Power and energy dissipation in subsequent return strokes as predicted by a new return stroke model

NASA Technical Reports Server (NTRS)

Cooray, Vernon

1991-01-01

Recently, Cooray introduced a new return stroke model which is capable of predicting the temporal behavior of the return stroke current and the return stroke velocity as a function of the height along the return stroke channel. The authors employed this model to calculate the power and energy dissipation in subsequent return strokes. The results of these calculations are presented here. It was concluded that a large fraction of the total energy available for the dart leader-subsequent stroke process is dissipated in the dart leader stage. The peak power per unit length dissipated in a subsequent stroke channel element decreases with increasing height of that channel element from ground level. For a given channel element, the peak power dissipation increases with increasing current in that channel element. The peak electrical power dissipation in a typical subsequent return stroke is about 1.5 times 10(exp 11) W. The energy dissipation in a subsequent stroke increases with increasing current in the return stroke channel, and for a typical subsequent stroke, the energy dissipation per unit length is about 5.0 times 10(exp 3) J/m.

Experimental study on Response Parameters of Ni-rich NiTi Shape Memory Alloy during Wire Electric Discharge Machining

NASA Astrophysics Data System (ADS)

Bisaria, Himanshu; Shandilya, Pragya

2018-03-01

Nowadays NiTi SMAs are gaining more prominence due to their unique properties such as superelasticity, shape memory effect, high fatigue strength and many other enriched physical and mechanical properties. The current studies explore the effect of machining parameters namely, peak current (Ip), pulse off time (TOFF), and pulse on time (TON) on wire wear ratio (WWR), and dimensional deviation (DD) in WEDM. It was found that high discharge energy was mainly ascribed to high WWR and DD. The WWR and DD increased with the increase in pulse on time and peak current whereas high pulse off time was favourable for low WWR and DD.

C-axis orientated AlN films deposited using deep oscillation magnetron sputtering

NASA Astrophysics Data System (ADS)

Lin, Jianliang; Chistyakov, Roman

2017-02-01

Highly <0001> c-axis orientated aluminum nitride (AlN) films were deposited on silicon (100) substrates by reactive deep oscillation magnetron sputtering (DOMS). No epitaxial favored bond layer and substrate heating were applied for assisting texture growth. The effects of the peak target current density (varied from 0.39 to 0.8 Acm-2) and film thickness (varied from 0.25 to 3.3 μm) on the c-axis orientation, microstructure, residual stress and mechanical properties of the AlN films were investigated by means of X-ray diffraction rocking curve methodology, transmission electron microscopy, optical profilometry, and nanoindentation. All AlN films exhibited a <0001> preferred orientation and compressive residual stresses. At similar film thicknesses, an increase in the peak target current density to 0.53 Acm-2 improved the <0001> orientation. Further increasing the peak target current density to above 0.53 Acm-2 showed limited contribution to the texture development. The study also showed that an increase in the thickness of the AlN films deposited by DOMS improved the c-axis alignment accompanied with a reduction in the residual stress.

Acetylcholine-activated ionic currents in parasympathetic neurons of bullfrog heart.

PubMed

Tateishi, N; Kim, D K; Akaike, N

1990-05-01

1. The electrical and pharmacologic properties of acetylcholine (ACh)-induced current (IACh) were studied in the parasympathetic neurons isolated from bullfrog heart with the use of the concentration-clamp technique, which allows intracellular perfusion and rapid change of external solution within 2 ms under the single-electrode voltage-clamp condition. 2. The IACh consisted of an initial transient peak component and a successive steady-state plateau component. Both currents increased in a sigmoidal fashion with increasing ACh concentration. The dissociation constant (Kd value) and the Hill coefficient for each component were 2.2 X 10(-5) M and 1.6, respectively. 3. In the K(+)-free solution, the reversal potential (EACh) of IACh was close to the Na+ equilibrium potential (ENa). The current-voltage (I-V) relation showed inward rectification at positive potentials. 4. Nicotine mimicked only the peak component of IACh. However both peak and steady-state components were blocked nonselectively by the nicotinic blockers d-tubocurarine and hexamethonium. 5. Carbamylcholine (CCh) mimicked the steady-state component of IACh. The steady-state component was selectively inhibited by atropine at concentrations 1,000 times lower than that required for inhibition of the peak component. The steady state was blocked equally by either pirenzepine (M1 blocker) or AF-DX-116 (M2 blocker). 6. It was concluded that the IACh consisted of a peak component having double exponential activation and inactivation, mediated through the nicotinic actions, and a steady-state component having no inactivation, mediated through the muscarinic action.

Performance of the LANSCE H^- Source and Low Energy Transport at Higher Peak Current

NASA Astrophysics Data System (ADS)

Pillai, Chandra; Stevens, Ralph; Fitzgerald, Daniel; Garnett, Robert; Ingllas, William; Merrill, Frank; Rybarcyk, Larry; Sander, Oscar

1997-05-01

The Los Alamos Neutron Science Center (LANSCE) 800 MeV linac facility uses a multicusp field, surface ion source to produce H^- beam for delivery to the Proton Storage Ring (PSR) and to the Weapon Neutron Research (WNR) areas. The source typically operates at a duty factor of 9.4% delivering a peak current of about 14 mA into the 750 keV LEBT. Each beam macropulse is chopped to create a sequence of 360 ns pulse, each with a 100 ns ``extraction notch'' for injection into PSR. The average current delivered to the short-pulse spallation target is nominally 70μA. One goal of the present PSR upgrade projects is an increase in the average beam current to 200μA. This will be accomplished by a combination of increased repetition rate (to 30 Hz), upgraded PSR bunchers, and a brighter H^- ion source that will produce higher peak current with lower beam emittance. The present ion source and injector system was studied to investigate the beam qualities of the source and the performance of the low energy transpot. The performance of the ion source at higher currents and the change in beam parameters in the low energy transport compared to those in the standard source conditions will be presented.

Flexible one-structure arched triboelectric nanogenerator based on common electrode for high efficiency energy harvesting and self-powered motion sensing

NASA Astrophysics Data System (ADS)

Chen, Xi; He, Jian; Song, Linlin; Zhang, Zengxing; Tian, Zhumei; Wen, Tao; Zhai, Cong; Chen, Yi; Cho, Jundong; Chou, Xiujian; Xue, Chenyang

2018-04-01

Triboelectric nanogenerators are widely used because of low cost, simple manufacturing process and high output performance. In this work, a flexible one-structure arched triboelectric nanogenerator (FOAT), based on common electrode to combine the single-electrode mode and contact-separation, was designed using silicone rubber, epoxy resin and flexible electrode. The peak-to-peak short circuit current of 18μ A and the peak-to-peak open circuit voltage of 570V can be obtained from the FOAT with the size of 5×7 cm2 under the frequency of 3Hz and the pressure of 300N. The peak-to-peak short circuit current of FOAT is increased by 29% and 80%, and the peak-to-peak open circuit voltage is increased by 33% and 54% compared with single-electrode mode and contact-separation mode, respectively. FOAT realizes the combination of two generation modes, which improves the output performance of triboelectric nanogenerator (TENG). 62 light-emitting-diodes (LEDs) can be completely lit up and 2.2μ F capacitor can be easily charged to 1.2V in 9s. When the FOAT is placed at different parts of the human body, the human motion energy can be harvested and be the sensing signal for motion monitoring sensor. Based on the above characteristics, FOAT exhibits great potential in illumination, power supplies for wearable electronic devices and self-powered motion monitoring sensor via harvesting the energy of human motion.

Method and apparatus for current-output peak detection

DOE Office of Scientific and Technical Information (OSTI.GOV)

De Geronimo, Gianluigi

2017-01-24

A method and apparatus for a current-output peak detector. A current-output peak detector circuit is disclosed and works in two phases. The peak detector circuit includes switches to switch the peak detector circuit from the first phase to the second phase upon detection of the peak voltage of an input voltage signal. The peak detector generates a current output with a high degree of accuracy in the second phase.

Numerical investigation of the effect of driving voltage pulse shapes on the characteristics of low-pressure argon dielectric barrier discharge

DOE Office of Scientific and Technical Information (OSTI.GOV)

Eslami, E., E-mail: eeslami@iust.ac.ir; Barjasteh, A.; Morshedian, N.

2015-06-15

In this work, we numerically compare the effect of a sinusoidal, triangular, and rectangular pulsed voltage profile on the calculated particle production, electric current, and gas voltage in a dielectric barrier discharge. The total argon gas pressure of 400 Pa, the distance between dielectrics of 5 mm, the dielectric thickness of 0.7 mm, and the temperature of T = 300 K were considered as input parameters. The different driving voltage pulse shapes (triangular, rectangular, and sinusoidal) are considered as applied voltage with a frequency of 7 kHz and an amplitude of 700 V peak to peak. It is shown thatmore » applying a rectangular voltage, as compared with a sinusoidal or triangle voltage, increases the current peak, while the peak width is decreased. Higher current density is related to high production of charged particles, which leads to the generation of some highly active species, such as Ar* (4s level), and Ar** (4p level) in the gap.« less

Current responsive devices for synchronous generators

DOEpatents

Karlicek, Robert F.

1983-01-01

A device for detecting current imbalance between phases of a polyphase alternating current generator. A detector responds to the maximum peak current in the generator, and detecting means generates an output for each phase proportional to the peak current of each phase. Comparing means generates an output when the maximum peak current exceeds the phase peak current.

Current responsive devices for synchronous generators

DOEpatents

Karlicek, R.F.

1983-09-27

A device for detecting current imbalance between phases of a polyphase alternating current generator. A detector responds to the maximum peak current in the generator, and detecting means generates an output for each phase proportional to the peak current of each phase. Comparing means generates an output when the maximum peak current exceeds the phase peak current. 11 figs.

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.

Lower limb joint kinetics in walking: the role of industry recommended footwear.

PubMed

Keenan, Geoffrey S; Franz, Jason R; Dicharry, Jay; Della Croce, Ugo; Kerrigan, D Casey

2011-03-01

The effects of current athletic footwear on lower extremity biomechanics are unknown. The aim of this study was to examine the changes, if any, that occur in peak lower extremity net joint moments while walking in industry recommended athletic footwear. Sixty-eight healthy young adults underwent kinetic evaluation of lower extremity extrinsic joint moments while walking barefoot and while walking in current standard athletic footwear matched to the foot mechanics of each subject while controlling for speed. A secondary analysis was performed comparing peak knee joint extrinsic moments during barefoot walking to those while walking in three different standard footwear types: stability, motion control, and cushion. 3-D motion capture data were collected in synchrony with ground reaction force data collected from an instrumented treadmill. The shod condition was associated with a 9.7% increase in the first peak knee varus moment, and increases in the hip flexion and extension moments. These increases may be largely related to a 6.5% increase in stride length with shoes associated with increases in the ground reaction forces in all three axes. The changes from barefoot walking observed in the peak knee joint moments were similar when subjects walked in all three footwear types. It is unclear to what extent these increased joint moments may be clinically relevant, or potentially adverse. Nonetheless, these differences should be considered in the recommendation as well as the design of footwear in the future. Copyright © 2010 Elsevier B.V. All rights reserved.

Influence of driving frequency on discharge modes in a dielectric-barrier discharge with multiple current pulses

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jiang, Weiman; Tang, Jie; Wang, Yishan

2013-07-15

A one-dimensional self-consistent fluid model was employed to investigate the effect of the driving frequency on the discharge modes in atmospheric-pressure argon discharge with multiple current pulses. The discharge mode was discussed in detail not only at current peaks but also between two adjacent peaks. The simulation results show that different transitions between the Townsend and glow modes during the discharge take place with the driving frequency increased. A complicated transition from the Townsend mode, through glow, Townsend, and glow, and finally back to the Townsend one is found in the discharge with the driving frequency of 8 kHz. Theremore » is a tendency of transition from the Townsend to glow mode for the discharge both at the current peaks and troughs with the increasing frequency. The discharge in the half period can all along operate in the glow mode with the driving frequency high enough. This is resulted from the preservation of more electrons in the gas gap and acquisition of more electron energy from the swiftly varying electric field with the increase in driving frequency. Comparison of the spatial and temporal evolutions of the electron density at different driving frequencies indicates that the increment of the driving frequency allows the plasma chemistry to be enhanced. This electrical characteristic is important for the applications, such as surface treatment and biomedical sterilization.« less

Wigner Transport Simulation of Resonant Tunneling Diodes with Auxiliary Quantum Wells

NASA Astrophysics Data System (ADS)

Lee, Joon-Ho; Shin, Mincheol; Byun, Seok-Joo; Kim, Wangki

2018-03-01

Resonant-tunneling diodes (RTDs) with auxiliary quantum wells ( e.g., emitter prewell, subwell, and collector postwell) are studied using a Wigner transport equation (WTE) discretized by a thirdorder upwind differential scheme. A flat-band potential profile is used for the WTE simulation. Our calculations revealed functions of the auxiliary wells as follows: The prewell increases the current density ( J) and the peak voltage ( V p ) while decreasing the peak-to-valley current ratio (PVCR), and the postwell decreases J while increasing the PVCR. The subwell affects J and PVCR, but its main effect is to decrease V p . When multiple auxiliary wells are used, each auxiliary well contributes independently to the transport without producing side effects.

Silicon nanowire Esaki diodes.

PubMed

Schmid, Heinz; Bessire, Cedric; Björk, Mikael T; Schenk, Andreas; Riel, Heike

2012-02-08

We report on the fabrication and characterization of silicon nanowire tunnel diodes. The silicon nanowires were grown on p-type Si substrates using Au-catalyzed vapor-liquid-solid growth and in situ n-type doping. Electrical measurements reveal Esaki diode characteristics with peak current densities of 3.6 kA/cm(2), peak-to-valley current ratios of up to 4.3, and reverse current densities of up to 300 kA/cm(2) at 0.5 V reverse bias. Strain-dependent current-voltage (I-V) measurements exhibit a decrease of the peak tunnel current with uniaxial tensile stress and an increase of 48% for 1.3 GPa compressive stress along the <111> growth direction, revealing the strain dependence of the Si band structure and thus the tunnel barrier. The contributions of phonons to the indirect tunneling process were probed by conductance measurements at 4.2 K. These measurements show phonon peaks at energies corresponding to the transverse acoustical and transverse optical phonons. In addition, the low-temperature conductance measurements were extended to higher biases to identify potential impurity states in the band gap. The results demonstrate that the most likely impurity, namely, Au from the catalyst particle, is not detectable, a finding that is also supported by the excellent device properties of the Esaki diodes reported here. © 2012 American Chemical Society

An electrochemical sensor based on polyaniline for monitoring hydroquinone and its damage on DNA.

PubMed

Tang, Wenwei; Zhang, Min; Li, Weihao; Zeng, Xinping

2014-09-01

A dsDNA/PANI/CTS/GCE biosensor was constructed by using the biocompatible chitosan (CTS) and the polyaniline (PANI) with excellent electric catalytic properties and large specific surface areas. The electrochemical behavior of hydroquinone on biosensor and its DNA-damaging mechanisms were investigated. Results showed that the redox peak current was remarkably increased after glassy carbon electrode (GCE) was modified by PANI/CTS. The dsDNA damage by hydroquinone was concentration dependent, and increased along with the increase of hydroquinone oxidation peak current and the reduction of dsDNA guanine oxidation peak current. The linear detection range of hydroquinone with dsDNA/PANI/CTS/GCE was 1.25×10(-6)-3.2×10(-4) M, and the detection limit was 9.65×10(-7) M. It was confirmed by the UV method that applying dsDNA/PANI/CTS/GCE to monitor hydroquinone was accurate and reliable. In addition, it could be deduced that the mode of interaction between the hydroquinone and dsDNA was intercalation. The electrochemical oxidation of hydroquinone on the dsDNA/PANI/CTS/GCE electrode was an adsorption-controlled irreversible and a two-electron two-proton transfer process. Copyright © 2014 Elsevier B.V. All rights reserved.

Response of nickel to zinc cells to electric vehicle chopper discharge waveforms

NASA Technical Reports Server (NTRS)

Cataldo, R. L.

1981-01-01

The preliminary results of simulated electric vehicle chopper controlled discharge of a Nickel/Zinc battery shows delivered energy increases of 5 to 25 percent compared to constant current discharges of the same average current. The percentage increase was a function of chopper frequency, the ratio of peak to average current, and the magnitude of the discharge current. Because the chopper effects are of a complex nature, electric vehicle battery/speed controller interaction must be carefully considered in vehicle design to optimize battery performance.

Cell membrane organization is important for inner hair cell MET-channel gating

NASA Astrophysics Data System (ADS)

Effertz, Thomas; Scharr, Alexandra L.; Ricci, Anthony J.

2018-05-01

Specialized sensory cells, hair cells, translate mechanical stimuli into electro/chemical responses. This process, termed mechano-electrical transduction (MET), is localized to the hair cell's sensory organelle, the hair bundle. The mature hair bundle comprises three rows of actin filled stereocilia, arranged in a staircase pattern. Deflections towards the tallest row of stereocilia activate MET channels, residing at the top of stereocilia. While other MET channels can be activated or modulated by changes to their lipid environment, this remains unknown for the mammalian auditory MET channel. We show here that the effect of lipid and cholesterol depletion from the cell membrane affect the MET current as well. We used γ-cyclodextrin to extract lipids form the membrane, reversibly reducing the peak MET current, current adaptation, and decreasing the channels resting open probability. The recovery after γ-cyclodextrin treatment was slower than the initial peak current reduction, suggesting that a specific lipid organization is required for normal MET channel function, which requires time reestablish. Extraction of cholesterol, using Mβ-cyclodextrin, irreversibly reduces the peak MET current and reversibly increases the channel resting open probability, suggesting that cholesterol restricts MET channel opening. This restriction could be useful to increase the channel's signal to noise ratio. Together this data suggests that the cell membrane is part of the force relay machinery to the MET channel and could possibly restrict gating associated conformational changes of the MET channel.

The Effect of Driver Rise-Time on Pinch Current and its Impact on Plasma Focus Performance and Neutron Yield

NASA Astrophysics Data System (ADS)

Sears, Jason; Schmidt, Andrea; Link, Anthony; Welch, Dale

2016-10-01

Experiments have suggested that dense plasma focus (DPF) neutron yield increases with faster drivers [Decker NIMP 1986]. Using the particle-in-cell code LSP [Schmidt PRL 2012], we reproduce this trend in a kJ DPF [Ellsworth 2014], and demonstrate how driver rise time is coupled to neutron output. We implement a 2-D model of the plasma focus including self-consistent circuit-driven boundary conditions. Driver capacitance and voltage are varied to modify the current rise time, and anode length is adjusted so that run-in coincides with the peak current. We observe during run down that magnetohydrodynamic (MHD) instabilities of the sheath shed blobs of plasma that remain in the inter-electrode gap during run in. This trailing plasma later acts as a low-inductance restrike path that shunts current from the pinch during maximum compression. While the MHD growth rate increases slightly with driver speed, the shorter anode of the fast driver allows fewer e-foldings and hence reduces the trailing mass between electrodes. As a result, the fast driver postpones parasitic restrikes and maintains peak current through the pinch during maximum compression. The fast driver pinch therefore achieves best simultaneity between its ion beam and peak target density, which maximizes neutron production. Prepared by LLNL under Contract DE-AC52-07NA27344.

Si /SiGe n-type resonant tunneling diodes fabricated using in situ hydrogen cleaning

NASA Astrophysics Data System (ADS)

Suet, Z.; Paul, D. J.; Zhang, J.; Turner, S. G.

2007-05-01

In situ hydrogen cleaning to reduce the surface segregation of n-type dopants in SiGe epitaxy has been used to fabricate Si /SiGe resonant tunneling diodes in a joint gas source chemical vapor deposition and molecular beam epitaxial system. Diodes fabricated without the in situ clean demonstrate linear current-voltage characteristics, while a 15min hydrogen clean produces negative differential resistance with peak-to-valley current ratios up to 2.2 and peak current densities of 5.0A/cm2 at 30K. Analysis of the valley current and the band structure of the devices suggest methods for increasing the operating temperature of Si /SiGe resonant tunneling diodes as required for applications.

Reduced event-related current density in the anterior cingulate cortex in schizophrenia.

PubMed

Mulert, C; Gallinat, J; Pascual-Marqui, R; Dorn, H; Frick, K; Schlattmann, P; Mientus, S; Herrmann, W M; Winterer, G

2001-04-01

There is good evidence from neuroanatomic postmortem and functional imaging studies that dysfunction of the anterior cingulate cortex plays a prominent role in the pathophysiology of schizophrenia. So far, no electrophysiological localization study has been performed to investigate this deficit. We investigated 18 drug-free schizophrenic patients and 25 normal subjects with an auditory choice reaction task and measured event-related activity with 19 electrodes. Estimation of the current source density distribution in Talairach space was performed with low-resolution electromagnetic tomography (LORETA). In normals, we could differentiate between an early event-related potential peak of the N1 (90-100 ms) and a later N1 peak (120-130 ms). Subsequent current-density LORETA analysis in Talairach space showed increased activity in the auditory cortex area during the first N1 peak and increased activity in the anterior cingulate gyrus during the second N1 peak. No activation difference was observed in the auditory cortex between normals and patients with schizophrenia. However, schizophrenics showed significantly less anterior cingulate gyrus activation and slowed reaction times. Our results confirm previous findings of an electrical source in the anterior cingulate and an anterior cingulate dysfunction in schizophrenics. Our data also suggest that anterior cingulate function in schizophrenics is disturbed at a relatively early time point in the information-processing stream (100-140 ms poststimulus). Copyright 2001 Academic Press.

Algal cell disruption using microbubbles to localize ultrasonic energy

PubMed Central

Krehbiel, Joel D.; Schideman, Lance C.; King, Daniel A.; Freund, Jonathan B.

2015-01-01

Microbubbles were added to an algal solution with the goal of improving cell disruption efficiency and the net energy balance for algal biofuel production. Experimental results showed that disruption increases with increasing peak rarefaction ultrasound pressure over the range studied: 1.90 to 3.07 MPa. Additionally, ultrasound cell disruption increased by up to 58% by adding microbubbles, with peak disruption occurring in the range of 108 microbubbles/ml. The localization of energy in space and time provided by the bubbles improve efficiency: energy requirements for such a process were estimated to be one-fourth of the available heat of combustion of algal biomass and one-fifth of currently used cell disruption methods. This increase in energy efficiency could make microbubble enhanced ultrasound viable for bioenergy applications and is expected to integrate well with current cell harvesting methods based upon dissolved air flotation. PMID:25311188

Optical response at 10.6 microns in tungsten silicide Schottky barrier diodes

NASA Technical Reports Server (NTRS)

Kumar, Sandeep; Boyd, Joseph T.; Jackson, Howard E.

1987-01-01

Optical response to radiation at a wavelength of 10.6 microns in tungsten silicide-silicon Schottky barrier diodes has been observed. Incident photons excite electrons by means of junction plasmon assisted inelastic electron tunneling. At 78 K, a peak in the second derivative of current versus junction bias voltage was observed at a voltage corresponding to the energy of photons having a wavelength of 10.6 microns. This peak increased with increasing incident laser power, saturating at the highest laser powers investigated.

Numerical Analysis of the Temperature Impact on Performance of GaN-Based 460-nm Light-Emitting Diode.

PubMed

Tawfik, Wael Z; Lee, June Key

2018-03-01

The influence of temperature on the characteristics of a GaN-based 460-nm light-emitting diode (LED) prepared on sapphire substrate was simulated using the SiLENSe and SpeCLED software programs. High temperatures impose negative effects on the performance of GaN-based LEDs. As the temperature increases, electrons acquire higher thermal energies, and therefore LEDs may suffer more from high-current loss mechanisms, which in turn causes a reduction in the radiative recombination rate in the active region. The internal quantum efficiency was reduced by about 24% at a current density of 35 A/cm2, and the electroluminescence spectral peak wavelength was redshifted. The LED operated at 260 K and exhibited its highest light output power of ~317.5 mW at a maximum injection current of 350 mA, compared to 212.2 mW for an LED operated at 400 K. However, increasing temperature does not cause a droop in efficiency under high injection conditions. The peak efficiency at 1 mA of injection current decreases more rapidly by ~15% with increasing temperature from 260 to 400 K than the efficiency at high injection current of 350 mA by ~11%.

Discharge Oscillations in a Permanent Magnet Cylindrical Hall-Effect Thruster

NASA Technical Reports Server (NTRS)

Polzin, K. A.; Sooby, E. S.; Raitses, Y.; Merino, E.; Fisch, N. J.

2009-01-01

Measurements of the discharge current in a cylindrical Hall thruster are presented to quantify plasma oscillations and instabilities without introducing an intrusive probe into the plasma. The time-varying component of the discharge current is measured using a current monitor that possesses a wide frequency bandwidth and the signal is Fourier transformed to yield the frequency spectra present, allowing for the identification of plasma oscillations. The data show that the discharge current oscillations become generally greater in amplitude and complexity as the voltage is increased, and are reduced in severity with increasing flow rate. The breathing mode ionization instability is identified, with frequency as a function of discharge voltage not increasing with discharge voltage as has been observed in some traditional Hall thruster geometries, but instead following a scaling similar to a large-amplitude, nonlinear oscillation mode recently predicted in for annular Hall thrusters. A transition from lower amplitude oscillations to large relative fluctuations in the oscillating discharge current is observed at low flow rates and is suppressed as the mass flow rate is increased. A second set of peaks in the frequency spectra are observed at the highest propellant flow rate tested. Possible mechanisms that might give rise to these peaks include ionization instabilities and interactions between various oscillatory modes.

Measured close lightning leader-step electric-field-derivative waveforms.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jordan, Doug M.; Hill, Dustin; Biagi, Christopher J.

2010-12-01

We characterize the measured electric field-derivative (dE/dt) waveforms of lightning stepped-leader steps from three negative lightning flashes at distances of tens to hundreds of meters. Electromagnetic signatures of leader steps at such close distances have rarely been documented in previous literature. Individual leader-step three-dimensional locations are determined by a dE/dt TOA system. The leader-step field derivative is typically a bipolar pulse with a sharp initial half-cycle of the same polarity as that of the return stroke, followed by an opposite polarity overshoot that decays relatively slowly to background level. This overshoot increases in amplitude relative to the initial peak andmore » becomes dominant as range decreases. The initial peak is often preceded by a 'slow front,' similar to the slow front that precedes the fast transition to peak in first return stroke dE/dt and E waveforms. The overall step-field waveform duration is typically less than 1 {micro}s. The mean initial peak of dE/dt, range-normalized to 100 km, is 7.4 V m{sup -1} {micro}s{sup -1} (standard deviation (S.D.), 3.7 V m{sup -1} {micro}s{sup -1}, N = 103), the mean half-peak width is 33.5 ns (S.D., 11.9 ns, N = 69), and the mean 10-to-90% risetime is 43.6 ns (S.D., 24.2 ns, N = 69). From modeling, we determine the properties of the leader step currents which produced two typical measured field derivatives, and we use one of these currents to calculate predicted leader step E and dE/dt as a function of source range and height, the results being in good agreement with our observations. The two modeled current waveforms had maximum rates of current rise-to-peak near 100 kA {micro}s{sup -1}, peak currents in the 5-7 kA range, current half-peak widths of about 300 ns, and charge transfers of {approx}3 mC. As part of the modeling, those currents were propagated upward at 1.5 x 10{sup 8} m s{sup -1}, with their amplitudes decaying exponentially with a decay height constant of 25 m.« less

Study of Drug Metabolism by Xanthine Oxidase

PubMed Central

Zhao, Jing; He, Xiaolin; Yang, Nana; Sun, Lizhou; Li, Genxi

2012-01-01

In this work, we report the studies of drug metabolism by xanthine oxidase (XOD) with electrochemical techniques. Firstly, a pair of stable, well-defined and quasi-reversible oxidation/reduction peaks is obtained with the formal potential at −413.1 mV (vs. SCE) after embedding XOD in salmon sperm DNA membrane on the surface of pyrolytic graphite electrode. Then, a new steady peak can be observed at −730 mV (vs. SCE) upon the addition of 6-mercaptopurine (6-MP) to the electrochemical system, indicating the metabolism of 6-MP by XOD. Furthermore, the chronoamperometric response shows that the current of the catalytic peak located at −730 mV increases with addition of 6-MP in a concentration-dependent manner, and the increase of the chronoamperometric current can be inhibited by an XOD inhibitor, quercetin. Therefore, our results prove that XOD/DNA modified electrode can be efficiently used to study the metabolism of 6-MP, which may provide a convenient approach for in vitro studies on enzyme-catalyzed drug metabolism. PMID:22606015

Screening for Chronic Obstructive Pulmonary Disease (COPD) in an Urban HIV Clinic: A Pilot Study

PubMed Central

Kaner, Robert J.; Glesby, Marshall J.

2015-01-01

Abstract Increased smoking and a detrimental response to tobacco smoke in the lungs of HIV/AIDS patients result in an increased risk for COPD. We aimed to determine the predictive value of a COPD screening strategy validated in the general population and to identify HIV-related factors associated with decreased lung function. Subjects at least 35 years of age at an HIV clinic in New York City completed a COPD screening questionnaire and peak flow measurement. Those with abnormal results and a random one-third of normal screens had spirometry. 235 individuals were included and 89 completed spirometry. Eleven (12%) had undiagnosed airway obstruction and 5 had COPD. A combination of a positive questionnaire and abnormal peak flow yielded a sensitivity of 20% (specificity 93%) for detection of COPD. Peak flow alone had a sensitivity of 80% (specificity 80%). Abnormal peak flow was associated with an AIDS diagnosis (p=0.04), lower nadir (p=0.001), and current CD4 counts (p=0.001). Nadir CD4 remained associated in multivariate analysis (p=0.05). Decreased FEV1 (<80% predicted) was associated with lower CD4 count nadir (p=0.04) and detectable current HIV viral load (p=0.01) in multivariate analysis. Questionnaire and peak flow together had low sensitivity, but abnormal peak flow shows potential as a screening tool for COPD in HIV/AIDS. These data suggest that lung function may be influenced by HIV-related factors. PMID:25723842

Impact of urban WWTP and CSO fluxes on river peak flow extremes under current and future climate conditions.

PubMed

Keupers, Ingrid; Willems, Patrick

2013-01-01

The impact of urban water fluxes on the river system outflow of the Grote Nete catchment (Belgium) was studied. First the impact of the Waste Water Treatment Plant (WWTP) and the Combined Sewer Overflow (CSO) outflows on the river system for the current climatic conditions was determined by simulating the urban fluxes as point sources in a detailed, hydrodynamic river model. Comparison was made of the simulation results on peak flow extremes with and without the urban point sources. In a second step, the impact of climate change scenarios on the urban fluxes and the consequent impacts on the river flow extremes were studied. It is shown that the change in the 10-year return period hourly peak flow discharge due to climate change (-14% to +45%) was in the same order of magnitude as the change due to the urban fluxes (+5%) in current climate conditions. Different climate change scenarios do not change the impact of the urban fluxes much except for the climate scenario that involves a strong increase in rainfall extremes in summer. This scenario leads to a strong increase of the impact of the urban fluxes on the river system.

Direct current force sensing device based on compressive spring, permanent magnet, and coil-wound magnetostrictive/piezoelectric laminate.

PubMed

Leung, Chung Ming; Or, Siu Wing; Ho, S L

2013-12-01

A force sensing device capable of sensing dc (or static) compressive forces is developed based on a NAS106N stainless steel compressive spring, a sintered NdFeB permanent magnet, and a coil-wound Tb(0.3)Dy(0.7)Fe(1.92)/Pb(Zr, Ti)O3 magnetostrictive∕piezoelectric laminate. The dc compressive force sensing in the device is evaluated theoretically and experimentally and is found to originate from a unique force-induced, position-dependent, current-driven dc magnetoelectric effect. The sensitivity of the device can be increased by increasing the spring constant of the compressive spring, the size of the permanent magnet, and/or the driving current for the coil-wound laminate. Devices of low-force (20 N) and high-force (200 N) types, showing high output voltages of 262 and 128 mV peak, respectively, are demonstrated at a low driving current of 100 mA peak by using different combinations of compressive spring and permanent magnet.

Globally optimal superconducting magnets part I: minimum stored energy (MSE) current density map.

PubMed

Tieng, Quang M; Vegh, Viktor; Brereton, Ian M

2009-01-01

An optimal current density map is crucial in magnet design to provide the initial values within search spaces in an optimization process for determining the final coil arrangement of the magnet. A strategy for obtaining globally optimal current density maps for the purpose of designing magnets with coaxial cylindrical coils in which the stored energy is minimized within a constrained domain is outlined. The current density maps obtained utilising the proposed method suggests that peak current densities occur around the perimeter of the magnet domain, where the adjacent peaks have alternating current directions for the most compact designs. As the dimensions of the domain are increased, the current density maps yield traditional magnet designs of positive current alone. These unique current density maps are obtained by minimizing the stored magnetic energy cost function and therefore suggest magnet coil designs of minimal system energy. Current density maps are provided for a number of different domain arrangements to illustrate the flexibility of the method and the quality of the achievable designs.

Manifestation of counteracting photovoltaic effect on IV characteristics in multi-junction solar cells

NASA Astrophysics Data System (ADS)

Mintairov, M. A.; Evstropov, V. V.; Mintairov, S. A.; Shvarts, M. Z.; Kozhukhovskaia, S. A.; Kalyuzhnyy, N. A.

2017-11-01

The existence within monolithic double- and triple-junction solar cells of a photoelectric source, which counteracts the basic photovoltaic p-n junctions, is proved. The paper presents a detailed analysis of the shape of the light IV-characteristics, as well as the dependence Voc-Jsc (open circuit voltage - short-circuit current). It is established that the counteracting source is tunnel p+-n+ junction. The photoelectric characteristics of samples with different tunnel diode peak current values were investigated, including the case of a zero value. When the tunnel p+-n+ junction is photoactive, the Voc-Jsc dependence has a dropping part, including a sharp jump. This undesirable effect decreases with increasing peak current.

Analysis of the Diurnal Variation of the Global Electric Circuit Obtained From Different Numerical Models

NASA Astrophysics Data System (ADS)

Jánský, Jaroslav; Lucas, Greg M.; Kalb, Christina; Bayona, Victor; Peterson, Michael J.; Deierling, Wiebke; Flyer, Natasha; Pasko, Victor P.

2017-12-01

This work analyzes different current source and conductivity parameterizations and their influence on the diurnal variation of the global electric circuit (GEC). The diurnal variations of the current source parameterizations obtained using electric field and conductivity measurements from plane overflights combined with global Tropical Rainfall Measuring Mission satellite data give generally good agreement with measured diurnal variation of the electric field at Vostok, Antarctica, where reference experimental measurements are performed. An approach employing 85 GHz passive microwave observations to infer currents within the GEC is compared and shows the best agreement in amplitude and phase with experimental measurements. To study the conductivity influence, GEC models solving the continuity equation in 3-D are used to calculate atmospheric resistance using yearly averaged conductivity obtained from the global circulation model Community Earth System Model (CESM). Then, using current source parameterization combining mean currents and global counts of electrified clouds, if the exponential conductivity is substituted by the conductivity from CESM, the peak to peak diurnal variation of the ionospheric potential of the GEC decreases from 24% to 20%. The main reason for the change is the presence of clouds while effects of 222Rn ionization, aerosols, and topography are less pronounced. The simulated peak to peak diurnal variation of the electric field at Vostok is increased from 15% to 18% from the diurnal variation of the global current in the GEC if conductivity from CESM is used.

Correlated peak relative light intensity and peak current in triggered lightning subsequent return strokes

NASA Technical Reports Server (NTRS)

Idone, V. P.; Orville, R. E.

1985-01-01

The correlation between peak relative light intensity L(R) and stroke peak current I(R) is examined for 39 subsequent return strokes in two triggered lightning flashes. One flash contained 19 strokes and the other 20 strokes for which direct measurements were available of the return stroke peak current at ground. Peak currents ranged from 1.6 to 21 kA. The measurements of peak relative light intensity were obtained from photographic streak recordings using calibrated film and microsecond resolution. Correlations, significant at better than the 0.1 percent level, were found for several functional relationships. Although a relation between L(R) and I(R) is evident in these data, none of the analytical relations considered is clearly favored. The correlation between L(R) and the maximum rate of current rise is also examined, but less correlation than between L(R) and I(R) is found. In addition, the peak relative intensity near ground is evaluated for 22 dart leaders, and a mean ratio of peak dart leader to peak return stroke relative light intensity was found to be 0.1 with a range of 0.02-0.23. Using two different methods, the peak current near ground in these dart leaders is estimated to range from 0.1 to 6 kA.

Trap-assisted tunneling in Si-InAs nanowire heterojunction tunnel diodes.

PubMed

Bessire, Cedric D; Björk, Mikael T; Schmid, Heinz; Schenk, Andreas; Reuter, Kathleen B; Riel, Heike

2011-10-12

We report on the electrical characterization of one-sided p(+)-si/n-InAs nanowire heterojunction tunnel diodes to provide insight into the tunnel process occurring in this highly lattice mismatched material system. The lattice mismatch gives rise to dislocations at the interface as confirmed by electron microscopy. Despite this, a negative differential resistance with peak-to-valley current ratios of up to 2.4 at room temperature and with large current densities is observed, attesting to the very abrupt and high-quality interface. The presence of dislocations and other defects that increase the excess current is evident in the first and second derivative of the I-V characteristics as distinct peaks arising from trap-and phonon-assisted tunneling via the corresponding defect levels. We observe this assisted tunneling mainly in the forward direction and at low reverse bias but not at higher reverse biases because the band-to-band generation rates are peaked in the InAs, which is also confirmed by modeling. This indicates that most of the peaks are due to dislocations and defects in the immediate vicinity of the interface. Finally, we also demonstrate that these devices are very sensitive to electrical stress, in particular at room temperature, because of the extremely high electrical fields obtained at the abrupt junction even at low bias. The electrical stress induces additional defect levels in the band gap, which reduce the peak-to-valley current ratios.

Climate change is projected to have severe impacts on the frequency and intensity of peak electricity demand across the United States.

PubMed

Auffhammer, Maximilian; Baylis, Patrick; Hausman, Catherine H

2017-02-21

It has been suggested that climate change impacts on the electric sector will account for the majority of global economic damages by the end of the current century and beyond [Rose S, et al. (2014) Understanding the Social Cost of Carbon: A Technical Assessment ]. The empirical literature has shown significant increases in climate-driven impacts on overall consumption, yet has not focused on the cost implications of the increased intensity and frequency of extreme events driving peak demand, which is the highest load observed in a period. We use comprehensive, high-frequency data at the level of load balancing authorities to parameterize the relationship between average or peak electricity demand and temperature for a major economy. Using statistical models, we analyze multiyear data from 166 load balancing authorities in the United States. We couple the estimated temperature response functions for total daily consumption and daily peak load with 18 downscaled global climate models (GCMs) to simulate climate change-driven impacts on both outcomes. We show moderate and heterogeneous changes in consumption, with an average increase of 2.8% by end of century. The results of our peak load simulations, however, suggest significant increases in the intensity and frequency of peak events throughout the United States, assuming today's technology and electricity market fundamentals. As the electricity grid is built to endure maximum load, our findings have significant implications for the construction of costly peak generating capacity, suggesting additional peak capacity costs of up to 180 billion dollars by the end of the century under business-as-usual.

Role of peak current in conversion of patients with ventricular fibrillation.

PubMed

Anantharaman, Venkataraman; Wan, Paul Weng; Tay, Seow Yian; Manning, Peter George; Lim, Swee Han; Chua, Siang Jin Terrance; Mohan, Tiru; Rabind, Antony Charles; Vidya, Sudarshan; Hao, Ying

2017-07-01

Peak currents are the final arbiter of defibrillation in patients with ventricular fibrillation (VF). However, biphasic defibrillators continue to use energy in joules for electrical conversion in hopes that their impedance compensation properties will address transthoracic impedance (TTI), which must be overcome when a fixed amount of energy is delivered. However, optimal peak currents for conversion of VF remain unclear. We aimed to determine the role of peak current and optimal peak levels for conversion in collapsed VF patients. Adult, non-pregnant patients presenting with non-traumatic VF were included in the study. All defibrillations that occurred were included. Impedance values during defibrillation were used to calculate peak current values. The endpoint was return of spontaneous circulation (ROSC). Of the 197 patients analysed, 105 had ROSC. Characteristics of patients with and without ROSC were comparable. Short duration of collapse < 10 minutes correlated positively with ROSC. Generally, patients with average or high TTI converted at lower peak currents. 25% of patients with high TTI converted at 13.3 ± 2.3 A, 22.7% with average TTI at 18.2 ± 2.5 A and 18.6% with low TTI at 27.0 ± 4.7 A (p = 0.729). Highest peak current conversions were at < 15 A and 15-20 A. Of the 44 patients who achieved first-shock ROSC, 33 (75.0%) received < 20 A peak current vs. > 20 A for the remaining 11 (25%) patients (p = 0.002). For best effect, priming biphasic defibrillators to deliver specific peak currents should be considered. Copyright: © Singapore Medical Association

Role of peak current in conversion of patients with ventricular fibrillation

PubMed Central

Anantharaman, Venkataraman; Wan, Paul Weng; Tay, Seow Yian; Manning, Peter George; Lim, Swee Han; Chua, Siang Jin Terrance; Mohan, Tiru; Rabind, Antony Charles; Vidya, Sudarshan; Hao, Ying

2017-01-01

INTRODUCTION Peak currents are the final arbiter of defibrillation in patients with ventricular fibrillation (VF). However, biphasic defibrillators continue to use energy in joules for electrical conversion in hopes that their impedance compensation properties will address transthoracic impedance (TTI), which must be overcome when a fixed amount of energy is delivered. However, optimal peak currents for conversion of VF remain unclear. We aimed to determine the role of peak current and optimal peak levels for conversion in collapsed VF patients. METHODS Adult, non-pregnant patients presenting with non-traumatic VF were included in the study. All defibrillations that occurred were included. Impedance values during defibrillation were used to calculate peak current values. The endpoint was return of spontaneous circulation (ROSC). RESULTS Of the 197 patients analysed, 105 had ROSC. Characteristics of patients with and without ROSC were comparable. Short duration of collapse < 10 minutes correlated positively with ROSC. Generally, patients with average or high TTI converted at lower peak currents. 25% of patients with high TTI converted at 13.3 ± 2.3 A, 22.7% with average TTI at 18.2 ± 2.5 A and 18.6% with low TTI at 27.0 ± 4.7 A (p = 0.729). Highest peak current conversions were at < 15 A and 15–20 A. Of the 44 patients who achieved first-shock ROSC, 33 (75.0%) received < 20 A peak current vs. > 20 A for the remaining 11 (25%) patients (p = 0.002). CONCLUSION For best effect, priming biphasic defibrillators to deliver specific peak currents should be considered. PMID:28741007

Cortical inhibition and excitation by bilateral transcranial alternating current stimulation.

PubMed

Cancelli, Andrea; Cottone, Carlo; Zito, Giancarlo; Di Giorgio, Marina; Pasqualetti, Patrizio; Tecchio, Franca

2015-01-01

Transcranial electric stimulations (tES) with amplitude-modulated currents are promising tools to enhance neuromodulation effects. It is essential to select the correct cortical targets and inhibitory/excitatory protocols to reverse changes in specific networks. We aimed at assessing the dependence of cortical excitability changes on the current amplitude of 20 Hz transcranial alternating current stimulation (tACS) over the bilateral primary motor cortex. We chose two amplitude ranges of the stimulations, around 25 μA/cm2 and 63 μA/cm2 from peak to peak, with three values (at steps of about 2.5%) around each, to generate, respectively, inhibitory and excitatory effects of the primary motor cortex. We checked such changes online through transcranial magnetic stimulation (TMS)-induced motor evoked potentials (MEPs). Cortical excitability changes depended upon current density (p = 0.001). Low current densities decreased MEP amplitudes (inhibition) while high current densities increased them (excitation). tACS targeting bilateral homologous cortical areas can induce online inhibition or excitation as a function of the current density.

Alternative Regression Equations for Estimation of Annual Peak-Streamflow Frequency for Undeveloped Watersheds in Texas using PRESS Minimization

USGS Publications Warehouse

Asquith, William H.; Thompson, David B.

2008-01-01

The U.S. Geological Survey, in cooperation with the Texas Department of Transportation and in partnership with Texas Tech University, investigated a refinement of the regional regression method and developed alternative equations for estimation of peak-streamflow frequency for undeveloped watersheds in Texas. A common model for estimation of peak-streamflow frequency is based on the regional regression method. The current (2008) regional regression equations for 11 regions of Texas are based on log10 transformations of all regression variables (drainage area, main-channel slope, and watershed shape). Exclusive use of log10-transformation does not fully linearize the relations between the variables. As a result, some systematic bias remains in the current equations. The bias results in overestimation of peak streamflow for both the smallest and largest watersheds. The bias increases with increasing recurrence interval. The primary source of the bias is the discernible curvilinear relation in log10 space between peak streamflow and drainage area. Bias is demonstrated by selected residual plots with superimposed LOWESS trend lines. To address the bias, a statistical framework based on minimization of the PRESS statistic through power transformation of drainage area is described and implemented, and the resulting regression equations are reported. Compared to log10-exclusive equations, the equations derived from PRESS minimization have PRESS statistics and residual standard errors less than the log10 exclusive equations. Selected residual plots for the PRESS-minimized equations are presented to demonstrate that systematic bias in regional regression equations for peak-streamflow frequency estimation in Texas can be reduced. Because the overall error is similar to the error associated with previous equations and because the bias is reduced, the PRESS-minimized equations reported here provide alternative equations for peak-streamflow frequency estimation.

Performance, Facility Pressure Effects, and Stability Characterization Tests of NASA's Hall Effect Rocket with Magnetic Shielding Thruster

NASA Technical Reports Server (NTRS)

Kamhawi, Hani; Huang, Wensheng; Haag, Thomas; Yim, John; Herman, Daniel; Peterson, Peter Y.; Williams, George J.; Gilland, James; Hofer, Richard; Mikellides, Ioannis

2016-01-01

NASA's Hall Effect Rocket with Magnetic Shielding (HERMeS) 12.5 kW Technology Demonstration Unit-1 (TDU-1) has been the subject of extensive technology maturation in preparation for flight system development. Part of the technology maturation effort included experimental evaluation of the TDU-1 thruster with conducting and dielectric front pole cover materials in two different electrical configurations. A graphite front magnetic pole cover thruster configuration with the thruster body electrically tied to cathode, and an alumina front pole cover thruster configuration with the thruster body floating were evaluated. Both configurations were also evaluated at different facility background pressure conditions to evaluate background pressure effects on thruster operation. Performance characterization tests found that higher thruster performance was attained with the graphite front pole cover configuration with the thruster electrically tied to cathode. A total thrust efficiency of 68% and a total specific impulse of 2,820 s was demonstrated at a discharge voltage of 600 V and a discharge power of 12.5 kW. Thruster stability regimes were characterized with respect to the thruster discharge current oscillations and with maps of the discharge current-voltage-magnetic field (IVB). Analysis of TDU-1 discharge current waveforms found that lower normalized discharge current peak-to-peak and root mean square magnitudes were attained when the thruster was electrically floated with alumina front pole covers. Background pressure effects characterization tests indicated that the thruster performance and stability were mostly invariant to changes in the facility background pressure for vacuum chamber pressure below 1×10-5 Torr-Xe (for thruster flow rates of 20.5 mg/s). Power spectral density analysis of the discharge current waveforms showed that increasing the vacuum chamber background pressure resulted in a higher discharge current dominant breathing mode frequency. Finally, IVB maps of the TDU-1 thruster indicated that the discharge current became more oscillatory with higher discharge current peak-to-peak and RMS values with increased facility background pressure at lower thruster mass flow rates; thruster operation at higher flow rates resulted in less change to the thruster's IVB characteristics with elevated background pressure.

Torsion and Antero-Posterior Bending in the In Vivo Human Tibia Loading Regimes during Walking and Running

PubMed Central

Yang, Peng-Fei; Sanno, Maximilian; Ganse, Bergita; Koy, Timmo; Brüggemann, Gert-Peter; Müller, Lars Peter; Rittweger, Jörn

2014-01-01

Bending, in addition to compression, is recognized to be a common loading pattern in long bones in animals. However, due to the technical difficulty of measuring bone deformation in humans, our current understanding of bone loading patterns in humans is very limited. In the present study, we hypothesized that bending and torsion are important loading regimes in the human tibia. In vivo tibia segment deformation in humans was assessed during walking and running utilizing a novel optical approach. Results suggest that the proximal tibia primarily bends to the posterior (bending angle: 0.15°–1.30°) and medial aspect (bending angle: 0.38°–0.90°) and that it twists externally (torsion angle: 0.67°–1.66°) in relation to the distal tibia during the stance phase of overground walking at a speed between 2.5 and 6.1 km/h. Peak posterior bending and peak torsion occurred during the first and second half of stance phase, respectively. The peak-to-peak antero-posterior (AP) bending angles increased linearly with vertical ground reaction force and speed. Similarly, peak-to-peak torsion angles increased with the vertical free moment in four of the five test subjects and with the speed in three of the test subjects. There was no correlation between peak-to-peak medio-lateral (ML) bending angles and ground reaction force or speed. On the treadmill, peak-to-peak AP bending angles increased with walking and running speed, but peak-to-peak torsion angles and peak-to-peak ML bending angles remained constant during walking. Peak-to-peak AP bending angle during treadmill running was speed-dependent and larger than that observed during walking. In contrast, peak-to-peak tibia torsion angle was smaller during treadmill running than during walking. To conclude, bending and torsion of substantial magnitude were observed in the human tibia during walking and running. A systematic distribution of peak amplitude was found during the first and second parts of the stance phase. PMID:24732724

Torsion and antero-posterior bending in the in vivo human tibia loading regimes during walking and running.

PubMed

Yang, Peng-Fei; Sanno, Maximilian; Ganse, Bergita; Koy, Timmo; Brüggemann, Gert-Peter; Müller, Lars Peter; Rittweger, Jörn

2014-01-01

Bending, in addition to compression, is recognized to be a common loading pattern in long bones in animals. However, due to the technical difficulty of measuring bone deformation in humans, our current understanding of bone loading patterns in humans is very limited. In the present study, we hypothesized that bending and torsion are important loading regimes in the human tibia. In vivo tibia segment deformation in humans was assessed during walking and running utilizing a novel optical approach. Results suggest that the proximal tibia primarily bends to the posterior (bending angle: 0.15°-1.30°) and medial aspect (bending angle: 0.38°-0.90°) and that it twists externally (torsion angle: 0.67°-1.66°) in relation to the distal tibia during the stance phase of overground walking at a speed between 2.5 and 6.1 km/h. Peak posterior bending and peak torsion occurred during the first and second half of stance phase, respectively. The peak-to-peak antero-posterior (AP) bending angles increased linearly with vertical ground reaction force and speed. Similarly, peak-to-peak torsion angles increased with the vertical free moment in four of the five test subjects and with the speed in three of the test subjects. There was no correlation between peak-to-peak medio-lateral (ML) bending angles and ground reaction force or speed. On the treadmill, peak-to-peak AP bending angles increased with walking and running speed, but peak-to-peak torsion angles and peak-to-peak ML bending angles remained constant during walking. Peak-to-peak AP bending angle during treadmill running was speed-dependent and larger than that observed during walking. In contrast, peak-to-peak tibia torsion angle was smaller during treadmill running than during walking. To conclude, bending and torsion of substantial magnitude were observed in the human tibia during walking and running. A systematic distribution of peak amplitude was found during the first and second parts of the stance phase.

Average current is better than peak current as therapeutic dosage for biphasic waveforms in a ventricular fibrillation pig model of cardiac arrest.

PubMed

Chen, Bihua; Yu, Tao; Ristagno, Giuseppe; Quan, Weilun; Li, Yongqin

2014-10-01

Defibrillation current has been shown to be a clinically more relevant dosing unit than energy. However, the effects of average and peak current in determining shock outcome are still undetermined. The aim of this study was to investigate the relationship between average current, peak current and defibrillation success when different biphasic waveforms were employed. Ventricular fibrillation (VF) was electrically induced in 22 domestic male pigs. Animals were then randomized to receive defibrillation using one of two different biphasic waveforms. A grouped up-and-down defibrillation threshold-testing protocol was used to maintain the average success rate of 50% in the neighborhood. In 14 animals (Study A), defibrillations were accomplished with either biphasic truncated exponential (BTE) or rectilinear biphasic waveforms. In eight animals (Study B), shocks were delivered using two BTE waveforms that had identical peak current but different waveform durations. Both average and peak currents were associated with defibrillation success when BTE and rectilinear waveforms were investigated. However, when pathway impedance was less than 90Ω for the BTE waveform, bivariate correlation coefficient was 0.36 (p=0.001) for the average current, but only 0.21 (p=0.06) for the peak current in Study A. In Study B, a high defibrillation success (67.9% vs. 38.8%, p<0.001) was observed when the waveform delivered more average current (14.9±2.1A vs. 13.5±1.7A, p<0.001) while keeping the peak current unchanged. In this porcine model of VF, average current was better than peak current to be an adequate parameter to describe the therapeutic dosage when biphasic defibrillation waveforms were used. The institutional protocol number: P0805. Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.

Three years of lightning impulse charge moment change measurements in the United States

NASA Astrophysics Data System (ADS)

Cummer, Steven A.; Lyons, Walter A.; Stanley, Mark A.

2013-06-01

We report and analyze 3 years of lightning impulse charge moment change (iCMC) measurements obtained from an automated, real time lightning charge moment change network (CMCN). The CMCN combines U.S. National Lightning Detection Network (NLDN) lightning event geolocations with extremely low frequency (≲1 kHz) data from two stations to provide iCMC measurements across the entire United States. Almost 14 million lightning events were measured in the 3 year period. We present the statistical distributions of iCMC versus polarity and NLDN-measured peak current, including corrections for the detection efficiency of the CMCN versus peak current. We find a broad distribution of iCMC for a given peak current, implying that these parameters are at best only weakly correlated. Curiously, the mean iCMC does not monotonically increase with peak current, and in fact, drops for positive CG strokes above +150 kA. For all positive strokes, there is a boundary near 20 C km that separates seemingly distinct populations of high and low iCMC strokes. We also explore the geographic distribution of high iCMC lightning strokes. High iCMC positive strokes occur predominantly in the northern midwest portion of the U.S., with a secondary peak over the gulf stream region just off the U.S. east coast. High iCMC negative strokes are also clustered in the midwest, although somewhat south of most of the high iCMC positive strokes. This is a region far from the locations of maximum occurrence of high peak current negative strokes. Based on assumed iCMC thresholds for sprite production, we estimate that approximately 35,000 positive polarity and 350 negative polarity sprites occur per year over the U.S. land and near-coastal areas. Among other applications, this network is useful for the nowcasting of sprite-producing storms and storm regions.

A High Peak Current Source for the CEBAF Injector

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yunn, Byung; Sinclair, Charles; Krafft, Geoffrey

1992-07-01

The CEBAF accelerator can drive high power IR and UV FELs, if a high peak current source is added to the existing front end. We present a design for a high peak current injector which is compatible with simultaneous operation of the accelerator for cw nulear physics (NP) beam. The high peak current injector provides 60 A peak current in 2 psec long bunches carrying 120 pC charge at 7.485 MHz. At 10 MeV that beam is combined with 5 MeV NP beam (0.13pC, 2 psec long bunches at 1497 MHz) in an energy combination chicane for simultaneous acceleration inmore » the injector linac. The modifications to the low-energy NP transport are described. Results of optical and beam dynamics calculations for both high peak current and NP beams in combined operation are presented.« less

A Preliminary Study of the Effects of pH upon Fluorescence in Suspensions of Prevotella intermedia.

PubMed

Hope, Christopher K; Billingsley, Karen; de Josselin de Jong, Elbert; Higham, Susan M

2016-01-01

The quantification of fluorescence in dental plaque is currently being developed as a diagnostic tool to help inform and improve oral health. The oral anaerobe Prevotella intermedia exhibits red fluorescence due to the accumulation of porphyrins. pH affects the fluorescence of abiotic preparations of porphyrins caused by changes in speciation between monomers, higher aggregates and dimers, but this phenomenon has not been demonstrated in bacteria. Fluorescence spectra were obtained from suspensions of P. intermedia that were adjusted to pHs commensurate with the range found within dental plaque. Two fluorescent motifs were identified; 410 nm excitation / 634 nm emission (peak A) and 398 nm excitation / 622 nm emission (peak B). A transition in the fluorescence spectra was observed from peak A to peak B with increasing pH which was also evident as culture age increased from 24 hours to 96 hours. In addition to these 'blue-shifts', the intensity of peak A increased with pH whilst decreasing with culture age from 24 to 96 hours. A bacterium's relationship with the local physiochemical environment at the time of image capture may therefore affect the quantification of dental plaque fluorescence.

A mechanistic diagnosis of the simulation of soil CO2 efflux of the ACME Land Model

NASA Astrophysics Data System (ADS)

Liang, J.; Ricciuto, D. M.; Wang, G.; Gu, L.; Hanson, P. J.; Mayes, M. A.

2017-12-01

Accurate simulation of the CO2 efflux from soils (i.e., soil respiration) to the atmosphere is critical to project global biogeochemical cycles and the magnitude of climate change in Earth system models (ESMs). Currently, the simulated soil respiration by ESMs still have a large uncertainty. In this study, a mechanistic diagnosis of soil respiration in the Accelerated Climate Model for Energy (ACME) Land Model (ALM) was conducted using long-term observations at the Missouri Ozark AmeriFlux (MOFLUX) forest site in the central U.S. The results showed that the ALM default run significantly underestimated annual soil respiration and gross primary production (GPP), while incorrectly estimating soil water potential. Improved simulations of soil water potential with site-specific data significantly improved the modeled annual soil respiration, primarily because annual GPP was simultaneously improved. Therefore, accurate simulations of soil water potential must be carefully calibrated in ESMs. Despite improved annual soil respiration, the ALM continued to underestimate soil respiration during peak growing seasons, and to overestimate soil respiration during non-peak growing seasons. Simulations involving increased GPP during peak growing seasons increased soil respiration, while neither improved plant phenology nor increased temperature sensitivity affected the simulation of soil respiration during non-peak growing seasons. One potential reason for the overestimation of the soil respiration during non-peak growing seasons may be that the current model structure is substrate-limited, while microbial dormancy under stress may cause the system to become decomposer-limited. Further studies with more microbial data are required to provide adequate representation of soil respiration and to understand the underlying reasons for inaccurate model simulations.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Friedmann, T.A.; Tallant, D.R.; Barbour, J.C.

Carbon Nitride (CN{sub x}) films have been grown by ion-assisted pulsed-laser deposition (IAPLD). Graphite targets were laser ablated while bombarding the substrate with ions from a broad-beam Kaufman-type ion source. Ion voltage, current density, substrate temperature, and feed gas composition (N{sub 2} in Ar) were varied. Resultant films were characterized by Raman. Fourier transform infrared (FTIR), and Rutherford back scattering (RBS) spectroscopy. Samples with {approximately} 30% N/C ratio have been fabricated. The corresponding Raman and FTIR spectra indicate that nitrogen is incorporated into the samples by insertion into sp{sup 2}-bonded structures. A low level of C{identical_to}N triple bonds is alsomore » found. As the ion current and voltage are increased with a pure Ar ion beam, Raman peaks associated with nanocrystalline graphite appear in the spectra. Adding low levels of nitrogen to the ion beam first reduces the Raman intensity in the vicinity of the graphite disorder peak without adding detectable amounts of nitrogen to the films (as measured by RBS). At higher nitrogen levels in the ion beam, significant amounts of nitrogen are incorporated into the samples, and the magnitude of the ``disorder`` peak increases. By increasing the temperature of the substrate during deposition, the broad peak due mainly to sp{sup 2}-bonded C-N in the FTIR spectra is shifted to lower wavenumber. This could be interpreted as evidence of single-bonded C-N; however, it is more likely that the character of the sp{sup 2} bonding is changing.« less

Climate change is projected to have severe impacts on the frequency and intensity of peak electricity demand across the United States

PubMed Central

Auffhammer, Maximilian; Baylis, Patrick; Hausman, Catherine H.

2017-01-01

It has been suggested that climate change impacts on the electric sector will account for the majority of global economic damages by the end of the current century and beyond [Rose S, et al. (2014) Understanding the Social Cost of Carbon: A Technical Assessment]. The empirical literature has shown significant increases in climate-driven impacts on overall consumption, yet has not focused on the cost implications of the increased intensity and frequency of extreme events driving peak demand, which is the highest load observed in a period. We use comprehensive, high-frequency data at the level of load balancing authorities to parameterize the relationship between average or peak electricity demand and temperature for a major economy. Using statistical models, we analyze multiyear data from 166 load balancing authorities in the United States. We couple the estimated temperature response functions for total daily consumption and daily peak load with 18 downscaled global climate models (GCMs) to simulate climate change-driven impacts on both outcomes. We show moderate and heterogeneous changes in consumption, with an average increase of 2.8% by end of century. The results of our peak load simulations, however, suggest significant increases in the intensity and frequency of peak events throughout the United States, assuming today’s technology and electricity market fundamentals. As the electricity grid is built to endure maximum load, our findings have significant implications for the construction of costly peak generating capacity, suggesting additional peak capacity costs of up to 180 billion dollars by the end of the century under business-as-usual. PMID:28167756

Longitudinal relationship between wheelchair exercise capacity and life satisfaction in patients with spinal cord injury: A cohort study in the Netherlands.

PubMed

van Koppenhagen, Casper Floris; Post, Marcel; de Groot, Sonja; van Leeuwen, Christel; van Asbeck, Floris; Stolwijk-Swüste, Janneke; van der Woude, Lucas; Lindeman, Eline

2014-05-01

To examine the relationship between wheelchair exercise capacity and life satisfaction in persons with spinal cord injury from the start of active inpatient rehabilitation up to 5 years after discharge. Prospective cohort study. Persons with spinal cord injury, aged 18-65 years, and wheelchair dependent at least for long distances. Measurements at the start of active rehabilitation, after 3 months, at discharge from inpatient rehabilitation, and 1 and 5 years after discharge. A peak wheelchair exercise test was performed to record peak oxygen uptake (VO2peak) and peak power output (POpeak). Life satisfaction was measured as current life satisfaction and change of life satisfaction in comparison with life after spinal cord injury. Relationships between (changes in) exercise capacity and (changes in) life satisfaction were analyzed random coefficient analysis, corrected for possible confounders (age, gender, level of lesion, functional status, secondary impairments, pain, and sports activity) if necessary. Of 225 persons included, 130 attended two or more peak exercise tests, who were include in the analyses. Mean age at start was 39 years, 75% were male, 73% had paraplegia, and 76% had a traumatic lesion. Mean POpeak increased during the study from 32.9 to 55.9 Watts, mean VO2peak from 1.02 to 1.38 l/minute, and mean life satisfaction from 5.7 to 7.8. An increase of POpeak with 10 W was associated with a 0.3-point increase of life satisfaction (P = 0.01). An increase of VO2peak with 0.1 l/minute was associated with a 0.1-point increase of life satisfaction (P = 0.049). Conclusion High(er) wheelchair exercise capacity is related to high(er) life satisfaction in spinal cord injury patients.

Parameters of triggered-lightning flashes in Florida and Alabama

NASA Astrophysics Data System (ADS)

Fisher, R. J.; Schnetzer, G. H.; Thottappillil, R.; Rakov, V. A.; Uman, M. A.; Goldberg, J. D.

1993-12-01

Channel base currents from triggered lightning were measured at the NASA Kennedy Space Center, Florida, during summer 1990 and at Fort McClellan, Alabama, during summer 1991. Additionally, 16-mm cinematic records with 3- or 5-ms resolution were obtained for all flashes, and streak camera records were obtained for three of the Florida flashes. The 17 flashes analyzed here contained 69 strokes, all lowering negative charge from cloud to ground. Statistics on interstroke interval, no-current interstroke interval, total stroke duration, total stroke charge, total stroke action integral (∫ i2dt), return stroke current wave front characteristics, time to half peak value, and return stroke peak current are presented. Return stroke current pulses, characterized by rise times of the order of a few microseconds or less and peak values in the range of 4 to 38 kA, were found not to occur until after any preceding current at the bottom of the lightning channel fell below the noise level of less than 2 A. Current pulses associated with M components, characterized by slower rise times (typically tens to hundreds of microseconds) and peak values generally smaller than those of the return stroke pulses, occurred during established channel current flow of some tens to some hundreds of amperes. A relatively strong positive correlation was found between return stroke current average rate of rise and current peak. There was essentially no correlation between return stroke current peak and 10-90% rise time or between return stroke peak and the width of the current waveform at half of its peak value. Parameters of the lightning flashes triggered in Florida and Alabama are similar to each other but are different from those of triggered lightning recorded in New Mexico during the 1981 Thunderstorm Research International Program. Continuing currents that follow return stroke current peaks and last for more than 10 ms exhibit a variety of wave shapes that we have subdivided into four categories. All such continuing currents appear to start with a current pulse presumably associated with an M component. A brief summary of lightning parameters important for lightning protection, in a form convenient for practical use, is presented in an appendix.

Nonlinear conductivity of a holographic superconductor under constant electric field

NASA Astrophysics Data System (ADS)

Zeng, Hua Bi; Tian, Yu; Fan, Zheyong; Chen, Chiang-Mei

2017-02-01

The dynamics of a two-dimensional superconductor under a constant electric field E is studied by using the gauge-gravity correspondence. The pair breaking current induced by E first increases to a peak value and then decreases to a constant value at late times, where the superconducting gap goes to zero, corresponding to a normal conducting phase. The peak value of the current is found to increase linearly with respect to the electric field. Moreover, the nonlinear conductivity, defined as an average of the conductivity in the superconducting phase, scales as ˜E-2 /3 when the system is close to the critical temperature Tc, which agrees with predictions from solving the time-dependent Ginzburg-Landau equation. Away from Tc, the E-2 /3 scaling of the conductivity still holds when E is large.

Current drive by spheromak injection into a tokamak

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brown, M.R.; Bellan, P.M.

1990-04-30

We report the first observation of current drive by injection of a spheromak plasma into a tokamak (Caltech ENCORE small reasearch tokamak) due to the process of helicity injection. After an abrupt 30% increase, the tokamak current decays by a factor of 3 due to plasma cooling caused by the merging of the relatively cold spheromak with the tokamak. The tokamak density profile peaks sharply due to the injected spheromak plasma ({ital {bar n}}{sub 3} increases by a factor of 6) then becomes hollow, suggestive of an interchange instability.

Influence of Sample Size of Polymer Materials on Aging Characteristics in the Salt Fog Test

NASA Astrophysics Data System (ADS)

Otsubo, Masahisa; Anami, Naoya; Yamashita, Seiji; Honda, Chikahisa; Takenouchi, Osamu; Hashimoto, Yousuke

Polymer insulators have been used in worldwide because of some superior properties; light weight, high mechanical strength, good hydrophobicity etc., as compared with porcelain insulators. In this paper, effect of sample size on the aging characteristics in the salt fog test is examined. Leakage current was measured by using 100 MHz AD board or 100 MHz digital oscilloscope and separated three components as conductive current, corona discharge current and dry band arc discharge current by using FFT and the current differential method newly proposed. Each component cumulative charge was estimated automatically by a personal computer. As the results, when the sample size increased under the same average applied electric field, the peak values of leakage current and each component current increased. Especially, the cumulative charges and the arc discharge length of dry band arc discharge increased remarkably with the increase of gap length.

Plasma bullet current measurements in a free-stream helium capillary jet

NASA Astrophysics Data System (ADS)

Oh, Jun-Seok; Walsh, James L.; Bradley, James W.

2012-06-01

A commercial current monitor has been used to measure the current associated with plasma bullets created in both the positive and negative half cycles of the sinusoidal driving voltage sustaining a plasma jet. The maximum values of the positive bullet current are typically ˜750 µA and persist for 10 µs, while the peaks in the negative current of several hundred μA are broad, persisting for about 40 µs. From the time delay of the current peaks with increasing distance from the jet nozzle, an average bullet propagation speed has been measured; the positive and negative bullets travel at 17.5 km s-1 and 3.9 km s-1 respectively. The net space charge associated with the bullet(s) has also been calculated; the positive and negative bullets contain a similar net charge of the order of 10-9 C measured at all monitor positions, with estimated charged particle densities nb of ˜1010-1011 cm-3 in the bullet.

Controlling Gilbert damping in a YIG film using nonlocal spin currents

NASA Astrophysics Data System (ADS)

Haidar, M.; Dürrenfeld, P.; Ranjbar, M.; Balinsky, M.; Fazlali, M.; Dvornik, M.; Dumas, R. K.; Khartsev, S.; Åkerman, J.

2016-11-01

We demonstrate the control of Gilbert damping in 65-nm-thick yttrium iron garnet (YIG) films using a spin-polarized current generated by a direct current through a nanocontact, spin filtered by a thin Co layer. The magnetodynamics of both the YIG and the Co layers can be excited by a pulse-modulated microwave current injected through the nanocontact and the response detected as a lock-in amplified voltage over the device. The spectra show three clear peaks, two associated with the ferromagnetic resonance (FMR) in each layer, and an additional Co mode with a higher wave vector proportional to the inverse of the nanocontact diameter. By varying the sign and magnitude of the direct nanocontact current, we can either increase or decrease the linewidth of the YIG FMR peak consistent with additional positive or negative damping being exerted by the nonlocal spin current injected into the YIG film. Our nanocontact approach thus offers an alternative route in the search for auto-oscillations in YIG films.

Experimental Investigations on Combustion Behaviors of Live PVC Cables

NASA Astrophysics Data System (ADS)

Wang, Liufang; Zhang, Jiaqing; Zhang, Bosi; Liu, Min; Fan, Minghao; Li, Qiang

2018-03-01

This paper investigated the combustion behaviors of live PVC cables with overload currents experimentally. The smoke coefficient of released smoke and the released gas concentration were examined. The results indicate that the combustion of live PVC cables can be divided into four stages, i.e., core exposed with a little smoke, obvious flame, maximum smoke and smoke depress. For most cases, using blue laser is better than using rad laser, since the extinction coefficient of the rad laser was larger than that of the blue laser. The response time of the detection of the released typical gases due to cable pyrolysis decreased and the peak values of the typical gases increased with the overload currents. In addition, the time to reach the peak value of gas concentration also decreased with the overload currents.

Zero bias thermally stimulated currents in synthetic diamond

NASA Astrophysics Data System (ADS)

Mori, R.; Miglio, S.; Bruzzi, M.; Bogani, F.; De Sio, A.; Pace, E.

2009-06-01

Zero bias thermally stimulated currents (ZBTSCs) have been observed in single crystal high pressure high temperature (HPHT) and polycrystalline chemical vapor deposited (pCVD) diamond films. The ZBTSC technique is characterized by an increased sensitivity with respect to a standard TSC analysis. Due to the absence of the thermally activated background current, new TSC peaks have been observed in both HPHT and pCVD diamond films, related to shallow activation energies usually obscured by the emission of the dominant impurities. The ZBTSC peaks are explained in terms of defect discharge in the nonequilibrium potential distribution created by a nonuniform traps filling at the metal-diamond junctions. The electric field due to the charged defects has been estimated in a quasizero bias TSC experiment by applying an external bias.

Electrochemical sensor for hazardous food colourant quinoline yellow based on carbon nanotube-modified electrode.

PubMed

Zhao, Jun; Zhang, Yu; Wu, Kangbing; Chen, Jianwei; Zhou, Yikai

2011-09-15

A novel electrochemical method using multi-wall carbon nanotube (MWNT) film-modified electrode was developed for the detection of quinoline yellow. In pH 8 phosphate buffer, an irreversible oxidation peak at 0.71V was observed for quinoline yellow. Compared with the unmodified electrode, the MWNT film-modified electrode greatly increases the oxidation peak current of quinoline yellow, showing notable enhancement effect. The effects of pH value, amount of MWNT, accumulation potential and time were studied on the oxidation peak current of quinoline yellow. The linear range is from 0.75 to 20mgL(-1), and the limit of detection is 0.5mgL(-1). It was applied to the detection of quinoline yellow in commercial soft drinks, and the results consisted with the value that obtained by high-performance liquid chromatography. Copyright © 2011 Elsevier Ltd. All rights reserved.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Parkin, William M.; Balan, Adrian; Liang, Liangbo

Here, we report how the presence of electron-beam-induced sulfur vacancies affects first-order Raman modes and correlate the effects with the evolution of the in situ transmission-electron microscopy (TEM) two-terminal conductivity of monolayer MoS 2 under electron irradiation. We observe a redshift in the E Raman peak and a less pronounced blueshift in the A' 1 peak with increasing electron dose. Using energy-dispersive X-ray spectroscopy (EDS), we show that irradiation causes partial removal of sulfur and correlate the dependence of the Raman peak shifts with S vacancy density (a few %), which is confirmed by first-principles density functional theory calculations. Inmore » situ device current measurements show exponential decrease in channel current upon irradiation. Our analysis demonstrates that the observed frequency shifts are intrinsic properties of the defective systems and that Raman spectroscopy can be used as a quantitative diagnostic tool to characterize MoS 2-based transport channels.« less

Study on the mechanism of Si-glass-Si two step anodic bonding process

NASA Astrophysics Data System (ADS)

Hu, Lifang; Wang, Hao; Xue, Yongzhi; Shi, Fangrong; Chen, Shaoping

2018-04-01

Si-glass-Si was successfully bonded together through a two-step anodic bonding process. The bonding current in each step of the two-step bonding process was investigated, and found to be quite different. The first bonding current decreased quickly to a relatively small value, but for the second bonding step, there were two current peaks; the current first decreased, then increased, and then decreased again. The second current peak occurred earlier with higher temperature and voltage. The two-step anodic bonding process was investigated in terms of bonding current. SEM and EDS tests were conducted to investigate the interfacial structure of the Si-glass-Si samples. The two bonding interfaces were almost the same, but after an etching process, transitional layers could be found in the bonding interface and a deeper trench with a thickness of ~1.5 µm could be found in the second bonding interface. Atomic force microscopy mapping results indicated that sodium precipitated from the back of the glass, which makes the roughness of the surface become coarse. Tensile tests indicated that the fracture occurred at the glass substrate and that the bonding strength increased with the increment of bonding temperature and voltage with the maximum strength of 6.4 MPa.

The influence of high-intensity compared with moderate-intensity exercise training on cardiorespiratory fitness and body composition in colorectal cancer survivors: a randomised controlled trial.

PubMed

Devin, James L; Sax, Andrew T; Hughes, Gareth I; Jenkins, David G; Aitken, Joanne F; Chambers, Suzanne K; Dunn, Jeffrey C; Bolam, Kate A; Skinner, Tina L

2016-06-01

Following colorectal cancer diagnosis and anti-cancer therapy, declines in cardiorespiratory fitness and body composition lead to significant increases in morbidity and mortality. There is increasing interest within the field of exercise oncology surrounding potential strategies to remediate these adverse outcomes. This study compared 4 weeks of moderate-intensity exercise (MIE) and high-intensity exercise (HIE) training on peak oxygen consumption (V̇O2peak) and body composition in colorectal cancer survivors. Forty seven post-treatment colorectal cancer survivors (HIE = 27 months post-treatment; MIE = 38 months post-treatment) were randomised to either HIE [85-95 % peak heart rate (HRpeak)] or MIE (70 % HRpeak) in equivalence with current physical activity guidelines and completed 12 training sessions over 4 weeks. HIE was superior to MIE in improving absolute (p = 0.016) and relative (p = 0.021) V̇O2peak. Absolute (+0.28 L.min(-1), p < 0.001) and relative (+3.5 ml.kg(-1).min(-1), p < 0.001) V̇O2 peak were increased in the HIE group but not the MIE group following training. HIE led to significant increases in lean mass (+0.72 kg, p = 0.002) and decreases in fat mass (-0.74 kg, p < 0.001) and fat percentage (-1.0 %, p < 0.001), whereas no changes were observed for the MIE group. There were no severe adverse events. In response to short-term training, HIE is a safe, feasible and efficacious intervention that offers clinically meaningful improvements in cardiorespiratory fitness and body composition for colorectal cancer survivors. HIE appears to offer superior improvements in cardiorespiratory fitness and body composition in comparison to current physical activity recommendations for colorectal cancer survivors and therefore may be an effective clinical utility following treatment.

Magnetic Field Observations of Partial Ring Current during Storm Recovery Phase

NASA Technical Reports Server (NTRS)

Le, G.; Russell, C. T.; Slavin, J. A.; Lucek, E. A.

2008-01-01

We present results of an extensive survey of the magnetic field observations in the inner magnetosphere using 30 years of magnetospheric magnetic field data from Polar, Cluster, ISEE, and AMPTE/CCE missions. The purpose of this study is to understand the magnetic field evolution during the recovery phase of geomagnetic storms, and its implication to the ring current recovery and loss mechanisms of ring current particles. It is now commonly believed that a strong partial ring current is formed during the storm main phase due to the enhanced earthward convection of energetic ions from nightside plasma sheet. But the presence of a strong partial ring current throughout the recovery phase remains controversial. The magnetic field generated by the ring current inflates the inner magnetosphere and causes magnetic field depressions in the equatorial magnetosphere. During the storm recovery phase, we find that the distribution of the equatorial magnetic field depression exhibits similar local time dependence as the ring current distribution obtained from the combined dataset in the earlier study. It shows that a strong partial ring current is a permanent feature throughout the recovery phase. In the early recovery phase, the partial ring current peaks near the dusk terminator as indicated by the peak of the magnetic field depression. As the recovery phase progresses, the partial ring current decays most quickly near the dusk and results in a dusk-to-midnight moving of the peak of the partial ring current. Thus the loss mechanisms work most effectively near the dusk. The magnetic field depression increases the gyroradius of ring current protons to a scale greater or comparable to the thickness of the magnetopause, which increases the chance of ion drift loss near the dusk magnetopause at larger L-shell (L greater than 5). But the drift loss mechanism alone cannot explain the loss of ring current ions especially in the smaller L-shell (L less than 5). The precipitation loss due to wave-particle interaction is most likely the dominant loss mechanism in the small L-shell as it works most effectively at the same local time.

Anodic stripping voltammetry enhancement by redox magnetohydrodynamics.

PubMed

Clark, Emily A; Fritsch, Ingrid

2004-04-15

The effect of an external magnetic field on linear scan anodic stripping voltammetry (ASV) in solutions of 10(-6)-10(-7) M concentrations of lead, cadmium, and copper at mercury films on glassy carbon electrodes has been investigated. A high concentration of Hg(2+) was added to the analyte solution to induce a large cathodic current during the deposition step. Therefore, a large Lorentz force from the net flux of charge through the magnetic field resulted in convection due to magnetohydrodynamics. The faster delivery of analytes to the mercury film electrode during deposition caused an increase in the anodic stripping peaks. The effect of varying Hg(2+) concentrations (0-60 mM) and magnetic field strengths (0-1.77 T) on the enhancement of the stripping peaks was investigated. Enhancements as large as 129% for peak currents and 167% for peak areas were observed. An enhancement of approximately 100% was observed when 60 mM Fe(3+) replaced high concentrations of Hg(2+). This method of convection exhibits promise for small-volume ASV analysis with possible improved limits of detection and decreased preconcentration times.

Direct Electrodeposition of Gold Nanoparticles on Glassy Carbon Electrode for Selective Determination Catechol in the Presence of Hydroquinone.

PubMed

Jayakumar, C; Magdalane, C Maria; Kaviyarasu, K; Kulandainathan, M Anbu; Jeyaraj, Boniface; Maaza, M

2018-07-01

A simple and reliable voltammetric sensor for simultaneous determination of Catechol (CT) and Hydroquinone (HQ) was developed by electrodepositing the gold nanoparticles on the surface of the Glassy Carbon Electrode (GCE). The cyclic voltammograms in a mixed solution of CT and HQ have shown that the oxidation peaks become well resolved and were separated by 110 mV, although the bare GCE gave a single broad oxidation peak. Moreover, the oxidation peak currents of both CT and HQ were remarkably increased three times in comparison with the bare GCE. This makes gold nanoparticles deposited GCE a suitable candidate for the determination of these isomers. In the presence of 1 mM HQ isomer, the oxidation peak currents of differential pulse voltammograms are proportional to the concentration of CT in the range of 21 μM to 323 μM with limit of detection 3.0 μM (S/N = 3). The proposed sensor has some important advantages such as low cost, ease of preparation, good stability and high reproducibility.

Concentration-jump analysis of voltage-dependent conductances activated by glutamate and kainate in neurons of the avian cochlear nucleus.

PubMed Central

Raman, I M; Trussell, L O

1995-01-01

We have examined the mechanisms underlying the voltage sensitivity of alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate receptors in voltage-clamped outside-out patches and whole cells taken from the nucleus magnocellularis of the chick. Responses to either glutamate or kainate had outwardly rectifying current-voltage relations. The rate and extent of desensitization during prolonged exposure to agonist, and the rate of deactivation after brief exposure to agonist, decreased at positive potentials, suggesting that a kinetic transition was sensitive to membrane potential. Voltage dependence of the peak conductance and of the deactivation kinetics persisted when desensitization was reduced with aniracetam or blocked with cyclothiazide. Furthermore, the rate of recovery from desensitization to glutamate was not voltage dependent. Upon reduction of extracellular divalent cation concentration, kainate-evoked currents increased but preserved rectifying current-voltage relations. Rectification was strongest at lower kainate concentrations. Surprisingly, nonstationary variance analysis of desensitizing responses to glutamate or of the current deactivation after kainate removal revealed an increase in the mean single-channel conductance with more positive membrane potentials. These data indicate that the rectification of the peak response to a high agonist concentration reflects an increase in channel conductance, whereas rectification of steady-state current is dominated by voltage-sensitive channel kinetics. Images FIGURE 2 FIGURE 3 PMID:8580330

Electromagnetic pulse-induced current measurement device

NASA Astrophysics Data System (ADS)

Gandhi, Om P.; Chen, Jin Y.

1991-08-01

To develop safety guidelines for exposure to high fields associated with an electromagnetic pulse (EMP), it is necessary to devise techniques that would measure the peak current induced in the human body. The main focus of this project was to design, fabricate, and test a portable, self-contained stand-on device that would measure and hold the peak current and the integrated change Q. The design specifications of the EMP-Induced Current Measurement Device are as follows: rise time of the current pulse, 5 ns; peak current, 20-600 A; charge Q, 0-20 microcoulombs. The device uses a stand-on parallel-plate bilayer sensor and fast high-frequency circuit that are well-shielded against spurious responses to high incident fields. Since the polarity of the incident peak electric field of the EMP may be either positive or negative, the induced peak current can also be positive or negative. Therefore, the device is designed to respond to either of these polarities and measure and hold both the peak current and the integrated charge which are simultaneously displayed on two separate 3-1/2 digit displays. The prototype device has been preliminarily tested with the EMP's generated at the Air Force Weapons Laboratory (ALECS facility) at Kirtland AFB, New Mexico.

High peak current operation of x-ray free-electron laser multiple beam lines by suppressing coherent synchrotron radiation effects

NASA Astrophysics Data System (ADS)

Hara, Toru; Kondo, Chikara; Inagaki, Takahiro; Togawa, Kazuaki; Fukami, Kenji; Nakazawa, Shingo; Hasegawa, Taichi; Morimoto, Osamu; Yoshioka, Masamichi; Maesaka, Hirokazu; Otake, Yuji; Tanaka, Hitoshi

2018-04-01

The parallel operation of multiple beam lines is an important means to expand the opportunity of user experiments at x-ray free-electron laser (XFEL) facilities. At SPring-8 Angstrom free-electron laser (SACLA), the multi-beam-line operation had been tested using two beam lines, but transverse coherent synchrotron radiation (CSR) effects at a dogleg beam transport severely limited the laser performance. To suppress the CSR effects, a new beam optics based on two double bend achromat (DBA) structures was introduced for the dogleg. After the replacement of the beam optics, high peak current bunches of more than 10 kA are now stably transported through the dogleg and the laser pulse output is increased by a factor of 2-3. In the multi-beam-line operation of SACLA, the electron beam parameters, such as the beam energy and peak current, can be adjusted independently for each beam line. Thus the laser output can be optimized and wide spectral tunability is ensured for all beam lines.

Sensitive electrochemical immunosensor for α-fetoprotein based on graphene/SnO2/Au nanocomposite.

PubMed

Liu, Junfeng; Lin, Guanhua; Xiao, Can; Xue, Ying; Yang, Ankang; Ren, Hongxuan; Lu, Wensheng; Zhao, Hong; Li, Xiangjun; Yuan, Zhuobin

2015-09-15

A label-free electrochemical immunosensor for sensitive detection of α-fetoprotein (AFP) was developed based on graphene/SnO2/Au nanocomposite. The graphene/SnO2/Au nanocomposite modified glassy carbon electrode was used to immobilize α-fetoprotein antibody (anti-AFP) and to construct the immunosensor. Results demonstrated that the peak currents of [Ru(NH3)6](3+) decreased due to the interaction between antibody and antigen on the modified electrode. Thus, a label-free immunosensor for the detection of AFP was realized by monitoring the peak current change of [Ru(NH3)6](3+). The factors influencing the performance of the immunosensor were investigated in details. Under optimal conditions, the peak currents obtained by DPV decreased linearly with the increasing AFP concentrations in the range from 0.02 to 50 ng mL(-1) with a linear coefficient of 0.9959. This electrochemical immunoassay has a low detection limit of 0.01 ng mL(-1) (S/N=3) and was successfully applied to the determination of AFP in serum samples. Copyright © 2015 Elsevier B.V. All rights reserved.

Optical monitoring of ion beam Y-Ba-Cu-O sputtering

NASA Astrophysics Data System (ADS)

Klein, J. D.; Yen, A.

1990-11-01

The emission spectra resulting from ion beam sputtering a Y-Ba-Cu-O target were observed as a function of beam voltage and beam current. The spectra were relatively clean with several peaks readily attributed to each of Y, Ba, and Ar. Monitoring of copper and oxygen was more difficult with a single CuO peak and one O peak evident. The intensities of the cation peaks were linear with respect to beam voltage above 400 V. Since target current was found not to be directly proportional to beam current, target power was defined as the product of beam voltage and target current. The response of cation peak height to changes in target power was linear and similar for variations of either beam voltage or target current.

Characteristics of exploding metal wires in water with three discharge types

NASA Astrophysics Data System (ADS)

Han, Ruoyu; Wu, Jiawei; Zhou, Haibin; Ding, Weidong; Qiu, Aici; Clayson, Thomas; Wang, Yanan; Ren, Hang

2017-07-01

This paper presents the characteristics of underwater electrical wire explosion (UEWE) with three discharge types, namely, Type-A, Type-B, and Type-C. Experiments were carried out with copper and tungsten wires (4 cm long and 50-300 μm in diameter) driven by a microsecond time-scale pulsed current source with 500 J stored energy. A time-integrated spectrometer and a photodiode were used to measure the optical emission of UEWE. A Polyvinylidene Fluoride probe was adopted to record the pressure waveforms. Experimental results indicate that from Type-A to Type-C, more energy deposits prior to the voltage peak and the first peak power increases drastically. This variation of energy deposition influences the optical emission and shock wave generation process. Specifically, the light intensity decreases by more than 90% and the peak of continuous spectra moves from ˜400 nm to ˜700 nm. In addition, the peak pressure of the first shock wave increases from ˜2 MPa to more than 7.5 MPa.

Effect of extracellular ATP on contraction, cytosolic calcium activity, membrane voltage and ion currents of rat mesangial cells in primary culture.

PubMed Central

Pavenstädt, H.; Gloy, J.; Leipziger, J.; Klär, B.; Pfeilschifter, J.; Schollmeyer, P.; Greger, R.

1993-01-01

1. The effects of extracellular ATP on contraction, membrane voltage (Vm), ion currents and intracellular calcium activity [Ca2+]i were studied in rat mesangial cells (MC) in primary culture. 2. Addition of extracellular ATP (10(-5) and 10(-4) M) to MC led to a cell contraction which was independent of extracellular calcium. 3. Membrane voltage (Vm) and ion currents were measured with the nystatin patch clamp technique. ATP induced a concentration-dependent transient depolarization of Vm (ED50: 2 x 10(-6) M). During the transient depolarization ion currents were monitored simultaneously and showed an increase of the inward- and outward current. 4. In a buffer with a reduced extracellular chloride concentration (from 145 to 30 mM) ATP induced a depolarization augmented to -4 +/- 4 mV. 5. ATP-gamma-S and 2-methylthio-ATP depolarized Vm to the same extent as ATP, whereas alpha,beta-methylene-ATP (all 10(-5) M) had no effect on Vm. 6. The Ca2+ ionophore, A23187, depolarized Vm transiently from -51 +/- 2 to -28 +/- 4 mV and caused an increase of the inward current. 7. The intracellular calcium activity [Ca2+]i was measured with the fura-2 technique. ATP stimulated a concentration-dependent increase of [Ca2+]i (ED50: 5 x 10(-6) M). The increase of [Ca2+]i was biphasic with an initial peak followed by a sustained plateau. 8. The [Ca2+]i peak was still present in an extracellular Ca(2+)-free buffer, whereas the plateau was abolished. Verapamil (10(-4) M) did not inhibit the [Ca2+]i increase induced by ATP.(ABSTRACT TRUNCATED AT 250 WORDS) Images Figure 1 PMID:7691366

Effects of dithiothreitol on end-plate currents.

PubMed Central

Terrar, D A

1978-01-01

1. End-plate currents have been studied in frog cutaneus pectoris nerve-muscle preparations mounted in continuously flowing solution, using the voltage clamp technique. 2. Exposure of the muscle to 1 mM-dithiothreitol reduced the amplitude of end-plate currents by a factor of 2.7 (mean; range 1.6-3.4; twelve fibres). 3. 1 mM-dithiothreitol also caused a 2.7-fold (2.3-3.1) increase in the rate of decay, and a 1.4-fold (1.3-1.6) decrease in the time to peak of end-plate currents. During the onset of action of dithiothreitol, there was little or no indication of departure of end-plate current decay from a simple exponential. 4. Dithiothreitol actions on amplitude and decay of end-plate currents developed with similar time courses and both effects were slower in onset at pH 7.2 than at pH 8.5. 5. The actions of dithiothreitol were reversed by exposure of the muscle to 1 mM-5,5'-dithio-bis-(2-nitrobenzoic acid). 6. Following dithiothreitol treatment, the rates of decay of end-plate currents continued to depend on membrane potential; there was little or no change in the slope of the relation between in (rate of decay) and membrane potential, consistent with little or no change in the dipole moment of a gating molecule for ion channels. 7. Dithiothreitol changed the relation between peak end-plate current and membrane potential, so that peak conductance increased at more negative membrane potentials; this finding could be accounted for in terms of the closure of ion-channel gates becoming faster though remaining voltage-sensitive after exposure to dithiothreitol. 8. It is concluded that dithiothreitol causes changes in the kinetics of gating of ion channels associated with receptors and that these changes accompany changes in the binding of ACh to receptors. PMID:25960

Adjusting measured peak discharges from an urbanizing watershed to reflect a stationary land use signal

NASA Astrophysics Data System (ADS)

Beighley, R. Edward; Moglen, Glenn E.

2003-04-01

A procedure to adjust gauged streamflow data from watersheds urbanized during or after their gauging period is presented. The procedure adjusts streamflow to be representative of a fixed land use condition, which may reflect current or future development conditions. Our intent is to determine what an event resulting in a peak discharge in, for example, 1950 (i.e., before urbanization) would produce on the current urban watershed. While past approaches assumed uniform spatial and temporal changes in urbanization, this study focuses on the use of geographic information systems (GIS) based methodologies for precisely locating in space and time where land use change has occurred. This information is incorporated into a hydrologic model to simulate the change in discharge as a result of changing land use conditions. In this paper, we use historical aerial photographs, GIS linked tax-map data, and recent land use/land cover data to recreate the spatial development history of eight gauged watersheds in the Baltimore-Washington, D. C., metropolitan area. Using our procedure to determine discharge series representative of the current urban watersheds, we found that the increase of the adjusted 2-year discharge ranged from 16 to 70 percent compared with the measured annual maximum discharge series. For the 100-year discharge the adjusted values ranged from 0 to 47 percent greater than the measured values. Additionally, relationships between the increase in flood flows and four measures of urbanization (increase in urban land, decrease in forested land, increase in high-density development, and the spatial development pattern) are investigated for predicting the increase in flood flows for ungauged watersheds. Watersheds with the largest increases in flood flows typically had more extensive development in the areas far removed from the outlet. In contrast, watersheds with development located nearer to the outlet typically had the smallest increases in peak discharge.

Examining the effects of urban agglomeration polders on flood events in Qinhuai River basin, China with HEC-HMS model.

PubMed

Gao, Yuqin; Yuan, Yu; Wang, Huaizhi; Schmidt, Arthur R; Wang, Kexuan; Ye, Liu

2017-05-01

The urban agglomeration polders type of flood control pattern is a general flood control pattern in the eastern plain area and some of the secondary river basins in China. A HEC-HMS model of Qinhuai River basin based on the flood control pattern was established for simulating basin runoff, examining the impact of urban agglomeration polders on flood events, and estimating the effects of urbanization on hydrological processes of the urban agglomeration polders in Qinhuai River basin. The results indicate that the urban agglomeration polders could increase the peak flow and flood volume. The smaller the scale of the flood, the more significant the influence of the polder was to the flood volume. The distribution of the city circle polder has no obvious impact on the flood volume, but has effect on the peak flow. The closer the polder is to basin output, the smaller the influence it has on peak flows. As the level of urbanization gradually improving of city circle polder, flood volumes and peak flows gradually increase compared to those with the current level of urbanization (the impervious rate was 20%). The potential change in flood volume and peak flow with increasing impervious rate shows a linear relationship.

Electron acceleration in downward auroral field-aligned currents

NASA Astrophysics Data System (ADS)

Cran-McGreehin, Alexandra P.; Wright, Andrew N.

2005-10-01

The auroral downward field-aligned current is mainly carried by electrons accelerated up from the ionosphere into the magnetosphere along magnetic field lines. Current densities are typically of the order of a few μ Am-2, and the associated electrons are accelerated to energies of several hundred eV up to a few keV. This downward current has been modeled by Temerin and Carlson (1998) using an electron fluid. This paper extends that model by describing the electron populations via distribution functions and modeling all of the F region. We assume a given ion density profile, and invoke quasi-neutrality to solve for the potential along the field line. Several important locations and quantities emerge from this model: the ionospheric trapping point, below which the ionospheric population is trapped by an ambipolar electric field; the location of maximum E∥, of the order of a few mVm-1, which lies earthward of the B/n peak; the acceleration region, located around the B/n peak, which normally extends between altitudes of 500 and 3000 km; and the total potential increase along the field line, of the order of a few hundred V up to several kV. The B/n peak is found to be the central factor determining the altitude and magnitude of the accelerating potential required. Indeed, the total potential drop is found to depend solely on the equilibrium properties in the immediate vicinity of the B/n peak.

2D modeling of DC potential structures induced by RF sheaths with transverse currents in front of ICRF antenna

NASA Astrophysics Data System (ADS)

Faudot, E.; Heuraux, S.; Colas, L.

2005-09-01

Understanding DC potential generation in front of ICRF antennas is crucial for long pulse high RF power systems. DC potentials are produced by sheath rectification of these RF potentials. To reach this goal, near RF parallel electric fields have to be computed in 3D and integrated along open magnetic field lines to yield a 2D RF potential map in a transverse plane. DC potentials are produced by sheath rectification of these RF potentials. As RF potentials are spatially inhomogeneous, transverse polarization currents are created, modifying RF and DC maps. Such modifications are quantified on a `test map' having initially a Gaussian shape and assuming that the map remains Gaussian near its summit,the time behavior of the peak can be estimated analytically in presence of polarization current as a function of its width r0 and amplitude φ0 (normalized to a characteristic length for transverse transport and to the local temperature). A `peaking factor' is built from the DC peak potential normalized to φ0, and validated with a 2D fluid code and a 2D PIC code (XOOPIC). In an unexpected way transverse currents can increase this factor. Realistic situations of a Tore Supra antenna are also studied, with self-consistent near fields provided by ICANT code. Basic processes will be detailed and an evaluation of the `peaking factor' for ITER will be presented for a given configuration.

2D modeling of DC potential structures induced by RF sheaths with transverse currents in front of ICRF antenna

DOE Office of Scientific and Technical Information (OSTI.GOV)

Faudot, E.; Heuraux, S.; Colas, L.

2005-09-26

Understanding DC potential generation in front of ICRF antennas is crucial for long pulse high RF power systems. DC potentials are produced by sheath rectification of these RF potentials. To reach this goal, near RF parallel electric fields have to be computed in 3D and integrated along open magnetic field lines to yield a 2D RF potential map in a transverse plane. DC potentials are produced by sheath rectification of these RF potentials. As RF potentials are spatially inhomogeneous, transverse polarization currents are created, modifying RF and DC maps. Such modifications are quantified on a 'test map' having initially amore » Gaussian shape and assuming that the map remains Gaussian near its summit,the time behavior of the peak can be estimated analytically in presence of polarization current as a function of its width r0 and amplitude {phi}0 (normalized to a characteristic length for transverse transport and to the local temperature). A 'peaking factor' is built from the DC peak potential normalized to {phi}0, and validated with a 2D fluid code and a 2D PIC code (XOOPIC). In an unexpected way transverse currents can increase this factor. Realistic situations of a Tore Supra antenna are also studied, with self-consistent near fields provided by ICANT code. Basic processes will be detailed and an evaluation of the 'peaking factor' for ITER will be presented for a given configuration.« less

Performance Evaluation of III-V Hetero/Homojunction Esaki Tunnel Diodes on Si and Lattice Matched Substrates

NASA Astrophysics Data System (ADS)

Thomas, Paul M.

Understanding of quantum tunneling phenomenon in semiconductor systems is increasingly important as CMOS replacement technologies are investigated. This work studies a variety of heterojunction materials and types to increase tunnel currents to CMOS competitive levels and to understand how integration onto Si substrates affects performance. Esaki tunnel diodes were grown by Molecular Beam Epitaxy (MBE) on Si substrates via a graded buffer and control Esaki tunnel diodes grown on lattice matched substrates for this work. Peak current density for each diode is extracted and benchmarked to build an empirical data set for predicting diode performance. Additionally, statistics are used as tool to show peak to valley ratio for the III-V on Si sample and the control perform similarly below a threshold area. This work has applications beyond logic, as multijunction solar cell, heterojunction bipolar transistor, and light emitting diode designs all benefit from better tunnel contact design.

Silicon-Based Quantum MOS Technology Development

DTIC Science & Technology

2000-03-07

resonant interband tunnel diodes were demonstrated with peak current density greater than 104 A/cm2; peak-to-valley current ratio exceeding 2 was...photon emission reduce the peak-to-valley current ratio and device performance. Therefore, interband tunnel devices should be more resilient to...Comparison of bipolar interband tunnel and optical devices: (a) Esaki diode biased into the valley current region and (b) optical light emitter. The Esaki

In situ electrochemical detection of embryonic stem cell differentiation.

PubMed

Yea, Cheol-Heon; An, Jeung Hee; Kim, Jungho; Choi, Jeong-Woo

2013-06-20

Stem cell sensors have emerged as a promising technique to electrochemically monitor the functional status and viability of stem cells. However, efficient electrochemical analysis techniques are required for the development of effective electrochemical stem cell sensors. In the current study, we report a newly developed electrochemical cyclic voltammetry (CV) system to determine the status of mouse embryonic stem (ES) cells. 1-Naphthly phosphate (1-NP), which was dephosphorylated by alkaline phosphatase into a 1-naphthol on an undifferentiated mouse ES cell, was used as a substrate to electrochemically monitor the differentiation status of mouse ES cells. The peak current in the cyclic voltammetry of 1-NP increased linearly with the concentration of pure 1-NP (R(2)=0.9623). On the other hand, the peak current in the electrochemical responses of 1-NP decreased as the number of undifferentiated ES cells increased. The increased dephosphorylation of 1-NP to 1-naphthol made a decreased electrochemical signal. Non-toxicity of 1-NP was confirmed. In conclusion, the proposed electrochemical analysis system can be applied to an electrical stem cell chip for diagnosis, drug detection and on-site monitoring. Copyright © 2013 Elsevier B.V. All rights reserved.

Caffeine depression of spontaneous activity in rabbit sino-atrial node cells.

PubMed

Satoh, H

1993-05-01

1. Effects of caffeine on the action potentials and the membrane currents in spontaneously beating rabbit sino-atrial (SA) node cells were examined using a two-microelectrode technique. 2. Cumulative administrations of caffeine (1-10 mM) caused a negative chronotropic effect in a concentration-dependent manner, which was not modified by atropine (0.1 microM). At 10 mM, caffeine increased the amplitude and prolonged the duration of action potentials significantly; the other parameters were unaffected. 3. In 3 of 16 preparations, caffeine (5 mM) elicited arrhythmia. At high Ca2+ (8.1 mM), caffeine (5 mM) increased the incidence of arrhythmia. 4. Caffeine (0.5-10 mM) enhanced the slow inward current, but at 10 mM decreased the enhanced peak current by 5 mM. The hyperpolarization-activated inward current was also enhanced by caffeine, but 10 mM caffeine decreased the current peak as compared with that at 5 mM. In addition, caffeine inhibited the delayed rectifying outward current in a concentration-dependent manner, accompanied by a depressed activation curve without any shift in the half-maximum activation voltage. 5. Caffeine elevated the cytoplasmic Ca2+ level in the SA node cells loaded with Ca(2+)-sensitive fluorescent dye (fura-2). 6. These results suggest that caffeine enhances and/or inhibits the ionic currents and elicits arrhythmia due to the induction of cellular calcium overload.

Integrating between-host transmission and within-host immunity to analyze the impact of varicella vaccination on zoster

PubMed Central

Ogunjimi, Benson; Willem, Lander; Beutels, Philippe; Hens, Niel

2015-01-01

Varicella-zoster virus (VZV) causes chickenpox and reactivation of latent VZV causes herpes zoster (HZ). VZV reactivation is subject to the opposing mechanisms of declining and boosted VZV-specific cellular mediated immunity (CMI). A reduction in exogenous re-exposure ‘opportunities’ through universal chickenpox vaccination could therefore lead to an increase in HZ incidence. We present the first individual-based model that integrates within-host data on VZV-CMI and between-host transmission data to simulate HZ incidence. This model allows estimating currently unknown pivotal biomedical parameters, including the duration of exogenous boosting at 2 years, with a peak threefold to fourfold increase of VZV-CMI; the VZV weekly reactivation probability at 5% and VZV subclinical reactivation having no effect on VZV-CMI. A 100% effective chickenpox vaccine given to 1 year olds would cause a 1.75 times peak increase in HZ 31 years after implementation. This increase is predicted to occur mainly in younger age groups than is currently assumed. DOI: http://dx.doi.org/10.7554/eLife.07116.001 PMID:26259874

Study on transport properties of silicene monolayer under external field using NEGF method

DOE Office of Scientific and Technical Information (OSTI.GOV)

Syaputra, Marhamni, E-mail: marhamni@students.itb.ac.id; Wella, Sasfan Arman; Wungu, Triati Dewi Kencana

2015-09-30

We investigate the current-voltage (I-V) characteristics of a pristine monolayer silicene using non-equilibrium Green function (NEGF) method combining with density functional theory (DFT). This method succeeded in showing the relationship of I and V on silicene corresponding to the electronic characteristics such as density of states. The external field perpendicular to the silicene monolayer affects in increasing of the current. Under 0.2 eV external field, the current reaches the maximum peak at Vb = 0.3 eV with the increase is about 60% from what it is in zero external field.

Role of vanguard counter-potential in terahertz emission due to surface currents explicated by three-dimensional ensemble Monte Carlo simulation

NASA Astrophysics Data System (ADS)

Cortie, D. L.; Lewis, R. A.

2011-10-01

The discovery that short pulses of near-infrared radiation striking a semiconductor may lead to emission of radiation at terahertz frequencies paved the way for terahertz time-domain spectroscopy. Previous modeling has allowed the physical mechanisms to be understood in general terms but it has not fully explored the role of key physical parameters of the emitter material nor has it fully revealed the competing nature of the surface-field and photo-Dember effects. In this context, our purpose has been to more fully explicate the mechanisms of terahertz emission from transient currents at semiconductor surfaces and to determine the criteria for efficient emission. To achieve this purpose we employ an ensemble Monte Carlo simulation in three dimensions. To ground the calculations, we focus on a specific emitter, InAs. We separately vary distinct physical parameters to determine their specific contribution. We find that scattering as a whole has relatively little impact on the terahertz emission. The emission is found to be remarkably resistant to alterations of the dark surface potential. Decreasing the band gap leads to a strong increase in terahertz emission, as does decreasing the electron mass. Increasing the absorption dramatically influences the peak-peak intensity and peak shape. We conclude that increasing absorption is the most direct path to improve surface-current semiconductor terahertz emitters. We find for longer pump pulses that the emission is limited by a newly identified vanguard counter-potential mechanism: Electrons at the leading edge of longer laser pulses repel subsequent electrons. This discovery is the main result of our work.

Interaction of Lightning Electromagnetic Pulse with the Ionosphere as Inferred from Wideband Measurements and Modeling

NASA Astrophysics Data System (ADS)

Somu, Vijaya Bhaskar

Apparent ionospheric reflection heights estimated using the zero-to-zero and peak-to-peak methods to measure skywave delay relative to the groundwave were compared for 108 first and 124 subsequent strokes observed at LOG in 2009. For either metric there was a considerable decrease in average re ection height for subsequent strokes relative to first strokes. Median uncertainties in daytime re ection heights did not exceed 0.7 km. The standard errors in mean re ection heights were less than 3% of the mean value. Apparent changes in re ection height (estimated using the peak-to-peak method) within individual ashes for 54 daytime and 11 nighttime events at distances ranging from 50 km to 330 km were compared. For daytime conditions, the majority of the ashes showed a monotonic decrease in re ection height. For nighttime ashes, the monotonic decrease was found to be considerably less frequent. The apparent ionospheric re ection height tends to increase with return-stroke peak current. In order to increase the sample size for nighttime conditions, additional data for 43 nighttime flashes observed at LOG in 2014 were analyzed. The "fast-break-point" method of measuring skywave delay (McDonald et al., 1979) was additionally used. The 2014 results for return strokes are generally consistent with the 2009 results. The 2014 data were also used for estimating ionospheric re ection heights for elevated sources (6 CIDs and 3 PB pulses) using the double-skywave feature. The results were compared with re ection heights estimated for corresponding return strokes (if any), and fairly good agreement was generally found. It has been shown, using two different FDTD simulation codes, that the observed differences in re ection height cannot be explained by the difference in the frequency content of first and subsequent return-stroke currents. FDTD simulations showed that within 200 km the re ection heights estimated using the peak-to-peak method are close to the hOE parameter of the ionospheric profile for both daytime and nighttime conditions and for both first and second skywaves. The TL model was used to estimate the radial extent of elves produced by the interaction of LEMP with the ionosphere as a function of return-stroke peak current. For a peak current of 100 kA and the speed equal to one-half of the speed of light, the expected radius of elves is 157 km. Skywaves associated with 24 return strokes in 6 lightning ashes triggered at CB in 2015 and recorded at LOG (at a distance of 45 km from CB) were not found for any of the strokes recorded. In contrast, natural-lightning strokes do produce skywaves at comparable distances. One possible reason is the difference in the higher-frequency content (field waveforms for triggered lightning are more narrow than for natural lightning).

Exploring storage and runoff generation processes for urban flooding through a physically based watershed model

NASA Astrophysics Data System (ADS)

Smith, B. K.; Smith, J. A.; Baeck, M. L.; Miller, A. J.

2015-03-01

A physically based model of the 14 km2 Dead Run watershed in Baltimore County, MD was created to test the impacts of detention basin storage and soil storage on the hydrologic response of a small urban watershed during flood events. The Dead Run model was created using the Gridded Surface Subsurface Hydrologic Analysis (GSSHA) algorithms and validated using U.S. Geological Survey stream gaging observations for the Dead Run watershed and 5 subbasins over the largest 21 warm season flood events during 2008-2012. Removal of the model detention basins resulted in a median peak discharge increase of 11% and a detention efficiency of 0.5, which was defined as the percent decrease in peak discharge divided by percent detention controlled area. Detention efficiencies generally decreased with increasing basin size. We tested the efficiency of detention basin networks by focusing on the "drainage network order," akin to the stream order but including storm drains, streams, and culverts. The detention efficiency increased dramatically between first-order detention and second-order detention but was similar for second and third-order detention scenarios. Removal of the soil compacted layer, a common feature in urban soils, resulted in a 7% decrease in flood peak discharges. This decrease was statistically similar to the flood peak decrease caused by existing detention. Current soil storage within the Dead Run watershed decreased flood peak discharges by a median of 60%. Numerical experiment results suggested that detention basin storage and increased soil storage have the potential to substantially decrease flood peak discharges.

Effect of resistivity profile on current decay time of initial phase of current quench in neon-gas-puff inducing disruptions of JT-60U

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kawakami, S.; Ohno, N.; Shibata, Y.

2013-11-15

According to an early work [Y. Shibata et al., Nucl. Fusion 50, 025015 (2010)] on the behavior of the plasma current decay in the JT-60U disruptive discharges caused by the radiative collapse with a massive neon-gas-puff, the increase of the internal inductance mainly determined the current decay time of plasma current during the initial phase of current quench. To investigate what determines the increase of the internal inductance, we focus attention on the relationship between the electron temperature (or the resistivity) profile and the time evolution of the current density profile and carry out numerical calculations. As a result, wemore » find the reason of the increase of the internal inductance: The current density profile at the start of the current quench is broader than an expected current density profile in the steady state, which is determined by the temperature (or resistivity) profile. The current density profile evolves into peaked one and the internal inductance is increasing.« less

Shot noise of charge current in a quantum dot responded by rotating and oscillating magnetic fields

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhao, Hong-Kang, E-mail: zhaohonk@yahoo.com; Zou, Wei-Ke; Chen, Qiao

We have investigated the shot noise and Fano factor of the dynamic spin-polarized quantum dot under the perturbations of a rotating magnetic field (RMF), and an oscillating magnetic field (OMF) by employing the non-equilibrium Green's function approach. The shot noise is enhanced from sub-Poissonian to super-Poissonian due to the application of RMF and OMF, and it is controlled sensitively by the tilt angle θ of RMF. The magnitude of shot noise increases as the photon energy ℏω of OMF increases, and its valley eventually is reversed to peaks as the photon energy is large enough. Double-peak structure of Fano factormore » is exhibited as the frequency of OMF increases to cover a large regime. The Zeeman energy μ{sub 0}B{sub 0} acts as an effective gate bias to exhibit resonant behavior, and novel peak emerges associated with the applied OMF.« less

Properties of micro-arc oxidation coatings on aluminum alloy at different negative peak current densities

NASA Astrophysics Data System (ADS)

Gu, Xin; Jiang, Bailing; Li, Hongtao; Liu, Cancan; Shao, Lianlian

2018-05-01

Micro-arc oxidation coatings were fabricated on 6061 aluminum alloy using whereby bipolar pulse mode in the case of different negative peak current densities. The phase composition, microstructures and wear properties were studied using x-ray diffraction, scanning electron microscopy and ball-on-disk wear tester, respectively. As results indicate, by virtue of negative peak current density, the oxygen can be expelled by produced hydrogen on anode in the case of negative pulse width and via the opened discharge channel. The results of x-ray diffraction, surface and cross-sectional morphology indicated that the coating was structured compactly taking on less small-diameter micro-pores and defects with negative peak current density of 75 A dm‑2. Additionally, as the results of wear tracks and weight loss bespeak, by virtue of appropriate negative peak current density, coatings resisted the abrasive wear and showed excellent wear resistance.

Method and apparatus for clockless analog-to-digital conversion and peak detection

DOEpatents

DeGeronimo, Gianluigi

2007-03-06

An apparatus and method for analog-to-digital conversion and peak detection includes at least one stage, which includes a first switch, second switch, current source or capacitor, and discriminator. The discriminator changes state in response to a current or charge associated with the input signal exceeding a threshold, thereby indicating whether the current or charge associated with the input signal is greater than the threshold. The input signal includes a peak or a charge, and the converter includes a peak or charge detect mode in which a state of the switch is retained in response to a decrease in the current or charge associated with the input signal. The state of the switch represents at least a portion of a value of the peak or of the charge.

Longitudinal relationship between wheelchair exercise capacity and life satisfaction in patients with spinal cord injury: A cohort study in the Netherlands

PubMed Central

van Koppenhagen, Casper Floris; Post, Marcel; de Groot, Sonja; van Leeuwen, Christel; van Asbeck, Floris; Stolwijk-Swüste, Janneke; van der Woude, Lucas; Lindeman, Eline

2014-01-01

Objective To examine the relationship between wheelchair exercise capacity and life satisfaction in persons with spinal cord injury from the start of active inpatient rehabilitation up to 5 years after discharge. Design Prospective cohort study. Subjects Persons with spinal cord injury, aged 18–65 years, and wheelchair dependent at least for long distances. Method Measurements at the start of active rehabilitation, after 3 months, at discharge from inpatient rehabilitation, and 1 and 5 years after discharge. A peak wheelchair exercise test was performed to record peak oxygen uptake (VO2peak) and peak power output (POpeak). Life satisfaction was measured as current life satisfaction and change of life satisfaction in comparison with life after spinal cord injury. Relationships between (changes in) exercise capacity and (changes in) life satisfaction were analyzed random coefficient analysis, corrected for possible confounders (age, gender, level of lesion, functional status, secondary impairments, pain, and sports activity) if necessary. Results Of 225 persons included, 130 attended two or more peak exercise tests, who were include in the analyses. Mean age at start was 39 years, 75% were male, 73% had paraplegia, and 76% had a traumatic lesion. Mean POpeak increased during the study from 32.9 to 55.9 Watts, mean VO2peak from 1.02  to 1.38 l/minute, and mean life satisfaction from 5.7 to 7.8. An increase of POpeak with 10 W was associated with a 0.3-point increase of life satisfaction (P = 0.01). An increase of VO2peak with 0.1 l/minute was associated with a 0.1-point increase of life satisfaction (P = 0.049). Conclusion High(er) wheelchair exercise capacity is related to high(er) life satisfaction in spinal cord injury patients. PMID:24621019

ZnS nanoparticles electrodeposited onto ITO electrode as a platform for fabrication of enzyme-based biosensors of glucose.

PubMed

Du, Jian; Yu, Xiuping; Wu, Ying; Di, Junwei

2013-05-01

The electrochemical and photoelectrochemical biosensors based on glucose oxidase (GOD) and ZnS nanoparticles modified indium tin oxide (ITO) electrode were investigated. The ZnS nanoparticles were electrodeposited directly on the surface of ITO electrode. The enzyme was immobilized on ZnS/ITO electrode surface by sol-gel method to fabricate glucose biosensor. GOD could electrocatalyze the reduction of dissolved oxygen, which resulted in a great increase of the reduction peak current. The reduction peak current decreased linearly with the addition of glucose, which could be used for glucose detection. Moreover, ZnS nanoparticles deposited on ITO electrode surface showed good photocurrent response under illumination. A photoelectrochemical biosensor for the detection of glucose was also developed by monitoring the decreases in the cathodic peak photocurrent. The results indicated that ZnS nanoparticles deposited on ITO substrate were a good candidate material for the immobilization of enzyme in glucose biosensor construction. Copyright © 2013 Elsevier B.V. All rights reserved.

Raman shifts in electron-irradiated monolayer MoS 2

DOE PAGES

Parkin, William M.; Balan, Adrian; Liang, Liangbo; ...

2016-03-21

Here, we report how the presence of electron-beam-induced sulfur vacancies affects first-order Raman modes and correlate the effects with the evolution of the in situ transmission-electron microscopy (TEM) two-terminal conductivity of monolayer MoS 2 under electron irradiation. We observe a redshift in the E Raman peak and a less pronounced blueshift in the A' 1 peak with increasing electron dose. Using energy-dispersive X-ray spectroscopy (EDS), we show that irradiation causes partial removal of sulfur and correlate the dependence of the Raman peak shifts with S vacancy density (a few %), which is confirmed by first-principles density functional theory calculations. Inmore » situ device current measurements show exponential decrease in channel current upon irradiation. Our analysis demonstrates that the observed frequency shifts are intrinsic properties of the defective systems and that Raman spectroscopy can be used as a quantitative diagnostic tool to characterize MoS 2-based transport channels.« less

Cyclic variation in seasonal recruitment and the evolution of the seasonal decline in Ural owl clutch size.

PubMed Central

Brommer, Jon E; Pietiäinen, Hannu; Kokko, Hanna

2002-01-01

Plastic life-history traits can be viewed as adaptive responses to environmental conditions, described by a reaction norm. In birds, the decline in clutch size with advancing laying date has been viewed as a reaction norm in response to the parent's own (somatic or local environmental) condition and the seasonal decline in its offspring's reproductive value. Theory predicts that differences in the seasonal recruitment are mirrored in the seasonal decrease in clutch size. We tested this prediction in the Ural owl. The owl's main prey, voles, show a cycle of low, increase and peak phases. Recruitment probability had a humped distribution in both increase and peak phases. Average recruitment probability was two to three times higher in the increase phase and declined faster in the latter part of the season when compared with the peak phase. Clutch size decreased twice as steep in the peak (0.1 eggs day-1) as in the increase phase (0.05 eggs day-1). This result appears to refute theoretical predictions of seasonal clutch size declines. However, a re-examination of current theory shows that the predictions of modelling are less robust to details of seasonal condition accumulation in birds than originally thought. The observed pattern can be predicted, assuming specifically shaped seasonal increases in condition across individuals. PMID:11916482

Silicon Carbide Diodes Characterization at High Temperature and Comparison With Silicon Devices

NASA Technical Reports Server (NTRS)

Lebron-Velilla, Ramon C.; Schwarze, Gene E.; Gardner, Brent G.; Adams, Jerry D., Jr.

2004-01-01

Commercially available silicon carbide (SiC) Schottky diodes from different manufacturers rated at 200, 300, 600, and 1200 V, were electrically tested and characterized as a function of temperature up to 300 C. Electrical tests included both steady state and dynamic tests. Steady state tests produced forward and reverse I-V characteristic curves. Transient tests evaluated the switching performance of the diodes in either a hard-switched DC to DC buck converter or a half-bridge boost converter. For evaluation and comparison purposes, the same tests were performed with current state-of-the-art ultra fast silicon (Si) pn-junction diodes of similar ratings and also a Si Schottky diode. The comparisons made were forward voltage drop at rated current, reverse current at rated voltage, and turn-off peak reverse recovery current and reverse recovery time. In addition, efficiency measurements were taken for the buck DC to DC converter using both the SiC Schottky diodes and the Si pn-junction diodes at different temperatures and frequencies. The test results showed that at high temperature, the forward voltage drop for SiC Schottky diodes is higher than the forward drop of the ultra fast Si pn-junction diodes. As the temperature increased, the forward voltage drop of the SiC Schottky increased while for the ultra fast Si pn-junction diodes, the forward voltage drop decreased as temperature increased. For the elevated temperature steady state reverse voltage tests, the SiC Schottky diodes showed low leakage current at their rated voltage. Likewise, for the transient tests, the SiC Schottky diodes displayed low reverse recovery currents over the range of temperatures tested. Conversely, the Si pn-junction diodes showed increasing peak reverse current values and reverse recovery times with increasing temperature. Efficiency measurements in the DC to DC buck converter showed the advantage of the SiC Schottky diodes over the ultra fast Si pn-junction diodes, especially at the higher temperatures and higher frequencies.

Acetylene black paste electrode modified with graphene as the voltammetric sensor for selective determination of tryptophan in the presence of high concentrations of tyrosine.

PubMed

Deng, Peihong; Xu, Zhifeng; Feng, Yonglan

2014-02-01

A reliable sensor was fabricated by modifying an acetylene black paste electrode with graphene (denoted as GR/ABPE) for sensitive and selective determination of tryptophan (Trp). Due to the high sorption ability, large surface area and numerous active sites, the GR/ABPE showed a strong enhancement effect on the oxidation of Trp, and greatly increased the peak current. The parameters affecting the Trp determination were investigated. In 1.0 M H2SO4 the voltammetric responses of Trp and tyrosine (Tyr) were well separated into two distinct peaks with peak potential difference (ΔE(pa)) of 115 mV. Under the optimized conditions, in the presence of 0.1 mM Tyr, the oxidation peak current of Trp was proportional to its concentration in the range between 0.1 μM and 0.1 mM, with the limit of detection of 60 nM (S/N=3). The GR/ABPE was applied to the direct detection of Trp in pharmaceutical and biological samples with satisfactory results. This work provides a simple and easy approach to selective detection of Trp in the presence of Tyr. © 2013.

Methanol and ethanol electroxidation using Pt electrodes prepared by the polymeric precursor method

NASA Astrophysics Data System (ADS)

Freitas, R. G.; Santos, M. C.; Oliveira, R. T. S.; Bulhões, L. O. S.; Pereira, E. C.

The results of methanol and ethanol oxidation in acidic medium on Pt electrodes deposited on Ti substrate using the Pechini method are presented. In this route the metallic salts were dissolved in a mixture of ethylene glycol (EG) and citric acid (CA) forming a polyester network, which is painted onto a Ti substrate and then heat treated at 600 °C in order to obtain the metallic Pt thin films. The X-ray diffraction analysis showed the presence of Pt pattern peaks. The presence of the (4 2 0) plane in a higher amount compared to bulk Pt was observed and the peak position of the planes (2 0 0) and (4 2 0) were displaced by approximately -0.3°. The roughness data presented almost the same values for Ti and Ti/Pt. The electrochemical characterization of the electrodes in 0.1 M HClO 4 showed a typical Pt voltammetric profile. Although the voltammetric profiles of Ti/Pt and bulk Pt were the same, the electrocatalytical behavior for methanol oxidation showed an enhancement of the oxidation current density peak, which increased by 170% compared to bulk platinum. Although, the current density peak for ethanol oxidation on Ti/Pt is smaller than for Pt, it began at 0.11 V less positive than the same process on bulk Pt. The chronoamperometric experiments for methanol and ethanol oxidation on Ti/Pt increased by almost 934% and 440%, respectively, compared with Pt bulk.

Wide Temperature Magnetization Characteristics of Transverse Magnetically Annealed Amorphous Tapes for High Frequency Aerospace Magnetics

NASA Technical Reports Server (NTRS)

Niedra, Janis M.; Schwarze, Gene E.

1999-01-01

100 kHz magnetization properties of sample transverse magnetically annealed, cobalt-based amorphous and iron-based nanocrystalline tape wound magnetic cores are presented over the temperature range of -150 C to 150 C, at selected values of B(sub peak). Frequency resolved characteristics are given over the range of 50 kHz to 1 MHz, but at B(sub peak) = 0.1 T and 50 C only. Basic exciting winding current and induced voltage data were taken on bare toroidal cores, in a standard type measurement setup. A linear permeability model, which represents the core by a parallel L-R circuit, is used to interpret and present the magnetization characteristics and several figures of merit applicable to inductor materials are reviewed. The 100 kHz permeability thus derived decreases with increasing temperature for the Fe-based, nanocrystalline material, but increases roughly linearly with temperature for the two Co-based materials, as long as B(sub peak) is sufficiently low to avoid saturation effects. Due to the high permeabilities, rather low values of the 'quality factor' Q, from about 20 to below unity, were obtained over the frequency range of 50 kHz to 1 MHz (50 C, B(sub peak) = 0.1 T). Therefore these cores must be gapped in order to make up high Q or high current inductors. However, being rugged, low core loss materials with flat B-H loop characteristics, they may provide new solutions to specialty inductor applications.

Ordered mesoporous carbon modified carbon ionic liquid electrode for the electrochemical detection of double-stranded DNA.

PubMed

Zhu, Zhihong; Li, Xia; Zeng, Yan; Sun, Wei

2010-06-15

In this paper the direct electrochemistry of double-stranded DNA (dsDNA) was investigated on ordered mesoporous carbon (OMC) modified carbon ionic liquid electrode (CILE). CILE was prepared by mixing graphite powder with 1-ethyl-3-methylimidazolium ethylsulphate ([EMIM]EtOSO(3)) and liquid paraffin. A stable OMC film was formed on the surface of CILE with the help of Nafion to get a modified electrode denoted as Nafion-OMC/CILE. Due to the specific characteristics of OMC and IL present on the electrode surface, the fabricated electrode showed good electrochemical performances to different electroactive molecules. The electrochemical responses of dsDNA were carefully investigated on this electrode with two irreversible oxidation peak appeared at +1.250 V and +0.921 V (vs. SCE), which was corresponding to the oxidation of adenine and guanine residues in dsDNA structure. The electrochemical behaviors of dsDNA were carefully investigated on the Nafion-OMC/CILE. Experimental results indicated that the electron transfer rate was promoted with the increase of the oxidation peak current and the decrease of the oxidation peak potential, which was due to the electrocatalytic ability of OMC on the electrode surface. Under the optimal conditions the oxidation peak current increased with dsDNA concentration in the range of 10.0-600.0 microg mL(-1) by differential pulse voltammetry (DPV) with the detection limit of 1.2 microg mL(-1) (3sigma). Copyright 2010 Elsevier B.V. All rights reserved.

Evaluation of the antibacterial activity of a cationic polymer in aqueous solution with a convenient electrochemical method.

PubMed

Wang, Yihong; Guo, Qing; Wang, Huafu; Qian, Kun; Tian, Liang; Yao, Chen; Song, Wei; Shu, Weixia; Chen, Ping; Qi, Jinxu

2017-02-01

Quaternized chitosan is a cationic biopolymer with good antibacterial activity, biocompatibility, and biodegradability, and it has been widely applied in many fields. We have developed a convenient method to evaluate the antibacterial activity of hydroxypropyltrimethylammonium chloride chitosan (HACC) with a nonionic surfactant poloxamer in aqueous solution by monitoring the change of the oxidation peak current in cyclic voltammetry. Increasing values of the oxidation peak current were positively correlated with the antibacterial activity of HACC-poloxamer solutions. Optical microscope images, the zeta potential, and fluorescence spectroscopy showed that the aggregation state of HACC-poloxamer was related to the ratio of the two polymers and also to the antibacterial activity and oxidation peak current. At an HACC-to-poloxamer ratio of 1:0.75, the maximum surface charge density and the smooth edge of HACC-poloxamer aggregates can accelerate diffusion in aqueous solution. It is expected that this convenient method can be applied for a quick evaluation of the antibacterial activity of cationic biopolymers in aqueous solution. Graphical Abstract The cyclic voltammograms of MB in HACC/poloxamer solution, and the antibacterial efficiency against S. aureus after incubated with HACC (a) and 1/0.75 of HACC/poloxamer (b).

Strong electroluminescence from direct band and defects in Ge n+/p shallow junctions at room temperature

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lin, Guangyang; Li, Cheng, E-mail: lich@xmu.edu.cn; Chen, Chaowen

2016-05-09

Strong room temperature electroluminescence with two emission peaks at around 0.786 eV and 0.747 eV from Ge n+/p shallow junctions was reported. The peak at around 0.786 eV comes from direct band luminescence (DBL) in n + Ge regions, while the peak fixing at 0.747 eV is resulted from defects induced by ion implantation. Heavy n-type doping in Ge renders realization of strong defect-related luminescence (DRL) feasible. The peak intensity ratio of DRL/DBL decreases with increase of injection current since more electrons are filled in Γ valley. Above all, the Ge n+/p shallow junction is fully compatible with the source and drain in Gemore » metal-oxide-semiconductor field effect transistors.« less

Optical absorption and thermally stimulated depolarization current studies of nickel chloride-doped poly(vinyl alcohol) irradiated with low-level fast neutron doses

DOE Office of Scientific and Technical Information (OSTI.GOV)

Abd El-Kader, F.H.; Ibrahim, S.S.; Attia, G.

1993-11-15

The influence of neutron irradiation on ultraviolet/visible absorption and thermally stimulated depolarization current in nickel chloride-poly(vinyl alcohol) (PVA) cast films has been investigated. The spectral measurements indicate the responsibility of the Ni[sup 2][sup +] ion in its octahedral symmetry. Dopant concentrations higher than 10 wt % NiCl[sub 2] are found to make the samples more resistant to a degradation effect caused by neutron irradiation. The thermally stimulated depolarization currents (TSDC) of pure PVA revealed the existence of the glass transition T[sub g] and space charge relaxation peaks, whereas doped-PVA samples show a new sub-T[sub g] relaxation peak. A proposed mechanismmore » is introduced to account for the neutron effects on both glass transition and space charge relaxation peaks. The peak positions, peak currents, and stored charges of the sub-T[sub g] relaxation peak are strongly affected by both the concentration of the dopant and neutron exposure doses.« less

Relation of field-aligned currents measured by AMPERE project to solar wind and substorms

NASA Astrophysics Data System (ADS)

McPherron, R. L.; Anderson, B. J.; Chu, X.

2016-12-01

Magnetic perturbations measured in the Active Magnetosphere and Planetary Electrodynamics Response Experiment (AMPERE) by the Iridium constellation of spacecraft have been processed to obtain the time history of field-aligned currents (FAC) connecting the magnetosphere to the ionosphere. We find that the strength of these currents is closely related to the strength of the solar wind driver defined as a running average of the previous three hours of the optimum AL (auroral lower) coupling function. The relation is well represented by a saturation model I = A*S*Ss/(S+Ss) with I the current strength in mega Amps, S the driver strength in mV/m, Ss the saturation value of 7.78 mV/m, and A = 2.55 scales the relation to units of current. We also find that in general the upward current on the nightside increases with each substorm expansion onset defined by a combination of the SuperMag SML (SuperMag AL) and midlatitude positive bay (MPB) onset lists. A superposed epoch analysis using 700 onsets in 2010 shows the following: solar wind coupling peaks at expansion onset; dayside outward current starts to increase one hour before onset while nightside outward current starts suddenly at onset; nightside outward current reaches a peak at 28 minutes as do SML and MPB indices; FAC, SML, and MPB respectively take 1, 2, and 3 hours to decay to background. The data indicate that the substorm current wedge is superposed on a pre-existing field-aligned current system and that the location and properties of the current wedge can be studied with the AMPERE data.

Integrated Multi-process Microfluidic Systems for Automating Analysis

PubMed Central

Yang, Weichun; Woolley, Adam T.

2010-01-01

Microfluidic technologies have been applied extensively in rapid sample analysis. Some current challenges for standard microfluidic systems are relatively high detection limits, and reduced resolving power and peak capacity compared to conventional approaches. The integration of multiple functions and components onto a single platform can overcome these separation and detection limitations of microfluidics. Multiplexed systems can greatly increase peak capacity in multidimensional separations and can increase sample throughput by analyzing many samples simultaneously. On-chip sample preparation, including labeling, preconcentration, cleanup and amplification, can all serve to speed up and automate processes in integrated microfluidic systems. This paper summarizes advances in integrated multi-process microfluidic systems for automated analysis, their benefits and areas for needed improvement. PMID:20514343

Photoinduced currents in pristine and ion irradiated kapton-H polyimide

NASA Astrophysics Data System (ADS)

Sharma, Anu; Sridharbabu, Y.; Quamara, J. K.

2014-10-01

The photoinduced currents in pristine and ion irradiated kapton-H polyimide have been investigated for different applied electric fields at 200°C. Particularly the effect of illumination intensity on the maximum current obtained as a result of photoinduced polarization has been studied. Samples were irradiated by using PELLETRON facility, IUAC, New Delhi. The photo-carrier charge generation depends directly on intensity of illumination. The samples irradiated at higher fluence show a decrease in the peak current with intensity of illumination. The secondary radiation induced crystallinity (SRIC) is responsible for the increase in maximum photoinduced currents generated with intensity of illumination.

Photoinduced currents in pristine and ion irradiated kapton-H polyimide

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sharma, Anu, E-mail: sharmaanu81@gmail.com; Sridharbabu, Y., E-mail: sharmaanu81@gmail.com; Quamara, J. K., E-mail: sharmaanu81@gmail.com

2014-10-15

The photoinduced currents in pristine and ion irradiated kapton-H polyimide have been investigated for different applied electric fields at 200°C. Particularly the effect of illumination intensity on the maximum current obtained as a result of photoinduced polarization has been studied. Samples were irradiated by using PELLETRON facility, IUAC, New Delhi. The photo-carrier charge generation depends directly on intensity of illumination. The samples irradiated at higher fluence show a decrease in the peak current with intensity of illumination. The secondary radiation induced crystallinity (SRIC) is responsible for the increase in maximum photoinduced currents generated with intensity of illumination.

Magnetic Field Observations of Partial Ring Current during Storm Recovery Phase

NASA Technical Reports Server (NTRS)

Le, Guan; Russell, C. T.; Slavin, J. A.; Lucek, E. A.

2007-01-01

We present results of an extensive survey of the magnetic field observations in the inner magnetosphere using 30 years of magnetospheric magnetic field data from Polar, Cluster, ISEE, and AMPTE/CCE missions. The purpose of this study is to understand the magnetic field evolution during the recovery phase of geomagnetic storms, and its implication to the ring current recovery and loss mechanisms of ring current particles. Our previous work on global ring current distribution [Le et al., 2004] has shown that a significant partial ring current is always present at all Dst levels (regardless of storm phases) even for quiet time ring current. The total current carried by the partial ring current is much stronger than (during stormtime) or at least comparable to (during quiet time) the symmetric ring current. It is now commonly believed that a strong partial ring current is formed during the storm main phase due to the enhanced earthward convection of energetic ions from nightside plasma sheet. But the presence of a strong partial ring current throughout the recovery phase remains controversial. The magnetic field generated by the ring current inflates the inner magnetosphere and causes magnetic field depressions in the equatorial magnetosphere. During the storm recovery phase, we find that the distribution of the equatorial magnetic field depression exhibits similar local time dependence as the ring current distribution obtained from the combined dataset in the earlier study. It shows that a strong partial ring current is a permanent feature throughout the recovery phase. In the early recovery phase, the partial ring current peaks near the dusk terminator as indicated by the peak of the magnetic field depression. As the recovery phase progresses, the partial ring current decays most quickly near the dusk and results in a dusk-to-midnight moving of the peak of the partial ring current. Thus the loss mechanisms work most effectively near the dusk. The magnetic field depression increases the gyroradius of ring current protons to a scale greater or comparable to the thickness of the magnetopause, which increases the chance of ion drift loss near the dusk magnetopause at larger L-shell (L>5). But the drift loss mechanism alone cannot explain the loss of ring current ions especially in the smaller L-shell (L<5). The precipitation loss due to wave-particle interaction is most likely the dominant loss mechanism in the small L-shell as it works most effectively at the same local time.

The Association of Dorsiflexion Flexibility on Landing Mechanics during a Drop Vertical Jump

PubMed Central

Malloy, Philip; Meinerz, Carolyn; Geiser, Christopher; Kipp, Kristof

2016-01-01

Purpose While previous studies have examined the association between ankle dorsiflexion flexibility and deleterious landing postures, it is not currently known how landing kinetics are influenced by ankle dorsiflexion flexibility. The purpose of this study was to examine if ankle dorsiflexion flexibility was associated with landing kinematics and kinetics that have been shown to increase the risk of ACL injury in female athletes. Methods Twenty-three female collegiate soccer players participated in a preseason screening that included the assessment of ankle dorsiflexion flexibility and lower-body kinematics and kinetics during a drop vertical jump task. Results The results demonstrated that females with less ankle dorsiflexion flexibility exhibited greater peak knee abduction moments (r = −.442), greater peak knee abduction angles (r = .355), and less peak knee flexion angles (r = −.385) during landing. The range of dorsiflexion flexibility for the current study was between 9°–23° degrees (mean = 15.0°; SD 3.9°). Conclusion Dorsiflexion flexibility may serve as a useful clinical measure to predict poor landing postures and external forces that have been associated with increased knee injury risk. Rehabilitation specialists can provide interventions aimed at improving dorsiflexion flexibility in order to ameliorate the impact of this modifiable factor on deleterious landing kinematics and kinetics in female athletes. PMID:25112598

Detectivity enhancement in quantum well infrared photodetectors utilizing a photonic crystal slab resonator.

PubMed

Kalchmair, S; Gansch, R; Ahn, S I; Andrews, A M; Detz, H; Zederbauer, T; Mujagić, E; Reininger, P; Lasser, G; Schrenk, W; Strasser, G

2012-02-27

We characterize the performance of a quantum well infrared photodetector (QWIP), which is fabricated as a photonic crystal slab (PCS) resonator. The strongest resonance of the PCS is designed to coincide with the absorption peak frequency at 7.6 µm of the QWIP. To accurately characterize the detector performance, it is illuminated by using single mode mid-infrared lasers. The strong resonant absorption enhancement yields a detectivity increase of up to 20 times. This enhancement is a combined effect of increased responsivity and noise current reduction. With increasing temperature, we observe a red shift of the PCS-QWIP resonance peak of -0.055 cm(-1)/K. We attribute this effect to a refractive index change and present a model based on the revised plane wave method.

Effect of Photogenerated Carriers on Ferroelectric Polarization Reversal

NASA Astrophysics Data System (ADS)

Weis, Martin; Li, Jun; Taguchi, Dai; Manaka, Takaaki; Iwamoto, Mitsumasa

2011-12-01

Three non-symmetric switching peaks were observed in current-voltage (J-V) characteristic of the pentacene/poly(vinylidene fluoride-trifluoroethylene) double-layer device. However, upon illumination only two symmetric switching peaks appeared during the same J-V measurement. The similar difference between dark and illumination were also obtained in capacitance-voltage characteristics. These results showed the strong influence of internal fields by photogenerated carriers, which modifies the polarization reversal process of ferroelectric layer. The gradual shift of the polarization reversal with increase of illumination intensity is assigned to the space-charge field of trapped electrons.

Assessment of the magnetic field exposure due to the battery current of digital mobile phones.

PubMed

Jokela, Kari; Puranen, Lauri; Sihvonen, Ari-Pekka

2004-01-01

Hand-held digital mobile phones generate pulsed magnetic fields associated with the battery current. The peak value and the waveform of the battery current were measured for seven different models of digital mobile phones, and the results were applied to compute approximately the magnetic flux density and induced currents in the phone-user's head. A simple circular loop model was used for the magnetic field source and a homogeneous sphere consisting of average brain tissue equivalent material simulated the head. The broadband magnetic flux density and the maximal induced current density were compared with the guidelines of ICNIRP using two various approaches. In the first approach the relative exposure was determined separately at each frequency and the exposure ratios were summed to obtain the total exposure (multiple-frequency rule). In the second approach the waveform was weighted in the time domain with a simple low-pass RC filter and the peak value was divided by a peak limit, both derived from the guidelines (weighted peak approach). With the maximum transmitting power (2 W) the measured peak current varied from 1 to 2.7 A. The ICNIRP exposure ratio based on the current density varied from 0.04 to 0.14 for the weighted peak approach and from 0.08 to 0.27 for the multiple-frequency rule. The latter values are considerably greater than the corresponding exposure ratios 0.005 (min) to 0.013 (max) obtained by applying the evaluation based on frequency components presented by the new IEEE standard. Hence, the exposure does not seem to exceed the guidelines. The computed peak magnetic flux density exceeded substantially the derived peak reference level of ICNIRP, but it should be noted that in a near-field exposure the external field strengths are not valid indicators of exposure. Currently, no biological data exist to give a reason for concern about the health effects of magnetic field pulses from mobile phones.

Relation of Field-Aligned Currents Measured by the Network of Iridium® Spacecraft to Solar Wind and Substorms

NASA Astrophysics Data System (ADS)

McPherron, R. L.; Anderson, B. J.; Chu, Xiangning

2018-03-01

The strength of field-aligned currents coupling the magnetosphere to the ionosphere was obtained by the Active Magnetosphere and Planetary Electrodynamics Response Experiment (AMPERE) using the network of Iridium® spacecraft. The distribution of current was integrated giving total current in and out of the ionosphere on the dayside and nightside of the Earth in both hemispheres. The onset of auroral zone negative bays and midlatitude positive bays corresponds to an increase in nightside upward current. The total outward current tends toward saturation with increasing solar wind driver strength. The optimum solar wind coupling function for AL index predicts 73% of the variance in nightside upward current. The dayside and nightside predictors of upward current rise to a peak at 30-45 min and decay slowly over 2.5 hr. Nightside response is delayed relative to dayside.

Analysis and Assessment of Peak Lightning Current Probabilities at the NASA Kennedy Space Center

NASA Technical Reports Server (NTRS)

Johnson, D. L.; Vaughan, W. W.

1999-01-01

This technical memorandum presents a summary by the Electromagnetics and Aerospace Environments Branch at the Marshall Space Flight Center of lightning characteristics and lightning criteria for the protection of aerospace vehicles. Probability estimates are included for certain lightning strikes (peak currents of 200, 100, and 50 kA) applicable to the National Aeronautics and Space Administration Space Shuttle at the Kennedy Space Center, Florida, during rollout, on-pad, and boost/launch phases. Results of an extensive literature search to compile information on this subject are presented in order to answer key questions posed by the Space Shuttle Program Office at the Johnson Space Center concerning peak lightning current probabilities if a vehicle is hit by a lightning cloud-to-ground stroke. Vehicle-triggered lightning probability estimates for the aforementioned peak currents are still being worked. Section 4.5, however, does provide some insight on estimating these same peaks.

Critical current density and microstructure of screen-printed (Bi,Pb)2Sr2Ca2Cu3O(x) thick film sandwiched between Ag substrates

NASA Astrophysics Data System (ADS)

Oota, A.; Matsui, H.; Funakura, M.; Iwaya, J.; Maeda, J.

1993-07-01

A process of combined rolling and uniaxial pressing with intermediate sintering steps for fabrication of screen-printed (Bi,Pb)2Sr2Ca2Cu3O(x) thick films sandwiched between Ag substrates yields c-axis-oriented microstructures with a high critical current density (Jc) of 1.5 x 10 exp 4 A/sq cm (77 K, 0 T) and 9.0 x 10 exp 4 A/sq cm (23 K, 0 T). The measured Jc anisotropy at 77 K, as a function of the angle Theta between B and c axis, is pronounced. An increase in B sharpens a peak at Theta = 90 deg in the Jc vs Theta curve, together with enhancement of the anisotropy ratio. In high fields above 0.5 T, the half-height angular width of the peak approaches an average misalignment angle between the grains with increasing B.

Oceanic Lightning versus Continental Lightning: VLF Peak Current Discrepancies

NASA Astrophysics Data System (ADS)

Dupree, N. A., Jr.; Moore, R. C.

2015-12-01

Recent analysis of the Vaisala global lightning data set GLD360 suggests that oceanic lightning tends to exhibit larger peak currents than continental lightning (lightning occurring over land). The GLD360 peak current measurement is derived from distant measurements of the electromagnetic fields emanated during the lightning flash. Because the GLD360 peak current measurement is a derived quantity, it is not clear whether the actual peak currents of oceanic lightning tend to be larger, or whether the resulting electromagnetic field strengths tend to be larger. In this paper, we present simulations of VLF signal propagation in the Earth-ionosphere waveguide to demonstrate that the peak field values for oceanic lightning can be significantly stronger than for continental lightning. Modeling simulations are performed using the Long Wave Propagation Capability (LWPC) code to directly evaluate the effect of ground conductivity on VLF signal propagation in the 5-15 kHz band. LWPC is an inherently narrowband propagation code that has been modified to predict the broadband response of the Earth-Ionosphere waveguide to an impulsive lightning flash while preserving the ability of LWPC to account for an inhomogeneous waveguide. Furthermore, we evaluate the effect of return stroke speed on these results.

Active cooling of pulse compression diffraction gratings for high energy, high average power ultrafast lasers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Alessi, David A.; Rosso, Paul A.; Nguyen, Hoang T.

Laser energy absorption and subsequent heat removal from diffraction gratings in chirped pulse compressors poses a significant challenge in high repetition rate, high peak power laser development. In order to understand the average power limitations, we have modeled the time-resolved thermo-mechanical properties of current and advanced diffraction gratings. We have also developed and demonstrated a technique of actively cooling Petawatt scale, gold compressor gratings to operate at 600W of average power - a 15x increase over the highest average power petawatt laser currently in operation. As a result, combining this technique with low absorption multilayer dielectric gratings developed in ourmore » group would enable pulse compressors for petawatt peak power lasers operating at average powers well above 40kW.« less

Hydrogen production at hydro-power plants

NASA Astrophysics Data System (ADS)

Tarnay, D. S.

A tentative design for hydrogen-producing installations at hydropower facilities is discussed from technological, economic and applications viewpoints. The plants would use alternating current to electrolyze purified river water. The hydrogen would be stored in gas or liquid form and oxygen would be sold or vented to the atmosphere. The hydrogen could later be burned in a turbine generator for meeting peak loads, either in closed or open cycle systems. The concept would allow large hydroelectric plants to function in both base- and peak-load modes, thus increasing the hydraulic utilization of the plant and the capacity factor to a projected 0.90. Electrolyzer efficiencies ranging from 0.85-0.90 have been demonstrated. Excess hydrogen can be sold for other purposes or, eventually, as domestic and industrial fuel, at prices competitive with current industrial hydrogen.

Active cooling of pulse compression diffraction gratings for high energy, high average power ultrafast lasers

DOE PAGES

Alessi, David A.; Rosso, Paul A.; Nguyen, Hoang T.; ...

2016-12-26

Laser energy absorption and subsequent heat removal from diffraction gratings in chirped pulse compressors poses a significant challenge in high repetition rate, high peak power laser development. In order to understand the average power limitations, we have modeled the time-resolved thermo-mechanical properties of current and advanced diffraction gratings. We have also developed and demonstrated a technique of actively cooling Petawatt scale, gold compressor gratings to operate at 600W of average power - a 15x increase over the highest average power petawatt laser currently in operation. As a result, combining this technique with low absorption multilayer dielectric gratings developed in ourmore » group would enable pulse compressors for petawatt peak power lasers operating at average powers well above 40kW.« less

Multiple negative differential resistance devices with ultra-high peak-to-valley current ratio for practical multi-valued logic and memory applications

NASA Astrophysics Data System (ADS)

Shin, Sunhae; Rok Kim, Kyung

2015-06-01

In this paper, we propose a novel multiple negative differential resistance (NDR) device with ultra-high peak-to-valley current ratio (PVCR) over 106 by combining tunnel diode with a conventional MOSFET, which suppresses the valley current with transistor off-leakage level. Band-to-band tunneling (BTBT) in tunnel junction provides the first peak, and the second peak and valley are generated from the suppression of diffusion current in tunnel diode by the off-state MOSFET. The multiple NDR curves can be controlled by doping concentration of tunnel junction and the threshold voltage of MOSFET. By using complementary multiple NDR devices, five-state memory is demonstrated only with six transistors.

An Experimental Investigation of the Risk of Triggering Geological Disasters by Injection under Shear Stress

PubMed Central

Liu, Yixin; Xu, Jiang; Peng, Shoujian

2016-01-01

Fluid injection has been applied in many fields, such as hazardous waste deep well injection, forced circulation in geothermal fields, hydraulic fracturing, and CO2 geological storage. However, current research mainly focuses on geological data statistics and the dominating effects of pore pressure. There are only a few laboratory-conditioned studies on the role of drilling boreholes and the effect of injection pressure on the borehole wall. Through experimental phenomenology, this study examines the risk of triggering geological disasters by fluid injection under shear stress. We developed a new direct shear test apparatus, coupled Hydro-Mechanical (HM), to investigate mechanical property variations when an intact rock experienced step drilling borehole, fluid injection, and fluid pressure acting on the borehole and fracture wall. We tested the peak shear stress of sandstone under different experimental conditions, which showed that drilling borehole, water injection, and increased pore pressure led to the decrease in peak shear stress. Furthermore, as pore pressure increased, peak shear stress dispersion increased due to crack propagation irregularity. Because the peak shear stress changed during the fluid injection steps, we suggest that the risk of triggering geological disaster with injection under shear stress, pore, borehole, and fluid pressure should be considered. PMID:27929142

An Experimental Investigation of the Risk of Triggering Geological Disasters by Injection under Shear Stress.

PubMed

Liu, Yixin; Xu, Jiang; Peng, Shoujian

2016-12-08

Fluid injection has been applied in many fields, such as hazardous waste deep well injection, forced circulation in geothermal fields, hydraulic fracturing, and CO 2 geological storage. However, current research mainly focuses on geological data statistics and the dominating effects of pore pressure. There are only a few laboratory-conditioned studies on the role of drilling boreholes and the effect of injection pressure on the borehole wall. Through experimental phenomenology, this study examines the risk of triggering geological disasters by fluid injection under shear stress. We developed a new direct shear test apparatus, coupled Hydro-Mechanical (HM), to investigate mechanical property variations when an intact rock experienced step drilling borehole, fluid injection, and fluid pressure acting on the borehole and fracture wall. We tested the peak shear stress of sandstone under different experimental conditions, which showed that drilling borehole, water injection, and increased pore pressure led to the decrease in peak shear stress. Furthermore, as pore pressure increased, peak shear stress dispersion increased due to crack propagation irregularity. Because the peak shear stress changed during the fluid injection steps, we suggest that the risk of triggering geological disaster with injection under shear stress, pore, borehole, and fluid pressure should be considered.

Lightning Characteristics and Lightning Strike Peak Current Probabilities as Related to Aerospace Vehicle Operations

NASA Technical Reports Server (NTRS)

Johnson, Dale L.; Vaughan, William W.

1998-01-01

A summary is presented of basic lightning characteristics/criteria for current and future NASA aerospace vehicles. The paper estimates the probability of occurrence of a 200 kA peak lightning return current, should lightning strike an aerospace vehicle in various operational phases, i.e., roll-out, on-pad, launch, reenter/land, and return-to-launch site. A literature search was conducted for previous work concerning occurrence and measurement of peak lighting currents, modeling, and estimating probabilities of launch vehicles/objects being struck by lightning. This paper presents these results.

The Sidebands of the Equatorial Electrojet: General Characteristic of the Westward Currents, as Deduced From CHAMP

NASA Astrophysics Data System (ADS)

Zhou, Yun-Liang; Lühr, Hermann; Alken, Patrick

2018-02-01

Based on 5 years (2001-2005) of magnetic field measurements made by the CHAMP satellite, latitudinal profiles of the equatorial electrojet (EEJ) have been derived. This study provides a comprehensive characterization of the reverse current EEJ sidebands. These westward currents peak at ±5° quasi-dipole latitude with typical amplitudes of 35% of the main EEJ. The diurnal amplitude variation is quite comparable with that of the EEJ. Similarly to the EEJ, the intensity is increasing with solar EUV flux, but with a steeper slope, indicating that not only the conductivity plays a role. For the longitude distribution we find, in general, larger amplitudes in the Western than in the Eastern Hemisphere. It is presently a common understanding that the reverse current EEJ sidebands are generated by eastward zonal winds at altitudes above about 120 km. In particular, a positive vertical gradient of wind speed generates westward currents at magnetic latitudes outside of 2° dip latitude. Interesting information about these features can be deduced from the sidebands' tidal characteristics. The longitudinal variation of the amplitude is dominated by a wave-1 pattern, which can primarily be attributed to the tidal components SPW1 and SW3. In case of the hemispheric amplitude differences these same two wave-1 components dominate. The ratio between sideband amplitude and main EEJ is largely controlled by the tidal features of the EEJ. The longitudinal patterns of the latitude, where the sidebands peak, resemble to some extent those of the amplitude. Current densities become larger when the peaks move closer to the magnetic equator.

Asymmetric SOL Current in Vertically Displaced Plasma

NASA Astrophysics Data System (ADS)

Cabrera, J. D.; Navratil, G. A.; Hanson, J. M.

2017-10-01

Experiments at the DIII-D tokamak demonstrate a non-monotonic relationship between measured scrape-off layer (SOL) currents and vertical displacement event (VDE) rates with SOL currents becoming largely n=1 dominant as plasma is displaced by the plasma control system (PCS) at faster rates. The DIII-D PCS is used to displace the magnetic axis 10x slower than the intrinsic growth time of similar instabilities in lower single-null plasmas. Low order (n <=2) mode decomposition is done on toroidally spaced current monitors to attain measures of asymmetry in SOL current. Normalized to peak n=0 response, a 2-4x increase is seen in peak n=1 response in plasmas displaced by the PCS versus previous VDE instabilities observed when vertical control is disabled. Previous inquiry shows VDE asymmetry characterized by SOL current fraction and geometric parameters of tokamak plasmas. We note that, of plasmas displaced by the PCS, short displacement time scales near the limit of the PCS temporal control appear to result in larger n=1/n=2 asymmetries. Work supported under USDOE Cooperative Agreement DE-FC02-04ER54698 and DE-FG02-04ER54761.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Lijun; Deng, Jie; Zhou, Xin

In this paper, cathode spot plasma jet (CSPJ) rotation and cathode spots behavior subjected to two kinds of large diameter axial magnetic field (AMF) electrode (cup-shaped and coil-shaped) are studied and analyzed based on experiments. The influence of gap distances on the CSPJ rotational behavior is analyzed. Experimental results show that CSPJ rotational phenomena extensively exist in the vacuum interrupters, and CSPJ rotational direction is along the direction of composite magnetic field (mainly the combination of the axial and azimuthal components). For coil-shaped and cup-shaped AMF electrodes, the rotational or inclination phenomena before the current peak value are much moremore » significant than that after current peak value (for the same arc current), which is related to the larger ratio of azimuthal magnetic field B{sub t} and AMF B{sub z} (B{sub t}/B{sub z}). With the increase of the gap distance, the AMF strength decreases, when the arc current is kept as constant, the azimuthal magnetic field is kept invariable, the ratio between azimuthal magnetic field and AMF is increased, which results in the increase of rotational effect. For cathode spots motion, compared with cup-shaped electrode, coil-shaped electrode has the inverse AMF direction. The Robson drift direction of cathode spots of coil-shaped electrode is opposite to that of cup-shaped electrode. With the increase of gap distance, the Robson angle is decreased, which is associated with the reduced AMF strength. Erosion imprints of anode and cathode are also related to the CSPJ rotational phenomena and cathode spots behavior. The noise of arc voltage in the initial arcing stage is related to the weaker AMF.« less

Ionic mechanisms of transient inward current in the absence of Na(+)-Ca2+ exchange in rabbit cardiac Purkinje fibres.

PubMed Central

Han, X; Ferrier, G R

1992-01-01

1. Membrane currents were measured with a two-microelectrode technique in voltage clamped rabbit cardiac Purkinje fibres under conditions known to cause intracellular calcium overload and to eliminate or minimize Na(+)-Ca2+ exchange. 2. Increasing [Ca2+]o from 2.5 to 5 mM or above and substituting external sodium with either sucrose, choline or Li+ induced an oscillatory transient inward current (TI) which peaked 200-300 ms after repolarization from a previous depolarizing pulse. The TI quickly disappeared upon return to normal Tyrode solution. Both the rate and configuration of action potentials of Purkinje fibres also returned to control upon return to Tyrode solution after 30 min of high Ca2+ exposure, if the Ca2+ concentration was 30 mM or less. 3. The TI in Na(+)-free solution was Ca2+ dependent. Either zero or low (2.5 mM) [Ca2+]o, or replacement of [Ca2+]o by BaCl prevented induction of the TI current upon repolarization from a previous depolarizing pulse. 4. In the presence of 30 mM-CaCl2 and with choline chloride as the substitute for NaCl, TI had a distinct reversal potential (Erev) of -25 mV. The time-to-peak TI, either inward or outward, did not shift significantly with change in voltage. Both inward and outward TI were simultaneously abolished by exposure to 1 microM-ryanodine, suggesting they were both activated by transient release of Ca2+ from the sarcoplasmic reticulum. The occurrence of TI in the absence of [Na+]o is not compatible with an electrogenic Na(+)-Ca2+ exchange mechanism. The existence of a clear-cut reversal potential suggests that an ionic channel may be responsible for the TI under these conditions. 5. Both the magnitude of peak TI and the Erev were affected by changes of CaCl2 concentration. (i) Under steady-state conditions, peak inward TI was significantly increased when the [Ca2+]o was elevated from 5 to 15 mM. The peak TI in the outward direction was significantly increased when [Ca2+]o was elevated from 15 to 30 mM; however, the difference in peak inward TI at 15 and 30 mM [Ca2+]o was small. (ii) Clear-cut reversals of TI were found at Ca2+ concentrations of 10 mM (Erev = -19.5 mV) or greater, and elevation of [Ca2+]o to 20, 30, 50 and 105 mM shifted the Erev to more negative potentials. (iii) In the presence of 5 mM [Ca2+]o the inward TI declined to zero at about -30 mV, and test voltages between -55 and +5 mV failed to reveal a distinct outward TI.(ABSTRACT TRUNCATED AT 400 WORDS) PMID:1284077

Performance of the Volumetric Diffusive Respirator at Altitude

DTIC Science & Technology

2014-08-18

information if it does not display a currently valid OMB control number. PLEASE DO NOT RETURN YOUR FORM TO THE ABOVE ADDRESS. 1. REPORT DATE (DD-MM...increased by 30-40%. Tidal volume remained within 15% of sea level values. Respiratory rate fell, while inspiratory time increased and high frequency...altitude, positive end expiratory pressure and peak inspiratory pressure were increased by 30-40%. Tidal volume remained within 15% of sea level

Early detection of Candida albicans biofilms at porous electrodes.

PubMed

Congdon, Robert B; Feldberg, Alexander S; Ben-Yakar, Natalie; McGee, Dennis; Ober, Christopher; Sammakia, Bahgat; Sadik, Omowunmi A

2013-02-15

We describe the development of an electrochemical sensor for early detection of biofilm using Candida albicans. The electrochemical sensor used the ability of biofilms to accept electrons from redox mediators relative to the number of metabolically active cells present. Cyclic voltammetry and differential pulse voltammetry techniques were used to monitor the redox reaction of K(3)Fe(CN)(6) at porous reticulated vitreous carbon (RVC) (238.7 cm(2)) working electrodes versus Ag/AgCl reference. A shift in the peak potential occurred after 12 h of film growth, which is attributed to the presence of C. albicans. Moreover, the intensity of the ferricyanide reduction peak first increased as C. albicans deposited onto the porous electrodes at various growth times. The peak current subsequently decreased at extended periods of growth of 48 h. The reduction in peak current was attributed to the biofilm reaching its maximum growth thickness, which correlated with the maximum number of metabolically active cells. The observed diffusion coefficients for the bare RVC and biofilm-coated electrodes were 2.2 × 10(-3) and 7.0 × 10(-6) cm(2)/s, respectively. The increase in diffusivity from the bare electrode to the biofilm-coated electrode indicated some enhancement of electron transfer mediated by the biofilm to the porous electrode. Verification of the growth of biofilm was achieved using scanning electron microcopy and laser scanning confocal imaging microscopy. Validation with conventional plating techniques confirmed that the correlation (R(2) = 0.9392) could be achieved between the electrochemical sensors data and colony-forming units. Copyright © 2012 Elsevier Inc. All rights reserved.

InP tunnel junctions for InP/InGaAs tandem solar cells

NASA Technical Reports Server (NTRS)

Vilela, Mauro F.; Freundlich, Alex; Renaud, P.; Medelci, N.; Bensaoula, A.

1996-01-01

We report, for the first time, an epitaxially grown InP p(+)/n(++) tunnel junction. A diode with peak current densities up to 1600 A/cm and maximum specific resistivities (Vp/Ip - peak voltage to peak current ratio) in the range of 10(exp -4)Omega cm(exp 2) is obtained. This peak current density is comparable to the highest results previously reported for lattice matched In(0.53)Ga(0.47)As tunnel junctions. Both results were obtained using chemical beam epitaxy (CBE). In this paper we discuss the electrical characteristics of these tunnel diodes and how the growth conditions influence them.

InP Tunnel Junctions for InP/InGaAs Tandem Solar Cells

NASA Technical Reports Server (NTRS)

Vilela, M. F.; Medelci, N.; Bensaoula, A.; Freundlich, A.; Renaud, P.

1995-01-01

We report, for the first time, an epitaxially grown InP p(+)/n(++) tunnel junction. A diode with peak current densities up to 1600 Al/sq cm and maximum specific resistivities (Vp/lp - peak voltage to peak current ratio) in the range of 10(exp -4)Om sq cm is obtained. This peak current density is comparable to the highest results previously reported for lattice matched In(0.53)Ga(0.47)As tunnel junctions. Both results were obtained using chemical beam epitaxy (CBE). In this paper we discuss the electrical characteristics of these tunnel diodes and how the growth conditions influence them.

Growth and characterization of high current density, high-speed InAs/AlSb resonant tunneling diodes

NASA Technical Reports Server (NTRS)

Soderstrom, J. R.; Brown, E. R.; Parker, C. D.; Mahoney, L. J.; Yao, J. Y.

1991-01-01

InAs/AlSb double-barrier resonant tunneling diodes with peak current densities up to 370,000 A/sq cm and high peak-to-valley current ratios of 3.2 at room temperature have been fabricated. The peak current density is well-explained by a stationary-state transport model with the two-band envelope function approximation. The valley current density predicted by this model is less than the experimental value by a factor that is typical of the discrepancy found in other double-barrier structures. It is concluded that threading dislocations are largely inactive in the resonant tunneling process.

External noise-induced transitions in a current-biased Josephson junction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Huang, Qiongwei; Xue, Changfeng, E-mail: cfxue@163.com; Tang, Jiashi

We investigate noise-induced transitions in a current-biased and weakly damped Josephson junction in the presence of multiplicative noise. By using the stochastic averaging procedure, the averaged amplitude equation describing dynamic evolution near a constant phase difference is derived. Numerical results show that a stochastic Hopf bifurcation between an absorbing and an oscillatory state occurs. This means the external controllable noise triggers a transition into the non-zero junction voltage state. With the increase of noise intensity, the stationary probability distribution peak shifts and is characterised by increased width and reduced height. And the different transition rates are shown for large andmore » small bias currents.« less

Helicon double layer thruster operation in a low magnetic field mode

NASA Astrophysics Data System (ADS)

Harle, T.; Pottinger, S. J.; Lappas, V. J.

2013-02-01

Direct thrust measurements are made of a helicon double layer thruster operating in a low magnetic field mode. The relationship between the imposed axial magnetic field and generated thrust is investigated for a radio frequency input power range 200-500 W for propellant flow rates of 16.5 and 20 sccm (0.46 and 0.55 mg s-1) of argon. The measured thrust shows a strong dependence on the magnetic field strength, increasing by up to a factor of 5 compared with the minimum thrust level recorded. A peak thrust of 0.4-1.1 mN depending on thruster operating conditions is obtained. This increase is observed to take place over a small range of peak magnetic field strengths in the region of 70-110 G. The magnitude of the thrust and the corresponding magnitude of the magnetic field at which the peak thrust occurs is shown to increase with increasing input power for a given propellant flow rate. The ion current determined using a retarding field energy analyser and the electron number density found using a microwave resonator probe both correlate with the observed trend in thrust as a function of applied magnetic field.

WE-E-17A-01: Characterization of An Imaging-Based Model of Tumor Angiogenesis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Adhikarla, V; Jeraj, R

2014-06-15

Purpose: Understanding the transient dynamics of tumor oxygenation is important when evaluating tumor-vasculature response to anti-angiogenic therapies. An imaging-based tumor-vasculature model was used to elucidate factors that affect these dynamics. Methods: Tumor growth depends on its doubling time (Td). Hypoxia increases pro-angiogenic factor (VEGF) concentration which is modeled to reduce vessel perfusion, attributing to its effect of increasing vascular permeability. Perfused vessel recruitment depends on the existing perfused vasculature, VEGF concentration and maximum VEGF concentration (VEGFmax) for vessel dysfunction. A convolution-based algorithm couples the tumor to the normal tissue vessel density (VD-nt). The parameters are benchmarked to published pre-clinical datamore » and a sensitivity study evaluating the changes in the peak and time to peak tumor oxygenation characterizes them. The model is used to simulate changes in hypoxia and proliferation PET imaging data obtained using [Cu- 61]Cu-ATSM and [F-18]FLT respectively. Results: Td and VD-nt were found to be the most influential on peak tumor pO2 while VEGFmax was marginally influential. A +20 % change in Td, VD-nt and VEGFmax resulted in +50%, +25% and +5% increase in peak pO2. In contrast, Td was the most influential on the time to peak oxygenation with VD-nt and VEGFmax playing marginal roles. A +20% change in Td, VD-nt and VEGFmax increased the time to peak pO2 by +50%, +5% and +0%. A −20% change in the above parameters resulted in comparable decreases in the peak and time to peak pO2. Model application to the PET data was able to demonstrate the voxel-specific changes in hypoxia of the imaged tumor. Conclusion: Tumor-specific doubling time and vessel density are important parameters to be considered when evaluating hypoxia transients. While the current model simulates the oxygen dynamics of an untreated tumor, incorporation of therapeutic effects can make the model a potent tool for analyzing anti-angiogenic therapies.« less

Compact type-I coil planet centrifuge for counter-current chromatography

PubMed Central

Yang, Yi; Gu, Dongyu; Liu, Yongqiang; Aisa, Haji Akber; Ito, Yoichiro

2009-01-01

A compact type-I coil planet centrifuge has been developed for performing counter-current chromatography. It has a revolution radius of 10 cm and a column holder height of 5 cm compared with 37 cm and 50 cm in the original prototype, respectively. The reduction in the revolution radius and column length permits application of higher revolution speed and more stable balancing of the rotor which leads us to learn more about its performance and the future potential of type-I coil planet centrifuge. The chromatographic performance of this apparatus was evaluated in terms of retention of the stationary phase (Sf), peak resolution (Rs), theoretical plate (N) and peak retention time (tR). The results of the experiment indicated that increasing the revolution speed slightly improved both the retention of the stationary phase and the peak resolution while the separation time is remarkably shortened to yield an excellent peak resolution at a revolution speed of 800 rpm. With a 12 ml capacity coiled column, DNP-glu, DNP-β-ala and DNP-ala were resolved at Rs of 2.75 and 2.16 within 90 min at a flow rate of 0.4 ml/min. We believe that the compact type-I coil planet centrifuge has a high analytical potential. PMID:20060979

Compact type-I coil planet centrifuge for counter-current chromatography.

PubMed

Yang, Yi; Gu, Dongyu; Liu, Yongqiang; Aisa, Haji Akber; Ito, Yoichiro

2010-02-19

A compact type-I coil planet centrifuge has been developed for performing counter-current chromatography. It has a revolution radius of 10 cm and a column holder height of 5 cm compared with 37 and 50 cm in the original prototype, respectively. The reduction in the revolution radius and column length permits application of higher revolution speed and more stable balancing of the rotor which leads us to learn more about its performance and the future potential of type-I coil planet centrifuge. The chromatographic performance of this apparatus was evaluated in terms of retention of the stationary phase (S(f)), peak resolution (R(s)), theoretical plate (N) and peak retention time (t(R)). The results of the experiment indicated that increasing the revolution speed slightly improved both the retention of the stationary phase and the peak resolution while the separation time is remarkably shortened to yield an excellent peak resolution at a revolution speed of 800 rpm. With a 12 ml capacity coiled column, DNP-DL-glu, DNP-beta-ala and DNP-l-ala were resolved at R(s) of 2.75 and 2.16 within 90 min at a flow rate of 0.4 ml/min. We believe that the compact type-I coil planet centrifuge has a high analytical potential. Published by Elsevier B.V.

Use of alternating and pulsed direct current electrified fields for zebra mussel control

USGS Publications Warehouse

Luoma, James A.; Dean, Jan C.; Severson, Todd J.; Wise, Jeremy K.; Barbour, Matthew

2017-01-01

Alternatives to chemicals for controlling dreissenid mussels are desirable for environmental compatibility, but few alternatives exist. Previous studies have evaluated the use of electrified fields for stunning and/or killing planktonic life stages of dreissenid mussels, however, the available literature on the use of electrified fields to control adult dreissenid mussels is limited. We evaluated the effects of sinusoidal alternating current (AC) and 20% duty cycle square-wave pulsed direct current (PDC) exposure on the survival of adult zebra mussels at water temperatures of 10, 15, and 22 °C. Peak voltage gradients of ~ 17 and 30 Vp/cm in the AC and PDC exposures, respectively, were continuously applied for 24, 48, or 72 h. Peak power densities ranged from 77,999 to 107,199 µW/cm3 in the AC exposures and 245,320 to 313,945 µW/cm3 in the PDC exposures. The peak dose ranged from 6,739 to 27,298 Joules/cm3 and 21,306 to 80,941 Joules/cm3 in the AC and PDC exposures, respectively. The applied power ranged from 16.6 to 68.9 kWh in the AC exposures and from 22.2 to 86.4 kWh in the PDC exposures. Mortality ranged from 2.7 to 92.7% in the AC exposed groups and from 24.0 to 98.7% in PDC exposed groups. Mortality increased with corresponding increases in water temperature and exposure duration, and we observed more zebra mussel mortality in the PDC exposures. Exposures conducted with AC required less of a peak dose (Joules/cm3) but more applied power (kWh) to achieve the same level of adult zebra mussel mortality as corresponding PDC exposures. The results demonstrate that 20% duty cycle square-wave PDC requires less energy than sinusoidal AC to inducing the same level of adult zebra mussel mortality.

Predicting Peak Flows following Forest Fires

NASA Astrophysics Data System (ADS)

Elliot, William J.; Miller, Mary Ellen; Dobre, Mariana

2016-04-01

Following forest fires, peak flows in perennial and ephemeral streams often increase by a factor of 10 or more. This increase in peak flow rate may overwhelm existing downstream structures, such as road culverts, causing serious damage to road fills at stream crossings. In order to predict peak flow rates following wildfires, we have applied two different tools. One is based on the U.S.D.A Natural Resource Conservation Service Curve Number Method (CN), and the other is by applying the Water Erosion Prediction Project (WEPP) to the watershed. In our presentation, we will describe the science behind the two methods, and present the main variables for each model. We will then provide an example of a comparison of the two methods to a fire-prone watershed upstream of the City of Flagstaff, Arizona, USA, where a fire spread model was applied for current fuel loads, and for likely fuel loads following a fuel reduction treatment. When applying the curve number method, determining the time to peak flow can be problematic for low severity fires because the runoff flow paths are both surface and through shallow lateral flow. The WEPP watershed version incorporates shallow lateral flow into stream channels. However, the version of the WEPP model that was used for this study did not have channel routing capabilities, but rather relied on regression relationships to estimate peak flows from individual hillslope polygon peak runoff rates. We found that the two methods gave similar results if applied correctly, with the WEPP predictions somewhat greater than the CN predictions. Later releases of the WEPP model have incorporated alternative methods for routing peak flows that need to be evaluated.

The use of satellites in non-goestationary orbits for unloading geostationary communication satellite traffic peaks. Volume 2: Technical report

NASA Technical Reports Server (NTRS)

Price, K.; Turner, A.; Nguyen, T.; Doong, W.; Weyandt, C.

1987-01-01

The part of the geostationary (GEO) orbital arc used for United States domestic fixed, communications service is rapidly becoming filled with satellites. One of the factors currently limiting its utilization is that communications satellites must be designed to have sufficient capacity to handle peak traffic leads, and thus are under utilized most of the time. A solution is to use satellites in suitable non-geostationary orbits to unload the traffic peaks. Three different designs for a non-geostationary orbit communications satellite system are presented for the 1995 time frame. The economic performance is analyzed and compared with geostationary satellites for two classes of service, trunking and customer premise service. The result is that the larger payload of the non-geostationary satellite offsets the burdens of increased complexity and worse radiation environment to give improved economic performance. Depending on ground terminal configuration, the improved economic performance of the space segment may be offset by increased ground terminal expenses.

TRADABLE CREDITS FOR STORM WATER VOLUME: AN ALTERNATIVE APPROACH FOR SUSTAINABLE URBAN WATERSHED MANAGEMENT

EPA Science Inventory

The increased storm water runoff rate and volume caused by urbanization, and their detrimental effects on stream habitat and morphology, is well documented. In most cases, current storm water management policies are focused on attenuating peak flow rates. While these policies may...

The effect of guide-field and boundary conditions on collisionless magnetic reconnection in a stressed X-point collapse

DOE Office of Scientific and Technical Information (OSTI.GOV)

Graf von der Pahlen, J.; Tsiklauri, D.

2014-01-15

Works of Tsiklauri and Haruki [Phys. Plasmas 15, 102902 (2008); 14, 112905 (2007)] are extended by inclusion of the out-of-plane magnetic (guide) field. In particular, magnetic reconnection during collisionless, stressed X-point collapse for varying out-of-plane guide-fields is studied using a kinetic, 2.5D, fully electromagnetic, relativistic particle-in-cell numerical code. For zero guide-field, cases for both open and closed boundary conditions are investigated, where magnetic flux and particles are lost and conserved, respectively. It is found that reconnection rates, out-of-plane currents and density in the X-point increase more rapidly and peak sooner in the closed boundary case, but higher values are reachedmore » in the open boundary case. The normalized reconnection rate is fast: 0.10-0.25. In the open boundary case it is shown that an increase of guide-field yields later onsets in the reconnection peak rates, while in the closed boundary case initial peak rates occur sooner but are suppressed. The reconnection current changes similarly with increasing guide-field; however for low guide-fields the reconnection current increases, giving an optimal value for the guide-field between 0.1 and 0.2 times the in-plane field in both cases. Also, in the open boundary case, it is found that for guide-fields of the order of the in-plane magnetic field, the generation of electron vortices occurs. Possible causes of the vortex generation, based on the flow of decoupled particles in the diffusion region and localized plasma heating, are discussed. Before peak reconnection onset, oscillations in the out-of-plane electric field at the X-point are found, ranging in frequency from approximately 1 to 2 ω{sub pe} and coinciding with oscillatory reconnection. These oscillations are found to be part of a larger wave pattern in the simulation domain. Mapping the out-of-plane electric field along the central lines of the domain over time and applying a 2D Fourier transform reveal that the waves predominantly correspond to the ordinary and the extraordinary mode and hence may correspond to observable radio waves such as solar radio burst fine structure spikes.« less

Lightning Strike Peak Current Probabilities as Related to Space Shuttle Operations

NASA Technical Reports Server (NTRS)

Johnson, Dale L.; Vaughan, William W.

2000-01-01

A summary is presented of basic lightning characteristics/criteria applicable to current and future aerospace vehicles. The paper provides estimates on the probability of occurrence of a 200 kA peak lightning return current, should lightning strike an aerospace vehicle in various operational phases, i.e., roll-out, on-pad, launch, reenter/land, and return-to-launch site. A literature search was conducted for previous work concerning occurrence and measurement of peak lighting currents, modeling, and estimating the probabilities of launch vehicles/objects being struck by lightning. This paper presents a summary of these results.

Asymmetric giant magnetoimpedance effect created by micro magnets

NASA Astrophysics Data System (ADS)

Atalay, S.; Izgi, T.; Buznikov, N. A.; Kolat, V. S.

2018-05-01

Asymmetric giant magnetoimpedance (AGMI) effect has been investigated in as-prepared and current annealed amorphous (Co0.9Fe0.05Ni0.05)75Si15B10 ribbons. Asymmetry was created by micro magnets. Different numbers of magnets were used and it was found that increasing number of magnet, the shift in AGMI curves increases. When two micro magnets were placed 1 cm away from the ends of ribbon, a distortion in two peak shape of the GMI curve was observed. At high frequency range, a linear change in the AGMI was observed for the current annealed sample.

Effect of External Loading on Force and Power Production During Plyometric Push-ups.

PubMed

Hinshaw, Taylour J; Stephenson, Mitchell L; Sha, Zhanxin; Dai, Boyi

2018-04-01

Hinshaw, TJ, Stephenson, ML, Sha, Z, and Dai, B. Effect of external loading on force and power production during plyometric push-ups. J Strength Cond Res 32(4): 1099-1108, 2018-One common exercise to train upper-body strength and power is the push-up. Training at the loads that would produce the greatest power is an effective way to increase peak power. The purpose of the current study was to quantify the changes in peak force, peak power, and peak velocity among a modified plyometric push-up and plyometric push-ups with or without external loading in physically active young adults. Eighteen male and 17 female participants completed 4 push-ups: (a) modified plyometric push-up on the knees, (b) plyometric push-up without external loading, (c) plyometric push-up with an external load of 5% of body weight, and (d) plyometric push-up with an external load of 10% of body weight. Two force platforms were set up to collect vertical ground reaction forces at the hands and feet. The modified plyometric push-up demonstrated the lowest force, power, and velocity (5.4≥ Cohen's dz ≥1.2). Peak force and force at peak velocity increased (3.8≥ Cohen's dz ≥0.3) and peak velocity and velocity at peak power decreased (1.4≥ Cohen's dz ≥0.8) for the push-up without external loading compared with the 2 push-ups with external loading. No significant differences were observed for peak power among the push-ups with or without external loading (0.4≥ Cohen's dz ≥0.1). Although peak power is similar with or without external loading, push-ups without external loading may be more beneficial for a quick movement, and push-ups with external loading may be more beneficial for a greater force production.

The effect of PS porosity on the structure, optical and electrical properties of ZnS/PS

NASA Astrophysics Data System (ADS)

Wang, Cai-Feng; Hu, Bo; Yi, Hou-Hui; Li, Wei-Bing

2014-03-01

ZnS films were deposited on porous silicon (PS) substrates with different porosities by pulsed laser deposition (PLD). The crystalline structure, surface morphology of ZnS films on PS substrates and optical, electrical properties of ZnS/PS composites were studied. The results show that, ZnS films deposited on PS substrates were grown in preferred orientation along β-ZnS (111) direction corresponding to crystalline structure of cubic phase. With the increase of PS porosity, the XRD diffraction peak intensity of ZnS films decreases. Some voids and cracks appear in the films. Compared with as-prepared PS, the PL peak of PS for ZnS/PS has a blueshift. The larger the porosity of PS, the greater the blueshift is. A new green light emission located around 550 nm is observed with increasing PS porosity, which is ascribed to defect-center luminescence of ZnS. The blue, green emission of ZnS combined with the red emission of PS, a broad photoluminescence band (450-750 nm) is formed. ZnS/PS composites exhibited intense white light emission. The I-V characteristics of ZnS/PS heterojunctions showed rectifying behavior. Under forward bias conditions, the current density is large. Under reverse bias conditions, the current density nearly to be zero. The forward current increases with increasing PS porosity. This work lay a foundation for the realization of electroluminescence of ZnS/PS and solid white light emission devices.

Artificial stimulation of auroral electron acceleration by intense field aligned currents

NASA Technical Reports Server (NTRS)

Holmgren, G.; Bostrom, R.; Kelley, M. C.; Kintner, P. M.; Lundin, R.; Bering, E. A.; Sheldon, W. R.; Fahleson, U. V.

1979-01-01

A cesium-doped high explosion was detonated at 165 km altitude in the auroral ionosphere during quiet conditions. An Alfven wave pulse with a 200-mV/m electric field was observed, with the peak occurring 135 ms after the explosion at a distance of about 1 km. The count rate of fixed energy 2-keV electron detectors abruptly increased at 140 ms, peaked at 415 ms, and indicated a downward field-aligned beam of accelerated electrons. An anomalously high-field aligned beam of backscattered electrons was also detected. The acceleration is interpreted as due to production of an electrostatic shock or double layer between 300 and 800 km altitude. The structure was probably formed by an instability of the intense field-aligned currents in the Alfven wave launched by the charge-separation electric field due to the explosion.

Molten salt thermal energy storage for utility peaking loads

NASA Technical Reports Server (NTRS)

Ferrara, A.; Haslett, R.; Joyce, J.

1977-01-01

This paper considers the use of thermal energy storage (TES) in molten salts to increase the capacity of power plants. Five existing fossil and nuclear electric utility plants were selected as representative of current technology. A review of system load diagrams indicated that TES to meet loads over 95% of peak was a reasonable goal. Alternate TES heat exchanger locations were evaluated, showing that the stored energy should be used either for feedwater heating or to generate steam for an auxiliary power cycle. Specific salts for each concept are recommended. Design layouts were prepared for one plant, and it was shown that a TES tube/shell heat exchanger system could provide about 7% peaking capability at lower cost than adding steam generation capacity. Promising alternate heat exchanger concepts were also identified.

Intravenous anaesthetics inhibit nicotinic acetylcholine receptor-mediated currents and Ca2+ transients in rat intracardiac ganglion neurons

PubMed Central

Weber, Martin; Motin, Leonid; Gaul, Simon; Beker, Friederike; Fink, Rainer H A; Adams, David J

2004-01-01

The effects of intravenous (i.v.) anaesthetics on nicotinic acetylcholine receptor (nAChR)-induced transients in intracellular free Ca2+ concentration ([Ca2+]i) and membrane currents were investigated in neonatal rat intracardiac neurons. In fura-2-loaded neurons, nAChR activation evoked a transient increase in [Ca2+]I, which was inhibited reversibly and selectively by clinically relevant concentrations of thiopental. The half-maximal concentration for thiopental inhibition of nAChR-induced [Ca2+]i transients was 28 μM, close to the estimated clinical EC50 (clinically relevant (half-maximal) effective concentration) of thiopental. In fura-2-loaded neurons, voltage clamped at −60 mV to eliminate any contribution of voltage-gated Ca2+ channels, thiopental (25 μM) simultaneously inhibited nAChR-induced increases in [Ca2+]i and peak current amplitudes. Thiopental inhibited nAChR-induced peak current amplitudes in dialysed whole-cell recordings by ∼ 40% at −120, −80 and −40 mV holding potential, indicating that the inhibition is voltage independent. The barbiturate, pentobarbital and the dissociative anaesthetic, ketamine, used at clinical EC50 were also shown to inhibit nAChR-induced increases in [Ca2+]i by ∼40%. Thiopental (25 μM) did not inhibit caffeine-, muscarine- or ATP-evoked increases in [Ca2+]i, indicating that inhibition of Ca2+ release from internal stores via either ryanodine receptor or inositol-1,4,5-trisphosphate receptor channels is unlikely. Depolarization-activated Ca2+ channel currents were unaffected in the presence of thiopental (25 μM), pentobarbital (50 μM) and ketamine (10 μM). In conclusion, i.v. anaesthetics inhibit nAChR-induced currents and [Ca2+]i transients in intracardiac neurons by binding to nAChRs and thereby may contribute to changes in heart rate and cardiac output under clinical conditions. PMID:15644873

Method for reducing peak phase current and decreasing staring time for an internal combustion engine having an induction machine

DOEpatents

Amey, David L.; Degner, Michael W.

2002-01-01

A method for reducing the starting time and reducing the peak phase currents for an internal combustion engine that is started using an induction machine starter/alternator. The starting time is reduced by pre-fluxing the induction machine and the peak phase currents are reduced by reducing the flux current command after a predetermined period of time has elapsed and concurrent to the application of the torque current command. The method of the present invention also provides a strategy for anticipating the start command for an internal combustion engine and determines a start strategy based on the start command and the operating state of the internal combustion engine.

Thermo-Mechanical Fatigue Crack Growth of RR1000

PubMed Central

Pretty, Christopher John; Whitaker, Mark Thomas; Williams, Steve John

2017-01-01

Non-isothermal conditions during flight cycles have long led to the requirement for thermo-mechanical fatigue (TMF) evaluation of aerospace materials. However, the increased temperatures within the gas turbine engine have meant that the requirements for TMF testing now extend to disc alloys along with blade materials. As such, fatigue crack growth rates are required to be evaluated under non-isothermal conditions along with the development of a detailed understanding of related failure mechanisms. In the current work, a TMF crack growth testing method has been developed utilising induction heating and direct current potential drop techniques for polycrystalline nickel-based superalloys, such as RR1000. Results have shown that in-phase (IP) testing produces accelerated crack growth rates compared with out-of-phase (OOP) due to increased temperature at peak stress and therefore increased time dependent crack growth. The ordering of the crack growth rates is supported by detailed fractographic analysis which shows intergranular crack growth in IP test specimens, and transgranular crack growth in 90° OOP and 180° OOP tests. Isothermal tests have also been carried out for comparison of crack growth rates at the point of peak stress in the TMF cycles. PMID:28772394

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Li-Fang; Ou, Chin-Ching; Striebel, Kathryn A.

The goal of this research was to measure Mn dissolution from a thin porous spinel LiMn{sub 2}O{sub 4} electrode by rotating ring-disk collection experiments. The amount of Mn dissolution from the spinel LiMn{sub 2}O{sub 4} electrode under various conditions was detected by potential step chronoamperometry. The concentration of dissolved Mn was found to increase with increasing cycle numbers and elevated temperature. The dissolved Mn was not dependent on disk rotation speed, which indicated that the Mn dissolution from the disk was under reaction control. The in situ monitoring of Mn dissolution from the spinel was carried out under various conditions.more » The ring currents exhibited maxima corresponding to the end-of-charge (EOC) and end-of-discharge (EOD), with the largest peak at EOC. The results suggest that the dissolution of Mn from spinel LiMn{sub 2}O{sub 4} occurs during charge/discharge cycling, especially in a charged state (at >4.1 V) and in a discharged state (at <3.1 V). The largest peak at EOC demonstrated that Mn dissolution took place mainly at the top of charge. At elevated temperatures, the ring cathodic currents were larger due to the increase of Mn dissolution rate.« less

Interaction of 3beta, 5alpha-tetrahydrodeoxycorticosterone in rat and guinea-pig neurons: a comparison of Ca2+ - and GABA(A)-CI- -channel current modulation.

PubMed

ffrench-Mullen, J M

1999-01-01

A comparison of the interaction of 3beta, 5alpha-tetrahydrodeoxycorticosterone (TDOC) on voltage-gated Ca2+ -and the gamma-aminobutyric receptor (GABA(A)) gated-Cl- -channels was examined in freshly dissociated guinea-pig (GP) and rat hippocampal CA1 neurons and rat hypothalamic ventromedial nucleus (VMN) neurons. The steady-state inhibition of the peak Ca2+ channel current evoked by depolarized steps from -80 to -10 mV by TDOC increased in concentration-dependent manner with IC50 values of 1 and 6 pM for rat and GP CA1 neurons, respectively and 3 nM for rat VMN neurons. TDOC rapidly and reversibly inhibited a fraction (up to 26%) of the total Ca2+ channel current in all neurons. Intracellular dialysis with GDP-beta-S (500 microM) significantly diminished the TDOC inhibition of the Ca2+ channel current, suggesting a G-protein involvement. In neurons isolated from pertussis-toxin-treated animals by chronic intracerebroventricular (1000 ng/24/48 h) infusion, the TDOC inhibition was also significantly diminished, suggesting modulation by the Galphai and/or Galphao G-protein subunits. The peak GABA-gated inward Cl- current was enhanced in both species from 0.1 to 10 microM with the greatest increase (48% at 10 microM) seen in the VMN. There was no difference in the enhancement of the GABA current in the CA1 region of both species. The results show that in contrast to the 3a-series, the 3beta-series weakly enhance the GABA-evoked Cl- current but potently inhibit the Ca2+ channel current. In addition, these results also suggest a common mode of action and a lack of interspecies difference for this steroid.

Submicrosecond characteristics of lightning return-stroke currents

NASA Technical Reports Server (NTRS)

Leteinturier, Christiane; Hamelin, Joel H.; Eybert-Berard, Andre

1991-01-01

The authors describe the experimental results obtained during 1987 and 1988 triggered-lightning experiments in Florida. Seventy-four simultaneous submicrosecond time-resolved measurements of triggered return-stroke current (I) and current derivative (dI/dt) were made in Florida in 1987 and 1988. Peak currents ranged from about 5 to 76 kA, peak dI/dt amplitude from 13 to 411 kA/microsec and rise time from 90 to 1000 ns. The mean peak dI/dt values of 110 kA/microsec were 2-3 times higher than data from instrumented towers and peak I and dI/dt appear to be positively correlated. These data confirm previous experiments and conclusions supported by forty measurements. They are important in order to define, for example, standards for lightning protection. Present standards give a dI/dt maximum of 140 kA/microsec.

On the road to self-sputtering in high power impulse magnetron sputtering: particle balance and discharge characteristics

NASA Astrophysics Data System (ADS)

Huo, Chunqing; Lundin, Daniel; Raadu, Michael A.; Anders, André; Tomas Gudmundsson, Jon; Brenning, Nils

2014-04-01

The onset and development of self-sputtering (SS) in a high power impulse magnetron sputtering (HiPIMS) discharge have been studied using a plasma chemical model and a set of experimental data, taken with an aluminum target and argon gas. The model is tailored to duplicate the discharge in which the data are taken. The pulses are long enough to include both an initial transient and a following steady state. The model is used to unravel how the internal discharge physics evolves with pulse power and time, and how it is related to features in the discharge current-voltage-time characteristics such as current densities, maxima, kinks and slopes. The connection between the self-sputter process and the discharge characteristics is quantified and discussed in terms of three parameters: a critical target current density Jcrit based on the maximum refill rate of process (argon) gas above the target, an SS recycling factor ΠSS-recycle, and an approximation \\tilde{\\alpha} of the probabilities of ionization of species that come from the target (both sputtered metal and embedded argon atoms). For low power pulses, discharge voltages UD ⩽ 380 V with peak current densities below ≈ 0.2 A cm-2, the discharge is found to be dominated by process gas sputtering. In these pulses there is an initial current peak in time, associated with partial gas rarefaction, which is followed by a steady-state-like plateau in all parameters similar to direct current magnetron sputtering. In contrast, high power pulses, with UD ⩾ 500 V and peak current densities above JD ≈ 1.6 A cm-2, make a transition to a discharge mode where SS dominates. The transition is found not to be driven by process gas rarefaction which is only about 10% at this time. Maximum gas rarefaction is found later in time and always after the initial peak in the discharge current. With increasing voltage, and pulse power, the discharge can be described as following a route where the role of SS increases in four steps: process gas sputtering, gas-sustained SS, self-sustained SS and SS runaway. At the highest voltage, 1000 V, the discharge is very close to, but does not go into, the SS runaway mode. This absence of runaway is proposed to be connected to an unexpected finding: that twice ionized ions of the target species play almost no role in this discharge, not even at the highest powers. This reduces ionization by secondary-emitted energetic electrons almost to zero in the highest power range of the discharge.

Carbon nanotube wires with continuous current rating exceeding 20 Amperes

NASA Astrophysics Data System (ADS)

Cress, Cory D.; Ganter, Matthew J.; Schauerman, Christopher M.; Soule, Karen; Rossi, Jamie E.; Lawlor, Colleen C.; Puchades, Ivan; Ubnoske, Stephen M.; Bucossi, Andrew R.; Landi, Brian J.

2017-07-01

A process to fabricate carbon nanotube (CNT) wires with diameters greater than 1 cm and continuous current carrying capability exceeding 20 A is demonstrated. Wires larger than 5 mm are formed using a multi-step radial densification process that begins with a densified CNT wire core followed by successive wrapping of additional CNT material to increase the wire size. This process allows for a wide range of wire diameters to be fabricated, with and without potassium tetrabromoaurate (KAuBr4) chemical doping, and the resulting electrical and thermal properties to be characterized. Electrical measurements are performed with on/off current steps to obtain the maximum current before reaching a peak CNT wire temperature of 100 °C and before failure, yielding values of instantaneous currents in excess of 45 A for KAuBr4 doped CNT wires with a diameter of 6 mm achieved prior to failure. The peak temperature of the wires at failure (˜530 °C) is correlated with the primary decomposition peak observed in thermal gravimetric analysis of a wire sample confirming that oxidation is the primary failure mode of CNT wires operated in air. The in operando stability of doped CNT wires is confirmed by monitoring the resistance and temperature, which remain largely unaltered over 40 days and 1 day for wires with 1.5 mm and 11.2 mm diameters, respectively. The 100 °C continuous current rating, or ampacity, is measured for a range of doped CNT wire diameters and corresponding linear mass densities ρL. To describe the results, a new form of the fuse-law, where the critical current is defined as I ∝ρL3 /4, is developed and shows good agreement with the experimental data. Ultimately, CNT wires are shown to be stable electrical conductors, with failure current densities in excess of 50 A in the case of a convectively cooled 11.2 mm doped CNT wire, and amenable for use in applications that have long-term, high-current demands.

Influence of inclination angles on intra- and inter-limb load-sharing during uphill walking.

PubMed

Hong, Shih-Wun; Leu, Tsai-Hsueh; Li, Jia-Da; Wang, Ting-Ming; Ho, Wei-Ping; Lu, Tung-Wu

2014-01-01

Uphill walking is an inevitable part of daily living, placing more challenges on the locomotor system with greater risk of falls than level walking does. The current study aimed to investigate the effects of inclination angles on the inter-joint and inter-limb load-sharing during uphill walking in terms of total support moment and contributions of individual joint moments to the total support moment. Fifteen young adults walked up walkways with 0°, 5°, 10° and 15° of slope while kinematic and kinetic data were collected and analyzed. With increasing inclination angles, the first peak of the total support moment was increased with unaltered individual joint contributions, suggesting an unaltered inter-joint control pattern in the leading limb to meet the increased demands. The second peak of the total support moment remained unchanged with increasing inclination angles primarily through a compensatory redistribution of the hip and knee moments. During DLS, the leading limb shared the majority of the whole body support moments. The current results reveal basic intra- and inter-limb load-sharing patterns of uphill walking, which will be helpful for a better understanding of the control strategies adopted and for subsequent clinical applications. Copyright © 2013 Elsevier B.V. All rights reserved.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Wei; Zhao, De Gang, E-mail: dgzhao@red.semi.ac.cn; Jiang, De Sheng

The electroluminescence (EL) spectra of blue–green light emitting InGaN/GaN multiple quantum well (MQW) structures grown via metal-organic chemical vapor deposition are investigated. With increasing In content in InGaN well layers, the peak energy redshifts, the emission intensity reduces and the inhomogeneous broadening of the luminescence band increases. In addition, it is found that the EL spectra shrink with increasing injection current at low excitation condition, which may be ascribed to both Coulomb screening of polarization field and carrier transferring from shallower localization states to the deeper ones, while at high currents the state-filling effect in all localization states may becomemore » significant and lead to a broadening of EL spectra. However, surprisingly, for the MQW sample with much higher In content, the EL spectral bandwidth can be almost unchanged with increasing current at the high current range, since a large number of carriers may be captured by the nonradiative recombination centers distributed outside the localized potential traps and the state-filling effect in the localization states is suppressed.« less

Quantum calculations for one-dimensional cooling of helium

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vredenbregt, E.; Doery, M.; Bergeman, T.

1993-05-01

We report theoretical velocity distributions for sub-Doppler laser cooling of metastable He*(2{sup 3}S), calculated with the Density Matrix and Monte Carlo Wavefunction approaches. For low-field (B = 50 mG) magnetic-field induced laser cooling on the 2{sup 3}S {yields} (2{sup 3}P, J = 2) transition ({lambda} = 1083 nm), we get a narrow, sub-Doppler structure, consisting of three, {approximately}1 photon recoil wide peaks, spaced {approximately}1 recoil apart. With increasing field, this three-peak structure develops into two velocity-selective resonance (VSR) peaks, each {approximately}2 recoils wide. For the 2{sup 3}S {yields} (3{sup 3}P, J = 2) transition ({lambda} 389 nm), VSR peaks aremore » predicted to appear at low field without the third, central peak, which only develops at higher field (B = 200 mG). Additional computations deal with polarization-gradient cooling. In general, we find that for one-dimensional cooling calculations, the Density Matrix method is more efficient than the Monte Carlo Wavefunction approach. Experiments are currently under way to test the results.« less

Increased vertical impact forces and altered running mechanics with softer midsole shoes.

PubMed

Baltich, Jennifer; Maurer, Christian; Nigg, Benno M

2015-01-01

To date it has been thought that shoe midsole hardness does not affect vertical impact peak forces during running. This conclusion is based partially on results from experimental data using homogeneous samples of participants that found no difference in vertical impact peaks when running in shoes with different midsole properties. However, it is currently unknown how apparent joint stiffness is affected by shoe midsole hardness. An increase in apparent joint stiffness could result in a harder landing, which should result in increased vertical impact peaks during running. The purpose of this study was to quantify the effect of shoe midsole hardness on apparent ankle and knee joint stiffness and the associated vertical ground reaction force for age and sex subgroups during heel-toe running. 93 runners (male and female) aged 16-75 years ran at 3.33 ± 0.15 m/s on a 30 m-long runway with soft, medium and hard midsole shoes. The vertical impact peak increased as the shoe midsole hardness decreased (mean(SE); soft: 1.70BW(0.03), medium: 1.64BW(0.03), hard: 1.54BW(0.03)). Similar results were found for the apparent ankle joint stiffness where apparent stiffness increased as the shoe midsole hardness decreased (soft: 2.08BWm/º x 100 (0.05), medium: 1.92 BWm/º x 100 (0.05), hard: 1.85 BWm/º x 100 (0.05)). Apparent knee joint stiffness increased for soft (1.06BWm/º x 100 (0.04)) midsole compared to the medium (0.95BWm/º x 100 (0.04)) and hard (0.96BWm/º x 100 (0.04)) midsoles for female participants. The results from this study confirm that shoe midsole hardness can have an effect on vertical impact force peaks and that this may be connected to the hardness of the landing. The results from this study may provide useful information regarding the development of cushioning guidelines for running shoes.

Increased Vertical Impact Forces and Altered Running Mechanics with Softer Midsole Shoes

PubMed Central

Baltich, Jennifer; Maurer, Christian; Nigg, Benno M.

2015-01-01

To date it has been thought that shoe midsole hardness does not affect vertical impact peak forces during running. This conclusion is based partially on results from experimental data using homogeneous samples of participants that found no difference in vertical impact peaks when running in shoes with different midsole properties. However, it is currently unknown how apparent joint stiffness is affected by shoe midsole hardness. An increase in apparent joint stiffness could result in a harder landing, which should result in increased vertical impact peaks during running. The purpose of this study was to quantify the effect of shoe midsole hardness on apparent ankle and knee joint stiffness and the associated vertical ground reaction force for age and sex subgroups during heel-toe running. 93 runners (male and female) aged 16-75 years ran at 3.33 ± 0.15 m/s on a 30 m-long runway with soft, medium and hard midsole shoes. The vertical impact peak increased as the shoe midsole hardness decreased (mean(SE); soft: 1.70BW(0.03), medium: 1.64BW(0.03), hard: 1.54BW(0.03)). Similar results were found for the apparent ankle joint stiffness where apparent stiffness increased as the shoe midsole hardness decreased (soft: 2.08BWm/º x 100 (0.05), medium: 1.92 BWm/º x 100 (0.05), hard: 1.85 BWm/º x 100 (0.05)). Apparent knee joint stiffness increased for soft (1.06BWm/º x 100 (0.04)) midsole compared to the medium (0.95BWm/º x 100 (0.04)) and hard (0.96BWm/º x 100 (0.04)) midsoles for female participants. The results from this study confirm that shoe midsole hardness can have an effect on vertical impact force peaks and that this may be connected to the hardness of the landing. The results from this study may provide useful information regarding the development of cushioning guidelines for running shoes. PMID:25897963

Photoelectric return-stroke velocity and peak current estimates in natural and triggered lightning

NASA Technical Reports Server (NTRS)

Mach, Douglas M.; Rust, W. David

1989-01-01

Two-dimensional photoelectric return stroke velocities from 130 strokes are presented, including 86 negative natural, 41 negative triggered, one positive triggered, and two positive natural return strokes. For strokes starting near the ground and exceeding 500 m in length, the average velocity is 1.3 + or - 0.3 X 10 to the 8th m/s for natural return strokes and 1.2 + or - 0.3 X 10 to the 8th m/s for triggered return strokes. For strokes with lengths less than 500 m, the average velocities are slightly higher. Using the transmission line model (TLM), the shortest segment one-dimensional return stroke velocity, and either the maximum or plateau electric field, it is shown that natural strokes have a peak current distribution that is lognormal with a median value of 16 kA (maximum E) or 12 kA (plateau E). Triggered lightning has a medium peak current value of 21 kA (maximum E) or 15 kA (plateau E). Correlations are found between TLM peak currents and velocities for triggered and natural subsequent return strokes, but not between TLM peak currents and natural first return stroke velocities.

Modulation of ventricular transient outward K+ current by acidosis and its effects on excitation-contraction coupling

PubMed Central

Saegusa, Noriko; Garg, Vivek

2013-01-01

The contribution of transient outward current (Ito) to changes in ventricular action potential (AP) repolarization induced by acidosis is unresolved, as is the indirect effect of these changes on calcium handling. To address this issue we measured intracellular pH (pHi), Ito, L-type calcium current (ICa,L), and calcium transients (CaTs) in rabbit ventricular myocytes. Intracellular acidosis [pHi 6.75 with extracellular pH (pHo) 7.4] reduced Ito by ∼50% in myocytes with both high (epicardial) and low (papillary muscle) Ito densities, with little effect on steady-state inactivation and activation. Of the two candidate α-subunits underlying Ito, human (h)Kv4.3 and hKv1.4, only hKv4.3 current was reduced by intracellular acidosis. Extracellular acidosis (pHo 6.5) shifted Ito inactivation toward less negative potentials but had negligible effect on peak current at +60 mV when initiated from −80 mV. The effects of low pHi-induced inhibition of Ito on AP repolarization were much greater in epicardial than papillary muscle myocytes and included slowing of phase 1, attenuation of the notch, and elevation of the plateau. Low pHi increased AP duration in both cell types, with the greatest lengthening occurring in epicardial myocytes. The changes in epicardial AP repolarization induced by intracellular acidosis reduced peak ICa,L, increased net calcium influx via ICa,L, and increased CaT amplitude. In summary, in contrast to low pHo, intracellular acidosis has a marked inhibitory effect on ventricular Ito, perhaps mediated by Kv4.3. By altering the trajectory of the AP repolarization, low pHi has a significant indirect effect on calcium handling, especially evident in epicardial cells. PMID:23585132

Theoretical and experimental investigation into high current hollow cathode arc attachment

NASA Astrophysics Data System (ADS)

Downey, Ryan T.

This research addresses several concerns of the mechanisms controlling performance and lifetime of high-current single-channel-hollow-cathodes, the central electrode and primary life-limiting component in Magnetoplasmadynamic thrusters. Specifically covered are the trends, and the theorized governing mechanisms, seen in the discharge efficiency and power, the size of the plasma attachment to the cathode (the active zone), cathode exit plume plasma density and energy, along with plasma property distributions of the internal plasma column (the IPC) of a single-channel-hollow-cathode. Both experiment and computational modeling were employed in the analysis of the cathodes. Employing Tantalum and Tungsten cathodes (of 2, 6 and 10 mm inner diameter), experiments were conducted to measure the temperature profile of operating cathodes, the width of the active zone, the discharge voltage, power, plasma arc resistance and efficiency, with mass flow rates of 50 to 300 sccm of Argon, and discharge currents of 15 to 50 Amps. Langmuir probing was used to obtain measurements for the electron temperature, plasma density and plasma potential at the cathode exit plane (down stream tip). A computational model was developed to predict the distribution of plasma inside the cathode, based upon experimentally determined boundary conditions. It was determined that the peak cathode temperature is a function of both interior cathode density and discharge current, though the location of the peak temperature is controlled gas density but not discharge current. The active zone width was found to be an increasing function of the discharge current, but a decreasing function of the mass flow rate. The width of the active zone was found to not be controlled by the magnitude of the peak cathode wall temperature. The discharge power consumed per unit of mass throughput is seen as a decreasing function of the mass flow rate, showing the increasing efficiency of the cathode. Finally, this new understanding of the mechanisms of the plasma attachment phenomena of a single-channel-hollow-cathode were extrapolated to the multi-channel-hollow-cathode environment, to explain performance characteristics of these devices seen in previous research.

Evolution of ionosphere-thermosphere (IT) parameters in the cusp region related to ion upflow events

NASA Astrophysics Data System (ADS)

Kervalishvili, Guram; Lühr, Hermann

2017-04-01

In this study we investigate the relationships of various IT parameters with the intensity of vertical ion flow. Our study area is the ionospheric cusp region in the northern hemisphere. The approach uses superposed epoch analysis (SEA) method, centered alternately on peaks of the three different variables: neutral density enhancement, vertical plasma flow, and electron temperature. Further parameters included are large-scale field-aligned currents (LSFACs) and thermospheric zonal wind velocity profiles over magnetic latitude (MLat), which are centered at the event time and location. The dependence on the interplanetary magnetic field (IMF) By component orientation and the local (Lloyd) season is of particular interest. Our investigations are based on CHAMP and DMSP (F13 and F15) satellite observations and the OMNI online database collected during the years 2002-2007. The three Lloyd seasons of 130 days each are defined as follows: local winter (1 January ± 65 days), combined equinoxes (1 April and 1 October ± 32 days), and local summer (1 July ± 65 days). A period of 130 days corresponds to the time needed by CHAMP to sample all local times. The SEA MLat profiles with respect to neutral density enhancement and vertical plasma flow peaks show no significant but only slight (decreasing towards local summer) seasonal variations for both IMF By orientations. The latitude profiles of median LSFACs show a clear dependence on the IMF By orientation. As expected, the maximum and minimum values of LSFAC amplitudes are increasing towards local summer for both IMF By signs. With respect to zero epoch latitude, FAC peaks appear equatorward (negative MLat) related to Region 1 (R1) and poleward (positive MLat) to Region 0 (R0) FACs. However, there is an imbalance between the amplitudes of LSFACs, depending on the current latitude. R1 currents are systematically stronger than R0 FACs. A somewhat different distribution of density enhancements and large-scale FACs emerges when the SEA is centered on electron temperature peaks. As expected, the background electron temperature increases towards summer and shows no dependence on the IMF By orientation. In contrast to the previous sorting the mass density enhancement shows a dependence on the IMF By sign and increases towards local summer in case of IMF By<0. As before LSFAC peak values are increasing towards local summer, but there is no clear latitudinal profile of upward and downward FACs. We think that intense precipitation of soft electrons (<100 eV) cause the electron temperature enhancement in the cusp region. But there is no direct dependence on the FAC intensity. But for neutral density enhancement and vertical plasma flow the combination of Joule heating and soft electron precipitation, causing electron temperature and conductivity enhancements, are required.

Calcium currents in a fast-twitch skeletal muscle of the rat.

PubMed

Donaldson, P L; Beam, K G

1983-10-01

Slow ionic currents were measured in the rat omohyoid muscle with the three-microelectrode voltage-clamp technique. Sodium and delayed rectifier potassium currents were blocked pharmacologically. Under these conditions, depolarizing test pulses elicited an early outward current, followed by a transient slow inward current, followed in turn by a late outward current. The early outward current appeared to be a residual delayed rectifier current. The slow inward current was identified as a calcium current on the basis that (a) its magnitude depended on extracellular calcium concentration, (b) it was blocked by the addition of the divalent cations cadmium or nickel, and reduced in magnitude by the addition of manganese or cobalt, and (c) barium was able to replace calcium as an inward current carrier. The threshold potential for inward calcium current was around -20 mV in 10mM extracellular calcium and about -35 mV in 2 mM calcium. Currents were net inward over part of their time course for potentials up to at least +30 mV. At temperatures of 20-26 degrees C, the peak inward current (at approximately 0 mV) was 139 +/- 14 microA/cm2 (mean +/- SD), increasing to 226 +/- 28 microA/cm2 at temperatures of 27-37 degrees C. The late outward current exhibited considerable fiber-to-fiber variability. In some fibers it was primarily a time-independent, nonlinear leakage current. In other fibers it was primarily a time-independent, nonlinear leakage current. In other fibers it appeared to be the sum of both leak and a slowly activated outward current. The rate of activation of inward calcium current was strongly temperature dependent. For example, in a representative fiber, the time-to-peak inward current for a +10-mV test pulse decreased from approximately 250 ms at 20 degrees C to 100 ms at 30 degrees C. At 37 degrees C, the time-to-peak current was typically approximately 25 ms. The earliest phase of activation was difficult to quantify because the ionic current was partially obscured by nonlinear charge movement. Nonetheless, at physiological temperatures, the rate of calcium channel activation in rat skeletal muscle is about five times faster than activation of calcium channels in frog muscle. This pathway may be an important source of calcium entry in mammalian muscle.

What Has Created California's School Facilities Predicament? EdFact.

ERIC Educational Resources Information Center

EdSource, Inc., Palo Alto, CA.

The growth in California's student population currently exceeds the peak years of the baby boom generation by more than one million students. This increase, combined with deferred maintenance, has created a strain on the state's educational facilities. An analysis of this predicament is presented in this bulletin. It describes why California needs…

Spontaneous electric current flow during deformation of non-piezoelectric marble samples: an indicator of stress state?

NASA Astrophysics Data System (ADS)

Cartwright-Taylor, A. L.; Sammonds, P. R.; Vallianatos, F.

2016-12-01

We recorded spontaneous electric current flow in non-piezoelectric Carrara marble samples during triaxial deformation. Mechanical data, ultrasonic velocities and acoustic emissions were acquired simultaneously with electric current to constrain the relationship between electric current flow, differential stress and damage. Under strain-controlled loading, spontaneous electric current signals (nA) were generated and sustained under all conditions tested. In dry samples, a detectable electric current arises only during dilatancy and is correlated with the damage induced by microcracking. Signal variations with confining pressure correspond to microcrack suppression, while variations with strain rate are associated with time-dependent differences in deformation mechanism across the brittle to semi-brittle transition. In the brittle regime, the signal exhibits a precursory change as damage localises and the stress drop accelerates towards failure. This change is particularly distinct at dynamic strain rates. Similar changes are seen in the semi-brittle regime although the signal is more oscillatory in nature. Current flow in dry samples is proportional to stress within 90% of peak stress. In fluid-saturated samples proportionality holds from 40% peak stress, with a significant increase in the rate of current production from 90% peak stress associated with fluid flow during dilatancy. This direct relationship demonstrates that electric current could be used as a proxy for stress, indicating when the rock is reaching the limit of its strength. The experimental power law relationship between electric current and strain rate, which mirrors the power-law creep equation, supports this observation. High-frequency fluctuations of electric current are not normally distributed - they exhibit `heavy-tails'. We model these distributions with q-Gaussian statistics and evolution of the q-parameter during deformation reveals a two-stage precursory anomaly prior to sample failure, consistent with the acoustic emissions b-value and stress intensity evolution as modelled from fracture mechanics. Our findings support the idea that electric currents in the crust can be generated purely from solid state fracture processes and that these currents may reflect the stress state within the damaged rock.

High yield Cu-Co CPP GMR multilayer sensors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Spallas, J.; Mao, M.; Law, B.

1997-01-15

We have fabricated and tested GMR magnetic flux sensors that operate in the CPP mode. This work is a continuation of the ultra-high density magnetic sensor research introduced at INTERMAG 96. We have made two significant modifications to the process sequence. First, contact to the sensor is made through a metal conduit deposited in situ with the multilayers. This deposition replaces electroplating. This configuration ensures a good electrical interface between the top of multilayer stack and the top contact, and a continuous, conductive current path to the sensor. The consequences of this modification are an increase in yield of operationalmore » devices to {ge}90% per wafer and a significant reduction of the device resistance to {le}560 milliohms and of the uniformity of the device resistance to {le}3%. Second, the as-deposited multilayer structure has been changed from [Cu 30 {angstrom}/Co 20 {angstrom}]{sub 18} (third peak) to [Cu 20.5 {angstrom}/Co 12 {angstrom}]{sub 30} (second peak) to increase the CPP and CIP responses. The sheet film second peak CIP GMR response is 18% and the sensitivity is 0.08 %/Oe. The sheet film third peak CIP GMR response is 8% and the sensitivity is 0. 05 %/Oe. The second peak CPP GMR response averaged over twenty devices on a four inch silicon substrate is 28% {+-} 6%. The response decreases radially from the substrate center. The average response at the center of the substrate is 33% {+-} 4%. The average second peak CPP sensitivity is 0.09 %/Oe {+-} 0.02 %/Oe. The best second peak CPP response from a single device is 39%. The sensitivity of that device is 0.13 %/Oe. The third peak CPP GMR response is approximately 14 %. The third peak CPP response sensitivity is 0.07 %/Oe. 6 refs., 3 figs.« less

Burden of Type 2 Diabetes in Mexico: Past, Current and Future Prevalence and Incidence Rates

PubMed Central

Meza, Rafael; Barrientos-Gutierrez, Tonatiuh; Rojas-Martinez, Rosalba; Reynoso-Noverón, Nancy; Palacio-Mejia, Lina Sofia; Lazcano-Ponce, Eduardo; Hernández-Ávila, Mauricio

2015-01-01

Introduction Mexico diabetes prevalence has increased dramatically in recent years. However, no national incidence estimates exist, hampering the assessment of diabetes trends and precluding the development of burden of disease analyses to inform public health policy decision-making. Here we provide evidence regarding current magnitude of diabetes in Mexico and its future trends. Methods We used data from the Mexico National Health and Nutrition Survey, and age-period-cohort models to estimate prevalence and incidence of self-reported diagnosed diabetes by age, sex, calendar-year (1960–2012), and birth-cohort (1920–1980). We project future rates under three alternative incidence scenarios using demographic projections of the Mexican population from 2010–2050 and a Multi-cohort Diabetes Markov Model. Results Adult (ages 20+) diagnosed diabetes prevalence in Mexico increased from 7% to 8.9% from 2006 to 2012. Diabetes prevalence increases with age, peaking around ages 65–68 to then decrease. Age-specific incidence follows similar patterns, but peaks around ages 57–59. We estimate that diagnosed diabetes incidence increased exponentially during 1960–2012, roughly doubling every 10 years. Projected rates under three age-specific incidence scenarios suggest diabetes prevalence among adults (ages 20+) may reach 13.7–22.5% by 2050, affecting 15–25 million individuals, with a lifetime risk of 1 in 3 to 1 in 2. Conclusions Diabetes prevalence in Mexico will continue to increase even if current incidence rates remain unchanged. Continued implementation of policies to reduce obesity rates, increase physical activity, and improve population diet, in tandem with diabetes surveillance and other risk control measures is paramount to substantially reduce the burden of diabetes in Mexico. PMID:26546108

Burden of type 2 diabetes in Mexico: past, current and future prevalence and incidence rates.

PubMed

Meza, Rafael; Barrientos-Gutierrez, Tonatiuh; Rojas-Martinez, Rosalba; Reynoso-Noverón, Nancy; Palacio-Mejia, Lina Sofia; Lazcano-Ponce, Eduardo; Hernández-Ávila, Mauricio

2015-12-01

Mexico diabetes prevalence has increased dramatically in recent years. However, no national incidence estimates exist, hampering the assessment of diabetes trends and precluding the development of burden of disease analyses to inform public health policy decision-making. Here we provide evidence regarding current magnitude of diabetes in Mexico and its future trends. We used data from the Mexico National Health and Nutrition Survey, and age-period-cohort models to estimate prevalence and incidence of self-reported diagnosed diabetes by age, sex, calendar-year (1960-2012), and birth-cohort (1920-1980). We project future rates under three alternative incidence scenarios using demographic projections of the Mexican population from 2010-2050 and a Multi-cohort Diabetes Markov Model. Adult (ages 20+) diagnosed diabetes prevalence in Mexico increased from 7% to 8.9% from 2006 to 2012. Diabetes prevalence increases with age, peaking around ages 65-68 to then decrease. Age-specific incidence follows similar patterns, but peaks around ages 57-59. We estimate that diagnosed diabetes incidence increased exponentially during 1960-2012, roughly doubling every 10 years. Projected rates under three age-specific incidence scenarios suggest diabetes prevalence among adults (ages 20+) may reach 13.7-22.5% by 2050, affecting 15-25 million individuals, with a lifetime risk of 1 in 3 to 1 in 2. Diabetes prevalence in Mexico will continue to increase even if current incidence rates remain unchanged. Continued implementation of policies to reduce obesity rates, increase physical activity, and improve population diet, in tandem with diabetes surveillance and other risk control measures is paramount to substantially reduce the burden of diabetes in Mexico. Copyright © 2015 Elsevier Inc. All rights reserved.

Investigating the origin of efficiency droop by profiling the temperature across the multi-quantum well of an operating light-emitting diode

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jung, Euihan; Hwang, Gwangseok; Chung, Jaehun

2015-01-26

Performance degradation resulting from efficiency droop during high-power operation is a critical problem in the development of high-efficiency light-emitting diodes (LEDs). In order to resolve the efficiency droop and increase the external quantum efficiency of LEDs, the droop's origin should be identified first. To experimentally investigate the cause of efficiency droop, we used null-point scanning thermal microscopy to quantitatively profile the temperature distribution on the cross section of the epi-layers of an operating GaN-based vertical LED with nanoscale spatial resolution at four different current densities. The movement of temperature peak towards the p-GaN side as the current density increases suggestsmore » that more heat is generated by leakage current than by Auger recombination. We therefore suspect that at higher current densities, current leakage becomes the dominant cause of the droop problem.« less

Correlated observations of three triggered lightning flashes

NASA Technical Reports Server (NTRS)

Idone, V. P.; Orville, R. E.; Hubert, P.; Barret, L.; Eybert-Berard, A.

1984-01-01

Three triggered lightning flashes, initiated during the Thunderstorm Research International Program (1981) at Langmuir Laboratory, New Mexico, are examined on the basis of three-dimensional return stroke propagation speeds and peak currents. Nonlinear relationships result between return stroke propagation speed and stroke peak current for 56 strokes, and between return stroke propagation speed and dart leader propagation speed for 32 strokes. Calculated linear correlation coefficients include dart leader propagation speed and ensuing return stroke peak current (32 strokes; r = 0.84); and stroke peak current and interstroke interval (69 strokes; r = 0.57). Earlier natural lightning data do not concur with the weak positive correlation between dart leader propagation speed and interstroke interval. Therefore, application of triggered lightning results to natural lightning phenomena must be made with certain caveats. Mean values are included for the three-dimensional return stroke propagation speed and for the three-dimensional dart leader propagation speed.

[Electrochemically reductive dechlorination of chloroform in aqueous medium by codeposited palladium-nickel glassy carbon as cathode].

PubMed

Sun, Zhi-Rong; Li, Bao-Hua; Hu, Xiang; Shi, Min; Peng, Yong-Zhen

2008-05-01

The electrochemical deposition behaviors of Pd-Ni bimetal on glassy carbon (GC) electrode were studied by means of cyclic voltammetry (CV) based on orthogonal experiments. CV results reveal that Pd-Ni bimetal shows larger hydrogen adsorption peak than that of single Pd or Ni. The mixture of Ni2+ and Pd2+ can get hydrogen adsorption peak of -24.83 mA at - 500 mV (vs Hg/Hg2SO4). Scanning Electron Microscope (SEM) images reveal that nickel addition changes the distributing configuration of Pd microparticles on GC. And the appearance of Pd-Ni bimetal microparticles is distinctly different from that of single Pd and single Ni microparticles. Diameter of Pd-Ni microparticle is bigger than that of Pd microparticle and smaller than that of Ni microparticle. Effects of dechlorination current and time on removal efficiency of chloroform were also studied. The removal efficiency of chloroform increases at higher dechlorination current and longer dechlorination time. It reaches 42.53% when the dechlorination current and time are 0.5 mA and 180 min respectively on Pd-Ni/GC electrode prepared at optimum conditions. It can be envisioned that the removal efficiency of chloroform would increase further at longer dechlorination time.

Selection of patients for heart transplantation in the current era of heart failure therapy.

PubMed

Butler, Javed; Khadim, Ghazanfar; Paul, Kimberly M; Davis, Stacy F; Kronenberg, Marvin W; Chomsky, Don B; Pierson, Richard N; Wilson, John R

2004-03-03

We sought to assess the relationship between survival, peak exercise oxygen consumption (VO(2)), and heart failure survival score (HFSS) in the current era of heart failure (HF) therapy. Based on predicted survival, HF patients with peak VO(2) <14 ml/min/kg or medium- to high-risk HFSS are currently considered eligible for heart transplantation. However, these criteria were developed before the widespread use of beta-blockers, spironolactone, and defibrillators-interventions known to improve the survival of HF patients. Peak VO(2) and HFSS were assessed in 320 patients followed from 1994 to 1997 (past era) and in 187 patients followed from 1999 to 2001 (current era). Outcomes were compared between these two groups of patients and those who underwent heart transplantation from 1993 to 2000. Survival in the past era was 78% at one year and 67% at two years, as compared with 88% and 79%, respectively, in the current era (both p < 0.01). One-year event-free survival (without urgent transplantation or left ventricular assist device) was improved in the current era, regardless of initial peak VO(2): 64% vs. 48% for peak VO(2) <10 ml/min/kg (p = 0.09), 81% vs. 70% for 10 to 14 ml/min/kg (p = 0.05), and 93% vs. 82% for >14 ml/min/kg (p = 0.04). Of the patients with peak VO(2) of 10 to 14 ml/min/kg, 55% had low-risk HFSS and exhibited 88% one-year event-free survival. One-year survival after transplantation was 88%, which is similar to the 85% rate reported by the United Network for Organ Sharing for 1999 to 2000. Survival for HF patients in the current era has improved significantly, necessitating re-evaluation of the listing criteria for heart transplantation.

Do diurnal patterns of branch carbon uptake and transpiration recover after heat waves? Results from a Mediterranean-type ecosystem experiencing seasonal and exceptional drought

NASA Astrophysics Data System (ADS)

Pivovaroff, A. L.; Pesqueira, A.; Sun, W.; Seibt, U.

2016-12-01

Mediterranean-type ecosystems are biodiversity hotspots, but increasing temperature and changes in precipitation will have significant impacts on vegetation, as evidenced by the current die-back of many woody species in southern California, USA, due to exceptional drought conditions. We installed flow-through chambers on four native woody plant species at Stunt Ranch, a University of California Natural Reserve System site, in order to continuously monitor fluxes of carbon and water at the branch-scale from the growing season through the annual seasonal drought period. Study species included Heteromeles arbutifolia, Malosma laurina, Salvia leucophylla, and Quercus agrifolia. Here we present the results of diurnal flux patterns before, during, and after two extreme heat waves events, when daily maximum temperatures doubled. Under typical summer conditions, which include hot, sunny days, study species exhibited two peaks in carbon assimilation during a diurnal cycle: a peak in the morning and a smaller, secondary peak in the afternoon, separated by a midday depression. During heat wave events, which generally lasted 3 days, species exhibited a small morning peak and no afternoon peak at all. All study species returned to their pre-heat wave diurnal flux patterns, which included the second afternoon peak, when weather conditions returned to normal. Since soil moisture was not affected by the short-term heat wave events, we conclude that the pronounced changes in diurnal patterns, including disappearance of the secondary afternoon peak, are the result of stomatal regulation in response to atmospheric water demand rather than root responses to soil moisture deficits. Our results demonstrate that carbon uptake of native species may be impacted under ongoing climate change when increased temperatures and drought conditions may be sustained.

Effectiveness of Neuromuscular Training Based on the Neuromuscular Risk Profile.

PubMed

Hewett, Timothy E; Ford, Kevin R; Xu, Yingying Y; Khoury, Jane; Myer, Gregory D

2017-07-01

The effects of targeted neuromuscular training (TNMT) on movement biomechanics associated with the risk of anterior cruciate ligament (ACL) injuries are currently unknown. Purpose/Hypotheses: To determine the effectiveness of TNMT specifically designed to increase trunk control and hip strength. The hypotheses were that (1) TNMT would decrease biomechanical and neuromuscular factors related to an increased ACL injury risk and (2) TNMT would decrease these biomechanical and neuromuscular factors to a greater extent in athletes identified as being at a high risk for future ACL injuries. Controlled laboratory study. Female athletes who participated in jumping, cutting, and pivoting sports underwent 3-dimensional biomechanical testing before the season and after completing TNMT. During testing, athletes performed 3 different types of tasks: (1) drop vertical jump, (2) single-leg drop, and (3) single-leg cross drop. Analysis of covariance was used to examine the treatment effects of TNMT designed to enhance core and hip strength on biomechanical and neuromuscular characteristics. Differences were also evaluated by risk profile. Differences were considered statistically significant at P < .05. TNMT significantly increased hip external rotation moments and moment impulses, increased peak trunk flexion, and decreased peak trunk extension. Athletes with a high risk before the intervention (risk profile III) had a more significant treatment effect of TNMT than low-risk groups (risk profiles I and II). TNMT significantly improved proximal biomechanics, including increased hip external rotation moments and moment impulses, increased peak trunk flexion, and decreased peak trunk extension. TNMT that focuses exclusively on proximal leg and trunk risk factors is not, however, adequate to induce significant changes in frontal-plane knee loading. Biomechanical changes varied across the risk profile groups, with higher risk groups exhibiting greater improvements in their biomechanics.

Trafficking Defect and Proteasomal Degradation Contribute to the Phenotype of a Novel KCNH2 Long QT Syndrome Mutation

PubMed Central

Mihic, Anton; Chauhan, Vijay S.; Gao, Xiaodong; Oudit, Gavin Y.; Tsushima, Robert G.

2011-01-01

The Kv11.1 (hERG) K+ channel plays a fundamental role in cardiac repolarization. Missense mutations in KCNH2, the gene encoding Kv11.1, cause long QT syndrome (LQTS) and frequently cause channel trafficking-deficiencies. This study characterized the properties of a novel KCNH2 mutation discovered in a LQT2 patient resuscitated from a ventricular fibrillation arrest. Proband genotyping was performed by SSCP and DNA sequencing. The electrophysiological and biochemical properties of the mutant channel were investigated after expression in HEK293 cells. The proband manifested a QTc of 554 ms prior to electrolyte normalization. Mutation analysis revealed an autosomal dominant frameshift mutation at proline 1086 (P1086fs+32X; 3256InsG). Co-immunoprecipitation demonstrated that wild-type Kv11.1 and mutant channels coassemble. Western blot showed that the mutation did not produce mature complex-glycosylated Kv11.1 channels and coexpression resulted in reduced channel maturation. Electrophysiological recordings revealed mutant channel peak currents to be similar to untransfected cells. Co-expression of channels in a 1∶1 ratio demonstrated dominant negative suppression of peak Kv11.1 currents. Immunocytochemistry confirmed that mutant channels were not present at the plasma membrane. Mutant channel trafficking rescue was attempted by incubation at reduced temperature or with the pharmacological agents E-4031. These treatments did not significantly increase peak mutant currents or induce the formation of mature complex-glycosylated channels. The proteasomal inhibitor lactacystin increased the protein levels of the mutant channels demonstrating proteasomal degradation, but failed to induce mutant Kv11.1 protein trafficking. Our study demonstrates a novel dominant-negative Kv11.1 mutation, which results in degraded non-functional channels leading to a LQT2 phenotype. PMID:21483829

Quantifying the economic value and quality of life impact of earlier influenza vaccination.

PubMed

Lee, Bruce Y; Bartsch, Sarah M; Brown, Shawn T; Cooley, Philip; Wheaton, William D; Zimmerman, Richard K

2015-03-01

Influenza vaccination is administered throughout the influenza disease season, even as late as March. Given such timing, what is the value of vaccinating the population earlier than currently being practiced? We used real data on when individuals were vaccinated in Allegheny County, Pennsylvania, and the following 2 models to determine the value of vaccinating individuals earlier (by the end of September, October, and November): Framework for Reconstructing Epidemiological Dynamics (FRED), an agent-based model (ABM), and FluEcon, our influenza economic model that translates cases from the ABM to outcomes and costs [health care and lost productivity costs and quality-adjusted life-years (QALYs)]. We varied the reproductive number (R0) from 1.2 to 1.6. Applying the current timing of vaccinations averted 223,761 influenza cases, $16.3 million in direct health care costs, $50.0 million in productivity losses, and 804 in QALYs, compared with no vaccination (February peak, R0 1.2). When the population does not have preexisting immunity and the influenza season peaks in February (R0 1.2-1.6), moving individuals who currently received the vaccine after September to the end of September could avert an additional 9634-17,794 influenza cases, $0.6-$1.4 million in direct costs, $2.1-$4.0 million in productivity losses, and 35-64 QALYs. Moving the vaccination of just children to September (R0 1.2-1.6) averted 11,366-1660 influenza cases, $0.6-$0.03 million in direct costs, $2.3-$0.2 million in productivity losses, and 42-8 QALYs. Moving the season peak to December increased these benefits, whereas increasing preexisting immunity reduced these benefits. Even though many people are vaccinated well after September/October, they likely are still vaccinated early enough to provide substantial cost-savings.

Influence of Substrate, Additives, and Pulse Parameters on Electrodeposition of Gold Nanoparticles from Potassium Dicyanoaurate

NASA Astrophysics Data System (ADS)

Vahdatkhah, Parisa; Sadrnezhaad, Sayed Khatiboleslam

2015-12-01

Gold nanoparticles (AuNPs) of less than 50 nm diameter were electrodeposited from cyanide solution by pulsating electric current on modified copper and indium tin oxide (ITO) films coated on glass. Morphology, size, and composition of the deposited AuNPs were studied by X-ray photoelectron spectroscopy, atomic force microscopy, and field emission scanning electron microscopy. Effects of peak current density, pulse frequency, potassium iodide and cysteine on grain size, and morphology of the AuNPs were determined. Experiments showed that cathode current efficiency increases with the pulse frequency and the iodide ion. Size of the AuNPs increased with the current density. The number of nucleation sites was larger on ITO than on Cu layer; while the average diameter of the crystallites on ITO was smaller than on Cu layer.

Carbon nanotube modified glassy carbon electrode for electrochemical oxidation of alkylphenol ethoxylate.

PubMed

Patiño, Yolanda; Díaz, Eva; Lobo-Castañón, María Jesús; Ordóñez, Salvador

2018-06-01

Electrochemical oxidation of an emerging pollutant, 2-(4-methylphenoxy)ethanol (MPET), from water has been studied by cyclic voltammetry (CV). Multiwall carbon nanotubes glassy carbon electrodes (MWCNT-GCE) were used as working electrode due to their extraordinary properties. The oxidation process is irreversible, since no reduction peaks were observed in the reverse scan. The electrocatalytic effect of MWCNT was confirmed as the oxidation peak intensity increases in comparison to bare-GCE. The effect of functional groups on MWCNT was also studied by MWCNT functionalized with NH 2 (MWCNT-NH 2 ) and COOH (MWCNT-COOH) groups. The oxidation peak current decreases in the following order: MWCNT > MWCNT-NH 2 > MWCNT-COOH. Taking into account the normalized peak current, MWCNT-NH 2 exhibits the best results due to its strong interaction with MPET. Under optimal conditions (pH = 5.0 and volume of MWCNT = 10 μL), degradation was studied for MWCNT-GCE and MWCNT-NH 2 -GCE. A complete MPET removal was observed using MWCNT-GCE after four CV cycles, for a volume/area (V/A) ratio equal to 19. In the case of MWCNT-NH 2 -GCE, the maximum MPET removal was close to 90% for V/A = 37, higher than that obtained for MWCNT-GCE at the same conditions (≈80%). In both cases, no organic by-products were detected.

Evaluation of Drying Process on the Composition of Black Pepper Ethanolic Extract by High Performance Liquid Chromatography With Diode Array Detector

PubMed Central

Namjoyan, Foroogh; Hejazi, Hoda; Ramezani, Zahra

2012-01-01

Background Black pepper (Piper nigrum) is one of the well-known spices extensively used worldwide especially in India, and Southeast Asia. The presence of alkaloids in the pepper, namely, piperine and its three stereoisomers, isopiperine, chavicine and isochavicine are well noticed. Objectives The current study evaluated the effect of lyophilization and oven drying on the stability and decomposition of constituents of black pepper ethanolic extract. Materials and Methods In the current study ethanolic extract of black pepper obtained by maceration method was dried using two methods. The effect of freeze and oven drying on the chemical composition of the extract especially piperine and its three isomers were evaluated by HPLC analysis of the ethanolic extract before and after drying processes using diode array detector. The UV Vis spectra of the peaks at piperine retention time before and after each drying methods indicated maximum absorbance at 341.2 nm corresponding to standard piperine. Results The results indicated a decrease in intensity of the chromatogram peaks at approximately all retention times after freeze drying, indicating a few percent loss of piperine and its isomers upon lyophilization. Two impurity peaks were completely removed from the extract. Conclusions In oven dried samples two of the piperine stereoisomers were completely removed from the extract and the intensity of piperine peak was increased. PMID:24624176

Tunable negative differential resistance in planar graphene superlattice resonant tunneling diode

NASA Astrophysics Data System (ADS)

Sattari-Esfahlan, S. M.; Fouladi-Oskuei, J.; Shojaei, S.

2017-04-01

Here, we study the negative differential resistance (NDR) of Dirac electrons in biased planar graphene superlattice (PGSL) and investigate the transport characteristics by adopted transfer matrix method within Landauer-Buttiker formalism. Our model device is based on one-dimensional Kronig-Penney type electrostatic potential in monolayer graphene deposited on a substrate, where the bias voltage is applied by two electrodes in the left and right. At Low bias voltages, we found that NDR appears due to breaking of minibands to Wannier-Stark ladders (WSLs). At the critical bias voltage, delocalization appeared by WS states leads to tunneling peak current in current-voltage (I-V) characteristics. With increasing bias voltage, crossing of rungs from various WSL results in multi-peak NDR. The results demonstrate that the structure parameters like barrier/well thickness and barrier height have remarkable effect on I-V characteristics of PGSL. In addition, Dirac gap enhances peak to valley (PVR) value due to suppressing Klein tunneling. Our results show that the tunable PVR in PGSL resonant tunneling diode can be achievable by structure parameters engineering. NDR at ultra-low bias voltages, such as 100 mV, with giant PVR of 20 is obtained. In our device, the multiple same NDR peaks with ultra-low bias voltage provide promising prospect for multi-valued memories and the low power nanoelectronic tunneling devices.

Structural and optical properties of semi-polar (11-22) InGaN/GaN green light-emitting diode structure

NASA Astrophysics Data System (ADS)

Zhao, Guijuan; Wang, Lianshan; Li, Huijie; Meng, Yulin; Li, Fangzheng; Yang, Shaoyan; Wang, Zhanguo

2018-01-01

Semi-polar (11-22) InGaN multiple quantum well (MQW) green light-emitting diode (LED) structures have been realized by metal-organic chemical vapor deposition on an m-plane sapphire substrate. By introducing double GaN buffer layers, we improve the crystal quality of semi-polar (11-22) GaN significantly. The vertical alignment of the diffraction peaks in the (11-22) X-ray reciprocal space mapping indicates the fully strained MQW on the GaN layer. The photoluminescence spectra of the LED structure show stronger emission intensity along the [1-100] InGaN/GaN direction. The electroluminescence emission of the LED structure is very broad with peaks around 550 nm and 510 nm at the 100 mA current injection for samples A and B, respectively, and exhibits a significant blue-shift with increasing drive current.

Experimental measurement of stationary SS 304, SS 316L and 8630 GTA weld pool surface temperatures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kraus, H.G.

1989-07-01

The optical spectral radiometric/laser reflectance experimental method, previously developed by the author, was extended to obtain high-resolution surface temperature maps of stationary GTA molten weld pools using thick-plate SS 304, SS316L, and 8630 steel. Increasing the welding current from 50 to 200 A resulted in peak pool surface temperatures from 1050{sup 0} to 2400{sup 0}C for the SS 304. At a constant welding current of 150 A, the SS 304 and various heats of SS 316L and 8630 resulted in peak weld pool temperatures from 2300{sup 0} to 2700{sup 0}C. Temperature contour plots of all the welds made are given.more » Surface temperature maps are classified into types that are believed to be indicative of the convective circulation patterns present in the weld pools.« less

Development of a Novel Electrochemical Sensor for Determination of Matrine in Sophora flavescens.

PubMed

Zhang, Junping; Wang, Yanchun; Zheng, Wei

2017-04-01

A simple and sensitive electrochemical sensor fabricated with graphene nanosheets (GNs) and a hydroxyapatite (HA) nanocomposite-modified glassy carbon electrode (GCE) was developed for the determination of matrine (MT). The as-prepared electrode (GNs/HA/GCE) was verified to outperform bare a GCE and GNs-modified electrode with increased oxidation peak currents and the decreased over-potential in the redox process of MT, indicating the great enhancement of electrocatalytic activity toward the oxidation of MT by the composite of GNs and HA. Under the optimized conditions, the oxidation peak currents were related linearly with the concentration of MT, ranging from 2 μM to 3 mM, and the detection limit (S/N = 3) was 1.2 μM. In addition, the proposed electrochemical sensor can be successfully applied in the quantitative determination of MT in Sophora flavescens extract.

An experimental system for controlled exposure of biological samples to electrostatic discharges.

PubMed

Marjanovič, Igor; Kotnik, Tadej

2013-12-01

Electrostatic discharges occur naturally as lightning strokes, and artificially in light sources and in materials processing. When an electrostatic discharge interacts with living matter, the basic physical effects can be accompanied by biophysical and biochemical phenomena, including cell excitation, electroporation, and electrofusion. To study these phenomena, we developed an experimental system that provides easy sample insertion and removal, protection from airborne particles, observability during the experiment, accurate discharge origin positioning, discharge delivery into the sample either through an electric arc with adjustable air gap width or through direct contact, and reliable electrical insulation where required. We tested the system by assessing irreversible electroporation of Escherichia coli bacteria (15 mm discharge arc, 100 A peak current, 0.1 μs zero-to-peak time, 0.2 μs peak-to-halving time), and gene electrotransfer into CHO cells (7 mm discharge arc, 14 A peak current, 0.5 μs zero-to-peak time, 1.0 μs peak-to-halving time). Exposures to natural lightning stroke can also be studied with this system, as due to radial current dissipation, the conditions achieved by a stroke at a particular distance from its entry are also achieved by an artificial discharge with electric current downscaled in magnitude, but similar in time course, correspondingly closer to its entry. © 2013.

First-principles study on electron transport properties of carbon-silicon mixed chains

NASA Astrophysics Data System (ADS)

Hu, Wei; Zhou, Qinghua; Liang, Yan; Liu, Wenhua; Wang, Tao; Wan, Haiqing

2018-03-01

In this paper, the transport properties of carbon-silicon mixed chains are studied by using the first-principles. We studied five atomic chain models. In these studies, we found that the equilibrium conductances of atomic chains appear to oscillate, the maximum conductance and the minimum conductance are more than twice the difference. Their I-V curves are linear and show the behavior of metal resistance, M5 system and M2 system current ratio is the largest in 0.9 V, which is 3.3, showing a good molecular switch behavior. In the case of bias, while the bias voltage increases, the transmission peaks move from the Fermi level. The resonance transmission peak height is reduced near the Fermi level. In the higher energy range, a large resonance transmission peak reappears, there is still no energy cut-off range.

Surface gas pollutants in Lhasa, a highland city of Tibet: current levels and pollution implications

NASA Astrophysics Data System (ADS)

Ran, L.; Lin, W. L.; Deji, Y. Z.; La, B.; Tsering, P. M.; Xu, X. B.; Wang, W.

2014-05-01

Through several years of development, the city of Lhasa has become one of the most populated and urbanized areas on the highest plateau in the world. In the process of urbanization, current and potential air quality issues have been gradually concerned. To investigate the current status of air pollution in Lhasa, various gas pollutants including NOx, CO, SO2 and O3 were continuously measured from June 2012 to May 2013 at an urban site (29.40° N, 91.08° E, 3650 m a.s.l.). The seasonal variations of primary gas pollutants exhibited a peak from November to January with a large variability. High concentrations of primary trace gases almost exclusively occurred under low wind speed and showed no distinct dependence on wind direction, implying local urban emissions to be predominant. A comparison of NO2, CO and SO2 concentrations in summer between 1998 and 2012 indicated a significant increase in emissions of these gas pollutants and a change in their intercorrelations, as a result of a substantial growth in the demand of energy consumption using fossil fuels instead of previously widely used biofuels. The pronounced diurnal double peaks of primary trace gases in all seasons suggested automobile exhaust to be a major emission source in Lhasa. The secondary gas pollutant O3 displayed an average diurnal cycle of a shallow flat peak for about 4-5 h in the afternoon and a minimum in the early morning. Nighttime O3 was sometimes completely consumed by the high level of NOx. Seasonally, the variations of O3 concentrations displayed a low valley in winter and a peak in spring. In autumn and winter, transport largely contributed to the observed O3 concentrations, given its dependence on wind speed and wind direction, while in spring and summer photochemistry played an important role. A more efficient buildup of O3 concentrations in the morning and a higher peak in the afternoon was found in summer 2012 than in 1998. An enhancement in O3 concentrations would be expected in the future and more attention should be given to O3 photochemistry in response to increasing precursor emissions in this area.

Surface gas pollutants in Lhasa, a highland city of Tibet - current levels and pollution implications

NASA Astrophysics Data System (ADS)

Ran, L.; Lin, W. L.; Deji, Y. Z.; La, B.; Tsering, P. M.; Xu, X. B.; Wang, W.

2014-10-01

Through several years of development, the city of Lhasa has become one of the most populated and urbanized areas on the highest plateau in the world. In the process of urbanization, current and potential air quality issues have been gradually concerned. To investigate the current status of air pollution in Lhasa, various gas pollutants including NOx, CO, SO2, and O3, were continuously measured from June 2012 to May 2013 at an urban site (29.40° N, 91.08° E, 3650 m a.s.l.). The seasonal variations of primary gas pollutants exhibited a peak from November to January with a large variability. High mixing ratios of primary trace gases almost exclusively occurred under low wind speed and showed no distinct dependence on wind direction, implying local urban emissions to be predominant. A comparison of NO2, CO, and SO2 mixing ratios in summer between 1998 and 2012 indicated a significant increase in emissions of these gas pollutants and a change in their intercorrelations, as a result of a substantial growth in the demand of energy consumption using fossil fuels instead of previously widely used biomass. The pronounced diurnal double peaks of primary trace gases in all seasons suggested automobile exhaust to be a major emission source in Lhasa. The secondary gas pollutant O3 displayed an average diurnal cycle of a shallow flat peak for about 4-5 h in the afternoon and a minimum in the early morning. Nighttime O3 was sometimes completely consumed by the high level of NOx. Seasonally, the variations of O3 mixing ratios displayed a low valley in winter and a peak in spring. In autumn and winter, transport largely contributed to the observed O3 mixing ratios, given its dependence on wind speed and wind direction, while in spring and summer photochemistry played an important role. A more efficient buildup of O3 mixing ratios in the morning and a higher peak in the afternoon was found in summer 2012 than in 1998. An enhancement in O3 mixing ratios would be expected in the future and more attention should be given to O3 photochemistry in response to increasing precursor emissions in this area.

METHOD OF PEAK CURRENT MEASUREMENT

DOEpatents

Baker, G.E.

1959-01-20

The measurement and recording of peak electrical currents are described, and a method for utilizing the magnetic field of the current to erase a portion of an alternating constant frequency and amplitude signal from a magnetic mediums such as a magnetic tapes is presented. A portion of the flux from the current carrying conductor is concentrated into a magnetic path of defined area on the tape. After the current has been recorded, the tape is played back. The amplitude of the signal from the portion of the tape immediately adjacent the defined flux area and the amplitude of the signal from the portion of the tape within the area are compared with the amplitude of the signal from an unerased portion of the tape to determine the percentage of signal erasure, and thereby obtain the peak value of currents flowing in the conductor.

Magnetic field cycling effect on the non-linear current-voltage characteristics and magnetic field induced negative differential resistance in α-Fe1.64Ga0.36O3 oxide

NASA Astrophysics Data System (ADS)

Bhowmik, R. N.; Vijayasri, G.

2015-06-01

We have studied current-voltage (I-V) characteristics of α-Fe1.64Ga0.36O3, a typical canted ferromagnetic semiconductor. The sample showed a transformation of the I-V curves from linear to non-linear character with the increase of bias voltage. The I-V curves showed irreversible features with hysteresis loop and bi-stable electronic states for up and down modes of voltage sweep. We report positive magnetoresistance and magnetic field induced negative differential resistance as the first time observed phenomena in metal doped hematite system. The magnitudes of critical voltage at which I-V curve showed peak and corresponding peak current are affected by magnetic field cycling. The shift of the peak voltage with magnetic field showed a step-wise jump between two discrete voltage levels with least gap (ΔVP) 0.345(± 0.001) V. The magnetic spin dependent electronic charge transport in this new class of magnetic semiconductor opens a wide scope for tuning large electroresistance (˜500-700%), magnetoresistance (70-135 %) and charge-spin dependent conductivity under suitable control of electric and magnetic fields. The electric and magnetic field controlled charge-spin transport is interesting for applications of the magnetic materials in spintronics, e.g., magnetic sensor, memory devices and digital switching.

Thermal energy storage for power generation applications

NASA Astrophysics Data System (ADS)

Drost, M. K.; Antoniak, Zen I.; Brown, D. R.

1990-03-01

Studies strongly indicate that the United States will face widespread electrical power constraints in the 1990s. In many cases, the demand for increased power will occur during peak and intermediate demand periods. While natural gas is currently plentiful and economically attractive for meeting peak and intermediate loads, the development of a coal-fired peaking option would give utilities insurance against unexpected supply shortages or cost increases. This paper discusses a conceptual evaluation of using thermal energy storage (TES) to improve the economics of coal-fired peak and intermediate load power generation. The use of TES can substantially improve the economic attractiveness of meeting peak and intermediate loads with coal-fired power generation. In this case, conventional pulverized coal combustion equipment is continuously operated to heat molten nitrate salt, which is then stored. During peak demand periods, hot salt is withdrawn from storage and used to generate steam for a Rankine steam power cycle. This allows the coal-fired salt heater to be approximately one-third the size of a coal-fired boiler in a conventional cycling plant. The general impact is to decouple the generation of thermal energy from its conversion to electricity. The present study compares a conventional cycling pulverized coal-fired power plant to a pulverized coal-fired plant using nitrate salt TES. The study demonstrates that a coal-fired salt heater is technically feasible and should be less expensive than a similar coal-fired boiler. The results show the use of nitrate salt TES reduced the levelized cost of power by between 5 and 24 percent, depending on the operating schedule.

Peak Running Intensity of International Rugby: Implications for Training Prescription.

PubMed

Delaney, Jace A; Thornton, Heidi R; Pryor, John F; Stewart, Andrew M; Dascombe, Ben J; Duthie, Grant M

2017-09-01

To quantify the duration and position-specific peak running intensities of international rugby union for the prescription and monitoring of specific training methodologies. Global positioning systems (GPS) were used to assess the activity profile of 67 elite-level rugby union players from 2 nations across 33 international matches. A moving-average approach was used to identify the peak relative distance (m/min), average acceleration/deceleration (AveAcc; m/s 2 ), and average metabolic power (P met ) for a range of durations (1-10 min). Differences between positions and durations were described using a magnitude-based network. Peak running intensity increased as the length of the moving average decreased. There were likely small to moderate increases in relative distance and AveAcc for outside backs, halfbacks, and loose forwards compared with the tight 5 group across all moving-average durations (effect size [ES] = 0.27-1.00). P met demands were at least likely greater for outside backs and halfbacks than for the tight 5 (ES = 0.86-0.99). Halfbacks demonstrated the greatest relative distance and P met outputs but were similar to outside backs and loose forwards in AveAcc demands. The current study has presented a framework to describe the peak running intensities achieved during international rugby competition by position, which are considerably higher than previously reported whole-period averages. These data provide further knowledge of the peak activity profiles of international rugby competition, and this information can be used to assist coaches and practitioners in adequately preparing athletes for the most demanding periods of play.

Deep-levels in gallium arsenide for device applications

NASA Astrophysics Data System (ADS)

McManis, Joseph Edward

Defects in semiconductors have been studied for over 40 years as a diagnostic of the quality of crystal growth. In this thesis, we investigate GaAs deep-levels specifically intended for devices. This thesis summarizes our efforts to characterize the near-infrared photoluminescence from deep-levels, study optical transitions via absorption, and fabricate and characterize deep-level light-emitting diodes (LEDs). This thesis also describes the first tunnel diodes which explicitly make use of GaAs deep-levels. Photoluminescence measurements of GaAs deep-levels showed a broad peak around a wavelength extending from 1.0--1.7 mum, which includes important wavelengths for fiber-optic communications (1.3--1.55 mum). Transmission measurements show the new result that very little of the radiative emission is self-absorbed. We measured the deep-level photoluminescence at several temperatures. We are also the first to report the internal quantum efficiency associated with the deep-level transitions. We have fabricated LEDs that, utilize the optical transitions of GaAs deep-levels. The electroluminescence spectra showed a broad peak from 1.0--1.7 mum at low currents, but the spectrum exhibited a blue-shift as the current was increased. To improve device performance, we designed an AlGaAs layer into the structure of the LEDs. The AlGaAs barrier layer acts as a resistive barrier so that the holes in the p-GaAs layer are swept away from underneath the gold p-contact. The AlGaAs layer also reduces the blue-shift by acting as a potential barrier so that only higher-energy holes are injected. We found that the LEDs with AlGaAs were brighter at long wavelengths, which was a significant improvement. Photoluminescence measurements show that the spectral blue-shift is not due to sample heating. We have developed a new physical model to explain the blue-shift: it is caused by Coloumb charging of the deep-centers. We have achieved the first tunnel diodes with which specifically utilize deep-levels in low-temperature-grown (LTG) GaAs. Our devices show the largest ever peak current density in a GaAs tunnel diode at room temperature. Our devices also show significant room-temperature peak-to-valley current ratios. The shape of the current-voltage characteristic and the properties of the optical emission enable us to determine the peak and valley transport mechanisms.

Ultrafast disk technology enables next generation micromachining laser sources

NASA Astrophysics Data System (ADS)

Heckl, Oliver H.; Weiler, Sascha; Luzius, Severin; Zawischa, Ivo; Sutter, Dirk

2013-02-01

Ultrashort pulsed lasers based on thin disk technology have entered the 100 W regime and deliver several tens of MW peak power without chirped pulse amplification. Highest uptime and insensitivity to back reflections make them ideal tools for efficient and cost effective industrial micromachining. Frequency converted versions allow the processing of a large variety of materials. On one hand, thin disk oscillators deliver more than 30 MW peak power directly out of the resonator in laboratory setups. These peak power levels are made possible by recent progress in the scaling of the pulse energy in excess of 40 μJ. At the corresponding high peak intensity, thin disk technology profits from the limited amount of material and hence the manageable nonlinearity within the resonator. Using new broadband host materials like for example the sesquioxides will eventually reduce the pulse duration during high power operation and further increase the peak power. On the other hand industry grade amplifier systems deliver even higher peak power levels. At closed-loop controlled 100W, the TruMicro Series 5000 currently offers the highest average ultrafast power in an industry proven product, and enables efficient micromachining of almost any material, in particular of glasses, ceramics or sapphire. Conventional laser cutting of these materials often requires UV laser sources with pulse durations of several nanoseconds and an average power in the 10 W range. Material processing based on high peak power laser sources makes use of multi-photon absorption processes. This highly nonlinear absorption enables micromachining driven by the fundamental (1030 nm) or frequency doubled (515 nm) wavelength of Yb:YAG. Operation in the IR or green spectral range reduces the complexity and running costs of industrial systems initially based on UV light sources. Where UV wavelength is required, the TruMicro 5360 with a specified UV crystal life-time of more than 10 thousand hours of continues operation at 15W is an excellent choice. Currently this is the world's most powerful industrial sub-10 ps UV laser.

DNA binding studies of Sunset Yellow FCF using spectroscopy, viscometry and electrochemical techniques

NASA Astrophysics Data System (ADS)

Asaadi, Sara; Hajian, Reza

2017-10-01

Color is one of the important factors in food industry. All food companies use synthetic pigments to improve the aesthetic of products. Studies on the interaction between deoxyribonucleic acid (DNA) and food dye molecules is important because DNA is responsible for some processes including replication and transcription of cells, mutations, genetic diseases, and some synthetic chemical nucleases. In this study, the molecular interaction between Sunset Yellow FCF (SY) as a common food coloring additive and calf thymus DNA (ct-DNA) has been studied using UV-Vis spectrophotometry, spectrofluorometry, Fourier transform infrared (FTIR) spectroscopy, cyclic voltammetry and viscometry techniques. The binding constant between ct-DNA and SY in phosphate buffer solution (pH 7.4) was calculated as 2.09 × 103 L mol-1. The non-electrostatic bonding constant (K0t) was almost consistent and the ratio of K0t/Kb increased by increasing the ionic strength in the range of 0.01-0.1 mol L-1 of KCl. This observation shows that, the molecular bonding of SY to ct-DNA is a combination of electrostatic and intercalation interactions. In the electrochemical studies, an oxidation peak at 0.71 V and a reduction peak at about 0.63 V was observed with the peak potential difference (ΔEp) of 0.08 V, showing a reversible process. The oxidation and reduction peaks were significantly decreased in the presence of ct-DNA and the reduction peak current shifted to negative values. In spectrofluorometric study, the fluorescence intensity of SY increased dramatically after successive addition of DNA due to the increasing of molecular surface area and decreasing of impact frequency between solvent and SY-DNA adduct. Moreover, viscometric study shows that the increasing of viscosity for SY solution in the presence of DNA is due to the intercalation mechanism with double strand DNA (ds-DNA).

Variation of froude number with discharge for large-gradient steams

USGS Publications Warehouse

Wahl, Kenneth L.; ,

1993-01-01

Under chemical-control conditions, the Froude number (f) for a cross-section can be approximated as a function of the ratio R2/ 3/d 1/2 , where R is the hydraulic radius and d is the average depth. For cross sections where the ratio increases with increasing depth, F can also increase with depth Current-meter measurement data for 433 streamflow gaging stations in Colorado were reviewed, and 62 stations were identified at which F increases with depth of flow. Data for four streamflow gaging stations are presented. In some cases, F approaches 1 as the discharge approaches the magnitude of the median annual peak discharge. The data also indicate that few actual current meter measurement have been made at the large discharges where velocities can be supercritical.

Selective and sensitive determination of uric acid in the presence of ascorbic acid and dopamine by PDDA functionalized graphene/graphite composite electrode.

PubMed

Yu, Yanyan; Chen, Zuanguang; Zhang, Beibei; Li, Xinchun; Pan, Jianbin

2013-08-15

In this work, a facile electrochemical sensor based on poly(diallyldimethylammonium chloride) (PDDA) functionalized graphene (PDDA-G) and graphite was fabricated. The composite electrode exhibited excellent selectivity and sensitivity towards uric acid (UA), owing to the electrocatalytic effect of graphene nanosheets and the electrostatic attractions between PDDA-G and UA. The anodic peak current of UA obtained by cyclic voltammetry (CV) increased over 10-fold compared with bare carbon paste electrode (CPE). And the reversibility of the oxidation process was improved significantly. Differential pulse voltammetry (DPV) was used to determine UA in the presence of ascorbic acid (AA) and dopamine (DA). It was found that all of oxidation peaks of three species could be well resolved, and the peak current of UA was much stronger than the other two components. More importantly, considerable-amount of AA and DA showed negligible interference to UA assay. The calibration curve for UA ranged from 0.5 to 20 μmol L(-1) with a correlation coefficient of 0.9934. The constructed sensor has been employed to quantitatively determine UA in urine samples. Copyright © 2013 Elsevier B.V. All rights reserved.

Electrochemical determination of Sudan I in food samples at graphene modified glassy carbon electrode based on the enhancement effect of sodium dodecyl sulphonate.

PubMed

Ma, Xinying; Chao, Mingyong; Wang, Zhaoxia

2013-06-01

This paper describes a novel electrochemical method for the determination of Sudan I in food samples based on the electrochemical catalytic activity of graphene modified glassy carbon electrode (GMGCE) and the enhancement effect of an anionic surfactant: sodium dodecyl sulphonate (SDS). Using pH 6.0 phosphate buffer solution (PBS) as supporting electrolyte and in the presence of 1.5 × 10(-4)mol L(-1) SDS, Sudan I yielded a well-defined and sensitive oxidation peak at a GMGCE. The oxidation peak current of Sudan I remarkably increased in the presence of SDS. The experimental parameters, such as supporting electrolyte, concentration of SDS, and accumulation time, were optimised for Sudan I determination. The oxidation peak current showed a linear relationship with the concentrations of Sudan I in the range of 7.50 × 10(-8)-7.50 × 10(-6)mol L(-1), with the detection limit of 4.0 × 10(-8)mol L(-1). This new voltammetric method was successfully used to determine Sudan I in food products such as ketchup and chili sauce with satisfactory results. Copyright © 2012 Elsevier Ltd. All rights reserved.

Direct electrochemistry of glucose oxidase on novel free-standing nitrogen-doped carbon nanospheres@carbon nanofibers composite film.

PubMed

Zhang, Xueping; Liu, Dong; Li, Libo; You, Tianyan

2015-05-06

We have proposed a novel free-standing nitrogen-doped carbon nanospheres@carbon nanofibers (NCNSs@CNFs) composite film with high processability for the investigation of the direct electron transfer (DET) of glucose oxidase (GOx) and the DET-based glucose biosensing. The composites were simply prepared by controlled thermal treatment of electrospun polypyrrole nanospheres doped polyacrylonitrile nanofibers (PPyNSs@PAN NFs). Without any pretreatment, the as-prepared material can directly serve as a platform for GOx immobilization. The cyclic voltammetry of immobilized GOx showed a pair of well-defined redox peaks in O2-free solution, indicating the DET of GOx. With the addition of glucose, the anodic peak current increased, while the cathodic peak current decreased, which demonstrated the DET-based bioelectrocatalysis. The detection of glucose based on the DET of GOx was achieved, which displayed high sensitivity, stability and selectivity, with a low detection limit of 2 μM and wide linear range of 12-1000 μM. These results demonstrate that the as-obtained NCNSs@CNFs can serve as an ideal platform for the construction of the third-generation glucose biosensor.

Voltammetric Response of Alizarin Red S-Confined Film-Coated Electrodes to Diol and Polyol Compounds: Use of Phenylboronic Acid-Modified Poly(ethyleneimine) as Film Component.

PubMed

Takahashi, Shigehiro; Suzuki, Iwao; Ojima, Takuto; Minaki, Daichi; Anzai, Jun-Ichi

2018-01-22

Alizarin red S (ARS) was confined in layer-by-layer (LbL) films composed of phenylboronic acid-modified poly(ethyleneimine) (PBA-PEI) and carboxymethylcellulose (CMC) to study the voltammetric response to diol and polyol compounds. The LbL film-coated gold (Au) electrode and quartz slide were immersed in an ARS solution to uptake ARS into the film. UV-visible absorption spectra of ARS-confined LbL film suggested that ARS formed boronate ester (ARS-PBS) in the film. The cyclic voltammetry of the ARS-confined LbL film-coated electrodes exhibited oxidation peaks at -0.50 and -0.62 V, which were ascribed to the oxidation reactions of ARS-PBS and free ARS, respectively, in the LbL film. The peak current at -0.62 V increased upon the addition of diol or polyol compounds such as L-dopa, glucose, and sorbitol into the solution, depending on the concentration, whereas the peak current at -0.50 V decreased. The results suggest a possible use of ARS-confined PBA-PEI/CMC LbL film-coated Au electrodes for the construction of voltammetric sensors for diol and polyol compounds.

Direct Electrochemistry of Glucose Oxidase on Novel Free-Standing Nitrogen-Doped Carbon Nanospheres@Carbon Nanofibers Composite Film

PubMed Central

Zhang, Xueping; Liu, Dong; Li, Libo; You, Tianyan

2015-01-01

We have proposed a novel free-standing nitrogen-doped carbon nanospheres@carbon nanofibers (NCNSs@CNFs) composite film with high processability for the investigation of the direct electron transfer (DET) of glucose oxidase (GOx) and the DET-based glucose biosensing. The composites were simply prepared by controlled thermal treatment of electrospun polypyrrole nanospheres doped polyacrylonitrile nanofibers (PPyNSs@PAN NFs). Without any pretreatment, the as-prepared material can directly serve as a platform for GOx immobilization. The cyclic voltammetry of immobilized GOx showed a pair of well-defined redox peaks in O2-free solution, indicating the DET of GOx. With the addition of glucose, the anodic peak current increased, while the cathodic peak current decreased, which demonstrated the DET-based bioelectrocatalysis. The detection of glucose based on the DET of GOx was achieved, which displayed high sensitivity, stability and selectivity, with a low detection limit of 2 μM and wide linear range of 12–1000 μM. These results demonstrate that the as-obtained NCNSs@CNFs can serve as an ideal platform for the construction of the third-generation glucose biosensor. PMID:25943704

Diagnostics of an AC driven atmospheric pressure non-thermal plasma jet and its use for radially directed jet array

NASA Astrophysics Data System (ADS)

Zhu, W.; Wang, R.

2017-08-01

An alternating current atmospheric pressure plasma jet is generated with noble gas or noble gas/oxygen admixture as working gas. A "core plasma filament" is observed at the center of the dielectric tube and extends to the plasma jet at higher peak-to-peak voltages. This type of plasma jet is believed to be of the same nature with the reported plasma bullet driven by pulsed DC power sources. Double current probes are used to assess the speed of the plasma bullet and show that the speed is around 104-105 m/s. The time dependence of the downstream bullet speed is attributed to the gas heating and in turn the increase of the reduced electric field E/N. Optical emission spectra show the dependence of helium and oxygen emission intensities on the concentration of oxygen additive in the carrier gas, with peak values found at 0.5% O2. Multiple radial jets are realized on dielectric tubes of different sizes. As a case study, one of these multi-jet devices is used to treat B. aureus on the inner surface of a plastic beaker and is shown to be more effective than a single jet.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Dong, E-mail: wang.dong.539@m.kyushu-u.ac.jp; Maekura, Takayuki; Kamezawa, Sho

We demonstrated direct band gap (DBG) electroluminescence (EL) at room temperature from n-type bulk germanium (Ge) using a fin type asymmetric lateral metal/Ge/metal structure with TiN/Ge and HfGe/Ge contacts, which was fabricated using a low temperature (<400 °C) process. Small electron and hole barrier heights were obtained for TiN/Ge and HfGe/Ge contacts, respectively. DBG EL spectrum peaked at 1.55 μm was clearly observed even at a small current density of 2.2 μA/μm. Superlinear increase in EL intensity was also observed with increasing current density, due to superlinear increase in population of elections in direct conduction band. The efficiency of hole injection was alsomore » clarified.« less

Water- and humidity-enhanced UV detector by using p-type La-doped ZnO nanowires on flexible polyimide substrate.

PubMed

Hsu, Cheng-Liang; Li, Hsieh-Heng; Hsueh, Ting-Jen

2013-11-13

High-density La-doped ZnO nanowires (NWs) were grown hydrothermally on flexible polyimide substrate. The length and diameter of the NWs were around 860 nm and 80-160 nm, respectively. All XRD peaks of the La-doped sample shift to a larger angle. The strong PL peak of the La-doped sample is 380 nm, which is close to the 3.3 eV ZnO bandgap. That PL dominated indicates that the La-doped sample has a great amount of oxygen vacancies. The lattice constants ~0.514 nm of the ZnO:La NW were smaller when measured by HR-TEM. The EDX spectrum determined that the La-doped sample contains approximately 1.27 at % La. The La-doped sample was found to be p-type by Hall Effect measurement. The dark current of the p-ZnO:La NWs decreased with increased relative humidity (RH), while the photocurrent of the p-ZnO:La nanowires increased with increased RH. The higher RH environment was improved that UV response performance. Based on the highest 98% RH, the photocurrent/dark current ratio was around 47.73. The UV response of water drops on the p-ZnO:La NWs was around 2 orders compared to 40% RH. In a water environment, the photocurrent/dark current ratio of p-ZnO:La NWs was 212.1, which is the maximum UV response.

Preparation of Al-Si Master Alloy by Electrochemical Reduction of Fly Ash in Molten Salt

NASA Astrophysics Data System (ADS)

Liu, Aimin; Li, Liangxing; Xu, Junli; Shi, Zhongning; Hu, Xianwei; Gao, Bingliang; Wang, Zhaowen; Yu, Jiangyu; Chen, Gong

2014-05-01

An electrochemical method on preparation of Al-Si master alloy was investigated in fluoride-based molten salts of 47.7wt.%NaF-43.3wt.%AlF3-4wt.%CaF2 containing 5 wt.% fly ash at 1233 K. The cathodic products obtained by galvanostatic electrolysis were analyzed by means of x-ray diffraction, x-ray fluorescence, scanning electron microscopy, and energy-dispersive spectrometry. The result showed that the compositions of the products are Al, Si, and Al3.21Si0.47. Meanwhile, the cathodic electrochemical process was studied by cyclic voltammetry, and the results showed the reduction peak of aluminum deposition is at -1.3 V versus the platinum quasi-reference electrode in 50.3wt.%NaF-45.7wt.%AlF3-4wt.%CaF2 molten salts, while the reduction peak at -1.3 V was the co-deposition of aluminum and silicon when the fly ash was added. The silicon and iron were formed via both co-deposition and aluminothermic reduction. In the electrolysis experiments, current efficiency first increased to a maximum value of 40.7% at a current density of 0.29 A/cm2, and then it decreased with the increase of current density. With the electrolysis time lasting, the content of aluminum in the alloys decreased from 76.05 wt.% to 48.29 wt.% during 5 h, while the content of silicon increased from 15.94 wt.% to 37.89 wt.%.

Tidal and near-inertial peak variations around the diurnal critical latitude

NASA Astrophysics Data System (ADS)

van Haren, Hans

2005-12-01

Spectra from historic long-term open-ocean moored current meter data between latitudes 0° < |$\\varphi$| < 45° reveal a significant drop in semidiurnal tidal band (D2) energy by ~50% at |$\\varphi$| ~ 25-27°, whilst the peak near the local inertial frequency f is increased by a factor of ~10 up to the level of D2-energy at |$\\varphi$| ~ 28-30°, where f coincides with diurnal frequencies. The increase in f-energy is accompanied by a red-shift of the peak frequency to 0.97 +/- 0.01f, or a poleward spreading of enhanced energy. This contrasts with more common blue-shift. The enhancement may be the result of sub-harmonic instability, as supported by sparse significant bicoherence at half-D2, although i) systematic enhancement of diurnal tidal frequencies, notably M1, was not observed, ii) the latitudes of low D2-energy and high f-energy do not coincide. This may be due to a mix of coupled and independent waves, whilst the poleward trapping of sub-f energy suggests non-traditional effects.

Synthesis and characterization of porous silicon gas sensors

NASA Astrophysics Data System (ADS)

abbas, Roaa A.; Alwan, Alwan M.; Abdulhamied, Zainab T.

2018-05-01

In this work, photo-electrochemical etching process of n-type Silicon of resistivity(10 Ω.cm) and (100) orientation, using two illumination sources IR and violet wavelength in HF acid have been used to produce PSi gas detection device. The fabrication process was carried out at a fixed etching current density of 25mA/cm2 and at different etching time (5, 10, 15 and 20) min and (8, 16, 24, and 30) min. Two configurations of gas sensor configuration planer and sandwich have been made and investigated. The morphological properties have been studied using SEM,the FTIR measurement show that the (Si-Hx) and (Si-O-Si) absorption peak were increases with increasing etching time,and Photoluminescence properties of PSi layer show decrease in the peak of PL peak toward the violet shift. The gas detection process is made on the CO2 gas at different operating temperature and fixed gas concentration. In the planner structure, the gas sensing was measured through, the change in the resistance readout as a function to the exposure time, while for sandwich structure J-V characteristic have been made to determine the sensitivity.

An Autonomous Mobile Agent-Based Distributed Learning Architecture: A Proposal and Analytical Analysis

ERIC Educational Resources Information Center

Ahmed, Iftikhar; Sadeq, Muhammad Jafar

2006-01-01

Current distance learning systems are increasingly packing highly data-intensive contents on servers, resulting in the congestion of network and server resources at peak service times. A distributed learning system based on faded information field (FIF) architecture that employs mobile agents (MAs) has been proposed and simulated in this work. The…

Transition from the Unipolar Region to the Sector Zone: Voyager 2, 2013 and 2014

NASA Astrophysics Data System (ADS)

Burlaga, L. F.; Ness, N. F.; Richardson, J. D.

2017-05-01

We discuss magnetic field and plasma observations of the heliosheath made by Voyager 2 (V2) during 2013 and 2014 near solar maximum. A transition from a unipolar region to a sector zone was observed in the azimuthal angle λ between ˜2012.45 and 2013.82. The distribution of λ was strongly singly peaked at 270^\\circ in the unipolar region and double peaked in the sector zone. The δ-distribution was strongly peaked in the unipolar region and very broad in the sector zone. The distribution of daily averages of the magnetic field strength B was Gaussian in the unipolar region and lognormal in the sector zone. The correlation function of B was exponential with an e-folding time of ˜5 days in both regions. The distribution of hourly increments of B was a Tsallis distribution with nonextensivity parameter q = 1.7 ± 0.04 in the unipolar region and q = 1.44 ± 0.12 in the sector zone. The CR-B relationship qualitatively describes the 2013 observations, but not the 2014 observations. A 40 km s-1 increase in the bulk speed associated with an increase in B near 2013.5 might have been produced by the merging of streams. A “D sheet” (a broad depression in B containing a current sheet moved past V2 from days 320 to 345, 2013. The R- and N-components of the plasma velocity changed across the current sheet.

Ion cyclotron resonance heating for tungsten control in various JET H-mode scenarios

NASA Astrophysics Data System (ADS)

Goniche, M.; Dumont, R. J.; Bobkov, V.; Buratti, P.; Brezinsek, S.; Challis, C.; Colas, L.; Czarnecka, A.; Drewelow, P.; Fedorczak, N.; Garcia, J.; Giroud, C.; Graham, M.; Graves, J. P.; Hobirk, J.; Jacquet, P.; Lerche, E.; Mantica, P.; Monakhov, I.; Monier-Garbet, P.; Nave, M. F. F.; Noble, C.; Nunes, I.; Pütterich, T.; Rimini, F.; Sertoli, M.; Valisa, M.; Van Eester, D.; Contributors, JET

2017-05-01

Ion cyclotron resonance heating (ICRH) in the hydrogen minority scheme provides central ion heating and acts favorably on the core tungsten transport. Full wave modeling shows that, at medium power level (4 MW), after collisional redistribution, the ratio of power transferred to the ions and the electrons vary little with the minority (hydrogen) concentration n H/n e but the high-Z impurity screening provided by the fast ions temperature increases with the concentration. The power radiated by tungsten in the core of the JET discharges has been analyzed on a large database covering the 2013-2014 campaign. In the baseline scenario with moderate plasma current (I p = 2.5 MA) ICRH modifies efficiently tungsten transport to avoid its accumulation in the plasma centre and, when the ICRH power is increased, the tungsten radiation peaking evolves as predicted by the neo-classical theory. At higher current (3-4 MA), tungsten accumulation can be only avoided with 5 MW of ICRH power with high gas injection rate. For discharges in the hybrid scenario, the strong initial peaking of the density leads to strong tungsten accumulation. When this initial density peaking is slightly reduced, with an ICRH power in excess of 4 MW,very low tungsten concentration in the core (˜10-5) is maintained for 3 s. MHD activity plays a key role in tungsten transport and modulation of the tungsten radiation during a sawtooth cycle is correlated to the fishbone activity triggered by the fast ion pressure gradient.

Two types of peak emotional responses to music: The psychophysiology of chills and tears

PubMed Central

Mori, Kazuma; Iwanaga, Makoto

2017-01-01

People sometimes experience a strong emotional response to artworks. Previous studies have demonstrated that the peak emotional experience of chills (goose bumps or shivers) when listening to music involves psychophysiological arousal and a rewarding effect. However, many aspects of peak emotion are still not understood. The current research takes a new perspective of peak emotional response of tears (weeping, lump in the throat). A psychophysiological experiment showed that self-reported chills increased electrodermal activity and subjective arousal whereas tears produced slow respiration during heartbeat acceleration, although both chills and tears induced pleasure and deep breathing. A song that induced chills was perceived as being both happy and sad whereas a song that induced tears was perceived as sad. A tear-eliciting song was perceived as calmer than a chill-eliciting song. These results show that tears involve pleasure from sadness and that they are psychophysiologically calming; thus, psychophysiological responses permit the distinction between chills and tears. Because tears may have a cathartic effect, the functional significance of chills and tears seems to be different. We believe that the distinction of two types of peak emotions is theoretically relevant and further study of tears would contribute to more understanding of human peak emotional response. PMID:28387335

Off-Axis Driven Current Effects on ETB and ITB Formations based on Bifurcation Concept

NASA Astrophysics Data System (ADS)

Pakdeewanich, J.; Onjun, T.; Chatthong, B.

2017-09-01

This research studies plasma performance in fusion Tokamak system by investigating parameters such as plasma pressure in the presence of an edge transport barrier (ETB) and an internal transport barrier (ITB) as the off-axis driven current position is varied. The plasma is modeled based on the bifurcation concept using a suppression function that can result in formation of transport barriers. In this model, thermal and particle transport equations, including both neoclassical and anomalous effects, are solved simultaneously in slab geometry. The neoclassical coefficients are assumed to be constant while the anomalous coefficients depend on gradients of local pressure and density. The suppression function, depending on flow shear and magnetic shear, is assumed to affect only on the anomalous channel. The flow shear can be calculated from the force balance equation, while the magnetic shear is calculated from the given plasma current. It is found that as the position of driven current peak is moved outwards from the plasma center, the central pressure is increased. But at some point it stars to decline, mostly when the driven current peak has reached the outer half of the plasma. The higher pressure value results from the combination of ETB and ITB formations. The drop in central pressure occurs because ITB stats to disappear.

Capacitor charging FET switcher with controller to adjust pulse width

DOEpatents

Mihalka, Alex M.

1986-01-01

A switching power supply includes an FET full bridge, a controller to drive the FETs, a programmable controller to dynamically control final output current by adjusting pulse width, and a variety of protective systems, including an overcurrent latch for current control. Power MOSFETS are switched at a variable frequency from 20-50 kHz to charge a capacitor load from 0 to 6 kV. A ferrite transformer steps up the DC input. The transformer primary is a full bridge configuration with the FET switches and the secondary is fed into a high voltage full wave rectifier whose output is connected directly to the energy storage capacitor. The peak current is held constant by varying the pulse width using predetermined timing resistors and counting pulses. The pulse width is increased as the capacitor charges to maintain peak current. A digital ripple counter counts pulses, and after the desired number is reached, an up-counter is clocked. The up-counter output is decoded to choose among different resistors used to discharge a timing capacitor, thereby determining the pulse width. A current latch shuts down the supply on overcurrent due to either excessive pulse width causing transformer saturation or a major bridge fault, i.e., FET or transformer failure, or failure of the drive circuitry.

Pulsed characterization of a UV LED for pulsed power applications on a silicon carbide photoconductive semiconductor switch

NASA Astrophysics Data System (ADS)

Wilson, Nicholas; Mauch, Daniel; Meyers, Vincent; Feathers, Shannon; Dickens, James; Neuber, Andreas

2017-08-01

The electrical and optical characteristics of a high-power UV light emitting diode (LED) (365 nm wavelength) were evaluated under pulsed operating conditions at current amplitudes several orders of magnitude beyond the LED's manufacturer specifications. Geared towards triggering of photoconductive semiconductor switches (PCSSs) for pulsed power applications, measurements were made over varying pulse widths (25 ns-100 μs), current (0 A-250 A), and repetition rates (single shot-5 MHz). The LED forward voltage was observed to increase linearly with increasing current (˜3.5 V-53 V) and decrease with increasing pulse widths. The peak optical power observed was >30 W, and a maximum system efficiency of 23% was achieved. The evaluated LED and auxiliary hardware were successfully used as the optical trigger source for a 4H-SiC PCSS. The lowest measured on-resistance of SiC was approximately 67 kΩ.

Pulsed characterization of a UV LED for pulsed power applications on a silicon carbide photoconductive semiconductor switch.

PubMed

Wilson, Nicholas; Mauch, Daniel; Meyers, Vincent; Feathers, Shannon; Dickens, James; Neuber, Andreas

2017-08-01

The electrical and optical characteristics of a high-power UV light emitting diode (LED) (365 nm wavelength) were evaluated under pulsed operating conditions at current amplitudes several orders of magnitude beyond the LED's manufacturer specifications. Geared towards triggering of photoconductive semiconductor switches (PCSSs) for pulsed power applications, measurements were made over varying pulse widths (25 ns-100 μs), current (0 A-250 A), and repetition rates (single shot-5 MHz). The LED forward voltage was observed to increase linearly with increasing current (∼3.5 V-53 V) and decrease with increasing pulse widths. The peak optical power observed was >30 W, and a maximum system efficiency of 23% was achieved. The evaluated LED and auxiliary hardware were successfully used as the optical trigger source for a 4H-SiC PCSS. The lowest measured on-resistance of SiC was approximately 67 kΩ.

Across-site patterns of electrically evoked compound action potential amplitude-growth functions in multichannel cochlear implant recipients and the effects of the interphase gap.

PubMed

Schvartz-Leyzac, Kara C; Pfingst, Bryan E

2016-11-01

Electrically evoked compound action potential (ECAP) measures of peak amplitude, and amplitude-growth function (AGF) slope have been shown to reflect characteristics of cochlear health (primarily spiral ganglion density) in anesthetized cochlear-implanted guinea pigs. Likewise, the effect of increasing the interphase gap (IPG) in each of these measures also reflects SGN density in the implanted guinea pig. Based on these findings, we hypothesize that suprathreshold ECAP measures, and also how they change as the IPG is increased, have the potential to be clinically applicable in human subjects. However, further work is first needed in order to determine the characteristics of these measures in humans who use cochlear implants. The current study examined across-site patterns of suprathreshold ECAP measures in 10 bilaterally-implanted, adult cochlear implant users. Results showed that both peak amplitude and slope of the AGF varied significantly from electrode to electrode in ear-specific patterns across the subjects' electrode arrays. As expected, increasing the IPG on average increased the peak amplitude and slope. Across ears, there was a significant, negative correlation between the slope of the ECAP AGF and the duration of hearing loss. Across-site patterns of ECAP peak amplitude and AGF slopes were also compared with common ground impedance values and significant correlations were observed in some cases, depending on the subject and condition. The results of this study, coupled with previous studies in animals, suggest that it is feasible to measure the change in suprathreshold ECAP measures as the IPG increases on most electrodes. Further work is needed to investigate the relationship between these measures and cochlear implant outcomes, and determine how these measures might be used when programming a cochlear-implant processor. Published by Elsevier B.V.

A mathematical model of action potential heterogeneity in adult rat left ventricular myocytes.

PubMed Central

Pandit, S V; Clark, R B; Giles, W R; Demir, S S

2001-01-01

Mathematical models were developed to reconstruct the action potentials (AP) recorded in epicardial and endocardial myocytes isolated from the adult rat left ventricle. The main goal was to obtain additional insight into the ionic mechanisms responsible for the transmural AP heterogeneity. The simulation results support the hypothesis that the smaller density and the slower reactivation kinetics of the Ca(2+)-independent transient outward K(+) current (I(t)) in the endocardial myocytes can account for the longer action potential duration (APD), and more prominent rate dependence in that cell type. The larger density of the Na(+) current (I(Na)) in the endocardial myocytes results in a faster upstroke (dV/dt(max)). This, in addition to the smaller magnitude of I(t), is responsible for the larger peak overshoot of the simulated endocardial AP. The prolonged APD in the endocardial cell also leads to an enhanced amplitude of the sustained K(+) current (I(ss)), and a larger influx of Ca(2+) ions via the L-type Ca(2+) current (I(CaL)). The latter results in an increased sarcoplasmic reticulum (SR) load, which is mainly responsible for the higher peak systolic value of the Ca(2+) transient [Ca(2+)](i), and the resultant increase in the Na(+)-Ca(2+) exchanger (I(NaCa)) activity, associated with the simulated endocardial AP. In combination, these calculations provide novel, quantitative insights into the repolarization process and its naturally occurring transmural variations in the rat left ventricle. PMID:11720973

Hydrophobic polymer covered by a grating electrode for converting the mechanical energy of water droplets into electrical energy

NASA Astrophysics Data System (ADS)

Helseth, L. E.; Guo, X. D.

2016-04-01

Water contact electric harvesting has a great potential as a new energy technology for powering small-scale electronics, but a better understanding of the dynamics governing the conversion from mechanical to electrical energy on the polymer surfaces is needed. Important questions are how current correlates with droplet kinetic energy and what happens to the charge dynamics when a large number of droplets are incident on the polymer simultaneously. Here we address these questions by studying the current that is generated in an external electrical circuit when water droplets impinge on hydrophobic fluorinated ethylene propylene film containing a grating electrode on the back side. Droplets moving down an inclined polymer plane exhibit a characteristic periodic current time trace, and it is found that the peak current scales with sine of the inclination angle. For single droplets in free fall impinging onto the polymer, it is found that the initial peak current scales with the height of the free fall. The transition from individual droplets to a nearly continuous stream was investigated using the spectral density of the current signal. In both regimes, the high frequency content of the spectral density scales as f -2. For low frequencies, the low frequency content at low volume rates was noisy but nearly constant, whereas for high volume rates an increase with frequency is observed. It is demonstrated that the output signal from the system exposed to water droplets from a garden hose can be rectified and harvested by a 33 μF capacitor, where the stored energy increases at a rate of about 20 μJ in 100 s.

MO-F-16A-02: Simulation of a Medical Linear Accelerator for Teaching Purposes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Carlone, M; Lamey, M; Anderson, R

Purpose: Detailed functioning of linear accelerator physics is well known. Less well developed is the basic understanding of how the adjustment of the linear accelerator's electrical components affects the resulting radiation beam. Other than the text by Karzmark, there is very little literature devoted to the practical understanding of linear accelerator functionality targeted at the radiotherapy clinic level. The purpose of this work is to describe a simulation environment for medical linear accelerators with the purpose of teaching linear accelerator physics. Methods: Varian type lineacs were simulated. Klystron saturation and peak output were modelled analytically. The energy gain of anmore » electron beam was modelled using load line expressions. The bending magnet was assumed to be a perfect solenoid whose pass through energy varied linearly with solenoid current. The dose rate calculated at depth in water was assumed to be a simple function of the target's beam current. The flattening filter was modelled as an attenuator with conical shape, and the time-averaged dose rate at a depth in water was determined by calculating kerma. Results: Fifteen analytical models were combined into a single model called SIMAC. Performance was verified systematically by adjusting typical linac control parameters. Increasing klystron pulse voltage increased dose rate to a peak, which then decreased as the beam energy was further increased due to the fixed pass through energy of the bending magnet. Increasing accelerator beam current leads to a higher dose per pulse. However, the energy of the electron beam decreases due to beam loading and so the dose rate eventually maximizes and the decreases as beam current was further increased. Conclusion: SIMAC can realistically simulate the functionality of a linear accelerator. It is expected to have value as a teaching tool for both medical physicists and linear accelerator service personnel.« less

Effects of shoe sole hardness on plantar pressure and comfort in older people with forefoot pain.

PubMed

Lane, Tamara J; Landorf, Karl B; Bonanno, Daniel R; Raspovic, Anita; Menz, Hylton B

2014-01-01

Plantar forefoot pain is common in older people and is related to increased peak pressures under the foot during gait. Variations in the hardness of the shoe sole may therefore influence both the magnitude of loading under the foot and the perceived comfort of the shoe in this population. The aim of this investigation was to determine the effect of varying shoe sole hardness on plantar pressures and comfort in older people with forefoot pain. In-shoe plantar pressures under the forefoot, midfoot and rearfoot were recorded from 35 older people (mean age 73.2, SD 4.5 years) with current or previous forefoot pain using the pedar-X(®) system. Participants walked at their normal comfortable speed along an 8m walkway in shoes with three different levels of sole hardness: soft (Shore A25), medium (Shore A40) and hard (Shore A58). Shoe comfort was measured on a 100mm visual analogue scale. There were statistically significant differences in peak pressure of between 5% and 23% across the forefoot, midfoot and rearfoot (p<0.01). The hard-soled shoe registered the highest peak pressures and the soft-soled shoe the lowest peak pressures. However, no differences in comfort scores across the three shoe conditions were observed. These findings demonstrate that as shoe sole hardness increases, plantar pressure increases, however this does not appear to have a significant effect on shoe comfort. Crown Copyright © 2013. Published by Elsevier B.V. All rights reserved.

Competition between ionic adsorption and desorption on electrochemical double layer capacitor electrodes in acetonitrile solutions at different currents and temperatures

NASA Astrophysics Data System (ADS)

Park, Sieun; Kang, Seok-Won; Kim, Ketack

2017-12-01

The operation of electrochemical double layer capacitors at high currents and viscosities and at low temperatures is difficult. Under these conditions, ion transport is limited, and some of the electrode area is unavailable for adsorption, which results in a low capacitance. Increasing the temperature helps to increase the ionic movement, leading to enhanced adsorption and increased capacitance. In contrast, ion desorption (self-discharge) surpasses the capacitance improvement when ions gain a high amount of energy with increasing temperature. For example, temperatures as high as 70 °C cause a very high rate of ionic desorption in acetonitrile solutions in which the individual properties of the two electrolytes-tetraethylammonium tetrafluoroborate (TEA BF4) and ethylmethylimidazolium tetrafluoroborate (EMI BF4)-are not distinguishable. The capacitance improvement and self-discharge are balanced, resulting in a capacitance peak at mid-range temperatures, i.e., 35-45 °C, in the more viscous electrolyte, i.e., TEA BF4. The less viscous electrolyte, i.e., EMI BF4 has a wider capacitance peak from 25 to 45 °C and higher capacitance than that of TEA BF4. Because the maximum power is obtained in the mid-temperature range (35-45 °C), it is necessary to control the viscosity and temperature to obtain the maximum power in a given device.

Evaluation of Lightning Incidence to Elements of a Complex Structure: A Monte Carlo Approach

NASA Technical Reports Server (NTRS)

Mata, Carlos T.; Rakov, V. A.

2008-01-01

There are complex structures for which the installation and positioning of the lightning protection system (LPS) cannot be done using the lightning protection standard guidelines. As a result, there are some "unprotected" or "exposed" areas. In an effort to quantify the lightning threat to these areas, a Monte Carlo statistical tool has been developed. This statistical tool uses two random number generators: a uniform distribution to generate origins of downward propagating leaders and a lognormal distribution to generate returns stroke peak currents. Downward leaders propagate vertically downward and their striking distances are defined by the polarity and peak current. Following the electrogeometrical concept, we assume that the leader attaches to the closest object within its striking distance. The statistical analysis is run for 10,000 years with an assumed ground flash density and peak current distributions, and the output of the program is the probability of direct attachment to objects of interest with its corresponding peak current distribution.

Demonstration of Tokamak Ohmic Flux Saving by Transient Coaxial Helicity Injection in the National Spherical Torus Experiment

NASA Astrophysics Data System (ADS)

Raman, R.; Mueller, D.; Nelson, B. A.; Jarboe, T. R.; Gerhardt, S.; Kugel, H. W.; Leblanc, B.; Maingi, R.; Menard, J.; Ono, M.; Paul, S.; Roquemore, L.; Sabbagh, S.; Soukhanovskii, V.

2010-03-01

Transient coaxial helicity injection (CHI) started discharges in the National Spherical Torus Experiment (NSTX) have attained peak currents up to 300 kA and when coupled to induction, it has produced up to 200 kA additional current over inductive-only operation. CHI in NSTX has shown to be energetically quite efficient, producing a plasma current of about 10 A/J of capacitor bank energy. In addition, for the first time, the CHI-produced toroidal current that couples to induction continues to increase with the energy supplied by the CHI power supply at otherwise similar values of the injector flux, indicating the potential for substantial current generation capability by CHI in NSTX and in future toroidal devices.

Start current of dielectric-loaded grating in Smith-Purcell radiation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Wenxin, E-mail: lwenxin@mail.ie.ac.cn; Wang, Yong, E-mail: wangyong3845@sina.com; Cao, Miaomiao, E-mail: mona486@yeah.net

In this paper, a three-dimensional dielectric loaded grating (DLG) is proposed for the Smith-Purcell (SP) device. Taking into the considerations of thickness and width of electron beam, the dispersion equation is derived by using field matches method. The complex frequency is obtained by the numerical solution of dispersion equation, in which the imaginary part represents linear growth rate. The impacts of the electron beam filling factor (EBFF) on growth rate are discussed under the condition that the beam current and beam current density are kept as constants, respectively. In addition, the start current for SP oscillator is obtained by usingmore » the dispersion relation combined with boundary conditions. The relationship between the start current and other parameters is discussed and compared with the conventional metal grating. The results show that with the increasing of EBFF, the peak growth rate increases rapidly firstly and then decreases slowly, in which the current and current density are kept as constants, respectively. For the SP oscillator, the start current is increased with the shifting up beam voltage, but it is decreased with the improved EBFF, and only it has a slightly increasing trend when EBFF is close to 1. In addition, the start current is decreased with the increasing of relative dielectric constant, which indicates that by introducing DLG, the start current can be effectively reduced. Theoretical results are in good agreement with that of the simulations.« less

Author Correction: Low frequency transcranial electrical stimulation does not entrain sleep rhythms measured by human intracranial recordings.

PubMed

Lafon, Belen; Henin, Simon; Huang, Yu; Friedman, Daniel; Melloni, Lucia; Thesen, Thomas; Doyle, Werner; Buzsáki, György; Devinsky, Orrin; Parra, Lucas C; Liu, Anli

2018-02-28

It has come to our attention that we did not specify whether the stimulation magnitudes we report in this Article are peak amplitudes or peak-to-peak. All references to intensity given in mA in the manuscript refer to peak-to-peak amplitudes, except in Fig. 2, where the model is calibrated to 1 mA peak amplitude, as stated. In the original version of the paper we incorrectly calibrated the computational models to 1 mA peak-to-peak, rather than 1 mA peak amplitude. This means that we divided by a value twice as large as we should have. The correct estimated fields are therefore twice as large as shown in the original Fig. 2 and Supplementary Figure 11. The corrected figures are now properly calibrated to 1 mA peak amplitude. Furthermore, the sentence in the first paragraph of the Results section 'Intensity ranged from 0.5 to 2.5 mA (current density 0.125-0.625 mA mA/cm 2 ), which is stronger than in previous reports', should have read 'Intensity ranged from 0.5 to 2.5 mA peak to peak (peak current density 0.0625-0.3125 mA/cm 2 ), which is stronger than in previous reports.' These errors do not affect any of the Article's conclusions.

New types of high field pinning centers and pinning centers for the peak effect

NASA Astrophysics Data System (ADS)

Gajda, Daniel; Zaleski, Andrzej; Morawski, Andrzej; Hossain, Md Shahriar A.

2017-08-01

In this article, we report the results of a study that shows the existence of pinning centers inside grains and between grains in NbTi wires. We accurately show the ranges of magnetic fields in which the individual pinning centers operate. The pinning centers inside grains are activated in high magnetic fields above 6 T. We show the range of magnetic fields in which individual defects, dislocations, precipitates inside grains and substitutions in the crystal lattice can operate. We show the existence of a new kind of high field pinning center, which operates in high magnetic fields from 8 to ˜9.5 T. We indicate that dislocations create pinning centers in the range of magnetic fields from 6 to 8 T. In addition, our measurements suggest that the peak effect (increased critical current density (J c) near the upper critical field (B c2)) could be attributed to martensitic (needle-shaped) α‧-Ti inclusions inside grains. These centers are very important because they work very effectively in magnetic fields above 9.5-10 T. We also show that the α-Ti precipitates (between grains) with a thickness similar to the coherence length create pinning centers which work very effectively in magnetic fields from 3 to 6 T. In magnetic fields below 3 T, they act very efficiently in grain boundaries. The measurements indicate that the pinning centers created by dislocations only can be tested by transport measurements. This indicates that dislocations do not increase the magnetic critical current density (J cm). Cold drawing improves pinning centers at grain boundaries and increases the dislocation density, and cold-drawing pinning centers are responsible for the peak effect.

Effect of substrate thinning on the electronic transport characteristics of AlGaN/GaN HEMTs

NASA Astrophysics Data System (ADS)

Zhu, Hui; Meng, Xiao; Zheng, Xiang; Yang, Ying; Feng, Shiwei; Zhang, Yamin; Guo, Chunsheng

2018-07-01

We studied how substrate thinning affected the electronic transport characteristics of AlGaN/GaN HEMTs. By thinning their sapphire substrate from 460 μm to 80 μm, we varied the residual stress in these HEMTs. The thinned sample showed decreased drain-source current and occurrence of kink effect. Furthermore, shown by current transient measurements and time constant analysis, the detrapping behaviors of trap states shifted toward a larger time constant, and the detrapping behavior under the gate and in the gate-drain access region showed increased amplitude. By using pulsed current-voltage measurements, the thinned sample showed a positive shift of the threshold voltage, a decrease in peak transconductance, and an aggravation in current collapse, as compared with the thick one. The degradation of electrical behavior were associated with the structural degradation, as confirmed by the increase of pit density on the thinned sample surface.

The changes of potassium currents in RCS rat Müller cell during retinal degeneration.

PubMed

Zhao, TongTao; Li, YaoChen; Weng, ChuanHuang; Yin, ZhengQin

2012-01-03

Müller cells are the principal glial cells expressing membrane-bound potassium channel and predominantly mediating the homeostatic regulation of extracellular K+ produced by neuronal activity in retina. It's well known that Müller cells can be activated in many pathological conditions, but little is known about the change of potassium currents of Müller cells during the progression of retinitis pigmentosa. Herein, the Royal College of Surgeons rats (RCS rat) were employed to investigate some phenotypic and functional changes of Müller cells during retinal degeneration such as the expression of Kir4.1, membrane properties and K+ channel currents by using immunohistochemistry, RT-PCR, western blot and whole-cell patch clamping respectively. Compared with Müller cells in control retina, increased glutamine synthetase (GS) mRNA levels were seen at P30 and P60, and then decreased gradually in RCS rat retina. Morphologically, Müller cells showed significant hypertrophy and proliferation after p60. The increased expression of intermediate filament, glial fibrillary acidic protein (GFAP) and vimentin began at P30 and reached a peak at p60. Kir4.1 channels presented a peak expression at P30. Concomitantly, K(+) currents of Müller cells increased at P30 and decreased at P90 significantly. We concluded that retinal Müller cells of RCS rats underwent an activation initiated by the onset of retinal degeneration before p60 and then an obvious reactive gliosis, which led the basic membrane properties to suffer marked changes, and caused the Kir4.1 channels of Müller cells to occur a clear functional shift, even lose their normal electrophysiological properties. This process aggravates the impairment caused by the initial photoreceptor degeneration. Copyright © 2011 Elsevier B.V. All rights reserved.

Voltage-clamp analysis of membrane currents and excitation-contraction coupling in a crustacean muscle.

PubMed

Weiss, T; Erxleben, C; Rathmayer, W

2001-01-01

A single fibre preparation from the extensor muscle of a marine isopod crustacean is described which allows the analysis of membrane currents and simultaneously recorded contractions under two-electrode voltage-clamp conditions. We show that there are three main depolarisation-gated currents, two are outward and carried by K+, the third is an inward Ca2+ current, I(Ca). Normally, the K+ currents which can be isolated by using K+ channel blockers, mask I(Ca). I(Ca) activates at potentials more positive than -40 mV, is maximal around 0 mV, and shows strong inactivation at higher depolarisation. Inactivation depends on current rather than voltage. Ba2+, Sr2+ and Mg2+ can substitute for Ca2+. Ba2+ currents are about 80% larger than Ca2+ currents and inactivate little. The properties of I(Ca) characterise it as a high threshold L-type current. The outward current consists primarily of a fast, transient A current, I(K(A)) and a maintained, delayed rectifier current, I(K(V)). In some fibres, a small Ca2+-dependent K+ current is also present. I(K(A)) activates fast at depolarisation above -45 mV, shows pronounced inactivation and is almost completely inactivated at holding potentials more positive than -40 mV. I(K(A)) is half-maximally blocked by 70 microM 4-aminopyridine (4-AP), and 70 mM tetraethylammonium (TEA). I(K(V)) activates more slowly, at about -30 mV, and shows no inactivation. It is half-maximally blocked by 2 mM TEA but rather insensitive to 4-AP. Physiologically, the two K+ currents prevent all-or-nothing action potentials and determine the graded amplitude of active electrical responses and associated contractions. Tension development depends on and is correlated with depolarisation-induced Ca2+ influx mediated by I(Ca). The voltage dependence of peak tension corresponds directly to the voltage dependence of the integrated I(Ca). The threshold potential for contraction is at about -38 mV. Peak tension increases with increasing voltage steps, reaches maximum at around 0 mV, and declines with further depolarisation.

Theoretical investigation of gain-clamped semiconductor optical amplifiers using the amplified spontaneous emission compensating effect

NASA Astrophysics Data System (ADS)

Jia, Xin-Hong

2006-12-01

The theoretical model on gain-clamped semiconductor optical amplifiers (GC-SOAs) based on compensating light has been constructed. Using this model, the effects of insertion position and peak reflectivity of the fiber Bragg grating (FBG) on the gain clamping and noise figure (NF) characteristics of GC-SOA are analyzed. The results show that the effect of the FBG insertion position on gain clamping is slight, but the lower NF can be obtained for input FBG-type GC-SOA; when the FBG peak wavelength is designed to close the signal wavelength, the gain clamping and NF characteristics that can be reached are better. Further study shows that, with the increased peak reflectivity of the FBG, the critical input power is broadened and the gain tends to be varied slowly; the larger bias current is helpful to raise gain and decrease the noise figure but is harmful to a gain flatness characteristic.

Analysis of the local worst-case SAR exposure caused by an MRI multi-transmit body coil in anatomical models of the human body.

PubMed

Neufeld, Esra; Gosselin, Marie-Christine; Murbach, Manuel; Christ, Andreas; Cabot, Eugenia; Kuster, Niels

2011-08-07

Multi-transmit coils are increasingly being employed in high-field magnetic resonance imaging, along with a growing interest in multi-transmit body coils. However, they can lead to an increase in whole-body and local specific absorption rate (SAR) compared to conventional body coils excited in circular polarization for the same total incident input power. In this study, the maximum increase of SAR for three significantly different human anatomies is investigated for a large 3 T (128 MHz) multi-transmit body coil using numerical simulations and a (generalized) eigenvalue-based approach. The results demonstrate that the increase of SAR strongly depends on the anatomy. For the three models and normalization to the sum of the rung currents squared, the whole-body averaged SAR increases by up to a factor of 1.6 compared to conventional excitation and the peak spatial SAR (averaged over any 10 cm(3) of tissue) by up to 13.4. For some locations the local averaged SAR goes up as much as 800 times (130 when looking only at regions where it is above 1% of the peak spatial SAR). The ratio of the peak spatial SAR to the whole-body SAR increases by a factor of up to 47 and can reach values above 800. Due to the potentially much larger power deposition, additional, preferably patient-specific, considerations are necessary to avoid injuries by such systems.

Generation of a pulsed low-energy electron beam using the channel spark device

DOE Office of Scientific and Technical Information (OSTI.GOV)

Elgarhy, M. A. I., E-mail: elgarhy@azhar.edu.eg; Hassaballa, S. E.; Rashed, U. M.

2015-12-15

For the generation of low-energy electron beam, the design and characteristics of channel spark discharge (CSD) operating at a low voltage are presented in this paper. The discharge voltage, discharge current, X-ray emissions, and electron beam current were experimentally determined. The effects of the applied voltage, working gas pressure, and external capacitance on the CSD and beam parameters were measured. At an applied voltage of 11 kV, an oxygen gas pressure of 25 mTorr, and an external capacitance of 16.45 nF, the maximum measured current was 900 A. The discharge current increased with the increase in the pressure and capacitance,more » while its periodic time decreased with the increase in the pressure. Two types of the discharge were identified and recorded: the hollow cathode discharge and the conduction discharge. A Faraday cup was used to measure the beam current. The maximum measured beam current was 120 A, and the beam signal exhibited two peaks. The increase in both the external capacitance and the applied discharge voltage increased the maximum electron beam current. The electron-beam pulse time decreased with the increase in the gas pressure at a constant voltage and increased with the decrease in the applied discharge voltage. At an applied voltage of 11 kV and an oxygen gas pressure of 15 mTorr, the maximum beam energy was 2.8 keV. The X-ray signal intensity decreased with the increase in the gas pressure and increased with the increase in the capacitance.« less

Estimating peak-flow frequency statistics for selected gaged and ungaged sites in naturally flowing streams and rivers in Idaho

USGS Publications Warehouse

Wood, Molly S.; Fosness, Ryan L.; Skinner, Kenneth D.; Veilleux, Andrea G.

2016-06-27

The U.S. Geological Survey, in cooperation with the Idaho Transportation Department, updated regional regression equations to estimate peak-flow statistics at ungaged sites on Idaho streams using recent streamflow (flow) data and new statistical techniques. Peak-flow statistics with 80-, 67-, 50-, 43-, 20-, 10-, 4-, 2-, 1-, 0.5-, and 0.2-percent annual exceedance probabilities (1.25-, 1.50-, 2.00-, 2.33-, 5.00-, 10.0-, 25.0-, 50.0-, 100-, 200-, and 500-year recurrence intervals, respectively) were estimated for 192 streamgages in Idaho and bordering States with at least 10 years of annual peak-flow record through water year 2013. The streamgages were selected from drainage basins with little or no flow diversion or regulation. The peak-flow statistics were estimated by fitting a log-Pearson type III distribution to records of annual peak flows and applying two additional statistical methods: (1) the Expected Moments Algorithm to help describe uncertainty in annual peak flows and to better represent missing and historical record; and (2) the generalized Multiple Grubbs Beck Test to screen out potentially influential low outliers and to better fit the upper end of the peak-flow distribution. Additionally, a new regional skew was estimated for the Pacific Northwest and used to weight at-station skew at most streamgages. The streamgages were grouped into six regions (numbered 1_2, 3, 4, 5, 6_8, and 7, to maintain consistency in region numbering with a previous study), and the estimated peak-flow statistics were related to basin and climatic characteristics to develop regional regression equations using a generalized least squares procedure. Four out of 24 evaluated basin and climatic characteristics were selected for use in the final regional peak-flow regression equations.Overall, the standard error of prediction for the regional peak-flow regression equations ranged from 22 to 132 percent. Among all regions, regression model fit was best for region 4 in west-central Idaho (average standard error of prediction=46.4 percent; pseudo-R2>92 percent) and region 5 in central Idaho (average standard error of prediction=30.3 percent; pseudo-R2>95 percent). Regression model fit was poor for region 7 in southern Idaho (average standard error of prediction=103 percent; pseudo-R2<78 percent) compared to other regions because few streamgages in region 7 met the criteria for inclusion in the study, and the region’s semi-arid climate and associated variability in precipitation patterns causes substantial variability in peak flows.A drainage area ratio-adjustment method, using ratio exponents estimated using generalized least-squares regression, was presented as an alternative to the regional regression equations if peak-flow estimates are desired at an ungaged site that is close to a streamgage selected for inclusion in this study. The alternative drainage area ratio-adjustment method is appropriate for use when the drainage area ratio between the ungaged and gaged sites is between 0.5 and 1.5.The updated regional peak-flow regression equations had lower total error (standard error of prediction) than all regression equations presented in a 1982 study and in four of six regions presented in 2002 and 2003 studies in Idaho. A more extensive streamgage screening process used in the current study resulted in fewer streamgages used in the current study than in the 1982, 2002, and 2003 studies. Fewer streamgages used and the selection of different explanatory variables were likely causes of increased error in some regions compared to previous studies, but overall, regional peak‑flow regression model fit was generally improved for Idaho. The revised statistical procedures and increased streamgage screening applied in the current study most likely resulted in a more accurate representation of natural peak-flow conditions.The updated, regional peak-flow regression equations will be integrated in the U.S. Geological Survey StreamStats program to allow users to estimate basin and climatic characteristics and peak-flow statistics at ungaged locations of interest. StreamStats estimates peak-flow statistics with quantifiable certainty only when used at sites with basin and climatic characteristics within the range of input variables used to develop the regional regression equations. Both the regional regression equations and StreamStats should be used to estimate peak-flow statistics only in naturally flowing, relatively unregulated streams without substantial local influences to flow, such as large seeps, springs, or other groundwater-surface water interactions that are not widespread or characteristic of the respective region.

The sensitivity of human mesenchymal stem cells to vibration and cold storage conditions representative of cold transportation

PubMed Central

Nikolaev, N. I.; Liu, Y.; Hussein, H.; Williams, D. J.

2012-01-01

In the current study, the mechanical and hypothermic damage induced by vibration and cold storage on human mesenchymal stem cells (hMSCs) stored at 2–8°C was quantified by measuring the total cell number and cell viability after exposure to vibration at 50 Hz (peak acceleration 140 m s−2 and peak displacement 1.4 mm), 25 Hz (peak acceleration 140 m s−2, peak displacement 5.7 mm), 10 Hz (peak acceleration 20 m s−2, peak displacement 5.1 mm) and cold storage for several durations. To quantify the viability of the cells, in addition to the trypan blue exclusion method, the combination of annexin V-FITC and propidium iodide was applied to understand the mode of cell death. Cell granularity and a panel of cell surface markers for stemness, including CD29, CD44, CD105 and CD166, were also evaluated for each condition. It was found that hMSCs were sensitive to vibration at 25 Hz, with moderate effects at 50 Hz and no effects at 10 Hz. Vibration at 25 Hz also increased CD29 and CD44 expression. The study further showed that cold storage alone caused a decrease in cell viability, especially after 48 h, and also increased CD29 and CD44 and attenuated CD105 expressions. Cell death would most likely be the consequence of membrane rupture, owing to necrosis induced by cold storage. The sensitivity of cells to different vibrations within the mechanical system is due to a combined effect of displacement and acceleration, and hMSCs with a longer cold storage duration were more susceptible to vibration damage, indicating a coupling between the effects of vibration and cold storage. PMID:22628214

Ignition study of a petrol/CNG single cylinder engine

NASA Astrophysics Data System (ADS)

Khan, N.; Saleem, Z.; Mirza, A. A.

2005-11-01

Benefits of laser ignition over the electrical ignition system for Compressed Natural Gas (CNG) engines have fuelled automobile industry and led to an extensive research on basic characteristics to switch over to the emerging technologies. This study was undertaken to determine the electrical and physical characteristics of the electric spark ignition of single cylinder petrol/CNG engine to determine minimum ignition requirements and timeline of ignition events to use in subsequent laser ignition study. This communication briefly reviews the ongoing research activities and reports the results of this experimental study. The premixed petrol and CNG mixtures were tested for variation of current and voltage characteristics of the spark with speed of engine. The current magnitude of discharge circuit was found to vary linearly over a wide range of speed but the stroke to stroke fire time was found to vary nonlinearly. The DC voltage profiles were observed to fluctuate randomly during ignition process and staying constant in rest of the combustion cycle. Fire to fire peaks of current amplitudes fluctuated up to 10% of the peak values at constant speed but increased almost linearly with increase in speed. Technical barriers of laser ignition related to threshold minimum ignition energy, inter-pulse durations and firing sequence are discussed. Present findings provide a basic initiative and background information for designing suitable timeline algorithms for laser ignited leaner direct injected CNG engines.

Biosensor based on ds-DNA decorated chitosan modified multiwall carbon nanotubes for voltammetric biodetection of herbicide amitrole.

PubMed

Ensafi, Ali A; Amini, Maryam; Rezaei, Behzad

2013-09-01

The interaction of amitrole and salmon sperm ds-DNA was studied using UV-vis and differential pulse voltammetry (DPV) at both bare and DNA-modified electrodes. Amitrole showed an oxidation peak at 0.445 V at a bare pencil graphite electrode (PGE). When ds-DNA was added into the amitrole solution, the peak current of amitrole decreased and the peak potential underwent a shift. UV-vis spectra showed that the absorption intensity of the ds-DNA at 260 nm decreased with increasing amitrole concentration, proving the interaction between amitrole and the ds-DNA. The results also showed that amitrole could interact with the ds-DNA molecules via the intercalative binding mode. Finally, a pretreated pencil graphite electrode (PGE) modified with multiwall carbon nanotubes (MWCNTs) and chitosan (CHIT) decorated with the ds-DNA were tested in order to determine amitrole content in solution. Electrochemical oxidation of amitrole bonded on DNA/MWCNTs-CHIT/PGE was used to obtain an analytical signal. A linear dependence was observed to exist between the peak current and 0.025-2.4 ng mL(-1) amitrole with a detection limit of 0.017 ng mL(-1). The sensor showed a good selectivity and precision for the determination of amitrole. Finally, applicability of the biosensor was evaluated by measuring the analyte in soil and water samples with good selectivity. Copyright © 2013 Elsevier B.V. All rights reserved.

Southern hardwood growth-use gap closing fast as inventories peak

Treesearch

William A. Bechtold

1989-01-01

The use of hardwood for pulp and paper furnish and other fiber products is steadily increasing in the U.S. Pulpwood now accounts for half of all hardwood roundwood currently harvested for industrial timber products in the Southeast. In addition to domestic consumption, hardwood exports to Europe and Asia are also expanding, and good portion of these are shipped from...

Beam brilliance investigation of high current ion beams at GSI heavy ion accelerator facility.

PubMed

Adonin, A A; Hollinger, R

2014-02-01

In this work the emittance measurements of high current Ta-beam provided by VARIS (Vacuum Arc Ion Source) ion source are presented. Beam brilliance as a function of beam aperture at various extraction conditions is investigated. Influence of electrostatic ion beam compression in post acceleration gap on the beam quality is discussed. Use of different extraction systems (single aperture, 7 holes, and 13 holes) in order to achieve more peaked beam core is considered. The possible ways to increase the beam brilliance are discussed.

Glutathionylation-Dependence of Na+-K+-Pump Currents Can Mimic Reduced Subsarcolemmal Na+ Diffusion

PubMed Central

Garcia, Alvaro; Liu, Chia-Chi; Cornelius, Flemming; Clarke, Ronald J.; Rasmussen, Helge H.

2016-01-01

The existence of a subsarcolemmal space with restricted diffusion for Na+ in cardiac myocytes has been inferred from a transient peak electrogenic Na+-K+ pump current beyond steady state on reexposure of myocytes to K+ after a period of exposure to K+-free extracellular solution. The transient peak current is attributed to enhanced electrogenic pumping of Na+ that accumulated in the diffusion-restricted space during pump inhibition in K+-free extracellular solution. However, there are no known physical barriers that account for such restricted Na+ diffusion, and we examined if changes of activity of the Na+-K+ pump itself cause the transient peak current. Reexposure to K+ reproduced a transient current beyond steady state in voltage-clamped ventricular myocytes as reported by others. Persistence of it when the Na+ concentration in patch pipette solutions perfusing the intracellular compartment was high and elimination of it with K+-free pipette solution could not be reconciled with restricted subsarcolemmal Na+ diffusion. The pattern of the transient current early after pump activation was dependent on transmembrane Na+- and K+ concentration gradients suggesting the currents were related to the conformational poise imposed on the pump. We examined if the currents might be accounted for by changes in glutathionylation of the β1 Na+-K+ pump subunit, a reversible oxidative modification that inhibits the pump. Susceptibility of the β1 subunit to glutathionylation depends on the conformational poise of the Na+-K+ pump, and glutathionylation with the pump stabilized in conformations equivalent to those expected to be imposed on voltage-clamped myocytes supported this hypothesis. So did elimination of the transient K+-induced peak Na+-K+ pump current when we included glutaredoxin 1 in patch pipette solutions to reverse glutathionylation. We conclude that transient K+-induced peak Na+-K+ pump current reflects the effect of conformation-dependent β1 pump subunit glutathionylation, not restricted subsarcolemmal diffusion of Na+. PMID:26958887

Glutathionylation-Dependence of Na(+)-K(+)-Pump Currents Can Mimic Reduced Subsarcolemmal Na(+) Diffusion.

PubMed

Garcia, Alvaro; Liu, Chia-Chi; Cornelius, Flemming; Clarke, Ronald J; Rasmussen, Helge H

2016-03-08

The existence of a subsarcolemmal space with restricted diffusion for Na(+) in cardiac myocytes has been inferred from a transient peak electrogenic Na(+)-K(+) pump current beyond steady state on reexposure of myocytes to K(+) after a period of exposure to K(+)-free extracellular solution. The transient peak current is attributed to enhanced electrogenic pumping of Na(+) that accumulated in the diffusion-restricted space during pump inhibition in K(+)-free extracellular solution. However, there are no known physical barriers that account for such restricted Na(+) diffusion, and we examined if changes of activity of the Na(+)-K(+) pump itself cause the transient peak current. Reexposure to K(+) reproduced a transient current beyond steady state in voltage-clamped ventricular myocytes as reported by others. Persistence of it when the Na(+) concentration in patch pipette solutions perfusing the intracellular compartment was high and elimination of it with K(+)-free pipette solution could not be reconciled with restricted subsarcolemmal Na(+) diffusion. The pattern of the transient current early after pump activation was dependent on transmembrane Na(+)- and K(+) concentration gradients suggesting the currents were related to the conformational poise imposed on the pump. We examined if the currents might be accounted for by changes in glutathionylation of the β1 Na(+)-K(+) pump subunit, a reversible oxidative modification that inhibits the pump. Susceptibility of the β1 subunit to glutathionylation depends on the conformational poise of the Na(+)-K(+) pump, and glutathionylation with the pump stabilized in conformations equivalent to those expected to be imposed on voltage-clamped myocytes supported this hypothesis. So did elimination of the transient K(+)-induced peak Na(+)-K(+) pump current when we included glutaredoxin 1 in patch pipette solutions to reverse glutathionylation. We conclude that transient K(+)-induced peak Na(+)-K(+) pump current reflects the effect of conformation-dependent β1 pump subunit glutathionylation, not restricted subsarcolemmal diffusion of Na(+). Copyright © 2016 Biophysical Society. Published by Elsevier Inc. All rights reserved.

Electrical Characteristics and Preparation of (Ba0.5Sr0.5)TiO3 Films by Spray Pyrolysis and Rapid Thermal Annealing

NASA Astrophysics Data System (ADS)

Koo, Horng-Show; Chen, Mi; Ku, Hong-Kou; Kawai, Tomoji

2007-04-01

Functional films of (Ba0.5Sr0.5)TiO3 on Pt (1000 Å)/Ti (100 Å)/SiO2 (2000 Å)/Si substrates are prepared by spray pyrolysis and subsequently rapid thermal annealing. Barium nitrate, strontium nitrate and titanium isopropoxide are used as starting materials with ethylene glycol as solvent. For (Ba0.5Sr0.5)TiO3 functional thin film, thermal characteristics of the precursor powder scratched from as-sprayed films show a remarkable peak around 300-400 °C and 57.7% weight loss up to 1000 °C. The as-sprayed precursor film with coffee-like color and amorphous-like phase is transformed into the resultant film with white, crystalline perovskite phase and characteristic peaks (110) and (100). The resultant films show correspondent increases of dielectric constant, leakage current and dissipation factor with increasing annealing temperatures. The dielectric constant is 264 and tangent loss is 0.21 in the resultant films annealed at 750 °C for 5 min while leakage current density is 1.5× 10-6 A/cm2 in the film annealed at 550 °C for 5 min.

Facilitation of NADH Electrooxidation at Treated Carbon Nanotubes

PubMed Central

Wooten, Marilyn; Gorski, Waldemar

2010-01-01

The relationship between the state of the surface of carbon nanotubes (CNT) and their electrochemical activity was investigated using the enzyme cofactor dihydronicotinamide adenine dinucleotide (NADH) as a redox probe. The boiling of CNT in water, while nondestructive, activated them toward the oxidation of NADH as indicated by a shift in the anodic peak potential of NADH (ENADH) from 0.4 to 0.0 V. The shift in ENADH was due to the redox mediation of NADH oxidation by traces of quinone species that were formed on the surface of treated CNT. The harsher treatment that comprised of microwaving of CNT in concentrated nitric acid had a similar effect on the ENADH and, additionally, it increased the anodic peak current of NADH. The latter correlated with the formation of defects on the surface of acid-microwaved CNT as indicated by their Raman spectra. The increase in current was discussed considering a role of surface mediators on the buckled graphene sheets of acid-microwaved CNT. The other carbon allotropes including the edge plane pyrolytic graphite, graphite powder, and glassy carbon did not display a comparable activation toward the oxidation of NADH. PMID:20088562

The target material influence on the current pulse during high power pulsed magnetron sputtering

NASA Astrophysics Data System (ADS)

Moens, Filip; Konstantinidis, Stéphanos; Depla, Diederik

2017-10-01

The current-time characteristic during high power pulsed magnetron sputtering is measured under identical conditions for seventeen different target materials. Based on physical processes such as gas rarefaction, ion-induced electron emission, and electron impact ionization, two test parameters were derived that significantly correlate with specific features of the current-time characteristic: i) the peak current is correlated to the momentum transfer between the sputtered material and the argon gas, ii) while the observed current plateau after the peak is connected to the metal ionization rate.

Discharging dynamics in an electrolytic cell

NASA Astrophysics Data System (ADS)

Feicht, Sarah E.; Frankel, Alexandra E.; Khair, Aditya S.

2016-07-01

We analyze the dynamics of a discharging electrolytic cell comprised of a binary symmetric electrolyte between two planar, parallel blocking electrodes. When a voltage is initially applied, ions in the electrolyte migrate towards the electrodes, forming electrical double layers. After the system reaches steady state and the external current decays to zero, the applied voltage is switched off and the cell discharges, with the ions eventually returning to a uniform spatial concentration. At voltages on the order of the thermal voltage VT=kBT /q ≃25 mV, where kB is Boltzmann's constant, T is temperature, and q is the charge of a proton, experiments on surfactant-doped nonpolar fluids observe that the temporal evolution of the external current during charging and discharging is not symmetric [V. Novotny and M. A. Hopper, J. Electrochem. Soc. 126, 925 (1979), 10.1149/1.2129195; P. Kornilovitch and Y. Jeon, J. Appl. Phys. 109, 064509 (2011), 10.1063/1.3554445]. In fact, at sufficiently large voltages (several VT), the current during discharging is no longer monotonic: it displays a "reverse peak" before decaying in magnitude to zero. We analyze the dynamics of discharging by solving the Poisson-Nernst-Planck equations governing ion transport via asymptotic and numerical techniques in three regimes. First, in the "linear regime" when the applied voltage V is formally much less than VT, the charging and discharging currents are antisymmetric in time; however, the potential and charge density profiles during charging and discharging are asymmetric. The current evolution is on the R C timescale of the cell, λDL /D , where L is the width of the cell, D is the diffusivity of ions, and λD is the Debye length. Second, in the (experimentally relevant) thin-double-layer limit ɛ =λD/L ≪1 , there is a "weakly nonlinear" regime defined by VT≲V ≲VTln(1 /ɛ ) , where the bulk salt concentration is uniform; thus the R C timescale of the evolution of the current magnitude persists. However, nonlinear, voltage-dependent, capacitance of the double layer is responsible for a break in temporal antisymmetry of the charging and discharging currents. Third, the reverse peak in the discharging current develops in a "strongly nonlinear" regime V ≳VTln(1 /ɛ ) , driven by neutral salt adsorption into the double layers and consequent bulk depletion during charging. The strongly nonlinear regime features current evolution over three timescales. The current decays in magnitude on the double layer relaxation timescale, λD2/D ; then grows exponentially in time towards the reverse peak on the diffusion timescale, L2/D , indicating that the reverse peak is the results of fast diffusion of ions from the double layer layer to the bulk. Following the reverse peak, the current decays exponentially to zero on the R C timescale. Notably, the current at the reverse peak and the time of the reverse peak saturate at large voltages V ≫VTln(1 /ɛ ) . We provide semi-analytic expressions for the saturated reverse peak time and current, which can be used to infer charge carrier diffusivity and concentration from experiments.

Current-voltage characteristics influenced by the nanochannel diameter and surface charge density in a fluidic field-effect-transistor.

PubMed

Singh, Kunwar Pal; Guo, Chunlei

2017-06-21

The nanochannel diameter and surface charge density have a significant impact on current-voltage characteristics in a nanofluidic transistor. We have simulated the effect of the channel diameter and surface charge density on current-voltage characteristics of a fluidic nanochannel with positive surface charge on its walls and a gate electrode on its surface. Anion depletion/enrichment leads to a decrease/increase in ion current with gate potential. The ion current tends to increase linearly with gate potential for narrow channels at high surface charge densities and narrow channels are more effective to control the ion current at high surface charge densities. The current-voltage characteristics are highly nonlinear for wide channels at low surface charge densities and they show different regions of current change with gate potential. The ion current decreases with gate potential after attaining a peak value for wide channels at low values of surface charge densities. At low surface charge densities, the ion current can be controlled by a narrow range of gate potentials for wide channels. The current change with source drain voltage shows ohmic, limiting and overlimiting regions.

Single nanowire green InGaN/GaN light emitting diodes

NASA Astrophysics Data System (ADS)

Zhang, Guogang; Li, Ziyuan; Yuan, Xiaoming; Wang, Fan; Fu, Lan; Zhuang, Zhe; Ren, Fang-Fang; Liu, Bin; Zhang, Rong; Tan, Hark Hoe; Jagadish, Chennupati

2016-10-01

Single nanowire (NW) green InGaN/GaN light-emitting diodes (LEDs) were fabricated by top-down etching technology. The electroluminescence (EL) peak wavelength remains approximately constant with an increasing injection current in contrast to a standard planar LED, which suggests that the quantum-confined Stark effect is significantly reduced in the single NW device. The strain relaxation mechanism is studied in the single NW LED using Raman scattering analysis. As compared to its planar counterpart, the EL peak of the NW LED shows a redshift, due to electric field redistribution as a result of changes in the cavity mode pattern after metallization. Our method has important implication for single NW optoelectronic device applications.

The unique contribution of manual chest compression-vibrations to airflow during physiotherapy in sedated, fully ventilated children.

PubMed

Gregson, Rachael K; Shannon, Harriet; Stocks, Janet; Cole, Tim J; Peters, Mark J; Main, Eleanor

2012-03-01

This study aimed to quantify the specific effects of manual lung inflations with chest compression-vibrations, commonly used to assist airway clearance in ventilated patients. The hypothesis was that force applied during the compressions made a significant additional contribution to increases in peak expiratory flow and expiratory to inspiratory flow ratio over and above that resulting from accompanying increases in inflation volume. Prospective observational study. Cardiac and general pediatric intensive care. Sedated, fully ventilated children. Customized force-sensing mats and a commercial respiratory monitor recorded force and respiration during physiotherapy. Percentage changes in peak expiratory flow, peak expiratory to inspiratory flow ratios, inflation volume, and peak inflation pressure between baseline and manual inflations with and without compression-vibrations were calculated. Analysis of covariance determined the relative contribution of changes in pressure, volume, and force to influence changes in peak expiratory flow and peak expiratory to inspiratory flow ratio. Data from 105 children were analyzed (median age, 1.3 yrs; range, 1 wk to 15.9 yrs). Force during compressions ranged from 15 to 179 N (median, 46 N). Peak expiratory flow increased on average by 76% during compressions compared with baseline ventilation. Increases in peak expiratory flow were significantly related to increases in inflation volume, peak inflation pressure, and force with peak expiratory flow increasing by, on average, 4% for every 10% increase in inflation volume (p < .001), 5% for every 10% increase in peak inflation pressure (p = .005), and 3% for each 10 N of applied force (p < .001). By contrast, increase in peak expiratory to inspiratory flow ratio was only related to applied force with a 4% increase for each 10 N of force (p < .001). These results provide evidence of the unique contribution of compression forces in increasing peak expiratory flow and peak expiratory to inspiratory flow ratio bias over and above that related to accompanying changes from manual hyperinflations. Force generated during compression-vibrations was the single significant factor in multivariable analysis to explain the increases in expiratory flow bias. Such increases in the expiratory bias provide theoretically optimal physiological conditions for cephalad mucus movement in fully ventilated children.

The acoustic structure of male giant panda bleats varies according to intersexual context.

PubMed

Charlton, Benjamin D; Keating, Jennifer L; Rengui, Li; Huang, Yan; Swaisgood, Ronald R

2015-09-01

Although the acoustic structure of mammal vocal signals often varies according to the social context of emission, relatively few mammal studies have examined acoustic variation during intersexual advertisement. In the current study male giant panda bleats were recorded during the breeding season in three behavioural contexts: vocalising alone, during vocal interactions with females outside of peak oestrus, and during vocal interactions with peak-oestrous females. Male bleats produced during vocal interactions with peak-oestrous females were longer in duration and had higher mean fundamental frequency than those produced when males were either involved in a vocal interaction with a female outside of peak oestrus or vocalising alone. In addition, males produced bleats with higher rates of fundamental frequency modulation when they were vocalising alone than when they were interacting with females. These results show that acoustic features of male giant panda bleats have the potential to signal the caller's motivational state, and suggest that males increase the rate of fundamental frequency modulation in bleats when they are alone to maximally broadcast their quality and promote close-range contact with receptive females during the breeding season.

Magnetic field cycling effect on the non-linear current-voltage characteristics and magnetic field induced negative differential resistance in α-Fe{sub 1.64}Ga{sub 0.36}O{sub 3} oxide

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bhowmik, R. N., E-mail: rnbhowmik.phy@pondiuni.edu.in; Vijayasri, G.

2015-06-15

We have studied current-voltage (I-V) characteristics of α-Fe{sub 1.64}Ga{sub 0.36}O{sub 3}, a typical canted ferromagnetic semiconductor. The sample showed a transformation of the I-V curves from linear to non-linear character with the increase of bias voltage. The I-V curves showed irreversible features with hysteresis loop and bi-stable electronic states for up and down modes of voltage sweep. We report positive magnetoresistance and magnetic field induced negative differential resistance as the first time observed phenomena in metal doped hematite system. The magnitudes of critical voltage at which I-V curve showed peak and corresponding peak current are affected by magnetic field cycling.more » The shift of the peak voltage with magnetic field showed a step-wise jump between two discrete voltage levels with least gap (ΔV{sub P}) 0.345(± 0.001) V. The magnetic spin dependent electronic charge transport in this new class of magnetic semiconductor opens a wide scope for tuning large electroresistance (∼500-700%), magnetoresistance (70-135 %) and charge-spin dependent conductivity under suitable control of electric and magnetic fields. The electric and magnetic field controlled charge-spin transport is interesting for applications of the magnetic materials in spintronics, e.g., magnetic sensor, memory devices and digital switching.« less

Bridging the gap between peak and average loads on science networks

DOE PAGES

Nickolay, Sam; Jung, Eun -Sung; Kettimuthu, Rajkumar; ...

2017-05-12

Backbone networks are typically overprovisioned in order to support peak loads. Research and education networks (RENs), for example, are often designed to operate at 20–30% of capacity. Thus, Internet2 upgrades its backbone interconnects when the weekly 95th-percentile load is reliably above 30% of link capacity, and analysis of ESnet traffic between major laboratories shows a substantial gap between peak and average utilization. As science data volumes increase exponentially, it is unclear whether this overprovisioning trend can continue into the future. Even if overprovisioning is possible, it may not be the most cost-effective (and desirable) approach going forward. Under the currentmore » mode of free access to RENs, traffic at peak load may include both flows that need to be transferred in near-real time–for example, for computation and instrument monitoring and steering–and flows that are less time-critical, for example, archival and storage replication operations. Thus, peak load does not necessarily indicate the capacity that is absolutely required at that moment. We thus examine how data transfers are impacted when the average network load is increased while the network capacity is kept at the current levels. We also classify data transfers into on-demand (time-critical) and best-effort (less time-critical) and study the impact on both classes for different proportions of both the number of on-demand transfers and amount of bandwidth allocated for on-demand transfers. For our study, we use real transfer logs from production GridFTP servers to do simulation-based experiments as well as real experiments on a testbed. We find that when the transfer load is doubled and the network capacity is fixed at the current level, the gap between peak and average throughput decreases by an average of 18% in the simulation experiments and 16% in the testbed experiments, and the average slowdown experienced by the data transfers is under 1.5×. Moreover, when transfers are classified as on-demand or best-effort, on-demand transfers experience almost no slowdown and the mean slowdown experienced by best-effort transfers is under 2× in the simulation experiments and under 1.2× in the testbed experiments.« less

Bridging the gap between peak and average loads on science networks

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nickolay, Sam; Jung, Eun -Sung; Kettimuthu, Rajkumar

Backbone networks are typically overprovisioned in order to support peak loads. Research and education networks (RENs), for example, are often designed to operate at 20–30% of capacity. Thus, Internet2 upgrades its backbone interconnects when the weekly 95th-percentile load is reliably above 30% of link capacity, and analysis of ESnet traffic between major laboratories shows a substantial gap between peak and average utilization. As science data volumes increase exponentially, it is unclear whether this overprovisioning trend can continue into the future. Even if overprovisioning is possible, it may not be the most cost-effective (and desirable) approach going forward. Under the currentmore » mode of free access to RENs, traffic at peak load may include both flows that need to be transferred in near-real time–for example, for computation and instrument monitoring and steering–and flows that are less time-critical, for example, archival and storage replication operations. Thus, peak load does not necessarily indicate the capacity that is absolutely required at that moment. We thus examine how data transfers are impacted when the average network load is increased while the network capacity is kept at the current levels. We also classify data transfers into on-demand (time-critical) and best-effort (less time-critical) and study the impact on both classes for different proportions of both the number of on-demand transfers and amount of bandwidth allocated for on-demand transfers. For our study, we use real transfer logs from production GridFTP servers to do simulation-based experiments as well as real experiments on a testbed. We find that when the transfer load is doubled and the network capacity is fixed at the current level, the gap between peak and average throughput decreases by an average of 18% in the simulation experiments and 16% in the testbed experiments, and the average slowdown experienced by the data transfers is under 1.5×. Moreover, when transfers are classified as on-demand or best-effort, on-demand transfers experience almost no slowdown and the mean slowdown experienced by best-effort transfers is under 2× in the simulation experiments and under 1.2× in the testbed experiments.« less

Bomb-14C Peak in the North Pacific Recorded in Long-Lived Bivalve Shells (Mercenaria stimpsoni)

NASA Astrophysics Data System (ADS)

Kubota, Kaoru; Shirai, Kotaro; Murakami-Sugihara, Naoko; Seike, Koji; Minami, Masayo; Nakamura, Toshio; Tanabe, Kazushige

2018-04-01

The excess radiocarbon produced by nuclear bomb testing in the atmosphere in the 1950s-1960s (bomb-14C) is used as a tracer in the surface ocean, extending our understanding of geophysics and biogeochemical cycles. However, there is no bomb-14C record for the high-latitude western North Pacific Ocean because of the paucity of long-lived marine calcifying organisms equivalent to reef-building corals. The shells of Stimpson's hard clam, Mercenaria stimpsoni, potentially provide such a record because the clam's lifespan is very long (>100 years). We analyzed 14C in six live-caught M. stimpsoni shells from the western North Pacific (39.4°N, 142°E) and report, for the first time, the bomb-14C record with robust calendar ages based on annual growth increments. The value was constant in 1934-1952 (Δ14C = -66‰), with a sudden increase in 1959, a peak in 1974 (107‰), which was 60‰ lower than that of the Kuroshio Current, a gradual decline after 1974, and a current value of 16-18‰, which is ˜10‰ higher than the atmospheric value. The bomb-14C values are between the Kuroshio Current (the northwestern subtropical gyre) and Oyashio Current (the Western Subarctic Gyre) values, suggesting that the Tsugaru Current, downstream from the Kuroshio Current, mixes with the Oyashio Current after passing through Tsugaru Strait.

Toward large-scale solar energy systems with peak concentrations of 20,000 suns

NASA Astrophysics Data System (ADS)

Kribus, Abraham

1997-10-01

The heliostat field plays a crucial role in defining the achievable limits for central receiver system efficiency and cost. Increasing system efficiency, thus reducing the reflective area and system cost, can be achieved by increasing the concentration and the receiver temperature. The concentration achievable in central receiver plants, however, is constrained by current heliostat technology and design practices. The factors affecting field performance are surface and tracking errors, astigmatism, shadowing, blocking and dilution. These are geometric factors that can be systematically treated and reduced. We present improvements in collection optics and technology that may boost concentration (up to 20,000 peak), achievable temperature (2,000 K), and efficiency in solar central receiver plants. The increased performance may significantly reduce the cost of solar energy in existing applications, and enable solar access to new ultra-high-temperature applications, such as: future gas turbines approaching 60% combined cycle efficiency; high-temperature thermo-chemical processes; and gas-dynamic processes.

Changes in streamflow characteristics in Wisconsin as related to precipitation and land use

USGS Publications Warehouse

Gebert, Warren A.; Garn, Herbert S.; Rose, William J.

2016-01-19

Streamflow characteristics were determined for 15 longterm streamflow-gaging stations for the periods 1915–2008, 1915–68, and 1969–2008 to identify trends. Stations selected represent flow characteristics for the major river basins in Wisconsin. Trends were statistically significant at the 95 percent confidence level at 13 of the 15 streamflow-gaging stations for various streamflow characteristics for 1915–2008. Most trends indicated increases in low flows for streams with agriculture as the dominant land use. The three most important findings are: increases in low flows and average flows in agricultural watersheds, decreases in flood peak discharge for many streams in both agricultural and forested watersheds, and climatic change occurred with increasing annual precipitation and changes in monthly occurrence of precipitation. When the 1915–68 period is compared to the 1969–2008 period, the annual 7-day low flow increased an average of 60 percent for nine streams in agricultural areas as compared to a 15 percent increase for the five forested streams. Average annual flow for the same periods increased 23 percent for the agriculture streams and 0.6 percent for the forested streams. The annual flood peak discharge for the same periods decreased 15 percent for agriculture streams and 8 percent for forested streams. The largest increase in the annual 7-day low flow was 117 percent, the largest increase in annual average flow was 41 percent, and the largest decrease in annual peak discharge was 51 percent. The trends in streamflow characteristics affect frequency characteristics, which are used for a variety of design and compliance purposes. The frequencies for the 1969–2008 period were compared to frequencies for the 1915–68 period. The 7-day, 10-year (Q7, 10) low flow increased 91 percent for nine agricultural streams, while the five forested streams had an increase of 18 percent. The 100-year flood peak discharge decreased an average of 15 percent for streams in the agriculture area and 27 percent for streams in the forested area. Increases in low flow for agriculture streams are attributed to changes in agricultural practices and land use as well as increased precipitation. The decrease in annual flood peak discharge with increased annual precipitation is less clear, but is attributed to increased infiltration from changes in agricultural practices and climatic changes. For future low-flow studies, the 1969–2008 period should be used to determine low-flow characteristics since it represents current (2014) conditions and was generally free of significant trends.

In vitro effects of recombinant activated factor VII on thrombin generation and coagulation following inhibition of platelet procoagulant activity by prasugrel.

PubMed

Mazzeffi, Michael; Szlam, Fania; Jakubowski, Joseph A; Tanaka, Kenichi A; Sugidachi, Atsuhiro; Levy, Jerrold H

2013-07-01

Prasugrel is a thienopyridyl P2Y12 antagonist with potent antiplatelet effects. At present, little is known about its effects on thrombin generation or what strategies may emergently reverse its anticoagulant effects. In the current study we evaluated whether recombinant activated factor VII may reverse prasugrel induced effects and increase thrombin generation in an in vitro model. The effect of prasugrel active metabolite, PAM (R-138727), was evaluated on platelet aggregation, thrombin generation, and rotational thromboelastometry parameters using blood from 20 healthy volunteers. Additionally, we evaluated the effects of adenosine diphosphate (ADP) and recombinant activated factor VII on restoring these parameters towards baseline values. PAM reduced maximum platelet aggregation and led to platelet disaggregation. It also decreased peak thrombin, increased lag time, and increased time to peak thrombin. Treatment with recombinant activated factor VII restored all three parameters of thrombin generation towards baseline. ADP decreased lag time and time to peak thrombin, but had no effect on peak thrombin. When recombinant activated factor VII and ADP were combined they had a greater effect on thrombin parameters than either drug alone. PAM also increased thromboelastometric clotting time and clot formation time, but had no effect on maximum clot firmness. Treatment with either recombinant activated factor VII or ADP restored these values towards baseline. Recombinant activated factor VII restores thrombin generation in the presence of PAM. In patients taking prasugrel with life-threatening refractory bleeding it has the potential to be a useful therapeutic approach. Additional clinical studies are needed to validate our findings. Copyright © 2013 Elsevier Ltd. All rights reserved.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stoltzfus-Dueck, T.; Scott, B.

An often-neglected portion of the radialmore » $$\\boldsymbol{E}\\times \\boldsymbol{B}$$ drift is shown to drive an outward flux of co-current momentum when free energy is transferred from the electrostatic potential to ion parallel flows. This symmetry breaking is fully nonlinear, not quasilinear, necessitated simply by free-energy balance in parameter regimes for which significant energy is dissipated via ion parallel flows. The resulting rotation peaking is counter-current and has a scaling and order of magnitude that are comparable with experimental observations. Finally, the residual stress becomes inactive when frequencies are much higher than the ion transit frequency, which may explain the observed relation of density peaking and counter-current rotation peaking in the core.« less

Electrochemical detection of copper ions leached from CuO nanoparticles in saline buffers and biological media using a gold wire working electrode

NASA Astrophysics Data System (ADS)

Baldisserri, Carlo; Costa, Anna Luisa

2016-04-01

We performed explorative cyclic voltammetry in phosphate-buffered saline buffers, Dulbecco's modified Eagle's medium (DMEM), and fetal bovine serum-added DMEM using Au wire as working electrode, both in the absence and in the presence of known nominal concentrations of Cu2+ ions or 15 nm CuO nanoparticles. Addition of either Cu2+ ions or aqueous suspension of CuO nanoparticles caused a single anodic peak to appear in the double-layer region of all three pristine media. The height of the anodic peak was found to increase in a monotonic fashion vs. Cu2+ concentration in Cu2+-added media, and versus time since CuO addition in CuO-added media. Stepwise addition of glycine to Cu2+-added phosphate-buffered saline buffer caused an increasing cathodic shift of the anodic peak accompanied by decreasing peak currents. Results indicate that preparing Cu2+-free suspensions of CuO nanoparticles in such media is difficult, owing to the presence of leached copper ions. The implications on results of experiments in which CuO nanoparticle-added biological media are used as cell culture substrates are discussed. Literature data on the interactions between Cu2+ ions, dissolved carbon dioxide in aqueous CuO suspensions, and amino acids present in such media are compared to our results.

Hydrodynamic flow in capillary-channel fiber columns for liquid chromatography.

PubMed

Stanelle, Rayman D; Sander, Lane C; Marcus, R Kenneth

2005-12-23

The flow characteristics of capillary-channel polymer (C-CP) fiber liquid chromatographic (LC) columns have been investigated. The C-CP fibers are manufactured with eight longitudinal grooves (capillary channels) extending the length of the fibers. Three C-CP fiber examples were studied, with fiber dimensions ranging from approximately 35 microm to 65 microm, and capillary-channel dimensions ranging from approximately 6 microm to 35 microm. The influence of fiber packing density and column inner diameter on peak asymmetry, peak width, and run-to-run reproducibility have been studied for stainless steel LC columns packed with polyester (PET) and polypropylene (PP) C-CP fibers. The van Deemter A-term was evaluated as a function of fiber packing density (approximately 0.3 g/cm(3)-0.75 g/cm(3)) for columns of 4.6 mm inner diameter (i.d.) and at constant packing densities for 1.5 mm, 3.2 mm, 4.6 mm, and 7.7 mm i.d. columns. Although column diameter had little influence on the eluting peak widths, peak asymmetry increased with increasing column diameter. The A-terms for the C-CP fiber packed columns are somewhat larger than current commercial, microparticulate-packed columns, and means for improvement are discussed. Applications in the area of protein (macromolecule) separations appear the most promising at this stage of the system development.

Electrochemical determination of paraquat in citric fruit based on electrodeposition of silver particles onto carbon paste electrode.

PubMed

Farahi, Abdelfettah; Achak, Mounia; El Gaini, Laila; El Mhammedi, Moulay Abderrahim; Bakasse, Mina

2015-09-01

Carbon paste electrodes (CPEs) modified with silver particles present an interesting tool in the determination of paraquat (PQ) using square wave voltammetry. Metallic silver particle deposits have been obtained via electrochemical deposition in acidic media using cyclic voltammetry. Scanning electron microscopy and X-ray diffraction measurements show that the silver particles are deposited onto carbon surfaces in aggregate form. The response of PQ with modified electrode (Ag-CPE) related to Ag/CP loading, preconcentration time, and measuring solution pH was investigated. The result shows that the increase in the two cathodic peak currents (Peak 1 and Peak 2), under optimized conditions, was linear with the increase in PQ concentration in the range 1.0 × 10 -7  mol/L to 1.0 × 10 -3  mol/L. The detection limit and quantification limit were 2.01 × 10 -8  mol/L and 6.073 × 10 -8  mol/L, respectively for Peak 1. The precision expressed as relative standard deviation for the concentration level 1.0 × 10 -5  mol/L (n = 8) was found to be 1.45%. The methodology was satisfactorily applied for the determination of PQ in citric fruit cultures. Copyright © 2015. Published by Elsevier B.V.

Onset of hydrodynamic mix in high-velocity, highly compressed inertial confinement fusion implosions.

PubMed

Ma, T; Patel, P K; Izumi, N; Springer, P T; Key, M H; Atherton, L J; Benedetti, L R; Bradley, D K; Callahan, D A; Celliers, P M; Cerjan, C J; Clark, D S; Dewald, E L; Dixit, S N; Döppner, T; Edgell, D H; Epstein, R; Glenn, S; Grim, G; Haan, S W; Hammel, B A; Hicks, D; Hsing, W W; Jones, O S; Khan, S F; Kilkenny, J D; Kline, J L; Kyrala, G A; Landen, O L; Le Pape, S; MacGowan, B J; Mackinnon, A J; MacPhee, A G; Meezan, N B; Moody, J D; Pak, A; Parham, T; Park, H-S; Ralph, J E; Regan, S P; Remington, B A; Robey, H F; Ross, J S; Spears, B K; Smalyuk, V; Suter, L J; Tommasini, R; Town, R P; Weber, S V; Lindl, J D; Edwards, M J; Glenzer, S H; Moses, E I

2013-08-23

Deuterium-tritium inertial confinement fusion implosion experiments on the National Ignition Facility have demonstrated yields ranging from 0.8 to 7×10(14), and record fuel areal densities of 0.7 to 1.3 g/cm2. These implosions use hohlraums irradiated with shaped laser pulses of 1.5-1.9 MJ energy. The laser peak power and duration at peak power were varied, as were the capsule ablator dopant concentrations and shell thicknesses. We quantify the level of hydrodynamic instability mix of the ablator into the hot spot from the measured elevated absolute x-ray emission of the hot spot. We observe that DT neutron yield and ion temperature decrease abruptly as the hot spot mix mass increases above several hundred ng. The comparison with radiation-hydrodynamic modeling indicates that low mode asymmetries and increased ablator surface perturbations may be responsible for the current performance.

Observation and measurement of negative differential resistance on PtSi Schottky junctions on porous silicon.

PubMed

Banihashemian, Seyedeh Maryam; Hajghassem, Hassan; Erfanian, Alireza; Aliahmadi, Majidreza; Mohtashamifar, Mansor; Mosakazemi, Seyed Mohamadhosein

2010-01-01

Nanosize porous Si is made by two step controlled etching of Si. The first etching step is carried on the Si surface and the second is performed after deposition of 75 Å of platinum on the formed surface. A platinum silicide structure with a size of less than 25 nm is formed on the porous Si surface, as measured with an Atomic Forced Microscope (AFM). Differential resistance curve as a function of voltage in 77 K and 100 K shows a negative differential resistance and indicates the effect of quantum tunneling. In general form, the ratio of maximum to minimum tunneling current (PVR) and the number of peaks in I-V curves reduces by increasing the temperature. However, due to accumulation of carriers behind the potential barrier and superposition of several peaks, it is observed that the PVR increases at 100 K and the maximum PVR at 100 K is 189.6.

Coral mass spawning predicted by rapid seasonal rise in ocean temperature

PubMed Central

Maynard, Jeffrey A.; Edwards, Alasdair J.; Guest, James R.; Rahbek, Carsten

2016-01-01

Coral spawning times have been linked to multiple environmental factors; however, to what extent these factors act as generalized cues across multiple species and large spatial scales is unknown. We used a unique dataset of coral spawning from 34 reefs in the Indian and Pacific Oceans to test if month of spawning and peak spawning month in assemblages of Acropora spp. can be predicted by sea surface temperature (SST), photosynthetically available radiation, wind speed, current speed, rainfall or sunset time. Contrary to the classic view that high mean SST initiates coral spawning, we found rapid increases in SST to be the best predictor in both cases (month of spawning: R2 = 0.73, peak: R2 = 0.62). Our findings suggest that a rapid increase in SST provides the dominant proximate cue for coral mass spawning over large geographical scales. We hypothesize that coral spawning is ultimately timed to ensure optimal fertilization success. PMID:27170709

Long-Term Visuo-Gustatory Appetitive and Aversive Conditioning Potentiate Human Visual Evoked Potentials

PubMed Central

Christoffersen, Gert R. J.; Laugesen, Jakob L.; Møller, Per; Bredie, Wender L. P.; Schachtman, Todd R.; Liljendahl, Christina; Viemose, Ida

2017-01-01

Human recognition of foods and beverages are often based on visual cues associated with flavors. The dynamics of neurophysiological plasticity related to acquisition of such long-term associations has only recently become the target of investigation. In the present work, the effects of appetitive and aversive visuo-gustatory conditioning were studied with high density EEG-recordings focusing on late components in the visual evoked potentials (VEPs), specifically the N2-P3 waves. Unfamiliar images were paired with either a pleasant or an unpleasant juice and VEPs evoked by the images were compared before and 1 day after the pairings. In electrodes located over posterior visual cortex areas, the following changes were observed after conditioning: the amplitude from the N2-peak to the P3-peak increased and the N2 peak delay was reduced. The percentage increase of N2-to-P3 amplitudes was asymmetrically distributed over the posterior hemispheres despite the fact that the images were bilaterally symmetrical across the two visual hemifields. The percentage increases of N2-to-P3 amplitudes in each experimental subject correlated with the subject’s evaluation of positive or negative hedonic valences of the two juices. The results from 118 scalp electrodes gave surface maps of theta power distributions showing increased power over posterior visual areas after the pairings. Source current distributions calculated from swLORETA revealed that visual evoked currents rose as a result of conditioning in five cortical regions—from primary visual areas and into the inferior temporal gyrus (ITG). These learning-induced changes were seen after both appetitive and aversive training while a sham trained control group showed no changes. It is concluded that long-term visuo-gustatory conditioning potentiated the N2-P3 complex, and it is suggested that the changes are regulated by the perceived hedonic valence of the US. PMID:28983243

Modeled future peak streamflows in four coastal Maine rivers

USGS Publications Warehouse

Hodgkins, Glenn A.; Dudley, Robert W.

2013-01-01

To safely and economically design bridges and culverts, it is necessary to compute the magnitude of peak streamflows that have specified annual exceedance probabilities (AEPs). Annual precipitation and air temperature in the northeastern United States are, in general, projected to increase during the 21st century. It is therefore important for engineers and resource managers to understand how peak flows may change in the future. This report, prepared in cooperation with the Maine Department of Transportation (MaineDOT), presents modeled changes in peak flows at four basins in coastal Maine on the basis of projected changes in air temperature and precipitation. To estimate future peak streamflows at the four basins in this study, historical values for climate (temperature and precipitation) in the basins were adjusted by different amounts and input to a hydrologic model of each study basin. To encompass the projected changes in climate in coastal Maine by the end of the 21st century, air temperatures were adjusted by four different amounts, from -3.6 degrees Fahrenheit (ºF) (-2 degrees Celsius (ºC)) to +10.8 ºF (+6 ºC) of observed temperatures. Precipitation was adjusted by three different percentage values from -15 percent to +30 percent of observed precipitation. The resulting 20 combinations of temperature and precipitation changes (includes the no-change scenarios) were input to Precipitation-Runoff Modeling System (PRMS) watershed models, and annual daily maximum peak flows were calculated for each combination. Modeled peak flows from the adjusted changes in temperature and precipitation were compared to unadjusted (historical) modeled peak flows. Annual daily maximum peak flows increase or decrease, depending on whether temperature or precipitation is adjusted; increases in air temperature (with no change in precipitation) lead to decreases in peak flows, whereas increases in precipitation (with no change in temperature) lead to increases in peak flows. As the magnitude of air temperatures increase in the four basins, peak flows decrease by larger amounts. If precipitation is held constant (no change from historical values), 17 to 26 percent decreases in peak flow occur at the four basins when temperature is increased by 7.2°F. If temperature is held constant, 26 to 38 percent increases in peak flow result from a 15-percent increase in precipitation. The largest decreases in peak flows at the four basins result from 15-percent decreases in precipitation combined with temperature increases of 10.8°F. The largest increases in peak flows generally result from 30-percent increases in precipitation combined with 3.6 °F decreases in temperatures. In many cases when temperature and precipitation both increase, small increases or decreases in annual daily maximum peak flows result. For likely changes projected for the northeastern United States for the middle of the 21st century (temperature increase of 3.6 °F and precipitation increases of 0 to 15 percent), peak-flow changes at the four coastal Maine basins in this study are modeled to be evenly distributed between increases and decreases of less than 25 percent. Peak flows with 50-percent and 1-percent AEPs (equivalent to 2-year and 100-year recurrence interval peak flows, respectively) were calculated for the four basins in the study using the PRMS-modeled annual daily maximum peak flows. Modeled peak flows with 50-percent and 1-percent AEPs with adjusted temperatures and precipitation were compared to unadjusted (historical) modeled values. Changes in peak flows with 50-percent AEPs are similar to changes in annual daily maximum peak flow; changes in peak flows with 1-percent AEPs are similar in pattern to changes in annual daily maximum peak flow, but some of the changes associated with increasing precipitation are much larger than changes in annual daily maximum peak flow. Substantial decreases in maximum annual winter snowpack water equivalent are modeled to occur with increasing air temperatures at the four basins in the study. (Snowpack is the snow on the ground that accumulates during a winter, and water equivalent is the amount of water in a snowpack if it were melted.) The decrease in modeled peak flows with increasing air temperature, given no change in precipitation amount, is likely caused by these decreases in winter snowpack and resulting decreases in snowmelt runoff. This Scientific Investigations Report, prepared in cooperation with the Maine Department of Transportation, presents a summary of modeled changes in peak flows at four basins in coastal Maine on the basis of projected changes in air temperature and precipitation. The full Fact Sheet (Hodgkins and Dudley, 2013) is available at http://pubs.usgs.gov/fs/2013/3021/.

B-973, a novel piperazine positive allosteric modulator of the α7 nicotinic acetylcholine receptor.

PubMed

Post-Munson, Debra J; Pieschl, Rick L; Molski, Thaddeus F; Graef, John D; Hendricson, Adam W; Knox, Ronald J; McDonald, Ivar M; Olson, Richard E; Macor, John E; Weed, Michael R; Bristow, Linda J; Kiss, Laszlo; Ahlijanian, Michael K; Herrington, James

2017-03-15

The alpha7 (α7) nicotinic acetylcholine receptor is a therapeutic target for cognitive disorders. Here we describe 3-(3,4-difluorophenyl)-N-(1-(6-(4-(pyridin-2-yl)piperazin-1-yl)pyrazin-2-yl)ethyl)propanamide (B-973), a novel piperazine-containing molecule that acts as a positive allosteric modulator of the α7 receptor. We characterize the action of B-973 on the α7 receptor using electrophysiology and radioligand binding. At 0.1mM acetylcholine, 1μM B-973 potentiated peak acetylcholine-induced currents 6-fold relative to maximal acetylcholine (3mM) and slowed channel desensitization, resulting in a 6900-fold increase in charge transfer. The EC 50 of B-973 was approximately 0.3μM at acetylcholine concentrations ranging from 0.03 to 3mM. At a concentration of 1μM, B-973 shifted the acetylcholine EC 50 of peak currents from 0.30mM in control to 0.007mM. B-973 slowed channel deactivation upon acetylcholine removal (τ=50s) and increased the affinity of the α7 agonist [ 3 H]A-585539. In the absence of exogenously added acetylcholine, application of B-973 at concentrations >1μM induced large methyllycaconitine-sensitive currents, suggesting B-973 can function as an Ago-PAM at high concentrations. B-973 will be a useful probe for investigating the biological consequences of increasing α7 receptor activity through allosteric modulation. Copyright © 2017 Elsevier B.V. All rights reserved.

Excitation Patterns of Standard and Steered Partial Tripolar Stimuli in Cochlear Implants.

PubMed

Wu, Ching-Chih; Luo, Xin

2016-04-01

Current steering in partial tripolar (pTP) mode has been shown to improve pitch perception and spectral resolution with cochlear implants (CIs). In this mode, a fraction (σ) of the main electrode current is returned within the cochlea and steered between the basal and apical flanking electrodes (with a proportion of α and 1 - α, respectively). Pitch generally decreases when α increases from 0 to 1, although the salience of pitch change varies across CI users. This study aimed to identify the mechanism of pitch changes with pTP-mode current steering and the factors contributing to the intersubject variability in pitch-ranking sensitivity. The electrical fields were measured for steered pTP stimuli on the same main electrode with α = 0, 0.5, and 1 in five implanted ears using electrical field imaging (EFI). The related excitation patterns were also measured physiologically using evoked compound action potential (ECAP) and psychophysically using psychophysical forward masking (PFM). Consistent with the pitch-ranking results in this study, the EFI, ECAP, and PFM centroids shifted apically with increasing α. An apical shift was also observed for the PFM peak but not for the EFI or ECAP peak. The pattern width was similar with different α values within a given measure (e.g., EFI, ECAP, or PFM), but the ECAP patterns were broader than the EFI and PFM patterns, possibly because ECAP was measured with smaller σ values than EFI and PFM. The amount of pattern shift with α depended on σ (i.e., the total amount of current used for steering) but was not correlated with the pitch-ranking sensitivity across subjects. The results revealed that the pitch changes elicited by pTP-mode current steering were not only driven by the shifts of excitation centroid.

Photoelectrochemical Stability and Alteration Products of n-Type Single-Crystal ZnO Photoanodes

DOE PAGES

Paulauskas, I. E.; Jellison, G. E.; Boatner, L. A.; ...

2011-01-01

The photoelectrochemical stability and surface-alteration characteristics of doped and undoped n-type ZnO single-crystal photoanode electrodes were investigated. The single-crystal ZnO photoanode properties were analyzed using current-voltage measurements plus spectral and time-dependent quantum-yield methods. These measurements revealed a distinct anodic peak and an accompanying cathodic surface degradation process at negative potentials. The features of this peak depended on time and the NaOH concentration in the electrolyte, but were independent of the presence of electrode illumination. Current measurements performed at the peak indicate that charging and discharging effects are apparently taking place at the semiconductor/electrolyte interface. This result is consistent with themore » significant reactive degradation that takes place on the ZnO single crystal photoanode surface and that ultimately leads to the reduction of the ZnO surface to Zn metal. The resulting Zn-metal reaction products create unusual, dendrite-like, surface alteration structural features that were analyzed using x-ray diffraction, energy-dispersive analysis, and scanning electron microscopy. ZnO doping methods were found to be effective in increasing the n-type character of the crystals. Higher doping levels result in smaller depletion widths and lower quantum yields, since the minority carrier diffusion lengths are very short in these materials.« less

Voltammetric Response of Alizarin Red S-Confined Film-Coated Electrodes to Diol and Polyol Compounds: Use of Phenylboronic Acid-Modified Poly(ethyleneimine) as Film Component

PubMed Central

Takahashi, Shigehiro; Suzuki, Iwao; Ojima, Takuto; Minaki, Daichi

2018-01-01

Alizarin red S (ARS) was confined in layer-by-layer (LbL) films composed of phenylboronic acid-modified poly(ethyleneimine) (PBA-PEI) and carboxymethylcellulose (CMC) to study the voltammetric response to diol and polyol compounds. The LbL film-coated gold (Au) electrode and quartz slide were immersed in an ARS solution to uptake ARS into the film. UV-visible absorption spectra of ARS-confined LbL film suggested that ARS formed boronate ester (ARS-PBS) in the film. The cyclic voltammetry of the ARS-confined LbL film-coated electrodes exhibited oxidation peaks at −0.50 and −0.62 V, which were ascribed to the oxidation reactions of ARS-PBS and free ARS, respectively, in the LbL film. The peak current at −0.62 V increased upon the addition of diol or polyol compounds such as L-dopa, glucose, and sorbitol into the solution, depending on the concentration, whereas the peak current at −0.50 V decreased. The results suggest a possible use of ARS-confined PBA-PEI/CMC LbL film-coated Au electrodes for the construction of voltammetric sensors for diol and polyol compounds. PMID:29361775

Design and fabrication of low power GaAs/AlAs resonant tunneling diodes

NASA Astrophysics Data System (ADS)

Md Zawawi, Mohamad Adzhar; Missous, Mohamed

2017-12-01

A very low peak voltage GaAs/AlAs resonant tunneling diode (RTD) grown by molecular beam epitaxy (MBE) has been studied in detail. Excellent growth control with atomic-layer precision resulted in a peak voltage of merely 0.28 V (0.53 V) in forward (reverse) direction. The peak current density in forward bias is around 15.4 kA/cm2 with variation of within 7%. As for reverse bias, the peak current density is around 22.8 kA/cm2 with 4% variation which implies excellent scalability. In this work, we have successfully demonstrated the fabrication of a GaAs/AlAs RTD by using a conventional optical lithography and chemical wet-etching with very low peak voltage suitable for application in low dc input power RTD-based sub-millimetre wave oscillators.

Sensor-triggered sampling to determine instantaneous airborne vapor exposure concentrations.

PubMed

Smith, Philip A; Simmons, Michael K; Toone, Phillip

2018-06-01

It is difficult to measure transient airborne exposure peaks by means of integrated sampling for organic chemical vapors, even with very short-duration sampling. Selection of an appropriate time to measure an exposure peak through integrated sampling is problematic, and short-duration time-weighted average (TWA) values obtained with integrated sampling are not likely to accurately determine actual peak concentrations attained when concentrations fluctuate rapidly. Laboratory analysis for integrated exposure samples is preferred from a certainty standpoint over results derived in the field from a sensor, as a sensor user typically must overcome specificity issues and a number of potential interfering factors to obtain similarly reliable data. However, sensors are currently needed to measure intra-exposure period concentration variations (i.e., exposure peaks). In this article, the digitized signal from a photoionization detector (PID) sensor triggered collection of whole-air samples when toluene or trichloroethylene vapors attained pre-determined levels in a laboratory atmosphere generation system. Analysis by gas chromatography-mass spectrometry of whole-air samples (with both 37 and 80% relative humidity) collected using the triggering mechanism with rapidly increasing vapor concentrations showed good agreement with the triggering set point values. Whole-air samples (80% relative humidity) in canisters demonstrated acceptable 17-day storage recoveries, and acceptable precision and bias were obtained. The ability to determine exceedance of a ceiling or peak exposure standard by laboratory analysis of an instantaneously collected sample, and to simultaneously provide a calibration point to verify the correct operation of a sensor was demonstrated. This latter detail may increase the confidence in reliability of sensor data obtained across an entire exposure period.

Monitoring vegetation dynamics with medium resolution MODIS-EVI time series at sub-regional scale in southern Africa

NASA Astrophysics Data System (ADS)

Dubovyk, Olena; Landmann, Tobias; Erasmus, Barend F. N.; Tewes, Andreas; Schellberg, Jürgen

2015-06-01

Currently there is a lack of knowledge on spatio-temporal patterns of land surface dynamics at medium spatial scale in southern Africa, even though this information is essential for better understanding of ecosystem response to climatic variability and human-induced land transformations. In this study, we analysed vegetation dynamics across a large area in southern Africa using the 14-years (2000-2013) of medium spatial resolution (250 m) MODIS-EVI time-series data. Specifically, we investigated temporal changes in the time series of key phenometrics including overall greenness, peak and timing of annual greenness over the monitoring period and study region. In order to specifically capture spatial and per pixel vegetation changes over time, we calculated trends in these phenometrics using a robust trend analysis method. The results showed that interannual vegetation dynamics followed precipitation patterns with clearly differentiated seasonality. The earliest peak greenness during 2000-2013 occurred at the end of January in the year 2000 and the latest peak greenness was observed at the mid of March in 2012. Specifically spatial patterns of long-term vegetation trends allowed mapping areas of (i) decrease or increase in overall greenness, (ii) decrease or increase of peak greenness, and (iii) shifts in timing of occurrence of peak greenness over the 14-year monitoring period. The observed vegetation decline in the study area was mainly attributed to human-induced factors. The obtained information is useful to guide selection of field sites for detailed vegetation studies and land rehabilitation interventions and serve as an input for a range of land surface models.

Plasma fluctuations in a Kaufman thruster

NASA Technical Reports Server (NTRS)

Serafini, J. S.; Terdan, F. F.

1973-01-01

Measurements of the RMS magnitude, spectra, and cross correlations for the fluctuations in the beam, discharge, and neutralizer keeper currents are presented for a 30 cm diameter dished grid ion thruster for a range of magnetic baffle currents. The ratio of RMS to mean ion beam current varied from 0.04 to 0.23. The spectra of the amplitudes of the beam and discharge current fluctuations were taken up to 9 MHz and show that the predominant amplitudes occur at frequencies of 10 kHz or below. The falloff with increasing frequency is rapid. Frequencies above 100 kHz the spectral levels are 45 kb or more below the maximum peak amplitudes. The cross correlations revealed the ion beam fluctuations to have large radial and axial scales.

Toxicity of graphene nanoflakes evaluated by cell-based electrochemical impedance biosensing.

PubMed

Yoon, Ok Ja; Kim, Insu; Sohn, Il Yung; Kieu, Truong Thuy; Lee, Nae-Eung

2014-07-01

Graphene nanoflake toxicity was analyzed using cell-based electrochemical impedance biosensing with interdigitated indium tin oxide (ITO) electrodes installed in a custom-built mini-incubator positioned on an inverted optical microscope. Sensing with electrochemical measurements from interdigitated ITO electrodes was highly linear (R(2) = 0.93 and 0.96 for anodic peak current (Ipa) and cathodic peak current (Ipc), respectively). Size-dependent analysis of Graphene nanoflake toxicity was carried out in a mini-incubator system with cultured HeLa cells treated with Graphene nanoflakes having an average size of 80 or 30 nm for one day. Biological assays of cell proliferation and viability complemented electrochemical impedance measurements. The increased toxicity of smaller Graphene nanoflakes (30 nm) as measured by electrochemical impedance sensing and optical monitoring of treated cells was consistent with the biological assay results. Cell-based electrochemical impedance biosensing can be used to assess the toxicity of nanomaterials with different biomedical and environmental applications. © 2013 Wiley Periodicals, Inc.

Evaluating the Magnitude and Duration of Cold Load Pick-up on Residential Distribution Feeders Using Multi-State Load Models

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schneider, Kevin P.; Sortomme, Eric; Venkata, S. S.

The increased level of demand that is associated with the restoration of service after an outage, Cold Load Pick-Up (CLPU), can be significantly higher than pre-outage levels, even exceeding the normal distribution feeder peak demand. These high levels of demand can delay restoration efforts and in extreme cases damage equipment. The negative impacts of CLPU can be mitigated with strategies that restore the feeder in sections, minimizing the load current. The challenge for utilities is to manage the current level on critical equipment while minimizing the time to restore service to all customers. Accurately modeling CLPU events is the firstmore » step in developing improved restoration strategies that minimize restoration times. This paper presents a new method for evaluating the magnitude of the CLPU peak, and its duration, using multi-state load models. The use of multi-state load models allows for a more accurate representation of the end-use loads that are present on residential distribution feeders.« less

Influence of InGaN sub-quantum-well on performance of InAlN/GaN/InAlN resonant tunneling diodes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, Haoran; Yang, Lin'an, E-mail: layang@xidian.edu.cn; Hao, Yue

The resonant tunneling mechanism of the GaN based resonant tunneling diode (RTD) with an InGaN sub-quantum-well has been investigated by means of numerical simulation. At resonant-state, Electrons in the InGaN/InAlN/GaN/InAlN RTD tunnel from the emitter region through the aligned discrete energy levels in the InGaN sub-quantum-well and GaN main-quantum-well into the collector region. The implantation of the InGaN sub-quantum-well alters the dominant transport mechanism, increase the transmission coefficient and give rise to the peak current and peak-to-valley current ratio. We also demonstrate that the most pronounced negative-differential-resistance characteristic can be achieved by choosing appropriately the In composition of In{sub x}Ga{submore » 1−x}N at around x = 0.06.« less

Fabrication of n-ZnO:Al/p-Si(100) heterojunction diode and its characterization

NASA Astrophysics Data System (ADS)

Parvathy Venu, M.; Dharmaprakash, S. M.; Byrappa, K.

2018-04-01

Aluminum doped ZnO (n-ZnO:Al) nanostructured thin films were grown on ZnO seed layer coated p-Si(100) substrate employing hydrothermal technique. X-ray diffraction pattern revealed that the ZnO:Al film possess hexagonal wurtzite structure with preferential orientation along (002) direction. Photoluminescence of the sample displayed near band edge emission peak in the ultra-violet region and defect level emission peak in the visible region. The as grown thin film was used in the fabrication of n-ZnO:Al/p-Si heterojunction diode and the room temperature current-voltage (I-V) and capacitance-voltage (C-V) characteristics were studied. The heterojunction exhibited fairly good rectification with an ideality of 2.49 and reverse saturation current of 2 nA. The barrier height was found to be 0.668 eV from the I-V measurements. The C-V measurements showed a decrease in the capacitance of the heterojunction with an increase in the reverse bias voltage.

Transverse emittance-preserving arc compressor for high-brightness electron beam-based light sources and colliders

NASA Astrophysics Data System (ADS)

Di Mitri, S.; Cornacchia, M.

2015-03-01

Bunch length magnetic compression is used in high-brightness linacs driving free-electron lasers (FELs) and particle colliders to increase the peak current of the injected beam. To date, it is performed in dedicated insertions made of few degrees bending magnets and the compression factor is limited by the degradation of the beam transverse emittance owing to emission of coherent synchrotron radiation (CSR). We reformulate the known concept of CSR-driven optics balance for the general case of varying bunch length and demonstrate, through analytical and numerical results, that a 500 pC charge beam can be time-compressed in a periodic 180 deg arc at 2.4 GeV beam energy and lower, by a factor of up to 45, reaching peak currents of up to 2 kA and with a normalized emittance growth at the 0.1 μ \\text{m} rad level. The proposed solution offers new schemes of beam longitudinal gymnastics; an application to an energy recovery linac driving FEL is discussed.

A contraction-related component of slow inward current in dog ventricular muscle and its relation to Na(+)-Ca2+ exchange.

PubMed Central

Simurda, J; Simurdová, M; Bravený, P; Sumbera, J

1992-01-01

1. The slow inward current component related to contraction (Isic) was studied in voltage clamp experiments on canine ventricular trabeculae at 30 degrees C with the aims of (a) estimating its relation to electrogenic Na(+)-Ca2+ exchange and (b) comparing it with similar currents as reported in cardiac myocytes. 2. Isic may be recorded under conditions of augmented contractility in response to depolarizing pulses below the threshold of the classic slow inward current (presumably mediated by L-type Ca2+ channels). In responses to identical depolarizing clamp pulses the peak value of Isic is directly related to the amplitude of contraction (Fmax). Isic peaks about 60 ms after the onset of depolarization and declines with a half-time of about 110 ms. 3. The voltage threshold of Isic activation is the same as the threshold of contraction. The positive inotropic clamp preconditions shift both thresholds to more negative values of membrane voltage, i.e. below the threshold of the classic slow inward current. 4. Isic may also be recorded as a slowly decaying inwardly directed current 'tail' after depolarizing pulses. In this representation the peak value of Isic changes with duration of the depolarizing pulses, again in parallel with Fmax. In response to pulses shorter than 100 ms both variables increase with depolarization time. If initial conditions remain constant, further prolongation of the pulse does not significantly influence either one (tail currents follow a common envelope). 5. Isic differs from classic slow inward current by: (a) its direct relation to contraction, (b) the slower decay of the current tail on repolarization, (c) slower restitution corresponding to the mechanical restitution, (d) its relative insensitivity to Ca(2+)-blocking agents (the decrease of Isic is secondary to the negative inotropic of Ca(2+)-blocking agents (the decrease of Isic is secondary to the negative inotropic effect) and (e) its disappearance after Sr2+ substitution for Ca2+. 6. The manifestations of Isic in multicellular preparations do not differ significantly from those reported in isolated myocytes (in contrast to calcium current). 7. The analysis of the correlation between Isic and Fmax transients during trains of identical test depolarizing pulses at variable extra- and intracellular ionic concentrations (changes of [Ca2+]o, 50% Li+ substitution for Na+, strophanthidin) indicate that the observed effects conform to the predictions based on a quantitative model of Na(+)-Ca2+ exchange. 8. It is concluded that Isic is activated by a transient increase of [Ca2+]i, in consequence of the release from the reticular stores.(ABSTRACT TRUNCATED AT 400 WORDS) PMID:1293284

Environmental variation and macrofauna response in a coastal area influenced by land runoff

NASA Astrophysics Data System (ADS)

Akoumianaki, Ioanna; Papaspyrou, Sokratis; Kormas, Konstantinos Ar.; Nicolaidou, Artemis

2013-11-01

Macrofauna community interactions with environmental variables in the water column (salinity, temperature, turbidity, transparency, suspended particulate matter, particulate organic matter, choloroplastic pigments) and in the sediment (granulometric variables, organic carbon and pigments) were investigated in a coastal area with high land runoff due to riverine and temporary stream discharges (Greece, Aegean Sea, Maliakos Gulf). Samples were taken along a distance-depositional gradient from the river mouth to the open sea at eight stations, at times of different precipitation regime from August 2000 to May 2001. The physical variables, such as transparency and median grain size, generally increased seawards, and parallelled the depositional gradient as opposed to measures of food inputs and hydrodynamic regime. High environmental heterogeneity was observed during peak precipitation. The total number of species increased seawards and from August (122 species) to May (170 species). Maximum abundance also increased from August (4953 m-2) to May (10,220 individuals m-2), irrespective of distance from river mouth. Species belonging to different functional groups, as to recolonization, feeding, motility and substrate preferences, coexisted at all times indicating high functional diversity. Non-parametric multivariate regression showed that at times of low, rising and falling precipitation 78-81% of community variation was explained by environmental variables, indicating that macrofauna distribution and species composition respond to food inputs and sediment characteristics. During peak land runoff the community-environment relationship weakened (57% of the variability explained). The diversity of functional traits of the most abundant species indicates that the macrofauna community can absorb the impact of increased turbidity, sedimentation and current-driven dispersion. The study offers baseline information for the integrated coastal zone management in microtidal areas with high land runoff under Mediterranean-type climate conditions. During peak land runoff the community-environment relationship weakened (57% of the variability explained) whilst species distribution ranges increased. The study shows that the functional diversity in the study area prior to high discharge period enable macrofauna community to absorb the impact of increased turbidity, sedimentation and current-driven dispersion. The study offers baseline information for the impact of high land runoff in microtidal areas under Mediterranean-type climate conditions.

Electromagnetic and optical characteristics of Nb5+-doped double-crossover and salmon DNA thin films

NASA Astrophysics Data System (ADS)

Babu Mitta, Sekhar; Reddy Dugasani, Sreekantha; Jung, Soon-Gil; Vellampatti, Srivithya; Park, Tuson; Park, Sung Ha

2017-10-01

We report the fabrication and physical characteristics of niobium ion (Nb5+)-doped double-crossover DNA (DX-DNA) and salmon DNA (SDNA) thin films. Different concentrations of Nb5+ ([Nb5+]) are coordinated into the DNA molecules, and the thin films are fabricated via substrate-assisted growth (DX-DNA) and drop-casting (SDNA) on oxygen plasma treated substrates. We conducted atomic force microscopy to estimate the optimum concentration of Nb5+ ([Nb5+]O = 0.08 mM) in Nb5+-doped DX-DNA thin films, up to which the DX-DNA lattices maintain their structures without deformation. X-ray photoelectron spectroscopy (XPS) was performed to probe the chemical nature of the intercalated Nb5+ in the SDNA thin films. The change in peak intensities and the shift in binding energy were witnessed in XPS spectra to explicate the binding and charge transfer mechanisms between Nb5+ and SDNA molecules. UV-visible, Raman, and photoluminescence (PL) spectra were measured to determine the optical properties and thus investigate the binding modes, Nb5+ coordination sites in Nb5+-doped SDNA thin films, and energy transfer mechanisms, respectively. As [Nb5+] increases, the absorbance peak intensities monotonically increase until ˜[Nb5+]O and then decrease. However, from the Raman measurements, the peak intensities gradually decrease with an increase in [Nb5+] to reveal the binding mechanism and binding sites of metal ions in the SDNA molecules. From the PL, we observe the emission intensities to reduce them at up to ˜[Nb5+]O and then increase after that, expecting the energy transfer between the Nb5+ and SDNA molecules. The current-voltage measurement shows a significant increase in the current observed as [Nb5+] increases in the SDNA thin films when compared to that of pristine SDNA thin films. Finally, we investigate the temperature dependent magnetization in which the Nb5+-doped SDNA thin films reveal weak ferromagnetism due to the existence of tiny magnetic dipoles in the Nb5+-doped SDNA complex.

Induction linear accelerators

NASA Astrophysics Data System (ADS)

Birx, Daniel

1992-03-01

Among the family of particle accelerators, the Induction Linear Accelerator is the best suited for the acceleration of high current electron beams. Because the electromagnetic radiation used to accelerate the electron beam is not stored in the cavities but is supplied by transmission lines during the beam pulse it is possible to utilize very low Q (typically<10) structures and very large beam pipes. This combination increases the beam breakup limited maximum currents to of order kiloamperes. The micropulse lengths of these machines are measured in 10's of nanoseconds and duty factors as high as 10-4 have been achieved. Until recently the major problem with these machines has been associated with the pulse power drive. Beam currents of kiloamperes and accelerating potentials of megavolts require peak power drives of gigawatts since no energy is stored in the structure. The marriage of liner accelerator technology and nonlinear magnetic compressors has produced some unique capabilities. It now appears possible to produce electron beams with average currents measured in amperes, peak currents in kiloamperes and gradients exceeding 1 MeV/meter, with power efficiencies approaching 50%. The nonlinear magnetic compression technology has replaced the spark gap drivers used on earlier accelerators with state-of-the-art all-solid-state SCR commutated compression chains. The reliability of these machines is now approaching 1010 shot MTBF. In the following paper we will briefly review the historical development of induction linear accelerators and then discuss the design considerations.

Physical activity self-definition among adolescents.

PubMed

Robbins, Lorraine B; Pis, Monika B; Pender, Nola J; Kazanis, Anamaria S

2004-01-01

Since research involving adults indicates that physical activity (PA) self-definition influences PA participation, understanding PA self-definition and related factors, such as PA frequency and enjoyment, in youth is essential for designing interventions to reverse the decline in PA that occurs from childhood through adolescence. The objective of this study was to explore correlates of PA self-definition and assess differences in PA self-definition among African American and European American boys and girls in early, middle, and late puberty. A 3 (developmental stage) x 2 (gender) design was used. African American and European American boys and girls, ages 9 to 17, participated. A total of 168 adolescents completed demographic data, developmental stage, and current and future PA self-definition questionnaires. Peak VO2 was obtained as a measure of physical fitness. Current PA self-definition was positively correlated with peak VO2 (p < .01) and future PA self-definition (p <.01). Males had higher current (p = .032) and future (p = .021) PA self-definition than females. The finding that boys have stronger current and future PA self-definitions than girls highlights the challenge for health professionals to enact immediate and effective measures to alter girls' perceptions of themselves in terms of PA participation. Since current PA self-definition is also significantly correlated with future PA participation, strategies to assist girls in developing a strong PA self-definition may contribute to increased PA in their adult years.

Improved test methods for determining lightning-induced voltages in aircraft

NASA Technical Reports Server (NTRS)

Crouch, K. E.; Plumer, J. A.

1980-01-01

A lumped parameter transmission line with a surge impedance matching that of the aircraft and its return lines was evaluated as a replacement for earlier current generators. Various test circuit parameters were evaluated using a 1/10 scale relative geometric model. Induced voltage response was evaluated by taking measurements on the NASA-Dryden Digital Fly by Wire F-8 aircraft. Return conductor arrangements as well as other circuit changes were also evaluated, with all induced voltage measurements being made on the same circuit for comparison purposes. The lumped parameter transmission line generates a concave front current wave with the peak di/dt near the peak of the current wave which is more representative of lightning. However, the induced voltage measurements when scaled by appropriate scale factors (peak current or di/dt) resulting from both techniques yield comparable results.

1300 nm wavelength InAs quantum dot photodetector grown on silicon.

PubMed

Sandall, Ian; Ng, Jo Shien; David, John P R; Tan, Chee Hing; Wang, Ting; Liu, Huiyun

2012-05-07

The optical and electrical properties of InAs quantum dots epitaxially grown on a silicon substrate have been investigated to evaluate their potential as both photodiodes and avalanche photodiodes (APDs) operating at a wavelength of 1300 nm. A peak responsivity of 5 mA/W was observed at 1280 nm, with an absorption tail extending beyond 1300 nm, while the dark currents were two orders of magnitude lower than those reported for Ge on Si photodiodes. The diodes exhibited avalanche breakdown at 22 V reverse bias which is probably dominated by impact ionisation occurring in the GaAs and AlGaAs barrier layers. A red shift in the absorption peak of 61.2 meV was measured when the reverse bias was increased from 0 to 22 V, which we attributed to the quantum confined stark effect. This shift also leads to an increase in the responsivity at a fixed wavelength as the bias is increased, yielding a maximum increase in responsivity by a factor of 140 at the wavelength of 1365 nm, illustrating the potential for such a structure to be used as an optical modulator.

Communication: Nanoscale structure of tetradecyltrihexylphosphonium based ionic liquids

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hettige, Jeevapani J.; Araque, Juan C.; Margulis, Claudio J., E-mail: claudio-margulis@uiowa.edu

In a recent communication [J. J. Hettige et al., J. Chem. Phys. 140, 111102 (2014)], we investigated the anomalous temperature dependence of the X-ray first sharp diffraction peak (or prepeak) in the tetradecyltrihexylphosphonium bis(trifluoromethylsulfonyl)-amide ionic liquid. Contrary to what was expected and often observed, the first sharp diffraction peak in this system was shown to increase in intensity with increasing temperature. This implies higher intermediate-range periodicity at a higher temperature. Is this counter-intuitive behavior specific to the combination of cation and anion? The current work analyzes the structural behavior of the same cation coupled with six different anions ranging frommore » the small and spherically symmetric Cl{sup −} to the more structurally complex and charge-diffuse NTf{sub 2}{sup −}. In all cases, the same temperature behavior trend for the prepeak is observed independent of anionic nature. We will show that the intensity increase in the prepeak region is associated with the structural behavior of charged liquid subcomponents. Instead, upon a temperature increase, the apolar subcomponents contribute to what would be an expected decrease of prepeak intensity.« less

The dichotomous response of flood and storm extremes to rising global temperatures

NASA Astrophysics Data System (ADS)

Sharma, A.; Wasko, C.

2017-12-01

Rising temperature have resulted in increases in short-duration rainfall extremes across the world. Additionally it has been shown (doi:10.1038/ngeo2456) that storms will intensify, causing derived flood peaks to rise even more. This leads us to speculate that flood peaks will increase as a result, complying with the storyline presented in past IPCC reports. This talk, however, shows that changes in flood extremes are much more complex. Using global data on extreme flow events, the study conclusively shows that while the very extreme floods may be rising as a result of storm intensification, the more frequent flood events are decreasing in magnitude. The study argues that changes in the magnitude of floods are a function of changes in storm patterns and as well as pre-storm or antecedent conditions. It goes on to show that while changes in storms dominate for the most extreme events and over smaller, more urbanised catchments, changes in pre-storm conditions are the driving factor in modulating flood peaks in large rural catchments. The study concludes by providing recommendations on how future flood design should proceed, arguing that current practices (or using a design storm to estimate floods) are flawed and need changing.

AC losses in (Bi,Pb) 2Sr 2Ca 2Cu 3O x tapes

NASA Astrophysics Data System (ADS)

D'Anna, G.; Indenbom, M. V.; André, M.-O.; Benoit, W.; Grivel, J.-C.; Hensel, B.; Flükiger, R.

1994-05-01

A double peak structure is observed in the AC losses of (Bi,Pb) 2Sr 2Ca 2Cu 3O x silver-sheathed tapes using a torsion-pendulum oscillator. The low-temperature peak is associated to the intragrain flux expulsion, while the high-temperature peak results from a macroscopic current path around the whole sample due to a well-coupled fraction of the grains. The flux pinning by the dislocations forming small-angle grain boundaries is suggested to control the transport current.

Digital processing with single electrons for arbitrary waveform generation of current

NASA Astrophysics Data System (ADS)

Okazaki, Yuma; Nakamura, Shuji; Onomitsu, Koji; Kaneko, Nobu-Hisa

2018-03-01

We demonstrate arbitrary waveform generation of current using a GaAs-based single-electron pump. In our experiment, a digital processing algorithm known as delta-sigma modulation is incorporated into single-electron pumping to generate a density-modulated single-electron stream, by which we demonstrate the generation of arbitrary waveforms of current including sinusoidal, square, and triangular waves with a peak-to-peak amplitude of approximately 10 pA and an output bandwidth ranging from dc to close to 1 MHz. The developed current generator can be used as the precise and calculable current reference required for measurements of current noise in low-temperature experiments.

Influence of emission threshold of explosive emission cathodes on current waveform in foilless diodes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wu, P.; Liu, G. Z.; Science and Technology on High Power Microwave Laboratory, Northwest Institute of Nuclear Technology, Xi'an 710024

The emission threshold of explosive emission cathodes (EECs) is an important factor for beam quality. It can affect the explosive emission delay time, the plasma expansion process on the cathode surface, and even the current amplitude when the current is not fully space-charge-limited. This paper researches the influence of the emission threshold of an annular EEC on the current waveform in a foilless diode when the current is measured by a Rogowski coil. The particle-in-cell simulation which is performed under some tolerable and necessary simplifications shows that the long explosive emission delay time of high-threshold cathodes may leave an apparentmore » peak of displacement current on the rise edge of the current waveform, and this will occur only when the electron emission starts after this peak. The experimental researches, which are performed under a diode voltage of 1 MV and a repetitive frequency of 20 Hz, demonstrate that the graphite cathode has a lower emission threshold and a longer lifetime than the stainless steel cathode according to the variation of the peak of displacement current on the rise edge of the current waveform.« less

Calculation of induced current densities for humans by magnetic fields from electronic article surveillance devices

NASA Astrophysics Data System (ADS)

Gandhi, Om P.; Kang, Gang

2001-11-01

This paper illustrates the use of the impedance method to calculate the electric fields and current densities induced in millimetre resolution anatomic models of the human body, namely an adult and 10- and 5-year-old children, for exposure to nonuniform magnetic fields typical of two assumed but representative electronic article surveillance (EAS) devices at 1 and 30 kHz, respectively. The devices assumed for the calculations are a solenoid type magnetic deactivator used at store checkouts and a pass-by panel-type EAS system consisting of two overlapping rectangular current-carrying coils used at entry and exit from a store. The impedance method code is modified to obtain induced current densities averaged over a cross section of 1 cm2 perpendicular to the direction of induced currents. This is done to compare the peak current densities with the limits or the basic restrictions given in the ICNIRP safety guidelines. Because of the stronger magnetic fields at lower heights for both the assumed devices, the peak 1 cm2 area-averaged current densities for the CNS tissues such as the brain and the spinal cord are increasingly larger for smaller models and are the highest for the model of the 5-year-old child. For both the EAS devices, the maximum 1 cm2 area-averaged current densities for the brain of the model of the adult are lower than the ICNIRP safety guideline, but may approach or exceed the ICNIRP basic restrictions for models of 10- and 5-year-old children if sufficiently strong magnetic fields are used.

Calculation of induced current densities for humans by magnetic fields from electronic article surveillance devices.

PubMed

Gandhi, O P; Kang, G

2001-11-01

This paper illustrates the use of the impedance method to calculate the electric fields and current densities induced in millimetre resolution anatomic models of the human body, namely an adult and 10- and 5-year-old children, for exposure to nonuniform magnetic fields typical of two assumed but representative electronic article surveillance (EAS) devices at 1 and 30 kHz, respectively. The devices assumed for the calculations are a solenoid type magnetic deactivator used at store checkouts and a pass-by panel-type EAS system consisting of two overlapping rectangular current-carrying coils used at entry and exit from a store. The impedance method code is modified to obtain induced current densities averaged over a cross section of 1 cm2 perpendicular to the direction of induced currents. This is done to compare the peak current densities with the limits or the basic restrictions given in the ICNIRP safety guidelines. Because of the stronger magnetic fields at lower heights for both the assumed devices, the peak 1 cm2 area-averaged current densities for the CNS tissues such as the brain and the spinal cord are increasingly larger for smaller models and are the highest for the model of the 5-year-old child. For both the EAS devices, the maximum 1 cm2 area-averaged current densities for the brain of the model of the adult are lower than the ICNIRP safety guideline, but may approach or exceed the ICNIRP basic restrictions for models of 10- and 5-year-old children if sufficiently strong magnetic fields are used.

A Quantitative Study of an Interactive Whiteboard Implementation in a Suburban School District: Years of Teaching Experience and Grade Level Taught Compared to Peak Stage of Concern

ERIC Educational Resources Information Center

Kotch, Jason M.

2011-01-01

Integrating technology into the classroom is thought to motivate students, keep them engaged, increase available resources, and improve student achievement. Interactive whiteboards (IWBs) are currently being implemented in many classrooms. The purpose of this causal-comparative quantitative study was to identify if years of teaching experience or…

HISTONE ACETYLTRANSFERASE p300 MODULATES GENE EXPRESSION IN AN EPIGENETIC MANNER AT HIGH BLOOD ALCOHOL LEVELS

PubMed Central

Bardag-Gorce, Fawzia; French, Barbara A.; Joyce, Michael; Baires, Mercedes; Montgomery, Rosalyn O.; Li, Jun; French., Samuel

2007-01-01

When rats are fed ethanol intragastrically at a constant rate for 1 month, the urinary alcohol level (UAL) cycles over 7–9 day intervals. At the peak UAL, the liver is hypoxic shifting from a redox state to a reduced rate. Microarray analysis done on livers at the UAL peaks shows changes in ~1300 gene expression compared to the pair-fed controls. To determine the mechanism of the gene expression changes, histone acetylation regulation was investigated in liver nuclear extracts at the peaks and troughs of the UAL and their pair-fed controls. No change occurred in SirT-1. P300, a histone acetyltransferase (HAT), which acetylates histone H3 on lysine 9, was increased at the peaks. Histone 3 acetylated at lysine 9 was also increased at the peaks. This indicates that the up regulated genes at the UAL peaks resulted from an increase in p300 transcription regulation, epigenetically. P300 activates transcription of numerous genes in response to signal transcription factors such as H1F 1α, increased in the nucleus at UAL peaks. Signal transduction pathways, such as NFκB, AP-1, ERK, JNK, and p38 were not increased at the peaks. β-catenin was increased in the nuclear extract at the UAL peaks and troughs, where increased gene expression was absent. The increase in gene expression at the peaks was due, in part, to increased acetylation of histone 3 at lysine 9. PMID:17208223

Laser Based Phosphor Converted Solid State White Light Emitters

NASA Astrophysics Data System (ADS)

Cantore, Michael

Artificial lighting and as a consequence the ability to be productive when the sun does not shine may be a profound achievement in society that is largely taken for granted. As concerns arise due to our dependence on energy sources with finite lifespan or environmentally negative effects, efforts to reduce energy consumption and create clean renewable alternatives has become highly valued. In the scope of artificial lighting, the use of incandescent lamps has shifted to more efficient light sources. Fluorescent lighting made the first big gains in efficiency over incandescent lamps with peak efficiency for mature designs reaching luminous efficacy of approximately 90 lm/W; more than three times as efficient as an incandescent lamp. Lamps based on light emitting diodes (LEDs) which can produce light at even greater efficiency, color quality and without the potential for hazardous chemical release from lamp failure. There is a significant challenge with LED based light sources. Their peak efficiency occurs at low current densities and then droops as the current density increases. Laser diodes (LDs) do not suffer from decreasing efficiency due to increased current. An alternative solid state light source using LDs has potential to make further gains in efficiency as well as allow novel illuminant designs which may be impractical or even impossible even with LED or other conventional sources. While similar to LEDS, the use of LDs does present new challenges largely due to the increased optical power density which must be accommodated in optics and phosphor materials. Single crystal YAG:Ce has been shown to be capable of enduring this more extreme operating environment while retaining the optical and fluorescing qualities desired for use as a wavelength converter in phosphor converted LD based white emitting systems. The incorporation of this single crystal phosphor in a system with a commercial laser diode with peak wall plug efficiency of 31% resulted in emission of white light with a luminous efficacy of 86.7 lm/W at a current of 1.4A. A total luminous flux of 1100 lm with luminous efficacy of 76 lm/W at 3.0 A current was achieved. Simulations have been conducted which show that as the InGaN LD technology matures towards the efficiencies of about 75%, which has been observed in the GaAs material system, luminous efficacy of similar blue LD with single crystal YAG:Ce systems will exceed 200 lm/W.

Climate Change Impacts on Peak Electricity Consumption: US vs. Europe.

NASA Astrophysics Data System (ADS)

Auffhammer, M.

2016-12-01

It has been suggested that climate change impacts on the electric sector will account for the majority of global economic damages by the end of the current century and beyond. This finding is at odds with the relatively modest increase in climate driven impacts on consumption. Comprehensive high frequency load balancing authority level data have not been used previously to parameterize the relationship between electric demand and temperature for any major economy. Using statistical models we analyze multi-year data from load balancing authorities in the United States of America and the European Union, which are responsible for more than 90% of the electricity delivered to residential, industrial, commercial and agricultural customers. We couple the estimated response functions between total daily consumption and daily peak load with an ensemble of downscaled GCMs from the CMIP5 archive to simulate climate change driven impacts on both outcomes. We show moderate and highly spatially heterogeneous changes in consumption. The results of our peak load simulations, however, suggest significant changes in the intensity and frequency of peak events throughout the United States and Europe. As the electricity grid is built to endure maximum load, which usually occurs on the hottest day of the year, our findings have significant implications for the construction of costly peak generating and transmission capacity.

Mathematical model of a parallel plate ammonia electrolyzer for combined wastewater remediation and hydrogen production.

PubMed

Estejab, Ali; Daramola, Damilola A; Botte, Gerardine G

2015-06-15

A mathematical model was developed for the simulation of a parallel plate ammonia electrolyzer to convert ammonia in wastewater to nitrogen and hydrogen under basic conditions. The model consists of fundamental transport equations, the ammonia oxidation kinetics at the anode, and the hydrogen evolution kinetics at the cathode of the electrochemical reactor. The model shows both qualitative and quantitative agreement with experimental measurements at ammonia concentrations found within wastewater (200-1200 mg L(-1)). The optimum electrolyzer performance is dependent on both the applied voltage and the inlet concentrations. Maximum conversion of ammonia to nitrogen at the rates of 0.569 and 0.766 mg L(-1) min(-1) are achieved at low (0.01 M NH4Cl and 0.1 M KOH) and high (0.07 M NH4Cl and 0.15 M KOH) inlet concentrations, respectively. At high and low concentrations, an initial increase in the cell voltage will cause an increase in the system response - current density generated and ammonia converted. These system responses will approach a peak value before they start to decrease due to surface blockage and/or depletion of solvated species at the electrode surface. Furthermore, the model predicts that by increasing the reactant and electrolyte concentrations at a certain voltage, the peak current density will plateau, showing an asymptotic response. Copyright © 2015 Elsevier Ltd. All rights reserved.

Characterization of carbon fiber polymer matrix composites subjected to simultaneous application of electric current pulse and low velocity impact

NASA Astrophysics Data System (ADS)

Hart, Robert James

2011-12-01

The use of composite materials in aerospace, electronics, and wind industries has become increasingly common, and these composite components are required to carry mechanical, electrical, and thermal loads simultaneously. A unique property of carbon fiber composites is that when an electric current is applied to the specimen, the mechanical strength of the specimen increases. Previous studies have shown that the higher the electric current, the greater the increase in impact strength. However, as current passes through the composite, heat is generated through Joule heating. This Joule heating can cause degradation of the composite and thus a loss in strength. In order to minimize the negative effects of heating, it is desired to apply a very high current for a very short duration of time. This thesis investigated the material responses of carbon fiber composite plates subjected to electrical current pulse loads of up to 1700 Amps. For 32 ply unidirectional IM7/977-3 specimens, the peak impact load and absorbed energy increased slightly with the addition of a current pulse at the time of an impact event. In 16 ply cross-ply IM7/977-2 specimens, the addition of the current pulse caused detrimental effects due to electrical arcing at the interface between the composite and electrodes. Further refinement of the experimental setup should minimize the risk of electrical arcing and should better elucidate the effects of a current pulse on the impact strength of the specimens.

Lightning Return-Stroke Current Waveforms Aloft, From Measured Field Change, Current, and Channel Geometry

NASA Technical Reports Server (NTRS)

Willett, J. C.; LeVine, D. M.

2002-01-01

Direct current measurements are available near the attachment point from both natural cloud-to-ground lightning and rocket-triggered lightning, but little is known about the rise time and peak amplitude of return-stroke currents aloft. We present, as functions of height, current amplitudes, rise times, and effective propagation velocities that have been estimated with a novel remote-sensing technique from data on 24 subsequent return strokes in six different lightning flashes that were triggering at the NASA Kennedy Space Center, FL, during 1987. The unique feature of this data set is the stereo pairs of still photographs, from which three-dimensional channel geometries were determined previously. This has permitted us to calculate the fine structure of the electric-field-change (E) waveforms produced by these strokes, using the current waveforms measured at the channel base together with physically reasonable assumptions about the current distributions aloft. The computed waveforms have been compared with observed E waveforms from the same strokes, and our assumptions have been adjusted to maximize agreement. In spite of the non-uniqueness of solutions derived by this technique, several conclusions seem inescapable: 1) The effective propagation speed of the current up the channel is usually significantly (but not unreasonably) faster than the two-dimensional velocity measured by a streak camera for 14 of these strokes. 2) Given the deduced propagation speed, the peak amplitude of the current waveform often must decrease dramatically with height to prevent the electric field from being over-predicted. 3) The rise time of the current wave front must always increase rapidly with height in order to keep the fine structure of the calculated field consistent with the observations.

Quantifying the Economic Value and Quality of Life Impact of Earlier Influenza Vaccination

PubMed Central

Lee, Bruce Y.; Bartsch, Sarah M.; Brown, Shawn T.; Cooley, Philip; Wheaton, William D.; Zimmerman, Richard K.

2015-01-01

Background Influenza vaccination is administered throughout the influenza disease season, even as late as March. Given such timing, what is the value of vaccinating the population earlier than currently being practiced? Methods We used real data on when individuals were vaccinated in Allegheny County, Pennsylvania, and the following 2 models to determine the value of vaccinating individuals earlier (by the end of September, October, and November): Framework for Reconstructing Epidemiological Dynamics (FRED), an agent-based model (ABM), and FluEcon, our influenza economic model that translates cases from the ABM to outcomes and costs [health care and lost productivity costs and quality-adjusted life-years (QALYs)]. We varied the reproductive number (R0) from 1.2 to 1.6. Results Applying the current timing of vaccinations averted 223,761 influenza cases, $16.3 million in direct health care costs, $50.0 million in productivity losses, and 804 in QALYs, compared with no vaccination (February peak, R0 1.2). When the population does not have preexisting immunity and the influenza season peaks in February (R0 1.2–1.6), moving individuals who currently received the vaccine after September to the end of September could avert an additional 9634–17,794 influenza cases, $0.6–$1.4 million in direct costs, $2.1–$4.0 million in productivity losses, and 35–64 QALYs. Moving the vaccination of just children to September (R0 1.2–1.6) averted 11,366–1660 influenza cases, $0.6–$0.03 million in direct costs, $2.3–$0.2 million in productivity losses, and 42–8 QALYs. Moving the season peak to December increased these benefits, whereas increasing preexisting immunity reduced these benefits. Conclusion Even though many people are vaccinated well after September/October, they likely are still vaccinated early enough to provide substantial cost-savings. PMID:25590676

Preliminary Upper Estimate of Peak Currents in Transcranial Magnetic Stimulation at Distant Locations from a TMS Coil

PubMed Central

Makarov, Sergey N.; Yanamadala, Janakinadh; Piazza, Matthew W.; Helderman, Alex M.; Thang, Niang S.; Burnham, Edward H.; Pascual-Leone, Alvaro

2016-01-01

Goals Transcranial magnetic stimulation (TMS) is increasingly used as a diagnostic and therapeutic tool for numerous neuropsychiatric disorders. The use of TMS might cause whole-body exposure to undesired induced currents in patients and TMS operators. The aim of the present study is to test and justify a simple analytical model known previously, which may be helpful as an upper estimate of eddy current density at a particular distant observation point for any body composition and any coil setup. Methods We compare the analytical solution with comprehensive adaptive mesh refinement-based FEM simulations of a detailed full-body human model, two coil types, five coil positions, about 100,000 observation points, and two distinct pulse rise times, thus providing a representative number of different data sets for comparison, while also using other numerical data. Results Our simulations reveal that, after a certain modification, the analytical model provides an upper estimate for the eddy current density at any location within the body. In particular, it overestimates the peak eddy currents at distant locations from a TMS coil by a factor of 10 on average. Conclusion The simple analytical model tested in the present study may be valuable as a rapid method to safely estimate levels of TMS currents at different locations within a human body. Significance At present, safe limits of general exposure to TMS electric and magnetic fields are an open subject, including fetal exposure for pregnant women. PMID:26685221

186 K Operation of Terahertz Quantum-Cascade Lasers Based on a Diagonal Design

NASA Technical Reports Server (NTRS)

Kumar, Sushil; Hu, Qing; Reno, John L.

2009-01-01

Resonant-phonon terahertz quantum-cascade lasers operating up to a heat-sink temperature of 186 K are demonstrated. This record temperature performance is achieved based on a diagonal design, with the objective to increase the upper-state lifetime and therefore the gain at elevated temperatures. The increased diagonality also lowers the operating current densities by limiting the flow of parasitic leakage current. Quantitatively, the diagonality is characterized by a radiative oscillator strength that is smaller by a factor of two from the least of any previously published designs. At the lasing frequency of 3.9 THz, 63 mW of peak optical power was measured at 5 K, and approximately 5 mW could still be detected at 180 K.

[Analysis of electrically evoked response (EER) in relation to the central visual pathway of the cat (1). Wave shape of the cat EER].

PubMed

Fukatsu, Y; Miyake, Y; Sugita, S; Saito, A; Watanabe, S

1990-11-01

To analyze the Electrically evoked response (EER) in relation to the central visual pathway, the authors studied the properties of wave patterns and peak latencies of EER in 35 anesthetized adult cats. The cat EER showed two early positive waves on outward current (cornea cathode) stimulus and three or four early positive waves on inward current (cornea anode) stimulus. These waves were recorded within 50 ms after stimulus onset, and were the most consistent components in cat EER. The stimulus threshold for EER showed a less individual variation than amplitude. The difference of stimulus threshold between outward and inward current stimulus was also essentially negligible. The stimulus threshold was higher in early components than in late components. The peak latency of EER became shorter and the amplitude became higher, as the stimulus intensity was increased. However, this tendency was reversed and some wavelets started to appear when the stimulus was extremely strong. The recording using short stimulus duration and bipolar electrodes enabled us to reduce the electrical artifact of EER. These results obtained from cats were compared with those of humans and rabbits.

Growth mechanism of surface roughed platinum nanowires through electrodeposition current control and their electrochemical applications

NASA Astrophysics Data System (ADS)

Ruan, Dajiang

The aim of this work is to investigate the effect of current density on the grain size and surface morphology of electrodeposited platinum nanowires and their applications. Platinum (Pt) nanowires were fabricated by a galvanostatic electrodeposition method in a porous anodic alumina oxide (AAO) template with different current densities. Both direct current and pulse current electrodeposition were used to synthesize the Pt nanowires. The grain size and surface morphology of the Pt nanowires were studied by field emission scanning electron microscopy (FE-SEM), transmission electron microcopy (TEM) and X-ray diffraction (XRD). The experimental results showed that the current density was the key factor to control the surface roughness. The surface of the Pt nanowires became rougher and the grain sizes were increased by increasing the current densities. From the experimental results, a growth mechanism of Pt nanowires based on progressive nucleation and crystallization was proposed in order to find out the relationship between the surface morphology and current density. The electrochemical properties and catalytic activities of these surface roughed Pt nanowires were investigated in the detection of H20 2 and for the methanol oxidation. Cyclic voltammograms of Pt nanowire modified electrodes were obtained using a potentiostat, which showed that rougher Pt nanowires have higher response and better activity than that of smooth nanowires. For H202 detection, the effect of scan rate and H202 concentration were studied and it was found that the peak current for hydrogen peroxide reduction became larger with the increasing of either scan rate or H202 concentration. It can be inferred that the process of electrocatalytic hydrogen peroxide reduction may be controlled by diffusion of hydrogen peroxide and the Pt nanowire modified glassy carbon electrode (GCE) is well suited for the detection of H202. From the relationship between the peak current and square root of scan rates for methanol oxidation, it can be inferred that the process of electrocatalytic methanol oxidation was controlled by diffusion of methanol. To understand the effect of the morphological feature on the electrocatalytic activity of the Pt nanowire catalysts, the electrochemically active surface area (ECSA) as a function of deposited current density was investigated, which suggests that Pt nanowire catalysts deposited at highest current density had the most ECSA surface morphology of the Pt nanowires. The chronoamperometric curves and electrochemical impedance spectroscopy (EIS) results confirmed that the Pt nanowire catalyst synthesized at higher current density possessed longer durability and gave more efficient electrochemical performance.

Mysteries of LiF TLD response following high ionisation density irradiation: nanodosimetry and track structure theory, dose response and glow curve shapes.

PubMed

Horowitz, Y; Fuks, E; Datz, H; Oster, L; Livingstone, J; Rosenfeld, A

2011-06-01

Three outstanding effects of ionisation density on the thermoluminescence (TL) mechanisms giving rise to the glow peaks of LiF:Mg,Ti (TLD-100) are currently under investigation: (1) the dependence of the heavy charged particle (HCP) relative efficiency with increasing ionisation density and the effectiveness of its modelling by track structure theory (TST), (2) the behaviour of the TL efficiency, f(D), as a function of photon energy and dose. These studies are intended to promote the development of a firm theoretical basis for the evaluation of relative TL efficiencies to assist in their application in mixed radiation fields. And (3) the shape of composite peak 5 in the glow curve for various HCP types and energies and following high-dose electron irradiation, i.e. the ratio of the intensity of peak 5a to peak 5. Peak 5a is a low-temperature satellite of peak 5 arising from electron-hole capture in a spatially correlated trapping centre/luminescent centre (TC/LC) complex that has been suggested to possess a potential as a solid-state nanodosemeter due to the preferential electron/hole population of the TC/LC at high ionisation density. It is concluded that (1) the predictions of TST are very strongly dependent on the choice of photon energy used in the determination of f(D); (2) modified TST employing calculated values of f(D) at 2 keV is in agreement with 5-MeV alpha particle experimental results for composite peak 5 but underestimates the 1.5-MeV proton relative efficiencies. Both the proton and alpha particle relative TL efficiencies of the high-temperature TL (HTTL) peaks 7 and 8 are underestimated by an order of magnitude suggesting that the HTTL efficiencies are affected by other factors in addition to radial electron dose; (3) the dose-response supralinearity of peaks 7 and 8 change rapidly with photon energy: this behaviour is explained in the framework of the unified interaction model as due to a very strong dependence on photon energy of the relative intensity of localised recombination and (4) the increased width and decrease in T(max) of composite peak 5 as a function of ionisation density is due to the greater relative intensity of peak 5a (a low-temperature component of peak 5 arising from two-energy transfer events, which leads to localised recombination).

Mysteries of LiF TLD response following high ionisation density irradiation: nanodosimetry and track structure theory, dose response and glow curve shapes

PubMed Central

Horowitz, Y.; Fuks, E.; Datz, H.; Oster, L.; Livingstone, J.; Rosenfeld, A.

2011-01-01

Three outstanding effects of ionisation density on the thermoluminescence (TL) mechanisms giving rise to the glow peaks of LiF:Mg,Ti (TLD-100) are currently under investigation: (1) the dependence of the heavy charged particle (HCP) relative efficiency with increasing ionisation density and the effectiveness of its modelling by track structure theory (TST), (2) the behaviour of the TL efficiency, f(D), as a function of photon energy and dose. These studies are intended to promote the development of a firm theoretical basis for the evaluation of relative TL efficiencies to assist in their application in mixed radiation fields. And (3) the shape of composite peak 5 in the glow curve for various HCP types and energies and following high-dose electron irradiation, i.e. the ratio of the intensity of peak 5a to peak 5. Peak 5a is a low-temperature satellite of peak 5 arising from electron-hole capture in a spatially correlated trapping centre/luminescent centre (TC/LC) complex that has been suggested to possess a potential as a solid-state nanodosemeter due to the preferential electron/hole population of the TC/LC at high ionisation density. It is concluded that (1) the predictions of TST are very strongly dependent on the choice of photon energy used in the determination of f(D); (2) modified TST employing calculated values of f(D) at 2 keV is in agreement with 5-MeV alpha particle experimental results for composite peak 5 but underestimates the 1.5-MeV proton relative efficiencies. Both the proton and alpha particle relative TL efficiencies of the high-temperature TL (HTTL) peaks 7 and 8 are underestimated by an order of magnitude suggesting that the HTTL efficiencies are affected by other factors in addition to radial electron dose; (3) the dose–response supralinearity of peaks 7 and 8 change rapidly with photon energy: this behaviour is explained in the framework of the unified interaction model as due to a very strong dependence on photon energy of the relative intensity of localised recombination and (4) the increased width and decrease in Tmax of composite peak 5 as a function of ionisation density is due to the greater relative intensity of peak 5a (a low-temperature component of peak 5 arising from two-energy transfer events, which leads to localised recombination). PMID:21106636

Momentum flux parasitic to free-energy transfer

DOE PAGES

Stoltzfus-Dueck, T.; Scott, B.

2017-05-11

An often-neglected portion of the radialmore » $$\\boldsymbol{E}\\times \\boldsymbol{B}$$ drift is shown to drive an outward flux of co-current momentum when free energy is transferred from the electrostatic potential to ion parallel flows. This symmetry breaking is fully nonlinear, not quasilinear, necessitated simply by free-energy balance in parameter regimes for which significant energy is dissipated via ion parallel flows. The resulting rotation peaking is counter-current and has a scaling and order of magnitude that are comparable with experimental observations. Finally, the residual stress becomes inactive when frequencies are much higher than the ion transit frequency, which may explain the observed relation of density peaking and counter-current rotation peaking in the core.« less

Lightning Attachment to Wind Turbines in Central Kansas: Video Observations, Correlation with the NLDN and in-situ Peak Current Measurements

NASA Astrophysics Data System (ADS)

Myers, J.; Cummins, K. L.; Hutchinson, M.; Nag, A.

2012-12-01

Lightning attachment to tall objects has been studied for decades. The attachment of lightning to electric power transmission towers in elevated terrain has driven much of the quantitative assessment of lightning characteristics in the 1970's and 80's. This has led to the understanding that in flat terrain, the probability of upward-initiated lightning is negligible for tower heights less than 100 m. For tower heights greater than 100, the probability increases roughly linearly with the log of height, reaching 100% at a height of 400 m. Additionally, the probability of upward initiation increases when the object resides on locally-elevated terrain. Over the last decade, there has been renewed interest in the study of lightning attachment to tall objects in general, and wind turbines in particular, following the establishment of large "wind farms" in lightning-prone regions. In this study, we present video observations, radiation magnetic field, and in-situ peak current measurements of lightning from an ongoing field program in a large wind farm in north-central Kansas, located in the U.S. Central Great Plains. The terrain variations within the wind farm are small rolling hills with peak variations on the order of 25 m. All turbines had a turbine hub height of 80 m, and a blade tip maximum height of 125 m. Two digital video camera systems (60 fields-per-second) were configured to self-trigger 2-second video sequences using a sequential-field-subtraction scene analysis (ufo-Capture). The two cameras had a common field of view that included 8 of the wind turbines. Nearby NLDN sensors were configured to record information that allows reconstruction of magnetic field waveforms within the bandwidth of the NLDN sensors. Some of the turbines were equipped with semi-quantitative in-situ peak current measuring devices. To date, more than 100 cloud-to-ground (CG) flashes have terminated within the perimeter of the wind farm. Video observations of flashes that attached to turbines (all to turbine blades) include five natural (downward leader) flashes and two "upward flashes" (fully developed upward leaders lasting 10's of milliseconds). Both upward flashes appear to have been triggered by nearby positive CG flashes, resulting in upward (presumably positive) leaders. Selected video observations in conjunction with NLDN data and waveform measurements, and in situ current measurements obtained during this campaign, will be presented and discussed in the context of storm characteristics. Differences with previous findings for fixed towers (no rotating blades) will also be discussed.

Energy Storage Systems Are Coming: Are You Ready

DOE Office of Scientific and Technical Information (OSTI.GOV)

Conover, David R.

2015-12-05

Energy storage systems (batteries) are not a new concept, but the technology being developed and introduced today with an increasing emphasis on energy storage, is new. The increased focus on energy, environmental and economic issues in the built environment is spurring increased application of renewables as well as reduction in peak energy use - both of which create a need for energy storage. This article provides an overview of current and anticipated energy storage technology, focusing on ensuring the safe application and use of energy storage on both the grid and customer side of the utility meter.

Novel five-state latch using double-peak negative differential resistance and standard ternary inverter

NASA Astrophysics Data System (ADS)

Shin, Sunhae; Rok Kim, Kyung

2016-04-01

We propose complement double-peak negative differential resistance (NDR) devices with ultrahigh peak-to-valley current ratio (PVCR) over 106 by combining tunnel diode with conventional CMOS and its compact five-state latch circuit by introducing standard ternary inverter (STI). At the “high”-state of STI, n-type NDR device (tunnel diode with nMOS) has 1st NDR characteristics with 1st peak and valley by band-to-band tunneling (BTBT) and trap-assisted tunneling (TAT), whereas p-type NDR device (tunnel diode with pMOS) has second NDR characteristics from the suppression of diode current by off-state MOSFET. The “intermediate”-state of STI permits double-peak NDR device to operate five-state latch with only four transistors, which has 33% area reduction compared with that of binary inverter and 57% bit-density reduction compared with binary latch.

Particle in cell simulation of peaking switch for breakdown evaluation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Umbarkar, Sachin B.; Bindu, S.; Mangalvedekar, H.A.

2014-07-01

Marx generator connected to peaking capacitor and peaking switch can generate Ultra-Wideband (UWB) radiation. A new peaking switch is designed for converting the existing nanosecond Marx generator to a UWB source. The paper explains the particle in cell (PIC) simulation for this peaking switch, using MAGIC 3D software. This peaking switch electrode is made up of copper tungsten material and is fixed inside the hermitically sealed derlin material. The switch can withstand a gas pressure up to 13.5 kg/cm{sup 2}. The lower electrode of the switch is connected to the last stage of the Marx generator. Initially Marx generator (withoutmore » peaking stage) in air; gives the output pulse with peak amplitude of 113.75 kV and pulse rise time of 25 ns. Thus, we design a new peaking switch to improve the rise time of output pulse and to pressurize this peaking switch separately (i.e. Marx and peaking switch is at different pressure). The PIC simulation gives the particle charge density, current density, E counter plot, emitted electron current, and particle energy along the axis of gap between electrodes. The charge injection and electric field dependence on ionic dissociation phenomenon are briefly analyzed using this simulation. The model is simulated with different gases (N{sub 2}, H{sub 2}, and Air) under different pressure (2 kg/cm{sup 2}, 5 kg/cm{sup 2}, 10 kg/cm{sup 2}). (author)« less

Latitude-dependent delay in the responses of the equatorial electrojet and Sq currents to X-class solar flares

NASA Astrophysics Data System (ADS)

Nogueira, Paulo A. B.; Abdu, Mangalathayil A.; Souza, Jonas R.; Denardini, Clezio M.; Barbosa Neto, Paulo F.; Serra de Souza da Costa, João P.; Silva, Ana P. M.

2018-01-01

We have analyzed low-latitude ionospheric current responses to two intense (X-class) solar flares that occurred on 13 May 2013 and 11 March 2015. Sudden intensifications, in response to solar flare radiation impulses, in the Sq and equatorial electrojet (EEJ) currents, as detected by magnetometers over equatorial and low-latitude sites in South America, are studied. In particular we show for the first time that a 5 to 8 min time delay is present in the peak effect in the EEJ, with respect that of Sq current outside the magnetic equator, in response to the flare radiation enhancement. The Sq current intensification peaks close to the flare X-ray peak, while the EEJ peak occurs 5 to 8 min later. We have used the Sheffield University Plasmasphere-Ionosphere Model at National Institute for Space Research (SUPIM-INPE) to simulate the E-region conductivity enhancement as caused by the flare enhanced solar extreme ultraviolet (EUV) and soft X-rays flux. We propose that the flare-induced enhancement in neutral wind occurring with a time delay (with respect to the flare radiation) could be responsible for a delayed zonal electric field disturbance driving the EEJ, in which the Cowling conductivity offers enhanced sensitivity to the driving zonal electric field.

The evolution of discharge current and channel radius in cloud-to-ground lightning return stroke process

NASA Astrophysics Data System (ADS)

Fan, Tingting; Yuan, Ping; Wang, Xuejuan; Cen, Jianyong; Chang, Xuan; Zhao, Yanyan

2017-09-01

The spectra of two negative cloud-to-ground lightning discharge processes with multi-return strokes are obtained by a slit-less high-speed spectrograph, which the temporal resolution is 110 μs. Combined with the synchronous electrical observation data and theoretical calculation, the physical characteristics during return strokes process are analysed. A positive correlation between discharge current and intensity of ionic lines in the spectra is verified, and based on this feature, the current evolution characteristics during four return strokes are investigated. The results show that the time from peak current to the half-peak value estimated by multi point-fitting is about 101 μs-139 μs. The Joule heat in per unit length of four return strokes channel is in the order of 105J/m-106 J/m. The radius of arc discharge channel is positively related to the discharge current, and the more intense the current is, the greater the radius of channel is. Furthermore, the evolution for radius of arc core channel in the process of return stroke is consistent with the change trend of discharge current after the peak value. Compared with the decay of the current, the temperature decreases more slowly.

Improvement in operational characteristics of KEPCO’s line-commutation-type superconducting hybrid fault current limiter

NASA Astrophysics Data System (ADS)

Yim, S.-W.; Park, B.-C.; Jeong, Y.-T.; Kim, Y.-J.; Yang, S.-E.; Kim, W.-S.; Kim, H.-R.; Du, H.-I.

2013-01-01

A 22.9 kV class hybrid fault current limiter (FCL) developed by Korea Electric Power Corporation and LS Industrial Systems in 2006 operates using the line commutation mechanism and begins to limit the fault current after the first half-cycle. The first peak of the fault current is available for protective coordination in the power system. However, it also produces a large electromagnetic force and imposes a huge stress on power facilities such as the main transformer and gas-insulated switchgear. In this study, we improved the operational characteristics of the hybrid FCL in order to reduce the first peak of the fault current. While maintaining the structure of the hybrid FCL system, we developed a superconducting module that detects and limits the fault current during the first half-cycle. To maintain the protective coordination capacity, the hybrid FCL was designed to reduce the first peak value of the fault current by up to approximately 30%. The superconducting module was also designed to produce a minimum AC loss, generating a small, uniform magnetic field distribution during normal operation. Performance tests confirmed that when applied to the hybrid FCL, the superconducting module showed successful current limiting operation without any damage.

Veff Scaling of Te and ne Measurements During Local Helicity Injection on the Pegasus Toroidal Experiment

NASA Astrophysics Data System (ADS)

Bodner, G. M.; Bongard, M. W.; Fonck, R. J.; Perry, J. M.; Reusch, J. A.; Rodriguez Sanchez, C.

2017-10-01

Understanding the electron confinement of local helicity injection (LHI) is critical in order to evaluate its scalability as a startup technique to MA-class devices. Electron confinement in the Pegasus Toroidal Experiment is investigated using multi-point Thomson scattering (TS). The Pegasus TS system utilizes a set of high-throughput transmission gratings and intensified CCDs to measure Te and ne profiles. Previous TS measurements indicated peaked Te profiles 120 eV in outboard injector discharges characterized by strong inductive drive and low LHI drive. Injectors designed to have dominant non-inductive drive have recently been installed in the divertor region of Pegasus to understand the relationship between effective drive voltage, Veff, and plasma performance. At low Veff and reduced plasma current, Ip 60 kA, TS measurements reveal a flat Te profile 50 eV, with a peaked ne profile 1 ×1019 m-3, resulting in a slightly peaked pe profile. As current drive is increased, the Te profiles become hollow with a core Te 50 eV and an edge Te 120 -150 eV. These hollow profiles appear after the start of the Ip flattop and are sustained until the discharge terminates. The ne profiles drop in magnitude to < 1 ×1019 m-3 but remain somewhat peaked. Initial results suggest a weak scaling between input power and core Te. Additional studies are planned to identify the mechanisms behind the anomalous profile features. Work supported by US DOE Grant DE-FG02-96ER54375.

A simplified controller and detailed dynamics of constant off-time peak current control

NASA Astrophysics Data System (ADS)

Van den Bossche, Alex; Dimitrova, Ekaterina; Valchev, Vencislav; Feradov, Firgan

2017-09-01

A fast and reliable current control is often the base of power electronic converters. The traditional constant frequency peak control is unstable above 50 % duty ratio. In contrast, the constant off-time peak current control (COTCC) is unconditionally stable and fast, so it is worth analyzing it. Another feature of the COTCC is that one can combine a current control together with a current protection. The time dynamics show a zero-transient response, even when the inductor changes in a wide range. It can also be modeled as a special transfer function for all frequencies. The article shows also that it can be implemented in a simple analog circuit using a wide temperature range IC, such as the LM2903, which is compatible with PV conversion and automotive temperature range. Experiments are done using a 3 kW step-up converter. A drawback is still that the principle does not easily fit in usual digital controllers up to now.

431 kA/cm2 peak tunneling current density in GaN/AlN resonant tunneling diodes

NASA Astrophysics Data System (ADS)

Growden, Tyler A.; Zhang, Weidong; Brown, Elliott R.; Storm, David F.; Hansen, Katurah; Fakhimi, Parastou; Meyer, David J.; Berger, Paul R.

2018-01-01

We report on the design and fabrication of high current density GaN/AlN double barrier resonant tunneling diodes grown via plasma assisted molecular-beam epitaxy on bulk GaN substrates. A quantum-transport solver was used to model and optimize designs with high levels of doping and ultra-thin AlN barriers. The devices displayed repeatable room temperature negative differential resistance with peak-to-valley current ratios ranging from 1.20 to 1.60. A maximum peak tunneling current density (Jp) of 431 kA/cm2 was observed. Cross-gap near-UV (370-385 nm) electroluminescence (EL) was observed above +6 V when holes, generated from a polarization induced Zener tunneling effect, recombine with electrons in the emitter region. Analysis of temperature dependent measurements, thermal resistance, and the measured EL spectra revealed the presence of severe self-heating effects.

Scaling magnetized liner inertial fusion on Z and future pulsed-power accelerators

DOE PAGES

Slutz, Stephen A.; Stygar, William A.; Gomez, Matthew R.; ...

2016-02-04

In this study, the MagLIF (Magnetized Liner Inertial Fusion) concept [S. A. Slutz et al., Phys. Plasmas 17, 056303 (2010)] has demonstrated fusion–relevant plasma conditions [M. R. Gomez et al., Phys. Rev. Lett. 113, 155003 (2014)] on the Z accelerator with a peak drive current of about 18 MA. We present 2D numerical simulations of the scaling of MagLIF on Z as a function of drive current, preheat energy, and applied magnetic field. The results indicate that deuterium-tritium (DT) fusion yields greater than 100 kJ could be possible on Z when all of these parameters are at the optimum values:more » i.e., peak current = 25 MA, deposited preheat energy = 5 kJ, and B z = 30 T. Much higher yields have been predicted [S. A. Slutz and R. A. Vesey, Phys. Rev. Lett. 108, 025003 (2012)] for MagLIF driven with larger peak currents. Two high performance pulsed-power accelerators (Z300 and Z800) based on linear-transformer-driver technology have been designed [W. A. Stygar et al., Phys. Rev. ST Accel. Beams 18, 110401 (2015)]. The Z300 design would provide 48 MA to a MagLIF load, while Z800 would provide 65 MA. Parameterized Thevenin-equivalent circuits were used to drive a series of 1D and 2D numerical MagLIF simulations with currents ranging from what Z can deliver now to what could be achieved by these conceptual future pulsed-power accelerators. 2D simulations of simple MagLIF targets containing just gaseous DT have yields of 18 MJ for Z300 and 440 MJ for Z800. The 2D simulated yield for Z800 is increased to 7 GJ by adding a layer of frozen DT ice to the inside of the liner.« less

Scaling magnetized liner inertial fusion on Z and future pulsed-power accelerators

DOE Office of Scientific and Technical Information (OSTI.GOV)

Slutz, Stephen A.; Stygar, William A.; Gomez, Matthew R.

In this study, the MagLIF (Magnetized Liner Inertial Fusion) concept [S. A. Slutz et al., Phys. Plasmas 17, 056303 (2010)] has demonstrated fusion–relevant plasma conditions [M. R. Gomez et al., Phys. Rev. Lett. 113, 155003 (2014)] on the Z accelerator with a peak drive current of about 18 MA. We present 2D numerical simulations of the scaling of MagLIF on Z as a function of drive current, preheat energy, and applied magnetic field. The results indicate that deuterium-tritium (DT) fusion yields greater than 100 kJ could be possible on Z when all of these parameters are at the optimum values:more » i.e., peak current = 25 MA, deposited preheat energy = 5 kJ, and B z = 30 T. Much higher yields have been predicted [S. A. Slutz and R. A. Vesey, Phys. Rev. Lett. 108, 025003 (2012)] for MagLIF driven with larger peak currents. Two high performance pulsed-power accelerators (Z300 and Z800) based on linear-transformer-driver technology have been designed [W. A. Stygar et al., Phys. Rev. ST Accel. Beams 18, 110401 (2015)]. The Z300 design would provide 48 MA to a MagLIF load, while Z800 would provide 65 MA. Parameterized Thevenin-equivalent circuits were used to drive a series of 1D and 2D numerical MagLIF simulations with currents ranging from what Z can deliver now to what could be achieved by these conceptual future pulsed-power accelerators. 2D simulations of simple MagLIF targets containing just gaseous DT have yields of 18 MJ for Z300 and 440 MJ for Z800. The 2D simulated yield for Z800 is increased to 7 GJ by adding a layer of frozen DT ice to the inside of the liner.« less

Modelling of electric characteristics of 150-watt peak solar panel using Boltzmann sigmoid function under various temperature and irradiance

NASA Astrophysics Data System (ADS)

Sapteka, A. A. N. G.; Narottama, A. A. N. M.; Winarta, A.; Amerta Yasa, K.; Priambodo, P. S.; Putra, N.

2018-01-01

Solar energy utilized with solar panel is a renewable energy that needs to be studied further. The site nearest to the equator, it is not surprising, receives the highest solar energy. In this paper, a modelling of electrical characteristics of 150-Watt peak solar panels using Boltzmann sigmoid function under various temperature and irradiance is reported. Current, voltage, temperature and irradiance data in Denpasar, a city located at just south of equator, was collected. Solar power meter is used to measure irradiance level, meanwhile digital thermometer is used to measure temperature of front and back panels. Short circuit current and open circuit voltage data was also collected at different temperature and irradiance level. Statistically, the electrical characteristics of 150-Watt peak solar panel can be modelled using Boltzmann sigmoid function with good fit. Therefore, it can be concluded that Boltzmann sigmoid function might be used to determine current and voltage characteristics of 150-Watt peak solar panel under various temperature and irradiance.

Wind, Circulation, and Topographic Effects on Alongshore Phytoplankton Variability in the California Current

NASA Astrophysics Data System (ADS)

Fiechter, Jerome; Edwards, Christopher A.; Moore, Andrew M.

2018-04-01

A physical-biogeochemical model is used to produce a retrospective analysis at 3-km resolution of alongshore phytoplankton variability in the California Current during 1988-2010. The simulation benefits from downscaling a regional circulation reanalysis, which provides improved physical ocean state estimates in the high-resolution domain. The emerging pattern is one of local upwelling intensification in response to increased alongshore wind stress in the lee of capes, modulated by alongshore meanders in the geostrophic circulation. While stronger upwelling occurs near most major topographic features, substantial increases in phytoplankton biomass only ensue where local circulation patterns are conducive to on-shelf retention of upwelled nutrients. Locations of peak nutrient delivery and chlorophyll accumulation also exhibit interannual variability and trends noticeably larger than the surrounding shelf regions, thereby suggesting that long-term planktonic ecosystem response in the California Current exhibits a significant local scale (O(100 km)) alongshore component.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Volkov, M. S.; Gusev, Yu. P., E-mail: GusevYP@mpei.ru; Monakov, Yu. V.

The insertion of current-limiting reactors into electrical equipment operating at a voltage of 110 and 220 kV produces a change in the parameters of the transient recovery voltages at the contacts of the circuit breakers for disconnecting short circuits, which could be the reason for the increase in the duration of the short circuit, damage to the electrical equipment and losses in the power system. The results of mathematical modeling of the transients, caused by tripping of the short circuit in a reactive electric power transmission line are presented, and data are given on the negative effect of a current-limitingmore » resistor on the rate of increase and peak value of the transient recovery voltages. Methods of ensuring the standard requirements imposed on the parameters of the transient recovery voltages when using current-limiting reactors in the high-voltage electrical equipment of power plants and substations are proposed and analyzed.« less

Current Voltage Characteristics and Excess Noise at the Trap Filling Transition in Polyacenes

NASA Astrophysics Data System (ADS)

Pousset, Jeremy; Alfinito, Eleonora; Carbone, Anna; Pennetta, Cecilia; Reggiani, Lino

Experiments in organic semiconductors (polyacenes) evidence a strong super quadratic increase of the current-voltage (I-V) characteristic at voltages in the transition region between linear (Ohmic) and quadratic (trap-free space-charge-limited current) behaviors. Similarly, excess noise measurements at a given frequency and increasing voltages evidence a sharp peak of the relative spectral density of the current noise in concomitance with the strong superquadratic I-V characteristics. Here, we discuss the physical interpretation of these experiments in terms of an essential contribution from field-assisted trapping-detrapping processes of injected carriers. To this purpose, the fraction of filled traps determined by the I-V characteristics is used to evaluate the excess noise in the trap-filled transition (TFT) regime. We have found an excellent agreement between the predictions of our model and existing experimental results in tetracene and pentacene thin films of different length in the range 0.65÷35μm.

Influence of different gaps among the split targets with gradient potential to the discharge effects generated by hypervelocity impact

NASA Astrophysics Data System (ADS)

Tang, Enling; Zhao, Liangliang; Han, Yafei; Zhang, Qingming; Wang, Ruizhi; He, Liping; Liu, Shuhua

2018-04-01

Due to the actual situation of spacecraft surface' charging, such as convex corners, weld line, whalebone and a multiple-interfaces with different materials, all these are main factors leading to uneven charging of spacecraft surface, even creating gradient potential. If the charging spacecraft surface is impacted by debris or micrometeor, discharge effect induced by impacting will pose a serious threat to spacecraft in orbit. So realizing spacecraft charging surface with different potential differences and grasping discharge characteristics are a decisive importance at the different experimental conditions in laboratory. To simulate the spacecraft surface with a gradient potential in laboratory, spacecraft surface is split into different parts, which different gaps reserved in 2 adjacent surface is added resistance to create different potential surfaces, and the high potential surface as a impact target in the split targets. Charging circuit system realizing different gradient potential and discharge test system are built by ourselves, combining with two-stage light gas gun loading system, six sets of experiments have been performed about hypervelocity impact on 2A12 aluminum split targets with gradient potentials. In the experiments, gaps of 2A12 aluminum target are the same among different parts in every experiments, the gaps of the split targets are 2mm, 3mm, 5mm, 7mm and 10mm in the experiments, respectively. And the applied voltage is 300V in all the experiments and high-potential 2A12 aluminum plate as the impact target. The experiments have been performed at the impact velocity of about 3km/s and the incidence angles of 60o and 90o (between projectile flying trajectory and target plane), respectively. Voltage probe and current probes are used for acquiring discharge voltages and currents during the process of the impact. The experimental results showed that the discharge induced by impact plasma were generated among high and low-potential target by forming a plasma discharge channel. With the increasing of the gaps among the high and low-potential targets, the peak values of the discharge current decreased first then increased. When the gaps of split targets reached a certain value, the peak values of the discharge current decreased again. Meanwhile, the gaps among high and low-potential targets was 5mm, the peak value of the discharge current was the smallest. With the increasing of the gaps among the split targets, a primary discharge duration also increased. However, when the gaps among the split targets were greater than 5mm, increasing trend of discharge duration would slow down. When the gaps among the split targets were greater than 7mm, there was a secondary discharge phenomenon, and the physical explanations were given about the influence of different gaps among the split targets on the discharge effects created by hypervelocity impact.

Elastic tunneling identification through crossings, anti-crossings and splitting of states in the complex electronic current of systems based on mesoscopic molecules

NASA Astrophysics Data System (ADS)

López, Luis I. A.; Mendoza, Michel; Ujevic, Sebastian

2013-09-01

We have systematically studied the conductance σ( E,B) and the electronic current line shapes J( V ex ) through complex mesoscopic molecules in an elastic resonant tunneling regime. The studied systems are based on GaAs/AlGaAs hetero-structures, with several discrete states in each coupled mesoscopic molecule. The molecules were formed using different wells and barrier widths. These systems allow effective couplings and uncouplings that lead to elastic processes as a function of the electronic potential V ex and magnetic field B. In this situation, the J( V ex ) and σ( E, B) curves exhibit a sequence of peaks of difficult interpretation, in which crossings and anti-crossings (a splitting if it is generated in the resonance condition) of states contribute in a way that they cannot be easily identified. Performing a systematic analysis of the evolution of these states (before the resonance condition), we were able to determine the origin of these current peaks. We have found that the coupling of states (anti-crossing) around the resonance region can be identified as a broad mirrored- D line shape in the J( V ex ) curves. The mirrored- D line shape peaks can be clearly differentiated from the neighboring peaks because the last ones follow a very defined increasing sequence in their intensities and widths. Also, this behavior (fingerprint) can be used to identify possible splitting of states in the J( V ex ). The splittings that are generated between states with different quantum numbers (quantum numbers associated to the individual well) follow an unexpected opposite behavior when compared with those generated between states with the same quantum numbers (quasi-miniband). All these results are also observed in the conductance σ( E, B) associated with complex mesoscopic molecules based on a two-dimensional electron gas.

InGaN-Based Light-Emitting Diodes Grown on a Micro/Nanoscale Hybrid Patterned Sapphire Substrate.

PubMed

Ke, Wen-Cheng; Lee, Fang-Wei; Chiang, Chih-Yung; Liang, Zhong-Yi; Chen, Wei-Kuo; Seong, Tae-Yeon

2016-12-21

A hybrid patterned sapphire substrate (hybrid-PSS) was prepared using an anodic aluminum oxide etching mask to transfer nanopatterns onto a conventional patterned sapphire substrate with microscale patterns (bare-PSS). The threading dislocation (TD) suppression of light-emitting diodes (LEDs) grown on a hybrid-PSS (HP-LED) exhibits a smaller reverse leakage current compared with that of LEDs grown on a bare-PSS (BP-LED). The strain-free GaN buffer layer and fully strained InGaN active layer were evidenced by cross-sectional Raman spectra and reciprocal space mapping of the X-ray diffraction intensity for both samples. The calculated piezoelectric fields for both samples are close, implying that the quantum-confined Stark effect was not a dominant mechanism influencing the electroluminescence (EL) peak wavelength under a high injection current. The bandgap shrinkage effect of the InGaN well layer was considered to explain the large red-shifted EL peak wavelength under high injection currents. The estimated LED chip temperatures rise from room temperature to 150 °C and 75 °C for BP-LED and HP-LED, respectively, at a 600-mA injection current. This smaller temperature rise of the LED chip is attributed to the increased contact area between the sapphire and the LED structural layer because of the embedded nanopattern. Although the chip generates more heat at high injection currents, the accumulated heat can be removed to outside the chip effectively. The high diffuse reflection (DR) rate of hybrid-PSS increases the escape probability of photons, resulting in an increase in the viewing angle of the LEDs from 130° to 145°. The efficiency droop was reduced from 46% to 35%, effects which can be attributed to the elimination of TDs and strain relaxation by embedded nanopatterns. In addition, the light output power of HP-LED at 360-mA injection currents exhibits a ∼ 22.3% enhancement, demonstrating that hybrid-PSSs are beneficial to apply in high-power LEDs.

A new microplatform based on titanium dioxide nanofibers/graphene oxide nanosheets nanocomposite modified screen printed carbon electrode for electrochemical determination of adenine in the presence of guanine.

PubMed

Arvand, Majid; Ghodsi, Navid; Zanjanchi, Mohammad Ali

2016-03-15

The current techniques for determining adenine have several shortcomings such as high cost, high time consumption, tedious pretreatment steps and the requirements for highly skilled personnel often restrict their use in routine analytical practice. This paper describes the development and utilization of a new nanocomposite consisting of titanium dioxide nanofibers (TNFs) and graphene oxide nanosheets (GONs) for screen printed carbon electrode (SPCE) modification. The synthesized GONs and TNFs were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR). The modified electrode (TNFs/GONs/SPCE) was used for electrochemical characterization of adenine. The TNFs/GONs/SPCE exhibited an increase in peak current and the electron transfer kinetics and decrease in the overpotential for the oxidation reaction of adenine. Using differential pulse voltammetry (DPV), the prepared sensor showed good sensitivity for determining adenine in two ranges from 0.1-1 and 1-10 μM, with a detection limit (DL) of 1.71 nM. Electrochemical studies suggested that the TNFs/GONs/SPCE provided a synergistic augmentation on the voltammetric behavior of electrochemical oxidation of adenine, which was indicated by the improvement of anodic peak current and a decrease in anodic peak potential. The amount of adenine in pBudCE4.1 plasmid was determined via the proposed sensor and the result was in good compatibility with the sequence data of pBudCE4.1 plasmid. Copyright © 2015 Elsevier B.V. All rights reserved.

Techniques for the measurement of disruption halo currents in the National Spherical Torus Experiment.

PubMed

Gerhardt, S P; Fredrickson, E; Guttadora, L; Kaita, R; Kugel, H; Menard, J; Takahashi, H

2011-10-01

This paper describes techniques for measuring halo currents, and their associated toroidal peaking, in the National Spherical Torus Experiments [M. Ono et al., Nucl. Fusion 40, 557 (2000)]. The measurements are based on three techniques: (1) measurement of the toroidal field created by the poloidal halo current, either with segmented Rogowski coils or discrete toroidal field sensors, (2) the direct measurement of halo currents into specially instrument tiles, and (3) small Rogowski coils placed on the mechanical supports of in-vessel components. For the segmented Rogowski coils and discrete toroidal field detectors, it is shown that the toroidal peaking factor inferred from the data is significantly less than the peaking factor of the underlying halo current distribution, and a simple model is developed to relate the two. For the array of discrete toroidal field detectors and small Rogowski sensors, the compensation steps that are used to isolate the halo current signal are described. The electrical and mechanical design of compact under-tile resistive shunts and mini-Rogowski coils is described. Example data from the various systems are shown.

Calibration tests on magnetic tape lightning current detectors

NASA Technical Reports Server (NTRS)

Crouch, K. E.

1980-01-01

The low cost, passive, peak lightning current detector (LCD) invented at the NASA/Kennedy Space Center, uses magnetic audio recording tape to sense the magnitude of the peak magnetic field around a conductor carrying lightning currents. Test results show that the length of audio tape erased was linearly related to the peak simulated lightning currents in a round conductor. Accuracies of + or - 10% were shown for measurements made using a stopwatch readout technique to determine the amount of tape erased by the lightning current. The stopwatch technique is a simple, low cost means of obtaining LCD readouts and can be used in the field to obtain immediate results. Where more accurate data are desired, the tape is played and the output recorded on a strip chart, oscilloscope, or some other means so that measurements can be made on that recording. Conductor dimensions, tape holder dimensions, and tape formulation must also be considered to obtain a more accurate result. If the shape of the conductor is other than circular (i.e., angle, channel, H-beam), an analysis of the magnetic field is required to use an LCD, especially at low current levels.

Motion Perception and Manual Control Performance During Passive Tilt and Translation Following Space Flight

NASA Technical Reports Server (NTRS)

Clement, Gilles; Wood, Scott J.

2010-01-01

This joint ESA-NASA study is examining changes in motion perception following Space Shuttle flights and the operational implications of post-flight tilt-translation ambiguity for manual control performance. Vibrotactile feedback of tilt orientation is also being evaluated as a countermeasure to improve performance during a closed-loop nulling task. METHODS. Data has been collected on 5 astronaut subjects during 3 preflight sessions and during the first 8 days after Shuttle landings. Variable radius centrifugation (216 deg/s) combined with body translation (12-22 cm, peak-to-peak) is utilized to elicit roll-tilt perception (equivalent to 20 deg, peak-to-peak). A forward-backward moving sled (24-390 cm, peak-to-peak) with or without chair tilting in pitch is utilized to elicit pitch tilt perception (equivalent to 20 deg, peak-to-peak). These combinations are elicited at 0.15, 0.3, and 0.6 Hz for evaluating the effect of motion frequency on tilt-translation ambiguity. In both devices, a closed-loop nulling task is also performed during pseudorandom motion with and without vibrotactile feedback of tilt. All tests are performed in complete darkness. PRELIMINARY RESULTS. Data collection is currently ongoing. Results to date suggest there is a trend for translation motion perception to be increased at the low and medium frequencies on landing day compared to pre-flight. Manual control performance is improved with vibrotactile feedback. DISCUSSION. The results of this study indicate that post-flight recovery of motion perception and manual control performance is complete within 8 days following short-duration space missions. Vibrotactile feedback of tilt improves manual control performance both before and after flight.

Ozone generation in a kHz-pulsed He-O2 capillary dielectric barrier discharge operated in ambient air

NASA Astrophysics Data System (ADS)

Sands, Brian L.; Ganguly, Biswa N.

2013-12-01

The generation of reactive oxygen species using nonequilibrium atmospheric pressure plasma jet devices has been a subject of recent interest due to their ability to generate localized concentrations from a compact source. To date, such studies with plasma jet devices have primarily utilized radio-frequency excitation. In this work, we characterize ozone generation in a kHz-pulsed capillary dielectric barrier discharge configuration comprised of an active discharge plasma jet operating in ambient air that is externally grounded. The plasma jet flow gas was composed of helium with an admixture of up to 5% oxygen. A unipolar voltage pulse train with a 20 ns pulse risetime was used to drive the discharge at repetition rates between 2-25 kHz. Using UVLED absorption spectroscopy centered at 255 nm near the Hartley-band absorption peak, ozone was detected over 1 cm from the capillary axis. We observed roughly linear scaling of ozone production with increasing pulse repetition rate up to a "turnover frequency," beyond which ozone production steadily dropped and discharge current and 777 nm O(5P→5S°) emission sharply increased. The turnover in ozone production occurred at higher pulse frequencies with increasing flow rate and decreasing applied voltage with a common energy density of 55 mJ/cm3 supplied to the discharge. The limiting energy density and peak ozone production both increased with increasing O2 admixture. The power dissipated in the discharge was obtained from circuit current and voltage measurements using a modified parallel plate dielectric barrier discharge circuit model and the volume-averaged ozone concentration was derived from a 2D ozone absorption measurement. From these measurements, the volume-averaged efficiency of ozone production was calculated to be 23 g/kWh at conditions for peak ozone production of 41 mg/h at 11 kV applied voltage, 3% O2, 2 l/min flow rate, and 13 kHz pulse repetition rate, with 1.79 W dissipated in the discharge.

Structure zone diagram and particle incorporation of nickel brush plated composite coatings

PubMed Central

Isern, L.; Impey, S.; Almond, H.; Clouser, S. J.; Endrino, J. L.

2017-01-01

This work studies the deposition of aluminium-incorporated nickel coatings by brush electroplating, focusing on the electroplating setup and processing parameters. The setup was optimised in order to increase the volume of particle incorporation. The optimised design focused on increasing the plating solution flow to avoid sedimentation, and as a result the particle transport experienced a three-fold increase when compared with the traditional setup. The influence of bath load, current density and the brush material used was investigated. Both current density and brush material have a significant impact on the morphology and composition of the coatings. Higher current densities and non-abrasive brushes produce rough, particle-rich samples. Different combinations of these two parameters influence the surface characteristics differently, as illustrated in a Structure Zone Diagram. Finally, surfaces featuring crevices and peaks incorporate between 3.5 and 20 times more particles than smoother coatings. The presence of such features has been quantified using average surface roughness Ra and Abbott-Firestone curves. The combination of optimised setup and rough surface increased the particle content of the composite to 28 at.%. PMID:28300159

Electricity production coupled to ammonium in a microbial fuel cell.

PubMed

He, Zhen; Kan, Jinjun; Wang, Yanbing; Huang, Yuelong; Mansfeld, Florian; Nealson, Kenneth H

2009-05-01

The production of electricity from ammonium was examined using a rotating-cathode microbial fuel cell (MFC). The addition of ammonium chloride, ammonium sulfate, or ammonium phosphate (monobasic) resulted in electricity generation, while adding sodium chloride, nitrate, or nitrite did not cause any increase in current production. The peak current increased with increasing amount of ammonium addition up to 62.3 mM of ammonium chloride, suggesting that ammonium was involved in electricity generation either directly as the anodic fuel or indirectly as substrates for nitrifiers to produce organic compounds for heterotrophs. Adding nitrate or nitrite with ammonium increased current production compared to solely ammonium addition. Using 16S rRNA-linked molecular analyses, we found ammonium-oxidizing bacteria and denitrifying bacteria on both the anode and cathode electrodes, whereas no anammox bacteria were detected. The dominant ammonium-oxidizing bacteria were closely related to Nitrosomonas europaea. The present MFC achieved an ammonium removal efficiency of 49.2 +/- 5.9 or 69.7 +/- 3.6%, depending on hydraulic retention time, but exhibited a very low Coulombic efficiency.

Structure zone diagram and particle incorporation of nickel brush plated composite coatings

NASA Astrophysics Data System (ADS)

Isern, L.; Impey, S.; Almond, H.; Clouser, S. J.; Endrino, J. L.

2017-03-01

This work studies the deposition of aluminium-incorporated nickel coatings by brush electroplating, focusing on the electroplating setup and processing parameters. The setup was optimised in order to increase the volume of particle incorporation. The optimised design focused on increasing the plating solution flow to avoid sedimentation, and as a result the particle transport experienced a three-fold increase when compared with the traditional setup. The influence of bath load, current density and the brush material used was investigated. Both current density and brush material have a significant impact on the morphology and composition of the coatings. Higher current densities and non-abrasive brushes produce rough, particle-rich samples. Different combinations of these two parameters influence the surface characteristics differently, as illustrated in a Structure Zone Diagram. Finally, surfaces featuring crevices and peaks incorporate between 3.5 and 20 times more particles than smoother coatings. The presence of such features has been quantified using average surface roughness Ra and Abbott-Firestone curves. The combination of optimised setup and rough surface increased the particle content of the composite to 28 at.%.

Structure zone diagram and particle incorporation of nickel brush plated composite coatings.

PubMed

Isern, L; Impey, S; Almond, H; Clouser, S J; Endrino, J L

2017-03-16

This work studies the deposition of aluminium-incorporated nickel coatings by brush electroplating, focusing on the electroplating setup and processing parameters. The setup was optimised in order to increase the volume of particle incorporation. The optimised design focused on increasing the plating solution flow to avoid sedimentation, and as a result the particle transport experienced a three-fold increase when compared with the traditional setup. The influence of bath load, current density and the brush material used was investigated. Both current density and brush material have a significant impact on the morphology and composition of the coatings. Higher current densities and non-abrasive brushes produce rough, particle-rich samples. Different combinations of these two parameters influence the surface characteristics differently, as illustrated in a Structure Zone Diagram. Finally, surfaces featuring crevices and peaks incorporate between 3.5 and 20 times more particles than smoother coatings. The presence of such features has been quantified using average surface roughness Ra and Abbott-Firestone curves. The combination of optimised setup and rough surface increased the particle content of the composite to 28 at.%.

The effects of γ-ray on charging behaviour using polyimide

NASA Astrophysics Data System (ADS)

Qin, Sichen; Tu, Youping; Tan, Tian; Wang, Shaohe; Yuan, Zhikang; Wang, Cong; Li, Laifeng; Wu, Zhixiong

2018-06-01

Insulation material is a key component of electrical equipment in satellites; its electrical properties determine the reliability and lifetime of the whole satellite. High-energy radioactive rays in space affect the molecular structure of the polymeric insulating materials. Under the action of plasma, high energy particles, along with the magnetic fields experienced in orbits, electric charges get injected into and trapped by the insulating material creating distortions in the electric field and even electrostatic discharges. Polyimides have been widely used for insulation in spacecraft. Choosing Co-60 gamma ray with irradiation doses of 1 MGy and 5 MGy to simulate the radiation environment of space, we investigated the effect of radiation on charging behaviour. The thermal stimulated current (TSC) from a high electric field over a wide range of temperatures was measured from which the activation energy was calculated. These results for the two sources show that the percentage increase in total charge was 133.3% and 119.4%. The γ, β 3, and α charge peaks of specimens after an irradiation dose of 1 MGy rose. In comparison, the β 2 peak of the 5 MGy-dosed specimens was enhanced. Also, there is almost no change in the γ, β 3, and α peaks. To understand the mechanism behind the TSC changes, the resulting physicochemical characteristics of an irradiated specimen were observed employing various analyses of chemical characteristics (x-ray photoelectron spectroscopy, differential scanning calorimetry and x-ray diffraction). Compared with the non-dosed specimen, the relative content of C–N and the glass transition temperature of the 1 MGy sample decreased, and the crystallinity increased, thus increasing the γ and α peak intensities. Compared with the 1 MGy sample, only the glass transition temperature had risen, thereby enhancing the β peak intensity. With the foregoing, a theoretical base for the selection and modification of insulation materials for spacecraft is provided.

The Use of Dexamethasone in Support of High-Altitude Ground Operations: Review of the Literature & Current Training of U.S. Special Operations Medical Members

DTIC Science & Technology

2013-03-14

Dexamethasone increased maximal aerobic capacity compared with placebo. For example, pulse oximeter oxygen saturation at rest was significantly lower...IHE for 6 to 7 days reduces AMS by an estimated 20% and increases oxygen saturation levels by 1% to 3%. Several IHE protocols exist, but none have... oxygen kinetics (pɘ.05) and reduced ventilator equivalent for CO2 (pɘ.01); no significant difference in peak O2 saturation between groups

Intense ion beam generator

DOEpatents

Humphries, Jr., Stanley; Sudan, Ravindra N.

1977-08-30

Methods and apparatus for producing intense megavolt ion beams are disclosed. In one embodiment, a reflex triode-type pulsed ion accelerator is described which produces ion pulses of more than 5 kiloamperes current with a peak energy of 3 MeV. In other embodiments, the device is constructed so as to focus the beam of ions for high concentration and ease of extraction, and magnetic insulation is provided to increase the efficiency of operation.

Efficiency enhancement of organic solar cells using transparent plasmonic Ag nanowire electrodes.

PubMed

Kang, Myung-Gyu; Xu, Ting; Park, Hui Joon; Luo, Xiangang; Guo, L Jay

2010-10-15

Surface plasmon enhanced photo-current and power conversion efficiency of organic solar cells using periodic Ag nanowires as transparent electrodes are reported, as compared to the device with conventional ITO electrodes. External quantum efficiencies are enhanced about 2.5 fold around the peak solar spectrum wavelength of 560 nm, resulting in 35% overall increase in power conversion efficiency than the ITO control device under normal unpolarized light.

The impact of weather on women's tendency to wear red or pink when at high risk for conception.

PubMed

Tracy, Jessica L; Beall, Alec T

2014-01-01

Women are particularly motivated to enhance their sexual attractiveness during their most fertile period, and men perceive shades of red, when associated with women, as sexually attractive. Building on this research, we recently found that women are more likely to wear reddish clothing when at peak fertility (Beall & Tracy, 2013), presumably as a way of increasing their attractiveness. Here, we first report results from a methodological replication, conducted during warmer weather, which produced a null effect. Investigating this discrepancy, we considered the impact of a potentially relevant contextual difference between previous research and the replication: current weather. If the red-dress effect is driven by a desire to increase one's sexual appeal, then it should emerge most reliably when peak-fertility women have few alternative options for accomplishing this goal (e.g., wearing minimal clothing). Results from re-analyses of our previously collected data and a new experiment support this account, by demonstrating that the link between fertility and red/pink dress emerges robustly in cold, but not warm, weather. Together, these findings suggest that the previously documented red-dress effect is moderated by current climate concerns, and provide further evidence that under certain circumstances red/pink dress is reliably associated with female fertility.

Simultaneous Forbush decreases and associated geomagnetic storms during the last three solar cycles

NASA Astrophysics Data System (ADS)

Okpala, K. C.

2013-12-01

Forbush decrease (FD) are observed reduction in galactic cosmic ray (GCR) intensity as measured by ground neutron monitors. FD is associated with increased activity of the sun as reflected in the size of the interplanetary coronal mass ejections passing around the Earth and the corotating regions in the Heliosphere. Since the interplanetary anisotropy evolves itself during a geomagnetic storm in addition to the reconfiguration of external magnetospheric currents, it is expected that changes in transmissivity of cosmic rays of glactic origin will occur during Geomagnetic storms. In this study we examine over one hundred and fifty (150) FD events and associated geomagnetic storms over the last three solar cycles from 1970 to 2003. The negative peaks of the FDs and the Dst coincided for most of the events (~70%). There was good correlation (>0.65) between the FDs and Dst. Fresh evidence of the influence of external magnetospheric currents on the count rates of the neutron monitors stations during periods of Forbush decreases (FDs) is provided. This evidence is observed as sudden increases in the count rates during the main phase of simultaneous FD. The magnitude of the sudden rise in the count rates of Neutron monitors and peak dst correlated well (>0.50) both for high latitude and mid latitude stations.

Risk Management and Physical Modelling for Mountainous Natural Hazards

NASA Astrophysics Data System (ADS)

Lehning, Michael; Wilhelm, Christian

Population growth and climate change cause rapid changes in mountainous regions resulting in increased risks of floods, avalanches, debris flows and other natural hazards. Xevents are of particular concern, since attempts to protect against them result in exponentially growing costs. In this contribution, we suggest an integral risk management approach to dealing with natural hazards that occur in mountainous areas. Using the example of a mountain pass road, which can be protected from the danger of an avalanche by engineering (galleries) and/or organisational (road closure) measures, we show the advantage of an optimal combination of both versus the traditional approach, which is to rely solely on engineering structures. Organisational measures become especially important for Xevents because engineering structures cannot be designed for those events. However, organisational measures need a reliable and objective forecast of the hazard. Therefore, we further suggest that such forecasts should be developed using physical numerical modelling. We present the status of current approaches to using physical modelling to predict snow cover stability for avalanche warnings and peak runoff from mountain catchments for flood warnings. While detailed physical models can already predict peak runoff reliably, they are only used to support avalanche warnings. With increased process knowledge and computer power, current developments should lead to a enhanced role for detailed physical models in natural mountain hazard prediction.

Photoluminescence emission spectra of Makrofol® DE 1-1 upon irradiation with ultraviolet radiation

NASA Astrophysics Data System (ADS)

El Ghazaly, M.; Aydarous, Abdulkadir

Photoluminescence (PL) emission spectra of Makrofol® DE 1-1 (bisphenol-A based polycarbonate) upon irradiation with ultraviolet radiation of different wavelengths were investigated. The absorption-and attenuation coefficient measurements revealed that the Makrofol® DE 1-1 is characterized by high absorbance in the energy range 6.53-4.43 eV but for a lower energy than 4.43 eV, it is approximately transparent. Makrofol® DE 1-1 samples were irradiated with ultraviolet radiation of wavelength in the range from 250 (4.28 eV) to 400 (3.10 eV) nm in step of 10 nm and the corresponding photoluminescence (PL) emission spectra were measured with a spectrofluorometer. It is found that the integrated counts and the peak height of the photoluminescence emission (PL) bands are strongly correlated with the ultraviolet radiation wavelength. They are increased at the ultraviolet radiation wavelength 280 nm and have maximum at 290 nm, thereafter they decrease and diminish at 360 nm of ultraviolet wavelength. The position of the PL emission band peak was red shifted starting from 300 nm, which increased with the increase the ultraviolet radiation wavelength. The PL bandwidth increases linearly with the increase of the ultraviolet radiation wavelength. When Makrofol® DE 1-1 is irradiated with ultraviolet radiation of short wavelength (UVC), the photoluminescence emission spectra peaks also occur in the UVC but of a relatively longer wavelength. The current new findings should be considered carefully when using Makrofol® DE 1-1 in medical applications related to ultraviolet radiation.

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

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.

Hormones, Nicotine and Cocaine: Clinical Studies

PubMed Central

Mello, Nancy K.

2009-01-01

Nicotine and cocaine each stimulate hypothalamic-pituitary-adrenal and -gonadal axis hormones, and there is increasing evidence that the hormonal milieu may modulate the abuse-related effects of these drugs. This review summarizes some clinical studies of the acute effects of cigarette smoking or IV cocaine on plasma drug and hormone levels, and subjective effects ratings. The temporal covariance between these dependent measures was assessed with a rapid (two min) sampling procedure in nicotine-dependent volunteers or current cocaine users. Cigarette smoking and IV cocaine each stimulated a rapid increase in LH and ACTH, followed by gradual increases in cortisol and DHEA. Positive subjective effects ratings increased immediately after initiation of cigarette smoking or IV cocaine administration. However, in contrast to cocaine’s sustained positive effects (< 20 min), ratings of “High” and “Rush” began to decrease within one or two puffs of a high nicotine cigarette while nicotine levels were increasing. Peak nicotine levels increased progressively after each of three successive cigarettes smoked at 60 min intervals, but the magnitude of the subjective effects ratings and peak ACTH and cortisol levels diminished. Only DHEA increased consistently after successive cigarettes. The possible influence of neuroactive hormones on nicotine dependence and cocaine abuse, and implications for treatment of these addictive disorders is discussed. PMID:19835877

Thermally induced spin-dependent current based on Zigzag Germanene Nanoribbons

NASA Astrophysics Data System (ADS)

Majidi, Danial; Faez, Rahim

2017-02-01

In this paper, using first principle calculation and non-equilibrium Green's function, the thermally induced spin current in Hydrogen terminated Zigzag-edge Germanene Nanoribbon (ZGeNR-H) is investigated. In this model, because of the difference between the source and the drain temperature of ZGeNR device, the spin up and spin down currents flow in the opposite direction with two different threshold temperatures (Tth). Hence, a pure spin polarized current which belongs to spin down is obtained. It is shown that, for temperatures above the threshold temperature spin down current increases with the increasing temperature up to 75 K and then decreases. But spin up current rises steadily and in the high temperature we can obtain polarized spin up current. In addition, we show an acceptable spin current around the room temperature for ZGeNR. The transmission peaks in ZGeNR which are closer to the Fermi level rather than Zigzag Graphene Nanoribbon (ZGNRS) which causes ZGeNR to have spin current at higher temperatures. Finally, it is indicated that by tuning the back gate voltage, the spin current can be completely modulated and polarized. Simulation results verify the Zigzag Germanene Nanoribbon as a promising candidate for spin caloritronics devices, which can be applied in future low power consumption technology.

Characterization of dipole defects in MgAl2O4 spinel

NASA Astrophysics Data System (ADS)

Carvalhaes, R. P. M.; da Rocha, M. S. F.; de Souza, S. S.; Blak, A. R.

2005-01-01

Dipole defects in gamma-irradiated and thermal treated MgAl2O4 samples have been studied through thermally stimulated depolarisation currents(TSDC) technique and computer modelling methods. The presence of TSDC bands varies from sample to sample and some crystals do not present any band. The origin of these bands has been investigated in several different samples. In the spectra of spinels showing TSDC peaks, three bands at 130K, 160K and 320K are observed. The peaks at 130K and 160K have been attributed to dipole defects. After 1200kGy of gamma irradiation the broad band at 320K dislocates to 290K and increases ten times. Pulsed thermal treatments between 350K and 470K produce a progressive reduction of the peak area and a shift in the peak position back to 320K. A detailed analysis of the curve indicates the possibility of a superposition of peaks. Gamma irradiation restores the 320K TSDC peak. Taking into account optical absorption(OA) and electron paramagnetic resonance(EPR) results, the thermal reduction of the 320K TSDC band was attributed to V-type centres as a result of hole trapping at tetrahedral and octahedral cation vacancies. Computer modelling methods, based on lattice energy and defect minimisation, were applied to identify dipole defects that occur in these crystals. The calculations were made in normal and inverse spinel structures, doped with Cr, Co, Mn and Fe in order to justify the presence of dipole bands.

High-accuracy peak picking of proteomics data using wavelet techniques.

PubMed

Lange, Eva; Gröpl, Clemens; Reinert, Knut; Kohlbacher, Oliver; Hildebrandt, Andreas

2006-01-01

A new peak picking algorithm for the analysis of mass spectrometric (MS) data is presented. It is independent of the underlying machine or ionization method, and is able to resolve highly convoluted and asymmetric signals. The method uses the multiscale nature of spectrometric data by first detecting the mass peaks in the wavelet-transformed signal before a given asymmetric peak function is fitted to the raw data. In an optional third stage, the resulting fit can be further improved using techniques from nonlinear optimization. In contrast to currently established techniques (e.g. SNAP, Apex) our algorithm is able to separate overlapping peaks of multiply charged peptides in ESI-MS data of low resolution. Its improved accuracy with respect to peak positions makes it a valuable preprocessing method for MS-based identification and quantification experiments. The method has been validated on a number of different annotated test cases, where it compares favorably in both runtime and accuracy with currently established techniques. An implementation of the algorithm is freely available in our open source framework OpenMS.

Monte Carlo evaluation of magnetically focused proton beams for radiosurgery

NASA Astrophysics Data System (ADS)

McAuley, Grant A.; Heczko, Sarah L.; Nguyen, Theodore T.; Slater, James M.; Slater, Jerry D.; Wroe, Andrew J.

2018-03-01

The purpose of this project is to investigate the advantages in dose distribution and delivery of proton beams focused by a triplet of quadrupole magnets in the context of potential radiosurgery treatments. Monte Carlo simulations were performed using various configurations of three quadrupole magnets located immediately upstream of a water phantom. Magnet parameters were selected to match what can be commercially manufactured as assemblies of rare-earth permanent magnetic materials. Focused unmodulated proton beams with a range of ~10 cm in water were target matched with passive collimated beams (the current beam delivery method for proton radiosurgery) and properties of transverse dose, depth dose and volumetric dose distributions were compared. Magnetically focused beams delivered beam spots of low eccentricity to Bragg peak depth with full widths at the 90% reference dose contour from ~2.5 to 5 mm. When focused initial beam diameters were larger than matching unfocused beams (10 of 11 cases) the focused beams showed 16%–83% larger peak-to-entrance dose ratios and 1.3 to 3.4-fold increases in dose delivery efficiency. Peak-to-entrance and efficiency benefits tended to increase with larger magnet gradients and larger initial diameter focused beams. Finally, it was observed that focusing tended to shift dose in the water phantom volume from the 80%–20% dose range to below 20% of reference dose, compared to unfocused beams. We conclude that focusing proton beams immediately upstream from tissue entry using permanent magnet assemblies can produce beams with larger peak-to-entrance dose ratios and increased dose delivery efficiencies. Such beams could potentially be used in the clinic to irradiate small-field radiosurgical targets with fewer beams, lower entrance dose and shorter treatment times.

Positive inotropic effects of RP 62719, a new pure class III antiarrhythmic agent, on guinea pig myocardium.

PubMed

Beregi, J P; Escande, D; Coudray, N; Mery, P; Mestre, M; Chemla, D; Lecarpentier, Y

1992-12-01

The mechanical effects of RP 62719 [(-)1-[-2-(3,4-dihydro-2H-1- benzopyran-4-yl)ethyl]-4-(3,4-dimethoxyphenyl)-piperidine] were tested in vitro on guinea pig left ventricular papillary muscle. RP 62719 is a novel pure class III antiarrhythmic agent known to prolong the cardiac action potential duration by selectively blocking the inward rectifying K+ current. Mechanical parameters were determined from contraction and relaxation phases under isotonic and isometric conditions. At a concentration of 0.02 microM, RP 62719 did not produce significant effects on inotropy or lusitropy. At 0.2 and 2 microM, the drug improved contraction under both heavy and low loading conditions, as evidenced by a 30% increase in maximum unloaded shortening velocity (Vmax, P < .001), peak amplitude of shortening (delta L, P < .001), peak isometric active force normalized per cross-sectional area (AF/s, P < .001) and positive peak of the force derivative per mm2 (+dF/s, P < .001). At the same concentrations, positive lusitropic effects were evidenced by an increase in maximum lengthening velocity (maxVr) and negative peak of force derivative per mm2 (-dF/s, P < .001). At a higher concentration (20 microM), effects of RP 62719 on inotropy and lusitropy were less marked, thus accounting for the bell-shaped form of the dose-response curve. An increase in the extracellular Ca++ concentration from 2.5 to 3.75 mM improved inotropy to a similar extent (+30-50%) as did 2 microM RP 62719. However, lusitropy and mechanical coupling between contraction and relaxation were not modified in the same proportion under RP 62719 and under 3.75 mM Ca++.(ABSTRACT TRUNCATED AT 250 WORDS)

Experimental study of effect of magnetic field on anode temperature distribution in an ATON-type Hall thruster

NASA Astrophysics Data System (ADS)

Liu, Jinwen; Li, Hong; Mao, Wei; Ding, Yongjie; Wei, Liqiu; Li, Jianzhi; Yu, Daren; Wang, Xiaogang

2018-05-01

The energy deposition caused by the absorption of electrons by the anode is an important cause of power loss in a Hall thruster. The resulting anode heating is dangerous, as it can potentially reduce the thruster lifetime. In this study, by considering the ring shape of the anode of an ATON-type Hall thruster, the effects of the magnetic field strength and gradient on the anode ring temperature distribution are studied via experimental measurement. The results show that the temperature distribution is not affected by changes in the magnetic field strength and that the position of the peak temperature is essentially unchanged; however, the overall temperature does not change monotonically with the increase of the magnetic field strength and is positively correlated with the change in the discharge current. Moreover, as the magnetic field gradient increases, the position of the peak temperature gradually moves toward the channel exit and the temperature tends to decrease as a whole, regardless of the discharge current magnitude; in any case, the position of the peak temperature corresponds exactly to the intersection of the magnetic field cusp with the anode ring. Further theoretical analysis shows that the electrons, coming from the ionization region, travel along two characteristic paths to reach the anode under the guidance of the cusped magnetic field configuration. The change of the magnetic field strength or gradient changes the transfer of momentum and energy of the electrons in these two paths, which is the main reason for the changes in the temperature and distribution. This study is instructive for matching the design of the ring-shaped anode and the cusp magnetic field of an ATON-type Hall thruster.

Osteoclastogenesis in Local Alveolar Bone in Early Decortication-Facilitated Orthodontic Tooth Movement

PubMed Central

Liu, Chang; Jiang, Yu-Xi; Qu, Hong; Li, Cui-Ying; Jiang, Jiu-Hui

2016-01-01

Objective In the current study, we aimed to investigate the effects of alveolar decortication on local bone remodeling, and to explore the possible mechanism by which decortication facilitates tooth movement. Materials and Methods Forty rabbits were included in the experiment. The left mandible was subjected to decortication-facilitated orthodontics, and the right mandible underwent traditional orthodontics as a control. The animals were sacrificed on the days 1, 3, 5, 7 and 14, after undergoing orthodontic procedures. Tooth movement was measured by Micro-CT, and the local periodontal tissues were investigated using H&E, Masson's trichrome and tartrate-resistant acid phosphatase (TRAP) staining. The mRNA levels of genes related to bone remodeling in the alveolar bone were analyzed using real-time PCR. Result On days 3, 5, 7 and 14, tooth movement was statistically accelerated by decortication (P < 0.05) and was accompanied by increased hyperemia. Despite the lack of new bone formation in both groups, more osteoclasts were noted in the decorticated group, with two peak counts (P < 0.05). The first peak count was consistent with the maximum values of ctsk and TRAP expression, and the second peak counts accompanied the maximum nfatc1 and jdp2 expression. The increased fra2 expression and the ratio of rankl/opg also accompanied the second peak counts. Conclusions Following alveolar decortication, osteoclastogenesis was initially induced to a greater degree than the new bone formation which was thought to have caused a regional acceleratory phenomenon (RAP). The amount of steoclastogenesis in the decorticated alveolar bone was found to have two peaks, perhaps due to attenuated local resistance. The first peak count in osteoclasts may have been due to previously existing osteoclast precursors, whereas the second may represent the differentiation of peripheral blood mononuclear cells which came from circulation as the result of hyperemia. PMID:27096621

Competitive inhibition of the nondepolarizing muscle relaxant rocuronium on nicotinic acetylcholine receptor channels in the rat superior cervical ganglia.

PubMed

Zhang, Chengmi; Wang, Zhenmeng; Zhang, Jinmin; Qiu, Haibo; Sun, Yuming; Yang, Liqun; Wu, Feixiang; Zheng, Jijian; Yu, Weifeng

2014-05-01

A number of case reports now indicate that rocuronium can induce a number of serious side effects. We hypothesized that these side effects might be mediated by the inhibition of nicotinic acetylcholine receptors (nAChRs) at superior cervical ganglion (SCG) neurons. Conventional patch clamp recordings were used to study the effects of rocuronium on nAChR currents from enzymatically dissociated rat SCG neurons. We found that ACh induced a peak transient inward current in rat SCG neurons. Additionally, rocuronium suppressed the peak ACh-evoked currents in rat SCG neurons in a concentration-dependent and competitive manner, and it increased the extent of desensitization of nAChRs. The inhibitory rate of rocuronium on nAChR currents did not change significantly at membrane potentials between -70 and -20 mV, suggesting that this inhibition was voltage independent. Lastly, rocuronium preapplication enhanced its inhibitory effect, indicating that this drug might prefer to act on the closed state of nAChR channels. In conclusion, rocuronium, at clinically relevant concentrations, directly inhibits nAChRs at the SCG by interacting with both opened and closed states. This inhibition is competitive, dose dependent, and voltage independent. Blockade of synaptic transmission in the sympathetic ganglia by rocuronium might have potentially inhibitory effects on the cardiovascular system.

Zn2+ reduction induces neuronal death with changes in voltage-gated potassium and sodium channel currents.

PubMed

Tian, Kun; He, Cong-Cong; Xu, Hui-Nan; Wang, Yu-Xiang; Wang, Hong-Gang; An, Di; Heng, Bin; Pang, Wei; Jiang, Yu-Gang; Liu, Yan-Qiang

2017-05-01

In the present study, cultured rat primary neurons were exposed to a medium containing N,N,N',N'-tetrakis(2-pyridylmethyl)ethylenediamine (TPEN), a specific cell membrane-permeant Zn 2+ chelator, to establish a model of free Zn 2+ deficiency in neurons. The effects of TPEN-mediated free Zn 2+ ion reduction on neuronal viability and on the performance of voltage-gated sodium channels (VGSCs) and potassium channels (Kvs) were assessed. Free Zn 2+ deficiency 1) markedly reduced the neuronal survival rate, 2) reduced the peak amplitude of I Na , 3) shifted the I Na activation curve towards depolarization, 4) modulated the sensitivity of sodium channel voltage-dependent inactivation to a depolarization voltage, and 5) increased the time course of recovery from sodium channel inactivation. In addition, free Zn 2+ deficiency by TPEN notably enhanced the peak amplitude of transient outward K + currents (I A ) and delayed rectifier K + currents (I K ), as well as caused hyperpolarization and depolarization directional shifts in their steady-state activation curves, respectively. Zn 2+ supplementation reversed the effects induced by TPEN. Our results indicate that free Zn 2+ deficiency causes neuronal damage and alters the dynamic characteristics of VGSC and Kv currents. Thus, neuronal injury caused by free Zn 2+ deficiency may correlate with its modulation of the electrophysiological properties of VGSCs and Kvs. Copyright © 2017 Elsevier GmbH. All rights reserved.

Field-effect amperometric immuno-detection of protein biomarker.

PubMed

Wang, Jiapeng; Yau, Siu-Tung

2011-11-15

The field-effect enzymatic detection technique has been applied to the amperometric immunoassay of the cancer biomarker, carcinoma antigen 125 (CA 125). The detection adopted a reagentless approach, in which the analyte, CA 125, was immobilized on the detecting electrode, which was modified using carbon nanotubes, and the detection signal was obtained by measuring the reduction peak current of the enzyme that was used to label the antibody. A gating voltage was applied to the detecting electrode, inducing increase in the signal current and therefore providing amplification of the detection signal. The voltage-controlled signal amplification of the detection system has increased the sensitivity and lowered the detection limit of the system. A detection limit of 0.9U/ml was obtained in the work. Copyright © 2011 Elsevier B.V. All rights reserved.

Wide step width reduces knee abduction moment of obese adults during stair negotiation.

PubMed

Yocum, Derek; Weinhandl, Joshua T; Fairbrother, Jeffrey T; Zhang, Songning

2018-05-15

An increased likelihood of developing obesity-related knee osteoarthritis may be associated with increased peak internal knee abduction moments (KAbM). Increases in step width (SW) may act to reduce this moment. The purpose of this study was to determine the effects of increased SW on knee biomechanics during stair negotiation of healthy-weight and obese participants. Participants (24: 10 obese and 14 healthy-weight) used stairs and walked over level ground while walking at their preferred speed in two different SW conditions - preferred and wide (200% preferred). A 2 × 2 (group × condition) mixed model analysis of variance was performed to analyze differences between groups and conditions (p < 0.05). Increased SW increased the loading-response peak knee extension moment during descent and level gait, decreased loading-response KAbMs, knee extension and abduction range of motion (ROM) during ascent, and knee adduction ROM during descent. Increased SW increased loading-response peak mediolateral ground reaction force (GRF), increased peak knee abduction angle during ascent, and decreased peak knee adduction angle during descent and level gait. Obese participants experienced disproportionate changes in loading-response mediolateral GRF, KAbM and peak adduction angle during level walking, and peak knee abduction angle and ROM during ascent. Increased SW successfully decreased loading-response peak KAbM. Implications of this finding are that increased SW may decrease medial compartment knee joint loading, decreasing pain and reducing joint deterioration. Increased SW influenced obese and healthy-weight participants differently and should be investigated further. Copyright © 2018. Published by Elsevier Ltd.

The Potential for Energy Storage to Provide Peaking Capacity in California under Increased Penetration of Solar Photovoltaics: Report Summary

DOE Office of Scientific and Technical Information (OSTI.GOV)

Denholm, Paul L; Margolis, Robert M

Opportunities to provide peaking capacity with low-cost energy storage are emerging. But adding storage changes the ability of subsequent storage additions to meet peak demand. Increasing photovoltaic (PV) deployment also affects storage's ability to provide peak capacity. This study examines storage's potential to replace conventional peak capacity in California.

The Orphan Drug Act: Restoring the Mission to Rare Diseases.

PubMed

Daniel, Michael G; Pawlik, Timothy M; Fader, Amanda N; Esnaola, Nestor F; Makary, Martin A

2016-04-01

The Orphan Drug Act has fostered drug development for patients with rare cancers and other diseases; however, current data suggest that companies are gaming the system to use the law for mainstream drugs. We identify a pattern of pharmaceutical companies submitting drugs to the Food and Drug Administration (FDA) as orphan drugs but once approved, the drugs are used broadly off-label with the lucrative orphan drug protections and exclusivity benefits. Since the law was passed, the proportion of new FDA-approved drugs that were submitted as orphan drugs has increased with a peak last year of 41% of all FDA-approved drugs approved as orphan drugs. On the basis of the current data, we suggest that patients with rare cancers and other diseases may suffer due to dilution of the incentives and benefits. We propose reform to increase submission scrutiny, decrease benefits based on off-label use, and increase price transparency.

Control algorithms for dynamic attenuators.

PubMed

Hsieh, Scott S; Pelc, Norbert J

2014-06-01

The authors describe algorithms to control dynamic attenuators in CT and compare their performance using simulated scans. Dynamic attenuators are prepatient beam shaping filters that modulate the distribution of x-ray fluence incident on the patient on a view-by-view basis. These attenuators can reduce dose while improving key image quality metrics such as peak or mean variance. In each view, the attenuator presents several degrees of freedom which may be individually adjusted. The total number of degrees of freedom across all views is very large, making many optimization techniques impractical. The authors develop a theory for optimally controlling these attenuators. Special attention is paid to a theoretically perfect attenuator which controls the fluence for each ray individually, but the authors also investigate and compare three other, practical attenuator designs which have been previously proposed: the piecewise-linear attenuator, the translating attenuator, and the double wedge attenuator. The authors pose and solve the optimization problems of minimizing the mean and peak variance subject to a fixed dose limit. For a perfect attenuator and mean variance minimization, this problem can be solved in simple, closed form. For other attenuator designs, the problem can be decomposed into separate problems for each view to greatly reduce the computational complexity. Peak variance minimization can be approximately solved using iterated, weighted mean variance (WMV) minimization. Also, the authors develop heuristics for the perfect and piecewise-linear attenuators which do not require a priori knowledge of the patient anatomy. The authors compare these control algorithms on different types of dynamic attenuators using simulated raw data from forward projected DICOM files of a thorax and an abdomen. The translating and double wedge attenuators reduce dose by an average of 30% relative to current techniques (bowtie filter with tube current modulation) without increasing peak variance. The 15-element piecewise-linear dynamic attenuator reduces dose by an average of 42%, and the perfect attenuator reduces dose by an average of 50%. Improvements in peak variance are several times larger than improvements in mean variance. Heuristic control eliminates the need for a prescan. For the piecewise-linear attenuator, the cost of heuristic control is an increase in dose of 9%. The proposed iterated WMV minimization produces results that are within a few percent of the true solution. Dynamic attenuators show potential for significant dose reduction. A wide class of dynamic attenuators can be accurately controlled using the described methods.

Measurements of file transfer rates over dedicated long-haul connections

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rao, Nageswara S; Settlemyer, Bradley W; Imam, Neena

2016-01-01

Wide-area file transfers are an integral part of several High-Performance Computing (HPC) scenarios. Dedicated network connections with high capacity, low loss rate and low competing traffic, are increasingly being provisioned over current HPC infrastructures to support such transfers. To gain insights into these file transfers, we collected transfer rate measurements for Lustre and xfs file systems between dedicated multi-core servers over emulated 10 Gbps connections with round trip times (rtt) in 0-366 ms range. Memory transfer throughput over these connections is measured using iperf, and file IO throughput on host systems is measured using xddprof. We consider two file systemmore » configurations: Lustre over IB network and xfs over SSD connected to PCI bus. Files are transferred using xdd across these connections, and the transfer rates are measured, which indicate the need to jointly optimize the connection and host file IO parameters to achieve peak transfer rates. In particular, these measurements indicate that (i) peak file transfer rate is lower than peak connection and host IO throughput, in some cases by as much as 50% or lower, (ii) xdd request sizes that achieve peak throughput for host file IO do not necessarily lead to peak file transfer rates, and (iii) parallelism in host IO and TCP transport does not always improve the file transfer rates.« less

Reference values for blood pressure response to cycle ergometry in the first two decades of life: comparison with patients with a repaired coarctation of the aorta.

PubMed

Kaafarani, Mirna; Schroer, Christian; Takken, Tim

2017-12-01

Hemodynamic responses to exercise are used as markers of diagnosis for cardiac diseases, systolic blood pressure (SBP) especially. However, the reference values for SBP in children at peak exertion level are outdated. This study aimed to establish current reference values for SBP, rate pressure product (RPP), and circulatory power (CircP). Data from children who previously underwent cardiopulmonary exercise testing were categorized as healthy (N = 184; age 12.6 ± 2.9 years), and CoA patients (N = 25; age 13.0 ± 3.2 years). With the Lambda-Mu-Sigma (LMS) method, percentile curves were made for SBP, CircP, and RPP in function of peak work rate (Wpeak). Data of CoA patients were used to validate the reference values. Wpeak was the best predictor of peak SBP during exercise. The prediction equations for SBP, CircP and RPP were: (0.2853 x Wpeak) + 111.46; (10.56 x Wpeak) + 2550.2 and (61.879 x Wpeak) + 19.887, respectively. CoA patients showed significantly increased values for peak SBP (Z-score 1.063 ± 1.347). This study provides reference values for SBP, RPP, and CircP at peak exercise. These values can be used for objective evaluation of participants 6-18 years of age in a Dutch population.

Thermal Energy Storage for Electricity Peak-demand Mitigation: A Solution in Developing and Developed World Alike

DOE Office of Scientific and Technical Information (OSTI.GOV)

DeForest, Nicholas; Mendes, Goncalo; Stadler, Michael

2013-06-02

In much of the developed world, air-conditioning in buildings is the dominant driver of summer peak electricity demand. In the developing world a steadily increasing utilization of air-conditioning places additional strain on already-congested grids. This common thread represents a large and growing threat to the reliable delivery of electricity around the world, requiring capital-intensive expansion of capacity and draining available investment resources. Thermal energy storage (TES), in the form of ice or chilled water, may be one of the few technologies currently capable of mitigating this problem cost effectively and at scale. The installation of TES capacity allows a buildingmore » to meet its on-peak air conditioning load without interruption using electricity purchased off-peak and operating with improved thermodynamic efficiency. In this way, TES has the potential to fundamentally alter consumption dynamics and reduce impacts of air conditioning. This investigation presents a simulation study of a large office building in four distinct geographical contexts: Miami, Lisbon, Shanghai, and Mumbai. The optimization tool DER-CAM (Distributed Energy Resources Customer Adoption Model) is applied to optimally size TES systems for each location. Summer load profiles are investigated to assess the effectiveness and consistency in reducing peak electricity demand. Additionally, annual energy requirements are used to determine system cost feasibility, payback periods and customer savings under local utility tariffs.« less

A Review of Worldwide Patents: Innovations in Peak Flow Meters for Asthma.

PubMed

Klingman, Karen J; Castner, Jessica; Titus, Albert H

2016-01-01

Contemporary healthcare nurses increasingly rely on innovative technology for assessment, treatment, and patient self-management. Funding opportunities as well are increasingly steering toward technology development and innovation. Health researchers, including nursing scientists, who are engaged in medical device innovation need to assess the state of the art of current technology. This requires an intellectual property analysis, or patent search, which is not covered by the types of literature reviews customarily used in health science research. The purposes of this article are to illustrate a methodical review of worldwide patents and to show how those results can be used to identify possible products available for use. An application of peak flow meters for use by patients with asthma is used to illustrate the process. The Derwent Innovations Index interface with keyword searching is illustrated, as is the use of Google Patents. From the 14 patent document results, six possible technologies were identified. The patent search revealed innovations in asthma peak flow meters for use in future research and identified future directions for device development. These results support the claim that patent literature must be included in reviews that seek to identify technology state-of-the-art healthcare applications and that advances in the nursing research paradigm should include patents as background and scholarly products.

Spectroscopic and electrochemical studies of the interaction between oleuropein, the major bio-phenol in olives, and salmon sperm DNA

NASA Astrophysics Data System (ADS)

Mohamadi, Maryam; Afzali, Daryoush; Esmaeili-Mahani, Saeed; Mostafavi, Ali; Torkzadeh-Mahani, Masoud

2015-09-01

Interaction of oleuropein, the major bio-phenol in olive leaf and fruit, with salmon sperm double-stranded DNA was investigated by employing electronic absorption titrations, fluorescence quenching spectroscopy, competitive fluorescence spectroscopy, thermal denaturation and voltammetric studies. Titration of oleuropein with the DNA caused a hypochromism accompanied with a red shift indicating an intercalative mode of interaction. Binding constant of 1.4 × 104 M-1 was obtained for this interaction. From the curves of fluorescence titration of oleuropein with the DNA, binding constant and binding sites were calculated to be 8.61 × 103 M-1 and 1.05, respectively. Competitive studies with ethidium bromide (a well-known DNA intercalator) showed that the bio-phenol could take the place of ethidium bromide in the DNA intercalation sites. The interaction of oleuropein with DNA was also studied electrochemically. In the presence of the DNA, the anodic and cathodic peak currents of oleuropein decreased accompanied with increases in peak-to-peak potential separation and formal potential, indicating the intercalation of oleuropein into the DNA double helix. Moreover, melting temperature of the DNA was found to increase in the presence of oleuropein, indicating the stabilization of the DNA double helix due to an intercalative interaction.

The Ar-NO van der Waals complex studied by resonant multiphoton ionization spectroscopy involving photoion and photoelectron measurements

NASA Astrophysics Data System (ADS)

Sato, Kenji; Achiba, Yohji; Kimura, Katsumi

1984-07-01

Using a 5% mixture of NO in Ar in a supersonic free jet, in the present work we have carried out measurements of the total ion current in the 380-385 nm laser wavelength region. We have also measured photoelectron kinetic energy spectra at individual ion current peaks. In the ion-current spectrum we have observed a new vibrational progression which consists of four peaks in the wavelength region longer than the peak of the two-photon transition of the free NO molecule NO(X, v″=0) →2hν NO(C,v'=0). It has been concluded that the new ion-current peaks are attributed to bound-to-bound transitions of the Ar-NO van der Waals complex from its ground state to the two-photon resonant state expressed by Ar-NO*(C 2Π, v'=0), in which the NO component is in the 3p Rydberg state. The whole resonant ionization process studied may be expressed by Ar-NO(X, v″=0) →2hνAr-NO*(C, v'=0) →hν Ar-NO+(X, v+=0). Each ion-current peak separation is about 50 cm-1, which may correspond to the frequency of the Ar-NO intermolecular stretching vibration, showing a strong anharmonicity. The dissociation energy (D0) of the Ar-NO*(C 2Π) state has been found to be 0.055±0.001 eV. From the photoelectron spectra, we also conclude that the adiabatic ionization energy of Ar-NO is Ia =9.148±0.005 eV and the dissociation energy of the Ar-NO+(X 1Σ) ion is D0=0.129±0.005 eV.

Sensitivity of Rabbit Ventricular Action Potential and Ca2+ Dynamics to Small Variations in Membrane Currents and Ion Diffusion Coefficients

PubMed Central

Lo, Yuan Hung; Peachey, Tom; Abramson, David; McCulloch, Andrew

2013-01-01

Little is known about how small variations in ionic currents and Ca2+ and Na+ diffusion coefficients impact action potential and Ca2+ dynamics in rabbit ventricular myocytes. We applied sensitivity analysis to quantify the sensitivity of Shannon et al. model (Biophys. J., 2004) to 5%–10% changes in currents conductance, channels distribution, and ion diffusion in rabbit ventricular cells. We found that action potential duration and Ca2+ peaks are highly sensitive to 10% increase in L-type Ca2+ current; moderately influenced by 10% increase in Na+-Ca2+ exchanger, Na+-K+ pump, rapid delayed and slow transient outward K+ currents, and Cl− background current; insensitive to 10% increases in all other ionic currents and sarcoplasmic reticulum Ca2+ fluxes. Cell electrical activity is strongly affected by 5% shift of L-type Ca2+ channels and Na+-Ca2+ exchanger in between junctional and submembrane spaces while Ca2+-activated Cl−-channel redistribution has the modest effect. Small changes in submembrane and cytosolic diffusion coefficients for Ca2+, but not in Na+ transfer, may alter notably myocyte contraction. Our studies highlight the need for more precise measurements and further extending and testing of the Shannon et al. model. Our results demonstrate usefulness of sensitivity analysis to identify specific knowledge gaps and controversies related to ventricular cell electrophysiology and Ca2+ signaling. PMID:24222910

ABH secretor status and pulmonary function.

PubMed

Haines, A P; Imeson, J D; Meade, T W

1982-03-01

Among current cigarette smokers in the Northwick Park Heart Study in N.W. London, England, secretors of ABH antigen had a higher mean peak expiratory flow rate than did nonsecretors. The relationship was independent of other factors known to affect peak expiratory flow rate. No significant differences in peak expiratory flow rate by secretor status were detected in nonsmokers or in pipe and cigar smokers, although a smaller difference was seen among secretors and nonsecretors who were ex-cigarette smokers than among those who were current cigarette smokers. It is concluded that secretion of ABH antigen into the respiratory tract may have a protective effect against pulmonary damage by noxious agents.

Electrogenerated Chemiluminescence and Fluorescence Lifetime Spatial Heterogeneity of Poly (2-methoxy-5-(2-ethylhexyloxy)-1, 4-phenylenevinylene) in Presence of [6,6]-phenyl-C61-butyric Acid Methyl Ester

DOE Office of Scientific and Technical Information (OSTI.GOV)

Geng, Hongwei; Pan, Shanlin; Hu, Dehong

In this paper, we studied the luminescence property and fluorescence lifetime mapping of MEH-PPV/PCBM system by using electrogenerated chemiluminescence (ECL) and time-correlated single photo counting (TC-SPC) technologies. The ECL results showed that the oxidation peak of MEH-PPV near 0.7 V (vs. SCE) and ECL response of films shifted positively towards 1.2 V when in the presence of PCBM. At the same time, the oxidation peak current density of MEH-PPV increases while the ECL response decreased with the loading of PCBM in the composite films. The fluorescence lifetime images clearly show that the lifetime fluctuation is effected by different substrates andmore » MEH-PPV/PCBM ratios. Meanwhile, the lifetime of MEH-PPV decreases with the increasing of film thickness. The lifetimes of MEH-PPV films on TiO2 substrate are lower than them of films on cover slips.« less

Electrochromic and optical properties of tungsten oxide films deposited with DC sputtering by introducing hydrogen.

PubMed

Chen, Hsi-Chao; Jan, Der-Jun; Luo, Yu-Siang; Huang, Kuo-Ting

2014-02-01

Research was undertaken to investigate the electrochromic and optical properties of tungsten oxide (WO3) films deposited by introducing hydrogen with a direct current (DC) and pulsed DC sputtering. The results show that WO3 films have optimum electrochromic properties at a hydrogen flow of 4 and 3 sccm for DC and pulsed DC, respectively. In the Raman spectra, the peak intensity increased with the increase of hydrogen flow at both 770  cm1 and 950  cm(-1) peaks, which resulted in bonds of W(6+)-O and W(6+)=O, respectively. Simultaneously, the transmittance (ΔT550  nm) variations were 65.6% and 64.4%, and the average transmittance (ΔT400-500  nm) variations were 56.7% and 56.4% for DC and pulsed DC, respectively. The bleached/colored ability of the cyclic voltammograms (CVs) was DC>pulsed DC, and the resistances of AC impedance were pulsed DC>DC.

Direct electron-impact mechanism of excitation of mercury monobromide in a double-pulse dielectric-barrier-discharge HgBr lamp

NASA Astrophysics Data System (ADS)

Datsyuk, V. V.; Izmailov, I. A.; Naumov, V. V.; Kochelap, V. A.

2016-08-01

In a nonequlibrium plasma of a gas-discharge HgBr lamp, the terminal electronic state of the HgBr(B-X) radiative transition with a peak wavelength of 502 nm remains populated for a relatively long time and is repeatedly excited to the B state in collisions with plasma electrons. This transfer of the HgBr molecules from the ground state X to the excited state B is the main mechanism of formation of the light-emitting molecules especially when the lamp is excited by double current pulses. According to our simulations, due to the electron-induced transitions between HgBr(X) and HgBr(B), the output characteristics of the DBD lamp operating in a double-pulse regime are better than those of the lamp operating in a single-pulse regime. In the considered case, the peak power is calculated to increase by a factor of about 2 and the lamp efficiency increases by about 50%.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Roberts, D.; Winkler, J.

As energy-efficiency efforts focus increasingly on existing homes, we scratch our heads about construction decisions made 30, 40, 50-years ago and ask: 'What were they thinking?' A logical follow-on question is: 'What will folks think in 2050 about the homes we're building today?' This question can lead to a lively discussion, but the current practice that we find most alarming is placing ducts in the attic. In this paper, we explore through literature and analysis the impact duct location has on cooling load, peak demand, and energy cost in hot climates. For a typical new home in these climates, wemore » estimate that locating ducts in attics rather than inside conditioned space increases the cooling load 0.5 to 1 ton, increases cooling costs 15% and increases demand by 0.75 kW. The aggregate demand to service duct loss in homes built in Houston, Las Vegas, and Phoenix during the period 2000 through 2009 is estimated to be 700 MW. We present options for building homes with ducts in conditioned space and demonstrate that these options compare favorably with other common approaches to achieving electricity peak demand and consumption savings in homes.« less

Facile method for the synthesis of gold nanoparticles using an ion coater

NASA Astrophysics Data System (ADS)

Lee, Seung Han; Jung, Hyun Kyu; Kim, Tae Cheol; Kim, Chang Hee; Shin, Chang Hwan; Yoon, Tae-Sik; Hong, A.-Ra; Jang, Ho Seong; Kim, Dong Hun

2018-03-01

Herein we report a metal nanoparticle synthesis method based on a physical vapor deposition process instead of the conventional wet process of chemical reactions in liquids. A narrow size distribution of synthesized gold nanoparticles was obtained using an ion coater on glycerin at low vapor pressure. The nanoparticle size could be modulated by controlling the sputtering conditions especially the discharge current. Due to the formation of gold nanoparticles, a surface plasmon resonance peak appeared at ∼530 nm in the absorption spectrum. The surface plasmon resonance peak exhibited red-shift with increasing size of the gold nanoparticles. Our results provide a simple, environmental friendly method for the synthesis of metal nanoparticles by combine low-cost deposition apparatus and a liquid medium, which is free from toxic reagents.

Combining axial and radial nanowire heterostructures: radial Esaki diodes and tunnel field-effect transistors.

PubMed

Dey, Anil W; Svensson, Johannes; Ek, Martin; Lind, Erik; Thelander, Claes; Wernersson, Lars-Erik

2013-01-01

The ever-growing demand on high-performance electronics has generated transistors with very impressive figures of merit (Radosavljevic et al., IEEE Int. Devices Meeting 2009, 1-4 and Cho et al., IEEE Int. Devices Meeting 2011, 15.1.1-15.1.4). The continued scaling of the supply voltage of field-effect transistors, such as tunnel field-effect transistors (TFETs), requires the implementation of advanced transistor architectures including FinFETs and nanowire devices. Moreover, integration of novel materials with high electron mobilities, such as III-V semiconductors and graphene, are also being considered to further enhance the device properties (del Alamo, Nature 2011, 479, 317-323, and Liao et al., Nature 2010, 467, 305-308). In nanowire devices, boosting the drive current at a fixed supply voltage or maintaining a constant drive current at a reduced supply voltage may be achieved by increasing the cross-sectional area of a device, however at the cost of deteriorated electrostatics. A gate-all-around nanowire device architecture is the most favorable electrostatic configuration to suppress short channel effects; however, the arrangement of arrays of parallel vertical nanowires to address the drive current predicament will require additional chip area. The use of a core-shell nanowire with a radial heterojunction in a transistor architecture provides an attractive means to address the drive current issue without compromising neither chip area nor device electrostatics. In addition to design advantages of a radial transistor architecture, we in this work illustrate the benefit in terms of drive current per unit chip area and compare the experimental data for axial GaSb/InAs Esaki diodes and TFETs to their radial counterparts and normalize the electrical data to the largest cross-sectional area of the nanowire, i.e. the occupied chip area, assuming a vertical device geometry. Our data on lateral devices show that radial Esaki diodes deliver almost 7 times higher peak current, Jpeak = 2310 kA/cm(2), than the maximum peak current of axial GaSb/InAs(Sb) Esaki diodes per unit chip area. The radial TFETs also deliver high peak current densities Jpeak = 1210 kA/cm(2), while their axial counterparts at most carry Jpeak = 77 kA/cm(2), normalized to the largest cross-sectional area of the nanowire.

Room temperature microwave oscillations in GaN/AlN resonant tunneling diodes with peak current densities up to 220 kA/cm2

NASA Astrophysics Data System (ADS)

Encomendero, Jimy; Yan, Rusen; Verma, Amit; Islam, S. M.; Protasenko, Vladimir; Rouvimov, Sergei; Fay, Patrick; Jena, Debdeep; Xing, Huili Grace

2018-03-01

We report the generation of room temperature microwave oscillations from GaN/AlN resonant tunneling diodes, which exhibit record-high peak current densities. The tunneling heterostructure grown by molecular beam epitaxy on freestanding GaN substrates comprises a thin GaN quantum well embedded between two AlN tunneling barriers. The room temperature current-voltage characteristics exhibit a record-high maximum peak current density of ˜220 kA/cm2. When biased within the negative differential conductance region, microwave oscillations are measured with a fundamental frequency of ˜0.94 GHz, generating an output power of ˜3.0 μW. Both the fundamental frequency and the output power of the oscillator are limited by the external biasing circuit. Using a small-signal equivalent circuit model, the maximum intrinsic frequency of oscillation for these diodes is predicted to be ˜200 GHz. This work represents a significant step towards microwave power generation enabled by resonant tunneling transport, an ultra-fast process that goes beyond the limitations of current III-Nitride high electron mobility transistors.

Parasitic momentum flux in the tokamak core

DOE PAGES

Stoltzfus-Dueck, T.

2017-03-06

A geometrical correction to the E × B drift causes an outward flux of co-current momentum whenever electrostatic potential energy is transferred to ion parallel flows. The robust, fully nonlinear symmetry breaking follows from the free-energy flow in phase space and does not depend on any assumed linear eigenmode structure. The resulting rotation peaking is counter-current and scales as temperature over plasma current. Lastly, this peaking mechanism can only act when fluctuations are low-frequency enough to excite ion parallel flows, which may explain some recent experimental observations related to rotation reversals.

Time-dependent characteristics of the dielectric barrier discharge in Xe-Cl2 mixture and kinetics of the XeCl∗ molecules

NASA Astrophysics Data System (ADS)

Avtaeva, Svetlana

2014-04-01

Time-dependent characteristics of the dielectric barrier discharge in Xe-Cl2 mixture at chlorine concentration of 0.5% and kinetic processes governing the generation of XeCl∗ molecules are studied using the 1D fluid model. It is shown that at low voltage amplitude (5 kV) a one-peak mode of the discharge is observed and at high voltage amplitude (7 kV) a two-peak mode of the discharge appears. The radiation power of the XeCl∗ band increases with amplitude of the supply voltage. It is demonstrated that the harpoon reaction Xe∗ + Cl2 → XeCl∗ + Cl provides the greatest contribution into generation of XeCl∗ exciplex molecules during short current pulses and the ion-ion recombination Xe+ 2 + Cl- → XeCl* + Xe provides the greatest contribution during afterglow. Quenching of XeCl∗ molecules is a result of the radiative decay XeCl∗ → Xe + Cl + hv (308 nm). During current spike the great contribution into quenching of XeCl∗ provides also the dissociative ionization e + XeCl∗ → Xe+ + Cl + 2e.

Correlation between optical properties surface morphology of porous silicon electrodeposited by Fe3+ ion

NASA Astrophysics Data System (ADS)

Mabrouk, Asma; Lorrain, N.; Haji, M. L.; Oueslati, Meherzi

2015-01-01

In this paper, we analyze the photoluminescence spectra (PL) of porous silicon (PS) layer which is elaborated by electrochemical etching and passivated by Fe3+ ions (PSF) via current density, electro-deposition and temperature measurements. We observe unusual surface morphology of PSF surface and anomalous emission behavior. The PSF surface shows regular distribution of cracks, leaving isolated regions or ;platelets; of nearly uniform thickness. These cracks become more pronounced for high current densities. The temperature dependence of the PL peak energy (EPL) presents anomalous behaviors, i.e., the PL peak energy shows a successive red/blue/redshift (S-shaped behavior) with increasing temperature that we attribute to the existence of strong potential fluctuations induced by the electrochemical etching of PS layers. A competition process between localized and delocalized excitons is used to discuss these PL properties. In this case, the potential confinement plays a key role on the enhancement of PL intensity in PSF. To explain the temperature dependence of the PL intensity, we have proposed a recombination model based on the tunneling and dissociation of excitons.

Hybrid Ion-Detector/Data-Acquisition System for a TOF-MS

NASA Technical Reports Server (NTRS)

Burton, William D., Jr.; Schultz, J. Albert; Vaughn, Valentine; McCully, Michael; Ulrich, Steven; Egan, Thomas F.

2006-01-01

A modified ion-detector/data-acquisition system has been devised to increase the dynamic range of a time-of-flight mass spectrometer (TOF-MS) that, previously, included a microchannel-plate detector and a data-acquisition system based on counting pulses and time-tagging them by use of a time-to-digital converter (TDC). The dynamic range of the TOF-MS was limited by saturation of the microchannel plate detector, which can handle no more than a few million counts per second. The modified system includes (1) a combined microchannel plate/discrete ion multiplier and (2) a hybrid data-acquisition system that simultaneously performs analog current or voltage measurements and multianode single-ion-pulse-counting time-of-flight measurements to extend the dynamic range of a TDC into the regime in which a mass peak comprises multiple ions arriving simultaneously at the detector. The multianode data are used to determine, in real time, whether the detector is saturated. When saturation is detected, the data-acquisition system selectively enables circuitry that simultaneously determines the ion-peak intensity by measuring the time profile of the analog current or voltage detector-output signal.

Silent calcium channels in skeletal muscle fibers of the crustacean Atya lanipes.

PubMed

Monterrubio, J; Lizardi, L; Zuazaga, C

2000-01-01

The superficial (tonic) abdominal flexor muscles of Atya lanipes do not generate Ca(2+) action potentials when depolarized and have no detectable inward Ca(2+) current. These fibers, however, are strictly dependent on Ca(2+) influx for contraction, suggesting that they depend on Ca(2+)-induced Ca(2+) release for contractile activation. The nature of the communication between Ca(2+) channels in the sarcolemmal/tubular membrane and Ca(2+) release channels in the sarcoplasmic reticulum in this crustacean muscle was investigated. The effects of dihydropyridines on tension generation and the passive electrical response were examined in current-clamped fibers: Bay K 8644 enhanced tension about 100% but did not alter the passive electrical response; nifedipine inhibited tension by about 70%. Sr(2+) and Ba(2+) action potentials could be elicited in Ca(2+)-free solutions. The spikes generated by these divalent cations were abolished by nifedipine. As the Sr(2+) or Ba(2+) concentrations were increased, the amplitudes of the action potentials and their maximum rate of rise, V(max), increased and tended towards saturation. Three-microelectrode voltage-clamp experiments showed that even at high (138 mm) extracellular Ca(2+) concentration the channels were silent, i.e., no inward Ca(2+) current was detected. In Ca(2+)-free solutions, inward currents carried by 138 mm Sr(2+) or Ba(2+) were observed. The currents activated at voltages above -40 mV and peaked at about 0 mV. This voltage-activation profile and the sensitivity of the channels to dihydropyridines indicate that they resemble L-type Ca(2+) channels. Peak inward current density values were low, ca. -33 microA/cm(2) for Sr(2+) and -14 microA/cm(2) for Ba(2+), suggesting that Ca(2+) channels are present at a very low density. It is concluded that Ca(2+)-induced Ca(2+) release in this crustacean muscle operates with an unusually high gain: Ca(2+) influx through the silent Ca(2+) channels is too low to generate a macroscopic inward current, but increases sufficiently the local concentration of Ca(2+) in the immediate vicinity of the sarcoplasmic reticulum Ca(2+) release channels to trigger the highly amplified release of Ca(2+) required for tension generation.

High performance direct methanol fuel cell with thin electrolyte membrane

NASA Astrophysics Data System (ADS)

Wan, Nianfang

2017-06-01

A high performance direct methanol fuel cell is achieved with thin electrolyte membrane. 320 mW cm-2 of peak power density and over 260 mW cm-2 at 0.4 V are obtained when working at 90 °C with normal pressure air supply. It is revealed that the increased anode half-cell performance with temperature contributes primarily to the enhanced performance at elevated temperature. From the comparison of iR-compensated cathode potential of methanol/air with that of H2/air fuel cell, the impact of methanol crossover on cathode performance decreases with current density and becomes negligible at high current density. Current density is found to influence fuel efficiency and methanol crossover significantly from the measurement of fuel efficiency at different current density. At high current density, high fuel efficiency can be achieved even at high temperature, indicating decreased methanol crossover.

Spatiotemporal and spectral characteristics of X-ray radiation emitted by the Z-pinch during the current implosion of quasispherical multiwire arrays

NASA Astrophysics Data System (ADS)

Gritsuk, A. N.

2017-12-01

For the first time, a quasi-spherical current implosion has been experimentally realized on a multimegaampere facility with the peak current of up to 4 MA and a soft X-ray source has been created with high radiation power density on its surface of up to 3 TW/cm2. An increase in the energy density at the centre of the source of soft X-ray radiation (SXR) was experimentally observed upon compression of quasi-spherical arrays with the linear-mass profiling. In this case, the average power density on the surface of the SXR source is three times higher than for implosions of cylindrical arrays of the same mass and close values of the discharge current. Obtained experimental data are compared with the results of modelling the current implosion of multi-wire arrays performed with the help of a three-dimensional radiation-magneto-hydrodynamic code.

Loading of Hip Measured by Hip Contact Forces at Different Speeds of Walking and Running.

PubMed

Giarmatzis, Georgios; Jonkers, Ilse; Wesseling, Mariska; Van Rossom, Sam; Verschueren, Sabine

2015-08-01

Exercise plays a pivotal role in maximizing peak bone mass in adulthood and maintaining it through aging, by imposing mechanical loading on the bone that can trigger bone mineralization and growth. The optimal type and intensity of exercise that best enhances bone strength remains, however, poorly characterized, partly because the exact peak loading of the bone produced by the diverse types of exercises is not known. By means of integrated motion capture as an input to dynamic simulations, contact forces acting on the hip of 20 young healthy adults were calculated during walking and running at different speeds. During walking, hip contact forces (HCFs) have a two-peak profile whereby the first peak increases from 4.22 body weight (BW) to 5.41 BW and the second from 4.37 BW to 5.74 BW, by increasing speed from 3 to 6 km/h. During running, there is only one peak HCF that increases from 7.49 BW to 10.01 BW, by increasing speed from 6 to 12 km/h. Speed related profiles of peak HCFs and ground reaction forces (GRFs) reveal a different progression of the two peaks during walking. Speed has a stronger impact on peak HCFs rather than on peak GRFs during walking and running, suggesting an increasing influence of muscle activity on peak HCF with increased speed. Moreover, results show that the first peak of HCF during walking can be predicted best by hip adduction moment, and the second peak of HCF by hip extension moment. During running, peak HCF can be best predicted by hip adduction moment. The present study contributes hereby to a better understanding of musculoskeletal loading during walking and running in a wide range of speeds, offering valuable information to clinicians and scientists exploring bone loading as a possible nonpharmacological osteogenic stimulus. © 2015 American Society for Bone and Mineral Research. © 2015 American Society for Bone and Mineral Research.

Weakening of ion-channel interactions of Na+ and Li+ in acetylcholine-receptor channels of frog skeletal muscle with an increase in agonist concentration.

PubMed

Manthey, A A

1998-05-01

The possibility that increases in agonist concentration beyond threshold levels may force changes in the character of high-conductance open states of skeletal muscle nicotinic acetylcholine receptor channels (nAChR) was examined by seeing whether differences in several critical ionic properties of nAChR currents could be detected with changes in agonist level. Single- and bi-ionic whole-cell currents of Na+ and Li+ in voltage-clamped frog (Rana pipiens) muscle fibers were measured during local superfusion of endplates with carbamylcholine (carb) at concentrations of 54 microm (low-carb) and 270 microM (high-carb). Three ionic properties that would be affected by changes in the open-state configuration of channel subunits were tested. First, ion-saturation characteristics. Peak Na+ and Li+ currents in low-carb trials showed sublinear dependence on ion concentrations from 0 to 60 mM with Km values of 78 (Na+) and 49 (Li+) mM and a power function slope of 0. 75 on double-log plot. In contrast, the concentration dependence of Na+ and Li+ currents in high-carb tests was linear through the origin with a power function slope of 1.02. Second, Na+/Li+ selectivity. The ratio of peak Na+ and Li+ currents in low-carb tests varied from 1.86 to 2.28 for ion concentrations of from 20 to 60 mM [mean = 2.02 +/- 0.06 (SEM)] whereas the ratio for high-carb trials ranged from only 1.29 to 1.52 [mean = 1.42 +/- 0.40 (SEM)]. Third, competitive interactions of Na+ and Li+ currents. Equimolar mixtures of Na+ and Li+ in low-carb tests produced bi-ionic inward currents which were never larger than the single-ion Na+ current alone, but bi-ionic currents at the high-carb level were always greater than the single-ion Na+ current, approximating the sum of the single-ion Na+ and Li+ currents in most cases. The results are consistent with a decrease in ion-channel binding at the high-carb level and support the possibility of agonist-induced changes in the high-conductance open-state configuration of nAChR subunits which result in a weakening of constraints on cation movements through the channel.

Cardiorespiratory Fitness and Body Composition Responses to Different Intensities and Frequencies of Exercise Training in Colorectal Cancer Survivors.

PubMed

Devin, James L; Jenkins, David G; Sax, Andrew T; Hughes, Gareth I; Aitken, Joanne F; Chambers, Suzanne K; Dunn, Jeffrey C; Bolam, Kate A; Skinner, Tina L

2018-06-01

Deteriorations in cardiorespiratory fitness (V˙o 2peak ) and body composition are associated with poor prognosis after colorectal cancer treatment. However, the optimal intensity and frequency of aerobic exercise training to improve these outcomes in colorectal cancer survivors is unknown. This trial compared 8 weeks of moderate-intensity continuous exercise (MICE; 50 minutes; 70% peak heart rate [HR peak ]; 24 sessions), with high-intensity interval exercise (HIIE; 4 × 4 minutes; 85%-95% HR peak ) at an equivalent (HIIE; 24 sessions) and tapered frequency (HIIE-T; 16 sessions) on V˙o 2peak and on lean and fat mass, measured at baseline, 4, 8, and 12 weeks. Increases in V˙o 2peak were significantly greater after both 4 (+3.0 mL·kg -1 ·min -1 , P = .008) and 8 (+2.3 mL·kg -1 ·min -1 , P = .049) weeks of HIIE compared to MICE. After 8 weeks, there was a significantly greater reduction in fat mass after HIIE compared to MICE (-0.7 kg, P = .038). Four weeks after training, the HIIE group maintained elevated V˙o 2peak (+3.3 mL·kg -1 ·min -1 , P = .006) and reduced fat mass (-0.7 kg, P = .045) compared to the MICE group, with V˙o 2peak in the HIIE-T also being superior to the MICE group (+2.8 mL·kg -1 ·min -1 , P = .013). Compared to MICE, HIIE promotes superior improvements and short-term maintenance of V˙o 2peak and fat mass improvements. HIIE training at a reduced frequency also promotes maintainable cardiorespiratory fitness improvements. In addition to promoting accelerated and superior benefits to the current aerobic exercise guidelines, HIIE promotes clinically relevant improvements even with a substantial reduction in exercise training and for a period after withdrawal. Copyright © 2018 Elsevier Inc. All rights reserved.

Toll-like receptor 4 enhancement of non-NMDA synaptic currents increases dentate excitability after brain injury.

PubMed

Li, Ying; Korgaonkar, Akshata A; Swietek, Bogumila; Wang, Jianfeng; Elgammal, Fatima S; Elkabes, Stella; Santhakumar, Vijayalakshmi

2015-02-01

Concussive brain injury results in neuronal degeneration, microglial activation and enhanced excitability in the hippocampal dentate gyrus, increasing the risk for epilepsy and memory dysfunction. Endogenous molecules released during injury can activate innate immune responses including toll-like receptor 4 (TLR4). Recent studies indicate that immune mediators can modulate neuronal excitability. Since non-specific agents that reduce TLR4 signaling can limit post-traumatic neuropathology, we examined whether TLR4 signaling contributes to early changes in dentate excitability after brain injury. Concussive brain injury caused a transient increase in hippocampal TLR4 expression within 4h, which peaked at 24h. Post-injury increase in TLR4 expression in the dentate gyrus was primarily neuronal and persisted for one week. Acute, in vitro treatment with TLR4 ligands caused bidirectional modulation of dentate excitability in control and brain-injured rats, with a reversal in the direction of modulation after brain injury. TLR4 antagonists decreased, and agonist increased, afferent-evoked dentate excitability one week after brain injury. NMDA receptor antagonist did not occlude the ability of LPS-RS, a TLR4 antagonist, to decrease post-traumatic dentate excitability. LPS-RS failed to modulate granule cell NMDA EPSCs but decreased perforant path-evoked non-NMDA EPSC peak amplitude and charge transfer in both granule cells and mossy cells. Our findings indicate an active role for TLR4 signaling in early post-traumatic dentate hyperexcitability. The novel TLR4 modulation of non-NMDA glutamatergic currents, identified herein, could represent a general mechanism by which immune activation influences neuronal excitability in neurological disorders that recruit sterile inflammatory responses. Copyright © 2014 Elsevier Inc. All rights reserved.

Alteration of the fast excitatory postsynaptic current by barium in voltage-clamped amphibian sympathetic ganglion cells.

PubMed Central

Connor, E. A.; Parsons, R. L.

1984-01-01

Barium-induced alterations in fast excitatory postsynaptic currents (e.p.s.cs) have been studied in voltage-clamped bullfrog sympathetic ganglion B cells. In the presence of 2-8 mM barium, e.p.s.c. decay was prolonged and in many cells the e.p.s.c. decay phase deviated from a single exponential function. The decay phase in these cases was more accurately described as the sum of two exponential functions. The frequency of occurrence of a complex decay increased both with increasing barium concentration and with hyperpolarization. Miniature e.p.s.c. decay also was prolonged in barium-treated cells. E.p.s.c. amplitude was not markedly affected by barium (2-8 mM) in cells voltage-clamped to -50 mV whereas at -90 mV there was a progressive increase in peak size with increasing barium concentration. In control cells the e.p.s.c.-voltage relationship was linear between -20 and -100 mV; however, this relationship became progressively non-linear with membrane hyperpolarization in barium-treated cells. The e.p.s.c. reversal potential was shifted to a more negative value in the presence of barium. There was a voltage-dependent increase in charge movement during the e.p.s.c. in barium-treated cells which was not present in control cells. We conclude that the voltage-dependent alteration in e.p.s.c. decay time course, peak amplitude and charge movement in barium-treated cells is due to a direct postsynaptic action of barium on the kinetics of receptor-channel gating in postganglionic sympathetic neurones. PMID:6333261

Higher fine particulate matter and temperature levels impair exercise capacity in cardiac patients.

PubMed

Giorgini, Paolo; Rubenfire, Melvyn; Das, Ritabrata; Gracik, Theresa; Wang, Lu; Morishita, Masako; Bard, Robert L; Jackson, Elizabeth A; Fitzner, Craig A; Ferri, Claudio; Brook, Robert D

2015-08-01

Fine particulate matter (PM2.5) air pollution and variations in ambient temperature have been linked to increased cardiovascular morbidity and mortality. However, no large-scale study has assessed their effects on directly measured aerobic functional capacity among high-risk patients. Using a cross-sectional observational design, we evaluated the effects of ambient PM2.5 and temperature levels over 7 days on cardiopulmonary exercise test results performed among 2078 patients enrolling into a cardiac rehabilitation programme at the University of Michigan (from January 2003 to August 2011) using multiple linear regression analyses (controlling for age, sex, body mass index). Peak exercise oxygen consumption was significantly decreased by approximately 14.9% per 10 μg/m(3) increase in ambient PM2.5 levels (median 10.7 μg/m(3), IQR 10.1 μg/m(3)) (lag days 6-7). Elevations in PM2.5 were also related to decreases in ventilatory threshold (lag days 5-7) and peak heart rate (lag days 2-3) and increases in peak systolic blood pressure (lag days 4-5). A 10°C increase in temperature (median 10.5°C, IQR 17.5°C) was associated with reductions in peak exercise oxygen consumption (20.6-27.3%) and ventilatory threshold (22.9-29.2%) during all 7 lag days. In models including both factors, the outcome associations with PM2.5 were attenuated whereas the effects of temperature remained significant. Short-term elevations in ambient PM2.5, even at low concentrations within current air quality standards, and/or higher temperatures were associated with detrimental changes in aerobic exercise capacity, which can be linked to a worse quality of life and cardiovascular prognosis among cardiac rehabilitation patients. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://group.bmj.com/group/rights-licensing/permissions.

Integrating a Silicon Solar Cell with a Triboelectric Nanogenerator via a Mutual Electrode for Harvesting Energy from Sunlight and Raindrops.

PubMed

Liu, Yuqiang; Sun, Na; Liu, Jiawei; Wen, Zhen; Sun, Xuhui; Lee, Shuit-Tong; Sun, Baoquan

2018-03-27

Solar cells, as promising devices for converting light into electricity, have a dramatically reduced performance on rainy days. Here, an energy harvesting structure that integrates a solar cell and a triboelectric nanogenerator (TENG) device is built to realize power generation from both sunlight and raindrops. A heterojunction silicon (Si) solar cell is integrated with a TENG by a mutual electrode of a poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) film. Regarding the solar cell, imprinted PEDOT:PSS is used to reduce light reflection, which leads to an enhanced short-circuit current density. A single-electrode-mode water-drop TENG on the solar cell is built by combining imprinted polydimethylsiloxane (PDMS) as a triboelectric material combined with a PEDOT:PSS layer as an electrode. The increasing contact area between the imprinted PDMS and water drops greatly improves the output of the TENG with a peak short-circuit current of ∼33.0 nA and a peak open-circuit voltage of ∼2.14 V, respectively. The hybrid energy harvesting system integrated electrode configuration can combine the advantages of high current level of a solar cell and high voltage of a TENG device, promising an efficient approach to collect energy from the environment in different weather conditions.

UH-FLUX: Compact, Energy Efficient Superconducting Asymmetric Energy Recovery LINAC for Ultra-high Fluxes of X-ray and THz Radiation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Konoplev, Ivan; Ainsworth, Robert; Burt, Graeme

The conventional ERLs have limited peak beam current because increasing the beam charge and repetition rate leads to appearance of the beam break-up instabilities. At this stage the highest current, from the SRF ERL, is around 300 mA. A single-turn (the beam will be transported through the accelerating section, interaction point and deceleration section of the AERL only once) Asymmetric Energy Recovery LINAC (AERL) is proposed. The RF cells in different sections of the cavity are tuned in such a way that only operating mode is uniform inside all of the cells. The AERL will drive the electron beams withmore » typical energies of 10 - 30 MeV and peak currents above 1 A, enabling the generation of high flux UV/X-rays and high power coherent THz radiation. We aim to build a copper prototype of the RF cavity for a compact AERL to study its EM properties. The final goal is to build AERL based on the superconducting RF cavity. Preliminary design for AERL's cavity has been developed and will be presented. The results of numerical and analytical models and the next steps toward the AERL operation will also be discussed.« less

Hot-carrier-induced current capability degradation and optimization for lateral IGBT on thick SOI substrate

NASA Astrophysics Data System (ADS)

Zhang, Chunwei; Li, Yang; Yue, Wenjing; Fu, Xiaoqian; Li, Zhiming

2018-07-01

In this paper, the hot-carrier-induced current capability degradation of a 600 V lateral insulated gate bipolar transistor (LIGBT) on thick silicon on insulator (SOI) substrate is investigated. Our experiments found that, for the SOI-LIGBT, the worst stress condition is the maximum gate voltage (Vgmax) condition and the current degradation is dominated by the damages in the channel region under the Vgmax stress condition. However, further analyses show that the influence of channel region damages on the collector current degradation increases with the increase of measured collector voltage and is maximum in the current saturation region. Therefore, in our opinion, the hot-carrier-induced current capability degradation of the SOI-LIGBT should be evaluated by the degradation of saturation current under the Vgmax stress condition. In addition, a novel SOI-LIGBT structure with an external p-type region was also proposed, which can alleviate the damage in the channel region by reducing the lateral electric field peak. Our experimental results demonstrate that the proposed structure could optimize the hot-carrier reliability effectively with the other characteristics maintained. He is currently a lecturer at the University of Jinan, Jinan, China. His research interests include power electronics, high voltage devices and the electronics reliability.

Monitoring and remediation of on-farm and off-farm ground current measured as step potential on a Wisconsin dairy farm: A case study.

PubMed

Stetzer, Dave; Leavitt, Adam M; Goeke, Charles L; Havas, Magda

2016-01-01

Ground current commonly referred to as "stray voltage" has been an issue on dairy farms since electricity was first brought to rural America. Equipment that generates high-frequency voltage transients on electrical wires combined with a multigrounded (electrical distribution) system and inadequate neutral returns all contribute to ground current. Despite decades of problems, we are no closer to resolving this issue, in part, due to three misconceptions that are addressed in this study. Misconception 1. The current standard of 1 V at cow contact is adequate to protect dairy cows; Misconception 2. Frequencies higher than 60 Hz do not need to be considered; and Misconception 3. All sources of ground current originate on the farm that has a ground current problem. This case study of a Wisconsin dairy farm documents, 1. how to establish permanent monitoring of ground current (step potential) on a dairy farm; 2. how to determine and remediate both on-farm and off-farm sources contributing to step potential; 3. which step-potential metrics relate to cow comfort and milk production; and 4. how these metrics relate to established standards. On-farm sources include lighting, variable speed frequency drives on motors, radio frequency identification system and off-farm sources are due to a poor primary neutral return on the utility side of the distribution system. A step-potential threshold of 1 V root mean square (RMS) at 60 Hz is inadequate to protect dairy cows as decreases of a few mV peak-peak at higher frequencies increases milk production, reduces milking time and improves cow comfort.

Room Temperature Electroluminescence from Tensile-Strained Si0.13Ge0.87/Ge Multiple Quantum Wells on a Ge Virtual Substrate

PubMed Central

Lin, Guangyang; Chen, Ningli; Zhang, Lu; Huang, Zhiwei; Huang, Wei; Wang, Jianyuan; Xu, Jianfang; Chen, Songyan; Li, Cheng

2016-01-01

Direct band electroluminescence (EL) from tensile-strained Si0.13Ge0.87/Ge multiple quantum wells (MQWs) on a Ge virtual substrate (VS) at room temperature is reported herein. Due to the competitive result of quantum confinement Stark effect and bandgap narrowing induced by tensile strain in Ge wells, electroluminescence from Γ1-HH1 transition in 12-nm Ge wells was observed at around 1550 nm. As injection current density increases, additional emission shoulders from Γ2-HH2 transition in Ge wells and Ge VS appeared at around 1300–1400 nm and 1600–1700 nm, respectively. The peak energy of EL shifted to the lower energy side superquadratically with an increase of injection current density as a result of the Joule heating effect. During the elevation of environmental temperature, EL intensity increased due to a reduction of energy between L and Γ valleys of Ge. Empirical fitting of the relationship between the integrated intensity of EL (L) and injection current density (J) with L~Jm shows that the m factor increased with injection current density, suggesting higher light emitting efficiency of the diode at larger injection current densities, which can be attributed to larger carrier occupations in the Γ valley and the heavy hole (HH) valance band at higher temperatures. PMID:28773923

Room Temperature Electroluminescence from Tensile-Strained Si0.13Ge0.87/Ge Multiple Quantum Wells on a Ge Virtual Substrate.

PubMed

Lin, Guangyang; Chen, Ningli; Zhang, Lu; Huang, Zhiwei; Huang, Wei; Wang, Jianyuan; Xu, Jianfang; Chen, Songyan; Li, Cheng

2016-09-27

Direct band electroluminescence (EL) from tensile-strained Si 0.13 Ge 0.87 /Ge multiple quantum wells (MQWs) on a Ge virtual substrate (VS) at room temperature is reported herein. Due to the competitive result of quantum confinement Stark effect and bandgap narrowing induced by tensile strain in Ge wells, electroluminescence from Γ1-HH1 transition in 12-nm Ge wells was observed at around 1550 nm. As injection current density increases, additional emission shoulders from Γ2-HH2 transition in Ge wells and Ge VS appeared at around 1300-1400 nm and 1600-1700 nm, respectively. The peak energy of EL shifted to the lower energy side superquadratically with an increase of injection current density as a result of the Joule heating effect. During the elevation of environmental temperature, EL intensity increased due to a reduction of energy between L and Γ valleys of Ge. Empirical fitting of the relationship between the integrated intensity of EL ( L ) and injection current density ( J ) with L ~ J m shows that the m factor increased with injection current density, suggesting higher light emitting efficiency of the diode at larger injection current densities, which can be attributed to larger carrier occupations in the Γ valley and the heavy hole (HH) valance band at higher temperatures.

CME productivity associated with Solar Flare peak X-ray emission flux

NASA Astrophysics Data System (ADS)

Suryanarayana, G. S.; Balakrishna, K. M.

2018-05-01

It is often noticed that the occurrence rate of Coronal Mass Ejections (CMEs) increases with increase in flare duration where peak flux too increase. However, there is no complete association between the duration and peak flux. Distinct characteristics have been reported for active regions (ARs) where flares and CMEs occur in contrast to ARs where flares alone occur. It is observed that peak flux of flares is higher when associated with CMEs compared to peak flux of flares with which CMEs are not associated. In other words, it is likely that flare duration and peak flux are independently affected by distinct active region dynamics. Hence, we examine the relative ability of flare duration and peak flux in enhancing the CME productivity. We report that CME productivity is distinctly higher in association with the enhancement of flare peak flux in comparison to corresponding enhancement of flare duration.

Amyloid precursor protein modulates Nav1.6 sodium channel currents through a Go-coupled JNK pathway.

PubMed

Li, Shao; Wang, Xi; Ma, Quan-Hong; Yang, Wu-Lin; Zhang, Xiao-Gang; Dawe, Gavin S; Xiao, Zhi-Cheng

2016-12-23

Amyloid precursor protein (APP), commonly associated with Alzheimer's disease, also marks axonal degeneration. In the recent studies, we demonstrated that APP aggregated at nodes of Ranvier (NORs) in myelinated central nervous system (CNS) axons and interacted with Nav1.6. However, the physiological function of APP remains unknown. In this study, we described reduced sodium current densities in APP knockout hippocampal neurons. Coexpression of APP or its intracellular domains containing a VTPEER motif with Na v 1.6 sodium channels in Xenopus oocytes resulted in an increase in peak sodium currents, which was enhanced by constitutively active Go mutant and blocked by a dominant negative mutant. JNK and CDK5 inhibitor attenuated increases in Nav1.6 sodium currents induced by overexpression of APP. Nav1.6 sodium currents were increased by APPT668E (mutant Thr to Glu) and decreased by T668A (mutant Thr to ALa) mutant, respectively. The cell surface expression of Nav1.6 sodium channels in the white matter of spinal cord and the spinal conduction velocity is decreased in APP, p35 and JNK3 knockout mice. Therefore, APP modulates Nav1.6 sodium channels through a Go-coupled JNK pathway, which is dependent on phosphorylation of APP at Thr668.

Amyloid precursor protein modulates Nav1.6 sodium channel currents through a Go-coupled JNK pathway

PubMed Central

Li, Shao; Wang, Xi; Ma, Quan-Hong; Yang, Wu-lin; Zhang, Xiao-Gang; Dawe, Gavin S.; Xiao, Zhi-Cheng

2016-01-01

Amyloid precursor protein (APP), commonly associated with Alzheimer’s disease, also marks axonal degeneration. In the recent studies, we demonstrated that APP aggregated at nodes of Ranvier (NORs) in myelinated central nervous system (CNS) axons and interacted with Nav1.6. However, the physiological function of APP remains unknown. In this study, we described reduced sodium current densities in APP knockout hippocampal neurons. Coexpression of APP or its intracellular domains containing a VTPEER motif with Nav1.6 sodium channels in Xenopus oocytes resulted in an increase in peak sodium currents, which was enhanced by constitutively active Go mutant and blocked by a dominant negative mutant. JNK and CDK5 inhibitor attenuated increases in Nav1.6 sodium currents induced by overexpression of APP. Nav1.6 sodium currents were increased by APPT668E (mutant Thr to Glu) and decreased by T668A (mutant Thr to ALa) mutant, respectively. The cell surface expression of Nav1.6 sodium channels in the white matter of spinal cord and the spinal conduction velocity is decreased in APP, p35 and JNK3 knockout mice. Therefore, APP modulates Nav1.6 sodium channels through a Go-coupled JNK pathway, which is dependent on phosphorylation of APP at Thr668. PMID:28008944

Dynamics of current sheath in a hollow electrode Z-pinch discharge using slug model

NASA Astrophysics Data System (ADS)

Abd Al-Halim, Mohamed A.; Afify, M. S.

2017-03-01

The hollow electrode Z-pinch (HEZP) experiment is a new construction for the electromagnetic propulsion application in which the plasma is formed by the discharge between a plate and ring electrodes through which the plasma is propelled. The experimental results for 8 kV charging voltage shows that the peak discharge current is about 109 kA, which is in good agreement with the value obtained from the simulation in the slug model that simulates the sheath dynamics in the HEZP. The fitting of the discharge current from the slug model indicates that the total system inductance is 238 nH which is relatively a high static inductance accompanied with a deeper pinch depth indicating that the fitted anomalous resistance would be about 95 mΩ. The current and mass factors vary with the changing the gas pressure and the charging voltage. The current factor is between 0.4 and 0.5 on average which is relatively low value. The mass factor decreases by increasing the gas pressure indicating that the sheath is heavy to be driven by the magnetic pressure, which is also indicated from the decreases of the drive factor, hence the radial sheath velocity decreases. The plasma inductance and temperature increase with the increase of the drive factor while the minimum pinch radius decreases.

Design of electrodes and current limits for low frequency electrical impedance tomography of the brain.

PubMed

Gilad, O; Horesh, L; Holder, D S

2007-07-01

For the novel application of recording of resistivity changes related to neuronal depolarization in the brain with electrical impedance tomography, optimal recording is with applied currents below 100 Hz, which might cause neural stimulation of skin or underlying brain. The purpose of this work was to develop a method for application of low frequency currents to the scalp, which delivered the maximum current without significant stimulation of skin or underlying brain. We propose a recessed electrode design which enabled current injection with an acceptable skin sensation to be increased from 100 muA using EEG electrodes, to 1 mA in 16 normal volunteers. The effect of current delivered to the brain was assessed with an anatomically realistic finite element model of the adult head. The modelled peak cerebral current density was 0.3 A/m(2), which was 5 to 25-fold less than the threshold for stimulation of the brain estimated from literature review.

Electrical field imaging as a means to predict the loudness of monopolar and tripolar stimuli in cochlear implant patients.

PubMed

Berenstein, Carlo K; Vanpoucke, Filiep J; Mulder, Jef J S; Mens, Lucas H M

2010-12-01

Tripolar and other electrode configurations that use simultaneous stimulation inside the cochlea have been tested to reduce channel interactions compared to the monopolar stimulation conventionally used in cochlear implant systems. However, these "focused" configurations require increased current levels to achieve sufficient loudness. In this study, we investigate whether highly accurate recordings of the intracochlear electrical field set up by monopolar and tripolar configurations correlate to their effect on loudness. We related the intra-scalar potential distribution to behavioral loudness, by introducing a free parameter (α) which parameterizes the degree to which the potential field peak set up inside the scala tympani is still present at the location of the targeted neural tissue. Loudness balancing was performed on four levels between behavioral threshold and the most comfortable loudness level in a group of 10 experienced Advanced Bionics cochlear implant users. The effect of the amount of focusing on loudness was well explained by α per subject location along the basilar membrane. We found that α was unaffected by presentation level. Moreover, the ratios between the monopolar and tripolar currents, balanced for equal loudness, were approximately the same for all presentation levels. This suggests a linear loudness growth with increasing current level and that the equal peak hypothesis may predict the loudness of threshold as well as at supra-threshold levels. These results suggest that advanced electrical field imaging, complemented with limited psychophysical testing, more specifically at only one presentation level, enables estimation of the loudness growth of complex electrode configurations. Copyright © 2010 Elsevier B.V. All rights reserved.

Effects of acidic pH on voltage-gated ion channels in rat trigeminal mesencephalic nucleus neurons.

PubMed

Han, Jin-Eon; Cho, Jin-Hwa; Choi, In-Sun; Kim, Do-Yeon; Jang, Il-Sung

2017-03-01

The effects of acidic pH on several voltage-dependent ion channels, such as voltage-dependent K + and Ca 2+ channels, and hyperpolarization-gated and cyclic nucleotide-activated cation (HCN) channels, were examined using a whole-cell patch clamp technique on mechanically isolated rat mesencephalic trigeminal nucleus neurons. The application of a pH 6.5 solution had no effect on the peak amplitude of voltage-dependent K + currents. A pH 6.0 solution slightly, but significantly inhibited the peak amplitude of voltage-dependent K + currents. The pH 6.0 also shifted both the current-voltage and conductance-voltage relationships to the depolarization range. The application of a pH 6.5 solution scarcely affected the peak amplitude of membrane currents mediated by HCN channels, which were profoundly inhibited by the general HCN channel blocker Cs + (1 mM). However, the pH 6.0 solution slightly, but significantly inhibited the peak amplitude of HCN-mediated currents. Although the pH 6.0 solution showed complex modulation of the current-voltage and conductance-voltage relationships, the midpoint voltages for the activation of HCN channels were not changed by acidic pH. On the other hand, voltage-dependent Ca 2+ channels were significantly inhibited by an acidic pH. The application of an acidic pH solution significantly shifted the current-voltage and conductance-voltage relationships to the depolarization range. The modulation of several voltage-dependent ion channels by an acidic pH might affect the excitability of mesencephalic trigeminal nucleus neurons, and thus physiological functions mediated by the mesencephalic trigeminal nucleus could be affected in acidic pH conditions.

Can You Hear That Peak? Utilization of Auditory and Visual Feedback at Peak Limb Velocity

ERIC Educational Resources Information Center

Loria, Tristan; de Grosbois, John; Tremblay, Luc

2016-01-01

Purpose: At rest, the central nervous system combines and integrates multisensory cues to yield an optimal percept. When engaging in action, the relative weighing of sensory modalities has been shown to be altered. Because the timing of peak velocity is the critical moment in some goal-directed movements (e.g., overarm throwing), the current study…

Scaling magnetized liner inertial fusion on Z and future pulsed-power accelerators

DOE Office of Scientific and Technical Information (OSTI.GOV)

Slutz, S. A.; Stygar, W. A.; Gomez, M. R.

The MagLIF (Magnetized Liner Inertial Fusion) concept [S. A. Slutz et al., Phys. Plasmas 17, 056303 (2010)] has demonstrated fusion–relevant plasma conditions [M. R. Gomez et al., Phys. Rev. Lett. 113, 155003 (2014)] on the Z accelerator with a peak drive current of about 18 MA. We present 2D numerical simulations of the scaling of MagLIF on Z as a function of drive current, preheat energy, and applied magnetic field. The results indicate that deuterium-tritium (DT) fusion yields greater than 100 kJ could be possible on Z when all of these parameters are at the optimum values: i.e., peak current = 25 MA, deposited preheatmore » energy = 5 kJ, and B{sub z} = 30 T. Much higher yields have been predicted [S. A. Slutz and R. A. Vesey, Phys. Rev. Lett. 108, 025003 (2012)] for MagLIF driven with larger peak currents. Two high performance pulsed-power accelerators (Z300 and Z800) based on linear-transformer-driver technology have been designed [W. A. Stygar et al., Phys. Rev. ST Accel. Beams 18, 110401 (2015)]. The Z300 design would provide 48 MA to a MagLIF load, while Z800 would provide 65 MA. Parameterized Thevenin-equivalent circuits were used to drive a series of 1D and 2D numerical MagLIF simulations with currents ranging from what Z can deliver now to what could be achieved by these conceptual future pulsed-power accelerators. 2D simulations of simple MagLIF targets containing just gaseous DT have yields of 18 MJ for Z300 and 440 MJ for Z800. The 2D simulated yield for Z800 is increased to 7 GJ by adding a layer of frozen DT ice to the inside of the liner.« less

Cardiorespiratory fitness as a predictor of intestinal microbial diversity and distinct metagenomic functions.

PubMed

Estaki, Mehrbod; Pither, Jason; Baumeister, Peter; Little, Jonathan P; Gill, Sandeep K; Ghosh, Sanjoy; Ahmadi-Vand, Zahra; Marsden, Katelyn R; Gibson, Deanna L

2016-08-08

Reduced microbial diversity in human intestines has been implicated in various conditions such as diabetes, colorectal cancer, and inflammatory bowel disease. The role of physical fitness in the context of human intestinal microbiota is currently not known. We used high-throughput sequencing to analyze fecal microbiota of 39 healthy participants with similar age, BMI, and diets but with varying cardiorespiratory fitness levels. Fecal short-chain fatty acids were analyzed using gas chromatography. We showed that peak oxygen uptake (VO2peak), the gold standard measure of cardiorespiratory fitness, can account for more than 20 % of the variation in taxonomic richness, after accounting for all other factors, including diet. While VO2peak did not explain variation in beta diversity, it did play a significant role in explaining variation in the microbiomes' predicted metagenomic functions, aligning positively with genes related to bacterial chemotaxis, motility, and fatty acid biosynthesis. These predicted functions were supported by measured increases in production of fecal butyrate, a short-chain fatty acid associated with improved gut health, amongst physically fit participants. We also identified increased abundances of key butyrate-producing taxa (Clostridiales, Roseburia, Lachnospiraceae, and Erysipelotrichaceae) amongst these individuals, which likely contributed to the observed increases in butyrate levels. Results from this study show that cardiorespiratory fitness is correlated with increased microbial diversity in healthy humans and that the associated changes are anchored around a set of functional cores rather than specific taxa. The microbial profiles of fit individuals favor the production of butyrate. As increased microbiota diversity and butyrate production is associated with overall host health, our findings warrant the use of exercise prescription as an adjuvant therapy in combating dysbiosis-associated diseases.

Performance, Facility Pressure Effects, and Stability Characterization Tests of NASA's Hall Effect Rocket with Magnetic Shielding Thruster

NASA Technical Reports Server (NTRS)

Kamhawi, Hani; Huang, Wensheng; Haag, Thomas; Yim, John; Herman, Daniel; Williams, George; Gilland, James; Peterson, Peter; Hofer, Richard; Mikellides, Ioannis

2016-01-01

NASAs Hall Effect Rocket with Magnetic Shielding (HERMeS) 12.5 kW Technology Demonstration Unit-1 (TDU-1) Hall thruster has been the subject of extensive technology maturation in preparation for flight system development. Part of the technology maturation effort included experimental evaluation of the TDU-1 thruster with conducting and dielectric front pole cover materials in two different electrical configurations. A graphite front pole cover thruster configuration with the thruster body electrically tied to cathode and an alumina front pole cover thruster configuration with the thruster body floating were evaluated. Both configurations were also evaluated at different facility background pressure conditions to evaluate background pressure effects on thruster operation. Performance characterization tests found that higher thruster performance was attained with the graphite front pole cover configuration with the thruster electrically tied to cathode. A total thrust efficiency of 68 and a total specific impulse of 2,820 s was demonstrated at a discharge voltage of 600 V and a discharge power of 12.5 kW. Thruster stability regimes were characterized with respect to the thruster discharge current oscillations and with maps of the current-voltage-magnetic field (IVB). Analysis of TDU-1 discharge current waveforms found that lower normalized discharge current peak-to-peak and root mean square magnitudes were attained when the thruster was electrically floated with alumina front pole covers. Background pressure effects characterization tests indicated that the thruster performance and stability was mostly invariant to changes in the facility background pressure for vacuum chamber pressure below 110-5 Torr-Xe (for thruster flow rate above 8 mgs). Power spectral density analysis of the discharge current waveform showed that increasing the vacuum chamber background pressure resulted in a higher discharge current dominant frequency. Finally the IVB maps of the TDU-1 thruster taken at elevated magnetic fields indicated that the discharge current became more oscillatory with increased facility background pressure at lower thruster mass flow rates, where thruster operation at higher flow rates resulted in less change to the thrusters IVB characteristics.

Acceleration characteristics of human ocular accommodation.

PubMed

Bharadwaj, Shrikant R; Schor, Clifton M

2005-01-01

Position and velocity of accommodation are known to increase with stimulus magnitude, however, little is known about acceleration properties. We investigated three acceleration properties: peak acceleration, time-to-peak acceleration and total duration of acceleration to step changes in defocus. Peak velocity and total duration of acceleration increased with response magnitude. Peak acceleration and time-to-peak acceleration remained independent of response magnitude. Independent first-order and second-order dynamic components of accommodation demonstrate that neural control of accommodation has an initial open-loop component that is independent of response magnitude and a closed-loop component that increases with response magnitude.

Enhancement in c-Si solar cells using 16 nm InN nanoparticles

NASA Astrophysics Data System (ADS)

Imtiaz Chowdhury, Farsad; Alnuaimi, Aaesha; Alkis, Sabri; Ortaç, Bülend; Aktürk, Selçuk; Alevli, Mustafa; Dietz, Nikolaus; Kemal Okyay, Ali; Nayfeh, Ammar

2016-05-01

In this work, 16 nm indium nitride (InN) nanoparticles (NPs) are used to increase the performance of thin-film c-Si HIT solar cells. InN NPs were spin-coated on top of an ITO layer of c-Si HIT solar cells. The c-Si HIT cell is a stack of 2 μm p type c-Si, 4-5 nm n type a-Si, 15 nm n+ type a-Si and 80 nm ITO grown on a p+ type Si substrate. On average, short circuit current density (Jsc) increases from 19.64 mA cm-2 to 21.54 mA cm-2 with a relative improvement of 9.67% and efficiency increases from 6.09% to 7.09% with a relative improvement of 16.42% due to the presence of InN NPs. Reflectance and internal/external quantum efficiency (IQE/EQE) of the devices were also measured. Peak EQE was found to increase from 74.1% to 81.3% and peak IQE increased from 93% to 98.6% for InN NPs coated c-Si HIT cells. Lower reflection of light due to light scattering is responsible for performance enhancement between 400-620 nm while downshifted photons are responsible for performance enhancement from 620 nm onwards.

Studies on sildenafil citrate (Viagra) interaction with DNA using electrochemical DNA biosensor.

PubMed

Rauf, Sakandar; Nawaz, Haq; Akhtar, Kalsoom; Ghauri, Muhammad A; Khalid, Ahmad M

2007-05-15

The interaction of sildenafil citrate (Viagra) with DNA was studied by using an electrochemical DNA biosensor. The binding mechanism of sildenafil citrate was elucidated by using constant current potentiometry and differential pulse voltammetry at DNA-modified glassy carbon electrode. The decrease in the guanine oxidation peak area or peak current was used as an indicator for the interaction in 0.2M acetate buffer (pH 5). The binding constant (K) values obtained were 2.01+/-0.05 x 10(5) and 1.97+/-0.01 x 10(5)M(-1) with constant current potentiometry and differential pulse voltammetry, respectively. A linear dependence of the guanine peak area or peak current was observed within the range of 1-40 microM sildenafil citrate with slope=-2.74 x 10(-4)s/microM, r=0.989 and slope=-2.78 x 10(-3)microA/microM, r=0.995 by using constant current potentiometry and differential pulse voltammetry, respectively. Additionally, binding constant values for sildenafil citrate-DNA interaction were determined for the pH range of 4-8 and in biological fluids (serum and urine) at pH 5. The influence of sodium and calcium ions was also studied to elucidate the mechanism of sildenafil citrate-DNA interaction under different solution conditions. The present study may prove to be helpful in extending our understanding of the anticancer activity of sildenafil citrate from cellular to DNA level.

High-performance single nanowire tunnel diodes.

PubMed

Wallentin, Jesper; Persson, Johan M; Wagner, Jakob B; Samuelson, Lars; Deppert, Knut; Borgström, Magnus T

2010-03-10

We demonstrate single nanowire tunnel diodes with room temperature peak current densities of up to 329 A/cm(2). Despite the large surface to volume ratio of the type-II InP-GaAs axial heterostructure nanowires, we measure peak to valley current ratios (PVCR) of up to 8.2 at room temperature and 27.6 at liquid helium temperature. These sub-100-nm-diameter structures are promising components for solar cells as well as electronic applications.

Two Ca current components of the receptor current in the electroreceptors of the marine catfish Plotosus.

PubMed

Sugawara, Y

1989-02-01

In the isolated sensory epithelium of the Plotosus electroreceptor, the receptor current has been dissected into inward Ca current, ICa, and superimposed outward transient of Ca-gated K current, IK(Ca). In control saline (170 mM/liter Na), with IK(Ca) abolished by K blockers, ICa declined in two successive exponential phases with voltage-dependent time constants. Double-pulse experiments revealed that the test ICa was partially depressed by prepulses, maximally near voltage levels for the control ICa maximum, which suggests current-dependent inactivation. In low Na saline (80 mM/liter), ICa declined in a single phase with time constants similar to those of the slower phase in control saline. The test ICa was then unaffected by prepulses. The implied presence of two Ca current components, the fast and slow ICa's, were further examined. In control saline, the PSP externally recorded from the afferent nerve showed a fast peak and a slow tonic phase. The double-pulse experiments revealed that IK(Ca) and the peak PSP were similarly depressed, i.e., secondarily to inactivation of the peak current. The steady inward current, however, was unaffected by prolonged prepulses that were stepped to 0 mV, the in situ DC level. Therefore, the fast ICa seems to initiate IK(Ca) and phasic release of transmitter, which serves for phasic receptor responses. The slow ICa may provide persistent active current, which has been shown to maintain tonic receptor operation.

Peak tree: a new tool for multiscale hierarchical representation and peak detection of mass spectrometry data.

PubMed

Zhang, Peng; Li, Houqiang; Wang, Honghui; Wong, Stephen T C; Zhou, Xiaobo

2011-01-01

Peak detection is one of the most important steps in mass spectrometry (MS) analysis. However, the detection result is greatly affected by severe spectrum variations. Unfortunately, most current peak detection methods are neither flexible enough to revise false detection results nor robust enough to resist spectrum variations. To improve flexibility, we introduce peak tree to represent the peak information in MS spectra. Each tree node is a peak judgment on a range of scales, and each tree decomposition, as a set of nodes, is a candidate peak detection result. To improve robustness, we combine peak detection and common peak alignment into a closed-loop framework, which finds the optimal decomposition via both peak intensity and common peak information. The common peak information is derived and loopily refined from the density clustering of the latest peak detection result. Finally, we present an improved ant colony optimization biomarker selection method to build a whole MS analysis system. Experiment shows that our peak detection method can better resist spectrum variations and provide higher sensitivity and lower false detection rates than conventional methods. The benefits from our peak-tree-based system for MS disease analysis are also proved on real SELDI data.

Inflammatory mediator bradykinin increases population of sensory neurons expressing functional T-type Ca2+ channels

PubMed Central

Huang, Dongyang; Liang, Ce; Zhang, Fan; Men, Hongchao; Du, Xiaona; Gamper, Nikita; Zhang, Hailin

2016-01-01

T-type Ca2+ channels are important regulators of peripheral sensory neuron excitability. Accordingly, T-type Ca2+ currents are often increased in various pathological pain conditions, such as inflammation or nerve injury. Here we investigated effects of inflammation on functional expression of T-type Ca2+ channels in small-diameter cultured dorsal root ganglion (DRG) neurons. We found that overnight treatment of DRG cultures with a cocktail of inflammatory mediators bradykinin (BK), adenosine triphosphate (ATP), norepinephrine (NE) and prostaglandin E2 (PGE2) strongly increased the population size of the small-diameter neurons displaying low-voltage activated (LVA, T-type) Ca2+ currents while having no effect on the peak LVA current amplitude. When applied individually, BK and ATP also increased the population size of LVA-positive neurons while NE and PGE2 had no effect. The PLC inhibitor U-73122 and B2 receptor antagonist, Hoe-140, both abolished the increase of the population of LVA-positive DRG neurons. Inflammatory treatment did not affect CaV3.2 mRNA or protein levels in DRG cultures. Furthermore, an ubiquitination inhibitor, MG132, did not increase the population of LVA-positive neurons. Our data suggest that inflammatory mediators BK and ATP increase the abundance of LVA-positive DRG neurons in total neuronal population by stimulating the recruitment of a ‘reserve pool’ of CaV3.2 channels, particularly in neurons that do not display measurable LVA currents under control conditions. PMID:26944020

Drain current enhancement induced by hole injection from gate of 600-V-class normally off gate injection transistor under high temperature conditions up to 200 °C

NASA Astrophysics Data System (ADS)

Ishii, Hajime; Ueno, Hiroaki; Ueda, Tetsuzo; Endoh, Tetsuo

2018-06-01

In this paper, the current–voltage (I–V) characteristics of a 600-V-class normally off GaN gate injection transistor (GIT) from 25 to 200 °C are analyzed, and it is revealed that the drain current of the GIT increases during high-temperature operation. It is found that the maximum drain current (I dmax) of the GIT is 86% higher than that of a conventional 600-V-class normally off GaN metal insulator semiconductor hetero-FET (MIS-HFET) at 150 °C, whereas the GIT obtains 56% I dmax even at 200 °C. Moreover, the mechanism of the drain current increase of the GIT is clarified by examining the relationship between the temperature dependence of the I–V characteristics of the GIT and the gate hole injection effect determined from the shift of the second transconductance (g m) peak of the g m–V g characteristic. From the above, the GIT is a promising device with enough drivability for future power switching applications even under high-temperature conditions.

Theoretical study of closed-loop recycling liquid-liquid chromatography and experimental verification of the theory.

PubMed

Kostanyan, Artak E; Erastov, Andrey A

2016-09-02

The non-ideal recycling equilibrium-cell model including the effects of extra-column dispersion is used to simulate and analyze closed-loop recycling counter-current chromatography (CLR CCC). Previously, the operating scheme with the detector located before the column was considered. In this study, analysis of the process is carried out for a more realistic and practical scheme with the detector located immediately after the column. Peak equation for individual cycles and equations describing the transport of single peaks and complex chromatograms inside the recycling closed-loop, as well as equations for the resolution between single solute peaks of the neighboring cycles, for the resolution of peaks in the recycling chromatogram and for the resolution between the chromatograms of the neighboring cycles are presented. It is shown that, unlike conventional chromatography, increasing of the extra-column volume (the recycling line length) may allow a better separation of the components in CLR chromatography. For the experimental verification of the theory, aspirin, caffeine, coumarin and the solvent system hexane/ethyl acetate/ethanol/water (1:1:1:1) were used. Comparison of experimental and simulated processes of recycling and distribution of the solutes in the closed-loop demonstrated a good agreement between theory and experiment. Copyright © 2016 Elsevier B.V. All rights reserved.

Nitric oxide decreases the excitability of interstitial cells of Cajal through activation of the BK channel

PubMed Central

Zhu, Yaohui; Huizinga, Jan D

2008-01-01

Abstract Nitrergic nerves are structurally and functionally associated with ICC. To further understand mechanisms of communication, the hypothesis was investigated that NO might affect large conductance K channels. To that end, we searched for IbTX-sensitive currents in ICC obtained through explant cultures from the mouse small intestine and studied effects of the NOS inhibitor omega N-nitro-L-arginine (LNNA) and the NO donor sodium nitroprusside (SNP). IbTX-sensitive currents acquired in the whole-cell configuration through nystatin perforated patches exhibited high noise levels but relatively low amplitude, whereas currents obtained in the conventional whole-cell configuration exhibited less noise and higher amplitudes; depolarization from −80 to + 40 mV evoked 357 ± 159 pA current in the nystatin perforated patch configuration and 1075 ± 597 pA using the conventional whole-cell configuration. Immunohistochemistry showed that ICC associated with ganglia and Auerbach's plexus nerve fibers were immunoreactive to BK antibodies. The IbTX-sensitive currents were increased by SNP and inhibited by LNNA. BK blockers suppressed spontaneous transit outward currents in ICC. After block of BK currents, or before these currents became prominent, calcium currents were activated by depolarization in the same cells. Their peak amplitude occurred at −25 mV and the currents were increased with increasing extracellular calcium and inhibited by cobalt. The hypothesis is warranted that nitrergic innervation inhibits ICC excitability in part through activation of BK channels. In addition, NO is an intracellular regulator of ICC excitability. PMID:18194464

Production of high transient heat and particle fluxes in a linear plasma device

NASA Astrophysics Data System (ADS)

De Temmerman, G.; Zielinski, J. J.; van der Meiden, H.; Melissen, W.; Rapp, J.

2010-08-01

We report on the generation of high transient heat and particle fluxes in a linear plasma device by pulsed operation of the plasma source. A capacitor bank is discharged into the source to transiently increase the discharge current up to 1.7 kA, allowing peak densities and temperature of 70×1020 m-3 and 6 eV corresponding to a surface power density of about 400 MW m-2.

A rapid electrochemical monitoring platform for sensitive determination of thiamethoxam based on β-cyclodextrin-graphene composite.

PubMed

Zhai, XingChen; Zhang, Hua; Zhang, Min; Yang, Xin; Gu, Cheng; Zhou, GuoPeng; Zhao, HaiTian; Wang, ZhenYu; Dong, AiJun; Wang, Jing

2017-08-01

A rapid monitoring platform for sensitive voltammetric detection of thiamethoxam residues is reported in the present study. A β-cyclodextrin-reduced graphene oxide composite was used as a reinforcing material in electrochemical determination of thiamethoxam. Compared with bare glassy carbon electrodes, the reduction peak currents of thiamethoxam at reduced graphene oxide/glassy carbon electrode and β-cyclodextrin-reduced graphene oxide/glassy carbon electrode were increased by 70- and 124-fold, respectively. The experimental conditions influencing voltammetric determination of thiamethoxam, such as the amount of β-cyclodextrin-reduced graphene oxide, solution pH, temperature, and accumulation time, were optimized. The reduction mechanism and binding affinity of this material is also discussed. Under optimal conditions, the reduction peak currents increased linearly between 0.5 µM and 16 µM concentration of thiamethoxam. The limit of detection was 0.27 µM on the basis of a signal-to-noise ratio of 3. When the proposed method was applied to brown rice in a recovery test, the recoveries were between 92.20% and 113.75%. The results were in good concordance with the high-performance liquid chromatography method. The proposed method therefore provides a promising and effective platform for sensitive and rapid determination of thiamethoxam. Environ Toxicol Chem 2017;36:1991-1997. © 2017 SETAC. © 2017 SETAC.

Hysteresis in Lanthanide Zirconium Oxides Observed Using a Pulse CV Technique and including the Effect of High Temperature Annealing.

PubMed

Lu, Qifeng; Zhao, Chun; Mu, Yifei; Zhao, Ce Zhou; Taylor, Stephen; Chalker, Paul R

2015-07-29

A powerful characterization technique, pulse capacitance-voltage (CV) technique, was used to investigate oxide traps before and after annealing for lanthanide zirconium oxide thin films deposited on n-type Si (111) substrates at 300 °C by liquid injection Atomic Layer Deposition (ALD). The results indicated that: (1) more traps were observed compared to the conventional capacitance-voltage characterization method in LaZrO x ; (2) the time-dependent trapping/de-trapping was influenced by the edge time, width and peak-to-peak voltage of a gate voltage pulse. Post deposition annealing was performed at 700 °C, 800 °C and 900 °C in N₂ ambient for 15 s to the samples with 200 ALD cycles. The effect of the high temperature annealing on oxide traps and leakage current were subsequently explored. It showed that more traps were generated after annealing with the trap density increasing from 1.41 × 10 12 cm -2 for as-deposited sample to 4.55 × 10 12 cm -2 for the 800 °C annealed one. In addition, the leakage current density increase from about 10 - ⁶ A/cm² at V g = +0.5 V for the as-deposited sample to 10 -3 A/cm² at V g = +0.5 V for the 900 °C annealed one.

The relation between schizotypy and early attention to rejecting interactions: The influence of neuroticism

PubMed Central

Premkumar, Preethi; Onwumere, Juliana; Albert, Jacobo; Kessel, Dominique; Kumari, Veena; Kuipers, Elizabeth; Carretié, Luis

2015-01-01

Abstract Objectives: Schizotypy relates to rejection sensitivity (anxiety reflecting an expectancy of social exclusion) and neuroticism (excessive evaluation of negative emotions). Positive schizotypy (e.g., perceptual aberrations and odd beliefs) and negative schizotypy (e.g., social and physical anhedonia) could relate to altered attention to rejection because of neuroticism. Methods: Forty-one healthy individuals were assessed on positive and negative schizotypy and neuroticism, and event-related potentials during rejecting, accepting and neutral scenes. Participants were categorised into high, moderate and low neuroticism groups. Using temporo-spatial principal components analyses, P200 (peak latency =290 ms) and P300 amplitudes (peak latency = 390 ms) were measured, reflecting mobilisation of attention and early attention, respectively. Results: Scalp-level and cortical source analysis revealed elevated fronto-parietal N300/P300 amplitude and P200-related dorsal anterior cingulate current density during rejection than acceptance/neutral scenes. Positive schizotypy related inversely to parietal P200 amplitude during rejection. Negative schizotypy related positively to P200 middle occipital current density. Negative schizotypy related positively to parietal P300, where the association was stronger in high and moderate, than low, neuroticism groups. Conclusions: Positive and negative schizotypy relate divergently to attention to rejection. Positive schizotypy attenuates, but negative schizotypy increases rejection-related mobilisation of attention. Negative schizotypy increases early attention to rejection partly due to elevated neuroticism. PMID:26452584

Fabrication of a transparent ultraviolet detector by using n-type Ga2O3 and p-type Ga-doped SnO2 core-shell nanowires.

PubMed

Hsu, Cheng-Liang; Lu, Ying-Ching

2012-09-21

This study investigates the feasibility of synthesizing high-density transparent Ga(2)O(3)/SnO(2):Ga core-shell nanowires on a sapphire substrate at 1000 °C by VLS. The doping Ga concentrations are 0.46, 1.07, 2.30 and 17.53 atomic%. The XRD spectrum and HR-TEM reveal Ga(2)O(3) and SnO(2) as having monoclinic and tetragonal rutile structures, respectively. Experimental results indicate that the XRD peak shift of SnO(2) to a larger angle increases with the increasing amount of Ga doping. According to the CL spectrum, SnO(2) and Ga(2)O(3) peak at approximately 528-568 nm and 422-424 nm, respectively. The maximum quantum efficiency of Ga(2)O(3)/SnO(2):Ga core-shell nanowires is around 0.362%. The UV light on-off current contrast ratio of Ga(2)O(3)/SnO(2):Ga core-shell nanowires is around 1066.7 at a bias of 5 V. Moreover, the dynamic response of Ga(2)O(3)/SnO(2):Ga core-shell nanowires has an on-off current contrast ratio of around 16. Furthermore, the Ga(2)O(3) region functions similar to a capacitor and continues to accumulate SnO(2):Ga excited electrons under UV light exposure.

Photo-triggering and secondary electron produced ionization in electric discharge ArF* excimer lasers

NASA Astrophysics Data System (ADS)

Xiong, Zhongmin; Kushner, Mark J.

2011-10-01

Electric discharge excimer lasers are sustained in multi-atmosphere attaching gas mixtures that are typically preionized to enable a reproducible, uniform glow, which maximizes optical quality and gain. This preionization is often accomplished using UV light produced by a corona discharge within the plasma cavity. To quantify the relationship between corona discharge properties and those of the laser discharge, the triggering of electron avalanche by preionizing UV light in an electric discharge-pumped ArF* excimer laser was numerically investigated using a two-dimensional model. The preionizing UV fluxes were generated by a corona-bar discharge driven by the same voltage pulse as the main discharge sustained in a multi-atmospheric Ne/Ar/Xe/F2 gas mixture. The resulting peak photo-electron density in the inter-electrode spacing is around 108 cm-3, and its distribution is biased toward the UV source. The preionization density increases with increasing dielectric constant and capacitance of the corona bar. The symmetry and uniformity of the discharge are, however, improved significantly once the main avalanche develops. In addition to bulk electron impact ionization, the ionization generated by sheath accelerated secondary electrons was found to be important in sustaining the discharge current at experimentally observed values. At peak current, the magnitude of the ionization by sheath accelerated electrons is comparable to that from bulk electron impact in the vicinity of the cathode.

The Peak Structure and Future Changes of the Relationships Between Extreme Precipitation and Temperature

NASA Technical Reports Server (NTRS)

Wang, Guiling; Wang, Dagang; Trenberth, Kevin E.; Erfanian, Amir; Yu, Miao; Bosilovich, Michael G.; Parr, Dana T.

2017-01-01

Theoretical models predict that, in the absence of moisture limitation, extreme precipitation intensity could exponentially increase with temperatures at a rate determined by the Clausius-Clapeyron (C-C) relationship. Climate models project a continuous increase of precipitation extremes for the twenty-first century over most of the globe. However, some station observations suggest a negative scaling of extreme precipitation with very high temperatures, raising doubts about future increase of precipitation extremes. Here we show for the present-day climate over most of the globe,the curve relating daily precipitation extremes with local temperatures has a peak structure, increasing as expected at the low medium range of temperature variations but decreasing at high temperatures. However, this peak-shaped relationship does not imply a potential upper limit for future precipitation extremes. Climate models project both the peak of extreme precipitation and the temperature at which it peaks (T(sub peak)) will increase with warming; the two increases generally conform to the C-C scaling rate in mid- and high-latitudes,and to a super C-C scaling in most of the tropics. Because projected increases of local mean temperature (T(sub mean)) far exceed projected increases of T(sub peak) over land, the conventional approach of relating extreme precipitation to T(sub mean) produces a misleading sub-C-C scaling rate.

The comprehensive electrophysiological study of curcuminoids on delayed-rectifier K+ currents in insulin-secreting cells.

PubMed

Kuo, Ping-Chung; Yang, Chia-Jung; Lee, Yu-Chi; Chen, Pei-Chun; Liu, Yen-Chin; Wu, Sheng-Nan

2018-01-15

Curcumin (CUR) has been demonstrated to induce insulin release from pancreatic β-cells; however, how curcuminoids (including demethoxycurcumin (DMC) and bisdemethoxycurcumin (BDMC)) exert any possible effects on membrane ion currents inherently in insulin-secreting cells remains largely unclear. The effects of CUR and other structurally similar curcuminoids on ion currents in rat insulin-secreting (INS-1) insulinoma cells were therefore investigated in this study. The effects of these compounds on ionic currents and membrane potential were studied by patch-clamp technique. CUR suppressed the amplitude of delayed-rectifier K + current (I K(DR) ) in a time-, state- and concentration-dependent manner in these cells and the inhibition was not reversed by diazoxide, nicorandil or chlorotoxin. The value of dissociation constant for CUR-induced suppression of I K(DR) in INS-1 cells was 1.26μM. Despite the inability of CUR to alter the activation rate of I K(DR) , it accelerated current inactivation elicited by membrane depolarization. Increasing CUR concentrations shifted the inactivation curve of I K(DR) to hyperpolarized potential and slowed the recovery of I K(DR) inactivation. CUR, DMC, and BDMC all exerted depressant actions on I K(DR) amplitude to a similar magnitude, although DMC and BDMC did not increase current inactivation clearly. CUR slightly suppressed the peak amplitude of voltage-gated Na + current. CUR, DMC and BDMC depolarized the resting potential and increased firing frequency of action potentials. The CUR-mediated decrease of I K(DR) and the increase of current inactivation also occurred in βTC-6 INS-1 cells. Taken these results together, these effects may be one of the possible mechanisms contributing their insulin-releasing effect. Copyright © 2017 Elsevier B.V. All rights reserved.

Influence of etching current density on microstructural, optical and electrical properties of porous silicon (PS):n-Si heterostructure

NASA Astrophysics Data System (ADS)

Das, M.; Nath, P.; Sarkar, D.

2016-02-01

In this article effect of etching current density (J) on the microstructural, optical and electrical properties of photoelectrochemically prepared heterostructure is reported. Prepared samples are characterized by FESEM, XRD, UV-Visible, Raman and photoluminescence (PL) spectra and current-voltage (I-V) characteristics. FESEM shows presence of mixture of randomly distributed meso- and micro-pores. Porous layer thickness determined by cross section view of SEM is proportional to J. XRD shows crystalline nature but gradually extent of crystallinity decreases with increasing J. Raman spectra show large red-shift and asymmetric broadening with respect to crystalline silicon (c-Si). UV-visible reflectance and PL show blue shift in peaks with increasing J. The I-V characteristics are analyzed by the conventional thermionic emission (TE) model and Cheung's model to estimate the barrier height (φb), ideality factor (n) and series resistance (Rs) for comparison between the two models. The latter model is found to fit better.

Influence of thermal aging on AC leakage current in XLPE insulation

NASA Astrophysics Data System (ADS)

Geng, Pulong; Song, Jiancheng; Tian, Muqin; Lei, Zhipeng; Du, Yakun

2018-02-01

Cross-linked polyethylene (XLPE) has been widely used as cable insulation material because of its excellent dielectric properties, thermal stability and solvent resistance. To understand the influence of thermal aging on AC leakage current in XLPE insulation, all XLPE specimens were aged in oven in temperature range from 120 °C to 150 °C, and a series of tests were conducted on these XLPE specimens in different aging stages to measure the characteristic parameters, such as complex permittivity, leakage current and complex dielectric modulus. In the experiments, the effects of thermal aging, temperature and frequency on the AC leakage current in XLPE insulation were studied by analyzing complex dielectric constant and dielectric relaxation modulus spectrum, the change of relaxation peak and activation energy. It has been found that the active part of leakage current increases sharply with the increase of aging degree, and the test temperature and frequency have an influence on AC leakage current but the influence of test temperature is mainly reflected in the low frequency region. In addition, it has been shown by the experiments that the reactive part of leakage current exhibits a strong frequency dependent characteristic in the testing frequency range from 10-2 Hz to 105 Hz, but the influence of test temperature and thermal aging on it is relatively small.

Load controller and method to enhance effective capacity of a photovotaic power supply using a dynamically determined expected peak loading

DOEpatents

Perez, Richard

2003-04-01

A load controller and method are provided for maximizing effective capacity of a non-controllable, renewable power supply coupled to a variable electrical load also coupled to a conventional power grid. Effective capacity is enhanced by monitoring power output of the renewable supply and loading, and comparing the loading against the power output and a load adjustment threshold determined from an expected peak loading. A value for a load adjustment parameter is calculated by subtracting the renewable supply output and the load adjustment parameter from the current load. This value is then employed to control the variable load in an amount proportional to the value of the load control parameter when the parameter is within a predefined range. By so controlling the load, the effective capacity of the non-controllable, renewable power supply is increased without any attempt at operational feedback control of the renewable supply. The expected peak loading of the variable load can be dynamically determined within a defined time interval with reference to variations in the variable load.

Evaluating the diffusion coefficient of dopamine at the cell surface during amperometric detection: disk vs ring microelectrodes.

PubMed

Trouillon, Raphaël; Lin, Yuqing; Mellander, Lisa J; Keighron, Jacqueline D; Ewing, Andrew G

2013-07-02

During exocytosis, small quantities of neurotransmitters are released by the cell. These neurotransmitters can be detected quantitatively using electrochemical methods, principally with disk carbon fiber microelectrode amperometry. An exocytotic event then results in the recording of a current peak whose characteristic features are directly related to the mechanisms of exocytosis. We have compared two exocytotic peak populations obtained from PC12 cells with a disk carbon fiber microelectrode and with a pyrolyzed carbon ring microelectrode array, with a 500 nm ring thickness. The specific shape of the ring electrode allows for precise analysis of diffusion processes at the vicinity of the cell membrane. Peaks obtained with a ring microelectrode array show a distorted average shape, owing to increased diffusion pathways. This result has been used to evaluate the diffusion coefficient of dopamine at the surface of a cell, which is up to an order of magnitude smaller than that measured in free buffer. The lower rate of diffusion is discussed as resulting from interactions with the glycocalyx.

Fabrication of Amine-Modified Magnetite-Electrochemically Reduced Graphene Oxide Nanocomposite Modified Glassy Carbon Electrode for Sensitive Dopamine Determination

PubMed Central

He, Quanguo; Liu, Jun; Liu, Xiaopeng; Li, Guangli; Chen, Dongchu; Deng, Peihong; Liang, Jing

2018-01-01

Amine-modified magnetite (NH2–Fe3O4)/reduced graphene oxide nanocomposite modified glassy carbon electrodes (NH2–Fe3O4/RGO/GCEs) were developed for the sensitive detection of dopamine (DA). The NH2-Fe3O4/RGO/GCEs were fabricated using a drop-casting method followed by an electrochemical reduction process. The surface morphologies, microstructure and chemical compositions of the NH2–Fe3O4 nanoparticles (NPs), reduced graphene oxide (RGO) sheets and NH2–Fe3O4/RGO nanocomposites were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-Ray diffraction (XRD) and Fourier-transform infrared (FTIR) spectroscopy. The electrochemical behaviors of DA on the bare and modified GCEs were investigated in phosphate buffer solution (PBS) by cyclic voltammetry (CV). Compared with bare electrode and RGO/GCE, the oxidation peak current (ipa) on the NH2–Fe3O4/RGO/GCE increase significantly, owing to the synergistic effect between NH2–Fe3O4 NPs and RGO sheets. The oxidation peak currents (ipa) increase linearly with the concentrations of DA in the range of 1 × 10−8 mol/L – 1 × 10−7 mol/L, 1 × 10−7 mol/L – 1 × 10−6 mol/L and 1 × 10−6 mol/L – 1 × 10−5 mol/L. The detection limit is (4.0 ± 0.36) ×10−9 mol/L (S/N = 3). Moreover, the response peak currents of DA were hardly interfered with the coexistence of ascorbic acid (AA) and uric acid (UA). The proposed NH2–Fe3O4/RGO/GCE is successfully applied to the detection of dopamine hydrochloride injections with satisfactory results. Together with low cost, facile operation, good selectivity and high sensitivity, the NH2–Fe3O4/RGO/GCEs have tremendous prospects for the detection of DA in various real samples. PMID:29584682

Measuring Method for Lightning Channel Temperature.

PubMed

Li, X; Zhang, J; Chen, L; Xue, Q; Zhu, R

2016-09-26

In this paper, we demonstrate the temperature of lightning channel utilizing the theory of lightning spectra and the model of local thermodynamic equilibrium (LTE). The impulse current generator platform (ICGS) was used to simulate the lightning discharge channel, and the spectral energy of infrared spectroscopy (930 nm) and the visible spectroscopy (648.2 nm) of the simulated lightning has been calculated. Results indicate that the peaks of luminous intensity of both infrared and visible spectra increase with the lightning current intensity in range of 5-50 kA. Based on the results, the temperature of the lightning channel is derived to be 6140.8-10424 K. Moreover, the temperature of the channel is approximately exponential to the lightning current intensity, which shows good agreement with that of the natural lightning cases.

Observation of linear I-V curves on vertical GaAs nanowires with atomic force microscope

NASA Astrophysics Data System (ADS)

Geydt, P.; Alekseev, P. A.; Dunaevskiy, M.; Lähderanta, E.; Haggrén, T.; Kakko, J.-P.; Lipsanen, H.

2015-12-01

In this work we demonstrate the possibility of studying the current-voltage characteristics for single vertically standing semiconductor nanowires on standard AFM equipped by current measuring module in PeakForce Tapping mode. On the basis of research of eight different samples of p-doped GaAs nanowires grown on different GaAs substrates, peculiar electrical effects were revealed. It was found how covering of substrate surface by SiOx layer increases the current, as well as phosphorous passivation of the grown nanowires. Elimination of the Schottky barrier between golden cap and the top parts of nanowires was observed. It was additionally studied that charge accumulation on the shell of single nanowires affects its resistivity and causes the hysteresis loops on I-V curves.

Power Generation Evaluated on a Bismuth Telluride Unicouple Module

NASA Astrophysics Data System (ADS)

Hu, Xiaokai; Nagase, Kazuo; Jood, Priyanka; Ohta, Michihiro; Yamamoto, Atsushi

2015-06-01

The power generated by a thermoelectric unicouple module made of Bi2Te3 alloy was evaluated by use of a newly developed instrument. An electrical load was connected to the module, and the terminal voltage and output power of the module were obtained by altering electric current. Water flow was used to cool the cold side of the module and for heat flow measurement, by monitoring inlet and outlet temperatures. When the electric current was increased, heat flow was enhanced as a result of the Peltier effect and Joule heating. Voltage, power, heat flow, and efficiency as functions of current were determined for hot-side temperatures from 50 to 220°C. Maximum power output and peak conversion efficiency could thus be easily derived for each temperature.

Measuring Method for Lightning Channel Temperature

NASA Astrophysics Data System (ADS)

Li, X.; Zhang, J.; Chen, L.; Xue, Q.; Zhu, R.

2016-09-01

In this paper, we demonstrate the temperature of lightning channel utilizing the theory of lightning spectra and the model of local thermodynamic equilibrium (LTE). The impulse current generator platform (ICGS) was used to simulate the lightning discharge channel, and the spectral energy of infrared spectroscopy (930 nm) and the visible spectroscopy (648.2 nm) of the simulated lightning has been calculated. Results indicate that the peaks of luminous intensity of both infrared and visible spectra increase with the lightning current intensity in range of 5-50 kA. Based on the results, the temperature of the lightning channel is derived to be 6140.8-10424 K. Moreover, the temperature of the channel is approximately exponential to the lightning current intensity, which shows good agreement with that of the natural lightning cases.

The human Nav1.5 F1486 deletion associated with long QT syndrome leads to impaired sodium channel inactivation and reduced lidocaine sensitivity

PubMed Central

Song, Weihua; Xiao, Yucheng; Chen, Hanying; Ashpole, Nicole M; Piekarz, Andrew D; Ma, Peilin; Hudmon, Andy; Cummins, Theodore R; Shou, Weinian

2012-01-01

The deletion of phenylalanine 1486 (F1486del) in the human cardiac voltage-gated sodium channel (hNav1.5) is associated with fatal long QT (LQT) syndrome. In this study we determined how F1486del impairs the functional properties of hNav1.5 and alters action potential firing in heterologous expression systems (human embryonic kidney (HEK) 293 cells) and their native cardiomyocyte background. Cells expressing hNav1.5-F1486del exhibited a loss-of-function alteration, reflected by an 80% reduction of peak current density, and several gain-of-function alterations, including reduced channel inactivation, enlarged window current, substantial augmentation of persistent late sodium current and an increase in ramp current. We also observed substantial action potential duration (APD) prolongation and prominent early afterdepolarizations (EADs) in neonatal cardiomyocytes expressing the F1486del channels, as well as in computer simulations of myocyte activity. In addition, lidocaine sensitivity was dramatically reduced, which probably contributed to the poor therapeutic outcome observed in the patient carrying the hNav1.5-F1486del mutation. Therefore, despite the significant reduction in peak current density, the F1486del mutation also leads to substantial gain-of-function alterations that are sufficient to cause APD prolongation and EADs, the predominant characteristic of LQTs. These data demonstrate that hNav1.5 mutations can have complex functional consequences and highlight the importance of identifying the specific molecular defect when evaluating potential treatments for individuals with prolonged QT intervals. PMID:22826127

Anodic stripping voltammetric determination of mercury using multi-walled carbon nanotubes film coated glassy carbon electrode.

PubMed

Yi, Hongchao

2003-10-01

An electrochemical method for the determination of trace levels of mercury based on a multi-walled carbon nanotubes (MWNT) film coated glassy carbon electrode (GCE) is described. In 0.1 mol L(-1) HCl solution containing 0.02 mol L(-1) KI, Hg(2+) was firstly preconcentrated at the MWNT film and then reduced at -0.60 V. During the anodic potential sweep, reduced mercury was oxidized, and then a sensitive and well-defined stripping peak at about -0.20 V appeared. Under identical conditions, a MWNT film coated GCE greatly enhances the stripping peak current of mercury in contrast to a bare GCE. Low concentrations of I(-) remarkably improve the determining sensitivity, since this increases the accumulation efficiency of Hg(2+) at the MWNT film coated GCE. The stripping peak current is proportional to the concentration of Hg(2+) over the range 8 x 10(-10)-5 x 10(-7) mol L(-1). The lowest detectable concentration of Hg(2+) is 2 x 10(-10) mol L(-1) at 5 min accumulation. The relative standard deviation (RSD) at 1 x 10(-8) mol L(-1) Hg(2+) was about 6% ( n=10). By using this proposed method, Hg(2+) in some water samples was determined, and the results were compared with those obtained by atomic absorption spectrometry (AAS). The two results are similar, suggesting that the MWNT-film coated GCE has great potential in practical analysis.

Experiment study on an inductive superconducting fault current limiter using no-insulation coils

NASA Astrophysics Data System (ADS)

Qiu, D.; Li, Z. Y.; Gu, F.; Huang, Z.; Zhao, A.; Hu, D.; Wei, B. G.; Huang, H.; Hong, Z.; Ryu, K.; Jin, Z.

2018-03-01

No-insulation (NI) coil made of 2 G high temperature superconducting (HTS) tapes has been widely used in DC magnet due to its excellent performance of engineering current density, thermal stability and mechanical strength. However, there are few AC power device using NI coil at present. In this paper, the NI coil is firstly applied into inductive superconducting fault current limiter (iSFCL). A two-winding structure air-core iSFCL prototype was fabricated, composed of a primary copper winding and a secondary no-insulation winding using 2 G HTS coated conductors. Firstly, in order to testify the feasibility to use NI coil as the secondary winding, the impedance variation of the prototype at different currents and different cycles was tested. The result shows that the impedance increases rapidly with the current rises. Then the iSFCL prototype was tested in a 40 V rms/ 3.3 kA peak short circuit experiment platform, both of the fault current limiting and recovery property of the iSFCL are discussed.

Contribution for Iron Vapor and Radiation Distribution Affected by Current Frequency of Pulsed Arc

NASA Astrophysics Data System (ADS)

Shimokura, Takuya; Mori, Yusuke; Iwao, Toru; Yumoto, Motoshige

Pulsed GTA welding has been used for improvement of stability, weld speed, and heat input control. However, the temperature and radiation power of the pulsed arc have not been elucidated. Furthermore, arc contamination by metal vapor changes the arc characteristics, e.g. by increasing radiation power. In this case, the metal vapor in pulsed GTA welding changes the distribution of temperature and radiation power as a function of time. This paper presents the relation between metal vapor and radiation power at different pulse frequencies. We calculate the Fe vapor distribution of the pulsed current. Results show that the Fe vapor is transported at fast arc velocity during the peak current period. During the base current period, the Fe vapor concentration is low and distribution is diffuse. The transition of Fe vapor distribution does not follow the pulsed current; the radiation power density distribution differs for high frequencies and low frequencies. In addition, the Fe vapor and radiation distribution are affected by the pulsed arc current frequency.

Efficient prediction of terahertz quantum cascade laser dynamics from steady-state simulations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Agnew, G.; Lim, Y. L.; Nikolić, M.

2015-04-20

Terahertz-frequency quantum cascade lasers (THz QCLs) based on bound-to-continuum active regions are difficult to model owing to their large number of quantum states. We present a computationally efficient reduced rate equation (RE) model that reproduces the experimentally observed variation of THz power with respect to drive current and heat-sink temperature. We also present dynamic (time-domain) simulations under a range of drive currents and predict an increase in modulation bandwidth as the current approaches the peak of the light–current curve, as observed experimentally in mid-infrared QCLs. We account for temperature and bias dependence of the carrier lifetimes, gain, and injection efficiency,more » calculated from a full rate equation model. The temperature dependence of the simulated threshold current, emitted power, and cut-off current are thus all reproduced accurately with only one fitting parameter, the interface roughness, in the full REs. We propose that the model could therefore be used for rapid dynamical simulation of QCL designs.« less

Effects of Pulse Parameters on Weld Microstructure and Mechanical Properties of Extra Pulse Current Aided Laser Welded 2219 Aluminum Alloy Joints.

PubMed

Zhang, Xinge; Li, Liqun; Chen, Yanbin; Yang, Zhaojun; Chen, Yanli; Guo, Xinjian

2017-09-15

In order to expand the application range of laser welding and improve weld quality, an extra pulse current was used to aid laser-welded 2219 aluminum alloy, and the effects of pulse current parameters on the weld microstructure and mechanical properties were investigated. The effect mechanisms of the pulse current interactions with the weld pool were evaluated. The results indicated that the coarse dendritic structure in the weld zone changed to a fine equiaxed structure using an extra pulse current, and the pulse parameters, including medium peak current, relatively high pulse frequency, and low pulse duty ratio benefited to improving the weld structure. The effect mechanisms of the pulse current were mainly ascribed to the magnetic pinch effect, thermal effect, and electromigration effect caused by the pulse current. The effect of the pulse parameters on the mechanical properties of welded joints were consistent with that of the weld microstructure. The tensile strength and elongation of the optimal pulse current-aided laser-welded joint increased by 16.4% and 105%, respectively, compared with autogenous laser welding.

Effects of Pulse Parameters on Weld Microstructure and Mechanical Properties of Extra Pulse Current Aided Laser Welded 2219 Aluminum Alloy Joints

PubMed Central

Zhang, Xinge; Li, Liqun; Chen, Yanbin; Yang, Zhaojun; Chen, Yanli; Guo, Xinjian

2017-01-01

In order to expand the application range of laser welding and improve weld quality, an extra pulse current was used to aid laser-welded 2219 aluminum alloy, and the effects of pulse current parameters on the weld microstructure and mechanical properties were investigated. The effect mechanisms of the pulse current interactions with the weld pool were evaluated. The results indicated that the coarse dendritic structure in the weld zone changed to a fine equiaxed structure using an extra pulse current, and the pulse parameters, including medium peak current, relatively high pulse frequency, and low pulse duty ratio benefited to improving the weld structure. The effect mechanisms of the pulse current were mainly ascribed to the magnetic pinch effect, thermal effect, and electromigration effect caused by the pulse current. The effect of the pulse parameters on the mechanical properties of welded joints were consistent with that of the weld microstructure. The tensile strength and elongation of the optimal pulse current-aided laser-welded joint increased by 16.4% and 105%, respectively, compared with autogenous laser welding. PMID:28914825

Shrinking of core neoclassical tearing mode magnetic islands due to edge localized modes and the role of ion-scale turbulence in island recovery in DIII-D

NASA Astrophysics Data System (ADS)

Bardóczi, L.; Rhodes, T. L.; Carter, T. A.; La Haye, R. J.; Bañón Navarro, A.; McKee, G. R.

2017-06-01

Experimental signature of long-wavelength turbulence accelerating the recovery of Neoclassical Tearing Mode (NTM) magnetic islands after they have been transiently reduced in size due to interaction with Edge Localized Modes (ELMs) is reported for the first time. This work shows that perturbations associated with ELMs result in peaking of the electron temperature (Te) in the O-point region of saturated core m/n = 2/1 islands (m/n being the poloidal/toroidal mode numbers). In synchronization with this Te peak, the island width shrinks by as much as 30% suggesting a key role of the Te peak in NTM stability due to modified pressure gradient (∇p) and perturbed bootstrap current (δjBS) at the O-point. Next, this Te peak relaxes via anomalous transport (i.e., the diffusivity is 2 orders of magnitude larger than the neoclassical value) and the island recovers. Long-wavelength turbulent density fluctuations ( n ˜ ) are reduced at the O-point of flat islands but these fluctuations are increased when Te is peaked which offers an explanation for the observed anomalous transport that is responsible for the relaxation of the Te peak. Linear gyrokinetic simulations indicate that n ˜ inside the peaked island is dominantly driven by the Ion Temperature Gradient instability. These measurements suggest that n ˜ accelerates NTM recovery after an ELM crash via accelerating the relaxation of ∇p at the O-point. These observations are qualitatively replicated by coupled predator-prey equations and modified Rutherford equation. In this simple model, turbulence accelerates NTM recovery via relaxing ∇p and therefore restoring δjBS at the O-point. The key physics of the relationship between the Te peak and NTM stability has potentially far-reaching consequences, such as NTM control via pellet injection in high-β tokamak plasmas.

Variation in light intensity with height and time from subsequent lightning return strokes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jordan, D.M.; Uman, M.A.

1983-08-20

Relative light intensity has been measured photographically as a function of height and time for seven subsequent return strokes in two lightning flashes at ranges of 7.8 and 8.7 km. The film used was Kodak 5474 Shellburst, which has a roughly constant spectral response between 300 and 670 nm. The time resolution was about 1.0 ..mu..s, and the spatial resolution was about 4 m. The observed light signals consisted of a fast rise to peak, followed by a slower decrease to a relatively constant value. The amplitude of the initial light peak decreases exponentially with height with a decay constantmore » of about 0.6 to 0.8 km. The 20% to 80% rise time of the initial light signal is between 1 and 4 ..mu..s near ground and increases by an additional 1 to 2 ..mu..s by the time the return stroke reaches the cloud base, a height between 1 and 2 km. The light intensity 30 ..mu..s after the initial peak is relatively constant with height and has an amplitude that is 15% to 30% of the initial peak near the ground and 50% to 100% of the initial peak at cloud base. The logarithm of the peak light intensity near the ground is roughly proportional to the initial peak electric field intensity, and this in turn implies that the current decrease with height may be much slower than the light decrease. The absolute light intensity has been estimated by integrating the photographic signals from individual channel segments to simulate the calibrated all-sky photoelectric data of Guo and Krider (1982). Using this method, the authors find that the mean peak radiance near the ground is 8.3 x 10/sup 5/ W/m, with a total range from 1.4 x 10/sup 5/ to 3.8 x 10/sup 6/ W/m. 16 references, 11 figures.« less

3D electrostatic gyrokinetic electron and fully kinetic ion simulation of lower-hybrid drift instability of Harris current sheet

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Zhenyu; Lin, Yu; Wang, Xueyi

The eigenmode stability properties of three-dimensional lower-hybrid-drift-instabilities (LHDI) in a Harris current sheet with a small but finite guide magnetic field have been systematically studied by employing the gyrokinetic electron and fully kinetic ion (GeFi) particle-in-cell (PIC) simulation model with a realistic ion-to-electron mass ratio m i/m e. In contrast to the fully kinetic PIC simulation scheme, the fast electron cyclotron motion and plasma oscillations are systematically removed in the GeFi model, and hence one can employ the realistic m i/m e. The GeFi simulations are benchmarked against and show excellent agreement with both the fully kinetic PIC simulation and the analytical eigenmode theory. Our studies indicate that, for small wavenumbers, ky, along the current direction, the most unstable eigenmodes are peaked at the location wheremore » $$\\vec{k}$$• $$\\vec{B}$$ =0, consistent with previous analytical and simulation studies. Here, $$\\vec{B}$$ is the equilibrium magnetic field and $$\\vec{k}$$ is the wavevector perpendicular to the nonuniformity direction. As ky increases, however, the most unstable eigenmodes are found to be peaked at $$\\vec{k}$$ •$$\\vec{B}$$ ≠0. Additionally, the simulation results indicate that varying m i/m e, the current sheet width, and the guide magnetic field can affect the stability of LHDI. Simulations with the varying mass ratio confirm the lower hybrid frequency and wave number scalings.« less

3D electrostatic gyrokinetic electron and fully kinetic ion simulation of lower-hybrid drift instability of Harris current sheet

DOE PAGES

Wang, Zhenyu; Lin, Yu; Wang, Xueyi; ...

2016-07-07

The eigenmode stability properties of three-dimensional lower-hybrid-drift-instabilities (LHDI) in a Harris current sheet with a small but finite guide magnetic field have been systematically studied by employing the gyrokinetic electron and fully kinetic ion (GeFi) particle-in-cell (PIC) simulation model with a realistic ion-to-electron mass ratio m i/m e. In contrast to the fully kinetic PIC simulation scheme, the fast electron cyclotron motion and plasma oscillations are systematically removed in the GeFi model, and hence one can employ the realistic m i/m e. The GeFi simulations are benchmarked against and show excellent agreement with both the fully kinetic PIC simulation and the analytical eigenmode theory. Our studies indicate that, for small wavenumbers, ky, along the current direction, the most unstable eigenmodes are peaked at the location wheremore » $$\\vec{k}$$• $$\\vec{B}$$ =0, consistent with previous analytical and simulation studies. Here, $$\\vec{B}$$ is the equilibrium magnetic field and $$\\vec{k}$$ is the wavevector perpendicular to the nonuniformity direction. As ky increases, however, the most unstable eigenmodes are found to be peaked at $$\\vec{k}$$ •$$\\vec{B}$$ ≠0. Additionally, the simulation results indicate that varying m i/m e, the current sheet width, and the guide magnetic field can affect the stability of LHDI. Simulations with the varying mass ratio confirm the lower hybrid frequency and wave number scalings.« less

Mitigating Structural Defects in Droop-Minimizing InGaN/GaN Quantum Well Heterostructures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhao, Zhibo; Chesin, Jordan; Singh, Akshay

2016-12-01

Modern commercial InGaN/GaN blue LEDs continue to suffer from efficiency droop, a reduction in efficiency with increasing drive current. External quantum efficiency (EQE) typically peaks at low drive currents (< 10 A cm 2) and drops monotonically at higher current densities, falling to <85% of the peak EQE at a drive current of 100 A cm 2. Mitigating droop-related losses will yield tremendous gains in both luminous efficacy (lumens/W) and cost (lumens/$). Such improvements are critical for continued large-scale market penetration of LED technologies, particularly in high-power and high flux per unit area applications. However, device structures that reduce droopmore » typically require higher indium content and are accompanied by a corresponding degradation in material quality which negates the droop improvement via enhanced Shockley-Read-Hall (SRH) recombination. In this work, we use advanced characterization techniques to identify and classify structural defects in InGaN/GaN quantum well (QW) heterostructures that share features with low-droop designs. Using aberration-corrected scanning transmission electron microscopy (C s-STEM), we find the presence of severe well width fluctuations (WWFs) in a number of low droop device architectures. However, the presence of WWFs does not correlate strongly with external quantum efficiency nor defect densities measured via deep level optical spectroscopy (DLOS). Hence, performance losses in the heterostructures of interest are likely dominated by nanoscale point or interfacial defects rather than large-scale extended defects.« less

Disruption of crystalline structure of Sn3.5Ag induced by electric current

DOE Office of Scientific and Technical Information (OSTI.GOV)

Huang, Han-Chie; Lin, Kwang-Lung, E-mail: matkllin@mail.ncku.edu.tw; Wu, Albert T.

2016-03-21

This study presented the disruption of the Sn and Ag{sub 3}Sn lattice structures of Sn3.5Ag solder induced by electric current at 5–7 × 10{sup 3} A/cm{sup 2} with a high resolution transmission electron microscope investigation and electron diffraction analysis. The electric current stressing induced a high degree of strain on the alloy, as estimated from the X-ray diffraction (XRD) peak shift of the current stressed specimen. The XRD peak intensity of the Sn matrix and the Ag{sub 3}Sn intermetallic compound diminished to nearly undetectable after 2 h of current stressing. The electric current stressing gave rise to a high dislocation density ofmore » up to 10{sup 17}/m{sup 2}. The grain morphology of the Sn matrix became invisible after prolonged current stressing as a result of the coalescence of dislocations.« less

Analysis of Wien filter spectra from Hall thruster plumes.

PubMed

Huang, Wensheng; Shastry, Rohit

2015-07-01

A method for analyzing the Wien filter spectra obtained from the plumes of Hall thrusters is derived and presented. The new method extends upon prior work by deriving the integration equations for the current and species fractions. Wien filter spectra from the plume of the NASA-300M Hall thruster are analyzed with the presented method and the results are used to examine key trends. The new integration method is found to produce results slightly different from the traditional area-under-the-curve method. The use of different velocity distribution forms when performing curve-fits to the peaks in the spectra is compared. Additional comparison is made with the scenario where the current fractions are assumed to be proportional to the heights of peaks. The comparison suggests that the calculated current fractions are not sensitive to the choice of form as long as both the height and width of the peaks are accounted for. Conversely, forms that only account for the height of the peaks produce inaccurate results. Also presented are the equations for estimating the uncertainty associated with applying curve fits and charge-exchange corrections. These uncertainty equations can be used to plan the geometry of the experimental setup.

A homogeneous superconducting magnet design using a hybrid optimization algorithm

NASA Astrophysics Data System (ADS)

Ni, Zhipeng; Wang, Qiuliang; Liu, Feng; Yan, Luguang

2013-12-01

This paper employs a hybrid optimization algorithm with a combination of linear programming (LP) and nonlinear programming (NLP) to design the highly homogeneous superconducting magnets for magnetic resonance imaging (MRI). The whole work is divided into two stages. The first LP stage provides a global optimal current map with several non-zero current clusters, and the mathematical model for the LP was updated by taking into account the maximum axial and radial magnetic field strength limitations. In the second NLP stage, the non-zero current clusters were discretized into practical solenoids. The superconducting conductor consumption was set as the objective function both in the LP and NLP stages to minimize the construction cost. In addition, the peak-peak homogeneity over the volume of imaging (VOI), the scope of 5 Gauss fringe field, and maximum magnetic field strength within superconducting coils were set as constraints. The detailed design process for a dedicated 3.0 T animal MRI scanner was presented. The homogeneous magnet produces a magnetic field quality of 6.0 ppm peak-peak homogeneity over a 16 cm by 18 cm elliptical VOI, and the 5 Gauss fringe field was limited within a 1.5 m by 2.0 m elliptical region.

Rapidly Evolving Transients in the Dark Energy Survey

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pursiainen, M.; et al.

We present the results of a search for rapidly evolving transients in the Dark Energy Survey Supernova Programme. These events are characterized by fast light curve evolution (rise to peak inmore » $$\\lesssim 10$$ d and exponential decline in $$\\lesssim30$$ d after peak). We discovered 72 events, including 37 transients with a spectroscopic redshift from host galaxy spectral features. The 37 events increase the total number of rapid optical transients by more than factor of two. They are found at a wide range of redshifts ($0.05M_\\mathrm{g}>-22.25$$). The multiband photometry is well fit by a blackbody up to few weeks after peak. The events appear to be hot ($$T\\approx10000-30000$$ K) and large ($$R\\approx 10^{14}-2\\cdot10^{15}$$ cm) at peak, and generally expand and cool in time, though some events show evidence for a receding photosphere with roughly constant temperature. Spectra taken around peak are dominated by a blue featureless continuum consistent with hot, optically thick ejecta. We compare our events with a previously suggested physical scenario involving shock breakout in an optically thick wind surrounding a core-collapse supernova (CCSNe), we conclude that current models for such a scenario might need an additional power source to describe the exponential decline. We find these transients tend to favor star-forming host galaxies, which could be consistent with a core-collapse origin. However, more detailed modeling of the light curves is necessary to determine their physical origin.« less

Eddy response to variable atmospheric forcing in the Southern Ocean

NASA Astrophysics Data System (ADS)

Ward, M. L.; McC. Hogg, A.

2009-04-01

Satellite altimeter data of the Southern Ocean (SO) reveal an anomalous peak in eddy kinetic energy (EKE) in the Antarctic Circumpolar Current (ACC) in 2000-2002. This peak has been attributed to a delayed response to an earlier peak in the Southern Annular Mode (SAM) and its associated circumpolar eastward winds that occurred around 1998, where the delay is due to the formation and adjustment of the eddy field associated with the increased winds (Meredith & Hogg, 2006). A more recent analysis reveals that the EKE response varies regionally, with the strongest response in the Pacific, and it has been suggested that this variability is due to the additional influence of ENSO. The 2000-2002 peak in EKE is therefore attributed to the coincident peak in SAM and ENSO 2-3 years earlier, and that the EKE response was weaker in past years when modes were out of phase (Morrow & Pasquet, 2008). We investigate this issue by applying SAM-like and ENSO-like wind forcings to Q-GCM, the eddy-resolving model used in Meredith & Hogg and configured for the Southern Ocean. We analyze the EKE response to each individual forcing as well as a simultaneous forcing of the two, both in and out of phase. From these results, we are able to quantify both the global and regional response to each forcing, and the degree to which each mode is responsible for the EKE strength and distribution across the ACC.

Footprint Reduction for the Acoustic Electric Feedthrough Technique

DTIC Science & Technology

2010-03-01

input current measured using a 1 Ω sense resistor . Modulation depth of the peak- to-peak input current was 2Δ ~ 20...behaviour of an AEF arrangement formed using piezo -ceramic disks with diameter 38 mm and thickness 2 mm, across an aluminium plate with thickness 1.6 to 5...the 38 mm diameter piezo -ceramic disks. In an attempt to resolve this matter, the DSTO has examined an AEF system formed using disks with 10 mm

Reflex effects on components of synchronized renal sympathetic nerve activity.

PubMed

DiBona, G F; Jones, S Y

1998-09-01

The effects of peripheral thermal receptor stimulation (tail in hot water, n = 8, anesthetized) and cardiac baroreceptor stimulation (volume loading, n = 8, conscious) on components of synchronized renal sympathetic nerve activity (RSNA) were examined in rats. The peak height and peak frequency of synchronized RSNA were determined. The renal sympathoexcitatory response to peripheral thermal receptor stimulation was associated with an increase in the peak height. The renal sympathoinhibitory response to cardiac baroreceptor stimulation was associated with a decrease in the peak height. Although heart rate was significantly increased with peripheral thermal receptor stimulation and significantly decreased with cardiac baroreceptor stimulation, peak frequency was unchanged. As peak height reflects the number of active fibers, reflex increases and decreases in synchronized RSNA are mediated by parallel increases and decreases in the number of active renal nerve fibers rather than changes in the centrally based rhythm or peak frequency. The increase in the number of active renal nerve fibers produced by peripheral thermal receptor stimulation reflects the engagement of a unique group of silent renal sympathetic nerve fibers with a characteristic response pattern to stimulation of arterial baroreceptors, peripheral and central chemoreceptors, and peripheral thermal receptors.

Ranolazine inhibits shear sensitivity of endogenous Na+ current and spontaneous action potentials in HL-1 cells

PubMed Central

Strege, Peter; Beyder, Arthur; Bernard, Cheryl; Crespo-Diaz, Ruben; Behfar, Atta; Terzic, Andre; Ackerman, Michael; Farrugia, Gianrico

2012-01-01

NaV1.5 is a mechanosensitive voltage-gated Na+ channel encoded by the gene SCN5A, expressed in cardiac myocytes and required for phase 0 of the cardiac action potential (AP). In the cardiomyocyte, ranolazine inhibits depolarizing Na+ current and delayed rectifier (IKr) currents. Recently, ranolazine was also shown to be an inhibitor of NaV1.5 mechanosensitivity. Stretch also accelerates the firing frequency of the SA node, and fluid shear stress increases the beating rate of cultured cardiomyocytes in vitro. However, no cultured cell platform exists currently for examination of spontaneous electrical activity in response to mechanical stimulation. In the present study, flow of solution over atrial myocyte-derived HL-1 cultured cells was used to study shear stress mechanosensitivity of Na+ current and spontaneous, endogenous rhythmic action potentials. In voltage-clamped HL-1 cells, bath flow increased peak Na+ current by 14 ± 5%. In current-clamped cells, bath flow increased the frequency and decay rate of AP by 27 ± 12% and 18 ± 4%, respectively. Ranolazine blocked both responses to shear stress. This study suggests that cultured HL-1 cells are a viable in vitro model for detailed study of the effects of mechanical stimulation on spontaneous cardiac action potentials. Inhibition of the frequency and decay rate of action potentials in HL-1 cells are potential mechanisms behind the antiarrhythmic effect of ranolazine. PMID:23018927

Generation and Characterization of Electron Bunches with Ramped Current Profiles in a Dual-Frequency Superconducting Linear Accelerator

DOE PAGES

Piot, P.; Behrens, C.; Gerth, C.; ...

2011-09-07

We report on the successful experimental generation of electron bunches with ramped current profiles. The technique relies on impressing nonlinear correlations in the longitudinal phase space using a superconducing radiofrequency linear accelerator operating at two frequencies and a current-enhancing dispersive section. The produced {approx} 700-MeV bunches have peak currents of the order of a kilo-Ampere. Data taken for various accelerator settings demonstrate the versatility of the method and in particular its ability to produce current profiles that have a quasi-linear dependency on the longitudinal (temporal) coordinate. The measured bunch parameters are shown, via numerical simulations, to produce gigavolt-per-meter peak acceleratingmore » electric fields with transformer ratios larger than 2 in dielectric-lined waveguides.« less

Generation and characterization of electron bunches with ramped current profiles in a dual-frequency superconducting linear accelerator.

PubMed

Piot, P; Behrens, C; Gerth, C; Dohlus, M; Lemery, F; Mihalcea, D; Stoltz, P; Vogt, M

2012-01-20

We report on the successful experimental generation of electron bunches with ramped current profiles. The technique relies on impressing nonlinear correlations in the longitudinal phase space using a superconducing radio frequency linear accelerator operating at two frequencies and a current-enhancing dispersive section. The produced ~700-MeV bunches have peak currents of the order of a kilo-Ampère. Data taken for various accelerator settings demonstrate the versatility of the method and, in particular, its ability to produce current profiles that have a quasilinear dependency on the longitudinal (temporal) coordinate. The measured bunch parameters are shown, via numerical simulations, to produce gigavolt-per-meter peak accelerating electric fields with transformer ratios larger than 2 in dielectric-lined waveguides. © 2012 American Physical Society

Fast-scale non-linear distortion analysis of peak-current-controlled buck-boost inverters

NASA Astrophysics Data System (ADS)

Zhang, Hao; Dong, Shuai; Yi, Chuanzhi; Guan, Weimin

2018-02-01

This paper deals with fast-scale non-linear distortion behaviours including asymmetrical period-doubling bifurcation and zero-crossing distortion in peak-current-controlled buck-boost inverters. The underlying mechanisms of the fast-scale non-linear distortion behaviours in inverters are revealed. The folded bifurcation diagram is presented to analyse the asymmetrical phenomenon of fast-scale period-doubling bifurcation. In view of the effect of phase shift and current ripple, the analytical expressions for one pair of critical phase angles are derived by using the design-oriented geometrical current approach. It is shown that the phase shift between inductor current and capacitor voltage should be responsible for the zero-crossing distortion phenomenon. These results obtained here are useful to optimise the circuit design and improve the circuit performance.

The relationship between leg preference and knee mechanics during sidestepping in collegiate female footballers.

PubMed

Brown, Scott R; Wang, Henry; Dickin, D Clark; Weiss, Kaitlyn J

2014-11-01

This study examined the relationship between leg preference and knee mechanics in females during sidestepping. Three-dimensional data were recorded on 16 female collegiate footballers during a planned 45° sidestep manoeuvre with their preferred and non-preferred kicking leg. Knee kinematics and kinetics during initial contact, weight acceptance, peak push-off, and final push-off phases of sidestepping were analysed in both legs. The preferred leg showed trivial to small increases (ES = 0.19-0.36) in knee flexion angle at initial contact, weight acceptance, and peak push-off, and small increases (ES = 0.21-0.34) in peak power production and peak knee extension velocity. The non-preferred leg showed a trivial increase (ES = 0.10) in knee abduction angle during weight acceptance; small to moderate increases (ES = 0.22-0.64) in knee internal rotation angle at weight acceptance, peak push-off, and final push-off; a small increase (ES = 0.22) in knee abductor moment; and trivial increases (ES = 0.09-0.14) in peak power absorption and peak knee flexion velocity. The results of this study show that differences do exist between the preferred and non-preferred leg in females. The findings of this study will increase the knowledge base of anterior cruciate ligament injury in females and can aid in the design of more appropriate neuromuscular, plyometric, and strength training protocols for injury prevention.

A modular computational framework for automated peak extraction from ion mobility spectra

PubMed Central

2014-01-01

Background An ion mobility (IM) spectrometer coupled with a multi-capillary column (MCC) measures volatile organic compounds (VOCs) in the air or in exhaled breath. This technique is utilized in several biotechnological and medical applications. Each peak in an MCC/IM measurement represents a certain compound, which may be known or unknown. For clustering and classification of measurements, the raw data matrix must be reduced to a set of peaks. Each peak is described by its coordinates (retention time in the MCC and reduced inverse ion mobility) and shape (signal intensity, further shape parameters). This fundamental step is referred to as peak extraction. It is the basis for identifying discriminating peaks, and hence putative biomarkers, between two classes of measurements, such as a healthy control group and a group of patients with a confirmed disease. Current state-of-the-art peak extraction methods require human interaction, such as hand-picking approximate peak locations, assisted by a visualization of the data matrix. In a high-throughput context, however, it is preferable to have robust methods for fully automated peak extraction. Results We introduce PEAX, a modular framework for automated peak extraction. The framework consists of several steps in a pipeline architecture. Each step performs a specific sub-task and can be instantiated by different methods implemented as modules. We provide open-source software for the framework and several modules for each step. Additionally, an interface that allows easy extension by a new module is provided. Combining the modules in all reasonable ways leads to a large number of peak extraction methods. We evaluate all combinations using intrinsic error measures and by comparing the resulting peak sets with an expert-picked one. Conclusions Our software PEAX is able to automatically extract peaks from MCC/IM measurements within a few seconds. The automatically obtained results keep up with the results provided by current state-of-the-art peak extraction methods. This opens a high-throughput context for the MCC/IM application field. Our software is available at http://www.rahmannlab.de/research/ims. PMID:24450533

A modular computational framework for automated peak extraction from ion mobility spectra.

PubMed

D'Addario, Marianna; Kopczynski, Dominik; Baumbach, Jörg Ingo; Rahmann, Sven

2014-01-22

An ion mobility (IM) spectrometer coupled with a multi-capillary column (MCC) measures volatile organic compounds (VOCs) in the air or in exhaled breath. This technique is utilized in several biotechnological and medical applications. Each peak in an MCC/IM measurement represents a certain compound, which may be known or unknown. For clustering and classification of measurements, the raw data matrix must be reduced to a set of peaks. Each peak is described by its coordinates (retention time in the MCC and reduced inverse ion mobility) and shape (signal intensity, further shape parameters). This fundamental step is referred to as peak extraction. It is the basis for identifying discriminating peaks, and hence putative biomarkers, between two classes of measurements, such as a healthy control group and a group of patients with a confirmed disease. Current state-of-the-art peak extraction methods require human interaction, such as hand-picking approximate peak locations, assisted by a visualization of the data matrix. In a high-throughput context, however, it is preferable to have robust methods for fully automated peak extraction. We introduce PEAX, a modular framework for automated peak extraction. The framework consists of several steps in a pipeline architecture. Each step performs a specific sub-task and can be instantiated by different methods implemented as modules. We provide open-source software for the framework and several modules for each step. Additionally, an interface that allows easy extension by a new module is provided. Combining the modules in all reasonable ways leads to a large number of peak extraction methods. We evaluate all combinations using intrinsic error measures and by comparing the resulting peak sets with an expert-picked one. Our software PEAX is able to automatically extract peaks from MCC/IM measurements within a few seconds. The automatically obtained results keep up with the results provided by current state-of-the-art peak extraction methods. This opens a high-throughput context for the MCC/IM application field. Our software is available at http://www.rahmannlab.de/research/ims.

Responses to GABA(A) receptor activation are altered in NTS neurons isolated from chronic hypoxic rats.

PubMed

Tolstykh, Gleb; Belugin, Sergei; Mifflin, Steve

2004-04-23

The inhibitory amino acid GABA is released within the nucleus of the solitary tract (NTS) during hypoxia and modulates the respiratory response to hypoxia. To determine if responses of NTS neurons to activation of GABA(A) receptors are altered following exposure to chronic hypoxia, GABA(A) receptor-evoked whole cell currents were measured in enzymatically dispersed NTS neurons from normoxic and chronic hypoxic rats. Chronic hypoxic rats were exposed to 10% O(2) for 9-12 days. Membrane capacitance was the same in neurons from normoxic (6.9+/-0.5 pF, n=16) and hypoxic (6.3+/-0.5 pF, n=15) rats. The EC(50) for peak GABA-evoked current density was significantly greater in neurons from hypoxic (21.7+/-2.2 microM) compared to normoxic rats (12.2+/-0.9 microM) (p<0.001). Peak and 5-s adapted GABA currents evoked by 1, 3 and 10 microM were greater in neurons from normoxic compared to hypoxic rats (p<0.05) whereas peak and 5-s adapted responses to 30 and 100 microM GABA were not different comparing normoxic to hypoxic rats. Desensitization of GABA(A)-evoked currents was observed at concentrations greater than 3 microM and, measured as the ratio of the current 5 s after the onset of 100 microM GABA application to the peak GABA current, was the same in neurons from normoxic (0.37+/-0.03) and hypoxic rats (0.33+/-0.04). Reduced sensitivity to GABA(A) receptor-evoked inhibition in chronic hypoxia could influence chemoreceptor afferent integration by NTS neurons.

Protocols for sagebrush seed processing and seedling production at the Lucky Peak Nursery

Treesearch

Clark D. Fleege

2010-01-01

This paper presents the production protocols currently practiced at the USDA Forest Service Lucky Peak Nursery (Boise, ID) for seed processing and bareroot and container seedling production for three subspecies of big sagebrush (Artemisia tridentata).

Experimental investigation of the 100 keV X-ray dose response of the high-temperature thermoluminescence in LiF:Mg,Ti (TLD-100): theoretical interpretation using the unified interaction model.

PubMed

Livingstone, J; Horowitz, Y S; Oster, L; Datz, H; Lerch, M; Rosenfeld, A; Horowitz, A

2010-03-01

The dose response of LiF:Mg,Ti (TLD-100) chips was measured from 1 to 50,000 Gy using 100 keV X rays at the European Synchroton Radiation Facility. Glow curves were deconvoluted into component glow peaks using a computerised glow curve deconvolution (CGCD) code based on first-order kinetics. The normalised dose response, f(D), of glow peaks 4 and 5 and 5b (the major components of composite peak 5), as well as peaks 7 and 8 (two of the major components of the high-temperature thermoluminescence (HTTL) at high levels of dose) was separately determined and theoretically interpreted using the unified interaction model (UNIM). The UNIM is a nine-parameter model encompassing both the irradiation/absorption stage and the thermally induced relaxation/recombination stage with an admixture of both localised and delocalised recombination mechanisms. The effects of radiation damage are included in the present modelling via the exponential removal of luminescent centres (LCs) at high dose levels. The main features of the experimentally measured dose response are: (i) increase in f(D)(max) with glow peak temperature, (ii) increase in D(max) (the dose level at which f(D)(max) occurs) with increasing glow peak temperature, and (iii) decreased effects of radiation damage with increasing glow peak temperature. The UNIM interpretation of this behaviour requires both strongly decreasing values of ks (the relative contribution of localised recombination) as a function of glow peak temperature and, as well, significantly different values of the dose-filling constants of the trapping centre (TC) and LC for peaks 7 and 8 than those used for peaks 4 and 5. This suggests that different TC/LC configurations are responsible for HTTL. The relative intensity of peak 5a (a low-temperature satellite of peak 5 arising from localised recombination) was found to significantly increase at higher dose levels due to preferential electron and hole population of the trapping/recombination complex giving rise to composite glow peak 5. It is also demonstrated that possible changes in the trapping cross section of the LC and the competitive centres due to increasing sample/glow peak temperature do not significantly influence these observations/conclusions.

Effect of cobalt doping level of ferrites in enhancing sensitivity of analytical performances of carbon paste electrode for simultaneous determination of catechol and hydroquinone.

PubMed

Lakić, Mladen; Vukadinović, Aleksandar; Kalcher, Kurt; Nikolić, Aleksandar S; Stanković, Dalibor M

2016-12-01

This work presents the simultaneous determination of catechol (CC) and hydroquinone (HQ), employing a modified carbon paste electrode (CPE) with ferrite nanomaterial. Ferrite nanomaterial was doped with different amount of cobalt and this was investigated toward simultaneous oxidation of CC and HQ. It was shown that this modification strongly increases electrochemical characteristics of the CPE. Also, electrocatalytic activity of such materials strongly depends on the level of substituted Co in the ferrite nanoparticles. The modified electrodes, labeled as CoFerrite/CPE, showed two pairs of well-defined redox peaks for the electrochemical processes of catechol and hydroquinone. Involving of ferrite material in the structure of CPE, cause increase in the potentials differences between redox couples of the investigated compounds, accompanied with increases in peaks currents. Several important parameters were optimized and calibration curves, with limits of detection (LOD) of 0.15 and 0.3µM for catechol and hydroquinone, respectively, were constructed by employing amperometric detection. Effect of possible interfering compounds was also studied, and proposed method was successfully applied for CC and HQ quantification in real samples. Copyright © 2016 Elsevier B.V. All rights reserved.

Bipolar square-wave current source for transient electromagnetic systems based on constant shutdown time

NASA Astrophysics Data System (ADS)

Wang, Shilong; Yin, Changchun; Lin, Jun; Yang, Yu; Hu, Xueyan

2016-03-01

Cooperative work of multiple magnetic transmitting sources is a new trend in the development of transient electromagnetic system. The key is the bipolar current waves shutdown, concurrently in the inductive load. In the past, it was difficult to use the constant clamping voltage technique to realize the synchronized shutdown of currents with different peak values. Based on clamping voltage technique, we introduce a new controlling method with constant shutdown time. We use the rising time to control shutdown time and use low voltage power source to control peak current. From the viewpoint of the circuit energy loss, by taking the high-voltage capacitor bypass resistance and the capacitor of the passive snubber circuit into account, we establish the relationship between the rising time and the shutdown time. Since the switch is not ideal, we propose a new method to test the shutdown time by the low voltage, the high voltage and the peak current. Experimental results show that adjustment of the current rising time can precisely control the value of the clamp voltage. When the rising time is fixed, the shutdown time is unchanged. The error for shutdown time deduced from the energy consumption is less than 6%. The new controlling method on current shutdown proposed in this paper can be used in the cooperative work of borehole and ground transmitting system.

Bipolar square-wave current source for transient electromagnetic systems based on constant shutdown time.

PubMed

Wang, Shilong; Yin, Changchun; Lin, Jun; Yang, Yu; Hu, Xueyan

2016-03-01

Cooperative work of multiple magnetic transmitting sources is a new trend in the development of transient electromagnetic system. The key is the bipolar current waves shutdown, concurrently in the inductive load. In the past, it was difficult to use the constant clamping voltage technique to realize the synchronized shutdown of currents with different peak values. Based on clamping voltage technique, we introduce a new controlling method with constant shutdown time. We use the rising time to control shutdown time and use low voltage power source to control peak current. From the viewpoint of the circuit energy loss, by taking the high-voltage capacitor bypass resistance and the capacitor of the passive snubber circuit into account, we establish the relationship between the rising time and the shutdown time. Since the switch is not ideal, we propose a new method to test the shutdown time by the low voltage, the high voltage and the peak current. Experimental results show that adjustment of the current rising time can precisely control the value of the clamp voltage. When the rising time is fixed, the shutdown time is unchanged. The error for shutdown time deduced from the energy consumption is less than 6%. The new controlling method on current shutdown proposed in this paper can be used in the cooperative work of borehole and ground transmitting system.

Approximation of wave action flux velocity in strongly sheared mean flows

NASA Astrophysics Data System (ADS)

Banihashemi, Saeideh; Kirby, James T.; Dong, Zhifei

2017-08-01

Spectral wave models based on the wave action equation typically use a theoretical framework based on depth uniform current to account for current effects on waves. In the real world, however, currents often have variations over depth. Several recent studies have made use of a depth-weighted current U˜ due to [Skop, R. A., 1987. Approximate dispersion relation for wave-current interactions. J. Waterway, Port, Coastal, and Ocean Eng. 113, 187-195.] or [Kirby, J. T., Chen, T., 1989. Surface waves on vertically sheared flows: approximate dispersion relations. J. Geophys. Res. 94, 1013-1027.] in order to account for the effect of vertical current shear. Use of the depth-weighted velocity, which is a function of wavenumber (or frequency and direction) has been further simplified in recent applications by only utilizing a weighted current based on the spectral peak wavenumber. These applications do not typically take into account the dependence of U˜ on wave number k, as well as erroneously identifying U˜ as the proper choice for current velocity in the wave action equation. Here, we derive a corrected expression for the current component of the group velocity. We demonstrate its consistency using analytic results for a current with constant vorticity, and numerical results for a measured, strongly-sheared current profile obtained in the Columbia River. The effect of choosing a single value for current velocity based on the peak wave frequency is examined, and we suggest an alternate strategy, involving a Taylor series expansion about the peak frequency, which should significantly extend the range of accuracy of current estimates available to the wave model with minimal additional programming and data transfer.

Thermoluminescence solid-state nanodosimetry—the peak 5A/5 dosemeter

PubMed Central

Fuks, E.; Horowitz, Y. S.; Horowitz, A.; Oster, L.; Marino, S.; Rainer, M.; Rosenfeld, A.; Datz, H.

2011-01-01

The shape of composite peak 5 in the glow curve of LiF:Mg,Ti (TLD-100) following 90Sr/90Y beta irradiation, previously demonstrated to be dependent on the cooling rate used in the 400°C pre-irradiation anneal, is shown to be dependent on ionisation density in both naturally cooled and slow-cooled samples. Following heavy-charged particle high-ionisation density (HID) irradiation, the temperature of composite peak 5 decreases by ∼5°C and the peak becomes broader. This behaviour is attributed to an increase in the relative intensity of peak 5a (a low-temperature satellite of peak 5). The relative intensity of peak 5a is estimated using a computerised glow curve deconvolution code based on first-order kinetics. The analysis uses kinetic parameters for peaks 4 and 5 determined from ancillary measurements resulting in nearly ‘single-glow peak’ curves for both the peaks. In the slow-cooled samples, owing to the increased relative intensity of peak 5a compared with the naturally cooled samples, the precision of the measurement of the 5a/5 intensity ratio is found to be ∼15 % (1 SD) compared with ∼25 % for the naturally cooled samples. The ratio of peak 5a/5 in the slow-cooled samples is found to increase systematically and gradually through a variety of radiation fields from a minimum value of 0.13±0.02 for 90Sr/90Y low-ionisation density irradiations to a maximum value of ∼0.8 for 20 MeV Cu and I ion HID irradiations. Irradiation by low-energy electrons of energy 0.1–1.5 keV results in values between 1.27 and 0.95, respectively. The increasing values of the ratio of peak 5a/5 with increasing ionisation density demonstrate the viability of the concept of the peak 5a/5 nanodosemeter and its potential in the measurement of average ionisation density in a ‘nanoscopic’ mass containing the trapping centre/luminescent centre spatially correlated molecule giving rise to composite peak 5. PMID:21149323

Alcohols potentiate the function of 5-HT3 receptor–channels on NCB-20 neuroblastoma cells by favouring and stabilizing the open channel state

PubMed Central

Zhou, Qing; Verdoorn, Todd A; Lovinger, David M

1998-01-01

5-HT3 receptor-mediated ion current was recorded from NCB-20 neuroblastoma cells using the whole-cell patch-clamp technique. Rapid drug superfusion was used to study the mechanism of alcohol potentiation of 5-HT3 receptor function and to analyse effects of alcohols on receptor-channel kinetics in detail.Trichloroethanol (TCEt) increased in a dose-dependent way the initial slope, 20–80 % rise time and measured desensitization rate of the current induced by low concentrations (1–2 μm) of 5-HT. Ethanol (EtOH) and butanol (ButOH) had similar effects on the 5-HT3 receptor-induced current.TCEt and ButOH decreased the measured desensitization rate of current induced by 10 μm 5-HT, a maximally effective concentration of agonist. These alcohols also increased the relative amplitude of steady state to peak current induced by 2 or 10 μm 5-HT, indicating a possible decrease in the intrinsic rate of desensitization.TCEt also decreased the deactivation rate of the current activated by 2 μm 5-HT after a short pulse of agonist application.Current sweeps generated by 1 μm 5-HT in the presence or absence of 10 mm TCEt or 100 mm EtOH were well fitted using a modified standard kinetic model derived from the nicotinic acetylcholine receptor. This analysis indicated that potentiation by alcohols could be accounted for by increases in the association rate constant coupled with decreases in the dissociation and desensitization rate constants.This study suggests that alcohols potentiate 5-HT3 receptor-mediated current by both increasing the rate of channel activation and stabilizing the open state by decreasing the rates of channel deactivation and desensitization. PMID:9518697

MMS, Van Allen Probes, and Ground-based Magnetometer Observations of a Compression-induced EMIC Wave Event

NASA Astrophysics Data System (ADS)

Capman, N.; Engebretson, M.; Posch, J. L.; Cattell, C. A.; Tian, S.; Wygant, J. R.; Kletzing, C.; Lessard, M.; Anderson, B. J.; Russell, C. T.; Reeves, G. D.; Fuselier, S. A.

2016-12-01

A 0.5-1.0 Hz electromagnetic ion cyclotron (EMIC) wave event was observed on December 14, 2015 from 13:26 to 13:28 UT at the four MMS satellites (L= 9.5, MLT= 13.0, MLAT= -24.4, peak amplitude 7 nT), and both Van Allen probes (RBSP-A: L= 5.7, MLT= 12.8, MLAT= 19.5, peak amplitude 5 nT; RBSP-B: L= 4.3, MLT= 14.2, MLAT= 11.3, peak amplitude 1 nT). On the ground, it was observed by search coil magnetometers at Halley Bay and South Pole, Antarctica, and Sondrestromfjord, Greenland, and by fluxgate magnetometers of the MACCS array at Pangnirtung and Cape Dorset in Arctic Canada. This event was preceded by a small increase of the solar wind pressure of 3 nPa from 13:10 to 13:20 UT. The proton distributions at Van Allen probe A confirm that the compression increased the pitch angle anisotropy in 10 keV ring current protons. The wave forms were very similar at the four MMS spacecraft indicating that the coherence-scale of the wave packets is larger than the inter-spacecraft separations of 20 km at the time. Inter-comparison of the wave signals at the four MMS spacecraft are used to assess the characteristics of the waves and estimate their spatial scales transverse and parallel to the background magnetic field.

Electricity demand and storage dispatch modeling for buildings and implications for the smartgrid

NASA Astrophysics Data System (ADS)

Zheng, Menglian; Meinrenken, Christoph

2013-04-01

As an enabler for demand response (DR), electricity storage in buildings has the potential to lower costs and carbon footprint of grid electricity while simultaneously mitigating grid strain and increasing its flexibility to integrate renewables (central or distributed). We present a stochastic model to simulate minute-by-minute electricity demand of buildings and analyze the resulting electricity costs under actual, currently available DR-enabling tariffs in New York State, namely a peak/offpeak tariff charging by consumed energy (monthly total kWh) and a time of use tariff charging by power demand (monthly peak kW). We then introduce a variety of electrical storage options (from flow batteries to flywheels) and determine how DR via temporary storage may increase the overall net present value (NPV) for consumers (comparing the reduced cost of electricity to capital and maintenance costs of the storage). We find that, under the total-energy tariff, only medium-term storage options such as batteries offer positive NPV, and only at the low end of storage costs (optimistic scenario). Under the peak-demand tariff, however, even short-term storage such as flywheels and superconducting magnetic energy offer positive NPV. Therefore, these offer significant economic incentive to enable DR without affecting the consumption habits of buildings' residents. We discuss implications for smartgrid communication and our future work on real-time price tariffs.

Efficiency enhancement of semitransparent organic solar cells by using printed dielectric mirrors (Presentation Recording)

NASA Astrophysics Data System (ADS)

Bronnbauer, Carina; Forberich, Karen K.; Guo, Fei; Gasparini, Nicola; Brabec, Christoph J.

2015-09-01

Building integrated thin film solar cells are a strategy for future eco-friendly power generation. Such solar cells have to be semi-transparent, long-term stable and show the potential to be fabricated by a low-cost production process. Organic photovoltaics are a potential candidate because an absorber material with its main absorption in the infrared spectral region where the human eye is not sensitive can be chosen. We can increase the number of absorbed photons, at the same time, keep the transparency almost constant by using a dielectric, wavelength-selective mirror. The mirror reflects only in the absorption regime of the active layer material and shows high transparencies in the spectral region around 550 nm where the human eye is most sensitive. We doctor bladed a fully solution processed dielectric mirror at low temperatures below 80 °C. Both inks, which are printed alternatingly are based on nanoparticles and have a refractive index of 1.29 or 1.98, respectively, at 500 nm. The position and the intensity of the main reflection peak can be easily shifted and thus adjusted to the solar cell absorption spectrum. Eventually, the dielectric mirror was combined with different organic solar cells. For instance, the current increases by 20.6 % while the transparency decreases by 23.7 % for the low band gap absorber DPP and silver nanowires as top electrode. Moreover we proved via experiment and optical simulations, that a variation of the active layer thickness and the position of the main reflection peak affect the transparency and the increase in current.

Lvad pump speed increase is associated with increased peak exercise cardiac output and vo2, postponed anaerobic threshold and improved ventilatory efficiency.

PubMed

Vignati, Carlo; Apostolo, Anna; Cattadori, Gaia; Farina, Stefania; Del Torto, Alberico; Scuri, Silvia; Gerosa, Gino; Bottio, Tomaso; Tarzia, Vincenzo; Bejko, Jonida; Sisillo, Erminio; Nicoli, Flavia; Sciomer, Susanna; Alamanni, Francesco; Paolillo, Stefania; Agostoni, Piergiuseppe

2017-03-01

Peak exercise cardiac output (CO) increase is associated with an increase of peak oxygen uptake (VO 2 ), provided that arteriovenous O 2 difference [Δ(Ca-Cv)O 2 ] does not decrease. At anaerobic threshold, VO 2 , is related to CO. We tested the hypothesis that, in heart failure (HF) patients with left ventricular assistance device (LVAD), an acute increase of CO obtained through changes in LVAD pump speed is associated with peak exercise and anaerobic threshold VO 2 increase. Fifteen of 20 patients bearing LVAD (Jarvik 2000) enrolled in the study successfully performed peak exercise evaluation. All patients had severe HF as shown by clinical evaluation, laboratory tests, echocardiography, spirometry with alveolar-capillary diffusion, and maximal cardiopulmonary exercise testing (CPET). CPETs with non-invasive CO measurements at rest and peak exercise were done on 2days at LVAD pump speed set randomly at 2 and 4. Increasing LVAD pump speed from 2 to 4 increased CO from 3.4±0.9 to 3.8±1.0L/min (ΔCO 0.4±0.6L/min, p=0.04) and from 5.3±1.3 to 5.9±1.4L/min (ΔCO 0.6±0.7L/min, p<0.01) at rest and peak exercise, respectively. Similarly, VO 2 increased from 788±169 to 841±152mL/min (ΔVO 2 52±76mL/min, p=0.01) and from 568±116 to 619±124mL/min (ΔVO 2 69±96mL/min, p=0.02) at peak exercise and at anaerobic threshold, respectively. Δ(Ca-Cv)O 2 did not change significantly, while ventilatory efficiency improved (VE/VCO 2 slope from 39.9±5.4 to 34.9±8.3, ΔVE/VCO 2 -5.0±6.4, p<0.01). In HF, an increase in CO with a higher LVAD pump speed is associated with increased peak VO 2 , postponed anaerobic threshold, and improved ventilatory efficiency. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

High Voltage, Low Inductance Hydrogen Thyratron Study Program.

DTIC Science & Technology

1981-01-01

E-E Electrode Spacing Ef Cathode Heater Voltage egy Peak Forward Grid Voltage epy Peak Forward Anode Voltage epx Peak Inverse Anode Voltage Eres... electrodes . ........... 68 30 Marx generator used for sample testing. ........... 68 31 Waveforms showing sample holdoff and sample breakdown 73 32...capability (a function of gas pressure and electrode spacing) could be related to its current rise time capability (a function of gas pressure and inductance

Design of Advanced Blading for a High-Speed HP Compressor Using an S1-S2 Flow Calculation System.

DTIC Science & Technology

1990-11-01

Howell multistage compressor speed squared) and pressure ratio for the initial prediction method (7), with an arbitrary increase of design are given in...improved performance of axial compressors with leading designs to be produced with the current SI-S2 edge normal shock waves, system. However, it is...performance of the new (7) Howell A R and Calvert W J, A new stage- design was extremely encouraging, with a peak stacking technique for axial -flow

Impact of mountain pine beetle outbreaks on forest albedo and radiative forcing, as derived from Moderate Resolution Imaging Spectroradiometer, Rocky Mountains, USA

NASA Astrophysics Data System (ADS)

Vanderhoof, M.; Williams, C. A.; Ghimire, B.; Rogan, J.

2013-12-01

pine beetle (Dendroctonus ponderosae) outbreaks in North America are widespread and have potentially large-scale impacts on albedo and associated radiative forcing. Mountain pine beetle outbreaks in Colorado and southern Wyoming have resulted in persistent and significant increases in both winter albedo (change peaked 10 years post outbreak at 0.06 ± 0.01 and 0.05 ± 0.01, in lodgepole pine (Pinus contorta) and ponderosa pine (Pinus ponderosa) stands, respectively) and spring albedo (change peaked 10 years post outbreak at 0.06 ± 0.01 and 0.04 ± 0.01, in lodgepole pine and ponderosa pine stands, respectively). Instantaneous top-of-atmosphere radiative forcing peaked for both lodgepole pine and ponderosa pine stands in winter at 10 years post outbreak at -1.7 ± 0.2 W m-2 and -1.4 ± 0.2 W m-2, respectively. The persistent increase in albedo with time since mountain pine beetle disturbance combined with the continued progression of the attack across the landscape from 1994-2011 resulted in an exponential increase in winter and annual radiative cooling (MW) over time. In 2011 the rate of radiative forcing within the study area reached -982.7 ± 139.0 MW, -269.8 ± 38.2 MW, -31.1 ± 4.4 MW, and -147.8 ± 20.9 MW in winter, spring, summer, and fall, respectively. An increase in radiative cooling has the potential to decrease sensible and/or latent heat flux by reducing available energy. Such changes could affect current mountain pine beetle outbreaks which are influenced by climatic conditions.

Combined effects of projected sea level rise, storm surge, and peak river flows on water levels in the Skagit Floodplain

USGS Publications Warehouse

Hamman, Josheph J; Hamlet, Alan F.; Fuller, Roger; Grossman, Eric E.

2016-01-01

Current understanding of the combined effects of sea level rise (SLR), storm surge, and changes in river flooding on near-coastal environments is very limited. This project uses a suite of numerical models to examine the combined effects of projected future climate change on flooding in the Skagit floodplain and estuary. Statistically and dynamically downscaled global climate model scenarios from the ECHAM-5 GCM were used as the climate forcings. Unregulated daily river flows were simulated using the VIC hydrology model, and regulated river flows were simulated using the SkagitSim reservoir operations model. Daily tidal anomalies (TA) were calculated using a regression approach based on ENSO and atmospheric pressure forcing simulated by the WRF regional climate model. A 2-D hydrodynamic model was used to estimate water surface elevations in the Skagit floodplain using resampled hourly hydrographs keyed to regulated daily flood flows produced by the reservoir simulation model, and tide predictions adjusted for SLR and TA. Combining peak annual TA with projected sea level rise, the historical (1970–1999) 100-yr peak high water level is exceeded essentially every year by the 2050s. The combination of projected sea level rise and larger floods by the 2080s yields both increased flood inundation area (+ 74%), and increased average water depth (+ 25 cm) in the Skagit floodplain during a 100-year flood. Adding sea level rise to the historical FEMA 100-year flood resulted in a 35% increase in inundation area by the 2040's, compared to a 57% increase when both SLR and projected changes in river flow were combined.

Relation between aerobic capacity and walking ability in older adults with a lower-limb amputation.

PubMed

Wezenberg, Daphne; van der Woude, Lucas H; Faber, Willemijn X; de Haan, Arnold; Houdijk, Han

2013-09-01

To determine the relative aerobic load, walking speed, and walking economy of older adults with a lower-limb prosthesis, and to predict the effect of an increased aerobic capacity on their walking ability. Cross-sectional. Human motion laboratory at a rehabilitation center. Convenience sample of older adults (n=36) who underwent lower-limb amputation because of vascular deficiency or trauma and able-bodied controls (n=21). Not applicable. Peak aerobic capacity and oxygen consumption while walking were determined. The relative aerobic load and walking economy were assessed as a function of walking speed, and a data-based model was constructed to predict the effect of an increased aerobic capacity on walking ability. People with a vascular amputation walked at a substantially higher (45.2%) relative aerobic load than people with an amputation because of trauma. The preferred walking speed in both groups of amputees was slower than that of able-bodied controls and below their most economical walking speed. We predicted that a 10% increase in peak aerobic capacity could potentially result in a reduction in the relative aerobic load of 9.1%, an increase in walking speed of 17.3% and 13.9%, and an improvement in the walking economy of 6.8% and 2.9%, for people after a vascular or traumatic amputation, respectively. Current findings corroborate the notion that, especially in people with a vascular amputation, the peak aerobic capacity is an important determinant for walking ability. The data provide quantitative predictions on the effect of aerobic training; however, future research is needed to experimentally confirm these predictions. Copyright © 2013 American Congress of Rehabilitation Medicine. Published by Elsevier Inc. All rights reserved.

Observation of coherent diffractive charged current interactions of antineutrinos on neon nuclei

NASA Astrophysics Data System (ADS)

Marage, P.; Aderholz, M.; Armenise, N.; Azemoon, T.; Barnham, K. W. J.; Bartley, J. H.; Baton, J. P.; Bertrand, D.; Brisson, V.; Bullock, F. W.; Calicchio, M.; Cooper, A. M.; Chwastowski, J.; Clayton, E. F.; Coghen, T.; Erriquez, O.; Fitch, P. J.; Gerbier, G.; Guy, J.; Hulth, P. O.; Jones, G. T.; Kasper, P.; Kochowski, C.; Leighton-Davies, S.; Middleton, R. P.; Mobayyen, M. M.; Morrison, D. R. O.; Neveu, M.; Nuzzo, S.; O'Neale, S. W.; Parker, M. A.; Petiau, P.; Ruggieri, F.; Sacton, J.; Sansum, R. A.; Simopoulou, E.; Talebzadeh, M.; Vallee, C.; Varvell, K.; Vayaki, A.; Venus, W.; Wells, J.; Wernhard, K. L.; Wittek, W.; Zevgolatakos, E.; WA59 Collaboration

1984-05-01

First observation is reported of semi-inclusive coherent diffractive charged current interactions of antineutrinos on neon nuclei. A sharp peaking towards zero is observed in the | t| distribution of interactions for which the final state charge is 0 and from which only one negative hadron is emitted, unaccompanied by any evidence of nuclear fragmentation or reinteraction. This peak is correlated with high momentum of the outgoing charged hadron and with small values of Q2 and x.

Does Peak Urine Flow Rate Predict the Development of Incident Lower Urinary Tract Symptoms in Men with Mild to No Current Symptoms? Results from REDUCE.

PubMed

Simon, Ross M; Howard, Lauren E; Moreira, Daniel M; Roehrborn, Claus; Vidal, Adriana; Castro-Santamaria, Ramiro; Freedland, Stephen J

2017-09-01

We determined whether decreased peak urine flow is associated with future incident lower urinary tract symptoms in men with mild to no lower urinary tract symptoms. Our population consisted of 3,140 men from the REDUCE (Reduction by Dutasteride of Prostate Cancer Events) trial with mild to no lower urinary tract symptoms, defined as I-PSS (International Prostate Symptom Score) less than 8. REDUCE was a randomized trial of dutasteride vs placebo for prostate cancer prevention in men with elevated prostate specific antigen and negative biopsy. I-PSS measures were obtained every 6 months throughout the 4-year study. The association between peak urine flow rate and progression to incident lower urinary tract symptoms, defined as the first of medical treatment, surgery or sustained and clinically significant lower urinary tract symptoms, was tested by multivariable Cox models, adjusting for various baseline characteristics and treatment arm. On multivariable analysis as a continuous variable, decreased peak urine flow rate was significantly associated with an increased risk of incident lower urinary tract symptoms (p = 0.002). Results were similar in the dutasteride and placebo arms. On univariable analysis when peak flow was categorized as 15 or greater, 10 to 14.9 and less than 10 ml per second, flow rates of 10 to 14.9 and less than 10 ml per second were associated with a significantly increased risk of incident lower urinary tract symptoms (HR 1.39, p = 0.011 and 1.67, p <0.001, respectively). Results were similar on multivariable analysis, although in the 10 to 14.9 ml per second group findings were no longer statistically significant (HR 1.26, p = 0.071). In men with mild to no lower urinary tract symptoms a decreased peak urine flow rate is independently associated with incident lower urinary tract symptoms. If confirmed, these men should be followed closer for incident lower urinary tract symptoms. Copyright © 2017 American Urological Association Education and Research, Inc. Published by Elsevier Inc. All rights reserved.

Fructose intake at current levels in the United States may cause gastrointestinal distress in normal adults.

PubMed

Beyer, Peter L; Caviar, Elena M; McCallum, Richard W

2005-10-01

Fructose intake has increased considerably in the United States, primarily as a result of increased consumption of high-fructose corn syrup, fruits and juices, and crystalline fructose. The purpose was to determine how often fructose, in amounts commonly consumed, would result in malabsorption and/or symptoms in healthy persons. Fructose absorption was measured using 3-hour breath hydrogen tests and symptom scores were used to rate subjective responses for gas, borborygmus, abdominal pain, and loose stools. The study included 15 normal, free-living volunteers from a medical center community and was performed in a gastrointestinal specialty clinic. Subjects consumed 25- and 50-g doses of crystalline fructose with water after an overnight fast on separate test days. Mean peak breath hydrogen, time of peak, area under the curve (AUC) for breath hydrogen and gastrointestinal symptoms were measured during a 3-hour period after subjects consumed both 25- and 50-g doses of fructose. Differences in mean breath hydrogen, AUC, and symptom scores between doses were analyzed using paired t tests. Correlations among peak breath hydrogen, AUC, and symptoms were also evaluated. More than half of the 15 adults tested showed evidence of fructose malabsorption after 25 g fructose and greater than two thirds showed malabsorption after 50 g fructose. AUC, representing overall breath hydrogen response, was significantly greater after the 50-g dose. Overall symptom scores were significantly greater than baseline after each dose, but scores were only marginally greater after 50 g than 25 g. Peak hydrogen levels and AUC were highly correlated, but neither was significantly related to symptoms. Fructose, in amounts commonly consumed, may result in mild gastrointestinal distress in normal people. Additional study is warranted to evaluate the response to fructose-glucose mixtures (as in high-fructose corn syrup) and fructose taken with food in both normal people and those with gastrointestinal dysfunction. Because breath hydrogen peaks occurred at 90 to 114 minutes and were highly correlated with 180-minute breath hydrogen AUC, the use of peak hydrogen measures may be considered to shorten the duration of the exam.