The Unprecedented Properties of the First Electromagnetic Counterpart to a Gravitational-wave Source

NASA Astrophysics Data System (ADS)

Siebert, M. R.; Foley, R. J.; Drout, M. R.; Kilpatrick, C. D.; Shappee, B. J.; Coulter, D. A.; Kasen, D.; Madore, B. F.; Murguia-Berthier, A.; Pan, Y.-C.; Piro, A. L.; Prochaska, J. X.; Ramirez-Ruiz, E.; Rest, A.; Contreras, C.; Morrell, N.; Rojas-Bravo, C.; Simon, J. D.

2017-10-01

We discovered Swope Supernova Survey 2017a (SSS17a) in the LIGO/Virgo Collaboration (LVC) localization volume of GW170817, the first detected binary neutron star (BNS) merger, only 10.9 hr after the trigger. No object was present at the location of SSS17a only a few days earlier, providing a qualitative spatial and temporal association with GW170817. Here, we quantify this association, finding that SSS17a is almost certainly the counterpart of GW170817, with the chance of a coincidence being ≤9× {10}-6 (90% confidence). We arrive at this conclusion by comparing the optical properties of SSS17a to other known astrophysical transients, finding that SSS17a fades and cools faster than any other observed transient. For instance, SSS17a fades >5 mag in g within 7 days of our first data point, while all other known transients of similar luminosity fade by <1 mag during the same time period. Its spectra are also unique, being mostly featureless, even as it cools. The rarity of “SSS17a-like” transients combined with the relatively small LVC localization volume and recent non-detection imply the extremely unlikely chance coincidence. We find that the volumetric rate of SSS17a-like transients is ≤1.6× {10}4 Gpc-3 yr-1 and the Milky Way rate is ≤slant 0.19 per century. A transient survey designed to discover similar events should be high cadence and observe in red filters. The LVC will likely detect substantially more BNS mergers than current optical surveys will independently discover SSS17a-like transients, however a 1 day cadence survey with the Large Synoptic Survey Telescope (LSST) could discover an order of magnitude more events.

Dual Transformer Model based on Standard Circuit Elements for the Study of Low- and Mid-frequency Transients

NASA Astrophysics Data System (ADS)

Jazebi, Saeed

This thesis is a step forward toward achieving the final objective of creating a fully dual model for transformers including eddy currents and nonlinearities of the iron core using the fundamental electrical components already available in the EMTP-type programs. The model is effective for the study of the performance of transformers during power system transients. This is very important for transformer designers, because the insulation of transformers is determined with the overvoltages caused by lightning or switching operations. There are also internally induced transients that occur when a switch is actuated. For example switching actions for reconfiguration of distribution systems that offers economic advantages, or protective actions to clear faults and large short-circuit currents. Many of the smart grid concepts currently under development by many utilities rely heavily on switching to optimize resources that produce transients in the system. On the other hand, inrush currents produce mechanical forces which deform transformer windings and cause malfunction of the differential protection. Also, transformer performance under ferroresonance and geomagnetic induced currents are necessary to study. In this thesis, a physically consistent dual model applicable to single-phase two-winding transformers is proposed. First, the topology of a dual electrical equivalent circuit is obtained from the direct application of the principle of duality. Then, the model parameters are computed considering the variations of the transformer electromagnetic behavior under various operating conditions. Current modeling techniques use different topological models to represent diverse transient situations. The reversible model proposed in this thesis unifies the terminal and topological equivalent circuits. The model remains invariable for all low-frequency transients including deep saturation conditions driven from any of the two windings. The very high saturation region of the iron core magnetizing characteristic is modified with the accurate measurement of the air-core inductance. The air-core inductance is measured using a non-ideal low-power rectifier. Its dc output serves to drive the transformer into deep saturation, and its ripple provides low-amplitude variable excitation. The principal advantage of this method is its simplicity. To model the eddy current effects in the windings, a novel equivalent circuit is proposed. The circuit is derived from the principle of duality and therefore, matches the electromagnetic physical behavior of the transformer windings. It properly models the flux paths and current distribution from dc to MHz. The model is synthesized from a non-uniform concentric discretization of the windings. Concise guidelines are given to optimally calculate the width of the sub-divisions for various transient simulations. To compute the circuit parameters only information about the geometry of the windings and about their material properties is needed. The calculation of the circuit parameters does not require an iterative process. Therefore, the parameters are always real, positive, and free from convergence problems. The proposed model is tested with single-phase transformers for the calculation of magnetizing inrush currents, series ferroresonance, and Geomagnetic Induced Currents (GIC). The electromagnetic transient response of the model is compared to laboratory measurements for validation. Also, 3D finite element simulations are used to validate the electromagnetic behavior of the transformer model. Large manufacturer of transformers, power system designers, and electrical utility companies can benefit from the new model. It simplifies the design and optimization of the transformers' insulation, thereby reducing cost, and enhancing reliability of the system. The model could also be used for inrush current and differential protection studies, geomagnetic induced current studies, harmonic penetration studies, and switching transient studies.

Analytic Thermoelectric Couple Modeling: Variable Material Properties and Transient Operation

NASA Technical Reports Server (NTRS)

Mackey, Jonathan A.; Sehirlioglu, Alp; Dynys, Fred

2015-01-01

To gain a deeper understanding of the operation of a thermoelectric couple a set of analytic solutions have been derived for a variable material property couple and a transient couple. Using an analytic approach, as opposed to commonly used numerical techniques, results in a set of useful design guidelines. These guidelines can serve as useful starting conditions for further numerical studies, or can serve as design rules for lab built couples. The analytic modeling considers two cases and accounts for 1) material properties which vary with temperature and 2) transient operation of a couple. The variable material property case was handled by means of an asymptotic expansion, which allows for insight into the influence of temperature dependence on different material properties. The variable property work demonstrated the important fact that materials with identical average Figure of Merits can lead to different conversion efficiencies due to temperature dependence of the properties. The transient couple was investigated through a Greens function approach; several transient boundary conditions were investigated. The transient work introduces several new design considerations which are not captured by the classic steady state analysis. The work helps to assist in designing couples for optimal performance, and also helps assist in material selection.

Transient sodium current at subthreshold voltages: activation by EPSP waveforms

PubMed Central

Carter, Brett C.; Giessel, Andrew J.; Sabatini, Bernardo L.; Bean, Bruce P.

2012-01-01

Summary Tetrodotoxin (TTX)-sensitive sodium channels carry large transient currents during action potentials and also “persistent” sodium current, a non-inactivating TTX-sensitive current present at subthreshold voltages. We examined gating of subthreshold sodium current in dissociated cerebellar Purkinje neurons and hippocampal CA1 neurons, studied at 37 °C with near-physiological ionic conditions. Unexpectedly, in both cell types small voltage steps at subthreshold voltages activated a substantial component of transient sodium current as well as persistent current. Subthreshold EPSP-like waveforms also activated a large component of transient sodium current, but IPSP-like waveforms engaged primarily persistent sodium current with only a small additional transient component. Activation of transient as well as persistent sodium current at subthreshold voltages produces amplification of EPSPs that is sensitive to the rate of depolarization and can help account for the dependence of spike threshold on depolarization rate, as previously observed in vivo. PMID:22998875

TEM Systems Design: Using Full Maxwell FDTD Modelling to Study the Transient Response of Custom-madeTx and Rx Coils.

NASA Astrophysics Data System (ADS)

Chevalier, A.; Rejiba, F.; Schamper, C.; Thiesson, J.; Hovhannissian, G.

2016-12-01

From airborne applications to field scale measurements of Transient Electromagnetic Methods(TEM), an accurate knowledge of the sensitivity of the inductive coil sensors (system response) is aprerequisite to interpret the measured transient magnetic flux density into a subsurface distributionof conductivity. The system response is a term that refers to the cumulative effect of inductive andcapacitive couplings (cross-talks) between each component constituting a TEM apparatus and thenearby conductive structures. As a result, the frequency sensitivity of the voltage coil sensor (Rx)along with the emitted current waveform in the current emitting coil (Tx) are controlled by thegeometry and electronic characteristic of the set-up as well as the near surface electromagneticproperties. During the early development of an innovative airborne TEM solutions (French nationalTEMas project), determining the coil geometries and the impedance matching between all parts ofthe transmission link (electronic parts and coils) for various environmental set-ups, has been a majorissue. In this study, we review the required theoretical framework and propose a versatile numericalmethodology to ease the coil design and impedance matching process while extending ourunderstanding of short-time transient that operates from DC to moderately high frequencies (0 to 20Mhz). We used a full Maxwell equations FDTD model along with a semi-analytical 1D modeler to infercoils emitting and receiving properties, for various coil geometries and site-dependent conditions.Results highlight the influence of the environment on the emitting and sensing properties. Theincreasing effects of cross-talks between the Tx and the Rx coils depending on their size is shown.Strategies regarding the impedance adaptation between the electronical components and the coilsensors are then discussed for different geophysical specifications.

Kinetic and functional analysis of transient, persistent and resurgent sodium currents in rat cerebellar granule cells in situ: an electrophysiological and modelling study

PubMed Central

Magistretti, Jacopo; Castelli, Loretta; Forti, Lia; D'Angelo, Egidio

2006-01-01

Cerebellar neurones show complex and differentiated mechanisms of action potential generation that have been proposed to depend on peculiar properties of their voltage-dependent Na+ currents. In this study we analysed voltage-dependent Na+ currents of rat cerebellar granule cells (GCs) by performing whole-cell, patch-clamp experiments in acute rat cerebellar slices. A transient Na+ current (INaT) was always present and had the properties of a typical fast-activating/inactivating Na+ current. In addition to INaT, robust persistent (INaP) and resurgent (INaR) Na+ currents were observed. INaP peaked at ∼−40 mV, showed half-maximal activation at ∼−55 mV, and its maximal amplitude was about 1.5% of that of INaT. INaR was elicited by repolarizing pulses applied following step depolarizations able to activate/inactivate INaT, and showed voltage- and time-dependent activation and voltage-dependent decay kinetics. The conductance underlying INaR showed a bell-shaped voltage dependence, with peak at −35 mV. A significant correlation was found between GC INaR and INaT peak amplitudes; however, GCs expressing INaT of similar size showed marked variability in terms of INaR amplitude, and in a fraction of cells INaR was undetectable. INaT, INaP and INaR could be accounted for by a 13-state kinetic scheme comprising closed, open, inactivated and blocked states. Current-clamp experiments carried out to identify possible functional correlates of INaP and/or INaR revealed that in GCs single action potentials were followed by depolarizing afterpotentials (DAPs). In a majority of cells, DAPs showed properties consistent with INaR playing a role in their generation. Computer modelling showed that INaR promotes DAP generation and enhances high-frequency firing, whereas INaP boosts near-threshold firing activity. Our findings suggest that special properties of voltage-dependent Na+ currents provides GCs with mechanisms suitable for shaping activity patterns, with potentially important consequences for cerebellar information transfer and computation. PMID:16527854

Diminished A-type potassium current and altered firing properties in presympathetic PVN neurones in renovascular hypertensive rats

PubMed Central

Sonner, Patrick M; Filosa, Jessica A; Stern, Javier E

2008-01-01

Accumulating evidence supports a contribution of the hypothalamic paraventricular nucleus (PVN) to sympathoexcitation and elevated blood pressure in renovascular hypertension. However, the underlying mechanisms resulting in altered neuronal function in hypertensive rats remain largely unknown. Here, we aimed to address whether the transient outward potassium current (IA) in identified rostral ventrolateral medulla (RVLM)-projecting PVN neurones is altered in hypertensive rats, and whether such changes affected single and repetitive action potential properties and associated changes in intracellular Ca2+ levels. Patch-clamp recordings obtained from PVN-RVLM neurons showed a reduction in IA current magnitude and single channel conductance, and an enhanced steady-state current inactivation in hypertensive rats. Morphometric reconstructions of intracellularly labelled PVN-RVLM neurons showed a diminished dendritic surface area in hypertensive rats. Consistent with a diminished IA availability, action potentials in PVN-RVLM neurons in hypertensive rats were broader, decayed more slowly, and were less sensitive to the K+ channel blocker 4-aminopyridine. Simultaneous patch clamp recordings and confocal Ca2+ imaging demonstrated enhanced action potential-evoked intracellular Ca2+ transients in hypertensive rats. Finally, spike broadening during repetitive firing discharge was enhanced in PVN-RVLM neurons from hypertensive rats. Altogether, our results indicate that diminished IA availability constitutes a contributing mechanism underlying aberrant central neuronal function in renovascular hypertension. PMID:18238809

Trapping effect of metal nanoparticle mono- and multilayer in the organic field-effect transistor

NASA Astrophysics Data System (ADS)

Lee, Keanchuan; Weis, Martin; Lin, Jack; Taguchi, Dai; Majková, Eva; Manaka, Takaaki; Iwamoto, Mitsumasa

2011-03-01

The effect of silver nanoparticles self-assembled monolayer (Ag NPs SAM) on charge transport in pentacene organic field-effect transistors (OFET) was investigated by both steady-state and transient-state methods, which are current-voltage measurements in steady-state and time-resolved microscopic (TRM) second harmonic generation (SHG) in transient-state, respectively. The analysis of electronic properties revealed that OFET with SAM exhibited significant charge trapping effect due to the space-charge field formed by immobile charges. Lower transient-state mobility was verified by the direct probing of carrier motion by TRM-SHG technique. It was shown that the trapping effect rises together with increase of SAM layers suggesting the presence of traps in the bulk of NP films. The model based on the electrostatic charge barrier is suggested to explain the phenomenon.

Characterization of two distinct depolarization-activated K+ currents in isolated adult rat ventricular myocytes

PubMed Central

1991-01-01

Depolarization-activated outward K+ currents in isolated adult rat ventricular myocytes were characterized using the whole-cell variation of the patch-clamp recording technique. During brief depolarizations to potentials positive to -40 mV, Ca(2+)-independent outward K+ currents in these cells rise to a transient peak, followed by a slower decay to an apparent plateau. The analyses completed here reveal that the observed outward current waveforms result from the activation of two kinetically distinct voltage-dependent K+ currents: one that activates and inactivates rapidly, and one that activates and inactivates slowly, on membrane depolarization. These currents are referred to here as Ito (transient outward) and IK (delayed rectifier), respectively, because their properties are similar (although not identical) to these K+ current types in other cells. Although the voltage dependences of Ito and IK activation are similar, Ito activates approximately 10-fold and inactivates approximately 30-fold more rapidly than IK at all test potentials. In the composite current waveforms measured during brief depolarizations, therefore, the peak current predominantly reflects Ito, whereas IK is the primary determinant of the plateau. There are also marked differences in the voltage dependences of steady-state inactivation of these two K+ currents: IK undergoes steady-state inactivation at all potentials positive to -120 mV, and is 50% inactivated at -69 mV; Ito, in contrast, is insensitive to steady-state inactivation at membrane potentials negative to -50 mV. In addition, Ito recovers from steady-state inactivation faster than IK: at -90 mV, for example, approximately 70% recovery from the inactivation produced at -20 mV is observed within 20 ms for Ito; IK recovers approximately 25-fold more slowly. The pharmacological properties of Ito and IK are also distinct: 4-aminopyridine preferentially attenuates Ito, and tetraethylammonium suppresses predominantly IK. The voltage- and time- dependent properties of these currents are interpreted here in terms of a model in which Ito underlies the initial, rapid repolarization phase of the action potential (AP), and IK is responsible for the slower phase of AP repolarization back to the resting membrane potential, in adult rat ventricular myocytes. PMID:1865177

Electrical properties associated with wide intercellular clefts in rabbit Purkinje fibres.

PubMed Central

Colatsky, T J; Tsien, R W

1979-01-01

1. Rabbit Purkinje fibres were studied using micro-electrode recordings of electrical activity or a two-micro-electrode voltage clamp. Previous morphological work had suggested that these preparations offer structural advantages for the analysis of ionic permeability mechanisms. 2. Viable preparations could be obtained consistently by exposure to a K glutamate Tyrode solution during excision and recovery. In NaCl Tyrode solution, the action potential showed a large overshoot and fully developed plateau, but no pacemaker depolarization at negative potentials. 3. The passive electrical properties were consistent with morphological evidence for the accessibility of cleft membranes within the cell bundle. Electrotonic responses to intracellular current steps showed the behaviour expected for a simple leaky capacitative cable. Capacitative current transients under voltage clamp were changed very little by an eightfold reduction in the external solution conductivity. 4. Slow current changes attributable to K depletion were small compared to those found in other cardiac preparations. The amount of depletion was close to that predicted by a cleft model which assumed free K diffusion in 1 micron clefts. 5. Step depolarizations over the plateau range of potentials evoked a slow inward current which was resistant to tetrodotoxin but blocked by D600. 6. Strong depolarizations to potentials near 0 mV elicited a transient outward current and a slowly activating late outward current. Both components resembled currents found in sheep or calf Purkinje fibres. 7. These experiments support previous interpretations of slow plateau currents in terms of genuine permeability changes. The rabbit Purkinje fibre may allow various ionic channels to be studied with relatively little interference from radial non-uniformities in membrane potential or ion concentration. Images Fig. 7 PMID:469754

Rapid chlorophyll a fluorescence transient of Lemna gibba leaf as an indication of light and hydroxylamine effect on photosystem II activity.

PubMed

Dewez, David; Ali, Nadia Ait; Perreault, François; Popovic, Radovan

2007-05-01

Rapid chlorophyll fluorescence transient induced by saturating flash (3000 micromol of photons m-2 s-1) was investigated when Lemna gibba had been exposed to light (100 micromol of photons m-2 s-1) causing the Kautsky effect or in low light intensity unable to trigger PSII photochemistry. Measurements were made by using, simultaneously, a pulse amplitude modulated fluorometer and plant efficiency analyzer system, either on non-treated L. gibba leaf or those treated with different concentrations of hydroxylamine (1-50 mM) causing gradual inhibition of the water splitting system. When any leaf was exposed to continuous light during the Kautsky effect, a rapid fluorescence transient may reflect current activity of photosystem II within the photosystem II complex. Under those conditions, a variation of transition steps appearing over time was related to a drastic change to the photosystem II functional properties. This value indicated that the energy dissipation through non-photochemical pathways was undergoing extreme change. The change of rapid fluorescence transient, induced under continuous light, when compared to those obtained under very low light intensity, confirmed the ability of photosystem II to be capable to undergo rapid adaptation lasting about two minutes. When the water splitting system was inhibited and electron donation partially substituted by hydroxylamine, the adaptation ability of photosystem II to different light conditions was lost. In this study, the change of rapid fluorescence kinetic and transient appearing over time was shown to be a good indication for the change of the functional properties of photosystem II induced either by light or by hydroxylamine.

Bioresorbable scaffolds for percutaneous coronary interventions

PubMed Central

Gogas, Bill D.

2014-01-01

Innovations in drug-eluting stents (DES) have substantially reduced rates of in-segment restenosis and early stent thrombosis, improving clinical outcomes following percutaneous coronary interventions (PCI). However a fixed metallic implant in a vessel wall with restored patency and residual disease remains a precipitating factor for sustained local inflammation, in-stent neo-atherosclerosis and impaired vasomotor function increasing the risk for late complications attributed to late or very late stent thrombosis and late target lesion revascularization (TLR) (late catch-up). The quest for optimal coronary stenting continues by further innovations in stent design and by using biocompatible materials other than cobalt chromium, platinum chromium or stainless steel for engineering coronary implants. Bioresorbable scaffolds made of biodegradable polymers or biocorrodible metals with properties of transient vessel scaffolding, local drug-elution and future restoration of vessel anatomy, physiology and local hemodynamics have been recently developed. These devices have been utilized in selected clinical applications so far providing preliminary evidence of safety showing comparable performance with current generation drug-eluting stents (DES). Herein we provide a comprehensive overview of the current status of these technologies, we elaborate on the potential benefits of transient coronary scaffolds over permanent stents in the context of vascular reparation therapy, and we further focus on the evolving challenges these devices have to overcome to compete with current generation DES. Condensed Abstract:: The quest for optimizing percutaneous coronary interventions continues by iterative innovations in device materials beyond cobalt chromium, platinum chromium or stainless steel for engineering coronary implants. Bioresorbable scaffolds made of biodegradable polymers or biocorrodible metals with properties of transient vessel scaffolding; local drug-elution and future restoration of vessel anatomy, physiology and local hemodynamics were recently developed. These devices have been utilized in selected clinical applications providing preliminary evidence of safety showing comparable intermediate term clinical outcomes with current generation drug-eluting stents. PMID:25780795

Recrystallization and grain growth induced by ELMs-like transient heat loads in deformed tungsten samples

NASA Astrophysics Data System (ADS)

Suslova, A.; El-Atwani, O.; Sagapuram, D.; Harilal, S. S.; Hassanein, A.

2014-11-01

Tungsten has been chosen as the main candidate for plasma facing components (PFCs) due to its superior properties under extreme operating conditions in future nuclear fusion reactors such as ITER. One of the serious issues for PFCs is the high heat load during transient events such as ELMs and disruption in the reactor. Recrystallization and grain size growth in PFC materials caused by transients are undesirable changes in the material, since the isotropic microstructure developed after recrystallization exhibits a higher ductile-to-brittle transition temperature which increases with the grain size, a lower thermal shock fatigue resistance, a lower mechanical strength, and an increased surface roughening. The current work was focused on careful determination of the threshold parameters for surface recrystallization, grain growth rate, and thermal shock fatigue resistance under ELM-like transient heat events. Transient heat loads were simulated using long pulse laser beams for two different grades of ultrafine-grained tungsten. It was observed that cold rolled tungsten demonstrated better power handling capabilities and higher thermal stress fatigue resistance compared to severely deformed tungsten. Higher recrystallization threshold, slower grain growth, and lower degree of surface roughening were observed in the cold rolled tungsten.

Recrystallization and grain growth induced by ELMs-like transient heat loads in deformed tungsten samples

PubMed Central

Suslova, A.; El-Atwani, O.; Sagapuram, D.; Harilal, S. S.; Hassanein, A.

2014-01-01

Tungsten has been chosen as the main candidate for plasma facing components (PFCs) due to its superior properties under extreme operating conditions in future nuclear fusion reactors such as ITER. One of the serious issues for PFCs is the high heat load during transient events such as ELMs and disruption in the reactor. Recrystallization and grain size growth in PFC materials caused by transients are undesirable changes in the material, since the isotropic microstructure developed after recrystallization exhibits a higher ductile-to-brittle transition temperature which increases with the grain size, a lower thermal shock fatigue resistance, a lower mechanical strength, and an increased surface roughening. The current work was focused on careful determination of the threshold parameters for surface recrystallization, grain growth rate, and thermal shock fatigue resistance under ELM-like transient heat events. Transient heat loads were simulated using long pulse laser beams for two different grades of ultrafine-grained tungsten. It was observed that cold rolled tungsten demonstrated better power handling capabilities and higher thermal stress fatigue resistance compared to severely deformed tungsten. Higher recrystallization threshold, slower grain growth, and lower degree of surface roughening were observed in the cold rolled tungsten. PMID:25366885

Recrystallization and grain growth induced by ELMs-like transient heat loads in deformed tungsten samples.

PubMed

Suslova, A; El-Atwani, O; Sagapuram, D; Harilal, S S; Hassanein, A

2014-11-04

Tungsten has been chosen as the main candidate for plasma facing components (PFCs) due to its superior properties under extreme operating conditions in future nuclear fusion reactors such as ITER. One of the serious issues for PFCs is the high heat load during transient events such as ELMs and disruption in the reactor. Recrystallization and grain size growth in PFC materials caused by transients are undesirable changes in the material, since the isotropic microstructure developed after recrystallization exhibits a higher ductile-to-brittle transition temperature which increases with the grain size, a lower thermal shock fatigue resistance, a lower mechanical strength, and an increased surface roughening. The current work was focused on careful determination of the threshold parameters for surface recrystallization, grain growth rate, and thermal shock fatigue resistance under ELM-like transient heat events. Transient heat loads were simulated using long pulse laser beams for two different grades of ultrafine-grained tungsten. It was observed that cold rolled tungsten demonstrated better power handling capabilities and higher thermal stress fatigue resistance compared to severely deformed tungsten. Higher recrystallization threshold, slower grain growth, and lower degree of surface roughening were observed in the cold rolled tungsten.

Computational modeling of the effect of external electron injection into a direct-current microdischarge

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

Panneer Chelvam, Prem Kumar; Raja, Laxminarayan L.

2015-12-28

Electron emission from the electrode surface plays an important role in determining the structure of a direct-current microdischarge. Here we have developed a computational model of a direct-current microdischarge to study the effect of external electron injection from the cathode surface into the discharge to manipulate its properties. The model provides a self-consistent, multi-species, multi-temperature fluid representation of the plasma. A microdischarge with a metal-insulator-metal configuration is chosen for this study. The effect of external electron injection on the structure and properties of the microdischarge is described. The transient behavior of the microdischarge during the electron injection is examined. Themore » nonlinearities in the dynamics of the plasma result in a large increase of conduction current after active electron injection. For the conditions simulated a switching time of ∼100 ns from a low-current to high-current discharge state is realized.« less

Steady state and transient simulation of anion exchange membrane fuel cells

NASA Astrophysics Data System (ADS)

Dekel, Dario R.; Rasin, Igal G.; Page, Miles; Brandon, Simon

2018-01-01

We present a new model for anion exchange membrane fuel cells. Validation against experimental polarization curve data is obtained for current densities ranging from zero to above 2 A cm-2. Experimental transient data is also successfully reproduced. The model is very flexible and can be used to explore the system's sensitivity to a wide range of material properties, cell design specifications, and operating parameters. We demonstrate the impact of gas inlet relative humidity (RH), operating current density, ionomer loading and ionomer ion exchange capacity (IEC) values on cell performance. In agreement with the literature, high air RH levels are shown to improve cell performance. At high current densities (>1 A cm-2) this effect is observed to be especially significant. Simulated hydration number distributions across the cell reveal the related critical dependence of cathode hydration on air RH and current density values. When exploring catalyst layer design, optimal intermediate ionomer loading values are demonstrated. The benefits of asymmetric (cathode versus anode) electrode design are revealed, showing enhanced performance using higher cathode IEC levels. Finally, electrochemical reaction profiles across the electrodes uncover inhomogeneous catalyst utilization. Specifically, at high current densities the cathodic reaction is confined to a narrow region near the membrane.

Deep level transient spectroscopy (DLTS) on colloidal-synthesized nanocrystal solids.

PubMed

Bozyigit, Deniz; Jakob, Michael; Yarema, Olesya; Wood, Vanessa

2013-04-24

We demonstrate current-based, deep level transient spectroscopy (DLTS) on semiconductor nanocrystal solids to obtain quantitative information on deep-lying trap states, which play an important role in the electronic transport properties of these novel solids and impact optoelectronic device performance. Here, we apply this purely electrical measurement to an ethanedithiol-treated, PbS nanocrystal solid and find a deep trap with an activation energy of 0.40 eV and a density of NT = 1.7 × 10(17) cm(-3). We use these findings to draw and interpret band structure models to gain insight into charge transport in PbS nanocrystal solids and the operation of PbS nanocrystal-based solar cells.

Gate frequency sweep: An effective method to evaluate the dynamic performance of AlGaN/GaN power heterojunction field effect transistors

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

Santi, C. de; Meneghini, M., E-mail: matteo.meneghini@dei.unipd.it; Meneghesso, G.

2014-08-18

With this paper we propose a test method for evaluating the dynamic performance of GaN-based transistors, namely, gate-frequency sweep measurements: the effectiveness of the method is verified by characterizing the dynamic performance of Gate Injection Transistors. We demonstrate that this method can provide an effective description of the impact of traps on the transient performance of Heterojunction Field Effect Transistors, and information on the properties (activation energy and cross section) of the related defects. Moreover, we discuss the relation between the results obtained by gate-frequency sweep measurements and those collected by conventional drain current transients and double pulse characterization.

Compact Models for Defect Diffusivity in Semiconductor Alloys.

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

Wright, Alan F.; Modine, Normand A.; Lee, Stephen R.

Predicting transient effects caused by short - pulse neutron irradiation of electronic devices is an important part of Sandia's mission. For example , predicting the diffusion of radiation - induced point defects is needed with in Sandia's Qualification Alternative to the Sandia Pulsed Reactor (QASPR) pro gram since defect diffusion mediates transient gain recovery in QASPR electronic devices. Recently, the semiconductors used to fabricate radiation - hard electronic devices have begun to shift from silicon to III - V compounds such as GaAs, InAs , GaP and InP . An advantage of this shift is that it allows engineers tomore » optimize the radiation hardness of electronic devices by using alloy s such as InGaAs and InGaP . However, the computer codes currently being used to simulate transient radiation effects in QASP R devices will need to be modified since they presume that defect properties (charge states, energy levels, and diffusivities) in these alloys do not change with time. This is not realistic since the energy and properties of a defect depend on the types of atoms near it and , therefore, on its location in the alloy. In particular, radiation - induced defects are created at nearly random locations in an alloy and the distribution of their local environments - and thus their energies and properties - evolves with time as the defects diffuse through the alloy . To incorporate these consequential effects into computer codes used to simulate transient radiation effects, we have developed procedures to accurately compute the time dependence of defect energies and properties and then formulate them within compact models that can be employed in these computer codes. In this document, we demonstrate these procedures for the case of the highly mobile P interstitial (I P ) in an InGaP alloy. Further dissemination only as authorized to U.S. Government agencies and their contractors; other requests shall be approved by the originating facility or higher DOE programmatic authority.« less

The influence of tyre transient side force properties on vehicle lateral acceleration for a time-varying vertical force

NASA Astrophysics Data System (ADS)

Takahashi, Toshimichi

2018-05-01

The tyre model which formerly developed by the author et al. and describes the tyre transient responses of side force and aligning moment under the time-varying vertical force was implemented to the vehicle dynamics simulation software and the influence of tyre side force transient property on the vehicle behaviour was investigated. The vehicle responses with/without tyre transient property on sinusoidally undulated road surfaces were simulated and compared. It was found that the average lateral acceleration of the vehicle at the sinusoidal steering wheel angle input decreases on the undulated road of long wavelength (3 m) for both cases, but when the wavelength becomes shorter (1 m), the average lateral acceleration increases only in the case that the transient property is considered. The cause of those changes is explained by using the tyre-related variables. Also the steady-state turning behaviour of the vehicle on undulated roads are shown and discussed.

Transient Heat Transfer Properties in a Pulse Detonation Combustor

DTIC Science & Technology

2011-03-01

strategies for future systems. 15. NUMBER OF PAGES 89 14. SUBJECT TERMS Pulse Detonation Engines, PDE , Heat Transfer 16. PRICE CODE 17. SECURITY...GUI Graphical User Interface NPS Naval Postgraduate School PDC Pulse Detonation Combustion PDE Pulse Detonation Engine RPL Rocket...a tactical missile with a Pulse Detonation Engine ( PDE ) and provide greater range for the same amount of fuel as compared to other current

Investigation of interface property in Al/SiO2/ n-SiC structure with thin gate oxide by illumination

NASA Astrophysics Data System (ADS)

Chang, P. K.; Hwu, J. G.

2017-04-01

The reverse tunneling current of Al/SiO2/ n-SiC structure employing thin gate oxide is introduced to examine the interface property by illumination. The gate current at negative bias decreases under blue LED illumination, yet increases under UV lamp illumination. Light-induced electrons captured by interface states may be emitted after the light sources are off, leading to the recovery of gate currents. Based on transient characteristics of gate current, the extracted trap level is close to the light energy for blue LED, indicating that electron capture induced by lighting may result in the reduction of gate current. Furthermore, bidirectional C- V measurements exhibit a positive voltage shift caused by electron trapping under blue LED illumination, while a negative voltage shift is observed under UV lamp illumination. Distinct trapping and detrapping behaviors can be observed from variations in I- V and C- V curves utilizing different light sources for 4H-SiC MOS capacitors with thin insulators.

Transient interaction model of electromagnetic field generated by lightning current pulses and human body

NASA Astrophysics Data System (ADS)

Iváncsy, T.; Kiss, I.; Szücs, L.; Tamus, Z. Á.

2015-10-01

The lightning current generates time-varying magnetic field near the down- conductor and the down-conductors are mounted on the wall of the buildings where residential places might be situated. It is well known that the rapidly changing magnetic fields can generate dangerous eddy currents in the human body.The higher duration and gradient of the magnetic field can cause potentially life threatening cardiac stimulation. The coupling mechanism between the electromagnetic field and the human body is based on a well-known physical phenomena (e.g. Faradays law of induction). However, the calculation of the induced current is very complicated because the shape of the organs is complex and the determination of the material properties of living tissues is difficult, as well. Our previous study revealed that the cardiac stimulation is independent of the rising time of the lightning current and only the peak of the current counts. In this study, the authors introduce an improved model of the interaction of electromagnetic fields of lighting current near down-conductor and human body. Our previous models are based on the quasi stationer field calculations, the new improved model is a transient model. This is because the magnetic field around the down-conductor and in the human body can be determined more precisely, therefore the dangerous currents in the body can be estimated.

Effects of premature stimulation on HERG K+ channels

PubMed Central

Lu, Yu; Mahaut-Smith, Martyn P; Varghese, Anthony; Huang, Christopher L-H; Kemp, Paul R; Vandenberg, Jamie I

2001-01-01

The unusual kinetics of human ether-à-go-go-related gene (HERG) K+ channels are consistent with a role in the suppression of arrhythmias initiated by premature beats. Action potential clamp protocols were used to investigate the effect of premature stimulation on HERG K+ channels, transfected in Chinese hamster ovary cells, at 37 °C. HERG K+ channel currents peaked during the terminal repolarization phase of normally paced action potential waveforms. However, the magnitude of the current and the time point at which conductance was maximal depended on the type of action potential waveform used (epicardial, endocardial, Purkinje fibre or atrial). HERG K+ channel currents recorded during premature action potentials consisted of an early transient outward current followed by a sustained outward current. The magnitude of the transient current component showed a biphasic dependence on the coupling interval between the normally paced and premature action potentials and was maximal at a coupling interval equivalent to 90% repolarization (APD90) for ventricular action potentials. The largest transient current response occurred at shorter coupling intervals for Purkinje fibre (APD90– 20 ms) and atrial (APD90– 30 ms) action potentials. The magnitude of the sustained current response following premature stimulation was similar to that recorded during the first action potential for ventricular action potential waveforms. However, for Purkinje and atrial action potentials the sustained current response was significantly larger during the premature action potential than during the normally paced action potential. A Markov model that included three closed states, one open and one inactivated state with transitions permitted between the pre-open closed state and the inactivated state, successfully reproduced our results for the effects of premature stimuli, both during square pulse and action potential clamp waveforms. These properties of HERG K+ channels may help to suppress arrhythmias initiated by early afterdepolarizations and premature beats in the ventricles, Purkinje fibres or atria. PMID:11744759

Understanding Charge Collection Mechanisms in InGaAs FinFETs Using High-Speed Pulsed-Laser Transient Testing With Tunable Wavelength

NASA Astrophysics Data System (ADS)

Ni, Kai; Sternberg, Andrew L.; Zhang, En Xia; Kozub, John A.; Jiang, Rong; Schrimpf, Ronald D.; Reed, Robert A.; Fleetwood, Daniel M.; Alles, Michael L.; McMorrow, Dale; Lin, Jianqiang; Vardi, Alon; del Alamo, Jesús

2017-08-01

A tunable wavelength laser system and high-resolution transient capture system are introduced to characterize transients in high-mobility MOSFETs. The experimental configuration enables resolution of fast transient signals and new understanding of charge collection mechanisms. The channel layer is critical in the charge collection process for the InGaAs FinFETs examined here. The transient current mainly comes from the channel current, due to shunt effects and parasitic bipolar effects, instead of the junction collection. The charge amplification factor is found to be as high as 14, which makes this technology relatively sensitive to transient radiation. The peak current is inversely proportional to the device gate length. Simulations show that the parasitic bipolar effect is due to source-to-channel barrier lowering caused by hole accumulation in the source and channel. Charge deposited in the channel causes prompt current, while charge deposited below the channel causes delayed and slow current.

Inhibitory effect of aniracetam on N-type calcium current in acutely isolated rat neuronal cells.

PubMed

Koike, H; Saito, H; Matsuki, N

1993-04-01

Effects of aniracetam on whole-cell calcium currents were studied in acutely isolated neuronal cells from postnatal rat ventromedial hypothalamus. There were three types of inward calcium currents, one low-threshold transient current and two high-threshold sustained currents. The nicardipine sensitive L-type current was activated at -20 mV or more depolarized potentials, and the omega-conotoxin sensitive N-type current was recorded at more positive potentials than the L-type. Aniracetam inhibited the N-type current in a dose-dependent manner without affecting the other two types of calcium currents. The effect appeared soon after the addition and lasted for several minutes during washing. Since the N-type current is thought to regulate the release of transmitters, the inhibitory effect may contribute to the nootropic property of aniracetam by modifying the neurotransmission.

Transient dynamics of a quantum-dot: From Kondo regime to mixed valence and to empty orbital regimes

NASA Astrophysics Data System (ADS)

Cheng, YongXi; Li, ZhenHua; Wei, JianHua; Nie, YiHang; Yan, YiJing

2018-04-01

Based on the hierarchical equations of motion approach, we study the time-dependent transport properties of a strongly correlated quantum dot system in the Kondo regime (KR), mixed valence regime (MVR), and empty orbital regime (EOR). We find that the transient current in KR shows the strongest nonlinear response and the most distinct oscillation behaviors. Both behaviors become weaker in MVR and diminish in EOR. To understand the physical insight, we examine also the corresponding dot occupancies and the spectral functions, with their dependence on the Coulomb interaction, temperature, and applied step bias voltage. The above nonlinear and oscillation behaviors could be understood as the interplay between dynamical Kondo resonance and single electron resonant-tunneling.

Profiling of the injected charge drift current transients by cross-sectional scanning technique

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

Gaubas, E., E-mail: eugenijus.gaubas@ff.vu.lt; Ceponis, T.; Pavlov, J.

2014-02-07

The electric field distribution and charge drift currents in Si particle detectors are analyzed. Profiling of the injected charge drift current transients has been implemented by varying charge injection position within a cross-sectional boundary of the particle detector. The obtained profiles of the induction current density and duration of the injected charge drift pulses fit well the simulated current variations. Induction current transients have been interpreted by different stages of the bipolar and monopolar drift of the injected carriers. Profiles of the injected charge current transients registered in the non-irradiated and neutron irradiated Si diodes are compared. It has beenmore » shown that the mixed regime of the competing processes of drift, recombination, and diffusion appears in the measured current profiles on the irradiated samples. The impact of the avalanche effects can be ignored based on the investigations presented. It has been shown that even a simplified dynamic model enabled us to reproduce the main features of the profiled transients of induced charge drift current.« less

Toward an Integrative Computational Model of the Guinea Pig Cardiac Myocyte

PubMed Central

Gauthier, Laura Doyle; Greenstein, Joseph L.; Winslow, Raimond L.

2012-01-01

The local control theory of excitation-contraction (EC) coupling asserts that regulation of calcium (Ca2+) release occurs at the nanodomain level, where openings of single L-type Ca2+ channels (LCCs) trigger openings of small clusters of ryanodine receptors (RyRs) co-localized within the dyad. A consequence of local control is that the whole-cell Ca2+ transient is a smooth continuous function of influx of Ca2+ through LCCs. While this so-called graded release property has been known for some time, its functional importance to the integrated behavior of the cardiac ventricular myocyte has not been fully appreciated. We previously formulated a biophysically based model, in which LCCs and RyRs interact via a coarse-grained representation of the dyadic space. The model captures key features of local control using a low-dimensional system of ordinary differential equations. Voltage-dependent gain and graded Ca2+ release are emergent properties of this model by virtue of the fact that model formulation is closely based on the sub-cellular basis of local control. In this current work, we have incorporated this graded release model into a prior model of guinea pig ventricular myocyte electrophysiology, metabolism, and isometric force production. The resulting integrative model predicts the experimentally observed causal relationship between action potential (AP) shape and timing of Ca2+ and force transients, a relationship that is not explained by models lacking the graded release property. Model results suggest that even relatively subtle changes in AP morphology that may result, for example, from remodeling of membrane transporter expression in disease or spatial variation in cell properties, may have major impact on the temporal waveform of Ca2+ transients, thus influencing tissue level electromechanical function. PMID:22783206

Toward an integrative computational model of the Guinea pig cardiac myocyte.

PubMed

Gauthier, Laura Doyle; Greenstein, Joseph L; Winslow, Raimond L

2012-01-01

The local control theory of excitation-contraction (EC) coupling asserts that regulation of calcium (Ca(2+)) release occurs at the nanodomain level, where openings of single L-type Ca(2+) channels (LCCs) trigger openings of small clusters of ryanodine receptors (RyRs) co-localized within the dyad. A consequence of local control is that the whole-cell Ca(2+) transient is a smooth continuous function of influx of Ca(2+) through LCCs. While this so-called graded release property has been known for some time, its functional importance to the integrated behavior of the cardiac ventricular myocyte has not been fully appreciated. We previously formulated a biophysically based model, in which LCCs and RyRs interact via a coarse-grained representation of the dyadic space. The model captures key features of local control using a low-dimensional system of ordinary differential equations. Voltage-dependent gain and graded Ca(2+) release are emergent properties of this model by virtue of the fact that model formulation is closely based on the sub-cellular basis of local control. In this current work, we have incorporated this graded release model into a prior model of guinea pig ventricular myocyte electrophysiology, metabolism, and isometric force production. The resulting integrative model predicts the experimentally observed causal relationship between action potential (AP) shape and timing of Ca(2+) and force transients, a relationship that is not explained by models lacking the graded release property. Model results suggest that even relatively subtle changes in AP morphology that may result, for example, from remodeling of membrane transporter expression in disease or spatial variation in cell properties, may have major impact on the temporal waveform of Ca(2+) transients, thus influencing tissue level electromechanical function.

Transient outward currents and changes of their gating properties after cell activation in thrombocytes of the newt.

PubMed Central

Kawa, K

1987-01-01

1. The electrical properties of the cell membrane of thrombocytes in the newt, Triturus pyrrhogaster, were studied using the whole-cell variation of the patch-electrode voltage-clamp technique. 2. In medium containing Ca2+ (1.8 mM), activated thrombocytes became round and then spread on the glass. Activation of thrombocytes was inhibited by the removal of external Ca2+ and addition of 1 w/v% albumin to the external media. 3. For thrombocytes kept in the resting state, depolarizations more positive than -30 mV evoked transient outward currents which decayed completely during the duration of the depolarization (150 ms). The half-decay time of the currents became smaller as the depolarizing pulse strengthened, reaching about 20 ms at +30 mV (20 degrees C). 4. The outward currents are identified as K+ currents, since (1) their reversal potential depended on extracellular K+ concentration and (2) the outward currents were suppressed either by external application of 4-aminopyridine (1 mM) or by internal application of Cs+ (120 mM). The monovalent cation selectivities of the K+ channels were evaluated from the reversal potential as Tl (1.68) greater than K(1.0) greater than Rb (0.89) greater than NH4 (0.13) greater than Na(less than 0.03). 5. When the thrombocytes had been activated, depolarization again evoked K+ currents. The currents, however, showed negligible or small decay during the duration of the depolarization (150 ms). The rate of recovery from preceding depolarization was also reduced to about one-sixth. 6. The sensitivity to 4-aminopyridine and the selectivity of the K+ channels were not changed by cell activation. 7. We conclude that during activation of thrombocytes the inactivation of the K+ channels is almost eliminated. Removal of inactivation of the K+ channels was also induced in resting thrombocytes by intracellular application of 4-bromoacetamide (50 microM). PMID:2443665

An investigation of transient pressure and plasma properties in a pinched plasma column. M.S. Thesis

NASA Technical Reports Server (NTRS)

Stover, E. K.; York, T. M.

1971-01-01

The transient pinched plasma column generated in a linear Z-pinch was studied experimentally and analytically. The plasma column was investigated experimentally with the following plasma diagnostics: a special rapid response pressure transducer, a magnetic field probe, a voltage probe and discharge luminosity. Axial pressure profiles on the discharge chamber axis were used to identify three characteristic regions of plasma column behavior; they were in temporal sequence: strong axial pressure asymmetry noted early in plasma column lifetime followed by plasma heating in which there is a rapid rise in static pressure and a slight decrease static pressure before plasma column breakup. Plasma column lifetime was approximately 5 microseconds. The axial pressure asymmetry was attributed to nonsimultaneous pinching of the imploding current sheet along the discharge chamber axis. The rapid heating is attributed in part to viscous effects introduced by radial gradients in the axial streaming velocity. Turbulent heating arising from discharge current excitation of the ion acoustic wave instability is also considered a possible heating mechanism.

KChIP2 genotype dependence of transient outward current (Ito) properties in cardiomyocytes isolated from male and female mice

PubMed Central

Waldschmidt, Lara; Junkereit, Vera; Bähring, Robert

2017-01-01

The transient outward current (Ito) in cardiomyocytes is largely mediated by Kv4 channels associated with Kv Channel Interacting Protein 2 (KChIP2). A knockout model has documented the critical role of KChIP2 in Ito expression. The present study was conducted to characterize in both sexes the dependence of Ito properties, including current magnitude, inactivation kinetics, recovery from inactivation and voltage dependence of inactivation, on the number of functional KChIP2 alleles. For this purpose we performed whole-cell patch-clamp experiments on isolated left ventricular cardiomyocytes from male and female mice which had different KChIP2 genotypes; i.e., wild-type (KChIP2+/+), heterozygous knockout (KChIP2+/-) or complete knockout of KChIP2 (KChIP2-/-). We found in both sexes a KChIP2 gene dosage effect (i.e., a proportionality between number of alleles and phenotype) on Ito magnitude, however, concerning other Ito properties, KChIP2+/- resembled KChIP2+/+. Only in the total absence of KChIP2 (KChIP2-/-) we observed a slowing of Ito kinetics, a slowing of recovery from inactivation and a negative shift of a portion of the voltage dependence of inactivation. In a minor fraction of KChIP2-/- myocytes Ito was completely lost. The distinct KChIP2 genotype dependences of Ito magnitude and inactivation kinetics, respectively, seen in cardiomyocytes were reproduced with two-electrode voltage-clamp experiments on Xenopus oocytes expressing Kv4.2 and different amounts of KChIP2. Our results corroborate the critical role of KChIP2 in controlling Ito properties. They demonstrate that the Kv4.2/KChIP2 interaction in cardiomyocytes is highly dynamic, with a clear KChIP2 gene dosage effect on Kv4 channel surface expression but not on inactivation gating. PMID:28141821

KChIP2 genotype dependence of transient outward current (Ito) properties in cardiomyocytes isolated from male and female mice.

PubMed

Waldschmidt, Lara; Junkereit, Vera; Bähring, Robert

2017-01-01

The transient outward current (Ito) in cardiomyocytes is largely mediated by Kv4 channels associated with Kv Channel Interacting Protein 2 (KChIP2). A knockout model has documented the critical role of KChIP2 in Ito expression. The present study was conducted to characterize in both sexes the dependence of Ito properties, including current magnitude, inactivation kinetics, recovery from inactivation and voltage dependence of inactivation, on the number of functional KChIP2 alleles. For this purpose we performed whole-cell patch-clamp experiments on isolated left ventricular cardiomyocytes from male and female mice which had different KChIP2 genotypes; i.e., wild-type (KChIP2+/+), heterozygous knockout (KChIP2+/-) or complete knockout of KChIP2 (KChIP2-/-). We found in both sexes a KChIP2 gene dosage effect (i.e., a proportionality between number of alleles and phenotype) on Ito magnitude, however, concerning other Ito properties, KChIP2+/- resembled KChIP2+/+. Only in the total absence of KChIP2 (KChIP2-/-) we observed a slowing of Ito kinetics, a slowing of recovery from inactivation and a negative shift of a portion of the voltage dependence of inactivation. In a minor fraction of KChIP2-/- myocytes Ito was completely lost. The distinct KChIP2 genotype dependences of Ito magnitude and inactivation kinetics, respectively, seen in cardiomyocytes were reproduced with two-electrode voltage-clamp experiments on Xenopus oocytes expressing Kv4.2 and different amounts of KChIP2. Our results corroborate the critical role of KChIP2 in controlling Ito properties. They demonstrate that the Kv4.2/KChIP2 interaction in cardiomyocytes is highly dynamic, with a clear KChIP2 gene dosage effect on Kv4 channel surface expression but not on inactivation gating.

Grand unification of neutron stars

PubMed Central

Kaspi, Victoria M.

2010-01-01

The last decade has shown us that the observational properties of neutron stars are remarkably diverse. From magnetars to rotating radio transients, from radio pulsars to isolated neutron stars, from central compact objects to millisecond pulsars, observational manifestations of neutron stars are surprisingly varied, with most properties totally unpredicted. The challenge is to establish an overarching physical theory of neutron stars and their birth properties that can explain this great diversity. Here I survey the disparate neutron stars classes, describe their properties, and highlight results made possible by the Chandra X-Ray Observatory, in celebration of its 10th anniversary. Finally, I describe the current status of efforts at physical “grand unification” of this wealth of observational phenomena, and comment on possibilities for Chandra’s next decade in this field. PMID:20404205

Optical and near-infrared study of the Ca-rich transient iPTF15eqv in the early phase

NASA Astrophysics Data System (ADS)

Kawahara, Naoki; Yamanaka, Masayuki; Kawabata, Koji; Nakaoka, Tatsuya; Kawabata, Miho; Maeda, Keiichi; Takaki, Katsutoshi; Akitaya, Hiroshi; Itoh, Ryosuke; Moritani, Yuki; Uemura, Makoto; Yoshida, Michitoshi

2018-01-01

Supernovae (SNe) exhibiting strong calcium features in their spectra are called Ca-rich transients. Frequently their early-phase spectra also exhibit helium absorption lines. They are mostly discovered in elliptical galaxies or at a remote location far from the host galaxy center. Well-observed samples are still too limited to clarify the explosion and progenitor properties. We present optical and near-infrared observations of a Ca-rich transient iPTF15eqv in the spiral galaxy NGC 3430. The data are obtained using 1.5-m Kanata telescope since Sep 28, 2015. While the discovery was at a post-maximum-phase, we infer the maximum date to be 30 days before the discovery date, by comparing its light curve and spectroscopic evolution to those of well-observed samples. The spectra exhibit absorption lines of He I and prominent emission lines of Ca II IR and [Ca II] from +31 to 69 d after the maximum date. We find that iPTF15eqv is more luminous than other Ca-rich transients by 1.5 to 2 mag on +31 d, and we estimate that the peak absolute magnitude in the R band is approximately -18 to -16.5 mag. The decline rate of the light curve between 30 and 60 d is similar to those of SNe Ib/c. The line velocity of the helium is similar to those of Ca-rich transients but also to SNe Ib. The ejecta properties inferred from our observations indicate that iPTF15eqv has a larger nickel mass than typical Ca-rich transients. While these properties show similarity to SNe Ib, we show that most of these properties are indeed shared by other Ca-rich transients. The properties of iPTF15eqv may thus still be regarded to be within the diversities among the Ca-rich transients.

Potassium and ANO1/TMEM16A chloride channel profiles distinguish atypical and typical smooth muscle cells from interstitial cells in the mouse renal pelvis

PubMed Central

Iqbal, Javed; Tonta, Mary A; Mitsui, Retsu; Li, Qun; Kett, Michelle; Li, Jinhua; Parkington, Helena C; Hashitani, Hikaru; Lang, Richard J

2012-01-01

BACKGROUND AND PURPOSE Although atypical smooth muscle cells (SMCs) in the proximal renal pelvis are thought to generate the pacemaker signals that drive pyeloureteric peristalsis, their location and electrical properties remain obscure. EXPERIMENTAL APPROACH Standard patch clamp, intracellular microelectrode and immunohistochemistry techniques were used. To unequivocally identify SMCs, transgenic mice with enhanced yellow fluorescent protein (eYFP) expressed in cells containing α-smooth muscle actin (α-SMA) were sometimes used. KEY RESULTS Atypical SMCs were distinguished from typical SMCs by the absence of both a transient 4-aminopyridine-sensitive K+ current (IKA) and spontaneous transient outward currents (STOCs) upon the opening of large-conductance Ca2+-activated K+ (BK) channels. Many typical SMCs displayed a slowly activating, slowly decaying Cl- current blocked by niflumic acid (NFA). Immunostaining for KV4.3 and ANO1/ TMEM16A Cl- channel subunits co-localized with α-SMA immunoreactive product predominately in the distal renal pelvis. Atypical SMCs fired spontaneous inward currents that were either selective for Cl- and blocked by NFA, or cation-selective and blocked by La3+. α-SMA- interstitial cells (ICs) were distinguished by the presence of a Xe991-sensitive KV7 current, BK channel STOCs and Cl- selective, NFA-sensitive spontaneous transient inward currents (STICs). Intense ANO1/ TMEM16A and KV7.5 immunostaining was present in Kit-α-SMA- ICs in the suburothelial and adventitial regions of the renal pelvis. CONCLUSIONS AND IMPLICATIONS We conclude that KV4.3+α-SMA+ SMCs are typical SMCs that facilitate muscle wall contraction, that ANO1/ TMEM16A and KV7.5 immunoreactivity may be selective markers of Kit- ICs and that atypical SMCs which discharge spontaneous inward currents are the pelviureteric pacemakers. PMID:22014103

Local Membrane Deformations Activate Ca2+-Dependent K+ and Anionic Currents in Intact Human Red Blood Cells

PubMed Central

Dyrda, Agnieszka; Cytlak, Urszula; Ciuraszkiewicz, Anna; Lipinska, Agnieszka; Cueff, Anne; Bouyer, Guillaume; Egée, Stéphane; Bennekou, Poul; Lew, Virgilio L.; Thomas, Serge L. Y.

2010-01-01

Background The mechanical, rheological and shape properties of red blood cells are determined by their cortical cytoskeleton, evolutionarily optimized to provide the dynamic deformability required for flow through capillaries much narrower than the cell's diameter. The shear stress induced by such flow, as well as the local membrane deformations generated in certain pathological conditions, such as sickle cell anemia, have been shown to increase membrane permeability, based largely on experimentation with red cell suspensions. We attempted here the first measurements of membrane currents activated by a local and controlled membrane deformation in single red blood cells under on-cell patch clamp to define the nature of the stretch-activated currents. Methodology/Principal Findings The cell-attached configuration of the patch-clamp technique was used to allow recordings of single channel activity in intact red blood cells. Gigaohm seal formation was obtained with and without membrane deformation. Deformation was induced by the application of a negative pressure pulse of 10 mmHg for less than 5 s. Currents were only detected when the membrane was seen domed under negative pressure within the patch-pipette. K+ and Cl− currents were strictly dependent on the presence of Ca2+. The Ca2+-dependent currents were transient, with typical decay half-times of about 5–10 min, suggesting the spontaneous inactivation of a stretch-activated Ca2+ permeability (PCa). These results indicate that local membrane deformations can transiently activate a Ca2+ permeability pathway leading to increased [Ca2+]i, secondary activation of Ca2+-sensitive K+ channels (Gardos channel, IK1, KCa3.1), and hyperpolarization-induced anion currents. Conclusions/Significance The stretch-activated transient PCa observed here under local membrane deformation is a likely contributor to the Ca2+-mediated effects observed during the normal aging process of red blood cells, and to the increased Ca2+ content of red cells in certain hereditary anemias such as thalassemia and sickle cell anemia. PMID:20195477

Local membrane deformations activate Ca2+-dependent K+ and anionic currents in intact human red blood cells.

PubMed

Dyrda, Agnieszka; Cytlak, Urszula; Ciuraszkiewicz, Anna; Lipinska, Agnieszka; Cueff, Anne; Bouyer, Guillaume; Egée, Stéphane; Bennekou, Poul; Lew, Virgilio L; Thomas, Serge L Y

2010-02-26

The mechanical, rheological and shape properties of red blood cells are determined by their cortical cytoskeleton, evolutionarily optimized to provide the dynamic deformability required for flow through capillaries much narrower than the cell's diameter. The shear stress induced by such flow, as well as the local membrane deformations generated in certain pathological conditions, such as sickle cell anemia, have been shown to increase membrane permeability, based largely on experimentation with red cell suspensions. We attempted here the first measurements of membrane currents activated by a local and controlled membrane deformation in single red blood cells under on-cell patch clamp to define the nature of the stretch-activated currents. The cell-attached configuration of the patch-clamp technique was used to allow recordings of single channel activity in intact red blood cells. Gigaohm seal formation was obtained with and without membrane deformation. Deformation was induced by the application of a negative pressure pulse of 10 mmHg for less than 5 s. Currents were only detected when the membrane was seen domed under negative pressure within the patch-pipette. K(+) and Cl(-) currents were strictly dependent on the presence of Ca(2+). The Ca(2+)-dependent currents were transient, with typical decay half-times of about 5-10 min, suggesting the spontaneous inactivation of a stretch-activated Ca(2+) permeability (PCa). These results indicate that local membrane deformations can transiently activate a Ca(2+) permeability pathway leading to increased [Ca(2+)](i), secondary activation of Ca(2+)-sensitive K(+) channels (Gardos channel, IK1, KCa3.1), and hyperpolarization-induced anion currents. The stretch-activated transient PCa observed here under local membrane deformation is a likely contributor to the Ca(2+)-mediated effects observed during the normal aging process of red blood cells, and to the increased Ca(2+) content of red cells in certain hereditary anemias such as thalassemia and sickle cell anemia.

Quench dynamics of the Josephson current in a topological Josephson junction

NASA Astrophysics Data System (ADS)

Sun, Dihao; Liu, Jie

2018-01-01

The 4 π -periodic Josephson effect is a distinguishing feature of a topological Josephson junction. However, stringent conditions make it hard to observe in experiments. In this work, we study the transient transport properties in a topological Josephson junction numerically. We show that the 4 π Josephson current can be sustained under nonequilibrium conditions. The properties of the Josephson current are analyzed for different conditions and three main regimes are identified. First, when both the superconducting wires of the Josephson junction lie in the topologically nontrivial region, a 4 π Josephson current can appear upon suddenly applying a dc voltage. Second, when one superconducting wire lies in the trivial region, while the other wire lies in the nontrivial region, the Josephson current is 2 π periodic but the component of the higher-order Josephson current increases. Third, when both wires lie in the trivial region, a stable 2 π Josephson current is observed. Most importantly, the fractional Josephson effect is fragile in the presence of disorder. Hence experiments should be designed carefully to eliminate the effect of disorder. These results could be helpful to optimize fine-tuning of the experimental parameters to observe the 4 π -periodic Josephson current in a topological Josephson junction.

A Few Examples of Spacecraft Anomalies Attributed to Transient Voltages and Currents Issues

NASA Technical Reports Server (NTRS)

Perez, Ray

2006-01-01

It is easy to address voltage and current transient related issues when the hardware in question or similar type of hardware is always available to you and when such issues are deterministic in nature. Unexpected or unforeseen transient related problems are not always a challenge but become a severe concern when a unique piece of the hardware, which developed the problem, is in space; as it is with all satellites. This paper addresses in a qualitative manner, a few examples of voltage and current events of transient origin which disabled space hardware.

Transient Electric Changes Immediately After Surgical Trauma

PubMed Central

Driban, Jeffrey B; Swanik, C. Buz; Huxel, Kellie C; Balsubramanian, Easwaran

2007-01-01

Context: Electric stimulation is frequently used to promote soft tissue healing, although we do not have a complete understanding of the tissue's electromagnetic properties. Objective: To measure the transient electric changes in skin and muscle tissue immediately after trauma. Design: 1-group time series. Setting: Climate-controlled operating room in a public urban hospital. Patients or Other Participants: Eleven participants (8 females, 3 males) with a mean age of 65.18 ± 11.36 years undergoing total hip arthroplasty. Intervention(s): An incision approximately 10 cm distal to the posterior superior iliac spine extended distally over the greater trochanter and along the lateral limb. The incision was completed in 2 cuts: (1) skin and subcutaneous fat and (2) muscle tissue. Main Outcome Measure(s): Three measurement sessions were performed with an electrometer before and after a skin incision and after a muscle incision. Potential differences and current intensity were measured immediately after acute trauma to determine the transient electric changes associated with soft tissue injury. Results: The electric potentials were significantly more negative after the skin incision (P = .036) and skin plus muscle incision (P = .008; preincision = 0.001 ± 0.015 V, skin incision = −0.127 ± 0.134 V, skin plus muscle incision = −0.192 ± 0.153V). Current intensity changed significantly after the skin plus muscle incision (P = .008; preincision = 0.046 ± 0.112 pA, skin incision = −0.803 ± 0.904 pA, skin plus muscle incision = −1.708 ± 1.302 pA). Conclusions: Soft tissue trauma generated negative transient electric changes. PMID:18174941

Evaluating transient performance of servo mechanisms by analysing stator current of PMSM

NASA Astrophysics Data System (ADS)

Zhang, Qing; Tan, Luyao; Xu, Guanghua

2018-02-01

Smooth running and rapid response are the desired performance goals for the transient motions of servo mechanisms. Because of the uncertain and unobservable transient behaviour of servo mechanisms, it is difficult to evaluate their transient performance. Under the effects of electromechanical coupling, the stator current signals of a permanent-magnet synchronous motor (PMSM) potentially contain the performance information regarding servo mechanisms in use. In this paper, a novel method based on analysing the stator current of the PMSM is proposed for quantifying the transient performance. First, a vector control model is constructed to simulate the stator current behaviour in the transient processes of consecutive speed changes, consecutive load changes, and intermittent start-stops. It is discovered that the amplitude and frequency of the stator current are modulated by the transient load torque and motor speed, respectively. The stator currents under different performance conditions are also simulated and compared. Then, the stator current is processed using a local means decomposition (LMD) algorithm to extract the instantaneous amplitude and instantaneous frequency. The sample entropy of the instantaneous amplitude, which reflects the complexity of the load torque variation, is calculated as a performance indicator of smooth running. The peak-to-peak value of the instantaneous frequency, which defines the range of the motor speed variation, is set as a performance indicator of rapid response. The proposed method is applied to both simulated data in an intermittent start-stops process and experimental data measured for a batch of servo turrets for turning lathes. The results show that the performance evaluations agree with the actual performance.

Transient Performance Improvement Circuit (TPIC)s for DC-DC converter applications

NASA Astrophysics Data System (ADS)

Lim, Sungkeun

Gordon Moore famously predicted the exponential increase in transistor integration and computing power that has been witnessed in recent decades [1]. In the near future, it is expected that more than one billion transistors will be integrated per chip, and advanced microprocessors will require clock speeds in excess of several GHz. The increasing number of transistors and high clock speeds will necessitate the consumption of more power. By 2014, it is expected that the maximum power consumption of the microprocessor will reach approximately 150W, and the maximum load current will be around 150A. Today's trend in power and thermal management is to reduce supply voltage as low as possible to reduce delivered power. It is anticipated that the Intel cores will operate on 0.8V of supply voltage by 2014 [2]. A significant challenge in Voltage Regulator Module (VRM) development for next generation microprocessors is to regulate the supply voltage within a certain tolerance band during high slew rate load transitions, since the required supply voltage tolerance band will be much narrower than the current requirement. If VR output impedance is maintained at a constant value from DC to high frequency, large output voltage spikes can be avoided during load cur- rent transients. Based on this, the Adaptive Voltage Position (AVP) concept was developed to achieve constant VR output impedance to improve transient response performance [3]. However, the VR output impedance can not be made constant over the entire frequency range with AVP design, because the AVP design makes the VR output impedance constant only at low frequencies. To make the output impedance constant at high frequencies, many bulk capacitors and ceramic capacitors are required. The tight supply voltage tolerance for the next generation of microprocessors during high slew rate load transitions requires fast transient response power supplies. A VRM can not follow the high slew rate load current transients, because of the slow inductor current slew rate which is determined by the input voltage, output voltage, and the inductance. The remaining inductor current in the power delivery path will charge the output capacitors and develop a voltage across the ESR. As a result, large output voltage spikes occur during load current transients. Due to their limited control bandwidth, traditional VRs can not sufficiently respond rapidly to certain load transients. As a result, a large output voltage spike can occur during load transients, hence requiring a large amount of bulk capacitance to decouple the VR from the load [2]. If the remaining inductor current is removed from the power stage or the inductor current slew rate is changed, the output voltage spikes can be clamped, allowing the output capacitance to be reduced. A new design methodology for a Transient Performance Improvement Circuit(TPIC) based on controlling the output impedance of a regulator is presented. The TPIC works in parallel with a voltage regulator (VR)'s ceramic capacitors to achieve faster voltage regulation without the need for a large bulk capacitance, and can serve as a replacement for bulk capacitors. The specific function of the TPIC is to mimic the behavior of the bulk capacitance in a traditional VRM by sinking and sourcing large currents during transients, allowing the VR to respond quickly to current transients without the need for a large bulk capacitance. This will allow fast transient response without the need for a large bulk capacitor. The main challenge in applying the TPIC is creating a design which will not interfere with VR operation. A TPIC for a 4 Switch Buck-Boost (4SBB) converter is presented which functions by con- trolling the inductor current slew rate during load current transients. By increasing the inductor current slew rate, the remaining inductor current can be removed from the 4SBB power delivery path and the output voltage spike can be clamped. A second TPIC is presented which is designed to improve the performance of an LDO regulator during output current transients. A TPIC for a LDO regulator is proposed to reduce the over voltage spike settling time. During a load current step down transient, the only current discharging path is a light load current. However, it takes a long time to discharge the current charged in the output capacitors with the light load current. The proposed TPIC will make an additional current discharging path to reduce the long settling time. By reducing the settling time, the load current transient frequency of the LDO regulator can be increased. A Ripple Cancellation Circuit (RCC) is proposed to reduce the output voltage ripple. The RCC has a very similar concept with the TPIC which is sinking or injecting additional current to the power stage to compensate the inductor ripple current. The proposed TPICs and RCC have been implemented with a 0.6m CMOS process. A single-phase VR, a 4SBB converter, and a LDO regulator have been utilized with the proposed TPIC to evaluate its performance. The theoretical analysis will be confirmed by Cadence simulation results and experimental results.

Transient analysis for alternating over-current characteristics of HTSC power transmission cable

NASA Astrophysics Data System (ADS)

Lim, S. H.; Hwang, S. D.

2006-10-01

In this paper, the transient analysis for the alternating over-current distribution in case that the over-current was applied for a high-TC superconducting (HTSC) power transmission cable was performed. The transient analysis for the alternating over-current characteristics of HTSC power transmission cable with multi-layer is required to estimate the redistribution of the over-current between its conducting layers and to protect the cable system from the over-current in case that the quench in one or two layers of the HTSC power cable happens. For its transient analysis, the resistance generation of the conducting layers for the alternating over-current was reflected on its equivalent circuit, based on the resistance equation obtained by applying discrete Fourier transform (DFT) for the voltage and the current waveforms of the HTSC tape, which comprises each layer of the HTSC power transmission cable. It was confirmed through the numerical analysis on its equivalent circuit that after the current redistribution from the outermost layer into the inner layers first happened, the fast current redistribution between the inner layers developed as the amplitude of the alternating over-current increased.

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.

Estimating soil hydraulic parameters from transient flow experiments in a centrifuge using parameter optimization technique

USGS Publications Warehouse

Šimůnek, Jirka; Nimmo, John R.

2005-01-01

A modified version of the Hydrus software package that can directly or inversely simulate water flow in a transient centrifugal field is presented. The inverse solver for parameter estimation of the soil hydraulic parameters is then applied to multirotation transient flow experiments in a centrifuge. Using time‐variable water contents measured at a sequence of several rotation speeds, soil hydraulic properties were successfully estimated by numerical inversion of transient experiments. The inverse method was then evaluated by comparing estimated soil hydraulic properties with those determined independently using an equilibrium analysis. The optimized soil hydraulic properties compared well with those determined using equilibrium analysis and steady state experiment. Multirotation experiments in a centrifuge not only offer significant time savings by accelerating time but also provide significantly more information for the parameter estimation procedure compared to multistep outflow experiments in a gravitational field.

How to Achieve Fast Entrainment? The Timescale to Synchronization

PubMed Central

Granada, Adrián E.; Herzel, Hanspeter

2009-01-01

Entrainment, where oscillators synchronize to an external signal, is ubiquitous in nature. The transient time leading to entrainment plays a major role in many biological processes. Our goal is to unveil the specific dynamics that leads to fast entrainment. By studying a generic model, we characterize the transient time to entrainment and show how it is governed by two basic properties of an oscillator: the radial relaxation time and the phase velocity distribution around the limit cycle. Those two basic properties are inherent in every oscillator. This concept can be applied to many biological systems to predict the average transient time to entrainment or to infer properties of the underlying oscillator from the observed transients. We found that both a sinusoidal oscillator with fast radial relaxation and a spike-like oscillator with slow radial relaxation give rise to fast entrainment. As an example, we discuss the jet-lag experiments in the mammalian circadian pacemaker. PMID:19774087

Ion track etching revisited: II. Electronic properties of aged tracks in polymers

NASA Astrophysics Data System (ADS)

Fink, D.; Muñoz Hernández, G.; Cruz, S. A.; Garcia-Arellano, H.; Vacik, J.; Hnatowicz, V.; Kiv, A.; Alfonta, L.

2018-02-01

We compile here electronic ion track etching effects, such as capacitive-type currents, current spike emission, phase shift, rectification and background currents that eventually emerge upon application of sinusoidal alternating voltages across thin, aged swift heavy ion-irradiated polymer foils during etching. Both capacitive-type currents and current spike emission occur as long as obstacles still prevent a smooth continuous charge carrier passage across the foils. In the case of sufficiently high applied electric fields, these obstacles are overcome by spike emission. These effects vanish upon etchant breakthrough. Subsequent transmitted currents are usually of Ohmic type, but shortly after breakthrough (during the track' core etching) often still exhibit deviations such as strong positive phase shifts. They stem from very slow charge carrier mobility across the etched ion tracks due to retarding trapping/detrapping processes. Upon etching the track's penumbra, one occasionally observes a split-up into two transmitted current components, one with positive and another one with negative phase shifts. Usually, these phase shifts vanish when bulk etching starts. Current rectification upon track etching is a very frequent phenomenon. Rectification uses to inverse when core etching ends and penumbra etching begins. When the latter ends, rectification largely vanishes. Occasionally, some residual rectification remains which we attribute to the aged polymeric bulk itself. Last not least, we still consider background currents which often emerge transiently during track etching. We could assign them clearly to differences in the electrochemical potential of the liquids on both sides of the etched polymer foils. Transient relaxation effects during the track etching cause their eventually chaotic behaviour.

The novel product of a five-exon stargazin-related gene abolishes CaV2.2 calcium channel expression

PubMed Central

Moss, Fraser J.; Viard, Patricia; Davies, Anthony; Bertaso, Federica; Page, Karen M.; Graham, Alex; Cantí, Carles; Plumpton, Mary; Plumpton, Christopher; Clare, Jeffrey J.; Dolphin, Annette C.

2002-01-01

We have cloned and characterized a new member of the voltage-dependent Ca2+ channel γ subunit family, with a novel gene structure and striking properties. Unlike the genes of other potential γ subunits identified by their homology to the stargazin gene, CACNG7 is a five-, and not four-exon gene whose mRNA encodes a protein we have designated γ7. Expression of human γ7 has been localized specifically to brain. N-type current through CaV2.2 channels was almost abolished when co-expressed transiently with γ7 in either Xenopus oocytes or COS-7 cells. Furthermore, immunocytochemistry and western blots show that γ7 has this effect by causing a large reduction in expression of CaV2.2 rather than by interfering with trafficking or biophysical properties of the channel. No effect of transiently expressed γ7 was observed on pre-existing endogenous N-type calcium channels in sympathetic neurones. Low homology to the stargazin-like γ subunits, different gene structure and the unique functional properties of γ7 imply that it represents a distinct subdivision of the family of proteins identified by their structural and sequence homology to stargazin. PMID:11927536

Tungsten polyoxometalate molecules as active nodes for dynamic carrier exchange in hybrid molecular/semiconductor capacitors

NASA Astrophysics Data System (ADS)

Balliou, A.; Douvas, A. M.; Normand, P.; Tsikritzis, D.; Kennou, S.; Argitis, P.; Glezos, N.

2014-10-01

In this work we study the utilization of molecular transition metal oxides known as polyoxometalates (POMs), in particular the Keggin structure anions of the formula PW12O403-, as active nodes for potential switching and/or fast writing memory applications. The active molecules are being integrated in hybrid Metal-Insulator/POM molecules-Semiconductor capacitors, which serve as prototypes allowing investigation of critical performance characteristics towards the design of more sophisticated devices. The charging ability as well as the electronic structure of the molecular layer is probed by means of electrical characterization, namely, capacitance-voltage and current-voltage measurements, as well as transient capacitance measurements, C (t), under step voltage polarization. It is argued that the transient current peaks observed are manifestations of dynamic carrier exchange between the gate electrode and specific molecular levels, while the transient C (t) curves under conditions of molecular charging can supply information for the rate of change of the charge that is being trapped and de-trapped within the molecular layer. Structural characterization via surface and cross sectional scanning electron microscopy as well as atomic force microscopy, spectroscopic ellipsometry, UV and Fourier-transform IR spectroscopies, UPS, and XPS contribute to the extraction of accurate electronic structure characteristics and open the path for the design of new devices with on-demand tuning of their interfacial properties via the controlled preparation of the POM layer.

Linear analysis of time dependent properties of Child-Langmuir flow

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

Rokhlenko, A.

We continue our analysis of the time dependent behavior of the electron flow in the Child-Langmuir system, removing an approximation used earlier. We find a modified set of oscillatory decaying modes with frequencies of the same order as the inverse of the electron transient time. This range (typically MHz) allows simple experimental detection and maybe exploitation. We then study the time evolution of the current in response to a slow change of the anode voltage where the same modes of oscillations appear too. The cathode current in this case is systematically advanced or retarded depending on the direction of themore » voltage change.« less

Linear analysis of time dependent properties of Child-Langmuir flow

NASA Astrophysics Data System (ADS)

Rokhlenko, A.

2013-01-01

We continue our analysis of the time dependent behavior of the electron flow in the Child-Langmuir system, removing an approximation used earlier. We find a modified set of oscillatory decaying modes with frequencies of the same order as the inverse of the electron transient time. This range (typically MHz) allows simple experimental detection and maybe exploitation. We then study the time evolution of the current in response to a slow change of the anode voltage where the same modes of oscillations appear too. The cathode current in this case is systematically advanced or retarded depending on the direction of the voltage change.

Cell dialysis by sharp electrodes can cause nonphysiological changes in neuron properties

PubMed Central

Hooper, Scott L.; Guschlbauer, Christoph; Schmidt, Joachim; Büschges, Ansgar

2015-01-01

We recorded from lobster and leech neurons with two sharp electrodes filled with solutions often used with these preparations (lobster: 0.6 M K2SO4 or 2.5 M KAc; leech: 4 M KAc), with solutions approximately matching neuron cytoplasm ion concentrations, and with 6.5 M KAc (lobster, leech) and 0.6 M KAc (lobster). We measured membrane potential, input resistance, and transient and sustained depolarization-activated outward current amplitudes in leech and these neuron properties and hyperpolarization-activated current time constant in lobster, every 10 min for 60 min after electrode penetration. Neuron properties varied with electrode fill. For fills with molarities ≥2.5 M, neuron properties also varied strongly with time after electrode penetration. Depending on the property being examined, these variations could be large. In leech, cell size also increased with noncytoplasmic fills. The changes in neuron properties could be due to the ions being injected from the electrodes during current injection. We tested this possibility in lobster with the 2.5 M KAc electrode fill by making measurements only 10 and 60 min after penetration. Neuron properties still changed, although the changes were less extreme. Making measurements every 2 min showed that the time-dependent variations in neuron properties occurred in concert with each other. Neuron property changes with high molarity electrode-fill solutions were great enough to decrease neuron firing strongly. An experiment with 14C-glucose electrode fill confirmed earlier work showing substantial leak from sharp electrodes. Sharp electrode work should thus be performed with cytoplasm-matched electrode fills. PMID:26063785

Cell dialysis by sharp electrodes can cause nonphysiological changes in neuron properties.

PubMed

Hooper, Scott L; Thuma, Jeffrey B; Guschlbauer, Christoph; Schmidt, Joachim; Büschges, Ansgar

2015-08-01

We recorded from lobster and leech neurons with two sharp electrodes filled with solutions often used with these preparations (lobster: 0.6 M K2SO4 or 2.5 M KAc; leech: 4 M KAc), with solutions approximately matching neuron cytoplasm ion concentrations, and with 6.5 M KAc (lobster, leech) and 0.6 M KAc (lobster). We measured membrane potential, input resistance, and transient and sustained depolarization-activated outward current amplitudes in leech and these neuron properties and hyperpolarization-activated current time constant in lobster, every 10 min for 60 min after electrode penetration. Neuron properties varied with electrode fill. For fills with molarities ≥2.5 M, neuron properties also varied strongly with time after electrode penetration. Depending on the property being examined, these variations could be large. In leech, cell size also increased with noncytoplasmic fills. The changes in neuron properties could be due to the ions being injected from the electrodes during current injection. We tested this possibility in lobster with the 2.5 M KAc electrode fill by making measurements only 10 and 60 min after penetration. Neuron properties still changed, although the changes were less extreme. Making measurements every 2 min showed that the time-dependent variations in neuron properties occurred in concert with each other. Neuron property changes with high molarity electrode-fill solutions were great enough to decrease neuron firing strongly. An experiment with (14)C-glucose electrode fill confirmed earlier work showing substantial leak from sharp electrodes. Sharp electrode work should thus be performed with cytoplasm-matched electrode fills. Copyright © 2015 the American Physiological Society.

Supplementation of exogenous adenosine 5'-triphosphate enhances mechanical properties of 3D cell-agarose constructs for cartilage tissue engineering.

PubMed

Gadjanski, Ivana; Yodmuang, Supansa; Spiller, Kara; Bhumiratana, Sarindr; Vunjak-Novakovic, Gordana

2013-10-01

Formation of tissue-engineered cartilage is greatly enhanced by mechanical stimulation. However, direct mechanical stimulation is not always a suitable method, and the utilization of mechanisms underlying mechanotransduction might allow for a highly effective and less aggressive alternate means of stimulation. In particular, the purinergic, adenosine 5'-triphosphate (ATP)-mediated signaling pathway is strongly implicated in mechanotransduction within the articular cartilage. We investigated the effects of transient and continuous exogenous ATP supplementation on mechanical properties of cartilaginous constructs engineered using bovine chondrocytes and human mesenchymal stem cells (hMSCs) encapsulated in an agarose hydrogel. For both cell types, we have observed significant increases in equilibrium and dynamic compressive moduli after transient ATP treatment applied in the fourth week of cultivation. Continuous ATP treatment over 4 weeks of culture only slightly improved the mechanical properties of the constructs, without major changes in the total glycosaminoglycan (GAG) and collagen content. Structure-function analyses showed that transiently ATP-treated constructs, and in particular those based on hMSCs, had the highest level of correlation between compositional and mechanical properties. Transiently treated groups showed intense staining of the territorial matrix for GAGs and collagen type II. These results indicate that transient ATP treatment can improve functional mechanical properties of cartilaginous constructs based on chondrogenic cells and agarose hydrogels, possibly by improving the structural organization of the bulk phase and territorial extracellular matrix (ECM), that is, by increasing correlation slopes between the content of the ECM components (GAG, collagen) and mechanical properties of the construct.

Model-based elastography: a survey of approaches to the inverse elasticity problem

PubMed Central

Doyley, M M

2012-01-01

Elastography is emerging as an imaging modality that can distinguish normal versus diseased tissues via their biomechanical properties. This article reviews current approaches to elastography in three areas — quasi-static, harmonic, and transient — and describes inversion schemes for each elastographic imaging approach. Approaches include: first-order approximation methods; direct and iterative inversion schemes for linear elastic; isotropic materials; and advanced reconstruction methods for recovering parameters that characterize complex mechanical behavior. The paper’s objective is to document efforts to develop elastography within the framework of solving an inverse problem, so that elastography may provide reliable estimates of shear modulus and other mechanical parameters. We discuss issues that must be addressed if model-based elastography is to become the prevailing approach to quasi-static, harmonic, and transient elastography: (1) developing practical techniques to transform the ill-posed problem with a well-posed one; (2) devising better forward models to capture the transient behavior of soft tissue; and (3) developing better test procedures to evaluate the performance of modulus elastograms. PMID:22222839

Fabrication of porous anodic alumina using normal anodization and pulse anodization

NASA Astrophysics Data System (ADS)

Chin, I. K.; Yam, F. K.; Hassan, Z.

2015-05-01

This article reports on the fabrication of porous anodic alumina (PAA) by two-step anodizing the low purity commercial aluminum sheets at room temperature. Different variations of the second-step anodization were conducted: normal anodization (NA) with direct current potential difference; pulse anodization (PA) alternate between potential differences of 10 V and 0 V; hybrid pulse anodization (HPA) alternate between potential differences of 10 V and -2 V. The method influenced the film homogeneity of the PAA and the most homogeneous structure was obtained via PA. The morphological properties are further elucidated using measured current-transient profiles. The absent of current rise profile in PA indicates the anodization temperature and dissolution of the PAA structure were greatly reduced by alternating potential differences.

Effects of interfacial stability between electron transporting layer and cathode on the degradation process of organic light-emitting diodes

NASA Astrophysics Data System (ADS)

Chu, Ta-Ya; Lee, Yong-Han; Song, Ok-Keun

2007-11-01

The authors have demonstrated that the increase of electron injection barrier height between tris(8-hydroxyquinoline)aluminum (Alq3) and LiF /Al cathode is one of the most critical parameters to determine the reliability of organic light-emitting diode with the typical structure of indium tin oxide/N ,N'-bis(naphthalen-1-yl)-N ,N'-bis(phenyl) benzidine/Alq3/LiF /Al. The electrical properties of several devices (hole only, electron only, and integrated double-layered devices) have been measured in the function of operating time to analyze the bulk and interface property changes. Bulk properties of trap energy and mobility in an organic layer have been estimated by using trap-charge-limited currents and transient electroluminescence measurements.

Lightning induced currents in aircraft wiring using low level injection techniques

NASA Technical Reports Server (NTRS)

Stevens, E. G.; Jordan, D. T.

1991-01-01

Various techniques were studied to predict the transient current induced into aircraft wiring bundles as a result of an aircraft lightning strike. A series of aircraft measurements were carried out together with a theoretical analysis using computer modeling. These tests were applied to various aircraft and also to specially constructed cylinders installed within coaxial return conductor systems. Low level swept frequency CW (carrier waves), low level transient and high level transient injection tests were applied to the aircraft and cylinders. Measurements were made to determine the transfer function between the aircraft drive current and the resulting skin currents and currents induced on the internal wiring. The full threat lightning induced transient currents were extrapolated from the low level data using Fourier transform techniques. The aircraft and cylinders used were constructed from both metallic and CFC (carbon fiber composite) materials. The results show the pulse stretching phenomenon which occurs for CFC materials due to the diffusion of the lightning current through carbon fiber materials. Transmission Line Matrix modeling techniques were used to compare theoretical and measured currents.

HIRAX: a probe of dark energy and radio transients

NASA Astrophysics Data System (ADS)

Newburgh, L. B.; Bandura, K.; Bucher, M. A.; Chang, T.-C.; Chiang, H. C.; Cliche, J. F.; Davé, R.; Dobbs, M.; Clarkson, C.; Ganga, K. M.; Gogo, T.; Gumba, A.; Gupta, N.; Hilton, M.; Johnstone, B.; Karastergiou, A.; Kunz, M.; Lokhorst, D.; Maartens, R.; Macpherson, S.; Mdlalose, M.; Moodley, K.; Ngwenya, L.; Parra, J. M.; Peterson, J.; Recnik, O.; Saliwanchik, B.; Santos, M. G.; Sievers, J. L.; Smirnov, O.; Stronkhorst, P.; Taylor, R.; Vanderlinde, K.; Van Vuuren, G.; Weltman, A.; Witzemann, A.

2016-08-01

The Hydrogen Intensity and Real-time Analysis eXperiment (HIRAX) is a new 400{800MHz radio interferometer under development for deployment in South Africa. HIRAX will comprise 1024 six meter parabolic dishes on a compact grid and will map most of the southern sky over the course of four years. HIRAX has two primary science goals: to constrain Dark Energy and measure structure at high redshift, and to study radio transients and pulsars. HIRAX will observe unresolved sources of neutral hydrogen via their redshifted 21-cm emission line (`hydrogen intensity mapping'). The resulting maps of large-scale structure at redshifts 0.8{2.5 will be used to measure Baryon Acoustic Oscillations (BAO). BAO are a preferential length scale in the matter distribution that can be used to characterize the expansion history of the Universe and thus understand the properties of Dark Energy. HIRAX will improve upon current BAO measurements from galaxy surveys by observing a larger cosmological volume (larger in both survey area and redshift range) and by measuring BAO at higher redshift when the expansion of the universe transitioned to Dark Energy domination. HIRAX will complement CHIME, a hydrogen intensity mapping experiment in the Northern Hemisphere, by completing the sky coverage in the same redshift range. HIRAX's location in the Southern Hemisphere also allows a variety of cross-correlation measurements with large-scale structure surveys at many wavelengths. Daily maps of a few thousand square degrees of the Southern Hemisphere, encompassing much of the Milky Way galaxy, will also open new opportunities for discovering and monitoring radio transients. The HIRAX correlator will have the ability to rapidly and efficiently detect transient events. This new data will shed light on the poorly understood nature of fast radio bursts (FRBs), enable pulsar monitoring to enhance long-wavelength gravitational wave searches, and provide a rich data set for new radio transient phenomena searches. This paper discusses the HIRAX instrument, science goals, and current status.

Activation of Mechanosensitive Transient Receptor Potential/Piezo Channels in Odontoblasts Generates Action Potentials in Cocultured Isolectin B4-negative Medium-sized Trigeminal Ganglion Neurons.

PubMed

Sato, Masaki; Ogura, Kazuhiro; Kimura, Maki; Nishi, Koichi; Ando, Masayuki; Tazaki, Masakazu; Shibukawa, Yoshiyuki

2018-06-01

Various stimuli to the dentin surface elicit dentinal pain by inducing dentinal fluid movement causing cellular deformation in odontoblasts. Although odontoblasts detect deformation by the activation of mechanosensitive ionic channels, it is still unclear whether odontoblasts are capable of establishing neurotransmission with myelinated A delta (Aδ) neurons. Additionally, it is still unclear whether these neurons evoke action potentials by neurotransmitters from odontoblasts to mediate sensory transduction in dentin. Thus, we investigated evoked inward currents and evoked action potentials form trigeminal ganglion (TG) neurons after odontoblast mechanical stimulation. We used patch clamp recordings to identify electrophysiological properties and record evoked responses in TG neurons. We classified TG cells into small-sized and medium-sized neurons. In both types of neurons, we observed voltage-dependent inward currents. The currents from medium-sized neurons showed fast inactivation kinetics. When mechanical stimuli were applied to odontoblasts, evoked inward currents were recorded from medium-sized neurons. Antagonists for the ionotropic adenosine triphosphate receptor (P2X 3 ), transient receptor potential channel subfamilies, and Piezo1 channel significantly inhibited these inward currents. Mechanical stimulation to odontoblasts also generated action potentials in the isolectin B 4 -negative medium-sized neurons. Action potentials in these isolectin B 4 -negative medium-sized neurons showed a short duration. Overall, electrophysiological properties of neurons indicate that the TG neurons with recorded evoked responses after odontoblast mechanical stimulation were myelinated Aδ neurons. Odontoblasts established neurotransmission with myelinated Aδ neurons via P2X 3 receptor activation. The results also indicated that mechanosensitive TRP/Piezo1 channels were functionally expressed in odontoblasts. The activation of P2X 3 receptors induced an action potential in the Aδ neurons, underlying a sensory generation mechanism of dentinal pain. Copyright © 2018 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.

Tutorial: Junction spectroscopy techniques and deep-level defects in semiconductors

NASA Astrophysics Data System (ADS)

Peaker, A. R.; Markevich, V. P.; Coutinho, J.

2018-04-01

The term junction spectroscopy embraces a wide range of techniques used to explore the properties of semiconductor materials and semiconductor devices. In this tutorial review, we describe the most widely used junction spectroscopy approaches for characterizing deep-level defects in semiconductors and present some of the early work on which the principles of today's methodology are based. We outline ab-initio calculations of defect properties and give examples of how density functional theory in conjunction with formation energy and marker methods can be used to guide the interpretation of experimental results. We review recombination, generation, and trapping of charge carriers associated with defects. We consider thermally driven emission and capture and describe the techniques of Deep Level Transient Spectroscopy (DLTS), high resolution Laplace DLTS, admittance spectroscopy, and scanning DLTS. For the study of minority carrier related processes and wide gap materials, we consider Minority Carrier Transient Spectroscopy (MCTS), Optical DLTS, and deep level optical transient spectroscopy together with some of their many variants. Capacitance, current, and conductance measurements enable carrier exchange processes associated with the defects to be detected. We explain how these methods are used in order to understand the behaviour of point defects and the determination of charge states and negative-U (Hubbard correlation energy) behaviour. We provide, or reference, examples from a wide range of materials including Si, SiGe, GaAs, GaP, GaN, InGaN, InAlN, and ZnO.

How animals move along? Exactly solvable model of superdiffusive spread resulting from animal's decision making.

PubMed

Tilles, Paulo F C; Petrovskii, Sergei V

2016-07-01

Patterns of individual animal movement have been a focus of considerable attention recently. Of particular interest is a question how different macroscopic properties of animal dispersal result from the stochastic processes occurring on the microscale of the individual behavior. In this paper, we perform a comprehensive analytical study of a model where the animal changes the movement velocity as a result of its behavioral response to environmental stochasticity. The stochasticity is assumed to manifest itself through certain signals, and the animal modifies its velocity as a response to the signals. We consider two different cases, i.e. where the change in the velocity is or is not correlated to its current value. We show that in both cases the early, transient stage of the animal movement is super-diffusive, i.e. ballistic. The large-time asymptotic behavior appears to be diffusive in the uncorrelated case but super-ballistic in the correlated case. We also calculate analytically the dispersal kernel of the movement and show that, whilst it converge to a normal distribution in the large-time limit, it possesses a fatter tail during the transient stage, i.e. at early and intermediate time. Since the transients are known to be highly relevant in ecology, our findings may indicate that the fat tails and superdiffusive spread that are sometimes observed in the movement data may be a feature of the transitional dynamics rather than an inherent property of the animal movement.

Investigations of an Environmentally Induced Long Duration Hall Thruster Start Transient (PREPRINT)

DTIC Science & Technology

2006-02-06

Hall thruster start transient is produced by exposure of the thruster to ambient laboratory atmosphere. This behavior was first observed during operation of a cluster of four 200 W BHT-200 Hall effect thrusters where large anode discharge fluctuations, visible as increased anode current and a diffuse plume structure, occurred in an apparently random manner. During operation of a single thruster, the start transient appears as a quickly rising and later smoothly decaying elevated anode current with a diffuse plume that persists for less than 500 seconds. The start transient

Origin of switching current transients in TIPS-pentacene based organic thin-film transistor with polymer dielectric

NASA Astrophysics Data System (ADS)

Singh, Subhash; Mohapatra, Y. N.

2017-06-01

We have investigated switch-on drain-source current transients in fully solution-processed thin film transistors based on 6,13-bis(triisopropylsilylethynyl) pentacene (TIPS-pentacene) using cross-linked poly-4-vinylphenol as a dielectric. We show that the nature of the transient (increasing or decreasing) depends on both the temperature and the amplitude of the switching pulse at the gate. The isothermal transients are analyzed spectroscopically in a time domain to extract the degree of non-exponentiality and its possible origin in trap kinetics. We propose a phenomenological model in which the exchange of electrons between interfacial ions and traps controls the nature of the drain current transients dictated by the Fermi level position. The origin of interfacial ions is attributed to the essential fabrication step of UV-ozone treatment of the dielectric prior to semiconductor deposition.

Photoinduced current transient spectroscopy of deep levels and transport mechanisms in iron-doped GaN thin films grown by low pressure-metalorganic vapor phase epitaxy

NASA Astrophysics Data System (ADS)

Muret, P.; Pernot, J.; Azize, M.; Bougrioua, Z.

2007-09-01

Electrical transport and deep levels are investigated in GaN:Fe layers epitaxially grown on sapphire by low pressure metalorganic vapor phase epitaxy. Photoinduced current transient spectroscopy and current detected deep level spectroscopy are performed between 200 and 650 K on three Fe-doped samples and an undoped sample. A detailed study of the detected deep levels assigns dominant centers to a deep donor 1.39 eV below the conduction band edge EC and to a deep acceptor 0.75 eV above the valence band edge EV at low electric field. A strong Poole-Frenkel effect is evidenced for the donor. Schottky diodes characteristics and transport properties in the bulk GaN:Fe layer containing a homogenous concentration of 1019 Fe/cm3 are typical of a compensated semiconductor. They both indicate that the bulk Fermi level is located typically 1.4 eV below EC, in agreement with the neutrality equation and dominance of the deep donor concentration. This set of results demonstrates unambiguously that electrical transport in GaN:Fe is governed by both types, either donor or acceptor, of the iron impurity, either substitutional in gallium sites or associated with other defects.

Enhanced simulation software for rocket turbopump, turbulent, annular liquid seals

NASA Technical Reports Server (NTRS)

Padavala, Satya; Palazzolo, Alan

1994-01-01

One of the main objectives of this work is to develop a new dynamic analysis for liquid annular seals with arbitrary profile and to analyze a general distorted interstage seal of the space shuttle main engine high pressure oxygen turbopump (SSME-ATD-HPOTP). The dynamic analysis developed is based on a method originally proposed by Nelson and Nguyen. A simpler scheme based on cubic splines is found to be computationally more efficient and has better convergence properties at higher eccentricities. The first order solution of the original analysis is modified by including a more exact solution that takes into account the variation of perturbed variables along the circumference. A new set of equations for dynamic analysis are derived based on this more general model. A unified solution procedure that is valid for both Moody's and Hirs' friction models is presented. Dynamic analysis is developed for three different models: constant properties, variable properties, and thermal effects with variable properties. Arbitrarily varying seal profiles in both axial and circumferential directions are considered. An example case of an elliptical seal with varying degrees of axial curvature is analyzed in detail. A case study based on predicted clearances of an interstage seal of the SSME-ATD-HPOTP is presented. Dynamic coefficients based on external specified load are introduced to analyze seals that support a preload. The other objective of this work is to study the effect of large rotor displacements of SSME-ATD-HPOTP on the dynamics of the annular seal and the resulting transient motion. One task is to identify the magnitude of motion of the rotor about the centered position and establish limits of effectiveness of using current linear models. This task is accomplished by solving the bulk flow model seal governing equations directly for transient seal forces for any given type of motion, including motion with large eccentricities. Based on the above study, an equivalence is established between linearized coefficients based transient motion and the same motion as predicted by the original governing equations. An innovative method is developed to model nonlinearities in an annular seal based on dynamic coefficients computed at various static eccentricities. This method is thoroughly tested for various types of transient motion using bulk flow model results as a benchmark.

EFFECTS OF A TRANSIENT CANCER SCARE ON PROPERTY VALUES: IMPLICATIONS FOR RISK VALUATION AND THE VALUE OF LIFE. (R825173)

EPA Science Inventory

Abstract

A transient cancer scare is presented as a rare opportunity to observe the effect of a perceived increase in risk on the price of residential property. The temporary nature of the perceived excess risk allows for the isolation of a risk premium from the change...

Cardiac transient outward potassium current: a pulse chemistry model of frequency-dependent properties.

PubMed

Liu, L; Krinsky, V I; Grant, A O; Starmer, C F

1996-01-01

Recent voltage-clamp studies of isolated myocytes have demonstrated widespread occurrence of a transient outward current (I(to)) carried by potassium ions. In the canine ventricle, this current is well developed in epicardial cells but not in endocardial cells. The resultant spatial dispersion of refractoriness is potentially proarrhythmic and may be amplified by channel blockade. The inactivation and recovery time constants of this channel are in excess of several hundred milliseconds, and consequently channel availability is frequency dependent at physiological stimulation rates. When the time constants associated with transitions between different channel conformations are rapid relative to drug binding kinetics, the interactions between drugs and an ion channel can be approximated by a sequence of first-order reactions, in which binding occurs in pulses in response to pulse train stimulation (pulse chemistry). When channel conformation transition time constants do not meet this constraint, analytical characterizations of the drug-channel interaction must then be modified to reflect the channel time-dependent properties. Here we report that the rate and steady-state amount of frequency-dependent inactivation of I(to) are consistent with a generalization of the channel blockade model: channel availability is reduced in a pulsatile exponential pattern as the stimulation frequency is increased, and the rate of reduction is a linear function of the pulse train depolarizing and recovery intervals. I(to) was reduced in the presence of quinidine. After accounting for the use-dependent availability of I(to) channels, we found little evidence of an additional use-dependent component of block after exposure to quinidine, suggesting that quinidine reacts with both open and closed I(to) channels as though the binding site is continuously accessible. The model provides a useful tool for assessing drug-channel interactions when the reaction cannot be continuously monitored.

Imaging mitochondrial flux in single cells with a FRET sensor for pyruvate.

PubMed

San Martín, Alejandro; Ceballo, Sebastián; Baeza-Lehnert, Felipe; Lerchundi, Rodrigo; Valdebenito, Rocío; Contreras-Baeza, Yasna; Alegría, Karin; Barros, L Felipe

2014-01-01

Mitochondrial flux is currently accessible at low resolution. Here we introduce a genetically-encoded FRET sensor for pyruvate, and methods for quantitative measurement of pyruvate transport, pyruvate production and mitochondrial pyruvate consumption in intact individual cells at high temporal resolution. In HEK293 cells, neurons and astrocytes, mitochondrial pyruvate uptake was saturated at physiological levels, showing that the metabolic rate is determined by intrinsic properties of the organelle and not by substrate availability. The potential of the sensor was further demonstrated in neurons, where mitochondrial flux was found to rise by 300% within seconds of a calcium transient triggered by a short theta burst, while glucose levels remained unaltered. In contrast, astrocytic mitochondria were insensitive to a similar calcium transient elicited by extracellular ATP. We expect the improved resolution provided by the pyruvate sensor will be of practical interest for basic and applied researchers interested in mitochondrial function.

Solar Coronal Jets: Observations, Theory, and Modeling

NASA Technical Reports Server (NTRS)

Raouafi, N. E.; Patsourakos, S.; Pariat, E.; Young, P. R.; Sterling, A. C.; Savcheva, A.; Shimojo, M.; Moreno-Insertis, F.; DeVore, C. R.; Archontis, V.;

Imaging Mitochondrial Flux in Single Cells with a FRET Sensor for Pyruvate

PubMed Central

Baeza-Lehnert, Felipe; Lerchundi, Rodrigo; Valdebenito, Rocío; Contreras-Baeza, Yasna; Alegría, Karin; Barros, L. Felipe

2014-01-01

Mitochondrial flux is currently accessible at low resolution. Here we introduce a genetically-encoded FRET sensor for pyruvate, and methods for quantitative measurement of pyruvate transport, pyruvate production and mitochondrial pyruvate consumption in intact individual cells at high temporal resolution. In HEK293 cells, neurons and astrocytes, mitochondrial pyruvate uptake was saturated at physiological levels, showing that the metabolic rate is determined by intrinsic properties of the organelle and not by substrate availability. The potential of the sensor was further demonstrated in neurons, where mitochondrial flux was found to rise by 300% within seconds of a calcium transient triggered by a short theta burst, while glucose levels remained unaltered. In contrast, astrocytic mitochondria were insensitive to a similar calcium transient elicited by extracellular ATP. We expect the improved resolution provided by the pyruvate sensor will be of practical interest for basic and applied researchers interested in mitochondrial function. PMID:24465702

An investigation of transient pressures and plasma properties in a pinched plasma column. M.S. Thesis

NASA Technical Reports Server (NTRS)

Stover, E. K.; York, T. M.

1971-01-01

The transient pinched plasma column generated in a linear Z-pinch was studied experimentally and analytically. The plasma column was investigated experimentally with several plasma diagnostics; they were: a rapid response pressure transducer, a magnetic field probe, a voltage probe, and discharge luminosity. Axial pressure profiles on the discharge chamber axis were used to identify three characteristic regions of plasma column behavior: (1) strong axial pressure asymmetry noted early in plasma column lifetime, (2) followed by plasma heating in which there is a rapid rise in static pressure, and (3) a slight decrease static pressure before plasma column breakup. Plasma column lifetime was approximately 5 microseconds. The axial pressure asymmetry was attributed to nonsimultaneous pinching of the imploding current sheet along the discharge chamber axis. The rapid heating could be attributed in part to viscous effects introduced by radial gradients in the axial streaming velocity.

Solar Coronal Jets: Observations, Theory, and Modeling

NASA Technical Reports Server (NTRS)

Raouafi, N. E.; Patsourakos, S.; Pariat, E.; Young, P. R.; Sterling, A.; Savcheva, A.; Shimojo, M.; Moreno-Insertis, F.; Devore, C. R.; Archontis, V.;

Magnetic thin-film split-domain current sensor-recorder

DOEpatents

Hsieh, Edmund J.

1979-01-01

A sensor-recorder for recording a representation of the direction and peak amplitude of a transient current. A magnetic thin film is coated on a glass substrate under the influence of a magnetic field so that the finished film is magnetically uniaxial and anisotropic. The film is split into two oppositely magnetized contiguous domains with a central boundary by subjecting adjacent portions of the film simultaneously to magnetic fields that are opposed 180.degree.. With the split-domain sensor-recorder placed with the film plane and domain boundary either perpendicular or parallel to the expected conductive path of a transient current, the occurrence of the transient causes switching of a portion of one domain to the direction of the other domain. The amount of the switched domain portion is indicative of the amplitude of the peak current of the transient, while the particular domain that is switched is indicative of the direction of the current. The resulting domain patterns may be read with a passive magnetic tape viewer.

A universal procedure for evaluation and application of surge-protective devices

NASA Technical Reports Server (NTRS)

1980-01-01

The source, nature, and frequency of occurrence of transients must be identified and a representative standard test wave chosen for proof testing. The performance of candidate suppressor devices then can be evaluated against the withstand goals set for the equipment. The various suppressors divide into two classes of generic behavior. The key to a universal procedure for evaluating both classes lies in representing transients as quasi-current sources of defined current impulse duration. The available surge current is established by the Thevenin equivalent transient voltage and source impedance. A load line drawn on the V-I characteristic graph of the suppressor quickly determines the clamping voltage and peak current. These values then can be compared to the requirement. The deposited energy and average power dissipation for multiple transients also can be calculated. The method is illustrated with a design example for motor vehicle alternator load dump suppression.

MIS capacitor studies on silicon carbide single crystals

NASA Technical Reports Server (NTRS)

Kopanski, J. J.

1990-01-01

Cubic SIC metal-insulator-semiconductor (MIS) capacitors with thermally grown or chemical-vapor-deposited (CVD) insulators were characterized by capacitance-voltage (C-V), conductance-voltage (G-V), and current-voltage (I-V) measurements. The purpose of these measurements was to determine the four charge densities commonly present in an MIS capacitor (oxide fixed charge, N(f); interface trap level density, D(it); oxide trapped charge, N(ot); and mobile ionic charge, N(m)) and to determine the stability of the device properties with electric-field stress and temperature. The section headings in the report include the following: Capacitance-voltage and conductance-voltage measurements; Current-voltage measurements; Deep-level transient spectroscopy; and Conclusions (Electrical characteristics of SiC MIS capacitors).

Hyperexcitability of bladder afferent neurons associated with reduction of Kv1.4 α-subunit in rats with spinal cord injury.

PubMed

Takahashi, Ryosuke; Yoshizawa, Tsuyoshi; Yunoki, Takakazu; Tyagi, Pradeep; Naito, Seiji; de Groat, William C; Yoshimura, Naoki

2013-12-01

To clarify the functional and molecular mechanisms inducing hyperexcitability of C-fiber bladder afferent pathways after spinal cord injury we examined changes in the electrophysiological properties of bladder afferent neurons, focusing especially on voltage-gated K channels. Freshly dissociated L6-S1 dorsal root ganglion neurons were prepared from female spinal intact and spinal transected (T9-T10 transection) Sprague Dawley® rats. Whole cell patch clamp recordings were performed on individual bladder afferent neurons. Kv1.2 and Kv1.4 α-subunit expression levels were also evaluated by immunohistochemical and real-time polymerase chain reaction methods. Capsaicin sensitive bladder afferent neurons from spinal transected rats showed increased cell excitability, as evidenced by lower spike activation thresholds and a tonic firing pattern. The peak density of transient A-type K+ currents in capsaicin sensitive bladder afferent neurons from spinal transected rats was significantly less than that from spinal intact rats. Also, the KA current inactivation curve was displaced to more hyperpolarized levels after spinal transection. The protein and mRNA expression of Kv1.4 α-subunits, which can form transient A-type K+ channels, was decreased in bladder afferent neurons after spinal transection. Results indicate that the excitability of capsaicin sensitive C-fiber bladder afferent neurons is increased in association with reductions in transient A-type K+ current density and Kv1.4 α-subunit expression in injured rats. Thus, the Kv1.4 α-subunit could be a molecular target for treating overactive bladder due to neurogenic detrusor overactivity. Copyright © 2013 American Urological Association Education and Research, Inc. Published by Elsevier Inc. All rights reserved.

A calibration-free electrode compensation method

PubMed Central

Rossant, Cyrille; Fontaine, Bertrand; Magnusson, Anna K.

2012-01-01

In a single-electrode current-clamp recording, the measured potential includes both the response of the membrane and that of the measuring electrode. The electrode response is traditionally removed using bridge balance, where the response of an ideal resistor representing the electrode is subtracted from the measurement. Because the electrode is not an ideal resistor, this procedure produces capacitive transients in response to fast or discontinuous currents. More sophisticated methods exist, but they all require a preliminary calibration phase, to estimate the properties of the electrode. If these properties change after calibration, the measurements are corrupted. We propose a compensation method that does not require preliminary calibration. Measurements are compensated offline by fitting a model of the neuron and electrode to the trace and subtracting the predicted electrode response. The error criterion is designed to avoid the distortion of compensated traces by spikes. The technique allows electrode properties to be tracked over time and can be extended to arbitrary models of electrode and neuron. We demonstrate the method using biophysical models and whole cell recordings in cortical and brain-stem neurons. PMID:22896724

A novel transient rotor current control scheme of a doubly-fed induction generator equipped with superconducting magnetic energy storage for voltage and frequency support

NASA Astrophysics Data System (ADS)

Shen, Yang-Wu; Ke, De-Ping; Sun, Yuan-Zhang; Daniel, Kirschen; Wang, Yi-Shen; Hu, Yuan-Chao

2015-07-01

A novel transient rotor current control scheme is proposed in this paper for a doubly-fed induction generator (DFIG) equipped with a superconducting magnetic energy storage (SMES) device to enhance its transient voltage and frequency support capacity during grid faults. The SMES connected to the DC-link capacitor of the DFIG is controlled to regulate the transient dc-link voltage so that the whole capacity of the grid side converter (GSC) is dedicated to injecting reactive power to the grid for the transient voltage support. However, the rotor-side converter (RSC) has different control tasks for different periods of the grid fault. Firstly, for Period I, the RSC injects the demagnetizing current to ensure the controllability of the rotor voltage. Then, since the dc stator flux degenerates rapidly in Period II, the required demagnetizing current is low in Period II and the RSC uses the spare capacity to additionally generate the reactive (priority) and active current so that the transient voltage capability is corroborated and the DFIG also positively responds to the system frequency dynamic at the earliest time. Finally, a small amount of demagnetizing current is provided after the fault clearance. Most of the RSC capacity is used to inject the active current to further support the frequency recovery of the system. Simulations are carried out on a simple power system with a wind farm. Comparisons with other commonly used control methods are performed to validate the proposed control method. Project supported by the National Natural Science Foundation of China (Grant No. 51307124) and the Major Program of the National Natural Science Foundation of China (Grant No. 51190105).

Emergence of currents as a transient quantum effect in nonequilibrium systems

NASA Astrophysics Data System (ADS)

Granot, Er'El; Marchewka, Avi

2011-09-01

Most current calculations are based on equilibrium or semi-equilibrium models. However, except for very special scenarios (like ring configuration), the current cannot exist in equilibrium. Moreover, unlike with equilibrium scenarios, there is no generic approach to confront out-of-equilibrium currents. In this paper we used recent studies on transient quantum mechanics to solve the current, which appears in the presence of very high density gradients and fast transients. It shows that the emerging current appears instantaneously, and although the density beyond the discontinuity is initially negligible the currents there have a finite value, and remain constant for a finite period. It is shown that this nonequilibrium effect can be measured in real experiments (such as cooled rubidium atoms), where the discontinuity is replaced with a finite width (hundreds of nanometers) gradient.

The joy of transient chaos.

PubMed

Tél, Tamás

2015-09-01

We intend to show that transient chaos is a very appealing, but still not widely appreciated, subfield of nonlinear dynamics. Besides flashing its basic properties and giving a brief overview of the many applications, a few recent transient-chaos-related subjects are introduced in some detail. These include the dynamics of decision making, dispersion, and sedimentation of volcanic ash, doubly transient chaos of undriven autonomous mechanical systems, and a dynamical systems approach to energy absorption or explosion.

A Role for DPPX Modulating External TEA Sensitivity of Kv4 Channels

PubMed Central

Colinas, Olaia; Pérez-Carretero, Francisco D.; López-López, José R.; Pérez-García, M. Teresa

2008-01-01

Shal-type (Kv4) channels are expressed in a large variety of tissues, where they contribute to transient voltage-dependent K+ currents. Kv4 are the molecular correlate of the A-type current of neurons (ISA), the fast component of ITO current in the heart, and also of the oxygen-sensitive K+ current (KO2) in rabbit carotid body (CB) chemoreceptor cells. The enormous degree of variability in the physiological properties of Kv4-mediated currents can be attributable to the complexity of their regulation together with the large number of ancillary subunits and scaffolding proteins that associate with Kv4 proteins to modify their trafficking and their kinetic properties. Among those, KChIPs and DPPX proteins have been demonstrated to be integral components of ISA and ITO currents, as their coexpression with Kv4 subunits recapitulates the kinetics of native currents. Here, we explore the presence and functional contribution of DPPX to KO2 currents in rabbit CB chemoreceptor cells by using DPPX functional knockdown with siRNA. Additionally, we investigate if the presence of DPPX endows Kv4 channels with new pharmacological properties, as we have observed anomalous tetraethylammonium (TEA) sensitivity in the native KO2 currents. DPPX association with Kv4 channels induced an increased TEA sensitivity both in heterologous expression systems and in CB chemoreceptor cells. Moreover, TEA application to Kv4-DPPX heteromultimers leads to marked kinetic effects that could be explained by an augmented closed-state inactivation. Our data suggest that DPPX proteins are integral components of KO2 currents, and that their association with Kv4 subunits modulate the pharmacological profile of the heteromultimers. PMID:18411327

Transitional circuitry for studying the properties of DNA

NASA Astrophysics Data System (ADS)

Trubochkina, N.

2018-01-01

The article is devoted to a new view of the structure of DNA as an intellectual scheme possessing the properties of logic and memory. The theory of transient circuitry, developed by the author for optimal computer circuits, revealed an amazing structural similarity between mathematical models of transition silicon elements and logic and memory circuits of solid state transient circuitry and atomic models of parts of DNA.

A transient laboratory method for determining the hydraulic properties of 'tight' rocks-I. Theory

USGS Publications Warehouse

Hsieh, P.A.; Tracy, J.V.; Neuzil, C.E.; Bredehoeft, J.D.; Silliman, Stephen E.

1981-01-01

Transient pulse testing has been employed increasingly in the laboratory to measure the hydraulic properties of rock samples with low permeability. Several investigators have proposed a mathematical model in terms of an initial-boundary value problem to describe fluid flow in a transient pulse test. However, the solution of this problem has not been available. In analyzing data from the transient pulse test, previous investigators have either employed analytical solutions that are derived with the use of additional, restrictive assumptions, or have resorted to numerical methods. In Part I of this paper, a general, analytical solution for the transient pulse test is presented. This solution is graphically illustrated by plots of dimensionless variables for several cases of interest. The solution is shown to contain, as limiting cases, the more restrictive analytical solutions that the previous investigators have derived. A method of computing both the permeability and specific storage of the test sample from experimental data will be presented in Part II. ?? 1981.

Ca2+ permeability through rat cloned alpha9-containing nicotinic acetylcholine receptors.

PubMed

Fucile, Sergio; Sucapane, Antonietta; Eusebi, Fabrizio

2006-04-01

We investigated the functional properties of rat alpha9 and alpha9alpha10 nicotinic acetylcholine receptors (nAChRs) expressed by transient transfection in the rat GH4C1 cell line, using both Ca(2+) imaging and whole-cell recording. Acute applications of ACh generated short-delay fast-rising and quick-decaying Ca(2+) transients, suppressed in Ca(2+)-free medium and invariably accompanied by the activation of whole-cell inward currents. The mean amplitude of ACh-induced currents was as small as -16 pA in alpha9 subunit cDNA-transfected GH4C1 cells (alpha9-GH4C1), while they were much larger (range: -150 to -300 pA) in alpha9alpha10 subunit cDNAs-transfected GH4C1 cells (alpha9alpha10-GH4C1). Currents were not activated by nicotine, were blocked by methyllycaconitine and were ACh concentration-dependent. Because the Ca(2+) permeability of alpha9-containing nAChRs has been estimated in immortalized cochlear UB/OC-2 mouse cells, we also characterized the ACh-induced responses in these cells. Unlike alpha9- and alpha9alpha10-GH4C1 cells, UB/OC-2 cells responded to ACh with both long-delay methyllycaconitine-insensitive whole-cell currents and long-lasting Ca(2+) transients, the latter being detected in the absence of Ca(2+) in the extracellular medium and being suppressed by the Ca(2+)-ATPase inhibitor thapsigargin, known to deplete IP(3)-sensitive stores. These results indicated the involvement of muscarinic nAChRs and the lack of functional ACh-gated receptor channels in UB/OC-2 cells. Thus, we measured the fractional Ca(2+) current (P(f), i.e. the percentage of total current carried by Ca(2+) ions) in alpha9alpha10-GH4C1, obtaining a P(f) value of 22 +/- 4%; this is the largest value estimated to date for a ligand-gated receptor channel. The physiological role played by Ca(2+) entry through alpha9-containing nAChRs gated by ACh is discussed.

Nonlinear Optical Spectroscopy of Two-Dimensional Materials

NASA Astrophysics Data System (ADS)

Cui, Qiannan

Nonlinear optical properties of two-dimensional (2D) materials, such as transition metal dichalcogenides (TMDs), graphene, black phosphorus, and so on, play a key role of understanding nanoscale light-matter interactions, as well as developing nanophotonics applications from solar cells to quantum computation. With ultrafast lasers, we experimentally study nonlinear optical properties of 2D materials. Employing transient absorption microscopy, we study several members of 2D materials, such as WSe2, TiS3 and ReS2. The dynamical saturable absorption process of 2D excitons is spatiotemporally resolved. Intrinsic parameters of these 2D materials, such as exciton lifetime, exciton diffusion coefficient, and exciton mobility, are effectively measured. Especially, in-plane anisotropy of transient absorption and diffusive transport is observed for 2D excitons in monolayer ReS2, demonstrating the in-plane degree of freedom. Furthermore, with quantum interference and control nanoscopy, we all-optically inject, detect and manipulate nanoscale ballistic charge currents in a ReS2 thin film. By tuning the phase difference between one photon absorption and two photon absorption transition paths, sub-picosecond timescale of ballistic currents is coherently controlled for the first time in TMDs. In addition, the spatial resolution is two-order of magnitude smaller than optical diffraction limit. The second-order optical nonlinearity of 2D monolayers is resolved by second harmonic generation (SHG) microscopy. We measure the second-order susceptibility of monolayer MoS 2. The angular dependence of SHG in monolayer MoS2 shows strong symmetry dependence on its crystal lattice structure. Hence, second harmonic generation microscopy can serve as a powerful tool to noninvasively determine the crystalline directions of 2D monolayers. The real and imaginary parts of third-order optical nonlinearity of 2D monolayers are resolved by third harmonic generation (THG) microscopy and two-photon transient absorption microscopy, respectively. With third harmonic generation microscopy, we observe strong and anisotropic THG in monolayer and multilayer ReS2. Comparing with 2D materials with hexagonal lattice, such as MoS2, the third-order susceptibility is higher by one order of magnitude in ReS2 with a distorted 1T structure. The in-plane anisotropy of THG is attributed to the lattice distortion in ReS2 after comparing with a symmetry analysis. With two-photon transient absorption microscopy, we observe a giant two-photon absorption coefficient of monolayer WS2.

Field induced transient current in one-dimensional nanostructure

NASA Astrophysics Data System (ADS)

Sako, Tokuei; Ishida, Hiroshi

2018-07-01

Field-induced transient current in one-dimensional nanostructures has been studied by a model of an electron confined in a 1D attractive Gaussian potential subjected both to electrodes at the terminals and to an ultrashort pulsed oscillatory electric field with the central frequency ω and the FWHM pulse width Γ. The time-propagation of the electron wave packet has been simulated by integrating the time-dependent Schrödinger equation directly relying on the second-order symplectic integrator method. The transient current has been calculated as the flux of the probability density of the escaping wave packet emitted from the downstream side of the confining potential. When a static bias-field E0 is suddenly applied, the resultant transient current shows an oscillatory decay behavior with time followed by a minimum structure before converging to a nearly constant value. The ω-dependence of the integrated transient current induced by the pulsed electric field has shown an asymmetric resonance line-shape for large Γ while it shows a fringe pattern on the spectral line profile for small Γ. These observations have been rationalized on the basis of the energy-level structure and lifetime of the quasibound states in the bias-field modified confining potential obtained by the complex-scaling Fourier grid Hamiltonian method.

Cultural Resource Investigations for the Resumption of Transient Testing of Nuclear Fuels and Material at the Idaho National Laboratory

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

Pace, Brenda R.; Williams, Julie B.

2013-11-01

The U. S. Department of Energy (DOE) has a need to test nuclear fuels under conditions that subject them to short bursts of intense, high-power radiation called ‘transient testing’ in order to gain important information necessary for licensing new nuclear fuels for use in U.S. nuclear power plants, for developing information to help improve current nuclear power plant performance and sustainability, for improving the affordability of new generation reactors, for developing recyclable nuclear fuels, and for developing fuels that inhibit any repurposing into nuclear weapons. To meet this mission need, DOE is considering alternatives for re-use and modification of existingmore » nuclear reactor facilities to support a renewed transient testing program. One alternative under consideration involves restarting the Transient Reactor Test (TREAT) reactor located at the Materials and Fuels Complex (MFC) on the Idaho National Laboratory (INL) site in southeastern Idaho. This report summarizes cultural resource investigations conducted by the INL Cultural Resource Management Office in 2013 to support environmental review of activities associated with restarting the TREAT reactor at the INL. These investigations were completed in order to identify and assess the significance of cultural resources within areas of potential effect associated with the proposed action and determine if the TREAT alternative would affect significant cultural resources or historic properties that are eligible for nomination to the National Register of Historic Places. No archaeological resources were identified in the direct area of potential effects for the project, but four of the buildings proposed for modifications are evaluated as historic properties, potentially eligible for nomination to the National Register of Historic Places. This includes the TREAT reactor (building #), control building (building #), guardhouse (building #), and warehouse (building #). The proposed re-use of these historic properties is consistent with original missions related to nuclear reactor testing and is expected to result in no adverse effects to their historic significance. Cultural resource investigations also involved communication with representatives from the Shoshone-Bannock Tribes to characterize cultural resources of potential tribal concern. This report provides a summary of the cultural resources inventoried and assessed within the defined areas of potential effect for the resumption of transient testing at the INL. Based on these analyses, proposed activities would have no adverse effects on historic properties within the APEs that have been defined. Other archaeological resources and cultural resources of potential concern to the Shoshone-Bannock Tribes and others that are located near the APEs are also discussed with regard to potential indirect impacts. The report concludes with general recommendations for measures to reduce impacts to all identified resources.« less

An Extended Trajectory Mechanics Approach for Calculating the Path of a Pressure Transient: Derivation and Illustration

NASA Astrophysics Data System (ADS)

Vasco, D. W.

2018-04-01

Following an approach used in quantum dynamics, an exponential representation of the hydraulic head transforms the diffusion equation governing pressure propagation into an equivalent set of ordinary differential equations. Using a reservoir simulator to determine one set of dependent variables leaves a reduced set of equations for the path of a pressure transient. Unlike the current approach for computing the path of a transient, based on a high-frequency asymptotic solution, the trajectories resulting from this new formulation are valid for arbitrary spatial variations in aquifer properties. For a medium containing interfaces and layers with sharp boundaries, the trajectory mechanics approach produces paths that are compatible with travel time fields produced by a numerical simulator, while the asymptotic solution produces paths that bend too strongly into high permeability regions. The breakdown of the conventional asymptotic solution, due to the presence of sharp boundaries, has implications for model parameter sensitivity calculations and the solution of the inverse problem. For example, near an abrupt boundary, trajectories based on the asymptotic approach deviate significantly from regions of high sensitivity observed in numerical computations. In contrast, paths based on the new trajectory mechanics approach coincide with regions of maximum sensitivity to permeability changes.

Multi-physics transient simulation of monolithic niobium dioxide-tantalum dioxide memristor-selector structures

NASA Astrophysics Data System (ADS)

Sevic, John F.; Kobayashi, Nobuhiko P.

2017-10-01

Self-assembled niobium dioxide (NbO2) thin-film selectors self-aligned to tantalum dioxide (TaO2) memristive memory cells are studied by a multi-physics transient solution of the heat equation coupled to the nonlinear current continuity equation. While a compact model can resolve the quasi-static bulk negative differential resistance (NDR), a self-consistent coupled transport formulation provides a non-equilibrium picture of NbO2-TaO2 selector-memristor operation ab initio. By employing the drift-diffusion transport approximation, a finite element method is used to study the dynamic electrothermal behavior of our experimentally obtained selector-memristor devices, showing that existing conditions are suitable for electroformation of NbO2 selector thin-films. Both transient and steady-state simulations support our theory, suggesting that the phase change due to insulator-metal transition is responsible for NbO2 selector NDR in our as-fabricated selector-memristor devices. Simulation results further suggest that TiN nano-via may play a central role in electroforming, as its dimensions and material properties establish the mutual electrothermal interaction between TiN nano-via and the selector-memristor.

Effects of Iron Contamination and Hydrogen Passivation on the Electrical Properties of Oxygen Precipitates in CZ-Si

NASA Astrophysics Data System (ADS)

Li, Jiyang; Song, Lihui; Yu, Xuegong; Yang, Deren

2018-04-01

Oxygen precipitates (OPs) are unavoidably formed in Czochralski silicon (CZ-Si) containing relatively high concentrations of oxygen. The recombination behavior of such defects is also vital for bulk devices like solar cells as they can reduce the minority carrier lifetime and degrade the cell performance. In our experiments, the characteristics of oxygen precipitation in n-type CZ-Si are systematically investigated by means of Fourier transform infrared spectroscopy (FTIR), deep level transient spectroscopy (DLTS) and electron beam induced current (EBIC). It is found that the iron contamination in n-type CZ-Si can strongly influence the OPs generation and their electrical properties, whereas the hydrogen passivation can effectively reduce the recombination activity of OPs.

Statistical properties of the time histories of cosmic gamma-ray bursts detected by the BATSE experiment of the Compton gamma-ray observatory

NASA Technical Reports Server (NTRS)

Sagdeev, Roald

1995-01-01

The main scientific objectives of the project were: (1) Calculation of average time history for different subsets of BATSE gamma-ray bursts; (2) Comparison of averaged parameters and averaged time history for different Burst And Transient Source Experiments (BASTE) Gamma Ray Bursts (GRB's) sets; (3) Comparison of results obtained with BATSE data with those obtained with APEX experiment at PHOBOS mission; and (4) Use the results of (1)-(3) to compare current models of gamma-ray bursts sources.

Metal transfer and V-I transients in GMAW of aluminium

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

Pandey, S.; Rao, U.R.K.; Aghakhani, M.

1996-12-31

The mode of metal transfer in arc welding significantly affects the positional weldability; particularly the overhead welding, the chemical composition and properties of weld metal, metallurgy of weld metal, weld pool stability, arc stability, spatter losses, and weld bead geometry. The mode of metal transfer is affected mainly by the type of the arc, welding current, electrode polarity, arc voltage, contact tube to plate distance (CTPD)/Stand-off, type and flow rate of the shielding gas, torch angle and alloying elements in GMAW of aluminium and its alloys.

Dynamical Networks Characterization of Space Weather Events

NASA Astrophysics Data System (ADS)

Orr, L.; Chapman, S. C.; Dods, J.; Gjerloev, J. W.

2017-12-01

Space weather can cause disturbances to satellite systems, impacting navigation technology and telecommunications; it can cause power loss and aviation disruption. A central aspect of the earth's magnetospheric response to space weather events are large scale and rapid changes in ionospheric current patterns. Space weather is highly dynamic and there are still many controversies about how the current system evolves in time. The recent SuperMAG initiative, collates ground-based vector magnetic field time series from over 200 magnetometers with 1-minute temporal resolution. In principle this combined dataset is an ideal candidate for quantification using dynamical networks. Network properties and parameters allow us to characterize the time dynamics of the full spatiotemporal pattern of the ionospheric current system. However, applying network methodologies to physical data presents new challenges. We establish whether a given pair of magnetometers are connected in the network by calculating their canonical cross correlation. The magnetometers are connected if their cross correlation exceeds a threshold. In our physical time series this threshold needs to be both station specific, as it varies with (non-linear) individual station sensitivity and location, and able to vary with season, which affects ground conductivity. Additionally, the earth rotates and therefore the ground stations move significantly on the timescales of geomagnetic disturbances. The magnetometers are non-uniformly spatially distributed. We will present new methodology which addresses these problems and in particular achieves dynamic normalization of the physical time series in order to form the network. Correlated disturbances across the magnetometers capture transient currents. Once the dynamical network has been obtained [1][2] from the full magnetometer data set it can be used to directly identify detailed inferred transient ionospheric current patterns and track their dynamics. We will show our first results that use network properties such as cliques and clustering coefficients to map these highly dynamic changes in ionospheric current patterns.[l] Dods et al, J. Geophys. Res 120, doi:10.1002/2015JA02 (2015). [2] Dods et al, J. Geophys. Res. 122, doi:10.1002/2016JA02 (2017).

High-speed holographic system for full-field transient vibrometry of the human tympanic membrane

NASA Astrophysics Data System (ADS)

Dobrev, I.; Harrington, E. J.; Cheng, T.; Furlong, C.; Rosowski, J. J.

2014-07-01

Understanding of the human hearing process requires the quantification of the transient response of the human ear and the human tympanic membrane (TM or eardrum) in particular. Current state-of-the-art medical methods to quantify the transient acousto-mechanical response of the TM provide only averaged acoustic or local information at a few points. This may be insufficient to fully describe the complex patterns unfolding across the full surface of the TM. Existing engineering systems for full-field nanometer measurements of transient events, typically based on holographic methods, constrain the maximum sampling speed and/or require complex experimental setups. We have developed and implemented of a new high-speed (i.e., > 40 Kfps) holographic system (HHS) with a hybrid spatio-temporal local correlation phase sampling method that allows quantification of the full-field nanometer transient (i.e., > 10 kHz) displacement of the human TM. The HHS temporal accuracy and resolution is validated versus a LDV on both artificial membranes and human TMs. The high temporal (i.e., < 24 μs) and spatial (i.e., >100k data points) resolution of our HHS enables simultaneous measurement of the time waveform of the full surface of the TM. These capabilities allow for quantification of spatially-dependent motion parameters such as energy propagation delays surface wave speeds, which can be used to infer local material properties across the surface of the TM. The HHS could provide a new tool for the investigation of the auditory system with applications in medical research, in-vivo clinical diagnosis as well as hearing aids design.

Cavβ2 transcription start site variants modulate calcium handling in newborn rat cardiomyocytes.

PubMed

Moreno, Cristian; Hermosilla, Tamara; Morales, Danna; Encina, Matías; Torres-Díaz, Leandro; Díaz, Pablo; Sarmiento, Daniela; Simon, Felipe; Varela, Diego

2015-12-01

In the heart, the main pathway for calcium influx is mediated by L-type calcium channels, a multi-subunit complex composed of the pore-forming subunit CaV1.2 and the auxiliary subunits CaVα2δ1 and CaVβ2. To date, five distinct CaVβ2 transcriptional start site (TSS) variants (CaVβ2a-e) varying only in the composition and length of the N-terminal domain have been described, each of them granting distinct biophysical properties to the L-type current. However, the physiological role of these variants in Ca(2+) handling in the native tissue has not been explored. Our results show that four of these variants are present in neonatal rat cardiomyocytes. The contribution of those CaVβ2 TSS variants on endogenous L-type current and Ca(2+) handling was explored by adenoviral-mediated overexpression of each CaVβ2 variant in cultured newborn rat cardiomyocytes. As expected, all CaVβ2 TSS variants increased L-type current density and produced distinctive changes on L-type calcium channel (LTCC) current activation and inactivation kinetics. The characteristics of the induced calcium transients were dependent on the TSS variant overexpressed. Moreover, the amplitude of the calcium transients varied depending on the subunit involved, being higher in cardiomyocytes transduced with CaVβ2a and smaller in CaVβ2d. Interestingly, the contribution of Ca(2+) influx and Ca(2+) release on total calcium transients, as well as the sarcoplasmic calcium content, was found to be TSS-variant-dependent. Remarkably, determination of atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP) messenger RNA (mRNA) abundance and cell size change indicates that CaVβ2 TSS variants modulate the cardiomyocyte hypertrophic state. In summary, we demonstrate that expression of individual CaVβ2 TSS variants regulates calcium handling in cardiomyocytes and, consequently, has significant repercussion in the development of hypertrophy.

Transient Dynamics of Double Quantum Dots Coupled to Two Reservoirs

NASA Astrophysics Data System (ADS)

Fukadai, Takahisa; Sasamoto, Tomohiro

2018-05-01

We study the time-dependent properties of double quantum dots coupled to two reservoirs using the nonequilibrium Green function method. For an arbitrary time-dependent bias, we derive an expression for the time-dependent electron density of a dot and several currents, including the current between the dots in the wide-band-limit approximation. For the special case of a constant bias, we calculate the electron density and the currents numerically. As a result, we find that these quantities oscillate and that the number of crests in a single period of the current from a dot changes with the bias voltage. We also obtain an analytical expression for the relaxation time, which expresses how fast the system converges to its steady state. From the expression, we find that the relaxation time becomes constant when the coupling strength between the dots is sufficiently large in comparison with the difference of coupling strength between the dots and the reservoirs.

The Reactive Stabilisation of Aluminum-Zinc-X Foams via the Formation of a Transient Liquid Phase Using the Powder Metallurgy Approach

NASA Astrophysics Data System (ADS)

Lafrance, Maxime

During the past few decades, aluminum foam research has focused on the improvement of properties. These properties include pore structure and process reproducibility. High energy absorption capacity, lightweight and high stiffness to weight ratio are some of the properties that make these foams desirable for a number of diverse applications. The use of a transient liquid phase and melting point depressant was studied in order to improve aluminum foam manufactured through the powder metallurgy process and to create reactive Stabilisation. The transient liquid phase reacts with aluminum and helps encapsulate higher levels of hydrogen, simultaneously reducing the difference between the melting point of the alloy and the gas release temperature of the blowing agent (TiH2). A large difference is known to adversely affect foam properties. The study of pure aluminum foam formation was undertaken to understand the basic foaming mechanisms related to crack formations under in-situ conditions. Elemental zinc powder at various concentrations (Al-10wt%Zn, Al-33wt%Zn and Al-50wt%Zn) was added to produce a transient liquid phase. Subsequently, an Al-12wt%Si pre-alloyed powder was added to the Al-Zn mixture in order to further reduce the melting point of the alloy and to increase the amount of transient liquid phase available (Al-3.59wtSi-9.6%Zn and Al-2.4wt%Si-9.7wt%Zn). The mechanical properties of each system at optimal foaming conditions were assessed and compared. It was determined that pure aluminum foam crack formation could be suppressed at higher heating rates, improving the structure through the nucleation of uniform pores. The Al-10wt%Zn foams generated superior pore properties, post maximum expansion stability and mechanical properties at lower temperatures, compared to pure aluminum. The Al-Si-Zn foams revealed remarkable stability and pore structure at very low temperatures (640 to 660°C). Overall, the Al-10wt%Zn and Al-3.59wt%Si-9.6wt%Zn foams offer superior properties compared to pure aluminum.

Transiently thermoresponsive polymers and their applications in biomedicine.

PubMed

Vanparijs, Nane; Nuhn, Lutz; De Geest, Bruno G

2017-02-20

The focus of this review is on the class of transiently thermoresponsive polymers. These polymers are thermoresponsive, but gradually lose this property upon chemical transformation - often a hydrolysis reaction - in the polymer side chain or backbone. An overview of the different approaches used for the design of these polymers along with their physicochemical properties is given. Their amphiphilic properties and degradability into fully soluble compounds make this class of responsive polymers attractive for drug delivery and tissue engineering applications. Examples of these are also provided in this review.

Transient Dynamic Mechanical Analysis of Resilin-based Elastomeric Hydrogels

NASA Astrophysics Data System (ADS)

Li, Linqing; Kiick, Kristi

2014-04-01

The outstanding high-frequency properties of emerging resilin-like polypeptides (RLPs) have motivated their development for vocal fold tissue regeneration and other applications. Recombinant RLP hydrogels show efficient gelation, tunable mechanical properties, and display excellent extensibility, but little has been reported about their transient mechanical properties. In this manuscript, we describe the transient mechanical behavior of new RLP hydrogels investigated via both sinusoidal oscillatory shear deformation and uniaxial tensile testing. Oscillatory stress relaxation and creep experiments confirm that RLP-based hydrogels display significantly reduced stress relaxation and improved strain recovery compared to PEG-based control hydrogels. Uniaxial tensile testing confirms the negligible hysteresis, reversible elasticity and superior resilience (up to 98%) of hydrated RLP hydrogels, with Young’s modulus values that compare favorably with those previously reported for resilin and that mimic the tensile properties of the vocal fold ligament at low strain (< 15%). These studies expand our understanding of the properties of these RLP materials under a variety of conditions, and confirm the unique applicability, for mechanically demanding tissue engineering applications, of a range of RLP hydrogels.

Heavy Ion Microbeam- and Broadbeam-Induced Current Transients in SiGe HBTs

NASA Technical Reports Server (NTRS)

Pellish, Jonathan A.; Reed, R. A.; McMorrow, D.; Vizkelethy, G.; Ferlet-Cavrois, V.; Baggio, J.; Duhamel, O.; Moen, K. A.; Phillips, S. D.; Diestelhorst, R. M.;

Ultrafast laser processing of copper: A comparative study of experimental and simulated transient optical properties

NASA Astrophysics Data System (ADS)

Winter, Jan; Rapp, Stephan; Schmidt, Michael; Huber, Heinz P.

2017-09-01

In this paper, we present ultrafast measurements of the complex refractive index for copper up to a time delay of 20 ps with an accuracy <1% at laser fluences in the vicinity of the ablation threshold. The measured refractive index n and extinction coefficient k are supported by a simulation including the two-temperature model with an accurate description of thermal and optical properties and a thermomechanical model. Comparison of the measured time resolved optical properties with results of the simulation reveals underlying physical mechanisms in three distinct time delay regimes. It is found that in the early stage (-5 ps to 0 ps) the thermally excited d-band electrons make a major contribution to the laser pulse absorption and create a steep increase in transient optical properties n and k. In the second time regime (0-10 ps) the material expansion influences the plasma frequency, which is also reflected in the transient extinction coefficient. In contrast, the refractive index n follows the total collision frequency. Additionally, the electron-ion thermalization time can be attributed to a minimum of the extinction coefficient at ∼10 ps. In the third time regime (10-20 ps) the transient extinction coefficient k indicates the surface cooling-down process.

The Na conductance in the sarcolemma and the transverse tubular system membranes of mammalian skeletal muscle fibers

PubMed Central

DiFranco, Marino

2011-01-01

Na (and Li) currents and fluorescence transients were recorded simultaneously under voltage-clamp conditions from mouse flexor digitorum brevis fibers stained with the potentiometric dye di-8-ANEPPS to investigate the distribution of Na channels between the surface and transverse tubular system (TTS) membranes. In fibers rendered electrically passive, voltage pulses resulted in step-like fluorescence changes that were used to calibrate the dye response. The effects of Na channel activation on the TTS voltage were investigated using Li, instead of Na, because di-8-ANEPPS transients show anomalies in the presence of the latter. Na and Li inward currents (INa, ILi; using half of the physiological ion concentration) showed very steep voltage dependences, with no reversal for depolarizations beyond the calculated equilibrium potential, suggesting that most of the current originates from a noncontrolled membrane compartment. Maximum peak ILi was ∼30% smaller than for INa, suggesting a Li-blocking effect. ILi activation resulted in the appearance of overshoots in otherwise step-like di-8-ANEPPS transients. Overshoots had comparable durations and voltage dependence as those of ILi. Simultaneously measured maximal overshoot and peak ILi were 54 ± 5% and 773 ± 53 µA/cm2, respectively. Radial cable model simulations predicted the properties of ILi and di-8-ANEPPS transients when TTS access resistances of 10–20 Ωcm2, and TTS-to-surface Na permeability density ratios in the range of 40:60 to 70:30, were used. Formamide-based osmotic shock resulted in incomplete detubulation. However, results from a subpopulation of treated fibers (low capacitance) provide confirmatory evidence that a significant proportion of ILi, and the overshoot in the optical signals, arises from the TTS in normal fibers. The quantitative evaluation of the distribution of Na channels between the sarcolemma and the TTS membranes, as provided here, is crucial for the understanding of the radial and longitudinal propagation of the action potential, which ultimately govern the mechanical activation of muscle in normal and diseased conditions. PMID:21948948

Properties of the late transient outward current in isolated intestinal smooth muscle cells of the guinea-pig.

PubMed

Zholos, A V; Baidan, L V; Shuba, M F

1991-11-01

1. Whole-cell membrane currents in voltage-clamped single isolated cells of longitudinal smooth muscle of guinea-pig ileum were studied at room temperature using patch pipettes filled with either high-K+ solution or high-Cs+ solution, to suppress K+ outward current, and containing 0.3 mM-EGTA. 2. In the presence of high-K+ solution in the pipette, membrane depolarization from the holding potential of -50 mV evoked an initial inward calcium current (ICa) followed by a large initial transient outward current and a sustained outward current with spontaneous oscillations superimposed. Prolonged depolarization above -20 mV produced a late transient outward current which reached a maximum (up to several nanoamps at +10 mV) within approximately 1 s and lasted several seconds. 3. The late outward current (ILTO) was voltage dependent and reversed at the EK (potassium equilibrium potential) in cells exposed to high-K+ external solution. It was blocked by TEA+ (tetraethylammonium) or Ba2+ applied externally (calculated Kd (dissociation constant) values were 0.67 and 4.43 mM, respectively) or by high-Cs+ solution perfusing the cell. The removal of extracellular Ca2+, application of Ca2+ channel blockers (3 mM-Co2+, 0.2 mM-Cd2+ or 1 microM-nifedipine) or perfusion of 5 mM-EGTA inside the cell also abolished the current. Thus, the current seems to be a Ca(2+)-activated K+ current. 4. There is a great discrepancy between the time course of the ICa and that of the late ILTO, which suggests that Ca2+ release from intracellular storage sites may contribute to the generation of the ILTO. 5. Bath application of caffeine (10 mM) during the development of ILTO enhanced the current. However, in the presence of caffeine ILTO was inhibited. Moderate inhibition of ICa by caffeine was also observed. 6. Ryanodine (5 microM) applied to the bathing solution completely inhibited ILTO within 3.5 min; however, it had no or little effect on the ICa. 7. Ruthenium Red (10 microM) completely blocked the ILTO and slightly and more slowly inhibited the ICa. 8. Increasing Mg2+ concentration in the pipette solution from 1 to 6 mM abolished the ILTO. 9. It was concluded that the ILTO was activated mainly by Ca2+ released from the intracellular storage sites following Ca2+ entry, presumably by a Ca(2+)-induced Ca2+ release mechanism.

Sustained and transient calcium currents in horizontal cells of the white bass retina.

PubMed

Sullivan, J M; Lasater, E M

1992-01-01

Calcium currents were recorded from cultured horizontal cells (HCs) isolated from adult white bass retinas, using the whole-cell patch-clamp technique. Ca2+ currents were enhanced using 10 mM extracellular Ca2+, while Na+ and K+ currents were pharmacologically suppressed. Two components of the Ca2+ current, one transient, the other sustained, were found. The large transient component of the Ca2+ current, which has not been seen before in HCs, is similar, but not identical, to the T-type Ca2+ current described previously in a variety of preparations. The sustained component of the Ca2+ current is similar, but not identical, to the L-type current described in other preparations. FTX, a factor isolated from the venom of the funnel-web spider, Agelenopsis aperta, preferentially and irreversibly blocks the sustained component of the Ca2+ current at very dilute concentrations. The sustained component of the Ca2+ current inactivates slowly, over the course of 15-60 s, in some HCs. This inactivation of the sustained Ca2+ current, when present, is primarily voltage dependent rather than Ca2+ dependent.

Sustained and transient calcium currents in horizontal cells of the white bass retina

PubMed Central

1992-01-01

Calcium currents were recorded from cultured horizontal cells (HCs) isolated from adult white bass retinas, using the whole-cell patch- clamp technique. Ca2+ currents were enhanced using 10 mM extracellular Ca2+, while Na+ and K+ currents were pharmacologically suppressed. Two components of the Ca2+ current, one transient, the other sustained, were found. The large transient component of the Ca2+ current, which has not been seen before in HCs, is similar, but not identical, to the T-type Ca2+ current described previously in a variety of preparations. The sustained component of the Ca2+ current is similar, but not identical, to the L-type current described in other preparations. FTX, a factor isolated from the venom of the funnel-web spider, Agelenopsis aperta, preferentially and irreversibly blocks the sustained component of the Ca2+ current at very dilute concentrations. The sustained component of the Ca2+ current inactivates slowly, over the course of 15- 60 s, in some HCs. This inactivation of the sustained Ca2+ current, when present, is primarily voltage dependent rather than Ca2+ dependent. PMID:1371309

Mechanical behavior of polymer-based vs. metallic-based bioresorbable stents

PubMed Central

Ang, Hui Ying; Huang, Ying Ying; Lim, Soo Teik; Wong, Philip; Joner, Michael

2017-01-01

Bioresorbable scaffolds (BRS) were developed to overcome the drawbacks of current metallic drug-eluting stents (DES), such as late in-stent restenosis and caging of the vessel permanently. The concept of the BRS is to provide transient support to the vessel during healing before being degraded and resorbed by the body, freeing the vessel and restoring vasomotion. The mechanical properties of the BRS are influenced by the choice of the material and processing methods. Due to insufficient radial strength of the bioresorbable material, BRS often required large strut profile as compared to conventional metallic DES. Having thick struts will in turn affect the deliverability of the device and may cause flow disturbance, thereby increasing the incidence of acute thrombotic events. Currently, the bioresorbable poly-l-lactic acid (PLLA) polymer and magnesium (Mg) alloys are being investigated as materials in BRS technologies. The bioresorption process, mechanical properties, in vitro observations and clinical outcomes of PLLA-based and Mg-based BRS will be examined in this review. PMID:28894598

Effect of the Crystal Structure on the Electrical Properties of Thin-Film PZT Structures

NASA Astrophysics Data System (ADS)

Delimova, L. A.; Gushchina, E. V.; Zaitseva, N. V.; Seregin, D. S.; Vorotilov, K. A.; Sigov, A. S.

2018-03-01

A new method of two-stage crystallization of lead zirconate-titanate (PZT) films using a seed sublayer with a low excess lead content has been proposed and realized. A seed layer with a strong texture of perovskite Pe(111) grains is formed from a solution with a lead excess of 0-5 wt %; the fast growth of the grains is provided by the deposition of the main film from a solution with high lead content. As a result, a strong Pe(111) texture with complete suppression of the Pe(100) orientation forms. An analysis of current-voltage dependences of the transient currents and the distributions of the local conductivity measured by the contact AFM method reveals two various mechanisms of current percolation that are determined by traps in the bulk and at the perovskite grain interfaces.

Strain and thermally induced magnetic dynamics and spin current in magnetic insulators subject to transient optical grating

NASA Astrophysics Data System (ADS)

Wang, Xi-Guang; Chotorlishvili, Levan; Berakdar, Jamal

2017-07-01

We analyze the magnetic dynamics and particularlythe spin current in an open-circuit ferromagnetic insulator irradiated by two intense, phase-locked laser pulses. The interference of the laser beams generates a transient optical grating and a transient spatio-temporal temperature distribution. Both effects lead to elastic and heat waves at the surface and into the bulk of the sample. The strain induced spin current as well as the thermally induced magnonic spin current are evaluated numerically on the basis of micromagnetic simulations using solutions of the heat equation. We observe that the thermo-elastically induced magnonic spin current propagates on a distance larger than the characteristic size of thermal profile, an effect useful for applications in remote detection of spin caloritronics phenomena. Our findings point out that exploiting strain adds a new twist to heat-assisted magnetic switching and spin-current generation for spintronic applications.

On the nature of high field charge transport in reinforced silicone dielectrics: Experiment and simulation

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

Huang, Yanhui, E-mail: huangy12@rpi.edu; Schadler, Linda S.

The high field charge injection and transport properties in reinforced silicone dielectrics were investigated by measuring the time-dependent space charge distribution and the current under dc conditions up to the breakdown field and were compared with the properties of other dielectric polymers. It is argued that the energy and spatial distribution of localized electronic states are crucial in determining these properties for polymer dielectrics. Tunneling to localized states likely dominates the charge injection process. A transient transport regime arises due to the relaxation of charge carriers into deep traps at the energy band tails and is successfully verified by amore » Monte Carlo simulation using the multiple-hopping model. The charge carrier mobility is found to be highly heterogeneous due to the non-uniform trapping. The slow moving electron packet exhibits a negative field dependent drift velocity possibly due to the spatial disorder of traps.« less

Temperature Dependence of Density, Viscosity and Electrical Conductivity for Hg-Based II-VI Semiconductor Melts

NASA Technical Reports Server (NTRS)

Li, C.; Ban, H.; Lin, B.; Scripa, R. N.; Su, C.-H.; Lehoczky, S. L.

2004-01-01

The relaxation phenomenon of semiconductor melts, or the change of melt structure with time, impacts the crystal growth process and the eventual quality of the crystal. The thermophysical properties of the melt are good indicators of such changes in melt structure. Also, thermophysical properties are essential to the accurate predication of the crystal growth process by computational modeling. Currently, the temperature dependent thermophysical property data for the Hg-based II-VI semiconductor melts are scarce. This paper reports the results on the temperature dependence of melt density, viscosity and electrical conductivity of Hg-based II-VI compounds. The melt density was measured using a pycnometric method, and the viscosity and electrical conductivity were measured by a transient torque method. Results were compared with available published data and showed good agreement. The implication of the structural changes at different temperature ranges was also studied and discussed.

Delocalisation of photoexcited triplet states probed by transient EPR and hyperfine spectroscopy

NASA Astrophysics Data System (ADS)

Richert, Sabine; Tait, Claudia E.; Timmel, Christiane R.

2017-07-01

Photoexcited triplet states play a crucial role in photochemical mechanisms: long known to be of paramount importance in the study of photosynthetic reaction centres, they have more recently also been shown to play a major role in a number of applications in the field of molecular electronics. Their characterisation is crucial for an improved understanding of these processes with a particular focus on the determination of the spatial distribution of the triplet state wavefunction providing information on charge and energy transfer efficiencies. Currently, active research in this field is mostly focussed on the investigation of materials for organic photovoltaics (OPVs) and organic light emitting diodes (OLEDs). As the properties of triplet states and their spatial extent are known to have a major impact on device performance, a detailed understanding of the factors governing triplet state delocalisation is at the basis of the further development and improvement of these devices. Electron Paramagnetic Resonance (EPR) has proven a valuable tool in the study of triplet state properties and both experimental methods as well as data analysis and interpretation techniques have continuously improved over the last few decades. In this review, we discuss the theoretical and practical aspects of the investigation of triplet states and triplet state delocalisation by transient continuous wave and pulse EPR and highlight the advantages and limitations of the presently available techniques and the current trends in the field. Application of EPR in the study of triplet state delocalisation is illustrated on the example of linear multi-porphyrin chains designed as molecular wires.

Global Precipitation Measurement (GPM) Spacecraft Lithium Ion Battery Micro-Cycling Investigation

NASA Technical Reports Server (NTRS)

Dakermanji, George; Lee, Leonine; Spitzer, Thomas

2016-01-01

The Global Precipitation Measurement (GPM) spacecraft was jointly developed by NASA and JAXA. It is a Low Earth Orbit (LEO) spacecraft launched on February 27, 2014. The power system is a Direct Energy Transfer (DET) system designed to support 1950 watts orbit average power. The batteries use SONY 18650HC cells and consist of three 8s by 84p batteries operated in parallel as a single battery. During instrument integration with the spacecraft, large current transients were observed in the battery. Investigation into the matter traced the cause to the Dual-Frequency Precipitation Radar (DPR) phased array radar which generates cyclical high rate current transients on the spacecraft power bus. The power system electronics interaction with these transients resulted in the current transients in the battery. An accelerated test program was developed to bound the effect, and to assess the impact to the mission.

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

Design of transient light signal simulator based on FPGA

NASA Astrophysics Data System (ADS)

Kang, Jing; Chen, Rong-li; Wang, Hong

2014-11-01

A design scheme of transient light signal simulator based on Field Programmable gate Array (FPGA) was proposed in this paper. Based on the characteristics of transient light signals and measured feature points of optical intensity signals, a fitted curve was created in MATLAB. And then the wave data was stored in a programmed memory chip AT29C1024 by using SUPERPRO programmer. The control logic was realized inside one EP3C16 FPGA chip. Data readout, data stream cache and a constant current buck regulator for powering high-brightness LEDs were all controlled by FPGA. A 12-Bit multiplying CMOS digital-to-analog converter (DAC) DAC7545 and an amplifier OPA277 were used to convert digital signals to voltage signals. A voltage-controlled current source constituted by a NPN transistor and an operational amplifier controlled LED array diming to achieve simulation of transient light signal. LM3405A, 1A Constant Current Buck Regulator for Powering LEDs, was used to simulate strong background signal in space. Experimental results showed that the scheme as a transient light signal simulator can satisfy the requests of the design stably.

Measurement of Thermal Properties of Rocks at Temperature up to 1,000°C with Transient Plane Source Techniques

NASA Astrophysics Data System (ADS)

Kim, S. K.; Lee, Y.

2017-12-01

A set of devices that can measure thermal properties of rocks over a temperature range from room temperature up to 1,000°C with transient plane source techniques (also known as a Hot Disk method) is introduced. It consists of a main control system (e.g., TPS 2500 S from Hot Disk), mica-insulated sensor, tubular furnace, N2 gas supplier, and pressure regulator. The TPS 2500 S is the core instrument designed for precise analysis of thermal transport properties including thermal conductivity, thermal diffusivity, and volumetric heat capacity. The mica-insulated sensor is composed of an insulated nickel double spiral, which is utilized for both transient heating and precise temperature reading; a mica insulator protects the sensor against mechanical and thermal damage at high temperatures. The tubular furnace can hold two rock core samples of 50-mm-diameter and 25-mm-height with increasing temperatures up to 1,000°C. N2 gas supplier and pressure regulator are used to keep the inside the furnace away from oxygen. Thermal properties of most rocks and minerals vary with increasing temperatures. Experimental measurements of thermal properties at high temperatures have been made mostly using laser flash, needle probe, and divided bar methods in the previous researches, and no previous measurements with the Hot Disk method have been reported yet. We report thermal conductivities, thermal diffusivities, and volumetric heat capacities determined by a transient plane heat source method for fused silica and mafic rock samples using the introduced transient plane source apparatus. The thermal properties of fused silica have been measured mainly over the temperature range from ambient temperature to 500°C. The results seem to agree moderately with the previously reported values by Birch and Clark (Am. J. Sci., 1940). We now check the possible causes of measurement errors in our measurements and prepare to measure thermal properties of the mafic rock samples at temperatures up to 1,000°C using the hot disk method.

Basally activated nonselective cation currents regulate the resting membrane potential in human and monkey colonic smooth muscle

PubMed Central

Dwyer, Laura; Rhee, Poong-Lyul; Lowe, Vanessa; Zheng, Haifeng; Peri, Lauren; Ro, Seungil; Sanders, Kenton M.

2011-01-01

Resting membrane potential (RMP) plays an important role in determining the basal excitability of gastrointestinal smooth muscle. The RMP in colonic muscles is significantly less negative than the equilibrium potential of K+, suggesting that it is regulated not only by K+ conductances but by inward conductances such as Na+ and/or Ca2+. We investigated the contribution of nonselective cation channels (NSCC) to the RMP in human and monkey colonic smooth muscle cells (SMC) using voltage- and current-clamp techniques. Qualitative reverse transcriptase-polymerase chain reaction was performed to examine potential molecular candidates for these channels among the transient receptor potential (TRP) channel superfamily. Spontaneous transient inward currents and holding currents were recorded in human and monkey SMC. Replacement of extracellular Na+ with equimolar tetraethylammonium or Ca2+ with Mn2+ inhibited basally activated nonselective cation currents. Trivalent cations inhibited these channels. Under current clamp, replacement of extracellular Na+ with N-methyl-d-glucamine or addition of trivalent cations caused hyperpolarization. Three unitary conductances of NSCC were observed in human and monkey colonic SMC. Molecular candidates for basally active NSCC were TRPC1, C3, C4, C7, M2, M4, M6, M7, V1, and V2 in human and monkey SMC. Comparison of the biophysical properties of these TRP channels with basally active NSCC (bINSCC) suggests that TRPM4 and specific TRPC heteromultimer combinations may underlie the three single-channel conductances of bINSCC. In conclusion, these findings suggest that basally activated NSCC contribute to the RMP in human and monkey colonic SMC and therefore may play an important role in determining basal excitability of colonic smooth muscle. PMID:21566016

Transient thermal effect, nonlinear refraction and nonlinear absorption properties of graphene oxide sheets in dispersion.

PubMed

Zhang, Xiao-Liang; Liu, Zhi-Bo; Li, Xiao-Chun; Ma, Qiang; Chen, Xu-Dong; Tian, Jian-Guo; Xu, Yan-Fei; Chen, Yong-Sheng

2013-03-25

The nonlinear refraction (NLR) properties of graphene oxide (GO) in N, N-Dimethylformamide (DMF) was studied in nanosecond, picosecond and femtosecond time regimes by Z-scan technique. Results show that the dispersion of GO in DMF exhibits negative NLR properties in nanosecond time regime, which is mainly attributed to transient thermal effect in the dispersion. The dispersion also exhibits negative NLR in picosecond and femtosecond time regimes, which are arising from sp(2)- hybridized carbon domains and sp(3)- hybridized matrix in GO sheets. To illustrate the relations between NLR and nonlinear absorption (NLA), NLA properties of the dispersion were also studied in nanosecond, picosecond and femtosecond time regimes.

Simulation study and experimental results for detection and classification of the transient capacitor inrush current using discrete wavelet transform and artificial intelligence

NASA Astrophysics Data System (ADS)

Patcharoen, Theerasak; Yoomak, Suntiti; Ngaopitakkul, Atthapol; Pothisarn, Chaichan

2018-04-01

This paper describes the combination of discrete wavelet transforms (DWT) and artificial intelligence (AI), which are efficient techniques to identify the type of inrush current, analyze the origin and possible cause on the capacitor bank switching. The experiment setup used to verify the proposed techniques can be detected and classified the transient inrush current from normal capacitor rated current. The discrete wavelet transforms are used to detect and classify the inrush current. Then, output from wavelet is acted as input of fuzzy inference system for discriminating the type of switching transient inrush current. The proposed technique shows enhanced performance with a discrimination accuracy of 90.57%. Both simulation study and experimental results are quite satisfactory with providing the high accuracy and reliability which can be developed and implemented into a numerical overcurrent (50/51) and unbalanced current (60C) protection relay for an application of shunt capacitor bank protection in the future.

An Unusual Transient in the Extremely Metal-Poor Galaxy SDSS J094332.35+332657.6 (Leoncino Dwarf)

NASA Astrophysics Data System (ADS)

Filho, Mercedes E.; Sánchez Almeida, J.

2018-05-01

We have serendipitously discovered that Leoncino Dwarf, an ultra-faint, low-metallicity record-holder dwarf galaxy, may have hosted a transient source, and possibly exhibited a change in morphology, a shift in the center of brightness, and peak variability of the main (host) source in images taken approximately 40 yr apart; it is highly likely that these phenomena are related. Scenarios involving a Solar System object, a stellar cluster, dust enshrouding, and accretion variability have been considered, and discarded, as the origin of the transient. Although a combination of time-varying strong and weak lensing effects, induced by an intermediate mass black hole (104 - 5 × 105 M⊙) moving within the Milky Way halo (0.1 - 4 kpc), can conceivably explain all of the observed variable galaxy properties, it is statistically highly unlikely according to current theoretical predictions, and, therefore, also discarded. A cataclysmic event such as a supernova/hypernova could have occurred, as long as the event was observed towards the later/late-stage descent of the light curve, but this scenario fails to explain the absence of a post-explosion source and/or host HII region in recent optical images. An episode related to the giant eruption of a luminous blue variable star, a stellar merger or a nova, observed at, or near, peak magnitude may explain the transient source and possibly the change in morphology/center of brightness, but can not justify the main source peak variability, unless stellar variability is evoked.

Substance P modulates localized calcium transients and membrane current responses in murine colonic myocytes

PubMed Central

Bayguinov, Orline; Hagen, Brian; Sanders, Kenton M

2003-01-01

Neurokinins contribute to the neural regulation of gastrointestinal (GI) smooth muscles. We studied responses of murine colonic smooth muscle cells to substance P (SP) and NK1 and NK2 agonists using confocal microscopy and the patch clamp technique. Colonic myocytes generated localized Ca2+ transients that were coupled to spontaneous transient outward currents (STOCs). SP (10−10 M) increased Ca2+ transients and STOCs. Higher concentrations of SP (10−6 M) increased basal Ca2+ and inhibited Ca2+ transients and STOCs. Effects of SP were due to increased Ca2+ entry via L-type Ca2+ channels, and were mediated by protein kinase C (PKC). Nifedipine (10−6 M) and the PKC inhibitor, GF 109203X (10−6 M) reduced L-type Ca2+ current and blocked the effects of SP. SP responses depended upon parallel stimulation of NK1 and NK2 receptors. NK1 agonist ([Sar9,Met(O2)11]-substance P; SSP) and NK2 agonists (neurokinin A (NKA) or GR-64349) did not mimic the effects of SP alone, but NK1 and NK2 agonists were effective when added in combination (10−10–10−6 M). Consistent with this, either an NK1-specific antagonist (GR-82334; 10−7 M) or an NK2-specific antagonist (MEN 10,627; 10−7 M) blocked responses to SP (10−6 M). Ryanodine (10−5 M) blocked the increase in Ca2+ transients and STOCs in response to SP (10−10 M). Our findings show that low concentrations of SP, via PKC-dependent enhancement of L-type Ca2+ current and recruitment of ryanodine receptors, stimulate Ca2+ transients. At higher concentrations of SP (10−6 M), basal Ca2+ increases and spontaneous Ca2+ transients and STOCs are inhibited. PMID:12711623

Thresholds of Transient Cavitation Produced by Pulsed Ultrasound in a Controlled Nuclei Environment.

NASA Astrophysics Data System (ADS)

Holland, Christy Katherine Smith

The possibility of hazardous bioeffects from medical ultrasound examinations and therapy, although not demonstrated in current epidemiologic data, is still of interest to the medical community. In particular, concern persists over the potential of damage at the cellular level due to transient cavitation produced by diagnostic and high intensity therapeutic ultrasound. Transient cavitation is a discrete phenomenon which relies on the existence of stabilized nuclei, or pockets of gas within a host fluid, for its genesis. A convenient descriptor for assessing the likelihood of transient cavitation is the threshold pressure, or the minimum acoustic pressure necessary to initiate bubble growth and subsequent collapse. Experimental measurements of cavitation thresholds are presented here which elucidate the importance of ultrasound host fluid and nuclei parameters in determining these thresholds. These results are interpreted in the context of an approximate theory, included as an appendix, describing the relationship between these parameters and cavitation threshold pressures. An automated experimental apparatus has been developed to determine thresholds for cavitation produced in a fluid by short tone bursts of ultrasound at 0.76, 0.99, and 2.30 MHz. A fluid jet was used to convect potential cavitation nuclei through the focal region of the insonifying transducer. Potential nuclei tested include 1mum polystyrene spheres, microbubbles in the 1-10 μm range that are stabilized with human serum albumin, and whole blood constituents. Cavitation was detected by a passive acoustical technique which is sensitive to sound scattered from cavitation bubbles. Measurements of the transient cavitation threshold in water, in a fluid of higher viscosity, and in diluted whole blood are presented. Results from these experiments which permit the control of nuclei and host fluid properties are compared to the approximate analytical theory for the prediction of the onset of cavitation.

Non-equilibrium transport and spin dynamics in single-molecule magnets

NASA Astrophysics Data System (ADS)

Moldoveanu, V.; Dinu, I. V.; Tanatar, B.

2015-11-01

The time-dependent transport through single-molecule magnets (SMM) coupled to magnetic or non-magnetic electrodes is studied in the framework of the generalized Master equation (GME) method. We calculate the transient currents which develop when the molecule is smoothly coupled to the source and drain electrodes. The signature of the electrically induced magnetic switching on these transient currents is investigated. Our simulations show that the magnetic switching of the molecular spin can be read indirectly from the transient currents if one lead is magnetic and it is much faster if the leads have opposite spin polarizations. We identify effects of the transverse anisotropy on the dynamics of molecular states.

Transient tracking of low and high-order eccentricity-related components in induction motors via TFD tools

NASA Astrophysics Data System (ADS)

Climente-Alarcon, V.; Antonino-Daviu, J.; Riera-Guasp, M.; Pons-Llinares, J.; Roger-Folch, J.; Jover-Rodriguez, P.; Arkkio, A.

2011-02-01

The present work is focused on the diagnosis of mixed eccentricity faults in induction motors via the study of currents demanded by the machine. Unlike traditional methods, based on the analysis of stationary currents (Motor Current Signature Analysis (MCSA)), this work provides new findings regarding the diagnosis approach proposed by the authors in recent years, which is mainly focused on the fault diagnosis based on the analysis of transient quantities, such as startup or plug stopping currents (Transient Motor Current Signature Analysis (TMCSA)), using suitable time-frequency decomposition (TFD) tools. The main novelty of this work is to prove the usefulness of tracking the transient evolution of high-order eccentricity-related harmonics in order to diagnose the condition of the machine, complementing the information obtained with the low-order components, whose transient evolution was well characterised in previous works. Tracking of high-order eccentricity-related harmonics during the transient, through their associated patterns in the time-frequency plane, may significantly increase the reliability of the diagnosis, since the set of fault-related patterns arising after application of the corresponding TFD tool is very unlikely to be caused by other faults or phenomena. Although there are different TFD tools which could be suitable for the transient extraction of these harmonics, this paper makes use of a Wigner-Ville distribution (WVD)-based algorithm in order to carry out the time-frequency decomposition of the startup current signal, since this is a tool showing an excellent trade-off between frequency resolution at both high and low frequencies. Several simulation results obtained with a finite element-based model and experimental results show the validity of this fault diagnosis approach under several faulty and operating conditions. Also, additional signals corresponding to the coexistence of the eccentricity and other non-fault related phenomena making difficult the diagnosis (fluctuating load torque) are included in the paper. Finally, a comparison with an alternative TFD tool - the discrete wavelet transform (DWT) - applied in previous papers, is also carried out in the contribution. The results are promising regarding the usefulness of the methodology for the reliable diagnosis of eccentricities and for their discrimination against other phenomena.

Analysis of switching surges generated by current interruption in an energy-storge coil

NASA Astrophysics Data System (ADS)

Chowdhuri, P.

1981-10-01

The transient voltages which are generated when the current in a large magnetic energy storage coil is interruped by a dc vacuum circuit breaker is analyzed. The effect of the various parameters in the circuit on the transient voltage is dicussed. The self inductance of the dump resistor must be minimized to control the generated transient. Contrary to general belief, a capacitor across the coil is not an effective surge suppressor. In fact, the capacitor may excite oscillations of higher magnitude. However, a capacitor, in addition to a surge suppressor, may be used to modify the frequency components of the transient voltage so that these frequency components are not coincident with the natural frequencies of the coil. Otherwise, resonant oscillations inside the coil may attain damaging magnitudes. The capacitor would also reduce the steepness of the wavefront of the transient across the coil, thus reducing the nonlinear voltage distribution inside the coil.

Advances in transient (pulsed) eddy current for inspection of multi-layer aluminum structures in the presence of ferrous fasteners

NASA Astrophysics Data System (ADS)

Desjardins, D. R.; Vallières, G.; Whalen, P. P.; Krause, T. W.

2012-05-01

An experimental investigation of the electromagnetic processes underlying transient (pulsed) eddy current inspection of aircraft wing structures in the vicinity of ferrous fasteners is performed. The separate effects of transient excitation of ferrous fastener and eddy currents induced in the surrounding aluminum structure are explored using a transmit-receive configuration with transient excitation of a steel rod, an aluminum plate with a bore hole and a steel rod through the bore hole. Observations are used to interpret results from a coupled driving and differential coil sensing unit applied to detect fatigue cracks emanating from bolt holes in aluminum structures with ferrous fasteners present. In particular, it is noted that abrupt magnetization of the fastener, by the probe's central driving unit, can transfer flux and consequently, induce strong eddy current responses deep within the aluminum structure in the vicinity of the bore hole. Rotation of the probe, centered over the fastener, permits detection of subsurface discontinuities, such as cracks, by the pair of differentially connected pickup coils.

Pickpocket1 Is an Ionotropic Molecular Sensory Transducer*

PubMed Central

Boiko, Nina; Kucher, Volodymyr; Stockand, James D.; Eaton, Benjamin A.

2012-01-01

The molecular transformation of an external stimulus into changes in sensory neuron activity is incompletely described. Although a number of molecules have been identified that can respond to stimuli, evidence that these molecules can transduce stimulation into useful neural activity is lacking. Here we demonstrate that pickpocket1 (ppk1), a Drosophila homolog of mammalian Degenerin/epithelial sodium channels, encodes an acid-sensing sodium channel that conducts a transient depolarizing current in multidendritic sensory neurons of Drosophila melanogaster. Stimulation of Ppk1 is sufficient to bring these sensory neurons to threshold, eliciting a burst of action potentials. The transient nature of the neural activity produced by Ppk1 activation is the result of Ppk1 channel gating properties. This model is supported by the observation of enhanced bursting activity in neurons expressing a gain of function ppk1 mutant harboring the degenerin mutation. These findings demonstrate that Ppk1 can function as an ionotropic molecular sensory transducer capable of transforming the perception of a stimulus into phasic neuronal activity in sensory neurons. PMID:23033486

Transient thermal state of an active Braille matrix with incorporated thermal actuators by means of finite element method.

PubMed

Aluţei, Alexandra-Maria; Szelitzky, Emoke; Mândru, Dan

2013-01-01

In this article the authors present the transient thermal analysis for a developed thermal linear actuator based on wax paraffin used to drive the cells of a Braille device. A numerical investigation of transient heat transfer phenomenon during paraffin melting and solidification in an encapsulated recipient has been carried out using the ANSYS v.12 software. The researchers offer data on the heat distribution in the proposed model of the actuator as well as on the material properties required for these applications and provide the opportunity to identify new problems specific to thermal actuation, such as the heater properties and the cooling process of the active material in the structure of the Braille cell.

Brain electromagnetic activity and lightning: potentially congruent scale-invariant quantitative properties

PubMed Central

Persinger, Michael A.

2012-01-01

The space-time characteristics of the axonal action potential are remarkably similar to the scaled equivalents of lightning. The energy and current densities from these transients within their respective volumes or cross-sectional areas are the same order of magnitude. Length–velocity ratios and temporal durations are nearly identical. There are similar chemical consequences such as the production of nitric oxide. Careful, quantitative examination of the characteristics of lightning may reveal analogous features of the action potential that could lead to a more accurate understanding of these powerful correlates of neurocognitive processes. PMID:22615688

Rapid Polymer Transport in a Single Nanometer-Scale Pore

NASA Astrophysics Data System (ADS)

Kasianowicz, J. J.

1998-03-01

Protein ion channels are nanometer-scale pores that control the transport of ions and polymers across cell membranes. We compared the ability of charged and nonelectrolyte linear polymers to partition into a single channel reconstituted into a planar lipid bilayer membrane. The entry of each polymer (e.g. monodisperse length single-stranded homopolymeric RNA1 or poly(ethylene glycol)2,3) into the pore caused characteristic transient decreases in the channel's ionic conductance. The ionic current blockades yield detailed information about the physical properties of the polymers and the pore. The biological and technological significance of the results will be discussed.

Nonlinear Optical Properties of Semiconducting Polymers.

DTIC Science & Technology

1990-01-01

geberation in both cis and trans- polyacetylene. In the fast transient photoconductivity area, we will attempt to move into the sub-picosecond regime...spectroscopy (ir through visible) of third harmonic geberation in both cis and trans- polyacetylene. In the fast transient photoconductivity area, we will

Real-time detection of transients in OGLE-IV with application of machine learning

NASA Astrophysics Data System (ADS)

Klencki, Jakub; Wyrzykowski, Łukasz

2016-06-01

The current bottleneck of transient detection in most surveys is the problem of rejecting numerous artifacts from detected candidates. We present a triple-stage hierarchical machine learning system for automated artifact filtering in difference imaging, based on self-organizing maps. The classifier, when tested on the OGLE-IV Transient Detection System, accepts 97% of real transients while removing up to 97.5% of artifacts.

Full-field transient vibrometry of the human tympanic membrane by local phase correlation and high-speed holography

NASA Astrophysics Data System (ADS)

Dobrev, Ivo; Furlong, Cosme; Cheng, Jeffrey T.; Rosowski, John J.

2014-09-01

Understanding the human hearing process would be helped by quantification of the transient mechanical response of the human ear, including the human tympanic membrane (TM or eardrum). We propose a new hybrid high-speed holographic system (HHS) for acquisition and quantification of the full-field nanometer transient (i.e., >10 kHz) displacement of the human TM. We have optimized and implemented a 2+1 frame local correlation (LC) based phase sampling method in combination with a high-speed (i.e., >40 K fps) camera acquisition system. To our knowledge, there is currently no existing system that provides such capabilities for the study of the human TM. The LC sampling method has a displacement difference of <11 nm relative to measurements obtained by a four-phase step algorithm. Comparisons between our high-speed acquisition system and a laser Doppler vibrometer indicate differences of <10 μs. The high temporal (i.e., >40 kHz) and spatial (i.e., >100 k data points) resolution of our HHS enables parallel measurements of all points on the surface of the TM, which allows quantification of spatially dependent motion parameters, such as modal frequencies and acoustic delays. Such capabilities could allow inferring local material properties across the surface of the TM.

The activity of spontaneous action potentials in developing hair cells is regulated by Ca(2+)-dependence of a transient K+ current.

PubMed

Levic, Snezana; Lv, Ping; Yamoah, Ebenezer N

2011-01-01

Spontaneous action potentials have been described in developing sensory systems. These rhythmic activities may have instructional roles for the functional development of synaptic connections. The importance of spontaneous action potentials in the developing auditory system is underpinned by the stark correlation between the time of auditory system functional maturity, and the cessation of spontaneous action potentials. A prominent K(+) current that regulates patterning of action potentials is I(A). This current undergoes marked changes in expression during chicken hair cell development. Although the properties of I(A) are not normally classified as Ca(2+)-dependent, we demonstrate that throughout the development of chicken hair cells, I(A) is greatly reduced by acute alterations of intracellular Ca(2+). As determinants of spike timing and firing frequency, intracellular Ca(2+) buffers shift the activation and inactivation properties of the current to more positive potentials. Our findings provide evidence to demonstrate that the kinetics and functional expression of I(A) are tightly regulated by intracellular Ca(2+). Such feedback mechanism between the functional expression of I(A) and intracellular Ca(2+) may shape the activity of spontaneous action potentials, thus potentially sculpting synaptic connections in an activity-dependent manner in the developing cochlea. © 2011 Levic et al.

Use of updated material properties in parametric optimization of spaceborne mirrors

NASA Astrophysics Data System (ADS)

Hull, Tony; Westerhoff, Thomas; Weidmann, Guenter; Kirchhoff, Rule

2016-07-01

Spaceborne sensor mirrors need to be both structurally efficient and to maintain figure through thermal transients. Both properties can be represented in a plot showing structural efficiency on one axis and thermal transient resilience on the other. For material selection, engineers have effectively used such charts. However in some cases thermal attributes have improved considerably. Using contemporary values, this comparison chart looks differently. We will discuss how lines of equal merit may be formulated differently depending on the orbit of the mission.

A new transiently chaotic flow with ellipsoid equilibria

NASA Astrophysics Data System (ADS)

Panahi, Shirin; Aram, Zainab; Jafari, Sajad; Pham, Viet-Thanh; Volos, Christos; Rajagopal, Karthikeyan

2018-03-01

In this article, a simple autonomous transiently chaotic flow with cubic nonlinearities is proposed. This system represents some unusual features such as having a surface of equilibria. We shall describe some dynamical properties and behaviours of this system in terms of eigenvalue structures, bifurcation diagrams, time series, and phase portraits. Various behaviours of this system such as periodic and transiently chaotic dynamics can be shown by setting special parameters in proper values. Our system belongs to a newly introduced category of transiently chaotic systems: systems with hidden attractors. Transiently chaotic behaviour of our proposed system has been implemented and tested by the OrCAD-PSpise software. We have found a proper qualitative similarity between circuit and simulation results.

Calcium channels in solitary retinal ganglion cells from post-natal rat.

PubMed Central

Karschin, A; Lipton, S A

1989-01-01

1. Calcium currents from identified, post-natal retinal ganglion cell neurones from rat were studied with whole-cell and single-channel patch-clamp techniques. Na+ and K+ currents were suppressed with pharmacological agents, allowing isolation of current carried by either 10 mM-Ca2+ or Ba2- during whole-cell recordings. For cell-attached patch recordings, the recording pipette contained 96-110 mM-BaCl2 while the bath solution consisted of isotonic potassium aspartate in order to zero the neuronal membrane potential. 2. A transient component, present in approximately one-third of the whole-cell recordings resembles closely the T-type calcium current observed previously in other tissues. This component activates at low voltages (-40 to -50 mV from holding potentials negative to -80 mV), inactivates with a time constant of 10-30 ms at 35 degrees C, and is carried equally well by Ba2+ or Ca2+. In single-channel recordings small (8 pS) channels are observed whose aggregate microscopic kinetics correspond well to the macroscopic current obtained during whole-cell measurements. 3. During whole-cell recordings, a more prolonged component activates in all retinal ganglion cells at -40 to -20 mV from a holding potential of -90 mV. This component is substantially larger when equimolar Ba2+ replaces Ca2+ as the charge carrier, and is sensitive to the dihydropyridine agonist Bay K8644 (5 microM) and antagonists nifedipine (1-10 microM) and nimodipine (1-10 microM). Thus, the dihydropyridine pharmacology of this prolonged component resembles that of the L-type calcium current found in dorsal root ganglion neurones and in heart cells. Also reminiscent of the L-current, the prolonged component in this preparation is less inactivated at depolarized holding potentials (-60 to -40 mV) than the transient component. In cell-attached recordings, large (20 pS) channels are observed with activation properties similar to those of the prolonged portion of the whole-cell current. 4. omega-Conotoxin fraction GVIA (omega-CgTX VIA), a peptide from the venom of the snail Conus geographus, produces a readily reversible blockade of all components of the calcium current in these central mammalian neurones. This finding is in contrast to that of other preparations in which this toxin is responsible for an ephemeral block of T-current but a long-lasting block of other components of calcium current. 5. In summary, at least two components of calcium current with discrete underlying unitary events are present in post-natal retinal ganglion cells from rat. One component closely resembles the T or transient current observed in other cell types.(ABSTRACT TRUNCATED AT 400 WORDS) PMID:2559971

Connections Between Theory and Experiment for Gold and Silver Nanoclusters.

PubMed

Weerawardene, K L Dimuthu M; Häkkinen, Hannu; Aikens, Christine M

2018-04-20

Ligand-stabilized gold and silver nanoparticles are of tremendous current interest in sensing, catalysis, and energy applications. Experimental and theoretical studies have closely interacted to elucidate properties such as the geometric and electronic structures of these fascinating systems. In this review, the interplay between theory and experiment is described; areas such as optical absorption and doping, where the theory-experiment connections are well established, are discussed in detail; and the current status of these connections in newer fields of study, such as luminescence, transient absorption, and the effects of solvent and the surrounding environment, are highlighted. Close communication between theory and experiment has been extremely valuable for developing an understanding of these nanocluster systems in the past decade and will undoubtedly continue to play a major role in future years.

Connections Between Theory and Experiment for Gold and Silver Nanoclusters

NASA Astrophysics Data System (ADS)

Weerawardene, K. L. Dimuthu M.; Häkkinen, Hannu; Aikens, Christine M.

2018-04-01

Ligand-stabilized gold and silver nanoparticles are of tremendous current interest in sensing, catalysis, and energy applications. Experimental and theoretical studies have closely interacted to elucidate properties such as the geometric and electronic structures of these fascinating systems. In this review, the interplay between theory and experiment is described; areas such as optical absorption and doping, where the theory-experiment connections are well established, are discussed in detail; and the current status of these connections in newer fields of study, such as luminescence, transient absorption, and the effects of solvent and the surrounding environment, are highlighted. Close communication between theory and experiment has been extremely valuable for developing an understanding of these nanocluster systems in the past decade and will undoubtedly continue to play a major role in future years.

Schottky x-ray detectors based on a bulk β-Ga2O3 substrate

NASA Astrophysics Data System (ADS)

Lu, Xing; Zhou, Leidang; Chen, Liang; Ouyang, Xiaoping; Liu, Bo; Xu, Jun; Tang, Huili

2018-03-01

β-Ga2O3 Schottky barrier diodes (SBDs) have been fabricated on a bulk (100) β-Ga2O3 substrate and tested as X-ray detectors in this study. The devices exhibited good rectification properties, such as a high rectification ratio and a close-to-unity ideality factor. A high photo-to-dark current ratio exceeding 800 was achieved for X-ray detection, which was mainly attributed to the low reverse leakage current in the β-Ga2O3 SBDs. Furthermore, transient response of the β-Ga2O3 X-ray detectors was investigated, and two different detection mechanisms, photovoltaic and photoconductive, were identified. The results imply the great potential of β-Ga2O3 based devices for X-ray detection.

Selective block of late Na+ current by local anaesthetics in rat large sensory neurones

PubMed Central

Baker, Mark D

2000-01-01

The actions of lignocaine and benzocaine on transient and late Na+ current generated by large diameter (⩾50 μm) adult rat dorsal root ganglion neurones, were studied using patch-clamp techniques.Both drugs blocked whole-cell late Na+ current in a concentration-dependent manner. At 200 ms following the onset of a clamp step from −110 to −40 mV, the apparent K for block of late Na+ current by lignocaine was 57.8±15 μM (mean±s.e.mean, n=4). The value for benzocaine was 24.9±3.3 μM, (mean±s.e.mean, n=3).The effect of lignocaine on transient current, in randomly selected neurones, appeared variable (n=8, half-block from ∼50 to 400 μM). Half-block by benzocaine was not attained, but both whole-cell (n=11) and patch data suggested a high apparent K,>250 μM. Transient current always remained after late current was blocked.The voltage-dependence of residual late current steady-state inactivation was not shifted by 20 μM benzocaine (n=3), whereas 200 μM benzocaine shifted the voltage-dependence of transient current steady-state inactivation by −18.7±5.9 mV (mean±s.e.mean, n=4).In current-clamp, benzocaine (250 μM) could block subthreshold, voltage-dependent inward current, increasing the threshold for eliciting action potentials, without preventing their generation (n=2).Block of late Na+ current by systemic local anaesthetic may play a part in preventing ectopic impulse generation in sensory neurones. PMID:10780966

Kinetically Controlled Lifetimes in Redox-Responsive Transient Supramolecular Hydrogels.

PubMed

Wojciechowski, Jonathan P; Martin, Adam D; Thordarson, Pall

2018-02-28

It remains challenging to program soft materials to show dynamic, tunable time-dependent properties. In this work, we report a strategy to design transient supramolecular hydrogels based on kinetic control of competing reactions. Specifically, the pH-triggered self-assembly of a redox-active supramolecular gelator, N,N'-dibenzoyl-l-cystine (DBC) in the presence of a reducing agent, which acts to disassemble the system. The lifetimes of the transient hydrogels can be tuned simply by pH or reducing agent concentration. We find through kinetic analysis that gel formation hinders the ability of the reducing agent and enables longer transient hydrogel lifetimes than would be predicted. The transient hydrogels undergo clean cycles, with no kinetically trapped aggregates observed. As a result, multiple transient hydrogel cycles are demonstrated and can be predicted. This work contributes to our understanding of designing transient assemblies with tunable temporal control.

A biophysical model examining the role of low-voltage-activated potassium currents in shaping the responses of vestibular ganglion neurons.

PubMed

Hight, Ariel E; Kalluri, Radha

2016-08-01

The vestibular nerve is characterized by two broad groups of neurons that differ in the timing of their interspike intervals; some fire at highly regular intervals, whereas others fire at highly irregular intervals. Heterogeneity in ion channel properties has been proposed as shaping these firing patterns (Highstein SM, Politoff AL. Brain Res 150: 182-187, 1978; Smith CE, Goldberg JM. Biol Cybern 54: 41-51, 1986). Kalluri et al. (J Neurophysiol 104: 2034-2051, 2010) proposed that regularity is controlled by the density of low-voltage-activated potassium currents (IKL). To examine the impact of IKL on spike timing regularity, we implemented a single-compartment model with three conductances known to be present in the vestibular ganglion: transient sodium (gNa), low-voltage-activated potassium (gKL), and high-voltage-activated potassium (gKH). Consistent with in vitro observations, removing gKL depolarized resting potential, increased input resistance and membrane time constant, and converted current step-evoked firing patterns from transient (1 spike at current onset) to sustained (many spikes). Modeled neurons were driven with a time-varying synaptic conductance that captured the random arrival times and amplitudes of glutamate-driven synaptic events. In the presence of gKL, spiking occurred only in response to large events with fast onsets. Models without gKL exhibited greater integration by responding to the superposition of rapidly arriving events. Three synaptic conductance were modeled, each with different kinetics to represent a variety of different synaptic processes. In response to all three types of synaptic conductance, models containing gKL produced spike trains with irregular interspike intervals. Only models lacking gKL when driven by rapidly arriving small excitatory postsynaptic currents were capable of generating regular spiking. Copyright © 2016 the American Physiological Society.

Transient analysis of a solid oxide fuel cell stack with crossflow configuration

NASA Astrophysics Data System (ADS)

Yuan, P.; Liu, S. F.

2018-05-01

This study investigates the transient response of the cell temperature and current density of a solid oxide fuel cell having 6 stacks with crossflow configuration. A commercial software repeatedly solves the governing equations of each stack, and get the convergent results of the whole SOFC stack. The preliminary results indicate that the average current density of each stack is similar to others, so the power output between different stacks are uniform. Moreover, the average cell temperature among stacks is different, and the central stacks have higher temperature due to its harder heat dissipation. For the operating control, the cell temperature difference among stacks is worth to concern because the temperature difference will be over 10 °C in the analysis case. The increasing of the inlet flow rate of the fuel and air will short the transient state, increase the average current density, and drop the cell temperature difference among the stacks. Therefore, the inlet flow rate is an important factor for transient performance of a SOFC stack.

Effects of funnel web spider toxin on Ca2+ currents in neurohypophysial terminals.

PubMed

Wang, G; Lemos, J R

1994-11-14

Funnel web spider toxin (FTX) is reportedly a specific blocker of P-type Ca2+ channels. The effects of FTX on the Ca2+ currents of isolated neurohypophysial nerve terminals of the rat were investigated using the 'whole-cell' patch-clamp technique. Both the transient and long-lasting Ca2+ current components were maximally elicited by depolarization from a holding potential equal to the normal terminal resting potential (-90 mV). Externally applied FTX inhibited the high-voltage-threshold, transient component of the Ca2+ current in a concentration-dependent manner, with a half-maximal inhibition at a dilution of approximately 1:10000. FTX also shifted the peak current of the I-V relationship by +10 mV. The long-lasting Ca2+ current component, which is sensitive to L-type Ca2+ channel blockers, was insensitive to FTX. The transient current, which is sensitive to omega-conotoxin GVIA, was completely blocked by FTX. These results suggest that there could be a novel, inactivating Ca2+ channel in the rat neurohypophysial terminals which is affected by both N-type and P-type Ca2+ channel blockers.

Longitudinal gradient coil optimization in the presence of transient eddy currents.

PubMed

Trakic, A; Liu, F; Lopez, H Sanchez; Wang, H; Crozier, S

2007-06-01

The switching of magnetic field gradient coils in magnetic resonance imaging (MRI) inevitably induces transient eddy currents in conducting system components, such as the cryostat vessel. These secondary currents degrade the spatial and temporal performance of the gradient coils, and compensation methods are commonly employed to correct for these distortions. This theoretical study shows that by incorporating the eddy currents into the coil optimization process, it is possible to modify a gradient coil design so that the fields created by the coil and the eddy currents combine together to generate a spatially homogeneous gradient that follows the input pulse. Shielded and unshielded longitudinal gradient coils are used to exemplify this novel approach. To assist in the evaluation of transient eddy currents induced within a realistic cryostat vessel, a low-frequency finite-difference time-domain (FDTD) method using the total-field scattered-field (TFSF) scheme was performed. The simulations demonstrate the effectiveness of the proposed method for optimizing longitudinal gradient fields while taking into account the spatial and temporal behavior of the eddy currents.

Analysis of transient state in HTS tapes under ripple DC load current

NASA Astrophysics Data System (ADS)

Stepien, M.; Grzesik, B.

2014-05-01

The paper concerns the analysis of transient state (quench transition) in HTS tapes loaded with the current having DC component together with a ripple component. Two shapes of the ripple were taken into account: sinusoidal and triangular. Very often HTS tape connected to a power electronic current supply (i.e. superconducting coil for SMES) that delivers DC current with ripples and it needs to be examined under such conditions. Additionally, measurements of electrical (and thermal) parameters under such ripple excitation is useful to tape characterization in broad range of load currents. The results presented in the paper were obtained using test bench which contains programmable DC supply and National Instruments data acquisition system. Voltage drops and load currents were measured vs. time. Analysis of measured parameters as a function of the current was used to tape description with quench dynamics taken into account. Results of measurements were also used to comparison with the results of numerical modelling based on FEM. Presented provisional results show possibility to use results of measurements in transient state to prepare inverse models of superconductors and their detailed numerical modelling.

Thermosensitive transient receptor potential channels (thermo-TRPs) in human corneal epithelial cells

PubMed Central

Mergler, Stefan; Garreis, Fabian; Sahlmüller, Monika; Reinach, Peter S.; Paulsen, Friedrich; Pleyer, Uwe

2010-01-01

Thermosensitive transient receptor potential proteins (TRPs) such as TRPV1-TRPV4 are all heat-activated non-selective cation channels that are modestly permeable to Ca2+. TRPV1, TRPV3 and TRPV4 functional expression were previously identified in human corneal epithelial cells (HCEC). However, the membrane currents were not described underlying their activation by either selective agonists or thermal variation. This study characterized the membrane currents and [Ca 2+]i transients induced by thermal and agonist TRPV1 and 4 stimulation. TRPV1 and 4 expressions were confirmed by RT-PCR and TRPV2 transcripts were also detected. In fura2-loaded HCEC, a TRPV1-3 selective agonist, 100 µM 2-aminoethoxydiphenyl borate (2-APB), induced intracellular Ca2+ transients and an increase in non-selective cation outward currents that were suppressed by ruthenium-red (RuR) (10–20 µM), a nonselective TRPV channel blocker. These changes were also elicited by rises in ambient temperature from 25 °C to over 40 °C. RuR (5 µM) and a selective TRPV1 channel blocker capsazepine (CPZ) (10 µM) or another related blocker, lanthanum chloride (La3+) (100 µM) suppressed these temperature-induced Ca2+ increases. Planar patch-clamp technique was used to characterize the currents underlying Ca2+ transients. Increasing the temperature to over 40 °C induced reversible rises in non-selective cation currents. Moreover, a hypotonic challenge (25 %) increased non-selective cation currents confirming TRPV4 activity. We conclude that HCEC possess in addition to thermo-sensitive TRPV3 activity TRPV1, TRPV2 and TRPV4 activity. Their activation confers temperature sensitivity at the ocular surface, which may protect the cornea against such stress. PMID:21506114

Simulation of transient effects in the heavy ion fusion injectors

NASA Astrophysics Data System (ADS)

Chen, Yu-Jiuan; Hewett, D. W.

1993-05-01

We have used the 2-D PIC code, GYMNOS, to study the transient behaviors in the Heavy Ion Fusion (HIF) injectors. GYMNOS simulations accurately provide the steady state Child-Langmuir current and the beam transient behavior within a planar diode. The simulations of the LBL HIF ESAC injector experiments agree well with the experimental data and EGUN steady state results. Simulations of the nominal HIF injectors have revealed the need to design the accelerating electrodes carefully to control the ion beam current, particularly the ion loss at the end of the bunch as the extraction voltage is reduced.

Electric Field and Current Transport Mechanisms in Schottky CdTe X-ray Detectors under Perturbing Optical Radiation

PubMed Central

Cola, Adriano; Farella, Isabella

2013-01-01

Schottky CdTe X-ray detectors exhibit excellent spectroscopic performance but suffer from instabilities. Hence it is of extreme relevance to investigate their electrical properties. A systematic study of the electric field distribution and the current flowing in such detectors under optical perturbations is presented here. The detector response is explored by varying experimental parameters, such as voltage, temperature, and radiation wavelength. The strongest perturbation is observed under 850 nm irradiation, bulk carrier recombination becoming effective there. Cathode and anode irradiations evidence the crucial role of the contacts, the cathode being Ohmic and the anode blocking. In particular, under irradiation of the cathode, charge injection occurs and peculiar kinks, typical of trap filling, are observed both in the current-voltage characteristic and during transients. The simultaneous access to the electric field and the current highlights the correlation between free and fixed charges, and unveils carrier transport/collection mechanisms otherwise hidden. PMID:23881140

Study of gain homogeneity and radiation effects of Low Gain Avalanche Pad Detectors

NASA Astrophysics Data System (ADS)

Gallrapp, C.; Fernández García, M.; Hidalgo, S.; Mateu, I.; Moll, M.; Otero Ugobono, S.; Pellegrini, G.

2017-12-01

Silicon detectors with intrinsic charge amplification implementing a n++-p+-p structure are considered as a sensor technology for future tracking and timing applications in high energy physics experiments. The performance of the intrinsic gain in Low Gain Avalanche Detectors (LGAD) after irradiation is crucial for the characterization of radiation hardness and timing properties in this technology. LGAD devices irradiated with reactor neutrons or 800 MeV protons reaching fluences of 2.3 × 1016 neq/cm2 were characterized using Transient Current Technique (TCT) measurements with red and infra-red laser pulses. Leakage current variations observed in different production lots and within wafers were investigated using Thermally Stimulated Current (TSC). Results showed that the intrinsic charge amplification is reduced with increasing fluence up to 1015 neq/cm2 which is related to an effective acceptor removal. Further relevant issues were charge collection homogeneity across the detector surface and leakage current performance before and after irradiation.

Current and anticipated use of thermal-hydraulic codes for BWR transient and accident analyses in Japan

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

Arai, Kenji; Ebata, Shigeo

1997-07-01

This paper summarizes the current and anticipated use of the thermal-hydraulic and neutronic codes for the BWR transient and accident analyses in Japan. The codes may be categorized into the licensing codes and the best estimate codes for the BWR transient and accident analyses. Most of the licensing codes have been originally developed by General Electric. Some codes have been updated based on the technical knowledge obtained in the thermal hydraulic study in Japan, and according to the BWR design changes. The best estimates codes have been used to support the licensing calculations and to obtain the phenomenological understanding ofmore » the thermal hydraulic phenomena during a BWR transient or accident. The best estimate codes can be also applied to a design study for a next generation BWR to which the current licensing model may not be directly applied. In order to rationalize the margin included in the current BWR design and develop a next generation reactor with appropriate design margin, it will be required to improve the accuracy of the thermal-hydraulic and neutronic model. In addition, regarding the current best estimate codes, the improvement in the user interface and the numerics will be needed.« less

Reversible pyroelectric and photogalvanic current in epitaxial Pb(Zr0.52Ti0.48)O3 thin films

NASA Astrophysics Data System (ADS)

Lee, J.; Esayan, S.; Prohaska, J.; Safari, A.

1994-01-01

The pyroelectric and photogalvanic effects have been studied in epitaxial Pb(Zr0.52Ti0.48)O3 (PZT) thin films. Photoinduced currents, which were completely reversible by electrical voltage, were observed. The photoinduced currents exhibited transient and steady state components. The transient component, in turn, consisted of two components with fast (<1 s) and slow (˜hours) relaxation times. The mechanisms of the photoinduced currents in PZT films and their possible applications in nondestructive readout ferroelectric memory are discussed.

Control of Phasic Firing by a Background Leak Current in Avian Forebrain Auditory Neurons

PubMed Central

Dagostin, André A.; Lovell, Peter V.; Hilscher, Markus M.; Mello, Claudio V.; Leão, Ricardo M.

2015-01-01

Central neurons express a variety of neuronal types and ion channels that promote firing heterogeneity among their distinct neuronal populations. Action potential (AP) phasic firing, produced by low-threshold voltage-activated potassium currents (VAKCs), is commonly observed in mammalian brainstem neurons involved in the processing of temporal properties of the acoustic information. The avian caudomedial nidopallium (NCM) is an auditory area analogous to portions of the mammalian auditory cortex that is involved in the perceptual discrimination and memorization of birdsong and shows complex responses to auditory stimuli We performed in vitro whole-cell patch-clamp recordings in brain slices from adult zebra finches (Taeniopygia guttata) and observed that half of NCM neurons fire APs phasically in response to membrane depolarizations, while the rest fire transiently or tonically. Phasic neurons fired APs faster and with more temporal precision than tonic and transient neurons. These neurons had similar membrane resting potentials, but phasic neurons had lower membrane input resistance and time constant. Surprisingly phasic neurons did not express low-threshold VAKCs, which curtailed firing in phasic mammalian brainstem neurons, having similar VAKCs to other NCM neurons. The phasic firing was determined not by VAKCs, but by the potassium background leak conductances, which was more prominently expressed in phasic neurons, a result corroborated by pharmacological, dynamic-clamp, and modeling experiments. These results reveal a new role for leak currents in generating firing diversity in central neurons. PMID:26696830

Determination of charge transfer resistance and capacitance of microbial fuel cell through a transient response analysis of cell voltage.

PubMed

Ha, Phuc Thi; Moon, Hyunsoo; Kim, Byung Hong; Ng, How Yong; Chang, In Seop

2010-03-15

An alternative method for determining the charge transfer resistance and double-layer capacitance of microbial fuel cells (MFCs), easily implemented without a potentiostat, was developed. A dynamic model with two parameters, the charge transfer resistance and double-layer capacitance of electrodes, was derived from a linear differential equation to depict the current generation with respect to activation overvoltage. This model was then used to fit the transient cell voltage response to the current step change during the continuous operation of a flat-plate type MFC fed with acetate. Variations of the charge transfer resistance and the capacitance value with respect to the MFC design conditions (biocatalyst existence and electrode area) and operating parameters (acetate concentration and buffer strength in the catholyte) were then determined to elucidate the validity of the proposed method. This model was able to describe the dynamic behavior of the MFC during current change in the activation loss region; having an R(2) value of over 0.99 in most tests. Variations of the charge transfer resistance value (thousands of Omega) according to the change of the design factors and operational factors were well-correlated with the corresponding MFC performances. However, though the capacitance values (approximately 0.02 F) reflected the expected trend according to the electrode area change and catalyst property, they did not show significant variation with changes in either the acetate concentration or buffer strength. (c) 2009 Elsevier B.V. All rights reserved.

49 CFR 21.23 - Definitions.

Code of Federal Regulations, 2010 CFR

2010-10-01

... personal property or interests therein, and the provision of facilities includes the construction... interests in property; (3) The detail of Federal personnel; (4) The sale and lease of, and the permission to use (on other than a casual or transient basis), Federal property or any interest in such property...

7 CFR 15.2 - Definitions.

Code of Federal Regulations, 2010 CFR

2010-01-01

... care, housing, social services, or parks and recreation; or (ii) The entire plant or other comparable... of Federal funds, (2) the grant or donation of Federal property and interests in property, (3) the... or transient basis), Federal property or any interest in such property or the furnishing of services...

38 CFR 18.13 - Definitions.

Code of Federal Regulations, 2010 CFR

2010-07-01

... care, housing, social services, or parks and recreation; or (ii) The entire plant or other comparable...) grants of Federal funds, (2) the grant or donation of Federal property and interests in property, (3) the... or transient basis), Federal property or any interest in such property without consideration or at a...

Temperature dependent GaAs MMIC radiation effects

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

Anderson, W.T.; Roussos, J.A.; Gerdes, J.

1993-12-01

The temperature dependence of pulsed neutron and flash x-ray radiation effects was studied in GaAs MMICs. Above room temperature the long term current transients are dominated by electron trapping in previously existing defects. At low temperature in the range 126 to 259 K neutron induced lattice damage appears to play an increasingly important role in producing long term current transients.

Do Magnetic Fields Drive High-Energy Explosive Transients?

NASA Astrophysics Data System (ADS)

Mundell, Carole

2017-10-01

I will review the current state-of-the-art in real-time, rapid response optical imaging and polarimetric followup of transient sources such as Gamma Ray Bursts. I will interpret current results within the context of the external shock model and present predictions for future mm- and cm-wave radio observatories. Recent observational results from new radio pilot studies will also be presented.

Properties of spontaneous Ca2+ transients recorded from interstitial cells of Cajal-like cells of the rabbit urethra in situ

PubMed Central

Hashitani, Hikaru; Suzuki, Hikaru

2007-01-01

Interstitial cells of Cajal-like cells (ICC-LCs) in the urethra may act as electrical pacemakers of spontaneous contractions. However, their properties in situ and their interaction with neighbouring urethral smooth muscle cells (USMCs) remain to be elucidated. To further explore the physiological role of ICC-LCs, spontaneous changes in [Ca2+]i (Ca2+ transients) were visualized in fluo-4 loaded preparations of rabbit urethral smooth muscle. ICC-LCs were sparsely distributed, rather than forming an extensive network. Ca2+ transients in ICC-LCs had a lower frequency and a longer half-width than those of USMCs. ICC-LCs often exhibited Ca2+ transients synchronously with each other, but did not often show a close temporal relationship with Ca2+ transients in USMCs. Nicardipine (1 μm) suppressed Ca2+ transients in USMCs but not in ICC-LCs. Ca2+ transients in ICC-LCs were abolished by cyclopiazonic acid (10 μm), ryanodine (50 μm) and caffeine (10 mm) or by removing extracellular Ca2+, and inhibited by 2-aminoethoxydiphenyl borate (50 μm) and 3-morpholino-sydnonimine (SIN-1; 10 μm), but facilitated by increasing extracellular Ca2+ or phenylephrine (1–10 μm). These results indicated that Ca2+ transients in urethral ICC-LCs in situ rely on both Ca2+ release from intracellular Ca2+ stores and Ca2+ influx through non-L-type Ca2+ channel pathways. ICC-LCs may not act as a coordinated pacemaker electrical network as do ICC in the gastrointestinal (GI) tract. Rather they may randomly increase excitability of USMCs to maintain the tone of urethral smooth muscles. PMID:17615099

Technical Note: MR-visualization of interventional devices using transient field alterations and balanced steady-state free precession imaging.

PubMed

Eibofner, Frank; Martirosian, Petros; Würslin, Christian; Graf, Hansjörg; Syha, Roland; Clasen, Stephan

2015-11-01

In interventional magnetic resonance imaging, instruments can be equipped with conducting wires for visualization by current application. The potential of sequence triggered application of transient direct currents in balanced steady-state free precession (bSSFP) imaging is demonstrated. A conductor and a modified catheter were examined in water phantoms and in an ex vivo porcine liver. The current was switched by a trigger pulse in the bSSFP sequence in an interval between radiofrequency pulse and signal acquisition. Magnitude and phase images were recorded. Regions with transient field alterations were evaluated by a postprocessing algorithm. A phase mask was computed and overlaid with the magnitude image. Transient field alterations caused continuous phase shifts, which were separated by the postprocessing algorithm from phase jumps due to persistent field alterations. The overlaid images revealed the position of the conductor. The modified catheter generated visible phase offset in all orientations toward the static magnetic field and could be unambiguously localized in the ex vivo porcine liver. The application of a sequence triggered, direct current in combination with phase imaging allows conspicuous localization of interventional devices with a bSSFP sequence.

Transient radiation in an anisotropic magnetodielectric plate in a waveguide

NASA Astrophysics Data System (ADS)

Gevorkyan, E. A.

2017-02-01

We have considered transient radiation of a charged particle in an anisotropic magnetodielectric plate placed into a regular waveguide. It is assumed that the charged particle passes through the plate moving at a constant velocity perpendicularly to the waveguide axis. Wave equations and analytical expressions for transverse electric (TE) and transverse magnetic (TM) fields in different regions of the waveguide have been obtained. Energies of transient radiation of the moving particle have been calculated. The properties of transient radiation and Vavilov-Cherenkov radiation have been analyzed for the case of a rectangular waveguide. Energies of transient radiation have been calculated for the case of a "thin" plate in the waveguide, when the wavelength in the plate is much greater than the length of the plate.

Distinct Neural Circuits Support Transient and Sustained Processes in Prospective Memory and Working Memory

PubMed Central

West, Robert; Braver, Todd

2009-01-01

Current theories are divided as to whether prospective memory (PM) involves primarily sustained processes such as strategic monitoring, or transient processes such as the retrieval of intentions from memory when a relevant cue is encountered. The current study examined the neural correlates of PM using a functional magnetic resonance imaging design that allows for the decomposition of brain activity into sustained and transient components. Performance of the PM task was primarily associated with sustained responses in a network including anterior prefrontal cortex (lateral Brodmann area 10), and these responses were dissociable from sustained responses associated with active maintenance in working memory. Additionally, the sustained responses in anterior prefrontal cortex correlated with faster response times for prospective responses. Prospective cues also elicited selective transient activity in a region of interest along the right middle temporal gyrus. The results support the conclusion that both sustained and transient processes contribute to efficient PM and provide novel constraints on the functional role of anterior PFC in higher-order cognition. PMID:18854581

Method for detecting moment connection fracture using high-frequency transients in recorded accelerations

USGS Publications Warehouse

Rodgers, J.E.; Elebi, M.

2011-01-01

The 1994 Northridge earthquake caused brittle fractures in steel moment frame building connections, despite causing little visible building damage in most cases. Future strong earthquakes are likely to cause similar damage to the many un-retrofitted pre-Northridge buildings in the western US and elsewhere. Without obvious permanent building deformation, costly intrusive inspections are currently the only way to determine if major fracture damage that compromises building safety has occurred. Building instrumentation has the potential to provide engineers and owners with timely information on fracture occurrence. Structural dynamics theory predicts and scale model experiments have demonstrated that sudden, large changes in structure properties caused by moment connection fractures will cause transient dynamic response. A method is proposed for detecting the building-wide level of connection fracture damage, based on observing high-frequency, fracture-induced transient dynamic responses in strong motion accelerograms. High-frequency transients are short (<1 s), sudden-onset waveforms with frequency content above 25 Hz that are visually apparent in recorded accelerations. Strong motion data and damage information from intrusive inspections collected from 24 sparsely instrumented buildings following the 1994 Northridge earthquake are used to evaluate the proposed method. The method's overall success rate for this data set is 67%, but this rate varies significantly with damage level. The method performs reasonably well in detecting significant fracture damage and in identifying cases with no damage, but fails in cases with few fractures. Combining the method with other damage indicators and removing records with excessive noise improves the ability to detect the level of damage. ?? 2010 Elsevier B.V. All rights reserved.

Detectability of compact binary merger macronovae

NASA Astrophysics Data System (ADS)

Rosswog, S.; Feindt, U.; Korobkin, O.; Wu, M.-R.; Sollerman, J.; Goobar, A.; Martinez-Pinedo, G.

2017-05-01

We study the optical and near-infrared luminosities and detectability of radioactively powered electromagnetic transients (‘macronovae’) occuring in the aftermath of binary neutron star and neutron star black hole mergers. We explore the transients that result from the dynamic ejecta and those from different types of wind outflows. Based on full nuclear network simulations we calculate the resulting light curves in different wavelength bands. We scrutinize the robustness of the results by comparing (a) two different nuclear reaction networks and (b) two macronova models. We explore in particular how sensitive the results are to the production of α-decaying trans-lead nuclei. We compare two frequently used mass models: the finite-range Droplet model (FRDM) and the nuclear mass model of Duflo and Zuker (DZ31). We find that the abundance of α-decaying trans-lead nuclei has a significant impact on the observability of the resulting macronovae. For example, the DZ31 model yields considerably larger abundances resulting in larger heating rates and thermalization efficiencies and therefore predicts substantially brighter macronova transients. We find that the dynamic ejecta from NSNS models can reach peak K-band magnitudes in excess of  -15 while those from NSBH cases can reach beyond  -16. Similar values can be reached by some of our wind models. Several of our models (both wind and dynamic ejecta) yield properties that are similar to the transient that was observed in the aftermath of the short GRB 130603B. We further explore the expected macronova detection frequencies for current and future instruments such as VISTA, ZTF and LSST.

A Systematic Mid-Infrared Survey of A Sample of Tidal Disruption Events Discovered by ZTF

NASA Astrophysics Data System (ADS)

Yan, Lin; Van, Sjoert; Kulkarni, Shri; Kasliwal, Mansi; Gezari, Suvi; Cenko, Brad; Blagorodnova, Nadia; Hung, Tiara

2017-12-01

Zwicky Transient Facility (ZTF) saw its first light (press release on Nov 14, 2017) and is currently in the commissioning phase. The science operation is scheduled to start on Feb 1, 2018. Based on the data from Palomar Transient Factory (PTF), ZTF is expected to discover 30 new tidal disruption events (TDE) in the centers of galaxies containing supermassive blackholes. TDEs are rare transient events, and have only been discovered in recent years by large area transient surveys. Observations of optically discovered TDEs appear to show common characteristics, including blackbody temperatures of a few 10,000K, derived bolometric peak luminosities of several 10^43 - 10^44 erg/s, and photospheric radius of 10^15 - 10^16 cm. These properties are in conflict with the classic TDE model predictions, which suggest an order of magnitude higher temperature and peak luminosity. One proposed explanation is the possible existence of a reprocessing gas layer which absorbs X-ray, UV/optical photons and produces a cooler spectral energy distribution (SED). So far, there are only two published mid-IR light curves of TDEs, each with two epochal data. To solve this mystery, we require higher cadence Spitzer observations of a sample of uniformly selected TDEs. Next year is the only opportunity to obtain the critical observations because Spitzer is expected to operate only to March 2019. We request 24.1 hours of Spitzer time to observe 7 ZTF TDEs. This will produce a unique legacy dataset for many future studies of physics of TDEs.

Proton-Mediated Block of Ca2+ Channels during Multivesicular Release Regulates Short-Term Plasticity at an Auditory Hair Cell Synapse

PubMed Central

Cho, Soyoun

2014-01-01

Synaptic vesicles release both neurotransmitter and protons during exocytosis, which may result in a transient acidification of the synaptic cleft that can block Ca2+ channels located close to the sites of exocytosis. Evidence for this effect has been reported for retinal ribbon-type synapses, but not for hair cell ribbon synapses. Here, we report evidence for proton release from bullfrog auditory hair cells when they are held at more physiological, in vivo–like holding potentials (Vh = −60 mV) that facilitate multivesicular release. During paired recordings of hair cells and afferent fibers, L-type voltage-gated Ca2+ currents showed a transient block, which was highly correlated with the EPSC amplitude (or the amount of glutamate release). This effect was masked at Vh = −90 mV due to the presence of a T-type Ca2+ current and blocked by strong pH buffering with HEPES or TABS. Increasing vesicular pH with internal methylamine in hair cells also abolished the transient block. High concentrations of intracellular Ca2+ buffer (10 mm BAPTA) greatly reduced exocytosis and abolished the transient block of the Ca2+ current. We estimate that this transient block is due to the rapid multivesicular release of ∼600–1300 H+ ions per synaptic ribbon. Finally, during a train of depolarizing pulses, paired pulse plasticity was significantly changed by using 40 mm HEPES in addition to bicarbonate buffer. We propose that this transient block of Ca2+ current leads to more efficient exocytosis per Ca2+ ion influx and it may contribute to spike adaptation at the auditory nerve. PMID:25429130

Dynamic Optoelectronic Properties in Perovskite Oxide Thin Films Measured with Ultrafast Transient Absorption & Reflectance Spectroscopy

NASA Astrophysics Data System (ADS)

Smolin, Sergey Y.

Ultrafast transient absorption and reflectance spectroscopy are foundational techniques for studying photoexcited carrier recombination mechanisms, lifetimes, and charge transfer rates. Because quantifying photoexcited carrier dynamics is central to the intelligent design and improvement of many solid state devices, these transient optical techniques have been applied to a wide range of semiconductors. However, despite their promise, interpretation of transient absorption and reflectance data is not always straightforward and often relies on assumptions of physical processes, especially with respect to the influence of heating. Studying the material space of perovskite oxides, the careful collection, interpretation, and analysis of ultrafast data is presented here as a guide for future research into novel semiconductors. Perovskite oxides are a class of transition metal oxides with the chemical structure ABO3. Although traditionally studied for their diverse physical, electronic, and magnetic properties, perovskite oxides have gained recent research attention as novel candidates for light harvesting applications. Indeed, strong tunable absorption, unique interfacial properties, and vast chemical flexibility make perovskite oxides a promising photoactive material system. However, there is limited research characterizing dynamic optoelectronic properties, such as recombination lifetimes, which are critical to know in the design of any light-harvesting device. In this thesis, ultrafast transient absorption and reflectance spectroscopy was used to understand these dynamic optoelectronic properties in highquality, thin (<50 nm) perovskite oxide films grown by molecular beam epitaxy. Starting with epitaxial LaFeO3 (LFO) grown on (LaAlO 3)0.3(Sr2AlTaO6)0.7 (LSAT), transient absorption spectroscopy reveals two photoinduced absorption features at the band gap of LFO at 2.4 eV and at the higher energy absorption edge at 3.5 eV. Using a combination of temperature-dependent, variable-angle spectroscopic ellipsometry and time-resolved ultrafast optical spectroscopy on a type I heterostructure, we clarify thermal and electronic contributions to spectral transients in LaFeO3. Upon comparison to thermally-derived static spectra of LaFeO3, we find that thermal contributions dominate the transient absorption and reflectance spectra above the band gap. A transient photoinduced absorption feature below the band gap at 1.9 eV is not reproduced in the thermally derived spectra and has significantly longer decay kinetics from the thermallyinduced features; therefore, this long lived photoinduced absorption is likely derived, at least partially, from photoexcited carriers with lifetimes much longer than 3 nanoseconds. LaFeO3 has a wide band gap of 2.4 eV but its absorption can be decreased with chemical substitution of Sr for Fe to make it more suitable for various applications. This type of A-site substitution is a common route to change static optical absorption in perovskite oxides, but there are no systematic studies looking at how A-site substitution changes dynamic optoelectronic properties. To understand the relationship between composition and static and dynamic optical properties we worked with the model system of La1-xSrxFeO 3-delta epitaxial films grown on LSAT, uncovering the effects of A-site cation substitution and oxygen stoichiometry. Variable-angle spectroscopic ellipsometry was used to measure static optical properties, revealing a linear increase in absorption coefficient at 1.25 eV and a red-shifting of the optical absorption edge with increasing Sr fraction. The absorption spectra can be similarly tuned through the introduction of oxygen vacancies, indicating the critical role that nominal Fe valence plays in optical absorption. Dynamic optoelectronic properties were studied with ultrafast transient reflectance spectroscopy with broadband visible (1.6 eV to 4 eV) and near-infrared (0.9 eV to 1.5 eV) probes. The sign of the reflectance change in the near-infrared region in LSFO is indicative of carrier bandfilling of newly created electronic states by photoexcited carriers. Moreover, we find that similar transient spectral trends can be induced with A-site substitution or through oxygen vacancies, which is a surprising result. Probing the near-infrared region reveals similar nanosecond (1-3 ns) photoexcited carrier lifetimes for oxygen deficient and stoichiometric films. These results demonstrate that while the static optical absorption is strongly dependent on nominal Fe valence tuned through cation or anion stoichiometry, oxygen vacancies do not appear to play a significantly detrimental role in long lived recombination kinetics. Although this thesis represents one of the first comprehensive studies using broad band transient absorption and reflectance spectroscopy to study dynamic optoelectronic phenomena in perovskite oxides, it can also serve as a guide for the implementation and interpretation of ultrafast spectroscopy in other material systems. Moreover, the ultrafast work on perovskite oxides indicates that these materials have long nanosecond lifetimes required for light harvesting devices and should be investigated further.

The Effects of Low Dose-Rate Ionizing Radiation on the Shapes of Transients in the LM124 Operational Amplifier

NASA Technical Reports Server (NTRS)

Buchner, Stephen; McMorrow, Dale; Roche, Nicholas; Dusseau, Laurent; Pease, Ron L.

2008-01-01

Shapes of single event transients (SETs) in a linear bipolar circuit (LM124) change with exposure to total ionizing dose (TID) radiation. SETs shape changes are a direct consequence of TID-induced degradation of bipolar transistor gain. A reduction in transistor gain causes a reduction in the drive current of the current sources in the circuit, and it is the lower drive current that most affects the shapes of large amplitude SETs.

Profound regulation of Na/K pump activity by transient elevations of cytoplasmic calcium in murine cardiac myocytes

PubMed Central

Lu, Fang-Min; Deisl, Christine; Hilgemann, Donald W

2016-01-01

Small changes of Na/K pump activity regulate internal Ca release in cardiac myocytes via Na/Ca exchange. We now show conversely that transient elevations of cytoplasmic Ca strongly regulate cardiac Na/K pumps. When cytoplasmic Na is submaximal, Na/K pump currents decay rapidly during extracellular K application and multiple results suggest that an inactivation mechanism is involved. Brief activation of Ca influx by reverse Na/Ca exchange enhances pump currents and attenuates current decay, while repeated Ca elevations suppress pump currents. Pump current enhancement reverses over 3 min, and results are similar in myocytes lacking the regulatory protein, phospholemman. Classical signaling mechanisms, including Ca-activated protein kinases and reactive oxygen, are evidently not involved. Electrogenic signals mediated by intramembrane movement of hydrophobic ions, such as hexyltriphenylphosphonium (C6TPP), increase and decrease in parallel with pump currents. Thus, transient Ca elevation and Na/K pump inactivation cause opposing sarcolemma changes that may affect diverse membrane processes. DOI: http://dx.doi.org/10.7554/eLife.19267.001 PMID:27627745

Transient Reliability Analysis Capability Developed for CARES/Life

NASA Technical Reports Server (NTRS)

Nemeth, Noel N.

2001-01-01

The CARES/Life software developed at the NASA Glenn Research Center provides a general-purpose design tool that predicts the probability of the failure of a ceramic component as a function of its time in service. This award-winning software has been widely used by U.S. industry to establish the reliability and life of a brittle material (e.g., ceramic, intermetallic, and graphite) structures in a wide variety of 21st century applications.Present capabilities of the NASA CARES/Life code include probabilistic life prediction of ceramic components subjected to fast fracture, slow crack growth (stress corrosion), and cyclic fatigue failure modes. Currently, this code can compute the time-dependent reliability of ceramic structures subjected to simple time-dependent loading. For example, in slow crack growth failure conditions CARES/Life can handle sustained and linearly increasing time-dependent loads, whereas in cyclic fatigue applications various types of repetitive constant-amplitude loads can be accounted for. However, in real applications applied loads are rarely that simple but vary with time in more complex ways such as engine startup, shutdown, and dynamic and vibrational loads. In addition, when a given component is subjected to transient environmental and or thermal conditions, the material properties also vary with time. A methodology has now been developed to allow the CARES/Life computer code to perform reliability analysis of ceramic components undergoing transient thermal and mechanical loading. This means that CARES/Life will be able to analyze finite element models of ceramic components that simulate dynamic engine operating conditions. The methodology developed is generalized to account for material property variation (on strength distribution and fatigue) as a function of temperature. This allows CARES/Life to analyze components undergoing rapid temperature change in other words, components undergoing thermal shock. In addition, the capability has been developed to perform reliability analysis for components that undergo proof testing involving transient loads. This methodology was developed for environmentally assisted crack growth (crack growth as a function of time and loading), but it will be extended to account for cyclic fatigue (crack growth as a function of load cycles) as well.

Reactivity Initiated Accident Simulation to Inform Transient Testing of Candidate Advanced Cladding

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

Brown, Nicholas R; Wysocki, Aaron J; Terrani, Kurt A

2016-01-01

Abstract. Advanced cladding materials with potentially enhanced accident tolerance will yield different light water reactor performance and safety characteristics than the present zirconium-based cladding alloys. These differences are due to different cladding material properties and responses to the transient, and to some extent, reactor physics, thermal, and hydraulic characteristics. Some of the differences in reactors physics characteristics will be driven by the fundamental properties (e.g., absorption in iron for an iron-based cladding) and others will be driven by design modifications necessitated by the candidate cladding materials (e.g., a larger fuel pellet to compensate for parasitic absorption). Potential changes in thermalmore » hydraulic limits after transition from the current zirconium-based cladding to the advanced materials will also affect the transient response of the integral fuel. This paper leverages three-dimensional reactor core simulation capabilities to inform on appropriate experimental test conditions for candidate advanced cladding materials in a control rod ejection event. These test conditions are using three-dimensional nodal kinetics simulations of a reactivity initiated accident (RIA) in a representative state-of-the-art pressurized water reactor with both nuclear-grade iron-chromium-aluminum (FeCrAl) and silicon carbide based (SiC-SiC) cladding materials. The effort yields boundary conditions for experimental mechanical tests, specifically peak cladding strain during the power pulse following the rod ejection. The impact of candidate cladding materials on the reactor kinetics behavior of RIA progression versus reference zirconium cladding is predominantly due to differences in: (1) fuel mass/volume/specific power density, (2) spectral effects due to parasitic neutron absorption, (3) control rod worth due to hardened (or softened) spectrum, and (4) initial conditions due to power peaking and neutron transport cross sections in the equilibrium cycle cores due to hardened (or softened) spectrum. This study shows minimal impact of SiC-based cladding configurations on the transient response versus reference zirconium-based cladding. However, the FeCrAl cladding response indicates similar energy deposition, but with significantly shorter pulses of higher magnitude. Therefore the FeCrAl-based cases have a more rapid fuel thermal expansion rate and the resultant pellet-cladding interaction occurs more rapidly.« less

UNSUPERVISED TRANSIENT LIGHT CURVE ANALYSIS VIA HIERARCHICAL BAYESIAN INFERENCE

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

Sanders, N. E.; Soderberg, A. M.; Betancourt, M., E-mail: nsanders@cfa.harvard.edu

2015-02-10

Historically, light curve studies of supernovae (SNe) and other transient classes have focused on individual objects with copious and high signal-to-noise observations. In the nascent era of wide field transient searches, objects with detailed observations are decreasing as a fraction of the overall known SN population, and this strategy sacrifices the majority of the information contained in the data about the underlying population of transients. A population level modeling approach, simultaneously fitting all available observations of objects in a transient sub-class of interest, fully mines the data to infer the properties of the population and avoids certain systematic biases. Wemore » present a novel hierarchical Bayesian statistical model for population level modeling of transient light curves, and discuss its implementation using an efficient Hamiltonian Monte Carlo technique. As a test case, we apply this model to the Type IIP SN sample from the Pan-STARRS1 Medium Deep Survey, consisting of 18,837 photometric observations of 76 SNe, corresponding to a joint posterior distribution with 9176 parameters under our model. Our hierarchical model fits provide improved constraints on light curve parameters relevant to the physical properties of their progenitor stars relative to modeling individual light curves alone. Moreover, we directly evaluate the probability for occurrence rates of unseen light curve characteristics from the model hyperparameters, addressing observational biases in survey methodology. We view this modeling framework as an unsupervised machine learning technique with the ability to maximize scientific returns from data to be collected by future wide field transient searches like LSST.« less

Macro Scale Independently Homogenized Subcells for Modeling Braided Composites

NASA Technical Reports Server (NTRS)

Blinzler, Brina J.; Goldberg, Robert K.; Binienda, Wieslaw K.

2012-01-01

An analytical method has been developed to analyze the impact response of triaxially braided carbon fiber composites, including the penetration velocity and impact damage patterns. In the analytical model, the triaxial braid architecture is simulated by using four parallel shell elements, each of which is modeled as a laminated composite. Currently, each shell element is considered to be a smeared homogeneous material. The commercial transient dynamic finite element code LS-DYNA is used to conduct the simulations, and a continuum damage mechanics model internal to LS-DYNA is used as the material constitutive model. To determine the stiffness and strength properties required for the constitutive model, a top-down approach for determining the strength properties is merged with a bottom-up approach for determining the stiffness properties. The top-down portion uses global strengths obtained from macro-scale coupon level testing to characterize the material strengths for each subcell. The bottom-up portion uses micro-scale fiber and matrix stiffness properties to characterize the material stiffness for each subcell. Simulations of quasi-static coupon level tests for several representative composites are conducted along with impact simulations.

A New Comprehensive Lightning Instrumentation System for Pad 39B at the Kennedy Space Center, Florida

NASA Technical Reports Server (NTRS)

Mata, Carlos T.; Rakov, Vladimir A.; Mata, Angel G.; Bonilla Tatiana; Navedo, Emmanuel; Snyder, Gary P.

2010-01-01

A new comprehensive lightning instrumentation system has been designed for Launch Complex 39B at the Kennedy Space Center, Florida. This new instrumentation system includes the synchronized recording of six high-speed video cameras, currents through the nine downconductors of the new lightning protection system, four B-dot, 3-axis measurement stations, and five D-dot stations composed of two antennas each. The instrumentation system is composed of centralized transient recorders and digitizers that located close to the sensors in the field. The sensors and transient recorders communicate via optical fiber. The transient recorders are triggered by the B-dot sensors, the E-dot sensors, or the current through the downlead conductors. The high-speed cameras are triggered by the transient recorders when the latter perceives a qualified trigger.

Capabilities Development for Transient Testing of Advanced Nuclear Fuels at TREAT

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

Woolstenhulme, N. E.; Baker, C. C.; Bess, J. D.

2016-09-01

The TREAT facility is a unique capability at the Idaho National Laboratory currently being prepared for resumption of nuclear transient testing. Accordingly, designs for several transient irradiation tests are being pursued to enable development of advanced nuclear fuels and materials. In addition to the reactor itself, the foundation for TREAT’s capabilities also include a suite of irradiation vehicles and supporting infrastructure to provide the desired specimen boundary conditions while supporting a variety of instrumentation needs. The challenge of creating these vehicles, especially since many of the modern data needs were not historically addressed in TREAT experiment vehicles, has necessitated amore » sizeable engineering effort. This effort is currently underway and maturing rapidly. This paper summarizes the status, future plans, and rationale for TREAT experiment vehicle capabilities. Much of the current progress is focused around understanding and demonstrating the behavior of fuel design with enhanced accident tolerance in water-cooled reactors. Additionally, several related efforts are underway to facilitate transient testing in liquid sodium, inert gas, and steam environments. This paper discusses why such a variety of capabilities are needed, outlines plans to accomplish them, and describes the relationship between transient data needs and the irradiation hardware that will support the gathering of this information.« less

A Suzaku View of Cyclotron Line Sources and Candidates

NASA Technical Reports Server (NTRS)

Pottschmidt, K.; Suchy, S.; Rivers, E.; Rothschild, R. E.; Marcu, D. M.; Barragan, L.; Kuehnel, M.; Fuerst, F.; Schwarm, F.; Kreykenbohm, I.;

Development of a scanning time of flight microscope and its application to the study of charge transport in phase separated structured organic semiconductors

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

Paul, Sanjoy; Ellman, Brett, E-mail: bellman@kent.edu; Singh, Gautam

We describe a tool for studying the two-dimensional spatial variation in electronic properties of organic semiconductors: the scanning time-of-flight microscope (STOFm). The STOFm simultaneously measures the transmittance of polarized light and time-of-flight current transients with a pixel size <30 μm, making it especially valuable for studies of the correlations of structure with charge generation and transport in liquid crystalline organic semiconductors (LC OSCs). Adapting a previously developed photopolymerization technique, we characterize the instrument using patterned samples of a LC OSC bounded by a non-semiconducting polymer matrix.

Conceptualization and calibration of anisotropic, dynamic alluvial systems: Pitfalls and biases in current modelling practices

NASA Astrophysics Data System (ADS)

Gianni, Guillaume; Doherty, John; Perrochet, Pierre; Brunner, Philip

2017-04-01

Physical properties of alluvial environments are typically featuring a high degree of anisotropy and are characterized by dynamic interactions between the surface and the subsurface. A literature review on current modelling practice shows that hydrogeological models are often calibrated using isotropic hydraulic conductivity fields and steady state conditions. We aim at understanding how these simplifications affect the predictions of hydraulic heads and exchange fluxes using fully coupled, physically based synthetic models and advanced calibration approaches. Specifically, we present an analysis of the information content provided by averaged, steady state hydraulic data compared to transient data with respect to the determination of aquifer hydraulic properties. We show that the information content in average hydraulic heads is insufficient to inform anisotropic properties of alluvial aquifers and can lead to important biases on the calibrated parameters. We further explore the consequences of these biases on predictions of fluxes and water table dynamics. The results of this synthetic analysis are considered in the calibration of a highly dynamic and anisotropic alluvial aquifer system in Switzerland (the Rhône River). The results of the synthetic and real-world modelling and calibration exercises provide insight on future data acquisition, modelling and calibration strategies for these environments.

Transient nanobubbles in short-time electrolysis

NASA Astrophysics Data System (ADS)

Svetovoy, Vitaly B.; Sanders, Remco G. P.; Elwenspoek, Miko C.

2013-05-01

Water electrolysis in a microsystem is observed and analyzed on a short-time scale of ∼10 μs. The very unusual properties of the process are stressed. An extremely high current density is observed because the process is not limited by the diffusion of electroactive species. The high current is accompanied by a high relative supersaturation, S > 1000, that results in homogeneous nucleation of bubbles. On the short-time scale only nanobubbles can be formed. These nanobubbles densely cover the electrodes and aggregate at a later time to microbubbles. The effect is significantly intensified with a small increase of temperature. Application of alternating polarity voltage pulses produces bubbles containing a mixture of hydrogen and oxygen. Spontaneous reaction between gases is observed for stoichiometric bubbles with sizes smaller than ∼150 nm. Such bubbles disintegrate violently affecting the surfaces of the electrodes.

Studies of Low Luminosity Active Galactic Nuclei with Monte Carlo and Magnetohydrodynamic Simulations

NASA Astrophysics Data System (ADS)

Hilburn, Guy Louis

Results from several studies are presented which detail explorations of the physical and spectral properties of low luminosity active galactic nuclei. An initial Sagittarius A* general relativistic magnetohydrodynamic simulation and Monte Carlo radiation transport model suggests accretion rate changes as the dominant flaring method. A similar study on M87 introduces new methods to the Monte Carlo model for increased consistency in highly energetic sources. Again, accretion rate variation seems most appropriate to explain spectral transients. To more closely resolve the methods of particle energization in active galactic nuclei accretion disks, a series of localized shearing box simulations explores the effect of numerical resolution on the development of current sheets. A particular focus on numerically describing converged current sheet formation will provide new methods for consideration of turbulence in accretion disks.

Which key properties controls the preferential transport in the vadose zone under transient hydrological conditions

NASA Astrophysics Data System (ADS)

Groh, J.; Vanderborght, J.; Puetz, T.; Gerke, H. H.; Rupp, H.; Wollschlaeger, U.; Stumpp, C.; Priesack, E.; Vereecken, H.

2015-12-01

Understanding water flow and solute transport in the unsaturated zone is of great importance for an appropriate land use management strategy. The quantification and prediction of water and solute fluxes through the vadose zone can help to improve management practices in order to limit potential risk on our fresh water resources. Water related solute transport and residence time is strongly affected by preferential flow paths in the soil. Water flow in soils depends on soil properties and site factors (climate or experiment conditions, land use) and are therefore important factors to understand preferential solute transport in the unsaturated zone. However our understanding and knowledge of which on-site properties or conditions define and enhance preferential flow and transport is still poor and mostly limited onto laboratory experimental conditions (small column length and steady state boundary conditions). Within the TERENO SOILCan lysimeter network, which was designed to study the effects of climate change on soil functions, a bromide tracer was applied on 62 lysimeter at eight different test sites between Dec. 2013 and Jan. 2014. The TERENO SOILCan infrastructure offers the unique possibility to study the occurrence of preferential flow and transport of various soil types under different natural transient hydrological conditions and land use (crop, bare and grassland) at eight TERENO SOILCan observatories. Working with lysimeter replicates at each observatory allows defining the spatial variability of preferential transport and flow. Additionally lysimeters in the network were transferred within and between observatories in order to subject them to different rainfall and temperature regimes and enable us to relate the soil type susceptibility of preferential flow and transport not only to site specific physical and land use properties, but also to different transient boundary conditions. Comparison and statistical analysis between preferential flow indicators 5% arrival time and potential key soil properties, site factors and boundary conditions will be presented in order to identify key properties which control the preferential transport in the vadose zone under transient hydrological conditions.

Simultaneous Determination of Thermal Conductivity and Thermal Diffusivity of Food and Agricultural Materials Using a Transient Plane-Source Method

USDA-ARS?s Scientific Manuscript database

Thermal conductivity and thermal diffusivity are two important physical properties essential for designing any food engineering processes. Recently a new transient plane-source method was developed to measure a variety of materials, but its application in foods has not been documented. Therefore, ...

Formation of sex hormone transients resulting from attack of free radicals.

PubMed

Getoff, Nikola; Schittl, Heike; Gerschpacher, Marion; Quint, Ruth Maria

2013-03-01

Transients of the sex hormones testosterone (TES) and estrone (E1) exhibit an impact on the carcinogenesis of most prostate and breast cancer types. For elucidation of involved reaction mechanisms, in vitro, experiments using γ-ray for generation of attacking hormone transients and UV-light (λ=254 nm) for excitation of hormone molecules were applied. Materials and Methods. Experiments in vitro (Escherichia coli AB1157) incubated with TES and E1, individually as well as in mixture with vitamin C (electron donor), were performed under γ-irradiation in water-alcohol (40/60) medium for clarifying-up the reaction mechanism. The hormone degradation/regeneration processes were studied by high performance liquid chromatography analysis. Independently of hormone molecular structure, the determining factor for the biological properties, such as carcinogenity, were found to be based on the hormone transients. The biological ability of these, however, depends on the chemical properties of the species attacking the corresponding hormone. Hormone degradation can be, at least partly, converted into hormone regeneration by electron transfer from an electron donor (e.g. vitamin C), when available during the period of status nascendi of the hormone radicals.

Geometrically nonlinear transient vibrations of actively damped anti-symmetric angle ply laminated composite shallow shell using active fibre composite (AFC) actuators

NASA Astrophysics Data System (ADS)

Ashok, M. H.; Shivakumar, J.; Nandurkar, Santosh; Khadakbhavi, Vishwanath; Pujari, Sanjay

2018-02-01

In present work, the thin laminated composite shallow shell as smart structure with AFC material’s ACLD treatment is analyzed for geometrically nonlinear transient vibrations. The AFC material is used to make the constraining layer of the ACLD treatment. Golla-Hughes-McTavish (GHM) is used to model the constrained viscoelastic layer of the ACLD treatment in time domain. Along with a simple first-order shear deformation theory the Von Kármán type non-linear strain displacement relations are used for deriving this electromechanical coupled problem. A 3-dimensional finite element model of smart composite panels integrated with the ACLD treated patches has been modelled to reveal the performance of ACLD treated patches on improving the damping properties of slender anti-symmetric angle-ply laminated shallow shell, in controlling the transient vibrations which are geometrically nonlinear. The mathematical results explain that the ACLD treated patches considerably enhance the damping properties of anti-symmetric angle-ply panels undergoing geometrically nonlinear transient vibrations.

Actions of bis(7)-tacrine and tacrine on transient potassium current in rat DRG neurons and potassium current mediated by K(V)4.2 expressed in Xenopus oocyte.

PubMed

Li, Xiang-Yuan; Zhang, Jian; Dai, Jia-Pei; Liu, Xiang-Ming; Li, Zhi-Wang

2010-03-08

Bis(7)-tacrine [bis(7)-tetrahydroaminacrine] is a dimeric AChE inhibitor derived from tacrine with a potential to treat Alzheimer's disease. Actions of bis(7)-tacrine on ligand-gated ion channels and voltage-gated cation channels have been identified on neurons of both central and peripheral nervous systems. In the present study, the effect of bis(7)-tacrine was investigated on the K(V)4.2 encoded potassium currents expressed in Xenopus oocytes and the transient A-type potassium current (I(K(A))) on rat DRG neurons. Bis(7)-tacrine suppressed recombinant Kv4.2 potassium channels in a concentration-dependent manner, with IC(50) value of 0.53+/-0.13 muM. Tacrine also inhibited Kv4.2 channels, but with a much lower potency (IC(50) 74+/-15 muM).The possible mechanisms underlying the inhibition on potassium currents by bis(7)-tacrine/tacrine could be that inactivation of the transient potassium currents was accelerated and recovery of the native or Kv4.2 expressed potassium currents was suppressed by bis(7)-tacrine/tacrine. Copyright 2010 Elsevier B.V. All rights reserved.

Transient fault behavior in a microprocessor: A case study

NASA Technical Reports Server (NTRS)

Duba, Patrick

1989-01-01

An experimental analysis is described which studies the susceptibility of a microprocessor based jet engine controller to upsets caused by current and voltage transients. A design automation environment which allows the run time injection of transients and the tracing from their impact device to the pin level is described. The resulting error data are categorized by the charge levels of the injected transients by location and by their potential to cause logic upsets, latched errors, and pin errors. The results show a 3 picoCouloumb threshold, below which the transients have little impact. An Arithmetic and Logic Unit transient is most likely to result in logic upsets and pin errors (i.e., impact the external environment). The transients in the countdown unit are potentially serious since they can result in latched errors, thus causing latent faults. Suggestions to protect the processor against these errors, by incorporating internal error detection and transient suppression techniques, are also made.

Characterizing Nanoscale Transient Communication.

PubMed

Chen, Yifan; Anwar, Putri Santi; Huang, Limin; Asvial, Muhamad

2016-04-01

We consider the novel paradigm of nanoscale transient communication (NTC), where certain components of the small-scale communication link are physically transient. As such, the transmitter and the receiver may change their properties over a prescribed lifespan due to their time-varying structures. The NTC systems may find important applications in the biomedical, environmental, and military fields, where system degradability allows for benign integration into life and environment. In this paper, we analyze the NTC systems from the channel-modeling and capacity-analysis perspectives and focus on the stochastically meaningful slow transience scenario, where the coherence time of degeneration Td is much longer than the coding delay Tc. We first develop novel and parsimonious models to characterize the NTC channels, where three types of physical layers are considered: electromagnetism-based terahertz (THz) communication, diffusion-based molecular communication (DMC), and nanobots-assisted touchable communication (TouchCom). We then revisit the classical performance measure of ϵ-outage channel capacity and take a fresh look at its formulations in the NTC context. Next, we present the notion of capacity degeneration profile (CDP), which describes the reduction of channel capacity with respect to the degeneration time. Finally, we provide numerical examples to demonstrate the features of CDP. To the best of our knowledge, the current work represents a first attempt to systematically evaluate the quality of nanoscale communication systems deteriorating with time.

Dissection of the Effects of Quercetin on Mouse Myocardium.

PubMed

Santos, Michel Santana; Oliveira, Evaleide Diniz; Santos-Miranda, Artur; Cruz, Jader Santos; Gondim, Antônio Nei Santana; Menezes-Filho, José Evaldo Rodrigues; Souza, Diego Santos; Pinho-da-Silva, Leidiane; Jesus, Itamar Couto Guedes; Roman-Campos, Danilo; Guatimosim, Silvia; Lara, Aline; Conde-Garcia, Eduardo Antônio; Vasconcelos, Carla Maria Lins

2017-06-01

Quercetin is a plant flavonoid with several biological activities. This study aimed to describe quercetin effects on contractile and electrophysiological properties of the cardiac muscle as well as on calcium handling. Quercetin elicited positive inotropism that was significantly reduced by propranolol indicating an involvement of the sympathetic nervous system. In cardiomyocytes, 30 μM quercetin increased I Ca,L at 0 mV from -0.95 ± 0.01 A/F to -1.21 ± 0.08 A/F. The membrane potential at which 50% of the channels are activated (V 0.5 ) shifted towards more negative potentials from -13.06 ± 1.52 mV to -19.26 ± 1.72 mV and did not alter the slope factor. Furthermore, quercetin increased [Ca 2+ ] i transient by 28% when compared to control. Quercetin accelerated [Ca 2+ ] i transient decay time, which could be attributed to SERCA activation. In resting cardiomyocytes, quercetin did not change amplitude or frequency of Ca 2+ sparks. In isolated heart, quercetin increased heart rate and decreased PRi, QTc and duration of the QRS complex. Thus, we showed that quercetin activates β-adrenoceptors, leading to increased L-type Ca 2+ current and cell-wide intracellular Ca 2+ transient without visible changes in Ca 2+ sparks. © 2016 Nordic Association for the Publication of BCPT (former Nordic Pharmacological Society).

Full-field transient vibrometry of the human tympanic membrane by local phase correlation and high-speed holography

PubMed Central

Dobrev, Ivo; Furlong, Cosme; Cheng, Jeffrey T.; Rosowski, John J.

2014-01-01

Abstract. Understanding the human hearing process would be helped by quantification of the transient mechanical response of the human ear, including the human tympanic membrane (TM or eardrum). We propose a new hybrid high-speed holographic system (HHS) for acquisition and quantification of the full-field nanometer transient (i.e., >10  kHz) displacement of the human TM. We have optimized and implemented a 2+1 frame local correlation (LC) based phase sampling method in combination with a high-speed (i.e., >40  K fps) camera acquisition system. To our knowledge, there is currently no existing system that provides such capabilities for the study of the human TM. The LC sampling method has a displacement difference of <11  nm relative to measurements obtained by a four-phase step algorithm. Comparisons between our high-speed acquisition system and a laser Doppler vibrometer indicate differences of <10  μs. The high temporal (i.e., >40  kHz) and spatial (i.e., >100  k data points) resolution of our HHS enables parallel measurements of all points on the surface of the TM, which allows quantification of spatially dependent motion parameters, such as modal frequencies and acoustic delays. Such capabilities could allow inferring local material properties across the surface of the TM. PMID:25191832

Effects of cannabidiol on contractions and calcium signaling in rat ventricular myocytes.

PubMed

Ali, Ramez M; Al Kury, Lina T; Yang, Keun-Hang Susan; Qureshi, Anwar; Rajesh, Mohanraj; Galadari, Sehamuddin; Shuba, Yaroslav M; Howarth, Frank Christopher; Oz, Murat

2015-04-01

Cannabidiol (CBD), a major nonpsychotropic cannabinoid found in Cannabis plant, has been shown to influence cardiovascular functions under various physiological and pathological conditions. In the present study, the effects of CBD on contractility and electrophysiological properties of rat ventricular myocytes were investigated. Video edge detection was used to measure myocyte shortening. Intracellular Ca(2+) was measured in cells loaded with the Ca(2+) sensitive fluorescent indicator fura-2 AM. Whole-cell patch clamp was used to measure action potential and Ca(2+) currents. Radioligand binding was employed to study pharmacological characteristics of CBD binding. CBD (1μM) caused a significant decrease in the amplitudes of electrically evoked myocyte shortening and Ca(2+) transients. However, the amplitudes of caffeine-evoked Ca(2+) transients and the rate of recovery of electrically evoked Ca(2+) transients following caffeine application were not altered. CBD (1μM) significantly decreased the duration of APs. Further studies on L-type Ca(2+) channels indicated that CBD inhibits these channels with IC50 of 0.1μM in a voltage-independent manner. Radioligand studies indicated that the specific binding of [(3)H]Isradipine, was not altered significantly by CBD. The results suggest that CBD depresses myocyte contractility by suppressing L-type Ca(2+) channels at a site different than dihydropyridine binding site and inhibits excitation-contraction coupling in cardiomyocytes. Copyright © 2015 Elsevier Ltd. All rights reserved.

Some exact properties of the nonequilibrium response function for transient photoabsorption

NASA Astrophysics Data System (ADS)

Perfetto, E.; Stefanucci, G.

2015-03-01

The physical interpretation of time-resolved photoabsorption experiments is not as straightforward as for the more conventional photoabsorption experiments conducted on equilibrium systems. In fact, the relation between the transient photoabsorption spectrum and the properties of the examined sample can be rather intricate since the former is a complicated functional of both the driving pump and the feeble probe fields. In this work, we critically review the derivation of the time-resolved photoabsorption spectrum in terms of the nonequilibrium dipole response function χ and assess its domain of validity. We then analyze χ in detail and discuss a few exact properties useful to interpret the transient spectrum during (overlapping regime) and after (nonoverlapping regime) the action of the pump. The nonoverlapping regime is the simplest to address. The absorption energies are indeed independent of the delay between the pump and probe pulses and hence the transient spectrum can change only by a rearrangement of the spectral weights. We give a close expression of these spectral weights in two limiting cases (ultrashort and everlasting monochromatic probes) and highlight their strong dependence on coherence and probe envelope. In the overlapping regime, we obtain a Lehmann-type representation of χ in terms of light-dressed states and provide a unifying framework of various well-known effects in pump-driven systems. We also show the emergence of spectral substructures due to the finite duration of the pump pulse.

Nicotine is a potent blocker of the cardiac A-type K(+) channels. Effects on cloned Kv4.3 channels and native transient outward current.

PubMed

Wang, H; Shi, H; Zhang, L; Pourrier, M; Yang, B; Nattel, S; Wang, Z

2000-09-05

Nicotine is a main constituent of cigarette smoke and smokeless tobacco, known to increase the risk of sudden cardiac death. This study aimed at establishing ionic mechanisms underlying potential electrophysiological effects of nicotine. Effects of nicotine on Kv4.3 and Kv4.2 channels expressed in Xenopus oocytes were studied at the whole-cell and single-channel levels. The effects of nicotine on the transient outward K(+) current (I:(to)) were studied by use of whole-cell patch-clamp techniques in canine ventricular myocytes. Nicotine potently inhibited Kv4 current. The concentration for half-maximal inhibition (IC(50)) was 40+/-4 nmol/L, and the current was abolished by 100 micromol/L nicotine. The IC(50) for block of native I:(to) was 270+/-43 nmol/L. The steady-state activation properties of Kv4.3 and I:(to) were unaltered by nicotine, whereas positive shifts of the inactivation curves were observed. Of the total inhibition of Kv4.3 and I:(to) by nicotine, 40% was due to tonic block and 60% was attributable to use-dependent block. Activation, inactivation, and reactivation kinetics were not significantly changed by nicotine. Nicotine reduced single-channel conductance, open probability, and open time but increased the closed time of Kv4.3. The effects of nicotine were not altered by antagonists to various neurotransmitter receptors, indicating direct effects on I:(to) channels. Nicotine is a potent inhibitor of cardiac A-type K(+) channels, with blockade probably due to block of closed and open channels. This action may contribute to the ability of nicotine to affect cardiac electrophysiology and induce arrhythmias.

Pre-Steady-State Kinetics of Ba-Ca Exchange Reveals a Second Electrogenic Step Involved in Ca2+ Translocation by the Na-Ca Exchanger

PubMed Central

Haase, Andreas; Hartung, Klaus

2009-01-01

Kinetic properties of the Na-Ca exchanger (guinea pig NCX1) expressed in Xenopus oocytes were investigated with excised membrane patches in the inside-out configuration and photolytic Ca2+ concentration jumps with either 5 mM extracellular Sr2+ or Ba2+. After a Ca2+ concentration jump on the cytoplasmic side, the exchanger performed Sr-Ca or Ba-Ca exchange. In the Sr-Ca mode, currents are transient and decay in a monoexponential manner similar to that of currents in the Ca-Ca exchange mode described before. Currents recorded in the Ba-Ca mode are also transient, but the decay is biphasic. In the Sr-Ca mode the amount of charge translocated increases at negative potentials in agreement with experiments performed in the Ca-Ca mode. In the Ba-Ca mode the total amount of charge translocated after a Ca2+ concentration jump is ∼4 to 5 times that in Ca-Ca or Sr-Ca mode. In the Ba-Ca mode the voltage dependence of charge translocation depends on the Ca2+ concentration on the cytosolic side before the Ca2+ concentration jump. At low initial Ca2+ levels (∼0.5 μM), charge translocation is voltage independent. At a higher initial concentration (1 μM Ca2+), the amount of charge translocated increases at positive potentials. Biphasic relaxation of the current was also observed in the Ca-Ca mode if the external Ca2+ concentration was reduced to ≤0.5 mM. The results reported here and in previous publications can be described by using a 6-state model with two voltage-dependent conformational transitions. PMID:19486679

Bio-inspired metal-coordinate hydrogels with programmable viscoelastic material functions controlled by longwave UV light.

PubMed

Grindy, Scott C; Holten-Andersen, Niels

2017-06-07

Control over the viscoelastic mechanical properties of hydrogels intended for use as biomedical materials has long been a goal of soft matter scientists. Recent research has shown that materials made from polymers with reversibly associating transient crosslinks are a promising strategy for controlling viscoelasticity in hydrogels, for example leading to systems with precisely tunable mechanical energy-dissipation. We and others have shown that bio-inspired histidine:transition metal ion complexes allow highly precise and tunable control over the viscoelastic properties of transient network hydrogels. In this paper, we extend the design of these hydrogels such that their viscoelastic properties respond to longwave UV radiation. We show that careful selection of the histidine:transition metal ion crosslink mixtures allows unique control over pre- and post-UV viscoelastic properties. We anticipate that our strategy for controlling stimuli-responsive viscoelastic properties will aid biomedical materials scientists in the development of soft materials with specific stress-relaxing or energy-dissipating properties.

Pre-conceptual Development and characterization of an extruded graphite composite fuel for the TREAT Reactor

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

Luther, Erik; Rooyen, Isabella van; Leckie, Rafael

2015-03-01

In an effort to explore fuel systems that are more robust under accident scenarios, the DOE-NE has identified the need to resume transient testing. The Transient Reactor Test (TREAT) facility has been identified as the preferred option for the resumption of transient testing of nuclear fuel in the United States. In parallel, NNSA’s Global Threat Reduction Initiative (GTRI) Convert program is exploring the needs to replace the existing highly enriched uranium (HEU) core with low enriched uranium (LEU) core. In order to construct a new LEU core, materials and fabrication processes similar to those used in the initial core fabricationmore » must be identified, developed and characterized. In this research, graphite matrix fuel blocks were extruded and materials properties of were measured. Initially the extrusion process followed the historic route; however, the project was expanded to explore methods to increase the graphite content of the fuel blocks and explore modern resins. Materials properties relevant to fuel performance including density, heat capacity and thermal diffusivity were measured. The relationship between process defects and materials properties will be discussed.« less

Application of the modified transient plane source technique for early detection of liquid explosives

NASA Astrophysics Data System (ADS)

Bateman, Robert; Harris, Adam; Lee, Linda; Howle, Christopher R.; Ackermann, Sarah L. G.

2016-05-01

The paper will review the feasibility of adapting the Modified Transient Plane Source (MTPS) method as a screening tool for early-detection of explosives and hazardous materials. Materials can be distinguished from others based on their inherent thermal properties (e.g. thermal effusivity) in testing through different types of barrier materials. A complimentary advantage to this technique relative to other traditional detection technologies is that it can penetrate reflective barrier materials, such as aluminum, easily. A strong proof-of-principle is presented on application of the MTPS transient thermal property measuring in the early-screening of liquid explosives. The work demonstrates a significant sensitivity to distinguishing a wide range of fluids based on their thermal properties through a barrier material. The work covers various complicating factors to the longer-term adoption of such a method including the impact of carbonization and viscosity. While some technical challenges remain, the technique offers significant advantages in complimenting existing detection methods in being able to penetrate reflective metal containers (e.g. aluminum soft drinkscans) with ease.

Methods and apparatus for measurement of electronic properties of geological formations through borehole casing

DOEpatents

Vail, W.B. III.

1991-08-27

Methods and apparatus are provided for measuring electronic properties of geological formations and cement layers adjacent to cased boreholes including resistivities, polarization phenomena and dielectric constants. Current is passed from an electrode in electrical contact with the interior of the borehole casing to an electrode on the surface of the earth. At least three voltage measuring electrodes in electrical contact with the interior of the casing measure the voltage at various points thereon. The voltage differences between discrete pairs of the voltage measuring electrodes provide a measurement of the differential current conducted into the formation in the vicinity of those electrodes. These measurements facilitate calculation of the resistivities of the adjacent geological formations as well as an indication of whether cement is present. Measurements of the differential voltage response to transient currents provide a measurement of the polarization phenomena in formation as well as the capacitance of the casing in contact with the formation which is useful for determining whether oil and gas are present. Lithological characteristics of the formation such as the presence or absence of clay can also be determined. A calibration procedure is provided for minimizing errors induced by variations in the casing. The device also may be placed within the pipe attached to a drill bit while drilling open holes. 48 figures.

Methods and apparatus for measurement of electronic properties of geological formations through borehole casing

DOEpatents

Vail, W.B. III.

1989-11-21

Methods and apparatus are provided for measuring electronic properties of geological formations and cement layers adjacent to cased boreholes including resistivities, polarization phenomena and dielectric constants. Current is passed from an electrode in electrical contact with the interior of the borehole casing to an electrode on the surface of the earth. At least three voltage measuring electrodes in electrical contact with the interior of the casing measure the voltage at various points thereon. The voltage differences between discrete pairs of the voltage measuring electrodes provide a measurement of differential current conducted into formation in the vicinity of those electrodes. These measurements facilitate calculation of the resistivities of the adjacent geological formations as well as an indication of whether cement is present. Measurements of the differential voltage response to transient currents provide a measurement of the polarization phenomena in formation as well as the capacitance of the casing in contact with the formation which is useful for determining whether oil and gas are present. Lithological characteristics of the formation such as the presence or absence of clay can also be determined. A calibration procedure is provided for minimizing errors induced by variations in the casing. The device also may be placed within the pipe attached to a drill bit while drilling open holes. 48 figs.

Methods and apparatus for measurement of electronic properties of geological formations through borehole casing

DOEpatents

Vail, III, William B.

1991-01-01

Methods and apparatus are provided for measuring electronic properties of geological formations and cement layers adjacent to cased boreholes including resistivities, polarization phenomena and dielectric constants. Current is passed from an electrode in electrical contact with the interior of the borehole casing to an electrode on the surface of the earth. At least three voltage measuring electrodes in electrical contact with the interior of the casing measure the voltage at various points thereon. The voltage differences between discrete pairs of the voltage measuring electrodes provide a measurement of the differential current conducted into formation in the vicinity of those electrodes. These measurements facilitate calculation of the resistivities of the adjacent geological formations as well as an indication of whether cement is present. Measurements of the differential voltage response to transient currents provide a measurement of the polarization phenomena in formation as well as the capacitance of the casing in contact with the formation which is useful for determining whether oil and gas present. Lithological characteristics of the formation such as the pressence or absence of clay can also be determined. A calibration procedure is provided for minimizing errors induced by variations in the casing. The device also may be placed within the pipe attached to a drill bit while drilling open holes.

Methods and apparatus for measurement of electronic properties of geological formations through borehole casing

DOEpatents

Vail, III, William B.

1989-01-01

Methods and apparatus are provided for measuring electronic properties of geological formations and cement layers adjacent to cased boreholes including resistivities, polarization phenomena and dielectric constants. Current is passed from an electrode in electrical contact with the interior of the borehole casing to an electrode on the surface of the earth. At least three voltage measuring electrodes in electrical contact with the interior of the casing measure the voltage at various points thereon. The voltage differences between discrete pairs of the voltage measuring electrodes provide a measurement of differential current conducted into formation in the vicinity of those electrodes. These measurements facilitate calculation of the resistivities of the adjacent geological formations as well as an indication of whether cement is present. Measurements of the differential voltage response to transient currents provide a measurement of the polarization phenomena in formation as well as the capacitance of the casing in contact with the formation which is useful for determining whether oil and gas are present. Lithological characteristics of the formation such as the presence or absence of clay can also be determined. A calibration procedure is provided for minimizing errors induced by variations in the casing. The device also may be placed within the pipe attached to a drill bit while drilling open holes.

Potential energy barriers to ion transport within lipid bilayers. Studies with tetraphenylborate.

PubMed Central

Andersen, P S; Fuchs, M

1975-01-01

Tetraphenylborate-induced current transients were studied in lipid bilayers formed from bacterial phosphatidylethanolamine in decane. This ion movement was essentially confined to the membrane in terior during the current transients. Charge movement through the interior of the membrane during the current transients was studied as a function of the applied potential. The transferred charge approached an upper limit with increasing potential, which is interpreted to be the amount of charge due to tetraphenylborate ions absorbed into the boundary regions of the bilayer. A further analysis of the charge transfer as a function of potential indicates that the movement of tetraphenylborate ions is only influenced by a certain farction of the applied potential. For bacterial phosphatidylethanolamine bilayers the effective potential is 77 +/- 4% of the applied potential. The initial conductance and the time constant of the current transients were studied as a function of the applied potential using a Nernst-Planck electrodiffusion regime. It was found that an image-force potential energy barrier gave a good prediction of the observed behavior, provided that the effective potential was used in the calculations. We could not get a satisfactory prediction of the observed behavior with an Eyring rate theory model or a trapezoidal potential energy barrier. PMID:1148364

Heavy Ion Microbeam and Broadbeam Transients in SiGe HBTs

NASA Technical Reports Server (NTRS)

Pellish, Jonathan A.; Reed, Robert A.; McMorrow, Dale; Vizkelethy, Gyorgy; Dodd, Paul E.; Ferlet-Cavrois, Veronique; Baggio, Jacques; Paillet, Philippe; Duhamel, Olivier; Phillips, Stanley D.;

The Astrophysical Multimessenger Observatory Network (AMON)

NASA Technical Reports Server (NTRS)

Smith. M. W. E.; Fox, D. B.; Cowen, D. F.; Meszaros, P.; Tesic, G.; Fixelle, J.; Bartos, I.; Sommers, P.; Ashtekar, Abhay; Babu, G. Jogesh;

Surface magnetometer experiments - Internal lunar properties

NASA Technical Reports Server (NTRS)

Dyal, P.; Daily, W. D.; Parkin, C. W.

1973-01-01

Magnetic fields have been measured on the lunar surface at the Apollo 12, 14, 15, and 16 landing sites. The remanent field values at these sites are respectively 38, 103 (maximum), 3, and 327 gamma (maximum). Simultaneous magnetic field and solar plasma pressure measurements show that the remanent fields at the Apollo 12 and 16 sites are compressed and that the scale size of the Apollo 16 remanent field is 5 less than or equal to L less than 100 km. The global eddy current fields, induced by magnetic step transients in the solar wind, have been analyzed to calculate an electrical conductivity profile. From nightside data it has been found that deeper than 170 km into the moon, the conductivity rises from .0003 mho/m to .01 mho/m at 1000 km depth. Analysis of dayside transient data using a spherically symmetric two-layer model yields a homogeneous conducting core with a radius equal to 0.9 lunar radius and a conductivity of .001 mho/m, surrounded by a nonconducting shell of thickness equal to 0.1 lunar radius.

Two-phase SLIPI for instantaneous LIF and Mie imaging of transient fuel sprays.

PubMed

Storch, Michael; Mishra, Yogeshwar Nath; Koegl, Matthias; Kristensson, Elias; Will, Stefan; Zigan, Lars; Berrocal, Edouard

2016-12-01

We report in this Letter a two-phase structured laser illumination planar imaging [two-pulse SLIPI (2p-SLIPI)] optical setup where the "lines structure" is spatially shifted by exploiting the birefringence property of a calcite crystal. By using this optical component and two cross-polarized laser pulses, the shift of the modulated pattern is not "time-limited" anymore. Consequently, two sub-images with spatially mismatched phases can be recorded within a few hundred of nanoseconds only, freezing the motion of the illuminated transient flow. In comparison with previous setups for instantaneous imaging based on structured illumination, the current optical design presents the advantage of having a single optical path, greatly simplifying its complexity. Due to its virtue of suppressing the effects from multiple light scattering, the 2p-SLIPI technique is applied here in an optically dense multi-jet direct-injection spark-ignition (DISI) ethanol spray. The fast formation of polydispersed droplets and appearance of voids after fuel injection are investigated by simultaneous detection of Mie scattering and liquid laser-induced fluorescence. The results allow for significantly improved analysis of the spray structure.

Modelling the transient behaviour of pulsed current tungsten-inert-gas weldpools

NASA Astrophysics Data System (ADS)

Wu, C. S.; Zheng, W.; Wu, L.

1999-01-01

A three-dimensional model is established to simulate the pulsed current tungsten-inert-gas (TIG) welding process. The goal is to analyse the cyclic variation of fluid flow and heat transfer in weldpools under periodic arc heat input. To this end, an algorithm, which is capable of handling the transience, nonlinearity, multiphase and strong coupling encountered in this work, is developed. The numerical simulations demonstrate the transient behaviour of weldpools under pulsed current. Experimental data are compared with numerical results to show the effectiveness of the developed model.

Effects of Ta2O5 Addition on Electrical Properties of ZnO-V2O5 Based Varistor Ceramics

NASA Astrophysics Data System (ADS)

Fan, J. W.; Zhao, H. J.; Zhang, X. L.

2018-05-01

ZnO varistors are widely used for the protection of electronic and electrical equipment against transient surges. ZnO–V2O5 based varistor system is a potential candidate which can co-fire with Ag, and avoids the use of expensive Pa and Pt as the inner electrode in making multilayer chip varistors. However, the study of ZnO–V2O5-based ceramics is still in the initial stage for practical applications. The current work reports the effects of Ta2O5 on the electrical properties of ZnO-V2O5 based varistor ceramics. It shows that within 850-925°C experimental sintering temperature, the addition of Ta2O5 (0.05-0.20 mol%) may not improve the nonlinear coefficient but reduces the breakdown field of ZnO–V2O5 varistor ceramics.

On current transients in MoS2 Field Effect Transistors.

PubMed

Macucci, Massimo; Tambellini, Gerry; Ovchinnikov, Dmitry; Kis, Andras; Iannaccone, Giuseppe; Fiori, Gianluca

2017-09-14

We present an experimental investigation of slow transients in the gate and drain currents of MoS 2 -based transistors. We focus on the measurement of both the gate and drain currents and, from the comparative analysis of the current transients, we conclude that there are at least two independent trapping mechanisms: trapping of charges in the silicon oxide substrate, occurring with time constants of the order of tens of seconds and involving charge motion orthogonal to the MoS 2 sheet, and trapping at the channel surface, which occurs with much longer time constants, in particular when the device is in a vacuum. We observe that the presence of such slow phenomena makes it very difficult to perform reliable low-frequency noise measurements, requiring a stable and repeatable steady-state bias point condition, and may explain the sometimes contradictory results that can be found in the literature about the dependence of the flicker noise power spectral density on gate bias.

Improved Transient and Steady-State Performances of Series Resonant ZCS High-Frequency Inverter-Coupled Voltage Multiplier Converter with Dual Mode PFM Control Scheme

NASA Astrophysics Data System (ADS)

Chu, Enhui; Gamage, Laknath; Ishitobi, Manabu; Hiraki, Eiji; Nakaoka, Mutsuo

The A variety of switched-mode high voltage DC power supplies using voltage-fed type or current-fed type high-frequency transformer resonant inverters using MOS gate bipolar power transistors; IGBTs have been recently developed so far for a medical-use X-ray high power generator. In general, the high voltage high power X-ray generator using voltage-fed high frequency inverter with a high voltage transformer link has to meet some performances such as (i) short rising period in start transient of X-ray tube voltage (ii) no overshoot transient response in tube voltage, (iii) minimized voltage ripple in periodic steady-state under extremely wide load variations and filament heater current fluctuation conditions of the X-ray tube. This paper presents two lossless inductor snubber-assisted series resonant zero current soft switching high-frequency inverter using a diode-capacitor ladder type voltage multiplier called Cockcroft-Walton circuit, which is effectively implemented for a high DC voltage X-ray power generator. This DC high voltage generator which incorporates pulse frequency modulated series resonant inverter using IGBT power module packages is based on the operation principle of zero current soft switching commutation scheme under discontinuous resonant current and continuous resonant current transition modes. This series capacitor compensated for transformer resonant power converter with a high frequency transformer linked voltage boost multiplier can efficiently work a novel selectively-changed dual mode PFM control scheme in order to improve the start transient and steady-state response characteristics and can completely achieve stable zero current soft switching commutation tube filament current dependent for wide load parameter setting values with the aid of two lossless inductor snubbers. It is proved on the basis of simulation and experimental results in which a simple and low cost control implementation based on selectively-changed dual-mode PFM for high-voltage X-ray DC-DC power converter with a voltage multiplier strategy has some specified voltage pattern tracking voltage response performances under rapid rising time and no overshoot in start transient tube voltage as well as the minimized steady-state voltage ripple in tube voltage.

Exact analytical solution to a transient conjugate heat-transfer problem

NASA Technical Reports Server (NTRS)

Sucec, J.

1973-01-01

An exact analytical solution is found for laminar, constant-property, slug flow over a thin plate which is also convectively cooled from below. The solution is found by means of two successive Laplace transformations when a transient in the plate and the fluid is initiated by a step change in the fluid inlet temperature. The exact solution yields the transient fluid temperature, surface heat flux, and surface temperature distributions. The results of the exact transient solution for the surface heat flux are compared to the quasi-steady values, and a criterion for the validity of the quasi-steady results is found. Also the effect of the plate coupling parameter on the surface heat flux are investigated.

RAPIDLY EVOLVING AND LUMINOUS TRANSIENTS DRIVEN BY NEWLY BORN NEUTRON STARS

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

Yu, Yun-Wei; Li, Shao-Ze; Dai, Zi-Gao, E-mail: yuyw@mail.ccnu.edu.cn

2015-06-10

We provide a general analysis on the properties of the emitting material of some rapidly evolving and luminous transients discovered recently with the Pan-STARRS1 Medium Deep Survey. It was found that these transients are probably produced by a low-mass non-relativistic outflow that is continuously powered by a newly born, rapidly spinning, and highly magnetized neutron star (NS). Such a system could originate from an accretion-induced collapse of a white dwarf or a merger of an NS–NS binary. Therefore, observations of these transients would be helpful for constraining white dwarf and NS physics and/or for searching and identifying gravitational wave signals frommore » the mergers.« less

Effects of a parallel resistor on electrical characteristics of a piezoelectric transformer in open-circuit transient state.

PubMed

Chang, Kuo-Tsai

2007-01-01

This paper investigates electrical transient characteristics of a Rosen-type piezoelectric transformer (PT), including maximum voltages, time constants, energy losses and average powers, and their improvements immediately after turning OFF. A parallel resistor connected to both input terminals of the PT is needed to improve the transient characteristics. An equivalent circuit for the PT is first given. Then, an open-circuit voltage, involving a direct current (DC) component and an alternating current (AC) component, and its related energy losses are derived from the equivalent circuit with initial conditions. Moreover, an AC power control system, including a DC-to-AC resonant inverter, a control switch and electronic instruments, is constructed to determine the electrical characteristics of the OFF transient state. Furthermore, the effects of the parallel resistor on the transient characteristics at different parallel resistances are measured. The advantages of adding the parallel resistor also are discussed. From the measured results, the DC time constant is greatly decreased from 9 to 0.04 ms by a 10 k(omega) parallel resistance under open output.

Dopamine alters glutamate receptor desensitization in retinal horizontal cells of the perch (Perca fluviatilis).

PubMed Central

Schmidt, K F; Kruse, M; Hatt, H

1994-01-01

The patch-clamp technique in combination with a fast liquid filament application system was used to study the effect of dopamine on the glutamate receptor desensitization in horizontal cells of the perch (Perca fluviatilis). Kinetics of ligand-gated ion channels in fish horizontal cells are modulated by dopamine. This modulation is presumably mediated by a cAMP-dependent protein phosphorylation. Before incubation with dopamine, the glutamate receptors of horizontal cells activate and desensitize with fast time constants. In the whole-cell recording mode, fast application of the agonists L-glutamate, quisqualate, or alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid prior to the dopamine incubation gives rise to fast transient currents with peak values of about 200 pA that desensitize within 100 ms. Kainate as agonist produced higher steady-state currents but no transient currents. After incubation of the cells with dopamine for 3 min, the desensitization was significantly reduced and the agonists L-glutamate, quisqualate, or alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid induced steady-state currents with amplitudes that were similar to the previously observed transient currents. Kainate-induced currents were only slightly affected. Fast desensitizing currents upon fast application of L-glutamate were also recorded from outside-out patches that were excised from horizontal cells before incubation with dopamine. The currents from excised patches desensitized to a steady-state level of about 0.2 of the peak amplitude with time constants of less than 2 ms. When the outside-out patches were excised from cells after dopamine incubation, steady-state currents were enhanced and no transient currents were observed. The results may indicate that the dopamine-dependent modulation of glutamate-induced currents, which is presumably mediated by a protein phosphorylation, is due to an alteration of the desensitization of the glutamate receptors. PMID:7520178

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

Inflammation-induced increase in nicotinic acetylcholine receptor current in cutaneous nociceptive DRG neurons from the adult rat.

PubMed

Zhang, X-L; Albers, K M; Gold, M S

2015-01-22

The goals of the present study were to determine (1) the properties of the nicotinic acetylcholine receptor (nAChR) currents in rat cutaneous dorsal root ganglion (DRG) neurons; (2) the impact of nAChR activation on the excitability of cutaneous DRG neurons; and (3) the impact of inflammation on the density and distribution of nAChR currents among cutaneous DRG neurons. Whole-cell patch-clamp techniques were used to study retrogradely labeled DRG neurons from naïve and complete Freund's adjuvant inflamed rats. Nicotine-evoked currents were detectable in ∼70% of the cutaneous DRG neurons, where only one of two current types, fast or slow currents based on rates of activation and inactivation, was present in each neuron. The biophysical and pharmacological properties of the fast current were consistent with nAChRs containing an α7 subunit while those of the slow current were consistent with nAChRs containing α3/β4 subunits. The majority of small diameter neurons with fast current were IB4- while the majority of small diameter neurons with slow current were IB4+. Preincubation with nicotine (1 μM) produced a transient (1 min) depolarization and increase in the excitability of neurons with fast current and a decrease in the amplitude of capsaicin-evoked current in neurons with slow current. Inflammation increased the current density of both slow and fast currents in small diameter neurons and increased the percentage of neurons with the fast current. With the relatively selective distribution of nAChR currents in putative nociceptive cutaneous DRG neurons, our results suggest that the role of these receptors in inflammatory hyperalgesia is likely to be complex and dependent on the concentration and timing of acetylcholine release in the periphery. Copyright © 2014 IBRO. Published by Elsevier Ltd. All rights reserved.

Coherent Transient Systems Evaluation

DTIC Science & Technology

1993-06-17

europium doped yttrium silicate in collaboration with IBM Almaden Research Center. Research into divalent ion doped crystals as photon gated materials...noise limited model and ignore the non-ideal properties of the medium, nonlinear effects, spatial crosstalk, gating efficiencies, local heating, the...demonstration of the coherent transient continuous optical processor was performed in europium doped yttrium silicate. Though hyperfine split ground

A Matched Filter Technique for Slow Radio Transient Detection and First Demonstration with the Murchison Widefield Array

NASA Astrophysics Data System (ADS)

Feng, L.; Vaulin, R.; Hewitt, J. N.; Remillard, R.; Kaplan, D. L.; Murphy, Tara; Kudryavtseva, N.; Hancock, P.; Bernardi, G.; Bowman, J. D.; Briggs, F.; Cappallo, R. J.; Deshpande, A. A.; Gaensler, B. M.; Greenhill, L. J.; Hazelton, B. J.; Johnston-Hollitt, M.; Lonsdale, C. J.; McWhirter, S. R.; Mitchell, D. A.; Morales, M. F.; Morgan, E.; Oberoi, D.; Ord, S. M.; Prabu, T.; Udaya Shankar, N.; Srivani, K. S.; Subrahmanyan, R.; Tingay, S. J.; Wayth, R. B.; Webster, R. L.; Williams, A.; Williams, C. L.

2017-03-01

Many astronomical sources produce transient phenomena at radio frequencies, but the transient sky at low frequencies (<300 MHz) remains relatively unexplored. Blind surveys with new wide-field radio instruments are setting increasingly stringent limits on the transient surface density on various timescales. Although many of these instruments are limited by classical confusion noise from an ensemble of faint, unresolved sources, one can in principle detect transients below the classical confusion limit to the extent that the classical confusion noise is independent of time. We develop a technique for detecting radio transients that is based on temporal matched filters applied directly to time series of images, rather than relying on source-finding algorithms applied to individual images. This technique has well-defined statistical properties and is applicable to variable and transient searches for both confusion-limited and non-confusion-limited instruments. Using the Murchison Widefield Array as an example, we demonstrate that the technique works well on real data despite the presence of classical confusion noise, sidelobe confusion noise, and other systematic errors. We searched for transients lasting between 2 minutes and 3 months. We found no transients and set improved upper limits on the transient surface density at 182 MHz for flux densities between ˜20 and 200 mJy, providing the best limits to date for hour- and month-long transients.

Turbulence evolution and transport behavior during current ramp-up in ITER-like plasmas on DIII-D

DOE PAGES

McKee, George R.; Austin, Max E.; Boedo, Jose A.; ...

2017-07-12

Low-wavenumber density fluctuations exhibit unique characteristics during the current ramp-up phase of ITER-like discharges that can partially explain the challenges of correctly modeling transport behavior and predicting global plasma parameters during this period. A strong interaction takes place between the evolving transport, safety factor (q) and kinetic profiles as well as the appearance and evolution of low-order rational surfaces. Density fluctuations from 0.75 < ρ < 0.9 are transiently reduced to exceptionally low levels during early times and from 0.8 < ρ < 0.9 at late times in the ramp-up in a manner that is different from behavior observed duringmore » steady-state plasma conditions with similar values of q 95. Turbulence is suppressed as low-order-rational q-surfaces enter the plasma; the local electron temperature likewise exhibits transient increases during these periods of reduced fluctuations indicating changes in transport that impact temperature and consequently the evolution of current density and plasma inductance. These observations can explain discrepancies between CORSICA modelling and the higher electron temperature found previously over the outer half radius. Comparison of turbulence properties with time-varying linear growth rates with GYRO and GENE demonstrate qualitative consistency with measured fluctuation levels, but calculations don’t exhibit reduced growth rates near low-order rational surfaces, which is inconsistent with experimental observations. Here, this indicates a mechanism that can contribute to reconciling observed turbulence behavior with transport models, allowing for the development of more accurate predictive tools.« less

Turbulence evolution and transport behavior during current ramp-up in ITER-like plasmas on DIII-D

NASA Astrophysics Data System (ADS)

McKee, G. R.; Austin, M.; Boedo, J.; Bravenec, R.; Holland, C.; Jackson, G.; Luce, T. C.; Rhodes, T. L.; Rudakov, D.; Wang, G.; Yan, Z.; Zeng, L.; Zhao, Y.

2017-08-01

Low-wavenumber density fluctuations exhibit unique characteristics during the current ramp-up phase of ITER-like discharges that can partially explain the challenges of correctly modeling transport behavior and predicting global plasma parameters during this period. A strong interaction takes place between the evolving transport, safety factor (q) and kinetic profiles as well as the appearance and evolution of low-order rational surfaces. Density fluctuations from 0.75  <  ρ  <  0.9 are transiently reduced to exceptionally low levels during early times and from 0.8  <  ρ  <  0.9 at late times in the ramp-up in a manner that is different from behavior observed during steady-state plasma conditions with similar values of q 95. Turbulence is suppressed as low-order-rational q-surfaces enter the plasma; the local electron temperature likewise exhibits transient increases during these periods of reduced fluctuations indicating changes in transport that impact temperature and consequently the evolution of current density and plasma inductance. These observations can explain discrepancies between CORSICA modelling and the higher electron temperature found previously over the outer half radius. Comparison of turbulence properties with time-varying linear growth rates with GYRO and GENE demonstrate qualitative consistency with measured fluctuation levels, but calculations don’t exhibit reduced growth rates near low-order rational surfaces, which is inconsistent with experimental observations. This indicates a mechanism that can contribute to reconciling observed turbulence behavior with transport models, allowing for the development of more accurate predictive tools.

Immersed transient eddy current flow metering: a calibration-free velocity measurement technique for liquid metals

NASA Astrophysics Data System (ADS)

Krauter, N.; Stefani, F.

2017-10-01

Eddy current flow meters are widely used for measuring the flow velocity of electrically conducting fluids. Since the flow induced perturbations of a magnetic field depend both on the geometry and the conductivity of the fluid, extensive calibration is needed to get accurate results. Transient eddy current flow metering has been developed to overcome this problem. It relies on tracking the position of an impressed eddy current system that is moving with the same velocity as the conductive fluid. We present an immersed version of this measurement technique and demonstrate its viability by numerical simulations and a first experimental validation.

Hyperpolarizing muscarinic responses of freshly dissociated rat hippocampal CA1 neurones.

PubMed Central

Wakamori, M; Hidaka, H; Akaike, N

1993-01-01

1. Intracellular mechanisms of the muscarinic acetylcholine (ACh) response were investigated in pyramidal neurones freshly dissociated from the rat hippocampal CA1 region. Current recordings were made in the whole-cell mode using the nystatin 'perforated'-patch technique, by which the muscarinic ACh response can be continuously recorded without so-called 'run-down' phenomenon. The amount of intracellular free Ca2+ ([Ca2+]i) was fluorometrically measured using fura-2. 2. In current clamp conditions, ACh induced a transient hyperpolarization accompanied by a decrease in membrane input resistance. 3. Under voltage clamp conditions at a holding potential (Vh) of -40 mV, ACh induced two types of muscarinic currents observed either alone or together: a transient outward current and a slowly activating sustained inward current. 4. The ACh-induced transient outward current reversed the direction at K+ equilibrium potential (EK), and the reversal potential (EACh) shifted 56.7 mV for a tenfold change of extracellular K+ concentration ([K+]o). 5. The ACh-induced transient outward current increased in a sigmoidal fashion with increase in ACh concentration, where the half-maximal concentration (EC50) and the Hill coefficient (n) were 8 x 10(-7) M and 1.9, respectively. Both muscarine and carbamylcholine mimicked the ACh response, but neither McN-A-343 (M1 agonist) nor oxotremorine (cardiac M2 agonist) induced any current. 6. Muscarinic antagonists reversibly blocked the ACh response in a concentration-dependent manner. The inhibitory potency was in the order of atropine > pirenzepine > AF-DX-116. 7. The ACh-induced transient outward current was never recorded when [Ca2+]i was chelated by the acetoxymethyl ester form of 1,2-bis(O-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid (BAPTA AM). On the other hand, in Ca(2+)-free external solution containing 2 mM EGTA and 10 mM Mg2+, the ACh response was elicited by the first application and successive ACh applications did not induce any response. Fura-2 imaging showed that [Ca2+]i was increased when ACh was added to the external medium with or without Ca2+, though in Ca(2+)-free medium only the first application of ACh increased the [Ca2+]i. 8. The ACh response was not affected by pretreatment with pertussis toxin (PTX) but the inhibitory effect of ACh on the high-threshold Ca2+ channel was abolished completely. 9. Pretreatment with Li+ enhanced the amplitude of the transient outward current and the increase in [Ca2+]i induced by ACh. 10. The calmodulin antagonists W-7, chlorpromazine and trifluoperazine reversibly inhibited the ACh response in a concentration-dependent manner.(ABSTRACT TRUNCATED AT 400 WORDS) PMID:7504109

A new offshore transport mechanism for shoreline-released tracer induced by transient rip currents and stratification

NASA Astrophysics Data System (ADS)

Kumar, Nirnimesh; Feddersen, Falk

2017-03-01

Offshore transport from the shoreline across the inner shelf of early-stage larvae and pathogens is poorly understood yet is critical for understanding larval fate and dilution of polluted shoreline water. With a novel coupling of a transient rip current (TRC) generating surf zone model and an ocean circulation model, we show that transient rip currents ejected onto a stratified inner shelf induce a new, previously unconsidered offshore transport pathway. For incident waves and stratification typical for Southern California in the fall, this mechanism subducts surf zone-origin tracers and transports them at least 800 m offshore at 1.2 km/d analogous to subduction at ocean fronts. This mechanism requires both TRCs and stratification. As TRCs are ubiquitous and the inner shelf is often stratified, this mechanism may have an important role in exporting early-stage larvae, pathogens, or other tracers onto the shelf.

Slowly inactivating component of Na+ current in peri-somatic region of hippocampal CA1 pyramidal neurons

PubMed Central

Park, Yul Young; Johnston, Daniel

2013-01-01

The properties of voltage-gated ion channels on the neuronal membrane shape electrical activity such as generation and backpropagation of action potentials, initiation of dendritic spikes, and integration of synaptic inputs. Subthreshold currents mediated by sodium channels are of interest because of their activation near rest, slow inactivation kinetics, and consequent effects on excitability. Modulation of these currents can also perturb physiological responses of a neuron that might underlie pathological states such as epilepsy. Using nucleated patches from the peri-somatic region of hippocampal CA1 neurons, we recorded a slowly inactivating component of the macroscopic Na+ current (which we have called INaS) that shared many biophysical properties with the persistent Na+ current, INaP, but showed distinctively faster inactivating kinetics. Ramp voltage commands with a velocity of 400 mV/s were found to elicit this component of Na+ current reliably. INaS also showed a more hyperpolarized I-V relationship and slower inactivation than those of the fast transient Na+ current (INaT) recorded in the same patches. The peak amplitude of INaS was proportional to the peak amplitude of INaT but was much smaller in amplitude. Hexanol, riluzole, and ranolazine, known Na+ channel blockers, were tested to compare their effects on both INaS and INaT. The peak conductance of INaS was preferentially blocked by hexanol and riluzole, but the shift of half-inactivation voltage (V1/2) was only observed in the presence of riluzole. Current-clamp measurements with hexanol suggested that INaS was involved in generation of an action potential and in upregulation of neuronal excitability. PMID:23236005

Transient-state kinetic approach to mechanisms of enzymatic catalysis.

PubMed

Fisher, Harvey F

2005-03-01

Transient-state kinetics by its inherent nature can potentially provide more directly observed detailed resolution of discrete events in the mechanistic time courses of enzyme-catalyzed reactions than its more widely used steady-state counterpart. The use of the transient-state approach, however, has been severely limited by the lack of any theoretically sound and applicable basis of interpreting the virtual cornucopia of time and signal-dependent phenomena that it provides. This Account describes the basic kinetic behavior of the transient state, critically examines some currently used analytic methods, discusses the application of a new and more soundly based "resolved component transient-state time-course method" to the L-glutamate-dehydrogenase reaction, and establishes new approaches for the analysis of both single- and multiple-step substituted transient-state kinetic isotope effects.

Effects of phloretin and phloridzin on Ca2+ handling, the action potential, and ion currents in rat ventricular myocytes.

PubMed

Olson, Marnie L; Kargacin, Margaret E; Ward, Christopher A; Kargacin, Gary J

2007-06-01

The effects of the phytoestrogens phloretin and phloridzin on Ca(2+) handling, cell shortening, the action potential, and Ca(2+) and K(+) currents in freshly isolated cardiac myocytes from rat ventricle were examined. Phloretin increased the amplitude and area and decreased the rate of decline of electrically evoked Ca(2+) transients in the myocytes. These effects were accompanied by an increase in the Ca(2+) load of the sarcoplasmic reticulum, as determined by the area of caffeine-evoked Ca(2+) transients. An increase in the extent of shortening of the myocytes in response to electrically evoked action potentials was also observed in the presence of phloretin. To further examine possible mechanisms contributing to the observed changes in Ca(2+) handling and contractility, the effects of phloretin on the cardiac action potential and plasma membrane Ca(2+) and K(+) currents were examined. Phloretin markedly increased the action potential duration in the myocytes, and it inhibited the Ca(2+)-independent transient outward K(+) current (I(to)). The inwardly rectifying K(+) current, the sustained outward delayed rectifier K(+) current, and L-type Ca(2+) currents were not significantly different in the presence and absence of phloretin, nor was there any evidence that the Na(+)/Ca(2+) exchanger was affected. The effects of phloretin on Ca(2+) handling in the myocytes are consistent with its effects on I(to). Phloridzin did not significantly alter the amplitude or area of electrically evoked Ca(2+) transients in the myocytes, nor did it have detectable effects on the sarcoplasmic reticulum Ca(2+) load, cell shortening, or the action potential.

Evaluation of Ferrite Chip Beads as Surge Current Limiters in Circuits with Tantalum Capacitors

NASA Technical Reports Server (NTRS)

Teverovsky, Alexander

2014-01-01

Limiting resistors are currently required to be connected in series with tantalum capacitors to reduce the risk of surge current failures. However, application of limiting resistors decreases substantially the efficiency of the power supply systems. An ideal surge current limiting device should have a negligible resistance for DC currents and high resistance at frequencies corresponding to transients in tantalum capacitors. This work evaluates the possibility of using chip ferrite beads (FB) as such devices. Twelve types of small size FBs from three manufacturers were used to evaluate their robustness under soldering stresses and at high surge current spikes associated with transients in tantalum capacitors. Results show that FBs are capable to withstand current pulses that are substantially greater than the specified current limits. However, due to a sharp decrease of impedance with current, FBs do not reduce surge currents to the required level that can be achieved with regular resistors.

Calculating transient rates from surveys

NASA Astrophysics Data System (ADS)

Carbone, D.; van der Horst, A. J.; Wijers, R. A. M. J.; Rowlinson, A.

2017-03-01

We have developed a method to determine the transient surface density and transient rate for any given survey, using Monte Carlo simulations. This method allows us to determine the transient rate as a function of both the flux and the duration of the transients in the whole flux-duration plane rather than one or a few points as currently available methods do. It is applicable to every survey strategy that is monitoring the same part of the sky, regardless the instrument or wavelength of the survey, or the target sources. We have simulated both top-hat and Fast Rise Exponential Decay light curves, highlighting how the shape of the light curve might affect the detectability of transients. Another application for this method is to estimate the number of transients of a given kind that are expected to be detected by a survey, provided that their rate is known.

Ultrafast relaxation dynamics of amine-substituted bipyridyl ruthenium(II) complexes

NASA Astrophysics Data System (ADS)

Song, Hongwei; Wang, Xian; Yang, WenWen; He, Guiying; Kuang, Zhuoran; Li, Yang; Xia, Andong; Zhong, Yu-Wu; Kong, Fan'ao

2017-09-01

The excited state properties of a series of ruthenium(II) amine-substituted bipyridyl complexes, [Ru(bpy)n(NNbpy)3-n]2+, were investigated by steady-state and transient absorption spectroscopy, as well as quantum chemical calculations. The steady-state absorption spectra of these complexes in CH3CN show a distinct red-shift of the 1MLCT absorption with increasing numbers of amine substituent, whereas the emission spectra indicate an energy gap order of [Ru(bpy)3]2+ > [Ru(bpy)2(NNbpy)]2+ > [Ru(NNbpy)3]2+ > [Ru(bpy)(NNbpy)2]2+. Nanosecond, femtosecond transient absorption and electrochemical measurements suggest that NNbpy ligand has a strong influence on the electronic and emission properties of these complexes, due to electron-rich amine substituent. We illustrate how the numbers of amine substituent modulate the spectroscopic properties of transition metal complexes, which is related to the design of new electro-active systems with novel photoelectrochemical properties.

Airy beam self-focusing in a photorefractive medium

PubMed Central

Wiersma, Noémi; Marsal, Nicolas; Sciamanna, Marc; Wolfersberger, Delphine

2016-01-01

The unique bending and shape-preserving properties of optical Airy beams offer a large range of applications in for example beam routing, optical waveguiding, particle manipulation and plasmonics. In these applications and others, the Airy beam may experience nonlinear light-matter interactions which in turn modify the Airy beam properties and propagation. A well-known example is light self-focusing that leads to the formation of spatial soliton. Here, we unveil experimentally the self-focusing properties of a 1D-Airy beam in a photorefractive crystal under focusing conditions. The transient evolution involves both self-bending and acceleration of the initially launched Airy beam due to the onset of an off-shooting soliton and the resulting nonlocal refractive index perturbation. Both the transient and stationary self-focusing properties can be tuned by varying the bias electric field, the injected Airy beam power and the background illumination. PMID:27731356

Electroluminescence and other diagnostic techniques for the study of hot-electron effects in compound semiconductor devices

NASA Astrophysics Data System (ADS)

Zanoni, Enrico; Meneghesso, Gaudenzio; Menozzi, Roberto

2000-03-01

Hot electron in III-V FETs can be indirectly monitored by measuring the current coming out from the gate when the device is biased at high electric fields. This negative current is due to the collection of holes generated by impact ionization in the gate-to drain region. Electroluminescence represents a powerful tool in order to characterize not only hot electrons but also material properties. By using spatially resolved emission microscopy it is possible to show that the light due to cold electron/hole recombination is emitted between the gate and the source (low electric field region), while the contribution due to hot electrons is emitted between the gate and the drain (high electric field region). Deep-traps created in the device by hot carriers can be analysed by means of drain current deep level transient spectroscopy and by transconductance frequency dispersion. Cathodoluminescence, optical beam induced current, X-ray spectroscopy, electron energy loss spectroscopy in combination with a transmission electron microscopy are powerful tools in order to identify and localize surface modification following hot-electron stress tests.

Sensitivity analysis of reactive ecological dynamics.

PubMed

Verdy, Ariane; Caswell, Hal

2008-08-01

Ecological systems with asymptotically stable equilibria may exhibit significant transient dynamics following perturbations. In some cases, these transient dynamics include the possibility of excursions away from the equilibrium before the eventual return; systems that exhibit such amplification of perturbations are called reactive. Reactivity is a common property of ecological systems, and the amplification can be large and long-lasting. The transient response of a reactive ecosystem depends on the parameters of the underlying model. To investigate this dependence, we develop sensitivity analyses for indices of transient dynamics (reactivity, the amplification envelope, and the optimal perturbation) in both continuous- and discrete-time models written in matrix form. The sensitivity calculations require expressions, some of them new, for the derivatives of equilibria, eigenvalues, singular values, and singular vectors, obtained using matrix calculus. Sensitivity analysis provides a quantitative framework for investigating the mechanisms leading to transient growth. We apply the methodology to a predator-prey model and a size-structured food web model. The results suggest predator-driven and prey-driven mechanisms for transient amplification resulting from multispecies interactions.

Cross-bridge elasticity in single smooth muscle cells

PubMed Central

1983-01-01

In smooth muscle, a cross-bridge mechanism is believed to be responsible for active force generation and fiber shortening. In the present studies, the viscoelastic and kinetic properties of the cross- bridge were probed by eliciting tension transients in response to small, rapid, step length changes (delta L = 0.3-1.0% Lcell in 2 ms). Tension transients were obtained in a single smooth muscle cell isolated from the toad (Bufo marinus) stomach muscularis, which was tied between a force transducer and a displacement device. To record the transients, which were of extremely small magnitude (0.1 microN), a high-frequency (400 Hz), ultrasensitive force transducer (18 mV/microN) was designed and built. The transients obtained during maximal force generation (Fmax = 2.26 microN) were characterized by a linear elastic response (Emax = 1.26 X 10(4) mN/mm2) coincident with the length step, which was followed by a biphasic tension recovery made up of two exponentials (tau fast = 5-20 ms, tau slow = 50-300 ms). During the development of force upon activation, transients were elicited. The relationship between stiffness and force was linear, which suggests that the transients originate within the cross-bridge and reflect the cross-bridge's viscoelastic and kinetic properties. The observed fiber elasticity suggests that the smooth muscle cross-bridge is considerably more compliant than in fast striated muscle. A thermodynamic model is presented that allows for an analysis of the factors contributing to the increased compliance of the smooth muscle cross-bridge. PMID:6413640

Detonation failure characterization of non-ideal explosives

NASA Astrophysics Data System (ADS)

Janesheski, Robert S.; Groven, Lori J.; Son, Steven

2012-03-01

Non-ideal explosives are currently poorly characterized, hence limiting the modeling of them. Current characterization requires large-scale testing to obtain steady detonation wave characterization for analysis due to the relatively thick reaction zones. Use of a microwave interferometer applied to small-scale confined transient experiments is being implemented to allow for time resolved characterization of a failing detonation. The microwave interferometer measures the position of a failing detonation wave in a tube that is initiated with a booster charge. Experiments have been performed with ammonium nitrate and various fuel compositions (diesel fuel and mineral oil). It was observed that the failure dynamics are influenced by factors such as chemical composition and confiner thickness. Future work is planned to calibrate models to these small-scale experiments and eventually validate the models with available large scale experiments. This experiment is shown to be repeatable, shows dependence on reactive properties, and can be performed with little required material.

Quantitative Investigation of Room-Temperature Breakdown Effects in Pixelated TlBr Detectors

NASA Astrophysics Data System (ADS)

Koehler, Will; He, Zhong; Thrall, Crystal; O'Neal, Sean; Kim, Hadong; Cirignano, Leonard; Shah, Kanai

2014-10-01

Due to favorable material properties such as high atomic number (Tl: 81, Br: 35), high density ( 7.56 g/cm3), and a wide band gap (2.68 eV), thallium-bromide (TlBr) is currently under investigation for use as an alternative room-temperature semiconductor gamma-ray spectrometer. TlBr detectors can achieve less than 1% FWHM energy resolution at 662 keV, but these results are limited to stable operation at - 20°C. After days to months of room-temperature operation, ionic conduction causes these devices to fail. This work correlates the varying leakage current with alpha-particle and gamma-ray spectroscopic performances at various operating temperatures. Depth-dependent photopeak centroids exhibit time-dependent transient behavior, which indicates trapping sites form near the anode surface during room-temperature operation. After refabrication, similar performance and functionality of failed detectors returned.

Follow-up observations of SN 2010dn

NASA Astrophysics Data System (ADS)

Botticella, Maria Teresa; Kotak, Rubina; Meikle, Peter; Smartt, Stephen; Pastorello, Andrea; Benetti, Stefano

2010-06-01

A new intriguing transient, SN 2010dn in NGC 3184, was discovered ten days ago. The spectroscopic and photometric evolution make this transient similar to SN 2008S, the 2006 optical transient in M85 and the 2008 optical transient in NGC 300, members of a new class of transient events given the similar pre-explosion?and post-explosion properties. The nature of these transient is still debated?and our experience with SN 2008S proved that?Spitzer data are?invaluable to shed light on it providing a critical information in the understanding?the geometry of the circumstellar environment of these transients both for the dust enshrouded progenitor stars and after?their explosion. We would like to obtain a rapid follow-up of SN 2010dn with Spitzer to check if also this transient is producing an IR echo from substantial circumstellar material around the progenitor star. The modeling of the light echo will allow us to constrain the mass and?physical scale?of the circumstellar dust around this transient and as consequence to probe the mass loss history of the progenitor star. The proposed observations will be coordinated with an extensive optical follow up and?will be of interest to the broad scientific community. To obtain prompt observations after the discovery?is crucial.

The Alberta Stroke Prevention in TIAs and mild strokes (ASPIRE) intervention: rationale and design for evaluating the implementation of a province-wide TIA triaging system.

PubMed

Jeerakathil, Thomas; Shuaib, Ashfaq; Majumdar, Sumit R; Demchuk, Andrew M; Butcher, Kenneth S; Watson, Tim J; Dean, Naeem; Gordon, Deb; Edmond, Cathy; Coutts, Shelagh B

2014-10-01

Stroke risk after transient ischaemic attack is high and, it is a challenge worldwide to provide urgent assessment and preventive services to entire populations. To determine whether a province-wide transient ischaemic attack Triaging algorithm and transient ischaemic attack hotline (the Alberta Stroke Prevention in transient ischaemic attacks and mild strokes intervention) can reduce the rate of stroke recurrence following transient ischaemic attack across the population of Alberta, Canada (population 3·7 million, 90-day rate of post-stroke transient ischaemic attack currently 9·5%). It also seeks to improve upon current transient ischaemic attack triaging rules by incorporating time from symptom onset as a predictive variable. The transient ischaemic attack algorithm and hotline were developed with a broad consensus of clinicians, patients, policy-makers, and researchers and based on local adaptation of the work of others and research and insights developed within the province. Because neither patient-level nor region-level randomization was possible, we conducted a quasi-experimental design examining changes in the post-transient ischaemic attack rate of stroke recurrence before and after the 15-month implementation period using an interrupted time-series regression analysis. The design controls for changes in case-mix, co-interventions, and secular trends. A prospective transient ischaemic attack cohort will also be concurrently created with telephone follow-up at seven-days and 90 days as well as passive follow-up over the longer term using linkages to provincial healthcare administrative databases. The primary outcome measure is the change in recurrence rate of stroke following transient ischaemic attack at seven-days and 90 days, comparing a period of two-years before vs. two-years after the intervention is implemented. All cases of recurrent stroke will be validated. Secondary outcomes include functional status, hospitalizations, morbidity, and mortality. We are undertaking a rigorous evaluation of a population-based approach to improving quality of transient ischaemic attack care. Whether positive or negative, our work should provide important insights for all potential stakeholders. © 2012 The Authors. International Journal of Stroke © 2012 World Stroke Organization.

Light-water-reactor safety research program. Quarterly progress report, July--September 1975

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

Not Available

1975-01-01

Progress is summarized in the following research and development areas: (1) loss-of-coolant accident research; heat transfer and fluid dynamics; (2) transient fuel response and fission-product release; and (3) mechanical properties of Zircaloy containing oxygen. Also included is an appendix on Kinetics of Fission Gas and Volatile Fission-product Behavior under Transient Conditions in LWR Fuel.

NICER observations of MAXI J1820+070: Continuing evolution of X-ray variability properties

NASA Astrophysics Data System (ADS)

Homan, J.; Altamirano, D.; Arzoumanian, Z.; Buisson, D.; Eikenberry, S.; Fabian, A. C.; Gendreau, K.; Kara, E.; Ludlam, R.; Neilsen, J.; Ray, P. S.; Remillard, R.; Steiner, J.; Uttley, P.; Nicer Team

2018-04-01

The X-ray transient MAXI J1820+070 has been in outburst since its discovery on March 11 2018 (ATel #11399). Observations at various wavelengths, including the optical counterpart ASASSN-18ey (ATel #11400), suggest that the source is a black hole transient in the hard spectral state (e.g., ATel #11418, #11423, #11420, #11426).

Mach 14 Flow Restrictor Thermal Stress Analysis

DTIC Science & Technology

1984-08-01

tranfer analysis, thermal stress analysis, results translation from ABAQUS to PATRAN-G, and the method used to determine the heat transfer film...G, model translation into ABAQUS format, transient heat transfer analysis and thermal stress analysis input decks, results translation from ABAQUS ...TRANSLATION FROM PATRAN-G TO ABAQUS 3 ABAQUS CONSIDERATIONS 8 MATERIAL PROPERTIES OF COLUMBIUM C-103 10 USER SUBROUTINE FILM 11 TRANSIENT

Transient deformational properties of high temperature alloys used in solid oxide fuel cell stacks

NASA Astrophysics Data System (ADS)

Molla, Tesfaye Tadesse; Kwok, Kawai; Frandsen, Henrik Lund

2017-05-01

Stresses and probability of failure during operation of solid oxide fuel cells (SOFCs) is affected by the deformational properties of the different components of the SOFC stack. Though the overall stress relaxes with time during steady state operation, large stresses would normally appear through transients in operation including temporary shut downs. These stresses are highly affected by the transient creep behavior of metallic components in the SOFC stack. This study investigates whether a variation of the so-called Chaboche's unified power law together with isotropic hardening can represent the transient behavior of Crofer 22 APU, a typical iron-chromium alloy used in SOFC stacks. The material parameters for the model are determined by measurements involving relaxation and constant strain rate experiments. The constitutive law is implemented into commercial finite element software using a user-defined material model. This is used to validate the developed constitutive law to experiments with constant strain rate, cyclic and creep experiments. The predictions from the developed model are found to agree well with experimental data. It is therefore concluded that Chaboche's unified power law can be applied to describe the high temperature inelastic deformational behaviors of Crofer 22 APU used for metallic interconnects in SOFC stacks.

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.

Current transformer model with hysteresis for improving the protection response in electrical transmission systems

NASA Astrophysics Data System (ADS)

Matussek, Robert; Dzienis, Cezary; Blumschein, Jörg; Schulte, Horst

2014-12-01

In this paper, a generic enhanced protection current transformer (CT) model with saturation effects and transient behavior is presented. The model is used for the purpose of analysis and design of power system protection algorithms. Three major classes of protection CT have been modeled which all take into account the nonlinear inductance with remanence effects. The transient short-circuit currents in power systems are simulated under CT saturation condition. The response of a common power system protection algorithm with respect to robustness to nominal parameter variations and sensitivity against maloperation is demonstrated by simulation studies.

Transient Current Behaviour of Poly (p-hydroxybenzoic acid-co-ethylene terephthalate) Liquid Crystal Polymers

NASA Astrophysics Data System (ADS)

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

2011-07-01

Transient current behaviour of pristine Poly (p-hydroxybenzoic acid-co-ethylene terephthalate) Liquid crystal polymer which is a copolymer of poly ethylene terephthalate and poly p-hydroxybenzoic acid referred as PET/x.PHB polymer liquid crystals have been studied at different biasing electric fields ranging from 13 kV/cm to 104.3 kV/cm and at temperatures 120° C and 250° C for molar ratio x =0.8.

A time-based potential step analysis of electrochemical impedance incorporating a constant phase element: a study of commercially pure titanium in phosphate buffered saline.

PubMed

Ehrensberger, Mark T; Gilbert, Jeremy L

2010-05-01

The measurement of electrochemical impedance is a valuable tool to assess the electrochemical environment that exists at the surface of metallic biomaterials. This article describes the development and validation of a new technique, potential step impedance analysis (PSIA), to assess the electrochemical impedance of materials whose interface with solution can be modeled as a simplified Randles circuit that is modified with a constant phase element. PSIA is based upon applying a step change in voltage to a working electrode and analyzing the subsequent current transient response in a combined time and frequency domain technique. The solution resistance, polarization resistance, and interfacial capacitance are found directly in the time domain. The experimental current transient is numerically transformed to the frequency domain to determine the constant phase exponent, alpha. This combined time and frequency approach was tested using current transients generated from computer simulations, from resistor-capacitor breadboard circuits, and from commercially pure titanium samples immersed in phosphate buffered saline and polarized at -800 mV or +1000 mV versus Ag/AgCl. It was shown that PSIA calculates equivalent admittance and impedance behavior over this range of potentials when compared to standard electrochemical impedance spectroscopy. This current transient approach characterizes the frequency response of the system without the need for expensive frequency response analyzers or software. Copyright 2009 Wiley Periodicals, Inc.

On-Die Sensors for Transient Events

NASA Astrophysics Data System (ADS)

Suchak, Mihir Vimal

Failures caused by transient electromagnetic events like Electrostatic Discharge (ESD) are a major concern for embedded systems. The component often failing is an integrated circuit (IC). Determining which IC is affected in a multi-device system is a challenging task. Debugging errors often requires sophisticated lab setups which require intentionally disturbing and probing various parts of the system which might not be easily accessible. Opening the system and adding probes may change its response to the transient event, which further compounds the problem. On-die transient event sensors were developed that require relatively little area on die, making them inexpensive, they consume negligible static current, and do not interfere with normal operation of the IC. These circuits can be used to determine the pin involved and the level of the event in the event of a transient event affecting the IC, thus allowing the user to debug system-level transient events without modifying the system. The circuit and detection scheme design has been completed and verified in simulations with Cadence Virtuoso environment. Simulations accounted for the impact of the ESD protection circuits, parasitics from the I/O pin, package and I/O ring, and included a model of an ESD gun to test the circuit's response to an ESD pulse as specified in IEC 61000-4-2. Multiple detection schemes are proposed. The final detection scheme consists of an event detector and a level sensor. The event detector latches on the presence of an event at a pad, to determine on which pin an event occurred. The level sensor generates current proportional to the level of the event. This current is converted to a voltage and digitized at the A/D converter to be read by the microprocessor. Detection scheme shows good performance in simulations when checked against process variations and different kind of events.

Absolute Steady-State Thermal Conductivity Measurements by Use of a Transient Hot-Wire System.

PubMed

Roder, H M; Perkins, R A; Laesecke, A; Nieto de Castro, C A

2000-01-01

A transient hot-wire apparatus was used to measure the thermal conductivity of argon with both steady-state and transient methods. The effects of wire diameter, eccentricity of the wire in the cavity, axial conduction, and natural convection were accounted for in the analysis of the steady-state measurements. Based on measurements on argon, the relative uncertainty at the 95 % level of confidence of the new steady-state measurements is 2 % at low densities. Using the same hot wires, the relative uncertainty of the transient measurements is 1 % at the 95 % level of confidence. This is the first report of thermal conductivity measurements made by two different methods in the same apparatus. The steady-state method is shown to complement normal transient measurements at low densities, particularly for fluids where the thermophysical properties at low densities are not known with high accuracy.

Radio and white-light observations of coronal transients

NASA Technical Reports Server (NTRS)

Dulk, G. A.

1980-01-01

Optical, radio and X-ray evidence of violent mass motions in the corona has existed for some years but only recently have the form, nature, frequency and implication of the transients become obvious. In this paper the observed properties of coronal transients are reviewed, with concentration on the white-light and radio manifestations. The classification according to speeds seems to be meaningful, with the slow transients having thermal emissions at radio wavelengths and the fast ones nonthermal. The possible mechanisms involved in the radio bursts are then discussed and estimates of various forms of energy are reviewed. It appears that the magnetic energy transported from the sun by the transient exceeds that of any other form, and that magnetic forces dominate in the dynamics of the motions. The conversion of magnetic energy into mechanical energy, by expansion of the field, provides a possible driving force for the coronal and interplanetary shock waves.

Unique Cardiac Purkinje Fiber Transient Outward Current β-Subunit Composition

PubMed Central

Xiao, Ling; Koopmann, Tamara T.; Ördög, Balázs; Postema, Pieter G.; Verkerk, Arie O.; Iyer, Vivek; Sampson, Kevin J.; Boink, Gerard J.J.; Mamarbachi, Maya A.; Varro, Andras; Jordaens, Luc; Res, Jan; Kass, Robert S.; Wilde, Arthur A.; Bezzina, C.R.; Nattel, Stanley

2015-01-01

Rationale A chromosomal haplotype producing cardiac overexpression of dipeptidyl peptidase-like protein-6 (DPP6) causes familial idiopathic ventricular fibrillation. The molecular basis of transient outward current (Ito) in Purkinje fibers (PFs) is poorly understood. We hypothesized that DPP6 contributes to PF Ito and that its overexpression might specifically alter PF Ito properties and repolarization. Objective To assess the potential role of DPP6 in PF Ito. Methods and Results Clinical data in 5 idiopathic ventricular fibrillation patients suggested arrhythmia origin in the PF-conducting system. PF and ventricular muscle Ito had similar density, but PF Ito differed from ventricular muscle in having tetraethylammonium sensitivity and slower recovery. DPP6 overexpression significantly increased, whereas DPP6 knockdown reduced, Ito density and tetraethylammonium sensitivity in canine PF but not in ventricular muscle cells. The K+-channel interacting β-subunit K+-channel interacting protein type-2, essential for normal expression of Ito in ventricular muscle, was weakly expressed in human PFs, whereas DPP6 and frequenin (neuronal calcium sensor-1) were enriched. Heterologous expression of Kv4.3 in Chinese hamster ovary cells produced small Ito; Ito amplitude was greatly enhanced by coexpression with K+-channel interacting protein type-2 or DPP6. Coexpression of DPP6 with Kv4.3 and K+-channel interacting protein type-2 failed to alter Ito compared with Kv4.3/K+-channel interacting protein type-2 alone, but DPP6 expression with Kv4.3 and neuronal calcium sensor-1 (to mimic PF Ito composition) greatly enhanced Ito compared with Kv4.3/neuronal calcium sensor-1 and recapitulated characteristic PF kinetic/pharmacological properties. A mathematical model of cardiac PF action potentials showed that Ito enhancement can greatly accelerate PF repolarization. Conclusions These results point to a previously unknown central role of DPP6 in PF Ito, with DPP6 gain of function selectively enhancing PF current, and suggest that a DPP6-mediated PF early-repolarization syndrome might be a novel molecular paradigm for some forms of idiopathic ventricular fibrillation. PMID:23532596

Thermal protection for hypervelocity flight in earth's atmosphere by use of radiation backscattering ablating materials

NASA Technical Reports Server (NTRS)

Howe, John T.; Yang, Lily

1991-01-01

A heat-shield-material response code predicting the transient performance of a material subject to the combined convective and radiative heating associated with the hypervelocity flight is developed. The code is dynamically interactive to the heating from a transient flow field, including the effects of material ablation on flow field behavior. It accomodates finite time variable material thickness, internal material phase change, wavelength-dependent radiative properties, and temperature-dependent thermal, physical, and radiative properties. The equations of radiative transfer are solved with the material and are coupled to the transfer energy equation containing the radiative flux divergence in addition to the usual energy terms.

Determination of a transient heat transfer property of acrylic using thermochromic liquid crystals

NASA Technical Reports Server (NTRS)

Heidmann, James D.

1994-01-01

An experiment was performed to determine a transient heat transfer property of acrylic. The experiment took advantage of the known analytical solution for heat conduction in a homogeneous semi-infinite solid with a constant surface heat flux. Thermochromic liquid crystals were used to measure the temperature nonintrusively. The relevant property in this experiment was the transient thermal conduction coefficient h(sub t), which is the square root of the product of density p, specific heat c(sub p), and thermal conductivity k (i.e., square root of pc(sub p)k). A value of 595.6 W square root of s/sq m K was obtained for h(sub t), with a standard deviation of 5.1 W square root of s/sq m K. Although there is no generally accepted value for h(sub t), a commonly used one is 580 W square root of s/sq m K, which is almost 3 percent less than the h(sub t) value obtained in this experiment. Since these results were highly repeatable and since there is no definitive value for h(sub t), the new value is recommended for future use.

Comparison of observed rheological properties of hard wheat flour dough with predictions of the Giesekus-Leonov, White-Metzner and Phan-Thien Tanner models

NASA Technical Reports Server (NTRS)

Dhanasekharan, M.; Huang, H.; Kokini, J. L.; Janes, H. W. (Principal Investigator)

1999-01-01

The measured rheological behavior of hard wheat flour dough was predicted using three nonlinear differential viscoelastic models. The Phan-Thien Tanner model gave good zero shear viscosity prediction, but overpredicted the shear viscosity at higher shear rates and the transient and extensional properties. The Giesekus-Leonov model gave similar predictions to the Phan-Thien Tanner model, but the extensional viscosity prediction showed extension thickening. Using high values of the mobility factor, extension thinning behavior was observed but the predictions were not satisfactory. The White-Metzner model gave good predictions of the steady shear viscosity and the first normal stress coefficient but it was unable to predict the uniaxial extensional viscosity as it exhibited asymptotic behavior in the tested extensional rates. It also predicted the transient shear properties with moderate accuracy in the transient phase, but very well at higher times, compared to the Phan-Thien Tanner model and the Giesekus-Leonov model. None of the models predicted all observed data consistently well. Overall the White-Metzner model appeared to make the best predictions of all the observed data.

Physiological Characterization of Vestibular Efferent Brainstem Neurons Using a Transgenic Mouse Model

PubMed Central

Leijon, Sara; Magnusson, Anna K.

2014-01-01

The functional role of efferent innervation of the vestibular end-organs in the inner ear remains elusive. This study provides the first physiological characterization of the cholinergic vestibular efferent (VE) neurons in the brainstem by utilizing a transgenic mouse model, expressing eGFP under a choline-acetyltransferase (ChAT)-locus spanning promoter in combination with targeted patch clamp recordings. The intrinsic electrical properties of the eGFP-positive VE neurons were compared to the properties of the lateral olivocochlear (LOC) brainstem neurons, which gives rise to efferent innervation of the cochlea. Both VE and the LOC neurons were marked by their negative resting membrane potential <−75 mV and their passive responses in the hyperpolarizing range. In contrast, the response properties of VE and LOC neurons differed significantly in the depolarizing range. When injected with positive currents, VE neurons fired action potentials faithfully to the onset of depolarization followed by sparse firing with long inter-spike intervals. This response gave rise to a low response gain. The LOC neurons, conversely, responded with a characteristic delayed tonic firing upon depolarizing stimuli, giving rise to higher response gain than the VE neurons. Depolarization triggered large TEA insensitive outward currents with fast inactivation kinetics, indicating A-type potassium currents, in both the inner ear-projecting neuronal types. Immunohistochemistry confirmed expression of Kv4.3 and 4.2 ion channel subunits in both the VE and LOC neurons. The difference in spiking responses to depolarization is related to a two-fold impact of these transient outward currents on somatic integration in the LOC neurons compared to in VE neurons. It is speculated that the physiological properties of the VE neurons might be compatible with a wide-spread control over motion and gravity sensation in the inner ear, providing likewise feed-back amplification of abrupt and strong phasic signals from the semi-circular canals and of tonic signals from the gravito-sensitive macular organs. PMID:24867596

Free Fatty Acid Effects on the Atrial Myocardium: Membrane Ionic Currents Are Remodeled by the Disruption of T-Tubular Architecture

PubMed Central

O’Connell, Ryan P.; Musa, Hassan; Gomez, Mario San Martin; Avula, Uma Mahesh; Herron, Todd J.; Kalifa, Jerome; Anumonwo, Justus M. B.

2015-01-01

Background Epicardial adiposity and plasma levels of free fatty acids (FFAs) are elevated in atrial fibrillation, heart failure and obesity, with potentially detrimental effects on myocardial function. As major components of epicardial fat, FFAs may be abnormally regulated, with a potential to detrimentally modulate electro-mechanical function. The cellular mechanisms underlying such effects of FFAs are unknown. Objective To determine the mechanisms underlying electrophysiological effects of palmitic (PA), stearic (SA) and oleic (OA) FFAs on sheep atrial myocytes. Methods We used electrophysiological techniques, numerical simulations, biochemistry and optical imaging to examine the effects of acutely (≤ 15 min), short-term (4–6 hour) or 24-hour application of individual FFAs (10 μM) on isolated ovine left atrial myocytes (LAMs). Results Acute and short-term incubation in FFAs resulted in no differences in passive or active properties of isolated left atrial myocytes (LAMs). 24-hour application had differential effects depending on the FFA. PA did not affect cellular passive properties but shortened (p<0.05) action potential duration at 30% repolarization (APD30). APD50 and APD80 were unchanged. SA had no effect on resting membrane potential but reduced membrane capacitance by 15% (p<0.05), and abbreviated APD at all values measured (p≤0.001). OA did not significantly affect passive or active properties of LAMs. Measurement of the major voltage-gated ion channels in SA treated LAMs showed a ~60% reduction (p<0.01) of the L-type calcium current (ICa-L) and ~30% reduction (p<0.05) in the transient outward potassium current (ITO). A human atrial cell model recapitulated SA effects on APD. Optical imaging showed that SA incubated for 24 hours altered t-tubular structure in isolated cells (p<0.0001). Conclusions SA disrupts t-tubular architecture and remodels properties of membrane ionic currents in sheep atrial myocytes, with potential implications in arrhythmogenesis. PMID:26274906

Free Fatty Acid Effects on the Atrial Myocardium: Membrane Ionic Currents Are Remodeled by the Disruption of T-Tubular Architecture.

PubMed

O'Connell, Ryan P; Musa, Hassan; Gomez, Mario San Martin; Avula, Uma Mahesh; Herron, Todd J; Kalifa, Jerome; Anumonwo, Justus M B

2015-01-01

Epicardial adiposity and plasma levels of free fatty acids (FFAs) are elevated in atrial fibrillation, heart failure and obesity, with potentially detrimental effects on myocardial function. As major components of epicardial fat, FFAs may be abnormally regulated, with a potential to detrimentally modulate electro-mechanical function. The cellular mechanisms underlying such effects of FFAs are unknown. To determine the mechanisms underlying electrophysiological effects of palmitic (PA), stearic (SA) and oleic (OA) FFAs on sheep atrial myocytes. We used electrophysiological techniques, numerical simulations, biochemistry and optical imaging to examine the effects of acutely (≤ 15 min), short-term (4-6 hour) or 24-hour application of individual FFAs (10 μM) on isolated ovine left atrial myocytes (LAMs). Acute and short-term incubation in FFAs resulted in no differences in passive or active properties of isolated left atrial myocytes (LAMs). 24-hour application had differential effects depending on the FFA. PA did not affect cellular passive properties but shortened (p<0.05) action potential duration at 30% repolarization (APD30). APD50 and APD80 were unchanged. SA had no effect on resting membrane potential but reduced membrane capacitance by 15% (p<0.05), and abbreviated APD at all values measured (p≤0.001). OA did not significantly affect passive or active properties of LAMs. Measurement of the major voltage-gated ion channels in SA treated LAMs showed a ~60% reduction (p<0.01) of the L-type calcium current (ICa-L) and ~30% reduction (p<0.05) in the transient outward potassium current (ITO). A human atrial cell model recapitulated SA effects on APD. Optical imaging showed that SA incubated for 24 hours altered t-tubular structure in isolated cells (p<0.0001). SA disrupts t-tubular architecture and remodels properties of membrane ionic currents in sheep atrial myocytes, with potential implications in arrhythmogenesis.

13 CFR 112.2 - Application of this part.

Code of Federal Regulations, 2010 CFR

2010-01-01

...) Grants and loans of Federal funds; (2) the grant or donation of Federal property and interests in... other than a casual or transient basis), Federal property or any interest in such property without... assisting the recipient, or in recognition of the public interest to be served by such sale or lease to the...

Water Hammer Simulations of Monomethylhydrazine Propellant

NASA Technical Reports Server (NTRS)

Burkhardt, Zachary; Ramachandran, N.; Majumdar, A.

2017-01-01

Fluid Transient analysis is important for the design of spacecraft propulsion system to ensure structural stability of the system in the event of sudden closing or opening of the valve. Generalized Fluid System Simulation Program (GFSSP), a general purpose flow network code developed at NASA/MSFC is capable of simulating pressure surge due to sudden opening or closing of valve when thermodynamic properties of real fluid are available for the entire range of simulation. Specifically GFSSP needs an accurate representation of pressure density relationship in order to predict pressure surge during a fluid transient. Unfortunately, the available thermodynamic property programs such as REFPROP, GASP or GASPAK do not provide the thermodynamic properties of Monomethylhydrazine(MMH). This work illustrates the process used for building a customized table of properties of state variables from available properties and speed of sound that is required by GFSSP for simulation. Good agreement was found between the simulations and measured data. This method can be adopted for modeling flow networks and systems with other fluids whose properties are not known in detail in order to obtain general technical insight.

Systematic characterization of the ionic basis of rabbit cellular electrophysiology using two ventricular models.

PubMed

Romero, Lucía; Carbonell, Beatriz; Trenor, Beatriz; Rodríguez, Blanca; Saiz, Javier; Ferrero, José M

2011-10-01

Several mathematical models of rabbit ventricular action potential (AP) have been proposed to investigate mechanisms of arrhythmias and excitation-contraction coupling. Our study aims at systematically characterizing how ionic current properties modulate the main cellular biomarkers of arrhythmic risk using two widely-used rabbit ventricular models, and comparing simulation results using the two models with experimental data available for rabbit. A sensitivity analysis of AP properties, Ca²⁺ and Na⁺ dynamics, and their rate dependence to variations (±15% and ±30%) in the main transmembrane current conductances and kinetics was performed using the Shannon et al. (2004) and the Mahajan et al. (2008a,b) AP rabbit models. The effects of severe transmembrane current blocks (up to 100%) on steady-state AP and calcium transients, and AP duration (APD) restitution curves were also simulated using both models. Our simulations show that, in both virtual rabbit cardiomyocytes, APD is significantly modified by most repolarization currents, AP triangulation is regulated mostly by the inward rectifier K⁺ current (I(K1)) whereas APD rate adaptation as well as [Na⁺](i) rate dependence is influenced by the Na⁺/K⁺ pump current (I(NaK)). In addition, steady-state [Ca²⁺](i) levels, APD restitution properties and [Ca²⁺](i) rate dependence are strongly dependent on I(NaK), the L-Type Ca²⁺ current (I(CaL)) and the Na⁺/Ca²⁺ exchanger current (I(NaCa)), although the relative role of these currents is markedly model dependent. Furthermore, our results show that simulations using both models agree with many experimentally-reported electrophysiological characteristics. However, our study shows that the Shannon et al. model mimics rabbit electrophysiology more accurately at normal pacing rates, whereas Mahajan et al. model behaves more appropriately at faster rates. Our results reinforce the usefulness of sensitivity analysis for further understanding of cellular electrophysiology and validation of cardiac AP models. Copyright © 2011 Elsevier Ltd. All rights reserved.

Compound activity prediction using models of binding pockets or ligand properties in 3D

PubMed Central

Kufareva, Irina; Chen, Yu-Chen; Ilatovskiy, Andrey V.; Abagyan, Ruben

2014-01-01

Transient interactions of endogenous and exogenous small molecules with flexible binding sites in proteins or macromolecular assemblies play a critical role in all biological processes. Current advances in high-resolution protein structure determination, database development, and docking methodology make it possible to design three-dimensional models for prediction of such interactions with increasing accuracy and specificity. Using the data collected in the Pocketome encyclopedia, we here provide an overview of two types of the three-dimensional ligand activity models, pocket-based and ligand property-based, for two important classes of proteins, nuclear and G-protein coupled receptors. For half the targets, the pocket models discriminate actives from property matched decoys with acceptable accuracy (the area under ROC curve, AUC, exceeding 84%) and for about one fifth of the targets with high accuracy (AUC > 95%). The 3D ligand property field models performed better than 95% in half of the cases. The high performance models can already become a basis of activity predictions for new chemicals. Family-wide benchmarking of the models highlights strengths of both approaches and helps identify their inherent bottlenecks and challenges. PMID:23116466

Silicon Carbide Diodes Performance Characterization and Comparison With Silicon Devices

NASA Technical Reports Server (NTRS)

Lebron-Velilla, Ramon C.; Schwarze, Gene E.; Trapp, Scott

2003-01-01

Commercially available silicon carbide (SiC) Schottky diodes from different manufacturers were electrically tested and characterized at room temperature. Performed electrical tests include steady state forward and reverse I-V curves, as well as switching transient tests performed with the diodes operating in a hard switch dc-to-dc buck converter. The same tests were performed in current state of the art silicon (Si) and gallium arsenide (GaAs) Schottky and pn junction devices for evaluation and comparison purposes. The SiC devices tested have a voltage rating of 200, 300, and 600 V. The comparison parameters are forward voltage drop at rated current, reverse current at rated voltage and peak reverse recovery currents in the dc to dc converter. Test results show that steady state characteristics of the tested SiC devices are not superior to the best available Si Schottky and ultra fast pn junction devices. Transient tests reveal that the tested SiC Schottky devices exhibit superior transient behavior. This is more evident at the 300 and 600 V rating where SiC Schottky devices showed drastically lower reverse recovery currents than Si ultra fast pn diodes of similar rating.

Tetrodotoxin-sensitive, voltage-dependent sodium currents in hair cells from the alligator cochlea.

PubMed

Evans, M G; Fuchs, P A

1987-10-01

We have used whole-cell patch clamp techniques to record from tall hair cells isolated from the apical half of the alligator cochlea. Some of these cells gave action potentials in response to depolarizing current injections. When the same cells were voltage clamped, large transient inward currents followed by smaller outward currents were seen in response to depolarizing steps. We studied the transient inward current after the outward current had been blocked by external tetraethylammonium (20 mM) or by replacing internal potassium with cesium. It was found to be a sodium current because it was abolished by either replacing external sodium with choline or by external application of tetrodotoxin (100 nM). The sodium current showed voltage-dependent activation and inactivation. Most of the spiking hair cells came from the apex of the cochlea, where they would be subject to low-frequency mechanical stimulation in vivo.

Advanced LIGO low-latency searches

NASA Astrophysics Data System (ADS)

Kanner, Jonah; LIGO Scientific Collaboration, Virgo Collaboration

2016-06-01

Advanced LIGO recently made the first detection of gravitational waves from merging binary black holes. The signal was first identified by a low-latency analysis, which identifies gravitational-wave transients within a few minutes of data collection. More generally, Advanced LIGO transients are sought with a suite of automated tools, which collectively identify events, evaluate statistical significance, estimate source position, and attempt to characterize source properties. This low-latency effort is enabling a broad multi-messenger approach to the science of compact object mergers and other transients. This talk will give an overview of the low-latency methodology and recent results.

A Novel Transient Fault Current Sensor Based on the PCB Rogowski Coil for Overhead Transmission Lines

PubMed Central

Liu, Yadong; Xie, Xiaolei; Hu, Yue; Qian, Yong; Sheng, Gehao; Jiang, Xiuchen

2016-01-01

The accurate detection of high-frequency transient fault currents in overhead transmission lines is the basis of malfunction detection and diagnosis. This paper proposes a novel differential winding printed circuit board (PCB) Rogowski coil for the detection of transient fault currents in overhead transmission lines. The interference mechanism of the sensor surrounding the overhead transmission line is analyzed and the guideline for the interference elimination is obtained, and then a differential winding printed circuit board (PCB) Rogowski coil is proposed, where the branch and return line of the PCB coil were designed to be strictly symmetrical by using a joining structure of two semi-rings and collinear twisted pair differential windings in each semi-ring. A serial test is conducted, including the frequency response, linearity, and anti-interference performance as well as a comparison with commercial sensors. Results show that a PCB Rogowski coil has good linearity and resistance to various external magnetic field interferences, thus enabling it to be widely applied in fault-current-collecting devices. PMID:27213402

5 CFR 900.403 - Definitions.

Code of Federal Regulations, 2010 CFR

2010-01-01

... Federal financial assistance, and application means that application, request, or plan. (b) Facility..., alteration, or acquisition of facilities. (c) Federal financial assistance includes: (1) Grants and loans of... transient basis), Federal property or any interest in the property without consideration or at a nominal...

A Current Sensor Based on the Giant Magnetoresistance Effect: Design and Potential Smart Grid Applications

PubMed Central

Ouyang, Yong; He, Jinliang; Hu, Jun; Wang, Shan X.

2012-01-01

Advanced sensing and measurement techniques are key technologies to realize a smart grid. The giant magnetoresistance (GMR) effect has revolutionized the fields of data storage and magnetic measurement. In this work, a design of a GMR current sensor based on a commercial analog GMR chip for applications in a smart grid is presented and discussed. Static, dynamic and thermal properties of the sensor were characterized. The characterizations showed that in the operation range from 0 to ±5 A, the sensor had a sensitivity of 28 mV·A−1, linearity of 99.97%, maximum deviation of 2.717%, frequency response of −1.5 dB at 10 kHz current measurement, and maximum change of the amplitude response of 0.0335%·°C−1 with thermal compensation. In the distributed real-time measurement and monitoring of a smart grid system, the GMR current sensor shows excellent performance and is cost effective, making it suitable for applications such as steady-state and transient-state monitoring. With the advantages of having a high sensitivity, high linearity, small volume, low cost, and simple structure, the GMR current sensor is promising for the measurement and monitoring of smart grids. PMID:23202221

A current sensor based on the giant magnetoresistance effect: design and potential smart grid applications.

PubMed

Ouyang, Yong; He, Jinliang; Hu, Jun; Wang, Shan X

2012-11-09

Advanced sensing and measurement techniques are key technologies to realize a smart grid. The giant magnetoresistance (GMR) effect has revolutionized the fields of data storage and magnetic measurement. In this work, a design of a GMR current sensor based on a commercial analog GMR chip for applications in a smart grid is presented and discussed. Static, dynamic and thermal properties of the sensor were characterized. The characterizations showed that in the operation range from 0 to ±5 A, the sensor had a sensitivity of 28 mV·A(-1), linearity of 99.97%, maximum deviation of 2.717%, frequency response of −1.5 dB at 10 kHz current measurement, and maximum change of the amplitude response of 0.0335%·°C(-1) with thermal compensation. In the distributed real-time measurement and monitoring of a smart grid system, the GMR current sensor shows excellent performance and is cost effective, making it suitable for applications such as steady-state and transient-state monitoring. With the advantages of having a high sensitivity, high linearity, small volume, low cost, and simple structure, the GMR current sensor is promising for the measurement and monitoring of smart grids.

Erosion products of plasma facing materials formed under ITER-like transient load and deuterium retention in them

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

Putrik, A. B., E-mail: putrik@triniti.ru; Klimov, N. S.; Gasparyan, Yu. M., E-mail: yura@plasma.mephi.ru

2015-12-15

Erosion of the plasma-facing materials in particular evaporation of the materials in a fusion reactor under intense transient events is one of the problems of the ITER. The current experimental data are insufficient to predict the properties of the erosion products, a significant part of which will be formed during transient events (edge-localized modes (ELMs) and disruptions). The paper concerns the experimental investigation of the graphite and tungsten erosion products deposited under pulsed plasma load at the QSPA-T: heat load on the target was 2.6 MJ/m{sup 2} with 0.5 ms pulse duration. The designed diagnostics for measuring the deposition ratemore » made it possible to determine that the deposition of eroded material occurs during discharge, and the deposition rate is in the range (0.1–100) × 10{sup 19} at/(cm{sup 2} s), which is much higher than that for stationary processes. It is found that the relative atomic concentrations D/C and D/(W + C) in the erosion products deposited during the pulse process are on the same level as for the stationary processes. An exposure of erosion products to photonic energy densities typical of those expected at mitigated disruptions in the ITER (pulse duration of 0.5–1 ms, integral energy density of radiation of 0.1–0.5 MJ/m2) significantly decreases the concentration of trapped deuterium.« less

Time-resolved single-shot terahertz time-domain spectroscopy for ultrafast irreversible processes

NASA Astrophysics Data System (ADS)

Zhai, Zhao-Hui; Zhong, Sen-Cheng; Li, Jun; Zhu, Li-Guo; Meng, Kun; Li, Jiang; Liu, Qiao; Peng, Qi-Xian; Li, Ze-Ren; Zhao, Jian-Heng

2016-09-01

Pulsed terahertz spectroscopy is suitable for spectroscopic diagnostics of ultrafast events. However, the study of irreversible or single shot ultrafast events requires ability to record transient properties at multiple time delays, i.e., time resolved at single shot level, which is not available currently. Here by angular multiplexing use of femtosecond laser pulses, we developed and demonstrated a time resolved, transient terahertz time domain spectroscopy technique, where burst mode THz pulses were generated and then detected in a single shot measurement manner. The burst mode THz pulses contain 2 sub-THz pulses, and the time gap between them is adjustable up to 1 ns with picosecond accuracy, thus it can be used to probe the single shot event at two different time delays. The system can detect the sub-THz pulses at 0.1 THz-2.5 THz range with signal to noise ratio (SNR) of ˜400 and spectrum resolution of 0.05 THz. System design was described here, and optimizations of single shot measurement of THz pulses were discussed in detail. Methods to improve SNR were also discussed in detail. A system application was demonstrated where pulsed THz signals at different time delays of the ultrafast process were successfully acquired within single shot measurement. This time resolved transient terahertz time domain spectroscopy technique provides a new diagnostic tool for irreversible or single shot ultrafast events where dynamic information can be extracted at terahertz range within one-shot experiment.

Time-resolved single-shot terahertz time-domain spectroscopy for ultrafast irreversible processes.

PubMed

Zhai, Zhao-Hui; Zhong, Sen-Cheng; Li, Jun; Zhu, Li-Guo; Meng, Kun; Li, Jiang; Liu, Qiao; Peng, Qi-Xian; Li, Ze-Ren; Zhao, Jian-Heng

2016-09-01

Pulsed terahertz spectroscopy is suitable for spectroscopic diagnostics of ultrafast events. However, the study of irreversible or single shot ultrafast events requires ability to record transient properties at multiple time delays, i.e., time resolved at single shot level, which is not available currently. Here by angular multiplexing use of femtosecond laser pulses, we developed and demonstrated a time resolved, transient terahertz time domain spectroscopy technique, where burst mode THz pulses were generated and then detected in a single shot measurement manner. The burst mode THz pulses contain 2 sub-THz pulses, and the time gap between them is adjustable up to 1 ns with picosecond accuracy, thus it can be used to probe the single shot event at two different time delays. The system can detect the sub-THz pulses at 0.1 THz-2.5 THz range with signal to noise ratio (SNR) of ∼400 and spectrum resolution of 0.05 THz. System design was described here, and optimizations of single shot measurement of THz pulses were discussed in detail. Methods to improve SNR were also discussed in detail. A system application was demonstrated where pulsed THz signals at different time delays of the ultrafast process were successfully acquired within single shot measurement. This time resolved transient terahertz time domain spectroscopy technique provides a new diagnostic tool for irreversible or single shot ultrafast events where dynamic information can be extracted at terahertz range within one-shot experiment.

Voltage-clamp study of the activation currents and fast block to polyspermy in the egg of Xenopus laevis.

PubMed

Glahn, David; Nuccitelli, Richard

2003-04-01

Voltage-clamped mature, jelly-intact Xenopus eggs were used to carefully examine the ionic currents crossing the plasma membrane before, during, and after fertilization. The bulk of the fertilization current was transient, of large amplitude, and reversed at the predicted Cl- reversal potential. However, the large amplitude fertilization current was preceded by a small, step-like increase in holding current. This small increase in holding current is referred to in this paper as Ion to acknowledge its qualitative similarity to the Ion current previously described in the sea urchin. It was observed in both fertilized and artificially activated eggs, and was found to be unaffected by 10 mm tetra-ethyl ammonium (TEA), a concentration found to block K+ currents in Rana pipiens. Current-voltage relationships are presented for the large fertilization potential, and show that the fertilization currents have a marked outward rectification and are voltage sensitive. These properties are in contrast to the total lack of rectification and slight voltage sensitivity seen before or after the fertilization currents. The time required for sperm to fertilize the egg was found to be voltage dependent with a relatively more depolarized voltage requiring a longer time for fertilization to occur. The percentage of eggs blocked with varying potential levels was determined and this information was fitted to a modified Boltzmann equation having a midpoint of -9 mV.

Electrophysiological characteristics of IB4-negative TRPV1-expressing muscle afferent DRG neurons.

PubMed

Lin, Yi-Wen; Chen, Chih-Cheng

2015-01-01

Muscle afferent neurons that express transient receptor potential vanilloid type I (TRPV1) are responsible for muscle pain associated with tissue acidosis. We have previously found that TRPV1 of isolectin B4 (IB4)-negative muscle nociceptors plays an important role in the acid-induced hyperalgesic priming and the development of chronic hyperalgesia in a mouse model of fibromyalgia. To understand the electrophysiological properties of the TRPV1-expressing muscle afferent neurons, we used whole-cell patch clamp recording to study the acid responsiveness and action potential (AP) configuration of capsaicin-sensitive neurons innervating to gastrocnemius muscle. Here we showed that IB4-negative TRPV1-expressing muscle afferent neurons are heterogeneous in terms of cell size, resting membrane potential, AP configuration, tetrodotoxin (TTX)-resistance, and acid-induced current (I acid), as well as capsaicin-induced current (I cap). TRPV1-expressing neurons were all acid-sensitive and could be divided into two acid-sensitive groups depending on an acid-induced sustained current (type I) or an acid-induced biphasic ASIC3-like current (type II). Type I TRPV1-expressing neurons were distinguishable from type II TRPV1-expressing neurons in AP overshoot, after-hyperpolarization duration, and all I acid parameters, but not in AP threshold, TTX-resistance, resting membrane potential, and I cap parameters. These differential biophysical properties of TRPV1-expressing neurons might partially annotate their different roles involved in the development and maintenance of chronic muscle pain.

Plasma jets in the near-Earth's magnetotail (Julius Bartels Medal Lecture)

NASA Astrophysics Data System (ADS)

Nakamura, Rumi

2014-05-01

The Earth's magnetosphere is formed as a consequence of the interaction between the magnetized solar wind and the terrestrial magnetic field. While the large-scale and average (>hours) properties of the Earth's magnetotail current sheet can be well described by overall solar wind-magnetosphere interaction, the most dramatic energy conversion process takes place in an explosive manner involving transient (up to several minutes) and localized (up to a few RE) phenomena in the plasma sheet/current sheet regions. One of the most clear observables of such processes are the localized and transient plasma jets called Bursty bulk flows (BBF), embedding velocity peaks of 1-min duration, which are called flow bursts. This talk is a review of the current understanding of these plasma jets by highlighting the results from multi-spacecraft observations by the Cluster and THEMIS spacecraft. The first four-spacecraft mission Cluster crossed the near-Earth plasma sheet with inter-spacecraft distance of about 250 km to 10000 km, ideal for studying local structures of the flow bursts. The five-spacecraft THEMIS mission , separated by larger distances , succeeded to monitor the large-scale evolution of the fast flows from the mid-tail to the inner magnetosphere. Multi-point observations of BBFS have established the importance of measuring local gradients of the fields and the plasma to understand the BBF structures such as the spatial scales and 3D structure of localized Earthward convecting flux tubes. Among others the magnetic field disturbance forming at the front of BBF, called dipolarization front (DF), has been intensively studied. From the propagation properties of DF relative to the flows and by comparing with ionospheric data, the evolution of the fast flows in terms of magnetosphere-ionospheric coupling through field-aligned currents are established. An important aspect of BBF is the interaction of the Earthward plasma jets and the Earth's dipole field. Multi-point observations combined with ground-based observations enabled to resolve how the BBFs are braked , diverted, or bounced back at the high-pressure gradient region. The multi-point capabilities in space enabled to study the BBF structure as well as large-scale evolution of BBFs. These processes are also universal processes in space plasmas and are, for example, associated with the reconnection process during the solar flares or leading to auroral phenomena at different planets.

Numerical approach for ECT by using boundary element method with Laplace transform

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

Enokizono, M.; Todaka, T.; Shibao, K.

1997-03-01

This paper presents an inverse analysis by using BEM with Laplace transform. The method is applied to a simple problem in the eddy current testing (ECT). Some crack shapes in a conductive specimen are estimated from distributions of the transient eddy current on its sensing surface and magnetic flux density in the liftoff space. Because the transient behavior includes information on various frequency components, the method is applicable to the shape estimation of a comparative small crack.

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.

Post-traumatic transient cortical blindness in a child with occipital bone fracture.

PubMed

Ng, Rachel H C

2016-12-01

Cortical blindness as sequelae of trauma has been reported in literature but mostly in the setting of occipital cortex or visual tract damages. We present a case of transient cortical blindness in a child following a closed head injury with a non-displaced occipital bone fracture and underlying occipital lobe contusion. We discuss the pathophysiology behind Post-traumatic transient cortical blindness, relevant investigations, and current management. Copyright © 2016 Elsevier Ltd. All rights reserved.

A Shear Deformable Shell Element for Laminated Composites

NASA Technical Reports Server (NTRS)

Chao, W. C.; Reddy, J. N.

1984-01-01

A three-dimensional element based on the total Lagrangian description of the motion of a layered anisotropic composite medium is developed, validated, and used to analyze layered composite shells. The element contains the following features: geometric nonlinearity, dynamic (transient) behavior, and arbitrary lamination scheme and lamina properties. Numerical results of nonlinear bending, natural vibration, and transient response are presented to illustrate the capabilities of the element.

18 CFR 705.2 - Definitions.

Code of Federal Regulations, 2010 CFR

2010-04-01

... Federal financial assistance, and the term application means such an application, request, or plan. (b..., alteration or acquisition of facilities. (c) Federal financial assistance includes: (1) Grants and loans of... transient basis), Federal property or any interest in such property without consideration or at a nominal...

Optical properties and electronic energy relaxation of metallic Au144(SR)60 nanoclusters.

PubMed

Yi, Chongyue; Tofanelli, Marcus A; Ackerson, Christopher J; Knappenberger, Kenneth L

2013-12-04

Electronic energy relaxation of Au144(SR)60(q) ligand-protected nanoclusters, where SR = SC6H13 and q = -1, 0, +1, and +2, was examined using femtosecond time-resolved transient absorption spectroscopy. The observed differential transient spectra contained three distinct components: (1) transient bleaches at 525 and 600 nm, (2) broad visible excited-state absorption (ESA), and (3) stimulated emission (SE) at 670 nm. The bleach recovery kinetics depended upon the excitation pulse energy and were thus attributed to electron-phonon coupling typical of metallic nanostructures. The prominent bleach at 525 nm was assigned to a core-localized plasmon resonance (CLPR). ESA decay kinetics were oxidation-state dependent and could be described using a metal-sphere charging model. The dynamics, emission energy, and intensity of the SE peak exhibited dielectric-dependent responses indicative of Superatom charge transfer states. On the basis of these data, the Au144(SR)60 system is the smallest-known nanocluster to exhibit quantifiable electron dynamics and optical properties characteristic of metals.

Fast and efficient STT switching in MTJ using additional transient pulse current

NASA Astrophysics Data System (ADS)

Pathak, Sachin; Cha, Jongin; Jo, Kangwook; Yoon, Hongil; Hong, Jongill

2017-06-01

We propose a profile of write pulse current-density to switch magnetization in a perpendicular magnetic tunnel junction to reduce switching time and write energy as well. Our simulated results show that an overshoot transient pulse current-density (current spike) imposed to conventional rectangular-shaped pulse current-density (main pulse) significantly improves switching speed that yields the reduction in write energy accordingly. For example, we could dramatically reduce the switching time by 80% and thereby reduce the write energy over 9% in comparison to the switching without current spike. The current spike affects the spin dynamics of the free layer and reduces the switching time mainly due to spin torque induced. On the other hand, the large Oersted field induced causes changes in spin texture. We believe our proposed write scheme can make a breakthrough in magnetic random access memory technology seeking both high speed operation and low energy consumption.

The modelling of an SF6 arc in a supersonic nozzle: II. Current zero behaviour of the nozzle arc

NASA Astrophysics Data System (ADS)

Zhang, Q.; Liu, J.; Yan, J. D.; Fang, M. T. C.

2016-08-01

The present work (part II) forms the second part of an investigation into the behaviour of SF6 nozzle arc. It is concerned with the aerodynamic and electrical behaviour of a transient nozzle arc under a current ramp specified by a rate of current decay (di/dt) before current zero and a voltage ramp (dV/dt) after current zero. The five flow models used in part I [1] for cold gas flow and DC nozzle arcs have been applied to study the transient arc at three stagnation pressures (P 0) and two values of di/dt for the current ramp, representing a wide range of arcing conditions. An analysis of the physical mechanisms encompassed in each flow model is given with an emphasis on the adequacy of a particular model in describing the rapidly varying arc around current zero. The critical rate of rise of recovery voltage (RRRV) is found computationally and compared with test results of Benenson et al [2]. For transient nozzle arcs, the RRRV is proportional to the square of P 0, rather than to the square root of P 0 for DC nozzle arcs. The physical mechanisms responsible for the strong dependence of RRRV on P 0 have been investigated. The relative merits of the flow models employed are discussed.

The effect of applied control strategy on the current-voltage correlation of a solid oxide fuel cell stack during dynamic operation

NASA Astrophysics Data System (ADS)

Szmyd, Janusz S.; Komatsu, Yosuke; Brus, Grzegorz; Ghigliazza, Francesco; Kimijima, Shinji; Ściążko, Anna

2014-09-01

This paper discusses the transient characteristics of the planar type SOFC cell stack, of which the standard output is 300 W. The transient response of the voltage to the manipulation of an electric current was investigated. The effects of the response and of the operating condition determined by the operating temperature of the stack were studied by mapping a current-voltage (I-V) correlation. The current-based fuel control (CBFC) was adopted for keeping the fuel utilization factor at constant while the value of the electric current was ramped at the constant rate. The present experimental study shows that the transient characteristics of the cell voltage are determined by primarily the operating temperature caused by the manipulation of the current. Particularly, the slope of the I-V curve and the overshoot found on the voltage was remarkably influenced by the operating temperature. The different values of the fuel utilization factor influence the height of the settled voltages. The CBFC has significance in determining the slope of the I-V characteristic, but the different values ofthe fuel utilization factor does not affect the slope as the operating temperature does. The CBFC essentially does not alter the amplitude of the overshoot on the voltage response, since this is dominated by the operating temperature and its change is caused by manipulating the current.

Emerin plays a crucial role in nuclear invagination and in the nuclear calcium transient

PubMed Central

Shimojima, Masaya; Yuasa, Shinsuke; Motoda, Chikaaki; Yozu, Gakuto; Nagai, Toshihiro; Ito, Shogo; Lachmann, Mark; Kashimura, Shin; Takei, Makoto; Kusumoto, Dai; Kunitomi, Akira; Hayashiji, Nozomi; Seki, Tomohisa; Tohyama, Shugo; Hashimoto, Hisayuki; Kodaira, Masaki; Egashira, Toru; Hayashi, Kenshi; Nakanishi, Chiaki; Sakata, Kenji; Yamagishi, Masakazu; Fukuda, Keiichi

2017-01-01

Alteration of the nuclear Ca2+ transient is an early event in cardiac remodeling. Regulation of the nuclear Ca2+ transient is partly independent of the cytosolic Ca2+ transient in cardiomyocytes. One nuclear membrane protein, emerin, is encoded by EMD, and an EMD mutation causes Emery-Dreifuss muscular dystrophy (EDMD). It remains unclear whether emerin is involved in nuclear Ca2+ homeostasis. The aim of this study is to elucidate the role of emerin in rat cardiomyocytes by means of hypertrophic stimuli and in EDMD induced pluripotent stem (iPS) cell-derived cardiomyocytes in terms of nuclear structure and the Ca2+ transient. The cardiac hypertrophic stimuli increased the nuclear area, decreased nuclear invagination, and increased the half-decay time of the nuclear Ca2+ transient in cardiomyocytes. Emd knockdown cardiomyocytes showed similar properties after hypertrophic stimuli. The EDMD-iPS cell-derived cardiomyocytes showed increased nuclear area, decreased nuclear invagination, and increased half-decay time of the nuclear Ca2+ transient. An autopsied heart from a patient with EDMD also showed increased nuclear area and decreased nuclear invagination. These data suggest that Emerin plays a crucial role in nuclear structure and in the nuclear Ca2+ transient. Thus, emerin and the nuclear Ca2+ transient are possible therapeutic targets in heart failure and EDMD. PMID:28290476

A transient-enhanced NMOS low dropout voltage regulator with parallel feedback compensation

NASA Astrophysics Data System (ADS)

Han, Wang; Lin, Tan

2016-02-01

This paper presents a transient-enhanced NMOS low-dropout regulator (LDO) for portable applications with parallel feedback compensation. The parallel feedback structure adds a dynamic zero to get an adequate phase margin with a load current variation from 0 to 1 A. A class-AB error amplifier and a fast charging/discharging unit are adopted to enhance the transient performance. The proposed LDO has been implemented in a 0.35 μm BCD process. From experimental results, the regulator can operate with a minimum dropout voltage of 150 mV at a maximum 1 A load and IQ of 165 μA. Under the full range load current step, the voltage undershoot and overshoot of the proposed LDO are reduced to 38 mV and 27 mV respectively.

Recent activity in the moon; Proceedings of the Special Symposium, Houston, Tex., March 16, 1976

NASA Technical Reports Server (NTRS)

Runcorn, S. K.; Oreilly, W.; Srnka, L. J.

1977-01-01

The papers review evidence for recent activity within the moon as manifested by lunar grid system, transient phenomena, moonquakes, and episodic emissions of radiogenic gases. Topics include a survey of lunar transient phenomena, possible causes of such phenomena, evidence that high-frequency seismic events may be shallow moonquakes, lunar seismicity and tectonics, a hypothesis on the nature of sites of lunar gas venting, and a search for sporadic gas emissions from the moon. Other contributions discuss the release of radiogenic argon-40 from the moon, radon-222 emission as an indicator of current activity on the moon, upper limits to gas emission from sites of lunar transient phenomena, physical processes that could produce transient changes on the lunar surface, critical-velocity gas-plasma interaction as a mechanism for lunar transient phenomena, and tidal triggering of moonquakes, transient phenomena, and radiogenic-gas emissions.

Transient Response of Arc Temperature and Iron Vapor Concentration Affected by Current Frequency with Iron Vapor in Pulsed Arc

NASA Astrophysics Data System (ADS)

Tanaka, Tatsuro; Maeda, Yoshifumi; Yamamoto, Shinji; Iwao, Toru

2016-10-01

TIG arc welding is chemically a joining technology with melting the metallic material and it can be high quality. However, this welding should not be used in high current to prevent cathode melting. Thus, the heat transfer is poor. Therefore, the deep penetration cannot be obtained and the weld defect sometimes occurs. The pulsed arc welding has been used for the improvement of this defect. The pulsed arc welding can control the heat flux to anode. The convention and driving force in the weld pool are caused by the arc. Therefore, it is important to grasp the distribution of arc temperature. The metal vapor generate from the anode in welding. In addition, the pulsed current increased or decreased periodically. Therefore, the arc is affected by such as a current value and current frequency, the current rate of increment and the metal vapor. In this paper, the transient response of arc temperature and the iron vapor concentration affected by the current frequency with iron vapor in pulsed arc was elucidated by the EMTF (ElectroMagnetic Thermal Fluid) simulation. As a result, the arc temperature and the iron vapor were transient response as the current frequency increase. Thus, the temperature and the electrical conductivity decreased. Therefore, the electrical field increased in order to maintain the current continuity. The current density and electromagnetic force increased at the axial center. In addition, the electronic flow component of the heat flux increased at the axial center because the current density increased. However, the heat conduction component of the heat flux decreased.

Development of a full-waveform voltage and current recording device for multichannel transient electromagnetic transmitters

NASA Astrophysics Data System (ADS)

Zhang, Xinyue; Zhang, Qisheng; Wang, Meng; Kong, Qiang; Zhang, Shengquan; He, Ruihao; Liu, Shenghui; Li, Shuhan; Yuan, Zhenzhong

2017-11-01

Due to the pressing demand for metallic ore exploration technology in China, several new technologies are being employed in the relevant exploration instruments. In addition to possessing the high resolution of the traditional transient electromagnetic method, high-efficiency measurements, and a short measurement time, the multichannel transient electromagnetic method (MTEM) technology can also sensitively determine the characteristics of a low-resistivity geologic body, without being affected by the terrain. Besides, the MTEM technology also solves the critical, existing interference problem in electrical exploration technology. This study develops a full-waveform voltage and current recording device for MTEM transmitters. After continuous acquisition and storage of the large, pseudo-random current signals emitted by the MTEM transmitter, these signals are then convoluted with the signals collected by the receiver to obtain the earth's impulse response. In this paper, the overall design of the full-waveform recording apparatus, including the hardware and upper-computer software designs, the software interface display, and the results of field test, is discussed in detail.

Field enhanced charge carrier reconfiguration in electronic and ionic coupled dynamic polymer resistive memory.

PubMed

Zhao, Jun Hui; Thomson, Douglas J; Pilapil, Matt; Pillai, Rajesh G; Rahman, G M Aminur; Freund, Michael S

2010-04-02

Dynamic resistive memory devices based on a conjugated polymer composite (PPy(0)DBS(-)Li(+) (PPy: polypyrrole; DBS(-): dodecylbenzenesulfonate)), with field-driven ion migration, have been demonstrated. In this work the dynamics of these systems has been investigated and it has been concluded that increasing the applied field can dramatically increase the rate at which information can be 'written' into these devices. A conductance model using space charge limited current coupled with an electric field induced ion reconfiguration has been successfully utilized to interpret the experimentally observed transient conducting behaviors. The memory devices use the rising and falling transient current states for the storage of digital states. The magnitude of these transient currents is controlled by the magnitude and width of the write/read pulse. For the 500 nm length devices used in this work an increase in 'write' potential from 2.5 to 5.5 V decreased the time required to create a transient conductance state that can be converted into the digital signal by 50 times. This work suggests that the scaling of these devices will be favorable and that 'write' times for the conjugated polymer composite memory devices will decrease rapidly as ion driving fields increase with decreasing device size.

Investigation of the cardiomyocyte dysfunction in bradykinin type 2 receptor knockout mice.

PubMed

Roman-Campos, Danilo; Duarte, Hugo Leonardo; Gomes, Enéas Ricardo; Castro, Carlos Henrique; Guatimosim, Silvia; Natali, Antonio José; Almeida, Alvair Pinto; Pesquero, João Bosco; Pesquero, Jorge Luiz; Cruz, Jader Santos

2010-12-18

Bradykinin type 2 receptor (B(2)R) is the key component to trigger the intracellular signaling pathway in response to bradykinin under physiological conditions. The present study sought to investigate whether the B(2)R gene deletion will have an impact on myocardial function. Isolated cell shortening, patch-clamp technique, Western blot and confocal microscopy. Isolated cell shortening measurements showed significant reduction in B(2)R knockout (B(2)R(-/-)) left ventricular cardiac myocytes' shortening. Whole-cell recordings were used to study the electrophysiological aspects of the left ventricular B(2)R(-/-) cardiomyocytes. Results showed: 1) action potential lengthening; 2) unchanged inwardly rectifying K(+) current; 3) reduced transient outward K(+) (I(to)) and L-type Ca(2+) current densities; 5) changes in kinetic properties related to I(to) and I(Ca,L). In addition, transient sarcoplasmic reticulum (SR) Ca(2+) release was found to be smaller in B(2)R(-/-) cardiomyocytes. Importantly, evidence is provided that NO constitutive production is, at least in part, responsible for the reported electrophysiological modifications observed in cardiomyocytes from B(2)R(-/-) mice. Surprisingly, NO is not involved in the SR Ca(2+) release reduction as demonstrated in the present study. Taken together, our findings indicate that B(2)R plays a fundamental role in the regulation of cardiac function and Ca(2+) homeostasis, probably through a NO dependent pathway. These results may contribute to our understanding of the kinins participation in the control of cardiac function. Copyright © 2010 Elsevier Inc. All rights reserved.

Lignan from Thyme Possesses Inhibitory Effect on ASIC3 Channel Current*

PubMed Central

Dubinnyi, Maxim A.; Osmakov, Dmitry I.; Koshelev, Sergey G.; Kozlov, Sergey A.; Andreev, Yaroslav A.; Zakaryan, Naira A.; Dyachenko, Igor A.; Bondarenko, Dmitry A.; Arseniev, Alexander S.; Grishin, Eugene V.

2012-01-01

A novel compound was identified in the acidic extract of Thymus armeniacus collected in the Lake Sevan region of Armenia. This compound, named “sevanol,” to our knowledge is the first low molecular weight natural molecule that has a reversible inhibition effect on both the transient and the sustained current of human ASIC3 channels expressed in Xenopus laevis oocytes. Sevanol completely blocked the transient component (IC50 353 ± 23 μm) and partially (∼45%) inhibited the amplitude of the sustained component (IC50 of 234 ± 53 μm). Other types of acid-sensing ion channel (ASIC) channels were intact to sevanol application, except ASIC1a, which showed more than six times less affinity to it as compared with the inhibitory action on the ASIC3 channel. To elucidate the structure of sevanol, the set of NMR spectra in two solvents (d6-DMSO and D2O) was collected, and the complete chemical structure was confirmed by liquid chromatography-mass spectrometry with electrospray ionization (LC-ESI+-MS) fragmentation. This compound is a new lignan built up of epiphyllic acid and two isocitryl esters in positions 9 and 10. In vivo administration of sevanol (1–10 mg/kg) significantly reversed thermal hyperalgesia induced by complete Freund's adjuvant injection and reduced response to acid in a writhing test. Thus, we assume the probable considerable role of sevanol in known analgesic and anti-inflammatory properties of thyme. PMID:22854960

Dual-Gate p-GaN Gate High Electron Mobility Transistors for Steep Subthreshold Slope.

PubMed

Bae, Jong-Ho; Lee, Jong-Ho

2016-05-01

A steep subthreshold slope characteristic is achieved through p-GaN gate HEMT with dual-gate structure. Obtained subthreshold slope is less than 120 μV/dec. Based on the measured and simulated data obtained from single-gate device, breakdown of parasitic floating-base bipolar transistor and floating gate charged with holes are responsible to increase abruptly in drain current. In the dual-gate device, on-current degrades with high temperature but subthreshold slope is not changed. To observe the switching speed of dual-gate device and transient response of drain current are measured. According to the transient responses of drain current, switching speed of the dual-gate device is about 10(-5) sec.

Cold starting of fluorescent lamps - part I: a description of the transient regime

NASA Astrophysics Data System (ADS)

Langer, Reinhard; Garner, Richard; Paul, Irina; Horn, Siegfried; Tidecks, Reinhard

2016-10-01

In this paper we give a proposal for the transient behaviour of a cold-started fluorescent lamp, from the generation of the first conductive channel over the normal and abnormal glow discharge and the glow-to-arc (GTA) transition to the arc discharge in the steady state. Starting from the equilibrium voltage-current characteristics of the lamp and considering recent experimental results a qualitative description of the transient regime is developed, which was so far not available in the literature.

Thermal shock behavior of W-ZrC/Sc2O3 composites under two different transient events by electron and laser irradiation

NASA Astrophysics Data System (ADS)

Chen, Hong-Yu; Luo, Lai-Ma; Zan, Xiang; Xu, Qiu; Tokunaga, Kazutoshi; Liu, Jia-Qin; Zhu, Xiao-Yong; Cheng, Ji-Gui; Wu, Yu-Cheng

2018-02-01

The transient thermal shock behaviors of W-ZrC/Sc2O3 composites with different ZrC contents were evaluated using transient thermal shock test by electron and laser beams. The effects of different ZrC doping contents on the surface morphology and thermal shock resistance of W-ZrC/Sc2O3 composites were then investigated. Similarity and difference between effects of electron and laser beam transient heat loading were also discussed in this study. Repeated heat loading resulted in thermal fatigue of the irradiated W-ZrC/Sc2O3 samples by thermal stress, leading to the rough surface morphologies with cracks. After different transient thermal tests, significant surface roughening, cracks, surface melting, and droplet ejection occurred. W-2vol.%Sc2O3 sample has superior thermal properties and greater resistance to surface modifications under transient thermal shock, and with the increasing ZrC content in W alloys, thermal shock resistance of W-Zr/Sc2O3 sample tends to be unsatisfied.

Properties of the electrostatically driven helical plasma state

NASA Astrophysics Data System (ADS)

Akçay, Cihan; Finn, John M.; Nebel, Richard A.; Barnes, Daniel C.; Martin, Neal

2018-02-01

A novel plasma state has been found [Akçay et al., Phys. Plasmas 24, 052503 (2017)] in the presence of a uniform applied axial magnetic field in periodic cylindrical geometry. This state is driven by external electrostatic fields provided by helical electrodes with a (m =1 ,n =1 ) (helical) symmetry where m and n represent the poloidal and axial harmonics. The resulting plasma is a function of the cylinder radius r

Action potentials and ion conductances in wild-type and CALHM1-knockout type II taste cells

PubMed Central

Saung, Wint Thu; Foskett, J. Kevin

2017-01-01

Taste bud type II cells fire action potentials in response to tastants, triggering nonvesicular ATP release to gustatory neurons via voltage-gated CALHM1-associated ion channels. Whereas CALHM1 regulates mouse cortical neuron excitability, its roles in regulating type II cell excitability are unknown. In this study, we compared membrane conductances and action potentials in single identified TRPM5-GFP-expressing circumvallate papillae type II cells acutely isolated from wild-type (WT) and Calhm1 knockout (KO) mice. The activation kinetics of large voltage-gated outward currents were accelerated in cells from Calhm1 KO mice, and their associated nonselective tail currents, previously shown to be highly correlated with ATP release, were completely absent in Calhm1 KO cells, suggesting that CALHM1 contributes to all of these currents. Calhm1 deletion did not significantly alter resting membrane potential or input resistance, the amplitudes and kinetics of Na+ currents either estimated from action potentials or recorded from steady-state voltage pulses, or action potential threshold, overshoot peak, afterhyperpolarization, and firing frequency. However, Calhm1 deletion reduced the half-widths of action potentials and accelerated the deactivation kinetics of transient outward currents, suggesting that the CALHM1-associated conductance becomes activated during the repolarization phase of action potentials. NEW & NOTEWORTHY CALHM1 is an essential ion channel component of the ATP neurotransmitter release mechanism in type II taste bud cells. Its contribution to type II cell resting membrane properties and excitability is unknown. Nonselective voltage-gated currents, previously associated with ATP release, were absent in cells lacking CALHM1. Calhm1 deletion was without effects on resting membrane properties or voltage-gated Na+ and K+ channels but contributed modestly to the kinetics of action potentials. PMID:28202574

Action potentials and ion conductances in wild-type and CALHM1-knockout type II taste cells.

PubMed

Ma, Zhongming; Saung, Wint Thu; Foskett, J Kevin

2017-05-01

Taste bud type II cells fire action potentials in response to tastants, triggering nonvesicular ATP release to gustatory neurons via voltage-gated CALHM1-associated ion channels. Whereas CALHM1 regulates mouse cortical neuron excitability, its roles in regulating type II cell excitability are unknown. In this study, we compared membrane conductances and action potentials in single identified TRPM5-GFP-expressing circumvallate papillae type II cells acutely isolated from wild-type (WT) and Calhm1 knockout (KO) mice. The activation kinetics of large voltage-gated outward currents were accelerated in cells from Calhm1 KO mice, and their associated nonselective tail currents, previously shown to be highly correlated with ATP release, were completely absent in Calhm1 KO cells, suggesting that CALHM1 contributes to all of these currents. Calhm1 deletion did not significantly alter resting membrane potential or input resistance, the amplitudes and kinetics of Na + currents either estimated from action potentials or recorded from steady-state voltage pulses, or action potential threshold, overshoot peak, afterhyperpolarization, and firing frequency. However, Calhm1 deletion reduced the half-widths of action potentials and accelerated the deactivation kinetics of transient outward currents, suggesting that the CALHM1-associated conductance becomes activated during the repolarization phase of action potentials. NEW & NOTEWORTHY CALHM1 is an essential ion channel component of the ATP neurotransmitter release mechanism in type II taste bud cells. Its contribution to type II cell resting membrane properties and excitability is unknown. Nonselective voltage-gated currents, previously associated with ATP release, were absent in cells lacking CALHM1. Calhm1 deletion was without effects on resting membrane properties or voltage-gated Na + and K + channels but contributed modestly to the kinetics of action potentials. Copyright © 2017 the American Physiological Society.

Mechanisms of Firing Patterns in Fast-Spiking Cortical Interneurons

PubMed Central

Golomb, David; Donner, Karnit; Shacham, Liron; Shlosberg, Dan; Amitai, Yael; Hansel, David

2007-01-01

Cortical fast-spiking (FS) interneurons display highly variable electrophysiological properties. Their spike responses to step currents occur almost immediately following the step onset or after a substantial delay, during which subthreshold oscillations are frequently observed. Their firing patterns include high-frequency tonic firing and rhythmic or irregular bursting (stuttering). What is the origin of this variability? In the present paper, we hypothesize that it emerges naturally if one assumes a continuous distribution of properties in a small set of active channels. To test this hypothesis, we construct a minimal, single-compartment conductance-based model of FS cells that includes transient Na+, delayed-rectifier K+, and slowly inactivating d-type K+ conductances. The model is analyzed using nonlinear dynamical system theory. For small Na+ window current, the neuron exhibits high-frequency tonic firing. At current threshold, the spike response is almost instantaneous for small d-current conductance, g d, and it is delayed for larger g d. As g d further increases, the neuron stutters. Noise substantially reduces the delay duration and induces subthreshold oscillations. In contrast, when the Na+ window current is large, the neuron always fires tonically. Near threshold, the firing rates are low, and the delay to firing is only weakly sensitive to noise; subthreshold oscillations are not observed. We propose that the variability in the response of cortical FS neurons is a consequence of heterogeneities in their g d and in the strength of their Na+ window current. We predict the existence of two types of firing patterns in FS neurons, differing in the sensitivity of the delay duration to noise, in the minimal firing rate of the tonic discharge, and in the existence of subthreshold oscillations. We report experimental results from intracellular recordings supporting this prediction. PMID:17696606

Mechanisms of firing patterns in fast-spiking cortical interneurons.

PubMed

Golomb, David; Donner, Karnit; Shacham, Liron; Shlosberg, Dan; Amitai, Yael; Hansel, David

2007-08-01

Cortical fast-spiking (FS) interneurons display highly variable electrophysiological properties. Their spike responses to step currents occur almost immediately following the step onset or after a substantial delay, during which subthreshold oscillations are frequently observed. Their firing patterns include high-frequency tonic firing and rhythmic or irregular bursting (stuttering). What is the origin of this variability? In the present paper, we hypothesize that it emerges naturally if one assumes a continuous distribution of properties in a small set of active channels. To test this hypothesis, we construct a minimal, single-compartment conductance-based model of FS cells that includes transient Na(+), delayed-rectifier K(+), and slowly inactivating d-type K(+) conductances. The model is analyzed using nonlinear dynamical system theory. For small Na(+) window current, the neuron exhibits high-frequency tonic firing. At current threshold, the spike response is almost instantaneous for small d-current conductance, gd, and it is delayed for larger gd. As gd further increases, the neuron stutters. Noise substantially reduces the delay duration and induces subthreshold oscillations. In contrast, when the Na(+) window current is large, the neuron always fires tonically. Near threshold, the firing rates are low, and the delay to firing is only weakly sensitive to noise; subthreshold oscillations are not observed. We propose that the variability in the response of cortical FS neurons is a consequence of heterogeneities in their gd and in the strength of their Na(+) window current. We predict the existence of two types of firing patterns in FS neurons, differing in the sensitivity of the delay duration to noise, in the minimal firing rate of the tonic discharge, and in the existence of subthreshold oscillations. We report experimental results from intracellular recordings supporting this prediction.

Properties of the low threshold Ca current in single frog atrial cardiomyocytes. A comparison with the high threshold Ca current

PubMed Central

1992-01-01

The properties of the low threshold Ca current (ICaT) in bullfrog (Rana catesbeiana) isolated atrial cardiomyocytes were studied using the whole-cell recording patch-clamp technique and compared with those of the high threshold Ca current (ICaL). In 91% of atrial cells we observed both ICaT and ICaL when collagenase and trypsin were used to dissociate the cells. But when pronase was used, only 30% of the cells exhibited ICaT. ICaT was never found in ventricular cells. ICaT could be investigated more easily when ICaL was inhibited by Cd ions (50 microM). Its kinetics were unchanged by substituting Ba for Ca, or in the presence of high concentrations of Ba. Both ICaT and ICaL exhibited reduced inactivation after high depolarizing prepulses. ICaT was found to be sensitive to dihydropyridines: 1 microM nifedipine decreased this current while 1 microM BAY K 8644 increased it; this occurred without significant variations in the steady-state inactivation curve. ICaT was more sensitive than ICaL to alpha 1-adrenergic and P2-purinergic stimulations, while ICaL was more sensitive to beta-adrenergic stimulation. Isoproterenol was still able to increase ICaT in the presence of high intracellular cAMP. Both currents were increased by 1 microM ouabain (although ICaL only transiently) and decreased by 10 microM ouabain. It is concluded that the two types of Ca channels can be observed in bullfrog atrial cells and that they are specifically altered by pharmacological agents and neuromediators. This may have implications for cardiac behavior. PMID:1279097

Search for transient gravitational waves in coincidence with short-duration radio transients during 2007-2013

NASA Astrophysics Data System (ADS)

Abbott, B. P.; Abbott, R.; Abbott, T. D.; Abernathy, M. R.; Acernese, F.; Ackley, K.; Adams, C.; Adams, T.; Addesso, P.; Adhikari, R. X.; Adya, V. B.; Affeldt, C.; Agathos, M.; Agatsuma, K.; Aggarwal, N.; Aguiar, O. D.; Aiello, L.; Ain, A.; Ajith, P.; Allen, B.; Allocca, A.; Altin, P. A.; Anderson, S. B.; Anderson, W. G.; Arai, K.; Araya, M. C.; Arceneaux, C. C.; Areeda, J. S.; Arnaud, N.; Arun, K. G.; Ascenzi, S.; Ashton, G.; Ast, M.; Aston, S. M.; Astone, P.; Aufmuth, P.; Aulbert, C.; Babak, S.; Bacon, P.; Bader, M. K. M.; Baker, P. T.; Baldaccini, F.; Ballardin, G.; Ballmer, S. W.; Barayoga, J. C.; Barclay, S. E.; Barish, B. C.; Barker, D.; Barone, F.; Barr, B.; Barsotti, L.; Barsuglia, M.; Barta, D.; Bartlett, J.; Bartos, I.; Bassiri, R.; Basti, A.; Batch, J. C.; Baune, C.; Bavigadda, V.; Bazzan, M.; Behnke, B.; Bejger, M.; Bell, A. S.; Bell, C. J.; Berger, B. K.; Bergman, J.; Bergmann, G.; Berry, C. P. L.; Bersanetti, D.; Bertolini, A.; Betzwieser, J.; Bhagwat, S.; Bhandare, R.; Bilenko, I. A.; Billingsley, G.; Birch, J.; Birney, R.; Biscans, S.; Bisht, A.; Bitossi, M.; Biwer, C.; Bizouard, M. A.; Blackburn, J. K.; Blair, C. D.; Blair, D. G.; Blair, R. M.; Bloemen, S.; Bock, O.; Bodiya, T. P.; Boer, M.; Bogaert, G.; Bogan, C.; Bohe, A.; Bojtos, P.; Bond, C.; Bondu, F.; Bonnand, R.; Boom, B. A.; Bork, R.; Boschi, V.; Bose, S.; Bouffanais, Y.; Bozzi, A.; Bradaschia, C.; Brady, P. R.; Braginsky, V. B.; Branchesi, M.; Brau, J. E.; Briant, T.; Brillet, A.; Brinkmann, M.; Brisson, V.; Brockill, P.; Brooks, A. F.; Brown, D. A.; Brown, D. D.; Brown, N. M.; Buchanan, C. C.; Buikema, A.; Bulik, T.; Bulten, H. J.; Buonanno, A.; Buskulic, D.; Buy, C.; Byer, R. L.; Cadonati, L.; Cagnoli, G.; Cahillane, C.; Calderón Bustillo, J.; Callister, T.; Calloni, E.; Camp, J. B.; Cannon, K. C.; Cao, J.; Capano, C. D.; Capocasa, E.; Carbognani, F.; Caride, S.; Casanueva Diaz, J.; Casentini, C.; Caudill, S.; Cavaglià, M.; Cavalier, F.; Cavalieri, R.; Cella, G.; Cepeda, C. B.; Cerboni Baiardi, L.; Cerretani, G.; Cesarini, E.; Chakraborty, R.; Chalermsongsak, T.; Chamberlin, S. J.; Chan, M.; Chao, S.; Charlton, P.; Chassande-Mottin, E.; Chen, H. Y.; Chen, Y.; Cheng, C.; Chincarini, A.; Chiummo, A.; Cho, H. S.; Cho, M.; Chow, J. H.; Christensen, N.; Chu, Q.; Chua, S.; Chung, S.; Ciani, G.; Clara, F.; Clark, J. A.; Cleva, F.; Coccia, E.; Cohadon, P.-F.; Colla, A.; Collette, C. G.; Cominsky, L.; Constancio, M.; Conte, A.; Conti, L.; Cook, D.; Corbitt, T. R.; Cornish, N.; Corsi, A.; Cortese, S.; Costa, C. A.; Coughlin, M. W.; Coughlin, S. B.; Coulon, J.-P.; Countryman, S. T.; Couvares, P.; Coward, D. M.; Cowart, M. J.; Coyne, D. C.; Coyne, R.; Craig, K.; Creighton, J. D. E.; Cripe, J.; Crowder, S. G.; Cumming, A.; Cunningham, L.; Cuoco, E.; Dal Canton, T.; Danilishin, S. L.; D'Antonio, S.; Danzmann, K.; Darman, N. S.; Dattilo, V.; Dave, I.; Daveloza, H. P.; Davier, M.; Davies, G. S.; Daw, E. J.; Day, R.; DeBra, D.; Debreczeni, G.; Degallaix, J.; De Laurentis, M.; Deléglise, S.; Del Pozzo, W.; Denker, T.; Dent, T.; Dergachev, V.; De Rosa, R.; DeRosa, R. T.; DeSalvo, R.; Dhurandhar, S.; Díaz, M. C.; Di Fiore, L.; Di Giovanni, M.; Di Girolamo, T.; Di Lieto, A.; Di Pace, S.; Di Palma, I.; Di Virgilio, A.; Dojcinoski, G.; Dolique, V.; Donovan, F.; Dooley, K. L.; Doravari, S.; Douglas, R.; Downes, T. P.; Drago, M.; Drever, R. W. P.; Driggers, J. C.; Du, Z.; Ducrot, M.; Dwyer, S. E.; Edo, T. B.; Edwards, M. C.; Effler, A.; Eggenstein, H.-B.; Ehrens, P.; Eichholz, J.; Eikenberry, S. S.; Engels, W.; Essick, R. C.; Etzel, T.; Evans, M.; Evans, T. M.; Everett, R.; Factourovich, M.; Fafone, V.; Fair, H.; Fairhurst, S.; Fan, X.; Fang, Q.; Farinon, S.; Farr, B.; Farr, W. M.; Favata, M.; Fays, M.; Fehrmann, H.; Fejer, M. M.; Ferrante, I.; Ferreira, E. C.; Ferrini, F.; Fidecaro, F.; Fiori, I.; Fiorucci, D.; Fisher, R. P.; Flaminio, R.; Fletcher, M.; Fournier, J.-D.; Frasca, S.; Frasconi, F.; Frei, Z.; Freise, A.; Frey, R.; Frey, V.; Fricke, T. T.; Fritschel, P.; Frolov, V. V.; Fulda, P.; Fyffe, M.; Gabbard, H. A. G.; Gair, J. R.; Gammaitoni, L.; Gaonkar, S. G.; Garufi, F.; Gaur, G.; Gehrels, N.; Gemme, G.; Genin, E.; Gennai, A.; George, J.; Gergely, L.; Germain, V.; Ghosh, Archisman; Ghosh, S.; Giaime, J. A.; Giardina, K. D.; Giazotto, A.; Gill, K.; Glaefke, A.; Goetz, E.; Goetz, R.; Gondan, L.; González, G.; Gonzalez Castro, J. M.; Gopakumar, A.; Gordon, N. A.; Gorodetsky, M. L.; Gossan, S. E.; Gosselin, M.; Gouaty, R.; Grado, A.; Graef, C.; Graff, P. B.; Granata, M.; Grant, A.; Gras, S.; Gray, C.; Greco, G.; Green, A. C.; Groot, P.; Grote, H.; Grunewald, S.; Guidi, G. M.; Guo, X.; Gupta, A.; Gupta, M. K.; Gushwa, K. E.; Gustafson, E. K.; Gustafson, R.; Hacker, J. J.; Hall, B. R.; Hall, E. D.; Hammond, G.; Haney, M.; Hanke, M. M.; Hanks, J.; Hanna, C.; Hannam, M. D.; Hanson, J.; Hardwick, T.; Harms, J.; Harry, G. M.; Harry, I. W.; Hart, M. J.; Hartman, M. T.; Haster, C.-J.; Haughian, K.; Heidmann, A.; Heintze, M. C.; Heitmann, H.; Hello, P.; Hemming, G.; Hendry, M.; Heng, I. S.; Hennig, J.; Heptonstall, A. W.; Heurs, M.; Hild, S.; Hoak, D.; Hodge, K. A.; Hofman, D.; Hollitt, S. E.; Holt, K.; Holz, D. E.; Hopkins, P.; Hosken, D. J.; Hough, J.; Houston, E. A.; Howell, E. J.; Hu, Y. M.; Huang, S.; Huerta, E. A.; Huet, D.; Hughey, B.; Husa, S.; Huttner, S. H.; Huynh-Dinh, T.; Idrisy, A.; Indik, N.; Ingram, D. R.; Inta, R.; Isa, H. N.; Isac, J.-M.; Isi, M.; Islas, G.; Isogai, T.; Iyer, B. R.; Izumi, K.; Jacqmin, T.; Jang, H.; Jani, K.; Jaranowski, P.; Jawahar, S.; Jiménez-Forteza, F.; Johnson, W. W.; Jones, D. I.; Jones, R.; Jonker, R. J. G.; Ju, L.; Haris, K.; Kalaghatgi, C. V.; Kalogera, V.; Kandhasamy, S.; Kang, G.; Kanner, J. B.; Karki, S.; Kasprzack, M.; Katsavounidis, E.; Katzman, W.; Kaufer, S.; Kaur, T.; Kawabe, K.; Kawazoe, F.; Kéfélian, F.; Kehl, M. S.; Keitel, D.; Kelley, D. B.; Kells, W.; Kennedy, R.; Key, J. S.; Khalaidovski, A.; Khalili, F. Y.; Khan, I.; Khan, S.; Khan, Z.; Khazanov, E. A.; Kijbunchoo, N.; Kim, Chunglee; Kim, J.; Kim, K.; Kim, Nam-Gyu; Kim, Namjun; Kim, Y.-M.; King, E. J.; King, P. J.; Kinzel, D. L.; Kissel, J. S.; Kleybolte, L.; Klimenko, S.; Koehlenbeck, S. M.; Kokeyama, K.; Koley, S.; Kondrashov, V.; Kontos, A.; Korobko, M.; Korth, W. Z.; Kowalska, I.; Kozak, D. B.; Kringel, V.; Królak, A.; Krueger, C.; Kuehn, G.; Kumar, P.; Kuo, L.; Kutynia, A.; Lackey, B. D.; Landry, M.; Lange, J.; Lantz, B.; Lasky, P. D.; Lazzarini, A.; Lazzaro, C.; Leaci, P.; Leavey, S.; Lebigot, E. O.; Lee, C. H.; Lee, H. K.; Lee, H. M.; Lee, K.; Lenon, A.; Leonardi, M.; Leong, J. R.; Leroy, N.; Letendre, N.; Levin, Y.; Levine, B. M.; Li, T. G. F.; Libson, A.; Littenberg, T. B.; Lockerbie, N. A.; Logue, J.; Lombardi, A. L.; Lord, J. E.; Lorenzini, M.; Loriette, V.; Lormand, M.; Losurdo, G.; Lough, J. D.; Lück, H.; Lundgren, A. P.; Luo, J.; Lynch, R.; Ma, Y.; MacDonald, T.; Machenschalk, B.; MacInnis, M.; Macleod, D. M.; Magaña-Sandoval, F.; Magee, R. M.; Mageswaran, M.; Majorana, E.; Maksimovic, I.; Malvezzi, V.; Man, N.; Mandic, V.; Mangano, V.; Mansell, G. L.; Manske, M.; Mantovani, M.; Marchesoni, F.; Marion, F.; Márka, S.; Márka, Z.; Markosyan, A. S.; Maros, E.; Martelli, F.; Martellini, L.; Martin, I. W.; Martin, R. M.; Martynov, D. V.; Marx, J. N.; Mason, K.; Masserot, A.; Massinger, T. J.; Masso-Reid, M.; Mastrogiovanni, S.; Matichard, F.; Matone, L.; Mavalvala, N.; Mazumder, N.; Mazzolo, G.; McCarthy, R.; McClelland, D. E.; McCormick, S.; McGuire, S. C.; McIntyre, G.; McIver, J.; McManus, D. J.; McWilliams, S. T.; Meacher, D.; Meadors, G. D.; Meidam, J.; Melatos, A.; Mendell, G.; Mendoza-Gandara, D.; Mercer, R. A.; Merilh, E. L.; Merzougui, M.; Meshkov, S.; Messenger, C.; Messick, C.; Metzdorff, R.; Meyers, P. M.; Mezzani, F.; Miao, H.; Michel, C.; Middleton, H.; Mikhailov, E. E.; Milano, L.; Miller, A. L.; Miller, J.; Millhouse, M.; Minenkov, Y.; Ming, J.; Mirshekari, S.; Mishra, C.; Mitra, S.; Mitrofanov, V. P.; Mitselmakher, G.; Mittleman, R.; Moggi, A.; Mohan, M.; Mohapatra, S. R. P.; Montani, M.; Moore, B. C.; Moore, C. J.; Moraru, D.; Moreno, G.; Morriss, S. R.; Mossavi, K.; Mours, B.; Mow-Lowry, C. M.; Mueller, C. L.; Mueller, G.; Muir, A. W.; Mukherjee, Arunava; Mukherjee, D.; Mukherjee, S.; Mukund, K. N.; Mullavey, A.; Munch, J.; Murphy, D. J.; Murray, P. G.; Mytidis, A.; Nardecchia, I.; Naticchioni, L.; Nayak, R. K.; Necula, V.; Nedkova, K.; Nelemans, G.; Neri, M.; Neunzert, A.; Newton, G.; Nguyen, T. T.; Nielsen, A. B.; Nissanke, S.; Nitz, A.; Nocera, F.; Nolting, D.; Normandin, M. E. N.; Nuttall, L. K.; Oberling, J.; Ochsner, E.; O'Dell, J.; Oelker, E.; Ogin, G. H.; Oh, J. J.; Oh, S. H.; Ohme, F.; Oliver, M.; Oppermann, P.; Oram, Richard J.; O'Reilly, B.; O'Shaughnessy, R.; Ott, C. D.; Ottaway, D. J.; Ottens, R. S.; Overmier, H.; Owen, B. J.; Pai, A.; Pai, S. A.; Palamos, J. R.; Palashov, O.; Palomba, C.; Pal-Singh, A.; Pan, H.; Pankow, C.; Pannarale, F.; Pant, B. C.; Paoletti, F.; Paoli, A.; Papa, M. A.; Paris, H. R.; Parker, W.; Pascucci, D.; Pasqualetti, A.; Passaquieti, R.; Passuello, D.; Patricelli, B.; Patrick, Z.; Pearlstone, B. L.; Pedraza, M.; Pedurand, R.; Pekowsky, L.; Pele, A.; Penn, S.; Pereira, R.; Perreca, A.; Phelps, M.; Piccinni, O. J.; Pichot, M.; Piergiovanni, F.; Pierro, V.; Pillant, G.; Pinard, L.; Pinto, I. M.; Pitkin, M.; Pletsch, H. J.; Poggiani, R.; Popolizio, P.; Post, A.; Powell, J.; Prasad, J.; Predoi, V.; Premachandra, S. S.; Prestegard, T.; Price, L. R.; Prijatelj, M.; Principe, M.; Privitera, S.; Prodi, G. A.; Prokhorov, L.; Puncken, O.; Punturo, M.; Puppo, P.; Pürrer, M.; Qi, H.; Qin, J.; Quetschke, V.; Quintero, E. A.; Quitzow-James, R.; Raab, F. J.; Rabeling, D. S.; Radkins, H.; Raffai, P.; Raja, S.; Rakhmanov, M.; Rapagnani, P.; Raymond, V.; Razzano, M.; Re, V.; Read, J.; Reed, C. M.; Regimbau, T.; Rei, L.; Reid, S.; Reitze, D. H.; Rew, H.; Ricci, F.; Riles, K.; Robertson, N. A.; Robie, R.; Robinet, F.; Rocchi, A.; Rolland, L.; Rollins, J. G.; Roma, V. J.; Romano, J. D.; Romano, R.; Romanov, G.; Romie, J. H.; Rosińska, D.; Rowan, S.; Rüdiger, A.; Ruggi, P.; Ryan, K.; Sachdev, S.; Sadecki, T.; Sadeghian, L.; Salconi, L.; Saleem, M.; Salemi, F.; Samajdar, A.; Sammut, L.; Sanchez, E. J.; Sandberg, V.; Sandeen, B.; Sanders, J. R.; Sassolas, B.; Sathyaprakash, B. S.; Saulson, P. R.; Sauter, O. E. S.; Savage, R. L.; Sawadsky, A.; Schale, P.; Schilling, R.; Schmidt, J.; Schmidt, P.; Schnabel, R.; Schofield, R. M. S.; Schönbeck, A.; Schreiber, E.; Schuette, D.; Schutz, B. F.; Scott, J.; Scott, S. M.; Sellers, D.; Sentenac, D.; Sequino, V.; Sergeev, A.; Serna, G.; Setyawati, Y.; Sevigny, A.; Shaddock, D. A.; Shahriar, M. S.; Shaltev, M.; Shao, Z.; Shapiro, B.; Shawhan, P.; Sheperd, A.; Shoemaker, D. H.; Shoemaker, D. M.; Siellez, K.; Siemens, X.; Sieniawska, M.; Sigg, D.; Silva, A. D.; Simakov, D.; Singer, A.; Singer, L. P.; Singh, A.; Singh, R.; Singhal, A.; Sintes, A. M.; Slagmolen, B. J. J.; Smith, J. R.; Smith, N. D.; Smith, R. J. E.; Son, E. J.; Sorazu, B.; Sorrentino, F.; Souradeep, T.; Srivastava, A. K.; Staley, A.; Steinke, M.; Steinlechner, J.; Steinlechner, S.; Steinmeyer, D.; Stephens, B. C.; Stiles, D.; Stone, R.; Strain, K. A.; Straniero, N.; Stratta, G.; Strauss, N. A.; Strigin, S.; Sturani, R.; Stuver, A. L.; Summerscales, T. Z.; Sun, L.; Sutton, P. J.; Swinkels, B. L.; Szczepańczyk, M. J.; Tacca, M.; Talukder, D.; Tanner, D. B.; Tápai, M.; Tarabrin, S. P.; Taracchini, A.; Taylor, R.; Theeg, T.; Thirugnanasambandam, M. P.; Thomas, E. G.; Thomas, M.; Thomas, P.; Thorne, K. A.; Thrane, E.; Tiwari, S.; Tiwari, V.; Tokmakov, K. V.; Tomlinson, C.; Tonelli, M.; Torres, C. V.; Torrie, C. I.; Töyrä, D.; Travasso, F.; Traylor, G.; Trifirò, D.; Tringali, M. C.; Trozzo, L.; Tse, M.; Turconi, M.; Tuyenbayev, D.; Ugolini, D.; Unnikrishnan, C. S.; Urban, A. L.; Usman, S. A.; Vahlbruch, H.; Vajente, G.; Valdes, G.; van Bakel, N.; van Beuzekom, M.; van den Brand, J. F. J.; Van Den Broeck, C.; Vander-Hyde, D. C.; van der Schaaf, L.; van Heijningen, J. V.; van Veggel, A. A.; Vardaro, M.; Vass, S.; Vasúth, M.; Vaulin, R.; Vecchio, A.; Vedovato, G.; Veitch, J.; Veitch, P. J.; Venkateswara, K.; Verkindt, D.; Vetrano, F.; Viceré, A.; Vinciguerra, S.; Vine, D. J.; Vinet, J.-Y.; Vitale, S.; Vo, T.; Vocca, H.; Vorvick, C.; Voss, D. V.; Vousden, W. D.; Vyatchanin, S. P.; Wade, A. R.; Wade, L. E.; Wade, M.; Walker, M.; Wallace, L.; Walsh, S.; Wang, G.; Wang, H.; Wang, M.; Wang, X.; Wang, Y.; Ward, R. L.; Warner, J.; Was, M.; Weaver, B.; Wei, L.-W.; Weinert, M.; Weinstein, A. J.; Weiss, R.; Welborn, T.; Wen, L.; Weßels, P.; Westphal, T.; Wette, K.; Whelan, J. T.; Whitcomb, S. E.; White, D. J.; Whiting, B. F.; Williams, R. D.; Williamson, A. R.; Willis, J. L.; Willke, B.; Wimmer, M. H.; Winkler, W.; Wipf, C. C.; Wittel, H.; Woan, G.; Worden, J.; Wright, J. L.; Wu, G.; Yablon, J.; Yam, W.; Yamamoto, H.; Yancey, C. C.; Yap, M. J.; Yu, H.; Yvert, M.; ZadroŻny, A.; Zangrando, L.; Zanolin, M.; Zendri, J.-P.; Zevin, M.; Zhang, F.; Zhang, L.; Zhang, M.; Zhang, Y.; Zhao, C.; Zhou, M.; Zhou, Z.; Zhu, X. J.; Zucker, M. E.; Zuraw, S. E.; Zweizig, J.; Archibald, A. M.; Banaszak, S.; Berndsen, A.; Boyles, J.; Cardoso, R. F.; Chawla, P.; Cherry, A.; Dartez, L. P.; Day, D.; Epstein, C. R.; Ford, A. J.; Flanigan, J.; Garcia, A.; Hessels, J. W. T.; Hinojosa, J.; Jenet, F. A.; Karako-Argaman, C.; Kaspi, V. M.; Keane, E. F.; Kondratiev, V. I.; Kramer, M.; Leake, S.; Lorimer, D.; Lunsford, G.; Lynch, R. S.; Martinez, J. G.; Mata, A.; McLaughlin, M. A.; McPhee, C. A.; Penucci, T.; Ransom, S.; Roberts, M. S. E.; Rohr, M. D. W.; Stairs, I. H.; Stovall, K.; van Leeuwen, J.; Walker, A. N.; Wells, B. L.; LIGO Scientific Collaboration; Virgo Collaboration

2016-06-01

We present an archival search for transient gravitational-wave bursts in coincidence with 27 single-pulse triggers from Green Bank Telescope pulsar surveys, using the LIGO, Virgo, and GEO interferometer network. We also discuss a check for gravitational-wave signals in coincidence with Parkes fast radio bursts using similar methods. Data analyzed in these searches were collected between 2007 and 2013. Possible sources of emission of both short-duration radio signals and transient gravitational-wave emission include starquakes on neutron stars, binary coalescence of neutron stars, and cosmic string cusps. While no evidence for gravitational-wave emission in coincidence with these radio transients was found, the current analysis serves as a prototype for similar future searches using more sensitive second-generation interferometers.

The performance of hafnium and gadolinium self powered neutron detectors in the TREAT reactor

NASA Astrophysics Data System (ADS)

Imel, G. R.; Hart, P. R.

1996-05-01

The use of gadolinium and hafnium self powered neutron detectors in a transient reactor is described in this paper. The detectors were calibrated to the fission rate of U-235 using calibrated fission chambers; the calibration factors were tested in two reactors in steady state and found to be consistent. Calibration of the detectors in transient reactor conditions was done by using uranium wires that were analyzed by radiochemistry techniques to determine total fissions during the transient. This was correlated to the time-integrated current of the detectors during the transient. A temperature correction factor was derived to account for self-shielding effects in the hafnium and gadolinium detectors. The dynamic response of the detectors under transient conditions was studied, and found to be excellent.

A case study of the response of the magnetosphere to changes in the interplanetary medium

NASA Technical Reports Server (NTRS)

Rostoker, G.; Baumjohann, W.; Russell, C. T.

1983-01-01

A detailed analysis of world-wide ground based magnetometer data is presented, together with information on the plasma and magnetic field properties of the interplanetary medium and magnetosheath obtained from the ISEE 1 and 2 and IMP 8 spacecraft. The event concerned exhibited an interval of relatively stable southward IMF followed by a sharp northward turning. It is pointed out that during the interval of southward IMF there were occasional transient northward turnings with significant substorm expansive phase activity appearing to be triggered by these transient northward turnings. The final northward turning of the IMF was linked with an episode of strong magnetospheric substorm expansive phase activity after which the level of high latitude magnetic activity declined to a low level. Evidence is presented indicating that the driven system auroral electrojets begin to decay at the time of the northward turning of the IMF, even as the substorm expansive phase activity is initiated in the midnight sector. The collapse of the substorm current wedge during the final decay of high latitude activity is described in some detail, and it is shown that this collapse occurs progressively from east to west in a series of impulsive episodes.

The Swift Burst and Transient Telescope (BAT)

NASA Technical Reports Server (NTRS)

Mushotzky, Richard

2008-01-01

The Swift Burst and Transient telescope (BAT) has surveyed the entire sky for the last 3.5 years obtaining the first sensitive all sky survey of the 14-195 kev sky. At high galactic latitudes the vast majority of the detected sources are AGN. Since hard x-rays penetrate all but Compton thick obscuring material (Column densities of 1.6324 atms/sq cm) this survey is unbiased with respect to obscuration, host galaxy type, optical , radio or IR properties. We will present results on the broad band x-ray properties, the nature of the host galaxies, the luminosity function and will discuss a few of the optical, IR and x-ray results in detail.

Analysis of Spontaneous and Nerve-Evoked Calcium Transients in Intact Extraocular Muscles in Vitro

PubMed Central

Feng, Cheng-Yuan; Hennig, Grant W.; Corrigan, Robert D.; Smith, Terence K.; von Bartheld, Christopher S.

2012-01-01

Extraocular muscles (EOMs) have unique calcium handling properties, yet little is known about the dynamics of calcium events underlying ultrafast and tonic contractions in myofibers of intact EOMs. Superior oblique EOMs of juvenile chickens were dissected with their nerve attached, maintained in oxygenated Krebs buffer, and loaded with fluo-4. Spontaneous and nerve stimulation-evoked calcium transients were recorded and, following calcium imaging, some EOMs were double-labeled with rhodamine-conjugated alpha-bungarotoxin (rhBTX) to identify EOM myofiber types. EOMs showed two main types of spontaneous calcium transients, one slow type (calcium waves with 1/2max duration of 2–12 s, velocity of 25–50 μm/s) and two fast “flash-like” types (Type 1, 30–90 ms; Type 2, 90–150 ms 1/2max duration). Single pulse nerve stimulation evoked fast calcium transients identical to the fast (Type 1) calcium transients. Calcium waves were accompanied by a local myofiber contraction that followed the calcium transient wavefront. The magnitude of calcium-wave induced myofiber contraction far exceeded those of movement induced by nerve stimulation and associated fast calcium transients. Tetrodotoxin eliminated nerve-evoked transients, but not spontaneous transients. Alpha-bungarotoxin eliminated both spontaneous and nerve-evoked fast calcium transients, but not calcium waves, and caffeine increased wave activity. Calcium waves were observed in myofibers lacking spontaneous or evoked fast transients, suggestive of multiply-innervated myofibers, and this was confirmed by double-labeling with rhBTX. We propose that the abundant spontaneous calcium transients and calcium waves with localized contractions that do not depend on innervation may contribute to intrinsic generation of tonic functions of EOMs. PMID:22579493

Study on acoustical properties of sintered bronze porous material for transient exhaust noise of pneumatic system

NASA Astrophysics Data System (ADS)

Li, Jingxiang; Zhao, Shengdun; Ishihara, Kunihiko

2013-05-01

A novel approach is presented to study the acoustical properties of sintered bronze material, especially used to suppress the transient noise generated by the pneumatic exhaust of pneumatic friction clutch and brake (PFC/B) systems. The transient exhaust noise is impulsive and harmful due to the large sound pressure level (SPL) that has high-frequency. In this paper, the exhaust noise is related to the transient impulsive exhaust, which is described by a one-dimensional aerodynamic model combining with a pressure drop expression of the Ergun equation. A relation of flow parameters and sound source is set up. Additionally, the piston acoustic source approximation of sintered bronze silencer with cylindrical geometry is presented to predict SPL spectrum at a far-field observation point. A semi-phenomenological model is introduced to analyze the sound propagation and reduction in the sintered bronze materials assumed as an equivalent fluid with rigid frame. Experiment results under different initial cylinder pressures are shown to corroborate the validity of the proposed aerodynamic model. In addition, the calculated sound pressures according to the equivalent sound source are compared with the measured noise signals both in time-domain and frequency-domain. Influences of porosity of the sintered bronze material are also discussed.

Thermal diffusivity determination using heterodyne phase insensitive transient grating spectroscopy

NASA Astrophysics Data System (ADS)

Dennett, Cody A.; Short, Michael P.

2018-06-01

The elastic and thermal transport properties of opaque materials may be measured using transient grating spectroscopy (TGS) by inducing and monitoring periodic excitations in both reflectivity and surface displacement. The "phase grating" response encodes both properties of interest, but complicates quantitative analysis by convolving temperature dynamics with surface displacement dynamics. Thus, thermal transport characteristics are typically determined using the "amplitude grating" response to isolate the surface temperature dynamics. However, this signal character requires absolute heterodyne phase calibration and contains no elastic property information. Here, a method is developed by which phase grating TGS measurements may be consistently analyzed to determine thermal diffusivity with no prior knowledge of the expected properties. To demonstrate this ability, the wavelength-dependent 1D effective thermal diffusivity of pure germanium is measured using this type of response and found to be consistent with theoretical predictions made by solving the Boltzmann transport equation. This ability to determine the elastic and thermal properties from a single set of TGS measurements will be particularly advantageous for new in situ implementations of the technique being used to study dynamic materials systems.

Dimensionless figure of merit and its efficiency estimation for transient response of thermoelectric module based on impedance spectroscopy

NASA Astrophysics Data System (ADS)

Otsuka, Mioko; Hasegawa, Yasuhiro; Arisaka, Taichi; Shinozaki, Ryo; Morita, Hiroyuki

2017-11-01

The dimensionless figure of merit and its efficiency for the transient response of a Π-shaped thermoelectric module are estimated according to the theory of impedance spectroscopy. The effective dimensionless figure of merit is described as a function of the product of the characteristic time to reduce the temperature and the representative angular frequency of the module, which is expressed by the thermal diffusivity and the length of the elements used. The characteristic time required for achieving a higher dimensionless figure of merit and efficiency is derived quantitatively for the transient response using the properties of a commercial thermoelectric module.

Comparison of simulations to experiment for a detailed analysis of space-charge-limited transient current measurements in organic semiconductors

NASA Astrophysics Data System (ADS)

Szymanski, Marek Z.; Kulszewicz-Bajer, Irena; Faure-Vincent, Jérôme; Djurado, David

2012-05-01

Space-charge-limited current transients (also referred as time resolved dark injection) is an attractive technique for mobility measurements in low mobility materials, particularly the organic semiconductors. Transients are generally analyzed in terms of the Many-Rakavy theory, which is an approximate analytical solution of the time-dependent drift-diffusion problem after application of a voltage step. In this contribution, we perform full time-dependent drift-diffusion simulation and compare simulated and experimental transients measured on a sample of triaryl-amine based electroactive dendrimer (experimental conditions: μ≈10-5 cm2/(Vs), L=300 nm, E<105 V/cm). We have found that the Many-Rakavy theory is indeed valid for estimating the mobility value, but it fails to predict quantitatively the time-dependent current response. In order to obtain a good agreement in between simulation and experiment, trapping and quasi-ohmic contact models were needed to be taken into account. In the case of the studied electroactive dendrimer, the experimental results were apparently consistent with the constant mobility Many-Rakavy theory, but with this model, a large uncertainty of 20% was found for the mobility value. We show that this uncertainty can be significantly reduced to 10% if a field-dependent mobility is taken into account in the framework of the extended Gaussian disorder model. Finally, we demonstrate that this fitting procedure between simulated and experimental transient responses also permits to unambiguously provide the values of the contact barrier, the trap concentration, the trap depth in addition to that of the mobility of carriers.

Land-ocean contrast on electrical characteristics of lightning discharge derived from satellite optical measurements

NASA Astrophysics Data System (ADS)

Adachi, T.; Said, R.; Cummer, S. A.; Li, J.; Takahashi, Y.; Hsu, R.; Su, H.; Chen, A. B.; Mende, S. B.; Frey, H. U.

2010-12-01

Comparative studies on the electrical properties of oceanic and continental lightning are crucial to elucidate air discharge processes occurring under different conditions. Past studies however have primarily focused on continental lightning because of the limited coverage of ground-based instruments. Recent satellite measurements by FORMOSAT-2/ISUAL provided a new way to survey the global characteristics of lightning and transient luminous events regardless of land and ocean. In this study, we analyze ISUAL/spectrophotometer data to clarify the electrical properties of lightning on a global level. Based on the results obtained by Cummer et al. [2006] and Adachi et al. [2009], the OI-777.4nm emission intensity is used to infer lightning electrical parameters. Results show a clear land-ocean contrast on the parameters of lightning discharge: in oceanic lightning, peak luminosity is 60 % higher and the time scale of return stroke is 30 % shorter. These results suggest higher peak current in oceanic lightning, which is consistent with the fact that elves, EMP-driven phenomena, also tend to occur over the ocean [Chen et al., 2008]. Further analysis of lightning events occurring around the Caribbean Sea shows that the transition-line of lightning electrical properties is precisely located along the coastline. We suggest that the differences in these electrical properties may be due to the boundary conditions (conductivity, surface terrain, etc). In this talk, based on the calibration with NLDN and Duke magnetometer data, current moment change and charge moment change will be globally evaluated using a complete set of the ISUAL-observed lightning events.

Molecular Mechanism of TRP Channels

PubMed Central

Zheng, Jie

2013-01-01

Transient receptor potential (TRP) channels are cellular sensors for a wide spectrum of physical and chemical stimuli. They are involved in the formation of sight, hearing, touch, smell, taste, temperature, and pain sensation. TRP channels also play fundamental roles in cell signaling and allow the host cell to respond to benign or harmful environmental changes. As TRP channel activation is controlled by very diverse processes and, in many cases, exhibits complex polymodal properties, understanding how each TRP channel responds to its unique forms of activation energy is both crucial and challenging. The past two decades witnessed significant advances in understanding the molecular mechanisms that underlie TRP channels activation. This review focuses on our current understanding of the molecular determinants for TRP channel activation. PMID:23720286

Influence of deposition conditions on electrical and mechanical properties of Sm2O3-doped CeO2 thin films prepared by EB-PVD (+IBAD) methods. Part 1: Effective relative permittivity

NASA Astrophysics Data System (ADS)

Hartmanová, Mária; Nádaždy, Vojtech; Kundracik, František; Mansilla, Catina

2013-03-01

Study is devoted to the effective relative permittivity ɛr of CeO2 + x. Sm2O3 thin films prepared by electron-beam physical vapour deposition and ionic beam-assisted deposition methods; ɛr was investigated by three independent ways from the bulk parallel capacitance Cp, impedance capacitance Cimp, and accumulation capacitance Cacc in dependence on the deposition conditions (deposition temperature, dopant amount x and Ar+ ion bombardment during the film deposition) used. Investigations were performed using impedance spectroscopy, capacitance-voltage and current-voltage characteristics as well as deep level transient spectroscopy. Results obtained are described and discussed.

Probing the Fluctuations of Optical Properties in Time-Resolved Spectroscopy

NASA Astrophysics Data System (ADS)

Randi, Francesco; Esposito, Martina; Giusti, Francesca; Misochko, Oleg; Parmigiani, Fulvio; Fausti, Daniele; Eckstein, Martin

2017-11-01

We show that, in optical pump-probe experiments on bulk samples, the statistical distribution of the intensity of ultrashort light pulses after interaction with a nonequilibrium complex material can be used to measure the time-dependent noise of the current in the system. We illustrate the general arguments for a photoexcited Peierls material. The transient noise spectroscopy allows us to measure to what extent electronic degrees of freedom dynamically obey the fluctuation-dissipation theorem, and how well they thermalize during the coherent lattice vibrations. The proposed statistical measurement developed here provides a new general framework to retrieve dynamical information on the excited distributions in nonequilibrium experiments, which could be extended to other degrees of freedom of magnetic or vibrational origin.

CHI Research on NSTX-U

NASA Astrophysics Data System (ADS)

Lay, W.-S.; Raman, R.; Jarboe, T. R.; Nelson, B. A.; Mueller, D.; Ebrahimi, F.; Ono, M.; Jardin, S. C.; Taylor, G.

2017-10-01

At present about 20% of the total plasma current required for sustained operation has been generated by transient CHI. The present understanding suggests that it may be possible to generate all of the needed current in a ST / tokamak using transient CHI. In such a scenario, one could transition directly from a CHI produced plasma to a non-inductively sustained plasma, without the difficult intermediate step that involves non-inductive current ramp-up. STs based on this new configuration would take advantage of evolving developments in high-temperature superconductor technology to develop a simpler design ST that relies primarily on CHI for plasma current generation. Motivated by the very good results from NSTX and HIT-II, we are examining the potential application of transient CHI for reactor configurations through these studies. (1) Study of the maximum levels of start-up currents that could be generated on NSTX-U, (2) application of a single biased electrode configuration on QUEST to protect the insulator from neutron damage in a CHI reactor installation, and (3) QUEST-like, but a double biased electrode configuration for PEGASUS and NSTX-U. Results from these on-going studies will be described. This work is supported by U.S. DOE Contracts: DE-AC02-09CH11466, DE-FG02-99ER54519 AM08, and DE-SC0006757.

Plasmoid formation in the elongated current sheet during transient CHI on HIST

NASA Astrophysics Data System (ADS)

Nagata, Masayoshi; Fujita, Akihiro; Matsui, Takahiro; Kikuchi, Yusuke; Fukumoto, Naoyuki; Kanki, Takashi

2016-10-01

The Transient-Coaxial Helicity Injection (T-CHI) is a promising candidate for the non-inductive plasma start-up on Spherical Torus (ST). The problem of the flux closure in the T-CHI is important and related to understand the physics of fast magnetic reconnection. The recent MHD simulation (F. Ebrahimi and R. Raman, Phys. Rev. Lett. 114, 205003 (2015)) on T-CHI for NSTX predicts the formation and breakup of an elongated Sweet-Parker (S-P) current sheet and a transient to plasmoid instability. According to this simulation, the reconnection rate based on the plasmoid instability is faster than that by S-P model and becomes nearly independent of the Lundquist number S. In this meeting, we will present that the formation of multiple X-points and plasmoids has been observed in T-CHI start-up plasmas on HIST. The stronger external guide (toroidal) magnetic field makes plasma less compressible, leading to slower reconnection time and longer current sheet. The experimental observation shows that 2/3 plasmoids are generated in the elongated current sheet with the narrow width comparable to the ion skin depth or the ion sound gyro-radius. The small plasmoids develop to a large-scale flux structure due to a current inward diffusion during the decay phase.

Non-dispersive carrier transport in molecularly doped polymers and the convection-diffusion equation

NASA Astrophysics Data System (ADS)

Tyutnev, A. P.; Parris, P. E.; Saenko, V. S.

2015-08-01

We reinvestigate the applicability of the concept of trap-free carrier transport in molecularly doped polymers and the possibility of realistically describing time-of-flight (TOF) current transients in these materials using the classical convection-diffusion equation (CDE). The problem is treated as rigorously as possible using boundary conditions appropriate to conventional time of flight experiments. Two types of pulsed carrier generation are considered. In addition to the traditional case of surface excitation, we also consider the case where carrier generation is spatially uniform. In our analysis, the front electrode is treated as a reflecting boundary, while the counter electrode is assumed to act either as a neutral contact (not disturbing the current flow) or as an absorbing boundary at which the carrier concentration vanishes. As expected, at low fields transient currents exhibit unusual behavior, as diffusion currents overwhelm drift currents to such an extent that it becomes impossible to determine transit times (and hence, carrier mobilities). At high fields, computed transients are more like those typically observed, with well-defined plateaus and sharp transit times. Careful analysis, however, reveals that the non-dispersive picture, and predictions of the CDE contradict both experiment and existing disorder-based theories in important ways, and that the CDE should be applied rather cautiously, and even then only for engineering purposes.

Simplified Modeling of Steady-State and Transient Brillouin Gain in Magnetoactive Non-Centrosymmetric Semiconductors

NASA Astrophysics Data System (ADS)

Singh, M.; Aghamkar, P.; Sen, P. K.

With the aid of a hydrodynamic model of semiconductor-plasmas, a detailed analytical investigation is made to study both the steady-state and the transient Brillouin gain in magnetized non-centrosymmetric III-V semiconductors arising from the nonlinear interaction of an intense pump beam with the internally-generated acoustic wave, due to piezoelectric and electrostrictive properties of the crystal. Using the fact that the origin of coherent Brillouin scattering (CBS) lies in the third-order (Brillouin) susceptibility of the medium, we obtained an expression of the gain coefficient of backward Stokes mode in steady-state and transient regimes and studied the dependence of piezoelectricity, magnetic field and pump pulse duration on its growth rate. The threshold-pump intensity and optimum pulse duration for the onset of transient CBS are estimated. The piezoelectricity and externally-applied magnetic field substantially enhances the transient CBS gain coefficient in III-V semiconductors which can be of great use in the compression of scattered pulses.

EXTraS unveils a supernova shock break-out candidate in XMM-Newton archival data

NASA Astrophysics Data System (ADS)

Tiengo, A.; Novara, G.; Lisini, G.; De Luca, A.; Salvaterra, R.; Belfiore, A.; Marelli, M.; Salvetti, D.; Mereghetti, S.; Vianello, G.

2017-10-01

During the search for short X-ray transients within the Exploring the X-ray Transient and variable Sky (EXTraS) project, we discovered a new X-ray source that can be detected only in a ˜5 minutes interval of a ˜21 hours long XMM-Newton observation. Thanks to dedicated follow-up observations, we found that its position is consistent with a galaxy at redshift z=0.092. At this redshift, the transient released 2×10^{46} erg in the 0.3-10 keV energy band. Its luminosity and spectral and timing properties make it an analogue of the X-ray transient associated to SN2008, detected by Swift/XRT during an observation of the nearby supernova-rich galaxy NGC 2770. The discovery of this much more distant transient in a field galaxy during a systematic analysis of the full XMM-Newton archive allows us to better constrain the rate of these rare events.

Efficient Suppression of Electron–Hole Recombination in Oxygen-Deficient Hydrogen-Treated TiO2 Nanowires for Photoelectrochemical Water Splitting

PubMed Central

2013-01-01

There is an increasing level of interest in the use of black TiO2 prepared by thermal hydrogen treatments (H:TiO2) due to the potential to enhance both the photocatalytic and the light-harvesting properties of TiO2. Here, we examine oxygen-deficient H:TiO2 nanotube arrays that have previously achieved very high solar-to-hydrogen (STH) efficiencies due to incident photon-to-current efficiency (IPCE) values of >90% for photoelectrochemical water splitting at only 0.4 V vs RHE under UV illumination. Our transient absorption (TA) mechanistic study provides strong evidence that the improved electrical properties of oxygen-deficient TiO2 enables remarkably efficient spatial separation of electron–hole pairs on the submicrosecond time scale at moderate applied bias, and this coupled to effective suppression of microsecond to seconds charge carrier recombination is the primary factor behind the dramatically improved photoelectrochemical activity. PMID:24376902

Theory of Phase Separation and Polarization for Pure Ionic Liquids.

PubMed

Gavish, Nir; Yochelis, Arik

2016-04-07

Room temperature ionic liquids are attractive to numerous applications and particularly, to renewable energy devices. As solvent free electrolytes, they demonstrate a paramount connection between the material morphology and Coulombic interactions: the electrode/RTIL interface is believed to be a product of both polarization and spatiotemporal bulk properties. Yet, theoretical studies have dealt almost exclusively with independent models of morphology and electrokinetics. Introduction of a distinct Cahn-Hilliard-Poisson type mean-field framework for pure molten salts (i.e., in the absence of any neutral component), allows a systematic coupling between morphological evolution and the electrokinetic phenomena, such as transient currents. Specifically, linear analysis shows that spatially periodic patterns form via a finite wavenumber instability and numerical simulations demonstrate that while labyrinthine type patterns develop in the bulk, lamellar structures are favored near charged surfaces. The results demonstrate a qualitative phenomenology that is observed empirically and thus, provide a physically consistent methodology to incorporate phase separation properties into an electrochemical framework.

Friction Hydro-Pillar Processing of a High Carbon Steel: Joint Structure and Properties

NASA Astrophysics Data System (ADS)

Kanan, Luis Fernando; Vicharapu, Buchibabu; Bueno, Antonio Fernando Burkert; Clarke, Thomas; De, Amitava

2018-04-01

A coupled experimental and theoretical study is reported here on friction hydro-pillar processing of AISI 4140 steel, which is a novel solid-state joining technique to repair and fill crack holes in thick-walled components by an external stud. The stud is rotated and forced to fill a crack hole by plastic flow. During the process, frictional heating occurs along the interface of the stud and the wall of crack hole leading to thermal softening of the stud that eases its plastic deformation. The effect of the stud force, its rotational speed and the total processing time on the rate of heat generation and resulting transient temperature field is therefore examined to correlate the processing variables with the joint structure and properties in a systematic and quantitative manner, which is currently scarce in the published literature. The results show that a gentler stud force rate and greater processing time can promote proper filling of the crack hole and facilitate a defect-free joint between the stud and original component.

[Characteristics of electrophysiology and effects of ouabain on transient outward potassium current and L-type calcium current of left atrium posterior wall in rabbits].

PubMed

Wang, Teng; Huang, Cong-xin; Jiang, Hong; Tang, Qi-zhu; Yang, Bo; Li, Geng-shan

2009-12-01

To investigate the properties of electrophysiology and effects of ouabain upon transient outward potassium current (I(to)) and L-type calcium current (I(Ca-L)) of left atrium posterior wall (LAPW) and left atrium appendage tissue (LAA)in rabbit so as to provide the scientific explanations that LAPW and ouabain can enhance atrial fibrillation (AF) vulnerability through increasing electrophysiological heterogeneity and electrical remodeling of different regions of left atrium in rabbits. Atrial myocytes from LAPWs and LAAs of rabbits on an in vitro heart perfusion system were obtained by enzymatic dissociation. The whole-cell patch-clamp technique was used to assess the effects of ouabain upon I(to) and I(Ca-L). The current-voltage (I-V) curves of I(to) and I(Ca-L) in LAPW and LAA myocytes were fitted before and after ouabain administration. (1) With holding potential +50 mV and commanding potential +50 mV, the current densities of LAPW I(to) decreased slightly less than that of LAA I(to) in control groups (P > 0.05). After ouabain administration, the current densities of LAPW I(to) were significantly larger than that of LAA I(to) [(10.97 +/- 0.58) pA/pF vs (9.39 +/- 0.83) pA/pF, P < 0.05]. The I-V curve of LAPW I(to) was slightly lowered to I-V curve of LAA I(to) in control groups. But with perfusion of ouabain, the I-V curve of LAPW I(to) opposed to I-V curve of LAA I(to) significantly changed from the bottom to the top with the same upward direction. (2) With the voltage clamp protocol of I(Ca-L), the current densities of LAPW I(Ca-L) markedly decreased compared with that of LAA I(Ca-L) in control groups (P < 0.05). With the addition of ouabain, the peak of amplitude of LAPW I(Ca-L) at +20 mV obviously increased to that of LAA I(Ca-L) [(-11.13 +/- 0.99) pA/pF vs (-8.86 +/- 0.51) pA/pF, P < 0.01]. In the control groups, the I-V curve of LAPW I(Ca-L) was shifted to the bottom of all I-V curves of I(Ca-L). Through the effects of ouabain, the I-V curve of LAPW I(Ca-L) was completely upgraded to the top of other I-V curves of I(Ca-L). However, all shapes and directions of current peak of I-V curves of I(Ca-L) remained unchanged in both groups. The distribution properties of I(Ca-L) have significant difference in LAPW. Ouabain can accentuate the electrophysiological heterogeneity and electrical remodeling of I(to) and I(Ca-L) in LAPW of rabbits. It may become the triggering factor and persisting basis of AF vulnerability.

Water Hammer Simulations of MMH Propellant - New Capability Demonstration of the Generalized Fluid Flow Simulation Program

NASA Technical Reports Server (NTRS)

Burkhardt, Z.; Ramachandran, N.; Majumdar, A.

2017-01-01

Fluid Transient analysis is important for the design of spacecraft propulsion system to ensure structural stability of the system in the event of sudden closing or opening of the valve. Generalized Fluid System Simulation Program (GFSSP), a general purpose flow network code developed at NASA/MSFC is capable of simulating pressure surge due to sudden opening or closing of valve when thermodynamic properties of real fluid are available for the entire range of simulation. Specifically GFSSP needs an accurate representation of pressure-density relationship in order to predict pressure surge during a fluid transient. Unfortunately, the available thermodynamic property programs such as REFPROP, GASP or GASPAK does not provide the thermodynamic properties of Monomethylhydrazine (MMH). This paper will illustrate the process used for building a customized table of properties of state variables from available properties and speed of sound that is required by GFSSP for simulation. Good agreement was found between the simulations and measured data. This method can be adopted for modeling flow networks and systems with other fluids whose properties are not known in detail in order to obtain general technical insight. Rigorous code validation of this approach will be done and reported at a future date.

Advanced simulation study on bunch gap transient effect

NASA Astrophysics Data System (ADS)

Kobayashi, Tetsuya; Akai, Kazunori

2016-06-01

Bunch phase shift along the train due to a bunch gap transient is a concern in high-current colliders. In KEKB operation, the measured phase shift along the train agreed well with a simulation and a simple analytical form in most part of the train. However, a rapid phase change was observed at the leading part of the train, which was not predicted by the simulation or by the analytical form. In order to understand the cause of this observation, we have developed an advanced simulation, which treats the transient loading in each of the cavities of the three-cavity system of the accelerator resonantly coupled with energy storage (ARES) instead of the equivalent single cavities used in the previous simulation, operating in the accelerating mode. In this paper, we show that the new simulation reproduces the observation, and clarify that the rapid phase change at the leading part of the train is caused by a transient loading in the three-cavity system of ARES. KEKB is being upgraded to SuperKEKB, which is aiming at 40 times higher luminosity than KEKB. The gap transient in SuperKEKB is investigated using the new simulation, and the result shows that the rapid phase change at the leading part of the train is much larger due to higher beam currents. We will also present measures to mitigate possible luminosity reduction or beam performance deterioration due to the rapid phase change caused by the gap transient.

Perturbed atrial calcium handling in an ovine model of heart failure: Potential roles for reductions in the L-type calcium current

PubMed Central

Clarke, Jessica D.; Caldwell, Jessica L.; Horn, Margaux A.; Bode, Elizabeth F.; Richards, Mark A.; Hall, Mark C.S.; Graham, Helen K.; Briston, Sarah J.; Greensmith, David J.; Eisner, David A.; Dibb, Katharine M.; Trafford, Andrew W.

2015-01-01

Heart failure (HF) is commonly associated with reduced cardiac output and an increased risk of atrial arrhythmias particularly during β-adrenergic stimulation. The aim of the present study was to determine how HF alters systolic Ca2 + and the response to β-adrenergic (β-AR) stimulation in atrial myocytes. HF was induced in sheep by ventricular tachypacing and changes in intracellular Ca2 + concentration studied in single left atrial myocytes under voltage and current clamp conditions. The following were all reduced in HF atrial myocytes; Ca2 + transient amplitude (by 46% in current clamped and 28% in voltage clamped cells), SR dependent rate of Ca2 + removal (kSR, by 32%), L-type Ca2 + current density (by 36%) and action potential duration (APD90 by 22%). However, in HF SR Ca2 + content was increased (by 19%) when measured under voltage-clamp stimulation. Inhibiting the L-type Ca2 + current (ICa-L) in control cells reproduced both the decrease in Ca2 + transient amplitude and increase of SR Ca2 + content observed in voltage-clamped HF cells. During β-AR stimulation Ca2 + transient amplitude was the same in control and HF cells. However, ICa-L remained less in HF than control cells whilst SR Ca2 + content was highest in HF cells during β-AR stimulation. The decrease in ICa-L that occurs in HF atrial myocytes appears to underpin the decreased Ca2 + transient amplitude and increased SR Ca2 + content observed in voltage-clamped cells. PMID:25463272

VEGF attenuated increase of outward delayed-rectifier potassium currents in hippocampal neurons induced by focal ischemia via PI3-K pathway.

PubMed

Wu, K W; Yang, P; Li, S S; Liu, C W; Sun, F Y

2015-07-09

We recently indicated that the vascular endothelial growth factor (VEGF) protects neurons against hypoxic death via enhancement of tyrosine phosphorylation of Kv1.2, an isoform of the delayed-rectifier potassium channels through activation of the phosphatidylinositol 3-kinase (PI3-K) signaling pathway. The present study investigated whether VEGF could attenuate ischemia-induced increase of the potassium currents in the hippocampal pyramidal neurons of rats after ischemic injury. Adult male Sprague-Dawley rats were subjected to transient middle cerebral artery occlusion (MCAO) to induce brain ischemia. The whole-cell patch-clamp technique was used to record the potassium currents of hippocampal neurons in brain slices from the ischemically injured brains of the rats 24h after MCAO. We detected that transient MCAO caused a significant increase of voltage-gated potassium currents (Kv) and outward delayed-rectifier potassium currents (IK), but not outward transient potassium currents (IA), in the ipsilateral hippocampus compared with the sham. Moreover, we found that VEGF could acutely, reversibly and voltage-dependently inhibit the ischemia-induced IK increase. This inhibitory effect of VEGF could be completely abolished by wortmannin, an inhibitor of PI3-K. Our data indicate that VEGF attenuates the ischemia-induced increase of IK via activation of the PI3-K signaling pathway. Published by Elsevier Ltd.

Dynamic properties of ceramic materials

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

Grady, D.E.

1995-02-01

The present study offers new data and analysis on the transient shock strength and equation-of-state properties of ceramics. Various dynamic data on nine high strength ceramics are provided with wave profile measurements, through velocity interferometry techniques, the principal observable. Compressive failure in the shock wave front, with emphasis on brittle versus ductile mechanisms of deformation, is examined in some detail. Extensive spall strength data are provided and related to the theoretical spall strength, and to energy-based theories of the spall process. Failure waves, as a mechanism of deformation in the transient shock process, are examined. Strength and equation-of-state analysis ofmore » shock data on silicon carbide, boron carbide, tungsten carbide, silicon dioxide and aluminum nitride is presented with particular emphasis on phase transition properties for the latter two. Wave profile measurements on selected ceramics are investigated for evidence of rate sensitive elastic precursor decay in the shock front failure process.« less

Anticipatory control of xenon in a pressurized water reactor

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

Impink, A.J. Jr.

1987-02-10

A method is described for automatically dampening xenon-135 spatial transients in the core of a pressurized water reactor having control rods which regulate reactor power level, comprising the steps of: measuring the neutron flu in the reactor core at a plurality of axially spaced locations on a real-time, on-line basis; repetitively generating from the neutron flux measurements, on a point-by-point basis, signals representative of the current axial distribution of xenon-135, and signals representative of the current rate of change of the axial distribution of xenon-135; generating from the xenon-135 distribution signals and the rate of change of xenon distribution signals,more » control signals for reducing the xenon transients; and positioning the control rods as a function of the control signals to dampen the xenon-135 spatial transients.« less

Transient photocurrent in molecular junctions: singlet switching on and triplet blocking.

PubMed

Petrov, E G; Leonov, V O; Snitsarev, V

2013-05-14

The kinetic approach adapted to describe charge transmission in molecular junctions, is used for the analysis of the photocurrent under conditions of moderate light intensity of the photochromic molecule. In the framework of the HOMO-LUMO model for the single electron molecular states, the analytic expressions describing the temporary behavior of the transient and steady state sequential (hopping) as well as direct (tunnel) current components have been derived. The conditions at which the current components achieve their maximal values are indicated. It is shown that if the rates of charge transmission in the unbiased molecular diode are much lower than the intramolecular singlet-singlet excitation/de-excitation rate, and the threefold degenerated triplet excited state of the molecule behaves like a trap blocking the charge transmission, a possibility of a large peak-like transient switch-on photocurrent arises.

Transport dynamics of a high-power-density matrix-type hydrogen-oxygen fuel cell

NASA Technical Reports Server (NTRS)

Prokopius, P. R.; Hagedorn, N. H.

1974-01-01

Experimental transport dynamics tests were made on a space power fuel cell of current design. Various operating transients were introduced and transport-related response data were recorded with fluidic humidity sensing instruments. Also, sampled data techniques were developed for measuring the cathode-side electrolyte concentration during transient operation.

Voltage and Current Clamp Transients with Membrane Dielectric Loss

PubMed Central

Fitzhugh, R.; Cole, K. S.

1973-01-01

Transient responses of a space-clamped squid axon membrane to step changes of voltage or current are often approximated by exponential functions of time, corresponding to a series resistance and a membrane capacity of 1.0 μF/cm2. Curtis and Cole (1938, J. Gen. Physiol. 21:757) found, however, that the membrane had a constant phase angle impedance z = z1(jωτ)-α, with a mean α = 0.85. (α = 1.0 for an ideal capacitor; α < 1.0 may represent dielectric loss.) This result is supported by more recently published experimental data. For comparison with experiments, we have computed functions expressing voltage and current transients with constant phase angle capacitance, a parallel leakage conductance, and a series resistance, at nine values of α from 0.5 to 1.0. A series in powers of tα provided a good approximation for short times; one in powers of t-α, for long times; for intermediate times, a rational approximation matching both series for a finite number of terms was used. These computations may help in determining experimental series resistances and parallel leakage conductances from membrane voltage or current clamp data. PMID:4754194

Profiling of Current Transients in Capacitor Type Diamond Sensors.

PubMed

Gaubas, Eugenijus; Ceponis, Tomas; Meskauskaite, Dovile; Kazuchits, Nikolai

2015-06-08

The operational characteristics of capacitor-type detectors based on HPHT and CVD diamond have been investigated using perpendicular and parallel injection of carrier domain regimes. Simulations of the drift-diffusion current transients have been implemented by using dynamic models based on Shockley-Ramo's theorem, under injection of localized surface domains and of bulk charge carriers. The bipolar drift-diffusion regimes have been analyzed for the photo-induced bulk domain (packet) of excess carriers. The surface charge formation and polarization effects dependent on detector biasing voltage have been revealed. The screening effects ascribed to surface charge and to dynamics of extraction of the injected bulk excess carrier domain have been separated and explained. The parameters of drift mobility of the electrons μ(e) = 4000 cm2/Vs and holes μ(h) = 3800 cm2/Vs have been evaluated for CVD diamond using the perpendicular profiling of currents. The coefficient of carrier ambipolar diffusion D(a) = 97 cm2/s and the carrier recombination lifetime τ(R,CVD) ≌ 110 ns in CVD diamond were extracted by combining analysis of the transients of the sensor current and the microwave probed photoconductivity. The carrier trapping with inherent lifetime τR,HPHT ≌ 2 ns prevails in HPHT diamond.

The structure and mechanical properties of articular cartilage are highly resilient towards transient dehydration.

PubMed

Boettcher, K; Kienle, S; Nachtsheim, J; Burgkart, R; Hugel, T; Lieleg, O

2016-01-01

Articular cartilage is a mechanically highly challenged material with very limited regenerative ability. In contrast to elastic cartilage, articular cartilage is exposed to recurring partial dehydration owing to ongoing compression but maintains its functionality over decades. To extend our current understanding of the material properties of articular cartilage, specifically the interaction between the fluid and solid phase, we here analyze the reversibility of tissue dehydration. We perform an artificial dehydration that extends beyond naturally occurring levels and quantify material recovery as a function of the ionic strength of the rehydration buffer. Mechanical (indentation, compression, shear, and friction) measurements are used to evaluate the influence of de- and rehydration on the viscoelastic properties of cartilage. The structure and composition of native and de/rehydrated cartilage are analyzed using histology, scanning electron microscopy, and atomic force microscopy along with a 1,9-dimethylmethylene blue (DMMB) assay. A broad range of mechanical and structural properties of cartilage can be restored after de- and rehydration provided that a physiological salt solution is used for rehydration. We detect only minor alterations in the microarchitecture of rehydrated cartilage in the superficial zone and find that these alterations do not interfere with the viscoelastic and tribological properties of the tissue. We here demonstrate the sturdiness of articular cartilage towards changes in fluid content and show that articular cartilage recovers a broad range of its material properties after dehydration. We analyze the reversibility of tissue dehydration to extend our current understanding of how the material properties of cartilage are established, focusing on the interaction between the fluid and solid phase. Our findings suggest that the high resilience of the tissue minimizes the risk of irreversible material failure and thus compensates, at least in part, its poor regenerative abilities. Tissue engineering approaches should thus not only reproduce the correct tissue mechanics but also its pronounced sturdiness to guarantee a similar longevity. Copyright © 2015 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

High temperature experimental characterization of microscale thermoelectric effects

NASA Astrophysics Data System (ADS)

Favaloro, Tela

Thermoelectric devices have been employed for many years as a reliable energy conversion technology for applications ranging from the cooling of sensors or charge coupled devices to the direct conversion of heat into electricity for remote power generation. However, its relatively low conversion efficiency has limited the implementation of thermoelectric materials for large scale cooling and waste heat recovery applications. Recent advances in semiconductor growth technology have enabled the precise and selective engineering of material properties to improve the thermoelectric figure of merit and thus the efficiency of thermoelectric devices. Accurate characterization at the intended operational temperature of novel thermoelectric materials is a crucial component of the optimization process in order to fundamentally understand material behavior and evaluate performance. The objective of this work is to provide the tools necessary to characterize high efficiency bulk and thin-film materials for thermoelectric energy conversion. The techniques developed here are not bound to specific material or devices, but can be generalized to any material system. Thermoreflectance imaging microscopy has proven to be invaluable for device thermometry owing to its high spatial and temporal resolutions. It has been utilized in this work to create two-dimensional temperature profiles of thermoelectric devices during operation used for performance analysis of novel materials, identification of defects, and visualization of high speed transients in a high-temperature imaging thermostat. We report the development of a high temperature imaging thermostat capable of high speed transient thermoelectric characterization. In addition, we present a noninvasive method for thermoreflectance coefficient calibration ideally suited for vacuum and thus high temperature employment. This is the first analysis of the thermoreflectance coefficient of commonly used metals at high-temperatures. High temperature vacuum thermostats are designed and fabricated with optical imaging capability and interchangeable measurement stages for various electrical and thermoelectric characterizations. We demonstrate the simultaneous measurement of in-plane electrical conductivity and Seebeck coefficient of thin-film or bulk thermoelectric materials. Furthermore, we utilize high-speed circuitry to implement the transient Harman technique and directly determine the cross-plane figure of merit of thin film thermoelectric materials at high temperatures. Transient measurements on thin film devices are subject to complications from the growth substrate, non-ideal contacts and other detrimental thermal and electrical effects. A strategy is presented for optimizing device geometry to mitigate the impact of these parasitics. This design enabled us to determine the cross-plane thermoelectric material properties in a single high temperature measurement of a 25mum InGaAs thin film with embedded ErAs (0.2%) nanoparticles using the bipolar transient Harman technique in conjunction with thermoreflectance thermal imaging. This approach eliminates discrepancies and potential device degradation from the multiple measurements necessary to obtain individual material parameters. Finite element method simulations are used to analyze non-uniform current and temperature distributions over the device area and determine the three dimensional current path for accurate extraction of material properties from the thermal images. Results match with independent measurements of thermoelectric material properties for the same material composition, validating this approach. We apply high magnification thermoreflectance imaging to create temperature maps of vanadium dioxide nanobeams and examine electro-thermal energy conversion along the nanobeam length. The metal to insulator transition of strongly correlated materials is subject to strong lattice coupling which brings about the unique one-dimensional alignment of metal-insulator domains along nanobeams. Many studies have investigated the effects of stress on the metal to insulator transition and hence the phase boundary, but few have directly examined the temperature profile across the metal-insulating interface. Here, thermoreflectance microscopy reveals the underlying behavior of single-crystalline VO2 nanobeams in the phase coexisting regime. We directly observe highly localized alternating Peltier heating and cooling as well as Joule heating concentrated at the domain interfaces, indicating the significance of the domain walls and band offsets. Moreover, we are able to elucidate strain accumulation along the nanobeam and distinguish between two insulating phases of VO 2 through detection of the opposite polarity of their respective thermoreflectance coefficients.

Very long transients, irregular firing, and chaotic dynamics in networks of randomly connected inhibitory integrate-and-fire neurons.

PubMed

Zillmer, Rüdiger; Brunel, Nicolas; Hansel, David

2009-03-01

We present results of an extensive numerical study of the dynamics of networks of integrate-and-fire neurons connected randomly through inhibitory interactions. We first consider delayed interactions with infinitely fast rise and decay. Depending on the parameters, the network displays transients which are short or exponentially long in the network size. At the end of these transients, the dynamics settle on a periodic attractor. If the number of connections per neuron is large ( approximately 1000) , this attractor is a cluster state with a short period. In contrast, if the number of connections per neuron is small ( approximately 100) , the attractor has complex dynamics and very long period. During the long transients the neurons fire in a highly irregular manner. They can be viewed as quasistationary states in which, depending on the coupling strength, the pattern of activity is asynchronous or displays population oscillations. In the first case, the average firing rates and the variability of the single-neuron activity are well described by a mean-field theory valid in the thermodynamic limit. Bifurcations of the long transient dynamics from asynchronous to synchronous activity are also well predicted by this theory. The transient dynamics display features reminiscent of stable chaos. In particular, despite being linearly stable, the trajectories of the transient dynamics are destabilized by finite perturbations as small as O(1/N) . We further show that stable chaos is also observed for postsynaptic currents with finite decay time. However, we report in this type of network that chaotic dynamics characterized by positive Lyapunov exponents can also be observed. We show in fact that chaos occurs when the decay time of the synaptic currents is long compared to the synaptic delay, provided that the network is sufficiently large.

Characteristics of action potentials and their underlying outward currents in rat taste receptor cells.

PubMed

Chen, Y; Sun, X D; Herness, S

1996-02-01

1. Taste receptor cells produce action potentials as a result of transduction mechanisms that occur when these cells are stimulated with tastants. These action potentials are thought to be key signaling events in relaying information to the central nervous system. We explored the ionic basis of action potentials from dissociated posterior rat taste cells using the patch-clamp recording technique in both voltage-clamp and current-clamp modes. 2. Action potentials were evoked by intracellular injection of depolarizing current pulses from a holding potential of -80 mV. The threshold potential for firing of action potentials was approximately -35 mV; the input resistance of these cells averaged 6.9 G omega. With long depolarizing pulses, two or three action potentials could be elicited with successive attenuation of the spike height. Afterhyperpolarizations were observed often. 3. Both sodium and calcium currents contribute to depolarizing phases of the action potential. Action potentials were blocked completely in the presence of the sodium channel blocker tetrodotoxin. Calcium contributions could be visualized as prolonged calcium plateaus when repolarizing potassium currents were blocked and barium was used as a charge carrier. 4. Outward currents were composed of sustained delayed rectifier current, transient potassium current, and calcium-activated potassium current. Transient and sustained potassium currents activated close to -30 mV and increased monotonically with further depolarization. Up to half the outward current inactivated with decay constants on the order of seconds. Sustained and transient currents displayed steep voltage dependence in conductance and inactivation curves. Half inactivation occurred at -20 +/- 3.1 mV (mean +/- SE) with a decrease of 11.2 +/- 0.5 mV per e-fold. Half maximal conductance occurred at 3.6 +/- 1.8 mV and increased 12.2 +/- 0.6 mV per e-fold. Calcium-activated potassium current was evidenced by application of apamin and the use of calcium-free bathing solution. It was most obvious at more depolarized holding potentials that inactivated much of the transient and sustained outward currents. 5. Potassium currents contribute to both the repolarization and afterhyperpolarization phases of the action potential. These currents were blocked by bath application of tetraethylammonium, which also substantially broadened the action potential. Application of 4-aminopyridine was able to selectively block transient potassium currents without affecting sustained currents. This also broadened the action potential as well as eliminated the afterhyperpolarization. 6. A second type of action potential was observed that differed in duration. These slow action potentials had t1/2 durations of 9.6 ms compared with 1.4 ms for fast action potentials. Input resistances of the two groups were indistinguishable. Approximately one-fourth of the cells eliciting action potentials were of the slow type. 7. Cells eliciting fast action potentials had large outward currents capable of producing a quick repolarization, whereas cells with slow action potentials had small outward currents by comparison. The average values of fast cells were 2,563 pA and 1.4 ms compared with 373 pA and 9.6 ms for slow cells. Current and duration values were related exponentially. No significant difference was noted for inward currents. 8. These results suggest that many taste receptor cells conduct action potentials, which may be classified broadly into two groups on the basis of action potential duration and potassium current magnitude. These groups may be related to cell turnover. The physiological role of action potentials remains to be elucidated but may be important for communication within the taste bud as well as to the afferent nerve.

Efficient Charge Collection in Coplanar-Grid Radiation Detectors

NASA Astrophysics Data System (ADS)

Kunc, J.; Praus, P.; Belas, E.; Dědič, V.; Pekárek, J.; Grill, R.

2018-05-01

We model laser-induced transient-current waveforms in radiation coplanar-grid detectors. Poisson's equation is solved by the finite-element method and currents induced by a photogenerated charge are obtained using the Shockley-Ramo theorem. The spectral response on a radiation flux is modeled by Monte Carlo simulations. We show a 10 × improved spectral resolution of the coplanar-grid detector using differential signal sensing. We model the current waveform dependence on the doping, depletion width, diffusion, and detector shielding, and their mutual dependence is discussed in terms of detector optimization. The numerical simulations are successfully compared to experimental data, and further model simplifications are proposed. The space charge below electrodes and a nonhomogeneous electric field on a coplanar-grid anode are found to be the dominant contributions to laser-induced transient-current waveforms.

Transient Properties of Probability Distribution for a Markov Process with Size-dependent Additive Noise

NASA Astrophysics Data System (ADS)

Yamada, Yuhei; Yamazaki, Yoshihiro

2018-04-01

This study considered a stochastic model for cluster growth in a Markov process with a cluster size dependent additive noise. According to this model, the probability distribution of the cluster size transiently becomes an exponential or a log-normal distribution depending on the initial condition of the growth. In this letter, a master equation is obtained for this model, and derivation of the distributions is discussed.

Various DC-driven point-to-plain discharges as non-thermal plasma sources and their bactericidal effects

NASA Astrophysics Data System (ADS)

Khun, Josef; Scholtz, Vladimír; Hozák, Pavel; Fitl, Přemysl; Julák, Jaroslav

2018-06-01

The appearance of several types of ballast serial impedance-stabilized DC-driven electric corona discharges in the point-to-plane configuration is described. In addition to well-known corona discharges, new ones were observed, namely curved transient spark, interrupted channel and branched transient spark. Their properties are described by volt-ampere characteristics and UV-vis emission spectra. Their bactericidal ability for two bacterial species is also given.

FeOx-TiO2 Film with Different Microstructures Leading to Femtosecond Transients with Different Properties: Biological Implications under Visible Light

PubMed Central

Rtimi, Sami; Pulgarin, Cesar; Nadtochenko, Victor A.; Gostev, Fedor E.; Shelaev, Ivan V.; Kiwi, John

2016-01-01

This study presents the first report addressing the effect of FeOx-TiO2 films microstructure on the transients detected by fast spectroscopy related to the long-range bacterial inactivation performance. The different fast kinetic femtosecond transient spectroscopy is reported for each FeOx+TiO2 microstructure. The lifetime of the short transient-species and the oxidative intermediate radicals generated under light were identified. Co-sputtered FeOx-TiO2 on polyethylene films presenting random distribution for both oxides were compared with sequentially sputtered FeOx/TiO2 films made up only by FeOx in the topmost layers. The ratio FeOx:TiO2 was optimized to attain the highest photo-conversion. By X-ray fluorescence, the Fe:Ti ration was found to be ~1.4 in the film bulk and by XPS-etching a ratio of 4:1 was found on the photocatalyst top-most layers. For co-sputtered FeOx-TiO2-PE films, the FeOx-TiO2 heterojunction led to electron injection from the FeOx to lower-lying TiO2 trapping states. The film optical properties, particle size, roughness, hydrophobic-hydrophilic shift and temporal evolution of the transient redox states were characterized in detail. Films with different microstructure led to different antibacterial activity. This suggests that the FeOx-TiO2-PE microstructure and not the position of the potential energy level of the semiconductors FeOx and TiO2 control the charge transfer under light irradiation. PMID:27443505

FeOx-TiO2 Film with Different Microstructures Leading to Femtosecond Transients with Different Properties: Biological Implications under Visible Light.

PubMed

Rtimi, Sami; Pulgarin, Cesar; Nadtochenko, Victor A; Gostev, Fedor E; Shelaev, Ivan V; Kiwi, John

2016-07-22

This study presents the first report addressing the effect of FeOx-TiO2 films microstructure on the transients detected by fast spectroscopy related to the long-range bacterial inactivation performance. The different fast kinetic femtosecond transient spectroscopy is reported for each FeOx+TiO2 microstructure. The lifetime of the short transient-species and the oxidative intermediate radicals generated under light were identified. Co-sputtered FeOx-TiO2 on polyethylene films presenting random distribution for both oxides were compared with sequentially sputtered FeOx/TiO2 films made up only by FeOx in the topmost layers. The ratio FeOx:TiO2 was optimized to attain the highest photo-conversion. By X-ray fluorescence, the Fe:Ti ration was found to be ~1.4 in the film bulk and by XPS-etching a ratio of 4:1 was found on the photocatalyst top-most layers. For co-sputtered FeOx-TiO2-PE films, the FeOx-TiO2 heterojunction led to electron injection from the FeOx to lower-lying TiO2 trapping states. The film optical properties, particle size, roughness, hydrophobic-hydrophilic shift and temporal evolution of the transient redox states were characterized in detail. Films with different microstructure led to different antibacterial activity. This suggests that the FeOx-TiO2-PE microstructure and not the position of the potential energy level of the semiconductors FeOx and TiO2 control the charge transfer under light irradiation.

FeOx-TiO2 Film with Different Microstructures Leading to Femtosecond Transients with Different Properties: Biological Implications under Visible Light

NASA Astrophysics Data System (ADS)

Rtimi, Sami; Pulgarin, Cesar; Nadtochenko, Victor A.; Gostev, Fedor E.; Shelaev, Ivan V.; Kiwi, John

2016-07-01

This study presents the first report addressing the effect of FeOx-TiO2 films microstructure on the transients detected by fast spectroscopy related to the long-range bacterial inactivation performance. The different fast kinetic femtosecond transient spectroscopy is reported for each FeOx+TiO2 microstructure. The lifetime of the short transient-species and the oxidative intermediate radicals generated under light were identified. Co-sputtered FeOx-TiO2 on polyethylene films presenting random distribution for both oxides were compared with sequentially sputtered FeOx/TiO2 films made up only by FeOx in the topmost layers. The ratio FeOx:TiO2 was optimized to attain the highest photo-conversion. By X-ray fluorescence, the Fe:Ti ration was found to be ~1.4 in the film bulk and by XPS-etching a ratio of 4:1 was found on the photocatalyst top-most layers. For co-sputtered FeOx-TiO2-PE films, the FeOx-TiO2 heterojunction led to electron injection from the FeOx to lower-lying TiO2 trapping states. The film optical properties, particle size, roughness, hydrophobic-hydrophilic shift and temporal evolution of the transient redox states were characterized in detail. Films with different microstructure led to different antibacterial activity. This suggests that the FeOx-TiO2-PE microstructure and not the position of the potential energy level of the semiconductors FeOx and TiO2 control the charge transfer under light irradiation.

Magnetic dipole discharges. II. Cathode and anode spot discharges and probe diagnostics

NASA Astrophysics Data System (ADS)

Stenzel, R. L.; Urrutia, J. M.; Ionita, C.; Schrittwieser, R.

2013-08-01

The high current regime of a magnetron-type discharge has been investigated. The discharge uses a permanent magnet as a cold cathode which emits secondary electrons while the chamber wall or a grounded electrode serves as the anode. As the discharge voltage is increased, the magnet develops cathode spots, which are short duration arcs that provide copious electrons to increase the discharge current dramatically. Short (1 μs), high current (200 A) and high voltage (750 V) discharge pulses are produced in a relaxation instability between the plasma and a charging capacitor. Spots are also observed on a negatively biased plane Langmuir probe. The probe current pulses are as large as those on the magnet, implying that the high discharge current does not depend on the cathode surface area but on the properties of the spots. The fast current pulses produce large inductive voltages, which can reverse the electrical polarity of the magnet and temporarily operate it as an anode. The discharge current may also oscillate at the frequency determined by the charging capacitor and the discharge circuit inductance. Each half cycle of high-current current pulses exhibits a fast (≃10 ns) current rise when a spot is formed. It induces high frequency (10-100 MHz) transients and ringing oscillations in probes and current circuits. Most probes behave like unmatched antennas for the electromagnetic pulses of spot discharges. Examples are shown to distinguish the source of oscillations and some rf characteristics of Langmuir probes.

Kv4 channels underlie A-currents with highly variable inactivation time courses but homogeneous other gating properties in the nucleus tractus solitarii.

PubMed

Strube, Caroline; Saliba, Layal; Moubarak, Estelle; Penalba, Virginie; Martin-Eauclaire, Marie-France; Tell, Fabien; Clerc, Nadine

2015-04-01

In the nucleus of the tractus solitarii (NTS), a large proportion of neurones express transient A-type potassium currents (I KA) having deep influence on the fidelity of the synaptic transmission of the visceral primary afferent inputs to second-order neurones. Up to now, the strong impact of I KA within the NTS was considered to result exclusively from its variation in amplitude, and its molecular correlate(s) remained unknown. In order to identify which Kv channels underlie I KA in NTS neurones, the gating properties and the pharmacology of this current were determined using whole cell patch clamp recordings in slices. Complementary information was brought by immunohistochemistry. Strikingly, two neurone subpopulations characterized by fast or slow inactivation time courses (respectively about 50 and 200 ms) were discriminated. Both characteristics matched those of the Kv4 channel subfamily. The other gating properties, also matching the Kv4 channel ones, were homogeneous through the NTS. The activation and inactivation occurred at membrane potentials around the threshold for generating action potentials, and the time course of recovery from inactivation was rapid. Pharmacologically, I KA in NTS neurones was found to be resistant to tetraethylammonium (TEA), sea anemone toxin blood-depressing substance (BDS) and dendrotoxin (DTX), whereas Androctonus mauretanicus mauretanicus toxin 3 (AmmTX3), a scorpion toxin of the α-KTX 15 family that has been shown to block all the members of the Kv4 family, inhibited 80 % of I KA irrespectively of its inactivation time course. Finally, immunohistochemistry data suggested that, among the Kv4 channel subfamily, Kv4.3 is the prevalent subunit expressed in the NTS.

Neutronics and Transient Calculations for the Conversion of the Transient Reactor Rest Facility (TREAT)

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

Kontogeorgakos, Dimitrios C.; Connaway, Heather M.; Papadias, Dionissios D.

2015-01-01

The Transient Reactor Test Facility (TREAT) is a graphite-reflected, graphitemoderated, and air-cooled reactor fueled with 93.1% enriched UO2 particles dispersed in graphite, with a carbon-to-235U ratio of ~10000:1. TREAT was used to simulate accident conditions by subjecting fuel test samples placed at the center of the core to high energy transient pulses. The transient pulse production is based on the core’s selflimiting nature due to the negative reactivity feedback provided by the fuel graphite as the core temperature rises. The analysis of the conversion of TREAT to low enriched uranium (LEU) is currently underway. This paper presents the analytical methodsmore » used to calculate the transient performance of TREAT in terms of power pulse production and resulting peak core temperatures. The validation of the HEU neutronics TREAT model, the calculation of the temperature distribution and the temperature reactivity feedback as well as the number of fissions generated inside fuel test samples are discussed.« less

Fast transient currents in Na,K-ATPase induced by ATP concentration jumps from the P3-[1-(3',5'-dimethoxyphenyl)-2-phenyl-2-oxo]ethyl ester of ATP.

PubMed Central

Sokolov, V S; Apell, H J; Corrie, J E; Trentham, D R

1998-01-01

Electrogenic ion transport by Na,K-ATPase was investigated by analysis of transient currents in a model system of protein-containing membrane fragments adsorbed to planar lipid bilayers. Sodium transport was triggered by ATP concentration jumps in which ATP was released from an inactive precursor by an intense near-UV light flash. The method has been used previously with the P3-1-(2-nitrophenyl)ethyl ester of ATP (NPE-caged ATP), from which the relatively slow rate of ATP release limits analysis of processes in the pump mechanism controlled by rate constants greater than 100 s(-1) at physiological pH. Here Na,K-ATPase was reinvestigated using the P3-[1-(3,5-dimethoxyphenyl)-2-phenyl-2-oxo]ethyl ester of ATP (DMB-caged ATP), which has an ATP release rate of >10(5) s(-1). Under otherwise identical conditions, photorelease of ATP from DMB-caged ATP showed faster kinetics of the transient current compared to that from NPE-caged ATP. With DMB-caged ATP, transient currents had rate profiles that were relatively insensitive to pH and the concentration of caged compound. Rate constants of ATP binding and of the E1 to E2 conformational change were compatible with earlier studies. Rate constants of enzyme phosphorylation and ADP-dependent dephosphorylation were 600 s(-1) and 1.5 x 10(6) M(-1) s(-1), respectively, at pH 7.2 and 22 degrees C. PMID:9591656

Examining within- and across-day relationships between transient and chronic stress and parent food-related parenting practices in a racially/ethnically diverse and immigrant population : Stress types and food-related parenting practices.

PubMed

Berge, Jerica M; Tate, Allan; Trofholz, Amanda; Fertig, Angela; Crow, Scott; Neumark-Sztainer, Dianne; Miner, Michael

2018-01-16

Although prior research suggests that stress may play a role in parent's use of food-related parenting practices, it is unclear whether certain types of stress (e.g., transient, chronic) result in different food-related parenting practices. Identifying whether and how transient (i.e., momentary; parent/child conflict) and chronic (i.e., long-term; unemployment >6 months) sources of stress are related to parent food-related parenting practices is important with regard to childhood obesity. This is particularly important within racially/ethnically diverse parents who may be more likely to experience both types of stress and who have higher levels of obesity and related health problems. The current study examined the association between transient and chronic stressors and food-related parenting practices in a racially/ethnically diverse and immigrant sample. The current study is a cross-sectional, mixed-methods study using ecological momentary assessment (EMA). Parents (mean age = 35; 95% mothers) of children ages 5-7 years old (n = 61) from six racial/ethnic groups (African American, American Indian, Hispanic, Hmong, Somali, White) participated in this ten-day in-home observation with families. Transient stressors, specifically interpersonal conflicts, had significant within-day effects on engaging in more unhealthful food-related parenting practices the same evening with across-day effects weakening by day three. In contrast, financial transient stressors had stronger across-day effects. Chronic stressors, including stressful life events were not consistently associated with more unhealthful food-related parenting practices. Transient sources of stress were significantly associated with food-related parenting practices in racially/ethnically diverse and immigrant households. Chronic stressors were not consistently associated with food-related parenting practices. Future research and interventions may want to assess for transient sources of stress in parents and target these momentary factors in order to promote healthful food-related parenting practices.

Recent Advances in Laplace Transform Analytic Element Method (LT-AEM) Theory and Application to Transient Groundwater Flow

NASA Astrophysics Data System (ADS)

Kuhlman, K. L.; Neuman, S. P.

2006-12-01

Furman and Neuman (2003) proposed a Laplace Transform Analytic Element Method (LT-AEM) for transient groundwater flow. LT-AEM applies the traditionally steady-state AEM to the Laplace transformed groundwater flow equation, and back-transforms the resulting solution to the time domain using a Fourier Series numerical inverse Laplace transform method (de Hoog, et.al., 1982). We have extended the method so it can compute hydraulic head and flow velocity distributions due to any two-dimensional combination and arrangement of point, line, circular and elliptical area sinks and sources, nested circular or elliptical regions having different hydraulic properties, and areas of specified head, flux or initial condition. The strengths of all sinks and sources, and the specified head and flux values, can all vary in both space and time in an independent and arbitrary fashion. Initial conditions may vary from one area element to another. A solution is obtained by matching heads and normal fluxes along the boundary of each element. The effect which each element has on the total flow is expressed in terms of generalized Fourier series which converge rapidly (<20 terms) in most cases. As there are more matching points than unknown Fourier terms, the matching is accomplished in Laplace space using least-squares. The method is illustrated by calculating the resulting transient head and flow velocities due to an arrangement of elements in both finite and infinite domains. The 2D LT-AEM elements already developed and implemented are currently being extended to solve the 3D groundwater flow equation.

Amphetamine Paradoxically Augments Exocytotic Dopamine Release and Phasic Dopamine Signals

PubMed Central

Daberkow, DP; Brown, HD; Bunner, KD; Kraniotis, SA; Doellman, MA; Ragozzino, ME; Garris, PA; Roitman, MF

2013-01-01

Drugs of abuse hijack brain reward circuitry during the addiction process by augmenting action potential-dependent phasic dopamine release events associated with learning and goal-directed behavior. One prominent exception to this notion would appear to be amphetamine (AMPH) and related analogs, which are proposed instead to disrupt normal patterns of dopamine neurotransmission by depleting vesicular stores and promoting non-exocytotic dopamine efflux via reverse transport. This mechanism of AMPH action, though, is inconsistent with its therapeutic effects and addictive properties - which are thought to be reliant on phasic dopamine signaling. Here we used fast-scan cyclic voltammetry in freely moving rats to interrogate principal neurochemical responses to AMPH in the striatum and relate these changes to behavior. First, we showed that AMPH dose-dependently enhanced evoked dopamine responses to phasic-like current pulse trains for up to two hours. Modeling the data revealed that AMPH inhibited dopamine uptake but also unexpectedly potentiated vesicular dopamine release. Second, we found that AMPH increased the amplitude, duration and frequency of spontaneous dopamine transients, the naturally occurring, non-electrically evoked, phasic increases in extracellular dopamine. Finally, using an operant sucrose reward paradigm, we showed that low-dose AMPH augmented dopamine transients elicited by sucrose-predictive cues. However, operant behavior failed at high-dose AMPH, which was due to phasic dopamine hyperactivity and the decoupling of dopamine transients from the reward predictive cue. These findings identify up-regulation of exocytotic dopamine release as a key AMPH action in behaving animals and support a unified mechanism of abused drugs to activate phasic dopamine signaling. PMID:23303926

Pore helix domain is critical to camphor sensitivity of transient receptor potential vanilloid 1 channel.

PubMed

Marsakova, Lenka; Touska, Filip; Krusek, Jan; Vlachova, Viktorie

2012-04-01

The recent discovery that camphor activates and strongly desensitizes the capsaicin-sensitive and noxious heat-sensitive channel transient receptor potential vanilloid subfamily member 1 (TRPV1) has provided new insights and opened up new research paths toward understanding why this naturally occurring monoterpene is widely used in human medicine for its local counter-irritant, antipruritic, and anesthetic properties. However, the molecular basis for camphor sensitivity remains mostly unknown. The authors attempt to explore the nature of the activation pathways evoked by camphor and narrow down a putative interaction site at TRPV1. The authors transiently expressed wild-type or specifically mutated recombinant TRPV1 channels in human embryonic kidney cells HEK293T and recorded cation currents with the whole cell, patch clamp technique. To monitor changes in the spatial distribution of phosphatidylinositol 4,5-bisphosphate, they used fluorescence resonance energy transfer measurements from cells transfected with the fluorescent protein-tagged pleckstrin homology domains of phospholipase C. The results revealed that camphor modulates TRPV1 channel through the outer pore helix domain by affecting its overall gating equilibrium. In addition, camphor, which generally is known to decrease the fluidity of cell plasma membranes, may also regulate the activity of TRPV1 by inducing changes in the spatial distribution of phosphatidylinositol-4,5-bisphosphate on the inner leaflet of the plasma membrane. The findings of this study provide novel insights into the structural basis for the modulation of TRPV1 channel by camphor and may provide an explanation for the mechanism by which camphor modulates thermal sensation in vivo.

Repeated Transient Jets from a Warped Disk in the Symbiotic Prototype Z And: A Link to the Long-lasting Active Phase

NASA Astrophysics Data System (ADS)

Skopal, Augustin; Tarasova, Taya. N.; Wolf, Marek; Dubovský, Pavol A.; Kudzej, Igor

2018-05-01

Active phases of some symbiotic binaries survive for a long time, from years to decades. The accretion process onto a white dwarf (WD) sustaining long-lasting activity, and sometimes leading to collimated ejection, is not well understood. We present the repeated emergence of highly collimated outflows (jets) from the symbiotic prototype Z And during its 2008 and 2009–10 outbursts and suggest their link to the current long-lasting (from 2000) active phase. We monitored Z And with high-resolution spectroscopy, multicolor UBVR C—and high time resolution—photometry. The well-pronounced bipolar jets were ejected again during the 2009–10 outburst together with the simultaneous emergence of the rapid photometric variability (Δm ≈ 0.06 mag) on the timescale of hours, showing similar properties as those during the 2006 outburst. These phenomena and the measured disk–jets connection could be caused by the radiation-induced warping of the inner disk due to a significant increase of the burning WD luminosity. Ejection of transient jets by Z And around outburst maxima signals a transient accretion at rates above the upper limit of the stable hydrogen burning on the WD surface, and thus proves the nature of Z And-type outbursts. The enhanced accretion through the disk warping, supplemented by the accretion from the giant’s wind, can keep a high luminosity of the WD for a long time, until depletion of the disk. In this way, the jets provide a link to long-lasting active phases of Z And.

Coronal mass ejections and their sheath regions in interplanetary space

NASA Astrophysics Data System (ADS)

Kilpua, Emilia; Koskinen, Hannu E. J.; Pulkkinen, Tuija I.

2017-11-01

Interplanetary coronal mass ejections (ICMEs) are large-scale heliospheric transients that originate from the Sun. When an ICME is sufficiently faster than the preceding solar wind, a shock wave develops ahead of the ICME. The turbulent region between the shock and the ICME is called the sheath region. ICMEs and their sheaths and shocks are all interesting structures from the fundamental plasma physics viewpoint. They are also key drivers of space weather disturbances in the heliosphere and planetary environments. ICME-driven shock waves can accelerate charged particles to high energies. Sheaths and ICMEs drive practically all intense geospace storms at the Earth, and they can also affect dramatically the planetary radiation environments and atmospheres. This review focuses on the current understanding of observational signatures and properties of ICMEs and the associated sheath regions based on five decades of studies. In addition, we discuss modelling of ICMEs and many fundamental outstanding questions on their origin, evolution and effects, largely due to the limitations of single spacecraft observations of these macro-scale structures. We also present current understanding of space weather consequences of these large-scale solar wind structures, including effects at the other Solar System planets and exoplanets. We specially emphasize the different origin, properties and consequences of the sheaths and ICMEs.

Photoperiod Modulates Fast Delayed Rectifier Potassium Currents in the Mammalian Circadian Clock.

PubMed

Farajnia, Sahar; Meijer, Johanna H; Michel, Stephan

2016-10-01

One feature of the mammalian circadian clock, situated in the suprachiasmatic nucleus (SCN), is its ability to measure day length and thereby contribute to the seasonal adaptation of physiology and behavior. The timing signal from the SCN, namely the 24 hr pattern of electrical activity, is adjusted according to the photoperiod being broader in long days and narrower in short days. Vasoactive intestinal peptide and gamma-aminobutyric acid play a crucial role in intercellular communication within the SCN and contribute to the seasonal changes in phase distribution. However, little is known about the underlying ionic mechanisms of synchronization. The present study was aimed to identify cellular mechanisms involved in seasonal encoding by the SCN. Mice were adapted to long-day (light-dark 16:8) and short-day (light-dark 8:16) photoperiods and membrane properties as well as K + currents activity of SCN neurons were measured using patch-clamp recordings in acute slices. Remarkably, we found evidence for a photoperiodic effect on the fast delayed rectifier K + current, that is, the circadian modulation of this ion channel's activation reversed in long days resulting in 50% higher peak values during the night compared with the unaltered day values. Consistent with fast delayed rectifier enhancement, duration of action potentials during the night was shortened and afterhyperpolarization potentials increased in amplitude and duration. The slow delayed rectifier, transient K + currents, and membrane excitability were not affected by photoperiod. We conclude that photoperiod can change intrinsic ion channel properties of the SCN neurons, which may influence cellular communication and contribute to photoperiodic phase adjustment. © The Author(s) 2016.

Stability of infinite slopes under transient partially saturated seepage conditions

NASA Astrophysics Data System (ADS)

Godt, Jonathan W.; ŞEner-Kaya, BaşAk; Lu, Ning; Baum, Rex L.

2012-05-01

Prediction of the location and timing of rainfall-induced shallow landslides is desired by organizations responsible for hazard management and warnings. However, hydrologic and mechanical processes in the vadose zone complicate such predictions. Infiltrating rainfall must typically pass through an unsaturated layer before reaching the irregular and usually discontinuous shallow water table. This process is dynamic and a function of precipitation intensity and duration, the initial moisture conditions and hydrologic properties of the hillside materials, and the geometry, stratigraphy, and vegetation of the hillslope. As a result, pore water pressures, volumetric water content, effective stress, and thus the propensity for landsliding vary over seasonal and shorter time scales. We apply a general framework for assessing the stability of infinite slopes under transient variably saturated conditions. The framework includes profiles of pressure head and volumetric water content combined with a general effective stress for slope stability analysis. The general effective stress, or suction stress, provides a means for rigorous quantification of stress changes due to rainfall and infiltration and thus the analysis of slope stability over the range of volumetric water contents and pressure heads relevant to shallow landslide initiation. We present results using an analytical solution for transient infiltration for a range of soil texture and hydrological properties typical of landslide-prone hillslopes and show the effect of these properties on the timing and depth of slope failure. We follow by analyzing field-monitoring data acquired prior to shallow landslide failure of a hillside near Seattle, Washington, and show that the timing of the slide was predictable using measured pressure head and volumetric water content and show how the approach can be used in a forward manner using a numerical model for transient infiltration.

Transient electrokinetic transport in a finite length microchannel: currents, capacitance, and an electrical analogy.

PubMed

Mansouri, Ali; Bhattacharjee, Subir; Kostiuk, Larry W

2007-11-08

Numerical simulations with the fluid mechanics based on the unsteady Navier-Stokes equations and the Poisson-Nernst-Planck formulation of electrostatics and ion transport were used to explore the transient transport of charge through a finite length cylindrical microchannel that is driven by a pressure difference. The evolution of the transcapillary potential from a no-flow equilibrium to the steady-state-steady-flow streaming potential was analyzed by following the convection, migration, and net currents. Observations of the unsteady characteristics of the streaming current, electrical resistance, and capacitance led to an electrical analogy. This electrical analogy was made from a current source (to represent convection current), which was placed in parallel with a capacitor (to allow the accumulation of charge) and a resistor (to permit a migration current). A parametric study involving a range of geometries, fluid mechanics, electrostatics, and mass transfer states allowed predictive submodels for the current source, capacitor, and resistor to be developed based on a dimensional analysis.

Hypoalgesia in response to transcutaneous electrical nerve stimulation (TENS) depends on stimulation intensity.

PubMed

Moran, Fidelma; Leonard, Tracey; Hawthorne, Stephanie; Hughes, Ciara M; McCrum-Gardner, Evie; Johnson, Mark I; Rakel, Barbara A; Sluka, Kathleen A; Walsh, Deirdre M

2011-08-01

Transcutaneous electrical nerve stimulation (TENS) is an electrophysical modality used for pain management. This study investigated the dose response of different TENS intensities on experimentally induced pressure pain. One hundred and thirty TENS naïve healthy individuals (18-64 years old; 65 males, 65 females) were randomly allocated to 5 groups (n = 26 per group): Strong Non Painful TENS; Sensory Threshold TENS; Below Sensory Threshold TENS; No Current Placebo TENS; and Transient Placebo TENS. Active TENS (80 Hz) was applied to the forearm for 30 minutes. Transient Placebo TENS was applied for 42 seconds after which the current amplitude automatically reset to 0 mA. Pressure pain thresholds (PPT) were recorded from 2 points on the hand and forearm before and after TENS to measure hypoalgesia. There were significant differences between groups at both the hand and forearm (ANOVA; P = .005 and .002). At 30 minutes, there was a significant hypoalgesic effect in the Strong Non Painful TENS group compared to: Below Sensory Threshold TENS, No Current Placebo TENS and Transient Placebo TENS groups (P < .0001) at the forearm; Transient Placebo TENS and No Current Placebo TENS groups at the hand (P = .001). There was no significant difference between Strong Non Painful TENS and Sensory Threshold TENS groups. The area under the curve for the changes in PPT significantly correlated with the current amplitude (r(2) = .33, P = .003). These data therefore show that there is a dose-response effect of TENS with the largest effect occurring with the highest current amplitudes. This study shows a dose response for the intensity of TENS for pain relief with the strongest intensities showing the greatest effect; thus, we suggest that TENS intensity should be titrated to achieve the strongest possible intensity to achieve maximum pain relief. Copyright © 2011 American Pain Society. Published by Elsevier Inc. All rights reserved.

Simulation study on transient electric shock characteristics of human body under high voltage ac transmission lines

NASA Astrophysics Data System (ADS)

Huang, Tao; Zou, Yanhui; Lv, Jianhong; Yang, Jinchun; Tao, Li; Zhou, Jianfei

2017-09-01

Human body under high-voltage AC transmission lines will produce a certain induced voltage due to the electrostatic induction. When the human body contacts with some grounded objects, the charges transfer from the body to the ground and produce contact current which may cause transient electric shock. Using CDEGS and ATP/EMTP, the paper proposes a method for quantitatively calculating the transient electric shock characteristics. It calculates the human body voltage, discharge current and discharge energy under certain 500kV compact-type transmission lines and predicts the corresponding human feelings. The results show that the average root value of discharge current is less than 10mA when the human body is under the 500kV compact-type transmission lines and the human body is overall safe if the transmission lines satisfy the relevant design specifications. It concludes that the electric field strength above the ground should be limited to 4kV/m through the residential area for the purpose of reducing the electromagnetic impact.

Fault Diagnosis of Induction Machines in a Transient Regime Using Current Sensors with an Optimized Slepian Window.

PubMed

Burriel-Valencia, Jordi; Puche-Panadero, Ruben; Martinez-Roman, Javier; Sapena-Bano, Angel; Pineda-Sanchez, Manuel

2018-01-06

The aim of this paper is to introduce a new methodology for the fault diagnosis of induction machines working in the transient regime, when time-frequency analysis tools are used. The proposed method relies on the use of the optimized Slepian window for performing the short time Fourier transform (STFT) of the stator current signal. It is shown that for a given sequence length of finite duration, the Slepian window has the maximum concentration of energy, greater than can be reached with a gated Gaussian window, which is usually used as the analysis window. In this paper, the use and optimization of the Slepian window for fault diagnosis of induction machines is theoretically introduced and experimentally validated through the test of a 3.15-MW induction motor with broken bars during the start-up transient. The theoretical analysis and the experimental results show that the use of the Slepian window can highlight the fault components in the current's spectrogram with a significant reduction of the required computational resources.

Transient times in linear metabolic pathways under constant affinity constraints.

PubMed

Lloréns, M; Nuño, J C; Montero, F

1997-10-15

In the early seventies, Easterby began the analytical study of transition times for linear reaction schemes [Easterby (1973) Biochim. Biophys. Acta 293, 552-558]. In this pioneer work and in subsequent papers, a state function (the transient time) was used to measure the period before the stationary state, for systems constrained to work under both constant and variable input flux, was reached. Despite the undoubted usefulness of this quantity to describe the time-dependent features of these kinds of systems, its application to the study of chemical reactions under other constraints is questionable. In the present work, a generalization of these magnitudes to linear metabolic pathways functioning under a constant-affinity constraint is carried out. It is proved that classical definitions of transient times do not reflect the actual properties of the transition to the steady state in systems evolving under this restriction. Alternatively, a more adequate framework for interpretation of the transient times for systems with both constant and variable input flux is suggested. Within this context, new definitions that reflect more accurately the transient characteristics of constant affinity systems are stated. Finally, the meaning of these transient times is discussed.

Thermoelastic steam turbine rotor control based on neural network

NASA Astrophysics Data System (ADS)

Rzadkowski, Romuald; Dominiczak, Krzysztof; Radulski, Wojciech; Szczepanik, R.

2015-12-01

Considered here are Nonlinear Auto-Regressive neural networks with eXogenous inputs (NARX) as a mathematical model of a steam turbine rotor for controlling steam turbine stress on-line. In order to obtain neural networks that locate critical stress and temperature points in the steam turbine during transient states, an FE rotor model was built. This model was used to train the neural networks on the basis of steam turbine transient operating data. The training included nonlinearity related to steam turbine expansion, heat exchange and rotor material properties during transients. Simultaneous neural networks are algorithms which can be implemented on PLC controllers. This allows for the application neural networks to control steam turbine stress in industrial power plants.

Supra- and Sub-Baseline Phosphocreatine Recovery in Developing Brain after Transient Hypoxia-Ischaemia: Relation to Baseline Energetics, Insult Severity and Outcome

ERIC Educational Resources Information Center

Iwata, Osuke; Iwata, Sachiko; Bainbridge, Alan; De Vita, Enrico; Matsuishi, Toyojiro; Cady, Ernest B.; Robertson, Nicola J.

2008-01-01

Following hypoxia-ischaemia (HI), an early biomarker of insult severity is desirable to target neuroprotective therapies to patients most likely to benefit; currently there are no biomarkers within the "latent phase" period before the establishment of secondary energy failure. Brief transient phosphocreatine (PCr) recovery overshoot (measured…

Radio Non-Detection of the Currently Outbursting Transient Source in NGC 6440

NASA Astrophysics Data System (ADS)

Tetarenko, A. J.; Bahramian, A.; Sivakoff, G. R.; Heinke, C. O.; Shaw, A. W.; Wijnands, R.; Degenaar, N.; Miller-Jones, J. C. A.; Kuulkers, R. Plotkin E.; Chomiuk, L.; Strader, J.; Tremou, E.; Kennea, J. A.; Altamirano, D.; in't Zand, J. J. M.; Deller, A.; Maccarone, T. J.

2017-10-01

We report follow-up VLA radio observations of NGC 6440, which has recently shown evidence of transient X-ray activity (ATel #10821, #10826). Our VLA observations occurred on 2017 Oct 11, with scans on source between 01:07:09 - 02:48:18 UTC (MJD = 58037.0466 - 58037.1169), in X band (8 - 12 GHz).

Transient potentials in dendritic systems of arbitrary geometry.

PubMed

Butz, E G; Cowan, J D

1974-09-01

A simple graphical calculus is developed that generates analytic solutions for membrane potential transforms at any point on the dendritic tree of neurons with arbitrary dendritic geometries, in response to synaptic "current" inputs. Such solutions permit the computation of transients in neurons with arbitrary geometry and may facilitate analysis of the role of dendrites in such cells.

A Framework for Finding and Interpreting Stellar CMEs

NASA Astrophysics Data System (ADS)

Osten, Rachel A.; Wolk, Scott J.

2017-10-01

The astrophysical study of mass loss, both steady-state and transient, on the cool half of the HR diagram has implications both for the star itself and the conditions created around the star that can be hospitable or inimical to supporting life. Stellar coronal mass ejections (CMEs) have not been conclusively detected, despite the ubiquity with which their radiative counterparts in an eruptive event (flares) have been. I will review some of the different observational methods which have been used and possibly could be used in the future in the stellar case, emphasizing some of the difficulties inherent in such attempts. I will provide a framework for interpreting potential transient stellar mass loss in light of the properties of flares known to occur on magnetically active stars. This uses a physically motivated way to connect the properties of flares and coronal mass ejections and provides a testable hypothesis for observing or constraining transient stellar mass loss. Finally I will describe recent results using observations at low radio frequencies to detect stellar coronal mass ejections, and give updates on prospects using future facilities to make headway in this important area.

Properties of the cromakalim-induced potassium conductance in smooth muscle cells isolated from the rabbit portal vein.

PubMed Central

Beech, D. J.; Bolton, T. B.

1989-01-01

1. Single smooth muscle cells were isolated freshly from the rabbit portal vein and membrane currents were recorded by the whole-cell or excised patch configurations of the patch-clamp technique at room temperature. 2. Cromakalim (Ckm, 10 microM) induced a potassium current (ICkm) that showed no pronounced voltage-dependence and had low current noise. 3. This current, ICkm, was inhibited by (in order of potency): phencyclidine greater than quinidine greater than 4-aminopyridine greater than tetraethylammonium ions (TEA). These drugs inhibited the delayed rectifier current, IdK, which is activated by depolarization of the cell, with the same order of potency. 4. Large conductance calcium-activated potassium channels (LKCa) in isolated membrane patches were blocked by (in order of potency) quinidine greater than TEA approximately phencyclidine. 4-Aminopyridine was ineffective. A similar order of potency was found for block of spontaneous transient outward currents thought to represent bursts of openings of LKCa channels. 5. The low current noise of ICkm at positive potentials, and its susceptibility to inhibitors indicated that it was not carried by LKCa channels, and that it may be carried by channels which underlie IdK. It was observed that when ICkm was activated, IdK was reduced. However, in two experiments, ICkm was much more susceptible to glibenclamide than IdK; possible reasons for this are discussed. PMID:2590772

Cumulant generating function formula of heat transfer in ballistic systems with lead-lead coupling

NASA Astrophysics Data System (ADS)

Li, Huanan; Agarwalla, Bijay Kumar; Wang, Jian-Sheng

2012-10-01

Based on a two-time observation protocol, we consider heat transfer in a given time interval tM in a lead-junction-lead system taking coupling between the leads into account. In view of the two-time observation, consistency conditions are carefully verified in our specific family of quantum histories. Furthermore, its implication is briefly explored. Then using the nonequilibrium Green's function method, we obtain an exact formula for the cumulant generating function for heat transfer between the two leads, valid in both transient and steady-state regimes. Also, a compact formula for the cumulant generating function in the long-time limit is derived, for which the Gallavotti-Cohen fluctuation symmetry is explicitly verified. In addition, we briefly discuss Di Ventra's repartitioning trick regarding whether the repartitioning procedure of the total Hamiltonian affects the nonequilibrium steady-state current fluctuation. All kinds of properties of nonequilibrium current fluctuations, such as the fluctuation theorem in different time regimes, could be readily given according to these exact formulas.

Bioengineered Tooth Buds Exhibit Features of Natural Tooth Buds.

PubMed

Smith, E E; Angstadt, S; Monteiro, N; Zhang, W; Khademhosseini, A; Yelick, P C

2018-06-01

Tooth loss is a significant health issue currently affecting millions of people worldwide. Artificial dental implants, the current gold standard tooth replacement therapy, do not exhibit many properties of natural teeth and can be associated with complications leading to implant failure. Here we propose bioengineered tooth buds as a superior alternative tooth replacement therapy. We describe improved methods to create highly cellularized bioengineered tooth bud constructs that formed hallmark features that resemble natural tooth buds such as the dental epithelial stem cell niche, enamel knot signaling centers, transient amplifying cells, and mineralized dental tissue formation. These constructs were composed of postnatal dental cells encapsulated within a hydrogel material that were implanted subcutaneously into immunocompromised rats. To our knowledge, this is the first report describing the use of postnatal dental cells to create bioengineered tooth buds that exhibit evidence of these features of natural tooth development. We propose future bioengineered tooth buds as a promising, clinically relevant tooth replacement therapy.

Transient and Big Are Key Features of an Invertebrate T-type Channel (LCav3) from the Central Nervous System of Lymnaea stagnalis*

PubMed Central

Senatore, Adriano; Spafford, J. David

2010-01-01

Here we describe features of the first non-mammalian T-type calcium channel (LCav3) expressed in vitro. This molluscan channel possesses combined biophysical properties that are reminiscent of all mammalian T-type channels. It exhibits T-type features such as “transient” kinetics, but the “tiny” label, usually associated with Ba2+ conductance, is hard to reconcile with the “bigness” of this channel in many respects. LCav3 is 25% larger than any voltage-gated ion channel expressed to date. It codes for a massive, 322-kDa protein that conducts large macroscopic currents in vitro. LCav3 is also the most abundant Ca2+ channel transcript in the snail nervous system. A window current at typical resting potentials appears to be at least as large as that reported for mammalian channels. This distant gene provides a unique perspective to analyze the structural, functional, drug binding, and evolutionary aspects of T-type channels. PMID:20056611

Late Na+ current and protracted electrical recovery are critical determinants of the aging myopathy

PubMed Central

Signore, Sergio; Sorrentino, Andrea; Borghetti, Giulia; Cannata, Antonio; Meo, Marianna; Zhou, Yu; Kannappan, Ramaswamy; Pasqualini, Francesco; O'Malley, Heather; Sundman, Mark; Tsigkas, Nikolaos; Zhang, Eric; Arranto, Christian; Mangiaracina, Chiara; Isobe, Kazuya; Sena, Brena F.; Kim, Junghyun; Goichberg, Polina; Nahrendorf, Matthias; Isom, Lori L.; Leri, Annarosa; Anversa, Piero; Rota, Marcello

2015-01-01

The aging myopathy manifests itself with diastolic dysfunction and preserved ejection fraction. We raised the possibility that, in a mouse model of physiological aging, defects in electromechanical properties of cardiomyocytes are important determinants of the diastolic characteristics of the myocardium, independently from changes in structural composition of the muscle and collagen framework. Here we show that an increase in the late Na+ current (INaL) in aging cardiomyocytes prolongs the action potential (AP) and influences temporal kinetics of Ca2+ cycling and contractility. These alterations increase force development and passive tension. Inhibition of INaL shortens the AP and corrects dynamics of Ca2+ transient, cell contraction and relaxation. Similarly, repolarization and diastolic tension of the senescent myocardium are partly restored. Thus, INaL offers inotropic support, but negatively interferes with cellular and ventricular compliance, providing a new perspective of the biology of myocardial aging and the aetiology of the defective cardiac performance in the elderly. PMID:26541940

Substance P modulation of TRPC3/7 channels improves respiratory rhythm regularity and ICAN-dependent pacemaker activity.

PubMed

Ben-Mabrouk, Faiza; Tryba, Andrew K

2010-04-01

Neuromodulators, such as substance P (SubP), play an important role in modulating many rhythmic activities driven by central pattern generators (e.g. locomotion, respiration). However, the mechanism by which SubP enhances breathing regularity has not been determined. Here, we used mouse brainstem slices containing the pre-Bötzinger complex to demonstrate, for the first time, that SubP activates transient receptor protein canonical (TRPC) channels to enhance respiratory rhythm regularity. Moreover, SubP enhancement of network regularity is accomplished via selective enhancement of ICAN (inward non-specific cation current)-dependent intrinsic bursting properties. In contrast to INaP (persistent sodium current)-dependent pacemakers, ICAN-dependent pacemaker bursting activity is TRPC-dependent. Western Blots reveal TRPC3 and TRPC7 channels are expressed in rhythmically active ventral respiratory group island preparations. Taken together, these data suggest that SubP-mediated activation of TRPC3/7 channels underlies rhythmic ICAN-dependent pacemaker activity and enhances the regularity of respiratory rhythm activity.

A novel eddy current damper: theory and experiment

NASA Astrophysics Data System (ADS)

Ebrahimi, Babak; Khamesee, Mir Behrad; Golnaraghi, Farid

2009-04-01

A novel eddy current damper is developed and its damping characteristics are studied analytically and experimentally. The proposed eddy current damper consists of a conductor as an outer tube, and an array of axially magnetized ring-shaped permanent magnets separated by iron pole pieces as a mover. The relative movement of the magnets and the conductor causes the conductor to undergo motional eddy currents. Since the eddy currents produce a repulsive force that is proportional to the velocity of the conductor, the moving magnet and the conductor behave as a viscous damper. The eddy current generation causes the vibration to dissipate through the Joule heating generated in the conductor part. An accurate, analytical model of the system is obtained by applying electromagnetic theory to estimate the damping properties of the proposed eddy current damper. A prototype eddy current damper is fabricated, and experiments are carried out to verify the accuracy of the theoretical model. The experimental test bed consists of a one-degree-of-freedom vibration isolation system and is used for the frequency and transient time response analysis of the system. The eddy current damper model has a 0.1 m s-2 (4.8%) RMS error in the estimation of the mass acceleration. A damping coefficient as high as 53 Ns m-1 is achievable with the fabricated prototype. This novel eddy current damper is an oil-free, inexpensive damper that is applicable in various vibration isolation systems such as precision machinery, micro-mechanical suspension systems and structure vibration isolation.

Mechanism of potassium ion uptake by the Na+/K+-ATPase

PubMed Central

Castillo, Juan P.; Rui, Huan; Basilio, Daniel; Das, Avisek; Roux, Benoît; Latorre, Ramon; Bezanilla, Francisco; Holmgren, Miguel

2015-01-01

The Na+/K+-ATPase restores sodium (Na+) and potassium (K+) electrochemical gradients dissipated by action potentials and ion-coupled transport processes. As ions are transported, they become transiently trapped between intracellular and extracellular gates. Once the external gate opens, three Na+ ions are released, followed by the binding and occlusion of two K+ ions. While the mechanisms of Na+ release have been well characterized by the study of transient Na+ currents, smaller and faster transient currents mediated by external K+ have been more difficult to study. Here we show that external K+ ions travelling to their binding sites sense only a small fraction of the electric field as they rapidly and simultaneously become occluded. Consistent with these results, molecular dynamics simulations of a pump model show a wide water-filled access channel connecting the binding site to the external solution. These results suggest a mechanism of K+ gating different from that of Na+ occlusion. PMID:26205423

Pursuing optimal electric machines transient diagnosis: The adaptive slope transform

NASA Astrophysics Data System (ADS)

Pons-Llinares, Joan; Riera-Guasp, Martín; Antonino-Daviu, Jose A.; Habetler, Thomas G.

2016-12-01

The aim of this paper is to introduce a new linear time-frequency transform to improve the detection of fault components in electric machines transient currents. Linear transforms are analysed from the perspective of the atoms used. A criterion to select the atoms at every point of the time-frequency plane is proposed, taking into account the characteristics of the searched component at each point. This criterion leads to the definition of the Adaptive Slope Transform, which enables a complete and optimal capture of the different components evolutions in a transient current. A comparison with conventional linear transforms (Short-Time Fourier Transform and Wavelet Transform) is carried out, showing their inherent limitations. The approach is tested with laboratory and field motors, and the Lower Sideband Harmonic is captured for the first time during an induction motor startup and subsequent load oscillations, accurately tracking its evolution.

High-altitude electrical discharges associated with thunderstorms and lightning

NASA Astrophysics Data System (ADS)

Liu, Ningyu; McHarg, Matthew G.; Stenbaek-Nielsen, Hans C.

2015-12-01

The purpose of this paper is to introduce electrical discharge phenomena known as transient luminous events above thunderstorms to the lightning protection community. Transient luminous events include the upward electrical discharges from thunderstorms known as starters, jets, and gigantic jets, and electrical discharges initiated in the lower ionosphere such as sprites, halos, and elves. We give an overview of these phenomena with a focus on starters, jets, gigantic jets, and sprites, because similar to ordinary lightning, streamers and leaders are basic components of these four types of transient luminous events. We present a few recent observations to illustrate their main properties and briefly review the theories. The research in transient luminous events has not only advanced our understanding of the effects of thunderstorms and lightning in the middle and upper atmosphere, but also improved our knowledge of basic electrical discharge processes critical for sparks and lightning.

Enhancing the ABAQUS Thermomechanics Code to Simulate Steady and Transient Fuel Rod Behavior

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

R. L. Williamson; D. A. Knoll

2009-09-01

A powerful multidimensional fuels performance capability, applicable to both steady and transient fuel behavior, is developed based on enhancements to the commercially available ABAQUS general-purpose thermomechanics code. Enhanced capabilities are described, including: UO2 temperature and burnup dependent thermal properties, solid and gaseous fission product swelling, fuel densification, fission gas release, cladding thermal and irradiation creep, cladding irradiation growth , gap heat transfer, and gap/plenum gas behavior during irradiation. The various modeling capabilities are demonstrated using a 2D axisymmetric analysis of the upper section of a simplified multi-pellet fuel rod, during both steady and transient operation. Computational results demonstrate the importancemore » of a multidimensional fully-coupled thermomechanics treatment. Interestingly, many of the inherent deficiencies in existing fuel performance codes (e.g., 1D thermomechanics, loose thermo-mechanical coupling, separate steady and transient analysis, cumbersome pre- and post-processing) are, in fact, ABAQUS strengths.« less

Modification of a Macromechanical Finite-Element Based Model for Impact Analysis of Triaxially-Braided Composites

NASA Technical Reports Server (NTRS)

Goldberg, Robert K.; Blinzler, Brina J.; Binienda, Wieslaw K.

2010-01-01

A macro level finite element-based model has been developed to simulate the mechanical and impact response of triaxially-braided polymer matrix composites. In the analytical model, the triaxial braid architecture is simulated by using four parallel shell elements, each of which is modeled as a laminated composite. For the current analytical approach, each shell element is considered to be a smeared homogeneous material. The commercial transient dynamic finite element code LS-DYNA is used to conduct the simulations, and a continuum damage mechanics model internal to LS-DYNA is used as the material constitutive model. The constitutive model requires stiffness and strength properties of an equivalent unidirectional composite. Simplified micromechanics methods are used to determine the equivalent stiffness properties, and results from coupon level tests on the braided composite are utilized to back out the required strength properties. Simulations of quasi-static coupon tests of several representative braided composites are conducted to demonstrate the correlation of the model. Impact simulations of a represented braided composites are conducted to demonstrate the capability of the model to predict the penetration velocity and damage patterns obtained experimentally.

Search for Transient Gravitational Waves in Coincidence with Short-Duration Radio Transients During 2007-2013

NASA Technical Reports Server (NTRS)

Abbott, B. P.; Hughey, Brennan; Zanolin, Michele; Szczepanczyk, Marek; Gill, Kiranjyot; Abbott, R.; Abbott, T. D.; Abernathy, M. R.; Acernese, F.; Ackley, K.;

Transient deterministic shallow landslide modeling: Requirements for susceptibility and hazard assessments in a GIS framework

USGS Publications Warehouse

Godt, J.W.; Baum, R.L.; Savage, W.Z.; Salciarini, D.; Schulz, W.H.; Harp, E.L.

2008-01-01

Application of transient deterministic shallow landslide models over broad regions for hazard and susceptibility assessments requires information on rainfall, topography and the distribution and properties of hillside materials. We survey techniques for generating the spatial and temporal input data for such models and present an example using a transient deterministic model that combines an analytic solution to assess the pore-pressure response to rainfall infiltration with an infinite-slope stability calculation. Pore-pressures and factors of safety are computed on a cell-by-cell basis and can be displayed or manipulated in a grid-based GIS. Input data are high-resolution (1.8??m) topographic information derived from LiDAR data and simple descriptions of initial pore-pressure distribution and boundary conditions for a study area north of Seattle, Washington. Rainfall information is taken from a previously defined empirical rainfall intensity-duration threshold and material strength and hydraulic properties were measured both in the field and laboratory. Results are tested by comparison with a shallow landslide inventory. Comparison of results with those from static infinite-slope stability analyses assuming fixed water-table heights shows that the spatial prediction of shallow landslide susceptibility is improved using the transient analyses; moreover, results can be depicted in terms of the rainfall intensity and duration known to trigger shallow landslides in the study area.

High-speed Particle Image Velocimetry Near Surfaces

PubMed Central

Lu, Louise; Sick, Volker

2013-01-01

Multi-dimensional and transient flows play a key role in many areas of science, engineering, and health sciences but are often not well understood. The complex nature of these flows may be studied using particle image velocimetry (PIV), a laser-based imaging technique for optically accessible flows. Though many forms of PIV exist that extend the technique beyond the original planar two-component velocity measurement capabilities, the basic PIV system consists of a light source (laser), a camera, tracer particles, and analysis algorithms. The imaging and recording parameters, the light source, and the algorithms are adjusted to optimize the recording for the flow of interest and obtain valid velocity data. Common PIV investigations measure two-component velocities in a plane at a few frames per second. However, recent developments in instrumentation have facilitated high-frame rate (> 1 kHz) measurements capable of resolving transient flows with high temporal resolution. Therefore, high-frame rate measurements have enabled investigations on the evolution of the structure and dynamics of highly transient flows. These investigations play a critical role in understanding the fundamental physics of complex flows. A detailed description for performing high-resolution, high-speed planar PIV to study a transient flow near the surface of a flat plate is presented here. Details for adjusting the parameter constraints such as image and recording properties, the laser sheet properties, and processing algorithms to adapt PIV for any flow of interest are included. PMID:23851899

Characterization of electrical appliances in transient state

NASA Astrophysics Data System (ADS)

Wójcik, Augustyn; Winiecki, Wiesław

2017-08-01

The article contains the study about electrical appliance characterization on the basis of power grid signals. To represent devices, parameters of current and voltage signals recorded during transient states are used. In this paper only transients occurring as a result of switching on devices are considered. The way of data acquisition performed in specialized measurement setup developed for electricity load monitoring is described. The paper presents the method of transients detection and the method of appliance parameters calculation. Using the set of acquired measurement data and appropriate software the set of parameters for several household appliances operating in different operating conditions was processed. Usefulness of appliances characterization in Non-Intrusive Appliance Load Monitoring System (NIALMS) with the use of proposed method is discussed focusing on obtained results.

Functional role of A-type potassium currents in rat presympathetic PVN neurones

PubMed Central

Sonner, Patrick M; Stern, Javier E

2007-01-01

Despite the fact that paraventricular nucleus (PVN) neurones innervating the rostral ventrolateral medulla (RVLM) play important roles in the control of sympathetic function both in physiological and pathological conditions, the precise mechanisms controlling their activity are still incompletely understood. In the present study, we evaluated whether the transient outward potassium current IA is expressed in PVN-RVLM neurones, characterized its biophysical and pharmacological properties, and determined its role in shaping action potentials and firing discharge in these neurones. Patch-clamp recordings obtained from retrogradely labelled, PVN-RVLM neurones indicate that a 4-AP sensitive, TEA insensitive current, with biophysical properties consistent with IA, is present in these neurones. Pharmacological blockade of IA depolarized resting Vm and prolonged Na+ action potential duration, by increasing its width and by slowing down its decay time course. Interestingly, blockade of IA either increased or decreased the firing activity of PVN-RVLM neurones, supporting the presence of subsets of PVN-RVLM neurones differentially modulated by IA. In all cases, the effects of IA on firing activity were prevented by a broad spectrum Ca2+ channel blocker. Immunohistochemical studies suggest that IA in PVN-RVLM neurons is mediated by Kv1.4 and/or Kv4.3 channel subunits. Overall, our results demonstrate the presence of IA in PVN-RVLM neurones, which actively modulates their action potential waveform and firing activity. These studies support IA as an important intrinsic mechanism controlling neuronal excitability in this central presympathetic neuronal population. PMID:17525115

Persistent photocurrent and deep level traps in PLD-grown In-Ga-Zn-O thin films studied by thermally stimulated current spectroscopy

NASA Astrophysics Data System (ADS)

Wang, Buguo; Anders, Jason; Leedy, Kevin; Schuette, Michael; Look, David

2018-02-01

InGaZnO (IGZO) is a promising semiconductor material for thin-film transistors (TFTs) used in DC and RF switching applications, especially since it can be grown at low temperatures on a wide variety of substrates. Enhancement-mode TFTs based on IGZO thin films grown by pulsed laser deposition (PLD) have been recently fabricated and these transistors show excellent performance; however, compositional variations and defects can adversely affect film quality, especially in regard to electrical properties. In this study, we use thermally stimulated current (TSC) spectroscopy to characterize the electrical properties and the deep traps in PLD-grown IGZO thin films. It was found that the as-grown sample has a DC activation energy of 0.62 eV, and two major traps with activation energies at 0.16-0.26 eV and at 0.90 eV. However, a strong persistent photocurrent (PPC) sometimes exists in the as-grown sample, so we carry out post-growth annealing in an attempt to mitigate the effect. It was found that annealing in argon increases the conduction, produces more PPC and also makes more traps observable. Annealing in air makes the film more resistive, and removes PPC and all traps but one. This work demonstrates that current-based trap emission, such as that associated with the TSC, can effectively reveal electronic defects in highlyresistive semiconductor materials, especially those are not amenable to capacitance-based techniques, such as deeplevel transient spectroscopy (DLTS).

[Regulation of pyloric rhythm by I(A) and I(h) in crayfish stomatogastric ganglion].

PubMed

Kuang, Guo-Hui; Liu, Yi-Hui; Ren, Wei

2012-06-25

The stomatogastric ganglion (STG) of shellfish includes 30 neurons and produces pyloric rhythms. It is the common model to study central pattern generator (CPG). Regulation of pyloric rhythms not only is related to the property of single neurons in STG but also depends on the connections and property of the whole neuronal network. It has been found that transient potassium current (I(A)) and hyperpolarization-activated cation current (I(h)) exist in certain types of neurons of STG. However, roles played by these two currents in maintaining and regulating the pyloric rhythms are unknown. In the present study, in vitro electrophysiological recordings were performed on crayfish STG to examine the role played by I(A) and I(h) in regulation of pyloric rhythm. 4AP (2 mmol/L), a specific inhibitor of I(A), caused a decrease in pyloric cycle (P < 0.01), an increase in PD (pyloric dilator) ratio, a decrease in PY (pyloric) ratio (P < 0.01) and delay of phases of LP and PY firing. ZD7288 (100 μmol/L), a specific inhibitor of I(h), caused a decrease in pyloric cycle (P < 0.01), an increase in PD ratio (P < 0.01), an increase in LP (lateral pyloric) ratio (P < 0.01), a decrease in PY ratio (P < 0.01) and delay of phases of LP and PY firing. These results indicate that I(A) and I(h) play important roles in regulating pyloric rhythms in crayfish STG.

Investigation of thermally evaporated high resistive B-doped amorphous selenium alloy films and metal contact studies

NASA Astrophysics Data System (ADS)

Oner, Cihan; Nguyen, Khai V.; Pak, Rahmi O.; Mannan, Mohammad A.; Mandal, Krishna C.

2015-08-01

Amorphous selenium (a-Se) alloy materials with arsenic, chlorine, boron, and lithium doping were synthesized for room temperature nuclear radiation detector applications using an optimized alloy composition for enhanced charge transport properties. A multi-step synthetic process has been implemented to first synthesize Se-As and Se-Cl master alloys from zone-refined Se (~ 7N), and then synthesized the final alloys for thermally evaporated large-area thin-film deposition on oxidized aluminum (Al/Al2O3) and indium tin oxide (ITO) coated glass substrates. Material purity, morphology, and compositional characteristics of the alloy materials and films were examined using glow discharge mass spectroscopy (GDMS), inductively coupled plasma mass spectroscopy (ICP-MS), differential scanning calorimetry (DSC), x-ray photoelectron spectroscopy (XPS), x-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive analysis by x-rays (EDAX). Current-Voltage (I-V) measurements were carried out to confirm very high resistivity of the alloy thin-films. We have further investigated the junction properties of the alloy films with a wide variety of metals with different work functions (Au, Ni, W, Pd, Cu, Mo, In, and Sn). The aim was to investigate whether the choice of metal can improve the performance of fabricated detectors by minimizing the dark leakage current. For various metal contacts, we have found significant dependencies of metal work functions on current transients by applying voltages from -800 V to +1000 V.

Rapid Measurement of Room Temperature Ionic Liquid Electrochemical Gas Sensor using Transient Double Potential Amperometry

PubMed Central

Wan, Hao; Yin, Heyu; Mason, Andrew J.

2016-01-01

Intense study on gas sensors has been conducted to implement fast gas sensing with high sensitivity, reliability and long lifetime. This paper presents a rapid amperometric method for gas sensing based on a room temperature ionic liquid electrochemical gas sensor. To implement a miniaturized sensor with a fast response time, a three electrode system with gold interdigitated electrodes was fabricated by photolithography on a porous polytetrafluoroethylene substrate that greatly enhances gas diffusion. Furthermore, based on the reversible reaction of oxygen, a new transient double potential amperometry (DPA) was explored for electrochemical analysis to decrease the measurement time and reverse reaction by-products that could cause current drift. Parameters in transient DPA including oxidation potential, oxidation period, reduction period and sample point were investigated to study their influence on the performance of the sensor. Oxygen measurement could be accomplished in 4 s, and the sensor presented a sensitivity of 0.2863 μA/[%O2] and a linearity of 0.9943 when tested in air samples with different oxygen concentrations. Repeatability and long-term stability were also investigated, and the sensor was shown to exhibit good reliability. In comparison to conventional constant potential amperometry, transient DPA was shown to reduce relative standard deviation by 63.2%. With transient DPA, the sensitivity, linearity, repeatability, measurement time and current drift characteristics demonstrated by the presented gas sensor are promising for acute exposure applications. PMID:28603384

Rapid Measurement of Room Temperature Ionic Liquid Electrochemical Gas Sensor using Transient Double Potential Amperometry.

PubMed

Wan, Hao; Yin, Heyu; Mason, Andrew J

2017-04-01

Intense study on gas sensors has been conducted to implement fast gas sensing with high sensitivity, reliability and long lifetime. This paper presents a rapid amperometric method for gas sensing based on a room temperature ionic liquid electrochemical gas sensor. To implement a miniaturized sensor with a fast response time, a three electrode system with gold interdigitated electrodes was fabricated by photolithography on a porous polytetrafluoroethylene substrate that greatly enhances gas diffusion. Furthermore, based on the reversible reaction of oxygen, a new transient double potential amperometry (DPA) was explored for electrochemical analysis to decrease the measurement time and reverse reaction by-products that could cause current drift. Parameters in transient DPA including oxidation potential, oxidation period, reduction period and sample point were investigated to study their influence on the performance of the sensor. Oxygen measurement could be accomplished in 4 s, and the sensor presented a sensitivity of 0.2863 μA/[%O 2 ] and a linearity of 0.9943 when tested in air samples with different oxygen concentrations. Repeatability and long-term stability were also investigated, and the sensor was shown to exhibit good reliability. In comparison to conventional constant potential amperometry, transient DPA was shown to reduce relative standard deviation by 63.2%. With transient DPA, the sensitivity, linearity, repeatability, measurement time and current drift characteristics demonstrated by the presented gas sensor are promising for acute exposure applications.

Ion transfer through solvent polymeric membranes driven by an exponential current flux.

PubMed

Molina, A; Torralba, E; González, J; Serna, C; Ortuño, J A

2011-03-21

General analytical equations which govern ion transfer through liquid membranes with one and two polarized interfaces driven by an exponential current flux are derived. Expressions for the transient and stationary E-t, dt/dE-E and dI/dE-E curves are obtained, and the evolution from transient to steady behaviour has been analyzed in depth. We have also shown mathematically that the voltammetric and stationary chronopotentiometric I(N)-E curves are identical (with E being the applied potential for voltammetric techniques and the measured potential for chronopotentiometric techniques), and hence, their derivatives provide identical information.

Kinetic Monte Carlo simulations of nucleation and growth in electrodeposition.

PubMed

Guo, Lian; Radisic, Aleksandar; Searson, Peter C

2005-12-22

Nucleation and growth during bulk electrodeposition is studied using kinetic Monte Carlo (KMC) simulations. Ion transport in solution is modeled using Brownian dynamics, and the kinetics of nucleation and growth are dependent on the probabilities of metal-on-substrate and metal-on-metal deposition. Using this approach, we make no assumptions about the nucleation rate, island density, or island distribution. The influence of the attachment probabilities and concentration on the time-dependent island density and current transients is reported. Various models have been assessed by recovering the nucleation rate and island density from the current-time transients.

Spatial profile of thermoelectric effects during Peltier pulsing in Bi and Bi/MnBi eutectic

NASA Technical Reports Server (NTRS)

Silberstein, R. P.; Larson, D. J., Jr.

1987-01-01

The spatial profile of the thermal transients that occur during and following the current pulsing associated with Peltier Interface Demarcation during directional solidification is studied. Results for pure Bi are presented in detail and compared with corresponding results for the Bi/MnBi eutectic. Significant thermal transients occur throughout the sample that can be accounted for by the Peltier effect, the Thomson effect, and Joule heating. These effects are separated and their behavior is studied as a function of time, current density, and position with respect to the solid/liquid interface.

Theory of passive proton conductance in lipid bilayers.

PubMed

Nagle, J F

1987-10-01

The large permeability of lipid bilayers to protons compared to other small ions calls for a special proton transport mechanism. At the present time, only mechanisms involving transient hydrogen-bonded chains of water can account for the experimental result that the conductance is nearly independent of pH. Three models involving transient hydrogen-bonded chains are discussed, including an outline of the kinetic calculations that lead to predictions of current versus voltage drop and current versus pH differences. These calculations can be compared to experiment to determine which, if any, of these models pertains to lipid bilayers.

Monitoring transients in low inductance circuits

DOEpatents

Guilford, Richard P.; Rosborough, John R.

1987-01-01

A pair of flat cable transmission lines are monitored for transient current spikes by using a probe connected to a current transformer by a pickup loop and monitoring the output of the current transformer. The approach utilizes a U-shaped pickup probe wherein the pair of flat cable transmission lines are received between the legs of the U-shaped probe. The U-shaped probe is preferably formed of a flat coil conductor adhered to one side of a flexible substrate. On the other side of the flexible substrate there is a copper foil shield. The copper foil shield is connected to one end of the flat conductor coil and connected to one leg of the pickup loop which passes through the current transformer. The other end of the flat conductor coil is connected to the other leg of the pickup loop.

Pseudomonas fluorescens lipopolysaccharide inhibits both delayed rectifier and transient A-type K+ channels of cultured rat cerebellar granule neurons.

PubMed

Mezghani-Abdelmoula, Sana; Chevalier, Sylvie; Lesouhaitier, Olivier; Orange, Nicole; Feuilloley, Marc G J; Cazin, Lionel

2003-09-05

Pseudomonas fluorescens is a Gram-negative bacillus closely related to the pathogen P. aeruginosa known to provoke infectious disorders in the central nervous system (CNS). The endotoxin lipopolysaccharide (LPS) expressed by the bacteria is the first infectious factor that can interact with the plasma membrane of host cells. In the present study, LPS extracted from P. fluorescens MF37 was examined for its actions on delayed rectifier and A-type K(+) channels, two of the main types of voltage-activated K(+) channels involved in the action potential firing. Current recordings were performed in cultured rat cerebellar granule neurons at days 7 or 8, using the whole-cell patch-clamp technique. A 3-h incubation with LPS (200 ng/ml) markedly depressed both the delayed rectifier (I(KV)) and transient A-type (I(A)) K(+) currents evoked by depolarizations above 0 and -40 mV, respectively. The percent decrease of I(KV) and I(A) ( approximately 30%) did not vary with membrane potential, suggesting that inhibition of both types of K(+) channels by LPS was voltage-insensitive. The endotoxin did neither modify the steady-state voltage-dependent activation properties of I(KV) and I(A) nor the steady-state inactivation of I(A). The present results suggest that, by inhibiting I(KV) and I(A), LPS applied extracellulary increases the action potential firing in cerebellar granule neurons. It is concluded that P. fluorescens MF37 may provoke in the CNS disorders associated with sever alterations of membrane ionic channel functions.

The Studies of a Vacuum Gap Breakdown after High-Current Arc Interruption with Increasing the Voltage

NASA Astrophysics Data System (ADS)

Schneider, A. V.; Popov, S. A.; Batrakov, A. V.; Dubrovskaya, E. L.; Lavrinovich, V. A.

2017-12-01

Vacuum-gap breakdown has been studied after high-current arc interruption with a subsequent increase in the transient recovery voltage across a gap. The effects of factors, such as the rate of the rise in the transient voltage, the potential of the shield that surrounds a discharge gap, and the arc burning time, have been determined. It has been revealed that opening the contacts earlier leads to the formation of an anode spot, which is the source of electrode material vapors into the discharge gap after current zero moment. Under the conditions of increasing voltage, this fact results in the breakdown. Too late opening leads to the breakdown of a short gap due to the high electric fields.

Stiffness characteristics of airfoils under pulse loading

NASA Astrophysics Data System (ADS)

Turner, Kevin Eugene

The turbomachinery industry continually struggles with the adverse effects of contact rubs between airfoils and casings. The key parameter controlling the severity of a given rub event is the contact load produced when the airfoil tips incur into the casing. These highly non-linear and transient forces are difficult to calculate and their effects on the static and rotating components are not well understood. To help provide this insight, experimental and analytical capabilities have been established and exercised through an alliance between GE Aviation and The Ohio State University Gas Turbine Laboratory. One of the early findings of the program is the influence of blade flexibility on the physics of rub events. The core focus of the work presented in this dissertation is to quantify the influence of airfoil flexibility through a novel modeling approach that is based on the relationship between applied force duration and maximum tip deflection. This relationship is initially established using a series of forward, non-linear and transient analyses in which simulated impulse rub loads are applied. This procedure, although effective, is highly inefficient and costly to conduct by requiring numerous explicit simulations. To alleviate this issue, a simplified model, named the pulse magnification model, is developed that only requires a modal analysis and a static analyses to fully describe how the airfoil stiffness changes with respect to load duration. Results from the pulse magnification model are compared to results from the full transient simulation method and to experimental results, providing sound verification for the use of the modeling approach. Furthermore, a unique and highly efficient method to model airfoil geometries was developed and is outlined in this dissertation. This method produces quality Finite Element airfoil definitions directly from a fully parameterized mathematical model. The effectiveness of this approach is demonstrated by comparing modal properties of the simulated geometries to modal properties of various current airfoil designs. Finally, this modeling approach was used in conjunction with the pulse magnification model to study the effects of various airfoil geometric features on the stiffness of the blade under impulsive loading.

Discovery of the Transient Magnetar 3XMM J185246.6+003317 near Supernova Remnant Kesteven 79 with XMM-Newton

NASA Astrophysics Data System (ADS)

Zhou, Ping; Chen, Yang; Li, Xiang-Dong; Safi-Harb, Samar; Mendez, Mariano; Terada, Yukikatsu; Sun, Wei; Ge, Ming-Yu

2014-01-01

We report the serendipitous discovery with XMM-Newton that 3XMM J185246.6+003317 is an 11.56 s X-ray pulsar located 1' away from the southern boundary of supernova remnant Kes 79. The spin-down rate of 3XMM J185246.6+003317 is <1.1 × 10-13 s s-1, which, together with the long period P = 11.5587126(4) s, indicates a dipolar surface magnetic field of <3.6 × 1013 G, a characteristic age of >1.7 Myr, and a spin-down luminosity of <2.8 × 1030 erg s-1. Its X-ray spectrum is best-fitted with a resonant Compton scattering model and also can be adequately described by a blackbody model. The observations covering a seven-month span from 2008 to 2009 show variations in the spectral properties of the source, with the luminosity decreasing from 2.7 × 1034 erg s-1 to 4.6 × 1033 erg s-1, along with a decrease of the blackbody temperature from kT ≈ 0.8 keV to ≈0.6 keV. The X-ray luminosity of the source is higher than its spin-down luminosity, ruling out rotation as a power source. The combined timing and spectral properties, the non-detection of any optical or infrared counterpart, together with the lack of detection of the source in archival X-ray data prior to the 2008 XMM-Newton observation, point to 3XMM J185246.6+003317 being a newly discovered transient low-B magnetar undergoing an outburst decay during the XMM-Newton observations. The non-detection by Chandra in 2001 sets an upper limit of 4 × 1032 erg s-1 to the quiescent luminosity of 3XMM J185246.6+003317. Its period is the longest among currently known transient magnetars. The foreground absorption toward 3XMM J185246.6+003317 is similar to that of Kes 79, suggesting a similar distance of ~7.1 kpc.

Discovery of the transient magnetar 3XMM J185246.6+003317 near supernova remnant Kesteven 79 with XMM-Newton

NASA Astrophysics Data System (ADS)

Zhou, Ping; Mendez, Mariano; Chen, Yang; Li, Xiangdong; Safi-Harb, Samar; Terada, Yukikatsu; Sun, Wei; Ge, Mingyu

We report the serendipitous discovery with XMM-Newton that 3XMM J185246.6+003317 is an 11.56 s X-ray pulsar located 1' away from the southern boundary of supernova remnant Kes 79. The spin-down rate of 3XMM J185246.6+003317 is <1.1× 10(-13) s s(-1) , which, together with the long period P=11.558714(2) s, indicates a dipolar surface magnetic field of <3.6× 10(13) G, a characteristic age of >1.7 Myr, and a spin-down luminosity of <2.8× 10(30) erg s(-1) . The X-ray spectrum of the source is best-fitted with a resonant Compton scattering model, and can be also adequately described by a blackbody model. The observations covering a seven month span from 2008 to 2009 show variations in the spectral properties of the source, with the luminosity decreasing from 2.7× 10(34) erg s(-1) to 4.6 × 10(33) erg s(-1) , along with a decrease of the blackbody temperature from kT≈ 0.8 keV to ≈0.6 keV. The X-ray luminosity of the source is higher than its spin-down luminosity, ruling out rotation as a power source. The combined timing and spectral properties, the non-detection of any optical or infrared counterpart, together with the lack of detection of the source in archival X-ray data prior to the 2008 XMM-Newton observation, point to this source being a newly discovered transient low-B magnetar undergoing an outburst decay during the XMM-Newton observations. The non-detection by Chandra in 2001 sets an upper limit 4× 10(32) erg s(-1) to the quiescent luminosity of 3XMM J185246.6+003317. Its period is the longest among currently known transient magnetars. The foreground absorption toward 3XMM J185246.6+003317 is similar to that of Kes 79, suggesting a similar distance of ˜7.1 kpc.

Small Volume Fuel Testers Report

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

Schoegl, I.; McNenly, M. J.; Killingsworth, N. J.

Micro-liter fuel ignition testing (μ-FIT) is based on the premise that characteristics FREI (Flames with Repetitive Extinction and Ignition, i.e. cyclically occurring combustion events within heated capillaries), are linked to fuel properties. In early FY16, proof-of-concept measurements with primary reference fuel (PRF) mixtures, i.e. blends of n-heptane and iso-octane, yielded clear evidence for the feasibility of the approach. Our experiments showed that it is critical to accurately link observed flame positions to local temperatures, which provides information on ignition, extinction and flame propagation, all of which are known to be impacted by fuel properties. In FY16, one major hurdle wasmore » uncertainty of temperature calibration, which required significant efforts for corrective action that were not included in the original scope of work. Temperature calibrations are obtained by translating a thermocouple within the capillary in absence of a flame. While measurements have good repeatability when accounting for transient and insertion effects, results from nominally identical thermocouples reveal unacceptable uncertainty (up to ±50K), which is attributed to variations in thermocouple placement and manufacturing tolerances. This issue is currently being resolved by switching to non-intrusive optical temperature measurements. Updates are expected to yield uncertainties of less than ±10K, while also eliminating transient and insertion effects. The experimental work was complemented by computational efforts where it was shown that a simplified Lagrangian zero-D model with detailed kinetics yields fuelspecific differentiation of ignition temperatures for simple fuels that are consistent with experiments. Further, a 2D transient model was implemented in OpenFOAM to investigate combustion behavior of simple fuels at elevated pressure. In an upcoming visit to LLNL, more advanced simulations using LLNL’s computational tools (e.g. zero-RK) are planned, which will yield additional numerical insights on FREI behavior of more realistic spark ignited (SI) engine fuel surrogates. As there is a lag between DOE FY16 and the time frame of the LSU subcontract, it is anticipated that deliverables outlined in the scope of work will be met by the end of the subcontract (January 2017).« less

Aerial Transient Electromagnetic Surveys of Alluvial Aquifers in Rural Watersheds of Arizona

NASA Astrophysics Data System (ADS)

Pool, D. R.; Callegary, J. B.; Groom, R. W.

2006-12-01

Development in rural areas of Arizona has led the State of Arizona (Arizona Department of Water Resources), in cooperation with the Arizona Water Science Center of the U.S. Geological Survey, to sponsor investigations of the hydrogeologic framework of several alluvial-basin aquifers. An efficient method for mapping the aquifer extent and lithology was needed due to sparse subsurface information. Aerial Transient Electro-Magnetic (ATEM) methods were selected because they can be used to quickly survey large areas and with a great depth of investigation. Both helicopter and fixed-wing ATEM methods are available. A fixed-wing method (GEOTEM) was selected because of the potential for a depth of investigation of 300 m or more and because previous surveys indicated the method is useful in alluvial basins in southeastern Arizona. About 2,900 km of data along flight lines were surveyed across five alluvial basins, including the Middle San Pedro and Willcox Basins in southeastern Arizona, and Detrital, Hualapai, and Sacramento Basins in northwestern Arizona. Data initially were analyzed by the contractor (FUGRO Airborne Surveys) to produce conductivity-depth-transforms, which approximate the general subsurface electrical-property distribution along profiles. Physically based two-dimensional physical models of the profile data were then developed by PetRos- Eikon by using EMIGMA software. Hydrologically important lithologies can have different electrical properties. Several types of crystalline and sedimentary rocks generally are poor aquifers that have low porosity and high electrical resistivity. Good alluvial aquifers of sand and gravel generally have an intermediate electrical resistivity. Poor aquifer materials, such as silt and clay, and areas of poor quality water have low electrical resistivity values. Several types of control data were available to constrain the models including drill logs, electrical logs, water levels , and water quality information from wells; and gravity, seismic, direct-current resistivity, and transient-electromagnetic information from ground-based geophysical surveys. Results of the surveys will be used along with available subsurface information to describe the spatial extent of the alluvial aquifers and the general lithologic distribution within the alluvial aquifers.

A Quantitative Comparison of the Behavior of Human Ventricular Cardiac Electrophysiology Models in Tissue

PubMed Central

Elshrif, Mohamed M.; Cherry, Elizabeth M.

2014-01-01

Numerical integration of mathematical models of heart cell electrophysiology provides an important computational tool for studying cardiac arrhythmias, but the abundance of available models complicates selecting an appropriate model. We study the behavior of two recently published models of human ventricular action potentials, the Grandi-Pasqualini-Bers (GPB) and the O'Hara-Virág-Varró-Rudy (OVVR) models, and compare the results with four previously published models and with available experimental and clinical data. We find the shapes and durations of action potentials and calcium transients differ between the GPB and OVVR models, as do the magnitudes and rate-dependent properties of transmembrane currents and the calcium transient. Differences also occur in the steady-state and S1–S2 action potential duration and conduction velocity restitution curves, including a maximum conduction velocity for the OVVR model roughly half that of the GPB model and well below clinical values. Between single cells and tissue, both models exhibit differences in properties, including maximum upstroke velocity, action potential amplitude, and minimum diastolic interval. Compared to experimental data, action potential durations for the GPB and OVVR models agree fairly well (although OVVR epicardial action potentials are shorter), but maximum slopes of steady-state restitution curves are smaller. Although studies show alternans in normal hearts, it occurs only in the OVVR model, and only for a narrow range of cycle lengths. We find initiated spiral waves do not progress to sustained breakup for either model. The dominant spiral wave period of the GPB model falls within clinically relevant values for ventricular tachycardia (VT), but for the OVVR model, the dominant period is longer than periods associated with VT. Our results should facilitate choosing a model to match properties of interest in human cardiac tissue and to replicate arrhythmia behavior more closely. Furthermore, by indicating areas where existing models disagree, our findings suggest avenues for further experimental work. PMID:24416228

On The Constitutive Properties Of Strongly Magnetized Matter Observed In A Class Of Solar Ejecta

NASA Astrophysics Data System (ADS)

Berdichevsky, D. B.

2013-12-01

Several studies of the transient events known as magnetic clouds at 1 AU suggest that they possess the ';1/2' anomalous value for its adiabatic, polytropic index, i.e., γ= 1/2, which implies that the temperature of the plasma decreases with increased density[1-3]. Coronal mass ejections commonly observed by missions like The Solar Terrestrial Relations Observatory (STEREO) have been successfully modeled previously by Berdichevsky Stenborg and Vourlidas[4] as magnetic flux-ropes which propagate from the Sun with uniform velocity. Building on this existing analytical three-dimensional magnetohydrodynamic (MHD) model of a magnetic flux-rope, we present an interpretation of the anomalous and somewhat counterintuitive dynamic property mentioned above. Using plasma and magnetic field observations by the Wind spacecraft for the magnetic cloud of June 2, 1998, we argue that this anomalous polytropic index is indeed a consequence of thermodynamic processes in this strongly magnetized matter. We show that the derived models of Berdichevsky et al.[5, 6] easily accommodate a familiar thermodynamic explanation of this property. Such an explanation may shed light also on the evolution of other astrophysical observations such as remnants in nebulae of past super-novae, as well other transient interstellar events. This MHD solution may be a good way to go beyond gas-dynamics in the development of a coherent picture of shock and its driver, as they are becoming a current interpretation. 1Osherovich, V.A., 1997, Proc. 31st, ESLAB Symp. Correlated Phenomena at the Sun, in the Heliosphere and in Geospace. 2Sittler, E.C., and L.F., Burlaga, 1998, J. Geophys. Res., 103, 17447. 3Nieves-Chinchilla T., and A., Figueroa-Viñas, 2008, J. Geophys. Res., 113, DOI: 10.1029/2007JA012703 4Berdichevsky, Stenborg, and Vourlidas, 2011, ApJ, 741, 47. 5Berdichevsky, D.B., R.L., Lepping, C.J., Farrugia, 2003, Phys.Rev. E, 67, DOI: 10.1103/PhysRevE036405. 6Berdichevsky, D.B. , 2012, Sol. Phys., 284, 245.

Long-time observation of meteor induced layers with ionosonde

NASA Astrophysics Data System (ADS)

Yusupov, Kamil; Akchurin, Adel

2016-07-01

It is considered that the main theory explaining appearance of sporadic E is the theory of wind shear, which means (includes) the presence and movement of nodes converging tidal wind through the height region of the most frequent occurrence Es (120-140km) [Mathew et. all, 1998]. However, the appearance of intense layers, following its name, are sporadic, and such variability cannot to explain by the influence of tidal waves only. Another indication inconsistency theory of wind shear is the appearance of so-called transient Es layers [Maruiama, 2003]. The distinctive feature of this trace is the high critical frequency (> 5 MHz), a constant height, weak amplitude, all trace semitransparent and short lifetime [Maruiama et. all, 2003 and 2008 and references there]. Because of duration, such layer is opposite to the traditional persistent Es layer, which we do not consider in this paper. Various researchers have used different terms for such spontaneous Es, it is meteor echo, meteor induced Es, spontaneously formed sporadic Es patches resulting of the Fresnel scattering from a region of enhanced plasma density along the meteor trail, transitory Es and transient Es. Since the term transient Es is unstable, to avoid confusion, we will stick to this term. Since meteor echo is not fully satisfy this term by some parameter, we will describe the properties of transient Es based on the ionogram properties and not from physics of its origin. We used data from our ionosonde with one-minute ionogram repetition rate for 2010-2014 years. For processing performed a method are using to select beatings and the ionosphere reflectivity of the layers by means A-, H-and AΣ-map [Akchurin, 2011; Yusupov, 2014]. This maps allow to collect transient Es appearance over a long-time. Such statistics comparison with meteor showers activity showed good agreement. It shows the presence of the transient Es formation mechanism, which coupling with meteors.

Effects of viscosity and conductivity stratification on the linear stability and transient growth within compressible Couette flow

NASA Astrophysics Data System (ADS)

Saikia, Bijaylakshmi; Ramachandran, Ashwin; Sinha, Krishnendu; Govindarajan, Rama

2017-02-01

Accurate prediction of laminar to turbulent transition in compressible flows is a challenging task, as it can be affected by a combination of factors. Compressibility causes large variations in thermodynamic as well as transport properties of a gas, which in turn are known to affect flow stability. We study the stratification of individual transport properties and their combined behavior. We also examine the effect of a change in the magnitude of viscosity and conductivity on flow stability. The Couette flow of a perfect gas is our model problem and both modal and non-modal analyses are carried out. We notice a large destabilizing role of the increase in the conductivity value and a dramatic stabilizing effect of mean viscosity stratification, over a range of free-stream Mach number, Reynolds number, Prandtl number, and disturbance wavenumber. In the combined case, viscosity stratification plays a dominant role. We find this to be the case for finite-time transient growth in the parameter regime below linear instability as well as asymptotically at large time. A budget of the transient growth energy amplification is also shown to identify the effects of transport properties on the constituents of perturbation energy. The extensive results presented in this paper, we believe should motivate those studying more realistic flows to examine how these contrasting effects of stratification come together.

Diiodobodipy-styrylbodipy Dyads: Preparation and Study of the Intersystem Crossing and Fluorescence Resonance Energy Transfer.

PubMed

Wang, Zhijia; Xie, Yun; Xu, Kejing; Zhao, Jianzhang; Glusac, Ksenija D

2015-07-02

2,6-Diiodobodipy-styrylbodipy dyads were prepared to study the competing intersystem crossing (ISC) and the fluorescence-resonance-energy-transfer (FRET), and its effect on the photophysical property of the dyads. In the dyads, 2,6-diiodobodipy moiety was used as singlet energy donor and the spin converter for triplet state formation, whereas the styrylbodipy was used as singlet and triplet energy acceptors, thus the competition between the ISC and FRET processes is established. The photophysical properties were studied with steady-state UV-vis absorption and fluorescence spectroscopy, electrochemical characterization, and femto/nanosecond time-resolved transient absorption spectroscopies. FRET was confirmed with steady state fluorescence quenching and fluorescence excitation spectra and ultrafast transient absorption spectroscopy (kFRET = 5.0 × 10(10) s(-1)). The singlet oxygen quantum yield (ΦΔ = 0.19) of the dyad was reduced as compared with that of the reference spin converter (2,6-diiodobodipy, ΦΔ = 0.85), thus the ISC was substantially inhibited by FRET. Photoinduced intramolecular electron transfer (ET) was studied by electrochemical data and fluorescence quenching. Intermolecular triplet energy transfer was studied with nanosecond transient absorption spectroscopy as an efficient (ΦTTET = 92%) and fast process (kTTET = 5.2 × 10(4) s(-1)). These results are useful for designing organic triplet photosensitizers and for the study of the photophysical properties.

Searching for MHz Transients with the VLA Low-band Ionosphere and Transient Experiment (VLITE)

NASA Astrophysics Data System (ADS)

Polisensky, Emil; Peters, Wendy; Giacintucci, Simona; Clarke, Tracy; Kassim, Namir E.; hyman, Scott D.; van der Horst, Alexander; Linford, Justin; Waldron, Zach; Frail, Dale

2018-01-01

NRL and NRAO have expanded the low frequency capabilities of the VLA through the VLA Low-band Ionosphere and Transient Experiment (VLITE, http://vlite.nrao.edu/ ), effectively making the instrument two telescopes in one. VLITE is a commensal observing system that harvests data from the prime focus in parallel with normal Cassegrain focus observing on a subset of VLA antennas. VLITE provides over 6000 observing hours per year in a > 5 square degree field-of-view using 64 MHz bandwidth centered on 352 MHz. By operating in parallel, VLITE offers invaluable low frequency data to targeted observations of transient sources detected at higher frequencies. With arcsec resolution and mJy sensitivity, VLITE additionally offers great potential for blind searches of rarer radio-selected transients. We use catalog matching software on the imaging products from the daily astrophysics pipeline and the LOFAR Transients Pipeline (TraP) on repeated observations of the same fields to search for coherent and incoherent astronomical transients on timescales of a few seconds to years. We present the current status of the VLITE transient science program from its initial deployment on 10 antennas in November 2014 through its expansion to 16 antennas in the summer of 2017. Transient limits from VLITE’s first year of operation (Polisensky et al. 2016) are updated per the most recent analysis.

Electronic properties of defects in silicon and related materials

NASA Astrophysics Data System (ADS)

Mitromara, Niki

Efforts in the current semiconductor industry are focused on the production of smaller, more efficient and inexpensive devices of higher packing density. As silicon is the dominant semiconductor implemented for the fabrication of the majority of semiconductor devices, perpetual research has focused on the improvement of its properties and the realisation of the most efficient structures. This thesis presents the electrical characterisation of two different diode structures that are important for the present and future generations of electronic devices.The first part of the thesis is focused on the electrical characterisation of Ultra-Shallow Junction (USJs) Si diodes. Both p+n and n+p USJ structures that contained different implants were examined. These were very highly doped and intended to simulate the situation where a doping well is formed after heavy doping in Si for the fabrication of transistors currently used in Complementary-Metal-Oxide-Semiconductor (CMOS) technology. The implanted USJ diodes were provided by NXP, Belgium and contact deposition was performed before their electrical characterisation as part of this project. Subsequently the p+n and n+p USJ diodes were characterised by the use of Capacitance-Voltage (CV), Current-Voltage (IV), Deep Level Transient Spectroscopy (DLTS) and high resolution Laplace DLTS (LDLTS). DLTS and LDLTS are very powerful spectroscopic techniques for the profiling of defects in the bandgap of a semiconductor as well as for the identification of the electrical signatures of these defects. Transient-Enhanced Diffusion (TED) related defects were detected in these diodes as the presence of mainly carbon-related interstitial complexes was observed. In addition, certain vacancy or vacancy-dopant related levels were also discerned.The second part of this thesis presents the electrical characterisation from Schottky p-diamond/p-Si and p-diamond/n-Si p-n diodes. These diodes were readily provided, grown by the Chemical Vapour Deposition (CVD) technique, for the electrical characterisation that was performed as part of this project. The purpose of characterising both Schottky and p-n diamond on Si diodes was to detect defects near the surface of the films and near the interface with Si and hence provide a comparison between defects present at the beginning and end of growth. More defects were found near the interface with Si and the majority of observed defects were related to extended defects while the presence of grain boundaries in polycrystalline diamond was discussed.

A Generalised Fault Protection Structure Proposed for Uni-grounded Low-Voltage AC Microgrids

NASA Astrophysics Data System (ADS)

Bui, Duong Minh; Chen, Shi-Lin; Lien, Keng-Yu; Jiang, Jheng-Lun

2016-04-01

This paper presents three main configurations of uni-grounded low-voltage AC microgrids. Transient situations of a uni-grounded low-voltage (LV) AC microgrid (MG) are simulated through various fault tests and operation transition tests between grid-connected and islanded modes. Based on transient simulation results, available fault protection methods are proposed for main and back-up protection of a uni-grounded AC microgrid. In addition, concept of a generalised fault protection structure of uni-grounded LVAC MGs is mentioned in the paper. As a result, main contributions of the paper are: (i) definition of different uni-grounded LVAC MG configurations; (ii) analysing transient responses of a uni-grounded LVAC microgrid through line-to-line faults, line-to-ground faults, three-phase faults and a microgrid operation transition test, (iii) proposing available fault protection methods for uni-grounded microgrids, such as: non-directional or directional overcurrent protection, under/over voltage protection, differential current protection, voltage-restrained overcurrent protection, and other fault protection principles not based on phase currents and voltages (e.g. total harmonic distortion detection of currents and voltages, using sequence components of current and voltage, 3I0 or 3V0 components), and (iv) developing a generalised fault protection structure with six individual protection zones to be suitable for different uni-grounded AC MG configurations.

Prolonged action potential duration in cardiac ablation of PDK1 mice.

PubMed

Han, Zhonglin; Jiang, Yu; Yang, Zhongzhou; Cao, Kejiang; Wang, Dao W

2015-01-01

The involvement of the AGC protein kinase family in regulating arrhythmia has drawn considerable attention, but the underlying mechanisms are still not clear. The aim of this study is to explore the role of 3-phosphoinositide-dependent protein kinase-1 (PDK1), one of upstream protein kinases of the AGC protein kinase family, in the pathogenesis of dysregulated electrophysiological basis. PDK1(F/F) αMHC-Cre mice and PDK1(F/F) mice were divided into experiment group and control group. Using patch clamping technology, we explored action potential duration in both groups, and investigated the functions of transient outward potassium channel and L-type Ca(2+) channel to explain the abnormal action potential duration. Significant prolongation action potential duration was found in mice with PDK1 deletion. Further, the peak current of transient outward potassium current and L-type Ca(2+) current were decreased by 84% and 49% respectively. In addition, dysregulation of channel kinetics lead to action potential duration prolongation further. In conclusion, we have demonstrated that PDK1 participates in action potential prolongation in cardiac ablation of PDK1 mice. This effect is likely to be mediated largely through downregulation of transient outward potassium current. These findings indicate the modulation of the PDK1 pathway could provide a new mechanism for abnormal electrophysiological basis.

Profiling of Current Transients in Capacitor Type Diamond Sensors

PubMed Central

Gaubas, Eugenijus; Ceponis, Tomas; Meskauskaite, Dovile; Kazuchits, Nikolai

2015-01-01

The operational characteristics of capacitor-type detectors based on HPHT and CVD diamond have been investigated using perpendicular and parallel injection of carrier domain regimes. Simulations of the drift-diffusion current transients have been implemented by using dynamic models based on Shockley-Ramo’s theorem, under injection of localized surface domains and of bulk charge carriers. The bipolar drift-diffusion regimes have been analyzed for the photo-induced bulk domain (packet) of excess carriers. The surface charge formation and polarization effects dependent on detector biasing voltage have been revealed. The screening effects ascribed to surface charge and to dynamics of extraction of the injected bulk excess carrier domain have been separated and explained. The parameters of drift mobility of the electrons μe = 4000 cm2/Vs and holes μh = 3800 cm2/Vs have been evaluated for CVD diamond using the perpendicular profiling of currents. The coefficient of carrier ambipolar diffusion Da = 97 cm2/s and the carrier recombination lifetime τR,CVD ≌ 110 ns in CVD diamond were extracted by combining analysis of the transients of the sensor current and the microwave probed photoconductivity. The carrier trapping with inherent lifetime τR,HPHT ≌ 2 ns prevails in HPHT diamond. PMID:26061200

Transient transition from free carrier metallic state to exciton insulating state in GaAs by ultrafast photoexcitation

NASA Astrophysics Data System (ADS)

Nie, X. C.; Song, Hai-Ying; Zhang, Xiu; Gu, Peng; Liu, Shi-Bing; Li, Fan; Meng, Jian-Qiao; Duan, Yu-Xia; Liu, H. Y.

2018-03-01

We present systematic studies of the transient dynamics of GaAs by ultrafast time-resolved reflectivity. In photoexcited non-equilibrium states, we found a sign reverse in reflectivity change ΔR/R, from positive around room temperature to negative at cryogenic temperatures. The former corresponds to a free carrier metallic state, while the latter is attributed to an exciton insulating state, in which the transient electronic properties is mostly dominated by excitons, resulting in a transient metal–insulator transition (MIT). Two transition temperatures (T 1 and T 2) are well identified by analyzing the intensity change of the transient reflectivity. We found that photoexcited MIT starts emerging at T 1 as high as ∼ 230 K, in terms of a dip feature at 0.4 ps, and becomes stabilized below T 2 that is up to ∼ 180 K, associated with a negative constant after 40 ps. Our results address a phase diagram that provides a framework for the inducing of MIT through temperature and photoexcitation, and may shed light on the understanding of light-semiconductor interaction and exciton physics.

Novae as a Class of Transient X-ray Sources

NASA Technical Reports Server (NTRS)

Mukai, K.; Orio, M.; Valle, M. Della

2007-01-01

Motivated by the recently discovered class of faint (10(exp 34)-10(exp 35) ergs/s) X-ray transients in the Galactic Center region, we investigate the 2-10 keV properties of classical and recurrent novae. Existing data are consistent with the idea that all classical novae are transient X-ray sources with durations of months to years and peak luminosities in the 10(exp 34)-10(exp 35)ergs/s range. This makes classical novae a viable candidate class for the faint Galactic Center transients. We estimate the rate of classical novae within a 15 arcmin radius region centered on the Galactic Center (roughly the field of view of XMM-Newton observations centered on Sgr A*) to be approx.0.1 per year. Therefore, it is plausible that some of the Galactic Center transients that have been announced to date are unrecognized classical novae. The continuing monitoring of the Galactic Center region carried out by Chandra and XMM-Newton may therefore provide a new method to detect classical novae in this crowded and obscured region, an

VOEventNet: An Open Source of Transient Alerts for Astronomers.

NASA Astrophysics Data System (ADS)

Drake, Andrew J.; Williams, R.; Graham, M. J.; Mahabal, A.; Djorgovski, S. G.; White, R. R.; Vestrand, W. T.; Bloom, J.

2007-12-01

Event based astronomy is acquiring an increasingly important role in astronomy as large time-domain surveys such as Palomar Transient Factory (PTF), Pan-STARRs, SkyMapper and Allan Telescope Array (ATA) surveys come online. These surveys are expected to discover thousands of transients each year ranging from near earth asteroids to distant SNe. Although the primary instruments for of these surveys are in place, in order to fully utilize these event discovery streams, automated alerting and follow-up is a necessity. For the past two years the VOEventNet network has been globally distributing information about transient astronomical events using the VOEvent format, a Virtual Observatory standard. Events messages are openly distributed so that follow-up can utilize the most appropriate resources available in order to characterize the nature of the transients. Since its inception VOEventNet has broadcast more than 3500 SDSSSS Supernova candidates, 3300 GRB alert and follow-up notices from GCN, 700 OGLE microlensing event candidates, and 4300 newly discovered asteroid and optical transient candidates from the Palomar Quest survey. Additional transient event streams are expected this season including optical transients from the Catalina Sky Survey. VOEventNet astronomical transient events streams are available to all astronomers via traditional HTML tables, RSS news-feeds, real-time publication (via Jabber and TCP), and Google Sky mashups. VOEventNet currently carries out optical transient event follow-up with the Palomar 60 and 200in (Caltech), Faulkes Telescopes North and South (LCOGTN), RAPTOR (LANL), and PARITEL (UCB; CfA).

Changes in the action potential and transient outward potassium current in cardiomyocytes during acute cardiac rejection in rats.

PubMed

Luo, Wenqi; Jia, Yixin; Zheng, Shuai; Li, Yan; Han, Jie; Meng, Xu

2017-01-01

Acute cardiac rejection contributes to the changes in the electrophysiological properties of grafted hearts. However, the electrophysiological changes of cardiomyocytes during acute cardiac rejection are still unknown. An understanding of the electrophysiological mechanisms of cardiomyocytes could improve the diagnosis and treatment of acute cardiac rejection. So it is important to characterize the changes in the action potential ( AP ) and the transient outward potassium current ( I to ) in cardiomyocytes during acute cardiac rejection. Heterotopic heart transplantation was performed in allogeneic [Brown Norway (BN)-to-Lewis] and isogeneic (BN-to-BN) rats. Twenty models were established in each group. Ten recipients were sacrificed at the 2nd day and the other ten recipients were sacrificed at the 4 th day after the operation in each group. Histopathological examinations of the grafted hearts were performed in half of the recipients in each group randomly. The other half of the grafted hearts were excised rapidly and enzymatically dissociated to obtain single cardiomyocytes. The AP and I to current were recorded using the whole cell patch-clamp technique. Forty grafted hearts were successfully harvested and used in experiments. Histologic examination showed mild rejection at the 2 nd day and moderate rejection at the 4 th day in the allogeneic group after cardiac transplantation, while no evidence of histologic lesions of rejection were observed in the isogeneic group. Compared with the isogeneic group, the action potential duration ( APD ) of cardiomyocytes in the allogeneic group was significantly prolonged ( APD 90 was 49.28±5.621 mV in the isogeneic group and 88.08±6.445 mV in the allogeneic group at the 2 nd day, P=0.0016; APD 90 was 59.34±5.183 mV in the isogeneic group and 104.0±9.523 mV in the allogeneic group at the 4 th day, P=0.0064). The current density of I to was significantly decreased at the 4 th day after cardiac transplantation. The APD of cardiomyocytes was significantly prolonged during acute cardiac rejection in rats, which might be partly attributed to decreased current densities of I to .

Transient behavior of an actively mode-locked semiconductor laser diode

NASA Technical Reports Server (NTRS)

Auyeung, J. C.; Bergman, L. A.; Johnston, A. R.

1982-01-01

Experimental investigation was carried out to study the transient regimes during the buildup and decay of the active mode-locked state in a laser diode. The mode locking was achieved through a sinusoidal modulation of the diode current with the laser in an external cavity. The pulse shape evolution and the time constants for the buildup and decay were determined.

Finite difference time domain calculation of transients in antennas with nonlinear loads

NASA Technical Reports Server (NTRS)

Luebbers, Raymond J.; Beggs, John H.; Kunz, Karl S.; Chamberlin, Kent

1991-01-01

Determining transient electromagnetic fields in antennas with nonlinear loads is a challenging problem. Typical methods used involve calculating frequency domain parameters at a large number of different frequencies, then applying Fourier transform methods plus nonlinear equation solution techniques. If the antenna is simple enough so that the open circuit time domain voltage can be determined independently of the effects of the nonlinear load on the antennas current, time stepping methods can be applied in a straightforward way. Here, transient fields for antennas with more general geometries are calculated directly using Finite Difference Time Domain (FDTD) methods. In each FDTD cell which contains a nonlinear load, a nonlinear equation is solved at each time step. As a test case, the transient current in a long dipole antenna with a nonlinear load excited by a pulsed plane wave is computed using this approach. The results agree well with both calculated and measured results previously published. The approach given here extends the applicability of the FDTD method to problems involving scattering from targets, including nonlinear loads and materials, and to coupling between antennas containing nonlinear loads. It may also be extended to propagation through nonlinear materials.

Investigation of transient melting of tungsten by ELMs in ASDEX Upgrade

NASA Astrophysics Data System (ADS)

Krieger, K.; Sieglin, B.; Balden, M.; Coenen, J. W.; Göths, B.; Laggner, F.; de Marne, P.; Matthews, G. F.; Nille, D.; Rohde, V.; Dejarnac, R.; Faitsch, M.; Giannone, L.; Herrmann, A.; Horacek, J.; Komm, M.; Pitts, R. A.; Ratynskaia, S.; Thoren, E.; Tolias, P.; ASDEX-Upgrade Team; EUROfusion MST1 Team

2017-12-01

Repetitive melting of tungsten by power transients originating from edge localized modes (ELMs) has been studied in the tokamak experiment ASDEX Upgrade. Tungsten samples were exposed to H-mode discharges at the outer divertor target plate using the Divertor Manipulator II system. The exposed sample was designed with an elevated sloped surface inclined against the incident magnetic field to increase the projected parallel power flux to a level were transient melting by ELMs would occur. Sample exposure was controlled by moving the outer strike point to the sample location. As extension to previous melt studies in the new experiment both the current flow from the sample to vessel potential and the local surface temperature were measured with sufficient time resolution to resolve individual ELMs. The experiment provided for the first time a direct link of current flow and surface temperature during transient ELM events. This allows to further constrain the MEMOS melt motion code predictions and to improve the validation of its underlying model assumptions. Post exposure ex situ analysis of the retrieved samples confirms the decreased melt motion observed at shallower magnetic field line to surface angles compared to that at leading edges exposed to the parallel power flux.

The performance of cable braids and terminations to lightning induced transients

NASA Technical Reports Server (NTRS)

Crofts, David

1991-01-01

The latest specification detailing the test waveforms for indirect lightning transients as applied to aircraft wiring systems specify very high voltages and currents. Although considerable data exists for measuring cable screen leakage using such methods as surface transfer impedance and bulk cable injection, there is little data on the likely core transient level that is likely to be induced from these threats. In particular, the new Waveform 5 at very high current levels (10 kA) is reputed to cause severe cable damage. A range of representative cables were made with various screen termination techniques and screening levels. These were tested first to determine their relative screening performance and then they were subjected to lightning transient testing to all the specified waveforms. Core voltages were measured for each test. Tests were also performed on bundles with fewer wires to determine the failure criteria with Waveform 5 and these tests also include flat conductor cables. The test showed that correctly terminated cable bundles performed well in all the tests and would provide a high level of protection to the electronic systems. The use of overbraides, provided the individual screens are well terminated, appears to be unnecessary.

Advanced analysis technique for the evaluation of linear alternators and linear motors

NASA Technical Reports Server (NTRS)

Holliday, Jeffrey C.

1995-01-01

A method for the mathematical analysis of linear alternator and linear motor devices and designs is described, and an example of its use is included. The technique seeks to surpass other methods of analysis by including more rigorous treatment of phenomena normally omitted or coarsely approximated such as eddy braking, non-linear material properties, and power losses generated within structures surrounding the device. The technique is broadly applicable to linear alternators and linear motors involving iron yoke structures and moving permanent magnets. The technique involves the application of Amperian current equivalents to the modeling of the moving permanent magnet components within a finite element formulation. The resulting steady state and transient mode field solutions can simultaneously account for the moving and static field sources within and around the device.

Gingerols: a novel class of vanilloid receptor (VR1) agonists

PubMed Central

Dedov, Vadim N; Tran, Van H; Duke, Colin C; Connor, Mark; Christie, MacDonald J; Mandadi, Sravan; Roufogalis, Basil D

2002-01-01

Gingerols, the pungent constituents of ginger, were synthesized and assessed as agonists of the capsaicin-activated VR1 (vanilloid) receptor. [6]-Gingerol and [8]-gingerol evoked capsaicin-like intracellular Ca2+ transients and ion currents in cultured DRG neurones. These effects of gingerols were blocked by capsazepine, the VR1 receptor antagonist. The potency of gingerols increased with increasing size of the side chain and with the overall hydrophobicity in the series. We conclude that gingerols represent a novel class of naturally occurring VR1 receptor agonists that may contribute to the medicinal properties of ginger, which have been known for centuries. The gingerol structure may be used as a template for the development of drugs acting as moderately potent activators of the VR1 receptor. PMID:12411409

Towards a unified description of the hydrogen bond network of liquid water: A dynamics based approach

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

Ozkanlar, Abdullah, E-mail: abdullah.ozkanlar@wsu.edu; Zhou, Tiecheng; Clark, Aurora E., E-mail: auclark@wsu.edu

2014-12-07

The definition of a hydrogen bond (H-bond) is intimately related to the topological and dynamic properties of the hydrogen bond network within liquid water. The development of a universal H-bond definition for water is an active area of research as it would remove many ambiguities in the network properties that derive from the fixed definition employed to assign whether a water dimer is hydrogen bonded. This work investigates the impact that an electronic-structure based definition, an energetic, and a geometric definition of the H-bond has upon both topological and dynamic network behavior of simulated water. In each definition, the usemore » of a cutoff (either geometric or energetic) to assign the presence of a H-bond leads to the formation of transiently bonded or broken dimers, which have been quantified within the simulation data. The relative concentration of transient species, and their duration, results in two of the three definitions sharing similarities in either topological or dynamic features (H-bond distribution, H-bond lifetime, etc.), however no two definitions exhibit similar behavior for both classes of network properties. In fact, two networks with similar local network topology (as indicated by similar average H-bonds) can have dramatically different global network topology (as indicated by the defect state distributions) and altered H-bond lifetimes. A dynamics based correction scheme is then used to remove artificially transient H-bonds and to repair artificially broken bonds within the network such that the corrected network exhibits the same structural and dynamic properties for two H-bond definitions (the properties of the third definition being significantly improved). The algorithm described represents a significant step forward in the development of a unified hydrogen bond network whose properties are independent of the original hydrogen bond definition that is employed.« less

Patterning of wound-induced intercellular Ca2+ flashes in a developing epithelium

NASA Astrophysics Data System (ADS)

Narciso, Cody; Wu, Qinfeng; Brodskiy, Pavel; Garston, George; Baker, Ruth; Fletcher, Alexander; Zartman, Jeremiah

2015-10-01

Differential mechanical force distributions are increasingly recognized to provide important feedback into the control of an organ’s final size and shape. As a second messenger that integrates and relays mechanical information to the cell, calcium ions (Ca2+) are a prime candidate for providing important information on both the overall mechanical state of the tissue and resulting behavior at the individual-cell level during development. Still, how the spatiotemporal properties of Ca2+ transients reflect the underlying mechanical characteristics of tissues is still poorly understood. Here we use an established model system of an epithelial tissue, the Drosophila wing imaginal disc, to investigate how tissue properties impact the propagation of Ca2+ transients induced by laser ablation. The resulting intercellular Ca2+ flash is found to be mediated by inositol 1,4,5-trisphosphate and depends on gap junction communication. Further, we find that intercellular Ca2+ transients show spatially non-uniform characteristics across the proximal-distal axis of the larval wing imaginal disc, which exhibit a gradient in cell size and anisotropy. A computational model of Ca2+ transients is employed to identify the principle factors explaining the spatiotemporal patterning dynamics of intercellular Ca2+ flashes. The relative Ca2+ flash anisotropy is principally explained by local cell shape anisotropy. Further, Ca2+ velocities are relatively uniform throughout the wing disc, irrespective of cell size or anisotropy. This can be explained by the opposing effects of cell diameter and cell elongation on intercellular Ca2+ propagation. Thus, intercellular Ca2+ transients follow lines of mechanical tension at velocities that are largely independent of tissue heterogeneity and reflect the mechanical state of the underlying tissue.

A New Solution for Confined-Unconfined Flow Toward a Fully Penetrating Well in a Confined Aquifer.

PubMed

Xiao, Liang; Ye, Ming; Xu, Yongxin

2018-02-08

Transient confined-unconfined flow conversion caused by pumping in a confined aquifer (i.e., piezometric head drops below the top confined layer) is complicated, partly due to different hydraulic properties between confined and unconfined regions. For understanding mechanism of the transient confined-unconfined conversion, this paper develops a new analytical solution for the transient confined-unconfined flow toward a fully penetrating well in a confined aquifer. The analytical solution is used to investigate the impacts on drawdown simulation by differences of hydraulic properties, including transmissivity, storativity, and diffusivity defined as a ratio of transmissivity and storativity, between the confined and unconfined regions. It is found that neglecting the transmissivity difference may give an overestimation of drawdown. Instead, neglecting the diffusivity difference may lead to an underestimation of drawdown. The shape of drawdown-time curve is sensitive to the change of storativity ratio, S/S y , between the confined and unconfined regions. With a series of drawdown data from pumping tests, the analytical solution can also be used to inversely estimate following parameters related to the transient confined-unconfined conversion: radial distance of conversion interface, diffusivity, and specific yield of the unconfined region. It is concluded that using constant transmissivity and diffusivity in theory can result in biased estimates of radial distance of the conversion interface and specific yield of the unconfined region in practice. The analytical solution is useful to gain insight about various factors related to the transient confined-unconfined conversion and can be used for the design of mine drainage and groundwater management in the mining area. © 2018, National Ground Water Association.

Activation of muscarinic M3 receptors inhibits large-conductance voltage- and Ca2+-activated K+ channels in rat urinary bladder smooth muscle cells

PubMed Central

Parajuli, Shankar P.

2013-01-01

Large conductance voltage- and Ca2+-activated K+ (BK) channels are key regulators of detrusor smooth muscle (DSM) contraction and relaxation during urine voiding and storage. Here, we explored whether BK channels are regulated by muscarinic receptors (M-Rs) in native freshly isolated rat DSM cells under physiological conditions using the perforated whole cell patch-clamp technique and pharmacological inhibitors. M-R activation with carbachol (1 μM) initially evoked large transient outward BK currents, followed by inhibition of the spontaneous transient outward BK currents (STBKCs) in DSM cells. Carbachol (1 μM) also inhibited the amplitude and frequency of spontaneous transient hyperpolarizations (STHs) and depolarized the DSM cell membrane potential. Selective inhibition of the muscarinic M3 receptors (M3-Rs) with 4-diphenylacetoxy-N-methylpiperidine (4-DAMP; 0.1 μM), but not muscarinic M2 receptors with methoctramine (1 μM), blocked the carbachol inhibitory effects on STBKCs. Furthermore, blocking the inositol 1,4,5-triphosphate (IP3) receptors with xestospongin-C (1 μM) inhibited the carbachol-induced large transient outward BK currents without affecting carbachol inhibitory effects on STBKCs. Upon pharmacological inhibition of all known cellular sources of Ca2+ for BK channel activation, carbachol (1 μM) did not affect the voltage-step-induced steady-state BK currents, suggesting that the muscarinic effects in DSM cells are mediated by mobilization of intracellular Ca2+. In conclusion, our findings provide strong evidence that activation of M3-Rs leads to inhibition of the STBKCs, STHs, and depolarization of DSM cells. Collectively, the data suggest the existence of functional interactions between BK channels and M3-Rs at a cellular level in DSM. PMID:23703523

Experiments on transient melting of tungsten by ELMs in ASDEX Upgrade

NASA Astrophysics Data System (ADS)

Krieger, K.; Balden, M.; Coenen, J. W.; Laggner, F.; Matthews, G. F.; Nille, D.; Rohde, V.; Sieglin, B.; Giannone, L.; Göths, B.; Herrmann, A.; de Marne, P.; Pitts, R. A.; Potzel, S.; Vondracek, P.; ASDEX-Upgrade Team; EUROfusion MST1 Team

2018-02-01

Repetitive melting of tungsten by power transients originating from edge localized modes (ELMs) has been studied in ASDEX Upgrade. Tungsten samples were exposed to H-mode discharges at the outer divertor target plate using the divertor manipulator II (DIM-II) system (Herrmann et al 2015 Fusion Eng. Des. 98-9 1496-9). Designed as near replicas of the geometries used also in separate experiments on the JET tokamak (Coenen et al 2015 J. Nucl. Mater. 463 78-84 Coenen et al 2015 Nucl. Fusion 55 023010; Matthews et al 2016 Phys. Scr. T167 7), the samples featured a misaligned leading edge and a sloped ridge respectively. Both structures protrude above the default target plate surface thus receiving an increased fraction of the parallel power flux. Transient melting by ELMs was induced by moving the outer strike point to the sample location. The temporal evolution of the measured current flow from the samples to vessel potential confirmed transient melting. Current magnitude and dependency from surface temperature provided strong evidence for thermionic electron emission as main origin of the replacement current driving the melt motion. The different melt patterns observed after exposures at the two sample geometries support the thermionic electron emission model used in the MEMOS melt motion code, which assumes a strong decrease of the thermionic net current at shallow magnetic field to surface angles (Pitts et al 2017 Nucl. Mater. Energy 12 60-74). Post exposure ex situ analysis of the retrieved samples show recrystallization of tungsten at the exposed surface areas to a depth of up to several mm. The melt layer transport to less exposed surface areas leads to ratcheting pile up of re-solidified debris with zonal growth extending from the already enlarged grains at the surface.

Transient, biocompatible electronics and energy harvesters based on ZnO.

PubMed

Dagdeviren, Canan; Hwang, Suk-Won; Su, Yewang; Kim, Stanley; Cheng, Huanyu; Gur, Onur; Haney, Ryan; Omenetto, Fiorenzo G; Huang, Yonggang; Rogers, John A

2013-10-25

The combined use of ZnO, Mg, MgO, and silk provides routes to classes of thin-film transistors and mechanical energy harvesters that are soluble in water and biofluids. Experimental and theoretical studies of the operational aspects and dissolution properties of this type of transient electronics technology illustrate its various capabilities. Application opportunities range from resorbable biomedical implants, to environmentally dissolvable sensors, and degradable consumer electronics. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Shear Forces during Blast, Not Abrupt Changes in Pressure Alone, Generate Calcium Activity in Human Brain Cells

DTIC Science & Technology

2012-06-29

the tissue-force interaction(s) and the cellular damage properties remain unresolved. Studies on a mechanical head model demonstrated high transient...that pressure transient. In vitro models of primary blast injury [5,18,19] are likewise limited by an absence of real-time, high spatial and temporal... models , as well as with human injuries in which expression of bTBI symptoms among different individuals that are exposed to the same blast is

Transient Plume Model Testing Using LADEE Spacecraft Attitude Control System Operations

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

Woronowicz, M. S.

2011-05-20

The Lunar Atmosphere Dust Environment Explorer (LADEE) spacecraft is being designed for a mission featuring low altitude orbits of the Moon to take relevant ambient measurements before that environment becomes altered by future exploration activities. Instruments include a neutral mass spectrometer capable of measuring ambient species density levels below 100 molecules/cm{sup 3}. Coincidentally, with a favorable combination of spacecraft orientations, it is also possible to measure plume gases from LADEE attitude control system thruster operations as they are reflected from the daytime lunar surface and subsequently intercepted by the spacecraft as it orbits overhead. Under such circumstances, it may bemore » possible to test a variety of properties and assumptions associated with various transient plume models or to infer certain aspects regarding lunar surface properties.« less

Transient Plume Model Testing Using LADEE Spacecraft Attitude Control System Operations

NASA Technical Reports Server (NTRS)

Woronowicz, M. S.

2010-01-01

The Lunar Atmosphere Dust Environment Explorer (LADEE) spacecraft is being designed for a mission featuring low altitude orbits of the Moon to take relevant ambient measurements before that environment becomes altered by future exploration activities. Instruments include a neutral mass spectrometer capable of measuring ambient species density levels below 100 molecules/cu cm. Coincidentally, with a favorable combination of spacecraft orientations, it is also possible to measure plume gases from LADEE attitude control system thruster operations as they are reflected from the daytime lunar surface and subsequently intercepted by the spacecraft as it orbits overhead. Under such circumstances, it may be possible to test a variety of properties and assumptions associated with various transient plume models or to infer certain aspects regarding lunar surface properties.

Inhibition of spontaneous activity of rabbit atrioventricular node cells by KB-R7943 and inhibitors of sarcoplasmic reticulum Ca2+ ATPase

PubMed Central

Cheng, Hongwei; Smith, Godfrey L.; Hancox, Jules C.; Orchard, Clive H.

2011-01-01

The atrioventricular node (AVN) can act as a subsidiary cardiac pacemaker if the sinoatrial node fails. In this study, we investigated the effects of the Na–Ca exchange (NCX) inhibitor KB-R7943, and inhibition of the sarcoplasmic reticulum calcium ATPase (SERCA), using thapsigargin or cyclopiazonic acid (CPA), on spontaneous action potentials (APs) and [Ca2+]i transients from cells isolated from the rabbit AVN. Spontaneous [Ca2+]i transients were monitored from undialysed AVN cells at 37 °C using Fluo-4. In separate experiments, spontaneous APs and ionic currents were recorded using the whole-cell patch clamp technique. Rapid application of 5 μM KB-R7943 slowed or stopped spontaneous APs and [Ca2+]i transients. However, in voltage clamp experiments in addition to blocking NCX current (INCX) KB-R7943 partially inhibited L-type calcium current (ICa,L). Rapid reduction of external [Na+] also abolished spontaneous activity. Inhibition of SERCA (using 2.5 μM thapsigargin or 30 μM CPA) also slowed or stopped spontaneous APs and [Ca2+]i transients. Our findings are consistent with the hypothesis that sarcoplasmic reticulum (SR) Ca2+ release influences spontaneous activity in AVN cells, and that this occurs via [Ca2+]i-activated INCX; however, the inhibitory action of KB-R7943 on ICa,L means that care is required in the interpretation of data obtained using this compound. PMID:21163524

Changes in left ventricular repolarization and ion channel currents following a transient rate increase superimposed on bradycardia in anesthetized dogs.

PubMed

Rubart, M; Lopshire, J C; Fineberg, N S; Zipes, D P

2000-06-01

We previously demonstrated in dogs that a transient rate increase superimposed on bradycardia causes prolongation of ventricular refractoriness that persists for hours after resumption of bradycardia. In this study, we examined changes in membrane currents that are associated with this phenomenon. The whole cell, patch clamp technique was used to record transmembrane voltages and currents, respectively, in single mid-myocardial left ventricular myocytes from dogs with 1 week of complete AV block; dogs either underwent 1 hour of left ventricular pacing at 120 beats/min or did not undergo pacing. Pacing significantly heightened mean phase 1 and peak plateau amplitudes by approximately 6 and approximately 3 mV, respectively (P < 0.02), and prolonged action potential duration at 90% repolarization from 235+/-8 msec to 278+/-8 msec (1 Hz; P = 0.02). Rapid pacing-induced changes in transmembrane ionic currents included (1) a more pronounced cumulative inactivation of the 4-aminopyridine-sensitive transient outward K+ current, Ito, over the range of physiologic frequencies, resulting from a approximately 30% decrease in the population of quickly reactivating channels; (2) increases in peak density of L-type Ca2+ currents, I(Ca.L), by 15% to 35 % between +10 and +60 mV; and (3) increases in peak density of the Ca2+-activated chloride current, I(Cl.Ca), by 30% to 120% between +30 and +50 mV. Frequency-dependent reduction in Ito combined with enhanced I(Ca.L) causes an increase in net inward current that may be responsible for the observed changes in ventricular repolarization. This augmentation of net cation influx is partially antagonized by an increase in outward I(Ca.Cl).

Hypotonic Shock Modulates Na+ Current via a Cl- and Ca2+/Calmodulin Dependent Mechanism in Alveolar Epithelial Cells

PubMed Central

Tatur, Sabina; Brochiero, Emmanuelle; Grygorczyk, Ryszard; Berthiaume, Yves

2013-01-01

Alveolar epithelial cells are involved in Na+ absorption via the epithelial Na+ channel (ENaC), an important process for maintaining an appropriate volume of liquid lining the respiratory epithelium and for lung oedema clearance. Here, we investigated how a 20% hypotonic shock modulates the ionic current in these cells. Polarized alveolar epithelial cells isolated from rat lungs were cultured on permeant filters and their electrophysiological properties recorded. A 20% bilateral hypotonic shock induced an immediate, but transient 52% rise in total transepithelial current and a 67% increase in the amiloride-sensitive current mediated by ENaC. Amiloride pre-treatment decreased the current rise after hypotonic shock, showing that ENaC current is involved in this response. Since Cl- transport is modulated by hypotonic shock, its contribution to the basal and hypotonic-induced transepithelial current was also assessed. Apical NPPB, a broad Cl- channel inhibitor and basolateral DIOA a potassium chloride co-transporter (KCC) inhibitor reduced the total and ENaC currents, showing that transcellular Cl- transport plays a major role in that process. During hypotonic shock, a basolateral Cl- influx, partly inhibited by NPPB is essential for the hypotonic-induced current rise. Hypotonic shock promoted apical ATP secretion and increased intracellular Ca2+. While apyrase, an ATP scavenger, did not inhibit the hypotonic shock current response, W7 a calmodulin antagonist completely prevented the hypotonic current rise. These results indicate that a basolateral Cl- influx as well as Ca2+/calmodulin, but not ATP, are involved in the acute transepithelial current rise elicited by hypotonic shock. PMID:24019969

Properties of Supergiant Fast X-Ray Transients as Observed by Swift

NASA Technical Reports Server (NTRS)

Romano, P.; Vercellone, S.; Krimm, H. A.; Esposito, P.; Cusumano, C.; LaParola, V.; Mangano, V.; Kennea, J. A.; Burrows, D. N.; Pagani, C.;

Transient cnoidal waves explain the formation and geometry of fault damage zones

NASA Astrophysics Data System (ADS)

Veveakis, Manolis; Schrank, Christoph

2017-04-01

The spatial footprint of a brittle fault is usually dominated by a wide area of deformation bands and fractures surrounding a narrow, highly deformed fault core. This diffuse damage zone relates to the deformation history of a fault, including its seismicity, and has a significant impact on flow and mechanical properties of faulted rock. Here, we propose a new mechanical model for damage-zone formation. It builds on a novel mathematical theory postulating fundamental material instabilities in solids with internal mass transfer associated with volumetric deformation due to elastoviscoplastic p-waves termed cnoidal waves. We show that transient cnoidal waves triggered by fault slip events can explain the characteristic distribution and extent of deformation bands and fractures within natural fault damage zones. Our model suggests that an overpressure wave propagating away from the slipping fault and the material properties of the host rock control damage-zone geometry. Hence, cnoidal-wave theory may open a new chapter for predicting seismicity, material and geometrical properties as well as the location of brittle faults.

Analyzing neuronal networks using discrete-time dynamics

NASA Astrophysics Data System (ADS)

Ahn, Sungwoo; Smith, Brian H.; Borisyuk, Alla; Terman, David

2010-05-01

We develop mathematical techniques for analyzing detailed Hodgkin-Huxley like models for excitatory-inhibitory neuronal networks. Our strategy for studying a given network is to first reduce it to a discrete-time dynamical system. The discrete model is considerably easier to analyze, both mathematically and computationally, and parameters in the discrete model correspond directly to parameters in the original system of differential equations. While these networks arise in many important applications, a primary focus of this paper is to better understand mechanisms that underlie temporally dynamic responses in early processing of olfactory sensory information. The models presented here exhibit several properties that have been described for olfactory codes in an insect’s Antennal Lobe. These include transient patterns of synchronization and decorrelation of sensory inputs. By reducing the model to a discrete system, we are able to systematically study how properties of the dynamics, including the complex structure of the transients and attractors, depend on factors related to connectivity and the intrinsic and synaptic properties of cells within the network.

Unique membrane properties and enhanced signal processing in human neocortical neurons.

PubMed

Eyal, Guy; Verhoog, Matthijs B; Testa-Silva, Guilherme; Deitcher, Yair; Lodder, Johannes C; Benavides-Piccione, Ruth; Morales, Juan; DeFelipe, Javier; de Kock, Christiaan Pj; Mansvelder, Huibert D; Segev, Idan

2016-10-06

The advanced cognitive capabilities of the human brain are often attributed to our recently evolved neocortex. However, it is not known whether the basic building blocks of the human neocortex, the pyramidal neurons, possess unique biophysical properties that might impact on cortical computations. Here we show that layer 2/3 pyramidal neurons from human temporal cortex (HL2/3 PCs) have a specific membrane capacitance ( C m ) of ~0.5 µF/cm 2 , half of the commonly accepted 'universal' value (~1 µF/cm 2 ) for biological membranes. This finding was predicted by fitting in vitro voltage transients to theoretical transients then validated by direct measurement of C m in nucleated patch experiments. Models of 3D reconstructed HL2/3 PCs demonstrated that such low C m value significantly enhances both synaptic charge-transfer from dendrites to soma and spike propagation along the axon. This is the first demonstration that human cortical neurons have distinctive membrane properties, suggesting important implications for signal processing in human neocortex.

Layer-Dependent Ultrafast Carrier and Coherent Phonon Dynamics in Black Phosphorus.

PubMed

Miao, Xianchong; Zhang, Guowei; Wang, Fanjie; Yan, Hugen; Ji, Minbiao

2018-05-09

Black phosphorus is a layered semiconducting material, demonstrating strong layer-dependent optical and electronic properties. Probing the photophysical properties on ultrafast time scales is of central importance in understanding many-body interactions and nonequilibrium quasiparticle dynamics. Here, we applied temporally, spectrally, and spatially resolved pump-probe microscopy to study the transient optical responses of mechanically exfoliated few-layer black phosphorus, with layer numbers ranging from 2 to 9. We have observed layer-dependent resonant transient absorption spectra with both photobleaching and red-shifted photoinduced absorption features, which could be attributed to band gap renormalization of higher subband transitions. Surprisingly, coherent phonon oscillations with unprecedented intensities were observed when the probe photons were in resonance with the optical transitions, which correspond to the low-frequency layer-breathing mode. Our results reveal strong Coulomb interactions and electron-phonon couplings in photoexcited black phosphorus, providing important insights into the ultrafast optical, nanomechanical, and optoelectronic properties of this novel two-dimensional material.

Emergent ultrafast phenomena in correlated oxides and heterostructures

NASA Astrophysics Data System (ADS)

Gandolfi, M.; Celardo, G. L.; Borgonovi, F.; Ferrini, G.; Avella, A.; Banfi, F.; Giannetti, C.

2017-03-01

The possibility of investigating the dynamics of solids on timescales faster than the thermalization of the internal degrees of freedom has disclosed novel non-equilibrium phenomena that have no counterpart at equilibrium. Transition metal oxides (TMOs) provide an interesting playground in which the correlations among the charges in the metal d-orbitals give rise to a wealth of intriguing electronic and thermodynamic properties involving the spin, charge, lattice and orbital orders. Furthermore, the physical properties of TMOs can be engineered at the atomic level, thus providing the platform to investigate the transport phenomena on timescales of the order of the intrinsic decoherence time of the charge excitations. Here, we review and discuss three paradigmatic examples of transient emerging properties that are expected to open new fields of research: (i) the creation of non-thermal magnetic states in spin-orbit Mott insulators; (ii) the possible exploitation of quantum paths for the transport and collection of charge excitations in heterostructures; (iii) the transient wave-like behavior of the temperature field in strongly anisotropic TMOs.

Supergiant fast X-ray transients with Swift: Spectroscopic and temporal properties

NASA Astrophysics Data System (ADS)

Romano, P.; Mangano, V.; Ducci, L.; Esposito, P.; Farinelli, R.; Ceccobello, C.; Vercellone, S.; Burrows, D. N.; Kennea, J. A.; Krimm, H. A.; Gehrels, N.

2012-12-01

Supergiant fast X-ray transients (SFXTs) are a class of high-mass X-ray binaries with possible counterparts in the high energy gamma rays. The Swift SFXT Project1 has conducted a systematic investigation of the properties of SFTXs on timescales ranging from minutes to years and in several intensity states (from bright flares, to intermediate intensity states, and down to almost quiescence). We also performed broad-band spectroscopy of outbursts, and intensity-selected spectroscopy outside of outbursts. We demonstrated that while the brightest phase of the outburst only lasts a few hours, further activity is observed at lower fluxes for a remarkably longer time, up to weeks. Furthermore, we assessed the fraction of the time these sources spend in each phase, and their duty cycle of inactivity. We present the most recent results from our investigation. The spectroscopic and, most importantly, timing properties of SFXTs we have uncovered with Swift will serve as a guide in search for the high energy emission from these enigmatic objects.

A transient laboratory method for determining the hydraulic properties of 'tight' rocks-II. Application

USGS Publications Warehouse

Neuzil, C.E.; Cooley, C.; Silliman, Stephen E.; Bredehoeft, J.D.; Hsieh, P.A.

1981-01-01

In Part I a general analytical solution for the transient pulse test was presented. Part II presents a graphical method for analyzing data from a test to obtain the hydraulic properties of the sample. The general solution depends on both hydraulic conductivity and specific storage and, in theory, analysis of the data can provide values for both of these hydraulic properties. However, in practice, one of two limiting cases may apply in which case it is possible to calculate only hydraulic conductivity or the product of hydraulic conductivity times specific storage. In this paper we examine the conditions when both hydraulic parameters can be calculated. The analyses of data from two tests are presented. In Appendix I the general solution presented in Part I is compared with an earlier analysis, in which compressive storage in the sample is assumed negligible, and the error in calculated hydraulic conductivity due to this simplifying assumption is examined. ?? 1981.

Modeling of environmentally induced transients within satellites

NASA Technical Reports Server (NTRS)

Stevens, N. John; Barbay, Gordon J.; Jones, Michael R.; Viswanathan, R.

1987-01-01

A technique is described that allows an estimation of possible spacecraft charging hazards. This technique, called SCREENS (spacecraft response to environments of space), utilizes the NASA charging analyzer program (NASCAP) to estimate the electrical stress locations and the charge stored in the dielectric coatings due to spacecraft encounter with a geomagnetic substorm environment. This information can then be used to determine the response of the spacecraft electrical system to a surface discharge by means of lumped element models. The coupling into the electronics is assumed to be due to magnetic linkage from the transient currents flowing as a result of the discharge transient. The behavior of a spinning spacecraft encountering a severe substorm is predicted using this technique. It is found that systems are potentially vulnerable to upset if transient signals enter through the ground lines.

Effect of Intense Optical Excitation on Internal Electric Field Evolution in CdTe Gamma-Ray Detectors

NASA Astrophysics Data System (ADS)

Suzuki, K.; Ichinohe, Y.; Seto, S.

2018-03-01

The time-of-flight (TOF) transient currents in radiation detectors made of CdTe and Cd0.9Zn0.1Te (CZT) have been measured at several optical excitation intensities to investigate the effect of drifting carriers on the internal field. Both detectors show so-called space-charge-perturbed (SCP) current under intense optical excitation. A Monte Carlo (MC) simulation combined with an iterative solution of Poisson's equation is used to reproduce the observed currents under several bias voltages and excitation intensities. The SCP theory describes well the transient current in the CZT detector, whereas injection of holes from the anode and a corresponding reduction of the electron lifetime are further required to describe that in the CdTe detector. We visualize the temporal changes in the charge distribution and internal electric field profiles of both detectors.

Effect of load transients on SOFC operation—current reversal on loss of load

NASA Astrophysics Data System (ADS)

Gemmen, Randall S.; Johnson, Christopher D.

The dynamics of solid oxide fuel cell (SOFC) operation have been considered previously, but mainly through the use of one-dimensional codes applied to co-flow fuel cell systems. In this paper several geometries are considered, including cross-flow, co-flow, and counter-flow. The details of the model are provided, and the model is compared with some initial experimental data. For parameters typical of SOFC operation, a variety of transient cases are investigated, including representative load increase and decrease and system shutdown. Of particular note for large load decrease conditions (e.g., shutdown) is the occurrence of reverse current over significant portions of the cell, starting from the moment of load loss up to the point where equilibrated conditions again provide positive current. Consideration is given as to when such reverse current conditions might most significantly impact the reliability of the cell.

Protection of Renewable-dominated Microgrids: Challenges and Potential Solutions.

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

Elkhatib, Mohamed; Ellis, Abraham; Milan Biswal

keywords : Microgrid Protection, Impedance Relay, Signal Processing-based Fault Detec- tion, Networked Microgrids, Communication-Assisted Protection In this report we address the challenge of designing efficient protection system for inverter- dominated microgrids. These microgrids are characterised with limited fault current capacity as a result of current-limiting protection functions of inverters. Typically, inverters limit their fault contribution in sub-cycle time frame to as low as 1.1 per unit. As a result, overcurrent protection could fail completely to detect faults in inverter-dominated microgrids. As part of this project a detailed literature survey of existing and proposed microgrid protection schemes were conducted. The surveymore » concluded that there is a gap in the available microgrid protection methods. The only credible protection solution available in literature for low- fault inverter-dominated microgrids is the differential protection scheme which represents a robust transmission-grade protection solution but at a very high cost. Two non-overcurrent protection schemes were investigated as part of this project; impedance-based protection and transient-based protection. Impedance-based protection depends on monitoring impedance trajectories at feeder relays to detect faults. Two communication-based impedance-based protection schemes were developed. the first scheme utilizes directional elements and pilot signals to locate the fault. The second scheme depends on a Central Protection Unit that communicates with all feeder relays to locate the fault based on directional flags received from feeder relays. The later approach could potentially be adapted to protect networked microgrids and dynamic topology microgrids. Transient-based protection relies on analyzing high frequency transients to detect and locate faults. This approach is very promising but its implementation in the filed faces several challenges. For example, high frequency transients due to faults can be confused with transients due to other events such as capacitor switching. Additionally, while detecting faults by analyzing transients could be doable, locating faults based on analyzing transients is still an open question.« less

Protection of Renewable-dominated Microgrids: Challenges and Potential Solutions

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

Elkhatib, Mohamed; Ellis, Abraham; Biswal, Milan

In this report we address the challenge of designing efficient protection system for inverter- dominated microgrids. These microgrids are characterised with limited fault current capacity as a result of current-limiting protection functions of inverters. Typically, inverters limit their fault contribution in sub-cycle time frame to as low as 1.1 per unit. As a result, overcurrent protection could fail completely to detect faults in inverter-dominated microgrids. As part of this project a detailed literature survey of existing and proposed microgrid protection schemes were conducted. The survey concluded that there is a gap in the available microgrid protection methods. The only crediblemore » protection solution available in literature for low- fault inverter-dominated microgrids is the differential protection scheme which represents a robust transmission-grade protection solution but at a very high cost. Two non-overcurrent protection schemes were investigated as part of this project; impedance-based protection and transient-based protection. Impedance-based protection depends on monitoring impedance trajectories at feeder relays to detect faults. Two communication-based impedance-based protection schemes were developed. the first scheme utilizes directional elements and pilot signals to locate the fault. The second scheme depends on a Central Protection Unit that communicates with all feeder relays to locate the fault based on directional flags received from feeder relays. The later approach could potentially be adapted to protect networked microgrids and dynamic topology microgrids. Transient-based protection relies on analyzing high frequency transients to detect and locate faults. This approach is very promising but its implementation in the filed faces several challenges. For example, high frequency transients due to faults can be confused with transients due to other events such as capacitor switching. Additionally, while detecting faults by analyzing transients could be doable, locating faults based on analyzing transients is still an open question.« less

BIN1 is reduced and Cav1.2 trafficking is impaired in human failing cardiomyocytes.

PubMed

Hong, Ting-Ting; Smyth, James W; Chu, Kevin Y; Vogan, Jacob M; Fong, Tina S; Jensen, Brian C; Fang, Kun; Halushka, Marc K; Russell, Stuart D; Colecraft, Henry; Hoopes, Charles W; Ocorr, Karen; Chi, Neil C; Shaw, Robin M

2012-05-01

Heart failure is a growing epidemic, and a typical aspect of heart failure pathophysiology is altered calcium transients. Normal cardiac calcium transients are initiated by Cav1.2 channels at cardiac T tubules. Bridging integrator 1 (BIN1) is a membrane scaffolding protein that causes Cav1.2 to traffic to T tubules in healthy hearts. The mechanisms of Cav1.2 trafficking in heart failure are not known. To study BIN1 expression and its effect on Cav1.2 trafficking in failing hearts. Intact myocardium and freshly isolated cardiomyocytes from nonfailing and end-stage failing human hearts were used to study BIN1 expression and Cav1.2 localization. To confirm Cav1.2 surface expression dependence on BIN1, patch-clamp recordings were performed of Cav1.2 current in cell lines with and without trafficking-competent BIN1. Also, in adult mouse cardiomyocytes, surface Cav1.2 and calcium transients were studied after small hairpin RNA-mediated knockdown of BIN1. For a functional readout in intact heart, calcium transients and cardiac contractility were analyzed in a zebrafish model with morpholino-mediated knockdown of BIN1. BIN1 expression is significantly decreased in failing cardiomyocytes at both mRNA (30% down) and protein (36% down) levels. Peripheral Cav1.2 is reduced to 42% by imaging, and a biochemical T-tubule fraction of Cav1.2 is reduced to 68%. The total calcium current is reduced to 41% in a cell line expressing a nontrafficking BIN1 mutant. In mouse cardiomyocytes, BIN1 knockdown decreases surface Cav1.2 and impairs calcium transients. In zebrafish hearts, BIN1 knockdown causes a 75% reduction in calcium transients and severe ventricular contractile dysfunction. The data indicate that BIN1 is significantly reduced in human heart failure, and this reduction impairs Cav1.2 trafficking, calcium transients, and contractility. Copyright © 2012 Heart Rhythm Society. Published by Elsevier Inc. All rights reserved.

BIN1 is Reduced and Cav1.2 Trafficking is Impaired in Human Failing Cardiomyocytes

PubMed Central

Hong, Ting-Ting; Smyth, James W.; Chu, Kevin Y.; Vogan, Jacob M.; Fong, Tina S.; Jensen, Brian C.; Fang, Kun; Halushka, Marc K.; Russell, Stuart D.; Colecraft, Henry; Hoopes, Charles W.; Ocorr, Karen; Chi, Neil C.; Shaw, Robin M.

2011-01-01

Background Heart failure is a growing epidemic and a typical aspect of heart failure pathophysiology is altered calcium transients. Normal cardiac calcium transients are initiated by Cav1.2 channels at cardiac T-tubules. BIN1 is a membrane scaffolding protein that causes Cav1.2 to traffic to T-tubules in healthy hearts. The mechanisms of Cav1.2 trafficking in heart failure are not known. Objective To study BIN1 expression and its effect on Cav1.2 trafficking in failing hearts. Methods Intact myocardium and freshly isolated cardiomyocytes from non-failing and end-stage failing human hearts were used to study BIN1 expression and Cav1.2 localization. To confirm Cav1.2 surface expression dependence on BIN1, patch clamp recordings were performed of Cav1.2 current in cell lines with and without trafficking competent BIN1. Also, in adult mouse cardiomyocytes, surface Cav1.2 and calcium transients were studied after shRNA mediated knockdown of BIN1. For a functional readout in intact heart, calcium transients and cardiac contractility were analyzed in a zebrafish model with morpholino mediated knockdown of BIN1. Results BIN1 expression is significantly decreased in failing cardiomyocytes at both mRNA (30% down) and protein (36% down) levels. Peripheral Cav1.2 is reduced 42% by imaging and biochemical T-tubule fraction of Cav1.2 is reduced 68%. Total calcium current is reduced 41% in a cell line expressing non-trafficking BIN1 mutant. In mouse cardiomyocytes, BIN1 knockdown decreases surface Cav1.2 and impairs calcium transients. In zebrafish hearts, BIN1 knockdown causes a 75% reduction in calcium transients and severe ventricular contractile dysfunction. Conclusions The data indicate that BIN1 is significantly reduced in human heart failure, and this reduction impairs Cav1.2 trafficking, calcium transients, and contractility. PMID:22138472

Starting Performance Analysis for Universal Motors by FEM

NASA Astrophysics Data System (ADS)

Kurihara, Kazumi; Sakamoto, Shin-Ichi

This paper presents a novel transient analysis of the universal motors taking into account the time-varying brush-contact resistance and mechanical loss. The transient current, torque and speed during the starting process are computed by solving the electromagnetic, circuit and dynamic motion equations, simultaneously. The computed performances have been validated by tests in a 500-W, 2-pole, 50Hz, 100V universal motor.

High energy transients: The millisecond domain

NASA Astrophysics Data System (ADS)

Rao, A. R.

2018-02-01

The search for high energy transients in the millisecond domain has come to the focus in recent times due to the detection of gravitational wave events and the identification of fast radio bursts as cosmological sources. Here we highlight the sensitivity limitations in the currently operating hard X-ray telescopes and give some details of the search for millisecond events in the AstroSat CZT Imager data.

Simulations for the Development of Thermoelectric Measurements

NASA Astrophysics Data System (ADS)

Zabrocki, Knud; Ziolkowski, Pawel; Dasgupta, Titas; de Boor, Johannes; Müller, Eckhard

2013-07-01

In thermoelectricity, continuum theoretical equations are usually used for the calculation of the characteristics and performance of thermoelectric elements, modules or devices as a function of external parameters (material, geometry, temperatures, current, flow, load, etc.). An increasing number of commercial software packages aimed at applications, such as COMSOL and ANSYS, contain vkernels using direct thermoelectric coupling. Application of these numerical tools also allows analysis of physical measurement conditions and can lead to specifically adapted methods for developing special test equipment required for the determination of TE material and module properties. System-theoretical and simulation-based considerations of favorable geometries are taken into account to create draft sketches in the development of such measurement systems. Particular consideration is given to the development of transient measurement methods, which have great advantages compared with the conventional static methods in terms of the measurement duration required. In this paper the benefits of using numerical tools in designing measurement facilities are shown using two examples. The first is the determination of geometric correction factors in four-point probe measurement of electrical conductivity, whereas the second example is focused on the so-called combined thermoelectric measurement (CTEM) system, where all thermoelectric material properties (Seebeck coefficient, electrical and thermal conductivity, and Harman measurement of zT) are measured in a combined way. Here, we want to highlight especially the measurement of thermal conductivity in a transient mode. Factors influencing the measurement results such as coupling to the environment due to radiation, heat losses via the mounting of the probe head, as well as contact resistance between the sample and sample holder are illustrated, analyzed, and discussed. By employing the results of the simulations, we have developed an improved sample head that allows for measurements over a larger temperature interval with enhanced accuracy.

Possible use of the 'Pi of the Sky' system in a space situational awareness program

NASA Astrophysics Data System (ADS)

Wawrzaszek, Roman; Wawer, Piotr; Sokolowski, Marcin; Nawrocki, Krzysztof; Pietrzak, Robert; Malek, Katarzyna; Zaremba, Marcin; Piotrowski, Lech W.

2009-06-01

The "Pi of the Sky" system was initially created for searching of optical partners of gamma ray bursts [5,7]. The system is located in Chile and consists of two CCD cameras on a common mounting base [1]. Currently, it performs various astronomical observations [1,5,7,8]. Among others, system also records passages of satellites and fragments of Earth's artificial satellites, so called "space debris". Since now, this kind of data was identify as a disturbing transient signal and team members usually focus on identify and eliminating it. Handle of this problem is especially important, because software algorithm which search for optical companion of gamma ray bursts focus on transient phenomena events. On the other hand, comparison of the "Pi of the Sky" system parameters with different facilities which are used for space debris searching and monitoring shows, that its properties are similar to some of those systems. It means, that it should be possible, to obtain valuable data of artificial satellites motion analyzing "Pi of the Sky" data. Moreover, expected in the near future system upgraded to 6 small telescopes equipped totally with 24 CCD detectors system [1] will cover a major part of the sky (field of view of each detector equals 20 x 20 degrees) which gives possibility of visual measurements objects up to 16 magnitude. It will be an unusual advantage in the field of system categories with that size. In the paper, we would like to shortly describe a space debris community activities, present properties of selected systems which are using for space debris surveys and finally examples of observational data will be presented.

Compensation and persistent photocapacitance in homoepitaxial Sn-doped β-Ga2O3

NASA Astrophysics Data System (ADS)

Polyakov, A. Y.; Smirnov, N. B.; Shchemerov, I. V.; Gogova, D.; Tarelkin, S. A.; Pearton, S. J.

2018-03-01

The electrical properties of epitaxial β-Ga2O3 doped with Sn (1016-9 × 1018 cm-3) and grown by metalorganic chemical vapor deposition on semi-insulating β-Ga2O3 substrates are reported. Shallow donors attributable to Sn were observed only in a narrow region near the film/substrate interface and with a much lower concentration than the total Sn density. For heavily Sn doped films (Sn concentration, 9 × 1018 cm-3), the electrical properties in the top portion of the layer were determined by deep centers with a level at Ec-0.21 eV not described previously. In more lightly doped layers, the Ec-0.21 eV centers and deeper traps at Ec-0.8 eV were present, with the latter pinning the Fermi level. Low temperature photocapacitance and capacitance voltage measurements of illuminated samples indicated the presence of high densities (1017-1018 cm-3) of deep acceptors with an optical ionization threshold of 2.3 eV. Optical deep level transient spectroscopy (ODLTS) and photoinduced current transient spectroscopy (PICTS) detected electron traps at Ec-0.8 eV and Ec-1.1 eV. For lightly doped layers, the compensation of film conductivity was mostly provided by the Ec-2.3 eV acceptors. For heavily Sn doped films, deep acceptor centers possibly related to Ga vacancies were significant. The photocapacitance and the photocurrent caused by illumination at low temperatures were persistent, with an optical threshold of 1.9 eV and vanished only at temperatures of ˜400 K. The capture barrier for electrons causing the persistent photocapacitance effect was estimated from ODLTS and PICTS to be 0.25-0.35 eV.

Dynamical Networks Characterization of Geomagnetic Substorms and Transient Response to the Solar Wind State.

NASA Astrophysics Data System (ADS)

Chapman, S. C.; Dods, J.; Gjerloev, J. W.

2017-12-01

Observations of how the solar wind interacts with earth's magnetosphere, and its dynamical response, are increasingly becoming a data analytics challenge. Constellations of satellites observe the solar corona, the upstream solar wind and throughout earth's magnetosphere. These data are multipoint in space and extended in time, so in principle are ideal for study using dynamical networks to characterize the full time evolving spatial pattern. We focus here on analysis of data from the full set of 100+ auroral ground based magnetometer stations that have been collated by SuperMAG. Spatio-temporal patterns of correlation between the magnetometer time series can be used to form a dynamical network [1]. The properties of the network can then be captured by (time dependent) network parameters. This offers the possibility of characterizing detailed spatio-temporal pattern by a few parameters, so that many events can then be compared [2] with each other. Whilst networks are in widespread use in the data analytics of societal and commercial data, there are additional challenges in their application to physical timeseries. Determining whether two nodes (here, ground based magnetometer stations) are connected in a network (seeing the same dynamics) requires normalization w.r.t. the detailed sensitivities and dynamical responses of specific observing stations and seasonal conductivity variations and we have developed methods to achieve this dynamical normalization. The detailed properties of the network capture time dependent spatial correlation in the magnetometer responses and we will show how this can be used to infer a transient current system response to magnetospheric activity. [l] Dods et al, J. Geophys. Res 120, doi:10.1002/2015JA02 (2015). [2] Dods et al, J. Geophys. Res. 122, doi:10.1002/2016JA02 (2017).

Optimization methodology for the global 10 Hz orbit feedback in RHIC

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

Liu, Chuyu; Hulsart, R.; Mernick, K.

To combat beam oscillations induced by triplet vibrations at the Relativistic Heavy Ion Collider (RHIC), a global orbit feedback system was developed and applied at injection and top energy in 2011, and during beam acceleration in 2012. Singular Value Decomposition (SVD) was employed to determine the strengths and currents of the applied corrections. The feedback algorithm was optimized for different magnetic configurations (lattices) at fixed beam energies and during beam acceleration. While the orbit feedback performed well since its inception, corrector current transients and feedback-induced beam oscillations were observed during the polarized proton program in 2015. In this paper, wemore » present the feedback algorithm, the optimization of the algorithm for various lattices and the solution adopted to mitigate the observed current transients during beam acceleration.« less

Optimization methodology for the global 10 Hz orbit feedback in RHIC

DOE PAGES

Liu, Chuyu; Hulsart, R.; Mernick, K.; ...

2018-05-08

To combat beam oscillations induced by triplet vibrations at the Relativistic Heavy Ion Collider (RHIC), a global orbit feedback system was developed and applied at injection and top energy in 2011, and during beam acceleration in 2012. Singular Value Decomposition (SVD) was employed to determine the strengths and currents of the applied corrections. The feedback algorithm was optimized for different magnetic configurations (lattices) at fixed beam energies and during beam acceleration. While the orbit feedback performed well since its inception, corrector current transients and feedback-induced beam oscillations were observed during the polarized proton program in 2015. In this paper, wemore » present the feedback algorithm, the optimization of the algorithm for various lattices and the solution adopted to mitigate the observed current transients during beam acceleration.« less

Pulsed Eddy Current Probe Design Based on Transient Circuit Analysis

NASA Astrophysics Data System (ADS)

Cadeau, Trevor J.; Krause, Thomas W.

2009-03-01

Probe design parameters affecting depth of penetration of pulsed eddy currents in multi-layer aluminum 2024-T3 were examined. Several probe designs were evaluated for their ability to detect a discontinuity at the bottom of a stack of aluminum plates. The reflection type probes, consisting of pick-up coil and encircling drive coil, were characterized based on their transient response to a square pulse excitation. Probes with longer fundamental time constants, equivalent to a lower driving frequency, generated greater depth of penetration. However, additional factors such as inductive and resistive load, and excessive coil heating were also factors that limited signal-to-noise response with increasing layer thickness.

Modeling of two-phase flow instabilities during startup transients utilizing RAMONA-4B methodology

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

Paniagua, J.; Rohatgi, U.S.; Prasad, V.

1996-10-01

RAMONA-4B code is currently under development for simulating thermal hydraulic instabilities that can occur in Boiling Water Reactors (BWRs) and the Simplified Boiling Water Reactor (SBWR). As one of the missions of RAMONA-4B is to simulate SBWR startup transients, where geysering or condensation-induced instability may be encountered, the code needs to be assessed for this application. This paper outlines the results of the assessments of the current version of RAMONA-4B and the modifications necessary for simulating the geysering or condensation-induced instability. The test selected for assessment are the geysering tests performed by Prof Aritomi (1993).

Single Protein Structural Analysis with a Solid-state Nanopore Sensor

NASA Astrophysics Data System (ADS)

Li, Jiali; Golovchenko, Jene; McNabb, David

2005-03-01

We report on the use of solid-state nanopore sensors to detect single polypeptides. These solid-state nanopores are fabricated in thin membranes of silicon nitride by ion beam sculpting...[1]. When an electrically biased nanopore is exposed to denatured proteins in ionic solution, discrete transient electronic signals: current blockages are observed. We demonstrate examples of such transient electronic signals for Bovine Serum Albumin (BSA) and human placental laminin M proteins in Guanidine hydrochloride solution, which suggest that these polypeptides are individually translocating through the nanopore during the detecting process. The amplitude of the current blockages is proportional to the bias voltage. No transient current blockages are observed when proteins are not present in the solution. To probe protein-folding state, pH and temperature dependence experiments are performed. The results demonstrate a solid-state nanopore sensor can be used to detect and analyze single polypeptide chains. Similarities and differences with signals obtained from double stranded DNA in a solid-state nanopore and single stranded DNA in a biological nanopore are discussed. [.1] Li, J., D. Stein, C. McMullan, D. Branton, M.J. Aziz, and J.A. Golovchenko, Ion-beam sculpting at nanometre length scales. Nature, 2001. 412(12 July): p. 166-169.

Repassivation Investigations on Aluminium: Physical Chemistry of the Passive State

NASA Astrophysics Data System (ADS)

Nagy, Tristan Oliver; Weimerskirch, Morris Jhängi Joseph; Pacher, Ulrich; Kautek, Wolfgang

2016-09-01

We show the temporal change in repassivation mechanism as a time-dependent linear combination of a high-field model of oxide growth (HFM) and the point defect model (PDM). The observed switch in transient repassivation current-decrease under potentiostatic control occurs independently of the active electrode size and effective repassivation time for all applied overpotentials. For that, in situ depassivation of plasma electrolytically oxidized (PEO) coatings on aluminium was performed with nanosecond laser pulses at 266 nm and the repassivation current transients were recorded as a function of pulse number. A mathematical model combines the well established theories of oxide-film formation and growth kinetics, giving insight in the non linear transient behaviour of micro-defect passivation. According to our findings, the repassivation process can be described as a charge consumption via two concurrent channels. While the major current-decay at the very beginning of the fast healing oxide follows a point-defect type exponential damping, the HFM mechanism supersedes gradually, the longer the repassivation evolves. Furthermore, the material seems to reminisce former laser treatments via defects built-in during depassivation, leading to a higher charge contribution of the PDM mechanism at higher pulse numbers.

Agonist-dependence of recovery from desensitization of P2X3 receptors provides a novel and sensitive approach for their rapid up or downregulation

PubMed Central

Sokolova, Elena; Skorinkin, Andrei; Fabbretti, Elsa; Masten, Lara; Nistri, Andrea; Giniatullin, Rashid

2004-01-01

Fast-desensitizing P2X3 receptors of nociceptive dorsol root ganglion (DRG) neurons are thought to mediate pain sensation. Since P2X3 receptor efficiency is powerfully modulated by desensitization, its underlying properties were studied with patch-clamp recording. On rat cultured DRG neurons, 2 s application of ATP (EC50=1.52 μM), ADP (EC50=1.1 μM) or α,β-meATP (EC50=1.78 μM) produced similar inward currents that fully desensitized, at the same rate, back to baseline. Recovery from desensitization was much slower after ATP and ADP than after α,β-meATP and, in all cases, it had sigmoidal time course. By alternating the application of ATP and α,β-meATP, we observed complete cross-desensitization indicating that these agonists activated the same receptors. This notion was confirmed by the similar antagonism induced by 2′, 3′-O-(2,4,6,trinitrophenyl)-adenosine triphosphate (TNP-ATP). Recovery from desensitization elicited by ATP was unexpectedly shaped by transient application of α,β-methylene-adenosine triphosphate (α,β-meATP), and vice versa. Thus, short-lasting, full desensitization produced by α,β-meATP protected receptors from long-lasting desensitization induced by subsequent ATP applications. ATP and ADP had similar properties of recovery from desensitization. Low nM concentrations of α,β-meATP (unable to evoke membrane currents) could speed up recovery from ATP-induced desensitization, while low nM concentrations of ATP enhanced it. Ambient ATP levels were found to be in the pM range (52±3 pM). The phenomenon of cross-desensitization and protection was reproduced by rP2X3 receptors expressed by rat osteoblastic cell 17/2.8 or human embryonic kidney cell 293 cells, indicating P2X3 receptor specificity. It is suggested that transient application of an agonist that generates rapid recovery from desensitization, is a novel, powerful tool to modulate P2X3 receptor responsiveness to the natural agonist ATP. PMID:14980981

Electrochemical, Structural and Magnetic Analysis of Electrodeposited CoCu/Cu Multilayers: Influence of Cu Layer Deposition Potential

NASA Astrophysics Data System (ADS)

Tekgül, Atakan; Kockar, Hakan; Kuru, Hilal; Alper, Mürsel; ÜnlÜ, C. Gökhan

2018-03-01

The electrochemical, structural and magnetic properties of CoCu/Cu multilayers electrodeposited at different cathode potentials were investigated from a single bath. The Cu layer deposition potentials were selected as - 0.3, V - 0.4 V, and - 0.5 V with respect to saturated calomel electrode (SCE) while the Co layer deposition potential was constant at - 1.5 V versus SCE. For the electrochemical analysis, the current-time transients were obtained. The amount of noble non-magnetic (Cu) metal materials decreased with the increase of deposition potentials due to anomalous codeposition. Further, current-time transient curves for the Co layer deposition and capacitance were calculated. In the structural analysis, the multilayers were found to be polycrystalline with both Co and Cu layers adopting the face-centered cubic structure. The (111) peak shifts towards higher angle with the increase of the deposition potentials. Also, the lattice parameters of the multilayers decrease from 0.3669 nm to 0.3610 nm with the increase of the deposition potentials from - 0.3 V to - 0.5 V, which corresponds to the bulk values of Cu and Co, respectively. The electrochemical and structural results demonstrate that the amount of Co atoms increased and the Cu atoms decreased in the layers with the increase of deposition potentials due to anomalous codeposition. For magnetic measurements, the saturation magnetizations, M_s obtained from the magnetic curves of the multilayers were obtained as 212 kA/m, 276 kA/m, and 366 kA/m with - 0.3 V, - 0.4 V, and - 0.5 V versus SCE, respectively. It is seen that the M_s values increased with the increase of the deposition potentials confirming the increase of the Co atoms and decrease of the Cu amount. The results of electrochemical and structural analysis show that the deposition potentials of non-magnetic layers plays important role on the amount of magnetic and non-magnetic materials in the layers and thus on the magnetic properties of the multilayers.

Slow Crack Growth and Fatigue Life Prediction of Ceramic Components Subjected to Variable Load History

NASA Technical Reports Server (NTRS)

Jadaan, Osama

2001-01-01

Present capabilities of the NASA CARES/Life (Ceramic Analysis and Reliability Evaluation of Structures/Life) code include probabilistic life prediction of ceramic components subjected to fast fracture, slow crack growth (stress corrosion), and cyclic fatigue failure modes. Currently, this code has the capability to compute the time-dependent reliability of ceramic structures subjected to simple time-dependent loading. For example, in slow crack growth (SCG) type failure conditions CARES/Life can handle the cases of sustained and linearly increasing time-dependent loads, while for cyclic fatigue applications various types of repetitive constant amplitude loads can be accounted for. In real applications applied loads are rarely that simple, but rather vary with time in more complex ways such as, for example, engine start up, shut down, and dynamic and vibrational loads. In addition, when a given component is subjected to transient environmental and or thermal conditions, the material properties also vary with time. The objective of this paper is to demonstrate a methodology capable of predicting the time-dependent reliability of components subjected to transient thermomechanical loads that takes into account the change in material response with time. In this paper, the dominant delayed failure mechanism is assumed to be SCG. This capability has been added to the NASA CARES/Life (Ceramic Analysis and Reliability Evaluation of Structures/Life) code, which has also been modified to have the ability of interfacing with commercially available FEA codes executed for transient load histories. An example involving a ceramic exhaust valve subjected to combustion cycle loads is presented to demonstrate the viability of this methodology and the CARES/Life program.

Temporal and spatial adaptation of transient responses to local features

PubMed Central

O'Carroll, David C.; Barnett, Paul D.; Nordström, Karin

2012-01-01

Interpreting visual motion within the natural environment is a challenging task, particularly considering that natural scenes vary enormously in brightness, contrast and spatial structure. The performance of current models for the detection of self-generated optic flow depends critically on these very parameters, but despite this, animals manage to successfully navigate within a broad range of scenes. Within global scenes local areas with more salient features are common. Recent work has highlighted the influence that local, salient features have on the encoding of optic flow, but it has been difficult to quantify how local transient responses affect responses to subsequent features and thus contribute to the global neural response. To investigate this in more detail we used experimenter-designed stimuli and recorded intracellularly from motion-sensitive neurons. We limited the stimulus to a small vertically elongated strip, to investigate local and global neural responses to pairs of local “doublet” features that were designed to interact with each other in the temporal and spatial domain. We show that the passage of a high-contrast doublet feature produces a complex transient response from local motion detectors consistent with predictions of a simple computational model. In the neuron, the passage of a high-contrast feature induces a local reduction in responses to subsequent low-contrast features. However, this neural contrast gain reduction appears to be recruited only when features stretch vertically (i.e., orthogonal to the direction of motion) across at least several aligned neighboring ommatidia. Horizontal displacement of the components of elongated features abolishes the local adaptation effect. It is thus likely that features in natural scenes with vertically aligned edges, such as tree trunks, recruit the greatest amount of response suppression. This property could emphasize the local responses to such features vs. those in nearby texture within the scene. PMID:23087617

A novel SOD mimic with a redox-modulating mn (II) complex, ML1 attenuates high glucose-induced abnormalities in intracellular Ca2+ transients and prevents cardiac cell death through restoration of mitochondrial function.

PubMed

Kain, Vasundhara; Sawant, Mithila A; Dasgupta, Aparajita; Jaiswal, Gaurav; Vyas, Alok; Padhye, Subhash; Sitasawad, Sandhya L

2016-03-01

A key contributor to the pathophysiology of diabetic cardiomyopathy, mitochondrial superoxide can be adequately countered by Mn-superoxide dismutase, which constitutes the first line of defense against mitochondrial oxidative stress. Our group has recently synthesized low molecular weight SOD mimics, demonstrating superior protection against oxidative damages to kidney cells. In the current study, we sought to evaluate the protective effect of the SOD mimic ML1 against high glucose induced cardiomyopathy in diabetes. Mechanistic studies using rat cardiac myoblast H9c2 showed that ML1 markedly inhibited High Glucose (HG) induced cytotoxicity. This was associated with increased Mn-SOD expression along with decreased mitochondrial [Formula: see text], ONOO- and Ca 2+ accumulation, unveiling its anti-oxidant potentials. ML1 also attenuated HG-induced loss of mitochondrial membrane potential (Δ Ψ m ) and release of cytochrome c, suggesting that ML1 effectuates its cytoprotective action via the preservation of mitochondrial function. In an ex-vivo model normal adult rat ventricular myocytes (ARVMs) were isolated and cultured in either normal glucose (5.5 mmol/l glucose) or HG (25.5 mmol/l glucose) conditions and the efficiency of ML-1 was analyzed by studying contractile function and calcium indices. Mechanical properties were assessed using a high-speed video-edge detection system, and intracellular Ca 2+ transients were recorded in fura-2-loaded myocytes. Pretreatment of myocytes with ML1 (10 nM) ameliorated HG induced abnormalities in relaxation including depressed peak shortening, prolonged time to 90% relenghthening, and slower Ca 2+ transient decay. Thus, ML1 exhibits significant cardio protection against oxidative damage, perhaps through its potent antioxidant action via activation of Mn-SOD.

Two New Calcium-rich Gap Transients in Group and Cluster Environments

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

Lunnan, R.; Kasliwal, M. M.; Cao, Y.

We present the Palomar Transient Factory discoveries and the photometric and spectroscopic observations of PTF11kmb and PTF12bho. We show that both transients have properties consistent with the class of calcium-rich gap transients, specifically lower peak luminosities and rapid evolution compared to ordinary supernovae, and a nebular spectrum dominated by [Ca ii] emission. A striking feature of both transients is their host environments: PTF12bho is an intracluster transient in the Coma Cluster, while PTF11kmb is located in a loose galaxy group, at a physical offset ~150 kpc from the most likely host galaxy. Deep Subaru imaging of PTF12bho rules out anmore » underlying host system to a limit of M R > -8.0 mag, while Hubble Space Telescope imaging of PTF11kmb reveals a marginal counterpart that, if real, could be either a background galaxy or a globular cluster. Here, we show that the offset distribution of Ca-rich gap transients is significantly more extreme than that seen for SNe Ia or even short-hard gamma-ray bursts (sGRBs). Thus, if the offsets are caused by a kick, they require higher kick velocities and/or longer merger times than sGRBs. Finally, we also show that almost all Ca-rich transients found to date are in group and cluster environments with elliptical host galaxies, indicating a very old progenitor population; the remote locations could partially be explained by these environments having the largest fraction of stars in the intragroup/intracluster light following galaxy-galaxy interactions.« less

Two New Calcium-rich Gap Transients in Group and Cluster Environments

DOE PAGES

Lunnan, R.; Kasliwal, M. M.; Cao, Y.; ...

2017-02-08

We present the Palomar Transient Factory discoveries and the photometric and spectroscopic observations of PTF11kmb and PTF12bho. We show that both transients have properties consistent with the class of calcium-rich gap transients, specifically lower peak luminosities and rapid evolution compared to ordinary supernovae, and a nebular spectrum dominated by [Ca ii] emission. A striking feature of both transients is their host environments: PTF12bho is an intracluster transient in the Coma Cluster, while PTF11kmb is located in a loose galaxy group, at a physical offset ~150 kpc from the most likely host galaxy. Deep Subaru imaging of PTF12bho rules out anmore » underlying host system to a limit of M R > -8.0 mag, while Hubble Space Telescope imaging of PTF11kmb reveals a marginal counterpart that, if real, could be either a background galaxy or a globular cluster. Here, we show that the offset distribution of Ca-rich gap transients is significantly more extreme than that seen for SNe Ia or even short-hard gamma-ray bursts (sGRBs). Thus, if the offsets are caused by a kick, they require higher kick velocities and/or longer merger times than sGRBs. Finally, we also show that almost all Ca-rich transients found to date are in group and cluster environments with elliptical host galaxies, indicating a very old progenitor population; the remote locations could partially be explained by these environments having the largest fraction of stars in the intragroup/intracluster light following galaxy-galaxy interactions.« less

Characterization of silicon-on-insulator wafers

NASA Astrophysics Data System (ADS)

Park, Ki Hoon

The silicon-on-insulator (SOI) is attracting more interest as it is being used for an advanced complementary-metal-oxide-semiconductor (CMOS) and a base substrate for novel devices to overcome present obstacles in bulk Si scaling. Furthermore, SOI fabrication technology has improved greatly in recent years and industries produce high quality wafers with high yield. This dissertation investigated SOI material properties with simple, yet accurate methods. The electrical properties of as-grown wafers such as electron and hole mobilities, buried oxide (BOX) charges, interface trap densities, and carrier lifetimes were mainly studied. For this, various electrical measurement techniques were utilized such as pseudo-metal-oxide-semiconductor field-effect-transistor (PseudoMOSFET) static current-voltage (I-V) and transient drain current (I-t), Hall effect, and MOS capacitance-voltage/capacitance-time (C-V/C-t). The electrical characterization, however, mainly depends on the pseudo-MOSFET method, which takes advantage of the intrinsic SOI structure. From the static current-voltage and pulsed measurement, carrier mobilities, lifetimes and interface trap densities were extracted. During the course of this study, a pseudo-MOSFET drain current hysteresis regarding different gate voltage sweeping directions was discovered and the cause was revealed through systematic experiments and simulations. In addition to characterization of normal SOI, strain relaxation of strained silicon-on-insulator (sSOI) was also measured. As sSOI takes advantage of wafer bonding in its fabrication process, the tenacity of bonding between the sSOI and the BOX layer was investigated by means of thermal treatment and high dose energetic gamma-ray irradiation. It was found that the strain did not relax with processes more severe than standard CMOS processes, such as anneals at temperature as high as 1350 degree Celsius.

Molecular and functional differences in voltage-activated sodium currents between GABA projection neurons and dopamine neurons in the substantia nigra

PubMed Central

Ding, Shengyuan; Wei, Wei

2011-01-01

GABA projection neurons (GABA neurons) in the substantia nigra pars reticulata (SNr) and dopamine projection neurons (DA neurons) in substantia nigra pars compacta (SNc) have strikingly different firing properties. SNc DA neurons fire low-frequency, long-duration spikes, whereas SNr GABA neurons fire high-frequency, short-duration spikes. Since voltage-activated sodium (NaV) channels are critical to spike generation, the different firing properties raise the possibility that, compared with DA neurons, NaV channels in SNr GABA neurons have higher density, faster kinetics, and less cumulative inactivation. Our quantitative RT-PCR analysis on immunohistochemically identified nigral neurons indicated that mRNAs for pore-forming NaV1.1 and NaV1.6 subunits and regulatory NaVβ1 and Navβ4 subunits are more abundant in SNr GABA neurons than SNc DA neurons. These α-subunits and β-subunits are key subunits for forming NaV channels conducting the transient NaV current (INaT), persistent Na current (INaP), and resurgent Na current (INaR). Nucleated patch-clamp recordings showed that INaT had a higher density, a steeper voltage-dependent activation, and a faster deactivation in SNr GABA neurons than in SNc DA neurons. INaT also recovered more quickly from inactivation and had less cumulative inactivation in SNr GABA neurons than in SNc DA neurons. Furthermore, compared with nigral DA neurons, SNr GABA neurons had a larger INaR and INaP. Blockade of INaP induced a larger hyperpolarization in SNr GABA neurons than in SNc DA neurons. Taken together, these results indicate that NaV channels expressed in fast-spiking SNr GABA neurons and slow-spiking SNc DA neurons are tailored to support their different spiking capabilities. PMID:21880943

Solar energetic particle events in different types of solar wind

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

Kahler, S. W.; Vourlidas, A., E-mail: stephen.kahler@kirtland.af.mil

2014-08-10

We examine statistically some properties of 96 20 MeV gradual solar energetic proton (SEP) events as a function of three different types of solar wind (SW) as classified by Richardson and Cane. Gradual SEP (E > 10 MeV) events are produced in shocks driven by fast (V ≳ 900 km s{sup –1}) and wide (W > 60°) coronal mass ejections (CMEs). We find no differences among the transient, fast, and slow SW streams for SEP 20 MeV proton event timescales. It has recently been found that the peak intensities Ip of these SEP events scale with the ∼2 MeV protonmore » background intensities, which may be a proxy for the near-Sun shock seed particles. Both the intensities Ip and their 2 MeV backgrounds are significantly enhanced in transient SW compared to those of fast and slow SW streams, and the values of Ip normalized to the 2 MeV backgrounds only weakly correlate with CME V for all SW types. This result implies that forecasts of SEP events could be improved by monitoring both the Sun and the local SW stream properties and that the well known power-law size distributions of Ip may differ between transient and long-lived SW streams. We interpret an observed correlation between CME V and the 2 MeV background for SEP events in transient SW as a manifestation of enhanced solar activity.« less

On tridimensional rip current modeling

NASA Astrophysics Data System (ADS)

Marchesiello, Patrick; Benshila, Rachid; Almar, Rafael; Uchiyama, Yusuke; McWilliams, James C.; Shchepetkin, Alexander

2015-12-01

Do lateral shear instabilities of nearshore circulation account for a substantial part of Very Low-Frequency (VLF) variability? If yes, it would promote stirring and mixing of coastal waters and surf-shelf exchanges. Another question is whether tridimensional transient processes are important for instability generation. An innovative modeling system with tridimensional wave-current interactions was designed to investigate transient nearshore currents and interactions between nearshore and innershelf circulations. We present here some validation of rip current modeling for the Aquitanian coast of France, using in-situ and remote video sensing. We then proceed to show the benefits of 3D versus 2D (depth-mean flow) modeling of rip currents and their low-frequency variability. It appears that a large part of VLF motions is due to intrinsic variability of the tridimensional flow. 3D models may thus provide a valuable, only marginally more expensive alternative to conventional 2D approaches that miss the vertical flow structure and its nonlinear interaction with the depth-averaged flow.

Neutron detection using the superconducting Nb-based current-biased kinetic inductance detector

NASA Astrophysics Data System (ADS)

Shishido, Hiroaki; Yamaguchi, Hiroyuki; Miki, Yuya; Miyajima, Shigeyuki; Oikawa, Kenichi; Harada, Masahide; Hidaka, Mutsuo; Oku, Takayuki; Arai, Masatoshi; Fujimaki, Akira; Ishida, Takekazu

2017-09-01

We demonstrate neutron detection using a solid-state 3He-free superconducting current-biased kinetic inductance detector (CB-KID), which consists of a superconducting Nb meander line and 10B neutron absorption layer. The CB-KID is based on the transient process of kinetic inductance of Cooper pairs induced by the nuclear reaction between 10B and neutrons. Therefore, the CB-KID can be operated in a wide superconducting region in the bias current-temperature diagram, as demonstrated in this paper. The transient change of the kinetic inductance induces the electromagnetic wave pulse under a DC bias current. The signal propagates along the meander line toward both sides with opposite polarity, where the signal polarity is dominated by the bias current direction. The full width at half maximum of the signals remains on the order of a few tens of ns, which confirms the high-speed operation of our detectors. We determine the neutron incident position within 1.3 mm accuracy in one dimension using the multichannel CB-KIDs.

Ultrafast terahertz control of extreme tunnel currents through single atoms on a silicon surface

NASA Astrophysics Data System (ADS)

Jelic, Vedran; Iwaszczuk, Krzysztof; Nguyen, Peter H.; Rathje, Christopher; Hornig, Graham J.; Sharum, Haille M.; Hoffman, James R.; Freeman, Mark R.; Hegmann, Frank A.

2017-06-01

Ultrafast control of current on the atomic scale is essential for future innovations in nanoelectronics. Extremely localized transient electric fields on the nanoscale can be achieved by coupling picosecond duration terahertz pulses to metallic nanostructures. Here, we demonstrate terahertz scanning tunnelling microscopy (THz-STM) in ultrahigh vacuum as a new platform for exploring ultrafast non-equilibrium tunnelling dynamics with atomic precision. Extreme terahertz-pulse-driven tunnel currents up to 107 times larger than steady-state currents in conventional STM are used to image individual atoms on a silicon surface with 0.3 nm spatial resolution. At terahertz frequencies, the metallic-like Si(111)-(7 × 7) surface is unable to screen the electric field from the bulk, resulting in a terahertz tunnel conductance that is fundamentally different than that of the steady state. Ultrafast terahertz-induced band bending and non-equilibrium charging of surface states opens new conduction pathways to the bulk, enabling extreme transient tunnel currents to flow between the tip and sample.

Ferroelectric negative capacitance domain dynamics

NASA Astrophysics Data System (ADS)

Hoffmann, Michael; Khan, Asif Islam; Serrao, Claudy; Lu, Zhongyuan; Salahuddin, Sayeef; Pešić, Milan; Slesazeck, Stefan; Schroeder, Uwe; Mikolajick, Thomas

2018-05-01

Transient negative capacitance effects in epitaxial ferroelectric Pb(Zr0.2Ti0.8)O3 capacitors are investigated with a focus on the dynamical switching behavior governed by domain nucleation and growth. Voltage pulses are applied to a series connection of the ferroelectric capacitor and a resistor to directly measure the ferroelectric negative capacitance during switching. A time-dependent Ginzburg-Landau approach is used to investigate the underlying domain dynamics. The transient negative capacitance is shown to originate from reverse domain nucleation and unrestricted domain growth. However, with the onset of domain coalescence, the capacitance becomes positive again. The persistence of the negative capacitance state is therefore limited by the speed of domain wall motion. By changing the applied electric field, capacitor area or external resistance, this domain wall velocity can be varied predictably over several orders of magnitude. Additionally, detailed insights into the intrinsic material properties of the ferroelectric are obtainable through these measurements. A new method for reliable extraction of the average negative capacitance of the ferroelectric is presented. Furthermore, a simple analytical model is developed, which accurately describes the negative capacitance transient time as a function of the material properties and the experimental boundary conditions.

GCN/TAN: A Status Report

NASA Astrophysics Data System (ADS)

Barthelmy, Scott

2015-04-01

The Gamma-ray Coordinates Network / Transient Astronomy Network (GCN/TAN) is your one-stop shopping place for all transient astronomy. It collects nearly all the astrophysical transients from the missions (space-based and ground-based), puts them into a standard format, and distributes them to whomever wishes to receive them. This is all done autonomously (completely autonomous within GCN/TAN, and almost always autonomously within the producer end of operations). This automation means minimal time delays (<0.1 sec within GCN for socket-based distribution methods, and up to 30 sec for email-based which is dependant on the internet email protocol and the number of hops (both of which are out of the control of GCN/TAN). A status report on the current set of sources of transient information, plus recently-added and soon-to-be-added source will be given. Also, a standing request for GCN/TAN to incorporate your transient data stream; plus instruction for customers to receive GCN/TAAN Notice and Circular information.

Transient electro-thermal characterization of Si-Ge heterojunction bipolar transistors

NASA Astrophysics Data System (ADS)

Sahoo, Amit Kumar; Weiß, Mario; Fregonese, Sébastien; Malbert, Nathalie; Zimmer, Thomas

2012-08-01

In this paper, a comprehensive evaluation of the transient self-heating in microwave heterojunction bipolar transistors (HBTs) have been carried out through simulations and measurements. Three dimensional thermal TCAD simulations have been performed to investigate precisely the influence of backend metallization on transient thermal behavior of a submicron SiGe:C BiCMOS technology with fT and fmax of 230 GHz and 290 GHz, respectively. Transient variation of Collector current caused by self-heating is obtained through pulse measurements. For thermal characterization, different electro-thermal networks have been employed at the temperature node of HiCuM compact model. Thermal parameters have been extracted by means of compact model simulation using a scalable transistor library. It has been shown that, the conventional R-C thermal network is not sufficient to accurately model the transient thermal spreading behavior and therefore a recursive network needs to be used. Recursive network is verified with device simulations as well as measurements and found to be in excellent agreement.

Using a PFET To Commutate an SCR

NASA Technical Reports Server (NTRS)

Edwards, D. B.; Ripple, W. E.

1984-01-01

Accidental turn-on prevented. PFET diverts load current around SCR to prevent false SCR triggering from current and voltage switching transients. New circuit used in all types of single phase and polyphase inverters and in buck-boost-, and flyback regulators.

Semiconducting lithium indium diselenide: Charge-carrier properties and the impacts of high flux thermal neutron irradiation

NASA Astrophysics Data System (ADS)

Hamm, Daniel S.; Rust, Mikah; Herrera, Elan H.; Matei, Liviu; Buliga, Vladimir; Groza, Michael; Burger, Arnold; Stowe, Ashley; Preston, Jeff; Lukosi, Eric D.

2018-06-01

This paper reports on the charge carrier properties of several lithium indium diselenide (LISe) semiconductors. It was found that the charge collection efficiency of LISe was improved after high flux thermal neutron irradiation including the presence of a typically unobservable alpha peak from hole-only collection. Charge carrier trap energies of the irradiated sample were measured using photo-induced current transient spectroscopy. Compared to previous studies of this material, no significant differences in trap energies were observed. Through trap-filled limited voltage measurements, neutron irradiation was found to increase the density of trap states within the bulk of the semiconductor, which created a polarization effect under alpha exposure but not neutron exposure. Further, the charge collection efficiency of the irradiated sample was higher (14-15 fC) than that of alpha particles (3-5 fC), indicating that an increase in hole signal contribution resulted from the neutron irradiation. Finally, it was observed that significant charge loss takes place near the point of generation, producing a significant scintillation response and artificially inflating the W-value of all semiconducting LISe crystals.

Deciphering the contribution of intrinsic and synaptic currents to the effects of transient synaptic inputs on human motor unit discharge

PubMed Central

Powers, Randall K.; Türker, Kemal S.

2010-01-01

The amplitude and time course of synaptic potentials in human motoneurons can be estimated in tonically discharging motor units by measuring stimulus-evoked changes in the rate and probability of motor unit action potentials. However, in spite of the fact that some of these techniques have been used for over thirty years, there is still no consensus on the best way to estimate the characteristics of synaptic potentials or on the accuracy of these estimates. In this review, we compare different techniques for estimating synaptic potentials from human motor unit discharge and also discuss relevant animal models in which estimated synaptic potentials can be compared to those directly measured from intracellular recordings. We also review the experimental evidence on how synaptic noise and intrinsic motoneuron properties influence their responses to synaptic inputs. Finally, we consider to what extent recordings of single motor unit discharge in humans can be used to distinguish the contribution of changes in synaptic inputs versus changes in intrinsic motoneuron properties to altered motoneuron responses following CNS injury. PMID:20427230

Thermophysical Properties and Structural Transition of Hg(0.8)Cd(0.2)Te Melt

NASA Technical Reports Server (NTRS)

Li, C.; Scripa, R. N.; Ban, H.; Lin, B.; Su, C.; Lehoczky, S. L.

2004-01-01

Thermophysical properties, namely, density, viscosity, and electrical conductivity of Hg(sub o.8)Cd(sub 0.2)Te melt were measured as a function of temperature. A pycnometric method was used to measure the melt density in the temperature range of 1072 to 1122 K. The viscosity and electrical conductivity were simultaneously determined using a transient torque method from 1068 to 1132 K. The density result from this study is within 0.3% of the published data. However, the current viscosity result is approximately 30% lower than the existing data. The electrical conductivity of Hg(sub o.8)Cd(sub 0.2)Te melt as a function of temperature, which is not available in the literature, is also determined. The analysis of the temperature dependent electrical conductivity and the relationship between the kinematic viscosity and density indicated that the structure of the melt appeared to be homogeneous when the temperature was above 1090 K. A structural transition occurred in the Hg(sub 0.8)Cd(0.2)Te melt as the temperature was decreased from 1090 K to the liquidus temperature.