Modeling the response of small myelinated axons in a compound nerve to kilohertz frequency signals.

PubMed

Pelot, N A; Behrend, C E; Grill, W M

2017-08-01

There is growing interest in electrical neuromodulation of peripheral nerves, particularly autonomic nerves, to treat various diseases. Electrical signals in the kilohertz frequency (KHF) range can produce different responses, including conduction block. For example, EnteroMedics' vBloc ® therapy for obesity delivers 5 kHz stimulation to block the abdominal vagus nerves, but the mechanisms of action are unclear. We developed a two-part computational model, coupling a 3D finite element model of a cuff electrode around the human abdominal vagus nerve with biophysically-realistic electrical circuit equivalent (cable) model axons (1, 2, and 5.7 µm in diameter). We developed an automated algorithm to classify conduction responses as subthreshold (transmission), KHF-evoked activity (excitation), or block. We quantified neural responses across kilohertz frequencies (5-20 kHz), amplitudes (1-8 mA), and electrode designs. We found heterogeneous conduction responses across the modeled nerve trunk, both for a given parameter set and across parameter sets, although most suprathreshold responses were excitation, rather than block. The firing patterns were irregular near transmission and block boundaries, but otherwise regular, and mean firing rates varied with electrode-fibre distance. Further, we identified excitation responses at amplitudes above block threshold, termed 're-excitation', arising from action potentials initiated at virtual cathodes. Excitation and block thresholds decreased with smaller electrode-fibre distances, larger fibre diameters, and lower kilohertz frequencies. A point source model predicted a larger fraction of blocked fibres and greater change of threshold with distance as compared to the realistic cuff and nerve model. Our findings of widespread asynchronous KHF-evoked activity suggest that conduction block in the abdominal vagus nerves is unlikely with current clinical parameters. Our results indicate that compound neural or downstream muscle force recordings may be unreliable as quantitative measures of neural activity for in vivo studies or as biomarkers in closed-loop clinical devices.

Giant Electric Field Enhancement in Split Ring Resonators Featuring Nanometer-Sized Gaps

NASA Astrophysics Data System (ADS)

Bagiante, S.; Enderli, F.; Fabiańska, J.; Sigg, H.; Feurer, T.

2015-01-01

Today's pulsed THz sources enable us to excite, probe, and coherently control the vibrational or rotational dynamics of organic and inorganic materials on ultrafast time scales. Driven by standard laser sources THz electric field strengths of up to several MVm-1 have been reported and in order to reach even higher electric field strengths the use of dedicated electric field enhancement structures has been proposed. Here, we demonstrate resonant electric field enhancement structures, which concentrate the incident electric field in sub-diffraction size volumes and show an electric field enhancement as high as ~14,000 at 50 GHz. These values have been confirmed through a combination of near-field imaging experiments and electromagnetic simulations.

Laser ignition

DOEpatents

Early, James W.; Lester, Charles S.

2002-01-01

In the apparatus of the invention, a first excitation laser or other excitation light source is used in tandem with an ignitor laser to provide a compact, durable, engine deployable fuel ignition laser system. The beam from the excitation light source is split with a portion of it going to the ignitor laser and a second portion of it being recombined with the first portion after a delay before injection into the ignitor laser. Reliable fuel ignition is provided over a wide range of fuel conditions by using a single remote excitation light source for one or more small lasers located proximate to one or more fuel combustion zones.

Three chamber negative ion source

DOEpatents

Leung, Ka-Ngo; Ehlers, Kenneth W.; Hiskes, John R.

1985-01-01

A negative ion vessel is divided into an excitation chamber, a negative ionization chamber and an extraction chamber by two magnetic filters. Input means introduces neutral molecules into a first chamber where a first electron discharge means vibrationally excites the molecules which migrate to a second chamber. In the second chamber a second electron discharge means ionizes the molecules, producing negative ions which are extracted into or by a third chamber. A first magnetic filter prevents high energy electrons from entering the negative ionization chamber from the excitation chamber. A second magnetic filter prevents high energy electrons from entering the extraction chamber from the negative ionizing chamber. An extraction grid at the end of the negative ion vessel attracts negative ions into the third chamber and accelerates them. Another grid, located adjacent to the extraction grid, carries a small positive voltage in order to inhibit positive ions from migrating into the extraction chamber and contour the plasma potential. Additional electrons can be suppressed from the output flux using ExB forces provided by magnetic field means and the extractor grid electric potential.

Ultrasound acoustic wave energy transfer and harvesting

NASA Astrophysics Data System (ADS)

Shahab, Shima; Leadenham, Stephen; Guillot, François; Sabra, Karim; Erturk, Alper

2014-04-01

This paper investigates low-power electricity generation from ultrasound acoustic wave energy transfer combined with piezoelectric energy harvesting for wireless applications ranging from medical implants to naval sensor systems. The focus is placed on an underwater system that consists of a pulsating source for spherical wave generation and a harvester connected to an external resistive load for quantifying the electrical power output. An analytical electro-acoustic model is developed to relate the source strength to the electrical power output of the harvester located at a specific distance from the source. The model couples the energy harvester dynamics (piezoelectric device and electrical load) with the source strength through the acoustic-structure interaction at the harvester-fluid interface. Case studies are given for a detailed understanding of the coupled system dynamics under various conditions. Specifically the relationship between the electrical power output and system parameters, such as the distance of the harvester from the source, dimensions of the harvester, level of source strength, and electrical load resistance are explored. Sensitivity of the electrical power output to the excitation frequency in the neighborhood of the harvester's underwater resonance frequency is also reported.

Understanding the Electrical Behavior of the Action Potential in Terms of Elementary Electrical Sources

ERIC Educational Resources Information Center

Rodriguez-Falces, Javier

2015-01-01

A concept of major importance in human electrophysiology studies is the process by which activation of an excitable cell results in a rapid rise and fall of the electrical membrane potential, the so-called action potential. Hodgkin and Huxley proposed a model to explain the ionic mechanisms underlying the formation of action potentials. However,…

Laser ignition

DOEpatents

Early, James W.; Lester, Charles S.

2003-01-01

In the apparatus of the invention, a first excitation laser or other excitation light source is used in tandem with an ignitor laser to provide a compact, durable, engine deployable fuel ignition laser system. Reliable fuel ignition is provided over a wide range of fuel conditions by using a single remote excitation light source for one or more small lasers located proximate to one or more fuel combustion zones. In a third embodiment, alternating short and long pulses of light from the excitation light source are directed into the ignitor laser. Each of the embodiments of the invention can be multiplexed so as to provide laser light energy sequentially to more than one ignitor laser.

Rf capacitively-coupled electrodeless light source

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

Manos, Dennis M.; Diggs, Jessie; Ametepe, Joseph D.

2000-01-01

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

Modeling the response of small myelinated axons in a compound nerve to kilohertz frequency signals

NASA Astrophysics Data System (ADS)

Pelot, N. A.; Behrend, C. E.; Grill, W. M.

2017-08-01

Objective. There is growing interest in electrical neuromodulation of peripheral nerves, particularly autonomic nerves, to treat various diseases. Electrical signals in the kilohertz frequency (KHF) range can produce different responses, including conduction block. For example, EnteroMedics’ vBloc® therapy for obesity delivers 5 kHz stimulation to block the abdominal vagus nerves, but the mechanisms of action are unclear. Approach. We developed a two-part computational model, coupling a 3D finite element model of a cuff electrode around the human abdominal vagus nerve with biophysically-realistic electrical circuit equivalent (cable) model axons (1, 2, and 5.7 µm in diameter). We developed an automated algorithm to classify conduction responses as subthreshold (transmission), KHF-evoked activity (excitation), or block. We quantified neural responses across kilohertz frequencies (5-20 kHz), amplitudes (1-8 mA), and electrode designs. Main results. We found heterogeneous conduction responses across the modeled nerve trunk, both for a given parameter set and across parameter sets, although most suprathreshold responses were excitation, rather than block. The firing patterns were irregular near transmission and block boundaries, but otherwise regular, and mean firing rates varied with electrode-fibre distance. Further, we identified excitation responses at amplitudes above block threshold, termed ‘re-excitation’, arising from action potentials initiated at virtual cathodes. Excitation and block thresholds decreased with smaller electrode-fibre distances, larger fibre diameters, and lower kilohertz frequencies. A point source model predicted a larger fraction of blocked fibres and greater change of threshold with distance as compared to the realistic cuff and nerve model. Significance. Our findings of widespread asynchronous KHF-evoked activity suggest that conduction block in the abdominal vagus nerves is unlikely with current clinical parameters. Our results indicate that compound neural or downstream muscle force recordings may be unreliable as quantitative measures of neural activity for in vivo studies or as biomarkers in closed-loop clinical devices.

Charge transport in organic multi-layer devices under electric and optical fields

NASA Astrophysics Data System (ADS)

Park, June Hyoung

2007-12-01

Charge transport in small organic molecules and conjugated conducting polymers under electric or optical fields is studied by using field effect transistors and photo-voltaic cells with multiple thin layers. With these devices, current under electric field, photo-current under optical field, and luminescence of optical materials are measured to characterize organic and polymeric materials. For electric transport studies, poly(3,4-ethylenedioxythiophene) doped by polystyrenesulfonic acid is used, which is conductive with conductivity of approximately 25 S/cm. Despite their high conductance, field effect transistors based on the films are successfully built and characterized by monitoring modulations of drain current by gate voltage and IV characteristic curves. Due to very thin insulating layers of poly(vinylphenol), the transistors are relative fast under small gate voltage variation although heavy ions are involved in charge transport. In IV characteristic curves, saturation effects can be observed. Analysis using conventional field effect transistor model indicates high mobility of charge carriers, 10 cm2/V·sec, which is not consistent with the mobility of the conducting polymer. It is proposed that the effect of a small density of ions injected via polymer dielectric upon application of gate voltage and the ion compensation of key hopping sites accounts for the operation of the field effect transistors. For the studies of transport under optical field, photovoltaic cells with 3 different dendrons, which are efficient to harvest photo-excited electrons, are used. These dendrons consist of two electron-donors (tetraphenylporphyrin) and one electron-accepter (naphthalenediimide). Steady-state fluorescence measurements show that inter-molecular interaction is dominant in solid dendron film, although intra-molecular interaction is still present. Intra-molecular interaction is suggested by different fluorescence lifetimes between solutions of donor and dendrons. This intra-molecular interaction has two processes, transport via pi-stackings and transport via linking functional groups in the dendrons. IV characteristic spectra of the photovoltaic cells suggest that the transport route of photo-excited charges depends on wavelength of incident light on the cells. For excitation by the Soret band and the lowest Q band, a photo-excited electron can transport directly to a neighbor dendron. For excitation by high-energy Q bands, a photo-excited electron transports via the electron-accepters.

Group-Velocity-Controlled and Gate-Tunable Directional Excitation of Polaritons in Graphene-Boron Nitride Heterostructures

NASA Astrophysics Data System (ADS)

Jiang, Yuyu; Lin, Xiao; Low, Tony; Zhang, Baile; Chen, Hongsheng

2018-05-01

A fundamental building block in nano-photonics is the ability to directionally excite highly squeezed optical mode dynamically, particularly with an electrical bias. Such capabilities would enable the active manipulation of light propagation for information processing and transfer. However, when the optical source is built-in, it remains challenging to steer the excitation directionality in a flexible way. Here, we reveal a novel mechanism for tunable directional excitation of highly squeezed polaritons in graphene-hexagonal boron nitride (hBN) heterostructures. The effect relies on controlling the sign of the group velocity of the coupled plasmon-phonon polaritons, which can be flipped by simply tuning the chemical potential of graphene (through electrostatic gating) in the heterostructures. Graphene-hBN heterostructure thus present a promising platform toward nano-photonic circuits and nano-devices with electrically reconfigurable functionalities.

Design Comparison of Inner and Outer Rotor of Permanent Magnet Flux Switching Machine for Electric Bicycle Application

NASA Astrophysics Data System (ADS)

Jusoh, L. I.; Sulaiman, E.; Bahrim, F. S.; Kumar, R.

2017-08-01

Recent advancements have led to the development of flux switching machines (FSMs) with flux sources within the stators. The advantage of being a single-piece machine with a robust rotor structure makes FSM an excellent choice for speed applications. There are three categories of FSM, namely, the permanent magnet (PM) FSM, the field excitation (FE) FSM, and the hybrid excitation (HE) FSM. The PMFSM and the FEFSM have their respective PM and field excitation coil (FEC) as their key flux sources. Meanwhile, as the name suggests, the HEFSM has a combination of PM and FECs as the flux sources. The PMFSM is a simple and cheap machine, and it has the ability to control variable flux, which would be suitable for an electric bicycle. Thus, this paper will present a design comparison between an inner rotor and an outer rotor for a single-phase permanent magnet flux switching machine with 8S-10P, designed specifically for an electric bicycle. The performance of this machine was validated using the 2D- FEA. As conclusion, the outer-rotor has much higher torque approximately at 54.2% of an innerrotor PMFSM. From the comprehensive analysis of both designs it can be conclude that output performance is lower than the SRM and IPMSM design machine. But, it shows that the possibility to increase the design performance by using “deterministic optimization method”.

Magneto-acoustic imaging by continuous-wave excitation.

PubMed

Shunqi, Zhang; Zhou, Xiaoqing; Tao, Yin; Zhipeng, Liu

2017-04-01

The electrical characteristics of tissue yield valuable information for early diagnosis of pathological changes. Magneto-acoustic imaging is a functional approach for imaging of electrical conductivity. This study proposes a continuous-wave magneto-acoustic imaging method. A kHz-range continuous signal with an amplitude range of several volts is used to excite the magneto-acoustic signal and improve the signal-to-noise ratio. The magneto-acoustic signal amplitude and phase are measured to locate the acoustic source via lock-in technology. An optimisation algorithm incorporating nonlinear equations is used to reconstruct the magneto-acoustic source distribution based on the measured amplitude and phase at various frequencies. Validation simulations and experiments were performed in pork samples. The experimental and simulation results agreed well. While the excitation current was reduced to 10 mA, the acoustic signal magnitude increased up to 10 -7  Pa. Experimental reconstruction of the pork tissue showed that the image resolution reached mm levels when the excitation signal was in the kHz range. The signal-to-noise ratio of the detected magneto-acoustic signal was improved by more than 25 dB at 5 kHz when compared to classical 1 MHz pulse excitation. The results reported here will aid further research into magneto-acoustic generation mechanisms and internal tissue conductivity imaging.

Ultraviolet radiation induced discharge laser

DOEpatents

Gilson, Verle A.; Schriever, Richard L.; Shearer, James W.

1978-01-01

An ultraviolet radiation source associated with a suitable cathode-anode electrode structure, disposed in a gas-filled cavity of a high pressure pulsed laser, such as a transverse electric atmosphere (TEA) laser, to achieve free electron production in the gas by photoelectric interaction between ultraviolet radiation and the cathode prior to the gas-exciting cathode-to-anode electrical discharge, thereby providing volume ionization of the gas. The ultraviolet radiation is produced by a light source or by a spark discharge.

Nonreciprocity of electrically excited thermal spin signals in CoFeAl-Cu-Py lateral spin valves

NASA Astrophysics Data System (ADS)

Hu, Shaojie; Cui, Xiaomin; Nomura, Tatsuya; Min, Tai; Kimura, Takashi

2017-03-01

Electrical and thermal spin currents excited by an electric current have been systematically investigated in lateral spin valves consisting of CoFeAl and Ni80Fe20 (Py) wires bridged by a Cu strip. In the electrical spin signal, the reciprocity between the current and voltage probes was clearly confirmed. However, a significant nonreciprocity was observed in the thermal spin signal. This provides clear evidence that a large spin-dependent Seebeck coefficient is more important than the spin polarization for efficient thermal spin injection and detection. We demonstrate that the spin-dependent Seebeck coefficient can be simply evaluated from the thermal spin signals for two configurations. Our experimental description paves a way for evaluating a small spin-dependent Seebeck coefficient for conventional ferromagnets without using complicated parameters.

Effects of uniform extracellular DC electric fields on excitability in rat hippocampal slices in vitro.

PubMed

Bikson, Marom; Inoue, Masashi; Akiyama, Hiroki; Deans, Jackie K; Fox, John E; Miyakawa, Hiroyoshi; Jefferys, John G R

2004-05-15

The effects of uniform steady state (DC) extracellular electric fields on neuronal excitability were characterized in rat hippocampal slices using field, intracellular and voltage-sensitive dye recordings. Small electric fields (1 s) changes in neuronal excitability. Electric fields perpendicular to the apical-dendritic axis did not induce somatic polarization, but did modulate orthodromic responses, indicating an effect on afferents. These results demonstrate that DC fields can modulate neuronal excitability in a time-dependent manner, with no clear threshold, as a result of interactions between neuronal compartments, the non-linear properties of the cell membrane, and effects on afferents.

Laser ignition

DOEpatents

Early, James W.; Lester, Charles S.

2002-01-01

In the apparatus of the invention, a first excitation laser or other excitation light source is used in tandem with an ignitor laser to provide a compact, durable, engine deployable fuel ignition laser system. Reliable fuel ignition is provided over a wide range of fuel conditions by using a single remote excitation light source for one or more small lasers located proximate to one or more fuel combustion zones. In the embodiment of the invention claimed herein, the beam from the excitation light source is split with a portion of it going to the ignitor laser and a second portion of it being combined with either the first portion after a delay before injection into the ignitor laser.

Fractional diffusion models of cardiac electrical propagation: role of structural heterogeneity in dispersion of repolarization

PubMed Central

Bueno-Orovio, Alfonso; Kay, David; Grau, Vicente; Rodriguez, Blanca; Burrage, Kevin

2014-01-01

Impulse propagation in biological tissues is known to be modulated by structural heterogeneity. In cardiac muscle, improved understanding on how this heterogeneity influences electrical spread is key to advancing our interpretation of dispersion of repolarization. We propose fractional diffusion models as a novel mathematical description of structurally heterogeneous excitable media, as a means of representing the modulation of the total electric field by the secondary electrical sources associated with tissue inhomogeneities. Our results, analysed against in vivo human recordings and experimental data of different animal species, indicate that structural heterogeneity underlies relevant characteristics of cardiac electrical propagation at tissue level. These include conduction effects on action potential (AP) morphology, the shortening of AP duration along the activation pathway and the progressive modulation by premature beats of spatial patterns of dispersion of repolarization. The proposed approach may also have important implications in other research fields involving excitable complex media. PMID:24920109

Design study and performance analysis of 12S-14P field excitation flux switching motor for hybrid electric vehicle

NASA Astrophysics Data System (ADS)

Husin, Zhafir Aizat; Sulaiman, Erwan; Khan, Faisal; Mazlan, Mohamed Mubin Aizat; Othman, Syed Muhammad Naufal Syed

2015-05-01

This paper presents a new structure of 12slot-14pole field excitation flux switching motor (FEFSM) as an alternative candidate of non-Permanent Magnet (PM) machine for HEV drives. Design study, performance analysis and optimization of field excitation flux switching machine with non-rare-earth magnet for hybrid electric vehicle drive applications is done. The stator of projected machine consists of iron core made of electromagnetic steels, armature coils and field excitation coils as the only field mmf source. The rotor is consisted of only stack of iron and hence, it is reliable and appropriate for high speed operation. The design target is a machine with the maximum torque, power and power density, more than 210Nm, 123kW and 3.5kW/kg, respectively, which competes with interior permanent magnet synchronous machine used in existing hybrid electric vehicle. Some design feasibility studies on FEFSM based on 2D-FEA and deterministic optimization method will be applied to design the proposed machine.

A Simultaneous and Continuous Excitation Method for High-Speed Electrical Impedance Tomography with Reduced Transients and Noise Sensitivity

PubMed Central

Mylvaganam, Saba

2018-01-01

This paper presents a concept for soft field tomographic scan of all the projections of electromagnetic waves emanating from an array of electrodes. Instead of the sequential excitation of all pairs of electrodes in the list of all projections, the new method present here consists of a single and continuous excitation. This excitation signal is the linear combination of the excitation signals in the projection set at different AC frequencies. The response to a given projection is discriminated by selecting the corresponding AC frequency component in the signal spectra of the digitally demodulated signals. The main advantage of this method is the suppression of transients after each projection, which is particularly problematic in electrical impedance tomography due to contact impedance phenomena and skin effect. The second benefit over the sequential scan method is the increased number of samples for each measurement for reduced noise sensitivity with digital demodulation. The third benefit is the increased temporal resolution in high-speed applications. The main drawback is the increased number of signal sources required (one per electrode). This paper focuses on electrical impedance tomography, based on earlier work by the authors. An experimental proof-of-concept using a simple 4-electrodes electrical impedance tomographic system is presented using simulations and laboratory data. The method presented here may be extended to other modalities (ultrasonic, microwave, optical, etc.). PMID:29597327

Engineering biosynthetic excitable tissues from unexcitable cells for electrophysiological and cell therapy studies.

PubMed

Kirkton, Robert D; Bursac, Nenad

2011-01-01

Patch-clamp recordings in single-cell expression systems have been traditionally used to study the function of ion channels. However, this experimental setting does not enable assessment of tissue-level function such as action potential (AP) conduction. Here we introduce a biosynthetic system that permits studies of both channel activity in single cells and electrical conduction in multicellular networks. We convert unexcitable somatic cells into an autonomous source of electrically excitable and conducting cells by stably expressing only three membrane channels. The specific roles that these expressed channels have on AP shape and conduction are revealed by different pharmacological and pacing protocols. Furthermore, we demonstrate that biosynthetic excitable cells and tissues can repair large conduction defects within primary 2- and 3-dimensional cardiac cell cultures. This approach enables novel studies of ion channel function in a reproducible tissue-level setting and may stimulate the development of new cell-based therapies for excitable tissue repair.

Reverse flow events and small-scale effects in the cusp ionosphere

NASA Astrophysics Data System (ADS)

Spicher, A.; Ilyasov, A. A.; Miloch, W. J.; Chernyshov, A. A.; Clausen, L. B. N.; Moen, J. I.; Abe, T.; Saito, Y.

2016-10-01

We report in situ measurements of plasma irregularities associated with a reverse flow event (RFE) in the cusp F region ionosphere. The Investigation of Cusp Irregularities 3 (ICI-3) sounding rocket, while flying through a RFE, encountered several regions with density irregularities down to meter scales. We address in detail the region with the most intense small-scale fluctuations in both the density and in the AC electric field, which were observed on the equatorward edge of a flow shear, and coincided with a double-humped jet of fast flow. Due to its long-wavelength and low-frequency character, the Kelvin-Helmholtz instability (KHI) alone cannot be the source of the observed irregularities. Using ICI-3 data as inputs, we perform a numerical stability analysis of the inhomogeneous energy-density-driven instability (IEDDI) and demonstrate that it can excite electrostatic ion cyclotron waves in a wide range of wave numbers and frequencies for the electric field configuration observed in that region, which can give rise to the observed small-scale turbulence. The IEDDI can seed as a secondary process on steepened vortices created by a primary KHI. Such an interplay between macroprocesses and microprocesses could be an important mechanism for ion heating in relation to RFEs.

Laser ignition

DOEpatents

Early, James W.; Lester, Charles S.

2002-01-01

In the apparatus of the invention, a first excitation laser or other excitation light source capable of producing alternating beams of light having different wavelengths is used in tandem with one or more ignitor lasers to provide a compact, durable, engine deployable fuel ignition laser system. Reliable fuel ignition is provided over a wide range of fuel conditions by using the single remote excitation light source for pumping one or more small lasers located proximate to one or more fuel combustion zones with alternating wavelengths of light.

Ultraviolet 320 nm laser excitation for flow cytometry.

PubMed

Telford, William; Stickland, Lynn; Koschorreck, Marco

2017-04-01

Although multiple lasers and high-dimensional analysis capability are now standard on advanced flow cytometers, ultraviolet (UV) lasers (usually 325-365 nm) remain an uncommon excitation source for cytometry. This is primarily due to their cost, and the small number of applications that require this wavelength. The development of the Brilliant Ultraviolet (BUV fluorochromes, however, has increased the importance of this formerly niche excitation wavelength. Historically, UV excitation was usually provided by water-cooled argon- and krypton-ion lasers. Modern flow cytometers primary rely on diode pumped solid state lasers emitting at 355 nm. While useful for all UV-excited applications, DPSS UV lasers are still large by modern solid state laser standards, and remain very expensive. Smaller and cheaper near UV laser diodes (NUVLDs) emitting at 375 nm make adequate substitutes for 355 nm sources in many situations, but do not work as well with very short wavelength probes like the fluorescent calcium chelator indo-1. In this study, we evaluate a newly available UV 320 nm laser for flow cytometry. While shorter in wavelength that conventional UV lasers, 320 is close to the 325 nm helium-cadmium wavelength used in the past on early benchtop cytometers. A UV 320 nm laser was found to excite almost all Brilliant Ultraviolet dyes to nearly the same level as 355 nm sources. Both 320 nm and 355 nm sources worked equally well for Hoechst and DyeCycle Violet side population analysis of stem cells in mouse hematopoetic tissue. The shorter wavelength UV source also showed excellent excitation of indo-1, a probe that is not compatible with NUVLD 375 nm sources. In summary, a 320 nm laser module made a suitable substitute for conventional 355 nm sources. This laser technology is available in a smaller form factor than current 355 nm units, making it useful for small cytometers with space constraints. © 2017 International Society for Advancement of Cytometry. © 2017 International Society for Advancement of Cytometry.

Low-energy Control of Electrical Turbulence in the Heart

PubMed Central

Luther, Stefan; Fenton, Flavio H.; Kornreich, Bruce G.; Squires, Amgad; Bittihn, Philip; Hornung, Daniel; Zabel, Markus; Flanders, James; Gladuli, Andrea; Campoy, Luis; Cherry, Elizabeth M.; Luther, Gisa; Hasenfuss, Gerd; Krinsky, Valentin I.; Pumir, Alain; Gilmour, Robert F.; Bodenschatz, Eberhard

2011-01-01

Controlling the complex spatio-temporal dynamics underlying life-threatening cardiac arrhythmias such as fibrillation is extremely difficult due to the nonlinear interaction of excitation waves within a heterogeneous anatomical substrate1–4. Lacking a better strategy, strong, globally resetting electrical shocks remain the only reliable treatment for cardiac fibrillation5–7. Here, we establish the relation between the response of the tissue to an electric field and the spatial distribution of heterogeneities of the scale-free coronary vascular structure. We show that in response to a pulsed electric field E, these heterogeneities serve as nucleation sites for the generation of intramural electrical waves with a source density ρ(E), and a characteristic time τ for tissue depolarization that obeys a power law τ∝Eα. These intramural wave sources permit targeting of electrical turbulence near the cores of the vortices of electrical activity that drive complex fibrillatory dynamics. We show in vitro that simultaneous and direct access to multiple vortex cores results in rapid synchronization of cardiac tissue and therefore efficient termination of fibrillation. Using this novel control strategy, we demonstrate, for the first time, low-energy termination of fibrillation in vivo. Our results give new insights into the mechanisms and dynamics underlying the control of spatio-temporal chaos in heterogeneous excitable media and at the same time provide new research perspectives towards alternative, life-saving low-energy defibrillation techniques. PMID:21753855

Energy storage cell impedance measuring apparatus, methods and related systems

DOEpatents

Morrison, John L.; Morrison, William H.; Christophersen, Jon P.

2017-12-26

Energy storage cell impedance testing devices, circuits, and related methods are disclosed. An energy storage cell impedance measuring device includes a sum of sinusoids (SOS) current excitation circuit including differential current sources configured to isolate a ground terminal of the differential current sources from a positive terminal and a negative terminal of an energy storage cell. A method includes applying an SOS signal comprising a sum of sinusoidal current signals to the energy storage cell with the SOS current excitation circuit, each of the sinusoidal current signals oscillating at a different one of a plurality of different frequencies. The method also includes measuring an electrical signal at a positive terminal and a negative terminal of the energy storage cell, and computing an impedance of the energy storage cell at each of the plurality of different frequencies using the measured electrical signal.

Effect of frequency on the uniformity of symmetrical RF CCP discharges

NASA Astrophysics Data System (ADS)

Liu, Yue; Booth, Jean-Paul; Chabert, Pascal

2018-05-01

A 2D Cartesian electrostatic particle-in-cell/Monte Carlo collision (PIC/MCC) model presented previously (Liu et al 2018 Plasma Sources Sci. Technol. 27 025006) is used to investigate the effect of the driving frequency (over the range of 15–45 MHz) on the plasma uniformity in radio frequency (RF) capacitively coupled plasma (CCP) discharges in a geometrically symmetric reactor with a dielectric side wall in argon gas. The reactor size (12 cm electrode length, 2.5 cm gap) and driving frequency are sufficiently small that electromagnetic effects can be ignored. Previously, we showed (Liu et al 2018 Plasma Sources Sci. Technol. 27 025006) that for 15 MHz excitation, Ohmic heating of electrons by the electric field perpendicular to the electrodes is enhanced in a region in front of the dielectric side wall, leading to a maximum in electron density there. In this work we show that increasing the excitation frequency (at constant applied voltage amplitude) not only increases the overall electron heating and density but also causes a stronger, narrower peak in electron heating closer to the dielectric wall, improving the plasma uniformity along the electrodes. This heating peak comes both from enhanced perpendicular electron heating and from the appearance at high frequency of significant parallel heating. The latter is caused by the presence of a significant parallel-direction RF oscillating electric field in the corners. Whereas at the reactor center the sheaths oscillate perpendicularly to the electrodes, near the dielectric edge they move in and out of the corners and must be treated in two dimensions.

Localised excitation of a single photon source by a nanowaveguide.

PubMed

Geng, Wei; Manceau, Mathieu; Rahbany, Nancy; Sallet, Vincent; De Vittorio, Massimo; Carbone, Luigi; Glorieux, Quentin; Bramati, Alberto; Couteau, Christophe

2016-01-29

Nowadays, integrated photonics is a key technology in quantum information processing (QIP) but achieving all-optical buses for quantum networks with efficient integration of single photon emitters remains a challenge. Photonic crystals and cavities are good candidates but do not tackle how to effectively address a nanoscale emitter. Using a nanowire nanowaveguide, we realise an hybrid nanodevice which locally excites a single photon source (SPS). The nanowire acts as a passive or active sub-wavelength waveguide to excite the quantum emitter. Our results show that localised excitation of a SPS is possible and is compared with free-space excitation. Our proof of principle experiment presents an absolute addressing efficiency ηa ~ 10(-4) only ~50% lower than the one using free-space optics. This important step demonstrates that sufficient guided light in a nanowaveguide made of a semiconductor nanowire is achievable to excite a single photon source. We accomplish a hybrid system offering great potentials for electrically driven SPSs and efficient single photon collection and detection, opening the way for optimum absorption/emission of nanoscale emitters. We also discuss how to improve the addressing efficiency of a dipolar nanoscale emitter with our system.

Localised excitation of a single photon source by a nanowaveguide

PubMed Central

Geng, Wei; Manceau, Mathieu; Rahbany, Nancy; Sallet, Vincent; De Vittorio, Massimo; Carbone, Luigi; Glorieux, Quentin; Bramati, Alberto; Couteau, Christophe

2016-01-01

Nowadays, integrated photonics is a key technology in quantum information processing (QIP) but achieving all-optical buses for quantum networks with efficient integration of single photon emitters remains a challenge. Photonic crystals and cavities are good candidates but do not tackle how to effectively address a nanoscale emitter. Using a nanowire nanowaveguide, we realise an hybrid nanodevice which locally excites a single photon source (SPS). The nanowire acts as a passive or active sub-wavelength waveguide to excite the quantum emitter. Our results show that localised excitation of a SPS is possible and is compared with free-space excitation. Our proof of principle experiment presents an absolute addressing efficiency ηa ~ 10−4 only ~50% lower than the one using free-space optics. This important step demonstrates that sufficient guided light in a nanowaveguide made of a semiconductor nanowire is achievable to excite a single photon source. We accomplish a hybrid system offering great potentials for electrically driven SPSs and efficient single photon collection and detection, opening the way for optimum absorption/emission of nanoscale emitters. We also discuss how to improve the addressing efficiency of a dipolar nanoscale emitter with our system. PMID:26822999

Spatial Analysis of Slowly Oscillating Electric Activity in the Gut of Mice Using Low Impedance Arrayed Microelectrodes

PubMed Central

Taniguchi, Mizuki; Kajioka, Shunichi; Shozib, Habibul B.; Sawamura, Kenta; Nakayama, Shinsuke

2013-01-01

Smooth and elaborate gut motility is based on cellular cooperation, including smooth muscle, enteric neurons and special interstitial cells acting as pacemaker cells. Therefore, spatial characterization of electric activity in tissues containing these electric excitable cells is required for a precise understanding of gut motility. Furthermore, tools to evaluate spatial electric activity in a small area would be useful for the investigation of model animals. We thus employed a microelectrode array (MEA) system to simultaneously measure a set of 8×8 field potentials in a square area of ∼1 mm2. The size of each recording electrode was 50×50 µm2, however the surface area was increased by fixing platinum black particles. The impedance of microelectrode was sufficiently low to apply a high-pass filter of 0.1 Hz. Mapping of spectral power, and auto-correlation and cross-correlation parameters characterized the spatial properties of spontaneous electric activity in the ileum of wild-type (WT) and W/Wv mice, the latter serving as a model of impaired network of pacemaking interstitial cells. Namely, electric activities measured varied in both size and cooperativity in W/Wv mice, despite the small area. In the ileum of WT mice, procedures suppressing the excitability of smooth muscle and neurons altered the propagation of spontaneous electric activity, but had little change in the period of oscillations. In conclusion, MEA with low impedance electrodes enables to measure slowly oscillating electric activity, and is useful to evaluate both histological and functional changes in the spatio-temporal property of gut electric activity. PMID:24124480

A novel small molecule mediate 18F-FDG excited fluorescence molecular imaging

NASA Astrophysics Data System (ADS)

Zhang, Zeyu; Guo, Hongbo; Hu, Zhenhua; Tian, Jie

2018-02-01

Fluorescence molecular imaging (FMI) has been widely used in many medical fields with small molecule indocyanine green (ICG). However, low signal-background ratio and limited specificity to tumor remain big challenges for FMI. In this study, a novel excitation strategy is proposed on the basis of clinical approved ICG and 18F-FDG. A series of in vitro experiments are designed to reveal the mechanism and results show obvious decreasing of ICG fluorescence intensity with the increasing distance to excitation source. Meanwhile, the ICG fluorescence intensity is proportional to the activity of radiopharmaceutical. Results from different respects illustrate the promising of this proposed excitation strategy.

A novel technique to measure interface trap density in a GaAs MOS capacitor using time-varying magnetic fields

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

Choudhury, Aditya N. Roy, E-mail: aditya@physics.iisc.ernet.in; Venkataraman, V.

Interface trap density (D{sub it}) in a GaAs metal-oxide-semiconductor (MOS) capacitor can be measured electrically by measuring its impedance, i.e. by exciting it with a small signal voltage source and measuring the resulting current through the circuit. We propose a new method of measuring D{sub it} where the MOS capacitor is subjected to a (time-varying) magnetic field instead, which produces an effect equivalent to a (time-varying) voltage drop across the sample. This happens because the electron chemical potential of GaAs changes with a change in an externally applied magnetic field (unlike that of the gate metal); this is not themore » voltage induced by Faraday’s law of electromagnetic induction. So, by measuring the current through the MOS, D{sub it} can be found similarly. Energy band diagrams and equivalent circuits of a MOS capacitor are drawn in the presence of a magnetic field, and analyzed. The way in which a magnetic field affects a MOS structure is shown to be fundamentally different compared to an electrical voltage source.« less

A theoretical investigation on the parametric instability excited by X-mode polarized electromagnetic wave at Tromsø

NASA Astrophysics Data System (ADS)

Wang, Xiang; Cannon, Patrick; Zhou, Chen; Honary, Farideh; Ni, Binbin; Zhao, Zhengyu

2016-04-01

Recent ionospheric modification experiments performed at Tromsø, Norway, have indicated that X-mode pump wave is capable of stimulating high-frequency enhanced plasma lines, which manifests the excitation of parametric instability. This paper investigates theoretically how the observation can be explained by the excitation of parametric instability driven by X-mode pump wave. The threshold of the parametric instability has been calculated for several recent experimental observations at Tromsø, illustrating that our derived equations for the excitation of parametric instability for X-mode heating can explain the experimental observations. According to our theoretical calculation, a minimum fraction of pump wave electric field needs to be directed along the geomagnetic field direction in order for the parametric instability threshold to be met. A full-wave finite difference time domain simulation has been performed to demonstrate that a small parallel component of pump wave electric field can be achieved during X-mode heating in the presence of inhomogeneous plasma.

High energy XeBr electric discharge laser

DOEpatents

Sze, Robert C.; Scott, Peter B.

1981-01-01

A high energy XeBr laser for producing coherent radiation at 282 nm. The XeBr laser utilizes an electric discharge as the excitation source to minimize formation of molecular ions thereby minimizing absorption of laser radiation by the active medium. Additionally, HBr is used as the halogen donor which undergoes harpooning reactions with Xe.sub.M * to form XeBr*.

High energy XeBr electric discharge laser

DOEpatents

Sze, R.C.; Scott, P.B.

A high energy XeBr laser for producing coherent radiation at 282 nm is disclosed. The XeBr laser utilizes an electric discharge as the excitation source to minimize formation of molecular ions thereby minimizing absorption of laser radiation by the active medium. Additionally, HBr, is used as the halogen donor which undergoes harpooning reactions with Xe/sub M/ to form XeBr.

Investigation of voltage source design's for Electrical Impedance Mammography (EIM) Systems.

PubMed

Qureshi, Tabassum R; Chatwin, Chris R; Zhou, Zhou; Li, Nan; Wang, W

2012-01-01

According to Jossient, interesting characteristics of breast tissues mostly lie above 1MHz; therefore a wideband excitation source covering higher frequencies (i.e. above 1MHz) is required. The main objective of this research is to establish a feasible bandwidth envelope that can be used to design a constant EIM voltage source over a wide bandwidth with low output impedance for practical implementation. An excitation source is one of the major components in bio-impedance measurement systems. In any bio-impedance measurement system the excitation source can be achieved either by injecting current and measuring the resulting voltages, or by applying voltages and measuring the current developed. This paper describes three voltage source architectures and based on their bandwidth comparison; a differential voltage controlled voltage source (VCVS) is proposed, which can be used over a wide bandwidth (>15MHz). This paper describes the performance of the designed EIM voltage source for different load conditions and load capacitances reporting signal-to-noise ratio of approx 90dB at 10MHz frequency, signal phase and maximum of 4.75kΩ source output impedance at 10MHz. Optimum data obtained using Pspice® is used to demonstrate the high-bandwidth performance of the source.

Ink-jet printed fluorescent materials as light sources for planar optical waveguides on polymer foils

NASA Astrophysics Data System (ADS)

Bollgruen, Patrick; Gleissner, Uwe; Wolfer, Tim; Megnin, Christof; Mager, Dario; Overmeyer, Ludger; Korvink, Jan G.; Hanemann, Thomas

2016-10-01

Polymer-based optical sensor networks on foils (planar optronic systems) are a promising research field, but it can be challenging to supply them with light. We present a solvent-free, ink-jet printable material system with optically active substances to create planar light sources for these networks. The ink is based on a UV-curable monomer, the fluorescent agents are EuDBMPhen or 9,10-diphenylantracene, which fluoresce at 612 or 430 nm, respectively. We demonstrate the application as light source by printing a small area of fluorescent material on an optical waveguide fabricated by flexographic printing on PMMA foil, resulting in a simple polymer-optical device fabricated entirely by additive deposition techniques. When excited by a 405-nm laser of 10 mW, the emitted light couples into the waveguide and appears at the end of the waveguide. In comparison to conventional light sources, the intensity is weak but could be detected with a photodiode power sensor. In return, the concept has the advantage of being completely independent of any electrical elements or external cable connections.

Small, Optically-Driven Power Source

NASA Technical Reports Server (NTRS)

Cockrum, Richard H.; Wang, Ke-Li J.

1988-01-01

Power transmitted along fiber-optic cables. Transmitted as infrared light along fiber-optic cable, converted to electricity to supply small electronic circuit. Power source and circuit remains electrically isolated from each other for safety or reduces electromagnetic interference. Array of diodes made by standard integrated-circuit techniques and packaged for mounting at end of fiber-optic cable.

A nonequilibrium model for a moderate pressure hydrogen microwave discharge plasma

NASA Technical Reports Server (NTRS)

Scott, Carl D.

1993-01-01

This document describes a simple nonequilibrium energy exchange and chemical reaction model to be used in a computational fluid dynamics calculation for a hydrogen plasma excited by microwaves. The model takes into account the exchange between the electrons and excited states of molecular and atomic hydrogen. Specifically, electron-translation, electron-vibration, translation-vibration, ionization, and dissociation are included. The model assumes three temperatures, translational/rotational, vibrational, and electron, each describing a Boltzmann distribution for its respective energy mode. The energy from the microwave source is coupled to the energy equation via a source term that depends on an effective electric field which must be calculated outside the present model. This electric field must be found by coupling the results of the fluid dynamics and kinetics solution with a solution to Maxwell's equations that includes the effects of the plasma permittivity. The solution to Maxwell's equations is not within the scope of this present paper.

1.54 micron Emission from Erbium implanted GaN for Photonic Applications

NASA Technical Reports Server (NTRS)

Thaik, Myo; Hommerich, U.; Schwartz, R. N.; Wilson, R. G.; Zavada, J. M.

1998-01-01

The development of efficient and compact light sources operating at 1.54 micron is of enormous importance for the advancement of new optical communication systems. Erbium (1%) doped fiber amplifiers (EDFA's) or semiconductor lasers are currently being employed as near infrared light sources. Both devices, however, have inherent limitations due to their mode of operation. EDFA's employ an elaborate optical pumping scheme, whereas diode lasers have a strongly temperature dependent lasing wavelength. Novel light emitters based on erbium doped III-V semiconductors could overcome these limitations. Er doped semiconductors combine the convenience of electrical excitation with the excellent luminescence properties of Er(3+) ions. Electrically pumped, compact, and temperature stable optoelectronic devices are envisioned from this new class of luminescent materials. In this paper we discuss the potential of Er doped GaN for optoelectronic applications based on temperature dependent photoluminescence excitation studies.

Nanopore formation in neuroblastoma cells following ultrashort electric pulse exposure

NASA Astrophysics Data System (ADS)

Roth, Caleb C.; Payne, Jason A.; Wilmink, Gerald J.; Ibey, Bennett L.

2011-03-01

Ultrashort or nanosecond electrical pulses (USEP) cause repairable damage to the plasma membranes of cells through formation of nanopores. These nanopores are able to pass small ions such as sodium, calcium, and potassium, but remain impermeable to larger molecules like trypan blue and propidium iodide. What remains uncertain is whether generation of nanopores by ultrashort electrical pulses can inhibit action potentials in excitable cells. In this paper, we explored the sensitivity of excitable cells to USEP using Calcium Green AM 1 ester fluorescence to measure calcium uptake indicative of nanopore formation in the plasma membrane. We determined the threshold for nanopore formation in neuroblastoma cells for three pulse parameters (amplitude, pulse width, and pulse number). Measurement of such thresholds will guide future studies to determine if USEP can inhibit action potentials without causing irreversible membrane damage.

Engineering biosynthetic excitable tissues from unexcitable cells for electrophysiological and cell therapy studies

PubMed Central

Kirkton, Robert D.; Bursac, Nenad

2012-01-01

Patch-clamp recordings in single-cell expression systems have been traditionally used to study the function of ion channels. However, this experimental setting does not enable assessment of tissue-level function such as action potential (AP) conduction. Here we introduce a biosynthetic system that permits studies of both channel activity in single cells and electrical conduction in multicellular networks. We convert unexcitable somatic cells into an autonomous source of electrically excitable and conducting cells by stably expressing only three membrane channels. The specific roles that these expressed channels have on AP shape and conduction are revealed by different pharmacological and pacing protocols. Furthermore, we demonstrate that biosynthetic excitable cells and tissues can repair large conduction defects within primary 2- and 3-dimensional cardiac cell cultures. This approach enables novel studies of ion channel function in a reproducible tissue-level setting and may stimulate the development of new cell-based therapies for excitable tissue repair. PMID:21556054

[Microsecond Pulsed Hollow Cathode Lamp as Enhanced Excitation Source of Hydride Generation Atomic Fluorescence Spectrometry].

PubMed

Zhang, Shuo

2015-09-01

The spectral, electrical and atomic fluorescence characteristics of As, Se, Sb and Pb hollow cathode lamps (HCLs) powered by a laboratory-built high current microsecond pulse (HCMP) power supply were studied, and the feasibility of using HCMP-HCLs as the excitation source of hydride generation atomic fluorescence spectrometry (HG-AFS) was evaluated. Under the HCMP power supply mode, the As, Se, Sb, Pb HCLs can maintain stable glow discharge at frequency of 100~1000 Hz, pulse width of 4.0~20 μs and pulse current up to 4.0 A. Relationship between the intensity of characteristic emission lines and HCMP power supply parameters, such as pulse current, power supply voltage, pulse width and frequency, was studied in detail. Compared with the conventional pulsed (CP) HCLs used in commercial AFS instruments, HCMP-HCLs have a narrower pulse width and much stronger pulse current. Under the optimized HCMP power supply parameters, the intensity of atomic emission lines of As, Se, Sb HCLs had sharp enhancement and that indicated their capacity of being a novel HG-AFS excitation source. However, the attenuation of atomic lines and enhancement of ionic lines negated such feasibility of HCMP-Pb HCL. Then the HG-AFS analytical capability of using the HCMP-As/Se/Sb HCLs excitation source was established and results showed that the HCMP-HCL is a promising excitation source for HG-AFS.

Photoconductive circuit element pulse generator

DOEpatents

Rauscher, Christen

1989-01-01

A pulse generator for characterizing semiconductor devices at millimeter wavelength frequencies where a photoconductive circuit element (PCE) is biased by a direct current voltage source and produces short electrical pulses when excited into conductance by short laser light pulses. The electrical pulses are electronically conditioned to improve the frequency related amplitude characteristics of the pulses which thereafter propagate along a transmission line to a device under test.

Method for surface plasmon amplification by stimulated emission of radiation (SPASER)

DOEpatents

Stockman, Mark I [Atlanta, GA; Bergman, David J [Ramat Hasharon, IL

2011-09-13

A nanostructure is used to generate a highly localized nanoscale optical field. The field is excited using surface plasmon amplification by stimulated emission of radiation (SPASER). The SPASER radiation consists of surface plasmons that undergo stimulated emission, but in contrast to photons can be localized within a nanoscale region. A SPASER can incorporate an active medium formed by two-level emitters, excited by an energy source, such as an optical, electrical, or chemical energy source. The active medium may be quantum dots, which transfer excitation energy by radiationless transitions to a resonant nanosystem that can play the same role as a laser cavity in a conventional laser. The transitions are stimulated by the surface plasmons in the nanostructure, causing the buildup of a macroscopic number of surface plasmons in a single mode.

Surface plasmon amplification by stimulated emission of radiation (SPASER)

DOEpatents

Stockman, Mark I [Atlanta, GA; Bergman, David J [Ramat Hasharon, IL

2009-08-04

A nanostructure is used to generate a highly localized nanoscale optical field. The field is excited using surface plasmon amplification by stimulated emission of radiation (SPASER). The SPASER radiation consists of surface plasmons that undergo stimulated emission, but in contrast to photons can be localized within a nanoscale region. A SPASER can incorporate an active medium formed by two-level emitters, excited by an energy source, such as an optical, electrical, or chemical energy source. The active medium may be quantum dots, which transfer excitation energy by radiationless transitions to a resonant nanosystem that can play the same role as a laser cavity in a conventional laser. The transitions are stimulated by the surface plasmons in the nanostructure, causing the buildup of a macroscopic number of surface plasmons in a single mode.

Electric machine and current source inverter drive system

DOEpatents

Hsu, John S

2014-06-24

A drive system includes an electric machine and a current source inverter (CSI). This integration of an electric machine and an inverter uses the machine's field excitation coil for not only flux generation in the machine but also for the CSI inductor. This integration of the two technologies, namely the U machine motor and the CSI, opens a new chapter for the component function integration instead of the traditional integration by simply placing separate machine and inverter components in the same housing. Elimination of the CSI inductor adds to the CSI volumetric reduction of the capacitors and the elimination of PMs for the motor further improve the drive system cost, weight, and volume.

Design comparison of single phase outer and inner-rotor hybrid excitation flux switching motor for hybrid electric vehicles

NASA Astrophysics Data System (ADS)

Mazlan, Mohamed Mubin Aizat; Sulaiman, Erwan; Husin, Zhafir Aizat; Othman, Syed Muhammad Naufal Syed; Khan, Faisal

2015-05-01

In hybrid excitation machines (HEMs), there are two main flux sources which are permanent magnet (PM) and field excitation coil (FEC). These HEMs have better features when compared with the interior permanent magnet synchronous machines (IPMSM) used in conventional hybrid electric vehicles (HEVs). Since all flux sources including PM, FEC and armature coils are located on the stator core, the rotor becomes a single piece structure similar with switch reluctance machine (SRM). The combined flux generated by PM and FEC established more excitation fluxes that are required to produce much higher torque of the motor. In addition, variable DC FEC can control the flux capabilities of the motor, thus the machine can be applied for high-speed motor drive system. In this paper, the comparisons of single-phase 8S-4P outer and inner rotor hybrid excitation flux switching machine (HEFSM) are presented. Initially, design procedures of the HEFSM including parts drawing, materials and conditions setting, and properties setting are explained. Flux comparisons analysis is performed to investigate the flux capabilities at various current densities. Then the flux linkages of PM with DC FEC of various DC FEC current densities are examined. Finally torque performances are analyzed at various armature and FEC current densities for both designs. As a result, the outer-rotor HEFSM has higher flux linkage of PM with DC FEC and higher average torque of approximately 10% when compared with inner-rotor HEFSM.

Antenna radiation patterns in the whistler wave regime measured in a large laboratory plasma

NASA Technical Reports Server (NTRS)

Stenzel, R. L.

1976-01-01

Antenna radiation patterns of balanced electric dipoles and shielded magnetic loop antennas are obtained by measuring the relative wave amplitude with a small receiver antenna scanned around the exciter in a large uniform collisionless magnetized laboratory plasma in the whistler wave regime. The boundary effects are assumed to be negligible even for many farfield patterns. Characteristic differences are observed between electrically short and long antennas, the former exhibiting resonance cones and the latter showing dipole-like antenna patterns along the magnetic field. Resonance cones due to small electric dipoles and magnetic loops are observed in both the near zone and the far zone. A self-focusing process is revealed which produces a pencil-shaped field-aligned radiation pattern.

Line-source excitation of realistic conformal metasurface cloaks

NASA Astrophysics Data System (ADS)

Padooru, Yashwanth R.; Yakovlev, Alexander B.; Chen, Pai-Yen; Alù, Andrea

2012-11-01

Following our recently introduced analytical tools to model and design conformal mantle cloaks based on metasurfaces [Padooru et al., J. Appl. Phys. 112, 034907 (2012)], we investigate their performance and physical properties when excited by an electric line source placed in their close proximity. We consider metasurfaces formed by 2-D arrays of slotted (meshes and Jerusalem cross slots) and printed (patches and Jerusalem crosses) sub-wavelength elements. The electromagnetic scattering analysis is carried out using a rigorous analytical model, which utilizes the two-sided impedance boundary conditions at the interface of the sub-wavelength elements. It is shown that the homogenized grid-impedance expressions, originally derived for planar arrays of sub-wavelength elements and plane-wave excitation, may be successfully used to model and tailor the surface reactance of cylindrical conformal mantle cloaks illuminated by near-field sources. Our closed-form analytical results are in good agreement with full-wave numerical simulations, up to sub-wavelength distances from the metasurface, confirming that mantle cloaks may be very effective to suppress the scattering of moderately sized objects, independent of the type of excitation and point of observation. We also discuss the dual functionality of these metasurfaces to boost radiation efficiency and directivity from confined near-field sources.

Resonance of a fluid-driven crack: radiation properties and implications for the source of long-period events and harmonic tremor.

USGS Publications Warehouse

Chouet, B.

1988-01-01

A dynamic source model is presented, in which a 3-D crack containing a viscous compressible fluid is excited into resonance by an impulsive pressure transient applied over a small area DELTA S of the crack surface. The crack excitation depends critically on two dimensionless parameters called the crack stiffness and viscous damping loss. According to the model, the long-period event and harmonic tremor share the same source but differ in the boundary conditions for fluid flow and in the triggering mechanism setting up the resonance of the source, the former being viewed as the impulse response of the tremor generating system and the later representing the excitation due to more complex forcing functions.-from Author

The effect of cardiac electric anisotropy on epicardial potential fields during ventricular repolarization.

PubMed

Spaggiari, S; Baruffi, S; Macchi, E; Traversa, M; Arisi, G; Taccardi, B

1986-11-01

We tried to establish whether some of the manifestations of electrical anisotropy previously observed on the canine ventricular epicardium during the spread of excitation were also present during repolarization, with the appropriate polarity. To this end we determined the potential distribution on the ventricular surface of exposed dog hearts during ventricular excitation and repolarization. The ventricles were paced by means of epicardial or intramural electrodes. During the early stages of ventricular excitation following epicardial pacing we observed typical, previously described potential patterns, with negative, elliptical equipotential lines surrounding the pacing site, and two maxima aligned along the direction of subepicardial fibers. Intramural pacing gave rise to similar patterns. The axis joining the maxima, however, was oriented along the direction of intramural fibers. The repolarization potential pattern relating to epicardial excitation exhibited some features similar to those observed during the spread of excitation, namely the presence of families of elliptical equipotential lines around the pacing site, with pairs of potential extrema along the major or minor axes of the ellipses or both. The location of the extrema and the distribution of the epicardial potential gradients during repolarization suggested the presence of anisotropic current generators mainly oriented along the direction of deep myocardial fibers, with some contribution from more superficial sources which were oriented along the direction of subepicardial fibers. Deep stimulation elicited more complicated epicardial patterns whose interpretation is still obscure. We conclude that the electrical anisotropy of the heart affects the distribution of repolarization potentials and probably the strength of electrical generators during ventricular repolarization.

Combining THz laser excitation with resonant soft X-ray scattering at the Linac Coherent Light Source

DOE PAGES

Turner, Joshua J.; Dakovski, Georgi L.; Hoffmann, Matthias C.; ...

2015-04-11

This paper describes the development of new instrumentation at the Linac Coherent Light Source for conducting THz excitation experiments in an ultra high vacuum environment probed by soft X-ray diffraction. This consists of a cantilevered, fully motorized mirror system which can provide 600 kV cm⁻¹ electric field strengths across the sample and an X-ray detector that can span the full Ewald sphere with in-vacuum motion. The scientific applications motivated by this development, the details of the instrument, and spectra demonstrating the field strengths achieved using this newly developed system are discussed.

Piezoelectric devices for generating low power

NASA Astrophysics Data System (ADS)

Chilibon, Irinela

2016-12-01

This paper reviews concepts and applications in low-power electronics and energy harvesting technologies. Various piezoelectric materials and devices for small power generators useful in renewable electricity are presented. The vibrating piezoelectric device differs from the typical electrical power source in that it has capacitive rather than inductive source impedance, and may be driven by mechanical vibrations of varying amplitude. In general, vibration energy could be converted into electrical energy using one of three techniques: electrostatic charge, magnetic fields and piezoelectric. A low power piezoelectric generator, having a PZT element was realised in order to supply small electronic elements, such as optoelectronic small devices, LEDs, electronic watches, small sensors, interferometry with lasers or Micro-electro-mechanical System (MEMS) array with multi-cantilevers.

Device, system and method for a sensing electrical circuit

NASA Technical Reports Server (NTRS)

Vranish, John M. (Inventor)

2009-01-01

The invention relates to a driven ground electrical circuit. A driven ground is a current-measuring ground termination to an electrical circuit with the current measured as a vector with amplification. The driven ground module may include an electric potential source V.sub.S driving an electric current through an impedance (load Z) to a driven ground. Voltage from the source V.sub.S excites the minus terminal of an operational amplifier inside the driven ground which, in turn, may react by generating an equal and opposite voltage to drive the net potential to approximately zero (effectively ground). A driven ground may also be a means of passing information via the current passing through one grounded circuit to another electronic circuit as input. It may ground one circuit, amplify the information carried in its current and pass this information on as input to the next circuit.

Linear diffusion into a Faraday cage.

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

Warne, Larry Kevin; Lin, Yau Tang; Merewether, Kimball O.

2011-11-01

Linear lightning diffusion into a Faraday cage is studied. An early-time integral valid for large ratios of enclosure size to enclosure thickness and small relative permeability ({mu}/{mu}{sub 0} {le} 10) is used for this study. Existing solutions for nearby lightning impulse responses of electrically thick-wall enclosures are refined and extended to calculate the nearby lightning magnetic field (H) and time-derivative magnetic field (HDOT) inside enclosures of varying thickness caused by a decaying exponential excitation. For a direct strike scenario, the early-time integral for a worst-case line source outside the enclosure caused by an impulse is simplified and numerically integrated tomore » give the interior H and HDOT at the location closest to the source as well as a function of distance from the source. H and HDOT enclosure response functions for decaying exponentials are considered for an enclosure wall of any thickness. Simple formulas are derived to provide a description of enclosure interior H and HDOT as well. Direct strike voltage and current bounds for a single-turn optimally-coupled loop for all three waveforms are also given.« less

Understanding the electrical behavior of the action potential in terms of elementary electrical sources.

PubMed

Rodriguez-Falces, Javier

2015-03-01

A concept of major importance in human electrophysiology studies is the process by which activation of an excitable cell results in a rapid rise and fall of the electrical membrane potential, the so-called action potential. Hodgkin and Huxley proposed a model to explain the ionic mechanisms underlying the formation of action potentials. However, this model is unsuitably complex for teaching purposes. In addition, the Hodgkin and Huxley approach describes the shape of the action potential only in terms of ionic currents, i.e., it is unable to explain the electrical significance of the action potential or describe the electrical field arising from this source using basic concepts of electromagnetic theory. The goal of the present report was to propose a new model to describe the electrical behaviour of the action potential in terms of elementary electrical sources (in particular, dipoles). The efficacy of this model was tested through a closed-book written exam. The proposed model increased the ability of students to appreciate the distributed character of the action potential and also to recognize that this source spreads out along the fiber as function of space. In addition, the new approach allowed students to realize that the amplitude and sign of the extracellular electrical potential arising from the action potential are determined by the spatial derivative of this intracellular source. The proposed model, which incorporates intuitive graphical representations, has improved students' understanding of the electrical potentials generated by bioelectrical sources and has heightened their interest in bioelectricity. Copyright © 2015 The American Physiological Society.

Magnetic dipole strength in 128Xe and 134Xe in the spin-flip resonance region

NASA Astrophysics Data System (ADS)

Massarczyk, R.; Rusev, G.; Schwengner, R.; Dönau, F.; Bhatia, C.; Gooden, M. Â. E.; Kelley, J. Â. H.; Tonchev, A. Â. P.; Tornow, W.

2014-11-01

The magnetic dipole strength in the energy region of the spin-flip resonance is investigated in 128Xe and 134Xe using quasimonoenergetic and linearly polarized γ -ray beams at the High-Intensity γ -Ray Source facility in Durham, North Carolina, USA. Absorption cross sections were deduced for the magnetic and electric and dipole strength distributions separately for various intervals of excitation energy, including the strength of states in the unresolved quasicontinuum. The magnetic dipole strength distributions show structures resembling a resonance in the spin-flip region around an excitation energy of 8 MeV. The electric dipole strength distributions obtained from the present experiments are in agreement with the ones deduced from an earlier experiment using broad-band bremsstrahlung instead of a quasimonoenergetic beam. The experimental magnetic and electric dipole strength distributions are compared with phenomenological approximations and with predictions of a quasiparticle random phase approximation in a deformed basis.

Experimental Demonstration of a Multiphysics Cloak: Manipulating Heat Flux and Electric Current Simultaneously

NASA Astrophysics Data System (ADS)

Ma, Yungui; Liu, Yichao; Raza, Muhammad; Wang, Yudong; He, Sailing

2014-11-01

Invisible cloaks have been widely explored in many different physical systems but usually for a single phenomenon for one device. In this Letter we make an experimental attempt to show a multidisciplinary framework that has the capability to simultaneously respond to two different physical excitations according to predetermined scenarios. As a proof of concept, we implement an electric-thermal bifunctional device that can guide both electric current and heat flux "across" a strong `scatterer' (air cavity) and restore their original diffusion directions as if nothing exists along the paths, thus rendering dual cloaking effects for objects placed inside the cavity. This bifunctional cloaking performance is also numerically verified for a line-source nonuniform excitation. Our results and the fabrication technique presented here will help broaden the current research scope for multiple disciplines and may pave a way to manipulate multiple flows and create new functional devices, e.g., for on-chip applications.

A novel torsional exciter for modal vibration testing of large rotating machinery

NASA Astrophysics Data System (ADS)

Sihler, Christof

2006-10-01

A novel exciter for applying a dynamic torsional force to a rotating structure is presented in this paper. It has been developed at IPP in order to perform vibration tests with shaft assemblies of large flywheel generators (synchronous machines). The electromagnetic exciter (shaker) needs no fixture to the rotating shaft because the torque is applied by means of the stator winding of an electrical machine. Therefore, the exciter can most easily be applied in cases where a three-phase electrical machine (a motor or generator) is part of the shaft assembly. The oscillating power for the shaker is generated in a separate current-controlled DC circuit with an inductor acting as a buffer storage of magnetic energy. An AC component with adjustable frequency is superimposed on the inductor current in order to generate pulsating torques acting on the rotating shaft with the desired waveform and frequency. Since this torsional exciter does not require an external power source, can easily be installed (without contact to the rotating structure) and provides dynamic torsional forces which are sufficient for multi-megawatt applications, it is best suited for on-site tests of large rotating machinery.

Numerical simulation of operation modes in atmospheric pressure uniform barrier discharge excited by a saw-tooth voltage

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

Li Xuechen; Niu Dongying; Yin Zengqian

2012-08-15

The characteristics of dielectric barrier discharge excited by a saw-tooth voltage are simulated in atmospheric pressure helium based on a one-dimensional fluid model. A stepped discharge is obtained per half voltage cycle with gas gap width less than 2 mm by the simulation, which is different to the pulsed discharge excited by a sinusoidal voltage. For the stepped discharge, the plateau duration increases with increasing the voltage amplitude and decreasing the gas gap. Therefore, uniform discharge with high temporal duty ratio can be realized with small gap through increasing the voltage amplitude. The maximal densities of both electron and ionmore » appear near the anode and the electric field is almost uniformly distributed along the gap, which indicates that the stepped discharge belongs to a Townsend mode. In contrast to the stepped discharge with small gas gap, a pulsed discharge can be obtained with large gas gap. Through analyzing the spatial density distributions of electron and ion and the electric field, the pulsed discharge is in a glow mode. The voltage-current (V-I) characteristics are analyzed for the above mentioned discharges under different gas gaps, from which the different discharge modes are verified.« less

Permanent magnet machine and method with reluctance poles and non-identical PM poles for high density operation

DOEpatents

Hsu, John S.

2010-05-18

A method and apparatus in which a stator (11) and a rotor (12) define a primary air gap (20) for receiving AC flux and at least one source (23, 40), and preferably two sources (23, 24, 40) of DC excitation are positioned for inducing DC flux at opposite ends of the rotor (12). Portions of PM material (17, 17a) are provided as boundaries separating PM rotor pole portions from each other and from reluctance poles. The PM poles (18) and the reluctance poles (19) can be formed with poles of one polarity having enlarged flux paths in relation to flux paths for pole portions of an opposite polarity, the enlarged flux paths communicating with a core of the rotor (12) so as to increase reluctance torque produced by the electric machine. Reluctance torque is increased by providing asymmetrical pole faces. The DC excitation can also use asymmetric poles and asymmetric excitation sources. Several embodiments are disclosed with additional variations.

An SCR inverter for electric vehicles

NASA Technical Reports Server (NTRS)

Latos, T.; Bosack, D.; Ehrlich, R.; Jahns, T.; Mezera, J.; Thimmesch, D.

1980-01-01

An inverter for an electric vehicle propulsion application has been designed and constructed to excite a polyphase induction motor from a fixed propulsion battery source. The inverter, rated at 35kW peak power, is fully regenerative and permits vehicle operation in both the forward and reverse directions. Thyristors are employed as the power switching devices arranged in a dc bus commutated topology. This paper describes the major role the controller plays in generating the motor excitation voltage and frequency to deliver performance similar to dc systems. Motoring efficiency test data for the controller are presented. It is concluded that an SCR inverter in conjunction with an ac induction motor is a viable alternative to present dc vehicle propulsion systems on the basis of performance and size criteria.

Evidence that dirty electricity is causing the worldwide epidemics of obesity and diabetes.

PubMed

Milham, Samuel

2014-01-01

The epidemics of obesity and diabetes most apparent in recent years had their origins with Thomas Edison's development of distributed electricity in New York City in 1882. His original direct current (DC) generators suffered serious commutator brush arcing which is a major source of high-frequency voltage transients (dirty electricity). From the onset of the electrical grid, electrified populations have been exposed to dirty electricity. Diesel generator sets are a major source of dirty electricity today and are used almost universally to electrify small islands and places unreachable by the conventional electric grid. This accounts for the fact that diabetes prevalence, fasting plasma glucose and obesity are highest on small islands and other places electrified by generator sets and lowest in places with low levels of electrification like sub-Saharan Africa and east and Southeast Asia.

Two-color ionization injection using a plasma beatwave accelerator

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

Schroeder, C. B.; Benedetti, C.; Esarey, E.

Two-color laser ionization injection is a method to generate ultra-low emittance (sub-100 nm transverse normalized emittance) beams in a laser-driven plasma accelerator. A plasma beatwave accelerator is proposed to drive the plasma wave for ionization injection, where the beating of the lasers effectively produces a train of long-wavelength pulses. The plasma beatwave accelerator excites a large amplitude plasma wave with low peak laser electric fields, leaving atomically-bound electrons with low ionization potential. A short-wavelength, low-amplitude ionization injection laser pulse (with a small ponderomotive force and large peak electric field) is used to ionize the remaining bound electrons at a wakemore » phase suitable for trapping, generating an ultra-low emittance electron beam that is accelerated in the plasma wave. Using a plasma beatwave accelerator for wakefield excitation, compared to short-pulse wakefield excitation, allows for a lower amplitude injection laser pulse and, hence, a lower emittance beam may be generated.« less

Two-color ionization injection using a plasma beatwave accelerator

DOE PAGES

Schroeder, C. B.; Benedetti, C.; Esarey, E.; ...

2018-01-10

Two-color laser ionization injection is a method to generate ultra-low emittance (sub-100 nm transverse normalized emittance) beams in a laser-driven plasma accelerator. A plasma beatwave accelerator is proposed to drive the plasma wave for ionization injection, where the beating of the lasers effectively produces a train of long-wavelength pulses. The plasma beatwave accelerator excites a large amplitude plasma wave with low peak laser electric fields, leaving atomically-bound electrons with low ionization potential. A short-wavelength, low-amplitude ionization injection laser pulse (with a small ponderomotive force and large peak electric field) is used to ionize the remaining bound electrons at a wakemore » phase suitable for trapping, generating an ultra-low emittance electron beam that is accelerated in the plasma wave. Using a plasma beatwave accelerator for wakefield excitation, compared to short-pulse wakefield excitation, allows for a lower amplitude injection laser pulse and, hence, a lower emittance beam may be generated.« less

Generation, Detection and characterization of Gas-Phase Transition Metal containing Molecules

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

Steimle, Timothy

The objective of this project was to generate, detect, and characterize small, gas-phase, metal containing molecules. In addition to being relevant to high temperature chemical environments (e.g. plasmas and combustion), gas-phase experiments on metal containing molecules serve as the most direct link to a molecular-level theoretical model for catalysis. Catalysis (i.e. the addition of a small about of recoverable material to control the rate and direction of a chemical reaction) is critical to the petroleum and pharmaceutical industries as well as environmental remediation. Currently, the majority of catalytic materials are based on very expensive metals such as platinum (Pt), palladiummore » (Pd), iridium (Ir,) rhenium (Re), and rhodium (Rh). For example, the catalyst used for converting linear hydrocarbon molecules (e.g. hexane) to cyclic molecules (e.g. cyclohexane) is a mixture of Pt and Re suspended on alumina. It enables straight chain alkanes to be converted into branched-chain alkanes, cyclohexanes and aromatic hydrocarbons which are used, amongst other things, to enhance the octane number of petrol. A second example is the heterogeneous catalysis used in automobile exhaust systems to: a) decrease nitrogen oxide; b) reduce carbon monoxide; and c) oxidize unburned hydrocarbons. The exhaust is vented through a high-surface area chamber lined with Pt, Pd, and Rh. For example, the carbon monoxide is catalytically converted to carbon dioxide by reaction with oxygen. The research results from this work have been published in readily accessible journals1-28. The ground and excited electronic state properties of small metal containing molecules that we determine were: a) electronic state distributions and lifetimes, b) vibrational frequencies, c) bond lengths and angles, d) hyperfine interactions, e) permanent electric dipole moments, mel, and f) magnetic dipoles, μ m. In general terms, μ el, gives insight into the charge distribution and mm into the number and nature of the unpaired electrons. Analysis of the hyperfine interactions (i.e. Fermi-contact, nuclear electric quadrupole, etc.) is particularly insightful because it results from the interaction of nuclei with non-zero spin and the chemically important valence electrons. The bulk of the spectroscopic techniques used in these studies exploit the sensitivity of laser induced fluorescence (LIF) detection. The spectroscopic schemes employed include: a) cw and pulsed laser field-free(FF) excitation and dispersed LIF (DLIF); b) optical Stark; c) optical Zeeman; d) pump/probe microwave double resonance (PPMODR); e) fluorescence lifetimes, and f) resonant and non-resonant two-photon ionization TOF mass spectrometry. Vibrational spacing, force constants and electronic states distributions are derived from the analysis of pulsed dye laser excitation and DLIF spectra. Geometric structure (bond lengths and angles) and hyperfine parameters are derived from the analysis of cw-laser LIF and PPMODR spectra. Permanent electric dipole moments, mel,, and magnetic dipole moments, mm, are derived from the analysis of optical Stark and Zeeman spectra, respectively. Transition moments are derived from the analysis of radiative lifetimes. A supersonic molecular beam sample of these ephemeral molecules is generated by skimming the products of either a laser ablation/reaction source or a d.c. discharge source.« less

Source phase shift - A new phenomenon in wave propagation due to anelasticity. [in free oscillations of earth model

NASA Technical Reports Server (NTRS)

Buland, R.; Yuen, D. A.; Konstanty, K.; Widmer, R.

1985-01-01

The free oscillations of an anelastic earth model due to earthquakes were calculated directly by means of the correspondence principle from wave propagation theory. The formulation made it possible to find the source phase which is not predictable using first order perturbation theory. The predicted source phase was largest for toroidal modes with source components proportional to the radial strain scalar instead of the radial displacement scalar. The source phase increased in relation to the overtone number. In addition, large relative differences were found in the excitation modulus and the phase when the elastic excitation was small. The effect was sufficient to bias estimates of source properties and elastic structure.

Investigation of a vibration-damping unit for reduction in low-frequency vibrations of electric motors

NASA Technical Reports Server (NTRS)

Grigoryey, N. V.; Fedorovich, M. A.

1973-01-01

The vibroacoustical characteristics of different types of electric motors are discussed. It is shown that the basic source of low frequency vibrations is rotor unbalance. A flexible damping support, with an antivibrator, is used to obtain the vibroacoustical effect of reduction in the basic harmonic of the electric motor. A model of the electric motor and the damping apparatus is presented. Mathematical models are developed to show the relationships of the parameters. The basic purpose in using a calculation model id the simultaneous replacement of the exciting force created by the rotor unbalance and its inertial rigidity characteristics by a limiting kinematic disturbance.

Thermal Electron Contributions to Current-Driven Instabilities: SCIFER Observations in the 1400-km Cleft Ion Fountain and Their Implications to Thermal Ion Energization

NASA Technical Reports Server (NTRS)

Adrian, Mark L.; Pollock, C. J.; Moore, T. E.; Kintner, P. M.; Arnoldy, R. L.; Whitaker, Ann F. (Technical Monitor)

2001-01-01

SCIFER TECHS observations of the variations in the thermal electron distribution in the 1400-km altitude cleft are associated with periods of intense ion heating and field-aligned currents. Energization of the thermal ion plasma in the mid-altitude cleft occurs within density cavities accompanied by enhanced thermal electron temperatures, large field-aligned thermal electron plasma flows and broadband low-frequency electric fields. Variations in the thermal electron contribution to field-aligned current densities indicate small scale (approximately 100's m) filamentary structure embedded within the ion energization periods. TECHS observations of the field-aligned drift velocities and temperatures of the thermal electron distribution are presented to evaluate the critical velocity thresholds necessary for the generation of electrostatic ion cyclotron and ion acoustic instabilities. This analysis suggests that, during periods of thermal ion energization, sufficient drift exists in the thermal electron distribution to excite the electrostatic ion cyclotron instability. In addition, brief periods exist within the same interval where the drift of the thermal electron distribution is sufficient to marginally excite the ion acoustic instability. In addition, the presence an enhancement in Langmuir emission at the plasma frequency at the center of the ion energization region, accompanied by the emission's second-harmonic, and collocated with observations of high-frequency electric field solitary structures suggest the presence of electron beam driven decay of Langmuir waves to ion acoustic modes as an additional free energy source for ion energization.

Delayed Ionization in Transition Metal Carbon Clusters

NASA Astrophysics Data System (ADS)

Kooi, S. E.; Castleman, A. W., Jr.

1997-03-01

Mass spectrometric studies of several single and binary transition metal carbon cluster systems, produced in a laser vaporization source, reveal several species that undergo delayed ionization. Pulsed extraction and blocking electric fields, in a time-of-flight mass spectrometer, allow the study of delayed ionization over a time window after excitation with a pulsed laser. In systems where metallocarbohedrenes (Met-Cars) are produced, the Met-Cars are the dominate delayed species. Delayed ionization of binary metal Met-Cars Ti_xM_yC_12 (M=Zr,Nb,Y; x+y=8) is dependent on the ratio of the two metals. Delayed behavior is investigated over a range of photoionization wavelengths and fluences. In order to determine the degree to which the delayed ionization is thermionic in character, the experimental data have been compared to Klots's model for thermionic emission from small particles.

Defects formation and wave emitting from defects in excitable media

NASA Astrophysics Data System (ADS)

Ma, Jun; Xu, Ying; Tang, Jun; Wang, Chunni

2016-05-01

Abnormal electrical activities in neuronal system could be associated with some neuronal diseases. Indeed, external forcing can cause breakdown even collapse in nervous system under appropriate condition. The excitable media sometimes could be described by neuronal network with different topologies. The collective behaviors of neurons can show complex spatiotemporal dynamical properties and spatial distribution for electrical activities due to self-organization even from the regulating from central nervous system. Defects in the nervous system can emit continuous waves or pulses, and pacemaker-like source is generated to perturb the normal signal propagation in nervous system. How these defects are developed? In this paper, a network of neurons is designed in two-dimensional square array with nearest-neighbor connection type; the formation mechanism of defects is investigated by detecting the wave propagation induced by external forcing. It is found that defects could be induced under external periodical forcing under the boundary, and then the wave emitted from the defects can keep balance with the waves excited from external forcing.

16. EXCITERS, AND SYNCHROSCOPE GAUGE ON WALL. ACTIVE ELECTRIC EXCITER ...

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

16. EXCITERS, AND SYNCHROSCOPE GAUGE ON WALL. ACTIVE ELECTRIC EXCITER AT REAR; UNUSED WATER-DRIVEN EXCITER IN FOREGROUND. VIEW TO SOUTH-SOUTHWEST. - Santa Ana River Hydroelectric System, SAR-2 Powerhouse, Redlands, San Bernardino County, CA

Optical emission from a small scale model electric arc furnace in 250-600 nm region.

PubMed

Mäkinen, A; Niskanen, J; Tikkala, H; Aksela, H

2013-04-01

Optical emission spectroscopy has been for long proposed for monitoring and studying industrial steel making processes. Whereas the radiative decay of thermal excitations is always taking place in high temperatures needed in steel production, one of the most promising environment for such studies are electric arc furnaces, creating plasma in excited electronic states that relax with intense characteristic emission in the optical regime. Unfortunately, large industrial scale electric arc furnaces also present a challenging environment for optical emission studies and application of the method is not straightforward. To study the usability of optical emission spectroscopy in real electric arc furnaces, we have developed a laboratory scale DC electric arc furnace presented in this paper. With the setup, optical emission spectra of Fe, Cr, Cr2O3, Ni, SiO2, Al2O3, CaO, and MgO were recorded in the wavelength range 250-600 nm and the results were analyzed with the help of reference data. The work demonstrates that using characteristic optical emission, obtaining in situ chemical information from oscillating plasma of electric arc furnaces is indeed possible. In spite of complications, the method could possibly be applied to industrial scale steel making process in order to improve its efficiency.

Numerical simulation of seismic wave propagation from land-excited large volume air-gun source

NASA Astrophysics Data System (ADS)

Cao, W.; Zhang, W.

2017-12-01

The land-excited large volume air-gun source can be used to study regional underground structures and to detect temporal velocity changes. The air-gun source is characterized by rich low frequency energy (from bubble oscillation, 2-8Hz) and high repeatability. It can be excited in rivers, reservoirs or man-made pool. Numerical simulation of the seismic wave propagation from the air-gun source helps to understand the energy partitioning and characteristics of the waveform records at stations. However, the effective energy recorded at a distance station is from the process of bubble oscillation, which can not be approximated by a single point source. We propose a method to simulate the seismic wave propagation from the land-excited large volume air-gun source by finite difference method. The process can be divided into three parts: bubble oscillation and source coupling, solid-fluid coupling and the propagation in the solid medium. For the first part, the wavelet of the bubble oscillation can be simulated by bubble model. We use wave injection method combining the bubble wavelet with elastic wave equation to achieve the source coupling. Then, the solid-fluid boundary condition is implemented along the water bottom. And the last part is the seismic wave propagation in the solid medium, which can be readily implemented by the finite difference method. Our method can get accuracy waveform of land-excited large volume air-gun source. Based on the above forward modeling technology, we analysis the effect of the excited P wave and the energy of converted S wave due to different water shapes. We study two land-excited large volume air-gun fields, one is Binchuan in Yunnan, and the other is Hutubi in Xinjiang. The station in Binchuan, Yunnan is located in a large irregular reservoir, the waveform records have a clear S wave. Nevertheless, the station in Hutubi, Xinjiang is located in a small man-made pool, the waveform records have very weak S wave. Better understanding of the characteristics of land-excited large volume air-gun can help to better use of the air-gun source.

Investigating line- versus point-laser excitation for three-dimensional fluorescence imaging and tomography employing a trimodal imaging system

NASA Astrophysics Data System (ADS)

Cao, Liji; Peter, Jörg

2013-06-01

The adoption of axially oriented line illumination patterns for fluorescence excitation in small animals for fluorescence surface imaging (FSI) and fluorescence optical tomography (FOT) is being investigated. A trimodal single-photon-emission-computed-tomography/computed-tomography/optical-tomography (SPECT-CT-OT) small animal imaging system is being modified for employment of point- and line-laser excitation sources. These sources can be arbitrarily positioned around the imaged object. The line source is set to illuminate the object along its entire axial direction. Comparative evaluation of point and line illumination patterns for FSI and FOT is provided involving phantom as well as mouse data. Given the trimodal setup, CT data are used to guide the optical approaches by providing boundary information. Furthermore, FOT results are also being compared to SPECT. Results show that line-laser illumination yields a larger axial field of view (FOV) in FSI mode, hence faster data acquisition, and practically acceptable FOT reconstruction throughout the whole animal. Also, superimposed SPECT and FOT data provide additional information on similarities as well as differences in the distribution and uptake of both probe types. Fused CT data enhance further the anatomical localization of the tracer distribution in vivo. The feasibility of line-laser excitation for three-dimensional fluorescence imaging and tomography is demonstrated for initiating further research, however, not with the intention to replace one by the other.

Line-source excited impulsive EM field response of thin plasmonic metal films

NASA Astrophysics Data System (ADS)

Štumpf, Martin; Vandenbosch, Guy A. E.

2013-08-01

In this paper, reflection against and transmission through thin plasmonic metal films, basic building blocks of many plasmonic devices, are analytically investigated directly in the time domain for an impulsive electric and magnetic line-source excitation. The electromagnetic properties of thin metallic films are modeled via the Drude model. The problem is formulated with the help of approximate thin-sheet boundary conditions and the analysis is carried out using the Cagniard-DeHoop technique. Closed-form space-time expressions are found and discussed. The obtained time-domain analytical expressions reveal the existence of the phenomenon of transient oscillatory surface effects along a plasmonic metal thin sheet. Illustrative numerical examples of transmitted/reflected pulsed fields are provided.

Rg-Lg coupling as a Lg-wave excitation mechanism

NASA Astrophysics Data System (ADS)

Ge, Z.; Xie, X.

2003-12-01

Regional phase Lg is predominantly comprised of shear wave energy trapped in the crust. Explosion sources are expected to be less efficient for excitation of Lg phases than earthquakes to the extent that the source can be approximated as isotropic. Shallow explosions generate relatively large surface wave Rg compared to deeper earthquakes, and Rg is readily disrupted by crustal heterogeneity. Rg energy may thus scatter into trapped crustal S-waves near the source region and contribute to low-frequency Lg wave. In this study, a finite-difference modeling plus the slowness analysis are used for investigating the above mentioned Lg-wave excitation mechanism. The method allows us to investigate near source energy partitioning in multiple domains including frequency, slowness and time. The main advantage of this method is that it can be applied at close range, before Lg is actually formed, which allows us to use very fine near source velocity model to simulate the energy partitioning process. We use a layered velocity structure as the background model and add small near source random velocity patches to the model to generate the Rg to Lg coupling. Two types of simulations are conducted, (1) a fixed shallow explosion source vs. randomness at different depths and (2) a fixed shallow randomness vs. explosion sources at different depths. The results show apparent couplings between the Rg and Lg waves at lower frequencies (0.3-1.5 Hz). A shallow source combined with shallow randomness generates the maximum Lg-wave, which is consistent with the Rg energy distribution of a shallow explosion source. The Rg energy and excited Lg energy show a near linear relationship. The numerical simulation and slowness analysis suggest that the Rg to Lg coupling is an effective excitation mechanism for low frequency Lg-waves from a shallow explosion source.

14. POWERHOUSE INTERIOR, EXCITER No. 2 SHOWING GENERAL ELECTRIC INDUCTION ...

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

14. POWERHOUSE INTERIOR, EXCITER No. 2 SHOWING GENERAL ELECTRIC INDUCTION MOTOR IN SERIES BETWEEN PELTON-DOBLE IMPULSE WHEEL AND GENERAL ELECTRIC GENERATOR. VIEW TO EAST. - Rush Creek Hydroelectric System, Powerhouse Exciters, Rush Creek, June Lake, Mono County, CA

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

Noda, Akira; Iwashita, Yoshihisa; Souda, Hikaru

A phase rotation scheme of laser-produced ions from a solid target by the application of a synchronized RF electric voltage with a pulsed laser has been experimentally investigated with the use of a 100 TW laser, J-KAREN at JAEA, KPSI. Up to now, energy peaks of up to around 2.0 MeV have been created with a FWHM of 2.6% with good reproducibility using a two-gap resonator of a quarter wave length with the same frequency as the source laser (approx80 MHz). It is also found that the position of the peak can be well controlled by adjusting the relative phasemore » between the RF electric field and the laser, which is very promising for real applications of such laser-produced protons. In order to also apply such a phase rotation system for higher energy protons (<200 MeV), a scheme to use a small linear accelerator (LINAC) with multi-gaps is proposed as a phase rotator. With multi-gap structure, alternating focusing between longitudinal and transverse degrees of freedoms can be realized. From the point of compactness and realizing a small focused spot, however, a scheme combining separate quadrupole magnets just before and after the RF cavity excited with the Wideroee mode, might be more effective. The scheme presented here will realize laser-produced ions (protons) with good reproducibility by combining with RF technology.« less

Prediction of Francis Turbine Prototype Part Load Pressure and Output Power Fluctuations with Hydroelectric Model

NASA Astrophysics Data System (ADS)

Alligné, S.; Nicolet, C.; Béguin, A.; Landry, C.; Gomes, J.; Avellan, F.

2017-04-01

The prediction of pressure and output power fluctuations amplitudes on Francis turbine prototype is a challenge for hydro-equipment industry since it is subjected to guarantees to ensure smooth and reliable operation of the hydro units. The European FP7 research project Hyperbole aims to setup a methodology to transpose the pressure fluctuations induced by the cavitation vortex rope from the reduced scale model to the prototype generating units. A Francis turbine unit of 444MW with a specific speed value of ν = 0.29, is considered as case study. A SIMSEN model of the power station including electrical system, controllers, rotating train and hydraulic system with transposed draft tube excitation sources is setup. Based on this model, a frequency analysis of the hydroelectric system is performed for all technologies to analyse potential interactions between hydraulic excitation sources and electrical components. Three technologies have been compared: the classical fixed speed configuration with Synchronous Machine (SM) and the two variable speed technologies which are Doubly Fed Induction Machine (DFIM) and Full Size Frequency Converter (FSFC).

Electric oxygen-iodine laser discharge scaling and laser performance

NASA Astrophysics Data System (ADS)

Woodard, Brian S.

In 2004, a research partnership between the University of Illinois and CU Aerospace demonstrated the first electric discharge pumped oxygen-iodine laser referred to as ElectricOIL. This exciting improvement over the standard oxygen-iodine laser utilizes a gas discharge to produce the necessary electronically-excited molecular oxygen, O2(a 1Delta), that serves as the energy reservoir in the laser system. Pumped by a near-resonant energy transfer, the atomic iodine lases on the I(2P1/2) → I(2P3/2) transition at 1315 nm. Molecular oxygen diluted with helium and a small fraction of nitric oxide flows through a radiofrequency discharge where O2(a 1Delta) and many other excited species are created. Careful investigations to understand the benefits and problems associated with these other states in the laser system allowed this team to succeed where other research groups had failed, and after the initial demonstration, the ElectricOIL research focus shifted to increasing the efficiencies along with the output laser energy. Among other factors, the laser power scales with the flow rate of oxygen in the desired excited state. Therefore, high yields of O2(a 1Delta) are desired along with high input oxygen flow rates. In the early ElectricOIL experiments, the pressure in the discharge was approximately 10 Torr, but increased flow rates forced the pressure to between 50 and 60 Torr requiring a number of new discharge designs in order to produce similar yields of O2(a1Delta) efficiently. Experiments were conducted with only the electric discharge portion of the laser system using emission diagnostics to study the effects of changing the discharge geometry, flow residence time, and diluent. The power carried by O2(a 1Delta) is the maximum power that could be extracted from the laser, and the results from these studies showed approximately 2500 W stored in the O2(a1Delta) state. Transferring this energy into the atomic iodine has been another challenge in ElectricOIL as experiments have shown that the iodine is pumped into the excited state slower than is predicted by the known kinetics, resulting in reduced output power. An elementary model is presented that may partially explain this problem. Larger laser resonator volumes are employed to improve power extraction by providing more flow time for iodine pumping. The results presented in this work in conjunction with the efforts of others led to ElectricOIL scaling from 200 mW in the initial demonstration to nearly 500 W.

Wave excitations of drifting two-dimensional electron gas under strong inelastic scattering

NASA Astrophysics Data System (ADS)

Korotyeyev, V. V.; Kochelap, V. A.; Varani, L.

2012-10-01

We have analyzed low-temperature behavior of two-dimensional electron gas in polar heterostructures subjected to a high electric field. When the optical phonon emission is the fastest relaxation process, we have found existence of collective wave-like excitations of the electrons. These wave-like excitations are periodic in time oscillations of the electrons in both real and momentum spaces. The excitation spectra are of multi-branch character with considerable spatial dispersion. There are one acoustic-type and a number of optical-type branches of the spectra. Their small damping is caused by quasi-elastic scattering of the electrons and formation of relevant space charge. Also there exist waves with zero frequency and finite spatial periods—the standing waves. The found excitations of the electron gas can be interpreted as synchronous in time and real space manifestation of well-known optical-phonon-transient-time-resonance. Estimates of parameters of the excitations for two polar heterostructures, GaN/AlGaN and ZnO/MgZnO, have shown that excitation frequencies are in THz-frequency range, while standing wave periods are in sub-micrometer region.

Fluorescent optical position sensor

DOEpatents

Weiss, Jonathan D.

2005-11-15

A fluorescent optical position sensor and method of operation. A small excitation source side-pumps a localized region of fluorescence at an unknown position along a fluorescent waveguide. As the fluorescent light travels down the waveguide, the intensity of fluorescent light decreases due to absorption. By measuring with one (or two) photodetectors the attenuated intensity of fluorescent light emitted from one (or both) ends of the waveguide, the position of the excitation source relative to the waveguide can be determined by comparing the measured light intensity to a calibrated response curve or mathematical model. Alternatively, excitation light can be pumped into an end of the waveguide, which generates an exponentially-decaying continuous source of fluorescent light along the length of the waveguide. The position of a photodetector oriented to view the side of the waveguide can be uniquely determined by measuring the intensity of the fluorescent light emitted radially at that location.

FDTD simulation of field performance in reverberation chamber excited by two excitation antennas

NASA Astrophysics Data System (ADS)

Wang, Song; Wu, Zhan-cheng; Cui, Yao-zhong

2013-03-01

The excitation source is one of the critical items that determine the electromagnetic fields in a reverberation chamber (RC). In order to optimize the electromagnetic fields performance, a new method of exciting RC with two antennas is proposed based on theoretical analysis. The full 3D simulation of RC is carried out by the finite difference time domain (FDTD) method on two excitation conditions of one antenna and two antennas. The broadband response of RC is obtained by fast Fourier transformation (FFT) after only one simulation. Numerical data show that the field uniformity in the test space is improved on the condition of two transmitting antennas while the normalized electric fields decreased slightly compared to the one antenna condition. It is straightforward to recognize that two antennas excitation can reduce the demands on power amplifier as the total input power is split among the two antennas, and consequently the cost of electromagnetic compatibility (EMC) test in large-scale RC can be reduced.

On the Addition of EM Field Propagation and Coupling Effects in the BLT Equation. Revision

DTIC Science & Technology

2004-06-08

which collectively are referred to as high power electromagnetic ( HPEM ) fields, could be inadvertent, like the environment produced by a search...either case, the effects of these HPEM fields may include system upset, and in some cases, permanent damage. Figure 1 illustrates a simple example of...an electrical system excited by an external HPEM source. This energy source can provide either a narrow-band pulsed EM field, or a fast transient

Portable plant chlorophyll fluorimeter based on blue LED rapid induced technology

NASA Astrophysics Data System (ADS)

Zheng, Yibo; Mi, Ting; Zhang, Lei; Zhao, Jun

2018-01-01

Fluorimeter is an effective device for detecting chlorophyll a content in plants. In order to realize real-time nondestructive detection of plant blades, a camera based fluorescence instrument based on two color mirrors has been developed. The blue light LED is used as the excitation light source, and the lens is used for shaping and focusing the excitation light to ensure the excitation intensity and uniform illumination of the light source. The device uses a 45 degree two color mirror to separate the chlorophyll a excited light path and the fluorescence receiving light path. Finally, the fluorescent signal is collected by the silicon photocell, and the signal is processed by the circuit to transmit the digital information to the display. Through the analysis of the experimental data, the device has the advantages of small size, easy to carry, fast induction, etc., and can be widely applied in outdoor teaching and field investigation.

The direct-current response of electrically conducting fractures excited by a grounded current source

DOE PAGES

Weiss, Chester J.; Aldridge, David F.; Knox, Hunter A.; ...

2016-05-01

Hydraulic fracture stimulation of low permeability reservoir rocks is an established and cross–cutting technology for enhancing hydrocarbon production in sedimentary formations and increasing heat exchange in crystalline geothermal systems. Whereas the primary measure of success is the ability to keep the newly generated fractures sufficiently open, long–term reservoir management requires a knowledge of the spatial extent, morphology, and distribution of the fractures — knowledge primarily informed by microseismic and ground deformation monitoring. To minimize the uncertainty associated with interpreting such data, we investigate through numerical simulation the usefulness of direct-current (DC) resistivity data for characterizing subsurface fractures with elevated electricalmore » conductivity by considering a geophysical experiment consisting of a grounded current source deployed in a steel cased borehole. In doing so, the casing efficiently energizes the fractures with steady current. Finite element simulations of this experiment for a horizontal well intersecting a small set of vertical fractures indicate that the fractures manifest electrically in (at least) two ways: (1) a local perturbation in electric potential proximal to the fracture set, with limited farfield expression and (2) an overall reduction in the electric potential along the borehole casing due to enhanced current flow through the fractures into the surrounding formation. The change in casing potential results in a measurable effect that can be observed far from fractures themselves. Under these conditions, our results suggest that farfield, timelapse measurements of DC potentials can be interpreted by simple, linear inversion for a Coulomb charge distribution along the borehole path, including a local charge perturbation due to the fractures. As a result, this approach offers an inexpensive method for detecting and monitoring the time-evolution of electrically conducting fractures while ultimately providing an estimate of their effective conductivity — the latter providing an important measure independent of seismic methods on fracture shape, size, and hydraulic connectivity.« less

The direct-current response of electrically conducting fractures excited by a grounded current source

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

Weiss, Chester J.; Aldridge, David F.; Knox, Hunter A.

Hydraulic fracture stimulation of low permeability reservoir rocks is an established and cross–cutting technology for enhancing hydrocarbon production in sedimentary formations and increasing heat exchange in crystalline geothermal systems. Whereas the primary measure of success is the ability to keep the newly generated fractures sufficiently open, long–term reservoir management requires a knowledge of the spatial extent, morphology, and distribution of the fractures — knowledge primarily informed by microseismic and ground deformation monitoring. To minimize the uncertainty associated with interpreting such data, we investigate through numerical simulation the usefulness of direct-current (DC) resistivity data for characterizing subsurface fractures with elevated electricalmore » conductivity by considering a geophysical experiment consisting of a grounded current source deployed in a steel cased borehole. In doing so, the casing efficiently energizes the fractures with steady current. Finite element simulations of this experiment for a horizontal well intersecting a small set of vertical fractures indicate that the fractures manifest electrically in (at least) two ways: (1) a local perturbation in electric potential proximal to the fracture set, with limited farfield expression and (2) an overall reduction in the electric potential along the borehole casing due to enhanced current flow through the fractures into the surrounding formation. The change in casing potential results in a measurable effect that can be observed far from fractures themselves. Under these conditions, our results suggest that farfield, timelapse measurements of DC potentials can be interpreted by simple, linear inversion for a Coulomb charge distribution along the borehole path, including a local charge perturbation due to the fractures. As a result, this approach offers an inexpensive method for detecting and monitoring the time-evolution of electrically conducting fractures while ultimately providing an estimate of their effective conductivity — the latter providing an important measure independent of seismic methods on fracture shape, size, and hydraulic connectivity.« less

High Pressure Microwave Powered UV Light Sources

NASA Astrophysics Data System (ADS)

Cekic, M.; Frank, J. D.; Popovic, S.; Wood, C. H.

1997-10-01

Industrial microwave powered (*electrodeless*) light sources have been limited to quiescent pressures of 300 Torr of buffer gas and metal- halide fills. Recently developed multi-atmospheric electronegative bu lb fills (noble gas-halide excimers, metal halide) require electric field s for ionization that are often large multiples of the breakdown voltage for air. For these fills an auxiliary ignition system is necessary. The most successful scheme utilizes a high voltage pulse power supply and a novel field emission source. Acting together they create localized condition of pressure reduction and high free electron density. This allows the normal microwave fields to drive this small region into avalanche, ignite the bulb, and heat the plasma to it's operating poin t Standard diagnostic techniques of high density discharges are inapplicable to the excimer bulbs, because of the ionic molecular exci ted state structure and absence of self-absorption. The method for temperature determination is based on the equilibrium population of certain vibrational levels of excimer ionic excited states. Electron d ensity was determined from the measurements of Stark profiles of H_β radiation from a small amount of hydrogen mixed with noble gas and halogens. At the present time, high pressure (Te 0.5eV, ne 3 x 10^17 cm-3) production bulbs produce over 900W of radiation in a 30nm band, centered at 30nm. Similarly, these prototypes when loaded with metal-halide bulb fills produce 1 kW of radiation in 30nm wide bands, centered about the wavelength of interest.

Laser-excited pulses in a crystallized dusty plasma

NASA Astrophysics Data System (ADS)

Nosenko, V.; Nunomura, S.; Goree, J.

2000-10-01

A dusty plasma is an ionized gas containing small particles of solid matter. These particles acquire a large negative electric charge. Polymer microspheres were shaken into a capacitively-coupled parallel-plate rf plasma. The particles were levitated by the electric field in the sheath above the lower electrode. The particles settled in a single horizontal layer, arranged in a hexagonal lattice. They were imaged using a video camera, to record the particle motion. Like any crystal, this so-called ``plasma crystal'' sustains compressional sound waves, which can be launched as a pulse. There are several ways these waves can be excited, including applying a force from the radiation pressure of a laser beam. By chopping an argon laser beam that is directed at the lattice, it is possible to launch a pulsed wave in the lattice. We evaluate the pulse's shape and propagation speed, and test whether it has the properties of a shock.

Power quality and protection of electric distribution systems with small, dispersed generation devices

NASA Astrophysics Data System (ADS)

Rizy, D. T.; Jewell, W. T.

1984-10-01

There are several operational problems associated with the connection of small power sources, such as wind turbines and photovoltaic (PV) arrays, to an electric distribution system. In one study the harmonic distortion produced by a subdivision of PV arrays connected through line-commutated inverters was simulated. A second simulation study evaluated protection problems associated with the operation of dispersed ac generators. The purpose of these studies was to examine the adequacy of the electric utility industry's traditional practices and hardware for the operation of dispersed power sources. The results of these simulation studies are discussed and recommendations are given for hardware and system operation needed for accommodating this new technology.

Fiber optical assembly for fluorescence spectrometry

DOEpatents

Carpenter, II, Robert W.; Rubenstein, Richard; Piltch, Martin; Gray, Perry

2010-12-07

A system for analyzing a sample for the presence of an analyte in a sample. The system includes a sample holder for containing the sample; an excitation source, such as a laser, and at least one linear array radially disposed about the sample holder. Radiation from the excitation source is directed to the sample, and the radiation induces fluorescent light in the sample. Each linear array includes a plurality of fused silica optical fibers that receive the fluorescent light and transmits a fluorescent light signal from the first end to an optical end port of the linear array. An end port assembly having a photo-detector is optically coupled to the optical end port. The photo-detector detects the fluorescent light signal and converts the fluorescent light signal into an electrical signal.

Electrical source of pseudothermal light

NASA Astrophysics Data System (ADS)

Kuusela, Tom A.

2018-06-01

We describe a simple and compact electrical version of a pseudothermal light source. The source is based on electrical white noise whose spectral properties are tailored by analog filters. This signal is used to drive a light-emitting diode. The type of second-order coherence of the output light can be either Gaussian or Lorentzian, and the intensity distribution can be either Gaussian or non-Gaussian. The output light field is similar in all viewing angles, and thus, there is no need for a small aperture or optical fiber in temporal coherence analysis.

46 CFR 111.12-3 - Excitation.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 46 Shipping 4 2011-10-01 2011-10-01 false Excitation. 111.12-3 Section 111.12-3 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) ELECTRICAL ENGINEERING ELECTRIC SYSTEMS-GENERAL REQUIREMENTS Generator Construction and Circuits § 111.12-3 Excitation. In general, excitation must meet...

46 CFR 111.12-3 - Excitation.

Code of Federal Regulations, 2013 CFR

2013-10-01

... 46 Shipping 4 2013-10-01 2013-10-01 false Excitation. 111.12-3 Section 111.12-3 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) ELECTRICAL ENGINEERING ELECTRIC SYSTEMS-GENERAL REQUIREMENTS Generator Construction and Circuits § 111.12-3 Excitation. In general, excitation must meet...

46 CFR 111.12-3 - Excitation.

Code of Federal Regulations, 2014 CFR

2014-10-01

... 46 Shipping 4 2014-10-01 2014-10-01 false Excitation. 111.12-3 Section 111.12-3 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) ELECTRICAL ENGINEERING ELECTRIC SYSTEMS-GENERAL REQUIREMENTS Generator Construction and Circuits § 111.12-3 Excitation. In general, excitation must meet...

46 CFR 111.12-3 - Excitation.

Code of Federal Regulations, 2012 CFR

2012-10-01

... 46 Shipping 4 2012-10-01 2012-10-01 false Excitation. 111.12-3 Section 111.12-3 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) ELECTRICAL ENGINEERING ELECTRIC SYSTEMS-GENERAL REQUIREMENTS Generator Construction and Circuits § 111.12-3 Excitation. In general, excitation must meet...

Varying the forcing scale in low Prandtl number dynamos

NASA Astrophysics Data System (ADS)

Brandenburg, A.; Haugen, N. E. L.; Li, Xiang-Yu; Subramanian, K.

2018-06-01

Small-scale dynamos are expected to operate in all astrophysical fluids that are turbulent and electrically conducting, for example the interstellar medium, stellar interiors, and accretion disks, where they may also be affected by or competing with large-scale dynamos. However, the possibility of small-scale dynamos being excited at small and intermediate ratios of viscosity to magnetic diffusivity (the magnetic Prandtl number) has been debated, and the possibility of them depending on the large-scale forcing wavenumber has been raised. Here we show, using four values of the forcing wavenumber, that the small-scale dynamo does not depend on the scale-separation between the size of the simulation domain and the integral scale of the turbulence, i.e., the forcing scale. Moreover, the spectral bottleneck in turbulence, which has been implied as being responsible for raising the excitation conditions of small-scale dynamos, is found to be invariant under changing the forcing wavenumber. However, when forcing at the lowest few wavenumbers, the effective forcing wavenumber that enters in the definition of the magnetic Reynolds number is found to be about twice the minimum wavenumber of the domain. Our work is relevant to future studies of small-scale dynamos, of which several applications are being discussed.

Scattering from Artificial Piezoelectriclike Meta-Atoms and Molecules

NASA Astrophysics Data System (ADS)

Goltcman, Leonid; Hadad, Yakir

2018-01-01

Inspired by natural piezoelectricity, we introduce hybrid-wave electromechanical meta-atoms and metamolecules that consist of coupled electrical and mechanical oscillators with similar resonance frequencies. We explore the linearized electromechanical scattering process and demonstrate that by exploiting the hybrid-wave interaction one may enable functionalities that are forbidden otherwise. For example, we study a dimer metamolecule that is highly directional for electromagnetic waves, although it is electrically deep subwavelength. This unique behavior is a consequence of the fact that, while the metamolecule is electrically small, it is acoustically large. This idea opens vistas for a plethora of exciting dynamics and phenomena in electromagnetics and acoustics, with implications for miniaturized sensors, superresolution imaging, compact nonreciprocal antennas, and more.

Experimental Testing of a Metamaterial Slow Wave Structure for High-Power Microwave Generation

NASA Astrophysics Data System (ADS)

Shipman, K.; Prasad, S.; Andreev, D.; Fisher, D. M.; Reass, D. B.; Schamiloglu, E.; Gilmore, M.

2017-10-01

A high-power L band source has been developed using a metamaterial (MTM) to produce a double negative slow wave structure (SWS) for interaction with an electron beam. The beam is generated by a 700 kV, 6 kA short pulse (10 ns) accelerator. The design of the SWS consists of a cylindrical waveguide, loaded with alternating split-rings that are arrayed axially down the waveguide. The beam is guided down the center of the rings, where electrons interact with the MTM-SWS producing radiation. Power is extracted axially via a circular waveguide, and radiated by a horn antenna. Microwaves are characterized by an external detector placed in a waveguide. Mode characterization is performed using a neon bulb array. The bulbs are lit by the electric field, resulting in an excitation pattern that resembles the field pattern. This is imaged using an SLR camera. The MTM structure has electrically small features so breakdown is a concern. In addition to high speed cameras, a fiber-optic-fed, sub-ns photomultiplier tube array diagnostic has been developed and used to characterize breakdown light. Work supported by the Air Force Office of Scientific Research, MURI Grant FA9550-12-1-0489.

Compensation for Harmonic Currents and Reactive Power in Wind Power Generation System using PWM Inverter

NASA Astrophysics Data System (ADS)

Shinohara, Katsuji; Shinhatsubo, Kurato; Iimori, Kenichi; Yamamoto, Kichiro; Saruban, Takamichi; Yamaemori, Takahiro

In recent year, consciousness of environmental problems is enhancing, and the price of the electric power purchased by an electric power company is established expensive for the power plant utilizing the natural energy. So, the introduction of the wind power generation is promoted in Japan. Generally, squirrel-cage induction machines are widely used as a generator in wind power generation system because of its small size, lightweight and low-cost. However, the induction machines do not have a source of excitation. Thus, it causes the inrush currents and the instantaneous voltage drop when the generator is directly connected to a power grid. To reduce the inrush currents, an AC power regulator is used. Wind power generations are frequently connected to and disconnected from the power grid. However, when the inrush currents are reduced, harmonic currents are caused by phase control of the AC power regulator. And the phase control of AC power regulator cannot control the power factor. Therefore, we propose the use of the AC power regulator to compensate for the harmonic currents and reactive power in the wind power generation system, and demonstrate the validity of its system by simulated and experimental results.

Opportunities of energy supply of farm holdings on the basis of small-scale renewable energy sources

NASA Astrophysics Data System (ADS)

Efendiev, A. M.; Nikolaev, Yu. E.; Evstaf'ev, D. P.

2016-02-01

One of the major national economic problems of Russia is raising of agricultural production, which will provide strategic security and sustainable supply of the population with provisions. Creation of subsidiary small holdings, farm holdings, and peasant farm holdings will require addressing issues of energy supply. At considerable distance of small farms from centralized energy systems (by fuel, electricity and thermal energy) it is proposed to create a system of local energy networks on the basis of low-powered power plants using renewable energy sources (RES). There is economic unreasonableness of use of imported components of small power plants. Creation of new combined small power plants on renewable energy sources produced by domestic manufacturers is recommended. Schemes of arrangements of small power plants based on renewable energy sources are proposed, variants and characteristics of a basic source are provided—biogas plants developed by the authors. Calculations revealed that heat and power supply of self-contained farms distant from small power plants based on renewable energy sources is 2.5-2.6 times cheaper than from centralized networks. Production of biogas through anaerobic fermentation of organic waste of cattle complexes is considered as the basis. The analysis of biowaste output in various cattle farms is carried out, and the volume of biogas is determined to meet the requirements of these farms in electrical and thermal energy. The objective of the present article is to study the possibility of creating small combined power plants in Russia based on renewable sources of energy for independent consumers.

13. POWERHOUSE INTERIOR, DETAIL OF EXCITER No. 2 GENERAL ELECTRIC ...

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

13. POWERHOUSE INTERIOR, DETAIL OF EXCITER No. 2 GENERAL ELECTRIC INDUCTION MOTOR NAMEPLATE. VIEW TO EAST. - Rush Creek Hydroelectric System, Powerhouse Exciters, Rush Creek, June Lake, Mono County, CA

Solar Energy and Other Appropriate Technologies for Small ...

EPA Pesticide Factsheets

This Region 2 research demonstration project presentation studied the efficacy of sustainable solar-powered water delivery and monitoring systems to reduce the economic burden of operating and maintaining Non-PRASA drinking water systems and to reduce the impact of climate change resulting from the use of fossil fuels in Puerto Rico. In Puerto Rico, petroleum (65%), natural gas (18%) and coal (16%) are imported to generate electricity resulting in electrical rates that are more than twice the US average. In 2012, only 1% of electricity came from renewable energy (US Energy Information Administration). One major cost for electricity for small communities in Puerto Rico is the transfer, treatment and distribution of drinking water. These small communities (Non-PRASA communities) are not able to afford electrical costs and many have abandoned their groundwater sources and reverted to unfiltered surface water systems, creating serious public health risks and non-compliance. Many Non-PRASA groundwater systems (141 out of 247) could use solar-powered pumps to extract and deliver groundwater. Solar power would also extend the life of system electrical components by improving the quality of electrical power supply. Solar power as a renewable energy source for Non-PRASA water systems is a viable approach that also reduces the impact of climate change in the Caribbean.

Research on battery-operated electric road vehicles

NASA Technical Reports Server (NTRS)

Varpetian, V. S.

1977-01-01

Mathematical analysis of battery-operated electric vehicles is presented. Attention is focused on assessing the influence of the battery on the mechanical and dynamical characteristics of dc electric motors with series and parallel excitation, as well as on evaluating the influence of the excitation mode and speed control system on the performance of the battery. The superiority of series excitation over parallel excitation with respect to vehicle performance is demonstrated. It is also shown that pulsed control of the electric motor, as compared to potentiometric control, provides a more effective use of the battery and decreases the cost of recharging.

Generation and Radiation of Acoustic Waves from a 2D Shear Layer

NASA Technical Reports Server (NTRS)

Dahl, Milo D.

2000-01-01

A thin free shear layer containing an inflection point in the mean velocity profile is inherently unstable. Disturbances in the flow field can excite the unstable behavior of a shear layer, if the appropriate combination of frequencies and shear layer thicknesses exists, causing instability waves to grow. For other combinations of frequencies and thicknesses, these instability waves remain neutral in amplitude or decay in the downstream direction. A growing instability wave radiates noise when its phase velocity becomes supersonic relative to the ambient speed of sound. This occurs primarily when the mean jet flow velocity is supersonic. Thus, the small disturbances in the flow, which themselves may generate noise, have generated an additional noise source. It is the purpose of this problem to test the ability of CAA to compute this additional source of noise. The problem is idealized such that the exciting disturbance is a fixed known acoustic source pulsating at a single frequency. The source is placed inside of a 2D jet with parallel flow; hence, the shear layer thickness is constant. With the source amplitude small enough, the problem is governed by the following set of linear equations given in dimensional form.

Method and Apparatus for Characterizing Pressure Sensors using Modulated Light Beam Pressure

NASA Technical Reports Server (NTRS)

Youngquist, Robert C. (Inventor)

2003-01-01

Embodiments of apparatuses and methods are provided that use light sources instead of sound sources for characterizing and calibrating sensors for measuring small pressures to mitigate many of the problems with using sound sources. In one embodiment an apparatus has a light source for directing a beam of light on a sensing surface of a pressure sensor for exerting a force on the sensing surface. The pressure sensor generates an electrical signal indicative of the force exerted on the sensing surface. A modulator modulates the beam of light. A signal processor is electrically coupled to the pressure sensor for receiving the electrical signal.

Photoconductive circuit element reflectometer

DOEpatents

Rauscher, Christen

1990-01-01

A photoconductive reflectometer for characterizing semiconductor devices at millimeter wavelength frequencies where a first photoconductive circuit element (PCE) is biased by a direct current voltage source and produces short electrical pulses when excited into conductance by short first laser light pulses. The electrical pulses are electronically conditioned to improve the frequency related amplitude characteristics of the pulses which thereafter propagate along a transmission line to a device under test. Second PCEs are connected along the transmission line to sample the signals on the transmission line when excited into conductance by short second laser light pulses, spaced apart in time a variable period from the first laser light pulses. Electronic filters connected to each of the second PCEs act as low-pass filters and remove parasitic interference from the sampled signals and output the sampled signals in the form of slowed-motion images of the signals on the transmission line.

Photoconductive circuit element reflectometer

DOEpatents

Rauscher, C.

1987-12-07

A photoconductive reflectometer for characterizing semiconductor devices at millimeter wavelength frequencies where a first photoconductive circuit element (PCE) is biased by a direct current voltage source and produces short electrical pulses when excited into conductance by short first laser light pulses. The electrical pulses are electronically conditioned to improve the frequency related amplitude characteristics of the pulses which thereafter propagate along a transmission line to a device under test. Second PCEs are connected along the transmission line to sample the signals on the transmission line when excited into conductance by short second laser light pulses, spaced apart in time a determinable period from the first laser light pulses. Electronic filters connected to each of the second PCEs act as low-pass filters and remove parasitic interference from the sampled signals and output the sampled signals in the form of slowed-motion images of the signals on the transmission line. 4 figs.

Near-ultraviolet laser diodes for brilliant ultraviolet fluorophore excitation.

PubMed

Telford, William G

2015-12-01

Although multiple lasers are now standard equipment on most modern flow cytometers, ultraviolet (UV) lasers (325-365 nm) remain an uncommon excitation source for cytometry. Nd:YVO4 frequency-tripled diode pumped solid-state lasers emitting at 355 nm are now the primary means of providing UV excitation on multilaser flow cytometers. Although a number of UV excited fluorochromes are available for flow cytometry, the cost of solid-state UV lasers remains prohibitively high, limiting their use to all but the most sophisticated multilaser instruments. The recent introduction of the brilliant ultraviolet (BUV) series of fluorochromes for cell surface marker detection and their importance in increasing the number of simultaneous parameters for high-dimensional analysis has increased the urgency of including UV sources in cytometer designs; however, these lasers remain expensive. Near-UV laser diodes (NUVLDs), a direct diode laser source emitting in the 370-380 nm range, have been previously validated for flow cytometric analysis of most UV-excited probes, including quantum nanocrystals, the Hoechst dyes, and 4',6-diamidino-2-phenylindole. However, they remain a little-used laser source for cytometry, despite their significantly lower cost. In this study, the ability of NUVLDs to excite the BUV dyes was assessed, along with their compatibility with simultaneous brilliant violet (BV) labeling. A NUVLD emitting at 375 nm was found to excite most of the available BUV dyes at least as well as a UV 355 nm source. This slightly longer wavelength did produce some unwanted excitation of BV dyes, but at sufficiently low levels to require minimal additional compensation. NUVLDs are compact, relatively inexpensive lasers that have higher power levels than the newest generation of small 355 nm lasers. They can, therefore, make a useful, cost-effective substitute for traditional UV lasers in multicolor analysis involving the BUV and BV dyes. Published 2015 Wiley Periodicals Inc. on behalf of ISAC.

Radioisotope Sources of Electric Power

DTIC Science & Technology

1973-09-20

u) watt/cm-3 O) specific activity f) curia/watt (curie/a) a) half-life c) specific power output h) years (capacity) 1) days d) watt/p Polonium - 210 ...AD/A-001 210 RADIOISOTOPE SOURCES OF ELECTRIC POWER G. M. Fradkin, et al Army Foreign Science and Technology Center Charlottesville, Virginia 20...ormed. 6v usino this effect , one may make small-sized 3ources of electrical eneruv. Batteries with direct charde collection may be used to create accel

Adaptive Back Sheet Material for Acoustic Liner Applications-ARMD Seedling Fund Phase I Final Report

NASA Technical Reports Server (NTRS)

Gerhold, Carl H.; Jones, Michael G.; Farrar, Dawnielle

2014-01-01

A recently developed piezo-electric composite film is evaluated for its usefulness in application in acoustic liners. Researchers at the NASA Langley Research Center Liner Technology Facility developed experiments to measure the electrical response of the material to acoustic excitation and the vibrational response of the material to electrical excitation. The robustness of the piezo-electric film was also assessed. The material's electrical response to acoustic excitation is found to be comparable to a commercial microphone in the range of frequencies from 500 to 3000 Hz. However, the vibrational response to electrical excitation in the frequency range of interest is an order of magnitude less than may be necessary for application to acoustic liners. Nevertheless, experimental results indicate that the potential exists for the material to produce a measurable change in the impedance spectrum of a liner. Work continues to improve the authority of the piezo-electric film.

Floating electrode dielectrophoresis.

PubMed

Golan, Saar; Elata, David; Orenstein, Meir; Dinnar, Uri

2006-12-01

In practice, dielectrophoresis (DEP) devices are based on micropatterned electrodes. When subjected to applied voltages, the electrodes generate nonuniform electric fields that are necessary for the DEP manipulation of particles. In this study, electrically floating electrodes are used in DEP devices. It is demonstrated that effective DEP forces can be achieved by using floating electrodes. Additionally, DEP forces generated by floating electrodes are different from DEP forces generated by excited electrodes. The floating electrodes' capabilities are explained theoretically by calculating the electric field gradients and demonstrated experimentally by using test-devices. The test-devices show that floating electrodes can be used to collect erythrocytes (red blood cells). DEP devices which contain many floating electrodes ought to have fewer connections to external signal sources. Therefore, the use of floating electrodes may considerably facilitate the fabrication and operation of DEP devices. It can also reduce device dimensions. However, the key point is that DEP devices can integrate excited electrodes fabricated by microtechnology processes and floating electrodes fabricated by nanotechnology processes. Such integration is expected to promote the use of DEP devices in the manipulation of nanoparticles.

DNA complexes with dyes designed for energy transfer as fluorescent markers

DOEpatents

Glazer, Alexander M.; Benson, Scott C.

1999-01-01

Heteromultimeric fluorophores are provided for binding to DNA, which allow for the detection of DNA in electrical separations and preparation of probes having high-fluorescent efficiencies and large Stokes shifts. In addition, by appropriate choice of fluorescent molecules, one can use a single narrow wavelength band excitation light source, while obtaining fluorescent emissions having sufficient separation to be readily discriminated.

DNA complexes with dyes designed for energy transfer as fluorescent markers

DOEpatents

Glazer, Alexander M.; Benson, Scott C.

1998-01-01

Heteromultimeric fluorophores are provided for binding to DNA, which allow for the detection of DNA in electrical separations and preparation of probes having high-fluorescent efficiencies and large Stokes shifts. In addition, by appropriate choice of fluorescent molecules, one can use a single narrow wavelength band excitation light source, while obtaining fluorescent emissions having sufficient separation to be readily discriminated.

DNA complexes with dyes designed for energy transfer as fluorescent markers

DOEpatents

Glazer, Alexander N.; Benson, Scott C.

1995-01-01

Heteromultimeric fluorophores are provided for binding to DNA, which allow for the detection of DNA in electrical separations and preparation of probes having high-fluorescent efficiencies and large Stokes shifts. In addition, by appropriate choice of fluorescent molecules, one can use a single narrow wavelength band excitation light source, while obtaining fluorescent emissions having sufficient separation to be readily discriminated.

DNA complexes with dyes designed for energy transfer as fluorescent markers

DOEpatents

Glazer, Alexander N.; Benson, Scott C.

1997-01-01

Heteromultimeric fluorophores are provided for binding to DNA, which allow for the detection of DNA in electrical separations and preparation of probes having high-fluorescent efficiencies and large Stokes shifts. In addition, by appropriate choice of fluorescent molecules, one can use a single narrow wavelength band excitation light source, while obtaining fluorescent emissions having sufficient separation to be readily discriminated.

Rotational excitation of hydrogen molecules by collisions with hydrogen atoms. [interstellar gas energetics

NASA Technical Reports Server (NTRS)

Green, S.; Truhlar, D. G.

1979-01-01

Rate constants for rotational excitation of hydrogen molecules by collisions with hydrogen atoms have been obtained from quantum-mechanical calculations for kinetic temperatures between 100 and 5000 K. These calculations involve the rigid-rotator approximation, but other possible sources of error should be small. The calculations indicate that the early values of Nishimura are larger than accurate rigid-rotator values by about a factor of 20 or more.

Branches of electrostatic turbulence inside solitary plasma structures in the auroral ionosphere

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

Golovchanskaya, Irina V.; Kozelov, Boris V.; Chernyshov, Alexander A.

2014-08-15

The excitation of electrostatic turbulence inside space-observed solitary structures is a central topic of this exposition. Three representative solitary structures observed in the topside auroral ionosphere as large-amplitude nonlinear signatures in the electric field and magnetic-field-aligned current on the transverse scales of ∼10{sup 2}–10{sup 3} m are evaluated by the theories of electrostatic wave generation in inhomogeneous background configurations. A quantitative analysis shows that the structures are, in general, effective in destabilizing the inhomogeneous energy-density-driven (IEDD) waves, as well as of the ion acoustic waves modified by a shear in the parallel drift of ions. It is demonstrated that the dominatingmore » branch of the electrostatic turbulence is determined by the interplay of various driving sources inside a particular solitary structure. The sources do not generally act in unison, so that their common effect may be inhibiting for excitation of electrostatic waves of a certain type. In the presence of large magnetic-field-aligned current, which is not correlated to the inhomogeneous electric field inside the structure, the ion-acoustic branch becomes dominating. In other cases, the IEDD instability is more central.« less

Spectral fluorescent properties of tissues in vivo with excitation in the red wavelength range

NASA Astrophysics Data System (ADS)

Stratonnikov, Alexander A.; Loschenov, Victor B.; Klimov, D. V.; Edinac, N. E.; Wolnukhin, V. A.; Strashkevich, I. A.

1997-12-01

The spectral fluorescence analysis is a promising method for differential tissue diagnostic. Usually the UV and visible light is used for fluorescence excitation with emission registration in the visible wavelength range. The light penetration length in this wavelength range is very small allowing one to analyze only the surface region of the tissue. Here we present the tissue fluorescent spectra in vivo excited in the red wavelength region. As excitation light source we used compact He-Ne laser (632.8 nm) and observed the fluorescence in 650 - 800 nm spectral range. The various tissues including normal skin, psoriasis, tumors, necrosis as well as photosensitized tissues have been measured.

Fluorescent image tracking velocimeter

DOEpatents

Shaffer, Franklin D.

1994-01-01

A multiple-exposure fluorescent image tracking velocimeter (FITV) detects and measures the motion (trajectory, direction and velocity) of small particles close to light scattering surfaces. The small particles may follow the motion of a carrier medium such as a liquid, gas or multi-phase mixture, allowing the motion of the carrier medium to be observed, measured and recorded. The main components of the FITV include: (1) fluorescent particles; (2) a pulsed fluorescent excitation laser source; (3) an imaging camera; and (4) an image analyzer. FITV uses fluorescing particles excited by visible laser light to enhance particle image detectability near light scattering surfaces. The excitation laser light is filtered out before reaching the imaging camera allowing the fluoresced wavelengths emitted by the particles to be detected and recorded by the camera. FITV employs multiple exposures of a single camera image by pulsing the excitation laser light for producing a series of images of each particle along its trajectory. The time-lapsed image may be used to determine trajectory and velocity and the exposures may be coded to derive directional information.

Constraining nuclear photon strength functions by the decay properties of photo-excited states

NASA Astrophysics Data System (ADS)

Isaak, J.; Savran, D.; Krtička, M.; Ahmed, M. W.; Beller, J.; Fiori, E.; Glorius, J.; Kelley, J. H.; Löher, B.; Pietralla, N.; Romig, C.; Rusev, G.; Scheck, M.; Schnorrenberger, L.; Silva, J.; Sonnabend, K.; Tonchev, A. P.; Tornow, W.; Weller, H. R.; Zweidinger, M.

2013-12-01

A new approach for constraining the low-energy part of the electric dipole Photon Strength Function (E1-PSF) is presented. Experiments at the Darmstadt High-Intensity Photon Setup and the High Intensity γ→-Ray Source have been performed to investigate the decay properties of 130Te between 5.50 and 8.15 MeV excitation energy. In particular, the average γ-ray branching ratio to the ground state and the population intensity of low-lying excited states have been studied. A comparison to the statistical model shows that the latter is sensitive to the low-energy behavior of the E1-PSF, while the average ground state branching ratio cannot be described by the statistical model in the energy range between 5.5 and 6.5 MeV.

The relationship between form and function throughout the history of excitation-contraction coupling.

PubMed

Franzini-Armstrong, Clara

2018-02-05

The concept of excitation-contraction coupling is almost as old as Journal of General Physiology It was understood as early as the 1940s that a series of stereotyped events is responsible for the rapid contraction response of muscle fibers to an initial electrical event at the surface. These early developments, now lost in what seems to be the far past for most young investigators, have provided an endless source of experimental approaches. In this Milestone in Physiology, I describe in detail the experiments and concepts that introduced and established the field of excitation-contraction coupling in skeletal muscle. More recent advances are presented in an abbreviated form, as readers are likely to be familiar with recent work in the field. © 2018 Franzini-Armstrong.

Excitation of plasma waves by nonlinear currents induced by a high-frequency electromagnetic pulse

NASA Astrophysics Data System (ADS)

Grishkov, V. E.; Uryupin, S. A.

2017-03-01

Excitation of plasma waves by nonlinear currents induced by a high-frequency electromagnetic pulse is analyzed within the kinetic approach. It is shown that the most efficient source of plasma waves is the nonlinear current arising due to the gradient of the energy density of the high-frequency field. Generation of plasma waves by the drag current is usually less efficient but not negligibly small at relatively high frequencies of electron-ion collisions. The influence of electron collisions on the excitation of plasma waves by pulses of different duration is described quantitatively.

Excitation of plasma waves by nonlinear currents induced by a high-frequency electromagnetic pulse

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

Grishkov, V. E.; Uryupin, S. A., E-mail: uryupin@sci.lebedev.ru

Excitation of plasma waves by nonlinear currents induced by a high-frequency electromagnetic pulse is analyzed within the kinetic approach. It is shown that the most efficient source of plasma waves is the nonlinear current arising due to the gradient of the energy density of the high-frequency field. Generation of plasma waves by the drag current is usually less efficient but not negligibly small at relatively high frequencies of electron–ion collisions. The influence of electron collisions on the excitation of plasma waves by pulses of different duration is described quantitatively.

Nonlinear Right-Hand Polarized Wave in Plasma in the Electron Cyclotron Resonance Region

NASA Astrophysics Data System (ADS)

Krasovitskiy, V. B.; Turikov, V. A.

2018-05-01

The propagation of a nonlinear right-hand polarized wave along an external magnetic field in subcritical plasma in the electron cyclotron resonance region is studied using numerical simulations. It is shown that a small-amplitude plasma wave excited in low-density plasma is unstable against modulation instability with a modulation period equal to the wavelength of the excited wave. The modulation amplitude in this case increases with decreasing detuning from the resonance frequency. The simulations have shown that, for large-amplitude waves of the laser frequency range propagating in plasma in a superstrong magnetic field, the maximum amplitude of the excited longitudinal electric field increases with the increasing external magnetic field and can reach 30% of the initial amplitude of the electric field in the laser wave. In this case, the energy of plasma electrons begins to substantially increase already at magnetic fields significantly lower than the resonance value. The laser energy transferred to plasma electrons in a strong external magnetic field is found to increase severalfold compared to that in isotropic plasma. It is shown that this mechanism of laser radiation absorption depends only slightly on the electron temperature.

Motoneuron excitability of the quadriceps decreases during a fatiguing submaximal isometric contraction.

PubMed

Finn, Harrison T; Rouffet, David M; Kennedy, David S; Green, Simon; Taylor, Janet L

2018-04-01

During fatiguing voluntary contractions, the excitability of motoneurons innervating arm muscles decreases. However, the behavior of motoneurons innervating quadriceps muscles is unclear. Findings may be inconsistent because descending cortical input influences motoneuron excitability and confounds measures during exercise. To overcome this limitation, we examined effects of fatigue on quadriceps motoneuron excitability tested during brief pauses in descending cortical drive after transcranial magnetic stimulation (TMS). Participants ( n = 14) performed brief (~5-s) isometric knee extension contractions before and after a 10-min sustained contraction at ~25% maximal electromyogram (EMG) of vastus medialis (VM) on one ( n = 5) or two ( n = 9) days. Electrical stimulation over thoracic spine elicited thoracic motor evoked potentials (TMEP) in quadriceps muscles during ongoing voluntary drive and 100 ms into the silent period following TMS (TMS-TMEP). Femoral nerve stimulation elicited maximal M-waves (M max ). On the 2 days, either large (~50% M max ) or small (~15% M max ) TMS-TMEPs were elicited. During the 10-min contraction, VM EMG was maintained ( P = 0.39), whereas force decreased by 52% (SD 13%) ( P < 0.001). TMEP area remained unchanged ( P = 0.9), whereas large TMS-TMEPs decreased by 49% (SD 28%) ( P = 0.001) and small TMS-TMEPs by 71% (SD 22%) ( P < 0.001). This decline was greater for small TMS-TMEPs ( P = 0.019; n = 9). Therefore, without the influence of descending drive, quadriceps TMS-TMEPs decreased during fatigue. The greater reduction for smaller responses, which tested motoneurons that were most active during the contraction, suggests a mechanism related to repetitive activity contributes to reduced quadriceps motoneuron excitability during fatigue. By contrast, the unchanged TMEP suggests that ongoing drive compensates for altered motoneuron excitability. NEW & NOTEWORTHY We provide evidence that the excitability of quadriceps motoneurons decreases with fatigue. Our results suggest that altered intrinsic properties brought about by repetitive activation of the motoneurons underlie their decreased excitability. Furthermore, we note that testing during voluntary contraction may not reflect the underlying depression of motoneuron excitability because of compensatory changes in ongoing voluntary drive. Thus, this study provides evidence that processes intrinsic to the motoneuron contribute to muscle fatigue of the knee extensors.

Smart grid technologies in local electric grids

NASA Astrophysics Data System (ADS)

Lezhniuk, Petro D.; Pijarski, Paweł; Buslavets, Olga A.

2017-08-01

The research is devoted to the creation of favorable conditions for the integration of renewable sources of energy into electric grids, which were designed to be supplied from centralized generation at large electric power stations. Development of distributed generation in electric grids influences the conditions of their operation - conflict of interests arises. The possibility of optimal functioning of electric grids and renewable sources of energy, when complex criterion of the optimality is balance reliability of electric energy in local electric system and minimum losses of electric energy in it. Multilevel automated system for power flows control in electric grids by means of change of distributed generation of power is developed. Optimization of power flows is performed by local systems of automatic control of small hydropower stations and, if possible, solar power plants.

Creating Rydberg electron wave packets using terahertz pulses

NASA Astrophysics Data System (ADS)

Bromage, Jake

1999-10-01

In this thesis I present experiments in which we excited classical-limit states of an atom using terahertz pulses. In a classical-limit state, an atom's outer electron is confined to a wave packet that orbits the core along a classical trajectory. Researchers have excited states with classical traits, but wave packets localized in all three dimensions have proved elusive. Theoretical studies have shown such states can be created using terahertz pulses. Using these techniques, we created a linear-orbit wave packet (LOWP), that is three-dimensionally localized and orbits along a line on one side of the atom's core. Terahertz pulses are sub-picosecond bursts of far- infrared radiation. Unlike ultrashort optical pulses, the electric field of terahertz pulses barely completes a single cycle. Our simulations of the atom-pulse interaction show that this electric field profile is critical in determining the quality of the wave packet. To characterize our terahertz pulses, we invented dithered-edge sampling which time- resolves the electric field using a photoconductive receiver and a triggered attenuator. We also studied how pulses are distorted after propagating through metallic structures, and used our findings to design our atomic experiments. We excited wave packets in atomic sodium using a two-step process. First, we used tunable, nanosecond dye lasers to excite an extreme Stark state. Next, we used a terahertz pump pulse to coherently redistribute population among extreme Stark states in neighboring manifolds. Interference between the final states produces a localized, dynamic LOWP. To analyze the LOWP, we ionized it with a stronger terahertz probe pulse, varying the pump-probe delay to map out its motion. We observed two strong LOWP signatures. Changing the static electric field produced small changes (2%) in the orbital period that agreed with our theoretical predictions. Secondly, because the LOWP scatters off the core, the pump-probe signal depended on the direction of the kick the LOWP received from the robe pulse. These observations, combined with our detailed simulations that used sodium parameters and the actual shape of the terahertz pulse, lead us to conclude that we excited a LOWP.

Implantable power generation system utilizing muscle contractions excited by electrical stimulation.

PubMed

Sahara, Genta; Hijikata, Wataru; Tomioka, Kota; Shinshi, Tadahiko

2016-06-01

An implantable power generation system driven by muscle contractions for supplying power to active implantable medical devices, such as pacemakers and neurostimulators, is proposed. In this system, a muscle is intentionally contracted by an electrical stimulation in accordance with the demands of the active implantable medical device for electrical power. The proposed system, which comprises a small electromagnetic induction generator, electrodes with an electrical circuit for stimulation and a transmission device to convert the linear motion of the muscle contractions into rotational motion for the magneto rotor, generates electrical energy. In an ex vivo demonstration using the gastrocnemius muscle of a toad, which was 28 mm in length and weighed 1.3 g, the electrical energy generated by the prototype exceeded the energy consumed for electrical stimulation, with the net power being 111 µW. It was demonstrated that the proposed implantable power generation system has the potential to replace implantable batteries for active implantable medical devices. © IMechE 2016.

Improved transistor-controlled and commutated brushless DC motors for electric vehicle propulsion

NASA Technical Reports Server (NTRS)

Demerdash, N. A.; Miller, R. H.; Nehl, T. W.; Nyamusa, T. A.

1983-01-01

The development, design, construction, and testing processes of two electronically (transistor) controlled and commutated permanent magnet brushless dc machine systems, for propulsion of electric vehicles are detailed. One machine system was designed and constructed using samarium cobalt for permanent magnets, which supply the rotor (field) excitation. Meanwhile, the other machine system was designed and constructed with strontium ferrite permanent magnets as the source of rotor (field) excitation. These machine systems were designed for continuous rated power output of 15 hp (11.2 kw), and a peak one minute rated power output of 35 hp (26.1 kw). Both power ratings are for a rated voltage of 115 volts dc, assuming a voltage drop in the source (battery) of about 5 volts. That is, an internal source voltage of 120 volts dc. Machine-power conditioner system computer-aided simulations were used extensively in the design process. These simulations relied heavily on the magnetic field analysis in these machines using the method of finite elements, as well as methods of modeling of the machine power conditioner system dynamic interaction. These simulation processes are detailed. Testing revealed that typical machine system efficiencies at 15 hp (11.2 kw) were about 88% and 84% for the samarium cobalt and strontium ferrite based machine systems, respectively. Both systems met the peak one minute rating of 35 hp.

Optimization study on inductive-resistive circuit for broadband piezoelectric energy harvesters

NASA Astrophysics Data System (ADS)

Tan, Ting; Yan, Zhimiao

2017-03-01

The performance of cantilever-beam piezoelectric energy harvester is usually analyzed with pure resistive circuit. The optimal performance of such a vibration-based energy harvesting system is limited by narrow bandwidth around its modified natural frequency. For broadband piezoelectric energy harvesting, series and parallel inductive-resistive circuits are introduced. The electromechanical coupled distributed parameter models for such systems under harmonic base excitations are decoupled with modified natural frequency and electrical damping to consider the coupling effect. Analytical solutions of the harvested power and tip displacement for the electromechanical decoupled model are confirmed with numerical solutions for the coupled model. The optimal performance of piezoelectric energy harvesting with inductive-resistive circuits is revealed theoretically as constant maximal power at any excitation frequency. This is achieved by the scenarios of matching the modified natural frequency with the excitation frequency and equating the electrical damping to the mechanical damping. The inductance and load resistance should be simultaneously tuned to their optimal values, which may not be applicable for very high electromechanical coupling systems when the excitation frequency is higher than their natural frequencies. With identical optimal performance, the series inductive-resistive circuit is recommended for relatively small load resistance, while the parallel inductive-resistive circuit is suggested for relatively large load resistance. This study provides a simplified optimization method for broadband piezoelectric energy harvesters with inductive-resistive circuits.

A numerical study on piezoelectric energy harvesting by combining transverse galloping and parametric instability phenomena

NASA Astrophysics Data System (ADS)

Franzini, Guilherme Rosa; Santos, Rebeca Caramêz Saraiva; Pesce, Celso Pupo

2017-12-01

This paper aims to numerically investigate the effects of parametric instability on piezoelectric energy harvesting from the transverse galloping of a square prism. A two degrees-of-freedom reduced-order model for this problem is proposed and numerically integrated. A usual quasi-steady galloping model is applied, where the transverse force coefficient is adopted as a cubic polynomial function with respect to the angle of attack. Time-histories of nondimensional prism displacement, electric voltage and power dissipated at both the dashpot and the electrical resistance are obtained as functions of the reduced velocity. Both, oscillation amplitude and electric voltage, increased with the reduced velocity for all parametric excitation conditions tested. For low values of reduced velocity, 2:1 parametric excitation enhances the electric voltage. On the other hand, for higher reduced velocities, a 1:1 parametric excitation (i.e., the same as the natural frequency) enhances both oscillation amplitude and electric voltage. It has been also found that, depending on the parametric excitation frequency, the harvested electrical power can be amplified in 70% when compared to the case under no parametric excitation.

Temperature Effects of Electric Field on the First Excited State of Strong Coupling Polaron in a CsI Quantum Pseudodot

NASA Astrophysics Data System (ADS)

Sun, Yong; Ding, Zhao-Hua; Xiao, Jing-Lin

2017-03-01

Employing variational method of Pekar type (VMPT), this paper investigates the first-excited state energy (FESE), excitation energy and transition frequency of the strongly-coupled polaron in the CsI quantum pseudodot (QPD) with electric field. The temperature effects on the strong-coupling polaron in electric field are calculated by using the quantum statistical theory (QST). The results from the present investigation show that the FESE, excitation energy and transition frequency increase (decrease) firstly and then at lower (higher) temperature regions. They are decreasing functions of the electric field strength. Supported by the National Natural Science Foundation of China under Grant No. 11464033

Electric discharge in water as a source of UV radiation, ozone and hydrogen peroxide

NASA Astrophysics Data System (ADS)

Anpilov, A. M.; Barkhudarov, E. M.; Bark, Yu B.; Zadiraka, Yu V.; Christofi, M.; Kozlov, Yu N.; Kossyi, I. A.; Kop'ev, V. A.; Silakov, V. P.; Taktakishvili, M. I.; Temchin, S. M.

2001-03-01

Results are presented from investigations of multispark electric discharge in water excited along multielectrode metal-dielectric systems with gas supply into the interelectrode gaps. The intensity distribution of discharge radiation in the region covering the biologically active soft UV (190≤λ≤430 nm) has been determined and the absolute number of quanta in this wavelength interval has been measured. The potentiality of the slipping surface discharge in water for its disinfection is analysed. The energy expenditure for water cleansing is estimated to be as low as ~10-4 kWh l-1.

Experimental observation of polarized electroluminescence from edge-emission organic light emitting devices

NASA Astrophysics Data System (ADS)

Ran, G. Z.; Jiang, D. F.; Kan, Q.; Chen, H. D.

2010-12-01

We have observed a strongly polarized edge-emission from an organic light emitting device (OLED) with a silicon anode and a stacked Sm/Au (or Ag) cathode. For the OLED with a Sm/Au cathode, the transverse magnetic (TM) mode is stronger than the transverse electric (TE) mode by a factor of 2, while the polarization ratio of TM:TE is close to 300 for that with a Sm/Ag cathode. The polarization results from the scattering of surface plasmon polaritons at the device boundary. Such a silicon-based OLED is potentially an electrically excited SPP source in plasmonics.

Non-Migrating Diurnal Tides Generated with Planetary Waves in the Mesosphere

NASA Technical Reports Server (NTRS)

Mayr, H. G.; Mengel, J. G.; Talaat, E. R.; Porter, H. S.; Chan, K. L.

2003-01-01

We report here the results from a modeling study with our Numerical Spectral Model (NSM) that extends from the ground into thermosphere. The NSM incorporates Hines Doppler Spread Parameterization for small-scale gravity waves (GWs) and describes the major dynamical features of the atmosphere, including the wave driven equatorial oscillations (QBO and SAO), and the seasonal variations of tides and planetary waves. Accounting solely for the solar migrating tidal excitation sources, the NSM generates through dynamical interactions also non-migrating tides in the mesosphere that have amplitudes comparable to those observed. The model produces the diurnal (and semidiurnal) oscillations of the zonal mean (m = 0), and eastward and westward propagating tides for zonal wave numbers m = 1 to 4. To identify the mechanism of excitation for these tides, a numerical experiment is performed. The NSM is run without the heat source for the zonal-mean circulation and temperature variation, and the amplitudes of the resulting nonmigrating tides are then negligibly small. This leads to the conclusion that the planetary waves, which normally are excited in the NSM by instabilities but are suppressed in this case, generate the nonmigrating tides through nonlinear interactions with the migrating tides.

PI3K Phosphorylation Is Linked to Improved Electrical Excitability in an In Vitro Engineered Heart Tissue Disease Model System.

PubMed

Kana, Kujaany; Song, Hannah; Laschinger, Carol; Zandstra, Peter W; Radisic, Milica

2015-09-01

Myocardial infarction, a prevalent cardiovascular disease, is associated with cardiomyocyte cell death, and eventually heart failure. Cardiac tissue engineering has provided hopes for alternative treatment options, and high-fidelity tissue models for drug discovery. The signal transduction mechanisms relayed in response to mechanoelectrical (physical) stimulation or biochemical stimulation (hormones, cytokines, or drugs) in engineered heart tissues (EHTs) are poorly understood. In this study, an EHT model was used to elucidate the signaling mechanisms involved when insulin was applied in the presence of electrical stimulation, a stimulus that mimics functional heart tissue environment in vitro. EHTs were insulin treated, electrically stimulated, or applied in combination (insulin and electrical stimulation). Electrical excitability parameters (excitation threshold and maximum capture rate) were measured. Protein kinase B (AKT) and phosphatidylinositol-3-kinase (PI3K) phosphorylation revealed that insulin and electrical stimulation relayed electrical excitability through two separate signaling cascades, while there was a negative crosstalk between sustained activation of AKT and PI3K.

Simulation of electrostatic ion instabilities in the presence of parallel currents and transverse electric fields

NASA Technical Reports Server (NTRS)

Nishikawa, K.-I.; Ganguli, G.; Lee, Y. C.; Palmadesso, P. J.

1989-01-01

A spatially two-dimensional electrostatic PIC simulation code was used to study the stability of a plasma equilibrium characterized by a localized transverse dc electric field and a field-aligned drift for L is much less than Lx, where Lx is the simulation length in the x direction and L is the scale length associated with the dc electric field. It is found that the dc electric field and the field-aligned current can together play a synergistic role to enable the excitation of electrostatic waves even when the threshold values of the field aligned drift and the E x B drift are individually subcritical. The simulation results show that the growing ion waves are associated with small vortices in the linear stage, which evolve to the nonlinear stage dominated by larger vortices with lower frequencies.

Use of CFD to predict trapped gas excitation as source of vibration and noise in screw compressors

NASA Astrophysics Data System (ADS)

Willie, James

2017-08-01

This paper investigates the source of noise in oil free screw compressors mounted on highway trucks and driven by a power take-off (PTO) transmission system. Trapped gas at the discharge side is suggested as possible source of the excitation of low frequency torsional resonance in these compressors that can lead to noise and vibration. Measurements and lumped mass torsional models have shown low frequency torsional resonance in the drive train of these compressors when they are mounted on trucks. This results in high torque peak at the compressor input shaft and in part to pulsating noise inside the machine. The severity of the torque peak depends on the amplitude of the input torque fluctuation from the drive (electric motor or truck engine). This in turn depends on the prop-shaft angle. However, the source of the excitation of this low torsional resonance inside the machine is unknown. Using CFD with mesh motion at every 1° rotation of the rotors, it is shown that the absence of a pressure equalizing chamber at the discharge can lead to trapped gas creation, which can lead to over-compression, over-heating of the rotors, and to high pressure pulsations at the discharge. Over-compression can lead to shock wave generation at the discharge plenum and the pulsation in pressure can lead to noise generation. In addition, if the frequency of the pressure pulsation in the low frequency range coincides with the first torsional frequency of the drive train the first torsional resonance mode can be excited.

A Study of Power Systems Stability Enhancement Effects by Excitation Control of Superconducting Generator with High Response Excitation based on Detailed Excitation Circuit Model

NASA Astrophysics Data System (ADS)

Wu, Guohong; Shirato, Hideyuki

SCG (Superconducting Generator) has a superconducting field winding, which leads to many advantages such as small size, high generation efficiency, low impedance, and so on, and be considered as one of the candidates to meet the needs of high stability and high efficiency in the future power system networks. SCG with high response excitation is especially expected to be able to enhance the transient stability of power system by its SMES (Superconducting Magnetic Energy System) effect. The SMES effect of SCG is recognized that its behaviors are dominated by the structures and controls of its excitation system. For this reason, in order to verify exactly how the SMES effect of SCG influences on the power system stability, the electrical circuits of SCG high response excitation are modeled in detail for conducting digital simulation, and its influence on excitation voltage and active power output of SCG are discussed as well. The simulation results with a typical one machine - infinite bus power system model shows that the SMES effect can be certainly obtained when its exciting power is supplied from SCG terminal bus and may considerably lead to an improvement of power system transient stability.

Self-excitation of microwave oscillations in plasma-assisted slow-wave oscillators by an electron beam with a movable focus

NASA Astrophysics Data System (ADS)

Bliokh, Yu. P.; Nusinovich, G. S.; Shkvarunets, A. G.; Carmel, Y.

2004-10-01

Plasma-assisted slow-wave oscillators (pasotrons) operate without external magnetic fields, which makes these devices quite compact and lightweight. Beam focusing in pasotrons is provided by ions, which appear in the device due to the impact ionization of a neutral gas by beam electrons. Typically, the ionization time is on the order of the rise time of the beam current. This means that, during the rise of the current, beam focusing by ions becomes stronger. Correspondingly, a beam of electrons, which was initially diverging radially due to the self-electric field, starts to be focused by ions, and this focus moves towards the gun as the ion density increases. This feature makes the self-excitation of electromagnetic (em) oscillations in pasotrons quite different from practically all other microwave sources where em oscillations are excited by a stationary electron beam. The process of self-excitation of em oscillations has been studied both theoretically and experimentally. It is shown that in pasotrons, during the beam current rise the amount of current entering the interaction space and the beam coupling to the em field vary. As a result, the self-excitation can proceed faster than in conventional microwave sources with similar operating parameters such as the operating frequency, cavity quality-factor and the beam current and voltage.

Needle-array to Plate DBD Plasma Using Sine AC and Nanosecond Pulse Excitations for Purpose of Improving Indoor Air Quality

PubMed Central

Zhang, Li; Yang, Dezheng; Wang, Wenchun; Wang, Sen; Yuan, Hao; Zhao, Zilu; Sang, Chaofeng; Jia, Li

2016-01-01

In this study, needle-array to plate electrode configuration was employed to generate an atmospheric air diffuse discharge using both nanosecond pulse and sine AC voltage as excitation voltage for the purpose of improving indoor air quality. Different types of voltage sources and electrode configurations are employed to optimize electrical field distribution and improve discharge stability. Discharge images, electrical characteristics, optical emission spectra, and plasma gas temperatures in both sine AC discharge and nanosecond pulse discharge were compared and the discharge stability during long operating time were discussed. Compared with the discharge excited by sine AC voltage, the nanosecond pulsed discharge is more homogenous and stable, besides, the plasma gas temperature of nanosecond pulse discharge is much lower. Using packed-bed structure, where γ- Al2O3 pellets are filled in the electrode gap, has obvious efficacy in the production of homogenous discharge. Furthermore, both sine AC discharge and nanosecond pulse discharge were used for removing formaldehyde from flowing air. It shows that nanosecond pulse discharge has a significant advantage in energy cost. And the main physiochemical processes for the generation of active species and the degradation of formaldehyde were discussed. PMID:27125663

DNA complexes with dyes designed for energy transfer as fluorescent markers

DOEpatents

Glazer, A.N.; Benson, S.C.

1997-07-08

Heteromultimeric fluorophores are provided for binding to DNA, which allow for the detection of DNA in electrical separations and preparation of probes having high-fluorescent efficiencies and large Stokes shifts. In addition, by appropriate choice of fluorescent molecules, one can use a single narrow wavelength band excitation light source, while obtaining fluorescent emissions having sufficient separation to be readily discriminated. 4 figs.

DNA complexes with dyes designed for energy transfer as fluorescent markers

DOEpatents

Glazer, A.M.; Benson, S.C.

1998-06-16

Heteromultimeric fluorophores are provided for binding to DNA, which allow for the detection of DNA in electrical separations and preparation of probes having high-fluorescent efficiencies and large Stokes shifts. In addition, by appropriate choice of fluorescent molecules, one can use a single narrow wavelength band excitation light source, while obtaining fluorescent emissions having sufficient separation to be readily discriminated. 4 figs.

Leaky Waves in Metamaterials for Antenna Applications

DTIC Science & Technology

2011-07-01

excitation problems, electromagnetic fields are often represented as Sommerfeld integrals [31,32]. A detailed discussion about Sommerfeld integral is...source removed. In the rest of this section, a de- tailed discussion about Sommerfeld Integral Path is presented. 4.1 Spectral Domain Approach 4.1.1... Sommerfeld integral path for evaluating fields accurately and efficiently, the radiation intensity and directivity of electric/magnetic dipoles over a grounded

DNA complexes with dyes designed for energy transfer as fluorescent markers

DOEpatents

Glazer, A.N.; Benson, S.C.

1995-03-28

Heteromultimeric fluorophores are provided for binding to DNA, which allow for the detection of DNA in electrical separations and preparation of probes having high-fluorescent efficiencies and large Stokes shifts. In addition, by appropriate choice of fluorescent molecules, one can use a single narrow wavelength band excitation light source, while obtaining fluorescent emissions having sufficient separation to be readily discriminated. 4 figures.

A cardiac electrical activity model based on a cellular automata system in comparison with neural network model.

PubMed

Khan, Muhammad Sadiq Ali; Yousuf, Sidrah

2016-03-01

Cardiac Electrical Activity is commonly distributed into three dimensions of Cardiac Tissue (Myocardium) and evolves with duration of time. The indicator of heart diseases can occur randomly at any time of a day. Heart rate, conduction and each electrical activity during cardiac cycle should be monitor non-invasively for the assessment of "Action Potential" (regular) and "Arrhythmia" (irregular) rhythms. Many heart diseases can easily be examined through Automata model like Cellular Automata concepts. This paper deals with the different states of cardiac rhythms using cellular automata with the comparison of neural network also provides fast and highly effective stimulation for the contraction of cardiac muscles on the Atria in the result of genesis of electrical spark or wave. The specific formulated model named as "States of automaton Proposed Model for CEA (Cardiac Electrical Activity)" by using Cellular Automata Methodology is commonly shows the three states of cardiac tissues conduction phenomena (i) Resting (Relax and Excitable state), (ii) ARP (Excited but Absolutely refractory Phase i.e. Excited but not able to excite neighboring cells) (iii) RRP (Excited but Relatively Refractory Phase i.e. Excited and able to excite neighboring cells). The result indicates most efficient modeling with few burden of computation and it is Action Potential during the pumping of blood in cardiac cycle.

Development of a 5.5 m diameter vertical axis wind turbine, phase 3

NASA Astrophysics Data System (ADS)

Dekitsch, A.; Etzler, C. C.; Fritzsche, A.; Lorch, G.; Mueller, W.; Rogalla, K.; Schmelzle, J.; Schuhwerk, W.; Vollan, A.; Welte, D.

1982-06-01

In continuation of development of a 5.5 m diameter vertical axis windmill that consists in conception, building, and wind tunnel testing, a Darrieus rotor windpowered generator feeding an isolated network under different wind velocity conditions and with optimal energy conversion efficiency was designed built, and field tested. The three-bladed Darrieus rotor tested in the wind tunnel was equiped with two variable pitch Savonius rotors 2 m in diameter. By means of separate measures of the aerodynamic factors and the energy consumption, effect of revisions and optimizations on different elements was assessed. Pitch adjustement of the Savonius blades, lubrication of speed reducer, rotor speed at cut-in of generator field excitation, time constant of field excitation, stability conditions, switch points of ohmic resistors which combined with a small electric battery simulated a larger isolated network connected with a large storage battery, were investigated. Fundamentals for the economic series production of windpowered generators with Darrieus rotors for the control and the electric conversion system are presented.

Plasmon enhanced terahertz emission from single layer graphene.

PubMed

Bahk, Young-Mi; Ramakrishnan, Gopakumar; Choi, Jongho; Song, Hyelynn; Choi, Geunchang; Kim, Yong Hyup; Ahn, Kwang Jun; Kim, Dai-Sik; Planken, Paul C M

2014-09-23

We show that surface plasmons, excited with femtosecond laser pulses on continuous or discontinuous gold substrates, strongly enhance the generation and emission of ultrashort, broadband terahertz pulses from single layer graphene. Without surface plasmon excitation, for graphene on glass, 'nonresonant laser-pulse-induced photon drag currents' appear to be responsible for the relatively weak emission of both s- and p-polarized terahertz pulses. For graphene on a discontinuous layer of gold, only the emission of the p-polarized terahertz electric field is enhanced, whereas the s-polarized component remains largely unaffected, suggesting the presence of an additional terahertz generation mechanism. We argue that in the latter case, 'surface-plasmon-enhanced optical rectification', made possible by the lack of inversion symmetry at the graphene on gold surface, is responsible for the strongly enhanced emission. The enhancement occurs because the electric field of surface plasmons is localized and enhanced where the graphene is located: at the surface of the metal. We believe that our results point the way to small, thin, and more efficient terahertz photonic devices.

The Effect of Transcranial Direct Current Stimulation (tDCS) Electrode Size and Current Intensity on Motor Cortical Excitability: Evidence From Single and Repeated Sessions.

PubMed

Ho, Kerrie-Anne; Taylor, Janet L; Chew, Taariq; Gálvez, Verònica; Alonzo, Angelo; Bai, Siwei; Dokos, Socrates; Loo, Colleen K

2016-01-01

Current density is considered an important factor in determining the outcomes of tDCS, and is determined by the current intensity and electrode size. Previous studies examining the effect of these parameters on motor cortical excitability with small sample sizes reported mixed results. This study examined the effect of current intensity (1 mA, 2 mA) and electrode size (16 cm(2), 35 cm(2)) on motor cortical excitability over single and repeated tDCS sessions. Data from seven studies in 89 healthy participants were pooled for analysis. Single-session data were analyzed using mixed effects models and repeated-session data were analyzed using mixed design analyses of variance. Computational modeling was used to examine the electric field generated. The magnitude of increases in excitability after anodal tDCS was modest. For single-session tDCS, the 35 cm(2) electrodes produced greater increases in cortical excitability compared to the 16 cm(2) electrodes. There were no differences in the magnitude of cortical excitation produced by 1 mA and 2 mA tDCS. The repeated-sessions data also showed that there were greater increases in excitability with the 35 cm(2) electrodes. Further, repeated sessions of tDCS with the 35 cm(2) electrodes resulted in a cumulative increase in cortical excitability. Computational modeling predicted higher electric field at the motor hotspot for the 35 cm(2) electrodes. 2 mA tDCS does not necessarily produce larger effects than 1 mA tDCS in healthy participants. Careful consideration should be given to the exact positioning, size and orientation of tDCS electrodes relative to cortical regions. Copyright © 2016 Elsevier Inc. All rights reserved.

Signal characteristics of electroseismic conversion

NASA Astrophysics Data System (ADS)

Peng, Rong; Di, Bangrang; Wei, Jianxin; Ding, Pinbo; Liu, Zichun; Guan, Bingyan; Huang, Shiqi

2018-04-01

Electric fields applying on the fluid-filled porous materials can induce small relative pore-fluid motions due to electroseismic conversions. In order to characterize the electroseismic propagation phenomena, we have designed an experimental apparatus to acquire the electroseismic (ES) signals. The electroseismic measurements on different samples have been conducted to confirm the origin of the recorded signals. We find that a strong acoustic signal generates around the electrode and affects the identification of ES signals. To further confirm and distinguish the ES signal as well as the acoustic signal around the electrode, we have analyzed records obtained with regular movements of the receiver, the sample and the source. Analysis has been made on the characteristics of the traveltime, polarity and frequency of ES signals. Our results show that the traveltime of ES signal relates to the distance between the rock sample and the receiver, the location of the exciting electrode has little impact on the traveltime. The applied electric field influences the polarity of ES signal, the polarity of ES signal reverses along with the changes of the electric field direction. While it has no polarity effects on the acoustic signal generated around the electrode. The frequency spectrum of ES signal is absolutely different with that of the acoustic signal generated around the electrode. The acoustic signal around the electrode has multiple dominant frequencies which are mainly in low-frequency range without being affected by the frequency of the electric field. The ES signal has only one dominant frequency which closely relates to the frequency of the electric field. The understanding of the signal characteristics on electroseismic conversion can contribute to a better application and interpretation of ES exploration.

Modal forced vibration analysis of aerodynamically excited turbosystems

NASA Technical Reports Server (NTRS)

Elchuri, V.

1985-01-01

Theoretical aspects of a new capability to determine the vibratory response of turbosystems subjected to aerodynamic excitation are presented. Turbosystems such as advanced turbopropellers with highly swept blades, and axial-flow compressors and turbines can be analyzed using this capability. The capability has been developed and implemented in the April 1984 release of the general purpose finite element program NASTRAN. The dynamic response problem is addressed in terms of the normal modal coordinates of these tuned rotating cyclic structures. Both rigid and flexible hubs/disks are considered. Coriolis and centripetal accelerations, as well as differential stiffness effects are included. Generally non-uniform steady inflow fields and uniform flow fields arbitrarily inclined at small angles with respect to the axis of rotation of the turbosystem are considered sources of aerodynamic excitation. The spatial non-uniformities are considered to be small deviations from a principally uniform inflow. Subsonic and supersonic relative inflows are addressed, with provision for linearly interpolating transonic airloads.

Modeling of surface-dominated plasmas: from electric thruster to negative ion source.

PubMed

Taccogna, F; Schneider, R; Longo, S; Capitelli, M

2008-02-01

This contribution shows two important applications of the particle-in-cell/monte Carlo technique on ion sources: modeling of the Hall thruster SPT-100 for space propulsion and of the rf negative ion source for ITER neutral beam injection. In the first case translational degrees of freedom are involved, while in the second case inner degrees of freedom (vibrational levels) are excited. Computational results show how in both cases, plasma-wall and gas-wall interactions play a dominant role. These are secondary electron emission from the lateral ceramic wall of SPT-100 and electron capture from caesiated surfaces by positive ions and atoms in the rf negative ion source.

Microwave produced plasma in a Toroidal Device

NASA Astrophysics Data System (ADS)

Singh, A. K.; Edwards, W. F.; Held, E. D.

2010-11-01

A currentless toroidal plasma device exhibits a large range of interesting basic plasma physics phenomena. Such a device is not in equilibrium in a strict magneto hydrodynamic sense. There are many sources of free energy in the form of gradients in plasma density, temperature, the background magnetic field and the curvature of the magnetic field. These free energy sources excite waves and instabilities which have been the focus of studies in several devices in last two decades. A full understanding of these simple plasmas is far from complete. At Utah State University we have recently designed and installed a microwave plasma generation system on a small tokamak borrowed from the University of Saskatchewan, Saskatoon, Canada. Microwaves are generated at 2.45 GHz in a pulsed dc mode using a magnetron from a commercial kitchen microwave oven. The device is equipped with horizontal and vertical magnetic fields and a transformer to impose a toroidal electric field for current drive. Plasmas can be obtained over a wide range of pressure with and without magnetic fields. We present some preliminary measurements of plasma density and potential profiles. Measurements of plasma temperature at different operating conditions are also presented.

60-GHz integrated-circuit high data rate quadriphase shift keying exciter and modulator

NASA Technical Reports Server (NTRS)

Grote, A.; Chang, K.

1984-01-01

An integrated-circuit quadriphase shift keying (QPSK) exciter and modulator have demonstrated excellent performance directly modulating a carrier frequency of 60 GHz with an output phase error of less than 3 degrees and maximum amplitude error of 0.5 dB. The circuit consists of a 60-GHz Gunn VCO phase-locked to a low-frequency reference source, a 4th subharmonic mixer, and a QPSK modlator packaged into a small volume of 1.8 x 2.5 x 0.35 in. The use of microstrip has the advantages of small size, light-weight, and low-cost fabrication. The unit has the potential for multigigabit data rate applications.

Diagnostics development for E-beam excited air channels

NASA Astrophysics Data System (ADS)

Eckstrom, D. J.; Dickenson, J. S.

1982-02-01

As the tempo of development of particle beam weapons increases, more detailed diagnostics of the interaction of the particle beam with the atmosphere are being proposed and implemented. Some of these diagnostics involve probing of the excited air channel with visible wavelength laser radiation. Examples include the use of visible wavelength interferometry to measure electron density profiles in the nose of the beam Ri81 and Stark shift measurements to determine self-induced electric fields Hi81, DR81. In these diagnostics, the change in laser intensity due to the desired diagnostic effect can be quite small, leading to the possibility that other effects, such as gas phase absorption, could seriously interfere with the measurement.

Excitation of helicons by current antennas

NASA Astrophysics Data System (ADS)

Gospodchikov, E. D.; Timofeev, A. V.

2017-06-01

Depending on the angle θ between the wave vector and the magnetic field, helicons are conventionally divided into two branches: proper helicons (H mode), propagating at small θ, and Trivelpiece-Gould waves (TG mode), propagating at large θ. The latter are close to potential waves and have a significant electric component along the external magnetic field. It is believed that it is these waves that provide electron heating in helicon discharges. There is also commonly believed that current antennas, widely used to ignite helicon discharges, excite essentially nonpotential H modes, which then transform into TG modes due to plasma inhomogeneity. In this work, it is demonstrated that electromagnetic energy can also be efficiently introduced in plasma by means of TG modes.

Electric current heating calibration of a laser holographic nondestructive test system

NASA Technical Reports Server (NTRS)

Liu, H.-K.; Kurtz, R. L.

1975-01-01

Holographic NDT was used to measure small surface displacements controlled by electric heating by detecting the difference of the interference fringe patterns as viewed through the hologram on a real time basis. A perforated aluminum test plate, with the holes used to position thin metal foils, was used in the experiment. One of the foils was connected to an electric power source and small displacements of the foil were caused and controlled by Ohmic heating. An He-Ne laser was used to perform the holography.

Four-dimensional ultrasound current source density imaging of a dipole field

NASA Astrophysics Data System (ADS)

Wang, Z. H.; Olafsson, R.; Ingram, P.; Li, Q.; Qin, Y.; Witte, R. S.

2011-09-01

Ultrasound current source density imaging (UCSDI) potentially transforms conventional electrical mapping of excitable organs, such as the brain and heart. For this study, we demonstrate volume imaging of a time-varying current field by scanning a focused ultrasound beam and detecting the acoustoelectric (AE) interaction signal. A pair of electrodes produced an alternating current distribution in a special imaging chamber filled with a 0.9% NaCl solution. A pulsed 1 MHz ultrasound beam was scanned near the source and sink, while the AE signal was detected on remote recording electrodes, resulting in time-lapsed volume movies of the alternating current distribution.

Boundary Conditions for Jet Flow Computations

NASA Technical Reports Server (NTRS)

Hayder, M. E.; Turkel, E.

1994-01-01

Ongoing activities are focused on capturing the sound source in a supersonic jet through careful large eddy simulation (LES). One issue that is addressed is the effect of the boundary conditions, both inflow and outflow, on the predicted flow fluctuations, which represent the sound source. In this study, we examine the accuracy of several boundary conditions to determine their suitability for computations of time-dependent flows. Various boundary conditions are used to compute the flow field of a laminar axisymmetric jet excited at the inflow by a disturbance given by the corresponding eigenfunction of the linearized stability equations. We solve the full time dependent Navier-Stokes equations by a high order numerical scheme. For very small excitations, the computed growth of the modes closely corresponds to that predicted by the linear theory. We then vary the excitation level to see the effect of the boundary conditions in the nonlinear flow regime.

Numerical Modeling of Electroacoustic Logging Including Joule Heating

NASA Astrophysics Data System (ADS)

Plyushchenkov, Boris D.; Nikitin, Anatoly A.; Turchaninov, Victor I.

It is well known that electromagnetic field excites acoustic wave in a porous elastic medium saturated with fluid electrolyte due to electrokinetic conversion effect. Pride's equations describing this process are written in isothermal approximation. Update of these equations, which allows to take influence of Joule heating on acoustic waves propagation into account, is proposed here. This update includes terms describing the initiation of additional acoustic waves excited by thermoelastic stresses and the heat conduction equation with right side defined by Joule heating. Results of numerical modeling of several problems of propagation of acoustic waves excited by an electric field source with and without consideration of Joule heating effect in their statements are presented. From these results, it follows that influence of Joule heating should be taken into account at the numerical simulation of electroacoustic logging and at the interpretation of its log data.

Multi-Channel Hyperspectral Fluorescence Detection Excited by Coupled Plasmon-Waveguide Resonance

PubMed Central

Du, Chan; Liu, Le; Zhang, Lin; Guo, Jun; Guo, Jihua; Ma, Hui; He, Yonghong

2013-01-01

We propose in this paper a biosensor scheme based on coupled plasmon-waveguide resonance (CPWR) excited fluorescence spectroscopy. A symmetrical structure that offers higher surface electric field strengths, longer surface propagation lengths and depths is developed to support guided waveguide modes for the efficient excitation of fluorescence. The optimal parameters for the sensor films are theoretically and experimentally investigated, leading to a detection limit of 0.1 nM (for a Cy5 solution). Multiplex analysis possible with the fluorescence detection is further advanced by employing the hyperspectral fluorescence technique to record the full spectra for every pixel on the sample plane. We demonstrate experimentally that highly overlapping fluorescence (Cy5 and Dylight680) can be distinguished and ratios of different emission sources can be determined accurately. This biosensor shows great potential for multiplex detections of fluorescence analytes. PMID:24129023

Characteristics of High-Density Helicon Plasma Sources and Their Application to Electrodeless Electric Propulsion

NASA Astrophysics Data System (ADS)

Shinohara, S.; Nishida, H.; Nakamura, T.; Mishio, A.; Ishii, H.; Teshigahara, N.; Fujitsuka, H.; Waseda, S.; Tanikawa, T.; Hada, T.; Otsuka, F.; Funaki, I.; Matsuoka, T.; Shamrai, K.; Rudenko, T.

2012-10-01

High-density but low temperature helicon plasmas have been proved to be very useful for fundamental research as well as for various applications. First, we introduce our very large helicon sources [1] with a diameter up to 74 cm. For the industrial and propulsion applications, we have reduced the aspect ratio (axial length-to-diameter) down to 0.075, and examined the discharge performance and wave characteristics. Then, we discuss our small helicon sources [1] for developing new electrodeless acceleration schemes. Some experimental and theoretical results [2] by applying the rotating magnetic (or electric) fields to the helicon plasma under the divergent magnetic field will be presented, along with other propulsion schemes. In addition, an initial plasma production experiment with very small diameter will be described.[4pt] [1] S. Shinohara et al., Jpn. J. Appl. Phys. 35 (1996) 4503; Rev. Sci. Instrum. 75 (2004) 1941; Phys. Plasmas 16 (2009) 057104.[0pt] [2] S. Shinohara et al., 32th Int. Electric Propul. Conf., IEPC-2011-056, 2011.

Near field Rayleigh wave on soft porous layers.

PubMed

Geebelen, N; Boeckx, L; Vermeir, G; Lauriks, W; Allard, J F; Dazel, O

2008-03-01

Simulations performed for a typical semi-infinite reticulated plastic foam saturated by air show that, at distances less than three Rayleigh wavelengths from the area of mechanical excitation by a circular source, the normal frame velocity is close to the Rayleigh pole contribution. Simulated measurements show that a good order of magnitude estimate of the phase speed and damping can be obtained at small distances from the source. Simulations are also performed for layers of finite thickness, where the phase velocity and damping depend on frequency. They indicate that the normal frame velocity at small distances from the source is always close to the Rayleigh pole contribution and that a good order of magnitude estimate of the phase speed of the Rayleigh wave can be obtained at small distances from the source. Furthermore, simulations show that precise measurements of the damping of the Rayleigh wave need larger distances. Measurements performed on a layer of finite thickness confirm these trends.

Excitation of parasitic waves in forward-wave amplifiers with weak guiding fields.

PubMed

Nusinovich, G S; Romero-Talamás, C A; Han, Y

2012-12-01

To produce high-power coherent electromagnetic radiation at frequencies from microwaves up to terahertz, the radiation sources should have interaction circuits of large cross sections, i.e., the sources should operate in high-order modes. In such devices, the excitation of higher-order parasitic modes near cutoff where the group velocity is small and, hence, start currents are low can be a serious problem. The problem is especially severe in the sources of coherent, phase-controlled radiation, i.e., the amplifiers or phase-locked oscillators. This problem was studied earlier [Nusinovich, Sinitsyn, and Antonsen, Phys. Rev. E 82, 046404 (2010)] for the case of electron focusing by strong guiding magnetic fields. For many applications it is desirable to minimize these focusing fields. Therefore in this paper we analyze the problem of excitation of parasitic modes near cutoff in forward-wave amplifiers with weak focusing fields. First, we study the large-signal operation of such a device with a signal wave only. Then, we analyze the self-excitation conditions of parasitic waves near cutoff in the presence of the signal wave. It is shown that the main effect is the suppression of the parasitic wave in large-signal regimes. At the same time, there is a region of device parameters where the presence of signal waves can enhance excitation of parasitic modes. The role of focusing fields in such effects is studied.

Modeling an Excitable Biosynthetic Tissue with Inherent Variability for Paired Computational-Experimental Studies.

PubMed

Gokhale, Tanmay A; Kim, Jong M; Kirkton, Robert D; Bursac, Nenad; Henriquez, Craig S

2017-01-01

To understand how excitable tissues give rise to arrhythmias, it is crucially necessary to understand the electrical dynamics of cells in the context of their environment. Multicellular monolayer cultures have proven useful for investigating arrhythmias and other conduction anomalies, and because of their relatively simple structure, these constructs lend themselves to paired computational studies that often help elucidate mechanisms of the observed behavior. However, tissue cultures of cardiomyocyte monolayers currently require the use of neonatal cells with ionic properties that change rapidly during development and have thus been poorly characterized and modeled to date. Recently, Kirkton and Bursac demonstrated the ability to create biosynthetic excitable tissues from genetically engineered and immortalized HEK293 cells with well-characterized electrical properties and the ability to propagate action potentials. In this study, we developed and validated a computational model of these excitable HEK293 cells (called "Ex293" cells) using existing electrophysiological data and a genetic search algorithm. In order to reproduce not only the mean but also the variability of experimental observations, we examined what sources of variation were required in the computational model. Random cell-to-cell and inter-monolayer variation in both ionic conductances and tissue conductivity was necessary to explain the experimentally observed variability in action potential shape and macroscopic conduction, and the spatial organization of cell-to-cell conductance variation was found to not impact macroscopic behavior; the resulting model accurately reproduces both normal and drug-modified conduction behavior. The development of a computational Ex293 cell and tissue model provides a novel framework to perform paired computational-experimental studies to study normal and abnormal conduction in multidimensional excitable tissue, and the methodology of modeling variation can be applied to models of any excitable cell.

A photosynthetic-plasmonic-voltaic cell: Excitation of photosynthetic bacteria and current collection through a plasmonic substrate

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

Samsonoff, Nathan; Ooms, Matthew D.; Sinton, David

2014-01-27

Excitation of photosynthetic biofilms using surface-confined evanescent light fields enables energy dense photobioreactors, while electrode-adhered biofilms can provide electricity directly. Here, we demonstrate concurrent light delivery and electron transport through a plasmonically excited metal film. Biofilms of cyanobacterium Synechococcus bacillaris on 50-nm gold films are excited via the Kretschmann configuration at λ = 670 nm. Cells show light/dark response to plasmonic excitation and grow denser biofilms, closer to the electrode surface, as compared to the direct irradiated case. Directly irradiated biofilms produced average electrical powers of 5.7 μW/m{sup 2} and plasmonically excited biofilms produced average electrical powers of 5.8 μW/m{sup 2}, with individual biofilmsmore » producing as much as 12 μW/m{sup 2}.« less

Self-sustaining, solar-driven bioelectricity generation in micro-sized microbial fuel cell using co-culture of heterotrophic and photosynthetic bacteria

NASA Astrophysics Data System (ADS)

Liu, Lin; Choi, Seokheun

2017-04-01

Among many energy harvesting techniques with great potential, microbial fuel cell (MFC) technology is arguably the most underdeveloped. Even so, excitement is building, as microorganisms can harvest electrical power from any biodegradable organic source (e.g. wastewater) that is readily available in resource-limited settings. Nevertheless, the requirement for endless introduction of organic matter imposes a limiting factor to this technology, demanding an active feeding system and additional power. Here, we demonstrated self-sustaining bioelectricity generation from a microliter-scale microbial fuel cell (MFC) by using the syntrophic interaction between heterotrophic exoelectrogenic bacteria and phototrophs. The MFC continuously generated light-responsive electricity from the heterotrophic bacterial metabolic respiration with the organic substrates produced by photosynthetic bacteria. Without additional organic fuel, the mixed culture in a 90-μL-chamber MFC generated self-sustained current for more than 13 days, while the heterotrophic culture produced current that decreased dramatically within a few hours. The current from the mixed culture was about 70 times greater than that of the device with only photosynthetic bacteria. The miniaturization provided a short start-up time, a well-controlled environment, and small internal resistance. Those advantages will become the general design platform for micropower generation.

An investigation of the direct-drive method of susceptibility testing

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

Bonn, R.H.

1992-07-01

The Naval Surface Weapons Laboratory has constructed a small electrical subsystem for the purpose of evaluating electrical upset from various electromagnetic sources. The subsystem consists of three boxes, two of which are intended to be illuminated by electromagnetic waves. The two illuminated boxes are connected by two unshielded cable bundles. The goal of the Navy test series is to expose the subsystem to electromagnetic illumination from several different types of excitation, document upset levels, and compare the results. Before its arrival at Sandia National Laboratories (SNL) the system was illuminated in a mode stirred chamber and in an anechoic chamber.more » This effort was a continuation of that test program. The Sandia tests involved the test methodology referred to as bulk current injection (BCI). Because this is a poorly-shielded, multiple-aperture system, the method was not expected to compare closely to the other test methods. The test results show that. The BCI test methodology is a useful test technique for a subset of limited aperture systems; the methodology will produce incorrect answers when used improperly on complex systems; the methodology can produce accurate answers on simple systems with a well-controlled electromagnetic topology. This is a preliminary study and the results should be interpreted carefully.« less

Nonadiabatic excited-state molecular dynamics modeling of photoinduced dynamics in conjugated molecules.

PubMed

Nelson, Tammie; Fernandez-Alberti, Sebastian; Chernyak, Vladimir; Roitberg, Adrian E; Tretiak, Sergei

2011-05-12

Nonadiabatic dynamics generally defines the entire evolution of electronic excitations in optically active molecular materials. It is commonly associated with a number of fundamental and complex processes such as intraband relaxation, energy transfer, and light harvesting influenced by the spatial evolution of excitations and transformation of photoexcitation energy into electrical energy via charge separation (e.g., charge injection at interfaces). To treat ultrafast excited-state dynamics and exciton/charge transport we have developed a nonadiabatic excited-state molecular dynamics (NA-ESMD) framework incorporating quantum transitions. Our calculations rely on the use of the Collective Electronic Oscillator (CEO) package accounting for many-body effects and actual potential energy surfaces of the excited states combined with Tully's fewest switches algorithm for surface hopping for probing nonadiabatic processes. This method is applied to model the photoinduced dynamics of distyrylbenzene (a small oligomer of polyphenylene vinylene, PPV). Our analysis shows intricate details of photoinduced vibronic relaxation and identifies specific slow and fast nuclear motions that are strongly coupled to the electronic degrees of freedom, namely, torsion and bond length alternation, respectively. Nonadiabatic relaxation of the highly excited mA(g) state is predicted to occur on a femtosecond time scale at room temperature and on a picosecond time scale at low temperature.

Electric Dipole Polarizability of ^{48}Ca and Implications for the Neutron Skin.

PubMed

Birkhan, J; Miorelli, M; Bacca, S; Bassauer, S; Bertulani, C A; Hagen, G; Matsubara, H; von Neumann-Cosel, P; Papenbrock, T; Pietralla, N; Ponomarev, V Yu; Richter, A; Schwenk, A; Tamii, A

2017-06-23

The electric dipole strength distribution in ^{48}Ca between 5 and 25 MeV has been determined at RCNP, Osaka from proton inelastic scattering experiments at forward angles. Combined with photoabsorption data at higher excitation energy, this enables the first extraction of the electric dipole polarizability α_{D}(^{48}Ca)=2.07(22)  fm^{3}. Remarkably, the dipole response of ^{48}Ca is found to be very similar to that of ^{40}Ca, consistent with a small neutron skin in ^{48}Ca. The experimental results are in good agreement with ab initio calculations based on chiral effective field theory interactions and with state-of-the-art density-functional calculations, implying a neutron skin in ^{48}Ca of 0.14-0.20 fm.

Electric Dipole Polarizability of Ca 48 and Implications for the Neutron Skin

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

Birkhan, J.; Miorelli, M.; Bacca, S.

The electric dipole strength distribution in 48Ca between 5 and 25 MeV has been determined at RCNP, Osaka, from proton inelastic scattering experiments at forward angles. Combined with photoabsorption data at higher excitation energy, this enables the rst extraction of the electric dipole polarizability D( 48Ca) = 2:07(22) fm 3. Remarkably, the dipole response of 48Ca is found to be very similar to that of 40Ca, consistent with a small neutron skin in 48Ca. The experimental results are in good agreement with ab initio calculations based on chiral e ective eld theory interactions and with state-of-the-art density-functional calculations, implying amore » neutron skin in 48Ca of 0:14 - 0:20 fm.« less

Electric Dipole Polarizability of Ca 48 and Implications for the Neutron Skin

DOE PAGES

Birkhan, J.; Miorelli, M.; Bacca, S.; ...

2017-06-23

The electric dipole strength distribution in 48Ca between 5 and 25 MeV has been determined at RCNP, Osaka, from proton inelastic scattering experiments at forward angles. Combined with photoabsorption data at higher excitation energy, this enables the rst extraction of the electric dipole polarizability D( 48Ca) = 2:07(22) fm 3. Remarkably, the dipole response of 48Ca is found to be very similar to that of 40Ca, consistent with a small neutron skin in 48Ca. The experimental results are in good agreement with ab initio calculations based on chiral e ective eld theory interactions and with state-of-the-art density-functional calculations, implying amore » neutron skin in 48Ca of 0:14 - 0:20 fm.« less

Cavity-excited Huygens' metasurface antennas for near-unity aperture illumination efficiency from arbitrarily large apertures

PubMed Central

Epstein, Ariel; Wong, Joseph P. S.; Eleftheriades, George V.

2016-01-01

One of the long-standing problems in antenna engineering is the realization of highly directive beams using low-profile devices. In this paper, we provide a solution to this problem by means of Huygens' metasurfaces (HMSs), based on the equivalence principle. This principle states that a given excitation can be transformed to a desirable aperture field by inducing suitable electric and (equivalent) magnetic surface currents. Building on this concept, we propose and demonstrate cavity-excited HMS antennas, where the single-source-fed cavity is designed to optimize aperture illumination, while the HMS facilitates the current distribution that ensures phase purity of aperture fields. The HMS breaks the coupling between the excitation and radiation spectra typical to standard partially reflecting surfaces, allowing tailoring of the aperture properties to produce a desirable radiation pattern, without incurring edge-taper losses. The proposed low-profile design yields near-unity aperture illumination efficiencies from arbitrarily large apertures, offering new capabilities for microwave, terahertz and optical radiators. PMID:26790605

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

Gabriel, O.; Harskamp, W. E. N. van; Schram, D. C.

The cascaded arc is a plasma source providing high fluxes of excited and reactive species such as ions, radicals and rovibrationally excited molecules. The plasma is produced under pressures of some kPa in a direct current arc with electrical powers up to 10 kW. The plasma leaves the arc channel through a nozzle and expands with supersonic velocity into a vacuum-chamber kept by pumps at low pressures. We investigated the case of a pure hydrogen plasma jet with and without an applied axial magnetic field that confines ions and electrons in the jet. Highly excited molecules and atoms were detectedmore » by means of laser-induced fluorescence and optical emission spectroscopy. In case of an applied magnetic field the atomic state distribution of hydrogen atoms shows an overpopulation between the electronic states p = 5, 4 and 3. The influence of the highly excited hydrogen molecules on H{sup -} ion formation and a possible mechanism involving this negative ion and producing atomic hydrogen in state p = 3 will be discussed.« less

Cavity-excited Huygens' metasurface antennas for near-unity aperture illumination efficiency from arbitrarily large apertures.

PubMed

Epstein, Ariel; Wong, Joseph P S; Eleftheriades, George V

2016-01-21

One of the long-standing problems in antenna engineering is the realization of highly directive beams using low-profile devices. In this paper, we provide a solution to this problem by means of Huygens' metasurfaces (HMSs), based on the equivalence principle. This principle states that a given excitation can be transformed to a desirable aperture field by inducing suitable electric and (equivalent) magnetic surface currents. Building on this concept, we propose and demonstrate cavity-excited HMS antennas, where the single-source-fed cavity is designed to optimize aperture illumination, while the HMS facilitates the current distribution that ensures phase purity of aperture fields. The HMS breaks the coupling between the excitation and radiation spectra typical to standard partially reflecting surfaces, allowing tailoring of the aperture properties to produce a desirable radiation pattern, without incurring edge-taper losses. The proposed low-profile design yields near-unity aperture illumination efficiencies from arbitrarily large apertures, offering new capabilities for microwave, terahertz and optical radiators.

Terahertz radiation in graphene hyperbolic medium excited by an electric dipole.

PubMed

Feng, Xiaodong; Gong, Sen; Zhong, Renbin; Zhao, Tao; Hu, Min; Zhang, Chao; Liu, Shenggang

2018-03-01

In this Letter, the enhanced and directional radiation in a wide terahertz (THz) frequency range in a graphene hyperbolic medium excited by an electric dipole is presented. The numerical simulations and theoretical analyses indicate that the enhanced radiation comes from the strong surface plasmon couplings in the graphene hyperbolic medium, consisting of alternative graphene and dielectric substrate layers. The simulation results also show that the peak power flow of the enhanced THz radiation in the graphene hyperbolic medium is dramatically enhanced by more than 1 order of magnitude over that in a general medium within a certain distance from the dipole, and the electromagnetic fields are strongly concentrated in a narrow angle. Also, the radiation fields can be manipulated, and the fields' angular distributions can be tuned by adjusting the dielectric permittivity and thickness of the substrates, and the chemical potential of graphene. Accordingly, it provides a good opportunity for developing miniature, integratable, high-power-density, and tunable radiation sources in the THz band at room temperature.

Performance of a Fuel-Cell-Powered, Small Electric Airplane Assessed

NASA Technical Reports Server (NTRS)

Berton, Jeffrey J.

2004-01-01

Rapidly emerging fuel-cell-power technologies may be used to launch a new revolution of electric propulsion systems for light aircraft. Future small electric airplanes using fuel cell technologies hold the promise of high reliability, low maintenance, low noise, and - with the exception of water vapor - zero emissions. An analytical feasibility and performance assessment was conducted by NASA Glenn Research Center's Airbreathing Systems Analysis Office of a fuel-cell-powered, propeller-driven, small electric airplane based on a model of the MCR-01 two-place kitplane (Dyn'Aero, Darois, France). This assessment was conducted in parallel with an ongoing effort by the Advanced Technology Products Corporation and the Foundation for Advancing Science and Technology Education. Their project - partially funded by a NASA grant - is to design, build, and fly the first manned, continuously propelled, nongliding electric airplane. In our study, an analytical performance model of a proton exchange membrane (PEM) fuel cell propulsion system was developed and applied to a notional, two-place light airplane modeled after the MCR-01 kitplane. The PEM fuel cell stack was fed pure hydrogen fuel and humidified ambient air via a small automotive centrifugal supercharger. The fuel cell performance models were based on chemical reaction analyses calibrated with published data from the fledgling U.S. automotive fuel cell industry. Electric propeller motors, rated at two shaft power levels in separate assessments, were used to directly drive a two-bladed, variable-pitch propeller. Fuel sources considered were compressed hydrogen gas and cryogenic liquid hydrogen. Both of these fuel sources provided pure, contaminant-free hydrogen for the PEM cells.

Novel composite piezoelectric material for energy harvesting applications

NASA Astrophysics Data System (ADS)

Janusas, Giedrius; Guobiene, Asta; Palevicius, Arvydas; Prosycevas, Igoris; Ponelyte, Sigita; Baltrusaitis, Valentinas; Sakalys, Rokas

2015-04-01

Past few decades were concentrated on researches related to effective energy harvesting applied in modern technologies, MEMS or MOEMS systems. There are many methods for harvesting energy as, for example, usage of electromagnetic devices, but most dramatic changes were noticed in the usage of piezoelectric materials in small scale devices. Major limitation faced was too small generated power by piezoelectric materials or high resonant frequencies of such smallscale harvesters. In this research, novel composite piezoelectric material was created by mixing PZT powder with 20% solution of polyvinyl butyral in benzyl alcohol. Obtained paste was screen printed on copper foil using 325 mesh stainless steel screen and dried for 30 min at 100 °C. Polyvinyl butyral ensures good adhesion and flexibility of a new material at the conditions that requires strong binding. Five types of a composite piezoelectric material with different concentrations of PZT (40%, 50%, 60%, 70% and 80 %) were produced. As the results showed, these harvesters were able to transform mechanical strain energy into electric potential and, v.v. In experimental setup, electromagnetic shaker was used to excite energy harvester that is fixed in the custom-built clamp, while generated electric potential were registered with USB oscilloscope PICO 3424. The designed devices generate up to 80 μV at 50 Hz excitation. This property can be applied to power microsystem devices or to use them in portable electronics and wireless sensors. However, the main advantage of the created composite piezoelectric material is possibility to apply it on any uniform or nonuniform vibrating surface and to transform low frequency vibrations into electricity.

On square-wave-driven stochastic resonance for energy harvesting in a bistable system

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

Su, Dongxu, E-mail: sudx@iis.u-tokyo.ac.jp; Zheng, Rencheng; Nakano, Kimihiko

Stochastic resonance is a physical phenomenon through which the throughput of energy within an oscillator excited by a stochastic source can be boosted by adding a small modulating excitation. This study investigates the feasibility of implementing square-wave-driven stochastic resonance to enhance energy harvesting. The motivating hypothesis was that such stochastic resonance can be efficiently realized in a bistable mechanism. However, the condition for the occurrence of stochastic resonance is conventionally defined by the Kramers rate. This definition is inadequate because of the necessity and difficulty in estimating white noise density. A bistable mechanism has been designed using an explicit analyticalmore » model which implies a new approach for achieving stochastic resonance in the paper. Experimental tests confirm that the addition of a small-scale force to the bistable system excited by a random signal apparently leads to a corresponding amplification of the response that we now term square-wave-driven stochastic resonance. The study therefore indicates that this approach may be a promising way to improve the performance of an energy harvester under certain forms of random excitation.« less

Regenerative flywheel energy storage system. Volume 3: Life cycle and cost-benefit analysis of a battery-flywheel electric car

NASA Astrophysics Data System (ADS)

1980-06-01

Fabrication of the inductor motor, the flywheel, the power conditioner, and the system control is described. Test results of the system operating over the SAE j227a Schedule D driving cycle are given and are compared to the calculated value. The flywheel energy storage system consists of a solid rotor, synchronous, inductor-type, flywheel drive machine electrically coupled to a dc battery electric propulsion system through a load-commutated inverter. The motor/alernator unit is coupled mechanically to a small steel flywheel which provides a portion of the vehicle's accelerating energy and regenerates the vehicle's braking energy. Laboratory simulation of the electric vehicle propulsion system included a 108 volt, lead-acid battery bank and a separately excited dc propulsion motor coupled to a flywheel and generator which simulate the vehicle's inertia and losses.

High energy KrCl electric discharge laser

DOEpatents

Sze, Robert C.; Scott, Peter B.

1981-01-01

A high energy KrCl laser for producing coherent radiation at 222 nm. Output energies on the order of 100 mJ per pulse are produced utilizing a discharge excitation source to minimize formation of molecular ions, thereby minimizing absorption of laser radiation by the active medium. Additionally, HCl is used as a halogen donor which undergoes a harpooning reaction with metastable Kr.sub.M * to form KrCl.

High energy KrCl electric discharge laser

DOEpatents

Sze, R.C.; Scott, P.B.

A high energy KrCl laser is presented for producing coherent radiation at 222 nm. Output energies on the order of 100 mJ per pulse are produced utilizing a discharge excitation source to minimize formation of molecular ions, thereby minimizing absorption of laser radiation by the active medium. Additionally, HCl is used as a halogen donor which undergoes a harpooning reaction with metastable Kr/sub M/ to form KrCl.

Electromagnetic resonance in the asymmetric terahertz metamaterials with triangle microstructure

NASA Astrophysics Data System (ADS)

Xing, Yuanyuan; Zhang, Xiaoyu; Zhang, Qiang; Gu, Yanping; Qian, Yunan; Lin, Xingyue; Tang, Yunhai; Cheng, Xinli; Qin, Changfa; Shen, Jiaoyan; Zang, Taocheng; Ma, Chunlan

2018-05-01

We investigate terahertz transmission properties and electromagnetic resonance modes in the asymmetric triangle structures with the change of asymmetric distance and the direction of electric field. When the THz electric field is perpendicular to the split gap of triangle, the electric field can better excite the THz absorption in the triangle structures. Importantly, electromagnetically induced transparency (EIT) characteristics are observed in the triangle structures due to the destructive interference of the different excited modes. The distributions of electric field and surface current density simulated by finite difference time domain indicate that the bright mode is excited by the side of triangle structures and dark mode is excited by the gap-side of triangle. The present study is helpful to understand the electromagnetic resonance in the asymmetric triangular metamaterials.

Electron-Beam Produced Air Plasma: Optical and Electrical Diagnostics

NASA Astrophysics Data System (ADS)

Vidmar, Robert; Stalder, Kenneth; Seeley, Megan

2006-10-01

High energy electron impact excitation is used to stimulate optical emissions that quantify the measurement of electron beam current. A 100 keV 10-ma electron beam source is used to produce air plasma in a test cell at a pressure between 1 mTorr and 760 Torr. Optical emissions originating from the N2 2^nd positive line at 337.1 nm and the N2^+ 1^st negative line at 391.4 nm are observed. Details on calibration using signals from an isolated transmission window and a Faraday plate are discussed. Results using this technique and other electrical signal are presented.

Analysis of UV-excited fluorochromes by flow cytometry using near-ultraviolet laser diodes.

PubMed

Telford, William G

2004-09-01

Violet laser diodes have become common and reliable laser sources for benchtop flow cytometers. While these lasers are very useful for a variety of violet and some ultraviolet-excited fluorochromes (e.g., DAPI), they do not efficiently excite most UV-stimulated probes. In this study, the next generation of InGaN near-UV laser diodes (NUVLDs) emitting in the 370-375-nm range have been evaluated as laser sources for cuvette-based flow cytometers. Several NUVLDs, ranging in wavelength from 370 to 374 nm and in power level from 1.5 to 10 mW, were mounted on a BD Biosciences LSR II and evaluated for their ability to excite cells labeled with the UV DNA binding dye DAPI, several UV phenotyping fluorochromes (including Alexa Fluor 350, Marina Blue, and quantum dots), and the fluorescent calcium chelator indo-1. NUVLDs at the 8-10-mW power range gave detection sensitivity levels comparable to more powerful solid-state and ion laser sources, using low-fluorescence microsphere beads as measurement standards. NUVLDs at all tested power levels allowed extremely high-resolution DAPI cell cycle analysis, and sources in the 8-10-mW power range excited Alexa Fluor 350, Marina Blue, and a variety of quantum dots at virtually the same signal-to-noise ratios as more powerful UV sources. These evaluations indicate that near-UV laser diodes installed on a cuvette-based flow cytometer performed nearly as well as more powerful solid-state UV lasers on the same instrumentation, and comparably to more powerful ion lasers on a jet-in-air system, and. Despite their limited power, integration of these small and inexpensive lasers into benchtop flow cytometers should allow the use of flow cytometric applications requiring UV excitation on a wide variety of instruments. Copyright 2004 Wiley-Liss, Inc.

Speedup computation of HD-sEMG signals using a motor unit-specific electrical source model.

PubMed

Carriou, Vincent; Boudaoud, Sofiane; Laforet, Jeremy

2018-01-23

Nowadays, bio-reliable modeling of muscle contraction is becoming more accurate and complex. This increasing complexity induces a significant increase in computation time which prevents the possibility of using this model in certain applications and studies. Accordingly, the aim of this work is to significantly reduce the computation time of high-density surface electromyogram (HD-sEMG) generation. This will be done through a new model of motor unit (MU)-specific electrical source based on the fibers composing the MU. In order to assess the efficiency of this approach, we computed the normalized root mean square error (NRMSE) between several simulations on single generated MU action potential (MUAP) using the usual fiber electrical sources and the MU-specific electrical source. This NRMSE was computed for five different simulation sets wherein hundreds of MUAPs are generated and summed into HD-sEMG signals. The obtained results display less than 2% error on the generated signals compared to the same signals generated with fiber electrical sources. Moreover, the computation time of the HD-sEMG signal generation model is reduced to about 90% compared to the fiber electrical source model. Using this model with MU electrical sources, we can simulate HD-sEMG signals of a physiological muscle (hundreds of MU) in less than an hour on a classical workstation. Graphical Abstract Overview of the simulation of HD-sEMG signals using the fiber scale and the MU scale. Upscaling the electrical source to the MU scale reduces the computation time by 90% inducing only small deviation of the same simulated HD-sEMG signals.

Fluid jet electric discharge source

DOEpatents

Bender, Howard A [Ripon, CA

2006-04-25

A fluid jet or filament source and a pair of coaxial high voltage electrodes, in combination, comprise an electrical discharge system to produce radiation and, in particular, EUV radiation. The fluid jet source is composed of at least two serially connected reservoirs, a first reservoir into which a fluid, that can be either a liquid or a gas, can be fed at some pressure higher than atmospheric and a second reservoir maintained at a lower pressure than the first. The fluid is allowed to expand through an aperture into a high vacuum region between a pair of coaxial electrodes. This second expansion produces a narrow well-directed fluid jet whose size is dependent on the size and configuration of the apertures and the pressure used in the reservoir. At some time during the flow of the fluid filament, a high voltage pulse is applied to the electrodes to excite the fluid to form a plasma which provides the desired radiation; the wavelength of the radiation being determined by the composition of the fluid.

High-Power Piezoelectric Acoustic-Electric Power Feedthru for Metal Walls

NASA Technical Reports Server (NTRS)

Bao, Xiaoqi; Biederman, Will; Sherrit, Stewart; Badescu, Mircea; Bar-Cohen, Yoseph; Jones, Christopher; Aldrich, Jack; Chang, Zensheu

2008-01-01

Piezoelectric acoustic-electric power feed-through devices transfer electric power wirelessly through a solid wall by using acoustic waves. This approach allows for the removal of holes through structures. The technology is applicable to power supply for electric equipment inside sealed containers, vacuum or pressure vessels, etc where the holes on the wall are prohibitive or result in significant performance degrade or complex designs. In the author's previous work, 100-W electric power was transferred through a metal wall by a small, simple-structure piezoelectric device. To meet requirements of higher power applications, the feasibility to transfer kilowatts level power was investigated. Pre-stressed longitudinal piezoelectric feedthru devices were analyzed by finite element model. An equivalent circuit model was developed to predict the power transfer characteristics to different electric loads. Based on the analysis results, a prototype device was designed, fabricated and a demonstration of the transmission of electric power up to 1-kW was successfully conducted. The methods to minimize the plate wave excitation on the wall were also analyzed. Both model analysis and experimental results are presented in detail in this presentation.

Decreased electrical excitability of peripheral nerves in demyelinating polyneuropathies.

PubMed Central

Meulstee, J; Darbas, A; van Doorn, P A; van Briemen, L; van der Meché, F G

1997-01-01

Not recognising the presence of decreased excitability may give rise to a seemingly low compound muscle action potential, which may lead erroneously to the conclusion of conduction block. To quantify decreased electrical excitability, stimulation-response curves and the current needed to achieve 90% of the maximal compound muscle action potential amplitude, i90, were obtained in 17 healthy controls, eight patients with Guillain-Barre syndrome, 14 with chronic inflammatory demyelinating polyneuropathy, and 10 with hereditary motor sensory neuropathy type I. Decreased electrical excitability was found in patients with chronic inflammatory demyelinating polyneuropathy and hereditary motor sensory neuropathy type I, by contrast with patients with Guillain-Barré syndrome. Recognising decreased excitability prevents the false assertion of conduction block and has electrodiagnostic importance for the differential diagnosis of demyelinating polyneuropathies. PMID:9120460

Acoustically levitated dancing drops: Self-excited oscillation to chaotic shedding.

PubMed

Lin, Po-Cheng; I, Lin

2016-02-01

We experimentally demonstrate self-excited oscillation and shedding of millimeter-sized water drops, acoustically levitated in a single-node standing waves cavity, by decreasing the steady acoustic wave intensity below a threshold. The perturbation of the acoustic field by drop motion is a possible source for providing an effective negative damping for sustaining the growing amplitude of the self-excited motion. Its further interplay with surface tension, drop inertia, gravity and acoustic intensities, select various self-excited modes for different size of drops and acoustic intensity. The large drop exhibits quasiperiodic motion from a vertical mode and a zonal mode with growing coupling, as oscillation amplitudes grow, until falling on the floor. For small drops, chaotic oscillations constituted by several broadened sectorial modes and corresponding zonal modes are self-excited. The growing oscillation amplitude leads to droplet shedding from the edges of highly stretched lobes, where surface tension no longer holds the rapid expanding flow.

Acoustically levitated dancing drops: Self-excited oscillation to chaotic shedding

NASA Astrophysics Data System (ADS)

Lin, Po-Cheng; I, Lin

2016-02-01

We experimentally demonstrate self-excited oscillation and shedding of millimeter-sized water drops, acoustically levitated in a single-node standing waves cavity, by decreasing the steady acoustic wave intensity below a threshold. The perturbation of the acoustic field by drop motion is a possible source for providing an effective negative damping for sustaining the growing amplitude of the self-excited motion. Its further interplay with surface tension, drop inertia, gravity and acoustic intensities, select various self-excited modes for different size of drops and acoustic intensity. The large drop exhibits quasiperiodic motion from a vertical mode and a zonal mode with growing coupling, as oscillation amplitudes grow, until falling on the floor. For small drops, chaotic oscillations constituted by several broadened sectorial modes and corresponding zonal modes are self-excited. The growing oscillation amplitude leads to droplet shedding from the edges of highly stretched lobes, where surface tension no longer holds the rapid expanding flow.

Decay pattern of the Pygmy Dipole Resonance in 130Te

NASA Astrophysics Data System (ADS)

Isaak, J.; Beller, J.; Fiori, E.; Krtička, M.; Löher, B.; Pietralla, N.; Romig, C.; Rusev, G.; Savran, D.; Scheck, M.; Silva, J.; Sonnabend, K.; Tonchev, A.; Tornow, W.; Weller, H.; Zweidinger, M.

2014-03-01

The electric dipole strength distribution in 130Te has been investigated using the method of Nuclear Resonance Fluorescence. The experiments were performed at the Darmstadt High Intensity Photon Setup using bremsstrahlung as photon source and at the High Intensity overrightarrow γ -Ray Source, where quasi-monochromatic and polarized photon beams are provided. Average decay properties of 130Te below the neutron separation energy are determined. Comparing the experimental data to the predictions of the statistical model indicate, that nuclear structure effects play an important role even at sufficiently high excitation energies. Preliminary results will be presented.

History of special metallurgical (SM) building remediation

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

Maul, G.F. Jr.

1996-12-31

Throughout most of the 1960s the SM-Building was a very busy and undoubtedly exciting place to work. The SNAP Program was in full swing then, producing heat sources, first for demonstration purposes, then for communications and weather satellites. As the program evolved, Mound was engaged in producing plutonium-powered heat sources for medical applications, including the famous cardiac pacemaker, which supplied rhythmic electrical pulses to the human heart in order to regulate the heart beat. This paper reviews the steps the building went through in the process of being shut down, decommissioned, and finally removed.

Quantum electric-dipole liquid on a triangular lattice.

PubMed

Shen, Shi-Peng; Wu, Jia-Chuan; Song, Jun-Da; Sun, Xue-Feng; Yang, Yi-Feng; Chai, Yi-Sheng; Shang, Da-Shan; Wang, Shou-Guo; Scott, James F; Sun, Young

2016-02-04

Geometric frustration and quantum fluctuations may prohibit the formation of long-range ordering even at the lowest temperature, and therefore liquid-like ground states could be expected. A good example is the quantum spin liquid in frustrated magnets. Geometric frustration and quantum fluctuations can happen beyond magnetic systems. Here we propose that quantum electric-dipole liquids, analogues of quantum spin liquids, could emerge in frustrated dielectrics where antiferroelectrically coupled electric dipoles reside on a triangular lattice. The quantum paraelectric hexaferrite BaFe12O19 with geometric frustration represents a promising candidate for the proposed electric-dipole liquid. We present a series of experimental lines of evidence, including dielectric permittivity, heat capacity and thermal conductivity measured down to 66 mK, to reveal the existence of an unusual liquid-like quantum phase in BaFe12O19, characterized by itinerant low-energy excitations with a small gap. The possible quantum liquids of electric dipoles in frustrated dielectrics open up a fresh playground for fundamental physics.

A comprehensive generator-line-infinite-bus micromachine model

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

Swift, G.W.

For almost twenty years, a miniature three-phase electric power system has been used by students at the University of Manitoba, in several courses and for many student hands on'' projects. It features a realistic natural frequency of about one hertz, a realistic exciter/field time constant of about five seconds, a solid state exciter, many short time constant transducers, a unique synchroscope'', and a storage oscilloscope. On the storage oscilloscope power-versus-phase curves can be observed-something seldom seen by practicing engineers or students in the usual laboratory situation. Advanced students can construct operational amplifier based stabilizers on a bread-board close to themore » regulator which is also on a small bread-broad.« less

Reliability and cost evaluation of small isolated power systems containing photovoltaic and wind energy

NASA Astrophysics Data System (ADS)

Karki, Rajesh

Renewable energy application in electric power systems is growing rapidly worldwide due to enhanced public concerns for adverse environmental impacts and escalation in energy costs associated with the use of conventional energy sources. Photovoltaics and wind energy sources are being increasingly recognized as cost effective generation sources. A comprehensive evaluation of reliability and cost is required to analyze the actual benefits of utilizing these energy sources. The reliability aspects of utilizing renewable energy sources have largely been ignored in the past due the relatively insignificant contribution of these sources in major power systems, and consequently due to the lack of appropriate techniques. Renewable energy sources have the potential to play a significant role in the electrical energy requirements of small isolated power systems which are primarily supplied by costly diesel fuel. A relatively high renewable energy penetration can significantly reduce the system fuel costs but can also have considerable impact on the system reliability. Small isolated systems routinely plan their generating facilities using deterministic adequacy methods that cannot incorporate the highly erratic behavior of renewable energy sources. The utilization of a single probabilistic risk index has not been generally accepted in small isolated system evaluation despite its utilization in most large power utilities. Deterministic and probabilistic techniques are combined in this thesis using a system well-being approach to provide useful adequacy indices for small isolated systems that include renewable energy. This thesis presents an evaluation model for small isolated systems containing renewable energy sources by integrating simulation models that generate appropriate atmospheric data, evaluate chronological renewable power outputs and combine total available energy and load to provide useful system indices. A software tool SIPSREL+ has been developed which generates risk, well-being and energy based indices to provide realistic cost/reliability measures of utilizing renewable energy. The concepts presented and the examples illustrated in this thesis will help system planners to decide on appropriate installation sites, the types and mix of different energy generating sources, the optimum operating policies, and the optimum generation expansion plans required to meet increasing load demands in small isolated power systems containing photovoltaic and wind energy sources.

Electrically actuatable temporal tristimulus-color device

DOEpatents

Koehler, Dale R.

1992-01-01

The electrically actuated light filter operates in a cyclical temporal mode to effect a tristimulus-color light analyzer. Construction is based on a Fabry-Perot interferometer comprised of a high-speed movable mirror pair and cyclically powered electrical actuators. When combined with a single vidicon tube or a monochrome solid state image sensor, a temporally operated tristimulus-color video camera is effected. A color-generated is accomplished when constructed with a companion light source and is a flicker-free colored-light source for transmission type display systems. Advantages of low cost and small physical size result from photolithographic batch-processing manufacturability.

Cyclic Parameter Refinement of 4S-10 Hybrid Flux-Switching Motor for Lightweight Electric Vehicle

NASA Astrophysics Data System (ADS)

Rani, J. Abd; Sulaiman, E.; Kumar, R.

2017-08-01

A great deal of attention has been given to the reduction of lighting the vehicle because the lighter the vehicle the energy consumption is comparatively low. Hence, the lightweight electric vehicle was introduced for lower carbon footprint and the sizing of the vehicle itself. One of the components to reduce the weight of the vehicle is the propulsion system which comprised of electric motor functioning as the source of torque to drive the propulsion system of the machine. This paper presents the refinement methodology for the optimized design of the 4S-10P E-Core hybrid excitation flux switching motor. The purpose of the refinement methodology is to improve the torque production of the optimized motor. The result of the successful improvement of the torque production is justifiable for a lightweight electric vehicle to drive the propulsion system.

Diversity of fuel sources for electricity generation in an evolving U.S. power sector

NASA Astrophysics Data System (ADS)

DiLuccia, Janelle G.

Policymakers increasingly have shown interest in options to boost the relative share of renewable or clean electricity generating sources in order to reduce negative environmental externalities from fossil fuels, guard against possible resource constraints, and capture economic advantages from developing new technologies and industries. Electric utilities and non-utility generators make decisions regarding their generation mix based on a number of different factors that may or may not align with societal goals. This paper examines the makeup of the electric power sector to determine how the type of generator and the presence (or lack) of competition in electricity markets at the state level may relate to the types of fuel sources used for generation. Using state-level electricity generation data from the U.S. Energy Information Administration from 1990 through 2010, this paper employs state and time fixed-effects regression modeling to attempt to isolate the impacts of state-level restructuring policies and the emergence of non-utility generators on states' generation from coal, from fossil fuel and from renewable sources. While the analysis has significant limitations, I do find that state-level electricity restructuring has a small but significant association with lowering electricity generation from coal specifically and fossil fuels more generally. Further research into the relationship between competition and fuel sources would aid policymakers considering legislative options to influence the generation mix.

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

Birkhan, J.; Miorelli, M.; Bacca, S.

The electric dipole strength distribution in 48Ca between 5 and 25 MeV has been determined at RCNP, Osaka, from proton inelastic scattering experiments at forward angles. Combined with photoabsorption data at higher excitation energy, this enables the rst extraction of the electric dipole polarizability D( 48Ca) = 2:07(22) fm 3. Remarkably, the dipole response of 48Ca is found to be very similar to that of 40Ca, consistent with a small neutron skin in 48Ca. The experimental results are in good agreement with ab initio calculations based on chiral e ective eld theory interactions and with state-of-the-art density-functional calculations, implying amore » neutron skin in 48Ca of 0:14 - 0:20 fm.« less

Laser spectroscopy of the 5P3/2 → 6Pj (j = 1/2 and 3/2) electric dipole forbidden transitions in atomic rubidium

NASA Astrophysics Data System (ADS)

Ponciano-Ojeda, F.; Hernández-Gómez, S.; Mojica-Casique, C.; Hoyos, L. M.; Flores-Mijangos, J.; Ramírez-Martínez, F.; Sahagún, D.; Jáuregui, R.; Jiménez-Mier, J.

2018-04-01

Doppler-free optical double-resonance spectroscopy is used to study the 5S1/2 → 5P3/2 → 6Pj (j = 3/2,1/2) excitation sequence in room-temperature rubidium atoms. This involves a 5S1/2 → 5P3/2 electric dipole preparation step followed by the 5P3/2 → 6Pj electric quadrupole excitation. The electric dipole forbidden transitions occur at 911.0 nm (j = 3/2) and 917.5 nm (j = 1/2). Production of atoms in the 6Pj states is detected by observing their direct decay to the ground state through emission of blue photons (λ ≈ 420 nm). A detailed experimental and theoretical study of the dependence on the relative linear polarizations of excitation beams is made. It is shown that specific electric quadrupole selection rules over magnetic quantum numbers are directly related to the relative orientation of the linear polarization of the excitation beams.

Structural contributions to fibrillatory rotors in a patient-derived computational model of the atria

PubMed Central

Gonzales, Matthew J.; Vincent, Kevin P.; Rappel, Wouter-Jan; Narayan, Sanjiv M.; McCulloch, Andrew D.

2014-01-01

Aims The aim of this study was to investigate structural contributions to the maintenance of rotors in human atrial fibrillation (AF) and possible mechanisms of termination. Methods and results A three-dimensional human biatrial finite element model based on patient-derived computed tomography and arrhythmia observed at electrophysiology study was used to study AF. With normal physiological electrical conductivity and effective refractory periods (ERPs), wave break failed to sustain reentrant activity or electrical rotors. With depressed excitability, decreased conduction anisotropy, and shorter ERP characteristic of AF, reentrant rotors were readily maintained. Rotors were transiently or permanently trapped by fibre discontinuities on the lateral wall of the right atrium near the tricuspid valve orifice and adjacent to the crista terminalis, both known sites of right atrial arrhythmias. Modelling inexcitable regions near the rotor tip to simulate fibrosis anchored the rotors, converting the arrhythmia to macro-reentry. Accordingly, increasing the spatial core of inexcitable tissue decreased the frequency of rotation, widened the excitable gap, and enabled an external wave to impinge on the rotor core and displace the source. Conclusion These model findings highlight the importance of structural features in rotor dynamics and suggest that regions of fibrosis may anchor fibrillatory rotors. Increasing extent of fibrosis and scar may eventually convert fibrillation to excitable gap reentry. Such macro-reentry can then be eliminated by extending the obstacle or by external stimuli that penetrate the excitable gap. PMID:25362167

Hollow cathode startup using a microplasma discharge

NASA Technical Reports Server (NTRS)

Aston, G.

1981-01-01

Attention is given to a microplasma discharge to initiate a hollow cathode discharge for such applications as plasma flow experiments, the electric propulsion of space vehicles, and as a replacement for filament cathodes in neutral beam injector ion sources. The technique results in a cathode that is easy to start, simple in design, and which does not require external RF exciters, inserts or heating elements. Future applications may include ion beam milling and ion implantation.

Polarized electroluminescence from edge-emission organic light emitting devices

NASA Astrophysics Data System (ADS)

Ran, G. Z.; Jiang, D. F.

2011-01-01

We report the experimental observation and measurement of the polarized electroluminescence from an edge-emission Si based- organic light emitting device (OLED) with a Sm/Au or Sm/Ag cathode. Light collected from the OLED edge comes from the scattering of the surface plasmon polaritons (SPPs) at the device boundary. This experiment shows that such Si-OLED can be an electrically excited SPP source on a silicon chip for optical interconnect based on SPPs.

High-density stretchable microelectrode arrays: An integrated technology platform for neural and muscular surface interfacing

NASA Astrophysics Data System (ADS)

Guo, Liang

2011-12-01

Numerous applications in neuroscience research and neural prosthetics, such as retinal prostheses, spinal-cord surface stimulation for prosthetics, electrocorticogram (ECoG) recording for epilepsy detection, etc., involve electrical interaction with soft excitable tissues using a surface stimulation and/or recording approach. These applications require an interface that is able to set up electrical communications with a high throughput between electronics and the excitable tissue and that can dynamically conform to the shape of the soft tissue. Being a compliant and biocompatible material with mechanical impedance close to that of soft tissues, polydimethylsiloxane (PDMS) offers excellent potential as the substrate material for such neural interfaces. However, fabrication of electrical functionalities on PDMS has long been very challenging. This thesis work has successfully overcome many challenges associated with PDMS-based microfabrication and achieved an integrated technology platform for PDMS-based stretchable microelectrode arrays (sMEAs). This platform features a set of technological advances: (1) we have fabricated uniform current density profile microelectrodes as small as 10 mum in diameter; (2) we have patterned high-resolution (feature as small as 10 mum), high-density (pitch as small as 20 mum) thin-film gold interconnects on PDMS substrate; (3) we have developed a multilayer wiring interconnect technology within the PDMS substrate to further boost the achievable integration density of such sMEA; and (4) we have invented a bonding technology---via-bonding---to facilitate high-resolution, high-density integration of the sMEA with integrated circuits (ICs) to form a compact implant. Taken together, this platform provides a high-resolution, high-density integrated system solution for neural and muscular surface interfacing. sMEAs of example designs are evaluated through in vitro and in vivo experimentations on their biocompatibility, surface conformability, and surface recording/stimulation capabilities, with a focus on epimysial (i.e. on the surface of muscle) applications. Finally, as an example medical application, we investigate a prosthesis for unilateral vocal cord paralysis (UVCP) based on simultaneous multichannel epimysial recording and stimulation.

Connecting Biology to Electronics: Molecular Communication via Redox Modality.

PubMed

Liu, Yi; Li, Jinyang; Tschirhart, Tanya; Terrell, Jessica L; Kim, Eunkyoung; Tsao, Chen-Yu; Kelly, Deanna L; Bentley, William E; Payne, Gregory F

2017-12-01

Biology and electronics are both expert at for accessing, analyzing, and responding to information. Biology uses ions, small molecules, and macromolecules to receive, analyze, store, and transmit information, whereas electronic devices receive input in the form of electromagnetic radiation, process the information using electrons, and then transmit output as electromagnetic waves. Generating the capabilities to connect biology-electronic modalities offers exciting opportunities to shape the future of biosensors, point-of-care medicine, and wearable/implantable devices. Redox reactions offer unique opportunities for bio-device communication that spans the molecular modalities of biology and electrical modality of devices. Here, an approach to search for redox information through an interactive electrochemical probing that is analogous to sonar is adopted. The capabilities of this approach to access global chemical information as well as information of specific redox-active chemical entities are illustrated using recent examples. An example of the use of synthetic biology to recognize external molecular information, process this information through intracellular signal transduction pathways, and generate output responses that can be detected by electrical modalities is also provided. Finally, exciting results in the use of redox reactions to actuate biology are provided to illustrate that synthetic biology offers the potential to guide biological response through electrical cues. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

An energy harvesting type ultrasonic motor.

PubMed

Wang, Guangqing; Xu, Wentan; Gao, Shuaishuai; Yang, Binqiang; Lu, Guoli

2017-03-01

An energy harvesting type ultrasonic motor is presented in this work. The novel motor not only can drive and/or position the motion mechanism, but also can harvest and convert the vibration-induced energy of the stator into electric energy to power small electronic devices. In the new motor, the stator is a sandwich structure of two PZT rings and an elastic metal body. The PZT ring bonded on the bottom surface is used to excite the stator metal body to generate a traveling wave with converse piezoelectric effect, and the other PZT ring bonded on top surface is used to harvest and convert the vibration-induced energy of the stator into electric energy with direct piezoelectric effect. Finite element method is adopted to analyze the vibration characteristics and the energetic characteristic. After the fabrication of a prototype, the mechanical output and electric energy output abilities are measured. The maximum no-load speed and maximum output torque of the prototype are 117rpm and 0.65Nm at an exciting voltage with amplitude of 134 V p-p and frequency of 40kHz, and the maximum harvesting output power of per sector area of the harvesting PZT is 327mW under an optimal equivalent load resistance of 6.9kΩ. Copyright © 2016 Elsevier B.V. All rights reserved.

Electric vehicles

NASA Astrophysics Data System (ADS)

1990-03-01

Quiet, clean, and efficient, electric vehicles (EVs) may someday become a practical mode of transportation for the general public. Electric vehicles can provide many advantages for the nation's environment and energy supply because they run on electricity, which can be produced from many sources of energy such as coal, natural gas, uranium, and hydropower. These vehicles offer fuel versatility to the transportation sector, which depends almost solely on oil for its energy needs. Electric vehicles are any mode of transportation operated by a motor that receives electricity from a battery or fuel cell. EVs come in all shapes and sizes and may be used for different tasks. Some EVs are small and simple, such as golf carts and electric wheel chairs. Others are larger and more complex, such as automobile and vans. Some EVs, such as fork lifts, are used in industries. In this fact sheet, we will discuss mostly automobiles and vans. There are also variations on electric vehicles, such as hybrid vehicles and solar-powered vehicles. Hybrid vehicles use electricity as their primary source of energy, however, they also use a backup source of energy, such as gasoline, methanol or ethanol. Solar-powered vehicles are electric vehicles that use photovoltaic cells (cells that convert solar energy to electricity) rather than utility-supplied electricity to recharge the batteries. These concepts are discussed.

NASTRAN supplemental documentation for modal forced vibration analysis of aerodynamically excited turbosystems

NASA Technical Reports Server (NTRS)

Elchuri, V.; Pamidi, P. R.

1985-01-01

This report is a supplemental NASTRAN document for a new capability to determine the vibratory response of turbosystems subjected to aerodynamic excitation. Supplements of NASTRAN Theoretical, User's, Programmer's, and Demonstration Manuals are included. Turbosystems such as advanced turbopropellers with highly swept blades, and axial-flow compressors and turbines can be analyzed using this capability, which has been developed and implemented in the April 1984 release of the general purpose finite element program NASTRAN. The dynamic response problem is addressed in terms of the normal modal coordinates of these tuned rotating cyclic structures. Both rigid and flexible hubs/disks are considered. Coriolis and centripetal accelerations, as well as differential stiffness effects are included. Generally nonuniform steady inflow fields and uniform flow fields arbitrarily inclined at small angles with respect to the axis of rotation of the turbosystem are considered as the sources of aerodynamic excitation. The spatial nonuniformities are considered to be small deviations from a principally uniform inflow. Subsonic relative inflows are addressed, with provision for linearly interpolating transonic airloads.

Lp-Norm Regularization in Volumetric Imaging of Cardiac Current Sources

PubMed Central

Rahimi, Azar; Xu, Jingjia; Wang, Linwei

2013-01-01

Advances in computer vision have substantially improved our ability to analyze the structure and mechanics of the heart. In comparison, our ability to observe and analyze cardiac electrical activities is much limited. The progress to computationally reconstruct cardiac current sources from noninvasive voltage data sensed on the body surface has been hindered by the ill-posedness and the lack of a unique solution of the reconstruction problem. Common L2- and L1-norm regularizations tend to produce a solution that is either too diffused or too scattered to reflect the complex spatial structure of current source distribution in the heart. In this work, we propose a general regularization with Lp-norm (1 < p < 2) constraint to bridge the gap and balance between an overly smeared and overly focal solution in cardiac source reconstruction. In a set of phantom experiments, we demonstrate the superiority of the proposed Lp-norm method over its L1 and L2 counterparts in imaging cardiac current sources with increasing extents. Through computer-simulated and real-data experiments, we further demonstrate the feasibility of the proposed method in imaging the complex structure of excitation wavefront, as well as current sources distributed along the postinfarction scar border. This ability to preserve the spatial structure of source distribution is important for revealing the potential disruption to the normal heart excitation. PMID:24348735

Electromagnon excitation in the field-induced nonlinear ferrimagnetic phase of Ba 2Mg 2Fe 12O 22 studied by polarized inelastic neutron and terahertz time-domain optical spectroscopy

DOE PAGES

Nakajima, Taro; Takahashi, Youtarou; Kibayashi, Shunsuke; ...

2016-01-19

We have studied magnetic excitations in a field-induced noncollinear commensurate ferrimagnetic phase of Ba 2Mg 2Fe 12O 22 by means of polarized inelastic neutron scattering (PINS) and terahertz (THz) time-domain optical spectroscopy under magnetic field. A previous THz spectroscopy study reported that the field-induced phase exhibits electric-dipole-active excitations with energies of around 5 meV [Kida et al., Phys. Rev. B 83, 064422 (2011)]. In the present PINS measurements, we observed inelastic scattering signals around 5 meV at the zone center in the spin-flip channel. This directly shows that the electric-dipole-active excitations are indeed of magnetic origin, that is, electromagnons. Inmore » addition, the present THz spectroscopy confirms that the excitations have oscillating electric polarization parallel to the c axis. In terms of the spin-current model (Katsura-Nagaosa-Balatsky model), the noncollinear magnetic order in the field-induced phase can induce static electric polarization perpendicular to the c axis, but not dynamic electric polarization along the c axis. Furthermore, we suggest that the electromagnon excitations can be explained by applying the magnetostriction model to the out-of-phase oscillations of the magnetic moments, which is deduced from the present experimental results.« less

Electrical Transport Signature of the Magnetic Fluctuation-Structure Relation in α-RuCl3 Nanoflakes.

PubMed

Mashhadi, Soudabeh; Weber, Daniel; Schoop, Leslie M; Schulz, Armin; Lotsch, Bettina V; Burghard, Marko; Kern, Klaus

2018-05-09

The small gap semiconductor α-RuCl 3 has emerged as a promising candidate for quantum spin liquid materials. Thus far, Raman spectroscopy, neutron scattering, and magnetization measurements have provided valuable hints for collective spin behavior in α-RuCl 3 bulk crystals. However, the goal of implementing α-RuCl 3 into spintronic devices would strongly benefit from the possibility of electrically probing these phenomena. To address this, we first investigated nanoflakes of α-RuCl 3 by Raman spectroscopy and observed similar behavior as in the case of the bulk material, including the signatures of possible fractionalized excitations. In complementary experiments, we investigated the electrical charge transport properties of individual α-RuCl 3 nanoflakes in the temperature range between 120 and 290 K. The observed temperature-dependent electrical resistivity is consistent with variable range hopping behavior and exhibits a transition at about 180 K, close to the onset temperature observed in our Raman measurements. In conjunction with the established relation between structure and magnetism in the bulk, we interpret this transition to coincide with the emergence of fractionalized excitations due to the Kitaev interactions in the nanoflakes. Compared to the bulk samples, the transition temperature of the underlying structural change is larger in the nanoflakes. This difference is tentatively attributed to the dimensionality of the nanoflakes as well as the formation of stacking faults during mechanical exfoliation. The demonstrated devices open up novel perspectives toward manipulating the Kitaev-phase in α-RuCl 3 via electrical means.

High-power piezoelectric acoustic-electric power feedthru for metal walls

NASA Astrophysics Data System (ADS)

Bao, Xiaoqi; Biederman, Will; Sherrit, Stewart; Badescu, Mircea; Bar-Cohen, Yoseph; Jones, Christopher; Aldrich, Jack; Chang, Zensheu

2008-03-01

Piezoelectric acoustic-electric power feed-through devices transfer electric power wirelessly through a solid wall using elastic waves. This approach allows for the elimination of the need for holes through structures for cabling or electrical feed-thrus . The technology supplies power to electric equipment inside sealed containers, vacuum or pressure vessels, etc where holes in the wall are prohibitive or may result in significant performance degradation or requires complex designs. In the our previous work, 100-W of electric power was transferred through a metal wall by a small, piezoelectric device with a simple-structure. To meet requirements of higher power applications, the feasibility to transfer kilowatts level power was investigated. Pre-stressed longitudinal piezoelectric feed-thru devices were analyzed by finite element modeling. An equivalent circuit model was developed to predict the characteristics of power transfer to different electric loads. Based on the analytical results, a prototype device was designed, fabricated and successfully demonstrated to transfer electric power at a level of 1-kW. Methods of minimizing plate wave excitation on the wall were also analyzed. Both model analysis and experimental results are presented in detail in this paper.

Harnessing Alternative Energy Sources to Enhance the Design of a Wave Generator

NASA Astrophysics Data System (ADS)

Bravo, A.

2017-12-01

Wave energy has the power to replace a non-renewable source of electricity for a home near the ocean. I built a small-scale wave generator capable of producing approximately 5 volts of electricity. The generator is an array of 16 small generators, each consisting of 200 feet of copper wire, 12 magnets, and a buoy. I tested my design in the Pacific Ocean and was able to power a string of lights I had attached to the generator. While the waves in the ocean moved my buoys, my design was powered by the vertical motion of the waves. My generator was hit with significant horizontal wave motion, and I realized I wasn't taking advantage of that direction of motion. To make my generator produce more electricity, I experimented with capturing the energy of the horizontal motion of water and incorporated that into my generator design. My generator, installed in the ocean, is also exposed to sun and wind, and I am exploring the potential of solar and wind energy collection in my design to increase the electricity output. Once I have maximized my electricity output, I would like to explore scaling up my design.

Fluidic Active Transducer for Electricity Generation

PubMed Central

Yang, YoungJun; Park, Junwoo; Kwon, Soon-Hyung; Kim, Youn Sang

2015-01-01

Flows in small size channels have been studied for a long time over multidisciplinary field such as chemistry, biology and medical through the various topics. Recently, the attempts of electricity generation from the small flows as a new area for energy harvesting in microfluidics have been reported. Here, we propose for the first time a new fluidic electricity generator (FEG) by modulating the electric double layer (EDL) with two phase flows of water and air without external power sources. We find that an electric current flowed by the forming/deforming of the EDL with a simple separated phase flow of water and air at the surface of the FEG. Electric signals between two electrodes of the FEG are checked from various water/air passing conditions. Moreover, we verify the possibility of a self-powered air slug sensor by applying the FEG in the detection of an air slug. PMID:26511626

Possible Mechanism for Damping of Electrostatic Instability Related to Inhomogeneous Distribution of Energy Density in the Auroral Ionosphere

NASA Astrophysics Data System (ADS)

Golovchanskaya, I. V.; Kozelov, B. V.; Chernyshov, A. A.; Ilyasov, A. A.; Mogilevsky, M. M.

2018-03-01

Satellite observations show that the electrostatic instability, which is expected to occur in most cases due to an inhomogeneous energy density caused by a strongly inhomogeneous transverse electric field (shear of plasma convection velocity), occasionally does not develop inside nonlinear plasma structures in the auroral ionosphere, even though the velocity shear is sufficient for its excitation. In this paper, it is shown that the instability damping can be caused by out-of-phase variations of the electric field and field-aligned current acting in these structures. Therefore, the mismatch of sources of free energy required for the wave generation nearly nullifies their common effect.

Carbon Nanotube Purification

NASA Technical Reports Server (NTRS)

Delzeit, Lance D. (Inventor); Delzeit, Clement J. (Inventor)

2005-01-01

A method for cleaning or otherwise removing amorphous carbon and other residues that arise in growth of a carbon nanotube (CNT) array. The CNT array is exposed to a plurality of hydroxyls or hydrogen, produced from a selected vapor or liquid source such as H2O or H2O2. and the hydroxyls or hydrogen (neutral or electrically charged) react with the residues to produce partly or fully dissolved or hydrogenated or hydroxylizated products that can be removed or separated from the CNT array. The hydroxyls or hydrogen can be produced by heating the CNT array, residue and selected vapor or liquid source or by application of an electromagnetic excitation signal with a selected frequency or range of frequencies to dissociate the selected vapor or liquid. The excitation frequency can be chirped to cover a selected range of frequencies corresponding to dissociation of the selected vapor or liquid. Sonication may be uscd to supplement dissociation of the H2O and/or H2O2.

Nanoscale mass conveyors

DOEpatents

Regan, Brian C [Oakland, CA; Aloni, Shaul [Albany, CA; Zettl, Alexander K [Kensington, CA

2008-03-11

A mass transport method and device for individually delivering chargeable atoms or molecules from source particles is disclosed. It comprises a channel; at least one source particle of chargeable material fixed to the surface of the channel at a position along its length; a means of heating the channel; and a means for applying an controllable electric field along the channel, whereby the device transports the atoms or molecules along the channel in response to applied electric field. In a preferred embodiment, the mass transport device will comprise a multiwalled carbon nanotube (MWNT), although other one dimensional structures may also be used. The MWNT or other structure acts as a channel for individual or small collections of atoms due to the atomic smoothness of the material. Also preferred is a source particle of a metal such as indium. The particles move by dissociation into small units, in some cases, individual atoms. The particles are preferably less than 100 nm in size.

Spiral waves in driven dusty plasma medium: Generalized hydrodynamic fluid description

NASA Astrophysics Data System (ADS)

Kumar, Sandeep; Patel, Bhavesh; Das, Amita

2018-04-01

Spiral waves are observed in many natural phenomena. They have been extensively represented by the mathematical FitzHugh-Nagumo model [Barkley et al., Phys. Rev. A 42, 2489 (1990)] of excitable media. Also, in incompressible fluid simulations, the excitation of thermal spiral waves has been reported by Li et al. [Phys. of Fluids 22, 011701 (2010)]. In the present paper, the spatiotemporal development of spiral waves in the context of weak and strong coupling limits has been shown. While the weakly coupled medium has been represented by a simple fluid description, for strong coupling, a generalized visco-elastic fluid description has been employed. The medium has been driven by an external force in the form of a rotating electric field. It is shown that when the amplitude of force is small, the density perturbations in the medium are also small. In this case, the excitations do not develop as a spiral wave. Only when the amplitude of force is high so as to drive the density perturbations to nonlinear amplitudes does the spiral density wave formation occurs. The role of the forcing frequency and the effect of strong coupling and the sound velocity of medium in the formation and evolution of spiral waves have been investigated in detail.

Electric dipole moment of diatomic molecules by configuration interaction. IV.

NASA Technical Reports Server (NTRS)

Green, S.

1972-01-01

The theory of basis set dependence in configuration interaction calculations is discussed, taking into account a perturbation model which is valid for small changes in the self-consistent field orbitals. It is found that basis set corrections are essentially additive through first order. It is shown that an error found in a previously published dipole moment calculation by Green (1972) for the metastable first excited state of CO was indeed due to an inadequate basis set as claimed.

Cavitation induced Becquerel effect.

PubMed

Prevenslik, T V

2003-06-01

The observation of an electrical current upon the ultraviolet (UV) illumination of one of a pair of identical electrodes in liquid water, called the Becquerel effect, was made over 150 years ago. More recently, an electrical current was found if the water surrounding one electrode was made to cavitate by focused acoustic radiation, the phenomenon called the cavitation induced Becquerel effect. Since cavitation is known to produce UV light, the electrode may simply absorb the UV light and produce the current by the photo-emission theory of photoelectrochemistry. But the current was found to be semi-logarithmic with the standard electrode potential which is characteristic of the oxidation of the electrode surface in the photo-decomposition theory, and not the photo-emission theory. High bubble collapse temperatures may oxidize the electrode, but this is unlikely because melting was not observed on the electrode surfaces. At ambient temperature, oxidation may proceed by chemical reaction provided a source of vacuum ultraviolet (VUV) radiation is available to produce the excited OH* states of water to react with the electrode. The source of VUV radiation is shown to be the spontaneous emission of coherent infrared (IR) radiation from water molecules in particles that form in bubbles because of surface tension, the spontaneous IR emission induced by cavity quantum electrodynamics. The excited OH* states are produced as the IR radiation accumulates to VUV levels in the bubble wall molecules.

Development of double-pulse lasers ablation system for generating gold ion source under applying an electric field

NASA Astrophysics Data System (ADS)

Khalil, A. A. I.

2015-12-01

Double-pulse lasers ablation (DPLA) technique was developed to generate gold (Au) ion source and produce high current under applying an electric potential in an argon ambient gas environment. Two Q-switched Nd:YAG lasers operating at 1064 and 266 nm wavelengths are combined in an unconventional orthogonal (crossed-beam) double-pulse configuration with 45° angle to focus on a gold target along with a spectrometer for spectral analysis of gold plasma. The properties of gold plasma produced under double-pulse lasers excitation were studied. The velocity distribution function (VDF) of the emitted plasma was studied using a dedicated Faraday-cup ion probe (FCIP) under argon gas discharge. The experimental parameters were optimized to attain the best signal to noise (S/N) ratio. The results depicted that the VDF and current signals depend on the discharge applied voltage, laser intensity, laser wavelength and ambient argon gas pressure. A seven-fold increases in the current signal by increasing the discharge applied voltage and ion velocity under applying double-pulse lasers field. The plasma parameters (electron temperature and density) were also studied and their dependence on the delay (times between the excitation laser pulse and the opening of camera shutter) was investigated as well. This study could provide significant reference data for the optimization and design of DPLA systems engaged in laser induced plasma deposition thin films and facing components diagnostics.

Interface-Free Area-Scalable Self-Powered Electroluminescent System Driven by Triboelectric Generator

PubMed Central

Yan Wei, Xiao; Kuang, Shuang Yang; Yang Li, Hua; Pan, Caofeng; Zhu, Guang; Wang, Zhong Lin

2015-01-01

Self-powered system that is interface-free is greatly desired for area-scalable application. Here we report a self-powered electroluminescent system that consists of a triboelectric generator (TEG) and a thin-film electroluminescent (TFEL) lamp. The TEG provides high-voltage alternating electric output, which fits in well with the needs of the TFEL lamp. Induced charges pumped onto the lamp by the TEG generate an electric field that is sufficient to excite luminescence without an electrical interface circuit. Through rational serial connection of multiple TFEL lamps, effective and area-scalable luminescence is realized. It is demonstrated that multiple types of TEGs are applicable to the self-powered system, indicating that the system can make use of diverse mechanical sources and thus has potentially broad applications in illumination, display, entertainment, indication, surveillance and many others. PMID:26338365

A theoretical and experimental investigation of the linear and nonlinear impulse responses from a magnetoplasma column

NASA Technical Reports Server (NTRS)

Grody, N. C.

1973-01-01

Linear and nonlinear responses of a magnetoplasma resulting from inhomogeneity in the background plasma density are studied. The plasma response to an impulse electric field was measured and the results are compared with the theory of an inhomogeneous cold plasma. Impulse responses were recorded for the different plasma densities, static magnetic fields, and neutral pressures and generally appeared as modulated, damped oscillations. The frequency spectra of the waveforms consisted of two separated resonance peaks. For weak excitation, the results correlate with the linear theory of a cold, inhomogeneous, cylindrical magnetoplasma. The damping mechanism is identified with that of phase mixing due to inhomogeneity in plasma density. With increasing excitation voltage, the nonlinear impulse responses display stronger damping and a small increase in the frequency of oscillation.

Development of a Three Dimensional Perfectly Matched Layer for Transient Elasto-Dynamic Analyses

DTIC Science & Technology

2006-12-01

MacLean [Ref. 47] intro- duced a small tracked vehicle with dual inertial mass shakers mounted on top as a mobile source. It excited Rayleigh waves, but...routine initializes and set default values for; * the aplication parameters * the material data base parameters * the entries to appear on the...Underground seismic array experiments. National In- stitute of Nuclear Physics, 2005. [47] D. J. MacLean. Mobile source development for seismic-sonar based

Low-intensity electric fields induce two distinct response components in neocortical neuronal populations

PubMed Central

Xu, Weifeng; Wolff, Brian S.

2014-01-01

Low-intensity alternating electric fields applied to the scalp are capable of modulating cortical activity and brain functions, but the underlying mechanisms remain largely unknown. Here, we report two distinct components of voltage-sensitive dye signals induced by low-intensity, alternating electric fields in rodent cortical slices: a “passive component,” which corresponds to membrane potential changes directly induced by the electric field; and an “active component,” which is a widespread depolarization that is dependent on excitatory synaptic transmission. The passive component is stationary, with amplitude and phase accurately reflecting the cortical cytoarchitecture. In contrast, the active component is initiated from a local “hot spot” of activity and spreads to a large population as a propagating wave with rich local dynamics. The propagation of the active component may play a role in modulating large-scale cortical activity by spreading a low level of excitation from a small initiation point to a vast neuronal population. PMID:25122710

Energy harvesting with stacked dielectric elastomer transducers: Nonlinear theory, optimization, and linearized scaling law

NASA Astrophysics Data System (ADS)

Tutcuoglu, A.; Majidi, C.

2014-12-01

Using principles of damped harmonic oscillation with continuous media, we examine electrostatic energy harvesting with a "soft-matter" array of dielectric elastomer (DE) transducers. The array is composed of infinitely thin and deformable electrodes separated by layers of insulating elastomer. During vibration, it deforms longitudinally, resulting in a change in the capacitance and electrical enthalpy of the charged electrodes. Depending on the phase of electrostatic loading, the DE array can function as either an actuator that amplifies small vibrations or a generator that converts these external excitations into electrical power. Both cases are addressed with a comprehensive theory that accounts for the influence of viscoelasticity, dielectric breakdown, and electromechanical coupling induced by Maxwell stress. In the case of a linearized Kelvin-Voigt model of the dielectric, we obtain a closed-form estimate for the electrical power output and a scaling law for DE generator design. For the complete nonlinear model, we obtain the optimal electrostatic voltage input for maximum electrical power output.

Electron-ion hybrid instability experiment upgrades to the Auburn Linear Experiment for Instability Studies.

PubMed

DuBois, A M; Arnold, I; Thomas, E; Tejero, E; Amatucci, W E

2013-04-01

The Auburn Linear EXperiment for Instability Studies (ALEXIS) is a laboratory plasma physics experiment used to study spatially inhomogeneous flows in a magnetized cylindrical plasma column that are driven by crossed electric (E) and magnetic (B) fields. ALEXIS was recently upgraded to include a small, secondary plasma source for a new dual source, interpenetrating plasma experiment. Using two plasma sources allows for highly localized electric fields to be made at the boundary of the two plasmas, inducing strong E × B velocity shear in the plasma, which can give rise to a regime of instabilities that have not previously been studied in ALEXIS. The dual plasma configuration makes it possible to have independent control over the velocity shear and the density gradient. This paper discusses the recent addition of the secondary plasma source to ALEXIS, as well as the plasma diagnostics used to measure electric fields and electron densities.

Electron energy recovery system for negative ion sources

DOEpatents

Dagenhart, W.K.; Stirling, W.L.

1979-10-25

An electron energy recovery system for negative ion sources is provided. The system, employing crossed electric and magnetic fields, separates the electrons from the ions as they are extracted from the ion source plasma generator and before the ions are accelerated to their full energy. With the electric and magnetic fields oriented 90/sup 0/ to each other, the electrons remain at approximately the electrical potential at which they were generated. The electromagnetic forces cause the ions to be accelerated to the full accelerating supply voltage energy while being deflected through an angle of less than 90/sup 0/. The electrons precess out of the accelerating field region into an electron recovery region where they are collected at a small fraction of the full accelerating supply energy. It is possible, by this method, to collect > 90% of the electrons extracted along with the negative ions from a negative ion source beam at < 4% of full energy.

A coupler for parasitic mode diagnosis in an X-band triaxial klystron amplifier

NASA Astrophysics Data System (ADS)

Zhang, Wei; Ju, Jin-chuan; Zhang, Jun; Qi, Zu-min; Zhong, Hui-huang

2017-10-01

The traditional methods of parasitic mode excitation diagnosis in an X-band triaxial klystron amplifier (TKA) meet two difficulties: limited installation space and vacuum sealing. In order to solve these issues, a simple and compact coupler with good sealing performance, which can prevent air flow between the main and the auxiliary waveguides, is proposed and investigated experimentally. The coupler is designed with the aperture diffraction theory and the finite-different time-domain (FDTD) method. The designed coupler consists of a main coaxial waveguide (for microwave transmission) and a rectangular auxiliary waveguide (for parasitic mode diagnosis). The entire coupler structure has been fabricated by macromolecule polymer which is transparent to microwave signal in frequency range of X-band. The metal coating of about 200 microns has been performed through electroplating technique to ensure that the device operates well at high power. A small aperture is made in the metal coating. Hence, microwave can couple through the hole and the wave-transparent medium, whereas air flow is blocked by the wave-transparent medium. The coupling coefficient is analyzed and simulated with CST software. The coupler model is also included in particle-in-cell (PIC) simulation with CHIPIC software and the associated parasitic mode excitation is studied. A frequency component of 11.46 GHz is observed in the FFT of the electric field of the drift tube and its corresponding competition mode appears as TE61 mode according to the electric field distribution. Besides, a frequency component of 10.8 GHz is also observed in the FFT of the electric field. After optimization of TE61 mode suppression, an experiment of the TKA with the designed coupler is carried out and the parasitic mode excitation at 10.8 GHz is observed through the designed coupler.

Electrical stimulation of the midbrain excites the auditory cortex asymmetrically.

PubMed

Quass, Gunnar Lennart; Kurt, Simone; Hildebrandt, Jannis; Kral, Andrej

2018-05-17

Auditory midbrain implant users cannot achieve open speech perception and have limited frequency resolution. It remains unclear whether the spread of excitation contributes to this issue and how much it can be compensated by current-focusing, which is an effective approach in cochlear implants. The present study examined the spread of excitation in the cortex elicited by electric midbrain stimulation. We further tested whether current-focusing via bipolar and tripolar stimulation is effective with electric midbrain stimulation and whether these modes hold any advantage over monopolar stimulation also in conditions when the stimulation electrodes are in direct contact with the target tissue. Using penetrating multielectrode arrays, we recorded cortical population responses to single pulse electric midbrain stimulation in 10 ketamine/xylazine anesthetized mice. We compared monopolar, bipolar, and tripolar stimulation configurations with regard to the spread of excitation and the characteristic frequency difference between the stimulation/recording electrodes. The cortical responses were distributed asymmetrically around the characteristic frequency of the stimulated midbrain region with a strong activation in regions tuned up to one octave higher. We found no significant differences between monopolar, bipolar, and tripolar stimulation in threshold, evoked firing rate, or dynamic range. The cortical responses to electric midbrain stimulation are biased towards higher tonotopic frequencies. Current-focusing is not effective in direct contact electrical stimulation. Electrode maps should account for the asymmetrical spread of excitation when fitting auditory midbrain implants by shifting the frequency-bands downward and stimulating as dorsally as possible. Copyright © 2018 Elsevier Inc. All rights reserved.

Projected Growth in Small-Scale, Fossil-Fueled Distributed Generation: Potential Implications for the U.S. Greenhouse Gas Inventory

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

Eberle, Annika; Heath, Garvin A

The generation capacity of small-scale (less than one megawatt) fossil-fueled electricity in the United States is anticipated to grow by threefold to twenty-fold from 2015 to 2040. However, in adherence with internationally agreed upon carbon accounting methods, the Environmental Protection Agency's (EPA's) U.S. Greenhouse Inventory (GHGI) does not currently attribute greenhouse gases (GHGs) from these small-scale distributed generation sources to the electric power sector and instead accounts for these emissions in the sector that uses the distributed generation (e.g., the commercial sector). In addition, no other federal electric-sector GHG emission data product produced by the EPA or the U.S. Energymore » Information Administration (EIA) can attribute these emissions to electricity. We reviewed the technical documentation for eight federal electric-sector GHG emission data products, interviewed the data product owners, collected their GHG emission estimates, and analyzed projections for growth in fossil-fueled distributed generation. We show that, by 2040, these small-scale generators could account for at least about 1%- 5% of total CO2 emissions from the U.S. electric power sector. If these emissions fall outside the electric power sector, the United States may not be able to completely and accurately track changes in electricity-related CO2 emissions, which could impact how the country sets GHG reduction targets and allocates mitigation resources. Because small-scale, fossil-fueled distributed generation is expected to grow in other countries as well, the results of this work also have implications for global carbon accounting.« less

Trapped-ion quantum simulation of excitation transport: Disordered, noisy, and long-range connected quantum networks

NASA Astrophysics Data System (ADS)

Trautmann, N.; Hauke, P.

2018-02-01

The transport of excitations governs fundamental properties of matter. Particularly rich physics emerges in the interplay between disorder and environmental noise, even in small systems such as photosynthetic biomolecules. Counterintuitively, noise can enhance coherent quantum transport, which has been proposed as a mechanism behind the high transport efficiencies observed in photosynthetic complexes. This effect has been called "environment-assisted quantum transport". Here, we propose a quantum simulation of the excitation transport in an open quantum network, taking advantage of the high controllability of current trapped-ion experiments. Our scheme allows for the controlled study of various different aspects of the excitation transfer, ranging from the influence of static disorder and interaction range, over the effect of Markovian and non-Markovian dephasing, to the impact of a continuous insertion of excitations. Our paper discusses experimental error sources and realistic parameters, showing that it can be implemented in state-of-the-art ion-chain experiments.

Current source enhancements in Electrical Impedance Spectroscopy (EIS) to cancel unwanted capacitive effects

NASA Astrophysics Data System (ADS)

Zarafshani, Ali; Bach, Thomas; Chatwin, Chris; Xiang, Liangzhong; Zheng, Bin

2017-03-01

Electrical Impedance Spectroscopy (EIS) has emerged as a non-invasive imaging modality to detect and quantify functional or electrical properties related to the suspicious tumors in cancer screening, diagnosis and prognosis assessment. A constraint on EIS systems is that the current excitation system suffers from the effects of stray capacitance having a major impact on the hardware subsystem as the EIS is an ill-posed inverse problem which depends on the noise level in EIS measured data and regularization parameter in the reconstruction algorithm. There is high complexity in the design of stable current sources, with stray capacitance reducing the output impedance and bandwidth of the system. To confront this, we have designed an EIS current source which eliminates the effect of stray capacitance and other impacts of the capacitance via a variable inductance. In this paper, we present a combination of operational CCII based on a generalized impedance converter (OCCII-GIC) with a current source. The aim of this study is to use the EIS system as a biomedical imaging technique, which is effective in the early detection of breast cancer. This article begins with the theoretical description of the EIS structure, current source topologies and proposes a current conveyor in application of a Gyrator to eliminate the current source limitations and its development followed by simulation and experimental results. We demonstrated that the new design could achieve a high output impedance over a 3MHz frequency bandwidth when compared to other types of GIC circuits combined with an improved Howland topology.

Temporal evolution of atmosphere pressure plasma jets driven by microsecond pulses with positive and negative polarities

NASA Astrophysics Data System (ADS)

Shao, Tao; Yang, Wenjin; Zhang, Cheng; Fang, Zhi; Zhou, Yixiao; Schamiloglu, Edl

2014-09-01

Current-voltage characteristics, discharge images, and optical spectra of atmospheric pressure plasma jets (APPJs) are studied using a microsecond pulse length generator producing repetitive output pulses with different polarities. The experimental results show that the APPJs excited by the pulses with positive polarity have longer plume, faster propagation speed, higher power, and more excited species, such as \\text{N}2 , O, He, \\text{N}2+ , than that with the negatively excited APPJs. The images taken using an intensified charge-coupled device show that the APPJs excited by pulses with positive polarity are characterized by a bullet-like structure, while the APPJs excited by pulses with negative polarity are continuous. The propagation speed of the APPJs driven by a microsecond pulse length generator is about tens of km/s, which is similar to the APPJs driven by a kHz frequency sinusoidal voltage source. The analysis shows that the space charge accumulation effect plays an important role during the discharge. The transient enhanced electric field induced by the accumulated ions between the needle-like electrode and the nozzle in the APPJs excited by pulses with negative polarity enhances electron field emission from the cathode, which is illustrated by the bright line on the time-integrated images. This makes the shape of the APPJ excited using pulses with negative polarity different from the bullet-like shape of the APPJs excited by pulses with positive polarity.

Structural contributions to fibrillatory rotors in a patient-derived computational model of the atria.

PubMed

Gonzales, Matthew J; Vincent, Kevin P; Rappel, Wouter-Jan; Narayan, Sanjiv M; McCulloch, Andrew D

2014-11-01

The aim of this study was to investigate structural contributions to the maintenance of rotors in human atrial fibrillation (AF) and possible mechanisms of termination. A three-dimensional human biatrial finite element model based on patient-derived computed tomography and arrhythmia observed at electrophysiology study was used to study AF. With normal physiological electrical conductivity and effective refractory periods (ERPs), wave break failed to sustain reentrant activity or electrical rotors. With depressed excitability, decreased conduction anisotropy, and shorter ERP characteristic of AF, reentrant rotors were readily maintained. Rotors were transiently or permanently trapped by fibre discontinuities on the lateral wall of the right atrium near the tricuspid valve orifice and adjacent to the crista terminalis, both known sites of right atrial arrhythmias. Modelling inexcitable regions near the rotor tip to simulate fibrosis anchored the rotors, converting the arrhythmia to macro-reentry. Accordingly, increasing the spatial core of inexcitable tissue decreased the frequency of rotation, widened the excitable gap, and enabled an external wave to impinge on the rotor core and displace the source. These model findings highlight the importance of structural features in rotor dynamics and suggest that regions of fibrosis may anchor fibrillatory rotors. Increasing extent of fibrosis and scar may eventually convert fibrillation to excitable gap reentry. Such macro-reentry can then be eliminated by extending the obstacle or by external stimuli that penetrate the excitable gap. Published on behalf of the European Society of Cardiology. All rights reserved. © The Author 2014. For permissions please email: journals.permissions@oup.com.

A full-field transmission x-ray microscope for time-resolved imaging of magnetic nanostructures

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

Ewald, J.; Nisius, T.; Abbati, G.

Sub-nanosecond magnetization dynamics of small permalloy (Ni{sub 80}Fe{sub 20}) elements has been investigated with a new full-field transmission microscope at the soft X-ray beamline P04 of the high brilliance synchrotron radiation source PETRA III. The soft X-ray microscope generates a flat-top illumination field of 20 μm diameter using a grating condenser. A tilted nanostructured magnetic sample can be excited by a picosecond electric current pulse via a coplanar waveguide. The transmitted light of the sample plane is directly imaged by a micro zone plate with < 65 nm resolution onto a 2D gateable X-ray detector to select one particular bunch in themore » storage ring that probes the time evolution of the dynamic information successively via XMCD spectromicroscopy in a pump-probe scheme. In the experiments it was possible to generate a homogeneously magnetized state in patterned magnetic layers by a strong magnetic Oersted field pulse of 200 ps duration and directly observe the recovery to the initial flux-closure vortex patterns.« less

Torque shudder protection device and method

DOEpatents

King, Robert D.; De Doncker, Rik W. A. A.; Szczesny, Paul M.

1997-01-01

A torque shudder protection device for an induction machine includes a flux command generator for supplying a steady state flux command and a torque shudder detector for supplying a status including a negative status to indicate a lack of torque shudder and a positive status to indicate a presence of torque shudder. A flux adapter uses the steady state flux command and the status to supply a present flux command identical to the steady state flux command for a negative status and different from the steady state flux command for a positive status. A limiter can receive the present flux command, prevent the present flux command from exceeding a predetermined maximum flux command magnitude, and supply the present flux command to a field oriented controller. After determining a critical electrical excitation frequency at which a torque shudder occurs for the induction machine, a flux adjuster can monitor the electrical excitation frequency of the induction machine and adjust a flux command to prevent the monitored electrical excitation frequency from reaching the critical electrical excitation frequency.

Torque shudder protection device and method

DOEpatents

King, R.D.; Doncker, R.W.A.A. De.; Szczesny, P.M.

1997-03-11

A torque shudder protection device for an induction machine includes a flux command generator for supplying a steady state flux command and a torque shudder detector for supplying a status including a negative status to indicate a lack of torque shudder and a positive status to indicate a presence of torque shudder. A flux adapter uses the steady state flux command and the status to supply a present flux command identical to the steady state flux command for a negative status and different from the steady state flux command for a positive status. A limiter can receive the present flux command, prevent the present flux command from exceeding a predetermined maximum flux command magnitude, and supply the present flux command to a field oriented controller. After determining a critical electrical excitation frequency at which a torque shudder occurs for the induction machine, a flux adjuster can monitor the electrical excitation frequency of the induction machine and adjust a flux command to prevent the monitored electrical excitation frequency from reaching the critical electrical excitation frequency. 5 figs.

The Characteristics of Electromagnetic Fields Induced by Different Type Sources

NASA Astrophysics Data System (ADS)

Di, Q.; Fu, C.; Wang, R.; Xu, C.; An, Z.

2011-12-01

Controlled source audio-frequence magnetotelluric (CSAMT) method has played an important role in the shallow exploration (less than 1.5km) in the field of resources, environment and engineering geology. In order to prospect the deeper target, one has to increase the strength of the source and offset. However, the exploration is nearly impossible for the heavy larger power transmitting source used in the deeper prospecting and mountain area. So an EM method using a fixed large power source, such as long bipole current source, two perpendicular "L" shape long bipole current source and large radius circle current source, is beginning to take shape. In order to increase the strength of the source, the length of the transmitting bipole in one direction or in perpendicular directions has to be much larger, such as L=100km, or the radius of the circle current source is much larger. The electric field strength are IL2and IL2/4π separately for long bipole source and circle current source with the same wire length. Just considering the effectiveness of source, the strength of the circle current source is larger than that of long bipole source if is large enough. However, the strength of the electromagnetic signal doesn't totally depend on the transmitting source, the effect of ionosphere on the electromagnetic (EM) field should be considered when observation is carried at a very far (about several thousands kilometers) location away from the source for the long bipole source or the large radius circle current source. We firstly calculate the electromagnetic fields with the traditional controlled source (CSEM) configuration using the integral equation (IE) code developed by our research group for a three layers earth-ionosphere model which consists of ionosphere, atmosphere and earth media. The modeling results agree well with the half space analytical results because the effect of ionosphere for this small scale source can be ignorable, which means the integral equation method is reliable and effective for modeling models including ionosphere, atmosphere and earth media. In order to discuss EM fields' characters for complicate earth-ionosphere media excited by long bipole, "L" shape bipole and circle current sources in the far-field and wave-guide zones, we modeled the frequency responses and decay characters of EM fields for three layers earth-ionosphere model. Because of the effect of ionosphere, the earth-ionosphere electromagnetic fields' decay curves with given frequency show that the fields of Ex and Hy , excited by a long bipole and "L" shape bipole, can be divided into an extra wave-guide field with slower attenuation and strong amplititude than that in half space, but the EM fields of circle current source does not show the same characteristics, ionosphere makes the amplitude of the EM field weaker for the circle current source. For this reason, it is better to use long bipole source while working in the wave-guide field with a fixed large power source.

ARC: An open-source library for calculating properties of alkali Rydberg atoms

NASA Astrophysics Data System (ADS)

Šibalić, N.; Pritchard, J. D.; Adams, C. S.; Weatherill, K. J.

2017-11-01

We present an object-oriented Python library for the computation of properties of highly-excited Rydberg states of alkali atoms. These include single-body effects such as dipole matrix elements, excited-state lifetimes (radiative and black-body limited) and Stark maps of atoms in external electric fields, as well as two-atom interaction potentials accounting for dipole and quadrupole coupling effects valid at both long and short range for arbitrary placement of the atomic dipoles. The package is cross-referenced to precise measurements of atomic energy levels and features extensive documentation to facilitate rapid upgrade or expansion by users. This library has direct application in the field of quantum information and quantum optics which exploit the strong Rydberg dipolar interactions for two-qubit gates, robust atom-light interfaces and simulating quantum many-body physics, as well as the field of metrology using Rydberg atoms as precise microwave electrometers. Program Files doi:http://dx.doi.org/10.17632/hm5n8w628c.1 Licensing provisions: BSD-3-Clause Programming language: Python 2.7 or 3.5, with C extension External Routines: NumPy [1], SciPy [1], Matplotlib [2] Nature of problem: Calculating atomic properties of alkali atoms including lifetimes, energies, Stark shifts and dipole-dipole interaction strengths using matrix elements evaluated from radial wavefunctions. Solution method: Numerical integration of radial Schrödinger equation to obtain atomic wavefunctions, which are then used to evaluate dipole matrix elements. Properties are calculated using second order perturbation theory or exact diagonalisation of the interaction Hamiltonian, yielding results valid even at large external fields or small interatomic separation. Restrictions: External electric field fixed to be parallel to quantisation axis. Supplementary material: Detailed documentation (.html), and Jupyter notebook with examples and benchmarking runs (.html and .ipynb). [1] T.E. Oliphant, Comput. Sci. Eng. 9, 10 (2007). http://www.scipy.org/. [2] J.D. Hunter, Comput. Sci. Eng. 9, 90 (2007). http://matplotlib.org/.

Impedance-based structural health monitoring of wind turbine blades

NASA Astrophysics Data System (ADS)

Pitchford, Corey; Grisso, Benjamin L.; Inman, Daniel J.

2007-04-01

Wind power is a fast-growing source of non-polluting, renewable energy with vast potential. However, current wind turbine technology must be improved before the potential of wind power can be fully realized. Wind turbine blades are one of the key components in improving this technology. Blade failure is very costly because it can damage other blades, the wind turbine itself, and possibly other wind turbines. A successful damage detection system incorporated into wind turbines could extend blade life and allow for less conservative designs. A damage detection method which has shown promise on a wide variety of structures is impedance-based structural health monitoring. The technique utilizes small piezoceramic (PZT) patches attached to a structure as self-sensing actuators to both excite the structure with high-frequency excitations, and monitor any changes in structural mechanical impedance. By monitoring the electrical impedance of the PZT, assessments can be made about the integrity of the mechanical structure. Recently, advances in hardware systems with onboard computing, including actuation and sensing, computational algorithms, and wireless telemetry, have improved the accessibility of the impedance method for in-field measurements. This paper investigates the feasibility of implementing such an onboard system inside of turbine blades as an in-field method of damage detection. Viability of onboard detection is accomplished by running a series of tests to verify the capability of the method on an actual wind turbine blade section from an experimental carbon/glass/balsa composite blade developed at Sandia National Laboratories.

Energy harvesting concepts for small electric unmanned systems

NASA Astrophysics Data System (ADS)

Qidwai, Muhammad A.; Thomas, James P.; Kellogg, James C.; Baucom, Jared N.

2004-07-01

In this study, we identify and survey energy harvesting technologies for small electrically powered unmanned systems designed for long-term (>1 day) time-on-station missions. An environmental energy harvesting scheme will provide long-term, energy additions to the on-board energy source. We have identified four technologies that cover a broad array of available energy sources: solar, kinetic (wind) flow, autophagous structure-power (both combustible and metal air-battery systems) and electromagnetic (EM) energy scavenging. We present existing conceptual designs, critical system components, performance, constraints and state-of-readiness for each technology. We have concluded that the solar and autophagous technologies are relatively matured for small-scale applications and are capable of moderate power output levels (>1 W). We have identified key components and possible multifunctionalities in each technology. The kinetic flow and EM energy scavenging technologies will require more in-depth study before they can be considered for implementation. We have also realized that all of the harvesting systems require design and integration of various electrical, mechanical and chemical components, which will require modeling and optimization using hybrid mechatronics-circuit simulation tools. This study provides a starting point for detailed investigation into the proposed technologies for unmanned system applications under current development.

Luminescent Photoelectrochemical Cells. 2. Doped Cadmium Sulfide Photoelectrodes as Probes of Excited-State Processes Which Influence Optical to Electrical Energy Conversion.

DTIC Science & Technology

1980-08-12

evidence for electrolyte oxidation processes, and the temporalL ._4 7 variation of photocurrent and emission. 1. Stoichiometrlc Data The stoichiometric...every 48 h. The electrodes, electrolyte compositions, and light sources are given in Table I. The HP 6214A power supply was connected in series with the... series 10 or 100 S resistor. At the end of the experiment, the crystal was demounted and re-weighed. Surface Effects The surfaces of several samples

Mean carrier transport properties and charge collection dynamics of single-crystal, natural type IIa diamonds from ion-induced conductivity measurements

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

Han, Sung Su

1993-09-01

Ion-induced conductivity has been used to investigate the detector characteristics of diamond detectors. Both integrated-charge, and time-resolved current measurements were performed to examine the mean carrier transport properties of diamond and the dynamics of charge collection under highly-localized and high-density excitation conditions. The integrated-charge measurements were conducted with a standard pulse-counting system with 241Am radioactivity as the excitation source for the detectors. The time-resolved current measurements were performed using a 70 GHz random sampling oscilloscope with the detectors incorporated into high-speed microstrip transmission lines and the excitation source for these measurements was an ion beam of either 5-MeV He +more » or 10-MeV Si 3+. The detectors used in both experiments can be described as metal-semiconductor-metal (MSM) devices where a volume of the detector material is sandwiched between two metal plates. A charge collection model was developed to interpret the integrated-charge measurements which enabled estimation of the energy required to produce an electron-hole pair (ϵ di) and the mean carrier transport properties in diamond, such as carrier mobility and lifetime, and the behavior of the electrical contacts to diamond.« less

Electric Vehicles Mileage Extender Kinetic Energy Storage

NASA Astrophysics Data System (ADS)

Jivkov, Venelin; Draganov, Vutko; Stoyanova, Yana

2015-03-01

The proposed paper considers small urban vehicles with electric hybrid propulsion systems. Energy demands are examined on the basis of European drive cycle (NEUDC) and on an energy recuperation coefficient and are formulated for description of cycle energy transfers. Numerical simulation results show real possibilities for increasing in achievable vehicle mileage at the same energy levels of a main energy source - the electric battery. Kinetic energy storage (KES), as proposed to be used as an energy buffer and different structural schemes of the hybrid propulsion system are commented. Minimum energy levels for primary (the electric battery) and secondary (KES) sources are evaluated. A strategy for reduced power flows control is examined, and its impact on achievable vehicle mileage is investigated. Results show an additional increase in simulated mileage at the same initial energy levels.

Long lifetime, low intensity light source for use in nighttime viewing of equipment maps and other writings

DOEpatents

Frank, Alan M.; Edwards, William R.

1983-01-01

A long-lifetime light source with sufficiently low intensity to be used for reading a map or other writing at nighttime, while not obscuring the user's normal night vision. This light source includes a diode electrically connected in series with a small power source and a lens properly positioned to focus at least a portion of the light produced by the diode.

Dipole response of 76Se above 4 MeV

NASA Astrophysics Data System (ADS)

Goddard, P. M.; Cooper, N.; Werner, V.; Rusev, G.; Stevenson, P. D.; Rios, A.; Bernards, C.; Chakraborty, A.; Crider, B. P.; Glorius, J.; Ilieva, R. S.; Kelley, J. H.; Kwan, E.; Peters, E. E.; Pietralla, N.; Raut, R.; Romig, C.; Savran, D.; Schnorrenberger, L.; Smith, M. K.; Sonnabend, K.; Tonchev, A. P.; Tornow, W.; Yates, S. W.

2013-12-01

The dipole response of 3476Se in the energy range from 4 to 9 MeV has been analyzed using a (γ⃗,γ') polarized photon scattering technique, performed at the High Intensity γ-Ray Source facility at Triangle Universities Nuclear Laboratory, to complement previous work performed using unpolarized photons. The results of this work offer both an enhanced sensitivity scan of the dipole response and an unambiguous determination of the parities of the observed J=1 states. The dipole response is found to be dominated by E1 excitations, and can reasonably be attributed to a pygmy dipole resonance. Evidence is presented to suggest that a significant amount of directly unobserved excitation strength is present in the region, due to unobserved branching transitions in the decays of resonantly excited states. The dipole response of the region is underestimated when considering only ground state decay branches. We investigate the electric dipole response theoretically, performing calculations in a three-dimensional (3D) Cartesian-basis time-dependent Skyrme-Hartree-Fock framework.

Current driven transition from Abrikosov-Josephson to Josephson-like vortex in mesoscopic lateral S/S’/S superconducting weak links

PubMed Central

Carapella, G.; Sabatino, P.; Barone, C.; Pagano, S.; Gombos, M.

2016-01-01

Vortices are topological defects accounting for many important effects in superconductivity, superfluidity, and magnetism. Here we address the stability of a small number of such excitations driven by strong external forces. We focus on Abrikosov-Josephson vortex that appears in lateral superconducting S/S’/S weak links with suppressed superconductivity in S’. In such a system the vortex is nucleated and confined in the narrow S’ region by means of a small magnetic field and moves under the effect of a force proportional to an applied electrical current with a velocity proportional to the measured voltage. Our numerical simulations show that when a slow moving Abrikosov-Josephson vortex is driven by a strong constant current it becomes unstable with respect to a faster moving excitation: the Josephon-like vortex. Such a current-driven transition explains the structured dissipative branches that we observe in the voltage-current curve of the weak link. When vortex matter is strongly confined phenomena as magnetoresistance oscillations and reentrance of superconductivity can possibly occur. We experimentally observe these phenomena in our weak links. PMID:27752137

Capacitively coupled hydrogen plasmas sustained by tailored voltage waveforms: excitation dynamics and ion flux asymmetry

DOE PAGES

Bruneau, B.; Diomede, P.; Economou, D. J.; ...

2016-06-08

Parallel plate capacitively coupled plasmas in hydrogen at relatively high pressure (~1 Torr) are excited with tailored voltage waveforms containing up to five frequencies. Predictions of a hybrid model combining a particle-in-cell simulation with Monte Carlo collisions and a fluid model are compared to phase resolved optical emission spectroscopy measurements, yielding information on the dynamics of the excitation rate in these discharges. When the discharge is excited with amplitude asymmetric waveforms, the discharge becomes electrically asymmetric, with different ion energies at each of the two electrodes. Unexpectedly, large differences in themore » $$\\text{H}_{2}^{+}$$ fluxes to each of the two electrodes are caused by the different $$\\text{H}_{3}^{+}$$ energies. When the discharge is excited with slope asymmetric waveforms, only weak electrical asymmetry of the discharge is observed. In this case, electron power absorption due to fast sheath expansion at one electrode is balanced by electron power absorption at the opposite electrode due to a strong electric field reversal.« less

Modelling Feedback Excitation, Pacemaker Properties and Sensory Switching of Electrically Coupled Brainstem Neurons Controlling Rhythmic Activity

PubMed Central

Hull, Michael J.; Soffe, Stephen R.; Willshaw, David J.; Roberts, Alan

2016-01-01

What cellular and network properties allow reliable neuronal rhythm generation or firing that can be started and stopped by brief synaptic inputs? We investigate rhythmic activity in an electrically-coupled population of brainstem neurons driving swimming locomotion in young frog tadpoles, and how activity is switched on and off by brief sensory stimulation. We build a computational model of 30 electrically-coupled conditional pacemaker neurons on one side of the tadpole hindbrain and spinal cord. Based on experimental estimates for neuron properties, population sizes, synapse strengths and connections, we show that: long-lasting, mutual, glutamatergic excitation between the neurons allows the network to sustain rhythmic pacemaker firing at swimming frequencies following brief synaptic excitation; activity persists but rhythm breaks down without electrical coupling; NMDA voltage-dependency doubles the range of synaptic feedback strengths generating sustained rhythm. The network can be switched on and off at short latency by brief synaptic excitation and inhibition. We demonstrate that a population of generic Hodgkin-Huxley type neurons coupled by glutamatergic excitatory feedback can generate sustained asynchronous firing switched on and off synaptically. We conclude that networks of neurons with NMDAR mediated feedback excitation can generate self-sustained activity following brief synaptic excitation. The frequency of activity is limited by the kinetics of the neuron membrane channels and can be stopped by brief inhibitory input. Network activity can be rhythmic at lower frequencies if the neurons are electrically coupled. Our key finding is that excitatory synaptic feedback within a population of neurons can produce switchable, stable, sustained firing without synaptic inhibition. PMID:26824331

Portable multiwavelength laser diode source for handheld photoacoustic devices

NASA Astrophysics Data System (ADS)

Canal, Celine; Laugustin, Arnaud; Kohl, Andreas; Rabot, Olivier

2016-04-01

The ageing population faces today an increase of chronic diseases such as rheumatism/arthritis, cancer and cardio vascular diseases for which appropriate treatments based on a diagnosis at an early-stage of the disease are required. Some imaging techniques are already available in order to get structural information. Within the non-invasive group, ultrasound images are common in these fields of medicine. However, there is a need for a point-of-care device for imaging smaller structures such as blood vessels that cannot be observed with purely ultrasound based devices. Photoacoustics proved to be an attractive candidate. This novel imaging technique combines pulsed laser light for excitation of tissues and an ultrasound transducer as a receptor. Introduction of this technique into the clinic requires to drastically shrink the size and cost of the expensive and bulky nanosecond lasers generally used for light emission. In that context, demonstration of ultra-short pulse emission with highly efficient laser diodes in the near-infrared range has been performed by Quantel, France. A multi-wavelength laser source as small as a hand emitted more than 1 mJ per wavelength with four different wavelengths available in pulses of about 90 ns. Such a laser source can be integrated into high sensitivity photoacoustic handheld systems due to their outstanding electrical-to-optical efficiency of about 25 %. Further work continues to decrease the pulse length as low as 40 ns while increasing the pulse energy to 2 mJ.

Electrode structure of a compact microwave driven capacitively coupled atomic beam source

NASA Astrophysics Data System (ADS)

Shimabukuro, Yuji; Takahashi, Hidenori; Wada, Motoi

2018-01-01

A compact magnetic field free atomic beam source was designed, assembled and tested the performance to produce hydrogen and nitrogen atoms. A forced air-cooled solid-state microwave power supply at 2.45 GHz frequency drives the source up to 100 W through a coaxial transmission cable coupled to a triple stub tuner for realizing a proper matching condition to the discharge load. The discharge structure of the source affected the range of operation pressure, and the pressure was reduced by four orders of magnitude through improving the electrode geometry to enhance the local electric field intensity. Optical emission spectra of the produced plasmas indicate production of hydrogen and nitrogen atoms, while the flux intensity of excited nitrogen atoms monitored by a surface ionization type detector showed the signal level close to a source developed for molecular beam epitaxy applications with 500 W RF power.

Improving confocal microscopy with solid-state semiconductor excitation sources

NASA Astrophysics Data System (ADS)

Sivers, Nelson L.

To efficiently excite the fluorescent dyes used in imaging biological samples with a confocal microscope, the wavelengths of the exciting laser must be near the fluorochrome absorption peak. However, this causes imaging problems when the fluorochrome absorption and emission spectra overlap significantly, i.e. have small Stokes shifts, which is the case for most fluorochromes that emit in the red to infrared. As a result, the reflected laser excitation cannot be distinguished from the information-containing fluorescence signal. However, cryogenically cooling the exciting laser diode enabled the laser emission wavelengths to be tuned to shorter wavelengths, decreasing the interference between the laser and the fluorochrome's fluorescence. This reduced the amount of reflected laser light in the confocal image. However, the cooled laser diode's shorter wavelength signal resulted in slightly less efficient fluorochrome excitation. Spectrophotometric analysis showed that as the laser diodes were cooled, their output power increased, which more than compensated for the lower fluorochrome excitation and resulted in significantly more intense fluorescence. Thus, by tuning the laser diode emission wavelengths away from the fluorescence signal, less reflected laser light and more fluorescence information reached the detector, creating images with better signal to noise ratios. Additionally, new, high, luminous flux, light-emitting diodes (LEDs) are now powerful enough to create confocal fluorescence signals comparable to those produced by the traditional laser excitation sources in fluorescence confocal microscopes. The broader LED spectral response effectively excited the fluorochrome, yet was spectrally limited enough for standard filter sets to separate the LED excitation from the fluorochrome fluorescence signal. Spectrophotometric analysis of the excitation and fluorescence spectra of several fluorochromes showed that high-powered, LED-induced fluorescence contained the same spectral information and could be more intense than that produced by lasers. An alternative, LED-based, confocal microscope is proposed in this thesis that would be capable of exciting multiple fluorochromes in a single specimen, producing images of several distinct cellular components simultaneously. The inexpensive, LED-based, confocal microscope would require lower peak excitation intensities to produce fluorescence signals equal to those produced by laser excitation, reducing cellular damage and slowing fluorochrome photobleaching.

Optical magnetic mirrors without metals

DOE PAGES

Liu, Sheng; Sinclair, Michael B.; Mahony, Thomas S.; ...

2014-01-01

The reflection of an optical wave from metal, arising from strong interactions between the optical electric field and the free carriers of the metal, is accompanied by a phase reversal of the reflected electric field. A far less common route to achieving high reflectivity exploits strong interactions between the material and the optical magnetic field to produce a “magnetic mirror” that does not reverse the phase of the reflected electric field. At optical frequencies, the magnetic properties required for strong interaction can be achieved only by using artificially tailored materials. Here, we experimentally demonstrate, for the first time to themore » best of our knowledge, the magnetic mirror behavior of a low-loss all-dielectric metasurface at infrared optical frequencies through direct measurements of the phase and amplitude of the reflected optical wave. The enhanced absorption and emission of transverse-electric dipoles placed close to magnetic mirrors can lead to exciting new advances in sensors, photodetectors, and light sources.« less

Experimental demonstration of a single-molecule electric motor.

PubMed

Tierney, Heather L; Murphy, Colin J; Jewell, April D; Baber, Ashleigh E; Iski, Erin V; Khodaverdian, Harout Y; McGuire, Allister F; Klebanov, Nikolai; Sykes, E Charles H

2011-09-04

For molecules to be used as components in molecular machines, methods that couple individual molecules to external energy sources and that selectively excite motion in a given direction are required. Significant progress has been made in the construction of molecular motors powered by light and by chemical reactions, but electrically driven motors have not yet been built, despite several theoretical proposals for such motors. Here we report that a butyl methyl sulphide molecule adsorbed on a copper surface can be operated as a single-molecule electric motor. Electrons from a scanning tunnelling microscope are used to drive the directional motion of the molecule in a two-terminal setup. Moreover, the temperature and electron flux can be adjusted to allow each rotational event to be monitored at the molecular scale in real time. The direction and rate of the rotation are related to the chiralities of both the molecule and the tip of the microscope (which serves as the electrode), illustrating the importance of the symmetry of the metal contacts in atomic-scale electrical devices.

Excited-state dynamics of acetylene excited to individual rotational level of the V04K01 subband

NASA Astrophysics Data System (ADS)

Makarov, Vladimir I.; Kochubei, Sergei A.; Khmelinskii, Igor V.

2006-01-01

Dynamics of the IR emission induced by excitation of the acetylene molecule using the (32Ka0,1,2,ÃAu1←41la1,X˜Σg+1) transition was investigated. The observed IR emission was assigned to transitions between the ground-state vibrational levels. Acetylene fluorescence quenching induced by external electric and magnetic fields acting upon the system prepared using the (34Ka1,ÃAu1←00la0,X˜Σg+1) excitation was also studied. External electric field creates an additional radiationless pathway to the ground-state levels, coupling levels of the ÃAu1 excited state to the quasiresonant levels of the X˜Σg+1 ground state. The level density of the ground state in the vicinity of the excited state is very high, thus the electric-field-induced transition is irreversible, with the rate constant described by the Fermi rule. Magnetic field alters the decay profile without changing the fluorescence quantum yield in collisionless conditions. IR emission from the CCH transient was detected, and was also affected by the external electric and magnetic fields. Acetylene predissociation was demonstrated to proceed by the direct S1→S0 mechanism. The results were explained using the previously developed theoretical approach, yielding values of the relevant model parameters.

Influence of excitability on unpinning and termination of spiral waves.

PubMed

Luengviriya, Jiraporn; Sutthiopad, Malee; Phantu, Metinee; Porjai, Porramain; Kanchanawarin, Jarin; Müller, Stefan C; Luengviriya, Chaiya

2014-11-01

Application of electrical forcing to release pinned spiral waves from unexcitable obstacles and to terminate the rotation of free spiral waves at the boundary of excitable media has been investigated in thin layers of the Belousov-Zhabotinsky (BZ) reaction, prepared with different initial concentrations of H_{2}SO_{4}. Increasing [H_{2}SO_{4}] raises the excitability of the reaction and reduces the core diameter of free spiral waves as well as the wave period. An electric current with density stronger than a critical value Junpin causes a pinned spiral wave to drift away from the obstacle. For a given obstacle size, Junpin increases with [H_{2}SO_{4}]. Under an applied electrical current, the rotation center of a free spiral wave drifts along a straight path to the boundary. When the current density is stronger than a critical value Jterm, the spiral tip is forced to hit the boundary, where the spiral wave is terminated. Similar to Junpin for releasing a pinned spiral wave, Jterm also increases with [H_{2}SO_{4}]. These experimental findings were confirmed by numerical simulations using the Oregonator model, in which the excitability was adjusted via the ratio of the excitation rate to the recovery rate of the BZ reaction. Therefore, our investigation shows that decreasing the excitability can facilitate elimination of spiral waves by electrical forcing, either in the presence of obstacles or not.

Excitation of small-scale waves in the F region of the ionosphere by powerful HF radio waves

NASA Astrophysics Data System (ADS)

Blagoveshchenskaya, N. F.; Chernyshev, M. Y.; Kornienko, V. A.

1998-01-01

Ionospheric small-scale waves in the F region, initiated by heating facilities in Nizhniy Novgorod, have been studied by the method of field-aligned scattering of diagnostic HF radio signals. Experimental data have been obtained on the radio path Kiev-N. Novgorod-St. Petersburg during heating campaigns with heater radiated power ERP = 20 MW and 100 MW. Observations of scattered HF signals have been made by a Doppler spectrum device with high temporal resolution. Analysis of the experimental data shows a relation between the heater power level and the parameters of ionospheric small-scale oscillations falling within the range of Pc 3-4 magnetic pulsations. It is found that the periods of wave processes in the F region of the ionosphere, induced by the heating facility, decrease with increasing heating power. The level of heating power also has an impact on the horizontal east-west component of the electric field E, the vertical component of the Doppler velocity Vd and the amplitude of the vertical displacements M of the heated region. Typical magnitudes of these parameters are the following: E = 1.25 mVm, Vd = 6 ms, M = 600-1500 m for ERP = 20 MW and E = 2.5-4.5 mVm, Vd = 11-25 ms, M = 1000-5000 m for ERP = 100 MW. The results obtained confirm the hypothesis of excitation of the Alfvén resonator by powerful HF radio waves which leads to the generation of magnetic field oscillations in the heated region giving rise to artificial Pc 3-4 magnetic pulsations and ionospheric small-scale wave processes. In this situation an increase of the heater power would lead to a growth of the electric field of hydromagnetic waves propagating in the ionosphere as well as the amplitude of the vertical displacements of the heated region.

18 CFR 292.602 - Exemption to qualifying facilities from the Public Utility Holding Company Act of 2005 and...

Code of Federal Regulations, 2014 CFR

2014-04-01

... PRODUCTION AND COGENERATION Exemption of Qualifying Small Power Production Facilities and Cogeneration... small power production facility with a power production capacity over 30 megawatts if such facility produces electric energy solely by the use of biomass as a primary energy source. (b) Exemption from the...

18 CFR 292.602 - Exemption to qualifying facilities from the Public Utility Holding Company Act of 2005 and...

Code of Federal Regulations, 2012 CFR

2012-04-01

... PRODUCTION AND COGENERATION Exemption of Qualifying Small Power Production Facilities and Cogeneration... small power production facility with a power production capacity over 30 megawatts if such facility produces electric energy solely by the use of biomass as a primary energy source. (b) Exemption from the...

18 CFR 292.602 - Exemption to qualifying facilities from the Public Utility Holding Company Act of 2005 and...

Code of Federal Regulations, 2013 CFR

2013-04-01

... PRODUCTION AND COGENERATION Exemption of Qualifying Small Power Production Facilities and Cogeneration... small power production facility with a power production capacity over 30 megawatts if such facility produces electric energy solely by the use of biomass as a primary energy source. (b) Exemption from the...

Resonance energy transfer: when a dipole fails.

PubMed

Andrews, David L; Leeder, Jamie M

2009-05-14

The Coulombic coupling of electric dipole (E1) transition moments is the most commonly studied and widely operative mechanism for energy migration in multichromophore systems. However a significant number of exceptions exist, in which donor decay and/or acceptor excitation processes are E1-forbidden. The alternative transfer mechanisms that can apply in such cases include roles for higher multipole transitions, exciton- or phonon-assisted interactions, and non-Coulombic interactions based on electron exchange. A quantum electrodynamical formulation provides a rigorous basis to assess the first of these, specifically addressing the relative significance of higher multipole contributions to the process of energy transfer in donor-acceptor systems where electric dipole transitions are precluded by symmetry. Working within the near-zone limit, where donor-acceptor separations are small in comparison to the chromophore scale, the analysis highlights the contributions of both electric quadrupole-electric quadrupole (E2-E2) coupling and the seldom considered second-order electric dipole-electric dipole (E1(2)-E1(2)) coupling. For both forms of interaction, experimentally meaningful rate equations are secured by the use of orientational averaging, and the mechanisms are analyzed with reference to systems in which E1-forbidden transitions are commonly reported.

A small animal time-resolved optical tomography platform using wide-field excitation

NASA Astrophysics Data System (ADS)

Venugopal, Vivek

Small animal imaging plays a critical role in present day biomedical research by filling an important gap in the translation of research from the bench to the bedside. Optical techniques constitute an emerging imaging modality which have tremendous potential in preclinical applications. Optical imaging methods are capable of non-invasive assessment of the functional and molecular characteristics of biological tissue. The three-dimensional optical imaging technique, referred to as diffuse optical tomography, provides an approach for the whole-body imaging of small animal models and can provide volumetric maps of tissue functional parameters (e.g. blood volume, oxygen saturation etc.) and/or provide 3D localization and quantification of fluorescence-based molecular markers in vivo. However, the complex mathematical reconstruction problem associated with optical tomography and the cumbersome instrumental designs limits its adoption as a high-throughput quantitative whole-body imaging modality in current biomedical research. The development of new optical imaging paradigms is thus necessary for a wide-acceptance of this new technology. In this thesis, the design, development, characterization and optimization of a small animal optical tomography system is discussed. Specifically, the platform combines a highly sensitive time-resolved imaging paradigm with multi-spectral excitation capability and CCD-based detection to provide a system capable of generating spatially, spectrally and temporally dense measurement datasets. The acquisition of such data sets however can take long and translate to often unrealistic acquisition times when using the classical point source based excitation scheme. The novel approach in the design of this platform is the adoption of a wide-field excitation scheme which employs extended excitation sources and in the process allows an estimated ten-fold reduction in the acquisition time. The work described herein details the design of the imaging platform employing DLP-based excitation and time-gated intensified CCD detection and the optimal system operation parameters are determined. The feasibility this imaging approach and accuracy of the system in reconstructing functional parameters and fluorescence markers based on lifetime contrast is established through phantom studies. As a part of the system characterization, the effect of noise in time-resolved optical tomography is investigated and propagation of system noise in optical reconstructions is established. Furthermore, data processing and measurement calibration techniques aimed at reducing the effect of noise in reconstructions are defined. The optimization of excitation pattern selection is established through a novel measurement-guided iterative pattern correction scheme. This technique referred to as Adaptive Full-Field Optical Tomography was shown to improve reconstruction performances in murine models by reducing the dynamic range in photon flux measurements on the surface. Lastly, the application of the unique attributes of this platform to a biologically relevant imaging application, referred to as Forster Resonance Energy Transfer is described. The tomographic imaging of FRET interaction in vivo on a whole-body scale is achieved using the wide-field imaging approach based on lifetime contrast. This technique represents the first demonstration of tomographic FRET imaging in small animals and has significant potential in the development of optical imaging techniques in varied applications ranging from drug discovery to in vivo study of protein-protein interaction.

Meson and baryon spectrum for QCD with two light dynamical quarks

NASA Astrophysics Data System (ADS)

Engel, Georg P.; Lang, C. B.; Limmer, Markus; Mohler, Daniel; Schäfer, Andreas

2010-08-01

We present results of meson and baryon spectroscopy using the Chirally Improved Dirac operator on lattices of size 163×32 with two mass-degenerate light sea quarks. Three ensembles with pion masses of 322(5), 470(4), and 525(7) MeV and lattice spacings close to 0.15 fm are investigated. Results for ground and excited states for several channels are given, including spin two mesons and hadrons with strange valence quarks. The analysis of the states is done with the variational method, including two kinds of Gaussian sources and derivative sources. We obtain several ground states fairly precisely and find radial excitations in various channels. Excited baryon results seem to suffer from finite size effects, in particular, at small pion masses. We discuss the possible appearance of scattering states, considering masses and eigenvectors. Partially quenched results in the scalar channel suggest the presence of a 2-particle state, however, in most channels we cannot identify them. Where available, we compare our results to results of quenched simulations using the same action.

Periodic cycles of social outbursts of activity

NASA Astrophysics Data System (ADS)

Berestycki, H.; Rossi, L.; Rodríguez, N.

2018-01-01

We study the long-time behavior of a 2 × 2 continuous dynamical system with a time-periodic source term which is either of cooperative-type or activator-inhibitor type. This system was recently introduced in the literature [2] to model the dynamics of social outbursts and consists of an explicit field measuring the level of activity and an implicit field measuring the effective tension. The system can be used to represent a general type of phenomena in which one variable exhibits self-excitement once the other variable has reached a critical value. The time-periodic source term allows one to analyze the effect that periodic external shocks to the system play in the dynamics of the outburst of activity. For cooperative systems we prove that for small shocks the level of activity dies down whereas, as the intensity of the shocks increases, the level of activity converges to a positive periodic solution (excited cycle). We further show that in some cases there is multiplicity of excited cycles. We derive a subset of these results for the activator-inhibitor system.

Low-lying dipole strength of the open-shell nucleus 94Mo

NASA Astrophysics Data System (ADS)

Romig, C.; Beller, J.; Glorius, J.; Isaak, J.; Kelley, J. H.; Kwan, E.; Pietralla, N.; Ponomarev, V. Yu.; Sauerwein, A.; Savran, D.; Scheck, M.; Schnorrenberger, L.; Sonnabend, K.; Tonchev, A. P.; Tornow, W.; Weller, H. R.; Zilges, A.; Zweidinger, M.

2013-10-01

The low-lying dipole strength of the open-shell nucleus 94Mo was studied via the nuclear resonance fluorescence technique up to 8.7 MeV excitation energy at the bremsstrahlung facility at the Superconducting Darmstadt Electron Linear Accelerator (S-DALINAC), and with Compton backscattered photons at the High Intensity γ-ray Source (HIγS) facility. In total, 83 excited states were identified. Exploiting polarized quasi-monoenergetic photons at HIγS, parity quantum numbers were assigned to 41 states excited by dipole transitions. The electric dipole-strength distribution was determined up to 8.7 MeV and compared to microscopic calculations within the quasiparticle phonon model. Calculations and experimental data are in good agreement for the fragmentation, as well as for the integrated strength. The average decay pattern of the excited states was investigated exploiting the HIγS measurements at five energy settings. Mean branching ratios to the ground state and first excited 21+ state were extracted from the measurements with quasi-monoenergetic photons and compared to γ-cascade simulations within the statistical model. The experimentally deduced mean branching ratios exhibit a resonance-like maximum at 6.4 MeV which cannot be reproduced within the statistical model. This indicates a nonstatistical structure in the energy range between 5.5 and 7.5 MeV.

Multi-Excitation Magnetoacoustic Tomography with Magnetic Induction for Bioimpedance Imaging

PubMed Central

Li, Xu; He, Bin

2011-01-01

Magnetoacoustic tomography with magnetic induction (MAT-MI) is an imaging approach proposed to conduct non-invasive electrical conductivity imaging of biological tissue with high spatial resolution. In the present study, based on the analysis of the relationship between the conductivity distribution and the generated MAT-MI acoustic source, we propose a new multi-excitation MAT-MI approach and the corresponding reconstruction algorithms. In the proposed method, multiple magnetic excitations using different coil configurations are employed and ultrasound measurements corresponding to each excitation are collected to derive the conductivity distribution inside the sample. A modified reconstruction algorithm is also proposed for the multi-excitation MAT-MI imaging approach when only limited bandwidth acoustic measurements are available. Computer simulation and phantom experiment studies have been done to demonstrate the merits of the proposed method. It is shown that if unlimited bandwidth acoustic data is available, we can accurately reconstruct the internal conductivity contrast of an object using the proposed method. With limited bandwidth data and the use of the modified algorithm we can reconstruct the relative conductivity contrast of an object instead of only boundaries at the conductivity heterogeneity. Benefits that come with this new method include better differentiation of tissue types with conductivity contrast using the MAT-MI approach, specifically for potential breast cancer screening application in the future. PMID:20529729

PHOBOS Exploration using Two Small Solar Electric Propulsion Spacecraft

NASA Technical Reports Server (NTRS)

Lang, Jared J.; Baker, John D.; Castillo-Rogez, Julie C.; McElrath, Timothy P.; Piacentine, Jamie S.; Snyder, J. Steve

2012-01-01

Primitive bodies are exciting targets for exploration as they provide clues to the early Solar system conditions and dynamical evolution. The two moons of Mars are particularly interesting because of their proximity to an astrobiological target. However, after four decades of Mars exploration, their origin and nature remain enigmatic. In addition, when considering the long-term objectives of the flexible path for the potential human exploration to Mars, Phobos and Deimos present exciting intermediate opportunities without the complication and expense of landing and ascending from the surface. As interest in these targets for the next frontier of human exploration grows, characterization missions designed specifically to examine surface properties, landing environments, and surface mapping prior to human exploration are becoming increasingly important. A precursor mission concept of this sort has been developed using two identical spacecraft designed from low cost, flight proven and certified off-the-shelf component and utilizing Solar Electric Propulsion (SEP) to orbit both targets as secondary payloads launched aboard any NASA or GTO launch. This precursor mission has the potential to address both precursor measurements that are strategic knowledge gaps and decadal science, including soil physical properties at the global and local (human) scale and the search for in situ resources.

Direct charge radioisotope activation and power generation

DOEpatents

Lal, Amit; Li, Hui; Blanchard, James P.; Henderson, Douglass L.

2002-01-01

An activator has a base on which is mounted an elastically deformable micromechanical element that has a section that is free to be displaced toward the base. An absorber of radioactively emitted particles is formed on the base or the displaceable section of the deformable element and a source is formed on the other of the displaceable section or the base facing the absorber across a small gap. The radioactive source emits charged particles such as electrons, resulting in a buildup of charge on the absorber, drawing the absorber and source together and storing mechanical energy as the deformable element is bent. When the force between the absorber and the source is sufficient to bring the absorber into effective electrical contact with the source, discharge of the charge between the source and absorber allows the deformable element to spring back, releasing the mechanical energy stored in the element. An electrical generator such as a piezoelectric transducer may be secured to the deformable element to convert the released mechanical energy to electrical energy that can be used to provide power to electronic circuits.

High-flux beam source of fast neutral helium.

PubMed

Fahey, D W; Schearer, L D; Parks, W F

1978-04-01

A high-flux beam source of fast neutral helium has been constructed by extending the designs of previous authors. The source is a dc or pulsed electric discharge in an expanding gas nozzle. The beam produced has a flux on the order of 10(15) atoms/s sr and a mean velocity on the order of 10(7) cm/s. The composition of the beam has been determined by the use of particle detectors and by the observation of the excitation of certain target gases. An upper bound of 3.7 x 10(-5) has been estimated for the He(2(3)S(1))/He((1)S(0))beam density ratio and a value of 0.2 found for the He(+)/He(1(1)S(0)) beam density ratio.

Experimental setup for camera-based measurements of electrically and optically stimulated luminescence of silicon solar cells and wafers.

PubMed

Hinken, David; Schinke, Carsten; Herlufsen, Sandra; Schmidt, Arne; Bothe, Karsten; Brendel, Rolf

2011-03-01

We report in detail on the luminescence imaging setup developed within the last years in our laboratory. In this setup, the luminescence emission of silicon solar cells or silicon wafers is analyzed quantitatively. Charge carriers are excited electrically (electroluminescence) using a power supply for carrier injection or optically (photoluminescence) using a laser as illumination source. The luminescence emission arising from the radiative recombination of the stimulated charge carriers is measured spatially resolved using a camera. We give details of the various components including cameras, optical filters for electro- and photo-luminescence, the semiconductor laser and the four-quadrant power supply. We compare a silicon charged-coupled device (CCD) camera with a back-illuminated silicon CCD camera comprising an electron multiplier gain and a complementary metal oxide semiconductor indium gallium arsenide camera. For the detection of the luminescence emission of silicon we analyze the dominant noise sources along with the signal-to-noise ratio of all three cameras at different operation conditions.

Long lifetime, low intensity light source for use in nighttime viewing of equipment maps and other writings

DOEpatents

Frank, A.M.; Edwards, W.R.

1983-10-11

A long-lifetime light source with sufficiently low intensity to be used for reading a map or other writing at nighttime, while not obscuring the user's normal night vision is disclosed. This light source includes a diode electrically connected in series with a small power source and a lens properly positioned to focus at least a portion of the light produced by the diode. 1 fig.

Long lifetime, low intensity light source for use in nighttime viewing of equipment maps and other writings

DOEpatents

Frank, A.M.; Edwards, W.R.

1982-03-23

A long-lifetime light source is discussed with sufficiently low intensity to be used for reading a map or other writing at nightime, while not obscuring the user's normal night vision. This light source includes a diode electrically connected in series with a small power source and a lens properly positioned to focus at least a portion of the light produced by the diode.

Excitation power quantities in phase resonance testing of nonlinear systems with phase-locked-loop excitation

NASA Astrophysics Data System (ADS)

Peter, Simon; Leine, Remco I.

2017-11-01

Phase resonance testing is one method for the experimental extraction of nonlinear normal modes. This paper proposes a novel method for nonlinear phase resonance testing. Firstly, the issue of appropriate excitation is approached on the basis of excitation power considerations. Therefore, power quantities known from nonlinear systems theory in electrical engineering are transferred to nonlinear structural dynamics applications. A new power-based nonlinear mode indicator function is derived, which is generally applicable, reliable and easy to implement in experiments. Secondly, the tuning of the excitation phase is automated by the use of a Phase-Locked-Loop controller. This method provides a very user-friendly and fast way for obtaining the backbone curve. Furthermore, the method allows to exploit specific advantages of phase control such as the robustness for lightly damped systems and the stabilization of unstable branches of the frequency response. The reduced tuning time for the excitation makes the commonly used free-decay measurements for the extraction of backbone curves unnecessary. Instead, steady-state measurements for every point of the curve are obtained. In conjunction with the new mode indicator function, the correlation of every measured point with the associated nonlinear normal mode of the underlying conservative system can be evaluated. Moreover, it is shown that the analysis of the excitation power helps to locate sources of inaccuracies in the force appropriation process. The method is illustrated by a numerical example and its functionality in experiments is demonstrated on a benchmark beam structure.

A new type of localized fast moving electronic excitations in molecular chains

NASA Astrophysics Data System (ADS)

Korshunova, A. N.; Lakhno, V. D.

2014-06-01

It is shown that in a Holstein molecular chain placed in a strong longitudinal electric field some new types of excitations can arise. These excitations can transfer a charge over large distance (more than 1000 nucleotide pairs) along the chain retaining approximately their shapes. Excitations are formed only when a strong electric field either exists or quickly arises under especially preassigned conditions. These excitations transfer a charge even in the case when Holstein polarons are practically immobile. The results obtained are applied to synthetic homogeneous PolyG/PolyC DNA duplexes. They can also be provide the basis for explanation of famous H.W. Fink and C. Schönenberger experiment on long-range charge transfer in DNA.

Endoplasmic Reticulum-Plasma Membrane Contacts Regulate Cellular Excitability.

PubMed

Dickson, Eamonn J

2017-01-01

Cells that have intrinsic electrical excitability utilize changes in membrane potential to communicate with neighboring cells and initiate cellular cascades. Excitable cells like neurons and myocytes have evolved highly specialized subcellular architectures to translate these electrical signals into cellular events. One such structural specialization is sarco-/endoplasmic reticulum-plasma membrane contact sites. These membrane contact sites are positioned by specific membrane-membrane tethering proteins and contain an ever-expanding list of additional proteins that organize information transfer across the junctional space (~ 15-25 nm distance) to shape membrane identity and control cellular excitability. In this chapter we discuss how contacts between the sarco-/endoplasmic reticulum and plasma membrane are essential for regulated excitation-contraction coupling in striated muscle and control of lipid-dependent ion channels.

Comparison Study of Three Different Image Reconstruction Algorithms for MAT-MI

PubMed Central

Xia, Rongmin; Li, Xu

2010-01-01

We report a theoretical study on magnetoacoustic tomography with magnetic induction (MAT-MI). According to the description of signal generation mechanism using Green’s function, the acoustic dipole model was proposed to describe acoustic source excited by the Lorentz force. Using Green’s function, three kinds of reconstruction algorithms based on different models of acoustic source (potential energy, vectored acoustic pressure, and divergence of Lorenz force) are deduced and compared, and corresponding numerical simulations were conducted to compare these three kinds of reconstruction algorithms. The computer simulation results indicate that the potential energy method and vectored pressure method can directly reconstruct the Lorentz force distribution and give a more accurate reconstruction of electrical conductivity. PMID:19846363

Modulation of cardiac tissue electrophysiological properties with light-sensitive proteins.

PubMed

Nussinovitch, Udi; Shinnawi, Rami; Gepstein, Lior

2014-04-01

Optogenetics approaches, utilizing light-sensitive proteins, have emerged as unique experimental paradigms to modulate neuronal excitability. We aimed to evaluate whether a similar strategy could be used to control cardiac-tissue excitability. A combined cell and gene therapy strategy was developed in which fibroblasts were transfected to express the light-activated depolarizing channel Channelrhodopsin-2 (ChR2). Patch-clamp studies confirmed the development of a robust inward current in the engineered fibroblasts following monochromatic blue-light exposure. The engineered cells were co-cultured with neonatal rat cardiomyocytes (or human embryonic stem cell-derived cardiomyocytes) and studied using a multielectrode array mapping technique. These studies revealed the ability of the ChR2-fibroblasts to electrically couple and pace the cardiomyocyte cultures at varying frequencies in response to blue-light flashes. Activation mapping pinpointed the source of this electrical activity to the engineered cells. Similarly, diffuse seeding of the ChR2-fibroblasts allowed multisite optogenetics pacing of the co-cultures, significantly shortening their electrical activation time and synchronizing contraction. Next, optogenetics pacing in an in vitro model of conduction block allowed the resynchronization of the tissue's electrical activity. Finally, the ChR2-fibroblasts were transfected to also express the light-sensitive hyperpolarizing proton pump Archaerhodopsin-T (Arch-T). Seeding of the ChR2/ArchT-fibroblasts allowed to either optogentically pace the cultures (in response to blue-light flashes) or completely suppress the cultures' electrical activity (following continuous illumination with 624 nm monochromatic light, activating ArchT). The results of this proof-of-concept study highlight the unique potential of optogenetics for future biological pacemaking and resynchronization therapy applications and for the development of novel anti-arrhythmic strategies.

69. Credit TCL. Housing of Pelton exciter impulse wheel and ...

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

69. Credit TCL. Housing of Pelton exciter impulse wheel and attached General Electric 60 kW exciter generator. - Battle Creek Hydroelectric System, Battle Creek & Tributaries, Red Bluff, Tehama County, CA

The effects of nanoparticles and organic additives with controlled dispersion on dielectric properties of polymers: Charge trapping and impact excitation

NASA Astrophysics Data System (ADS)

Huang, Yanhui; Wu, Ke; Bell, Michael; Oakes, Andrew; Ratcliff, Tyree; Lanzillo, Nicholas A.; Breneman, Curt; Benicewicz, Brian C.; Schadler, Linda S.

2016-08-01

This work presents a comprehensive investigation into the effects of nanoparticles and organic additives on the dielectric properties of insulating polymers using reinforced silicone rubber as a model system. TiO2 and ZrO2 nanoparticles (d = 5 nm) were well dispersed into the polymer via a bimodal surface modification approach. Organic molecules with the potential of voltage stabilization were further grafted to the nanoparticle to ensure their dispersion. These extrinsic species were found to provide deep traps for charge carriers and exhibited effective charge trapping properties at a rather small concentration (˜1017 cm-3). The charge trapping is found to have the most significant effect on breakdown strength when the electrical stressing time is long enough that most charges are trapped in the deep states. To establish a quantitative correlation between the trap depth and the molecular properties, the electron affinity and ionization energy of each species were calculated by an ab initio method and were compared with the experimentally measured values. The correlation however remains elusive and is possibly complicated by the field effect and the electronic interactions between different species that are not considered in this computation. At high field, a super-linear increase of current density was observed for TiO2 filled composites and is likely caused by impact excitation due to the low excitation energy of TiO2 compared to ZrO2. It is reasoned that the hot charge carriers with energies greater than the excitation energy of TiO2 may excite an electron-hole pair upon collision with the NP, which later will be dissociated and contribute to free charge carriers. This mechanism can enhance the energy dissipation and may account for the retarded electrical degradation and breakdown of TiO2 composites.

The effects of nanoparticles and organic additives with controlled dispersion on dielectric properties of polymers: Charge trapping and impact excitation

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

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

This work presents a comprehensive investigation into the effects of nanoparticles and organic additives on the dielectric properties of insulating polymers using reinforced silicone rubber as a model system. TiO{sub 2} and ZrO{sub 2} nanoparticles (d = 5 nm) were well dispersed into the polymer via a bimodal surface modification approach. Organic molecules with the potential of voltage stabilization were further grafted to the nanoparticle to ensure their dispersion. These extrinsic species were found to provide deep traps for charge carriers and exhibited effective charge trapping properties at a rather small concentration (∼10{sup 17} cm{sup −3}). The charge trapping is found to havemore » the most significant effect on breakdown strength when the electrical stressing time is long enough that most charges are trapped in the deep states. To establish a quantitative correlation between the trap depth and the molecular properties, the electron affinity and ionization energy of each species were calculated by an ab initio method and were compared with the experimentally measured values. The correlation however remains elusive and is possibly complicated by the field effect and the electronic interactions between different species that are not considered in this computation. At high field, a super-linear increase of current density was observed for TiO{sub 2} filled composites and is likely caused by impact excitation due to the low excitation energy of TiO{sub 2} compared to ZrO{sub 2}. It is reasoned that the hot charge carriers with energies greater than the excitation energy of TiO{sub 2} may excite an electron-hole pair upon collision with the NP, which later will be dissociated and contribute to free charge carriers. This mechanism can enhance the energy dissipation and may account for the retarded electrical degradation and breakdown of TiO{sub 2} composites.« less

Protein carboxyl methylation increases in parallel with differentiation of neuroblastoma cells.

PubMed

Kloog, Y; Axelrod, J; Spector, I

1983-02-01

Cells of mouse neuroblastoma clone N1E-115 in the confluent phase of growth can catalyze the formation of endogenous protein carboxyl methyl esters, using a protein carboxyl methylase and membrane-bound methyl acceptor proteins. The enzyme is localized predominantly in the cytosol of the cells and has a molecular weight of about 20,000 daltons. Treatment of the cells with dimethylsulfoxide (DMSO) or hexamethylene-bisacetamide (HMBA), agents that induce morphological and electrophysiological differentiation, results in a marked increase in protein carboxyl methylase activity. Maximal levels are reached 6-7 days after exposure to the agents, a time course that closely parallels the development of electrical excitability mechanisms in these cells. Serum deprivation also causes neurite outgrowth but does not enhance electrical excitability or enzyme activity. The capacity of membrane-bound neuroblastoma protein(s) to be carboxyl methylated is increased by the differentiation procedures that have been examined. However, the increase in methyl acceptor proteins induced by DMSO or HMBA is the largest, and its time course parallels electrophysiological differentiation. In contrast, serum deprivation induced a small increase that reached maximal levels within 24 h. The data suggest that increased protein carboxyl methylation is a developmentally regulated property of neuroblastoma cells and that at least two groups of methyl acceptor proteins are induced during differentiation: a minor group related to morphological differentiation, and a major group that may be related to ionic permeability mechanisms of the excitable membrane.

Voltage-gated calcium flux mediates Escherichia coli mechanosensation.

PubMed

Bruni, Giancarlo N; Weekley, R Andrew; Dodd, Benjamin J T; Kralj, Joel M

2017-08-29

Electrically excitable cells harness voltage-coupled calcium influx to transmit intracellular signals, typically studied in neurons and cardiomyocytes. Despite intense study in higher organisms, investigations of voltage and calcium signaling in bacteria have lagged due to their small size and a lack of sensitive tools. Only recently were bacteria shown to modulate their membrane potential on the timescale of seconds, and little is known about the downstream effects from this modulation. In this paper, we report on the effects of electrophysiology in individual bacteria. A genetically encoded calcium sensor expressed in Escherichia coli revealed calcium transients in single cells. A fusion sensor that simultaneously reports voltage and calcium indicated that calcium influx is induced by voltage depolarizations, similar to metazoan action potentials. Cytoplasmic calcium levels and transients increased upon mechanical stimulation with a hydrogel, and single cells altered protein concentrations dependent on the mechanical environment. Blocking voltage and calcium flux altered mechanically induced changes in protein concentration, while inducing calcium flux reproduced these changes. Thus, voltage and calcium relay a bacterial sense of touch and alter cellular lifestyle. Although the calcium effectors remain unknown, these data open a host of new questions about E. coli , including the identity of the underlying molecular players, as well as other signals conveyed by voltage and calcium. These data also provide evidence that dynamic voltage and calcium exists as a signaling modality in the oldest domain of life, and therefore studying electrophysiology beyond canonical electrically excitable cells could yield exciting new findings.

Voltage-gated calcium flux mediates Escherichia coli mechanosensation

PubMed Central

Weekley, R. Andrew; Dodd, Benjamin J. T.

2017-01-01

Electrically excitable cells harness voltage-coupled calcium influx to transmit intracellular signals, typically studied in neurons and cardiomyocytes. Despite intense study in higher organisms, investigations of voltage and calcium signaling in bacteria have lagged due to their small size and a lack of sensitive tools. Only recently were bacteria shown to modulate their membrane potential on the timescale of seconds, and little is known about the downstream effects from this modulation. In this paper, we report on the effects of electrophysiology in individual bacteria. A genetically encoded calcium sensor expressed in Escherichia coli revealed calcium transients in single cells. A fusion sensor that simultaneously reports voltage and calcium indicated that calcium influx is induced by voltage depolarizations, similar to metazoan action potentials. Cytoplasmic calcium levels and transients increased upon mechanical stimulation with a hydrogel, and single cells altered protein concentrations dependent on the mechanical environment. Blocking voltage and calcium flux altered mechanically induced changes in protein concentration, while inducing calcium flux reproduced these changes. Thus, voltage and calcium relay a bacterial sense of touch and alter cellular lifestyle. Although the calcium effectors remain unknown, these data open a host of new questions about E. coli, including the identity of the underlying molecular players, as well as other signals conveyed by voltage and calcium. These data also provide evidence that dynamic voltage and calcium exists as a signaling modality in the oldest domain of life, and therefore studying electrophysiology beyond canonical electrically excitable cells could yield exciting new findings. PMID:28808010

Start-up and control method and apparatus for resonant free piston Stirling engine

DOEpatents

Walsh, Michael M.

1984-01-01

A resonant free-piston Stirling engine having a new and improved start-up and control method and system. A displacer linear electrodynamic machine is provided having an armature secured to and movable with the displacer and having a stator supported by the Stirling engine housing in juxtaposition to the armature. A control excitation circuit is provided for electrically exciting the displacer linear electrodynamic machine with electrical excitation signals having substantially the same frequency as the desired frequency of operation of the Stirling engine. The excitation control circuit is designed so that it selectively and controllably causes the displacer electrodynamic machine to function either as a generator load to extract power from the displacer or the control circuit selectively can be operated to cause the displacer electrodynamic machine to operate as an electric drive motor to apply additional input power to the displacer in addition to the thermodynamic power feedback to the displacer whereby the displacer linear electrodynamic machine also is used in the electric drive motor mode as a means for initially starting the resonant free-piston Stirling engine.

Effect of the architecture of the left ventricle on the speed of the excitation wave in muscle fibers

NASA Astrophysics Data System (ADS)

Nezlobinsky, T. V.; Pravdin, S. F.; Katsnelson, L. B.; Solovyova, O. E.

2016-07-01

It is known that preferential paths for the propagation of an electrical excitation wave in the human ventricular myocardium are associated with muscle fibers in tissue. The speed of the excitation wave along a fiber is several times higher than that across the direction of the fiber. To estimate the effect of the architecture and anisotropy of the myocardium of the left ventricle on the process of its electrical activation, we have studied the relation between the speed of the electrical excitation wave in a one-dimensional isolated myocardial fiber consisting of sequentially coupled cardiomyocytes and in an identical fiber located in the wall of a threedimensional anatomical model of the left ventricle. It has been shown that the speed of a wavefront along the fiber in the three-dimensional myocardial tissue is much higher than that in the one-dimensional fiber. The acceleration of the signal is due to the rotation of directions of fibers in the wall and to the position of the excitation wavefront with respect to the direction of this fiber. The observed phenomenon is caused by the approach of the excitable tissue with rotational anisotropy in its properties to a pseudoisotropic tissue.

Effects of electrical stimulation of the hunger center in the lateral hypothalamus and food reinforcement on impulse activity of the stomach in rabbits under conditions of hunger and satiation.

PubMed

Zenina, O Yu; Kromin, A A

2012-10-01

Stimulation of the lateral hypothalamus in preliminary fed animals in the presence of the food is associated with successful food-procuring behavior, accompanied by regular generation of high-amplitude slow electrical waves by muscles of the lesser curvature, body, and antrum of the stomach, which was reflected in the structure of temporal organization of slow electrical activity in the form of unimodal distribution of slow wave periods typical of satiation state. Despite increased level of food motivation caused by stimulation of the lateral hypothalamus, the additional food intake completely abolished the inhibitory effects of hunger motivation excitement on slow electrical muscle activity in the lesser curvature, body, and antrum of the stomach of satiated rabbits. Changes in slow electrical activity of the stomach muscles in rabbits deprived of food over 24 h and offered food and associated food-procuring behavior during electrical stimulation of the lateral hypothalamus have a two-phase pattern. Despite food intake during phase I of electrical stimulation, the downstream inhibitory effect of hunger motivation excitement on myogenic pacemaker of the lesser curvature of stomach abolishes the stimulating effect of food reinforcement on slow electrical muscle activity in the lesser curvature, body, and antrum of the stomach. During phase II of electrical stimulation, the food reinforcement decreases inhibitory effect of hunger motivation excitement on myogenic pacemaker of the lesser curvature that paces maximal rhythm of slow electrical waves for muscles activity in the lesser curvature, body, and antrum of the stomach, which is reflected by unimodal distribution of slow electrical wave periods. Our results indicated that the structure of temporal organization of slow electrical activity of the stomach muscles reflects convergent interactions of food motivation and reinforcement excitations on the dorsal vagal complex neurons in medulla oblongata.

Aperture excited dielectric antennas

NASA Technical Reports Server (NTRS)

Crosswell, W. F.; Chatterjee, J. S.; Mason, V. B.; Tai, C. T.

1974-01-01

The results of a comprehensive experimental and theoretical study of the effect of placing dielectric objects over the aperture of waveguide antennas are presented. Experimental measurements of the radiation patterns, gain, impedance, near-field amplitude, and pattern and impedance coupling between pairs of antennas are given for various Plexiglas shapes, including the sphere and the cube, excited by rectangular, circular, and square waveguide feed apertures. The waveguide excitation of a dielectric sphere is modeled using the Huygens' source, and expressions for the resulting electric fields, directivity, and efficiency are derived. Calculations using this model show good overall agreement with experimental patterns and directivity measurements. The waveguide under an infinite dielectric slab is used as an impedance model. Calculations using this model agree qualitatively with the measured impedance data. It is concluded that dielectric loaded antennas such as the waveguide excited sphere, cube, or sphere-cylinder can produce directivities in excess of that obtained by a uniformly illuminated aperture of the same cross section, particularly for dielectric objects with dimensions of 2 wavelengths or less. It is also shown that for certain configurations coupling between two antennas of this type is less than that for the same antennas without dielectric loading.

Micro-Cogeneration Incl. The Conversion of Chemical Energy of Biomass to Electric Energy and the Low Potential Heat

NASA Astrophysics Data System (ADS)

Huzvar, Jozef; Kapjor, Andrej

2011-06-01

This article deals with combined production of heat and electricity for small premises, such as households, where energy consumption is around few kilowatts. This proposal of micro co-generation unit uses as a heat source an automatic burner for combustion of wood pellets. Construction of an equipment for the heat transport can be designed using different basic ways of heat transfer. Electricity is produced by the two-stroke steam engine and the generator.

Sound-by-sound thalamic stimulation modulates midbrain auditory excitability and relative binaural sensitivity in frogs

PubMed Central

Ponnath, Abhilash; Farris, Hamilton E.

2014-01-01

Descending circuitry can modulate auditory processing, biasing sensitivity to particular stimulus parameters and locations. Using awake in vivo single unit recordings, this study tested whether electrical stimulation of the thalamus modulates auditory excitability and relative binaural sensitivity in neurons of the amphibian midbrain. In addition, by using electrical stimuli that were either longer than the acoustic stimuli (i.e., seconds) or presented on a sound-by-sound basis (ms), experiments addressed whether the form of modulation depended on the temporal structure of the electrical stimulus. Following long duration electrical stimulation (3–10 s of 20 Hz square pulses), excitability (spikes/acoustic stimulus) to free-field noise stimuli decreased by 32%, but returned over 600 s. In contrast, sound-by-sound electrical stimulation using a single 2 ms duration electrical pulse 25 ms before each noise stimulus caused faster and varied forms of modulation: modulation lasted <2 s and, in different cells, excitability either decreased, increased or shifted in latency. Within cells, the modulatory effect of sound-by-sound electrical stimulation varied between different acoustic stimuli, including for different male calls, suggesting modulation is specific to certain stimulus attributes. For binaural units, modulation depended on the ear of input, as sound-by-sound electrical stimulation preceding dichotic acoustic stimulation caused asymmetric modulatory effects: sensitivity shifted for sounds at only one ear, or by different relative amounts for both ears. This caused a change in the relative difference in binaural sensitivity. Thus, sound-by-sound electrical stimulation revealed fast and ear-specific (i.e., lateralized) auditory modulation that is potentially suited to shifts in auditory attention during sound segregation in the auditory scene. PMID:25120437

Sound-by-sound thalamic stimulation modulates midbrain auditory excitability and relative binaural sensitivity in frogs.

PubMed

Ponnath, Abhilash; Farris, Hamilton E

2014-01-01

Descending circuitry can modulate auditory processing, biasing sensitivity to particular stimulus parameters and locations. Using awake in vivo single unit recordings, this study tested whether electrical stimulation of the thalamus modulates auditory excitability and relative binaural sensitivity in neurons of the amphibian midbrain. In addition, by using electrical stimuli that were either longer than the acoustic stimuli (i.e., seconds) or presented on a sound-by-sound basis (ms), experiments addressed whether the form of modulation depended on the temporal structure of the electrical stimulus. Following long duration electrical stimulation (3-10 s of 20 Hz square pulses), excitability (spikes/acoustic stimulus) to free-field noise stimuli decreased by 32%, but returned over 600 s. In contrast, sound-by-sound electrical stimulation using a single 2 ms duration electrical pulse 25 ms before each noise stimulus caused faster and varied forms of modulation: modulation lasted <2 s and, in different cells, excitability either decreased, increased or shifted in latency. Within cells, the modulatory effect of sound-by-sound electrical stimulation varied between different acoustic stimuli, including for different male calls, suggesting modulation is specific to certain stimulus attributes. For binaural units, modulation depended on the ear of input, as sound-by-sound electrical stimulation preceding dichotic acoustic stimulation caused asymmetric modulatory effects: sensitivity shifted for sounds at only one ear, or by different relative amounts for both ears. This caused a change in the relative difference in binaural sensitivity. Thus, sound-by-sound electrical stimulation revealed fast and ear-specific (i.e., lateralized) auditory modulation that is potentially suited to shifts in auditory attention during sound segregation in the auditory scene.

Comparison between electric dipole and magnetic loop antennas for emitting whistler modes

NASA Astrophysics Data System (ADS)

Stenzel, R.; Urrutia, J. M.

2016-12-01

In a large uniform and unbounded laboratory plasma low frequency whistler modes are excited from an electric dipole and a magnetic loop. The excited waves are measured with a magnetic probe which resolves the three field components in 3D space and time. This yields the group velocity and energy density, from which one obtains the emitted power. The same rf generator is used for both antennas and the radiated power is measured under identical plasma conditions. The magnetic loop radiates 8000 times more power than the electric dipole. The reason is that the loop antenna carries a large conduction current while the electric dipole current is a much smaller displacement current through the sheath. The current, hence magnetic field excites whistlers, not the dipole electric field. Incidentally, a dipole antenna does not launch plane waves but m = 1 helicon modes. The findings suggest that active wave injections into the magnetosphere should be done with magnetic antennas. Two parallel dipoles connected at the free end could serve as an elongated loop.

Excitation of whistler waves by reflected auroral electrons

NASA Technical Reports Server (NTRS)

Wu, C. S.; Dillenburg, D.; Ziebell, L. F.; Freund, H. P.

1983-01-01

Excitation of electron waves and whistlers by reflected auroral electrons which possess a loss-cone distribution is investigated. Based on a given magnetic field and density model, the instability problem is studied over a broad region along the auroral field lines. This region covers altitudes ranging from one quarter of an earth radius to five earth radii. It is found that the growth rate is significant only in the region of low altitude, say below the source region of the auroral kilometric radiation. In the high altitude region the instability is insignificant either because of low refractive indices or because of small loss cone angles.

Stable isotopes in mid-ocean ridge hydrothermal systems: Interactions between fluids, minerals, and organisms

NASA Astrophysics Data System (ADS)

Shanks, W. C., III; Böhlke, J. K.; Seal, R. R., II

Studies of abundance variations of light stable isotopes in nature have had a tremendous impact on all aspects of geochemistry since the development, in 1947, of a gas source isotope ratio mass spectrometer capable of measuring small variations in stable isotope ratios [Nier, 1947] Stable isotope geochemistry is now a mature field, as witnessed by the proliferation of commercially available mass spectrometers installed at virtually every major academic, government, and private-sector research geochemistry laboratory. A recent search of a literature database revealed over 3,000 articles that utilized stable isotope geochemistry over the last 20 years. Nonetheless, many exciting new technical developments are leading to exciting new discoveries and applications. In particular, micro analytical techniques involving new generations of laser- and ion-microprobes are revolutionizing the types of analyses that can be done on spot sizes as small as a few tens of micrometers [Shanks and Criss, 1989]. New generations of conventional gas source and thermal ionization mass spectrometers, with high levels of automation and increased sensitivity and precision, are allowing analyses of large numbers of samples, like those needed for stable isotope stratigraphy in marine sediments, and are enabling the development and application of new isotopic systems.

Stable isotopes in mid-ocean ridge hydrothermal systems: Interactions between fluids, minerals, and organisms

USGS Publications Warehouse

Shanks, Wayne C.; Böhlke, John Karl; Seal, Robert R.; Humphries, S.D.; Zierenberg, Robert A.; Mullineaux, Lauren S.; Thomson, Richard E.

1995-01-01

Studies of abundance variations of light stable isotopes in nature have had a tremendous impact on all aspects of geochemistry since the development, in 1947, of a gas source isotope ratio mass spectrometer capable of measuring small variations in stable isotope ratios (Nice, 1947]. Stable isotope geochemistry is now a mature field, as witnessed by the proliferation of commercially available mass spectrometers installed at virtually every major academic, government, and private-sector research geochemistry laboratory. A recent search of a literature database revealed over 3,000 articles that utilized stable isotope geochemistry over the last 20 years. Nonetheless, many exciting new technical developments are leading to exciting new discoveries and applications. In particular, micro-analytical techniques involving new generations of laser- and ion-microprobes are revolutionizing the types of analyses that can be done on spot sizes as small as a few tens of micrometers [Shanks and Criss, 1989]. New generations of conventional gas source and thermal ionization mass spectrometers, with high levels of automation and increased sensitivity and precision, are allowing analyses of large numbers of samples, like those needed for stable isotope stratigraphy in marine sediments, and are enabling the development and application of new isotopic systems.

Design of portable ultraminiature flow cytometers for medical diagnostics

NASA Astrophysics Data System (ADS)

Leary, James F.

2018-02-01

Design of portable microfluidic flow/image cytometry devices for measurements in the field (e.g. initial medical diagnostics) requires careful design in terms of power requirements and weight to allow for realistic portability. True portability with high-throughput microfluidic systems also requires sampling systems without the need for sheath hydrodynamic focusing both to avoid the need for sheath fluid and to enable higher volumes of actual sample, rather than sheath/sample combinations. Weight/power requirements dictate use of super-bright LEDs with top-hat excitation beam architectures and very small silicon photodiodes or nanophotonic sensors that can both be powered by small batteries. Signal-to-noise characteristics can be greatly improved by appropriately pulsing the LED excitation sources and sampling and subtracting noise in between excitation pulses. Microfluidic cytometry also requires judicious use of small sample volumes and appropriate statistical sampling by microfluidic cytometry or imaging for adequate statistical significance to permit real-time (typically in less than 15 minutes) initial medical decisions for patients in the field. This is not something conventional cytometry traditionally worries about, but is very important for development of small, portable microfluidic devices with small-volume throughputs. It also provides a more reasonable alternative to conventional tubes of blood when sampling geriatric and newborn patients for whom a conventional peripheral blood draw can be problematical. Instead one or two drops of blood obtained by pin-prick should be able to provide statistically meaningful results for use in making real-time medical decisions without the need for blood fractionation, which is not realistic in the doctor's office or field.

Feasibility Study of Thin Film Thermocouple Piles

NASA Technical Reports Server (NTRS)

Sisk, R. C.

2001-01-01

Historically, thermopile detectors, generators, and refrigerators based on bulk materials have been used to measure temperature, generate power for spacecraft, and cool sensors for scientific investigations. New potential uses of small, low-power, thin film thermopiles are in the area of microelectromechanical systems since power requirements decrease as electrical and mechanical machines shrink in size. In this research activity, thin film thermopile devices are fabricated utilizing radio frequency sputter coating and photoresist lift-off techniques. Electrical characterizations are performed on two designs in order to investigate the feasibility of generating small amounts of power, utilizing any available waste heat as the energy source.

Time-Varying Seismogenic Coulomb Electric Fields as a Probable Source for Pre-Earthquake Variation in the Ionospheric F2-Layer

NASA Astrophysics Data System (ADS)

Kim, Vitaly P.; Hegai, Valery V.; Liu, Jann Yenq; Ryu, Kwangsun; Chung, Jong-Kyun

2017-12-01

The electric coupling between the lithosphere and the ionosphere is examined. The electric field is considered as a time- varying irregular vertical Coulomb field presumably produced on the Earth’s surface before an earthquake within its epicentral zone by some micro-processes in the lithosphere. It is shown that the Fourier component of this electric field with a frequency of 500 Hz and a horizontal scale-size of 100 km produces in the nighttime ionosphere of high and middle latitudes a transverse electric field with a magnitude of 20 mV/m if the peak value of the amplitude of this Fourier component is just 30 V/m. The time-varying vertical Coulomb field with a frequency of 500 Hz penetrates from the ground into the ionosphere by a factor of 7×105 more efficient than a time independent vertical electrostatic field of the same scale size. The transverse electric field with amplitude of 20 mV/m will cause perturbations in the nighttime F region electron density through heating the F region plasma resulting in a reduction of the downward plasma flux from the protonosphere and an excitation of acoustic gravity waves.

Investigation on discharge characteristics of a coaxial dielectric barrier discharge reactor driven by AC and ns power sources

NASA Astrophysics Data System (ADS)

Qian, WANG; Feng, LIU; Chuanrun, MIAO; Bing, YAN; Zhi, FANG

2018-03-01

A coaxial dielectric barrier discharge (DBD) reactor with double layer dielectric barriers has been developed for exhaust gas treatment and excited either by AC power or nanosecond (ns) pulse to generate atmospheric pressure plasma. The comparative study on the discharge characteristics of the discharge uniformity, power deposition, energy efficiency, and operation temperature between AC and ns pulsed coaxial DBD is carried out in terms of optical and electrical characteristics and operation temperature for optimizing the coaxial DBD reactor performance. The voltages across the air gap and dielectric layer and the conduction and displacement currents are extracted from the applied voltages and measured currents of AC and ns pulsed coaxial DBDs for the calculation of the power depositions and energy efficiencies through an equivalent electrical model. The discharge uniformity and operating temperature of the coaxial DBD reactor are monitored and analyzed by optical images and infrared camera. A heat conduction model is used to calculate the temperature of the internal quartz tube. It is found that the ns pulsed coaxial DBD has a much higher instantaneous power deposition in plasma, a lower total power consumption, and a higher energy efficiency compared with that excited by AC power and is more homogeneous and stable. The temperature of the outside wall of the AC and ns pulse excited coaxial DBD reaches 158 °C and 64.3 °C after 900 s operation, respectively. The experimental results on the comparison of the discharge characteristics of coaxial DBDs excited by different powers are significant for understanding of the mechanism of DBDs, reducing energy loss, and optimizing the performance of coaxial DBD in industrial applications.

Subspace-based analysis of the ERT inverse problem

NASA Astrophysics Data System (ADS)

Ben Hadj Miled, Mohamed Khames; Miller, Eric L.

2004-05-01

In a previous work, we proposed a source-type formulation to the electrical resistance tomography (ERT) problem. Specifically, we showed that inhomogeneities in the medium can be viewed as secondary sources embedded in the homogeneous background medium and located at positions associated with variation in electrical conductivity. Assuming a piecewise constant conductivity distribution, the support of equivalent sources is equal to the boundary of the inhomogeneity. The estimation of the anomaly shape takes the form of an inverse source-type problem. In this paper, we explore the use of subspace methods to localize the secondary equivalent sources associated with discontinuities in the conductivity distribution. Our first alternative is the multiple signal classification (MUSIC) algorithm which is commonly used in the localization of multiple sources. The idea is to project a finite collection of plausible pole (or dipole) sources onto an estimated signal subspace and select those with largest correlations. In ERT, secondary sources are excited simultaneously but in different ways, i.e. with distinct amplitude patterns, depending on the locations and amplitudes of primary sources. If the number of receivers is "large enough", different source configurations can lead to a set of observation vectors that span the data subspace. However, since sources that are spatially close to each other have highly correlated signatures, seperation of such signals becomes very difficult in the presence of noise. To overcome this problem we consider iterative MUSIC algorithms like R-MUSIC and RAP-MUSIC. These recursive algorithms pose a computational burden as they require multiple large combinatorial searches. Results obtained with these algorithms using simulated data of different conductivity patterns are presented.

Field-circuit analysis and measurements of a single-phase self-excited induction generator

NASA Astrophysics Data System (ADS)

Makowski, Krzysztof; Leicht, Aleksander

2017-12-01

The paper deals with a single-phase induction machine operating as a stand-alone self-excited single-phase induction generator for generation of electrical energy from renewable energy sources. By changing number of turns and size of wires in the auxiliary stator winding, an improvement of performance characteristics of the generator were obtained as regards no-load and load voltage of the stator windings as well as stator winding currents of the generator. Field-circuit simulation models of the generator were developed using Flux2D software package for the generator with shunt capacitor in the main stator winding. The obtained results have been validated experimentally at the laboratory setup using the single-phase capacitor induction motor of 1.1 kW rated power and 230 V voltage as a base model of the generator.

Ways to improve the efficiency and reliability of radio frequency driven negative ion sources for fusion.

PubMed

Kraus, W; Briefi, S; Fantz, U; Gutmann, P; Doerfler, J

2014-02-01

Large RF driven negative hydrogen ion sources are being developed at IPP Garching for the future neutral beam injection system of ITER. The overall power efficiency of these sources is low, because for the RF power supply self-excited generators are utilized and the plasma is generated in small cylindrical sources ("drivers") and expands into the source main volume. At IPP experiments to reduce the primary power and the RF power required for the plasma production are performed in two ways: The oscillator generator of the prototype source has been replaced by a transistorized RF transmitter and two alternative driver concepts, a spiral coil, in which the field is concentrated by ferrites, which omits the losses by plasma expansion and a helicon source are being tested.

Finite-difference modeling of the electroseismic logging in a fluid-saturated porous formation

NASA Astrophysics Data System (ADS)

Guan, Wei; Hu, Hengshan

2008-05-01

In a fluid-saturated porous medium, an electromagnetic (EM) wavefield induces an acoustic wavefield due to the electrokinetic effect. A potential geophysical application of this effect is electroseismic (ES) logging, in which the converted acoustic wavefield is received in a fluid-filled borehole to evaluate the parameters of the porous formation around the borehole. In this paper, a finite-difference scheme is proposed to model the ES logging responses to a vertical low frequency electric dipole along the borehole axis. The EM field excited by the electric dipole is calculated separately by finite-difference first, and is considered as a distributed exciting source term in a set of extended Biot's equations for the converted acoustic wavefield in the formation. This set of equations is solved by a modified finite-difference time-domain (FDTD) algorithm that allows for the calculation of dynamic permeability so that it is not restricted to low-frequency poroelastic wave problems. The perfectly matched layer (PML) technique without splitting the fields is applied to truncate the computational region. The simulated ES logging waveforms approximately agree with those obtained by the analytical method. The FDTD algorithm applies also to acoustic logging simulation in porous formations.

Transient Control of Synchronous Machine Active and Reactive Power in Micro-grid Power Systems

NASA Astrophysics Data System (ADS)

Weber, Luke G.

There are two main topics associated with this dissertation. The first is to investigate phase-to-neutral fault current magnitude occurring in generators with multiple zero-sequence current sources. The second is to design, model, and tune a linear control system for operating a micro-grid in the event of a separation from the electric power system. In the former case, detailed generator, AC8B excitation system, and four-wire electric power system models are constructed. Where available, manufacturers data is used to validate the generator and exciter models. A gain-delay with frequency droop control is used to model an internal combustion engine and governor. The four wire system is connected through a transformer impedance to an infinite bus. Phase-to-neutral faults are imposed on the system, and fault magnitudes analyzed against three-phase faults to gauge their severity. In the latter case, a balanced three-phase system is assumed. The model structure from the former case - but using data for a different generator - is incorporated with a model for an energy storage device and a net load model to form a micro-grid. The primary control model for the energy storage device has a high level of detail, as does the energy storage device plant model in describing the LC filter and transformer. A gain-delay battery and inverter model is used at the front end. The net load model is intended to be the difference between renewable energy sources and load within a micro-grid system that has separated from the grid. Given the variability of both renewable generation and load, frequency and voltage stability are not guaranteed. This work is an attempt to model components of a proposed micro-grid system at the University of Wisconsin Milwaukee, and design, model, and tune a linear control system for operation in the event of a separation from the electric power system. The control module is responsible for management of frequency and active power, and voltage and reactive power. The scope of this work is to • develop a mathematical model for a salient pole, 2 damper winding synchronous generator with d axis saturation suitable for transient analysis, • develop a mathematical model for a voltage regulator and excitation system using the IEEE AC8B voltage regulator and excitation system template, • develop mathematical models for an energy storage primary control system, LC filter and transformer suitable for transient analysis, • combine the generator and energy storage models in a micro-grid context, • develop mathematical models for electric system components in the stationary abc frame and rotating dq reference frame, • develop a secondary control network for dispatch of micro-grid assets, • establish micro-grid limits of stable operation for step changes in load and power commands based on simulations of model data assuming net load on the micro-grid, and • use generator and electric system models to assess the generator current magnitude during phase-to-ground faults.

Multi-channel medical imaging system

DOEpatents

Frangioni, John V

2013-12-31

A medical imaging system provides simultaneous rendering of visible light and fluorescent images. The system may employ dyes in a small-molecule form that remain in the subject's blood stream for several minutes, allowing real-time imaging of the subject's circulatory system superimposed upon a conventional, visible light image of the subject. The system may provide an excitation light source to excite the fluorescent substance and a visible light source for general illumination within the same optical guide used to capture images. The system may be configured for use in open surgical procedures by providing an operating area that is closed to ambient light. The systems described herein provide two or more diagnostic imaging channels for capture of multiple, concurrent diagnostic images and may be used where a visible light image may be usefully supplemented by two or more images that are independently marked for functional interest.

Multi-channel medical imaging system

DOEpatents

Frangioni, John V.

2016-05-03

A medical imaging system provides simultaneous rendering of visible light and fluorescent images. The system may employ dyes in a small-molecule form that remain in a subject's blood stream for several minutes, allowing real-time imaging of the subject's circulatory system superimposed upon a conventional, visible light image of the subject. The system may provide an excitation light source to excite the fluorescent substance and a visible light source for general illumination within the same optical guide used to capture images. The system may be configured for use in open surgical procedures by providing an operating area that is closed to ambient light. The systems described herein provide two or more diagnostic imaging channels for capture of multiple, concurrent diagnostic images and may be used where a visible light image may be usefully supplemented by two or more images that are independently marked for functional interest.

Infrasound from thunder: A natural seismic source

NASA Astrophysics Data System (ADS)

Lin, Ting-L.; Langston, Charles A.

2007-07-01

A small array consisting of five three-component short-period surface seismometers, a three-component borehole seismometer, and five infrasound microphones was built to investigate thunder-induced ground motions. Data from two thunder events with similar N-wave waveforms but different horizontal slownesses are chosen as examples of data collected by the array. These impulsive acoustic waves excited P and S reverberations in the near surface that depend on both the incident wave horizontal slowness and the velocity structure in the upper 30 meters at the site. Although the depth of the borehole is relatively shallow compared to a seismic wave wavelength, velocity amplitude in the radial component decays as much as 63 percent with depth but vertical component amplitudes are unaffected consistent with air-coupled Rayleigh wave excitation. Naturally occurring thunder appears to be a useful seismic source to empirically determine site resonance characteristics for hazards assessments.

Model of a thin film optical fiber fluorosensor

NASA Technical Reports Server (NTRS)

Egalon, Claudio O.; Rogowski, Robert S.

1991-01-01

The efficiency of core-light injection from sources in the cladding of an optical fiber is modeled analytically by means of the exact field solution of a step-profile fiber. The analysis is based on the techniques by Marcuse (1988) in which the sources are treated as infinitesimal electric currents with random phase and orientation that excite radiation fields and bound modes. Expressions are developed based on an infinite cladding approximation which yield the power efficiency for a fiber coated with fluorescent sources in the core/cladding interface. Marcuse's results are confirmed for the case of a weakly guiding cylindrical fiber with fluorescent sources uniformly distributed in the cladding, and the power efficiency is shown to be practically constant for variable wavelengths and core radii. The most efficient fibers have the thin film located at the core/cladding boundary, and fibers with larger differences in the indices of refraction are shown to be the most efficient.

Frenkel and Charge-Transfer Excitations in Donor-acceptor Complexes from Many-Body Green's Functions Theory.

PubMed

Baumeier, Björn; Andrienko, Denis; Rohlfing, Michael

2012-08-14

Excited states of donor-acceptor dimers are studied using many-body Green's functions theory within the GW approximation and the Bethe-Salpeter equation. For a series of prototypical small-molecule based pairs, this method predicts energies of local Frenkel and intermolecular charge-transfer excitations with the accuracy of tens of meV. Application to larger systems is possible and allowed us to analyze energy levels and binding energies of excitons in representative dimers of dicyanovinyl-substituted quarterthiophene and fullerene, a donor-acceptor pair used in state of the art organic solar cells. In these dimers, the transition from Frenkel to charge transfer excitons is endothermic and the binding energy of charge transfer excitons is still of the order of 1.5-2 eV. Hence, even such an accurate dimer-based description does not yield internal energetics favorable for the generation of free charges either by thermal energy or an external electric field. These results confirm that, for qualitative predictions of solar cell functionality, accounting for the explicit molecular environment is as important as the accurate knowledge of internal dimer energies.

Non-linear optical response by functionalized gold nanospheres: identifying design principles to maximize the molecular photo-release.

PubMed

Bergamini, Luca; Voliani, Valerio; Cappello, Valentina; Nifosì, Riccardo; Corni, Stefano

2015-08-28

In a recent study by Voliani et al. [Small, 2011, 7, 3271], the electromagnetic field enhancement in the vicinity of the gold nanoparticle surface has been exploited to achieve photocontrolled release of a molecular cargo conjugated to the nanoparticles via 1,2,3-triazole, a photocleavable moiety. The aim of the present study is to investigate the mechanism of the photorelease by characterizing the nanoparticle aggregation status within the cells and simulating the electric field enhancement in a range of experimentally realistic geometries, such as single Au nanoparticles, dimers, trimers and random aggregates. Two plasmon-enhanced processes are examined for triazole photocleavage, i.e. three-photon excitation and third-harmonic-generation (one-photon) excitation. Taking into account the absorption cross sections of the triazole, we conclude that the latter mechanism is more efficient, and provides a photocleavage rate that explains the experimental findings. Moreover, we determine which aggregate geometries are required to maximize the field enhancement, and the dependence of such enhancement on the excitation wavelength. Our results provide design principles for maximizing the multiphoton molecular photorelease by such functionalized gold nanoparticles.

Uncovering Highly-Excited State Mixing in Acetone Using Ultrafast VUV Pulses and Coincidence Imaging Techniques

DOE PAGES

Couch, David E.; Kapteyn, Henry C.; Murnane, Margaret M.; ...

2017-03-17

Here, understanding the ultrafast dynamics of highly-excited electronic states of small molecules is critical for a better understanding of atmospheric and astrophysical processes, as well as for designing coherent control strategies for manipulating chemical dynamics. In highly excited states, nonadiabatic coupling, electron-electron interactions, and the high density of states govern dynamics. However, these states are computationally and experimentally challenging to access. Fortunately, new sources of ultrafast vacuum ultraviolet pulses, in combination with electron-ion coincidence spectroscopies, provide new tools to unravel the complex electronic landscape. Here we report time-resolved photoelectron-photoion coincidence experiments using 8 eV pump photons to study the highlymore » excited states of acetone. We uncover for the first time direct evidence that the resulting excited state consists of a mixture of both n y → 3p and π → π* character, which decays with a time constant of 330 fs. In the future, this approach can inform models of VUV photochemistry and aid in designing coherent control strategies for manipulating chemical reactions.« less

Uncovering Highly-Excited State Mixing in Acetone Using Ultrafast VUV Pulses and Coincidence Imaging Techniques

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

Couch, David E.; Kapteyn, Henry C.; Murnane, Margaret M.

Here, understanding the ultrafast dynamics of highly-excited electronic states of small molecules is critical for a better understanding of atmospheric and astrophysical processes, as well as for designing coherent control strategies for manipulating chemical dynamics. In highly excited states, nonadiabatic coupling, electron-electron interactions, and the high density of states govern dynamics. However, these states are computationally and experimentally challenging to access. Fortunately, new sources of ultrafast vacuum ultraviolet pulses, in combination with electron-ion coincidence spectroscopies, provide new tools to unravel the complex electronic landscape. Here we report time-resolved photoelectron-photoion coincidence experiments using 8 eV pump photons to study the highlymore » excited states of acetone. We uncover for the first time direct evidence that the resulting excited state consists of a mixture of both n y → 3p and π → π* character, which decays with a time constant of 330 fs. In the future, this approach can inform models of VUV photochemistry and aid in designing coherent control strategies for manipulating chemical reactions.« less

77 FR 72294 - Reconsideration of Certain New Source and Startup/Shutdown Issues: National Emission Standards...

Federal Register 2010, 2011, 2012, 2013, 2014

2012-12-05

... Emission Standards for Hazardous Air Pollutants From Coal- and Oil-Fired Electric Utility Steam Generating...-Institutional, and Small Industrial-Commercial- Institutional Steam Generating Units Correction Proposed rule...

Formation of a strong electric field resulting in the excitation of microplasma discharges at the edge of a dielectric film on a metal in a plasma flow

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

Ivanov, V. A., E-mail: ivanov@fpl.gpi.ru; Sakharov, A. S.; Konyzhev, M. E.

2016-06-15

Results are presented from experimental and analytical studies of the processes resulting in the excitation of microplasma discharges (MPDs) on a metal surface partially covered with a thin dielectric film under the action of an external plasma flow in vacuum. It is shown experimentally that MPDs are excited at the interface between the open metal surface and the region covered by the dielectric film. The probability of MPD excitation is investigated as a function of the thickness of the dielectric film deposited on the metal. It is found that, for a film thickness of 1 μm, the probability of MPDmore » excitation is close to unity. As the film thickness decreases below ~10 nm or increases above ~10 μm, the probability of MPD excitation is reduced by more than two orders of magnitude. A two-dimensional kinetic numerical code is developed that allows one to model the processes of Debye sheath formation and generation of a strong electric field near the edge of a finite-thickness dielectric film on a metal surface in a plasma flow for different configurations of the film edge. It is shown that the maximum value of the tangential component of the electric field is reached at the film edge and amounts to E{sub max} ≈ |φ{sub 0}|/2d (where φ{sub 0} < 0 is the electric potential applied to the metal and d is the film thickness), which for typical conditions of experiments on the excitation of MPDs on metal surfaces (φ{sub 0} ≈–400 V, d ≈ 1 μm) yields E{sub max} ≈ 2 MV/cm. The results of kinetic simulations confirm the qualitative idea about the mechanism of the formation of a strong electric field resulting in the excitation of MPDs at the edge of a dielectric film on a metal surface in a plasma flow and agree with experimental data.« less

Control of wave propagation in a biological excitable medium by an external electric field.

PubMed

Sebestikova, Lenka; Slamova, Elena; Sevcikova, Hana

2005-03-01

We present an experimental evidence of effects of external electric fields (EFs) on the velocity of pulse waves propagating in a biological excitable medium. The excitable medium used is formed by a layer of starving cells of Dictyostelium discoideum through which the waves of increased concentration of cAMP propagate by reaction-diffusion mechanism. External dc EFs of low intensities (up to 5 V/cm) are shown to speed up the propagation of cAMP waves towards the positive electrode and slow it down towards the negative electrode. Electric fields were also found to support an emergence of new centers, emitting cAMP waves, in front of cAMP waves propagating towards the negative electrode.

Reconfigurable lateral optical force achieved by selectively exciting plasmonic dark modes near Fano resonance

NASA Astrophysics Data System (ADS)

Chen, Huajin; Ye, Qian; Zhang, Yiwen; Shi, Lei; Liu, Shiyang; Jian, Zi; Lin, Zhifang

2017-08-01

We demonstrate a reconfigurable lateral optical force (OF) on a plasmonic nanoparticle immersed in a simple optical field invariant along the lateral direction and formed by two interfering plane waves. This lateral OF is shown, from the multipolar expansion technique, attributed to several coupling channels established between multiple multipoles excited on a plasmonic nanoparticle, in particular, the adjacent electric multipole modes that bring about the Fano interferences, which can substantially enhance the lateral scattering asymmetry, leading to an augmented lateral OF comparable to the longitudinal OF. More importantly, by engineering Fano interference either intrinsically through particle size or extrinsically through selectively exciting narrow plasmonic dark modes the direction of the lateral OF is reversibly switchable. The lateral OF can even be modulated continuously from positive to negative by controlling the incident angle of the interfering plane waves due to the variation of relative phase of the excited plasmonic dark modes near Fano resonance, facilitating the plasmonic nanoparticle as a controllable conveyor as well as the optical selection and separation. Besides, a fundamental and counterintuitive physical consequence emerges in that the simple proportional relation between the lateral OF and the Belinfante spin momentum derived in the small particle limit breaks down when the Fano interference comes into play, in particular, a negative lateral OF opposite the Belinfante spin momentum can be induced by properly controlling the selective excitation.

Full-dimensional quantum dynamics study on the mode-specific unimolecular dissociation reaction of HFCO

NASA Astrophysics Data System (ADS)

Yamamoto, Takeshi; Kato, Shigeki

2000-05-01

The mode specificity of the unimolecular reaction of HFCO is studied by six-dimensional quantum dynamics calculations. The energy and mode dependency of the dissociation rate is examined by propagating a number of wave packets with a small energy dispersion representing highly excited states with respect to a specific vibrational mode. The wave packets are generated by applying a set of filter operators onto a source vibrational state. All the information necessary for propagating the wave packets is obtained from a single propagation of the source state, thus allowing a significant decrease of computational effort. The relevant spectral peaks are assigned using the three-dimensional CH chromophore Hamiltonian. The resulting dissociation rate of the CH stretching excited state is in agreement with that obtained from a statistical theory, while the rates of the out-of-plane bending excited states are about one order of magnitude smaller than the statistical rates. A local-mode analysis also shows that the relaxation of the out-of-plane excitation proceeds very slowly within 3 ps. These results clearly indicate weak couplings of the out-of-plane bending excited states with other in-plane vibrational states, which is in qualitative agreement with experimental findings. From a computational point of view, a parallel supercomputer is utilized efficiently to handle an ultra large basis set of an order of 108, and 200 Gflops rate on average is achieved in the dynamics calculations.

Evaluation and optimization of quartz resonant-frequency retuned fork force sensors with high Q factors, and the associated electric circuits, for non-contact atomic force microscopy.

PubMed

Ooe, Hiroaki; Fujii, Mikihiro; Tomitori, Masahiko; Arai, Toyoko

2016-02-01

High-Q factor retuned fork (RTF) force sensors made from quartz tuning forks, and the electric circuits for the sensors, were evaluated and optimized to improve the performance of non-contact atomic force microscopy (nc-AFM) performed under ultrahigh vacuum (UHV) conditions. To exploit the high Q factor of the RTF sensor, the oscillation of the RTF sensor was excited at its resonant frequency, using a stray capacitance compensation circuit to cancel the excitation signal leaked through the stray capacitor of the sensor. To improve the signal-to-noise (S/N) ratio in the detected signal, a small capacitor was inserted before the input of an operational (OP) amplifier placed in an UHV chamber, which reduced the output noise from the amplifier. A low-noise, wideband OP amplifier produced a superior S/N ratio, compared with a precision OP amplifier. The thermal vibrational density spectra of the RTF sensors were evaluated using the circuit. The RTF sensor with an effective spring constant value as low as 1000 N/m provided a lower minimum detection limit for force differentiation. A nc-AFM image of a Si(111)-7 × 7 surface was produced with atomic resolution using the RTF sensor in a constant frequency shift mode; tunneling current and energy dissipation images with atomic resolution were also simultaneously produced. The high-Q factor RTF sensor showed potential for the high sensitivity of energy dissipation as small as 1 meV/cycle and the high-resolution analysis of non-conservative force interactions.

Portable device for the detection of nitro-explosives based on optical properties of sensor's material

NASA Astrophysics Data System (ADS)

Baranova, A. A.; Khokhlov, K. O.

2014-11-01

The aim of this study was to design a device for explosives detection. The study design is based on excited steady-state luminescence quenching registration. Sensor's material luminescence intensity reduction occurs due to an interaction of explosives vapours contained in the air. The decrease rate of the luminescence intensity indicates the concentration of vapours. To study the luminescent properties of the sensor element, its luminescence spectra excited by photons with energies in the range 280 - 425 nm were measured. The excitation photoluminescence spectra for luminescence bands of the sensor element were also measured. Excitation source was light emitting diode (375 nm) and luminescent signal receiver was a photodiode (430 - 650 nm) in device designed. The device is operated under control of a program. The algorithm provides multiple operating modes (configuration, calibration, measurement etc.). Thus this device is referred to the class of devices with increased sensitivity to the explosives vapors. The advantages of device are autonomic power, small weight and sizes, simplicity of device operation for measurements.

Jet-induced medium excitation in γ-hadron correlation at RHIC

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

Chen, Wei; Cao, Shanshan; Luo, Tan

Both jet transport and jet-induced medium excitation are investigated simultaneously within the coupled Linear Boltzmann Transport and hydro (CoLBT-hydro) model. In this coupled approach, energy-momentum deposition from propagating jet shower partons in the elastic and radiation processes is taken as a source term in hydrodynamics and the hydro background for LBT simulation is updated for next time step. We use CoLBT-hydro model to simulate γ-jet events of Au+Au collisions at RHIC. Hadron spectra from both the hadronization of jet shower partons and jet-induced medium excitation are calculated and compared to experimental data. Parton energy loss of jet shower partons leadsmore » to the suppression of hadron yields at large z T = p h T/p γ T while medium excitations leads to enhancement of hadron yields at small z T. Meanwhile, a significant broadening of low p T hadron yields and the depletion of soft hadrons in the γ direction are observed in the calculation of γ-hadron angular correlation.« less

Jet-induced medium excitation in γ-hadron correlation at RHIC

DOE PAGES

Chen, Wei; Cao, Shanshan; Luo, Tan; ...

2017-09-25

Both jet transport and jet-induced medium excitation are investigated simultaneously within the coupled Linear Boltzmann Transport and hydro (CoLBT-hydro) model. In this coupled approach, energy-momentum deposition from propagating jet shower partons in the elastic and radiation processes is taken as a source term in hydrodynamics and the hydro background for LBT simulation is updated for next time step. We use CoLBT-hydro model to simulate γ-jet events of Au+Au collisions at RHIC. Hadron spectra from both the hadronization of jet shower partons and jet-induced medium excitation are calculated and compared to experimental data. Parton energy loss of jet shower partons leadsmore » to the suppression of hadron yields at large z T = p h T/p γ T while medium excitations leads to enhancement of hadron yields at small z T. Meanwhile, a significant broadening of low p T hadron yields and the depletion of soft hadrons in the γ direction are observed in the calculation of γ-hadron angular correlation.« less

Direct observation of spin-quadrupolar excitations in Sr2CoGe2O7 by high-field electron spin resonance

NASA Astrophysics Data System (ADS)

Akaki, Mitsuru; Yoshizawa, Daichi; Okutani, Akira; Kida, Takanori; Romhányi, Judit; Penc, Karlo; Hagiwara, Masayuki

2017-12-01

Exotic spin-multipolar ordering in spin transition metal insulators has so far eluded unambiguous experimental observation. A less studied, but perhaps more feasible fingerprint of multipole character emerges in the excitation spectrum in the form of quadrupolar transitions. Such multipolar excitations are desirable as they can be manipulated with the use of light or electric field and can be captured by means of conventional experimental techniques. Here we study single crystals of multiferroic Sr2CoGe2O7 and observe a two-magnon spin excitation appearing above the saturation magnetic field in electron spin resonance (ESR) spectra. Our analysis of the selection rules reveals that this spin excitation mode does not couple to the magnetic component of the light, but it is excited by the electric field only, in full agreement with the theoretical calculations. Due to the nearly isotropic nature of Sr2CoGe2O7 , we identify this excitation as a purely spin-quadrupolar two-magnon mode.

Study of np{sup 2}P{sub 1/2,3/2} Rydberg series of AlI by the method of laser stepwise excitation and ionization by electric field

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

Kasimov, A.K.; Tursunov, A.T.; Tukhlibaev, O.

Frequencies of the 4s{sup 2}S{sub 1/2}-np{sup 2}P{sub 1/2, 3/2} transitions are measured and the energies of high-lying P states, as well as the ionization energy of aluminum atoms, are determined by the method of two-step laser excitation and ionization of excited atoms of AlI by an electric field. 4 refs., 3 figs., 1 tab.

Excitability and optical pulse generation in semiconductor lasers driven by resonant tunneling diode photo-detectors.

PubMed

Romeira, Bruno; Javaloyes, Julien; Ironside, Charles N; Figueiredo, José M L; Balle, Salvador; Piro, Oreste

2013-09-09

We demonstrate, experimentally and theoretically, excitable nanosecond optical pulses in optoelectronic integrated circuits operating at telecommunication wavelengths (1550 nm) comprising a nanoscale double barrier quantum well resonant tunneling diode (RTD) photo-detector driving a laser diode (LD). When perturbed either electrically or optically by an input signal above a certain threshold, the optoelectronic circuit generates short electrical and optical excitable pulses mimicking the spiking behavior of biological neurons. Interestingly, the asymmetric nonlinear characteristic of the RTD-LD allows for two different regimes where one obtain either single pulses or a burst of multiple pulses. The high-speed excitable response capabilities are promising for neurally inspired information applications in photonics.

Extrasynaptic exocytosis and its mechanisms: a source of molecules mediating volume transmission in the nervous system.

PubMed

Trueta, Citlali; De-Miguel, Francisco F

2012-01-01

We review the evidence of exocytosis from extrasynaptic sites in the soma, dendrites, and axonal varicosities of central and peripheral neurons of vertebrates and invertebrates, with emphasis on somatic exocytosis, and how it contributes to signaling in the nervous system. The finding of secretory vesicles in extrasynaptic sites of neurons, the presence of signaling molecules (namely transmitters or peptides) in the extracellular space outside synaptic clefts, and the mismatch between exocytosis sites and the location of receptors for these molecules in neurons and glial cells, have long suggested that in addition to synaptic communication, transmitters are released, and act extrasynaptically. The catalog of these molecules includes low molecular weight transmitters such as monoamines, acetylcholine, glutamate, gama-aminobutiric acid (GABA), adenosine-5-triphosphate (ATP), and a list of peptides including substance P, brain-derived neurotrophic factor (BDNF), and oxytocin. By comparing the mechanisms of extrasynaptic exocytosis of different signaling molecules by various neuron types we show that it is a widespread mechanism for communication in the nervous system that uses certain common mechanisms, which are different from those of synaptic exocytosis but similar to those of exocytosis from excitable endocrine cells. Somatic exocytosis has been measured directly in different neuron types. It starts after high-frequency electrical activity or long experimental depolarizations and may continue for several minutes after the end of stimulation. Activation of L-type calcium channels, calcium release from intracellular stores and vesicle transport towards the plasma membrane couple excitation and exocytosis from small clear or large dense core vesicles in release sites lacking postsynaptic counterparts. The presence of synaptic and extrasynaptic exocytosis endows individual neurons with a wide variety of time- and space-dependent communication possibilities. Extrasynaptic exocytosis may be the major source of signaling molecules producing volume transmission and by doing so may be part of a long duration signaling mode in the nervous system.

Helix structure for low frequency acoustic energy harvesting

NASA Astrophysics Data System (ADS)

Yuan, Ming; Cao, Ziping; Luo, Jun; Pang, Zongqiang

2018-05-01

In this study, a novel helix acoustic resonator is proposed to realize acoustic energy harvesting (AEH). Compared with the traditional acoustic resonators, the proposed structure occupies a small volume and is suitable for the low frequency range. At a specific incident frequency, the mechanical component of the AEH device can be intensely excited and the bonded piezoelectric patch is utilized to convert the strain energy into electrical energy. Analytical studies are carried out to disclose the acoustic resonant system properties. Meanwhile, the pure acoustic and coupled vibro-acoustic properties of the proposed device are analyzed via the finite element method. The major part of the AEH device is fabricated via 3D printing for experimental study, which is favored for rapid prototyping. At acoustic resonance frequency 175 Hz, 100 dB sound pressure level excitation working condition, the measured experimental data show that the harvested power can be up to 7.3 μW.

Helix structure for low frequency acoustic energy harvesting.

PubMed

Yuan, Ming; Cao, Ziping; Luo, Jun; Pang, Zongqiang

2018-05-01

In this study, a novel helix acoustic resonator is proposed to realize acoustic energy harvesting (AEH). Compared with the traditional acoustic resonators, the proposed structure occupies a small volume and is suitable for the low frequency range. At a specific incident frequency, the mechanical component of the AEH device can be intensely excited and the bonded piezoelectric patch is utilized to convert the strain energy into electrical energy. Analytical studies are carried out to disclose the acoustic resonant system properties. Meanwhile, the pure acoustic and coupled vibro-acoustic properties of the proposed device are analyzed via the finite element method. The major part of the AEH device is fabricated via 3D printing for experimental study, which is favored for rapid prototyping. At acoustic resonance frequency 175 Hz, 100 dB sound pressure level excitation working condition, the measured experimental data show that the harvested power can be up to 7.3 μW.

Hydrodynamic-to-ballistic crossover in Dirac materials

NASA Astrophysics Data System (ADS)

Svintsov, D.

2018-03-01

We develop an analytically solvable classical kinetic model of spatially dispersive transport in Dirac materials accounting for strong electron-electron (e-e) and electron-hole (e-h) collisions. We use this model to track the evolution of graphene conductivity and properties of its collective excitations across the hydrodynamic-to-ballistic crossover. We find the relaxation rate of electric current by e-e collisions that is possible due to the lack of Galilean invariance and introduce a universal numerical measure of this noninvariance. We find the two branches of collective excitations in the Dirac fluid: plasmons and electron-hole sound. The sound waves persist at frequencies exceeding the e-e collision frequency, have a small viscous damping at the neutrality point, but acquire large damping due to e-h friction even at slight doping. On the contrary, plasmons acquire strong frictional damping at the neutrality point and become well defined in doped samples.

Corticospinal excitability is dependent on the parameters of peripheral electric stimulation: a preliminary study.

PubMed

Chipchase, Lucy S; Schabrun, Siobhan M; Hodges, Paul W

2011-09-01

To evaluate the effect of 6 electric stimulation paradigms on corticospinal excitability. Using a same subject pre-post test design, transcranial magnetic stimulation (TMS) was used to measure the responsiveness of corticomotor pathway to biceps and triceps brachii muscles before and after 30 minutes of electric stimulation over the biceps brachii. Six different electric stimulation paradigms were applied in random order, at least 3 days apart. Motor control research laboratory. Healthy subjects (N=10; 5 women, 5 men; mean age ± SD, 26 ± 3.6y). Six different electric stimulation paradigms with varied stimulus amplitude, frequency, and ramp settings. Amplitudes of TMS-induced motor evoked potentials at biceps and triceps brachii normalized to maximal M-wave amplitudes. Electric stimulation delivered at stimulus amplitude sufficient to evoke a sensory response at both 10 Hz and 100 Hz, and stimulus amplitude to create a noxious response at 10 Hz decreased corticomotor responsiveness (all P<0.01). Stimulation sufficient to induce a motor contraction (30 Hz) applied in a ramped pattern to mimic a voluntary activation increased corticomotor responsiveness (P=0.002), whereas constant low- and high-intensity motor stimulation at 10 Hz did not. Corticomotor excitability changes were similar for both the stimulated muscle and its antagonist. Stimulus amplitude (intensity) and the nature (muscle flicker vs contraction) of motor stimulation have a significant impact on changes in corticospinal excitability induced by electric stimulation. Here, we demonstrate that peripheral electric stimulation at stimulus amplitude to create a sensory response reduces corticomotor responsiveness. Conversely, stimulus amplitude to create a motor response increases corticomotor responsiveness, but only the parameters that create a motor response that mimics a voluntary muscle contraction. Copyright © 2011 American Congress of Rehabilitation Medicine. Published by Elsevier Inc. All rights reserved.

A preliminary assessment of small steam Rankine and Brayton point-focusing solar modules

NASA Technical Reports Server (NTRS)

Roschke, E. J.; Wen, L.; Steele, H.; Elgabalawi, N.; Wang, J.

1979-01-01

A preliminary assessment of three conceptual point-focusing distributed solar modules is presented. The basic power conversion units consist of small Brayton or Rankine engines individually coupled to two-axis, tracking, point-focusing solar collectors. An array of such modules can be linked together, via electric transport, to form a small power station. Each module also can be utilized on a stand-alone basis, as an individual power source.

Role of sinoatrial node architecture in maintaining a balanced source-sink relationship and synchronous cardiac pacemaking

PubMed Central

Unudurthi, Sathya D.; Wolf, Roseanne M.; Hund, Thomas J.

2014-01-01

Normal heart rhythm (sinus rhythm) depends on regular activity of the sinoatrial node (SAN), a heterogeneous collection of specialized myocytes in the right atrium. SAN cells, in general, possess a unique electrophysiological profile that promotes spontaneous electrical activity (automaticity). However, while automaticity is required for normal pacemaking, it is not necessarily sufficient. Less appreciated is the importance of the elaborate structure of the SAN complex for proper pacemaker function. Here, we review the important structural features of the SAN with a focus on how these elements help manage a precarious balance between electrical charge generated by the SAN (“source”) and the charge needed to excite the surrounding atrial tissue (“sink”). We also discuss how compromised “source-sink” balance due, for example to fibrosis, may promote SAN dysfunction, characterized by slow and/or asynchronous pacemaker activity and even failure, in the setting of cardiovascular disease (e.g., heart failure, atrial fibrillation). Finally, we discuss implications of the “source-sink” balance in the SAN complex for cell and gene therapies aimed at creating a biological pacemaker as replacement or bridge to conventional electronic pacemakers. PMID:25505419

Development of a Small Thermoelectric Generators Prototype for Energy Harvesting from Low Temperature Waste Heat at Industrial Plant.

PubMed

Chiarotti, Ugo; Moroli, Valerio; Menchetti, Fernando; Piancaldini, Roberto; Bianco, Loris; Viotto, Alberto; Baracchini, Giulia; Gaspardo, Daniele; Nazzi, Fabio; Curti, Maurizio; Gabriele, Massimiliano

2017-03-01

A 39-W thermoelectric generator prototype has been realized and then installed in industrial plant for on-line trials. The prototype was developed as an energy harvesting demonstrator using low temperature cooling water waste heat as energy source. The objective of the research program is to measure the actual performances of this kind of device working with industrial water below 90 °C, as hot source, and fresh water at a temperature of about 15 °C, as cold sink. The article shows the first results of the research program. It was verified, under the tested operative conditions, that the produced electric power exceeds the energy required to pump the water from the hot source and cold sink to the thermoelectric generator unit if they are located at a distance not exceeding 50 m and the electric energy conversion efficiency is 0.33%. It was calculated that increasing the distance of the hot source and cold sink to the thermoelectric generator unit to 100 m the produced electric energy equals the energy required for water pumping, while reducing the distance of the hot source and cold sink to zero meters the developed unit produces an electric energy conversion efficiency of 0.61%.

Chronic muscle stimulation improves muscle function and reverts the abnormal surface EMG pattern in Myotonic Dystrophy: a pilot study

PubMed Central

2013-01-01

Background To date, in Myotonic Dystrophy type 1 (DM1) the rehabilitative interventions have always been aimed at muscle strengthening, increasing of fatigue resistance and improving of aerobic metabolism efficiency whereas the electrical membrane fault has always been addressed pharmacologically. Neuromuscular electrical stimulation (NMES) is a useful therapeutic tool in sport medicine and in the rehabilitation of many clinical conditions characterized by motor impairment such as stroke, cerebral palsy and spinal cord injury. The aim of our pilot study was to evaluate the effects of chronic electrical stimulation both on functional and electrical properties of muscle in a small group of DM1 patients. Methods Five DM1 patients and one patient with Congenital Myotonia (CM) performed a home electrical stimulation of the tibialis anterior muscle lasting 15 days with a frequency of two daily sessions of 60 minutes each. Muscle strength was assessed according to the MRC scale (Medical Research Council) and functional tests (10 Meter Walking Test, 6 Minutes Walking Test and Timed Up and Go Test) were performed. We analyzed the average rectified value of sEMG signal amplitude (ARV) to characterize the sarcolemmal excitability. Results After the treatment an increase of muscle strength in those DM1 patients with a mild strength deficit was observed. In all subjects an improvement of 10MWT was recorded. Five patients improved their performance in the 6MWT. In TUG test 4 out of 6 patients showed a slight reduction in execution time. All patients reported a subjective improvement when walking. A complete recovery of the normal increasing ARV curve was observed in 4 out of 5 DM1 patients; the CM patient didn’t show modification of the ARV pattern. Conclusions NMES determined a clear-cut improvement of both the muscular weakness and the sarcolemmal excitability alteration in our small group of DM1 patients. Therefore this rehabilitative approach, if confirmed by further extensive studies, could be considered early in the management of muscular impairment in these patients. An attractive hypothesis to explain our encouraging result could be represented by a functional inhibition of SK3 channels expressed in muscle of DM1 subjects. PMID:23938156

Split-mode ultrasonic transducer.

PubMed

Ostrovskii, Igor; Cremaldi, Lucien

2013-08-01

A split-mode ultrasonic transducer is investigated in both theory and experiment. This transducer is a two-dimensional structure of periodically poled domains in a ferroelectric wafer with free surfaces. The acoustic vibrations are excited by a radio frequency electric current applied along the length of the wafer, which allows the basal-plane surfaces to be free of metal coatings and thus ready for further biomedical applications. A specific physical property of this transducer consists of the multiple acousto-electric resonances, which occur due to an acoustic mode split when the acoustic half-wavelength is equal to the domain length. Possible applications include ultrasonic generation and detection at the micro-scale, intravascular sonification and visualization, ultrasound therapy of localized small areas such as the eye, biomedical applications for cell cultures, and traditional nondestructive testing including bones and tissues. A potential use of a non-metallized wafer is a therapeutic application with double action that is both ultrasound itself and an electric field over the wafer. The experimental measurements and theoretical calculations are in good agreement.

Magnetospheric electric fields and currents

NASA Technical Reports Server (NTRS)

Mauk, B. H.; Zanetti, L. J.

1987-01-01

The progress made in the years 1983-1986 in understanding the character and operation of magnetospheric electric fields and electric currents is discussed, with emphasis placed on the connection with the interior regions. Special attention is given to determinations of global electric-field configurations, measurements of the response of magnetospheric particle populations to the electric-field configurations, and observations of the magnetospheric currents at high altitude and during northward IMF. Global simulations of current distributions are discussed, and the sources of global electric fields and currents are examined. The topics discussed in the area of impulsive and small-scale phenomena include substorm current systems, impulsive electric fields and associated currents, and field-aligned electrodynamics. A key finding of these studies is that the electric fields and currents are interrelated and cannot be viewed as separate entities.

Fuel change possibilities in small heat source

NASA Astrophysics Data System (ADS)

Durčanský, Peter; Kapjor, Andrej; Jandačka, Jozef

2017-09-01

Rural areas are characterized by a larger number of older family houses with higher fuel consumption for heating. Some areas are not gasified, which means that the fuel base for heating the buildings is very limited. Heating is mainly covered by solid fuels with high emissions and low efficiency. But at the same time, the amount of energy in the form of biowaste can be evaluated and used further. We will explore the possibilities to convert biogas to heat of using a gas burner in a small heat source. However, the heat produced can be used other than for heating or hot water production. The added value for heat generation can be the production of electricity, in the use of heat energy through cogeneration unit with unconventional heat engine. The proposed solution could economically benefit the entire system, because electricity is a noble form of energy and its use is versatile.

Selective Emitters

NASA Technical Reports Server (NTRS)

Chubb, Donald L. (Inventor)

1992-01-01

This invention relates to a small particle selective emitter for converting thermal energy into narrow band radiation with high efficiency. The small particle selective emitter is used in combination with a photovoltaic array to provide a thermal to electrical energy conversion device. An energy conversion apparatus of this type is called a thermo-photovoltaic device. In the first embodiment, small diameter particles of a rare earth oxide are suspended in an inert gas enclosed between concentric cylinders. The rare earth oxides are used because they have the desired property of large emittance in a narrow wavelength band and small emittance outside the band. However, it should be emphasized that it is the smallness of the particles that enhances the radiation property. The small particle selective emitter is surrounded by a photovoltaic array. In an alternate embodiment, the small particle gas mixture is circulated through a thermal energy source. This thermal energy source can be a nuclear reactor, solar receiver, or combustor of a fossil fuel.

A novel low cost pulse excitation source to study trap spectroscopy of persistent luminescent materials

NASA Astrophysics Data System (ADS)

Chandrasekhar, Ngangbam; Singh, Nungleppam Monorajan; Gartia, R. K.

2018-04-01

Luminescent techniques require one or the other source of excitations which may vary from high cost X-rays, γ-rays, β-rays etc. to low cost LED. Persistent luminescent materials or Glow-in-the-Dark phosphors are the optical harvesters which store the optical energy from day light illuminating a whole night. They are so sensitive that they can be excited even with the low light of firefly. Therefore, instead of using a high cost excitation source authors have developed a low cost functioning of excitation source controlling short pulses of LED to excite persistent phosphors with the aid of ExpEYES Junior (Hardware/software framework developed by IUAC, New Delhi). Using this, the authors have excited the sample under investigation upto 10 ms. Trap spectroscopy of the pre-excited sample with LED is studied using Thermoluminescence (TL) technique. In this communication, development of the excitation source is discussed and demonstrate the its usefulness in the study of trap spectroscopy of commercially available CaS:Eu2+, Sm3+. Trapping parameters are also evaluated using Computerized Glow Curve Deconvolution (CGCD) technique.

New technique for the direct analysis of food powders confined in a small hole using transversely excited atmospheric CO(2) laser-induced gas plasma.

PubMed

Khumaeni, Ali; Ramli, Muliadi; Deguchi, Yoji; Lee, Yong Inn; Idris, Nasrullah; Kurniawan, Koo Hendrik; Lie, Tjung Jie; Kagawa, Kiichiro

2008-12-01

Taking advantage of the differences between the interactions of transversely excited atmospheric (TEA) CO(2) lasers with metal and with organic powder, a new technique for the direct analysis of food powder samples has been developed. In this technique, the powder samples were placed into a small hole with a diameter of 2 mm and a depth of 3 mm and covered by a metal mesh. The TEA CO(2) laser (1500 mJ, 200 ns) was focused on the powder sample surfaces, passing through the metal mesh, at atmospheric pressure in nitrogen gas. It is hypothesized that the small hole functions to confine the powder particles and suppresses the blowing-off of sample, while the metal mesh works as the source of electrons to initiate the strong gas breakdown plasma. The confined powder particles are then ablated by laser irradiation and the ablated particles move into the strong gas breakdown plasma region to be atomized and excited; this method cannot be applied for the case of Nd:YAG lasers because in such case the metal mesh itself was ablated by the laser irradiation. A quantitative analysis of a milk powder sample containing different concentrations of Ca was successfully demonstrated, resulting in a good linear calibration curve with high precision.

Atmospheric-pressure diffuse dielectric barrier discharges in Ar/O2 gas mixture using 200 kHz/13.56 MHz dual frequency excitation

NASA Astrophysics Data System (ADS)

Liu, Y.; Starostin, S. A.; Peeters, F. J. J.; van de Sanden, M. C. M.; de Vries, H. W.

2018-03-01

Atmospheric-pressure diffuse dielectric barrier discharges (DBDs) were obtained in Ar/O2 gas mixture using dual-frequency (DF) excitation at 200 kHz low frequency (LF) and 13.56 MHz radio frequency (RF). The excitation dynamics and the plasma generation mechanism were studied by means of electrical characterization and phase resolved optical emission spectroscopy (PROES). The DF excitation results in a time-varying electric field which is determined by the total LF and RF gas voltage and the spatial ion distribution which only responds to the LF component. By tuning the amplitude ratio of the superimposed LF and RF signals, the effect of each frequency component on the DF discharge mechanism was analysed. The LF excitation results in a transient plasma with the formation of an electrode sheath and therefore a pronounced excitation near the substrate. The RF oscillation allows the electron trapping in the gas gap and helps to improve the plasma uniformity by contributing to the pre-ionization and by controlling the discharge development. The possibility of temporally modifying the electric field and thus the plasma generation mechanism in the DF discharge exhibits potential applications in plasma-assisted surface processing and plasma-assisted gas phase chemical conversion.

A novel energy transfer inducing strong enhancement of electric dipole transition in Na3Mo12PO40:xEu3+ phosphors

NASA Astrophysics Data System (ADS)

Long, Jinqiao; Wang, Tianman; Luo, Zhirong; Gao, Yong; Song, Baoling; Liang, Jing; Liao, Sen; Huang, Yingheng; Zhang, Huaxin

2017-08-01

A series of Na3Mo12PO40:xEu3+ phosphors have been successfully synthesized by a solid-state method, and characterized by powder x-ray diffraction (PXRD). The PXRD results confirm that the samples have crystal phases of Na3Mo12PO40. For PL spectra of Na3Mo12PO40:2.0Eu3+ excited by 394 and 465 nm, R (R is the peak area ratio of 5D0  →  7F2 to 5D0  →  7F1) is only 1.46 with an excitation of 394 nm, but increases to 3.03 with an excitation of 465 nm. Furthermore, a new enhancement of electric dipole transition is observed. Emission spectrum (PL) intensity at 617 nm excited by 465 nm is 1.95 times as high as the excitation spectrum (PLE) intensity at 465 nm. Thus, cooperative energy transfers from the magnetic dipole (MD) Eu3+ center to the electric dipole (ED) Eu3+ center when excited by 465 nm is demonstrated for the new fluorescent behavior.

Neutron spectroscopic study of crystalline electric field excitations in stoichiometric and lightly stuffed Yb 2 Ti 2 O 7

DOE PAGES

Gaudet, J.; Maharaj, D. D.; Sala, G.; ...

2015-10-27

Time-of-flight neutron spectroscopy has been used to determine the crystalline electric field Hamiltonian, eigenvalues and eigenvectors appropriate to the J=7/2 Yb 3+ ion in the candidate quantum spin ice pyrochlore magnet Yb 2Ti 2O 7. The precise ground state of this exotic, geometrically frustrated magnet is known to be sensitive to weak disorder associated with the growth of single crystals from the melt. Such materials display weak “stuffing,” wherein a small proportion, approximately 2%, of the nonmagnetic Ti 4+ sites are occupied by excess Yb 3+. We have carried out neutron spectroscopic measurements on a stoichiometric powder sample of Ybmore » 2Ti 2O 7, as well as a crushed single crystal with weak stuffing and an approximate composition of Yb 2+xTi 2–xO 7+y with x = 0.046. All samples display three crystalline electric field transitions out of the ground state, and the ground state doublet itself is identified as primarily composed of m J = ±1/2, as expected. However, stuffing at low temperatures in Yb 2+xTi 2–xO 7+y induces a similar finite crystalline electric field lifetime as is induced in stoichiometric Yb 2Ti 2O 7 by elevated temperature. In conclusion, an extended strain field exists about each local “stuffed” site, which produces a distribution of random crystalline electric field environments in the lightly stuffed Yb 2+xTi 2–xO 7+y, in addition to producing a small fraction of Yb ions in defective environments with grossly different crystalline electric field eigenvalues and eigenvectors.« less

Changes of Excitability in M1 Induced by Neuromuscular Electrical Stimulation Differ Between Presence and Absence of Voluntary Drive

ERIC Educational Resources Information Center

Sugawara, Kenichi; Tanabe, Shigeo; Higashi, Toshio; Tsurumi, Takamasa; Kasai, Tatsuya

2011-01-01

The aim of this study is to investigate excitability changes in the human motor cortex induced by variable therapeutic electrical stimulations (TESs) with or without voluntary drive. We recorded motor-evoked potentials (MEPs) from extensor and flexor carpi radialis (FCR) muscles at rest and during FCR muscle contraction after the application of…

Optimization of an electrokinetic mixer for microfluidic applications.

PubMed

Bockelmann, Hendryk; Heuveline, Vincent; Barz, Dominik P J

2012-06-01

This work is concerned with the investigation of the concentration fields in an electrokinetic micromixer and its optimization in order to achieve high mixing rates. The mixing concept is based on the combination of an alternating electrical excitation applied to a pressure-driven base flow in a meandering microchannel geometry. The electrical excitation induces a secondary electrokinetic velocity component, which results in a complex flow field within the meander bends. A mathematical model describing the physicochemical phenomena present within the micromixer is implemented in an in-house finite-element-method code. We first perform simulations comparable to experiments concerned with the investigation of the flow field in the bends. The comparison of the complex flow topology found in simulation and experiment reveals excellent agreement. Hence, the validated model and numerical schemes are employed for a numerical optimization of the micromixer performance. In detail, we optimize the secondary electrokinetic flow by finding the best electrical excitation parameters, i.e., frequency and amplitude, for a given waveform. Two optimized electrical excitations featuring a discrete and a continuous waveform are discussed with respect to characteristic time scales of our mixing problem. The results demonstrate that the micromixer is able to achieve high mixing degrees very rapidly.

Optimization of an electrokinetic mixer for microfluidic applications

PubMed Central

Bockelmann, Hendryk; Heuveline, Vincent; Barz, Dominik P. J.

2012-01-01

This work is concerned with the investigation of the concentration fields in an electrokinetic micromixer and its optimization in order to achieve high mixing rates. The mixing concept is based on the combination of an alternating electrical excitation applied to a pressure-driven base flow in a meandering microchannel geometry. The electrical excitation induces a secondary electrokinetic velocity component, which results in a complex flow field within the meander bends. A mathematical model describing the physicochemical phenomena present within the micromixer is implemented in an in-house finite-element-method code. We first perform simulations comparable to experiments concerned with the investigation of the flow field in the bends. The comparison of the complex flow topology found in simulation and experiment reveals excellent agreement. Hence, the validated model and numerical schemes are employed for a numerical optimization of the micromixer performance. In detail, we optimize the secondary electrokinetic flow by finding the best electrical excitation parameters, i.e., frequency and amplitude, for a given waveform. Two optimized electrical excitations featuring a discrete and a continuous waveform are discussed with respect to characteristic time scales of our mixing problem. The results demonstrate that the micromixer is able to achieve high mixing degrees very rapidly. PMID:22712034

The mechanism of high-T(sub c) superconductivity due to bound hole mediators: Relationship to ferroelectricity

NASA Technical Reports Server (NTRS)

Vezzoli, G. C.; Stanley, William

1990-01-01

The mediation by bound holes creating Cooper pairing in high T(sub c) superconductors has its origin in charge transfer excitations on the multivalence cation (virtual excitions) and in bound excitions or polarizations associated with the oxygen 2p electrons. These phenomena are produced and/or enhanced by a high internal electric field which is itself created by virtue of the unique crystal structures and polyhedral building blocks of high T(sub c) materials. The polarizations which can create oxygen holes (in addition to excitions) may be due to simply the internal electric field or to polaronic and electron-deficient bond behavior. This gives rise to two energy-dependent oxygen bands near the Fermi level. The magnitude and direction of the internal electric fields were calculated for Y1Ba2Cu3O(7-delta) (1-2-3) and show strong z-direction fields at the Cu(2), O2, and O3 sites and an even stronger -z direction field at the O4 site. The field calculations also show why electrical conductivity in the 1-2-3 material is essentially in the base plane of the CuO5 pyramid (the CuO2 plane).

Using Entanglement to Measure Temperatures and Frequencies of Individual Normal Modes in a Strongly Coupled 2D Plasma of Be+

NASA Astrophysics Data System (ADS)

Sawyer, Brian; Britton, Joseph; Keith, Adam; Wang, C.-C. Joseph; Freericks, James; Bollinger, John

2013-10-01

Confined non-neutral plasmas of ions in the regime of strong coupling serve as a platform for studying a diverse range of phenomena including: dense astrophysical matter, quantum computation/simulation, dynamical decoupling, and precision measurements. We describe a method of simultaneously detecting and measuring the temperature of transverse plasma modes in two-dimensional crystals of cold 9Be+ confined within a Penning trap. We employ a spin-dependent optical dipole force (ODF) generated from off-resonant laser beams to directly excite plasma modes transverse to the crystal plane of ~ 100 ions. Extremely small mode excitations (~ 1 nm) may be detected through spin-motion entanglement induced by an ODF as small as 10 yN , and even the shortest-wavelength (~ 20 μm) modes are excited and detected through the spin dependence of the force. This mode-specific thermometry has facilitated characterization and mitigation of ion heating sources in this system. Future work may include sub-yN force detection, spectroscopy/thermometry of the more complex in-plane oscillations, and implementation/confirmation of sub-Doppler cooling. The authors acknowledge support from the DARPA-OLE program.

Development of a Novel Wireless Electric Power Transfer System for Space Applications

NASA Technical Reports Server (NTRS)

VazquezRamos, Gabriel; Yuan, Jiann-Shiun

2011-01-01

This paper will introduce a new implementation for wireless electric power transfer systems: space applications. Due to the risks that constitute the use of electrical connector for some space missions/applications, a simple wireless power system design approach will be evaluated as an alternative for the use of electrical connectors. This approach takes into consideration the overall system performance by designing the magnetic resonance elements and by verifying the overall system electrical behavior. System characterization is accomplished by executing circuit and analytical simulations using Matlab(TradeMark) and LTSpiceIV(TradeMark) software packages. The design methodology was validated by two different experiments: frequency consideration (design of three magnetic elements) and a small scale proof-ofconcept prototype. Experiment results shows successful wireless power transfer for all the cases studied. The proof-of-concept prototype provided approx.4 W of wireless power to the load (light bulb) at a separation of 3 cm from the source. In addition. a resonant circuit was designed and installed to the battery terminals of a handheld radio without batteries, making it tum on at a separation of approx.5 cm or less from the source. It was also demonstrated by prototype experimentation that multiple loads can be powered wirelessly at the same time with a single electric power source.

Nonvolatile Ionic Two-Terminal Memory Device

NASA Technical Reports Server (NTRS)

Williams, Roger M.

1990-01-01

Conceptual solid-state memory device nonvolatile and erasable and has only two terminals. Proposed device based on two effects: thermal phase transition and reversible intercalation of ions. Transfer of sodium ions between source of ions and electrical switching element increases or decreases electrical conductance of element, turning switch "on" or "off". Used in digital computers and neural-network computers. In neural networks, many small, densely packed switches function as erasable, nonvolatile synaptic elements.

Frequency dependence of excitation-contraction of multicellular smooth muscle preparations: the relevance to bipolar electrosurgery.

PubMed

Vladimirova, Irina A; Lankin, Yuri N; Philyppov, Igor B; Sushiy, Lyudmyla F; Shuba, Yaroslav M

2014-01-01

Bipolar electrosurgical tissue welding uses forceps-like electrodes for grasping the tissues and delivering high-frequency electric current (HFEC) to produce local heat, desiccation, and protein denaturation, resulting in the fusion of the contacting tissues. Although in this technique no electric current is flowing through the whole body to cause electric injury, depending on the frequency of applied energy, it may produce local excitation of intramural nerves, which can propagate beyond the surgical site potentially causing harmful effects. The effects of varying frequency of HFEC on tissue excitability in bipolar electrosurgical modality were studied in vitro using electric field stimulation (EFS) method on multicellular smooth muscle strips of rat vas deferens. Contractile response to 5-s-long sine wave EFS train was taken as the measure of excitation of intramural nerves. EFS-induced contraction consisted of phasic and tonic components. The amplitude of both components decreased with increasing frequency, with tonic component disappearing at about 10 kHz and phasic component at about 50 kHz. Because components of EFS-induced contraction depend on different neurotransmitters, this indicates that various neurotransmitter systems are characterized by distinct frequency dependence, but above 50 kHz they all become inactivated. Bipolar electrosurgical sealing of porcine gut showed no difference in the structure of seal area at HFEC of 67 and 533 kHz. EFS frequency of 50 kHz represents the upper limit for excitation. HFEC above 50 kHz is safe to use for bipolar electrosurgical tissue welding without concerns of excitation propagating beyond the surgical site. Copyright © 2014 Elsevier Inc. All rights reserved.

Engineering of Machine tool’s High-precision electric drives

NASA Astrophysics Data System (ADS)

Khayatov, E. S.; Korzhavin, M. E.; Naumovich, N. I.

2018-03-01

In the article it is shown that in mechanisms with numerical program control, high quality of processes can be achieved only in systems that provide adjustment of the working element’s position with high accuracy, and this requires an expansion of the regulation range by the torque. In particular, the use of synchronous reactive machines with independent excitation control makes it possible to substantially increase the moment overload in the sequential excitation circuit. Using mathematical and physical modeling methods, it is shown that in the electric drive with a synchronous reactive machine with independent excitation in a circuit with sequential excitation, it is possible to significantly expand the range of regulation by the torque and this is achieved by the effect of sequential excitation, which makes it possible to compensate for the transverse reaction of the armature.

Tribo-electric charging of dielectric solids of identical composition

NASA Astrophysics Data System (ADS)

Angus, John C.; Greber, Isaac

2018-05-01

Despite its long history and importance in many areas of science and technology, there is no agreement on the mechanisms responsible for tribo-electric charging, including especially the tribo-charging of chemically identical dielectric solids. Modeling of the excitation, diffusional transport, and de-excitation of electrons from hot spots shows that a difference in local surface roughness of otherwise identical solid dielectric objects leads to different transient excited electron concentrations during tribo-processes. The model predicts that excited electron concentrations are lower and concentration gradients higher in solids with rougher rather than smoother surfaces. Consequently, during contact, the flux of charge carriers (electrons or holes) from hot spots will be greater into the rougher solid than into the smoother solid. These predictions are in agreement with current and historical observations of tribo-electric charge transfer between solids of the same composition. This effect can take place in parallel with other processes and may also play a role in the charging of solids of different composition.

Force sensor characterization under sinusoidal excitations.

PubMed

Medina, Nieves; de Vicente, Jesús

2014-10-06

The aim in the current work is the development of a method to characterize force sensors under sinusoidal excitations using a primary standard as the source of traceability. During this work the influence factors have been studied and a method to minimise their contributions, as well as the corrections to be performed under dynamic conditions have been established. These results will allow the realization of an adequate characterization of force sensors under sinusoidal excitations, which will be essential for its further proper use under dynamic conditions. The traceability of the sensor characterization is based in the direct definition of force as mass multiplied by acceleration. To do so, the sensor is loaded with different calibrated loads and is maintained under different sinusoidal accelerations by means of a vibration shaker system that is able to generate accelerations up to 100 m/s2 with frequencies from 5 Hz up to 2400 Hz. The acceleration is measured by means of a laser vibrometer with traceability to the units of time and length. A multiple channel data acquisition system is also required to simultaneously acquire the electrical output signals of the involved instrument in real time.

Three-dimensional printing physiology laboratory technology.

PubMed

Sulkin, Matthew S; Widder, Emily; Shao, Connie; Holzem, Katherine M; Gloschat, Christopher; Gutbrod, Sarah R; Efimov, Igor R

2013-12-01

Since its inception in 19th-century Germany, the physiology laboratory has been a complex and expensive research enterprise involving experts in various fields of science and engineering. Physiology research has been critically dependent on cutting-edge technological support of mechanical, electrical, optical, and more recently computer engineers. Evolution of modern experimental equipment is constrained by lack of direct communication between the physiological community and industry producing this equipment. Fortunately, recent advances in open source technologies, including three-dimensional printing, open source hardware and software, present an exciting opportunity to bring the design and development of research instrumentation to the end user, i.e., life scientists. Here we provide an overview on how to develop customized, cost-effective experimental equipment for physiology laboratories.

Method and apparatus for the guided ablative therapy of fast ventricular arrhythmia

NASA Technical Reports Server (NTRS)

Cohen, Richard J. (Inventor); Barley, Maya (Inventor)

2010-01-01

Method and apparatus for guiding ablative therapy of abnormal biological electrical excitation. The excitation from the previous excitatory wave is significant at the beginning of the next excitation. In particular, it is designed for treatment of fast cardiac arrhythmias. Electrical signals are acquired from recording electrodes, and an inverse dipole method is used to identify the site of origin of an arrhythmia. The location of the tip of an ablation catheter is similarly localized from signals acquired from the recording electrodes while electrical pacing energy is delivered to the tip of the catheter close to or in contact with the cardiac tissue. The catheter tip is then guided to the site of origin of the arrhythmia, and ablative radio frequency energy is delivered to its tip to ablate the site.

THERMO-ELECTRIC GENERATOR

DOEpatents

Jordan, K.C.

1958-07-22

The conversion of heat energy into electrical energy by a small compact device is descrtbed. Where the heat energy is supplied by a radioactive material and thermopIIes convert the heat to electrical energy. The particular battery construction includes two insulating discs with conductive rods disposed between them to form a circular cage. In the center of the cage is disposed a cup in which the sealed radioactive source is located. Each thermopile is formed by connecting wires from two adjacent rods to a potnt on an annular ring fastened to the outside of the cup, the ring having insulation on its surface to prevent electrica1 contact with the thermopiles. One advantage of this battery construction is that the radioactive source may be inserted after the device is fabricated, reducing the radiation hazard to personnel assembling the battery.

LED deep UV source for charge management of gravitational reference sensors

NASA Astrophysics Data System (ADS)

Sun, Ke-Xun; Allard, Brett; Buchman, Saps; Williams, Scott; Byer, Robert L.

2006-04-01

Proof mass electrical charge management is an important functionality for the ST-7-LTP technology demonstration flight and for LISA. Photoemission for charge control is accomplished by using deep ultraviolet (UV) light to excite photoelectron emission from an Au alloy. The conventional UV source is a mercury vapour lamp. We propose and demonstrate charge management using a deep UV light emitting diode (LED) source. We have acquired selected AlGaN UV LEDs, characterized their performance and successfully used them to realize charge management. The UV LEDs emit at a 257 nm central wavelength with a bandwidth of ~12 nm. The UV power for a free-space LED is ~120 µW, and after fibre coupling is ~16 µW, more than sufficient for LISA applications. We have directly observed the LED UV light-induced photocurrent response from an Au photocathode and an Au-coated GRS/ST-7 proof mass. We demonstrated fast switching of UV LEDs and associated fast changes in photocurrent. This allows modulation and continuous discharge to meet stringent LISA disturbance reduction requirements. We propose and demonstrate AC charge management outside the gravitational wave signal band. Further, the megahertz bandwidth for UV LED switching allows for up to six orders of magnitude dynamic power range and a number of novel modes of operations. The UV LED based charge management system offers the advantages of small-size, lightweight, fibre-coupled operation with very low power consumption. Presented at 'Amaldi6', Poster 73, Space Detector, 6th Edoardo Almadi Conference on Gravitational Waves, 20-24 June 2005.

Robustness of free and pinned spiral waves against breakup by electrical forcing in excitable chemical media.

PubMed

Phantu, Metinee; Sutthiopad, Malee; Luengviriya, Jiraporn; Müller, Stefan C; Luengviriya, Chaiya

2017-04-01

We present an investigation on the breakup of free and pinned spiral waves under an applied electrical current in the Belousov-Zhabotinsky reaction. Spiral fronts propagating towards the negative electrode are decelerated. A breakup of the spiral waves occurs when some segments of the fronts are stopped by a sufficiently strong electrical current. In the absence of obstacles (i.e., free spiral waves), the critical value of the electrical current for the wave breakup increases with the excitability of the medium. For spiral waves pinned to circular obstacles, the critical electrical current increases with the obstacle diameter. Analysis of spiral dynamics shows that the enhancement of the robustness against the breakup of both free and pinned spiral waves is originated by the increment of wave speed when either the excitability is strengthened or the obstacle size is enlarged. The experimental findings are reproduced by numerical simulations using the Oregonator model. In addition, the simulations reveal that the robustness against the forced breakup increases with the activator level in both cases of free and pinned spiral waves.

Analysis of electrical tomography sensitive field based on multi-terminal network and electric field

NASA Astrophysics Data System (ADS)

He, Yongbo; Su, Xingguo; Xu, Meng; Wang, Huaxiang

2010-08-01

Electrical tomography (ET) aims at the study of the conductivity/permittivity distribution of the interested field non-intrusively via the boundary voltage/current. The sensor is usually regarded as an electric field, and finite element method (FEM) is commonly used to calculate the sensitivity matrix and to optimize the sensor architecture. However, only the lumped circuit parameters can be measured by the data acquisition electronics, it's very meaningful to treat the sensor as a multi terminal network. Two types of multi terminal network with common node and common loop topologies are introduced. Getting more independent measurements and making more uniform current distribution are the two main ways to minimize the inherent ill-posed effect. By exploring the relationships of network matrixes, a general formula is proposed for the first time to calculate the number of the independent measurements. Additionally, the sensitivity distribution is analyzed with FEM. As a result, quasi opposite mode, an optimal single source excitation mode, that has the advantages of more uniform sensitivity distribution and more independent measurements, is proposed.

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

BARTONE, ERIK

DBS Energy Inc. (“DBS”) intends on using the Connecticut Biofuels Technology Project for the purpose of developing a small-scale electric generating systems that are located on a distributed basis and utilize biodiesel as its principle fuel source. This project will include research and analysis on the quality and applied use of biodiesel for use in electricity production, 2) develop dispatch center for testing and analysis of the reliability of dispatching remote generators operating on a blend of biodiesel and traditional fossil fuels, and 3) analysis and engineering research on fuel storage options for biodiesel of fuels for electric generation.

5. POWERHOUSE INTERIOR SHOWING EXCITER No. 1. SMALL PELTONDOBLE IMPULSE ...

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

5. POWERHOUSE INTERIOR SHOWING EXCITER No. 1. SMALL PELTON-DOBLE IMPULSE WHEEL IN FOREGROUND. VIEW TO NORTHWEST. - Rush Creek Hydroelectric System, Powerhouse Exciters, Rush Creek, June Lake, Mono County, CA

Social and Economic Impact of Solar Electricity at Schuchuli Village

NASA Technical Reports Server (NTRS)

Bifano, W. J.; Ratajczak, A. F.; Bahr, D. M.; Garrett, B. G.

1979-01-01

Schuchuli, a small remote village on the Papago Indian Reservation in southwest Arizona, is 27 kilometers (17 miles) from the nearest available utility power. Its lack of conventional power is due to the prohibitive cost of supplying a small electrical load with a long-distance distribution line. Furthermore, alternate energy sources are expensive and place a burden on the resources of the villagers. On December 16, 1978, as part of a federally funded project, a solar cell power system was put into operation at Schuchuli. The system powers the village water pump, lighting for homes and other village buildings, family refrigerators and a communal washing machine and sewing machine.

Electromagnetic radiation from filamentary sources in the presence of axially magnetized cylindrical plasma scatterers

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

Es’kin, V. A.; Ivoninsky, A. V.; Kudrin, A. V., E-mail: kud@rf.unn.ru

Electromagnetic radiation from filamentary electric-dipole and magnetic-current sources of infinite length in the presence of gyrotropic cylindrical scatterers in the surrounding free space is studied. The scatterers are assumed to be infinitely long, axially magnetized circular plasma columns parallel to the axis of the filamentary source. The field and the radiation pattern of each source are calculated in the case where the source frequency is equal to one of the surface plasmon resonance frequencies of the cylindrical scatterers. It is shown that the presence of even a single resonant magnetized plasma scatterer of small electrical radius or a few suchmore » scatterers significantly affects the total fields of the filamentary sources, so that their radiation patterns become essentially different from those in the absence of scatterers or the presence of isotropic scatterers of the same shape and size. It is concluded that the radiation characteristics of the considered sources can efficiently be controlled using their resonance interaction with the neighboring gyrotropic scatterers.« less

Emission line shapes produced by dissociative excitation of atmospheric gases

NASA Technical Reports Server (NTRS)

Zipf, E. C.; Wells, W. C.

1980-01-01

The spectral line shapes of the radiation emitted from O atoms produced by the dissociative excitation of O2, CO, CO2 and NO are investigated. Doppler line shapes are derived from time-of-flight spectra of O (5S0) atoms decaying by the emission of 1356-A radiation after being produced in electron impact experiments at incident electron energies from 25 to 300 eV. It is shown that the effective line width of the radiation is large compared with the Doppler absorption widths of ambient O atoms in both photoelectron and auroral excitation, and thus the dissociatively excited component of the O I 1304-A airglow will behave as though it were optically thin, exhibiting pronounced limb brightening effects and a scale height characteristic of the initial, local source function. It is found that the average kinetic energy of the dissociation fragments inferred from O I (5S) time-of-flight spectra is in good agreement with that of O I (3S) atoms in the electron impact dissociation of CO2, although not for O2. Finally, it is suggested that although electron impact dissociation of CO and CO2 contributes to the 1304-A emission in the upper atmosphere of Venus, it cannot be the dominant source of this radiation since the absolute cross sections for the reaction are too small.

Philippines Country Analysis Brief

EIA Publications

2014-01-01

The Philippines is a net energy importer in spite of low consumption levels relative to its Southeast Asian neighbors. The country produces small volumes of oil, natural gas, and coal. Geothermal, hydropower, and other renewable sources constitute a significant share of electricity generation.

Studies of small-scale plasma inhomogeneities in the cusp ionosphere using sounding rocket data

NASA Astrophysics Data System (ADS)

Chernyshov, Alexander A.; Spicher, Andres; Ilyasov, Askar A.; Miloch, Wojciech J.; Clausen, Lasse B. N.; Saito, Yoshifumi; Jin, Yaqi; Moen, Jøran I.

2018-04-01

Microprocesses associated with plasma inhomogeneities are studied on the basis of data from the Investigation of Cusp Irregularities (ICI-3) sounding rocket. The ICI-3 rocket is devoted to investigating a reverse flow event in the cusp F region ionosphere. By numerical stability analysis, it is demonstrated that inhomogeneous-energy-density-driven (IEDD) instability can be a mechanism for the excitation of small-scale plasma inhomogeneities. The Local Intermittency Measure (LIM) method also applied the rocket data to analyze irregular structures of the electric field during rocket flight in the cusp. A qualitative agreement between high values of the growth rates of the IEDD instability and the regions with enhanced LIM is observed. This suggests that IEDD instability is connected to turbulent non-Gaussian processes.

Performance of a CW double electric discharge for supersonic CO lasers

NASA Technical Reports Server (NTRS)

Stanton, A. C.; Hanson, R. K.; Mitchner, M.

1980-01-01

The results of an experimental investigation of a CW double discharge in supersonic CO mixtures are reported. Stable discharges in CO/N2 and CO/Ar mixtures, with a maximum energy loading of 0.5 eV/CO molecule, were achieved in a small-scale continuous-flow supersonic channel. Detailed measurements of the discharge characteristics were performed, including electrostatic probe measurements of floating potential and electron number density and spectroscopic measurements of the CO vibrational population distributions. The results of these measurements indicate that the vibrational excitation efficiency of the discharge is approximately 60%, for moderate levels of main discharge current. These experiments, on a small scale, demonstrate that the double-discharge scheme provides adequate vibrational energy loading for efficient CO laser operation under CW supersonic flow conditions.

Diffusion approximation with polarization and resonance effects for the modelling of seismic waves in strongly scattering small-scale media

NASA Astrophysics Data System (ADS)

Margerin, Ludovic

2013-01-01

This paper presents an analytical study of the multiple scattering of seismic waves by a collection of randomly distributed point scatterers. The theory assumes that the energy envelopes are smooth, but does not require perturbations to be small, thereby allowing the modelling of strong, resonant scattering. The correlation tensor of seismic coda waves recorded at a three-component sensor is decomposed into a sum of eigenmodes of the elastodynamic multiple scattering (Bethe-Salpeter) equation. For a general moment tensor excitation, a total number of four modes is necessary to describe the transport of seismic waves polarization. Their spatio-temporal dependence is given in closed analytical form. Two additional modes transporting exclusively shear polarizations may be excited by antisymmetric moment tensor sources only. The general solution converges towards an equipartition mixture of diffusing P and S waves which allows the retrieval of the local Green's function from coda waves. The equipartition time is obtained analytically and the impact of absorption on Green's function reconstruction is discussed. The process of depolarization of multiply scattered waves and the resulting loss of information is illustrated for various seismic sources. It is shown that coda waves may be used to characterize the source mechanism up to lapse times of the order of a few mean free times only. In the case of resonant scatterers, a formula for the diffusivity of seismic waves incorporating the effect of energy entrapment inside the scatterers is obtained. Application of the theory to high-contrast media demonstrates that coda waves are more sensitive to slow rather than fast velocity anomalies by several orders of magnitude. Resonant scattering appears as an attractive physical phenomenon to explain the small values of the diffusion constant of seismic waves reported in volcanic areas.

Investigation of small transverse electric CO/sub 2/ waveguide lasers for fuzing applications. Contractor report

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

Hochuli, U.; McGuire, D.

1982-10-01

The properties of a compact, transversely excited, pulsed CO/sub 2/ waveguide laser are studied experimentally with the application of such a laser for an optical fuze transmitter in mind. Such parameters as peak power, pulse width, pulse shape, pulse jitter, repetition rate, beam profile, polarization, laser life, and optimum as mixture are investigated both for 10.6 and 9.6 micron output wavelengths, and for both sealed-off and flowing-gas operation of the laser. A computer simulation of the laser's operation is compared with the experimental results.

Low power energy harvesting and storage techniques from ambient human powered energy sources

NASA Astrophysics Data System (ADS)

Yildiz, Faruk

Conventional electrochemical batteries power most of the portable and wireless electronic devices that are operated by electric power. In the past few years, electrochemical batteries and energy storage devices have improved significantly. However, this progress has not been able to keep up with the development of microprocessors, memory storage, and sensors of electronic applications. Battery weight, lifespan and reliability often limit the abilities and the range of such applications of battery powered devices. These conventional devices were designed to be powered with batteries as required, but did not allow scavenging of ambient energy as a power source. In contrast, development in wireless technology and other electronic components are constantly reducing the power and energy needed by many applications. If energy requirements of electronic components decline reasonably, then ambient energy scavenging and conversion could become a viable source of power for many applications. Ambient energy sources can be then considered and used to replace batteries in some electronic applications, to minimize product maintenance and operating cost. The potential ability to satisfy overall power and energy requirements of an application using ambient energy can eliminate some constraints related to conventional power supplies. Also power scavenging may enable electronic devices to be completely self-sustaining so that battery maintenance can eventually be eliminated. Furthermore, ambient energy scavenging could extend the performance and the lifetime of the MEMS (Micro electromechanical systems) and portable electronic devices. These possibilities show that it is important to examine the effectiveness of ambient energy as a source of power. Until recently, only little use has been made of ambient energy resources, especially for wireless networks and portable power devices. Recently, researchers have performed several studies in alternative energy sources that could provide small amounts of electricity to low-power electronic devices. These studies were focused to investigate and obtain power from different energy sources, such as vibration, light, sound, airflow, heat, waste mechanical energy and temperature variations. This research studied forms of ambient energy sources such as waste mechanical (rotational) energy from hydraulic door closers, and fitness exercise bicycles, and its conversion and storage into usable electrical energy. In both of these examples of applications, hydraulic door closers and fitness exercise bicycles, human presence is required. A person has to open the door in order for the hydraulic door closer mechanism to function. Fitness exercise bicycles need somebody to cycle the pedals to generate electricity (while burning calories.) Also vibrations, body motions, and compressions from human interactions were studied using small piezoelectric fiber composites which are capable of recovering waste mechanical energy and converting it to useful electrical energy. Based on ambient energy sources, electrical energy conversion and storage circuits were designed and tested for low power electronic applications. These sources were characterized according to energy harvesting (scavenging) methods, and power and energy density. At the end of the study, the ambient energy sources were matched with possible electronic applications as a viable energy source.

Detection of radio frequency perturbations using an ion beam diagnostic (abstract)

NASA Astrophysics Data System (ADS)

Howard, S.; Si, J.; Crowley, T. P.; Connor, K. A.; Schoch, P. M.; Schatz, J. G.

2001-01-01

Presently, experiments are underway at the Plasma Dynamics Laboratory at Rensselaer Polytechnic Institute to demonstrate that the techniques developed for heavy ion beam probe diagnostics (HIBP) can be used to measure radio frequency (rf) fluctuations in plasmas. We hope to measure fluctuations in plasma density and magnetic and electric fields. This will provide a direct measurement of the electric and magnetic fields in the plasma during ICRF heating and thereby improve understanding of heating deposition and wave physics. In addition, the field and the density measurements will be used to determine the plasma reaction to the heating experiments. It is expected that the density measurements will be easiest to interpret, while the electric field measurement will be the most difficult to interpret. The diagnostic issues that will be important in taking data at rf frequencies include faster electronics, signal levels, and path effects. We have used a current to voltage amplifier design to measure 0-500 kHz fluctuations in several previous experiments. By reducing the gain and changing some components, a very similar design is capable of operation at rf frequencies. The modified circuit has been tested up to 15 MHz and worked well. The number of beam ions striking the detector plate in one rf period will be too small to obtain good enough statistics for fluctuation measurements, and therefore, averages over many cycles will be required. We expect to be able to achieve millisecond time resolution in the experiments. The global nature of the modes will tend to make path effects important in the HIBP signals. On the other hand, since the beam will take more than one period to cross the plasma, phase shifts may cancel some of these effects. In addition, a path effect term due to dA/dt will be much more important relative to the electric potential than in lower frequency experiments. The initial experimental plan is to do a series of measurements in which a lithium ion beam passes through an argon helicon plasma. The helicon plasma was chosen because its high density (of order 1019 m-3) will produce a larger HIBP signal than can be obtained from other small plasmas. The helicon plasma is formed within a solenoidal magnetic field of 1 kG on axis. The plasma is excited by an rf antenna that is a modification of the type used in Boswell's experiments.1 The rf power source is presently a 500 W, 13.56 MHz generator. From calculation of final trajectories we have determined that 16-29 keV Li ions can be used to probe a plasma with 1 kG magnetic field on axis. If the signal levels with a lithium beam are too small, a molecular hydrogen source will be used. For testing the basic operation of the ion beam probe we will use a simple plate detector mounted on the output flange. These preliminary experiments will be used to determine the feasibility of measuring density and magnetic field fluctuations. A second set of experiments using a more traditional HIBP energy analyzer as a detector is also planned. This detector will also be able to measure electric field effects on the probing ions. It will also be less sensitive to UV noise from the plasma.

Utility involvement in cogeneration and small power production since PURPA

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

Hallaron, S.A.

One of the objectives of PURPA was more efficient energy production through cogeneration and the use of renewable resources. Under PURPA regulations, cogeneration and small power-producing plants may file for qualifying status to receive benefits allowed by the National Energy Act. There has been a steady increase in the number of qualifying facilities (QFs) and some electric utilities have increased ownership of small power-producing facilities as well as electric purchases from QFs. QFs are not only exempt from federal and state utility regulations under PURPA, but they also may be eligible for an exemption from the provisions of the Fuelmore » Use Act of 1978 which prohibits or limits use of oil and natural gas in power plants and other major fuel-burning installations. To obtain QF status under PURPA, small power-producing facilities are limited to a capacity of 80 MW or less and must use some combination of biomass, waste, geothermal, or other renewable resource as the primary energy source. Cogenerators are not limited in size or fuel. The purchase of electricity from cogenerators and small power producers can be an attractive alternative for utilities in meeting future demands.« less

Self-consistent multidimensional electron kinetic model for inductively coupled plasma sources

NASA Astrophysics Data System (ADS)

Dai, Fa Foster

Inductively coupled plasma (ICP) sources have received increasing interest in microelectronics fabrication and lighting industry. In 2-D configuration space (r, z) and 2-D velocity domain (νθ,νz), a self- consistent electron kinetic analytic model is developed for various ICP sources. The electromagnetic (EM) model is established based on modal analysis, while the kinetic analysis gives the perturbed Maxwellian distribution of electrons by solving Boltzmann-Vlasov equation. The self- consistent algorithm combines the EM model and the kinetic analysis by updating their results consistently until the solution converges. The closed-form solutions in the analytical model provide rigorous and fast computing for the EM fields and the electron kinetic behavior. The kinetic analysis shows that the RF energy in an ICP source is extracted by a collisionless dissipation mechanism, if the electron thermovelocity is close to the RF phase velocities. A criterion for collisionless damping is thus given based on the analytic solutions. To achieve uniformly distributed plasma for plasma processing, we propose a novel discharge structure with both planar and vertical coil excitations. The theoretical results demonstrate improved uniformity for the excited azimuthal E-field in the chamber. Non-monotonic spatial decay in electric field and space current distributions was recently observed in weakly- collisional plasmas. The anomalous skin effect is found to be responsible for this phenomenon. The proposed model successfully models the non-monotonic spatial decay effect and achieves good agreements with the measurements for different applied RF powers. The proposed analytical model is compared with other theoretical models and different experimental measurements. The developed model is also applied to two kinds of ICP discharges used for electrodeless light sources. One structure uses a vertical internal coil antenna to excite plasmas and another has a metal shield to prevent the electromagnetic radiation. The theoretical results delivered by the proposed model agree quite well with the experimental measurements in many aspects. Therefore, the proposed self-consistent model provides an efficient and reliable means for designing ICP sources in various applications such as VLSI fabrication and electrodeless light sources.

Permanent-magnet-less machine having an enclosed air gap

DOEpatents

Hsu, John S [Oak Ridge, TN

2012-02-07

A permanent magnet-less, brushless synchronous system includes a stator that generates a magnetic rotating field when sourced by an alternating current. An uncluttered rotor disposed within the magnetic rotating field is spaced apart from the stator to form an air gap relative to an axis of rotation. A stationary excitation core spaced apart from the uncluttered rotor by an axial air gap and a radial air gap substantially encloses the stationary excitation core. Some permanent magnet-less, brushless synchronous systems include stator core gaps to reduce axial flux flow. Some permanent magnet-less, brushless synchronous systems include an uncluttered rotor coupled to outer laminations. The quadrature-axis inductance may be increased in some synchronous systems. Some synchronous systems convert energy such as mechanical energy into electrical energy (e.g., a generator); other synchronous systems may convert any form of energy into mechanical energy (e.g., a motor).

Permanent-magnet-less machine having an enclosed air gap

DOEpatents

Hsu, John S.

2013-03-05

A permanent magnet-less, brushless synchronous system includes a stator that generates a magnetic rotating field when sourced by an alternating current. An uncluttered rotor disposed within the magnetic rotating field is spaced apart from the stator to form an air gap relative to an axis of rotation. A stationary excitation core spaced apart from the uncluttered rotor by an axial air gap and a radial air gap substantially encloses the stationary excitation core. Some permanent magnet-less, brushless synchronous systems include stator core gaps to reduce axial flux flow. Some permanent magnet-less, brushless synchronous systems include an uncluttered rotor coupled to outer laminations. The quadrature-axis inductance may be increased in some synchronous systems. Some synchronous systems convert energy such as mechanical energy into electrical energy (e.g., a generator); other synchronous systems may convert any form of energy into mechanical energy (e.g., a motor).

Stark effect and dipole moments of the ammonia dimer in different vibration-rotation-tunneling states

NASA Astrophysics Data System (ADS)

Cotti, Gina; Linnartz, Harold; Meerts, W. Leo; van der Avoird, Ad; Olthof, Edgar H. T.

1996-03-01

In this paper we present Stark measurements on the G:K=-1 vibration-rotation-tunneling (VRT) transition, band origin 747.2 GHz, of the ammonia dimer. The observed splitting pattern and selection rules can be explained by considering the G36 and G144 symmetries of the inversion states involved, and almost complete mixing of these states by the applied electric field. The absolute values of the electric dipole moments of the ground and excited state are determined to be 0.763(15) and 0.365(10) D, respectively. From the theoretical analysis and the observed selection rules it is possible to establish that the dipole moments of the two interchange states must have opposite sign. The theoretical calculations are in good agreement with the experimental results: The calculated dipole moments are -0.74 D for the lower and +0.35 D for the higher state. Our results, in combination with the earlier dipole measurements on the G:K=0 ground state and the G:K=1 transition with band origin 486.8 GHz, confirm that the ammonia dimer is highly nonrigid. Its relatively small and strongly K-dependent dipole moment, which changes sign upon far-infrared excitation, originates from the difference in dynamical behavior of ortho and para NH3.

Electromagnetic Flow Meter Having a Driver Circuit Including a Current Transducer

NASA Technical Reports Server (NTRS)

Patel, Sandeep K. (Inventor); Karon, David M. (Inventor); Cushing, Vincent (Inventor)

2014-01-01

An electromagnetic flow meter (EMFM) accurately measures both the complete flow rate and the dynamically fluctuating flow rate of a fluid by applying a unipolar DC voltage to excitation coils for a predetermined period of time, measuring the electric potential at a pair of electrodes, determining a complete flow rate and independently measuring the dynamic flow rate during the "on" cycle of the DC excitation, and correcting the measurements for errors resulting from galvanic drift and other effects on the electric potential. The EMFM can also correct for effects from the excitation circuit induced during operation of the EMFM.

Parametric distribution approach for flow availability in small hydro potential analysis

NASA Astrophysics Data System (ADS)

Abdullah, Samizee; Basri, Mohd Juhari Mat; Jamaluddin, Zahrul Zamri; Azrulhisham, Engku Ahmad; Othman, Jamel

2016-10-01

Small hydro system is one of the important sources of renewable energy and it has been recognized worldwide as clean energy sources. Small hydropower generation system uses the potential energy in flowing water to produce electricity is often questionable due to inconsistent and intermittent of power generated. Potential analysis of small hydro system which is mainly dependent on the availability of water requires the knowledge of water flow or stream flow distribution. This paper presented the possibility of applying Pearson system for stream flow availability distribution approximation in the small hydro system. By considering the stochastic nature of stream flow, the Pearson parametric distribution approximation was computed based on the significant characteristic of Pearson system applying direct correlation between the first four statistical moments of the distribution. The advantage of applying various statistical moments in small hydro potential analysis will have the ability to analyze the variation shapes of stream flow distribution.

The relationship between anatomically correct electric and magnetic field dosimetry and publishe delectric and magnetic field exposure limits.

PubMed

Kavet, Robert; Dovan, Thanh; Reilly, J Patrick

2012-12-01

Electric and magnetic field exposure limits published by International Commission for Non-Ionizing Radiation Protection and Institute of Electrical and Electronics Engineers are aimed at protection against adverse electrostimulation, which may occur by direct coupling to excitable tissue and, in the case of electric fields, through indirect means associated with surface charge effects (e.g. hair vibration, skin sensations), spark discharge and contact current. For direct coupling, the basic restriction (BR) specifies the not-to-be-exceeded induced electric field. The key results of anatomically based electric and magnetic field dosimetry studies and the relevant characteristics of excitable tissue were first identified. This permitted us to assess the electric and magnetic field exposure levels that induce dose in tissue equal to the basic restrictions, and the relationships of those exposure levels to the limits now in effect. We identify scenarios in which direct coupling of electric fields to peripheral nerve could be a determining factor for electric field limits.

Artifacts, assumptions, and ambiguity: Pitfalls in comparing experimental results to numerical simulations when studying electrical stimulation of the heart.

PubMed

Roth, Bradley J.

2002-09-01

Insidious experimental artifacts and invalid theoretical assumptions complicate the comparison of numerical predictions and observed data. Such difficulties are particularly troublesome when studying electrical stimulation of the heart. During unipolar stimulation of cardiac tissue, the artifacts include nonlinearity of membrane dyes, optical signals blocked by the stimulating electrode, averaging of optical signals with depth, lateral averaging of optical signals, limitations of the current source, and the use of excitation-contraction uncouplers. The assumptions involve electroporation, membrane models, electrode size, the perfusing bath, incorrect model parameters, the applicability of a continuum model, and tissue damage. Comparisons of theory and experiment during far-field stimulation are limited by many of these same factors, plus artifacts from plunge and epicardial recording electrodes and assumptions about the fiber angle at an insulating boundary. These pitfalls must be overcome in order to understand quantitatively how the heart responds to an electrical stimulus. (c) 2002 American Institute of Physics.

Multipolar second-harmonic generation by Mie-resonant dielectric nanoparticles

NASA Astrophysics Data System (ADS)

Smirnova, Daria; Smirnov, Alexander I.; Kivshar, Yuri S.

2018-01-01

By combining analytical and numerical approaches, we study resonantly enhanced second-harmonic generation by individual high-index dielectric nanoparticles made of centrosymmetric materials. Considering both bulk and surface nonlinearities, we describe second-harmonic nonlinear scattering from a silicon nanoparticle optically excited in the vicinity of the magnetic and electric dipolar resonances. We discuss the contributions of different nonlinear sources and the effect of the low-order optical Mie modes on the characteristics of the generated far field. We demonstrate that the multipolar expansion of the radiated field is dominated by dipolar and quadrupolar modes (two axially symmetric electric quadrupoles, an electric dipole, and a magnetic quadrupole) and the interference of these modes can ensure directivity of the nonlinear scattering. The developed multipolar analysis can be instructive for interpreting the far-field measurements of the nonlinear scattering and it provides prospective insights into a design of complementary metal-oxide-semiconductor compatible nonlinear nanoantennas fully integrated with silicon-based photonic circuits, as well as methods of nonlinear diagnostics.

All-Electrical Measurement of Interfacial Dzyaloshinskii-Moriya Interaction Using Collective Spin-Wave Dynamics.

PubMed

Lee, Jong Min; Jang, Chaun; Min, Byoung-Chul; Lee, Seo-Won; Lee, Kyung-Jin; Chang, Joonyeon

2016-01-13

Dzyaloshinskii-Moriya interaction (DMI), which arises from the broken inversion symmetry and spin-orbit coupling, is of prime interest as it leads to a stabilization of chiral magnetic order and provides an efficient manipulation of magnetic nanostructures. Here, we report all-electrical measurement of DMI using propagating spin wave spectroscopy based on the collective spin wave with a well-defined wave vector. We observe a substantial frequency shift of spin waves depending on the spin chirality in Pt/Co/MgO structures. After subtracting the contribution from other sources to the frequency shift, it is possible to quantify the DMI energy in Pt/Co/MgO systems. The result reveals that the DMI in Pt/Co/MgO originates from the interfaces, and the sign of DMI corresponds to the inversion asymmetry of the film structures. The electrical excitation and detection of spin waves and the influence of interfacial DMI on the collective spin-wave dynamics will pave the way to the emerging field of spin-wave logic devices.

Observation of Schumann Resonances in the Earth's Ionosphere

NASA Technical Reports Server (NTRS)

Simoes, Fernando; Pfaff, Robert; Freudenreich, Henry

2011-01-01

The surface of the Earth and the lower edge of the ionosphere define a cavity in which electromagnetic waves propagate. When the cavity is excited by broadband electromagnetic sources, e.g., lightning, a resonant state can develop provided the average equatorial circumference is approximately equal to an integral number of wavelengths of the electromagnetic waves. This phenomenon, known as Schumann resonance, corresponds to electromagnetic oscillations of the surface-ionosphere cavity, and has been used extensively to investigate atmospheric electricity. Using measurements from the Communications/Navigation Outage Forecasting System (C/NOFS) satellite, we report, for the first time, Schumann resonance signatures detected well beyond the upper boundary of the cavity. These results offer new means for investigating atmospheric electricity, tropospheric-ionospheric coupling mechanisms related to lightning activity, and wave propagation in the ionosphere. The detection of Schumann resonances in the ionosphere calls for revisions to the existing models of extremely low frequency wave propagation in the surface-ionosphere cavity. Additionally, these measurements suggest new remote sensing capabilities for investigating atmospheric electricity at other planets.

Solar Thermal Small Power Systems Study. Inventory of US industrial small electric power generating systems. [Less than 10 MW

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

Not Available

This inventory of small industrial electric generating systems was assembled by The Aerospace Corporation to provide a data base for analyses being conducted to estimate the potential for displacement of these fossil-fueled systems by solar thermal electric systems no larger than 10 MW in rated capacity. The approximately 2100 megawatts generating capacity of systems in this category constitutes a potential market for small solar thermal and other solar electric power systems. The sources of data for this inventory were the (former) Federal Power Commission (FPC) Form 4 Industrial Ledger and Form 12-C Ledger for 1976. Table 1 alphabetically lists generatingmore » systems located at industrial plants and at Federal government installations in each of the 50 states. These systems are differentiated by type of power plant: steam turbine, diesel generator, or gas turbine. Each listing is designated as a power system rather than a power unit because the FPC Ledgers do not provide a means of determining whether more than one unit is associated with each industrial installation. Hence, the user should consider each listing to be a system capacity rating wherein the system may consist of one or more generating units with less than 10 MW/sub e/ combined rating. (WHK)« less

Piezoelectric-based hybrid reserve power sources for munitions

NASA Astrophysics Data System (ADS)

Rastegar, J.; Kwok, P.

2017-04-01

Reserve power sources are used extensively in munitions and other devices, such as emergency devices or remote sensors that need to be powered only once and for a relatively short duration. Current chemical reserve power sources, including thermal batteries and liquid reserve batteries sometimes require more than 100 msec to become fully activated. In many applications, however, electrical energy is required in a few msec following the launch event. In such applications, other power sources are needed to provide power until the reserve battery is fully activated. The amount of electrical energy that is required by most munitions before chemical reserve batteries are fully activated is generally small and can be provided by properly designed piezoelectric-based energy harvesting devices. In this paper, the development of a hybrid reserve power source that is constructed by integration of a piezoelectric-based energy harvesting device with a reserve battery to provide power almost instantaneously upon munitions firing or other similar events is being reported. A review of the state of the art in piezoelectric-based electrical energy harvesting methods and devices and their charge collection electronics for use in the developed hybrid power sources is provided together with the results of testing of the piezoelectric component of the power source and its electronic safety and charge collection electronics.

12. POWERHOUSE INTERIOR SHOWING EXCITER No. 2 SMALL PELTONDOBLE IMPULSE ...

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

12. POWERHOUSE INTERIOR SHOWING EXCITER No. 2 SMALL PELTON-DOBLE IMPULSE WHEEL, HAND-CONTROLLED GATE VALVE, AND NOZZLE. VIEW TO SOUTHWEST. - Rush Creek Hydroelectric System, Powerhouse Exciters, Rush Creek, June Lake, Mono County, CA

Effects of cold temperatures on the excitability of rat trigeminal ganglion neurons that are not for cold-sensing

PubMed Central

Kanda, Hirosato; Gu, Jianguo G.

2016-01-01

Except a small population of primary afferent neurons for sensing cold to generate the sensations of innocuous and noxious cold, it is generally believed that cold temperatures suppress the excitability of other primary afferent neurons that are not for cold-sensing. These not-for-cold-sensing neurons include the majority of non-nociceptive and nociceptive afferent neurons. In the present study we have found that not-for-cold-sensing neurons of rat trigeminal ganglia (TG) change their excitability in several ways at cooling temperatures. In nearly 70% of not-for-cold-sensing TG neurons, the cooling temperature of 15°C increases their membrane excitability. We regard these neurons as cold-active neurons. For the remaining 30% of not-for-cold-sensing TG neurons, the cooling temperature of 15°C either has no effect (regarded as cold-ineffective neurons) or suppress (regarded as cold-suppressive neurons) their membrane excitability. For cold-active neurons, the cold temperature of 15°C increases their excitability as is evidenced by the increases in action potential (AP) firing numbers and/or reduction of AP rheobase when these neurons are depolarized electrically. The cold temperature of 15°C significantly inhibits M-currents and increases membrane input resistance of cold-active neurons. Retigabine, an M-current activator, abolishes the effect of cold temperatures on AP firing but not the effect of cold temperature on AP rheobase levels. The inhibition of M-currents and the increases of membrane input resistance are likely two mechanisms by which cooling temperatures increase the excitability of not-for-cold-sensing TG neurons. PMID:26709732

Effects of cold temperatures on the excitability of rat trigeminal ganglion neurons that are not for cold sensing.

PubMed

Kanda, Hirosato; Gu, Jianguo G

2017-05-01

Aside from a small population of primary afferent neurons for sensing cold, which generate sensations of innocuous and noxious cold, it is generally believed that cold temperatures suppress the excitability of primary afferent neurons not responsible for cold sensing. These not-for-cold-sensing neurons include the majority of non-nociceptive and nociceptive afferent neurons. In this study we have found that the not-for-cold-sensing neurons of rat trigeminal ganglia (TG) change their excitability in several ways at cooling temperatures. In nearly 70% of not-for-cold-sensing TG neurons, a cooling temperature of 15°C increases their membrane excitability. We regard these neurons as cold-active neurons. For the remaining 30% of not-for-cold-sensing TG neurons, the cooling temperature of 15°C either has no effect (cold-ineffective neurons) or suppress their membrane excitability (cold-suppressive neurons). For cold-active neurons, the cold temperature of 15°C increases their excitability as is evidenced by increases in action potential (AP) firing numbers and/or the reduction in AP rheobase when these neurons are depolarized electrically. The cold temperature of 15°C significantly inhibits M-currents and increases membrane input resistance of cold-active neurons. Retigabine, an M-current activator, abolishes the effect of cold temperatures on AP firing, but not the effect of cold temperature on AP rheobase levels. The inhibition of M-currents and the increases of membrane input resistance are likely two mechanisms by which cooling temperatures increase the excitability of not-for-cold-sensing TG neurons. This article is part of the special article series "Pain". © 2015 International Society for Neurochemistry.

Electromagnetic toroidal excitations in matter and free space.

PubMed

Papasimakis, N; Fedotov, V A; Savinov, V; Raybould, T A; Zheludev, N I

2016-03-01

The toroidal dipole is a localized electromagnetic excitation, distinct from the magnetic and electric dipoles. While the electric dipole can be understood as a pair of opposite charges and the magnetic dipole as a current loop, the toroidal dipole corresponds to currents flowing on the surface of a torus. Toroidal dipoles provide physically significant contributions to the basic characteristics of matter including absorption, dispersion and optical activity. Toroidal excitations also exist in free space as spatially and temporally localized electromagnetic pulses propagating at the speed of light and interacting with matter. We review recent experimental observations of resonant toroidal dipole excitations in metamaterials and the discovery of anapoles, non-radiating charge-current configurations involving toroidal dipoles. While certain fundamental and practical aspects of toroidal electrodynamics remain open for the moment, we envision that exploitation of toroidal excitations can have important implications for the fields of photonics, sensing, energy and information.

A Decision Model for Choosing Among Photovoltaic Technologies to Generate Electricity at Grid-Connected Air Force Facilities: A Value-Focused Approach

DTIC Science & Technology

2006-03-01

goals, but it is also carries significant political interest. 1.1.4. Photovoltaic Effect A monocrystalline silicon photovoltaic cell (Figure 2) is...developed the industry by creating small photovoltaic panels to power watches and calculators (Archer, 2001; Wronski and Carlson, 2001). Amorphous silicon...Clinton, 1999). One particularly promising renewable energy source is solar energy converted to electricity by solar photovoltaic panels . Previous

Energy Systems Integration Partnerships: NREL + Cogent Energy Systems

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

Berdahl, Sonja E

2017-08-09

NREL is collaborating with Cogent Energy Systems (Cogent) to introduce small-scale waste-to-energy technology in microgrids.The focus of the project is to test and demonstrate the feasibility, reliability, and usefulness of integrating electricity generated using a simulated syngas composition matching the syngas stream to be produced by a HelioStorm-based WTE gasifier to power a microgrid as a means of addressing and complementing the intermittency of other sources of electricity.

Regional Small-Event Identification Using Networks and Arrays of Seismic and Acoustic Sensors

DTIC Science & Technology

2006-04-01

ground displacement and excite infra - sonic waves in the atmosphere (Blanc, 1989) near-surface explosions are much more efficient sources of...valuable advice on the portable infrasonic deployment at MNTA. Several of the images in this report are attributable to David Anderson at Southern...populations. This study has focused on seismic observations from mining explosions. There is increasing evidence that infrasonic observations may help in

Advances in Acoustic Landmine Detection

DTIC Science & Technology

2006-10-01

8] A. Petculescu and J. M. Sabatier, “ Feasibility study of an air - coupled acoustic sensor for measuring small vibrations, Proc. SPIE 17th...the acoustic-to-seismic (A/S) coupling of airborne sound into the ground for buried anti-personnel and anti-tank landmine detection is well established...113, pp.1333-1341 (2003)]. A sound source is used to insonify the ground surface. The airborne sound couples into the soil and excites the

Analytical and experimental comparisons of electromechanical vibration response of a piezoelectric bimorph beam for power harvesting

NASA Astrophysics Data System (ADS)

Lumentut, M. F.; Howard, I. M.

2013-03-01

Power harvesters that extract energy from vibrating systems via piezoelectric transduction show strong potential for powering smart wireless sensor devices in applications of health condition monitoring of rotating machinery and structures. This paper presents an analytical method for modelling an electromechanical piezoelectric bimorph beam with tip mass under two input base transverse and longitudinal excitations. The Euler-Bernoulli beam equations were used to model the piezoelectric bimorph beam. The polarity-electric field of the piezoelectric element is excited by the strain field caused by base input excitation, resulting in electrical charge. The governing electromechanical dynamic equations were derived analytically using the weak form of the Hamiltonian principle to obtain the constitutive equations. Three constitutive electromechanical dynamic equations based on independent coefficients of virtual displacement vectors were formulated and then further modelled using the normalised Ritz eigenfunction series. The electromechanical formulations include both the series and parallel connections of the piezoelectric bimorph. The multi-mode frequency response functions (FRFs) under varying electrical load resistance were formulated using Laplace transformation for the multi-input mechanical vibrations to provide the multi-output dynamic displacement, velocity, voltage, current and power. The experimental and theoretical validations reduced for the single mode system were shown to provide reasonable predictions. The model results from polar base excitation for off-axis input motions were validated with experimental results showing the change to the electrical power frequency response amplitude as a function of excitation angle, with relevance for practical implementation.

Vertical electric field induced suppression of fine structure splitting of excited state excitons in a single GaAs/AlGaAs island quantum dots

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

Ghali, Mohsen; Laboratory of Nanophotonics, Physics Department, Faculty of Science, Kafrelsheikh University, 33516 Kafrelsheikh; Ohno, Yuzo

2015-09-21

We report experimentally on fine structure splitting (FSS) of various excitonic transitions in single GaAs island quantum dots, formed by a monolayer thickness fluctuation in the narrow GaAs/AlGaAs quantum well, and embedded in an n-i-Schottky diode device. By applying a forward vertical electric field (F) between the top metallic contact and the sample substrate, we observed an in-plane polarization rotation of both the ground and the excited state excitons with increasing the electric field. The polarization rotations were accompanied with a strong decrease in the FSS of the ground as well as the excited state excitons with the field, untilmore » the FSS vanished as F approached 30 kV/cm.« less

Method and apparatus for guiding ablative therapy of abnormal biological electrical excitation

NASA Technical Reports Server (NTRS)

Armoundas, Antonis A. (Inventor); Feldman, Andrew B. (Inventor); Sherman, Derin A. (Inventor); Cohen, Richard J. (Inventor)

2001-01-01

This invention involves method and apparatus for guiding ablative therapy of abnormal biological electrical excitation. In particular, it is designed for treatment of cardiac arrhythmias. In the method of this invention electrical signals are acquired from passive electrodes, and an inverse dipole method is used to identify the site of origin of an arrhytmia. The location of the tip of the ablation catheter is similarly localized from signals acquired from the passive electrodes while electrical energy is delivered to the tip of the catheter. The catheter tip is then guided to the site of origin of the arrhythmia, and ablative radio frequency energy is delivered to its tip to ablate the site.

A 2D finite element study on the role of material properties on eddy current losses in soft magnetic composites

NASA Astrophysics Data System (ADS)

Ren, Xiaotao; Corcolle, Romain; Daniel, Laurent

2016-02-01

The use of soft magnetic composites (SMCs) in electrical engineering applications is growing. SMCs provide an effective alternative to laminated steels because they exhibit a high permeability with low eddy current losses. Losses are a critical feature in the design of electrical machines, and it is necessary to evaluate the role of microstructure and constitutive properties of SMCs during the predesign stage. In this paper we propose a simplified finite element approach to compute eddy current losses in these materials. The computations allow to quantify the role of exciting source and material properties on eddy current losses. This analysis can later be used in the development of homogenization models for SMC. Contribution to the topical issue "Numelec 2015 - Elected submissions", edited by Adel Razek

Fabrication and electrical characterization of planar lighting devices with Cs3Sb photocathode emitters

NASA Astrophysics Data System (ADS)

Jeong, Hyo-Soo; Keller, Kris; Culkin, Brad

2017-03-01

Non-vacuum process technology was used to produce Cs3Sb photocathodes on substrates, and in-situ panel devices were fabricated. The performance of the devices was characterized by measuring the anode current as functions of the devices' operation times. An excitation light source with a 475-nm wavelength was used for the photocathodes. The device has a simple diode structure, providing unique characteristics such as a large gap, vertical electron beam directionality, and resistance to surface contamination from ion bombardment and poisoning by outgassing species. Accordingly, Cs3Sb photocathodes function as flat emitters, and the emission properties of the photocathode emitters depend on the vacuum level of the devices. An improved current stability has been observed after conducting an electrical conditioning process to remove possible adsorbates on the Cs3Sb flat emitters.

Time-dependent analysis of the mixed-field orientation of molecules without rotational symmetry

NASA Astrophysics Data System (ADS)

Thesing, Linda V.; Küpper, Jochen; González-Férez, Rosario

2017-06-01

We present a theoretical study of the mixed-field orientation of molecules without rotational symmetry. The time-dependent one-dimensional and three-dimensional orientation of a thermal ensemble of 6-chloropyridazine-3-carbonitrile molecules in combined linearly or elliptically polarized laser fields and tilted dc electric fields is computed. The results are in good agreement with recent experimental results of one-dimensional orientation for weak dc electric fields [J. L. Hansen, J. Chem. Phys. 139, 234313 (2013)]. Moreover, they predict that using elliptically polarized laser fields or strong dc fields, three-dimensional orientation is obtained. The field-dressed dynamics of excited rotational states is characterized by highly non-adiabatic effects. We analyze the sources of these non-adiabatic effects and investigate their impact on the mixed-field orientation for different field configurations in mixed-field-orientation experiments.

Correspondence between discrete and continuous models of excitable media: trigger waves

NASA Technical Reports Server (NTRS)

Chernyak, Y. B.; Feldman, A. B.; Cohen, R. J.

1997-01-01

We present a theoretical framework for relating continuous partial differential equation (PDE) models of excitable media to discrete cellular automata (CA) models on a randomized lattice. These relations establish a quantitative link between the CA model and the specific physical system under study. We derive expressions for the CA model's plane wave speed, critical curvature, and effective diffusion constant in terms of the model's internal parameters (the interaction radius, excitation threshold, and time step). We then equate these expressions to the corresponding quantities obtained from solution of the PDEs (for a fixed excitability). This yields a set of coupled equations with a unique solution for the required CA parameter values. Here we restrict our analysis to "trigger" wave solutions obtained in the limiting case of a two-dimensional excitable medium with no recovery processes. We tested the correspondence between our CA model and two PDE models (the FitzHugh-Nagumo medium and a medium with a "sawtooth" nonlinear reaction source) and found good agreement with the numerical solutions of the PDEs. Our results suggest that the behavior of trigger waves is actually controlled by a small number of parameters.

Ultra-bright pulsed electron beam with low longitudinal emittance

DOEpatents

Zolotorev, Max

2010-07-13

A high-brightness pulsed electron source, which has the potential for many useful applications in electron microscopy, inverse photo-emission, low energy electron scattering experiments, and electron holography has been described. The source makes use of Cs atoms in an atomic beam. The source is cycled beginning with a laser pulse that excites a single Cs atom on average to a band of high-lying Rydberg nP states. The resulting valence electron Rydberg wave packet evolves in a nearly classical Kepler orbit. When the electron reaches apogee, an electric field pulse is applied that ionizes the atom and accelerates the electron away from its parent ion. The collection of electron wave packets thus generated in a series of cycles can occupy a phase volume near the quantum limit and it can possess very high brightness. Each wave packet can exhibit a considerable degree of coherence.

Crystalline Electric Field Level Scheme of the Non-Centrosymmetric CePtSi3

NASA Astrophysics Data System (ADS)

Ueta, Daichi; Kobuke, Tomohiro; Yoshida, Masahiro; Yoshizawa, Hideki; Ikeda, Yoichi; Itoh, Shinichi; Yokoo, Tetsuya

2018-05-01

The crystalline electric field (CEF) excitations in CePtSi3 with the non-centrosymmetric structure were investigated by inelastic neutron scattering (INS) experiment. CEF excitations were observed at 5.3 and 17.5 meV. We discuss the CEF parameters and wave function of CePtSi3 by comparing those of other CeTX3(T: transition metal, X: Si, Ge) systems.

Modeling of THz Lasers Based on Intersubband Transitions in Semiconductor Quantum Wells

NASA Technical Reports Server (NTRS)

Liu, Ansheng; Woo, Alex C. (Technical Monitor)

1999-01-01

In semiconductor quantum well structures, the intersubband energy separation can be adjusted to the terahertz (THz) frequency range by changing the well width and material combinations. The electronic and optical properties of these nanostructures can also be controlled by an applied dc electric field. These unique features lead to a large frequency tunability of the quantum well devices. In the on-going project of modeling of the THz lasers, we investigate the possibility of using optical pumping to generate THz radiation based on intersubband transitions in semiconductor quantum wells. We choose the optical pumping because in the electric current injection it is difficult to realize population inversion in the THz frequency range due to the small intersubband separation (4-40 meV). We considered both small conduction band offset (GaAs/AlGaAs) and large band offset (InGaAs/AlAsSb) quantum well structures. For GaAs/AlGaAs quantum wells, mid-infrared C02 lasers are used as pumping sources. For InGaAs/AlAsSb quantum wells, the resonant intersubband transitions can be excited by the near-infrared diode lasers. For three- and four-subband quantum wells, we solve the pumpfield-induced nonequilibrium distribution function for each subband of the quantum well system from a set of rate equations that include both intrasubband and intersubband relaxation processes. Taking into account the coherent interactions between pump and THz (signal) waves, we calculate the optical gain for the THz field. The gain arising from population inversion and stimulated Raman processes is calculated in a unified manner. A graph shows the calculated THz gain spectra for three-subband GaAs/AlGaAs quantum wells. We see that the coherent pump and signal wave interactions contribute significantly to the gain. The pump intensity dependence of the THz gain is also studied. The calculated results are shown. Because of the optical Stark effect and pump-induced population redistribution, the maximum THz gain saturates at larger pump intensities.

Electromagnetic Modeling of Distributed-Source-Excitation of Coplanar Waveguides: Applications to Traveling-Wave Photomixers

NASA Technical Reports Server (NTRS)

Pasqualini, Davide; Neto, Andrea; Wyss, Rolf A.

2001-01-01

In this work an electromagnetic model and subsequent design is presented for a traveling-wave, coplanar waveguide (CPW) based source that will operate in the THz frequency regime. The radio frequency (RF) driving current is a result of photoexcitation of a thin GaAs membrane using two frequency-offset lasers. The GaAs film is grown by molecular-beam-epitaxy (MBE) and displays sub-ps carrier lifetimes which enable the material conductivity to be modulated at a very high rate. The RF current flows between electrodes deposited on the GaAs membrane which are biased with a DC voltage source. The electrodes form a CPW and are terminated with a double slot antenna that couples the power to a quasi-optical system. The membrane is suspended above a metallic reflector to launch all radiation in one direction. The theoretical investigation and consequent design is performed in two steps. The first step consists of a direct evaluation of the magnetic current distribution on an infinitely extended coplanar waveguide excited by an impressed electric current distributed over a finite area. The result of the analysis is the difference between the incident angle of the laser beams and the length of the excited area that maximizes the RF power coupled to the CPW. The optimal values for both parameters are found as functions of the CPW and membrane dimensions as well as the dielectric constants of the layers. In the second step, a design is presented of a double slot antenna that matches the CPW characteristic impedance and gives good overall performance. The design is presently being implemented and measurements will soon be available.

Acceleration of 500 keV Negative Ion Beams By Tuning Vacuum Insulation Distance On JT-60 Negative Ion Source

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

Kojima, A.; Hanada, M.; Tanaka, Y.

2011-09-26

Acceleration of a 500 keV beam up to 2.8 A has been achieved on a JT-60U negative ion source with a three-stage accelerator by overcoming low voltage holding which is one of the critical issues for realization of the JT-60SA ion source. In order to improve the voltage holding, preliminary voltage holding tests with small-size grids with uniform and locally intense electric fields were carried out, and suggested that the voltage holding was degraded by both the size and local electric field effects. Therefore, the local electric field was reduced by tuning gap lengths between the large size grids andmore » grid support structures of the accelerator. Moreover, a beam radiation shield which limited extension of the minimum gap length was also optimized so as to reduce the local electric field while maintaining the shielding effect. These modifications were based on the experiment results, and significantly increased the voltage holding from <150 kV/stage for the original configuration to 200 kV/stage. These techniques for improvement of voltage holding should also be applicable to other large ion sources accelerators such as those for ITER.« less

Acoustic field of a pulsating cylinder in a rarefied gas: Thermoviscous and curvature effects

NASA Astrophysics Data System (ADS)

Ben Ami, Y.; Manela, A.

2017-09-01

We study the acoustic field of a circular cylinder immersed in a rarefied gas and subject to harmonic small-amplitude normal-to-wall displacement and heat-flux excitations. The problem is analyzed in the entire range of gas rarefaction rates and excitation frequencies, considering both single cylinder and coaxial cylinders setups. Numerical calculations are carried out via the direct simulation Monte Carlo method, applying a noniterative algorithm to impose the boundary heat-flux condition. Analytical predictions are obtained in the limits of ballistic- and continuum-flow conditions. Comparing with a reference inviscid continuum solution, the results illustrate the specific impacts of gas rarefaction and boundary curvature on the acoustic source efficiency. Inspecting the far-field properties of the generated disturbance, the continuum-limit solution exhibits an exponential decay of the signal with the distance from the source, reflecting thermoviscous effects, and accompanied by an inverse square-root decay, characteristic of the inviscid problem. Stronger attenuation is observed in the ballistic limit, where boundary curvature results in "geometric reduction" of the molecular layer affected by the source, and the signal vanishes at a distance of few acoustic wavelengths from the cylinder. The combined effects of mechanical and thermal excitations are studied to seek for optimal conditions to monitor the vibroacoustic signal. The impact of boundary curvature becomes significant in the ballistic-flow regime, where the optimal heat-flux amplitude required for sound reduction decreases with the distance from the source and is essentially a function of the acoustic-wavelength-scaled distance only.

Interaction of Low Frequency External Electric Fields and Pancreatic β-Cell: A Mathematical Modeling Approach to Identify the Influence of Excitation Parameters.

PubMed

Farashi, Sajjad; Sasanpour, Pezhman; Rafii-Tabar, Hashem

2018-05-24

Purpose-Although the effect of electromagnetic fields on biological systems has attracted attraction in recent years, there has not been any conclusive result concerning the effects of interaction and the underlying mechanisms involved. Besides the complexity of biological systems, the parameters of the applied electromagnetic field have not been estimated in most of the experiments. Material and Method-In this study, we have used computational approach in order to find the excitation parameters of an external electric field which produces sensible effects in the function of insulin secretory machinery, whose failure triggers the diabetes disease. A mathematical model of the human β-cell has been used and the effects of external electric fields with different amplitudes, frequencies and wave shapes have been studied. Results-The results from our simulations show that the external electric field can influence the membrane electrical activity and perhaps the insulin secretion when its amplitude exceeds a threshold value. Furthermore, our simulations reveal that different waveforms have distinct effects on the β-cell membrane electrical activity and the characteristic features of the excitation like frequency would change the interaction mechanism. Conclusion-The results could help the researchers to investigate the possible role of the environmental electromagnetic fields on the promotion of diabetes disease.

Removal of pinned scroll waves in cardiac tissues by electric fields in a generic model of three-dimensional excitable media.

PubMed

Pan, De-Bei; Gao, Xiang; Feng, Xia; Pan, Jun-Ting; Zhang, Hong

2016-02-24

Spirals or scroll waves pinned to heterogeneities in cardiac tissues may cause lethal arrhythmias. To unpin these life-threatening spiral waves, methods of wave emission from heterogeneities (WEH) induced by low-voltage pulsed DC electric fields (PDCEFs) and circularly polarized electric fields (CPEFs) have been used in two-dimensional (2D) cardiac tissues. Nevertheless, the unpinning of scroll waves in three-dimensional (3D) cardiac systems is much more difficult than that of spiral waves in 2D cardiac systems, and there are few reports on the removal of pinned scroll waves in 3D cardiac tissues by electric fields. In this article, we investigate in detail the removal of pinned scroll waves in a generic model of 3D excitable media using PDCEF, AC electric field (ACEF) and CPEF, respectively. We find that spherical waves can be induced from the heterogeneities by these electric fields in initially quiescent excitable media. However, only CPEF can induce spherical waves with frequencies higher than that of the pinned scroll wave. Such higher-frequency spherical waves induced by CPEF can be used to drive the pinned scroll wave out of the cardiac systems. We hope this remarkable ability of CPEF can provide a better alternative to terminate arrhythmias caused by pinned scroll waves.

Energy-optimal electrical excitation of nerve fibers.

PubMed

Jezernik, Saso; Morari, Manfred

2005-04-01

We derive, based on an analytical nerve membrane model and optimal control theory of dynamical systems, an energy-optimal stimulation current waveform for electrical excitation of nerve fibers. Optimal stimulation waveforms for nonleaky and leaky membranes are calculated. The case with a leaky membrane is a realistic case. Finally, we compare the waveforms and energies necessary for excitation of a leaky membrane in the case where the stimulation waveform is a square-wave current pulse, and in the case of energy-optimal stimulation. The optimal stimulation waveform is an exponentially rising waveform and necessitates considerably less energy to excite the nerve than a square-wave pulse (especially true for larger pulse durations). The described theoretical results can lead to drastically increased battery lifetime and/or decreased energy transmission requirements for implanted biomedical systems.

Solid-state radiation-emitting compositions and devices

DOEpatents

Ashley, Carol S.; Brinker, C. Jeffrey; Reed, Scott; Walko, Robert J.

1992-01-01

The invention relates to a composition for the volumetric generation of radiation, wherein a first substance functions as a source of exciting radiation, and a second substance interacts with the exciting radiation to provide a second radiation. The compositions comprise a porous substrate which is loaded with: a source of exciting radiation, a component capable of emitting radiation upon interaction with the exciting radiation, or both. Preferably, the composition is an aerogel substrate loaded with both a source of exciting radiation, such as tritium, and a component capable of interacting with the exciting radiation, e.g., a phosphor, to produce radiation of a second energy.

Solid-state radiation-emitting compositions and devices

DOEpatents

Ashley, C.S.; Brinker, C.J.; Reed, S.; Walko, R.J.

1992-08-11

The invention relates to a composition for the volumetric generation of radiation, wherein a first substance functions as a source of exciting radiation, and a second substance interacts with the exciting radiation to provide a second radiation. The compositions comprise a porous substrate which is loaded with: a source of exciting radiation, a component capable of emitting radiation upon interaction with the exciting radiation, or both. Preferably, the composition is an aerogel substrate loaded with both a source of exciting radiation, such as tritium, and a component capable of interacting with the exciting radiation, e.g., a phosphor, to produce radiation of a second energy. 4 figs.

Multipactor experiment on a dielectric surface

NASA Astrophysics Data System (ADS)

Anderson, Rex Beach, III

2001-12-01

Multipactor is an electron multiplication process, or electron avalanche, that occurs on metallic and dielectric surfaces in the presence of rf microwave fields. Just as a rock avalanche only needs one rock to cause a larger slide of destruction, one electron under multipactor conditions can cause a tremendous amount of damage to electrical components. Multipactor is a nuisance that can cause excessive noise in communication satellites and radar, and damage to vacuum windows in particle accelerators. Single-surface multipactor on dielectrics is responsible for poor transmission properties of vacuum windows and can eventually lead to vacuum window failure. The repercussions of multipactor affect a wide range of people. For example, a civilian placing a call on a cell phone, or a captain dependent on radar for his ship's safety could both be affected by multipactor. In order to combat this expensive annoyance, a unique experiment to investigate single-surface multipactor on a dielectric surface was developed and tested. The motivation of this thesis is to introduce a novel experiment for multipactor that is designed to verify theoretical calculations and explore the physics behind the phenomenon. The compact apparatus consists of a small brass microwave cavity in a high vacuum system. Most single-surface multipactor experiments consist of a large resonant ring wave guide with a MW power supply. This experiment is the first to utilize a high Q resonant cavity and kW-level power supply to create multipactor on a dielectric surface. The small brass resonant cavity has an inner length of 9.154 cm with an inner diameter of 9.045 cm. A pulsed, variable frequency microwave source at ˜2.4 GHz, 2 kW peak excites the TE111 mode with a strong electric field parallel to a dielectric plate (˜0.2 cm thickness) that is inserted at the mid-plane of the cavity. The microwave pulses from the power supply are monitored by calibrated microwave diodes. These calibrated diodes along with a bead pull perturbation method are used to calculate the threshold rf fields at the dielectric surface when multipactor occurs. This experiment is the first to measure electron current from the dielectric using an electron probe. The electron probe provides temporal measurements of the multipactor electron current with respect to the microwave pulses. Another unique electron diagnostic utilized in this multipactor experiment is phosphor. Phosphor on the dielectric surface is used to detect multipactor electrons by photoemission. Phosphors with different excitation energies are used as a crude electron energy analyzer. Experimental results from these diagnostics match well with theoretical calculations.

Magneto- to electroactive transmutation of spin waves in ErMnO3.

PubMed

Chaix, L; de Brion, S; Petit, S; Ballou, R; Regnault, L-P; Ollivier, J; Brubach, J-B; Roy, P; Debray, J; Lejay, P; Cano, A; Ressouche, E; Simonet, V

2014-04-04

The low-energy dynamical properties of the multiferroic hexagonal perovskite ErMnO3 have been studied by inelastic neutron scattering as well as terahertz and far infrared spectroscopies on a synchrotron source. From these complementary techniques, we have determined the magnon and crystal field spectra and identified a zone center magnon excitable only by the electric field of an electromagnetic wave. Using a comparison with the isostructural YMnO3 compound and crystal field calculations, we propose that this dynamical magnetoelectric process is due to the hybridization of a magnon with an electroactive crystal field transition.

Analysis of renewable energy sources and electric vehicle penetration into energy systems predominantly based on lignite

NASA Astrophysics Data System (ADS)

Dedinec, A.; Jovanovski, B.; Gajduk, A.; Markovska, N.; Kocarev, L.

2016-05-01

We consider an integration of renewable energy into transport and electricity sectors through vehicle to grid (V2G) technologies for an energy system that is predominantly based on lignite. The national energy system of Macedonia is modeled using EnergyPLAN which integrates energy for electricity, transport and heat, and includes hourly fluctuations in human needs and the environment. We show that electric-vehicles can provide the necessary storage enabling a fully renewable energy profile for Macedonia that can match the country's growing demand for energy. Furthermore, a large penetration of electric vehicles leads to a dramatic reduction of 47% of small particles and other air pollutants generated by car traffic in 2050.

Exploiting Electric and Magnetic Fields for Underwater Characterization

DTIC Science & Technology

2011-03-01

geophysical surveys are primarily limited to passive magnetic systems towed from a surface vessel. These systems utilize fluxgate , Overhauser, or atomic... magnetometer sensors, often deployed in arrays towed from the stern of small to moderate-size vessels. Active source electromagnetic methods have been

An Impulse Electric Motor for Driving Recording Instruments

NASA Technical Reports Server (NTRS)

Joachim, W F

1923-01-01

The chief purpose in undertaking the development of this synchronous motor was the creation of a very small, compact power source, capable of driving the film drums of the recording aircraft instruments designed by the staff of the National Advisory Committee for Aeronautics.

Basic and functional effects of transcranial Electrical Stimulation (tES)-An introduction.

PubMed

Yavari, Fatemeh; Jamil, Asif; Mosayebi Samani, Mohsen; Vidor, Liliane Pinto; Nitsche, Michael A

2018-02-01

Non-invasive brain stimulation (NIBS) has been gaining increased popularity in human neuroscience research during the last years. Among the emerging NIBS tools is transcranial electrical stimulation (tES), whose main modalities are transcranial direct, and alternating current stimulation (tDCS, tACS). In tES, a small current (usually less than 3mA) is delivered through the scalp. Depending on its shape, density, and duration, the applied current induces acute or long-lasting effects on excitability and activity of cerebral regions, and brain networks. tES is increasingly applied in different domains to (a) explore human brain physiology with regard to plasticity, and brain oscillations, (b) explore the impact of brain physiology on cognitive processes, and (c) treat clinical symptoms in neurological and psychiatric diseases. In this review, we give a broad overview of the main mechanisms and applications of these brain stimulation tools. Copyright © 2017 Elsevier Ltd. All rights reserved.

Nature-inspired polymer actuators for micro-fluidic mixing.

NASA Astrophysics Data System (ADS)

den Toonder, Jaap M. J.; Bos, Femke; de Goede, Judith; Anderson, Patrick

2007-11-01

One particular micro-fluidics manipulation mechanism ``designed'' by nature is that due to a covering of beating cilia over the external surface of micro-organisms (e.g. Paramecium). A cilium can be viewed as a small hair or flexible rod (in protozoa: typical length 10 microns and diameter 0.1 microns) which is attached to the surface. We have developed polymer micro-actuators, made with standard micro-technology processing, which respond to an applied electrical or magnetic field by changing their shape. The shape and size of the polymer actuators mimics that of cilia occurring in nature. Flow visualization experiments show that the cilia can generate substantial fluid velocities, in the order of 1 mm/s. In addition, using specially designed geometrical configurations of the cilia, very efficient mixing is obtained. Since the artificial cilia can be actively controlled using electrical signals, they have exciting applications in micro-fluidic devices.

Modifying Surface Energy of Graphene via Plasma-Based Chemical Functionalization to Tune Thermal and Electrical Transport at Metal Interfaces.

PubMed

Foley, Brian M; Hernández, Sandra C; Duda, John C; Robinson, Jeremy T; Walton, Scott G; Hopkins, Patrick E

2015-08-12

The high mobility exhibited by both supported and suspended graphene, as well as its large in-plane thermal conductivity, has generated much excitement across a variety of applications. As exciting as these properties are, one of the principal issues inhibiting the development of graphene technologies pertains to difficulties in engineering high-quality metal contacts on graphene. As device dimensions decrease, the thermal and electrical resistance at the metal/graphene interface plays a dominant role in degrading overall performance. Here we demonstrate the use of a low energy, electron-beam plasma to functionalize graphene with oxygen, fluorine, and nitrogen groups, as a method to tune the thermal and electrical transport properties across gold-single layer graphene (Au/SLG) interfaces. We find that while oxygen and nitrogen groups improve the thermal boundary conductance (hK) at the interface, their presence impairs electrical transport leading to increased contact resistance (ρC). Conversely, functionalization with fluorine has no impact on hK, yet ρC decreases with increasing coverage densities. These findings indicate exciting possibilities using plasma-based chemical functionalization to tailor the thermal and electrical transport properties of metal/2D material contacts.

Experimental Identification of Electric Field Excitation Mechanisms in a Structural Transition of Tokamak Plasmas

PubMed Central

Kobayashi, T.; Itoh, K.; Ido, T.; Kamiya, K.; Itoh, S.-I.; Miura, Y.; Nagashima, Y.; Fujisawa, A.; Inagaki, S.; Ida, K.; Hoshino, K.

2016-01-01

Self-regulation between structure and turbulence, which is a fundamental process in the complex system, has been widely regarded as one of the central issues in modern physics. A typical example of that in magnetically confined plasmas is the Low confinement mode to High confinement mode (L-H) transition, which is intensely studied for more than thirty years since it provides a confinement improvement necessary for the realization of the fusion reactor. An essential issue in the L-H transition physics is the mechanism of the abrupt “radial” electric field generation in toroidal plasmas. To date, several models for the L-H transition have been proposed but the systematic experimental validation is still challenging. Here we report the systematic and quantitative model validations of the radial electric field excitation mechanism for the first time, using a data set of the turbulence and the radial electric field having a high spatiotemporal resolution. Examining time derivative of Poisson’s equation, the sum of the loss-cone loss current and the neoclassical bulk viscosity current is found to behave as the experimentally observed radial current that excites the radial electric field within a few factors of magnitude. PMID:27489128

Neuronal excitability level transition induced by electrical stimulation

NASA Astrophysics Data System (ADS)

Florence, G.; Kurths, J.; Machado, B. S.; Fonoff, E. T.; Cerdeira, H. A.; Teixeira, M. J.; Sameshima, K.

2014-12-01

In experimental studies, electrical stimulation (ES) has been applied to induce neuronal activity or to disrupt pathological patterns. Nevertheless, the underlying mechanisms of these activity pattern transitions are not clear. To study these phenomena, we simulated a model of the hippocampal region CA1. The computational simulations using different amplitude levels and duration of ES revealed three states of neuronal excitability: burst-firing mode, depolarization block and spreading depression wave. We used the bifurcation theory to analyse the interference of ES in the cellular excitability and the neuronal dynamics. Understanding this process would help to improve the ES techniques to control some neurological disorders.

Excitation-resolved multispectral method for imaging pharmacokinetic parameters in dynamic fluorescent molecular tomography

NASA Astrophysics Data System (ADS)

Chen, Maomao; Zhou, Yuan; Su, Han; Zhang, Dong; Luo, Jianwen

2017-04-01

Imaging of the pharmacokinetic parameters in dynamic fluorescence molecular tomography (DFMT) can provide three-dimensional metabolic information for biological studies and drug development. However, owing to the ill-posed nature of the FMT inverse problem, the relatively low quality of the parametric images makes it difficult to investigate the different metabolic processes of the fluorescent targets with small distances. An excitation-resolved multispectral DFMT method is proposed; it is based on the fact that the fluorescent targets with different concentrations show different variations in the excitation spectral domain and can be considered independent signal sources. With an independent component analysis method, the spatial locations of different fluorescent targets can be decomposed, and the fluorescent yields of the targets at different time points can be recovered. Therefore, the metabolic process of each component can be independently investigated. Simulations and phantom experiments are carried out to evaluate the performance of the proposed method. The results demonstrated that the proposed excitation-resolved multispectral method can effectively improve the reconstruction accuracy of the parametric images in DFMT.

Three-dimensional photoacoustic imaging of vascular anatomy in small animals using an optical detection system

NASA Astrophysics Data System (ADS)

Zhang, Edward Z.; Laufer, Jan; Beard, Paul

2007-02-01

A 3D photoacoustic imaging instrument for characterising small animal models of human disease processes has been developed. The system comprises an OPO excitation source and a backward-mode planar ultrasound imaging head based upon a Fabry Perot polymer film sensing interferometer (FPI). The mirrors of the latter are transparent between 590 - 1200nm but highly reflective between 1500-1600nm. This enables nanosecond excitation laser pulses in the former wavelength range, where biological tissues are relatively transparent, to be transmitted through the sensor head into the tissue. The resulting photoacoustic signals arrive at the sensor where they modulate the optical thickness of the FPI and therefore its reflectivity. By scanning a CW focused interrogating laser beam at 1550nm across the surface of the sensor, the spatial-temporal distribution of the photoacoustic signals can therefore be mapped in 2D enabling a 3D photoacoustic image to be reconstructed. To demonstrate the application of the system to imaging small animals such as mice, 3D images of the vascular anatomy of the mouse brain and the microvasculature in the skin around the abdomen were obtained non invasively. It is considered that this system provides a practical alternative to photoacoustic scanners based upon piezoelectric detectors for high resolution non invasive small animal imaging.

Medical imaging systems

DOEpatents

Frangioni, John V [Wayland, MA

2012-07-24

A medical imaging system provides simultaneous rendering of visible light and fluorescent images. The system may employ dyes in a small-molecule form that remains in a subject's blood stream for several minutes, allowing real-time imaging of the subject's circulatory system superimposed upon a conventional, visible light image of the subject. The system may also employ dyes or other fluorescent substances associated with antibodies, antibody fragments, or ligands that accumulate within a region of diagnostic significance. In one embodiment, the system provides an excitation light source to excite the fluorescent substance and a visible light source for general illumination within the same optical guide that is used to capture images. In another embodiment, the system is configured for use in open surgical procedures by providing an operating area that is closed to ambient light. More broadly, the systems described herein may be used in imaging applications where a visible light image may be usefully supplemented by an image formed from fluorescent emissions from a fluorescent substance that marks areas of functional interest.

Electric field tomography for contactless imaging of resistivity in biomedical applications.

PubMed

Korjenevsky, A V

2004-02-01

The technique of contactless imaging of resistivity distribution inside conductive objects, which can be applied in medical diagnostics, has been suggested and analyzed. The method exploits the interaction of a high-frequency electric field with a conductive medium. Unlike electrical impedance tomography, no electric current is injected into the medium from outside. The interaction is accompanied with excitation of high-frequency currents and redistribution of free charges inside the medium leading to strong and irregular perturbation of the field's magnitude outside and inside the object. Along with this the considered interaction also leads to small and regular phase shifts of the field in the area surrounding the object. Measuring these phase shifts using a set of electrodes placed around the object enables us to reconstruct the internal structure of the medium. The basics of this technique, which we name electric field tomography (EFT), are described, simple analytical estimations are made and requirements for measuring equipment are formulated. The realizability of the technique is verified by numerical simulations based on the finite elements method. Results of simulation have confirmed initial estimations and show that in the case of EFT even a comparatively simple filtered backprojection algorithm can be used for reconstructing the static resistivity distribution in biological tissues.

Neuron matters: electric activation of neuronal tissue is dependent on the interaction between the neuron and the electric field.

PubMed

Ye, Hui; Steiger, Amanda

2015-08-12

In laboratory research and clinical practice, externally-applied electric fields have been widely used to control neuronal activity. It is generally accepted that neuronal excitability is controlled by electric current that depolarizes or hyperpolarizes the excitable cell membrane. What determines the amount of polarization? Research on the mechanisms of electric stimulation focus on the optimal control of the field properties (frequency, amplitude, and direction of the electric currents) to improve stimulation outcomes. Emerging evidence from modeling and experimental studies support the existence of interactions between the targeted neurons and the externally-applied electric fields. With cell-field interaction, we suggest a two-way process. When a neuron is positioned inside an electric field, the electric field will induce a change in the resting membrane potential by superimposing an electrically-induced transmembrane potential (ITP). At the same time, the electric field can be perturbed and re-distributed by the cell. This cell-field interaction may play a significant role in the overall effects of stimulation. The redistributed field can cause secondary effects to neighboring cells by altering their geometrical pattern and amount of membrane polarization. Neurons excited by the externally-applied electric field can also affect neighboring cells by ephaptic interaction. Both aspects of the cell-field interaction depend on the biophysical properties of the neuronal tissue, including geometric (i.e., size, shape, orientation to the field) and electric (i.e., conductivity and dielectricity) attributes of the cells. The biophysical basis of the cell-field interaction can be explained by the electromagnetism theory. Further experimental and simulation studies on electric stimulation of neuronal tissue should consider the prospect of a cell-field interaction, and a better understanding of tissue inhomogeneity and anisotropy is needed to fully appreciate the neural basis of cell-field interaction as well as the biological effects of electric stimulation.

Nonlinear Transport in Organic Thin Film Transistors with Soluble Small Molecule Semiconductor.

PubMed

Kim, Hyeok; Song, Dong-Seok; Kwon, Jin-Hyuk; Jung, Ji-Hoon; Kim, Do-Kyung; Kim, SeonMin; Kang, In Man; Park, Jonghoo; Tae, Heung-Sik; Battaglini, Nicolas; Lang, Philippe; Horowitz, Gilles; Bae, Jin-Hyuk

2016-03-01

Nonlinear transport is intensively explained through Poole-Frenkel (PF) transport mechanism in organic thin film transistors with solution-processed small molecules, which is, 6,13-bis(triisopropylsilylethynyl) (TIPS) pentacene. We outline a detailed electrical study that identifies the source to drain field dependent mobility. Devices with diverse channel lengths enable the extensive exhibition of field dependent mobility due to thermal activation of carriers among traps.

Small gas-turbine units for the power industry: Ways for improving the efficiency and the scale of implementation

NASA Astrophysics Data System (ADS)

Kosoi, A. S.; Popel', O. S.; Beschastnykh, V. N.; Zeigarnik, Yu. A.; Sinkevich, M. V.

2017-10-01

Small power units (<1 MW) see increasing application due to enhanced growth of the distributed power generation and smart power supply systems. They are usually used for feeding facilities whose connection to centralized networks involves certain problems of engineering or economical nature. Small power generation is based on a wide range of processes and primary sources, including renewable and local ones, such as nonconventional hydrocarbon fuel comprising associated gas, biogas, coalmine methane, etc. Characteristics of small gas-turbine units (GTU) that are most widely available on the world market are reviewed. The most promising lines for the development of the new generation of small GTUs are examined. Special emphasis is placed on the three lines selected for improving the efficiency of small GTUs: increasing the fuel efficiency, cutting down the maintenance cost, and integration with local or renewable power sources. It is demonstrated that, as to the specific fuel consumption, small GTUs of the new generation can have an efficiency 20-25% higher than those of the previous generation, require no maintenance between overhauls, and can be capable of efficient integration into intelligent electrical networks with power facilities operating on renewable or local power sources.

Magnetic structures and excitations in a multiferroic Y-type hexaferrite BaSrCo 2 Fe 11 AlO 22

DOE PAGES

Nakajima, Taro; Tokunaga, Yusuke; Matsuda, Masaaki; ...

2016-11-30

Here, we have investigated magnetic orders and excitations in a Y-type hexaferrite BaSrCo 2Fe 11AlO 22 (BSCoFAO), which was reported to exhibit spin-driven ferroelectricity at room temperature. By means of magnetization, electric polarization, and neutron-diffraction measurements using single-crystal samples, we establish a H-T magnetic phase diagram for magnetic field perpendicular to the c axis (H ⟂c). This system exhibits an alternating longitudinal conical (ALC) magnetic structure in the ground state, and it turns into a non-co-planar commensurate magnetic order with spin-driven ferroelectricity under H ⟂c. The field-induced ferroelectric phase remains as a metastable state after removing magnetic field below 250more » K. This metastability is the key to understanding of magnetic field reversal of the spin-driven electric polarization in this system. Inelastic polarized neutron-scattering measurements in the ALC phase reveal a magnetic excitation at around 7.5 meV, which is attributed to spin components oscillating in a plane perpendicular to the cone axis. This phasonlike excitation is expected to be an electric-field active magnon, i.e., electromagnon excitation, in terms of the magnetostriction mechanism.« less

Magnetic structures and excitations in a multiferroic Y-type hexaferrite BaSrCo2Fe11AlO22

NASA Astrophysics Data System (ADS)

Nakajima, Taro; Tokunaga, Yusuke; Matsuda, Masaaki; Dissanayake, Sachith; Fernandez-Baca, Jaime; Kakurai, Kazuhisa; Taguchi, Yasujiro; Tokura, Yoshinori; Arima, Taka-hisa

2016-11-01

We have investigated magnetic orders and excitations in a Y-type hexaferrite BaSrCo2Fe11AlO22 (BSCoFAO), which was reported to exhibit spin-driven ferroelectricity at room temperature [S. Hirose, K. Haruki, A. Ando, and T. Kimura, Appl. Phys. Lett. 104, 022907 (2014), 10.1063/1.4862432]. By means of magnetization, electric polarization, and neutron-diffraction measurements using single-crystal samples, we establish a H -T magnetic phase diagram for magnetic field perpendicular to the c axis (H⊥c). This system exhibits an alternating longitudinal conical (ALC) magnetic structure in the ground state, and it turns into a non-co-planar commensurate magnetic order with spin-driven ferroelectricity under H⊥c. The field-induced ferroelectric phase remains as a metastable state after removing magnetic field below ˜250 K. This metastability is the key to understanding of magnetic field reversal of the spin-driven electric polarization in this system. Inelastic polarized neutron-scattering measurements in the ALC phase reveal a magnetic excitation at around 7.5 meV, which is attributed to spin components oscillating in a plane perpendicular to the cone axis. This phasonlike excitation is expected to be an electric-field active magnon, i.e., electromagnon excitation, in terms of the magnetostriction mechanism.

Linear excitation and detection in Fourier transform ion cyclotron resonance mass spectrometry

NASA Astrophysics Data System (ADS)

Grosshans, Peter B.; Chen, Ruidan; Limbach, Patrick A.; Marshall, Alan G.

1994-11-01

We present the first Fourier transform ion cyclotron resonance (FT-ICR) ion trap designed to produce both a linear spatial variation of the excitation electric potential field and a linear response of the detection circuit to the motion of the confined ions. With this trap, the magnitude of the detected signal at a given ion cyclotron frequency varies linearly with both the number of ions of given mass-to-charge ratio and also with the magnitude-mode excitation signal at the ion cyclotron orbital frequency; the proportionality constant is mass independent. Interestingly, this linearization may be achieved with any ion trap geometry. The excitation/detection design consists of an array of capacitively coupled electrodes which provide a voltage-divider network that produces a nearly spatially homogeneous excitation electric field throughout the linearized trap; resistive coupling to the electrodes isolates the a.c. excitation (or detection) circuit from the d.c. (trapping) potential. The design is based on analytical expressions for the potential associated with each electrode, from which we are able to compute the deviation from linearity for a trap with a finite number of elements. Based on direct experimental comparisons to an unmodified cubic trap, the linearized trap demonstrates the following performance advantages at the cost of some additional mechanical complexity: (a) signal response linearly proportional to excitation electric field amplitude; (b) vastly reduced axial excitation/ejection for significantly improved ion relative abundance accuracy; (c) elimination of harmonics and sidebands of the fundamental frequencies of ion motion. As a result, FT-ICR mass spectra are now more reproducible. Moreover, the linearized trap should facilitate the characterization of other fundamental aspects of ion behavior in an ICR ion trap, e.g. effects of space charge, non-quadrupolar electrostatic trapping field, etc. Furthermore, this novel design should improve significantly the precision of ion relative abundance and mass accuracy measurements, while removing spectral artifacts of the detection process. We discuss future modifications that linearize the spatial variation of the electrostatic trapping electric field as well, thereby completing the linearization of the entire FT-ICR mass spectrometric techniques. Suggested FT-ICR mass spectrometric applications for the linearized trap are discussed.

Nanocrystal powered nanomotor

DOEpatents

Regan, Brian C [Los Angeles, CA; Zettl, Alexander K [Kensington, CA; Aloni, Shaul [Albany, CA

2011-01-04

A nanoscale nanocrystal which may be used as a reciprocating motor is provided, comprising a substrate having an energy differential across it, e.g. an electrical connection to a voltage source at a proximal end; an atom reservoir on the substrate distal to the electrical connection; a nanoparticle ram on the substrate distal to the atom reservoir; a nanolever contacting the nanoparticle ram and having an electrical connection to a voltage source, whereby a voltage applied between the electrical connections on the substrate and the nanolever causes movement of atoms between the reservoir and the ram. Movement of the ram causes movement of the nanolever relative to the substrate. The substrate and nanolever preferably comprise multiwalled carbon nanotubes (MWNTs) and the atom reservoir and nanoparticle ram are preferably metal (e.g. indium) deposited as small particles on the MWNTs. The substrate may comprise a silicon chip that has been fabricated to provide the necessary electrodes and other electromechanical structures, and further supports an atomic track, which may comprise an MWNT.

Investigation of a 129Xe magnetometer for the Neutron Electric Dipole Moment Experiment at TRIUMF

NASA Astrophysics Data System (ADS)

Lang, Michael; Nedm At Triumf Collaboration

2016-03-01

A non-zero neutron electric dipole moment (nEDM) would signify a previously unknown source of CP (or T) violation. New sources of CP violation are believed to be required to explain the baryon asymmetry of the universe. Employing a newly developed high-density UCN source, an experiment at TRIUMF aims to measure the nEDM to the level of 10-27 e . cm in its initial phase. Precession frequency differences for UCN stored in a bottle subject to parallel and anti-parallel E and B fields signify a permanent nEDM. Magnetic field instability and inhomogeneity, as well as field changes resulting from leakage currents (correlated with E fields) are the dominant systematic effects in nEDM measurements. To address this, passive and active magnetic shielding are in development along with a dual species (129Xe and 199Hg) atomic comagnetometer. Simultaneously introducing both atomic species into the UCN cell, the comagnetometer can mitigate false EDMs. 199Hg precession will be detected by Faraday rotation spectroscopy, and 129Xe precession will measured via two-photon excitation and emission. The present comagnetometer progress will be discussed, with focus on polarized 129Xe production and delivery. Work supported by the Natural Sciences and Engineering Research Council of Canada.

The local density of optical states of a metasurface

NASA Astrophysics Data System (ADS)

Lunnemann, Per; Koenderink, A. Femius

2016-02-01

While metamaterials are often desirable for near-field functions, such as perfect lensing, or cloaking, they are often quantified by their response to plane waves from the far field. Here, we present a theoretical analysis of the local density of states near lattices of discrete magnetic scatterers, i.e., the response to near field excitation by a point source. Based on a pointdipole theory using Ewald summation and an array scanning method, we can swiftly and semi-analytically evaluate the local density of states (LDOS) for magnetoelectric point sources in front of an infinite two-dimensional (2D) lattice composed of arbitrary magnetoelectric dipole scatterers. The method takes into account radiation damping as well as all retarded electrodynamic interactions in a self-consistent manner. We show that a lattice of magnetic scatterers evidences characteristic Drexhage oscillations. However, the oscillations are phase shifted relative to the electrically scattering lattice consistent with the difference expected for reflection off homogeneous magnetic respectively electric mirrors. Furthermore, we identify in which source-surface separation regimes the metasurface may be treated as a homogeneous interface, and in which homogenization fails. A strong frequency and in-plane position dependence of the LDOS close to the lattice reveals coupling to guided modes supported by the lattice.

Equivalent circuit and characteristic simulation of a brushless electrically excited synchronous wind power generator

NASA Astrophysics Data System (ADS)

Wang, Hao; Zhang, Fengge; Guan, Tao; Yu, Siyang

2017-09-01

A brushless electrically excited synchronous generator (BEESG) with a hybrid rotor is a novel electrically excited synchronous generator. The BEESG proposed in this paper is composed of a conventional stator with two different sets of windings with different pole numbers, and a hybrid rotor with powerful coupling capacity. The pole number of the rotor is different from those of the stator windings. Thus, an analysis method different from that applied to conventional generators should be applied to the BEESG. In view of this problem, the equivalent circuit and electromagnetic torque expression of the BEESG are derived on the basis of electromagnetic relation of the proposed generator. The generator is simulated and tested experimentally using the established equivalent circuit model. The experimental and simulation data are then analyzed and compared. Results show the validity of the equivalent circuit model.

Comparison of electric dipole and magnetic loop antennas for exciting whistler modes

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

Stenzel, R. L.; Urrutia, J. M.

2016-08-15

The excitation of low frequency whistler modes from different antennas has been investigated experimentally in a large laboratory plasma. One antenna consists of a linear electric dipole oriented across the uniform ambient magnetic field B{sub 0}. The other antenna is an elongated loop with dipole moment parallel to B{sub 0}. Both antennas are driven by the same rf generator which produces a rf burst well below the electron cyclotron frequency. The antenna currents as well as the wave magnetic fields from each antenna are measured. Both the antenna currents and the wave fields of the loop antenna exceed that ofmore » the electric dipole by two orders of magnitude. The conclusion is that loop antennas are far superior to dipole antennas for exciting large amplitude whistler modes, a result important for active wave experiments in space plasmas.« less

Reliability and cost/worth evaluation of generating systems utilizing wind and solar energy

NASA Astrophysics Data System (ADS)

Bagen

The utilization of renewable energy resources such as wind and solar energy for electric power supply has received considerable attention in recent years due to adverse environmental impacts and fuel cost escalation associated with conventional generation. At the present time, wind and/or solar energy sources are utilized to generate electric power in many applications. Wind and solar energy will become important sources for power generation in the future because of their environmental, social and economic benefits, together with public support and government incentives. The wind and sunlight are, however, unstable and variable energy sources, and behave far differently than conventional sources. Energy storage systems are, therefore, often required to smooth the fluctuating nature of the energy conversion system especially in small isolated applications. The research work presented in this thesis is focused on the development and application of reliability and economic benefits assessment associated with incorporating wind energy, solar energy and energy storage in power generating systems. A probabilistic approach using sequential Monte Carlo simulation was employed in this research and a number of analyses were conducted with regards to the adequacy and economic assessment of generation systems containing wind energy, solar energy and energy storage. The evaluation models and techniques incorporate risk index distributions and different operating strategies associated with diesel generation in small isolated systems. Deterministic and probabilistic techniques are combined in this thesis using a system well-being approach to provide useful adequacy indices for small isolated systems that include renewable energy and energy storage. The concepts presented and examples illustrated in this thesis will help power system planners and utility managers to assess the reliability and economic benefits of utilizing wind energy conversion systems, solar energy conversion systems and energy storage in electric power systems and provide useful input to the managerial decision process.

BCI federal legislative & regulatory update

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

NONE

1995-02-01

Several updates on recent government actions that affect the battery industry are outlined. The National Highway Traffic Safety Administration is requesting public comments on how to regulate electric vehicles (EV) with respect to battery electrolyte spillage and electric shock hazard during crashes or rollovers, as well as during repair or maintenance. The Environmental Protection Agency (EPA) was mentioned in two actions: the monitoring rule regarding major sources of air pollution and the reccomendation of reasearch concerning hazardous air pollutants from small stationary sources. OSHA will develop a new standards planning process to ensure that the agency`s limited resources are usedmore » appropriately. This includes a list of fifty workplace hazards or issues that would warrant OSHA action.« less

Nerve Impulses in Plants

ERIC Educational Resources Information Center

Blatt, F. J.

1974-01-01

Summarizes research done on the resting and action potential of nerve impulses, electrical excitation of nerve cells, electrical properties of Nitella, and temperature effects on action potential. (GS)

Electric currents induced by twisted light in Quantum Rings.

PubMed

Quinteiro, G F; Berakdar, J

2009-10-26

We theoretically investigate the generation of electric currents in quantum rings resulting from the optical excitation with twisted light. Our model describes the kinetics of electrons in a two-band model of a semiconductor-based mesoscopic quantum ring coupled to light having orbital angular momentum (twisted light). We find the analytical solution, which exhibits a "circular" photon-drag effect and an induced magnetization, suggesting that this system is the circular analog of that of a bulk semiconductor excited by plane waves. For realistic values of the electric field and material parameters, the computed electric current can be as large as microA; from an applied perspective, this opens new possibilities to the optical control of the magnetization in semiconductors.

Solid-state radiation-emitting compositions and devices

DOEpatents

Ashley, Carol S.; Brinker, C. Jeffrey; Reed, Scott; Shepodd, Timothy J.; Leonard, Leroy E.; Ellefson, Robert E.; Gill, John T.; Walko, Robert J.; Renschler, Clifford L.

1992-01-01

The invention relates to a composition for the volumetric generation of radiation, wherein a first substance functions as a source of exciting radiation, and a second substance interacts with the exciting radiation to provide a second radiation. The compositions comprise a porous substrate which is loaded with: a source of exciting radiation, a component capable of emitting radiation upon interaction with the exciting radiation, or both. In the composition, a composite is formed from a carrier material and at least one of the source of the exciting radiation or the component which is capable of interacting with the exciting radiation. The composite is then employed for loading a porous substrate, preferably an aerogel substrate.

Introduction to power-frequency electric and magnetic fields.

PubMed Central

Kaune, W T

1993-01-01

This paper introduces the reader to electric and magnetic fields, particularly those fields produced by electric power systems and other sources using frequencies in the power-frequency range. Electric fields are produced by electric charges; a magnetic field also is produced if these charges are in motion. Electric fields exert forces on other charges; if in motion, these charges will experience magnetic forces. Power-frequency electric and magnetic fields induce electric currents in conducting bodies such as living organisms. The current density vector is used to describe the distribution of current within a body. The surface of the human body is an excellent shield for power-frequency electric fields, but power-frequency magnetic fields penetrate without significant attenuation; the electric fields induced inside the body by either exposure are comparable in magnitude. Electric fields induced inside a human by most environmental electric and magnetic fields appear to be small in magnitude compared to levels naturally occurring in living tissues. Detection of such fields thus would seem to require the existence of unknown biological mechanisms. Complete characterization of a power-frequency field requires measurement of the magnitudes and electrical phases of the fundamental and harmonic amplitudes of its three vector components. Most available instrumentation measures only a small subset, or some weighted average, of these quantities. Hand-held survey meters have been used widely to measure power-frequency electric and magnetic fields. Automated data-acquisition systems have come into use more recently to make electric- and magnetic-field recordings, covering periods of hours to days, in residences and other environments.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:8206045

Radiative rates and electron impact excitation rate coefficients for Ne-like selenium, Se XXV

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

Wang, K.; Chen, C.Y., E-mail: chychen@fudan.edu.cn; Huang, M.

2011-07-15

In this article we report calculations of energy levels, radiative rates, electron impact collision strengths, and effective collision strengths for transitions among the 241 fine-structure levels arising from 2l{sup 8} and 2l{sup 7}n{sup '}l{sup '} (n{sup '{<=}}6 and l{sup '{<=}}n{sup '}-1) configurations of Ne-like Se XXV using the Flexible Atomic Code. Energy levels and radiative rates are calculated within the relativistic configuration-interaction method. Direct excitation collision strengths are calculated using the relativistic distorted-wave approximation and high-energy collision strengths are obtained in the relativistic plane-wave approximation. Resonance contributions through the relevant Na-like doubly-excited configurations 2l{sup 7}n'l'n''l'' (3{<=}n'{<=}7, l'{<=}n'-1, n'{<=}n''{<=}50, and l''{<=}8)more » are explicitly taken into account via the independent-process and isolated-resonance approximation using distorted waves. Resonant stabilizing transitions and possibly important radiative decays from the resonances toward low-lying autoionizing levels are considered. In addition, the resonance contributions from Na-like 2l{sup 6}3l'3l'''n''' (n'''=3-6) configurations are included and found to be predominant for many transitions among the singly-excited states in Ne-like Se XXV. We present the radiative rates, oscillator strengths, and line strengths for all electric dipole, magnetic dipole, electric quadrupole, magnetic quadrupole, electric octopole, and magnetic octopole transitions among the 241 levels. The effective collision strengths are reported for all 28920 transitions among the 241 levels over a wide temperature range up to 10 keV. To assess the reliability and accuracy of the present collisional data, we have performed a 27-state close-coupling calculation, employing the Dirac R-matrix theory. The results from the close-coupling calculation and the independent-process calculation for the identical target states are found to be in good agreement. - Highlights: {yields} Radiative and collisional atomic data are presented for the lowest 241 fine-structure levels in Ne-like Se. {yields} Calculations are performed using the FAC package. {yields} Resonances enhance significantly a large amount of transitions. {yields} Radiative damping effects are significant for many transitions. {yields} Close-coupling effects are small in Ne-like Se.« less

46 CFR 183.370 - General grounding requirements.

Code of Federal Regulations, 2012 CFR

2012-10-01

... 46 Shipping 7 2012-10-01 2012-10-01 false General grounding requirements. 183.370 Section 183.370 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) SMALL PASSENGER VESSELS (UNDER 100 GROSS TONS) ELECTRICAL INSTALLATION Power Sources and Distribution Systems § 183.370 General grounding...

46 CFR 183.378 - Ungrounded systems.

Code of Federal Regulations, 2013 CFR

2013-10-01

... 46 Shipping 7 2013-10-01 2013-10-01 false Ungrounded systems. 183.378 Section 183.378 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) SMALL PASSENGER VESSELS (UNDER 100 GROSS TONS) ELECTRICAL INSTALLATION Power Sources and Distribution Systems § 183.378 Ungrounded systems. Each ungrounded...

46 CFR 183.378 - Ungrounded systems.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 46 Shipping 7 2011-10-01 2011-10-01 false Ungrounded systems. 183.378 Section 183.378 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) SMALL PASSENGER VESSELS (UNDER 100 GROSS TONS) ELECTRICAL INSTALLATION Power Sources and Distribution Systems § 183.378 Ungrounded systems. Each ungrounded...

46 CFR 183.360 - Semiconductor rectifier systems.

Code of Federal Regulations, 2014 CFR

2014-10-01

... 46 Shipping 7 2014-10-01 2014-10-01 false Semiconductor rectifier systems. 183.360 Section 183.360 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) SMALL PASSENGER VESSELS (UNDER 100 GROSS TONS) ELECTRICAL INSTALLATION Power Sources and Distribution Systems § 183.360 Semiconductor rectifier...

46 CFR 183.324 - Dual voltage generators.

Code of Federal Regulations, 2013 CFR

2013-10-01

... 46 Shipping 7 2013-10-01 2013-10-01 false Dual voltage generators. 183.324 Section 183.324 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) SMALL PASSENGER VESSELS (UNDER 100 GROSS TONS) ELECTRICAL INSTALLATION Power Sources and Distribution Systems § 183.324 Dual voltage generators...

46 CFR 183.360 - Semiconductor rectifier systems.

Code of Federal Regulations, 2012 CFR

2012-10-01

... 46 Shipping 7 2012-10-01 2012-10-01 false Semiconductor rectifier systems. 183.360 Section 183.360 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) SMALL PASSENGER VESSELS (UNDER 100 GROSS TONS) ELECTRICAL INSTALLATION Power Sources and Distribution Systems § 183.360 Semiconductor rectifier...

46 CFR 183.324 - Dual voltage generators.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 46 Shipping 7 2011-10-01 2011-10-01 false Dual voltage generators. 183.324 Section 183.324 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) SMALL PASSENGER VESSELS (UNDER 100 GROSS TONS) ELECTRICAL INSTALLATION Power Sources and Distribution Systems § 183.324 Dual voltage generators...

46 CFR 183.324 - Dual voltage generators.

Code of Federal Regulations, 2014 CFR

2014-10-01

... 46 Shipping 7 2014-10-01 2014-10-01 false Dual voltage generators. 183.324 Section 183.324 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) SMALL PASSENGER VESSELS (UNDER 100 GROSS TONS) ELECTRICAL INSTALLATION Power Sources and Distribution Systems § 183.324 Dual voltage generators...

46 CFR 183.324 - Dual voltage generators.

Code of Federal Regulations, 2012 CFR

2012-10-01

... 46 Shipping 7 2012-10-01 2012-10-01 false Dual voltage generators. 183.324 Section 183.324 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) SMALL PASSENGER VESSELS (UNDER 100 GROSS TONS) ELECTRICAL INSTALLATION Power Sources and Distribution Systems § 183.324 Dual voltage generators...

46 CFR 183.360 - Semiconductor rectifier systems.

Code of Federal Regulations, 2013 CFR

2013-10-01

... 46 Shipping 7 2013-10-01 2013-10-01 false Semiconductor rectifier systems. 183.360 Section 183.360 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) SMALL PASSENGER VESSELS (UNDER 100 GROSS TONS) ELECTRICAL INSTALLATION Power Sources and Distribution Systems § 183.360 Semiconductor rectifier...

46 CFR 183.370 - General grounding requirements.

Code of Federal Regulations, 2013 CFR

2013-10-01

... 46 Shipping 7 2013-10-01 2013-10-01 false General grounding requirements. 183.370 Section 183.370 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) SMALL PASSENGER VESSELS (UNDER 100 GROSS TONS) ELECTRICAL INSTALLATION Power Sources and Distribution Systems § 183.370 General grounding...

Angular distribution and polarization of atomic radiative emission in electric and magnetic fields

NASA Astrophysics Data System (ADS)

Jacobs, V. L.; Filuk, A. B.

1999-09-01

A density-matrix approach has been developed for the angular distribution and polarization of radiative emission during single-photon atomic transitions for a general set of steady-state excitation processes in an arbitrary arrangement of static (or quasistatic) electric and magnetic fields. Particular attention has been directed at spectroscopic observations in the intense fields of the high-power ion diodes on the Particle Beam Fusion Accelerator II (PBFA II) and SABRE devices at Sandia National Laboratories and at magnetic-field measurements in tokamak plasmas. The field-dependent atomic eigenstates are represented as expansions in a complete basis set of field-free bound and continuum eigenstates. Particular emphasis has been given to directed-electron collisional excitations, which may be produced by an anisotropic incident-electron velocity distribution. We have allowed for the possibility of the coherent excitation of the nearly degenerate field-dependent atomic substates, which can give rise to a complex spectral pattern of overlapping Stark-Zeeman components. Coherent excitations may be produced by a beam of electrons that are spin-polarized at an angle with respect to the propagation direction or by nonparallel electric and magnetic fields. Our main result is a general expression for the matrix elements of the photon-polarization density operator representing the total intensity, angular distribution, and polarization of the atomic radiative emission. For the observation of radiative emission in the direction of the magnetic field, the detection of linearly polarized emission, in addition to the usual circularly polarized radiation, can reveal the presence of a perpendicular electric field or a coherent excitation mechanism.

Angular distribution and polarization of atomic radiative emission in electric and magnetic fields

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

Jacobs, V.L.; Filuk, A.B.

A density-matrix approach has been developed for the angular distribution and polarization of radiative emission during single-photon atomic transitions for a general set of steady-state excitation processes in an arbitrary arrangement of static (or quasistatic) electric and magnetic fields. Particular attention has been directed at spectroscopic observations in the intense fields of the high-power ion diodes on the Particle Beam Fusion Accelerator II (PBFA II) and SABRE devices at Sandia National Laboratories and at magnetic-field measurements in tokamak plasmas. The field-dependent atomic eigenstates are represented as expansions in a complete basis set of field-free bound and continuum eigenstates. Particular emphasismore » has been given to directed-electron collisional excitations, which may be produced by an anisotropic incident-electron velocity distribution. We have allowed for the possibility of the coherent excitation of the nearly degenerate field-dependent atomic substates, which can give rise to a complex spectral pattern of overlapping Stark-Zeeman components. Coherent excitations may be produced by a beam of electrons that are spin-polarized at an angle with respect to the propagation direction or by nonparallel electric and magnetic fields. Our main result is a general expression for the matrix elements of the photon-polarization density operator representing the total intensity, angular distribution, and polarization of the atomic radiative emission. For the observation of radiative emission in the direction of the magnetic field, the detection of linearly polarized emission, in addition to the usual circularly polarized radiation, can reveal the presence of a perpendicular electric field or a coherent excitation mechanism.« less

Medical aspects of power generation, present and future.

PubMed

Linnemann, R E

1979-01-01

It can be seen that the radiation emissions of nuclear power plants are small indeed, compared to natural background radiation and other man-made sources of radiation. For example, the poulation is exposed to 100 times more radiation from television sets than from nuclear power reactors. The assumed risks to the people in this country from nuclear power reactors are also small compared to the normal risks which are tolerated in this society. The complete elimination of all hazards is a most difficult if not impossible task. If we need and desire a certain level of electrical energy, if we must choose between alternative sourves of the energy, then it is apparent that the total impact on our health from nuclear power generation of electricity, under normal operations and in consideration of catastrophic accident probabilities, is significantly less than that of continuing or increasing use of fossil fuels to generate electricity.

Economic analysis of small wind-energy conversion systems

NASA Astrophysics Data System (ADS)

Haack, B. N.

1982-05-01

A computer simulation was developed for evaluating the economics of small wind energy conversion systems (SWECS). Input parameters consisted of initial capital investment, maintenance and operating costs, the cost of electricity from other sources, and the yield of electricity. Capital costs comprised the generator, tower, necessity for an inverter and/or storage batteries, and installation, in addition to interest on loans. Wind data recorded every three hours for one year in Detroit, MI was employed with a 0.16 power coefficient to extrapolate up to hub height as an example, along with 10 yr of use variances. A maximum return on investment was found to reside in using all the energy produced on site, rather than selling power to the utility. It is concluded that, based on a microeconomic analysis, SWECS are economically viable at present only where electric rates are inordinately high, such as in remote regions or on islands.

What Gets a Cell Excited? Kinky Curves

ERIC Educational Resources Information Center

Kay, Alan R.

2014-01-01

Hodgkin and Huxley's (5) revealing the origins of cellular excitability is one of the great triumphs of physiology. In an extraordinarily deft series of papers, they were able to measure the essential electrical characteristics of neurons and synthesize them into a quantitative model that accounts for the excitability of neurons and other…

Integration and Utilization of Nuclear Systems on the Moon and Mars

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

Houts, Michael G.; Schmidt, George R.; Bragg-Sitton, Shannon

2006-01-20

Over the past five decades numerous studies have identified nuclear energy as an enhancing or enabling technology for planetary surface exploration missions. This includes both radioisotope and fission sources for providing both heat and electricity. Nuclear energy sources were used to provide electricity on Apollo missions 12, 14, 15, 16, and 17, and on the Mars Viking landers. Very small nuclear energy sources were used to provide heat on the Mars Pathfinder, Spirit, and Opportunity rovers. Research has been performed at NASA MSFC to help assess potential issues associated with surface nuclear energy sources, and to generate data that couldmore » be useful to a future program. Research areas include System Integration, use of Regolith as Radiation Shielding, Waste Heat Rejection, Surface Environmental Effects on the Integrated System, Thermal Simulators, Surface System Integration / Interface / Interaction Testing, End-to-End Breadboard Development, Advanced Materials Development, Surface Energy Source Coolants, and Planetary Surface System Thermal Management and Control. This paper provides a status update on several of these research areas.« less

Pulsed excitation system to measure the resonant frequency of magnetoelastic biosensors

NASA Astrophysics Data System (ADS)

Xie, Hong; Chai, Yating; Horikawa, Shin; Wikle, Howard C.; Chin, Bryan A.

2014-05-01

An electrical circuit was designed and tested to measure the resonant frequency of micron-scale magnetoelastic (ME) biosensors using a pulsed wave excitation technique. In this circuit, a square pulse current is applied to an excitation coil to excite the vibration of ME biosensors and a pick-up coil is used to sense the ME biosensor's mechanical vibration and convert it to an electrical output signal. The output signal is filtered and amplified by a custom designed circuit to allow the measurement of the resonant frequency of the ME biosensor from which the detection of specific pathogens can be made. As a proof-in-concept experiment, JRB7 phage-coated ME biosensors were used to detect different concentrations of Bacillus anthracis Sterne strain spores. A statistically significant difference was observed for concentrations of 5 × 102 spore/ml and above.

Actively adjustable step-type ultrasonic horns in longitudinal vibration

NASA Astrophysics Data System (ADS)

Lin, Shuyu; Guo, Hao; Xu, Jie

2018-04-01

Actively adjustable longitudinal step-type ultrasonic horns are proposed and studied. The horn is composed of a traditional ultrasonic horn and piezoelectric material. In practical applications, this kind of step-type ultrasonic horn is mechanically excited by an ultrasonic transducer and the piezoelectric material is connected to an adjustable electric impedance. In this research, the effects of the electric impedance and of the location of the piezoelectric material on the performance of the horn are studied. It is shown that when the electric resistance is increased, the resonance frequency of the horn is increased; the displacement magnification is increased when the piezoelectric material is located in the large end and decreased when the piezoelectric material is located in the small end of the horn. The displacement magnification for the piezoelectric material in the large end is larger than that for the piezoelectric material in the small end of the horn. Some step-type ultrasonic horns are designed and manufactured; the resonance frequency and the displacement magnification are measured by means of POLYTEC Laser Scanning vibrometer. It is shown that the theoretical resonance frequency and the displacement magnification are in good agreement with the measured results. It is concluded that by means of the insertion of the piezoelectric material in the longitudinal horn, the horn performance can be adjusted by changing the electric impedance and the location of the piezoelectric material in the horn. It is expected that this kind of adjustable ultrasonic horns can be used in traditional and potential ultrasonic technologies where the vibrational performance adjustment is needed.

Deep subwavelength fourfold rotationally symmetric split-ring-resonator metamaterials for highly sensitive and robust biosensing platform

PubMed Central

Tobing, Landobasa Y. M.; Tjahjana, Liliana; Zhang, Dao Hua; Zhang, Qing; Xiong, Qihua

2013-01-01

Metamaterials provide a good platform for biochemical sensing due to its strong field localization at nanoscale. In this work, we show that electric and magnetic resonant modes in split-ring-resonator (SRR) can be efficiently excited under unpolarized light illumination when the SRRs are arranged in fourfold rotationally symmetric lattice configuration. The fabrication and characterization of deep subwavelength (~λ/15) gold-based SRR structures with resonator size as small as ~ 60 nm are reported with magnetic resonances in Vis-NIR spectrum range. The feasibility for sensing is demonstrated with refractive index sensitivity as high as ~ 636 nm/RIU. PMID:23942416

Nonlinear cascades in two-dimensional turbulent magnetoconvection.

PubMed

Skandera, Dan; Müller, Wolf-Christian

2009-06-05

The dynamics of spectral transport in two-dimensional turbulent convection of electrically conducting fluids is studied by means of direct numerical simulations in the frame of the magnetohydrodynamic Boussinesq approximation. The system performs quasioscillations between two different regimes of small-scale turbulence: one dominated by nonlinear magnetohydrodynamic interactions; the other governed by buoyancy forces. The self-excited change of turbulent states is reported here for the first time. The process is controlled by the ideal invariant cross helicity, H;{C}=integral_{S}dSv.b. The observations are explained by the interplay of convective driving with the nonlinear spectral transfer of total magnetohydrodynamic energy and cross helicity.

Non-Gaussian Multi-resolution Modeling of Magnetosphere-Ionosphere Coupling Processes

NASA Astrophysics Data System (ADS)

Fan, M.; Paul, D.; Lee, T. C. M.; Matsuo, T.

2016-12-01

The most dynamic coupling between the magnetosphere and ionosphere occurs in the Earth's polar atmosphere. Our objective is to model scale-dependent stochastic characteristics of high-latitude ionospheric electric fields that originate from solar wind magnetosphere-ionosphere interactions. The Earth's high-latitude ionospheric electric field exhibits considerable variability, with increasing non-Gaussian characteristics at decreasing spatio-temporal scales. Accurately representing the underlying stochastic physical process through random field modeling is crucial not only for scientific understanding of the energy, momentum and mass exchanges between the Earth's magnetosphere and ionosphere, but also for modern technological systems including telecommunication, navigation, positioning and satellite tracking. While a lot of efforts have been made to characterize the large-scale variability of the electric field in the context of Gaussian processes, no attempt has been made so far to model the small-scale non-Gaussian stochastic process observed in the high-latitude ionosphere. We construct a novel random field model using spherical needlets as building blocks. The double localization of spherical needlets in both spatial and frequency domains enables the model to capture the non-Gaussian and multi-resolutional characteristics of the small-scale variability. The estimation procedure is computationally feasible due to the utilization of an adaptive Gibbs sampler. We apply the proposed methodology to the computational simulation output from the Lyon-Fedder-Mobarry (LFM) global magnetohydrodynamics (MHD) magnetosphere model. Our non-Gaussian multi-resolution model results in characterizing significantly more energy associated with the small-scale ionospheric electric field variability in comparison to Gaussian models. By accurately representing unaccounted-for additional energy and momentum sources to the Earth's upper atmosphere, our novel random field modeling approach will provide a viable remedy to the current numerical models' systematic biases resulting from the underestimation of high-latitude energy and momentum sources.

Numerical Simulation of Electromagnetic Field Variation in the Lithosphere-Atmosphere-Ionosphere Associated with Seismogenic Process in a Curvature Coordinate System

NASA Astrophysics Data System (ADS)

Liu, L.; Zhao, Z.; Wang, Y.; Huang, Q.

2013-12-01

The lithosphere-atmosphere- ionosphere (LAI) system formed an electromagnetic (EM) cavity that hosts the EM field excited by electric currents generated by lightning and other natural sources. There have also been numerous reports on variations of the EM field existing in LAI system prior to some significance earthquakes. We simulated the EM field in the lithosphere-ionosphere waveguide with a whole-earth model using a curvature coordinate by the hybrid pseudo-spectral and finite difference time domain method. Considering the seismogensis as a fully coupled seismoelectric process, we simulate the seismic wave and the EM wave in this 2D model. In the model we have observed the excitation of the Schumann Resonance (SR) as the background EM field generated by randomly placed electric-current impulses within the lowest 10 kilometers of the atmosphere. The diurnal variation and the latitude-dependence in ion concentration in the ionosphere are included in the model. After the SR reaching a steady state, an electric impulse is introduced in the shallow lithosphere to mimic the seismogenic process (pre-, co- and post-seismic) to assess the possible precursory effects on SR strength and frequency. The modeling results can explain the observed fact of why SR has a much more sensitive response to continental earthquakes, and much less response to oceanic events. The fundamental reason is simply due to the shielding effect of the conductive ocean that prevents effective radiation of the seismoelectric signals from oceanic earthquake events into the LAI waveguide.

Tachometers Derived From a Brushless DC Motor

NASA Technical Reports Server (NTRS)

Howard, David E.; Smith, Dennis A.

2007-01-01

The upper part of the figure illustrates the major functional blocks of a direction-sensitive analog tachometer circuit based on the use of an unexcited two-phase brushless dc motor as a rotation transducer. The primary advantages of this circuit over many older tachometer circuits include the following: Its output inherently varies linearly with the rate of rotation of the shaft. Unlike some tachometer circuits that rely on differentiation of voltages with respect to time, this circuit relies on integration, which results in signals that are less noisy. There is no need for an additional shaft-angle sensor, nor is there any need to supply electrical excitation to a shaft-angle sensor. There is no need for mechanical brushes (which tend to act as sources of electrical noise). The underlying concept and electrical design are relatively simple. This circuit processes the back-electromagnetic force (back-emf) outputs of the two motor phases into a voltage directly proportional to the instantaneous rate (sign magnitude) of rotation of the shaft. The processing in this circuit effects a straightforward combination of mathematical operations leading to a final operation based on the well-known trigonometric identity (sin x)2 + (cos x)2 = 1 for any value of x. The principle of operation of this circuit is closely related to that of the tachometer circuit described in Tachometer Derived From Brushless Shaft-Angle Resolver (MFS-28845), NASA Tech Briefs, Vol. 19, No. 3 (March 1995), page 39. However, the present circuit is simpler in some respects because there is no need for sinusoidal excitation of shaftangle- resolver windings.

Measurement of transverse emittance and coherence of double-gate field emitter array cathodes

PubMed Central

Tsujino, Soichiro; Das Kanungo, Prat; Monshipouri, Mahta; Lee, Chiwon; Miller, R.J. Dwayne

2016-01-01

Achieving small transverse beam emittance is important for high brightness cathodes for free electron lasers and electron diffraction and imaging experiments. Double-gate field emitter arrays with on-chip focussing electrode, operating with electrical switching or near infrared laser excitation, have been studied as cathodes that are competitive with photocathodes excited by ultraviolet lasers, but the experimental demonstration of the low emittance has been elusive. Here we demonstrate this for a field emitter array with an optimized double-gate structure by directly measuring the beam characteristics. Further we show the successful application of the double-gate field emitter array to observe the low-energy electron beam diffraction from suspended graphene in minimal setup. The observed low emittance and long coherence length are in good agreement with theory. These results demonstrate that our all-metal double-gate field emitters are highly promising for applications that demand extremely low-electron bunch-phase space volume and large transverse coherence. PMID:28008918

Eyecup scope—optical recordings of light stimulus-evoked fluorescence signals in the retina

PubMed Central

Hausselt, Susanne E.; Breuninger, Tobias; Castell, Xavier; Denk, Winfried; Margolis, David J.; Detwiler, Peter B.

2009-01-01

Dendritic signals play an essential role in processing visual information in the retina. To study them in neurites too small for electrical recording, we developed an instrument that combines a multi-photon (MP) microscope with a through-the-objective high-resolution visual stimulator. An upright microscope was designed that uses the objective lens for both MP imaging and delivery of visual stimuli to functionally intact retinal explants or eyecup preparations. The stimulator consists of a miniature liquid-crystal-on-silicon display coupled into the optical path of an infrared-excitation laser-scanning microscope. A pair of custom-made dichroic filters allows light from the excitation laser and three spectral bands (‘colors’) from the stimulator to reach the retina, leaving two intermediate bands for fluorescence imaging. Special optics allow displacement of the stimulator focus relative to the imaging focus. Spatially resolved changes in calcium-indicator fluorescence in response to visual stimuli were recorded in dendrites of different types of mammalian retinal neurons. PMID:19023590

TRPM8 is a neuronal osmosensor that regulates eye blinking in mice

PubMed Central

Quallo, Talisia; Vastani, Nisha; Horridge, Elisabeth; Gentry, Clive; Parra, Andres; Moss, Sian; Viana, Felix; Belmonte, Carlos; Andersson, David A.; Bevan, Stuart

2015-01-01

Specific peripheral sensory neurons respond to increases in extracellular osmolality but the mechanism responsible for excitation is unknown. Here we show that small increases in osmolality excite isolated mouse dorsal root ganglion (DRG) and trigeminal ganglion (TG) neurons expressing the cold-sensitive TRPM8 channel (transient receptor potential channel, subfamily M, member 8). Hyperosmotic responses were abolished by TRPM8 antagonists, and were absent in DRG and TG neurons isolated from Trpm8−/− mice. Heterologously expressed TRPM8 was activated by increased osmolality around physiological levels and inhibited by reduced osmolality. Electrophysiological studies in a mouse corneal preparation demonstrated that osmolality regulated the electrical activity of TRPM8-expressing corneal afferent neurons. Finally, the frequency of eye blinks was reduced in Trpm8−/− compared with wild-type mice and topical administration of a TRPM8 antagonist reduced blinking in wild-type mice. Our findings identify TRPM8 as a peripheral osmosensor responsible for the regulation of normal eye-blinking in mice. PMID:25998021

Measurement of transverse emittance and coherence of double-gate field emitter array cathodes

NASA Astrophysics Data System (ADS)

Tsujino, Soichiro; Das Kanungo, Prat; Monshipouri, Mahta; Lee, Chiwon; Miller, R. J. Dwayne

2016-12-01

Achieving small transverse beam emittance is important for high brightness cathodes for free electron lasers and electron diffraction and imaging experiments. Double-gate field emitter arrays with on-chip focussing electrode, operating with electrical switching or near infrared laser excitation, have been studied as cathodes that are competitive with photocathodes excited by ultraviolet lasers, but the experimental demonstration of the low emittance has been elusive. Here we demonstrate this for a field emitter array with an optimized double-gate structure by directly measuring the beam characteristics. Further we show the successful application of the double-gate field emitter array to observe the low-energy electron beam diffraction from suspended graphene in minimal setup. The observed low emittance and long coherence length are in good agreement with theory. These results demonstrate that our all-metal double-gate field emitters are highly promising for applications that demand extremely low-electron bunch-phase space volume and large transverse coherence.

PHYSICAL EFFECTS OCCURRING DURING GENERATION AND AMPLIFICATION OF LASER RADIATION: Efficiency of the vibrational excitation of CO2 molecules pumped by a capacitative discharge

NASA Astrophysics Data System (ADS)

Baranov, G. A.; Efremov, Yu V.; Smirnov, A. S.; Frolov, K. S.; Shevchenko, Yu I.

1989-02-01

An investigation was made of the distributions of the gain and input energy per unit volume along the discharge chamber length in a CO2-N2-He mixture stream excited by an rf discharge. The dependences of the gain and discharge luminescence intensity on the coordinate x were determined along the direction of the gas flow. The discharge luminescence intensity was shown to characterize the input energy distribution along the X axis. Calculations were made of the small-signal gain in the rf discharge. Experimental data on the distributions of the input energy and of the electric field in the discharge and the average values of the kinetic coefficients were used in the calculations. The efficiency of pumping CO2 lasers with an rf discharge was found to be close to the dc pumping efficiency. The results obtained provide evidence of promising prospects for using an rf discharge in fast-flow industrial lasers.

Force Sensor Characterization Under Sinusoidal Excitations

PubMed Central

Medina, Nieves; de Vicente, Jesús

2014-01-01

The aim in the current work is the development of a method to characterize force sensors under sinusoidal excitations using a primary standard as the source of traceability. During this work the influence factors have been studied and a method to minimise their contributions, as well as the corrections to be performed under dynamic conditions have been established. These results will allow the realization of an adequate characterization of force sensors under sinusoidal excitations, which will be essential for its further proper use under dynamic conditions. The traceability of the sensor characterization is based in the direct definition of force as mass multiplied by acceleration. To do so, the sensor is loaded with different calibrated loads and is maintained under different sinusoidal accelerations by means of a vibration shaker system that is able to generate accelerations up to 100 m/s2 with frequencies from 5 Hz up to 2400 Hz. The acceleration is measured by means of a laser vibrometer with traceability to the units of time and length. A multiple channel data acquisition system is also required to simultaneously acquire the electrical output signals of the involved instrument in real time. PMID:25290287

A compactly integrated laser-induced fluorescence detector for microchip electrophoresis.

PubMed

Li, Hai-Fang; Lin, Jin-Ming; Su, Rong-Guo; Uchiyama, Katsumi; Hobo, Toshiyuki

2004-06-01

A simple and easy-to-use integrated laser-induced fluorescence detector for microchip electrophoresis was constructed and evaluated. The fluid channels and optical fiber channels in the glass microchip were fabricated using standard photolithographic techniques and wet chemical etching. A 473 nm diode-pumped laser was used as the excitation source, and the collimation and collection optics and mirrors were discarded by using a multimode optical fiber to couple the excitation light straight into the microchannel and placing the microchip directly on the top of the photomultiplier tube. A combination of filter systems was incorporated into a poly(dimethylsiloxane) layer, which was reversibly sealed to the bottom of the microchip to eliminate the scattering excitation light reaching to the photomultiplier tube. Fluorescein/calcein samples were taken as model analytes to evaluate the performance with respect to design factors. The detection limits were 0.05 microM for fluorescein and 0.18 microM for calcein, respectively. The suitability of this simple detector for fluorescence detection was demonstrated by baseline separation of fluorescein isothiocyanate (FITC)-labeled arginine, phenylalanine, and glycine and FITC within 30 s at separation length of 3.8 cm and electrical field strength of 600 V/cm.

Phase-resolved two-dimensional terahertz spectroscopy - a probe of highly nonlinear light-matter interactions

NASA Astrophysics Data System (ADS)

Elsaesser, Thomas

Terahertz (THz) spectroscopy gives insight into low-frequency excitations and charge dynamics in condensed matter. So far, most experiments in a frequency range from 0.5 to 30 THz have focused on the linear THz response to determine linear absorption and disperion spectra, and/or electric conductivities. The generation of ultrashort THz transients with peak electric fields up to megavolts/cm has allowed for addressing nonlinear light-matter interactions and inducing excitations far from equilibrium. The novel method of two-dimensional THz (2D-THz) spectroscopy allows for mapping ultrafast dynamics and couplings of elementary excitations up to arbitrary nonlinear order in the electric field, both under resonant and nonresonant excitation conditions. In particular, different contributions to the overall nonlinear response are separated by dissecting it as a function of excitation and detection frequencies and for different waiting times after excitation. This talk gives an introduction in 2D-THz spectroscopy, including its recent extension to 3-pulse sequences and interaction schemes. To illustrate the potential of the method, recent results on two-phonon coherences and high-order interband excitations in the semiconductor InSb will be presented. Nonlinear THz excitation of two-phonon coherences exploits a resonance enhancement by the large electronic interband dipole of InSb and is, thus, far more efficient than linear excitation via resonant two-phonon absorption. As a second application, the nonlinear softmode response in a crystal consisting of aspirin molecules will be discussed. At moderate THz driving fields, the pronounced correlation of rotational modes of CH3 groups with collective oscillations of π-electrons drives the system into the regime of nonperturbative light-matter interaction. Nonlinear absorption around 1.1 THz leads to a blue-shifted coherent emission at 1.5 THz, revealing a dynamic breakup of the strong electron-phonon correlations.

Evaluation of excitation strategy with multi-plane electrical capacitance tomography sensor

NASA Astrophysics Data System (ADS)

Mao, Mingxu; Ye, Jiamin; Wang, Haigang; Zhang, Jiaolong; Yang, Wuqiang

2016-11-01

Electrical capacitance tomography (ECT) is an imaging technique for measuring the permittivity change of materials. Using a multi-plane ECT sensor, three-dimensional (3D) distribution of permittivity may be represented. In this paper, three excitation strategies, including single-electrode excitation, dual-electrode excitation in the same plane, and dual-electrode excitation in different planes are investigated by numerical simulation and experiment for two three-plane ECT sensors with 12 electrodes in total. In one sensor, the electrodes on the middle plane are in line with the others. In the other sensor, they are rotated 45° with reference to the other two planes. A linear back projection algorithm is used to reconstruct the images and a correlation coefficient is used to evaluate the image quality. The capacitance data and sensitivity distribution with each measurement strategy and sensor model are analyzed. Based on simulation and experimental results using noise-free and noisy capacitance data, the performance of the three strategies is evaluated.