Capacitive Pressure Sensor

    NASA Technical Reports Server (NTRS)

    Harsh, Kevin

    2014-01-01

    Robust, miniaturized sensing systems are needed to improve performance, increase efficiency, and track system health status and failure modes of advanced propulsion systems. Because microsensors must operate in extremely harsh environments, there are many technical challenges involved in developing reliable systems. In addition to high temperatures and pressures, sensing systems are exposed to oxidation, corrosion, thermal shock, fatigue, fouling, and abrasive wear. In these harsh conditions, sensors must be able to withstand high flow rates, vibration, jet fuel, and exhaust. In order for existing and future aeropropulsion turbine engines to improve safety and reduce cost and emissions while controlling engine instabilities, more accurate and complete sensor information is necessary. High-temperature (300 to 1,350 C) capacitive pressure sensors are of particular interest due to their high measurement bandwidth and inherent suitability for wireless readout schemes. The objective of this project is to develop a capacitive pressure sensor based on silicon carbon nitride (SiCN), a new class of high-temperature ceramic materials, which possesses excellent mechanical and electric properties at temperatures up to 1,600 C.

  9. High Temperature Capacitive Strain Gage

    NASA Technical Reports Server (NTRS)

    Wnuk, Stephen P., Jr.; Wnuk, Stephen P., III; Wnuk, V. P.

    1990-01-01

    Capacitive strain gages designed for measurements in wind tunnels to 2000 F were built and evaluated. Two design approaches were followed. One approach was based on fixed capacitor plates with a movable ground plane inserted between the plates to effect differential capacitive output with strain. The second approach was based on movable capacitor plates suspended between sapphire bearings, housed in a rugged body, and arranged to operate as a differential capacitor. A sapphire bearing gage (1/4 in. diameter x 1 in. in size) was built with a range of 50,000 and a resolution of 200 microstrain. Apparent strain on Rene' 41 was less than + or - 1000 microstrain from room temperature to 2000 F. Three gage models were built from the Ground Plane Differential concept. The first was 1/4 in. square by 1/32 in. high and useable to 700 F. The second was 1/2 in. square by 1/16 in. high and useable to 1440 F. The third, also 1/2 in. square by 1/16 in. high was expected to operate in the 1600 to 2000 F range, but was not tested because time and funding ended.

  10. Capacitance densitometer for flow regime identification

    DOEpatents

    Shipp, Jr., Roy L.

    1978-01-01

    This invention relates to a capacitance densitometer for determining the flow regime of a two-phase flow system. A two-element capacitance densitometer is used in conjunction with a conventional single-beam gamma densitometer to unambiguously identify the prevailing flow regime and the average density of a flowing fluid.

  11. Capacitance-coupled wiper increases potentiometer life

    NASA Technical Reports Server (NTRS)

    Dimeff, J.

    1968-01-01

    Capacitively-coupled wiper reduces the friction between the sliding contact and the potentiometer element in conventional potentiometers. A small preamplifier employed close to the wiper reduces errors caused by output cable capacitance. The device is friction free with resultant low wear and has high speed and high resolution.

  12. Analysis of capacitive coupling within microelectrode array.

    PubMed

    Hu, Z; Troyk, P R; Detlefsen, D E

    2006-01-01

    Capacitive coupling within high-density microelectrode arrays can degrade neural recording signal or disperse neural stimulation current. Material deterioration in a chronically implanted neural stimulation/recording system can cause such an undesired effect. We present a simple method with an iterative algorithm to quantify the cross-coupling capacitance, in-situ. PMID:17947024

  13. Applications of electrostatic capacitance and charging

    NASA Astrophysics Data System (ADS)

    Sandu, Titus; Boldeiu, George; Moagar-Poladian, Victor

    2013-12-01

    The capacitance of an arbitrarily shaped object is calculated with the same second-kind integral equation method used for computing static and dynamic polarizabilities. The capacitance is simply the dielectric permittivity multiplied by the area of the object and divided by the squared norm of the Neumann-Poincaré operator eigenfunction corresponding to the largest eigenvalue. The norm of this eigenfunction varies slowly with shape thus enabling the definition of two scale-invariant shape factors and perturbative calculations of capacitance. The result is extended to a special class of capacitors in which the electrodes are the equipotential surfaces generated by the equilibrium charge on the object. This extension allows analytical expressions of capacitance for confocal spheroidal capacitors and finite cylinders. Moreover, a second order formula for thin constant-thickness capacitors is given with direct applications for capacitance of membranes in living cells and of supercapacitors. For axisymmetric geometries, a fast and accurate numerical method is provided.

  14. Reducing the capacitance of piezoelectric film sensors.

    PubMed

    González, Martín G; Sorichetti, Patricio A; Santiago, Guillermo D

    2016-04-01

    We present a novel design for large area, wideband, polymer piezoelectric sensor with low capacitance. The large area allows better spatial resolution in applications such as photoacoustic tomography and the reduced capacitance eases the design of fast transimpedance amplifiers. The metalized piezoelectric polymer thin film is segmented into N sections, electrically connected in series. In this way, the total capacitance is reduced by a factor 1/N(2), whereas the mechanical response and the active area of the sensor are not modified. We show the construction details for a two-section sensor, together with the impedance spectroscopy and impulse response experimental results that validate the design. PMID:27131698

  15. Reducing the capacitance of piezoelectric film sensors

    NASA Astrophysics Data System (ADS)

    González, Martín G.; Sorichetti, Patricio A.; Santiago, Guillermo D.

    2016-04-01

    We present a novel design for large area, wideband, polymer piezoelectric sensor with low capacitance. The large area allows better spatial resolution in applications such as photoacoustic tomography and the reduced capacitance eases the design of fast transimpedance amplifiers. The metalized piezoelectric polymer thin film is segmented into N sections, electrically connected in series. In this way, the total capacitance is reduced by a factor 1/N2, whereas the mechanical response and the active area of the sensor are not modified. We show the construction details for a two-section sensor, together with the impedance spectroscopy and impulse response experimental results that validate the design.

  16. Capacitive measurement of ECG for ubiquitous healthcare.

    PubMed

    Lim, Yong Gyu; Lee, Jeong Su; Lee, Seung Min; Lee, Hong Ji; Park, Kwang Suk

    2014-11-01

    The technology for measuring ECG using capacitive electrodes and its applications are reviewed. Capacitive electrodes are built with a high-input-impedance preamplifier and a shield on their rear side. Guarding and driving ground are used to reduce noise. An analysis of the intrinsic noise shows that the thermal noise caused by the resistance in the preamplifier is the dominant factor of the intrinsic noise. A fully non-contact capacitive measurement has been developed using capacitive grounding and applied to a non-intrusive ECG measurement in daily life. Many ongoing studies are examining how to enhance the quality and ease of applying electrodes, thus extending their applications in ubiquitous healthcare from attached-on-object measurements to wearable or EEG measurements. PMID:25052344

  17. Interconnection capacitance models for VLSI circuits

    NASA Astrophysics Data System (ADS)

    Wong, Shyh-Chyi; Liu, Patrick S.; Ru, Jien-Wen; Lin, Shi-Tron

    1998-06-01

    A new set of capacitance models is developed for delay estimation of VLSI interconnections. The set of models is derived for five representative wiring structures, with their combinations covering arbitrary VLSI layouts. A semi-empirical approach is adopted to deal with complicated geometry nature in VLSI and to allow for closed-form capacitance formulas to be developed to provide direct observation of capacitance variation vs process parameters as well as computational efficiency for circuit simulation. The formulas are given explicitly in terms of wire width, wire thickness, dielectric thickness and inter-wire spacing. The models show good agreement with numerical solutions from RAPHAEL and measurement data of fabricated capacitance test structures. The models are further applied and validated on a ring oscillator. It is shown that the frequency of the ring oscillator obtained from HSPICE simulation with our models agrees well with the bench measurement.

  18. Capacitive Cells for Dielectric Constant Measurement

    ERIC Educational Resources Information Center

    Aguilar, Horacio Munguía; Maldonado, Rigoberto Franco

    2015-01-01

    A simple capacitive cell for dielectric constant measurement in liquids is presented. As an illustrative application, the cell is used for measuring the degradation of overheated edible oil through the evaluation of their dielectric constant.

  19. Capacitation-Associated Glycocomponents of Mammalian Sperm.

    PubMed

    Liu, Min

    2016-05-01

    Mammalian fertilization is a series of events that are mostly carbohydrate mediated. The male gamete glycocomponents are extensively synthesized and modified during sperm development and sperm transport in the reproductive tracts. Freshly ejaculated mammalian sperm are required to undergo capacitation, which takes place in the female reproductive system, in order to become fully fertilizable. Several lines of evidence reveal changes in glycosylated sperm constituents during capacitation. Although the contributions of these molecular changes to capacitation are not completely understood, the presence, rearrangement, and/or modification of these sperm glycocomponents have been demonstrated to be important for fertilization. The following review summarizes mammalian sperm glycoconstituents, with emphasis on their molecular changes during capacitation. PMID:26363036

  20. High-temperature capacitive strain measurement system

    NASA Technical Reports Server (NTRS)

    Wilson, E. J.; Egger, R. L.

    1975-01-01

    Capacitive strain gage and signal conditioning system measures stress-induced strain and cancels thermal expansion strain at temperatures to 1,500 F (815 C). Gage does not significantly restrain or reinforce specimen.

  1. Interface capacitance of nano-patterned electrodes

    NASA Astrophysics Data System (ADS)

    Ibach, Harald; Beltramo, Guillermo; Giesen, Margret

    2011-01-01

    By employing numerical solutions of the Poisson-Boltzmann equation we have studied the interface capacitance of flat electrodes with stripes of different potentials of zero charge ϕpzc. The results depend on the ratio of the width of the stripes l to the dielectric screening length in the electrolyte, the Debye length dDebye, as well as on the difference Δϕpzc in relation kBT/e. As expected, the capacitance of a striped surface has its minimum at the mean potential of the surface if l/ dDebye << 1 and displays two minima if l/ dDebye >> 1. An unexpected result is that for Δϕpzc ≅ 0.2V, the transition between the two extreme cases does not occur when l ≅ dDebye, but rather when l > 10 dDebye. As a consequence, a single minimum in the capacitance is observed for dilute electrolytes even for 100 nm wide stripes. The capacitance at the minimum is however higher than for homogeneous surfaces. Furthermore, the potential at the minimum deviates significantly from the potential of zero mean charge on the surface if l > 3 dDebye and Δϕpzc is larger than about 4 kBT/e. The capacitance of stepped, partially reconstructed Au(11 n) surfaces is discussed as an example. Consequences for Parsons-Zobel-plots of the capacitances of inhomogeneous surfaces are likewise discussed.

  2. Negative Capacitance transients in a ferroelectric capacitor

    NASA Astrophysics Data System (ADS)

    Khan, Asif; Chatterjee, Korok; Wang, Brian; Drapcho, Steven; You, Long; Serrao, Claudy; Bakaul, Saidur; Ramesh, Ramamoorthy; Salahuddin, Sayeef

    2015-03-01

    The Boltzmann distribution of electrons poses a fundamental barrier to lowering energy dissipation in conventional electronics, often termed as Boltzmann Tyranny. Negative capacitance in ferroelectric materials, which stems from the stored energy of phase transition, could provide a solution, but a direct measurement of negative capacitance has so far been elusive. Here we demonstrate the negative differential capacitance in a thin, single crystalline ferroelectric film, by constructing a simple R-C network and monitoring the voltage dynamics across the ferroelectric capacitor6. When a voltage pulse is applied, the voltage across the ferroelectric capacitor is found to be decreasing with time-in exactly the opposite direction to which voltage for a regular capacitor should change. The results are analyzed on the basis of the Landau-Khalatnikov equation, which shows that as the ferroelectric polarization switches its direction, it passes through the unstable negative capacitance region resulting in the characteristic ``negative capacitance transients.'' Analysis of this ``inductance''-like behavior from a capacitor allows us to calculate the value of the negative capacitance directly and presents an unprecedented insight into the intrinsic energy profile of the ferroelectric material.

  3. Polymer coated Capacitive Deionization Electrode for Desalination: A mini review

    NASA Astrophysics Data System (ADS)

    Gaikwad, Mahendra S.; Balomajumder, Chandrajit

    2016-02-01

    This mini review deals with a recently developing water purification technology, i.e. capacitive deionization. It presents the current progress achieved with polymer coated electrodes in capacitive deionization for desalination. The introduction covers capacitive deionization, application of polymer or polymer composite in capacitive deionization electrode, comparative study and discussion on fabrication of electrode. This paper aims at indicating novel research prospects in capacitive deionization technology for desalination.

  4. Ion channels, phosphorylation and mammalian sperm capacitation

    PubMed Central

    Visconti, Pablo E; Krapf, Dario; de la Vega-Beltrán, José Luis; Acevedo, Juan José; Darszon, Alberto

    2011-01-01

    Sexually reproducing animals require an orchestrated communication between spermatozoa and the egg to generate a new individual. Capacitation, a maturational complex phenomenon that occurs in the female reproductive tract, renders spermatozoa capable of binding and fusing with the oocyte, and it is a requirement for mammalian fertilization. Capacitation encompasses plasma membrane reorganization, ion permeability regulation, cholesterol loss and changes in the phosphorylation state of many proteins. Novel tools to study sperm ion channels, image intracellular ionic changes and proteins with better spatial and temporal resolution, are unraveling how modifications in sperm ion transport and phosphorylation states lead to capacitation. Recent evidence indicates that two parallel pathways regulate phosphorylation events leading to capacitation, one of them requiring activation of protein kinase A and the second one involving inactivation of ser/thr phosphatases. This review examines the involvement of ion transporters and phosphorylation signaling processes needed for spermatozoa to achieve capacitation. Understanding the molecular mechanisms leading to fertilization is central for societies to deal with rising male infertility rates, to develop safe male gamete-based contraceptives and to preserve biodiversity through better assisted fertilization strategies. PMID:21540868

  5. Electrical Capacitance Volume Tomography: Design and Applications

    PubMed Central

    Wang, Fei; Marashdeh, Qussai; Fan, Liang-Shih; Warsito, Warsito

    2010-01-01

    This article reports recent advances and progress in the field of electrical capacitance volume tomography (ECVT). ECVT, developed from the two-dimensional electrical capacitance tomography (ECT), is a promising non-intrusive imaging technology that can provide real-time three-dimensional images of the sensing domain. Images are reconstructed from capacitance measurements acquired by electrodes placed on the outside boundary of the testing vessel. In this article, a review of progress on capacitance sensor design and applications to multi-phase flows is presented. The sensor shape, electrode configuration, and the number of electrodes that comprise three key elements of three-dimensional capacitance sensors are illustrated. The article also highlights applications of ECVT sensors on vessels of various sizes from 1 to 60 inches with complex geometries. Case studies are used to show the capability and validity of ECVT. The studies provide qualitative and quantitative real-time three-dimensional information of the measuring domain under study. Advantages of ECVT render it a favorable tool to be utilized for industrial applications and fundamental multi-phase flow research. PMID:22294905

  6. Capacitive Deionization of High-Salinity Solutions

    DOE PAGESBeta

    Sharma, Ketki; Gabitto, Jorge; Mayes, Richard T.; Yiacoumi, Sotira; Bilheux, Hassina Z.; Walker, Lakeisha M.H.; Dai, Sheng; Tsouris, Costas

    2014-12-22

    Desalination of high salinity solutions has been studied using a novel experimental technique and a theoretical model. Neutron imaging has been employed to visualize lithium ions in mesoporous carbon materials, which are used as electrodes in capacitive deionization for water desalination. Experiments were conducted with a flow-through capacitive deionization cell designed for neutron imaging and with lithium chloride (6LiCl) as the electrolyte. Sequences of neutron images have been obtained at a relatively high concentration of lithium chloride (6LiCl) solution to provide information on the transport of ions within the electrodes. A new model that computes the individual ionic concentration profilesmore » inside mesoporous carbon electrodes has been used to simulate the capacitive deionization process. Modifications have also been introduced into the simulation model to calculate results at high electrolyte concentrations. Experimental data and simulation results provide insight into why capacitive deionization is not effective for desalination of high ionic-strength solutions. The combination of experimental information, obtained through neutron imaging, with the theoretical model will help in the design of capacitive deionization devices, which can improve the process for high ionic-strength solutions.« less

  7. Capacitive Deionization of High-Salinity Solutions

    SciTech Connect

    Sharma, Ketki; Gabitto, Jorge; Mayes, Richard T.; Yiacoumi, Sotira; Bilheux, Hassina Z.; Walker, Lakeisha M.H.; Dai, Sheng; Tsouris, Costas

    2014-12-22

    Desalination of high salinity solutions has been studied using a novel experimental technique and a theoretical model. Neutron imaging has been employed to visualize lithium ions in mesoporous carbon materials, which are used as electrodes in capacitive deionization for water desalination. Experiments were conducted with a flow-through capacitive deionization cell designed for neutron imaging and with lithium chloride (6LiCl) as the electrolyte. Sequences of neutron images have been obtained at a relatively high concentration of lithium chloride (6LiCl) solution to provide information on the transport of ions within the electrodes. A new model that computes the individual ionic concentration profiles inside mesoporous carbon electrodes has been used to simulate the capacitive deionization process. Modifications have also been introduced into the simulation model to calculate results at high electrolyte concentrations. Experimental data and simulation results provide insight into why capacitive deionization is not effective for desalination of high ionic-strength solutions. The combination of experimental information, obtained through neutron imaging, with the theoretical model will help in the design of capacitive deionization devices, which can improve the process for high ionic-strength solutions.

  8. Signal processing electronics for a capacitive microsensor

    NASA Astrophysics Data System (ADS)

    Amendola, Gilles; Lu, Guo N.

    2000-04-01

    An interface circuit in a 0.8-micrometers CMOS process for the on- chip integration of a capacitive micro-sensor used as a microphone is presented. In order to circumvent 1/f noise contributions and to improve the signal/noise ratio, a synchronous modulation-demodulation technique has been applied. For the implementation of this technique, we have studied and designed several functional block, such as modulator with signal conversion, low-noise amplifier, demodulator, etc. To deal with problems related to dispersion of intrinsic capacitance of the sensor, a feedback compensating solution is suggested. The designed circuit has a sensibility of 1200 V/pF, with a minimum detectable capacitance variation of 2 10-6 pF.

  9. A high performance, variable capacitance accelerometer

    NASA Astrophysics Data System (ADS)

    Wilner, L. Bruce

    1988-12-01

    A variable capacitance acceleration sensor is described. Manufactured using silicon microfabrication techniques, the sensor uses a midplane, flat plate suspension, gas damping, and overrange stops. The sensor is assembled from three silicon wafers, using anodic bonds to inlays of borosilicate glass. Typical sensor properties are 7-pF active capacitance, 3-pF tare capacitance, a response of 0.05 pF/G, a resonance frequency of 3.4 kHz, and damping 0.7 critical. It is concluded that this sensor, with appropriate electronics, forms an accelerometer with an order-of-magnitude greater sensitivity-bandwidth product than a comparable piezoresistive acclerometer, and with extraordinary shock resistance.

  10. Capacitive behavior of highly-oxidized graphite

    NASA Astrophysics Data System (ADS)

    Ciszewski, Mateusz; Mianowski, Andrzej

    2014-09-01

    Capacitive behavior of a highly-oxidized graphite is presented in this paper. The graphite oxide was synthesized using an oxidizing mixture of potassium chlorate and concentrated fuming nitric acid. As-oxidized graphite was quantitatively and qualitatively analyzed with respect to the oxygen content and the species of oxygen-containing groups. Electrochemical measurements were performed in a two-electrode symmetric cell using KOH electrolyte. It was shown that prolonged oxidation causes an increase in the oxygen content while the interlayer distance remains constant. Specific capacitance increased with oxygen content in the electrode as a result of pseudo-capacitive effects, from 0.47 to 0.54 F/g for a scan rate of 20 mV/s and 0.67 to 1.15 F/g for a scan rate of 5 mV/s. Better cyclability was observed for the electrode with a higher oxygen amount.

  11. Design and simulation of MEMS capacitive magnetometer

    NASA Astrophysics Data System (ADS)

    Jyoti, Aditi, Tripathi, C. C.; Gopal, Ram

    2016-04-01

    This paper presents the design and simulation of a MEMS Capacitive Magnetometer using FEM (Finite Element Method) tool COMSOL Multiphysics 4.3b and results from this simulation are closely matched with analytically calculated results. A comb drive structure is used for actuation purpose which operates at resonant frequency of device is 11.791 kHz to achieve maximum displacement. A magnetic field in z-axis can be detected by this comb drive structure. Quality factor of MEMS capacitive magnetometer obtained is 18 and it has good linear response in the magnetic field range of 100 µT.

  12. Twin-capacitive shaft angle encoder with analog output signal

    NASA Technical Reports Server (NTRS)

    Hruby, R. J.; Wilson, R. L. (Inventor)

    1977-01-01

    A precision capacitive shaft encoder providing a dc signal corresponding to the angular position of a shaft is described. Two variable capacitances are coupled in tandem by a rotatable shaft. Each capacitor has a capacitance that varies linearly with a change in the angular position of the shaft. The sum of the two capacitances is always constant for any angular position of the shaft. Each capacitance is alternately coupled to a reference dc voltage and a discharge circuit. The capacitances are electrically coupled in series and the charge periodically acquired at the junction of the capacitance is a function of the position of the shaft. An error-compensating voltage is imposed on the junction when the capacitances are coupled to the reference voltages. The junction is coupled to sample-and-hold apparatus provided with a error-correcting circuit.

  13. Negative capacitance in multidomain ferroelectric superlattices

    NASA Astrophysics Data System (ADS)

    Zubko, Pavlo; Wojdeł, Jacek C.; Hadjimichael, Marios; Fernandez-Pena, Stéphanie; Sené, Anaïs; Luk’Yanchuk, Igor; Triscone, Jean-Marc; Íñiguez, Jorge

    2016-06-01

    The stability of spontaneous electrical polarization in ferroelectrics is fundamental to many of their current applications, which range from the simple electric cigarette lighter to non-volatile random access memories. Research on nanoscale ferroelectrics reveals that their behaviour is profoundly different from that in bulk ferroelectrics, which could lead to new phenomena with potential for future devices. As ferroelectrics become thinner, maintaining a stable polarization becomes increasingly challenging. On the other hand, intentionally destabilizing this polarization can cause the effective electric permittivity of a ferroelectric to become negative, enabling it to behave as a negative capacitance when integrated in a heterostructure. Negative capacitance has been proposed as a way of overcoming fundamental limitations on the power consumption of field-effect transistors. However, experimental demonstrations of this phenomenon remain contentious. The prevalent interpretations based on homogeneous polarization models are difficult to reconcile with the expected strong tendency for domain formation, but the effect of domains on negative capacitance has received little attention. Here we report negative capacitance in a model system of multidomain ferroelectric–dielectric superlattices across a wide range of temperatures, in both the ferroelectric and paraelectric phases. Using a phenomenological model, we show that domain-wall motion not only gives rise to negative permittivity, but can also enhance, rather than limit, its temperature range. Our first-principles-based atomistic simulations provide detailed microscopic insight into the origin of this phenomenon, identifying the dominant contribution of near-interface layers and paving the way for its future exploitation.

  14. Site Specific Evaluation of Multisensor Capacitance Probes

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Multisensor capacitance probes (MCPs) are widely used for measuring soil water content (SWC) at the field scale. Although manufacturers supply a generic MCP calibration, many researchers recognize that MCPs should be calibrated for specific field conditions. MCPs measurements are typically associa...

  15. Negative capacitance in multidomain ferroelectric superlattices.

    PubMed

    Zubko, Pavlo; Wojdeł, Jacek C; Hadjimichael, Marios; Fernandez-Pena, Stéphanie; Sené, Anaïs; Luk'yanchuk, Igor; Triscone, Jean-Marc; Íñiguez, Jorge

    2016-06-23

    The stability of spontaneous electrical polarization in ferroelectrics is fundamental to many of their current applications, which range from the simple electric cigarette lighter to non-volatile random access memories. Research on nanoscale ferroelectrics reveals that their behaviour is profoundly different from that in bulk ferroelectrics, which could lead to new phenomena with potential for future devices. As ferroelectrics become thinner, maintaining a stable polarization becomes increasingly challenging. On the other hand, intentionally destabilizing this polarization can cause the effective electric permittivity of a ferroelectric to become negative, enabling it to behave as a negative capacitance when integrated in a heterostructure. Negative capacitance has been proposed as a way of overcoming fundamental limitations on the power consumption of field-effect transistors. However, experimental demonstrations of this phenomenon remain contentious. The prevalent interpretations based on homogeneous polarization models are difficult to reconcile with the expected strong tendency for domain formation, but the effect of domains on negative capacitance has received little attention. Here we report negative capacitance in a model system of multidomain ferroelectric-dielectric superlattices across a wide range of temperatures, in both the ferroelectric and paraelectric phases. Using a phenomenological model, we show that domain-wall motion not only gives rise to negative permittivity, but can also enhance, rather than limit, its temperature range. Our first-principles-based atomistic simulations provide detailed microscopic insight into the origin of this phenomenon, identifying the dominant contribution of near-interface layers and paving the way for its future exploitation. PMID:27296225

  16. Capacitive system detects and locates fluid leaks

    NASA Technical Reports Server (NTRS)

    1966-01-01

    Electronic monitoring system automatically detects and locates minute leaks in seams of large fluid storage tanks and pipelines covered with thermal insulation. The system uses a capacitive tape-sensing element that is adhesively bonded over seams where fluid leaks are likely to occur.

  17. Fabrication of capacitively-shunted superconducting qubits

    NASA Astrophysics Data System (ADS)

    Yoder, Jonilyn L.; Gudmundsen, Theodore J.; Bolkhovsky, Vladimir; Welander, Paul B.; Gustavsson, Simon; Hover, David; Kerman, Andrew J.; Sears, Adam P.; Oliver, William D.

    2014-03-01

    Improvements in superconducting qubit coherence times and reproducibility have been demonstrated using capacitive shunting. In this study, we present methods for the preparation of both capacitively-shunted charge qubits (transmons) and capacitively-shunted flux qubits. Hybrid fabrication techniques were employed to combine high-quality-factor aluminum capacitive shunts with shadow-evaporated Josephson junctions, and the Josephson junctions were prepared using suspended-bridge germanium masks. We also will describe process testing results that were acquired to assess wafer-to-wafer reproducibility of our fabrication protocols. This research was funded in part by the Office of the Director of National Intelligence (ODNI), Intelligence Advanced Research Projects Activity (IARPA); and by the Assistant Secretary of Defense for Research and Engineering under Air Force Contract number FA8721-05-C-0002. All statements of fact, opinion or conclusions contained herein are those of the authors and should not be construed as representing the official views or policies of IARPA, the ODNI, or the U.S. Government.

  18. Capacitors and Resistance-Capacitance Networks.

    ERIC Educational Resources Information Center

    Balabanian, Norman; Root, Augustin A.

    This programed textbook was developed under a contract with the United States Office of Education as Number 5 in a series of materials for use in an electrical engineering sequence. It is divided into three parts--(1) capacitors, (2) voltage-current relationships, and (3) simple resistance-capacitance networks. (DH)

  19. Teaching of Inductive and Capacitive Reactance.

    ERIC Educational Resources Information Center

    MacInnes, I.; Jeffrey, W. S.

    1983-01-01

    Discusses how understanding mechanical systems and their graphic representation can be of value when teaching inductive and capacitive reactance, in particular, the response of inductors and capacitors to an alternating potential difference. Suggests that mechanical systems be taught, not just before introducing reactance but earlier in the…

  20. Phase-Discriminating Capacitive Sensor System

    NASA Technical Reports Server (NTRS)

    Vranish, John M.; Rahim, Wadi

    1993-01-01

    Crosstalk eliminated by maintaining voltages on all electrodes at same amplitude, phase, and frequency. Each output feedback-derived control voltage, change of which indicates proximity-induced change in capacitance of associated sensing electrode. Sensors placed close together, enabling imaging of sort. Images and/or output voltages used to guide robots in proximity to various objects.

  1. Capacitive Displacement Sensor With Frequency Readout

    NASA Technical Reports Server (NTRS)

    Fritsch, Klaus

    1989-01-01

    Simple displacement-measuring circuit senses capacitance between two parallel conducting plates and produces output signal, with frequency proportional to distance between plates. Principle of circuit provides advantages over other methods because of frequency-encoded output and high linearity. Used to measure displacements.

  2. Capacitive Proximity Sensors With Additional Driven Shields

    NASA Technical Reports Server (NTRS)

    Mcconnell, Robert L.

    1993-01-01

    Improved capacitive proximity sensors constructed by incorporating one or more additional driven shield(s). Sensitivity and range of sensor altered by adjusting driving signal(s) applied to shield(s). Includes sensing electrode and driven isolating shield that correspond to sensing electrode and driven shield.

  3. [Experience in developing and using capacitive electrodes].

    PubMed

    Grishanovich, A P; Iarmolinskiĭ, V I

    1984-01-01

    A capacitive-type electrode using titanium or tantalum oxide obtained through anodizing is described. Incorporated in the electrode is a source for a buffer amplifier. A shielding cap is used as an indifferent electrode. High performance allows using the electrodes for ECG, EEG, and other signal recording in clinical practice and researches. PMID:6708763

  4. Negative Capacitance in a Ferroelectric Capacitor

    NASA Astrophysics Data System (ADS)

    Khan, Asif; Chatterjee, Korok; Wang, Brian; Drapcho, Steven; You, Long; Serrao, Claudy; Bakaul, Saidur; Ramesh, Ramamoorthy; Salahuddin, Sayeef; UC Berkeley Team

    The Boltzmann distribution of electrons poses a fundamental barrier to lowering energy dissipation in conventional electronics, often termed as Boltzmann Tyranny. Negative capacitance in ferroelectric materials, which stems from the stored energy of phase transition, could provide a solution, but a direct measurement of negative capacitance has so far been elusive. Here we demonstrate the negative differential capacitance in an epitaxial ferroelectric film, by constructing a simple R-C network and monitoring the voltage dynamics across the ferroelectric capacitor. When a voltage pulse is applied, the voltage across the ferroelectric capacitor is found to be decreasing with time-in exactly the opposite direction to which voltage for a regular capacitor should change. The results are analyzed on the basis of the Landau-Khalatnikov equation, which shows that as the ferroelectric polarization switches its direction, it passes through the unstable negative capacitance region. Analysis of this behavior from a capacitor presents an unprecedented insight into the intrinsic energy profile of the ferroelectric material.

  5. Quantum Effects on the Capacitance of Graphene-Based Electrodes

    DOE PAGESBeta

    Zhan, Cheng; Neal, Justin; Wu, Jianzhong; Jiang, De-en

    2015-09-08

    We recently measured quantum capacitance for electric double layers (EDL) at electrolyte/graphene interfaces. However, the importance of quantum capacitance in realistic carbon electrodes is not clear. Toward understanding that from a theoretical perspective, here we studied the quantum capacitance and total capacitance of graphene electrodes as a function of the number of graphene layers. The quantum capacitance was obtained from electronic density functional theory based on fixed band approximation with an implicit solvation model, while the EDL capacitances were from classical density functional theory. We found that quantum capacitance plays a dominant role in total capacitance of the single-layer graphenemore » both in aqueous and ionic-liquid electrolytes but the contribution decreases as the number of graphene layers increases. Moreover, the total integral capacitance roughly levels off and is dominated by the EDL capacitance beyond about four graphene layers. Finally, because many porous carbons have nanopores with stacked graphene layers at the surface, this research provides a good estimate of the effect of quantum capacitance on their electrochemical performance.« less

  6. Quantum Effects on the Capacitance of Graphene-Based Electrodes

    SciTech Connect

    Zhan, Cheng; Neal, Justin; Wu, Jianzhong; Jiang, De-en

    2015-09-08

    We recently measured quantum capacitance for electric double layers (EDL) at electrolyte/graphene interfaces. However, the importance of quantum capacitance in realistic carbon electrodes is not clear. Toward understanding that from a theoretical perspective, here we studied the quantum capacitance and total capacitance of graphene electrodes as a function of the number of graphene layers. The quantum capacitance was obtained from electronic density functional theory based on fixed band approximation with an implicit solvation model, while the EDL capacitances were from classical density functional theory. We found that quantum capacitance plays a dominant role in total capacitance of the single-layer graphene both in aqueous and ionic-liquid electrolytes but the contribution decreases as the number of graphene layers increases. Moreover, the total integral capacitance roughly levels off and is dominated by the EDL capacitance beyond about four graphene layers. Finally, because many porous carbons have nanopores with stacked graphene layers at the surface, this research provides a good estimate of the effect of quantum capacitance on their electrochemical performance.

  7. Biochemical capacitance of Geobacter sulfurreducens biofilms.

    PubMed

    Bueno, Paulo R; Schrott, Germán D; Bonanni, Pablo S; Simison, Silvia N; Busalmen, Juan P

    2015-08-10

    An electrical model able to decouple the electron pathway from microbial cell machinery impedance terms is introduced. In this context, capacitance characteristics of the biofilm are clearly resolved. In other words, the model allows separating, according to the advantage of frequency and spectroscopic response approach, the different terms controlling the performance of the microbial biofilm respiratory process and thus the directly related electricity production process. The model can be accurately fitted to voltammetry measurements obtained under steady-state conditions and also to biofilm discharge amperometric measurements. The implications of biological aspects of the electrochemical or redox capacitance are discussed theoretically in the context of current knowledge with regard to structure and physiological activity of microbial Geobacter biofilms. PMID:26212121

  8. Electrostatic Capacitive Imaging: A New NDE Technique

    NASA Astrophysics Data System (ADS)

    Diamond, G.; Hutchins, D. A.; Leong, K. K.; Gan, T. H.

    2007-03-01

    A new technique for NDE has been developed which is capable of imaging a wide range of materials and structures, ranging from insulators to metallic conductors. The approach, known as Capacitive Imaging (CI) uses electrode arrays in air to produce an AC electric field distribution within the material. Scanning the electrodes over the material causes a change in the field distribution, and hence changes in output voltage. Capacitive coupling allows the technique to work on a wide variety of material conductivities without some of the disadvantages associated with conventional eddy current and potential drop methods. Images are presented of carbon fibre composite materials, concrete and Plexiglas, illustrating the range of application in NDE. The effect of electrode shape and excitation frequency will be discussed in terms of image resolution and depth of penetration.

  9. A simple and reproducible capacitive electrode.

    PubMed

    Spinelli, Enrique; Guerrero, Federico; García, Pablo; Haberman, Marcelo

    2016-03-01

    Capacitive Electrodes (CE) allow the acquisition of biopotentials through a dielectric layer, without the use of electrolytes, just by placing them on skin or clothing, but demands front-ends with ultra-high input impedances. This must be achieved while providing a path for bias currents, calling for ultra-high value resistors and special components and construction techniques. A simple CE that uses bootstrap techniques to avoid ultra-high value components and special materials is proposed. When electrodes are placed on the skin; that is, with coupling capacitances CS of around 100 pF, they present a noise level of 3.3 µVRMS in a 0.5-100 Hz bandwidth, which is appropriate for electrocardiography (ECG) measurements. Construction details of the CE and the complete circuit, including a fast recovery feature, are presented. PMID:26792172

  10. Layer resolved capacitive probing of graphene bilayers

    NASA Astrophysics Data System (ADS)

    Zibrov, Alexander; Parmentier, François; Li, Jia; Wang, Lei; Hunt, Benjamin; Dean, Cory; Hone, James; Taniguchi, Takashi; Watanabe, Kenji; Young, Andrea

    Compared to single layer graphene, graphene bilayers have an additional ``which-layer'' degree of freedom that can be controlled by an external electric field in a dual-gated device geometry. We describe capacitance measurements capable of directly probing this degree of freedom. By performing top gate, bottom gate, and penetration field capacitance measurements, we directly extract layer polarization of both Bernal and twisted bilayers. We will present measurements of hBN encapsulated bilayers at both zero and high magnetic field, focusing on the physics of the highly degenerate zero-energy Landau level in the high magnetic field limit where spin, valley, and layer degeneracy are all lifted by electronic interactions.

  11. Capacitive Sensors And Targets Would Measure Alignments

    NASA Technical Reports Server (NTRS)

    Jenstrom, Del T.

    1994-01-01

    Multiple capacitive sensors and active targets used to measure distance between, and relative orientation of, two objects. Sensed target signals processed and used by control systems to align objects to be joined. Shapes, sizes, and layouts of sensors and targets optimized for specific application. Particular layout of targets and sensors enables determination of relative position and orientation of two objects in all six degrees of freedom.

  12. Ultra-High-Frequency Capacitive Displacement Sensor

    NASA Technical Reports Server (NTRS)

    Vanzandt, Thomas R.; Kenny, Thomas W.; Kaiser, William J.

    1994-01-01

    Improved class of compact, high-resolution capacitive displacement sensors operates at excitation frequency of 915 MHz and measures about 7.5 by 4 by 2 centimeters. Contains commercially available 915-MHz oscillator and transmission-line resonator. Resonator contains stripline inductor in addition to variable capacitor. Ultrahigh excitation frequency offers advantages of resolution and frequency response. Not deleteriously affected by mechanical overdriving, or contact between electrodes.

  13. Resonant capacitive MEMS acoustic emission transducers

    NASA Astrophysics Data System (ADS)

    Ozevin, D.; Greve, D. W.; Oppenheim, I. J.; Pessiki, S. P.

    2006-12-01

    We describe resonant capacitive MEMS transducers developed for use as acoustic emission (AE) detectors, fabricated in the commercial three-layer polysilicon surface micromachining process (MUMPs). The 1 cm square device contains six independent transducers in the frequency range between 100 and 500 kHz, and a seventh transducer at 1 MHz. Each transducer is a parallel plate capacitor with one plate free to vibrate, thereby causing a capacitance change which creates an output signal in the form of a current under a dc bias voltage. With the geometric proportions we employed, each transducer responds with two distinct resonant frequencies. In our design the etch hole spacing was chosen to limit squeeze film damping and thereby produce an underdamped vibration when operated at atmospheric pressure. Characterization experiments obtained by capacitance and admittance measurements are presented, and transducer responses to physically simulated AE source are discussed. Finally, we report our use of the device to detect acoustic emissions associated with crack initiation and growth in weld metal.

  14. Carbon Materials for Chemical Capacitive Energy Storage

    SciTech Connect

    Zhai, Yunpu; Dou, Yuqian; Zhao, Dongyuan; Fulvio, Pasquale F.; Mayes, Richard T.; Dai, Sheng

    2011-09-26

    Carbon materials have attracted intense interests as electrode materials for electrochemical capacitors, because of their high surface area, electrical conductivity, chemical stability and low cost. Activated carbons produced by different activation processes from various precursors are the most widely used electrodes. Recently, with the rapid growth of nanotechnology, nanostructured electrode materials, such as carbon nanotubes and template-synthesized porous carbons have been developed. Their unique electrical properties and well controlled pore sizes and structures facilitate fast ion and electron transportation. In order to further improve the power and energy densities of the capacitors, carbon-based composites combining electrical double layer capacitors (EDLC)-capacitance and pseudo-capacitance have been explored. They show not only enhanced capacitance, but as well good cyclability. In this review, recent progresses on carbon-based electrode materials are summarized, including activated carbons, carbon nanotubes, and template-synthesized porous carbons, in particular mesoporous carbons. Their advantages and disadvantages as electrochemical capacitors are discussed. At the end of this review, the future trends of electrochemical capacitors with high energy and power are proposed.

  15. Effect of Astaxanthin on Human Sperm Capacitation

    PubMed Central

    Donà, Gabriella; Kožuh, Ivana; Brunati, Anna Maria; Andrisani, Alessandra; Ambrosini, Guido; Bonanni, Guglielmo; Ragazzi, Eugenio; Armanini, Decio; Clari, Giulio; Bordin, Luciana

    2013-01-01

    In order to be able to fertilize oocytes, human sperm must undergo a series of morphological and structural alterations, known as capacitation. It has been shown that the production of endogenous sperm reactive oxygen species (ROS) plays a key role in causing cells to undergo a massive acrosome reaction (AR). Astaxanthin (Asta), a photo-protective red pigment belonging to the carotenoid family, is recognized as having anti-oxidant, anti-cancer, anti-diabetic and anti-inflammatory properties and is present in many dietary supplements. This study evaluates the effect of Asta in a capacitating buffer which induces low ROS production and low percentages of acrosome-reacted cells (ARC). Sperm cells were incubated in the presence or absence of increasing concentrations of Asta or diamide (Diam) and analyzed for their ROS production, Tyr-phosphorylation (Tyr-P) pattern and percentages of ARC and non-viable cells (NVC). Results show that Asta ameliorated both sperm head Tyr-P and ARC values without affecting the ROS generation curve, whereas Diam succeeded in enhancing the Tyr-P level but only of the flagellum without increasing ARC values. It is suggested that Asta can be inserted in the membrane and therefore create capacitation-like membrane alteration which allow Tyr-P of the head. Once this has occurred, AR can take place and involves a higher numbers of cells. PMID:23736766

  16. Effect of astaxanthin on human sperm capacitation.

    PubMed

    Donà, Gabriella; Kožuh, Ivana; Brunati, Anna Maria; Andrisani, Alessandra; Ambrosini, Guido; Bonanni, Guglielmo; Ragazzi, Eugenio; Armanini, Decio; Clari, Giulio; Bordin, Luciana

    2013-06-01

    In order to be able to fertilize oocytes, human sperm must undergo a series of morphological and structural alterations, known as capacitation. It has been shown that the production of endogenous sperm reactive oxygen species (ROS) plays a key role in causing cells to undergo a massive acrosome reaction (AR). Astaxanthin (Asta), a photo-protective red pigment belonging to the carotenoid family, is recognized as having anti-oxidant, anti-cancer, anti-diabetic and anti-inflammatory properties and is present in many dietary supplements. This study evaluates the effect of Asta in a capacitating buffer which induces low ROS production and low percentages of acrosome-reacted cells (ARC). Sperm cells were incubated in the presence or absence of increasing concentrations of Asta or diamide (Diam) and analyzed for their ROS production, Tyr-phosphorylation (Tyr-P) pattern and percentages of ARC and non-viable cells (NVC). Results show that Asta ameliorated both sperm head Tyr-P and ARC values without affecting the ROS generation curve, whereas Diam succeeded in enhancing the Tyr-P level but only of the flagellum without increasing ARC values. It is suggested that Asta can be inserted in the membrane and therefore create capacitation-like membrane alteration which allow Tyr-P of the head. Once this has occurred, AR can take place and involves a higher numbers of cells. PMID:23736766

  17. Multi-Channel Capacitive Sensor Arrays.

    PubMed

    Wang, Bingnan; Long, Jiang; Teo, Koon Hoo

    2016-01-01

    In this paper, multi-channel capacitive sensor arrays based on microstrip band-stop filters are studied. The sensor arrays can be used to detect the proximity of objects at different positions and directions. Each capacitive sensing structure in the array is connected to an inductive element to form resonance at different frequencies. The resonances are designed to be isolated in the frequency spectrum, such that the change in one channel does not affect resonances at other channels. The inductive element associated with each capacitive sensor can be surface-mounted inductors, integrated microstrip inductors or metamaterial-inspired structures. We show that by using metamaterial split-ring structures coupled to a microstrip line, the quality factor of each resonance can be greatly improved compared to conventional surface-mounted or microstrip meander inductors. With such a microstrip-coupled split-ring design, more sensing elements can be integrated in the same frequency spectrum, and the sensitivity can be greatly improved. PMID:26821023

  18. A capacitive accelerometer suitable for telemetry

    NASA Technical Reports Server (NTRS)

    Coon, G. W.

    1972-01-01

    The design and development of a miniature 0.635 cm (0.25 in.) diameter capacitive accelerometer for use in free flight wind tunnel telemetry are presented. Instruments with full scale ranges from + or - 1 to + or - 200 g were constructed, calibrated, and used in several wind tunnel telemetry projects. Flat, high frequency response from 0 to 1000 Hz or more was obtained by employing the inherent damping and stiffness in the air film surrounding the diaphragm-type spring that supports the inertial mass of the accelerometer. Design features to achieve minimum off-axis sensitivity and temperature stability are discussed, and the design requirements for use of the transducer with telemetry systems are derived. A transducer capacitance change of 0.16 pF full scale gave excellent resolution and provided a frequency deviation of 0.75 MHz for a 100 MHz FM oscillator. Although the present design of the capacitive accelerometer was optimized by using units of 0.635 cm diameter, construction of experimental accelerometers as small as 0.36 cm (0.14 in.) diameter has demonstrated the feasibility of further miniaturization.

  19. Multi-Channel Capacitive Sensor Arrays

    PubMed Central

    Wang, Bingnan; Long, Jiang; Teo, Koon Hoo

    2016-01-01

    In this paper, multi-channel capacitive sensor arrays based on microstrip band-stop filters are studied. The sensor arrays can be used to detect the proximity of objects at different positions and directions. Each capacitive sensing structure in the array is connected to an inductive element to form resonance at different frequencies. The resonances are designed to be isolated in the frequency spectrum, such that the change in one channel does not affect resonances at other channels. The inductive element associated with each capacitive sensor can be surface-mounted inductors, integrated microstrip inductors or metamaterial-inspired structures. We show that by using metamaterial split-ring structures coupled to a microstrip line, the quality factor of each resonance can be greatly improved compared to conventional surface-mounted or microstrip meander inductors. With such a microstrip-coupled split-ring design, more sensing elements can be integrated in the same frequency spectrum, and the sensitivity can be greatly improved. PMID:26821023

  20. Distributed Capacitive Sensor for Sample Mass Measurement

    NASA Technical Reports Server (NTRS)

    Toda, Risaku; McKinney, Colin; Jackson, Shannon P.; Mojarradi, Mohammad; Manohara, Harish; Trebi-Ollennu, Ashitey

    2011-01-01

    Previous robotic sample return missions lacked in situ sample verification/ quantity measurement instruments. Therefore, the outcome of the mission remained unclear until spacecraft return. In situ sample verification systems such as this Distributed Capacitive (DisC) sensor would enable an unmanned spacecraft system to re-attempt the sample acquisition procedures until the capture of desired sample quantity is positively confirmed, thereby maximizing the prospect for scientific reward. The DisC device contains a 10-cm-diameter pressure-sensitive elastic membrane placed at the bottom of a sample canister. The membrane deforms under the weight of accumulating planetary sample. The membrane is positioned in close proximity to an opposing rigid substrate with a narrow gap. The deformation of the membrane makes the gap narrower, resulting in increased capacitance between the two parallel plates (elastic membrane and rigid substrate). C-V conversion circuits on a nearby PCB (printed circuit board) provide capacitance readout via LVDS (low-voltage differential signaling) interface. The capacitance method was chosen over other potential approaches such as the piezoelectric method because of its inherent temperature stability advantage. A reference capacitor and temperature sensor are embedded in the system to compensate for temperature effects. The pressure-sensitive membranes are aluminum 6061, stainless steel (SUS) 403, and metal-coated polyimide plates. The thicknesses of these membranes range from 250 to 500 m. The rigid substrate is made with a 1- to 2-mm-thick wafer of one of the following materials depending on the application requirements glass, silicon, polyimide, PCB substrate. The glass substrate is fabricated by a microelectromechanical systems (MEMS) fabrication approach. Several concentric electrode patterns are printed on the substrate. The initial gap between the two plates, 100 m, is defined by a silicon spacer ring that is anodically bonded to the glass

  1. Algorithm-supported visual error correction (AVEC) of heart rate measurements in dogs, Canis lupus familiaris.

    PubMed

    Schöberl, Iris; Kortekaas, Kim; Schöberl, Franz F; Kotrschal, Kurt

    2015-12-01

    Dog heart rate (HR) is characterized by a respiratory sinus arrhythmia, and therefore makes an automatic algorithm for error correction of HR measurements hard to apply. Here, we present a new method of error correction for HR data collected with the Polar system, including (1) visual inspection of the data, (2) a standardized way to decide with the aid of an algorithm whether or not a value is an outlier (i.e., "error"), and (3) the subsequent removal of this error from the data set. We applied our new error correction method to the HR data of 24 dogs and compared the uncorrected and corrected data, as well as the algorithm-supported visual error correction (AVEC) with the Polar error correction. The results showed that fewer values were identified as errors after AVEC than after the Polar error correction (p < .001). After AVEC, the HR standard deviation and variability (HRV; i.e., RMSSD, pNN50, and SDNN) were significantly greater than after correction by the Polar tool (all p < .001). Furthermore, the HR data strings with deleted values seemed to be closer to the original data than were those with inserted means. We concluded that our method of error correction is more suitable for dog HR and HR variability than is the customized Polar error correction, especially because AVEC decreases the likelihood of Type I errors, preserves the natural variability in HR, and does not lead to a time shift in the data. PMID:25540125

  2. Study the Z-Plane Strip Capacitance

    SciTech Connect

    Parikh, H.; Swain, S.; /SLAC

    2005-12-15

    The BaBaR detector at the Stanford Linear Accelerator Center is currently undergoing an upgrade to improve its muon and neutral hadron detection system. The Resistive Plate Chambers (RPCs) that had been used till now have deteriorated in performance over the past few years and are being replaced by Limited Streamer Tube (LSTs). Each layer of the system consists of a set of up to 10 streamer tube modules which provide one coordinate ({phi} coordinate) and a single ''Z-plane'' which provides the Z coordinate of the hit. The large area Z-planes (up to 12m{sup 2}) are 1mm thick and contain 96 copper strips that detect the induced charge from avalanches created in the streamer tube wires. All the Z-planes needed for the upgrade have already been constructed, but only a third of the planes were installed last summer. After installing the 24 Z-planes last year, it was learned that 0.7% of the strips were dead when put inside the detector. This was mainly due to the delicate solder joint between the read-out cable and the strip, and since it is difficult to access or replace the Z-planes inside the detector, it is very important to perform various tests to make sure that the Z-planes will be efficient and effective in the long term. We measure the capacitance between the copper strips and the ground plane, and compare it to the theoretical value that we expect. Instead of measuring the capacitance channel by channel, which would be a very tedious job, we developed a more effective method of measuring the capacitance. Since all the Z-planes were built at SLAC, we also built a smaller 46 cm by 30 cm Z-plane with 12 strips just to see how they were constructed and to gain a better understanding about the solder joints.

  3. Magnetic field tunable capacitive dielectric:ionic-liquid sandwich composites

    NASA Astrophysics Data System (ADS)

    Wu, Ye; Bhalla, Amar; Guo, Ruyan

    2016-03-01

    We examined the tunability of the capacitance for GaFeO3-ionic liquid-GaFeO3 composite material by external magnetic and electric field. Up to 1.6 folds of capacitance tunability could be achieved at 957 kHz with voltage 4 V and magnetic field 0.02 T applied. We show that the capacitance enhancement is due to the polarization coupling between dielectric layer and ionic liquid layer.

  4. Capacitive tool standoff sensor for dismantlement tasks

    SciTech Connect

    Schmitt, D.J.; Weber, T.M.; Liu, J.C.

    1996-12-31

    A capacitive sensing technology has been applied to develop a Standoff Sensor System for control of robotically deployed tools utilized in Decontamination and Dismantlement (D and D) activities. The system combines four individual sensor elements to provide non-contact, multiple degree-of-freedom control of tools at distances up to five inches from a surface. The Standoff Sensor has been successfully integrated to a metal cutting router and a pyrometer, and utilized for real-time control of each of these tools. Experiments demonstrate that the system can locate stationary surfaces with a repeatability of 0.034 millimeters.

  5. Quantum model of capacitance of nanostructures

    NASA Astrophysics Data System (ADS)

    Lu, Junqiang

    Modeling high-frequency electronic properties of nanostructures in nanocircuits presents particular challenge because of contribution from electrodes. In this talk, I present the difference in modeling steady and dynamic electronic transport properties of nano-gap structures and a quantum model to measure capacitance of nanostructures. This work is supported by NSF-EPSCOR program (Grants 1002410 and 1010094) and an award from Research Corporation for Science Advancement. JQL is also grateful for the support from the Faculty of Arts and Sciences, University of Puerto Rico at Mayaguez.

  6. 3-D capacitance density imaging system

    DOEpatents

    Fasching, G.E.

    1988-03-18

    A three-dimensional capacitance density imaging of a gasified bed or the like in a containment vessel is achieved using a plurality of electrodes provided circumferentially about the bed in levels and along the bed in channels. The electrodes are individually and selectively excited electrically at each level to produce a plurality of current flux field patterns generated in the bed at each level. The current flux field patterns are suitably sensed and a density pattern of the bed at each level determined. By combining the determined density patterns at each level, a three-dimensional density image of the bed is achieved. 7 figs.

  7. Variable-capacitance tachometer eliminates troublesome magnetic fields

    NASA Technical Reports Server (NTRS)

    1966-01-01

    Dual variable-capacitance tachometer measures angular speed and sense of rotation without magnetic components. Thus it eliminates magnetic flux interference with associated instrumentation in an electromechanical system.

  8. Quantum capacitance of graphene in contact with metal

    SciTech Connect

    Chang, Jin Hyun Dawson, Francis; Huzayyin, Ahmed; Lian, Keryn

    2015-11-09

    We report a versatile computation method to quantitatively determine the quantum capacitance of graphene when it is in contact with metal. Our results bridge the longstanding gap between the theoretically predicted and experimentally measured quantum capacitance of graphene. Contrary to popular assumptions, the presence of charged impurities or structural distortions of graphene are not the only sources of the asymmetric capacitance with respect to the polarity of the bias potential and the higher-than-expected capacitance at the Dirac point. They also originate from the field-induced electronic interactions between graphene and metal. We also provide an improved model representation of a metal–graphene junction.

  9. Lifetime characterization of capacitive RF MEMS switches

    NASA Astrophysics Data System (ADS)

    Ziaei, Afshin; Dean, Thierry; Polizzi, Jean-Philippe

    2004-12-01

    RF MEMS switches provide a low-cost, high performance solution to many RF/microwave applications and these switches will be important building blocks for designing phase shifters, switched filters and reflector array antennas for military and commercial markets. In this paper, progress in characterizing of THALES capacitive MEMS devices under high RF power is presented. The design, fabrication and testing of capacitive RF MEMS switches for microwave/mm- wave applications on high-resistivity silicon substrate is presented. The switches tested demonstrated power handling capabilities of 1W (30 dbm) for continuous RF power. The reliability of these switches was tested at various power levels indicating that under continuous RF power. In addition a description of the power failures and their associated operating conditions is presented. The PC-based test stations to cycle switches and measure lifetime under DC and RF loads have been developed. Best-case lifetimes of 1010 cycles have been achieved in several switches from different lots under 30 dbm RF power.

  10. Lifetime characterization of capacitive RF MEMS switches

    NASA Astrophysics Data System (ADS)

    Ziaei, Afshin; Dean, Thierry; Mancuso, Yves

    2005-05-01

    RF MEMS switches provide a low-cost, high performance solution to many RF/microwave applications and these switches will be important building blocks for designing phase shifters, switched filters and reflector array antennas for military and commercial markets. In this paper, progress in characterizing of THALES capacitive MEMS devices under high RF power is presented. The design, fabrication and testing of capacitive RF MEMS switches for microwave/mm- wave applications on high-resistivity silicon substrate is presented. The switches tested demonstrated power handling capabilities of 1W (30 dbm) for continuous RF power. The reliability of these switches was tested at various power levels indicating that under continuous RF power. In addition a description of the power failures and their associated operating conditions is presented. The PC-based test stations to cycle switches and measure lifetime under DC and RF loads have been developed. Best-case lifetimes of 1010 cycles have been achieved in several switches from different lots under 30 dbm RF power.

  11. Lifetime characterization of capacitive RF MEMS switches

    NASA Astrophysics Data System (ADS)

    Ziaei, Afshin; Dean, Thierry; Polizzi, Jean-Philippe

    2005-01-01

    RF MEMS switches provide a low-cost, high performance solution to many RF/microwave applications and these switches will be important building blocks for designing phase shifters, switched filters and reflector array antennas for military and commercial markets. In this paper, progress in characterizing of THALES capacitive MEMS devices under high RF power is presented. The design, fabrication and testing of capacitive RF MEMS switches for microwave/mm- wave applications on high-resistivity silicon substrate is presented. The switches tested demonstrated power handling capabilities of 1W (30 dbm) for continuous RF power. The reliability of these switches was tested at various power levels indicating that under continuous RF power. In addition a description of the power failures and their associated operating conditions is presented. The PC-based test stations to cycle switches and measure lifetime under DC and RF loads have been developed. Best-case lifetimes of 1010 cycles have been achieved in several switches from different lots under 30 dbm RF power.

  12. Kinetic simulations of magnetized capacitively coupled discharges

    NASA Astrophysics Data System (ADS)

    Trieschmann, Jan; Shihab, Mohammed; Eremin, Denis; Brinkmann, Ralf Peter; Schulze, Julian; Mussenbrock, Thomas

    2012-10-01

    Capacitive high frequency discharges are of crucial importance in the context of plasma etching, deposition and surface modification. As these single or multiple frequency discharges are oftentimes operated at low pressures of less than a few pascal, a high plasma density is commonly achieved with the use of external magnetic fields. In this work kinetic simulations are used to investigate the effect of inhomogeneous external magnetic fields on the discharge dynamics in a strongly nonlocal pressure regime. We found that capacitively coupled discharges can be largely asymmetrized by applying strong magnetic fields in front of a given target electrode. This not only has an effect on the plasma density, but also on the ion energy distribution functions (IEDF) at the electrodes and on the acceleration of fast electrons in the plasma sheath regions. In consequence in the discharge currents a generation of higher harmonics of the driving frequency can be observed. We investigate these scenarios in terms of 1D-3V Particle in Cell simulations.

  13. Active shunt capacitance cancelling oscillator circuit

    DOEpatents

    Wessendorf, Kurt O.

    2003-09-23

    An oscillator circuit is disclosed which can be used to produce oscillation using a piezoelectric crystal, with a frequency of oscillation being largely independent of any shunt capacitance associated with the crystal (i.e. due to electrodes on the surfaces of the crystal and due to packaging and wiring for the crystal). The oscillator circuit is based on a tuned gain stage which operates the crystal at a frequency, f, near a series resonance frequency, f.sub.S. The oscillator circuit further includes a compensation circuit that supplies all the ac current flow through the shunt resistance associated with the crystal so that this ac current need not be supplied by the tuned gain stage. The compensation circuit uses a current mirror to provide the ac current flow based on the current flow through a reference capacitor that is equivalent to the shunt capacitance associated with the crystal. The oscillator circuit has applications for driving piezoelectric crystals for sensing of viscous, fluid or solid media by detecting a change in the frequency of oscillation of the crystal and a resonator loss which occur from contact of an exposed surface of the crystal by the viscous, fluid or solid media.

  14. Proportional microvolume capacitive liquid level sensor array.

    PubMed

    Seliskar, D; Waterbury, R; Kearney, R

    2005-01-01

    A sensor array has been developed for use with laboratory automation to permit closed-loop control of liquid levels in a multiwell microplate geometry. We extended a simple electrical model for non-contact capacitance-based fluid sensors to describe a fluid-level dependency. The new model shows that a charge-transfer based capacitance transducer, employing a liquid-specific calibration, can be used to obtain an output signal that varies linearly with the liquid level. The calibration also compensates for liquid-to-liquid conductivity and permittivity differences. A prototype 3×3 sensor array was built and tested using NaCl and ethanol solutions to simulate the range of conductivity and permittivity typical in biological and chemical research. Calibrated output signals were linear with liquid volume for all tested solutions (R2>0.92). Measurement error averaged 1.3 % (2.0 μl) with a standard deviation of 6.0% (9.0 μl). These results demonstrate the feasibility of developing a microvolume sensor array in essentially any M×N microplate geometry. PMID:17281955

  15. Capacitive micromachined ultrasonic transducers: fabrication technology.

    PubMed

    Ergun, Arif Sanli; Huang, Yongli; Zhuang, Xuefeng; Oralkan, Omer; Yaralioglu, Goksen G; Khuri-Yakub, Butrus T

    2005-12-01

    Capacitive micromachined ultrasonic transducer (cMUT) technology is a prime candidate for next generation imaging systems. Medical and underwater imaging and the nondestructive evaluation (NDE) societies have expressed growing interest in cMUTs over the years. Capacitive micromachined ultrasonic transducer technology is expected to make a strong impact on imaging technologies, especially volumetric imaging, and to appear in commercial products in the near future. This paper focuses on fabrication technologies for cMUTs and reviews and compares variations in the production processes. We have developed two main approaches to the fabrication of cMUTs: the sacrificial release process and the recently introduced wafer-bonding method. This paper gives a thorough review of the sacrificial release processes, and it describes the new wafer-bonding method in detail. Process variations are compared qualitatively and quantitatively whenever possible. Through these comparisons, it was concluded that wafer-bonded cMUT technology was superior in terms of process control, yield, and uniformity. Because the number of steps and consequent process time were reduced (from six-mask process to four-mask process), turn-around time was improved significantly. PMID:16463490

  16. A capacitive electrode with fast recovery feature.

    PubMed

    Spinelli, Enrique; Haberman, Marcelo; García, Pablo; Guerrero, Federico

    2012-08-01

    Capacitive electrodes (CEs) allow for acquiring biopotentials without galvanic contact, avoiding skin preparation and the use of electrolytic gel. The signal quality provided by present CEs is similar to that of standard wet electrodes, but they are more sensitive to electrostatic charge interference and motion artifacts, mainly when biopotentials are picked up through clothing and coupling capacitances are reduced to tens of picofarads. When artifacts are large enough to saturate the preamplifier, several seconds (up to tens) are needed to recover a proper baseline level, and during this period biopotential signals are irremediably lost. To reduce this problem, a CE that includes a fast-recovery (FR) circuit is proposed. It works directly on the coupling capacitor, recovering the amplifier from saturation while preserving ultra-high input impedance, as a CE requires. A prototype was built and tested acquiring ECG signals. Several experimental data are presented, which show that the proposed circuit significantly reduces record segment losses due to amplifier saturation when working in real environments. PMID:22813845

  17. Improved circuit for measuring capacitive and inductive reactances

    NASA Technical Reports Server (NTRS)

    Dalins, I.; Mc Carty, V.

    1967-01-01

    Amplifier circuit measures very small changes of capacitive or inductive reactance, such as produced by a variable capacitance or a variable inductance displacement transducer. The circuit employs reactance-sensing oscillators in which field effect transistors serve as the active elements.

  18. Enhanced detection performance in electrosense through capacitive sensing.

    PubMed

    Bai, Yang; Neveln, Izaak D; Peshkin, Michael; MacIver, Malcolm A

    2016-01-01

    Weakly electric fish emit an AC electric field into the water and use thousands of sensors on the skin to detect field perturbations due to surrounding objects. The fish's active electrosensory system allows them to navigate and hunt, using separate neural pathways and receptors for resistive and capacitive perturbations. We have previously developed a sensing method inspired by the weakly electric fish to detect resistive perturbations and now report on an extension of this system to detect capacitive perturbations as well. In our method, an external object is probed by an AC field over multiple frequencies. We present a quantitative framework that relates the response of a capacitive object at multiple frequencies to the object's composition and internal structure, and we validate this framework with an electrosense robot that implements our capacitive sensing method. We define a metric for comparing the electrosensory range of different underwater electrosense systems. For detecting non-conductive objects, we show that capacitive sensing performs better than resistive sensing by almost an order of magnitude using this measure, while for conductive objects there is a four-fold increase in performance. Capacitive sensing could therefore provide electric fish with extended sensing range for capacitive objects such as prey, and gives artificial electrolocation systems enhanced range for targets that are capacitive. PMID:27501202

  19. Large Capacitance Measurement by Multiple Uses of MBL Charge Sensor

    ERIC Educational Resources Information Center

    Lee, Jung Sook; Chae, Min; Kim, Jung Bog

    2010-01-01

    A recent article by Morse described interesting electrostatics experiments using an MBL charge sensor. In this application, the charge sensor has a large capacitance compared to the charged test object, so nearly all charges can be transferred to the sensor capacitor from the capacitor to be measured. However, the typical capacitance of commercial…

  20. CRITICAL OVERVIEW OF THE PERFORMANCE OF A MULTISENSOR CAPACITANCE SYSTEM

    Technology Transfer Automated Retrieval System (TEKTRAN)

    During the last decade major advances have been made in capacitance based sensor technology that enhanced our ability to measure soil water content in the soil plant atmosphere system. Multisensor capacitance systems (MCS) took the lead in this regards. This objectives of the current work are to c...

  1. Electrostatic capacitance and Faraday cage behavior of carbon nanotube forests

    SciTech Connect

    Ya'akobovitz, A.; Bedewy, M.; Hart, A. J.

    2015-02-02

    Understanding of the electrostatic properties of carbon nanotube (CNT) forests is essential to enable their integration in microelectronic and micromechanical devices. In this study, we sought to understand how the hierarchical geometry and morphology of CNT forests determines their capacitance. First, we find that at small gaps, solid micropillars have greater capacitance, yet at larger gaps the capacitance of the CNT forests is greater. The surface area of the CNT forest accessible to the electrostatic field was extracted by analysis of the measured capacitance, and, by relating the capacitance to the average density of CNTs in the forest, we find that the penetration depth of the electrostatic field is on the order of several microns. Therefore, CNT forests can behave as a miniature Faraday cage. The unique electrostatic properties of CNT forests could therefore enable their use as long-range proximity sensors and as shielding elements for miniature electronic devices.

  2. Capacitance multiplier and filter synthesizing network

    NASA Technical Reports Server (NTRS)

    Kline, A. J. (Inventor)

    1974-01-01

    A circuit using a differential amplifier multiplies the capacitance of a discrete interating capacitor by (r sub 1 + R sub 2)/R sub 2, where R sub 1 and R sub 2 are values of discrete resistor coupling an input signal e sub 1 of the amplifier inputs. The output e sub 0 of the amplifier is fed back and added to the signal coupled by the resistor R sub 2 to the amplifier through a resistor of value R sub 1. A discrete resistor R sub x may be connected in series for a lag filter, and a discrete resistor may be connected in series with the capacitor for a lead-lag filter. Voltage dividing resistors R sub a and R sub b may be included in the feedback circuit of the amplifier output e sub o to independently adjust the circuit gain e sub i/e sub o.

  3. Miniaturized Wilkinson Power Dividers Utilizing Capacitive Loading

    NASA Technical Reports Server (NTRS)

    Scardelletti, Maximilian C.; Ponchak, George E.; Weller, Thomas M.

    2001-01-01

    This letter reports the miniaturization of a planar Wilkinson power divider by capacitive loading of the quarter wave transmission lines employed in conventional Wilkinson power dividers. Reduction of the transmission line segments from lambda/4 to between lambda/5 and lambda/12 are reported here. The input and output lines at the three ports and the lines comprising the divider itself are coplanar waveguide (CPW) and asymmetric coplanar stripline (ACPS), respectively. The 10 GHZ power dividers are fabricated on high resistivity silicon (HRS) and alumina wafers. These miniaturized dividers are 74% smaller than conventional Wilkinson power dividers, and have a return loss better than +30 dB and an insertion loss less than 0.55 dB. Design equations and a discussion about the effect of parasitic reactance on the isolation are presented for the first time.

  4. Electron heating in capacitively coupled plasmas revisited

    NASA Astrophysics Data System (ADS)

    Lafleur, T.; Chabert, P.; Booth, J. P.

    2014-06-01

    We revisit the problem of electron heating in capacitively coupled plasmas (CCPs), and propose a method for quantifying the level of collisionless and collisional heating in plasma simulations. The proposed procedure, based on the electron mechanical energy conservation equation, is demonstrated with particle-in-cell simulations of a number of single and multi-frequency CCPs operated in regimes of research and industrial interest. In almost all cases tested, the total electron heating is comprised of collisional (ohmic) and pressure heating parts. This latter collisionless component is in qualitative agreement with the mechanism of electron heating predicted from the recent re-evaluation of theoretical models. Finally, in very electrically asymmetric plasmas produced in multi-frequency discharges, we observe an additional collisionless heating mechanism associated with electron inertia.

  5. Further capacitive imaging experiments using modified probes

    NASA Astrophysics Data System (ADS)

    Yin, Xiaokang; Li, Zhen; Yan, An; Li, Wei; Chen, Guoming; Hutchins, David A.

    2016-02-01

    In recent years, capacitive imaging (CI) is growing in popularity within the NDE communities, as it has the potential to test materials and structures for defects that are not easily tested by other techniques. In previous work, The CI technique has been successfully used on a various types of materials, including concrete, glass/carbon fibre composite, steel, etc. In such CI experiments, the probes are normally with symmetric or concentric electrodes etched onto PCBs. In addition to these conventional coplanar PCB probes, modified geometries can be made and they can lead to different applications. A brief overview of these modified probes, including high resolution surface imaging probe, combined CI/eddy current probe, and CI probe using an oscilloscope probe as the sensing electrode, is presented in this work. The potential applications brought by these probes are also discussed.

  6. In-line rotating capacitive torque sensor

    DOEpatents

    Kronberg, James W.

    1991-01-01

    A method and apparatus for measuring torques developed along a rotating mechanical assembly comprising a rotating inner portion and a stationary outer portion. The rotating portion has an electrically-conductive flexing section fitted between two coaxial shafts in a configuration which varies radially in accordance with applied torque. The stationary portion comprises a plurality of conductive plates forming a surface concentric with and having a diameter slightly larger than the diameter of the rotating portion. The capacitance between the outer, nonrotating and inner, rotating portion varies with changes in the radial configuration of the rotating portion. Signal output varies approximately linearly with torque for small torques, nonlinearly for larger torques. The sensor is preferably surrounded by a conductive shell to minimize electrical interference from external sources.

  7. Rf capacitively-coupled electrodeless light source

    DOEpatents

    Manos, Dennis M.; Diggs, Jessie; Ametepe, Joseph D.; Fugitt, Jock A.

    2000-01-01

    An rf capacitively-coupled electrodeless light source is provided. The light source comprises a hollow, elongated chamber and at least one center conductor disposed within the hollow, elongated chamber. A portion of each center conductor extends beyond the hollow, elongated chamber. At least one gas capable of forming an electronically excited molecular state is contained within each center conductor. An electrical coupler is positioned concentric to the hollow, elongated chamber and the electrical coupler surrounds the portion of each center conductor that extends beyond the hollow, elongated chamber. A rf-power supply is positioned in an operable relationship to the electrical coupler and an impedance matching network is positioned in an operable relationship to the rf power supply and the electrical coupler.

  8. In-line rotating capacitive torque sensor

    DOEpatents

    Kronberg, J.W.

    1991-09-10

    Disclosed are a method and apparatus for measuring torques developed along a rotating mechanical assembly comprising a rotating inner portion and a stationary outer portion. The rotating portion has an electrically-conductive flexing section fitted between two coaxial shafts in a configuration which varies radially in accordance with applied torque. The stationary portion comprises a plurality of conductive plates forming a surface concentric with and having a diameter slightly larger than the diameter of the rotating portion. The capacitance between the outer, nonrotating and inner, rotating portion varies with changes in the radial configuration of the rotating portion. Signal output varies approximately linearly with torque for small torques, nonlinearly for larger torques. The sensor is preferably surrounded by a conductive shell to minimize electrical interference from external sources. 18 figures.

  9. Phase discriminating capacitive array sensor system

    NASA Technical Reports Server (NTRS)

    Vranish, John M. (Inventor); Rahim, Wadi (Inventor)

    1993-01-01

    A phase discriminating capacitive sensor array system which provides multiple sensor elements which are maintained at a phase and amplitude based on a frequency reference provided by a single frequency stabilized oscillator. Sensor signals provided by the multiple sensor elements are controlled by multiple phase control units, which correspond to the multiple sensor elements, to adjust the sensor signals from the multiple sensor elements based on the frequency reference. The adjustment made to the sensor signals is indicated by output signals which indicate the proximity of the object. The output signals may also indicate the closing speed of the object based on the rate of change of the adjustment made, and the edges of the object based on a sudden decrease in the adjustment made.

  10. Fund allocation using capacitated vehicle routing problem

    NASA Astrophysics Data System (ADS)

    Mamat, Nur Jumaadzan Zaleha; Jaaman, Saiful Hafizah; Ahmad, Rokiah Rozita; Darus, Maslina

    2014-09-01

    In investment fund allocation, it is unwise for an investor to distribute his fund into several assets simultaneously due to economic reasons. One solution is to allocate the fund into a particular asset at a time in a sequence that will either maximize returns or minimize risks depending on the investor's objective. The vehicle routing problem (VRP) provides an avenue to this issue. VRP answers the question on how to efficiently use the available fleet of vehicles to meet a given service demand, subjected to a set of operational requirements. This paper proposes an idea of using capacitated vehicle routing problem (CVRP) to optimize investment fund allocation by employing data of selected stocks in the FTSE Bursa Malaysia. Results suggest that CRVP can be applied to solve the issue of investment fund allocation and increase the investor's profit.

  11. The hysteresis-free negative capacitance field effect transistors using non-linear poly capacitance

    NASA Astrophysics Data System (ADS)

    Fan, S.-T.; Yan, J.-Y.; Lai, D.-C.; Liu, C. W.

    2016-08-01

    A gate structure design for negative capacitance field effect transistors (NCFETs) is proposed. The hysteresis loop in current-voltage performances is eliminated by the nonlinear C-V dependence of polysilicon in the gate dielectrics. Design considerations and optimizations to achieve the low SS and hysteresis-free transfer were elaborated. The effects of gate-to-source/drain overlap, channel length scaling, interface trap states and temperature impact on SS are also investigated.

  12. A review of reconstruction techniques for capacitance tomography

    NASA Astrophysics Data System (ADS)

    Isaksen, Øyvind

    1996-03-01

    Capacitance tomography has been used to image several processes, such as liquid/gas pipe flow, oil/water/gas gravity separation, pneumatic conveying, fluidized beds and flame combustion. The nature of the capacitance sensors is such that reconstruction algorithms well developed for medical tomography are not applicable. The main problem is that the relationship between the measured quantity (capacitance) and the parameter of interest (distribution of the dielectric constant) is nonlinear. Furthermore, it is impossible to establish an explicit expression which relates the dielectric constant distribution to the measured capacitance. Also it should be pointed out that the number of measurements in capacitance tomography is small (typically less than 100) compared to medical tomography. For these reasons the first tested algorithm in capacitance tomography was based on the crude back projection algorithm. This algorithm has over the years been enhanced for use with a capacitance tomograph. In addition other techniques, such as various iterative methods, algorithms based on artificial neural networks and `look-up' tables have been developed and tested. This paper outlines the working principles for the different techniques and presents the main results.

  13. The role of vascular capacitance in the coronary arteries.

    PubMed

    Lee, J; Chambers, D E; Akizuki, S; Downey, J M

    1984-12-01

    When the left coronary artery was perfused with nonpulsatile pressure, the onset of diastole was accompanied by a capacitance overshoot in flow with an exponential decay back to a steady state. Time constant for that decay ranged from 55 msec when tone was present to 105 msec with maximal dilation. Since the transient resulted from a fall in tissue pressure, this represents an estimation of intramural arterial capacitance only. Transients in perfusion pressure, which would also affect epicardial arteries, yielded similar time constants. We concluded that most of the coronary capacitance resides in the small intramural vessels. Analysis of transients yielded a value for capacitance of between 0.01 and 0.05 ml/mm Hg per 100 g. We then used the data from the transients to construct coronary pressure flow curves which were free of any back flow from capacitance. When coronary tone was present, the curves indicated that flow ceased at 30 mm Hg. With maximal dilation, flow ceased at only 18 mm Hg. Long diastoles in those same hearts indicated that flow ceased at about 10 mm Hg higher pressure. Although capacitance causes critical closing pressure as determined by a long diastole to be artifactually high, critical closing pressure is still appreciable in the heart, and tone dependent. Finally, three computer models were built, one of which included only small vessel capacitances, the second, only vascular waterfalls, and the third, both of the above. Only model 3 was capable of reproducing the flow patterns which were actually seen. PMID:6499131

  14. Complex Capacitance Scaling in Ionic Liquids-filled Nanopores

    SciTech Connect

    Qiao, Rui; Huang, Jingsong; Meunier, Vincent; Sumpter, Bobby G; Peng, Wu

    2011-01-01

    Recent experiments have shown that the capacitance of sub-nanometer pores increases anomalously as the pore width decreases, thereby opening a new avenue for developing supercapacitors with enhanced energy density. However, this behavior is still subject to some controversy since its physical origins are not well understood. Using atomistic simulations, we show that the capacitance of slit-shaped nanopores in contact with room-temperature ionic liquids exhibits a U-shaped scaling behavior in pores with width from 0.75 to 1.26 nm. The left branch of the capacitance scaling curve directly corresponds to the anomalous capacitance increase and thus reproduces the experimental observations. The right branch of the curve indirectly agrees with experimental findings that so far have received little attention. The overall U-shaped scaling behavior provides insights on the origins of the difficulty in experimentally observing the pore-width dependent capacitance. We establish a theoretical framework for understanding the capacitance of electrical double layers in nanopores and provide mechanistic details into the origins of the observed scaling behavior. The framework highlights the critical role of ion solvation in controlling pore capacitance and the importance of choosing anion/cation couples carefully for optimal energy storage in a given pore system.

  15. Complex Capacitance Scaling in Ionic Liquids-Filled Nanopores

    SciTech Connect

    Sumpter, Bobby G

    2011-01-01

    Recent experiments have shown that the capacitance of subnanometer pores increases anomalously as the pore width decreases, thereby opening a new avenue for developing supercapacitors with enhanced energy density. However, this behavior is still subject to some controversy since its physical origins are not well understood. Using atomistic simulations, we show that the capacitance of slit-shaped nanopores in contact with room-temperature ionic liquids exhibits a U-shaped scaling behavior in pores with widths from 0.75 to 1.26 nm. The left branch of the capacitance scaling curve directly corresponds to the anomalous capacitance increase and thus reproduces the experimental observations. The right branch of the curve indirectly agrees with experimental findings that so far have received little attention. The overall U-shaped scaling behavior provides insights on the origins of the difficulty in experimentally observing the pore-width-dependent capacitance. We establish a theoretical framework for understanding the capacitance of electrical double layers in nanopores and provide mechanistic details into the origins of the observed scaling behavior. The framework highlights the critical role of 'ion solvation' in controlling pore capacitance and the importance of choosing anion/cation couples carefully for optimal energy storage in a given pore system.

  16. A new physical interpretation of plant root capacitance

    PubMed Central

    Bengough, Anthony G.

    2012-01-01

    Capacitance has been used as a non-destructive measure of root system size for 30 years. The equipment required is cheap and simple to apply in both field and laboratory. Good linear correlations have been reported between capacitance and root mass. A model by F. N. Dalton, predicting a linear relationship between these two variables, has become accepted widely. This model was tested for barley (Hordeum vulgare) grown hydroponically using treatments that included: raising roots out of solution, cutting roots at positions below the solution surface, and varying the distance between plant electrode and the solution surface. Although good linear correlations were found between capacitance and mass for whole root systems, when roots were raised out of solution capacitances were not linearly related to submerged root mass. Excision of roots in the solution had negligible effect on the measured capacitance. These latter observations conflict with Dalton’s model. Capacitance correlated linearly with the sum of root cross-sectional areas at the solution surface and inversely with distance between plant electrode and solution surface. A new model for capacitance is proposed that is consistent with these observations. PMID:23028023

  17. Effect of heparin on in vitro capacitation of boar sperm.

    PubMed

    Dapino, Dora G; Marini, Patricia E; Cabada, Marcelo O

    2006-01-01

    Chlortetracycline (CTC) fluorescent pattern, the ability to undergo acrosome reaction (AR) upon exposure to 10 microM calcium ionophore A23187 and vitality estimation were used to investigate the effect of the sulfated glycosaminoglycan heparin on the in vitro capacitation of porcine spermatozoa. Sperm incubation in capacitating medium (CM) supplemented with 10 mM heparin for up to 120 min, showed an increase in the number of capacitated sperm (B pattern) and acrosome reacted sperm (AR pattern), without affecting their viability. In this condition, spermatozoa were incubated in CM depleted of albumin, calcium, bicarbonate or combinations, in the presence of heparin. In either calcium or bicarbonate-free media, capacitation was only basal and did not show variations in the presence of heparin. In absence of albumin the presence of calcium and bicarbonate stimulated capacitation, which was further increased by the addition of heparin. These results suggest that heparin enhances in vitro capacitation of porcine sperm only under capacitating conditions. Additionally, when sperm were incubated with 100 microg/ml biotinylated heparin in the presence or absence of unlabeled heparin, we observed that heparin binding sites were located mostly on the acrosomal region of boar sperm in an specific and saturable manner. The in vitro effect of heparin described in this work indicates that sulfated glycosaminoglycans, which are normally present in the female reproductive tract, might play an important role in the fertilization process in porcines. PMID:17657344

  18. A compact, low input capacitance neural recording amplifier.

    PubMed

    Ng, K A; Xu, Yong Ping

    2013-10-01

    Conventional capacitively coupled neural recording amplifiers often present a large input load capacitance to the neural signal source and hence take up large circuit area. They suffer due to the unavoidable trade-off between the input capacitance and chip area versus the amplifier gain. In this work, this trade-off is relaxed by replacing the single feedback capacitor with a clamped T-capacitor network. With this simple modification, the proposed amplifier can achieve the same mid-band gain with less input capacitance, resulting in a higher input impedance and a smaller silicon area. Prototype neural recording amplifiers based on this proposal were fabricated in 0.35 μm CMOS, and their performance is reported. The amplifiers occupy smaller area and have lower input loading capacitance compared to conventional neural amplifiers. One of the proposed amplifiers occupies merely 0.056 mm(2). It achieves 38.1-dB mid-band gain with 1.6 pF input capacitance, and hence has an effective feedback capacitance of 20 fF. Consuming 6 μW, it has an input referred noise of 13.3 μVrms over 8.5 kHz bandwidth and NEF of 7.87. In-vivo recordings from animal experiments are also demonstrated. PMID:24144666

  19. Four-point characterization using capacitive and ohmic contacts

    NASA Astrophysics Data System (ADS)

    Zhou, Wang; Kim, Brian; Shah, Yash; Zhou, Chuanle; Grayson, Matthew; Işik, Nebile

    2012-02-01

    A four-point characterization method is developed for semiconductor samples that have either capacitive or ohmic contacts. When capacitive contacts are used, capacitive current- and voltage-dividers result in a capacitive scaling factor which is not present in four-point measurements with only ohmic contacts. Both lock-in amplifier and pre-amplifier are used to measure low-noise response over a wide frequency range from 1 Hz -- 100 kHz. From a circuit equivalent of the complete measurement system after carefully being modeled, both the measurement frequency band and capacitive scaling factor can be determined for various four-point characterization configurations. This technique is first demonstrated with a discrete element four-point test device and then with a capacitively and ohmically contacted Hall bar sample using lock-in measurement techniques. In all cases, data fit well to a circuit simulation of the entire measurement system over the whole frequency range of interest, and best results are achieved with large area capacitive contacts and a high input-impedance preamplifier stage. Results of samples (substrates grown by Max Bichler Dieter Schuh, and Frank Fischer of the WSI) measured in the QHE regime in magnetic fields up to 15 T at temperatures down to 1.5 K will also be shown.

  20. Capacitance-level/density monitor for fluidized-bed combustor

    DOEpatents

    Fasching, George E.; Utt, Carroll E.

    1982-01-01

    A multiple segment three-terminal type capacitance probe with segment selection, capacitance detection and compensation circuitry and read-out control for level/density measurements in a fluidized-bed vessel is provided. The probe is driven at a high excitation frequency of up to 50 kHz to sense quadrature (capacitive) current related to probe/vessel capacitance while being relatively insensitive to the resistance current component. Compensation circuitry is provided for generating a negative current of equal magnitude to cancel out only the resistive component current. Clock-operated control circuitry separately selects the probe segments in a predetermined order for detecting and storing this capacitance measurement. The selected segment acts as a guarded electrode and is connected to the read-out circuitry while all unselected segments are connected to the probe body, which together form the probe guard electrode. The selected probe segment capacitance component signal is directed to a corresponding segment channel sample and hold circuit dedicated to that segment to store the signal derived from that segment. This provides parallel outputs for display, computer input, etc., for the detected capacitance values. The rate of segment sampling may be varied to either monitor the dynamic density profile of the bed (high sampling rate) or monitor average bed characteristics (slower sampling rate).

  1. Compact Two-Liquid Microfluidic Hyperelastic Capacitive Strain Sensors

    NASA Astrophysics Data System (ADS)

    Liu, Shanliangzi; Sun, Xiaoda; Rykaczewski, Konrad

    2014-11-01

    Applications of liquid metal microfluidic devices include flexible electronics, biomedical devices, and soft robotics. In addition to single channel resistive strain sensors, two channel capacitive sensors have also been developed. However, these capacitive strain sensors have low capacitance with a footprint of about a square centimeter, making strain-output correlation quite complex. To address this issue, we developed a compact two liquid single straight channel capacitive strain sensor with a dielectric liquid sandwiched between two liquid metal electrodes. Formation of the capacitor with a liquid dielectric instead of PDMS enables capacitance increase through selection of high permittivity liquid. Using a custom experimental setup, we show that use of water and glycerol instead of silicone oil in-between the liquid metal electrodes can increase the device capacitance by fivefold. We discuss the effect of channel diameter, dielectric spacing, interfacial meniscus shape, and the liquid flow on device capacitance as well as response to strain. In addition, we discuss the effect of gallium oxide shell formation at the dielectric-liquid metal interface. KR acknowledges startup funding from ASU.

  2. Correcting For Capacitance In Tests Of Solar Cells

    NASA Technical Reports Server (NTRS)

    Mueller, Robert L.

    1995-01-01

    Modified procedure for testing solar photovoltaic cells and modified software for processing test data provide corrections for effects of cell capacitance. Procedure and software needed because (a) some photovoltaic devices (for example, silicon solar cells with back-surface field region) store minority charge carriers in cell junction and thus exhibit significant capacitance, (b) capacitance affects current-vs.-voltage (I-V) measurements made when transient load connected to cell, and (c) transient load used in unmodified version of test procedure. Corrected I-V curve obtained in test of solar cell according to modified procedure approximates true cell voltage vs. cell current more closely.

  3. Flexible transparent iontronic film for interfacial capacitive pressure sensing.

    PubMed

    Nie, Baoqing; Li, Ruya; Cao, Jennifer; Brandt, James D; Pan, Tingrui

    2015-10-21

    A flexible, transparent iontronic film is introduced as a thin-film capacitive sensing material for emerging wearable and health-monitoring applications. Utilizing the capacitive interface at the ionic-electronic contact, the iontronic film sensor offers a large unit-area capacitance (of 5.4 μF cm(-2) ) and an ultrahigh sensitivity (of 3.1 nF kPa(-1) ), which is a thousand times greater than that of traditional solid-state counterparts. PMID:26333011

  4. Developing capacitive equipment on-line monitoring intelligence software

    NASA Astrophysics Data System (ADS)

    Zhang, Weicong; Yang, Lichun

    2011-12-01

    In order to improve the safety and reliability of capacitive equipment developed online monitoring system of capacitive equipment dielectric loss. Introduce the structure and function of the software, based on the B/S skeleton, uses the modular design, improve the readability and scalability. Detail the design of communication module, parameter setting module, data acquisition and processing module, the user management module, database systems, etc. The entire process is given. By testing the monitoring software work is stable, reliable, long-term continuous and effective monitoring capacitive equipment various insulation data, can satisfy the requirements on site application.

  5. Developing capacitive equipment on-line monitoring intelligence software

    NASA Astrophysics Data System (ADS)

    Zhang, Weicong; Yang, Lichun

    2012-01-01

    In order to improve the safety and reliability of capacitive equipment developed online monitoring system of capacitive equipment dielectric loss. Introduce the structure and function of the software, based on the B/S skeleton, uses the modular design, improve the readability and scalability. Detail the design of communication module, parameter setting module, data acquisition and processing module, the user management module, database systems, etc. The entire process is given. By testing the monitoring software work is stable, reliable, long-term continuous and effective monitoring capacitive equipment various insulation data, can satisfy the requirements on site application.

  6. Verification of overlap and fringing capacitance models for MOSFETs

    NASA Astrophysics Data System (ADS)

    Wakita, Naoki; Shigyo, Naoyuki

    2000-06-01

    Parasitic capacitance and resistance limit the VLSI device performance. Hence, a circuit model is needed to treat these effects correctly. This article focuses on the circuit models for the overlap capacitance ( Cgd,overlap) and the fringing capacitance ( Cgd,fringe) of MOSFETs. Comparisons between the models and the device simulations are carried out for verification of the models. Also, a limitation of Cgd,fringe model for a future device miniaturization is found based on SIA Road Map. We propose a modified Cgd,fringe model. The effectiveness of the modified model is demonstrated using two circuits.

  7. Acoustic lens for capacitive micromachined ultrasonic transducers

    NASA Astrophysics Data System (ADS)

    Chang, Chienliu; Firouzi, Kamyar; Park, Kwan Kyu; Sarioglu, Ali Fatih; Nikoozadeh, Amin; Yoon, Hyo-Seon; Vaithilingam, Srikant; Carver, Thomas; Khuri-Yakub, Butrus T.

    2014-08-01

    Capacitive micromachined ultrasonic transducers (CMUTs) have great potential to compete with traditional piezoelectric transducers in therapeutic ultrasound applications. In this paper we have designed, fabricated and developed an acoustic lens formed on the CMUT to mechanically focus ultrasound. The acoustic lens was designed based on the paraxial theory and made of silicone rubber for acoustic impedance matching and encapsulation. The CMUT was fabricated based on the local oxidation of silicon (LOCOS) and fusion-bonding. The fabricated CMUT was verified to behave like an electromechanical resonator in air and exhibited wideband response with a center frequency of 2.2 MHz in immersion. The fabrication for the acoustic lens contained two consecutive mold castings and directly formed on the surface of the CMUT. Applied with ac burst input voltages at the center frequency, the CMUT with the acoustic lens generated an output pressure of 1.89 MPa (peak-to-peak) at the focal point with an effective focal gain of 3.43 in immersion. Compared to the same CMUT without a lens, the CMUT with the acoustic lens demonstrated the ability to successfully focus ultrasound and provided a viable solution to the miniaturization of the multi-modality forward-looking endoscopes without electrical focusing.

  8. Tailored Voltage Waveform Capacitively-Coupled Plasmas

    NASA Astrophysics Data System (ADS)

    Booth, Jean-Paul; Lafleur, Trevor; Delattre, Pierre-Alexandre; Johnson, Erik

    2012-10-01

    A major limitation of large-area capacitively-coupled plasmas for materials processing is the inability to increase plasma density without increasing ion bombardment energy. Heil et al. (J. Phys. D 41. 165202, (2008)) demonstrated that for a driving voltage comprising one frequency, f, and it's harmonic 2f, the symmetry of the sheaths can be broken (the Electrical Asymmetry Effect, EAE). We have investigated large-area plasmas (50cm dia) in Ar driven by arbitrary voltage waveforms. Specifically we studied waveforms comprising sharp positive pulses (10-20ns wide, 15MHz repetition frequency). The voltage waveform was measured by an HV probe close to the powered electrode edge, the electron density was measured with a microwave hairpin resonator, the ion flux was measured by an array of planar ion flux probes in the grounded counter-electrode, and the power absorbed was determined from the current and voltage waveforms measured by a derivative probe. As well as the expected EAE observed in the electrode self-bias, we were able to demonstrate a dramatic increase in electron density (and concomitant increased power absorption) with reduced pulse-width at constant amplitude, in qualitative agreement with recent PIC simulations (Lafleur et al, APL 100, 194101(2012)).

  9. Instabilities in a capacitively coupled oxygen plasma

    SciTech Connect

    Küllig, C. Wegner, Th. Meichsner, J.

    2015-04-15

    Periodic fluctuations in the frequency range from 0.3 to 3 kHz were experimentally investigated in capacitively coupled radio frequency (13.56 MHz) oxygen plasma. The Gaussian beam microwave interferometry directly provides the line integrated electron density fluctuations. A system of two Langmuir probes measured the floating potential spatially (axial, radial) and temporally resolved. Hence, the floating potential fluctuation development is mapped within the discharge volume and provides a kind of discharge breathing and no wave propagation. Finally, it was measured the optical emission pattern of atomic oxygen during the fluctuation as well as the RF phase resolved optical emission intensity at selected phase position of the fluctuation by an intensified charge-coupled device camera. The deduced excitation rate pattern reveals the RF sheath dynamics and electron heating mechanisms, which is changing between low and high electronegativity during a fluctuation cycle. A perturbation calculation was taken into account using a global model with 15 elementary collision processes in the balance equations for the charged plasma species (O{sub 2}{sup +}, e, O{sup −}, O{sub 2}{sup −}) and a harmonic perturbation. The calculated frequencies agree with the experimentally observed frequencies. Whereby, the electron attachment/detachment processes are important for the generation of this instability.

  10. Energy recovery in membrane capacitive deionization.

    PubMed

    Długołęcki, Piotr; van der Wal, Albert

    2013-05-01

    Membrane capacitive deionization (MCDI) is a water desalination technology based on applying a cell voltage between two oppositely placed porous carbon electrodes. In front of each electrode, an ion-exchange membrane is positioned, and between them, a spacer is situated, which transports the water to be desalinated. In this work, we demonstrate for the first time that up to 83% of the energy used for charging the electrodes during desalination can be recovered in the regeneration step. This can be achieved by charging and discharging the electrodes in a controlled manner by using constant current conditions. By implementing energy recovery as an integral part of the MCDI operation, the overall energy consumption can be as low as 0.26 (kW·h)/m(3) of produced water to reduce the salinity by 10 mM, which means that MCDI is more energy efficient for treatment of brackish water than reverse osmosis. Nevertheless, the measured energy consumption is much higher than the thermodynamically calculated values for desalinating the water, and therefore, a further improvement in thermodynamic efficiency will be needed in the future. PMID:23477563

  11. Instabilities in a capacitively coupled oxygen plasma

    NASA Astrophysics Data System (ADS)

    Küllig, C.; Wegner, Th.; Meichsner, J.

    2015-04-01

    Periodic fluctuations in the frequency range from 0.3 to 3 kHz were experimentally investigated in capacitively coupled radio frequency (13.56 MHz) oxygen plasma. The Gaussian beam microwave interferometry directly provides the line integrated electron density fluctuations. A system of two Langmuir probes measured the floating potential spatially (axial, radial) and temporally resolved. Hence, the floating potential fluctuation development is mapped within the discharge volume and provides a kind of discharge breathing and no wave propagation. Finally, it was measured the optical emission pattern of atomic oxygen during the fluctuation as well as the RF phase resolved optical emission intensity at selected phase position of the fluctuation by an intensified charge-coupled device camera. The deduced excitation rate pattern reveals the RF sheath dynamics and electron heating mechanisms, which is changing between low and high electronegativity during a fluctuation cycle. A perturbation calculation was taken into account using a global model with 15 elementary collision processes in the balance equations for the charged plasma species ( O2+, e , O-, O2- ) and a harmonic perturbation. The calculated frequencies agree with the experimentally observed frequencies. Whereby, the electron attachment/detachment processes are important for the generation of this instability.

  12. Insulator charging in RF MEMS capacitive switches

    NASA Astrophysics Data System (ADS)

    Kucko, Jay F.

    2005-11-01

    While capacitive radio frequency microelectromechanical (RF MEM) switches are poised to provide a low cost, low power alternative to current RF switch technologies, there are still reliability issues limiting switch lifetime. Previous research identified insulator charging as a primary cause of switch failure. Changes in switch pull-in and release voltages were measured to provide insight into the mechanisms responsible for charging and switch failure. A spatial and temporal dependent model was developed to describe silicon nitride's time-dependent charging as a function of applied bias. This model was verified by applying constant biases to metal-silicon nitride-silicon capacitors and tracking flatband voltage shifts. This knowledge of silicon nitride was then applied to MEM switches. Using novel waveforms and exploiting differences in actuation characteristics allowed the determination of charging characteristics and the investigation of switch failure. Results show tunneling is responsible for changes in the pull-in voltages---this includes a super-saturation effect explained by a steady-state trap charge and discharge condition. A program that models switch actuation was enhanced to include the time-dependent tunneling model. Finally, it was discovered insulator charging cannot explain permanent switch failure; instead, stiction from a contaminant on the insulator surface is likely the cause.

  13. Mechano-capacitive properties of polarized membranes.

    PubMed

    Mosgaard, Lars D; Zecchi, Karis A; Heimburg, Thomas

    2015-10-28

    Biological membranes are capacitors that can be charged by applying a field across the membrane. The charges on the capacitor exert a force on the membrane that leads to electrostriction, i.e. a thinning of the membrane. Since the force is quadratic in voltage, negative and positive voltage have an identical influence on the physics of symmetric membranes. However, this is not the case for a membrane with an asymmetry leading to a permanent electric polarization. Positive and negative voltages of identical magnitude lead to different properties. Such an asymmetry can originate from a lipid composition that is different on the two monolayers of the membrane, or from membrane curvature. The latter effect is called 'flexoelectricity'. As a consequence of permanent polarization, the membrane capacitor is discharged at a voltage different from zero. This leads to interesting electrical phenomena such as outward or inward rectification of membrane permeability. Here, we introduce a generalized theoretical framework, that treats capacitance, polarization, flexoelectricity, piezoelectricity and thermoelectricity in the same language. We show applications to electrostriction, membrane permeability and piezoelectricity and thermoelectricity close to melting transitions, where such effects are especially pronounced. PMID:26324950

  14. Thermodynamic cycle analysis for capacitive deionization.

    PubMed

    Biesheuvel, P M

    2009-04-01

    Capacitive deionization (CDI) is an ion removal technology based on temporarily storing ions in the polarization layers of two oppositely positioned electrodes. Here we present a thermodynamic model for the minimum work required for ion separation in the fully reversible case by describing the ionic solution as an ideal gas of pointlike particles. The work input is fully utilized to decrease the entropy of the outflowing streams compared to that of the inflow. Based on the Gouy-Chapman-Stern (GCS) model for planar diffuse polarization layers-with and without including additional ion volume constraints in the diffuse part of the double layer-we analyze the electric work input during charging and the work output during discharging, for a reversible charging-discharging cycle. We present a graphical thermodynamic cycle analysis for the reversible net work input during one full cycle of batchwise operation of CDI based on the charge-voltage relations for different ionic strengths. For the GCS model, an analytical solution is derived for the charge efficiency Lambda, which is the number of salt molecules removed per electron transferred from one electrode to the other. Only in the high voltage limit and for an infinite Stern layer capacity does Lambda approach unity. PMID:19167009

  15. Complementary surface charge for enhanced capacitive deionization.

    PubMed

    Gao, X; Porada, S; Omosebi, A; Liu, K-L; Biesheuvel, P M; Landon, J

    2016-04-01

    Commercially available activated carbon cloth electrodes are treated using nitric acid and ethylenediamine solutions, resulting in chemical surface charge enhanced carbon electrodes for capacitive deionization (CDI) applications. Surface charge enhanced electrodes are then configured in a CDI cell to examine their salt removal at a fixed charging voltage and both reduced and opposite polarity discharge voltages, and subsequently compared to the salt removal of untreated electrodes. Substantially improved salt removal due to chemical surface charge and the use of a discharge voltage of opposite sign to the charging voltage is clearly demonstrated in these CDI cycling tests, an observation which for the first time validates both enhanced CDI and extended-voltage CDI effects predicted by the Donnan model [Biesheuvel et al., Colloids Interf. Sci. Comm., 10.1016/j.colcom.2015.12.001 (2016)]. Our experimental and theoretical results demonstrate that the use of carbon electrodes with optimized chemical surface charge can extend the CDI working voltage window through discharge voltages of opposite sign to the charging voltage, which can significantly enhance the salt adsorption capacity of CDI electrodes. Thus, in addition to carbon pore size distribution, chemical surface charge in carbon micropores is considered foundational for salt removal in CDI cells. PMID:26878361

  16. Design Considerations in Capacitively Coupled Plasmas

    NASA Astrophysics Data System (ADS)

    Song, Sang-Heon; Ventzek, Peter; Ranjan, Alok

    2015-11-01

    Microelectronics industry has driven transistor feature size scaling from 10-6 m to 10-9 m during the past 50 years, which is often referred to as Moore's law. It cannot be overstated that today's information technology would not have been so successful without plasma material processing. One of the major plasma sources for the microelectronics fabrication is capacitively coupled plasmas (CCPs). The CCP reactor has been intensively studied and developed for the deposition and etching of different films on the silicon wafer. As the feature size gets to around 10 nm, the requirement for the process uniformity is less than 1-2 nm across the wafer (300 mm). In order to achieve the desired uniformity, the hardware design should be as precise as possible before the fine tuning of process condition is applied to make it even better. In doing this procedure, the computer simulation can save a significant amount of resources such as time and money which are critical in the semiconductor business. In this presentation, we compare plasma properties using a 2-dimensional plasma hydrodynamics model for different kinds of design factors that can affect the plasma uniformity. The parameters studied in this presentation include chamber accessing port, pumping port, focus ring around wafer substrate, and the geometry of electrodes of CCP.

  17. Capacitance Probe Resonator for Multichannel Electrometer

    NASA Technical Reports Server (NTRS)

    Blaes, Brent R.; Schaefer, Rembrandt T> ; Glaser, Robert J.

    2012-01-01

    A multichannel electrometer voltmeter has been developed that employs a mechanical resonator with voltage-sensing capacitance-probe electrodes that enable high-impedance, high-voltage, radiation-hardened measurement of an Internal Electrostatic Discharge Monitor (IESDM) sensor. The IESDM is new sensor technology targeted for integration into a Space Environmental Monitor (SEM) subsystem used for the characterization and monitoring of deep dielectric charging on spacecraft. The resonator solution relies on a non-contact, voltage-sensing, sinusoidal-varying capacitor to achieve input impedances as high as 10 petaohms as determined by the resonator materials, geometries, cleanliness, and construction. The resonator is designed with one dominant mechanical degree of freedom, so it resonates as a simple harmonic oscillator and because of the linearity of the variable sense capacitor to displacement, generates a pure sinusoidal current signal for a fixed input voltage under measurement. This enables the use of an idealized phase-lock sensing scheme for optimal signal detection in the presence of noise.

  18. Composite metal-oxide device has voltage sensitive capacitance

    NASA Technical Reports Server (NTRS)

    Mattauch, R. J.; Viola, T. J., Jr.

    1970-01-01

    Device with step function variation of the capacitance is useful for voltage-controlled oscillator circuits and as a voltage-sensitive switch. Simplicity of construction makes the device suitable for large-scale integration, microelectronic circuits.

  19. Fringe Capacitance of a Parallel-Plate Capacitor.

    ERIC Educational Resources Information Center

    Hale, D. P.

    1978-01-01

    Describes an experiment designed to measure the forces between charged parallel plates, and determines the relationship among the effective electrode area, the measured capacitance values, and the electrode spacing of a parallel plate capacitor. (GA)

  20. Enhancement of the carbon electrode capacitance by brominated hydroquinones

    NASA Astrophysics Data System (ADS)

    Gastol, Dominika; Walkowiak, Jedrzej; Fic, Krzysztof; Frackowiak, Elzbieta

    2016-09-01

    This paper presents supercapacitors utilizing new redox-active electrolytes with bromine species. Two sources of Br specimen were investigated, i.e. dibromodihydroxybenzene dissolved in KOH and potassium bromide dissolved in KOH with hydroxybenzene additive. KOH-activated carbon, exhibiting a well-developed porosity, was incorporated as an electrode material. The tested systems revealed a capacitance enhancement explained by Br- and partial BrO3- redox activity. The optimisation of the electrolyte concentration resulted in a capacitance value of 314 F g-1 achieved at 1.1 V voltage range. Good cyclability performance (11% capacitance loss) combined with a high capacitance value (244 F g-1) were obtained for the system operating in 0.2 mol L- 1 C6H4Br2O2 in 2 mol L-1 KOH electrolytic solution.

  1. A metamaterial-inspired combined inductive-capacitive sensor

    NASA Astrophysics Data System (ADS)

    Long, Jiang; Wang, Bingnan

    2014-05-01

    This paper reports a metamaterial inspired combined inductive-capacitive sensing method for detecting and distinguishing metallic and non-metallic objects. Metallic and non-metallic objects can be distinguished by measuring both of their inductive and capacitive responses based on the fact that they respond differently to inductive and capacitive sensing. The proposed method is inspired by metamaterial structures. Both inductive and capacitive sensing are simultaneously realized when the sensor is operating at off-resonant frequencies. The proposed method is demonstrated with typical printed circuit board (PCB) technology. The designed sensor can distinguish the metallic and dielectric objects with a sensing range about 10 mm, showing a competitive performance compared with commercially available proximity sensors.

  2. Precision stabilization system for MIS-structure rf capacitance

    SciTech Connect

    Antonenko, V.I.; Zhdan, A.G.

    1987-02-01

    A relatively simple resonant small-signal system is described for stabilization of the rf capacitance of MIS structures in the frequency range of 1-30 MHz that is based on a VM560 Q-meter. The relative sensitivity to capacitance variation ..delta..C/C is 2 x 10/sup -6/ at a level of C approx. 500 pF, the absolute sensitivity ..delta..C approx. 1 fF, and the response time is approx. 0.1 sec. The system is designed for relaxation spectroscopy of boundary states in MIS structures in the constant-capacitance mode by methods of unsteady capacitance and thermostimulated discharge of an MIS capacitor.

  3. Capacitive Sensors for Measuring Masses of Cryogenic Fluids

    NASA Technical Reports Server (NTRS)

    Nurge, Mark; Youngquist, Robert

    2003-01-01

    An effort is under way to develop capacitive sensors for measuring the masses of cryogenic fluids in tanks. These sensors are intended to function in both microgravitational and normal gravitational settings, and should not be confused with level sensors, including capacitive ones. A sensor of this type is conceptually simple in the sense that (1) it includes only one capacitor and (2) if properly designed, its single capacitance reading should be readily convertible to a close approximation of the mass of the cryogenic fluid in the tank. Consider a pair of electrically insulated electrodes used as a simple capacitive sensor. In general, the capacitance is proportional to the permittivity of the dielectric medium (in this case, a cryogenic fluid) between the electrodes. The success of design and operation of a sensor of the present type depends on the accuracy of the assumption that to a close approximation, the permittivity of the cryogenic fluid varies linearly with the density of the fluid. Data on liquid nitrogen, liquid oxygen, and liquid hydrogen, reported by the National Institute of Standards and Technology, indicate that the permittivities and densities of these fluids are, indeed, linearly related to within a few tenths of a percent over the pressure and temperature regions of interest. Hence, ignoring geometric effects for the moment, the capacitance between two electrodes immersed in the fluid should vary linearly with the density, and, hence, with the mass of the fluid. Of course, it is necessary to take account of the tank geometry. Because most cryogenic tanks do not have uniform cross sections, the readings of level sensors, including capacitive ones, are not linearly correlated with the masses of fluids in the tanks. In a sensor of the present type, the capacitor electrodes are shaped so that at a given height, the capacitance per unit height is approximately proportional to the cross-sectional area of the tank in the horizontal plane at that

  4. Capacitance extraction from complex 3D interconnect structures

    SciTech Connect

    Cartwright, D.; Csanak, G.; George, D.; Walker, R.; Kuprat, A.; Dengi, A.; Grobman, W.

    1999-06-01

    A new tool has been developed for calculating the capacitance matrix for complex 3D interconnect structures involving multiple layers of irregularly shaped interconnect, imbedded in different dielectric materials. This method utilizes a new 3D adaptive unstructured grid capability, and a linear finite element algorithm. The capacitance is determined from the minimum in the total system energy as the nodes are varied to minimize the error in the electric field in the dielectric(s).

  5. Probing Quantum Capacitance in a 3D Topological Insulator

    NASA Astrophysics Data System (ADS)

    Kozlov, D. A.; Bauer, D.; Ziegler, J.; Fischer, R.; Savchenko, M. L.; Kvon, Z. D.; Mikhailov, N. N.; Dvoretsky, S. A.; Weiss, D.

    2016-04-01

    We measure the quantum capacitance and probe thus directly the electronic density of states of the high mobility, Dirac type two-dimensional electron system, which forms on the surface of strained HgTe. Here we show that observed magnetocapacitance oscillations probe—in contrast to magnetotransport—primarily the top surface. Capacitance measurements constitute thus a powerful tool to probe only one topological surface and to reconstruct its Landau level spectrum for different positions of the Fermi energy.

  6. Probing Quantum Capacitance in a 3D Topological Insulator.

    PubMed

    Kozlov, D A; Bauer, D; Ziegler, J; Fischer, R; Savchenko, M L; Kvon, Z D; Mikhailov, N N; Dvoretsky, S A; Weiss, D

    2016-04-22

    We measure the quantum capacitance and probe thus directly the electronic density of states of the high mobility, Dirac type two-dimensional electron system, which forms on the surface of strained HgTe. Here we show that observed magnetocapacitance oscillations probe-in contrast to magnetotransport-primarily the top surface. Capacitance measurements constitute thus a powerful tool to probe only one topological surface and to reconstruct its Landau level spectrum for different positions of the Fermi energy. PMID:27152818

  7. Current Progress of Capacitive Deionization for Removal of Pollutant Ions

    NASA Astrophysics Data System (ADS)

    Gaikwad, Mahendra S.; Balomajumder, Chandrajit

    2016-08-01

    A mini review of a recently developing water purification technology capacitive deionization (CDI) applied for removal of pollutant ions is provided. The current progress of CDI for removal of different pollutant ions such as arsenic, fluoride, boron, phosphate, lithium, copper, cadmium, ferric, and nitrate ions is presented. This paper aims at motivating new research opportunities in capacitive deionization technology for removal of pollutant ions from polluted water.

  8. Correlation effects in the capacitance of a gated carbon nanotube

    NASA Astrophysics Data System (ADS)

    Fu, Han; Shklovskii, B. I.; Skinner, Brian

    2015-04-01

    For a capacitor made of a semiconducting carbon nanotube (CNT) suspended above a metallic gate, Coulomb correlations between individual electrons can lead to a capacitance that is much larger than the geometric capacitance. We argue that when the average spacing n-1 between electrons within the low-density one-dimensional electron gas (1DEG) in the CNT is larger than the physical separation d between the CNT and the gate, the enhancement of capacitance is expected to be big. A recent experiment [J. Waissman et al., Nature Nanotechnol. 8, 569 (2013), 10.1038/nnano.2013.143], however, has observed no obvious increase of capacitance even at very low electron density. We show that this smaller capacitance can be understood as the result of the confining potential produced by the potential difference between the source/drain electrodes and the gate, which compresses the 1DEG when the electron number decreases. We suggest that by profiling the potential with the help of multiple split gates, one can return to the case of a uniform 1DEG with anomalously large capacitance.

  9. Void fraction measurements by quick acting valves and capacitance measurements

    NASA Astrophysics Data System (ADS)

    Chang, Jae H.; Best, Frederick R.

    1998-01-01

    Two-phase flow systems are widely estimated to have superior capability in comparison with single-phase thermal management systems for spacecraft. However, microgravity two-phase flow technology is insufficiently advanced to allow development with acceptable risk levels. A capacitance effect, void fraction measurement sensor has been developed by Creare Inc. to begin to satisfy microgravity technology needs. Under a NASA Johnson Space Center grant, microgravity tests of the capacitance void fraction sensors were performed aboard the NASA KC-135. Twelve KC-135 flights were conducted in three series. Test points were collected over a wide range of void fractions (0%-90%). Data were collected from stratified, slug, and annular flow regimes. Void fraction measurements from the capacitance sensors were compared with the void fractions from a trapped volume in the test section between two quick acting valves. Under the annular flow regime, void fractions measured by the capacitance sensors compared well with values from the trapped volume. In slug flow regime, some discrepancies between the sensors and trapped volumes were found. However, when the working fluid (Suva) mass flow rate increased from 0.00314 kg/s to 0.007756 kg/s, the void fraction measurements between the capacitance sensors and the trapped volume had better agreement. Overall, the FRIM experimental package produced satisfactory test conditions in the microgravity conditions of the KC-135 aircraft, to validate and calibrate the Creare capacitance void fraction sensors.

  10. Intramolecular phenotypic capacitance in a modular RNA molecule

    PubMed Central

    Hayden, Eric J.; Bendixsen, Devin P.; Wagner, Andreas

    2015-01-01

    Phenotypic capacitance refers to the ability of a genome to accumulate mutations that are conditionally hidden and only reveal phenotype-altering effects after certain environmental or genetic changes. Capacitance has important implications for the evolution of novel forms and functions, but experimentally studied mechanisms behind capacitance are mostly limited to complex, multicomponent systems often involving several interacting protein molecules. Here we demonstrate phenotypic capacitance within a much simpler system, an individual RNA molecule with catalytic activity (ribozyme). This naturally occurring RNA molecule has a modular structure, where a scaffold module acts as an intramolecular chaperone that facilitates folding of a second catalytic module. Previous studies have shown that the scaffold module is not absolutely required for activity, but dramatically decreases the concentration of magnesium ions required for the formation of an active site. Here, we use an experimental perturbation of magnesium ion concentration that disrupts the folding of certain genetic variants of this ribozyme and use in vitro selection followed by deep sequencing to identify genotypes with altered phenotypes (catalytic activity). We identify multiple conditional mutations that alter the wild-type ribozyme phenotype under a stressful environmental condition of low magnesium ion concentration, but preserve the phenotype under more relaxed conditions. This conditional buffering is confined to the scaffold module, but controls the catalytic phenotype, demonstrating how modularity can enable phenotypic capacitance within a single macromolecule. RNA’s ancient role in life suggests that phenotypic capacitance may have influenced evolution since life’s origins. PMID:26401020

  11. Intramolecular phenotypic capacitance in a modular RNA molecule.

    PubMed

    Hayden, Eric J; Bendixsen, Devin P; Wagner, Andreas

    2015-10-01

    Phenotypic capacitance refers to the ability of a genome to accumulate mutations that are conditionally hidden and only reveal phenotype-altering effects after certain environmental or genetic changes. Capacitance has important implications for the evolution of novel forms and functions, but experimentally studied mechanisms behind capacitance are mostly limited to complex, multicomponent systems often involving several interacting protein molecules. Here we demonstrate phenotypic capacitance within a much simpler system, an individual RNA molecule with catalytic activity (ribozyme). This naturally occurring RNA molecule has a modular structure, where a scaffold module acts as an intramolecular chaperone that facilitates folding of a second catalytic module. Previous studies have shown that the scaffold module is not absolutely required for activity, but dramatically decreases the concentration of magnesium ions required for the formation of an active site. Here, we use an experimental perturbation of magnesium ion concentration that disrupts the folding of certain genetic variants of this ribozyme and use in vitro selection followed by deep sequencing to identify genotypes with altered phenotypes (catalytic activity). We identify multiple conditional mutations that alter the wild-type ribozyme phenotype under a stressful environmental condition of low magnesium ion concentration, but preserve the phenotype under more relaxed conditions. This conditional buffering is confined to the scaffold module, but controls the catalytic phenotype, demonstrating how modularity can enable phenotypic capacitance within a single macromolecule. RNA's ancient role in life suggests that phenotypic capacitance may have influenced evolution since life's origins. PMID:26401020

  12. Uncertainty quantification in capacitive RF MEMS switches

    NASA Astrophysics Data System (ADS)

    Pax, Benjamin J.

    Development of radio frequency micro electrical-mechanical systems (RF MEMS) has led to novel approaches to implement electrical circuitry. The introduction of capacitive MEMS switches, in particular, has shown promise in low-loss, low-power devices. However, the promise of MEMS switches has not yet been completely realized. RF-MEMS switches are known to fail after only a few months of operation, and nominally similar designs show wide variability in lifetime. Modeling switch operation using nominal or as-designed parameters cannot predict the statistical spread in the number of cycles to failure, and probabilistic methods are necessary. A Bayesian framework for calibration, validation and prediction offers an integrated approach to quantifying the uncertainty in predictions of MEMS switch performance. The objective of this thesis is to use the Bayesian framework to predict the creep-related deflection of the PRISM RF-MEMS switch over several thousand hours of operation. The PRISM switch used in this thesis is the focus of research at Purdue's PRISM center, and is a capacitive contacting RF-MEMS switch. It employs a fixed-fixed nickel membrane which is electrostatically actuated by applying voltage between the membrane and a pull-down electrode. Creep plays a central role in the reliability of this switch. The focus of this thesis is on the creep model, which is calibrated against experimental data measured for a frog-leg varactor fabricated and characterized at Purdue University. Creep plasticity is modeled using plate element theory with electrostatic forces being generated using either parallel plate approximations where appropriate, or solving for the full 3D potential field. For the latter, structure-electrostatics interaction is determined through immersed boundary method. A probabilistic framework using generalized polynomial chaos (gPC) is used to create surrogate models to mitigate the costly full physics simulations, and Bayesian calibration and forward

  13. The electrical asymmetry effect in capacitive discharges

    NASA Astrophysics Data System (ADS)

    Czarnetzki, Uwe

    2009-10-01

    One of the major demands in plasma processing has always been the independent control of ion energy and ion flux. Dual-frequency capacitive discharges with one low and one typically an order of magnitude higher frequency are one of the concepts presently applied in industry. However, recent investigations have shown that there is in fact a coupling between the two frequency components that limits independent control by the two RF powers. Here, a novel concept is introduced based on the electrical asymmetry effect (EAE) that provides simple and stable control of ion energy and flux in an almost ideally independent way [1]. Also here two RF frequencies are applied but with the second frequency being exactly the second harmonic of the first and with a fixed but controllable phase. This phase is the control parameter for the ion energy that changes approximately linearly with the phase. Geometrically symmetric discharges can be made effectively asymmetric with one electrode showing a higher sheath potential than the other. Choosing the proper phase allows then to reverse the situation or to make the discharge symmetric. In geometrically asymmetric discharges the wall potential can be raised or lowered. When tuning the phase, the flux stays approximately constant and its absolute value can be set with the RF amplitudes. The concept of the EAE is developed and analyzed by 1) an analytical model, 2) a hydrodynamic and Monte-Carlo (MC) simulation, 3) a self consistent PIC/MC simulation, and 4) an experimental verification in a laboratory experiment. All four approaches show excellent agreement and confirm the above advantages. The technique has found successful application already in an industrial reactor for large area solar cell production (Leybold Optics). Compared to the standard single frequency case at 13.56 MHz the silicon deposition rate was easily more than doubled and the homogeneity improved. [4pt] [1] Brian G. Heil, U. Czarnetzki, R. P. Brinkmann, T

  14. Capacitance Transducers for Concentration Measurements in Two Component Flow.

    NASA Astrophysics Data System (ADS)

    Matoorianpour, Nasser

    Available from UMI in association with The British Library. This thesis is concerned with the design and development of instrumentation for non-intrusive measurements of component volumetric concentrations on industrial two component flow including gas/liquid and gas/solids systems. The design and optimisation of two amplitude modulated capacitance transducers for "steady state" or slowly varying concentration measurements are described. A new type of capacitance transducer is the symmetrical capacitance bridge which consists of capacitive voltage dividers based on the voltage measuring method. The sensing electrodes of the sensor in this system are driven at two opposite voltages to produce a symmetrical capacitance sensitivity across the sensing region. Optimum transducer parameters, the use of the driven guard technique and minimised input capacitance to the electronics provide maximum sensitivity in this capacitance bridge. The base line stability of the symmetrical capacitance bridge is further improved by applying a Commutating Auto Zero technique to the transducer. The capacitance sensitivity across the sensing volumes of three pairs of concave plate electrode systems, each subtending a different angle has been investigated experimentally. One application of this transducer, considered in this research, is the void fraction determination in air/water two component flow. A second type of high stability capacitance bridge, based on the current measuring method, is the "stray immune" transformer ratio amplifier bridge. Its high pass filter configuration, using an LCR network, provides noise immunity against the charged solids in the applications involving pneumatically conveyed solid materials. A non-intrusive mass flow rate determination system, based on the stray immune transformer ratio amplifier bridge for the steady state concentration measurements and a low cost hardware cross correlation flowmeter for component velocity measurements, has been developed

  15. Extracellular signal-regulated kinases modulate capacitation of human spermatozoa.

    PubMed

    Luconi, M; Barni, T; Vannelli, G B; Krausz, C; Marra, F; Benedetti, P A; Evangelista, V; Francavilla, S; Properzi, G; Forti, G; Baldi, E

    1998-06-01

    Recent evidence indicates the presence of p21 Ras and of a protein with characteristics similar to mitogen-activated protein kinases (MAPKs), also known as extracellular signal-regulated kinases (ERKs), in mammalian spermatozoa, suggesting the occurrence of the Ras/ERK cascade in these cells. In the present study we investigated the subcellular localization of ERKs and their biological functions in human spermatozoa. Immunohistochemistry, immunofluorescence, confocal microscopy, and immunoelectron microscopy demonstrated localization of ERKs in the postacrosomal region of spermatozoa. After stimulation of acrosome reaction with the calcium ionophore A23187 and progesterone, ERKs were mostly localized at the level of the equatorial region, indicating redistribution of these proteins in acrosome-reacted spermatozoa. Two proteins of 42 and 44 kDa that are tyrosine phosphorylated in a time-dependent manner during in vitro capacitation were identified as p42 (ERK-2) and p44 (ERK-1) by means of specific antibodies. The increase in tyrosine phosphorylation of these proteins during capacitation was accompanied by increased kinase activity, as determined by the ability of ERK-1 and ERK-2 to phosphorylate the substrate myelin basic protein. The role of this activity in the occurrence of sperm capacitation was also investigated by using PD098059, an inhibitor of the MAPK cascade. The presence of this compound during in vitro capacitation inhibits ERK activation and significantly reduces the ability of spermatozoa to undergo the acrosome reaction in response to progesterone. Since only capacitated spermatozoa are able to respond to progesterone, these data strongly indicate that ERKs are involved in the regulation of capacitation. In summary, our data demonstrate the presence of functional ERKs in human spermatozoa and indicate that these enzymes are involved in activation of these cells during capacitation, providing new insight in clarifying the molecular mechanisms and the

  16. Study on capacitance evolving mechanism of polypyrrole during prolonged cycling.

    PubMed

    Wang, JingPing; Xu, Youlong; Wang, Jie; Zhu, Jianbo; Bai, Yang; Xiong, Lilong

    2014-02-01

    A simple model on the evolution mechanism of PPy capacitance during prolonged cycling offers a reasonably description on the rapid increase and decay of PPy capacitance in 1 M 1-ethyl-3-methylimidazolium tetrafluoroborate/propylene carbonate (EtMeImBF4/PC). The capacitance of PPy films reached a very high specific capacitance of 420 F·g(-1) after 15 cycles when they worked in 1 M MeEt3ImBF4/PC. However, the capacitance rapidly decreased to 5% after only 400 cycles. The electronic conductivity and protonation level on the nitrogen site of PPy films rapidly decreased with the increase of cyclic number. The salt of EtMeImBF4 was monitored in PPy matrix by FTIR spectra after 400 cycles. The EQCM results indicated that a lot of 1-ethyl-3-methylimidazolium cations (EtMeIm(+)) were inserted during reduction process and retained in PPy matrix. The detained EtMeIm(+) cations bonded with doped p-toluenesulfonate anions (PTS(-)) in PPy matrix or BF4(-) anions from electrolyte and formed salts. Small amount of salts in PPy matrix can open more channels of ion insertion and resulted in a very high capacitance after 15 cycles. The continuous combination of detained EtMeIm(+) cations with doping anions of PTS(-) resulted in the rapid decrease of PPy protonation level on the nitrogen site and formation of compensate semiconductor state in PPy matrix. This should be responsible for the rapid decay of PPy conductivity and capacitance. The continuous accumulation of salts resulted in the great increase of PPy internal resistance. PMID:24428582

  17. Negative capacitance for ultra-low power computing

    NASA Astrophysics Data System (ADS)

    Khan, Asif Islam

    Owing to the fundamental physics of the Boltzmann distribution, the ever-increasing power dissipation in nanoscale transistors threatens an end to the almost-four-decade-old cadence of continued performance improvement in complementary metal-oxide-semiconductor (CMOS) technology. It is now agreed that the introduction of new physics into the operation of field-effect transistors---in other words, "reinventing the transistor'"--- is required to avert such a bottleneck. In this dissertation, we present the experimental demonstration of a novel physical phenomenon, called the negative capacitance effect in ferroelectric oxides, which could dramatically reduce power dissipation in nanoscale transistors. It was theoretically proposed in 2008 that by introducing a ferroelectric negative capacitance material into the gate oxide of a metal-oxide-semiconductor field-effect transistor (MOSFET), the subthreshold slope could be reduced below the fundamental Boltzmann limit of 60 mV/dec, which, in turn, could arbitrarily lower the power supply voltage and the power dissipation. The research presented in this dissertation establishes the theoretical concept of ferroelectric negative capacitance as an experimentally verified fact. The main results presented in this dissertation are threefold. To start, we present the first direct measurement of negative capacitance in isolated, single crystalline, epitaxially grown thin film capacitors of ferroelectric Pb(Zr0.2Ti0.8)O3. By constructing a simple resistor-ferroelectric capacitor series circuit, we show that, during ferroelectric switching, the ferroelectric voltage decreases, while the stored charge in it increases, which directly shows a negative slope in the charge-voltage characteristics of a ferroelectric capacitor. Such a situation is completely opposite to what would be observed in a regular resistor-positive capacitor series circuit. This measurement could serve as a canonical test for negative capacitance in any novel

  18. Logarithmic derivative method and system for capacitance measurement.

    PubMed

    Wu, Yichun; Wang, Lingzhi; Cai, Yuanfeng; Wu, Cunqiao

    2015-08-01

    A novel method based on logarithmic derivative is introduced to analyze multi-lifetime decay. As the discharge voltage signal of a RC circuit is a special kind of multi-lifetime exponential decay, the logarithmic derivative method can be used to measure single capacitance and multiple capacitances. With the logarithmic derivative method, a log(t) curve strongly peaked at precisely log(τ) is obtained, where the lifetime τ equals to RC. In a measurement system, if the resistance R is known, then the capacitance under test can be calculated. A logarithmic derivative curve fitting method is also presented, which has better anti-noise capability than the method that simply finds the maximum data on the peak. The curve fitting method can also be used for multiple capacitors measurement. To measure small capacitances, a large enough time window of the measuring instrument is required. Based on a field programmable gate array and a high speed analog-to-digital converter, a measurement system is developed. This system can provide the 16-bit resolution with sampling rate up to 250 MHz, which has a large enough time window for measuring lifetime shorter than 10(-8) s. To reduce the amount of data needed to be stored and the noise due to the derivative treatment of transient data, the interpolation and noise-filter algorithms are employed. Experiments indicate that the logarithmic derivative method and system are suitable for the measurement of capacitances discharge and other exponential decay processes. PMID:26329235

  19. Logarithmic derivative method and system for capacitance measurement

    NASA Astrophysics Data System (ADS)

    Wu, Yichun; Wang, Lingzhi; Cai, Yuanfeng; Wu, Cunqiao

    2015-08-01

    A novel method based on logarithmic derivative is introduced to analyze multi-lifetime decay. As the discharge voltage signal of a RC circuit is a special kind of multi-lifetime exponential decay, the logarithmic derivative method can be used to measure single capacitance and multiple capacitances. With the logarithmic derivative method, a log(t) curve strongly peaked at precisely log(τ) is obtained, where the lifetime τ equals to RC. In a measurement system, if the resistance R is known, then the capacitance under test can be calculated. A logarithmic derivative curve fitting method is also presented, which has better anti-noise capability than the method that simply finds the maximum data on the peak. The curve fitting method can also be used for multiple capacitors measurement. To measure small capacitances, a large enough time window of the measuring instrument is required. Based on a field programmable gate array and a high speed analog-to-digital converter, a measurement system is developed. This system can provide the 16-bit resolution with sampling rate up to 250 MHz, which has a large enough time window for measuring lifetime shorter than 10-8 s. To reduce the amount of data needed to be stored and the noise due to the derivative treatment of transient data, the interpolation and noise-filter algorithms are employed. Experiments indicate that the logarithmic derivative method and system are suitable for the measurement of capacitances discharge and other exponential decay processes.

  20. Quantum capacitance in thin film vanadium dioxide metal insulator transition

    NASA Astrophysics Data System (ADS)

    Wu, Zhe; Knighton, Talbot; Tarquini, Vinicio; Torres, David; Wang, Tongyu; Sepulveda, Nelson; Huang, Jian

    We present capacitance measurements of the electronic density of states performed in high quality vanadium dioxide (VO2) thin films on sapphire (Al2O3) substrate. These films show the expected metal insulator transition near 60 °C with resistivity changing by 3 orders of magnitude with a hysteresis of 10 °C. To make a capacitive probe, a gate is suspended above the film surface using a flip-chip method with microfabricated supports. The geometric capacitance per-area reached is 40 pF/mm2. Such a large capacitance can be significantly modified by electron interaction and band charging/discharging which appear as an extra term known as the quantum capacitance (Cq). An AC signal applied to the gate allows measurement of the changing density of states (DOS) across the MIT. The DOS abruptly increases as the sample is heated through the transition point. Conversely the low temperature drop of d μ / d n is consistent with an energy gap opening in the insulating phase. These parameters shed light on the transition mechanism. NSF DMR-1105183, NSF ECCS 1306311.

  1. Capacitive bridge-type probe and conversion circuitry

    NASA Astrophysics Data System (ADS)

    Dooley, Kevin A.

    1989-11-01

    This invention relates to a structure for a capacitive bridge-type probe which is suitable for measuring the clearance between a fixed surface, such as the inner surface of the turbine shroud, and a member movable in relation to the fixed surface, such as the tip of a movable turbine blade. The system is comprised of a capacitance to voltage conversion circuit for converting changes in capacitance in the probe to voltage. The probe has a bridge with a sensitive arm and excitation means for providing an excitation signal to the capacitive bridge and a detector capable of detecting changes in the excitation signal across the sensitive arm due to changes in capacitance. An advantage of the system is the extremely high sensitivity which can be maintained while maintaining stability and wide bandwidth. Lab tests show sensitivity to changes of less than 10(exp -16) farad at bandwidths of 1 megahertz. This enables the use of a very small sensitive plate which reduces the overall size of the probe and improves the accuracy.

  2. Development and Industrial Application of Electric Capacitance Tomography

    NASA Astrophysics Data System (ADS)

    Takei, Masahiro; Zhao, Tong

    2008-09-01

    A new reconstruction method called Generalized Vector Sampled Pattern Matching (GVSPM) has been applied to an ill-posed inverse problem involving an electrical capacitance CT for solid air two-phase flow. The characteristics of GVSPM method were examined using a simulation for pseudo particle concentration distribution images and real experiment data. Overall, the accuracy is strongly dependent upon the image type and the iteration number. However the GVSPM method was proved superior to the LW and the ITR methods in the case of annular pseudo particle images and particles with relatively low electric charge. Then, a sensor for capacitance CT was designed to visualize the powder concentration in the process of mixing air and FCC catalysts in a vertical pipeline. The concentration distribution images are obtained under certain air-catalyst parameter conditions. The relationship between the air-catalyst parameter condition and the powder distribution is analyzed in detail. The accuracy of the reconstructed image was also discussed systemically in terms of volume fraction, residual capacitance, and capacitance correlation. Moreover, the particle concentration distribution images of a dense two-phase solid/air (plug) flow have been obtained at 10 milli-second intervals in a horizontal pipeline using capacitance computed tomography. The formation of plug was clarified by these reconstructed images.

  3. Development and application of a real-time capacitive sensor.

    PubMed

    Wongkittisuksa, Booncharoen; Limsakul, Chusak; Kanatharana, Proespichaya; Limbut, Warakorn; Asawatreratanakul, Punnee; Dawan, Supaporn; Loyprasert, Suchera; Thavarungkul, Panote

    2011-01-15

    A real-time capacitive sensor based on a potentiostatic step method was developed. It can display in real-time the evoked current waveform, capacitance and the electrical resistance of elements serially connected to the insulation layer on the electrode as a function of time as well as the ohmic resistance of the insulation layer. These features enable the user to observe the association and dissociation of the affinity binding pairs and to evaluate the insulating property of the electrode surface during measurement. The system allows the setting of potential pulse height, pulse interval, gain, filter, and sampling frequency, enabling the system to be more flexible. The performance of the system was firstly evaluated with equivalent circuits. Under suitable parameter settings it provided good accuracy of both the capacitance and resistance. Using the affinity binding pair of human serum albumin (HSA) and anti human serum albumin (anti-HSA) the measured capacitance change was used for the direct detection of HSA. The developed system provided the same sensitivity as the commercially available potentiostat (P>0.05). The proposed system was then applied to analyse HSA in real urine samples and the results agreed well with the immunoturbidimetric assay (P>0.05). The proposed system can be applied for capacitance measurement to directly detect other target analytes using different affinity binding pairs. Other applications such as kinetics analysis of the interaction between affinity bindings, thickness analysis, and the study of the insulation property of the modified layer are also promising. PMID:21087852

  4. Realization of Negative Capacitance with Topological Insulator Based MOS Capacitor

    NASA Astrophysics Data System (ADS)

    Yuan, Hui; Zhang, Kai; Zhu, Hao; Li, Haitao; Ioannou, Dimitris; Baumgart, Helmut; Richter, Curt; Li, Qiliang; ECE, George Mason University Team; Semiconductor and Dimensional Metrology Division of NIST Team; ECE, Old Dominion University Team

    2013-03-01

    Negative capacitance is one of way to achieve steep subthreshold slope exceeding its thermal limit in metal-oxide-semiconductor field effect transistor (MOSFET). The common materials under study for negative capacitance are ferroelectric thin films. However, the integration of regular ferroelectric materials (e.g., PZT) into semiconductor based devices is usually difficult due to the high temperature required for crystallization and precise control of oxygen percentage in ferroelectric materials. In this work, we found that negative capacitance can be achieved by introducing a topological insulator interlayer into a conventional MOS capacitor. Three-dimensional topological insulators inherently contain a insulator/semiconductor bulk and a gapless conducting surface. When an electric field is added to topological insulator interlayer, imbalanced charge carriers (electrons and holes) would be generated and then accumulate on either surface of the film, resulting in a temporary residual polarization. As a result, a ferroelectric-like hysteresis and negative capacitance are achieved. We believe this approach will be very attractive to achieve steep subthreshold using negative capacitance. Supported by NSF Career grant 0846649.

  5. Nonlinear dynamics of capacitive charging and desalination by porous electrodes.

    PubMed

    Biesheuvel, P M; Bazant, M Z

    2010-03-01

    The rapid and efficient exchange of ions between porous electrodes and aqueous solutions is important in many applications, such as electrical energy storage by supercapacitors, water desalination and purification by capacitive deionization, and capacitive extraction of renewable energy from a salinity difference. Here, we present a unified mean-field theory for capacitive charging and desalination by ideally polarizable porous electrodes (without Faradaic reactions or specific adsorption of ions) valid in the limit of thin double layers (compared to typical pore dimensions). We illustrate the theory for the case of a dilute, symmetric, binary electrolyte using the Gouy-Chapman-Stern (GCS) model of the double layer, for which simple formulae are available for salt adsorption and capacitive charging of the diffuse part of the double layer. We solve the full GCS mean-field theory numerically for realistic parameters in capacitive deionization, and we derive reduced models for two limiting regimes with different time scales: (i) in the "supercapacitor regime" of small voltages and/or early times, the porous electrode acts like a transmission line, governed by a linear diffusion equation for the electrostatic potential, scaled to the RC time of a single pore, and (ii) in the "desalination regime" of large voltages and long times, the porous electrode slowly absorbs counterions, governed by coupled, nonlinear diffusion equations for the pore-averaged potential and salt concentration. PMID:20365735

  6. Low-Temperature Scanning Capacitance Probe for Imaging Electron Motion

    NASA Astrophysics Data System (ADS)

    Bhandari, S.; Westervelt, R. M.

    2014-12-01

    Novel techniques to probe electronic properties at the nanoscale can shed light on the physics of nanoscale devices. In particular, studying the scattering of electrons from edges and apertures at the nanoscale and imaging the electron profile in a quantum dot, have been of interest [1]. In this paper, we present the design and implementation of a cooled scanning capacitance probe that operates at liquid He temperatures to image electron waves in nanodevices. The conducting tip of a scanned probe microscope is held above the nanoscale structure, and an applied sample-to-tip voltage creates an image charge that is measured by a cooled charge amplifier [2] adjacent to the tip. The circuit is based on a low-capacitance, high- electron-mobility transistor (Fujitsu FHX35X). The input is a capacitance bridge formed by a low capacitance pinched-off HEMT transistor and tip-sample capacitance. We have achieved low noise level (0.13 e/VHz) and high spatial resolution (100 nm) for this technique, which promises to be a useful tool to study electronic behavior in nanoscale devices.

  7. Voltage-dependent capacitance in lipid bilayers made from monolayers.

    PubMed

    Alvarez, O; Latorre, R

    1978-01-01

    Electrocompression has been measured in lipid bilayers made by apposition of two monolayers. The capacitance C(V), as a function of membrane potential, V, was found to be well described by C(V) = C(O) [1 + alpha(V + delta psi)2] where C(O) is the capacitance at V = O, alpha is the fractional increase in capacitance per square volt, and delta psi is the surface potential difference. In lipid bilayers made from monolayers alpha has a value of 0.02 V-2, which is ca. 500-fold smaller than the value found in solvent containing membranes. In asymmetric bilayers made of one neutral and one negatively charged monolayer, delta psi values were found to be those expected from independent measurements of surface charge density. If the fractional increase in capacitance found here is a good approximation to that of biological membranes, nonlinear capacitative charge displacement derived from electrostriction is expected to be less than 1% of the total gating charge displacement found in squid axons. PMID:620076

  8. Sperm Capacitation and Acrosome Reaction in Mammalian Sperm.

    PubMed

    Stival, Cintia; Puga Molina, Lis Del C; Paudel, Bidur; Buffone, Mariano G; Visconti, Pablo E; Krapf, Dario

    2016-01-01

    Physiological changes that endow mammalian sperm with fertilizing capacity are known as sperm capacitation. As part of capacitation, sperm develop an asymmetrical flagellar beating known as hyperactivation and acquire the ability to undergo the acrosome reaction. Together, these processes promote fertilizing competence in sperm. At the molecular level, capacitation involves a series of signal transduction events which include activation of cAMP-dependent phosphorylation pathways, removal of cholesterol, hyperpolarization of the sperm plasma membrane, and changes in ion permeability. In recent years, new technologies have aided in the study of sperm signaling molecules with better resolution, at both spatial and temporal levels, unraveling how different cascades integrate and cooperate to render a fertilizing sperm. Despite this new information, the molecular mechanisms connecting capacitation with acrosomal exocytosis and hyperactivation are not well understood. This review brings together results obtained in mammalian species in the field of sperm capacitation with special focus on those pathways involved in the preparation to undergo the acrosomal reaction. PMID:27194351

  9. Method and apparatus for measuring low currents in capacitance devices

    DOEpatents

    Kopp, M.K.; Manning, F.W.; Guerrant, G.C.

    1986-06-04

    A method and apparatus for measuring subnanoampere currents in capacitance devices is reported. The method is based on a comparison of the voltages developed across the capacitance device with that of a reference capacitor in which the current is adjusted by means of a variable current source to produce a stable voltage difference. The current varying means of the variable current source is calibrated to provide a read out of the measured current. Current gain may be provided by using a reference capacitor which is larger than the device capacitance with a corresponding increase in current supplied through the reference capacitor. The gain is then the ratio of the reference capacitance to the device capacitance. In one illustrated embodiment, the invention makes possible a new type of ionizing radiation dose-rate monitor where dose-rate is measured by discharging a reference capacitor with a variable current source at the same rate that radiation is discharging an ionization chamber. The invention eliminates high-megohm resistors and low current ammeters used in low-current measuring instruments.

  10. Strategies for dynamic soft-landing in capacitive microelectromechanical switches

    NASA Astrophysics Data System (ADS)

    Jain, Ankit; Nair, Pradeep R.; Alam, Muhammad A.

    2011-06-01

    Electromechanical dielectric degradation associated with the hard landing of movable electrode is a technology-inhibiting reliability concern for capacitive RF-MEMS switches. In this letter, we propose two schemes for dynamic soft-landing that obviate the need for external feedback circuitry. Instead, the proposed resistive and capacitive braking schemes can reduce impact velocity significantly without compromising other performance characteristics like pull-in voltage and pull-in time. Resistive braking is achieved by inserting a resistance in series with the voltage source whereas capacitive braking requires patterning of the electrode or the dielectric. Our results have important implications to the design and optimization of reliability aware electrostatically actuated MEMS switches.

  11. New low-cost MEMS capacitive pressure sensor concept

    NASA Astrophysics Data System (ADS)

    Wang, Yun; Cheung, Kin P.; Sheng, Kuang; Pai, Chien-Shing

    2005-01-01

    Capacitive pressure sensors based on surface or bulk MEMS technology have many attributes that make them highly desirable for many applications. The biggest technical challenge of capacitive pressure sensor technology is the creation of a reference cavity. It dictates the packaging approach and therefore the cost of the sensor. In this paper we introduce a new design of capacitive pressure sensor that takes advantage of a novel new wafer level packaging technology - A thin-film sealing technology that allows independent pressure control from high vacuum to high pressure. The new technology seals the vacuum cavity formed by standard surface micro machining technology by a brief melting of a metal layer using a pulsed laser. The ability to form reference vacuum cavity without the need for fusing or bonding with another structure allows the design to be simplified, leading to low cost and high yield.

  12. Capacitive measurement of mercury column heights in capillaries.

    PubMed

    Frey, Sarah; Richert, Ranko

    2010-03-01

    The detection of changes in volume, e.g., in expansivity or aging measurements, are often translated into mercury column height within a glass capillary. We propose a capacitive technique for measuring the meniscus position using a cylindrical capacitor with mercury as the inner electrode, the capillary material as the dielectric, and a metal coat covering the outside surface of the capillary as the second electrode. The measured capacitance changes linearly with meniscus height, as long as the top mercury level remains within the range of the outer electrode. With the demonstrated noise level of 48 nm for our preliminary setup, meniscus height changes beyond 100 nm can be observed via the capacitance. PMID:20370203

  13. Wavelet approach to artifact noise removal from Capacitive coupled Electrocardiograph.

    PubMed

    Lee, Seung Min; Kim, Ko Keun; Park, Kwang Suk

    2008-01-01

    Capacitive coupled Electrocardiography (ECG) is introduced as non-invasive measurement technology for ubiquitous health care and appliance are spread out widely. Although it has many merits, however, capacitive coupled ECG is very weak for motion artifacts for its non-skin-contact property. There are many studies for artifact problems which treats all artifact signals below 0.8Hz. In our capacitive coupled ECG measurement system, artifacts exist not only below 0.8Hz but also over than 10Hz. Therefore, artifact noise removal algorithm using wavelet method is tested to reject artifact-wandered signal from measured signals. It is observed that using power calculation each decimation step, artifact-wandered signal is removed as low frequency artifacts as high frequency artifacts. Although some original ECG signal is removed with artifact signal, we could level the signal quality for long term measure which shows the best quality ECG signals as we can get. PMID:19163323

  14. On Machine Capacitance Dimensional and Surface Profile Measurement System

    NASA Technical Reports Server (NTRS)

    Resnick, Ralph

    1993-01-01

    A program was awarded under the Air Force Machine Tool Sensor Improvements Program Research and Development Announcement to develop and demonstrate the use of a Capacitance Sensor System including Capacitive Non-Contact Analog Probe and a Capacitive Array Dimensional Measurement System to check the dimensions of complex shapes and contours on a machine tool or in an automated inspection cell. The manufacturing of complex shapes and contours and the subsequent verification of those manufactured shapes is fundamental and widespread throughout industry. The critical profile of a gear tooth; the overall shape of a graphite EDM electrode; the contour of a turbine blade in a jet engine; and countless other components in varied applications possess complex shapes that require detailed and complex inspection procedures. Current inspection methods for complex shapes and contours are expensive, time-consuming, and labor intensive.

  15. Sialidases on Mammalian Sperm Mediate Deciduous Sialylation during Capacitation*

    PubMed Central

    Ma, Fang; Wu, Diana; Deng, Liwen; Secrest, Patrick; Zhao, June; Varki, Nissi; Lindheim, Steven; Gagneux, Pascal

    2012-01-01

    Sialic acids (Sias) mediate many biological functions, including molecular recognition during development, immune response, and fertilization. A Sia-rich glycocalyx coats the surface of sperm, allowing them to survive as allogeneic cells in the female reproductive tract despite female immunity. During capacitation, sperm lose a fraction of their Sias. We quantified shed Sia monosaccharides released from capacitated sperm and measured sperm sialidase activity. We report the presence of two sialidases (neuraminidases Neu1 and Neu3) on mammalian sperm. These are themselves shed from sperm during capacitation. Inhibiting sialidase activity interferes with sperm binding to the zona pellucida of the ovum. A survey of human sperm samples for the presence of sialidases NEU1 and NEU3 identified a lack of one or both sialidases in sperm of some male idiopathic infertility cases. The results contribute new insights into the dynamic remodeling of the sperm glycocalyx prior to fertilization. PMID:22989879

  16. Capacitive Micromachined Ultrasonic Transducers (CMUTs) for Underwater Imaging Applications.

    PubMed

    Song, Jinlong; Xue, Chenyang; He, Changde; Zhang, Rui; Mu, Linfeng; Cui, Juan; Miao, Jing; Liu, Yuan; Zhang, Wendong

    2015-01-01

    A capacitive micromachined ultrasonic transducer structure for use in underwater imaging is designed, fabricated and tested in this paper. In this structure, a silicon dioxide insulation layer is inserted between the top electrodes and the vibration membrane to prevent ohmic contact. The capacitance-voltage (C-V) characteristic curve shows that the transducer offers suitable levels of hysteresis and repeatability performance. The -6 dB center frequency is 540 kHz and the transducer has a bandwidth of 840 kHz for a relative bandwidth of 155%. Underwater pressure of 143.43 Pa is achieved 1 m away from the capacitive micromachined ultrasonic transducer under 20 Vpp excitation. Two-dimensional underwater ultrasonic imaging, which is able to prove that a rectangular object is present underwater, is achieved. The results presented here indicate that our work will be highly beneficial for the establishment of an underwater ultrasonic imaging system. PMID:26389902

  17. Capacitive Micromachined Ultrasonic Transducers (CMUTs) for Underwater Imaging Applications

    PubMed Central

    Song, Jinlong; Xue, Chenyang; He, Changde; Zhang, Rui; Mu, Linfeng; Cui, Juan; Miao, Jing; Liu, Yuan; Zhang, Wendong

    2015-01-01

    A capacitive micromachined ultrasonic transducer structure for use in underwater imaging is designed, fabricated and tested in this paper. In this structure, a silicon dioxide insulation layer is inserted between the top electrodes and the vibration membrane to prevent ohmic contact. The capacitance-voltage (C-V) characteristic curve shows that the transducer offers suitable levels of hysteresis and repeatability performance. The −6 dB center frequency is 540 kHz and the transducer has a bandwidth of 840 kHz for a relative bandwidth of 155%. Underwater pressure of 143.43 Pa is achieved 1 m away from the capacitive micromachined ultrasonic transducer under 20 Vpp excitation. Two-dimensional underwater ultrasonic imaging, which is able to prove that a rectangular object is present underwater, is achieved. The results presented here indicate that our work will be highly beneficial for the establishment of an underwater ultrasonic imaging system. PMID:26389902

  18. Label-Free Capacitance-Based Identification of Viruses

    PubMed Central

    Ahmad, Mahmoud Al; Mustafa, Farah; Ali, Lizna M.; Karakkat, Jimsheena V.; Rizvi, Tahir A.

    2015-01-01

    This study was undertaken to quantitate a single virus suspension in culture medium without any pre-processing. The electrical capacitance per virus particle was used to identify the kind of virus present by measuring the suspension (virus plus medium) capacitance, de-embedding the medium contribution, and dividing by the virus count. The proposed technique is based on finding the single virus effective dielectric constant which is directly related to the virus composition. This value was used to identify the virus type accordingly. Two types of viruses thus tested were further quantified by a biochemical technique to validate the results. Furthermore, non-organic nanoparticles with known concentration and capacitance per particle were identified using the proposed method. The selectivity of the method was demonstrated by performing electrical measurements on a third virus, revealing that the proposed technique is specific and sensitive enough to permit detection of a few hundred virus particles per milliliter within a few minutes. PMID:25966875

  19. A Wearable Capacitive Sensor for Monitoring Human Respiratory Rate

    NASA Astrophysics Data System (ADS)

    Kundu, Subrata Kumar; Kumagai, Shinya; Sasaki, Minoru

    2013-04-01

    Realizing an untethered, low-cost, and comfortably wearable respiratory rate sensor for long-term breathing monitoring application still remains a challenge. In this paper, a conductive-textile-based wearable respiratory rate sensing technique based on the capacitive sensing approach is proposed. The sensing unit consists of two conductive textile electrodes that can be easily fabricated, laminated, and integrated in garments. Respiration cycle is detected by measuring the capacitance of two electrodes placed on the inner anterior and posterior sides of a T-shirt at either the abdomen or chest position. A convenient wearable respiratory sensor setup with a capacitance-to-voltage converter has been devised. Respiratory rate as well as breathing mode can be accurately identified using the designed sensor. The sensor output provides significant information on respiratory flow. The effectiveness of the proposed system for different breathing patterns has been evaluated by experiments.

  20. Enabling large scale capacitive sensing for dielectric elastomers

    NASA Astrophysics Data System (ADS)

    Xu, Daniel; McKay, Thomas G.; Michel, Silvain; Anderson, Iain A.

    2014-03-01

    Hand motion is one of our most expressive abilities. By measuring our interactions with everyday objects, we can create smarter artificial intelligence that can learn and adapt from our behaviours and patterns. One way to achieve this is to apply wearable dielectric elastomer strain sensors directly onto the hand. Applications such as this require fast, efficient and scalable sensing electronics. Most capacitive sensing methods use an analogue sensing signal and a backend processor to calculate capacitance. This not only reduces scalability and speed of feedback but also increases the complexity of the sensing circuitry. A capacitive sensing method that uses a DC sensing signal and continuous tracking of charge is presented. The method is simple and efficient, allowing large numbers of dielectric elastomer sensors to be measured simulatenously.

  1. 77 FR 4853 - In the Matter of Airbee Wireless, Inc., Axial Vector Engine Corp. (n/k/a Avec Corporation), and...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-01-31

    ... From the Federal Register Online via the Government Publishing Office SECURITIES AND EXCHANGE COMMISSION In the Matter of Airbee Wireless, Inc., Axial Vector Engine Corp. (n/k/a Avec Corporation), and... accurate information concerning the securities of Axial Vector Engine Corp. (n/k/a Avec...

  2. Penicillamine prevents ram sperm agglutination in media that support capacitation.

    PubMed

    Leahy, T; Rickard, J P; Aitken, R J; de Graaf, S P

    2016-02-01

    Ram spermatozoa are difficult to capacitate in vitro. Here we describe a further complication, the unreported phenomenon of head-to-head agglutination of ram spermatozoa following dilution in the capacitation medium Tyrodes plus albumin, lactate and pyruvate (TALP). Sperm agglutination is immediate, specific and persistent and is not associated with a loss of motility. Agglutination impedes in vitro sperm handling and analysis. So the objectives of this study were to investigate the cause of sperm agglutination and potential agents which may reduce agglutination. The percentage of non-agglutinated, motile spermatozoa increased when bicarbonate was omitted from complete TALP suggesting that bicarbonate ions stimulate the agglutination process. d-penicillamine (PEN), a nucleophilic thiol, was highly effective at reducing agglutination. The inclusion of 250 μM PEN in TALP reduced the incidence of motile, agglutinated spermatozoa from 76.7 ± 2.7% to 2.8 ± 1.4%. It was then assessed if PEN (1 mM) could be included in existing ram sperm capacitation protocols (TALP +1 mM dibutyryl cAMP, caffeine and theophylline) to produce spermatozoa that were simultaneously capacitated and non-agglutinated. This protocol resulted in a sperm population which displayed high levels of tyrosine phosphorylated proteins and lipid disordered membranes (merocyanine-540) while remaining motile, viable, acrosome-intact and non-agglutinated. In summary, PEN (1 mM) can be included in ram sperm capacitation protocols to reduce sperm agglutination and allow for the in vitro assessment of ram sperm capacitation. PMID:26705263

  3. Flexible capacitive electrodes for minimizing motion artifacts in ambulatory electrocardiograms.

    PubMed

    Lee, Jeong Su; Heo, Jeong; Lee, Won Kyu; Lim, Yong Gyu; Kim, Youn Ho; Park, Kwang Suk

    2014-01-01

    This study proposes the use of flexible capacitive electrodes for reducing motion artifacts in a wearable electrocardiogram (ECG) device. The capacitive electrodes have conductive foam on their surface, a shield, an optimal input bias resistor, and guarding feedback. The electrodes are integrated in a chest belt, and the acquired signals are transmitted wirelessly for ambulatory heart rate monitoring. We experimentally validated the electrode performance with subjects standing and walking on a treadmill at speeds of up to 7 km/h. The results confirmed the highly accurate heart rate detection capacity of the developed system and its feasibility for daily-life ECG monitoring. PMID:25120162

  4. CONCEPTS FOR CAPACITIVELY RF-SHIELDED BELLOWS IN CRYOGENIC STRUCTURES.

    SciTech Connect

    ZHAO,Y.HAHN,H.

    2004-03-24

    Bellows are frequently required in accelerators and colliders. Usually RF-shields with spring fingers are employed to screen the bellows. The lack of accessibility in cryogenic systems can be a problem and asks for alternate solutions to eliminate possible overheating, sparking, etc that occurred in intensive beams. This note addresses an alternate kind of RF shield, which uses capacitive contact instead of mechanical contact. The analysis, as well as numerical example of a superconducting cavity structure, shows that the capacitive RF shield satisfies the impedance requirements of both beam and HOMs. The capability of thermal isolation is also analyzed.

  5. Faradaic and Capacitive Components of the CNT Electrochemical Responses

    NASA Astrophysics Data System (ADS)

    Otero, Toribio; Martinez, Jose G.; Asaka, Kinji

    2016-02-01

    The nature of the electrochemical responses from carbon nanotubes, capacitive (physical) or Faradaic (chemical, also named p-doping or n-doping) remain controversial. In this chapter the literature is reviewed and discussed trying to elucidate if some of the two processes prevails, how the presence of chemical reactions can be elucidate and which properties, specific from the chemical processes, can be exploited. Different electrochemical responses and theories trying to explain those responses are discussed. The separation and quantification methodologies of the capacitive and Faradaic components involved in some electro-chemical responses from CNTs are presented.

  6. The modelling of a capacitive microsensor for biosensing applications

    NASA Astrophysics Data System (ADS)

    Bezuidenhout, P. H.; Schoeman, J.; Joubert, T. H.

    2014-06-01

    Microsensing is a leading field in technology due to its wide application potential, not only in bio-engineering, but in other fields as well. Microsensors have potentially low-cost manufacturing processes, while a single device type can have various uses, and this consequently helps with the ever-growing need to provide better health conditions in rural parts of the world. Capacitive biosensors detect a change in permittivity (or dielectric constant) of a biological material, usually within a parallel plate capacitor structure which is often implemented with integrated electrodes of an inert metal such as gold or platinum on a microfluidic substrate typically with high dielectric constant. There exist parasitic capacitance components in these capacitive sensors, which have large influence on the capacitive measurement. Therefore, they should be considered for the development of sensitive and accurate sensing devices. An analytical model of a capacitive sensor device is discussed, which accounts for these parasitic factors. The model is validated with a laboratory device of fixed geometry, consisting of two parallel gold electrodes on an alumina (Al2O3) substrate mounted on a glass microscope slide, and with a windowed cover layer of poly-dimethyl-siloxane (PDMS). The thickness of the gold layer is 1μm and the electrode spacing is 300μm. The alumina substrate has a thickness of 200μm, and the high relative permittivity of 11.5 is expected to be a significantly contributing factor to the total device capacitance. The 155μm thick PDMS layer is also expected to contribute substantially to the total device capacitance since the relative permittivity for PDMS is 2.7. The wideband impedance analyser evaluation of the laboratory device gives a measurement result of 2pF, which coincides with the model results; while the handheld RLC meter readout of 4pF at a frequency of 10kHz is acceptable within the measurement accuracy of the instrument. This validated model will

  7. [Impact of sperm capacitation on various populations of human spermatozoa].

    PubMed

    Villanueva Díaz, C; Suárez Juárez, M; Díaz, M A; Ayala Ruiz, A

    1989-02-01

    With the purpose of evaluating the impact of spermatic capacitation on different spermatozooa populations, 49 samples of semen, before and after in vitro spermatic capacitation with Ham F-10 medium, were studied; motility of cells was evaluated according to WHO criteria. There was diminution of percentage of immobile cells, 27.8 to 20.0, as well as increase in population of cells with more mobility, 28.6% to 39.1%. Both difference were statistically significant (p = less than 0.05 and p = less than 0.005, respectively). These data suggest that spermatic capacitacion activates "in cascade" all groups of gametes. PMID:2486981

  8. Capacitively coupled RF voltage probe having optimized flux linkage

    DOEpatents

    Moore, James A.; Sparks, Dennis O.

    1999-02-02

    An RF sensor having a novel current sensing probe and a voltage sensing probe to measure voltage and current. The current sensor is disposed in a transmission line to link all of the flux generated by the flowing current in order to obtain an accurate measurement. The voltage sensor is a flat plate which operates as a capacitive plate to sense voltage on a center conductor of the transmission line, in which the measured voltage is obtained across a resistance leg of a R-C differentiator circuit formed by the characteristic impedance of a connecting transmission line and a capacitance of the plate, which is positioned proximal to the center conductor.

  9. Flexible Capacitive Electrodes for Minimizing Motion Artifacts in Ambulatory Electrocardiograms

    PubMed Central

    Lee, Jeong Su; Heo, Jeong; Lee, Won Kyu; Lim, Yong Gyu; Kim, Youn Ho; Park, Kwang Suk

    2014-01-01

    This study proposes the use of flexible capacitive electrodes for reducing motion artifacts in a wearable electrocardiogram (ECG) device. The capacitive electrodes have conductive foam on their surface, a shield, an optimal input bias resistor, and guarding feedback. The electrodes are integrated in a chest belt, and the acquired signals are transmitted wirelessly for ambulatory heart rate monitoring. We experimentally validated the electrode performance with subjects standing and walking on a treadmill at speeds of up to 7 km/h. The results confirmed the highly accurate heart rate detection capacity of the developed system and its feasibility for daily-life ECG monitoring. PMID:25120162

  10. Double-driven shield capacitive type proximity sensor

    NASA Technical Reports Server (NTRS)

    Vranish, John M. (Inventor)

    1993-01-01

    A capacity type proximity sensor comprised of a capacitance type sensor, a capacitance type reference, and two independent and mutually opposing driven shields respectively adjacent to the sensor and reference and which are coupled in an electrical bridge circuit configuration and driven by a single frequency crystal controlled oscillator is presented. The bridge circuit additionally includes a pair of fixed electrical impedance elements which form adjacent arms of the bridge and which comprise either a pair of precision resistances or capacitors. Detection of bridge unbalance provides an indication of the mutual proximity between an object and the sensor. Drift compensation is also utilized to improve performance and thus increase sensor range and sensitivity.

  11. Differential capacitance probe for process control involving aqueous dielectric fluids

    DOEpatents

    Svoboda, John M.; Morrison, John L.

    2002-10-08

    A differential capacitance probe device for process control involving aqueous dielectric fluids is disclosed. The device contains a pair of matched capacitor probes configured in parallel, one immersed in a sealed container of reference fluid, and the other immersed in the process fluid. The sealed container holding the reference fluid is also immersed in the process fluid, hence both probes are operated at the same temperature. Signal conditioning measures the difference in capacitance between the reference probe and the process probe. The resulting signal is a control error signal that can be used to control the process.

  12. Quantum capacitance in monolayers of silicene and related buckled materials

    NASA Astrophysics Data System (ADS)

    Nawaz, S.; Tahir, M.

    2016-02-01

    Silicene and related buckled materials are distinct from both the conventional two dimensional electron gas and the famous graphene due to strong spin orbit coupling and the buckled structure. These materials have potential to overcome limitations encountered for graphene, in particular the zero band gap and weak spin orbit coupling. We present a theoretical realization of quantum capacitance which has advantages over the scattering problems of traditional transport measurements. We derive and discuss quantum capacitance as a function of the Fermi energy and temperature taking into account electron-hole puddles through a Gaussian broadening distribution. Our predicted results are very exciting and pave the way for future spintronic and valleytronic devices.

  13. Enhancing Graphene Capacitance by Nitrogen: Effects of Doping Configuration and Concentration

    DOE PAGESBeta

    Zhan, Cheng; Cummings, Peter; Jiang, De-en

    2016-01-08

    Recent experiments have shown that nitrogen doping enhances capacitance in carbon electrode supercapacitors. However, a detailed study of the effect of N-doping on capacitance is still lacking. In this paper, we study the doping concentration and the configuration effect on the electric double-layer (EDL) capacitance, quantum capacitance, and total capacitance. It is found that pyridinic and graphitic nitrogens can increase the total capacitance by increasing quantum capacitance, but pyrrolic configuration limits the total capacitance due to its much lower quantum capacitance than the other two configurations. We also find that, unlike the graphitic and pyridinic nitrogens, the pyrrolic configuration's quantummore » capacitance does not depend on the nitrogen concentration, which may explain why some capacitance versus voltage measurements of N-doped graphene exhibit a V-shaped curve similar to that of undoped graphene. Our investigation provides a deeper understanding of the capacitance enhancement of the N-doping effect in carbon electrodes and suggests a potentially effective way to optimize the capacitance by controlling the type of N-doping.« less

  14. RC filter with low distributed capacitance provides 60 db isolation at 500 MHz

    NASA Technical Reports Server (NTRS)

    Cessna, J. R.

    1970-01-01

    Resistance-capacitance RC filter coupled to a high input impedance receiver preamplifier provides signal isolation from an RF transmitter. High isolation is achieved by minimizing the inductive impedance to ground and using the distributed capacitance of the filter components.

  15. Recent advances in capacitance type of blade tip clearance measurements

    NASA Technical Reports Server (NTRS)

    Barranger, John P.

    1988-01-01

    Two recent electronic advances at NASA-Lewis that meet the blade tip clearance needs of a wide class of fans, compressors, and turbines are described. The first is a frequency modulated (FM) oscillator that requires only a single low cost ultrahigh frequency operational amplifier. Its carrier frequency is 42.8 MHz when used with a 61 cm long hermetically sealed coaxial cable. The oscillator can be calibrated in the static mode and has a negative peak frequency deviation of 400 kHz for a typical rotor blade. High temperature performance tests of the probe and 13 cm of the adjacent cable show good accuracy up to 600 C, the maximum which produces a clearance error of + or - 10 microns at a clearance of 500 microns. In the second advance, a guarded probe configuration allows a longer cable capacitance. The capacitance of the probe is part of a small time constant feedback in a high speed operational amplifier. The solution of the governing differential equation is applied to a ramp type of input. The results show an amplifier output that contains a term which is proportional to the derivative of the feedback capacitance. The capacitance is obtained by subtracting a balancing reference channel followed by an integration stage.

  16. Capacitive type magnetoimpedance effect in piezoelectric-magnetostrictive composite resonator

    NASA Astrophysics Data System (ADS)

    Wang, Wei; Wang, Zhifeng; Luo, Xiaobin; Tao, Jin; Zhang, Ning; Xu, Xinran; Zhou, Lisheng

    2015-10-01

    In this article, a significant capacitive type magnetoimpedance effect of piezoelectric-magnetostrictive (PM) composite resonator is presented at room temperature. The variations of relatively effective permittivity of the PM resonator with a dc magnetic field are responsible for the capacitive type magnetoimpedance effect. About 225% and 50% of magnetoimpedance have been achieved at anti-resonance and resonance frequencies of the PM resonator, respectively, which reveals a stronger magnetoelectric coupling at the anti-resonance frequency than that at the resonance frequency of the PM resonator. A detailed analysis also indicates that the magnetocapacitance and magnetoinduction effects of the resonator were originated from the variations of relatively effective permittivity of the resonator. More than 200% and 170% of magnetocapacitance and magnetoinduction were achieved at room temperature in the anti-resonance window, respectively, and also about 150% and 60% of capacitance and induction modulation were observed in the resonance window by applying the dc magnetic fields. The capacitive type magnetoimpedance effect is expected to be used in the design of magnetic-field-tuned ultrasonic transducer.

  17. Solving the Quadratic Capacitated Facilities Location Problem by Computer.

    ERIC Educational Resources Information Center

    Cote, Leon C.; Smith, Wayland P.

    Several computer programs were developed to solve various versions of the quadratic capacitated facilities location problem. Matrices, which represent various business costs, are defined for the factors of sites, facilities, customers, commodities, and production units. The objective of the program is to find an optimization matrix for the lowest…

  18. RF-MEMS capacitive switches with high reliability

    SciTech Connect

    Goldsmith, Charles L.; Auciello, Orlando H.; Carlisle, John A.; Sampath, Suresh; Sumant, Anirudha V.; Carpick, Robert W.; Hwang, James; Mancini, Derrick C.; Gudeman, Chris

    2013-09-03

    A reliable long life RF-MEMS capacitive switch is provided with a dielectric layer comprising a "fast discharge diamond dielectric layer" and enabling rapid switch recovery, dielectric layer charging and discharging that is efficient and effective to enable RF-MEMS switch operation to greater than or equal to 100 billion cycles.

  19. Lightweight linear alternators with and without capacitive tuning

    NASA Astrophysics Data System (ADS)

    Niedra, Janis M.

    1993-06-01

    Permanent magnet excited linear alternators rated tens of kW and coupled to free-piston Stirling engines are presently viewed as promising candidates for long term generation of electric power in both space and terrestrial applications. Series capacitive cancellation of the internal inductive reactance of such alternators was considered a viable way to both increase power extraction and to suppress unstable modes of the thermodynamic oscillation. Idealized toroidal and cylindrical alternator geometries are used for a comparative study of the issues of specific mass and capacitive tuning, subject to stability criteria. The analysis shows that the stator mass of an alternator designed to be capacitively tuned is always greater than the minimum achievable stator mass of an alternator designed with no capacitors, assuming equal utilization of materials ratings and the same frequency and power to a resistive load. This conclusion is not substantially altered when the usually lesser masses of the magnets and of any capacitors are added. Within the reported stability requirements and under circumstances of normal materials ratings, this study finds no clear advantage to capacitive tuning. Comparative plots of the various constituent masses are presented versus the internal power factor taken as a design degree of freedom. The explicit formulas developed for stator core, coil, capacitor, and magnet masses and for the degree of magnet utilization provide useful estimates of scaling effects.

  20. High bandwidth on-chip capacitive tuning of microtoroid resonators.

    PubMed

    Baker, Christopher G; Bekker, Christiaan; McAuslan, David L; Sheridan, Eoin; Bowen, Warwick P

    2016-09-01

    We report on the design, fabrication and characterization of silica microtoroid based cavity opto-electromechanical systems (COEMS). Electrodes patterned onto the microtoroid resonators allow for rapid capacitive tuning of the optical whispering gallery mode resonances while maintaining their ultrahigh quality factor, enabling applications such as efficient radio to optical frequency conversion, optical routing and switching applications. PMID:27607646

  1. Capacitive soft strain sensors via multicore-shell fiber printing.

    PubMed

    Frutiger, Andreas; Muth, Joseph T; Vogt, Daniel M; Mengüç, Yiǧit; Campo, Alexandre; Valentine, Alexander D; Walsh, Conor J; Lewis, Jennifer A

    2015-04-17

    A new method for fabricating textile integrable capacitive soft strain sensors is reported, based on multicore-shell fiber printing. The fiber sensors consist of four concentric, alternating layers of conductor and dielectric, respectively. These wearable sensors provide accurate and hysteresis-free strain measurements under both static and dynamic conditions. PMID:25754237

  2. Micromachined low frequency rocking accelerometer with capacitive pickoff

    DOEpatents

    Lee, Abraham P.; Simon, Jonathon N.; McConaghy, Charles F.

    2001-01-01

    A micro electro mechanical sensor that uses capacitive readout electronics. The sensor involves a micromachined low frequency rocking accelerometer with capacitive pickoff fabricated by deep reactive ion etching. The accelerometer includes a central silicon proof mass, is suspended by a thin polysilicon tether, and has a moving electrode (capacitor plate or interdigitated fingers) located at each end the proof mass. During movement (acceleration), the tethered mass moves relative to the surrounding packaging, for example, and this defection is measured capacitively by a plate capacitor or interdigitated finger capacitor, having the cooperating fixed electrode (capacitor plate or interdigitated fingers) positioned on the packaging, for example. The micromachined rocking accelerometer has a low frequency (<500 Hz), high sensitivity (.mu.G), with minimal power usage. The capacitors are connected to a power supply (battery) and to sensor interface electronics, which may include an analog to digital (A/D) converter, logic, RF communication link, antenna, etc. The sensor (accelerometer) may be, for example, packaged along with the interface electronics and a communication system in a 2".times.2".times.2" cube. The proof mass may be asymmetric or symmetric. Additional actuating capacitive plates may be used for feedback control which gives a greater dynamic range.

  3. Probing 2D black phosphorus by quantum capacitance measurements.

    PubMed

    Kuiri, Manabendra; Kumar, Chandan; Chakraborty, Biswanath; Gupta, Satyendra N; Naik, Mit H; Jain, Manish; Sood, A K; Das, Anindya

    2015-12-01

    Two-dimensional materials and their heterostructures have emerged as a new class of materials, not only for fundamental physics but also for electronic and optoelectronic applications. Black phosphorus (BP) is a relatively new addition to this class of materials. Its strong in-plane anisotropy makes BP a unique material for making conceptually new types of electronic devices. However, the global density of states (DOS) of BP in device geometry has not been measured experimentally. Here, we report the quantum capacitance measurements together with the conductance measurements on an hBN-protected few-layer BP (∼six layers) in a dual-gated field effect transistor (FET) geometry. The measured DOS from our quantum capacitance is compared with density functional theory (DFT). Our results reveal that the transport gap for quantum capacitance is smaller than that in conductance measurements due to the presence of localized states near the band edge. The presence of localized states is confirmed by the variable range hopping seen in our temperature dependence conductivity. A large asymmetry is observed between the electron and hole side. This asymmetric nature is attributed to the anisotropic band dispersion of BP. Our measurements establish the uniqueness of quantum capacitance in probing the localized states near the band edge, hitherto not seen in conductance measurements. PMID:26559656

  4. Reconfigurable Prototyping Microfluidic Platform for DEP Manipulation and Capacitive Sensing.

    PubMed

    Miled, Amine; Auclair, Benoit; Srasra, Anis; Sawan, Mohamad

    2015-04-01

    In this paper, we present a new rapid prototyping platform dedicated to dielectrophoretic microfluidic manipulation and capacitive cell sensing. The proposed platform offers a reconfigurable design including 4 independently programmable output channels to be distributed across 64 electrodes. Although its range of frequency covers up to 3.4 MHz, signal amplitude accuracy ( +/-10%) was demonstrated for frequencies up to 1 MHz and channel-to-channel phase shift setting was stable up to 1.5 MHz. A test of maximum resistive load showed a 10% attenuation of a 12 V peak-to-peak signal with a 22 Ω load. The platform has an advanced capacitive sensor to measure capacitance variation between in-channel electrodes with a sampling frequency up to 5 kH z. Experimental data of capacitive sensor showed a sensitivity of 100 fF. The sensor can be extended to 4 parallel measurements with lower frequency. We also present a new assembly technique for reusable microfluidic chip based on anisotropic adhesive conductive film, epoxy and PDMS. The proposed platform provides a wide range of control signals depending on the type of manipulation as sine, rectangular or square wave. The frequency range is extendible up to 3.4 MHz, in addition to a programmable phase shift circuit with a minimum phase step of 3.6(°) for each signal. PMID:25879968

  5. Design and development of a MEMS capacitive bending strain sensor

    NASA Astrophysics Data System (ADS)

    Aebersold, J.; Walsh, K.; Crain, M.; Martin, M.; Voor, M.; Lin, J.-T.; Jackson, D.; Hnat, W.; Naber, J.

    2006-05-01

    The design, modeling, fabrication and testing of a MEMS-based capacitive bending strain sensor utilizing a comb drive is presented. This sensor is designed to be integrated with a telemetry system that will monitor changes in bending strain to assist with the diagnosis of spinal fusion. ABAQUS/CAE finite-element analysis (FEA) software was used to predict sensor actuation, capacitance output and avoid material failure. Highly doped boron silicon wafers with a low resistivity were fabricated into an interdigitated finger array employing deep reactive ion etching (DRIE) to create 150 µm sidewalls with 25 µm spacing between the adjacent fingers. The sensor was adhered to a steel beam and subjected to four-point bending to mechanically change the spacing between the interdigitated fingers as a function of strain. As expected, the capacitance output increased as an inverse function of the spacing between the interdigitated fingers. At the unstrained state, the capacitive output was 7.56 pF and increased inversely to 17.04 pF at 1571 µɛ of bending strain. The FEA and analytical models were comparable with the largest differential of 0.65 pF or 6.33% occurring at 1000 µɛ. Advantages of this design are a dice-free process without the use of expensive silicon-on-insulator (SOI) wafers.

  6. Miniature electrometer preamplifier effectively compensates for input capacitance

    NASA Technical Reports Server (NTRS)

    Burrous, C. N.; Deboo, G. J.

    1966-01-01

    Negative capacitance preamplifier using a dual MOS /Metal Oxide Silicon/ transistor in conjunction with bipolar transistors is used with intracellular microelectrodes in recording bioelectric potentials. Applications would include use as a pickup plate video amplifier in storage tube tests and for pH and ionization chamber measurements.

  7. Conductive versus capacitive coupling for cell electroporation with nanosecond pulses

    NASA Astrophysics Data System (ADS)

    French, David M.; Uhler, Michael D.; Gilgenbach, Ronald M.; Lau, Y. Y.

    2009-10-01

    Experiments and simulations were performed to determine the difference between capacitive coupling and conductive connection for the electroporation of cells. The pulses used in the experiments have a peak voltage of 24 kV, 0.6 ns rise time, and 1.6 ns full width at half maximum. Experiments performed compare the conductive connection of the cell suspension versus a capacitively coupled cell suspension. The magnitude of the electric field was 16 kV/cm in both cases; however, the pulse shape is different. For the conductively connected case the cells located between the electrodes experienced an electric field in one direction only, whereas cells located between the electrodes in the capacitive coupling case were subject to an electric field that reverses direction. For the capacitively coupled case the bipolar pulse leads to no net cell charging. The conductive connection case is different, in that cells are left with a net polarization after the pulse is applied. Experimentally, only cells subject to the pulse with conductive connection demonstrated electroporation with the drug Bleomycin.

  8. Concentration Fluctuations and Capacitive Response in Dense Ionic Solutions.

    PubMed

    Uralcan, Betul; Aksay, Ilhan A; Debenedetti, Pablo G; Limmer, David T

    2016-07-01

    We use molecular dynamics simulations in a constant potential ensemble to study the effects of solution composition on the electrochemical response of a double layer capacitor. We find that the capacitance first increases with ion concentration following its expected ideal solution behavior but decreases upon approaching a pure ionic liquid in agreement with recent experimental observations. The nonmonotonic behavior of the capacitance as a function of ion concentration results from the competition between the independent motion of solvated ions in the dilute regime and solvation fluctuations in the concentrated regime. Mirroring the capacitance, we find that the characteristic decay length of charge density correlations away from the electrode is also nonmonotonic. The correlation length first decreases with ion concentration as a result of better electrostatic screening but increases with ion concentration as a result of enhanced steric interactions. When charge fluctuations induced by correlated ion-solvent fluctuations are large relative to those induced by the pure ionic liquid, such capacitive behavior is expected to be generic. PMID:27259040

  9. Lightweight linear alternators with and without capacitive tuning

    NASA Technical Reports Server (NTRS)

    Niedra, Janis M.

    1993-01-01

    Permanent magnet excited linear alternators rated tens of kW and coupled to free-piston Stirling engines are presently viewed as promising candidates for long term generation of electric power in both space and terrestrial applications. Series capacitive cancellation of the internal inductive reactance of such alternators was considered a viable way to both increase power extraction and to suppress unstable modes of the thermodynamic oscillation. Idealized toroidal and cylindrical alternator geometries are used for a comparative study of the issues of specific mass and capacitive tuning, subject to stability criteria. The analysis shows that the stator mass of an alternator designed to be capacitively tuned is always greater than the minimum achievable stator mass of an alternator designed with no capacitors, assuming equal utilization of materials ratings and the same frequency and power to a resistive load. This conclusion is not substantially altered when the usually lesser masses of the magnets and of any capacitors are added. Within the reported stability requirements and under circumstances of normal materials ratings, this study finds no clear advantage to capacitive tuning. Comparative plots of the various constituent masses are presented versus the internal power factor taken as a design degree of freedom. The explicit formulas developed for stator core, coil, capacitor, and magnet masses and for the degree of magnet utilization provide useful estimates of scaling effects.

  10. Compact and high-accuracy RF MEMS capacitive series devices

    NASA Astrophysics Data System (ADS)

    Rottenberg, Xavier; Nauwelaers, Bart; De Raedt, Walter; Tilmans, Harrie A. C.

    2005-01-01

    MEMS technology is presented as a promising technology to realize high Q variable capacitors and RF switches with high performance and with high levels of integration. These devices are key elements for systems like phase shifters, tunable filters and matching networks. However, the reliability and the yield of the RF MEMS devices remain the key limiting factors holding the MEMS technology from spreading in the industrial applications. From a RF designer's point of view, reliability and yield are closely related to the accuracy of the definition of the up- and down-state capacitances of the devices. In this paper, we propose a novel compact series capacitive structure with improved predictability and RF performance. The new design mimics a clamped-clamped bridge to lower its sensitivity to the process-induced stress gradient in the up-state. The shape of the device and its consequent parameters, e.g. up- and down-capacitances, are thus more accurately defined even in presence of non-ideal clamping conditions. Unlike the series switchable capacitors with transverse restraining bridge, the novel device does not suffer from high frequency parasitic resonances. Finally, the novel device implements the floating top metal. This allows accurately defining the down-state capacitance of the design at will. Boosted series capacitive switches with inline-restrained cantilever beams have been realized and measured. The isolation is better than 20dB until 1GHz without optimization. The insertion loss in the down-state is better than 0.2dB in the range 1-20GHz. It further slowly and continuously decays to reach 0.4dB at 40GHz without any resonances.

  11. An improved junction capacitance model for junction field-effect transistors

    NASA Astrophysics Data System (ADS)

    Ding, Hao; Liou, Juin J.; Cirba, Claude R.; Green, Keith

    2006-07-01

    A new junction capacitance model for the four-terminal junction field-effect transistor (JFET) is presented. With a single expression, the model, which is valid for different temperatures and a wide range of bias conditions, describes correctly the JFET junction capacitance behavior and capacitance drop-off phenomenon. The model has been verified using experimental data measured at Texas Instruments.

  12. Simplified Capacitance Monitoring for the Determination of Campylobacter spp. Growth Rates

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Capacitance monitoring is commonly used as an efficient means to measure growth curves of bacterial pathogens. However, the use of capacitance monitoring with Campylobacter spp. was previously determined difficult due to the complexity of the required media. We investigated capacitance monitoring ...

  13. Study of materials for the design of MEMS capacitive pressure sensor

    NASA Astrophysics Data System (ADS)

    Jindal, Sumit Kumar; Raghuwanshi, Sanjeev Kumar

    2016-04-01

    Highly sensitive MEMS capacitive pressure sensor is nowadays used for many different applications such as aerospace, automobile, Bio-MEMS etc. This paper deals with study and comparison of different types of materials that can be used in design of MEMS capacitive pressure sensor. Initially principle and design of basic MEMS capacitive pressure sensor is explained. In the next section the properties of different materials is elaborated. The centre deflection of the diaphragm is calculated using COMSOL Multiphysics and Capacitance is calculated using MATLAB simulation. From the capacitance calculated sensitivity of the materials can be interpreted. The analysis is carried out for a pressure range of 0 to 0.1 MPa.

  14. Aptamer-modified anodized aluminum oxide-based capacitive sensor for the detection of bisphenol A

    NASA Astrophysics Data System (ADS)

    Kang, Bongkeun; Kim, Joo Hyoung; Kim, Soyoun; Yoo, Kyung-Hwa

    2011-02-01

    We describe a rapid, sensitive, and low-cost method to detect bisphenol A (BPA) using an anodized aluminum oxide-based capacitive sensor. BPA is detected by measuring the change in capacitance caused by the biospecific binding of BPA with a BPA aptamer that is immobilized on the electrode surface. For a solution containing 100 pM BPA, the capacitance decreased by approximately 3%. In addition, we fabricated a capacitive sensor array and demonstrated that BPA in environmental samples can be measured using our capacitive sensor.

  15. Capacitance effect on the oscillation and switching characteristics of spin torque oscillators

    PubMed Central

    2014-01-01

    We have studied the capacitance effect on the oscillation characteristics and the switching characteristics of the spin torque oscillators (STOs). We found that when the external field is applied, the STO oscillation frequency exhibits various dependences on the capacitance for injected current ranging from 8 to 20 mA. The switching characteristic is featured with the emerging of the canted region; the canted region increases with the capacitance. When the external field is absent, the STO free-layer switching time exhibits different dependences on the capacitance for different injected current. These results help to establish the foundation for capacitance-involved STO modeling. PMID:25404870

  16. A system for measuring thermal activation energy levels in silicon by thermally stimulated capacitance

    NASA Technical Reports Server (NTRS)

    Cockrum, R. H.

    1982-01-01

    One method being used to determine energy level(s) and electrical activity of impurities in silicon is described. The method is called capacitance transient spectroscopy (CTS). It can be classified into three basic categories: the thermally stimulated capacitance method, the voltage-stimulated capacitance method, and the light-stimulated capacitance method; the first two categories are discussed. From the total change in capacitance and the time constant of the capacitance response, emission rates, energy levels, and trap concentrations can be determined. A major advantage of using CTS is its ability to detect the presence of electrically active impurities that are invisible to other techniques, such as Zeeman effect atomic absorption, and the ability to detect more than one electrically active impurity in a sample. Examples of detection of majority and minority carrier traps from gold donor and acceptor centers in silicon using the capacitance transient spectrometer are given to illustrate the method and its sensitivity.

  17. Smart measurement system for resistive (bridge) or capacitive sensors

    NASA Astrophysics Data System (ADS)

    Wang, Guijie; Meijer, Gerard C. M.

    1998-07-01

    A low-cost smart measurement system for resistive (bridge) and capacitive sensors is presented and demonstrated. The measurement system consists of three main parts: the sensor element, a universal transducer interface (UTI) and a microcontroller. The UTI is a sensor-signal-to-time converter, based on a period-modulated oscillator, which is equipped with front-ends for many types of resistive (bridge) and capacitive sensors, and which generates a microcontroller-compatible output signal. The microcontroller performs data acquisition of the output signals from the interface UTI, controls the working status of the UTI for a specified application and communicates with a personal computer. Continuous auto-calibration of the offset and the gain of the complete system is applied to eliminate many nonidealities. Experimental results show that the accuracy and resolution are 14 bits and 16 bits, respectively, for a measurement time of about 100 ms.

  18. Research and development of novel wireless digital capacitive displacement sensor

    NASA Astrophysics Data System (ADS)

    Cui, Junning; He, Zhangqiang; Sun, Tao; Bian, Xingyuan; Han, Lu

    2015-02-01

    In order to solve the problem of noncontact, wireless and nonmagnetic displacement sensing with nanometer resolution within critical limited space for ultraprecision displacement monitoring in the Joule balance device, a novel wireless digital capacitive displacement sensor (WDCDS) is proposed. The WDCDS is fabricated with brass and other nonmagnetic material and powered with a small battery inside, a small integrated circuit is assembled inside for converting and processing of capacitive signal, and low power Bluetooth is used for wireless signal transmission and communication. Experimental results show that the WDCDS proposed has a resolution of better than 1nm and a nonlinearity of 0.077%, therefore it is a delicate design for ultraprecision noncontact displacement monitoring in the Joule balance device, meeting the demand for properties of wireless, nonmagnetic and miniaturized size.

  19. Capacitance of edge plane of pyrolytic graphite in acetonitrile solutions

    SciTech Connect

    Minick, S.K.; Ishida, Takanobu.

    1991-05-01

    The capacitance of the edge plane of pyrolytic graphite electrodes, in acetonitrile solutions, is measured by recording the current response to an applied triangular voltage sweep; TVS, and then fitting the current response with an appropriate function, (via a set of adjustable parameters). The pretreatment of the electrodes, the supporting electrolyte concentration used, and the frequency of the input TVS, were all found to affect the measured capacitance. In these experiments, a background current was also seen and the shape of the current output for the TVS; the charging/discharging curve, is shown to correlate with the magnitude of this background current. In addition, the size of the background current was found to have some dependence on the type of electrode pretreatment procedure used. 60 refs., 49 figs., 3 tabs.

  20. Measuring quantum capacitance in energetically addressable molecular layers.

    PubMed

    Bueno, Paulo R; Davis, Jason J

    2014-02-01

    The Fermi level or electrochemical signature of a molecular film containing accessible orbital states is ultimately governed by two measurable series energetic components, an energy loss term related to the charging of appropriately addressable molecular orbitals (resonant or charge transfer resistance), and an energy storage or electrochemical capacitance component. The latter conservative term is further divisible into two series contributions, one being a classic electrostatic term and the other arising from the involvement and charging of quantized molecular orbital states. These can be tuned in and out of resonance with underlying electrode states with an efficiency that governs electron transfer kinetics and an energetic spread dependent on solution dielectric. These features are experimentally resolved by an impedance derived capacitance analysis, a methodology which ultimately enables a convenient spectroscopic mapping of electron transfer efficacy, and of density of states within molecular films. PMID:24405523

  1. Capacitive micromachined ultrasonic transducers (CMUTs) with isolation posts.

    PubMed

    Huang, Yongli; Zhuang, Xuefeng; Haeggstrom, Edward O; Ergun, A Sanli; Cheng, Ching-Hsiang; Khuri-Yakub, Butrus T

    2008-03-01

    In this paper, an improved design of a capacitive micromachined ultrasonic transducer (CMUT) is presented. The design improvement aims to address the reliability issues of a CMUT and to extend the device operation beyond the contact (collapse) voltage. The major design novelty is the isolation posts in the vacuum cavities of the CMUT cells instead of full-coverage insulation layers in conventional CMUTs. This eliminates the contact voltage drifting due to charging caused by the insulation layer, and enables repeatable CMUT operation in the post-contact regime. Ultrasonic tests of the CMUTs with isolation posts (PostCMUTs) in air (electrical input impedance and capacitance vs. bias voltage) and immersion (transmission and reception) indicate acoustic performance similar to that obtained from conventional CMUTs while no undesired side effects of this new design is observed. PMID:18207212

  2. Capacitance probe for fluid flow and volume measurements

    NASA Technical Reports Server (NTRS)

    Arndt, G. Dickey (Inventor); Nguyen, Thanh X. (Inventor); Carl, James R. (Inventor)

    1995-01-01

    Method and apparatus for making measurements on fluids are disclosed, including the use of a capacitive probe for measuring the flow volume of a material within a flow stream. The capacitance probe has at least two elongate electrodes and, in a specific embodiment of the invention, has three parallel elongate electrodes with the center electrode being an extension of the center conductor of a co-axial cable. A conductance probe is also provided to provide more accurate flow volume data in response to conductivity of the material within the flow stream. A preferred embodiment of the present invention provides for a gas flow stream through a microgravity environment that allows for monitoring a flow volume of a fluid sample, such as a urine sample, that is entrained within the gas flow stream.

  3. Capacitance Probe for Fluid Flow and Volume Measurements

    NASA Technical Reports Server (NTRS)

    Arndt, G. Dickey (Inventor); Nguyen, Thanh X. (Inventor); Carl, James R. (Inventor)

    1997-01-01

    Method and apparatus for making measurements on fluids are disclosed, including the use of a capacitive probe for measuring the flow volume of a material within a flow stream. The capacitance probe has at least two elongate electrodes and, in a specific embodiment of the invention, has three parallel elongate electrodes with the center electrode being an extension of the center conductor of a co-axial cable. A conductance probe is also provided to provide more accurate flow volume data in response to conductivity of the material within the flow stream. A preferred embodiment of the present invention provides for a gas flow stream through a micro-gravity environment that allows for monitoring a flow volume of a fluid sample, such as a urine sample, that is entrained within the gas flow stream.

  4. A High Temperature Capacitive Humidity Sensor Based on Mesoporous Silica

    PubMed Central

    Wagner, Thorsten; Krotzky, Sören; Weiß, Alexander; Sauerwald, Tilman; Kohl, Claus-Dieter; Roggenbuck, Jan; Tiemann, Michael

    2011-01-01

    Capacitive sensors are the most commonly used devices for the detection of humidity because they are inexpensive and the detection mechanism is very specific for humidity. However, especially for industrial processes, there is a lack of dielectrics that are stable at high temperature (>200 °C) and under harsh conditions. We present a capacitive sensor based on mesoporous silica as the dielectric in a simple sensor design based on pressed silica pellets. Investigation of the structural stability of the porous silica under simulated operating conditions as well as the influence of the pellet production will be shown. Impedance measurements demonstrate the utility of the sensor at both low (90 °C) and high (up to 210 °C) operating temperatures. PMID:22163790

  5. Microbial desalination cell with capacitive adsorption for ion migration control.

    PubMed

    Forrestal, Casey; Xu, Pei; Jenkins, Peter E; Ren, Zhiyong

    2012-09-01

    A new microbial desalination cell with capacitive adsorption capability (cMDC) was developed to solve the ion migration problem facing current MDC systems. Traditional MDCs remove salts by transferring ions to the anode and cathode chambers, which may prohibit wastewater beneficial reuse due to increased salinity. The cMDC uses adsorptive activated carbon cloth (ACC) as the electrodes and utilizes the formed capacitive double layers for electrochemical ion adsorption. The cMDC removed an average of 69.4% of the salt from the desalination chamber through electrode adsorption during one batch cycle, and it did not add salts to the anode or cathode chamber. It was estimated that 61-82.2mg of total dissolved solids (TDS) was adsorbed to 1g of ACC electrode. The cMDC provides a new approach for salt management, organic removal, and energy production. Further studies will be conducted to optimize reactor configuration and achieve in situ electrode regeneration. PMID:22784594

  6. Electrically Small Folded Slot Antenna Utilizing Capacitive Loaded Slot Lines

    NASA Technical Reports Server (NTRS)

    Scardelletti, Maximilian C.; Ponchak, George E.; Merritt, Shane; Minor, John S.; Zorman, Christian A.

    2007-01-01

    This paper presents an electrically small, coplanar waveguide fed, folded slot antenna that uses capacitive loading. Several antennas are fabricated with and without capacitive loading to demonstrate the ability of this design approach to reduce the resonant frequency of the antenna, which is analogous to reducing the antenna size. The antennas are fabricated on Cu-clad Rogers Duriod(TM) 6006 with multilayer chip capacitors to load the antennas. Simulated and measured results show close agreement, thus, validating the approach. The electrically small antennas have a measured return loss greater than 15 dB and a gain of 5.4, 5.6, and 2.7 dBi at 4.3, 3.95, and 3.65 GHz, respectively.

  7. Mapping Capacitive Coupling Among Pixels in a Sensor Array

    NASA Technical Reports Server (NTRS)

    Seshadri, Suresh; Cole, David M.; Smith, Roger M.

    2010-01-01

    An improved method of mapping the capacitive contribution to cross-talk among pixels in an imaging array of sensors (typically, an imaging photodetector array) has been devised for use in calibrating and/or characterizing such an array. The method involves a sequence of resets of subarrays of pixels to specified voltages and measurement of the voltage responses of neighboring non-reset pixels.

  8. Biphasic Role of Calcium in Mouse Sperm Capacitation Signaling Pathways

    PubMed Central

    Alvau, Antonio; Escoffier, Jessica; Krapf, Dario; Sánchez-Cárdenas, Claudia; Salicioni, Ana M.; Darszon, Alberto; Visconti, Pablo E.

    2016-01-01

    Mammalian sperm acquire fertilizing ability in the female tract in a process known as capacitation. At the molecular level, capacitation is associated with up-regulation of a cAMP-dependent pathway, changes in intracellular pH, intracellular Ca2+ and an increase in tyrosine phosphorylation. How these signaling systems interact during capacitation is not well understood. Results presented in this study indicate that Ca2+ ions have a biphasic role in the regulation of cAMP-dependent signaling. Media without added Ca2+ salts (nominal zero Ca2+) still contain micromolar concentrations of this ion. Sperm incubated in this medium did not undergo PKA activation or the increase in tyrosine phosphorylation suggesting that these phosphorylation pathways require Ca2+. However, chelation of the extracellular Ca2+ traces by EGTA induced both cAMP-dependent phosphorylation and the increase in tyrosine phosphorylation. The EGTA effect in nominal zero Ca2+ media was mimicked by two calmodulin antagonists, W7 and calmidazolium, and by the calcineurin inhibitor cyclosporine A. These results suggest that Ca2+ ions regulate sperm cAMP and tyrosine phosphorylation pathways in a biphasic manner and that some of its effects are mediated by calmodulin. Interestingly, contrary to wild type mouse sperm, sperm from CatSper1 KO mice underwent PKA activation and an increase in tyrosine phosphorylation upon incubation in nominal zero Ca2+ media. Therefore, sperm lacking Catsper Ca2+ channels behave as wild-type sperm incubated in the presence of EGTA. This latter result suggests that Catsper transports the Ca2+ involved in the regulation of cAMP-dependent and tyrosine phosphorylation pathways required for sperm capacitation. PMID:25597298

  9. Capacitance-based damage detection sensing for aerospace structural composites

    NASA Astrophysics Data System (ADS)

    Bahrami, P.; Yamamoto, N.; Chen, Y.; Manohara, H.

    2014-04-01

    Damage detection technology needs improvement for aerospace engineering application because detection within complex composite structures is difficult yet critical to avoid catastrophic failure. Damage detection is challenging in aerospace structures because not all the damage detection technology can cover the various defect types (delamination, fiber fracture, matrix crack etc.), or conditions (visibility, crack length size, etc.). These defect states are expected to become even more complex with future introduction of novel composites including nano-/microparticle reinforcement. Currently, non-destructive evaluation (NDE) methods with X-ray, ultrasound, or eddy current have good resolutions (< 0.1 mm), but their detection capabilities is limited by defect locations and orientations and require massive inspection devices. System health monitoring (SHM) methods are often paired with NDE technologies to signal out sensed damage, but their data collection and analysis currently requires excessive wiring and complex signal analysis. Here, we present a capacitance sensor-based, structural defect detection technology with improved sensing capability. Thin dielectric polymer layer is integrated as part of the structure; the defect in the structure directly alters the sensing layer's capacitance, allowing full-coverage sensing capability independent of defect size, orientation or location. In this work, capacitance-based sensing capability was experimentally demonstrated with a 2D sensing layer consisting of a dielectric layer sandwiched by electrodes. These sensing layers were applied on substrate surfaces. Surface indentation damage (~1mm diameter) and its location were detected through measured capacitance changes: 1 to 250 % depending on the substrates. The damage detection sensors are light weight, and they can be conformably coated and can be part of the composite structure. Therefore it is suitable for aerospace structures such as cryogenic tanks and rocket

  10. Capacitive Extensometer Particularly Suited for Measuring in Vivo Bone Strain

    NASA Technical Reports Server (NTRS)

    Perusek, Gail P. (Inventor)

    2000-01-01

    The present invention provides for in vivo measurements of the principal strain magnitudes and directions, and maximum shear strain that occurs in a material, such as human bone, when it is loaded (or subjected to a load). In one embodiment the invention includes a capacitive delta extensometer arranged with six sensors in a three piece configuration, with each sensor of each pair spaced apart from each other by 120 degrees.