Science.gov

Sample records for capacite plastique des

  1. Analyse Pharmaceutique de la prescription des antibiotiques au service des brules et chirurgie plastique de l'Hopital Militaire d'Instruction Mohammed V, Maroc

    PubMed Central

    Benziane, H.; Karfo, R.; Siah, S.; Taoufik, J.

    2011-01-01

    Summary L'infection est longtemps restée la principale cause de mortalité chez le brûlé grave. Ce travail a pour but d'évaluer la prescription des antibiotiques dans notre Service des Brûlés et Chirurgie Plastique, au regard du dossier d'autorisation de mise sur le marché (Résumé des caractéristiques du produit). Tous les patients sous antibiothérapie, au Service des Brûlés et Chirurgie Plastique de l'Hôpital Militaire d'Instruction Mohammed V de Rabat, Maroc, durant la période janvier 2008/mai 2009, ont été inclus. Il s'agit d'une étude rétrospective qui a analysé 41 dossiers de patients. Les antibiotiques utilisés par le service appartiennent à différentes familles. Les plus utilisés sont les bêta-lactamines (65%), glycopeptides (10,5%), aminosides (9%), quinolones (7%) et colistine (4,3%), avec 4,2% pour les autres classes d'antibiotiques (métronidazole 500 mg en perfusion, fluconazole injectable 100 mg/50 ml, rifampicine 600 mg en perfusion, sulfadiazine argentique crème, acide fusidique 2% crème, etc.); 70% des prescriptions sont non documentées. La voie injectable est prépondérante (89%). En tout, 227 ordonnances nominatives d'antibiothérapie ont été analysées: la posologie et les contre-indications ont été respectées par rapport à l'autorisation de mise sur le marché. Trois cas d'interactions médicamenteuses ont été relevés (fluconazole-rifampicine, fluconazole-Saccharomyces boulardii, amikacine-vancomycine). Ce constat montre l'importance de l'analyse pharmaceutique des prescriptions des antibiotiques dans un service utilisant des antibiotiques de la réserve hospitalière, donc actifs mais très toxiques. PMID:22396670

  2. Épidémiologie des brûlures de la main chez les enfants vus dans le Centre National des Brûlés et de Chirurgie Plastique de Casablanca, Maroc

    PubMed Central

    Rafik, A.; Lahlou, M.; Diouri, M.; Bahechar, N.; Chlihi, A.

    2015-01-01

    Summary Les brûlures de la main chez l’enfant constituent une source de séquelles invalidantes. A cet régard, la conservation et la restauration complète de la fonction de la main demeurent le but primordial de la prise en charge. Afin de répertorier les caractéristiques épidémiologiques, cliniques et évolutives des mains brûlées, nous avons réalisé une étude rétrospective étalée sur 4 ans, de janvier 2011 à janvier 2015. Cette étude a permis de colliger les cas de 313 enfants atteints de brûlure de la main vus dans le Centre National des Brulés et de Chirurgie Plastique du CHU Ibn Rochd de Casablanca. La majorité des brûlures touche les enfants de 3 à 6 ans (70% des cas), avec une légère prédominance masculine. La principale cause des brûlures survenant à cet âge est l’ébouillantement. Les brûlures par flamme représentent 33% des cas, celles par électricité 4,5%. Les brûlures chimiques et par contact sont anecdotiques (1 cas chacune). L’accident survient le plus souvent à domicile. Soixante douze pour cent des brûlures ont guéri spontanément. Afin de diminuer l’incidence de ces accidents, une approche préventive faite de sensibilisation et d’éducation devrait faire partie du cursus scolaire. PMID:27777543

  3. La Greffe de Peau dans le Traitement des Sequelles de la Main Brulee. A Propos de 152 Cas - Experience du Service de Chirurgie Plastique du Centre Hospitalier Universitaire Ibn-Sina, Rabat, Maroc

    PubMed Central

    El Mazouz, S.; Fejjal, N.; Hafidi, J.; Cherkab, L.; Mejjati, H.; Belfqih, R.; Gharib, N.; Abbassi, A.

    2010-01-01

    Summary La main est fréquemment exposée aux brûlures, entraînant des séquelles esthétiques et fonctionnelles. Le traitement de ces séquelles est surtout chirurgical et consiste en la greffe de peau, dont le type dépend de la localisation de la brûlure et du type des séquelles. Dans ce travail rétrospectif, nous rapportons une série de 152 cas de brûlures des mains colligés au service de chirurgie plastique du Centre Hospitalier Universitaire Ibn-Sina de Rabat sur une période de dix ans, allant de 1998 à 2007. Les indications thérapeutiques dépendent du type de séquelles et de la localisation de la brûlure. En tout, 97 patients ont bénéficié d'une greffe cutanée, dont 76% par greffe de peau totale, 21% par greffe de peau demi-épaisse et 3% par peau fine. Les séquelles des brûlures des mains posent un problème thérapeutique majeur, malgré la diversité des procédés chirurgicaux, d'où l'intérêt de la prévention. PMID:21991196

  4. Cellules solaires photovoltaïques plastiques enjeux et perspectives

    NASA Astrophysics Data System (ADS)

    Sicot, L.; Dumarcher, V.; Raimond, P.; Rosilio, C.; Sentein, C.; Fiorini, C.

    2002-04-01

    Après avoir détaillé le fonctionnement d'une cellule photovoltaïque plastique et les paramètres photovoltaïques permettant de caractéiser son efficacité, un état de l'art des technologies de fabrication des cellules est présenté. Des moyens d'amélioration des performances des cellules photovoltaïques organiques sont ensuite illustrés par l'étude de dispositifs développés au Laboratoire Composants Organiques (LCO) du CEA Saclay.

  5. Ablation laser pour la microélectronique plastique

    NASA Astrophysics Data System (ADS)

    Alloncle, A.-P.; Thomas, B.; Grojo, D.; Delaporte, Ph.; Sentis, M.; Sanaur, S.; Barret, M.; Collot, Ph.

    2006-12-01

    La microélectronique plastique connaît un développement sans précédent dans le domaine de la recherche. Cette étude s'intéresse à l'utilisation des lasers impulsionnels pour la réalisation de composants organiques sur supports souples. Les deux aspects plus particulièrement étudiés sont d'une part la gravure de polymère pour réaliser un canal entre la source et le drain, et d'autre part le développement d'un procédéde dépôt appelé LIFT pour Laser Induced Forward Transfer. Ce dernier pourrait notamment permettre dedéposer des composés organiques non solubles.

  6. Optimisation thermique de moules d'injection construits par des processus génératifs

    NASA Astrophysics Data System (ADS)

    Boillat, E.; Glardon, R.; Paraschivescu, D.

    2002-12-01

    Une des potentialités les plus remarquables des procédés de production génératifs, comme le frittage sélectif par laser, est leur capacité à fabriquer des moules pour l'injection plastique équipés directement de canaux de refroidissement conformes, parfaitement adaptés aux empreintes Pour que l'industrie de l'injection puisse tirer pleinement parti de cette nouvelle opportunité, il est nécessaire de mettre à la disposition des moulistes des logiciels de simulation capables d'évaluer les gains de productivité et de qualité réalisables avec des systèmes de refroidissement mieux adaptés. Ces logiciels devraient aussi être capables, le cas échéant, de concevoir le système de refroidissement optimal dans des situations où l'empreinte d'injection est complexe. Devant le manque d'outils disponibles dans ce domaine, le but de cet article est de proposer un modèle simple de moules d'injection. Ce modèle permet de comparer différentes stratégies de refroidissement et peut être couplé avec un algorithme d'optimisation.

  7. Capacité de transport et de limitation du courant des matériaux YBaCuO texturés

    NASA Astrophysics Data System (ADS)

    Porcar, L.; Bourgault, D.; Belmont, O.; Noudem, J. G.; Barbut, J. M.; Barrault, M.; Tixador, P.; Chaud, X.; Tournier, R.

    1998-01-01

    Pulsed and permanent sinusoidal transport current have been applied to melt textured Y_1Ba_2Cu_3O_{7-δ} in order to estimate its current limitation capability. High pulsed transport currents reaching 9000 A (23 000 A / cm^2) crossed a 4 cm long sample. In permanent sinusoidal current, 3000 A (7800 A / cm^2) crossed the sample without showing any resistive losses. Above the critical current, the transition from the superconducting to the normal state is strongly abrupt. Afin de déterminer la capacité à limiter le courant du composé Y_1Ba_2Cu_3O_{7-δ} texturé, des études en courants de transport élevés, en régime pulsé et en régime permanent alternatif, ont été menées. Il en résulte que YBaCuO possède une forte capacité de transport du courant en régime pulsé (9000 A soit 23 000 A / cm^2 dans un barreau de 4 cm de long) et en régime permanent alternatif (3000 A soit 7800 A / cm^2) et que le retour à l'état normal par dépassement du courant critique est très abrupt.

  8. Validation and Verification of NATO Network Enabled Capabilities (Validation et verification des capacites reseau de l’OTAN (NNEC))

    DTIC Science & Technology

    2008-07-01

    V&V) correcte. L’objectif de cet atelier consistait à réunir des membres des pays participants de l’OTAN en vue de discuter de la V&V d’une NNEC...Pour cet atelier , le postulat était que la vérification détermine si la NNEC réalise ce pour quoi elle a été conçue, et la validation détermine si la...14 septembre 2007. Les pays participant à cet atelier comprenaient le Canada, l’Estonie, l’Italie, les Pays Bas, l’Espagne, la Turquie, le Royaume

  9. T-bone plastique for treatment of brachy-turricephaly.

    PubMed

    Donauer, E; Bernardy, M; Neuenfeldt, D

    1993-01-01

    The "T-Bone Plastique", which is presented in this paper, allows a surgical correction even of extreme cases of brachy-turricephaly together with malformations of the occipital region in one operative session. Brachy-turricephaly is characterized by abnormal vertical height of the skull and a shortening of its anterior-posterior length, frequently combined with malformations of the occipital region. Resection of the prematurely closed coronal suture, bi-parietal trepanations with 90 degrees rotation and side-exchange of the parietal bone flaps, double transverse trepanation of the occipital bone and outward bending and shifting of the bone fragments enable a bony remodeling and normalization of the deformed skull. Using this operative technique in three children we achieved a significant improvement of the skull form with an aesthetically pleasing result, without any neurologic sequelae and with normal development of the children during follow-up.

  10. Étude par la méthode de Monte Carlo de la phase plastique de la quinuclidine à différentes températures

    NASA Astrophysics Data System (ADS)

    Jumeau, Daniel; André, Daniel

    La phase plastique (c.f.c.) de la quinuclidine est étudiée à différentes températures par la méthode de Monte Carlo utilisant la technique des matrices de compatibilité. Afin de ne pas modifier la symétrie moyenne du réseau, les centres de masse de molécules sont supposés fixes. Les orientations moléculaires sont choisies de façon aléatoire parmi les 48 orientations équivalentes et discernables du groupe c.f.c. Cela permet une mémorisation préalable des énergies d'interaction entre molécules voisines et un gain de temps de calcul considérable. Nous observons alors un blocage des réorientations moléculaires à basse température, tandis que la symétrie cristalline devient monoclinique. Ceci est interprété en termes de transition de phase dont la température (215 K) et la variation d'énergie (5 kJ mol-1) sont très proches des valeurs expérimentales.

  11. Plastique: A synchrotron radiation beamline for time resolved fluorescence in the frequency domain

    NASA Astrophysics Data System (ADS)

    De Stasio, Gelsomina; Zema, N.; Antonangeli, F.; Savoia, A.; Parasassi, T.; Rosato, N.

    1991-06-01

    PLASTIQUE is the only synchrotron radiation beamline in the world that performs time resolved fluorescence experiments in frequency domain. These experiments are extremely valuable sources of information on the structure and dynamics of molecules. We describe the beamline and some initial data.

  12. Capacitive transducers

    NASA Technical Reports Server (NTRS)

    Lucifredi, A. L.

    1970-01-01

    The theory, applications, and possible structural designs of capacitive transducers are presented. Emphasis is placed on the circuits used in connection with the sensors, such as AM, FM, resonant circuits, mode circuits, direct current circuits, and special circuits. Some criteria for selection of a design or the purchase of a commercial device are given.

  13. Optimisation des structures métalliques fléchies dans un calcul plastique

    NASA Astrophysics Data System (ADS)

    Geara, F.; Raphael, W.; Kaddah, F.

    2005-05-01

    The steel structure is a type of construction that is very developed in civil engineering. In the phase of survey and then of execution and installation of a metal work, the phase of conception is often the place of discontinuities that prevents the global optimization of material steel. In our survey, we used the traditional approach of optimization that is essentially based on the minimization of the weight of the structure, while taking advantages of plastic properties of steel in the case of a bending structure. It has been permitted because of to the relation found between the areas of the sections of the steel elements and the plastic moment of these sections. These relations have been drawn for different types of steel. In order to take advantages of the linear programming, a simplification has been introduced in transforming these relation to linear relations, which permits us to use simple methods as the simplex theorem. This procedure proves to be very interesting in the first phases of the survey and give very interesting results.

  14. L’évaluation systématique des instruments pour mesurer la douleur chez les personnes âgées ayant des capacités réduites à communiquer*

    PubMed Central

    Aubin, Michèle; Giguère, Anik; Hadjistavropoulos, Thomas; Verreault, René

    2007-01-01

    La douleur chronique est souvent sous-détectée et insuffisamment traitée dans les milieux de soins de longue durée. Les outils d’autorapport (ou autoévaluation) de la douleur, comme l’échelle visuelle analogique, n’ont été validés que partiellement chez les populations âgées, en raison de la prévalence élevée de déficits visuels, auditifs, moteurs et cognitifs que l’on y trouve. Des outils d’observation des patients ont été développés pour pallier ces difficultés d’utilisation des échelles d’autorapport de la douleur. Le présent projet vise l’identification de ces échelles et leur évaluation sur la base de la validité de contenu (12 questions), de la validité de construit (12 questions), de la fiabilité (13 questions) et de l’utilité clinique (10 questions). Parmi les 24 instruments recensés, plusieurs apparaissent prometteurs pour évaluer la douleur chez les personnes âgées atteintes de démence sévère. Des efforts additionnels de validation sont cependant requis avant leur intégration à la pratique régulière en soins de longue durée. PMID:17717611

  15. Trielectrode capacitive pressure transducer

    NASA Technical Reports Server (NTRS)

    Coon, G. W. (Inventor)

    1976-01-01

    A capacitive transducer and circuit especially suited for making measurements in a high-temperature environment are described. The transducer includes two capacitive electrodes and a shield electrode. As the temperature of the transducer rises, the resistance of the insulation between the capacitive electrode decreases and a resistive current attempts to interfere with the capacitive current between the capacitive electrodes. The shield electrode and the circuit coupled there reduce the resistive current in the transducer. A bridge-type circuit coupled to the transducer ignores the resistive current and measures only the capacitive current flowing between the capacitive electrodes.

  16. Injectabilite des coulis de ciment dans des milieux fissures

    NASA Astrophysics Data System (ADS)

    Mnif, Thameur

    Le travail presente ici est un bilan du travaux de recherche effectues sur l'injectabilite des coulis de ciment dans lu milieux fissures. Un certain nombre de coulis a base de ciment Portland et microfin ont ete selectionnes afin de caracteriser leur capacite a penetrer des milieux fissures. Une partie des essais a ete menee en laboratoire. L'etude rheologique des differents melanges a permis de tester l'influence de l'ajout de superplastifiant et/ou de fumee de silice sur la distribution granulometrique des coulis et par consequent sur leur capacite a injecter des colonnes de sable simulant un milieu fissure donne. La classe granulometrique d'un coulis, sa stabilite et sa fluidite sont apparus comme les trois facteurs principaux pour la reussite d'une injection. Un facteur de finesse a ete defini au cours de cette etude: base sur la classe granulometrique du ciment et sa stabilite, il peut entrer dans la formulation theorique du debit d'injection avant application sur chantier. La deuxieme et derniere partie de l'etude presente les resultats de deux projets de recherche sur l'injection realises sur chantier. L'injection de dalles de beton fissurees a permis le suivi de l'evolution des pressions avec la distance au point d'injection. L'injection de murs de maconnerie a caractere historique a montre l'importance de la definition de criteres de performance des coulis a utiliser pour traiter un milieu donne et pour un objectif donne. Plusieurs melanges peuvent ainsi etre predefinis et mis a disposition sur le chantier. La complementarite des ciments traditionnels et des ciments microfins devient alors un atout important. Le choix d'utilisation de ces melanges est fonction du terrain rencontre. En conclusion, cette recherche etablit une methodologie pour la selection des coulis a base de ciment et des pressions d'injection en fonction de l'ouverture des fissures ou joints de construction.

  17. Capacitive Power Transfer

    DTIC Science & Technology

    2010-12-15

    capacitive charger achieves near 80% e ciency at 3.7W with only 63 pF of coupling capacitance. An automatic tuning loop adjusts the frequency from...find the optimum circuit component values and operating point. A prototype capacitive charger achieves near 80% efficiency at 3.7 W with only 63 pF of...delivery in a smartphone sized package . Section 5 presents work in progress on a capacitively isolated LED driver. 2 Analysis The analysis is based on a

  18. Capacitive electrodes in electroencephalography.

    PubMed

    von Ellenrieder, Nicolás; Spinelli, Enrique; Muravchik, Carlos H

    2006-01-01

    We present a forward problem formulation for computing biopotentials measured with dry or capacitive electrodes. This formulation is not quasistatic and has mixed boundary conditions. Our results show that simple approximations to the measurements based on capacitive coupling are adequate in most situations. We study the range of validity and errors committed in the EEG forward and inverse problems when using this approximation.

  19. 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.

  20. 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.

  1. 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).

  2. 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.

  3. Modelisation des emissions de particules microniques et nanometriques en usinage

    NASA Astrophysics Data System (ADS)

    Khettabi, Riad

    La mise en forme des pieces par usinage emet des particules, de tailles microscopiques et nanometriques, qui peuvent etre dangereuses pour la sante. Le but de ce travail est d'etudier les emissions de ces particules pour fins de prevention et reduction a la source. L'approche retenue est experimentale et theorique, aux deux echelles microscopique et macroscopique. Le travail commence par des essais permettant de determiner les influences du materiau, de l'outil et des parametres d'usinage sur les emissions de particules. E nsuite un nouveau parametre caracterisant les emissions, nomme Dust unit , est developpe et un modele predictif est propose. Ce modele est base sur une nouvelle theorie hybride qui integre les approches energetiques, tribologiques et deformation plastique, et inclut la geometrie de l'outil, les proprietes du materiau, les conditions de coupe et la segmentation des copeaux. Il ete valide au tournage sur quatre materiaux: A16061-T6, AISI1018, AISI4140 et fonte grise.

  4. Capacitance Flatness Gauge Prototype

    SciTech Connect

    Pitas, A.; Angstadt, R.; /Fermilab

    1986-03-20

    The DO calorimeter has within it thousands of large plates. Our ability to construct the detector depends on the flatness of these plates. The performance of the detector depends on the flatness of the plates after they are assembled into a module. It has been proposed that the flatness of the plates before and after assembly could be determined by measuring capacitance. This device demonstrates the viability of using capacitance to measure the flatness of individual plates. No attempt has been made to extrapolate the results to measuring the flatness of the plates once they are in a module.

  5. U.S. plastic surgeons who contributed to the Revue de Chirurgie Plastique and the Revue de Chirurgie Structive (1931-1938): "Giants" in our specialty.

    PubMed

    Rogers, B O

    1999-01-01

    The Revue de Chirurgie Plastique and the Revue de Chirurgie Structive, Brussels (1931-1938), edited by Maurice Coelst, M.D. from Brussels, were the first, full-fledged medical publications specifically devoted to plastic, reconstructive, and aesthetic surgery. Publishing original articles by J.W. Maliniac, J. Eastman Sheehan, and brief summaries of papers read at plastic surgery societies by C.R. Straatsma, L.A. Peer, G. Aufricht, and other well-known American plastic surgeons, these Revues drew attention to surgeons, most of whom were responsible for organizing the American Society of Plastic and Reconstructive Surgeons in 1931, the same year in which the Revue de Chirurgie Plastique first appeared.

  6. 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.

  7. 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.

  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. 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.

  10. 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.

  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. [Thoughts on the Revue de Chirurgie Plastique (1931-34) and the Revue de Chirurgie Structive (1935-38)].

    PubMed

    Vrebos, J

    2007-08-01

    The history of modern plastic surgery starts when a young, restless ENT man, Dr M. Coelst, started a training in Plastic Surgery with Sebileau in Paris and Joseph in Berlin. This man of vision and far-sighted imagination realized that the separated efforts and publications of so many pioneers, scaterred all over the world, would be lost if not gathered in a scientific journal only devoted to plastic surgery for the benefit of all. This brought him to the idea of establishing, in 1931, at his own initiative, the first international Journal of Plastic Surgery ever published, the Revue de Chirurgie Plastique, fifteen years before the USA Journal Plastic and Reconstructive Surgery and sixteen years before the British Journal of Plastic Surgery. The name of the journal was changed in 1935 to the Revue de Chirurgie Structive. Coelst' Revue was promptly accepted as the leading Journal of Plastic Surgery and all the internationally known plastic Surgeons contributed to it by scientific papers of great value, even today.

  13. Elaboration de nouvelles approches micromecaniques pour l'optimisation des performances mecaniques des materiaux heterogenes

    NASA Astrophysics Data System (ADS)

    Aboutajeddine, Ahmed

    donner de bons resultats. Finalement, ce modele de Mori-Tanaka corrige est utilise avec les operateurs de Hill pour construire un modele de transition d'echelle pour les materiaux ayant une interphase elastoplastique. La loi de comportement effective trouvee est de nature incrementale et elle est conjuguee a la relation de la plasticite de l'interphase. Des simulations d'essais mecaniques pour plusieurs proprietes de l'interphase plastique a permis de dresser des profils de l'enrobage octroyant un meilleur comportement au materiau.

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  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. British plastic surgeons who contributed to the Revue de Chirurgie Plastique and the Revue de Chirurgie Structive (1931-1938): "the Big Four" in their Speciality.

    PubMed

    Rogers, B O

    2001-01-01

    The Revue de Chirurgie Plastique and the Revue de Chirurgie Structive, Brussels (1931-1938), edited by Maurice Coelst, M.D. from Brussels, were the first, full-fledged medical publications devoted specifically to plastic, reconstructive, and aesthetic surgery. Publishing original articles by H.D. Gillies, P.T. Kilner, A.H. McIndoe, and R. Mowlem--the "Big Four" as they were known to both English and American plastic surgeons--the Revues drew attention to these four surgeons who were mainly responsible for developing the prestige of English plastic surgery in the early 1930s.

  20. Scientific contributions of U.S. plastic surgeons to the Revue de Chirurgie Plastique and the Revue de Chirurgie Structive, Brussels (1931-1938).

    PubMed

    Vrebos, J

    1999-01-01

    The author emphasizes the close cooperation between U.S. plastic surgeons and the first international journal entirely devoted to plastic surgery, the Revue de Chirurgie Plastique (1931-1934) later to become the Revue de Chirurgie Structive (1935-1938) published under the editorship of Maurice Coelst, M.D. from Brussels. By the accurate recording of original articles, book reviews, proceedings of their annual meetings and summaries in three different languages (English, French, German), the author stresses the intense scientific dynamism and the achievements made by the U.S. pioneers of this new speciality, which really started during World War I.

  1. A novel capacitive micro-accelerometer with grid strip capacitances and sensing gap alterable capacitances

    NASA Astrophysics Data System (ADS)

    Linxi, Dong; Jindan, Chen; Haixia, Yan; Weihong, Huo; Yongjie, Li; Lingling, Sun

    2009-03-01

    The comb capacitances fabricated by deep reactive ion etching (RIE) process have high aspect ratio which is usually smaller than 30: 1 for the complicated process factors, and the combs are usually not parallel due to the well-known micro-loading effect and other process factors, which restricts the increase of the seismic mass by increasing the thickness of comb to reduce the thermal mechanical noise and the decrease of the gap of the comb capacitances for increasing the sensitive capacitance to reduce the electrical noise. Aiming at the disadvantage of the deep RIE, a novel capacitive micro-accelerometer with grid strip capacitances and sensing gap alterable capacitances is developed. One part of sensing of inertial signal of the micro-accelerometer is by the grid strip capacitances whose overlapping area is variable and which do not have the non-parallel plate's effect caused by the deep RIE process. Another part is by the sensing gap alterable capacitances whose gap between combs can be reduced by the actuators. The designed initial gap of the alterable comb capacitances is relatively large to depress the effect of the maximum aspect ratio (30 : 1) of deep RIE process. The initial gap of the capacitance of the actuator is smaller than the one of the comb capacitances. The difference between the two gaps is the initial gap of the sensitive capacitor. The designed structure depresses greatly the requirement of deep RIE process. The effects of non-parallel combs on the accelerometer are also analyzed. The characteristics of the micro-accelerometer are discussed by field emission microscopy (FEM) tool ANSYS. The tested devices based on slide-film damping effect are fabricated, and the tested quality factor is 514, which shows that grid strip capacitance design can partly improve the resolution and also prove the feasibility of the designed silicon-glass anodically bonding process.

  2. Dislocations et propriétés mécaniques des matériaux céramiques: Quelques problèmes

    NASA Astrophysics Data System (ADS)

    Castaing, J.; Dominguez Rodriguez, A.

    1995-11-01

    The study of plastic deformation of ceramic materials raised new problems on low temperature dislocation glide and high temperature dislocation climb. Mechanical behaviour can be explained. In this paper, we review some examples related to oxides which are linked to the activity of J. Philibert. L'étude de la déformation plastique de matériaux céramiques monocristallins a donné l'occasion de poser des nouveaux problèmes sur le glissement des dislocations à basse température et sur leur montée à haute température. Le comportement mécanique peut ainsi être expliqué. Nous passons en revue des cas concernant les oxydes dans lesquels J. Philibert a joué un rôle important.

  3. Shielded capacitive electrode

    DOEpatents

    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.

  4. 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.

  5. Traitement de surface par explosif du cuivre polycristallin : caractérisation microstructurale et comportement en fatigue plastique

    NASA Astrophysics Data System (ADS)

    Gerland, M.; Dufour, J. P.; Presles, H. N.; Violan, P.; Mendez, J.

    1991-10-01

    A new surface treatment technique with a primary explosive deposited in thin layer was applied to a polycrystalline pure copper. After treatment, surface roughness remains of high quality especially when compared to shot peened surfaces. The treated zone extends over several hundreds microns in depth and the microhardness profile exhibits a significant increasing of hardness with a maximum reaching 100% at the surface. The transmission electron microscopy shows a microstructure which changes with depth : below the surface, there is a thin recrystallized layer with very small grains followed by a region with numerous mechanical twins the density of which decreases when depth increases. Tested in fatigue with a constant plastic strain amplitude, the treated copper specimens exhibit a strong hardening from the first cycles compared to the untreated specimen ; however this initial hardening erases after 2% of the fatigue life. The fatigue resistance is not modified by the treatment. Une nouvelle technique de traitement de surface à l'aide d'un explosif primaire déposé en couche mince a été utilisée sur du cuivre pur polycristallin. L'état de surface après traitement reste de très bonne qualité, surtout comparé aux surfaces grenaillées. La zone traitée s'étend sur une profondeur de quelques centaines de microns et le profil de microdureté montre une importante augmentation de dureté avec un maximum en surface pouvant atteindre 100%. La micrcrostructure, observée par microscopie électronique en transmission, est caractérisée par une fine recristallisation en surface, puis par un abondant maclage dont la densité décroît lorsque la profondeur augmente. Testé en fatigue à déformation plastique imposée, le cuivre traité présente un fort écrouissage initial dès les premiers cycles, mais qui s'efface progressivement au cours du cyclage après 2% de la durée de vie, cette dernière n'étant pas modifiée par le traitement.

  6. 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.

  7. 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.

  8. The scientific contributions of British Plastic Surgeons to the Revue de Chirurgie Plastique and the Revue de Chirurgie Structive, Brussels (1931-1938).

    PubMed

    Vrebos, J

    2001-01-01

    In 1931, Maurice Coelst, M.D. from Brussels started the publication of the first international journal of plastic surgery ever published: the Revue de Chirurgie Plastique (1931-1934), which eventually became the Revue de Chirurgie Structive (1935-1938). In 1936, he established the first European Society of Structive Surgery, which held its first congress in Brussels. Further congresses were held in London in 1937 and in Milan in 1938. It is the collaboration and the participation of British plastic surgeons in this Society, this journal, and these meetings that I want to stress, because I am firmly convinced that these documents fill a gap in the history of Plastic Surgery in Great Britain, since--as far as I know--no detailed information concerning this period was ever published in Plastic Surgery literature.

  9. 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.

  10. Unified capacitance modelling of MOSFETs

    NASA Astrophysics Data System (ADS)

    Johannessen, O. G.; Fjeldly, T. A.; Ytterdal, T.

    1994-01-01

    A unified physics based capacitance model for MOSFETs suitable for implementation in circuit simulators is presented. This model is based on the charge conserving, so-called Meyer-like approach proposed by Turchetti et al., and utilizes a unified charge control model to assure a continuous description of the MOSFET capacitances both above and below threshold. The capacitances associated with the model are comparable to those of the well-known BSIM model in the above-threshold regime, but it is more precise in the description of near-threshold and subthreshold behaviour. Moreover, the discontinuities at the transitions between the various regimes of operation are removed. The present modelling scheme was implemented in our circuit simulator AIM-Spice, and simulations of the dynamic behaviour of various demanding benchmark circuits clearly reveal its superiority over simulations using the simple Meyer model.

  11. Bioenergetics of Mammalian Sperm Capacitation

    PubMed Central

    Ferramosca, Alessandra; Zara, Vincenzo

    2014-01-01

    After ejaculation, the mammalian male gamete must undergo the capacitation process, which is a prerequisite for egg fertilization. The bioenergetics of sperm capacitation is poorly understood despite its fundamental role in sustaining the biochemical and molecular events occurring during gamete activation. Glycolysis and mitochondrial oxidative phosphorylation (OXPHOS) are the two major metabolic pathways producing ATP which is the primary source of energy for spermatozoa. Since recent data suggest that spermatozoa have the ability to use different metabolic substrates, the main aim of this work is to present a broad overview of the current knowledge on the energy-producing metabolic pathways operating inside sperm mitochondria during capacitation in different mammalian species. Metabolism of glucose and of other energetic substrates, such as pyruvate, lactate, and citrate, is critically analyzed. Such knowledge, besides its obvious importance for basic science, could eventually translate into the development of novel strategies for treatment of male infertility, artificial reproduction, and sperm selection methods. PMID:24791005

  12. A l'ecole maternelle francaise: Vivre ensemble et pratiquer des activities d'art plastique. [In a French Nursery School: Living and Creating Together].

    ERIC Educational Resources Information Center

    International Journal of Early Childhood, 1999

    1999-01-01

    Discusses the role of collective creative activity in developing preschool children's multicultural understanding and ability to live together. Notes artistic and language-based activities used in French preschools to teach these concepts and develop critical and responsible behavior. (JPB)

  13. High on/off capacitance ratio RF MEMS capacitive switches

    NASA Astrophysics Data System (ADS)

    Wei, Hao; Deng, Zhongliang; Guo, Xubing; Wang, Yucheng; Yang, Hongtao

    2017-05-01

    In this paper, high on/off capacitance ratio radio frequency micro-electro-mechanical-systems (RF MEMS) switches are designed, fabricated, measured and analyzed. Two types of RF MEMS switches, a shunt switch with a contact point and an inline switch without a contact point, are presented. Metal-insulator-metal (MIM) fixed capacitors are used in the MEMS switches. The electrode topologies of RF MEMS switches are analyzed. The parameter λ is defined to describe the relationship between the capacitance ratio, the height of the beam and the actuation voltage. The measured results indicate that, for MEMS switch #1 with a contact point and gap of 1 µm, the insertion loss is better than 0.64 dB up to 40 GHz, and the isolation is more than 20 dB from 11.28 to 30.38 GHz with an actuation voltage of 42 V. For the inline MEMS with a displacement of 1.5 µm, the insertion loss is better than 0.56 dB up to 40 GHz, and the isolation is more than 20 dB from 4.45 to 30.48 GHz with an actuation voltage of 36 V. Circuit models and measured results of the proposed MEMS switches show good agreement. From the fitted results, the on/off capacitance ratio is ~227 for the MEMS switch #1 and ~313 for the MEMS switch #2, respectively. Compared with traditional MEMS capacitive switches with dielectric material Si3N4 and a relatively lower gap (1.5 µm), the proposed MEMS switches exhibit high on/off capacitance ratios.

  14. 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.

  15. Linearization techniques for capacitive sensors

    NASA Astrophysics Data System (ADS)

    Kar, Barun K.; Joseph, Eric

    1995-09-01

    Capacitive sensors are essential elements in many instrumentation circuits. The widespread use of these instruments and the need for integrating sensors on the same chip as the signal processing circuitry has motivated the developement of linearization techniques for the sensor output. Presented here are four methods which can be used to 'linearize' the essentially nonlinear nature of capacitive transducers. Described first is the polynomial linearization scheme, in which the Taylor series expansion of the sensor output is linearized by Khachab's method. An improvement in accuracy is obtained by the direct linearization scheme which scales the sensor output by the nonlinear denominator. Though this scheme is useful in cases where the signal processing circuitry must be separated from the interface circuitry, the hardware requirements are pretty intense. An alternative approach is the Summer-Divide scheme, wherein the difference and the sum of the top and bottom capacitances are ratioed to yield the linearized output. The last method is the constant charge injection scheme. Here a constant charge is put on top of the top of the plates and the subsequent voltages are differenced to yield a linear output. Nonlinearity associated with parasitic capacitances can be easily removed by feedback schemes.

  16. 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.

  17. 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.

  18. Capacitance Property of a Resonant Tunneling Diode

    NASA Astrophysics Data System (ADS)

    Sheng, Hanyu; Chua, Soo-Jin; Sinkkonen, Juha

    A simple capacitance formula based on a semiclassical electron transport theory is given. The results show that the charges stored in the quantum well of a resonant tunneling diode have a considerable effect on the capacitance in the resonant region. The calculated capacitance is consistent with the experimental results.

  19. Lambeaux autofermants pour le traitement des brulures electriques du scalp par haut voltage

    PubMed Central

    Hafidi, J.; El Mazouz, S.; El Mejatti, H.; Fejjal, N.; Gharib, N.E.; Abbassi, A.; Belmahi, A.M.

    2011-01-01

    Summary Les brûlures électriques par haut voltage sont responsables de gros dégâts tissulaires en immédiat et dans les jours suivant l’accident du fait de la chaleur importante dégagée par effet joule et de la thrombose microvasculaire évolutive. Les pertes de substances du scalp secondaires à ces brûlures nécessitent une couverture par lambeaux vu la destruction du périoste et du calvarium en regard. De juin 1997 à juin 2008, 15 patients ont été traités pour des pertes de substance du scalp secondaires à des brûlures électriques par haut voltage de diamètre allant de 8 à 11 cm et siégeant dans la région tonsurale. Ces patients ont été opérés dans la première semaine suivant l’accident. Les pertes de substance du scalp de taille moyenne secondaires à ces brûlures peuvent être couvertes per primam de façon fiable par des lambeaux locaux axialisés et multiples. Nous relatons l’expérience du Service de Chirurgie Plastique du Centre Hospitalier Universitaire Ibn-Sina, Rabat, Maroc, dans la gestion et la prise en charge de ces brûlures. PMID:22262963

  20. 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

  1. 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.

  2. Capacitive de-ionization electrode

    DOEpatents

    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.

  3. Des Moines.

    ERIC Educational Resources Information Center

    Gore, Deborah, Ed.

    1988-01-01

    This document, intended for elementary students, contains articles and activities designed to acquaint young people with the history of Des Moines, Iowa. The articles are short, and new or difficult words are highlighted and defined for young readers. "The Raccoon River Indian Agency" discusses the archeological exploration of the indian…

  4. Des Moines.

    ERIC Educational Resources Information Center

    Gore, Deborah, Ed.

    1988-01-01

    This document, intended for elementary students, contains articles and activities designed to acquaint young people with the history of Des Moines, Iowa. The articles are short, and new or difficult words are highlighted and defined for young readers. "The Raccoon River Indian Agency" discusses the archeological exploration of the indian…

  5. Capacitance variation measurement method with a continuously variable measuring range for a micro-capacitance sensor

    NASA Astrophysics Data System (ADS)

    Lü, Xiaozhou; Xie, Kai; Xue, Dongfeng; Zhang, Feng; Qi, Liang; Tao, Yebo; Li, Teng; Bao, Weimin; Wang, Songlin; Li, Xiaoping; Chen, Renjie

    2017-10-01

    Micro-capacitance sensors are widely applied in industrial applications for the measurement of mechanical variations. The measurement accuracy of micro-capacitance sensors is highly dependent on the capacitance measurement circuit. To overcome the inability of commonly used methods to directly measure capacitance variation and deal with the conflict between the measurement range and accuracy, this paper presents a capacitance variation measurement method which is able to measure the output capacitance variation (relative value) of the micro-capacitance sensor with a continuously variable measuring range. We present the principles and analyze the non-ideal factors affecting this method. To implement the method, we developed a capacitance variation measurement circuit and carried out experiments to test the circuit. The result shows that the circuit is able to measure a capacitance variation range of 0–700 pF linearly with a maximum relative accuracy of 0.05% and a capacitance range of 0–2 nF (with a baseline capacitance of 1 nF) with a constant resolution of 0.03%. The circuit is proposed as a new method to measure capacitance and is expected to have applications in micro-capacitance sensors for measuring capacitance variation with a continuously variable measuring range.

  6. 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

  7. 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.

  8. 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

  9. 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.

  10. 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.

  11. 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.

  12. Versatile and compact capacitive dilatometer

    SciTech Connect

    Schmiedeshoff, G. M.; Lounsbury, A. W.; Luna, D. J.; Tracy, S. J.; Schramm, A. J.; Tozer, S. W.; Correa, V. F.; Hannahs, S. T.; Murphy, T. P.; Palm, E. C.; Lacerda, A. H.; Bud'ko, S. L.; Canfield, P. C.; Smith, J. L.; Lashley, J. C.; Cooley, J. C.

    2006-12-15

    We describe the design, construction, calibration, and operation of a relatively simple differential capacitive dilatometer suitable for measurements of thermal expansion and magnetostriction from 300 to below 1 K with a low-temperature resolution of about 0.05 A ring . The design is characterized by an open architecture permitting measurements on small samples with a variety of shapes. Dilatometers of this design have operated successfully with a commercial physical property measurement system, with several types of cryogenic refrigeration systems, in vacuum, in helium exchange gas, and while immersed in liquid helium (magnetostriction only) to temperatures of 30 mK and in magnetic fields to 45 T.

  13. Aspheric Surface Measurement Using Capacitive Sensors

    PubMed Central

    Yuan, Daocheng; Zhao, Huiying; Tao, Xin; Li, Shaobo; Zhu, Xueliang; Zhang, Chupeng

    2017-01-01

    This paper proposes a new method for the measurement of spherical coordinates by using capacitive sensors as a non-contact probe solution of measurement of aspheric surfaces. The measurement of the average effect of the capacitive probe and the influence of capacitive probe tilting were studied with respect to an eccentric spherical surface. Based on the tested characteristic curve of the average effect of the sphere and probe, it was found that nonlinear and linear compensation resulted in high measurement accuracy. The capacitance probe was found to be trying to fulfill a need for performing nm-level precision measurement of aspheric electromagnetic surfaces. PMID:28604613

  14. Nucleotide capacitance calculation for DNA sequencing

    SciTech Connect

    Lu, Jun-Qiang; Zhang, Xiaoguang

    2008-01-01

    Using a first-principles linear response theory, the capacitance of the DNA nucleotides, adenine, cytosine, guanine and thymine, are calculated. The difference in the capacitance between the nucleotides is studied with respect to conformational distortion. The result suggests that although an alternate current capacitance measurement of a single-stranded DNA chain threaded through a nano-gap electrodes may not sufficient to be used as a stand alone method for rapid DNA sequencing, the capacitance of the nucleotides should be taken into consideration in any GHz-frequency electric measurements and may also serve as an additional criterion for identifying the DNA sequence.

  15. 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.

  16. 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…

  17. High temperature capacitive strain gage

    NASA Astrophysics Data System (ADS)

    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.

  18. Capacitive Feedthroughs for Medical Implants

    PubMed Central

    Grob, Sven; Tass, Peter A.; Hauptmann, Christian

    2016-01-01

    Important technological advances in the last decades paved the road to a great success story for electrically stimulating medical implants, including cochlear implants or implants for deep brain stimulation. However, there are still many challenges in reducing side effects and improving functionality and comfort for the patient. Two of the main challenges are the wish for smaller implants on one hand, and the demand for more stimulation channels on the other hand. But these two aims lead to a conflict of interests. This paper presents a novel design for an electrical feedthrough, the so called capacitive feedthrough, which allows both reducing the size, and increasing the number of included channels. Capacitive feedthroughs combine the functionality of a coupling capacitor and an electrical feedthrough within one and the same structure. The paper also discusses the progress and the challenges of the first produced demonstrators. The concept bears a high potential in improving current feedthrough technology, and could be applied on all kinds of electrical medical implants, even if its implementation might be challenging. PMID:27660602

  19. 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.

  20. 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.

  1. 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.

  2. Characterization of Textile-Insulated Capacitive Biosensors.

    PubMed

    Ng, Charn Loong; Reaz, Mamun Bin Ibne

    2017-03-12

    Capacitive biosensors are an emerging technology revolutionizing wearable sensing systems and personal healthcare devices. They are capable of continuously measuring bioelectrical signals from the human body while utilizing textiles as an insulator. Different textile types have their own unique properties that alter skin-electrode capacitance and the performance of capacitive biosensors. This paper aims to identify the best textile insulator to be used with capacitive biosensors by analysing the characteristics of 6 types of common textile materials (cotton, linen, rayon, nylon, polyester, and PVC-textile) while evaluating their impact on the performance of a capacitive biosensor. A textile-insulated capacitive (TEX-C) biosensor was developed and validated on 3 subjects. Experimental results revealed that higher skin-electrode capacitance of a TEX-C biosensor yields a lower noise floor and better signal quality. Natural fabric such as cotton and linen were the two best insulating materials to integrate with a capacitive biosensor. They yielded the lowest noise floor of 2 mV and achieved consistent electromyography (EMG) signals measurements throughout the performance test.

  3. Characterization of Textile-Insulated Capacitive Biosensors

    PubMed Central

    Ng, Charn Loong; Reaz, Mamun Bin Ibne

    2017-01-01

    Capacitive biosensors are an emerging technology revolutionizing wearable sensing systems and personal healthcare devices. They are capable of continuously measuring bioelectrical signals from the human body while utilizing textiles as an insulator. Different textile types have their own unique properties that alter skin-electrode capacitance and the performance of capacitive biosensors. This paper aims to identify the best textile insulator to be used with capacitive biosensors by analysing the characteristics of 6 types of common textile materials (cotton, linen, rayon, nylon, polyester, and PVC-textile) while evaluating their impact on the performance of a capacitive biosensor. A textile-insulated capacitive (TEX-C) biosensor was developed and validated on 3 subjects. Experimental results revealed that higher skin-electrode capacitance of a TEX-C biosensor yields a lower noise floor and better signal quality. Natural fabric such as cotton and linen were the two best insulating materials to integrate with a capacitive biosensor. They yielded the lowest noise floor of 2 mV and achieved consistent electromyography (EMG) signals measurements throughout the performance test. PMID:28287493

  4. Capacitive Biosensors and Molecularly Imprinted Electrodes

    PubMed Central

    Ertürk, Gizem; Mattiasson, Bo

    2017-01-01

    Capacitive biosensors belong to the group of affinity biosensors that operate by registering direct binding between the sensor surface and the target molecule. This type of biosensors measures the changes in dielectric properties and/or thickness of the dielectric layer at the electrolyte/electrode interface. Capacitive biosensors have so far been successfully used for detection of proteins, nucleotides, heavy metals, saccharides, small organic molecules and microbial cells. In recent years, the microcontact imprinting method has been used to create very sensitive and selective biorecognition cavities on surfaces of capacitive electrodes. This chapter summarizes the principle and different applications of capacitive biosensors with an emphasis on microcontact imprinting method with its recent capacitive biosensor applications. PMID:28218689

  5. 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.

  6. Capacitive Biosensors and Molecularly Imprinted Electrodes.

    PubMed

    Ertürk, Gizem; Mattiasson, Bo

    2017-02-17

    Capacitive biosensors belong to the group of affinity biosensors that operate by registering direct binding between the sensor surface and the target molecule. This type of biosensors measures the changes in dielectric properties and/or thickness of the dielectric layer at the electrolyte/electrode interface. Capacitive biosensors have so far been successfully used for detection of proteins, nucleotides, heavy metals, saccharides, small organic molecules and microbial cells. In recent years, the microcontact imprinting method has been used to create very sensitive and selective biorecognition cavities on surfaces of capacitive electrodes. This chapter summarizes the principle and different applications of capacitive biosensors with an emphasis on microcontact imprinting method with its recent capacitive biosensor applications.

  7. Cognitive Task Analysis (l’Analyse des taches cognitives)

    DTIC Science & Technology

    2000-10-01

    pilotage, guidage, gestion de produits chimiques), aujourd’hui, le CTA est principalement utilisé pour des tâches décisionnelles telles que le...adéquation entre les fonctions système et les capacités cognitives humaines (2) optimisation des performances système et de la charge de travail (3...S.E. DGA Etas Division Facteurs Humains Professor Emeritus Cognitive & Neural S&T Division BP 36 Route de Laval The University of Warwick Office of

  8. Les infections à Pseudomonas aeruginosa au service des maladies infectieuses du CHU YO, Burkina Faso: à propos deux cas

    PubMed Central

    Mamoudou, Savadogo; Lassina, Dao; Fla, Koueta

    2015-01-01

    Nous rapportons deux cas d'infection à Pseudomonas aeruginosa: un cas de méningite et un cas d'infection urinaire. Les auteurs rappellent qu’à côté des étiologies classiques des méningites et des infections urinaires, des germes résistants comme Pseudomonas aeruginosa peuvent être responsables d'infections à localisation méningées et urinaires et dont il faut connaître pour une bonne prise en charge. Le traitement de ces infections requiert un antibiogramme au regard de la grande capacité de résistance de Pseudomonas aeruginosa en milieu hospitalier. La limitation des gestes invasifs et l'application rigoureuse des mesures de prévention des infections en milieu hospitalier contribueront à lutter efficacement contre ces infections en milieu de soins. PMID:26491521

  9. Measurement of internal capacitances of integrated circuits

    NASA Astrophysics Data System (ADS)

    White, K.; Palmer, D.; Hawkins, C. F.; Martin, G. L.

    Direct probe measurements have been made of intra-transistor and interconnection capacitances in integrated circuit CMOS technologies down to 2 microns detail. Resolution of measurements have been confirmed to 1 femtofarad. These differential capacitance measurements are taken at 1 MHz, comparable to the normal frequency range of circuit operation. These measurements are performed directly on structures normally occurring on integrated circuit wafers, not on special enhanced capacitive test keys or using custon on-chip amplifiers. The method used the HP-4062B semiconductor parameter extractor. Elaborate shielding and ac-guarding of adjacent microfeatures were necessary to measure only the capacitances of interest. Extensive signal averaging and system capacitance canceling was performed. Although elaborate and detailed, the method developed can be used by any semiconductor production facility on their standard test structures. The voltage dependence of the junction capacitances of the drain to p-well and the gate to p-well were found consistent with calculation down to 2 micron dimensions. The gate to drain overlap capacitance was also examined allowing an estimate of the fringing contribution.

  10. Reducing the capacitance of piezoelectric film sensors

    SciTech Connect

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

    2016-04-15

    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{sup 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.

  11. 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.

  12. Effect of surface asperities on the capacitances of capacitive RF MEMS switches

    NASA Astrophysics Data System (ADS)

    Chen, Zhiqiang; Tian, Wenchao; Zhang, Xiaotong

    2017-03-01

    The effects of surface asperities on the up- and down-state capacitances of the capacitive radio frequency (RF) micro electromechanical system (MEMS) switches were studied in this paper based on the single asperity model and statics. The research results demonstrated that surface asperities effects on the up-state capacitance could be neglected, whereas surface asperities must be taken into consideration at the down-state position in the RF MEMS switches because the surface asperities significantly affected the down-state capacitance. The down-state capacitance typically decreased as the root mean square (RMS) roughness and asperity radius increased. The down-state capacitance was approximately 26% of the theoretical value when the RMS roughness was 20 nm, and 32% of the theoretical value when the asperity radius was 100 nm. The experimental results were in good agreement with the simulation results.

  13. Taylor expansions of band-bending in MOS capacitance: application to scanning capacitance microscopy

    NASA Astrophysics Data System (ADS)

    Murray, Hugues; Martin, Patrick; Bardy, Serge; Murray, Franck

    2008-03-01

    The differential capacitance C(Vg) = dQM/dVg in a metal-oxide-semiconductor structure introduces the silicon capacitance Cs(ΨS) = -dQS/dΨS depending on the surface band-bending ΨS at the oxide-semiconductor interface. In order to calculate the dependence of Cs on the gate voltage Vg, we propose in this paper a simple numerical method, based on first-order Taylor expansions, to inverse the explicit equation Vg = f(ΨS). This method is then applied to calculate the analytic differential capacitance of the scanning capacitance microscope (SCM) in all conditions relative to physical parameters of SCM such as oxide thickness, doping profiles and probe erosion. It results in a competitive tool for SCM users to evaluate the theoretical values of capacitance and differential capacitance in all configurations.

  14. Improved capacitive melting curve measurements

    NASA Astrophysics Data System (ADS)

    Sebedash, Alexander; Tuoriniemi, Juha; Pentti, Elias; Salmela, Anssi

    2009-02-01

    Sensitivity of the capacitive method for determining the melting pressure of helium can be enhanced by loading the empty side of the capacitor with helium at a pressure nearly equal to that desired to be measured and by using a relatively thin and flexible membrane in between. This way one can achieve a nanobar resolution at the level of 30 bar, which is two orders of magnitude better than that of the best gauges with vacuum reference. This extends the applicability of melting curve thermometry to lower temperatures and would allow detecting tiny anomalies in the melting pressure, which must be associated with any phenomena contributing to the entropy of the liquid or solid phases. We demonstrated this principle in measurements of the crystallization pressure of isotopic helium mixtures at millikelvin temperatures by using partly solid pure 4He as the reference substance providing the best possible universal reference pressure. The achieved sensitivity was good enough for melting curve thermometry on mixtures down to 100 μK. Similar system can be used on pure isotopes by virtue of a blocked capillary giving a stable reference condition with liquid slightly below the melting pressure in the reference volume. This was tested with pure 4He at temperatures 0.08-0.3 K. To avoid spurious heating effects, one must carefully choose and arrange any dielectric materials close to the active capacitor. We observed some 100 pW loading at moderate excitation voltages.

  15. 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.

  16. 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.

  17. 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.

  18. Capacitance imaging of the skin surface.

    PubMed

    Batisse, Dominique; Giron, Franck; Lévêque, Jean Luc

    2006-05-01

    A new device allowing recording capacitance images of the skin surface was recently presented. Parameters, extracted from the gray-level histogram of the images, are tested for a new approach of skin surface hydration measurement in comparison with the classical capacitance method. Illustration of the interest of having both images and parameters for studying the homogeneity and the level of skin surface hydration are presented. Software for selecting a region of interest from an image and measuring the parameters derived from its gray-level histogram was used to characterize skin hydration. There is a very close correlation between a Corneometer and the parameters extracted from the SkinChip measurements. The importance of having capacitance images of skin is demonstrated in case of non-homogeneity of the skin hydration, either because of photoaging or following an inflammation process. Capacitance imaging is a necessary tool for both completely describing and quantifying skin surface hydration.

  19. The skin landscape following nonoptical capacitance imaging.

    PubMed

    Xhauflaire-Uhoda, Emmanuelle; Piérard, Gérald E; Quatresooz, Pascale

    2010-01-01

    Skin capacitance is an electrical property measurable at the level of the stratum corneum. Values are related to the moisture content of the tissue. Using the silicon image sensor technology, it has recently become possible to measure capacitance at 50 microm intervals on the skin surface. The resulting nonoptical picture corresponds to skin capacitance imaging. This novel tool for dermatologists highlights with precision the hollow skin surface patterns, including dermatoglyphics, the patterns of the shallow skin lines, and wrinkles. The topographic heterogeneity in skin surface hydration is made visible. In addition, the sweat gland and follicular openings are disclosed. Skin disorders induced by surfactants or presenting as hyperkeratotic areas, including some neoplasms, may show typical aspects. It is concluded that skin capacitance imaging brings added value to the clinical assessment performed by dermatologists.

  20. Modeling technique of capacitive discharge pumping of metal vapor lasers for electrode capacitance optimization

    NASA Astrophysics Data System (ADS)

    Gubarev, F. A.; Evtushenko, G. S.; Vuchkov, N. K.; Sukhanov, V. B.; Shiyanov, D. V.

    2012-05-01

    To estimate optimum gas discharge tube (GDT) electrode capacitance of metal vapor lasers (MVLs) pumped by a longitudinal capacitive discharge, we offer to use series connection of capacitors to the electrodes of a conventionally pumped GDT with inner electrodes. It has been demonstrated that the maximum output power in CuBr lasers is obtained when the capacitances of high-voltage and ground electrodes are equal. When using a model circuit an average output power reaches 12 W that suggests the possibility of generating high average output power (>10 W) in MVLs pumped using a capacitive discharge.

  1. Experimental determination of dielectric barrier discharge capacitance

    NASA Astrophysics Data System (ADS)

    Pipa, A. V.; Hoder, T.; Koskulics, J.; Schmidt, M.; Brandenburg, R.

    2012-07-01

    The determination of electrical parameters (such as instantaneous power, transferred charge, and gas gap voltage) in dielectric barrier discharge (DBD) reactors relies on estimates of key capacitance values. In the classic large-scale sinusoidal-voltage driven DBD, also known as silent or ozonizer discharge, capacitance values can be determined from charge-voltage (Q-V) plot, also called Lissajous figure. For miniature laboratory reactors driven by fast pulsed voltage waveforms with sub-microsecond rise time, the capacitance of the dielectric barriers cannot be evaluated from a single Q-V plot because of the limited applicability of the classical theory. Theoretical determination can be problematic due to electrode edge effects, especially in the case of asymmetrical electrodes. The lack of reliable capacitance estimates leads to a "capacitance bottleneck" that obstructs the determination of other DBD electrical parameters in fast-pulsed reactors. It is suggested to obtain capacitance of dielectric barriers from a plot of the maximal charge versus maximal voltage amplitude (Qmax - Vmax plot) in a manner analogous to the classical approach. The method is examined using measurements of current and voltage waveforms of a coaxial DBD reactor in argon at 100 mbar driven by square voltage pulses with a rise time of 20 ns and with different voltage amplitudes up to 10 kV. Additionally, the applicability of the method has been shown for the data reported in literature measured at 1 bar of nitrogen-oxygen gas mixtures and xenon.

  2. Energy breakdown in capacitive deionization

    SciTech Connect

    Hemmatifar, Ali; Palko, James W.; Stadermann, Michael; Santiago, Juan G.

    2016-08-12

    We explored the energy loss mechanisms in capacitive deionization (CDI). We hypothesize that resistive and parasitic losses are two main sources of energy losses. We measured contribution from each loss mechanism in water desalination with constant current (CC) charge/discharge cycling. Resistive energy loss is expected to dominate in high current charging cases, as it increases approximately linearly with current for fixed charge transfer (resistive power loss scales as square of current and charging time scales as inverse of current). On the other hand, parasitic loss is dominant in low current cases, as the electrodes spend more time at higher voltages. We built a CDI cell with five electrode pairs and standard flow between architecture. We performed a series of experiments with various cycling currents and cut-off voltages (voltage at which current is reversed) and studied these energy losses. To this end, we measured series resistance of the cell (contact resistances, resistance of wires, and resistance of solution in spacers) during charging and discharging from voltage response of a small amplitude AC current signal added to the underlying cycling current. We performed a separate set of experiments to quantify parasitic (or leakage) current of the cell versus cell voltage. We then used these data to estimate parasitic losses under the assumption that leakage current is primarily voltage (and not current) dependent. Our results confirmed that resistive and parasitic losses respectively dominate in the limit of high and low currents. We also measured salt adsorption and report energy-normalized adsorbed salt (ENAS, energy loss per ion removed) and average salt adsorption rate (ASAR). As a result, we show a clear tradeoff between ASAR and ENAS and show that balancing these losses leads to optimal energy efficiency.

  3. Energy breakdown in capacitive deionization

    DOE PAGES

    Hemmatifar, Ali; Palko, James W.; Stadermann, Michael; ...

    2016-08-12

    We explored the energy loss mechanisms in capacitive deionization (CDI). We hypothesize that resistive and parasitic losses are two main sources of energy losses. We measured contribution from each loss mechanism in water desalination with constant current (CC) charge/discharge cycling. Resistive energy loss is expected to dominate in high current charging cases, as it increases approximately linearly with current for fixed charge transfer (resistive power loss scales as square of current and charging time scales as inverse of current). On the other hand, parasitic loss is dominant in low current cases, as the electrodes spend more time at higher voltages.more » We built a CDI cell with five electrode pairs and standard flow between architecture. We performed a series of experiments with various cycling currents and cut-off voltages (voltage at which current is reversed) and studied these energy losses. To this end, we measured series resistance of the cell (contact resistances, resistance of wires, and resistance of solution in spacers) during charging and discharging from voltage response of a small amplitude AC current signal added to the underlying cycling current. We performed a separate set of experiments to quantify parasitic (or leakage) current of the cell versus cell voltage. We then used these data to estimate parasitic losses under the assumption that leakage current is primarily voltage (and not current) dependent. Our results confirmed that resistive and parasitic losses respectively dominate in the limit of high and low currents. We also measured salt adsorption and report energy-normalized adsorbed salt (ENAS, energy loss per ion removed) and average salt adsorption rate (ASAR). As a result, we show a clear tradeoff between ASAR and ENAS and show that balancing these losses leads to optimal energy efficiency.« less

  4. Energy breakdown in capacitive deionization.

    PubMed

    Hemmatifar, Ali; Palko, James W; Stadermann, Michael; Santiago, Juan G

    2016-11-01

    We explored the energy loss mechanisms in capacitive deionization (CDI). We hypothesize that resistive and parasitic losses are two main sources of energy losses. We measured contribution from each loss mechanism in water desalination with constant current (CC) charge/discharge cycling. Resistive energy loss is expected to dominate in high current charging cases, as it increases approximately linearly with current for fixed charge transfer (resistive power loss scales as square of current and charging time scales as inverse of current). On the other hand, parasitic loss is dominant in low current cases, as the electrodes spend more time at higher voltages. We built a CDI cell with five electrode pairs and standard flow between architecture. We performed a series of experiments with various cycling currents and cut-off voltages (voltage at which current is reversed) and studied these energy losses. To this end, we measured series resistance of the cell (contact resistances, resistance of wires, and resistance of solution in spacers) during charging and discharging from voltage response of a small amplitude AC current signal added to the underlying cycling current. We performed a separate set of experiments to quantify parasitic (or leakage) current of the cell versus cell voltage. We then used these data to estimate parasitic losses under the assumption that leakage current is primarily voltage (and not current) dependent. Our results confirmed that resistive and parasitic losses respectively dominate in the limit of high and low currents. We also measured salt adsorption and report energy-normalized adsorbed salt (ENAS, energy loss per ion removed) and average salt adsorption rate (ASAR). We show a clear tradeoff between ASAR and ENAS and show that balancing these losses leads to optimal energy efficiency. Copyright © 2016 Elsevier Ltd. All rights reserved.

  5. Energy breakdown in capacitive deionization

    SciTech Connect

    Hemmatifar, Ali; Palko, James W.; Stadermann, Michael; Santiago, Juan G.

    2016-08-12

    We explored the energy loss mechanisms in capacitive deionization (CDI). We hypothesize that resistive and parasitic losses are two main sources of energy losses. We measured contribution from each loss mechanism in water desalination with constant current (CC) charge/discharge cycling. Resistive energy loss is expected to dominate in high current charging cases, as it increases approximately linearly with current for fixed charge transfer (resistive power loss scales as square of current and charging time scales as inverse of current). On the other hand, parasitic loss is dominant in low current cases, as the electrodes spend more time at higher voltages. We built a CDI cell with five electrode pairs and standard flow between architecture. We performed a series of experiments with various cycling currents and cut-off voltages (voltage at which current is reversed) and studied these energy losses. To this end, we measured series resistance of the cell (contact resistances, resistance of wires, and resistance of solution in spacers) during charging and discharging from voltage response of a small amplitude AC current signal added to the underlying cycling current. We performed a separate set of experiments to quantify parasitic (or leakage) current of the cell versus cell voltage. We then used these data to estimate parasitic losses under the assumption that leakage current is primarily voltage (and not current) dependent. Our results confirmed that resistive and parasitic losses respectively dominate in the limit of high and low currents. We also measured salt adsorption and report energy-normalized adsorbed salt (ENAS, energy loss per ion removed) and average salt adsorption rate (ASAR). As a result, we show a clear tradeoff between ASAR and ENAS and show that balancing these losses leads to optimal energy efficiency.

  6. Narrow gap electronegative capacitive discharges

    SciTech Connect

    Kawamura, E.; Lieberman, M. A.; Lichtenberg, A. J.

    2013-10-15

    Narrow gap electronegative (EN) capacitive discharges are widely used in industry and have unique features not found in conventional discharges. In this paper, plasma parameters are determined over a range of decreasing gap length L from values for which an electropositive (EP) edge exists (2-region case) to smaller L-values for which the EN region connects directly to the sheath (1-region case). Parametric studies are performed at applied voltage V{sub rf}=500 V for pressures of 10, 25, 50, and 100 mTorr, and additionally at 50 mTorr for 1000 and 2000 V. Numerical results are given for a parallel plate oxygen discharge using a planar 1D3v (1 spatial dimension, 3 velocity components) particle-in-cell (PIC) code. New interesting phenomena are found for the case in which an EP edge does not exist. This 1-region case has not previously been investigated in detail, either numerically or analytically. In particular, attachment in the sheaths is important, and the central electron density n{sub e0} is depressed below the density n{sub esh} at the sheath edge. The sheath oscillations also extend into the EN core, creating an edge region lying within the sheath and not characterized by the standard diffusion in an EN plasma. An analytical model is developed using minimal inputs from the PIC results, and compared to the PIC results for a base case at V{sub rf}=500 V and 50 mTorr, showing good agreement. Selected comparisons are made at the other voltages and pressures. A self-consistent model is also developed and compared to the PIC results, giving reasonable agreement.

  7. 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.

  8. Comportement rhéologique des systèmes mixtes biopolymères / protéines

    NASA Astrophysics Data System (ADS)

    Rebiha, M.; Moulai-Mostefa, N.; Sadok, A. Hadj; Sabri, N.

    2005-05-01

    Dans ce travail, on s'est intéressé à l'étude des effets du caséinate de sodium et du xanthane sur les propriétés rhéologiques des solutions aqueuses, préparées suivant un plan d'expériences. Les caractéristiques mécaniques obtenues sont traduites par les coefficients du modèle rhéologique de Casson, en l'occurrence la contrainte seuil, τ 0, et la viscosité plastique, η _c. Ainsi, à l'issue de la modélisation en surface de réponses, il apparaît une interaction répulsive à l'échelle structurale entre le caséinate de sodium et le xanthane, traduite par un abaissement considérable de τ 0. Cet baissement de la rigidité peut conduire à une séparation de phases, phénomène conditionné par la viscosité limite de Casson,η _c.

  9. Developpement des betons semi autoplacants a rheologie adaptee pour des infrastructures

    NASA Astrophysics Data System (ADS)

    Sotomayor Cruz, Cristian Daniel

    BSAP-I optimisés à travers une caractérisation complète des propriétés mécaniques et de la durabilité a été réalisée. A la suite de cette étude, les résultats obtenus nous permettent de conclure que : (1) L'utilisation d'un BSAP-I avec un gros granulat de 5 - 14 mm, des rapports E/L = 0,37 et S/G = 0,52 et une teneur en air de 6 à 9% a été possible en conférant un équilibre optimal fluidité / stabilité à l'état frais, ainsi qu'un niveau de thixotropie adéquate au chantier permettant d'optimiser la conception du coffrage des piliers de pont et de conférer des qualités de surfaces très acceptables de ces infrastructures. (2) La méthode adaptée pour l'essai L-Box contenant 2 barres et une vibration de 5 secondes a permis de bien caractériser la capacité de remplissage d'un BSAP-I. (3) L'utilisation d'un plan factoriel 23 a permis d'obtenir des modèles statistiques fiables, capables de prédire les propriétés rhéologiques à l'état frais et les résistances en compression des BSAP-I avec des dosages en liant entre 370 et 420 kg/m3, des rapports E/L entre 0,34 et 0,40 et S/G entre 0,47 et 0,53. (4) Des mesures de vitesse d'écoulement T40 d'un BSAP-I sont très semblables à celles d'un BAP. En plus, des valeurs T40 montrent une bonne corrélation linéaire avec celles de T400 mesurés dans la boîte L-Box. (5) À la frontière du BAP et du BCV, une bande rhéologique possédant un τ0 entre 30 et 320 Pa et un η entre 10 et 140 Pa.s a été trouvée pour la conception optimale des BSAP-I. (6) Les BSAP-I optimisés ont également conféré une très bonne performance à l'état frais, en permettant maintenir un bon équilibre entre la rhéologie et la stabilité dans le temps, lorsqu'on utilise une énergie de vibration minimale pour amorcer son écoulement. (7) À l'état durci Les BSAP-I ont conféré une bonne performance présentant des résistances mécaniques élevées et des niveaux négligeables de pénétration aux ions chlores

  10. Reconnaissance optique des formes en parallele utilisant des reseaux de neurones et une mire de reduction de dimensions

    NASA Astrophysics Data System (ADS)

    Gagne, Philippe

    Cette recherche vise à la mise en OEuvre optique de la reconnaissance des images en utilisant une mire d'anneaux afin de générer des vecteurs caractéristiques qui seront ensuite classifiés par un réseau de neurones. On proposera deux architectures originales: une qui permettra la reconnaissance invariante sous rotation en utilisant un corrélateur conjoint; l'autre montage permettra une classification en parallèle de plusieurs images grâce à la capacité des mires d'anneaux de compresser l'information. Ce dernier montage est basé sur un corrélateur 4F. On présentera des résultats optiques expérimentaux pour ces deux montages. Pour arriver à des résultats concluants on analysera le comportement des vecteurs obtenus à partir d'une mire d'anneaux, on introduira une règle d'apprentissage optimisant le pic de corrélation en réduisant les pics parasites et on corrigera à l'aide d'un algorithme génétique les modulations de phases générées par le modulateur spatial à cristaux liquides.

  11. Instrumentation for direct, low frequency scanning capacitance microscopy, and analysis of position dependent stray capacitance

    NASA Astrophysics Data System (ADS)

    Lee, David T.; Pelz, J. P.; Bhushan, Bharat

    2002-10-01

    We describe instrumentation for scanning capacitance microscopy (SCM), using an atomic force microscope, that is designed to make calibrated, low frequency measurements of tip-sample capacitance and spreading resistance of thin dielectric films. We also characterize spatial variations in stray capacitance Cstray that must be understood before such measurements can be interpreted. Existing SCM circuits are generally optimized for measuring dC/dV, and not for calibrated low frequency measurements of absolute capacitance. Our circuit uses a commercially available current amplifier and low frequency (˜5 kHz) lock-in detection. This circuit adds an inverted, constant amplitude current to suppress the stray displacement current from the large (˜0.5 pF) stray capacitance Cstray between the sample and the mm-sized cantilever-probe assembly. The capacitance noise spectrum is ˜0.35 aF/√Hz and is flat down to 1 Hz measurement frequency, with an integrated noise <5 aF integrated over a 1-160 Hz bandwidth. We have also used this instrumentation to identify and characterize significant (>1 fF) variations in Cstray that must be understood in order to accurately measure aF-level variations in the nm-scale tip-sample capacitance. We find that Cstray varies with lateral probe position. This is due to tilting of the probe assembly as the piezoelectric scanner tube bends during scanning. We also find that Cstray varies significantly with probe-assembly height. This causes topography related artifacts in capacitance images of rough surfaces. However, we show that stray capacitance artifacts can be mostly eliminated by properly characterizing position and height dependent variations in Cstray and subtracting them from measured capacitance data.

  12. 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

  13. Capacitive Deionization of High-Salinity Solutions

    DOE PAGES

    Sharma, Ketki; Gabitto, Jorge; Mayes, Richard T.; ...

    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

  14. 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.

  15. 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

  16. 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.

  17. Negative capacitance in a ferroelectric capacitor.

    PubMed

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

    2015-02-01

    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 a phase transition, could provide a solution, but a direct measurement of negative capacitance has so far been elusive. Here, we report the observation of negative capacitance in a thin, epitaxial ferroelectric film. 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. Analysis of this 'inductance'-like behaviour from a capacitor presents an unprecedented insight into the intrinsic energy profile of the ferroelectric material and could pave the way for completely new applications.

  18. Studies of Electric Capacitance of Membranes

    PubMed Central

    Kobatake, Yonosuke; Irimajiri, Akihiko; Matsumoto, Nobuyoshi

    1970-01-01

    A hydrophobic filter paper of a given pore size containing a synthetic lipid, i.e. dioleyl phosphate, was interposed between aqueous electrolyte solutions having the same chemical composition and temperature. The electric capacitance and conductance of the membrane immersed in various concentrations of KCl were measured in the frequency range from 20 to 3 × 106 cycle/sec. The observed capacitance and conductance were found to be strongly dependent on the applied frequency. A theory is proposed to account for this dispersion of impedance observed in the present membrane-electrolyte system. The dispersion is attributed to the formation of bilayer membranes of the lipid inside the filter paper. The effects of the salt concentration, the adsorbed quantity of the lipid, and the pore size of the filter paper on the capacitance and conductance of the membrane are discussed in terms of the distribution function of bilayers formed within the filter paper. PMID:5475731

  19. Capacitive probes for rf process plasmas

    NASA Astrophysics Data System (ADS)

    Savas, S. E.; Donohoe, K. G.

    1989-11-01

    Easily built capacitive probes designed for rf potential measurements in low-density reactive process plasmas are shown. The probes use no auxiliary circuitry and are made from easily available materials. They permit accurate measurements of rf fundamental and harmonic amplitudes in the plasma, in sheaths, and on insulating or conducting surfaces in vacuum or plasma environments. Measured values of plasma, sheath, and electrode surface rf potential amplitudes are shown for ˜1010 cm-3 density, unmagnetized and magnetically enhanced 13.56-MHz capacitive discharges in oxygen and nitrogen. Overall probe accuracy is estimated to be about 10% in these plasmas with the spatial resolution as fine as 0.5 mm.

  20. Capacitive Behavior of Single Gallium Oxide Nanobelt

    PubMed Central

    Cai, Haitao; Liu, Hang; Zhu, Huichao; Shao, Pai; Hou, Changmin

    2015-01-01

    In this research, monocrystalline gallium oxide (Ga2O3) nanobelts were synthesized through oxidation of metal gallium at high temperature. An electronic device, based on an individual Ga2O3 nanobelt on Pt interdigital electrodes (IDEs), was fabricated to investigate the electrical characteristics of the Ga2O3 nanobelt in a dry atmosphere at room temperature. The current-voltage (I-V) and I/V-t characteristics show the capacitive behavior of the Ga2O3 nanobelt, indicating the existence of capacitive elements in the Pt/Ga2O3/Pt structure. PMID:28793506

  1. 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.

  2. Comparison of piezoresistive and capacitive ultrasonic transducers

    NASA Astrophysics Data System (ADS)

    Neumann, John J.; Greve, David W.; Oppenheim, Irving J.

    2004-07-01

    MEMS ultrasonic transducers for flaw detection have heretofore been built as capacitive diaphragm-type devices. A diaphragm forms a moveable electrode, placed at a short gap from a stationary electrode, and diaphragm movement has been detected by capacitance change. Although several research teams have successfully demonstrated that technology, the detection of capacitance change is adversely affected by stray and parasitic capacitances, limiting the sensitivity of such transducers and typically requiring relatively large diaphragm areas. We describe the design and fabrication of what to our knowledge is the first CMOS-MEMS ultrasonic phased array transducer using piezoresistive strain sensing. Piezoresistors have been patterned within the diaphragms, and diaphragm movement creates bending strain which is detected by a bridge circuit, for which conductor losses will be less significant. The prospective advantage of such piezoresistive transducers is that sufficient sensitivity may be achieved with very small diaphragms. We compare transducer response under fluid-coupled ultrasonic excitation and report the experimental gauge factor for the piezoresistors. We also discuss the phased array performance of the transducer in sensing the direction of an incoming wave.

  3. Impact of stray capacitance on hvdc harmonics

    SciTech Connect

    Larsen, E.V.; Sublich, M.; Kapoor, S.C.

    1989-01-01

    Recent experience suggests that a new approach is needed to determining harmonic generation from hvdc converters for the purpose of telephone interference evaluation. This paper presents simulation results showing the effect on harmonic generation of stray capacitances inherent to hvdc converters. These simulation results illustrate the basic characteristics of the phenomenon, which agree qualitatively with field experience.

  4. Site Specific Evaluation of Multisensor Capacitance Probes

    USDA-ARS?s Scientific Manuscript database

    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...

  5. 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.

  6. 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.

  7. Sensing gap reconfigurable capacitive type MEMS accelerometer

    NASA Astrophysics Data System (ADS)

    Je, Chang Han; Lee, Myunglae; Jung, Sunghye; Lee, Sungsik; Hwang, Gunn; Choi, Changauck

    2007-12-01

    A novel sensing gap reconfigurable capacitive type MEMS accelerometer with high sensitivity and high resolution is designed, fabricated and characterized. The present MEMS accelerometer is fabricated by using simple SOI process-DRIE. However, conventional Silicon on Insulator (SOI) process is hard to make patterns which is smaller than 1 um because of its high aspect ratio and ICP etching error such as loading-effect and under-cutting. So we have adopted a simple idea of the MEMS actuator-stopper system to modulate the sensing gap precisely. Unlike previous capacitive type MEMS accelerometer which has an anchored reference comb electrodes, the proposed accelerometer has a movable reference comb with MEMS electrostatic actuators and stoppers. By simply applying DC bias to MEMS actuators, the reference comb electrode is moved to the sensing comb structure until the actuators contacting the stoppers. The gap between sensing comb fingers and reference comb fingers is reduced by the gap between actuators and stoppers. In this paper, the initial sensing gap is 1.5um and it reduced to 0.5um, when working. Then, the overall capacitance and sensitivity is simple increased. The capacitance is increased from 3.47pF at the OFF state to 5.35pF at the ON state by applying 2V DC bias.

  8. 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…

  9. 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…

  10. 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)

  11. Constant capacitance in nanopores of carbon monoliths.

    PubMed

    García-Gómez, Alejandra; Moreno-Fernández, Gelines; Lobato, Belén; Centeno, Teresa A

    2015-06-28

    The results obtained for binder-free electrodes made of carbon monoliths with narrow micropore size distributions confirm that the specific capacitance in the electrolyte (C2H5)4NBF4/acetonitrile does not depend significantly on the micropore size and support the foregoing constant result of 0.094 ± 0.011 F m(-2).

  12. Capacitive connectors for digital-data lines

    NASA Technical Reports Server (NTRS)

    Studer, P. A.

    1977-01-01

    Proposed connector consisting of twin metal films separated by thin layers of insulating material transmits digital pulses capacitively. There is no direct contact between metal films; therefore, there is no ohmic contact drop and no wear when connections are changed. Since metal films are sealed in insulating material, there is no corrosion from exposure to atmosphere.

  13. Modelisations des effets de surface sur les jets horizontaux subsoniques d'hydrogene et de methane

    NASA Astrophysics Data System (ADS)

    Gomez, Luis Fernando

    Le developpement des codes et de normes bases sur une methodologie scientifique requiert la capacite de predire l'etendue inflammable de deversements gazeux d'hydrogene sous differentes conditions. Des etudes anterieures ont deja etabli des modeles bases sur les lois de conservation de la mecanique des fluides basees sur des correlations experimentales qui permettent de predire la decroissance de la concentration et de la vitesse d'un gaz le long de l'axe d'un jet libre vertical. Cette etude s'interesse aux effets de proximite a une surface horizontale parallele sur un jet turbulent. Nous nous interessons a son impact sur l'etendue du champ de la concentration et sur l'enveloppe inflammable en particulier. Cette etude est comparative : l'hydrogene est compare au methane. Ceci permet de degager l'influence des effets de difference de la densite sur le comportement du jet, et de comparer le comportement de l'hydrogene aux correlations experimentales, qui ont ete essentiellement etablies pour le methane. Un modele decrivant l'evolution spatio-temporelle du champ de concentration du gaz dilue est propose, base sur la mecanique des fluides computationnelle. Cette approche permet de varier systematiquement les conditions aux frontieres (proximite du jet a la surface, par exemple) et de connaitre en detail les proprietes de l'ecoulement. Le modele est implemente dans le code de simulations par volumes finis de FLUENT. Les resultats des simulations sont compares avec les lois de similitudes decoulant de la theorie des jets d'ecoulements turbulents libres ainsi qu'avec les resultats experimentaux disponibles. L'effet de la difference des masses molaires des constituantes du jet et des constituantes du milieu de dispersion est egalement etudie dans le contexte du comportement d'echelle de la region developpee du jet.

  14. ``Zeptofarad'' (10-21 F) resolution capacitance sensor for scanning capacitance microscopy

    NASA Astrophysics Data System (ADS)

    Tran, T.; Oliver, D. R.; Thomson, D. J.; Bridges, G. E.

    2001-06-01

    We describe a sensor for use in a scanning capacitance microscope (SCM) that is capable of "zeptofarad" (10-21 F) capacitance measurement resolution in a 1 Hz bandwidth with a peak-to-peak sense voltage on the probe tip of no more than 300 mV. This sensitivity is based on experimental data and simulation results that are in excellent agreement. The complete sensor incorporates an oscillator (phase locked to a 10 MHz crystal oscillator), a coupled transmission line resonator, an amplifier, and a peak detector. The resonator is fabricated from copper-clad, low-loss dielectric material and its size is such that it is easily incorporated with a scanning probe microscope. The sensor's use in the SCM enables capacitance resolution that has not previously been possible while retaining the instrumental advantages of imaging at low sense voltages. The performance of this sensor is discussed and compared to alternative scanning capacitance microscopy methodologies.

  15. Membrane hyperpolarization during human sperm capacitation

    PubMed Central

    López-González, I.; Torres-Rodríguez, P.; Sánchez-Carranza, O.; Solís-López, A.; Santi, C.M.; Darszon, A.; Treviño, C.L.

    2014-01-01

    Sperm capacitation is a complex and indispensable physiological process that spermatozoa must undergo in order to acquire fertilization capability. Spermatozoa from several mammalian species, including mice, exhibit a capacitation-associated plasma membrane hyperpolarization, which is necessary for the acrosome reaction to occur. Despite its importance, this hyperpolarization event has not been adequately examined in human sperm. In this report we used flow cytometry to show that a subpopulation of human sperm indeed undergo a plasma membrane hyperpolarization upon in vitro capacitation. This hyperpolarization correlated with two other well-characterized capacitation parameters, namely an increase in intracellular pH and Ca2+ concentration, measured also by flow cytometry. We found that sperm membrane hyperpolarization was completely abolished in the presence of a high external K+ concentration (60 mM), indicating the participation of K+ channels. In order to identify, which of the potential K+ channels were involved in this hyperpolarization, we used different K+ channel inhibitors including charybdotoxin, slotoxin and iberiotoxin (which target Slo1) and clofilium (a more specific blocker for Slo3). All these K+ channel antagonists inhibited membrane hyperpolarization to a similar extent, suggesting that both members of the Slo family may potentially participate. Two very recent papers recorded K+ currents in human sperm electrophysiologically, with some contradictory results. In the present work, we show through immunoblotting that Slo3 channels are present in the human sperm membrane. In addition, we found that human Slo3 channels expressed in CHO cells were sensitive to clofilium (50 μM). Considered altogether, our data indicate that Slo1 and Slo3 could share the preponderant role in the capacitation-associated hyperpolarization of human sperm in contrast to what has been previously reported for mouse sperm, where Slo3 channels are the main contributors to the

  16. Surface Pb nanoparticle aggregation, coalescence and differential capacitance in a deep eutectic solvent using a simultaneous sample-rotated small angle x-ray scattering and electrochemical methods approach [Surface Pb nanoparticle aggregation, coalescence and differential capacitance in a deep eutectic solvent using a simultaneous grazing transmission small angle x-ray scattering and electrochemical methods approach

    DOE PAGES

    Hammons, Joshua A.; Ilavsky, Jan

    2017-01-18

    Nanoparticle electrodeposition is a simple and scalable approach to synthesizing supported nanoparticles. Used with a deep eutectic solvent (DES), surface nanoparticles can be assembled and exhibit unique surface charge separation when the DES is adsorbed on the nanoparticle surface. Key to understanding and controlling the assembly and the capacitance is a thorough understanding of surface particle mobility and charge screening, which requires an in-situ approach. In this study, Pb particle formation, size, shape and capacitance are resolved in a 1:2 choline Cl–: urea deep eutectic solvent whilst sweeping the cell potential in the range: 0.2 V to –1.2 V (vs.more » Ag/AgCl). These system parameters were resolved using a complementary suite of sample-rotated small angle X-ray scattering (SR-SAXS) and electrochemical impedance spectroscopy (EIS), which are presented and discussed in detail. This approach is able to show that both particle and ion transport are impeded in the DES, as aggregation occurs over the course of 6 minutes, and dissolved Pb ions accumulate and remain near the surface after a nucleation pulse is applied. The DES-Pb interactions strongly depend on the cell potential as evidenced by the specific differential capacitance of the Pb deposit, which has a maximum value of 2.5 +/– 0.5 F g–1 at –1.0 V vs. Ag/AgCl. Together, the SR-SAXS-EIS approach is able to characterize the unique nanoparticle capacitance, mobility and ion mobility in a DES and can be used to study a wide range of nanoparticle deposition systems in-situ.« less

  17. Capacitive Measurement Of Coating Thickness On Carbon Fibers

    NASA Technical Reports Server (NTRS)

    Eftekhari, Abe; Chapman, John J.

    1994-01-01

    Technique for gauging coating thickness during prepreg processing of carbon fibers developed. Technique based on measurement of capacitance of cylindrical condenser through which bundle of prepregged fibers passed axially. Empirical results indicate capacitance linearly related to thickness of polymer coat on fibers in bundle. Capacitive transducer used successfully to measure thickness of polymer coats on several test bundles of fibers under static conditions.

  18. Quantification des besoins en intrants antipaludiques: contribution à l'actualisation des hypothèses pour la quantification des intrants de prise en charge des cas de paludisme grave en République Démocratique du Congo

    PubMed Central

    Likwela, Joris Losimba; Otokoye, John Otshudiema

    2015-01-01

    Les formes graves de paludisme à Plasmodium falciparum sont une cause majeure de décès des enfants de moins de 5 ans en Afrique Sub-saharienne. Un traitement rapide dépend de la disponibilité de médicaments appropriés au niveau des points de prestation de service. La fréquence des ruptures de stock des commodités antipaludiques, en particuliers celles utilisées pour le paludisme grave, avait nécessité une mise à jour des hypothèses de quantification. Les données issues de la collecte de routine du PNLP de 2007 à 2012 ont été comparées à celles rapportés par d'autres pays africains et utilisées pour orienter les discussions au cours d'un atelier organisé par le PNLP et ses partenaires techniques et financiers afin de dégager un consensus national. La proportion des cas de paludisme rapportés comme grave en RDC est resté autour d'une médiane de 7% avec un domaine de variation de 6 à 9%. Hormis la proportion rapportée au Kenya (2%), les pays africains ont rapporté une proportion de cas grave variant entre 5 et 7%. Il apparaît que la proportion de 1% précédemment utilisée pour la quantification en RDC a été sous-estimée dans le contexte de la gestion des cas graves sur terrain. Un consensus s'est dégagé autour de la proportion de 5% étant entendu que des efforts de renforcement des capacités seraient déployés afin d'améliorer le diagnostic au niveau des points de prestation des services. PMID:26213595

  19. 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.

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

    DOE PAGES

    Zhan, Cheng; Neal, Justin; Wu, Jianzhong; ...

    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

  1. 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 C(S) of around 100 pF, they present a noise level of 3.3 µV(RMS) 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.

  2. 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.

  3. Compressed magnetic flux amplifier with capacitive load

    SciTech Connect

    Stuetzer, O.M.

    1980-03-01

    A first-order analysis is presented for a compressed magnetic flux (CMF) current amplifier working into a load with a capacitive component. Since the purpose of the investigation was to gain a general understanding of the arrangement, a number of approximations and limitations were accepted. The inductance of the transducer varies with time; the inductance/resistance/capacitance (LRC) circuit therefore is parametric and solutions are different for the stable regime (high C), the oscillation regime (low C), and the transition case. Solutions and performance depend strongly on circuit boundary conditions, i.e., energization of the circuit by either an injected current or by an applied capacitor charge. The behavior of current and energy amplification for the various cases are discussed in detail. A number of experiments with small CMF devices showed that the first-order theory presented predicts transducer performance well in the linear regime.

  4. 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.

  5. Modeling of dielectric charging in capacitive structures

    NASA Astrophysics Data System (ADS)

    Amiaud, A.-C.; Leuliet, A.; Loiseaux, B.; Ganne, J.-P.; Nagle, J.

    2015-11-01

    In this paper, we investigate dielectric charging process in capacitive structure dielectrics under bias voltage. We particularly focus on the case of Si 3 N 4 dielectric layers. The main defects in silicon nitride involved in electronic transport are identified as shallow traps. A new model for dielectric charging is presented with trap assisted tunneling effect as interfacial electronic transport mechanism and Frenkel-Poole and hopping current as bulk transport mechanisms. Thanks to this model, electric field and charge carrier distribution in the dielectric layer can be calculated. The actuation bias shift versus time, which is responsible for RF capacitive structure failure, can also be determined. We find that after a 300 s actuation, the charge is concentrated in few nm in the dielectric layer and a voltage shift of few volts is calculated, depending on dielectric characteristics.

  6. Shear-mode scanning capacitance microscope

    NASA Astrophysics Data System (ADS)

    Naitou, Yuichi; Ookubo, Norio

    2001-05-01

    Scanning capacitance microscope (SCM) is developed using an all-metallic probe, whose distance from the sample is controlled by detecting the shear-force drag on the laterally oscillating probe. The oscillatory motion of the probe is electromechanically excited and detected. Using this SCM, a set of images of topography, dC/dV, and dC/dX is simultaneously obtained, where C and V are, respectively, capacitance and applied voltage between the probe and the sample, and X is the coordinate along probe tip oscillation. The SCM developed shows sensitivity for dC/dV higher than the conventional SCM. The dC/dX image clearly indicates the built-in depletion region due to the p-n junction.

  7. Variable Capacitance Electrostatic Energy Conversion System

    DTIC Science & Technology

    1976-04-01

    mtm , <m ■> Üii=ui.:iü„. AFAL-TR-75-92 b,5 capacitance C». The potent.a, ri» across Capacitor fl oooaU the potential drop across the ioad pios the...73) i, -1 44 M MliilillUlirXfrlVni .i 1^-..^i.-iif.vi.A,riahMi^-,, ■■ iirilllMrmiliiWiilfii iiiiitnii--— ■ftfrimMi.rMi’ii-—-J-*--- ^^^- ua

  8. Capacitance of Small Spheres, including Surface States

    NASA Astrophysics Data System (ADS)

    Krcmar, Maja; Saslow, Wayne M.

    2000-03-01

    We consider the capacitance of a small conducting sphere of radius a, with both bulk and surface states in the vicinity of the fermi level. Using Debye-Huckel theory, as appropriate to semiconductors, we introduce a uniform charge density to the sphere and determine how the system adjusts to maintain a uniform electrochemical potential. In the absence of surface states at the fermi level, the capacitance is C=a/α , where α =(1-tanh(kb a)/kb a)-1 and k_b=[(4π e^2)(dn_b/dμ _b)]^1\\over2 is the inverse bulk Thomas-Fermi screening length. (nb is the bulk number density and μ b is the bulk chemical potential.) In the presence of surface states at the fermi level, the inverse surface screening length is k_s=(4π e^2)(dn_s/dμ _s), where (ns is the surface number density and μ s is the bulk chemical potential). In this case the ratio of charge going to the surface to charge going to the bulk is given by dN_s/dN_b=k_sa(α -1), and the capacitance is C=a[1+ dN_s/dN_b]/[α +dN_s/dN_b].

  9. 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.

  10. Carbon materials for chemical capacitive energy storage.

    PubMed

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

    2011-11-09

    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. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  11. Multi-Channel Capacitive Sensor Arrays.

    PubMed

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

    2016-01-25

    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.

  12. A new desalination technique using capacitive deionization

    NASA Astrophysics Data System (ADS)

    Rostamy, Mohammad Sajjad; Khashechi, Morteza; Pipelzadeh, Ehsan; desalination Team

    2016-11-01

    Capacitive deionization (CDI) is an emerging energy efficient, low pressure and low capital intensive desalination process where ions are separated by a pure electrostatic force imposed by a small bias potential as low as 1 V That funded by an external Renewable (Solar) power supply to materials with high specific surface area. The main objective of this configuration is to separate the cation and anions on oppositely charged electrodes. Various electrode materials have been developed in the past, which have suffered from instability and lack of performance. Preliminary experimental results using carbon black, graphite powder, graphene ∖graphite ∖PTFE (Active ∖Conductive ∖binder), show that the graphene reduced via urea method is a suitable method to develop CDI electrode materials with capacitance as high as 52.2 mg/g for free standing graphene electrode. The focus of these studies has been mainly on developing electrodes with high specific surface area, high capacitance, excellent electronic conductivity and fast charge discharge cycles for desalination. Although some progress has been made, production of efficient and stable carbon based electrode materials for large scale desalination has not been fully realized.

  13. 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

  14. 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.

  15. Etude par émission acoustique de la dynamique des dislocations pendant la déformation cyclique de polycristaux d'aluminium

    NASA Astrophysics Data System (ADS)

    Slimani, A.; Fleischmann, P.; Fougères, R.

    1992-06-01

    The cyclic plasticity of 5N polycrystalline aluminium have been studied at room temperature by measuring the continuous acoustic emission (A.E.) due to dislocations movements in the metal. In this study, original data have been obtained in the understanding of continuous A.E. sources. In comparison with classical interpretation given in the literature, the fact that dislocations are arranged according to a dislocation cell structure from the first cycle has been included in the analysis of the results. From this, it has been shown that the amplitude of the A.E. signal is not directly connected with the plastic strain rate prescribed to the fatigue sample and that the probability density function of dislocation loops created during the cycling can be determined. La plasticité cyclique de l'AI 5N polycristallin a été étudiée à la température ambiante à partir de mesures d'émission acoustique continue (E.A.). L'application de la technique de l'E.A. nous a permis d'obtenir des données originales quant aux mécanismes sources d'E.A. Par rapport aux interprétations classiques de la littérature, nous avons fait intervenir le fait que, dès les premiers cycles, une structure cellulaire de dislocations est établie. Nous montrons que l'amplitude du signal d'E.A. n'est plus liée directement à la vitesse de déformation plastique macroscopique. A partir de cette donnée, l'analyse des résultats d'E.A. permet d'obtenir des informations sur la fonction distribution des boucles de dislocations créées au cours de la déformation cyclique.

  16. 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

  17. Gestion des ressources hydriques adaptee aux changements climatiques pour la production optimale d'hydroelectricite. Etude de cas: Bassin versant de la riviere Manicouagan

    NASA Astrophysics Data System (ADS)

    Haguma, Didier

    deversements non productibles dans le climat futur. Des strategies d'adaptation structurale ont ete analysees pour augmenter la capacite de production et la capacite d'ecoulement de certaines centrales hydroelectriques afin d'ameliorer la performance du systeme. Une analyse economique a permis de choisir les meilleures mesures d'adaptation et de determiner le moment opportun pour la mise en oeuvre de ces mesures. Les resultats de la recherche offrent aux gestionnaires des systemes hydriques un outil qui permet de mieux anticiper les consequences des changements climatiques sur la production hydroelectrique, incluant le rendement de centrales, les deversements non productibles et le moment le plus opportun pour inclure des modifications aux systemes hydriques. Mots-cles : systemes hydriques, adaptation aux changements climatiques, riviere Manicouagan

  18. Des ballons pour demain

    NASA Astrophysics Data System (ADS)

    Régipa, R.

    A partir d'une théorie sur la détermination des formes et des contraintes globales d'un ballon de révolution, ou s'en rapprochant, une nouvelle famille de ballons a été définie. Les ballons actuels, dits de ``forme naturelle'', sont calculés en général pour une tension circonférencielle nulle. Ainsi, pour une mission donnée, la tension longitudinale et la forme de l'enveloppe sont strictement imposées. Les ballons de la nouvelle génération sont globalement cylindriques et leurs pôles sont réunis par un câble axial, chargé de transmettre une partie des efforts depuis le crochet (pôle inférieur), directement au pôle supérieur. De plus, la zone latérale cylindrique est soumise à un faible champ de tensions circonférencielles. Ainsi, deux paramètres permettent de faire évoluer la distribution des tensions et la forme de l'enveloppe: - la tension du câble de liaison entre pôles (ou la longueur de ce câble) - la tension circonférencielle moyenne désirée (ou le rayon du ballon). On peut donc calculer et réaliser: - soit des ballons de forme adaptée, comme les ballons à fond plat pour le bon fonctionnement des montgolfières infrarouge (projet MIR); - soit des ballons optimisés pour une bonne répartition des contraintes et une meilleure utilisation des matériaux d'enveloppe, pour l'ensemble des programmes stratosphériques. Il s'ensuit une économie sensible des coûts de fabrication, une fiabilité accrue du fonctionnement de ces ballons et une rendement opérationnel bien supérieur, permettant entre autres, d'envisager des vols à très haute altitude en matériaux très légers.

  19. Chloride Is Essential for Capacitation and for the Capacitation-associated Increase in Tyrosine Phosphorylation*

    PubMed Central

    Wertheimer, Eva V.; Salicioni, Ana M.; Liu, Weimin; Trevino, Claudia L.; Chavez, Julio; Hernández-González, Enrique O.; Darszon, Alberto; Visconti, Pablo E.

    2008-01-01

    After epididymal maturation, sperm capacitation, which encompasses a complex series of molecular events, endows the sperm with the ability to fertilize an egg. This process can be mimicked in vitro in defined media, the composition of which is based on the electrolyte concentration of the oviductal fluid. It is well established that capacitation requires Na+, \\documentclass[10pt]{article} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{pmc} \\usepackage[Euler]{upgreek} \\pagestyle{empty} \\oddsidemargin -1.0in \\begin{document} \\begin{equation*}{\\mathrm{HCO}}_{3}^{-}\\end{equation*}\\end{document}, Ca2+, and a cholesterol acceptor; however, little is known about the function of Cl– during this important process. To determine whether Cl–, in addition to maintaining osmolarity, actively participates in signaling pathways that regulate capacitation, Cl– was replaced by either methanesulfonate or gluconate two nonpermeable anions. The absence of Cl– did not affect sperm viability, but capacitation-associated processes such as the increase in tyrosine phosphorylation, the increase in cAMP levels, hyperactivation, the zona pellucidae-induced acrosome reaction, and most importantly, fertilization were abolished or significantly reduced. Interestingly, the addition of cyclic AMP agonists to sperm incubated in Cl–-free medium rescued the increase in tyrosine phosphorylation and hyperactivation suggesting that Cl– acts upstream of the cAMP/protein kinase A signaling pathway. To investigate Cl– transport, sperm incubated in complete capacitation medium were exposed to a battery of anion transport inhibitors. Among them, bumetanide and furosemide, two blockers of Na+/K+/Cl– cotransporters (NKCC), inhibited all capacitation-associated events, suggesting that these transporters may mediate Cl– movements in sperm. Consistent with these results, Western blots

  20. Capacitation mechanisms, and the role of capacitation as seen in eutherian mammals.

    PubMed

    Harrison, R A

    1996-01-01

    Capacitation, the process whereby spermatozoa are rendered capable of interacting with and fertilizing the egg, was discovered more than 40 years ago. However, our understanding of it is still far from satisfactory. Several factors conspire to obfuscate studies of capacitation mechanisms: the inherent functional heterogeneity of sperm populations, the range of functions used as parameters of capacitation (whence the endpoint of the process has become conceptually uncertain), and the several profound differences between model in vitro fertilization (IVF) systems and the situation in vivo in the female reproductive tract. Recent investigations in the author's laboratory have shown that bicarbonate/CO2, an essential component for successful IVF, causes rapid changes in lipid architecture of the sperm plasma membrane and slower changes in surface coating. These changes are accompanied by membrane destabilization and cell death. Evidence suggests that bicarbonate's actions are mediated through cyclic nucleotide signalling. Of particular note is the heterogeneity in rate of response to bicarbonate shown by individual cells in the sperm populations. Taken together with other observations, the findings suggest that capacitation is a series of positive destabilizing events that eventually lead to cell death. The 'capacitated' state would then be a window of destabilization within which spermatozoa can undergo a zona-induced acrosome reaction and display hyperactivated motility. Further along the destabilization pathway, spontaneous acrosome reactions would occur before total membrane degeneration. In vivo, capacitation would be a conflict between destabilization and sperm survival. Concentrations of bicarbonate are maintained low in the cauda epididymidis, where sperm survive for long periods, and one may speculate that hormonal control of local bicarbonate/CO2 in oviducal 'storage' sites in the female tract could allow 'safe' sequestering of live spermatozoa until around

  1. Practical and simple circuitry for the measurement of small capacitance

    NASA Astrophysics Data System (ADS)

    Lin, D. Y.; Wu, J. D.; Chang, Y. J.; Wu, J. S.

    2007-01-01

    Practical and cost-effective circuitry with high sensitivity has been developed to measure a small capacitance using current compensation method. The circuitry uses an electronic switch to periodically connect or separate the capacitor under test (Cx) from a reference capacitor (Cr). When Cx is connected in parallel with Cr the total capacitance becomes Cx+Cr. On the other hand, as Cx is separated from Cr, the total capacitance is only Cr. This periodic change of the capacitance generates a periodic square-wave output with an amplitude in proportion to the capacitance of Cx. A high sensitivity of ΔV /ΔC=202.2mV/pF has been achieved, making the circuitry a powerful tool in measuring small capacitances. Three applications have been performed to present its capability: (a) displacement, (b) height of liquid, and (c) angle of tilt. The experimental results demonstrate the performance of the circuitry.

  2. Contact impedance of grounded and capacitive electrodes

    NASA Astrophysics Data System (ADS)

    Hördt, Andreas; Weidelt, Peter; Przyklenk, Anita

    2013-04-01

    The contact impedance of electrodes determines how much current can be injected into the ground for a given voltage. If the ground is very resistive, capacitive electrodes may be an alternative to galvanic coupling. The impedance of capacitive electrodes is often estimated with the assumption that the halfspace is an ideal conductor. Over resistive ground at high frequencies, however, the contact impedance will depend on the electrical properties, i.e. electrical conductivity and permittivity, of the subsurface. Here, we review existing equations for the resistance of a galvanically coupled, spherical electrode in a fullspace, and extend the theory to the general case of a sphere in a spherically layered fullspace. We then develop a method to calculate the impedance of a spherical disc over a homogeneous halfspace. We carry out modelling studies to demonstrate the consistency of the algorithms and to assess under which conditions the determination of the electrical parameters from the impedance may be feasible. For a capacitively coupled electrode, the common assumption of an ideally conducting fullspace (or halfspace) breaks down if the displacement currents in the fullspace become as large as the conduction currents. For a moderately resistive medium with 1000 Ωm this is the case for frequencies larger than 100 kHz. The transition from a galvanically coupled disc to a disc in the air is continuous as function of distance. However, depending on the electrical parameters and frequency, the impedance may vary by several orders of magnitude within a few nanometers distance or less. We derive a simple equation to assess under which conditions the impedance is independent of the electrode height, which may be important for determining subsurface permittivity and conductivity in cases where control on the exact geometry is difficult. Our theory is consistent with measured data obtained in a sandbox in the laboratory.

  3. 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.

  4. Experimental observation of negative capacitance in ferroelectrics at room temperature.

    PubMed

    Appleby, Daniel J R; Ponon, Nikhil K; Kwa, Kelvin S K; Zou, Bin; Petrov, Peter K; Wang, Tianle; Alford, Neil M; O'Neill, Anthony

    2014-07-09

    Effective negative capacitance has been postulated in ferroelectrics because there is a hysteresis in plots of polarization-electric field. Compelling experimental evidence of effective negative capacitance is presented here at room temperature in engineered devices, where it is stabilized by the presence of a paraelectric material. In future integrated circuits, the incorporation of such negative capacitance into MOSFET gate stacks would reduce the subthreshold slope, enabling low power operation and reduced self-heating.

  5. Programmable differential capacitance-to-voltage converter for MEMS accelerometers

    NASA Astrophysics Data System (ADS)

    Royo, G.; Sánchez-Azqueta, C.; Gimeno, C.; Aldea, C.; Celma, S.

    2017-05-01

    Capacitive MEMS sensors exhibit an excellent noise performance, high sensitivity and low power consumption. They offer a huge range of applications, being the accelerometer one of its main uses. In this work, we present the design of a capacitance-to-voltage converter in CMOS technology to measure the acceleration from the capacitance variations. It is based on a low-power, fully-differential transimpedance amplifier with low input impedance and a very low input noise.

  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. 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.

  8. Vehicle identification by capacitance and infrared sensors

    NASA Astrophysics Data System (ADS)

    Yang, S.; Yang, W.; Yang, Y.

    2007-07-01

    Currently, large inductance coils buried underground are commonly used to detect passing vehicles at road toll stations. The inductance-based systems are vulnerable to environmental magnetic interference and hence are inaccurate in counting passing vehicles. Also they cannot categorise the vehicles. This paper presents a capacitance sensor array, which has been developed not only for detection of passing vehicles but also for identification of types of the vehicles. Together with infrared sensors, the new system can be used to control a road barrier and to keep a record of passed vehicles through a driveway accurately. Tests have demonstrated that it is more reliable than the inductance-based systems.

  9. Circuit analysis and simulation of an ultrahigh-frequency capacitance sensor for scanning capacitance microscopy

    NASA Astrophysics Data System (ADS)

    Yang, Jing; Postula, A.; Bialkowski, M.

    2004-03-01

    Quantitative two-dimensional dopant profiling tools are urgently needed for nowadays semiconductor industry. Scanning Capacitance Microscopy (SCM) holds most promise to become such a tool. The key component of SCM is an ultra high frequency (UHF) capacitance sensor. The output of the sensor has been approximately regarded as dC/dV, the derivative of the capacitance between the SCM tip and the sample versus the applied bias voltage. The SCM dopant profiling involves extracting the dopant profile from the SCM signal using analytic or numerical simulation models of Metal-Oxide-Semiconductor physics. To achieve a quantitative SCM dopant profiling, the operational principle of the whole SCM measurement has to be well understood and correctly included in those models. Recently, experimental evidences show the SCM signal is dramatically affected by many SCM experimental factors, including the behavior of the UHF capacitance sensor. However, till now, very little research has been reported on the behavior of the sensor in SCM measurement of semiconductors. In this paper, we derive an analytic expression of the sensor output, a circuit simulation model of the sensor is established using Advanced Design System 2003, and the dependences of the sensor output on the SCM operational factors are simulated.

  10. 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.

  11. A capacitive biosensor based on an interdigitated electrode with nanoislands.

    PubMed

    Jung, Ha-Wook; Chang, Young Wook; Lee, Ga-yeon; Cho, Sungbo; Kang, Min-Jung; Pyun, Jae-Chul

    2014-09-24

    A capacitive biosensor based on an interdigitated electrode (IDE) with nanoislands was developed for label-free detection of antigen-antibody interactions. To enable sensitive capacitive detection of protein adsorption, the nanoislands were fabricated between finger electrodes of the IDE. The effect of the nanoislands on the sensitive capacitive measurement was estimated using horseradish peroxidase (HRP) as a model protein. Additionally, a parylene-A film was coated on the IDE with nanoislands to improve the efficiency of protein immobilization. By using HRP and hepatitis B virus surface antigen (HBsAg) as model analytes, the effect of the parylene-A film on the capacitive detection of protein adsorption was demonstrated.

  12. Optimization of polyhydroxyalkanoates fermentations with on-line capacitance measurement.

    PubMed

    Li, Lan; Wang, Ze-Jian; Chen, Xue-Jun; Chu, Ju; Zhuang, Ying-Ping; Zhang, Si-Liang

    2014-03-01

    The aim of this work was to provide an effective methodology for optimization of the polyhydroxyalkanoates (PHAs) fermentation with Ralstonia eutropha by the on-line capacitance measurement. The present study found the capacitance values could reflect variations of microbial morphology and viability. Furthermore, oxygen uptake rate, specific oxygen uptake rate and specific growth rate were measured in real-time and compared with the capacitance value. In addition, a fed-batch control strategy based on the on-line capacitance measurement was proposed to improve the PHAs production by 22%. Copyright © 2014 Elsevier Ltd. All rights reserved.

  13. Integration et evaluation de capacites interactives d'un robot humanoide

    NASA Astrophysics Data System (ADS)

    Rosseau, Vincent

    Le domaine de l'Interaction Humain-Robot (HRI) est en pleine expansion. En effet, de. plus en plus de plateformes robotiques sont mises en œuvre pour faire évoluer ce domaine. Sur ces plateformes, toujours plus de modalités d'interaction sont mises en place telles que les mouvements corporels, la reconnaissance de gestes ou d'objets, la reconnaissance et la synthèse vocale ou encore la mobilité, pour pouvoir effectuer l'interaction la plus complète et la plus naturelle pour l'humain. Mais ceci amène aussi une complexité croissante de l'intégration de ces modalités sur une seule et même plateforme. Aussi, le domaine HRI étant à ses débuts, la méthodologie expérimentale des travaux se limite le plus souvent à des preuves de concept éprouvées en laboratoire ou en milieux ouverts non contrôlés. Il se trouve que peu de chercheurs présentent une démarche structurée et rigoureuse pour l'évaluation expérimentale d'interaction humain-robot en milieux ouverts, et il en résulte des recherches de types exploratoires qui examinent principalement la complexité technologique des modalités interactives à mettre en œuvre, et non l'impact de ces modalités sur la qualité des interactions. Le but de l'étude présentée dans ce document est d'étudier l'intégration de plusieurs modalités interactives sur un robot mobile humanoïde telles que la parole, les gestes et la mobilité sur la qualité des interactions humain-robot. Plus spécifiquement, le contexte de l'étude consiste à examiner l'impact de modalités interactives sur la capacité du robot à attirer l'attention d'une personne et à engager une interaction avec elle. Le scénario expérimental consiste à permettre au robot, à partir de la parole, d'expressions faciales, de mouvement de la tête, de gestes avec son bras et de sa mobilité, de demander de l'assistance à une personne à proximité de lui remettre un objet se trouvant au sol. L'hypothèse sous-jacente est que l

  14. Maladie des vibrations

    PubMed Central

    Shen, Shixin (Cindy); House, Ronald A.

    2017-01-01

    Résumé Objectif Permettre aux médecins de famille de comprendre l’épidémiologie, la pathogenèse, les symptômes, le diagnostic et la prise en charge de la maladie des vibrations, une maladie professionnelle importante et courante au Canada. Sources d’information Une recherche a été effectuée sur MEDLINE afin de relever les recherches et comptes rendus portant sur la maladie des vibrations. Une recherche a été effectuée sur Google dans le but d’obtenir la littérature grise qui convient au contexte canadien. D’autres références ont été tirées des articles relevés. Message principal La maladie des vibrations est une maladie professionnelle répandue touchant les travailleurs de diverses industries qui utilisent des outils vibrants. La maladie est cependant sous-diagnostiquée au Canada. Elle compte 3 éléments : vasculaire, sous la forme d’un phénomène de Raynaud secondaire; neurosensoriel; et musculosquelettique. Aux stades les plus avancés, la maladie des vibrations entraîne une invalidité importante et une piètre qualité de vie. Son diagnostic exige une anamnèse minutieuse, en particulier des antécédents professionnels, un examen physique, des analyses de laboratoire afin d’éliminer les autres diagnostics, et la recommandation en médecine du travail aux fins d’investigations plus poussées. La prise en charge consiste à réduire l’exposition aux vibrations, éviter les températures froides, abandonner le tabac et administrer des médicaments. Conclusion Pour assurer un diagnostic rapide de la maladie des vibrations et améliorer le pronostic et la qualité de vie, les médecins de famille devraient connaître cette maladie professionnelle courante, et pouvoir obtenir les détails pertinents durant l’anamnèse, recommander les patients aux cliniques de médecine du travail et débuter les demandes d’indemnisation de manière appropriée. PMID:28292812

  15. 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.

  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.

  17. 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.

  18. Optimization of the coplanar interdigital capacitive sensor

    NASA Astrophysics Data System (ADS)

    Huang, Yunzhi; Zhan, Zheng; Bowler, Nicola

    2017-02-01

    Interdigital capacitive sensors are applied in nondestructive testing and material property characterization of low-conductivity materials. The sensor performance is typically described based on the penetration depth of the electric field into the sample material, the sensor signal strength and its sensitivity. These factors all depend on the geometry and material properties of the sensor and sample. In this paper, a detailed analysis is provided, through finite element simulations, of the ways in which the sensor's geometrical parameters affect its performance. The geometrical parameters include the number of digits forming the interdigital electrodes and the ratio of digit width to their separation. In addition, the influence of the presence or absence of a metal backplane on the sample is analyzed. Further, the effects of sensor substrate thickness and material on signal strength are studied. The results of the analysis show that it is necessary to take into account a trade-off between the desired sensitivity and penetration depth when designing the sensor. Parametric equations are presented to assist the sensor designer or nondestructive evaluation specialist in optimizing the design of a capacitive sensor.

  19. 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.

  20. Des Vents et des Jets Astrophysiques

    NASA Astrophysics Data System (ADS)

    Sauty, C.

    well expected result from the theory. Although, collimation may be conical, paraboloidal or cylindrical (Part 4), cylindrical collimation is the more likely to occur. The shape of outflows may then be used as a tool to predict physical conditions on the flows or on their source. L'éjection continue de plasma autour d'objets massifs est un phénomène largement répandu en astrophysique, que ce soit sous la forme du vent solaire, de vents stellaires, de jets d'étoiles en formation, de jets stellaires autour d'objets compacts ou de jets extra-galactiques. Cette zoologie diversifiée fait pourtant l'objet d'un commun effort de modélisation. Le but de cette revue est d'abord de présenter qualitativement le développement, depuis leur origine, des diverses théories de vents (Partie 1) et l'inter disciplinarité dans ce domaine. Il s'agit d'une énumération, plus ou moins exhaustive, des idées proposées pour expliquer l'accélération et la morphologie des vents et des jets, accompagnée d'une présentation sommaire des aspects observationnels. Cette partie s'abstient de tout aspect faisant appel au formalisme mathématique. Ces écoulements peuvent être décrits, au moins partiellement, en résolvant les équations magnétohydrodynamiques, axisymétriques et stationnaires. Ce formalisme, à la base de la plupart des théories, est exposé dans la Partie 2. Il permet d'introduire quantitativement les intégrales premières qu'un tel système possède. Ces dernières sont amenées à jouer un rôle important dans la compréhension des phénomènes d'accélération ou de collimation, en particulier le taux de perte de masse, le taux de perte de moment angulaire ou l'énergie du rotateur magnétique. La difficulté de modélisation réside dans l'existence de points critiques, propres aux équations non linéaires, qu'il faut franchir. La nature physique et la localisation de ces points critiques fait l'objet d'un débat important car ils sont la clef de voute de la r

  1. 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…

  2. Calibrated nanoscale capacitance measurements using a scanning microwave microscope.

    PubMed

    Huber, H P; Moertelmaier, M; Wallis, T M; Chiang, C J; Hochleitner, M; Imtiaz, A; Oh, Y J; Schilcher, K; Dieudonne, M; Smoliner, J; Hinterdorfer, P; Rosner, S J; Tanbakuchi, H; Kabos, P; Kienberger, F

    2010-11-01

    A scanning microwave microscope (SMM) for spatially resolved capacitance measurements in the attofarad-to-femtofarad regime is presented. The system is based on the combination of an atomic force microscope (AFM) and a performance network analyzer (PNA). For the determination of absolute capacitance values from PNA reflection amplitudes, a calibration sample of conductive gold pads of various sizes on a SiO(2) staircase structure was used. The thickness of the dielectric SiO(2) staircase ranged from 10 to 200 nm. The quantitative capacitance values determined from the PNA reflection amplitude were compared to control measurements using an external capacitance bridge. Depending on the area of the gold top electrode and the SiO(2) step height, the corresponding capacitance values, as measured with the SMM, ranged from 0.1 to 22 fF at a noise level of ~2 aF and a relative accuracy of 20%. The sample capacitance could be modeled to a good degree as idealized parallel plates with the SiO(2) dielectric sandwiched in between. The cantilever/sample stray capacitance was measured by lifting the tip away from the surface. By bringing the AFM tip into direct contact with the SiO(2) staircase structure, the electrical footprint of the tip was determined, resulting in an effective tip radius of ~60 nm and a tip-sample capacitance of ~20 aF at the smallest dielectric thickness.

  3. Nanoscale capacitance: A quantum tight-binding model

    NASA Astrophysics Data System (ADS)

    Zhai, Feng; Wu, Jian; Li, Yang; Lu, Jun-Qiang

    2017-01-01

    Landauer-Buttiker formalism with the assumption of semi-infinite electrodes as reservoirs has been the standard approach in modeling steady electron transport through nanoscale devices. However, modeling dynamic electron transport properties, especially nanoscale capacitance, is a challenging problem because of dynamic contributions from electrodes, which is neglectable in modeling macroscopic capacitance and mesoscopic conductance. We implement a self-consistent quantum tight-binding model to calculate capacitance of a nano-gap system consisting of an electrode capacitance C‧ and an effective capacitance Cd of the middle device. From the calculations on a nano-gap made of carbon nanotube with a buckyball therein, we show that when the electrode length increases, the electrode capacitance C‧ moves up while the effective capacitance Cd converges to a value which is much smaller than the electrode capacitance C‧. Our results reveal the importance of electrodes in modeling nanoscale ac circuits, and indicate that the concepts of semi-infinite electrodes and reservoirs well-accepted in the steady electron transport theory may be not applicable in modeling dynamic transport properties.

  4. Capacitive-discharge-pumped copper bromide vapour laser

    SciTech Connect

    Sukhanov, V B; Fedorov, V F; Troitskii, V O; Gubarev, F A; Evtushenko, Gennadii S

    2007-07-31

    A copper bromide vapour laser pumped by a high-frequency capacitive discharge is developed. It is shown that, by using of a capacitive discharge, it is possible to built a sealed off metal halide vapour laser of a simple design allowing the addition of active impurities into the working medium. (letters)

  5. Capacitive bioanodes enable renewable energy storage in microbial fuel cells.

    PubMed

    Deeke, Alexandra; Sleutels, Tom H J A; Hamelers, Hubertus V M; Buisman, Cees J N

    2012-03-20

    We developed an integrated system for storage of renewable electricity in a microbial fuel cell (MFC). The system contained a capacitive electrode that was inserted into the anodic compartment of an MFC to form a capacitive bioanode. This capacitive bioanode was compared with a noncapacitive bioanode on the basis of performance and storage capacity. The performance and storage capacity were investigated during polarization curves and charge-discharge experiments. During polarization curves the capacitive electrode reached a maximum current density of 1.02 ± 0.04 A/m(2), whereas the noncapacitive electrode reached a current density output of only 0.79 ± 0.03 A/m(2). During the charge-discharge experiment with 5 min of charging and 20 min of discharging, the capacitive electrode was able to store a total of 22,831 C/m(2), whereas the noncapacitive electrode was only able to store 12,195 C/m(2). Regarding the charge recovery of each electrode, the capacitive electrode was able to recover 52.9% more charge during each charge-discharge experiment compared with the noncapacitive electrode. The capacitive electrode outperformed the noncapacitive electrode throughout each charge-discharge experiment. With a capacitive electrode it is possible to use the MFC simultaneously for production and storage of renewable electricity.

  6. 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…

  7. Les reseaux de politique publique comme facteur d'influence du choix des instruments de politique energetique canadienne a des fins environnementales de 1993 a nos jours

    NASA Astrophysics Data System (ADS)

    Fathy El Dessouky, Naglaa

    Au cours de la derniere decennie, les modes de la gouvernance ont pris place dans un contexte totalement different de celui qu'ils avaient auparavant. Les gouvernements modernes se rendent compte qu'ils perdent de plus en plus leur capacite a elaborer et a gerer les changements d'une maniere autonome. Ainsi, les fonctions et les activites traditionnellement accomplies exclusivement par le gouvernement engagent de nos jours une gamme d'acteurs etatiques et non etatiques. A l'encontre du concept traditionnel de l'Etat controleur, la gouvernance contemporaine est ainsi devenue moins une question d'offre de service et davantage une gestion indirecte des reseaux de politique publique. Dans cette entreprise, les gouvernements contemporains, cherchant plus d'information, de soutien et de legitimite en matiere de formulation des decisions, ont besoin d'etablir des relations avec les divers groupes d'interet qui, a leur tour, voulaient plus de promotion et de protection en faveur de leurs interets a travers leur implication au processus de l'elaboration et de la mise en oeuvre des politiques publiques. Ainsi, l'approche des reseaux de politique publique represente aujourd'hui un courant considerable au sein du champ d'analyse des politiques publiques. Toutefois, les preoccupations des chercheurs pour cette approche, dans le domaine des politiques energetiques a des fins environnementales, semblent recentes, et les etudes realisees sont encore trop peu nombreuses. Au Canada, au debut des annees 1990, le gouvernement ainsi que plusieurs groupes d'interets, des differents secteurs energetique, industriel et environnemental, ont commence a intensifier leurs efforts pour s'attaquer au probleme du changement climatique d'origine energetique, genere surtout par le secteur de l'industrie. Au cours de la derniere decennie, la question touchant plutot le sujet du developpement energetique durable represente le plus important domaine des politiques publiques ayant surgi recemment dans

  8. Effect of estrogens on boar sperm capacitation in vitro

    PubMed Central

    2010-01-01

    Background Mammalian sperm must undergo a series of controlled molecular processes in the female reproductive tract called capacitation before they are capable of penetrating and fertilizing the egg. Capacitation, as a complex biological process, is influenced by many molecular factors, among which steroidal hormone estrogens play their role. Estrogens, present in a high concentration in the female reproductive tract are generally considered as primarily female hormones. However, there is increasing evidence of their important impact on male reproductive parameters. The purpose of this study is to investigate the effect of three natural estrogens such as estrone (E1), 17beta-estradiol (E2) and estriol (E3) as well as the synthetical one, 17alpha-ethynylestradiol (EE2) on boar sperm capacitation in vitro. Methods Boar sperm were capacitated in vitro in presence of estrogens. Capacitation progress in control and experimental samples was analyzed by flow cytometry with the anti-acrosin monoclonal antibody (ACR.2) at selected times of incubation. Sperm samples were analyzed at 120 min of capacitation by CTC (chlortetracycline) assay, immunocytochemistry and flow cytometry with anti-acrosin ACR.2 antibody. Furthermore, sperm samples and capacitating media were analyzed by immunocytochemistry, ELISA with the ACR.2 antibody, and the acrosin activity assay after induced acrosomal reaction (AR). Results Estrogens stimulate sperm capacitation of boar sperm collected from different individuals. The stimulatory effect depends on capacitation time and is highly influenced by differences in the response to estrogens such as E2 by individual animals. Individual estrogens have relatively same effect on capacitation progress. In the boar samples with high estrogen responsiveness, estrogens stimulate the capacitation progress in a concentration-dependent manner. Furthermore, estrogens significantly increase the number of acrosome-reacted sperm after zona pellucida- induced acrosomal

  9. 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.

  10. Local mapping of interface traps using contactless capacitance transient technique

    NASA Astrophysics Data System (ADS)

    Yoshida, Haruhiko; Mori, Hidenobu

    2016-10-01

    Contactless capacitance transient techniques have been applied to local mapping of interface traps of a semiconductor wafer. In contactless capacitance transient techniques, a Metal-Air gap-Oxide-Semiconductor (MAOS) structure is used instead of a conventional Metal-Oxide-Semiconductor (MOS) structure. The local mapping of interface traps was obtained by using a contactless Isothermal Capacitance Transient Spectroscopy (ICTS), which is one of the contactless capacitance transient techniques. The validity of the contactless ICTS was demonstrated by characterizing a partially Au-doped Si wafer. The results revealed that local mapping of interface traps using contactless capacitance transient techniques is effective in wafer inspection and is a promising technique for the development of MOS devices and solar cells with high reliability and high performance.

  11. Quantum and tunneling capacitance in charge and spin qubits

    NASA Astrophysics Data System (ADS)

    Mizuta, R.; Otxoa, R. M.; Betz, A. C.; Gonzalez-Zalba, M. F.

    2017-01-01

    We present a theoretical analysis of the capacitance of a double quantum dot in the charge and spin qubit configurations probed at high frequencies. We find that, in general, the total capacitance of the system consists of two state-dependent terms: the quantum capacitance arising from adiabatic charge motion and the tunneling capacitance that appears when repopulation occurs at a rate comparable or faster than the probing frequency. The analysis of the capacitance lineshape as a function of externally controllable variables offers a way to characterize the qubits' charge and spin state as well as relevant system parameters such as charge and spin relaxation rates, tunnel coupling, electron temperature, and electron g factor. Overall, our analysis provides a formalism to understand dispersive qubit-resonator interactions which can be applied to high-sensitivity and noninvasive quantum-state readout.

  12. A method for measuring low capacitance for tomography

    NASA Astrophysics Data System (ADS)

    Shao, FuQun; Mong, QinGuo

    1999-07-01

    The applications of electrical capacitance tomography (ECT) to image multiphase flows in pipelines, fluidization process, interfaces in separation vessels, and combustion phenomena in internal combustion engines have been studied for some years. In these applications, none of the equipment imaged has an inner diameter exceeding 1 m. When ECT techniques for large industrial equipment like blast furnaces are explored, the existing methods for measuring low capacitance have some limitations. This article proposes a method for measuring low capacitance which is suitable to construct ECT systems for imaging large industrial equipment. The method is based on single high-voltage excitation and magnetic C/V converting principle which can resist interference by stray capacitance. Experiment results indicated that the method has good performance in regard to resolution, linearity, and stability. Though the method was designed for imaging large equipment, it can also be applicable to other fields where low capacitance measurements are required.

  13. Circuit Model for Capacitive Coupling in Inductively Coupled Plasmas

    NASA Astrophysics Data System (ADS)

    Watanabe, M.; Shaw, D. M.; Collins, G. J.; Sugai, H.

    1998-10-01

    A crude circuit model has been developed to illustrate and account for capacitive coupling between the rf coil and the bulk plasma in a stove top inductively coupled plasma source. The circuit model is composed of three levels of capacitance: the dielectric window capacitance, sheath capacitance contiguous to the dielectric window, and the chamber to ground sheath capacitance. The model is verified by quantitative comparison with the measured rf plasma potential in the bulk plasma body, plasma feedstock gas (argon) pressures below 2 mTorr. At higher pressures above 5 mTorr, the measured results diverge from the circuit model due to the transition from a spatially uniform electron density throughout the bulk plasma at pressures less than 2 mTorr to a less spatially uniform electron density at pressures above 5 mTorr.

  14. Factors and pathways involved in capacitation: how are they regulated?

    PubMed Central

    Jin, Shi-Kai; Yang, Wan-Xi

    2017-01-01

    In mammals, fertilization occurs via a comprehensive progression of events. Freshly ejaculated sperm have yet to acquire progressive motility or fertilization ability. They must first undergo a series of biochemical and physiological changes, collectively known as capacitation. Capacitation is a significant prerequisite to fertilization. During the process of capacitation, changes in membrane properties, intracellular ion concentration and the activities of enzymes, together with other protein modifications, induce multiple signaling events and pathways in defined media in vitro or in the female reproductive tract in vivo. These, in turn, stimulate the acrosome reaction and prepare spermatozoa for penetration of the egg zona pellucida prior to fertilization. In the present review, we conclude all mainstream factors and pathways regulate capacitation and highlight their crosstalk. We also summarize the relationship between capacitation and assisted reproductive technology or human disease. In the end, we sum up the open questions and future avenues in this field. PMID:27690295

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. Shape recognition for capacitive touch display

    NASA Astrophysics Data System (ADS)

    Guarneri, I.; Capra, A.; Farinella, G. M.; Battiato, S.

    2013-03-01

    In this paper we present a technique to classify five common classes of shapes acquired with a capacitive touch display: finger, ear, cheek, hand hold, half ear-half cheek. The need of algorithms able to discriminate among the aforementioned shapes comes from the growing diffusion of touch screen based consumer devices (e.g. smartphones, tablet, etc.). In this context, detection and the recognition of fingers are fundamental tasks in many touch based user applications (e.g., mobile games). Shape recognition algorithms are also extremely useful to identify accidental touches in order to avoid involuntary activation of the device functionalities (e.g., accidental calls). Our solution makes use of simple descriptors designed to capture discriminative information of the considered classes of shapes. The recognition is performed through a decision tree based approach whose parameters are learned on a set of labeled samples. Experimental results demonstrate that the proposed solution achieves good recognition accuracy.

  20. 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.

  1. 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.

  2. 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.

  3. Creatinine Diffusion Modeling in Capacitive Sensors

    NASA Astrophysics Data System (ADS)

    Mohabbati-Kalejahi, Elham; Azimirad, Vahid; Bahrami, Manouchehr

    2016-12-01

    In this paper, creatinine diffusion in capacitive sensors is discussed. The factors influencing the response time of creatinine biosensors are mathematically formulated and then three novel approaches for decreasing the response time are presented. At first, a piezoelectric actuator is used to vibrate the microtube that contains the blood sample, in order to reduce the viscosity of blood, and thus to increase the coefficient of diffusion. Then, the blood sample is assumed to be pushed through a porous medium, and the relevant conditions are investigated. Finally, the effect of the dentate shape of dielectric on response time is studied. The algorithms and the mathematical models are presented and discussed, and the results of simulations are illustrated. The response times for the first, second and third method are 60, 0.036 and about 31 s, respectively. It is also found that pumping results in very fast responses.

  4. Biasing of Capacitive Micromachined Ultrasonic Transducers.

    PubMed

    Caliano, Giosue; Matrone, Giulia; Savoia, Alessandro Stuart

    2017-02-01

    Capacitive micromachined ultrasonic transducers (CMUTs) represent an effective alternative to piezoelectric transducers for medical ultrasound imaging applications. They are microelectromechanical devices fabricated using silicon micromachining techniques, developed in the last two decades in many laboratories. The interest for this novel transducer technology relies on its full compatibility with standard integrated circuit technology that makes it possible to integrate on the same chip the transducers and the electronics, thus enabling the realization of extremely low-cost and high-performance devices, including both 1-D or 2-D arrays. Being capacitive transducers, CMUTs require a high bias voltage to be properly operated in pulse-echo imaging applications. The typical bias supply residual ripple of high-quality high-voltage (HV) generators is in the millivolt range, which is comparable with the amplitude of the received echo signals, and it is particularly difficult to minimize. The aim of this paper is to analyze the classical CMUT biasing circuits, highlighting the features of each one, and to propose two novel HV generator architectures optimized for CMUT biasing applications. The first circuit proposed is an ultralow-residual ripple (<5 [Formula: see text]) HV generator that uses an extremely stable sinusoidal power oscillator topology. The second circuit employs a commercially available integrated step-up converter characterized by a particularly efficient switching topology. The circuit is used to bias the CMUT by charging a buffer capacitor synchronously with the pulsing sequence, thus reducing the impact of the switching noise on the received echo signals. The small area of the circuit (about 1.5 cm(2)) makes it possible to generate the bias voltage inside the probe, very close to the CMUT, making the proposed solution attractive for portable applications. Measurements and experiments are shown to demonstrate the effectiveness of the new approaches

  5. 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.

  6. Cartographie des disques

    NASA Astrophysics Data System (ADS)

    Hameury, Jean-Marie

    2001-01-01

    Two techniques are frequently used to produce images of the accretion disc in an eclipsing binary: eclipse mapping and Doppler tomography. From the light curve, one can deduce the radial distribution of the effective temperature, assuming axial symmetry. On the other hand, from the variation of the line profile one can reconstruct an image in the velocity space, which can be converted into a real image if one knows the kinematics of the system. Deux techniques sont couramment utilisées pour obtenir des images des disques dans les systèmes binaires à éclipses. En utilisant la courbe de lumière, on peut remonter à la distribution radiale de la brillance de surface, en supposant que celle-ci a une symètrie axiale. D'autre part, les profils de raies renseignent sur la distribution de vitesse des régions émissives leur variation temporelle permet de réaliser une image dans l'espace des vitesses, que l'on peut ensuite transformer en carte dans l'espace (x,y) si on connaît la cinématique du système.

  7. 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.

  8. 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).

  9. Computational insight into the capacitive performance of graphene edge planes

    DOE PAGES

    Zhan, Cheng; Zhang, Yu; Cummings, Peter T.; ...

    2017-02-01

    Recent experiments have shown that electric double-layer capacitors utilizing electrodes consisting of graphene edge plane exhibit higher capacitance than graphene basal plane. However, theoretical understanding of this capacitance enhancement is still limited. Here we applied a self-consistent joint density functional theory calculation on the electrode/electrolyte interface and found that the capacitance of graphene edge plane depends on the edge type: zigzag edge has higher capacitance than armchair edge due to the difference in their electronic structures. We further examined the quantum, dielectric, and electric double-layer (EDL) contributions to the total capacitance of the edge-plane electrodes. Classical molecular dynamics simulation foundmore » that the edge planes have higher EDL capacitance than the basal plane due to better adsorption of counter-ions and higher solvent accessible surface area. Finally, our work therefore has elucidated the capacitive energy storage in graphene edge planes that take into account both the electrode's electronic structure and the EDL structure.« less

  10. 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.

  11. 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.

  12. Double layer capacitance of anode/solid-electrolyte interfaces.

    PubMed

    Ge, Xiaoming; Fu, Changjing; Chan, Siew Hwa

    2011-09-07

    The double layer of electrode/electrolyte interfaces plays a fundamental role in determining the performance of solid state electrochemical cells. The double layer capacitance is one of the most-studied descriptors of the double layer. This work examines a case study on lanthanum strontium vanadate (LSV)/yttria-stabilized zirconia (YSZ) interfaces exposed in solid oxide fuel cell anode environment. The apparent double layer capacitance is obtained from impedance spectroscopy. The intrinsic double layer capacitance is evaluated based on Stern's method in conjunction with the Volta potential analysis across LSV/YSZ interfaces. Both the apparent and the intrinsic double layer capacitances exhibit right-skewed volcano patterns, when the interfaces are subjected to anodic biases from 0 to 150 mV. The apparent double layer capacitance is about one order of magnitude larger than the intrinsic double layer capacitance. This discrepancy roots in the inconsistent surface areas that are involved. This analysis of capacitance would provide a more realistic TPB estimate of a working solid-state electrochemical device. This journal is © the Owner Societies 2011

  13. Edge capacitance of a two-dimensional topological insulator

    NASA Astrophysics Data System (ADS)

    Entin, M. V.; Braginsky, L.

    2017-09-01

    We study capacitance of the two-dimensional topological insulator (TI) edge states. The total capacitance is combined as a serial circuit of three capacitors presenting geometrical CG, quantum CQ, and correlation Ccorr contributions to the electron energy. If the Coulomb interaction is weak, they obey an inequality CGcapacitance at the finite temperature is determined taking into account the edge states quantization with and without the magnetic field. We have concluded that, in the accepted approximations, Ccorr-1=0 .

  14. Intrinsic Capacitances and Inductances of Quantum Hall Effect Devices.

    PubMed

    Cage, M E; Jeffery, A

    1996-01-01

    Analytic solutions are obtained for the internal capacitances, kinetic inductances, and magnetic inductances of quantum Hall effect devices to investigate whether or not the quantized Hall resistance is the only intrinsic impedance of importance in measurements of the ac quantum Hall effect. The internal capacitances and inductances are obtained by using the results of Cage and Lavine, who determined the current and potential distributions across the widths of quantum Hall effect devices. These intrinsic capacitances and inductances produce small out-of-phase impedance corrections to the in-phase quantized Hall resistance and to the in-phase longitudinal resistance.

  15. Measurement of the sheath capacitance of a planar probe

    SciTech Connect

    Oh, Se-Jin; Lee, Young-Kwang; Chung, Chin-Wook

    2011-10-15

    The sheath capacitance was measured on a planar probe dc-biased with respect to the plasma potential using the phase sensitive detection method in the region separated from the rf discharge plasmas by an immersed grid. It was observed that the sheath capacitance was negative when the collecting electrode of the probe was positioned downward toward the grid and biased near the plasma potential. This indicates that a double sheath had built up near the probe electrode. This tendency can be explained by the sheath capacitance, which is calculated using Poisson's equation with a non-zero electrical field and an ion velocity condition at the sheath edge.

  16. 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.

  17. Hydrogen atom kinetics in capacitively coupled plasmas

    NASA Astrophysics Data System (ADS)

    Nunomura, Shota; Katayama, Hirotaka; Yoshida, Isao

    2017-05-01

    Hydrogen (H) atom kinetics has been investigated in capacitively coupled very high frequency (VHF) discharges at powers of 16-780 mW cm-2 and H2 gas pressures of 0.1-2 Torr. The H atom density has been measured using vacuum ultra violet absorption spectroscopy (VUVAS) with a micro-discharge hollow cathode lamp as a VUV light source. The measurements have been performed in two different electrode configurations of discharges: conventional parallel-plate diode and triode with an intermediate mesh electrode. We find that in the triode configuration, the H atom density is strongly reduced across the mesh electrode. The H atom density varies from ˜1012 cm-3 to ˜1010 cm-3 by crossing the mesh with 0.2 mm in thickness and 36% in aperture ratio. The fluid model simulations for VHF discharge plasmas have been performed to study the H atom generation, diffusion and recombination kinetics. The simulations suggest that H atoms are generated in the bulk plasma, by the electron impact dissociation (e + H2 \\to e + 2H) and the ion-molecule reaction (H2 + + H2 \\to {{{H}}}3+ + H). The diffusion of H atoms is strongly limited by a mesh electrode, and thus the mesh geometry influences the spatial distribution of the H atoms. The loss of H atoms is dominated by the surface recombination.

  18. Systematic interpretation of differential capacitance data

    NASA Astrophysics Data System (ADS)

    Gavish, Nir; Promislow, Keith

    2015-07-01

    Differential capacitance (DC) data have been widely used to characterize the structure of electrolyte solutions near charged interfaces and as experimental validation of models for electrolyte structure. Fixing a large class of models of electrolyte free energy that incorporate finite-volume effects, a reduction is identified which permits the identification of all free energies within that class that return identical DC data. The result is an interpretation of DC data through the equivalence classes of nonideality terms, and associated boundary layer structures, that cannot be differentiated by DC data. Specifically, for binary salts, DC data, even if measured over a range of ionic concentrations, are unable to distinguish among models which exhibit charge asymmetry, charge reversal, and even ion crowding. The reduction applies to capacitors which are much wider than the associated Debye length and to finite-volume terms that are algebraic in charge density. However, within these restrictions the free energy is shown to be uniquely identified if the DC data are supplemented with measurements of the excess chemical potential of the system in the bulk state.

  19. 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.

  20. 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.

  1. 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.

  2. 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.

  3. Micromachined capacitive transducer arrays for intravascular ultrasound

    NASA Astrophysics Data System (ADS)

    Degertekin, F. Levent; Guldiken, R. Oytun; Karaman, Mustafa

    2005-01-01

    Intravascular ultrasound (IVUS) imaging has become an essential imaging modality for the effective diagnosis and treatment of cardiovascular diseases during the past decade enabled by innovative applications of piezoelectric transducer technology. The limitations in the manufacture and performance of the same piezoelectric transducers have also impeded the improvement of IVUS for emerging clinically important applications such as forward viewing arrays for guiding interventions and high resolution imaging of arterial structure such as vulnerable plaque and fibrous cap, and also implementation of techniques such as harmonic imaging of the tissue and of the contrast agents. Capacitive micromachined ultrasonic transducer (CMUT) technology shows great potential for transforming IVUS not only to satisfy these clinical needs but also to open up possibilities for low-cost imaging devices integrated to therapeutic tools. We have developed manufacturing processes with a maximum process temperature of 250°C to build CMUTs on the same silicon chip with integrated electronics. Using these processes we fabricated CMUT arrays suitable for forward viewing IVUS in the 10-20MHz range. We characterized these array elements in terms of pulse-echo response, radiation pattern measurements and demonstrated its volumetric imaging capabilities on various imaging targets.

  4. 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. Copyright © 2016 Elsevier Ltd. All rights reserved.

  5. 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.

  6. Modeling electromagnetic effects in capacitive discharges

    NASA Astrophysics Data System (ADS)

    Lee, Insook; Graves, D. B.; Lieberman, M. A.

    2008-02-01

    We present a self-consistent two-dimensional axisymmetric model and simulation strategy to predict radial plasma uniformity in large-area high-frequency (up to 200 MHz) capacitive discharges of argon gas in the pressure range 2-150 mTorr. The model couples Maxwell equations, fluid plasma equations and a sheath model with stochastic heating effects taken into account, solving the equations using the finite element method. Electromagnetic effects (e.g. standing wave and skin effects) as well as the electrostatic edge effect are captured in the simulation, in good agreement with recent experiments. The model highlights differences between the edge effect and the skin effect, both of which can cause strong plasma production near the radial reactor edge. At higher frequencies and high pressures, we observe the 'stop band' where waves are highly damped as they propagate from the discharge edge into the center. We determine the transition from global-to-local power deposition as the pressure varies. An electrode asymmetry with a grounded reactor radial edge is found to suppress undesirable edge effects. For radial plasma uniformity, it is essential to consider the balancing of the standing wave effect (maximal at the reactor center) with the skin effect (maximal near the radial reactor edge), together with their coupling to the edge effect, which can be obtained by a choice of robust reactor design geometry and driving frequency, over the range of process parameter operating windows to be used.

  7. Capacitive Systems for Dielectric Plasma Etch

    NASA Astrophysics Data System (ADS)

    Hoffman, Daniel

    2005-09-01

    Two and three frequency capacitive systems are being used to generate weakly ionized plasma in Ar/O/CxFy chemistries at the millitorr pressure range. One or two of the frequencies are generally used to accelerate ions (by sheath rectification) while the third is generally used to independently raise plasma density to levels sufficient for etching. The choice of frequencies is based on plasma impedances, which then yield rf voltages that can either consume power by creating a DC plasma sheath or consume power by creating plasma density (when sheath power is minimized). Within the two frequencies that create sheaths, the choice of ion energy spreads is determined by ion sheath transit time relative to an rf cycle. Technology challenges arising from the required plasma creation include significant intermodulation, very high cross talk between generators, and the avoidance of arcing through on any of the surfaces in contact with the plasma (including the gas injection system). The etch chamber is designed such that all generators are directly linked on a single coupling point or the plasma directly connects one launcher to another. We discuss and analyze different frequency ranges and their impact on chamber design.

  8. Quantum Capacitance of a Topological Insulator-Ferromagnet Interface

    NASA Astrophysics Data System (ADS)

    Siu, Zhuo Bin; Chowdhury, Debashree; Jalil, Mansoor B. A.; Basu, Banasri

    2017-03-01

    We study the quantum capacitance in a topological insulator thin film system magnetized in the in-plane direction in the presence of an out-of-plane magnetic field and hexagonal warping. To first order, the modification in quantum capacitance due to hexagonal warping compared to the clean case, where both the in-plane magnetization and hexagonal warping are absent, is always negative, and increases in magnitude monotonically with the energy difference from the charge neutrality point. In contrast, the change in the quantum capacitance due to in-plane magnetization oscillates with the energy in general, except when a certain relation between the inter-surface coupling, out of plane Zeeman energy splitting and magnetic field strength is satisfied. In this special case, the quantum capacitance remains unchanged by the in-plane magnetization for all energies.

  9. Quantum Capacitance of a Topological Insulator-Ferromagnet Interface.

    PubMed

    Siu, Zhuo Bin; Chowdhury, Debashree; Jalil, Mansoor B A; Basu, Banasri

    2017-03-24

    We study the quantum capacitance in a topological insulator thin film system magnetized in the in-plane direction in the presence of an out-of-plane magnetic field and hexagonal warping. To first order, the modification in quantum capacitance due to hexagonal warping compared to the clean case, where both the in-plane magnetization and hexagonal warping are absent, is always negative, and increases in magnitude monotonically with the energy difference from the charge neutrality point. In contrast, the change in the quantum capacitance due to in-plane magnetization oscillates with the energy in general, except when a certain relation between the inter-surface coupling, out of plane Zeeman energy splitting and magnetic field strength is satisfied. In this special case, the quantum capacitance remains unchanged by the in-plane magnetization for all energies.

  10. 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.

  11. 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)

  12. Quantum Capacitance of a Topological Insulator-Ferromagnet Interface

    PubMed Central

    Siu, Zhuo Bin; Chowdhury, Debashree; Jalil, Mansoor B. A.; Basu, Banasri

    2017-01-01

    We study the quantum capacitance in a topological insulator thin film system magnetized in the in-plane direction in the presence of an out-of-plane magnetic field and hexagonal warping. To first order, the modification in quantum capacitance due to hexagonal warping compared to the clean case, where both the in-plane magnetization and hexagonal warping are absent, is always negative, and increases in magnitude monotonically with the energy difference from the charge neutrality point. In contrast, the change in the quantum capacitance due to in-plane magnetization oscillates with the energy in general, except when a certain relation between the inter-surface coupling, out of plane Zeeman energy splitting and magnetic field strength is satisfied. In this special case, the quantum capacitance remains unchanged by the in-plane magnetization for all energies. PMID:28337992

  13. 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)

  14. Apport de la simulation numérique à la compréhension des mécanismes d'interaction de cavités dans le cadre de la modélisation de l'endommagement ductile sous sollicitation dynamique

    NASA Astrophysics Data System (ADS)

    Roy, G.; Buy, F.; Llorca, F.

    2002-12-01

    L'étude présentée s'inscrit dans le cadre d'une démarche menant à la construction d'un modèle analytique ou semi analytique de comportement élasto-visco-plastique endommageable, applicable aux chargements rencontrés en configuration d'impact violent et générant de l'écaillage ductile. La prise en compte des effets de compressibilité et de micro inertie est essentielle pour modéliser la phase de croissance. Des simulations numériques globales de la structure et locales à l'échelle des hétérogénéités permettent d'évaluer les niveaux de sollicitations dans les zones susceptibles de s'endommager, dévaluer des critères analytiques de germination de l'endommagement et de comprendre les mécanismes d'interaction entre les défauts. Les effets micro inertiels et de compressibilité sont ainsi mis en évidence dans les phases de germination et de coalescence des micro défauts. II s'agit ici d'une illustration non exhaustive de travaux engagés au CEA Valduc sur le tantale, dans le cadre d'une thèse [10]. Un programme matériaux en partenariat CEA-CNRS sur la modélisation multi échelles du comportement de structures a également été initié dans ce contexte.

  15. 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

  16. The origin of grain boundary capacitance in highly doped ceria.

    PubMed

    Souza, Eduardo Caetano C; Goodenough, John B

    2016-02-17

    The origin of a grain-boundary capacitance in mixed oxide-ion/electronic conductors has been investigated for the case of Ce0.8Sm0.2O1.9-δ using a.c. impedance spectroscopy under low pO2 from 250 to 400 °C. The observed capacitance is interpreted in terms of Ce(III):4f(1) electrons first introduced into the grains and not into the grain boundaries.

  17. 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.

  18. Isothermal Capacitance Transient Spectroscopy for Determination of Deep Level Parameters

    NASA Astrophysics Data System (ADS)

    Okushi, Hideyo; Tokumaru, Yozo

    1980-06-01

    A new measurement method for deep levels in semiconductors is proposed, by which the measurement of the transient change of capacitance is performed under an isothermal condition (Isothermal Capacitance Transient Spectroscopy). The method allows us to construct a precise measurement and analysis system by a programmable calculator. Computer simulation and experiment by the method in the case of Au-doped Si are demonstrated. It is shown that the method is one of useful tools for spectroscopic analysis of deep levels in semiconductors.

  19. Modeling high-frequency capacitance in SOI MOS capacitors

    NASA Astrophysics Data System (ADS)

    Łukasiak, Lidia; Jasiński, Jakub; Beck, Romuald B.; Ikraiam, Fawzi A.

    2016-12-01

    This paper presents a model of high frequency capacitance of a SOI MOSCAP. The capacitance in strong inversion is described with minority carrier redistribution in the inversion layer taken into account. The efficiency of the computational process is significantly improved. Moreover, it is suitable for the simulation of thin-film SOI structures. It may also be applied to the characterization of non-standard SOI MOSCAPS e.g. with nanocrystalline body.

  20. Developpement d'un compresseur d'hydrogene base sur le cyclage thermique des hydrures metalliques

    NASA Astrophysics Data System (ADS)

    Laurencelle, Francois

    La compression de l'hydrogene est une etape incontournable de son utilisation dans l'industrie actuelle et dans les nouvelles applications energetiques de l'hydrogene (stockage stationnaire et transport). Les compresseurs mecaniques traditionnellement utilises posent plusieurs problemes d'ingenierie, de securite et de maintenance qui pourraient etre contournes en developpant de nouvelles technologies mieux adaptees a l'hydrogene. Dans cette these, notre objectif est de developper d'un compresseur d'hydrogene base sur les hydrures metalliques pouvant etre connecte a la sortie d'un electrolyseur fonctionnant a basse pression et d'ainsi repondre au besoin de productioncompression d'hydrogene decentralisee. La methodologie du projet comprend plusieurs etapes. Premierement, nous faisons la revue bibliographique des projets impliquant des compresseurs a hydrures metalliques. Deuxiemement, a travers des travaux experimentaux, nous recherchons des hydrures permettant une compression efficace entre 20 et 80°C. Les materiaux sont synthetises par fusion a arc electrique et caracterises sur bancs d'essais d'hydrogenation. La structure de certains materiaux est aussi investiguee par rayons X, methode de B.E.T. et microscopie electronique. Troisiemement, un reacteur d'hydrures est concu de maniere a promouvoir des echanges de chaleur rapides et efficaces. Quatriemement, le prototype et son interface de controle sont construits. Cinquiemement, le compresseur est caracterise pour en evaluer les performances en termes de debit et de capacite. Les resultats obtenus sont presentes dans trois articles publies et dans le chapitre 5 de cette these. Le compresseur (article I) est base sur trois hydrures (LaNi 4.8Sn0.2, LaNi5 et MMNi4.7Al0.3 ). Celui-ci permet d'atteindre un debit de compression de 10 a 20 L d'hydrogene par heure et son efficacite est, estimee a ˜5% par rapport a un compresseur adiabatique ideal. Il a ete demontre que l'efficacite pourrait etre augmentee en utilisant un

  1. A high voltage method for measuring low capacitance for tomography.

    PubMed

    Lu, Decai; Shao, Fuqun; Guo, Zhiheng

    2009-05-01

    Low capacitance measurement is involved in many industrial applications, especially in the applications of electrical capacitance tomography (ECT). Most of the low capacitance measurement circuits employ an ac-based method or a charge/discharge method because of high sensitivity, high resolution, and immunity to stray capacitance; and its excitation or charge voltage are not more than 20 V. When ECT techniques for large industrial equipment such as blast furnaces or grain barns are explored, the existing methods for measuring low capacitance have some limitations. This paper proposes a high excitation voltage ac-based method for measuring low capacitance to improve the resolution of measurement. The method uses a high excitation voltage of several hundred volts and a transformer ratio arms as the C/V transducer. Experimental results indicate that the new method has a resolution of 0.005 fF, a good stability (about 0.003 fF over 4 h) and linearity (0.9992).

  2. Reduced capacitative calcium entry correlates with vesicle accumulation and apoptosis.

    PubMed

    Jayadev, S; Petranka, J G; Cheran, S K; Biermann, J A; Barrett, J C; Murphy, E

    1999-03-19

    A preneoplastic variant of Syrian hamster embryo cells, sup(+), exhibits decreased endoplasmic reticulum calcium levels and subsequently undergoes apoptosis in low serum conditions (Preston, G. A., Barrett, J. C., Biermann, J. A., and Murphy, E. (1997) Cancer Res. 57, 537-542). This decrease in endoplasmic reticulum calcium appears to be due, at least in part, to reduced capacitative calcium entry at the plasma membrane. Thus we investigated whether inhibition of capacitative calcium entry per se could reduce endoplasmic reticulum calcium and induce apoptosis of cells. We find that treatment with either SKF96365 (30-100 microM) or cell-impermeant 1,2-bis(o-amino-5-bromophenoxy)ethane-N,N,N', N'-tetraacetic acid (5-10 mM) is able to induce apoptosis of cells in conditions where apoptosis does not normally occur. Because previous work has implicated vesicular trafficking as a mechanism of regulating capacitative calcium entry, we investigated whether disruption of vesicular trafficking could lead to decreased capacitative calcium entry and subsequent apoptosis of cells. Coincident with low serum-induced apoptosis, we observed an accumulation of vesicles within the cell, suggesting deregulated vesicle trafficking. Treatment of cells with bafilomycin (30-100 nM), an inhibitor of the endosomal proton ATPase, produced an accumulation of vesicles, decreased capacitative entry, and induced apoptosis. These data suggest that deregulation of vesicular transport results in reduced capacitative calcium entry which in turn results in apoptosis.

  3. Capacitance of carbon-based electrical double-layer capacitors.

    PubMed

    Ji, Hengxing; Zhao, Xin; Qiao, Zhenhua; Jung, Jeil; Zhu, Yanwu; Lu, Yalin; Zhang, Li Li; MacDonald, Allan H; Ruoff, Rodney S

    2014-01-01

    Experimental electrical double-layer capacitances of porous carbon electrodes fall below ideal values, thus limiting the practical energy densities of carbon-based electrical double-layer capacitors. Here we investigate the origin of this behaviour by measuring the electrical double-layer capacitance in one to five-layer graphene. We find that the capacitances are suppressed near neutrality, and are anomalously enhanced for thicknesses below a few layers. We attribute the first effect to quantum capacitance effects near the point of zero charge, and the second to correlations between electrons in the graphene sheet and ions in the electrolyte. The large capacitance values imply gravimetric energy storage densities in the single-layer graphene limit that are comparable to those of batteries. We anticipate that these results shed light on developing new theoretical models in understanding the electrical double-layer capacitance of carbon electrodes, and on opening up new strategies for improving the energy density of carbon-based capacitors.

  4. Capacitance of carbon-based electrical double-layer capacitors

    NASA Astrophysics Data System (ADS)

    Ji, Hengxing; Zhao, Xin; Qiao, Zhenhua; Jung, Jeil; Zhu, Yanwu; Lu, Yalin; Zhang, Li Li; MacDonald, Allan H.; Ruoff, Rodney S.

    2014-02-01

    Experimental electrical double-layer capacitances of porous carbon electrodes fall below ideal values, thus limiting the practical energy densities of carbon-based electrical double-layer capacitors. Here we investigate the origin of this behaviour by measuring the electrical double-layer capacitance in one to five-layer graphene. We find that the capacitances are suppressed near neutrality, and are anomalously enhanced for thicknesses below a few layers. We attribute the first effect to quantum capacitance effects near the point of zero charge, and the second to correlations between electrons in the graphene sheet and ions in the electrolyte. The large capacitance values imply gravimetric energy storage densities in the single-layer graphene limit that are comparable to those of batteries. We anticipate that these results shed light on developing new theoretical models in understanding the electrical double-layer capacitance of carbon electrodes, and on opening up new strategies for improving the energy density of carbon-based capacitors.

  5. Grundlagen des Tissue Engineering

    NASA Astrophysics Data System (ADS)

    Mayer, Jörg; Blum, Janaki; Wintermantel, Erich

    Die Organtransplantation stellt eine verbreitete Therapie dar, um bei krankheitsoder unfallbedingter Schädigung eines Organs die Gesamtheit seiner Funktionen wieder herzustellen, indem es durch ein Spenderorgan ersetzt wird. Organtransplantationen werden für die Leber, die Niere, die Lunge, das Herz oder bei schweren grossflächigen Verbrennungen der Haut vorgenommen. Der grosse apparative, personelle und logistische Aufwand und die Risiken der Transplantationschirurgie (Abstossungsreaktionen) sowie die mangelnde Verfügbarkeit von immunologisch kompatiblen Spenderorganen führen jedoch dazu, dass der Bedarf an Organtransplantaten nur zu einem sehr geringen Teil gedeckt werden kann. Sind Spenderorgane nicht verfügbar, können in einzelnen Fällen lebenswichtige Teilfunktionen, wie beispielsweise die Filtrationsfunktion der Niere durch die Blutreinigung mittels Dialyse ersetzt oder, bei mangelnder Funktion der Bauchspeicheldrüse (Diabetes), durch die Verabreichung von Insulin ein normaler Zustand des Gesamtorganismus auch über Jahre hinweg erhalten werden. Bei der notwendigen lebenslangen Anwendung apparativer oder medikamentöser Therapie können für den Patienten jedoch häufig schwerwiegende, möglicherweise lebensverkürzende Nebenwirkungen entstehen. Daher werden in der Forschung Alternativen gesucht, um die Funktionen des ausgefallenen Organs durch die Implantation von Zellen oder in vitro gezüchteten Geweben möglichst umfassend wieder herzustellen. Dies erfordert biologisch aktive Implantate, welche die für den Stoffwechsel des Organs wichtigen Zellen enthalten und einen organtypischen Stoffwechsel entfalten.

  6. 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

  7. Reticulation des fibres lignocellulosiques

    NASA Astrophysics Data System (ADS)

    Landrevy, Christel

    Pour faire face à la crise économique la conception de papier à valeur ajoutée est développée par les industries papetières. Le but de se projet est l'amélioration des techniques actuelles de réticulation des fibres lignocellulosiques de la pâte à papier visant à produire un papier plus résistant. En effet, lors des réactions de réticulation traditionnelles, de nombreuses liaisons intra-fibres se forment ce qui affecte négativement l'amélioration anticipée des propriétés physiques du papier ou du matériau produit. Pour éviter la formation de ces liaisons intra-fibres, un greffage sur les fibres de groupements ne pouvant pas réagir entre eux est nécessaire. La réticulation des fibres par une réaction de « click chemistry » appelée cycloaddition de Huisgen entre un azide et un alcyne vrai, catalysée par du cuivre (CuAAC) a été l'une des solutions trouvée pour remédier à ce problème. De plus, une adaptation de cette réaction en milieux aqueux pourrait favoriser son utilisation en milieu industriel. L'étude que nous désirons entreprendre lors de ce projet vise à optimiser la réaction de CuAAC et les réactions intermédiaires (propargylation, tosylation et azidation) sur la pâte kraft, en milieu aqueux. Pour cela, les réactions ont été adaptées en milieu aqueux sur la cellulose microcristalline afin de vérifier sa faisabilité, puis transférée à la pâte kraft et l'influence de différents paramètres comme le temps de réaction ou la quantité de réactifs utilisée a été étudiée. Dans un second temps, une étude des différentes propriétés conférées au papier par les réactions a été réalisée à partir d'une série de tests papetiers optiques et physiques. Mots Clés Click chemistry, Huisgen, CuAAC, propargylation, tosylation, azidation, cellulose, pâte kraft, milieu aqueux, papier.

  8. La diffraction des neutrons et des rayons X pour l'étude structurale des liquides et des verres

    NASA Astrophysics Data System (ADS)

    Fischer, H. E.; Salmon, P. S.; Barnes, A. C.

    2003-02-01

    La compréhension de mainte propriété physique d'un verre ou d'un liquide nécessite la connaissance des facteurs de structure partiels (PSFs) qui décrivent chacun la distribution d'une espèce atomique autour d'une autre. La technique de diffraction des neutrons avec substitution isotopique (NDIS) [1,2,3], ayant bien réussi a déterminer les PSFs de certains composés [4,5], est pourtant restreinte aux isotopes présentant un contraste suffisant en longueur de diffusion. D'un autre cote, la technique de diffusion anomale des rayons X (AXS ou AXD) [6] permet de faire varier la longueur de diffusion d'une espèce atomique pourvu que son énergie d'absorption soit à la fois accessible et suffisamment élevée pour donner un assez grand transfert du moment. La combinaison des techniques de diffraction des neutrons (avec ou sans substitution isotopique) et de diffraction des rayons X (avec ou sans diffusion anomale) peut donc permettre d'obtenir un meilleur contraste en longueurs de diffusion pour un système donné, mais exige une analyse de données plus soignée pour pouvoir bien tenir compte des erreurs systématiques qui sont différentes pour les 2 techniques [7]. Pour les atomes ayant des distributions électroniques quasi-sphériques, e.g. dans le cas d'un alliage liquide, la combinaison des techniques de NDIS et de diffraction des rayons X s'est déjà montrée très avantageuse pour la détermination des PSFs [8,9]. Dans le cas des verres ayant d'importantes liaisons covalentes, l'effective combinaison des 2 techniques peut être moins directe mais facilitée lorsqu'il s'agit des atomes de grand Z [10,11]. Nous présentons ici un sommaire du méthode et quelques exemples des résultats.

  9. Chloride and Salicylate Influence Prestin-dependent Specific Membrane Capacitance

    PubMed Central

    Santos-Sacchi, Joseph; Song, Lei

    2014-01-01

    The outer hair cell is electromotile, its membrane motor identified as the protein SLC26a5 (prestin). An area motor model, based on two-state Boltzmann statistics, was developed about two decades ago and derives from the observation that outer hair cell surface area is voltage-dependent. Indeed, aside from the nonlinear capacitance imparted by the voltage sensor charge movement of prestin, linear capacitance (Clin) also displays voltage dependence as motors move between expanded and compact states. Naturally, motor surface area changes alter membrane capacitance. Unit linear motor capacitance fluctuation (δCsa) is on the order of 140 zeptofarads. A recent three-state model of prestin provides an alternative view, suggesting that voltage-dependent linear capacitance changes are not real but only apparent because the two component Boltzmann functions shift their midpoint voltages (Vh) in opposite directions during treatment with salicylate, a known competitor of required chloride binding. We show here using manipulations of nonlinear capacitance with both salicylate and chloride that an enhanced area motor model, including augmented δCsa by salicylate, can accurately account for our novel findings. We also show that although the three-state model implicitly avoids measuring voltage-dependent motor capacitance, it registers δCsa effects as a byproduct of its assessment of Clin, which increases during salicylate treatment as motors are locked in the expanded state. The area motor model, in contrast, captures the characteristics of the voltage dependence of δCsa, leading to a better understanding of prestin. PMID:24554714

  10. 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

  11. Evaluation de methodes de controle non destructives (CND) alternatives pour remplacer l'attaque anodique des superalliages de nickel

    NASA Astrophysics Data System (ADS)

    Pourfard, Atousa

    Les superalliages de nickel, comme le Waspaloy, ont trouve leur place dans differentes industries grâce a leurs caracteristiques particulieres, notamment la bonne resistance a la corrosion a haute temperature. Ce memoire porte sur l'identification d'une methode d'inspection non destructive a sec, pour reveler les defauts microstructuraux sur un echantillon usine de disque de turbine de superalliage de nickel : le Waspaloy. Les precipites intermetalliques augmentent la resistance a la traction, la resistance au fluage, la limite d'elasticite et la limite de rupture du superalliage. Cependant, les defauts microstructuraux, les freckles et les white spots, ont des effets negatifs sur les proprietes mecaniques des superalliages de nickel. Ce document presente une etude approfondie de l'origine et de la nature des freckles et des white spots. Les travaux experimentaux sont principalement concentres sur les mesures de conductivite electrique par courants de Foucault et sur les mesures ultrasonores par ondes acoustiques de surface (les ondes de Rayleigh). Pour enrichir la capacite d'analyse, une etude sur la technique de l'imagerie magneto-optique est egalement presentee dans ce document. Le controle des parametres de mesure confirme l'efficacite de chaque technique. Ce rapport rend compte des resultats satisfaisants qui pourront servir pour les recherches et les travaux a venir.

  12. Capacitance-Based Frequency Adjustment of Micro Piezoelectric Vibration Generator

    PubMed Central

    Mao, Xinhua; He, Qing; Li, Hong; Chu, Dongliang

    2014-01-01

    Micro piezoelectric vibration generator has a wide application in the field of microelectronics. Its natural frequency is unchanged after being manufactured. However, resonance cannot occur when the natural frequencies of a piezoelectric generator and the source of vibration frequency are not consistent. Output voltage of the piezoelectric generator will sharply decline. It cannot normally supply power for electronic devices. In order to make the natural frequency of the generator approach the frequency of vibration source, the capacitance FM technology is adopted in this paper. Different capacitance FM schemes are designed by different locations of the adjustment layer. The corresponding capacitance FM models have been established. Characteristic and effect of the capacitance FM have been simulated by the FM model. Experimental results show that the natural frequency of the generator could vary from 46.5 Hz to 42.4 Hz when the bypass capacitance value increases from 0 nF to 30 nF. The natural frequency of a piezoelectric vibration generator could be continuously adjusted by this method. PMID:25133237

  13. 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.

  14. 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.

  15. 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.

  16. Distributed sensing: multiple capacitive stretch sensors on a single channel

    NASA Astrophysics Data System (ADS)

    Tairych, Andreas; Anderson, Iain A.

    2017-04-01

    "Soft, stretchable, and unobtrusive". These are some of the attributes frequently associated with capacitive dielectric elastomer (DE) sensors for body motion capture. While the sensors themselves are soft and elastic, they require rigid peripheral components for capacitance measurement. Each sensor is connected to a separate channel on the sensing circuitry through its own set of wires. In wearable applications with large numbers of sensors, this can lead to a considerable circuit board footprint, and cumbersome wiring. The additional equipment can obstruct movement and alter user behaviour. Previous work has demonstrated how a transmission line model can be applied to localise deformation on a single DE sensor. Building on this approach, we have developed a distributed sensing method by arranging capacitive DE sensors and external resistors to form a transmission line, which is connected to a single sensing channel with only one set of wires. The sensors are made from conductive fabric electrodes, and silicone dielectrics, and the external resistors are off-the-shelf metal film resistors. Excitation voltages with different frequencies are applied to the transmission line. The lumped transmission line capacitances at these frequencies are passed on to a mathematical model that calculates individual sensor capacitance changes. The prototype developed for this study is capable of obtaining separate readings for simultaneously stretched sensors.

  17. Capacitance-based frequency adjustment of micro piezoelectric vibration generator.

    PubMed

    Mao, Xinhua; He, Qing; Li, Hong; Chu, Dongliang

    2014-01-01

    Micro piezoelectric vibration generator has a wide application in the field of microelectronics. Its natural frequency is unchanged after being manufactured. However, resonance cannot occur when the natural frequencies of a piezoelectric generator and the source of vibration frequency are not consistent. Output voltage of the piezoelectric generator will sharply decline. It cannot normally supply power for electronic devices. In order to make the natural frequency of the generator approach the frequency of vibration source, the capacitance FM technology is adopted in this paper. Different capacitance FM schemes are designed by different locations of the adjustment layer. The corresponding capacitance FM models have been established. Characteristic and effect of the capacitance FM have been simulated by the FM model. Experimental results show that the natural frequency of the generator could vary from 46.5 Hz to 42.4 Hz when the bypass capacitance value increases from 0 nF to 30 nF. The natural frequency of a piezoelectric vibration generator could be continuously adjusted by this method.

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

    PubMed Central

    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

  19. Coherence properties of a capacitively-shunt flux qubit

    NASA Astrophysics Data System (ADS)

    Birenbaum, Jeffrey; Sears, Adam; Nugroho, Christopher; Gudmundsen, Ted; Welander, Paul; Yoder, Jonilyn; Kamal, Archana; Gustavsson, Simon; Kerman, Jamie; Oliver, William; Clarke, John

    2014-03-01

    Coherence times for typical flux qubits have plateaued at 5 - 10 μ s for T1 and 1 - 3 μ s for TRamsey. To achieve longer coherence times we study capacitively-shunted flux qubits using high-Q capacitors to individually shunt all four Josephson junctions (JJs). The additional shunt capacitance moves 90 + % of the qubit energy from the lossy capacitance of the JJs into the high-Q shunts while preserving an anharmonicity greater than 100 % and maintaining f01 capacitively-shunted flux qubit inductively coupled to a lumped-element readout resonator. The qubit junctions are deposited via aluminum e-beam evaporation using a bridgeless mask. We characterize the influence of qubit design parameters such as capacitance and geometry on the coherence time of the device. This research was funded in part by the Office of the Director of National Intelligence (ODNI), Intelligence Advanced Research Projects Activity (IARPA), through the Army Research Office.

  20. 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.

  1. Capacitance and compressibility of heterostructures with strong electronic correlations

    NASA Astrophysics Data System (ADS)

    Steffen, Kevin; Frésard, Raymond; Kopp, Thilo

    2017-01-01

    Strong electronic correlations related to a repulsive local interaction suppress the electronic compressibility in a single-band model, and the capacitance of a corresponding metallic film is directly related to its electronic compressibility. Both statements may be altered significantly when two extensions to the system are implemented which we investigate here: (i) we introduce an attractive nearest-neighbor interaction V as antagonist to the repulsive onsite repulsion U , and (ii) we consider nanostructured multilayers (heterostructures) assembled from two-dimensional layers of these systems. We determine the respective total compressibility κ and capacitance C of the heterostructures within a strong coupling evaluation, which builds on a Kotliar-Ruckenstein slave-boson technique. Whereas the capacitance C (n ) for electronic densities n close to half-filling is suppressed, illustrated by a correlation induced dip in C (n ) , it may be appreciably enhanced close to a van Hove singularity. Moreover, we show that the capacitance may be a nonmonotonic function of U close to half-filling for both attractive and repulsive V . The compressibility κ can differ from C substantially, as κ is very sensitive to internal electrostatic energies which in turn depend on the specific setup of the heterostructure. In particular, we show that a capacitor with a polar dielectric has a smaller electronic compressibility and is more stable against phase separation than a standard nonpolar capacitor with the same capacitance.

  2. a Capacitive Image Analysis System to Characterize the Skin Surface

    NASA Astrophysics Data System (ADS)

    Gherardi, Alessandro; Bevilacqua, Alessandro

    The assessment of the skin surface is of a great importance in the dermocosmetic field to evaluate the response of individuals to medical or cosmetic treatments. In vivo quantitative measurements of changes in skin topographic structures provide a valuable tool, thanks to noninvasive devices. However, the high cost of the systems commonly employed is limiting, in practice, the widespread use of these devices for a routine-based approach. In this work we resume the research activity carried out to develop a compact low-cost system for skin surface assessment based on capacitive image analysis. The accuracy of the capacitive measurements has been assessed by implementing an image fusion algorithm to enable a comparison between capacitive images and the ones obtained using high-cost profilometry, the most accurate method in the field. In particular, very encouraging results have been achieved in the measurement of the wrinkles' width. On the other hand, experiments show all the native design limitations of the capacitive device, primarily conceived to work with fingerprints, to measure the wrinkles' depth, which point toward a specific re-designing of the capacitive device.

  3. La participation des enfants et des adolescents à la boxe

    PubMed Central

    Purcell, Laura K; LeBlanc, Claire MA

    2012-01-01

    RÉSUMÉ Des milliers de garçons et de filles de moins de 19 ans font de la boxe en Amérique du Nord. Même si la boxe comporte des avantages pour ceux qui y participent, y compris l’exercice, l’autodiscipline et la confiance en soi, le sport lui-même favorise et récompense des coups délibérés à la tête et au visage. Les personnes qui font de la boxe risquent de subir des blessures à la tête, au visage et au cou, y compris des traumatismes neurologiques chroniques et même fatals. Les commotions cérébrales sont l’une des principales blessures causées par la boxe. En raison du risque de blessures crâniennes et faciales, la Société canadienne de pédiatrie et l’American Academy of Pediatrics s’opposent vigoureusement à la boxe comme activité sportive pour les enfants et les adolescents. Ces organismes recommandent que les médecins s’élèvent contre la boxe auprès des jeunes et les encouragent à participer à d’autres activités dans lesquelles les coups intentionnels à la tête ne constituent pas un élément essentiel du sport.

  4. Elaboration d'un dosimetre a fibres scintillantes

    NASA Astrophysics Data System (ADS)

    Archambault, Louis

    Le but de ce travail est de developper un dosimetre constitue d'une matrice de petits scintillateurs plastiques. Ce dosimetre doit presenter une bonne precision et reproductibilite pour satisfaire aux exigences imposees par des techniques de radiotherapie de pointe comme la radiotherapie d'intensite modulee, la radiochirurgie et la tomotherapie. Le desavantage majeur de cette forme de dosimetrie est la presence de bruit produit par l'effet de la radiation sur la fibre optique transportant la lumiere de scintillation jusqu'au photodetecteur. Pour en reduire l'impact, une etude approfondie des dosimetres a scintillation a ete effectuee. Commencant par une modelisation theorique de la collecte et du guidage lumineux, ce travail a ete suivi d'une comparaison experimentale de plusieurs scintillateurs plastiques, de methodes de couplage, de photodetecteurs et de techniques de filtrage. Ces etudes ont permis de choisir les fibres scintillantes pour leur gain de signal de 50% relativement aux autres scintillateurs plastiques. La camera CCD est le photodetecteur le plus adapte pour ce projet etant donne une sensibilite et une stabilite suffisantes, une capacite d'evaluer 3000 signaux dosimetriques simultanement et un systeme de separation chromatique. Apres la selection des meilleures composantes, un dosimetre a ete developpe pour etudier la performance des techniques de filtrage. Il a ete demontre que, apres utilisation du meilleur filtrage, une precision superieure a 1% pouvait etre atteinte. Un dosimetre a trois detecteurs de volumes differents (0,0014, 0,0034 et 0,0083 cm 3) a demontre une linearite face a des taux de doses allant de 10 a 600 cGy/min et pour des temps d'integration entre 0,05 et 50 s. Une reproductibilite superieure a 1% a ete observee pour des doses minimales de 45, 35 et 20 cGy respectivement pour le petit, le moyen et le grand detecteur. Une matrice de 10 detecteurs espaces de 5 mm sur une ligne a ensuite ete realisee. Ce dosimetre s'est montre

  5. 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.

  6. Anomalous high capacitance in a coaxial single nanowire capacitor.

    PubMed

    Liu, Zheng; Zhan, Yongjie; Shi, Gang; Moldovan, Simona; Gharbi, Mohamed; Song, Li; Ma, Lulu; Gao, Wei; Huang, Jiaqi; Vajtai, Robert; Banhart, Florian; Sharma, Pradeep; Lou, Jun; Ajayan, Pulickel M

    2012-06-06

    Building entire multiple-component devices on single nanowires is a promising strategy for miniaturizing electronic applications. Here we demonstrate a single nanowire capacitor with a coaxial asymmetric Cu-Cu(2)O-C structure, fabricated using a two-step chemical reaction and vapour deposition method. The capacitance measured from a single nanowire device corresponds to ~140 μF cm(-2), exceeding previous reported values for metal-insulator-metal micro-capacitors and is more than one order of magnitude higher than what is predicted by classical electrostatics. Quantum mechanical calculations indicate that this unusually high capacitance may be attributed to a negative quantum capacitance of the dielectric-metal interface, enhanced significantly at the nanoscale.

  7. 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

  8. 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.

  9. Surface coupling effects on the capacitance of thin insulating films

    NASA Astrophysics Data System (ADS)

    Jamali, Tayeb; Farahani, S. Vasheghani; Jannesar, Mona; Palasantzas, George; Jafari, G. R.

    2015-05-01

    A general form for the surface roughness effects on the capacitance of a capacitor is proposed. We state that a capacitor with two uncoupled rough surfaces could be treated as two capacitors in series which have been divided from the mother capacitor by a slit. This is in contrast to the case where the two rough surfaces are coupled. When the rough surfaces are coupled, the type of coupling decides the modification of the capacitance in comparison to the uncoupled case. It is shown that if the coupling between the two surfaces of the capacitor is positive (negative), the capacitance is less (higher) than the case of two uncoupled rough plates. Also, we state that when the correlation length and the roughness exponent are small, the coupling effect is not negligible.

  10. On machine capacitance dimensional and surface profile measurement system

    NASA Astrophysics Data System (ADS)

    Resnick, Ralph

    1993-02-01

    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.

  11. Superconducting flux qubit capacitively coupled to an LC resonator

    NASA Astrophysics Data System (ADS)

    Yamamoto, T.; Inomata, K.; Koshino, K.; Billangeon, P.-M.; Nakamura, Y.; Tsai, J. S.

    2014-01-01

    We study the system where a superconducting flux qubit is capacitively coupled to an LC resonator. In three devices with different coupling capacitance, the magnitude of the dispersive shift is enhanced by the third level of the qubit and quantitatively agrees with the theory. We show by numerical calculation that the capacitive coupling plays an essential role for the enhancement in the dispersive shift. We investigate the coherence properties in two of these devices, which are in the strong-dispersive regime, and show that the qubit energy relaxation is currently not limited by the coupling. We also observe the discrete ac-Stark effect, a hallmark of the strong-dispersive regime, in accordance with the theory.

  12. 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.

  13. Preamplifiers for non-contact capacitive biopotential measurements.

    PubMed

    Peng, GuoChen; Ignjatovic, Zeljko; Bocko, Mark F

    2013-01-01

    Non-contact biopotential sensing is an attractive measurement strategy for a number of health monitoring applications, primarily the ECG and the EEG. In all such applications a key technical challenge is the design of a low-noise trans-impedance preamplifier for the typically low-capacitance, high source impedance sensing electrodes. In this paper, we compare voltage and charge amplifier designs in terms of their common mode rejection ratio, noise performance, and frequency response. Both amplifier types employ the same operational-transconductance amplifier (OTA), which was fabricated in a 0.35 um CMOS process. The results show that a charge amplifier configuration has advantages for small electrode-to-subject coupling capacitance values (less than 10 pF--typical of noncontact electrodes) and that the voltage amplifier configuration has advantages for electrode capacitances above 10 pF.

  14. Preamplifiers for non-contact capacitive biopotential measurements*

    PubMed Central

    Peng, GuoChen; Ignjatovic, Zeljko; Bocko, Mark F.

    2014-01-01

    Non-contact biopotential sensing is an attractive measurement strategy for a number of health monitoring applications, primarily the ECG and the EEG. In all such applications a key technical challenge is the design of a low-noise trans-impedance preamplifier for the typically low-capacitance, high source impedance sensing electrodes. In this paper, we compare voltage and charge amplifier designs in terms of their common mode rejection ratio, noise performance, and frequency response. Both amplifier types employ the same operational-transconductance amplifier (OTA), which was fabricated in a 0.35um CMOS process. The results show that a charge amplifier configuration has advantages for small electrode-to-subject coupling capacitance values (less than 10 pF - typical of noncontact electrodes) and that the voltage amplifier configuration has advantages for electrode capacitances above 10 pF. PMID:24109979

  15. Quantum capacitance modifies interionic interactions in semiconducting nanopores

    NASA Astrophysics Data System (ADS)

    Lee, Alpha A.; Vella, Dominic; Goriely, Alain

    2016-02-01

    Nanopores made with low-dimensional semiconducting materials, such as carbon nanotubes and graphene slit pores, are used in supercapacitors. For modelling purposes, it is often assumed that such pores screen ion-ion interactions like metallic pores, i.e. that screening leads to an exponential decay of the interaction potential with ion separation. By introducing a quantum capacitance that accounts for the density of states in the material, we show that ion-ion interactions in carbon nanotubes and graphene slit pores actually decay algebraically with ion separation. This result suggests a new avenue of capacitance optimization based on tuning the electronic structure of a pore: a marked enhancement in capacitance might be achieved by developing nanopores made with metallic materials or bulk semimetallic materials.

  16. CMOS capacitive biosensors for highly sensitive biosensing applications.

    PubMed

    Chang, An-Yu; Lu, Michael S-C

    2013-01-01

    Magnetic microbeads are widely used in biotechnology and biomedical research for manipulation and detection of cells and biomolecules. Most lab-on-chip systems capable of performing manipulation and detection require external instruments to perform one of the functions, leading to increased size and cost. This work aims at developing an integrated platform to perform these two functions by implementing electromagnetic microcoils and capacitive biosensors on a CMOS (complementary metal oxide semiconductor) chip. Compared to most magnetic-type sensors, our detection method requires no externally applied magnetic fields and the associated fabrication is less complicated. In our experiment, microbeads coated with streptavidin were driven to the sensors located in the center of microcoils with functionalized anti-streptavidin antibody. Detection of a single microbead was successfully demonstrated using a capacitance-to-frequency readout. The average capacitance changes for the experimental and control groups were -5.3 fF and -0.2 fF, respectively.

  17. Extraction method for parasitic capacitances and inductances of HEMT models

    NASA Astrophysics Data System (ADS)

    Zhang, HengShuang; Ma, PeiJun; Lu, Yang; Zhao, BoChao; Zheng, JiaXin; Ma, XiaoHua; Hao, Yue

    2017-03-01

    A new method to extract parasitic capacitances and inductances for high electron-mobility transistors (HEMTs) is proposed in this paper. Compared with the conventional extraction method, the depletion layer is modeled as a physically significant capacitance model and the extrinsic values obtained are much closer to the actual results. In order to simulate the high frequency behaviour with higher precision, series parasitic inductances are introduced into the cold pinch-off model which is used to extract capacitances at low frequency and the reactive elements can be determined simultaneously over the measured frequency range. The values obtained by this method can be used to establish a 16-elements small-signal equivalent circuit model under different bias conditions. The results show good agreements between the simulated and measured scattering parameters up to 30 GHz.

  18. THE MEMBRANE CAPACITANCE OF THE SEA URCHIN EGG

    PubMed Central

    Rothschild, Lord

    1957-01-01

    1. The surface of the unfertilized sea urchin egg is folded and the folds are reversibly eliminated by exposing the egg to hypotonic sea water. If the plasma membrane is outside the layer of cortical granules, unfolding may explain why the membrane capacitance per unit area decreases (and does not increase) when a sea urchin egg is put into hypotonic sea water. 2. The degree of surface folding markedly increases after fertilization, which provides an explanation for the increase in membrane capacitance per unit area observed after fertilization. 3. The percentage reduction in membrane folding in fertilized eggs after immersion in hypotonic sea water is probably sufficient to explain the decrease in membrane capacitance per unit area observed in these conditions. PMID:13416315

  19. Etude experimentale des excitations topologiques de l'effet Hall quantique a nu = 1 dans les heterostructures semiconductrices a double puits quantique

    NASA Astrophysics Data System (ADS)

    Charlebois, Serge

    De nombreux travaux theoriques et experimentaux ont ete publies sur les excitations topologiques de gaz electroniques bidimensionnels (GE2D), appellees skyrmions, dans le regime de l'effet Hall quantique a remplissage unitaire. On attend des excitations semblables appellees bimerons dans les systemes formes de deux GE2D couples. Contrairement au cas des GE2D simples, aucune experience n'a, a notre connaissance, presente la mesure d'une propriete specifique aux bimerons. Nous presentons dans cette these des travaux experimentaux ayant pour objectif l'etude d'excitations topologiques dans les heterostructures a double puits quantique. Une manifestation attendue (les bimerons est la presence d'une anisotropie dans la conductivite a travers une constriction. Nous avons concu un dispositif original a point de contact a trois grilles non-coplanaires. Ce dispositif a trois grilles a la particularite de permettre la creation d'une constriction etroite dans le double GE2D tout en permettant l'equilibrage de la densite electronique entre les deux puits dans l'etroit canal de conduction. Nous avons fabrique ce dispositif de taille submicronique par electrolithographie sur des heterostructures a double puits. Les dispositifs ainsi fabriques ont ete etudies a basse temperature (0.3K) et ont montre un fonctionnement conforme aux attentes. Les travaux n'ont pas permis de mettre en evidence une anisotropie de transport revelatrice de l'existence de bimerons. Cette these est a notre connaissance la premiere etude experimentale visant la realisation de l'experience d'anisotropie de transport et est ainsi une contribution significative a l'avancement des connaissances dans ce domaine. Les travaux theoriques que nous presentons ont permis de montrer l'effet des excitations topologiques sur la capacite grille-GE2D du systeme. Ces travaux ouvrent la voie de la detection des bimerons par l'intermediaire de la mesure de la capacite grille-GE2D ou encore de la susceptibilite electrique du

  20. Traitement des séquelles de brûlures de la main dans les pays à ressources limitées ; notre expérience en république démocratique du Congo

    PubMed Central

    Kibadi, K.; Moutet, F.

    2015-01-01

    Summary Les séquelles de brûlures de la main sont encore fréquentes dans les pays à ressources limitées. Trente-deux patients, représentant 38 mains, ont été admis et traités, entre le 1er décembre 2010 et le 1er mai 2014 aux Cliniques Universitaires de Kinshasa en République Démocratique du Congo (RDC). nous avons observé 22 patients (69 %) dans le groupe de jeunes (patients âgés de moins de 18 ans), et 10 patients (31 %) chez les adultes (18 à 59 ans). Aucun patient dans le groupe de seniors (60 ans et plus) n’a été observé. Dans le groupe de jeunes, la tranche d’âge de 1 à 5 ans a été la plus atteinte avec 13 malades (40 %). l’accident à la maison était le plus fréquent (72 %). le mécanisme de la brûlure était le plus souvent thermique par flammes (51 %) ou par liquide chaud (34 %). les rétractions et brides sont les lésions le plus observées (84 %). la rétraction dorsale globale « main en griffe» est observée chez 40 % de patients traités, associée à des cicatrices hypertrophiques et chéloïdiennes dans 84 % de cas. Chez les 32 mains traitées chirurgicalement, des excision-greffes ont été réalisées dans 43,7 %, des lambeaux locaux dans 43,7 % et des lambeaux à distance dans 12,5 % de cas. A la sortie de l’hôpital, 84 % de « bons » résultats ont été observés. le suivi a été de 18 mois. le traitement des séquelles de brûlures de la main est possible dans ces pays, exemple de la rDC. Mais les défis à surmonter dans ces pays sont nombreux : la faible accessibilité aux techniques actuelles de la chirurgie plastique, la prise en charge initiale inadéquate des brûlures, la pauvreté. PMID:26668560

  1. 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.

  2. 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

  3. 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.

  4. High-resolution capacitance measurement and potentiometry by force microscopy

    NASA Astrophysics Data System (ADS)

    Martin, Yves; Abraham, David W.; Wickramasinghe, H. Kumar

    1988-03-01

    We demonstrate the usefulness and high sensitivity of the atomic force microscope (AFM) for imaging surface dielectric properties and for potentiometry through the detection of electrostatic forces. Electric forces as small as 10-10 N have been measured, corresponding to a capacitance of 10-19 farad. The sensitivity of our AFM should ultimately allow us to detect capacitances as low as 8×10-22 F. The method enables us to detect the presence of dielectric material over Si, and to measure the voltage in a p-n junction with submicron spatial resolution.

  5. 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.

  6. 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.

  7. 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.

  8. 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

    2014-08-12

    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.

  9. 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.

  10. Current Kink and Capacitance Frequency Dispersion in Silicon PIN Photodiodes

    NASA Astrophysics Data System (ADS)

    Guo, Xia; Feng, Yajie; Liu, Qiaoli; Wang, Huaqiang; Li, Chong; Hu, Zonghai; He, Xiaoying

    2017-09-01

    Silicon PIN photodiodes in the visible wavelength range have been widely applied in aerospace, defense, security, medical, and scientific instruments because of their high sensitivity and low cost. In this paper, the phenomena of the current kink and the capacitance frequency dispersion are observed. Contamination at the p-type Ohmic contact interface is proposed to explain the current kink effect and capacitance frequency dispersion, according to the temperature-dependent I-V measurement results in which trap-assisted tunneling process demonstrated.

  11. [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.

  12. Les Applications Therapeutiques Des Lasers

    NASA Astrophysics Data System (ADS)

    Brunetaud, J. M.; Mordon, S.; Bourez, J.; Mosquet, L.; Moschetto, Y.

    1984-03-01

    C'est de tres loin le mecanisme predominant dans les applications therapeutiques du laser. En concentrant le flux lumineux sur une surface redui-te, le laser chauffe localement les tissus qui se retractent (coagulation) pour etre elimines ensuite (detersion) ; si on chauffe plus intensement, les tissus peuvent etre volatilises. La coagulation est utilisee soit pour detruire de petits phenomenes tumoraux qui seront elimines lors du processus de detersion, soit pour arreter une hemorragie (hemo-stase) ; dans ce cas la retraction thermique des tissus va provoquer la fermeture de la lumiere des vaisseaux qui seront secondairement obliteres par des caillots formes sur place (thrombose). Par volatilisation it est possible de detruire des phenomenes tumoraux plus importants que ceux at-teints lors d'une simple coagulation. Si la zone volatilisee est tres etroite (de 0,1 a 1 mm) on obtient un effet de coupe avec une excellente hemostase au niveau des berges. Certes ces deux processus - coagulation et volatilisation - peuvent etre obtenus par d'autres procedes : echauffement par contact (sonde thermique) ou effet Joule (courant electrique haute frequence). Le laser a l'avantage de ne necessiter aucun contact mecanique entre le vecteur d'energie et les tissus ; on peut alors predire correctement la repartition d'energie au niveau des tissus et les effets sont tres repro-ductibles. Par ailleurs, l'absorption tissulaire variant considerablement avec la longueur d'onde on peut choisir la source laser en fonction des effets desires.

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

    DOE PAGES

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

    SciTech Connect

    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 quantum 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.

  15. Médecine des voyages

    PubMed Central

    Aw, Brian; Boraston, Suni; Botten, David; Cherniwchan, Darin; Fazal, Hyder; Kelton, Timothy; Libman, Michael; Saldanha, Colin; Scappatura, Philip; Stowe, Brian

    2014-01-01

    Résumé Objectif Définir la pratique de la médecine des voyages, présenter les éléments fondamentaux d’une consultation complète préalable aux voyages à des voyageurs internationaux et aider à identifier les patients qu’il vaudrait mieux envoyer en consultation auprès de professionnels de la médecine des voyages. Sources des données Les lignes directrices et les recommandations sur la médecine des voyages et les maladies liées aux voyages publiées par les autorités sanitaires nationales et internationales ont fait l’objet d’un examen. Une recension des ouvrages connexes dans MEDLINE et EMBASE a aussi été effectuée. Message principal La médecine des voyages est une spécialité très dynamique qui se concentre sur les soins préventifs avant un voyage. Une évaluation exhaustive du risque pour chaque voyageur est essentielle pour mesurer avec exactitude les risques particuliers au voyageur, à son itinéraire et à sa destination et pour offrir des conseils sur les interventions les plus appropriées en gestion du risque afin de promouvoir la santé et prévenir les problèmes médicaux indésirables durant le voyage. Des vaccins peuvent aussi être nécessaires et doivent être personnalisés en fonction des antécédents d’immunisation du voyageur, de son itinéraire et du temps qu’il reste avant son départ. Conclusion La santé et la sécurité d’un voyageur dépendent du degré d’expertise du médecin qui offre le counseling préalable à son voyage et les vaccins, au besoin. On recommande à ceux qui donnent des conseils aux voyageurs d’être conscients de l’ampleur de cette responsabilité et de demander si possible une consultation auprès de professionnels de la médecine des voyages pour tous les voyageurs à risque élevé.

  16. Organoaqueous calcium chloride electrolytes for capacitive charge storage in carbon nanotubes at sub-zero-temperatures.

    PubMed

    Gao, Yun; Qin, Zhanbin; Guan, Li; Wang, Xiaomian; Chen, George Z

    2015-07-11

    Solutions of calcium chloride in mixed water and formamide are excellent electrolytes for capacitive charge storage in partially oxidised carbon nanotubes at unprecedented sub-zero-temperatures (e.g. 67% capacitance retention at -60 °C).

  17. Design of capacitive sensor for water level measurement

    NASA Astrophysics Data System (ADS)

    Qurthobi, A.; Iskandar, R. F.; Krisnatal, A.; Weldzikarvina

    2016-11-01

    Capacitive sensor for water level detection has been fabricated. It has, typically, high-impedance sensor, particularly at low frequencies, as clear from the impedance (reactance) expression for a capacitor. Also, capacitive sensor is a noncontacting device in the common usage. In this research, water level sensor based on capacitive principal created using two copper plates with height (h), width (b), and distance (l) between two plates, respectively, 0.040 m, 0.015 m, and 0.010 m. 5 V pp 3 kHz AC signal is used as input signal for the system. Dielectric constant between two plates is proportional to water level. Hence, it can be used to determine water level from electrical characteristic as it inversely proportional to sensor impedance. Linearization, inverting amplifier, and rectifier circuits are used as signal conditioning for the system. Based on conducted experiment, the relationship between water level (x), capacitance (C), and output voltage (Vdc ) can be expressed as C(x) = 2.756x + 0.333 nF and Vdc (x) = 15.755 + 0.316 V.

  18. 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.

  19. Capacitive Sensing Of Gaseous Fraction In Two-Phase Flow

    NASA Technical Reports Server (NTRS)

    Crowley, Christopher J.; Sahm, Michael K.

    1995-01-01

    Instrument makes nonintrusive, real-time capacitive measurements to determine volume fraction of vapor or other gas in flowing, electrically nonconductive liquid/gas mixture. Works even with liquids having relatively low permittivities. Useful for measuring proportions of vapor in boiling, condensing, and flowing heat-transfer fluids and in cryogenic fluids.

  20. RF-MEMS capacitive switches with high reliability

    DOEpatents

    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.

  1. Capacitive bridge-type probe and conversion circuitry

    NASA Astrophysics Data System (ADS)

    Dooley, Kevin A.

    1989-11-01

    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, is described. The probe is comprised of a capacitance to voltage conversion circuit for converting changes in capacitance of the probe to a voltage. The conversion circuit uses offset means for providing a predetermined imbalance to the bridge thus providing automatic calibration of the circuit. The probe includes an elongated conductive casing filled with a dielectric material in which are embedded four arms, including at least one of which is a sensitive variable capacitance arm. The probe is mounted in the fixed surface such that the plate member of the sensitive arm faces the movable member. The character and magnitude of the dielectric medium between the plate member and the casing is sensitive to a change in clearance between the fixed surface and the movable member. 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. 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.

  3. Feasibility of a Gelatin Temperature Sensor Based on Electrical Capacitance

    PubMed Central

    Teixeira Silva, Fernando; Sorli, Brice; Calado, Veronica; Guillaume, Carole; Gontard, Nathalie

    2016-01-01

    The innovative use of gelatin as a temperature sensor based on capacitance was studied at a temperature range normally used for meat cooking (20–80 °C). Interdigital electrodes coated by gelatin solution and two sensors of different thicknesses (38 and 125 µm) were studied between 300 MHz and 900 MHz. At 38 µm, the capacitance was adequately measured, but for 125 µm the slope capacitance versus temperature curve decreased before 900 MHz due to the electrothermal breakdown between 60 °C and 80 °C. Thus, for 125 µm, the capacitance was studied applying 600 MHz. Sensitivity at 38 µm at 868 MHz (0.045 pF/°C) was lower than 125 µm at 600 MHz (0.14 pF/°C), influencing the results in the simulation (temperature range versus time) of meat cooking; at 125 µm, the sensitivity was greater, mainly during chilling steps. The potential of gelatin as a temperature sensor was demonstrated, and a balance between thickness and frequency should be considered to increase the sensitivity. PMID:27999415

  4. 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.

  5. 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.

  6. A Capacitated Facility Location Approach for the Tanker Employment Problem

    DTIC Science & Technology

    2005-03-01

    build a complete tanker scheduling tool. 69 Appendix A. TET Tool VBA Coding ’Module: Assign ’Author: Lt. Jeffrey R. Miller, USAF...A CAPACITATED FACILITY LOCATION APPROACH FOR THE TANKER EMPLOYMENT PROBLEM...FACILITY LOCATION APPROACH FOR THE TANKER EMPLOYMENT PROBLEM THESIS Presented to the Faculty Department of Operational Sciences

  7. Waterproof, Ultrahigh Areal-Capacitance, Wearable Supercapacitor Fabrics.

    PubMed

    Yang, Yu; Huang, Qiyao; Niu, Liyong; Wang, Dongrui; Yan, Casey; She, Yiyi; Zheng, Zijian

    2017-05-01

    High-performance supercapacitors (SCs) are promising energy storage devices to meet the pressing demand for future wearable applications. Because the surface area of a human body is limited to 2 m(2) , the key challenge in this field is how to realize a high areal capacitance for SCs, while achieving rapid charging, good capacitive retention, flexibility, and waterproofing. To address this challenge, low-cost materials are used including multiwall carbon nanotube (MWCNT), reduced graphene oxide (RGO), and metallic textiles to fabricate composite fabric electrodes, in which MWCNT and RGO are alternatively vacuum-filtrated directly onto Ni-coated cotton fabrics. The composite fabric electrodes display typical electrical double layer capacitor behavior, and reach an ultrahigh areal capacitance up to 6.2 F cm(-2) at a high areal current density of 20 mA cm(-2) . All-solid-state fabric-type SC devices made with the composite fabric electrodes and water-repellent treatment can reach record-breaking performance of 2.7 F cm(-2) at 20 mA cm(-2) at the first charge-discharge cycle, 3.2 F cm(-2) after 10 000 charge-discharge cycles, zero capacitive decay after 10 000 bending tests, and 10 h continuous underwater operation. The SC devices are easy to assemble into tandem structures and integrate into garments by simple sewing. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  8. 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.

  9. 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.

  10. 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…

  11. Performance analysis of a digital capacitance measuring circuit

    NASA Astrophysics Data System (ADS)

    Xu, Lijun; Sun, Shijie; Cao, Zhang; Yang, Wuqiang

    2015-05-01

    This paper presents the design and study of a digital capacitance measuring circuit with theoretical analysis, numerical simulation, and experimental evaluation. The static and dynamic performances of the capacitance measuring circuit are first defined, including signal-to-noise ratio (SNR), standard deviation, accuracy, linearity, sensitivity, and response time, within a given measurement range. Then numerical simulation is carried out to analyze the SNR and standard deviation of the circuit, followed by experiments to validate the overall performance of the circuit. The simulation results show that when the standard deviation of noise is 0.08 mV and the measured capacitance decreases from 6 pF to 3 fF, the SNR decreases from 90 dB to 22 dB and the standard deviation is between 0.17 fF and 0.24 fF. The experimental results show that when the measured capacitance decreases from 6 pF to 40 fF and the data sampled in a single period are used for demodulation, the SNR decreases from 88 dB to 40 dB and the standard deviation is between 0.18 fF and 0.25 fF. The maximum absolute error and relative error are 5.12 fF and 1.26%, respectively. The SNR and standard deviation can be further improved if the data sampled in more than one period are used for demodulation by the circuit.

  12. Interdigitated array microelectrode capacitive sensor for detection of paraffinophilic mycobacteria

    NASA Astrophysics Data System (ADS)

    Sampson, Andrew M.; Peterson, Erik T. K.; Papautsky, Ian

    2008-02-01

    Mycobacterium Avium Complex (MAC) is an opportunistic pathogen that threatens public health and has high clinical relevance. While culture-based and molecular biology techniques for identification are available, these methods are prone to error and require weeks to perform. There is a critical need for improved portable lab-on-a-chip sensor technology which will enable accurate and rapid point-of-care detection of these microorganisms. In this work, a new capacitive sensing strategy is explored utilizing interdigitated array (IDA) microelectrodes and exploiting the paraffinophilic nature of MAC. In this approach, paraffin wax is deposited over IDA microelectrodes to selectively extract these microorganisms from samples. As bacteria consume the dielectric paraffin layer, the charging current of the IDA capacitor changes to facilitate detection. Several IDA geometries were designed and simulated using CFD-ACE+ modeling software and compared with mathematical models. Capacitance of fabricated devices was determined using a charge-based capacitance measurement (CBCM) technique. Modeling and experimental results were in good agreement. Detection of femto-Farad changes in capacitance is possible, making this a feasible technique for sensing small changes in the paraffin for detection of paraffinophilic MAC.

  13. A Micro Dynamically Tuned Gyroscope with Adjustable Static Capacitance

    PubMed Central

    Xia, Dunzhu; Yu, Cheng; Kong, Lun

    2013-01-01

    This paper presents a novel micro dynamically tuned gyroscope (MDTG) with adjustable static capacitance. First, the principle of MDTG is theoretically analyzed. Next, some simulations under the optimized structure parameters are given as a reference for the mask design of the rotor wafer and electrode plates. As two key components, the process flows of the rotor wafer and electrode plates are described in detail. All the scanning electron microscopy (SEM) photos show that the fabrication process is effective and optimized. Then, an assembly model is designed for the static capacitance adjustable MDTG, whose static capacitance can be changed by rotating the lower electrode plate support and substituting gasket rings of different thicknesses. Thus, the scale factor is easily changeable. Afterwards, the digitalized closed-loop measurement circuit is simulated. The discrete correction and decoupling modules are designed to make the closed-loop stable and cross-coupling effect small. The dual axis closed-loop system bandwidths can reach more than 60 Hz and the dual axis scale factors are completely symmetrical. All the simulation results demonstrate the proposed fabrication of the MDTG can meet the application requirements. Finally, the paper presents the test results of static and dynamic capacitance values which are consistent with the simulation values. PMID:23389347

  14. Capacitively decoupled tunable loop microstrip (TLM) array at 7 T.

    PubMed

    Wu, Bing; Zhang, Xiaoliang; Qu, Peng; Shen, Gary X

    2007-04-01

    Microstrip transmission-line loop arrays have been recently proposed for parallel imaging at ultrahigh fields due to their advantages in element decoupling and to their increased coil quality factor. In the microstrip loop array design, interconnecting capacitors become necessary to further improve the decoupling between the adjacent elements when nonoverlapped loops are placed densely. However, at ultrahigh fields, the capacitance required for sufficient decoupling is very small. Hence, the isolations between the elements are usually not optimized and the array is extremely sensitive to the load. In this study, a theoretical model is developed to analyze the capacitive decoupling circuit. Then, a novel tunable loop microstrip (TLM) array that can accommodate capacitive decoupling more easily at ultrahigh fields is proposed. As an example, a four-element TLM array is constructed at 7 T. In this array, the decoupling capacitance is increased to a more reasonable value. Isolation between the adjacent elements is better than -37 dB with the load. The performance of this TLM array is also demonstrated by MRI experiments.

  15. Parasitic capacitance characteristics of deep submicrometre grooved gate MOSFETs

    NASA Astrophysics Data System (ADS)

    Sreelal, S.; Lau, C. K.; Samudra, G. S.

    2002-03-01

    Grooved gate metal-oxide-semiconductor field-effect transistors (MOSFETs) are known to alleviate many of the short channel and hot carrier effects that arise when MOSFET devices are scaled down to very short channel lengths. However, they exhibit much higher parasitic capacitance with stronger bias dependence when compared to conventional planar devices. In this paper, we present a model for gate-to-drain and gate-to-source capacitance characteristics of a deep submicrometre grooved gate MOSFET. Both the intrinsic and extrinsic parts of the capacitance are modelled separately. In particular, the model presents a novel but simple way to account for the accumulation layer formation in the source/drain region of MOSFETs due to the application of the gate voltage. The results are compared with those obtained from a two-dimensional device simulator. The close match between the modelled and simulated data establishes the validity of the model. The model is then used to account for the superiority of capacitance characteristics of planar device structures and to arrive at optimization guidelines for grooved gate devices to match these characteristics.

  16. 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.

  17. Alternating current electrokinetics enhanced in situ capacitive immunoassay.

    PubMed

    Li, Shanshan; Ren, Yukun; Cui, Haochen; Yuan, Quan; Wu, Jie; Eda, Shigetoshi; Jiang, Hongyuan

    2015-02-01

    A rapid in situ capacitive immunoassay is presented herein. Conventional immunoassay typically relies on diffusion for transport of analytes in many cases causing long detection time and lack of sensitivity. By integrating alternating current electrokinetics (ACEK) and impedance sensing, this work provides a rapid in situ capacitive affinity biosensing. ACEK induces both fluid flow and particle motion, conveying target molecules toward electrodes immobilized with probes, resulting in rapid enrichment of target molecules and a capacitance change at the ''electrode-fluid'' interface. The benefit of ACEK enhanced immunoassay was demonstrated using the antigen and antibody from Johne's disease (JD) as an example. To clarify the importance of DEP and ACET effects for binding reaction, two different electrode pattern designs for capacitive immunoassay are studied. The asymmetric array and symmetric electrodes exhibit very similar response at lower electric field due to DEP effects, while asymmetric array has remarkable higher response at high-electric field because the convection becomes more important at high field. The disease positive and negative serum samples are distinguished in few minutes. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  18. Towards a Dynamic DES model

    NASA Astrophysics Data System (ADS)

    Subbareddy, Pramod; Candler, Graham

    2009-11-01

    Hybrid RANS/LES methods are being increasingly used for turbulent flow simulations in complex geometries. Spalart's detached eddy simulation (DES) model is one of the more popular ones. We are interested in examining the behavior of the Spalart-Allmaras (S-A) Detached Eddy Simulation (DES) model in its ``LES mode.'' The role of the near-wall functions present in the equations is analyzed and an explicit analogy between the S-A and a one-equation LES model based on the sub-grid kinetic energy is presented. A dynamic version of the S-A DES model is proposed based on this connection. Validation studies and results from DES and LES applications will be presented and the effect of the proposed modification will be discussed.

  19. Electrical and capacitive methods for detecting degradation in wire insulation

    NASA Astrophysics Data System (ADS)

    Sheldon, Robert T.

    Motivated by a need within the aerospace industry to detect and characterize degradation in the insulation of onboard wires, this thesis reports testing of several extant methods and development of novel capacitive sensors. This work focuses on measuring the electrical parameters resistance and capacitance that are directly related to the material parameters conductivity and permittivity, respectively, of the insulation. It is shown that the measured electrical parameters successfully indicate degradation in the wire insulation. Insulation resistance tests were performed on 17 wire samples, removed from various locations on a retired aircraft, and compared with those conducted on pristine wire samples, in order to assess any change in conductivity exhibited by degraded insulation. Timed resistance tests were also performed to determine the dielectric absorption of the insulation. Curved patch-electrode sensors were applied in order to measure the capacitance and dissipation factor of the same wires. Results from the resistive and capacitive tests both identified wire samples that were apparently significantly degraded, as indicated qualitatively by visual inspection. Further, a novel cylindrical interdigital capacitive sensor was developed. The interdigital sensor is designed with the goal of achieving a good signal-to-noise ratio, the lowest instrument error possible at 1 MHz, full circumferential coverage of the wire, and the ability to adjust the penetration depth of the electric field into the insulation layer by adjusting the separation of the sensor digits. With the aim, ultimately, of quantitative measurement of insulation complex permittivity, a numerical model was developed using a cylindrical Green's function and the Method of Moments to calculate theoretically the capacitance of the interdigital sensor. Benchmark experiments were carried out on large-scale dielectric-coated conductive cylinders to test the validity of the model. Experimental results

  20. Effects of Frequency-Dependent Membrane Capacitance on Neural Excitability

    PubMed Central

    Grill, Warren M.

    2015-01-01

    Objective Models of excitable cells consider the membrane specific capacitance as a ubiquitous and constant parameter. However, experimental measurements show that the membrane capacitance declines with increasing frequency, i.e., exhibits dispersion. We quantified the effects of frequency-dependent membrane capacitance, c(f), on the excitability of cells and nerve fibers across the frequency range from dc to hundreds of kilohertz. Approach We implemented a model of c(f) using linear circuit elements, and incorporated it into several models of neurons with different channel kinetics: the Hodgkin-Huxley (HH) model of an unmyelinated axon, the McIntyre-Richardson-Grill (MRG) of a mammalian myelinated axon, and a model of a cortical neuron from prefrontal cortex. We calculated thresholds for excitation and kHz frequency conduction block, the conduction velocity, recovery cycle, strength-distance relationship and firing rate. Main results The impact of c(f) on activation thresholds depended on the stimulation waveform and channel kinetics. We observed no effect using rectangular pulse stimulation, and a reduction for frequencies of 10 kHz and above using sinusoidal signals only for the MRG model. c(f) had minimal impact on the recovery cycle and the strength-distance relationship, whereas the conduction velocity increased by up to 7.9% and 1.7% for myelinated and unmyelinated fibers, respectively. Block thresholds declined moderately when incorporating c(f), the effect was greater at higher frequencies, and the maximum reduction was 11.5%. Finally, c(f) marginally altered the firing pattern of a model of a prefrontal cortex cell, reducing the median interspike interval by less than 2%. Significance This is the first comprehensive analysis of the effects of dispersive capacitance on neural excitability, and as the interest on stimulation with kHz signals gains more attention, it defines the regions over which frequency-dependent membrane capacitance, c(f), should be

  1. Critical phases of viral production processes monitored by capacitance.

    PubMed

    Petiot, Emma; Ansorge, Sven; Rosa-Calatrava, Manuel; Kamen, Amine

    2017-01-20

    Over the last decade industrial manufacturing of viral vaccines and viral vectors for prophylactic and therapeutic applications is experiencing a remarkable growth. Currently, the quality attributes of viral derived products are assessed only at the end-point of the production process, essentially because in-process monitoring tools are not available or not implemented at industrial scale. However, to demonstrate process reproducibility and robustness, manufacturers are strongly advised by regulatory agencies to adopt more on-line process monitoring and control. Dielectric spectroscopy has been successfully used as an excellent indicator of the cell culture state in mammalian and yeast cell systems. We previously reported the use of this technique for monitoring influenza and lentiviral productions in HEK293 cell cultures. For both viruses, multi-frequency capacitance measurements allowed not only the on-line monitoring of the production kinetics, but also the identification of the viral release time from the cells. The present study demonstrates that the same approach can be successfully exploited for the on-line monitoring of different enveloped and non-enveloped virus production kinetics in cell culture processes. The on-line monitoring multi-frequency capacitance method was assessed in human HEK293 and Sf9 insect cells expression systems, with viral productions initiated by either infection or transfection. The comparative analyses of all the data acquired indicate that the characteristic capacitance signals were highly correlated with the occurrence of viral replication phases. Furthermore the evolution of the cell dielectric properties (intracellular conductivity and membrane capacitance) were indicative of each main replication steps. In conclusion, multi-frequency capacitance has a great potential for on-line monitoring, supervision and control of viral vector production in cell culture processes.

  2. Capacitive charging system for high power battery charging

    SciTech Connect

    1998-12-31

    This document describes a project to design, build, demonstrate, and document a Level 3 capacitive charging system, and it will be based on the existing PEZIC prototype capacitive coupler. The capacitive coupler will be designed to transfer power at a maximum of 600 kW, and it will transfer power by electric fields. The power electronics will transfer power at 100 kW. The coupler will be designed to function with future increases in the power electronics output power and increases in the amp/hours capacity of sealed batteries. Battery charging algorithms will be programmed into the control electronics. The finished product will be a programmable battery charging system capable of transferring 100 kW via a capacitive coupler. The coupler will have a low power loss of less than 25 watts when transferring 240 kW (400 amps). This system will increase the energy efficiency of high power battery charging, and it will enhance mobility by reducing coupler failures. The system will be completely documented. An important deliverable of this project is information. The information will be distributed to the Army`s TACOM-TARDEC`s Advanced Concept Group, and it will be distributed to commercial organizations by the Society of Automotive Engineers. The information will be valuable for product research, development, and specification. The capacitive charging system produced in this project will be of commercial value for future electric vehicles. The coupler will be designed to rapid charge batteries that have a capacity of several thousand amp/hours at hundreds of volts. The charging system built here will rapid charge batteries with several hundred amp/hours capacity, depending on the charging voltage.

  3. Effect of Microstructure on the Strength and Fracture Energy of Bimaterial Interfaces.

    DTIC Science & Technology

    1992-12-31

    croissance plastique des cavites et de decollement de l’interface. Les I energies de rupture sont beaucoup plus grandes que le travail d’adh6rence...dissipation plastique qui augmente pour les grandes ipasseurs de la couche m~tallique. Zusammeafassung-Die RiBausbreitung wird an der Grenzfliche Al2 03 /Au...On montre les influences importantes de [a relations plastique et de la difference de dilatation thermique et on d6,rit quelques caract6ristiques

  4. Emergence of Negative Capacitance in Multidomain Ferroelectric-Paraelectric Nanocapacitors at Finite Bias.

    PubMed

    Kasamatsu, Shusuke; Watanabe, Satoshi; Hwang, Cheol Seong; Han, Seungwu

    2016-01-13

    The emergence of negative capacitance in an ultrathin ferroelectric/paraelectric bilayer capacitor under electrical bias is examined using first-principles simulation. An antiferroelectric-like behavior is predicted, and negative capacitance is shown to emerge when the monodomain state becomes stable after bias application. The polydomain-monodomain transition is also shown to be a source of capacitance enhancement.

  5. Investigation of Plastic Zone Development in Dynamic Tear Test Specimens - Phase 2

    DTIC Science & Technology

    2000-09-01

    essats elastlques-plasttques et on a constate une concordance assez precise . Sommaire II est important de pouvOlr predire ]a taille des zones elastiques... precis de predire les defaillances. Nous avons done cherche a developper des modeles de zone plastique afin de definir le rapport entre le rayon de la...defmitwn de ce parametre nous permettra de defimr les vraies limites des essais sur les proprietes elastiques et plastiques des materiaux en ce qui

  6. Motion artifacts in capacitive ECG measurements: reducing the combined effect of DC voltages and capacitance changes using an injection signal.

    PubMed

    Serteyn, A; Vullings, R; Meftah, M; Bergmans, J W M

    2015-01-01

    Capacitive electrodes are a promising alternative to the conventional adhesive electrodes for ECG measurements. They provide more comfort to the patient when integrated in everyday objects (e.g., beds or seats) for long-term monitoring. However, the application of capacitive sensors is limited by their high sensitivity to motion artifacts. For example, motion at the body-electrode interface causes variations of the coupling capacitance which, in the presence of a dc voltage across the coupling capacitor, create strong artifacts in the measurements. The origin, relevance, and reduction of this specific and important type of artifacts are studied here. An injection signal is exploited to track the variations of the coupling capacitance in real time. This information is then used by an identification scheme to estimate the artifacts and subtract them from the measurements. The method was evaluated in simulations, lab environments, and in a real-life recording on an adult's chest. For the type of artifact under study, a strong artifact reduction ranging from 40 dB for simulated data to 9 dB for a given real-life recording was achieved. The proposed method is automated, does not require any knowledge about the measurement system parameters, and provides an online estimate for the dc voltage across the coupling capacitor.

  7. Prises de risques chez les jeunes de Bobo Dioulasso: une analyse des facteurs associés à la précocité et au multipartenariat sexuel

    PubMed Central

    Adohinzin, Clétus Come; Meda, Nicolas; Belem, Adrien Marie Gaston; Ouédraogo, Georges Anicet; Sombie, Issiaka; Berthe, Abdramane; Fond-Harmant, Laurence

    2016-01-01

    Introduction Malgré les efforts d'éducation à la santé, les jeunes continuent d'adopter des comportements sexuels à risques, susceptibles d'avoir des répercussions importantes sur leur santé. Cette étude visait à analyser les facteurs associés à la précocité sexuelle et au multipartenariat chez les jeunes de 19-24 ans de Bobo-Dioulasso. Méthodes Il s'agit d'une étude quantitative et transversale. Les données d'enquête ont été recueillies en décembre 2014 à Bobo-Dioulasso (Burkina Faso), auprès de 573 jeunes de 15 à 24 ans. Ces enquêtés ont été sélectionnés par un sondage en grappes à deux degrés. Des facteurs à risques relatifs à la précocité sexuelle et au multipartenariat ont été analysés à l'aide du logiciel Stata IC 13. Le seuil de signification de P<0,05 a été utilisée. Résultats Plus de la moitié des enquêtés (54%) étaient sexuellement actifs dont 14% avant l'âge de 16 ans. Le multipartenariat sexuel avait été observé chez 24% des jeunes sexuellement actifs. Parmi les facteurs déterminants de la précocité sexuelle et du multipartenariat figuraient l'âge, le sexe, le niveau d'étude, et la situation économique des parents. Nos données avaient aussi montré que les rapports sexuels trop précoces étaient associés au multipartenariat sexuel (p<0,005). Conclusion Les actions visant à renforcer les capacités des jeunes à retarder les premiers rapports sexuels et à mieux évaluer les risques seront de toute importance. Les capacités des parents, des enseignants et des prestataires devraient être aussi renforcées pour l'amélioration de la qualité des relations entre eux et les jeunes. PMID:28292094

  8. Development of closed-loop interface circuits for capacitive transducers with application to a MEMS capacitive microphone

    NASA Astrophysics Data System (ADS)

    Kadirvel, Karthik

    There has been a trend towards miniaturization and batch fabrication of sensors inspired by a similar trend in the electronics industry using novel fabrication techniques used in micro electromechanical system (MEMS) fabrication. Capacitive microphones, whose common applications include aeroacoustic measurement and cell phones, is one such sensor whose dimensions are being aggressively scaled down. In measurement microphones, miniaturization will facilitate improved measurement precision, and in cell phones, miniaturization will reduce printer circuit board space and complexity. Both applications will benefit from the potential cost reduction brought by the batch fabrication of sensors. As sensor geometry is scaled down, improved circuit techniques are required to measure the sensor output. This is because at small geometries sensor capacitance is comparable to unwanted parasitic capacitance which reduces the transducer sensitivity. Also, at reduced sensor geometry, the voltage required to bias the microphone could cause the microphone plates to pull in. The goal of this work is to design and characterize interface circuits that are suitable for miniature capacitive transducers. To achieve this goal, the performance of existing open and closed-loop interface circuits are investigated. Scaling of the performance metrics of the microphone and interface circuit as sensor geometry decreases is also investigated. A proof of concept closed-loop analog controller for a MEMS capacitive microphone is designed. A test apparatus is developed to characterize the system over the audio range by operating the microphone in a helium medium which increases the bandwidth of the test apparatus. Characterization of the microphone in open and closed loop mode of operation is presented. Results show that stable closed loop operation of the microphone is feasible with increased sensitivity and the potential to address pull-in issues.

  9. Reconnaissance des Formes a L'aide du Filtre de Phase D'harmoniques Circulaires

    NASA Astrophysics Data System (ADS)

    Leclerc, Luc

    Cette these porte sur l'etude d'une nouvelle generation de filtres fabriques a partir de la phase du filtre d'harmoniques circulaires (FHC). Il s'agit du FHC de phase (FHCP), du FHC de phase binaire (FHCPB) et du FHC binaire (FHCB) qui, tout en etant invariants par rapport a la position et a l'orientation des cibles, offrent une meilleure capacite de discrimination que le FHC. Nous presentons egalement le FHC de covariance (FHCC) et ses derives de phase, lesquels permettent d'accroi tre davantage la capacite de discrimination du FHC dans les cas ou les objets composants la scene sont tres semblables. La performance de chacun des filtres est evaluee au moyen de simulations sur ordinateur avant d'etre mesuree sur un correlateur optique. Le FHC, FHCP, FHCC et FHCCP sont encodes dans un hologramme genere par ordinateur tandis que les filtres binaires sont affiches sur un televiseur a cristaux liquides. Enfin, nous termions ce manuscrit en presentant le FHCB multiplexe qui permet de correler, en une seule operation, un objet et plusieurs FHC de differents ordres.

  10. Analyse par diffraction des neutrons des déformations résiduelles dans un alliage de zirconium après un chargement thermomécanique

    NASA Astrophysics Data System (ADS)

    Letouzé, N.; Brenner, R.; Béchade, J. L.; Castelnau, O.; Mathon, M. H.; Bacroix, B.

    2002-07-01

    After a thermomechanical loading, it resides within a polycrystalline material an heterogeneous elastic strain field resulting from accommodation of the plastic and/or thermal local deformations. X-rays or neutrons diffraction makes it possible to quantify the average strain and their fluctuations within the diffracting volume (displacement and broadening of the line profil). When measurements are taken in volume (neutrons in our case) on a massive sample containing a large number of grains, they can be compared precisely with the results of homogenisation methods. Indeed, they are, as well as diffraction, a statistical method to analysis local mechanical fields. Moreover, they give access not only to the average mechanical fields by family of orientation (first order moment), but also to the heterogeneity of these fields (second order moment) on the same family and thus by extension on a diffracting volume. We have the results obtained on Zircaloy-4 having undergone a creep in traction at 400^{circ}C, which validates the methodology of comparison between measurements and the simulation carried out with a model of nonlinear homogenisation (self-coherent type affine in thermoelastoviscoplasticity) via the “residual strain map”. Après un chargement thermomécanique, il réside au sein d'un matériau polycristallin un champ de déformation élastique hétérogène issu de l'accommodation des déformations locales plastiques et/ou thermiques. La diffraction des rayons X ou des neutrons permet de quantifier les déformations moyennes et leurs fluctuations au sein du volume diffractant (déplacement et élargissement de la raie de diffraction). Lorsque les mesures sont effectuées en volume (neutrons dans notre cas) sur un échantillon massif contenant un grand nombre de grains, elles peuvent être comparées précisément aux résultats des méthodes d'homogénéisation. En effet, ils sont, au même titre que la diffraction, une méthode statistique d'analyse des

  11. 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

  12. Peste des petits ruminants.

    PubMed

    Parida, S; Muniraju, M; Mahapatra, M; Muthuchelvan, D; Buczkowski, H; Banyard, A C

    2015-12-14

    Peste des petits ruminants virus causes a highly infectious disease of small ruminants that is endemic across Africa, the Middle East and large regions of Asia. The virus is considered to be a major obstacle to the development of sustainable agriculture across the developing world and has recently been targeted by the World Organisation for Animal Health (OIE) and the Food and Agriculture Organisation (FAO) for eradication with the aim of global elimination of the disease by 2030. Fundamentally, the vaccines required to successfully achieve this goal are currently available, but the availability of novel vaccine preparations to also fulfill the requisite for differentiation between infected and vaccinated animals (DIVA) may reduce the time taken and the financial costs of serological surveillance in the later stages of any eradication campaign. Here, we overview what is currently known about the virus, with reference to its origin, updated global circulation, molecular evolution, diagnostic tools and vaccines currently available to combat the disease. Further, we comment on recent developments in our knowledge of various recombinant vaccines and on the potential for the development of novel multivalent vaccines for small ruminants.

  13. Peste des petits ruminants

    PubMed Central

    Parida, S.; Muniraju, M.; Mahapatra, M.; Muthuchelvan, D.; Buczkowski, H.; Banyard, A.C.

    2015-01-01

    Peste des petits ruminants virus causes a highly infectious disease of small ruminants that is endemic across Africa, the Middle East and large regions of Asia. The virus is considered to be a major obstacle to the development of sustainable agriculture across the developing world and has recently been targeted by the World Organisation for Animal Health (OIE) and the Food and Agriculture Organisation (FAO) for eradication with the aim of global elimination of the disease by 2030. Fundamentally, the vaccines required to successfully achieve this goal are currently available, but the availability of novel vaccine preparations to also fulfill the requisite for differentiation between infected and vaccinated animals (DIVA) may reduce the time taken and the financial costs of serological surveillance in the later stages of any eradication campaign. Here, we overview what is currently known about the virus, with reference to its origin, updated global circulation, molecular evolution, diagnostic tools and vaccines currently available to combat the disease. Further, we comment on recent developments in our knowledge of various recombinant vaccines and on the potential for the development of novel multivalent vaccines for small ruminants. PMID:26443889

  14. 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.

  15. Skin capacitance in normal and atopic infants, and effects of moisturizers on atopic skin.

    PubMed

    Matsumoto, Tomoaki; Yuasa, Hiromi; Kai, Rie; Ueda, Hiromi; Ogura, Shunko; Honda, Yoshiko

    2007-07-01

    Skin capacitance depends on the water content of the stratum corneum, and moisturizers have beneficial effects in atopic dermatitis. This study was performed to determine the skin capacitance in normal and atopic infants, and to evaluate the effects of different moisturizers on infantile atopic skin. The skin capacitance in 186 normal infants and 37 atopic infants was measured with a Moisture Checker. Measurements were also made for atopic infants after an application of pure petrolatum or an oil-in-water cream containing a humectant. Age-related decreases in skin capacitance were observed at the majority of dermal sites in normal infants. The skin capacitance was significantly lower in atopic infants compared with normal infants at all body sites. Pure petrolatum and oil-in-water creams containing humectants significantly augmented the capacitance from 2% to 7%. The reference values for skin capacitance may be helpful for delineating normal from atopic skin. Certain moisturizers can increase skin hydration.

  16. Study of quantum capacitance in N doped few layer graphene

    NASA Astrophysics Data System (ADS)

    Karakaya, Mehmet; Zhu, Jingyi; Podila, Ramakrishna; Srivastava, Anurag; Rao, Apparao; Department Of Physics; Astronomy, Clemson Nanomaterials Center, Clemson University Team; Iiitm-Gwalior, Madhya Pradesh, India Team

    2015-03-01

    The intrinsically small density of states at the Fermi level in graphene results in a small serial quantum capacitance CQ, which diminishes the total device capacitance value (Ctot) in supercapacitors. In this work, we studied CQ of N doped graphene in pyrrolic(N1), graphitic (N2) and pyridinic (N3) configurations. The observed CQ value for sample N1 was significantly different from samples N2 and N3, as predicted by DFT calculations, thus implying that precisely engineered dopant configurations, rather than concentration, can enhance CQ. Such approaches are pivotal for alleviating the existing bottlenecks in both graphene-based device scaling and supercapacitor electrode limitations. NSF CMMI SNM Award #1246800.

  17. Corrugated graphene layers for sea water desalination using capacitive deionization.

    PubMed

    Dahanayaka, Madhavi; Liu, Bo; Hu, Zhongqiao; Chen, Zhong; Law, Adrian Wing-Keung; Zhou, Kun

    2017-03-14

    The effect of the electric field and surface morphology of corrugated graphene (GE) layers on their capacitive deionization process is studied using molecular dynamics simulations. Deionization performances are evaluated in terms of water flow rate and ion adsorption and explained by analysing the water density distribution, radial distribution function and distribution of the ions inside the GE layers. The simulation results reveal that corrugation of GE layers reduces the water flow rate but largely enhances ion adsorption in comparison to the flat GE layers. Such enhancement is mainly due to the adsorption of ions on the GE layers due to the anchoring effect in the regions with wide interlayer distances. Moreover, it reveals that the entrance configuration of the GE layers also has a significant effect on the performance of deionization. Overall, the results from this study will be helpful in designing effective electrode configurations for capacitive deionization.

  18. On the hydrophilicity of electrodes for capacitive energy extraction

    SciTech Connect

    Lian, Cheng; Kong, Xian; Liu, Honglai; Wu, Jianzhong

    2016-09-14

    The so-called Capmix technique for energy extraction is based on the cyclic expansion of electrical double layers to harvest dissipative energy arising from the salinity difference between freshwater and seawater. Its optimal performance requires a careful selection of the electrical potentials for the charging and discharging processes, which must be matched with the pore characteristics of the electrode materials. While a number of recent studies have examined the effects of the electrode pore size and geometry on the capacitive energy extraction processes, there is little knowledge on how the surface properties of the electrodes affect the thermodynamic efficiency. In this paper, we investigate the Capmix processes using the classical density functional theory for a realistic model of electrolyte solutions. The theoretical predictions allow us to identify optimal operation parameters for capacitive energy extraction with porous electrodes of different surface hydrophobicity. Finally, in agreement with recent experiments, we find that the thermodynamic efficiency can be much improved by using most hydrophilic electrodes.

  19. 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.

  20. 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.

  1. Holey graphene frameworks for highly efficient capacitive energy storage

    NASA Astrophysics Data System (ADS)

    Xu, Yuxi; Lin, Zhaoyang; Zhong, Xing; Huang, Xiaoqing; Weiss, Nathan O.; Huang, Yu; Duan, Xiangfeng

    2014-08-01

    Supercapacitors represent an important strategy for electrochemical energy storage, but are usually limited by relatively low energy density. Here we report a three-dimensional holey graphene framework with a hierarchical porous structure as a high-performance binder-free supercapacitor electrode. With large ion-accessible surface area, efficient electron and ion transport pathways as well as a high packing density, the holey graphene framework electrode can deliver a gravimetric capacitance of 298 F g-1 and a volumetric capacitance of 212 F cm-3 in organic electrolyte. Furthermore, we show that a fully packaged device stack can deliver gravimetric and volumetric energy densities of 35 Wh kg-1 and 49 Wh l-1, respectively, approaching those of lead acid batteries. The achievement of such high energy density bridges the gap between traditional supercapacitors and batteries, and can open up exciting opportunities for mobile power supply in diverse applications.

  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. An analytic model for MODFET capacitance-voltage characteristics

    NASA Astrophysics Data System (ADS)

    George, G.; Hauser, John R.

    1990-05-01

    An analytic model for the capacitance-voltage (C-V) characteristics of n-channel modulation doped FETs (MODFETs) is derived. Gauss law is used to relate the net areal gate charge density in an AlGaAs/GaAs MODFET to the electric field intensity at the metal-AlGaAs interface. An analytic expression for the electric field intensity which accounts for the neutralization of donors and the generation of free electrons is derived. The gate capacitance is derived as a closed-form analytic function of the gate voltage. The expression derived is easily computable and affords physical insight. The results, when compared with numerical calculations and experimental data, yield good agreement over a wide range of gate voltages.

  4. On the hydrophilicity of electrodes for capacitive energy extraction

    NASA Astrophysics Data System (ADS)

    Lian, Cheng; Kong, Xian; Liu, Honglai; Wu, Jianzhong

    2016-11-01

    The so-called Capmix technique for energy extraction is based on the cyclic expansion of electrical double layers to harvest dissipative energy arising from the salinity difference between freshwater and seawater. Its optimal performance requires a careful selection of the electrical potentials for the charging and discharging processes, which must be matched with the pore characteristics of the electrode materials. While a number of recent studies have examined the effects of the electrode pore size and geometry on the capacitive energy extraction processes, there is little knowledge on how the surface properties of the electrodes affect the thermodynamic efficiency. In this work, we investigate the Capmix processes using the classical density functional theory for a realistic model of electrolyte solutions. The theoretical predictions allow us to identify optimal operation parameters for capacitive energy extraction with porous electrodes of different surface hydrophobicity. In agreement with recent experiments, we find that the thermodynamic efficiency can be much improved by using most hydrophilic electrodes.

  5. 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.

  6. Mesoporous nanocrystalline film architecture for capacitive storage devices

    DOEpatents

    Dunn, Bruce S.; Tolbert, Sarah H.; Wang, John; Brezesinski, Torsten; Gruner, George

    2017-05-16

    A mesoporous, nanocrystalline, metal oxide construct particularly suited for capacitive energy storage that has an architecture with short diffusion path lengths and large surface areas and a method for production are provided. Energy density is substantially increased without compromising the capacitive charge storage kinetics and electrode demonstrates long term cycling stability. Charge storage devices with electrodes using the construct can use three different charge storage mechanisms immersed in an electrolyte: (1) cations can be stored in a thin double layer at the electrode/electrolyte interface (non-faradaic mechanism); (2) cations can interact with the bulk of an electroactive material which then undergoes a redox reaction or phase change, as in conventional batteries (faradaic mechanism); or (3) cations can electrochemically adsorb onto the surface of a material through charge transfer processes (faradaic mechanism).

  7. On the hydrophilicity of electrodes for capacitive energy extraction

    SciTech Connect

    Lian, Cheng; Kong, Xian; Liu, Honglai; Wu, Jianzhong

    2016-09-14

    The so-called Capmix technique for energy extraction is based on the cyclic expansion of electrical double layers to harvest dissipative energy arising from the salinity difference between freshwater and seawater. Its optimal performance requires a careful selection of the electrical potentials for the charging and discharging processes, which must be matched with the pore characteristics of the electrode materials. While a number of recent studies have examined the effects of the electrode pore size and geometry on the capacitive energy extraction processes, there is little knowledge on how the surface properties of the electrodes affect the thermodynamic efficiency. In this paper, we investigate the Capmix processes using the classical density functional theory for a realistic model of electrolyte solutions. The theoretical predictions allow us to identify optimal operation parameters for capacitive energy extraction with porous electrodes of different surface hydrophobicity. Finally, in agreement with recent experiments, we find that the thermodynamic efficiency can be much improved by using most hydrophilic electrodes.

  8. A high resolution capacitive imaging sensor for manufacturing applications

    SciTech Connect

    Novak, J.L.; Wiczer, J.J.

    1990-09-06

    A high resolution capacitive image sensing technique for measuring edge and surface profiles during manufacturing processes has been invented. A prototype device utilizing this technique consists of two 0.020 in. (500 {mu}m) diameter electrodes fabricated on a printed circuit board with a 0.010 in. (250 {mu}m) gap between them. As the device is mechanically scanned over the workpiece, the spatial variations in the edge or surface to be measured interfere with an electric field imposed between the electrodes, altering the mutual capacitance. The sensor functions as a near field proximity sensor producing range images of surface imperfections. This sensor has been used in applications requiring a preview image of burrs on the edge of a machined part and other processes requiring an inspection image after automated deburring operations. 10 refs., 8 figs.

  9. Sugar Cube Purity: Capacitive Sensing and Image Processing Approach

    NASA Astrophysics Data System (ADS)

    Madhumitha, S.; Rajath, R.; Venkatanathan, N.; Raajan, N. R.; Sridharan, M.

    2016-12-01

    Several methods have been implemented to find out if impurity is present in sugar cubes or powders so far. Several high end imaging techniques with X-ray scanners have been used to check the quality of the sugar. In this present study, without disturbing the physical nature of sugar, we have simply used the dielectric property analysis to check the purity of the sugar. This method can detect even infinitesimal amounts of impurity present in sugar with good accuracy. The positional accuracy is derived using artificial neural networks, which is been trained with various capacitance values when the impurity is present and gives the details on the change in capacitance value as the impurity position changes.

  10. Correlation analysis of waves above a capacitive plasma applicator.

    PubMed

    Gekelman, W; Barnes, M; Vincena, S; Pribyl, P

    2009-07-24

    Capacitively coupled plasma glow discharges have been extensively used for materials processing in numerous industrial applications. Considerable research has been performed on plasma sheaths and standing waves over a capacitive applicator, which typically holds the processed substrate (e.g., a semiconductor wafer). In this work, we demonstrate for the first time the existence of normal modes in electric potential analogous to the vibrational modes in circular membranes and plates. These modes are exhibited through cross spectral analysis of the plasma potential measured with an emissive probe at 208 spatial positions and sampled at 1 GHz. These modes exist at several frequencies and are described by a series of Bessel functions. The data further suggests a nonlinear interaction between modes of different frequencies.

  11. Correlation Analysis of Waves above a Capacitive Plasma Applicator

    SciTech Connect

    Gekelman, W.; Vincena, S.; Pribyl, P.; Barnes, M.

    2009-07-24

    Capacitively coupled plasma glow discharges have been extensively used for materials processing in numerous industrial applications. Considerable research has been performed on plasma sheaths and standing waves over a capacitive applicator, which typically holds the processed substrate (e.g., a semiconductor wafer). In this work, we demonstrate for the first time the existence of normal modes in electric potential analogous to the vibrational modes in circular membranes and plates. These modes are exhibited through cross spectral analysis of the plasma potential measured with an emissive probe at 208 spatial positions and sampled at 1 GHz. These modes exist at several frequencies and are described by a series of Bessel functions. The data further suggests a nonlinear interaction between modes of different frequencies.

  12. Capacitive network near the metal insulator transition in Vanadium Dioxide

    NASA Astrophysics Data System (ADS)

    Ramirez, J. G.; Patino, E. J.; Schmidt, R.; Sharoni, A.; Gomez, M. E.; Schuller, I. K.

    2011-03-01

    Recent infrared spectroscopy and transport measurements in nano-scaled junction of VO2 have revealed the existence of phase separation into metallic and insulating phases. Here we present Impedance spectroscopy measurements performed in high quality Vanadium dioxide (VO2) thin films for the first time. This technique allows distinguishing between the resistive and capacitive response of the VO2 films and provides the dielectric properties across the metal-insulator transition (MIT). The film capacitance exhibits an unusual increase close to the MIT which implies the formation of a capacitor network produced by the nanoscale phase separation of metallic and insulating phases. This work has been supported by AFOSR, COLCIENCIAS, CENM and Ramon y Cajal Fellowship.

  13. 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

  14. Power HV circuit breakers with severe capacitive switching duty

    SciTech Connect

    Canelhas, A.; Bengtsson, B.A.; Margaard, T.; Strandem, A.; Alvinsson, R.

    1994-04-01

    The analysis and control of temporary overvoltages at the ac busbars of an HVDC converter station has been treated in great detail. Often it has been found necessary to operate circuit breakers to disconnect a major capacitive load from the main ac buses under severe transient overvoltage conditions. This paper describes results of tests made on a conventional puffer breaker aimed at gaining knowledge of the consequences of a restrike on the breaker itself. The paper also proposes a method to reduce the transient recovery voltage (TRV) requirements imposed on power circuit breakers in order to be able, in most of the cases, to use standard devices for capacitive breaking. The method is based on application of metal-oxide resistors in parallel with the breaker contacts. The phenomena described in this paper are in all aspects valid for any power system which can have the cases here presented. Therefore this paper is not particular only for HVDC converter stations.

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

    SciTech Connect

    Minick, Steven Kent; 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.

  16. 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.

  17. Imagerie Resolue dans le Temps des Photons et Neutres Metastables Emis D'une Surface Par Stimulation Electronique

    NASA Astrophysics Data System (ADS)

    Leclerc, Gregoire

    L'appareil que nous presentons ici a ete mis au point pour permettre d'accumuler des images numeriques, resolues dans le temps, de la desorption par stimulation electronique (DSE) d'ions positifs et negatifs, de photons et de neutres metastables, tout en conservant des capacites de base de diffraction d'electrons lents (DEL) et de transmission d'electrons lents (TEL). Le spectrometre comporte un monochromateur d'electrons a secteur cylindrique de 127^ circ dont l'optique de sortie permet la focalisation du faisceau d'electrons sur une large gamme d'energies. Le detecteur consiste en un empilement de galettes de microcanaux et d'une anode resistive a encodage de division de charges. La reponse spatiale du detecteur a ete calibree et plusieurs causes de non-linearite ont ete localisees et corrigees. Des methodes de correction materielle et logicielle des distorsions spatiales sont presentees. La resolution temporelle des evenements est obtenue en pulsant le faisceau d'electrons, et de facon synchrone la detection, laquelle est couplee a un micro-ordinateur. La premiere partie de ce travail est consacree a la caracterisation du spectrometre et la presentation de nombreux parametres operationnels, obtenus soit au moment de la conception, soit experimentalement. Suit la presentation de donnees de DEL et de DSE pour le systeme Ar/Pt(111) en films minces a 15K. Les sequences temporelles d'images de metastables d'Ar desorbes ont revele la presence de plusieurs populations distinctes, ayant des distributions angulaires et distributions d'energie cinetique que nous avons pu separer. Les fonctions d'excitation de l'emission de photons et de la desorption de differentes composantes de metastables, ainsi que la dependance de ces signaux sur l'epaisseur des films d'Ar, sont aussi presentees et analysees. Les techniques que nous avons developpees ont permis de cerner les mecanismes en jeu pour la desorption et la luminescence.

  18. 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

  19. 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.

  20. 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.

  1. Feasibility study of simultaneous capacitance detection during STM of silicon

    NASA Astrophysics Data System (ADS)

    Kim, Hyun; Dwyer, Kevin; Pomeroy, Joshua

    2015-03-01

    We are examining the feasibility of capacitance detection during STM to image buried metal nanostructures in silicon. As the hydrogen STM lithography for quantum information enables us to fabricate the atomically precise devices such as single atom qubits, the accurate alignment of metal contacts such as electrodes to the buried nanostructures on the surface becomes very challenging. Using SCM with STM gives benefits to locate the buried nanostructures and image the surface morphology simultaneously.

  2. 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

  3. Can root electrical capacitance be used to predict root mass in soil?

    PubMed Central

    Dietrich, R. C.; Bengough, A. G.; Jones, H. G.; White, P. J.

    2013-01-01

    Background Electrical capacitance, measured between an electrode inserted at the base of a plant and an electrode in the rooting substrate, is often linearly correlated with root mass. Electrical capacitance has often been used as an assay for root mass, and is conventionally interpreted using an electrical model in which roots behave as cylindrical capacitors wired in parallel. Recent experiments in hydroponics show that this interpretation is incorrect and a new model has been proposed. Here, the new model is tested in solid substrates. Methods The capacitances of compost and soil were determined as a function of water content, and the capacitances of cereal plants growing in sand or potting compost in the glasshouse, or in the field, were measured under contrasting irrigation regimes. Key Results Capacitances of compost and soil increased with increasing water content. At water contents approaching field capacity, compost and soil had capacitances at least an order of magnitude greater than those of plant tissues. For plants growing in solid substrates, wetting the substrate locally around the stem base was both necessary and sufficient to record maximum capacitance, which was correlated with stem cross-sectional area: capacitance of excised stem tissue equalled that of the plant in wet soil. Capacitance measured between two electrodes could be modelled as an electrical circuit in which component capacitors (plant tissue or rooting substrate) are wired in series. Conclusions The results were consistent with the new physical interpretation of plant capacitance. Substrate capacitance and plant capacitance combine according to standard physical laws. For plants growing in wet substrate, the capacitance measured is largely determined by the tissue between the surface of the substrate and the electrode attached to the plant. Whilst the measured capacitance can, in some circumstances, be correlated with root mass, it is not a direct assay of root mass. PMID:23493014

  4. Can root electrical capacitance be used to predict root mass in soil?

    PubMed

    Dietrich, R C; Bengough, A G; Jones, H G; White, P J

    2013-07-01

    Electrical capacitance, measured between an electrode inserted at the base of a plant and an electrode in the rooting substrate, is often linearly correlated with root mass. Electrical capacitance has often been used as an assay for root mass, and is conventionally interpreted using an electrical model in which roots behave as cylindrical capacitors wired in parallel. Recent experiments in hydroponics show that this interpretation is incorrect and a new model has been proposed. Here, the new model is tested in solid substrates. The capacitances of compost and soil were determined as a function of water content, and the capacitances of cereal plants growing in sand or potting compost in the glasshouse, or in the field, were measured under contrasting irrigation regimes. Capacitances of compost and soil increased with increasing water content. At water contents approaching field capacity, compost and soil had capacitances at least an order of magnitude greater than those of plant tissues. For plants growing in solid substrates, wetting the substrate locally around the stem base was both necessary and sufficient to record maximum capacitance, which was correlated with stem cross-sectional area: capacitance of excised stem tissue equalled that of the plant in wet soil. Capacitance measured between two electrodes could be modelled as an electrical circuit in which component capacitors (plant tissue or rooting substrate) are wired in series. The results were consistent with the new physical interpretation of plant capacitance. Substrate capacitance and plant capacitance combine according to standard physical laws. For plants growing in wet substrate, the capacitance measured is largely determined by the tissue between the surface of the substrate and the electrode attached to the plant. Whilst the measured capacitance can, in some circumstances, be correlated with root mass, it is not a direct assay of root mass.

  5. Direct measurement of specific membrane capacitance in neurons.

    PubMed Central

    Gentet, L J; Stuart, G J; Clements, J D

    2000-01-01

    The specific membrane capacitance (C(m)) of a neuron influences synaptic efficacy and determines the speed with which electrical signals propagate along dendrites and unmyelinated axons. The value of this important parameter remains controversial. In this study, C(m) was estimated for the somatic membrane of cortical pyramidal neurons, spinal cord neurons, and hippocampal neurons. A nucleated patch was pulled and a voltage-clamp step was applied. The exponential decay of the capacitative charging current was analyzed to give the total membrane capacitance, which was then divided by the observed surface area of the patch. C(m) was 0.9 microF/cm(2) for each class of neuron. To test the possibility that membrane proteins may alter C(m), embryonic kidney cells (HEK-293) were studied before and after transfection with a plasmid coding for glycine receptor/channels. The value of C(m) was indistinguishable in untransfected cells and in transfected cells expressing a high level of glycine channels, indicating that differences in transmembrane protein content do not significantly affect C(m). Thus, to a first approximation, C(m) may be treated as a "biological constant" across many classes of neuron. PMID:10866957

  6. Plasma Treated Active Carbon for Capacitive Deionization of Saline Water

    SciTech Connect

    Zeng, Aiping; Shrestha, Maheshwar; Wang, Keliang; Neto, Victor F.; Gabriel, Bárbara; Fan, Qi Hua

    2017-01-01

    The plasma treatment on commercial active carbon (AC) was carried out in a capacitively coupled plasma system using Ar + 10% O2at pressure of 4.0 Torr. The RF plasma power ranged from 50 W to 100 W and the processing time was 10 min. The carbon film electrode was fabricated by electrophoretic deposition. Micro-Raman spectroscopy revealed the highly increased disorder of sp2C lattice for the AC treated at 75 W. An electrosorption capacity of 6.15 mg/g was recorded for the carbon treated at 75 W in a 0.1 mM NaCl solution when 1.5 V was applied for 5 hours, while the capacity of the untreated AC was 1.0 mg/g. The plasma treatment led to 5.09 times increase in the absorption capacity. The jump of electrosorption capacity by plasma treatment was consistent with the Raman spectra and electrochemical double layer capacitance. This work demonstrated that plasma treatment was a potentially efficient approach to activating biochar to serve as electrode material for capacitive deionization (CDI).

  7. Plasma Treated Active Carbon for Capacitive Deionization of Saline Water

    DOE PAGES

    Zeng, Aiping; Shrestha, Maheshwar; Wang, Keliang; ...

    2017-01-01

    The plasma treatment on commercial active carbon (AC) was carried out in a capacitively coupled plasma system using Ar + 10% O2at pressure of 4.0 Torr. The RF plasma power ranged from 50 W to 100 W and the processing time was 10 min. The carbon film electrode was fabricated by electrophoretic deposition. Micro-Raman spectroscopy revealed the highly increased disorder of sp2C lattice for the AC treated at 75 W. An electrosorption capacity of 6.15 mg/g was recorded for the carbon treated at 75 W in a 0.1 mM NaCl solution when 1.5 V was applied for 5 hours, whilemore » the capacity of the untreated AC was 1.0 mg/g. The plasma treatment led to 5.09 times increase in the absorption capacity. The jump of electrosorption capacity by plasma treatment was consistent with the Raman spectra and electrochemical double layer capacitance. This work demonstrated that plasma treatment was a potentially efficient approach to activating biochar to serve as electrode material for capacitive deionization (CDI).« less

  8. Investigation of capacitively coupled ultrasonic transducer system for nondestructive evaluation.

    PubMed

    Zhong, Cheng Huan; Wilcox, Paul D; Croxford, Anthony J

    2013-12-01

    Capacitive coupling offers a simple solution to wirelessly probe ultrasonic transducers. This paper investigates the theory, feasibility, and optimization of such a capacitively coupled transducer system (CCTS) in the context of nondestructive evaluation (NDE) applications. The noncontact interface relies on an electric field formed between four metal plates-two plates are physically connected to the electrodes of a transducer, the other two are in a separate probing unit connected to the transmit/receive channel of the instrumentation. The complete system is modeled as an electric network with the measured impedance of a bonded piezoelectric ceramic disc representing a transducer attached to an arbitrary solid substrate. A transmission line model is developed which is a function of the physical parameters of the capacitively coupled system, such as the permittivity of the material between the plates, the size of the metal plates, and their relative positions. This model provides immediate prediction of electric input impedance, pulse-echo response, and the effect of plate misalignment. The model has been validated experimentally and has enabled optimization of the various parameters. It is shown that placing a tuning inductor and series resistor on the transmitting side of the circuit can significantly improve the system performance in terms of the signal-to-crosstalk ratio. Practically, bulk-wave CCTSs have been built and demonstrated for underwater and through-composite testing. It has been found that electrical conduction in the media between the plates limits their applications.

  9. Capacitive energy storage and recovery for synchrotron magnets.

    PubMed

    Koseki, K

    2014-06-01

    Feasibility studies on capacitive energy storage and recovery in the main-ring synchrotron of the Japan Proton Accelerator Research Complex were conducted by circuit simulation. The estimated load fluctuation was 96 MVA in total for dipole magnets, which is likely to induce a serious disturbance in the main grid. It was found that the energy stored in the magnets after the excitation period can be recovered to the storage capacitor by controlling the voltage across the energy-storage capacitor using a pulse-width-modulation converter and reused in the next operational cycle. It was also found that the power fluctuation in the main grid can be reduced to 12 MVA. An experimental evaluation of an aluminum metalized film capacitor revealed that capacitance loss was induced by a fluctuating voltage applied to the storage capacitor when applying the proposed method. The capacitance loss was induced by corona discharge around the edges of segmented electrodes of a self-healing capacitor. The use of aluminum-zinc alloy was evaluated as a countermeasure to mitigate the effect induced by the corona discharge. For a zinc content of 8%, which was optimized experimentally, a capacitor with a sufficient life time expectancy of 20 years and a working potential gradient of 250 V/μm was developed.

  10. Capacitive energy storage and recovery for synchrotron magnets

    SciTech Connect

    Koseki, K.

    2014-06-15

    Feasibility studies on capacitive energy storage and recovery in the main-ring synchrotron of the Japan Proton Accelerator Research Complex were conducted by circuit simulation. The estimated load fluctuation was 96 MVA in total for dipole magnets, which is likely to induce a serious disturbance in the main grid. It was found that the energy stored in the magnets after the excitation period can be recovered to the storage capacitor by controlling the voltage across the energy-storage capacitor using a pulse-width-modulation converter and reused in the next operational cycle. It was also found that the power fluctuation in the main grid can be reduced to 12 MVA. An experimental evaluation of an aluminum metalized film capacitor revealed that capacitance loss was induced by a fluctuating voltage applied to the storage capacitor when applying the proposed method. The capacitance loss was induced by corona discharge around the edges of segmented electrodes of a self-healing capacitor. The use of aluminum-zinc alloy was evaluated as a countermeasure to mitigate the effect induced by the corona discharge. For a zinc content of 8%, which was optimized experimentally, a capacitor with a sufficient life time expectancy of 20 years and a working potential gradient of 250 V/μm was developed.

  11. Capacitive-coupled Series Spoof Surface Plasmon Polaritons

    PubMed Central

    Yin, Jia Yuan; Ren, Jian; Zhang, Hao Chi; Zhang, Qian; Cui, Tie Jun

    2016-01-01

    A novel method to realize stopband within the operating frequency of spoof surface plasmon polaritons (SPPs) is presented. The stopband is introduced by a new kind of capacitive-coupled series spoof SPPs. Two conventional H-shaped unit cells are proposed to construct a new unit cell, and every two new unit cells are separated by a gap with certain distance, which is designed to implement capacitive coupling. The original surface impedance matching is disturbed by the capacitive coupling, leading to the stopband during the transmission of SPPs. The proposed method is verified by both numerical simulations and experiments, and the simulated and measured results have good agreements. It is shown that the proposed structure exhibits a stopband in 9–9.5 GHz while the band-pass feature maintains in 5–9 GHz and 9.5–11 GHz. In the passband, the reflection coefficient is less than −10 dB, and the transmission loss is around 3 dB; in the stopband, the reflection coefficient is −2 dB, and the transmission coefficient is less than −30 dB. The compact size, easy fabrication and good band-pass and band-stop features make the proposed structure a promising plasmonic device in SPP communication systems. PMID:27089949

  12. Computational Insights into Materials and Interfaces for Capacitive Energy Storage

    PubMed Central

    Zhan, Cheng; Lian, Cheng; Zhang, Yu; Thompson, Matthew W.; Xie, Yu; Wu, Jianzhong; Kent, Paul R. C.; Cummings, Peter T.; Wesolowski, David J.

    2017-01-01

    Supercapacitors such as electric double‐layer capacitors (EDLCs) and pseudocapacitors are becoming increasingly important in the field of electrical energy storage. Theoretical study of energy storage in EDLCs focuses on solving for the electric double‐layer structure in different electrode geometries and electrolyte components, which can be achieved by molecular simulations such as classical molecular dynamics (MD), classical density functional theory (classical DFT), and Monte‐Carlo (MC) methods. In recent years, combining first‐principles and classical simulations to investigate the carbon‐based EDLCs has shed light on the importance of quantum capacitance in graphene‐like 2D systems. More recently, the development of joint density functional theory (JDFT) enables self‐consistent electronic‐structure calculation for an electrode being solvated by an electrolyte. In contrast with the large amount of theoretical and computational effort on EDLCs, theoretical understanding of pseudocapacitance is very limited. In this review, we first introduce popular modeling methods and then focus on several important aspects of EDLCs including nanoconfinement, quantum capacitance, dielectric screening, and novel 2D electrode design; we also briefly touch upon pseudocapactive mechanism in RuO2. We summarize and conclude with an outlook for the future of materials simulation and design for capacitive energy storage. PMID:28725531

  13. 3D Alignment of nanowriters using fringe capacitance

    NASA Astrophysics Data System (ADS)

    Lally, Richard; Stark, Thomas; Reeves, Jeremy; Barrett, Lawrence; Bishop, David

    With the introduction of atomic calligraphy, high resolution nanoscale structures can be fabricated rapidly over a large surface area. This reliable, chemically stable and cost effective nanoscale writing method can be applied to a number of interesting applications. One specific application of this writing approach is to fabricate metamaterials, a process that requires precise alignment of the MEMS and substrate. Here we present a MEMS based solution coupling the well-studied comb drive capacitance effects with the less predictable close order fringe effects. The combined capacitance allows for precise measurements in the nanometer range. Using two sets of orthogonal static MEMS comb drives, the capacitance is used to discern the x, y, and z spatial displacement from the substrate. The unique SOI wafer is prepared creating a periodic array of silicon pillars. Placement of additional MEMS comb drives at the MEMS device edges will allow stage corrections for tip, tilt and rotational alignment thereby reducing the effects generated by variations in wafer thickness and surface smoothness. This work is funded by the DARPA A2P Program.

  14. Hysteresis free negative total gate capacitance in junctionless transistors

    NASA Astrophysics Data System (ADS)

    Gupta, Manish; Kranti, Abhinav

    2017-09-01

    In this work, we report on the hysteresis free impact ionization induced off-to-on transition while preserving sub-60 mV/decade Subthreshold swing (S-swing) using asymmetric mode operation in double gate silicon (Si) and germanium (Ge) junctionless (JL) transistor. It is shown that sub-60 mV/decade steep switching due to impact ionization implies a negative value of the total gate capacitance. The performance of asymmetric gate JL transistor is compared with symmetric gate operation of JL device, and the condition for hysteresis free current transition with a sub-60 mV/decade switching is analyzed through the product of current density (J) and electric field (E). It is shown that asymmetric gate operation limits the degree of impact ionization inherent in the semiconductor film to levels sufficient for negative total gate capacitance but lower than that required for the occurrence of hysteresis. The work highlights new viewpoints related to the suppression of hysteresis associated with steep switching JL transistors while maintaining S-swing within the range 6-15 mV/decade leading to the negative value of total gate capacitance.

  15. Capacitance-modulated transistor detects odorant binding protein chiral interactions

    PubMed Central

    Mulla, Mohammad Yusuf; Tuccori, Elena; Magliulo, Maria; Lattanzi, Gianluca; Palazzo, Gerardo; Persaud, Krishna; Torsi, Luisa

    2015-01-01

    Peripheral events in olfaction involve odorant binding proteins (OBPs) whose role in the recognition of different volatile chemicals is yet unclear. Here we report on the sensitive and quantitative measurement of the weak interactions associated with neutral enantiomers differentially binding to OBPs immobilized through a self-assembled monolayer to the gate of an organic bio-electronic transistor. The transduction is remarkably sensitive as the transistor output current is governed by the small capacitance of the protein layer undergoing minute changes as the ligand–protein complex is formed. Accurate determination of the free-energy balances and of the capacitance changes associated with the binding process allows derivation of the free-energy components as well as of the occurrence of conformational events associated with OBP ligand binding. Capacitance-modulated transistors open a new pathway for the study of ultra-weak molecular interactions in surface-bound protein–ligand complexes through an approach that combines bio-chemical and electronic thermodynamic parameters. PMID:25591754

  16. Capacitive energy storage and recovery for synchrotron magnets

    NASA Astrophysics Data System (ADS)

    Koseki, K.

    2014-06-01

    Feasibility studies on capacitive energy storage and recovery in the main-ring synchrotron of the Japan Proton Accelerator Research Complex were conducted by circuit simulation. The estimated load fluctuation was 96 MVA in total for dipole magnets, which is likely to induce a serious disturbance in the main grid. It was found that the energy stored in the magnets after the excitation period can be recovered to the storage capacitor by controlling the voltage across the energy-storage capacitor using a pulse-width-modulation converter and reused in the next operational cycle. It was also found that the power fluctuation in the main grid can be reduced to 12 MVA. An experimental evaluation of an aluminum metalized film capacitor revealed that capacitance loss was induced by a fluctuating voltage applied to the storage capacitor when applying the proposed method. The capacitance loss was induced by corona discharge around the edges of segmented electrodes of a self-healing capacitor. The use of aluminum-zinc alloy was evaluated as a countermeasure to mitigate the effect induced by the corona discharge. For a zinc content of 8%, which was optimized experimentally, a capacitor with a sufficient life time expectancy of 20 years and a working potential gradient of 250 V/μm was developed.

  17. Rough Electrode Creates Excess Capacitance in Thin-Film Capacitors

    PubMed Central

    2017-01-01

    The parallel-plate capacitor equation is widely used in contemporary material research for nanoscale applications and nanoelectronics. To apply this equation, flat and smooth electrodes are assumed for a capacitor. This essential assumption is often violated for thin-film capacitors because the formation of nanoscale roughness at the electrode interface is very probable for thin films grown via common deposition methods. In this work, we experimentally and theoretically show that the electrical capacitance of thin-film capacitors with realistic interface roughness is significantly larger than the value predicted by the parallel-plate capacitor equation. The degree of the deviation depends on the strength of the roughness, which is described by three roughness parameters for a self-affine fractal surface. By applying an extended parallel-plate capacitor equation that includes the roughness parameters of the electrode, we are able to calculate the excess capacitance of the electrode with weak roughness. Moreover, we introduce the roughness parameter limits for which the simple parallel-plate capacitor equation is sufficiently accurate for capacitors with one rough electrode. Our results imply that the interface roughness beyond the proposed limits cannot be dismissed unless the independence of the capacitance from the interface roughness is experimentally demonstrated. The practical protocols suggested in our work for the reliable use of the parallel-plate capacitor equation can be applied as general guidelines in various fields of interest. PMID:28745040

  18. Rough Electrode Creates Excess Capacitance in Thin-Film Capacitors.

    PubMed

    Torabi, Solmaz; Cherry, Megan; Duijnstee, Elisabeth A; Le Corre, Vincent M; Qiu, Li; Hummelen, Jan C; Palasantzas, George; Koster, L Jan Anton

    2017-08-16

    The parallel-plate capacitor equation is widely used in contemporary material research for nanoscale applications and nanoelectronics. To apply this equation, flat and smooth electrodes are assumed for a capacitor. This essential assumption is often violated for thin-film capacitors because the formation of nanoscale roughness at the electrode interface is very probable for thin films grown via common deposition methods. In this work, we experimentally and theoretically show that the electrical capacitance of thin-film capacitors with realistic interface roughness is significantly larger than the value predicted by the parallel-plate capacitor equation. The degree of the deviation depends on the strength of the roughness, which is described by three roughness parameters for a self-affine fractal surface. By applying an extended parallel-plate capacitor equation that includes the roughness parameters of the electrode, we are able to calculate the excess capacitance of the electrode with weak roughness. Moreover, we introduce the roughness parameter limits for which the simple parallel-plate capacitor equation is sufficiently accurate for capacitors with one rough electrode. Our results imply that the interface roughness beyond the proposed limits cannot be dismissed unless the independence of the capacitance from the interface roughness is experimentally demonstrated. The practical protocols suggested in our work for the reliable use of the parallel-plate capacitor equation can be applied as general guidelines in various fields of interest.

  19. Flexible Capacitive Tactile Sensor Based on Micropatterned Dielectric Layer.

    PubMed

    Li, Tie; Luo, Hui; Qin, Lin; Wang, Xuewen; Xiong, Zuoping; Ding, Haiyan; Gu, Yang; Liu, Zheng; Zhang, Ting

    2016-09-01

    Flexible tactile sensors are considered as an effective way to realize the sense of touch, which can perform the synchronized interactions with surrounding environment. Here, the utilization of bionic microstructures on natural lotus leaves is demonstrated to design and fabricate new-type of high-performance flexible capacitive tactile sensors. Taking advantage of unique surface micropattern of lotus leave as the template for electrodes and using polystyrene microspheres as the dielectric layer, the proposed devices present stable and high sensing performance, such as high sensitivity (0.815 kPa(-1) ), wide dynamic response range (from 0 to 50 N), and fast response time (≈38 ms). In addition, the flexible capacitive sensor is not only applicable to pressure (touch of a single hair), but also to bending and stretching forces. The results indicate that the proposed capacitive tactile sensor is a promising candidate for the future applications in electronic skins, wearable robotics, and biomedical devices. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  20. DNA Nucleotides Detection via capacitance properties of Graphene

    NASA Astrophysics Data System (ADS)

    Khadempar, Nahid; Berahman, Masoud; Yazdanpanah, Arash

    2016-05-01

    In the present paper a new method is suggested to detect the DNA nucleotides on a first-principles calculation of the electronic features of DNA bases which chemisorbed to a graphene sheet placed between two gold electrodes in a contact-channel-contact system. The capacitance properties of graphene in the channel are surveyed using non-equilibrium Green's function coupled with the Density Functional Theory. Thus, the capacitance properties of graphene are theoretically investigated in a biological environment, and, using a novel method, the effect of the chemisorbed DNA nucleotides on electrical charges on the surface of graphene is deciphered. Several parameters in this method are also extracted including Electrostatic energy, Induced density, induced electrostatic potential, Electron difference potential and Electron difference density. The qualitative and quantitative differences among these parameters can be used to identify DNA nucleotides. Some of the advantages of this approach include its ease and high accuracy. What distinguishes the current research is that it is the first experiment to investigate the capacitance properties of gaphene changes in the biological environment and the effect of chemisorbed DNA nucleotides on the surface of graphene on the charge.

  1. Defect tolerance in microfluidic chambers for capacitive biosensors

    NASA Astrophysics Data System (ADS)

    Chapman, Glenn; Gray, Bonnie L.; Jain, Vijay K.

    2010-02-01

    Biomedical sensors combining microfluidic and electronics capabilities require defect avoidance in both the electronic processing circuits and microfluidic areas. Microfluidic sensors involve sealed channels through which sample fluids containing biomedical materials flow. Inserting microchannels between capacitive plates enable the detection of biomaterials by the changes in capacitance. However, faults occur when foreign particles, or fluid bubbles get lodged in the paths blocking a channel, thereby affecting the measured C. To achieve fault tolerance we investigate a Cathedral Chamber design, with pillars supporting the roof at regular intervals. This prevents single blockages from stopping fluid flow through the system in a channel, as there are many paths. We discuss the potential causes and effects of such blockages. Monte Carlo simulations show that the Cathedral Chamber design significantly increases lifetime of the system, an average of 6 times more particles are required before full blockage occurs compared to an array of parallel channels. Fluid flow modeling shows parallel channels show rapid rise of pressure with the number of blockages while the Cathedral chamber shows much slower rise, which reaches a plateau pressure until it is blocked. The impact of defects on the capacitive measurement is also discussed. Finally, an interesting application, one that uses patches of single chain Fragment variables (scFv's), the active part of antibodies, is also discussed.

  2. Capacitance-modulated transistor detects odorant binding protein chiral interactions

    NASA Astrophysics Data System (ADS)

    Mulla, Mohammad Yusuf; Tuccori, Elena; Magliulo, Maria; Lattanzi, Gianluca; Palazzo, Gerardo; Persaud, Krishna; Torsi, Luisa

    2015-01-01

    Peripheral events in olfaction involve odorant binding proteins (OBPs) whose role in the recognition of different volatile chemicals is yet unclear. Here we report on the sensitive and quantitative measurement of the weak interactions associated with neutral enantiomers differentially binding to OBPs immobilized through a self-assembled monolayer to the gate of an organic bio-electronic transistor. The transduction is remarkably sensitive as the transistor output current is governed by the small capacitance of the protein layer undergoing minute changes as the ligand-protein complex is formed. Accurate determination of the free-energy balances and of the capacitance changes associated with the binding process allows derivation of the free-energy components as well as of the occurrence of conformational events associated with OBP ligand binding. Capacitance-modulated transistors open a new pathway for the study of ultra-weak molecular interactions in surface-bound protein-ligand complexes through an approach that combines bio-chemical and electronic thermodynamic parameters.

  3. A silicon MEMS structure for characterization of femto-farad-level capacitive sensors with lock-in architecture

    NASA Astrophysics Data System (ADS)

    Wei, J.; Yue, C.; Chen, Z. L.; Liu, Z. W.; Sarro, P. M.

    2010-06-01

    This paper presents a silicon MEMS capacitive structure to investigate a test methodology for fF-level capacitive sensors' measurement. The device mimics a capacitive sensor with a changing intermediate layer between the electrodes. A single mask bulk micromachining process is used to fabricate the device, which has a nominal capacitance of 1.2 fF. A high performance measurement setup based on lock-in principle is developed to detect the capacitance variation. The maximum capacitance variation of the fabricated device is 0.31 fF, and the capacitance detection limit is 0.095 aF Hz-1/2.

  4. Etude des Abondances de MG et de fe dans la Composante Stellaire des Disques des Galaxies Spirales

    NASA Astrophysics Data System (ADS)

    Beauchamp, Dominique

    Je presente ici une technique d'observation par imagerie des disques stellaires des galaxies spirales. Je tente, a l'aide d'un modele evolutif multiphase, de determiner les abondances de fer et de magnesium dans les disques. Dans ce but, je mesure les indices Mg2 et Fe5270 du systeme de Lick. Ces elements representent un choix judicieux d'indicateurs car ils sont formes par des supernovae de deux types differents ayant des durees de vie differentes. Le rapport d'abondances de ces deux elements est un indicateur du taux de formation des populations stellaires. Je decris, en premier lieu, les observations, la technique de mesure, ainsi que son application. J'analyse ensuite les indices mesures. A partir du modele multiphase, j'explore differents parametres physiques des spirales comme le taux de formation stellaire, l'evolution des abondances, les effets possibles de la presence de la barre, etc.

  5. A negative-capacitance equivalent circuit model for parallel-plate capacitive-gap-transduced micromechanical resonators.

    PubMed

    Akgul, Mehmet; Wu, Lingqi; Ren, Zeying; Nguyen, Clark T-C

    2014-05-01

    A small-signal equivalent circuit for parallel-plate capacitive-gap-transduced micromechanical resonators is introduced that employs negative capacitance to model the dependence of resonance frequency on electrical stiffness in a way that facilitates circuit analysis, that better elucidates the mechanisms behind certain potentially puzzling measured phenomena, and that inspires circuit topologies that maximize performance in specific applications. For this work, a micromechanical disk resonator serves as the vehicle with which to derive the equivalent circuits for both radial-contour and wine-glass modes, which are then used in circuit simulations (via simulation) to match measurements on actual fabricated devices. The new circuit model not only correctly predicts the dependence of electrical stiffness on the impedances loading the input and output electrodes of parallel-plate capacitive- gap-transduced micromechanical device, but does so in a visually intuitive way that identifies current drive as most appropriate for applications that must be stable against environmental perturbations, such as acceleration or power supply variations. Measurements on fabricated devices confirm predictions by the new model of up to 4× improvement in frequency stability against dc-bias voltage variations for contour- mode disk resonators as the resistance loading their ports increases. By enhancing circuit visualization, this circuit model makes more obvious the circuit design procedures and topologies most beneficial for certain mechanical circuits, e.g., filters and oscillators.

  6. Estimation of stream depletion using values of capacitance

    NASA Astrophysics Data System (ADS)

    Baldenkov, Mikhail; Filimonova, Elena

    2014-05-01

    Compensation pumping is used to alleviate deficiencies in streamflow discharge during dry seasons. Short-term groundwater pumping can use aquifer storage instead of catchment-zone water until the drawdown reaches the edge of the stream. Stream-aquifer interactions are the key component of the hydrologic budgets and estimation of stream depletion has top-priority when evaluating the effectiveness of application of seasonal compensation pumping. Numerous analytical equations have been developed to assess the influence of groundwater pumping on nearby streams (C.V. Theis, R.E. Glover, C.G. Balmer, M.S. Hantush, C.T. Jenkins, B. Hunt, J. Bredehoeft, V.A. Zlotnik, E.L. Minkin, N.N. Lapshin, F.M. Bochever and other researchers). R.B. Wallace and Y. Darama obtained solution for cyclic conditions groundwater pumping. Numerical model approaches used in difficult hydrogeological conditions. It is offered to estimate stream depletion by seasonal pumping using values of capacitance (complex, dimensionless parameter of an aquifer system that defines the delayed effect on steamflow when there is groundwater pumping). Capacitance (C) is determined by the following equation: ( ) L* C = f( °---) , TS-Δt where S and T are the aquifer specific yield (or storage coefficient for a confined aquifer) and transmissivity, respectively; Δt is the pumping time inside one cycle, L* is the summarizing distance between the compensation well and stream edge; in some cases it can involve a function of the stream leakance and vertical leakance of the impermeable layer. Three typical hydraulic cases of compensation pumping were classified depending on their capacitance structure (i.e. the relationship between surface water and groundwater): (a) perfect hydraulic connection between the stream and aquifer; (b) imperfect hydraulic connection between the stream and aquifer; and (c) essentially imperfect hydraulic connection between the stream and the underlying confined aquifer. The form of

  7. Classification of 17 DES supernova with OzDES

    NASA Astrophysics Data System (ADS)

    Mudd, D.; Martini, P.; Lewis, G. F.; Moller, A.; Sharp, R. G.; Sommer, N. E.; Tucker, B. E.; Yuan, F.; Zhang, B.; Asorey, J.; Davis, T. M.; Hinton, S.; Muthukrishna, D.; Parkinson, D.; Carnero, A.; King, A.; Lidman, C.; Webb, S.; Uddin, S.; Kessler, R.; Lasker, J.; Scolnic, D.; Brout, D. J.; D'Andrea, C.; Gladney, L.; March, M.; Sako, M.; Wolf, R. C.; Brown, P. J.; Krisciunas, K.; Suntzeff, N.; Macaulay, E.; Nichol, R.; Childress, M.; Prajs, S.; Smith, M.; Sullivan, M.; Maartens, R.; Kovacs, E.; Kuhlmann, S.; Spinka, H.; Ahn, E.; Finley, D. A.; Frieman, J.; Marriner, J.; Wester, W.; Aldering, G.; Gupta, R.; Kim, A. G.; Thomas, R. C.; Barbary, K.; Bloom, J. S.; Goldstein, D.; Nugent, P.; Perlmutter, S.; Foley, R. J.; Pan, Y.-C.; Casas, R.; Castander, F. J.; Papadopoulos, A.; Morganson, E.; Desai, S.; Paech, K.; Smith, R. C.; Schubnell, M.

    2016-11-01

    We report new spectroscopic classifications by OzDES of supernovae discovered by the Dark Energy Survey (ATEL #4668). The spectra (370-885nm) were obtained with the AAOmega Spectrograph (Saunders et al. 2004, SPIE, 5492, 389) and the 2dF fibre positioner at the Anglo-Australian Telescope (AAT).

  8. Classification of 17 DES supernova with OzDES

    NASA Astrophysics Data System (ADS)

    Muthukrishna, D.; Sharp, R. G.; Tucker, B. E.; Moller, A.; Sommer, N. E.; Asorey, J.; Lewis, G. F.; Lidman, C.; Mould, J.; Macaulay, E.; Maartens, R.; Kovacs, E.; Kuhlmann, S.; Spinka, H.; Ahn, E.; Finley, D. A.; Frieman, J.; Marriner, J.; Wester, W.; Aldering, G.; Gupta, R.; Kim, A. G.; Thomas, R. C.; Barbary, K.; Bloom, J. S.; Goldstein, D.; Nugent, P.; Perlmutter, S.; Foley, R. J.; Pan, Y.-C.; Casas, R.; Castander, F. J.; Papadopoulos, A.; Morganson, E.; Desai, S.; Paech, K.; Smith, R. C.; Schubnell, M.; Yuan, F.; Zhang, B.; Davis, T. M.; Hinton, S.; Parkinson, D.; Uddin, S.; Kessler, R.; Lasker, J.; Scolnic, D.; Brout, D. J.; D'Andrea, C.; Gladney, L.; March, M.; Sako, M.; Wolf, R. C.; Brown, P. J.; Krisciunas, K.; Suntzeff, N.; Nichol, R.; Childress, M.; Prajs, S.; Smith, M.; Sullivan, M.

    2017-09-01

    We report new spectroscopic classifications by OzDES of supernovae discovered by the Dark Energy Survey (ATEL #4668). The spectra (370-885nm) were obtained with the AAOmega Spectrograph (Saunders et al. 2004, SPIE, 5492, 389) and the 2dF fibre positioner at the Anglo-Australian Telescope (AAT).

  9. Classification of 3 DES Supernovae with OzDES

    NASA Astrophysics Data System (ADS)

    Moller, A.; Tucker, B. E.; Yuan, F.; Lewis, G.; Lidman, C.; Macaulay, E.; Nichol, R.; Papadopoulos, A.; Childress, M.; D'Andrea, C.; Smith, M.; Sullivan, M.; Maartens, R.; Gupta, R.; Kovacs, E.; Kuhlmann, S.; Spinka, H.; Ahn, E.; Finley, D. A.; Frieman, J.; Marriner, J.; Wester, W.; Aldering, G.; Kim, A. G.; Thomas, R. C.; Barbary, K.; Bloom, J. S.; Goldstein, D.; Nugent, P.; Perlmutter, S.; Foley, R. J.; Pan, Y.-C.; Casas, R.; Castander, F. J.; Desai, S.; Paech, K.; Smith, R. C.; Schubnell, M.; Kessler, R.; Lasker, J.; Scolnic, D.; Brout, D. J.; Gladney, L.; Sako, M.; Wolf, R. C.; Brown, P. J.; Krisciunas, K.; Suntzeff, N.

    2016-02-01

    We report new spectroscopic classifications by OzDES of supernovae discovered by the Dark Energy Survey (ATEL #4668). The spectra (370-885nm) were obtained with the AAOmega Spectrograph (Saunders et al. 2004, SPIE, 5492, 389) and the 2dF fibre positioner at the Anglo-Australian Telescope (AAT).

  10. Classification of 20 DES Supernova with OzDES

    NASA Astrophysics Data System (ADS)

    Davis, T. M.; Kim, A. G.; Macualay, E.; Lidman, C.; Sharp, R.; Tucker, B. E.; Yuan, F.; Zhang, B.; Lewis, G. F.; Sommer, N. E.; Martini, P.; Mould, J.; Ahn, E.; Finley, D. A.; Frieman, J.; Marriner, J.; Wester, W.; Aldering, G.; Thomas, R. C.; Barbary, K.; Bloom, J. S.; Goldstein, D.; Nugent, P.; Perlmutter, S.; Foley, R. J.; Pan, Y.-C.; Casas, R.; Castander, F. J.; Desai, S.; Paech, K.; Smith, R. C.; Schubnell, M.; Kessler, R.; Lasker, J.; Scolnic, D.; Brout, D. J.; Gladney, L.; Sako, M.; Wolf, R. C.; Brown, P. J.; Krisciunas, K.; Suntzeff, N.; Nichol, R.; Papadopoulos, A.; Childress, M.; D'Andrea, C.; Smith, M.; Sullivan, M.; Maartens, R.; Gupta, R.; Kovacs, E.; Kuhlmann, S.; Spinka, H.

    2015-12-01

    We report new spectroscopic classifications by OzDES of supernovae discovered by the Dark Energy Survey (ATEL #4668). The spectra (370-885nm) were obtained with the AAOmega Spectrograph (Saunders et al. 2004, SPIE, 5492, 389) and the 2dF fibre positioner at the Anglo-Australian Telescope (AAT).

  11. Classification of 14 DES Supernova with OzDES

    NASA Astrophysics Data System (ADS)

    Tucker, B. E.; Sharp, R.; Yuan, F.; Zhang, B.; Lidman, C.; Davis, T. M.; Hinton, S.; Mould, J.; Smith, R. C.; Schubnell, M.; Kessler, R.; Scolnic, D.; Covarrubias, R. A.; Brout, D. J.; Fischer, J. A.; Gladney, L.; March, M.; Sako, M.; Wolf, R. C.; Brown, P. J.; Krisciunas, K.; Suntzeff, N.; Nichol, R.; Papadopoulos, A.; D'Andrea, C.; Smith, M.; Sullivan, M.; Childress, M.; Maartens, R.; Gupta, R.; Kovacs, E.; Kuhlmann, S.; Spinka, H.; Ahn, E.; Finley, D. A.; Frieman, J.; Marriner, J.; Wester, W.; Aldering, G.; Kim, A. G.; Thomas, R. C.; Barbary, K.; Bloom, J. S.; Goldstein, D.; Nugent, P.; Perlmutter, S.; Foley, R. J.; Castander, F. J.; Desai, S.; Paech, K.

    2015-10-01

    We report new spectroscopic classifications by OzDES of supernovae discovered by the Dark Energy Survey. The spectra (370-885nm) were obtained with the AAOmega Spectrograph (Saunders et al. 2004, SPIE, 5492, 389) and the 2dF fibre positioner at the Anglo-Australian Telescope (AAT).

  12. Classification of 4 DES supernovae by OzDES

    NASA Astrophysics Data System (ADS)

    Glazebrook, K.; Amon, A.; Lidman, C.; Martini, P.; Tucker, B. E.; Yuan, F.; Aldering, G.; Kim, A. G.; Thomas, R. C.; Barbary, K.; Bloom, J. S.; Goldstein, D.; Nugent, P.; Perlmutter, S.; Foley, R. J.; Pan, Y.-C.; Casas, R.; Castander, F. J.; Desai, S.; Paech, K.; Smith, R. C.; Schubnell, M.; Kessler, R.; Lasker, J.; Scolnic, D.; Brout, D. J.; Gladney, L.; Sako, M.; Wolf, R. C.; Brown, P. J.; Krisciunas, K.; Suntzeff, N.; Nichol, R.; Papadopoulos, A.; Childress, M.; D'Andrea, C.; Smith, M.; Sullivan, M.; Maartens, R.; Gupta, R.; Kovacs, E.; Kuhlmann, S.; Spinka, H.; Ahn, E.; Finley, D. A.; Frieman, J.; Marriner, J.; Wester, W.

    2015-12-01

    We report new spectroscopic classifications by OzDES of supernovae discovered by the Dark Energy Survey (ATEL #4668). The spectra (370-885nm) were obtained with the AAOmega Spectrograph (Saunders et al. 2004, SPIE, 5492, 389) and the 2dF fibre positioner at the Anglo-Australian Telescope (AAT).

  13. Classification of 6 DES Supernova with OzDES

    NASA Astrophysics Data System (ADS)

    Lewis, G. F.; Mould, J.; Lidman, C.; Tucker, B. E.; Sharp, R.; Yuan, F.; Martini, P.; Kessler, R.; Scolnic, D.; Covarrubias, R. A.; Brout, D. J.; Fischer, J. A.; Gladney, L.; March, M.; Sako, M.; Wolf, R. C.; Brown, P. J.; Krisciunas, K.; Suntzeff, N.; Nichol, R.; Papadopoulos, A.; D'Andrea, C.; Smith, M.; Sullivan, M.; Childress, M.; Maartens, R.; Gupta, R.; Kovacs, E.; Kuhlmann, S.; Spinka, H.; Ahn, E.; Finley, D. A.; Frieman, J.; Marriner, J.; Wester, W.; Aldering, G.; Kim, A. G.; Thomas, R. C.; Barbary, K.; Bloom, J. S.; Goldstein, D.; Nugent, P.; Perlmutter, S.; Foley, R. J.; Casas, R.; Castander, F. J.; Desai, S.; Paech, K.; Smith, R. C.; Schubnell, M.

    2015-10-01

    We report new spectroscopic classifications by OzDES of supernovae discovered by the Dark Energy Survey (ATEL #4668). The spectra (370-885nm) were obtained with the AAOmega Spectrograph (Saunders et al. 2004, SPIE, 5492, 389) and the 2dF fibre positioner at the Anglo-Australian Telescope (AAT).

  14. Classification of 15 DES supernovae by OzDES

    NASA Astrophysics Data System (ADS)

    Yuan, F.; Tucker, B. E.; Lidman, C.; Martini, P.; Gshwend, Julia; Moller, A.; Zhang, B.; Smith, R. C.; Schubnell, M.; Kessler, R.; Lasker, J.; Scolnic, D.; Brout, D. J.; Gladney, L.; Sako, M.; Wolf, R. C.; Brown, P. J.; Krisciunas, K.; Suntzeff, N.; Nichol, R.; Papadopoulos, A.; Childress, M.; D'Andrea, C.; Smith, M.; Sullivan, M.; Maartens, R.; Gupta, R.; Kovacs, E.; Kuhlmann, S.; Spinka, H.; Ahn, E.; Finley, D. A.; Frieman, J.; Marriner, J.; Wester, W.; Aldering, G.; Kim, A. G.; Thomas, R. C.; Barbary, K.; Bloom, J. S.; Goldstein, D.; Nugent, P.; Perlmutter, S.; Foley, R. J.; Pan, Y.-C.; Casas, R.; Castander, F. J.; Desai, S.; Paech, K.

    2015-12-01

    We report new spectroscopic classifications by OzDES of supernovae discovered by the Dark Energy Survey (ATEL #4668). The spectra (370-885nm) were obtained with the AAOmega Spectrograph (Saunders et al. 2004, SPIE, 5492, 389) and the 2dF fibre positioner at the Anglo-Australian Telescope (AAT).

  15. Classification of 8 DES Supernova with OzDES

    NASA Astrophysics Data System (ADS)

    King, A.; Moller, A.; Sommer, N. E.; Tucker, B. E.; Childress, M. J.; Lewis, G. F.; Lidman, C.; OâNeill, C.; Casas, R.; Castander, F. J.; Desai, S.; Paech, K.; Smith, R. C.; Schubnell, M.; Kessler, R.; Lasker, J.; Scolnic, D.; Brout, D. J.; Gladney, L.; Sako, M.; Wolf, R. C.; Brown, P. J.; Krisciunas, K.; Suntzeff, N.; Nichol, R.; Papadopoulos, A.; D'Andrea, C.; Prajs, S.; Smith, M.; Sullivan, M.; Maartens, R.; Gupta, R.; Kovacs, E.; Kuhlmann, S.; Spinka, H.; Ahn, E.; Finley, D. A.; Frieman, J.; Marriner, J.; Wester, W.; Aldering, G.; Kim, A. G.; Thomas, R. C.; Barbary, K.; Bloom, J. S.; Goldstein, D.; Nugent, P.; Perlmutter, S.; Foley, R. J.; Pan, Y.-C.

    2016-09-01

    We report new spectroscopic classifications by OzDES of supernovae discovered by the Dark Energy Survey (ATEL #4668). The spectra (370-885nm) were obtained with the AAOmega Spectrograph (Saunders et al. 2004, SPIE, 5492, 389) and the 2dF fibre positioner at the Anglo-Australian Telescope (AAT).

  16. Classification of 17 DES Supernova with OzDES

    NASA Astrophysics Data System (ADS)

    Hoormann, J. K.; Asorey, J.; Carollo, D.; Moller, A.; Sharp, R.; Sommer, N. E.; Tucker, B. E.; Zhang, B.; Lidman, C.; Brout, D. J.; D'Andrea, C.; Gladney, L.; March, M.; Sako, M.; Wolf, R. C.; Brown, P. J.; Krisciunas, K.; Suntzeff, N.; Macaulay, E.; Nichol, R.; Childress, M.; Prajs, S.; Smith, M.; Sullivan, M.; Maartens, R.; Kovacs, E.; Kuhlmann, S.; Spinka, H.; Ahn, E.; Finley, D. A.; Frieman, J.; Marriner, J.; Wester, W.; Aldering, G.; Gupta, R.; Kim, A. G.; Thomas, R. C.; Barbary, K.; Bloom, J. S.; Goldstein, D.; Nugent, P.; Perlmutter, S.; Foley, R. J.; Pan, Y.-C.; Casas, R.; Castander, F. J.; Papadopoulos, A.; Morganson, E.; Desai, S.; Paech, K.; Smith, R. C.; Schubnell, M.; Yuan, F.; Davis, T. M.; Hinton, S.; Muthukrishna, D.; Parkinson, D.; Lewis, G. F.; Uddin, S.; Kessler, R.; Lasker, J.; Scolnic, D.

    2016-12-01

    We report new spectroscopic classifications by OzDES of supernovae discovered by the Dark Energy Survey (ATEL #4668). The spectra (370-885nm) were obtained with the AAOmega Spectrograph (Saunders et al. 2004, SPIE, 5492, 389) and the 2dF fibre positioner at the Anglo-Australian Telescope (AAT).

  17. Classification of 13 DES supernova with OzDES

    NASA Astrophysics Data System (ADS)

    Sommer, N.; Tucker, B. E.; Moller, A.; Zhang, B.; Macualay, E.; Lidman, C.; Gshwend, J.; Martini, P.; Foley, R. J.; Pan, Y.-C.; Casas, R.; Castander, F. J.; Desai, S.; Paech, K.; Smith, R. C.; Schubnell, M.; Kessler, R.; Lasker, J.; Scolnic, D.; Brout, D. J.; Gladney, L.; Sako, M.; Wolf, R. C.; Brown, P. J.; Krisciunas, K.; Suntzeff, N.; Nichol, R.; Papadopoulos, A.; Childress, M.; D'Andrea, C.; Prajs, S.; Smith, M.; Sullivan, M.; Maartens, R.; Gupta, R.; Kovacs, E.; Kuhlmann, S.; Spinka, H.; Ahn, E.; Finley, D. A.; Frieman, J.; Marriner, J.; Wester, W.; Aldering, G.; Kim, A. G.; Thomas, R. C.; Barbary, K.; Bloom, J. S.; Goldstein, D.; Nugent, P.; Perlmutter, S.

    2016-09-01

    We report new spectroscopic classifications by OzDES of supernovae discovered by the Dark Energy Survey (ATEL #4668). The spectra (370-885nm) were obtained with the AAOmega Spectrograph (Saunders et al. 2004, SPIE, 5492, 389) and the 2dF fibre positioner at the Anglo-Australian Telescope (AAT).

  18. Classification of 11 DES supernova with OzDES

    NASA Astrophysics Data System (ADS)

    Sharp, R.; Zhang, B.; Sommer, N. E.; Tucker, B. E.; Lidman, C.; Davis, T. M.; Asorey, J.; Mould, J.; Smith, M.; Macaulay, E.; Nichol, R.; Childress, M.; Prajs, S.; Sullivan, M.; Maartens, R.; Kovacs, E.; Kuhlmann, S.; Spinka, H.; Ahn, E.; Finley, D. A.; Frieman, J.; Marriner, J.; Wester, W.; Aldering, G.; Gupta, R.; Kim, A. G.; Thomas, R. C.; Barbary, K.; Bloom, J. S.; Goldstein, D.; Nugent, P.; Perlmutter, S.; Foley, R. J.; Pan, Y.-C.; Casas, R.; Castander, F. J.; Papadopoulos, A.; Morganson, E.; Desai, S.; Paech, K.; Smith, R. C.; Schubnell, M.; Carollo, D.; Moller, A.; Yuan, F.; Hinton, S.; Muthukrishna, D.; Parkinson, D.; Lewis, G. F.; Uddin, S.; Kessler, R.; Lasker, J.; Scolnic, D.; Brout, D. J.; D'Andrea, C.; Gladney, L.; March, M.; Sako, M.; Wolf, R. C.; Brown, P. J.; Krisciunas, K.; Suntzeff, N.

    2017-01-01

    We report new spectroscopic classifications by OzDES of supernovae discovered by the Dark Energy Survey (ATEL #4668). The spectra (370-885nm) were obtained with the AAOmega Spectrograph (Saunders et al. 2004, SPIE, 5492, 389) and the 2dF fibre positioner at the Anglo-Australian Telescope (AAT).

  19. Classification of 2 DES supernova with OzDES

    NASA Astrophysics Data System (ADS)

    O'Neill, C. R.; Moller, A.; Sommer, N. E.; Tucker, B. E.; Childress, M. J.; Lewis, G. F.; Lidman, C.; Desai, S.; Paech, K.; Smith, R. C.; Schubnell, M.; Kessler, R.; Lasker, J.; Scolnic, D.; Brout, D. J.; D'Andrea, C.; Gladney, L.; March, M.; Sako, M.; Wolf, R. C.; Brown, P. J.; Krisciunas, K.; Suntzeff, N.; Macaulay, E.; Nichol, R.; Prajs, S.; Smith, M.; Sullivan, M.; Maartens, R.; Kovacs, E.; Kuhlmann, S.; Spinka, H.; Ahn, E.; Finley, D. A.; Frieman, J.; Marriner, J.; Wester, W.; Aldering, G.; Kim, A. G.; Thomas, R. C.; Barbary, K.; Bloom, J. S.; Goldstein, D.; Gupta, R.; Nugent, P.; Perlmutter, S.; Foley, R. J.; Pan, Y.-C.; Casas, R.; Castander, F. J.; Papadopoulos, A.; Morganson, E.

    2016-10-01

    We report new spectroscopic classifications by OzDES of supernovae discovered by the Dark Energy Survey (ATEL #4668). The spectra (370-885nm) were obtained with the AAOmega Spectrograph (Saunders et al. 2004, SPIE, 5492, 389) and the 2dF fibre positioner at the Anglo-Australian Telescope (AAT).

  20. Capacitation inducers act through diverse intracellular mechanisms in cryopreserved bovine sperm.

    PubMed

    Breininger, E; Cetica, P D; Beconi, M T

    2010-10-01

    The effect of various capacitation inducers, i.e. heparin, superoxide anion, bicarbonate, adenosine, and caffeine, and their role in intracellular mechanisms involved in capacitation, were studied in cryopreserved bovine sperm. Capacitation was determined by epifluorescence chlortetracycline, protein tyrosine phosphorylation, and the ability of capacitated sperm to undergo an acrosome reaction and fertilize in vitro matured oocytes. Participation of membrane adenylate cyclase and protein kinases (protein kinase A, protein kinase C, and protein tyrosine kinase) was evaluated indirectly (with specific inhibitors). Involvement of reactive oxygen species (ROS) was determined with scavengers of superoxide anion, hydrogen peroxide, or nitric oxide. Percentages of capacitated (27-29%) and acrosome-reacted sperm (23-26%) did not differ (P > 0.05) among various capacitation inducers. Significantly higher rates of IVF were obtained with heparin (43%) or bicarbonate plus caffeine (45%), when compared with control samples (17%). Adding the membrane adenylate cyclase inhibitor diminished capacitation rates with heparin (8%) or adenosine (10%). There was differential protein kinase participation in response to inducers; protein kinase inhibitors diminished cleavage rates in heparin-capacitated sperm relative to controls. There were differences between and within the studied inducers in protein tyrosine phosphorylation patterns. We inferred that capacitation in cryopreserved bovine sperm was promoted through diverse pathways. Mechanisms triggered by heparin, or caffeine plus bicarbonate-induced capacitation, involved activation of intracellular pathways to optimize fertilizing capability of cryopreserved bovine sperm.

  1. Effectiveness, active energy produced by molecular motors, and nonlinear capacitance of the cochlear outer hair cell.

    PubMed

    Spector, Alexander A

    2005-06-01

    Cochlear outer hair cells are crucial for active hearing. These cells have a unique form of motility, named electromotility, whose main features are the cell's length changes, active force production, and nonlinear capacitance. The molecular motor, prestin, that drives outer hair cell electromotility has recently been identified. We reveal relationships between the active energy produced by the outer hair cell molecular motors, motor effectiveness, and the capacitive properties of the cell membrane. We quantitatively characterize these relationships by introducing three characteristics: effective capacitance, zero-strain capacitance, and zero-resultant capacitance. We show that zero-strain capacitance is smaller than zero-resultant capacitance, and that the effective capacitance is between the two. It was also found that the differences between the introduced capacitive characteristics can be expressed in terms of the active energy produced by the cell's molecular motors. The effectiveness of the cell and its molecular motors is introduced as the ratio of the motors'active energy to the energy of the externally applied electric field. It is shown that the effectiveness is proportional to the difference between zero-strain and zero-resultant capacitance. We analyze the cell and motor's effectiveness within a broad range of cellular parameters and estimate it to be within a range of 12%-30%.

  2. A simple efficient model of parasitic capacitances of deep-submicron LDD MOSFETs

    NASA Astrophysics Data System (ADS)

    Prégaldiny, Fabien; Lallement, Christophe; Mathiot, Daniel

    2002-12-01

    Estimation of parasitic capacitances in a MOSFET device is very important, notably in mixed circuit simulation. For deep-submicron LDD MOSFETs, the extrinsic capacitance (overlap plus fringing capacitances) is a growing fraction of the total gate capacitance. A correct estimation of the extrinsic capacitance requires an accurate modeling of each of its constituents. However the major existing models do not correctly predict the overlap capacitance and the inner fringing capacitance (which is often ignored). In this paper a new approach to model the overlap Cov and fringing Cif+ Cof capacitances in the zero-current regime is presented. The bias dependence of the extrinsic capacitance is investigated and a detailed study of the influence of the LDD doping dose is also undertaken. Then, an efficient, simple and continuous model describing the evolution of overlap and fringing capacitances in all operating regimes of a n-channel LDD MOSFET is developed. Finally this model is incorporated in an existing compact-model for circuit simulation. It is shown that this new model leads to excellent results in comparison with full 2D numerical device simulation.

  3. Latina Voices of Des Moines.

    ERIC Educational Resources Information Center

    Taylor, P. Dawn

    This dissertation examines the lives of Hispanic women living in Des Moines and includes their views of problems and opportunities involved in living in that city. Interviews were conducted with 24 Latino women over the age of 17 who had been in the area for over 2 years. Findings indicate that learning to speak English was the single most…

  4. Etude du stockage de l'hydrogene sur des nanostructures de carbone microporeuses

    NASA Astrophysics Data System (ADS)

    Poirier, Eric

    2007-12-01

    Le stockage de l'hydrogene par adsorption sur des adsorbants nano-structures a ete etudie sous differentes conditions de pression et de temperature. Les adsorbants etudies sont principalement des nanotubes de carbone a simple paroi ainsi que des structures metallo-organiques. Les mesures ont ete realisees a l'aide de systemes gravimetriques et volumetriques tres sensibles specialement mis au point pour de petits echantillons necessitant un degazage in situ. Les appareils developpes, au nombre de quatre, comprennent deux systemes gravimetriques et deux systemes volumetriques. Ensemble, ces systemes couvrent la plage de pressions (0-100) bars ainsi que la plage de temperatures (77-295) K. Les differentes analyses montrent que l'adsorption d'hydrogene sur les adsorbants nano-structures etudies est maximale a 77 K et varie entre environ (1.5 et 4) % masse. A temperature ambiante, l'adsorption croit lineairement avec la pression et demeure sous les 1% masse pour des pressions inferieures a 100 bars. L'adsorption d'hydrogene sur ces materiaux dans ces conditions se compare notamment a celle obtenue sur des charbons actives. La modelisation de l'adsorption a egalement ete realisee dans des conditions cryogeniques a l'aide du modele de Dubinin-Astakhov sous une forme adaptee pour l'adsorption supercritique. Les enthalpies d'adsorption calculees a partir de ce modele varient sous les 6 kJ/mole et sont donc consistantes avec des processus de physisorption. L'applicabilite du modele de Dubinin-Astakhov suggere que l'adsorption d'hydrogene puisse etre representee par un processus de remplissage des pores par un pseudo-liquide. Ces travaux s'inscrivent dans un contexte ou la capacite d'adsorption reelle des nanostructures de carbone est sujette a la controverse. En consequence, l'approche experimentale adoptee se distingue par les differentes demarches mises de l'avant pour l'obtention de mesures fiables sur des echantillons de faibles masses ainsi que par son caractere

  5. L'astronomie des Anciens

    NASA Astrophysics Data System (ADS)

    Nazé, Yaël

    2009-04-01

    Quelle que soit la civilisation à laquelle il appartient, l'être humain cherche dans le ciel des réponses aux questions qu'il se pose sur son origine, son avenir et sa finalité. Le premier mérite de ce livre est de nous rappeler que l'astronomie a commencé ainsi à travers les mythes célestes imaginés par les Anciens pour expliquer l'ordre du monde et la place qu'ils y occupaient. Mais les savoirs astronomiques passés étaient loin d'être négligeables et certainement pas limités aux seuls travaux des Grecs : c'est ce que l'auteur montre à travers une passionnante enquête, de Stonehenge à Gizeh en passant par Pékin et Mexico, fondée sur l'étude des monuments anciens et des sources écrites encore accessibles. Les tablettes mésopotamiennes, les annales chinoises, les chroniques médiévales, etc. sont en outre d'une singulière utilité pour les astronomes modernes : comment sinon remonter aux variations de la durée du jour au cours des siècles, ou percer la nature de l'explosion qui a frappé tant d'observateurs en 1054 ? Ce livre offre un voyage magnifiquement illustré à travers les âges, entre astronomie et archéologie.

  6. Theoretical and experimental analysis of a piezoelectric plate connected to a negative capacitance at MHz frequencies

    NASA Astrophysics Data System (ADS)

    Mansoura, S. A.; Benard, P.; Morvan, B.; Maréchal, P.; Hladky-Hennion, A.-C.; Dubus, B.

    2015-11-01

    In this paper, a theoretical and experimental study of the electric impedance of a piezoelectric plate connected to a negative capacitance is performed in the MHz frequency range. The negative capacitance is realized with a circuit using current conveyors (CCII+). This circuit allows us to achieve important values of negative capacitance, of the same order of the static capacitance of the piezoelectric plate studied. Mason’s model is considered for the theoretical characterization of the piezoelectric plate connected to the negative capacitance circuit. The experimental results show a large tunability of the frequency of the piezoelectric parallel resonance over a range of 1.1 MHz to 1.28 MHz. Moreover, according to the value of the negative capacitance, the effective electromechanical coupling factor of the piezoelectric plate is evaluated. With a very good agreement with the theoretical estimation, an increase of approximately 50% of the effective electromechanical coupling factor is experimentally measured.

  7. Contribution of dielectric screening to the total capacitance of few-layer graphene electrodes

    SciTech Connect

    Zhan, Cheng; Jiang, De-en

    2016-02-17

    We apply joint density functional theory (JDFT), which treats the electrode/electrolyte interface self-consistently, to an electric double-layer capacitor (EDLC) based on few-layer graphene electrodes. The JDFT approach allows us to quantify a third contribution to the total capacitance beyond quantum capacitance (CQ) and EDL capacitance (CEDL). This contribution arises from the dielectric screening of the electric field by the surface of the few-layer graphene electrode, and we therefore term it the dielectric capacitance (CDielec). We find that CDielec becomes significant in affecting the total capacitance when the number of graphene layers in the electrode is more than three. In conclusion, our investigation sheds new light on the significance of the electrode dielectric screening on the capacitance of few-layer graphene electrodes.

  8. Contribution of dielectric screening to the total capacitance of few-layer graphene electrodes

    DOE PAGES

    Zhan, Cheng; Jiang, De-en

    2016-02-17

    We apply joint density functional theory (JDFT), which treats the electrode/electrolyte interface self-consistently, to an electric double-layer capacitor (EDLC) based on few-layer graphene electrodes. The JDFT approach allows us to quantify a third contribution to the total capacitance beyond quantum capacitance (CQ) and EDL capacitance (CEDL). This contribution arises from the dielectric screening of the electric field by the surface of the few-layer graphene electrode, and we therefore term it the dielectric capacitance (CDielec). We find that CDielec becomes significant in affecting the total capacitance when the number of graphene layers in the electrode is more than three. In conclusion,more » our investigation sheds new light on the significance of the electrode dielectric screening on the capacitance of few-layer graphene electrodes.« less

  9. Negative Capacitance in BaTiO3/BiFeO3 Bilayer Capacitors.

    PubMed

    Hou, Ya-Fei; Li, Wei-Li; Zhang, Tian-Dong; Yu, Yang; Han, Ren-Lu; Fei, Wei-Dong

    2016-08-31

    Negative capacitances provide an approach to reduce heat generations in field-effect transistors during the switch processes, which contributes to further miniaturization of the conventional integrated circuits. Although there are many studies about negative capacitances using ferroelectric materials, the direct observation of stable ferroelectric negative capacitances has rarely been reported. Here, we put forward a dc bias assistant model in bilayer capacitors, where one ferroelectric layer with large dielectric constant and the other ferroelectric layer with small dielectric constant are needed. Negative capacitances can be obtained when external dc bias electric fields are larger than a critical value. Based on the model, BaTiO3/BiFeO3 bilayer capacitors are chosen as study objects, and negative capacitances are observed directly. Additionally, the upward self-polarization effect in the ferroelectric layer reduces the critical electric field, which may provide a method for realizing zero and/or small dc bias assistant negative capacitances.

  10. Density of States and Its Local Fluctuations Determined by Capacitance of Strongly Disordered Graphene

    PubMed Central

    Li, Wei; Chen, Xiaolong; Wang, Lin; He, Yuheng; Wu, Zefei; Cai, Yuan; Zhang, Mingwei; Wang, Yang; Han, Yu; Lortz, Rolf W.; Zhang, Zhao-Qing; Sheng, Ping; Wang, Ning

    2013-01-01

    We demonstrate that fluctuations of the local density of states (LDOS) in strongly disordered graphene play an important role in determining the quantum capacitance of the top-gate graphene devices. Depending on the strength of the disorder induced by metal-cluster decoration, the measured quantum capacitance of disordered graphene can dramatically decrease in comparison with pristine graphene. This is opposite to the common belief that quantum capacitance should increase with disorder. To explain this counterintuitive behavior, we present a two-parameter model which incorporates both the non-universal power law behavior for the ADOS and a lognormal distribution of LDOS. We find excellent quantitative agreements between the model and measured quantum capacitance for three disordered samples in a wide range of Fermi energies. Thus, by measuring the quantum capacitance, we can simultaneously determine the ADOS and its fluctuations. It is the LDOS fluctuations that cause the dramatic reduction of the quantum capacitance.

  11. Comparison of pressure dependence of electron energy distributions in oxygen capacitively and inductively coupled plasmas.

    PubMed

    Lee, Min-Hyong; Lee, Hyo-Chang; Chung, Chin-Wook

    2010-04-01

    Electron energy distribution functions (EEDFs) were measured with increasing gas pressure in oxygen capacitively and inductively coupled plasmas. It was found that, in the capacitive discharge, abnormally low-energy electrons became highly populated and the EEDF evolved to a more distinct bi-Maxwellian distribution as the gas pressure was increased. This pressure dependence of the EEDF in the oxygen capacitive discharge is contrary to argon capacitively coupled plasma, where--at high gas pressure--low-energy electrons are significantly reduced due to collisional heating and the EEDF evolves to the Maxwellian. The highly populated low-energy electrons at high gas pressure, which was not observed in inductively coupled oxygen plasma, show that collisional heating is very inefficient in terms of the oxygen capacitive discharge. It appears that this inefficient collisional heating seems to be attributed to a low electric field strength at the center of the oxygen capacitive plasma.

  12. Multistatic Surveillance and Reconnaissance: Sensor, Signals and Data Fusion (Surveillance et Reconnaissance Multistatiques : Fusion des capteurs, des signaux et des donnees)

    DTIC Science & Technology

    2009-04-01

    capteurs , des signaux et des données) Research and Technology Organisation (NATO) BP 25, F-92201 Neuilly-sur-Seine Cedex, France RTO-EN-SET-133...Multistatiques : Fusion des capteurs , des signaux et des données) The material in this publication was assembled to support a Lecture Series under the...Surveillance et Reconnaissance Multistatiques : Fusion des capteurs , des signaux et des données (RTO-EN-SET-133) Synthèse Les systèmes radar

  13. The Semen pH Affects Sperm Motility and Capacitation.

    PubMed

    Zhou, Ji; Chen, Li; Li, Jie; Li, Hongjun; Hong, Zhiwei; Xie, Min; Chen, Shengrong; Yao, Bing

    2015-01-01

    As the chemical environment of semen can have a profound effect on sperm quality, we examined the effect of pH on the motility, viability and capacitation of human sperm. The sperm in this study was collected from healthy males to avoid interference from other factors. The spermatozoa cultured in sperm nutrition solution at pH 5.2, 6.2, 7.2 and 8.2 were analyzed for sperm total motility, progressive motility (PR), hypo-osmotic swelling (HOS) rate, and sperm penetration. Our results showed that these parameters were similar in pH 7.2 and 8.2 sperm nutrition solutions, but decreased in pH 5.2 and 6.2 solutions. The HOS rate exhibited positive correlation with the sperm total motility and PR. In addition, the sperm Na(+)/K(+)-ATPase activity at different pHs was measured, and the enzyme activity was significantly lower in pH 5.2 and 6.2 media, comparing with that in pH 8.2 and pH 7.2 solutions. Using flow cytometry (FCM) and laser confocal scanning microscopy (LCSM) analysis, the intracellular Ca2(+ )concentrations of sperm cultured in sperm capacitation solution at pH 5.2, 6.2, 7.2 and 8.2 were determined. Compared with that at pH 7.2, the mean fluorescence intensity of sperm in pH 5.2 and 6.2 media decreased significantly, while that of pH 8.2 group showed no difference. Our results suggested that the declined Na(+)/K(+)-ATPase activity at acidic pHs result in decreased sperm movement and capacitation, which could be one of the mechanisms of male infertility.

  14. Electromechanical coupling factor of capacitive micromachined ultrasonic transducers

    NASA Astrophysics Data System (ADS)

    Caronti, Alessandro; Carotenuto, Riccardo; Pappalardo, Massimo

    2003-01-01

    Recently, a linear, analytical distributed model for capacitive micromachined ultrasonic transducers (CMUTs) was presented, and an electromechanical equivalent circuit based on the theory reported was used to describe the behavior of the transducer [IEEE Trans. Ultrason. Ferroelectr. Freq. Control 49, 159-168 (2002)]. The distributed model is applied here to calculate the dynamic coupling factor kw of a lossless CMUT, based on a definition that involves the energies stored in a dynamic vibration cycle, and the results are compared with those obtained with a lumped model. A strong discrepancy is found between the two models as the bias voltage increases. The lumped model predicts an increasing dynamic k factor up to unity, whereas the distributed model predicts a more realistic saturation of this parameter to values substantially lower. It is demonstrated that the maximum value of kw, corresponding to an operating point close to the diaphragm collapse, is 0.4 for a CMUT single cell with a circular membrane diaphragm and no parasitic capacitance (0.36 for a cell with a circular plate diaphragm). This means that the dynamic coupling factor of a CMUT is comparable to that of a piezoceramic plate oscillating in the thickness mode. Parasitic capacitance decreases the value of kw, because it does not contribute to the energy conversion. The effective coupling factor keff is also investigated, showing that this parameter coincides with kw within the lumped model approximation, but a quite different result is obtained if a computation is made with the more accurate distributed model. As a consequence, keff, which can be measured from the transducer electrical impedance, does not give a reliable value of the actual dynamic coupling factor.

  15. Analytical comparison of circular diaphragm based simple, single and double touch mode - MEMS capacitive pressure sensor

    NASA Astrophysics Data System (ADS)

    Jindal, Sumit Kumar; Raghuwanshi, Sanjeev Kumar

    2016-03-01

    In this paper a comparative study is done between normal capacitive pressure sensor, a touch mode capacitive pressure sensor and a double touch mode capacitive pressure sensor. The diaphragm in use is of circular shape. The theory and underlying equations has been described for the said devices and then simulations have been done for different performance parameters to understand the advantage of one over the other.

  16. Material characteristics and equivalent circuit models of stacked graphene oxide for capacitive humidity sensors

    NASA Astrophysics Data System (ADS)

    Han, Kook In; Kim, Seung Du; Yang, Woo Seok; Kim, Hyeong Seok; Shin, Myunghun; Kim, Jong Pil; Lee, In Gyu; Cho, Byung Jin; Hwang, Wan Sik

    2016-03-01

    The oxidation properties of graphene oxide (GO) are systematically correlated with their chemical sensing properties. Based on an impedance analysis, the equivalent circuit models of the capacitive sensors are established, and it is demonstrated that capacitive operations are related to the degree of oxidation. This is also confirmed by X-ray diffraction and Raman analysis. Finally, highly sensitive stacked GO sensors are shown to detect humidity in capacitive mode, which can be useful in various applications requiring low power consumption.

  17. Electrical characteristics for capacitively coupled radio frequency discharges of helium and neon

    NASA Astrophysics Data System (ADS)

    Tanişli, Murat; Şahin, Neslihan; Demir, Süleyman

    2017-09-01

    In this study, a symmetric radio frequency (RF) (13.56 MHz) electrode discharge system of simple geometry has been designed and made. The electrical properties of capacitive RF discharge of pure neon and pure helium have been obtained from current and voltage waveforms using different reactor designs. Calculations are done, in detail, according to the homogeneous discharge model of capacitively coupled RF. Electrical properties of bulk plasma and sheath capacitance are also investigated at low pressure using this model.

  18. Material characteristics and equivalent circuit models of stacked graphene oxide for capacitive humidity sensors

    SciTech Connect

    Han, Kook In; Lee, In Gyu; Hwang, Wan Sik E-mail: whwang@kau.ac.kr; Kim, Seung Du; Yang, Woo Seok; Kim, Hyeong Seok; Shin, Myunghun E-mail: whwang@kau.ac.kr; Kim, Jong Pil; Cho, Byung Jin

    2016-03-15

    The oxidation properties of graphene oxide (GO) are systematically correlated with their chemical sensing properties. Based on an impedance analysis, the equivalent circuit models of the capacitive sensors are established, and it is demonstrated that capacitive operations are related to the degree of oxidation. This is also confirmed by X-ray diffraction and Raman analysis. Finally, highly sensitive stacked GO sensors are shown to detect humidity in capacitive mode, which can be useful in various applications requiring low power consumption.

  19. Large capacitance in the nanosecond-scale transient response of quantum point contacts

    NASA Astrophysics Data System (ADS)

    Naser, B.; Ferry, D. K.; Heeren, J.; Reno, J. L.; Bird, J. P.

    2006-08-01

    The transient electrical response of split-gate quantum point contacts (QPCs) is investigated using ultrashort voltage pulses with rise times as small as 2ns. Our measurements reveal a large (˜1nF) parallel capacitance under conditions where the QPC is formed. The capacitance is independent of the QPC gate geometry, and the amplitude and rise time of the applied transient pulse. Some speculations on the source of this capacitance are offered.

  20. Development of a high temperature capacitive pressure transducer

    NASA Technical Reports Server (NTRS)

    Egger, R. L.

    1977-01-01

    High temperature pressure transducers capable of continuous operation while exposed to 650 C were developed and evaluated over a full-scale differential pressure range of + or - 69 kPa. The design of the pressure transducers was based on the use of a diaphragm to respond to pressure, variable capacitive elements arranged to operate as a differential capacitor to measure diaphragm response and on the use of fused silica for the diaphragm and its supporting assembly. The uncertainty associated with measuring + or - 69 kPa pressures between 20C and 650C was less than + or - 6%.

  1. Concentric Coplanar Capacitive Sensor System with Quantitative Model

    NASA Technical Reports Server (NTRS)

    Bowler, Nicola (Inventor); Chen, Tianming (Inventor)

    2014-01-01

    A concentric coplanar capacitive sensor includes a charged central disc forming a first electrode, an outer annular ring coplanar with and outer to the charged central disc, the outer annular ring forming a second electrode, and a gap between the charged central disc and the outer annular ring. The first electrode and the second electrode may be attached to an insulative film. A method provides for determining transcapacitance between the first electrode and the second electrode and using the transcapacitance in a model that accounts for a dielectric test piece to determine inversely the properties of the dielectric test piece.

  2. 3-D capacitance density imaging of fluidized bed

    DOEpatents

    Fasching, George E.

    1990-01-01

    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.

  3. Charging characteritiscs of ultrananocrystalline diamond in RF MEMS capacitive switches.

    SciTech Connect

    Sumant, A. V.; Goldsmith, C.; Auciello, O.; Carlisle, J.; Zheng, H.; Hwang, J. C. M.; Palego, C.; Wang, W.; Carpick, R.; Adiga, V.; Datta, A.; Gudeman, C.; O'Brien, S.; Sampath, S.

    2010-05-01

    Modifications to a standard capacitive MEMS switch process have been made to allow the incorporation of ultra-nano-crystalline diamond as the switch dielectric. The impact on electromechanical performance is minimal. However, these devices exhibit uniquely different charging characteristics, with charging and discharging time constants 5-6 orders of magnitude quicker than conventional materials. This operation opens the possibility of devices which have no adverse effects of dielectric charging and can be operated near-continuously in the actuated state without significant degradation in reliability.

  4. Simulating Electric Double Layer Capacitance by Using Lattice Boltzmann Method

    NASA Astrophysics Data System (ADS)

    Sun, Ning; Gersappe, Dilip

    2015-03-01

    By using the Lattice Boltzmann Method (LBM) we studied diffuse-charge dynamics in electrochemical systems. We use the LBM to solve Poisson-Nernst-Planck equations (PNP) and Modified Poisson-Nernst-Planck equations (MPNP). The isotropic permittivity of electrolyte is modeled using the Booth model. The results show that both steric effect (MPNP) and isotropic permittivity (Booth model) can have large influence on diffuse-charge dynamics, especially when electrolyte concentration or applied potential is high. This model can be applied to simulate electric double layer capacitance of super capacitors with complex geometry and also incorporate other effects such as heat convection in a modular manner.

  5. Capacitive deionization of water: An innovative new process

    SciTech Connect

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

    1995-01-09

    The capacitive deionization of water with a stack of carbon aerogel electrodes has been successfully demonstrated for the first time. Unlike ion exchange, one of the more conventional deionization processes, no chemicals were required for regeneration of the system. Electricity was used instead. Water with various anions and cations was pumped through the electrochemical cell. After polarization, ions were electrostatically removed from the water and held in the electric double layers formed at electrode surfaces. The water leaving the cell was purified, as desired.

  6. Capacitive MEMS accelerometers for measuring high-g accelerations

    NASA Astrophysics Data System (ADS)

    Baginsky, I. L.; Kostsov, E. G.

    2017-05-01

    A possibility of creating a capacitive accelerometer for measuring high- g accelerations (up to 106 g and higher) is discussed. It is demonstrated that insertion of a thin electret film with a high surface potential into the gap between the electrodes ensures significant expansion of the frequency and amplitude ranges of acceleration measurements, whereas the size of the proposed device is smaller than that of available MEMS accelerometers for measuring high- g accelerations. A mathematical model of an electret accelerometer for high- g accelerations is developed, and the main specific features of accelerometer operation are analyzed.

  7. Analytical carrier density and quantum capacitance for graphene

    NASA Astrophysics Data System (ADS)

    Wang, Lingfei; Wang, Wei; Xu, Guangwei; Ji, Zhuoyu; Lu, Nianduan; Li, Ling; Liu, Ming

    2016-01-01

    A disorder based analytical carrier density for graphene is presented here. The carrier density, a basic property of all semiconductors, is obtained based on exponential distribution describing the potential fluctuations induced by impurities and shows good agreement with numerical results. The quantum capacitance is subsequently derived from the carrier density, with a good agreement with experimental measurements. A method for extracting the gate coupling function is also proposed, which relates the internal surface potential with the external applied gate voltage. The essential properties of graphene device physics, such as the temperature, material disorder, and surface potential dependences, are captured in these analytical equations.

  8. Pulse power applications of silicon diodes in EML capacitive pulsers

    NASA Astrophysics Data System (ADS)

    Dethlefsen, Rolf; McNab, Ian; Dobbie, Clyde; Bernhardt, Tom; Puterbaugh, Robert; Levine, Frank; Coradeschi, Tom; Rinaldi, Vito

    1993-01-01

    Crowbar diodes are used for increasing the energy transfer from capacitive pulse forming networks. They also prevent voltage reversal on the energy storage capacitors. 52 mm diameter diodes with a 5 kV reverse blocking voltage, rated 40 kA were successfully used for the 32 MJ SSG rail gun. An uprated diode with increased current capability and a 15 kV reverse blocking voltage has been developed. Transient thermal analysis has predicted the current ratings for different pulse length. Analysis verification is obtained from destructive testing.

  9. CAPACITIVE TOMOGRAPHY FOR THE LOCATION OF PLASTIC PIPE

    SciTech Connect

    Brian J. Huber

    2003-12-30

    The objective of this program was to develop and test a system that would detect and image buried plastic and ceramic pipe. The system is designed to detect variations in the electric permeability of soil corresponding to the presence of a buried plastic pipe. The Gas Technology Institute (GTI) proposed to develop a compact and inexpensive capacitive tomography-imaging sensor that can be placed on the ground to image objects embedded in the soil. The system provides a coarse image, which allows the operator to identify a buried object's location both horizontally and vertically.

  10. Capacitive micromachined ultrasonic transducer arrays as tunable acoustic metamaterials.

    PubMed

    Lani, Shane W; Wasequr Rashid, M; Hasler, Jennifer; Sabra, Karim G; Levent Degertekin, F

    2014-02-03

    Capacitive Micromachined Ultrasonic Transducers (CMUTs) operating in immersion support dispersive evanescent waves due to the subwavelength periodic structure of electrostatically actuated membranes in the array. Evanescent wave characteristics also depend on the membrane resonance which is modified by the externally applied bias voltage, offering a mechanism to tune the CMUT array as an acoustic metamaterial. The dispersion and tunability characteristics are examined using a computationally efficient, mutual radiation impedance based approach to model a finite-size array and realistic parameters of variation. The simulations are verified, and tunability is demonstrated by experiments on a linear CMUT array operating in 2-12 MHz range.

  11. Capacitive micromachined ultrasonic transducer arrays as tunable acoustic metamaterials

    SciTech Connect

    Lani, Shane W. E-mail: karim.sabra@me.gatech.edu Sabra, Karim G.; Wasequr Rashid, M.; Hasler, Jennifer; Levent Degertekin, F.

    2014-02-03

    Capacitive Micromachined Ultrasonic Transducers (CMUTs) operating in immersion support dispersive evanescent waves due to the subwavelength periodic structure of electrostatically actuated membranes in the array. Evanescent wave characteristics also depend on the membrane resonance which is modified by the externally applied bias voltage, offering a mechanism to tune the CMUT array as an acoustic metamaterial. The dispersion and tunability characteristics are examined using a computationally efficient, mutual radiation impedance based approach to model a finite-size array and realistic parameters of variation. The simulations are verified, and tunability is demonstrated by experiments on a linear CMUT array operating in 2-12 MHz range.

  12. Analytical carrier density and quantum capacitance for graphene

    SciTech Connect

    Wang, Lingfei; Wang, Wei; Xu, Guangwei; Ji, Zhuoyu; Lu, Nianduan Li, Ling Liu, Ming

    2016-01-04

    A disorder based analytical carrier density for graphene is presented here. The carrier density, a basic property of all semiconductors, is obtained based on exponential distribution describing the potential fluctuations induced by impurities and shows good agreement with numerical results. The quantum capacitance is subsequently derived from the carrier density, with a good agreement with experimental measurements. A method for extracting the gate coupling function is also proposed, which relates the internal surface potential with the external applied gate voltage. The essential properties of graphene device physics, such as the temperature, material disorder, and surface potential dependences, are captured in these analytical equations.

  13. A conical air-coupled capacitance transducer for surface imaging.

    PubMed

    Hutchins, D A; Robertson, T J; Billson, D R; Solanki, P

    2003-05-01

    This paper describes the construction and operation of an air-coupled capacitance transducer with a conical backplate. This was designed to produce a focal region over an extended distance along the transducer axis. Measurements were performed to examine both the frequency response of the transducer in pulse-echo mode, and the lateral resolution for imaging purposes. The radiated field was measured and compared to theory, and the extent of the focal region determined. Images of surface topography are presented, to illustrate the range of application of the transducer.

  14. A New Technique for Troubleshooting Large Capacitive Energy Storage Banks

    SciTech Connect

    Fulkerson, S E; Hammon, J

    2001-06-05

    The Power Conditioning System (PCS) of the National Ignition Facility (NIF) like many pulse power systems relies on large numbers of inductively isolated high voltage capacitors configured in parallel for energy storage. When an energy storage capacitor fails in such a capacitor bank, there is often little or no external indication showing which capacitor failed. Identifying the failed component can be a time consuming and potentially hazardous operation. Conventional methods using capacitance meters require that each capacitor be disconnected and tested independently. They have developed a new non-invasive technique (i.e. no dismantling of the bank is required) that greatly improves personnel safety as well reducing troubleshooting time.

  15. Scaling laws for dual radio-frequency capacitively coupled discharges

    SciTech Connect

    Chung, T.H.

    2005-10-01

    The characteristics of dual radio-frequency capacitively coupled discharges are studied based on a homogeneous analytic model. We are considering a planar plasma device that can be approximated using a one-dimensional model. A set of equations describing the dynamics of the system are presented and used to give the analytic scaling laws. Scaling laws relating the drive frequencies and the applied voltages of dual radio-frequency sources to operating functions such as plasma density and plasma potential are examined and compared with numerical simulations.

  16. Electrical characterization of a capacitive rf plasma sheath

    NASA Astrophysics Data System (ADS)

    Gahan, D.; Hopkins, M. B.

    2007-01-01

    The authors report on an experimental system designed to investigate and characterize capacitive radio frequency (rf) sheaths. An electrode mounted in an inductive plasma reactor and driven with separate rf and direct current (dc) power sources is used. The advantage of this design is that the electrode sheath is decoupled from the plasma parameters. This allows detailed investigation of the sheath with different bias conditions without perturbing the bulk plasma parameters. Power coupled to ions and electrons through the sheath, at low pressure, is investigated and a method to determine the electron conduction current to the electrode, using the external dc bias, is presented.

  17. Contrast distortion induced by modulation voltage in scanning capacitance microscopy

    NASA Astrophysics Data System (ADS)

    Chang, M. N.; Hu, C. W.; Chou, T. H.; Lee, Y. J.

    2012-08-01

    With a dark-mode scanning capacitance microscopy (SCM), we directly observed the influence of SCM modulation voltage (MV) on image contrasts. For electrical junctions, an extensive modulated area induced by MV may lead to noticeable changes in the SCM signal phase and intensity, resulting in a narrowed junction image and a broadened carrier concentration profile. This contrast distortion in SCM images may occur even if the peak-to-peak MV is down to 0.3 V. In addition, MV may shift the measured electrical junction depth. The balance of SCM signals components explain these MV-induced contrast distortions.

  18. Sensor Interface for Multimodal Evaluation of Capacitive Sensors

    NASA Astrophysics Data System (ADS)

    Schlegl, Thomas; Zangl, Hubert

    2013-06-01

    Capacitive proximity sensing can be done in different modes. The single ended mode usually offers a higher signal to noise ratio (SNR) and - in conjunction with active guarding - high robustness. However, it can be blind for objects with low permittivity close to the sensor surface. The differential mode usually has a worse SNR but has the capability to detect objects in situations where the single ended mode is blind. Thus, we propose a measurement circuitry to combine both modes. It is compared to state of the art sensors and the benefits of this approach are demonstrated by means of experimental investigations.

  19. Fabrication and radio frequency characterization of carbon nanotube field effect transistor: evidence of quantum capacitance.

    PubMed

    Hwang, D H; Kang, M G; Kim, T G; Hwang, J S; Kim, D W; Whang, D; Hwang, S W

    2011-08-01

    We fabricated an radio frequency (RF) carbon nanotube field effect transistor (CNTFET) whose electrode shapes were standard RF designed ground-signal-ground (GSG)-type pads. The S-parameters measured from our RF CNTFET in the frequency range up to 6 GHz were fitted with an RF equivalent circuit, and the extracted gate capacitance was shown to be the capacitance value of the series combination of the electrostatic capacitance and the quantum capacitance. The effect of the channel resistance and the kinetic inductance was also discussed.

  20. An exactly solvable model for the graphene transistor in the quantum capacitance limit

    NASA Astrophysics Data System (ADS)

    Parrish, Kristen N.; Akinwande, Deji

    2012-07-01

    We explore the ultimate behavior of the graphene transistor in the quantum capacitance limit. The quantum capacitance formulation allows for an exactly solvable model, and the ideal assumptions provide an upper bound on performance, including peak currents of 1 mA/μm with mobilities as low as 2000 cm2/V s for channel length of 1 μm, as well as linearly increasing transconductance not observed in conventional transistors. A negative differential resistance is predicted under certain conditions, with a maximum peak-to-valley-current ratio of 4. Finally, the effects of oxide scaling are elucidated and the oxide capacitances required for quantum capacitance limited behavior are quantified.

  1. Metal-insulator-semi-conductor studies of lead telluride. [capacitance and conductance-voltage characteristics

    NASA Technical Reports Server (NTRS)

    Lilly, D. A.; Joslin, D. E.; Kan, H. K. A.

    1976-01-01

    The capacitance and conductance-voltage characteristics were measured on metal-insulator-semiconductor capacitors fabricated with zirconium dioxide films on single-crystal lead telluride. At 77 K, on both n- and p-type substrates, evidence of surface potential control was obtained. Comparison of the measured capacitance-voltage characteristics with those calculated from the equilibrium solution of the one-dimensional Poisson equation indicated qualitative agreement, although the slope of the measured capacitance in the region near the capacitance minimum was less steep than calculated.

  2. Capacitive pressure-sensitive composites using nickel-silicone rubber: experiments and modeling

    NASA Astrophysics Data System (ADS)

    Fan, Yuqin; Liao, Changrong; Liao, Ganliang; Tan, Renbing; Xie, Lei

    2017-07-01

    Capacitive pressure (i.e., piezo-capacitive) sensors have manifested their superiority as a potential electronic skin. The mechanism of the traditional piezo-capacitive sensors is mainly to change the relative permittivity of the flexible composites by compressing the specially fabricated microstructures in the polymer matrix under pressure. Instead, we study the piezo-capacitive effect for a newly reported isotropic flexible composite consisting of silicone rubber (SR) and uniformly dispersed micron-sized conductive nickel particles experimentally and theoretically. The Young’s modulus of the nickel-SR composites (NSRCs) is designed to meet that of human skin. Experimental results show that the NSRCs exhibit remarkable particle concentration dependent capacitance response under uniaxial pressure, and the NSRCs present a good repeatability. We propose a mathematical model at particle level to provide deep insights into the piezo-capacitive mechanism, by considering the adjacent particles in the axial direction as micro capacitors connected in series and in parallel on the horizontal plane. The piezo-capacitive effect is determined by the relative permittivity induced by the particles rearrangement, longitudinal interparticle gap, and deflection angle of micro particle capacitors under pressure. Specifically, the relative capacitance of NSRC capacitor is deduced to be product of two factors: the degree of particle rearrangement, and the relative capacitance of a micro capacitor with the average longitudinal gap. The proposed model well matches and interprets the experimental results.

  3. Single-shot high-voltage circuit for electrical capacitance tomography

    NASA Astrophysics Data System (ADS)

    Smolik, W. T.; Kryszyn, J.; Radzik, B.; Stosio, M.; Wróblewski, P.; Wanta, D.; Dańko, Ł.; Olszewski, T.; Szabatin, R.

    2017-02-01

    A new method of capacitance measurement for electrical capacitance tomography is presented. A single-shot excitation is used to accelerate measurement. A high-voltage pulse and oversampling of received signal are applied to obtain an acceptable signal-to-noise ratio. The results of measurements of standard capacitors and mutual capacitance of electrodes in 16 electrode tomographic sensors are presented. The elaborated circuit is stray-immune. It can measure capacitance in a range from about 1 fF to 1 pF at one gain setting with good linearity and precision at the rate of 20 000 samples per second.

  4. Bovine serum albumin detection and quantitation based on capacitance measurements of liquid crystals

    NASA Astrophysics Data System (ADS)

    Lin, Chi-Hao; Lee, Mon-Juan; Lee, Wei

    2016-08-01

    Liquid crystal (LC)-based biosensing is generally limited by the lack of accurate quantitative strategies. This study exploits the unique electric capacitance properties of LCs to establish quantitative assay methods for bovine serum albumin (BSA) biomolecules. By measuring the voltage-dependent electric capacitance of LCs under an alternating-current field with increasing amplitude, positive correlations were derived between the BSA concentration and the electric capacitance parameters of LCs. This study demonstrates that quantitative analysis can be achieved in LC-based biosensing through electric capacitance measurements extensively employed in LCD research and development.

  5. Hyaluronic acid as capacitation inductor: metabolic changes and membrane-associated adenylate cyclase regulation.

    PubMed

    Fernández, S; Córdoba, M

    2014-12-01

    The aim of this research was to study the effect of hyaluronic acid on bovine cryopreserved spermatozoa compared with heparin as regards the variation of capacitation induction, cellular oxidative metabolism and intracellular signal induced by membrane-associated adenylate cyclase to propose hyaluronic acid as a capacitation inductor. Heparin or hyaluronic acid and lysophosphatidylcholine were used to induce sperm capacitation and acrosome reaction, respectively. 2',5'-dideoxyadenosine was used as a membrane-associated adenylate cyclase inhibitor. The highest percentages of capacitated spermatozoa and live spermatozoa with acrosome integrity were obtained by incubating sperm for 60 min using 1000 μg/ml hyaluronic acid. In these conditions, capacitation induced by hyaluronic acid was lower compared with heparin; nonetheless both glycosaminoglycans promote intracellular changes that allow true acrosome reaction in vitro induced by lysophosphatidylcholine in bovine spermatozoa. Oxygen consumption in heparin-capacitated spermatozoa was significantly higher than in hyaluronic acid-treated spermatozoa. With all treatments, mitochondrial coupling was observed when a specific uncoupler of the respiratory chain was added. The inhibition of membrane-associated adenylate cyclase significantly blocked capacitation induction produced by hyaluronic acid, maintaining a basal sperm oxygen uptake in contrast to heparin effect in which both sperm parameters were inhibited, suggesting that the membrane-associated adenylate cyclase activation is involved in the intracellular signal mechanisms induced by both capacitation inductors, but only regulates mitochondrial oxidative phosphorylation in heparin-capacitated spermatozoa.

  6. Double layer capacitance of porous platinum electrodes in zirconia electrochemical cells

    SciTech Connect

    Robertson, N.L.; Michaels, J.N. )

    1991-05-01

    This paper reports on the capacitance of the double layer at the interface between porous platinum electrodes and yttria-stabilized zirconia measured by potential step chronoampermetry. The capacitance is independent of oxygen partial pressure and electrode potential and increases from 0.2 {mu}F/cm{sup 2} at 555{degrees}C to 1.3 {mu}F/cm{sup 2} at 695{degrees}C. These value are at least an order of magnitude smaller than capacitances extracted from the low-frequency portion of ac impedance spectra. This indicates that the capacitive behavior of platinum electrodes in zirconia cells is dominated by time-dependent faradaic processes.

  7. Metal-insulator-semi-conductor studies of lead telluride. [capacitance and conductance-voltage characteristics

    NASA Technical Reports Server (NTRS)

    Lilly, D. A.; Joslin, D. E.; Kan, H. K. A.

    1976-01-01

    The capacitance and conductance-voltage characteristics were measured on metal-insulator-semiconductor capacitors fabricated with zirconium dioxide films on single-crystal lead telluride. At 77 K, on both n- and p-type substrates, evidence of surface potential control was obtained. Comparison of the measured capacitance-voltage characteristics with those calculated from the equilibrium solution of the one-dimensional Poisson equation indicated qualitative agreement, although the slope of the measured capacitance in the region near the capacitance minimum was less steep than calculated.

  8. A capacitive immunosensor measurement system with a lock-in amplifier and potentiostatic control by software

    NASA Astrophysics Data System (ADS)

    Prasad, B.; Lal, R.

    1999-11-01

    We report an elegant small-signal capacitance measurement system for capacitive immunosensors, prototyped around a computer-controlled two-phase lock-in amplifier. Capacitive immunosensors require low-ionic-strength electrolytes for effective antibody-antigen interaction and low dielectric thickness for high sensitivity to phenomena occurring at the insulator-electrolyte interface. The problem of measuring a high intrinsic sensor capacitance in the presence of a modest parasitic cell resistance is overcome by using a potential-sensing electrode close to the electrolyte-dielectric interface for measuring and controlling the stimulus to the intrinsic device. The current phasor through the capacitive sensor is measured after effecting potential control via a software feedback loop and the sensor capacitance calculated. Capacitance can be measured in the range 100 pF to 0.1 µF with an accuracy of ±0.5% at 1 kHz. The technique obviates the need for expensive high-speed potentiostats or impedance analysers for such measurements and can also be used for small-signal admittance measurements in other electrolyte-insulator-semiconductor or electrolyte-insulator-metal systems. The suitability of the proposed measurement system for immunodetection is shown by capacitance measurements on fibronectin-sensitive capacitive immunosensors.

  9. Developpement D'un Modele Climatique Regional: Fizr Simulation des Conditions de Janvier de la Cote Ouest Nord Americaine

    NASA Astrophysics Data System (ADS)

    Goyette, Stephane

    1995-11-01

    Le sujet de cette these concerne la modelisation numerique du climat regional. L'objectif principal de l'exercice est de developper un modele climatique regional ayant les capacites de simuler des phenomenes de meso-echelle spatiale. Notre domaine d'etude se situe sur la Cote Ouest nord americaine. Ce dernier a retenu notre attention a cause de la complexite du relief et de son controle sur le climat. Les raisons qui motivent cette etude sont multiples: d'une part, nous ne pouvons pas augmenter, en pratique, la faible resolution spatiale des modeles de la circulation generale de l'atmosphere (MCG) sans augmenter a outrance les couts d'integration et, d'autre part, la gestion de l'environnement exige de plus en plus de donnees climatiques regionales determinees avec une meilleure resolution spatiale. Jusqu'alors, les MCG constituaient les modeles les plus estimes pour leurs aptitudes a simuler le climat ainsi que les changements climatiques mondiaux. Toutefois, les phenomenes climatiques de fine echelle echappent encore aux MCG a cause de leur faible resolution spatiale. De plus, les repercussions socio-economiques des modifications possibles des climats sont etroitement liees a des phenomenes imperceptibles par les MCG actuels. Afin de circonvenir certains problemes inherents a la resolution, une approche pratique vise a prendre un domaine spatial limite d'un MCG et a y imbriquer un autre modele numerique possedant, lui, un maillage de haute resolution spatiale. Ce processus d'imbrication implique alors une nouvelle simulation numerique. Cette "retro-simulation" est guidee dans le domaine restreint a partir de pieces d'informations fournies par le MCG et forcee par des mecanismes pris en charge uniquement par le modele imbrique. Ainsi, afin de raffiner la precision spatiale des previsions climatiques de grande echelle, nous developpons ici un modele numerique appele FIZR, permettant d'obtenir de l'information climatique regionale valide a la fine echelle spatiale

  10. Optimisation des transferts de chaleur dans un systeme de stockage d'hydrogene a base d'alanate de sodium

    NASA Astrophysics Data System (ADS)

    Bhouri, Maha

    Le déploiement des applications de transport basées sur l'hydrogène comme source d'énergie est assujetti à l'identification d'une méthode efficace pour son stockage. En ce qui concerne la voie de stockage solide, les principaux inconvénients sont les faibles propriétés thermiques de l'hydrure, le long temps de chargement du réservoir et sa faible capacité gravimétrique. Dans ce cadre, l'alanate de sodium est choisi comme matériau de référence pour optimiser le fonctionnement d'un système de stockage d'un kilogramme d'hydrogène, en termes d'efficacité thermique et de capacités gravimétrique et volumétrique. Trois configurations ont été considérées en variant la disposition du lit d'hydrure et du fluide de refroidissement ainsi que le choix des échangeurs de chaleur et des structures permettant l'amélioration des propriétés thermiques de ce lit. Le modèle mathématique décrivant les transferts de chaleur et de masse au sein du lit d'hydrure a été résolu avec le logiciel commercial COMSOL Multiphysics® 3.5a. Les résultats numériques nous ont permis de déterminer l'interaction entre les propriétés géométriques des éléments d'échange de chaleur et le taux de stockage d'hydrogène ainsi que sa dépendance des conditions opérationnelles. L'efficacité thermique du système de stockage est déterminée en comparant le taux de stockage d'hydrogène calculé à celui issu du modèle de cinétique et validé avec les données expérimentales. Une fois que la quantité d'hydrogène stocké est optimisée, la contribution des éléments d'échange de chaleur au poids et au volume du réservoir et les capacités gravimétrique et volumétrique des configurations correspondantes sont déterminées et discutées en fonction des critères de sélection fixées par le DOE.

  11. Elaboration d'un environnement d'experimentation en simulation incluant un cadre theorique pour l'apprentissage de l'energie des fluides

    NASA Astrophysics Data System (ADS)

    Cervera, Daniel

    industriel avec deux autres co-auteurs. Nous avons effectue les mimses a l'essai fonctionnelle et empirique des prototypes selon la demarche du modele de recherche-developpement technologique en education de Nonnon. Les resultats de ces mises a l'essai indiquent que l'environnement d'apprentissage illustre le comportement des systemes selon un degre de fidelite technologique suffisamment proche de celui des systemes reels, en plus d'offrir les avantages propres a la simulation assistee par ordinateur, c'est-a-dire notamment la possibilite de creer des situations et de les experimenter, d'en faire varier les parametres, d'illustrer les phenomenes caches et d'observer simultanement et en temps reel le comportement des systemes et l'evolution des graphiques des variables. Les caracteristiques technologiques qui decoulent des techniques avancees de modelisation utilisees pour la realisation du deuxieme prototype, conferent a l'environnement d'apprentissage des capacites reliees a la conception de systemes et au diagnostic de pannes en milieu industriel. Cet aspect, que nous n'avions pas poursuivi specifiquement au plan didactique, constitue, selon nous, un serieux indice de sa valeur en tant que milieu d'etude representatif des systemes reels.

  12. Macroporous silicon for high-capacitance devices using metal electrodes.

    PubMed

    Vega, Didac; Reina, Jordi; Martí, Ferran; Pavón, Ramón; Rodríguez, Angel

    2014-01-01

    In this paper, high-capacity energy storage devices based on macroporous silicon are demonstrated. Small footprint devices with large specific capacitances up to 100 nF/mm(2), and an absolute capacitance above 15 μF, have been successfully fabricated using standard microelectronics and MEMS techniques. The fabricated devices are suitable for high-density system integration. The use of 3-D silicon structures allows achieving a large surface to volume ratio. The macroporous silicon structures are fabricated by electrochemical etching of silicon. This technique allows creating large structures of tubes with either straight or modulated radial profiles in depth. Furthermore, a very large aspect ratio is possible with this fabrication method. Macroporous silicon grown this way permits well-controlled structure definition with excellent repeatability and surface quality. Additionally, structure geometry can be accurately controlled to meet designer specifications. Macroporous silicon is used as one of the electrodes over which a silicon dioxide insulating layer is grown. Several insulator thicknesses have been tested. The second capacitor electrode is a solid nickel filling of the pores prepared by electroplating in a low-temperature industry standard process. The use of high-conductivity materials allows reaching small equivalent series resistance near 1 Ω. Thanks to these improvements, the presented devices are capable of operating up to 10 kHz. 84.32.Tt; 81.15.Pq; 81.05.Rm.

  13. Modeling the Capacitive Deionization Process in Dual-Porosity Electrodes

    DOE PAGES

    Gabitto, Jorge; Tsouris, Costas

    2016-04-28

    In many areas of the world, there is a need to increase water availability. Capacitive deionization (CDI) is an electrochemical water treatment process that can be a viable alternative for treating water and for saving energy. A model is presented to simulate the CDI process in heterogeneous porous media comprising two different pore sizes. It is based on a theory for capacitive charging by ideally polarizable porous electrodes without Faradaic reactions or specific adsorption of ions. A two steps volume averaging technique is used to derive the averaged transport equations in the limit of thin electrical double layers. A one-equationmore » model based on the principle of local equilibrium is derived. The constraints determining the range of application of the one-equation model are presented. The effective transport parameters for isotropic porous media are calculated solving the corresponding closure problems. The source terms that appear in the average equations are calculated using theoretical derivations. The global diffusivity is calculated by solving the closure problem.« less

  14. Detection of Electrocardiogram by Electrodes with Fabrics Using Capacitive Coupling

    NASA Astrophysics Data System (ADS)

    Ueno, Akinori; Furusawa, Yoichi; Hoshino, Hiroshi; Ishiyama, Yoji

    This article reports on a novel technique for detecting electrocardiogram (ECG) at a condition where thin cloth is interpolated between sensing electrodes and the skin to which the electrodes are attached. The technique is based upon capacitive coupling composed of the electrode, the cloth and the skin, so that the electrode can lead alternating electrocardiographic current through capacitance of the coupling. The technique is also founded on impedance transforming circuit that has extremely high input impedance around 1000GΩ and low output impedance, so as to match high output impedance of the electrode to low input impedance required by subsequent circuitry. A pilot ECG measuring device was manufactured using the technique and experiments showed (1) ECG recordings using the device with silk of 240μm thickness or with cotton of 564μm thickness were quite similar to ECGs recorded from the skin using conventional system, (2) stable ECGs were observed with the silk below 600μm thickness or with the cotton below 1128μm thickness, (3) effects of long-term measurement and perspiration on ECG waveform were negligible. These results prove feasibility of the proposed technique for detecting ECG by electrodes with fabrics.

  15. Synthesis of Two-Dimensional Materials for Capacitive Energy Storage

    SciTech Connect

    Mendoza-Sánchez, Beatriz; Gogotsi, Yury

    2016-06-02

    The unique properties and great variety of two-dimensional (2D) nanomaterials make them highly attractive for energy storage applications. Here, an insight into the progress made towards the application of 2D nanomaterials for capacitive energy storage is provided. Moreover, synthesis methods, and electrochemical performance of various classes of 2D nanomaterials, particularly based on graphene, transition metal oxides, dichalcogenides, and carbides, are presented. Some factors that directly influence capacitive performance are discussed throughout the text and include nanosheet composition, morphology and texture, electrode architecture, and device configuration. Recent progress in the fabrication of 2D-nanomaterials-based microsupercapacitors and flexible and free-standing supercapacitors is presented. The main electrode manufacturing techniques with emphasis on scalability and cost-effectiveness are discussed, and include laser scribing, printing, and roll-to-roll manufacture. Some various issues that prevent the use of the full energy-storage potential of 2D nanomaterials and how they have been tackled are discussed, and include nanosheet aggregation and the low electrical conductivity of some 2D nanomaterials. In particular, the design of hybrid and hierarchical 2D and 3D structures based on 2D nanomaterials is presented. Other challenges and opportunities are discussed and include: control of nanosheets size and thickness, chemical and electrochemical instability, and scale-up of electrode films.

  16. Capacitance-voltage measurement in memory devices using ferroelectric polymer

    NASA Astrophysics Data System (ADS)

    Nguyen, Chien A.; Lee, Pooi See

    2006-01-01

    Application of thin polymer film as storing mean for non-volatile memory devices is investigated. Capacitance-voltage (C-V) measurement of metal-ferroelectric-metal device using ferroelectric copolymer P(VDF-TrFE) as dielectric layer shows stable 'butter-fly' curve. The two peaks in C-V measurement corresponding to the largest capacitance are coincidental at the coercive voltages that give rise to zero polarization in the polarization hysteresis measurement. By comparing data of C-V and P-E measurement, a correlation between two types of hysteresis is established in which it reveals simultaneous electrical processes occurring inside the device. These processes are caused by the response of irreversible and reversible polarization to the applied electric field that can be used to present a memory window. The memory effect of ferroelectric copolymer is further demonstrated for fabricating polymeric non-volatile memory devices using metal-ferroelectric-insulator-semiconductor structure (MFIS). By applying different sweeping voltages at the gate, bidirectional flat-band voltage shift is observed in the ferroelectric capacitor. The asymmetrical shift after negative sweeping is resulted from charge accumulation at the surface of Si substrate caused by the dipole direction in the polymer layer. The effect is reversed for positive voltage sweeping.

  17. Synthesis of Two-Dimensional Materials for Capacitive Energy Storage

    DOE PAGES

    Mendoza-Sánchez, Beatriz; Gogotsi, Yury

    2016-06-02

    The unique properties and great variety of two-dimensional (2D) nanomaterials make them highly attractive for energy storage applications. Here, an insight into the progress made towards the application of 2D nanomaterials for capacitive energy storage is provided. Moreover, synthesis methods, and electrochemical performance of various classes of 2D nanomaterials, particularly based on graphene, transition metal oxides, dichalcogenides, and carbides, are presented. Some factors that directly influence capacitive performance are discussed throughout the text and include nanosheet composition, morphology and texture, electrode architecture, and device configuration. Recent progress in the fabrication of 2D-nanomaterials-based microsupercapacitors and flexible and free-standing supercapacitors is presented.more » The main electrode manufacturing techniques with emphasis on scalability and cost-effectiveness are discussed, and include laser scribing, printing, and roll-to-roll manufacture. Some various issues that prevent the use of the full energy-storage potential of 2D nanomaterials and how they have been tackled are discussed, and include nanosheet aggregation and the low electrical conductivity of some 2D nanomaterials. In particular, the design of hybrid and hierarchical 2D and 3D structures based on 2D nanomaterials is presented. Other challenges and opportunities are discussed and include: control of nanosheets size and thickness, chemical and electrochemical instability, and scale-up of electrode films.« less

  18. Synthesis of Two-Dimensional Materials for Capacitive Energy Storage

    SciTech Connect

    Mendoza-Sánchez, Beatriz; Gogotsi, Yury

    2016-06-02

    The unique properties and great variety of two-dimensional (2D) nanomaterials make them highly attractive for energy storage applications. Here, an insight into the progress made towards the application of 2D nanomaterials for capacitive energy storage is provided. Moreover, synthesis methods, and electrochemical performance of various classes of 2D nanomaterials, particularly based on graphene, transition metal oxides, dichalcogenides, and carbides, are presented. Some factors that directly influence capacitive performance are discussed throughout the text and include nanosheet composition, morphology and texture, electrode architecture, and device configuration. Recent progress in the fabrication of 2D-nanomaterials-based microsupercapacitors and flexible and free-standing supercapacitors is presented. The main electrode manufacturing techniques with emphasis on scalability and cost-effectiveness are discussed, and include laser scribing, printing, and roll-to-roll manufacture. Some various issues that prevent the use of the full energy-storage potential of 2D nanomaterials and how they have been tackled are discussed, and include nanosheet aggregation and the low electrical conductivity of some 2D nanomaterials. In particular, the design of hybrid and hierarchical 2D and 3D structures based on 2D nanomaterials is presented. Other challenges and opportunities are discussed and include: control of nanosheets size and thickness, chemical and electrochemical instability, and scale-up of electrode films.

  19. Capacitated arc routing problem and its extensions in waste collection

    SciTech Connect

    Fadzli, Mohammad; Najwa, Nurul; Luis, Martino

    2015-05-15

    Capacitated arc routing problem (CARP) is the youngest generation of graph theory that focuses on solving the edge/arc routing for optimality. Since many years, operational research devoted to CARP counterpart, known as vehicle routing problem (VRP), which does not fit to several real cases such like waste collection problem and road maintenance. In this paper, we highlighted several extensions of capacitated arc routing problem (CARP) that represents the real-life problem of vehicle operation in waste collection. By purpose, CARP is designed to find a set of routes for vehicles that satisfies all pre-setting constraints in such that all vehicles must start and end at a depot, service a set of demands on edges (or arcs) exactly once without exceeding the capacity, thus the total fleet cost is minimized. We also addressed the differentiation between CARP and VRP in waste collection. Several issues have been discussed including stochastic demands and time window problems in order to show the complexity and importance of CARP in the related industry. A mathematical model of CARP and its new version is presented by considering several factors such like delivery cost, lateness penalty and delivery time.

  20. Design and measurement of improved capacitively-shunted flux qubits

    NASA Astrophysics Data System (ADS)

    Sears, Adam; Birenbaum, Jeffrey; Hover, David; Gudmundsen, Theodore; Kerman, Andrew; Welander, Paul; Yoder, Jonilyn L.; Gustavsson, Simon; Jin, Xiaoyue; Kamal, Archana; Clarke, John; Oliver, William

    2014-03-01

    The addition of a capacitive or inductive shunt across one of the junctions can alter the coherence properties of a classic flux or RF-SQUID qubit. We have studied the performance of capacitively shunted flux qubits fabricated with MBE aluminum, starting from a 2D coplanar waveguide geometry used in similar high-performance transmon qubits, and measured dispersively. We will detail the importance of design parameters that preserve the flux qubit's anharmonicity and discuss conclusions about materials quality based on calculations of the participation of junction, dielectric, and superconductor components. 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 & 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 Present address: SLAC National Accelerator Laboratory, Menlo Park, CA.

  1. MOS flat-band capacitance method at low temperatures

    SciTech Connect

    Huang, C.L.; Gildenblat, G.H. . Dept. of Electrical Engineering)

    1989-08-01

    The expression C/sub FB/ = C/sub ox/ x ({element of}/sub si//L/sub D/)/(C/sub ox/ + ({Epsilon}/sub si//L/sub D/)) (where L/sub D/ is the Debye length), commonly used for the flat-band capacitance of the MOS structure, is invalid in the temperature range below 100 {Kappa}. Consequently, significant error may be encountered when the flat-band capacitance method is used to extract the flat-band voltage V/sub FB/, which is of considerable interest for both the modeling and characterization of MOS devices. To extend this method to low-temperature CMOS applications one has to use a more general model that can be obtained by applying Fermi-Dirac statistics and taking into account the impurity freezeout effect. The authors show that when the temperature dependence of V/sub FB/ is extracted using this approach, the experimental data for n/sup +/ polysilicon gate MOS capacitors are in a good agreement with a simple model.

  2. On the hydrophilicity of electrodes for capacitive energy extraction

    DOE PAGES

    Lian, Cheng; East China Univ. of Science and Technology, Shanghai; Kong, Xian; ...

    2016-09-14

    The so-called Capmix technique for energy extraction is based on the cyclic expansion of electrical double layers to harvest dissipative energy arising from the salinity difference between freshwater and seawater. Its optimal performance requires a careful selection of the electrical potentials for the charging and discharging processes, which must be matched with the pore characteristics of the electrode materials. While a number of recent studies have examined the effects of the electrode pore size and geometry on the capacitive energy extraction processes, there is little knowledge on how the surface properties of the electrodes affect the thermodynamic efficiency. In thismore » paper, we investigate the Capmix processes using the classical density functional theory for a realistic model of electrolyte solutions. The theoretical predictions allow us to identify optimal operation parameters for capacitive energy extraction with porous electrodes of different surface hydrophobicity. Finally, in agreement with recent experiments, we find that the thermodynamic efficiency can be much improved by using most hydrophilic electrodes.« less

  3. Single cell electric impedance topography: Mapping membrane capacitance

    PubMed Central

    Dharia, Sameera; Ayliffe, Harold E.

    2010-01-01

    Single-cell electric impedance topography (sceTopo), a technique introduced here, maps the spatial distribution of capacitance (i.e. displacement current) associated with the membranes of isolated, living cells. Cells were positioned in the center of a circular recording chamber surrounded by eight electrodes. Electrodes were evenly distributed on the periphery of the recording chamber. Electric impedance measured between adjacent electrode pairs (10 kHz–5 MHz) was used to construct topographical maps of the spatial distribution of membrane capacitance. Xenopus Oocytes were used as a model cell to develop sceTopo because these cells consist of two visually distinguishable hemispheres, each with distinct membrane composition and structure. Results showed significant differences in the imaginary component of the impedance between the two oocyte hemispheres. In addition, the same circumferential array was used to map the size of the extracellular electrical shunt path around the cell, providing a means to estimate the location and shape of the cell in the recording chamber. PMID:19904403

  4. Measurement strategy for rectangular electrical capacitance tomography sensor

    SciTech Connect

    Ye, Jiamin; Ge, Ruihuan; Qiu, Guizhi; Wang, Haigang

    2014-04-11

    To investigate the influence of the measurement strategy for the rectangular electrical capacitance tomography (ECT) sensor, a Finite Element Method (FEM) is utilized to create the model for simulation. The simulation was carried out using COMSOL Multiphysics(trade mark, serif) and Matlab(trade mark, serif). The length-width ratio of the rectangular sensing area is 5. Twelve electrodes are evenly arranged surrounding the pipe. The covering ratio of the electrodes is 90%. The capacitances between different electrode pairs are calculated for a bar distribution. The air of the relative permittivity 1.0 and the material of the permittivity 3.0 are used for the calibration. The relative permittivity of the second phase is 3.0. The noise free and noise data are used for the image reconstruction using the Linear Back Projection (LBP). The measurement strategies with 1-, 2- and 4- electrode excitation are compared using the correlation coefficient. Preliminary results show that the measurement strategy with 2-electrode excitation outperforms other measurement strategies with 1- or 4-electrode excitation.

  5. Graphene-containing flowable electrodes for capacitive energy storage

    DOE PAGES

    Boota, M.; Hatzell, K. B.; Alhabeb, M.; ...

    2015-04-10

    High conductivity and extended particle contacts are required for rapid charge percolation in flowable electrodes. In this study, carbon spheres (CS) were wrapped by highly conductive reduced graphene oxide sheets (rGO) to address these issues. We synthesized various compositions of the conductive, 3D interconnected hybrid materials (rGO@CS) using the hydrothermal method. Synergistic effects of both materials were utilized where CS served to minimize the sheet stacking for better flowability of the suspensions, and wrapped rGO sheets enabled higher conductivity for fast charge transport throughout the suspension network. When we tested as flowable electrodes, the composition with a 1:2 ratio ofmore » GO to CS exhibited the highest capacitance of 200 F/g and an improved rate performance. Moreover, the improved performance is attributed to the fast charge transport in the suspension network due to higher conductivity and enhanced connectivity of the active material particles. Optimized electrodes were also examined in a flow mode which yielded a capacitance of 45 F/g.« less

  6. High capacitance of coarse-grained carbide derived carbon electrodes

    DOE PAGES

    Dyatkin, Boris; Gogotsi, Oleksiy; Malinovskiy, Bohdan; ...

    2016-01-01

    Here, we report exceptional electrochemical properties of supercapacitor electrodes composed of large, granular carbide-derived carbon (CDC) particles. We synthesized 70–250 μm sized particles with high surface area and a narrow pore size distribution, using a titanium carbide (TiC) precursor. Electrochemical cycling of these coarse-grained powders defied conventional wisdom that a small particle size is strictly required for supercapacitor electrodes and allowed high charge storage densities, rapid transport, and good rate handling ability. Moreover, the material showcased capacitance above 100 F g-1 at sweep rates as high as 250 mV s-1 in organic electrolyte. 250–1000 micron thick dense CDC films withmore » up to 80 mg cm-2 loading showed superior areal capacitances. The material significantly outperformed its activated carbon counterpart in organic electrolytes and ionic liquids. Furthermore, large internal/external surface ratio of coarse-grained carbons allowed the resulting electrodes to maintain high electrochemical stability up to 3.1 V in ionic liquid electrolyte. In addition to presenting novel insights into the electrosorption process, these coarse-grained carbons offer a pathway to low-cost, high-performance implementation of supercapacitors in automotive and grid-storage applications.« less

  7. Effect of various commercial buffers on sperm viability and capacitation.

    PubMed

    Andrisani, Alessandra; Donà, Gabriella; Ambrosini, Guido; Bonanni, Guglielmo; Bragadin, Marcantonio; Cosmi, Erich; Clari, Giulio; Armanini, Decio; Bordin, Luciana

    2014-08-01

    A wide variety of sperm preparation protocols are currently available for assisted conception. They include density gradient separation and washing methods. Both aim at isolating and capacitating as much motile sperm as possible for subsequent oocyte fertilization. The aim of this study was to examine the effects of four commercial sperm washing buffers on sperm viability and capacitation. Semen samples from 48 healthy donors (normal values of sperm count, motility, morphology, and volume) were analyzed. After separation (density gradient 40/80%), sperm were incubated in various buffers then analysed for reactive oxygen species (ROS) production, viability, tyrosine phosphorylation (Tyr-P), cholera toxin B subunit (CTB) labeling, and the acrosome reaction (AR). The buffers affected ROS generation in various ways resulting either in rapid cell degeneration (when the amount of ROS was too high for cell survival) or the inability of the cells to maintain correct functioning (when ROS were too few). Only when the correct ROS generation curve was maintained, suitable membrane reorganization, evidenced by CTB labeling was achieved, leading to the highest percentages of both Tyr-P- and acrosome-reacted-cells. Distinguishing each particular pathological state of the sperm sample would be helpful to select the preferred buffer treatment since both ROS production and membrane reorganization can be significantly altered by commercial buffers.

  8. Macroporous silicon for high-capacitance devices using metal electrodes

    PubMed Central

    2014-01-01

    In this paper, high-capacity energy storage devices based on macroporous silicon are demonstrated. Small footprint devices with large specific capacitances up to 100 nF/mm2, and an absolute capacitance above 15 μF, have been successfully fabricated using standard microelectronics and MEMS techniques. The fabricated devices are suitable for high-density system integration. The use of 3-D silicon structures allows achieving a large surface to volume ratio. The macroporous silicon structures are fabricated by electrochemical etching of silicon. This technique allows creating large structures of tubes with either straight or modulated radial profiles in depth. Furthermore, a very large aspect ratio is possible with this fabrication method. Macroporous silicon grown this way permits well-controlled structure definition with excellent repeatability and surface quality. Additionally, structure geometry can be accurately controlled to meet designer specifications. Macroporous silicon is used as one of the electrodes over which a silicon dioxide insulating layer is grown. Several insulator thicknesses have been tested. The second capacitor electrode is a solid nickel filling of the pores prepared by electroplating in a low-temperature industry standard process. The use of high-conductivity materials allows reaching small equivalent series resistance near 1 Ω. Thanks to these improvements, the presented devices are capable of operating up to 10 kHz. PACS 84.32.Tt; 81.15.Pq; 81.05.Rm PMID:25242906

  9. Modeling the Capacitive Deionization Process in Dual-Porosity Electrodes

    SciTech Connect

    Gabitto, Jorge; Tsouris, Costas

    2016-04-28

    In many areas of the world, there is a need to increase water availability. Capacitive deionization (CDI) is an electrochemical water treatment process that can be a viable alternative for treating water and for saving energy. A model is presented to simulate the CDI process in heterogeneous porous media comprising two different pore sizes. It is based on a theory for capacitive charging by ideally polarizable porous electrodes without Faradaic reactions or specific adsorption of ions. A two steps volume averaging technique is used to derive the averaged transport equations in the limit of thin electrical double layers. A one-equation model based on the principle of local equilibrium is derived. The constraints determining the range of application of the one-equation model are presented. The effective transport parameters for isotropic porous media are calculated solving the corresponding closure problems. The source terms that appear in the average equations are calculated using theoretical derivations. The global diffusivity is calculated by solving the closure problem.

  10. A high-performance digital system for electrical capacitance tomography

    NASA Astrophysics Data System (ADS)

    Cui, Ziqiang; Wang, Huaxiang; Chen, Zengqiang; Xu, Yanbin; Yang, Wuqiang

    2011-05-01

    This paper describes a recently developed digital-based data acquisition system for electrical capacitance tomography (ECT). The system consists of high-capacity field-programmable gate arrays (FPGA) and fast data conversion circuits together with a specific signal processing method. In this system, digital phase-sensitive demodulation is implemented. A specific data acquisition scheme is employed to deal with residual charges in each measurement, resulting in a high signal-to-noise ratio (SNR) at high excitation frequency. A high-speed USB interface is employed between the FPGA and a host PC. Software in Visual C++ has been developed to accomplish operational functions. Various tests were performed to evaluate the system, e.g. frame rate, SNR, noise level, linearity, and static and dynamic imaging. The SNR is 60.3 dB at 1542 frames s-1 for a 12-electrode sensor. The mean absolute error between the measured capacitance and the linear fit value is 1.6 fF. The standard deviation of the measurements is in the order of 0.1 fF. The dynamic imaging test demonstrates the advantages of high temporal resolution of the system. The experimental results indicate that the digital signal processing devices can be used to construct a high-performance ECT system.

  11. Single cell electric impedance topography: mapping membrane capacitance.

    PubMed

    Dharia, Sameera; Ayliffe, Harold E; Rabbitt, Richard D

    2009-12-07

    Single-cell electric impedance topography (sceTopo), a technique introduced here, maps the spatial distribution of capacitance (i.e. displacement current) associated with the membranes of isolated, living cells. Cells were positioned in the center of a circular recording chamber surrounded by eight electrodes. Electrodes were evenly distributed on the periphery of the recording chamber. Electric impedance measured between adjacent electrode pairs (10 kHz-5 MHz) was used to construct topographical maps of the spatial distribution of membrane capacitance. Xenopus Oocytes were used as a model cell to develop sceTopo because these cells consist of two visually distinguishable hemispheres, each with distinct membrane composition and structure. Results showed significant differences in the imaginary component of the impedance between the two oocyte hemispheres. In addition, the same circumferential array was used to map the size of the extracellular electrical shunt path around the cell, providing a means to estimate the location and shape of the cell in the recording chamber.

  12. Flexible Bond Wire Capacitive Strain Sensor for Vehicle Tyres.

    PubMed

    Cao, Siyang; Pyatt, Simon; Anthony, Carl J; Kubba, Ammar I; Kubba, Ali E; Olatunbosun, Oluremi

    2016-06-21

    The safety of the driving experience and manoeuvrability of a vehicle can be improved by detecting the strain in tyres. To measure strain accurately in rubber, the strain sensor needs to be flexible so that it does not deform the medium that it is measuring. In this work, a novel flexible bond wire capacitive strain sensor for measuring the strain in tyres is developed, fabricated and calibrated. An array of 25 micron diameter wire bonds in an approximately 8 mm × 8 mm area is built to create an interdigitated structure, which consists of 50 wire loops resulting in 49 capacitor pairs in parallel. Laser machining was used to pattern copper on a flexible printed circuit board PCB to make the bond pads for the wire attachment. The wire array was finally packaged and embedded in polydimethylsiloxane (PDMS), which acts as the structural material that is strained. The capacitance of the device is in a linear like relationship with respect to the strain, which can measure the strain up to at least ±60,000 micro-strain (±6%) with a resolution of ~132 micro-strain (0.013%). In-tyre testing under static loading has shown the ability of the sensor to measure large tyre strains. The technology used for sensor fabrication lends itself to mass production and so the design is considered to be consistent with low cost commercialisable strain sensing technology.

  13. High capacitance of coarse-grained carbide derived carbon electrodes

    SciTech Connect

    Dyatkin, Boris; Gogotsi, Oleksiy; Malinovskiy, Bohdan; Zozulya, Yuliya; Simon, Patrice; Gogotsi, Yury

    2016-01-01

    Here, we report exceptional electrochemical properties of supercapacitor electrodes composed of large, granular carbide-derived carbon (CDC) particles. We synthesized 70–250 μm sized particles with high surface area and a narrow pore size distribution, using a titanium carbide (TiC) precursor. Electrochemical cycling of these coarse-grained powders defied conventional wisdom that a small particle size is strictly required for supercapacitor electrodes and allowed high charge storage densities, rapid transport, and good rate handling ability. Moreover, the material showcased capacitance above 100 F g-1 at sweep rates as high as 250 mV s-1 in organic electrolyte. 250–1000 micron thick dense CDC films with up to 80 mg cm-2 loading showed superior areal capacitances. The material significantly outperformed its activated carbon counterpart in organic electrolytes and ionic liquids. Furthermore, large internal/external surface ratio of coarse-grained carbons allowed the resulting electrodes to maintain high electrochemical stability up to 3.1 V in ionic liquid electrolyte. In addition to presenting novel insights into the electrosorption process, these coarse-grained carbons offer a pathway to low-cost, high-performance implementation of supercapacitors in automotive and grid-storage applications.

  14. High capacitance of coarse-grained carbide derived carbon electrodes

    NASA Astrophysics Data System (ADS)

    Dyatkin, Boris; Gogotsi, Oleksiy; Malinovskiy, Bohdan; Zozulya, Yuliya; Simon, Patrice; Gogotsi, Yury

    2016-02-01

    We report exceptional electrochemical properties of supercapacitor electrodes composed of large, granular carbide-derived carbon (CDC) particles. Using a titanium carbide (TiC) precursor, we synthesized 70-250 μm sized particles with high surface area and a narrow pore size distribution. Electrochemical cycling of these coarse-grained powders defied conventional wisdom that a small particle size is strictly required for supercapacitor electrodes and allowed high charge storage densities, rapid transport, and good rate handling ability. The material showcased capacitance above 100 F g-1 at sweep rates as high as 250 mV s-1 in organic electrolyte. 250-1000 micron thick dense CDC films with up to 80 mg cm-2 loading showed superior areal capacitances. The material significantly outperformed its activated carbon counterpart in organic electrolytes and ionic liquids. Furthermore, large internal/external surface ratio of coarse-grained carbons allowed the resulting electrodes to maintain high electrochemical stability up to 3.1 V in ionic liquid electrolyte. In addition to presenting novel insights into the electrosorption process, these coarse-grained carbons offer a pathway to low-cost, high-performance implementation of supercapacitors in automotive and grid-storage applications.

  15. A capacitive ultrasonic transducer based on parametric resonance

    NASA Astrophysics Data System (ADS)

    Surappa, Sushruta; Satir, Sarp; Levent Degertekin, F.

    2017-07-01

    A capacitive ultrasonic transducer based on a parametric resonator structure is described and experimentally demonstrated. The transducer structure, which we call capacitive parametric ultrasonic transducer (CPUT), uses a parallel plate capacitor with a movable membrane as part of a degenerate parametric series RLC resonator circuit with a resonance frequency of fo. When the capacitor plate is driven with an incident harmonic ultrasonic wave at the pump frequency of 2fo with sufficient amplitude, the RLC circuit becomes unstable and ultrasonic energy can be efficiently converted to an electrical signal at fo frequency in the RLC circuit. An important characteristic of the CPUT is that unlike other electrostatic transducers, it does not require DC bias or permanent charging to be used as a receiver. We describe the operation of the CPUT using an analytical model and numerical simulations, which shows drive amplitude dependent operation regimes including parametric resonance when a certain threshold is exceeded. We verify these predictions by experiments with a micromachined membrane based capacitor structure in immersion where ultrasonic waves incident at 4.28 MHz parametrically drive a signal with significant amplitude in the 2.14 MHz RLC circuit. With its unique features, the CPUT can be particularly advantageous for applications such as wireless power transfer for biomedical implants and acoustic sensing.

  16. Flexible Bond Wire Capacitive Strain Sensor for Vehicle Tyres

    PubMed Central

    Cao, Siyang; Pyatt, Simon; Anthony, Carl J.; Kubba, Ammar I.; Kubba, Ali E.; Olatunbosun, Oluremi

    2016-01-01

    The safety of the driving experience and manoeuvrability of a vehicle can be improved by detecting the strain in tyres. To measure strain accurately in rubber, the strain sensor needs to be flexible so that it does not deform the medium that it is measuring. In this work, a novel flexible bond wire capacitive strain sensor for measuring the strain in tyres is developed, fabricated and calibrated. An array of 25 micron diameter wire bonds in an approximately 8 mm × 8 mm area is built to create an interdigitated structure, which consists of 50 wire loops resulting in 49 capacitor pairs in parallel. Laser machining was used to pattern copper on a flexible printed circuit board PCB to make the bond pads for the wire attachment. The wire array was finally packaged and embedded in polydimethylsiloxane (PDMS), which acts as the structural material that is strained. The capacitance of the device is in a linear like relationship with respect to the strain, which can measure the strain up to at least ±60,000 micro-strain (±6%) with a resolution of ~132 micro-strain (0.013%). In-tyre testing under static loading has shown the ability of the sensor to measure large tyre strains. The technology used for sensor fabrication lends itself to mass production and so the design is considered to be consistent with low cost commercialisable strain sensing technology. PMID:27338402

  17. Capacitively Coupled CMOS VCSEL Driver Circuits for Optical Communication

    NASA Astrophysics Data System (ADS)

    Kozlov, Victor

    This thesis presents the analysis, design and implementation of a common-cathode capacitively-coupled VCSEL driver in 65nm CMOS intended for short-reach optical interconnects. The driver consists of an AC-coupled high-frequency path and a low-frequency path that provides DC signal components. By increasing the low-frequency path bandwidth by 10 times compared to previous AC-coupled drivers allowed the on-chip coupling capacitor to be reduced to 2.1pF, occupying 3 times less area than prior art. The driver introduces capacitively-coupled two-tap emphasis to equalize the VCSEL's optical response. The VCSEL was modulated with an OMA of up to 5.1dBm and an ER of 9dB, measuring an RMS jitter of 5ps at a data rate of 15Gb/s, which represents the highest OMA and ER achieved in high-speed anode-driving LDDs. The driver could be programmed for a low-power mode, outputting 2.3dBm OMA at power consumption of only 30mW, corresponding to an energy efficiency of 2pJ/bit.

  18. Modeling the Capacitive Deionization Process in Dual-Porosity Electrodes

    SciTech Connect

    Gabitto, Jorge; Tsouris, Costas

    2016-04-28

    In many areas of the world, there is a need to increase water availability. Capacitive deionization (CDI) is an electrochemical water treatment process that can be a viable alternative for treating water and for saving energy. A model is presented to simulate the CDI process in heterogeneous porous media comprising two different pore sizes. It is based on a theory for capacitive charging by ideally polarizable porous electrodes without Faradaic reactions or specific adsorption of ions. A two steps volume averaging technique is used to derive the averaged transport equations in the limit of thin electrical double layers. A one-equation model based on the principle of local equilibrium is derived. The constraints determining the range of application of the one-equation model are presented. The effective transport parameters for isotropic porous media are calculated solving the corresponding closure problems. The source terms that appear in the average equations are calculated using theoretical derivations. The global diffusivity is calculated by solving the closure problem.

  19. Implementing a capacitive pressure sensor realized on LTCC

    NASA Astrophysics Data System (ADS)

    Tămaş, Cosmin; Marghescu, Cristina; Ionescu, Ciprian; Vasile, Alexandru

    2010-11-01

    LTCC (Low Temperature Co-Fired Ceramic) has great potential in the field of sensors and transducers due to its thermal, electrical and mechanical properties. The paper describes work concerning a capacitive pressure sensor realized on LTCC with thick-film deposition technologies. A capacitive pressure sensor converts a change in the position of the conductive plates to an electrical signal; for this a deformable diaphragm is used. In the presented case one electrode is bonded to the deformable diaphragm (an edge-clamped, circular diaphragm) and the other electrode is fixed. The signal from the sensor is processed by the AD7745 circuit. This circuit is a high resolution digital capacity-signal converter with high performances, high linearity +/-0.01% and very good accuracy +/-4 fF. The circuit also encompasses a voltage reference and a temperature sensor with a resolution of 0.1°C. The external connection is made through the I2C interface, using a signal control unit which processes the signal and sends the information to an LCD (liquid crystal display) and/or to a computer which, in turn, records the information for later use through the USB interface.

  20. Graphene-containing flowable electrodes for capacitive energy storage

    SciTech Connect

    Boota, M.; Hatzell, K. B.; Alhabeb, M.; Kumbur, E. C.; Gogotsi, Y.

    2015-04-10

    High conductivity and extended particle contacts are required for rapid charge percolation in flowable electrodes. In this study, carbon spheres (CS) were wrapped by highly conductive reduced graphene oxide sheets (rGO) to address these issues. We synthesized various compositions of the conductive, 3D interconnected hybrid materials (rGO@CS) using the hydrothermal method. Synergistic effects of both materials were utilized where CS served to minimize the sheet stacking for better flowability of the suspensions, and wrapped rGO sheets enabled higher conductivity for fast charge transport throughout the suspension network. When we tested as flowable electrodes, the composition with a 1:2 ratio of GO to CS exhibited the highest capacitance of 200 F/g and an improved rate performance. Moreover, the improved performance is attributed to the fast charge transport in the suspension network due to higher conductivity and enhanced connectivity of the active material particles. Optimized electrodes were also examined in a flow mode which yielded a capacitance of 45 F/g.

  1. Fractal simulation of the resistivity and capacitance of arsenic selenide

    SciTech Connect

    Balkhanov, V. K. Bashkuev, Yu. B.

    2010-03-15

    The temperature dependences of the ac resistivity R and ac capacitance C of arsenic selenide were measured more than four decades ago [V. I. Kruglov and L. P. Strakhov, in Problems of Solid State Electronics, Vol. 2 (Leningrad Univ., Leningrad, 1968)]. According to these measurements, the frequency dependences are R {proportional_to} {omega}{sup -0.80{+-}0.01} and {Delta}C {proportional_to} {omega}{sup -0.120{+-}0.006} ({omega} is the circular frequency and {Delta}C is measured from the temperature-independent value C{sub 0}). According to fractal-geometry methods, R {proportional_to} {omega}{sup 1-3/h} and {Delta}C {proportional_to} {omega}{sup -2+3/h}, where h is the walk dimension of the electric current in arsenic selenide. Comparison of the experimental and theoretical results indicates that the walk dimensions calculated from the frequency dependences of resistivity and capacitance are h{sub R} = 1.67 {+-} 0.02 and h{sub C} = 1.60 {+-} 0.08, which are in agreement with each other within the measurement errors. The fractal dimension of the distribution of conducting sections is D = 1/h = 0.6. Since D < 1, the conducting sections are spatially separated and form a Cantor set.

  2. Capacitated arc routing problem and its extensions in waste collection

    NASA Astrophysics Data System (ADS)

    Fadzli, Mohammad; Najwa, Nurul; Luis, Martino

    2015-05-01

    Capacitated arc routing problem (CARP) is the youngest generation of graph theory that focuses on solving the edge/arc routing for optimality. Since many years, operational research devoted to CARP counterpart, known as vehicle routing problem (VRP), which does not fit to several real cases such like waste collection problem and road maintenance. In this paper, we highlighted several extensions of capacitated arc routing problem (CARP) that represents the real-life problem of vehicle operation in waste collection. By purpose, CARP is designed to find a set of routes for vehicles that satisfies all pre-setting constraints in such that all vehicles must start and end at a depot, service a set of demands on edges (or arcs) exactly once without exceeding the capacity, thus the total fleet cost is minimized. We also addressed the differentiation between CARP and VRP in waste collection. Several issues have been discussed including stochastic demands and time window problems in order to show the complexity and importance of CARP in the related industry. A mathematical model of CARP and its new version is presented by considering several factors such like delivery cost, lateness penalty and delivery time.

  3. A novel capacitance sensor for fireside corrosion measurement

    NASA Astrophysics Data System (ADS)

    Ban, Heng; Li, Zuoping

    2009-11-01

    Fireside corrosion in coal-fired power plants is a leading mechanism for boiler tube failures. Online monitoring of fireside corrosion can provide timely data to plant operators for mitigation implementation. This paper presents a novel sensor concept for measuring metal loss based on electrical capacitance. Laboratory-scale experiments demonstrated the feasibility of design, fabrication, and operation of the sensor. The fabrication of the prototype sensor involved sputtering deposition of a thin metal coating with varying thickness on a ceramic substrate. Corrosion metal loss resulted in a proportional decrease in electrical capacitance of the sensor. Laboratory experiments using a muffle furnace with an oxidation environment demonstrated that low carbon steel coatings on ceramic substrate survived cyclic temperatures over 500 °C. Measured corrosion rates of sputtered coating in air had an Arrhenius exponential dependence on temperature, with metal thickness loss ranging from 2.0 nm/h at 200 °C to 2.0 μm/h at 400 °C. Uncertainty analysis indicated that the overall measurement uncertainty was within 4%. The experimental system showed high signal-to-noise ratio, and the sensor could measure submicrometer metal thickness changes. The laboratory experiments demonstrated that the sensor concept and measurement system are capable of short term, online monitoring of metal loss, indicating the potential for the sensor to be used for fireside corrosion monitoring and other metal loss measurement.

  4. X-ray absorption measurement by scanning capacitance microscopy

    NASA Astrophysics Data System (ADS)

    Ishii, Masashi; Uchihashi, Takayuki

    2003-12-01

    This paper describes a demonstration of scanning capacitance microscopy (SCM) as a technique for measuring X-ray absorption fine structure (XAFS) in what is called the SCM-XAFS method. This method achieves the simultaneous analysis of the electrical and chemical characteristics of surface-trapping centers. In obtaining the XAFS spectrum of trapping centers, the method takes advantage of the fact that the X-ray-induced photoemission of a localized electron leads to a change in capacitance. When the Fermi level corresponds to the trapping level, the photoemission process is sensitively detected. Therefore, a specific trapping center may be selectively observed by controlling the bias. From SCM-XAFS measurements of a GaAs surface, we found that gallium oxide trapping centers capture electrons in the positive bias voltage region. Moreover, experimental findings that resonant intra-transition and resonant scattering of emitted photoelectrons enhance the SCM-XAFS signal at particular X-ray photon energy reveal the local density of states of the gallium oxide and the complex structure of the trapping centers.

  5. Capacitive sensor for high resolution weld seam tracking

    SciTech Connect

    Schmitt, D.J.; Novak, J.L.; Akins, J.L.

    1995-05-01

    A non-contact capacitive sensing system has been developed for guiding automated welding equipment along typical v-groove geometries. The Multi-Axis Seam Tracking (MAST) sensor has been designed to produce four electric fields for locating and measuring the v-groove geometry. In this system, the MAST sensor is coupled with a set of signal conditioning electronics making it possible to output four varying voltages proportional to the electric field perturbations. This output is used for motion control purposes by the automated welding platform to guide the weld torch directly over the center of the v-groove. This report discusses the development of this capacitive sensing system. A functional description of the system and MAST sensor response characteristics for typical weld v-groove geometries are provided. The effects of the harsh thermal and electrical noise environments of plasma arc welding on sensor performance are discussed. A comparison of MAST sensor fabrication from glass-epoxy and thick-film ceramic substrates is provided. Finally, results of v-groove tracking experiments on a robotic welding platform are described.

  6. Capacitive micromachined ultrasonic resonator for ultra sensitive trace gas detection

    NASA Astrophysics Data System (ADS)

    Ge, Li-Feng

    2013-01-01

    The ultra-sensitive trace gas detection has become increasingly important due to the demand for environment and sci-tech progress. In recent years a capacitive micromachined ultrasonic transducer (CMUT) with circular diaphragms used for imaging has been successfully used to detect chemical gases, and shows promising results. However, its behavior is the same as that of CMUTs for ranging, imaging and therapy applications, where the acoustic radiation with a certain power, produced by the vibration of circular diaphragms operating at the first bending mode, is required but is undesirable for gas sensing since it disturbs inevitably the environment to be measured. This paper, therefore, presents to optimize its behavior after an ideal capacitive micromachined ultrasonic resonator (CMUR) and then to utilize second-order and high-order bending modes of the circular diaphragm to minimize its acoustic radiation and obtain higher resonance frequency also. Since the resonance frequencies of high-order modes much higher than the fundamental frequency, an ultra-high operating frequency of GHz can be reached so that raising greatly the sensitivity of the CMUR and being able to realize the ultra-sensitive trace gas detections.

  7. Fundamental investigations of capacitive radio frequency plasmas: simulations and experiments

    NASA Astrophysics Data System (ADS)

    Donkó, Z.; Schulze, J.; Czarnetzki, U.; Derzsi, A.; Hartmann, P.; Korolov, I.; Schüngel, E.

    2012-12-01

    Capacitive radio frequency (RF) discharge plasmas have been serving hi-tech industry (e.g. chip and solar cell manufacturing, realization of biocompatible surfaces) for several years. Nonetheless, their complex modes of operation are not fully understood and represent topics of high interest. The understanding of these phenomena is aided by modern diagnostic techniques and computer simulations. From the industrial point of view the control of ion properties is of particular interest; possibilities of independent control of the ion flux and the ion energy have been utilized via excitation of the discharges with multiple frequencies. ‘Classical’ dual-frequency (DF) discharges (where two significantly different driving frequencies are used), as well as discharges driven by a base frequency and its higher harmonic(s) have been analyzed thoroughly. It has been recognized that the second solution results in an electrically induced asymmetry (electrical asymmetry effect), which provides the basis for the control of the mean ion energy. This paper reviews recent advances on studies of the different electron heating mechanisms, on the possibilities of the separate control of ion energy and ion flux in DF discharges, on the effects of secondary electrons, as well as on the non-linear behavior (self-generated resonant current oscillations) of capacitive RF plasmas. The work is based on a synergistic approach of theoretical modeling, experiments and kinetic simulations based on the particle-in-cell approach.

  8. Hair weathering and hair capacitance mapping: a pilot study.

    PubMed

    Piérard-Franchimont, Claudine; Piérard, Gérald E

    2012-09-01

    Currently, there is no reported objective method allowing confident assessment of hair hydration mapping. Thus, assessing hair moisture kinetics and versatility according to hair shaft damages and hair care products is difficult to perform. To explore a new method for assessing hair moisture. A new method of hair capacitance mapping (HCM) is introduced for monitoring hair surface damage and hydration. This study was performed on intact and weathered hair locks. Samples were soaked in 10% solutions of regular shampoos or in tap water alone. HCM was performed using the SkinChip(®) device based on a semiconductor image sensor technology. Time to complete water desorption from cuticular cells was recorded. Hair surface moisture was increased for <30 min after soaking in the shampoos or water alone. The method was sensitive enough to disclose a gradient of moisture from the base to the tip of the hair shafts. Weathered hairs lost their moisture more rapidly than intact hairs. Hair capacitance mapping appears to be a promising method in the assessment of the dynamics of hair surface moisture. © 2012 Wiley Periodicals, Inc.

  9. Fluid Modeling of a Very High Frequency Capacitively Coupled Reactor

    NASA Astrophysics Data System (ADS)

    Upadhyay, Rochan; Raja, Laxminarayan; Ventzek, Peter; Iwao, Toshihiko; Ishibashi, Kiyotaka; Esgee Technologies Inc. Collaboration; University of Texas at Austin Collaboration; Tokyo Electron Ltd. Collaboration

    2016-09-01

    Very High Frequency Capacitively Coupled Plasma (VHF-CCP) discharges have been studied extensively for semiconductor manufacturing applications for well over a decade. Modeling of these discharges however poses significant challenges owing to complexity associated with simulation of multiple coupled phenomena (electro-static/magnetic fields and plasma physics) over different scales and the representation of these phenomena in a computational framework. We present 2D simulations of a self-consistent plasma with the electromagnetic field represented using vector and scalar potentials. For a range of operating conditions, the ratio of capacitive and inductive power, calculated using empirical correlations available in the literature, are matched by adjusting both the electrostatic and electromagnetic fields in a decoupled manner. We present results using this model that demonstrate most of the important VHF-CCP discharge phenomena reported in the literature, such as electromagnetic wave versus electrostatic heating and its impact on plasma non-uniformity, wave resonances, etc. while realizing a practically feasible computational model.

  10. A capacitive ultrasonic transducer based on parametric resonance.

    PubMed

    Surappa, Sushruta; Satir, Sarp; Levent Degertekin, F

    2017-07-24

    A capacitive ultrasonic transducer based on a parametric resonator structure is described and experimentally demonstrated. The transducer structure, which we call capacitive parametric ultrasonic transducer (CPUT), uses a parallel plate capacitor with a movable membrane as part of a degenerate parametric series RLC resonator circuit with a resonance frequency of fo. When the capacitor plate is driven with an incident harmonic ultrasonic wave at the pump frequency of 2fo with sufficient amplitude, the RLC circuit becomes unstable and ultrasonic energy can be efficiently converted to an electrical signal at fo frequency in the RLC circuit. An important characteristic of the CPUT is that unlike other electrostatic transducers, it does not require DC bias or permanent charging to be used as a receiver. We describe the operation of the CPUT using an analytical model and numerical simulations, which shows drive amplitude dependent operation regimes including parametric resonance when a certain threshold is exceeded. We verify these predictions by experiments with a micromachined membrane based capacitor structure in immersion where ultrasonic waves incident at 4.28 MHz parametrically drive a signal with significant amplitude in the 2.14 MHz RLC circuit. With its unique features, the CPUT can be particularly advantageous for applications such as wireless power transfer for biomedical implants and acoustic sensing.

  11. Electronic hardware design of electrical capacitance tomography systems.

    PubMed

    Saied, I; Meribout, M

    2016-06-28

    Electrical tomography techniques for process imaging are very prominent for industrial applications, such as the oil and gas industry and chemical refineries, owing to their ability to provide the flow regime of a flowing fluid within a relatively high throughput. Among the various techniques, electrical capacitance tomography (ECT) is gaining popularity due to its non-invasive nature and its capability to differentiate between different phases based on their permittivity distribution. In recent years, several hardware designs have been provided for ECT systems that have improved its resolution of measurements to be around attofarads (aF, 10(-18) F), or the number of channels, that is required to be large for some applications that require a significant amount of data. In terms of image acquisition time, some recent systems could achieve a throughput of a few hundred frames per second, while data processing time could be achieved in only a few milliseconds per frame. This paper outlines the concept and main features of the most recent front-end and back-end electronic circuits dedicated for ECT systems. In this paper, multiple-excitation capacitance polling, a front-end electronic technique, shows promising results for ECT systems to acquire fast data acquisition speeds. A highly parallel field-programmable gate array (FPGA) based architecture for a fast reconstruction algorithm is also described. This article is part of the themed issue 'Supersensing through industrial process tomography'. © 2016 The Author(s).

  12. Non-contact capacitance based image sensing method and system

    DOEpatents

    Novak, J.L.; Wiczer, J.J.

    1995-01-03

    A system and a method is provided for imaging desired surfaces of a workpiece. A sensor having first and second sensing electrodes which are electrically isolated from the workpiece is positioned above and in proximity to the desired surfaces of the workpiece. An electric field is developed between the first and second sensing electrodes of the sensor in response to input signals being applied thereto and capacitance signals are developed which are indicative of any disturbances in the electric field as a result of the workpiece. An image signal of the workpiece may be developed by processing the capacitance signals. The image signals may provide necessary control information to a machining device for machining the desired surfaces of the workpiece in processes such as deburring or chamfering. Also, the method and system may be used to image dimensions of weld pools on a workpiece and surfaces of glass vials. The sensor may include first and second preview sensors used to determine the feed rate of a workpiece with respect to the machining device. 18 figures.

  13. Non-contact capacitance based image sensing method and system

    DOEpatents

    Novak, J.L.; Wiczer, J.J.

    1994-01-25

    A system and a method for imaging desired surfaces of a workpiece is described. A sensor having first and second sensing electrodes which are electrically isolated from the workpiece is positioned above and in proximity to the desired surfaces of the workpiece. An electric field is developed between the first and second sensing electrodes of the sensor in response to input signals being applied thereto and capacitance signals are developed which are indicative of any disturbances in the electric field as a result of the workpiece. An image signal of the workpiece may be developed by processing the capacitance signals. The image signals may provide necessary control information to a machining device for machining the desired surfaces of the workpiece in processes such as deburring or chamfering. Also, the method and system may be used to image dimensions of weld pools on a workpiece and surfaces of glass vials. The sensor may include first and second preview sensors used to determine the feed rate of a workpiece with respect to the machining device. 18 figures.

  14. Non-contact capacitance based image sensing method and system

    DOEpatents

    Novak, James L.; Wiczer, James J.

    1995-01-01

    A system and a method is provided for imaging desired surfaces of a workpiece. A sensor having first and second sensing electrodes which are electrically isolated from the workpiece is positioned above and in proximity to the desired surfaces of the workpiece. An electric field is developed between the first and second sensing electrodes of the sensor in response to input signals being applied thereto and capacitance signals are developed which are indicative of any disturbances in the electric field as a result of the workpiece. An image signal of the workpiece may be developed by processing the capacitance signals. The image signals may provide necessary control information to a machining device for machining the desired surfaces of the workpiece in processes such as deburring or chamfering. Also, the method and system may be used to image dimensions of weld pools on a workpiece and surfaces of glass vials. The sensor may include first and second preview sensors used to determine the feed rate of a workpiece with respect to the machining device.

  15. Non-contact capacitance based image sensing method and system

    DOEpatents

    Novak, James L.; Wiczer, James J.

    1994-01-01

    A system and a method for imaging desired surfaces of a workpiece. A sensor having first and second sensing electrodes which are electrically isolated from the workpiece is positioned above and in proximity to the desired surfaces of the workpiece. An electric field is developed between the first and second sensing electrodes of the sensor in response to input signals being applied thereto and capacitance signals are developed which are indicative of any disturbances in the electric field as a result of the workpiece. An image signal of the workpiece may be developed by processing the capacitance signals. The image signals may provide necessary control information to a machining device for machining the desired surfaces of the workpiece in processes such as deburring or chamfering. Also, the method and system may be used to image dimensions of weld pools on a workpiece and surfaces of glass vials. The sensor may include first and second preview sensors used to determine the feed rate of a workpiece with respect to the machining device.

  16. Redox-tagged peptide for capacitive diagnostic assays.

    PubMed

    Santos, Adriano; Piccoli, Julia P; Santos-Filho, Norival A; Cilli, Eduardo M; Bueno, Paulo R

    2015-06-15

    Early detection assays play a key role in the successful treatment of most diseases. Redox capacitive biosensors were recently introduced as a potential electroanalytical assay platform for point-of-care applications but alternative surfaces (besides a mixed layer containing ferrocene and antibody receptive component) for recruiting important clinical biomarkers are still needed. Aiming to develop alternative receptive surfaces for this novel electrochemical biosensing platform, we synthesized a ferrocene redox-tagged peptide capable of self-assembly into metallic interfaces, a potentially useful biological surface functionalization for bedside diagnostic assays. As a proof of concept we used C-reactive protein (CRP), as a model biomarker, and compared the obtained results to those of previously reported capacitive assays. The redox-tagged peptide approach shows a limit of detection of 0.8 nmol L(-1) (same as 94 ng mL(-1)) and a linear range (R(2)∼98%) with the logarithm of the concentration of the analyte comprising 0.5-10.0 nmol L(-1), within a clinical relevant range for CRP.

  17. Electrical Capacitance Volume Tomography with High-Contrast Dielectrics

    NASA Technical Reports Server (NTRS)

    Nurge, Mark

    2010-01-01

    The Electrical Capacitance Volume Tomography (ECVT) system has been designed to complement the tools created to sense the presence of water in nonconductive spacecraft materials, by helping to not only find the approximate location of moisture but also its quantity and depth. The ECVT system has been created for use with a new image reconstruction algorithm capable of imaging high-contrast dielectric distributions. Rather than relying solely on mutual capacitance readings as is done in traditional electrical capacitance tomography applications, this method reconstructs high-resolution images using only the self-capacitance measurements. The image reconstruction method assumes that the material under inspection consists of a binary dielectric distribution, with either a high relative dielectric value representing the water or a low dielectric value for the background material. By constraining the unknown dielectric material to one of two values, the inverse math problem that must be solved to generate the image is no longer ill-determined. The image resolution becomes limited only by the accuracy and resolution of the measurement circuitry. Images were reconstructed using this method with both synthetic and real data acquired using an aluminum structure inserted at different positions within the sensing region. The cuboid geometry of the system has two parallel planes of 16 conductors arranged in a 4 4 pattern. The electrode geometry consists of parallel planes of copper conductors, connected through custom-built switch electronics, to a commercially available capacitance to digital converter. The figure shows two 4 4 arrays of electrodes milled from square sections of copper-clad circuit-board material and mounted on two pieces of glass-filled plastic backing, which were cut to approximately square shapes, 10 cm on a side. Each electrode is placed on 2.0-cm centers. The parallel arrays were mounted with the electrode arrays approximately 3 cm apart. The open ends

  18. Signature spectrale des grains interstellaires.

    NASA Astrophysics Data System (ADS)

    Léger, A.

    Notre connaissance de la nature des grains interstellaires reposait sur un nombre très restreint de signatures spectrales dans la courbe d'extinction du milieu interstellaire. Une information considérable est contenue dans les 40 bandes interstellaires diffuses dans le visible, mais reste inexploitée. L'interprétation récente des cinq bandes IR en émission, en terme de molécules d'hydrocarbures aromatiques polycycliques, est développée. Elle permet l'utilisation d'une information spectroscopique comparable, à elle seule, à ce sur quoi était basée jusqu'alors notre connaissance de la matière interstellaire condensée. Différentes implications de cette mise en évidence sont proposées.

  19. Field-effect sensors with charged macromolecules: characterisation by capacitance-voltage, constant-capacitance, impedance spectroscopy and atomic-force microscopy methods.

    PubMed

    Poghossian, A; Abouzar, M H; Amberger, F; Mayer, D; Han, Y; Ingebrandt, S; Offenhäusser, A; Schöning, M J

    2007-04-15

    Field-effect-based capacitive electrolyte-insulator-semiconductor (EIS) sensors have been utilised for the deoxyribonucleic acid (DNA) immobilisation and hybridisation detection as well as for monitoring the layer-by-layer adsorption of polyelectrolytes (anionic poly(sodium 4-styrene sulfonate) (PSS) and cationic poly(allylamine hydrochloride) (PAH)). The EIS sensors with charged macromolecules have been systematically characterised by capacitance-voltage, constant-capacitance, impedance spectroscopy and atomic-force microscopy methods. The effect of the number and polarity of the polyelectrolyte layers on the shift of the capacitance-voltage curves has been investigated. Alternating potential shifts of about 30-90 mV have been observed after the adsorption of each polyanion and polycation layer, respectively. The DNA immobilisation and hybridisation signals were 35-55 and 24-33 mV, respectively. The possible mechanisms for the sensor responses are discussed.

  20. Annuaire du Bureau des longitudes - 2006

    NASA Astrophysics Data System (ADS)

    Imcce; Bureau Des Longitudes

    2005-07-01

    This annual publication provides ephemerides and data to the use of professionnal and amateur astronomers. Divided in 11 chapters it covers concordance of various calendars, explanation of fondamental astronomy and various time scales, explanation for the use of ephemerides; tables provide ephemerides (positions, rise/set/passage) of the Sun and the Moon, planets, planetary satellites, asteroids, comets, bright stars; data and explanation for the physical observation of the surface of the Sun, the Moon, and planets; chart of the sky and a list of constellations and galaxies; prediction and ephemerides for astronomical phenomenon: occultation by the moon, stellar occultations by asteroids and appulses, solar eclipses and lunar eclipses; and an additional review about a hot scientific topic, this year: "Legendre et le méridien terrestre, 200 ans après". Cette publication annuelle fournit des éphémérides et des données à l'usage des astronomes professionnels et des astronomes amateurs. Composée de 11 chapitres elle comprend les rubriques sur les différents calendriers et leurs concordance, les fêtes légales en France, les dates et décrets sur les heures légales en France métropolitaine ; une introduction à l'astronomie fondamentale et aux différentes échelles de temps, des explications sur l'utilisation des éphémérides ; des tables fournissent les éphémérides (positions, heures de lever/coucher/passage) du Soleil et de la Lune, de planètes, de satellites naturels, d'astéroïdes, de comètes, d'étoiles brillantes ; des données pour l'observation de la surface du Soleil, de la Lune, et des planètes ; des cartes du ciel ainsi qu'une liste de constellations et de galaxies ; des prédictions des phénomènes astronomiques : occultation par la Lune, occultation stellaires par des astéroïdes et appulses, éclipses de Soleil et de la Lune; la liste et les coordonnées des observatoires astronomiques les plus connus ; et enfin un cahier th