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Sample records for ac alternating current

  1. Concurrent Electroencephalography Recording During Transcranial Alternating Current Stimulation (tACS)

    PubMed Central

    Fehér, Kristoffer D.; Morishima, Yosuke

    2016-01-01

    Oscillatory brain activities are considered to reflect the basis of rhythmic changes in transmission efficacy across brain networks and are assumed to integrate cognitive neural processes. Transcranial alternating current stimulation (tACS) holds the promise to elucidate the causal link between specific frequencies of oscillatory brain activity and cognitive processes. Simultaneous electroencephalography (EEG) recording during tACS would offer an opportunity to directly explore immediate neurophysiological effects of tACS. However, it is not trivial to measure EEG signals during tACS, as tACS creates a huge artifact in EEG data. Here we explain how to set up concurrent tACS-EEG experiments. Two necessary considerations for successful EEG recording while applying tACS are highlighted. First, bridging of the tACS and EEG electrodes via leaking EEG gel immediately saturates the EEG amplifier. To avoid bridging via gel, the viscosity of the EEG gel is the most important parameter. The EEG gel must be viscous to avoid bridging, but at the same time sufficiently fluid to create contact between the tACS electrode and the scalp. Second, due to the large amplitude of the tACS artifact, it is important to consider using an EEG system with a high resolution analog-to-digital (A/D) converter. In particular, the magnitude of the tACS artifact can exceed 100 mV at the vicinity of a stimulation electrode when 1 mA tACS is applied. The resolution of the A/D converter is of importance to measure good quality EEG data from the vicinity of the stimulation site. By following these guidelines for the procedures and technical considerations, successful concurrent EEG recording during tACS will be realized. PMID:26862814

  2. Methods, systems and apparatus for controlling operation of two alternating current (AC) machines

    DOEpatents

    Gallegos-Lopez, Gabriel; Nagashima, James M.; Perisic, Milun; Hiti, Silva

    2012-06-05

    A system is provided for controlling two alternating current (AC) machines via a five-phase PWM inverter module. The system comprises a first control loop, a second control loop, and a current command adjustment module. The current command adjustment module operates in conjunction with the first control loop and the second control loop to continuously adjust current command signals that control the first AC machine and the second AC machine such that they share the input voltage available to them without compromising the target mechanical output power of either machine. This way, even when the phase voltage available to either one of the machines decreases, that machine outputs its target mechanical output power.

  3. Targeting the neurophysiology of cognitive systems with transcranial alternating current stimulation (tACS)

    PubMed Central

    Fröhlich, Flavio; Sellers, Kristin K.; Cordle, Asa L.

    2015-01-01

    Cognitive impairment represents one of the most debilitating and most difficult symptom to treat of many psychiatric illnesses. Human neurophysiology studies have suggested specific pathologies of cortical network activity correlate with cognitive impairment. However, we lack (1) demonstration of causal relationships between specific network activity patterns and cognitive capabilities and (2) treatment modalities that directly target impaired network dynamics of cognition. Transcranial alternating current stimulation (tACS), a novel non-invasive brain stimulation approach, may provide a crucial tool to tackle these challenges. We here propose that tACS can be used to elucidate the causal role of cortical synchronization in cognition and, eventually, to enhance pathologically weakened synchrony that may underlie cognitive deficits. To accelerate such development of tACS as a treatment for cognitive deficits, we discuss studies on tACS and cognition (all performed in healthy participants) according to the Research Domain Criteria (RDoC) of the National Institute of Mental Health. PMID:25547149

  4. The effects of theta transcranial alternating current stimulation (tACS) on fluid intelligence.

    PubMed

    Pahor, Anja; Jaušovec, Norbert

    2014-09-01

    The objective of the study was to explore the influence of transcranial alternating current stimulation (tACS) on resting brain activity and on measures of fluid intelligence. Theta tACS was applied to the left parietal and left frontal brain areas of healthy participants after which resting electroencephalogram (EEG) data was recorded. Following sham/active stimulation, the participants solved two tests of fluid intelligence while their EEG was recorded. The results showed that active theta tACS affected spectral power in theta and alpha frequency bands. In addition, active theta tACS improved performance on tests of fluid intelligence. This influence was more pronounced in the group of participants that received stimulation to the left parietal area than in the group of participants that received stimulation to the left frontal area. Left parietal tACS increased performance on the difficult test items of both tests (RAPM and PF&C) whereas left frontal tACS increased performance only on the easy test items of one test (RAPM). The observed behavioral tACS influences were also accompanied by changes in neuroelectric activity. The behavioral and neuroelectric data tentatively support the P-FIT neurobiological model of intelligence.

  5. The effects of theta transcranial alternating current stimulation (tACS) on fluid intelligence.

    PubMed

    Pahor, Anja; Jaušovec, Norbert

    2014-09-01

    The objective of the study was to explore the influence of transcranial alternating current stimulation (tACS) on resting brain activity and on measures of fluid intelligence. Theta tACS was applied to the left parietal and left frontal brain areas of healthy participants after which resting electroencephalogram (EEG) data was recorded. Following sham/active stimulation, the participants solved two tests of fluid intelligence while their EEG was recorded. The results showed that active theta tACS affected spectral power in theta and alpha frequency bands. In addition, active theta tACS improved performance on tests of fluid intelligence. This influence was more pronounced in the group of participants that received stimulation to the left parietal area than in the group of participants that received stimulation to the left frontal area. Left parietal tACS increased performance on the difficult test items of both tests (RAPM and PF&C) whereas left frontal tACS increased performance only on the easy test items of one test (RAPM). The observed behavioral tACS influences were also accompanied by changes in neuroelectric activity. The behavioral and neuroelectric data tentatively support the P-FIT neurobiological model of intelligence. PMID:24998643

  6. The effect of 10 Hz transcranial alternating current stimulation (tACS) on corticomuscular coherence

    PubMed Central

    Wach, Claudia; Krause, Vanessa; Moliadze, Vera; Paulus, Walter; Schnitzler, Alfons; Pollok, Bettina

    2013-01-01

    Synchronous oscillatory activity at alpha (8–12 Hz), beta (13–30 Hz), and gamma (30–90 Hz) frequencies is assumed to play a key role for motor control. Corticomuscular coherence (CMC) represents an established measure of the pyramidal system's integrity. Transcranial alternating current stimulation (tACS) offers the possibility to modulate ongoing oscillatory activity. Behaviorally, 20 Hz tACS in healthy subjects has been shown to result in movement slowing. However, the neurophysiological changes underlying these effects are not entirely understood yet. The present study aimed at ascertaining the effects of tACS at 10 and 20 Hz in healthy subjects on CMC and local power of the primary sensorimotor cortex. Neuromagnetic activity was recorded during isometric contraction before and at two time points (2–10 min and 30–38 min) after tACS of the left primary motor cortex (M1), using a 306 channel whole head magnetoencephalography (MEG) system. Additionally, electromyography (EMG) of the right extensor digitorum communis (EDC) muscle was measured. TACS was applied at 10 and 20 Hz, respectively, for 10 min at 1 mA. Sham stimulation served as control condition. The data suggest that 10 Hz tACS significantly reduced low gamma band CMC during isometric contraction. This implies that tACS does not necessarily cause effects at stimulation frequency. Rather, the findings suggest cross-frequency interplay between alpha and low gamma band activity modulating functional interaction between motor cortex and muscle. PMID:24009573

  7. Mapping entrained brain oscillations during transcranial alternating current stimulation (tACS).

    PubMed

    Witkowski, Matthias; Garcia-Cossio, Eliana; Chander, Bankim S; Braun, Christoph; Birbaumer, Niels; Robinson, Stephen E; Soekadar, Surjo R

    2016-10-15

    Transcranial alternating current stimulation (tACS), a non-invasive and well-tolerated form of electric brain stimulation, can influence perception, memory, as well as motor and cognitive function. While the exact underlying neurophysiological mechanisms are unknown, the effects of tACS are mainly attributed to frequency-specific entrainment of endogenous brain oscillations in brain areas close to the stimulation electrodes, and modulation of spike timing dependent plasticity reflected in gamma band oscillatory responses. tACS-related electromagnetic stimulator artifacts, however, impede investigation of these neurophysiological mechanisms. Here we introduce a novel approach combining amplitude-modulated tACS during whole-head magnetoencephalography (MEG) allowing for artifact-free source reconstruction and precise mapping of entrained brain oscillations underneath the stimulator electrodes. Using this approach, we show that reliable reconstruction of neuromagnetic low- and high-frequency oscillations including high gamma band activity in stimulated cortical areas is feasible opening a new window to unveil the mechanisms underlying the effects of stimulation protocols that entrain brain oscillatory activity.

  8. The AC (Alternating Current) Electrical Behavior of Multi-layered Thermoelectric Devices

    NASA Astrophysics Data System (ADS)

    Alim, Mohammad A.; Budak, Satilmis; Bhattacharjee, Sudip

    2016-08-01

    In this study the ac (alternating current) small-signal electrical data in the frequency range 5 Hz ≤ f ≤ 13 MHz are obtained for the multi-layered thermoelectric (TE) devices to extract underlying operative mechanisms via an equivalent circuit model. This model is developed from the complex plane plots in conjunction with the Bode plot. It is observed that the inductive behavior is prevalent for both unbombarded and bombarded TE devices regardless of the doses as both types are observed as somewhat weak in thermoelectric properties. The bombarded multi-layered devices followed a systematic pattern in ac behavior via semicircular relaxation both in the impedance and admittance planes for the same measured data. This pattern is attributed to the transition from one lumped behavior to two distinct mechanisms. It is observed that the␣conductive nature of the equivalent circuit model via non-blocking (non-capacitive) elements, attributed to the underlying operative electrical paths between the two opposite electrodes across the multi-layered device exists, satisfying direct current conditions of the equivalent circuit model. The inductive behavior at high frequencies originates from the conductive aspect of the lumped response of the device in addition to the contribution of the electrode leads. Thus, the proposed equivalent circuit model contains external inductance that verifies a meaningful representation of the multi-layered TE device, though weak in thermoelectric properties.

  9. The AC (Alternating Current) Electrical Behavior of Multi-layered Thermoelectric Devices

    NASA Astrophysics Data System (ADS)

    Alim, Mohammad A.; Budak, Satilmis; Bhattacharjee, Sudip

    2016-11-01

    In this study the ac (alternating current) small-signal electrical data in the frequency range 5 Hz ≤ f ≤ 13 MHz are obtained for the multi-layered thermoelectric (TE) devices to extract underlying operative mechanisms via an equivalent circuit model. This model is developed from the complex plane plots in conjunction with the Bode plot. It is observed that the inductive behavior is prevalent for both unbombarded and bombarded TE devices regardless of the doses as both types are observed as somewhat weak in thermoelectric properties. The bombarded multi-layered devices followed a systematic pattern in ac behavior via semicircular relaxation both in the impedance and admittance planes for the same measured data. This pattern is attributed to the transition from one lumped behavior to two distinct mechanisms. It is observed that the conductive nature of the equivalent circuit model via non-blocking (non-capacitive) elements, attributed to the underlying operative electrical paths between the two opposite electrodes across the multi-layered device exists, satisfying direct current conditions of the equivalent circuit model. The inductive behavior at high frequencies originates from the conductive aspect of the lumped response of the device in addition to the contribution of the electrode leads. Thus, the proposed equivalent circuit model contains external inductance that verifies a meaningful representation of the multi-layered TE device, though weak in thermoelectric properties.

  10. BOLD signal effects of transcranial alternating current stimulation (tACS) in the alpha range: A concurrent tACS-fMRI study.

    PubMed

    Vosskuhl, Johannes; Huster, René J; Herrmann, Christoph S

    2016-10-15

    Many studies have proven transcranial alternating current stimulation (tACS) to manipulate brain activity. Until now it is not known, however, how these manipulations in brain activity are represented in brain metabolism or how spatially specific these changes are. Alpha-tACS has been shown to enhance the amplitude of the individual alpha frequency (IAF) and a negative correlation between alpha amplitude and occipital BOLD signal was reported in numerous EEG/fMRI experiments. Thus, alpha-tACS was chosen to test the effects of tACS on the BOLD signal. A reduction thereof was expected during alpha-tACS which shows the spatial extent of tACS effects beyond modeling studies. Three groups of subjects were measured in an MRI scanner, receiving tACS at either their IAF (N=11), 1Hz (control; N=12) or sham (i.e., no stimulation - a second control; N=11) while responding to a visual vigilance task. Stimulation was administered in an interleaved pattern of tACS-on runs and tACS-free baseline periods. The BOLD signal was analyzed in response to tACS-onset during resting state and in response to seldom target stimuli. Alpha-tACS at 1.0mA reduced the task-related BOLD response to visual targets in the occipital cortex as compared to tACS-free baseline periods. The deactivation was strongest in an area where the BOLD signal was shown to correlate negatively with alpha amplitude. A direct effect of tACS on resting state BOLD signal levels could not be shown. Our findings suggest that tACS-related changes in BOLD activity occur only as a modulation of an existing BOLD response.

  11. Numerical and theoretical evaluations of AC losses for single and infinite numbers of superconductor strips with direct and alternating transport currents in external AC magnetic field

    NASA Astrophysics Data System (ADS)

    Kajikawa, K.; Funaki, K.; Shikimachi, K.; Hirano, N.; Nagaya, S.

    2010-11-01

    AC losses in a superconductor strip are numerically evaluated by means of a finite element method formulated with a current vector potential. The expressions of AC losses in an infinite slab that corresponds to a simple model of infinitely stacked strips are also derived theoretically. It is assumed that the voltage-current characteristics of the superconductors are represented by Bean’s critical state model. The typical operation pattern of a Superconducting Magnetic Energy Storage (SMES) coil with direct and alternating transport currents in an external AC magnetic field is taken into account as the electromagnetic environment for both the single strip and the infinite slab. By using the obtained results of AC losses, the influences of the transport currents on the total losses are discussed quantitatively.

  12. Methods, systems and apparatus for controlling operation of two alternating current (AC) machines

    DOEpatents

    Gallegos-Lopez, Gabriel; Nagashima, James M.; Perisic, Milun; Hiti, Silva

    2012-02-14

    A system is provided for controlling two AC machines. The system comprises a DC input voltage source that provides a DC input voltage, a voltage boost command control module (VBCCM), a five-phase PWM inverter module coupled to the two AC machines, and a boost converter coupled to the inverter module and the DC input voltage source. The boost converter is designed to supply a new DC input voltage to the inverter module having a value that is greater than or equal to a value of the DC input voltage. The VBCCM generates a boost command signal (BCS) based on modulation indexes from the two AC machines. The BCS controls the boost converter such that the boost converter generates the new DC input voltage in response to the BCS. When the two AC machines require additional voltage that exceeds the DC input voltage required to meet a combined target mechanical power required by the two AC machines, the BCS controls the boost converter to drive the new DC input voltage generated by the boost converter to a value greater than the DC input voltage.

  13. Some AC electrical properties of Li-Mg ferrites[Alternating Current

    SciTech Connect

    Bellad, S.S.; Watawe, S.C.; Chougule, B.K.

    1999-05-01

    The ac resistivity ({rho}{sub ac}), dielectric constant ({epsilon}{prime}), dielectric loss tangent (tan {delta}) and initial permeability ({mu}{sub i}) of mixed Li{sub 0.5{minus}x/2}Mg{sub x}Fe{sub 2.5{minus}x/2}O{sub 4} (where x = 0.1, 0.2, 0.3, 0.4, 0.5, and 0.6) ferrite system were measured at room temperature as a function of frequency in the range from 1 kHz to 1 MHz. The resistivity of all the samples decreased with increase in frequency, indicating that the samples exhibited normal ferrimagnetic behavior. The compositional variation of resistivity and dielectric constant indicated the inverse trends of each other. The sample with x = 0.3 showed the lowest resistivity and the highest dielectric constant. The dielectric loss tangent showed maxima at 3 kHz for x = 0.2 samples and at 15--20 kHz for x = 0.3 and 0.4 samples. All of the variations are explained on the basis of Fe{sup 2+}/Fe{sup 3+} ion concentration on octahedral sites as well as the electronic hopping frequency between Fe{sup 2+} {leftrightarrow} Fe{sup 3+} ions.

  14. Alpha Power Increase After Transcranial Alternating Current Stimulation at Alpha Frequency (α-tACS) Reflects Plastic Changes Rather Than Entrainment

    PubMed Central

    Vossen, Alexandra; Gross, Joachim; Thut, Gregor

    2015-01-01

    Background Periodic stimulation of occipital areas using transcranial alternating current stimulation (tACS) at alpha (α) frequency (8–12 Hz) enhances electroencephalographic (EEG) α-oscillation long after tACS-offset. Two mechanisms have been suggested to underlie these changes in oscillatory EEG activity: tACS-induced entrainment of brain oscillations and/or tACS-induced changes in oscillatory circuits by spike-timing dependent plasticity. Objective We tested to what extent plasticity can account for tACS-aftereffects when controlling for entrainment “echoes.” To this end, we used a novel, intermittent tACS protocol and investigated the strength of the aftereffect as a function of phase continuity between successive tACS episodes, as well as the match between stimulation frequency and endogenous α-frequency. Methods 12 healthy participants were stimulated at around individual α-frequency for 11–15 min in four sessions using intermittent tACS or sham. Successive tACS events were either phase-continuous or phase-discontinuous, and either 3 or 8 s long. EEG α-phase and power changes were compared after and between episodes of α-tACS across conditions and against sham. Results α-aftereffects were successfully replicated after intermittent stimulation using 8-s but not 3-s trains. These aftereffects did not reveal any of the characteristics of entrainment echoes in that they were independent of tACS phase-continuity and showed neither prolonged phase alignment nor frequency synchronization to the exact stimulation frequency. Conclusion Our results indicate that plasticity mechanisms are sufficient to explain α-aftereffects in response to α-tACS, and inform models of tACS-induced plasticity in oscillatory circuits. Modifying brain oscillations with tACS holds promise for clinical applications in disorders involving abnormal neural synchrony. PMID:25648377

  15. Cortico-muscular coupling and motor performance are modulated by 20 Hz transcranial alternating current stimulation (tACS) in Parkinson’s disease

    PubMed Central

    Krause, Vanessa; Wach, Claudia; Südmeyer, Martin; Ferrea, Stefano; Schnitzler, Alfons; Pollok, Bettina

    2014-01-01

    Parkinson’s disease (PD) is associated with pathologically altered oscillatory activity. While synchronized oscillations between 13 and 30 Hz are increased within a cortico-subcortical network, cortico-muscular coupling (CMC) is decreased. The present study aims at investigating the effect of non-invasive transcranial alternating current stimulation (tACS) of the primary motor cortex (M1) on motor symptoms and motor-cortical oscillations in PD. In 10 PD patients and 10 healthy control subjects, static isometric contraction, dynamic fast finger tapping, and diadochokinesia of the more severely affected hand were investigated prior to and shortly after tACS of the contralateral M1 at 10 Hz vs. 20 Hz vs. sham. During isometric contraction, neuromagnetic activity was recorded using magnetoencephalography. 20 Hz tACS attenuated beta band CMC during isometric contraction and amplitude variability during finger tapping in PD patients but not in healthy control subjects. 10 Hz tACS yielded no significant after-effects. The present data suggest that PD is associated with pathophysiological alterations which abet a higher responsiveness toward frequency-specific tACS – possibly due to pathologically altered motor-cortical oscillatory synchronization at frequencies between 13 and 30 Hz. PMID:24474912

  16. Beta Band Transcranial Alternating (tACS) and Direct Current Stimulation (tDCS) Applied After Initial Learning Facilitate Retrieval of a Motor Sequence

    PubMed Central

    Krause, Vanessa; Meier, Anna; Dinkelbach, Lars; Pollok, Bettina

    2016-01-01

    The primary motor cortex (M1) contributes to the acquisition and early consolidation of a motor sequence. Although the relevance of M1 excitability for motor learning has been supported, the significance of M1 oscillations remains an open issue. This study aims at investigating to what extent retrieval of a newly learned motor sequence can be differentially affected by motor-cortical transcranial alternating (tACS) and direct current stimulation (tDCS). Alpha (10 Hz), beta (20 Hz) or sham tACS was applied in 36 right-handers. Anodal or cathodal tDCS was applied in 30 right-handers. Participants learned an eight-digit serial reaction time task (SRTT; sequential vs. random) with the right hand. Stimulation was applied to the left M1 after SRTT acquisition at rest for 10 min. Reaction times were analyzed at baseline, end of acquisition, retrieval immediately after stimulation and reacquisition after eight further sequence repetitions. Reaction times during retrieval were significantly faster following 20 Hz tACS as compared to 10 Hz and sham tACS indicating a facilitation of early consolidation. tDCS yielded faster reaction times, too, independent of polarity. No significant differences between 20 Hz tACS and tDCS effects on retrieval were found suggesting that 20 Hz effects might be associated with altered motor-cortical excitability. Based on the behavioral modulation yielded by tACS and tDCS one might speculate that altered motor-cortical beta oscillations support early motor consolidation possibly associated with neuroplastic reorganization. PMID:26834593

  17. Electric characterization of (Sr, Sr-Ba, Ba) M-type ferrites by AC measurements[Alternating Current

    SciTech Connect

    Huanosta-Tera, A.; Lira-Hueso, R. de; Perez-Orta, O.; Palomares-Sanchez, S.A.; Ponce-Castaneda, S.; Mirabal-Garcia, M.

    2000-02-01

    Considering the electrical conductivity in ceramics, necessary reference should be given to dynamic processes occurring as a function of frequency and temperature. Although the most immediate interest in ferrites lies in their magnetic properties, technological applications require a wider knowledge of general physical properties as well. This is especially applicable when the materials are studied as a function of composition or when adding different modifiers. In this report, the authors present results of the ac and dc electric characteristics of a family of magneto-plumbite-type hexaferrites, where Ba gradually substitutes Sr in the Ba{sub x}Sr{sub 1{minus}x}Fe{sub 12}O{sub 19} compound (0 {le} x {le} 1). The results were determined over a wide range of frequencies and temperatures.

  18. AUTOMOTIVE DIESEL MAINTENANCE 2. UNIT XVII, LEARNING ABOUT AC GENERATOR (ALTERNATOR) PRINCIPLES (PART II).

    ERIC Educational Resources Information Center

    Minnesota State Dept. of Education, St. Paul. Div. of Vocational and Technical Education.

    THIS MODULE OF A 25-MODULE COURSE IS DESIGNED TO DEVELOP AN UNDERSTANDING OF THE OPERATING PRINCIPLES AND THE SERVICING AND TESTING PROCEDURES FOR ALTERNATING CURRENT (AC) GENERATORS AND REGULATORS USED ON DIESEL POWERED EQUIPMENT. TOPICS ARE REVIEW OF ALTERNATOR PRINCIPLES, ALTERNATOR SERVICING AND TESTING, ALTERNATOR REGULATOR OPERATING…

  19. Alternating current long range alpha particle detector

    DOEpatents

    MacArthur, D.W.; McAtee, J.L.

    1993-02-16

    An alpha particle detector, utilizing alternating currents, which is capable of detecting alpha particles from distinct sources. The use of alternating currents allows use of simpler ac circuits which, in turn, are not susceptible to dc error components. It also allows the benefit of gas gain, if desired. In the invention, a voltage source creates an electric field between two conductive grids, and between the grids and a conductive enclosure. Air containing air ions created by collision with alpha particles is drawn into the enclosure and detected. In some embodiments, the air flow into the enclosure is interrupted, creating an alternating flow of ions. In another embodiment, a modulated voltage is applied to the grid, also modulating the detection of ions.

  20. Alternating current long range alpha particle detector

    DOEpatents

    MacArthur, Duncan W.; McAtee, James L.

    1993-01-01

    An alpha particle detector, utilizing alternating currents, whcih is capable of detecting alpha particles from distinct sources. The use of alternating currents allows use of simpler ac circuits which, in turn, are not susceptible to dc error components. It also allows the benefit of gas gain, if desired. In the invention, a voltage source creates an electric field between two conductive grids, and between the grids and a conductive enclosure. Air containing air ions created by collision with alpha particles is drawn into the enclosure and detected. In some embodiments, the air flow into the enclosure is interrupted, creating an alternating flow of ions. In another embodiment, a modulated voltage is applied to the grid, also modulating the detection of ions.

  1. AUTOMOTIVE DIESEL MAINTENANCE 2. UNIT XVI, LEARNING ABOUT AC GENERATOR (ALTERNATOR) PRINCIPLES (PART I).

    ERIC Educational Resources Information Center

    Human Engineering Inst., Cleveland, OH.

    THIS MODULE OF A 25-MODULE COURSE IS DESIGNED TO DEVELOP AN UNDERSTANDING OF THE OPERATING PRINCIPLES OF ALTERNATING CURRENT GENERATORS USED ON DIESEL POWERED EQUIPMENT. TOPICS ARE REVIEWING ELECTRICAL FUNDAMENTALS, AND OPERATING PRINCIPLES OF ALTERNATORS. THE MODULE CONSISTS OF A SELF-INSTRUCTIONAL PROGRAMED TRAINING FILM "AC GENERATORS…

  2. Alternating parity structure in doubly odd /sup 218/Ac

    SciTech Connect

    Debray, M.E.; Davidson, M.; Kreiner, A.J.; Davidson, J.; Falcone, G.; Hojman, D.; Santos, D.

    1989-03-01

    States in doubly odd /sup 218/Ac have been studied using in-beam ..cap alpha..-, ..gamma..-, and e/sup -/-spectroscopy techniques mainly through the /sup 209/Bi(/sup 12/C,3n)= fusion-evaporation reaction. /sup 218/Ac shows a band structure, with interleaved states of alternating parities connected by enhanced B(E1) transitions, which is strikingly similar to the one in its isotone /sup 217/Ra.

  3. Alternating Current Influences Anaerobic Electroactive Biofilm Activity.

    PubMed

    Wang, Xin; Zhou, Lean; Lu, Lu; Lobo, Fernanda Leite; Li, Nan; Wang, Heming; Park, Jaedo; Ren, Zhiyong Jason

    2016-09-01

    Alternating current (AC) is known to inactivate microbial growth in suspension, but how AC influences anaerobic biofilm activities has not been systematically investigated. Using a Geobacter dominated anaerobic biofilm growing on the electrodes of microbial electrochemical reactors, we found that high frequency AC ranging from 1 MHz to 1 kHz (amplitude of 5 V, 30 min) showed only temporary inhibition to the biofilm activity. However, lower frequency (100 Hz, 1.2 or 5 V) treatment led to 47 ± 19% permanent decrease in limiting current on the same biofilm, which is attributed to the action of electrohydrodynamic force that caused biofilm damage and loss of intercellular electron transfer network. Confocal microscopy images show such inactivation mainly occurred at the interface between the biofilm and the electrode. Reducing the frequency further to 1 Hz led to water electrolysis, which generated gas bubbles that flushed all attached cells out of the electrode. These findings provide new references on understanding and regulating biofilm growth, which has broader implications in biofouling control, anaerobic waste treatment, energy and product recovery, and general understanding of microbial ecology and physiology. PMID:27485403

  4. Effect of the magnetic material on AC losses in HTS conductors in AC magnetic field carrying AC transport current

    NASA Astrophysics Data System (ADS)

    Wan, Xing-Xing; Huang, Chen-Guang; Yong, Hua-Dong; Zhou, You-He

    2015-11-01

    This paper presents an investigation on the AC losses in several typical superconducting composite conductors using the H-formulation model. A single superconducting strip with ferromagnetic substrate or cores and a stack of coated conductors with ferromagnetic substrates are studied. We consider all the coated conductors carrying AC transport currents and simultaneously exposed to perpendicular AC magnetic fields. The influences of the amplitude, frequency, phase difference and ferromagnetic materials on the AC losses are investigated. The results show that the magnetization losses of single strip and stacked strips have similar characteristics. The ferromagnetic substrate can increase the magnetization loss at low magnetic field, and decrease the loss at high magnetic field. The ferromagnetic substrate can obviously increase the transport loss in stacked strips. The trends of total AC losses of single strip and stacked strips are similar when they are carrying current or exposed to a perpendicular magnetic field. The effect of the frequency on the total AC losses of single strip is related to the amplitude of magnetic field. The AC losses decrease with increasing frequency in low magnetic field region while increase in high magnetic field region. As the phase difference changes, there is a periodic variation for the AC losses. Moreover, when the strip is under only the transport current and magnetic field, the ferromagnetic cores will increase the AC losses for large transport current or field.

  5. Frequency dependence of alternating current electrospray ionization mass spectrometry.

    PubMed

    Chetwani, Nishant; Cassou, Catherine A; Go, David B; Chang, Hsueh-Chia

    2011-04-15

    The novel effects resulting from the entrainment of low mobility ions during alternating current (ac) electrospray ionization are examined through mass spectrometry and voltage/current measurements. Curious phenomena such as pH modulation at high frequencies (>150 kHz) of an applied ac electric field are revealed and explained using simple mechanistic arguments. Current measurements are utilized to supplement these observations, and a simplified one-dimensional transient diffusion model for charge transport is used to arrive at a scaling law that provides better insight into the ac electrospray ionization process. Moreover, because of the different pathway for ion formation in comparison to direct current (dc) electrospray, ac electrospray (at frequencies >250 kHz) is shown to reduce the effects of ionization suppression in a mixture of two molecules with different surface activities. PMID:21417427

  6. Transcranial Alternating Current and Random Noise Stimulation: Possible Mechanisms

    PubMed Central

    Antal, Andrea; Herrmann, Christoph S.

    2016-01-01

    Background. Transcranial alternating current stimulation (tACS) is a relatively recent method suited to noninvasively modulate brain oscillations. Technically the method is similar but not identical to transcranial direct current stimulation (tDCS). While decades of research in animals and humans has revealed the main physiological mechanisms of tDCS, less is known about the physiological mechanisms of tACS. Method. Here, we review recent interdisciplinary research that has furthered our understanding of how tACS affects brain oscillations and by what means transcranial random noise stimulation (tRNS) that is a special form of tACS can modulate cortical functions. Results. Animal experiments have demonstrated in what way neurons react to invasively and transcranially applied alternating currents. Such findings are further supported by neural network simulations and knowledge from physics on entraining physical oscillators in the human brain. As a result, fine-grained models of the human skull and brain allow the prediction of the exact pattern of current flow during tDCS and tACS. Finally, recent studies on human physiology and behavior complete the picture of noninvasive modulation of brain oscillations. Conclusion. In future, the methods may be applicable in therapy of neurological and psychiatric disorders that are due to malfunctioning brain oscillations. PMID:27242932

  7. Transcranial Alternating Current and Random Noise Stimulation: Possible Mechanisms.

    PubMed

    Antal, Andrea; Herrmann, Christoph S

    2016-01-01

    Background. Transcranial alternating current stimulation (tACS) is a relatively recent method suited to noninvasively modulate brain oscillations. Technically the method is similar but not identical to transcranial direct current stimulation (tDCS). While decades of research in animals and humans has revealed the main physiological mechanisms of tDCS, less is known about the physiological mechanisms of tACS. Method. Here, we review recent interdisciplinary research that has furthered our understanding of how tACS affects brain oscillations and by what means transcranial random noise stimulation (tRNS) that is a special form of tACS can modulate cortical functions. Results. Animal experiments have demonstrated in what way neurons react to invasively and transcranially applied alternating currents. Such findings are further supported by neural network simulations and knowledge from physics on entraining physical oscillators in the human brain. As a result, fine-grained models of the human skull and brain allow the prediction of the exact pattern of current flow during tDCS and tACS. Finally, recent studies on human physiology and behavior complete the picture of noninvasive modulation of brain oscillations. Conclusion. In future, the methods may be applicable in therapy of neurological and psychiatric disorders that are due to malfunctioning brain oscillations. PMID:27242932

  8. Thermoelectric converters for alternating current standards

    NASA Astrophysics Data System (ADS)

    Anatychuk, L. I.; Taschuk, D. D.

    2012-06-01

    Thermoelectric converters of alternating current remain priority instruments when creating standard equipment. This work presents the results of design and manufacture of alternating current converter for a military standard of alternating current in Ukraine. Results of simulation of temperature distribution in converter elements, ways of optimization to improve the accuracy of alternating current signal reproduction are presented. Results of metrological trials are given. The quality of thermoelectric material specially created for alternating current metrology is verified. The converter was used in alternating current standard for the frequency range from 10 Hz to 30 MHz. The efficiency of using thermoelectric signal converters in measuring instruments is confirmed.

  9. A Comparison of Alternating Current and Direct Current Electrospray Ionization for Mass Spectrometry

    NASA Astrophysics Data System (ADS)

    Sarver, Scott A.; Chetwani, Nishant; Dovichi, Norman J.; Go, David B.; Gartner, Carlos A.

    2014-04-01

    A series of studies comparing the performance of alternating current electrospray ionization (AC ESI) mass spectrometry (MS) and direct current electrospray ionization (DC ESI) MS have been conducted, exploring the absolute signal intensity and signal-to-background ratios produced by both methods using caffeine and a model peptide as targets. Because the high-voltage AC signal was more susceptible to generating gas discharges, the operating voltage range of AC ESI was significantly smaller than that for DC ESI, such that the absolute signal intensities produced by DC ESI at peak voltages were one to two orders of magnitude greater than those for AC ESI. Using an electronegative nebulizing gas, sulfur hexafluoride (SF6), instead of nitrogen (N2) increased the operating range of AC ESI by ~50 %, but did not appreciably improve signal intensities. While DC ESI generated far greater signal intensities, both ionization methods produced comparable signal-to-background noise, with AC ESI spectra appearing qualitatively cleaner. A quantitative calibration analysis was performed for two analytes, caffeine and the peptide MRFA. AC ESI utilizing SF6 outperforms all other techniques for the detection of MRFA, producing chromatographic limits of detection nearly one order of magnitude lower than that of DC ESI utilizing N2, and one-half that of DC ESI utilizing SF6. However, DC ESI outperforms AC ESI for the analysis of caffeine, indicating that improvements in spectral quality may benefit certain compounds or classes of compounds, on an individual basis.

  10. Effect of ac on current-induced domain wall motion

    NASA Astrophysics Data System (ADS)

    Kim, W. J.; Lee, T. D.; Choa, S. H.; Seo, S. M.; Lee, K. J.

    2007-05-01

    Saitoh et al. [Nature (London) 432, 203 (2004)] have reported the experimental result showing the interplay of a transverse domain wall with an electrical ac of megahertz-range frequencies. They observed a single peak of resistance in the frequency range and interpreted it with a nonadiabatic spin torque. It was argued that an ac current can induce a micrometer-range displacement of domain wall. We reconstructed the experiment in micromagnetic simulations considering the local nonzero nonadiabatic spin torque. We could not observe either an explicit single peak in the frequency-dependent resistance or an eventual displacement of domain wall by use of an ac. It indicates the local nonadiabatic torque is inappropriate to explain the experimental results of ac-induced domain wall motion. Other approaches such as the nonlocal nonadiabatic spin torque may be needed.

  11. Modelling ac ripple currents in HTS coated conductors

    NASA Astrophysics Data System (ADS)

    Xu, Zhihan; Grilli, Francesco

    2015-10-01

    Dc transmission using high temperature superconducting (HTS) coated conductors (CCs) offers a promising solution to the globally growing demand for effective, reliable and economic transmission of green energy up to the gigawatt level over very long distances. The credible estimation of the losses and thereby the heat dissipation involved, where ac ripples (introduced in rectification/ac-dc conversion) are viewed as a potential source of notable contribution, is highly essential for the rational design of practical HTS dc transmission cables and corresponding cryogenic systems to fulfil this demand. Here we report a targeted modelling study into the ac losses in a HTS CC subject to dc and ac ripple currents simultaneously, by solving Maxwell’s equations using the finite element method (FEM) in the commercial software package COMSOL. It is observed that the instantaneous loss exhibits only one peak per cycle in the HTS CC subject to sinusoidal ripples, given that the amplitude of the ac ripples is smaller than approximately 20% of that of the dc current. This is a distinct contrast to the usual observation of two peaks per cycle in a HTS CC subject to ac currents only. The unique mechanism is also revealed, which is directly associated with the finding that, around any local minima of the applied ac ripples, the critical state of -J c is never reached at the edges of the HTS CC, as it should be according to the Bean model. When running further into the longer term, it is discovered that the ac ripple loss of the HTS CC in full-wave rectification decays monotonically, at a speed which is found to be insensitive to the frequency of the applied ripples within our targeted situations, to a relatively low level of approximately 1.38 × 10-4 W m-1 in around 1.7 s. Comparison between this level and other typical loss contributions in a HTS dc cable implies that ac ripple currents in HTS CCs should only be considered as a minor source of dissipation in superconducting dc

  12. Effects of alternating current stimulation on the healthy and diseased brain

    PubMed Central

    Abd Hamid, Aini Ismafairus; Gall, Carolin; Speck, Oliver; Antal, Andrea; Sabel, Bernhard A.

    2015-01-01

    Cognitive and neurological dysfunctions can severely impact a patient's daily activities. In addition to medical treatment, non-invasive transcranial alternating current stimulation (tACS) has been proposed as a therapeutic technique to improve the functional state of the brain. Although during the last years tACS was applied in numerous studies to improve motor, somatosensory, visual and higher order cognitive functions, our knowledge is still limited regarding the mechanisms as to which type of ACS can affect cortical functions and altered neuronal oscillations seem to be the key mechanism. Because alternating current send pulses to the brain at predetermined frequencies, the online- and after-effects of ACS strongly depend on the stimulation parameters so that “optimal” ACS paradigms could be achieved. This is of interest not only for neuroscience research but also for clinical practice. In this study, we summarize recent findings on ACS-effects under both normal conditions and in brain diseases. PMID:26578858

  13. An Alternating Current Electroosmotic Pump Based on Conical Nanopore Membranes.

    PubMed

    Wu, Xiaojian; Ramiah Rajasekaran, Pradeep; Martin, Charles R

    2016-04-26

    Electroosmotic flow (EOF) is used to pump solutions through microfluidic devices and capillary electrophoresis columns. We describe here an EOF pump based on membrane EOF rectification, an electrokinetic phenomenon we recently described. EOF rectification requires membranes with asymmetrically shaped pores, and conical pores in a polymeric membrane were used here. We show here that solution flow through the membrane can be achieved by applying a symmetrical sinusoidal voltage waveform across the membrane. This is possible because the alternating current (AC) carried by ions through the pore is rectified, and we previously showed that rectified currents yield EOF rectification. We have investigated the effect of both the magnitude and frequency of the voltage waveform on flow rate through the membrane, and we have measured the maximum operating pressure. Finally, we show that operating in AC mode offers potential advantages relative to conventional DC-mode EOF pumps. PMID:27046145

  14. Effects of Alternating Current Frequency and Permeation Enhancers upon Human Epidermal Membrane

    PubMed Central

    Xu, Qingfang; Kochambilli, Rajan P.; Song, Yang; Hao, Jinsong; Higuchi, William I.; Li, S. Kevin

    2009-01-01

    Previous studies have demonstrated the ability of AC iontophoresis to control skin resistance in different transdermal iontophoresis applications. The objectives of the present study were to (a) identify the alternating current (AC) frequency for the optimization of AC pore induction of human epidermal membrane (HEM) and (b) determine the effects of chemical permeation enhancers upon the extent of pore induction under AC conditions. Experiments with a synthetic membrane system were first conducted as the control. In these synthetic membrane experiments, the electrical resistance of the membrane remained essentially constant, suggesting constant electromobility of the background electrolyte ions under the AC conditions studied. In the HEM experiments, the electrical resistance data showed that higher applied voltages were required to induce the same extent of pore induction in HEM at AC frequency of 1 kHz compared with those at 30 Hz. Even higher voltages were needed at AC frequencies of 10 kHz and higher. AC frequency also influenced the recovery of HEM electrical resistance after AC iontophoresis application. An optimal AC frequency region for effective pore induction and least sensation was proposed. Permeation enhancers were shown to enhance pore induction in HEM during AC iontophoresis. The enhancers reversibly reduced the AC voltage required to sustain a constant state of pore induction in HEM during AC iontophoresis, consistent with the mechanism of lipid lamellae electroporation in the stratum corneum. PMID:19166921

  15. Experimental Study on Current Decay Characteristics of Persistent Current HTS Magnet by Alternating Magnetic Field

    NASA Astrophysics Data System (ADS)

    Park, Young Gun; Lee, Chang Young; Hwang, Young Jin; Lee, Woo Seung; Lee, Jiho; Jo, Hyun Chul; Chung, Yoon Do; Ko, Tae Kuk

    This paper deals with a current decay characteristics of a high temperature superconducting (HTS) magnet operated in persistent current mode (PCM). In superconducting synchronous machine applications such as linear synchronous motor (LSM), the superconducting coil is designed to operate in the PCM to obtain steady magnetic field with DC transport current. This superconducting magnet operates on a direct current, but it can be exposed to alternating magnetic field due to the armature winding. When the magnet is subjected to an external time-varying magnetic field, it is possible to result in a decay of the current in PCM system due to AC loss. In this research, a PCM system with armature coil which generates time-varying magnetic field was fabricated to verify current decay characteristics by external alternating magnetic field. The current decay rate was measured by using a hall sensor as functions of amplitude and frequency of armature coil.

  16. Fault current limiter and alternating current circuit breaker

    DOEpatents

    Boenig, H.J.

    1998-03-10

    A solid-state circuit breaker and current limiter are disclosed for a load served by an alternating current source having a source impedance, the solid-state circuit breaker and current limiter comprising a thyristor bridge interposed between the alternating current source and the load, the thyristor bridge having four thyristor legs and four nodes, with a first node connected to the alternating current source, and a second node connected to the load. A coil is connected from a third node to a fourth node, the coil having an impedance of a value calculated to limit the current flowing therethrough to a predetermined value. Control means are connected to the thyristor legs for limiting the alternating current flow to the load under fault conditions to a predetermined level, and for gating the thyristor bridge under fault conditions to quickly reduce alternating current flowing therethrough to zero and thereafter to maintain the thyristor bridge in an electrically open condition preventing the alternating current from flowing therethrough for a predetermined period of time. 9 figs.

  17. Fault current limiter and alternating current circuit breaker

    DOEpatents

    Boenig, Heinrich J.

    1998-01-01

    A solid-state circuit breaker and current limiter for a load served by an alternating current source having a source impedance, the solid-state circuit breaker and current limiter comprising a thyristor bridge interposed between the alternating current source and the load, the thyristor bridge having four thyristor legs and four nodes, with a first node connected to the alternating current source, and a second node connected to the load. A coil is connected from a third node to a fourth node, the coil having an impedance of a value calculated to limit the current flowing therethrough to a predetermined value. Control means are connected to the thyristor legs for limiting the alternating current flow to the load under fault conditions to a predetermined level, and for gating the thyristor bridge under fault conditions to quickly reduce alternating current flowing therethrough to zero and thereafter to maintain the thyristor bridge in an electrically open condition preventing the alternating current from flowing therethrough for a predetermined period of time.

  18. Depolarization of a piezoelectric film under an alternating current field

    NASA Astrophysics Data System (ADS)

    Kwok, K. W.; Cheung, M. K.; Chan, H. L. W.; Choy, C. L.

    2007-03-01

    In this article, we demonstrate that a sol-gel-derived niobium-doped lead zirconate titanate film can be depolarized by the application of alternating current (ac) fields of diminishing amplitude and we explain the phenomenon based on the concept of the Preisach model. The amplitude of the ac fields is decreased from 20 to 2 MV/m in ten steps. The observed piezoelectric coefficient of the film decreases after each ac field step. Depending on the initial polarization and the direction of the ac fields, the piezoelectric coefficient can decrease to a very small value indicating the complete depolarization of the film. Our results reveal the existence of a distribution of the switching fields in the microdomains (Preisach dipolar units), and that because of mutual interactions the magnitudes of the switch-up and switch-down fields for each microdomain are not necessarily the same. Our results also suggest that the sputter deposition of the top electrode can induce more "down-state" microdomains, thus giving rise to an initial polarization in the film. Because of interactions with other microdomains or other effects, part of these microdomains exhibit very high switching fields.

  19. Alternating-current relaxation of a rotating metallic particle

    NASA Astrophysics Data System (ADS)

    Guo-Xi, Nie; Wen-Jia, Tian; Ji-Ping, Huang; Guo-Qing, Gu

    2016-06-01

    Based on a first-principles approach, we establish an alternating-current (AC) relaxation theory for a rotating metallic particle with complex dielectric constant . Here is the real part, the conductivity, ω 0 the angular frequency of an AC electric field, and . Our theory yields an accurate interparticle force, which is in good agreement with the existing experiment. The agreement helps to show that the relaxations of two kinds of charges, namely, surface polarized charges (described by ) and free charges (corresponding to ), contribute to the unusually large reduction in the attracting interparticle force. This theory can be adopted to determine the relaxation time of dynamic particles in various fields. Project supported by the National Natural Science Foundation of China (Grant No. 11222544), the Fok Ying Tung Education Foundation (Grant No. 131008), the Program for New Century Excellent Talents in University, China (Grant No. NCET-12-0121), and the National Key Basic Research Program of China (Grant No. 2011CB922004).

  20. Input current shaped ac-to-dc converters

    NASA Technical Reports Server (NTRS)

    1985-01-01

    Input current shaping techniques for ac-to-dc converters were investigated. Input frequencies much higher than normal, up to 20 kHz were emphasized. Several methods of shaping the input current waveform in ac-to-dc converters were reviewed. The simplest method is the LC filter following the rectifier. The next simplest method is the resistor emulation approach in which the inductor size is determined by the converter switching frequency and not by the line input frequency. Other methods require complicated switch drive algorithms to construct the input current waveshape. For a high-frequency line input, on the order of 20 kHz, the simple LC cannot be discarded so peremptorily, since the inductor size can be compared with that for the resistor emulation method. In fact, since a dc regulator will normally be required after the filter anyway, the total component count is almost the same as for the resistor emulation method, in which the filter is effectively incorporated into the regulator.

  1. Input-current shaped ac to dc converters

    NASA Technical Reports Server (NTRS)

    1986-01-01

    The problem of achieving near unity power factor while supplying power to a dc load from a single phase ac source of power is examined. Power processors for this application must perform three functions: input current shaping, energy storage, and output voltage regulation. The methods available for performing each of these three functions are reviewed. Input current shaping methods are either active or passive, with the active methods divided into buck-like and boost-like techniques. In addition to large reactances, energy storage methods include resonant filters, active filters, and active storage schemes. Fast voltage regulation can be achieved by post regulation or by supplementing the current shaping topology with an extra switch. Some indications of which methods are best suited for particular applications concludes the discussion.

  2. Josephson junctions with alternating critical current density

    SciTech Connect

    Mints, R.G.; Kogan, V.G.

    1997-04-01

    The magnetic-field dependence of the critical current I{sub c}(H) is considered for a short Josephson junction with the critical current density j{sub c} alternating along the tunnel contact. Two model cases, periodic and randomly alternating j{sub c}, are treated in detail. Recent experimental data on I{sub c}(H) for grain-boundary Josephson junctions in YBa{sub 2}Cu{sub 3}O{sub x} are discussed. {copyright} {ital 1997} {ital The American Physical Society}

  3. Phase and Frequency-Dependent Effects of Transcranial Alternating Current Stimulation on Motor Cortical Excitability.

    PubMed

    Nakazono, Hisato; Ogata, Katsuya; Kuroda, Tsuyoshi; Tobimatsu, Shozo

    2016-01-01

    Transcranial alternating current stimulation (tACS) can entrain ongoing brain oscillations and modulate the motor system in a frequency-dependent manner. Recent animal studies have demonstrated that the phase of a sinusoidal current also has an important role in modulation of neuronal activity. However, the phase effects of tACS on the human motor system are largely unknown. Here, we systematically investigated the effects of tACS phase and frequency on the primary motor cortex (M1) by using motor evoked potentials (MEPs) with transcranial magnetic stimulation (TMS). First, we compared the phase effects (90°, 180°, 270° or 360°) of 10 and 20 Hz tACS on MEPs. The 20 Hz tACS significantly increased M1 excitability compared with the 10 Hz tACS at 90° phase only. Second, we studied the 90° phase effect on MEPs at different tACS frequencies (5, 10, 20 or 40 Hz). The 20 vs. 10 Hz difference was again observed, but the 90° phase in 5 and 40 Hz tACS did not influence M1 excitability. Third, the 90° phase effects of 10 and 20 Hz tACS were compared with sham stimulation. The 90° phase of 20 Hz tACS enhanced MEP amplitudes compared with sham stimulation, but there was no significant effect of 10 Hz tACS. Taken together, we assume that the differential 90° phase effects on 20 Hz and 10 Hz tACS can be attributed to the neural synchronization modulated by tACS. Our results further underline that phase and frequency are the important factors in the effects of tACS on M1 excitability.

  4. Phase and Frequency-Dependent Effects of Transcranial Alternating Current Stimulation on Motor Cortical Excitability.

    PubMed

    Nakazono, Hisato; Ogata, Katsuya; Kuroda, Tsuyoshi; Tobimatsu, Shozo

    2016-01-01

    Transcranial alternating current stimulation (tACS) can entrain ongoing brain oscillations and modulate the motor system in a frequency-dependent manner. Recent animal studies have demonstrated that the phase of a sinusoidal current also has an important role in modulation of neuronal activity. However, the phase effects of tACS on the human motor system are largely unknown. Here, we systematically investigated the effects of tACS phase and frequency on the primary motor cortex (M1) by using motor evoked potentials (MEPs) with transcranial magnetic stimulation (TMS). First, we compared the phase effects (90°, 180°, 270° or 360°) of 10 and 20 Hz tACS on MEPs. The 20 Hz tACS significantly increased M1 excitability compared with the 10 Hz tACS at 90° phase only. Second, we studied the 90° phase effect on MEPs at different tACS frequencies (5, 10, 20 or 40 Hz). The 20 vs. 10 Hz difference was again observed, but the 90° phase in 5 and 40 Hz tACS did not influence M1 excitability. Third, the 90° phase effects of 10 and 20 Hz tACS were compared with sham stimulation. The 90° phase of 20 Hz tACS enhanced MEP amplitudes compared with sham stimulation, but there was no significant effect of 10 Hz tACS. Taken together, we assume that the differential 90° phase effects on 20 Hz and 10 Hz tACS can be attributed to the neural synchronization modulated by tACS. Our results further underline that phase and frequency are the important factors in the effects of tACS on M1 excitability. PMID:27607431

  5. Phase and Frequency-Dependent Effects of Transcranial Alternating Current Stimulation on Motor Cortical Excitability

    PubMed Central

    Kuroda, Tsuyoshi; Tobimatsu, Shozo

    2016-01-01

    Transcranial alternating current stimulation (tACS) can entrain ongoing brain oscillations and modulate the motor system in a frequency-dependent manner. Recent animal studies have demonstrated that the phase of a sinusoidal current also has an important role in modulation of neuronal activity. However, the phase effects of tACS on the human motor system are largely unknown. Here, we systematically investigated the effects of tACS phase and frequency on the primary motor cortex (M1) by using motor evoked potentials (MEPs) with transcranial magnetic stimulation (TMS). First, we compared the phase effects (90°, 180°, 270° or 360°) of 10 and 20 Hz tACS on MEPs. The 20 Hz tACS significantly increased M1 excitability compared with the 10 Hz tACS at 90° phase only. Second, we studied the 90° phase effect on MEPs at different tACS frequencies (5, 10, 20 or 40 Hz). The 20 vs. 10 Hz difference was again observed, but the 90° phase in 5 and 40 Hz tACS did not influence M1 excitability. Third, the 90° phase effects of 10 and 20 Hz tACS were compared with sham stimulation. The 90° phase of 20 Hz tACS enhanced MEP amplitudes compared with sham stimulation, but there was no significant effect of 10 Hz tACS. Taken together, we assume that the differential 90° phase effects on 20 Hz and 10 Hz tACS can be attributed to the neural synchronization modulated by tACS. Our results further underline that phase and frequency are the important factors in the effects of tACS on M1 excitability. PMID:27607431

  6. Eddy Current Rail Inspection Using AC Bridge Techniques

    PubMed Central

    Liu, Ze; Koffman, Andrew D; Waltrip, Bryan C; Wang, Yicheng

    2013-01-01

    AC bridge techniques commonly used for precision impedance measurements have been adapted to develop an eddy current sensor for rail defect detection. By using two detection coils instead of just one as in a conventional sensor, we can balance out the large baseline signals corresponding to a normal rail. We have significantly enhanced the detection sensitivity of the eddy current method by detecting and demodulating the differential signal of the two coils induced by rail defects, using a digital lock-in amplifier algorithm. We have also explored compensating for the lift-off effect of the eddy current sensor due to vibrations by using the summing signal of the detection coils to measure the lift-off distance. The dominant component of the summing signal is a constant resulting from direct coupling from the excitation coil, which can be experimentally determined. The remainder of the summing signal, which decreases as the lift-off distance increases, is induced by the secondary eddy current. This dependence on the lift-off distance is used to calibrate the differential signal, allowing for a more accurate characterization of the defects. Simulated experiments on a sample rail have been performed using a computer controlled X-Y moving table with the X-axis mimicking the train’s motion and the Y-axis mimicking the train’s vibrational bumping. Experimental results demonstrate the effectiveness of the new detection method. PMID:26401427

  7. Finite element analysis of current flowing patterns and AC loss in the multifilament strand

    NASA Astrophysics Data System (ADS)

    Ta, Wurui; Li, Yingxu; Gao, Yuanwen

    2013-12-01

    Intrinsic current flow and field distribution scheme under the imposed low current injection and the applied weak field is meaningful to interpret Ic degradation and AC loss in a strand that performs as a normal composite conductor. A 2D finite element (FE) transport model is built in COMSOL to identify the various transverse resistance components and reveal the interrelation among them. Then the transverse resistivity components are taken as the basic electrical components in a 3D composite strand model. The 3D model follows the realistic trajectories of twisted filaments in strand composite and experimental material properties. To address the potential/current map in the stationary transport, the FE model is thoroughly analyzed for the short-sample and long-sample strand, imposed by two in-plane steady current injections and a potential boundary condition at one strand end with the other end grounded, respectively. The results show that the short-sample longitudinal current is uniform with little resistivity loss, and flows from the positive source and converges to the negative one in the cross section with different paths and current proportions between filaments and matrix. However, for the long-sample, there is a serious reduction in electric potential along the strand axis and the currents mostly concentrate on filaments. The time-varying problem is also implemented by computing AC loss induced by a relatively far-away alternating line current. It is discussed where appropriate that the effect of the twist pitch and contact resistivity on the pattern and magnitude of the current flow and AC loss.

  8. Note: High resolution alternating current/direct current Harman technique

    NASA Astrophysics Data System (ADS)

    Chavez, R.; Becker, A.; Bartel, M.; Kessler, V.; Schierning, G.; Schmechel, R.

    2013-10-01

    This note describes the construction and engineering of a high precision Harman set-up for metrology of the thermoelectric figure of merit (ZT) of modules and materials based on steady state AC and DC measurements. The Harman technique presented in this article has a resolution of milli-ZT and it does not employ lock-in amplifiers or AC bridges; rather, the technique is developed to avoid typical complications experienced in AC Harman systems. By one-time reference measurements the best operation point for the system is chosen, minimizing the effects of capacitive loads due to AC signals.

  9. Alternative Ac/Ds transposition induces major chromosomal rearrangements in maize.

    PubMed

    Zhang, Jianbo; Yu, Chuanhe; Pulletikurti, Vinay; Lamb, Jonathan; Danilova, Tatiana; Weber, David F; Birchler, James; Peterson, Thomas

    2009-03-15

    Barbara McClintock reported that the Ac/Ds transposable element system can generate major chromosomal rearrangements (MCRs), but the underlying mechanism has not been determined. Here, we identified a series of chromosome rearrangements derived from maize lines containing pairs of closely linked Ac transposable element termini. Molecular and cytogenetic analyses showed that the MCRs in these lines comprised 17 reciprocal translocations and two large inversions. The breakpoints of all 19 MCRs are delineated by Ac termini and characteristic 8-base-pair target site duplications, indicating that the MCRs were generated by precise transposition reactions involving the Ac termini of two closely linked elements. This alternative transposition mechanism may have contributed to chromosome evolution and may also occur during V(D)J recombination resulting in oncogenic translocations. PMID:19299561

  10. Alternative Ac/Ds transposition induces major chromosomal rearrangements in maize.

    PubMed

    Zhang, Jianbo; Yu, Chuanhe; Pulletikurti, Vinay; Lamb, Jonathan; Danilova, Tatiana; Weber, David F; Birchler, James; Peterson, Thomas

    2009-03-15

    Barbara McClintock reported that the Ac/Ds transposable element system can generate major chromosomal rearrangements (MCRs), but the underlying mechanism has not been determined. Here, we identified a series of chromosome rearrangements derived from maize lines containing pairs of closely linked Ac transposable element termini. Molecular and cytogenetic analyses showed that the MCRs in these lines comprised 17 reciprocal translocations and two large inversions. The breakpoints of all 19 MCRs are delineated by Ac termini and characteristic 8-base-pair target site duplications, indicating that the MCRs were generated by precise transposition reactions involving the Ac termini of two closely linked elements. This alternative transposition mechanism may have contributed to chromosome evolution and may also occur during V(D)J recombination resulting in oncogenic translocations.

  11. Electromagnetic stirring with alternating current during electroslag remelting

    NASA Astrophysics Data System (ADS)

    Mitchell, Alec; Hernandez-Morales, Bernardo

    1990-08-01

    An alternating current (AC)-operated electromagnetic stirring (EMS) device, using line frequency, was designed and built to operate on a laboratory electroslag remelting (ESR) furnace for 150-mm-diameter ingots. Laboratory-scale experiments were conducted employing both 4340 alloy steel and INCONEL 718 alloy as electrode material. The initiation of stirring is accompanied by a thin strip of segregated material and favors the formation of spot segregation. Changes produced in the fluid flow conditions in the liquid pool ahead of the solidification front result in a transition from a highly directional columnar to an unoriented, branched structure. Except for small pockets of segregated liquid, the flow of molten metal does not penetrate into the mushy zone. Both electrode material and molten metal pool shape play an important role on the extent of promoting an equiaxed structure.

  12. [Transcranial alternating current stimulation. Entrainment and function control of neuronal networks].

    PubMed

    Vosskuhl, J; Strüber, D; Herrmann, C S

    2015-12-01

    Transcranial alternating current stimulation (tACS) is a new technique for the modulation of oscillatory brain activity as measured in the electroencephalogram (EEG). In contrast to well-established stimulation techniques, such as transcranial direct current stimulation and transcranial magnetic stimulation, tACS applies a sinusoidal alternating current at a specific frequency. This enables the modulation of the amplitude and frequency of endogenous brain oscillations as well as related cognitive processes. Therefore, the use of tACS has the possibility to evaluate well-known correlations between brain oscillations and cognitive processes in terms of causality. Such causal relationships have been documented in numerous neurocognitive studies on sensory, motor and perceptual processes; however, the clinical application of tACS is still in its infancy. In principle, any pathology that can reliably be connected with brain oscillations of a defined frequency is treatable. A current main focus of clinical research is on symptoms of Parkinson's disease and to a lesser degree, tinnitus. For an effective application of tACS it is important to choose the electrode positions as well as the frequency, intensity and duration of the stimulation in a theory-based and symptom-related manner. A successful therapeutic intervention requires the persistence of the tACS effect after stimulation has ceased. A mechanism that offers not only an explanation to the origin of persistent tACS effects but is also of high therapeutic benefit is neural plasticity. Therefore, one current focus of research aims at a better understanding of tACS after effects. PMID:26440521

  13. Transcranial alternating current stimulation modulates spontaneous low frequency fluctuations as measured with fMRI.

    PubMed

    Cabral-Calderin, Yuranny; Williams, Kathleen A; Opitz, Alexander; Dechent, Peter; Wilke, Melanie

    2016-11-01

    Transcranial alternating current stimulation (tACS) is a promising tool for modulating brain oscillations. Combining tACS with functional magnetic resonance imaging (fMRI), we recently showed that tACS applied over the occipital cortex did not exert its strongest effect on regions below the electrodes, but mainly on more distant fronto-parietal regions. Theoretically, this effect could be explained by tACS-induced modulation of functional connectivity between directly stimulated areas and more distant but anatomically and functionally connected regions. In the present study, we aimed to characterize the effect of tACS on low frequency fMRI signal fluctuations. We employed simultaneous fMRI-tACS in 20 subjects during resting state (eyes open with central fixation for ~8min). Subjects received tACS at different frequencies (10, 16, 40Hz) and with different electrode montages (Cz-Oz, P5-P6) previously used in behavioral studies. Electric field simulations showed that tACS over Cz-Oz directly stimulates occipital cortex, while tACS over P5-P6 primarily targets parietal cortices. Group-level simulation-based functional connectivity maps for Cz-Oz and P5-P6 resembled the visual and fronto-parietal control resting-state networks, respectively. The effects of tACS were frequency and partly electrode montage dependent. In regions where frequency-dependent effects of tACS were observed, 10 and 40Hz tACS generally induced opposite effects. Most tACS effects on functional connectivity were observed between, as opposed to within, resting-state networks. The left fronto-parietal control network showed the most extensive frequency-dependent modulation in functional connectivity, mainly with occipito-parietal regions, where 10Hz tACS increased and 40Hz tACS decreased correlation values. Taken together, our results show that tACS modulates local spontaneous low frequency fluctuations and their correlations with more distant regions, which should be taken into account when

  14. Effect of an alternating current electric field on Co(OH)2 periodic precipitation

    NASA Astrophysics Data System (ADS)

    Karam, Tony; Sultan, Rabih

    2013-02-01

    The present paper studies the effect of an alternating current (AC) electric field on Co(OH)2 Liesegang patterns. In the presence of an AC electric field, the band spacing increases with spacing number, but reaches a plateau at large spacing (or band) numbers. The band spacing increases with applied AC voltage, but to a much lesser extent than the effect of a DC electric field under the same applied voltage [see R. Sultan, R. Halabieh, Chem. Phys. Lett. 332 (2000) 331][1]. At low enough applied voltage, the band spacing increases with frequency. At higher voltages, the band spacing becomes independent of the field frequency. The effect of concentration of the inner electrolyte (Co2+), exactly opposes that observed under DC electric field; i.e., the band spacing decreases with increasing concentration. The dynamics were shown to be governed by a competitive scenario between the diffusion gradient and the alternating current electric field factor.

  15. Friends, not foes: Magnetoencephalography as a tool to uncover brain dynamics during transcranial alternating current stimulation.

    PubMed

    Neuling, Toralf; Ruhnau, Philipp; Fuscà, Marco; Demarchi, Gianpaolo; Herrmann, Christoph S; Weisz, Nathan

    2015-09-01

    Brain oscillations are supposedly crucial for normal cognitive functioning and alterations are associated with cognitive dysfunctions. To demonstrate their causal role on behavior, entrainment approaches in particular aim at driving endogenous oscillations via rhythmic stimulation. Within this context, transcranial electrical stimulation, especially transcranial alternating current stimulation (tACS), has received renewed attention. This is likely due to the possibility of defining oscillatory stimulation properties precisely. Also, measurements comparing pre-tACS with post-tACS electroencephalography (EEG) have shown impressive modulations. However, the period during tACS has remained a blackbox until now, due to the enormous stimulation artifact. By means of application of beamforming to magnetoencephalography (MEG) data, we successfully recovered modulations of the amplitude of brain oscillations during weak and strong tACS. Additionally, we demonstrate that also evoked responses to visual and auditory stimuli can be recovered during tACS. The main contribution of the present study is to provide critical evidence that during ongoing tACS, subtle modulations of oscillatory brain activity can be reconstructed even at the stimulation frequency. Future tACS experiments will be able to deliver direct physiological insights in order to further the understanding of the contribution of brain oscillations to cognition and behavior.

  16. Alternative splicing of the maize Ac transposase transcript in transgenic sugar beet (Beta vulgaris L.).

    PubMed

    Lisson, Ralph; Hellert, Jan; Ringleb, Malte; Machens, Fabian; Kraus, Josef; Hehl, Reinhard

    2010-09-01

    The maize Activator/Dissociation (Ac/Ds) transposable element system was introduced into sugar beet. The autonomous Ac and non-autonomous Ds element excise from the T-DNA vector and integrate at novel positions in the sugar beet genome. Ac and Ds excisions generate footprints in the donor T-DNA that support the hairpin model for transposon excision. Two complete integration events into genomic sugar beet DNA were obtained by IPCR. Integration of Ac leads to an eight bp duplication, while integration of Ds in a homologue of a sugar beet flowering locus gene did not induce a duplication. The molecular structure of the target site indicates Ds integration into a double strand break. Analyses of transposase transcription using RT-PCR revealed low amounts of alternatively spliced mRNAs. The fourth intron of the transposase was found to be partially misspliced. Four different splice products were identified. In addition, the second and third exon were found to harbour two and three novel introns, respectively. These utilize each the same splice donor but several alternative splice acceptor sites. Using the SplicePredictor online tool, one of the two introns within exon two is predicted to be efficiently spliced in maize. Most interestingly, splicing of this intron together with the four major introns of Ac would generate a transposase that lacks the DNA binding domain and two of its three nuclear localization signals, but still harbours the dimerization domain.

  17. Alternative splicing of the maize Ac transposase transcript in transgenic sugar beet (Beta vulgaris L.)

    PubMed Central

    Lisson, Ralph; Hellert, Jan; Ringleb, Malte; Machens, Fabian; Kraus, Josef

    2010-01-01

    The maize Activator/Dissociation (Ac/Ds) transposable element system was introduced into sugar beet. The autonomous Ac and non-autonomous Ds element excise from the T-DNA vector and integrate at novel positions in the sugar beet genome. Ac and Ds excisions generate footprints in the donor T-DNA that support the hairpin model for transposon excision. Two complete integration events into genomic sugar beet DNA were obtained by IPCR. Integration of Ac leads to an eight bp duplication, while integration of Ds in a homologue of a sugar beet flowering locus gene did not induce a duplication. The molecular structure of the target site indicates Ds integration into a double strand break. Analyses of transposase transcription using RT–PCR revealed low amounts of alternatively spliced mRNAs. The fourth intron of the transposase was found to be partially misspliced. Four different splice products were identified. In addition, the second and third exon were found to harbour two and three novel introns, respectively. These utilize each the same splice donor but several alternative splice acceptor sites. Using the SplicePredictor online tool, one of the two introns within exon two is predicted to be efficiently spliced in maize. Most interestingly, splicing of this intron together with the four major introns of Ac would generate a transposase that lacks the DNA binding domain and two of its three nuclear localization signals, but still harbours the dimerization domain. PMID:20512402

  18. Alternative splicing of the maize Ac transposase transcript in transgenic sugar beet (Beta vulgaris L.).

    PubMed

    Lisson, Ralph; Hellert, Jan; Ringleb, Malte; Machens, Fabian; Kraus, Josef; Hehl, Reinhard

    2010-09-01

    The maize Activator/Dissociation (Ac/Ds) transposable element system was introduced into sugar beet. The autonomous Ac and non-autonomous Ds element excise from the T-DNA vector and integrate at novel positions in the sugar beet genome. Ac and Ds excisions generate footprints in the donor T-DNA that support the hairpin model for transposon excision. Two complete integration events into genomic sugar beet DNA were obtained by IPCR. Integration of Ac leads to an eight bp duplication, while integration of Ds in a homologue of a sugar beet flowering locus gene did not induce a duplication. The molecular structure of the target site indicates Ds integration into a double strand break. Analyses of transposase transcription using RT-PCR revealed low amounts of alternatively spliced mRNAs. The fourth intron of the transposase was found to be partially misspliced. Four different splice products were identified. In addition, the second and third exon were found to harbour two and three novel introns, respectively. These utilize each the same splice donor but several alternative splice acceptor sites. Using the SplicePredictor online tool, one of the two introns within exon two is predicted to be efficiently spliced in maize. Most interestingly, splicing of this intron together with the four major introns of Ac would generate a transposase that lacks the DNA binding domain and two of its three nuclear localization signals, but still harbours the dimerization domain. PMID:20512402

  19. Investigation of Si(001) stable surfaces in alternating current heating

    NASA Astrophysics Data System (ADS)

    Doi, T.; Koguchi, M.

    2016-11-01

    The topography of a Si(001) vicinal surface is investigated using reflection electron microscopy (REM) during alternating current (AC) heating of the surface in ultra-high vacuum. The normal direction of the surface is slightly tilted from the [001] direction at θx or θy on the x or y axis (they are orthogonal <110> directions in the Si(001) surface), and the average widths of the terraces (a or b in x or y axis) are determined by θx or θy; the direction perpendicular to the incidence electron beam on the surface is selected as the x (horizontal) axis in each REM image. Alternating current heating changes each initial surface from stable to double-domain (DD), in which 2 × 1 and 1 × 2 terraces are arranged regularly with approximately equal width, at its transition temperature Tc; the dimer rows are parallel to the x or y axis in the 1 × 2 or 2 × 1 terraces. There are two types of stable surfaces in the vicinal surface. At temperatures below its Tc, the surface with horizontally (vertically) long terraces, where b < a (b > a), changes to a 2 × 1 (1 × 2) surface with wide 2 × 1 (1 × 2) and narrow 1 × 2 (2 × 1) terraces. The terrace, the short side of which is parallel to its dimer row direction, grows to create a stable surface by thermal diffusion of Si atoms at temperatures below Tc. During AC heating, thermal diffusion plays a key role in analyzing the kinetics of the atoms on the surface because the thermal effect acts as the driving force for the atoms that have not yet evaporated from the surface. Then, by evaporating atoms from the vicinal surface, AC heating creates a DD surface at temperatures between its Tc and 1100 °C and a rugged surface consisting of small 2 × 1 and 1 × 2 terraces at temperatures above 1100 °C.

  20. Studying Effects of Transcranial Alternating Current Stimulation on Hearing and Auditory Scene Analysis.

    PubMed

    Riecke, Lars

    2016-01-01

    Recent studies have shown that perceptual detection of near-threshold auditory events may depend on the relative timing of the event and ongoing brain oscillations. Furthermore, transcranial alternating current stimulation (tACS), a non-invasive and silent brain stimulation technique, can entrain cortical alpha oscillations and thereby provide some experimental control over their timing. The present research investigates the potential of delta/theta-tACS to modulate hearing and auditory scene analysis. Detection of near-threshold auditory stimuli, which are modulated at 4 Hz and presented at various moments (phase lags) during ongoing tACS (two synchronous 4-Hz alternating currents applied transcranially to the two cerebral hemispheres), is measured in silence or in a masker. Results indicate that performance fluctuates as a function of phase lag and these fluctuations can be explained best by a sinusoid at the tACS frequency. This suggests that tACS may amplify/attenuate sounds that are temporally coherent/anticoherent with tACS-entrained cortical oscillations. PMID:27080678

  1. Method and apparatus for reducing the harmonic currents in alternating-current distribution networks

    DOEpatents

    Beverly, L.H.; Hance, R.D.; Kristalinski, A.L.; Visser, A.T.

    1996-11-19

    An improved apparatus and method reduce the harmonic content of AC line and neutral line currents in polyphase AC source distribution networks. The apparatus and method employ a polyphase Zig-Zag transformer connected between the AC source distribution network and a load. The apparatus and method also employs a mechanism for increasing the source neutral impedance of the AC source distribution network. This mechanism can consist of a choke installed in the neutral line between the AC source and the Zig-Zag transformer. 23 figs.

  2. Method and apparatus for reducing the harmonic currents in alternating-current distribution networks

    DOEpatents

    Beverly, Leon H.; Hance, Richard D.; Kristalinski, Alexandr L.; Visser, Age T.

    1996-01-01

    An improved apparatus and method reduce the harmonic content of AC line and neutral line currents in polyphase AC source distribution networks. The apparatus and method employ a polyphase Zig-Zag transformer connected between the AC source distribution network and a load. The apparatus and method also employs a mechanism for increasing the source neutral impedance of the AC source distribution network. This mechanism can consist of a choke installed in the neutral line between the AC source and the Zig-Zag transformer.

  3. Direct Current Contamination of Kilohertz Frequency Alternating Current Waveforms

    PubMed Central

    Franke, Manfred; Bhadra, Niloy; Bhadra, Narendra; Kilgore, Kevin

    2014-01-01

    Kilohertz Frequency Alternating Current (KHFAC) waveforms are being evaluated in a variety of physiological settings because of their potential to modulate neural activity uniquely when compared to frequencies in the sub-kilohertz range. However, the use of waveforms in this frequency range presents some unique challenges regarding the generator output. In this study we explored the possibility of undesirable contamination of the KHFAC waveforms by direct current (DC). We evaluated current- and voltage-controlled KHFAC waveform generators in configurations that included a capacitive coupling between generator and electrode, a resistive coupling and combinations of capacitive with inductive coupling. Our results demonstrate that both voltage- and current-controlled signal generators can unintentionally add DC-contamination to a KHFAC signal, and that capacitive coupling is not always sufficient to eliminate this contamination. We furthermore demonstrated that high value inductors, placed in parallel with the electrode, can be effective in eliminating DC-contamination irrespective of the type of stimulator, reducing the DC contamination to less than 1 μA. This study highlights the importance of carefully designing the electronic setup used in KHFAC studies and suggests specific testing that should be performed and reported in all studies that assess the neural response to KHFAC waveforms. PMID:24820914

  4. Ac losses for the self field of an ac transport current with a dc transport current offset in high {Tc} superconducting magnet coils for MagLev application

    SciTech Connect

    Koosh, V.F.

    1993-10-01

    Although much research has been conducted concerning the losses of high-{Tc} superconductors, very little has concentrated on the self-field losses in an actual magnet arrangement. The coils studied in this work were designed for use as actual magnets in an industrial application. Self field loss measurements were made upon tape-wound 2223 superconducting helix coils. The self-field losses were produced by an AC transport current with a DC transport current offset. Losses were taken for single, double and triple tape windings, giving essentially monofilament, dual, and three filament cases. The losses measured here were varied over a range of AC current values for several different DC values, and over a range of frequencies. The currents were all AC sinusoids with a DC offset. All measurements were made at T = 77K.

  5. Transcranial alternating current stimulation affects the BOLD signal in a frequency and task‐dependent manner

    PubMed Central

    Cabral‐Calderin, Yuranny; Anne Weinrich, Christiane; Schmidt‐Samoa, Carsten; Poland, Eva; Dechent, Peter; Bähr, Mathias

    2015-01-01

    Abstract Transcranial alternating current stimulation (tACS) has emerged as a promising tool for manipulating ongoing brain oscillations. While previous studies demonstrated frequency‐specific effects of tACS on diverse cognitive functions, its effect on neural activity remains poorly understood. Here we asked how tACS modulates regional fMRI blood oxygenation level dependent (BOLD) signal as a function of frequency, current strength, and task condition. TACS was applied over the posterior cortex of healthy human subjects while the BOLD signal was measured during rest or task conditions (visual perception, passive video viewing and motor task). TACS was applied in a blockwise manner at different frequencies (10, 16, 60 and 80 Hz). The strongest tACS effects on BOLD activity were observed with stimulation at alpha (10 Hz) and beta (16 Hz) frequency bands, while effects of tACS at the gamma range were rather modest. Specifically, we found that tACS at 16 Hz induced BOLD activity increase in fronto‐parietal areas. Overall, tACS effects varied as a function of frequency and task, and were predominantly seen in regions that were not activated by the task. Also, the modulated regions were poorly predicted by current density modeling studies. Taken together, our results suggest that tACS does not necessarily exert its strongest effects in regions below the electrodes and that region specificity might be achieved with tACS due to varying susceptibility of brain regions to entrain to a given frequency. Hum Brain Mapp 37:94–121, 2016. © 2015 The Authors. Human Brain Mapping Published by Wiley Periodicals, Inc PMID:26503692

  6. n value and Jc distribution dependence of AC transport current losses in HTS conductors

    NASA Astrophysics Data System (ADS)

    Ogawa, Jun; Sawai, Yusuke; Nakayama, Haruki; Tsukamoto, Osami; Miyagi, Daisuke

    2004-01-01

    Compared with LTS materials, HTS materials have some peculiarities affecting AC loss characteristics of the conductors. We measured the AC transport current losses in YBCO thin film coated conductors and a Bi2223/Ag sheathed tape. Comparing the measured data with analytical calculations, the dependence of the AC transport current losses on the n value and critical current density distributions are studied. It is shown that, considering the n values and Jc distributions, the peculiarities in the HTS materials can be taken into consideration and the transport current losses in HTS conductors can be calculated by the same analytical method used for LTS.

  7. Targeting the neurophysiology of cognitive systems with transcranial alternating current stimulation.

    PubMed

    Fröhlich, Flavio; Sellers, Kristin K; Cordle, Asa L

    2015-02-01

    Cognitive impairment represents one of the most debilitating and most difficult symptom to treat of many psychiatric illnesses. Human neurophysiology studies have suggested that specific pathologies of cortical network activity correlate with cognitive impairment. However, we lack demonstration of causal relationships between specific network activity patterns and cognitive capabilities and treatment modalities that directly target impaired network dynamics of cognition. Transcranial alternating current stimulation (tACS), a novel non-invasive brain stimulation approach, may provide a crucial tool to tackle these challenges. Here, we propose that tACS can be used to elucidate the causal role of cortical synchronization in cognition and, eventually, to enhance pathologically weakened synchrony that may underlie cognitive deficits. To accelerate such development of tACS as a treatment for cognitive deficits, we discuss studies on tACS and cognition performed in healthy participants, according to the Research Domain Criteria of the National Institute of Mental Health.

  8. Nonlinear alternating current conduction in polycrystalline manganites

    NASA Astrophysics Data System (ADS)

    Ghosh, T. N.; Nandi, U. N.; Jana, D.; Dey, K.; Giri, S.

    2014-06-01

    The real part of ac conductance Σ(T, f) of yttrium-doped mixed-valent polycrystalline manganite systems La1-x -yYyCaxMnO3 with x = 0.33 and 0.05 and y = 0.07 and iron doped LaMn1-xFexO3 with x = 0.15 is measured as a function of frequency f by varying zero-frequency Ohmic conductance Σ0 by T. The former shows a metal-insulator transition, whereas the latter exhibits insulating character throughout the measured temperature range. At a fixed temperature T, Σ(T, f) remains almost constant to the value Σ0 up to a certain frequency, known as the onset frequency fc and increases from Σ0 as frequency is increased from fc. Scaled appropriately, the data for Σ(T, f) at different T fall on the same universal curve, indicating the existence of a general scaling formalism for the ac conductance. fc scales with Σ0 as fc˜Σ0xf, where xf is the nonlinearity exponent characterising the onset. With the help of data for ac conduction, it is shown that xf is very much phase sensitive and can be used to characterize the different phases in a manganite system originated due to change in temperature or disorder. Scaling theories and existing theoretical models are used to analyze the results of ac conduction and the nonlinearity exponent xf.

  9. Eyes wide shut: Transcranial alternating current stimulation drives alpha rhythm in a state dependent manner

    PubMed Central

    Ruhnau, Philipp; Neuling, Toralf; Fuscá, Marco; Herrmann, Christoph S.; Demarchi, Gianpaolo; Weisz, Nathan

    2016-01-01

    Transcranial alternating current stimulation (tACS) is used to modulate brain oscillations to measure changes in cognitive function. It is only since recently that brain activity in human subjects during tACS can be investigated. The present study aims to investigate the phase relationship between the external tACS signal and concurrent brain activity. Subjects were stimulated with tACS at individual alpha frequency during eyes open and eyes closed resting states. Electrodes were placed at Cz and Oz, which should affect parieto-occipital areas most strongly. Source space magnetoencephalography (MEG) data were used to estimate phase coherence between tACS and brain activity. Phase coherence was significantly increased in areas in the occipital pole in eyes open resting state only. The lag between tACS and brain responses showed considerable inter-individual variability. In conclusion, tACS at individual alpha frequency entrains brain activity in visual cortices. Interestingly, this effect is state dependent and is clearly observed with eyes open but only to a lesser extent with eyes closed. PMID:27252047

  10. Effects of Transcranial Alternating Current Stimulation on Cognitive Functions in Healthy Young and Older Adults

    PubMed Central

    Antonenko, Daria; Faxel, Miriam; Grittner, Ulrike; Lavidor, Michal; Flöel, Agnes

    2016-01-01

    Recently, transcranial alternating current stimulation (tACS) has emerged as a tool to enhance human cognitive processes. Here, we provide a brief summary of the rationale behind tACS-induced effects on task-relevant brain oscillations and associated cognitive functions and review previous studies in young subjects that have applied tACS in cognitive paradigms. Additionally, we present pilot data where we administered theta-tACS (6 Hz) over the temporoparietal cortex and a supraorbital reference for 20 min during implicit language learning in healthy young (mean/SD age: 22/2) and older (mean/SD age: 66/4) adults, in a sham-controlled crossover design. Linear mixed models revealed significantly increased retrieval accuracy following tACS-accompanied associative learning, after controlling for session order and learning success. These data provide the first implementation of tACS during cognitive performance in older adults and support recent studies suggesting that tACS in the theta frequency range may serve as a tool to enhance cognition, possibly through direct modulation of task-relevant brain oscillations. So far, studies have been heterogeneous in their designs, leaving a number of issues to be addressed in future research, including the setup of electrodes and optimal stimulation frequencies to be employed, as well as the interaction with age and underlying brain pathologies in specific patient populations. PMID:27298740

  11. Nonlinear alternating current conduction in polycrystalline manganites

    SciTech Connect

    Ghosh, T. N.; Nandi, U. N.; Jana, D.; Dey, K.; Giri, S.

    2014-06-28

    The real part of ac conductance Σ(T, f) of yttrium-doped mixed-valent polycrystalline manganite systems La{sub 1−x−y}Y{sub y}Ca{sub x}MnO{sub 3} with x = 0.33 and 0.05 and y = 0.07 and iron doped LaMn{sub 1−x}Fe{sub x}O{sub 3} with x = 0.15 is measured as a function of frequency f by varying zero-frequency Ohmic conductance Σ{sub 0} by T. The former shows a metal-insulator transition, whereas the latter exhibits insulating character throughout the measured temperature range. At a fixed temperature T, Σ(T, f) remains almost constant to the value Σ{sub 0} up to a certain frequency, known as the onset frequency f{sub c} and increases from Σ{sub 0} as frequency is increased from f{sub c}. Scaled appropriately, the data for Σ(T, f) at different T fall on the same universal curve, indicating the existence of a general scaling formalism for the ac conductance. f{sub c} scales with Σ{sub 0} as f{sub c}∼Σ{sub 0}{sup x{sub f}}, where x{sub f} is the nonlinearity exponent characterising the onset. With the help of data for ac conduction, it is shown that x{sub f} is very much phase sensitive and can be used to characterize the different phases in a manganite system originated due to change in temperature or disorder. Scaling theories and existing theoretical models are used to analyze the results of ac conduction and the nonlinearity exponent x{sub f}.

  12. Preparation of scanning tunneling microscopy tips using pulsed alternating current etching

    SciTech Connect

    Valencia, Victor A.; Thaker, Avesh A.; Derouin, Jonathan; Valencia, Damian N.; Farber, Rachael G.; Gebel, Dana A.; Killelea, Daniel R.

    2015-03-15

    An electrochemical method using pulsed alternating current etching (PACE) to produce atomically sharp scanning tunneling microscopy (STM) tips is presented. An Arduino Uno microcontroller was used to control the number and duration of the alternating current (AC) pulses, allowing for ready optimization of the procedures for both Pt:Ir and W tips using a single apparatus. W tips prepared using constant and pulsed AC power were compared. Tips fashioned using PACE were sharper than those etched with continuous AC power alone. Pt:Ir tips were prepared with an initial coarse etching stage using continuous AC power followed by fine etching using PACE. The number and potential of the finishing AC pulses was varied and scanning electron microscope imaging was used to compare the results. Finally, tip quality using the optimized procedures was verified by UHV-STM imaging. With PACE, at least 70% of the W tips and 80% of the Pt:Ir tips were of sufficiently high quality to obtain atomically resolved images of HOPG or Ni(111)

  13. The development of monolithic alternating current light-emitting diode

    NASA Astrophysics Data System (ADS)

    Yeh, Wen-Yung; Yen, Hsi-Hsuan; Chan, Yi-Jen

    2011-02-01

    The monolithic alternating current light emitting diode (ACLED) has been revealed for several years and was regarded as a potential device for solid state lighting. In this study, we will discuss the characteristics, development status, future challenges, and ITRI's development strategy about ACLED, especially focusing on the development progress of the monolithic GaN-based Schottky barrier diodes integrated ACLED (SBD-ACLED). The SBD-ACLED design can not only improve the chip area utilization ratio but also provide much higher reverse breakdown voltage by integrating four SBDs with the micro-LEDs array in a single chip, which was regarded as a good on-chip ACLED design. According to the experimental results, higher chip efficiency can be reached through SBD-ACLED design since the chip area utilization ratio was increased. Since the principle and the operation condition of ACLED is quite different from those of the typical DCLED, critical issues for ACLED like the current droops, the flicker phenomenon, the safety regulations, the measurement standards and the power fluctuation have been studied for getting a practical and reliable ACLED design. Besides, the "AC LED application and research alliance" (AARA) lead by ITRI in Taiwan for the commercialization works of ACLED has also been introduced.

  14. Alternating current driven electroluminescence from ZnSe/ZnS:Mn/ZnS nanocrystals.

    PubMed

    Wood, Vanessa; Halpert, Jonathan E; Panzer, Matthew J; Bawendi, Moungi G; Bulović, Vladimir

    2009-06-01

    We present a novel technique for room temperature, solution-based fabrication of alternating current thin-film electroluminescent (AC-TFEL) devices using phosphor-doped nanocrystals. Synthesis for stable ZnSe/ZnS:Mn/ZnS nanocrystals that exhibit a quantum yield of 65 +/- 5% is outlined, and their electroluminescence is demonstrated in structures consisting of only wide band gap ceramic layers. Both the nanocrystal and the ceramic films have minimal absorption across the visible light spectrum, enabling us to demonstrate transparent AC-TFEL devices.

  15. Potential application of alternatively glycosylated serum MUC1 and MUC5AC in gastric cancer diagnosis.

    PubMed

    Xu, Ye; Zhang, Liang; Hu, Gengxi

    2009-01-01

    Post-transcription modification of proteins can be altered during carcinogenesis. In this study, quantitative sandwich enzyme immunoassays were utilized to explore the clinical diagnostic value of the alternatively glycosylated MUC1 and MUC5AC. Four pairs of antibodies were selected to construct quantitative sandwich enzyme immunoassay. Serum mucin levels of 104 primary gastric cancer patients and 120 healthy individuals were measured using the four antibody pairs. The detection sensitivities of each antibody pair against gastric cancers were 42.31%, 25.00%, 38.46% and 30.77% respectively, with a specificity of 90.00%, significantly higher than widely used tumor markers CEA (21.15%) and CA19-9 (18.27%). When monitoring in parallel with all of the four antibody pairs, the detection sensitivity increased to 75.00%, with the same 90.00% specificity. Immunoblotting of the serum samples using the anti-mucin antibodies revealed highly variable glycosylation patterns among gastric cancer patients. In addition, real-time PCR indicated the elevated mRNA levels of MUC1 and/or MUC5AC in gastric cancers. The cancer-specific epitopes were also detected in other alimentary canal epithelium cancers such as colonic, nasopharyngeal and esophageal cancers, but with much lower sensitivities. Our results suggested that alternatively glycosylated MUC1 and MUC5AC could be of significant potential as effective tumor markers in gastric cancer diagnosis.

  16. Transcranial Alternating Current Stimulation with Sawtooth Waves: Simultaneous Stimulation and EEG Recording.

    PubMed

    Dowsett, James; Herrmann, Christoph S

    2016-01-01

    Transcranial alternating current stimulation (tACS) has until now mostly been administered as an alternating sinusoidal wave. Despite modern tACS stimulators being able to deliver alternating current with any arbitrary shape there has been no systematic exploration into the relative benefits of different waveforms. As tACS is a relatively new technique there is a huge parameter space of unexplored possibilities which may prove superior or complimentary to the traditional sinusoidal waveform. Here, we begin to address this with an investigation into the effects of sawtooth wave tACS on individual alpha power. Evidence from animal models suggests that the gradient and direction of an electric current should be important factors for the subsequent neural firing rate; we compared positive and negative ramp sawtooth waves to test this. An additional advantage of sawtooth waves is that the resulting artifact in the electroencephalogram (EEG) recording is significantly simpler to remove than a sine wave; accordingly we were able to observe alpha oscillations both during and after stimulation. We found that positive ramp sawtooth, but not negative ramp sawtooth, significantly enhanced alpha power during stimulation relative to sham (p < 0.01). In addition we tested for an after-effect of both sawtooth and sinusoidal stimulation on alpha power but in this case did not find any significant effect. This preliminary study paves the way for further investigations into the effect of the gradient and direction of the current in tACS which could significantly improve the usefulness of this technique. PMID:27065835

  17. Roebel assembled coated conductor cables (RACC): Ac-Losses and current carrying potential

    NASA Astrophysics Data System (ADS)

    Frank, A.; Heller, R.; Goldacker, W.; Kling, A.; Schmidt, C.

    2008-02-01

    Low ac-loss HTS cables for transport currents well above 1 kA are required for application in transformers and generators and are taken into consideration for future generations of fusion reactor coils. Coated conductors (CC) are suitable candidates for high field application at an operation temperature in the range 50-77 K. Ac-field applications require cables with low ac-losses and hence twisting of the individual strands. We solved this problem using the Roebel technique. Short lengths of Roebel bar cables were prepared from industrial DyBCO and YBCO-CC. Meander shaped tapes of 4 or 5 mm width with twist pitches of 123 or 127 mm were cut from the 10 or 12 mm wide CC tapes using a specially designed tool. Eleven or twelve of these strands were assembled to a cable. The electrical and mechanical connection of the tapes was achieved using a silver powder filled conductive epoxy resin. Ac-losses of a short sample in an external ac-field were measured as a function of frequency and field amplitude as well as the coupling current decay time constant. We discuss the results in terms of available theories and compare measured time constants in transverse field with measured coupling losses. Finally the potential of this cable type for ac-use is discussed with respect to ac-losses and current carrying capability.

  18. Efficacy of lidocaine lontophoresis using either alternating or direct current in hairless rats.

    PubMed

    Nakajima, Atsushi; Wakita, Ryo; Haida, Haruka; Fukayama, Haruhisa

    2013-01-01

    The aim of this study was to determine transport of lidocaine ions through a hairless rat skin in vivo and to compare the efficacy of alternating current (AC) with that of direct current (DC) iontophoresis (IOP). We measured the concentration of lidocaine transported through a cellophane membrane or a hairless rat dorsal skin applying either AC-IOP or DC-IOP. The results revealed that lidocaine concentration increased in a time-dependent manner in vitro in both DC-IOP and AC-IOP. However, the in vivo study showed different tendencies in lidocaine concentration. In the DCIOP group, lidocaine concentration reached its maximum 20 min after current application and then decreased rapidly; the AC-IOP group showed an increase in lidocaine concentration in a time-dependent manner. There were no side effects such as electrical burns in the rats. In conclusion, AC can be applied for long periods and DC for short periods, or their application time can be appropriately scheduled. Our study also suggests the mechanism by which voltage waveforms affect the skin when applied by IOP. In the future, these findings will be a solid foundation for developing various kinds of medical equipment such as scheduled drug delivery system that can easily deliver various types of drug.

  19. Precision electronic speed controller for an alternating-current

    DOEpatents

    Bolie, Victor W.

    1988-01-01

    A high precision controller for an alternating-current multi-phase electrical motor that is subject to a large inertial load. The controller was developed for and is particularly suitable for controlling, in a neutron chopper system, a heavy spinning rotor that must be rotated in phase-locked synchronism with a reference pulse train that is representative of an ac power supply signal having a meandering line frequency. The controller includes a shaft revolution sensor which provides a feedback pulse train representative of the actual speed of the motor. An internal digital timing signal generator provides a reference signal which is compared with the feedback signal in a computing unit to provide a motor control signal. In the preferred embodiment, the motor control signal is a weighted linear sum of a speed error voltage, a phase error voltage, and a drift error voltage, each of which is computed anew with each revolution of the motor shaft. The stator windings of the motor are driven by two amplifiers which are provided with input signals having the proper quadrature relationship by an exciter unit consisting of a voltage controlled oscillator, a binary counter, a pair of readonly memories, and a pair of digital-to-analog converters.

  20. Flicker-Driven Responses in Visual Cortex Change during Matched-Frequency Transcranial Alternating Current Stimulation.

    PubMed

    Ruhnau, Philipp; Keitel, Christian; Lithari, Chrysa; Weisz, Nathan; Neuling, Toralf

    2016-01-01

    We tested a novel combination of two neuro-stimulation techniques, transcranial alternating current stimulation (tACS) and frequency tagging, that promises powerful paradigms to study the causal role of rhythmic brain activity in perception and cognition. Participants viewed a stimulus flickering at 7 or 11 Hz that elicited periodic brain activity, termed steady-state responses (SSRs), at the same temporal frequency and its higher order harmonics. Further, they received simultaneous tACS at 7 or 11 Hz that either matched or differed from the flicker frequency. Sham tACS served as a control condition. Recent advances in reconstructing cortical sources of oscillatory activity allowed us to measure SSRs during concurrent tACS, which is known to impose strong artifacts in magnetoencephalographic (MEG) recordings. For the first time, we were thus able to demonstrate immediate effects of tACS on SSR-indexed early visual processing. Our data suggest that tACS effects are largely frequency-specific and reveal a characteristic pattern of differential influences on the harmonic constituents of SSRs. PMID:27199707

  1. Flicker-Driven Responses in Visual Cortex Change during Matched-Frequency Transcranial Alternating Current Stimulation

    PubMed Central

    Ruhnau, Philipp; Keitel, Christian; Lithari, Chrysa; Weisz, Nathan; Neuling, Toralf

    2016-01-01

    We tested a novel combination of two neuro-stimulation techniques, transcranial alternating current stimulation (tACS) and frequency tagging, that promises powerful paradigms to study the causal role of rhythmic brain activity in perception and cognition. Participants viewed a stimulus flickering at 7 or 11 Hz that elicited periodic brain activity, termed steady-state responses (SSRs), at the same temporal frequency and its higher order harmonics. Further, they received simultaneous tACS at 7 or 11 Hz that either matched or differed from the flicker frequency. Sham tACS served as a control condition. Recent advances in reconstructing cortical sources of oscillatory activity allowed us to measure SSRs during concurrent tACS, which is known to impose strong artifacts in magnetoencephalographic (MEG) recordings. For the first time, we were thus able to demonstrate immediate effects of tACS on SSR-indexed early visual processing. Our data suggest that tACS effects are largely frequency-specific and reveal a characteristic pattern of differential influences on the harmonic constituents of SSRs. PMID:27199707

  2. Spatially variant red blood cell crenation in alternating current non-uniform fieldsa

    PubMed Central

    An, Ran; Wipf, David O.; Minerick, Adrienne R.

    2014-01-01

    Alternating-current (AC) electrokinetics involve the movement and behaviors of particles or cells. Many applications, including dielectrophoretic manipulations, are dependent upon charge interactions between the cell or particle and the surrounding medium. Medium concentrations are traditionally treated as spatially uniform in both theoretical models and experiments. Human red blood cells (RBCs) are observed to crenate, or shrink due to changing osmotic pressure, over 10 min experiments in non-uniform AC electric fields. Cell crenation magnitude is examined as functions of frequency from 250 kHz to 1 MHz and potential from 10 Vpp to 17.5 Vpp over a 100 μm perpendicular electrode gap. Experimental results show higher peak to peak potential and lower frequency lead to greater cell volume crenation up to a maximum volume loss of 20%. A series of experiments are conducted to elucidate the physical mechanisms behind the red blood cell crenation. Non-uniform and uniform electrode systems as well as high and low ion concentration experiments are compared and illustrate that AC electroporation, system temperature, rapid temperature changes, medium pH, electrode reactions, and convection do not account for the crenation behaviors observed. AC electroosmotic was found to be negligible at these conditions and AC electrothermal fluid flows were found to reduce RBC crenation behaviors. These cell deformations were attributed to medium hypertonicity induced by ion concentration gradients in the spatially nonuniform AC electric fields. PMID:24753734

  3. The Teaching of Three-Phase Alternating Current

    ERIC Educational Resources Information Center

    Bunker, C. A.

    1976-01-01

    Describes a series of experiments which use a modified automobile alternator as a portable source of three-phase alternating current. The low frequency capabilities of this source allow the phase relationships to be demonstrated using an ordinary galvanometer. (GS)

  4. Demodulation circuit for AC motor current spectral analysis

    DOEpatents

    Hendrix, Donald E.; Smith, Stephen F.

    1990-12-18

    A motor current analysis method for the remote, noninvasive inspection of electric motor-operated systems. Synchronous amplitude demodulation and phase demodulation circuits are used singly and in combination along with a frequency analyzer to produce improved spectral analysis of load-induced frequencies present in the electric current flowing in a motor-driven system.

  5. Computational analysis shows why transcranial alternating current stimulation induces retinal phosphenes

    NASA Astrophysics Data System (ADS)

    Laakso, Ilkka; Hirata, Akimasa

    2013-08-01

    Objective. Transcranial alternating current stimulation (tACS), which is a novel technique for the manipulation of cortical oscillations, can generate subjective visual sensations (phosphenes). In this work, we computationally investigate the current that reaches the eyes from tACS electrodes in order to show that phosphenes induced by tACS are retinal in origin. Approach. The finite-element method is used for modelling the path of the current in an anatomically realistic model of the head for various electrode montages. The computational results are used for analysing previous experimental data to investigate the sensitivity of the eye to electrical stimulation. Main results. Depending on the locations of both the stimulating and reference electrodes, a small portion of the stimulation current chooses a path that goes through the eyes. Due to the sensitivity of the retina to electrical stimulation, even distant electrodes can produce a sufficiently strong current at the eyes for inducing retinal phosphenes. Significance. The interference from retinal phosphenes needs to be considered in the design of tACS experiments. The occurrence of phosphenes can be reduced by optimizing the locations of the electrodes, or potentially increasing the number of reference electrodes to two or more. Computational modelling is an effective tool for guiding the electrode positioning.

  6. Alternating current line-filter based on electrochemical capacitor utilizing template-patterned graphene

    PubMed Central

    Wu, Zhenkun; Li, Liyi; Lin, Ziyin; Song, Bo; Li, Zhuo; Moon, Kyoung-Sik; Wong, Ching-Ping; Bai, Shu-Lin

    2015-01-01

    Aluminum electrolytic capacitors (AECs) are widely used for alternating current (ac) line-filtering. However, their bulky size is becoming more and more incompatible with the rapid development of portable electronics. Here we report a scalable process to fabricate miniaturized graphene-based ac line-filters on flexible substrates at room temperature. In this work, graphene oxide (GO) is reduced by patterned metal interdigits at room temperature and used directly as the electrode material. The as-fabricated device shows a phase angle of −75.4° at 120 Hz with a specific capacitance of 316 µF/cm2 and a RC time constant of 0.35 ms. In addition, it retains 97.2% of the initial capacitance after 10000 charge/discharge cycles. These outstanding performance characteristics of our device demonstrate its promising to replace the conventional AECs for ac line filtering. PMID:26084051

  7. AC and DC transport currents in melt-grown YBCO

    SciTech Connect

    Yi, Z.; Ashworth, S.; Becluz, C.; Scurlock, R.G. )

    1991-03-01

    It has been suggested that the transport J{sub c} in multi-grain samples of bulk YBCO are limited by the intergrain links. This paper reports on preliminary measurements of intergrain currents. The intergrain critical currents in melt grown YBCO do not appear to be as sensitive to the precise crystallographic alignment of adjacent grains a has been reported for thin films. The measured critical current of similar grain boundaries varies widely, between 15000 A/cm{sup 2} and 200A/Cm{sub 2} for adjacent boundaries in the same sample.

  8. Alternating-Current Motor Drive for Electric Vehicles

    NASA Technical Reports Server (NTRS)

    Krauthamer, S.; Rippel, W. E.

    1982-01-01

    New electric drive controls speed of a polyphase as motor by varying frequency of inverter output. Closed-loop current-sensing circuit automatically adjusts frequency of voltage-controlled oscillator that controls inverter frequency, to limit starting and accelerating surges. Efficient inverter and ac motor would give electric vehicles extra miles per battery charge.

  9. Characterization of antiarrhythmic drugs by alternating current induced arrhythmias in isolated heart tissues.

    PubMed

    Borchard, U; Bösken, R; Greeff, K

    1982-04-01

    A new method for inducing arrhythmias or asystolia by the application of a 50 HZ alternating current (ac) to electrically driven heart preparations has been developed and applied to isolated left atria and right ventricular papillary muscles of the guinea-pig. An increase in driving frequency from 1 to 3 HZ effects a significant reduction of the threshold of ac-arrhythmia in guinea-pig papillary muscles but no change in atria. A decrease in temperature from 31 degrees C to 25 degrees C and an increase in [Ca2+]0 from 1.25 to 5 mmol/l elevates threshold for ac-arrhythmia and -asystolia. The fast sodium channel inhibitors quinidine, carticaine and benzylamino-5,6-dihydro-8,9-dimethoxy-imidazo-5,1-a-isoquinoline hydrochloride (HE-36) increase threshold of ac-arrhythmia in left atria and papillary muscles, whereas the slow channel inhibitor verapamil is ineffective in concentrations up to 6 mumol/l. Threshold of ac-arrhythmia is elevated by quinidine predominantly in papillary muscles. Carticaine and HE-36 are effective in left atria and papillary muscles to almost the same extent. Threshold of ac-asystolia is increased mainly in papillary muscles by quinidine and HE-36; carticaine produces a similar increase in left atria and papillary muscles. Verapamil even leads to a decrease in threshold predominantly in papillary muscles. It is concluded that model arrhythmias induced by alternating current are brought about mainly by an increase in Na+-conductance of cardiac cell membranes. The negative chronotropic potency in right atria occurs in the sequence verapamil greater than quinidine greater than carticane approximately HE-36. The negative inotropic potency in papillary muscle occurs in the same sequence but HE-36 increases force of contraction.

  10. Sustained diffusive alternating current gliding arc discharge in atmospheric pressure air

    NASA Astrophysics Data System (ADS)

    Zhu, Jiajian; Gao, Jinlong; Li, Zhongshan; Ehn, Andreas; Aldén, Marcus; Larsson, Anders; Kusano, Yukihiro

    2014-12-01

    Rapid transition from glow discharge to thermal arc has been a common problem in generating stable high-power non-thermal plasmas especially at ambient conditions. A sustained diffusive gliding arc discharge was generated in a large volume in atmospheric pressure air, driven by an alternating current (AC) power source. The plasma column extended beyond the water-cooled stainless steel electrodes and was stabilized by matching the flow speed of the turbulent air jet with the rated output power. Comprehensive investigations were performed using high-speed movies measured over the plasma column, synchronized with simultaneously recorded current and voltage waveforms. Dynamic details of the novel non-equilibrium discharge are revealed, which is characterized by a sinusoidal current waveform with amplitude stabilized at around 200 mA intermediate between thermal arc and glow discharge, shedding light to the governing mechanism of the sustained spark-suppressed AC gliding arc discharge.

  11. Alternating current electromagnetic servo induction meter

    NASA Technical Reports Server (NTRS)

    Bogue, R. K.

    1968-01-01

    Electromagnetic device accurately indicates the responses of various sensors in high performance flight research aircraft to conditions encountered in flight. The device responds to sensor inputs to move a slideable armature along an indicator scale by the force of currents induced in the armature winding.

  12. Alternating Current Stimulation for Vision Restoration after Optic Nerve Damage: A Randomized Clinical Trial

    PubMed Central

    Schittkowski, Michael P.; Antal, Andrea; Ambrus, Géza Gergely; Paulus, Walter; Dannhauer, Moritz; Michalik, Romualda; Mante, Alf; Bola, Michal; Lux, Anke; Kropf, Siegfried; Brandt, Stephan A.; Sabel, Bernhard A.

    2016-01-01

    Background Vision loss after optic neuropathy is considered irreversible. Here, repetitive transorbital alternating current stimulation (rtACS) was applied in partially blind patients with the goal of activating their residual vision. Methods We conducted a multicenter, prospective, randomized, double-blind, sham-controlled trial in an ambulatory setting with daily application of rtACS (n = 45) or sham-stimulation (n = 37) for 50 min for a duration of 10 week days. A volunteer sample of patients with optic nerve damage (mean age 59.1 yrs) was recruited. The primary outcome measure for efficacy was super-threshold visual fields with 48 hrs after the last treatment day and at 2-months follow-up. Secondary outcome measures were near-threshold visual fields, reaction time, visual acuity, and resting-state EEGs to assess changes in brain physiology. Results The rtACS-treated group had a mean improvement in visual field of 24.0% which was significantly greater than after sham-stimulation (2.5%). This improvement persisted for at least 2 months in terms of both within- and between-group comparisons. Secondary analyses revealed improvements of near-threshold visual fields in the central 5° and increased thresholds in static perimetry after rtACS and improved reaction times, but visual acuity did not change compared to shams. Visual field improvement induced by rtACS was associated with EEG power-spectra and coherence alterations in visual cortical networks which are interpreted as signs of neuromodulation. Current flow simulation indicates current in the frontal cortex, eye, and optic nerve and in the subcortical but not in the cortical regions. Conclusion rtACS treatment is a safe and effective means to partially restore vision after optic nerve damage probably by modulating brain plasticity. This class 1 evidence suggests that visual fields can be improved in a clinically meaningful way. Trial Registration ClinicalTrials.gov NCT01280877 PMID:27355577

  13. Alternating current electrohydrodynamics induced nanoshearing and fluid micromixing for specific capture of cancer cells.

    PubMed

    Vaidyanathan, Ramanathan; Rauf, Sakandar; Dray, Eloïse; Shiddiky, Muhammad J A; Trau, Matt

    2014-03-24

    We report a new tuneable alternating current (ac) electrohydrodynamics (ac-EHD) force referred to as “nanoshearing” which involves fluid flow generated within a few nanometers of an electrode surface. This force can be externally tuned via manipulating the applied ac-EHD field strength. The ability to manipulate ac-EHD induced forces and concomitant fluid micromixing can enhance fluid transport within the capture domain of the channel (e.g., transport of analytes and hence increase target–sensor interactions). This also provides a new capability to preferentially select strongly bound analytes over nonspecifically bound cells and molecules. To demonstrate the utility and versatility of nanoshearing phenomenon to specifically capture cancer cells, we present proof-of-concept data in lysed blood using two microfluidic devices containing a long array of asymmetric planar electrode pairs. Under the optimal experimental conditions, we achieved high capture efficiency (e.g., approximately 90%; %RSD=2, n=3) with a 10-fold reduction in nonspecific adsorption of non-target cells for the detection of whole cells expressing Human Epidermal Growth Factor Receptor 2 (HER2). We believe that our ac-EHD devices and the use of tuneable nanoshearing phenomenon may find relevance in a wide variety of biological and medical applications. PMID:24677444

  14. Precision electronic speed controller for an alternating-current motor

    DOEpatents

    Bolie, V.W.

    A high precision controller for an alternating-current multi-phase electrical motor that is subject to a large inertial load. The controller was developed for controlling, in a neutron chopper system, a heavy spinning rotor that must be rotated in phase-locked synchronism with a reference pulse train that is representative of an ac power supply signal having a meandering line frequency. The controller includes a shaft revolution sensor which provides a feedback pulse train representative of the actual speed of the motor. An internal digital timing signal generator provides a reference signal which is compared with the feedback signal in a computing unit to provide a motor control signal. The motor control signal is a weighted linear sum of a speed error voltage, a phase error voltage, and a drift error voltage, each of which is computed anew with each revolution of the motor shaft. The speed error signal is generated by a novel vernier-logic circuit which is drift-free and highly sensitive to small speed changes. The phase error is also computed by digital logic, with adjustable sensitivity around a 0 mid-scale value. The drift error signal, generated by long-term counting of the phase error, is used to compensate for any slow changes in the average friction drag on the motor. An auxillary drift-byte status sensor prevents any disruptive overflow or underflow of the drift-error counter. An adjustable clocked-delay unit is inserted between the controller and the source of the reference pulse train to permit phase alignment of the rotor to any desired offset angle. The stator windings of the motor are driven by two amplifiers which are provided with input signals having the proper quadrature relationship by an exciter unit consisting of a voltage controlled oscillator, a binary counter, a pair of read-only memories, and a pair of digital-to-analog converters.

  15. ac current generation in chiral magnetic insulators and Skyrmion motion induced by the spin Seebeck effect.

    PubMed

    Lin, Shi-Zeng; Batista, Cristian D; Reichhardt, Charles; Saxena, Avadh

    2014-05-01

    We show that a temperature gradient induces an ac electric current in multiferroic insulators when the sample is embedded in a circuit. We also show that a thermal gradient can be used to move magnetic Skyrmions in insulating chiral magnets: the induced magnon flow from the hot to the cold region drives the Skyrmions in the opposite direction via a magnonic spin transfer torque. Both results are combined to compute the effect of Skyrmion motion on the ac current generation and demonstrate that Skyrmions in insulators are a promising route for spin caloritronics applications.

  16. ac current generation in chiral magnetic insulators and Skyrmion motion induced by the spin Seebeck effect.

    PubMed

    Lin, Shi-Zeng; Batista, Cristian D; Reichhardt, Charles; Saxena, Avadh

    2014-05-01

    We show that a temperature gradient induces an ac electric current in multiferroic insulators when the sample is embedded in a circuit. We also show that a thermal gradient can be used to move magnetic Skyrmions in insulating chiral magnets: the induced magnon flow from the hot to the cold region drives the Skyrmions in the opposite direction via a magnonic spin transfer torque. Both results are combined to compute the effect of Skyrmion motion on the ac current generation and demonstrate that Skyrmions in insulators are a promising route for spin caloritronics applications. PMID:24856718

  17. Semiconductor Thermoelectric Converters of Alternating Current Signals

    NASA Astrophysics Data System (ADS)

    Anatychuk, L. I.; Bodnaruk, V. I.; Taschuk, D. D.

    2011-05-01

    Measuring converters have been developed based on Bi2Te3 solid solutions optimized for temperature and temporal stability of the basic thermoelectric parameters (thermal conductivity, electrical conductivity, and the Seebeck coefficient). Semiconductor material was grown by the vertical zone melting method. High efficiency of the optimized semiconductor materials made it possible to reduce the operating temperature considerably, as well as facilitating selection of structural materials and the converter fabrication technique. The influence of the Peltier and Thomson effects on the accuracy of direct current conversion has been reduced, and the operating frequency range of measurements has been expanded. Thermoelectric converters with sensitivity up to 30 V W-1 have been created without evacuation of the working space, which is filled with an inert gas mixture. The engineered converters offer the advantages of high sensitivity and a wide operating frequency range (up to 30 MHz).

  18. Dynamics of laser-guided alternating current high voltage discharges

    NASA Astrophysics Data System (ADS)

    Daigle, J.-F.; Théberge, F.; Lassonde, P.; Kieffer, J.-C.; Fujii, T.; Fortin, J.; Châteauneuf, M.; Dubois, J.

    2013-10-01

    The dynamics of laser-guided alternating current high voltage discharges are characterized using a streak camera. Laser filaments were used to trigger and guide the discharges produced by a commercial Tesla coil. The streaking images revealed that the dynamics of the guided alternating current high voltage corona are different from that of a direct current source. The measured effective corona velocity and the absence of leader streamers confirmed that it evolves in a pure leader regime.

  19. Direct Detection of Pure ac Spin Current by X-Ray Pump-Probe Measurements.

    PubMed

    Li, J; Shelford, L R; Shafer, P; Tan, A; Deng, J X; Keatley, P S; Hwang, C; Arenholz, E; van der Laan, G; Hicken, R J; Qiu, Z Q

    2016-08-12

    Despite recent progress in spin-current research, the detection of spin current has mostly remained indirect. By synchronizing a microwave waveform with synchrotron x-ray pulses, we use the ferromagnetic resonance of the Py (Ni_{81}Fe_{19}) layer in a Py/Cu/Cu_{75}Mn_{25}/Cu/Co multilayer to pump a pure ac spin current into the Cu_{75}Mn_{25} and Co layers, and then directly probe the spin current within the Cu_{75}Mn_{25} layer and the spin dynamics of the Co layer by x-ray magnetic circular dichroism. This element-resolved pump-probe measurement unambiguously identifies the ac spin current in the Cu_{75}Mn_{25} layer. PMID:27563981

  20. Direct Detection of Pure ac Spin Current by X-Ray Pump-Probe Measurements

    NASA Astrophysics Data System (ADS)

    Li, J.; Shelford, L. R.; Shafer, P.; Tan, A.; Deng, J. X.; Keatley, P. S.; Hwang, C.; Arenholz, E.; van der Laan, G.; Hicken, R. J.; Qiu, Z. Q.

    2016-08-01

    Despite recent progress in spin-current research, the detection of spin current has mostly remained indirect. By synchronizing a microwave waveform with synchrotron x-ray pulses, we use the ferromagnetic resonance of the Py (Ni81Fe19 ) layer in a Py /Cu /Cu75Mn25/Cu /Co multilayer to pump a pure ac spin current into the Cu75Mn25 and Co layers, and then directly probe the spin current within the Cu75Mn25 layer and the spin dynamics of the Co layer by x-ray magnetic circular dichroism. This element-resolved pump-probe measurement unambiguously identifies the ac spin current in the Cu75Mn25 layer.

  1. AC current rectification in Nb films with or without symmetrical Nb/Ni periodic pinning arrays in perpendicular magnetic field

    NASA Astrophysics Data System (ADS)

    Pryadun, Vladimir

    2005-03-01

    Rectification of AC current has been observed in plain superconducting Nb films and in Nb/Ni films with symmetric periodic pinning centers. The rectified DC voltage appears for various sample geometries (cross or strip) both along and transverse to the alternating current direction, is nearly anti-symmetric with perpendicular magnetic field and strongly dependent on temperature below Tc. Analyses of the data at different temperatures, drive frequencies from 100kHz to 150MHz and at the different sample sides [1] shows that not far below Tc the rectification phenomena can be understood in terms of generation of electric fields due to local excess of critical current. Further below Tc anisotropic pinning effects could also contribute to the rectification. [1] F.G.Aliev, et al., Cond. Mat.405656. Supported by Comunidad Autonoma de Madrid -CAM/07N/0050/2002

  2. 27. LEUPOLD AND STEVENS MIDGET CURRENT METER (WITH ALTERNATE IMPELLER) ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    27. LEUPOLD AND STEVENS MIDGET CURRENT METER (WITH ALTERNATE IMPELLER) AND FOLDING SCALE (MEASURED IN INCHES). - Waterways Experiment Station, Hydraulics Laboratory, Halls Ferry Road, 2 miles south of I-20, Vicksburg, Warren County, MS

  3. From amusic to musical?--Improving pitch memory in congenital amusia with transcranial alternating current stimulation.

    PubMed

    Schaal, Nora K; Pfeifer, Jasmin; Krause, Vanessa; Pollok, Bettina

    2015-11-01

    Brain imaging studies highlighted structural differences in congenital amusia, a life-long perceptual disorder that is associated with pitch perception and pitch memory deficits. A functional anomaly characterized by decreased low gamma oscillations (30-40 Hz range) in the right dorsolateral prefrontal cortex (DLPFC) during pitch memory has been revealed recently. Thus, the present study investigates whether applying transcranial alternating current stimulation (tACS) at 35 Hz to the right DLPFC would improve pitch memory. Nine amusics took part in two tACS sessions (either 35 Hz or 90 Hz) and completed a pitch and visual memory task before and during stimulation. 35 Hz stimulation facilitated pitch memory significantly. No modulation effects were found with 90 Hz stimulation or on the visual task. While amusics showed a selective impairment of pitch memory before stimulation, the performance during 35 Hz stimulation was not significantly different to healthy controls anymore. Taken together, the study shows that modulating the right DLPFC with 35 Hz tACS in congenital amusia selectively improves pitch memory performance supporting the hypothesis that decreased gamma oscillations within the DLPFC are causally involved in disturbed pitch memory and highlight the potential use of tACS to interact with cognitive processes.

  4. Statistical evaluation of telephone noise interference caused by AC power line harmonic currents

    SciTech Connect

    Kuussaari, M. )

    1993-04-01

    A statistical approach is applied for the evaluation of the limits for harmonic currents in AC power lines, the goal being to prevent excessive telephone noise interference voltages in subscriber cables in rural areas. The analysis is based on Monte-Carlo simulation which takes into account the effect of the experiental probability distributions of the relevant parameters. In the Finnish conditions, the properties of communication cables permit equivalent disturbing phase currents of 8 to 10 A. The digital exchanges permit approximately the same currents. Some new telephone types that have a low balance may make it necessary to limit the currents to a level that is somewhat lower.

  5. Signature of cluster disruption within magnetic fluid samples: The key information provided by low frequency alternating current susceptibility measurements

    NASA Astrophysics Data System (ADS)

    Du, Zhongzhou; Liu, Wenzhong; Zhong, Jing; Zhou, Ming; Zhang, Pu; Cesar Morais, Paulo

    2014-05-01

    This paper is focused on the signature of thermal-assisted cluster disruption while analyzing the inverse alternating current (AC) susceptibility (1/χ) versus temperature (T) curves recorded at lower AC frequencies (f), below 300 Hz. A commercial oil-based magnetic fluid (MF) sample was used in the experiments to investigate the critical temperature (T*) that characterizes the thermal disruption of aggregates suspended within the MF sample. T* was found to reduce as f increased within the frequency range of our investigation (63-263 Hz). Furthermore, T* was found to scale with the square of the applied AC frequency. Both theoretical and experimental evidences support that the excitation field frequency (f) dependence of the critical temperature (T*) is well described by T*(f)=T*(0)-Af/21+Bf2. The model is based on energy absorption of magnetic nanoparticles in an AC magnetic field.

  6. The relation between the duty cycle and anesthetic effect in lidocaine iontophoresis using alternating current.

    PubMed

    Wakita, Ryo; Nakajima, Atsushi; Haida, Yu; Umino, Masahiro; Fukayama, Haruhisa

    2011-01-01

    We assessed the effect of the duty cycle on the anesthetic effect during lidocaine alternating current (AC) iontophoresis. A solution of 2% lidocaine was delivered to the medial antecubital skin for 20 minutes using AC iontophoresis with a duty cycle of 60%, 70%, or 80%. The von Frey test was then performed to evaluate the anesthetic effect. In the groups treated with a duty cycle of 80% or 70% the touch thresholds (TT) were significantly elevated from 0 minutes to 30 minutes and from 0 minutes to 20 minutes. TT were significantly elevated at 0 minutes in the group treated with a 60% duty cycle. The anesthetic effect was significantly enhanced in a duty cycle-dependent manner.

  7. Enhancement of crystal homogeneity of protein crystals under application of an external alternating current electric field

    SciTech Connect

    Koizumi, H.; Uda, S.; Fujiwara, K.; Nozawa, J.; Tachibana, M.; Kojima, K.

    2014-10-06

    X-ray diffraction rocking-curve measurements were performed on tetragonal hen egg white (HEW) lysozyme crystals grown with and without the application of an external alternating current (AC) electric field. The crystal quality was assessed by the full width at half maximum (FWHM) value for each rocking curve. For two-dimensional maps of the FWHMs measured on the 440 and the 12 12 0 reflection, the crystal homogeneity was improved under application of an external electric field at 1 MHz, compared with that without. In particular, the significant improvement of the crystal homogeneity was observed for the 12 12 0 reflection.

  8. CROSS-DISCIPLINARY PHYSICS AND RELATED AREAS OF SCIENCE AND TECHNOLOGY: Characteristics of alternating current hopping conductivity in DNA sequences

    NASA Astrophysics Data System (ADS)

    Ma, Song-Shan; Xu, Hui; Wang, Huan-You; Guo, Rui

    2009-08-01

    This paper presents a model to describe alternating current (AC) conductivity of DNA sequences, in which DNA is considered as a one-dimensional (1D) disordered system, and electrons transport via hopping between localized states. It finds that AC conductivity in DNA sequences increases as the frequency of the external electric field rises, and it takes the form of øac(ω) ~ ω2 ln2(1/ω). Also AC conductivity of DNA sequences increases with the increase of temperature, this phenomenon presents characteristics of weak temperature-dependence. Meanwhile, the AC conductivity in an off-diagonally correlated case is much larger than that in the uncorrelated case of the Anderson limit in low temperatures, which indicates that the off-diagonal correlations in DNA sequences have a great effect on the AC conductivity, while at high temperature the off-diagonal correlations no longer play a vital role in electric transport. In addition, the proportion of nucleotide pairs p also plays an important role in AC electron transport of DNA sequences. For p < 0.5, the conductivity of DNA sequence decreases with the increase of p, while for p >= 0.5, the conductivity increases with the increase of p.

  9. Switch contact device for interrupting high current, high voltage, AC and DC circuits

    DOEpatents

    Via, Lester C.; Witherspoon, F. Douglas; Ryan, John M.

    2005-01-04

    A high voltage switch contact structure capable of interrupting high voltage, high current AC and DC circuits. The contact structure confines the arc created when contacts open to the thin area between two insulating surfaces in intimate contact. This forces the arc into the shape of a thin sheet which loses heat energy far more rapidly than an arc column having a circular cross-section. These high heat losses require a dramatic increase in the voltage required to maintain the arc, thus extinguishing it when the required voltage exceeds the available voltage. The arc extinguishing process with this invention is not dependent on the occurrence of a current zero crossing and, consequently, is capable of rapidly interrupting both AC and DC circuits. The contact structure achieves its high performance without the use of sulfur hexafluoride.

  10. An Annotated Bibliography of High-Voltage Direct-Current Transmission and Flexible AC Transmission (FACTS) Devices, 1991-1993.

    SciTech Connect

    Litzenberger, Wayne; Lava, Val

    1994-08-01

    References are contained for HVDC systems, converter stations and components, overhead transmission lines, cable transmission, system design and operations, simulation of high voltage direct current systems, high-voltage direct current installations, and flexible AC transmission system (FACTS).

  11. SIM regional comparison of ac-dc current transfer difference SIM.EM-K12

    NASA Astrophysics Data System (ADS)

    Di Lillo, Lucas

    2015-01-01

    The ac-dc current transfer difference identified as SIM.EM.K-12 began in July 2010 and was completed in September 2012. Six NMIs in the SIM region and one NMI in the AFRIMET region took part: NRC (Canada), NIST (United States of America), CENAM (Mexico), INTI (Argentina), UTE (Uruguay), INMETRO (Brazil) and NIS (Egypt). The comparisons were proposed to assess the measurement capabilities in ac-dc current transfer difference of the participants NMIs. The ac-dc current transfer differences of the travelling standard had been measured at 10 mA and 5 A at 10 Hz, 55 Hz, 1 kHz, 10 kHz, 20 kHz, 50 kHz and 100 kHz. The test points were selected to link the results with the equivalent CCEM Key Comparisons (CCEM-K12), through three NMIs participating in both SIM and CCEM key comparisons (INTI, NRC and NIST). The report shows the degree of equivalence in the SIM region and also the degree of equivalence with the corresponding CCEM reference value. The results of all participants support the values and uncertainties of the applicable CMC entries for ac-dc current transfer difference in the Key Comparison Database held at the BIPM. Main text. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. The final report has been peer-reviewed and approved for publication by the CCEM, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

  12. Method for sputtering with low frequency alternating current

    DOEpatents

    Timberlake, J.R.

    1996-04-30

    Low frequency alternating current sputtering is provided by connecting a low frequency alternating current source to a high voltage transformer having outer taps and a center tap for stepping up the voltage of the alternating current. The center tap of the transformer is connected to a vacuum vessel containing argon or helium gas. Target electrodes, in close proximity to each other, and containing material with which the substrates will be coated, are connected to the outer taps of the transformer. With an applied potential, the gas will ionize and sputtering from the target electrodes onto the substrate will then result. The target electrodes can be copper or boron, and the substrate can be stainless steel, aluminum, or titanium. Copper coatings produced are used in place of nickel and/or copper striking. 6 figs.

  13. Method for sputtering with low frequency alternating current

    DOEpatents

    Timberlake, John R.

    1996-01-01

    Low frequency alternating current sputtering is provided by connecting a low frequency alternating current source to a high voltage transformer having outer taps and a center tap for stepping up the voltage of the alternating current. The center tap of the transformer is connected to a vacuum vessel containing argon or helium gas. Target electrodes, in close proximity to each other, and containing material with which the substrates will be coated, are connected to the outer taps of the transformer. With an applied potential, the gas will ionize and sputtering from the target electrodes onto the substrate will then result. The target electrodes can be copper or boron, and the substrate can be stainless steel, aluminum, or titanium. Copper coatings produced are used in place of nickel and/or copper striking.

  14. Simulation analysis of three-phase current type AC-to-DC converter with high power factor

    SciTech Connect

    Okui, Yoshiaki; Yamada, Hajime

    1997-03-01

    A new three-phase current type AC-to-DC converter has been developed by the authors. This paper describes the principle of the circuit operation and the circuit configuration of the AC-to-DC converter controlled by PWM. Simulation analysis of each waveform, such as AC and DC voltages and currents, are calculated by Euler`s method. The simulated values of the total power factor agreed with the measured values within the difference of 5.8% on the condition of full load, 10kW. When the AC side voltage is unbalanced, it is found by simulation that the total harmonic distortion controlled by both feedforward control and AC side current feedback control (proportion gain, k{sub 4} = 1) is restrained at only 38% compared with only feedforward control (k{sub 4} = 0).

  15. DC bias effect on alternating current electrical conductivity of poly(ethylene terephthalate)/alumina nanocomposites

    NASA Astrophysics Data System (ADS)

    Nikam, Pravin N.; Deshpande, Vineeta D.

    2016-05-01

    Polymer nanocomposites based on metal oxide (ceramic) nanoparticles are a new class of materials with unique properties and designed for various applications such as electronic device packaging, insulation, fabrication and automotive industries. Poly(ethylene terephthalate) (PET)/alumina (Al2O3) nanocomposites with filler content between 1 wt% and 5 wt% were prepared by melt compounding method using co-rotating twin screw extruder and characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and precision LCR meter techniques. The results revealed that proper uniform dispersion at lower content up to 2 wt% of nano-alumina observed by using TEM. Aggregation of nanoparticles was observed at higher content of alumina examined by using SEM and TEM. The frequency dependences of the alternating current (AC) conductivity (σAC) of PET/alumina nanocomposites on the filler content and DC bias were investigated in the frequency range of 20Hz - 1MHz. The results showed that the AC and direct current (DC) conductivity increases with increasing DC bias and nano-alumina content upto 3 wt%. It follows the Jonscher's universal power law of solids. It revealed that σAC of PET/alumina nanocomposites can be well characterized by the DC conductivity (σDC), critical frequency (ωc), critical exponent of the power law (s). Roll of DC bias potential led to an increase of DC conductivity (σDC) due to the creation of additional conducting paths with the polymer nanocomposites and percolation behavior achieved through co-continuous morphology.

  16. Nonlinear response of superconductors to alternating fields and currents

    SciTech Connect

    McDonald, J.

    1997-10-08

    This report discusses the following topics on superconductivity: nonlinearities in hard superconductors such as surface impedance of a type II superconductimg half space and harmonic generation and intermodulation due to alternating transport currents; and nonlinearities in superconducting weak links such as harmonic generation by a long Josephson Junction in a superconducting slab.

  17. 59. View of high voltage (4160 volts alternating current) electric ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    59. View of high voltage (4160 volts alternating current) electric load center and motor control center at mezzanine level in transmitter building no. 102. - Clear Air Force Station, Ballistic Missile Early Warning System Site II, One mile west of mile marker 293.5 on Parks Highway, 5 miles southwest of Anderson, Anderson, Denali Borough, AK

  18. Bead-on-string structure printed by electrohydrodynamic jet under alternating current electric field

    NASA Astrophysics Data System (ADS)

    Liu, Juan; Lin, Yihuang; Jiang, Jiaxin; Liu, Haiyan; Zhao, Yang; Zheng, Gaofeng

    2016-09-01

    Electrohydrodynamic printing (EHDP) under alternating current (AC) electric field provides a novel way for the precise micro-/nano-droplet printing. The AC electric field induces the free charge to reciprocate along the EHDP jet and changes the electric field force on the jet periodically. The stability of jet can be enhanced by increasing the voltage frequency, and the regular bead-on-string structure is direct-written along the trajectory of collector. The deposition frequency of bead structure increases with the increasing of voltage frequency, due to the short period of AC electric field. As the voltage frequency is increased from 10 to 60 Hz, the diameter of bead structure decreases from 200 to 110 µm. As the duty ration increased from 10 to 60 %, the diameter of bead structure increased from 100 to 140 µm. This work would accelerate the development and the application of micro-/nano-printing technology in the fields of flexible electronic and micro-/nano-system.

  19. A simple separation method with a microfluidic channel based on alternating current potential modulation.

    PubMed

    Noh, Hui-Bog; Chandra, Pranjal; Kim, You-Jeong; Shim, Yoon-Bo

    2012-11-20

    A simple separation and detection system based on an electrochemical potential modulated microchannel (EPMM) device was developed for the first time. The application of alternating current (AC) potential to the microfluidic separation channel walls, which were composed of screen printed carbon electrodes, resulted in the oscillation and fluctuation of analytes and in the formation of a perfect flat flow front. These events resulted in an increase in the effective concentration and in the fine separation of samples. The performance of the EPMM device was examined through the analysis of endocrine disruptors (EDs) and heavy metal ions (HMIs) as model compounds. The analytical parameters that affected the separation and detection of EDs and HMIs were studied in terms of AC amplitude, AC frequency, flow rate, buffer concentration, pH, detection potential, and temperature. The separation efficiency was evaluated through measurements of the theoretical plate number (N), the retention time, and the half-peak width. Linear calibration plots for the detection of EDs and HMIs were obtained between 0.15 and 250.0 nM (detection limit 86.4 ± 2.9 pM) and between 0.01 and 10.0 nM (detection limit 9.5 ± 0.3 pM), respectively. The new device was successfully demonstrated with authentic and real samples. PMID:23075295

  20. Spin Hall voltages from a.c. and d.c. spin currents

    PubMed Central

    Wei, Dahai; Obstbaum, Martin; Ribow, Mirko; Back, Christian H.; Woltersdorf, Georg

    2014-01-01

    In spin electronics, the spin degree of freedom is used to transmit and store information. To this end the ability to create pure spin currents—that is, without net charge transfer—is essential. When the magnetization vector in a ferromagnet–normal metal junction is excited, the spin pumping effect leads to the injection of pure spin currents into the normal metal. The polarization of this spin current is time-dependent and contains a very small d.c. component. Here we show that the large a.c. component of the spin currents can be detected efficiently using the inverse spin Hall effect. The observed a.c.-inverse spin Hall voltages are one order of magnitude larger than the conventional d.c.-inverse spin Hall voltages measured on the same device. Our results demonstrate that ferromagnet–normal metal junctions are efficient sources of pure spin currents in the gigahertz frequency range. PMID:24780927

  1. Describing current and potential markets for alternative-fuel vehicles

    SciTech Connect

    1996-03-26

    Motor vehicles are a major source of greenhouse gases, and the rising numbers of motor vehicles and miles driven could lead to more harmful emissions that may ultimately affect the world`s climate. One approach to curtailing such emissions is to use, instead of gasoline, alternative fuels: LPG, compressed natural gas, or alcohol fuels. In addition to the greenhouse gases, pollutants can be harmful to human health: ozone, CO. The Clean Air Act Amendments of 1990 authorized EPA to set National Ambient Air Quality Standards to control this. The Energy Policy Act of 1992 (EPACT) was the first new law to emphasize strengthened energy security and decreased reliance on foreign oil since the oil shortages of the 1970`s. EPACT emphasized increasing the number of alternative-fuel vehicles (AFV`s) by mandating their incremental increase of use by Federal, state, and alternative fuel provider fleets over the new few years. Its goals are far from being met; alternative fuels` share remains trivial, about 0.3%, despite gains. This report describes current and potential markets for AFV`s; it begins by assessing the total vehicle stock, and then it focuses on current use of AFV`s in alternative fuel provider fleets and the potential for use of AFV`s in US households.

  2. Combined transcranial alternating current stimulation and continuous theta burst stimulation: a novel approach for neuroplasticity induction.

    PubMed

    Goldsworthy, Mitchell R; Vallence, Ann-Maree; Yang, Ruiting; Pitcher, Julia B; Ridding, Michael C

    2016-02-01

    Non-invasive brain stimulation can induce functionally relevant plasticity in the human cortex, making it potentially useful as a therapeutic tool. However, the induced changes are highly variable between individuals, potentially limiting research and clinical utility. One factor that might contribute to this variability is the level of cortical inhibition at the time of stimulation. The alpha rhythm (~ 8-13 Hz) recorded with electroencephalography (EEG) is thought to reflect pulsatile cortical inhibition; therefore, targeting non-invasive brain stimulation to particular phases of the alpha rhythm may provide an approach to enhance plasticity induction. Transcranial alternating current stimulation (tACS) has been shown to entrain cortical oscillations in a frequency-specific manner. We investigated whether the neuroplastic response to continuous theta burst stimulation (cTBS) was enhanced by timing bursts of stimuli to the peak or the trough of a tACS-imposed alpha rhythm. While motor evoked potentials (MEPs) were unaffected when cTBS was applied in-phase with the peak of the tACS-imposed oscillation, MEP depression was enhanced when cTBS was applied in-phase with the trough. This enhanced MEP depression was dependent on the individual peak frequency of the endogenous alpha rhythm recorded with EEG prior to stimulation, and was strongest in those participants classified as non-responders to standard cTBS. These findings suggest that tACS may be used in combination with cTBS to enhance the plasticity response. Furthermore, the peak frequency of endogenous alpha, as measured with EEG, may be used as a simple marker to pre-select those individuals likely to benefit from this approach. PMID:26663460

  3. Effects of weak transcranial alternating current stimulation on brain activity-a review of known mechanisms from animal studies.

    PubMed

    Reato, Davide; Rahman, Asif; Bikson, Marom; Parra, Lucas C

    2013-01-01

    Rhythmic neuronal activity is ubiquitous in the human brain. These rhythms originate from a variety of different network mechanisms, which give rise to a wide-ranging spectrum of oscillation frequencies. In the last few years an increasing number of clinical research studies have explored transcranial alternating current stimulation (tACS) with weak current as a tool for affecting brain function. The premise of these interventions is that tACS will interact with ongoing brain oscillations. However, the exact mechanisms by which weak currents could affect neuronal oscillations at different frequency bands are not well known and this, in turn, limits the rational optimization of human experiments. Here we review the available in vitro and in vivo animal studies that attempt to provide mechanistic explanations. The findings can be summarized into a few generic principles, such as periodic modulation of excitability, shifts in spike timing, modulation of firing rate, and shifts in the balance of excitation and inhibition. These effects result from weak but simultaneous polarization of a large number of neurons. Whether this can lead to an entrainment or a modulation of brain oscillations, or whether AC currents have no effect at all, depends entirely on the specific dynamic that gives rise to the different brain rhythms, as discussed here for slow wave oscillations (∼1 Hz) and gamma oscillations (∼30 Hz). We conclude with suggestions for further experiments to investigate the role of AC stimulation for other physiologically relevant brain rhythms. PMID:24167483

  4. Effect of the combined action of Faradaic currents and mobility differences in ac electro-osmosis

    NASA Astrophysics Data System (ADS)

    González, A.; Ramos, A.; García-Sánchez, P.; Castellanos, A.

    2010-01-01

    In this work, we extend previous analyses of ac electro-osmosis to account for the combined action of two experimentally relevant effects: (i) Faradaic currents from electrochemical reactions at the electrodes and (ii) differences in ion mobilities of the electrolyte. In previous works, the ac electro-osmotic motion has been analyzed theoretically under the assumption that only forces in the diffuse (Debye) layer are relevant. Here, we first show that if the ion mobilities of a 1-1 aqueous solution are different, the charged zone expands from the Debye layer to include the diffusion layer. We later include the Faradaic currents and, as an attempt to explore both factors simultaneously, we perform a thin-layer, low-frequency, linear analysis of the system. Finally, the model is applied to the case of an electrolyte actuated by a traveling-wave signal. A steady liquid motion in opposite direction to the applied signal is predicted for some ranges of the parameters. This could serve as a partial explanation for the observed flow reversal in some experiments.

  5. Fractional Modeling of the AC Large-Signal Frequency Response in Magnetoresistive Current Sensors

    PubMed Central

    Arias, Sergio Iván Ravello; Muñoz, Diego Ramírez; Moreno, Jaime Sánchez; Cardoso, Susana; Ferreira, Ricardo; de Freitas, Paulo Jorge Peixeiro

    2013-01-01

    Fractional calculus is considered when derivatives and integrals of non-integer order are applied over a specific function. In the electrical and electronic domain, the transfer function dependence of a fractional filter not only by the filter order n, but additionally, of the fractional order α is an example of a great number of systems where its input-output behavior could be more exactly modeled by a fractional behavior. Following this aim, the present work shows the experimental ac large-signal frequency response of a family of electrical current sensors based in different spintronic conduction mechanisms. Using an ac characterization set-up the sensor transimpedance function Zt(if) is obtained considering it as the relationship between sensor output voltage and input sensing current, Zt(jf)=Vo,sensor(jf)/Isensor(jf). The study has been extended to various magnetoresistance sensors based in different technologies like anisotropic magnetoresistance (AMR), giant magnetoresistance (GMR), spin-valve (GMR-SV) and tunnel magnetoresistance (TMR). The resulting modeling shows two predominant behaviors, the low-pass and the inverse low-pass with fractional index different from the classical integer response. The TMR technology with internal magnetization offers the best dynamic and sensitivity properties opening the way to develop actual industrial applications. PMID:24351648

  6. Fractional modeling of the AC large-signal frequency response in magnetoresistive current sensors.

    PubMed

    Ravelo Arias, Sergio Iván; Ramírez Muñoz, Diego; Moreno, Jaime Sánchez; Cardoso, Susana; Ferreira, Ricardo; de Freitas, Paulo Jorge Peixeiro

    2013-01-01

    Fractional calculus is considered when derivatives and integrals of non-integer order are applied over a specific function. In the electrical and electronic domain, the transfer function dependence of a fractional filter not only by the filter order n, but additionally, of the fractional order α is an example of a great number of systems where its input-output behavior could be more exactly modeled by a fractional behavior. Following this aim, the present work shows the experimental ac large-signal frequency response of a family of electrical current sensors based in different spintronic conduction mechanisms. Using an ac characterization set-up the sensor transimpedance function Z(t)(JF) is obtained considering it as the relationship between sensor output voltage and input sensing current, Z(t)(jf)= V(o, sensor)(jf)/I(sensor)(jf). The study has been extended to various magnetoresistance sensors based in different technologies like anisotropic magnetoresistance (AMR), giant magnetoresistance (GMR), spin-valve (GMR-SV) and tunnel magnetoresistance (TMR). The resulting modeling shows two predominant behaviors, the low-pass and the inverse low-pass with fractional index different from the classical integer response. The TMR technology with internal magnetization offers the best dynamic and sensitivity properties opening the way to develop actual industrial applications. PMID:24351648

  7. A Treatise on the Theory of Alternating Currents

    NASA Astrophysics Data System (ADS)

    Russell, Alexander

    2014-05-01

    1. Introduction. Electrostatics. Magnetism. Electrodynamics; 2. Alternating current in an inductive circuit. Self inductance formulae. Rectangle concentric main. Cylindrical wires; 3. The inductance of circular and helical currents. Rayleigh's formula. Maximum inductance. Mutual inductance of coaxial coils. Lorenz's formula. Mathematical tables; 4. Effective values. Choking coil and condenser currents. Effects of wave shape. Resonance; 5. Electrostatic capacity. Maxwell's equations. Capacity formulae for parallel cylinders. The capacities of three core cables in terms of Maxwell's coefficients; 6. Capacity formulae for cables. The capacity coefficients of overhead wires; 7. High frequency currents. Complete solution for a concentric main. Parallel conductors. Mathematical tables; 8. Problems in connection with spherical electrodes. The capacity coefficients. The attractions and repulsion. The maximum value of the electric stress; 9. Current oscillations. Inductively coupled electric circuits. Forced oscillations; 10. The theory of the power factor. Phase difference; 11. The method of the complex variable. Graphical solution; 12. Vectors in space. Failure of graphical methods; 13. The measurement of power. Watt-hour meters; 14. The air core transformer. Circle diagrams; 15. The theory of three phase currents. Power measurement; 16. The theory of two phase currents. Power measurement; 17. The conversion of polyphase systems. Phase indicators; 18. Rotating magnetic fields. Guiding magnetic fields; 19. The magnetic field bound single and polyphase cables. Losses in single, two and three phase cables. Dielectric losses; 20. Eddy current losses. Metal plates. Metal cylinders; 21. The method of duality. Reciprocal theorems; Index; Symbols; Index.

  8. Microfabricated AC impedance sensor

    DOEpatents

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

    2002-01-01

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

  9. Alternating current electrohydrodynamics in microsystems: Pushing biomolecules and cells around on surfaces.

    PubMed

    Vaidyanathan, Ramanathan; Dey, Shuvashis; Carrascosa, Laura G; Shiddiky, Muhammad J A; Trau, Matt

    2015-11-01

    Electrohydrodynamics (EHD) deals with the fluid motion induced by an electric field. This phenomenon originally developed in physical science, and engineering is currently experiencing a renaissance in microfluidics. Investigations by Taylor on Gilbert's theory proposed in 1600 have evolved to include multiple contributions including the promising effects arising from electric field interactions with cells and particles to influence their behaviour on electrode surfaces. Theoretical modelling of electric fields in microsystems and the ability to determine shear forces have certainly reached an advanced state. The ability to deftly manipulate microscopic fluid flow in bulk fluid and at solid/liquid interfaces has enabled the controlled assembly, coagulation, or removal of microstructures, nanostructures, cells, and molecules on surfaces. Furthermore, the ability of electrohydrodynamics to generate fluid flow using surface shear forces generated within nanometers from the surface and their application in bioassays has led to recent advancements in biomolecule, vesicle and cellular detection across different length scales. With the integration of Alternating Current Electrohydrodynamics (AC-EHD) in cellular and molecular assays proving to be highly fruitful, challenges still remain with respect to understanding the discrepancies between each of the associated ac-induced fluid flow phenomena, extending their utility towards clinical diagnostic development, and utilising them in tandem as a standard tool for disease monitoring. In this regard, this article will review the history of electrohydrodynamics, followed by some of the recent developments in the field including a new dimension of electrohydrodynamics that deals with the utilization of surface shear forces for the manipulation of biological cells or molecules on electrode surfaces. Recent advances and challenges in the use of electrohydrodynamic forces such as dielectrophoresis and ac electrosmosis for the

  10. AC over-current characteristics of YBCO coated conductor with copper stabilizer layer considering insulation layer

    NASA Astrophysics Data System (ADS)

    Du, H.-I.; Kim, M.-J.; Kim, Y.-J.; Lee, D.-H.; Han, B.-S.; Song, S.-S.

    2010-11-01

    Compared with the first-generation BSCCO wire, the YBCO thin-film wire boasts low material costs and high Jc and superior magnetic-field properties, among other strengths. Meanwhile, the previous BSCCO wire material for superconducting cables has been researched on considerably with regard to its post-wire quenching characteristics during the application of an alternating over-current. In this regard, the promising YBCO thin-film wire has yet to be further researched on. Moreover, still lacking is research on the YBCO thin-film wire with insulating layers, which is essential in the manufacture of superconducting cables, along with the testing of the application of an alternating over-current to the wire. In this study, YBCO thin-film wires with copper-stabilizing layers were used in testing alternating over-current application according to the presence or absence of insulating layers and to the thickness of such layers, to examine the post-quenching wire resistance increase and quenching trends. The YBCO thin-film wire with copper-stabilizing layers has a critical temperature of 90 K and a critical current of 85 A rms. Moreover, its current application cycle is 5.5 cycles, and its applied currents are 354, 517, 712, and 915 A peak. These figures enabled the YBCO thin-film wires with copper-stabilizing layers to reach 90, 180, 250, and 300 K, respectively, in this study. These temperatures serve as a relative reference to examine the post-quenching wire properties following the application of an alternating over-current.

  11. Hybrid superconducting a.c. current limiter extrapolation 63 kV-1 250 A

    NASA Astrophysics Data System (ADS)

    Tixador, P.; Levêque, J.; Brunet, Y.; Pham, V. D.

    1994-04-01

    Following the developement of a.c. superconducting wires a.c. current superconducting limiters have emerged. These limiters limit the fault currents nearly instantaneously, without detection nor order giver and may be suitable for high voltages. They are based on the natural transition from the superconducting state to the normal resistive state by overstepping the critical current of a superconducting coil which limits or triggers the limitation. Our limiter device consists essentially of two copper windings coupled through a saturable magnetic circuit and of a non inductively wound superconducting coil with a reduced current compared to the line current. This design allows a simple superconducting cable and reduced cryogenic losses but the dielectric stresses are high during faults. A small model (150 V/50 A) has experimentally validated our design. An industrial scale current limiter is designed and the comparisons between this design and other superconducting current limiters are given. Les courants de court-circuit sur les grands réseaux électriques ne cessent d'augmenter. Dans ce contexte sont apparus les limiteurs supraconducteurs de courant suite au développement des brins supraconducteurs alternatifs. Ces limiteurs peuvent limiter les courants de défaut presque instantanément, sans détection de défaut ni donneur d'ordre et ils sont extrapolables aux hautes tensions. Ils sont fondés sur la transition naturelle de l'état supraconducteur à l'état normal très résistif par dépassement du courant critique d'un enroulement supraconducteur qui limite ou déclenche la limitation. Notre limiteur est composé de deux enroulements en cuivre couplés par un circuit magnétique saturable et d'une bobine supraconductrice à courant réduit par rapport au courant de la ligne. Cette conception permet un câble supraconducteur simple et des pertes cryogéniques réduites mais les contraintes diélectriques en régime de défaut sont importantes. Une maquette

  12. Renal perfusion evaluation by alternating current biosusceptometry of magnetic nanoparticles

    NASA Astrophysics Data System (ADS)

    Quini, Caio C.; Matos, Juliana F.; Próspero, André G.; Calabresi, Marcos Felipe F.; Zufelato, Nicholas; Bakuzis, Andris F.; Baffa, Oswaldo; Miranda, José Ricardo A.

    2015-04-01

    Alternating current susceptometry, a simple and affordable technique, was employed to study the sensitivity of this approach to assess rat kidney perfusion by the injection of 200 μL of magnetic nanoparticles with a concentration of 23 mg/mL in the femoral vein and the measurement of the signal above the kidney. The instrument was able to detect the signal and the transit time of the first and second pass were measured in five animals with average values of 13.6±4.3 s and 20.6±7.1 s.

  13. Training Course for Power Operating Personnel. Lesson No. 6: Alternating-Current Generator Excitation.

    ERIC Educational Resources Information Center

    Department of the Interior, Denver, CO. Engineering and Research Center.

    Subjects covered in this text are controlling the hydroelectric generator, generator excitation, basic principles of direct current generation, direction of current flow, basic alternating current generator, alternating and direct current voltage outputs, converting alternating current to direct current, review of the basic generator and…

  14. Magnetic phase characterization of nanocrystalline La2NiMnO6 using alternating current conductance

    NASA Astrophysics Data System (ADS)

    Chakraborty, D.; Nandi, U. N.; Jana, D.; Masud, Md G.; Giri, S.

    2015-07-01

    The signature of various disordered phases is inferred from the measurement of the real part of alternating current conductance Σ(T, f) of a nanocrystalline double perovskite La2NiMnO6. The system exhibits a paramagnetic insulating (PMI) phase at high temperatures, a ferromagnetic insulating (FMI) phase at low temperatures, and a Griffiths-like phase in the intermediate temperature range. In these three phases, Σ(T, f) shows qualitatively similar variation with frequency f. At a fixed temperature T, Σ(T, f) remains constant to its Ohmic value Σ0 up to a certain frequency, known as the onset frequency fc and increases with increasing f beyond fc. Scaled appropriately, Σ(T, f) versus f data corresponding to these three regimes fall on the same master curve indicating the universal nature of the scaling behaviour of alternating current conductance. This onset frequency fc scales with Σ0 as f c ˜ Σ0 x f with xf as the nonlinearity exponent. This exponent xf shows a gradual crossover from 1.025 ± 0.006 in FMI phase to 0.518 ± 0.07 in PMI phase in an intermediate temperature range signifying the presence of Griffiths-like phase. A simple phenomenological R-RC model consistent with the microstructural conduction mechanisms in PMI and FMI phases is developed to generate the qualitative non-Ohmic character of ac conductance, the onset frequency fc, and the nonlinearity exponent xf. Existing scaling theories with reliable models are used to analyze and compare the results of ac conductance in similar systems.

  15. Thin-film Josephson junctions with alternating critical current density

    NASA Astrophysics Data System (ADS)

    Moshe, Maayan; Kogan, V. G.; Mints, R. G.

    2009-01-01

    We study the field dependence of the maximum current Im(H) in narrow edge-type thin-film Josephson junctions with alternating critical current density. Im(H) is evaluated within nonlocal Josephson electrodynamics taking into account the stray fields that affect the difference of the order-parameter phases across the junction and therefore the tunneling currents. We find that the phase difference along the junction is proportional to the applied field, depends on the junction geometry, but is independent of the Josephson critical current density gc , i.e., it is universal. An explicit form for this universal function is derived for small currents through junctions of the width W≪Λ , the Pearl length. The result is used to calculate Im(H) . It is shown that the maxima of Im(H)∝1/H and the zeros of Im(H) are equidistant but only in high fields. We find that the spacing between zeros is proportional to 1/W2 . The general approach is applied to calculate Im(H) for a superconducting quantum interference device with two narrow edge-type junctions. If gc changes sign periodically or randomly, as it does in grain boundaries of high- Tc materials and superconductor-ferromagnet-superconductor heterostructures, Im(H) not only acquires the major side peaks, but due to nonlocality the following peaks decay much slower than in bulk junctions.

  16. Simultaneous distribution of AC and DC power

    DOEpatents

    Polese, Luigi Gentile

    2015-09-15

    A system and method for the transport and distribution of both AC (alternating current) power and DC (direct current) power over wiring infrastructure normally used for distributing AC power only, for example, residential and/or commercial buildings' electrical wires is disclosed and taught. The system and method permits the combining of AC and DC power sources and the simultaneous distribution of the resulting power over the same wiring. At the utilization site a complementary device permits the separation of the DC power from the AC power and their reconstruction, for use in conventional AC-only and DC-only devices.

  17. Demagnetization Treatment of Remanent Composite Microspheres Studied by Alternating Current Susceptibility Measurements

    PubMed Central

    van Berkum, Susanne; Erné, Ben H.

    2013-01-01

    The magnetic remanence of silica microspheres with a low concentration of embedded cobalt ferrite nanoparticles is studied after demagnetization and remagnetization treatments. When the microspheres are dispersed in a liquid, alternating current (AC) magnetic susceptibility spectra reveal a constant characteristic frequency, corresponding to the rotational diffusion of the microparticles; this depends only on particle size and liquid viscosity, making the particles suitable as a rheological probe and indicating that interactions between the microspheres are weak. On the macroscopic scale, a sample with the dry microparticles is magnetically remanent after treatment in a saturating field, and after a demagnetization treatment, the remanence goes down to zero. The AC susceptibility of a liquid dispersion, however, characterizes the remanence on the scale of the individual microparticles, which does not become zero after demagnetization. The reason is that an individual microparticle contains only a relatively small number of magnetic units, so that even if they can be reoriented magnetically at random, the average vector sum of the nanoparticle dipoles is not negligible on the scale of the microparticle. In contrast, on the macroscopic scale, the demagnetization procedure randomizes the orientations of a macroscopic number of magnetic units, resulting in a remanent magnetization that is negligible compared to the saturation magnetization of the entire sample. PMID:24009021

  18. Alternating current electrospinning for preparation of fibrous drug delivery systems.

    PubMed

    Balogh, Attila; Cselkó, Richárd; Démuth, Balázs; Verreck, Geert; Mensch, Jürgen; Marosi, György; Nagy, Zsombor Kristóf

    2015-11-10

    Alternating current electrospinning (ACES) was compared to direct current electrospinning (DCES) for the preparation of drug-loaded nanofibrous mats. It is generally considered that DCES is the solely technique to produce nanofibers using the electrostatic force from polymer solutions, however, less studied and also capable ACES provides further advantages such as increased specific productivities. A poorly water-soluble drug (carvedilol) was incorporated into the fibers based on three different polymeric matrices (an acid-soluble terpolymer (Eudragit(®) E), a base-soluble copolymer (Eudragit(®) L 100-55) and a nonionic homopolymer (polyvinylpyrrolidone K90)) to improve the dissolution of the weak base drug under different pH conditions. Morphology and fiber diameter evaluation showed similar electrospun fibers regardless the type of the high voltage and the major differences in feeding rates. The amorphous ACES and DCES fibers provided fast and total drug dissolutions in all cases. The presented results show that ACES can be a more feasible novel alternative to formulate fibers for drug delivery purposes.

  19. Application of alternating current impedance to fuel cell modeling

    SciTech Connect

    Springer, T.E.

    1999-05-02

    AC impedance has provided a useful diagnostic tool in the Los Alamos polymer electrolyte fuel cell (PEFC) program. The author reviews the techniques he has used in ac impedance modeling. These techniques include equation implementation, model simplification and verification, least squares fitting, application of two-dimensional Laplace equation solvers handling complex interfacial boundary conditions, and interpretation of impedance features. The separate features of the complete electrode model are explained by analytic examples.

  20. Improvement of immunoassay detection system by using alternating current magnetic susceptibility.

    PubMed

    Kawabata, R; Mizoguchi, T; Kandori, A

    2016-03-01

    A major goal with this research was to develop a low-cost and highly sensitive immunoassay detection system by using alternating current (AC) magnetic susceptibility. We fabricated an improved prototype of our previously developed immunoassay detection system and evaluated its performance. The prototype continuously moved sample containers by using a magnetically shielded brushless motor, which passes between two anisotropic magneto resistance (AMR) sensors. These sensors detected the magnetic signal in the direction where each sample container passed them. We used the differential signal obtained from each AMR sensor's output to improve the signal-to-noise ratio (SNR) of the magnetic signal measurement. Biotin-conjugated polymer beads with avidin-coated magnetic particles were prepared to examine the calibration curve, which represents the relation between AC magnetic susceptibility change and polymer-bead concentration. For the calibration curve measurement, we, respectively, measured the magnetic signal caused by the magnetic particles by using each AMR sensor installed near the upper or lower part in the lateral position of the passing sample containers. As a result, the SNR of the prototype was 4.5 times better than that of our previous system. Moreover, the data obtained from each AMR sensor installed near the upper part in the lateral position of the passing sample containers exhibited an accurate calibration curve that represented good correlation between AC magnetic susceptibility change and polymer-bead concentration. The conclusion drawn from these findings is that our improved immunoassay detection system will enable a low-cost and highly sensitive immunoassay.

  1. Improvement of immunoassay detection system by using alternating current magnetic susceptibility

    NASA Astrophysics Data System (ADS)

    Kawabata, R.; Mizoguchi, T.; Kandori, A.

    2016-03-01

    A major goal with this research was to develop a low-cost and highly sensitive immunoassay detection system by using alternating current (AC) magnetic susceptibility. We fabricated an improved prototype of our previously developed immunoassay detection system and evaluated its performance. The prototype continuously moved sample containers by using a magnetically shielded brushless motor, which passes between two anisotropic magneto resistance (AMR) sensors. These sensors detected the magnetic signal in the direction where each sample container passed them. We used the differential signal obtained from each AMR sensor's output to improve the signal-to-noise ratio (SNR) of the magnetic signal measurement. Biotin-conjugated polymer beads with avidin-coated magnetic particles were prepared to examine the calibration curve, which represents the relation between AC magnetic susceptibility change and polymer-bead concentration. For the calibration curve measurement, we, respectively, measured the magnetic signal caused by the magnetic particles by using each AMR sensor installed near the upper or lower part in the lateral position of the passing sample containers. As a result, the SNR of the prototype was 4.5 times better than that of our previous system. Moreover, the data obtained from each AMR sensor installed near the upper part in the lateral position of the passing sample containers exhibited an accurate calibration curve that represented good correlation between AC magnetic susceptibility change and polymer-bead concentration. The conclusion drawn from these findings is that our improved immunoassay detection system will enable a low-cost and highly sensitive immunoassay.

  2. Reversible Nerve Conduction Block Using Kilohertz Frequency Alternating Current

    PubMed Central

    Kilgore, Kevin L.; Bhadra, Niloy

    2013-01-01

    Objectives The features and clinical applications of balanced-charge kilohertz frequency alternating currents (KHFAC) are reviewed. Preclinical studies of KHFAC block have demonstrated that it can produce an extremely rapid and reversible block of nerve conduction. Recent systematic analysis and experimentation utilizing KHFAC block has resulted in a significant increase in interest in KHFAC block, both scientifically and clinically. Materials and Methods We review the history and characteristics of KHFAC block, the methods used to investigate this type of block, the experimental evaluation of block, and the electrical parameters and electrode designs needed to achieve successful block. We then analyze the existing clinical applications of high frequency currents, comparing the early results with the known features of KHFAC block. Results Although many features of KHFAC block have been characterized, there is still much that is unknown regarding the response of neural structures to rapidly fluctuating electrical fields. The clinical reports to date do not provide sufficient information to properly evaluate the mechanisms that result in successful or unsuccessful treatment. Conclusions KHFAC nerve block has significant potential as a means of controlling nerve activity for the purpose of treating disease. However, early clinical studies in the use of high frequency currents for the treatment of pain have not been designed to elucidate mechanisms or allow direct comparisons to preclinical data. We strongly encourage the careful reporting of the parameters utilized in these clinical studies, as well as the development of outcome measures that could illuminate the mechanisms of this modality. PMID:23924075

  3. Alternatives to animal testing: current status and future perspectives.

    PubMed

    Liebsch, Manfred; Grune, Barbara; Seiler, Andrea; Butzke, Daniel; Oelgeschläger, Michael; Pirow, Ralph; Adler, Sarah; Riebeling, Christian; Luch, Andreas

    2011-08-01

    On the occasion of the 20th anniversary of the Center for Alternative Methods to Animal Experiments (ZEBET), an international symposium was held at the German Federal Institute for Risk Assessment (BfR) in Berlin. At the same time, this symposium was meant to celebrate the 50th anniversary of the publication of the book "The Principles of Humane Experimental Technique" by Russell and Burch in 1959 in which the 3Rs principle (that is, Replacement, Reduction, and Refinement) has been coined and introduced to foster the development of alternative methods to animal testing. Another topic addressed by the symposium was the new vision on "Toxicology in the twenty-first Century", as proposed by the US-National Research Council, which aims at using human cells and tissues for toxicity testing in vitro rather than live animals. An overview of the achievements and current tasks, as well as a vision of the future to be addressed by ZEBET@BfR in the years to come is outlined in the present paper.

  4. Quantitative Thermal Microscopy Measurement with Thermal Probe Driven by dc+ac Current

    NASA Astrophysics Data System (ADS)

    Bodzenta, Jerzy; Juszczyk, Justyna; Kaźmierczak-Bałata, Anna; Firek, Piotr; Fleming, Austin; Chirtoc, Mihai

    2016-07-01

    Quantitative thermal measurements with spatial resolution allowing the examination of objects of submicron dimensions are still a challenging task. The quantity of methods providing spatial resolution better than 100 nm is very limited. One of them is scanning thermal microscopy (SThM). This method is a variant of atomic force microscopy which uses a probe equipped with a temperature sensor near the apex. Depending on the sensor current, either the temperature or the thermal conductivity distribution at the sample surface can be measured. However, like all microscopy methods, the SThM gives only qualitative information. Quantitative measuring methods using SThM equipment are still under development. In this paper, a method based on simultaneous registration of the static and the dynamic electrical resistances of the probe driven by the sum of dc and ac currents, and examples of its applications are described. Special attention is paid to the investigation of thin films deposited on thick substrates. The influence of substrate thermal properties on the measured signal and its dependence on thin film thermal conductivity and film thickness are analyzed. It is shown that in the case where layer thicknesses are comparable or smaller than the probe-sample contact diameter, a correction procedure is required to obtain actual thermal conductivity of the layer. Experimental results obtained for thin SiO2 and BaTiO_{3 }layers with thicknesses in the range from 11 nm to 100 nm are correctly confirmed with this approach.

  5. AC Electrokinetics of Physiological Fluids for Biomedical Applications.

    PubMed

    Lu, Yi; Liu, Tingting; Lamanda, Ariana C; Sin, Mandy L Y; Gau, Vincent; Liao, Joseph C; Wong, Pak Kin

    2015-12-01

    Alternating current (AC) electrokinetics is a collection of processes for manipulating bulk fluid mass and embedded objects with AC electric fields. The ability of AC electrokinetics to implement the major microfluidic operations, such as pumping, mixing, concentration, and separation, makes it possible to develop integrated systems for clinical diagnostics in nontraditional health care settings. The high conductivity of physiological fluids presents new challenges and opportunities for AC electrokinetics-based diagnostic systems. In this review, AC electrokinetic phenomena in conductive physiological fluids are described followed by a review of the basic microfluidic operations and the recent biomedical applications of AC electrokinetics. The future prospects of AC electrokinetics for clinical diagnostics are presented.

  6. Evaluation of calcium alginate gel as electrode material for alternating current iontophoresis of lidocaine using excised rat skin.

    PubMed

    Ebisawa, Tomoko; Nakajima, Atsushi; Haida, Haruka; Wakita, Ryo; Ando, Shizuka; Yoshioka, Tomohiko; Ikoma, Toshiyuki; Tanaka, Junzo; Fukayama, Haruhisa

    2014-01-01

    Iontophoresis (IOP) is a noninvasive method of delivering medication transcutaneously through the skin. The electrodes used in this method should tightly fit to rough and irregular surfaces and be biologically safe, easy to handle and prepare, and cost-effective. To satisfy these requirements, calcium alginate gel can be a candidate electrode for IOP. Using calcium alginate gel electrodes, we examined whether lidocaine can be effectively transported across an excised rat skin by squarewave alternating current (AC) application. A squarewave AC with either a 70% or 80% duty cycle was continuously applied to 0.5% calcium alginate gel electrodes containing 10% lidocaine at 10 V and 1 kHz for 60 min. Lidocaine concentration was measured using a spectrophotometer and the temperature of the gel was determined. The lidocaine concentrations for AC-IOP at the 70% and 80% duty cycles were significantly higher than that without AC-IOP. Furthermore, the group with the 80% duty cycle showed higher lidocaine concentrations than the group with the 70% duty cycle. The temperatures of all the groups were lower than 28 °C throughout the procedure. In conclusion, the calcium alginate gel can be used as a possible matrix for IOP electrodes.

  7. 46 CFR 111.05-27 - Grounded neutral alternating current systems.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 46 Shipping 4 2014-10-01 2014-10-01 false Grounded neutral alternating current systems. 111.05-27... Grounded neutral alternating current systems. Grounded neutral and high-impedance grounded neutral alternating current systems must have a suitably sensitive ground detection system which indicates current...

  8. 46 CFR 111.05-27 - Grounded neutral alternating current systems.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 46 Shipping 4 2010-10-01 2010-10-01 false Grounded neutral alternating current systems. 111.05-27... Grounded neutral alternating current systems. Grounded neutral and high-impedance grounded neutral alternating current systems must have a suitably sensitive ground detection system which indicates current...

  9. 46 CFR 111.05-27 - Grounded neutral alternating current systems.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 46 Shipping 4 2013-10-01 2013-10-01 false Grounded neutral alternating current systems. 111.05-27... Grounded neutral alternating current systems. Grounded neutral and high-impedance grounded neutral alternating current systems must have a suitably sensitive ground detection system which indicates current...

  10. 46 CFR 111.05-27 - Grounded neutral alternating current systems.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 46 Shipping 4 2011-10-01 2011-10-01 false Grounded neutral alternating current systems. 111.05-27... Grounded neutral alternating current systems. Grounded neutral and high-impedance grounded neutral alternating current systems must have a suitably sensitive ground detection system which indicates current...

  11. 46 CFR 111.05-27 - Grounded neutral alternating current systems.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 46 Shipping 4 2012-10-01 2012-10-01 false Grounded neutral alternating current systems. 111.05-27... Grounded neutral alternating current systems. Grounded neutral and high-impedance grounded neutral alternating current systems must have a suitably sensitive ground detection system which indicates current...

  12. Current Pharmaceutical Treatments and Alternative Therapies of Parkinson's Disease.

    PubMed

    Dong, Jie; Cui, Yanhua; Li, Song; Le, Weidong

    2016-01-01

    Over the decades, pharmaceutical treatments, particularly dopaminergic (DAergic) drugs have been considered as the main therapy against motor symptoms of Parkinson's disease (PD). It is proposed that DAergic drugs in combination with other medications, such as monoamine oxidase type B inhibitors, catechol-O-methyl transferase inhibitors, anticholinergics and other newly developed non-DAergic drugs can make a better control of motor symptoms or alleviate levodopa-induced motor complications. Moreover, non-motor symptoms of PD, such as cognitive, neuropsychiatric, sleep, autonomic and sensory disturbances caused by intrinsic PD pathology or drug-induced side effects, are gaining increasing attention and urgently need to be taken care of due to their impact on quality of life. Currently, neuroprotective therapies have been investigated extensively in pre-clinical studies, and some of them have been subjected to clinical trials. Furthermore, non-pharmaceutical treatments, including deep brain stimulation (DBS), gene therapy, cell replacement therapy and some complementary managements, such as Tai chi, Yoga, traditional herbs and molecular targeted therapies have also been considered as effective alternative therapies to classical pharmaceutics. This review will provide us updated information regarding the current drugs and non-drugs therapies for PD. PMID:26585523

  13. Comparison of direct current and 50 Hz alternating current microscopic corona characteristics on conductors

    SciTech Connect

    Zhang, Shuai Zhang, Bo He, Jinliang

    2014-06-15

    Corona discharge is one of the major design factors for extra-high voltage and ultra-high voltage DC/AC transmission lines. Under different voltages, corona discharge reveals different characteristics. This paper aims at investigating DC and AC coronas on the microscopic scale. To obtain the specific characteristics of DC and AC coronas, a new measurement approach that utilizes a coaxial wire-cylinder corona cage is designed in this paper, and wires of different diameters are used in the experiment. Based on the measurements, the respective microscopic characteristics of DC and AC coronas are analyzed and compared. With differences in characteristics between DC and AC coronas proposed, this study provides useful insights into DC/AC corona discharges on transmission line applications.

  14. Transcranial alternating current stimulation increases risk-taking behavior in the balloon analog risk task.

    PubMed

    Sela, Tal; Kilim, Adi; Lavidor, Michal

    2012-01-01

    The process of evaluating risks and benefits involves a complex neural network that includes the dorsolateral prefrontal cortex (DLPFC). It has been proposed that in conflict and reward situations, theta-band (4-8 Hz) oscillatory activity in the frontal cortex may reflect an electrophysiological mechanism for coordinating neural networks monitoring behavior, as well as facilitating task-specific adaptive changes. The goal of the present study was to investigate the hypothesis that theta-band oscillatory balance between right and left frontal and prefrontal regions, with a predominance role to the right hemisphere (RH), is crucial for regulatory control during decision-making under risk. In order to explore this hypothesis, we used transcranial alternating current stimulation, a novel technique that provides the opportunity to explore the functional role of neuronal oscillatory activities and to establish a causal link between specific oscillations and functional lateralization in risky decision-making situations. For this aim, healthy participants were randomly allocated to one of three stimulation groups (LH stimulation/RH stimulation/Sham stimulation), with active AC stimulation delivered in a frequency-dependent manner (at 6.5 Hz; 1 mA peak-to-peak). During the AC stimulation, participants performed the Balloon Analog Risk Task. This experiment revealed that participants receiving LH stimulation displayed riskier decision-making style compared to sham and RH stimulation groups. However, there was no difference in decision-making behaviors between sham and RH stimulation groups. The current study extends the notion that DLPFC activity is critical for adaptive decision-making in the context of risk-taking and emphasis the role of theta-band oscillatory activity during risky decision-making situations.

  15. Transcranial Alternating Current Stimulation Increases Risk-Taking Behavior in the Balloon Analog Risk Task

    PubMed Central

    Sela, Tal; Kilim, Adi; Lavidor, Michal

    2011-01-01

    The process of evaluating risks and benefits involves a complex neural network that includes the dorsolateral prefrontal cortex (DLPFC). It has been proposed that in conflict and reward situations, theta-band (4–8 Hz) oscillatory activity in the frontal cortex may reflect an electrophysiological mechanism for coordinating neural networks monitoring behavior, as well as facilitating task-specific adaptive changes. The goal of the present study was to investigate the hypothesis that theta-band oscillatory balance between right and left frontal and prefrontal regions, with a predominance role to the right hemisphere (RH), is crucial for regulatory control during decision-making under risk. In order to explore this hypothesis, we used transcranial alternating current stimulation, a novel technique that provides the opportunity to explore the functional role of neuronal oscillatory activities and to establish a causal link between specific oscillations and functional lateralization in risky decision-making situations. For this aim, healthy participants were randomly allocated to one of three stimulation groups (LH stimulation/RH stimulation/Sham stimulation), with active AC stimulation delivered in a frequency-dependent manner (at 6.5 Hz; 1 mA peak-to-peak). During the AC stimulation, participants performed the Balloon Analog Risk Task. This experiment revealed that participants receiving LH stimulation displayed riskier decision-making style compared to sham and RH stimulation groups. However, there was no difference in decision-making behaviors between sham and RH stimulation groups. The current study extends the notion that DLPFC activity is critical for adaptive decision-making in the context of risk-taking and emphasis the role of theta-band oscillatory activity during risky decision-making situations. PMID:22347844

  16. AC photovoltaic module magnetic fields

    SciTech Connect

    Jennings, C.; Chang, G.J.; Reyes, A.B.; Whitaker, C.M.

    1997-12-31

    Implementation of alternating current (AC) photovoltaic (PV) modules, particularly for distributed applications such as PV rooftops and facades, may be slowed by public concern about electric and magnetic fields (EMF). This paper documents magnetic field measurements on an AC PV module, complementing EMF research on direct-current PV modules conducted by PG and E in 1993. Although not comprehensive, the PV EMF data indicate that 60 Hz magnetic fields (the EMF type of greatest public concern) from PV modules are comparable to, or significantly less than, those from household appliances. Given the present EMF research knowledge, AC PV module EMF may not merit considerable concern.

  17. Study of corrosion of super martensitic stainless steel under alternating current in artificial seawater with electrochemical impedance spectroscopy

    SciTech Connect

    Reyes, T.; Bhola, S.; Olson, D. L.; Mishra, B.

    2011-06-23

    The assessment of corrosion requires the use of tools able to quantify the corrosion but often times also qualify it. Electrochemical Impedance Spectroscopy (EIS) is a laboratory tool that can provide both qualification and quantification of corrosion. EIS was successfully used to compare the thickness of the corrosion products formed during the application of different alternating current (AC) densities as well as to characterize pitting. When EIS is applied at the open circuit potential, the technique is nondestructive and predicts the corrosion behavior of the electrode. It can also be used at cathodic potentials while still being nondestructive, providing information about the electrode reaction kinetics, diffusion and electrical double layer.

  18. Mixing enhancement by biologically inspired convection in a micro-chamber using alternating current galvanotactic control of the Tetrahymena pyriformis

    NASA Astrophysics Data System (ADS)

    Kim, Jihoon; Jang, Yonghee; Byun, Doyoung; Hyung Kim, Dal; Jun Kim, Min

    2013-09-01

    Recently, there has been increasing interest in the swimming behavior of microorganisms and biologically inspired micro-robots. In this study, we investigated biologically induced convection flow with living microorganism using galvanotaxis. We fabricated and evaluated our micro-mixer with motile cells. For the cell based active micro-mixers, two miscible fluids were used to measure the mixing index. Under alternating current (AC) electric fields with varying frequency, a group of motile Tetrahymena pyriformis cells generated reciprocal motion with circulating flows around their pathline, enhancing the mixing ratio.

  19. Critical state solution and alternating current loss computation of polygonally arranged thin superconducting tapes

    NASA Astrophysics Data System (ADS)

    Brambilla, Roberto; Grilli, Francesco; Martini, Luciano

    2013-08-01

    The current density and field distributions in polygonally arranged thin superconducting tapes carrying AC current are derived under the assumption of the critical state model. Starting from the generic Biot-Savart law for a general polygonal geometry, we derive a suitable integral equation for the calculation of the current density and magnetic field in each tape. The model works for any transport current below Ic, which makes it attractive for studying cases of practical interest, particularly the dependence of AC losses on parameters such as the number of tapes, their distance from the center, and their separation.

  20. Alternating-current conductivity and dielectric relaxation of bulk iodoargentate

    SciTech Connect

    Duan, Hai-Bao Yu, Shan-Shan; Zhou, Hong

    2015-05-15

    Graphical abstract: The electric modulus shows single dielectric relaxation process in the measured frequency range. - Highlights: • The conduction mechanism is described by quantum mechanical tunneling model. • The applications of dielectric modulus give a simple method for evaluating the activation energy of the dielectric relaxation. • The [Ag{sub 2}I{sub 4}]{sup 2−}1-D chain and [Cu(en){sub 2}]{sup 2+} cation column form the layered stacks by hydrogen bond interactions. - Abstract: An inorganic-organic hybrid compound Cu(en){sub 2}Ag{sub 2}I{sub 4} (en = ethylenediamine) (1) was synthesized and single crystal structurally characterized. Along the [001] direction, the inorganic parts form an infinite 1-D chain and [Cu(en){sub 2}]{sup 2+} cations are separated by inorganic chain. The electrical conductivity and dielectric properties of 1 have been investigated over wide ranges of frequency. The alternating-current conductivities have been fitted to the Almond–West type power law expression with use of a single value of S. It is found that S values for 1 are nearly temperature-independent, which indicates that the conduction mechanism could be quantum mechanical tunneling (QMT) model. The dielectric loss and electric modulus show single dielectric relaxation process. The activation energy obtained from temperature-dependent electric modulus compare with the calculated from the dc conductivity plots.

  1. Internal heating of lithium-ion batteries using alternating current based on the heat generation model in frequency domain

    NASA Astrophysics Data System (ADS)

    Zhang, Jianbo; Ge, Hao; Li, Zhe; Ding, Zhanming

    2015-01-01

    This study develops a method to internally preheat lithium-ion batteries at low temperatures with sinusoidal alternating current (AC). A heat generation rate model in frequency domain is developed based on the equivalent electrical circuit. Using this model as the source term, a lumped energy conservation model is adopted to predict the temperature rise. These models are validated against the experimental results of preheating an 18650 cell at different thermal insulation conditions. The effects of current amplitude and frequency on the heating rate are illustrated with a series of simulated contours of heating time. These contours indicate that the heating rate increases with higher amplitude, lower frequency and better thermal insulation. The cell subjected to an alternating current with an amplitude of 7 A (2.25 C) and a frequency of 1 Hz, under a calibrated heat transfer coefficient of 15.9 W m-2 K-1, can be heated from -20 °C to 5 °C within 15 min and the temperature distribution remains essentially uniform. No capacity loss is found after repeated AC preheating tests, indicating this method incurs little damage to the battery health. These models are computationally-efficient and can be used in real time to control the preheating devices in electric vehicles.

  2. Current and Needed Research on Alternative Certification Programs

    ERIC Educational Resources Information Center

    Ham, Edward

    2010-01-01

    With alternative certification programs gaining popularity in teacher education, the need to evaluate these programs has become much more necessary. Without strict guidelines to classify alternative certification programs, it is difficult to make generalizations about these programs because of different requirements for completion and…

  3. Alternating current response of carbon nanotubes with randomly distributed impurities

    SciTech Connect

    Hirai, Daisuke; Watanabe, Satoshi; Yamamoto, Takahiro

    2014-10-27

    The increasing need for nanodevices has necessitated a better understanding of the electronic transport behavior of nanomaterials. We therefore theoretically examine the AC transport properties of metallic carbon nanotubes with randomly distributed impurities. We find that the long-range impurity scattering increases the emittance, but does not affect the DC conductance. The estimated dwell time of electrons increases with the potential amplitudes. That is, multiple scattering by the impurities increases the kinetic inductance in proportion to the dwell time, which eventually increases the emittance. We believe that our findings can contribute significantly to nanodevice development.

  4. Thermal Dissipation Modelling and Design of ITER PF Converter Alternating Current Busbar

    NASA Astrophysics Data System (ADS)

    Guo, Bin; Song, Zhiquan; Fu, Peng; Jiang, Li; Li, Jinchao; Wang, Min; Dong, Lin

    2016-10-01

    Because the larger metallic surrounds are heated by the eddy current, which is generated by the AC current flowing through the AC busbar in the International Thermonuclear Experimental Reactor (ITER) poloidal field (PF) converter system, shielding of the AC busbar is required to decrease the temperature rise of the surrounds to satisfy the design requirement. Three special types of AC busbar with natural cooling, air cooling and water cooling busbar structure have been proposed and investigated in this paper. For each cooling scheme, a 3D finite model based on the proposed structure has been developed to perform the electromagnetic and thermal analysis to predict their operation behavior. Comparing the analysis results of the three different cooling patterns, water cooling has more advantages than the other patterns and it is selected to be the thermal dissipation pattern for the AC busbar of ITER PF converter unit. The approach to qualify the suitable cooling scheme in this paper can be provided as a reference on the thermal dissipation design of AC busbar in the converter system. supported by National Natural Science Foundation of China (No. 51407179)

  5. High frequency alternating current chip nano calorimeter with laser heating

    SciTech Connect

    Shoifet, E.; Schick, C.; Chua, Y. Z.; Huth, H.

    2013-07-15

    Heat capacity spectroscopy at frequencies up to 100 kHz is commonly performed by thermal effusivity measurements applying the 3ω-technique. Here we show that AC-calorimetry using a thin film chip sensor allows for the measurement of frequency dependent heat capacity in the thin film limit up to about 1 MHz. Using films thinner than the thermal length of the thermal wave (∼1 μm) at such frequencies is advantageous because it provides heat capacity alone and not in combination with other quantities like thermal conductivity, at least on a qualitative basis. The used calorimetric sensor and the sample are each less than 1 μm thick. For high frequency AC-calorimetry, high cooling rates at very small temperature differences are required. This is realized by minimizing the heated spot to the size of the on chip thermocouple (3 × 6 μm{sup 2}). A modulated laser beam shaped and positioned by a glass fiber is used as the heat source. The device was used to measure the complex heat capacity in the vicinity of the dynamic glass transition (structural relaxation) of poly(methyl methacrylate). Combining different calorimeters finally provides data between 10{sup −3} Hz and 10{sup 6} Hz. In this frequency range the dynamic glass transition shifts about 120 K.

  6. Angular Dependence of Transport AC Losses in Superconducting Wire with Position-Dependent Critical Current Density in a DC Magnetic Field

    NASA Astrophysics Data System (ADS)

    Su, Xing-liang; Xiong, Li-ting; Gao, Yuan-wen; Zhou, You-he

    2013-07-01

    Transport AC losses play a very important role in high temperature superconductors (HTSs), which usually carry AC transport current under applied magnetic field in typical application-like conditions. In this paper, we propose the analytical formula for transport AC losses in HTS wire by considering critical current density of both inhomogeneous and anisotropic field dependent. The angular dependence of critical current density is described by effective mass theory, and the HTS wire has inhomogeneous distribution cross-section of critical current density. We calculate the angular dependence of normalized AC losses under different DC applied magnetic fields. The numerical results of this formula agree well with the experiment data and are better than the results of Norris formula. This analytical formula can explain the deviation of experimental transport current losses from the Norris formula and apply to calculate transport AC losses in realistic practical condition.

  7. Current Status of Helium-3 Alternative Technologies for Nuclear Safeguards

    SciTech Connect

    Henzlova, Daniela; Kouzes, R.; McElroy, R.; Peerani, P.; Aspinall, M.; Baird, K.; Bakel, A.; Borella, M.; Bourne, M.; Bourva, L.; Cave, F.; Chandra, R.; Chernikova, D.; Croft, S.; Dermody, G.; Dougan, A.; Ely, J.; Fanchini, E.; Finocchiaro, P.; Gavron, Victor; Kureta, M.; Ianakiev, Kiril Dimitrov; Ishiyama, K.; Lee, T.; Martin, Ch.; McKinny, K.; Menlove, Howard Olsen; Orton, Ch.; Pappalardo, A.; Pedersen, B.; Peranteau, D.; Plenteda, R.; Pozzi, S.; Schear, M.; Seya, M.; Siciliano, E.; Stave, S.; Sun, L.; Swinhoe, Martyn Thomas; Tagziria, H.; Vaccaro, S.; Takamine, J.; Weber, A. -L.; Yamaguchi, T.; Zhu, H.

    2015-12-01

    International safeguards inspectorates (e.g., International Atomic Energy Agency {IAEA}, or Euratom) rely heavily on neutron assay techniques, and in particular, on coincidence counters for the verification of declared nuclear materials under safeguards and for monitoring purposes. While 3He was readily available, the reliability, safety, ease of use, gamma-ray insensitivity, and high intrinsic thermal neutron detection efficiency of 3He-based detectors obviated the need for alternative detector technologies. However, the recent decline of the 3He gas supply has triggered international efforts to develop and field neutron detectors that make use of alternative materials. In response to this global effort, the U.S. Department of Energy’s (DOE) National Nuclear Security Administration (NNSA) and Euratom launched a joint effort aimed at bringing together international experts, technology users and developers in the field of nuclear safeguards to discuss and evaluate the proposed 3He alternative materials and technologies. The effort involved a series of two workshops focused on detailed overviews and viability assessments of various 3He alternative technologies for use in nuclear safeguards applications. The key objective was to provide a platform for collaborative discussions and technical presentations organized in a compact, workshop-like format to stimulate interactions among the participants. The meetings culminated in a benchmark exercise providing a unique opportunity for the first inter-comparison of several available alternative technologies. This report provides an overview of the alternative technology efforts presented during the two workshops along with a summary of the benchmarking activities and results. The workshop recommendations and key consensus observations are discussed in the report, and used to outline a proposed path forward and future needs foreseeable in the area of 3He-alternative

  8. Qualifications and Assignments of Alternatively Certified Teachers: Testing Core Assumptions

    ERIC Educational Resources Information Center

    Cohen-Vogel, Lora; Smith, Thomas M.

    2007-01-01

    By analyzing data from the Schools and Staffing Survey, the authors empirically test four of the core assumptions embedded in current arguments for expanding alternative teacher certification (AC): AC attracts experienced candidates from fields outside of education; AC attracts top-quality, well-trained teachers; AC disproportionately trains…

  9. Continuous flow nanoparticle concentration using alternating current-electroosmotic flow.

    PubMed

    Hoettges, Kai F; McDonnell, Martin B; Hughes, Michael P

    2014-02-01

    Achieving real-time detection of environmental pathogens such as viruses and bacterial spores requires detectors with both rapid action and a suitable detection threshold. However, most biosensors have detection limits of an order of magnitude or more above the potential infection threshold, limiting their usefulness. This can be improved through the use of automated sample preparation techniques such as preconcentration. In this paper, we describe the use of AC electroosmosis to concentrate nanoparticles from a continuous flow. Electrodes at an optimized angle across a flow cell, and energized by a 1 kHz signal, were used to push nanoparticles to one side of a flow cell, and to extract the resulting stream with a high particle concentration from that side of the flow cell. A simple model of the behavior of particles in the flow cell has been developed, which shows good agreement with experimental results. The method indicates potential for higher concentration factors through cascading devices. PMID:24166772

  10. Synthetic tactile perception induced by transcranial alternating-current stimulation can substitute for natural sensory stimulus in behaving rabbits

    PubMed Central

    Márquez-Ruiz, Javier; Ammann, Claudia; Leal-Campanario, Rocío; Ruffini, Giulio; Gruart, Agnès; Delgado-García, José M.

    2016-01-01

    The use of brain-derived signals for controlling external devices has long attracted the attention from neuroscientists and engineers during last decades. Although much effort has been dedicated to establishing effective brain-to-computer communication, computer-to-brain communication feedback for “closing the loop” is now becoming a major research theme. While intracortical microstimulation of the sensory cortex has already been successfully used for this purpose, its future application in humans partly relies on the use of non-invasive brain stimulation technologies. In the present study, we explore the potential use of transcranial alternating-current stimulation (tACS) for synthetic tactile perception in alert behaving animals. More specifically, we determined the effects of tACS on sensory local field potentials (LFPs) and motor output and tested its capability for inducing tactile perception using classical eyeblink conditioning in the behaving animal. We demonstrated that tACS of the primary somatosensory cortex vibrissa area could indeed substitute natural stimuli during training in the associative learning paradigm. PMID:26790614

  11. Rapid immunocytochemistry based on alternating current electric field using squash smear preparation of central nervous system tumors.

    PubMed

    Moriya, Jun; Tanino, Mishie Ann; Takenami, Tomoko; Endoh, Tomoko; Urushido, Masana; Kato, Yasutaka; Wang, Lei; Kimura, Taichi; Tsuda, Masumi; Nishihara, Hiroshi; Tanaka, Shinya

    2016-01-01

    The role of intraoperative pathological diagnosis for central nervous system (CNS) tumors is crucial for neurosurgery when determining the surgical procedure. Especially, treatment of carmustine (BCNU) wafers requires a conclusive diagnosis of high-grade glioma proven by intraoperative diagnosis. Recently, we demonstrated the usefulness of rapid immunohistochemistry (R-IHC) that facilitates antigen-antibody reaction under alternative current (AC) electric field in the intraoperative diagnosis of CNS tumors; however, a higher proportion of water and lipid in the brain parenchyma sometimes leads to freezing artifacts, resulting in poor quality of frozen sections. On the other hand, squash smear preparation of CNS tumors for cytology does not affect the frozen artifacts, and the importance of smear preparation is now being re-recognized as being better than that of the tissue sections. In this study, we established the rapid immunocytochemistry (R-ICC) protocol for squash smears of CNS tumors using AC electric field that takes only 22 min, and demonstrated its usefulness for semi-quantitative Ki-67/MIB-1 labeling index and CD 20 by R-ICC for intraoperative diagnosis. R-ICC by AC electric field may become a substantial tool for compensating R-IHC and will be applied for broad antibodies in the future.

  12. Synthetic tactile perception induced by transcranial alternating-current stimulation can substitute for natural sensory stimulus in behaving rabbits.

    PubMed

    Márquez-Ruiz, Javier; Ammann, Claudia; Leal-Campanario, Rocío; Ruffini, Giulio; Gruart, Agnès; Delgado-García, José M

    2016-01-01

    The use of brain-derived signals for controlling external devices has long attracted the attention from neuroscientists and engineers during last decades. Although much effort has been dedicated to establishing effective brain-to-computer communication, computer-to-brain communication feedback for "closing the loop" is now becoming a major research theme. While intracortical microstimulation of the sensory cortex has already been successfully used for this purpose, its future application in humans partly relies on the use of non-invasive brain stimulation technologies. In the present study, we explore the potential use of transcranial alternating-current stimulation (tACS) for synthetic tactile perception in alert behaving animals. More specifically, we determined the effects of tACS on sensory local field potentials (LFPs) and motor output and tested its capability for inducing tactile perception using classical eyeblink conditioning in the behaving animal. We demonstrated that tACS of the primary somatosensory cortex vibrissa area could indeed substitute natural stimuli during training in the associative learning paradigm. PMID:26790614

  13. Alternating current characterization of nano-Pt(II) octaethylporphyrin (PtOEP) thin film as a new organic semiconductor

    NASA Astrophysics Data System (ADS)

    M, Dongol; M, M. El-Nahass; A, El-Denglawey; A, A. Abuelwafa; T, Soga

    2016-06-01

    Alternating current (AC) conductivity and dielectric properties of thermally evaporated Au/PtOEP/Au thin films are investigated each as a function of temperature (303 K-473 K) and frequency (50 Hz-5 MHz). The frequency dependence of AC conductivity follows the Jonscher universal dynamic law. The AC-activation energies are determined at different frequencies. It is found that the correlated barrier hopping (CBH) model is the dominant conduction mechanism. The variation of the frequency exponent s with temperature is analyzed in terms of the CBH model. Coulombic barrier height W m , hopping distance R ω , and the density of localized states N(E F) are valued at different frequencies. Dielectric constant ɛ 1(ω,T) and dielectric loss ɛ 2(ω,T) are discussed in terms of the dielectric polarization process. The dielectric modulus shows the non-Debye relaxation in the material. The extracted relaxation time by using the imaginary part of modulus (M″) is found to follow the Arrhenius law.

  14. Thin-film alternating current nanocalorimeter for low temperatures and high magnetic fields

    SciTech Connect

    Minakov, A.A.; Roy, S.B.; Bugoslavsky, Y.V.; Cohen, L.F.

    2005-04-01

    Thin-film nanocalorimeter for low temperatures and high magnetic fields is described. The calorimeter is based on a commercial microchip module (thermal conductivity vacuum gauge TCG 3880 from Xensor Integration, NL). The gauge consists of submicron silicon nitride membrane with a film-thermopile and a resistive film-heater with dimensions of 50x100 {mu}m{sup 2} located at the center of the membrane. The gauge is mounted in a thermostat filled with helium exchange gas. The method of alternating current (ac) calorimetry is applied for heat capacity measurements. The noise-floor sensitivity of the calorimeter is better than 1 nJ/K below 100 K and about 3 nJ/K at 300 K. This allows for reliable measurements to be performed on sub-microgram samples. It is proved that the method is applicable for heat capacity measurements at temperatures in the range of 5-300 K and in high magnetic fields up to 8 T. We present a theoretical analysis of the thermal processes in the gauge-sample-surrounding gas system. On this basis a calibration method has been developed. We demonstrate that the technique yields correct heat capacity for test samples and that in special cases the thermal conductivity and the magnetostriction of the sample can be measured simultaneously with the heat capacity.

  15. Alternating Current Electrophoretic Deposition of Antibacterial Bioactive Glass-Chitosan Composite Coatings

    PubMed Central

    Seuss, Sigrid; Lehmann, Maja; Boccaccini, Aldo R.

    2014-01-01

    Alternating current (AC) electrophoretic deposition (EPD) was used to produce multifunctional composite coatings combining bioactive glass (BG) particles and chitosan. BG particles of two different sizes were used, i.e., 2 μm and 20–80 nm in average diameter. The parameter optimization and characterization of the coatings was conducted by visual inspection and by adhesion strength tests. The optimized coatings were investigated in terms of their hydroxyapatite (HA) forming ability in simulated body fluid (SBF) for up to 21 days. Fourier transform infrared (FTIR) spectroscopy results showed the successful HA formation on the coatings after 21 days. The first investigations were conducted on planar stainless steel sheets. In addition, scaffolds made from a TiAl4V6 alloy were considered to show the feasibility of coating of three dimensional structures by EPD. Because both BG and chitosan are antibacterial materials, the antibacterial properties of the as-produced coatings were investigated using E. coli bacteria cells. It was shown that the BG particle size has a strong influence on the antibacterial properties of the coatings. PMID:25007822

  16. Alternating current potential drop for measuring the case depth of hardened steel

    NASA Astrophysics Data System (ADS)

    Quddes, Mohammad R.; Ji, Yuan; Bowler, John R.

    2015-03-01

    Multi-frequency alternate current potential drop measurements have been made to estimate the case depth of case hardened steels using four point probes. The probes have four parallel sprung loaded pins in a line with a 1.5 mm separation between the contact points. A printed circuit board has been used to ensure the electrical connections to the pins are close to the surface of the material. This has the effect of reducing the mutual induction between driver and pick-up pins. The case depth is estimated from measurements at frequencies typically from 10 Hz to 10 kHz. The real part of the voltage phasor representing the AC potential drop is used to evaluate the case depth. The imaginary part includes the contribution due to mutual induction. To estimate the case depth of the hardened samples, the measured potential drop has been fitted to theoretical predictions. The substrate material properties of the hardened samples are extracted from multi-frequency potential drop measurements on non-harden samples. The estimated case hardened depths, deduced from potential drop measurements, are similar to those found from destructive measurements.

  17. Alternating-Current InGaN/GaN Tunnel Junction Nanowire White-Light Emitting Diodes.

    PubMed

    Sadaf, S M; Ra, Y-H; Nguyen, H P T; Djavid, M; Mi, Z

    2015-10-14

    The current LED lighting technology relies on the use of a driver to convert alternating current (AC) to low-voltage direct current (DC) power, a resistive p-GaN contact layer to inject positive charge carriers (holes) for blue light emission, and rare-earth doped phosphors to down-convert blue photons into green/red light, which have been identified as some of the major factors limiting the device efficiency, light quality, and cost. Here, we show that multiple-active region phosphor-free InGaN nanowire white LEDs connected through a polarization engineered tunnel junction can fundamentally address the afore-described challenges. Such a p-GaN contact-free LED offers the benefit of carrier regeneration, leading to enhanced light intensity and reduced efficiency droop. Moreover, through the monolithic integration of p-GaN up and p-GaN down nanowire LED structures on the same substrate, we have demonstrated, for the first time, AC operated LEDs on a Si platform, which can operate efficiently in both polarities (positive and negative) of applied voltage.

  18. Electro-optically responsive composites of gold nanospheres in 5CB liquid crystal under direct current and alternating current joint action

    SciTech Connect

    Hadjichristov, Georgi B.; Marinov, Yordan G.; Petrov, Alexander G.; Bruno, Emanuela; Marino, Lucia; Scaramuzza, Nicola

    2014-02-28

    Direct current (DC) electro-optical (EO) control of transmitted laser beam intensity based on EO controlled coherent light scattering and diffraction by stationary longitudinal texture pattern (LTP) is achieved in planar-oriented cells with a composite mixture of polymer-coated gold spherical nanoparticles (Au-NPs) with a mean diameter of about 12 nm and the room-temperature nematic pentylcyanobiphenyl (5CB). At relatively low DC voltage of about 5 V, the effective scattering/diffraction by Au-NPs/5CB composites leads to a spatial spreading of transmitted coherent light from a low-power continuous wave laser beam, resulting in a drastic reduction of its local intensity. The effect is polarization dependent and is strongest when the polarization of the input laser beam is along the LTP. The EO response of Au-NPs/5CB mixtures is studied under DC and alternating current (AC) joint action with the aim of the potential use of these composite materials as EO controlled diffusers. The specific V-shaped sharp dip in the DC voltage-dependent coherent light transmittance of Au-NPs/5CB planar films, as well as the possibility for erasing the scattering/diffractive LTP in the films by joint low AC voltage, can be useful for EO applications in the field of process control and for detection of weak dynamic electric fields.

  19. Electro-optically responsive composites of gold nanospheres in 5CB liquid crystal under direct current and alternating current joint action

    NASA Astrophysics Data System (ADS)

    Hadjichristov, Georgi B.; Marinov, Yordan G.; Petrov, Alexander G.; Bruno, Emanuela; Marino, Lucia; Scaramuzza, Nicola

    2014-02-01

    Direct current (DC) electro-optical (EO) control of transmitted laser beam intensity based on EO controlled coherent light scattering and diffraction by stationary longitudinal texture pattern (LTP) is achieved in planar-oriented cells with a composite mixture of polymer-coated gold spherical nanoparticles (Au-NPs) with a mean diameter of about 12 nm and the room-temperature nematic pentylcyanobiphenyl (5CB). At relatively low DC voltage of about 5 V, the effective scattering/diffraction by Au-NPs/5CB composites leads to a spatial spreading of transmitted coherent light from a low-power continuous wave laser beam, resulting in a drastic reduction of its local intensity. The effect is polarization dependent and is strongest when the polarization of the input laser beam is along the LTP. The EO response of Au-NPs/5CB mixtures is studied under DC and alternating current (AC) joint action with the aim of the potential use of these composite materials as EO controlled diffusers. The specific V-shaped sharp dip in the DC voltage-dependent coherent light transmittance of Au-NPs/5CB planar films, as well as the possibility for erasing the scattering/diffractive LTP in the films by joint low AC voltage, can be useful for EO applications in the field of process control and for detection of weak dynamic electric fields.

  20. I-BIEM calculations of the frequency dispersion and ac current distribution at disk and ring-disk electrodes

    NASA Technical Reports Server (NTRS)

    Cahan, Boris D.

    1991-01-01

    The Iterative Boundary Integral Equation Method (I-BIEM) has been applied to the problem of frequency dispersion at a disk electrode in a finite geometry. The I-BIEM permits the direct evaluation of the AC potential (a complex variable) using complex boundary conditions. The point spacing was made highly nonuniform, to give extremely high resolution in those regions where the variables change most rapidly, i.e., in the vicinity of the edge of the disk. Results are analyzed with respect to IR correction, equipotential surfaces, and reference electrode placement. The current distribution is also examined for a ring-disk configuration, with the ring and the disk at the same AC potential. It is shown that the apparent impedance of the disk is inductive at higher frequencies. The results are compared to analytic calculations from the literature, and usually agree to better than 0.001 percent.

  1. I-BIEM calculations of the frequency dispersion and AC current distribution at disk and ring-disk electrodes

    NASA Technical Reports Server (NTRS)

    Cahan, Boris D.

    1991-01-01

    The Iterative Boundary Integral Equation Method (I-BIEM) has been applied to the problem of frequency dispersion at a disk electrode in a finite geometry. The I-BIEM permits the direct evaluation of the AC potential (a complex variable) using complex boundary conditions. The point spacing was made highly nonuniform, to give extremely high resolution in those regions where the variables change most rapidly, i.e., in the vicinity of the edge of the disk. Results are analyzed with respect to IR correction, equipotential surfaces, and reference electrode placement. The current distribution is also examined for a ring-disk configuration, with the ring and the disk at the same AC potential. It is shown that the apparent impedance of the disk is inductive at higher frequencies. The results are compared to analytic calculations from the literature, and usually agree to better than 0.001 percent.

  2. Operation of AC Adapters Visualized Using Light-Emitting Diodes

    ERIC Educational Resources Information Center

    Regester, Jeffrey

    2016-01-01

    A bridge rectifier is a diamond-shaped configuration of diodes that serves to convert alternating current(AC) into direct current (DC). In our world of AC outlets and DC electronics, they are ubiquitous. Of course, most bridge rectifiers are built with regular diodes, not the light-emitting variety, because LEDs have a number of disadvantages. For…

  3. An Alternative Introduction to Maxwell's Displacement Current

    ERIC Educational Resources Information Center

    Reich, Gary

    2013-01-01

    In introductory texts Ampere's law is generally introduced in the steady-current form ?B · dl = µ[subscript 0]I, and it is later extended to a more general form involving the so-called displacement current I[subscript d], ?B · dl = µ[subscript 0](I + I[subscript d]) · (1). Here the line integral is to be taken along a closed…

  4. Alternating and direct current electrochemical studies of a wool wax-based corrosion preventive coating on aluminum alloy 2024

    SciTech Connect

    Su, P.C.; Devereux, O.F.

    1998-06-01

    The corrosion behavior of Al 2024-T3 treated with a wool wax (lanolin)-based corrosion preventive coating in aqueous 0.5 M sodium chloride was studied using electrochemical impedance spectroscopy (EIS) and direct current electrode polarization. DC measurements were modeled by three reactions: oxidation of aluminum, reduction of oxygen, and reduction of hydrogen. Alternating current behavior of untreated specimens was modeled using the Randles circuit, and that of inhibited specimens was modeled using parallel resistance-capacitance circuits representing the coating and the charge-transfer process. AC and DC estimates of the polarization resistance of coated specimens were 50 M{Omega}-cm{sup 2} and 32 M{Omega}-cm{sup 2}, respectively. AC and DC values for bare control specimens were of the order of 3 k{Omega}-cm{sup 2} and 15 k{Omega}-cm{sup 2}, respectively. The wool wax coating was found to be a very effective corrosion preventative for this alloy in the aqueous saline environment whether applied to freshly prepared surfaces or to corroded specimens removed from simulated service.

  5. An Alternative to the Current Research Model of Literature.

    ERIC Educational Resources Information Center

    Craige, Betty Jean

    1984-01-01

    Criticizes current practices of seeking and preserving knowledge which neither contribute to nor support the fields of "humanistic" interest. By confining specialized research to the scientists, it is suggested that a more generalized approach be taken towards literary studies, as a means of broadening and interrelating all the issues that affect…

  6. Taxation of Fringe Benefits: Alternative Approaches to Current Problems.

    ERIC Educational Resources Information Center

    Cohen, Anita E.

    1979-01-01

    The current IRS tax treatment of fringe benefits is seen as inadequate, and the judicial precept confusing, because groups of employee benefits are inappropriately excluded from taxation as perquisites. A tax equalization approach is proposed. Available from Suffolk University Law Review Office, 41 Temple St., Boston, MA 02114. (MSE)

  7. 46 CFR 111.30-25 - Alternating-current ship's service switchboards.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 46 Shipping 4 2011-10-01 2011-10-01 false Alternating-current ship's service switchboards. 111.30-25 Section 111.30-25 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) ELECTRICAL ENGINEERING ELECTRIC SYSTEMS-GENERAL REQUIREMENTS Switchboards § 111.30-25 Alternating-current ship's...

  8. 46 CFR 111.30-25 - Alternating-current ship's service switchboards.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 46 Shipping 4 2010-10-01 2010-10-01 false Alternating-current ship's service switchboards. 111.30-25 Section 111.30-25 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) ELECTRICAL ENGINEERING ELECTRIC SYSTEMS-GENERAL REQUIREMENTS Switchboards § 111.30-25 Alternating-current ship's...

  9. 46 CFR 111.30-25 - Alternating-current ship's service switchboards.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 46 Shipping 4 2014-10-01 2014-10-01 false Alternating-current ship's service switchboards. 111.30-25 Section 111.30-25 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) ELECTRICAL ENGINEERING ELECTRIC SYSTEMS-GENERAL REQUIREMENTS Switchboards § 111.30-25 Alternating-current ship's...

  10. 46 CFR 111.30-25 - Alternating-current ship's service switchboards.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 46 Shipping 4 2013-10-01 2013-10-01 false Alternating-current ship's service switchboards. 111.30-25 Section 111.30-25 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) ELECTRICAL ENGINEERING ELECTRIC SYSTEMS-GENERAL REQUIREMENTS Switchboards § 111.30-25 Alternating-current ship's...

  11. 46 CFR 111.30-25 - Alternating-current ship's service switchboards.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 46 Shipping 4 2012-10-01 2012-10-01 false Alternating-current ship's service switchboards. 111.30-25 Section 111.30-25 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) ELECTRICAL ENGINEERING ELECTRIC SYSTEMS-GENERAL REQUIREMENTS Switchboards § 111.30-25 Alternating-current ship's...

  12. Novel method for immunofluorescence staining of mammalian eggs using non-contact alternating-current electric-field mixing of microdroplets

    PubMed Central

    Hiromitsu, Shirasawa; Jin, Kumagai; Emiko, Sato; Katsuya, Kabashima; Yukiyo, Kumazawa; Wataru, Sato; Hiroshi, Miura; Ryuta, Nakamura; Hiroshi, Nanjo; Yoshihiro, Minamiya; Yoichi, Akagami; Yukihiro, Terada

    2015-01-01

    Recently, a new technique was developed for non-catalytically mixing microdroplets. In this method, an alternating-current (AC) electric field is used to promote the antigen–antibody reaction within the microdroplet. Previously, this technique has only been applied to histological examinations of flat structures, such as surgical specimens. In this study, we applied this technique for the first time to immunofluorescence staining of three-dimensional structures, specifically, mammalian eggs. We diluted an antibody against microtubules from 1:1,000 to 1:16,000, and compared the chromatic degree and extent of fading across dilutions. In addition, we varied the frequency of AC electric-field mixing from 5 Hz to 46 Hz and evaluated the effect on microtubule staining. Microtubules were more strongly stained after AC electric-field mixing for only 5 minutes, even when the concentration of primary antibody was 10 times lower than in conventional methods. AC electric-field mixing also alleviated microtubule fading. At all frequencies tested, AC electric-field mixing resulted in stronger microtubule staining than in controls. There was no clear difference in a microtubule staining between frequencies. These results suggest that the novel method could reduce antibody consumption and shorten immunofluorescence staining time. PMID:26477850

  13. Higher harmonics in voltage on superconductor carrying AC current due to non-linear I- V curve

    NASA Astrophysics Data System (ADS)

    Janíková, Edita; Gömöry, Fedor; Šouc, Ján

    2004-01-01

    When superconducting wire carries AC current with amplitude exceeding its critical current, additional losses appear due to non-zero resistivity. The voltage attributed to this mechanism will contain higher harmonics because of non-linear I- V curve of superconducting material. This curve can be derived using the following simple model: parallel combination of superconductor standing for the properties of all the filaments and the normal resistor representing the matrix. I- V relation is then characterized by three parameters: the critical current, I0, the n-exponent, n, and the ratio of the cross-section to the resistivity of metallic matrix. Expressions for Fourier coefficients have been calculated for this model. Extensive analysis of the influence that the model parameters exhibit on higher harmonics have revealed some useful features: 3rd harmonic could be nicely used to detect I0 and n, while from the maximum of 5th harmonic the value of matrix resistivity can be estimated.

  14. Efficacy of low level electric current (A-C) for controlling quagga mussles in the Welland Canal

    SciTech Connect

    Fears, C.; Mackie, G.L.

    1995-06-01

    The efficacy of systems (for which patents are pending) which use low-voltage A-C currents for preventing settlement and attachment by zebra mussels were tested with steel rods and plates placed near the intake of a pulp and paper plant in the Welland Canal at Thorold, Ontario. Six racks made of 16 ft. (4.9 m), 2x4s (5.1 x 10.2 cm) were placed into the Welland Canal on August 5, 1994. One rack had 1/8th in (3.2 mm) diam x 12 in (30.5 cm) long steel rods, each separated by 2 in (5.1 cm) attached to pressure treated wood and concrete blocks and an A-C current of 16 v (or 8 v/in); rack 2 had steel rods of the same configuration but 12 v (or 6 v/in) was applied; rack 3 was identical to these but no current was applied and was used as a rod control. The remaining three racks had steel plates, each plate being 3 in (7.6 cm) wide X 24 in (61 cm) long X 1/4 in (6.4 mm) thick and separated by 2 in (5.1 cm); one had 12 v applied (or 6 v/in), another had 16 v applied (or 8 v/in), and the third had no current and was used as a plate control. The racks were placed on the upstream and downstream side of the intake at a depth of about 7 ft (2.1 m) where the mussels populations were heaviest (as determined by SCUBA diving). All mussels were quagga mussels (Dreissena bugensis). The racks were pulled in mid November after settlement was complete and the results showed: (1) complete prevention of settlement of both new recruits and translocators at 8 volts/in with steel rods on both wood and concrete surfaces and with steel plate trash bars; (2) partial prevention of settlement at 6 volts/in with steel rods on both wood and concrete surfaces and steel plates; and (3) that, at current kilowatt hr rates, total efficacy at 8 volts/in would cost approximately $10.80/day/1000 sq ft using rods to protect concrete walls and about $16.32/day/1000 sq ft to protect 3 in wide x 1/4 in thick trash bars. These costs can be reduced even further with pulse dosed AC currents.

  15. Optimizing the internal electric field distribution of alternating current driven organic light-emitting devices for a reduced operating voltage

    NASA Astrophysics Data System (ADS)

    Fröbel, Markus; Hofmann, Simone; Leo, Karl; Gather, Malte C.

    2014-02-01

    The influence of the thickness of the insulating layer and the intrinsic organic layer on the driving voltage of p-i-n based alternating current driven organic light-emitting devices (AC-OLEDs) is investigated. A three-capacitor model is employed to predict the basic behavior of the devices, and good agreement with the experimental values is found. The proposed charge regeneration mechanism based on Zener tunneling is studied in terms of field strength across the intrinsic organic layers. A remarkable consistency between the measured field strength at the onset point of light emission (3-3.1 MV/cm) and the theoretically predicted breakdown field strength of around 3 MV/cm is obtained. The latter value represents the field required for Zener tunneling in wide band gap organic materials according to Fowler-Nordheim theory. AC-OLEDs with optimized thickness of the insulating and intrinsic layers show a reduction in the driving voltage required to reach a luminance of 1000 cd/m2 of up to 23% (8.9 V) and a corresponding 20% increase in luminous efficacy.

  16. Alternating Current Electric Fields of Varying Frequencies: Effects on Proliferation and Differentiation of Porcine Neural Progenitor Cells

    PubMed Central

    Lim, Ji-Hey; McCullen, Seth D.; Piedrahita, Jorge A.

    2013-01-01

    Abstract Application of sinusoidal electric fields (EFs) has been observed to affect cellular processes, including alignment, proliferation, and differentiation. In the present study, we applied low-frequency alternating current (AC) EFs to porcine neural progenitor cells (pNPCs) and investigated the effects on cell patterning, proliferation, and differentiation. pNPCs were grown directly on interdigitated electrodes (IDEs) localizing the EFs to a region accessible visually for fluorescence-based assays. Cultures of pNPCs were exposed to EFs (1 V/cm) of 1 Hz, 10 Hz, and 50 Hz for 3, 7, and 14 days and compared to control cultures. Immunocytochemistry was performed to evaluate the expression of neural markers. pNPCs grew uniformly with no evidence of alignment to the EFs and no change in cell numbers when compared with controls. Nestin expression was shown in all groups at 3 and 7 days, but not at 14 days. NG2 expression was low in all groups. Co-expression of glial fibrillary acidic protein (GFAP) and TUJ1 was significantly higher in the cultures exposed to 10- and 50-Hz EFs than the controls. In summary, sinusoidal AC EFs via IDEs did not alter the alignment and proliferation of pNPCs, but higher frequency stimulation appeared to delay differentiation into mature astrocytes. PMID:23961767

  17. Alternating current electric fields of varying frequencies: effects on proliferation and differentiation of porcine neural progenitor cells.

    PubMed

    Lim, Ji-Hey; McCullen, Seth D; Piedrahita, Jorge A; Loboa, Elizabeth G; Olby, Natasha J

    2013-10-01

    Application of sinusoidal electric fields (EFs) has been observed to affect cellular processes, including alignment, proliferation, and differentiation. In the present study, we applied low-frequency alternating current (AC) EFs to porcine neural progenitor cells (pNPCs) and investigated the effects on cell patterning, proliferation, and differentiation. pNPCs were grown directly on interdigitated electrodes (IDEs) localizing the EFs to a region accessible visually for fluorescence-based assays. Cultures of pNPCs were exposed to EFs (1 V/cm) of 1 Hz, 10 Hz, and 50 Hz for 3, 7, and 14 days and compared to control cultures. Immunocytochemistry was performed to evaluate the expression of neural markers. pNPCs grew uniformly with no evidence of alignment to the EFs and no change in cell numbers when compared with controls. Nestin expression was shown in all groups at 3 and 7 days, but not at 14 days. NG2 expression was low in all groups. Co-expression of glial fibrillary acidic protein (GFAP) and TUJ1 was significantly higher in the cultures exposed to 10- and 50-Hz EFs than the controls. In summary, sinusoidal AC EFs via IDEs did not alter the alignment and proliferation of pNPCs, but higher frequency stimulation appeared to delay differentiation into mature astrocytes.

  18. MEMS electrostatic inductive transformer using potassium ion electrets for up- or down-conversion of AC current

    NASA Astrophysics Data System (ADS)

    Suzuki, Masato; Moriyama, Takashi; Toshiyoshi, Hiroshi; Hashiguchi, Gen

    2016-10-01

    In this paper, we report on a novel MEMS electrostatic inductive transformer using potassium ion electrets on mechanically movable silicon microelectrodes. The device consists of a pair of electrostatic comb drive actuators that share a common mass in the middle part of a spring-mass-spring system. When an excitation AC voltage is applied to the electrode of the input-port comb drive at its mechanical resonant frequency, the mass in the middle oscillates to generate electrostatic inductive charges on the electrodes of the output-port comb drive, which could be read out as an output current. By appropriately designing the ratio of force factors of input- and output-port comb drives, the device operates as a transformer to amplify the current at a high efficiency over of 90% under the optimal load condition.

  19. Quench behavior of Sr0.6K0.4Fe2As2/Ag tapes with AC and DC transport currents at different temperature

    NASA Astrophysics Data System (ADS)

    Liu, Qi; Zhang, Guomin; Yang, Hua; Li, Zhenming; Liu, Wei; Jing, Liwei; Yu, Hui; Liu, Guole

    2016-09-01

    In applications, superconducting wires may carry AC or DC transport current. Thus, it is important to understand the behavior of normal zone propagation in conductors and magnets under different current conditions in order to develop an effective quench protection system. In this paper, quench behavior of Ag sheathed Sr0.6K0.4Fe2As2 (Sr-122 in the family of iron-based superconductor) tapes with AC and DC transport current is reported. The measurements are performed as a function of different temperature (20 K-30 K), varying transport current and operating frequency (50 Hz-250 Hz). The focus of the research is the minimum quench energy (MQE), the normal zone propagation velocity (NZPV) and the comparison of the related results with AC and DC transport current.

  20. Inter-strand current sharing and ac loss measurements in superconducting YBCO Roebel cables

    SciTech Connect

    sumption, Mike; Majoros, Milan; Collings, E. W.; Van der Laan, D. C.

    2014-11-07

    A Roebel cable, one twist pitch long, was modified from its as-received state by soldering copper strips between the strands to provide inter-strand connections enabling current sharing. Various DC transport currents (representing different percentages of its critical current) were applied to a single strand of such a modified cable at 77 K in a liquid nitrogen bath. Simultaneous monitoring of I–V curves in different parts of the strand as well as in its interconnections with other strands was made using a number of sensitive Keithley nanovoltmeters in combination with a multichannel high-speed data acquisition card, all controlled via LabView software. Current sharing onset was observed at about 1.02 of strand Ic. At a strand current of 1.3Ic about 5% of the current was shared through the copper strip interconnections. A finite element method modeling was performed to estimate the inter-strand resistivities required to enable different levels of current sharing. The relative contributions of coupling and hysteretic magnetization (and loss) were compared, and for our cable and tape geometry, and at dB/dt=1 T s-1, and our inter-strand resistance of 0.77 mΩ, (enabling a current sharing of 5% at 1.3Ic ) the coupling component was 0.32% of the hysteretic component. However, inter-strand contact resistance values of 100–1000 times smaller (close to those of NbTi and Nb3Sn based accelerator cables) would make the coupling components comparable in size to the hysteretic components.

  1. Inter-strand current sharing and ac loss measurements in superconducting YBCO Roebel cables

    SciTech Connect

    Majoros, M.; Sumption, M. D.; Collings, E. W.; Long, N. J.

    2015-04-08

    A Roebel cable, one twist pitch long, was modified from its as-received state by soldering copper strips between the strands to provide inter-strand connections enabling current sharing. Various DC transport currents (representing different percentages of its critical current) were applied to a single strand of such a modified cable at 77 K in a liquid nitrogen bath. Simultaneous monitoring of I–V curves in different parts of the strand as well as in its interconnections with other strands was made using a number of sensitive Keithley nanovoltmeters in combination with a multichannel high-speed data acquisition card, all controlled via LabView software. Current sharing onset was observed at about 1.02 of strand Ic. At a strand current of 1.3Ic about 5% of the current was shared through the copper strip interconnections. A finite element method modeling was performed to estimate the inter-strand resistivities required to enable different levels of current sharing. The relative contributions of coupling and hysteretic magnetization (and loss) were compared, and for our cable and tape geometry, and at dB/dt=1 T s-1, and our inter-strand resistance of 0.77 mΩ, (enabling a current sharing of 5% at 1.3Ic) the coupling component was 0.32% of the hysteretic component. However, inter-strand contact resistance values of 100–1000 times smaller (close to those of NbTi and Nb3Sn based accelerator cables) would make the coupling components comparable in size to the hysteretic components.

  2. Inter-strand current sharing and ac loss measurements in superconducting YBCO Roebel cables

    DOE PAGES

    Majoros, M.; Sumption, M. D.; Collings, E. W.; Long, N. J.

    2015-04-08

    A Roebel cable, one twist pitch long, was modified from its as-received state by soldering copper strips between the strands to provide inter-strand connections enabling current sharing. Various DC transport currents (representing different percentages of its critical current) were applied to a single strand of such a modified cable at 77 K in a liquid nitrogen bath. Simultaneous monitoring of I–V curves in different parts of the strand as well as in its interconnections with other strands was made using a number of sensitive Keithley nanovoltmeters in combination with a multichannel high-speed data acquisition card, all controlled via LabView software.more » Current sharing onset was observed at about 1.02 of strand Ic. At a strand current of 1.3Ic about 5% of the current was shared through the copper strip interconnections. A finite element method modeling was performed to estimate the inter-strand resistivities required to enable different levels of current sharing. The relative contributions of coupling and hysteretic magnetization (and loss) were compared, and for our cable and tape geometry, and at dB/dt=1 T s-1, and our inter-strand resistance of 0.77 mΩ, (enabling a current sharing of 5% at 1.3Ic) the coupling component was 0.32% of the hysteretic component. However, inter-strand contact resistance values of 100–1000 times smaller (close to those of NbTi and Nb3Sn based accelerator cables) would make the coupling components comparable in size to the hysteretic components.« less

  3. Inter-strand current sharing and ac loss measurements in superconducting YBCO Roebel cables

    DOE PAGES

    sumption, Mike; Majoros, Milan; Collings, E. W.; Van der Laan, D. C.

    2014-11-07

    A Roebel cable, one twist pitch long, was modified from its as-received state by soldering copper strips between the strands to provide inter-strand connections enabling current sharing. Various DC transport currents (representing different percentages of its critical current) were applied to a single strand of such a modified cable at 77 K in a liquid nitrogen bath. Simultaneous monitoring of I–V curves in different parts of the strand as well as in its interconnections with other strands was made using a number of sensitive Keithley nanovoltmeters in combination with a multichannel high-speed data acquisition card, all controlled via LabView software.more » Current sharing onset was observed at about 1.02 of strand Ic. At a strand current of 1.3Ic about 5% of the current was shared through the copper strip interconnections. A finite element method modeling was performed to estimate the inter-strand resistivities required to enable different levels of current sharing. The relative contributions of coupling and hysteretic magnetization (and loss) were compared, and for our cable and tape geometry, and at dB/dt=1 T s-1, and our inter-strand resistance of 0.77 mΩ, (enabling a current sharing of 5% at 1.3Ic ) the coupling component was 0.32% of the hysteretic component. However, inter-strand contact resistance values of 100–1000 times smaller (close to those of NbTi and Nb3Sn based accelerator cables) would make the coupling components comparable in size to the hysteretic components.« less

  4. Current Faculty Development Practices for Alternative Delivery Systems in Christian Higher Education Institutions: A Qualitative Study

    ERIC Educational Resources Information Center

    Yates, Steven Lowell

    2009-01-01

    This research study was an investigation of current faculty development practices for alternative delivery systems. Attention was given to faculty development in general as well as specific facets of faculty development for alternative delivery systems. Future or intended faculty development practices were pursued, along with factors that…

  5. Alternating current impedance spectroscopic analysis of biofunctionalized vertically-aligned silica nanospring surface for biosensor applications

    NASA Astrophysics Data System (ADS)

    Timalsina, Yukta P.

    In this dissertation, a process of vertically-aligned (silica) nanosprings (VANS) based biosensor development is presented. Alternating current (AC) impedance spectroscopy has been used to analyze sensor response as a function of saline phosphate (SP) buffer and biological solutions. The sensor is a parallel plate capacitor consisting of two glass substrates coated with indium tin oxide (ITO), where the VANS [or randomly-aligned nanosprings (RANS)] grown on one substrate serve as the dielectric spacer layer. The response of a VANS device as a function of ionic concentration in SP buffer was examined and an equivalent circuit model was developed. The results demonstrated that VANS sensors exhibited greater sensitivity to the changes in SP concentration relative to the ITO sensors, which serve as controls. The biofunctionalized VANS surface via physisorption and the cross-linker method demonstrates the repeatability, specificity, and selectivity of the binding. The physisorption of biotinylated immunoglobulin G (B-IgG) onto the VANS surface simplifies the whole sensing procedure for the detection of glucose oxidase, since the avidin-conjugated glucose oxidase (Av-GOx) can directly be immobilized on the B-IgG. The cross linker method involves the covalent attachment of antibodies onto the functionalized VANS surface via imine bond. The experiments revealed that the VANS sensor response is solely the result of the interaction of target molecule i.e. mouse IgG with the probe layer, i.e. goat antimouse IgG (GalphaM IgG). It was determined that VANS-based sensors exhibit a greater magnitude of change between successive bio-layers relative to the controls above 100 Hz, which indicates that the addition of biomolecules inhibits the diffusion of ions and changes the effective dielectric response of the VANS via biomolecular polarization. The study of ionic transport in nanosprings suggested that conductance follows a scaling law. It was demonstrated that a VANS-based device

  6. Alternating current-generated plasma discharges for the controlled direct current charging of ferroelectrets

    NASA Astrophysics Data System (ADS)

    Cury Basso, Heitor; Monteiro, José Roberto B. de A.; Baladelli Mazulquim, Daniel; Teixeira de Paula, Geyverson; Gonçalves Neto, Luiz; Gerhard, Reimund

    2013-09-01

    The standard charging process for polymer ferroelectrets, e.g., from polypropylene foams or layered film systems involves the application of high DC fields either to metal electrodes or via a corona discharge. In this often-used process, the DC field triggers the internal breakdown and limits the final charge densities inside the ferroelectret cavities and, thus, the final polarization. Here, an AC + DC charging procedure is proposed and demonstrated in which a high-voltage high-frequency (HV-HF) wave train is applied together with a DC poling voltage. Thus, the internal dielectric-barrier discharges in the ferroelectret cavities are induced by the HV-HF wave train, while the final charge and polarization level is controlled separately through the applied DC voltage. In the new process, the frequency and the amplitude of the HV-HF wave train must be kept within critical boundaries that are closely related to the characteristics of the respective ferroelectrets. The charging method has been tested and investigated on a fluoropolymer-film system with a single well-defined cylindrical cavity. It is found that the internal electrical polarization of the cavity can be easily controlled and increases linearly with the applied DC voltage up to the breakdown voltage of the cavity. In the standard charging method, however, the DC voltage would have to be chosen above the respective breakdown voltage. With the new method, control of the HV-HF wave-train duration prevents a plasma-induced deterioration of the polymer surfaces inside the cavities. It is observed that the frequency of the HV-HF wave train during ferroelectret charging and the temperature applied during poling of ferroelectrics serve an analogous purpose. The analogy and the similarities between the proposed ferroelectret charging method and the poling of ferroelectric materials or dipole electrets at elevated temperatures with subsequent cooling under field are discussed.

  7. Accumulation and Decay Characteristics of Exoelectron Sources at MgO Protective Layer Surface in Alternating-Current Plasma Display Panels

    NASA Astrophysics Data System (ADS)

    Yoshino, Kyohei; Nagatomi, Takaharu; Morita, Yukihiro; Oue, Toshiyasu; Kosugi, Naoki; Nishitani, Mikihiko; Kitagawa, Masatoshi; Takai, Yoshizo

    2010-08-01

    The accumulation and decay characteristics of exoelectron sources at a MgO protective layer surface in alternating-current plasma display panels (AC-PDPs) were investigated. The positively charged MgO surface provides a larger number of exoelectrons than the negatively charged surface, indicating that electrons trapped in shallow carrier traps coexist with trapped holes, and exoelectrons are emitted through Auger and/or photoionization processes after their recombination. The exoelectron sources are accumulated by sustain discharges and always decay. The half-life of the decay of the exoelectron sources is relatively long, of the order of a few tens of ms, confirming that the exoelectron emission property at the address discharge in a certain television (TV) field is strongly affected by sustain firings in the previous two TV fields or more. The effects of such a long-term decay of the exoelectron sources should be taken into consideration when designing the driving waveforms of AC-PDPs.

  8. Superconducting-magnetic heterostructures: a method of decreasing AC losses and improving critical current density in multifilamentary conductors.

    PubMed

    Glowacki, B A; Majoros, M

    2009-06-24

    Magnetic materials can help to improve the performance of practical superconductors on the macroscale/microscale as magnetic diverters and also on the nanoscale as effective pinning centres. It has been established by numerical modelling that magnetic shielding of the filaments reduces AC losses in self-field conditions due to decoupling of the filaments and, at the same time, it increases the critical current of the composite. This effect is especially beneficial for coated conductors, in which the anisotropic properties of the superconductor are amplified by the conductor architecture. However, ferromagnetic coatings are often chemically incompatible with YBa(2)Cu(3)O(7) and (Pb,Bi)(2)Sr(2)Ca(2)Cu(3)O(9) conductors, and buffer layers have to be used. In contrast, in MgB(2) conductors an iron matrix may remain in direct contact with the superconducting core. The application of superconducting-magnetic heterostructures requires consideration of the thermal and electromagnetic stability of the superconducting materials used. On one hand, magnetic materials reduce the critical current gradient across the individual filaments but, on the other hand, they often reduce the thermal conductivity between the superconducting core and the cryogen, which may cause destruction of the conductor in the event of thermal instability. A possible nanoscale method of improving the critical current density of superconducting conductors is the introduction of sub-micron magnetic pinning centres. However, the volumetric density and chemical compatibility of magnetic inclusions has to be controlled to avoid suppression of the superconducting properties. PMID:21828430

  9. Alternating current-driven microwave loss modulation in a fluxonic metamaterial

    NASA Astrophysics Data System (ADS)

    Dobrovolskiy, Oleksandr V.; Huth, Michael; Shklovskij, Valerij A.

    2015-10-01

    We introduce a fluxonic metamaterial on the basis of nanopatterned superconducting Nb microstrips and employ it for modulation and synthesis of quantized loss levels in the lower GHz range by a sine-wave quasistatic ac drive. The nanopatterns are uniaxial nanogrooves with identical and different slope steepness, which induce a pinning potential of the washboard type for Abrikosov vortices. For the fundamental matching field, when the location of vortex rows geometrically matches the nanogrooves, the following effects are observed: The forward transmission coefficient S21(f) of the microstrips can be controllably modulated within a range of about 3 dB by the ac. For the sample with symmetric grooves, depending on the choice of the operation point in the current-voltage curve, the shape and the duty cycle of the output signal can be tuned. For the sample with asymmetric grooves, depending on the ac amplitude, a sine-to-triangular or a sine-to-rectangular pulse shape conversion is observed. The possibility of synthesizing quantized loss levels by a serial connection of the two samples with different nanopatterns is exemplified and can be used for the development of multilevel excess-loss-based fluxonic devices.

  10. Effective variable switching point predictive current control for ac low-voltage drives

    NASA Astrophysics Data System (ADS)

    Stolze, Peter; Karamanakos, Petros; Kennel, Ralph; Manias, Stefanos; Endisch, Christian

    2015-07-01

    This paper presents an effective model predictive current control scheme for induction machines driven by a three-level neutral point clamped inverter, called variable switching point predictive current control. Despite the fact that direct, enumeration-based model predictive control (MPC) strategies are very popular in the field of power electronics due to their numerous advantages such as design simplicity and straightforward implementation procedure, they carry two major drawbacks. These are the increased computational effort and the high ripples on the controlled variables, resulting in a limited applicability of such methods. The high ripples occur because in direct MPC algorithms the actuating variable can only be changed at the beginning of a sampling interval. A possible remedy for this would be to change the applied control input within the sampling interval, and thus to apply it for a shorter time than one sample. However, since such a solution would lead to an additional overhead which is crucial especially for multilevel inverters, a heuristic preselection of the optimal control action is adopted to keep the computational complexity at bay. Experimental results are provided to verify the potential advantages of the proposed strategy.

  11. Differences between direct current and alternating current capacitance nonlinearities in high-k dielectrics and their relation to hopping conduction

    SciTech Connect

    Khaldi, O.; Kassmi, M.; Gonon, P. Vallée, C.; Mannequin, C.; Sylvestre, A.; Jomni, F.

    2014-08-28

    Capacitance nonlinearities were studied in atomic layer deposited HfO{sub 2} films using two types of signals: a pure ac voltage of large magnitude (ac nonlinearities) and a small ac voltage superimposed to a large dc voltage (dc nonlinearities). In theory, ac and dc nonlinearities should be of the same order of magnitude. However, in practice, ac nonlinearities are found to be an order of magnitude higher than dc nonlinearities. Besides capacitance nonlinearities, hopping conduction is studied using low-frequency impedance measurements and is discussed through the correlated barrier hopping model. The link between hopping and nonlinearity is established. The ac nonlinearities are ascribed to the polarization of isolated defect pairs, while dc nonlinearities are attributed to electrode polarization which originates from defect percolation paths. Both the ac and dc capacitance nonlinearities display an exponential variation with voltage, which results from field-induced lowering of the hopping barrier energy.

  12. 30 CFR 75.701-1 - Approved methods of grounding of equipment receiving power from ungrounded alternating current...

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... receiving power from ungrounded alternating current power systems. 75.701-1 Section 75.701-1 Mineral... receiving power from ungrounded alternating current power systems. For purposes of grounding metallic frames, casings and other enclosures of equipment receiving power from ungrounded alternating current...

  13. 30 CFR 77.701-1 - Approved methods of grounding of equipment receiving power from ungrounded alternating current...

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... receiving power from ungrounded alternating current power systems. 77.701-1 Section 77.701-1 Mineral...-1 Approved methods of grounding of equipment receiving power from ungrounded alternating current... receiving power from ungrounded alternating current power systems, the following methods of grounding...

  14. 30 CFR 77.701-1 - Approved methods of grounding of equipment receiving power from ungrounded alternating current...

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... receiving power from ungrounded alternating current power systems. 77.701-1 Section 77.701-1 Mineral...-1 Approved methods of grounding of equipment receiving power from ungrounded alternating current... receiving power from ungrounded alternating current power systems, the following methods of grounding...

  15. 30 CFR 75.701-1 - Approved methods of grounding of equipment receiving power from ungrounded alternating current...

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... receiving power from ungrounded alternating current power systems. 75.701-1 Section 75.701-1 Mineral... receiving power from ungrounded alternating current power systems. For purposes of grounding metallic frames, casings and other enclosures of equipment receiving power from ungrounded alternating current...

  16. 30 CFR 77.701-1 - Approved methods of grounding of equipment receiving power from ungrounded alternating current...

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... receiving power from ungrounded alternating current power systems. 77.701-1 Section 77.701-1 Mineral...-1 Approved methods of grounding of equipment receiving power from ungrounded alternating current... receiving power from ungrounded alternating current power systems, the following methods of grounding...

  17. Fabrication of alumina films with laminated structures by ac anodization

    NASA Astrophysics Data System (ADS)

    Segawa, Hiroyo; Okano, Hironaga; Wada, Kenji; Inoue, Satoru

    2014-02-01

    Anodization techniques by alternating current (ac) are introduced in this review. By using ac anodization, laminated alumina films are fabricated. Different types of alumina films consisting of 50-200 nm layers were obtained by varying both the ac power supply and the electrolyte. The total film thickness increased with an increase in the total charge transferred. The thickness of the individual layers increased with the ac voltage; however, the anodization time had little effect on the film thickness. The laminated alumina films resembled the nacre structure of shells, and the different morphologies exhibited by bivalves and spiral shells could be replicated by controlling the rate of increase of the applied potentials.

  18. An investigation of the dynamic behaviors of an MRE isolator subjected to constant and alternating currents

    NASA Astrophysics Data System (ADS)

    Shi, H. F.; Yu, M.; Zhu, M.; Fu, J.; Choi, S. B.; Xing, Z. W.

    2016-07-01

    This paper presents the dynamic behaviors of a magneto-rheological elastomer (MRE) isolator by applying constant and time-varying exciting currents. As the first step, a shear type of the MRE isolator is devised with a simplified design. Then, the distributions of the magnetic field in the MRE isolator under both constant and alternating exciting currents are analyzed by commercial software (ANSYS). Subsequently, the dynamic performances of the isolator are experimentally evaluated by applying three different inputs: constant, square and sinusoidal exciting current. It has been identified from the experimental results that the constant exciting current can provide optimal performances in static control, while the MRE isolator presents more advantages in dynamic control with the sine wave current excitation. This means that an attenuation coefficient of alternating current should be considered to achieve a better dynamic control effect. On the other hand, it has also been demonstrated that alternating the magnetic field can provide a broader variable range of the viscous damping coefficient than that under constant magnetic field.

  19. Effect of modulated alternating and direct current iontophoresis on transdermal delivery of lidocaine hydrochloride.

    PubMed

    Bhatia, Gaurav; Banga, Ajay K

    2014-01-01

    The objective of this study was to investigate the iontophoretic delivery of lidocaine hydrochloride through porcine skin and to compare the effects of modulated alternating and direct current iontophoresis. Continuous and modulated iontophoresis was applied for one hour and two hours (0-1 h and 4-5th h) using a 1% w/v solution of lidocaine hydrochloride. Tape stripping was done to quantify the amount of drug permeated into stratum corneum and skin extraction studies were performed to determine the amount of drug in stripped skin. Receptor was sampled and analyzed over predefined time periods. The amount of lidocaine delivered across porcine skin after modulated direct current iontophoresis for 2 h was 1069.87 ± 120.03 μ g/sq · cm compared to 744.81 ± 125.41 μ g/sq · cm after modulated alternating current iontophoresis for 2 h. Modulated direct current iontophoresis also enhanced lidocaine delivery by twelvefold compared to passive delivery as 91.27 ± 18.71 μ g/sq · cm of lidocaine was delivered after passive delivery. Modulated iontophoresis enhanced the delivery of lidocaine hydrochloride across porcine skin compared to the passive delivery. Modulated alternating current iontophoresis for duration of 2 h at frequency of 1 kHz was found to be comparable to the continuous direct current iontophoresis for 1 h.

  20. Effect of Modulated Alternating and Direct Current Iontophoresis on Transdermal Delivery of Lidocaine Hydrochloride

    PubMed Central

    Banga, Ajay K.

    2014-01-01

    The objective of this study was to investigate the iontophoretic delivery of lidocaine hydrochloride through porcine skin and to compare the effects of modulated alternating and direct current iontophoresis. Continuous and modulated iontophoresis was applied for one hour and two hours (0-1 h and 4-5th h) using a 1% w/v solution of lidocaine hydrochloride. Tape stripping was done to quantify the amount of drug permeated into stratum corneum and skin extraction studies were performed to determine the amount of drug in stripped skin. Receptor was sampled and analyzed over predefined time periods. The amount of lidocaine delivered across porcine skin after modulated direct current iontophoresis for 2 h was 1069.87 ± 120.03 μg/sq·cm compared to 744.81 ± 125.41 μg/sq·cm after modulated alternating current iontophoresis for 2 h. Modulated direct current iontophoresis also enhanced lidocaine delivery by twelvefold compared to passive delivery as 91.27 ± 18.71 μg/sq·cm of lidocaine was delivered after passive delivery. Modulated iontophoresis enhanced the delivery of lidocaine hydrochloride across porcine skin compared to the passive delivery. Modulated alternating current iontophoresis for duration of 2 h at frequency of 1 kHz was found to be comparable to the continuous direct current iontophoresis for 1 h. PMID:24959580

  1. Alternatives to Tenure. AAHE-ERIC/Higher Education Research Currents. March 1979.

    ERIC Educational Resources Information Center

    Linney, Thomas J.

    An overview of current literature about alternatives and variations to existing concepts of tenure of faculty is presented. Tenure continues the appointment of faculty until retirement unless there is dismissal for adequate cause or unavoidable termination because of financial exigency or change of institutional program. Academic freedom is…

  2. Assessment of Alternative Student Aid Delivery Systems: Analytic Agenda for the Current System.

    ERIC Educational Resources Information Center

    Advanced Technology, Inc., Reston, VA.

    A guide for analyzing the effects of the current student aid delivery system and for estimating the effects of system alternatives is presented. Attention is directed to measures, data sources, and analysis methods needed to evaluate the effects of each delivery system activity on the various participants (e.g., lenders, financial aid applicants,…

  3. A Brief Review of the Current Status of Alternatives of Chlorine Disinfection of Water

    PubMed Central

    Anderson, A. C.; Reimers, R. S.; DeKernion, P.

    1982-01-01

    This paper briefly outlines some of the alternative disinfectants being considered in lieu of chlorination. Methods currently in use as well as those in the research stage are included. Each method is assessed with respect to disinfection efficiency and environmental impact. (Am J Public Health 1982; 72:1290-1293.) PMID:7125035

  4. Influence of Critical Current Density on Guidance Force Decay of HTS Bulk Exposed to AC Magnetic Field Perturbation in a Maglev Vehicle System

    NASA Astrophysics Data System (ADS)

    Longcai, Zhang; Jianguo, Kong

    2012-07-01

    Superconducting maglev vehicle is one of the most promising applications of HTS bulks. In such a system, the HTS bulks are always exposed to AC external magnetic field, which is generated by the inhomogeneous surface magnetic field of the NdFeB guideway. In our previous work, we studied the guidance force decay of the YBCO bulk over the NdFdB guideway used in the High-temperature superconducting maglev vehicle system with the application of the AC external magnetic field, and calculated the guidance force decay as a function of time based on an analytic model. In this paper, we investigated the influence of the critical current density on the guidance force decay of HTS bulk exposed to AC field perturbation in the maglev vehicle system and try to adopt a method to suppress the decay. From the results, it was found that the guidance force decay rate was higher for the bulk with lower critical current density. Therefore, we could suppress the guidance force decay of HTS bulk exposed to AC external magnetic field perturbation in the maglev vehicle system by improving critical current density of the bulk.

  5. AC susceptibility and critical current in the organic superconductor {kappa}-(ET){sub 2}Cu(NCS){sub 2}

    SciTech Connect

    Gonzalez, M.A.; Velez, M.; Vicent, J.L.; Schleuter, J.; Williams, J.M.; Crabtree, G.W.

    1994-05-01

    The AC susceptibility (X{prime}, X{double_prime}) has bee measured in a single crystal of the organic superconductor K-(ET){sub 2}Cu(NCS){sub 2} ({Tc} = 9.5 K) as a function of the DC magnetic field, for several frequencies (10 {sup 2} Hz AC fields (l{mu}T

  6. Application of low-frequency alternating current electric fields via interdigitated electrodes: effects on cellular viability, cytoplasmic calcium, and osteogenic differentiation of human adipose-derived stem cells.

    PubMed

    McCullen, Seth D; McQuilling, John P; Grossfeld, Robert M; Lubischer, Jane L; Clarke, Laura I; Loboa, Elizabeth G

    2010-12-01

    Electric stimulation is known to initiate signaling pathways and provides a technique to enhance osteogenic differentiation of stem and/or progenitor cells. There are a variety of in vitro stimulation devices to apply electric fields to such cells. Herein, we describe and highlight the use of interdigitated electrodes to characterize signaling pathways and the effect of electric fields on the proliferation and osteogenic differentiation of human adipose-derived stem cells (hASCs). The advantage of the interdigitated electrode configuration is that cells can be easily imaged during short-term (acute) stimulation, and this identical configuration can be utilized for long-term (chronic) studies. Acute exposure of hASCs to alternating current (AC) sinusoidal electric fields of 1 Hz induced a dose-dependent increase in cytoplasmic calcium in response to electric field magnitude, as observed by fluorescence microscopy. hASCs that were chronically exposed to AC electric field treatment of 1 V/cm (4 h/day for 14 days, cultured in the osteogenic differentiation medium containing dexamethasone, ascorbic acid, and β-glycerol phosphate) displayed a significant increase in mineral deposition relative to unstimulated controls. This is the first study to evaluate the effects of sinusoidal AC electric fields on hASCs and to demonstrate that acute and chronic electric field exposure can significantly increase intracellular calcium signaling and the deposition of accreted calcium under osteogenic stimulation, respectively.

  7. Feedback-Controlled Transcranial Alternating Current Stimulation Reveals a Functional Role of Sleep Spindles in Motor Memory Consolidation.

    PubMed

    Lustenberger, Caroline; Boyle, Michael R; Alagapan, Sankaraleengam; Mellin, Juliann M; Vaughn, Bradley V; Fröhlich, Flavio

    2016-08-22

    Transient episodes of brain oscillations are a common feature of both the waking and the sleeping brain. Sleep spindles represent a prominent example of a poorly understood transient brain oscillation that is impaired in disorders such as Alzheimer's disease and schizophrenia. However, the causal role of these bouts of thalamo-cortical oscillations remains unknown. Demonstrating a functional role of sleep spindles in cognitive processes has, so far, been hindered by the lack of a tool to target transient brain oscillations in real time. Here, we show, for the first time, selective enhancement of sleep spindles with non-invasive brain stimulation in humans. We developed a system that detects sleep spindles in real time and applies oscillatory stimulation. Our stimulation selectively enhanced spindle activity as determined by increased sigma activity after transcranial alternating current stimulation (tACS) application. This targeted modulation caused significant enhancement of motor memory consolidation that correlated with the stimulation-induced change in fast spindle activity. Strikingly, we found a similar correlation between motor memory and spindle characteristics during the sham night for the same spindle frequencies and electrode locations. Therefore, our results directly demonstrate a functional relationship between oscillatory spindle activity and cognition. PMID:27476602

  8. Unusual dc electric fields induced by a high frequency alternating current in superconducting Nb films under a perpendicular magnetic field

    NASA Astrophysics Data System (ADS)

    Aliev, F. G.; Levanyuk, A. P.; Villar, R.; Sierra, J. F.; Pryadun, V. V.; Awad, A.; Moshchalkov, V. V.

    2009-06-01

    We report a systematic study of dc electric fields produced by sinusoidal high frequency ac currents in Nb superconducting films subject to a constant magnetic field perpendicular to the film plane. At frequencies in the 100 kHz to MHz range appears a new rectification effect which has not been previously observed at lower frequencies. We have observed the dc electric field generated in this regime in films without intentionally created anisotropic pinning centres, i.e. plain films, both in strip geometry as in cross-shape geometry, and also in films with symmetric periodic pinning centres. The electric field appears in both directions along and transverse to the alternating current and is essentially different at opposite film sides. It depends strongly on the intensity of the magnetic field and may exceed by nearly an order of magnitude the rectified electric fields recently reported at lower frequencies (few kHz) in systems with artificially induced anisotropic vortex pinning. The effect has a non-monotonic dependence on the drive current frequency, being maximum around a few 100 kHz to MHz, and shows a complicated temperature dependence. It is found to be different in long strips and cross shape samples. In the case of films with symmetric periodic pinning centres the rectified voltage shows a lower magnitude than in plain films, and shows an interesting structure when the applied magnetic field crosses the matching fields. We are only able to put forward tentative ideas to explain this phenomenon, which irrespective of its explanation should be taken into account in experimental studies of rectification effects in superconductors.

  9. Free piston variable-stroke linear-alternator generator

    DOEpatents

    Haaland, Carsten M.

    1998-01-01

    A free-piston variable stroke linear-alternator AC power generator for a combustion engine. An alternator mechanism and oscillator system generates AC current. The oscillation system includes two oscillation devices each having a combustion cylinder and a flying turnbuckle. The flying turnbuckle moves in accordance with the oscillation device. The alternator system is a linear alternator coupled between the two oscillation devices by a slotted connecting rod.

  10. Free piston variable-stroke linear-alternator generator

    DOEpatents

    Haaland, C.M.

    1998-12-15

    A free-piston variable stroke linear-alternator AC power generator for a combustion engine is described. An alternator mechanism and oscillator system generates AC current. The oscillation system includes two oscillation devices each having a combustion cylinder and a flying turnbuckle. The flying turnbuckle moves in accordance with the oscillation device. The alternator system is a linear alternator coupled between the two oscillation devices by a slotted connecting rod. 8 figs.

  11. AC corrosion -- A new challenge to pipeline integrity

    SciTech Connect

    Gummow, R.A.; Wakelin, R.G.; Segall, S.M.

    1998-12-31

    Corrosion of steel by alternating current was investigated as far back as the early 1900`s. These early studies and others in the 1950--60`s indicated that AC corrosion of steel was only a fraction of an equivalent amount of direct current (i.e. less than 1% of a like amount of DC) and in addition was controlled to negligible levels when cathodic protection was applied to industry standards. In 1986 however, an investigation into a corrosion failure on a high pressure gas pipeline in Germany indicated that the sole cause of the failure was AC corrosion. This corrosion failure on an otherwise well protected pipeline resulted in the initiation of several laboratory and field studies which indicated, that above a certain minimum AC current density, normal levels of cathodic protection will not control AC corrosion to acceptable levels and that AC mitigation is often required to prevent serious corrosion. Several other AC corrosion sites were discovered at coating holidays during the follow-up investigations in Germany. A graph, relating AC voltage to holiday size at the minimum AC current density for corrosion, is presented to assist the pipeline operator in determining whether or not a pipeline is susceptible to AC corrosion activity.

  12. Direct-current arc and alternating-current spark emission spectrographic field methods for the semiquantitative analysis of geologic materials

    USGS Publications Warehouse

    Grimes, D.J.; Marranzino, A.P.

    1968-01-01

    Two spectrographic methods are used in mobile field laboratories of the U. S. Geological Survey. In the direct-current arc method, the ground sample is mixed with graphite powder, packed into an electrode crater, and burned to completion. Thirty elements are determined. In the spark method, the sample, ground to pass a 150-mesh screen, is digested in hydrofluoric acid followed by evaporation to dryness and dissolution in aqua regia. The solution is fed into the spark gap by means of a rotating-disk electrode arrangement and is excited with an alternating-current spark discharge. Fourteen elements are determined. In both techniques, light is recorded on Spectrum Analysis No. 1, 35-millimeter film, and the spectra are compared visually with those of standard films.

  13. Alternating and direct current field effects on the structure-property relationships in Na{sub 0.5}Bi{sub 0.5}TiO{sub 3}-x%BaTiO{sub 3} textured ceramics

    SciTech Connect

    Ge, Wenwei; Li, Jiefang; Viehland, D.; Maurya, Deepam; Priya, Shashank

    2013-06-03

    The influence of alternating (ac) and direct current (dc) fields on the structural and dielectric properties of [001]{sub PC} textured Na{sub 0.5}Bi{sub 0.5}TiO{sub 3}-7%BaTiO{sub 3} (NBT-7%BT) ceramics has been investigated. X-ray diffraction measurements revealed that the depolarization at temperature T{sub d} in poled samples resulted from a tetragonal {yields} pseudo-cubic transition on heating. Moderate ac drive and dc bias had opposite influences on T{sub d}: ac drive decreased the T{sub d}, whereas dc bias increased it. These investigations suggested an effective method to expand the working temperature range of NBT-x%BT textured ceramics to a high temperature.

  14. Use of Biosensors as Alternatives to Current Regulatory Methods for Marine Biotoxins

    PubMed Central

    Vilariño, Natalia; Fonfría, Eva S.; Louzao, M. Carmen; Botana, Luis M.

    2009-01-01

    Marine toxins are currently monitored by means of a bioassay that requires the use of many mice, which poses a technical and ethical problem in many countries. With the exception of domoic acid, there is a legal requirement for the presence of other toxins (yessotoxin, saxitoxin and analogs, okadaic acid and analogs, pectenotoxins and azaspiracids) in seafood to be controlled by bioassay, but other toxins, such as palytoxin, cyclic imines, ciguatera and tetrodotoxin are potentially present in European food and there are no legal requirements or technical approaches available to identify their presence. The need for alternative methods to the bioassay is clearly important, and biosensors have become in recent years a feasible alternative to animal sacrifice. This review will discuss the advantages and disadvantages of using biosensors as alternatives to animal assays for marine toxins, with particular focus on surface plasmon resonance (SPR) technology. PMID:22291571

  15. Trace level determination of titanium in real samples by alternating current voltammetry

    SciTech Connect

    Locatelli, C.; Fagioli, F.; Garai, T.; Bighi, C.

    1988-11-01

    The fundamental and second harmonic alternating current voltammetric determination of titanium(IV) in the presence of a large excess of iron(III) is reported. The measurements were carried out with a semistationary mercury electrode (long-lasting sessile-drop mercury electrode) as the working electrode. The analytical procedure was controlled by the analysis of standard reference materials: Portland cement BCS 372, stainless steel (AISI 321) SRM 121 d, and highly alloyed steel (Eurostandard 281-1). The confidence interval of the experimental data was in agreement with the certified values for the titanium(IV) content of the samples. The precision, expressed by the relative standard deviation, and the accuracy, expressed by the relative error, were on the order of 3-5%. The standard addition technique was found to improve the resolution of alternating current voltammetric methods, even in the case of very high c/sub Fe:c/sub Tl/ concentration ratios.

  16. Alternating-Current Equipment for the Measurement of Fluctuations of Air Speed in Turbulent Flow

    NASA Technical Reports Server (NTRS)

    Mock, W C , Jr

    1937-01-01

    Recent electrical and mechanical improvements have been made in the equipment developed at the National Bureau of Standards for measurement of fluctuations of air speed in turbulent flow. Data useful in the design of similar equipment are presented. The design of rectified alternating-current power supplies for such apparatus is treated briefly, and the effect of the power supplies on the performance of the equipment is discussed.

  17. QPSK modulation for AC-power-signal-biased visible light communication system

    NASA Astrophysics Data System (ADS)

    Liu, Yu-Feng; Yeh, Chien-Hung; Chow, Chi-Wai; Liu, Yang

    2013-01-01

    With the integration of light emitting diode (LED), visible light communication (VLC) can provide wireless communication link using the lightning system. Due to the consideration of power efficiency, AC-LED has the design of reducing energy waste with alternating current from the power outlet. In this work, we propose an AC-power-signalbiased system that provides communication on both DC-LED and AC-LED. The bias circuit is designed to combine ACpower signal and the message signal with QPSK format. This driving scheme needs no AC-to-DC converters and it is suitable for driving AC LED. Synchronization is completed to avoid threshold effect of LED.

  18. AC corrosion -- a new threat to pipeline integrity?

    SciTech Connect

    Gummow, R.A.; Wakelin, R.G.; Segall, S.M.

    1996-12-31

    Corrosion of steel by alternating current was investigated as far back as the early 1900`s. These early studies and others in the 1950--60`s indicated that AC corrosion of steel was only a fraction of an equivalent amount of direct current (i.e., less than 1% of a like amount of DC) and in addition was controlled to negligible levels with cathodic protection applied to industry standards. In 1986 however, an investigation into a corrosion failure on a high pressure gas pipeline in Germany indicated that the sole cause of the failure was AC corrosion. This corrosion failure on an otherwise well protected pipeline resulted in several laboratory and field studies which indicated, that above a certain minimum AC current density, standard levels of cathodic protection will not control AC corrosion and AC mitigation is required to prevent further corrosion. Several other corrosion anomalies were discovered at coating holidays during the follow-up investigations in Germany. The authors have investigated several corrosion occurrences on pipelines in Ontario during the last 2--3 years which appear to be caused by AC corrosion. This presentation traces the literature record on AC electrolysis from the past to the present and discusses the key parameters which determine the likelihood of corrosion attack. Several case histories of suspected AC corrosion will be discussed and guidelines on how to assess whether or not a pipeline is susceptible to AC corrosion will be offered.

  19. Ring currents that survive bond alternation in constrained 8π and 6π monocycles

    NASA Astrophysics Data System (ADS)

    Havenith, Remco W. A.; Jenneskens, Leonardus W.; Fowler, Patrick W.

    2003-01-01

    Current density maps are computed at the ipsocentric CTOCD-DZ/6-31G **//RHF/6-31G ** level for angle-constrained planar 1,3,5,7-cyclooctatetraenes (COT) and benzene. Constraint of α(CCH) angles to 90° in D4 h COT ( 3b) leads to endo- 4 and exo- 4 valence isomers. The exo structure, with CH bonds perpendicular to long sides of the octagon, is lower in energy by 202 kJ/mol and has stronger bond alternation (Δ R 0.265 Å). However, endo- 4, exo- 4 and COT 3b at its best planar geometry all sustain intense paratropic ring currents, attributed to the rotational character of the HOMO-LUMO transition, and consistent, mutatis mutandis, with the diatropic current in D3 h benzene 5.

  20. 30 CFR 77.900 - Low- and medium-voltage circuits serving portable or mobile three-phase alternating current...

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Low- and medium-voltage circuits serving... Medium-Voltage Alternating Current Circuits § 77.900 Low- and medium-voltage circuits serving portable or mobile three-phase alternating current equipment; circuit breakers. Low- and medium-voltage...

  1. 30 CFR 75.900 - Low- and medium-voltage circuits serving three-phase alternating current equipment; circuit...

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Low- and medium-voltage circuits serving three... STANDARDS-UNDERGROUND COAL MINES Underground Low- and Medium-Voltage Alternating Current Circuits § 75.900 Low- and medium-voltage circuits serving three-phase alternating current equipment; circuit...

  2. 30 CFR 75.900 - Low- and medium-voltage circuits serving three-phase alternating current equipment; circuit...

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 30 Mineral Resources 1 2011-07-01 2011-07-01 false Low- and medium-voltage circuits serving three... STANDARDS-UNDERGROUND COAL MINES Underground Low- and Medium-Voltage Alternating Current Circuits § 75.900 Low- and medium-voltage circuits serving three-phase alternating current equipment; circuit...

  3. 30 CFR 77.900 - Low- and medium-voltage circuits serving portable or mobile three-phase alternating current...

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 30 Mineral Resources 1 2011-07-01 2011-07-01 false Low- and medium-voltage circuits serving... Medium-Voltage Alternating Current Circuits § 77.900 Low- and medium-voltage circuits serving portable or mobile three-phase alternating current equipment; circuit breakers. Low- and medium-voltage...

  4. Anomalies in vortex lattice dynamics driven by induced ac currents in superconducting films with magnetic arrays of two-fold symmetry

    NASA Astrophysics Data System (ADS)

    Moreno, A. J.; Chiliotte, C. E.; Pasquini, G.; Bekeris, V.; Gomez, A.; del Valle, J.; Gonzalez, E. M.; Prieto, J. L.; Vicent, J. L.

    2015-01-01

    We study the dynamics of the vortex lattice driven by ac induced currents in the critical state regime, for T > 0.70 TC. The samples are superconducting films grown on top of two-fold symmetry array of magnetic dots. In these heterostructures, the induced ac currents flow parallel to the short and to the long side of the pinning array in different areas of the samples simultaneously. This behavior produces remarkable effects in the vortex lattice dynamics. First of all, periodic features are observed in the ac susceptibility versus applied magnetic field measurements which are related to matching effects between the vortex lattices and the magnetic array. However, the vortex lattice reconfiguration observed in magnetotransport experiments is absent. Some of these features are revealed as maxima instead of being minima, indicating higher mobility at certain matching fields. Competing unstable vortex configurations could lead to increase vortex mobility precluding the reconfiguration transition. At high temperatures, where the matching effects show up, the magnetic permeability of the dots is the mechanism that governs the JC(T) behavior. Moreover, the temperature dependence of the pinning force FP(T) shows a temperature crossover related to an unexpected enhancement in vortex mobility. Vortex-vortex interaction and the interplay between trapped and interstitial vortices are a hint to explain these phenomena.

  5. A technique to form a porous silicon layer with no backside contact by alternating current electrochemical process

    NASA Astrophysics Data System (ADS)

    El-Bahar, A.; Nemirovsky, Y.

    2000-07-01

    We report here the formation of porous silicon under alternating current conditions. Instead of applying the usual direct current electrochemical process, an alternating current was applied with a given frequency and peak voltage. The porous silicon layer properties are equivalent to the properties that would be achieved by the standard direct current formation technique (i.e., same porosity level). The main advantages of this process are: (a) The alternating current formed porous silicon exhibits higher mechanical stability during the drying step than layers formed using the standard direct current technique. (b) The alternating current process can be performed without a deposited backside contact. These simplify the process and permit its integration with high temperature processing steps and clean furnaces of a modern very large sale-integrated technology.

  6. Alternating Current Cloud Point Extraction on a Microfluidic Chip: the Use of Ferrocenyl Surfactants.

    PubMed

    Usui, Yuya; Sasaki, Naoki

    2016-01-01

    Alternating current cloud point extraction (ACPE) is a preconcentration technique that can be employed in the analysis of membrane proteins on a microfluidic chip. However, the selectivity of ACPE relies on the hydrophobicity of the analytes. In this study, 11-ferrocenyltrimethylundecylammonium bromide (FTMA) was utilized to introduce electrostatic interaction as part of the ACPE technique. The use of ACPE with oxidized FTMA resulted in efficient concentration of fluorescently labeled anionic membrane proteins. We expect the approach outlined in this report to be useful in the preconcentration technique of microchip electrophoresis.

  7. Optical properties of the atmospheric pressure helium plasma jet generated by alternative current (a.c.) power supply

    NASA Astrophysics Data System (ADS)

    Ilik, Erkan; Akan, Tamer

    2016-05-01

    In this work, an atmospheric pressure plasma jet (APPJ) was produced to generate cold flowing post-discharge plasma of pure helium gas. The main aim of this study was to generate cold flowing APPJ of pure helium gas and to determine how their optical emission spectrum change influences varying different flow rates. Lengths of early, middle, and late post-discharge plasma (jet) regions and their fluctuations were determined, respectively. Then, ignition condition dependence of the post-discharge plasma for flow rate was specified at a constant voltage. Spectroscopic studies of an atmospheric pressure plasma jet of helium were presented via analyzing OH, N2, N2+, oxygen, and helium intensities for various flow rates.

  8. Air pollution control residues from waste incineration: current UK situation and assessment of alternative technologies.

    PubMed

    Rani, D Amutha; Boccaccini, A R; Deegan, D; Cheeseman, C R

    2008-11-01

    Current disposal options for APC residues in the UK and alternative treatment technologies developed world-wide have been reviewed. APC residues are currently landfilled in the UK where they undergo in situ solidification, although the future acceptability of this option is uncertain because the EU waste acceptance criteria (WAC) introduce strict limits on leaching that are difficult to achieve. Other APC residue treatment processes have been developed which are reported to reduce leaching to below relevant regulatory limits. The Ferrox process, the VKI process, the WES-PHix process, stabilisation/solidification using cementitious binders and a range of thermal treatment processes are reviewed. Thermal treatment technologies convert APC residues combined with other wastes into inert glass or glass-ceramics that encapsulate heavy metals. The waste management industry will inevitably use the cheapest available option for treating APC residues and strict interpretation and enforcement of waste legislation is required if new, potentially more sustainable technologies are to become commercially viable.

  9. Deformation analysis of vesicles in an alternating-current electric field.

    PubMed

    Tang, Yu-Gang; Liu, Ying; Feng, Xi-Qiao

    2014-08-01

    In this paper the shape equation for axisymmetric vesicles subjected to an ac electric field is derived on the basis of the liquid-crystal model. The equilibrium morphology of a lipid vesicle is determined by the minimization of its free energy in coupled mechanical and ac electric fields. Besides elastic bending, the effects of the osmotic pressure difference, surface tension, Maxwell pressure, and flexoelectric and dielectric properties of phospholipid membrane as well are taken into account. The influences of elastic bending, osmotic pressure difference, and surface tension on the frequency-dependent behavior of a vesicle membrane in an ac electric field are examined. The singularity of the ac electric field is also investigated. Our theoretical results of vesicle deformation agree well with previous experimental and numerical results. The present study provides insights into the physical mechanisms underpinning the frequency-dependent morphological evolution of vesicles in the electric and mechanical fields. PMID:25215760

  10. Deformation analysis of vesicles in an alternating-current electric field.

    PubMed

    Tang, Yu-Gang; Liu, Ying; Feng, Xi-Qiao

    2014-08-01

    In this paper the shape equation for axisymmetric vesicles subjected to an ac electric field is derived on the basis of the liquid-crystal model. The equilibrium morphology of a lipid vesicle is determined by the minimization of its free energy in coupled mechanical and ac electric fields. Besides elastic bending, the effects of the osmotic pressure difference, surface tension, Maxwell pressure, and flexoelectric and dielectric properties of phospholipid membrane as well are taken into account. The influences of elastic bending, osmotic pressure difference, and surface tension on the frequency-dependent behavior of a vesicle membrane in an ac electric field are examined. The singularity of the ac electric field is also investigated. Our theoretical results of vesicle deformation agree well with previous experimental and numerical results. The present study provides insights into the physical mechanisms underpinning the frequency-dependent morphological evolution of vesicles in the electric and mechanical fields.

  11. Current Perspectives on the Use of Alternative Species in Human Health and Ecological Hazard Assessments

    PubMed Central

    Ankley, Gerald T.; Crofton, Kevin M.; Garcia-Reyero, Natàlia; LaLone, Carlie A.; Johnson, Mark S.; Tietge, Joseph E.; Villeneuve, Daniel L.

    2013-01-01

    Background: Traditional animal toxicity tests can be time and resource intensive, thereby limiting the number of chemicals that can be comprehensively tested for potential hazards to humans and/or to the environment. Objective: We compared several types of data to demonstrate how alternative models can be used to inform both human and ecological risk assessment. Methods: We reviewed and compared data derived from high throughput in vitro assays to fish reproductive tests for seven chemicals. We investigated whether human-focused assays can be predictive of chemical hazards in the environment. We examined how conserved pathways enable the use of nonmammalian models, such as fathead minnow, zebrafish, and Xenopus laevis, to understand modes of action and to screen for chemical risks to humans. Results: We examined how dose-dependent responses of zebrafish embryos exposed to flusilazole can be extrapolated, using pathway point of departure data and reverse toxicokinetics, to obtain human oral dose hazard values that are similar to published mammalian chronic toxicity values for the chemical. We also examined how development/safety data for human health can be used to help assess potential risks of pharmaceuticals to nontarget species in the environment. Discussion: Using several examples, we demonstrate that pathway-based analysis of chemical effects provides new opportunities to use alternative models (nonmammalian species, in vitro tests) to support decision making while reducing animal use and associated costs. Conclusions: These analyses and examples demonstrate how alternative models can be used to reduce cost and animal use while being protective of both human and ecological health. Citation: Perkins EJ, Ankley GT, Crofton KM, Garcia-Reyero N, LaLone CA, Johnson MS, Tietge JE, Villeneuve DL. 2013. Current perspectives on the use of alternative species in human health and ecological hazard assessments. Environ Health Perspect 121:1002–1010;

  12. Time-dependent phase lag of biofunctionalized magnetic nanoparticles conjugated with biotargets studied with alternating current magnetic susceptometor for liquid phase immunoassays

    NASA Astrophysics Data System (ADS)

    Liao, S. H.; Yang, H. C.; Horng, H. E.; Chieh, J. J.; Chen, K. L.; Chen, H. H.; Chen, J. Y.; Liu, C. I.; Liu, C. W.; Wang, L. M.

    2013-12-01

    In this work, the time-dependent phase lag θ of biofunctionalized magnetic nanoparticles (BMNs) conjugated with biotargets is studied with a home-made alternating current (ac) susceptometor for liquid phase immunoassays. The sensing unit of the ac susceptometor composed of excitation, pick-up, and compensation coils are balanced to 0.03 ppm. The BMNs are anti-goat C-reactive protein coated onto dextran-coated magnetic nanoparticles composed of Fe3O4, labeled as Fe3O4-antiCRP. The bio-targets are human CRP. As the human CRP is conjugated with reagents Fe3O4-antiCRP, the magnetic clusters of Fe3O4-antiCRP-CRP are formulated. Due to the clustering effect, the Brownian relaxation of BMNs will be depressed, which in turn enhances the effective relaxation time. By monitoring the dynamic phase lag, we demonstrate a sensitive platform of assaying human CRP. The detection platform is robust, easy to use and can be applied for assaying a wide variety of biotargets including viruses, proteins, tumor markers, chemicals, etc.

  13. Alternative current conduction mechanisms of organic-inorganic compound [N(CH{sub 3}){sub 3}H]{sub 2}CuCl{sub 4}

    SciTech Connect

    Ben Bechir, M. Karoui, K.; Guidara, K.; Ben Rhaiem, A.; Tabellout, M.

    2014-05-28

    The [N(CH{sub 3}){sub 3}H]{sub 2}CuCl{sub 4} single crystal has been analyzed by X-ray powder diffraction patterns, differential scanning calorimetry (DSC), and electrical impedance spectroscopy. [N(CH{sub 3}){sub 3}H]{sub 2}CuCl{sub 4} crystallizes at room temperature in the monoclinic system with P2{sub 1}/{sub C} space group. Three phase transitions at T{sub 1} = 226 K, T{sub 2} = 264 K, and T{sub 3} = 297 K have been evidenced by DSC measurements. The electrical technique was measured in the 10{sup −1}–10{sup 7} Hz frequency range and 203–313 K temperature intervals. The frequency dependence of alternative current (AC) conductivity is interpreted in terms of Jonscher's law (developed). The AC electrical conduction in [N(CH{sub 3}){sub 3}H]{sub 2}CuCl{sub 4} compound is studied by two processes which can be attributed to a hopping transport mechanism: the correlated barrier hopping model in phases I, II, and III, the non-overlapping small polaron tunneling model in phase IV. The conduction mechanism is interpreted with the help of Elliot's theory, and the Elliot's parameters are found.

  14. Alternative current conduction mechanisms of organic-inorganic compound [N(CH3)3H]2CuCl4

    NASA Astrophysics Data System (ADS)

    Ben Bechir, M.; Karoui, K.; Tabellout, M.; Guidara, K.; Ben Rhaiem, A.

    2014-05-01

    The [N(CH3)3H]2CuCl4 single crystal has been analyzed by X-ray powder diffraction patterns, differential scanning calorimetry (DSC), and electrical impedance spectroscopy. [N(CH3)3H]2CuCl4 crystallizes at room temperature in the monoclinic system with P21/C space group. Three phase transitions at T1 = 226 K, T2 = 264 K, and T3 = 297 K have been evidenced by DSC measurements. The electrical technique was measured in the 10-1-107 Hz frequency range and 203-313 K temperature intervals. The frequency dependence of alternative current (AC) conductivity is interpreted in terms of Jonscher's law (developed). The AC electrical conduction in [N(CH3)3H]2CuCl4 compound is studied by two processes which can be attributed to a hopping transport mechanism: the correlated barrier hopping model in phases I, II, and III, the non-overlapping small polaron tunneling model in phase IV. The conduction mechanism is interpreted with the help of Elliot's theory, and the Elliot's parameters are found.

  15. Current progress on truffle submerged fermentation: a promising alternative to its fruiting bodies.

    PubMed

    Tang, Ya-Jie; Liu, Rui-Sang; Li, Hong-Mei

    2015-03-01

    Truffle (Tuber spp.), also known as "underground gold," is popular in various cuisines because of its unique and characteristic aroma. Currently, truffle fruiting bodies are mostly obtained from nature and semi-artificial cultivation. However, the former source is scarce, and the latter is time-consuming, usually taking 4 to 12 years before harvest of the fruiting body. The truffle submerged fermentation process was first developed in Tang's lab as an alternative to its fruiting bodies. To the best of our knowledge, most reports of truffle submerged fermentation come from Tang's group. This review examines the current state of the truffle submerged fermentation process. First, the strategy to optimize the truffle submerged fermentation process is summarized; the final conditions yielded not only the highest reported truffle biomass but also the highest production of extracellular and intracellular polysaccharides. Second, the comparison of metabolites produced by truffle fermentation and fruiting bodies is presented, and the former were superior to the latter. Third, metabolites (i.e., volatile organic compounds, equivalent umami concentration, and sterol) derived from truffle fermentation could be regulated by fermentation process optimization. These findings indicated that submerged fermentation of truffles can be used for commercial production of biomass and metabolites as a promising alternative to generating its fruiting bodies in bioreactor.

  16. Regional economic impacts of current and proposed management alternatives for Don Edwards National Wildlife Refuge

    USGS Publications Warehouse

    Richardson, Leslie; Huber, Chris; Koontz, Lynne

    2012-01-01

    The National Wildlife Refuge System Improvement Act of 1997 requires all units of the National Wildlife Refuge System to be managed under a Comprehensive Conservation Plan. The Comprehensive Conservation Plan must describe the desired future conditions of a Refuge and provide long-range guidance and management direction to achieve refuge purposes. The Don Edwards San Francisco Bay National Wildlife Refuge, located at the south end of California's San Francisco Bay and one of seven refuges in the San Francisco Bay National Wildlife Refuge Complex, is in the process of developing a range of management goals, objectives, and strategies for the Comprehensive Conservation Plan. The Comprehensive Conservation Plan must contain an analysis of expected effects associated with current and proposed Refuge management strategies. For Refuge Comprehensive Conservation Plan planning, a regional economic analysis provides a means of estimating how current management (No Action Alternative) and proposed management activities (alternatives) affect the local economy. This type of analysis provides two critical pieces of information: (1) it illustrates the Don Edwards San Francisco Bay National Wildlife Refuge's contribution to the local community, and (2) it can help in determining whether economic effects are or are not a real concern in choosing among management alternatives. This report first presents a description of the local community and economy near the Don Edwards San Francisco Bay National Wildlife Refuge. Next, the methods used to conduct a regional economic impact analysis are described. An analysis of the final Comprehensive Conservation Plan management strategies that could affect stakeholders, residents, and the local economy is then presented. The management activities of economic concern in this analysis are: * Spending in the local community by Refuge visitors; * Refuge personnel salary spending; and * Refuge purchases of goods and services within the local

  17. Dielectrophoretic particle-particle interaction under AC electrohydrodynamic flow conditions.

    PubMed

    Lee, Doh-Hyoung; Yu, Chengjie; Papazoglou, Elisabeth; Farouk, Bakhtier; Noh, Hongseok M

    2011-09-01

    We used the Maxwell stress tensor method to understand dielectrophoretic particle-particle interactions and applied the results to the interpretation of particle behaviors under alternating current (AC) electrohydrodynamic conditions such as AC electroosmosis (ACEO) and electrothermal flow (ETF). Distinct particle behaviors were observed under ACEO and ETF. Diverse particle-particle interactions observed in experiments such as particle clustering, particles keeping a certain distance from each other, chain and disc formation and their rotation, are explained based on the numerical simulation data. The improved understanding of particle behaviors in AC electrohydrodynamic flows presented here will enable researchers to design better particle manipulation strategies for lab-on-a-chip applications. PMID:21823132

  18. Impact of aviation emissions on UTLS and air quality in current and future climate - GEM-AC model simulations

    NASA Astrophysics Data System (ADS)

    Kaminski, J. W.

    2015-12-01

    The objective of this study is to investigate the potential impacts of aviation emissions on the upper troposphere and lower stratosphere (UTLS) and surface air quality. The tool that was used in our study is the GEM-AC (Global Environmental Multiscale with Atmospheric Chemistry) chemical weather model where air quality, free tropospheric and stratospheric chemistry processes are on-line and interactive in a weather forecast model of Environment Canada. In vertical, the model domain is defined on 70 hybrid levels from the surface to ~60km. The gas-phase chemistry includes a comprehensive set of reactions for Ox, NOx, HOx, CO, CH4, NMVOCs, halocarbons, ClOx and BrO. Also, the model can address aerosol microphysics and gas-aerosol partitioning. Aircraft emissions are provided by the AEDT 2006 database developed by the Federal Aviation Administration. Results from model simulations on a global variable grid with 1 degree uniform resolution in the northern hemisphere will be presented.

  19. Alternative (non-animal) methods for cosmetics testing: current status and future prospects-2010.

    PubMed

    Adler, Sarah; Basketter, David; Creton, Stuart; Pelkonen, Olavi; van Benthem, Jan; Zuang, Valérie; Andersen, Klaus Ejner; Angers-Loustau, Alexandre; Aptula, Aynur; Bal-Price, Anna; Benfenati, Emilio; Bernauer, Ulrike; Bessems, Jos; Bois, Frederic Y; Boobis, Alan; Brandon, Esther; Bremer, Susanne; Broschard, Thomas; Casati, Silvia; Coecke, Sandra; Corvi, Raffaella; Cronin, Mark; Daston, George; Dekant, Wolfgang; Felter, Susan; Grignard, Elise; Gundert-Remy, Ursula; Heinonen, Tuula; Kimber, Ian; Kleinjans, Jos; Komulainen, Hannu; Kreiling, Reinhard; Kreysa, Joachim; Leite, Sofia Batista; Loizou, George; Maxwell, Gavin; Mazzatorta, Paolo; Munn, Sharon; Pfuhler, Stefan; Phrakonkham, Pascal; Piersma, Aldert; Poth, Albrecht; Prieto, Pilar; Repetto, Guillermo; Rogiers, Vera; Schoeters, Greet; Schwarz, Michael; Serafimova, Rositsa; Tähti, Hanna; Testai, Emanuela; van Delft, Joost; van Loveren, Henk; Vinken, Mathieu; Worth, Andrew; Zaldivar, José-Manuel

    2011-05-01

    The 7th amendment to the EU Cosmetics Directive prohibits to put animal-tested cosmetics on the market in Europe after 2013. In that context, the European Commission invited stakeholder bodies (industry, non-governmental organisations, EU Member States, and the Commission's Scientific Committee on Consumer Safety) to identify scientific experts in five toxicological areas, i.e. toxicokinetics, repeated dose toxicity, carcinogenicity, skin sensitisation, and reproductive toxicity for which the Directive foresees that the 2013 deadline could be further extended in case alternative and validated methods would not be available in time. The selected experts were asked to analyse the status and prospects of alternative methods and to provide a scientifically sound estimate of the time necessary to achieve full replacement of animal testing. In summary, the experts confirmed that it will take at least another 7-9 years for the replacement of the current in vivo animal tests used for the safety assessment of cosmetic ingredients for skin sensitisation. However, the experts were also of the opinion that alternative methods may be able to give hazard information, i.e. to differentiate between sensitisers and non-sensitisers, ahead of 2017. This would, however, not provide the complete picture of what is a safe exposure because the relative potency of a sensitiser would not be known. For toxicokinetics, the timeframe was 5-7 years to develop the models still lacking to predict lung absorption and renal/biliary excretion, and even longer to integrate the methods to fully replace the animal toxicokinetic models. For the systemic toxicological endpoints of repeated dose toxicity, carcinogenicity and reproductive toxicity, the time horizon for full replacement could not be estimated.

  20. Alternative (non-animal) methods for cosmetics testing: current status and future prospects-2010.

    PubMed

    Adler, Sarah; Basketter, David; Creton, Stuart; Pelkonen, Olavi; van Benthem, Jan; Zuang, Valérie; Andersen, Klaus Ejner; Angers-Loustau, Alexandre; Aptula, Aynur; Bal-Price, Anna; Benfenati, Emilio; Bernauer, Ulrike; Bessems, Jos; Bois, Frederic Y; Boobis, Alan; Brandon, Esther; Bremer, Susanne; Broschard, Thomas; Casati, Silvia; Coecke, Sandra; Corvi, Raffaella; Cronin, Mark; Daston, George; Dekant, Wolfgang; Felter, Susan; Grignard, Elise; Gundert-Remy, Ursula; Heinonen, Tuula; Kimber, Ian; Kleinjans, Jos; Komulainen, Hannu; Kreiling, Reinhard; Kreysa, Joachim; Leite, Sofia Batista; Loizou, George; Maxwell, Gavin; Mazzatorta, Paolo; Munn, Sharon; Pfuhler, Stefan; Phrakonkham, Pascal; Piersma, Aldert; Poth, Albrecht; Prieto, Pilar; Repetto, Guillermo; Rogiers, Vera; Schoeters, Greet; Schwarz, Michael; Serafimova, Rositsa; Tähti, Hanna; Testai, Emanuela; van Delft, Joost; van Loveren, Henk; Vinken, Mathieu; Worth, Andrew; Zaldivar, José-Manuel

    2011-05-01

    The 7th amendment to the EU Cosmetics Directive prohibits to put animal-tested cosmetics on the market in Europe after 2013. In that context, the European Commission invited stakeholder bodies (industry, non-governmental organisations, EU Member States, and the Commission's Scientific Committee on Consumer Safety) to identify scientific experts in five toxicological areas, i.e. toxicokinetics, repeated dose toxicity, carcinogenicity, skin sensitisation, and reproductive toxicity for which the Directive foresees that the 2013 deadline could be further extended in case alternative and validated methods would not be available in time. The selected experts were asked to analyse the status and prospects of alternative methods and to provide a scientifically sound estimate of the time necessary to achieve full replacement of animal testing. In summary, the experts confirmed that it will take at least another 7-9 years for the replacement of the current in vivo animal tests used for the safety assessment of cosmetic ingredients for skin sensitisation. However, the experts were also of the opinion that alternative methods may be able to give hazard information, i.e. to differentiate between sensitisers and non-sensitisers, ahead of 2017. This would, however, not provide the complete picture of what is a safe exposure because the relative potency of a sensitiser would not be known. For toxicokinetics, the timeframe was 5-7 years to develop the models still lacking to predict lung absorption and renal/biliary excretion, and even longer to integrate the methods to fully replace the animal toxicokinetic models. For the systemic toxicological endpoints of repeated dose toxicity, carcinogenicity and reproductive toxicity, the time horizon for full replacement could not be estimated. PMID:21533817

  1. Phosphor-in-glass for high-powered remote-type white AC-LED.

    PubMed

    Lin, Hang; Wang, Bo; Xu, Ju; Zhang, Rui; Chen, Hui; Yu, Yunlong; Wang, Yuansheng

    2014-12-10

    The high-powered alternating current (AC) light-emitting diode (LED) (AC-LED), featuring low cost, high energy utilization efficiency, and long service life, will become a new economic growth point in the field of semiconductor lighting. However, flicker of AC-LED in the AC cycles is not healthy for human eyes, and therefore need to be restrained. Herein we report an innovation of persistent "phosphor-in-glass" (PiG) for the remote-type AC-LED, whose afterglow can be efficiently activated by the blue light. It is experimentally demonstrated that the afterglow decay of PiG in the microsecond range can partly compensate the AC time gap. Moreover, the substitution of inorganic glass for organic resins or silicones as the encapsulants would bring out several technological benefits to AC-LED, such as good heat-dissipation, low glare, and excellent physical/chemical stability. PMID:25329651

  2. Phosphor-in-glass for high-powered remote-type white AC-LED.

    PubMed

    Lin, Hang; Wang, Bo; Xu, Ju; Zhang, Rui; Chen, Hui; Yu, Yunlong; Wang, Yuansheng

    2014-12-10

    The high-powered alternating current (AC) light-emitting diode (LED) (AC-LED), featuring low cost, high energy utilization efficiency, and long service life, will become a new economic growth point in the field of semiconductor lighting. However, flicker of AC-LED in the AC cycles is not healthy for human eyes, and therefore need to be restrained. Herein we report an innovation of persistent "phosphor-in-glass" (PiG) for the remote-type AC-LED, whose afterglow can be efficiently activated by the blue light. It is experimentally demonstrated that the afterglow decay of PiG in the microsecond range can partly compensate the AC time gap. Moreover, the substitution of inorganic glass for organic resins or silicones as the encapsulants would bring out several technological benefits to AC-LED, such as good heat-dissipation, low glare, and excellent physical/chemical stability.

  3. A uniform laminar air plasma plume with large volume excited by an alternating current voltage

    NASA Astrophysics Data System (ADS)

    Li, Xuechen; Bao, Wenting; Chu, Jingdi; Zhang, Panpan; Jia, Pengying

    2015-12-01

    Using a plasma jet composed of two needle electrodes, a laminar plasma plume with large volume is generated in air through an alternating current voltage excitation. Based on high-speed photography, a train of filaments is observed to propagate periodically away from their birth place along the gas flow. The laminar plume is in fact a temporal superposition of the arched filament train. The filament consists of a negative glow near the real time cathode, a positive column near the real time anode, and a Faraday dark space between them. It has been found that the propagation velocity of the filament increases with increasing the gas flow rate. Furthermore, the filament lifetime tends to follow a normal distribution (Gaussian distribution). The most probable lifetime decreases with increasing the gas flow rate or decreasing the averaged peak voltage. Results also indicate that the real time peak current decreases and the real time peak voltage increases with the propagation of the filament along the gas flow. The voltage-current curve indicates that, in every discharge cycle, the filament evolves from a Townsend discharge to a glow one and then the discharge quenches. Characteristic regions including a negative glow, a Faraday dark space, and a positive column can be discerned from the discharge filament. Furthermore, the plasma parameters such as the electron density, the vibrational temperature and the gas temperature are investigated based on the optical spectrum emitted from the laminar plume.

  4. Alternating Current Dielectrophoresis Optimization of Pt-Decorated Graphene Oxide Nanostructures for Proficient Hydrogen Gas Sensor.

    PubMed

    Wang, Jianwei; Rathi, Servin; Singh, Budhi; Lee, Inyeal; Joh, Han-Ik; Kim, Gil-Ho

    2015-07-01

    Alternating current dielectrophoresis (DEP) is an excellent technique to assemble nanoscale materials. For efficient DEP, the optimization of the key parameters like peak-to-peak voltage, applied frequency, and processing time is required for good device. In this work, we have assembled graphene oxide (GO) nanostructures mixed with platinum (Pt) nanoparticles between the micro gap electrodes for a proficient hydrogen gas sensors. The Pt-decorated GO nanostructures were well located between a pair of prepatterned Ti/Au electrodes by controlling the DEP technique with the optimized parameters and subsequently thermally reduced before sensing. The device fabricated using the DEP technique with the optimized parameters showed relatively high sensitivity (∼10%) to 200 ppm hydrogen gas at room temperature. The results indicates that the device could be used in several industry applications, such as gas storage and leak detection. PMID:26042360

  5. Enhanced labeling of microalgae cellular lipids by application of an electric field generated by alternating current.

    PubMed

    Su, Li-Chien; Hsu, Yi-Hsiang; Wang, Hsiang-Yu

    2012-05-01

    An alternating current was used to generate an electric field to enhance the fluorescent labeling of microalgae cellular lipids with Nile red and LipidTOX. The decay of the fluorescence intensity of Chlorella vulgaris cells in 0 V/cm was more than 50% after 10 min, and the intensity variation was as high as 7% in 20s. At 2000 V/cm, the decay rate decreased to 1.22% per minute and the intensity fluctuation was less than 1% for LipidTOX-labeled cells. For Spirulina sp. cells at 0 V/cm, the fluorescence intensity increased by 10% after 10 min, whereas at 2000 V/cm, labeling was more rapid and fluorescence intensity doubled. These results show that applying an electric field can improve the quality of fluorescence detection by alleviating decay and fluctuation or by enhancing signal intensity.

  6. Emission characteristics in solution-processed asymmetric white alternating current field-induced polymer electroluminescent devices

    NASA Astrophysics Data System (ADS)

    Chen, Yonghua; Xia, Yingdong; Smith, Gregory M.; Gu, Yu; Yang, Chuluo; Carroll, David L.

    2013-01-01

    In this work, the emission characteristics of a blue fluorophor poly(9, 9-dioctylfluorene) (PFO) combined with a red emitting dye: Bis(2-methyl-dibenzo[f,h]quinoxaline)(acetylacetonate)iridium (III) [Ir(MDQ)2(acac)], are examined in two different asymmetric white alternating current field-induced polymer electroluminescent (FIPEL) device structures. The first is a top-contact device in which the triplet transfer is observed resulting in the concentration-dependence of the emission similar to the standard organic light-emitting diode (OLED) structure. The second is a bottom-contact device which, however, exhibits concentration-independence of emission. Specifically, both dye emission and polymer emission are found for the concentrations as high as 10% by weight of the dye in the emitter. We attribute this to the significant different carrier injection characteristics of the two FIPEL devices. Our results suggest a simple and easy way to realize high-quality white emission.

  7. Alternating current cloud point extraction on a microchip: the effect of electrode geometry.

    PubMed

    Sasaki, Naoki; Maekawa, Chisaki; Sato, Kae

    2015-02-01

    We report on the effect of electrode geometry on alternating current cloud point extraction (ACPE). ACPE is a technique utilized to extract membrane-associated biomolecules in an electrode-integrated microfluidic channel. In this study, we investigated the effect of gap size (4∼22 μm) between microband electrodes on ACPE. A decrease in gap size resulted in efficient and rapid concentration of fluorescent-labeled phospholipids, a model of membrane-associated biomolecules. We also investigated the effect of applied voltage amplitude on ACPE using devices with decreased electrode gap size. When the gap was small, ACPE was achieved with low applied voltages. ACPE of membrane proteins extracted from HeLa cells was also studied to demonstrate the applicability of the ACPE to real samples. The results provide a guideline to improve the performance of ACPE and facilitate application of the ACPE technique as part of an overall analytical process.

  8. Exploring the conformational preferences of 20-residue peptides in isolation: Ac-Ala19-Lys + H(+)vs. Ac-Lys-Ala19 + H(+) and the current reach of DFT.

    PubMed

    Schubert, Franziska; Rossi, Mariana; Baldauf, Carsten; Pagel, Kevin; Warnke, Stephan; von Helden, Gert; Filsinger, Frank; Kupser, Peter; Meijer, Gerard; Salwiczek, Mario; Koksch, Beate; Scheffler, Matthias; Blum, Volker

    2015-03-21

    Reliable, quantitative predictions of the structure of peptides based on their amino-acid sequence information are an ongoing challenge. We here explore the energy landscapes of two unsolvated 20-residue peptides that result from a shift of the position of one amino acid in otherwise the same sequence. Our main goal is to assess the performance of current state-of-the-art density-functional theory for predicting the structure of such large and complex systems, where weak interactions such as dispersion or hydrogen bonds play a crucial role. For validation of the theoretical results, we employ experimental gas-phase ion mobility-mass spectrometry and IR spectroscopy. While unsolvated Ac-Ala19-Lys + H(+) will be shown to be a clear helix seeker, the structure space of Ac-Lys-Ala19 + H(+) is more complicated. Our first-principles structure-screening strategy using the dispersion-corrected PBE functional (PBE + vdW(TS)) identifies six distinctly different structure types competing in the low-energy regime (≈16 kJ mol(-1)). For these structure types, we analyze the influence of the PBE and the hybrid PBE0 functional coupled with either a pairwise dispersion correction (PBE + vdW(TS), PBE0 + vdW(TS)) or a many-body dispersion correction (PBE + MBD*, PBE0 + MBD*). We also take harmonic vibrational and rotational free energy into account. Including this, the PBE0 + MBD* functional predicts only one unique conformer to be present at 300 K. We show that this scenario is consistent with both experiments. PMID:25700010

  9. Regional economic analysis of current and proposed management alternatives for Rappahannock River Valley National Wildlife Refuge

    USGS Publications Warehouse

    Koontz, Lynne; Sexton, Natalie; Donovan, Ryan

    2009-01-01

    The National Wildlife Refuge System Improvement Act of 1997 requires all units of the National Wildlife Refuge System to be managed under a Comprehensive Conservation Plan. The Comprehensive Conservation Plan must describe the desired future conditions of a refuge and provide long-range guidance and management direction to achieve refuge purposes. The Rappahannock River Valley National Wildlife Refuge (refuge) is in the process of developing a range of management goals, objectives, and strategies for the Comprehensive Conservation Plan. The Comprehensive Conservation Plan for the refuge must contain an analysis of expected effects associated with current and proposed refuge management strategies. The purpose of this study was to assess the regional economic implications associated with draft Comprehensive Conservation Plan management strategies. Special interest groups and local residents often criticize a change in refuge management, especially if there is a perceived negative impact to the local economy. Having objective data on economic impacts may show that these fears are overstated. Quite often, the extent of economic benefits a refuge provides to a local community is not fully recognized, yet at the same time the effects of negative changes is overstated. Spending associated with refuge recreational activities, such as wildlife viewing and hunting, can generate considerable tourist activity for surrounding communities. Additionally, refuge personnel typically spend considerable amounts of money purchasing supplies in local stores, repairing equipment and purchasing fuel at the local service stations, and reside and spend their salaries in the local community. For refuge Comprehensive Conservation Plan planning, a regional economic assessment provides a means of estimating how current management (no action alternative) and proposed management activities (alternatives) could affect the local economy. This type of analysis provides two critical pieces of

  10. Two-dimensional particle simulation of a sustained discharge in an alternating current plasma display panel

    NASA Astrophysics Data System (ADS)

    Ikeda, Y.; Suzuki, K.; Fukumoto, H.; Verboncoeur, J. P.; Christenson, P. J.; Birdsall, C. K.; Shibata, M.; Ishigaki, M.

    2000-12-01

    A plasma discharge due to a sustaining pulse of an alternating current plasma display panel was analyzed using a two-dimensional particle-in-cell code, and basic characteristics of the plasma discharge were calculated. The characteristics of the plasma discharge due to a sustaining pulse are as follows. (i) A large amount of space charge remained after drawing the discharge current. This excess space charge did not contribute to wall charge formation or ultraviolet radiation. (ii) The electron energy distribution function was evaluated and could be well fitted by the Druyvesteyn distribution in the high-energy region. The Druyvesteyn distribution was a consequence of the cross section for electron-Ne elastic scattering. (iii) The calculated ultraviolet radiation efficiency η of the plasma discharge due to a sustaining pulse was between 5.51% and 30.7%. Examination of the sensitivity of the efficiency to the electron temperature showed that reducing the electron temperature was a key to improving the efficiency. (iv) A detailed understanding of the conditions for a stable plasma discharge, memory margin, firing voltage, and electrode voltage of the sustaining pulse were obtained from the voltage transfer curve. The voltage transfer curve could be used to optimize the discharge cell design.

  11. An Analysis of Alternatives to New York City's Current Marijuana Arrest and Detention Policy.

    PubMed

    Johnson, Bruce D; Golub, Andrew; Dunlap, Eloise; Sifaneck, Stephen J

    2008-01-01

    During the 1990s, the New York Police Department (NYPD) instituted a policy of arresting and detaining people for minor offenses that occur in public as part of their quality-of-life (hereafter QOL) policing initiative. The number of NYPD arrests for smoking marijuana in public view (MPV) increased from 3,000 in 1994 to over 50,000 in 2000, and have been about 30,000 in the mid 2000s. Most of these arrestees (84%) have been minority; blacks have been 2.7 more likely and Hispanics 1.8 times more likely to be detained than whites for an MPV arrest. Minorities have been most likely to receive more severe dispositions, even controlling for demographics and prior arrest histories.This paper examines the pros and cons of the current policy; this is compared with possible alternatives including the following: arrest and issue a desk appearance ticket (DAT); issue a non-criminal citation (violation); street warnings; and tolerate public marijuana smoking. The authors recommend that the NYPD change to issuing DATs on a routine basis. Drug policy reformers might wish to further pursue changing statutes regarding smoking marijuana in public view into a violation (noncriminal) or encourage the wider use of street warnings. Any of these policy changes would help reduce the disproportionate burden on minorities associated with the current arrest and detention policy. These policies could help maintain civic norms against smoking marijuana in public. PMID:18726007

  12. An Analysis of Alternatives to New York City's Current Marijuana Arrest and Detention Policy

    PubMed Central

    Johnson, Bruce D.; Golub, Andrew; Dunlap, Eloise; Sifaneck, Stephen J.

    2008-01-01

    During the 1990s, the New York Police Department (NYPD) instituted a policy of arresting and detaining people for minor offenses that occur in public as part of their quality-of-life (hereafter QOL) policing initiative. The number of NYPD arrests for smoking marijuana in public view (MPV) increased from 3,000 in 1994 to over 50,000 in 2000, and have been about 30,000 in the mid 2000s. Most of these arrestees (84%) have been minority; blacks have been 2.7 more likely and Hispanics 1.8 times more likely to be detained than whites for an MPV arrest. Minorities have been most likely to receive more severe dispositions, even controlling for demographics and prior arrest histories. This paper examines the pros and cons of the current policy; this is compared with possible alternatives including the following: arrest and issue a desk appearance ticket (DAT); issue a non-criminal citation (violation); street warnings; and tolerate public marijuana smoking. The authors recommend that the NYPD change to issuing DATs on a routine basis. Drug policy reformers might wish to further pursue changing statutes regarding smoking marijuana in public view into a violation (noncriminal) or encourage the wider use of street warnings. Any of these policy changes would help reduce the disproportionate burden on minorities associated with the current arrest and detention policy. These policies could help maintain civic norms against smoking marijuana in public. PMID:18726007

  13. Effects of high-frequency alternating current on axonal conduction through the vagus nerve

    NASA Astrophysics Data System (ADS)

    Waataja, Jonathan J.; Tweden, Katherine S.; Honda, Christopher N.

    2011-10-01

    High-frequency alternating current (HFAC) is known to disrupt axonal conduction in peripheral nerves, and HFAC has much potential as a therapeutic approach for a number of pathological conditions. Many previous studies have utilized motor output as a bioassay of effects of HFAC on conduction through medium- to large-diameter motor axons. However, little is known about the effectiveness of HFAC on smaller, more slowly conducting nerve fibres. The present study tested whether HFAC influences axonal conduction through sub-diaphragmatic levels of the rat vagus nerve, which consists almost entirely of small calibre axons. Using an isolated nerve preparation, we tested the effects of HFAC on electrically evoked compound action potentials (CAPs). We found that delivery of charge-balanced HFAC at 5000 Hz for 1 min was effective in producing reversible blockade of axonal conduction. Both Aδ and C components of the vagus CAP were attenuated, and the degree of blockade as well as time to recovery was proportional to the amount of HFAC current delivered. The Aδ waves were more sensitive than C waves to HFAC blockade, but they required more time to recover.

  14. Effects of high-frequency alternating current on axonal conduction through the vagus nerve.

    PubMed

    Waataja, Jonathan J; Tweden, Katherine S; Honda, Christopher N

    2011-10-01

    High-frequency alternating current (HFAC) is known to disrupt axonal conduction in peripheral nerves, and HFAC has much potential as a therapeutic approach for a number of pathological conditions. Many previous studies have utilized motor output as a bioassay of effects of HFAC on conduction through medium- to large-diameter motor axons. However, little is known about the effectiveness of HFAC on smaller, more slowly conducting nerve fibres. The present study tested whether HFAC influences axonal conduction through sub-diaphragmatic levels of the rat vagus nerve, which consists almost entirely of small calibre axons. Using an isolated nerve preparation, we tested the effects of HFAC on electrically evoked compound action potentials (CAPs). We found that delivery of charge-balanced HFAC at 5000 Hz for 1 min was effective in producing reversible blockade of axonal conduction. Both Aδ and C components of the vagus CAP were attenuated, and the degree of blockade as well as time to recovery was proportional to the amount of HFAC current delivered. The Aδ waves were more sensitive than C waves to HFAC blockade, but they required more time to recover. PMID:21918293

  15. Method and apparatus for improved efficiency in a pulse-width-modulated alternating current motor drive

    DOEpatents

    Konrad, Charles E.; Boothe, Richard W.

    1994-01-01

    A scheme for optimizing the efficiency of an AC motor drive operated in a pulse-width-modulated mode provides that the modulation frequency of the power furnished to the motor is a function of commanded motor torque and is higher at lower torque requirements than at higher torque requirements.

  16. Method and apparatus for improved efficiency in a pulse-width-modulated alternating current motor drive

    DOEpatents

    Konrad, C.E.; Boothe, R.W.

    1996-01-23

    A scheme for optimizing the efficiency of an AC motor drive operated in a pulse-width-modulated mode provides that the modulation frequency of the power furnished to the motor is a function of commanded motor torque and is higher at lower torque requirements than at higher torque requirements. 6 figs.

  17. Method and apparatus for improved efficiency in a pulse-width-modulated alternating current motor drive

    DOEpatents

    Konrad, Charles E.; Boothe, Richard W.

    1996-01-01

    A scheme for optimizing the efficiency of an AC motor drive operated in a pulse-width-modulated mode provides that the modulation frequency of the power furnished to the motor is a function of commanded motor torque and is higher at lower torque requirements than at higher torque requirements.

  18. Method and apparatus for improved efficiency in a pulse-width-modulated alternating current motor drive

    DOEpatents

    Konrad, C.E.; Boothe, R.W.

    1994-02-15

    A scheme for optimizing the efficiency of an AC motor drive operated in a pulse-width-modulated mode provides that the modulation frequency of the power furnished to the motor is a function of commanded motor torque and is higher at lower torque requirements than at higher torque requirements. 6 figures.

  19. Three-phase ac-to-ac series-resonant power converter with a reduced number of thyristors

    SciTech Connect

    Klaassens, J.B.; de Beer, F. )

    1991-07-01

    This paper reports that ac-ac series-resonant converters have been proven to be functional and useful. Power pulse modulation with internal frequencies of tens of kHz and suited for multikilowatt power levels is applied to a series-resonant converter system for generating synthesized multiphase bipolar waveforms with reversible power flow and flow distortion. The use of a series-resonant circuit for power transfer and control obtains natural current commutation of the thyristors and the prevention of excessive stresses on components. Switches are required which have bidirectional current conduction and voltage blocking ability. The conventional series-resonant ac-ac converter applies a total for 24 anti-parallel thyristors. An alternative circuit configuration for the series-resonant ac-ac converter with only 12 thyristors is also presented. The alternative power circuit has three neutrals, related to the polyphase source, the load and the converter, which may be interconnected. If they are connected, the high-frequency component of the source and load currents will flow through the connection between the neutrals. The test results of a converter system generating three-phase sinusoidal input and output waveforms have demonstrated the significant aspects of this type of power interfaces.

  20. Evaluation of levels of defect sites present in highly ordered pyrolytic graphite electrodes using capacitive and faradaic current components derived simultaneously from large-amplitude Fourier transformed ac voltammetric experiments.

    PubMed

    Lee, Chong-Yong; Bond, Alan M

    2009-01-15

    The level of edge plane defect sites present in highly ordered pyrolytic graphite (HOPG) electrodes has been evaluated via analysis of dc, ac fundamental, and higher-order ac harmonics available from a single large-amplitude Fourier transformed (FT) ac voltammetric experiment. Deliberate introduction of a low level of edge plane defect was achieved by polishing, with a higher level being introduced via electrochemical pretreatment. Kinetics regimes associated with fast electron transfer on the edge plane defect sites and slow electron transfer on the basal plane surface are resolved under ac conditions when using the surface-sensitive [Fe(CN)(6)](3-/4-) redox probe. However, because of their insensitivity to slow electron transfer, higher-order ac faradaic harmonics almost exclusively detect only the much faster processes that emanate from edge plane defect sites. Thus, detection of fourth- and higher-order ac Faradaic harmonic components that are devoid of background capacitive current is possible at freshly cleaved HOPG in the region near the reversible potential for the [Fe(CN)(6)](3-/4-) process. Under these circumstances, dc cyclic voltammograms exhibit only reduction and oxidation peaks separated by more than 1 V. The fundamental ac harmonic provides detailed information on the capacitive current, which increases with the level of edge plane defect sites. Apparent charge transfer rate constants also can be derived from peak-to-peak separations obtained from the dc aperiodic component. Estimates of the percentage of edge plane defect sites based on ac higher harmonics, capacitance, and dc aperiodic component that are available from a single experiment have been compared. The edge plane defect levels deduced from capacitance (fundamental harmonic ac component) and higher harmonic Faradaic currents are considered to be more reliable than estimations based on apparent rate constants derived from the dc aperiodic component or conventional dc cyclic voltammogram.

  1. Activity-dependent alternative splicing increases persistent sodium current and promotes seizure

    PubMed Central

    Lin, Wei-Hsiang; Günay, Cengiz; Marley, Richard; Prinz, Astrid A.; Baines, Richard A.

    2012-01-01

    Activity of voltage-gated Na channels (Nav) is modified by alternative splicing. However, whether altered splicing of human Nav’s contributes to epilepsy remains to be conclusively shown. We show here that altered splicing of the Drosophila Nav (paralytic, DmNav) contributes to seizure-like behaviour in identified seizure-mutants. We focus attention on a pair of mutually-exclusive alternate exons (termed K and L), which form part of the voltage sensor (S4) in domain III of the expressed channel. The presence of exon L results in a large, non-inactivating, persistent INap. Many forms of human epilepsy are associated with an increase in this current. In wildtype (WT) Drosophila larvae ~70-80% of DmNav transcripts contain exon L, the remainder contain exon K. Splicing of DmNav to include exon L is increased to ~100% in both the slamdance and easily-shocked seizure-mutants. This change to splicing is prevented by reducing synaptic activity levels through exposure to the antiepileptic phenytoin or the inhibitory transmitter GABA. Conversely, enhancing synaptic activity in WT, by feeding of picrotoxin, is sufficient to increase INap and promote seizure through increased inclusion of exon L to 100%. We also show that the underlying activity-dependent mechanism requires the presence of Pasilla, an RNA-binding protein. Finally, we use computational modelling to show that increasing INap is sufficient to potentiate membrane excitability consistent with a seizure phenotype. Thus, increased synaptic excitation favors inclusion of exon L which, in turn, further increases neuronal excitability. Thus, at least in Drosophila, this self-reinforcing cycle may promote the incidence of seizure. PMID:22623672

  2. The Inequity in Illinois School Finance. An Analysis of: The Current Situation, the Historical Record, and Alternative Solutions. Second Edition.

    ERIC Educational Resources Information Center

    Hess, G. Alfred, Jr.; And Others

    This report provides an analysis of current inequities in school finance in Illinois, the historical roots of those inequities, and an analysis of alternative options for funding primary and secondary education. An introduction briefly describes the basis for the constitutional challenge to the current funding system. The next section describes…

  3. Early mastitis diagnosis through topological analysis of biosignals from low-voltage alternate current electrokinetics.

    PubMed

    Zhifei Zhang; Yang Song; Haochen Cui; Wu, Jayne; Schwartz, Fernando; Hairong Qi

    2015-08-01

    Mastitis is the most economically important disease of dairy cows worldwide, and it constantly plagues the dairy industry. A reliable biosensing method is thus imperative to detect this disease at its early stage and accurately identify the pathogen concentration level in order to better control the disease and consequently improve the quality of milk. Recent research indicates that shorter assay time and/or higher sensitivity can be achieved by integrating alternate current electrokinetics (ACEK) with biosensing. However, most existing ACEK devices use voltage levels around 10V at the risk of electrochemical reactions because a lower voltage may not effectively trigger the ACEK effect. Currently, there are no related works that can efficiently tackle the dilemma between avoiding electrochemical reaction and accelerating assay process. This paper adopts low-voltage (40~135mV) ACEK, which is safe but yields ambiguous biosignals within a short assay time, presenting great challenge to high-fidelity identification of pathogen concentration levels. This paper makes two distinctive contributions to the field of biosignal analysis. First, moving away from the traditional signal analysis in the time or spectral domain, we exploit the possibility of representing the biosignal through topological analysis that would reveal the intrinsic topological structure of point clouds generated from the biosignal. Second, in order to tackle another common challenge of biosignal analysis, i.e., limited sample size, we propose a so-called Gaussian-based decision tree (GDT), which can efficiently classify the biosignals even when the sample size is extremely small. Experimental results on the classification of five pathogen concentration levels using only 10 samples taken under various voltage levels demonstrate the robustness of the topological features as well as the advantage of GDT over some other conventional classifiers in handling small dataset. Our method reduces the voltage of

  4. Differential alternating current chip calorimeter for in situ investigation of vapor-deposited thin films

    NASA Astrophysics Data System (ADS)

    Ahrenberg, M.; Shoifet, E.; Whitaker, K. R.; Huth, H.; Ediger, M. D.; Schick, C.

    2012-03-01

    Physical vapor deposition can be used to produce thin films with interesting material properties including extraordinarily stable organic glasses. We describe an ac chip calorimeter for in situ heat capacity measurements of as-deposited nanometer thin films of organic glass formers. The calorimetric system is based on a differential ac chip calorimeter which is placed in the vacuum chamber for physical vapor deposition. The sample is directly deposited onto one calorimetric chip sensor while the other sensor is protected against deposition. The device and the temperature calibration procedure are described. The latter makes use of the phase transitions of cyclopentane and the frequency dependence of the dynamic glass transition of toluene and ethylbenzene. Sample thickness determination is based on a finite element modeling of the sensor sample arrangement. In the modeling, a layer of toluene was added to the sample sensor and its thickness was varied in an iterative way until the model fit the experimental data.

  5. An alternating current superconductor susceptometric system to evaluate liver iron overload

    NASA Astrophysics Data System (ADS)

    Carneiro, A. A. O.; Fernandes, J. P.; Zago, M. A.; Covas, D. T.; Ángulo, I. L.; Baffa, O.

    2003-06-01

    An ac susceptometric system to quantify liver iron overload composed of a second order axial gradiometer coil coupled to a rf superconducting quantum interference device detector and a large field coil array is presented. A homogeneous ac magnetizing field with low frequency (7.7 Hz) and low intensity (114 μT) is used. Preliminary measurements over a group of 34 normal individuals and 20 patients with iron overload show the ability of the instrument to perform the measurement and to distinguish normal and pathological individuals. The diamagnetic signature of the surrounding tissues is minimized using a special water bag on the torso. In summary it was shown that with a relatively simple instrumentation it was possible to build a superconducting susceptometer dedicated to quantify in vivo iron concentrations, which is clinically important information in the assessment and management of patients with liver iron overload, mainly those who regularly receive blood transfusion.

  6. Rapid immunohistochemistry based on alternating current electric field for intraoperative diagnosis of brain tumors.

    PubMed

    Tanino, Mishie; Sasajima, Toshio; Nanjo, Hiroshi; Akesaka, Shiori; Kagaya, Masami; Kimura, Taichi; Ishida, Yusuke; Oda, Masaya; Takahashi, Masataka; Sugawara, Taku; Yoshioka, Toshiaki; Nishihara, Hiroshi; Akagami, Yoichi; Goto, Akiteru; Minamiya, Yoshihiro; Tanaka, Shinya

    2015-01-01

    Rapid immunohistochemistry (R-IHC) can contribute to the intraoperative diagnosis of central nervous system (CNS) tumors. We have recently developed a new IHC method based on an alternating current electric field to facilitate the antigen-antibody reaction. To ensure the requirement of R-IHC for intraoperative diagnosis, 183 cases of CNS tumors were reviewed regarding the accuracy rate of diagnosis without R-IHC. The diagnostic accuracy was 90.7 % (166/183 cases) [corrected] in which definitive diagnoses were not provided in 17 cases because of the failure of glioma grading and differential diagnosis of lymphoma and glioma. To establish the clinicopathological application, R-IHC for frozen specimens was compared with standard IHC for permanent specimens. 33 gliomas were analyzed, and the Ki-67/MIB-1 indices of frozen specimens by R-IHC were consistent with the grade and statistically correlated with those of permanent specimens. Thus, R-IHC provided supportive information to determine the grade of glioma. For discrimination between glioma and lymphoma, R-IHC was able to provide clear results of CD20 and Ki-67/MIB-1 in four frozen specimens of CNS lymphoma as well as standard IHC. We conclude that the R-IHC for frozen specimens can provide important information for intraoperative diagnosis of CNS tumors.

  7. Application of broadband alternating current magnetic susceptibility to the characterization of magnetic nanoparticles in natural materials

    NASA Astrophysics Data System (ADS)

    Kodama, Kazuto

    2013-01-01

    A new method is proposed for characterizing magnetic particles by measuring low-field alternating current magnetic susceptibility at a number of frequency steps spanning four orders of magnitude, from 125 Hz to 512 kHz. This method was tested using natural samples with various grain size distributions, including basalt (Kilauea, Hawaii), loess and paleosol (Luochuan, China), tuff (Yucca Mountain, Nevada), granite (Minnesota Valley, Minnesota), and andesite (Sakurajima, Japan). The resulting frequency spectrum of magnetic susceptibility (FSMS) of the basalt, loess/paleosol, and tuff decreases with increasing frequency, but at different rates of decrease. The FSMS of the basalt is characterized by a monotonic decrease with increasing frequency over the entire range. The FSMS of the loess/paleosol and the tuff decreases more markedly than that of the basalt, which agrees with previous results showing that superparamagnetic particles are dominant in such material. Quantitative estimates using FSMSs allow reconstruction of characteristic grain size distributions and clearly identify differences in the distribution of superparamagnetic particles. The multidomain granite sample has no distinct frequency dependence, which is probably due to the smooth displacement of domain walls in the presence of the external field. In contrast, the FSMSs of the andesite samples exhibit maxima over a limited frequency range, between 16 and 128 kHz. This behavior, together with low-temperature measurements, can be accounted for by magnetic resonance of domain walls in the multidomain phenocrysts.

  8. Alternating current cloud point extraction on a microchip: a comprehensive study.

    PubMed

    Sasaki, Naoki; Takemura, Azusa; Sato, Kae

    2012-11-01

    We present a comprehensive study of alternating current cloud point extraction (ACPE) on a microchip. ACPE is an extraction technique for preconcentration of membrane-associated biomolecules. To characterize and optimize ACPE, we carried out ACPE experiments under various experimental conditions including amplitude and frequency of applied voltages, flow velocity, and concentration of surfactant, analyte, and salt. We found that ACPE has an amplitude threshold (15 V(p-p)), above which the extraction was more efficient. The dependence of the extraction on frequency (>5 MHz) was insignificant. Efficient extraction was achieved when the velocity of the test solution was 0.10∼0.67 mm s⁻¹ and the concentration of surfactant was 0.10∼1.0%. In contrast, the extraction was independent of the concentration of analytes (0.20∼20 μmol dm⁻³). The technique was applicable to solutions with a salt concentration of 0.050∼0.15 mol dm⁻³ under temperature control of the devices. Solution temperature in ACPE was also studied. These results provide guidelines for use of the ACPE technique in microfluidic chemical and biochemical analyses.

  9. A novel alternating current multiple array electrothermal micropump for lab-on-a-chip applications

    PubMed Central

    Salari, A.; Navi, M.

    2015-01-01

    The AC electrothermal technique is very promising for biofluid micropumping, due to its ability to pump high conductivity fluids. However, compared to electroosmotic micropumps, a lack of high fluid flow is a disadvantage. In this paper, a novel AC multiple array electrothermal (MAET) micropump, utilizing multiple microelectrode arrays placed on the side-walls of the fluidic channel of the micropump, is introduced. Asymmetric coplanar microelectrodes are placed on all sides of the microfluidic channel, and are actuated in different phases: one, two opposing, two adjacent, three, or all sides at the same time. Micropumps with different combinations of side electrodes and cross sections are numerically investigated in this paper. The effect of the governing parameters with respect to thermal, fluidic, and electrical properties are studied and discussed. To verify the simulations, the AC MAET concept was then fabricated and experimentally tested. The resulted fluid flow achieved by the experiments showed good agreement with the corresponding simulations. The number of side electrode arrays and the actuation patterns were also found to greatly influence the micropump performance. This study shows that the new multiple array electrothermal micropump design can be used in a wide range of applications such as drug delivery and lab-on-a-chip, where high flow rate and high precision micropumping devices for high conductivity fluids are needed. PMID:25713695

  10. Study on an alternating current electrothermal micropump for microneedle-based fluid delivery systems

    NASA Astrophysics Data System (ADS)

    Zhang, Rumi; Jullien, Graham A.; Dalton, Colin

    2013-07-01

    In this paper, we report on a modeling study of an AC electrothermal (ACET) micropump with high operating pressures as well as fast flow rates. One specific application area is for fluid delivery using microneedle arrays which require higher pressures and faster flow rates than have been previously reported with ACET devices. ACET is very suitable for accurate actuation and control of fluid flow, since the technique has been shown to be very effective in high conductivity fluids and has the ability to create a pulsation free flow. However, AC electrokinetic pumps usually can only generate low operating pressures of 1 to 100 Pa, where flow reversal is likely to occur with an external load. In order to realize a high performance ACET micropump for continuous fluid delivery, applying relatively high AC operating voltages (20 to 36 Vrms) to silicon substrate ACET actuators and using long serpentine channel allows the boosting of operating pressure as well as increasing the flow rates. Fast pumping flow rates (102-103 nl/s) and high operating pressures (1-12 kPa) can be achieved by applying both methods, making them of significant importance for continuous fluid delivery applications using microneedle arrays and other such biomedical devices.

  11. Alternating current-dielectrophoresis driven on-chip collection and chaining of green microalgae in freshwaters

    PubMed Central

    Suscillon, Coralie; Velev, Orlin D.; Slaveykova, Vera I.

    2013-01-01

    The capability of the AC dielectrophoresis (DEP) for on-chip capture and chaining of microalgae suspended in freshwaters was evaluated. The effects of freshwater composition as well as the electric field voltage, frequency, and duration, on the dielectrophoretic response of microalga Chlamydomonas reinhardtii were characterized systematically. Highest efficiency of cell alignment in one-dimensional arrays, determined by the percentage of cells in chain and the chain length, was obtained at AC-field of 20 V mm−1 and 1 kHz applied for 600 s. The DEP response and cell alignment of C. reinhardtii in water sampled from lake, pond, and river, as well as model media were affected by the chemical composition of the media. In the model media, the efficiency of DEP chaining was negatively correlated to the conductivity of the cell suspensions, being higher in suspensions with low conductivity. The cells suspended in freshwaters, however, showed anomalously high chaining at long exposure times. High concentrations of nitrate and dissolved organic matter decrease cell chaining efficiency, while phosphate and citrate concentrations increase it and favor formation of longer chains. Importantly, the application of AC-field had no effect on algal autofluorescence, cell membrane damage, or oxidative stress damages in C. reinhardtii. PMID:24404014

  12. Dielectric relaxation and alternating current conductivity of lanthanum, gadolinium, and erbium-polyvinyl alcohol doped films.

    PubMed

    Hanafy, Taha A

    2012-08-01

    Fourier transform infrared (FTIR) spectrum dielectric constant, ε', loss tangent, tan(δ), electric modulus, M*, and ac conductivity, σ(ac), of pure polyvinyl alcohol (PVA) as well as La-, Gd-, and Er-PVA doped samples have been carried out. The dielectric properties have been studied in the temperature and frequency ranges; 300-450 K and 1 kHz-4 MHz, respectively. FTIR measurements reveal that La(3+), Gd(3+), and Er(3+) ions form complex configuration within PVA structure. Two relaxation processes, namely, ρ and α were observed in pure PVA sample. The first process is due to the interfacial or Maxwell-Wagner-Sillers polarization. The second one is related to the micro-Brownian motion of the main chains. For doped PVA samples, α-relaxation process splits into α(a) and α(c). This splitting is due to the segmental motion in the amorphous (α(a)) and crystalline (α(c)) phases of PVA matrix. Electric modulus analysis was discussed to understand the mechanism of the electrical transport process. The behavior of ac conductivity for all PVA samples indicates that the conduction mechanism is correlated barrier hopping.

  13. Alternating-current thin-film electroluminescent device fabrication and characterization

    NASA Astrophysics Data System (ADS)

    Baukol, Beau Alexander

    The goals of this thesis are to provide an improved understanding of luminescent materials, and to exploit their properties to achieve bright, efficient, and manufacturable red, green, and blue (RGB) phosphors for use in full-color flat-panel displays. A high-luminance, high-efficiency, full-color alternating-current thin-film electroluminescent (ACTFEL) phosphor system, capable of being processed at temperatures below the glass substrate melting temperature, has been developed through the use of source layer diffusion doping (SLDD) of atomic layer epitaxy (ALE) deposited SrS thin-films. The development of ACTFEL phosphors has also been advanced through the exploration of alternate phosphor materials, such as SrxCa 1-xS:Eu,Cu and (Ba.Zn)S:Mn. This thesis offers new insight into the nature of ACTFEL device operation, especially SrS:Cu ACTFEL devices. A comparison of "EL" thermal quenching trends for evaporated ZnS:Mn, ALE ZnS:Mn, ALE SrS:Ce, sputtered SrS:Cu,Ag, and sputtered multi-layer SrS:Cu,Ag/SrS:Ce ACTFEL devices is presented. ZnS:Mn ACTFEL devices exhibit the least amount of EL thermal quenching, which is attributed to non-radiative recombination. SrS:Cu and SrS:Cu,Ag ACTFEL devices possess the greatest amount of thermal quenching, which is primarily EL thermal quenching. The extent of EL thermal quenching is significantly reduced in a multi-layer SrS:Cu,Ag/SrS:Ce ACTFEL device, compared to that of a single-layer SrS:Cu or SrS:Cu,Ag ACTFEL device. The operation of SrS:Cu is examined as a function of temperature; the space charge density is found to increase with temperature up to ˜250 K with an activation energy of 0.02 eV. The space charge density in SrS:Cu ACTFEL devices is estimated as ˜1.8 x 1016, which yields estimates of the cathode phosphor field and the interfacial trap depth of ˜1.3 MV/cm and ˜0.73 eV, respectively.

  14. 46 CFR 183.130 - Alternative standards.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... installation operating at less than 50 volts may meet the requirements in 33 CFR 183.430 instead of those in... applicable: (i) E-8, “Alternating Current (AC) Electrical Systems on Boats;” (ii) E-9, “Direct Current...

  15. Alternative current conduction mechanisms of organic-inorganic compound [N(CH{sub 3}){sub 3}H]{sub 2}ZnCl{sub 4}

    SciTech Connect

    Ben Bechir, M. Karoui, K.; Guidara, K.; Ben Rhaiem, A.; Tabellout, M.

    2014-04-21

    [N(CH{sub 3}){sub 3}H]{sub 2}ZnCl{sub 4} has been studied by X-ray powder diffraction patterns, differential scanning calorimetry (DSC), and impedance spectroscopy. The [N(CH{sub 3}){sub 3}H]{sub 2}ZnCl{sub 4} hybrid compound is crystallized at room temperature (T ≈ 300 K) in the orthorhombic system with Pnma space group. Five phase transitions (T{sub 1} = 255 K, T{sub 2} = 282 K, T{sub 3} = 302 K, T{sub 4} = 320 K, and T{sub 5} = 346 K) have been proved by DSC measurements. The electrical technique was measured in the 10{sup −1}-10{sup 7} Hz frequency range and 233–363 K temperature interval. The frequency dependence of alternative current (AC) conductivity is interpreted in terms of Jonscher's law. The AC electrical conduction in [N(CH{sub 3}){sub 3}H]{sub 2}ZnCl{sub 4} is analyzed by different processes, which can be attributed to several models: the correlated barrier hopping model in phase I, the overlapping large polaron tunneling model in phase II, the quantum mechanical tunneling model in phase IV, and the non-overlapping small polaron tunneling model in phases III, V, and VI. The conduction mechanism is studied with the help of Elliot's theory, and the Elliot's parameters are determined.

  16. AC and DC power transmission

    SciTech Connect

    Not Available

    1985-01-01

    The technical and economic assessment of AC and DC transmission systems; long distance transmission, cable transmission, system inter-connection, voltage support, reactive compensation, stabilisation of systems; parallel operation of DC links with AC systems; comparison between alternatives for particular schemes. Design and application equipment: design, testing and application of equipment for HVDC, series and shunt static compensated AC schemes, including associated controls. Installations: overall design of stations and conductor arrangements for HVDC, series and shunt static AC schemes including insulation co-ordination. System analysis and modelling.

  17. AC and Phase Sensing of Nanowires for Biosensing.

    PubMed

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

    2016-04-19

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

  18. AC and Phase Sensing of Nanowires for Biosensing

    PubMed Central

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

    2016-01-01

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

  19. Non-oxidized porous silicon-based power AC switch peripheries

    PubMed Central

    2012-01-01

    We present in this paper a novel application of porous silicon (PS) for low-power alternating current (AC) switches such as triode alternating current devices (TRIACs) frequently used to control small appliances (fridge, vacuum cleaner, washing machine, coffee makers, etc.). More precisely, it seems possible to benefit from the PS electrical insulation properties to ensure the OFF state of the device. Based on the technological aspects of the most commonly used AC switch peripheries physically responsible of the TRIAC blocking performances (leakage current and breakdown voltage), we suggest to isolate upper and lower junctions through the addition of a PS layer anodically etched from existing AC switch diffusion profiles. Then, we comment the voltage capability of practical samples emanating from the proposed architecture. Thanks to the characterization results of simple Al-PS-Si(P) structures, the experimental observations are interpreted, thus opening new outlooks in the field of AC switch peripheries. PMID:23057856

  20. Fish Alternatives in Environmental Risk Assessment: Overview of the Current Landscape

    EPA Science Inventory

    The need for alternative testing strategies has recently expanded into the realm of environmental risk assessment leading to the development of new alternatives to standard aquatic vertebrate testing such as the OECD 203 acute fish toxicity test. The fish embryo test (FET) is one...

  1. Evaluation of vascular wall elasticity of human digital arteries using alternating current-signal photoplethysmography

    PubMed Central

    Uangpairoj, Pichitra; Shibata, Masahiro

    2013-01-01

    Purpose A simple method of estimating arterial elasticity in the human finger using a volume-oscillometric technique with photoplethysmography was principally studied under the various effects of age, sex, and cold-stress stimulation for testing the capability of using this technique in arterial elasticity analysis. Methods Amplitude variations in the alternating current signal of the photoplethysmograph during a continuous change in transmural pressure were analyzed to obtain the blood pressure and the transmural pressure–relative volume difference relationship of the arteries. We first tested the effect of the occluding cuff size on the arterial elasticity analysis in eight subjects (ages 20–45 years) to obtain a suitable cuff size, resulting in the selection of a middle cuff with a 22 mm diameter. Blood pressure and arterial elasticity were measured in six groups of subjects separated into three age-groups of women and men (ages 20–25, 32–45, and over 50 years) for testing the effect of age and sex. Twelve subjects (ages 20–25 years) also had their blood pressure and arterial elasticity measured in three conditions under the influence of the cold-stress stimulation. Results Age, sex, and cold-stress stimulation had an impact on mean blood pressure (P < 0.0005, 0.025), whereas pulse pressure and heart rate were statistically unchanged by those factors. Furthermore, an advanced age (over 50 years) was found to induce an increase in relative volume difference values (P < 0.025) and upward shifting of the transmural pressure–relative volume difference relationships, whereas sex, level of mean blood pressure, and cold-stress stimulation had no influence on these forms of the index. Conclusion This study showed the usefulness of the relative volume difference as being a mean blood pressure-independent indicator for changes in arterial elasticity. PMID:23766653

  2. Anomalous satellite inductive peaks in alternating current response of defective carbon nanotubes

    SciTech Connect

    Hirai, Daisuke; Watanabe, Satoshi; Yamamoto, Takahiro

    2014-05-07

    AC response of defective metallic carbon nanotubes is investigated from first principles. We found that capacitive peaks appear at electron scattering states. Moreover, we show that satellite inductive peaks are seen adjacent to a main capacitive peak, which is in contrast to the conductance spectra having no satellite features. The appearance of satellite inductive peaks seems to depend on the scattering states. Our analysis with a simple resonant scattering model reveals that the origin of the satellite inductive peaks can be understood by just one parameter, i.e., the lifetime of electrons at a defect state.

  3. Electrohydrodynamic Displacement of Polarizable Liquid Interfaces in an Alternating Current Electric Field

    NASA Astrophysics Data System (ADS)

    Gagnon, Zachary

    2015-11-01

    In this work, we investigate Maxwell-Wagner polarization at electrically polarizable liquid interfaces. An AC electric field is applied across a liquid electrical interface created between two co-flowing microfluidic fluid streams with different electrical properties. When potentials as low as 2 volts are applied, we observe a frequency dependent interfacial displacement that is dependent on the relative differences in the electrical conductivity and dielectric constant between the two liquids. At low frequency this deflection is dependent on electrical conductivity, and only depends on dielectric constant at high frequency. At intermediate frequencies, we observe a crossover that is independent of applied voltage, sensitive to both fluid electrical properties, and where no displacement is observed. An analytical polarization model is presented that predicts the liquid interfacial crossover frequency, the dependence of interfacial displacement on liquid electrical conductivity and dielectric constant, and accurately scales the interface displacement measurements. The results show that liquid interfaces are capable of polarizing under AC electric fields and being precisely deflected in a direction and magnitude that is dependent on the applied electric field frequency.

  4. Effect of an Alternating Current Electric Field on the Plastic Deformation of Ultrafine-Grained 3Y-TZP at 1400 °C and 1500 °C

    NASA Astrophysics Data System (ADS)

    Conrad, Hans; Yang, Di

    2008-02-01

    The influence of a 60 Hz alternating current (ac) electric field E rms = 6.7 to 7.5 V/cm applied in the loading direction on the flow stress of 3 mol pct yittria-stabilized tetragonal zirconia polycrystals (3Y-TZPs) in uniaxial tension at 1400 °C and 1500 °C was determined. Two test types were performed: type a, where the field was applied continuously throughout the tension test; and type b, where the field was alternately applied and removed. The field reduced the flow stress in both test types but with an appreciably greater effect in type a. The reduction in flow stress in the type b tests was regained upon removal of the field and was attributed to a decrease in the energy to form the rate-controlling Zr4+ vacancies in the space charge zone adjacent to the grain boundaries. The larger reduction in flow stress in the type a tests was attributed to a retardation of grain growth by the field as a result of a decrease in the driving force. The results obtained with the ac field were in agreement with those with direct current (dc) field.

  5. AC electrophoretic deposition of organic-inorganic composite coatings.

    PubMed

    Yoshioka, T; Chávez-Valdez, A; Roether, J A; Schubert, D W; Boccaccini, A R

    2013-02-15

    Alternating current electrophoretic deposition (AC-EPD) of polyacrylic acid (PAA)-titanium oxide (TiO(2)) nanoparticle composites on stainless steel electrodes was investigated in basic aqueous solution. AC square wave with duty cycle of 80% was applied at a frequency of 1 kHz. FTIR-ATR spectra showed that both AC and direct current (DC) EPD successfully deposited PAA-TiO(2) composites. The deposition rate using AC-EPD was lower than that obtained in direct current DC-EPD. However, the microstructure and surface morphology of the deposited composite coatings were different depending on the type of electric field applied. AC-EPD applied for not more than 5 min led to smooth films without bubble formation, while DC-EPD for 1 min or more showed deposits with microstructural defects possibly as result of water electrolysis. AC-EPD was thus for the first time demonstrated to be a suitable technique to deposit organic-inorganic composite coatings from aqueous suspensions, showing that applying a square wave and frequency of 1 kHz leads to uniform PAA-TiO(2) composite coatings on conductive materials. PMID:23218240

  6. AC electrophoretic deposition of organic-inorganic composite coatings.

    PubMed

    Yoshioka, T; Chávez-Valdez, A; Roether, J A; Schubert, D W; Boccaccini, A R

    2013-02-15

    Alternating current electrophoretic deposition (AC-EPD) of polyacrylic acid (PAA)-titanium oxide (TiO(2)) nanoparticle composites on stainless steel electrodes was investigated in basic aqueous solution. AC square wave with duty cycle of 80% was applied at a frequency of 1 kHz. FTIR-ATR spectra showed that both AC and direct current (DC) EPD successfully deposited PAA-TiO(2) composites. The deposition rate using AC-EPD was lower than that obtained in direct current DC-EPD. However, the microstructure and surface morphology of the deposited composite coatings were different depending on the type of electric field applied. AC-EPD applied for not more than 5 min led to smooth films without bubble formation, while DC-EPD for 1 min or more showed deposits with microstructural defects possibly as result of water electrolysis. AC-EPD was thus for the first time demonstrated to be a suitable technique to deposit organic-inorganic composite coatings from aqueous suspensions, showing that applying a square wave and frequency of 1 kHz leads to uniform PAA-TiO(2) composite coatings on conductive materials.

  7. 30 CFR 77.701-1 - Approved methods of grounding of equipment receiving power from ungrounded alternating current...

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 30 Mineral Resources 1 2011-07-01 2011-07-01 false Approved methods of grounding of equipment receiving power from ungrounded alternating current power systems. 77.701-1 Section 77.701-1 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR COAL MINE SAFETY AND HEALTH MANDATORY SAFETY STANDARDS, SURFACE COAL MINES...

  8. 30 CFR 75.701-1 - Approved methods of grounding of equipment receiving power from ungrounded alternating current...

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 30 Mineral Resources 1 2011-07-01 2011-07-01 false Approved methods of grounding of equipment receiving power from ungrounded alternating current power systems. 75.701-1 Section 75.701-1 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR COAL MINE SAFETY AND HEALTH MANDATORY SAFETY STANDARDS-UNDERGROUND COAL...

  9. 30 CFR 77.701-1 - Approved methods of grounding of equipment receiving power from ungrounded alternating current...

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 30 Mineral Resources 1 2014-07-01 2014-07-01 false Approved methods of grounding of equipment receiving power from ungrounded alternating current power systems. 77.701-1 Section 77.701-1 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR COAL MINE SAFETY AND HEALTH MANDATORY SAFETY STANDARDS, SURFACE COAL MINES...

  10. 30 CFR 75.701-1 - Approved methods of grounding of equipment receiving power from ungrounded alternating current...

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 30 Mineral Resources 1 2014-07-01 2014-07-01 false Approved methods of grounding of equipment receiving power from ungrounded alternating current power systems. 75.701-1 Section 75.701-1 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR COAL MINE SAFETY AND HEALTH MANDATORY SAFETY STANDARDS-UNDERGROUND COAL...

  11. AC operation and runaway electron behaviour in HT-7 tokamak

    NASA Astrophysics Data System (ADS)

    Lu, Hong-Wei; Hu, Li-Qun; Zhou, Rui-Jie; Lin, Shi-Yao; Zhong, Guo-Qiang; Wang, Shao-Feng; Chen, Kai-Yun; Xu, Ping; Zhang, Ji-Zong; Ling, Bi-Li; Mao, Song-Tao; Duan, Yan-Min

    2010-06-01

    Operation of HT-7 tokamak in a multicycle alternating square wave plasma current regime is reported. A set of AC operation experiments, including LHW heating to enhance plasma ionization during the current transition and current sustainment, is described. The behaviour of runaway electrons is analysed by four HXR detectors tangentially viewing the plasma in the equatorial plane, within energy ranges 0.3-1.2 MeV and 0.3-7 MeV, separately. High energy runaway electrons (~MeV) are found to circulate predominantly in the opposite direction to the plasma current, while the number of low energy runaway electrons (~tens to hundreds of keV) circulating along the plasma current is comparable to that in the direction opposite to the plasma current. AC operation with lower hybrid current drive (LHCD) is observed to have an additional benefit of suppressing the runaway electrons if the drop of the loop voltage is large enough.

  12. Assembly of thermally reduced graphene oxide nanostructures by alternating current dielectrophoresis as hydrogen-gas sensors

    NASA Astrophysics Data System (ADS)

    Wang, Jianwei; Singh, Budhi; Maeng, Sunglyul; Joh, Han-Ik; Kim, Gil-Ho

    2013-08-01

    Chemo-resistive hydrogen-gas sensors based on thermally reduced graphene oxide (rGO) have been fabricated on a micro-hotplate by positive ac dielectrophoresis (DEP). The optimized DEP parameters for manipulating rGO nanostructures into Au electrodes for hydrogen sensing are: applied frequency = 1 MHz, peak-to-peak voltage = 5 V, and DEP time = 30 s. The device exhibits good sensitivity (˜6%) with fast response time (˜11 s) and recovery time (˜36 s) for 200 ppm hydrogen gas at room temperature. This result indicates that the DEP process has great potential for assembling rGO for hydrogen-gas sensor in many industrial and scientific applications.

  13. Novel method for rapid in-situ hybridization of HER2 using non-contact alternating-current electric-field mixing

    PubMed Central

    Saito, Yoshitaro; Imai, Kazuhiro; Nakamura, Ryuta; Nanjo, Hiroshi; Terata, Kaori; Konno, Hayato; Akagami, Yoichi; Minamiya, Yoshihiro

    2016-01-01

    Human epidermal growth factor receptor 2 (HER2)-targeted agents are an effective approach to treating HER2-positive breast cancer patients. However, the lack of survival benefit in HER2-negative patients as well as the toxic effects and high cost of the drugs highlight the need for accurate and prompt assessment of HER2 status. Our aim was to evaluate the clinical utility of a novel rapid dual in-situ hybridization (RISH) method developed to facilitate hybridization. The method takes advantage of the non-contact mixing effect of an alternating current (AC) electric field. One hundred sixty-three specimens were used from patients diagnosed with primary breast cancers identified immunohistochemically as HER2 0/1(+), (2+) or (3+). The specimens were all tested using conventional dual in-situ hybridization (DISH), DISH with an automated slide stainer, and RISH. With RISH the HER2 test was completed within 6 h, as compared to 20–22 h needed for the standard protocol. Although RISH produced results more promptly using smaller amounts of labeled antibody, the staining and accuracy of HER2 status evaluation with RISH was equal to or greater than with DISH. These results suggest RISH could be used as a clinical tool to promptly determine HER2 status. PMID:27443187

  14. Novel method for rapid in-situ hybridization of HER2 using non-contact alternating-current electric-field mixing.

    PubMed

    Saito, Yoshitaro; Imai, Kazuhiro; Nakamura, Ryuta; Nanjo, Hiroshi; Terata, Kaori; Konno, Hayato; Akagami, Yoichi; Minamiya, Yoshihiro

    2016-01-01

    Human epidermal growth factor receptor 2 (HER2)-targeted agents are an effective approach to treating HER2-positive breast cancer patients. However, the lack of survival benefit in HER2-negative patients as well as the toxic effects and high cost of the drugs highlight the need for accurate and prompt assessment of HER2 status. Our aim was to evaluate the clinical utility of a novel rapid dual in-situ hybridization (RISH) method developed to facilitate hybridization. The method takes advantage of the non-contact mixing effect of an alternating current (AC) electric field. One hundred sixty-three specimens were used from patients diagnosed with primary breast cancers identified immunohistochemically as HER2 0/1(+), (2+) or (3+). The specimens were all tested using conventional dual in-situ hybridization (DISH), DISH with an automated slide stainer, and RISH. With RISH the HER2 test was completed within 6 h, as compared to 20-22 h needed for the standard protocol. Although RISH produced results more promptly using smaller amounts of labeled antibody, the staining and accuracy of HER2 status evaluation with RISH was equal to or greater than with DISH. These results suggest RISH could be used as a clinical tool to promptly determine HER2 status. PMID:27443187

  15. Wind-powered asynchronous AC/DC/AC converter system. [for electric power supply regulation

    NASA Technical Reports Server (NTRS)

    Reitan, D. K.

    1973-01-01

    Two asynchronous ac/dc/ac systems are modelled that utilize wind power to drive a variable or constant hertz alternator. The first system employs a high power 60-hertz inverter tie to the large backup supply of the power company to either supplement them from wind energy, storage, or from a combination of both at a preset desired current; rectifier and inverter are identical and operate in either mode depending on the silicon control rectifier firing angle. The second system employs the same rectification but from a 60-hertz alternator arrangement; it provides mainly dc output, some sinusoidal 60-hertz from the wind bus and some high harmonic content 60-hertz from an 800-watt inverter.

  16. EVALUATION OF CURRENTLY AVAILABLE ALTERNATIVES TO METHYL BROMIDE FOR ORNAMENTAL CROP PRODUCTION IN FLORIDA

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Studies were designed to test the efficacy of the chemical alternatives, Midas™ (iodomethane:chloropicrin (pic) 50:50 [MI 50:50] and 98:2 [MI 98:2], Arysta LifeScience Corp., Cary, NC) and dimethyl disulfide:pic (Paladin™ 79:21 [DMDS], United Phosphorous, Inc., King of Prussia, PA) compared with met...

  17. Complementary and Alternative Medicine in Rural Communities: Current Research and Future Directions

    ERIC Educational Resources Information Center

    Wardle, Jon; Lui, Chi-Wai; Adams, Jon

    2012-01-01

    Contexts: The consumption of complementary and alternative medicine (CAM) in rural areas is a significant contemporary health care issue. An understanding of CAM use in rural health can provide a new perspective on health beliefs and practice as well as on some of the core service delivery issues facing rural health care generally. Purpose: This…

  18. Low-fidelity compensatory backup alternative DNA repair pathways may unify current carcinogenesis theories.

    PubMed

    Wu, Jiaxi; Starr, Shane

    2014-05-01

    The somatic mutation carcinogenesis theory has dominated for decades. The alternative theory, tissue organization field theory, argues that the development of cancer is determined by the surrounding microenvironment. However, neither theory can explain all features of cancer. As cancers share the features of uncontrolled proliferation and genomic instability, they are likely to have the same pathogenesis. It has been found that various DNA repair pathways within a cell crosstalk with one another, forming a DNA repair network. When one DNA repair pathways is defective, the others may work as compensatory backups. The latter pathways are explored for synthetic lethal anticancer therapy. In this article, we extend the concept of compensatory alternative DNA repair to unify the theories. We propose that the microenvironmental stress can activate low-fidelity compensatory alternative DNA repair, causing mutations. If the mutation occurs to a DNA repair gene, this secondarily mutated gene can lead to even more mutated genes, including those related to other DNA repair pathways, eventually destabilizing the genome. Therefore, the low-fidelity compensatory alternative DNA repair may mediate microenvironment-dependent carcinogenesis. The proposal seems consistent with the view of evolution: the environmental stress causes mutations to adapt to the changing environment.

  19. Benchmarking--Current Availability, Possible New National Alternatives, and Making a Contribution to the Discussion

    ERIC Educational Resources Information Center

    Atchison, Eric S.; Hosch, Braden J.

    2015-01-01

    This chapter synthesizes the national discussion on other solutions to the Integrated Postsecondary Education Data System (IPEDS), such as a national student record system, and complications. The authors will briefly examine the pros and cons of IPEDS while primarily focusing on national alternatives, as well providing specific examples for…

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

    ERIC Educational Resources Information Center

    Bureau of Naval Personnel, Washington, DC.

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

  1. Frequency spectrum of alternating current magnetic susceptibility: A new rock magnetic property

    NASA Astrophysics Data System (ADS)

    Kodama, K.

    2011-12-01

    Low-field alternating current magnetic susceptibility (MS) is among the most commonly used magnetic property, from fundamental rock magnetism to various applied fields such as environmental magnetism studies. The prevalence of MS is mainly due to the rapid and simple measurements by means of commercially available devices. Frequency dependent susceptibility, a magnetic parameter defined as the change in MS per decade frequency, has also been frequently used in environmental magnetism. However, the performance of conventional instruments has put some constraint when characterizing SP-SD particle ensemble in terms of grain size distribution. The limitation is due to the specific operating frequencies, generally with one fixed frequency in hundreds of Hz associated with one or two more frequency steps in the range of kHz at the highest. This study proposes a new MS-derived magnetic property, or Frequency Spectrum of MS (FSM), which consists of MS values measured at multiple frequencies ranging in three orders of magnitudes from hundreds of Hz to hundreds of kHz. The FSM analyses were made for selected volcanic rocks and sediments, each characterized by the inclusion of SP, SD, MD particles, or their mixtures. The studied samples include andesite (Sakurajima, Japan), basalt (Kilauea), granite (Minnesota), and less and paleosol (Luochuan, China). Most remarkable is the FSM from the andesite samples showing a susceptibility increase, as much as 5%, observed over a specific frequency interval between 16 kHz and 128 kHz. This anomalous increase is superimposed on a linear decay of MS over the entire frequency range, which obviously shows a broad distribution of SP particle ensemble. In contrast, the FSM of granite shows no frequency dependence, while the basalt and paleosol exhibit the patterns indicating the presence of SP grains with broad volume distributions. The characteristic FSM pattern from the andesite suggests a new rock magnetic phenomena, which is most likely a

  2. Tests of an alternating current propulsion subsystem for electric vehicles on a road load simulator

    NASA Technical Reports Server (NTRS)

    Stenger, F. J.

    1982-01-01

    The test results of a breadboard version of an ac electric-vehicle propulsion subsystem are presented. The breadboard was installed in the NASA Lewis Research Center Road Load Simulator facility and tested under steady-state and transient conditions. Steady-state tests were run to characterize the system and component efficiencies over the complete speed-torque range within the capability of the propulsion subsystem in the motoring mode of operation. Transient tests were performed to determine the energy consumption of the breadboard over the acceleration and cruise portions of SAE J227 and driving schedules B, C, and D. Tests in the regenerative mode were limited to the low-gear-speed range of the two speed transaxle used in the subsystem. The maximum steady-state subsystem efficiency observed for the breadboard was 81.5 percent in the high-gear-speed range in the motoring mode, and 76 percent in the regenerative braking mode (low gear). The subsystem energy efficiency during the transient tests ranged from 49.2 percent for schedule B to 68.4 percent for Schedule D.

  3. AC power generation from microbial fuel cells

    NASA Astrophysics Data System (ADS)

    Lobo, Fernanda Leite; Wang, Heming; Forrestal, Casey; Ren, Zhiyong Jason

    2015-11-01

    Microbial fuel cells (MFCs) directly convert biodegradable substrates to electricity and carry good potential for energy-positive wastewater treatment. However, the low and direct current (DC) output from MFC is not usable for general electronics except small sensors, yet commercial DC-AC converters or inverters used in solar systems cannot be directly applied to MFCs. This study presents a new DC-AC converter system for MFCs that can generate alternating voltage in any desired frequency. Results show that AC power can be easily achieved in three different frequencies tested (1, 10, 60 Hz), and no energy storage layer such as capacitors was needed. The DC-AC converter efficiency was higher than 95% when powered by either individual MFCs or simple MFC stacks. Total harmonic distortion (THD) was used to investigate the quality of the energy, and it showed that the energy could be directly usable for linear electronic loads. This study shows that through electrical conversion MFCs can be potentially used in household electronics for decentralized off-grid communities.

  4. Comparison of the stem-loop and linear probe-based electrochemical DNA sensors by alternating current voltammetry and cyclic voltammetry.

    PubMed

    Yang, Weiwei; Lai, Rebecca Y

    2011-12-01

    Here we systematically characterized the sensor performance of the stem-loop probe (SLP) and linear probe (LP) electrochemical DNA sensors using alternating current voltammetry (ACV) and cyclic voltammetry (CV), with the goal of generating the set of operational criteria that best suits each sensor architecture, in addition to elucidating the signaling mechanism behind these sensors. Although the LP sensor shows slightly better % signal suppression (SS) upon hybridization with the perfect match target at 10 Hz, our frequency-dependent study suggests that it shows optimal % SS only in a very limited AC frequency range. Similar results are observed in CV studies in which the LP sensor, when compared to the SLP sensor, displays a narrower range of voltammetric scan rates where the optimal % SS can be achieved. More importantly, the difference between the two sensors' performance is particularly pronounced if the change in integrated charge (Q) upon target hybridization, rather than the peak current (I), is measured in CV. The temperature-dependent study further highlights the differences between the two sensors, where the LP sensor, owing to the flexible linear probe architecture, is more readily perturbed by temperature changes. Both SLP and LP sensors, however, show a loss of % SS when operated at elevated temperatures, despite the significant improvement in the hybridization kinetics. In conjunction with the ACV, CV, and temperature-dependent studies, the electron-transfer kinetics study provides further evidence in support of the proposed signaling mechanism of these two sensors, in which the SLP sensor's signaling efficiency and sensor performance is directly linked to the hybridization-induced conformational change in the redox-labeled probe, whereas the performance of the LP sensor relies on the hybridization-induced change in probe dynamics.

  5. Dielectric relaxations and alternating current conductivity in manganese substituted cobalt ferrite

    SciTech Connect

    Kolekar, Y. D.; Sanchez, L. J.; Ramana, C. V.

    2014-04-14

    Manganese (Mn) substituted cobalt ferrites (CoFe{sub 2-x}Mn{sub x}O{sub 4}, referred to CFMO) have been synthesized by the solid state reaction method and their dielectric properties and ac conductivity have been evaluated as a function of applied frequency and temperature. X-ray diffraction measurements indicate that CFMO crystallize in the inverse cubic spinel phase with a lattice constant ∼8.38 Å. Frequency dependent dielectric measurements at room temperature obey the modified Debye model with relaxation time of 10{sup −4} s and spreading factor of 0.35(±0.05). The frequency (20 Hz–1 MHz) and temperature (T = 300–900 K) dependent dielectric constant analyses indicate that CFMO exhibit two dielectric relaxations at lower frequencies (1–10 kHz), while completely single dielectric relaxation for higher frequencies (100 kHz–1 MHz). The dielectric constant of CFMO is T-independent up to ∼400 K, at which point increasing trend prevails. The dielectric constant increase with T > 400 K is explained through impedance spectroscopy assuming a two-layer model, where low-resistive grains separated from each other by high-resistive grain boundaries. Following this model, the two electrical responses in impedance formalism are attributed to the grain and grain-boundary effects, respectively, which also satisfactorily accounts for the two dielectric relaxations. The capacitance of the bulk of the grain determined from impedance analyses is ∼10 pF, which remains constant with T, while the grain-boundary capacitance increases up to ∼3.5 nF with increasing T. The tan δ (loss tangent)-T also reveals the typical behavior of relaxation losses in CFMO.

  6. Optical properties and residual stress in aluminum nitride films prepared by alternating-current dual reactive magnetron sputtering.

    PubMed

    Tang, Chien-Jen; Jaing, Cheng-Chung; Lee, Kun-Hsien; Lee, Cheng-Chung

    2011-05-01

    Aluminum nitride films were deposited by alternating-current dual reactive magnetron sputtering. The influence of different nitrogen flow and working pressures at a sputtering power of 5 kW on the refractive index, extinction coefficient, crystalline structure, residual stress, and surface roughness of aluminum nitride films was discussed. The aluminum nitride film would have high refractive index, low extinction coefficient and small residual stress at suitable nitrogen flow rate and low working pressure.

  7. Overview of Alternative Bunching and Current-shaping Techniques for Low-Energy Electron Beams

    SciTech Connect

    Piot, Philippe

    2015-12-01

    Techniques to bunch or shape an electron beam at low energies (E <15 MeV) have important implications toward the realization of table-top radiation sources [1] or to the design of compact multi-user free-electron lasers[2]. This paper provides an overview of alternative methods recently developed including techniques such as wakefield-based bunching, space-charge-driven microbunching via wave-breaking [3], ab-initio shaping of the electron-emission process [4], and phase space exchangers. Practical applications of some of these methods to foreseen free-electron-laser configurations are also briefly discussed [5].

  8. Characteristics of electric arc furnaces powered by a low-frequency alternating current

    NASA Astrophysics Data System (ADS)

    Mironov, Yu. M.; Mironova, A. N.

    2016-06-01

    The changes in the parameters of a DSP-100 electric arc furnace that are induced by a decrease in the current frequency are considered. It is shown that the related decrease in the current lead resistances causes an increase in the arc power and voltage, a decrease in the reactive power, and an increase in the electrical efficiency and the power coefficient. The heat indices are expected to be significantly improved.

  9. An alternative explanation for the occurrence of short circuit current increases in the small intestine following challenge by bacterial enterotoxins.

    PubMed

    Lucas, M L

    2013-10-01

    Secretory diarrhoeal disease due to enterotoxins is thought to arise from the enhancement to pathologically high rates of normally occurring chloride ion and therefore fluid secretion from enterocytes. In support of this concept, many enterotoxins increase intestinal short-circuit current, regarded now as faithfully reflecting the increased chloride ion secretion. Contradicting this assumption, STa reduces absorption but does not cause secretion in vivo although short-circuit current is increased in vitro. There is therefore a mismatch between an assumed enterocyte mediated secretory event that should but does not cause net fluid secretion and an undoubtedly increased short-circuit current. It is proposed here that short-circuit current increases are not themselves secretory events but result from interrupted fluid absorption. A noteworthy feature of compounds that inhibit the increase in short-circuit current is that the majority are vasoactive, neuroactive or both. In general, vasodilator substances increase current. An alternative hypothesis for the origin of short-circuit current increases is that these result from reflex induction of electrogenic fluid absorption. This reflex enhances a compensatory response that is also present at a cellular level. An intestinal reflex is therefore proposed by which decreases in interstitial and intravascular volume or pressure within the intestine initiate an electrogenic fluid absorption mechanism that compensates for the loss of electrically neutral fluid absorption. This hypothesis would explain the apparently complex pharmacology of short-circuit current increases since many depressor substances have receptors in common with enterocytes and enteric nerves. The proposed alternative view of the origin of short-circuit current increases assumes that these do not represent chloride secretion from the enterocytes. This view may therefore aid the successful development of anti-diarrhoeal drugs to overcome a major cause of

  10. Complementary and alternative medicine in Korea: current status and future prospects.

    PubMed

    Hong, C D

    2001-01-01

    Traditional Oriental medicine has been an integral part of prevailing practice and belief systems throughout Korea's history. Beginning late in the nineteenth century, Western medical practices were introduced by Christian missionaries and these practices quickly supplanted traditional medicine in institutional health care. After the Korean War, the government revived interest in Oriental medicine and established colleges of Oriental medicine, in addition to supporting the colleges of Western medicine. A difference in standards between these medical traditions underlies a mistrust of complementary and alternative medicine (CAM) that is common among practitioners of Western medicine. Western medicine is built on reproducible experiments and statistical analysis, whereas complementary and alternative treatments are built on experience. Recent surveys show that CAM is widely used in Korea, with usage rates ranging from 29% to 53% among various patient populations. CAM also accounts for a large share of healthcare costs. Approximately 29% of out-of-pocket, health care expenditure in Korea is for CAM therapies. Both the Korean government and the medical community recognize a need to integrate the health care delivery system and to define the roles of physicians, Oriental medical doctors, and pharmacists better. To accomplish this, there will be a need for standards for judging the safety and effectiveness of treatments and consensus-building will be needed to overcome the differences among practitioners from various traditions and backgrounds.

  11. Test plan for performance testing of the Eaton AC-3 electric vehicle

    SciTech Connect

    Crumley, R.L.; Heiselmann, H.W.

    1985-04-01

    An alternating current (ac) propulsion system for an electric vehicle has been developed and tested by the Eaton Corporation. The test bed vehicle is a modified 1981 Mercury Lynx. The test plan has been prepared specifically for the third modification to this test bed and identified as the Eaton AC-3. The scope of the EG and G testing at INEL to be done on the Eaton AC-3 will include coastdown and dynamometer tests but will not include environmental, on-road, or track testing. Coastdown testing will be performed in accordance with SAE J-1263 (SAE Recommended Practice for Road Load Measurement and Dynamometer Simulation Using Coastdown Techniques).

  12. Many-body and spin-orbit aspects of the alternating current phenomena

    NASA Astrophysics Data System (ADS)

    Glenn, Rachel M.

    The thesis reports on research in the general field of light interaction with matter. According to the topics addressed, it can be naturally divided into two parts: Part I, many-body aspects of the Rabi oscillations which a two-level systems undergoes under a strong resonant drive; and Part II, absorption of the ac field between the spectrum branches of two-dimensional fermions that are split by the combined action of Zeeman and spin-orbit (SO) fields. The focus of Part I is the following many-body effects that modify the conventional Rabi oscillations: Chapter 1, coupling of a two-level system to a single vibrational mode of the environment. Chapter 2, correlated Rabi oscillations in two electron-hole systems coupled by tunneling with strong electron-hole attraction. In Chapter 1, a new effect of Rabi-vibronic resonance is uncovered. If the frequency of the Rabi oscillations, OR, is close to the frequency o0 of the vibrational mode, the oscillations acquire a collective character. It is demonstrated that the actual frequency of the collective oscillations exhibits a bistable behavior as a function of OR - o0. The main finding in Chapter 2 is, that the Fourier spectrum of the Rabi oscillations in two coupled electron-hole systems undergoes a strong transformation with increasing O R. For OR smaller than the tunneling frequency, the spectrum is dominated by a low-frequency (<< OR ) component and contains two additional weaker lines; conventional Rabi oscillations are restored only as OR exceeds the electron-hole attraction strength. The highlight of Part II is a finding that, while the spectrum of absorption between either Zeeman-split branches or SO-split branches is close to a delta-peak, in the presence of both, it transforms into a broad line with singular behavior at the edges. In particular, when the magnitudes of Zeeman and SO are equal, absorption of very low (much smaller than the splitting) frequencies become possible. The shape of the absorption spectrum

  13. Tevatron AC dipole system

    SciTech Connect

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

    2007-06-01

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

  14. A Current Update on the Rule of Alternative and Complementary Medicine in the Treatment of Liver Diseases

    PubMed Central

    Guan, Yong-Song; He, Qing

    2013-01-01

    There is a vast body of knowledge which is ever-increasing about the treatment of liver disease with alternative and complementary medicine for which hundreds of thousands of literatures have been documented. Liver disease is a general term. This term covers all the potential problems that cause the liver to fail to perform its specified operations. Liver disease has a variety of presentations and causes a great public health problem worldwide which threatens the wellness of billions of people. Incidences of many types of liver disease are currently rising. Although there is still a debate about the entity of alternative and complementary medicine, it is now widely used and it is improving. And it covers the shortages and compensates for the weaknesses of conventional methods in the treatment of liver diseases. Alternative and complementary medicine for liver diseases provides benefits by regulating immunity, controlling disease progression, improving quality of life, and prolonging survival. This paper reviews the increasing interest and growing research into alternative and complementary medicine for liver diseases, with a look at the rough classification, principle of management, evidence-based applications, and issues for prescription and perspectives. PMID:24109491

  15. Variable Uses of Alternative Conceptions: A Case Study in Current Electricity.

    ERIC Educational Resources Information Center

    Heller, Patricia; Finley, Fred

    In order to investigate the nature of students' prior knowledge of current electricity and how they applied their knowledge to different problems, 5 middle school science teachers and 11 elementary school teachers were given a written test that required them to: (1) predict what happens to the brightness of a bulb if a change is made to the…

  16. Skills Training for School Leavers: Some Alternative Approaches. Current Issues Brief No. 2.

    ERIC Educational Resources Information Center

    Fraser, Doug

    In the face of escalating youth unemployment, some new approaches are needed for training out-of-school youth in Australia. The current system of apprenticeship has become outmoded because many of the skilled trades that the system prepares young people for will soon be non-existent. One approach to this problem has been implementation of…

  17. Variable Uses of Alternative Conceptions: A Case Study in Current Electricity.

    ERIC Educational Resources Information Center

    Heller, Patricia M.; Finley, Fred N.

    1992-01-01

    Fourteen elementary and middle school teachers from an inservice physics course were found to share a common core of strongly held propositions that formed a coherent, but incorrect and contradictory, model of the sequential flow of electrical current. Theoretical and practical implications of these teachers' beliefs with respect to both…

  18. Regional economic effects of current and proposed management alternatives for Sand Lake National Wildlife Refuge

    USGS Publications Warehouse

    Koontz, Lynne; Lambert, Heather

    2005-01-01

    This report first provides a description of the local community and economy near the Refuge. An analysis of current and proposed management strategies that could affect the local economy is then presented. The Refuge management activities of economic concern in this analysis are Refuge personnel staffing and Refuge spending within the local community, and spending in the local community by Refuge visitors.

  19. Regional economic effects of current and proposed management alternatives for Arrowwood National Wildlife Refuge

    USGS Publications Warehouse

    Koontz, Lynne; Lambert, Heather

    2005-01-01

    This report first provides a description of the local community and economy near the Refuge. An analysis of current and proposed management strategies that could affect the local economy is then presented. The Refuge management activities of economic concern in this analysis are Refuge personnel staffing and Refuge spending within the local community, and spending in the local community by Refuge visitors.

  20. Fluid modeling of operating modes in a field emission driven alternating current (FEDAC) microdischarge

    NASA Astrophysics Data System (ADS)

    Venkattraman, Ayyaswamy; Alamatsaz, Arghavan; Shivaprasad, Therazhundur Ramesh

    2014-10-01

    The recent interest in electrostatic microscale devices has lead to a great emphasis on electrical breakdown of gases in microgaps. The breakdown process has been shown to be significantly different from its counterpart in macrogaps with field emission of electrons from the cathode playing a major role. This work aims to build on prior work dealing with pre-breakdown and post-breakdown operating modes in direct current field emission driven (FED) microdischarges. Specifically, charged particle dynamics in microscale gaps that are driven by time-varying fields are studied using an in-house two-fluid code with appropriate cathode boundary conditions including field emission. The model includes continuity and energy equations for both electrons and ions to account for the significant non-equilibrium and is augmented by the Poisson's equation for electrostatic potential. The frequency dependence of breakdown behavior as well as pre-breakdown and post-breakdown current-voltage characteristics is determined for a wide range of frequencies from low radio frequency (RF) to microwave and contrasted with existing results for direct current FED microdischarges. The results are also used to explain trends recently observed in an evanescent-mode cavity resonator operating in the microwave regime.

  1. Investigating Effects of Nano- to Micro-Ampere Alternating Current Stimulation on Trichophyton rubrum Growth

    PubMed Central

    Kwon, Dong Rak; Kwon, Hyunjung; Lee, Woo Ram

    2016-01-01

    Background Fungi are eukaryotic microorganisms including yeast and molds. Many studies have focused on modifying bacterial growth, but few on fungal growth. Microcurrent electricity may stimulate fungal growth. Objective This study aims to investigate effects of microcurrent electric stimulation on Trichophyton rubrum growth. Methods Standard-sized inoculums of T. rubrum derived from a spore suspension were applied to potato dextrose cornmeal agar (PDACC) plates, gently withdrawn with a sterile pipette, and were applied to twelve PDACC plates with a sterile spreader. Twelve Petri dishes were divided into four groups. The given amperage of electric current was 500 nA, 2 µA, and 4 µA in groups A, B, and C, respectively. No electric current was given in group D. Results In the first 48 hours, colonies only appeared in groups A and B (500 nA and 2 µA exposure). Colonies in group A (500 nA) were denser. Group C (4 µA) plates showed a barely visible film of fungus after 96 hours of incubation. Fungal growth became visible after 144 hours in the control group. Conclusion Lower intensities of electric current caused faster fungal growth within the amperage range used in this study. Based on these results, further studies with a larger sample size, various fungal species, and various intensities of electric stimulation should be conducted. PMID:27746636

  2. The outcomes of complementary and alternative medicine use among pregnant and birthing women: current trends and future directions.

    PubMed

    Steel, Amie; Adams, Jon; Sibbritt, David; Broom, Alex

    2015-06-01

    Complementary and alternative medicine is used by a substantial number of pregnant women and maternity care providers are often faced with the task of ensuring women are using safe and effective treatments while respecting a woman's right to autonomous decision-making. In the era of evidence-based medicine maternity health professionals are expected to draw upon the best available evidence when making clinical decisions and providing health advice. This review will outline the current trends in research evidence associated with the outcomes of complementary and alternative medicine use amongst pregnant and birthing women as well as highlight some potential directions for future development in this important yet largely unknown topic in contemporary maternity care.

  3. The Polarization of a Diffuse Soft Particle Subjected to an Alternating Current Field

    NASA Astrophysics Data System (ADS)

    Uppapalli, Sebastian; Zhao, Hui

    2012-11-01

    The polarization of a diffuse soft particle submerged in an aqueous electrolyte and subjected to a uniform, alternating electric field is theoretically analyzed with the standard electrokinetic model. The particle consists of a rigid uncharged core and a charged diffuse polyelectrolytic shell (soft layer), permeable to ions and solvent. Our focus is on the impact of the characteristics of the soft layer including Donnan potential, the soft layer thickness and the friction coefficient of the soft layer on the dipole coefficient, characterizing the strength of the polarization. Under the limits of thin double layers and thin polyelectrolytic shells, approximate, analytical expressions to evaluate dipole moment coefficients are derived, respectively, for high-frequency and low-frequency ranges. The analytical results are compared and agree favorably with those numerically computed by the standard model. Interestingly, we discover that when the double layer is comparable to the soft layer, the dipole moment behaves qualitatively differently at different Donnan potentials. When the Donnan potential is small, the dipole moment decreases as the double layer increases. In contrast, at large Donnan potentials, the dipole moment increases with the increase of the double layer. The distinct responses to Donnan potentials are attributed to the impact of the associated double layer on the charge distribution of mobile ions inside the soft layer. The theoretical model provides a fundamental basis for interpreting the polarization of heterogeneous systems including environmental or biological colloids or microgel particles.

  4. The role of augmentative and alternative communication for children with autism: current status and future trends

    PubMed Central

    Iacono, Teresa; Trembath, David; Erickson, Shane

    2016-01-01

    Background Augmentative and alternative communication (AAC) interventions are used for children with autism, often as stand-alone communication interventions for those who are minimally verbal. Our aim was to synthesize the evidence for AAC interventions for children (up to 21 years), and then consider the role of AAC within established, comprehensive, evidence-based autism interventions targeting learning across multiple developmental domains. Design We completed a systematic search of three databases (OVID Medline, PsycINFO, ERIC) as well as forward citation and hand searches to identify systematic reviews of AAC intervention efficacy research including children with autism, published between 2000 and March 2016 in peer-reviewed journals. Data pertaining to the quality indicators of included studies, effect sizes for intervention outcomes, and evidence for effectiveness were extracted for descriptive analysis. Results The search yielded 17 systematic reviews. Most provided indicators of research quality for included studies, of which only relatively few provided conclusive results. Communication targets tended to be focused on teaching children to make requests. Still, effect size measures for included studies indicated that AAC was effective to highly effective. Conclusion There is growing evidence for the potential benefits of AAC for children with autism, but there is a need for more well-designed studies and broader, targeted outcomes. Furthermore, a lack of evidence for the role of AAC within comprehensive intervention programs may account for a tendency by autism researchers and practitioners to neglect this intervention. Attempts to compare evidence for AAC with other interventions for children with autism, including those in which the use of AAC is delayed or excluded in pursuit of speech-only communication, must take into account the needs of children with the most significant learning needs. These children pose the greatest challenges to achieving large

  5. Including Alternative Resources in State Renewable Portfolio Standards: Current Design and Implementation Experience

    SciTech Connect

    Heeter, J.; Bird, L.

    2012-11-01

    Currently, 29 states, the District of Columbia, and Puerto Rico have instituted a renewable portfolio standard (RPS). An RPS sets a minimum threshold for how much renewable energy must be generated in a given year. Each state policy is unique, varying in percentage targets, timetables, and eligible resources. This paper examines state experience with implementing renewable portfolio standards that include energy efficiency, thermal resources, and non-renewable energy and explores compliance experience, costs, and how states evaluate, measure, and verify energy efficiency and convert thermal energy. It aims to gain insights from the experience of states for possible federal clean energy policy as well as to share experience and lessons for state RPS implementation.

  6. Analysis of operations and cyber security policies for a system of cooperating Flexible Alternating Current Transmission System (FACTS) devices.

    SciTech Connect

    Phillips, Laurence R.; Tejani, Bankim; Margulies, Jonathan; Hills, Jason L.; Richardson, Bryan T.; Baca, Micheal J.; Weiland, Laura

    2005-12-01

    Flexible Alternating Current Transmission Systems (FACTS) devices are installed on electric power transmission lines to stabilize and regulate power flow. Power lines protected by FACTS devices can increase power flow and better respond to contingencies. The University of Missouri Rolla (UMR) is currently working on a multi-year project to examine the potential use of multiple FACTS devices distributed over a large power system region in a cooperative arrangement in which the FACTS devices work together to optimize and stabilize the regional power system. The report describes operational and security challenges that need to be addressed to employ FACTS devices in this way and recommends references, processes, technologies, and policies to address these challenges.

  7. Wavefront velocity oscillations of carbon-nanotube-guided thermopower waves: nanoscale alternating current sources.

    PubMed

    Abrahamson, Joel T; Choi, Wonjoon; Schonenbach, Nicole S; Park, Jungsik; Han, Jae-Hee; Walsh, Michael P; Kalantar-Zadeh, Kourosh; Strano, Michael S

    2011-01-25

    The nonlinear coupling between exothermic chemical reactions and a nanowire or nanotube with large axial heat conduction results in a self-propagating thermal wave guided along the nanoconduit. The resulting reaction wave induces a concomitant thermopower wave of high power density (>7 kW/kg), resulting in an electrical current along the same direction. We develop the theory of such waves and analyze them experimentally, showing that for certain values of the chemical reaction kinetics and thermal parameters, oscillating wavefront velocities are possible. We demonstrate such oscillations experimentally using a cyclotrimethylene-trinitramine/multiwalled carbon nanotube system, which produces frequencies in the range of 400 to 5000 Hz. The propagation velocity oscillations and the frequency dispersion are well-described by Fourier's law with an Arrhenius source term accounting for reaction and a linear heat exchange with the nanotube scaffold. The frequencies are in agreement with oscillations in the voltage generated by the reaction. These thermopower oscillations may enable new types of nanoscale power and signal processing sources.

  8. NTM stabilization by alternating O-point EC current drive using a high-power diplexer

    NASA Astrophysics Data System (ADS)

    Kasparek, W.; Doelman, N.; Stober, J.; Maraschek, M.; Zohm, H.; Monaco, F.; Eixenberger, H.; Klop, W.; Wagner, D.; Schubert, M.; Schütz, H.; Grünwald, G.; Plaum, B.; Munk, R.; Schlüter, K. H.; ASDEX Upgrade Team

    2016-12-01

    At the tokamak ASDEX Upgrade, experiments to stabilize neoclassical tearing modes (NTMs) by electron cyclotron (EC) heating and current drive in the O-points of the magnetic islands were performed. For the first time, injection into the O-points of the revolving islands was performed via a fast directional switch, which toggled the EC power between two launchers synchronously to the island rotation. The switching was performed by a resonant diplexer employing a sharp resonance in the transfer function, and a small frequency modulation of the feeding gyrotron around the slope of the resonance. Thus, toggling of the power between the two outputs of the diplexer connected to two articulating launchers was possible. Phasing and control of the modulation were performed via a set of Mirnov coils and appropriate signal processing. In the paper, technological issues, the design of the diplexer, the tracking of the diplexer resonance to the gyrotron frequency, the generation and processing of control signals for the gyrotron, and the typical performance concerning switching contrast and efficiency are discussed. The plasma scenario is described, and plasma experiments are presented, where the launchers scanned the region of the resonant surface continuously and also where the launchers were at a fixed position near to the q  =  1.5-surface. In the second case, complete stabilization of a 3/2 NTM could be reached. These experiments are also seen as a technical demonstration for the applicability of diplexers in large-scale ECRH systems.

  9. Direct current uninterruptible power supply method and system

    DOEpatents

    Sinha, Gautam

    2003-12-02

    A method and system are described for providing a direct current (DC) uninterruptible power supply with the method including, for example: continuously supplying fuel to a turbine; converting mechanical power from the turbine into alternating current (AC) electrical power; converting the AC electrical power to DC power within a predetermined voltage level range; supplying the DC power to a load; and maintaining a DC load voltage within the predetermined voltage level range by adjusting the amount of fuel supplied to the turbine.

  10. Direct current power delivery system and method

    DOEpatents

    Zhang, Di; Garces, Luis Jose; Dai, Jian; Lai, Rixin

    2016-09-06

    A power transmission system includes a first unit for carrying out the steps of receiving high voltage direct current (HVDC) power from an HVDC power line, generating an alternating current (AC) component indicative of a status of the first unit, and adding the AC component to the HVDC power line. Further, the power transmission system includes a second unit for carrying out the steps of generating a direct current (DC) voltage to transfer the HVDC power on the HVDC power line, wherein the HVDC power line is coupled between the first unit and the second unit, detecting a presence or an absence of the added AC component in the HVDC power line, and determining the status of the first unit based on the added AC component.

  11. Solution pH change in non-uniform alternating current electric fields at frequencies above the electrode charging frequency

    PubMed Central

    An, Ran; Massa, Katherine

    2014-01-01

    AC Faradaic reactions have been reported as a mechanism inducing non-ideal phenomena such as flow reversal and cell deformation in electrokinetic microfluidic systems. Prior published work described experiments in parallel electrode arrays below the electrode charging frequency (fc), the frequency for electrical double layer charging at the electrode. However, 2D spatially non-uniform AC electric fields are required for applications such as in plane AC electroosmosis, AC electrothermal pumps, and dielectrophoresis. Many microscale experimental applications utilize AC frequencies around or above fc. In this work, a pH sensitive fluorescein sodium salt dye was used to detect [H+] as an indicator of Faradaic reactions in aqueous solutions within non-uniform AC electric fields. Comparison experiments with (a) parallel (2D uniform fields) electrodes and (b) organic media were employed to deduce the electrode charging mechanism at 5 kHz (1.5fc). Time dependency analysis illustrated that Faradaic reactions exist above the theoretically predicted electrode charging frequency. Spatial analysis showed [H+] varied spatially due to electric field non-uniformities and local pH changed at length scales greater than 50 μm away from the electrode surface. Thus, non-uniform AC fields yielded spatially varied pH gradients as a direct consequence of ion path length differences while uniform fields did not yield pH gradients; the latter is consistent with prior published data. Frequency dependence was examined from 5 kHz to 12 kHz at 5.5 Vpp potential, and voltage dependency was explored from 3.5 to 7.5 Vpp at 5 kHz. Results suggest that Faradaic reactions can still proceed within electrochemical systems in the absence of well-established electrical double layers. This work also illustrates that in microfluidic systems, spatial medium variations must be considered as a function of experiment time, initial medium conditions, electric signal potential, frequency, and spatial

  12. On utilizing alternating current-flow field effect transistor for flexibly manipulating particles in microfluidics and nanofluidics.

    PubMed

    Liu, Weiyu; Shao, Jinyou; Ren, Yukun; Liu, Jiangwei; Tao, Ye; Jiang, Hongyuan; Ding, Yucheng

    2016-05-01

    By imposing a biased gate voltage to a center metal strip, arbitrary symmetry breaking in induced-charge electroosmotic flow occurs on the surface of this planar gate electrode, a phenomenon termed as AC-flow field effect transistor (AC-FFET). In this work, the potential of AC-FFET with a shiftable flow stagnation line to flexibly manipulate micro-nano particle samples in both a static and continuous flow condition is demonstrated via theoretical analysis and experimental validation. The effect of finite Debye length of induced double-layer and applied field frequency on the manipulating flexibility factor for static condition is investigated, which indicates AC-FFET turns out to be more effective for achieving a position-controllable concentrating of target nanoparticle samples in nanofluidics compared to the previous trial in microfluidics. Besides, a continuous microfluidics-based particle concentrator/director is developed to deal with incoming analytes in dynamic condition, which exploits a design of tandem electrode configuration to consecutively flow focus and divert incoming particle samples to a desired downstream branch channel, as prerequisite for a following biochemical analysis. Our physical demonstrations with AC-FFET prove valuable for innovative designs of flexible electrokinetic frameworks, which can be conveniently integrated with other microfluidic or nanofluidic components into a complete lab-on-chip diagnostic platform due to a simple electrode structure. PMID:27190570

  13. The effect of γ-tACS on working memory performance in healthy controls.

    PubMed

    Hoy, Kate E; Bailey, Neil; Arnold, Sara; Windsor, Kirstyn; John, Joshua; Daskalakis, Zafiris J; Fitzgerald, Paul B

    2015-12-01

    Transcranial Direct Current Stimulation (tDCS) has been widely investigated for its potential to enhance cognition, and in particular working memory, however to date standard approaches to stimulation have shown only modest effects. Alternative, more specialised, forms of current delivery may be better suited to cognitive enhancement. One such method is transcranial Alternating Current Stimulation (tACS) which delivers stimulation at a specific frequency and has been shown to entrain endogenous cortical oscillations which underlie cognitive functioning. To date there has been no comparison of the effects of tACS to those of tDCS on cognitive enhancement. In a randomised repeated-measures study design we assessed the effect of gamma (γ)-tACS, tDCS and sham tDCS on working memory in 18 healthy participants who attended three sessions held at least 72h apart. Pre- and post-stimulation working memory performance was assessed using the 2 and 3-back. Our findings indicated the presence of a selective improvement in performance on the 3-back task following γ-tACS compared with tDCS and sham stimulation. The current findings provide support for further and more detailed investigation of the role of γ-tACS as a more specialised approach to neuromodulation. PMID:26580743

  14. Elicitors as alternative strategy to pesticides in grapevine? Current knowledge on their mode of action from controlled conditions to vineyard.

    PubMed

    Delaunois, Bertrand; Farace, Giovanni; Jeandet, Philippe; Clément, Christophe; Baillieul, Fabienne; Dorey, Stéphan; Cordelier, Sylvain

    2014-04-01

    Development and optimisation of alternative strategies to reduce the use of classic chemical inputs for protection against diseases in vineyard is becoming a necessity. Among these strategies, one of the most promising consists in the stimulation and/or potentiation of the grapevine defence responses by the means of elicitors. Elicitors are highly diverse molecules both in nature and origins. This review aims at providing an overview of the current knowledge on these molecules and will highlight their potential efficacy from the laboratory in controlled conditions to vineyards. Recent findings and concepts (especially on plant innate immunity) and the new terminology (microbe-associated molecular patterns, effectors, etc.) are also discussed in this context. Other objectives of this review are to highlight the difficulty of transferring elicitors use and results from the controlled conditions to the vineyard, to determine their practical and effective use in viticulture and to propose ideas for improving their efficacy in non-controlled conditions. PMID:23719689

  15. The history and current status of fallopian tube pressures - developing alternate methods for confirmation of tubal occlusion.

    PubMed

    Patil, Eva; Thurmond, Amy

    2015-08-01

    Permanent contraception with hysteroscopic tubal ligation is an increasingly popular choice for women around the world. However, inconveniences associated with the required confirmation test for tubal occlusion can be prohibitive. As new methods of permanent contraception are being investigated, ways of making all aspects of the procedure more accessible and comfortable for women should be considered. Means of examining tubal patency in the infertility population, such as tubal perfusion pressures measured at the time of hysterosalpingogram (HSG), provide inspiration for alternative methods of tubal occlusion confirmation after contraception. Evaluation of intrauterine pressures measured by a manometer attached to an intrauterine balloon catheter could serve as a preliminary tool for verification of tubal occlusion; higher pressures would indicate tubal occlusion and lower pressures would indicate the need for confirmatory HSG. The development and validation of this technique is ongoing and could reduce overall costs and patient burdens associated with the current tubal occlusion confirmation procedure.

  16. Individually addressable multi-chamber electroporation platform with dielectrophoresis and alternating-current-electro-osmosis assisted cell positioning

    PubMed Central

    Park, Sinwook; Bassat, Dana Ben; Yossifon, Gilad

    2014-01-01

    A multi-functional microfluidic platform was fabricated to demonstrate the feasibility of on-chip electroporation integrated with dielectrophoresis (DEP) and alternating-current-electro-osmosis (ACEO) assisted cell/particle manipulation. A spatial gradient of electroporation parameters was generated within a microchamber array and validated using normal human dermal fibroblast (NHDF) cells and red fluorescent protein-expressing human umbilical vein endothelial cells (RFP-HUVECs) with various fluorescent indicators. The edge of the bottom electrode, coinciding with the microchamber entrance, may act as an on-demand gate, functioning under either positive or negative DEP. In addition, at sufficiently low activation frequencies, ACEO vortices can complement the DEP to contribute to a rapid trapping/alignment of particles. As such, results clearly indicate that the microfluidic platform has the potential to achieve high-throughput screening for electroporation with spatial control and uniformity, assisted by DEP and ACEO manipulation/trapping of particles/cells into individual microchambers. PMID:24803966

  17. Flux-creep activation energy for a BaFe1.9Ni0.1As2 single crystal derived from alternating current susceptibility measurements

    NASA Astrophysics Data System (ADS)

    Ge, Jun-Yi; Li, Lin-Jun; Xu, Zhu-An; Moshchalkov, Victor V.

    2016-04-01

    Systematic ac susceptibility measurements have been performed to investigate the vortex dynamics in a BaFe1.9Ni0.1As2 single crystal as a function of temperature, frequency, ac field amplitude, and dc magnetic field. The complex activation energy U ( T , B , j ) is derived in the framework of thermally activated flux creep theory and can be expressed in one simple formula. A power law dependence of U ˜ B α with α = -0.46 is observed. The activation energy reaches 104 K at low fields, suggesting strong pinning in the material. The nonlinear function of the activation energy vs. the current density is determined, which has the expression of U ∝ j - 0.1 .

  18. Operation Method for AC Motor Control during Power Interruption in Direct AC/AC Converter System

    NASA Astrophysics Data System (ADS)

    Shizu, Keiichiro; Azuma, Satoshi

    Direct AC/AC converters have been studied due to their potential use in power converters with no DC-link capacitor, which can contribute to the miniaturization of power converters. However, the absence of a DC-link capacitor makes it difficult to control the AC motor during power interruption. First, this paper proposes a system that realizes AC motor control during power interruption by utilizing a clamp capacitor. In general, direct AC/AC converters have a clamp circuit consisting of a rectifier diode(s) and a clamp capacitor in order to avoid over-voltages. In the proposed system, there is an additional semiconductor switch reverse-parallel to the rectifier diode(s), and the clamp capacitor voltage can be utilized for AC motor control by turning on the additional switch. Second, this paper discusses an operation method for AC motor control and clamp capacitor voltage control during power interruption. In the proposed method “DC-link voltage control”, the kinetic energy in the AC motor is transformed into electrical energy and stored in the clamp capacitor; the clamp capacitor is therefore charged and the capacitor voltage is controlled to remain constant at an instruction value. Third, this paper discusses a switching operation during power interruption. A dead-time is introduced between the operation of turning off all switches on the rectifier side and the operation of turning on the additional switch, which prevents the occurrence of a short circuit between the interrupted power source and the clamp capacitor. Finally, experimental results are presented. During power interruptions, an output current was continuously obtained and the clamp capacitor voltage was maintained to be equal to the instruction value of the capacitor voltage. These results indicate that both AC motor control and capacitor voltage control were successfully achieved by using the proposed system.

  19. AC plasma anemometer—characteristics and design

    NASA Astrophysics Data System (ADS)

    Marshall, Curtis; Matlis, Eric; Corke, Thomas; Gogineni, Sivaram

    2015-08-01

    The characteristics and design of a high-bandwidth flow sensor that uses an AC glow discharge (plasma) as the sensing element is presented. The plasma forms in the air gap between two protruding low profile electrodes attached to a probe body. The output from the anemometer is an amplitude modulated version of the AC voltage input that contains information about the mean and fluctuating velocity components. The anemometer circuitry includes resistance and capacitance elements that simulate a dielectric-barrier to maintain a diffuse plasma, and a constant-current feedback control that maintains operation within the desired glow discharge regime over an extended range of air velocities. Mean velocity calibrations are demonstrated over a range from 0 to 140 m s-1. Over this velocity range, the mean output voltage varied linearly with air velocity, providing a constant static sensitivity. The effect of the electrode gap and input AC carrier frequency on the anemometer static sensitivity and dynamic response are investigated. Experiments are performed to compare measurements obtained with a plasma sensor operating at two AC carrier frequencies against that of a constant-temperature hot-wire. All three sensors were calibrated against the same known velocity reference. An uncertainty based on the standard deviation of the velocity calibration fit was applied to the mean and fluctuating velocity measurements of the three sensors. The motivation is not to replace hot-wires as a general measurement tool, but rather as an alternative to hot-wires in harsh environments or at high Mach numbers where they either have difficulty in surviving or lack the necessary frequency response.

  20. An alternative analysis of low- and high-altitude observations of ring current ions during a storm recovery phase

    NASA Technical Reports Server (NTRS)

    Lyons, L. R.

    1977-01-01

    Explorer 45 equatorial observations of ring current ions during a storm recovery phase have shown pitch angle distributions and decay rates inconsistent with proton charge exchange with neutral hydrogen. This inconsistency has led to the suggestion that recovery phase ring current ions at L less than or equal to 4 and energies not greater than 50 keV are dominated by He(+) rather than protons. The absence of He(+) on flux tubes from which H(+) and O(+) were precipitating in ion mass spectrometer measurements made during the same period by the low-altitude polar-orbiting satellite 1971-089A led Sharp et al. to suggest a source of H(+) and O(+) to L = 3 during this period. An alternative explanation, in which the magnetic field lines labeled L = 3 at the earth's surface near local midnight were mapped to about 3.7 earth radii in the equatorial plane during the storm recovery phase and during the period of enhanced activity, is proposed. If the proposed explanation is correct, the observations of Sharp et al. are not incompatible with the conclusion that the recovery phase ions at less than 50 keV were dominated by He(+) for L not greater than 3.7.

  1. Aneurysm Sac Pressure Measurement with Minimally Invasive Implantable Pressure Sensors: An Alternative to Current Surveillance Regimes after EVAR?

    SciTech Connect

    Springer, Fabian Guenther, Rolf W.; Schmitz-Rode, Thomas

    2008-05-15

    Current protocols for surveillance after endovascular repair (EVAR) of abdominal aortic aneurysms are mostly based on costly and time-consuming imaging procedures and aim to detect adverse events such as graft migration, endoleaks or aneurysm sac enlargement. These imaging procedures are either associated with radiation exposure to the patients or may be harmful to the patient due to the use of iodine- or gadolinium-containing contrast agents. Furthermore the advantages of EVAR in the short term might be negated by the necessity for endograft surveillance over years. Thus, alternative modalities for follow-up are being investigated. One of these technologies provides pressure information directly from the aneurysm sac. This noninvasive, telemetric pressure sensing was tested in vitro as well as in first clinical trials and was able to identify successful aneurysm exclusion after EVAR. The telemetric pressure sensors showed a promising efficacy and accuracy in detecting type I and type III endoleaks and will help to clarify the clinical relevance of type II endoleaks. This article provides an overview of the in vitro sensors investigated as well as the first clinical trials and the sensors' potential to change the current endograft surveillance regimes.

  2. Introducing high performance distributed logging service for ACS

    NASA Astrophysics Data System (ADS)

    Avarias, Jorge A.; López, Joao S.; Maureira, Cristián; Sommer, Heiko; Chiozzi, Gianluca

    2010-07-01

    The ALMA Common Software (ACS) is a software framework that provides the infrastructure for the Atacama Large Millimeter Array and other projects. ACS, based on CORBA, offers basic services and common design patterns for distributed software. Every properly built system needs to be able to log status and error information. Logging in a single computer scenario can be as easy as using fprintf statements. However, in a distributed system, it must provide a way to centralize all logging data in a single place without overloading the network nor complicating the applications. ACS provides a complete logging service infrastructure in which every log has an associated priority and timestamp, allowing filtering at different levels of the system (application, service and clients). Currently the ACS logging service uses an implementation of the CORBA Telecom Log Service in a customized way, using only a minimal subset of the features provided by the standard. The most relevant feature used by ACS is the ability to treat the logs as event data that gets distributed over the network in a publisher-subscriber paradigm. For this purpose the CORBA Notification Service, which is resource intensive, is used. On the other hand, the Data Distribution Service (DDS) provides an alternative standard for publisher-subscriber communication for real-time systems, offering better performance and featuring decentralized message processing. The current document describes how the new high performance logging service of ACS has been modeled and developed using DDS, replacing the Telecom Log Service. Benefits and drawbacks are analyzed. A benchmark is presented comparing the differences between the implementations.

  3. Digital ac monitor

    DOEpatents

    Hart, G.W.; Kern, E.C. Jr.

    1987-06-09

    An apparatus and method is provided for monitoring a plurality of analog ac circuits by sampling the voltage and current waveform in each circuit at predetermined intervals, converting the analog current and voltage samples to digital format, storing the digitized current and voltage samples and using the stored digitized current and voltage samples to calculate a variety of electrical parameters; some of which are derived from the stored samples. The non-derived quantities are repeatedly calculated and stored over many separate cycles then averaged. The derived quantities are then calculated at the end of an averaging period. This produces a more accurate reading, especially when averaging over a period in which the power varies over a wide dynamic range. Frequency is measured by timing three cycles of the voltage waveform using the upward zero crossover point as a starting point for a digital timer. 24 figs.

  4. Digital ac monitor

    DOEpatents

    Hart, George W.; Kern, Jr., Edward C.

    1987-06-09

    An apparatus and method is provided for monitoring a plurality of analog ac circuits by sampling the voltage and current waveform in each circuit at predetermined intervals, converting the analog current and voltage samples to digital format, storing the digitized current and voltage samples and using the stored digitized current and voltage samples to calculate a variety of electrical parameters; some of which are derived from the stored samples. The non-derived quantities are repeatedly calculated and stored over many separate cycles then averaged. The derived quantities are then calculated at the end of an averaging period. This produces a more accurate reading, especially when averaging over a period in which the power varies over a wide dynamic range. Frequency is measured by timing three cycles of the voltage waveform using the upward zero crossover point as a starting point for a digital timer.

  5. Current-induced spin torque resonance of a magnetic insulator

    NASA Astrophysics Data System (ADS)

    Schreier, Michael; Chiba, Takahiro; Niedermayr, Arthur; Lotze, Johannes; Huebl, Hans; Geprägs, Stephan; Takahashi, Saburo; Bauer, Gerrit E. W.; Gross, Rudolf; Goennenwein, Sebastian T. B.

    2015-10-01

    We report the observation of current-induced spin torque resonance in yttrium iron garnet/platinum bilayers. An alternating charge current at GHz frequencies in the platinum gives rise to dc spin pumping and spin Hall magnetoresistance rectification voltages, induced by the Oersted fields of the ac current and the spin Hall effect-mediated spin transfer torque. In ultrathin yttrium iron garnet films, we observe spin transfer torque actuated magnetization dynamics which are significantly larger than those generated by the ac Oersted field. Spin transfer torques thus efficiently couple charge currents and magnetization dynamics also in magnetic insulators, enabling charge current-based interfacing of magnetic insulators with microwave devices.

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

    SciTech Connect

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

    1982-09-01

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

  7. Alternating current calorimeter for specific heat capacity measurements at temperatures below 10 K and pressures up to 10 GPa

    NASA Astrophysics Data System (ADS)

    Umeo, Kazunori

    2016-06-01

    A developed alternating current calorimeter for measuring the absolute value of specific heat C of a very small sample under a pressure up to 10 GPa and low temperature below 10 K is described. A Bridgman anvil cell made of tungsten carbide with a top diameter of 3 mm is used. A hollow at the top prevents expansion of the sample space over the anvil top. Two chip resistors, which act as a thermometer and a heater, are mounted on the outer part of a copper-beryllium gasket with a frying pan-like shape. Thus, the thermometer is not pressurized. In order to isolate the gasket from the anvil thermally, diamond powder with a grain size of 0.25 μm is placed on the anvil top. Two jumps of C at the superconducting transitions of Pb (3.3 mg) and In (5.0 mg) are observed under various pressures up to 9 GPa, as clearly as those at the ambient pressure.

  8. Current Efforts to Develop Alternate "TB700-2" Test Protocols for the Hazard Classification of Large Rocket Motors

    NASA Astrophysics Data System (ADS)

    Schwartz, Daniel F.; Bennett, Robert R.; Graham, Kenneth J.; Boggs, Thomas L.; Atwood, Alice I.

    2001-09-01

    When the Department of Defense (DoD) revised Technical Bulletin (TB) 700-2, NAVSEAINST 8020.8B, TO 11A-1-47, DLAR 8220.12 hazard classification guidelines in January 1998 1, it significantly changed the procedures used to determine the explosive classification of rocket motors, to be shipped or placed in DoD storage facilities. The revised test protocols outlined in this document, (hereafter referred to as TB 700-2) are far more conservative and costly to implement than the previous ones. These changes could have a profound impact on the solid rocket community and in particular those involved with the research and development and manufacture of large (equal to or greater than) 304.8-millimeter (equal to or greater than 12-inch diameter solid rocket motors (SRMs). The ramifications may include higher development costs and limitations on performance improvements. This paper outlines current efforts of the solid rocket community to develop acceptable alternate test protocols for large rocket motors that could fulfill the intent of TB 700-2 and be considered by the Department of Defense Explosive Safety Board (DDESB) for incorporation into a future revision to TB 700-2.

  9. Current Efforts to Develop Alternate "TB 700-2" Test Protocols for the Hazard Classification of Large Rocket Motors

    NASA Astrophysics Data System (ADS)

    Schwartz, Daniel F.; Bennett, Robert R.; Graham, Kenneth J.; Boggs, Thomas L.; Atwood, Alice I.; Butcher, A. Garn

    2002-04-01

    When the Department of Defense (DoD) revised Technical Bulletin (TB) 700-2, NAVSEAINST 8020.8B, TO 11A-1-47, DLAR 8220.12 hazard classification guidelines in January 1998, it significantly changed the procedures used to determine the explosive classification of rocket motors, to be shipped or placed in DoD storage facilities. The revised test protocols outlined in this document, (hereafter referred to as TB 700-2) are far more conservative and costly to implement than the previous ones. These changes could have a profound impact on the solid rocket community and in particular those involved with the research and development and manufacture of large (less than or = 304.8-millimeter (less than or = 12-inch)) diameter solid rocket motors (SRMs). The ramifications may include higher development costs and limitations on performance improvements. This paper outlines current efforts of the solid rocket community to develop acceptable alternate test protocols for large rocket motors that could fulfill the intent of TB 700-2 and be considered by the Department of Defense Explosive Safety Board (DDESB) for incorporation into a future revision to TB 700-2.

  10. Current Efforts to Develop Alternate "TB 700-2" Test Protocols for the Hazard Classification of Large Rocket Motors

    NASA Astrophysics Data System (ADS)

    Schwartz, Daniel F.; Bennett, Robert R.; Graham, Kenneth J.; Boggs, Thomas L.; Atwood, Alice I.

    1998-01-01

    When the Department of Defense (DoD) revised Technical Bulletin (TB) 700-2, NAVSEAINST 8020.8B, TO 11A-1-47, DLAR 8220.12 hazard classification guidelines in January 1998 1, it significantly changed the procedures used to determine the explosive classification of rocket motors, to be shipped or placed in DoD storage facilities. The revised test protocols outlined in this document, (hereafter referred to as TB 700-2) are far more conservative and costly to implement than the previous ones. These changes could have a profound impact on the solid rocket community and in particular those involved with the research and development and manufacture of large (greater than or equal 304.8-millimeter (greater than or equal l2-inch)) diameter solid rocket motors (SRMs). The ramifications may include higher development costs and limitations on performance improvements. This paper outlines current efforts of the solid rocket community to develop acceptable alternate test protocols for large rocket motors that could fulfill the intent of TB 700-2 and be considered by the Department of Defense Explosive Safety Board (DDESB) for incorporation into a future revision to TB 700-2.

  11. Alternating current calorimeter for specific heat capacity measurements at temperatures below 10 K and pressures up to 10 GPa.

    PubMed

    Umeo, Kazunori

    2016-06-01

    A developed alternating current calorimeter for measuring the absolute value of specific heat C of a very small sample under a pressure up to 10 GPa and low temperature below 10 K is described. A Bridgman anvil cell made of tungsten carbide with a top diameter of 3 mm is used. A hollow at the top prevents expansion of the sample space over the anvil top. Two chip resistors, which act as a thermometer and a heater, are mounted on the outer part of a copper-beryllium gasket with a frying pan-like shape. Thus, the thermometer is not pressurized. In order to isolate the gasket from the anvil thermally, diamond powder with a grain size of 0.25 μm is placed on the anvil top. Two jumps of C at the superconducting transitions of Pb (3.3 mg) and In (5.0 mg) are observed under various pressures up to 9 GPa, as clearly as those at the ambient pressure. PMID:27370464

  12. Alternating current calorimeter for specific heat capacity measurements at temperatures below 10 K and pressures up to 10 GPa.

    PubMed

    Umeo, Kazunori

    2016-06-01

    A developed alternating current calorimeter for measuring the absolute value of specific heat C of a very small sample under a pressure up to 10 GPa and low temperature below 10 K is described. A Bridgman anvil cell made of tungsten carbide with a top diameter of 3 mm is used. A hollow at the top prevents expansion of the sample space over the anvil top. Two chip resistors, which act as a thermometer and a heater, are mounted on the outer part of a copper-beryllium gasket with a frying pan-like shape. Thus, the thermometer is not pressurized. In order to isolate the gasket from the anvil thermally, diamond powder with a grain size of 0.25 μm is placed on the anvil top. Two jumps of C at the superconducting transitions of Pb (3.3 mg) and In (5.0 mg) are observed under various pressures up to 9 GPa, as clearly as those at the ambient pressure.

  13. Comparison of atmospheric air plasmas excited by high-voltage nanosecond pulsed discharge and sinusoidal alternating current discharge

    NASA Astrophysics Data System (ADS)

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

    2013-10-01

    In this paper, atmospheric pressure air discharge plasma in quartz tube is excited by 15 ns high-voltage nanosecond pulsed discharge (HVNPD) and sinusoidal alternating current discharge (SACD), respectively, and a comparison study of these two kinds of discharges is made through visual imaging, electrical characterization, optical detection of active species, and plasma gas temperature. The peak voltage of the power supplies is kept at 16 kV while the pulse repetition rate of nanosecond pulse power supply is 100 Hz, and the frequency of sinusoidal power supply is 10 kHz. Results show that the HVNPD is uniform while the SACD presents filamentary mode. For exciting the same cycles of discharge, the average energy consumption in HVNPD is about 1/13 of the SACD. However, the chemical active species generated by the HVNPD is about 2-9 times than that excited by the SACD. Meanwhile, the rotational and vibrational temperatures have been obtained via fitting the simulated spectrum of N2 (C3Πu → B3Πg, 0-2) with the measured one, and the results show that the plasma gas temperature in the HVNPD remains close to room temperature whereas the plasma gas temperature in the SACD is about 200 K higher than that in HVNPD in the initial phase and continually increases as discharge exposure time goes on.

  14. Pore formation in lipid bilayer membranes made of phosphatidylinositol and oxidized cholesterol followed by means of alternating current.

    PubMed Central

    Gallucci, E; Micelli, S; Monticelli, G

    1996-01-01

    The kinetics of porin incorporation into black lipid membranes (BLM) made of phosphatidylinositol (PI) or oxidized cholesterol (Ox Ch) were studied by means of alternating current; the set-up was able to acquire resistance and capacitance simultaneously by means of a mixed double-frequency approach at 1 Hz and 1 KHz, respectively. Conductance was dependent on the interaction between protein-forming pores and lipids. For PI membranes below a porin concentration of 12.54 ng/ml, there was no membrane conductivity, whereas at 200 ng/ml a steady-state value was reached. Different behavior was displayed by Ox Ch membranes, in which a concentration of 12.54 ng/ml was sufficient to reach a steady state. The incorporation kinetics when porin was added after membrane formation were sigmoidal. When porin was present in the medium before membrane formation, the kinetics were sigmoidal for PI membranes but became exponential for Ox Ch membranes. Furthermore, for BLM made of PI, the conductance-versus-porin concentration relationship is sigmoidal, with a Hill coefficient of 5.6 +/- 0.07, which is functional evidence corroborating the six-channel repeating units seen previously. For BLM made of Ox Ch, this relationship followed a binding isotherm curve with a Hill coefficient of 0.934 +/- 0.129. PMID:8842220

  15. Dipole-dipole interaction and its concentration dependence of magnetic fluid evaluated by alternating current hysteresis measurement

    NASA Astrophysics Data System (ADS)

    Ota, Satoshi; Yamada, Tsutomu; Takemura, Yasushi

    2015-05-01

    Magnetic nanoparticles (MNPs) are used as therapeutic and diagnostic tools, such as for treating hyperthermia and in magnetic particle imaging, respectively. Magnetic relaxation is one of the heating mechanisms of MNPs. Brownian and Néel relaxation times are calculated conventional theories; however, the influence of dipole-dipole interactions has not been considered in conventional models. In this study, water-dispersed MNPs of different concentrations and MNPs fixed with an epoxy bond were prepared. dc and ac hysteresis loops for each sample were measured. With respect to both dc and ac hysteresis loops, magnetization decreased with the increase in MNP concentration because of inhibition of magnetic moment rotation due to dipole-dipole interactions. Moreover, intrinsic loss power (ILP) was estimated from the areas of the ac hysteresis loops. The dependence of ILP on the frequency of the magnetic field was evaluated for each MNP concentration. The peak frequency of ILP increased with the decrease in MNP concentration. These peaks were due to Brownian relaxation, as they were not seen with the fixed sample. This indicates that the Brownian relaxation time became shorter with lower MNP concentration, because the weaker dipole-dipole interactions with lower concentrations suggested that the magnetic moments could rotate more freely.

  16. Current sensor

    DOEpatents

    Yakymyshyn, Christopher Paul; Brubaker, Michael Allen; Yakymyshyn, Pamela Jane

    2007-01-16

    A current sensor is described that uses a plurality of magnetic field sensors positioned around a current carrying conductor. The sensor can be hinged to allow clamping to a conductor. The current sensor provides high measurement accuracy for both DC and AC currents, and is substantially immune to the effects of temperature, conductor position, nearby current carrying conductors and aging.

  17. Complementary and Alternative Medicine: Comparison of Current Knowledge, Attitudes and Interest among German Medical Students and Doctors

    PubMed Central

    Münstedt, Karsten; Harren, Hildegard; von Georgi, Richard; Hackethal, Andreas

    2011-01-01

    Although it has been agreed that complementary and alternative medicine (CAM) should be included in the German medical curriculum, there is no consensus on which methods and how it should be taught. This study aimed to assess needs for CAM education by evaluating current knowledge, attitudes and interests of medical students, general physicians and gynecologists. Two instruments based on established and validated questionnaires were developed. One was given to seventh semester medical students and the other to office-based doctors. Data were analyzed by bivariate correlation and cross-tabulation. Altogether 550 questionnaires were distributed—280 to doctors and 270 to medical students. Completed questionnaires were returned by 80.4% of students and 78.2% of doctors. Although 73.8% (160/219) of doctors and 40% (87/217) of students had already informed themselves about CAM, neither group felt that they knew much about CAM. Doctors believed that CAM was most useful in general medicine, supportive oncology, pediatrics, dermatology and gynecology, while students believed that dermatology, general medicine, psychiatry and rheumatology offered opportunities; both recommended that CAM should be taught in these areas. Both groups believed that CAM should be included in medical education; however, they believed that CAM needed more investigation and should be taught “critically". German doctors and students would like to be better informed about CAM. An approach which teaches fundamental competences to students, chooses specific content based on evidence, demographics and medical conditions and provides students with the skills they need for future learning should be adopted. PMID:19098296

  18. Broadband alternating current magnetic susceptibility: Method and application to the characterization of magnetic particles in igneous rocks

    NASA Astrophysics Data System (ADS)

    Kodama, K.

    2012-12-01

    Low-field alternating current magnetic susceptibility (MS) is among the most commonly used magnetic property, not only in rock and mineral magnetism but also in environmental magnetism studies. This study proposes a new rock magnetic method, Frequency Spectrum of MS (FSM), based on the measurement of the real component of MS over a wide range of frequency (100 Hz to 500 kHz) and the measurement of the imaginary component at high frequencies in the order of 10-102 kHz. This study presents the FSM results at room and low temperatures obtained from a variety of igneous rocks with SP to SD grain sizes, including acidic to basic volcanic rocks in Japan and a basalt in Hawaii. The FSMs from the andesite samples at room temperature unexceptionally show small but anomalous increase, as much as 5%, over a specific frequency interval between 10 kHz and 120 kHz. In contrast, FSMs of basalts from Oshima and Hawaii show no such peak, a typical pattern indicating the presence of SP grain ensembles. The anomalous FSM from the andesites suggests a new rock and mineral magnetic behavior indicating either magnetic resonance or magnetic relaxation. Considering the anomalous FSM patterns and their variations at low temperatures, it is suggested that the hypothetical resonance could be relevant to some magnetoelastic phenomenon, in which magnetic energy could be dissipated through a long-range, magnetostructural coupling, most likely, magnetostriction. The fact that the annealed andesite samples showed less developed FSM anomaly strongly supports this hypothesis, because annealing generally lowers the internal stress leading to the reduction of resistance in a forced oscillation system. Analyses of the low temperature results confirm magnetic relaxation phenomena taking place at low temperatures, and consequently support the above interpretation.

  19. Probing radiation damage by alternated current conductivity as a method to characterize electron hopping conduction in DNA molecules

    NASA Astrophysics Data System (ADS)

    Gomes, Paulo J.; Coelho, Margarida; Dionísio, Madalena; António Ribeiro, Paulo; Raposo, Maria

    2012-09-01

    Analysis of AC electrical conductivity of deoxyribonucleic acid (DNA) thin films, irradiated with ultraviolet (UV) light, revealed that electrical conduction arises from DNA chain electron hopping between base-pairs and phosphate groups. The hopping distance calculated from correlated barrier hopping model equals the distance between DNA base-pairs, which is consistent with the loss of conductivity with irradiation time arising from a decrease in phosphates groups. In the high frequency regime, at a given frequency, real part of conductivity strongly depends on irradiation time particularly for low dose levels suggesting the use of DNA based films for UV radiation sensors.

  20. Probing radiation damage by alternated current conductivity as a method to characterize electron hopping conduction in DNA molecules

    SciTech Connect

    Gomes, Paulo J.; Coelho, Margarida; Antonio Ribeiro, Paulo; Raposo, Maria; Dionisio, Madalena

    2012-09-17

    Analysis of AC electrical conductivity of deoxyribonucleic acid (DNA) thin films, irradiated with ultraviolet (UV) light, revealed that electrical conduction arises from DNA chain electron hopping between base-pairs and phosphate groups. The hopping distance calculated from correlated barrier hopping model equals the distance between DNA base-pairs, which is consistent with the loss of conductivity with irradiation time arising from a decrease in phosphates groups. In the high frequency regime, at a given frequency, real part of conductivity strongly depends on irradiation time particularly for low dose levels suggesting the use of DNA based films for UV radiation sensors.

  1. Module Nine: Relationships of Current, Counter EMF, and Voltage in LR Circuits; Basic Electricity and Electronics Individualized Learning System.

    ERIC Educational Resources Information Center

    Bureau of Naval Personnel, Washington, DC.

    The student will study the ways that inductance affects voltage and current in Direct Current (DC) and Alternating Current (AC) circuits and why and how inductors cause these actions. The module is divided into six lessons: rise and decay of current and voltage, LR (inductive-resistive) time constant, using the universal TC (time constant) chart,…

  2. Low-frequency ac electroporation shows strong frequency dependence and yields comparable transfection results to dc electroporation.

    PubMed

    Zhan, Yihong; Cao, Zhenning; Bao, Ning; Li, Jianbo; Wang, Jun; Geng, Tao; Lin, Hao; Lu, Chang

    2012-06-28

    Conventional electroporation has been conducted by employing short direct current (dc) pulses for delivery of macromolecules such as DNA into cells. The use of alternating current (ac) field for electroporation has mostly been explored in the frequency range of 10kHz-1MHz. Based on Schwan equation, it was thought that with low ac frequencies (10Hz-10kHz), the transmembrane potential does not vary with the frequency. In this report, we utilized a flow-through electroporation technique that employed continuous 10Hz-10kHz ac field (based on either sine waves or square waves) for electroporation of cells with defined duration and intensity. Our results reveal that electropermeabilization becomes weaker with increased frequency in this range. In contrast, transfection efficiency with DNA reaches its maximum at medium frequencies (100-1000Hz) in the range. We postulate that the relationship between the transfection efficiency and the ac frequency is determined by combined effects from electrophoretic movement of DNA in the ac field, dependence of the DNA/membrane interaction on the ac frequency, and variation of transfection under different electropermeabilization intensities. The fact that ac electroporation in this frequency range yields high efficiency for transfection (up to ~71% for Chinese hamster ovary cells) and permeabilization suggests its potential for gene delivery.

  3. Improving neuron-to-electrode surface attachment via alkanethiol self-assembly: an alternating current impedance study.

    PubMed

    Slaughter, Gymama E; Bieberich, Erhard; Wnek, Gary E; Wynne, Kenneth J; Guiseppi-Elie, Anthony

    2004-08-17

    examined by alternating current impedance (50 mV p-t-p at 4 kHz). CA- and 11-AUT-SAM-modified surfaces when serving as a foundation or covalently immobilized adhesion proteins produced highly stable and reproducible temporal impedance responses. On the basis of the magnitude and the reproducibility of the impedance responses, the CA-SAM-modified surfaces were identified as being best suited for optimal neuron-to-electrode contact with laminin. Laminin performed best when compared to collagen and fibronectin. Covalent immobilization of the adhesion-promoting proteins results in enhanced NESA by tightly anchoring cells to the electrode.

  4. Surface potential distribution and airflow performance of different air-exposed electrode plasma actuators at different alternating current/direct current voltages

    SciTech Connect

    Yang, Liang; Yan, Hui-Jie; Qi, Xiao-Hua; Hua, Yue; Ren, Chun-Sheng

    2015-04-15

    Asymmetric surface dielectric barrier discharge (SDBD) plasma actuators have been intensely studied for a number of years due to their potential applications for aerodynamic control. In this paper, four types of actuators with different configurations of exposed electrode are proposed. The SDBD actuators investigated are driven by dual-power supply, referred to as a fixed AC high voltage and an adjustable DC bias. The effects of the electrode structures on the dielectric surface potential distribution, the electric wind velocity, and the mean thrust production are studied, and the dominative factors of airflow acceleration behavior are revealed. The results have shown that the actions of the SDBD actuator are mainly dependent on the geometry of the exposed electrode. Besides, the surface potential distribution can effectively affect the airflow acceleration behavior. With the application of an appropriate additional DC bias, the surface potential will be modified. As a result, the performance of the electric wind produced by a single SDBD can be significantly improved. In addition, the work also illustrates that the actuators with more negative surface potential present better mechanical performance.

  5. RHIC spin flipper AC dipole controller

    SciTech Connect

    Oddo, P.; Bai, M.; Dawson, C.; Gassner, D.; Harvey, M.; Hayes, T.; Mernick, K.; Minty, M.; Roser, T.; Severino, F.; Smith, K.

    2011-03-28

    The RHIC Spin Flipper's five high-Q AC dipoles which are driven by a swept frequency waveform require precise control of phase and amplitude during the sweep. This control is achieved using FPGA based feedback controllers. Multiple feedback loops are used to and dynamically tune the magnets. The current implementation and results will be presented. Work on a new spin flipper for RHIC (Relativistic Heavy Ion Collider) incorporating multiple dynamically tuned high-Q AC-dipoles has been developed for RHIC spin-physics experiments. A spin flipper is needed to cancel systematic errors by reversing the spin direction of the two colliding beams multiple times during a store. The spin flipper system consists of four DC-dipole magnets (spin rotators) and five AC-dipole magnets. Multiple AC-dipoles are needed to localize the driven coherent betatron oscillation inside the spin flipper. Operationally the AC-dipoles form two swept frequency bumps that minimize the effect of the AC-dipole dipoles outside of the spin flipper. Both AC bumps operate at the same frequency, but are phase shifted from each other. The AC-dipoles therefore require precise control over amplitude and phase making the implementation of the AC-dipole controller the central challenge.

  6. The role of the defect levels in MgO in the low firing voltage, wide driving voltage margin operation of an alternate current plasma display panel

    NASA Astrophysics Data System (ADS)

    Ha, Chang Hoon; Kim, Joong Kyun; Whang, Ki-Woong

    2007-06-01

    In order to study the relationship between the discharge characteristics of an ac plasma display panel and the surface conductivity of a MgO thin film, we measured the surface current across a ring-shaped MgO film temporally induced by exposure to monochromatic vacuum ultraviolet radiation from a synchrotron radiation source whose wavelength ranges from 60 to 240 nm (5.5-25 eV). The experimental results show that the surface current begins to increase rapidly at a photon energy of about 9 eV which might correspond to the valence band edge of MgO. The differences in the surface current level correlate well with the differences in the preparation method of the MgO films and their respective discharge characteristics, such as firing, minimum sustained voltages, address voltage margins, and address discharge delay times. Surface charge measurements using the linear electro-optic effect also show consistent correlations with the surface current measurement of each MgO sample.

  7. First- and second-harmonic detection of spin accumulation in a multiterminal lateral spin valve under high-bias ac current

    NASA Astrophysics Data System (ADS)

    Hu, Shaojie; Nomura, Tatsuya; Uematsu, Ginga; Asam, Nagarjuna; Kimura, Takashi

    2016-07-01

    We have investigated the transport properties of electrically and thermally excited spin currents in a lateral spin valve consisting of a spin injector and detector with a middle ferromagnetic wire by detecting the first- and second-harmonic voltages. The first-harmonic spin signal was significantly suppressed by the middle ferromagnetic wire because of the spin absorption effect. On the other hand, in the second-harmonic signal, a small signal related to the middle ferromagnetic wire was observed in addition to a conventional spin signal with a reduced magnitude. This indicates that the additional ferromagnetic wire acts not only as the spin absorber but also as another spin injector under thermal spin injection, because the heat current caused by direct spin injection propagates to the middle ferromagnetic wire and creates another temperature gradient. By using this effect, we show that the magnetization direction of a ferromagnetic nanodot embedded in a nonmagnetic Cu wire becomes measurable.

  8. AC Conductivity and Dielectric Properties of Borotellurite Glass

    NASA Astrophysics Data System (ADS)

    Taha, T. A.; Azab, A. A.

    2016-10-01

    Borotellurite glasses with formula 60B2O3-10ZnO-(30 - x)NaF- xTeO2 ( x = 0 mol.%, 5 mol.%, 10 mol.%, and 15 mol.%) have been synthesized by thermal melting. X-ray diffraction (XRD) analysis confirmed that the glasses were amorphous. The glass density ( ρ) was determined by the Archimedes method at room temperature. The density ( ρ) and molar volume ( V m) were found to increase with increasing TeO2 content. The direct-current (DC) conductivity was measured in the temperature range from 473 K to 623 K, in which the electrical activation energy of ionic conduction increased from 0.27 eV to 0.48 eV with increasing TeO2 content from 0 mol.% to 15 mol.%. The dielectric parameters and alternating-current (AC) conductivity ( σ ac) were investigated in the frequency range from 1 kHz to 1 MHz and temperature range from 300 K to 633 K. The AC conductivity and dielectric constant decreased with increasing TeO2 content from 0 mol.% to 15 mol.%.

  9. AC Conductivity and Dielectric Properties of Borotellurite Glass

    NASA Astrophysics Data System (ADS)

    Taha, T. A.; Azab, A. A.

    2016-06-01

    Borotellurite glasses with formula 60B2O3-10ZnO-(30 - x)NaF-xTeO2 (x = 0 mol.%, 5 mol.%, 10 mol.%, and 15 mol.%) have been synthesized by thermal melting. X-ray diffraction (XRD) analysis confirmed that the glasses were amorphous. The glass density (ρ) was determined by the Archimedes method at room temperature. The density (ρ) and molar volume (V m) were found to increase with increasing TeO2 content. The direct-current (DC) conductivity was measured in the temperature range from 473 K to 623 K, in which the electrical activation energy of ionic conduction increased from 0.27 eV to 0.48 eV with increasing TeO2 content from 0 mol.% to 15 mol.%. The dielectric parameters and alternating-current (AC) conductivity (σ ac) were investigated in the frequency range from 1 kHz to 1 MHz and temperature range from 300 K to 633 K. The AC conductivity and dielectric constant decreased with increasing TeO2 content from 0 mol.% to 15 mol.%.

  10. High-latitude distributions of plasma waves and spatial irregularities from DE 2 alternating current electric field observations

    NASA Technical Reports Server (NTRS)

    Heppner, J. P.; Liebrecht, M. C.; Maynard, N. C.; Pfaff, R. F.

    1993-01-01

    The high-latitude spatial distributions of average signal intensities in 12 frequency channels between 4 Hz and 512 kHz as measured by the ac electric field spectrometers on the DE-2 spacecraft are analyzed for 18 mo of measurements. In MLT-INL (magnetic local time-invariant latitude) there are three distinct distributions that can be identified with 4-512 Hz signals from spatial irregularities and Alfven waves, 256-Hz to 4.1-kHz signals from ELF hiss, and 4.1-64 kHz signals from VLF auroral hiss, respectively. Overlap between ELF hiss and spatial irregularity signals occurs in the 256-512 Hz band. VLF hiss signals extend downward in frequency into the 1.0-4.1 kHz band and upward into the frequency range 128-512 kHz. The distinctly different spatial distribution patterns for the three bands, 4-256 Hz, 512-1204 Hz, and 4.1-64 kHz, indicate a lack of any causal relationships between VLF hiss, ELF hiss, and lower-frequency signals from spatial irregularities and Alfven waves.

  11. Phase Dependency of the Human Primary Motor Cortex and Cholinergic Inhibition Cancelation During Beta tACS

    PubMed Central

    Guerra, Andrea; Pogosyan, Alek; Nowak, Magdalena; Tan, Huiling; Ferreri, Florinda; Di Lazzaro, Vincenzo; Brown, Peter

    2016-01-01

    The human motor cortex has a tendency to resonant activity at about 20 Hz so stimulation should more readily entrain neuronal populations at this frequency. We investigated whether and how different interneuronal circuits contribute to such resonance by using transcranial magnetic stimulation (TMS) during transcranial alternating current stimulation (tACS) at motor (20 Hz) and a nonmotor resonance frequency (7 Hz). We tested different TMS interneuronal protocols and triggered TMS pulses at different tACS phases. The effect of cholinergic short-latency afferent inhibition (SAI) was abolished by 20 Hz tACS, linking cortical beta activity to sensorimotor integration. However, this effect occurred regardless of the tACS phase. In contrast, 20 Hz tACS selectively modulated MEP size according to the phase of tACS during single pulse, GABAAergic short-interval intracortical inhibition (SICI) and glutamatergic intracortical facilitation (ICF). For SICI this phase effect was more marked during 20 Hz stimulation. Phase modulation of SICI also depended on whether or not spontaneous beta activity occurred at ~20 Hz, supporting an interaction effect between tACS and underlying circuit resonances. The present study provides in vivo evidence linking cortical beta activity to sensorimotor integration, and for beta oscillations in motor cortex being promoted by resonance in GABAAergic interneuronal circuits. PMID:27522077

  12. Investigation of an alternating current plasma as an element selective atomic emission detector for high-resolution capillary gas chromatography and as a source for atomic absorption and atomic emission spectrometry

    NASA Astrophysics Data System (ADS)

    Ombaba, Jackson M.

    This thesis deals with the construction and evaluation of an alternating current plasma (ACP) as an element-selective detector for high resolution capillary gas chromatography (GC) and as an excitation source for atomic absorption spectrometry (AAS) and atomic emission spectrometry (AES). The plasma, constrained in a quartz discharge tube at atmospheric pressure, is generated between two copper electrodes and utilizes helium as the plasma supporting gas. The alternating current plasma power source consists of a step-up transformer with a secondary output voltage of 14,000 V at a current of 23 mA. The device exhibits a stable signal because the plasma is self-seeding and reignites itself every half cycle. A tesla coil is not required to commence generation of the plasma if the ac voltage applied is greater than the breakdown voltage of the plasma-supporting gas. The chromatographic applications studied included the following: (1) the separation and selective detection of the organotin species, tributyltin chloride (TBT) and tetrabutyltin (TEBT), in environmental matrices including mussels (Mvutilus edullus) and sediment from Boston Harbor, industrial waste water and industrial sludge, and (2) the detection of methylcyclopentadienyl manganesetricarbonyl (MMT) and similar compounds used as gasoline additives. An ultrasonic nebulizer (common room humidifier) was utilized as a sample introduction device for aqueous solutions when the ACP was employed as an atomization source for atomic absorption spectrometry and as an excitation source for atomic emission spectrometry. Plasma diagnostic parameters studied include spatial electron number density across the discharge tube, electronic, excitation and ionization temperatures. Interference studies both in absorption and emission modes were also considered. Figures of merits of selected elements both in absorption and emission modes are reported. The evaluation of a computer-aided optimization program, Drylab GC, using

  13. Current Status of Legislative Proposals on Greenhouse Gas Emissions and Alternative Energy in the U.S. Congress

    NASA Astrophysics Data System (ADS)

    Richardson, L. J.

    2007-12-01

    The 110th Congress is now beginning to grapple with the issue of human-induced climate change and what, if anything, to do about it. A number of bills are currently being considered that would limit greenhouse gas emissions using various policy mechanisms and over various time frames. With a commitment by the current Congressional leadership to pass legislation addressing global warming, and significant hurdles remaining, it promises to be an eventful fall session. I will review the current status of these legislative proposals and their prospects of becoming law.

  14. ACS: ALMA Common Software

    NASA Astrophysics Data System (ADS)

    Chiozzi, Gianluca; Šekoranja, Matej

    2013-02-01

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

  15. Subunit compositions of Arabidopsis RNA polymerases I and III reveal Pol I- and Pol III-specific forms of the AC40 subunit and alternative forms of the C53 subunit

    SciTech Connect

    Ream, Thomas S.; Haag, Jeremy R.; Pontvianne, Frederic; Nicora, Carrie D.; Norbeck, Angela D.; Pasa-Tolic, Ljiljana; Pikaard, Craig S.

    2015-05-02

    Using affinity purification and mass spectrometry, we identified the subunits of Arabidopsis thaliana multisubunit RNA Polymerases I and III (abbreviated as Pol I and Pol III), providing the first description of their physical compositions in plants. AC40 and AC19 subunits are typically common to Pol I (a.k.a. Pol A) and Pol III (a.k.a. Pol C) and are encoded by single genes whose mutation, in humans, is a cause of the craniofacial disorder, Treacher-Collins Syndrome. Surprisingly, A. thaliana, and related species, express two distinct AC40 paralogs, one of which assembles into Pol I and the other of which assembles into Pol III. Changes at eight amino acid positions correlate with this functional divergence of Pol I and Pol III-specific AC40 paralogs. Two genes encode homologs of the yeast C53 subunit, and either variant can assemble into Pol III. By contrast, only one of two potential C17 variants, and one of two potential C31 variants were detected in Pol III. We introduce a new nomenclature system for plant Pol I and Pol III subunits in which the twelve subunits that are structurally and functionally homologous among Pols I through V are assigned equivalent numbers.

  16. Subunit compositions of Arabidopsis RNA polymerases I and III reveal Pol I- and Pol III-specific forms of the AC40 subunit and alternative forms of the C53 subunit

    DOE PAGES

    Ream, Thomas S.; Haag, Jeremy R.; Pontvianne, Frederic; Nicora, Carrie D.; Norbeck, Angela D.; Pasa-Tolic, Ljiljana; Pikaard, Craig S.

    2015-05-02

    Using affinity purification and mass spectrometry, we identified the subunits of Arabidopsis thaliana multisubunit RNA Polymerases I and III (abbreviated as Pol I and Pol III), providing the first description of their physical compositions in plants. AC40 and AC19 subunits are typically common to Pol I (a.k.a. Pol A) and Pol III (a.k.a. Pol C) and are encoded by single genes whose mutation, in humans, is a cause of the craniofacial disorder, Treacher-Collins Syndrome. Surprisingly, A. thaliana, and related species, express two distinct AC40 paralogs, one of which assembles into Pol I and the other of which assembles into Polmore » III. Changes at eight amino acid positions correlate with this functional divergence of Pol I and Pol III-specific AC40 paralogs. Two genes encode homologs of the yeast C53 subunit, and either variant can assemble into Pol III. By contrast, only one of two potential C17 variants, and one of two potential C31 variants were detected in Pol III. We introduce a new nomenclature system for plant Pol I and Pol III subunits in which the twelve subunits that are structurally and functionally homologous among Pols I through V are assigned equivalent numbers.« less

  17. Why Current Doppler Ultrasound Methodology Is Inaccurate in Assessing Cerebral Venous Return: The Alternative of the Ultrasonic Jugular Venous Pulse

    PubMed Central

    2016-01-01

    Assessment of cerebral venous return is growing interest for potential application in clinical practice. Doppler ultrasound (DUS) was used as a screening tool. However, three meta-analyses of qualitative DUS protocol demonstrate a big heterogeneity among studies. In an attempt to improve accuracy, several authors alternatively measured the flow rate, based on the product of the time average velocity with the cross-sectional area (CSA). However, also the quantification protocols lacked of the necessary accuracy. The reasons are as follows: (a) automatic measurement of the CSA assimilates the jugular to a circle, while it is elliptical; (b) the use of just a single CSA value in a pulsatile vessel is inaccurate; (c) time average velocity assessment can be applied only in laminar flow. Finally, the tutorial describes alternative ultrasound calculation of flow based on the Womersley method, which takes into account the variation of the jugular CSA overtime. In the near future, it will be possible to synchronize the electrocardiogram with the brain inflow (carotid distension wave) and with the outflow (jugular venous pulse) in order to nicely have a noninvasive ultrasound picture of the brain-heart axis. US jugular venous pulse may have potential use in neurovascular, neurocognitive, neurosensorial, and neurodegenerative disorders. PMID:27006525

  18. A new green phosphor of SrAl{sub 2}O{sub 4}:Eu{sup 2+},Ce{sup 3+},Li{sup +} for alternating current driven light-emitting diodes

    SciTech Connect

    Chen, Lei; Zhang, Yao; Liu, Fayong; Luo, Anqi; Chen, Zhixin; Jiang, Yang; Chen, Shifu; Liu, Ru-Shi

    2012-12-15

    Graphical abstract: Display Omitted Highlights: ► This work focuses on exploring new phosphors of SrAl{sub 2}O{sub 4}:Eu{sup 2+},Ce{sup 3+},Li{sup +} for AC LEDs. ► The work provides a new route to synthesize the pure phase of SrAl{sub 2}O{sub 4}. ► The formation of the impurity phase of Sr{sub 4}Al{sub 14}O{sub 25} was suppressed by using Ce{sup 3+}. ► Charger defects were compensated by using Li{sup +}. ► The luminescence intensity was enhanced significantly by co-doping Ce{sup 3+} and Li{sup +}. -- Abstract: New phosphors are desired to overcoming the flickering luminescence of alternating current light-emitting diodes (AC-LEDs) by compensating dark duration with appropriately persistent luminescence. Here, the phosphor of SrAl{sub 2}O{sub 4}:Eu{sup 2+},Ce{sup 3+},Li{sup +} was developed for this application. The phosphor was synthesized with solid-state reaction method by using H{sub 3}BO{sub 3} as flux. The XRD patterns show that the impurity phase of Sr{sub 4}Al{sub 14}O{sub 25} which always formed together with SrAl{sub 2}O{sub 4} during reaction was suppressed by using Ce. The charger defects caused by the non-equivalent substitution of Sr{sup 2+} with Ce{sup 3+} were compensated with Li{sup +}. Thus, the luminescence intensity of SrAl{sub 2}O{sub 4}:Eu{sup 2+} was enhanced significantly by co-doping Ce{sup 3+} and Li{sup +}. The fluorescence lifetime of the phosphor is about 36.5 ms. The energy dispersive spectra (EDS) assisted with scanning electron microscope (SEM) pictures reveal that Ce ions mainly distribute along grain boundary.

  19. Effective AC needleless and collectorless electrospinning for yarn production.

    PubMed

    Pokorny, P; Kostakova, E; Sanetrnik, F; Mikes, P; Chvojka, J; Kalous, T; Bilek, M; Pejchar, K; Valtera, J; Lukas, D

    2014-12-28

    Nanofibrous materials are essential components for a wide range of applications, particularly in the fields of medicine and material engineering. These include protective materials, sensors, cosmetics, hygiene, filtration and energy storage. The most widely used and researched technology in these fields is electrospinning. This method for producing fibers yields highly promising results thanks to its versatility and simplicity. Electrospinning is employed in multiple forms, among which needle and needleless direct current (DC) variants are the most distinctive. The former is based on the generation of just one single jet from a nozzle; hence this fabrication process is not very productive. The latter uses the destabilization of free liquid surfaces by means of an electric field, which enhances the throughput since it produces numerous jets, emitted from the surfaces of rollers, spheres, strings and spirals. However, although some progress in total producibility has been achieved, the efficiency of the DC method still remains relatively low. A further drawback of DC electrospinning is that both variants need a collector, which makes it difficult to combine DC electrospinning easily with other technologies due to the presence of the high field strength within the entire spinning zone. This paper describes our experiments with AC electrospinning. We show that alternating current (AC) electrospinning based on a needleless spinning-electrode provides a highly productive smoke-like aerogel composed of nanofibers. This aerogel rises rapidly from the electrode like a thin plume of smoke, without any need for a collector. Our work shows that AC needleless electrospinning gains its efficiency and collector-less feature thanks to the creation of a perpetually charge-changing virtual counter-electrode composed of the nanofibers emitted. High-speed camera recordings demonstrate the formation mechanism of the nanofibrous plume, which is wafted by an electric wind. This wind

  20. Weldability of thin sheet metals during small-scale resistance spot welding using an alternating-current power supply

    NASA Astrophysics Data System (ADS)

    Zhou, Y.; Gorman, P.; Tan, W.; Ely, K. J.

    2000-09-01

    The resistance weldability of 0.2-mm-thick sheet aluminum, brass, and copper in small-scale resistance spot welding (SSRSW) was studied. The effects of electrode materials and process parameters on joint strength and nugget size were investigated. The welding current ranges for SSRSW of the sheet metals were determined based on the minimum current that produced a required nugget diameter and maximum currents that did not result in electrode-sheet sticking or weld metal expulsion. A qualitative analysis indicated that resistance weldability of the metals is not only determined by their resistivity (or thermal conductivity) but is also affected by other physical properties (such as melting point, latent heat of fusion and specific heat).

  1. A Study of Second-Year Engineering Students' Alternative Conceptions about Electric Potential, Current Intensity and Ohm's Law

    ERIC Educational Resources Information Center

    Periago, M. Cristina; Bohigas, Xavier

    2005-01-01

    The aim of this research was to evaluate and analyse second-year industrial engineering and chemical engineering students prior knowledge of conceptual aspects of "circuit theory". Specifically, we focused on the basic concepts of electric potential and current intensity and on the fundamental relationship between them as expressed by Ohm's law.…

  2. Complementary and Alternative Methods and Cancer

    MedlinePlus

    ... My Saved Articles » My ACS » Complementary and Alternative Methods and Cancer Download Printable Version [PDF] » ( En español ) ... with cancer here. What are complementary and alternative methods? How are complementary methods used to manage cancer? ...

  3. Transverse Mode Dynamics of VCSELs Undergoing Current Modulation

    NASA Technical Reports Server (NTRS)

    Goorjian, Peter M.; Ning, C. Z.; Agrawal, Govind

    2000-01-01

    Transverse mode dynamics of a 20-micron-diameter vertical-cavity surface-emitting laser (VCSEL) undergoing gain switching by deep current modulation is studied numerically. The direct current (dc) level is set slightly below threshold and is modulated by a large alternating current (ac). The resulting optical pulse train and transverse-mode patterns are obtained numerically. The ac frequency is varied from 2.5 GHz to 10 GHz, and the ac amplitude is varied from one-half to four times that of the dc level. At high modulation frequencies, a regular pulse train is not generated unless the ac amplitude is large enough. At all modulation frequencies, the transverse spatial profile switches from single-mode to multiple-mode pattern as the ac pumping level is increased. Optical pulse widths vary in the range 5-30 ps. with the pulse width decreasing when either the frequency is increased or the ac amplitude is decreased. The numerical modeling uses an approximation form of the semiconductor Maxwell-Bloch equations. Temporal evolution of the spatial profiles of the laser (and of carrier density) is determined without any assumptions about the type or number of modes. Keywords: VCSELs, current modulation, gain switching, transverse mode dynamics, computational modeling

  4. A Medicare Current Beneficiary Survey-Based Investigation of Alternative Primary Care Models in Nursing Homes: Cost and Utilization Differences.

    PubMed

    Lee, A James; Gautam, Ramraj; Melillo, Karen Devereaux; Abdallah, Lisa M; Remington, Ruth; Van Etten, Deborah; Gore, Rebecca

    2016-05-01

    The current study used the Medicare Current Beneficiary Survey-Based (MCBS) Cost and Use files for 2006-2008 to investigate whether health care costs and service utilization of nursing home residents varied with nurse practitioner (NP) and physician assistant (PA) involvement, compared to the use of medical doctors (MDs) only. The sample included Medicare beneficiaries 65 and older residing in a nursing home for the entire study year (433 annual observations). A generalized estimating equations procedure was used to assess whether health care cost and utilization measures varied by cohort. Point estimates indicated that the annual per-person cost of non-institutional services (total medical cost less the cost of the nursing home itself) was $3,847 and $3,170 more for individuals in the MD-only and MD-dominant cohorts, respectively, compared to those in the NP/PA-dominant cohort. [Res Gerontol Nurs. 2016; 9(3):115-122.].

  5. Inflight Microbial Monitoring - An Alternative Method to Culture Based Detection Currently Used on the International Space Station

    NASA Technical Reports Server (NTRS)

    Khodadad, Christina L.; Birmele, Michele N.; Hummerick, Mary E.; Roman, Monsi; Smith, David J.

    2015-01-01

    Microorganisms including potential human pathogens have been detected on the International Space Station (ISS). The potential to introduce new microorganisms occurs with every exchange of crew or addition of equipment or supplies. Current microbial monitoring methods require enrichment of microorganisms and a 48-hour incubation time resulting in an increase in microbial load, detecting a limited number of unidentified microorganisms. An expedient, low-cost, in-flight method of microbial detection, identification, and enumeration is warranted.

  6. Electroporation of cells using EM induction of ac fields by a magnetic stimulator

    NASA Astrophysics Data System (ADS)

    Chen, C.; Evans, J. A.; Robinson, M. P.; Smye, S. W.; O'Toole, P.

    2010-02-01

    This paper describes a method of effectively electroporating mammalian cell membranes with pulsed alternating-current (ac) electric fields at field strengths of 30-160 kV m-1. Although many in vivo electroporation protocols entail applying square wave or monotonically decreasing pulses via needles or electrode plates, relatively few have explored the use of pulsed ac fields. Following our previous study, which established the effectiveness of ac fields for electroporating cell membranes, a primary/secondary coil system was constructed to produce sufficiently strong electric fields by electromagnetic induction. The primary coil was formed from the applicator of an established transcranial magnetic stimulation (TMS) system, while the secondary coil was a purpose-built device of a design which could eventually be implanted into tissue. The effects of field strength, pulse interval and cumulative exposure time were investigated using microscopy and flow cytometry. Results from experiments on concentrated cell suspensions showed an optimized electroporation efficiency of around 50%, demonstrating that electroporation can be practicably achieved by inducing such pulsed ac fields. This finding confirms the possibility of a wide range of in vivo applications based on magnetically coupled ac electroporation.

  7. Stimulus Presentation at Specific Neuronal Oscillatory Phases Experimentally Controlled with tACS: Implementation and Applications

    PubMed Central

    ten Oever, Sanne; de Graaf, Tom A.; Bonnemayer, Charlie; Ronner, Jacco; Sack, Alexander T.; Riecke, Lars

    2016-01-01

    In recent years, it has become increasingly clear that both the power and phase of oscillatory brain activity can influence the processing and perception of sensory stimuli. Transcranial alternating current stimulation (tACS) can phase-align and amplify endogenous brain oscillations and has often been used to control and thereby study oscillatory power. Causal investigation of oscillatory phase is more difficult, as it requires precise real-time temporal control over both oscillatory phase and sensory stimulation. Here, we present hardware and software solutions allowing temporally precise presentation of sensory stimuli during tACS at desired tACS phases, enabling causal investigations of oscillatory phase. We developed freely available and easy to use software, which can be coupled with standard commercially available hardware to allow flexible and multi-modal stimulus presentation (visual, auditory, magnetic stimuli, etc.) at pre-determined tACS-phases, opening up a range of new research opportunities. We validate that stimulus presentation at tACS phase in our setup is accurate to the sub-millisecond level with high inter-trial consistency. Conventional methods investigating the role of oscillatory phase such as magneto-/electroencephalography can only provide correlational evidence. Using brain stimulation with the described methodology enables investigations of the causal role of oscillatory phase. This setup turns oscillatory phase into an independent variable, allowing innovative, and systematic studies of its functional impact on perception and cognition. PMID:27803651

  8. High-Resolution Hepatitis C Virus Subtyping Using NS5B Deep Sequencing and Phylogeny, an Alternative to Current Methods

    PubMed Central

    Gregori, Josep; Rodríguez-Frias, Francisco; Buti, Maria; Madejon, Antonio; Perez-del-Pulgar, Sofia; Garcia-Cehic, Damir; Casillas, Rosario; Blasi, Maria; Homs, Maria; Tabernero, David; Alvarez-Tejado, Miguel; Muñoz, Jose Manuel; Cubero, Maria; Caballero, Andrea; delCampo, Jose Antonio; Domingo, Esteban; Belmonte, Irene; Nieto, Leonardo; Lens, Sabela; Muñoz-de-Rueda, Paloma; Sanz-Cameno, Paloma; Sauleda, Silvia; Bes, Marta; Gomez, Jordi; Briones, Carlos; Perales, Celia; Sheldon, Julie; Castells, Lluis; Viladomiu, Lluis; Salmeron, Javier; Ruiz-Extremera, Angela; Quiles-Pérez, Rosa; Moreno-Otero, Ricardo; López-Rodríguez, Rosario; Allende, Helena; Romero-Gómez, Manuel; Guardia, Jaume; Esteban, Rafael; Garcia-Samaniego, Javier; Forns, Xavier

    2014-01-01

    Hepatitis C virus (HCV) is classified into seven major genotypes and 67 subtypes. Recent studies have shown that in HCV genotype 1-infected patients, response rates to regimens containing direct-acting antivirals (DAAs) are subtype dependent. Currently available genotyping methods have limited subtyping accuracy. We have evaluated the performance of a deep-sequencing-based HCV subtyping assay, developed for the 454/GS-Junior platform, in comparison with those of two commercial assays (Versant HCV genotype 2.0 and Abbott Real-time HCV Genotype II) and using direct NS5B sequencing as a gold standard (direct sequencing), in 114 clinical specimens previously tested by first-generation hybridization assay (82 genotype 1 and 32 with uninterpretable results). Phylogenetic analysis of deep-sequencing reads matched subtype 1 calling by population Sanger sequencing (69% 1b, 31% 1a) in 81 specimens and identified a mixed-subtype infection (1b/3a/1a) in one sample. Similarly, among the 32 previously indeterminate specimens, identical genotype and subtype results were obtained by direct and deep sequencing in all but four samples with dual infection. In contrast, both Versant HCV Genotype 2.0 and Abbott Real-time HCV Genotype II failed subtype 1 calling in 13 (16%) samples each and were unable to identify the HCV genotype and/or subtype in more than half of the non-genotype 1 samples. We concluded that deep sequencing is more efficient for HCV subtyping than currently available methods and allows qualitative identification of mixed infections and may be more helpful with respect to informing treatment strategies with new DAA-containing regimens across all HCV subtypes. PMID:25378574

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

    NASA Astrophysics Data System (ADS)

    Riba, Jordi-Roger

    2015-09-01

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

  10. Inflight Microbial Monitoring- An Alternative Method to Culture Based Detection Currently Used on the International Space Station

    NASA Technical Reports Server (NTRS)

    Khodadad, Christina L.; Birmele, Michele N.; Roman, Monsi; Hummerick, Mary E.; Smith, David J.; Wheeler, Raymond M.

    2015-01-01

    Previous research has shown that potentially destructive microorganisms and human pathogens have been detected on the International Space Station (ISS). The likelihood of introducing new microorganisms occurs with every exchange of crew or addition of equipment or supplies. Microorganisms introduced to the ISS are readily transferred between crew and subsystems (i.e. ECLSS, environmental control and life support systems). Current microbial characterization methods require enrichment of microorganisms and at least a 48-hour incubation time. This increases the microbial load while detecting only a limited number of the total microorganisms. The culture based method detects approximately 1-10% of the total organisms present and provides no identification. To identify and enumerate ISS microbes requires that samples be returned to Earth for complete analysis. Therefore, a more expedient, low-cost, in-flight method of microbial detection, identification, and enumeration is warranted. The RAZOR EX, a ruggedized, commercial off the shelf, real-time PCR field instrument was tested for its ability to detect microorganisms at low concentrations within one hour. Escherichia coli, Salmonella enterica Typhimurium, and Pseudomonas aeruginosa were detected at low levels using real-time DNA amplification. Total heterotrophic counts could also be detected using a 16S gene marker that can identify up to 98% of all bacteria. To reflect viable cells found in the samples, RNA was also detectable using a modified, single-step reverse transcription reaction.

  11. Inflight Microbial Monitoring-An Alternative Method to Culture Based Detection Currently Used on International Space Station

    NASA Technical Reports Server (NTRS)

    Khodadad, Christina L.; Birmele, Michele N.; Roman, Monsi; Hummerick, Mary E.; Smith, David J.; Wheeler, Raymond M.

    2015-01-01

    Previous research has shown that microorganisms and potential human pathogens have been detected on the International Space Station (ISS). The potential to introduce new microorganisms occurs with every exchange of crew or addition of equipment or supplies. Previous research has shown that microorganisms introduced to the ISS are readily transferred between crew and subsystems and back (i.e. ECLSS, environmental control and life support systems). Current microbial characterization methods require enrichment of microorganisms and a 48-hour incubation time. This increases the microbial load while detecting a limited number of microorganisms. The culture based method detects approximately 1-10% of the total organisms present and provides no identification, To identify and enumerate ISS samples requires that samples to be returned to Earth for complete analysis. Therefore, a more expedient, low-cost, in-flight method of microbial detection, identification, and enumeration is warranted. The RAZOR EX, a ruggedized, commercial off the shelf, real-time PCR field instrument was tested for its ability to detect microorganism at low concentrations within one hour. Escherichia coli, Salmonella enterica Typhimurium, and Pseudomonas aeruginosa were detected at low levels using real-time DNA amplification. Total heterotrophic counts could also be detected using a 16S gene marker that can identify up to 98% of all bacteria. To reflect viable cells found in the samples, RNA was also detectable using a modified, single-step reverse transcription reaction.

  12. The AC-120: The advanced commercial transport

    NASA Technical Reports Server (NTRS)

    Duran, David; Griffin, Ernest; Mendoza, Saul; Nguyen, Son; Pickett, Tim; Noernberg, Clemm

    1993-01-01

    The main objective of this design was to fulfill a need for a new airplane to replace the aging 100 to 150 passenger, 1500 nautical mile range aircraft such as the Douglas DC9 and Boeing 737-100 airplanes. After researching the future aircraft market, conducting extensive trade studies, and analysis on different configurations, the AC-120 Advanced Commercial Transport final design was achieved. The AC-120's main design features include the incorporation of a three lifting surface configuration which is powered by two turboprop engines. The AC-120 is an economically sensitive aircraft which meets the new FM Stage Three noise requirements, and has lower NO(x) emissions than current turbofan powered airplanes. The AC-120 also improves on its contemporaries in passenger comfort, manufacturing, and operating cost.

  13. AC magnetohydrodynamic microfluidic switch

    SciTech Connect

    Lemoff, A V; Lee, A P

    2000-03-02

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

  14. AC Conductivity and Dielectric Relaxation Behavior of Sb2S3 Bulk Material

    NASA Astrophysics Data System (ADS)

    Abd El-Rahman, K. F.; Darwish, A. A. A.; Qashou, Saleem I.; Hanafy, T. A.

    2016-07-01

    The Sb2S3 bulk material was used for next-generation anode for lithium-ion batteries. Alternative current (AC) conductivity, dielectric properties and electric modulus of Sb2S3 have been investigated. The measurements were carried out in the frequency range from 40 Hz to 5 MHz and temperature range from 293 K to 453 K. The direct current (DC) conductivity, σ DC, shows an activated behavior and the calculated activation energy is 0.50 eV. The AC conductivity, σ AC, was found to increase with the increase of temperature and frequency. The conduction mechanism of σ AC was controlled by the correlated barrier hopping model. The behavior of the dielectric constant, ɛ', and dielectric loss index, ɛ'', reveal that the polarization process of Sb2S3 is dipolar in nature. The behavior of both ɛ' and ɛ'' reveals that bulk Sb2S3 has no ferroelectric or piezoelectric phase transition. The dielectric modulus, M, gives a simple method for evaluating the activation energy of the dielectric relaxation. The calculated activation energy from M is 0.045 eV.

  15. Current status of neonatal care and alternate strategies for reduction of neonatal mortality in the decade of nineties.

    PubMed

    Bhargava, S K; Ramji, S; Sachdev, H P

    1991-12-01

    Improvement in neonatal care in India is needed in order to fulfill the National Health Policy to reduce infant and perinatal mortality and low birth weight babies. 50-60% of perinatal and infant mortality is due to neonatal mortality, specifically low birth weight. There have been no declines in any of the states even though there are literacy, fertility, poverty and health personnel differences between states. The health delivery system is described. Basic facilities are lacking in subcenters and primary health centers: weighing scales, blood pressure recorder, urine analysis, and blood transfusion capability; pregnancy registration is 40%. 40% of women believe that the female multipurpose worker (ANM) is a maternal and child health worker; Dais made postnatal visits to 25% of the women and infants, while physicians and ANM's visited 10%. The most frequent method of delivery is home delivery with a Dai or relative in attendance. Information on temperature control at birth, hand washing, feeding, and identification of high risk infants by health personnel is inadequate. There are no neonatal units in the entire country even though there are 8 million low birth weight babies/year and 1 million neonatal deaths/year. Neonatal causes are primarily birth injuries, aspiration syndrome, and neonatal infections (tetanus, pneumonia, and diarrhea). Studies have identified health service improvements to reduce neonatal mortality. In India, the priority should be to 1) establish delivery of neonatal and perinatal care at all 3 levels of care, 2) train and educate all health personnel in perinatal and neonatal care, and 3) improve community participation by involving the community in decision making on kind of care, perinatal care, and health education and by monitoring such services. Infant care must extend from prenatal through postnatal care, which is currently fragmented, through a 3-tiered system. 80-85% of all infants need care at Level I; 15-20% require Level II care

  16. Induced- and alternating-current electro-osmotic control of the diffusion layer growth in a microchannel-membrane interface device

    NASA Astrophysics Data System (ADS)

    Park, Sinwook; Yossifon, Gilad

    2014-11-01

    The passage of an electric current through an ionic permselective medium under an applied electric field is characterized by the formation of ionic concentration gradients, which result in regions of depleted and enriched ionic concentration at opposite ends of the medium. Induced-current electro-osmosis (ICEO) and alternating-current-electro-osmosis (ACEO) are shown to control the growth of the diffusion layer (DL) which, in turn, controls the diffusion limited ion transport through the microchannel-membrane system. We fabricated and tested devices made of a Nafion membrane connecting two opposite PDMS microchannels. An interdigitated electrode array was embedded within the microchannel with various distances from the microchannel-membrane interface. The induced ICEO (floating electrodes) / ACEO (active electrodes) vortices formed at the electrode array stir the fluid and thereby suppress the growth of the DL. The intensity of the ACEO vortices is controlled by either varying the voltage amplitude or the frequency, each having its own unique effect. Enhancement of the limiting current by on-demand control of the diffusion length is of importance in on-chip electro-dialysis, desalination and preconcentration of analytes.

  17. Isolation of sequences flanking Ac insertion sites by Ac casting.

    PubMed

    Wang, Dafang; Peterson, Thomas

    2013-01-01

    Localizing Ac insertions is a fundamental task in studying Ac-induced mutation and chromosomal rearrangements involving Ac elements. Researchers may sometimes be faced with the situation in which the sequence flanking one side of an Ac/Ds element is known, but the other flank is unknown. Or, a researcher may have a small sequence surrounding the Ac/Ds insertion site and needs to obtain additional flanking genomic sequences. One way to rapidly clone unknown Ac/Ds flanking sequences is via a PCR-based method termed Ac casting. This approach utilizes the somatic transposition activity of Ac during plant development, and provides an efficient means for short-range genome walking. Here we describe the principle of Ac casting, and show how it can be applied to isolate Ac macrotransposon insertion sites.

  18. Current level detector

    DOEpatents

    Kerns, Cordon R.

    1977-01-01

    A device is provided for detecting the current level of a DC signal. It includes an even harmonic modulator to which a reference AC signal is applied. The unknown DC signal acts on the reference AC signal so that the output of the modulator includes an even harmonic whose amplitude is proportional to the unknown DC current.

  19. Optimization of spin-torque switching using AC and DC pulses

    SciTech Connect

    Dunn, Tom; Kamenev, Alex

    2014-06-21

    We explore spin-torque induced magnetic reversal in magnetic tunnel junctions using combined AC and DC spin-current pulses. We calculate the optimal pulse times and current strengths for both AC and DC pulses as well as the optimal AC signal frequency, needed to minimize the Joule heat lost during the switching process. The results of this optimization are compared against numeric simulations. Finally, we show how this optimization leads to different dynamic regimes, where switching is optimized by either a purely AC or DC spin-current, or a combination AC/DC spin-current, depending on the anisotropy energies and the spin-current polarization.

  20. AC-3 audio coder

    NASA Astrophysics Data System (ADS)

    Todd, Craig

    1995-12-01

    AC-3 is a system for coding up to 5.1 channels of audio into a low bit-rate data stream. High quality may be obtained with compression ratios approaching 12-1 for multichannel audio programs. The high compression ratio is achieved by methods which do not increase decoder memory, and thus cost. The methods employed include: the transmission of a high frequency resolution spectral envelope; and a novel forward/backward adaptive bit allocation algorithm. In order to satisfy practical requirements of an emissions coder, the AC-3 syntax includes a number of features useful to broadcasters and consumers. These features include: loudness uniformity between programs; dynamic range control; and broadcaster control of downmix coefficients. The AC-3 coder has been formally selected for inclusion of the U.S. HDTV broadcast standard, and has been informally selected for several additional applications.

  1. ac bidirectional motor controller

    NASA Technical Reports Server (NTRS)

    Schreiner, K.

    1988-01-01

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

  2. Cyclotron and linac production of Ac-225.

    PubMed

    Melville, Graeme; Allen, Barry J

    2009-04-01

    Radium needles that were once implanted into tumours as a cancer treatment are now obsolete and constitute a radioactive waste problem, as their half-life is 1600 years. The reduction of radium by photonuclear transmutation by bombarding Ra-226 with high-energy photons from a medical linear accelerator (linac) has been investigated. A linac dose of 2800 Gy produced about 2.4 MBq (64 microCi) of Ra-225, which decays to Ac-225 and can then be used for 'Targeted Alpha Therapy' (TAT) of cancer. This result, while consistent with theoretical calculations, is far too low to be of practical use unless much larger quantities of radium are irradiated. The increasing application of Ac-225 for cancer therapy indicates the potential need for its increased production and availability. This paper investigates the possibility of producing of Ac-225 in commercial quantities, which could potentially reduce obsolete radioactive material and displace the need for expensive importation of Ac-225 from the USA and Russia in the years ahead. Scaled up production of Ac-225 could theoretically be achieved by the use of a high current cyclotron or linac. Production specifications are determined for a linac in terms of current, pulse length and frequency, as well as an examination of other factors such as radiation issues and radionuclei separation. Yields are compared with those calculated for the Australian National Cyclotron in Sydney.

  3. ac electroosmosis in rectangular microchannels.

    PubMed

    Campisi, Michele; Accoto, Dino; Dario, Paolo

    2005-11-22

    Motivated by the growing interest in ac electroosmosis as a reliable no moving parts strategy to control fluid motion in microfluidic devices for biomedical applications, such as lab-on-a-chip, we study transient and steady-state electrokinetic phenomena (electroosmosis and streaming currents) in infinitely extended rectangular charged microchannels. With the aid of Fourier series and Laplace transforms we provide a general formal solution of the problem, which is used to study the time-dependent response to sudden ac applied voltage differences in case of finite electric double layer. The Debye-Huckel approximation has been adopted to allow for an algebraic solution of the Poisson-Boltzmann problem in Fourier space. We obtain the expressions of flow velocity profiles, flow rates, streaming currents, as well as expressions of the complex hydraulic and electrokinetic conductances. We analyze in detail the dependence of the electrokinetic conductance on the extension of linear dimensions relative to the Debye length, with an eye on finite electric double layer effects. PMID:16351310

  4. AC biosusceptometry in the study of drug delivery.

    PubMed

    Corá, L A; Romeiro, F G; Stelzer, M; Américo, M F; Oliveira, R B; Baffa, O; Miranda, J R A

    2005-06-15

    Conventionally, pharmaceutical substances are administered orally because the gastrointestinal tract possesses the appropriate features for drug absorption. Nevertheless, the gastrointestinal tract physiology is complex and influenced by many factors. These factors must be completely understood for the optimization of oral drug delivery systems. Although in vitro tests provide information about release and drug absorption profiles, in vivo studies are essential, due to the biological variability. Several techniques have been employed in an attempt to conveniently characterize the behavior of solid dosage forms in vivo. The noninvasive biomagnetic technique of alternate current biosusceptometry (ACB) has been used in studies focusing on gastrointestinal motility and, more recently, to evaluate the performance of magnetic dosage forms. This article will discuss the main characteristics of AC biosusceptometry and its applicability for determination of the relationship between the human gastrointestinal tract and orally administered pharmaceutical dosage forms.

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

    DOEpatents

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

    2013-02-26

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

  6. Probing the causal role of prestimulus interregional synchrony for perceptual integration via tACS

    PubMed Central

    Stonkus, Rolandas; Braun, Verena; Kerlin, Jess R.; Volberg, Gregor; Hanslmayr, Simon

    2016-01-01

    The phase of prestimulus oscillations at 7–10 Hz has been shown to modulate perception of briefly presented visual stimuli. Specifically, a recent combined EEG-fMRI study suggested that a prestimulus oscillation at around 7 Hz represents open and closed windows for perceptual integration by modulating connectivity between lower order occipital and higher order parietal brain regions. We here utilized brief event-related transcranial alternating current stimulation (tACS) to specifically modulate this prestimulus 7 Hz oscillation, and the synchrony between parietal and occipital brain regions. To this end we tested for a causal role of this particular prestimulus oscillation for perceptual integration. The EEG was acquired at the same time allowing us to investigate frequency specific after effects phase-locked to stimulation offset. On a behavioural level our results suggest that tACS did modulate perceptual integration, however, in an unexpected manner. On an electrophysiological level our results suggest that brief tACS does induce oscillatory entrainment, as visible in frequency specific activity phase-locked to stimulation offset. Together, our results do not strongly support a causal role of prestimulus 7 Hz oscillations for perceptual integration. However, our results suggest that brief tACS is capable of modulating oscillatory activity in a temporally sensitive manner. PMID:27616188

  7. Contact-Free Templating of 3-D Colloidal Structures Using Spatially Nonuniform AC Electric Fields.

    PubMed

    Raveendran, Joshua; Wood, Jeffery A; Docoslis, Aristides

    2016-09-20

    The formation of ordered and regularly shaped structures of colloidal particles with the aid of spatially nonuniform electric fields is a modern research area of great interest. This work illustrates how alternating current (AC) electrokinetic effects (dielectrophoresis, electroosmosis) can serve as contact-free templates, inside which colloidal microspheres can assemble into a variety of shapes and sizes. We show how three-dimensional colloidal structures of square, circular, and diamond shape of many tens of micrometers in size can be reproducibly formed with a single set of quadrupolar microelectrodes. Numerical simulations performed help to explain the role of AC electroosmosis and AC dielectrophoresis on the shaping of these structures as a function of applied voltage and frequency. We also demonstrate how the templating repertoire is further enhanced with the simultaneous application of a second, individually controlled AC electric field, which enables a variety of asymmetric colloidal structures to be produced using the same set of quadrupolar microelectrodes. As the preservation of shape and size of such electric-field templated structures after medium evaporation still remains a big challenge, here we also report on a novel method that permits the stabilization and isolation of these particle assemblies through medium gelation and subsequent hydrogel removal with a UV/ozone treatment.

  8. Probing the causal role of prestimulus interregional synchrony for perceptual integration via tACS.

    PubMed

    Stonkus, Rolandas; Braun, Verena; Kerlin, Jess R; Volberg, Gregor; Hanslmayr, Simon

    2016-01-01

    The phase of prestimulus oscillations at 7-10 Hz has been shown to modulate perception of briefly presented visual stimuli. Specifically, a recent combined EEG-fMRI study suggested that a prestimulus oscillation at around 7 Hz represents open and closed windows for perceptual integration by modulating connectivity between lower order occipital and higher order parietal brain regions. We here utilized brief event-related transcranial alternating current stimulation (tACS) to specifically modulate this prestimulus 7 Hz oscillation, and the synchrony between parietal and occipital brain regions. To this end we tested for a causal role of this particular prestimulus oscillation for perceptual integration. The EEG was acquired at the same time allowing us to investigate frequency specific after effects phase-locked to stimulation offset. On a behavioural level our results suggest that tACS did modulate perceptual integration, however, in an unexpected manner. On an electrophysiological level our results suggest that brief tACS does induce oscillatory entrainment, as visible in frequency specific activity phase-locked to stimulation offset. Together, our results do not strongly support a causal role of prestimulus 7 Hz oscillations for perceptual integration. However, our results suggest that brief tACS is capable of modulating oscillatory activity in a temporally sensitive manner. PMID:27616188

  9. Individual differences and specificity of prefrontal gamma frequency-tACS on fluid intelligence capabilities.

    PubMed

    Santarnecchi, E; Muller, T; Rossi, S; Sarkar, A; Polizzotto, N R; Rossi, A; Cohen Kadosh, R

    2016-02-01

    Emerging evidence suggests that transcranial alternating current stimulation (tACS) is an effective, frequency-specific modulator of endogenous brain oscillations, with the potential to alter cognitive performance. Here, we show that reduction in response latencies to solve complex logic problem indexing fluid intelligence is obtained through 40 Hz-tACS (gamma band) applied to the prefrontal cortex. This improvement in human performance depends on individual ability, with slower performers at baseline receiving greater benefits. The effect could have not being explained by regression to the mean, and showed task and frequency specificity: it was not observed for trials not involving logical reasoning, as well as with the application of low frequency 5 Hz-tACS (theta band) or non-periodic high frequency random noise stimulation (101-640 Hz). Moreover, performance in a spatial working memory task was not affected by brain stimulation, excluding possible effects on fluid intelligence enhancement through an increase in memory performance. We suggest that such high-level cognitive functions are dissociable by frequency-specific neuromodulatory effects, possibly related to entrainment of specific brain rhythms. We conclude that individual differences in cognitive abilities, due to acquired or developmental origins, could be reduced during frequency-specific tACS, a finding that should be taken into account for future individual cognitive rehabilitation studies. PMID:26707084

  10. Contact-Free Templating of 3-D Colloidal Structures Using Spatially Nonuniform AC Electric Fields.

    PubMed

    Raveendran, Joshua; Wood, Jeffery A; Docoslis, Aristides

    2016-09-20

    The formation of ordered and regularly shaped structures of colloidal particles with the aid of spatially nonuniform electric fields is a modern research area of great interest. This work illustrates how alternating current (AC) electrokinetic effects (dielectrophoresis, electroosmosis) can serve as contact-free templates, inside which colloidal microspheres can assemble into a variety of shapes and sizes. We show how three-dimensional colloidal structures of square, circular, and diamond shape of many tens of micrometers in size can be reproducibly formed with a single set of quadrupolar microelectrodes. Numerical simulations performed help to explain the role of AC electroosmosis and AC dielectrophoresis on the shaping of these structures as a function of applied voltage and frequency. We also demonstrate how the templating repertoire is further enhanced with the simultaneous application of a second, individually controlled AC electric field, which enables a variety of asymmetric colloidal structures to be produced using the same set of quadrupolar microelectrodes. As the preservation of shape and size of such electric-field templated structures after medium evaporation still remains a big challenge, here we also report on a novel method that permits the stabilization and isolation of these particle assemblies through medium gelation and subsequent hydrogel removal with a UV/ozone treatment. PMID:27541583

  11. Individual differences and specificity of prefrontal gamma frequency-tACS on fluid intelligence capabilities.

    PubMed

    Santarnecchi, E; Muller, T; Rossi, S; Sarkar, A; Polizzotto, N R; Rossi, A; Cohen Kadosh, R

    2016-02-01

    Emerging evidence suggests that transcranial alternating current stimulation (tACS) is an effective, frequency-specific modulator of endogenous brain oscillations, with the potential to alter cognitive performance. Here, we show that reduction in response latencies to solve complex logic problem indexing fluid intelligence is obtained through 40 Hz-tACS (gamma band) applied to the prefrontal cortex. This improvement in human performance depends on individual ability, with slower performers at baseline receiving greater benefits. The effect could have not being explained by regression to the mean, and showed task and frequency specificity: it was not observed for trials not involving logical reasoning, as well as with the application of low frequency 5 Hz-tACS (theta band) or non-periodic high frequency random noise stimulation (101-640 Hz). Moreover, performance in a spatial working memory task was not affected by brain stimulation, excluding possible effects on fluid intelligence enhancement through an increase in memory performance. We suggest that such high-level cognitive functions are dissociable by frequency-specific neuromodulatory effects, possibly related to entrainment of specific brain rhythms. We conclude that individual differences in cognitive abilities, due to acquired or developmental origins, could be reduced during frequency-specific tACS, a finding that should be taken into account for future individual cognitive rehabilitation studies.

  12. Endogenous and exogenous electric fields as modifiers of brain activity: rational design of noninvasive brain stimulation with transcranial alternating current stimulation.

    PubMed

    Fröhlich, Flavio

    2014-03-01

    Synchronized neuronal activity in the cortex generates weak electric fields that are routinely measured in humans and animal models by electroencephalography and local field potential recordings. Traditionally, these endogenous electric fields have been considered to be an epiphenomenon of brain activity. Recent work has demonstrated that active cortical networks are surprisingly susceptible to weak perturbations of the membrane voltage of a large number of neurons by electric fields. Simultaneously, noninvasive brain stimulation with weak, exogenous electric fields (transcranial current stimulation, TCS) has undergone a renaissance due to the broad scope of its possible applications in modulating brain activity for cognitive enhancement and treatment of brain disorders. This review aims to interface the recent developments in the study of both endogenous and exogenous electric fields, with a particular focus on rhythmic stimulation for the modulation of cortical oscillations. The main goal is to provide a starting point for the use of rational design for the development of novel mechanism-based TCS therapeutics based on transcranial alternating current stimulation, for the treatment of psychiatric illnesses.

  13. Cytotoxicity of 213Bi- and 225Ac-immunoconjugates.

    PubMed

    Kaspersen, F M; Bos, E; Doornmalen, A V; Geerlings, M W; Apostolidis, C; Molinet, R

    1995-06-01

    This paper describes in vitro cytotoxicity experiments with 213Bi- and 225Ac-immunoconjugates on the human epidermoid tumour cell line A431 using a blood group A-reactive murine IgG (2D11) as the specific antibody and MOPC 21 as the control antibody. With both radionuclides, specific cell-killing was achieved. The observed cytotoxicity of 213Bi (T1/2 - 47 min) indicates that this radionuclide is a useful alternative for the alpha-emitter 212Bi in the treatment of blood-borne malignancies. 225Ac-immunoconjugates (T1/2 of 225Ac is 10 days) may be applicable for the treatment of solid tumours, since the daughter radionuclides of 225Ac contribute to the cytotoxic efficacy by a field effect (i.e. toxicity in an area distal from the antibody-binding site). The lack of an adequate chelator for 225Ac is a major drawback.

  14. Construction of AC Motor Controllers for NOvA Experiment Upgrades

    SciTech Connect

    Cooley, Patrick; /Fermilab

    2011-08-04

    I have been constructing Alternating Current (AC) motor controllers for manipulation of particle beam detectors. The capability and reliability of these motor controllers are essential to the Laboratory's mission of accurate analysis of the particle beam's position. The device is moved in and out of the beam's path by the motor controller followed by the Neutrinos at the Main Injector Off-Axis {nu}{sub e} Appearance (NOvA) Experiment further down the beam pipe. In total, I built and tested ten ac motor controllers for new beam operations in the NOvA experiment. These units will prove to be durable and provide extremely accurate beam placement for NOvA Experiment far into the future.

  15. High-frequency alternating-crossed-field gel electrophoresis with neutral or slightly charged interpenetrating networks to improve DNA separation.

    PubMed

    Boyd, B M; Prausnitz, J M; Blanch, H W

    1998-12-01

    Toward improving DNA separations, this work reports the effects of high-frequency square-wave AC fields superimposed perpendicular to the direct current (DC) separation field on DNA migration in both polyacrylamide-based interpenetrating networks (IPNs) and in agarose networks. Compared to standard polyacrylamide gels, IPNs allow the separation of larger DNA (9000 bp vs. 5000 bp at 5 V/cm). In novel polyacrylamide-based IPNs, an alternating current (AC) field of 5 Hz increased the maximum DNA size separable. This effect was extended to larger DNA sizes with increasing electric-field strength up to and apparently beyond the power supply-limited maximum electric-field strength of 48 V/cm. The orthogonal AC field also increased mobility. These two results combine to yield a reduction in separation time of up to a factor of 20 in novel polyacrylamide-based IPNs. When negatively charged acrylic-acid groups were incorporated into the IPNs, the use of the AC field changed the DNA-network interaction, which altered the size dependence of DNA mobility. In agarose gels, an AC field of 50 Hz increased the size range separable; however, there was no increase in DNA mobility. There was no change in size dependence of mobility in an AC field when the number of charged groups in the agarose network was increased. Based on results in the literature, possible mechanisms were examined for the effects of the AC field on DNA separation.

  16. AC/RF Superconductivity

    SciTech Connect

    Ciovati, Gianluigi

    2015-02-01

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

  17. Alternative Solar Indices

    SciTech Connect

    Lantz, L.J.

    1980-07-01

    Possible alternative Solar Indices which could either be a perturbation from the currently defined Solar Index or possible indices based on current technologies for other media markets are discussed. An overview is given of the current project, including the logic that was utilized in defining its current structure and then alternative indices and definitions are presented and finally, recommendations are made for adopting alternative indices.

  18. Alternative solar indices

    NASA Astrophysics Data System (ADS)

    Lantz, L. J.

    1980-07-01

    Possible alternative Solar Indices which could either be a perturbation from the currently defined Solar Index or possible indices based on current technologies for other media markets are discussed. An overview is given of the current project, including the logic that was utilized in defining its current structure and then alternative indices and definitions are presented and finally, recommendations are made for adopting alternative indices.

  19. ACS sampling system: design, implementation, and performance evaluation

    NASA Astrophysics Data System (ADS)

    Di Marcantonio, Paolo; Cirami, Roberto; Chiozzi, Gianluca

    2004-09-01

    By means of ACS (ALMA Common Software) framework we designed and implemented a sampling system which allows sampling of every Characteristic Component Property with a specific, user-defined, sustained frequency limited only by the hardware. Collected data are sent to various clients (one or more Java plotting widgets, a dedicated GUI or a COTS application) using the ACS/CORBA Notification Channel. The data transport is optimized: samples are cached locally and sent in packets with a lower and user-defined frequency to keep network load under control. Simultaneous sampling of the Properties of different Components is also possible. Together with the design and implementation issues we present the performance of the sampling system evaluated on two different platforms: on a VME based system using VxWorks RTOS (currently adopted by ALMA) and on a PC/104+ embedded platform using Red Hat 9 Linux operating system. The PC/104+ solution offers, as an alternative, a low cost PC compatible hardware environment with free and open operating system.

  20. Integrated electric alternators/active filters

    NASA Astrophysics Data System (ADS)

    Towliat Abolhassani, Mehdi

    In response to energy crisis and power quality concerns, three different methodologies to integrate the concept of active filtering into the alternators are proposed. Wind energy, due to its free availability and its clean and renewable character, ranks as the most promising renewable energy resource that could play a key role in solving the worldwide energy crisis. An Integrated Doubly-fed Electric Alternator/Active filter (IDEA) for wind energy conversion systems is proposed. The proposed IDEA is capable of simultaneously capturing maximum power of wind energy and improving power quality, which are achieved by canceling the most significant and troublesome harmonics of the utility grid and power factor correction and reactive power compensation in the grid. The back-to-back current regulated power converters are employed to excite the rotor of IDEA. The control strategy of rotor-side power converter is based on position sensorless field oriented control method with higher power density. Analysis and experimental results are presented to demonstrate the effectiveness of the proposed IDEA. In the next step, an integrated synchronous machine/active filter is discussed. The proposed technology is essentially a rotating synchronous machine with suitable modification to its field excitation circuit to allow dc and ac excitations. It is shown that by controlling the ac excitation, the 5 th and 7th harmonics currents of the utility are compensated. The proposed method is cost effective because it can be applied to existing standby generators in commercial and industrial plants with minimal modification to the excitation circuits. To boost the gain of harmonic compensatory, an advanced electric machine is proposed. An Asymmetric Airgap Concentrated Winding Synchronous Machine (AACWSM) with ac and dc excitation was designed and employed. It is shown that the AACWSM with its unique design, in addition to power generation capability, could be used to compensate the most

  1. Purification of Carbon Nanotubes: Alternative Methods

    NASA Technical Reports Server (NTRS)

    Files, Bradley; Scott, Carl; Gorelik, Olga; Nikolaev, Pasha; Hulse, Lou; Arepalli, Sivaram

    2000-01-01

    Traditional carbon nanotube purification process involves nitric acid refluxing and cross flow filtration using surfactant TritonX. This is believed to result in damage to nanotubes and surfactant residue on nanotube surface. Alternative purification procedures involving solvent extraction, thermal zone refining and nitric acid refiuxing are used in the current study. The effect of duration and type of solvent to dissolve impurities including fullerenes and P ACs (polyaromatic compounds) are monitored by nuclear magnetic reasonance, high performance liquid chromatography, and thermogravimetric analysis. Thermal zone refining yielded sample areas rich in nanotubes as seen by scanning electric microscopy. Refluxing in boiling nitric acid seem to improve the nanotube content. Different procedural steps are needed to purify samples produced by laser process compared to arc process. These alternative methods of nanotube purification will be presented along with results from supporting analytical techniques.

  2. ac propulsion system for an electric vehicle

    NASA Technical Reports Server (NTRS)

    Geppert, S.

    1980-01-01

    It is pointed out that dc drives will be the logical choice for current production electric vehicles (EV). However, by the mid-80's, there is a good chance that the price and reliability of suitable high-power semiconductors will allow for a competitive ac system. The driving force behind the ac approach is the induction motor, which has specific advantages relative to a dc shunt or series traction motor. These advantages would be an important factor in the case of a vehicle for which low maintenance characteristics are of primary importance. A description of an EV ac propulsion system is provided, taking into account the logic controller, the inverter, the motor, and a two-speed transmission-differential-axle assembly. The main barrier to the employment of the considered propulsion system in EV is not any technical problem, but inverter transistor cost.

  3. Dielectric properties and alternating current conductivity of sol-gel made La0.8Ca0.2FeO3 compound

    NASA Astrophysics Data System (ADS)

    Benali, A.; Souissi, A.; Bejar, M.; Dhahri, E.; Graça, M. F. P.; Valente, M. A.

    2015-09-01

    In this work, single phase La0.8Ca0.2FeO3 nanomaterial has been synthesized by the sol-gel method using the citric acid route. By employing impedance spectroscopy, ac electrical properties have been measured over a temperature range from 300 to 673 K at various frequencies. With the analysis based on Debye's theory and a series of Arrhenius relations, the relaxation was argued to be associated with the hopping motions of charge carriers between Fe ions. The relaxation in the La0.8Ca0.2FeO3 compound was ascribed to be a polaronic relaxation. The ac electrical conduction was studied and associated to the non-overlapping small polaron tunneling (NSPT) model.

  4. Production of AC-225 and application of the BI-213 daughter in cancer therapy

    NASA Astrophysics Data System (ADS)

    Koch, L.; Apostolidis, C.; Janssens, W.; Molinet, R.; van Geel, J.

    1999-01-01

    There are several ongoing medical trials to use Bi-213 conjugated to monoclonal antibodies to kill tumour-cells of various cancer types. The institute is supplying Ac-225 generators for the test and is itself engaged in in-vitro cytotoxicity tests. Nuclear reactions leading to Ac-225 are discussed. The present supply of Ac-225 stems from Th-229 decay obtained from aged U-233. From the possible alternative the reactions Ra-226 (p, 2n) Ac-225 is presently favoured. The fabrication of a Ac-225 for Bi-213 generator will be described.

  5. A FRAME response to the Draft Report on Alternative (Non-animal) Methods for Cosmetics Testing: Current Status and Future Prospects--2010.

    PubMed

    Balls, Michael; Clothier, Richard

    2010-10-01

    This response on behalf of FRAME to the European Commission's consultation on the five chapters of the Draft Report on Alternative (Non-animal) Methods for Cosmetics Testing: Current Status and Future Prospects--2010, is via a Comment in ATLA, rather than via the template supplied by the Commission. This is principally so that a number of general points about cosmetic ingredient testing can be made. It is concluded that the five draft chapters do not provide a credible basis for the Commission's forthcoming report to the European Parliament and the European Council on the five cosmetic ingredient safety issues for which the 7th Amendment to the Cosmetic Directive's ban on animal testing was postponed until 2013. This is mainly because there is insufficient focus in the draft chapters on the specific nature of cosmetic ingredients, their uses, their local effects and metabolism at their sites of application, and, in particular, on whether their possible absorption into the body would be likely to lead to their accumulation in target sites at levels approaching Thresholds of Toxicological Concern. Meanwhile, there continues to be uncertainty about how the provisions of the Cosmetics Directive should be applied, given the requirements of the REACH system and directives concerned with the safety of other chemicals and products.

  6. An SVM approach with alternating current potential drop technique to classify pits and cracks on the bottom of a metal plate

    NASA Astrophysics Data System (ADS)

    Li, Yuting; Gan, Fangji; Wan, Zhengjun; Liao, Junbi

    2016-09-01

    The alternating current potential drop (ACPD) is a nondestructive technique that is widely used to detect and size defects in conductive material. This paper describes a combined ACPD and support vector machine (SVM) approach to accurately recognize typical defects on the bottom surface of a metal plate, i.e., pits and cracks. We first conducted a simulation study, and then, based on ACPD, measured five voltage ratios between the test region and reference region. The analysis of finite simulation data enables the binary classification of two kinds of defects. To obtain an accurate separating hyperplane, key parameters of the SVM classifier were optimized using a genetic algorithm with training data from the simulations. Based on the optimized SVM classifier, reliable estimates of the defects in a metal plate were then obtained. The recognition results of the simulation dataset shows that the trained and optimized SVM model has a high classification accuracy, and the metal plate experiment also indicates that the model has good precision in actual defect classification.

  7. A network thermodynamic two-port element to represent the coupled flow of salt and current. Improved alternative for the equivalent circuit.

    PubMed Central

    Mikulecky, D C

    1979-01-01

    A two-port for coupled salt and current flow is created by using the network thermodynamic approach in the same manner as that for coupled solute and volume flow (Mikulecky et al., 1977b; Mikulecky, 1977). This electrochemical two-port has distinct advantages over the equivalent circuit representation and overcomes difficulties pointed out by Finkelstein and Mauro (1963). The electrochemical two-port is used to produce a schematic diagram of the coupled flows through a tissue. The network is superimposable on the tissue morphology and preserves the physical qualities of the flows and forces in each part of an organized structure (e.g., an epithelium). The topological properties are manipulated independently from the constitutive (flow-force) relations. The constitutive relations are chosen from a number of alternatives depending on the detail and rigor desired. With the topology and constitutive parameters specified, the steady-state behavior is simulated with a network simulation program. By using capacitance to represent the filling and depletion of compartments, as well as the traditional electrical capacitances, time-dependent behavior is also simulated. Nonlinear effects arising from the integration of equations describing local behavior (e.g., the Nernst-Planck equations) are dealt with explicitly. The network thermodynamic approach provides a simple, straightforward method for representing a system diagrammatically and then simulating the system's behavior from the diagram with a minimum of mathematical manipulation. PMID:262391

  8. The AC/DCs of Electricity.

    ERIC Educational Resources Information Center

    Calhoun, Michael J.

    1994-01-01

    Describes an activity that allows students to use a rectifier circuit to convert alternating current into direct current. Also informs teachers of how to obtain most of the equipment needed for free. (ZWH)

  9. AC power systems handbook

    SciTech Connect

    Whitaker, J.

    1991-01-01

    Transient disturbances are what headaches are made of. Whatever you call them-spikes, surges, are power bumps-they can take your equipment down and leave you with a complicated and expensive repair job. Protection against transient disturbances is a science that demands attention to detail. This book explains how the power distribution system works, what can go wrong with it, and how to protect a facility against abnormalities. system grounding and shielding are covered in detail. Each major method of transient protection is analyzed and its relative merits discussed. The book provides a complete look at the critical elements of the ac power system. Provides a complete look at the ac power system from generation to consumption. Discusses the mechanisms that produce transient disturbances and how to protect against them. Presents diagrams to facilitate system design. Covers new areas, such as the extent of the transient disturbance problem, transient protection options, and stand-by power systems.

  10. Enhancement of continuous-flow separation of viable/nonviable yeast cells using a nonuniform alternating current electric field with complex spatial distribution.

    PubMed

    Tada, Shigeru; Nakanishi, Arisa; Eguchi, Masanori; Ochi, Kengo; Baba, Megumi; Tsukamoto, Akira

    2016-05-01

    The variability in cell response to AC electric fields is selective enough to separate not only the cell types but also the activation states of similar cells. In this work, we use dielectrophoresis (DEP), which exploits the differences in the dielectric properties of cells, to separate nonviable and viable cells. A parallel-plate DEP device consisting of a bottom face with an array of micro-fabricated interdigitated electrodes and a top face with a plane electrode was proposed to facilitate the separation of cells by creating a nonuniform electric field throughout the flow channel. The operation and performance of the device were evaluated using live and dead yeast cells as model biological particles. Further, numerical simulations were conducted for the cell suspensions flowing in a channel with a nonuniform AC electric field, modeled on the basis of the equation of motion of particles, to characterize the separation efficiency by changing the frequency of applied AC voltage. Results demonstrated that dead cells traveling through the channel were focused onto a site around the minimum electric field gradient in the middle of the flow stream, while live cells were trapped on the bottom face. Cells were thus successfully separated under the appropriately tuned frequency of 1 MHz. Predictions showed good agreement with the observation. The proposed DEP device provides a new approach to, for instance, hematological analysis or the separation of different cancer cells for application in circulating tumor cell identification. PMID:27279934

  11. Enhancement of continuous-flow separation of viable/nonviable yeast cells using a nonuniform alternating current electric field with complex spatial distribution.

    PubMed

    Tada, Shigeru; Nakanishi, Arisa; Eguchi, Masanori; Ochi, Kengo; Baba, Megumi; Tsukamoto, Akira

    2016-05-01

    The variability in cell response to AC electric fields is selective enough to separate not only the cell types but also the activation states of similar cells. In this work, we use dielectrophoresis (DEP), which exploits the differences in the dielectric properties of cells, to separate nonviable and viable cells. A parallel-plate DEP device consisting of a bottom face with an array of micro-fabricated interdigitated electrodes and a top face with a plane electrode was proposed to facilitate the separation of cells by creating a nonuniform electric field throughout the flow channel. The operation and performance of the device were evaluated using live and dead yeast cells as model biological particles. Further, numerical simulations were conducted for the cell suspensions flowing in a channel with a nonuniform AC electric field, modeled on the basis of the equation of motion of particles, to characterize the separation efficiency by changing the frequency of applied AC voltage. Results demonstrated that dead cells traveling through the channel were focused onto a site around the minimum electric field gradient in the middle of the flow stream, while live cells were trapped on the bottom face. Cells were thus successfully separated under the appropriately tuned frequency of 1 MHz. Predictions showed good agreement with the observation. The proposed DEP device provides a new approach to, for instance, hematological analysis or the separation of different cancer cells for application in circulating tumor cell identification.

  12. Development of a new module for the measurement of the magneto-electric direct and converse effects based on an alternating current susceptometer

    NASA Astrophysics Data System (ADS)

    Bueno-Baques, D.; Hurtado-Lopez, G.; Corral-Flores, V.; Gomez, S.; Diley, N. R.; Glushchenko, A.

    2014-08-01

    A new module for the measurement of magneto-electric properties was developed as an add-on for a magnetic AC susceptibility option of a Physical Properties Measurement System (PPMS). The module is capable of recording direct dynamic and static converse magneto-electric effect, i.e., the change in electric polarization due to the application of a small AC magnetic field with a DC magnetic field bias, or the change in the magnetic moment induced by an applied electric field. The versatile module setup supports both measurements in a sequential order without the need of removing or repositioning the sample. Furthermore, AC and DC magnetic susceptibilities can be recorded while performing direct and inverse magneto-electric measurements, respectively, which adds outstanding capabilities to the existing instrument while saving time and resources. Measurements are fully automated and integrated in the PPMS Multivu software platform. Magneto-electric behavior of a BaTiO3/CoFe2O4 and BaTiO3/NiFe2O4 magneto-electric composites, and a Pb(Fe0.5Nb0.5)O3 single phase compound were recorded as test measurements.

  13. Increased Ac excision (iae): Arabidopsis thaliana mutations affecting Ac transposition.

    PubMed

    Jarvis, P; Belzile, F; Page, T; Dean, C

    1997-05-01

    The maize transposable element Ac is highly active in the heterologous hosts tobacco and tomato, but shows very much reduced levels of activity in Arabidopsis. A mutagenesis experiment was undertaken with the aim of identifying Arabidopsis host factors responsible for the observed low levels of Ac activity. Seed from a line carrying a single copy of the Ac element inserted into the streptomycin phosphotransferase (SPT) reporter fusion, and which displayed typically low levels of Ac activity, were mutagenized using gamma rays. Nineteen mutants displaying high levels of somatic Ac activity, as judged by their highly variegated phenotypes, were isolated after screening the M2 generation on streptomycin-containing medium. The mutations fall into two complementation groups, iae1 and iae2, are unlinked to the SPT::Ac locus and segregate in a Mendelian fashion. The iae1 mutation is recessive and the iae2 mutation is semi-dominant. The iae1 and iae2 mutants show 550- and 70-fold increases, respectively, in the average number of Ac excision sectors per cotyledon. The IAE1 locus maps to chromosome 2, whereas the SPT::Ac reporter maps to chromosome 3. A molecular study of Ac activity in the iae1 mutant confirmed the very high levels of Ac excision predicted using the phenotypic assay, but revealed only low levels of Ac re-insertion. Analyses of germinal transposition in the iae1 mutant demonstrated an average germinal excision frequency of 3% and a frequency of independent Ac re-insertions following germinal excision of 22%. The iae mutants represents a possible means of improving the efficiency of Ac/Ds transposon tagging systems in Arabidopsis, and will enable the dissection of host involvement in Ac transposition and the mechanisms employed for controlling transposable element activity.

  14. Dynamical Coulomb blockade of tunnel junctions driven by alternating voltages

    NASA Astrophysics Data System (ADS)

    Grabert, Hermann

    2015-12-01

    The theory of the dynamical Coulomb blockade is extended to tunneling elements driven by a time-dependent voltage. It is shown that, for standard setups where an external voltage is applied to a tunnel junction via an impedance, time-dependent driving entails an excitation of the modes of the electromagnetic environment by the applied voltage. Previous approaches for ac driven circuits need to be extended to account for the driven bath modes. A unitary transformation involving also the variables of the electromagnetic environment is introduced which allows us to split off the time dependence from the Hamiltonian in the absence of tunneling. This greatly simplifies perturbation-theoretical calculations based on treating the tunneling Hamiltonian as a perturbation. In particular, the average current flowing in the leads of the tunnel junction is studied. Explicit results are given for the case of an applied voltage with a constant dc part and a sinusoidal ac part. The connection with standard dynamical Coulomb blockade theory for constant applied voltage is established. It is shown that an alternating voltage source reveals significant additional effects caused by the electromagnetic environment. The hallmark of the dynamical Coulomb blockade in ac driven devices is a suppression of higher harmonics of the current by the electromagnetic environment. The theory presented basically applies to all tunneling devices driven by alternating voltages.

  15. A HTS scanning magnet and AC operation

    NASA Astrophysics Data System (ADS)

    Hatanaka, K.; Nakagawa, J.; Fukuda, M.; Yorita, T.; Saito, T.; Sakemi, Y.; Kawaguchi, T.; Noda, K.

    2010-04-01

    A scanning magnet using high-temperature superconductor (HTS) wire was designed, built, and tested for its suitability as a beam scanner. After successful cooling tests, the magnet performance was studied using DC and AC currents. With DC current the magnet was successfully operated to generate designed field distributions and effective length. In AC mode, the magnet was operated at frequencies of 30-59 Hz and a temperature of 77 K as well as 10-20 Hz and 20 K. The power losses dissipated in the coils were measured and compared with the model calculations. The observed losses per cycle were independent of the frequency and the scaling law of the transport current was consistent with theoretical predictions for hysteretic losses in HTS wires.

  16. Sustained Aftereffect of α-tACS Lasts Up to 70 min after Stimulation

    PubMed Central

    Kasten, Florian H.; Dowsett, James; Herrmann, Christoph S.

    2016-01-01

    Transcranial alternating current stimulation (tACS) has been repeatedly demonstrated to increase power of endogenous brain oscillations in the range of the stimulated frequency after stimulation. In the alpha band this aftereffect has been shown to persist for at least 30 min. However, in most experiments the aftereffect exceeded the duration of the measurement. Thus, it remains unclear how the effect develops beyond these 30 min and when it decays. The current study aimed to extend existing findings by monitoring the physiological aftereffect of tACS in the alpha range for an extended period of 90 min post-stimulation. To this end participants received either 20 min of tACS or sham stimulation with intensities below their individual sensation threshold at the individual alpha frequency (IAF). Electroencephalogram (EEG) was acquired during 3 min before and 90 min after stimulation. Subjects performed a visual vigilance task during the whole measurement. While the enhanced power in the individual alpha band did not return back to pre-stimulation baseline in the stimulation group, the difference between stimulation and sham diminishes after 70 min due to a natural alpha increase of the sham group. PMID:27252642

  17. Magnetostrictive Alternator

    NASA Technical Reports Server (NTRS)

    Dyson, Rodger; Bruder, Geoffrey

    2013-01-01

    This innovation replaces the linear alternator presently used in Stirling engines with a continuous-gradient, impedance-matched, oscillating magnetostrictive transducer that eliminates all moving parts via compression, maintains high efficiency, costs less to manufacture, reduces mass, and eliminates the need for a bearing system. The key components of this new technology are the use of stacked magnetostrictive materials, such as Terfenol-D, under a biased magnetic and stress-induced compression, continuous-gradient impedance-matching material, coils, force-focusing metallic structure, and supports. The acoustic energy from the engine travels through an impedancematching layer that is physically connected to the magnetostrictive mass. Compression bolts keep the structure under compressive strain, allowing for the micron-scale compression of the magnetostrictive material and eliminating the need for bearings. The relatively large millimeter displacement of the pressure side of the impedance-matching material is reduced to micron motion, and undergoes stress amplification at the magnetostrictive interface. The alternating compression and expansion of the magnetostrictive material creates an alternating magnetic field that then induces an electric current in a coil that is wound around the stack. This produces electrical power from the acoustic pressure wave and, if the resonant frequency is tuned to match the engine, can replace the linear alternator that is commonly used.

  18. Encapsulation of α-Particle–Emitting 225Ac3+ Ions Within Carbon Nanotubes

    PubMed Central

    Matson, Michael L.; Villa, Carlos H.; Ananta, Jeyarama S.; Law, Justin J.; Scheinberg, David A.; Wilson, Lon J.

    2016-01-01

    225Ac3+ is a generator of α-particle–emitting radionuclides with 4 net α-particle decays that can be used therapeutically. Targeting 225Ac3+ by use of ligands conjugated to traditional bifunctional chelates limits the amount of 225Ac3+ that can be delivered. Ultrashort, single-walled carbon nanotubes (US-tubes), previously demonstrated as sequestering agents of trivalent lanthanide ions and small molecules, also successfully incorporate 225Ac3+. Methods Aqueous loading of both 225Ac3+ ions and Gd3+ ions via bath sonication was used to construct 225Ac@gadonanotubes (225Ac@GNTs). The 225Ac@GNTs were subsequently challenged with heat, time, and human serum. Results US-tubes internally loaded with both 225Ac3+ ions and Gd3+ ions show 2 distinct populations of 225Ac3+ ions: one rapidly lost in human serum and one that remains bound to the US-tubes despite additional challenge with heat, time, and serum. The presence of the latter population depended on cosequestration of Gd3+ and 225Ac3+ ions. Conclusion US-tubes successfully sequester 225Ac3+ ions in the presence of Gd3+ ions and retain them after a human serum challenge, rendering 225Ac@GNTs candidates for radioimmunotherapy for delivery of 225Ac3+ ions at higher concentrations than is currently possible for traditional ligand carriers. PMID:25931476

  19. A randomized, double-blind, sham-controlled study of static electric field therapy by high voltage alternating current for active rheumatoid arthritis.

    PubMed

    Naito, Yuji; Yamaguchi, Shinnichi; Mori, Yasuhiro; Nakajima, Kouji; Hashimoto, Sanshiro; Tomaru, Masakazu; Satoh, Yoshihiko; Hitomi, Yuji; Karita, Masakazu; Hiwatashi, Tomoaki; Kawahito, Yutaka; Yoshikawa, Toshikazu

    2013-07-01

    Static electric field therapy by high voltage alternating current (EF-HVAC) is a traditional complementary Japanese medicine used for headache, shoulder stiffness, chronic constipation and insomnia. Open-label studies and clinical experience in Japan have suggested that this electric field therapy is safe and effective in treating chronic arthritis. We evaluated the efficacy of EF-HVAC therapy in a randomized, double-blinded, sham-controlled trial in patients with active rheumatoid arthritis (RA) in community-based general physician centers. Thirty patients fulfilling American College of Rheumatology (ACR) criteria for RA were treated with EF-HVAC therapy with the LEGACIS PLUS System (COCOROCA Corp., Tokyo, Japan) or sham therapy for 12 weeks and followed for 4 weeks without treatment. The disease activity score 28 (DAS28-CRP), visual analogue scale for pain (VAS), modified health assessment questionnaire (MHAQ), and inflammatory parameters were used as the outcome variable. Twenty four patients (n = 12 in each group) were analyzed by a per protocol analysis. Although a significant reduction in DAS28-CRP was observed in EF-HVAC group at 8 and 12 weeks compared to before treatment, there were no significant differences in DAS28-CRP scores during treatment between two groups. The scale of VAS was also significantly decreased by the treatment with EF-HVAC compared to before treatment, in addition, the scale of VAS in EF-HVAC group was significantly lower than sham group at 8 and 12 weeks. Changes in another parameters including MHAQ were not significant between before and after treatment, or by all comparative study between two groups. There were no adverse events related the treatment. In conclusion, the EF-HVAC therapy has a beneficial effect on the improvement to subjective pain of RA. PMID:23874073

  20. A randomized, double-blind, sham-controlled study of static electric field therapy by high voltage alternating current for active rheumatoid arthritis.

    PubMed

    Naito, Yuji; Yamaguchi, Shinnichi; Mori, Yasuhiro; Nakajima, Kouji; Hashimoto, Sanshiro; Tomaru, Masakazu; Satoh, Yoshihiko; Hitomi, Yuji; Karita, Masakazu; Hiwatashi, Tomoaki; Kawahito, Yutaka; Yoshikawa, Toshikazu

    2013-07-01

    Static electric field therapy by high voltage alternating current (EF-HVAC) is a traditional complementary Japanese medicine used for headache, shoulder stiffness, chronic constipation and insomnia. Open-label studies and clinical experience in Japan have suggested that this electric field therapy is safe and effective in treating chronic arthritis. We evaluated the efficacy of EF-HVAC therapy in a randomized, double-blinded, sham-controlled trial in patients with active rheumatoid arthritis (RA) in community-based general physician centers. Thirty patients fulfilling American College of Rheumatology (ACR) criteria for RA were treated with EF-HVAC therapy with the LEGACIS PLUS System (COCOROCA Corp., Tokyo, Japan) or sham therapy for 12 weeks and followed for 4 weeks without treatment. The disease activity score 28 (DAS28-CRP), visual analogue scale for pain (VAS), modified health assessment questionnaire (MHAQ), and inflammatory parameters were used as the outcome variable. Twenty four patients (n = 12 in each group) were analyzed by a per protocol analysis. Although a significant reduction in DAS28-CRP was observed in EF-HVAC group at 8 and 12 weeks compared to before treatment, there were no significant differences in DAS28-CRP scores during treatment between two groups. The scale of VAS was also significantly decreased by the treatment with EF-HVAC compared to before treatment, in addition, the scale of VAS in EF-HVAC group was significantly lower than sham group at 8 and 12 weeks. Changes in another parameters including MHAQ were not significant between before and after treatment, or by all comparative study between two groups. There were no adverse events related the treatment. In conclusion, the EF-HVAC therapy has a beneficial effect on the improvement to subjective pain of RA.

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

    SciTech Connect

    Ouyang, Jianyong

    2013-12-02

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

  2. Fault current limiter

    DOEpatents

    Darmann, Francis Anthony

    2013-10-08

    A fault current limiter (FCL) includes a series of high permeability posts for collectively define a core for the FCL. A DC coil, for the purposes of saturating a portion of the high permeability posts, surrounds the complete structure outside of an enclosure in the form of a vessel. The vessel contains a dielectric insulation medium. AC coils, for transporting AC current, are wound on insulating formers and electrically interconnected to each other in a manner such that the senses of the magnetic field produced by each AC coil in the corresponding high permeability core are opposing. There are insulation barriers between phases to improve dielectric withstand properties of the dielectric medium.

  3. AC resistance measuring instrument

    DOEpatents

    Hof, P.J.

    1983-10-04

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

  4. AC Resistance measuring instrument

    DOEpatents

    Hof, Peter J.

    1983-01-01

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

  5. High-Frequency Alternating-Crossed-Field Gel Electrophoresis WithNeutral or Slightly Charged Interpenetrating Networks to Improve DNASeparation

    SciTech Connect

    Boyd, B.; Prausnitz, J.; Blanch, H.

    1998-07-01

    Toward improving DNA separations, this work reports theeffects of high-frequency square-wave AC fields superimposedperpendicular to the direct current (DC) separation field on DNAmigration in both polyacrylamide-based interpenetrating networks (IPNs)and in agarose networks. Compared to standard polyacrylamide gels, IPNsallow the separation of larger DNA (9000 bp vs. 5000 bp at 5 V/cm). Innovel polyacrylamide-based IPNs, an alternating current (AC) field of 5Hz increased the maximum DNA size separable. This effect was extended tolarger DNA sizes with increasing electric-field strength up to andapparently beyond the power supply-limited maximum electric-fieldstrength of 48 V/cm. The orthogonal AC field also increased mobility.These two results combine to yield a reduction in separation time of upto a factor of 20 in novel polyacrylamide-based IPNs. When negativelycharged acrylic-acid groups were incorporated into the IPNs, the use ofthe AC field changed the DNA-network interaction, which altered the sizedependence of DNA mobility. In agarose gels, an AC field of 50 Hzincreased the size range separable; however, there was no increase in DNAmobility. There was no change in size dependence of mobility in an ACfield when the number of charged groups in the agarose network wasincreased. Based on results in the literature, possible mechanisms wereexamined for the effects of the AC field on DNA separation.

  6. Eddy Current Probe for Surface and Sub-Surface Inspection

    NASA Technical Reports Server (NTRS)

    Wincheski, Russell A. (Inventor); Simpson, John W. (Inventor)

    2014-01-01

    An eddy current probe includes an excitation coil for coupling to a low-frequency alternating current (AC) source. A magneto-resistive sensor is centrally disposed within and at one end of the excitation coil to thereby define a sensing end of the probe. A tubular flux-focusing lens is disposed between the excitation coil and the magneto-resistive sensor. An excitation wire is spaced apart from the magneto-resistive sensor in a plane that is perpendicular to the sensor's axis of sensitivity and such that, when the sensing end of the eddy current probe is positioned adjacent to the surface of a structure, the excitation wire is disposed between the magneto-resistive sensor and the surface of the structure. The excitation wire is coupled to a high-frequency AC source. The excitation coil and flux-focusing lens can be omitted when only surface inspection is required.

  7. 77 FR 31756 - Energy Conservation Program: Alternative Efficiency Determination Methods and Alternative Rating...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-05-30

    ... Parts 429, 430, and 431 RIN 1904-AC46 Energy Conservation Program: Alternative Efficiency Determination Methods and Alternative Rating Methods: Public Meeting AGENCY: Office of Energy Efficiency and Renewable... proposed modifications to the regulations authorizing the use of alternative methods of determining...

  8. Identification of /sup 233/Ac

    SciTech Connect

    Chu, Y.Y.; Zhou, M.L.

    1983-09-01

    We report in this paper identification of the new isotope /sup 233/Ac. Uranium targets were irradiated with 28 GeV protons; after rapid retrieval of the target and separation of actinium from thorium, /sup 233/Ac was allowed to decay into the known /sup 233/Th daughter. Exhaustive chemical purification was employed to permit the identification of /sup 233/Th via its characteristic ..gamma.. radiations. The half-life derived for /sup 233/Ac from several experiments is 2.3 +- 0.3 min. The production cross section for /sup 233/Ac is 100 ..mu..b.

  9. Alternative security

    SciTech Connect

    Weston, B.H. )

    1990-01-01

    This book contains the following chapters: The Military and Alternative Security: New Missions for Stable Conventional Security; Technology and Alternative Security: A Cherished Myth Expires; Law and Alternative Security: Toward a Just World Peace; Politics and Alternative Security: Toward a More Democratic, Therefore More Peaceful, World; Economics and Alternative Security: Toward a Peacekeeping International Economy; Psychology and Alternative Security: Needs, Perceptions, and Misperceptions; Religion and Alternative Security: A Prophetic Vision; and Toward Post-Nuclear Global Security: An Overview.

  10. Alternating vs. direct current: A transient study of the U.S. Coast Guard's 270 foot medium endurance cutter's electrical distribution system

    NASA Astrophysics Data System (ADS)

    Hutton, Keoni Alexander

    While the United States Navy has conducted extensive research into the use of shipboard DC zonal electrical distribution systems (ZED), no project has analyzed the benefits for installation on a Coast Guard cutter which has a significantly different load profile than Navy warships. Simulink models of the existing 270' medium endurance cutter (WMEC) AC radial electrical distribution system and a proposed DC ZED system were created and tested with three transients. The result demonstrated a significant reduction in settling time and an increased robustness caused by the insulation provided by the introduction of power electronic converters. Beyond the transients, a DC ZED provides better standardized installation for any ship reducing construction costs and timelines, and simplifying training and support. Additionally, the DCZED increases a ship's innate survivability by reducing longitudinal cables that penetrate watertight bulkheads increasing a boundaries effectiveness. The Coast Guard would be best served by pushing for a zonal distribution system on all future cutter acquisitions.

  11. Fabrication of cobalt-nickel binary nanowires in a highly ordered alumina template via AC electrodeposition

    PubMed Central

    2013-01-01

    Cobalt-nickel (Co-Ni) binary alloy nanowires of different compositions were co-deposited in the nanopores of highly ordered anodic aluminum oxide (AAO) templates from a single sulfate bath using alternating current (AC) electrodeposition. AC electrodeposition was accomplished without modifying or removing the barrier layer. Field emission scanning electron microscope was used to study the morphology of templates and alloy nanowires. Energy-dispersive X-ray analysis confirmed the deposition of Co-Ni alloy nanowires in the AAO templates. Average diameter of the alloy nanowires was approximately 40 nm which is equal to the diameter of nanopore. X-ray diffraction analysis showed that the alloy nanowires consisted of both hexagonal close-packed and face-centered cubic phases. Magnetic measurements showed that the easy x-axis of magnetization is parallel to the nanowires with coercivity of approximately 706 Oe. AC electrodeposition is very simple, fast, and is useful for the homogenous deposition of various secondary nanostuctured materials into the nanopores of AAO. PMID:23941234

  12. Scalable Heuristics for Planning, Placement and Sizing of Flexible AC Transmission System Devices

    SciTech Connect

    Frolov, Vladmir; Backhaus, Scott N.; Chertkov, Michael

    2015-07-02

    Aiming to relieve transmission grid congestion and improve or extend feasibility domain of the operations, we build optimization heuristics, generalizing standard AC Optimal Power Flow (OPF), for placement and sizing of Flexible Alternating Current Transmission System (FACTS) devices of the Series Compensation (SC) and Static VAR Compensation (SVC) type. One use of these devices is in resolving the case when the AC OPF solution does not exist because of congestion. Another application is developing a long-term investment strategy for placement and sizing of the SC and SVC devices to reduce operational cost and improve power system operation. SC and SVC devices are represented by modification of the transmission line inductances and reactive power nodal corrections respectively. We find one placement and sizing of FACTs devices for multiple scenarios and optimal settings for each scenario simultaneously. Our solution of the nonlinear and nonconvex generalized AC-OPF consists of building a convergent sequence of convex optimizations containing only linear constraints and shows good computational scaling to larger systems. The approach is illustrated on single- and multi-scenario examples of the Matpower case-30 model.

  13. Fabrication of cobalt-nickel binary nanowires in a highly ordered alumina template via AC electrodeposition.

    PubMed

    Ali, Ghafar; Maqbool, Muhammad

    2013-08-14

    Cobalt-nickel (Co-Ni) binary alloy nanowires of different compositions were co-deposited in the nanopores of highly ordered anodic aluminum oxide (AAO) templates from a single sulfate bath using alternating current (AC) electrodeposition. AC electrodeposition was accomplished without modifying or removing the barrier layer. Field emission scanning electron microscope was used to study the morphology of templates and alloy nanowires. Energy-dispersive X-ray analysis confirmed the deposition of Co-Ni alloy nanowires in the AAO templates. Average diameter of the alloy nanowires was approximately 40 nm which is equal to the diameter of nanopore. X-ray diffraction analysis showed that the alloy nanowires consisted of both hexagonal close-packed and face-centered cubic phases. Magnetic measurements showed that the easy x-axis of magnetization is parallel to the nanowires with coercivity of approximately 706 Oe. AC electrodeposition is very simple, fast, and is useful for the homogenous deposition of various secondary nanostuctured materials into the nanopores of AAO.

  14. Cooling Floor AC Systems

    NASA Astrophysics Data System (ADS)

    Jun, Lu; Hao, Ding; Hong, Zhang; Ce, Gao Dian

    The present HVAC equipments for the residential buildings in the Hot-summer-and-Cold-winter climate region are still at a high energy consuming level. So that the high efficiency HVAC system is an urgently need for achieving the preset government energy saving goal. With its advantage of highly sanitary, highly comfortable and uniform of temperature field, the hot-water resource floor radiation heating system has been widely accepted. This paper has put forward a new way in air-conditioning, which combines the fresh-air supply unit and such floor radiation system for the dehumidification and cooling in summer or heating in winter. By analyze its advantages and limitations, we found that this so called Cooling/ Heating Floor AC System can improve the IAQ of residential building while keep high efficiency quality. We also recommend a methodology for the HVAC system designing, which will ensure the reduction of energy cost of users.

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

    PubMed

    Harmer, Christopher J; Hall, Ruth M

    2015-07-01

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

  16. Non-contact current and voltage sensor

    SciTech Connect

    Carpenter, Gary D; El-Essawy, Wael; Ferreira, Alexandre Peixoto; Keller, Thomas Walter; Rubio, Juan C; Schappert, Michael A

    2014-03-25

    A detachable current and voltage sensor provides an isolated and convenient device to measure current passing through a conductor such as an AC branch circuit wire, as well as providing an indication of an electrostatic potential on the wire, which can be used to indicate the phase of the voltage on the wire, and optionally a magnitude of the voltage. The device includes a housing that contains the current and voltage sensors, which may be a ferrite cylinder with a hall effect sensor disposed in a gap along the circumference to measure current, or alternative a winding provided through the cylinder along its axis and a capacitive plate or wire disposed adjacent to, or within, the ferrite cylinder to provide the indication of the voltage.

  17. Determination of tunneling charge via current measurements

    NASA Astrophysics Data System (ADS)

    Safi, I.; Sukhorukov, E. V.

    2010-09-01

    We consider a tunnel junction between two arbitrary non-linear systems in any dimension, which can be different. We show that the tunneling charge can be detected using three alternative methods based on current measurements. Besides being technically easier compared to noise measurements, these methods present valuable advantages: they do not require the knowledge of the underlying models, and some are accessible in the experimentally convenient low-voltage regime, where heating effects are reduced. The first method is based on the AC conductance, while the two others are based on photo-assisted current (PAC) and can be implemented for any time dependence of the tunneling amplitude. These are promising for edge states in the regime of the fractional quantum Hall effect (FQHE): the Hamiltonian does not have to be specified and can incorporate non-universal interactions between the edges, and it is more convenient to use an AC gate voltage rather than an AC bias. These methods apply for instance to weak barriers in 1-D systems, Superconductor-Insulator-Normal (SIN) or graphene-like structures.

  18. Bandgap Tailoring via Si Doping in Inverse-Garnet Mg3Y2Ge3O12:Ce(3+) Persistent Phosphor Potentially Applicable in AC-LED.

    PubMed

    Lin, Hang; Xu, Ju; Huang, Qingming; Wang, Bo; Chen, Hui; Lin, Zebin; Wang, Yuansheng

    2015-10-01

    The state-of-the-art alternating-current light-emitting diode (AC-LED) technique suffers from adverse lighting flicker during each AC cycle. Aiming to compensate the dimming time of AC-LED, herein, we report a novel Mg3Y2(Ge1-xSix)3O12:Ce(3+) inverse-garnet persistent phosphor whose afterglow is efficiently activated by blue light with persistent luminescence in millisecond range. It is experimentally demonstrated that Si doping tailors the host bandgap, so that both the electron charging and detrapping in the persistent luminescence process are optimized. To explore the origin of the millisecond afterglow, we performed a series of thermoluminescence analyses, revealing three types of continuously distributed traps in the host. Finally, an AC-LED prototype device was fabricated, which exhibits the warm white emission with a reduced percent flicker of 71.7%. These results demonstrate that the newly developed persistent phosphor might be a promising candidate applicable in low flickering AC-LED which has advantages of cheaper price, longer lifetime, and higher energy utilization efficiency.

  19. Bandgap Tailoring via Si Doping in Inverse-Garnet Mg3Y2Ge3O12:Ce(3+) Persistent Phosphor Potentially Applicable in AC-LED.

    PubMed

    Lin, Hang; Xu, Ju; Huang, Qingming; Wang, Bo; Chen, Hui; Lin, Zebin; Wang, Yuansheng

    2015-10-01

    The state-of-the-art alternating-current light-emitting diode (AC-LED) technique suffers from adverse lighting flicker during each AC cycle. Aiming to compensate the dimming time of AC-LED, herein, we report a novel Mg3Y2(Ge1-xSix)3O12:Ce(3+) inverse-garnet persistent phosphor whose afterglow is efficiently activated by blue light with persistent luminescence in millisecond range. It is experimentally demonstrated that Si doping tailors the host bandgap, so that both the electron charging and detrapping in the persistent luminescence process are optimized. To explore the origin of the millisecond afterglow, we performed a series of thermoluminescence analyses, revealing three types of continuously distributed traps in the host. Finally, an AC-LED prototype device was fabricated, which exhibits the warm white emission with a reduced percent flicker of 71.7%. These results demonstrate that the newly developed persistent phosphor might be a promising candidate applicable in low flickering AC-LED which has advantages of cheaper price, longer lifetime, and higher energy utilization efficiency. PMID:26387847

  20. Alternative approaches for vertebrate ecotoxicity tests in the 21st century: A review of developments over the last 2 decades and current status

    EPA Science Inventory

    The need for alternative approaches to the use of vertebrate animals for hazard assessing chemicals and pollutants has become of increasing importance. It is now the first consideration when initiating a vertebrate ecotoxicity test, to ensure that unnecessary use of vertebrate or...

  1. Equivalent Electrical Circuit Representations of AC Quantized Hall Resistance Standards

    PubMed Central

    Cage, M. E.; Jeffery, A.; Matthews, J.

    1999-01-01

    We use equivalent electrical circuits to analyze the effects of large parasitic impedances existing in all sample probes on four-terminal-pair measurements of the ac quantized Hall resistance RH. The circuit components include the externally measurable parasitic capacitances, inductances, lead resistances, and leakage resistances of ac quantized Hall resistance standards, as well as components that represent the electrical characteristics of the quantum Hall effect device (QHE). Two kinds of electrical circuit connections to the QHE are described and considered: single-series “offset” and quadruple-series. (We eliminated other connections in earlier analyses because they did not provide the desired accuracy with all sample probe leads attached at the device.) Exact, but complicated, algebraic equations are derived for the currents and measured quantized Hall voltages for these two circuits. Only the quadruple-series connection circuit meets our desired goal of measuring RH for both ac and dc currents with a one-standard-deviation uncertainty of 10−8 RH or less during the same cool-down with all leads attached at the device. The single-series “offset” connection circuit meets our other desired goal of also measuring the longitudinal resistance Rx for both ac and dc currents during that same cool-down. We will use these predictions to apply small measurable corrections, and uncertainties of the corrections, to ac measurements of RH in order to realize an intrinsic ac quantized Hall resistance standard of 10−8 RH uncertainty or less.

  2. Spectroscopic AC Susceptibility Imaging (sASI) of Magnetic Nanoparticles

    PubMed Central

    Ficko, Bradley W.; Nadar, Priyanka M.; Diamond, Solomon G.

    2014-01-01

    This study demonstrates a method for alternating current (AC) susceptibility imaging (ASI) of magnetic nanoparticles (mNPs) using low cost instrumentation. The ASI method uses AC magnetic susceptibility measurement to create tomographic images using an array of drive coils, compensation coils and fluxgate magnetometers. Using a spectroscopic approach in conjunction with ASI, a series of tomographic images can be created for each frequency measurement and is termed sASI. The advantage of sASI is that mNPs can be simultaneously characterized and imaged in a biological medium. System calibration was performed by fitting the in-phase and out-of-phase susceptibility measurements of an mNP sample with a hydrodynamic diameter of 100 nm to a Brownian relaxation model (R2 = 0.96). Samples of mNPs with core diameters of 10 and 40 nm and a sample of 100 nm hydrodynamic diameter were prepared in 0.5 ml tubes. Three mNP samples were arranged in a randomized array and then scanned using sASI with six frequencies between 425 and 925 Hz. The sASI scans showed the location and quantity of the mNP samples (R2 = 0.97). Biological compatibility of the sASI method was demonstrated by scanning mNPs that were injected into a pork sausage. The mNP response in the biological medium was found to correlate with a calibration sample (R2 = 0.97, p <0.001). These results demonstrate the concept of ASI and advantages of sASI. PMID:25477704

  3. Spectroscopic AC Susceptibility Imaging (sASI) of Magnetic Nanoparticles.

    PubMed

    Ficko, Bradley W; Nadar, Priyanka M; Diamond, Solomon G

    2015-02-01

    This study demonstrates a method for alternating current (AC) susceptibility imaging (ASI) of magnetic nanoparticles (mNPs) using low cost instrumentation. The ASI method uses AC magnetic susceptibility measurement to create tomographic images using an array of drive coils, compensation coils and fluxgate magnetometers. Using a spectroscopic approach in conjunction with ASI, a series of tomographic images can be created for each frequency measurement and is termed sASI. The advantage of sASI is that mNPs can be simultaneously characterized and imaged in a biological medium. System calibration was performed by fitting the in-phase and out-of-phase susceptibility measurements of an mNP sample with a hydrodynamic diameter of 100 nm to a Brownian relaxation model (R(2) = 0.96). Samples of mNPs with core diameters of 10 and 40 nm and a sample of 100 nm hydrodynamic diameter were prepared in 0.5 ml tubes. Three mNP samples were arranged in a randomized array and then scanned using sASI with six frequencies between 425 and 925 Hz. The sASI scans showed the location and quantity of the mNP samples (R(2) = 0.97). Biological compatibility of the sASI method was demonstrated by scanning mNPs that were injected into a pork sausage. The mNP response in the biological medium was found to correlate with a calibration sample (R(2) = 0.97, p <0.001). These results demonstrate the concept of ASI and advantages of sASI. PMID:25477704

  4. Spectroscopic AC susceptibility imaging (sASI) of magnetic nanoparticles

    NASA Astrophysics Data System (ADS)

    Ficko, Bradley W.; Nadar, Priyanka M.; Diamond, Solomon G.

    2015-02-01

    This study demonstrates a method for alternating current (AC) susceptibility imaging (ASI) of magnetic nanoparticles (mNPs) using low cost instrumentation. The ASI method uses AC magnetic susceptibility measurements to create tomographic images using an array of drive coils, compensation coils and fluxgate magnetometers. Using a spectroscopic approach in conjunction with ASI, a series of tomographic images can be created for each frequency measurement set and is termed sASI. The advantage of sASI is that mNPs can be simultaneously characterized and imaged in a biological medium. System calibration was performed by fitting the in-phase and out-of-phase susceptibility measurements of an mNP sample with a hydrodynamic diameter of 100 nm to a Brownian relaxation model (R2=0.96). Samples of mNPs with core diameters of 10 and 40 nm and a sample of 100 nm hydrodynamic diameter were prepared in 0.5 ml tubes. Three mNP samples were arranged in a randomized array and then scanned using sASI with six frequencies between 425 and 925 Hz. The sASI scans showed the location and quantity of the mNP samples (R2=0.97). Biological compatibility of the sASI method was demonstrated by scanning mNPs that were injected into a pork sausage. The mNP response in the biological medium was found to correlate with a calibration sample (R2=0.97, p<0.001). These results demonstrate the concept of ASI and advantages of sASI.

  5. An AC-electromagnetic bearing for flywheel energy storage in space

    NASA Technical Reports Server (NTRS)

    Nikolajsen, Jorgen L.

    1993-01-01

    A repulsive type AC-electromagnetic bearing was developed and tested. It was conceived on the basis of the so-called Magnetic River suspension for high-speed trains. The appearance of the bearing is similar to the traditional DC-type electromagnetic bearing but the operating principle is different. The magnets are fed with alternating current instead of direct current and the rotor is fitted with a conducting sleeve (e.g. aluminum) instead of a ferromagnetic sleeve. The repulsion is due to induction of eddy-currents in the conducting sleeve. The bearing is inherently stable and requires no feedback control. It provides support in five degrees of freedom such that a short rotor may be fully supported by a single bearing. These capabilities were demonstrated experimentally. On the down side, the load carrying capacity and the damping obtained so far were quite low compared to the DC-type bearing. Also, significant heating of the conducting sleeve was experienced. The AC-bearing is essentially a modified induction motor and there are strong indications that it can be run both as a motor and as a generator with no commutator requirements. It is therefore considered to be a good candidate for support of energy storage flywheels in space.

  6. Software Development for ALMA in Chile: The ACS-UTFSM Group.

    NASA Astrophysics Data System (ADS)

    von Brand, H. H.

    ALMA Common Software (ACS) provides a common software framework for ALMA, the Atacama Large Millimeter Array in Chile. ACS is a collection of well-documented patterns for controlling systems and a set of components written to those patterns. In its core, ACS is a distributed, object-oriented system, written on top of CORBA. The ACS-UTFSM Group started as some students of informatics did summer jobs at the La Silla Observatory of ESO, where they became acquainted with ACS. Their interest led them to continue working on ACS on their own, and they eventually became official developers of the package. Now the group is being funded by project ALMA-CONICYT 31060008 ``Software Development for ALMA: Building Up Expertise to Meet ALMA Software Requirements within a Chilean University''. Several members of the original group are now working for ALMA, which fullfills one of the goals of the project. Some parts of ACS developed by the ACS-UTFSM Group include H3E (Hardware End-to-End Example), a Lego model of a telescope and its controlling software for training and demonstration purposes; and CDBChecker, a tool to verify the consistency of the configuration database for a ACS deployment. Currently we are working towards a general framework for telescope control using ACS, in order to simplify the deployment of new instruments; and repackaging ACS so it is easier to install and use. A master's thesis is exploring the real-time requirements of ACS.

  7. AC Losses in the MICE Channel Magnets -- Is This a Curse or aBlessing?

    SciTech Connect

    Green, M.A.; Wu, H.; Wang, L.; Kai, L.L.; Jia, L.X.; Yang, S.Q.

    2008-01-31

    This report discusses the AC losses in the MICE channelmagnets during magnet charging and discharging. This report talks aboutthe three types of AC losses in the MICE magnets; the hysteretic AC lossin the superconductor, the coupling AC loss in the superconductor and theeddy current AC loss in the magnet mandrel and support structure. AClosses increase the heat load at 4 K. The added heat load increases thetemperature of the second stage of the cooler. In addition, AC losscontributes to the temperature rise between the second stage cold headand the high field point of the magnet, which is usually close to themagnet hot spot. These are the curses of AC loss in the MICE magnet thatcan limit the rate at which the magnet can be charge or discharged. Ifone is willing to allow some of the helium that is around the magnet toboil away during a magnet charge or discharge, AC losses can become ablessing. The boil off helium from the AC losses can be used to cool theupper end of the HTS leads and the surrounding shield. The AC losses arepresented for all three types of MICE magnets. The AC loss temperaturedrops within the coupling magnet are presented as an example of how boththe curse and blessing of the AC losses can be combined.

  8. AC Loss Measurements on a 2G YBCO Coil

    SciTech Connect

    Rey, Christopher M; Duckworth, Robert C; Schwenterly, S W

    2011-01-01

    The Oak Ridge National Laboratory (ORNL) is collaborating with Waukesha Electric Systems (WES) to continue development of HTS power transformers. For compatibility with the existing power grid, a commercially viable HTS transformer will have to operate at high voltages in the range of 138 kV and above, and will have to withstand 550-kV impulse voltages as well. Second-generation (2G) YBCO coated conductors will be required for an economically-competitive design. In order to adequately size the refrigeration system for these transformers, the ac loss of these HTS coils must be characterized. Electrical AC loss measurements were conducted on a prototype high voltage (HV) coil with co-wound stainless steel at 60 Hz in a liquid nitrogen bath using a lock-in amplifier technique. The prototype HV coil consisted of 26 continuous (without splice) single pancake coils concentrically centered on a stainless steel former. For ac loss measurement purposes, voltage tap pairs were soldered across each set of two single pancake coils so that a total of 13 separate voltage measurements could be made across the entire length of the coil. AC loss measurements were taken as a function of ac excitation current. Results show that the loss is primarily concentrated at the ends of the coil where the operating fraction of critical current is the highest and show a distinct difference in current scaling of the losses between low current and high current regimes.

  9. ACS CCD Stability Monitor

    NASA Astrophysics Data System (ADS)

    Grogin, Norman

    2012-10-01

    A moderately crowded stellar field in the cluster 47 Tuc {6 arcmin West of the cluster core} is observed every four months with the WFC. The first visit exercises the full suite of broad and narrow band imaging filters and sub-array modes; following visits observe with only the six most popular Cycle 18 filters in full-frame mode. The positions and magnitudes of objects will be used to monitor local and large scale variations in the plate scale and the sensitivity of the detectors and to derive an independent measure of the detector CTE. One exposure in each sub-array mode with the WFC will allow us to verify that photometry obtained in full-frame and in sub-array modes are repeatable to better than 1%. This test is important for the ACS Photometric Cross-Calibration program, which uses sub-array exposures. This program may receive additional orbits to investigate ORIENT-dependent geometric distortion, which motivates the ORIENT and BETWEEN requirement on the first visit.

  10. AC electric field induced dipole-based on-chip 3D cell rotation.

    PubMed

    Benhal, Prateek; Chase, J Geoffrey; Gaynor, Paul; Oback, Björn; Wang, Wenhui

    2014-08-01

    The precise rotation of suspended cells is one of the many fundamental manipulations used in a wide range of biotechnological applications such as cell injection and enucleation in nuclear transfer (NT) cloning. Noticeably scarce among the existing rotation techniques is the three-dimensional (3D) rotation of cells on a single chip. Here we present an alternating current (ac) induced electric field-based biochip platform, which has an open-top sub-mm square chamber enclosed by four sidewall electrodes and two bottom electrodes, to achieve rotation about the two axes, thus 3D cell rotation. By applying an ac potential to the four sidewall electrodes, an in-plane (yaw) rotating electric field is generated and in-plane rotation is achieved. Similarly, by applying an ac potential to two opposite sidewall electrodes and the two bottom electrodes, an out-of-plane (pitch) rotating electric field is generated and rolling rotation is achieved. As a prompt proof-of-concept, bottom electrodes were constructed with transparent indium tin oxide (ITO) using the standard lift-off process and the sidewall electrodes were constructed using a low-cost micro-milling process and then assembled to form the chip. Through experiments, we demonstrate rotation of bovine oocytes of ~120 μm diameter about two axes, with the capability of controlling the rotation direction and the rate for each axis through control of the ac potential amplitude, frequency, and phase shift, and cell medium conductivity. The maximum observed rotation rate reached nearly 140° s⁻¹, while a consistent rotation rate reached up to 40° s⁻¹. Rotation rate spectra for zona pellucida-intact and zona pellucida-free oocytes were further compared and found to have no effective difference. This simple, transparent, cheap-to-manufacture, and open-top platform allows additional functional modules to be integrated to become a more powerful cell manipulation system.

  11. Alternative approaches to vertebrate ecotoxicity tests in the 21st century: A review of developments over the last 2 decades and current status

    USGS Publications Warehouse

    Lillicrap, Adam; Belanger, Scott; Burden, Natalie; Du Pasquier, David; Embry, Michelle; Halder, Marlies; Lampi, Mark; Lee, Lucy; Norberg-King, Teresa J.; Rattner, Barnett A.; Schirmer, Kristin; Thomas, Paul

    2016-01-01

    The need for alternative approaches to the use of vertebrate animals for hazard assessment of chemicals and pollutants has become of increasing importance. It is now the first consideration when initiating a vertebrate ecotoxicity test, to ensure that unnecessary use of vertebrate organisms is minimized wherever possible. For some regulatory purposes, the use of vertebrate organisms for environmental risk assessments has been banned; in other situations, the number of organisms tested has been dramatically reduced or the severity of the procedure refined. However, there is still a long way to go to achieve a complete replacement of vertebrate organisms to generate environmental hazard data. The development of animal alternatives is based not just on ethical considerations but also on reducing the cost of performing vertebrate ecotoxicity tests and in some cases on providing better information aimed at improving environmental risk assessments. The present Focus article provides an overview of the considerable advances that have been made toward alternative approaches for ecotoxicity assessments over the last few decades.

  12. Power factor control system for AC induction motors

    NASA Technical Reports Server (NTRS)

    Nola, F. J. (Inventor)

    1977-01-01

    A power factor control system for use with ac induction motors was designed which samples lines voltage and current through the motor and decreases power input to the motor proportional to the detected phase displacement between current and voltage. This system provides, less power to the motor, as it is less loaded.

  13. tACS Phase Locking of Frontal Midline Theta Oscillations Disrupts Working Memory Performance

    PubMed Central

    Chander, Bankim S.; Witkowski, Matthias; Braun, Christoph; Robinson, Stephen E.; Born, Jan; Cohen, Leonardo G.; Birbaumer, Niels; Soekadar, Surjo R.

    2016-01-01

    Background: Frontal midline theta (FMT) oscillations (4–8 Hz) are strongly related to cognitive and executive control during mental tasks such as memory processing, arithmetic problem solving or sustained attention. While maintenance of temporal order information during a working memory (WM) task was recently linked to FMT phase, a positive correlation between FMT power, WM demand and WM performance was shown. However, the relationship between these measures is not well understood, and it is unknown whether purposeful FMT phase manipulation during a WM task impacts FMT power and WM performance. Here we present evidence that FMT phase manipulation mediated by transcranial alternating current stimulation (tACS) can block WM demand-related FMT power increase (FMTΔpower) and disrupt normal WM performance. Methods: Twenty healthy volunteers were assigned to one of two groups (group A, group B) and performed a 2-back task across a baseline block (block 1) and an intervention block (block 2) while 275-sensor magnetoencephalography (MEG) was recorded. After no stimulation was applied during block 1, participants in group A received tACS oscillating at their individual FMT frequency over the prefrontal cortex (PFC) while group B received sham stimulation during block 2. After assessing and mapping phase locking values (PLV) between the tACS signal and brain oscillatory activity across the whole brain, FMT power and WM performance were assessed and compared between blocks and groups. Results: During block 2 of group A but not B, FMT oscillations showed increased PLV across task-related cortical areas underneath the frontal tACS electrode. While WM task-related FMTΔpower and WM performance were comparable across groups in block 1, tACS resulted in lower FMTΔpower and WM performance compared to sham stimulation in block 2. Conclusion: tACS-related manipulation of FMT phase can disrupt WM performance and influence WM task-related FMTΔpower. This finding may have important

  14. AC Electroosmotic Pumping in Nanofluidic Funnels.

    PubMed

    Kneller, Andrew R; Haywood, Daniel G; Jacobson, Stephen C

    2016-06-21

    We report efficient pumping of fluids through nanofluidic funnels when a symmetric AC waveform is applied. The asymmetric geometry of the nanofluidic funnel induces not only ion current rectification but also electroosmotic flow rectification. In the base-to-tip direction, the funnel exhibits a lower ion conductance and a higher electroosmotic flow velocity, whereas, in the tip-to-base direction, the funnel has a higher ion conductance and a lower electroosmotic flow velocity. Consequently, symmetric AC waveforms easily pump fluid through the nanofunnels over a range of frequencies, e.g., 5 Hz to 5 kHz. In our experiments, the nanofunnels were milled into glass substrates with a focused ion beam (FIB) instrument, and the funnel design had a constant 5° taper with aspect ratios (funnel tip width to funnel depth) of 0.1 to 1.0. We tracked ion current rectification by current-voltage (I-V) response and electroosmotic flow rectification by transport of a zwitterionic fluorescent probe. Rectification of ion current and electroosmotic flow increased with increasing electric field applied to the nanofunnel. Our results support three-dimensional simulations of ion transport and electroosmotic transport through nanofunnels, which suggest the asymmetric electroosmotic transport stems from an induced pressure at the junction of the nanochannel and nanofunnel tip. PMID:27230495

  15. 75 FR 13646 - Public Meeting With Interested Persons To Discuss the Proposed AC 20-42D, Hand Fire Extinguishers...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-03-22

    ... Federal Aviation Administration Public Meeting With Interested Persons To Discuss the Proposed AC 20-42D... received regarding proposed advisory circular (AC) 20-42D, Hand Fire Extinguishers for use in Aircraft... (IASFPWG) to draft a revision to the current AC 20-42C, issued on March 1984, by incorporating...

  16. Electron-radiation effects on the ac and dc electrical properties and unpaired electron densities of three aerospace polymers

    NASA Technical Reports Server (NTRS)

    Long, Sheila Ann T.; Long, Edward R., Jr.; Ries, Heidi R.; Harries, Wynford L.

    1986-01-01

    The effects of gigarad-level total absorbed doses from 1-MeV electrons on the post-irradiation alternating-current (ac) and direct-current (dc) electrical properties and the unpaired electron densities have been studied for Kapton, Ultem, and Mylar. The unpaired electron densities (determined from electron paramagnetic resonance spectroscopy) and the dc electrical conductivities of the irradiated materials were monitored as functions of time following the exposures to determine their decay characteristics at room temperature. The elevated-temperature ac electrical dissipations of the Ultem and Mylar were affected by the radiation. The dc conductivity of the Kapton increased by five orders of magnitude, while the dc conductivities of the Ultem and Mylar increased by less than an order of magnitude, due to the radiation. The observed radiation-generated changes in the ac electrical dissipations are explained in terms of known radiation-generated changes in the molecular structures of the three materials. A preliminary model relating the dc electrical conductivity and the unpaired electron density in the Kapton is proposed.

  17. Alternate drop pulse polarography

    USGS Publications Warehouse

    Christie, J.H.; Jackson, L.L.; Osteryoung, R.A.

    1976-01-01

    The new technique of alternate drop pulse polarography is presented. An experimental evaluation of alternate drop pulse polarography shows complete compensation of the capacitative background due to drop expansion. The capillary response phenomenon was studied in the absence of faradaic reaction and the capillary response current was found to depend on the pulse width to the -0.72 power. Increased signal-to-noise ratios were obtained using alternate drop pulse polarography at shorter drop times.

  18. Chromatin and alternative splicing.

    PubMed

    Alló, M; Schor, I E; Muñoz, M J; de la Mata, M; Agirre, E; Valcárcel, J; Eyras, E; Kornblihtt, A R

    2010-01-01

    Alternative splicing affects more than 90% of human genes. Coupling between transcription and splicing has become crucial in the complex network underlying alternative splicing regulation. Because chromatin is the real template for nuclear transcription, changes in its structure, but also in the "reading" and "writing" of the histone code, could modulate splicing choices. Here, we discuss the evidence supporting these ideas, from the first proposal of chromatin affecting alternative splicing, performed 20 years ago, to the latest findings including genome-wide evidence that nucleosomes are preferentially positioned in exons. We focus on two recent reports from our laboratories that add new evidence to this field. The first report shows that a physiological stimulus such as neuron depolarization promotes intragenic histone acetylation (H3K9ac) and chromatin relaxation, causing the skipping of exon 18 of the neural cell adhesion molecule gene. In the second report, we show how specific histone modifications can be created at targeted gene regions as a way to affect alternative splicing: Using small interfering RNAs (siRNAs), we increased the levels of H3K9me2 and H3K27me3 in the proximity of alternative exon 33 of the human fibronectin gene, favoring its inclusion into mature messenger RNA (mRNA) through a mechanism that recalls RNA-mediated transcriptional gene silencing.

  19. Distinctive translational and self-rotational motion of lymphoma cells in an optically induced non-rotational alternating current electric field.

    PubMed

    Liang, Wenfeng; Zhang, Ke; Yang, Xieliu; Liu, Lianqing; Yu, Haibo; Zhang, Weijing

    2015-01-01

    In this paper, the translational motion and self-rotational behaviors of the Raji cells, a type of B-cell lymphoma cell, in an optically induced, non-rotational, electric field have been characterized by utilizing a digitally programmable and optically activated microfluidics chip with the assistance of an externally applied AC bias potential. The crossover frequency spectrum of the Raji cells was studied by observing the different linear translation responses of these cells to the positive and negative optically induced dielectrophoresis force generated by a projected light pattern. This digitally projected spot served as the virtual electrode to generate an axisymmetric and non-uniform electric field. Then, the membrane capacitance of the Raji cells could be directly measured. Furthermore, Raji cells under this condition also exhibited a self-rotation behavior. The repeatable and controlled self-rotation speeds of the Raji cells to the externally applied frequency and voltage were systematically investigated and characterized via computer-vision algorithms. The self-rotational speed of the Raji cells reached a maximum value at 60 kHz and demonstrated a quadratic relationship with respect to the applied voltage. Furthermore, optically projected patterns of four orthogonal electrodes were also employed as the virtual electrodes to manipulate the Raji cells. These results demonstrated that Raji cells located at the center of the four electrode pattern could not be self-rotated. Instead any Raji cells that deviated from this center area would also self-rotate. Most importantly, the Raji cells did not exhibit the self-rotational behavior after translating and rotating with respect to the center of any two adjacent electrodes. The spatial distributions of the electric field generated by the optically projected spot and the pattern of four electrodes were also modeled using a finite element numerical simulation. These simulations validated that the electric field

  20. Distinctive translational and self-rotational motion of lymphoma cells in an optically induced non-rotational alternating current electric field

    PubMed Central

    Zhang, Ke; Yang, Xieliu; Liu, Lianqing; Yu, Haibo; Zhang, Weijing

    2015-01-01

    In this paper, the translational motion and self-rotational behaviors of the Raji cells, a type of B-cell lymphoma cell, in an optically induced, non-rotational, electric field have been characterized by utilizing a digitally programmable and optically activated microfluidics chip with the assistance of an externally applied AC bias potential. The crossover frequency spectrum of the Raji cells was studied by observing the different linear translation responses of these cells to the positive and negative optically induced dielectrophoresis force generated by a projected light pattern. This digitally projected spot served as the virtual electrode to generate an axisymmetric and non-uniform electric field. Then, the membrane capacitance of the Raji cells could be directly measured. Furthermore, Raji cells under this condition also exhibited a self-rotation behavior. The repeatable and controlled self-rotation speeds of the Raji cells to the externally applied frequency and voltage were systematically investigated and characterized via computer-vision algorithms. The self-rotational speed of the Raji cells reached a maximum value at 60 kHz and demonstrated a quadratic relationship with respect to the applied voltage. Furthermore, optically projected patterns of four orthogonal electrodes were also employed as the virtual electrodes to manipulate the Raji cells. These results demonstrated that Raji cells located at the center of the four electrode pattern could not be self-rotated. Instead any Raji cells that deviated from this center area would also self-rotate. Most importantly, the Raji cells did not exhibit the self-rotational behavior after translating and rotating with respect to the center of any two adjacent electrodes. The spatial distributions of the electric field generated by the optically projected spot and the pattern of four electrodes were also modeled using a finite element numerical simulation. These simulations validated that the electric field