Estimation of electric fields and current from ground-based magnetometer data

NASA Technical Reports Server (NTRS)

Kamide, Y.; Richmond, A. D.

1984-01-01

Recent advances in numerical algorithms for estimating ionospheric electric fields and currents from groundbased magnetometer data are reviewed and evaluated. Tests of the adequacy of one such algorithm in reproducing large-scale patterns of electrodynamic parameters in the high-latitude ionosphere have yielded generally positive results, at least for some simple cases. Some encouraging advances in producing realistic conductivity models, which are a critical input, are pointed out. When the algorithms are applied to extensive data sets, such as the ones from meridian chain magnetometer networks during the IMS, together with refined conductivity models, unique information on instantaneous electric field and current patterns can be obtained. Examples of electric potentials, ionospheric currents, field-aligned currents, and Joule heating distributions derived from ground magnetic data are presented. Possible directions for future improvements are also pointed out.

Photo ion spectrometer

DOEpatents

Gruen, Dieter M.; Young, Charles E.; Pellin, Michael J.

1992-01-01

A thin film structure for providing predetermined electric field boundary conditions. A thin film configuration is disposed on an insulator substrate in a selected spatial pattern with substantially uniform electrically resistive character in each of the different areas of the spatial pattern.

Photo-ion spectrometer

DOEpatents

Gruen, D.M.; Young, C.E.; Pellin, M.J.

1992-03-17

A thin film structure for providing predetermined electric field boundary conditions. A thin film configuration is disposed on an insulator substrate in a selected spatial pattern with substantially uniform electrically resistive character in each of the different areas of the spatial pattern.

Dependence of B1+ and B1- Field Patterns of Surface Coils on the Electrical Properties of the Sample and the MR Operating Frequency.

PubMed

Vaidya, Manushka V; Collins, Christopher M; Sodickson, Daniel K; Brown, Ryan; Wiggins, Graham C; Lattanzi, Riccardo

2016-02-01

In high field MRI, the spatial distribution of the radiofrequency magnetic ( B 1 ) field is usually affected by the presence of the sample. For hardware design and to aid interpretation of experimental results, it is important both to anticipate and to accurately simulate the behavior of these fields. Fields generated by a radiofrequency surface coil were simulated using dyadic Green's functions, or experimentally measured over a range of frequencies inside an object whose electrical properties were varied to illustrate a variety of transmit [Formula: see text] and receive [Formula: see text] field patterns. In this work, we examine how changes in polarization of the field and interference of propagating waves in an object can affect the B 1 spatial distribution. Results are explained conceptually using Maxwell's equations and intuitive illustrations. We demonstrate that the electrical conductivity alters the spatial distribution of distinct polarized components of the field, causing "twisted" transmit and receive field patterns, and asymmetries between [Formula: see text] and [Formula: see text]. Additionally, interference patterns due to wavelength effects are observed at high field in samples with high relative permittivity and near-zero conductivity, but are not present in lossy samples due to the attenuation of propagating EM fields. This work provides a conceptual framework for understanding B 1 spatial distributions for surface coils and can provide guidance for RF engineers.

Transient electroosmotic flow induced by AC electric field in micro-channel with patchwise surface heterogeneities.

PubMed

Luo, Win-Jet

2006-03-15

This paper investigates two-dimensional, time-dependent electroosmotic flow driven by an AC electric field via patchwise surface heterogeneities distributed along the micro-channel walls. The time-dependent flow fields through the micro-channel are simulated for various patchwise heterogeneous surface patterns using the backwards-Euler time stepping numerical method. Different heterogeneous surface patterns are found to create significantly different electrokinetic transport phenomena. The transient behavior characteristics of the generated electroosmotic flow are then discussed in terms of the influence of the patchwise surface heterogeneities, the direction of the applied AC electric field, and the velocity of the bulk flow. It is shown that the presence of oppositely charged surface heterogeneities on the micro-channel walls results in the formation of localized flow circulations within the bulk flow. These circulation regions grow and decay periodically in phase with the applied periodic AC electric field intensity. The location and rotational direction of the induced circulations are determined by the directions of the bulk flow velocity and the applied electric field.

Electric field induced microstructures in thin films on physicochemically heterogeneous and patterned substrates.

PubMed

Srivastava, Samanvaya; Reddy, P Dinesh Sankar; Wang, Cindy; Bandyopadhyay, Dipankar; Sharma, Ashutosh

2010-05-07

We study by nonlinear simulations the electric field induced pattern formation in a thin viscous film resting on a topographically or chemically patterned substrate. The thin film microstructures can be aligned to the substrate patterns within a window of parameters where the spinodal length scale of the field induced instability is close to the substrate periodicity. We investigate systematically the change in the film morphology and order when (i) the substrate pattern periodicity is varied at a constant film thickness and (ii) the film thickness is varied at a constant substrate periodicity. Simulations show two distinct pathway of evolution when the substrate-topography changes from protrusions to cavities. The isolated substrate defects generate locally ordered ripplelike structures distinct from the structures on a periodically patterned substrate. In the latter case, film morphology is governed by a competition between the pattern periodicity and the length scale of instability. Relating the thin film morphologies to the underlying substrate pattern has implications for field induced patterning and robustness of inter-interface pattern transfer, e.g., coding-decoding of information printed on a substrate.

Apparatus and method for laser beam diagnosis

DOEpatents

Salmon, Jr., Joseph T.

1991-01-01

An apparatus and method is disclosed for accurate, real time monitoring of the wavefront curvature of a coherent laser beam. Knowing the curvature, it can be quickly determined whether the laser beam is collimated, or focusing (converging), or de-focusing (diverging). The apparatus includes a lateral interferometer for forming an interference pattern of the laser beam to be diagnosed. The interference pattern is imaged to a spatial light modulator (SLM), whose output is a coherent laser beam having an image of the interference pattern impressed on it. The SLM output is focused to obtain the far-field diffraction pattern. A video camera, such as CCD, monitors the far-field diffraction pattern, and provides an electrical output indicative of the shape of the far-field pattern. Specifically, the far-field pattern comprises a central lobe and side lobes, whose relative positions are indicative of the radius of curvature of the beam. The video camera's electrical output may be provided to a computer which analyzes the data to determine the wavefront curvature of the laser beam.

Apparatus and method for laser beam diagnosis

DOEpatents

Salmon, J.T. Jr.

1991-08-27

An apparatus and method are disclosed for accurate, real time monitoring of the wavefront curvature of a coherent laser beam. Knowing the curvature, it can be quickly determined whether the laser beam is collimated, or focusing (converging), or de-focusing (diverging). The apparatus includes a lateral interferometer for forming an interference pattern of the laser beam to be diagnosed. The interference pattern is imaged to a spatial light modulator (SLM), whose output is a coherent laser beam having an image of the interference pattern impressed on it. The SLM output is focused to obtain the far-field diffraction pattern. A video camera, such as CCD, monitors the far-field diffraction pattern, and provides an electrical output indicative of the shape of the far-field pattern. Specifically, the far-field pattern comprises a central lobe and side lobes, whose relative positions are indicative of the radius of curvature of the beam. The video camera's electrical output may be provided to a computer which analyzes the data to determine the wavefront curvature of the laser beam. 11 figures.

Species-Specific Diversity of a Fixed Motor Pattern: The Electric Organ Discharge of Gymnotus

PubMed Central

Rodríguez-Cattaneo, Alejo; Pereira, Ana Carolina; Aguilera, Pedro A.; Crampton, William G. R.; Caputi, Angel A.

2008-01-01

Understanding fixed motor pattern diversity across related species provides a window for exploring the evolution of their underlying neural mechanisms. The electric organ discharges of weakly electric fishes offer several advantages as paradigmatic models for investigating how a neural decision is transformed into a spatiotemporal pattern of action. Here, we compared the far fields, the near fields and the electromotive force patterns generated by three species of the pulse generating New World gymnotiform genus Gymnotus. We found a common pattern in electromotive force, with the far field and near field diversity determined by variations in amplitude, duration, and the degree of synchronization of the different components of the electric organ discharges. While the rostral regions of the three species generate similar profiles of electromotive force and local fields, most of the species-specific differences are generated in the main body and tail regions of the fish. This causes that the waveform of the field is highly site dependant in all the studied species. These findings support a hypothesis of the relative separation of the electrolocation and communication carriers. The presence of early head negative waves in the rostral region, a species-dependent early positive wave at the caudal region, and the different relationship between the late negative peak and the main positive peak suggest three points of lability in the evolution of the electrogenic system: a) the variously timed neuronal inputs to different groups of electrocytes; b) the appearance of both rostrally and caudally innervated electrocytes, and c) changes in the responsiveness of the electrocyte membrane. PMID:18461122

Quantum Effects of Electric Fields and Potentials on Electron Motion: An Introduction to Theoretical and Practical Aspects

ERIC Educational Resources Information Center

Matteucci, G.

2007-01-01

In the so-called electric Aharonov-Bohm effect, a quantum interference pattern shift is produced when electrons move in an electric field free region but, at the same time, in the presence of a time-dependent electric potential. Analogous fringe shifts are observed in interference experiments where electrons, travelling through an electrostatic…

Low reflection and field localization over surface plasmon device with subwavelength patterned aluminum film

NASA Astrophysics Data System (ADS)

Yuan, Ying; Peng, Sha; Long, Huabao; Liu, Runhan; Wei, Dong; Zhang, Xinyu; Wang, Haiwei; Xie, Changsheng

2018-02-01

In this paper, we propose a new device composed of patterned sub-wavelength arrays to investigate surface plasmons (SPs) over sub-wavelength metal nano-structures. The device consists of silicon substrate and sub-wavelength patterns fabricated on a layer of aluminum film with nanometer thickness. Each sub-wavelength pattern formed in aluminum film is composed of a basic nano-square and twelve triangles for shaping single nano-pattern, which are uniformly distributed on the four sides of each square. Reflectance spectra and electric field distribution in infrared region are simulated. Numerical simulation results demonstrate that the device can efficiently lower its reflectance in infrared spectrum, and the response frequency can be controlled by only changing the device parameters such as square side length and then triangle vertex angle. Besides, the simulated electric field distribution of the device shows obviously field localization effect at the edges of aluminum film nano-structure. The electric filed around the tips of aluminum triangles is localized into sub-wavelength scale, so as to be beyond the common diffraction limitation. Our work will help to reveal the interesting properties of SPs device, and also bring new prospect of photonic device.

Ground-based studies of ionospheric convection associated with substorm expansion

NASA Technical Reports Server (NTRS)

Kamide, Y.; Richmond, A. D.; Emery, B. A.; Hutchins, C. F.; Ahn, B.-H.; De La Beaujardiere, O.; Foster, J. C.; Heelis, R. A.; Kroehl, H. W.; Rich, F. J.

1994-01-01

The instantaneous patterns of electric fields and currents in the high-latitude ionosphere are deduced by combining satellite and radar measurements of the ionospheric drift velocity, along with ground-based magnetometer observations for October 25, 1981. The period under study was characterized by a relatively stable southward interplanetary magnetic field (IMF), so that the obtained electric field patterns do reflect, in general, the state of sustained and enhanced plasma convection in the magnetosphere. During one of the satellite passes, however, an intense westward electrojet caused by a substorm intruded into the satellite (DE2) and radar (Chatanika, Alaska) field of view in the premidnight sector, providing a unique opportunity to differentiate the enhanced convection and substorm expansion fields. The distributions of the calculated electric potential for the expansion and maximum phases of the substorm show the first clear evidence of the coexistence of two physically different systems in the global convection pattern. The changes in the convection pattern during the substorm indicate that the large-scale potential distributions are indeed of general two-cell patterns representing the southward IMF status, but the night-morning cell has two positive peaks, one in the midnight sector and the other in the late morning hours, corresponding to the substorm expansion and the convection enhancement, respectively.

Complex Pattern Formation from Current-Driven Dynamics of Single-Layer Epitaxial Islands on Crystalline Conducting Substrates

NASA Astrophysics Data System (ADS)

Kumar, Ashish; Dasgupta, Dwaipayan; Maroudas, Dimitrios

We report a systematic study of complex pattern formation resulting from the driven dynamics of single-layer homoepitaxial islands on face-centered cubic (FCC) crystalline conducting substrate surfaces under the action of an externally applied electric field. The analysis is based on an experimentally validated nonlinear model of mass transport via island edge atomic diffusion, which also accounts for edge diffusional anisotropy. We analyze the morphological stability and simulate the field-driven evolution of rounded islands for an electric field oriented along the fast diffusion direction. For larger than critical island sizes on {110} and {100} FCC substrates, we show that multiple necking instabilities generate complex island patterns, including void-containing islands, mediated by sequences of breakup and coalescence events and distributed symmetrically with respect to the electric field direction. We analyze the dependence of the formed patterns on the original island size and on the duration of application of the external field. Starting from a single large rounded island, we characterize the evolution of the number of daughter islands and their average size and uniformity. The analysis reveals that the pattern formation kinetics follows a universal scaling relation. Division of Materials Sciences & Engineering, Office of Basic Energy Sciences, U.S. Department of Energy (Award No.: DE-FG02-07ER46407).

Spatial and temporal dependence of the convective electric field in Saturn’s inner magnetosphere

NASA Astrophysics Data System (ADS)

Andriopoulou, M.; Roussos, E.; Krupp, N.; Paranicas, C.; Thomsen, M.; Krimigis, S.; Dougherty, M. K.; Glassmeier, K.-H.

2014-02-01

The recently established presence of a convective electric field in Saturn’s inner and middle magnetosphere, with an average pointing approximately towards midnight and an intensity less than 1 mV/m, is one of the most puzzling findings by the Cassini spacecraft. In order to better characterize the properties of this electric field, we augmented the original analysis method used to identify it (Andriopoulou et al., 2012) and applied it to an extended energetic electron microsignature dataset, constructed from observations at the vicinity of four saturnian moons. We study the average characteristics of the convective pattern and additionally its temporal and spatial variations. In our updated dataset we include data from the recent Cassini orbits and also microsignatures from the two moons, Rhea and Enceladus, allowing us to further extend this analysis to cover a greater time period as well as larger radial distances within the saturnian magnetosphere. When data from the larger radial range and more recent orbits are included, we find that the originally inferred electric field pattern persists, and in fact penetrates at least as far in as the orbit of Enceladus, a region of particular interest due to the plasma loading that takes place there. We perform our electric field calculations by setting the orientation of the electric field as a free, time-dependent parameter, removing the pointing constraints from previous works. Analytical but also numerical techniques have been employed, that help us overcome possible errors that could have been introduced from simplified assumptions used previously. We find that the average electric field pointing is not directed exactly at midnight, as we initially assumed, but is found to be stably displaced by approximately 12-32° from midnight, towards dawn. The fact, however, that the field’s pointing is much more variable in short time scales, in addition to our observations that it penetrates inside the orbit of Enceladus (∼4 Rs), may suggest that the convective pattern is dominating all the way down to the main rings (2.2 Rs), when data from the Saturn Orbit Insertion are factored in. We also report changes of the electric field strength and pointing over the course of time, possibly related to seasonal effects, with the largest changes occurring during a period that envelopes the saturnian equinox. Finally, the average electric field strength seems to be sensitive to radial distance, exhibiting a drop as we move further out in the magnetosphere, confirming earlier results. This drop-off, however, appears to be more intense in the earlier years of the mission. Between 2010 and 2012 the electric field is quasi-uniform, at least between the L-shells of Tethys and Dione. These new findings provide constraints in the possible electric field sources that might be causing such a convection pattern that has not been observed before in other planetary magnetospheres. The very well defined values of the field’s average properties may suggest a periodic variation of the convective pattern, which can average out very effectively the much larger changes in both pointing and intensity over short time scales, although this period cannot be defined. The slight evidence of changes in the properties across the equinox (seasonal control), may also hint that the source of the electric field resides in the planet’s atmosphere/ionosphere system.

Electric-field-stimulated protein mechanics

PubMed Central

Hekstra, Doeke R.; White, K. Ian; Socolich, Michael A.; Henning, Robert W.; Šrajer, Vukica; Ranganathan, Rama

2017-01-01

The internal mechanics of proteins—the coordinated motions of amino acids and the pattern of forces constraining these motions—connects protein structure to function. Here we describe a new method combining the application of strong electric field pulses to protein crystals with time-resolved X-ray crystallography to observe conformational changes in spatial and temporal detail. Using a human PDZ domain (LNX2PDZ2) as a model system, we show that protein crystals tolerate electric field pulses strong enough to drive concerted motions on the sub-microsecond timescale. The induced motions are subtle, involve diverse physical mechanisms, and occur throughout the protein structure. The global pattern of electric-field-induced motions is consistent with both local and allosteric conformational changes naturally induced by ligand binding, including at conserved functional sites in the PDZ domain family. This work lays the foundation for comprehensive experimental study of the mechanical basis of protein function. PMID:27926732

Electrorheological effect of Ti-bearing blast furnace slag with different TiC contents at 1500°C

NASA Astrophysics Data System (ADS)

Yue, Hong-rui; Jiang, Tao; Zhang, Qiao-yi; Duan, Pei-ning; Xue, Xiang-xin

2017-07-01

The electrorheological properties of CaO-SiO2-Al2O3-MgO-TiO2-TiC slags were investigated to enhance understanding of the effect of TiC addition on the viscosity, yield stress, and fluid pattern of Ti-bearing slags in a direct-current electric field. The viscosities and shear stresses of 4wt% and 8wt% TiC slags were found to increase substantially with increasing electric field intensity, whereas virtually no rheological changes were observed in the 0wt% TiC slag. The Herschel-Bulkley model was applied to demonstrate that the fluid pattern of the 4wt% TiC slag was converted from that of a Newtonian fluid to that of a Bingham fluid in response to the applied electric field; and the static yield stress increased linearly with the square of the electric field intensity.

Near-field marking of gold nanostars by ultrashort pulsed laser irradiation: experiment and simulations

NASA Astrophysics Data System (ADS)

Møller, Søren H.; Vester-Petersen, Joakim; Nazir, Adnan; Eriksen, Emil H.; Julsgaard, Brian; Madsen, Søren P.; Balling, Peter

2018-02-01

Quantitative measurements of the electric near-field distribution of star-shaped gold nanoparticles have been performed by femtosecond laser ablation. Measurements were carried out on and off the plasmon resonance. A detailed comparison with numerical simulations of the electric fields is presented. Semi-quantitative agreement is found, with slight systematic differences between experimentally observed and simulated near-field patterns close to strong electric-field gradients. The deviations are attributed to carrier transport preceding ablation.

Chemical Detection using Electrically Open Circuits having no Electrical Connections

NASA Technical Reports Server (NTRS)

Woodward, Stanley E.; Olgesby, Donald M.; Taylor, Bryant D.; Shams, Qamar A.

2008-01-01

This paper presents investigations to date on chemical detection using a recently developed method for designing, powering and interrogating sensors as electrically open circuits having no electrical connections. In lieu of having each sensor from a closed circuit with multiple electrically connected components, an electrically conductive geometric pattern that is powered using oscillating magnetic fields and capable of storing an electric field and a magnetic field without the need of a closed circuit or electrical connections is used. When electrically active, the patterns respond with their own magnetic field whose frequency, amplitude and bandwidth can be correlated with the magnitude of the physical quantities being measured. Preliminary experimental results of using two different detection approaches will be presented. In one method, a thin film of a reactant is deposited on the surface of the open-circuit sensor. Exposure to a specific targeted reactant shifts the resonant frequency of the sensor. In the second method, a coating of conductive material is placed on a thin non-conductive plastic sheet that is placed over the surface of the sensor. There is no physical contact between the sensor and the electrically conductive material. When the conductive material is exposed to a targeted reactant, a chemical reaction occurs that renders the material non-conductive. The change in the material s electrical resistance within the magnetic field of the sensor alters the sensor s response bandwidth and amplitude, allowing detection of the reaction without having the reactants in physical contact with the sensor.

Inner Magnetospheric Electric Fields Derived from IMAGE EUV

NASA Technical Reports Server (NTRS)

Gallagher, D. L.; Adrian, M. L.

2007-01-01

The local and global patterns of plasmaspheric plasma transport reflect the influence of electric fields imposed by all sources in the inner magnetosphere. Image sequences of thermal plasma G:istribution obtained from the IMAGE Mission Extreme Ultraviolet Imager can be used to derive plasma motions and, using a magnetic field model, the corresponding electric fields. These motions and fields directly reflect the dynamic coupling of injected plasmasheet plasma and the ionosphere, in addition to solar wind and atmospheric drivers. What is being learned about the morphology of inner magnetospheric electric fields during storm and quite conditions from this new empirical tool will be presented and discussed.

The neutral wind 'flywheel' as a source of quiet-time, polar-cap currents

NASA Technical Reports Server (NTRS)

Lyons, L. R.; Walterscheid, R. L.; Killeen, T. L.

1985-01-01

The neutral wind pattern over the summer polar cap can be driven by plasma convection to resemble the convection pattern. For a north-south component of the interplanetary magnetic field Bz directed southward, the wind speeds in the conducting E-region can become approximately 25 percent of the electric field drift speeds. If convection ceases, this neutral wind distribution can drive a significant polar cap current system for approximately 6 hours. The currents are reversed from those driven by the electric fields for southward Bz, and the Hall and field-aligned components of the current system resemble those observed during periods of northward Bz. The current magnitudes are similar to those observed during periods of small, northward Bz; however, observations indicate that electric fields often contribute to the currents as much as, or more than, the neutral winds.

Transient electroosmotic flow induced by DC or AC electric fields in a curved microtube.

PubMed

Luo, W-J

2004-10-15

This study investigates transient electroosmotic flow in a rectangular curved microtube in which the fluid is driven by the application of an external DC or AC electric field. The resultant flow-field evolutions within the microtube are simulated using the backwards-Euler time-stepping numerical method to clarify the relationship between the changes in the axial-flow velocity and the intensity of the applied electric field. When the electric field is initially applied or varies, the fluid within the double layer responds virtually immediately, and the axial velocity within the double layer tends to follow the varying intensity of the applied electric field. The greatest net charge density exists at the corners of the microtube as a result of the overlapping electrical double layers of the two walls. It results in local maximum or minimum axial velocities in the corners during increasing or decreasing applied electric field intensity in either the positive or negative direction. As the fluid within the double layer starts to move, the bulk fluid is gradually dragged into motion through the diffusion of momentum from the double layer. A finite time is required for the full momentum of the double layer to diffuse to the bulk fluid; hence, a certain phase shift between the applied electric field and the flow response is inevitable. The patterns of the axial velocity contours during the transient evolution are investigated in this study. It is found that these patterns are determined by the efficiency of momentum diffusion from the double layer to the central region of the microtube.

Role of IMF B y in the prompt electric field disturbances over equatorial ionosphere during a space weather event

DOE PAGES

Chakrabarty, Dipu; Hui, Debrup; Rout, Diptiranjan; ...

2017-02-04

On 7 January 2005 (Ap=40) prompt penetration electric field perturbations of opposite polarities were observed over Thumba and Jicamarca on a few occasions during 13:45–16:30 UT. However, the electric field was found to be eastward during 14:45–15:30 UT over both Thumba and Jicamarca contrary to the general expectation wherein opposite polarities are expected at nearly antipodal points. On closer scrutiny, three important observational features are noticed during 14:10–15:15 UT. First, during 14:10–14:45 UT, despite increasing southward interplanetary magnetic field (IMF) B z condition, the already westward electric field over Thumba weakened (less westward) while the eastward electric field over Jicamarcamore » intensified (more eastward). Second, the electric field not only became anomalously eastward over Thumba but also got intensified further during 14:45–15:00 UT similar to Jicamarca. Third, during 15:00–15:15 UT, despite IMF B z remaining steadily southward, the eastward electric field continued to intensify over Thumba but weakened over Jicamarca. It is suggested that the changes in IMF B y component under southward IMF B z condition are responsible for skewing the ionospheric equipotential patterns over the dip equator in such a way that Thumba came into the same DP2 cell as that of Jicamarca leading to anomalous electric field variations. Magnetic field measurements along the Indian and Jicamarca longitude sectors and changes in high-latitude ionospheric convection patterns provide credence to this proposition. Therefore, in conclusion, the present investigation shows that the variations in IMF B y are fundamentally important to understand the prompt penetration effects over low latitudes.« less

Role of IMF B y in the prompt electric field disturbances over equatorial ionosphere during a space weather event

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

Chakrabarty, Dipu; Hui, Debrup; Rout, Diptiranjan

On 7 January 2005 (Ap=40) prompt penetration electric field perturbations of opposite polarities were observed over Thumba and Jicamarca on a few occasions during 13:45–16:30 UT. However, the electric field was found to be eastward during 14:45–15:30 UT over both Thumba and Jicamarca contrary to the general expectation wherein opposite polarities are expected at nearly antipodal points. On closer scrutiny, three important observational features are noticed during 14:10–15:15 UT. First, during 14:10–14:45 UT, despite increasing southward interplanetary magnetic field (IMF) B z condition, the already westward electric field over Thumba weakened (less westward) while the eastward electric field over Jicamarcamore » intensified (more eastward). Second, the electric field not only became anomalously eastward over Thumba but also got intensified further during 14:45–15:00 UT similar to Jicamarca. Third, during 15:00–15:15 UT, despite IMF B z remaining steadily southward, the eastward electric field continued to intensify over Thumba but weakened over Jicamarca. It is suggested that the changes in IMF B y component under southward IMF B z condition are responsible for skewing the ionospheric equipotential patterns over the dip equator in such a way that Thumba came into the same DP2 cell as that of Jicamarca leading to anomalous electric field variations. Magnetic field measurements along the Indian and Jicamarca longitude sectors and changes in high-latitude ionospheric convection patterns provide credence to this proposition. Therefore, in conclusion, the present investigation shows that the variations in IMF B y are fundamentally important to understand the prompt penetration effects over low latitudes.« less

Role of IMF By in the prompt electric field disturbances over equatorial ionosphere during a space weather event

NASA Astrophysics Data System (ADS)

Chakrabarty, D.; Hui, Debrup; Rout, Diptiranjan; Sekar, R.; Bhattacharyya, Archana; Reeves, G. D.; Ruohoniemi, J. M.

2017-02-01

On 7 January 2005 (Ap=40) prompt penetration electric field perturbations of opposite polarities were observed over Thumba and Jicamarca on a few occasions during 13:45-16:30 UT. However, the electric field was found to be eastward during 14:45-15:30 UT over both Thumba and Jicamarca contrary to the general expectation wherein opposite polarities are expected at nearly antipodal points. On closer scrutiny, three important observational features are noticed during 14:10-15:15 UT. First, during 14:10-14:45 UT, despite increasing southward interplanetary magnetic field (IMF) Bz condition, the already westward electric field over Thumba weakened (less westward) while the eastward electric field over Jicamarca intensified (more eastward). Second, the electric field not only became anomalously eastward over Thumba but also got intensified further during 14:45-15:00 UT similar to Jicamarca. Third, during 15:00-15:15 UT, despite IMF Bz remaining steadily southward, the eastward electric field continued to intensify over Thumba but weakened over Jicamarca. It is suggested that the changes in IMF By component under southward IMF Bz condition are responsible for skewing the ionospheric equipotential patterns over the dip equator in such a way that Thumba came into the same DP2 cell as that of Jicamarca leading to anomalous electric field variations. Magnetic field measurements along the Indian and Jicamarca longitude sectors and changes in high-latitude ionospheric convection patterns provide credence to this proposition. Thus, the present investigation shows that the variations in IMF By are fundamentally important to understand the prompt penetration effects over low latitudes.

47 CFR 22.529 - Application requirements for the Paging and Radiotelephone Service.

Code of Federal Regulations, 2011 CFR

2011-10-01

... horizontal radiation pattern of the electric field of the antenna, the height (in meters) to the tip of the... in the maximum lobe and the electric field polarization of the wave emitted by the antenna when...

47 CFR 22.529 - Application requirements for the Paging and Radiotelephone Service.

Code of Federal Regulations, 2010 CFR

2010-10-01

... horizontal radiation pattern of the electric field of the antenna, the height (in meters) to the tip of the... in the maximum lobe and the electric field polarization of the wave emitted by the antenna when...

Cephalopod-inspired design of electro-mechano-chemically responsive elastomers for on-demand fluorescent patterning

NASA Astrophysics Data System (ADS)

Wang, Qiming; Gossweiler, Gregory R.; Craig, Stephen L.; Zhao, Xuanhe

2014-09-01

Cephalopods can display dazzling patterns of colours by selectively contracting muscles to reversibly activate chromatophores - pigment-containing cells under their skins. Inspired by this novel colouring strategy found in nature, we design an electro-mechano-chemically responsive elastomer system that can exhibit a wide variety of fluorescent patterns under the control of electric fields. We covalently couple a stretchable elastomer with mechanochromic molecules, which emit strong fluorescent signals if sufficiently deformed. We then use electric fields to induce various patterns of large deformation on the elastomer surface, which displays versatile fluorescent patterns including lines, circles and letters on demand. Theoretical models are further constructed to predict the electrically induced fluorescent patterns and to guide the design of this class of elastomers and devices. The material and method open promising avenues for creating flexible devices in soft/wet environments that combine deformation, colorimetric and fluorescent response with topological and chemical changes in response to a single remote signal.

A monopole model for annihilation line emission from the Galactic center

NASA Astrophysics Data System (ADS)

Wang, D. Y.; Peng, Q. H.

Two traditional theoretical interpretations of the observed plasmapause are compared, namely, the plasmapause as: (1) the boundary between closed flux tubes that have been in the inner magnetosphere for several days and those that have recently drifted in from the magnetotail or (2) the last closed electric equipotential. Although the two interpretations become equivalent in the case where the electric-field pattern is steady for several days, interpretation 1 seems theoretically more secure for typical magnetospheric conditions. The results of old theoretical studies of the effects of time variations in the electric-field pattern on the shape of the plasmapause are reviewed briefly. The formulation of the present version of the Rice Convection Model is also reviewed. Preliminary results of recent computations of quiet-time electric fields, carried out with this model, are presented and discussed.

Ring discharge on the backsurface of a composite skin with ohmic anisotropy in response to frontal high current injection

NASA Astrophysics Data System (ADS)

Lee, T. S.; Robb, J. D.

The ring discharge hazard to a carbon-reinforced-composites fuel tank skin under lightning strike conditions is investigated. A model of anisotropy in electric conductivity is adopted whereby longitudinal conductivity and transverse conductivity are considered separately. It is concluded that the current flow pattern contains a stagnation-dominated near-field region and a geometry-dominated far-field decaying region. While this pattern is unaltered by anisotropy in conductivity, the accompanying nonliner electrical field pattern is greatly distorted. It is noted that conclusions applicable to the ignition hazard which were derived from the model of a uniform scalar conductivity for the skin still remain intact.

Simulations of electrically induced particle structuring on spherical drop surface

NASA Astrophysics Data System (ADS)

Hu, Yi; Vlahovska, Petia; Miksis, Michael

2016-11-01

Recent experiments (Ouriemi and Vlahovska, 2014) show intriguing surface patterns when a uniform electric field is applied to a droplet covered with colloidal particles. Depending on the particle properties and the electrical field intensity, particles organize into an equatorial belt, pole-to-pole chains, or dynamic vortices. Here we present a model to simulate the collective particle dynamics, which accounts for the electrohydrodynamic flow and particle dielectrophoresis due to the non-uniformity of local electrical field. In stronger electric fields, particles are expected to undergo Quincke rotation, inducing rotating clusters through inter-particle hydrodynamical interaction. We discuss how the field intensity influences the width, orientation and periodicity of the particle clusters. Our results provide insight into the various particle assembles discovered in the experiments.

Thunderstorm Hypothesis Reasoner

NASA Technical Reports Server (NTRS)

Mulvehill, Alice M.

1994-01-01

THOR is a knowledge-based system which incorporates techniques from signal processing, pattern recognition, and artificial intelligence (AI) in order to determine the boundary of small thunderstorms which develop and dissipate over the area encompassed by KSC and the Cape Canaveral Air Force Station. THOR interprets electric field mill data (derived from a network of electric field mills) by using heuristics and algorithms about thunderstorms that have been obtained from several domain specialists. THOR generates two forms of output: contour plots which visually describe the electric field activity over the network and a verbal interpretation of the activity. THOR uses signal processing and pattern recognition to detect signatures associated with noise or thunderstorm behavior in a near real time fashion from over 31 electrical field mills. THOR's AI component generates hypotheses identifying areas which are under a threat from storm activity, such as lightning. THOR runs on a VAX/VMS at the Kennedy Space Center. Its software is a coupling of C and FORTRAN programs, several signal processing packages, and an expert system development shell.

Electroluminescence from InGaN/GaN multi-quantum-wells nanorods light-emitting diodes positioned by non-uniform electric fields.

PubMed

Park, Hyunik; Kim, Byung-Jae; Kim, Jihyun

2012-11-05

We report that the nanorod light-emitting diodes (LEDs) with InGaN/GaN multi-quantum-wells (MQWs) emitted bright electroluminescence (EL) after they were positioned and aligned by non-uniform electric fields. Firstly, thin film LED structures with MQWs on sapphire substrate were coated with SiO(2) nanospheres, followed by inductively-coupled plasma etch to create nanorod-shapes with MQWs, which were transferred to the pre-patterned SiO(2)/Si wafer. This method allowed us to obtain nanorod LEDs with uniform length, diameter and qualities. Dielectrophoretic force created by non-uniform electric field was very effective at positioning the processed nanorods on the pre-patterned contacts. After aligned by non-uniform electric field, we observed bright EL from many nanorods, which had both cases (p-GaN/MQWs/n-GaN or n-GaN/MQWs/p-GaN). Therefore, bright ELs at different locations were observed under the various bias conditions.

Advanced electric-field scanning probe lithography on molecular resist using active cantilever

NASA Astrophysics Data System (ADS)

Kaestner, Marcus; Aydogan, Cemal; Ivanov, Tzvetan; Ahmad, Ahmad; Angelov, Tihomir; Reum, Alexander; Ishchuk, Valentyn; Krivoshapkina, Yana; Hofer, Manuel; Lenk, Steve; Atanasov, Ivaylo; Holz, Mathias; Rangelow, Ivo W.

2015-07-01

The routine "on demand" fabrication of features smaller than 10 nm opens up new possibilities for the realization of many devices. Driven by the thermally actuated piezoresistive cantilever technology, we have developed a prototype of a scanning probe lithography (SPL) platform which is able to image, inspect, align, and pattern features down to the single digit nanoregime. Here, we present examples of practical applications of the previously published electric-field based current-controlled scanning probe lithography. In particular, individual patterning tests are carried out on calixarene by using our developed table-top SPL system. We have demonstrated the application of a step-and-repeat SPL method including optical as well as atomic force microscopy-based navigation and alignment. The closed-loop lithography scheme was applied to sequentially write positive and negative tone features. Due to the integrated unique combination of read-write cycling, each single feature is aligned separately with the highest precision and inspected after patterning. This routine was applied to create a pattern step by step. Finally, we have demonstrated the patterning over larger areas, over existing topography, and the practical applicability of the SPL processes for lithography down to 13-nm pitch patterns. To enhance the throughput capability variable beam diameter electric field, current-controlled SPL is briefly discussed.

Self-consistent computation of the electric field near ICRH antennas. Application to the Tore Supra antenna

NASA Astrophysics Data System (ADS)

Pécoul, S.; Heuraux, S.; Koch, R.; Leclert, G.; Bécoulet, A.; Colas, L.

1999-09-01

Self-consistent calculations of the 3D electric field patterns between the screen and the plasma have been made with the ICANT code for realistic antennas. Here we explain how the ICRH antennas of the Tore Supra tokamak are modelled.

Self-consistent computation of the electric field near ICRH antennas. Application to the Tore Supra antenna

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

Pecoul, S.; Heuraux, S.; Koch, R.

1999-09-20

Self-consistent calculations of the 3D electric field patterns between the screen and the plasma have been made with the ICANT code for realistic antennas. Here we explain how the ICRH antennas of the Tore Supra tokamak are modelled.

Er Effect of Low Molecular Liquid Crystal on One-Sided Patterned Electrodes

NASA Astrophysics Data System (ADS)

Kikuchi, Takehito; Inoue, Akio; Furusho, Junji; Kawamuki, Ryohei

Several kinds of ER fluids (ERF) have been developed and have been applied to some mechatronics devices and processing technologies. In many conventional applications of ERFs, these devices consist of bilateral electrodes to apply electric field in ERF. However, the electric field of several kV/mm may be necessary to generate an ER effect sufficiently for practical purposes. The gap between a pair of electrodes should be, therefore, maintained narrowly and exactly for fears of short-circuit. At the same time, this electrode system also requires an interconnection on driving parts. To improve these disadvantages, we proposed "one-sided patterned electrode" (OSPE) systems in previous works. In this report, we confirmed the flow characteristics of low molecular liquid crystal (LMLC) on OSPE. Next, we also confirmed the different characteristics depending on the pattern type. Depending on results of electro-static analysis, we conclude that such a difference may results from the directors of LC molecules derived by electric field.

Etching-free patterning method for electrical characterization of atomically thin MoSe2 films grown by chemical vapor deposition

NASA Astrophysics Data System (ADS)

Utama, M. Iqbal Bakti; Lu, Xin; Zhan, Da; Ha, Son Tung; Yuan, Yanwen; Shen, Zexiang; Xiong, Qihua

2014-10-01

Patterning two-dimensional materials into specific spatial arrangements and geometries is essential for both fundamental studies of materials and practical applications in electronics. However, the currently available patterning methods generally require etching steps that rely on complicated and expensive procedures. We report here a facile patterning method for atomically thin MoSe2 films using stripping with an SU-8 negative resist layer exposed to electron beam lithography. Additional steps of chemical and physical etching were not necessary in this SU-8 patterning method. The SU-8 patterning was used to define a ribbon channel from a field effect transistor of MoSe2 film, which was grown by chemical vapor deposition. The narrowing of the conduction channel area with SU-8 patterning was crucial in suppressing the leakage current within the device, thereby allowing a more accurate interpretation of the electrical characterization results from the sample. An electrical transport study, enabled by the SU-8 patterning, showed a variable range hopping behavior at high temperatures.Patterning two-dimensional materials into specific spatial arrangements and geometries is essential for both fundamental studies of materials and practical applications in electronics. However, the currently available patterning methods generally require etching steps that rely on complicated and expensive procedures. We report here a facile patterning method for atomically thin MoSe2 films using stripping with an SU-8 negative resist layer exposed to electron beam lithography. Additional steps of chemical and physical etching were not necessary in this SU-8 patterning method. The SU-8 patterning was used to define a ribbon channel from a field effect transistor of MoSe2 film, which was grown by chemical vapor deposition. The narrowing of the conduction channel area with SU-8 patterning was crucial in suppressing the leakage current within the device, thereby allowing a more accurate interpretation of the electrical characterization results from the sample. An electrical transport study, enabled by the SU-8 patterning, showed a variable range hopping behavior at high temperatures. Electronic supplementary information (ESI) available: Further experiments on patterning and additional electrical characterizations data. See DOI: 10.1039/c4nr03817g

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

NASA Astrophysics Data System (ADS)

Karam, Tony; Sultan, Rabih

2013-02-01

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

Relationship of the interplanetary electric field to the high-latitude ionospheric electric field and currents Observations and model simulation

NASA Technical Reports Server (NTRS)

Clauer, C. R.; Banks, P. M.

1986-01-01

The electrical coupling between the solar wind, magnetosphere, and ionosphere is studied. The coupling is analyzed using observations of high-latitude ion convection measured by the Sondre Stromfjord radar in Greenland and a computer simulation. The computer simulation calculates the ionospheric electric potential distribution for a given configuration of field-aligned currents and conductivity distribution. The technique for measuring F-region in velocities at high time resolution over a large range of latitudes is described. Variations in the currents on ionospheric plasma convection are examined using a model of field-aligned currents linking the solar wind with the dayside, high-latitude ionosphere. The data reveal that high-latitude ionospheric convection patterns, electric fields, and field-aligned currents are dependent on IMF orientation; it is observed that the electric field, which drives the F-region plasma curve, responds within about 14 minutes to IMF variations in the magnetopause. Comparisons of the simulated plasma convection with the ion velocity measurements reveal good correlation between the data.

Physical deposition behavior of stiff amphiphilic polyelectrolytes in an external electric field

NASA Astrophysics Data System (ADS)

Hu, Dongmei; Zuo, Chuncheng; Cao, Qianqian; Chen, Hongli

2017-08-01

Coarse-grained molecular dynamics simulations are conducted to study the physical deposition behavior of stiff amphiphilic polyelectrolytes (APEs) in an external electric field. The effects of chain stiffness, the charge distribution of a hydrophilic block, and electric field strength are investigated. Amphiphilic multilayers, which consist of a monolayer of adsorbed hydrophilic monomers (HLMs), a hydrophobic layer, and another hydrophilic layer, are formed in a selective solvent. All cases exhibit locally ordered hydrophilic monolayers. Two kinds of hydrophobic micelles are distinguished based on local structures. Stripe and network hydrophobic patterns are formed in individual cases. Increasing the chain stiffness decreases the thickness of the deposited layer, the lateral size of the hydrophobic micelles, and the amount of deposition. Increasing the number of positively charged HLMs in a single chain has the same effect as increasing chain stiffness. Moreover, when applied normally to the substrate, the electric field compresses the deposited structures and increases the amount of deposition by pulling more PEs toward the substrate. A stronger electric field also facilitates the formation of a thinner and more ordered hydrophilic adsorption layer. These estimates help us explore how to tailor patterned nano-surfaces, nano-interfaces, or amphiphilic nanostructures by physically depositing semi-flexible APEs which is of crucial importance in physical sciences, life sciences and nanotechnology.

Wireless tamper detection sensor and sensing system

NASA Technical Reports Server (NTRS)

Woodard, Stanley E. (Inventor); Taylor, Bryant D. (Inventor)

2011-01-01

A wireless tamper detection sensor is defined by a perforated electrical conductor. The conductor is shaped to form a geometric pattern between first and second ends thereof such that the conductor defines an open-circuit that can store and transfer electrical and magnetic energy. The conductor resonates in the presence of a time-varying magnetic field to generate a harmonic response. The harmonic response changes when the conductor experiences a change in its geometric pattern due to severing of the conductor along at least a portion of the perforations. A magnetic field response recorder is used to wirelessly transmit the time-varying magnetic field and wirelessly detecting the conductor's harmonic response.

Active Colloids in Isotropic and Anisotropic Electrolytes

NASA Astrophysics Data System (ADS)

Peng, Chenhui

Electrically driven flows of fluids with respect to solid surfaces (electro-osmosis) and transport of particles in fluids (electrophoresis), collectively called electrokinetics, is a technologically important area of modern science. In this thesis, we study the electrokinetic phenomena in both isotropic and anisotropic fluids. A necessary condition of electrokinetics is separation of electric charges in space. In classic linear electrokinetics, with an isotropic electrolyte such as water, the charges are separated through dissociation of ionic groups at the solid-fluid interface; presence of the electric field is not required. In the nonlinear electrokinetics, the charges are separated with the assistance of the electric field. In the so-called induced-charge electro-osmosis (ICEO) the electric field separates charges near strongly polarizable surfaces such as metals. We establish the patterns of electro-osmotic velocities caused by nonlinear ICEO around an immobilized metallic and Janus (metallic-dielectric) spheres placed in water. In the case of the Janus particles, the flows are asymmetric, which results in pumping of water around the particle if it is immobilized, or in electrophoresis is the particle is free. When the isotropic electrolyte such as water is replaced with a LC electrolyte, the mechanism of the field-assisted charge separation becomes very different. Namely, the charges are separated at the director gradients, thanks to the anisotropy of electric conductivity and dielectric permittivity of the LC. These distortions can be created by the colloidal particles placed in the LC. We demonstrate the occurrence of nonlinear LC-enabled electro-osmosis (LCEO) by studying the flow patterns around colloidal spheres with different surface anchoring. LCEO velocities grow with the square of the electric field, which allows one to use an AC field to drive steady flows and to avoid electrode damage. Director distortions needed to trigger the LCEO can also be designed by surface-patterned modulated molecular orientation. The surface patterning is produced by photo-alignment. In the presence of an electric field, the spatially varying orientation induces space charges that trigger flows of the LC. The active patterned LC electrolyte converts the electric energy into the LC flows and transport of embedded particles of any type (fluid, solid, gaseous) along a predesigned trajectory, posing no limitation on the electric nature (charge, polarizability) of these particles and interfaces. The patterned LC electrolyte also induces persistent vortices of controllable rotation speed and direction that are quintessential for micro- and nanoscale mixing applications. The thesis also describes transport and placement of colloids by elasticity of a nematic LC with spatially varying molecular orientation. Colloidal particles in nematic environment are subject to the long-range elastic forces originating in the orientational order of the nematic. Gradients of the orientational order create an elastic energy landscape that drives the colloids into locations with preferred type of deformations. As an example, we demonstrate that colloidal spheres with perpendicular surface anchoring are driven into the regions of maximum splay, while spheres with tangential surface anchoring settle into the regions of bend. Elastic forces responsible for preferential placement are measured by exploring overdamped dynamics of the colloids. The results obtained in this thesis open new opportunities for design of materials and devices for micropumping, mixing, lab-on-a-chip and biosensing applications.

Simulations of particle structuring driven by electric fields

NASA Astrophysics Data System (ADS)

Hu, Yi; Vlahovska, Petia; Miksis, Michael

2015-11-01

Recent experiments (Ouriemi and Vlahovska, 2014) show intriguing surface patterns when a uniform electric field is applied to a droplet covered with colloidal particles. Depending on the particle properties and the electric field intensity, particles organize into an equatorial belt, pole-to-pole chains, or dynamic vortices. Here we present 3D simulations of the collective particle dynamics, which account for electrohydrodynamic flow and dielectrophoresis of particles. In stronger electric fields, particles are expected to undergo Quincke rotation and impose disturbance to the ambient flow. Transition from ribbon-shaped belt to rotating clusters is observed in the presence of the rotation-induced hydrodynamical interactions. Our results provide insight into the various particle assembles discovered in the experiments.

Ionosphere-magnetosphere coupling and convection

NASA Technical Reports Server (NTRS)

Wolf, R. A.; Spiro, R. W.

1984-01-01

The following international Magnetospheric Study quantitative models of observed ionosphere-magnetosphere events are reviewed: (1) a theoretical model of convection; (2) algorithms for deducing ionospheric current and electric-field patterns from sets of ground magnetograms and ionospheric conductivity information; and (3) empirical models of ionospheric conductances and polar cap potential drop. Research into magnetic-field-aligned electric fields is reviewed, particularly magnetic-mirror effects and double layers.

Electric-field-induced structural changes in multilayer piezoelectric actuators during electrical and mechanical loading

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

Esteves, Giovanni; Fancher, Chris M.; Röhrig, Sören

The effects of electrical and mechanical loading on the behavior of domains and phases in Multilayer Piezoelectric Actuators (MAs) is studied using in situ high-energy X-ray diffraction (XRD) and macroscopic property measurements. Rietveld refinement is carried out on measured diffraction patterns using a two-phase tetragonal (P4mm) and rhombohedral (R3m) model. Applying an electric field promotes the rhombohedral phase, while increasing compressive uniaxial pre-stress prior to electric field application favors the tetragonal phase. The competition between electrical and mechanical energy leads to a maximal difference between electric-field-induced phase fractions at 70 MPa pre-stress. Additionally, the available volume fraction of non-180° domainmore » reorientation that can be accessed during electric field application increases with compressive pre-stress up to 70 MPa. The origin for enhanced strain and polarization with applied pre-stress is attributed to a combination of enhanced non-180° domain reorientation and electric-field-induced phase transitions. The suppression of both the electric-field-induced phase transitions and domain reorientation at high pre-stresses (>70 MPa) is attributed to a large mechanical energy barrier, and alludes to the competition of the electrical and mechanical energy within the MA during applied stimuli.« less

Electric-field-induced structural changes in multilayer piezoelectric actuators during electrical and mechanical loading

DOE PAGES

Esteves, Giovanni; Fancher, Chris M.; Röhrig, Sören; ...

2017-04-08

The effects of electrical and mechanical loading on the behavior of domains and phases in Multilayer Piezoelectric Actuators (MAs) is studied using in situ high-energy X-ray diffraction (XRD) and macroscopic property measurements. Rietveld refinement is carried out on measured diffraction patterns using a two-phase tetragonal (P4mm) and rhombohedral (R3m) model. Applying an electric field promotes the rhombohedral phase, while increasing compressive uniaxial pre-stress prior to electric field application favors the tetragonal phase. The competition between electrical and mechanical energy leads to a maximal difference between electric-field-induced phase fractions at 70 MPa pre-stress. Additionally, the available volume fraction of non-180° domainmore » reorientation that can be accessed during electric field application increases with compressive pre-stress up to 70 MPa. The origin for enhanced strain and polarization with applied pre-stress is attributed to a combination of enhanced non-180° domain reorientation and electric-field-induced phase transitions. The suppression of both the electric-field-induced phase transitions and domain reorientation at high pre-stresses (>70 MPa) is attributed to a large mechanical energy barrier, and alludes to the competition of the electrical and mechanical energy within the MA during applied stimuli.« less

Analysis of Satellite Communications Antenna Patterns

NASA Technical Reports Server (NTRS)

Rahmat-Samii, Y.

1985-01-01

Computer program accurately and efficiently predicts far-field patterns of offset, or symmetric, parabolic reflector antennas. Antenna designer uses program to study effects of varying geometrical and electrical (RF) parameters of parabolic reflector and its feed system. Accurate predictions of far-field patterns help designer predict overall performance of antenna. These reflectors used extensively in modern communications satellites and in multiple-beam and low side-lobe antenna systems.

Dielectrophoretic systems without embedded electrodes

DOEpatents

Cummings, Eric B [Livermore, CA; Singh, Anup K [San Francisco, CA

2006-03-21

Method and apparatus for dielectrophoretic separation of particles in a fluid based using array of insulating structures arranged in a fluid flow channel. By utilizing an array of insulating structures, a spatially inhomogeneous electric field is created without the use of the embedded electrodes conventionally employed for dielectrophoretic separations. Moreover, by using these insulating structures a steady applied electric field has been shown to provide for dielectrophoresis in contrast to the conventional use of an alternating electric field. In a uniform array of posts, dielectrophoretic effects have been produced flows having significant pressure-driven and electrokinetic transport. Above a threshold applied electric field, filaments of concentrated and rarefied particles appear in the flow as a result of dielectrophoresis. Above a higher threshold applied voltage, dielectrophoresis produces zones of highly concentrated and immobilized particles. These patterns are strongly influenced by the angle of the array of insulating structures with respect to the mean applied electric field and the shape of the insulating structures.

A quasi-static model of global atmospheric electricity. II - Electrical coupling between the upper and lower atmosphere

NASA Technical Reports Server (NTRS)

Roble, R. G.; Hays, P. B.

1979-01-01

The paper presents a model of global atmospheric electricity used to examine the effect of upper atmospheric generators on the global electrical circuit. The model represents thunderstorms as dipole current generators randomly distributed in areas of known thunderstorm frequency; the electrical conductivity in the model increases with altitude, and electrical effects are coupled with a passive magnetosphere along geomagnetic field lines. The large horizontal-scale potential differences at ionospheric heights map downward into the lower atmosphere where the perturbations in the ground electric field are superimposed on the diurnal variation. Finally, changes in the upper atmospheric conductivity due to solar flares, polar cap absorptions, and Forbush decreases are shown to alter the downward mapping of the high-latitude potential pattern and the global distribution of fields and currents.

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.

Quantitative Imaging of Microwave Electric Fields through Near-Field Scanning Microwave Microscopy

NASA Astrophysics Data System (ADS)

Dutta, S. K.; Vlahacos, C. P.; Steinhauer, D. E.; Thanawalla, A.; Feenstra, B. J.; Wellstood, F. C.; Anlage, Steven M.; Newman, H. S.

1998-03-01

The ability to non-destructively image electric field patterns generated by operating microwave devices (e.g. filters, antennas, circulators, etc.) would greatly aid in the design and testing of these structures. Such detailed information can be used to reconcile discrepancies between simulated behavior and experimental data (such as scattering parameters). The near-field scanning microwave microscope we present uses a coaxial probe to provide a simple, broadband method of imaging electric fields.(S. M. Anlage, et al.) IEEE Trans. Appl. Supercond. 7, 3686 (1997).^,(See http://www.csr.umd.edu/research/hifreq/micr_microscopy.html) The signal that is measured is related to the incident electric flux normal to the face of the center conductor of the probe, allowing different components of the field to be measured by orienting the probe appropriately. By using a simple model of the system, we can also convert raw data to absolute electric field. Detailed images of standing waves on copper microstrip will be shown and compared to theory.

Atomic electric fields revealed by a quantum mechanical approach to electron picodiffraction.

PubMed

Müller, Knut; Krause, Florian F; Béché, Armand; Schowalter, Marco; Galioit, Vincent; Löffler, Stefan; Verbeeck, Johan; Zweck, Josef; Schattschneider, Peter; Rosenauer, Andreas

2014-12-15

By focusing electrons on probes with a diameter of 50 pm, aberration-corrected scanning transmission electron microscopy (STEM) is currently crossing the border to probing subatomic details. A major challenge is the measurement of atomic electric fields using differential phase contrast (DPC) microscopy, traditionally exploiting the concept of a field-induced shift of diffraction patterns. Here we present a simplified quantum theoretical interpretation of DPC. This enables us to calculate the momentum transferred to the STEM probe from diffracted intensities recorded on a pixel array instead of conventional segmented bright-field detectors. The methodical development yielding atomic electric field, charge and electron density is performed using simulations for binary GaN as an ideal model system. We then present a detailed experimental study of SrTiO3 yielding atomic electric fields, validated by comprehensive simulations. With this interpretation and upgraded instrumentation, STEM is capable of quantifying atomic electric fields and high-contrast imaging of light atoms.

Atomic electric fields revealed by a quantum mechanical approach to electron picodiffraction

NASA Astrophysics Data System (ADS)

Müller, Knut; Krause, Florian F.; Béché, Armand; Schowalter, Marco; Galioit, Vincent; Löffler, Stefan; Verbeeck, Johan; Zweck, Josef; Schattschneider, Peter; Rosenauer, Andreas

2014-12-01

By focusing electrons on probes with a diameter of 50 pm, aberration-corrected scanning transmission electron microscopy (STEM) is currently crossing the border to probing subatomic details. A major challenge is the measurement of atomic electric fields using differential phase contrast (DPC) microscopy, traditionally exploiting the concept of a field-induced shift of diffraction patterns. Here we present a simplified quantum theoretical interpretation of DPC. This enables us to calculate the momentum transferred to the STEM probe from diffracted intensities recorded on a pixel array instead of conventional segmented bright-field detectors. The methodical development yielding atomic electric field, charge and electron density is performed using simulations for binary GaN as an ideal model system. We then present a detailed experimental study of SrTiO3 yielding atomic electric fields, validated by comprehensive simulations. With this interpretation and upgraded instrumentation, STEM is capable of quantifying atomic electric fields and high-contrast imaging of light atoms.

Atomic electric fields revealed by a quantum mechanical approach to electron picodiffraction

PubMed Central

Müller, Knut; Krause, Florian F.; Béché, Armand; Schowalter, Marco; Galioit, Vincent; Löffler, Stefan; Verbeeck, Johan; Zweck, Josef; Schattschneider, Peter; Rosenauer, Andreas

2014-01-01

By focusing electrons on probes with a diameter of 50 pm, aberration-corrected scanning transmission electron microscopy (STEM) is currently crossing the border to probing subatomic details. A major challenge is the measurement of atomic electric fields using differential phase contrast (DPC) microscopy, traditionally exploiting the concept of a field-induced shift of diffraction patterns. Here we present a simplified quantum theoretical interpretation of DPC. This enables us to calculate the momentum transferred to the STEM probe from diffracted intensities recorded on a pixel array instead of conventional segmented bright-field detectors. The methodical development yielding atomic electric field, charge and electron density is performed using simulations for binary GaN as an ideal model system. We then present a detailed experimental study of SrTiO3 yielding atomic electric fields, validated by comprehensive simulations. With this interpretation and upgraded instrumentation, STEM is capable of quantifying atomic electric fields and high-contrast imaging of light atoms. PMID:25501385

Aharonov-Bohm Effect in the Photodetachment Microscopy of Hydrogen Negative Ions in an Electric Field

NASA Astrophysics Data System (ADS)

Wang, Dehua

2014-09-01

The Aharonov-Bohm (AB) effect in the photodetachment microscopy of the H- ions in an electric field has been studied on the basis of the semiclassical theory. After the H- ion is irradiated by a laser light, they provide a coherent electron source. When the detached electron is accelerated by a uniform electric field, two trajectories of a detached electron which run from the source to the same point on the detector, will interfere with each other and lead to an interference pattern in the photodetachment microscopy. After the solenoid is electrified beside the H- ion, even though no Lorentz force acts on the electron outside the solenoid, the photodetachment microscopy interference pattern on the detector is changed with the variation in the magnetic flux enclosed by the solenoid. This is caused by the AB effect. Under certain conditions, the interference pattern reaches the macroscopic dimensions and could be observed in a direct AB effect experiment. Our study can provide some predictions for the future experimental study of the AB effect in the photodetachment microscopy of negative ions.

Particle-in-cell simulations of asymmetric guide-field reconnection: quadrupolar structure of Hall magnetic field

NASA Astrophysics Data System (ADS)

Schmitz, R. G.; Alves, M. V.; Barbosa, M. V. G.

2017-12-01

One of the most important processes that occurs in Earth's magnetosphere is known as magnetic reconnection (MR). This process can be symmetric or asymmetric, depending basically on the plasma density and magnetic field in both sides of the current sheet. A good example of symmetric reconnection in terrestrial magnetosphere occurs in the magnetotail, where these quantities are similar on the north and south lobes. In the dayside magnetopause MR is asymmetric, since the plasma regimes and magnetic fields of magnetosheath and magnetosphere are quite different. Symmetric reconnection has some unique signatures. For example, the formation of a quadrupolar structure of Hall magnetic field and a bipolar Hall electric field that points to the center of the current sheet. The different particle motions in the presence of asymmetries change these signatures, causing the quadrupolar pattern to be distorted and forming a bipolar structure. Also, the bipolar Hall electric field is modified and gives rise to a single peak pointing toward the magnetosheat, considering an example of magnetopause reconnection. The presence of a guide-field can also distort the quadrupolar pattern, by giving a shear angle across the current sheet and altering the symmetric patterns, according to previous simulations and observations. Recently, a quadrupolar structure was observed in an asymmetric guide-field MR event using MMS (Magnetospheric Multiscale) mission data [Peng et al., JGR, 2017]. This event shows clearly that the density asymmetry and the guide-field were not sufficient to form signatures of asymmetric reconnection. Using the particle-in-cell code iPIC3D [Markidis et al, Mathematics and Computers in Simulation, 2010] with the MMS data from this event used to define input parameters, we found a quadrupolar structure of Hall magnetic field and a bipolar pattern of Hall electric field in ion scales, showing that our results are in an excellent agreement with the MMS observations. To our knowledge, this is the first time PIC simulations show this kind of results, since previous simulations have predicted bipolar pattern in the asymmetric guide-field reconnection.

The effect of longitudinal conductance variations on the ionospheric prompt penetration electric fields

NASA Astrophysics Data System (ADS)

Sazykin, S.; Wolf, R.; Spiro, R.; Fejer, B.

Ionospheric prompt penetration electric fields of magnetospheric origin, together with the atmospheric disturbance dynamo, represent the most important parameters controlling the storm-time dynamics of the low and mid-latitude ionosphere. These prompt penetration fields result from the disruption of region-2 field-aligned shielding currents during geomagnetically disturbed conditions. Penetration electric fields con- trol, to a large extent, the generation and development of equatorial spread-F plasma instabilities as well as other dynamic space weather phenomena in the ionosphere equatorward of the auroral zone. While modeling studies typically agree with average patterns of prompt penetration fields, experimental results suggest that longitudinal variations of the ionospheric con- ductivities play a non-negligible role in controlling spread-F phenomena, an effect that has not previously been modeled. We present first results of modeling prompt pene- tration electric fields using a version of the Rice Convection Model (RCM) that allows for longitudinal variations in the ionospheric conductance tensor. The RCM is a first- principles numerical ionosphere-magnetosphere coupling model that solves for the electric fields, field-aligned currents, and particle distributions in the ionosphere and inner/middle magnetosphere. We compare these new theoretical results with electric field observations.

Spatial Control of Photoacid Diffusion in Chemically Amplified Resist (CAR) via External Electric Field.

PubMed

Kim, Jinok; Yoo, Gwangwe; Park, Jin; Park, Jin-Hong

2018-09-01

We investigated the effect of an electric field-based post exposure bake (EF-PEB) process on photoacid diffusion and pattern formation. To investigate the control of photoacid diffusion experimentally, the EF-PEB processes was performed at various temperatures. Cross sectional images of various EF-PEB processed samples were obtained by scanning electron microscopy (SEM) after ion beam milling. In addition, we conducted a numerical analysis of photoacid distribution and diffusion with following Fick's second law and compared the experimental results with our theoretical model. The drift distance was theoretically predicted by multiplying drift velocity and EF-PEB time, and the experimental values were obtained by finding the difference in pattern depths of PEB/EFPEB samples. Finally, an EF-PEB temperature of 85 °C was confirmed as the optimum condition to maximize photoacid drift distance using the electric field.

Analysis of Electrokinetic Mixing Using AC Electric Field and Patchwise Surface Heterogeneities

NASA Astrophysics Data System (ADS)

Luo, Win-Jet; Yarn, Kao-Feng; Hsu, Shou-Ping

2007-04-01

In this paper, the authors investigate the use of an applied AC electric field and microchannel surface heterogeneities to carry out the microfluidic mixing of two-dimensional, time-dependent electroosmotic flows. The time-dependent flow fields within the microchannel are simulated using the backwards-Euler time-stepping numerical method. The mixing efficiencies obtained in microchannels with two different patchwise surface heterogeneity patterns are investigated. In general, the results show that the application of an AC electric field significantly reduces the required mixing length compared with the use of a DC electric field. Furthermore, the presence of oppositely charged surface heterogeneities on the microchannel walls results in the formation of localized flow circulation regions within the bulk flow. These circulation regions grow and decay periodically in accordance with the periodic variation of the AC electric field intensity and provide an effective means of enhancing species mixing in the microchannel. Consequently, the use of an AC electric field together with patchwise surface heterogeneities permits a significant reduction in both the mixing channel length and the retention time required to attain a homogeneous solution.

Field-aligned currents and large-scale magnetospheric electric fields

NASA Technical Reports Server (NTRS)

Dangelo, N.

1979-01-01

The existence of field-aligned currents (FAC) at northern and southern high latitudes was confirmed by a number of observations, most clearly by experiments on the TRIAD and ISIS 2 satellites. The high-latitude FAC system is used to relate what is presently known about the large-scale pattern of high-latitude ionospheric electric fields and their relation to solar wind parameters. Recently a simplified model was presented for polar cap electric fields. The model is of considerable help in visualizing the large-scale features of FAC systems. A summary of the FAC observations is given. The simplified model is used to visualize how the FAC systems are driven by their generators.

Film growth kinetics and electric field patterning during electrospray deposition of block copolymer thin films

NASA Astrophysics Data System (ADS)

Toth, Kristof; Hu, Hanqiong; Choo, Youngwoo; Loewenberg, Michael; Osuji, Chinedum

The delivery of sub-micron droplets of dilute polymer solutions to a heated substrate by electrospray deposition (ESD) enables precisely controlled and continuous growth of block copolymer (BCP) thin films. Here we explore patterned deposition of BCP films by spatially varying the electric field at the substrate using an underlying charged grid, as well as film growth kinetics. Numerical analysis was performed to examine pattern fidelity by considering the trajectories of charged droplets during flight through imposed periodic field variations in the vicinity of the substrate. Our work uncovered an unexpected modality for improving the resolution of the patterning process via stronger field focusing through the use of a second oppositely charged grid beneath a primary focusing array, with an increase in highly localized droplet deposition on the intersecting nodes of the grid. Substrate coverage kinetics are considered for homopolymer deposition in the context of simple kinetic models incorporating temperature and molecular weight dependence of diffusivity. By contrast, film coverage kinetics for block copolymer depositions are additionally convoluted with preferential wetting and thickness-periodicity commensurability effects. NSF GRFP.

Effect of the local electric field on the formation of an ordered structure in porous anodic alumina

NASA Astrophysics Data System (ADS)

Lazarouk, S. K.; Katsuba, P. S.; Leshok, A. A.; Vysotskii, V. B.

2015-09-01

Experimental data and a model are presented, and the electric field that appears in porous alumina during electrochemical anodic oxidation of aluminum in electrolytes based on an aqueous solution of oxalic acid at a voltage of 90-250 V is calculated. It is found that the electric field in the layers with a porosity of 1-10% in growing alumina reaches 109-1010 V/m, which exceeds the electric strength of the material and causes microplasma patterns emitting visible light at the pore bottom, the self-organization of the structure of porous alumina, and the anisotropy of local porous anodizing. Moreover, other new effects are to be expected during aluminum anodizing under the conditions that ensure a high electric field inside the barrier layer of porous oxide.

Anticipating electrical breakdown in dielectric elastomer actuators

NASA Astrophysics Data System (ADS)

Muffoletto, Daniel P.; Burke, Kevin M.; Zirnheld, Jennifer L.

2013-04-01

The output strain of a dielectric elastomer actuator is directly proportional to the square of its applied electric field. However, since the likelihood of electric breakdown is elevated with an increased applied field, the maximum operating electric field of the dielectric elastomer is significantly derated in systems employing these actuators so that failure due to breakdown remains unlikely even as the material ages. In an effort to ascertain the dielectric strength so that stronger electric fields can be applied, partial discharge testing is used to assess the health of the actuator by detecting the charge that is released when localized instances of breakdown partially bridge the insulator. Pre-stretched and unstretched samples of VHB4910 tape were submerged in dielectric oil to remove external sources of partial discharges during testing, and the partial discharge patterns were recorded just before failure of the dielectric sample.

The interplanetary electric field, cleft currents and plasma convection in the polar caps

NASA Technical Reports Server (NTRS)

Banks, P. M.; Clauer, C. R.; Araki, T.; St. Maurice, J. P.; Foster, J. C.

1984-01-01

The relationship between the pattern of plasma convection in the polar cleft and the dynamics of the interplanetary electric field (IEF) is examined theoretically. It is shown that owing to the geometrical properties of the magnetosphere, the East-West component of the IEF will drive field-aligned currents which connect to the ionosphere at points lying on either side of noon, while currents associated with the North-South component of the IEF will connect the two polar caps as sheet currents, also centered at 12 MLT. In order to describe the consequences of the Interplanetary Magnetic Field (IMF) effects upon high-latitude electric fields and convection patterns, a series of numerical simulations was carried out. The simulations were based on a solution to the steady-state equation of current continuity in a height-integrated ionospheric current. The simulations demonstrate that a simple hydrodynamical model can account for the narrow 'throats' of strong dayside antisunward convection observed during periods of southward interplanetary IMF drift, as well as the sunward convection observed during periods of strongly northward IMF drift.

An electrohydrodynamic flow in ac electrowetting.

PubMed

Lee, Horim; Yun, Sungchan; Ko, Sung Hee; Kang, Kwan Hyoung

2009-12-17

In ac electrowetting, hydrodynamic flows occur within a droplet. Two distinct flow patterns were observed, depending on the frequency of the applied electrical signal. The flow at low-frequency range was explained in terms of shape oscillation and a steady streaming process in conjunction with contact line oscillation. The origin of the flow at high-frequency range has not yet been explained. We suggest that the high-frequency flow originated mainly from the electrothermal effect, in which electrical charge is generated due to the gradient of electrical conductivity and permittivity, which is induced by the Joule heating of fluid medium. To support our argument, we analyzed the flow field numerically while considering the electrical body force generated by the electrothermal effect. We visualized the flow pattern and measured the flow velocity inside the droplet. The numerical results show qualitative agreement with experimental results with respect to electric field and frequency dependence of flow velocity. The effects of induced-charge electro-osmosis, natural convection, and the Marangoni flow are discussed.

Investigation of Physics Teacher Candidates' Cognitive Structures about "Electric Field": A Free Word Association Test Study

ERIC Educational Resources Information Center

Türkkan, Ercan

2017-01-01

The aim of this study is to investigate the cognitive structures of physics teacher candidates about "electric field." Phenomenographic research method, one of the qualitative research patterns, was used in the study. The data of the study was collected from 91 physics teacher candidates who had taken General Physics II course at…

Electroosmosis over charge-modulated surfaces with finite electrical double layer thicknesses: Asymptotic and numerical investigations

NASA Astrophysics Data System (ADS)

Ghosh, Uddipta; Mandal, Shubhadeep; Chakraborty, Suman

2017-06-01

Here we attempt to solve the fully coupled Poisson-Nernst-Planck-Navier-Stokes equations, to ascertain the influence of finite electric double layer (EDL) thickness on coupled charge and fluid dynamics over patterned charged surfaces. We go beyond the well-studied "weak-field" limit and obtain numerical solutions for a wide range of EDL thicknesses, applied electric field strengths, and the surface potentials. Asymptotic solutions to the coupled system are also derived using a combination of singular and regular perturbation, for thin EDLs and low surface potential, and good agreement between the two solutions is observed. Counterintuitively to common arguments, our analysis reveals that finite EDL thickness may either increase or decrease the "free-stream velocity" (equivalent to net throughput), depending on the strength of the applied electric field. We also unveil a critical EDL thickness for which the effect of finite EDL thickness on the free-stream velocity is the most prominent. Finally, we demonstrate that increasing the surface potential and the applied field tends to influence the overall flow patterns in the contrasting manners. These results may be of profound importance in developing a comprehensive theoretical basis for designing electro-osmotically actuated microfluidic mixtures.

Optoelectronic tweezers for medical diagnostics

NASA Astrophysics Data System (ADS)

Kremer, Clemens; Neale, Steven; Menachery, Anoop; Barrett, Mike; Cooper, Jonathan M.

2012-01-01

Optoelectronic tweezers (OET) allows the spatial patterning of electric fields through selected illumination of a photoconductive surface. This enables the manipulation of micro particles and cells by creating non-uniform electrical fields that then produce dielectrophoretic (DEP) forces. The DEP responses of cells differ and can produce negative or positive (repelled or attracted to areas of high electric field) forces. Therefore OET can be used to manipulate individual cells and separate different cell types from each other. Thus OET has many applications for medical diagnostics, demonstrated here with work towards diagnosing Human African Trypanosomiasis, also known as sleeping sickness.

Stimuli-Responsive Polymer-Clay Nanocomposites under Electric Fields

PubMed Central

Piao, Shang Hao; Kwon, Seung Hyuk; Choi, Hyoung Jin

2016-01-01

This short Feature Article reviews electric stimuli-responsive polymer/clay nanocomposites with respect to their fabrication, physical characteristics and electrorheological (ER) behaviors under applied electric fields when dispersed in oil. Their structural characteristics, morphological features and thermal degradation behavior were examined by X-ray diffraction pattern, scanning electron microscopy and transmission electron microscopy, and thermogravimetric analysis, respectively. Particular focus is given to the electro-responsive ER characteristics of the polymer/clay nanocomposites in terms of the yield stress and viscoelastic properties along with their applications. PMID:28787852

Electric field induced self-assembly of monolayers of gold nanoparticles for surface enhanced Raman scattering applications

NASA Astrophysics Data System (ADS)

Das, Suchandra; Musunuri, Naga; Kucheryavy, Pavel; Lockard, Jenny; Fischer, Ian; Singh, Pushpendra; New Jersey Institute of Technology Collaboration; Rutgers University Newark Collaboration

2017-11-01

We present a technique that uses an electric field in the direction normal to the interface for self-assembling monolayers of gold nanoparticles on fluid-liquid interfaces and freezing these monolayers onto the surface of a flexible thin film. The electric field gives rise to dipole-dipole and capillary forces which cause the particles to arrange in a triangular pattern. The technique involves assembling the monolayer on the interface between a UV-curable resin and another fluid by applying an electric field, and then curing the resin by applying UV light. The monolayer becomes embedded on the surface of the solidified resin film. We are using these films for surface enhanced Raman scattering (SERS) applications. Initial measurements indicate improved performance over commercially available SERS substrates.

Terahertz beam propagation measured through three-dimensional amplitude profile determination

NASA Astrophysics Data System (ADS)

Reiten, Matthew T.; Harmon, Stacee A.; Cheville, Richard Alan

2003-10-01

To determine the spatio-temporal field distribution of freely propagating terahertz bandwidth pulses, we measure the time-resolved electric field in two spatial dimensions with high resolution. The measured, phase-coherent electric-field distributions are compared with an analytic model in which the radiation from a dipole antenna near a dielectric interface is coupled to free space through a spherical lens. The field external to the lens is limited by reflection at the lens-air dielectric interface, which is minimized at Brewster's angle, leading to an annular field pattern. Field measurements compare favorably with theory. Propagation of terahertz beams is determined both by assuming a TEM0,0 Gaussian profile as well as expanding the beam into a superposition of Laguerre-Gauss modes. The Laguerre-Gauss model more accurately describes the beam profile for free-space propagation and after propagating through a simple optical system. The accuracy of both models for predicting far-field beam patterns depend upon accurately measuring complex field amplitudes of terahertz beams.

Pattern of mathematic representation ability in magnetic electricity problem

NASA Astrophysics Data System (ADS)

Hau, R. R. H.; Marwoto, P.; Putra, N. M. D.

2018-03-01

The mathematic representation ability in solving magnetic electricity problem gives information about the way students understand magnetic electricity. Students have varied mathematic representation pattern ability in solving magnetic electricity problem. This study aims to determine the pattern of students' mathematic representation ability in solving magnet electrical problems.The research method used is qualitative. The subject of this study is the fourth semester students of UNNES Physics Education Study Program. The data collection is done by giving a description test that refers to the test of mathematical representation ability and interview about field line topic and Gauss law. The result of data analysis of student's mathematical representation ability in solving magnet electric problem is categorized into high, medium and low category. The ability of mathematical representations in the high category tends to use a pattern of making known and asked symbols, writing equations, using quantities of physics, substituting quantities into equations, performing calculations and final answers. The ability of mathematical representation in the medium category tends to use several patterns of writing the known symbols, writing equations, using quantities of physics, substituting quantities into equations, performing calculations and final answers. The ability of mathematical representations in the low category tends to use several patterns of making known symbols, writing equations, substituting quantities into equations, performing calculations and final answer.

Direct measurement of the electric-field distribution in a light-emitting electrochemical cell

NASA Astrophysics Data System (ADS)

Slinker, Jason D.; Defranco, John A.; Jaquith, Michael J.; Silveira, William R.; Zhong, Yu-Wu; Moran-Mirabal, Jose M.; Craighead, Harold G.; Abruña, Héctor D.; Marohn, John A.; Malliaras, George G.

2007-11-01

The interplay between ionic and electronic charge carriers in mixed conductors offers rich physics and unique device potential. In light-emitting electrochemical cells (LEECs), for example, the redistribution of ions assists the injection of electronic carriers and leads to efficient light emission. The mechanism of operation of LEECs has been controversial, as there is no consensus regarding the distribution of electric field in these devices. Here, we probe the operation of LEECs using electric force microscopy on planar devices. We show that obtaining the appropriate boundary conditions is essential for capturing the underlying device physics. A patterning scheme that avoids overlap between the mixed-conductor layer and the metal electrodes enabled the accurate in situ measurement of the electric-field distribution. The results show that accumulation and depletion of mobile ions near the electrodes create high interfacial electric fields that enhance the injection of electronic carriers.

Modeling of Magnetoelastic Nanostructures with a Fully-coupled Mechanical-Micromagnetic Model and Its Applications

NASA Astrophysics Data System (ADS)

Liang, Cheng-Yen

Micromagnetic simulations of magnetoelastic nanostructures traditionally rely on either the Stoner-Wohlfarth model or the Landau-Lifshitz-Gilbert (LLG) model assuming uniform strain (and/or assuming uniform magnetization). While the uniform strain assumption is reasonable when modeling magnetoelastic thin films, this constant strain approach becomes increasingly inaccurate for smaller in-plane nanoscale structures. In this dissertation, a fully-coupled finite element micromagnetic method is developed. The method deals with the micromagnetics, elastodynamics, and piezoelectric effects. The dynamics of magnetization, non-uniform strain distribution, and electric fields are iteratively solved. This more sophisticated modeling technique is critical for guiding the design process of the nanoscale strain-mediated multiferroic elements such as those needed in multiferroic systems. In this dissertation, we will study magnetic property changes (e.g., hysteresis, coercive field, and spin states) due to strain effects in nanostructures. in addition, a multiferroic memory device is studied. The electric-field-driven magnetization switching by applying voltage on patterned electrodes simulation in a nickel memory device is shown in this work. The deterministic control law for the magnetization switching in a nanoring with electric field applied to the patterned electrodes is investigated. Using the patterned electrodes, we show that strain-induced anisotropy is able to be controlled, which changes the magnetization deterministically in a nano-ring.

SAR Reduction in 7T C-Spine Imaging Using a “Dark Modes” Transmit Array Strategy

PubMed Central

Eryaman, Yigitcan; Guerin, Bastien; Keil, Boris; Mareyam, Azma; Herraiz, Joaquin L.; Kosior, Robert K.; Martin, Adrian; Torrado-Carvajal, Angel; Malpica, Norberto; Hernandez-Tamames, Juan A.; Schiavi, Emanuele; Adalsteinsson, Elfar; Wald, Lawrence L.

2016-01-01

Purpose Local specific absorption rate (SAR) limits many applications of parallel transmit (pTx) in ultra high-field imaging. In this Note, we introduce the use of an array element, which is intentionally inefficient at generating spin excitation (a “dark mode”) to attempt a partial cancellation of the electric field from those elements that do generate excitation. We show that adding dipole elements oriented orthogonal to their conventional orientation to a linear array of conventional loop elements can lower the local SAR hotspot in a C-spine array at 7 T. Methods We model electromagnetic fields in a head/torso model to calculate SAR and excitation B1+ patterns generated by conventional loop arrays and loop arrays with added electric dipole elements. We utilize the dark modes that are generated by the intentional and inefficient orientation of dipole elements in order to reduce peak 10g local SAR while maintaining excitation fidelity. Results For B1+ shimming in the spine, the addition of dipole elements did not significantly alter the B1+ spatial pattern but reduced local SAR by 36%. Conclusion The dipole elements provide a sufficiently complimentary B1+ and electric field pattern to the loop array that can be exploited by the radiofrequency shimming algorithm to reduce local SAR. PMID:24753012

Electric-field distribution near rectangular microstrip radiators for hyperthermia heating: theory versus experiment in water.

PubMed

Underwood, H R; Peterson, A F; Magin, R L

1992-02-01

A rectangular microstrip antenna radiator is investigated for its near-zone radiation characteristics in water. Calculations of a cavity model theory are compared with the electric-field measurements of a miniature nonperturbing diode-dipole E-field probe whose 3 mm tip was positioned by an automatic three-axis scanning system. These comparisons have implications for the use of microstrip antennas in a multielement microwave hyperthermia applicator. Half-wavelength rectangular microstrip patches were designed to radiate in water at 915 MHz. Both low (epsilon r = 10) and high (epsilon r = 85) dielectric constant substrates were tested. Normal and tangential components of the near-zone radiated electric field were discriminated by appropriate orientation of the E-field probe. Low normal to transverse electric-field ratios at 3.0 cm depth indicate that the radiators may be useful for hyperthermia heating with an intervening water bolus. Electric-field pattern addition from a three-element linear array of these elements in water indicates that phase and amplitude adjustment can achieve some limited control over the distribution of radiated power.

Characteristics of colloidal aluminum nanoparticles prepared by nanosecond pulsed laser ablation in deionized water in presence of parallel external electric field

NASA Astrophysics Data System (ADS)

Mahdieh, Mohammad Hossein; Mozaffari, Hossein

2017-10-01

In this paper, we investigate experimentally the effect of electric field on the size, optical properties and crystal structure of colloidal nanoparticles (NPs) of aluminum prepared by nanosecond Pulsed Laser Ablation (PLA) in deionized water. The experiments were conducted for two different conditions, with and without the electric field parallel to the laser beam path and the results were compared. To study the influence of electric field, two polished parallel aluminum metals plates perpendicular to laser beam path were used as the electrodes. The NPs were synthesized for target in negative, positive and neutral polarities. The colloidal nanoparticles were characterized using the scanning electron microscopy (SEM), UV-vis absorption spectroscopy and X-ray Diffraction (XRD). The results indicate that initial charge on the target has strong effect on the size properties and concentration of the synthesized nanoparticles. The XRD patterns show that the structure of produced NPs with and without presence of electric field is Boehmite (AlOOH).

Hydrogel Actuation by Electric Field Driven Effects

NASA Astrophysics Data System (ADS)

Morales, Daniel Humphrey

Hydrogels are networks of crosslinked, hydrophilic polymers capable of absorbing and releasing large amounts of water while maintaining their structural integrity. Polyelectrolyte hydrogels are a subset of hydrogels that contain ionizable moieties, which render the network sensitive to the pH and the ionic strength of the media and provide mobile counterions, which impart conductivity. These networks are part of a class of "smart" material systems that can sense and adjust their shape in response to the external environment. Hence, the ability to program and modulate hydrogel shape change has great potential for novel biomaterial and soft robotics applications. We utilized electric field driven effects to manipulate the interaction of ions within polyelectrolyte hydrogels in order to induce controlled deformation and patterning. Additionally, electric fields can be used to promote the interactions of separate gel networks, as modular components, and particle assemblies within gel networks to develop new types of soft composite systems. First, we present and analyze a walking gel actuator comprised of cationic and anionic gel legs attached by electric field-promoted polyion complexation. We characterize the electro-osmotic response of the hydrogels as a function of charge density and external salt concentration. The gel walkers achieve unidirectional motion on flat elastomer substrates and exemplify a simple way to move and manipulate soft matter devices in aqueous solutions. An 'ionoprinting' technique is presented with the capability to topographically structure and actuate hydrated gels in two and three dimensions by locally patterning ions induced by electric fields. The bound charges change the local mechanical properties of the gel to induce relief patterns and evoke localized stress, causing rapid folding in air. The ionically patterned hydrogels exhibit programmable temporal and spatial shape transitions which can be tuned by the duration and/or strength of the applied electric field. We extend the use of ionoprinting to develop multi-responsive bilayer gel systems capable of more complex shape transformation. The localized crosslinked regions determine the bending axis as the gel responds to the external environment. The bending can be tuned to reverse direction isothermally by changing the solvent quality or by changing the temperature at a fixed concentration. The multi-responsive behavior is caused by the volume transitions of a non-ionic, thermos-sensitive hydrogel coupled with a superabsorbent ionic hydrogel. Lastly, electric field driven microparticle assembly, using dielectrophoretic (DEP) forces, organized colloidal microparticles within a hydrogel matrix. The use of DEP forces enables rapid, efficient and precise control over the colloidal distribution. The resulting supracolloidal endoskeleton structures impart directional bending as the hydrogel shrinks. We compare the ordered particles structures to random particle distributions in affecting the hydrogel sheet bending response. This study demonstrates a universal technique for imparting directional properties in hydrogels towards new generations of hybrid soft materials.

Toward microscale flow control using non-uniform electro-osmotic flow

NASA Astrophysics Data System (ADS)

Paratore, Federico; Boyko, Evgeniy; Gat, Amir D.; Kaigala, Govind V.; Bercovici, Moran

2018-02-01

We present a novel method that allows establishing desired flow patterns in a Hele-Shaw cell, solely by controlling the surface chemistry, without the use of physical walls. Using weak electrolytes, we locally pattern the chamber's ceiling and/or floor, thus defining a spatial distribution of surface charge. This translates to a non-uniform electric double layer which when subjected to an external electric field applied along the chamber, gives rise to non-uniform electroosmotic flow (EOF). We present the theory that allows prediction and design of such flows fields, as well as experimental demonstrations opening the door to configurable microfluidic devices.

Electric field measurements during the blowing snow in a cryogenic wind tunnel by a non-contact voltmeter

NASA Astrophysics Data System (ADS)

Sato, A.; Omiya, S.

2011-12-01

It is known that the average atmospheric electric field is +100V/m in fair weather (positive electric field vector points downward). An increase of atmospheric electric field is reported when the blowing snow occurred. This phenomenon is mainly explained by the fact that the blowing snow particles have negative charge in average. It is suggested that an electrostatic force, given by the product of the electric field and the charge of the particle, may influence the particle trajectory and change those movements, saltation and suspension. The purpose of this experiment is to clarify the characteristics of the electric field during blowing snow event. Experiments were carried out in the cryogenic wind tunnel of Snow and Ice Research Center, NIED. A non-contact voltmeter was used to measure the electric field. An artificial blowing snow was generated by a snow particle supply machine. The rolling brushes of the machine scratch the snow surface and supply snow particles into the airflow. This machine made it possible to supply the snow particles at an arbitrary rate. This experiment was conducted in the following experimental conditions; wind speed of 5 to 7 m/s (3 patterns), supply snow quantity of 8.7 to 34.9 g/m/s (4 patterns), air temperature of -10 degree Celsius, fetch of 10 m and hard snow surface. Measured electric field was all negative, which is opposite direction to the previous measurements. This means that the blowing snow particles had positive charges. The negative electric field tended to increase with increase of the wind speed and the mass flux. These results can be explained from the previous experiment by Omiya and Sato (2010). The snow particles gain positive charges by the friction with the rolling brush which is made from polypropylene, however the particles accumulate negative charges gradually with increase of the collisions to the snow surface. Probably, the positive charges might have remained on the snow particles that had passed over the measurement point. Moreover, it is thought that because the saltation length is longer when the wind speed is higher, fewer collision frequencies left the particles more positive charges. REFERENCE:Omiya and Sato(2010): Measurement of electrostatic charge of blowing snow particles in a wind tunnel focusing on collision frequency to the snow surface. Hokkaido University Collection of Scholarly and Academic Papers

Patterned Ferroelectric Films for Tunable Microwave Devices

NASA Technical Reports Server (NTRS)

Miranda, Felix A.; Mueller, Carl H.

2008-01-01

Tunable microwave devices based on metal terminals connected by thin ferroelectric films can be made to perform better by patterning the films to include suitably dimensioned, positioned, and oriented constrictions. The patterns can be formed during fabrication by means of selective etching processes. If the width of the ferroelectric film in such a device is reduced at one or more locations, then both the microwave field and any applied DC bias (tuning) electric field become concentrated at those locations. The magnitudes of both the permittivity and the dielectric loss of a ferroelectric material are reduced by application of a DC field. Because the concentration of the DC field in the constriction(s) magnifies the permittivity- and loss-reducing effects of the applied DC voltage, the permittivity and dielectric loss in the constriction(s) are smaller in the constriction(s) than they are in the wider parts of the ferroelectric film. Furthermore, inasmuch as displacement current must flow through either the constriction(s) or the low-loss dielectric substrate, the net effect of the constriction(s) is equivalent to that of incorporating one or more low-loss, low-permittivity region(s) in series with the high-loss, high-permittivity regions. In a series circuit, the properties of the low-capacitance series element (in this case, the constriction) dominate the overall performance. Concomitantly, the capacitance between the metal terminals is reduced. By making the capacitance between the metal terminals small but tunable, a constriction increases the upper limit of the frequency range amenable to ferroelectric tuning. The present patterning concept is expected to be most advantageous for devices and circuits that must operate at frequencies from about 4 to about 60 GHz. A constriction can be designed such that the magnitude of the microwave electric field and the effective width of the region occupied by the microwave electric field become functions of the applied DC electric field, so that tunability is enhanced. It should even be possible to design the constriction to obtain a specific tuning-versus-voltage profile.

Vector tomography for reconstructing electric fields with non-zero divergence in bounded domains

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

Koulouri, Alexandra, E-mail: koulouri@uni-muenster.de; Department of Electrical and Electronic Engineering, Imperial College London, Exhibition Road, London SW7 2BT; Brookes, Mike

In vector tomography (VT), the aim is to reconstruct an unknown multi-dimensional vector field using line integral data. In the case of a 2-dimensional VT, two types of line integral data are usually required. These data correspond to integration of the parallel and perpendicular projection of the vector field along the integration lines and are called the longitudinal and transverse measurements, respectively. In most cases, however, the transverse measurements cannot be physically acquired. Therefore, the VT methods are typically used to reconstruct divergence-free (or source-free) velocity and flow fields that can be reconstructed solely from the longitudinal measurements. In thismore » paper, we show how vector fields with non-zero divergence in a bounded domain can also be reconstructed from the longitudinal measurements without the need of explicitly evaluating the transverse measurements. To the best of our knowledge, VT has not previously been used for this purpose. In particular, we study low-frequency, time-harmonic electric fields generated by dipole sources in convex bounded domains which arise, for example, in electroencephalography (EEG) source imaging. We explain in detail the theoretical background, the derivation of the electric field inverse problem and the numerical approximation of the line integrals. We show that fields with non-zero divergence can be reconstructed from the longitudinal measurements with the help of two sparsity constraints that are constructed from the transverse measurements and the vector Laplace operator. As a comparison to EEG source imaging, we note that VT does not require mathematical modeling of the sources. By numerical simulations, we show that the pattern of the electric field can be correctly estimated using VT and the location of the source activity can be determined accurately from the reconstructed magnitudes of the field. - Highlights: • Vector tomography is used to reconstruct electric fields generated by dipole sources. • Inverse solutions are based on longitudinal and transverse line integral measurements. • Transverse line integral measurements are used as a sparsity constraint. • Numerical procedure to approximate the line integrals is described in detail. • Patterns of the studied electric fields are correctly estimated.« less

Electromagnetic fields due to a horizontal electric dipole antenna laid on the surface of a two-layer medium

NASA Technical Reports Server (NTRS)

Tsang, L.; Kong, J. A.

1974-01-01

With applications to geophysical subsurface probings, electromagnetic fields due to a horizontal electric dipole laid on the surface of a two-layer medium are solved by a combination of analytic and numerical methods. Interference patterns are calculated for various layer thickness. The results are interpreted in terms of normal modes, and the accuracies of the methods are discussed.

Control and near-field detection of surface plasmon interference patterns.

PubMed

Dvořák, Petr; Neuman, Tomáš; Břínek, Lukáš; Šamořil, Tomáš; Kalousek, Radek; Dub, Petr; Varga, Peter; Šikola, Tomáš

2013-06-12

The tailoring of electromagnetic near-field properties is the central task in the field of nanophotonics. In addition to 2D optics for optical nanocircuits, confined and enhanced electric fields are utilized in detection and sensing, photovoltaics, spatially localized spectroscopy (nanoimaging), as well as in nanolithography and nanomanipulation. For practical purposes, it is necessary to develop easy-to-use methods for controlling the electromagnetic near-field distribution. By imaging optical near-fields using a scanning near-field optical microscope, we demonstrate that surface plasmon polaritons propagating from slits along the metal-dielectric interface form tunable interference patterns. We present a simple way how to control the resulting interference patterns both by variation of the angle between two slits and, for a fixed slit geometry, by a proper combination of laser beam polarization and inhomogeneous far-field illumination of the structure. Thus the modulation period of interference patterns has become adjustable and new variable patterns consisting of stripelike and dotlike motifs have been achieved, respectively.

Seasonal Patterns of Melatonin, Cortisol, and Progesterone Secretion in Female Lambs Raised Beneath a 500-kV Transmission Line.

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

Lee, Jack M.

Although several kinds of biological effects of electric and magnetic fields have been reported from laboratory studies, few have been independently replicated. When this study was being planned, the suppression of nighttime melatonin in rodents was thought to represent one of the strongest known effects of these fields. The effect had been replicated by a single laboratory for 60-Hz electric fields, and by multiple laboratories for d-c magnetic fields. The primary objective of this study was to determine whether the effect of electric and magnetic fields on melatonin would also occur in sheep exposed to a high voltage transmission line.more » The specific hypothesis tested by this experiment was as follows: The electrical environment produced by a 60-Hz, 500-kV transmission line causes a depression in nocturnal melatonin in chronically exposed female lambs. This may mimic effects of pinealectomy or constant long-day photoperiods, thus delaying the onset of reproductive cycles. Results of the study do not provide evidence to support the hypothesis. Melatonin concentrations in the sheep exposed to the transmission line showed the normal pattern of low daytime and high nighttime serum levels. As compared to the control group, there were no statistically significant group differences in the mean amplitude, phase, or duration of the nighttime melatonin elevation.« less

Theoretical analysis of non-linear Joule heating effects over an electro-thermal patterned flow

NASA Astrophysics Data System (ADS)

Sanchez, Salvador; Ascanio, Gabriel; Mendez, Federico; Bautista, Oscar

2017-11-01

In this work, non-linear Joule heating effects for electro-thermal patterned flows driven inside of a slit microchannel are analyzed. Here, the movement of fluids is controlled by placing electro-thermal forces, which are generated through an imposed longitudinal electric field, E0, and the wall electric potential produced by electrodes inserted along the surface of the microchannel wall, ζ. For this analysis, viscosity and electrical conductivity of fluids are included as known functions, which depend on the temperature; therefore, in order to determine the flow, temperature and electric potential fields together with its simultaneous interactions, the equations of continuity, momentum, energy, charges distribution and electrical current have to be solved in a coupled manner. The main results obtained in the study reveal that with the presence of thermal gradients along of the microchannel, local electro-thermal forces, Fχ, are affected in a sensible manner, and consequently, the flow field is modified substantially, causing the interruption or intensification of recirculations along of the microchannel. This work was supported by the Fondo SEP-CONACYT through research Grants No. 220900 and 20171181 from SIP-IPN. F. Mendez acknowledges support from PAPIIT-UNAM under Contract Number IN112215. S. Sanchez thanks to DGAPA-UNAM for the postdoctoral fellowship.

Fourier analysis of polar cap electric field and current distributions

NASA Technical Reports Server (NTRS)

Barbosa, D. D.

1984-01-01

A theoretical study of high-latitude electric fields and currents, using analytic Fourier analysis methods, is conducted. A two-dimensional planar model of the ionosphere with an enhanced conductivity auroral belt and field-aligned currents at the edges is employed. Two separate topics are treated. A field-aligned current element near the cusp region of the polar cap is included to investigate the modifications to the convection pattern by the east-west component of the interplanetary magnetic field. It is shown that a sizable one-cell structure is induced near the cusp which diverts equipotential contours to the dawnside or duskside, depending on the sign of the cusp current. This produces characteristic dawn-dusk asymmetries to the electric field that have been previously observed over the polar cap. The second topic is concerned with the electric field configuration obtained in the limit of perfect shielding, where the field is totally excluded equatorward of the auroral oval. When realistic field-aligned current distributions are used, the result is to produce severely distorted, crescent-shaped equipotential contours over the cap. Exact, analytic formulae applicable to this case are also provided.

Plasma heating, electric fields and plasma flow by electron beam ionospheric injection

NASA Technical Reports Server (NTRS)

Winckler, J. R.; Erickson, K. N.

1990-01-01

The electric fields and the floating potentials of a Plasma Diagnostics Payload (PDP) located near a powerful electron beam injected from a large sounding rocket into the auroral zone ionosphere have been studied. As the PDP drifted away from the beam laterally, it surveyed a region of hot plasma extending nearly to 60 m radius. Large polarization electric fields transverse to B were imbedded in this hot plasma, which displayed large ELF wave variations and also an average pattern which has led to a model of the plasma flow about the negative line potential of the beam resembling a hydrodynamic vortex in a uniform flow field. Most of the present results are derived from the ECHO 6 sounding rocket mission.

Role of near-field enhancement in plasmonic laser nanoablation using gold nanorods on a silicon substrate.

PubMed

Harrison, R K; Ben-Yakar, Adela

2010-10-11

We present experimental results for the plasmonic laser ablation of silicon with nanoscale features as small as 22 x 66 nm using single near-infrared, femtosecond laser pulses incident on gold nanorods. Near the ablation threshold, these features are photo-imprints of gold nanorod particles positioned on the surface of the silicon and have feature sizes similar to the nanorods. The single rod-shaped ablation pattern matches the enhancement patterns of the Poynting vector magnitude on the surface of silicon, implying that the ablation is a result of the plasmonic enhancement of the incident electromagnetic waves in the near-field of the particles. Interestingly, the ablation pattern is different from the two separated holes at the ends of the nanorod, as would be expected from the electric field--|E|(2) enhancement pattern. We measured the plasmonic ablation threshold fluence to be almost two orders of magnitude less than the femtosecond laser ablation threshold of silica, present in the thin native oxide layer on the surface of silicon. This value also agrees with the enhancement of the Poynting vector of a nanorod on silicon as calculated with electromagnetic simulations. We thus conclude that plasmonic ablation with plasmonic nanoparticles depends directly on the polarization and the value of the near-field enhancement of the Poynting vector and not the square of the electric field as previously suggested.

Field-design optimization with triangular heliostat pods

NASA Astrophysics Data System (ADS)

Domínguez-Bravo, Carmen-Ana; Bode, Sebastian-James; Heiming, Gregor; Richter, Pascal; Carrizosa, Emilio; Fernández-Cara, Enrique; Frank, Martin; Gauché, Paul

2016-05-01

In this paper the optimization of a heliostat field with triangular heliostat pods is addressed. The use of structures which allow the combination of several heliostats into a common pod system aims to reduce the high costs associated with the heliostat field and therefore reduces the Levelized Cost of Electricity value. A pattern-based algorithm and two pattern-free algorithms are adapted to handle the field layout problem with triangular heliostat pods. Under the Helio100 project in South Africa, a new small-scale Solar Power Tower plant has been recently constructed. The Helio100 plant has 20 triangular pods (each with 6 heliostats) whose positions follow a linear pattern. The obtained field layouts after optimization are compared against the reference field Helio100.

Etching-free patterning method for electrical characterization of atomically thin MoSe2 films grown by chemical vapor deposition.

PubMed

Utama, M Iqbal Bakti; Lu, Xin; Zhan, Da; Ha, Son Tung; Yuan, Yanwen; Shen, Zexiang; Xiong, Qihua

2014-11-07

Patterning two-dimensional materials into specific spatial arrangements and geometries is essential for both fundamental studies of materials and practical applications in electronics. However, the currently available patterning methods generally require etching steps that rely on complicated and expensive procedures. We report here a facile patterning method for atomically thin MoSe2 films using stripping with an SU-8 negative resist layer exposed to electron beam lithography. Additional steps of chemical and physical etching were not necessary in this SU-8 patterning method. The SU-8 patterning was used to define a ribbon channel from a field effect transistor of MoSe2 film, which was grown by chemical vapor deposition. The narrowing of the conduction channel area with SU-8 patterning was crucial in suppressing the leakage current within the device, thereby allowing a more accurate interpretation of the electrical characterization results from the sample. An electrical transport study, enabled by the SU-8 patterning, showed a variable range hopping behavior at high temperatures.

Concurrent temporal stability of the apparent electrical conductivity and soil water content

USDA-ARS?s Scientific Manuscript database

Knowledge of spatio-temporal soil water content (SWC) variability within agricultural fields is useful to improve crop management. Spatial patterns of soil water contents can be characterized using the temporal stability analysis, however high density sampling is required. Soil apparent electrical c...

Melatonin secretion and puberty in female lambs exposed to environmental electric and magnetic fields

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

Lee, J.M. Jr.; Stormshak, F.; Thompson, J.M.

This study determined whether chronic exposure of female lambs to the electric and magnetic fields (EMF) of a high voltage transmission line can alter pineal secretion of melatonin and the normal occurrence of puberty. Twenty female Suffolk lambs were assigned randomly in equal numbers to a control and a treatment group. Treatment from 2 to 10 mo of age consisted of continuous exposure within the electrical environment of a 500-kV transmission line (mean electric field 6 kV/m, mean magnetic field 40 mG). Treated lambs were penned directly beneath the transmission line; control lambs were maintained in a pen of similarmore » construction 229 m from the line where EMF were at ambient levels (mean electric field < 10 V/m, mean magnetic field < 0.3 mG). Melatonin was analyzed by RIA in serum of blood samples collected at 0.5-3-h intervals over eight 48-h periods. To assess attainment of puberty, serum concentrations of progesterone were determined by RIA from blood samples collected twice weekly beginning at 19 wk of age. Concentrations of circulating melatonin in control and treated lambs were low during daylight hours and increased during nighttime hours. The characteristic pattern of melatonin secretion during nighttime (amplitude, phase, and duration) did not differ between control and treatment groups. Age at puberty and number of subsequent estrous cycles also did not differ between groups. These data suggest that chronic exposure of developing female sheep to 60-Hz environmental EMF does not affect the mechanisms underlying the generation of the circadian pattern of melatonin secretion or the mechanisms involved in the onset of reproductive activity.« less

D2+ Molecular complex in non-uniform height quantum ribbon under crossed electric and magnetic fields

NASA Astrophysics Data System (ADS)

Suaza, Y. A.; Laroze, D.; Fulla, M. R.; Marín, J. H.

2018-05-01

The D2+ molecular complex fundamental properties in a uniform and multi-hilled semiconductor quantum ribbon under orthogonal electric and magnetic fields are theoretically studied. The energy structure is calculated by using adiabatic approximation combined with diagonalization procedure. The D2+ energy structure is more strongly controlled by the geometrical structural hills than the Coulomb interaction. The formation of vibrational and rotational states is discussed. Aharanov-Bohm oscillation patterns linked to rotational states as well as the D2+ molecular complex stability are highly sensitive to the number of hills while electric field breaks the electron rotational symmetry and removes the energy degeneration between low-lying states.

Electric fields induced in the human body by time-varying magnetic field gradients in MRI: numerical calculations and correlation analysis.

PubMed

Bencsik, Martin; Bowtell, Richard; Bowley, Roger

2007-05-07

The spatial distributions of the electric fields induced in the human body by switched magnetic field gradients in MRI have been calculated numerically using the commercial software package, MAFIA, and the three-dimensional, HUGO body model that comprises 31 different tissue types. The variation of |J|, |E| and |B| resulting from exposure of the body model to magnetic fields generated by typical whole-body x-, y- and z-gradient coils has been analysed for three different body positions (head-, heart- and hips-centred). The magnetic field varied at 1 kHz, so as to produce a rate of change of gradient of 100 T m(-1) s(-1) at the centre of each coil. A highly heterogeneous pattern of induced electric field and current density was found to result from the smoothly varying magnetic field in all cases, with the largest induced electric fields resulting from application of the y-gradient, in agreement with previous studies. By applying simple statistical analysis to electromagnetic quantities within axial planes of the body model, it is shown that the induced electric field is strongly correlated to the local value of resistivity, and the induced current density exhibits even stronger correlation with the local conductivity. The local values of the switched magnetic field are however shown to bear little relation to the local values of the induced electric field or current density.

Electromagnetohydrodynamic vortices and corn circles

NASA Astrophysics Data System (ADS)

Kikuchi, H.

A novel type of large-scale vortex formation has theoretically been found in helical turbulence in terms of hydrodynamic, electric, magnetic, and space charge fields in an external electric (and magnetic) field. It is called 'electro-MHD (EMHD) vortices' and is generated as a result of self-organization processes in nonequilibrium media by the transfer of energy from small- to large-scale sizes. Explanations for 'corn circles', circular symmetric ground patterns found in a corn field in southern England, are provided on the basis of a new theory of the EMHD vortices under consideration.

Electrohydrodynamics of drops covered with small particles

NASA Astrophysics Data System (ADS)

Ouriemi, Malika; Vlahovska, Petia

2013-11-01

A weakly conductive drop immersed in a more conductive liquid first undergoes an oblate deformation, and then experiences a rotation similar to Quincke rotation when submitted to an increasing DC uniform electrical field. We present an experimental study of a drop with an interface partially or completely covered with microscopic particles. Depending on the field intensity, the surface coverage, and the characteristics of the particles, the drop exhibits: (i) prolate deformation, (ii) emergence of pattern of sustained particle motions, or (iii) decrease of the electrical field that induces rotation.

Probing domain switching dynamics in ferroelectric thick films by small field e31,f piezoelectric measurement

NASA Astrophysics Data System (ADS)

Cheng, Hongbo; Ouyang, Jun; Kanno, Isaku

2017-07-01

Epitaxial Pb(Zr0.53Ti0.47)O3 films were grown on (001) Pt/(001) MgO via rf-magnetron sputtering. Switching dynamics of 90° and 180° domains under bi-polar electric fields were probed by using small-field e31 ,f measurements in which the evolution of the transverse piezoelectric response with the bias voltage represents a set of fingerprints of the evolving domain structure. Furthermore, the asymmetric e31 ,f-V curves revealed a strong built-in electric field, which was verified by the standard polarization-electric field hysteresis measurement. Finally, X-ray 2θ-scan patterns under DC bias voltages were collected for the piezoelectric specimen. The domain switching sequence indicated by the XRD results is consistent with that revealed by the e31 ,f measurement.

Hemispheric Patterns in Electric Current Helicity of Solar Magnetic Fields During Solar Cycle 24: Results from SOLIS, SDO and Hinode

NASA Astrophysics Data System (ADS)

Gusain, S.

2017-12-01

We study the hemispheric patterns in electric current helicity distribution on the Sun. Magnetic field vector in the photosphere is now routinely measured by variety of instruments. SOLIS/VSM of NSO observes full disk Stokes spectra in photospheric lines which are used to derive vector magnetograms. Hinode SP is a space based spectropolarimeter which has the same observable as SOLIS albeit with limited field-of-view (FOV) but high spatial resolution. SDO/HMI derives vector magnetograms from full disk Stokes measurements, with rather limited spectral resolution, from space in a different photospheric line. Further, these datasets now exist for several years. SOLIS/VSM from 2003, Hinode SP from 2006, and SDO HMI since 2010. Using these time series of vector magnetograms we compute the electric current density in active regions during solar cycle 24 and study the hemispheric distributions. Many studies show that the helicity parameters and proxies show a strong hemispheric bias, such that Northern hemisphere has preferentially negative and southern positive helicity, respectively. We will confirm these results for cycle 24 from three different datasets and evaluate the statistical significance of the hemispheric bias. Further, we discuss the solar cycle variation in the hemispheric helicity pattern during cycle 24 and discuss its implications in terms of solar dynamo models.

Raise and collapse of pseudo Landau levels in graphene

NASA Astrophysics Data System (ADS)

Castro, Eduardo V.; Cazalilla, Miguel A.; Vozmediano, María A. H.

2017-12-01

Lattice deformations couple to the low-energy electronic excitations of graphene as vector fields similar to the electromagnetic potential. The observation of strain-induced pseudo Landau levels with scanning tunnel microscopy experiments has been one of the most exciting events in the history of graphene. Nevertheless, the experimental observation presents some ambiguities. Similar strain patterns show different images that are sometimes difficult to interpret. In this Rapid Communication, we show that, for some strain configurations, the deformation potential acts as a parallel electric field able to destabilize the Landau level structure via a mechanism identical to that occurring for real electromagnetic fields. This effect also alters the estimations of the value of the pseudomagnetic field, which can be significantly bigger. The mechanism applies equally if the electric field has an external origin, which opens the door to an electric control of giant pseudomagnetic fields in graphene.

Electric dipole-quadrupole hybridization induced enhancement of second-harmonic generation in T-shaped plasmonic heterodimers.

PubMed

Guo, Kai; Zhang, Yong-Liang; Qian, Cheng; Fung, Kin-Hung

2018-04-30

In this work, we demonstrate computationally that electric dipole-quadrupole hybridization (EDQH) could be utilized to enhance plasmonic SHG efficiency. To this end, we construct T-shaped plasmonic heterodimers consisting of a short and a long gold nanorod with finite element method simulation. By controlling the strength of capacitive coupling between two gold nanorods, we explore the effect of EDQH evolution on the SHG process, including the SHG efficiency enhancement, corresponding near-field distribution, and far-field radiation pattern. Simulation results demonstrate that EDQH could enhance the SHG efficiency by a factor >100 in comparison with that achieved by an isolated gold nanorod. Additionally, the far-field pattern of the SHG could be adjusted beyond the well-known quadrupolar distribution and confirms that EDQH plays an important role in the SHG process.

Tuning subwavelength-structured focus in the hyperbolic metamaterials

NASA Astrophysics Data System (ADS)

Pan, Rong; Tang, Zhixiang; Pan, Jin; Peng, Runwu

2016-10-01

In this paper, we have systematically investigated light propagating in the hyperbolic metamaterials (HMMs) covered by a subwavelength grating. Based on the equal-frequency contour analyses, light in the HMM is predicted to propagate along a defined direction because of its hyperbolic dispersion, which is similar to the self-collimating effects in photonic crystals. By using the finite-difference time-domain, numerical simulations demonstrate a subwavelength bright spot at the intersection of the adjacent directional beams. Different from the images in homogeneous media, the magnetic fields and electric fields at the spot are layered, especially for the electric fields Ez that is polarized to the propagating direction, i.e., the layer normal direction. Moreover, the Ez is hollow in the layer plane and is stronger than the other electric field component Ex. Therefore, the whole electric field is structured and its pattern can be tuned by the HMM's effective anisotropic electromagnetic parameters. Our results may be useful for generating subwavelength structured light.

3-D capacitance density imaging system

DOEpatents

Fasching, G.E.

1988-03-18

A three-dimensional capacitance density imaging of a gasified bed or the like in a containment vessel is achieved using a plurality of electrodes provided circumferentially about the bed in levels and along the bed in channels. The electrodes are individually and selectively excited electrically at each level to produce a plurality of current flux field patterns generated in the bed at each level. The current flux field patterns are suitably sensed and a density pattern of the bed at each level determined. By combining the determined density patterns at each level, a three-dimensional density image of the bed is achieved. 7 figs.

3-D capacitance density imaging of fluidized bed

DOEpatents

Fasching, George E.

1990-01-01

A three-dimensional capacitance density imaging of a gasified bed or the like in a containment vessel is achieved using a plurality of electrodes provided circumferentially about the bed in levels and along the bed in channels. The electrodes are individually and selectively excited electrically at each level to produce a plurality of current flux field patterns generated in the bed at each level. The current flux field patterns are suitably sensed and a density pattern of the bed at each level determined. By combining the determined density patterns at each level, a three-dimensional density image of the bed is achieved.

Negative ion formation and evolution in atmospheric pressure corona discharges between point-to-plane electrodes with arbitrary needle angle

NASA Astrophysics Data System (ADS)

Sekimoto, K.; Takayama, M.

2010-12-01

The change in the distribution pattern of negative ions HO-, NOx- and COx- observed on arbitrary point-to-plane electrode configuration has been investigated by varying the angle of needle to the plane electrode, under atmospheric pressure corona discharge conditions. The stationary inhomogeneous electric field distributions between the point-to-plane electrodes with arbitrary needle angle were calculated. The experimental and theoretical results obtained suggested that the negative ion evolutions progress along field lines established between the electrodes with arbitrary configurations and the resulting terminal ion formation on a given field line is attributable to the electric field strength on the needle tip surface where the field line arose. The NOx- and COx- ions were dominantly produced on the field lines arising from the needle tip apex region with the highest electric field strength, while the field lines emanating from the tip peripheral regions with lower field strength resulted in the formation of the HO- ion.

The Electric Field of a Weakly Electric Fish

NASA Astrophysics Data System (ADS)

Rasnow, Brian K.

Freshwater fish of the genus Apteronotus (family Gymnotidae) generate a weak, high frequency electric field (<100 mV/cm, 0.5-10 kHz) which permeates their local environment. These nocturnal fish are acutely sensitive to perturbations in their electric field caused by other electric fish, and nearby objects whose impedance is different from the surrounding water. This thesis presents high temporal and spatial resolution maps of the electric potential and field on and near Apteronotus. The fish's electric field is a complicated and highly stable function of space and time. Its characteristics, such as spectral composition, timing, and rate of attenuation, are examined in terms of physical constraints, and their possible functional roles in electroreception. Temporal jitter of the periodic field is less than 1 musec. However, electrocyte activity is not globally synchronous along the fish's electric organ. The propagation of electrocyte activation down the fish's body produces a rotation of the electric field vector in the caudal part of the fish. This may assist the fish in identifying nonsymmetrical objects, and could also confuse electrosensory predators that try to locate Apteronotus by following its fieldlines. The propagation also results in a complex spatiotemporal pattern of the EOD potential near the fish. Visualizing the potential on the same and different fish over timescales of several months suggests that it is stable and could serve as a unique signature for individual fish. Measurements of the electric field were used to calculate the effects of simple objects on the fish's electric field. The shape of the perturbation or "electric image" on the fish's skin is relatively independent of a simple object's size, conductivity, and rostrocaudal location, and therefore could unambiguously determine object distance. The range of electrolocation may depend on both the size of objects and their rostrocaudal location. Only objects with very large dielectric constants cause appreciable phase shifts, and these are strongly dependent on the water conductivity.

Gamma-Ray Light Curves from Pulsar Magnetospheres with Finite Conductivity

NASA Technical Reports Server (NTRS)

Harding, A. K.; Kalapotharakos, C.; Kazanas, D.; Contopoulos, I.

2012-01-01

The Fermi Large Area Telescope has provided an unprecedented database for pulsar emission studies that includes gamma-ray light curves for over 100 pulsars. Modeling these light curves can reveal and constrain the geometry of the particle accelerator, as well as the pulsar magnetic field structure. We have constructed 3D magnetosphere models with finite conductivity, that bridge the extreme vacuum and force-free solutions used in previous light curves modeling. We are investigating the shapes of pulsar gamma-ray light curves using these dissipative solutions with two different approaches: (l) assuming geometric emission patterns of the slot gap and outer gap, and (2) using the parallel electric field provided by the resistive models to compute the trajectories and . emission of the radiating particles. The light curves using geometric emission patterns show a systematic increase in gamma-ray peak phase with increasing conductivity, introducing a new diagnostic of these solutions. The light curves using the model electric fields are very sensitive to the conductivity but do not resemble the observed Fermi light curves, suggesting that some screening of the parallel electric field, by pair cascades not included in the models, is necessary

Electric field driven evolution of topological domain structure in hexagonal manganites

NASA Astrophysics Data System (ADS)

Yang, K. L.; Zhang, Y.; Zheng, S. H.; Lin, L.; Yan, Z. B.; Liu, J.-M.; Cheong, S.-W.

2017-10-01

Controlling and manipulating the topological state represents an important topic in condensed matters for both fundamental researches and applications. In this work, we focus on the evolution of a real-space topological domain structure in hexagonal manganites driven by electric field, using the analytical and numerical calculations based on the Ginzburg-Landau theory. It is revealed that the electric field drives a transition of the topological domain structure from the type-I pattern to the type-II one. In particular, it is identified that a high electric field can enforce the two antiphase-plus-ferroelectric (AP +FE ) domain walls with Δ Φ =π /3 to approach each other and to merge into one domain wall with Δ Φ = 2 π /3 eventually if the electric field is sufficiently high, where Δ Φ is the difference in the trimerization phase between two neighboring domains. Our simulations also reveal that the vortex cores of the topological structure can be disabled at a sufficiently high critical electric field by suppressing the structural trimerization therein, beyond which the vortex core region is replaced by a single ferroelectric domain without structural trimerization (Q = 0 ). Our results provide a stimulating reference for understanding the manipulation of real-space topological domain structure in hexagonal manganites.

Electrical stimulation systems for cardiac tissue engineering

PubMed Central

Tandon, Nina; Cannizzaro, Christopher; Chao, Pen-Hsiu Grace; Maidhof, Robert; Marsano, Anna; Au, Hoi Ting Heidi; Radisic, Milica; Vunjak-Novakovic, Gordana

2009-01-01

We describe a protocol for tissue engineering of synchronously contractile cardiac constructs by culturing cardiac cells with the application of pulsatile electrical fields designed to mimic those present in the native heart. Tissue culture is conducted in a customized chamber built to allow for cultivation of (i) engineered three-dimensional (3D) cardiac tissue constructs, (ii) cell monolayers on flat substrates or (iii) cells on patterned substrates. This also allows for analysis of the individual and interactive effects of pulsatile electrical field stimulation and substrate topography on cell differentiation and assembly. The protocol is designed to allow for delivery of predictable electrical field stimuli to cells, monitoring environmental parameters, and assessment of cell and tissue responses. The duration of the protocol is 5 d for two-dimensional cultures and 10 d for 3D cultures. PMID:19180087

EME 192 Report

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

Mora, J.; Pascall, A.; Dudoff, J.

I spent the quarter working in Lawrence Livermore National Laboratory’s (LLNL) Materials Engineering Division. The group I have been working with (I’ve been here for two summers already) focuses on advanced manufacturing techniques such as stereolithography, electrophoretic deposition, and the printing of silicon based inks. Part of the goal of what is done in our group is to create designer materials not by altering the composition but by altering the micro-architecture. Our technology can create shapes that are not possible with traditional manufacturing techniques. This allows us to create structures that are light, yet very strong and stiff. It alsomore » allows us to create materials with property gradients. In other words, we can make structures and parts that are stronger in some locations than others. I have been working with electrophoretic deposition for the duration of my stay and have focused on advancing the technology from a thin-film technique to a true additive manufacturing paradigm. Put succinctly, electrophoretic deposition is the deposition of particles in suspension with electric fields. Particles have a potential on the surface which allows them to be driven to an electrode using an electric field. The particles then deposit onto the conductive regions of the substrate, traditionally, the entire surface. Electrophoretic deposition is powerful in that it can handle a wide variety of materials (ceramics, metals, bacteria), create material gradients in the deposits, and create layered deposition of multiple materials. A drawback of traditional electrophoretic deposition is that patterned deposits are only possible with a non-reconfigurable patterned electrode. A technique was developed at LLNL that allows for the arbitrary patterning of the electric field using photoconductive electrodes and light. This way, you can create interesting shapes and reconfigure the pattern of the deposit using the same electrode. A photoconductive electrode is made by hydrothermally growing titania nanorods onto a transparent current collector. A photomask is used to block incoming some light and only allow the desired pattern of light through. The photoconductive electrode then activates when and where the light hits, once an electric field is applied. Particles will migrate to the areas of illumation and deposit.« less

CHAPTER: In-Situ Characterization of Stimulating Microelectrode Arrays: Study of an Idealized Structure Based on Argus II Retinal implantsBOOK TITLE: Implantable Neural Prostheses 2: Techniques and Engineering Approaches, D.M. Zhou and E. Greenbaum, Eds., Springer, NY 2009

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

Greenbaum, Elias; Sanders, Charlene A; Kandagor, Vincent

The development of a retinal prosthesis for artificial sight includes a study of the factors affecting the structural and functional stability of chronically implanted microelectrode arrays. Although neuron depolarization and propagation of electrical signals have been studied for nearly a century, the use of multielectrode stimulation as a proposed therapy to treat blindness is a frontier area of modern ophthalmology research. Mapping and characterizing the topographic information contained in the electric field potentials and understanding how this information is transmitted and interpreted in the visual cortex is still very much a work in progress. In order to characterize the electricalmore » field patterns generated by the device, an in vitro prototype that mimics several of the physical and chemical parameters of the in vivo visual implant device was fabricated. We carried out multiple electrical measurements in a model 'eye,' beginning with a single electrode, followed by a 9-electrode array structure, both idealized components based on the Argus II retinal implants. Correlating the information contained in the topographic features of the electric fields with psychophysical testing in patients may help reduce the time required for patients to convert the electrical patterns into graphic signals.« less

Endogenous electromagnetic fields in plant leaves: a new hypothesis for vascular pattern formation.

PubMed

Pietak, Alexis Mari

2011-06-01

Electromagnetic (EM) phenomena have long been implicated in biological development, but few detailed, practical mechanisms have been put forth to connect electromagnetism with morphogenetic processes. This work describes a new hypothesis for plant leaf veination, whereby an endogenous electric field forming as a result of a coherent Frohlich process, and corresponding to an EM resonant mode of the developing leaf structure, is capable of instigating leaf vascularisation. In order to test the feasibility of this hypothesis, a three-dimensional, EM finite-element model (FEM) of a leaf primordium was constructed to determine if suitable resonant modes were physically possible for geometric and physical parameters similar to those of developing leaf tissue. Using the FEM model, resonant EM modes with patterns of relevance to developing leaf vein modalities were detected. On account of the existence of shared geometric signatures in a leaf's vascular pattern and the electric field component of EM resonant modes supported by a developing leaf structure, further theoretical and experimental investigations are warranted. Significantly, this hypothesis is not limited to leaf vascular patterning, but may be applicable to a variety of morphogenetic phenomena in a number of living systems.

Unusual polarity-dependent patterns in a bent-core nematic liquid crystal under low-frequency ac field.

PubMed

Xiang, Ying; Zhou, Meng-jie; Xu, Ming-Ya; Salamon, Péter; Éber, Nándor; Buka, Ágnes

2015-04-01

Electric-field-induced patterns of diverse morphology have been observed over a wide frequency range in a recently synthesized bent-core nematic (BCN) liquid crystal. At low frequencies (up to ∼25 Hz), the BCN exhibited unusual polarity-dependent patterns. When the amplitude of the ac field was enhanced, these two time-asymmetrical patterns turned into time-symmetrical prewavylike stripes. At ac frequencies in the middle-frequency range (∼50-3000 Hz), zigzag patterns were detected whose obliqueness varied with the frequency. Finally, if the frequency was increased above 3 kHz, the zigzag pattern was replaced by another, prewavylike pattern, whose threshold voltage depended on the frequency; however, the wave vector did not. For a more complete characterization, material parameters such as elastic constants, dielectric permittivities, and the anisotropy of the diamagnetic susceptibility were also determined.

Micromachined electrical cauterizer

DOEpatents

Lee, Abraham P.; Krulevitch, Peter A.; Northrup, M. Allen

1999-01-01

A micromachined electrical cauterizer. Microstructures are combined with microelectrodes for highly localized electro cauterization. Using boron etch stops and surface micromachining, microneedles with very smooth surfaces are made. Micromachining also allows for precision placement of electrodes by photolithography with micron sized gaps to allow for concentrated electric fields. A microcauterizer is fabricated by bulk etching silicon to form knife edges, then parallelly placed microelectrodes with gaps as small as 5 .mu.m are patterned and aligned adjacent the knife edges to provide homeostasis while cutting tissue. While most of the microelectrode lines are electrically insulated from the atmosphere by depositing and patterning silicon dioxide on the electric feedthrough portions, a window is opened in the silicon dioxide to expose the parallel microelectrode portion. This helps reduce power loss and assist in focusing the power locally for more efficient and safer procedures.

Micromachined electrical cauterizer

DOEpatents

Lee, A.P.; Krulevitch, P.A.; Northrup, M.A.

1999-08-31

A micromachined electrical cauterizer is disclosed. Microstructures are combined with microelectrodes for highly localized electro cauterization. Using boron etch stops and surface micromachining, microneedles with very smooth surfaces are made. Micromachining also allows for precision placement of electrodes by photolithography with micron sized gaps to allow for concentrated electric fields. A microcauterizer is fabricated by bulk etching silicon to form knife edges, then parallelly placed microelectrodes with gaps as small as 5 {mu}m are patterned and aligned adjacent the knife edges to provide homeostasis while cutting tissue. While most of the microelectrode lines are electrically insulated from the atmosphere by depositing and patterning silicon dioxide on the electric feedthrough portions, a window is opened in the silicon dioxide to expose the parallel microelectrode portion. This helps reduce power loss and assist in focusing the power locally for more efficient and safer procedures. 7 figs.

Electric field measurements across the harang discontinuity. [of the auroral zone

NASA Technical Reports Server (NTRS)

Maynard, N. C.

1974-01-01

The Harang discontinuity, the area separating the positive and negative bay regions in the midnight sector of the auroral zone, is a focal point for changes in behavior of many phenomena. Through this region the electric field rotates through the west from a basically northward field in the positive bay region to a basically southward field in the negative bay region, appearing as a reversal in a single axis measurement; 32 of these reversals have been identified in the OGO-6 data from November and December, 1969. The discontinuity is dynamic in nature, moving southward and steepening its latitudinal profile as magnetic activity is increased. As activity decreases it relaxes poleward and spreads out in latitudinal width. It occurs over several hours of magnetic local time. The boundary in the electric field data is consistent with the reversal of ground magnetic disturbances from a positive to negative bay condition. The discontinuity is present in the electric field data both during substorms and during quiet times and appears to define a pattern on which other effects can occur.

Tunable Nanowire Patterning Using Standing Surface Acoustic Waves

PubMed Central

Chen, Yuchao; Ding, Xiaoyun; Lin, Sz-Chin Steven; Yang, Shikuan; Huang, Po-Hsun; Nama, Nitesh; Zhao, Yanhui; Nawaz, Ahmad Ahsan; Guo, Feng; Wang, Wei; Gu, Yeyi; Mallouk, Thomas E.; Huang, Tony Jun

2014-01-01

Patterning of nanowires in a controllable, tunable manner is important for the fabrication of functional nanodevices. Here we present a simple approach for tunable nanowire patterning using standing surface acoustic waves (SSAW). This technique allows for the construction of large-scale nanowire arrays with well-controlled patterning geometry and spacing within 5 seconds. In this approach, SSAWs were generated by interdigital transducers (IDTs), which induced a periodic alternating current (AC) electric field on the piezoelectric substrate and consequently patterned metallic nanowires in suspension. The patterns could be deposited onto the substrate after the liquid evaporated. By controlling the distribution of the SSAW field, metallic nanowires were assembled into different patterns including parallel and perpendicular arrays. The spacing of the nanowire arrays could be tuned by controlling the frequency of the surface acoustic waves. Additionally, we observed 3D spark-shape nanowire patterns in the SSAW field. The SSAW-based nanowire-patterning technique presented here possesses several advantages over alternative patterning approaches, including high versatility, tunability, and efficiency, making it promising for device applications. PMID:23540330

Gauged baby Skyrme model with a Chern-Simons term

NASA Astrophysics Data System (ADS)

Samoilenka, A.; Shnir, Ya.

2017-02-01

The properties of the multisoliton solutions of the (2 +1 )-dimensional Maxwell-Chern-Simons-Skyrme model are investigated numerically. Coupling to the Chern-Simons term allows for existence of the electrically charge solitons which may also carry magnetic fluxes. Two particular choices of the potential term is considered: (i) the weakly bounded potential and (ii) the double vacuum potential. In the absence of gauge interaction in the former case the individual constituents of the multisoliton configuration are well separated, while in the latter case the rotational invariance of the configuration remains unbroken. It is shown that coupling of the planar multi-Skyrmions to the electric and magnetic field strongly affects the pattern of interaction between the constituents. We analyze the dependency of the structure of the solutions, the energies, angular momenta, electric and magnetic fields of the configurations on the gauge coupling constant g , and the electric potential. It is found that, generically, the coupling to the Chern-Simons term strongly affects the usual pattern of interaction between the skyrmions, in particular the electric repulsion between the solitons may break the multisoliton configuration into partons. We show that as the gauge coupling becomes strong, both the magnetic flux and the electric charge of the solutions become quantized although they are not topological numbers.

Comparative Theoretical Analysis Between Parallel and Perpendicular Geomotries for 2D Particle Patterning in Photovoltaic Ferroelectric Substrates

NASA Astrophysics Data System (ADS)

Arregui, C.; Ramiro, J. B.; Alcázar, A.; Méndez, A.; Muñoz-Martínez, J. F.; Carrascosa, M.

2015-05-01

This paper describes the dielectrophoretic potential created by the evanescent electric field acting on a particle near a photovoltaic crystalsurface depending on the crystal cut. This electric field is obtained from the steady state solution of the Kukhtarev equations for thephotovoltaic effect, where the diffusion term has been disregarded. First, the space charge field generated by a small, square, light spotwhere d << l (being d a side of the square and l the crystal thickness) is studied. The surface charge density generated in both geometriesis calculated and compared as their relation determines the different properties of the dielectrophoretic potential for both cuts. The shapeof the dielectrophoretic potential is obtained and compared for several distances to the sample. Afterwards other light patterns are studiedby the superposition of square spots, and the resulting trapping profiles are analysed. Finally the surface charge densities and trappingprofiles for different d/l relations are studied.

The CDRH Helix-I: a physical evaluation.

PubMed

Gopal, M K; Cetas, T C

1990-01-01

The use of a resonant helical coil with predominantly axial electric fields for regional hyperthermia in the abdomen and pelvis is addressed. The Helix-I applicator, which consists of a three-turn, 36-cm-long, oval-wound helical coil measuring 60 and 43 cm along its major and minor axes, respectively, is described, and specific absorption rate (SAR) measurements for the device are reported. Measurements of the E-field are also described. Specific absorption patterns for the Helix, determined by transient temperature measurements using a gel phantom, and by E(2)-field scans using a liquid phantom, are in general agreement. The general agreement of electric power intensity distribution, inside and outside the phantom, with corresponding SAR distributions obtained from transient temperature data, ensures reliability of the distribution patterns. The E(2) contours provide a clear picture of hot and cold spots as well as the nature of the general distribution.

Geometric and material determinants of patterning efficiency by dielectrophoresis.

PubMed

Albrecht, Dirk R; Sah, Robert L; Bhatia, Sangeeta N

2004-10-01

Dielectrophoretic (DEP) forces have been used extensively to manipulate, separate, and localize biological cells and bioparticles via high-gradient electric fields. However, minimization of DEP exposure time is desirable, because of possible untoward effects on cell behavior. Toward this goal, this article investigates the geometric and material determinants of particle patterning kinetics and efficiency. In particular, the time required to achieve a steady-state pattern is theoretically modeled and experimentally validated for a planar, interdigitated bar electrode array energized in a standing-wave configuration. This measure of patterning efficiency is calculated from an improved Fourier series solution of DEP force, in which realistic boundary conditions and a finite chamber height are imposed to reflect typical microfluidic applications. The chamber height, electrode spacing, and fluid viscosity and conductivity are parameters that profoundly affect patterning efficiency, and optimization can reduce electric field exposure by orders of magnitude. Modeling strategies are generalizable to arbitrary electrode design as well as to conditions where DEP force may not act alone to cause particle motion. This improved understanding of DEP patterning kinetics provides a framework for new advances in the development of DEP-based biological devices and assays with minimal perturbation of cell behavior. Copyright 2004 Biophysical Society

Geometric and Material Determinants of Patterning Efficiency by Dielectrophoresis

PubMed Central

Albrecht, Dirk R.; Sah, Robert L.; Bhatia, Sangeeta N.

2004-01-01

Dielectrophoretic (DEP) forces have been used extensively to manipulate, separate, and localize biological cells and bioparticles via high-gradient electric fields. However, minimization of DEP exposure time is desirable, because of possible untoward effects on cell behavior. Toward this goal, this article investigates the geometric and material determinants of particle patterning kinetics and efficiency. In particular, the time required to achieve a steady-state pattern is theoretically modeled and experimentally validated for a planar, interdigitated bar electrode array energized in a standing-wave configuration. This measure of patterning efficiency is calculated from an improved Fourier series solution of DEP force, in which realistic boundary conditions and a finite chamber height are imposed to reflect typical microfluidic applications. The chamber height, electrode spacing, and fluid viscosity and conductivity are parameters that profoundly affect patterning efficiency, and optimization can reduce electric field exposure by orders of magnitude. Modeling strategies are generalizable to arbitrary electrode design as well as to conditions where DEP force may not act alone to cause particle motion. This improved understanding of DEP patterning kinetics provides a framework for new advances in the development of DEP-based biological devices and assays with minimal perturbation of cell behavior. PMID:15454417

Post-deposition control of ferroelastic stripe domains and internal electric field by thermal treatment

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

Feigl, L.; Iwanowska, M.; Sandu, C. S.

The dependence of the formation of ferroelastic stripe domain patterns on the thermal history is investigated by detailed piezoresponse force microscopy and X-ray diffraction experiments after and during annealing of tensile strained tetragonal Pb(Ti,Zr)O{sub 3} epitaxial thin films on DyScO{sub 3} substrates. In particular, the ferroelastic pattern is reversibly interchanged between a cross-hatched and a stripe domain pattern if the films are cooled at different rates after annealing above the formation temperature of a-domains. Different types of 180° and non-180° patterns can be created, depending on the thermal treatment. The changes in the 180° domain structure and lattice parameters aremore » attributed to a change of oxygen vacancy concentration, which results in a modification of the internal electric field and unit cell size, causing also a shift of T{sub C}. Thermal treatment is done on rhombohedral La:BiFeO{sub 3} thin films as well. It is observed that also in these films, appropriate heat treatment modifies the domain pattern and films with a stripe domain pattern can be created, confirming the general validity of the developed model.« less

Post-deposition control of ferroelastic stripe domains and internal electric field by thermal treatment

NASA Astrophysics Data System (ADS)

Feigl, L.; Janolin, P.-E.; Yamada, T.; Iwanowska, M.; Sandu, C. S.; Setter, N.

2015-01-01

The dependence of the formation of ferroelastic stripe domain patterns on the thermal history is investigated by detailed piezoresponse force microscopy and X-ray diffraction experiments after and during annealing of tensile strained tetragonal Pb(Ti,Zr)O3 epitaxial thin films on DyScO3 substrates. In particular, the ferroelastic pattern is reversibly interchanged between a cross-hatched and a stripe domain pattern if the films are cooled at different rates after annealing above the formation temperature of a-domains. Different types of 180° and non-180° patterns can be created, depending on the thermal treatment. The changes in the 180° domain structure and lattice parameters are attributed to a change of oxygen vacancy concentration, which results in a modification of the internal electric field and unit cell size, causing also a shift of TC. Thermal treatment is done on rhombohedral La:BiFeO3 thin films as well. It is observed that also in these films, appropriate heat treatment modifies the domain pattern and films with a stripe domain pattern can be created, confirming the general validity of the developed model.

From 1D to 3D: Tunable Sub-10 nm Gaps in Large Area Devices.

PubMed

Zhou, Ziwei; Zhao, Zhiyuan; Yu, Ye; Ai, Bin; Möhwald, Helmuth; Chiechi, Ryan C; Yang, Joel K W; Zhang, Gang

2016-04-20

Tunable sub-10 nm 1D nanogaps are fabricated based on nanoskiving. The electric field in different sized nanogaps is investigated theoretically and experimentally, yielding nonmonotonic dependence and an optimized gap-width (5 nm). 2D nanogap arrays are fabricated to pack denser gaps combining surface patterning techniques. Innovatively, 3D multistory nanogaps are built via a stacking procedure, processing higher integration, and much improved electric field. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Field alignment of bent-core smectic liquid crystals for analog optical phase modulation

NASA Astrophysics Data System (ADS)

Shen, Y.; Goodhew, L.; Shao, R.; Moran, M.; Korblova, E.; Walba, D. M.; Clark, N. A.; Maclennan, J. E.; Rudquist, P.

2015-05-01

A general method for aligning bent-core smectic liquid crystal materials is described. Alternating electric fields between interdigitated electrodes patterned on one cell surface create torques on the liquid crystal that result in uniform "bookshelf" orientation of the smectic layers. The aligned cell can then be driven in the conventional way by applying an electric field between all of the stripe electrodes connected together and a monolithic electrode on the other cell surface. Fast, analog, optical phase-only modulation is demonstrated in a device containing a polar, bent-core SmAPF material aligned using this technique.

Melatonin and puberty in female lambs exposed to EMF: A replicate study

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

Lee, J.M. Jr.; Stormshak, F.; Thompson, J.M.

1995-06-01

In an earlier study, the authors found no effects of 60 Hz electric and magnetic fields (EMF) from a 500 kV transmission line on serum melatonin patterns or on puberty in ten female Suffolk lambs (Ovis aries). The authors conducted a larger replicate study of 15 lambs exposed to a mean electric field of 6.3 kV/m and a mean magnetic field of 3.77 {mu}T and 15 controls exposed to EMF two orders of magnitude weaker than in the line area. The replicate produced essentially the same results as their previous study.

Electric radiation mapping of silver/zinc oxide nanoantennas by using electron holography

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

Sanchez, J. E.; Mendoza-Santoyo, F.; Cantu-Valle, J.

2015-01-21

In this work, we report the fabrication of self-assembled zinc oxide nanorods grown on pentagonal faces of silver nanowires by using microwaves irradiation. The nanostructures resemble a hierarchal nanoantenna and were used to study the far and near field electrical metal-semiconductor behavior from the electrical radiation pattern resulting from the phase map reconstruction obtained using off-axis electron holography. As a comparison, we use electric numerical approximations methods for a finite number of ZnO nanorods on the Ag nanowires and show that the electric radiation intensities maps match closely the experimental results obtained with electron holography. The time evolution of themore » radiation pattern as generated from the nanostructure was recorded under in-situ radio frequency signal stimulation, in which the generated electrical source amplitude and frequency were varied from 0 to 5 V and from 1 to 10 MHz, respectively. The phase maps obtained from electron holography show the change in the distribution of the electric radiation pattern for individual nanoantennas. The mapping of this electrical behavior is of the utmost importance to gain a complete understanding for the metal-semiconductor (Ag/ZnO) heterojunction that will help to show the mechanism through which these receiving/transmitting structures behave at nanoscale level.« less

Towards high efficiency heliostat fields

NASA Astrophysics Data System (ADS)

Arbes, Florian; Wöhrbach, Markus; Gebreiter, Daniel; Weinrebe, Gerhard

2017-06-01

CSP power plants have great potential to substantially contribute to world energy supply. To set this free, cost reductions are required for future projects. Heliostat field layout optimization offers a great opportunity to improve field efficiency. Field efficiency primarily depends on the positions of the heliostats around the tower, commonly known as the heliostat field layout. Heliostat shape also influences efficiency. Improvements to optical efficiency results in electricity cost reduction without adding any extra technical complexity. Due to computational challenges heliostat fields are often arranged in patterns. The mathematical models of the radial staggered or spiral patterns are based on two parameters and thus lead to uniform patterns. Optical efficiencies of a heliostat field do not change uniformly with the distance to the tower, they even differ in the northern and southern field. A fixed pattern is not optimal in many parts of the heliostat field, especially when used as large scaled heliostat field. In this paper, two methods are described which allow to modify field density suitable to inconsistent field efficiencies. A new software for large scale heliostat field evaluation is presented, it allows for fast optimizations of several parameters for pattern modification routines. It was used to design a heliostat field with 23,000 heliostats, which is currently planned for a site in South Africa.

AC Electric-Field-Induced Fluid Flow in Microelectrodes.

PubMed

Ramos; Morgan; Green; Castellanos

1999-09-15

During the AC electrokinetic manipulation of particles in suspension on microelectrode structures, strong frequency-dependent fluid flow is observed. The fluid movement is predominant at frequencies below the reciprocal charge relaxation time, with a reproducible pattern occurring close to and across the electrode surface. This paper reports measurements of the fluid velocity as a function of frequency and position across the electrode. Evidence is presented indicating that the flow occurs due to electroosmotic stress arising from the interaction of the electric field and the electrical double layer on the electrodes. The electrode polarization plays a significant role in controlling the frequency dependence of the flow. Copyright 1999 Academic Press.

Ionic messengers in development and cancer.

PubMed

Moreau, Marc; Leclerc, Catherine

2015-01-01

The idea that electrical fields can influence the development of an organism is not new. Electrical fields in cells are mainly due to the presence of channels which are permeable and selective for different ions and transporters. Modulation of their activities can affect cell cycle properties, proliferation and differentiation.Electrical fields are important for embryonic patterning, regeneration and tumour development. Membrane potential is a permanent signal which allows communication between cells, tissues and organs and has to be considered to have the same importance as biochemical signals. The activity of ion channels and pumps which maintain the electrical fields can now be dissected and visualized with new tools involving fluorescent reporters.Despite the fact that our understanding, at the molecular level, of the role of bioelectric signaling pathways, ion currents, voltage and pH gradients in developmental biology and tumor progression is increasing, therapeutic applications of this knowledge still appears to be far away. For the moment, research priorities seem to be on establishing the links between biochemical events, genetic regulation, and network interactions.

Local electric field direct writing – Electron-beam lithography and mechanism

DOE PAGES

Jiang, Nan; Su, Dong; Spence, John C. H.

2017-08-24

Local electric field induced by a focused electron probe in silicate glass thin films is evaluated in this paper by the migration of cations. Extremely strong local electric fields can be obtained by the focused electron probe from a scanning transmission electron microscope. As a result, collective atomic displacements occur. This newly revised mechanism provides an efficient tool to write patterned nanostructures directly, and thus overcome the low efficiency of the conventional electron-beam lithography. Applying this technique to silicate glass thin films, as an example, a grid of rods of nanometer dimension can be efficiently produced by rapidly scanning amore » focused electron probe. This nanopatterning is achieved through swift phase separation in the sample, without any post-development processes. The controlled phase separation is induced by massive displacements of cations (glass modifiers) within the glass-former network, driven by the strong local electric fields. The electric field is induced by accumulated charge within the electron probed region, which is generated by the excitation of atomic electrons by the incident electron. Throughput is much improved compared to other scanning probe techniques. Finally, the half-pitch spatial resolution of nanostructure in this particular specimen is 2.5 nm.« less

Local electric field direct writing – Electron-beam lithography and mechanism

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

Jiang, Nan; Su, Dong; Spence, John C. H.

Local electric field induced by a focused electron probe in silicate glass thin films is evaluated in this paper by the migration of cations. Extremely strong local electric fields can be obtained by the focused electron probe from a scanning transmission electron microscope. As a result, collective atomic displacements occur. This newly revised mechanism provides an efficient tool to write patterned nanostructures directly, and thus overcome the low efficiency of the conventional electron-beam lithography. Applying this technique to silicate glass thin films, as an example, a grid of rods of nanometer dimension can be efficiently produced by rapidly scanning amore » focused electron probe. This nanopatterning is achieved through swift phase separation in the sample, without any post-development processes. The controlled phase separation is induced by massive displacements of cations (glass modifiers) within the glass-former network, driven by the strong local electric fields. The electric field is induced by accumulated charge within the electron probed region, which is generated by the excitation of atomic electrons by the incident electron. Throughput is much improved compared to other scanning probe techniques. Finally, the half-pitch spatial resolution of nanostructure in this particular specimen is 2.5 nm.« less

Electrokinetic instability in microchannel ferrofluid/water co-flows

PubMed Central

Song, Le; Yu, Liandong; Zhou, Yilong; Antao, Asher Reginald; Prabhakaran, Rama Aravind; Xuan, Xiangchun

2017-01-01

Electrokinetic instability refers to unstable electric field-driven disturbance to fluid flows, which can be harnessed to promote mixing for various electrokinetic microfluidic applications. This work presents a combined numerical and experimental study of electrokinetic ferrofluid/water co-flows in microchannels of various depths. Instability waves are observed at the ferrofluid and water interface when the applied DC electric field is beyond a threshold value. They are generated by the electric body force that acts on the free charge induced by the mismatch of ferrofluid and water electric conductivities. A nonlinear depth-averaged numerical model is developed to understand and simulate the interfacial electrokinetic behaviors. It considers the top and bottom channel walls’ stabilizing effects on electrokinetic flow through the depth averaging of three-dimensional transport equations in a second-order asymptotic analysis. This model is found accurate to predict both the observed electrokinetic instability patterns and the measured threshold electric fields for ferrofluids of different concentrations in shallow microchannels. PMID:28406228

Wireless Fluid Level Measuring System

NASA Technical Reports Server (NTRS)

Taylor, Bryant D. (Inventor); Woodard, Stanley E. (Inventor)

2007-01-01

A level-sensing probe positioned in a tank is divided into sections with each section including (i) a fluid-level capacitive sensor disposed along the length thereof, (ii) an inductor electrically coupled to the capacitive sensor, (iii) a sensor antenna positioned for inductive coupling to the inductor, and (iv) an electrical conductor coupled to the sensor antenna. An electrically non-conductive housing accessible from a position outside of the tank houses antennas arrayed in a pattern. Each antenna is electrically coupled to the electrical conductor from a corresponding one of the sections. A magnetic field response recorder has a measurement head with transceiving antennas arrayed therein to correspond to the pattern of the housing's antennas. When a measurement is to be taken, the measurement head is mechanically coupled to the housing so that each housing antenna is substantially aligned with a specific one of the transceiving antennas.

Orientation selective deep brain stimulation

NASA Astrophysics Data System (ADS)

Lehto, Lauri J.; Slopsema, Julia P.; Johnson, Matthew D.; Shatillo, Artem; Teplitzky, Benjamin A.; Utecht, Lynn; Adriany, Gregor; Mangia, Silvia; Sierra, Alejandra; Low, Walter C.; Gröhn, Olli; Michaeli, Shalom

2017-02-01

Objective. Target selectivity of deep brain stimulation (DBS) therapy is critical, as the precise locus and pattern of the stimulation dictates the degree to which desired treatment responses are achieved and adverse side effects are avoided. There is a clear clinical need to improve DBS technology beyond currently available stimulation steering and shaping approaches. We introduce orientation selective neural stimulation as a concept to increase the specificity of target selection in DBS. Approach. This concept, which involves orienting the electric field along an axonal pathway, was tested in the corpus callosum of the rat brain by freely controlling the direction of the electric field on a plane using a three-electrode bundle, and monitoring the response of the neurons using functional magnetic resonance imaging (fMRI). Computational models were developed to further analyze axonal excitability for varied electric field orientation. Main results. Our results demonstrated that the strongest fMRI response was observed when the electric field was oriented parallel to the axons, while almost no response was detected with the perpendicular orientation of the electric field relative to the primary fiber tract. These results were confirmed by computational models of the experimental paradigm quantifying the activation of radially distributed axons while varying the primary direction of the electric field. Significance. The described strategies identify a new course for selective neuromodulation paradigms in DBS based on axonal fiber orientation.

First Results on the Variability of Mid- and High-Latitude Ionospheric Electric Fields at 1- Second Time Scales

NASA Astrophysics Data System (ADS)

Ruohoniemi, J. M.; Greenwald, R. A.; Oksavik, K.; Baker, J. B.

2007-12-01

The electric fields at high latitudes are often modeled as a static pattern in the absence of variation in solar wind parameters or geomagnetic disturbance. However, temporal variability in the local electric fields on time scales of minutes for stable conditions has been reported and characterized statistically as an intrinsic property amounting to turbulence. We describe the results of applying a new technique to SuperDARN HF radar observations of ionospheric plasma convection at middle and high latitudes that gives views of the variability of the electric fields at sub-second time scales. We address the question of whether there is a limit to the temporal scale of the electric field variability and consider whether the turbulence on minute time scales is due to organized but unresolved behavior. The basis of the measurements is the ability to record raw samples from the individual multipulse sequences that are transmitted during the standard 3 or 6-second SuperDARN integration period; a backscattering volume is then effectively sampled at a cadence of 200 ms. The returns from the individual sequences are often sufficiently well-ordered to permit a sequence-by-sequence characterization of the electric field and backscattered power. We attempt a statistical characterization of the variability at these heretofore inaccessible time scales and consider how variability is influenced by solar wind and magentospheric factors.

Optimization of return electrodes in neurostimulating arrays

NASA Astrophysics Data System (ADS)

Flores, Thomas; Goetz, Georges; Lei, Xin; Palanker, Daniel

2016-06-01

Objective. High resolution visual prostheses require dense stimulating arrays with localized inputs of individual electrodes. We study the electric field produced by multielectrode arrays in electrolyte to determine an optimal configuration of return electrodes and activation sequence. Approach. To determine the boundary conditions for computation of the electric field in electrolyte, we assessed current dynamics using an equivalent circuit of a multielectrode array with interleaved return electrodes. The electric field modeled with two different boundary conditions derived from the equivalent circuit was then compared to measurements of electric potential in electrolyte. To assess the effect of return electrode configuration on retinal stimulation, we transformed the computed electric fields into retinal response using a model of neural network-mediated stimulation. Main results. Electric currents at the capacitive electrode-electrolyte interface redistribute over time, so that boundary conditions transition from equipotential surfaces at the beginning of the pulse to uniform current density in steady state. Experimental measurements confirmed that, in steady state, the boundary condition corresponds to a uniform current density on electrode surfaces. Arrays with local return electrodes exhibit improved field confinement and can elicit stronger network-mediated retinal response compared to those with a common remote return. Connecting local return electrodes enhances the field penetration depth and allows reducing the return electrode area. Sequential activation of the pixels in large monopolar arrays reduces electrical cross-talk and improves the contrast in pattern stimulation. Significance. Accurate modeling of multielectrode arrays helps optimize the electrode configuration to maximize the spatial resolution, contrast and dynamic range of retinal prostheses.

Engineering support activities for the Apollo 17 Surface Electrical Properties Experiment.

NASA Technical Reports Server (NTRS)

Cubley, H. D.

1972-01-01

Description of the engineering support activities which were required to ensure fulfillment of objectives specified for the Apollo 17 SEP (Surface Electrical Properties) Experiment. Attention is given to procedural steps involving verification of hardware acceptability to the astronauts, computer simulation of the experiment hardware, field trials, receiver antenna pattern measurements, and the qualification test program.

Multi-mode horn antenna simulation

NASA Technical Reports Server (NTRS)

Dod, L. R.; Wolf, J. D.

1980-01-01

Radiation patterns were computed for a circular multimode horn antenna using waveguide electric field radiation expressions. The circular multimode horn was considered as a possible reflector feed antenna for the Large Antenna Multifrequency Microwave Radiometer (LAMMR). This horn antenna uses a summation of the TE sub 11 deg and TM sub 11 deg modes to generate far field primary radiation patterns with equal E and H plane beamwidths and low sidelobes. A computer program for the radiation field expressions using the summation of waveguide radiation modes is described. The sensitivity of the multimode horn antenna radiation patterns to phase variations between the two modes is given. Sample radiation pattern calculations for a reflector feed horn for LAMMR are shown. The multimode horn antenna provides a low noise feed suitable for radiometric applications.

Interference patterns of a horizontal electric dipole over layered dielectric media.

NASA Technical Reports Server (NTRS)

Tsang, L.; Kong, J. A.; Simmons, G.

1973-01-01

Interference patterns for electromagnetic fields due to a subsurface reflector below a layered lossy dielectric are calculated with the geometrical optics approximation for use in interpreting data to be collected on the moon by Apollo 17 as well as data currently being obtained on terrestrial glaciers. The radiating antenna lies on the surface. All six field components are calculated and studied. For the endfire solutions, the peak of the first reflected wave is found to be different from that of the broadside ones. To facilitate a physical discussion, we plotted the radiation patterns due to the antenna on the surface.

Controlling flows in microchannels with patterned surface charge and topography.

PubMed

Stroock, Abraham D; Whitesides, George M

2003-08-01

This Account reviews two procedures for controlling the flow of fluids in microchannels. The first procedure involves patterning the density of charge on the inner surfaces of a channel. These patterns generate recirculating electroosmotic flows in the presence of a steady electric field. The second procedure involves patterning topography on an inner surface of a channel. These patterns generate recirculation in the cross-section of steady, pressure-driven flows. This Account summarizes applications of these flow to mixing and to controlling dispersion (band broadening).

Advanced electric-field scanning probe lithography on molecular resist using active cantilever

NASA Astrophysics Data System (ADS)

Kaestner, Marcus; Aydogan, Cemal; Lipowicz, Hubert-Seweryn; Ivanov, Tzvetan; Lenk, Steve; Ahmad, Ahmad; Angelov, Tihomir; Reum, Alexander; Ishchuk, Valentyn; Atanasov, Ivaylo; Krivoshapkina, Yana; Hofer, Manuel; Holz, Mathias; Rangelow, Ivo W.

2015-03-01

The routine "on demand" fabrication of features smaller than 10 nm opens up new possibilities for the realization of many novel nanoelectronic, NEMS, optical and bio-nanotechnology-based devices. Based on the thermally actuated, piezoresistive cantilever technology we have developed a first prototype of a scanning probe lithography (SPL) platform able to image, inspect, align and pattern features down to single digit nano regime. The direct, mask-less patterning of molecular resists using active scanning probes represents a promising path circumventing the problems in today's radiation-based lithography. Here, we present examples of practical applications of the previously published electric field based, current-controlled scanning probe lithography on molecular glass resist calixarene by using the developed tabletop SPL system. We demonstrate the application of a step-and-repeat scanning probe lithography scheme including optical as well as AFM based alignment and navigation. In addition, sequential read-write cycle patterning combining positive and negative tone lithography is shown. We are presenting patterning over larger areas (80 x 80 μm) and feature the practical applicability of the lithographic processes.

Circularly polarized few-cycle optical rogue waves: rotating reduced Maxwell-Bloch equations.

PubMed

Xu, Shuwei; Porsezian, K; He, Jingsong; Cheng, Yi

2013-12-01

The rotating reduced Maxwell-Bloch (RMB) equations, which describe the propagation of few-cycle optical pulses in a transparent media with two isotropic polarized electronic field components, are derived from a system of complete Maxwell-Bloch equations without using the slowly varying envelope approximations. Two hierarchies of the obtained rational solutions, including rogue waves, which are also called few-cycle optical rogue waves, of the rotating RMB equations are constructed explicitly through degenerate Darboux transformation. In addition to the above, the dynamical evolution of the first-, second-, and third-order few-cycle optical rogue waves are constructed with different patterns. For an electric field E in the three lower-order rogue waves, we find that rogue waves correspond to localized large amplitude oscillations of the polarized electric fields. Further a complementary relationship of two electric field components of rogue waves is discussed in terms of analytical formulas as well as numerical figures.

Terahertz radiation generation through the nonlinear interaction of Hermite and Laguerre Gaussian laser beams with collisional plasma: Field profile optimization

NASA Astrophysics Data System (ADS)

Safari, Samaneh; Niknam, Ali Reza; Jahangiri, Fazel; Jazi, Bahram

2018-04-01

The nonlinear interaction of Hermite-Gaussian and Laguerre-Gaussian (LG) laser beams with a collisional inhomogeneous plasma is studied, and the amplitude of the emitted terahertz (THz) electric field is evaluated. The effects of laser beams and plasma parameters, including the beams width, LG modes, the plasma collision frequency, and the amplitude of density ripple on the evolution of THz electric field amplitude, are examined. It is found that the shape of the generated THz radiation pattern can be tuned by the laser parameters. In addition, the optimum values of the effective parameters for achieving the maximum THz electric field amplitude are proposed. It is shown that a significant enhancement up to 4.5% can be obtained in our scheme, which is much greater than the maximum efficiency obtained for laser beams with the same profiles.

Regularly scheduled, day-time, slow-onset 60 Hz electric and magnetic field exposure does not depress serum melatonin concentration in nonhuman primates

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

Rogers, W.R.; Smith, H.D.; Orr, J.L.

Experiments conducted with laboratory rodents indicate that exposure to 60 Hz electric fields or magnetic fields can suppress nocturnal melatonin concentrations in pineal gland and blood. In three experiments employing three field-exposed and three sham-exposed nonhuman primates, each implanted with an indwelling venous cannula to allow repeated blood sampling, the authors studied the effects of either 6 kV/m and 50 {micro}T (0.5 G) or 30 kV/m and 100 {micro}T (1.0 G) on serum melatonin patterns. The fields were ramped on and off slowly, so that no transients occurred. Extensive quality control for the melatonin assay, computerized control and monitoring ofmore » field intensities, and consistent exposure protocols were used. No changes in nocturnal serum melatonin concentration resulted from 6 weeks of day-time exposure with slow field onset/offset and a highly regular exposure protocol. These results indicate that, under the conditions tested, day-time exposure to 60 Hz electric and magnetic fields in combination does not result in melatonin suppression in primates.« less

Electrorheological crystallization of proteins and other molecules

DOEpatents

Craig, G.D.; Rupp, B.

1996-06-11

An electrorheological crystalline mass of a molecule is formed by dispersing the molecule in a dispersion fluid and subjecting the molecule dispersion to a uniform electrical field for a period of time during which time an electrorheological crystalline mass is formed. Molecules that may be used to form an electrorheological crystalline mass include any organic or inorganic molecule which has a permanent dipole and/or which is capable of becoming an induced dipole in the presence of an electric field. The molecules used to form the electrorheological crystalline mass are preferably macromolecules, such as biomolecules, such as proteins, nucleic acids, carbohydrates, lipoproteins and viruses. Molecules are crystallized by a method in which an electric field is maintained for a period of time after the electrorheological crystalline mass has formed during which time at least some of the molecules making up the electrorheological crystalline mass form a crystal lattice. The three dimensional structure of a molecule is determined by a method in which an electrorheological crystalline mass of the molecule is formed, an X-ray diffraction pattern of the electrorheological crystalline mass is obtained and the three dimensional structure of the molecule is calculated from the X-ray diffraction pattern. 4 figs.

Electrorheological crystallization of proteins and other molecules

DOEpatents

Craig, George D.; Rupp, Bernhard

1996-01-01

An electrorheological crystalline mass of a molecule is formed by dispersing the molecule in a dispersion fluid and subjecting the molecule dispersion to a uniform electrical field for a period of time during which time an electrorheological crystalline mass is formed. Molecules that may be used to form an electrorheological crystalline mass include any organic or inorganic molecule which has a permanent dipole and/or which is capable of becoming an induced dipole in the presence of an electric field. The molecules used to form the electrorheological crystalline mass are preferably macromolecules, such as biomolecules, such as proteins, nucleic acids, carbohydrates, lipoproteins and viruses. Molecules are crystallized by a method in which an electric field is maintained for a period of time after the electrorheological crystalline mass has formed during which time at least some of the molecules making up the electrorheological crystalline mass form a crystal lattice. The three dimensional structure of a molecule is determined by a method in which an electrorheological crystalline mass of the molecule is formed, an x-ray diffraction pattern of the electrorheological crystalline mass is obtained and the three dimensional structure of the molecule is calculated from the x-ray diffraction pattern.

Effects of E × B drift on electron transport across the magnetic field in a miniature microwave discharge neutralizer

NASA Astrophysics Data System (ADS)

Hiramoto, Kenta; Nakagawa, Yuichi; Koizumi, Hiroyuki; Takao, Yoshinori

2017-06-01

Using a three-dimensional particle-in-cell model, electron transport across a magnetic field has been investigated by obtaining the time-varying electric field and plasma parameters in a miniature microwave discharge neutralizer. The size of the neutralizer is 20 × 20 × 4 mm3. Ring-shaped antenna producing 4.2 GHz microwaves and permanent magnets for xenon plasma discharges are present inside. There are four orifices for electron extraction. The simulation area consists of both the discharge chamber and the vacuum region for the extraction. The numerical results show that radial striped patterns occur where the peak electron density is obtained, and the patterns seem to rotate in the azimuthal direction. This characteristic structure is very similar to recent results obtained in Hall thrusters and is probably due to the electron drift instability. Owing to the plasma structure, the azimuthal electric field is generated, which results in the E × B drift velocity in the axial direction with the radial magnetic field of the permanent magnets. This E × B drift velocity is a key factor in the electron transport across the magnetic field, leading to the electron extraction from the discharge chamber.

Open and closed loop manipulation of charged microchiplets in an electric field

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

Lu, J. P., E-mail: jplu@parc.com; Thompson, J. D.; Whiting, G. L.

We demonstrate the ability to orient, position, and transport microchips (“chiplets”) with electric fields. In an open-loop approach, modified four phase traveling wave potential patterns manipulate chiplets in a dielectric solution using dynamic template agitation techniques. Repeatable parallel assembly of chiplets is demonstrated to a positional accuracy of 6.5 μm using electrodes of 200 μm pitch. Chiplets with dipole surface charge patterns are used to show that orientation can be controlled by adding unique charge patterns on the chiplets. Chip path routing is also demonstrated. With a closed-loop control system approach using video feedback, dielectric, and electrophoretic forces are used to achievemore » positioning accuracy of better than 1 μm with 1 mm pitch driving electrodes. These chip assembly techniques have the potential to enable future printer systems where inputs are electronic chiplets and the output is a functional electronic system.« less

Fabrication of Vertically Aligned Carbon Nanotube or Zinc Oxide Nanorod Arrays for Optical Diffraction Gratings.

PubMed

Kim, Jeong; Kim, Sun Il; Cho, Seong-Ho; Hwang, Sungwoo; Lee, Young Hee; Hur, Jaehyun

2015-11-01

We report on new fabrication methods for a transparent, hierarchical, and patterned electrode comprised of either carbon nanotubes or zinc oxide nanorods. Vertically aligned carbon nanotubes or zinc oxide nanorod arrays were fabricated by either chemical vapor deposition or hydrothermal growth, in combination with photolithography. A transparent conductive graphene layer or zinc oxide seed layer was employed as the transparent electrode. On the patterned surface defined using photoresist, the vertically grown carbon nanotubes or zinc oxides could produce a concentrated electric field under applied DC voltage. This periodic electric field was used to align liquid crystal molecules in localized areas within the optical cell, effectively modulating the refractive index. Depending on the material and morphology of these patterned electrodes, the diffraction efficiency presented different behavior. From this study, we established the relationship between the hierarchical structure of the different electrodes and their efficiency for modulating the refractive index. We believe that this study will pave a new path for future optoelectronic applications.

Comparative study on luminescence extraction strategies of LED by large-scale fabrication of nanopillar and nanohole structures

NASA Astrophysics Data System (ADS)

Guo, Wei; Li, Junmei; Sheikhi, Moheb; Jiang, Jie’an; Yang, Zhenhai; Li, Hongwei; Guo, Shiping; Sheng, Jiang; Sun, Jie; Bo, Baoxue; Ye, Jichun

2018-06-01

Light extraction and current injection are two important considerations in the development of high efficiency light-emitting-diodes (LEDs), but usually cannot be satisfied simultaneously in nanostructure patterned devices. In this work, we investigated near-UV LEDs with nanopillar and nanohole patterns to improve light extraction efficiency. Photoluminescence (PL) intensities were enhanced by 8.0 and 4.1 times for nanopillar and nanohole LEDs compared to that of planar LED. Nanopillar LED exhibits higher PL emission than that of the nanohole LED, attributing to a convex shape sidewall for more effective outward light scattering, and reduction of quantum-confined-stark-effect owing to strain relaxation. However, nanopillar LED exhibits lower electroluminescence intensity than the nanohole sample, which calls for further optimization in carrier distributions. Experimental results were further supported by near-field electric field simulations. This work demonstrates the difference in optical and electrical behaviors between the nanopillar and nanohole LEDs, paving the way for detailed understanding on luminescence extraction mechanisms of nanostructure patterned UV emitters.

Electric Dipole Moment Results from lattice QCD

NASA Astrophysics Data System (ADS)

Dragos, Jack; Luu, Thomas; Shindler, Andrea; de Vries, Jordy

2018-03-01

We utilize the gradient flow to define and calculate electric dipole moments induced by the strong QCD θ-term and the dimension-6 Weinberg operator. The gradient flow is a promising tool to simplify the renormalization pattern of local operators. The results of the nucleon electric dipole moments are calculated on PACS-CS gauge fields (available from the ILDG) using Nf = 2+1, of discrete size 323×64 and spacing a ≃ 0.09 fm. These gauge fields use a renormalization-group improved gauge action and a nonperturbatively O(a) improved clover quark action at β = 1.90, with cSW = 1.715. The calculation is performed at pion masses of mπ ≃ 411, 701 MeV.

Defects formation and spiral waves in a network of neurons in presence of electromagnetic induction.

PubMed

Rostami, Zahra; Jafari, Sajad

2018-04-01

Complex anatomical and physiological structure of an excitable tissue (e.g., cardiac tissue) in the body can represent different electrical activities through normal or abnormal behavior. Abnormalities of the excitable tissue coming from different biological reasons can lead to formation of some defects. Such defects can cause some successive waves that may end up to some additional reorganizing beating behaviors like spiral waves or target waves. In this study, formation of defects and the resulting emitted waves in an excitable tissue are investigated. We have considered a square array network of neurons with nearest-neighbor connections to describe the excitable tissue. Fundamentally, electrophysiological properties of ion currents in the body are responsible for exhibition of electrical spatiotemporal patterns. More precisely, fluctuation of accumulated ions inside and outside of cell causes variable electrical and magnetic field. Considering undeniable mutual effects of electrical field and magnetic field, we have proposed the new Hindmarsh-Rose (HR) neuronal model for the local dynamics of each individual neuron in the network. In this new neuronal model, the influence of magnetic flow on membrane potential is defined. This improved model holds more bifurcation parameters. Moreover, the dynamical behavior of the tissue is investigated in different states of quiescent, spiking, bursting and even chaotic state. The resulting spatiotemporal patterns are represented and the time series of some sampled neurons are displayed, as well.

Multi-field electron emission pattern of 2D emitter: Illustrated with graphene

NASA Astrophysics Data System (ADS)

Luo, Ma; Li, Zhibing

2016-11-01

The mechanism of laser-assisted multi-field electron emission of two-dimensional emitters is investigated theoretically. The process is basically a cold field electron emission but having more controllable components: a uniform electric field controls the emission potential barrier, a magnetic field controls the quantum states of the emitter, while an optical field controls electron populations of specified quantum states. It provides a highly orientational vacuum electron line source whose divergence angle over the beam plane is inversely proportional to square root of the emitter height. Calculations are carried out for graphene with the armchair emission edge, as a concrete example. The rate equation incorporating the optical excitation, phonon scattering, and thermal relaxation is solved in the quasi-equilibrium approximation for electron population in the bands. The far-field emission patterns, that inherit the features of the Landau bands, are obtained. It is found that the optical field generates a characteristic structure at one wing of the emission pattern.

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

Electric-field-induced interferometric resonance of a one-dimensional spin-orbit-coupled electron

PubMed Central

Fan, Jingtao; Chen, Yuansen; Chen, Gang; Xiao, Liantuan; Jia, Suotang; Nori, Franco

2016-01-01

The efficient control of electron spins is of crucial importance for spintronics, quantum metrology, and quantum information processing. We theoretically formulate an electric mechanism to probe the electron spin dynamics, by focusing on a one-dimensional spin-orbit-coupled nanowire quantum dot. Owing to the existence of spin-orbit coupling and a pulsed electric field, different spin-orbit states are shown to interfere with each other, generating intriguing interference-resonant patterns. We also reveal that an in-plane magnetic field does not affect the interval of any neighboring resonant peaks, but contributes a weak shift of each peak, which is sensitive to the direction of the magnetic field. We find that this proposed external-field-controlled scheme should be regarded as a new type of quantum-dot-based interferometry. This interferometry has potential applications in precise measurements of relevant experimental parameters, such as the Rashba and Dresselhaus spin-orbit-coupling strengths, as well as the Landé factor. PMID:27966598

Kinetic Alfven wave explanation of the Hall signals in magnetic reconnection

NASA Astrophysics Data System (ADS)

Dai, L.; Wang, C.; Zhang, Y.; Duan, S.; Lavraud, B.; Burch, J. L.; Pollock, C.; Torbert, R. B.

2017-12-01

Magnetic reconnection is initiated in a small diffusion region but can drive global-scale dynamics in Earth's magnetosphere, solar flares, and astrophysical systems. Understanding the processes at work in the diffusion region remains a main challenge in space plasma physics. Recent in-situ observations from MMS and THEMIS reveal that the electric field normal to the reconnection current layer, often called the Hall electric field (En), is mainly balanced by the ion pressure gradient. Here we present theoretical explanations indicating that this observation fact is a manifestation of Kinetic Alfven Waves (KAW) physics. The ion pressure gradient represents the finite gyroradius effect of KAW, leading to ion intrusion across the magnetic field lines. Electrons stream along the magnetic field lines to track ions, resulting in field-aligned currents and the associated pattern of the out-of-plane Hall magnetic field (Bm). The ratio En/Bm is on the order of the Alfven speed, as predicted by the KAW theory. The KAW physics further provides new perspectives on how ion intrusion may trigger electric fields suitable for reconnection to occur.

Wireless sensing system for non-invasive monitoring of attributes of contents in a container

NASA Technical Reports Server (NTRS)

Woodard, Stanley E. (Inventor)

2010-01-01

A wireless sensing system monitors the level, temperature, magnetic permeability and electrical dielectric constant of a non-gaseous material in a container. An open-circuit electrical conductor is shaped to form a two-dimensional geometric pattern that can store and transfer electrical and magnetic energy. The conductor resonates in the presence of a time-varying magnetic field to generate a harmonic response. The conductor is mounted in an environmentally-sealed housing. A magnetic field response recorder wirelessly transmits the time-varying magnetic field to power the conductor, and wirelessly detects the harmonic response that is an indication of at least one of level of the material in the container, temperature of the material in the container, magnetic permeability of the material in the container, and dielectric constant of the material in the container.

Assessing the temporal stability of spatial patterns of soil apparent electrical conductivity using geophysical methods

NASA Astrophysics Data System (ADS)

De Caires, Sunshine A.; Wuddivira, Mark N.; Bekele, Isaac

2014-10-01

Cocoa remains in the same field for decades, resulting in plantations dominated with aging trees growing on variable and depleted soils. We determined the spatio-temporal variability of key soil properties in a (5.81 ha) field from the International Cocoa Genebank, Trinidad using geophysical methods. Multi-year (2008-2009) measurements of apparent electrical conductivity at 0-0.75 m (shallow) and 0.75-1.5 m (deep) were conducted. Apparent electrical conductivity at deep and shallow gave the strongest linear correlation with clay-silt content (R = 0.67 and R = 0.78, respectively) and soil solution electrical conductivity (R = 0.76 and R = 0.60, respectively). Spearman rank correlation coefficients ranged between 0.89-0.97 and 0.81- 0.95 for apparent electrical conductivity at deep and shallow, respectively, signifying a strong linear dependence between measurement days. Thus, in the humid tropics, cocoa fields with thick organic litter layer and relatively dense understory cover, experience minimal fluctuations in transient properties of soil water and temperature at the topsoil resulting in similarly stable apparent electrical conductivity at shallow and deep. Therefore, apparent electrical conductivity at shallow, which covers the depth where cocoa feeder roots concentrate, can be used as a fertility indicator and to develop soil zones for efficient application of inputs and management of cocoa fields.

Active Piezoelectric Diaphragms

NASA Technical Reports Server (NTRS)

Bryant, Robert G.; Effinger, Robert T., IV; Aranda, Isaiah, Jr.; Copeland, Ben M.; Covington, Ed W., III

2002-01-01

Several active piezoelectric diaphragms were fabricated by placing unelectroded piezoelectric disks between copper clad films patterned with Inter-Circulating Electrodes "ICE". When a voltage potential is applied to the electrodes, the result is radially distributed electric field that mechanically strains the piezo-ceramic along the Z-axis (perpendicular to the applied electric field), rather than the expected in-plane (XY-axis) direction. Unlike other out of plane piezoelectric actuators, which are benders, these Radial Field Diaphragms (RFDs) strain concentrically yet afford high displacements while maintaining a constant circumference. This paper covers the fabrication and characterization of these diaphragms as a function of poling field strength, ceramic diameter and line spacing, as well as the surface topography, the resulting strain field and displacement as a function of applied voltage ranging from DC to 10 Hz.

Zeeman perturbed nuclear quadrupole spin echo envelope modulations for spin 3/2 nuclei in polycrystalline specimens

NASA Astrophysics Data System (ADS)

Ramachandran, R.; Narasimhan, P. T.

The results of theoretical and experimental studies of Zeeman-perturbed nuclear quadrupole spin echo envelope modulations (ZSEEM) for spin 3/2 nuclei in polycrystalline specimens are presented. The response of the Zeeman-perturbed spin ensemble to resonant two pulse excitations has been calculated using the density matrix formalism. The theoretical calculation assumes a parallel orientation of the external r.f. and static Zeeman fields and an arbitrary orientation of these fields to the principal axes system of the electric field gradient. A numerical powder averaging procedure has been adopted to simulate the response of the polycrystalline specimens. Using a coherent pulsed nuclear quadrupole resonance spectrometer the ZSEEM patterns of the 35Cl nuclei have been recorded in polycrystalline specimens of potassium chlorate, barium chlorate, mercuric chloride (two sites) and antimony trichloride (two sites) using the π/2-τ-π/2 sequence. The theoretical and experimental ZSEEM patterns have been compared. In the case of mercuric chloride, the experimental 35Cl ZSEEM patterns are found to be nearly identical for the two sites and correspond to a near-zero value of the asymmetry parameter, η, of the electric field gradient tensor. The difference in the η values for the two 35Cl sites (η ˜0·06 and η˜0·16) in antimony trichloride is clearly reflected in the experimental and theoretical ZSEEM patterns. The present study indicates the feasibility of evaluating η for spin 3/2 nuclei in polycrystalline specimens from ZSEEM investigations.

Magnetic field and electric current structure in the chromosphere

NASA Technical Reports Server (NTRS)

Dravins, D.

1974-01-01

The three-dimensional vector magnetic field structure in the chromosphere above an active region is deduced by using high-resolution H-alpha filtergrams together with a simultaneous digital magnetogram. An analog model of the field is made with 400 metal wires representing field lines that outline the H-alpha structure. The height extent of the field is determined from vertical field-gradient observations around sunspots, from observed fibril heights, and from an assumption that the sources of the field are largely local. The computed electric currents (typically 10 mA/sq m) are found to flow in patterns not similar to observed features and not parallel to magnetic fields. Force structures correspond to observed solar features; the dynamics to be expected include: downward motion in bipolar areas in the lower chromosphere, an outflow of the outer chromosphere into the corona with radially outward flow above bipolar plage regions, and motion of arch filament systems.

Advances in Cochlear Implant Telemetry: Evoked Neural Responses, Electrical Field Imaging, and Technical Integrity

PubMed Central

Mens, Lucas H. M.

2007-01-01

During the last decade, cochlear implantation has evolved into a well-established treatment of deafness, predominantly because of many improvements in speech processing and the controlled excitation of the auditory nerve. Cochlear implants now also feature telemetry, which is highly useful to monitor the proper functioning of the implanted electronics and electrode contacts. Telemetry can also support the clinical management in young children and difficult cases where neural unresponsiveness is suspected. This article will review recent advances in the telemetry of the electrically evoked compound action potential that have made these measurements simple and routine procedures in most cases. The distribution of the electrical stimulus itself sampled by “electrical field imaging” reveals general patterns of current flow in the normal cochlea and gross abnormalities in individual patients; models have been developed to derive more subtle insights from an individual electrical field imaging. Finally, some thoughts are given to the extended application of telemetry, for example, in monitoring the neural responses or in combination with other treatments of the deaf ear. PMID:17709572

Patterning of polymer nanofiber meshes by electrospinning for biomedical applications

PubMed Central

Neves, Nuno M; Campos, Rui; Pedro, Adriano; Cunha, José; Macedo, Francisco; Reis, Rui L

2007-01-01

The end-product of the electrospinning process is typically a randomly aligned fiber mesh or membrane. This is a result of the electric field generated between the drop of polymer solution at the needle and the collector. The developed electric field causes the stretching of the fibers and their random deposition. By judicious selection of the collector architecture, it is thus possible to develop other morphologies on the nanofiber meshes. The aim of this work is to prepare fiber meshes using various patterned collectors with specific dimensions and designs and to evaluate how those patterns can affect the properties of the meshes relevant to biomedical applications. This study aims at verifying whether it is possible to control the architecture of the fiber meshes by tailoring the geometry of the collector. Three different metallic collector topographies are used to test this hypothesis. Electrospun nonwoven patterned meshes of polyethylene oxide (PEO) and poly(ε-capro-lactone) (PCL) were successfully prepared. Those fiber meshes were analyzed by scanning electron microscopy (SEM). Both mechanical properties of the meshes and cell contacting experiments were performed to test the effect of the produced patterns over the properties of the meshes relevant for biomedical applications. The present study will evaluate cell adhesion sensitivity to the patterns generated and the effect of those patterns on the tensile properties of the fiber meshes. PMID:18019842

Generation of high-density biskyrmions by electric current

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

Peng, Licong; Zhang, Ying; He, Min

Much interest has been focused on the manipulation of magnetic skyrmions, including the generation, annihilation, and motion behaviors, for potential applications in spintronics. We experimentally demonstrate that a high-density Bloch-type biskyrmion lattice in MnNiGa can be generated by applying electric current. It is revealed that the density of biskyrmions can be remarkably increased by increasing the electric current, in contrast to the scattered biskyrmions induced by a magnetic field alone. Furthermore, the transition from the ferromagnetic state to the stripe domain structure can be terminated by the electric current, leading to the biskyrmions dominated residual domain pattern. These biskyrmions inmore » such residual domain structure are extremely stable at zero magnetic and electric fields and can further evolve into the high-density biskyrmion lattice over a temperature range from 100 to 330 K. Finally, our experimental findings open up a new pathway for the generation of skyrmion lattice by electric current manipulation.« less

Generation of high-density biskyrmions by electric current

DOE PAGES

Peng, Licong; Zhang, Ying; He, Min; ...

2017-06-16

Much interest has been focused on the manipulation of magnetic skyrmions, including the generation, annihilation, and motion behaviors, for potential applications in spintronics. We experimentally demonstrate that a high-density Bloch-type biskyrmion lattice in MnNiGa can be generated by applying electric current. It is revealed that the density of biskyrmions can be remarkably increased by increasing the electric current, in contrast to the scattered biskyrmions induced by a magnetic field alone. Furthermore, the transition from the ferromagnetic state to the stripe domain structure can be terminated by the electric current, leading to the biskyrmions dominated residual domain pattern. These biskyrmions inmore » such residual domain structure are extremely stable at zero magnetic and electric fields and can further evolve into the high-density biskyrmion lattice over a temperature range from 100 to 330 K. Finally, our experimental findings open up a new pathway for the generation of skyrmion lattice by electric current manipulation.« less

Radiative Processes in Graphene and Similar Nanostructures in Strong Electric Fields

NASA Astrophysics Data System (ADS)

Gavrilov, S. P.; Gitman, D. M.

2017-03-01

Low-energy single-electron dynamics in graphene monolayers and similar nanostructures is described by the Dirac model, being a 2+1 dimensional version of massless QED with the speed of light replaced by the Fermi velocity vF ≃ c/300. Methods of strong-field QFT are relevant for the Dirac model, since any low-frequency electric field requires a nonperturbative treatment of massless carriers in the case it remains unchanged for a sufficiently long time interval. In this case, the effects of creation and annihilation of electron-hole pairs produced from vacuum by a slowly varying and small-gradient electric field are relevant, thereby substantially affecting the radiation pattern. For this reason, the standard QED text-book theory of photon emission cannot be of help. We construct the Fock-space representation of the Dirac model, which takes exact accounts of the effects of vacuum instability caused by external electric fields, and in which the interaction between electrons and photons is taken into account perturbatively, following the general theory (the generalized Furry representation). We consider the effective theory of photon emission in the first-order approximation and construct the corresponding total probabilities, taking into account the unitarity relation.

Unraveling the physics of vertical organic field effect transistors through nanoscale engineering of a self-assembled transparent electrode.

PubMed

Ben-Sasson, Ariel J; Tessler, Nir

2012-09-12

While organic transistors' performances are continually pushed to achieve lower power consumption, higher working frequencies, and higher current densities, a new type of organic transistors characterized by a vertical architecture offers a radically different design approach to outperform its traditional counterparts. Naturally, the distinct vertical architecture gives way to different governing physical ground rules and structural key features such as the need for an embedded transparent electrode. In this paper, we make use of a zero-frequency electric field-transparent patterned electrode produced through block-copolymer self-assembly based lithography to control the performances of the vertical organic field effect transistor (VOFET) and to study its governing physical mechanisms. Unlike other VOFET structures, this design, involving well-defined electrode architecture, is fully tractable, allowing for detailed modeling, analysis, and optimization. We provide for the first time a complete account of the physics underpinning the VOFET operation, considering two complementary mechanisms: the virtual contact formation (Schottky barrier lowering) and the induced potential barrier (solid-state triode-like shielding). We demonstrate how each mechanism, separately, accounts for the link between controllable nanoscale structural modifications in the patterned electrode and the VOFET performances. For example, the ON/OFF current ratio increases by up to 2 orders of magnitude when the perforations aspect ratio (height/width) decreases from ∼0.2 to ∼0.1. The patterned electrode is demonstrated to be not only penetrable to zero-frequency electric fields but also transparent in the visible spectrum, featuring uniformity, spike-free structure, material diversity, amenability with flexible surfaces, low sheet resistance (20-2000 Ω sq(-1)) and high transparency (60-90%). The excellent layer transparency of the patterned electrode and the VOFET's exceptional electrical performances make them both promising elements for future transparent and/or efficient organic electronics.

Electric Field Generation and Control of Bipartite Quantum Entanglement between Electronic Spins in Mixed Valence Polyoxovanadate [GeV14O40]8.

PubMed

Palii, Andrew; Aldoshin, Sergey; Tsukerblat, Boris; Borràs-Almenar, Juan José; Clemente-Juan, Juan Modesto; Cardona-Serra, Salvador; Coronado, Eugenio

2017-08-21

As part of the search for systems in which control of quantum entanglement can be achieved, here we consider the paramagnetic mixed valence polyoxometalate K 2 Na 6 [GeV 14 O 40 ]·10H 2 O in which two electrons are delocalized over the 14 vanadium ions. Applying a homogeneous electric field can induce an antiferromagnetic coupling between the two delocalized electronic spins that behave independently in the absence of the field. On the basis of the proposed theoretical model, we show that the external field can be used to generate controllable quantum entanglement between the two electronic spins traveling over a vanadium network of mixed valence polyoxoanion [GeV 14 O 40 ] 8- . Within a simplified two-level picture of the energy pattern of the electronic pair based on the previous ab initio analysis, we evaluate the temperature and field dependencies of concurrence and thus indicate that the entanglement can be controlled via the temperature, magnitude, and orientation of the electric field with respect to molecular axes of [GeV 14 O 40 ] 8- .

Fish Geometry and Electric Organ Discharge Determine Functional Organization of the Electrosensory Epithelium

PubMed Central

Sanguinetti-Scheck, Juan Ignacio; Pedraja, Eduardo Federico; Cilleruelo, Esteban; Migliaro, Adriana; Aguilera, Pedro; Caputi, Angel Ariel; Budelli, Ruben

2011-01-01

Active electroreception in Gymnotus omarorum is a sensory modality that perceives the changes that nearby objects cause in a self generated electric field. The field is emitted as repetitive stereotyped pulses that stimulate skin electroreceptors. Differently from mormyriformes electric fish, gymnotiformes have an electric organ distributed along a large portion of the body, which fires sequentially. As a consequence shape and amplitude of both, the electric field generated and the image of objects, change during the electric pulse. To study how G. omarorum constructs a perceptual representation, we developed a computational model that allows the determination of the self-generated field and the electric image. We verify and use the model as a tool to explore image formation in diverse experimental circumstances. We show how the electric images of objects change in shape as a function of time and position, relative to the fish's body. We propose a theoretical framework about the organization of the different perceptive tasks made by electroreception: 1) At the head region, where the electrosensory mosaic presents an electric fovea, the field polarizing nearby objects is coherent and collimated. This favors the high resolution sampling of images of small objects and perception of electric color. Besides, the high sensitivity of the fovea allows the detection and tracking of large faraway objects in rostral regions. 2) In the trunk and tail region a multiplicity of sources illuminate different regions of the object, allowing the characterization of the shape and position of a large object. In this region, electroreceptors are of a unique type and capacitive detection should be based in the pattern of the afferents response. 3) Far from the fish, active electroreception is not possible but the collimated field is suitable to be used for electrocommunication and detection of large objects at the sides and caudally. PMID:22096578

Effects of electric field on the fracture toughness (KIc) of ceramic PZT

NASA Astrophysics Data System (ADS)

Goljahi, Sam; Lynch, Christopher S.

2013-09-01

This work was motivated by the observation that a small percentage of the ceramic lead zirconate titanate (PZT) parts in a device application, one that requires an electrode pattern on the PZT surface, developed fatigue cracks at the edges of the electrodes; yet all of the parts were subjected to similar loading. To obtain additional information on the fracture behavior of this material, similar specimens were run at higher voltage in the laboratory under a microscope to observe the initiation and growth of the fatigue cracks. A sequence of experiments was next performed to determine whether there were fracture toughness variations that depended on material processing. Plates were cut from a single bar in different locations and the Vickers indentation technique was used to measure the relative fracture toughness as a function of position along the bar. Small variations in toughness were found, that may account for some of the devices developing fatigue cracks and not others. Fracture toughness was measured next as a function of electric field. The surface crack in flexure technique was modified to apply an electric field perpendicular to a crack. The results indicate that the fracture toughness drops under a positive electric field and increases under a negative electric field that is less than the coercive field, but as the negative coercive field is approached the fracture toughness drops. Examination of the fracture surfaces using an optical microscope and a surface profilometer reveal the initial indentation crack shape and (although less accurately) the crack shape and size at the transition from stable to unstable growth. These results are discussed in terms of a ferroelastic toughening mechanism that is dependent on electric field.

Electric line source illumination of a chiral cylinder placed in another chiral background medium

NASA Astrophysics Data System (ADS)

Aslam, M.; Saleem, A.; Awan, Z. A.

2018-05-01

An electric line source illumination of a chiral cylinder embedded in a chiral background medium is considered. The field expressions inside and outside of a chiral cylinder have been derived using the wave field decomposition approach. The effects of various chiral cylinders, chiral background media and source locations upon the scattering gain pattern have been investigated. It is observed that the chiral background reduces the backward scattering gain as compared to the free space background for a dielectric cylinder. It is also studied that by moving a line source away from a cylinder reduces the backward scattering gain for a chiral cylinder placed in a chiral background under some specific conditions. A unique phenomenon of reduced scattering gain has been observed at a specific observation angle for a chiral cylinder placed in a chiral background having an electric line source location of unity free space wavelength. An isotropic scattering gain pattern is observed for a chiral nihility background provided that if cylinder is chiral or chiral nihility type. It is also observed that this isotropic behaviour is independent of background and cylinder chirality.

FIBRE AND INTEGRATED OPTICS. OPTICAL PROCESSING OF INFORMATION: Mechanism of lock-in detection with the aid of an alternating field perpendicular to the surface of a planar photorefractive waveguide

NASA Astrophysics Data System (ADS)

Zel'dovich, Boris Ya; Miklyaev, Yu V.; Safonov, V. I.

1995-02-01

An analysis is made of the mechanism of formation of a stationary grating in a planar photorefractive waveguide by a travelling interference pattern with the aid of an alternating electric field applied perpendicular to the waveguide layer. A theoretical calculation is reported of the distribution of the space-charge field in a transverse section of the waveguide. Finite drift lengths and trap saturation are taken into account in these calculations, which are carried out on the assumption of a weak contrast in the interference pattern.

Micro-PIV/LIF measurements on electrokinetically-driven flow in surface modified microchannels

NASA Astrophysics Data System (ADS)

Ichiyanagi, Mitsuhisa; Sasaki, Seiichi; Sato, Yohei; Hishida, Koichi

2009-04-01

Effects of surface modification patterning on flow characteristics were investigated experimentally by measuring electroosmotic flow velocities, which were obtained by micron-resolution particle image velocimetry using a confocal microscope. The depth-wise velocity was evaluated by using the continuity equation and the velocity data. The microchannel was composed of a poly(dimethylsiloxane) chip and a borosilicate cover-glass plate. Surface modification patterns were fabricated by modifying octadecyltrichlorosilane (OTS) on the glass surface. OTS can decrease the electroosmotic flow velocity compared to the velocity in the glass microchannel. For the surface charge varying parallel to the electric field, the depth-wise velocity was generated at the boundary area between OTS and the glass surfaces. For the surface charge varying perpendicular to the electric field, the depth-wise velocity did not form because the surface charge did not vary in the stream-wise direction. The surface charge pattern with the oblique stripes yielded a three-dimensional flow in a microchannel. Furthermore, the oblique patterning was applied to a mixing flow field in a T-shaped microchannel, and mixing efficiencies were evaluated from heterogeneity degree of fluorescent dye intensity, which was obtained by laser-induced fluorescence. It was found that the angle of the oblique stripes is an important factor to promote the span-wise and depth-wise momentum transport and contributes to the mixing flow in a microchannel.

Steering Electromagnetic Fields in MRI: Investigating Radiofrequency Field Interactions with Endogenous and External Dielectric Materials for Improved Coil Performance at High Field

NASA Astrophysics Data System (ADS)

Vaidya, Manushka

Although 1.5 and 3 Tesla (T) magnetic resonance (MR) systems remain the clinical standard, the number of 7 T MR systems has increased over the past decade because of the promise of higher signal-to-noise ratio (SNR), which can translate to images with higher resolution, improved image quality and faster acquisition times. However, there are a number of technical challenges that have prevented exploiting the full potential of ultra-high field (≥ 7 T) MR imaging (MRI), such as the inhomogeneous distribution of the radiofrequency (RF) electromagnetic field and specific energy absorption rate (SAR), which can compromise image quality and patient safety. To better understand the origin of these issues, we first investigated the dependence of the spatial distribution of the magnetic field associated with a surface RF coil on the operating frequency and electrical properties of the sample. Our results demonstrated that the asymmetries between the transmit (B1+) and receive (B 1-) circularly polarized components of the magnetic field, which are in part responsible for RF inhomogeneity, depend on the electric conductivity of the sample. On the other hand, when sample conductivity is low, a high relative permittivity can result in an inhomogeneous RF field distribution, due to significant constructive and destructive interference patterns between forward and reflected propagating magnetic field within the sample. We then investigated the use of high permittivity materials (HPMs) as a method to alter the field distribution and improve transmit and receive coil performance in MRI. We showed that HPM placed at a distance from an RF loop coil can passively shape the field within the sample. Our results showed improvement in transmit and receive sensitivity overlap, extension of coil field-of-view, and enhancement in transmit/receive efficiency. We demonstrated the utility of this concept by employing HPM to improve performance of an existing commercial head coil for the inferior regions of the brain, where the specific coil's imaging efficiency was inherently poor. Results showed a gain in SNR, while the maximum local and head SAR values remained below the prescribed limits. We showed that increasing coil performance with HPM could improve detection of functional MR activation during a motor-based task for whole brain fMRI. Finally, to gain an intuitive understanding of how HPM improves coil performance, we investigated how HPM separately affects signal and noise sensitivity to improve SNR. For this purpose, we employed a theoretical model based on dyadic Green's functions to compare the characteristics of current patterns, i.e. the optimal spatial distribution of coil conductors, that would either maximize SNR (ideal current patterns), maximize signal reception (signal-only optimal current patterns), or minimize sample noise (dark mode current patterns). Our results demonstrated that the presence of a lossless HPM changed the relative balance of signal-only optimal and dark mode current patterns. For a given relative permittivity, increasing the thickness of the HPM altered the magnitude of the currents required to optimize signal sensitivity at the voxel of interest as well as decreased the net electric field in the sample, which is associated, via reciprocity, to the noise received from the sample. Our results also suggested that signal-only current patterns could be used to identify HPM configurations that lead to high SNR gain for RF coil arrays. We anticipate that physical insights from this work could be utilized to build the next generation of high performing RF coils integrated with HPM.

Patterns in Soil Electrical Resistivity Across Land Uses in the Calhoun Critical Zone Observatory Landscape

NASA Astrophysics Data System (ADS)

Markewitz, D.; Sutter, L.; Richter, D. D., Jr.

2017-12-01

Soil Electrical Resistivity Tomography (ERT) was measured across the Calhoun Critical Zone Observatory in relation to land use cover. ERT can help identify patterns in soil and saprolite physical attributes and moisture content through multiple meters. ERT data were generated with an AGI Supersting R8 with a 28 probe dipole-dipole array on a 1.5 meter spacing providing information through the upper 9 m. In Nov/Dec 2016 ten soil pits were dug to 3m depth in agricultural fields, pine forests, and hardwood forests across the CCZO and ERT measures were taken centered on these pits. ERT values ranged from 200 to 2500 Ohm-m. ERT patterns in the agricultural field demonstrated a limited resistivity gradient (200-700 Ohm-m) appearing moist throughout. In contrast, research areas under pine and hardwood forest had stronger resistivity gradients reflecting both moisture and physical attributes (i.e., texture or rock content). For example, research area 2 under pine had an area of higher resistivity that correlated with a band of saprolite that was readily visible in the exposed profile. In research area 7 and 8 that included both pine and hardwood forest resistivity gradients had contradictory patterns of high to low resistivity from top to bottom. In research area 7 resistivity was highest at the surface and decreased with depth, a common pattern when water table is at depth. In research area 8 the inverse was observed with low resistivity above and resistivity increasing with depth, a pattern observed in upper landscape positions on ridges with moist clay above dry saprolite. ERT patterns did reflect a large difference in the measured agricultural fields compared to forest while other difference appeared to reflect landscape position.

Modulation of Spatiotemporal Particle Patterning in Evaporating Droplets: Applications to Diagnostics and Materials Science.

PubMed

Guha, Rajarshi; Mohajerani, Farzad; Mukhopadhyay, Ahana; Collins, Matthew D; Sen, Ayusman; Velegol, Darrell

2017-12-13

Spatiotemporal particle patterning in evaporating droplets lacks a common design framework. Here, we demonstrate autonomous control of particle distribution in evaporating droplets through the imposition of a salt-induced self-generated electric field as a generalized patterning strategy. Through modeling, a new dimensionless number, termed "capillary-phoresis" (CP) number, arises, which determines the relative contributions of electrokinetic and convective transport to pattern formation, enabling one to accurately predict the mode of particle assembly by controlling the spontaneous electric field and surface potentials. Modulation of the CP number allows the particles to be focused in a specific region in space or distributed evenly. Moreover, starting with a mixture of two different particle types, their relative placement in the ensuing pattern can be controlled, allowing coassemblies of multiple, distinct particle populations. By this approach, hypermethylated DNA, prevalent in cancerous cells, can be qualitatively distinguished from normal DNA of comparable molecular weights. In other examples, we show uniform dispersion of several particle types (polymeric colloids, multiwalled carbon nanotubes, and molecular dyes) on different substrates (metallic Cu, metal oxide, and flexible polymer), as dictated by the CP number. Depending on the particle, the highly uniform distribution leads to surfaces with a lower sheet resistance, as well as superior dye-printed displays.

Rigorous Electromagnetic Analysis of the Focusing Action of Refractive Cylindrical Microlens

NASA Astrophysics Data System (ADS)

Liu, Juan; Gu, Ben-Yuan; Dong, Bi-Zhen; Yang, Guo-Zhen

The focusing action of refractive cylindrical microlens is investigated based on the rigorous electromagnetic theory with the use of the boundary element method. The focusing behaviors of these refractive microlenses with continuous and multilevel surface-envelope are characterized in terms of total electric-field patterns, the electric-field intensity distributions on the focal plane, and their diffractive efficiencies at the focal spots. The obtained results are also compared with the ones obtained by Kirchhoff's scalar diffraction theory. The present numerical and graphical results may provide useful information for the analysis and design of refractive elements in micro-optics.

Experimental validation of a transformation optics based lens for beam steering

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

Yi, Jianjia; Burokur, Shah Nawaz, E-mail: shah-nawaz.burokur@u-psud.fr; Lustrac, André de

2015-10-12

A transformation optics based lens for beam control is experimentally realized and measured at microwave frequencies. Laplace's equation is adopted to construct the mapping between the virtual and physical spaces. The metamaterial-based lens prototype is designed using electric LC resonators. A planar microstrip antenna source is used as transverse electric polarized wave launcher for the lens. Both the far field radiation patterns and the near-field distributions have been measured to experimentally demonstrate the beam steering properties. Measurements agree quantitatively and qualitatively with numerical simulations, and a non-narrow frequency bandwidth operation is observed.

Molecular-like hierarchical self-assembly of monolayers of mixtures of particles

PubMed Central

Singh, P.; Hossain, M.; Gurupatham, S. K.; Shah, K.; Amah, E.; Ju, D.; Janjua, M.; Nudurupati, S.; Fischer, I.

2014-01-01

We present a technique that uses an externally applied electric field to self-assemble monolayers of mixtures of particles into molecular-like hierarchical arrangements on fluid-liquid interfaces. The arrangements consist of composite particles (analogous to molecules) which are arranged in a pattern. The structure of a composite particle depends on factors such as the relative sizes of the particles and their polarizabilities, and the electric field intensity. If the particles sizes differ by a factor of two or more, the composite particle has a larger particle at its core and several smaller particles form a ring around it. The number of particles in the ring and the spacing between the composite particles depend on their polarizabilities and the electric field intensity. Approximately same sized particles form chains (analogous to polymeric molecules) in which positively and negatively polarized particles alternate. PMID:25510331

Electron avalanche structure determined by random walk theory

NASA Technical Reports Server (NTRS)

Englert, G. W.

1973-01-01

A self-consistent avalanche solution which accounts for collective long range Coulomb interactions as well as short range elastic and inelastic collisions between electrons and background atoms is made possible by a random walk technique. Results show that the electric field patterns in the early formation stages of avalanches in helium are close to those obtained from theory based on constant transport coefficients. Regions of maximum and minimum induced electrostatic potential phi are located on the axis of symmetry and within the volume covered by the electron swarm. As formation time continues, however, the region of minimum phi moves to slightly higher radii and the electric field between the extrema becomes somewhat erratic. In the intermediate formation periods the avalanche growth is slightly retarded by the high concentration of ions in the tail which oppose the external electric field. Eventually the formation of ions and electrons in the localized regions of high field strength more than offset this effect causing a very abrupt increase in avalanche growth.

Electrohydrodynamic instabilities of viscous drops*

NASA Astrophysics Data System (ADS)

Vlahovska, Petia M.

2016-10-01

A classic result due to Taylor is that a weakly conducting drop bearing zero net charge placed in a uniform electric field adopts a prolate or oblate spheroidal shape, the flow and shape being axisymmetrically aligned with the applied field. Here I overview some intriguing symmetry-breaking instabilities occurring in strong applied dc fields: Quincke rotation resulting in drop steady tilt or tumbling, and pattern formation on the surface of a particle-coated drop.

Physics Notes.

ERIC Educational Resources Information Center

School Science Review, 1981

1981-01-01

Outlines several laboratory procedures and demonstrations including electric fields using sawdust, experiments with capacitors, particle spacing in a vapor and a liquid, metrology, momentum, Moire patterns and interference fringes, equipping for practical electronics, and using programmable calculators for rapid plotting of graphs. (DS)

Electric organ discharges and electric images during electrolocation

NASA Technical Reports Server (NTRS)

Assad, C.; Rasnow, B.; Stoddard, P. K.

1999-01-01

Weakly electric fish use active electrolocation - the generation and detection of electric currents - to explore their surroundings. Although electrosensory systems include some of the most extensively understood circuits in the vertebrate central nervous system, relatively little is known quantitatively about how fish electrolocate objects. We believe a prerequisite to understanding electrolocation and its underlying neural substrates is to quantify and visualize the peripheral electrosensory information measured by the electroreceptors. We have therefore focused on reconstructing both the electric organ discharges (EODs) and the electric images resulting from nearby objects and the fish's exploratory behaviors. Here, we review results from a combination of techniques, including field measurements, numerical and semi-analytical simulations, and video imaging of behaviors. EOD maps are presented and interpreted for six gymnotiform species. They reveal diverse electric field patterns that have significant implications for both the electrosensory and electromotor systems. Our simulations generated predictions of the electric images from nearby objects as well as sequences of electric images during exploratory behaviors. These methods are leading to the identification of image features and computational algorithms that could reliably encode electrosensory information and may help guide electrophysiological experiments exploring the neural basis of electrolocation.

A comparison of in situ measurements of vector-E and - vector-V x vector-B from Dynamics Explorer 2

NASA Technical Reports Server (NTRS)

Hanson, W. B.; Coley, W. R.; Heelis, R. A.; Maynard, N. C.; Aggson, T. L.

1993-01-01

Dynamics Explorer-2 provided the first opportunity to make a direct comparison of in situ measurements of the high-latitude convection electric field by two distinctly different techniques. The vector electric field instrument (VEFI) used antennae to measure the intrinsic electric fields and the ion drift meter (IDM) and retarding potential analyzer (RPA) measured the ion drift velocity vector, from which the convection electric field can be deduced. The data from three orbits having large electric fields at high latitude are presented, one at high, one at medium, and one at low altitudes. The general agreement between the two measurements of electric field is very good, with typical differences at high latitudes of the order of a few millivolts per meter, but there are some regions where the particle fluxes are extremely large (e.g., the cusp) and the disagreement is worse, probably because of IDM difficulties. The auroral zone potential patterns derived from the two devices are in excellent agreement for two of the cases, but not in the third, where bad attitude data may be the problem. At low latitudes there are persistent differences in the measurements of a few millivolts per meter, though these differences are quite constant from orbit to orbit. This problem seems to arise from some shortcoming in the VEFI measurments. Overall, however, these measurements confirm the concept of `frozen-in' plasma that drifts with velocity vector-E x vector-B/B(exp 2) within the measurement errors of the two techniques.

Electrokinetic pump

DOEpatents

Hencken, Kenneth R.; Sartor, George B.

2004-08-03

An electrokinetic pump in which the porous dielectric medium of conventional electrokinetic pumps is replaced by a patterned microstructure. The patterned microstructure is fabricated by lithographic patterning and etching of a substrate and is formed by features arranged so as to create an array of microchannels. The microchannels have dimensions on the order of the pore spacing in a conventional porous dielectric medium. Embedded unitary electrodes are vapor deposited on either end of the channel structure to provide the electric field necessary for electroosmotic flow.

Optical transverse spin coupling through a plasmonic nanoparticle for particle-identification and field-mapping.

PubMed

Yang, A P; Du, L P; Meng, F F; Yuan, X C

2018-05-17

Electromagnetic fields at near-field exhibit distinctive properties with respect to their free-space counterparts. In particular, an optical transverse spin appearing in a confined electromagnetic field provides the foundation for many intriguing physical effects and applications. We present a transverse spin coupling configuration where plasmonic nanoparticles are employed to couple the transverse spin in a focused beam to that of a surface plasmon polariton. The plasmonic resonance of nanoparticles on a metal film plays a significant role in transverse spin coupling. We demonstrate in experiments that Ag and Au nanoparticles yield distinct imaging patterns when scanned over a focused field, because of their different plasmonic responses to the transverse and longitudinal electric fields. Such resonance-dependent spin-coupling enables the identification of nanoparticles using a focused field, as well as electric field mapping of a specific field component of a focused beam using a plasmonic nanoparticle. These interesting findings regarding the transverse spin coupling with a plasmonic nanoparticle may find valuable applications in near-field and nano-optics.

Visualizing Carrier Transport in Metal Halide Perovskite Nanoplates via Electric Field Modulated Photoluminescence Imaging.

PubMed

Hu, Xuelu; Wang, Xiao; Fan, Peng; Li, Yunyun; Zhang, Xuehong; Liu, Qingbo; Zheng, Weihao; Xu, Gengzhao; Wang, Xiaoxia; Zhu, Xiaoli; Pan, Anlian

2018-05-09

Metal halide perovskite nanostructures have recently been the focus of intense research due to their exceptional optoelectronic properties and potential applications in integrated photonics devices. Charge transport in perovskite nanostructure is a crucial process that defines efficiency of optoelectronic devices but still requires a deep understanding. Herein, we report the study of the charge transport, particularly the drift of minority carrier in both all-inorganic CsPbBr 3 and organic-inorganic hybrid CH 3 NH 3 PbBr 3 perovskite nanoplates by electric field modulated photoluminescence (PL) imaging. Bias voltage dependent elongated PL emission patterns were observed due to the carrier drift at external electric fields. By fitting the drift length as a function of electric field, we obtained the carrier mobility of about 28 cm 2 V -1 S -1 in the CsPbBr 3 perovskite nanoplate. The result is consistent with the spatially resolved PL dynamics measurement, confirming the feasibility of the method. Furthermore, the electric field modulated PL imaging is successfully applied to the study of temperature-dependent carrier mobility in CsPbBr 3 nanoplates. This work not only offers insights for the mobile carrier in metal halide perovskite nanostructures, which is essential for optimizing device design and performance prediction, but also provides a novel and simple method to investigate charge transport in many other optoelectronic materials.

Effect of high-latitude ionospheric convection on Sun-aligned polar caps

NASA Technical Reports Server (NTRS)

Sojka, J. J.; Zhu, L.; Crain, D. J.; Schunk, R. W.

1994-01-01

A coupled magnetospheric-ionospheric (M-I) magnetohydrodynamic (MHD) model has been used to simulate the formation of Sun-aligned polar cap arcs for a variety of interplanetary magnetic field (IMF) dependent polar cap convection fields. The formation process involves launching an Alfven shear wave from the magnetosphere to the ionosphere where the ionospheric conductance can react self-consistently to changes in the upward currents. We assume that the initial Alfven shear wave is the result of solar wind-magnetosphere interactions. The simulations show how the E region density is affected by the changes in the electron precipitation that are associated with the upward currents. These changes in conductance lead to both a modified Alfven wave reflection at the ionosphere and the generation of secondary Alfven waves in the ionosphere. The ensuing bouncing of the Alfven waves between the ionosphere and magnetosphere is followed until an asymptotic solution is obtained. At the magnetosphere the Alfven waves reflect at a fixed boundary. The coupled M-I Sun-aligned polar cap arc model of Zhu et al.(1993a) is used to carry out the simulations. This study focuses on the dependence of the polar cap arc formation on the background (global) convection pattern. Since the polar cap arcs occur for northward and strong B(sub y) IMF conditions, a variety of background convection patterns can exist when the arcs are present. The study shows that polar cap arcs can be formed for all these convection patterns; however, the arc features are dramatically different for the different patterns. For weak sunward convection a relatively confined single pair of current sheets is associated with the imposed Alfven shear wave structure. However, when the electric field exceeds a threshold, the arc structure intensifies, and the conductance increases as does the local Joule heating rate. These increases are faster than a linear dependence on the background electric field strength. Furthermore, above the threshold, the single current sheet pair splits into multiple current sheet pairs. For the fixed initial ionospheric and magnetospheric conditions used in this study, the separation distance between the current pairs was found to be almost independent of the background electric field strength. For either three-cell or distorted two-cell background convection patterns the arc formation favored the positive B(sub y) case in the northern hemisphere.

Electric Field Induced Interfacial Instabilities

NASA Technical Reports Server (NTRS)

Kusner, Robert E.; Min, Kyung Yang; Wu, Xiao-lun; Onuki, Akira

1999-01-01

The study of the interface in a charge-free, critical and near-critical binary fluid in the presence of an externally applied electric field is presented. At sufficiently large fields, the interface between the two phases of the binary fluid should become unstable and exhibit an undulation with a predefined wavelength on the order of the capillary length. As the critical point is approached, this wavelength is reduced, potentially approaching length-scales such as the correlation length or critical nucleation radius. At this point the critical properties of the system may be affected. In this paper, the flat interface of a marginally polar binary fluid mixture is stressed by a perpendicular alternating electric field and the resulting instability is characterized by the critical electric field E(sub c) and the pattern observed. The character of the surface dynamics at the onset of instability is found to be strongly dependent on the frequency f of the field applied. The plot of E(sub c) vs. f for a fixed temperature shows a sigmoidal shape, whose low and high frequency limits are well described by a power-law relationship, E(sub c) = epsilon(exp zeta) with zeta = 0.35 and zeta = 0.08, respectively. The low-limit exponent compares well with the value zeta = 4 for a system of conducting and non-conducting fluids. On the other hand, the high-limit exponent coincides with what was first predicted by Onuki. The instability manifests itself as the conducting phase penetrates the non-conducting phase. As the frequency increases, the shape of the pattern changes from an array of bifurcating strings to an array of column-like (or rod-like) protrusions, each of which spans the space between the plane interface and one of the electrodes. For an extremely high frequency, the disturbance quickly grows into a parabolic cone pointing toward the upper plate. As a result, the interface itself changes its shape from that of a plane to that of a high sloping pyramid.

The body electric 2.0: recent advances in developmental bioelectricity for regenerative and synthetic bioengineering.

PubMed

Mathews, Juanita; Levin, Michael

2018-04-20

Breakthroughs in biomedicine and synthetic bioengineering require predictive, rational control over anatomical structure and function. Recent successes in manipulating cellular and molecular hardware have not been matched by progress in understanding the patterning software implemented during embryogenesis and regeneration. A fundamental capability gap is driving desired changes in growth and form to address birth defects and traumatic injury. Here we review new tools, results, and conceptual advances in an exciting emerging field: endogenous non-neural bioelectric signaling, which enables cellular collectives to make global decisions and implement large-scale pattern homeostasis. Spatially distributed electric circuits regulate gene expression, organ morphogenesis, and body-wide axial patterning. Developmental bioelectricity facilitates the interface to organ-level modular control points that direct patterning in vivo. Cracking the bioelectric code will enable transformative progress in bioengineering and regenerative medicine. Copyright © 2018 Elsevier Ltd. All rights reserved.

Nanoparticle assembly on patterned "plus/minus" surfaces from electrospray of colloidal dispersion.

PubMed

Lenggoro, I Wuled; Lee, Hye Moon; Okuyama, Kikuo

2006-11-01

Selective deposition of metal (Au) and oxide (SiO2) nanoparticles with a size range of 10-30 nm on patterned silicon-silicon oxide substrate was performed using the electrospray method. Electrical charging characteristics of particles produced by the electrospray and patterned area created by contact charging of the electrical conductor with non- or semi-conductors were investigated. Colloidal droplets were electrosprayed and subsequently dried as individual nanoparticles which then were deposited on substrates, and observed using field emission-scanning electron microscopy. The number of elementary charge units on particles generated by the electrospray was 0.4-148, and patterned area created by contact charging contained sufficient negative charges to attract multiple charged particles. Locations where nanoparticles were (reversibly) deposited depended on voltage polarity applied to the spraying colloidal droplet and the substrate, and the existence of additional ions such as those from a stabilizer.

Characterization of applied fields for ion mobility in traveling wave based structures for lossless ion manipulations (SLIM)

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

Hamid, Ahmed M.; Prabhakaran Nair Syamala Amma, Aneesh; Garimella, Venkata BS

2018-03-21

Ion mobility (IM) is rapidly gaining attention for the analysis of biomolecules due to the ability to distinguish the shapes of ions. However, conventional constant electric field drift tube IM has limited resolving power, constrained by practical limitations on the path length and maximum applied voltage. The implementation of traveling waves (TW) in IM removes the latter limitation, allowing higher resolution to be achieved using extended path lengths. These can be readily obtainable in structures for lossless ion manipulations (SLIM), which are fabricated from electric fields that are generated by appropriate potentials applied to arrays of electrodes patterned on twomore » parallel surfaces. In this work we have investigated the relationship between the various SLIM variables, such as electrode dimensions, inter-surface gap, and the TW applied voltages, that directly impact the fields experienced by ions. Ion simulation and theoretical calculations have been utilized to understand the dependence of SLIM geometry and effective electric field. The variables explored impact both ion confinement and the observed IM resolution in Structures for Lossless Ion Manipulations (SLIM) modules.« less

Characterization of applied fields for ion mobility separations in traveling wave based structures for lossless ion manipulations (SLIM)

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

Hamid, Ahmed M.; Prabhakaran, Aneesh; Garimella, Sandilya V. B.

Ion mobility (IM) is rapidly gaining attention for the analysis of biomolecules due to the ability to distinguish the shapes of ions. However, conventional constant electric field drift tube IM has limited resolving power, constrained by practical limitations on the path length and maximum applied voltage. The implementation of traveling waves (TW) in IM removes the latter limitation, allowing higher resolution to be achieved using extended path lengths. These can be readily obtainable in structures for lossless ion manipulations (SLIM), which are fabricated from electric fields that are generated by appropriate potentials applied to arrays of electrodes patterned on twomore » parallel surfaces. In this work we have investigated the relationship between the various SLIM variables, such as electrode dimensions, inter-surface gap, and the TW applied voltages, that directly impact the fields experienced by ions. Ion simulation and theoretical calculations have been utilized to understand the dependence of SLIM geometry and effective electric field. The variables explored impact both ion confinement and the observed IM resolution in Structures for Lossless Ion Manipulations (SLIM) modules.« less

Effect of feature size on dielectric nonlinearity of patterned PbZr{sub 0.52}Ti{sub 0.48}O{sub 3} films

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

Yang, J. I., E-mail: jxy194@psu.edu; Trolier-McKinstry, S.; Polcawich, R. G.

2015-01-07

Lead zirconate titanate, PZT (52/48), thin films with a PbTiO{sub 3} seed layer were patterned into features of different widths, including various sizes of squares and 100 μm, 50 μm, and 10 μm serpentine designs, using argon ion beam milling. Patterns with different surface area/perimeter ratios were used to study the relative importance of damage produced by the patterning. It was found that as the pattern dimensions decreased, the remanent polarization increased, presumably due to the fact that the dipoles near the feature perimeter are not as severely clamped to the substrate. This investigation is in agreement with a model in which clampingmore » produces deep wells, which do not allow some fraction of the spontaneous polarization to switch at high field. The domain wall mobility at modest electric fields was investigated using the Rayleigh law. Both the reversible, ε{sub init}, and irreversible, α, Rayleigh coefficients increased with decreasing serpentine line width for de-aged samples. For measurements made immediately after annealing, ε{sub init} of 500 μm square patterns was 1510 ± 13; with decreasing serpentine line width, ε{sub init} rose from 1520 ± 10 for the 100 μm serpentine to 1568 ± 23 for the 10 μm serpentine. The irreversible parameter, α, for the square patterns was 39.4 ± 3.2 cm/kV and it increased to 44.1 ± 3.2 cm/kV as the lateral dimension is reduced. However, it was found that as the width of the serpentine features decreased, the aging rate rose. These observations are consistent with a model in which sidewall damage produces shallow wells that lower the Rayleigh constants of aged samples at small fields. These shallow wells can be overcome by the large fields used to measure the remanent polarization and the large unipolar electric fields typically used to drive thin film piezoelectric actuators.« less

Electrical stimulation of cardiac adipose tissue-derived progenitor cells modulates cell phenotype and genetic machinery.

PubMed

Llucià-Valldeperas, A; Sanchez, B; Soler-Botija, C; Gálvez-Montón, C; Prat-Vidal, C; Roura, S; Rosell-Ferrer, J; Bragos, R; Bayes-Genis, A

2015-11-01

A major challenge of cardiac tissue engineering is directing cells to establish the physiological structure and function of the myocardium being replaced. Our aim was to examine the effect of electrical stimulation on the cardiodifferentiation potential of cardiac adipose tissue-derived progenitor cells (cardiac ATDPCs). Three different electrical stimulation protocols were tested; the selected protocol consisted of 2 ms monophasic square-wave pulses of 50 mV/cm at 1 Hz over 14 days. Cardiac and subcutaneous ATDPCs were grown on biocompatible patterned surfaces. Cardiomyogenic differentiation was examined by real-time PCR and immunocytofluorescence. In cardiac ATDPCs, MEF2A and GATA-4 were significantly upregulated at day 14 after stimulation, while subcutaneous ATDPCs only exhibited increased Cx43 expression. In response to electrical stimulation, cardiac ATDPCs elongated, and both cardiac and subcutaneous ATDPCs became aligned following the linear surface pattern of the construct. Cardiac ATDPC length increased by 11.3%, while subcutaneous ATDPC length diminished by 11.2% (p = 0.013 and p = 0.030 vs unstimulated controls, respectively). Compared to controls, electrostimulated cells became aligned better to the patterned surfaces when the pattern was perpendicular to the electric field (89.71 ± 28.47º for cardiac ATDPCs and 92.15 ± 15.21º for subcutaneous ATDPCs). Electrical stimulation of cardiac ATDPCs caused changes in cell phenotype and genetic machinery, making them more suitable for cardiac regeneration approaches. Thus, it seems advisable to use electrical cell training before delivery as a cell suspension or within engineered tissue. Copyright © 2013 John Wiley & Sons, Ltd.

Modeling and measurement of electrostatic spray behavior in a rectangular throat of Pease-Anthony venturi scrubber.

PubMed

Yang, H T; Viswanathan, S; Balachandran, W; Ray, M B

2003-06-01

This paper presents the simulation and experimental results of the distribution of droplets produced by electrostatic nozzles inside a venturi scrubber. The simulation model takes into account initial liquid momentum, hydrodynamic, gravitational and electric forces, and eddy diffusion. The velocity and concentration profile of charged droplets injected from an electrostatic nozzle in the scrubber under the combined influence of hydrodynamic and electric fields were simulated. The effects of operating parameters, such as gas velocity, diameter of the scrubbing droplets, charge-to-mass ratio, and liquid-to-gas ratio on the distribution of the water droplets within the scrubber, were also investigated. The flux distribution of scrubbing liquid in the presence of electric field is improved considerably over a conventional venturi scrubber, and the effect increases with the increase in charge-to-mass ratio. Improved flux distribution using charged droplets increases the calculated overall collection efficiency of the submicron particles. However, the effect of an electric field on the droplet distribution pattern for small drop sizes in strong hydrodynamic field conditions is negligible. Simulated results are in good agreement with the experimental data obtained in the laboratory.

2d axisymmetric "beam-bulk" modelling of the generation of runaway electrons by streamers.

NASA Astrophysics Data System (ADS)

Chanrion, Olivier; Bonaventura, Zdenek; Bourdon, Anne; Neubert, Torsten

2017-04-01

We present results from a 2d axisymmetric numerical model of streamers based on a "beam-bulk" approach which describes cold electrons with a fluid model and high energy electrons with a particle model. The interest is motivated by the generation of runaway electrons by streamers which may participate in the recently observed TGFs and which challenge the modelling. Runaway electrons are known to be generated from streamers when the electric field in its negative tip is of sufficient magnitude. After overtaking the streamer tip, runaways can affect the streamer propagation ahead and may produce high energy photons through the bremsstrahlung process. In conventional model of streamers, the evolution of the streamer discharge is mostly governed by cold electrons. By including runaway electrons, we model their production, their impact on the discharge propagation and can address their role in TGFs. Results of streamer propagation in leader electric field show that the runaway electrons accelerate the streamers, reduce the electric field in its tip and enlarge its radius by pre-ionizing the gas ahead. We observed that if we increase the electric field, the discharge is getting more diffuse, with a pattern driven by the increase in runaway induced ionisation.

A gridded global description of the ionosphere and thermosphere for 1996 - 2000

NASA Astrophysics Data System (ADS)

Ridley, A.; Kihn, E.; Kroehl, H.

The modeling and simulation community has asked for a realistic representation of the near-Earth space environment covering a significant number of years to be used in scientific and engineering applications. The data, data management systems, assimilation techniques, physical models, and computer resources are now available to construct a realistic description of the ionosphere and thermosphere over a 5 year period. DMSP and NOAA POES satellite data and solar emissions were used to compute Hall and Pederson conductances in the ionosphere. Interplanetary magnetic field measurements on the ACE satellite define average electrostatic potential patterns over the northern and southern Polar Regions. These conductances, electric field patterns, and ground-based magnetometer data were input to the Assimilative Mapping of Ionospheric Electrodynamics model to compute the distribution of electric fields and currents in the ionosphere. The Global Thermosphere Ionosphere Model (GITM) used the ionospheric electrodynamic parameters to compute the distribution of particles and fields in the ionosphere and thermosphere. GITM uses a general circulation approach to solve the fundamental equations. Model results offer a unique opportunity to assess the relative importance of different forcing terms under a variety of conditions as well as the accuracies of different estimates of ionospheric electrodynamic parameters.

Electric Field Induced Interfacial Instabilities

NASA Technical Reports Server (NTRS)

Kusner, Robert E.; Min, Kyung Yang; Wu, Xiao-Lun; Onuki, Akira

1996-01-01

The study of the interface in a charge-free, nonpolar, critical and near-critical binary fluid in the presence of an externally applied electric field is presented. At sufficiently large fields, the interface between the two phases of the binary fluid should become unstable and exhibit an undulation with a predefined wavelength on the order of the capillary length. As the critical point is approached, this wavelength is reduced, potentially approaching length-scales such as the correlation length or critical nucleation radius. At this point the critical properties of the system may be affected. In zero gravity, the interface is unstable at all long wavelengths in the presence of a field applied across it. It is conjectured that this will cause the binary fluid to break up into domains small enough to be outside the instability condition. The resulting pattern formation, and the effects on the critical properties as the domains approach the correlation length are of acute interest. With direct observation, laser light scattering, and interferometry, the phenomena can be probed to gain further understanding of interfacial instabilities and the pattern formation which results, and dimensional crossover in critical systems as the critical fluctuations in a particular direction are suppressed by external forces.

Electrical and Electrorheological Properties of Alumina/Natural Rubber (STR XL) Composites

PubMed Central

Tangboriboon, Nuchnapa; Uttanawanit, Nuttapot; Longtong, Mean; Wongpinthong, Piraya; Sirivat, Anuvat; Kunanuruksapong, Ruksapong

2010-01-01

The electrorheological properties (ER) of natural rubber (XL)/alumina (Al2O3) composites were investigated in oscillatory shear mode under DC electrical field strengths between 0 to 2 kV/mm. SEM micrographs indicate a mean particle size of 9.873 ± 0.034 µm and particles that are moderately dispersed in the matrix. The XRD patterns indicate Al2O3 is of the β-phase polytype which possesses high ionic conductivity. The storage modulus (G′) of the composites, or the rigidity, increases by nearly two orders of magnitude, with variations in particle volume fraction and electrical field strength. The increase in the storage modulus is caused the ionic polarization of the alumina particles and the induced dipole moments set up in the natural rubber matrix.

Rigorous assessment of patterning solution of metal layer in 7 nm technology node

NASA Astrophysics Data System (ADS)

Gao, Weimin; Ciofi, Ivan; Saad, Yves; Matagne, Philippe; Bachmann, Michael; Gillijns, Werner; Lucas, Kevin; Demmerle, Wolfgang; Schmoeller, Thomas

2016-01-01

In a 7 nm node (N7), the logic design requires a critical poly pitch of 42 to 45 nm and a metal 1 (M1) pitch of 28 to 32 nm. Such high-pattern density pushes the 193 immersion lithography solution toward its limit and also brings extremely complex patterning scenarios. The N7 M1 layer may require a self-aligned quadruple patterning (SAQP) with a triple litho-etch (LE3) block process. Therefore, the whole patterning process flow requires multiple exposure+etch+deposition processes and each step introduces a particular impact on the pattern profiles and the topography. In this study, we have successfully integrated a simulation tool that enables emulation of the whole patterning flow with realistic process-dependent three-dimensional (3-D) profile and topology. We use this tool to study the patterning process variations of the N7 M1 layer including the overlay control, the critical dimension uniformity budget, and the lithographic process window (PW). The resulting 3-D pattern structure can be used to optimize the process flow, verify design rules, extract parasitics, and most importantly, simulate the electric field, and identify hot spots for dielectric reliability. As an example application, the maximum electric field at M1 tip-to-tip, which is one of the most critical patterning locations, has been simulated and extracted. The approach helps to investigate the impact of process variations on dielectric reliability. We have also assessed the alternative M1 patterning flow with a single exposure block using extreme ultraviolet lithography (EUVL) and analyzed its advantages compared to the LE3 block approach.

The Electric Honeycomb; an investigation of the Rose window instability

NASA Astrophysics Data System (ADS)

Niazi, Muhammad Shaheer

2017-10-01

The Rose window instability is a little-explored electrohydrodynamic instability that manifests when a layer of low-conducting oil is placed in an electric field generated by corona discharge in a point-to-plane configuration. Above a critical voltage, the instability starts as a single dimple in the oil layer right below the point electrode and subsequently evolves into a characteristic pattern of polygonal cells. In this study, we experimentally explore governing parameters that guide the instability and document geometric attributes of the characteristic cellular pattern. The driving force for the instability has been attributed to the buildup of charged ions which in turn apply an electric pressure on the oil surface. We confirm the charged surface distribution using thermal imaging and demonstrate that the instability can be locally inhibited by preventing charge buildup under an ion shadow.

The Electric Honeycomb; an investigation of the Rose window instability

PubMed Central

2017-01-01

The Rose window instability is a little-explored electrohydrodynamic instability that manifests when a layer of low-conducting oil is placed in an electric field generated by corona discharge in a point-to-plane configuration. Above a critical voltage, the instability starts as a single dimple in the oil layer right below the point electrode and subsequently evolves into a characteristic pattern of polygonal cells. In this study, we experimentally explore governing parameters that guide the instability and document geometric attributes of the characteristic cellular pattern. The driving force for the instability has been attributed to the buildup of charged ions which in turn apply an electric pressure on the oil surface. We confirm the charged surface distribution using thermal imaging and demonstrate that the instability can be locally inhibited by preventing charge buildup under an ion shadow. PMID:29134066

Electric and magnetic field modulated energy dispersion, conductivity and optical response in double quantum wire with spin-orbit interactions

NASA Astrophysics Data System (ADS)

Karaaslan, Y.; Gisi, B.; Sakiroglu, S.; Kasapoglu, E.; Sari, H.; Sokmen, I.

2018-02-01

We study the influence of electric field on the electronic energy band structure, zero-temperature ballistic conductivity and optical properties of double quantum wire. System described by double-well anharmonic confinement potential is exposed to a perpendicular magnetic field and Rashba and Dresselhaus spin-orbit interactions. Numerical results show up that the combined effects of internal and external agents cause the formation of crossing, anticrossing, camel-back/anomaly structures and the lateral, downward/upward shifts in the energy dispersion. The anomalies in the energy subbands give rise to the oscillation patterns in the ballistic conductance, and the energy shifts bring about the shift in the peak positions of optical absorption coefficients and refractive index changes.

Complex magnetohydrodynamic low-Reynolds-number flows.

PubMed

Xiang, Yu; Bau, Haim H

2003-07-01

The interaction between electric currents and a magnetic field is used to produce body (Lorentz) forces in electrolyte solutions. By appropriate patterning of the electrodes, one can conveniently control the direction and magnitude of the electric currents and induce spatially and temporally complicated flow patterns. This capability is useful, not only for fundamental flow studies, but also for inducing fluid flow and stirring in minute devices in which the incorporation of moving components may be difficult. This paper focuses on a theoretical and experimental study of magnetohydrodynamic flows in a conduit with a rectangular cross section. The conduit is equipped with individually controlled electrodes uniformly spaced at a pitch L. The electrodes are aligned transversely to the conduit's axis. The entire device is subjected to a uniform magnetic field. The electrodes are divided into two groups A and C in such a way that there is an electrode of group C between any two electrodes of group A. We denote the various A and C electrodes with subscripts, i.e., A(i) and C(i), where i=0,+/-1,+/-2, .... When positive and negative potentials are, respectively, applied to the even and odd numbered A electrodes, opposing electric currents are induced on the right and left hand sides of each A electrode. These currents generate transverse forces that drive cellular convection in the conduit. We refer to the resulting flow pattern as A. When electrodes of group C are activated, a similar flow pattern results, albeit shifted in space. We refer to this flow pattern as C. By alternating periodically between patterns A and C, one induces Lagrangian chaos. Such chaotic advection may be beneficial for stirring fluids, particularly in microfluidic devices. Since the flow patterns A and C are shifted in space, they also provide a mechanism for Lagrangian drift that allows net migration of passive tracers along the conduit's length.

Vlf/elf radiation patterns of arbitrarily oriented electric and magnetic dipoles in a cold lossless multicomponent magnetoplasma.

NASA Technical Reports Server (NTRS)

Wang, T. N. C.; Bell, T. F.

1972-01-01

With the use of a power integral formulation, a study is made of the vlf/elf radiation patterns of arbitrarily oriented electric and magnetic dipoles in a cold lossless multicomponent magnetoplasma. Expressions for the ray patterns are initially developed that apply for arbitrary values of driving frequency, static magnetic-field strength, plasma density, and composition. These expressions are subsequently specialized to vlf/elf radiation in a plasma modeled on the magnetosphere. A series of representative pattern plots are presented for frequencies between the proton and electron gyrofrequencies. These patterns illustrate the fact that focusing effects that arise from the geometrical properties of the refractive index surface tend to dominate the radiation distribution over the entire range from the electron gyrofrequency to 4.6 times the proton gyrofrequency. It is concluded that focusing effects should be of significant importance in the design of a vlf/elf satellite transmitting system in the magnetosphere.

Optics of short-pitch deformed-helix ferroelectric liquid crystals: Symmetries, exceptional points, and polarization-resolved angular patterns

NASA Astrophysics Data System (ADS)

Kiselev, Alexei D.; Chigrinov, Vladimir G.

2014-10-01

In order to explore electric-field-induced transformations of polarization singularities in the polarization-resolved angular (conoscopic) patterns emerging after deformed-helix ferroelectric liquid crystal (DHFLC) cells with subwavelength helix pitch, we combine the transfer matrix formalism with the results for the effective dielectric tensor of biaxial FLCs evaluated using an improved technique of averaging over distorted helical structures. Within the framework of the transfer matrix method, we deduce a number of symmetry relations and show that the symmetry axis of L lines (curves of linear polarization) is directed along the major in-plane optical axis which rotates under the action of the electric field. When the angle between this axis and the polarization plane of incident linearly polarized light is above its critical value, the C points (points of circular polarization) appear in the form of symmetrically arranged chains of densely packed star-monstar pairs. We also emphasize the role of phase singularities of a different kind and discuss the enhanced electro-optic response of DHFLCs near the exceptional point where the condition of zero-field isotropy is fulfilled.

Field-aligned current associated with a distorted two-cell convection pattern during northward interplanetary magnetic field

NASA Technical Reports Server (NTRS)

Zhu, L.; Schunk, R. W.; Sojka, J. J.

1991-01-01

The influence of the ionospheric conductance on the field-aligned current associated with a distorted two-cell convection pattern during northward IMF was investigated using the Heppner-Maynard (1987) convection model and the Utah State University conductivity model described by Rasmussen and Schunk (1987). Results show that the variation of the ionospheric conductivity distribution can significantly affect the features of the field-aligned current for northward IMF, where matching or mismatching between the conductance gradient and the convection electric field plays a key role. It was found that the increase of the field-aligned current in the polar cap observed during summer is mainly due to the increasing contribution from the Pedersen current, and that the increase of the field-aligned current in both the oval region and the evening-midnight sector during the active aurora period is mainly due to the increasing contribution from the Hall current.

Controlled nanopatterning of a polymerized ionic liquid in a strong electric field

DOE PAGES

Bocharova, Vera; Agapov, Alexander L.; Tselev, Alexander; ...

2014-12-17

Nanolithography has become a driving force in advancements of the modern day's electronics, allowing for miniaturization of devices and a steady increase of the calculation, power, and storage densities. Among various nanofabrication approaches, scanning probe techniques, including atomic force microscopy (AFM), are versatile tools for creating nanoscale patterns utilizing a range of physical stimuli such as force, heat, or electric field confined to the nanoscale. In this study, the potential of using the electric field localized at the apex of an AFM tip to induce and control changes in the mechanical properties of an ion containing polymer—a polymerized ionic liquidmore » (PolyIL)—on a very localized scale is explored. In particular, it is demonstrated that by means of AFM, one can form topographical features on the surface of PolyIL-based thin films with a significantly lower electric potential and power consumption as compared to nonconductive polymer materials. Lastly,, by tuning the applied voltage and ambient air humidity, control over dimensions of the formed structures is reproducibly achieved.« less

Nonradiating anapole modes in dielectric nanoparticles

PubMed Central

Miroshnichenko, Andrey E.; Evlyukhin, Andrey B.; Yu, Ye Feng; Bakker, Reuben M.; Chipouline, Arkadi; Kuznetsov, Arseniy I.; Luk'yanchuk, Boris; Chichkov, Boris N.; Kivshar, Yuri S.

2015-01-01

Nonradiating current configurations attract attention of physicists for many years as possible models of stable atoms. One intriguing example of such a nonradiating source is known as ‘anapole'. An anapole mode can be viewed as a composition of electric and toroidal dipole moments, resulting in destructive interference of the radiation fields due to similarity of their far-field scattering patterns. Here we demonstrate experimentally that dielectric nanoparticles can exhibit a radiationless anapole mode in visible. We achieve the spectral overlap of the toroidal and electric dipole modes through a geometry tuning, and observe a highly pronounced dip in the far-field scattering accompanied by the specific near-field distribution associated with the anapole mode. The anapole physics provides a unique playground for the study of electromagnetic properties of nontrivial excitations of complex fields, reciprocity violation and Aharonov–Bohm like phenomena at optical frequencies. PMID:26311109

Motion of polymer cholesteric liquid crystal flakes in an electric field

NASA Astrophysics Data System (ADS)

Kosc, Tanya Zoriana

Polymer cholesteric liquid crystal (PCLC) flakes suspended in a host fluid can be manipulated with an electric field. Controlling a flake's orientation provides the opportunity to change and control the amount of selective reflection from the flake surface. Flake motion results from charge accumulation and an induced dipole moment established due to Maxwell-Wagner polarization. The type of flake behavior, whether random motion or uniform reorientation, depends upon the dielectric properties of the host fluid, which in turn dictate whether a DC or an AC electric field must be applied. PCLC flakes suspended in highly dielectric silicone oil host fluids tend to move randomly in the presence of a DC electric field, and no motion is seen in AC fields. Flakes suspended in a moderately conductive host fluid reorient 90° in the presence of an AC field within a specific frequency range. The flake shape and size are also important parameters that need to be controlled in order to produce uniform motion. Several methods for patterning flakes were investigated and identical square flakes were produced. Square PCLC flakes (80 mum sides) suspended in propylene carbonate reorient in 400 ms when a 40mVrms/mum field at 70 Hz is applied to the test device. Theoretical modeling supported experimental observations well, particularly in identifying the inverse quadratic dependence on the applied electric field and the electric field frequency dependence that is governed by the host fluid conductivity. Future goals and suggested experiments are provided, as well as an explanation and comparison of possible commercial applications for PCLC flakes. This research has resulted in one patent application and a series of invention disclosures that could place this research group and any industrial collaborators in a strong position to pursue commercial applications, particularly in the area of displays, and more specifically, electronic paper.

DC Electric Fields, Associated Plasma Drifts, and Irregularities Observed on the C/NOFS Satellite

NASA Technical Reports Server (NTRS)

Pfaff, R.; Freudenreich, H.; Klenzing, J.

2011-01-01

Results are presented from the Vector Electric Field Investigation (VEFI) on the Air Force Communication/Navigation Outage Forecasting System (C/NOFS) satellite, a mission designed to understand, model, and forecast the presence of equatorial ionospheric irregularities. The VEFI instrument includes a vector DC electric field detector, a fixed-bias Langmuir probe operating in the ion saturation regime, a flux gate magnetometer, an optical lightning detector, and associated electronics including a burst memory. Compared to data obtained during more active solar conditions, the ambient DC electric fields and their associated E x B drifts are variable and somewhat weak, typically < 1 mV/m. Although average drift directions show similarities to those previously reported, eastward/outward during day and westward/downward at night, this pattern varies significantly with longitude and is not always present. Daytime vertical drifts near the magnetic equator are largest after sunrise, with smaller average velocities after noon. Little or no pre-reversal enhancement in the vertical drift near sunset is observed, attributable to the solar minimum conditions creating a much reduced neutral dynamo at the satellite altitude. The nighttime ionosphere is characterized by larger amplitude, structured electric fields, even where the plasma density appears nearly quiescent. Data from successive orbits reveal that the vertical drifts and plasma density are both clearly organized with longitude. The spread-F density depletions and corresponding electric fields that have been detected thus far have displayed a preponderance to appear between midnight and dawn. Associated with the narrow plasma depletions that are detected are broad spectra of electric field and plasma density irregularities for which a full vector set of measurements is available for detailed study. The VEFI data represents a new set of measurements that are germane to numerous fundamental aspects of the electrodynamics and irregularities inherent to the Earth s low latitude ionosphere.

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

Terahertz radiation induced chaotic electron transport in semiconductor superlattices with a tilted magnetic field.

PubMed

Wang, C; Wang, F; Cao, J C

2014-09-01

Chaotic electron transport in semiconductor superlattice induced by terahertz electric field that is superimposed on a dc electric field along the superlattice axis are studied using the semiclassical motion equations including the effect of dissipation. A magnetic field that is tilted relative to the superlattice axis is also applied to the system. Numerical simulation shows that electrons in superlattice miniband exhibit complicate nonlinear oscillating modes with the influence of terahertz radiation. Transitions between frequency-locking and chaos via pattern forming bifurcations are observed with the varying of terahertz amplitude. It is found that the chaotic regions gradually contract as the dissipation increases. We attribute the appearance of complicate nonlinear oscillation in superlattice to the interaction between terahertz radiation and internal cooperative oscillating mode relative to Bloch oscillation and cyclotron oscillation.

Dynamical properties of epitaxial ferroelectric superlattices

NASA Astrophysics Data System (ADS)

Kim, Y.; Gerhardt, R. A.; Erbil, A.

1997-04-01

The dynamical properties of epitaxial ferroelectric heterostructures have been investigated by studying the dielectric behavior under external electric field. A phenomenon with a giant permittivity was observed. At low frequencies, real permittivities as high as 420 000 have been measured. Real and imaginary parts of the dielectric constant show large dispersion at high frequencies. In dc measurements, a nonlinear resistance is observed with a well-defined threshold field, correlating with the dc bias-field dependence of ac permittivities. We model these observations as a result of the motion of pinned domain-wall lattices, having sliding-mode motion at high electric fields. The good agreement between the experimental and theoretical results suggests that the deposited interdigitated electrode pattern plays a crucial role in controlling domain-wall dynamics. The pinning of the domain wall comes from a nucleation barrier to the creation of new domain walls.

Seasonal Patterns of Melatonin, Cortisol, and Progesterone Secretion in Female Lambs Raised Beneath a 500-KV Transmission Line

NASA Astrophysics Data System (ADS)

Lee, Jack Monroe, Jr.

There is ongoing controversy about the possibility of adverse biological effects from environmental exposures to electric and magnetic fields. These fields are produced by all electrical equipment and appliances including electrical transmission lines. The objective of this environmental science study was to investigate the possible effects of a high voltage transmission line on domestic sheep (Ovis aries L.), a species that can often be found near such lines. The study was primarily designed to determine whether a specific effect of electric and magnetic fields found in laboratory animals also occurs in livestock under natural environmental conditions. The effect is the ability of fields, at levels found in the environment, to significantly depress the normally high nocturnal concentrations of the pineal hormone-melatonin. Ten female Suffolk lambs were penned for 10 months directly beneath a 500-kV transmission line near Estacada, Oregon. Ten other lambs of the same type were penned in a control area away from the transmission line where electric and magnetic fields were at ambient levels. Serum melatonin was analyzed by radioimmunoassay (RIA) from 6618 blood samples collected at 0.5 to 3-hour intervals over eight 48-hour periods. Serum progesterone was analyzed by RIA from blood samples collected twice weekly. Serum cortisol was also assayed by RIA from the blood samples collected during the 48-hour samples. Results showed that lambs in both the control and line groups had the typical pattern of melatonin secretion consisting of low daytime and high nighttime serum concentrations. There were no statistically significant differences between groups in melatonin levels, or in the phase or duration of the nighttime melatonin elevation. Age at puberty and number of reproductive cycles also did not differ between groups. Serum cortisol showed a circadian rhythm with highest concentrations during the day. There were, however, no differences in cortisol concentrations between groups. Statistical analyses on other biological parameters revealed no differences between groups for body weight gain, wool growth, or behavior.

Electric field controlled spin interference in a system with Rashba spin-orbit coupling

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

Ciftja, Orion, E-mail: ogciftja@pvamu.edu

There have been intense research efforts over the last years focused on understanding the Rashba spin-orbit coupling effect from the perspective of possible spintronics applications. An important component of this line of research is aimed at control and manipulation of electron’s spin degrees of freedom in semiconductor quantum dot devices. A promising way to achieve this goal is to make use of the tunable Rashba effect that relies on the spin-orbit interaction in a two-dimensional electron system embedded in a host semiconducting material that lacks inversion-symmetry. This way, the Rashba spin-orbit coupling effect may potentially lead to fabrication of amore » new generation of spintronic devices where control of spin, thus magnetic properties, is achieved via an electric field and not a magnetic field. In this work we investigate theoretically the electron’s spin interference and accumulation process in a Rashba spin-orbit coupled system consisting of a pair of two-dimensional semiconductor quantum dots connected to each other via two conducting semi-circular channels. The strength of the confinement energy on the quantum dots is tuned by gate potentials that allow “leakage” of electrons from one dot to another. While going through the conducting channels, the electrons are spin-orbit coupled to a microscopically generated electric field applied perpendicular to the two-dimensional system. We show that interference of spin wave functions of electrons travelling through the two channels gives rise to interference/conductance patterns that lead to the observation of the geometric Berry’s phase. Achieving a predictable and measurable observation of Berry’s phase allows one to control the spin dynamics of the electrons. It is demonstrated that this system allows use of a microscopically generated electric field to control Berry’s phase, thus, enables one to tune the spin-dependent interference pattern and spintronic properties with no need for injection of spin-polarized electrons.« less

Twice electric field poling for engineering multiperiodic Hex-PPLN microstructures

NASA Astrophysics Data System (ADS)

Pagliarulo, Vito; Gennari, Oriella; Rega, Romina; Mecozzi, Laura; Grilli, Simonetta; Ferraro, Pietro

2018-05-01

Satellite bulk ferroelectric domains were observed everywhere around the larger main inverted ferroelectric domains when a Twice Electric Field Poling (TEFP) process is applied on a z-cut lithium niobate substrate. TEFP approach can be very advantageous for engineering multiperiodic poled microstructures in ferroelectrics. In fact, it is very difficult in the experimental practice to avoid underpoling and/or overpoling when structures with different sizes are requested in the same crystal. TEFP was applied to photoresist patterned crystal with 100 μm period and then a second EP step, with a ten-times smaller periodicity of 10 μm, was accomplished on the same sample. The intriguing fact is that the shorter 10 μm pattern disappeared everywhere except that around the larger satellite ferroelectric domains. The formation of this double-periodicity in the reversed ferroelectric domains occurs very easily and in repeatedly way. We have experimentally investigated the formation of such HePPLN structures by an interference microscopy in digital holography (DH) modality. The reported results demonstrate the possibility of fabricating multi-periodic structures and open the way to investigate the possibility to achieve hierarchical PPLN structures by multiple subsequent electric poling processes.

A modified abstraction of Sierpiński fractals towards enhanced sensitivity of a cross-coupled bow-tie nanostructure

NASA Astrophysics Data System (ADS)

Hasan, Dihan; Lee, Chengkuo

2018-06-01

We experimentally demonstrate a modified abstraction of a fractal geometry (up to order M = 2), namely the Sierpiński fractal, with intrinsic self-similarity for a multitude of infrared sensing applications. The modification particularly strengthens the dipolar resonance and enables optical magnetism at longer wavelengths on a relatively miniaturized footprint. In contrast to the conventional resonant sensing, we harness the broadband electric field enhancement of the modified fractal patterns originating from the lightning rod effect in the non-resonant regime. We demonstrate strong enhancement of molecular absorption at mid-IR by the fractal patterns in the non-resonant regime even under extreme thermal broadening. Finally, we extend the work towards the functional study of the molecular fingerprint of ultra-thin film (∼5 nm) on a non-complementary metamaterial platform in the non-resonant regime. With the help of the solid state chemical dewetting of the monolayer, we also successfully demonstrate a new type of cross-coupling mediated sensitivity of the multispectral and mutually coupled fractal patterns. The research clearly indicates the usefulness of broadband electric field enhancement by the second order fractal pattern for on chip, complete profiling of mid-IR fingerprints of biological elements, i.e. cell, and protein monolayer on a limited footprint and under versatile morphological states.

Electrical Programming of Soft Matter: Using Temporally Varying Electrical Inputs To Spatially Control Self Assembly.

PubMed

Yan, Kun; Liu, Yi; Zhang, Jitao; Correa, Santiago O; Shang, Wu; Tsai, Cheng-Chieh; Bentley, William E; Shen, Jana; Scarcelli, Giuliano; Raub, Christopher B; Shi, Xiao-Wen; Payne, Gregory F

2018-02-12

The growing importance of hydrogels in translational medicine has stimulated the development of top-down fabrication methods, yet often these methods lack the capabilities to generate the complex matrix architectures observed in biology. Here we show that temporally varying electrical signals can cue a self-assembling polysaccharide to controllably form a hydrogel with complex internal patterns. Evidence from theory and experiment indicate that internal structure emerges through a subtle interplay between the electrical current that triggers self-assembly and the electrical potential (or electric field) that recruits and appears to orient the polysaccharide chains at the growing gel front. These studies demonstrate that short sequences (minutes) of low-power (∼1 V) electrical inputs can provide the program to guide self-assembly that yields hydrogels with stable, complex, and spatially varying structure and properties.

Speckle-field digital holographic microscopy.

PubMed

Park, YongKeun; Choi, Wonshik; Yaqoob, Zahid; Dasari, Ramachandra; Badizadegan, Kamran; Feld, Michael S

2009-07-20

The use of coherent light in conventional holographic phase microscopy (HPM) poses three major drawbacks: poor spatial resolution, weak depth sectioning, and fixed pattern noise due to unwanted diffraction. Here, we report a technique which can overcome these drawbacks, but maintains the advantage of phase microscopy - high contrast live cell imaging and 3D imaging. A speckle beam of a complex spatial pattern is used for illumination to reduce fixed pattern noise and to improve optical sectioning capability. By recording of the electric field of speckle, we demonstrate high contrast 3D live cell imaging without the need for axial scanning - neither objective lens nor sample stage. This technique has great potential in studying biological samples with improved sensitivity, resolution and optical sectioning capability.

Manipulating polymers and composites from the nanoscopic to microscopic length scales

NASA Astrophysics Data System (ADS)

Gupta, Suresh

2008-10-01

This thesis focuses on the manipulation of polymers and composites on length scales ranging from the nanoscopic to microscopic. In particular, on the microscopic length scale electric fields were used to produce instabilities at the air surface and at polymer interfaces that lead to novel three dimensional structures and patterns. On the nanoscopic length scale, the interaction of ligands attached to nanoparticles and polymer matrix were used to induce self-assembly processes that, in turn, lead to systems that self-heal, self-corral, or are patterned. For manipulation at the micron length scale, electrohydrodynamic instabilities were used in trilayer system composed of a layer of poly(methyl methacrylate) (PMMA), a second layer of polystyrene (PS) and a third layer of air. Dewetting of the polymer at the substrate at the polymer/polymer interface under an applied electric field was used to generate novel three dimensional structures. Also, electrohydrodynamic instabilities were used to pattern thin polymer films in conjunction with ultrasonic vibrations and patterned upper electrodes. Self-assembly processes involving polymers and nanoparticles offer a unique means of generating pattern materials or materials that self heal. Simple polymer/nanoparticle composites were investigated. Here, in the absence of interactions between the poly(ethylene oxide) ligands attached to the nanoparticles and PMMA polymer matrix, the opportunity to generate self-healing systems was opened. The size of the nanoparticle was varied and the effect on diffusion of nanoparticle in the polymer matrix was studied. CdSe nanorods were also assembled on a substrate templated with or guided by microphase separated diblock copolymers. The nanorods were incorporated in the diblock copolymer thin films by spin coating the co-solution of nanorods and polymer, surface adsorption of nanorods on to the patterned diblock copolymer films and surface reconstruction of PS/PMMA diblock copolymer thin film. Further, the interactions between the PMMA polymer matrix and the tri n-octyl phosphine oxide ligands attached to an anisotropic nanoparticle, i.e. nanorods, were used to influence the dispersion of the nanorods in the polymer. This led to a novel assembly, termed self-corralling where under an applied electric field highly oriented, highly ordered arrays of nanorods form. Further, self corralling of nanorods was directed by chemically patterned substrates.

Voltage-induced reduction of graphene oxide

NASA Astrophysics Data System (ADS)

Faucett, Austin C.

Graphene Oxide (GO) is being widely researched as a precursor for the mass production of graphene, and as a versatile material in its own right for flexible electronics, chemical sensors, and energy harvesting applications. Reduction of GO, an electrically insulating material, into reduced graphene oxide (rGO) restores electrical conductivity via removal of oxygen-containing functional groups. Here, a reduction method using an applied electrical bias, known as voltage-induced reduction, is explored. Voltage-induced reduction can be performed under ambient conditions and avoids the use of hazardous chemicals or high temperatures common with standard methods, but little is known about the reduction mechanisms and the quality of rGO produced with this method. This work performs extensive structural and electrical characterization of voltage-reduced GO (V-rGO) and shows that it is competitive with standard methods. Beyond its potential use as a facile and eco-friendly processing approach, V-rGO reduction also offers record high-resolution patterning capabilities. In this work, the spatial resolution limits of voltage-induced reduction, performed using a conductive atomic force microscope probe, are explored. It is shown that arbitrary V-rGO conductive features can be patterned into insulating GO with nanoscale resolution. The localization of voltage-induced reduction to length scales < 10 nm allows studies of reduction reaction kinetics, using electrical current obtained in-situ, with statistical robustness. Methods for patterning V-rGO nanoribbons are then developed. After presenting sub-10nm patterning of V-rGO nanoribbons in GO single sheets and films, the performance of V-rGO nanoribbon field effect transistors (FETs) are demonstrated. Preliminary measurements show an increase in electrical current on/off ratios as compared to large-area rGO FETs, indicating transport gap modulation that is possibly due to quantum confinement effects.

Modeling Microscale Electro-thermally Induced Vortex Flows

NASA Astrophysics Data System (ADS)

Paul, Rajorshi; Tang, Tian; Kumar, Aloke

2017-11-01

In presence of a high frequency alternating electric field and a laser induced heat source, vortex flows are generated inside micro-channels. Such electro-thermally influenced micro-vortices can be used for manipulating nano-particles, programming colloidal assemblies, trapping biological cells as well as for fabricating designed bacterial biofilms. In this study, a theoretical model is developed for microscale electro-thermally induced vortex flows with multiple heat sources. Semi-analytical solutions are obtained, using Hankel transformation and linear superposition, for the temperature, pressure and velocity fields. The effect of material properties such as electrical and thermal conductivities, as well as experimental parameters such as the frequency and strength of the alternating electric field, and the intensity and heating profile of the laser source, are systematically investigated. Resolution for a pair of laser sources is determined by analyzing the strength of the micro-vortices under the influence of two heating sources. Results from this work will provide useful insights into the design of efficient optical tweezers and Rapid Electrokinetic Patterning techniques.

Liquid-crystal microlenses with patterned ring-electrode arrays for multiple-mode two-dimensional imaging

NASA Astrophysics Data System (ADS)

Xie, Xingwang; Han, Xinjie; Long, Huabao; Dai, Wanwan; Xin, Zhaowei; Wei, Dong; Zhang, Xinyu; Wang, Haiwei; Xie, Changsheng

2018-02-01

In this paper, a new liquid-crystal microlens array (LCMLA) with patterned ring-electrode arrays (PREAs) is investigated, which has an ability to acquire multiple-mode two-dimensional images with better electrically tunable efficiency than common liquid-crystal devices. The new type of LCMLA can be used to overcome several remarkable disadvantage of conventional liquid-crystal microlens arrays switched and adjusted electrically by relatively complex mechanism. There are two layer electrodes in the LCMLA developed by us. The top electrode layer consists of PREAs with different featured diameter but the same center for each single cell, and the bottom is a plate electrode. When both electrode structures are driven independently by variable AC voltage signal, a gradient electric field distribution could be obtained, which can drive liquid-crystal molecules to reorient themselves along the gradient electric field shaped, so as to demonstrate a satisfactory refractive index distribution. The common experiments are carried out to validate the performances needed. As shown, the focal length of the LCMLA can be adjusted continuously according to the variable voltage signal applied. According to designing, the LCMLA will be integrated continuously with an image sensors to set up a camera with desired performances. The test results indicate that our camera based on the LCMLA can obtain distinct multiple-mode two-dimensional images under the condition of using relatively low driving signal voltage.

Charged particle dynamics in multiple colliding electromagnetic waves. Survey of random walk, Lévy flights, limit circles, attractors and structurally determinate patterns

NASA Astrophysics Data System (ADS)

Bulanov, S. V.; Esirkepov, T. Zh.; Koga, J. K.; Bulanov, S. S.; Gong, Z.; Yan, X. Q.; Kando, M.

2017-04-01

The multiple colliding laser pulse concept formulated by Bulanov et al. (Phys. Rev. Lett., vol. 104, 2010b, 220404) is beneficial for achieving an extremely high amplitude of coherent electromagnetic field. Since the topology of electric and magnetic fields of multiple colliding laser pulses oscillating in time is far from trivial and the radiation friction effects are significant in the high field limit, the dynamics of charged particles interacting with the multiple colliding laser pulses demonstrates remarkable features corresponding to random walk trajectories, limit circles, attractors, regular patterns and Lévy flights. Under extremely high intensity conditions the nonlinear dissipation mechanism stabilizes the particle motion resulting in the charged particle trajectory being located within narrow regions and in the occurrence of a new class of regular patterns made by the particle ensembles.

Charged particle dynamics in multiple colliding electromagnetic waves. Survey of random walk, Lévy flights, limit circles, attractors and structurally determinate patterns

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

Bulanov, S. V.; Esirkepov, T. Zh.; Koga, J. K.

The multiple colliding laser pulse concept formulated by Bulanovet al.(Phys. Rev. Lett., vol. 104, 2010b, 220404) is beneficial for achieving an extremely high amplitude of coherent electromagnetic field. Since the topology of electric and magnetic fields of multiple colliding laser pulses oscillating in time is far from trivial and the radiation friction effects are significant in the high field limit, the dynamics of charged particles interacting with the multiple colliding laser pulses demonstrates remarkable features corresponding to random walk trajectories, limit circles, attractors, regular patterns and Lévy flights. Lastly, under extremely high intensity conditions the nonlinear dissipation mechanism stabilizes the particle motionmore » resulting in the charged particle trajectory being located within narrow regions and in the occurrence of a new class of regular patterns made by the particle ensembles.« less

Charged particle dynamics in multiple colliding electromagnetic waves. Survey of random walk, Lévy flights, limit circles, attractors and structurally determinate patterns

DOE PAGES

Bulanov, S. V.; Esirkepov, T. Zh.; Koga, J. K.; ...

2017-03-09

The multiple colliding laser pulse concept formulated by Bulanovet al.(Phys. Rev. Lett., vol. 104, 2010b, 220404) is beneficial for achieving an extremely high amplitude of coherent electromagnetic field. Since the topology of electric and magnetic fields of multiple colliding laser pulses oscillating in time is far from trivial and the radiation friction effects are significant in the high field limit, the dynamics of charged particles interacting with the multiple colliding laser pulses demonstrates remarkable features corresponding to random walk trajectories, limit circles, attractors, regular patterns and Lévy flights. Lastly, under extremely high intensity conditions the nonlinear dissipation mechanism stabilizes the particle motionmore » resulting in the charged particle trajectory being located within narrow regions and in the occurrence of a new class of regular patterns made by the particle ensembles.« less

Dynamics Explorer measurements of particles, fields, and plasma drifts over a horse-collar auroral pattern

NASA Technical Reports Server (NTRS)

Sharber, J. R.; Hones, E. W., Jr.; Heelis, R. A.; Craven, J. D.; Frank, L. A.; Maynard, N. C.; Slavin, J. A.; Birn, J.

1992-01-01

As shown from ground-based measurements and satellite-borne imagers, one type of global auroral pattern characteristic of quiet (usually northward IMF) intervals is that of a contracted but thickened emission region in which the dawn and dusk portions can spread poleward to very high latitudes, (the type of a pattern referred to as a 'horse-collar' aurora by Hones et al., 1989). In this report we use a DE data set to examine a case in which this horse-collar pattern was observed by the DE-1 auroral imager while at the same time the DE-2, at lower altitude, measured precipitating particles, electric and magnetic fields, and plasma drifts. There is close agreement between the optical signatures and the particle precipitation patterns. The particle, plasma, and field measurements made along the satellite track and the 2-D perspective of the imager provide a means of determining the configuration of convective flows in the high-latitude ionosphere during this interval of northward IMF. Recent mapping studies are used to relate the low-altitude observations to possible magnetospheric source regions.

MOM3D method of moments code theory manual

NASA Technical Reports Server (NTRS)

Shaeffer, John F.

1992-01-01

MOM3D is a FORTRAN algorithm that solves Maxwell's equations as expressed via the electric field integral equation for the electromagnetic response of open or closed three dimensional surfaces modeled with triangle patches. Two joined triangles (couples) form the vector current unknowns for the surface. Boundary conditions are for perfectly conducting or resistive surfaces. The impedance matrix represents the fundamental electromagnetic interaction of the body with itself. A variety of electromagnetic analysis options are possible once the impedance matrix is computed including backscatter radar cross section (RCS), bistatic RCS, antenna pattern prediction for user specified body voltage excitation ports, RCS image projection showing RCS scattering center locations, surface currents excited on the body as induced by specified plane wave excitation, and near field computation for the electric field on or near the body.

Electric field induced short range to long range structural ordering and its influence on the Eu{sup +3} photoluminescence in the lead-free ferroelectric Na{sub 1/2}Bi{sub 1/2}TiO{sub 3}

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

Kalaskar, Abhijeet; Rao, Badari Narayana; Ranjan, Rajeev, E-mail: rajeev@materials.iisc.ernet.in

2015-06-28

Eu{sup +3} was incorporated into the lattice of a lead-free ferroelectric Na{sub 1/2}Bi{sub 1/2}TiO{sub 3} (NBT) as per the nominal formula Na{sub 0.5}Bi{sub 0.5−x}Eu{sub x}TiO{sub 3}. This system was investigated with regard to the Eu{sup +3} photoluminescence (PL) and structural behaviour as a function of composition and electric field. Electric field was found to irreversibly change the features in the PL spectra and also in the x-ray diffraction patterns below the critical composition x = 0.025. Detailed analysis revealed that below the critical composition, electric field irreversibly suppresses the structural heterogeneity inherent of the host matrix NBT and brings about a longmore » range ferroelectric state with rhombohedral (R3c) distortion. It is shown that the structural disorder on the nano-scale opens a new channel for radiative transition which manifests as a new emission line branching off from the main {sup 5}D{sub 0}→{sup 7}F{sub 0} line along with a concomitant change in the relative intensity of the other crystal field induced Stark lines with different J values. The study suggests that Eu{sup +3} luminescence can be used to probe the relative degree of field induced structural ordering in relaxor ferroelectrics and also in high performance piezoelectric alloys where electric field couples very strongly with the lattice and structural degrees of freedom.« less

Modification of electric and magnetic dipole emission in anisotropic plasmonic systems.

PubMed

Noginova, N; Hussain, R; Noginov, M A; Vella, J; Urbas, A

2013-10-07

In order to investigate the effects of plasmonic environments on spontaneous emission of magnetic and electric dipoles, we have studied luminescence of Eu³⁺ ions in close vicinity to gold nanostrip arrays. Significant changes in the emission kinetics, emission polarization, and radiation patterns have been observed in the wavelength range corresponding to the plasmonic resonance. The effect of the plasmonic resonance on the magnetic dipole transition ⁵D₀-->⁷F₁ is found to be very different from its effect on the electric dipole transitions. This makes Eu³⁺₋ containing complexes promising for mapping local distributions of magnetic and electric fields in metamaterials and plasmonic systems.

Characterization of applied fields for ion mobility separations in traveling wave based structures for lossless ion manipulations (SLIM)

DOE PAGES

Hamid, Ahmed M.; Prabhakaran, Aneesh; Garimella, Sandilya V. B.; ...

2018-03-26

Ion mobility (IM) is rapidly gaining attention for the separation and analysis of biomolecules due to the ability to distinguish the shapes of ions. However, conventional constant electric field drift tube IM separations have limited resolving power, constrained by practical limitations on the path length and maximum applied voltage. The implementation of traveling waves (TW) in IM removes the latter limitation, allowing higher resolution to be achieved using extended path lengths. Both of these can be readily obtained in Structures for Lossless Ion Manipulations (SLIM), which are fabricated from arrays of electrodes patterned on two parallel surfaces where potentials aremore » applied to generate appropriate electric fields between the surfaces. Here we have investigated the relationship between the primary SLIM variables, such as electrode dimensions, inter-surface gap, and the applied TW voltages, that directly impact the fields experienced by ions. Ion trajectory simulations and theoretical calculations have been utilized to understand the dependence of SLIM geometry and effective electric fields on IM resolution. The variables explored impact both ion confinement and the observed IM resolution using SLIM modules.« less

Characterization of applied fields for ion mobility separations in traveling wave based structures for lossless ion manipulations (SLIM)

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

Hamid, Ahmed M.; Prabhakaran, Aneesh; Garimella, Sandilya V. B.

Ion mobility (IM) is rapidly gaining attention for the separation and analysis of biomolecules due to the ability to distinguish the shapes of ions. However, conventional constant electric field drift tube IM separations have limited resolving power, constrained by practical limitations on the path length and maximum applied voltage. The implementation of traveling waves (TW) in IM removes the latter limitation, allowing higher resolution to be achieved using extended path lengths. Both of these can be readily obtained in Structures for Lossless Ion Manipulations (SLIM), which are fabricated from arrays of electrodes patterned on two parallel surfaces where potentials aremore » applied to generate appropriate electric fields between the surfaces. Here we have investigated the relationship between the primary SLIM variables, such as electrode dimensions, inter-surface gap, and the applied TW voltages, that directly impact the fields experienced by ions. Ion trajectory simulations and theoretical calculations have been utilized to understand the dependence of SLIM geometry and effective electric fields on IM resolution. The variables explored impact both ion confinement and the observed IM resolution using SLIM modules.« less

Electric-Field Induced Reversible Switching of the Magnetic Easy Axis in Co/BiFeO3 on SrTiO3.

PubMed

Gao, Tieren; Zhang, Xiaohang; Ratcliff, William; Maruyama, Shingo; Murakami, Makoto; Varatharajan, Anbusathaiah; Yamani, Zahra; Chen, Peijie; Wang, Ke; Zhang, Huairuo; Shull, Robert; Bendersky, Leonid A; Unguris, John; Ramesh, Ramamoorthy; Takeuchi, Ichiro

2017-05-10

Electric-field (E-field) control of magnetism enabled by multiferroic materials has the potential to revolutionize the landscape of present memory devices plagued with high energy dissipation. To date, this E-field controlled multiferroic scheme has only been demonstrated at room temperature using BiFeO 3 films grown on DyScO 3 , a unique and expensive substrate, which gives rise to a particular ferroelectric domain pattern in BiFeO 3 . Here, we demonstrate reversible electric-field-induced switching of the magnetic state of the Co layer in Co/BiFeO 3 (BFO) (001) thin film heterostructures fabricated on (001) SrTiO 3 (STO) substrates. The angular dependence of the coercivity and the remanent magnetization of the Co layer indicates that its easy axis reversibly switches back and forth 45° between the (100) and the (110) crystallographic directions of STO as a result of alternating application of positive and negative voltage pulses between the patterned top Co electrode layer and the (001) SrRuO 3 (SRO) layer on which the ferroelectric BFO is epitaxially grown. The coercivity (H C ) of the Co layer exhibits a hysteretic behavior between two states as a function of voltage. A mechanism based on the intrinsic magnetoelectric coupling in multiferroic BFO involving projection of antiferromagnetic G-type domains is used to explain the observation. We have also measured the exact canting angle of the G-type domain in strained BFO films for the first time using neutron diffraction. These results suggest a pathway to integrating BFO-based devices on Si wafers for implementing low power consumption and nonvolatile magnetoelectronic devices.

The Electrical Structure of Thunderstorms

NASA Technical Reports Server (NTRS)

Workman, E J; Helzer, R E; Pelsor, G T

1942-01-01

The time histories of thunderstorm charge distribution during three storms occurring during the summer of 1940 in the vicinity of the Albuquerque Airport were investigated by the use of eight synchronized recording electrometers arranged in a particular pattern over a field 1.6 kilometers above sea level.

Anti-parallel polarization switching in a triglycine sulfate organic ferroelectric insulator: The role of surface charges

NASA Astrophysics Data System (ADS)

Ma, He; Wu, Zhuangchun; Peng, Dongwen; Wang, Yaojin; Wang, Yiping; Yang, Ying; Yuan, Guoliang

2018-04-01

Four consecutive ferroelectric polarization switchings and an abnormal ring-like domain pattern can be introduced by a single tip bias of a piezoresponse force microscope in the (010) triglycine sulfate (TGS) crystal. The external electric field anti-parallel to the original polarization induces the first polarization switching; however, the surface charges of TGS can move toward the tip location and induce the second polarization switching once the tip bias is removed. The two switchings allow a ring-like pattern composed of the central domain with downward polarization and the outer domain with upward polarization. Once the two domains disappear gradually as a result of depolarization, the other two polarization switchings occur one by one at the TGS where the tip contacts. However, the backswitching phenomenon does not occur when the external electric field is parallel to the original polarization. These results can be explained according to the surface charges instead of the charges injected inside.

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

Computer prediction of large reflector antenna radiation properties

NASA Technical Reports Server (NTRS)

Botula, A.

1980-01-01

A FORTRAN program for calculating reflector antenna radiation patterns was rewritten and extended to include reflectors composed of a number of panels. These individual panels must be analytic surfaces. The theoretical foundation for the program is as follows: Geometrical optics techniques are used to trace rays from a feed antenna to the reflector surface and back to a mathematical plane just in front of the reflector. The resulting tangential electric field distribution, assumed to be the only source of forward radiation, is integrated numerically to calculate the radiation pattern for a desired set of angles. When the reflector is composed of more than one panel, each panel is treated as a separated antenna, the ray-tracing procedure and integration being repeated for each panel. The results of the individual aperture plane integrations are stored and summed to yield the relative electric field strength over the angles of interest. An example and several test cases are included to demonstrate the use of the program and verify the new method of computation.

Tailored optical vector fields for ultrashort-pulse laser induced complex surface plasmon structuring.

PubMed

Ouyang, J; Perrie, W; Allegre, O J; Heil, T; Jin, Y; Fearon, E; Eckford, D; Edwardson, S P; Dearden, G

2015-05-18

Precise tailoring of optical vector beams is demonstrated, shaping their focal electric fields and used to create complex laser micro-patterning on a metal surface. A Spatial Light Modulator (SLM) and a micro-structured S-waveplate were integrated with a picosecond laser system and employed to structure the vector fields into radial and azimuthal polarizations with and without a vortex phase wavefront as well as superposition states. Imprinting Laser Induced Periodic Surface Structures (LIPSS) elucidates the detailed vector fields around the focal region. In addition to clear azimuthal and radial plasmon surface structures, unique, variable logarithmic spiral micro-structures with a pitch Λ ∼1μm, not observed previously, were imprinted on the surface, confirming unambiguously the complex 2D focal electric fields. We show clearly also how the Orbital Angular Momentum(OAM) associated with a helical wavefront induces rotation of vector fields along the optic axis of a focusing lens and confirmed by the observed surface micro-structures.

Tip-Enhanced Raman Nanographs: Mapping Topography and Local Electric Fields

DOE PAGES

El-Khoury, Patrick Z.; Gong, Yu; Abellan, Patricia; ...

2015-03-05

We report tip-enhanced Raman scattering experiments in which topographic and local electric field images are recorded simultaneously. We employ a Raman-active 4,4’-dimercaptostilbene (DMS)-coated gold tip of an atomic force microscope to map the topography and image electric fields localized at nanometric (20 and 5 nm-wide) slits lithographically etched in silver. Bi-modal imaging is feasible by virtue of the recorded scanning probe position-dependent frequency-resolved optical response, which can be sub-divided into two components. The first is a 500-2250 cm-1 Raman-shifted signal, characteristic of DMS. The molecular response reports on topography through intensity contrast in the absence/presence of a plasmonic junction formedmore » between the scanning probe and patterned silver surface. Here, we demonstrate that sub-15 nm spatial resolution is attainable using a 30 nm DMS-coated gold tip. The second response consists of two correlated sub-500 cm-1 signals arising from mirror-like reflections of (i) the incident laser, and (ii) the Raman scattered response of an underlying glass support (at 100-500 cm-1) off the gold tip. We show that both the low-wavenumber signals trace the local electric fields in the vicinity of the nanometric slits.« less

Spontaneous and electrically modulated spatiotemporal dynamics of the neocortical slow oscillation and associated local fast activity.

PubMed

Greenberg, Anastasia; Dickson, Clayton T

2013-12-01

The neocortical slow oscillation (SO; ~1Hz) of non-REM sleep and anesthesia reflects synchronized network activity composed of alternating active and silent (ON/OFF) phases at the local network and cellular level. The SO itself shows self-organized spatiotemporal dynamics as it appears to originate at unique foci on each cycle and then propagates across the cortical surface. During sleep, this rhythm is relevant for neuroplastic processes mediating memory consolidation especially since its enhancement by slow, rhythmic electrical fields improves subsequent recall. However, the neurobiological mechanism by which spontaneous or enhanced SO activity might operate on memory traces is unknown. Here we show a series of original results, using cycle to cycle tracking across multiple neocortical sites in urethane anesthetized rats: The spontaneous spatiotemporal dynamics of the SO are complex, showing interfering propagation patterns in the anterior-to-posterior plane. These patterns compete for expression and tend to alternate following phase resets that take place during the silent OFF phase of the SO. Applying sinusoidal electrical field stimulation to the anterior pole of the cerebral cortex progressively entrained local field, gamma, and multi-unit activity at all sites, while disrupting the coordination of endogenous SO activity. Field stimulation also biased propagation in the anterior-to-posterior direction and more notably, enhanced the long-range gamma synchrony between cortical regions. These results are the first to show that changes to slow wave dynamics cause enhancements in high frequency cortico-cortical communication and provide mechanistic clues into how the SO is relevant for sleep-dependent memory consolidation. © 2013.

Initial Results of DC Electric Fields, Associated Plasma Drifts, Magnetic Fields, and Plasma Waves Observed on the C/NOFS Satellite

NASA Technical Reports Server (NTRS)

Pfaff, R.; Freudenreich, H.; Bromund, K.; Klenzing, J.; Rowland, D.; Maynard, N.

2010-01-01

Initial results are presented from the Vector Electric Field Investigation (VEFI) on the Air Force Communication/Navigation Outage Forecasting System (C/NOFS) satellite, a mission designed to understand, model, and forecast the presence of equatorial ionospheric irregularities. The VEFI instrument includes a vector DC electric field detector, a fixed-bias Langmuir probe operating in the ion saturation regime, a flux gate magnetometer, an optical lightning detector, and associated electronics including a burst memory. Compared to data obtained during more active solar conditions, the ambient DC electric fields and their associated E x B drifts are variable and somewhat weak, typically < 1 mV/m. Although average drift directions show similarities to those previously reported, eastward/outward during day and westward/downward at night, this pattern varies significantly with longitude and is not always present. Daytime vertical drifts near the magnetic equator are largest after sunrise, with smaller average velocities after noon. Little or no pre-reversal enhancement in the vertical drift near sunset is observed, attributable to the solar minimum conditions creating a much reduced neutral dynamo at the satellite altitude. The nighttime ionosphere is characterized by larger amplitude, structured electric fields, even where the plasma density appears nearly quiescent. Data from successive orbits reveal that the vertical drifts and plasma density are both clearly organized with longitude. The spread-F density depletions and corresponding electric fields that have been detected thus far have displayed a preponderance to appear between midnight and dawn. Associated with the narrow plasma depletions that are detected are broad spectra of electric field and plasma density irregularities for which a full vector set of measurements is available for detailed study. Finally, the data set includes a wide range of ELF/VLF/HF oscillations corresponding to a variety of plasma waves, in particular banded ELF hiss, whistlers, and lower hybrid wave turbulence triggered by lightning-induced sferics. The VEFI data represents a new set of measurements that are germane to numerous fundamental aspects of the electrodynamics and irregularities inherent to the Earth's low latitude ionosphere.

Vector tomography for reconstructing electric fields with non-zero divergence in bounded domains

NASA Astrophysics Data System (ADS)

Koulouri, Alexandra; Brookes, Mike; Rimpiläinen, Ville

2017-01-01

In vector tomography (VT), the aim is to reconstruct an unknown multi-dimensional vector field using line integral data. In the case of a 2-dimensional VT, two types of line integral data are usually required. These data correspond to integration of the parallel and perpendicular projection of the vector field along the integration lines and are called the longitudinal and transverse measurements, respectively. In most cases, however, the transverse measurements cannot be physically acquired. Therefore, the VT methods are typically used to reconstruct divergence-free (or source-free) velocity and flow fields that can be reconstructed solely from the longitudinal measurements. In this paper, we show how vector fields with non-zero divergence in a bounded domain can also be reconstructed from the longitudinal measurements without the need of explicitly evaluating the transverse measurements. To the best of our knowledge, VT has not previously been used for this purpose. In particular, we study low-frequency, time-harmonic electric fields generated by dipole sources in convex bounded domains which arise, for example, in electroencephalography (EEG) source imaging. We explain in detail the theoretical background, the derivation of the electric field inverse problem and the numerical approximation of the line integrals. We show that fields with non-zero divergence can be reconstructed from the longitudinal measurements with the help of two sparsity constraints that are constructed from the transverse measurements and the vector Laplace operator. As a comparison to EEG source imaging, we note that VT does not require mathematical modeling of the sources. By numerical simulations, we show that the pattern of the electric field can be correctly estimated using VT and the location of the source activity can be determined accurately from the reconstructed magnitudes of the field.

In situ synthesis of semiconducting single-walled carbon nanotubes by modified arc discharging method

NASA Astrophysics Data System (ADS)

Zhao, Tingkai; Ji, Xianglin; Jin, Wenbo; Yang, Wenbo; Zhao, Xing; Dang, Alei; Li, Hao; Li, Tiehu

2017-02-01

Semiconducting single-walled carbon nanotubes (s-SWCNTs) were in situ synthesized by a temperature-controlled arc discharging furnace with DC electric field using Co-Ni alloy powder as catalyst in helium gas. The microstructures of s-SWCNTs were characterized using high-resolution transmission electron microscopy, electron diffraction, and Raman spectrometry apparatus. The experimental results indicated that the best voltage value in DC electric field is 54 V, and the environmental temperature of the reaction chamber is 600 °C. The mean diameter of s-SWCNTs was estimated about 1.3 nm. The chiral vector ( n, m) of s-SWCNTs was calculated to be (10, 10) type according to the electron diffraction patterns.

Polymer-stabilized liquid crystalline topological defect network for micro-pixelated optical devices

NASA Astrophysics Data System (ADS)

Araoka, Fumito; Le, Khoa V.; Fujii, Shuji; Orihara, Hiroshi; Sasaki, Yuji

2018-02-01

Spatially and temporally controlled topological defects in nematic liquid crystals (NLCs) are promising for its potential in optical applications. Utilization of self-organization is a key to fabricate complex micro- and nano-structures which are often difficult to obtain by conventional lithographic tools. Using photo-polymerization technique, here we show a polymer-stabilized NLC having a micro-pixelated structure of regularly ordered umbilical defects which are induced by an electric field. Due to the formation of polymer network, the self-organized pattern is kept stable without deterioration. Moreover, the polymer network allows to template other LCs whose optical properties can be tuned with external stimuli such as temperature and electric fields.

Rotationally driven 'zebra stripes' in Earth's inner radiation belt.

PubMed

Ukhorskiy, A Y; Sitnov, M I; Mitchell, D G; Takahashi, K; Lanzerotti, L J; Mauk, B H

2014-03-20

Structured features on top of nominally smooth distributions of radiation-belt particles at Earth have been previously associated with particle acceleration and transport mechanisms powered exclusively by enhanced solar-wind activity. Although planetary rotation is considered to be important for particle acceleration at Jupiter and Saturn, the electric field produced in the inner magnetosphere by Earth's rotation can change the velocity of trapped particles by only about 1-2 kilometres per second, so rotation has been thought inconsequential for radiation-belt electrons with velocities of about 100,000 kilometres per second. Here we report that the distributions of energetic electrons across the entire spatial extent of Earth's inner radiation belt are organized in regular, highly structured and unexpected 'zebra stripes', even when the solar-wind activity is low. Modelling reveals that the patterns are produced by Earth's rotation. Radiation-belt electrons are trapped in Earth's dipole-like magnetic field, where they undergo slow longitudinal drift motion around the planet because of the gradient and curvature of the magnetic field. Earth's rotation induces global diurnal variations of magnetic and electric fields that resonantly interact with electrons whose drift period is close to 24 hours, modifying electron fluxes over a broad energy range into regular patterns composed of multiple stripes extending over the entire span of the inner radiation belt.

Confining standing waves in optical corrals.

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

Babayan, Y.; McMahon, J. M.; Li, S.

2009-03-01

Near-field scanning optical microscopy images of solid wall, circular, and elliptical microscale corrals show standing wave patterns confined inside the structures with a wavelength close to that of the incident light. The patterns inside the corrals can be tuned by changing the size and material of the walls, the wavelength of incident light, and polarization direction for elliptical corrals. Finite-difference time-domain calculations of the corral structures agree with the experimental observations and reveal that the electric and magnetic field intensities are out of phase inside the corral. A theoretical modal analysis indicates that the fields inside the corrals can bemore » attributed to p- and s-polarized waveguide modes, and that the superposition of the propagating and evanescent modes can explain the phase differences between the fields. These experimental and theoretical results demonstrate that electromagnetic fields on a dielectric surface can be controlled in a predictable manner.« less

Fundamentals of thinking, patterns

NASA Astrophysics Data System (ADS)

Gafurov, O. M.; Gafurov, D. O.; Syryamkin, V. I.

2018-05-01

The authors analyze the fundamentals of thinking and propose to consider a model of the brain based on the presence of magnetic properties of gliacytes (Schwann cells) because of their oxygen saturation (oxygen has paramagnetic properties). The authors also propose to take into account the motion of electrical discharges through synapses causing electric and magnetic fields as well as additional effects such as paramagnetic resonance, which allows combining multisensory object-related information located in different parts of the brain. Therefore, the events of the surrounding world are reflected and remembered in the cortex columns, thus, creating isolated subnets with altered magnetic properties (patterns) and subsequently participate in recognition of objects, form a memory, and so on. The possibilities for the pattern-based thinking are based on the practical experience of applying methods and technologies of artificial neural networks in the form of a neuroemulator and neuromorphic computing devices.

The use of MR B+1 imaging for validation of FDTD electromagnetic simulations of human anatomies.

PubMed

Van den Berg, Cornelis A T; Bartels, Lambertus W; van den Bergen, Bob; Kroeze, Hugo; de Leeuw, Astrid A C; Van de Kamer, Jeroen B; Lagendijk, Jan J W

2006-10-07

In this study, MR B(+)(1) imaging is employed to experimentally verify the validity of FDTD simulations of electromagnetic field patterns in human anatomies. Measurements and FDTD simulations of the B(+)(1) field induced by a 3 T MR body coil in a human corpse were performed. It was found that MR B(+)(1) imaging is a sensitive method to measure the radiofrequency (RF) magnetic field inside a human anatomy with a precision of approximately 3.5%. A good correlation was found between the B(+)(1) measurements and FDTD simulations. The measured B(+)(1) pattern for a human pelvis consisted of a global, diagonal modulation pattern plus local B(+)(1) heterogeneties. It is believed that these local B(+)(1) field variations are the result of peaks in the induced electric currents, which could not be resolved by the FDTD simulations on a 5 mm(3) simulation grid. The findings from this study demonstrate that B(+)(1) imaging is a valuable experimental technique to gain more knowledge about the dielectric interaction of RF fields with the human anatomy.

Magnetophoretic Conductors and Diodes in a 3D Magnetic Field.

PubMed

Abedini-Nassab, Roozbeh; Joh, Daniel Y; Van Heest, Melissa; Baker, Cody; Chilkoti, Ashutosh; Murdoch, David M; Yellen, Benjamin B

2016-06-14

We demonstrate magnetophoretic conductor tracks that can transport single magnetized beads and magnetically labeled single cells in a 3-dimensional time-varying magnetic field. The vertical field bias, in addition to the in-plane rotating field, has the advantage of reducing the attraction between particles, which inhibits the formation of particle clusters. However, the inclusion of a vertical field requires the re-design of magnetic track geometries which can transport magnetized objects across the substrate. Following insights from magnetic bubble technology, we found that successful magnetic conductor geometries defined in soft magnetic materials must be composed of alternating sections of positive and negative curvature. In addition to the previously studied magnetic tracks taken from the magnetic bubble literature, a drop-shape pattern was found to be even more adept at transporting small magnetic beads and single cells. Symmetric patterns are shown to achieve bi-directional conduction, whereas asymmetric patterns achieve unidirectional conduction. These designs represent the electrical circuit corollaries of the conductor and diode, respectively. Finally, we demonstrate biological applications in transporting single cells and in the size based separation of magnetic particles.

Magnetic Activity Dependence of the Electric Drift Below L = 3

NASA Astrophysics Data System (ADS)

Lejosne, Solène; Mozer, F. S.

2018-05-01

More than 2 years of magnetic and electric field measurements by the Van Allen Probes are analyzed with the objective of determining the average effects of magnetic activity on the electric drift below L = 3. The study finds that an increase in magnetospheric convection leads to a decrease in the magnitude of the azimuthal component of the electric drift, especially in the nightside. The amplitude of the slowdown is a function of L, magnetic local time, and Kp, in a pattern consistent with the storm time dynamics of the ionosphere and thermosphere. To a lesser extent, magnetic activity also alters the average radial component of the electric drift below L = 3. A global picture for the average variations of the electric drift with Kp is provided as a function of L and magnetic local time. It is the first time that the signature of the ionospheric disturbance dynamo is observed in near-equatorial electric drift measurements.

Structural, electrical, optical and magneto-electric characteristics of chemically synthesized CaCu3Ti4O12 dielectric ceramics

NASA Astrophysics Data System (ADS)

Parida, Kalpana; Choudhary, R. N. P.

2017-07-01

CaCu3Ti4O12 (CCTO) was prepared by a chemical reaction method. The pellets prepared from the calcined powder of the material were sintered at 1100 °C. Analysis of x-ray diffraction pattern, recorded on CCTO powder, confirms the phase formation of CCTO. Studies of dielectric (ɛ r, tanδ) and impedance parameters using dielectric and impedance spectroscopy of the compound have provided information about the electrical properties and the dielectric relaxation mechanism of the material. Detailed studies on the variation of electrical conductivity (dc) with temperature show semi-conducting nature of the material. Study of frequency (of applied electric field) dependence of ac conductivity at different temperatures suggests that the compound follows the Jonscher’s power law. Complex impedance spectroscopic analysis suggests that the semicircles formed in the Nyquist plot are connected to the grains, grain boundary and interface effects. An optical energy band gap of ~1.9 eV is obtained from the UV-visible absorbance spectrum. The magnetic data related to magneto-electric (ME) coefficient, measured by varying dc bias magnetic field, have been obtained at room temperature.

Surface electrical properties experiment. Part 2: Theory of radio-frequency interferometry in geophysical subsurface probing

NASA Technical Reports Server (NTRS)

Kong, J. A.; Tsang, L.

1974-01-01

The radiation fields due to a horizontal electric dipole laid on the surface of a stratified medium were calculated using a geometrical optics approximation, a modal approach, and direct numerical integration. The solutions were obtained from the reflection coefficient formulation and written in integral forms. The calculated interference patterns are compared in terms of the usefulness of the methods used to obtain them. Scattering effects are also discussed and all numerical results for anisotropic and isotropic cases are presented.

Method for imaging informational biological molecules on a semiconductor substrate

NASA Technical Reports Server (NTRS)

Coles, L. Stephen (Inventor)

1994-01-01

Imaging biological molecules such as DNA at rates several times faster than conventional imaging techniques is carried out using a patterned silicon wafer having nano-machined grooves which hold individual molecular strands and periodically spaced unique bar codes permitting repeatably locating all images. The strands are coaxed into the grooves preferably using gravity and pulsed electric fields which induce electric charge attraction to the molecular strands in the bottom surfaces of the grooves. Differential imaging removes substrate artifacts.

Induction of auroral zone electric currents within the Alaska pipeline

USGS Publications Warehouse

Campbell, W.H.

1978-01-01

The Alaskar pipeline is a highly conducting anomaly extending 800 miles (1300 km) from about 62?? to 69?? geomagnetic latitude beneath the most active regions of the ionospheric electrojet current. The spectral behavior of the magnetic field from this current was analyzed using data from standard geomagnetic observatories to establish the predictable patterns of temporal and spatial changes for field pulsation periods between 5 min and 4 hr. Such behavior is presented in a series of tables, graphs and formulae. Using 2- and 3-layer models of the conducting earth, the induced electric fields associated with the geomagnetic changes were established. From the direct relationship of the current to the geomagnetic field variation patterns one can infer counterpart temporal and spatial characteristics of the pipeline current. The relationship of the field amplitudes to geomagnetic activity indices, Ap, and the established occurrence of various levels of Ap over several solar cycles were employed to show that about half of the time the induced currents in the pipe would be under 1 A for the maximum response oscillatory periods near 1 hr. Such currents should be of minimal consequence in corrosion effects for even a section of the pipeline unprotected by sacrificial electrodes. Of greater interest was the result that the extreme surges of current should reach over one-hundred amperes in the pipeline during high activity. ?? 1978 Birkha??user Verlag.

Electrical manipulation of glycan-phosphatidyl inositol-tethered proteins in planar supported bilayers.

PubMed Central

Groves, J T; Wülfing, C; Boxer, S G

1996-01-01

Electric fields have been used to manipulate and concentrate glycan-phosphatidyl inositol (GPI)-tethered proteins in planar supported bilayers. Naturally GPI-linked CD48, along with engineered forms of I-Ek and B7-2, in which their transmembrane domains have been genetically replaced with the GPI linkage, were studied. The proteins were labeled with fluorescently tagged antibodies, allowing the electric field-induced behavior to be followed by epifluorescence microscopy. All three protein complexes were observed to migrate toward the cathode with the B7-2 and CD48, each tethered to the membrane by a single GPI linker, moving significantly faster than the I-Ek, which has two GPI linkers. Patterns scratched into the membrane function as barriers to lateral diffusion and were used to isolate the proteins into highly concentrated corrals. All field-induced concentration profiles were completely reversible, indicating that the supported bilayer provides a stable, fluid environment in which GPI-tethered proteins can be manipulated. The ability to electrically control the spatial distribution of membrane-tethered proteins provides new opportunities for the study of biological membranes and the development of membrane-based devices. Images FIGURE 2 FIGURE 3 FIGURE 4 FIGURE 5 FIGURE 6 PMID:8913608

Rapid Cellulose-Mediated Microwave Sintering for High-Conductivity Ag Patterns on Paper.

PubMed

Jung, Sunshin; Chun, Su Jin; Shon, Chae-Hwa

2016-08-10

Cellulose-based paper is essential in everyday life, but it also has further potentials for use in low-cost, printable, disposable, and eco-friendly electronics. Here, a method is developed for the cellulose-mediated microwave sintering of Ag patterns on conventional paper, in which the paper plays a significant role both as a flexible insulating substrate for the conductive Ag pattern and as a lossy dielectric media for rapid microwave heating. The anisotropic dielectric properties of the cellulose fibers mean that a microwave electric field applied parallel to the paper substrate provides sufficient heating to produce Ag patterns with a conductivity 29-38% that of bulk Ag in a short period of time (∼1 s) at 250-300 °C. Significantly, there is little thermal degradation of the substrate during this process. The microwave-sintered Ag patterns exhibit good mechanical stability against 10 000 bending cycles and can be easily soldered with lead-free solder. Therefore, cellulose-mediated microwave sintering presents a promising means of achieving short processing times and high electrical performance in flexible paper electronics.

Mechanisms for pattern specificity of deep-brain stimulation in Parkinson’s disease

PubMed Central

Mato, Germán; Dellavale, Damián

2017-01-01

Deep brain stimulation (DBS) has become a widely used technique for treating advanced stages of neurological and psychiatric illness. In the case of motor disorders related to basal ganglia (BG) dysfunction, several mechanisms of action for the DBS therapy have been identified which might be involved simultaneously or in sequence. However, the identification of a common key mechanism underlying the clinical relevant DBS configurations has remained elusive due to the inherent complexity related to the interaction between the electrical stimulation and the neural tissue, and the intricate circuital structure of the BG-thalamocortical network. In this work, it is shown that the clinically relevant range for both, the frequency and intensity of the electrical stimulation pattern, is an emergent property of the BG anatomy at the system-level that can be addressed using mean-field descriptive models of the BG network. Moreover, it is shown that the activity resetting mechanism elicited by electrical stimulation provides a natural explanation to the ineffectiveness of irregular (i.e., aperiodic) stimulation patterns, which has been commonly observed in previously reported pathophysiology models of Parkinson’s disease. Using analytical and numerical techniques, these results have been reproduced in both cases: 1) a reduced mean-field model that can be thought as an elementary building block capable to capture the underlying fundamentals of the relevant loops constituting the BG-thalamocortical network, and 2) a detailed model constituted by the direct and hyperdirect loops including one-dimensional spatial structure of the BG nuclei. We found that the optimal ranges for the essential parameters of the stimulation patterns can be understood without taking into account biophysical details of the relevant structures. PMID:28813460

Offshore windmills and the effects of electromagnetic fields on fish.

PubMed

Ohman, Marcus C; Sigray, Peter; Westerberg, Håkan

2007-12-01

With the large scale developments of offshore windpower the number of underwater electric cables is increasing with various technologies applied. A wind farm is associated with different types of cables used for intraturbine, array-to-transformer, and transformer-to-shore transmissions. As the electric currents in submarine cables induce electromagnetic fields there is a concern of how they may influence fishes. Studies have shown that there are fish species that are magneto-sensitive using geomagnetic field information for the purpose of orientation. This implies that if the geomagnetic field is locally altered it could influence spatial patterns in fish. There are also physiological aspects to consider, especially for species that are less inclined to move as the exposure could be persistent in a particular area. Even though studies have shown that magnetic fields could affect fish, there is at present limited evidence that fish are influenced by the electromagnetic fields that underwater cables from windmills generate. Studies on European eel in the Baltic Sea have indicated some minor effects. In this article we give an overview on the type of submarine cables that are used for electric transmissions in the sea. We also describe the character of the magnetic fields they induce. The effects of magnetic fields on fish are reviewed and how this may relate to the cables used for offshore wind power is discussed.

Interferometric imaging of nonlocal electromechanical power transduction in ferroelectric domains.

PubMed

Zheng, Lu; Dong, Hui; Wu, Xiaoyu; Huang, Yen-Lin; Wang, Wenbo; Wu, Weida; Wang, Zheng; Lai, Keji

2018-05-22

The electrical generation and detection of elastic waves are the foundation for acoustoelectronic and acoustooptic systems. For surface acoustic wave devices, microelectromechanical/nanoelectromechanical systems, and phononic crystals, tailoring the spatial variation of material properties such as piezoelectric and elastic tensors may bring significant improvements to the system performance. Due to the much slower speed of sound than speed of light in solids, it is desirable to study various electroacoustic behaviors at the mesoscopic length scale. In this work, we demonstrate the interferometric imaging of electromechanical power transduction in ferroelectric lithium niobate domain structures by microwave impedance microscopy. In sharp contrast to the traditional standing-wave patterns caused by the superposition of counterpropagating waves, the constructive and destructive fringes in microwave dissipation images exhibit an intriguing one-wavelength periodicity. We show that such unusual interference patterns, which are fundamentally different from the acoustic displacement fields, stem from the nonlocal interaction between electric fields and elastic waves. The results are corroborated by numerical simulations taking into account the sign reversal of piezoelectric tensor in oppositely polarized domains. Our work paves ways to probe nanoscale electroacoustic phenomena in complex structures by near-field electromagnetic imaging.

Numerical analysis of mixing enhancement for micro-electroosmotic flow

NASA Astrophysics Data System (ADS)

Tang, G. H.; He, Y. L.; Tao, W. Q.

2010-05-01

Micro-electroosmotic flow is usually slow with negligible inertial effects and diffusion-based mixing can be problematic. To gain an improved understanding of electroosmotic mixing in microchannels, a numerical study has been carried out for channels patterned with wall blocks, and channels patterned with heterogeneous surfaces. The lattice Boltzmann method has been employed to obtain the external electric field, electric potential distribution in the electrolyte, the flow field, and the species concentration distribution within the same framework. The simulation results show that wall blocks and heterogeneous surfaces can significantly disturb the streamlines by fluid folding and stretching leading to apparently substantial improvements in mixing. However, the results show that the introduction of such features can substantially reduce the mass flow rate and thus effectively prolongs the available mixing time when the flow passes through the channel. This is a non-negligible factor on the effectiveness of the observed improvements in mixing efficiency. Compared with the heterogeneous surface distribution, the wall block cases can achieve more effective enhancement in the same mixing time. In addition, the field synergy theory is extended to analyze the mixing enhancement in electroosmotic flow. The distribution of the local synergy angle in the channel aids to evaluate the effectiveness of enhancement method.

Electric Field Observations of Plasma Convection, Shear, Alfven Waves, and other Phenomena Observed on Sounding Rockets in the Cusp and Boundary Layer

NASA Technical Reports Server (NTRS)

Pfaff, R. F.

2009-01-01

On December 14,2002, a NASA Black Brant X sounding rocket was launched equatorward from Ny Alesund, Spitzbergen (79 N) into the dayside cusp and subsequently cut across the open/closed field line boundary, reaching an apogee of771 km. The launch occurred during Bz negative conditions with strong By negative that was changing during the flight. SuperDarn (CUTLASS) radar and subsequent model patterns reveal a strong westward/poleward convection, indicating that the rocket traversed a rotational reversal in the afternoon merging cell. The payload returned DC electric and magnetic fields, plasma waves, energetic particle, suprathermal electron and ion, and thermal plasma data. We provide an overview of the main observations and focus on the DC electric field results, comparing the measured E x B plasma drifts in detail with the CUTLASS radar observations of plasma drifts gathered simultaneously in the same volume. The in situ DC electric fields reveal steady poleward flows within the cusp with strong shears at the interface of the closed/open field lines and within the boundary layer. We use the observations to discuss ionospheric signatures of the open/closed character of the cusp/low latitude boundary layer as a function of the IMF. The electric field and plasma density data also reveal the presence of very strong plasma irregularities with a large range of scales (10 m to 10 km) that exist within the open field line cusp region yet disappear when the payload was equatorward of the cusp on closed field lines. These intense low frequency wave observations are consistent with strong scintillations observed on the ground at Ny Alesund during the flight. We present detailed wave characteristics and discuss them in terms of Alfven waves and static irregularities that pervade the cusp region at all altitudes.

Dynamics of Ring Current and Electric Fields in the Inner Magnetosphere During Disturbed Periods: CRCM-BATS-R-US Coupled Model

NASA Technical Reports Server (NTRS)

Buzulukova, N.; Fok, M.-C.; Pulkkinen, A.; Kuznetsova, M.; Moore, T. E.; Glocer, A.; Brandt, P. C.; Toth, G.; Rastaetter, L.

2010-01-01

We present simulation results from a one-way coupled global MHD model (Block-Adaptive-Tree Solar-Wind Roe-Type Upwind Scheme, BATS-R-US) and kinetic ring current models (Comprehensive Ring Current Model, CRCM, and Fok Ring Current, FokRC). The BATS-R-US provides the CRCM/FokRC with magnetic field information and plasma density/temperature at the polar CRCM/FokRC boundary. The CRCM uses an electric potential from the BATS-R-US ionospheric solver at the polar CRCM boundary in order to calculate the electric field pattern consistent with the CRCM pressure distribution. The FokRC electric field potential is taken from BATS-R-US ionospheric solver everywhere in the modeled region, and the effect of Region II currents is neglected. We show that for an idealized case with southward-northward-southward Bz IMF turning, CRCM-BATS-R-US reproduces well known features of inner magnetosphere electrodynamics: strong/weak convection under the southward/northward Bz; electric field shielding/overshielding/penetration effects; an injection during the substorm development; Subauroral Ion Drift or Polarization Jet (SAID/PJ) signature in the dusk sector. Furthermore, we find for the idealized case that SAID/PJ forms during the substorm growth phase, and that substorm injection has its own structure of field-aligned currents which resembles a substorm current wedge. For an actual event (12 August 2000 storm), we calculate ENA emissions and compare with Imager for Magnetopause-to-Aurora Global Exploration/High Energy Neutral Atom data. The CRCM-BATS-R-US reproduces both the global morphology of ring current and the fine structure of ring current injection. The FokRC-BATS-R-US shows the effect of a realistic description of Region II currents in ring current-MHD coupled models.

Uncertain Environmental Footprint of Current and Future Battery Electric Vehicles.

PubMed

Cox, Brian; Mutel, Christopher L; Bauer, Christian; Mendoza Beltran, Angelica; van Vuuren, Detlef P

2018-04-17

The future environmental impacts of battery electric vehicles (EVs) are very important given their expected dominance in future transport systems. Previous studies have shown these impacts to be highly uncertain, though a detailed treatment of this uncertainty is still lacking. We help to fill this gap by using Monte Carlo and global sensitivity analysis to quantify parametric uncertainty and also consider two additional factors that have not yet been addressed in the field. First, we include changes to driving patterns due to the introduction of autonomous and connected vehicles. Second, we deeply integrate scenario results from the IMAGE integrated assessment model into our life cycle database to include the impacts of changes to the electricity sector on the environmental burdens of producing and recharging future EVs. Future EVs are expected to have 45-78% lower climate change impacts than current EVs. Electricity used for charging is the largest source of variability in results, though vehicle size, lifetime, driving patterns, and battery size also strongly contribute to variability. We also show that it is imperative to consider changes to the electricity sector when calculating upstream impacts of EVs, as without this, results could be overestimated by up to 75%.

Ion Outflow and Convection in the Polar Cap and Cleft as Measured by Tide, EFI, MFE and Timas

NASA Technical Reports Server (NTRS)

Elliott, H. A.; Craven, P. D.; Chandler, M. O.; Moore, T. E.; Maynard, N. C.; Peterson, W. K.; Lennartsson, O. W.; Shelley, E. G.; Mozer, F. S.; Russell, C. T.

1997-01-01

This study examines high-latitude ion outflows and velocities perpendicular to the magnetic field derived from moments of ion distributions measured by the TIDE (Thermal Ion Dynamics Experiment) instrument on the Polar satellite. Hydrogen and oxygen ions are shown to be E X B drifting in the polar cap and cleft regions with a speed of about 5-20 km/s at apogee (approximately 9 Re) and a speed of 1-2 km/s at perigee (approximately 1. 8 Re). E X B drifts are calculated from electric fields measured by EFI (Electric Field Instrument) and magnetic fields measured by MFE (Magnetic Field Experiment) both of which are also on Polar. How convection at Polar's perigee relates to potential patterns of the ionosphere will be discussed. In the cusp/cleft the distribution of hydrogen extends over a large enough range of energy to be measured by both TIDE and the Toroidal Imaging Mass-Angle Spectrograph (TIMAS). Such comparisons will be also be presented.

Revision of empirical electric field modeling in the inner magnetosphere using Cluster data

NASA Astrophysics Data System (ADS)

Matsui, H.; Torbert, R. B.; Spence, H. E.; Khotyaintsev, Yu. V.; Lindqvist, P.-A.

2013-07-01

Using Cluster data from the Electron Drift (EDI) and the Electric Field and Wave (EFW) instruments, we revise our empirically-based, inner-magnetospheric electric field (UNH-IMEF) model at 22.662 mV/m; Kp<1, 1≤Kp<2, 2≤Kp<3, 3≤Kp<4, 4≤Kp<5, and Kp≥4+. Patterns consist of one set of data and processing for smaller activities, and another for higher activities. As activity increases, the skewed potential contour related to the partial ring current appears on the nightside. With the revised analysis, we find that the skewed potential contours get clearer and potential contours get denser on the nightside and morningside. Since the fluctuating components are not negligible, standard deviations from the modeled values are included in the model. In this study, we perform validation of the derived model more extensively. We find experimentally that the skewed contours are located close to the last closed equipotential, consistent with previous theories. This gives physical context to our model and serves as one validation effort. As another validation effort, the derived results are compared with other models/measurements. From these comparisons, we conclude that our model has some clear advantages over the others.

Shear-Modulated Electroosmotic Flow on a Patterned Charged Surface

NASA Astrophysics Data System (ADS)

Wei, Hsien-Hung

2004-11-01

The effect of imposing shear flow on a charge-modulated electroosmotic flow is theoretically investigated. The flow pattern can contain saddle points or closed streamlines, depending on the relative strength of an imposed shear to the applied electrical field. The formation of closed streamlines could be advantageous for trapping non-diffusive particles in desired locations. Different time periodic alternating flows and their corresponding particle trajectories are also examined for assessing strategies for creating efficient mixing.

A historical perspective of the popular use of electric and magnetic therapy.

PubMed

Basford, J R

2001-09-01

To review the history of the therapeutic use of static electric and magnetic fields and to understand its implications for current popular and medical acceptance of these and other alternative and complementary therapies. Comprehensive MEDLINE (1960-2000) and CINAHL (1982-2000) computer literature searches by using key words such as electricity, magnetism, electromagnetic, therapy, medicine, EMF, history of medicine, and fields. Additional references were obtained from the bibliographies of the selected articles. In addition, discussions were held with curators of medical history museums and supplemental searches were made of Internet sources through various search engines. Primary references were used whenever possible. In a few instances, secondary references, particularly those requiring translations of early texts, were used. The use of electric and magnetic forces to treat disease has intrigued the general public and the scientific community since at least the time of the ancient Greeks. The popularity of these therapies has waxed and waned over the millennia, but at all times the popular imagination, often spurred by dynamic and colorful practitioners of pseudoscience, has been more excited than the medical or political establishment. In fact, a pattern seems to reappear. In each era, unsophisticated public acceptance is met first with medical disdain, then with investigation, and, finally, with a failure to find objective evidence of efficacy. This pattern continues today with the public acceptance of magnetic therapy (and alternative and complementary medicine in general) far outstripping acceptance by the medical community. The therapeutic implications of applying electrical and magnetic fields to heal disease have continually captured the popular imagination. Approaches thousands of years apart can be remarkably similar, but, in each era, proof has been lacking and the prevailing medical establishment has remained unconvinced. Interest persists today. Although these agents may have a future role in the healing of human disease, their history and a minimal scientific rationale makes it unlikely that the dichotomy between the hopes of the public and the medical skepticism will disappear.

Dynamics Explorer measurements of particles, fields, and plasma drifts over a horse-collar auroral pattern

NASA Technical Reports Server (NTRS)

Sharber, J. R.; Hones, E. W., Jr.; Heelis, R. A.; Craven, J. D.; Frank, L. A.; Maynard, N. C.; Slavin, J. A.; Birn, J.

1992-01-01

As shown from ground-based measurements and satellite-borne imagers, one type of global auroral pattern characteristic of quiet (usually northward IMF) intervals is that of a contracted but thickened emission region of a pattern referred to as 'horse-collar' aurora (Hones et al., 1989). In this report we use the Dynamics Explorer data set to examine a case in which this horse-collar pattern was observed by the DE-1 auroral imager, while at the same time DE-2, at lower altitude, measured precipitating particles, electric and magnetic fields, and plasma drifts. Our analysis shows that, in general, there is close agreement between the optical signatures and the particle precipitation patterns. In many instances, over scales ranging from tens to a few hundred kilometers, electron precipitation features and upward field-aligned currents are observed at locations where the plasma flow gradients indicate negative V-average x E. The particle, plasma, and field measurements made along the satellite track and the 2D perspective of the imager provide a means of determining the configuration of convective flows in the high-latitude ionosphere during this interval of northward IMF. Recent mapping studies are used to relate the low-altitude observations to possible magnetospheric source regions.

Impact of gyro-motion and sheath acceleration on the flux distribution on rough surfaces

NASA Astrophysics Data System (ADS)

Schmid, K.; Mayer, M.; Adelhelm, C.; Balden, M.; Lindig, S.; ASDEX Upgrade Team

2010-10-01

As was already observed experimentally, the erosion of tungsten (W) coated graphite (C) tiles in ASDEX-Upgrade (AUG) exhibits regular erosion patterns on the micrometre rough surfaces whose origin is not fully understood: surfaces inclined towards the magnetic field direction show strong net W erosion while surfaces facing away from the magnetic field are shadowed from erosion and may even exhibit net W deposition. This paper presents a model which explains the observed erosion/deposition pattern. It is based on the calculation of ion trajectories dropping through the plasma sheath region to the rough surface with combined magnetic and electrical fields. The surface topography used in the calculations is taken from atomic force microscope measurement of real AUG tiles. The calculated erosion patterns are directly compared with secondary electron microscopy images of the erosion zones from the same location. The erosion on surfaces inclined towards the magnetic field is due to ions from the bulk plasma which enter the sheath gyrating along the magnetic field lines, while the deposition of W on surfaces facing away from the magnetic field is due to promptly re-deposited W that is ionized still within the magnetic pre-sheath.

Theoretical and measured electric field distributions within an annular phased array: consideration of source antennas.

PubMed

Zhang, Y; Joines, W T; Jirtle, R L; Samulski, T V

1993-08-01

The magnitude of E-field patterns generated by an annular array prototype device has been calculated and measured. Two models were used to describe the radiating sources: a simple linear dipole and a stripline antenna model. The stripline model includes detailed geometry of the actual antennas used in the prototype and an estimate of the antenna current based on microstrip transmission line theory. This more detailed model yields better agreement with the measured field patterns, reducing the rms discrepancy by a factor of about 6 (from approximately 23 to 4%) in the central region of interest where the SEM is within 25% of the maximum. We conclude that accurate modeling of source current distributions is important for determining SEM distributions associated with such heating devices.

Modeling of the coupled magnetospheric and neutral wind dynamos

NASA Technical Reports Server (NTRS)

Thayer, Jeff P.

1993-01-01

The solar wind interaction with the earth's magnetosphere generates electric fields and currents that flow from the magnetosphere to the ionosphere at high latitudes. Consequently, the neutral atmosphere is subject to the dissipation and conversion of this electrical energy to thermal and mechanical energy through Joule heating and Lorentz forcing. As a result of the mechanical energy stored within the neutral wind (caused in part by Lorentz--and pressure gradient--forces set up by the magnetospheric flux of electrical energy), electric currents and fields can be generated in the ionosphere through the neutral wind dynamo mechanism. At high latitudes this source of electrical energy has been largely ignored in past studies, owing to the assumed dominance of the solar wind/magnetospheric dynamo as an electrical energy source to the ionosphere. However, other researchers have demonstrated that the available electrical energy provided by the neutral wind is significant at high latitudes, particularly in the midnight sector of the polar cap and in the region of the magnetospheric convection reversal. As a result, the conclusions of a number of broad ranging high-latitude investigations may be modified if the neutral-wind contribution to high-latitude electrodynamics is properly accounted for. These include the following: studies assessing solar wind-magnetospheric coupling by comparing the cross polar cap potential with solar wind parameters; research based on the alignment of particle precipitation with convection or field aligned current boundaries; and synoptic investigations attributing seasonal variations in the observed electric field and current patterns to external sources. These research topics have been initiated by satellite and ground-based observations and have been attributed to magnetospheric causes. However, the contribution of the neutral wind to the high-latitude electric field and current systems and their seasonal and local time dependence has yet to be quantitatively evaluated. In this program, we are evaluating the coupled magnetospheric and neutral wind dynamos at high latitudes under various conditions. In addition to examining the impact of seasonal variations, we are investigating the consequences of the separate dynamos having pure current-source or voltage-source behaviors.

Endogenous electric fields as guiding cue for cell migration

PubMed Central

Funk, Richard H. W.

2015-01-01

This review covers two topics: (1) “membrane potential of low magnitude and related electric fields (bioelectricity)” and (2) “cell migration under the guiding cue of electric fields (EF).”Membrane potentials for this “bioelectricity” arise from the segregation of charges by special molecular machines (pumps, transporters, ion channels) situated within the plasma membrane of each cell type (including eukaryotic non-neural animal cells). The arising patterns of ion gradients direct many cell- and molecular biological processes such as embryogenesis, wound healing, regeneration. Furthermore, EF are important as guiding cues for cell migration and are often overriding chemical or topographic cues. In osteoblasts, for instance, the directional information of EF is captured by charged transporters on the cell membrane and transferred into signaling mechanisms that modulate the cytoskeleton and motor proteins. This results in a persistent directional migration along an EF guiding cue. As an outlook, we discuss questions concerning the fluctuation of EF and the frequencies and mapping of the “electric” interior of the cell. Another exciting topic for further research is the modeling of field concepts for such distant, non-chemical cellular interactions. PMID:26029113

A Plasma Trajectory Back-Tracing Tool Based on SuperDARN Convection Patterns

NASA Astrophysics Data System (ADS)

David, M.; Sojka, J. J.; Schunk, R. W.; Coster, A. J.; Sterne, K. T.

2017-12-01

Horizontal transport of plasma is one of the dominant factors in determining the distribution of plasma in the F-region ionosphere; this transport is driven by the magnetospheric convection electric field. When studying any electron density feature in the polar cap ionosphere, such as a density patch, TID, or tongue of ionization (TOI), one needs to know where that feature came from; was it generated by local production processes where it lies, or was it transported from another location? The path traveled by a plasma flux tube or plasma packet, which we call a trajectory, is determined by the time-varying convection electric field, and to whatever extent this electric field is known, one can back-trace the history of the plasma density feature in order to answer key questions about it, such as: Was this plasma exposed to sunlight in recent hours? Has this plasma packet passed through the auroral precipitation oval? Did it pass through the cusp? And since movement of a plasma flux tube toward the pole may cause upward ion drifts that result in density increases it is important to know whether the recent history of the density feature includes such convection toward (or away from) the pole.SuperDARN [Super Dual Auroral Radar Network] contains a data base of convection electric field patterns derived from ground station observations and the use of models to fill in gaps in the data. At Utah State University we have developed a software tool based on the SuperDARN convection patterns (which come at a time cadence of 2 minutes) to allow one to back-trace the history of polar cap plasma for an arbitrary length of time.The figure below shows a series of GPS TEC maps of the Northern Hemisphere in magnetic coordinates for 06 March 2016 in which a TOI feature forms at about 1700 UT. A series of locations, marked with X, are chosen such that they lie within the TOI at the time of the last panel (1730 UT); then, the plasma trajectory paths for these 15 locations are traced backward in time for 5 hours, and their locations are plotted on the TEC maps for universal times of 1230, 1330, 1430, 1530, and 1630.

Laser-induced erasable patterns in a N* liquid crystal on an iron doped lithium niobate surface.

PubMed

Habibpourmoghadam, Atefeh; Lucchetti, Liana; Evans, Dean R; Reshetnyak, Victor Y; Omairat, Faissal; Schafforz, Samuel L; Lorenz, Alexander

2017-10-16

A chiral nematic (N*) liquid crystal (LC) was hybridized with a z-cut iron doped lithium niobate (Fe:LN) substrate and exposed with a focused continuous wave diode laser beam. The N* LC layer was confined with a cover glass to provide a homogeneous LC layer thickness. Two distinct kinds of test cells were investigated, one with an uncoated glass covering slip and one with an indium tin oxide (ITO) coated cover glass. Photo generated electric fields (generated in the Fe:LN) resulted in a localized defect formation and textural transitions in the N* LC. Due to field confinement, the field induced responses were more localized in samples with ITO coated cover glasses. By scanning the laser beam on programmed trajectories, formation of persistent patterns could be achieved in the N* LC layer. Polarized optical microscopy of the exposed samples revealed that these patterns consisted of adjacent circular Frank-Pryce defects. Exposure with a slightly defocused laser beam could be applied selectively to erase these patterns. Thus, a promising method is reported to generate reconfigurable patterns, photonic motives, and touch sensitive devices in a hybridized N* LC with micron accuracy.

Direct observation of resonance scattering patterns in single silicon nanoparticles

NASA Astrophysics Data System (ADS)

Valuckas, Vytautas; Paniagua-Domínguez, Ramón; Fu, Yuan Hsing; Luk'yanchuk, Boris; Kuznetsov, Arseniy I.

2017-02-01

We present the first direct observation of the scattering patterns of electric and magnetic dipole resonances excited in a single silicon nanosphere. Almost perfectly spherical silicon nanoparticles were fabricated and deposited on a 30 nm-thick silicon nitride membrane in an attempt to minimize particle—substrate interaction. Measurements were carried out at visible wavelengths by means of the Fourier microscopy in a dark-field illumination setup. The obtained back-focal plane images clearly reveal the characteristic scattering patterns associated with each resonance and are found to be in a good agreement with the simulated results.

Thermometry in dielectrophoresis chips for contact-free cell handling

NASA Astrophysics Data System (ADS)

Jaeger, M. S.; Mueller, T.; Schnelle, T.

2007-01-01

Cell biology applications, protocols in immunology and stem cell research, require that individual cells are handled under strict control of their contacts to other cells or synthetic surfaces. Dielectrophoresis (DEP) in microfluidic chips is an established technique to investigate, group, wash, cultivate and sort cells contact-free under physiological conditions: microelectrode octode cages, versatile dielectrophoretic elements energized with radio frequency electric fields, stably trap single cells or cellular aggregates. For medical applications and cell cultivation, possible side effects of the dielectrophoretic manipulation, such as membrane polarization and Joule heating, have to be quantified. Therefore, we characterized the electric field-induced warming in dielectrophoretic cages using ohmic resistance measurements, fluorometry, liquid crystal beads, infra-red thermography and bubble size thermometry. We compare the results of these techniques with respect to the influences of voltage, electric conductivity of buffer, frequency, cage size and electrode surface. We conclude that in the culture medium thermal effects may be neglected if low voltages and an electric field-reducing phase pattern are used. Our experimental results provide explicit values for estimating the thermal effect on dielectrophoretically caged cells and show that Joule heating is best minimized by optimizing the cage geometry and reducing the buffer conductivity. The results may additionally serve to evaluate and improve theoretical predictions on field-induced effects. Based on present-day chip processing possibilities, DEP is well suited for the manipulation of cells.

Insects as unidentified flying objects.

PubMed

Callahan, P S; Mankin, R W

1978-11-01

Five species of insects were subjected to a large electric field. Each of the insects stimulated in this manner emitted visible glows of various colors and blacklight (uv). It is postulated that the Uintah Basin, Utah, nocturnal UFO display (1965-1968) was partially due to mass swarms of spruce budworms, Choristoneura fumiferana (Clemens), stimulated to emit this type of St. Elmo's fire by flying into high electric fields caused by thunderheads and high density particulate matter in the air. There was excellent time and spatial correlation between the 1965-1968 UFO nocturnal sightings and spruce budworm infestation. It is suggested that a correlation of nocturnal UFO sightings throughout the U.S. and Canada with spruce budworm infestations might give some insight into nocturnal insect flight patterns.

Transverse circular-polarized Bessel beam generation by inward cylindrical aperture distribution.

PubMed

Pavone, S C; Ettorre, M; Casaletti, M; Albani, M

2016-05-16

In this paper the focusing capability of a radiating aperture implementing an inward cylindrical traveling wave tangential electric field distribution directed along a fixed polarization unit vector is investigated. In particular, it is shown that such an aperture distribution generates a non-diffractive Bessel beam whose transverse component (with respect to the normal of the radiating aperture) of the electric field takes the form of a zero-th order Bessel function. As a practical implementation of the theoretical analysis, a circular-polarized Bessel beam launcher, made by a radial parallel plate waveguide loaded with several slot pairs, arranged on a spiral pattern, is designed and optimized. The proposed launcher performance agrees with the theoretical model and exhibits an excellent polarization purity.

D region disturbances caused by electromagnetic pulses from lightning

NASA Technical Reports Server (NTRS)

Rodriguez, Juan V.; Inan, Umran S.; Bell, Timothy F.

1992-01-01

Attention is given to a simple formulation of the propagation and absorption in a magnetized collisional plasma of EM pulses from lightning which describes the effect of discharge orientation and radiated electric field on the structure and magnitude of heating and secondary ionization in the D region. Radiation from most lightning discharges can heat substantially, but only the most intense (not less than 20 V/m) are likely to cause ionization enhancements not less than 10 percent of the ambient in a single ionization cycle. This dependence on the radiated electric field is modified by the discharge radiation pattern: a horizontal cloud discharge tends to cause larger heating and ionizaton maxima while a vertical return stroke causes disturbances of a larger horizontal extent.

Rotational spectrum of 14N 2 · H 35Cl and 14N 2 · H 37Cl: electric field gradients at the nitrogen nuclei

NASA Astrophysics Data System (ADS)

Kisiel, Z.; Pszczólkowski, L.; Fowler, P. W.; Legon, A. C.

1997-09-01

Rotational spectra of the most abundant isotopic species of the weakly bound dimer formed between dinitrogen and hydrogen chloride were investigated. Spectroscopic constants for 14N 2 · H 37Cl were determined for the first time and those for 14N 2 · H 35Cl improved. Analysis of observed nuclear quadrupole spliting patterns within the framework of coupling of three nonequivalent nuclear spins allowed determination of splitting constants for both nuclei in the complexed dinitrogen molecule. Electric field gradient calculations at the SCF supermolecule level for the dimer are presented and account for the observed values of the nitrogen splitting constants.

Micromachined mold-type double-gated metal field emitters

NASA Astrophysics Data System (ADS)

Lee, Yongjae; Kang, Seokho; Chun, Kukjin

1997-12-01

Electron field emitters with double gates were fabricated using micromachining technology and the effect of the electric potential of the focusing gate (or second gate) was experimentally evaluated. The molybdenum field emission tip was made by filling a cusplike mold formed when a conformal film was deposited on the hole-trench that had been patterned on stacked metals and dielectric layers. The hole-trench was patterned by electron beam lithography and reactive ion etching. Each field emitter has a 0960-1317/7/4/009/img1 diameter extraction gate (or first gate) and a 0960-1317/7/4/009/img2 diameter focusing gate (or second gate). To make a path for the emitted electrons, silicon bulk was etched anisotropically in KOH and EDP (ethylene-diamine pyrocatechol) solution successively. The I - V characteristics and anode current change due to the focusing gate potential were measured.

Wildlife and electric power transmission

USGS Publications Warehouse

Ellis, D.H.; Goodwin, J.G.; Hunt, J.R.; Fletcher, John L.; Busnel, R.G.

1978-01-01

Hundreds of thousands of miles of transmission lines have been introduced into our natural environment. These lines and their corridors can be damaging or beneficial to wildlife communities depending on how they are designed, where they are placed, and when they are constructed and maintained. With the current trend toward UHV systems, new problems (associated with additional increments in audible noise, electric and magnetic force fields, etc.) must be addressed. We recommend the following areas for careful study: (1) the response of wilderness species to transmission lines and line construction and maintenance activities (2) the magnitude of bird collision and electrocution mortality, (3) the response of power corridor and power tower in habiting wildlife to laboratory and field doses of electro-chemical oxidants, corona noise, electric and magnetic fields, etc., (4) the productivity of tower inhabiting birds compared with nearby non-tower nesters, and (5) the influence of powerline corridors on mammalian and avian migration patterns. It is our hope that the questions identified in this study will help stimulate further research so that we can maximize wildlife benefits and minimize wildlife detriments.

Spontaneous chiral symmetry breaking in two-dimensional aggregation

NASA Astrophysics Data System (ADS)

Sandler, Ilya Moiseevich

Recently, unusual and strikingly beautiful seahorse-like growth patterns have been discovered. These patterns possess a spontaneously broken chiral (left/right) symmetry. To explain this spontaneous chiral symmetry breaking, we develop a model for the growth of the aggregate, assuming that the latter is charged, and that the incoming particles are polarizable, and hence drawn preferentially to regions of strong electric field. This model is used both for numerical simulation and theoretical analysis of the aggregation process. We find that the broken symmetry (typically, an 'S' shape) appears in our simulations for some parameter values. Its origin is the long-range interaction (competition and repulsion) among growing branches of the aggregate, such that a right or left side consistently dominates the growth process. We show that the electrostatic interaction may account for the other geometrical properties of the aggregates, such as the existence of only 2 main arms, and the "finned" external edge of the main arms. The results of our simulations of growth in the presence of the external electric field are also in a good agreement with the results of new experiments, motivated by our ideas. Thus, we believe that our growth model provides a plausible explanation of the origin of the broken symmetry in the experimental patterns.

New perspectives on the dynamics of AC and DC plasma arcs exposed to cross-fields

NASA Astrophysics Data System (ADS)

Abdo, Youssef; Rohani, Vandad; Cauneau, François; Fulcheri, Laurent

2017-02-01

Interactions between an arc and external fields are crucially important for the design and the optimization of modern plasma torches. Multiple studies have been conducted to help better understand the behavior of DC and AC current arcs exposed to external and ‘self-induced’ magnetic fields, but the theoretical foundations remain very poorly explored. An analytical investigation has therefore been carried out in order to study the general behavior of DC and AC arcs under the effect of random cross-fields. A simple differential equation describing the general behavior of a planar DC or AC arc has been obtained. Several dimensionless numbers that depend primarily on arc and field parameters and the main arc characteristics (temperature, electric field strength) have also been determined. Their magnitude indicates the general tendency pattern of the arc evolution. The analytical results for many case studies have been validated using an MHD numerical model. The main purpose of this investigation was deriving a practical analytical model for the electric arc, rendering possible its stabilization and control, and the enhancement of the plasma torch power.

Geophysical characterization of soil moisture spatial patterns in a tillage experiment

NASA Astrophysics Data System (ADS)

Martinez, G.; Vanderlinden, K.; Giráldez, J. V.; Muriel, J. L.

2009-04-01

Knowledge on the spatial soil moisture pattern can improve the characterisation of the hydrological response of either field-plots or small watersheds. Near-surface geophysical methods, such as electromagnetic induction (EMI), provide a means to map such patterns using non-invasive and non-destructive measurements of the soil apparent electrical conductivity (ECa. In this study ECa was measured using an EMI sensor and used to characterize spatially the hydrologic response of a cropped field to an intense shower. The study site is part of a long-term tillage experiment in Southern Spain in which Conventional Tillage (CT), Direct Drilling (DD) and Minimum Tillage (MT) are being evaluated since 1982. Soil ECa was measured before and after a rain event of 115 mm, near the soil surface and at deeper depth (ECas and ECad, respectively) using the EM38-DD EMI sensor. Simultaneously, elevation data were collected at each sampling point to generate a Digital Elevation Model (DEM). Soil moisture during the first survey was close to permanent wilting point and near field capacity during the second survey. For the first survey, both ECas and ECad, were higher in the CT and MT than in the DD plots. After the rain event, rill erosion appeared only in CT and MT plots were soil was uncovered, matching the drainage lines obtained from the DEM. Apparent electrical conductivity increased all over the field plot with higher increments in the DD plots. These plots showed the highest ECas and ECad values, in contrast to the spatial pattern found during the first sampling. Difference maps obtained from the two ECas and ECad samplings showed a clear difference between DD plots and CT and MT plots due to their distinct hydrologic response. Water infiltration was higher in the soil of the DD plots than in the MT and CT plots, as reflected by their ECad increment. Higher ECa increments were observed in the depressions of the terrain, where water and sediments accumulated. On the contrary, the most elevated places of the field showed lower ECa increments. When soil is wet topography dominates the hydrologic response of the field, while under drier conditions, hydraulic conductivity controls the soil water dynamics. These results show that when static soil properties, e.g. clay content, are spatially uniform, ECa can detect changes in dynamic properties like soil moisture content, characterizing their spatial pattern.

Effects of electric fields on the photonic crystal formation from block copolymers

NASA Astrophysics Data System (ADS)

Lee, Taekun; Ju, Jin-wook; Ryoo, Won

2012-03-01

Effects of electric fields on the self-assembly of block copolymers have been investigated for thin films of polystyrene-bpoly( 2-vinyl pyridine); PS-b-P2VP, 52 kg/mol-b-57 kg/mol and 133 kg/mol-b-132 kg/mol. Block copolymers of polystyrene and poly(2-vinyl pyridine) have been demonstrated to form photonic crystals of 1D lamellar structure with optical band gaps that correspond to UV-to-visible light. The formation of lamellar structure toward minimum freeenergy state needs increasing polymer chain mobility, and the self-assembly process is accelerated usually by annealing, that is exposing the thin film to solvent vapor such as chloroform and dichloromethane. In this study, thin films of block copolymers were spin-coated on substrates and placed between electrode arrays of various patterns including pin-points, crossing and parallel lines. As direct or alternating currents were applied to electrode arrays during annealing process, the final structure of thin films was altered from the typical 1D lamellae in the absence of electric fields. The formation of lamellar structure was spatially controlled depending on the shape of electrode arrays, and the photonic band gap also could be modulated by electric field strength. The spatial formation of lamellar structure was examined with simulated distribution of electrical potentials by finite difference method (FDM). P2VP layers in self-assembled film were quaternized with methyl iodide vapor, and the remaining lamellar structure was investigated by field emission scanning electron microscope (FESEM). The result of this work is expected to provide ways of fabricating functional structures for display devices utilizing photonic crystal array.

Pattern-Directed Ordering of Spin-Dewetted Liquid Crystal Micro- or Nanodroplets as Pixelated Light Reflectors and Locomotives.

PubMed

Ravi, Bolleddu; Chakraborty, Snigdha; Bhattacharjee, Mitradip; Mitra, Shirsendu; Ghosh, Abir; Gooh Pattader, Partho Sarathi; Bandyopadhyay, Dipankar

2017-01-11

Chemical pattern directed spin-dewetting of a macroscopic droplet composed of a dilute organic solution of liquid crystal (LC) formed an ordered array of micro- and nanoscale LC droplets. Controlled evaporation of the spin-dewetted droplets through vacuum drying could further miniaturize the size to the level of ∼90 nm. The size, periodicity, and spacing of these mesoscale droplets could be tuned with the variations in the initial loading of LC in the organic solution, the strength of the centripetal force on the droplet, and the duration of the evaporation. A simple theoretical model was developed to predict the spacing between the spin-dewetted droplets. The patterned LC droplets showed a reversible phase transition from nematic to isotropic and vice versa with the periodic exposure of a solvent vapor and its removal. A similar phase transition behavior was also observed with the periodic increase or reduction of temperature, suggesting their usefulness as vapor or temperature sensors. Interestingly, when the spin-dewetted droplets were confined between a pair of electrodes and an external electric field was applied, the droplets situated at the hydrophobic patches showed light-reflecting properties under the polarization microscopy highlighting their importance in the development of micro- or nanoscale LC displays. The digitized LC droplets, which were stationary otherwise, showed dielectrophoretic locomotion under the guidance of the external electric field beyond a threshold intensity of the field. Remarkably, the motion of these droplets could be restricted to the hydrophilic zones, which were confined between the hydrophobic patches of the chemically patterned surface. The findings could significantly contribute in the development of futuristic vapor or temperature sensors, light reflectors, and self-propellers using the micro- or nanoscale digitized LC droplets.

Designing an Active Target Test Projection Chamber

NASA Astrophysics Data System (ADS)

Koci, James; Tan Ahn Collaboration, Dr.; Nicolas Dixneuf Collaboration

2015-10-01

The development of instrumentation in nuclear physics is crucial for advancing our ability to measure the properties of exotic nuclei. One limitation of the use of exotic nuclei in experiment is their very low production intensities. Recently, detectors, called active-target dectectors, have been developed to address this issue. Active-target detectors use a gas medium to image charged-particle tracks that are emitted in nuclear reactions. Last semester, I designed a vacuum chamber to be used in developing Micro-Pattern Gas detectors that will upgrade the capabilities of an active-target detector called the Prototype AT-TPC. With the exterior of the chamber complete, I have now been using an electric field modeling program, Garfield, developed by CERN to design a field cage to be placed within the vacuum chamber. The field cage will be a box-like apparatus consisting of two parallel metal plates connected with a resistor chain and attached to wires wrapped between them. The cage will provide a uniform electric field within the chamber to drift electrons from nuclear reactions down to the detector in the bottom of the chamber. These signals are then amplified by a proportional counter, and the data is sent to a computer. For the long term, we would like to incorporate a Micro-Pattern Gas Detectors in the interior of the chamber and eventually use the AT-TPC to examine various nuclei. Dr. Ahn is my advising professor.

Theory of electrohydrodynamic instabilities in electrolytic cells

NASA Technical Reports Server (NTRS)

Bruinsma, R.; Alexander, S.

1990-01-01

The paper develops the theory of the hydrodynamic stability of an electrolytic cell as a function of the imposed electric current. A new electrohydrodynamic instability is encountered when the current is forced to exceed the Nernst limit. The convection is driven by the volume force exerted by the electric field on space charges in the electrolyte. This intrinsic instability is found to be easily masked by extrinsic convection sources such as gravity or stirring. A linear stability analysis is performed and a dimensionless number Le is derived whose value determines the convection pattern.

Reconfigurable Full-Page Braille Displays

NASA Technical Reports Server (NTRS)

Garner, H. Douglas

1994-01-01

Electrically actuated braille display cells of proposed type arrayed together to form full-page braille displays. Like other braille display cells, these provide changeable patterns of bumps driven by digitally recorded text stored on magnetic tapes or in solid-state electronic memories. Proposed cells contain electrorheological fluid. Viscosity of such fluid increases in strong electrostatic field.

Large area and deep sub-wavelength interference lithography employing odd surface plasmon modes.

PubMed

Liu, Liqin; Luo, Yunfei; Zhao, Zeyu; Zhang, Wei; Gao, Guohan; Zeng, Bo; Wang, Changtao; Luo, Xiangang

2016-07-28

In this paper, large area and deep sub-wavelength interference patterns are realized experimentally by using odd surface plasmon modes in the metal/insulator/metal structure. Theoretical investigation shows that the odd modes possesses much higher transversal wave vector and great inhibition of tangential electric field components, facilitating surface plasmon interference fringes with high resolution and contrast in the measure of electric field intensity. Interference resist patterns with 45 nm (∼λ/8) half-pitch, 50 nm depth, and area size up to 20 mm × 20 mm were obtained by using 20 nm Al/50 nm photo resist/50 nm Al films with greatly reduced surface roughness and 180 nm pitch exciting grating fabricated with conventional laser interference lithography. Much deeper resolution down to 19.5 nm is also feasible by decreasing the thickness of PR. Considering that no requirement of expensive EBL or FIB tools are employed, it provides a cost-effective way for large area and nano-scale fabrication.

Controlling electrostatic charging of nanocrystalline diamond at nanoscale.

PubMed

Verveniotis, Elisseos; Kromka, Alexander; Rezek, Bohuslav

2013-06-11

Constant electrical current in the range of -1 to -200 pA is applied by an atomic force microscope (AFM) in contact mode regime to induce and study local electrostatic charging of oxygen-terminated nanocrystalline diamond (NCD) thin films. The NCD films are deposited on silicon in 70 nm thickness and with 60% relative sp(2) phase content. Charging current is monitored by conductive AFM. Electric potential contrast induced by the current is evaluated by Kelvin force microscopy (KFM). KFM shows well-defined, homogeneous, and reproducible microscopic patterns that are not influenced by inherent tip-surface junction fluctuations during the charging process. The charged patterns are persistent for at least 72 h due to charge trapping inside the NCD film. The current-induced charging also clearly reveals field-induced detrapping at current amplitudes >-50 pA and tip instability at >-150 pA, both of which limit the achievable potential contrast. In addition, we show that the field also determines the range of electronic states that can trap the charge. We present a model and discuss implications for control of the nanoscale charging process.

Electrical and thermoelectric transport properties of two-dimensional fermionic systems with k-cubic spin-orbit coupling.

PubMed

Mawrie, Alestin; Verma, Sonu; Ghosh, Tarun Kanti

2017-10-25

We investigate the effect of k-cubic spin-orbit interaction on the electrical and thermoelectric transport properties of two-dimensional fermionic systems. We obtain exact analytical expressions of the inverse relaxation time (IRT) and the Drude conductivity for long-range Coulomb and short-range delta scattering potentials. The IRT reveals that the scattering is completely suppressed along the three directions [Formula: see text] with [Formula: see text]. We also obtain analytical results of the thermopower and thermal conductivity at low temperature. The thermoelectric transport coefficients obey the Wiedemann-Franz law, even in the presence of k-cubic Rashba spin-orbit interaction (RSOI) at low temperature. In the presence of a quantizing magnetic field, the signature of the RSOI is revealed through the appearance of the beating pattern in the Shubnikov-de Haas (SdH) oscillations of thermopower and thermal conductivity in the low magnetic field regime. The empirical formulae for the SdH oscillation frequencies accurately describe the locations of the beating nodes. The beating pattern in magnetothermoelectric measurement can be used to extract the spin-orbit coupling constant.

Temperature profiles in the earth of importance to deep electrical conductivity models

NASA Astrophysics Data System (ADS)

Čermák, Vladimír; Laštovičková, Marcela

1987-03-01

Deep in the Earth, the electrical conductivity of geological material is extremely dependent on temperature. The knowledge of temperature is thus essential for any interpretation of magnetotelluric data in projecting lithospheric structural models. The measured values of the terrestrial heat flow, radiogenic heat production and thermal conductivity of rocks allow the extrapolation of surface observations to a greater depth and the calculation of the temperature field within the lithosphere. Various methods of deep temperature calculations are presented and discussed. Characteristic geotherms are proposed for major tectonic provinces of Europe and it is shown that the existing temperatures on the crust-upper mantle boundary may vary in a broad interval of 350 1,000°C. The present work is completed with a survey of the temperature dependence of electrical conductivity for selected crustal and upper mantle rocks within the interval 200 1,000°C. It is shown how the knowledge of the temperature field can be used in the evaluation of the deep electrical conductivity pattern by converting the conductivity-versustemperature data into the conductivity-versus-depth data.

A novel jet-based nano-hydroxyapatite patterning technique for osteoblast guidance

PubMed Central

Li, Xiang; Koller, Garrit; Huang, Jie; Di Silvio, Lucy; Renton, Tara; Esat, Minoo; Bonfield, William; Edirisinghe, Mohan

2010-01-01

Surface topography is well known to play a crucial role in influencing cellular responses to an implant material and is therefore important in bone tissue regeneration. A novel jet-based patterning technique, template-assisted electrohydrodynamic atomization spraying, was recently devised to control precisely the surface structure as well as its dimensions. In the present study, a detailed investigation of this patterning process was carried out. A range of nano-hydroxyapatite (nHA) line-shaped patterns <20 µm in width were successfully deposited on a commercially pure Ti surface by controlling the flow of an nHA suspension in an electric field. In vitro studies showed that the nHA patterns generated are capable of regulating the human osteoblast cell attachment and orientation. PMID:19493897

The magnetic evolution of AR 6555 which lead to two impulsive, readily compact, X-type flares

NASA Technical Reports Server (NTRS)

Ambastha, A.; Fontenla, J. M.; Kalman, B.; Csepura, GY.

1995-01-01

We study the evolution of the vector magnetic field and the sunspot motions observed in AR 6555 during 23-26 Mar. 1991. This region displays two locations of large magnetic shear that were also sites of flare activity. The first location produced two large (X-class) flares during the period covered by our observations. The second location had larger magnetic shear than the first, but produced only small (M- and C-class) flares during our observations. We study the evolution of the photospheric magnetic field in relation to the large flares in the first location. These flares occurred around the same included polarity, and have very similar characteristics (soft X-ray light curves, energies, etc.). However, the whole active region has changed substantially in the period between them. We found several characteristics of the region that appear related to the occurrence of these flares. (1) The flares occurred near regions of large magnetic 'shear,' but not at the locations of maximum shear or maximum field. (2) Potential field extrapolations of the observed field suggest that the topology changed, prior to the first of the two flares, in such a way that a null appeared in the coarse magnetic field. (3) This null was located close to both X-class flares, and remained in that location for a few days while the two flares were observed. (4) The flaring region has a pattern of vector field and sunspot motions in which material is 'squeezed' along the polarity inversion line. This pattern is very different from that usually associated with shearing arcades, but it is similar to that suggested previously by Fontenla and Davis. The vertical electric currents, inferred from the transverse field, are consistent with this pattern. (5) A major reconfiguration of the longitudinal field and the vertical electric currents occurred just prior to the first of the two flares. Both changes imply substantial variations of the magnetic structure of the region. On the basis of the available data we suggest that these changes made the flaring possible, and we develop a scenario that can explain the origin of the magnetic free energy that was released in these flares.

The Magnetic Evolution of AR 6555 which led to Two Impulsive, Relatively Compact, X-Type Flares

NASA Technical Reports Server (NTRS)

Fontenla, J. M.; Ambastha, A.; Kalman, B.; Csepura, Gy.

1995-01-01

We study the evolution of the vector magnetic field and the sunspot motions observed in AR 6555 during 1991 March 23-26. This region displays two locations of large magnetic shear that were also sites of flare activity. The first location produced two large (X-class) flares during the period covered by our observations. The second location had larger magnetic shear than the first but produced only small (M- and C-class) flares during our observations. We study the evolution of the photospheric magnetic field in relation to the large flares in the first location. These flares occurred around the same included polarity and have very similar characteristics (soft X-ray light curves, energies, etc,). However, the whole active region has changed substantially in the period between them. We found several characteristics of the region that appear related to the occurrence of these flares: (1) The flares occurred near regions of large magnetic 'shear' but not at the locations of maximum shear or maximum field. (2) Potential field extrapolations of the observed field suggest that the topology changed, prior to the first of the two flares, in such a way that a null appeared in the coarse magnetic field. (3) This null was located close to both X-class flares and remained in that location for a few days while the two flares were observed. (4) The flaring region has a pattern of vector field and sunspot motions in which material is 'squeezed' along the polarity inversion line. This pattern is very different from that usually associated with shearing arcades, but it is similar to that suggested previously by Fontenia and Davis. The vertical electric currents, inferred from the transverse field, are consistent with this pattern. (5) A major reconfiguration of the longitudinal field and the vertical electric currents occurred just prior to the first of the two flares. Both changes imply substantial variations of the magnetic structure of the region. On the basis of the available data we suggest that these changes made the flaring possible, and we develop a scenario that can explain the origin of the magnetic free-energy that was released in these flares.

Transparent conductor-embedding nanocones for selective emitters: optical and electrical improvements of Si solar cells

PubMed Central

Kim, Joondong; Yun, Ju-Hyung; Kim, Hyunyub; Cho, Yunae; Park, Hyeong-Ho; Kumar, M. Melvin David; Yi, Junsin; Anderson, Wayne A.; Kim, Dong-Wook

2015-01-01

Periodical nanocone-arrays were employed in an emitter region for high efficient Si solar cells. Conventional wet-etching process was performed to form the nanocone-arrays for a large area, which spontaneously provides the graded doping features for a selective emitter. This enables to lower the electrical contact resistance and enhances the carrier collection due to the high electric field distribution through a nanocone. Optically, the convex-shaped nanocones efficiently reduce light-reflection and the incident light is effectively focused into Si via nanocone structure, resulting in an extremely improved the carrier collection performances. This nanocone-arrayed selective emitter simultaneously satisfies optical and electrical improvement. We report the record high efficiency of 16.3% for the periodically nanoscale patterned emitter Si solar cell. PMID:25787933

Transparent conductor-embedding nanocones for selective emitters: optical and electrical improvements of Si solar cells.

PubMed

Kim, Joondong; Yun, Ju-Hyung; Kim, Hyunyub; Cho, Yunae; Park, Hyeong-Ho; Kumar, M Melvin David; Yi, Junsin; Anderson, Wayne A; Kim, Dong-Wook

2015-03-19

Periodical nanocone-arrays were employed in an emitter region for high efficient Si solar cells. Conventional wet-etching process was performed to form the nanocone-arrays for a large area, which spontaneously provides the graded doping features for a selective emitter. This enables to lower the electrical contact resistance and enhances the carrier collection due to the high electric field distribution through a nanocone. Optically, the convex-shaped nanocones efficiently reduce light-reflection and the incident light is effectively focused into Si via nanocone structure, resulting in an extremely improved the carrier collection performances. This nanocone-arrayed selective emitter simultaneously satisfies optical and electrical improvement. We report the record high efficiency of 16.3% for the periodically nanoscale patterned emitter Si solar cell.

“Beating speckles” via electrically-induced vibrations of Au nanorods embedded in sol-gel

PubMed Central

Ritenberg, Margarita; Beilis, Edith; Ilovitsh, Asaf; Barkai, Zehava; Shahmoon, Asaf; Richter, Shachar; Zalevsky, Zeev; Jelinek, Raz

2014-01-01

Generation of macroscopic phenomena through manipulating nano-scale properties of materials is among the most fundamental goals of nanotechnology research. We demonstrate cooperative “speckle beats” induced through electric-field modulation of gold (Au) nanorods embedded in a transparent sol-gel host. Specifically, we show that placing the Au nanorod/sol-gel matrix in an alternating current (AC) field gives rise to dramatic modulation of incident light scattered from the material. The speckle light patterns take form of “beats”, for which the amplitude and frequency are directly correlated with the voltage and frequency, respectively, of the applied AC field. The data indicate that the speckle beats arise from localized vibrations of the gel-embedded Au nanorods, induced through the interactions between the AC field and the electrostatically-charged nanorods. This phenomenon opens the way for new means of investigating nanoparticles in constrained environments. Applications in electro-optical devices, such as optical modulators, movable lenses, and others are also envisaged. PMID:24413086

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

PubMed

Wu, Ching-Chih; Luo, Xin

2016-04-01

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

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.

Biogenic volatile organic compound analyses by PTR-TOF-MS: Calibration, humidity effect and reduced electric field dependency.

PubMed

Pang, Xiaobing

2015-06-01

Green leaf volatiles (GLVs) emitted by plants after stress or damage induction are a major part of biogenic volatile organic compounds (BVOCs). Proton transfer reaction time-of-flight mass spectrometry (PTR-TOF-MS) is a high-resolution and sensitive technique for in situ GLV analyses, while its performance is dramatically influenced by humidity, electric field, etc. In this study the influence of gas humidity and the effect of reduced field (E/N) were examined in addition to measuring calibration curves for the GLVs. Calibration curves measured for seven of the GLVs in dry air were linear, with sensitivities ranging from 5 to 10 ncps/ppbv (normalized counts per second/parts per billion by volume). The sensitivities for most GLV analyses were found to increase by between 20% and 35% when the humidity of the sample gas was raised from 0% to 70% relative humidity (RH) at 21°C, with the exception of (E)-2-hexenol. Product ion branching ratios were also affected by humidity, with the relative abundance of the protonated molecular ions and higher mass fragment ions increasing with humidity. The effect of reduced field (E/N) on the fragmentation of GLVs was examined in the drift tube of the PTR-TOF-MS. The structurally similar GLVs are acutely susceptible to fragmentation following ionization and the fragmentation patterns are highly dependent on E/N. Overall the measured fragmentation patterns contain sufficient information to permit at least partial separation and identification of the isomeric GLVs by looking at differences in their fragmentation patterns at high and low E/N. Copyright © 2015. Published by Elsevier B.V.

Oppositely charged colloids out of equilibrium

NASA Astrophysics Data System (ADS)

Vissers, T.

2010-11-01

Colloids are particles with a size in the range of a few nanometers up to several micrometers. Similar to atomic and molecular systems, they can form gases, liquids, solids, gels and glasses. Colloids can be used as model systems because, unlike molecules, they are sufficiently large to be studied directly with light microscopy and move sufficiently slow to study their dynamics. In this thesis, we study binary systems of polymethylmethacrylate (PMMA) colloidal particles suspended in low-polar solvent mixtures. Since the ions can still partially dissociate, a surface charge builds up which causes electrostatic interactions between the colloids. By carefully tuning the conditions inside the suspension, we make two kinds of particles oppositely charged. To study our samples, we use Confocal Laser Scanning Microscopy (CLSM). The positively and negatively charged particles can be distinguished by a different fluorescent dye. Colloids constantly experience a random motion resulting from random kicks of surrounding solvent molecules. When the attractions between the oppositely charged particles are weak, the particles can attach and detach many times and explore a lot of possible configurations and the system can reach thermodynamic equilibrium. For example, colloidal ‘ionic’ crystals consisting of thousands to millions of particles can form under the right conditions. When the attractions are strong, the system can become kinetically trapped inside a gel-like state. We observe that when the interactions change again, crystals can even emerge again from this gel-like phase. By using local order parameters, we quantitatively study the crystallization of colloidal particles and identify growth defects inside the crystals. We also study the effect of gravity on the growth of ionic crystals by using a rotating stage. We find that sedimentation can completely inhibit crystal growth and plays an important role in crystallization from the gel-like state. The surface potential and charge are studied by electrophoresis. Here, the velocity of the particles is measured while they are moving in an electric field. Using our real-space CLSM setup, we find that for a single-component system, the charge on the particles decreases with increasing volume fraction. Apart from structures that oppositely charged particles form close to thermodynamic equilibrium, we also study pattern formation when the system is driven out of equilibrium by an electric field. When oppositely charged particles are driven in opposite directions, the collisions between them cause particle of the same kind to form lanes. By combining our CLSM experiments with Brownian dynamics computer simulations, we study the structure and the dynamics of the suspension on the single-particle level. We find that the number of particles in a lane increases continuously with the field strength. By studying the dynamics and fluctuations parallel and perpendicular to the electric field direction, we identify the key mechanism of lane-formation. We show that pattern formation can easily become more complicated when we introduce alternating current (AC) fields. In addition to the formation of lanes parallel to the field-axis, bands of like-charged particles can form perpendicular to it. When the particles are sufficiently mobile, the system can be remixed again by changing the frequency. When AC-fields with higher field strengths are used, we show that complex patterns, including rotating instabilities, can emerge. The results in this thesis yield fundamental insight in electrophoresis, crystallization and pattern formation when systems are driven out of equilibrium. The results on lane- and band-formation can be relevant for the design of electronic ink (e-ink), where electrically driven oppositely charged particles are used to change the image on a piece of electronic paper.

The use of electric bed heaters and the risk of clinically recognized spontaneous abortion.

PubMed

Lee, G M; Neutra, R R; Hristova, L; Yost, M; Hiatt, R A

2000-07-01

We conducted a prospective cohort study to evaluate the relation of spontaneous abortion and electric bed heater use during the first trimester of pregnancy. Compared with non-users, rates of spontaneous abortion were lower for women who used electric bed heaters. The adjusted odds ratio and 95% confidence interval (CI) for the two major devices used, electric blankets (N = 524) and waterbeds (N = 796), were, respectively, 0.8 (95% CI = 0.5-1.1) and 0.9 (95% CI = 0.7-1.2). An increase of risk with increasing intensity (setting-duration combination) of use was not observed. Users of electric blankets at low settings for most of the night (N = 171) had lower risks of spontaneous abortion than non-users (adjusted odds ratio = 0.5; 95% CI = 0.3-1.0). Twenty women who used electric blankets at a high setting for 1 hour or less had an adjusted odds ratio of 3.0 (95% CI = 1.1-8.3), but we found no spontaneous abortions among the few women (N = 13) who used a high setting for 2 or more hours. We found that exposure rankings of the magnetic field time-weighted average and a rate of change metric did not correspond monotonically to the pattern of spontaneous abortion risks and that electric blankets contribute less to overnight time-weighted average magnetic fields than has been thought.

Germanene on single-layer ZnSe substrate: novel electronic and optical properties.

PubMed

Ye, H Y; Hu, F F; Tang, H Y; Yang, L W; Chen, X P; Wang, L G; Zhang, G Q

2018-06-01

In this work, the structural, electronic and optical properties of germanene and ZnSe substrate nanocomposites have been investigated using first-principles calculations. We found that the large direct-gap ZnSe semiconductors and zero-gap germanene form a typical orbital hybridization heterostructure with a strong binding energy, which shows a moderate direct band gap of 0.503 eV in the most stable pattern. Furthermore, the heterostructure undergoes semiconductor-to-metal band gap transition when subjected to external out-of-plane electric field. We also found that applying external strain and compressing the interlayer distance are two simple ways of tuning the electronic structure. An unexpected indirect-direct band gap transition is also observed in the AAII pattern via adjusting the interlayer distance. Quite interestingly, the calculated results exhibit that the germanene/ZnSe heterobilayer structure has perfect optical absorption in the solar spectrum as well as the infrared and UV light zones, which is superior to that of the individual ZnSe substrate and germanene. The staggered interfacial gap and tunability of the energy band structure via interlayer distance and external electric field and strain thus make the germanene/ZnSe heterostructure a promising candidate for field effect transistors (FETs) and nanoelectronic applications.

Single layer multi-color luminescent display and method of making

NASA Technical Reports Server (NTRS)

Robertson, James B. (Inventor)

1992-01-01

The invention is a multi-color luminescent display comprising an insulator substrate and a single layer of host material, which may be a phosphor deposited thereon that hosts one or more different impurities, therein forming a pattern of selected and distinctly colored phosphors such as blue, green, and red phosphors in a single layer of host material. Transparent electrical conductor means may be provided for subjecting selected portions of the pattern of colored phosphors to an electric field, thereby forming a multi-color, single layer electroluminescent display. A method of forming a multi-color luminescent display includes the steps of depositing on an insulator substrate a single layer of host material, which itself may be a phosphor, with the properties to host varying quantities of different impurities and introducing one or more of said different impurities into selected areas of the said single layer of host material by thermal diffusion or ion implantation to form a pattern of phosphors of different colors in the said single layer of host material.

The Optimization Design of An AC-Electroosmotic Micro mixer

NASA Astrophysics Data System (ADS)

Wang, Yangyang; Suh, Yongkweon; Kang, Sangmo

2007-11-01

We propose the optimization design of an AC-electroosmotic micro-mixer, which is composed of a channel and a series of pairs of electrodes attached on the bottom wall in zigzag patterns. The AC electric field is applied to the electrodes so that a fluid flow takes place around the electrodes across the channel, thus contributing to the mixing of the fluid within the channel. We have performed numerical simulations by using a commercial code (CFX 10) to optimize the shape and pattern of the electrodes via the concept of mixing index. It is found that the best combination of two kinds of electrodes, which leads to good mixing performance, is not simply harmonic one. When the length ratio of the two kinds of electrodes closes to 2:1, we can get the best mixing effect. Furthermore, we will visualize the flow pattern and measure the velocity field with a PTV technique to validate the numerical simulations. In addition, the mixing pattern will be visualized via the experiment.

Optical properties of electrohydrodynamic convection patterns: rigorous and approximate methods.

PubMed

Bohley, Christian; Heuer, Jana; Stannarius, Ralf

2005-12-01

We analyze the optical behavior of two-dimensionally periodic structures that occur in electrohydrodynamic convection (EHC) patterns in nematic sandwich cells. These structures are anisotropic, locally uniaxial, and periodic on the scale of micrometers. For the first time, the optics of these structures is investigated with a rigorous method. The method used for the description of the electromagnetic waves interacting with EHC director patterns is a numerical approach that discretizes directly the Maxwell equations. It works as a space-grid-time-domain method and computes electric and magnetic fields in time steps. This so-called finite-difference-time-domain (FDTD) method is able to generate the fields with arbitrary accuracy. We compare this rigorous method with earlier attempts based on ray-tracing and analytical approximations. Results of optical studies of EHC structures made earlier based on ray-tracing methods are confirmed for thin cells, when the spatial periods of the pattern are sufficiently large. For the treatment of small-scale convection structures, the FDTD method is without alternatives.

Statistical patterns in the location of natural lightning

NASA Astrophysics Data System (ADS)

Zoghzoghy, F. G.; Cohen, M. B.; Said, R. K.; Inan, U. S.

2013-01-01

Lightning discharges are nature's way of neutralizing the electrical buildup in thunderclouds. Thus, if an individual discharge destroys a substantial fraction of the cloud charge, the probability of a subsequent flash is reduced until the cloud charge separation rebuilds. The temporal pattern of lightning activity in a localized region may thus inherently be a proxy measure of the corresponding timescales for charge separation and electric field buildup processes. We present a statistical technique to bring out this effect (as well as the subsequent recovery) using lightning geo-location data, in this case with data from the National Lightning Detection Network (NLDN) and from the GLD360 Network. We use this statistical method to show that a lightning flash can remove an appreciable fraction of the built up charge, affecting the neighboring lightning activity for tens of seconds within a ˜ 10 km radius. We find that our results correlate with timescales of electric field buildup in storms and suggest that the proposed statistical tool could be used to study the electrification of storms on a global scale. We find that this flash suppression effect is a strong function of flash type, flash polarity, cloud-to-ground flash multiplicity, the geographic location of lightning, and is proportional to NLDN model-derived peak stroke current. We characterize the spatial and temporal extent of the suppression effect as a function of these parameters and discuss various applications of our findings.

Understanding electric field-enhanced transport for the measurement of nanoparticles and their assembly on surfaces

NASA Astrophysics Data System (ADS)

Tsai, De-Hao

The goal of this dissertation is to understand the synthesis, characterization, and integration of nanoparticles and nanoparticle-based devices by electric field-enhanced transport of nanoparticles. Chapter I describes the factors used for determining particle trajectories and found that electric fields provide the directional electrostatic force to overcome other non-directional influences on particle trajectories. This idea is widely applied in the nanoparticle classification, characterization, and assembly onto substrate surfaces as investigated in the following chapters. Chapter 2 presents a new assembly method to position metal nanoparticles delivered from the gas phase onto surfaces using the electrostatic force generated by biased p-n junction patterned substrates. Aligned deposition patterns of metal nanoparticles were observed, and the patterning selectivity quantified. A simple model accounting for the generated electric field, and the electrostatic, van der Waals, and image forces was used to explain the observed results. Chapter 2.2 describes a data set for particle size resolved deposition, from which a Brownian dynamics model for the process can be evaluated. Brownian motion and fluid convection of nanoparticles, as well as the interactions between the charged nanoparticles and the patterned substrate, including electrostatic force, image force and van der Waals force, are accounted for in the simulation. Using both experiment and simulation the effects of the particle size, electric field intensity, and the convective flow on coverage selectivity have been investigated. Coverage selectivity is most sensitive to electric field, which is controlled by the applied reverse bias voltage across the p-n junction. A non-dimensional analysis of the competition between the electrostatic and diffusion force is found to provide a means to collapse a wide range of process operating conditions and an effective indicator or process performance. Directed assembly of size-selected nanoparticles has been applied in the study of nanoparticle enhanced fluorescence (NEF) bio-sensing devices. Chapter 3 presents results of a systematic examination of funct onalized gold nanoparticles by electrospray-differential mobility analysis (ES-DMA). Formation of selfassembled monolayers (SAMs) of alkylthiol molecules and singly stranded DNA (ssDNA) on the Au-NP surface was detected from a change in particle mobility, which could be modeled to extract the surface packing density. A gas-phase temperature-programmed desorption (TPD) kinetic study of SAMs on the Au-NP found the data to be consistent with a second order Arrhenius based rate law, yielding an Arrhenius-factor of 1x1011s -1 and an activation energy ˜105 kJ/mol. This study suggests that the ES-DMA can be added to the tool set of characterization methods being employed and developed to study the structure and properties of coated nanoparticles. Chapter 3.2 demonstrates this ES-DMA as a new method to investigate colloidal aggregation and the parameters that govern it. Nanoparticle suspensions were characterized by sampling a Au nanoparticle (Au-NP) colloidal solution via electrospray (ES), followed by differential ion-mobility analysis (DMA) to determine the mobility distribution, and thus the aggregate distribution. By sampling at various times, the degree of flocculation and the flocculation rate are determined and found to be inversely proportional to the ionic strength and proportional to the residence time. A stability ratio at different ionic strengths, the critical concentration, and surface potential or surface charge density of Au-NPs are obtained from these data. This method should be a generically useful tool to probe the early stages of colloidal aggregation. Study of ES-DMA is extended to include the characterizations of a variety of materials. Biologically interested materials such as viruses and antibodies could also be characterized. These results show ES-DMA provides a general way to characterize the colloidal materials as well as aerosolized particles.

Study of electrical conductivity and memory switching in the zinc-vanadium-phosphate glasses

NASA Astrophysics Data System (ADS)

Mirzayi, M.; Hekmatshoar, M. H.

2013-07-01

Vanadium zinc phosphate glasses were prepared by the conventional melt quenching technique and effect of V2O5 concentration on d.c. conductivity of prepared samples were investigated. X-ray diffraction patterns confirmed the glassy character of the samples. The d.c. conductivity increased with increase in V2O5 content. Results showed that activation energy has a single value in the investigated range of temperature, which can be explained in accordance with Mott small pollaron hopping model. I-V characteristics at high electric field showed that switching in these glasses was memory type. The threshold field of switching was found to decrease with increase in V2O5 content. Non-linear behavior and switching phenomenon was explained by Pool-Frenkel effect and thermal model.

A two-dimensional spin field-effect switch

NASA Astrophysics Data System (ADS)

Yan, Wenjing; Txoperena, Oihana; Llopis, Roger; Dery, Hanan; Hueso, Luis E.; Casanova, Fèlix

2016-11-01

Future development in spintronic devices will require an advanced control of spin currents, for example by an electric field. Here we demonstrate an approach that differs from previous proposals such as the Datta and Das modulator, and that is based on a van de Waals heterostructure of atomically thin graphene and semiconducting MoS2. Our device combines the superior spin transport properties of graphene with the strong spin-orbit coupling of MoS2 and allows switching of the spin current in the graphene channel between ON and OFF states by tuning the spin absorption into the MoS2 with a gate electrode. Our proposal holds potential for technologically relevant applications such as search engines or pattern recognition circuits, and opens possibilities towards electrical injection of spins into transition metal dichalcogenides and alike materials.

Field-aligned currents, convection electric fields, and ULF-ELF waves in the cusp

NASA Technical Reports Server (NTRS)

Saflekos, N. A.; Potemra, T. A.; Kintner, P. M., Jr.; Green, J. L.

1979-01-01

Nearly simultaneous observations from the Triad and Hawkeye satellites over the Southern Hemisphere, at low altitudes near the noon meridian and close to the usual polar cusp latitudes, show that in and near the polar cusp there exist several relationships between field-aligned currents (FACs), convection electric fields, ULF-ELF magnetic noise, broadband electrostatic noise and interplanetary magnetic fields. The most important findings are (1) the FACs directed into the ionosphere in the noon-to-dusk local time sector and directed away from the ionosphere in the noon-to-dawn local time sector and identified as region-1 permanent FACs (Iijima and Potemra, 1976a) and are located equatorward of the regions of antisunward (westward) convection; (2) the observations are consistent with a two-cell convection pattern symmetric in one case (throat positioned at noon) and asymmetric in another (throat located in a sector on the forenoon side in juxtaposition to the region of strong convection on the afternoon side); and (3) fine-structure FACs are responsible for the generation of ULF-ELF noise in the polar cusp.

Radial Field Piezoelectric Diaphragms

NASA Technical Reports Server (NTRS)

Bryant, R. G.; Effinger, R. T., IV; Copeland, B. M., Jr.

2002-01-01

A series of active piezoelectric diaphragms were fabricated and patterned with several geometrically defined Inter-Circulating Electrodes "ICE" and Interdigitated Ring Electrodes "ICE". When a voltage potential is applied to the electrodes, the result is a radially distributed electric field that mechanically strains the piezoceramic along the Z-axis (perpendicular to the applied electric field). Unlike other piezoelectric bender actuators, these Radial Field Diaphragms (RFDs) strain concentrically yet afford high displacements (several times that of the equivalent Unimorph) while maintaining a constant circumference. One of the more intriguing aspects is that the radial strain field reverses itself along the radius of the RFD while the tangential strain remains relatively constant. The result is a Z-deflection that has a conical profile. This paper covers the fabrication and characterization of the 5 cm. (2 in.) diaphragms as a function of poling field strength, ceramic thickness, electrode type and line spacing, as well as the surface topography, the resulting strain field and displacement as a function of applied voltage at low frequencies. The unique features of these RFDs include the ability to be clamped about their perimeter with little or no change in displacement, the environmentally insulated packaging, and a highly repeatable fabrication process that uses commodity materials.

Global MHD modeling of resonant ULF waves: Simulations with and without a plasmasphere.

PubMed

Claudepierre, S G; Toffoletto, F R; Wiltberger, M

2016-01-01

We investigate the plasmaspheric influence on the resonant mode coupling of magnetospheric ultralow frequency (ULF) waves using the Lyon-Fedder-Mobarry (LFM) global magnetohydrodynamic (MHD) model. We present results from two different versions of the model, both driven by the same solar wind conditions: one version that contains a plasmasphere (the LFM coupled to the Rice Convection Model, where the Gallagher plasmasphere model is also included) and another that does not (the stand-alone LFM). We find that the inclusion of a cold, dense plasmasphere has a significant impact on the nature of the simulated ULF waves. For example, the inclusion of a plasmasphere leads to a deeper (more earthward) penetration of the compressional (azimuthal) electric field fluctuations, due to a shift in the location of the wave turning points. Consequently, the locations where the compressional electric field oscillations resonantly couple their energy into local toroidal mode field line resonances also shift earthward. We also find, in both simulations, that higher-frequency compressional (azimuthal) electric field oscillations penetrate deeper than lower frequency oscillations. In addition, the compressional wave mode structure in the simulations is consistent with a radial standing wave oscillation pattern, characteristic of a resonant waveguide. The incorporation of a plasmasphere into the LFM global MHD model represents an advance in the state of the art in regard to ULF wave modeling with such simulations. We offer a brief discussion of the implications for radiation belt modeling techniques that use the electric and magnetic field outputs from global MHD simulations to drive particle dynamics.

Room temperature magnetoelectric coupling and electrical properties of Ni doped Co - ferrite - PZT nanocomposites

NASA Astrophysics Data System (ADS)

Chakraborty, Sarit; Mandal, S. K.; Dey, P.; Saha, B.

2018-04-01

Multiferroic magnetoelectric materials are very interesting for the researcher for the potential application in device preparation. We have prepared 0.3Ni0.5Co0.5Fe2O4 - 0.7PbZr0.58Ti0.42O3 magnetoelectric nanocomposites through chemical pyrophoric reaction process followed by solid state reaction and represented magnetoelectric coupling coefficient, thermally and magnetically tunable AC electrical properties. For the structural characterization XRD pattern and SEM micrograph have been analyzed. AC electrical properties reveal that the grain boundaries resistances are played dominating role in the conduction process in the system. Dielectric studies are represents that the dielectric polarization is decreased with frequency as well as magnetic field where it increases with increasing temperature. The dielectric profiles also represents the electromechanical resonance at a frequency of ˜183 kHz. High dielectric constant and low dielectric loss at room temperature makes the material very promising for the application of magnetic field sensor devices.

Apparatus for sensing patterns of electrical field variations across a surface

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

Warren, William L.; Devine, Roderick A. B.

An array of nonvolatile field effect transistors used to sense electric potential variations. The transistors owe their nonvolatility to the movement of protons within the oxide layer that occurs only in response to an externally applied electric potential between the gate on one side of the oxide and the source/drain on the other side. The position of the protons within the oxide layer either creates or destroys a conducting channel in the adjacent source/channel/drain layer below it, the current in the channel being measured as the state of the nonvolatile memory. The protons can also be moved by potentials createdmore » by other instrumentalities, such as charges on fingerprints or styluses above the gates, pressure on a piezoelectric layer above the gates, light shining upon a photoconductive layer above the gates. The invention allows sensing of fingerprints, handwriting, and optical images, which are converted into digitized images thereof in a nonvolatile format.« less

Microscopic model of quasiparticle wave packets in superfluids, superconductors, and paired Hall states.

PubMed

Parameswaran, S A; Kivelson, S A; Shankar, R; Sondhi, S L; Spivak, B Z

2012-12-07

We study the structure of Bogoliubov quasiparticles, bogolons, the fermionic excitations of paired superfluids that arise from fermion (BCS) pairing, including neutral superfluids, superconductors, and paired quantum Hall states. The naive construction of a stationary quasiparticle in which the deformation of the pair field is neglected leads to a contradiction: it carries a net electrical current even though it does not move. However, treating the pair field self-consistently resolves this problem: in a neutral superfluid, a dipolar current pattern is associated with the quasiparticle for which the total current vanishes. When Maxwell electrodynamics is included, as appropriate to a superconductor, this pattern is confined over a penetration depth. For paired quantum Hall states of composite fermions, the Maxwell term is replaced by a Chern-Simons term, which leads to a dipolar charge distribution and consequently to a dipolar current pattern.

Vertical motion of a charged colloidal particle near an AC polarized electrode with a nonuniform potential distribution: theory and experimental evidence.

PubMed

Fagan, Jeffrey A; Sides, Paul J; Prieve, Dennis C

2004-06-08

Electroosmotic flow in the vicinity of a colloidal particle suspended over an electrode accounts for observed changes in the average height of the particle when the electrode passes alternating current at 100 Hz. The main findings are (1) electroosmotic flow provides sufficient force to move the particle and (2) a phase shift between the purely electrical force on the particle and the particle's motion provides evidence of an E2 force acting on the particle. The electroosmotic force in this case arises from the boundary condition applied when faradaic reactions occur on the electrode. The presence of a potential-dependent electrode reaction moves the likely distribution of electrical current at the electrode surface toward uniform current density around the particle. In the presence of a particle the uniform current density is associated with a nonuniform potential; thus, the electric field around the particle has a nonzero radial component along the electrode surface, which interacts with unbalanced charge in the diffuse double layer on the electrode to create a flow pattern and impose an electroosmotic-flow-based force on the particle. Numerical solutions are presented for these additional height-dependent forces on the particle as a function of the current distribution on the electrode and for the time-dependent probability density of a charged colloidal particle near a planar electrode with a nonuniform electrical potential boundary condition. The electrical potential distribution on the electrode, combined with a phase difference between the electric field in solution and the electrode potential, can account for the experimentally observed motion of particles in ac electric fields in the frequency range from approximately 10 to 200 Hz.

Controlling Two-dimensional Tethered Vesicle Motion Using an Electric Field

PubMed Central

Yoshina-Ishii, Chiaki; Boxer, Steven G.

2008-01-01

We recently introduced methods to tether phospholipid vesicles or proteoliposomes onto a fluid supported lipid bilayer using DNA hybridization. These intact tethered vesicles diffuse in two dimensions parallel to the supporting membrane surface. In this paper, we report the dynamic response of individual tethered vesicles to an electric field applied parallel to the bilayer surface. Vesicles respond to the field by moving in the direction of electro-osmotic flow, and this can be used to reversibly concentrate tethered vesicles against a barrier. By adding increasing amounts of negatively charged phosphatidylserine to the supporting bilayer to increase electro-osmosis, the electrophoretic mobility of the tethered vesicles can be increased. The electro-osmotic contribution can be modeled well by a sphere connected to a cylindrical anchor in a viscous membrane with charged head groups. The electrophoretic force on the negatively charged tethered vesicles opposes the electro-osmotic force. By increasing the amount of negative charge on the tethered vesicle, drift in the direction of electro-osmotic flow can be slowed; at high negative charge on the tethered vesicle, motion can be forced in the direction of electrophoresis. The balance between these forces can be visualized on a patterned supporting bilayer containing negatively charged lipids which themselves reorganize in an externally applied electric field to create a gradient of charge within a corralled region. The charge gradient at the surface creates a gradient of electro-osmotic flow, and vesicles carrying similar amounts of negative charge can be focused to a region perpendicular to the applied field where electrophoresis is balanced by electro-osmosis, away from the corral boundary. Electric fields are effective tools to direct tethered vesicles, concentrate them and to measure the tethered vesicle’s electrostatic properties. PMID:16489833

Ephemeral Electric Potential and Electric Field Sensor

NASA Technical Reports Server (NTRS)

Generazio, Edward R. (Inventor)

2017-01-01

Systems, methods, and devices of the various embodiments provide for the minimization of the effects of intrinsic and extrinsic leakage electrical currents enabling true measurements of electric potentials and electric fields. In an embodiment, an ephemeral electric potential and electric field sensor system may have at least one electric field sensor and a rotator coupled to the electric field sensor and be configured to rotate the electric field sensor at a quasi-static frequency. In an embodiment, ephemeral electric potential and electric field measurements may be taken by rotating at least one electric field sensor at a quasi-static frequency, receiving electrical potential measurements from the electric field sensor when the electric field sensor is rotating at the quasi-static frequency, and generating and outputting images based at least in part on the received electrical potential measurements.

Field Emission Study of Carbon Nanotubes: High Current Density from Nanotube Bundle Arrays

NASA Technical Reports Server (NTRS)

Bronikowski, Micheal J.; Manohara, Harish M.; Siegel, Peter H.; Hunt, Brian D.

2004-01-01

We have investigated the field emission behavior of lithographically patterned bundles of multiwalled carbon nanotubes arranged in a variety of array geometries. Such arrays of nanotube bundles are found to perform significantly better in field emission than arrays of isolated nanotubes or dense, continuous mats of nanotubes, with the field emission performance depending on the bundle diameter and inter-bundle spacing. Arrays of 2-micrometers diameter nanotube bundles spaced 5 micrometers apart (edge-to-edge spacing) produced the largest emission densities, routinely giving 1.5 to 1.8 A/cm(sup 2) at approximately 4 V/micrometer electric field, and greater than 6 A/cm(sup 2) at 20 V/micrometers.

Convection and Dynamo Action in Ice Giant Dynamo Models with Electrical Conductivity Stratification

NASA Astrophysics Data System (ADS)

Soderlund, K. M.; Featherstone, N. A.; Heimpel, M. H.; Aurnou, J. M.

2017-12-01

Uranus and Neptune are relatively unexplored, yet critical for understanding the physical and chemical processes that control the behavior and evolution of giant planets. Because their multipolar magnetic fields, three-jet zonal winds, and extreme energy balances are distinct from other planets in our Solar System, the ice giants provide a unique opportunity to test hypotheses for internal dynamics and magnetic field generation. While it is generally agreed that dynamo action in the ionic ocean generates their magnetic fields, the mechanisms that control the morphology, strength, and evolution of the dynamos - which are likely distinct from those in the gas giants and terrestrial planets - are not well understood. We hypothesize that the dynamos and zonal winds are dynamically coupled and argue that their characteristics are a consequence of quasi-three-dimensional turbulence in their interiors. Here, we will present new dynamo simulations with an inner electrically conducting region and outer electrically insulating layer to self-consistently couple the ionic oceans and molecular envelopes of these planets. For each simulation, the magnetic field morphology and amplitude, zonal flow profile, and internal heat flux pattern will be compared against corresponding observations of Uranus and Neptune. We will also highlight how these simulations will both contribute to and benefit from a future ice giant mission.

Electric-field-induced strain contributions in morphotropic phase boundary composition of (Bi{sub 1/2}Na{sub 1/2})TiO{sub 3}-BaTiO{sub 3} during poling

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

Khansur, Neamul H.; Daniels, John E.; Hinterstein, Manuel

2015-12-14

The microscopic contributions to the electric-field-induced macroscopic strain in a morphotropic 0.93(Bi{sub 1/2}Na{sub 1/2}TiO{sub 3})−0.07(BaTiO{sub 3}) with a mixed rhombohedral and tetragonal structure have been quantified using full pattern Rietveld refinement of in situ high-energy x-ray diffraction data. The analysis methodology allows a quantification of all strain mechanisms for each phase in a morphotropic composition and is applicable to use in a wide variety of piezoelectric compositions. It is shown that during the poling of this material 24%, 44%, and 32% of the total macroscopic strain is generated from lattice strain, domain switching, and phase transformation strains, respectively. The resultsmore » also suggest that the tetragonal phase contributes the most to extrinsic domain switching strain, whereas the lattice strain primarily stems from the rhombohedral phase. The analysis also suggests that almost 32% of the total strain is lost or is a one-time effect due to the irreversible nature of the electric-field-induced phase transformation in the current composition. This information is relevant to on-going compositional development strategies to harness the electric-field-induced phase transformation strain of (Bi{sub 1/2}Na{sub 1/2})TiO{sub 3}-based lead-free piezoelectric materials for actuator applications.« less

Optimization and experimental validation of electrostatic adhesive geometry

NASA Astrophysics Data System (ADS)

Ruffatto, D.; Shah, J.; Spenko, M.

This paper introduces a method to optimize the electrode geometry of electrostatic adhesives for robotic gripping, attachment, and manipulation applications. Electrostatic adhesion is achieved by applying a high voltage potential, on the order of kV, to a set of electrodes, which generates an electric field. The electric field polarizes the substrate material and creates an adhesion force. Previous attempts at creating electro-static adhesives have shown them to be effective, but researchers have made no effort to optimize the electrode configuration and geometry. We have shown that by optimizing the geometry of the electrode configuration, the electric field strength, and therefore the adhesion force, is enhanced. To accomplish this, Comsol Multiphysics was utilized to evaluate the average electric field generated by a given electrode geometry. Several electrode patterns were evaluated, including parallel conductors, concentric circles, Hilbert curves (a fractal geometry) and spirals. The arrangement of the electrodes in concentric circles with varying electrode widths proved to be the most effective. The most effective sizing was to use the smallest gap spacing allowable coupled with a variable electrode width. These results were experimentally validated on several different surfaces including drywall, wood, tile, glass, and steel. A new manufacturing process allowing for the fabrication of thin, conformal electro-static adhesive pads was utilized. By combining the optimized electrode geometry with the new fabrication process we are able to demonstrate a marked improvement of up to 500% in shear pressure when compared to previously published values.

Application of sub-micrometer patterned permalloy thin film in tunable radio frequency inductors

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

Rahman, B.M. Farid; Divan, Ralu; Rosenmann, Daniel

Electrical tunable meander line inductor using coplanar waveguide structures with patterned permalloy (Py) thin film has been designed and implemented in this paper. High resistivity Si substrate is used to reduce the dielectric loss from the substrate. Inductor is implemented with a 60 nm thick Py deposited and patterned on top of the gold meander line, and Py film is patterned with dimension of 440 nm 10 lm to create the shape anisotropy field, which in turn increases the FMR frequency. Compared to a regular meanderline inductor without the application of sub-micrometer patterned Py thin film, the inductance density hasmore » been increased to 20% for the implemented inductor with patterned Py. Measured FMR frequency of the patterned Py is 4.51 GHz without the application of any external magnetic field. This has enabled the inductor application in the practical circuit boards, where the large external magnet is unavailable. Inductance tunability of the implemented inductor is demonstrated by applying a DC current. Applied DC current creates a magnetic field along the hard axis of the patterned Py thin film, which changes the magnetic moment of the thin film and thus, decreases the inductance of the line. Measured results show that the inductance density of the inductor can be varied 5% by applying 300 mA DC current, larger inductance tunability is achievable by increasing the thickness of Py film. VC 2015 AIP Publishing LLC. [http://dx.doi.org/10.1063/1.4918766]« less

Spatial channel interactions in cochlear implants

NASA Astrophysics Data System (ADS)

Tang, Qing; Benítez, Raul; Zeng, Fan-Gang

2011-08-01

The modern multi-channel cochlear implant is widely considered to be the most successful neural prosthesis owing to its ability to restore partial hearing to post-lingually deafened adults and to allow essentially normal language development in pre-lingually deafened children. However, the implant performance varies greatly in individuals and is still limited in background noise, tonal language understanding, and music perception. One main cause for the individual variability and the limited performance in cochlear implants is spatial channel interaction from the stimulating electrodes to the auditory nerve and brain. Here we systematically examined spatial channel interactions at the physical, physiological, and perceptual levels in the same five modern cochlear implant subjects. The physical interaction was examined using an electric field imaging technique, which measured the voltage distribution as a function of the electrode position in the cochlea in response to the stimulation of a single electrode. The physiological interaction was examined by recording electrically evoked compound action potentials as a function of the electrode position in response to the stimulation of the same single electrode position. The perceptual interactions were characterized by changes in detection threshold as well as loudness summation in response to in-phase or out-of-phase dual-electrode stimulation. To minimize potentially confounding effects of temporal factors on spatial channel interactions, stimulus rates were limited to 100 Hz or less in all measurements. Several quantitative channel interaction indexes were developed to define and compare the width, slope and symmetry of the spatial excitation patterns derived from these physical, physiological and perceptual measures. The electric field imaging data revealed a broad but uniformly asymmetrical intracochlear electric field pattern, with the apical side producing a wider half-width and shallower slope than the basal side. In contrast, the evoked compound action potential and perceptual channel interaction data showed much greater individual variability. It is likely that actual reduction in neural and higher level interactions, instead of simple sharpening of the electric current field, would be the key to predicting and hopefully improving the variable cochlear implant performance. The present results are obtained with auditory prostheses but can be applied to other neural prostheses, in which independent spatial channels, rather than a high stimulation rate, are critical to their performance.

Patterned, highly stretchable and conductive nanofibrous PANI/PVDF strain sensors based on electrospinning and in situ polymerization

NASA Astrophysics Data System (ADS)

Yu, Gui-Feng; Yan, Xu; Yu, Miao; Jia, Meng-Yang; Pan, Wei; He, Xiao-Xiao; Han, Wen-Peng; Zhang, Zhi-Ming; Yu, Liang-Min; Long, Yun-Ze

2016-01-01

A facile fabrication strategy via electrospinning and followed by in situ polymerization to fabricate a patterned, highly stretchable, and conductive polyaniline/poly(vinylidene fluoride) (PANI/PVDF) nanofibrous membrane is reported. Owing to the patterned structure, the nanofibrous PANI/PVDF strain sensor can detect a strain up to 110%, for comparison, which is 2.6 times higher than the common nonwoven PANI/PVDF mat and much larger than the previously reported values (usually less than 15%). Meanwhile, the conductivity of the patterned strain sensor shows a linear response to the applied strain in a wide range from 0% to about 85%. Additionally, the patterned PANI/PVDF strain sensor can completely recover to its original electrical and mechanical values within a strain range of more than 22%, and exhibits good durability over 10 000 folding-unfolding tests. Furthermore, the strain sensor also can be used to detect finger motion. The results demonstrate promising application of the patterned nanofibrous membrane in flexible electronic fields.A facile fabrication strategy via electrospinning and followed by in situ polymerization to fabricate a patterned, highly stretchable, and conductive polyaniline/poly(vinylidene fluoride) (PANI/PVDF) nanofibrous membrane is reported. Owing to the patterned structure, the nanofibrous PANI/PVDF strain sensor can detect a strain up to 110%, for comparison, which is 2.6 times higher than the common nonwoven PANI/PVDF mat and much larger than the previously reported values (usually less than 15%). Meanwhile, the conductivity of the patterned strain sensor shows a linear response to the applied strain in a wide range from 0% to about 85%. Additionally, the patterned PANI/PVDF strain sensor can completely recover to its original electrical and mechanical values within a strain range of more than 22%, and exhibits good durability over 10 000 folding-unfolding tests. Furthermore, the strain sensor also can be used to detect finger motion. The results demonstrate promising application of the patterned nanofibrous membrane in flexible electronic fields. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr08618c

Probe compensation in cylindrical near-field scanning: A novel simulation methodology

NASA Technical Reports Server (NTRS)

Hussein, Ziad A.; Rahmat-Samii, Yahya

1993-01-01

Probe pattern compensation is essential in near-field scanning geometry, where there is a great need to accurately know far-field patterns at wide angular range. This paper focuses on a novel formulation and computer simulation to determine the precise need for and effect of probe compensation in cylindrical near-field scanning. The methodology is applied to a linear test array antenna and the NASA scatterometer radar antenna. The formulation is based on representing the probe by its equivalent tangential magnetic currents. The interaction between the probe equivalent aperture currents and the test antenna fields is obtained with the application of a reciprocity theorem. This allows us to obtain the probe vector output pickup integral which is proportional to the amplitude and phase of the electric field induced in the probe aperture with respect to its position to the test antenna. The integral is evaluated for each probe position on the required sampling point on a cylindrical near-field surface enclosing the antenna. The use of a hypothetical circular-aperture probe with a different radius permits us to derive closed-form expressions for its far-field radiation patterns. These results, together with the probe vector output pickup, allow us to perform computer simulated synthetic measurements. The far-field patterns of the test antenna are formulated based on cylindrical wave expansions of both the probe and test antenna fields. In the limit as the probe radius becomes very small, the probe vector output is the direct response of the near-field at a point, and no probe compensation is needed. Useful results are generated to compare the far-field pattern of the test antenna constructed from the knowledge of the simulated near-field with and without probe pattern compensation and the exact results. These results are important since they clearly illustrate the angular range over which probe compensation is needed. It has been found that a probe with an aperture radius of 0.25(lambda), 0.5(lambda), and 1(lambda) needs a little probe compensation, if any, near the test antenna main beam. In addition, a probe with low directivity may provide a better signal-to-noise ratio than a highly directive one. This is evident in test antenna patterns without probe compensation at wide angles.

Offset-electrode profile acquisition strategy for electrical resistivity tomography

NASA Astrophysics Data System (ADS)

Robbins, Austin R.; Plattner, Alain

2018-04-01

We present an electrode layout strategy that allows electrical resistivity profiles to image the third dimension close to the profile plane. This "offset-electrode profile" approach involves laterally displacing electrodes away from the profile line in an alternating fashion and then inverting the resulting data using three-dimensional electrical resistivity tomography software. In our synthetic and field surveys, the offset-electrode method succeeds in revealing three-dimensional structures in the vicinity of the profile plane, which we could not achieve using three-dimensional inversions of linear profiles. We confirm and explain the limits of linear electrode profiles through a discussion of the three-dimensional sensitivity patterns: For a homogeneous starting model together with a linear electrode layout, all sensitivities remain symmetric with respect to the profile plane through each inversion step. This limitation can be overcome with offset-electrode layouts by breaking the symmetry pattern among the sensitivities. Thanks to freely available powerful three-dimensional resistivity tomography software and cheap modern computing power, the requirement for full three-dimensional calculations does not create a significant burden and renders the offset-electrode approach a cost-effective method. By offsetting the electrodes in an alternating pattern, as opposed to laying the profile out in a U-shape, we minimize shortening the profile length.

At the interface: convergence of neural regeneration and neural prostheses for restoration of function.

PubMed

Grill, W M; McDonald, J W; Peckham, P H; Heetderks, W; Kocsis, J; Weinrich, M

2001-01-01

The rapid pace of recent advances in development and application of electrical stimulation of the nervous system and in neural regeneration has created opportunities to combine these two approaches to restoration of function. This paper relates the discussion on this topic from a workshop at the International Functional Electrical Stimulation Society. The goals of this workshop were to discuss the current state of interaction between the fields of neural regeneration and neural prostheses and to identify potential areas of future research that would have the greatest impact on achieving the common goal of restoring function after neurological damage. Identified areas include enhancement of axonal regeneration with applied electric fields, development of hybrid neural interfaces combining synthetic silicon and biologically derived elements, and investigation of the role of patterned neural activity in regulating various neuronal processes and neurorehabilitation. Increased communication and cooperation between the two communities and recognition by each field that the other has something to contribute to their efforts are needed to take advantage of these opportunities. In addition, creative grants combining the two approaches and more flexible funding mechanisms to support the convergence of their perspectives are necessary to achieve common objectives.

The CDRH Helix: an in vivo evaluation.

PubMed

Anhalt, D; Hynynen, K; DeYoung, D; Shimm, D; Kundrat, M; Cetas, T

1990-01-01

The Helix is an electromagnetic heating device used to induce regional/systemic hyperthermia for cancer therapy. It is a resonant device operating at about 82 MHz with an aperture size of 60 cm x 40 cm (elliptical) x 40 cm long. The Helix deposits power in tissues (or phantoms) by producing a predominantly axial electric field within its radiating aperture. Five pig experiments were performed to provide in vivo verification of specific absorption rate (SAR) measurements and electric field measurements which were obtained earlier in tissue-equivalent phantom and 0.9% saline, respectively. In addition to verifying the power deposition patterns found in phantoms, the pig experiments provided valuable insight into the capabilities and limitations of electromagnetic regional heating. For example, a kidney with limited blood flow, simulating a necrotic tumor, heated very well-although the highest temperature was not always measured there. Also, fat heating may be a problem, since excessive temperatures in the fat were observed in approximately 20% of the heatings. This paper compares the in vivo temperature measurements in pigs with SARs and electric field measurements obtained in phantoms, and also provides a brief overview of results of the Helix in clinical situations.

Recurrent coronal jets induced by repetitively accumulated electric currents

NASA Astrophysics Data System (ADS)

Guo, Y.; Démoulin, P.; Schmieder, B.; Ding, M. D.; Vargas Domínguez, S.; Liu, Y.

2013-07-01

Context. Jets of plasma are frequently observed in the solar corona. A self-similar recurrent behavior is observed in a fraction of them. Aims: Jets are thought to be a consequence of magnetic reconnection; however, the physics involved is not fully understood. Therefore, we study some jet observations with unprecedented temporal and spatial resolutions. Methods: The extreme-ultraviolet (EUV) jets were observed by the Atmospheric Imaging Assembly on board the Solar Dynamics Observatory (SDO). The Helioseismic and Magnetic Imager (HMI) on board SDO measured the vector magnetic field, from which we derive the magnetic flux evolution, the photospheric velocity field, and the vertical electric current evolution. The magnetic configuration before the jets is derived by the nonlinear force-free field extrapolation. Results: Three EUV jets recurred in about one hour on 17 September 2010 in the following magnetic polarity of active region 11106. We derive that the jets are above a pair of parasitic magnetic bipoles that are continuously driven by photospheric diverging flows. The interaction drove the buildup of electric currents, which we observed as elongated patterns at the photospheric level. For the first time, the high temporal cadence of the HMI allows the evolution of such small currents to be followed. In the jet region, we found that the integrated absolute current peaks repetitively in phase with the 171 Å flux evolution. The current buildup and its decay are both fast, about ten minutes each, and the current maximum precedes the 171 Å also by about ten minutes. Then, the HMI temporal cadence is marginally fast enough to detect such changes. Conclusions: The photospheric current pattern of the jets is found to be associated with the quasi-separatrix layers deduced from the magnetic extrapolation. From previous theoretical results, the observed diverging flows are expected to continuously build such currents. We conclude that the magnetic reconnection occurs periodically, in the current layer created between the emerging bipoles and the large-scale active region field. The periodic magnetic reconnection induced the observed recurrent coronal jets and the decrease of the vertical electric current magnitude. Two movies are available in electronic form at http://www.aanda.org

Tripolar electric field Structure in guide field magnetic reconnection

NASA Astrophysics Data System (ADS)

Fu, Song; Huang, Shiyong; Zhou, Meng; Ni, Binbin; Deng, Xiaohua

2018-03-01

It has been shown that the guide field substantially modifies the structure of the reconnection layer. For instance, the Hall magnetic and electric fields are distorted in guide field reconnection compared to reconnection without guide fields (i.e., anti-parallel reconnection). In this paper, we performed 2.5-D electromagnetic full particle simulation to study the electric field structures in magnetic reconnection under different initial guide fields (Bg). Once the amplitude of a guide field exceeds 0.3 times the asymptotic magnetic field B0, the traditional bipolar Hall electric field is clearly replaced by a tripolar electric field, which consists of a newly emerged electric field and the bipolar Hall electric field. The newly emerged electric field is a convective electric field about one ion inertial length away from the neutral sheet. It arises from the disappearance of the Hall electric field due to the substantial modification of the magnetic field and electric current by the imposed guide field. The peak magnitude of this new electric field increases linearly with the increment of guide field strength. Possible applications of these results to space observations are also discussed.

Idealized model of polar cap currents, fields, and auroras

NASA Technical Reports Server (NTRS)

Cornwall, J. M.

1985-01-01

During periods of northward Bz, the electric field applied to the magnetosphere is generally opposite to that occurring during southward Bz and complicated patterns of convection result, showing some features reversed in comparison with the southward Bz case. A study is conducted of a simple generalization of early work on idealized convection models, which allows for coexistence of sunward convection over the central polar cap and antisunward convection elsewhere in the cap. The present model, valid for By approximately 0, has a four-cell convection pattern and is based on the combination of ionospheric current conservation with a relation between parallel auroral currents and parallel potential drops. Global magnetospheric issues involving, e.g., reconnection are not considered. The central result of this paper is an expression giving the parallel potential drop for polar cap auroras (with By approximately 0) in terms of the polar cap convection field profile.

Ionosonde observations of the effects of the major magnetic storm of September 22-26, 1999 at equatorial station in west Africa

NASA Astrophysics Data System (ADS)

Coulibaly, I. S.; Adohi, B. J.-P.; Tanoh, K. S.

2018-05-01

A new approach to study the mechanisms of storm-time variations in the F-layer height and critical frequency at dip-equator is proposed. The latitudinal variations in the magnetic disturbance index DP were combined with h'F and foF2 data from an IPS 42-type ionosonde at Korkogo (9.2° N, 5° W; 2.4° S dip lat), Ivory Coast, to investigate the nighttime ionospheric effects of the geomagnetic storm of September 22-26, 1999 in the West-African sector. A clear equatorward penetration of magnetic disturbances from high latitudes regions was observed. At dip-equator, the DP magnetic disturbance pattern showed up to four distinct regimes of disturbance electric fields, each associated with a specific phase of the storm. A regime of westward transient electric fields followed by a regime of eastward transient electric fields occurred during the main phase of the storm. This was preceded by a period of quasi-absence of disturbance during the compression phase, the whole followed by a regime of westward persistent disturbance electric fields during the recovery phase. From the latitudinal variations and the shapes of these perturbations, we could associate the regime of westward (resp. eastward) disturbance electric fields with prompt penetration (resp. overshielding) occasioned by magnetospheric convections and the persistent one with a cumulative effect of storm-time winds and magnetospheric convections from high latitudes regions. The h'F variations were found to be strongly correlated with the DP ones, clearly providing evidence for the prevalence of these electric fields on the observed F-layer motions. Additionally, the foF2 variations showed two periods of depleted electron density, one in the evening during the compression phase of the storm and the other near midnight. We discussed the mechanisms of these ionospheric negative storms in the light of earlier investigations of storm-time ionospheric disturbances and validated our method by comparison of the above results with those based on criteria by other authors.

Non-ultraviolet-based patterning of polymer structures by optically induced electrohydrodynamic instability

NASA Astrophysics Data System (ADS)

Wang, Feifei; Yu, Haibo; Liu, Na; Mai, John D.; Liu, Lianqing; Lee, Gwo-Bin; Jung Li, Wen

2013-11-01

We report here an approach to rapidly construct organized formations of micron-scale pillars from a thin polydimethylsiloxane (PDMS) film by optically induced electrohydrodynamic instability (OEHI). In OEHI, a heterogeneous electric field is induced across two thin fluidic layers by stimulating a photoconductive thin film in a parallel-plate capacitor configuration with visible light. We demonstrated that this OEHI method could control nucleation sites of pillars formed by electrohydrodynamic instability. To investigate this phenomenon, a tangential electric force component is assumed to have arisen from the surface polarization charge and is introduced into the traditional perfect dielectric model for PDMS films. Numerical simulation results showed that this tangential electric force played an important role in OEHI.

[Preclinical treatment of severe burn trauma due to an electric arc on an overhead railway cable].

PubMed

Spelten, O; Wetsch, W A; Hinkelbein, J

2013-09-01

Severe burns due to electrical accidents occur rarely in Germany but represent a challenge for emergency physicians and their team. Apart from extensive burns cardiac arrhythmia, neurological damage caused by electric current and osseous injury corresponding to the trauma mechanism are also common. It is important to perform a survey of the pattern of injuries and treat acute life-threatening conditions immediately in the field. Furthermore, specific conditions related to burns must be considered, e.g. fluid resuscitation, thermal management and analgesia. In addition, a correct strategy for further medical care in an appropriate hospital is essential. Exemplified by this case guidelines for the treatment of severe burns and typical pitfalls are presented.

Experimentally Observed Electrical Durability of 4H-SiC JFET ICs Operating from 500 C to 700 C

NASA Technical Reports Server (NTRS)

Neudeck, Philip G.; Spry, David J.; Chen, Liangyu; Lukco, Dorothy; Chang, Carl W.; Beheim, Glenn M.

2016-01-01

Prolonged 500 degrees Celsius to 700 degrees Celsius electrical testing data from 4H-SiC junction field effect transistor (JFET) integrated circuits (ICs) are combined with post-testing microscopic studies in order to gain more comprehensive understanding of the durability limits of the present version of NASA Glenn's extreme temperature microelectronics technology. The results of this study support the hypothesis that T = 500 degrees Celsius durability-limiting IC failure initiates with thermal-stress-related crack formation where dielectric passivation layers overcoat micron-scale vertical features including patterned metal traces.

Energy consumption and usage characteristics from field measurements of residential dishwashers, clothes washers and clothes dryers

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

Chang, Y.L.; Grot, R.A.

1980-10-01

The measured energy consumption and usage characteristics for household dishwashers, clothes washers, and clothes dryers for ten townhouses at Twin Rivers, N.J., are presented. Whenever the dishwashers and/or clothes washers were in use, the energy consumption, water consumption, frequency of usage, and water temperature were measured by a data acquisition system. The electrical energy of electric clothes dryers and the gas consumption of gas clothes dryers were measured, as well as their frequency and duration of use, and exhaust temperature. Typical household usage patterns of these major appliances are included.

Electrically tunable spatially variable switching in ferroelectric liquid crystal/water system

NASA Astrophysics Data System (ADS)

Choudhary, A.; Coondoo, I.; Prakash, J.; Sreenivas, K.; Biradar, A. M.

2009-04-01

An unusual switching phenomenon in the region outside conducting patterned area in ferroelectric liquid crystal (FLC) containing about 1-2 wt % of water has been observed. The presence of water in the studied heterogeneous system was confirmed by Fourier transform infrared spectroscopy. The observed optical studies have been emphasized on the "spatially variable switching" phenomenon of the molecules in the nonconducting region of the cell. The observed phenomenon is due to diffusion of water between the smectic layers of the FLC and the interaction of the curved electric field lines with the FLC molecules in the nonconducting region.

Electrohydrodynamic pressure enhanced by free space charge for electrically induced structure formation with high aspect ratio.

PubMed

Tian, Hongmiao; Wang, Chunhui; Shao, Jinyou; Ding, Yucheng; Li, Xiangming

2014-10-28

Electrically induced structure formation (EISF) is an interesting and unique approach for generating a microstructured duplicate from a rheological polymer by a spatially modulated electric field induced by a patterned template. Most of the research on EISF have so far used various dielectric polymers (with an electrical conductivity smaller than 10(-10) S/m that can be considered a perfect dielectric), on which the electric field induces a Maxwell stress only due to the dipoles (or bounded charges) in the polymer molecules, leading to a structure with a small aspect ratio. This paper presents a different approach for improving the aspect ratio allowed in EISF by doping organic salt into the perfect dielectric polymer, i.e., turning the perfect dielectric into a leaky dielectric, considering the fact that the free space charges enriched in the leaky dielectric polymer can make an additional contribution to the Maxwell stress, i.e., electrohydrodynamic pressure, which is desirable for high aspect ratio structuring. Our numerical simulations and experimental tests have shown that a leaky dielectric polymer, with a small conductivity comparable to that of deionized water, can be much more effective at being electrohydrodynamically deformed into a high aspect ratio in comparison with a perfect dielectric polymer when both of them have roughly the same dielectric constant.

Electrokinetic framework of dielectrophoretic deposition devices

NASA Astrophysics Data System (ADS)

Burg, Brian R.; Bianco, Vincenzo; Schneider, Julian; Poulikakos, Dimos

2010-06-01

Numerical modeling and experiments are performed investigating the properties of a dielectrophoresis-based deposition device, in order to establish the electrokinetic framework required to understand the effects of applied inhomogeneous electric fields while moving particles to desired locations. By capacitively coupling electrodes to a conductive substrate, the controlled large-scale parallel dielectrophoretic assembly of nanostructures in individually accessible devices at a high integration density is accomplished. Thermal gradients in the solution, which give rise to local permittivity and conductivity changes, and velocity fields are solved by coupling electric, thermal, and fluid-mechanical equations. The induced electrothermal flow (ETF) causes vortices above the electrode gap, attracting particles, such as single-walled carbon nanotubes (SWNTs), before they are trapped by the dielectrophoretic force and deposit across the electrodes. Long-range carbon nanotube transport is governed by hydrodynamic effects, while local trapping is dominated by dielectrophoretic forces in low concentration SWNT dispersions. Results show that by decreasing the ac frequency ac electroosmosis on the metallic electrodes occurs due to the emergence of an electric double layer, disturbing the initial flow pattern of the system. By superimposing a dc potential offset, a generated tangential electroosmotic fluid flow in the dielectric electrode gap also disrupts the ETF. Capacitive coupling is most efficient in the high frequency regime where it is the dominating impedance contribution. Understanding the occurrence and interaction of these different effects, including a self-limiting integration mechanism for individual nanostructures, allows an increased deposition yield at overall lower electric field strengths through a prudent choice of electric field parameters. The findings provide important avenues toward gentler particle handling, without direct current throughput, a relevant aspect for limiting process effects during device fabrication, all while increasing dielectrophoretic deposition efficiency in nanostructured networks.

The electromagnetic radiation from simple sources in the presence of a homogeneous dielectric sphere

NASA Technical Reports Server (NTRS)

Mason, V. B.

1973-01-01

In this research, the effect of a homogeneous dielectric sphere on the electromagnetic radiation from simple sources is treated as a boundary value problem, and the solution is obtained by the technique of dyadic Green's functions. Exact representations of the electric fields in the various regions due to a source located inside, outside, or on the surface of a dielectric sphere are formulated. Particular attention is given to the effect of sphere size, source location, dielectric constant, and dielectric loss on the radiation patterns and directivity of small spheres (less than 5 wavelengths in diameter) using the Huygens' source excitation. The computed results are found to closely agree with those measured for waveguide-excited plexiglas spheres. Radiation patterns for an extended Huygens' source and for curved electric dipoles located on the sphere's surface are also presented. The resonance phenomenon associated with the dielectric sphere is studied in terms of the modal representation of the radiated fields. It is found that when the sphere is excited at certain frequencies, much of the energy is radiated into the sidelobes. The addition of a moderate amount of dielectric loss, however, quickly attenuates this resonance effect. A computer program which may be used to calculate the directivity and radiation pattern of a Huygens' source located inside or on the surface of a lossy dielectric sphere is listed.

Dynamic interaction of CO/H 2O mixtures with gold nanocrystals: Real-time imaging and local chemical probing

NASA Astrophysics Data System (ADS)

Visart de Bocarmé, Thierry; Chau, Thoi-Dai; Kruse, Norbert

2006-09-01

The dynamic interaction of pure gold nanocrystals ("tips") with H 2O/CO gas mixtures was studied by means of video-field ion microscopy (FIM). While imaging with nano-scale resolution selected areas of the equivalent of ˜200 atomic Au sites were analysed for their chemical composition using short field pulses and injecting respective ions into a time-of-flight mass spectrometer (pulsed field desorption mass spectrometry, PFDMS). At room temperature the exposure of a clean Au sample to water gas at 10 -4 Pa, in the presence of an electric field of ˜10 V/nm, led to water adsorption and formation of bright patterns in FIM. Additional exposure to CO gas at 5 × 10 -3 Pa led to the removal of the water layer. This was associated with the occurrence of bright wave fronts which ignited simultaneously in several regions of the Au surface with no preference for a certain crystallographic surface plane. In some cases wave fronts were seen to collide resulting in more complicated patterns such as concentric rings. Surface areas free of water appeared with low brightness. The phenomena were completely reversible. PFDMS demonstrated water ions to be responsible for image formation. Surface hydroxyl was also detected mass spectrometrically and respective ion intensities decreased during the titration with CO. The results suggest that gold nanocrystals, in the absence of oxidic support materials, may be active in the reaction between water and CO at temperatures as low as 300 K and in the presence of an electric field of ˜10 V/nm.

Electrode Models for Electric Current Computed Tomography

PubMed Central

CHENG, KUO-SHENG; ISAACSON, DAVID; NEWELL, J. C.; GISSER, DAVID G.

2016-01-01

This paper develops a mathematical model for the physical properties of electrodes suitable for use in electric current computed tomography (ECCT). The model includes the effects of discretization, shunt, and contact impedance. The complete model was validated by experiment. Bath resistivities of 284.0, 139.7, 62.3, 29.5 Ω · cm were studied. Values of “effective” contact impedance z used in the numerical approximations were 58.0, 35.0, 15.0, and 7.5 Ω · cm2, respectively. Agreement between the calculated and experimentally measured values was excellent throughout the range of bath conductivities studied. It is desirable in electrical impedance imaging systems to model the observed voltages to the same precision as they are measured in order to be able to make the highest resolution reconstructions of the internal conductivity that the measurement precision allows. The complete electrode model, which includes the effects of discretization of the current pattern, the shunt effect due to the highly conductive electrode material, and the effect of an “effective” contact impedance, allows calculation of the voltages due to any current pattern applied to a homogeneous resistivity field. PMID:2777280

Electrode models for electric current computed tomography.

PubMed

Cheng, K S; Isaacson, D; Newell, J C; Gisser, D G

1989-09-01

This paper develops a mathematical model for the physical properties of electrodes suitable for use in electric current computed tomography (ECCT). The model includes the effects of discretization, shunt, and contact impedance. The complete model was validated by experiment. Bath resistivities of 284.0, 139.7, 62.3, 29.5 omega.cm were studied. Values of "effective" contact impedance zeta used in the numerical approximations were 58.0, 35.0, 15.0, and 7.5 omega.cm2, respectively. Agreement between the calculated and experimentally measured values was excellent throughout the range of bath conductivities studied. It is desirable in electrical impedance imaging systems to model the observed voltages to the same precision as they are measured in order to be able to make the highest resolution reconstructions of the internal conductivity that the measurement precision allows. The complete electrode model, which includes the effects of discretization of the current pattern, the shunt effect due to the highly conductive electrode material, and the effect of an "effective" contact impedance, allows calculation of the voltages due to any current pattern applied to a homogeneous resistivity field.

Two dimensional simulation of patternable conducting polymer electrode based organic thin film transistor

NASA Astrophysics Data System (ADS)

Nair, Shiny; Kathiresan, M.; Mukundan, T.

2018-02-01

Device characteristics of organic thin film transistor (OTFT) fabricated with conducting polyaniline:polystyrene sulphonic acid (PANi-PSS) electrodes, patterned by the Parylene lift-off method are systematically analyzed by way of two dimensional numerical simulation. The device simulation was performed taking into account field-dependent mobility, low mobility layer at the electrode-semiconductor interface, trap distribution in pentacene film and trapped charge at the organic/insulator interface. The electrical characteristics of bottom contact thin film transistor with PANi-PSS electrodes and pentacene active material is superior to those with palladium electrodes due to a lower charge injection barrier. Contact resistance was extracted in both cases by the transfer line method (TLM). The extracted charge concentration and potential profile from the two dimensional numerical simulation was used to explain the observed electrical characteristics. The simulated device characteristics not only matched the experimental electrical characteristics, but also gave an insight on the charge injection, transport and trap properties of the OTFTs as a function of different electrode materials from the perspectives of transistor operation.

Electric field driven mesoscale phase transition in polarized colloids

NASA Astrophysics Data System (ADS)

Khusid, Boris; Elele, Ezinwa; Lei, Qian

2016-11-01

A mesoscale phase transition in a polarized suspension was reported by Kumar, Khusid, Acrivos, PRL95, 2005 and Agarwal, Yethiraj, PRL102, 2009. Following the application of a strong AC field, particles aggregated head-to-tail into chains that bridged the interelectrode gap and then formed a cellular pattern, in which large particle-free domains were enclosed by particle-rich thin walls. Cellular structures were not observed in numerous simulations of field induced phase transitions in a polarized suspension. A requirement for matching the particle and fluid densities to avoid particle settling limits terrestrial experiments to negatively polarized particles. We present data on the phase diagram and kinetics of the phase transition in a neutrally buoyant, negatively polarized suspension subjected to a combination of AC and DC. Surprisingly, a weak DC component drastically speeds up the formation of a cellular pattern but does not affect its key characteristic. However, the application of a strong DC field destroys the cellular pattern, but it restores as the DC field strength is reduced. We also discuss the design of experiments to study phase transitions in a suspension of positively polarized, non-buoyancy-matched particles in the International Space Station. Supported by NASA's Physical Science Research Program, NNX13AQ53G.

Fuel cell with metal screen flow-field

DOEpatents

Wilson, M.S.; Zawodzinski, C.

1998-08-25

A polymer electrolyte membrane (PEM) fuel cell is provided with electrodes supplied with a reactant on each side of a catalyzed membrane assembly (CMA). The fuel cell includes a metal mesh defining a rectangular flow-field pattern having an inlet at a first corner and an outlet at a second corner located on a diagonal from the first corner, wherein all flow paths from the inlet to the outlet through the square flow field pattern are equivalent to uniformly distribute the reactant over the CMA. In a preferred form of metal mesh, a square weave screen forms the flow-field pattern. In a particular characterization of the present invention, a bipolar plate electrically connects adjacent fuel cells, where the bipolar plate includes a thin metal foil having an anode side and a cathode side; a first metal mesh on the anode side of the thin metal foil; and a second metal mesh on the cathode side of the thin metal foil. In another characterization of the present invention, a cooling plate assembly cools adjacent fuel cells, where the cooling plate assembly includes an anode electrode and a cathode electrode formed of thin conducting foils; and a metal mesh flow field there between for distributing cooling water flow over the electrodes to remove heat generated by the fuel cells. 11 figs.

Fuel cell with metal screen flow-field

DOEpatents

Wilson, Mahlon S.; Zawodzinski, Christine

2001-01-01

A polymer electrolyte membrane (PEM) fuel cell is provided with electrodes supplied with a reactant on each side of a catalyzed membrane assembly (CMA). The fuel cell includes a metal mesh defining a rectangular flow-field pattern having an inlet at a first corner and an outlet at a second corner located on a diagonal from the first corner, wherein all flow paths from the inlet to the outlet through the square flow field pattern are equivalent to uniformly distribute the reactant over the CMA. In a preferred form of metal mesh, a square weave screen forms the flow-field pattern. In a particular characterization of the present invention, a bipolar plate electrically connects adjacent fuel cells, where the bipolar plate includes a thin metal foil having an anode side and a cathode side; a first metal mesh on the anode side of the thin metal foil; and a second metal mesh on the cathode side of the thin metal foil. In another characterization of the present invention, a cooling plate assembly cools adjacent fuel cells, where the cooling plate assembly includes an anode electrode and a cathode electrode formed of thin conducting foils; and a metal mesh flow field therebetween for distributing cooling water flow over the electrodes to remove heat generated by the fuel cells.

Fuel cell with metal screen flow-field

DOEpatents

Wilson, Mahlon S.; Zawodzinski, Christine

1998-01-01

A polymer electrolyte membrane (PEM) fuel cell is provided with electrodes supplied with a reactant on each side of a catalyzed membrane assembly (CMA). The fuel cell includes a metal mesh defining a rectangular flow-field pattern having an inlet at a first corner and an outlet at a second corner located on a diagonal from the first corner, wherein all flow paths from the inlet to the outlet through the square flow field pattern are equivalent to uniformly distribute the reactant over the CMA. In a preferred form of metal mesh, a square weave screen forms the flow-field pattern. In a particular characterization of the present invention, a bipolar plate electrically connects adjacent fuel cells, where the bipolar plate includes a thin metal foil having an anode side and a cathode side; a first metal mesh on the anode side of the thin metal foil; and a second metal mesh on the cathode side of the thin metal foil. In another characterization of the present invention, a cooling plate assembly cools adjacent fuel cells, where the cooling plate assembly includes an anode electrode and a cathode electrode formed of thin conducting foils; and a metal mesh flow field therebetween for distributing cooling water flow over the electrodes to remove heat generated by the fuel cells.

Artificial ferroic systems: novel functionality from structure, interactions and dynamics.

PubMed

Heyderman, L J; Stamps, R L

2013-09-11

Lithographic processing and film growth technologies are continuing to advance, so that it is now possible to create patterned ferroic materials consisting of arrays of sub-1 μm elements with high definition. Some of the most fascinating behaviour of these arrays can be realised by exploiting interactions between the individual elements to create new functionality. The properties of these artificial ferroic systems differ strikingly from those of their constituent components, with novel emergent behaviour arising from the collective dynamics of the interacting elements, which are arranged in specific designs and can be activated by applying magnetic or electric fields. We first focus on artificial spin systems consisting of arrays of dipolar-coupled nanomagnets and, in particular, review the field of artificial spin ice, which demonstrates a wide range of fascinating phenomena arising from the frustration inherent in particular arrangements of nanomagnets, including emergent magnetic monopoles, domains of ordered macrospins, and novel avalanche behaviour. We outline how demagnetisation protocols have been employed as an effective thermal anneal in an attempt to reach the ground state, comment on phenomena that arise in thermally activated systems and discuss strategies for selectively generating specific configurations using applied magnetic fields. We then move on from slow field and temperature driven dynamics to high frequency phenomena, discussing spinwave excitations in the context of magnonic crystals constructed from arrays of patterned magnetic elements. At high frequencies, these arrays are studied in terms of potential applications including magnetic logic, linear and non-linear microwave optics, and fast, efficient switching, and we consider the possibility to create tunable magnonic crystals with artificial spin ice. Finally, we discuss how functional ferroic composites can be incorporated to realise magnetoelectric effects. Specifically, we discuss artificial multiferroics (or multiferroic composites), which hold promise for new applications that involve electric field control of magnetism, or electric and magnetic field responsive devices for high frequency integrated circuit design in microwave and terahertz signal processing. We close with comments on how enhanced functionality can be realised through engineering of nanostructures with interacting ferroic components, creating opportunities for novel spin electronic devices that, for example, make use of the transport of magnetic charges, thermally activated elements, and reprogrammable nanomagnet systems.

Volumetric HiLo microscopy employing an electrically tunable lens.

PubMed

Philipp, Katrin; Smolarski, André; Koukourakis, Nektarios; Fischer, Andreas; Stürmer, Moritz; Wallrabe, Ulrike; Czarske, Jürgen W

2016-06-27

Electrically tunable lenses exhibit strong potential for fast motion-free axial scanning in a variety of microscopes. However, they also lead to a degradation of the achievable resolution because of aberrations and misalignment between illumination and detection optics that are induced by the scan itself. Additionally, the typically nonlinear relation between actuation voltage and axial displacement leads to over- or under-sampled frame acquisition in most microscopic techniques because of their static depth-of-field. To overcome these limitations, we present an Adaptive-Lens-High-and-Low-frequency (AL-HiLo) microscope that enables volumetric measurements employing an electrically tunable lens. By using speckle-patterned illumination, we ensure stability against aberrations of the electrically tunable lens. Its depth-of-field can be adjusted a-posteriori and hence enables to create flexible scans, which compensates for irregular axial measurement positions. The adaptive HiLo microscope provides an axial scanning range of 1 mm with an axial resolution of about 4 μm and sub-micron lateral resolution over the full scanning range. Proof of concept measurements at home-built specimens as well as zebrafish embryos with reporter gene-driven fluorescence in the thyroid gland are shown.

Global Electric Circuit Implications of Combined Aircraft Storm Electric Current Measurements and Satellite-Based Diurnal Lightning Statistics

NASA Technical Reports Server (NTRS)

Mach, Douglas M.; Blakeslee, Richard J.; Bateman, Monte G.

2011-01-01

Using rotating vane electric field mills and Gerdien capacitors, we measured the electric field profile and conductivity during 850 overflights of thunderstorms and electrified shower clouds (ESCs) spanning regions including the Southeastern United States, the Western Atlantic Ocean, the Gulf of Mexico, Central America and adjacent oceans, Central Brazil, and the South Pacific. The overflights include storms over land and ocean, and with positive and negative fields above the storms. Over three-quarters (78%) of the land storms had detectable lightning, while less than half (43%) of the oceanic storms had lightning. Integrating our electric field and conductivity data, we determined total conduction currents and flash rates for each overpass. With knowledge of the storm location (land or ocean) and type (with or without lightning), we determine the mean currents by location and type. The mean current for ocean thunderstorms is 1.7 A while the mean current for land thunderstorms is 1.0 A. The mean current for ocean ESCs 0.41 A and the mean current for land ESCs is 0.13 A. We did not find any significant regional or latitudinal based patterns in our total conduction currents. By combining the aircraft derived storm currents and flash rates with diurnal flash rate statistics derived from the Lightning Imaging Sensor (LIS) and Optical Transient Detector (OTD) low Earth orbiting satellites, we reproduce the diurnal variation in the global electric circuit (i.e., the Carnegie curve) to within 4% for all but two short periods of time. The agreement with the Carnegie curve was obtained without any tuning or adjustment of the satellite or aircraft data. Given our data and assumptions, mean contributions to the global electric circuit are 1.1 kA (land) and 0.7 kA (ocean) from thunderstorms, and 0.22 kA (ocean) and 0.04 (land) from ESCs, resulting in a mean total conduction current estimate for the global electric circuit of 2.0 kA. Mean storm counts are 1100 for land thunderstorms, 530 for ocean ESCs, 390 for ocean thunderstorms, and 330 for land ESCs.

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.

Electrical and thermoelectric transport properties of two-dimensional fermionic systems with k-cubic spin-orbit coupling.

PubMed

Mawrie, Alestin; Verma, Sonu; Ghosh, Tarun Kanti

2017-09-01

We investigate effect of <i>k</i>-cubic spin-orbit interaction on electrical and thermoelectric transport properties of two-dimensional fermionic systems. We obtain exact analytical expressions of the inverse relaxation time (IRT) and the Drude conductivity for long-range Coulomb and short-range delta scattering potentials. The IRT reveals that the scattering is completely suppressed along the three directions θ = (2n+1)π/3 with n=1,2,3. We also obtain analytical results of the thermopower and thermal conductivity at low temperature. The thermoelectric transport coefficients obey the Wiedemann-Franz law, even in the presence of <i>k</i>-cubic Rashba spin-orbit interaction (RSOI) at low temperature. In the presence of quantizing magnetic field, the signature of the RSOI is revealed through the appearance of the beating pattern in the Shubnikov-de Haas (SdH) oscillations of thermopower and thermal conductivity in low magnetic field regime. The empirical formulae for the SdH oscillation frequencies accurately describe the locations of the beating nodes. The beating pattern in magnetothermoelectric measurement can be used to extract the spin-orbit coupling constant. © 2017 IOP Publishing Ltd.

Electrical and thermoelectric transport properties of two-dimensional fermionic systems with k-cubic spin-orbit coupling

NASA Astrophysics Data System (ADS)

Mawrie, Alestin; Verma, Sonu; Kanti Ghosh, Tarun

2017-11-01

We investigate the effect of k-cubic spin-orbit interaction on the electrical and thermoelectric transport properties of two-dimensional fermionic systems. We obtain exact analytical expressions of the inverse relaxation time (IRT) and the Drude conductivity for long-range Coulomb and short-range delta scattering potentials. The IRT reveals that the scattering is completely suppressed along the three directions θ^\\prime = (2n+1)π/3 with n=1, 2, 3 . We also obtain analytical results of the thermopower and thermal conductivity at low temperature. The thermoelectric transport coefficients obey the Wiedemann-Franz law, even in the presence of k-cubic Rashba spin-orbit interaction (RSOI) at low temperature. In the presence of a quantizing magnetic field, the signature of the RSOI is revealed through the appearance of the beating pattern in the Shubnikov-de Haas (SdH) oscillations of thermopower and thermal conductivity in the low magnetic field regime. The empirical formulae for the SdH oscillation frequencies accurately describe the locations of the beating nodes. The beating pattern in magnetothermoelectric measurement can be used to extract the spin-orbit coupling constant.

Pulsed electric field assisted assembly of polyaniline

NASA Astrophysics Data System (ADS)

Kumar, Arun; Kazmer, David O.; Barry, Carol M. F.; Mead, Joey L.

2012-08-01

Assembling conducting polyaniline (PANi) on pre-patterned nano-structures by a high rate, commercially viable route offers an opportunity for manufacturing devices with nanoscale features. In this work we report for the first time the use of pulsed electric field to assist electrophoresis for the assembly of conducting polyaniline on gold nanowire interdigitated templates. This technique offers dynamic control over heat build-up, which has been a main drawback in the DC electrophoresis and AC dielectrophoresis as well as the main cause of nanowire template damage. The use of this technique allowed higher voltages to be applied, resulting in shorter assembly times (e.g., 17.4 s, assembly resolution of 100 nm). Moreover, the area coverage increases with the increase in number of pulses. A similar trend was observed with the deposition height and the increase in deposition height followed a linear trend with a correlation coefficient of 0.95. When the experimental mass deposited was compared with Hamaker’s theoretical model, the two were found to be very close. The pre-patterned templates with PANi deposition were subsequently used to transfer the nanoscale assembled PANi from the rigid templates to thermoplastic polyurethane using the thermoforming process.

Tunable Schottky barrier and high responsivity in graphene/Si-nanotip optoelectronic device

NASA Astrophysics Data System (ADS)

Di Bartolomeo, Antonio; Giubileo, Filippo; Luongo, Giuseppe; Iemmo, Laura; Martucciello, Nadia; Niu, Gang; Fraschke, Mirko; Skibitzki, Oliver; Schroeder, Thomas; Lupina, Grzegorz

2017-03-01

We demonstrate tunable Schottky barrier height and record photo-responsivity in a new-concept device made of a single-layer CVD graphene transferred onto a matrix of nanotips patterned on n-type Si wafer. The original layout, where nano-sized graphene/Si heterojunctions alternate to graphene areas exposed to the electric field of the Si substrate, which acts both as diode cathode and transistor gate, results in a two-terminal barristor with single-bias control of the Schottky barrier. The nanotip patterning favors light absorption, and the enhancement of the electric field at the tip apex improves photo-charge separation and enables internal gain by impact ionization. These features render the device a photodetector with responsivity (3 {{A}} {{{W}}}-1 for white LED light at 3 {{mW}} {{{cm}}}-2 intensity) almost an order of magnitude higher than commercial photodiodes. We extensively characterize the voltage and the temperature dependence of the device parameters, and prove that the multi-junction approach does not add extra-inhomogeneity to the Schottky barrier height distribution. We also introduce a new phenomenological graphene/semiconductor diode equation, which well describes the experimental I-V characteristics both in forward and reverse bias.

A two-dimensional spin field-effect switch

DOE PAGES

Yan, Wenjing; Txoperena, Oihana; Llopis, Roger; ...

2016-11-11

Future development in spintronic devices will require an advanced control of spin currents, for example by an electric field. Here we demonstrate an approach that differs from previous proposals such as the Datta and Das modulator, and that is based on a van de Waals heterostructure of atomically thin graphene and semiconducting MoS 2. Our device combines the superior spin transport properties of graphene with the strong spin–orbit coupling of MoS 2 and allows switching of the spin current in the graphene channel between ON and OFF states by tuning the spin absorption into the MoS 2 with a gatemore » electrode. Lastly, our proposal holds potential for technologically relevant applications such as search engines or pattern recognition circuits, and opens possibilities towards electrical injection of spins into transition metal dichalcogenides and alike materials.« less

Symmetric tops in combined electric fields: Conditional quasisolvability via the quantum Hamilton-Jacobi theory

NASA Astrophysics Data System (ADS)

Schatz, Konrad; Friedrich, Bretislav; Becker, Simon; Schmidt, Burkhard

2018-05-01

We make use of the quantum Hamilton-Jacobi (QHJ) theory to investigate conditional quasisolvability of the quantum symmetric top subject to combined electric fields (symmetric top pendulum). We derive the conditions of quasisolvability of the time-independent Schrödinger equation as well as the corresponding finite sets of exact analytic solutions. We do so for this prototypical trigonometric system as well as for its anti-isospectral hyperbolic counterpart. An examination of the algebraic and numerical spectra of these two systems reveals mutually closely related patterns. The QHJ approach allows us to retrieve the closed-form solutions for the spherical and planar pendula and the Razavy system that had been obtained in our earlier work via supersymmetric quantum mechanics as well as to find a cornucopia of additional exact analytic solutions.

Chained nuclei and python pattern in skeletal muscle cells as histological markers for electrical injury.

PubMed

Tanaka, Hiroki; Okuda, Katsuhiro; Ohtani, Seiji; Asari, Masaru; Horioka, Kie; Isozaki, Shotaro; Hayakawa, Akira; Ogawa, Katsuhiro; Hiroshi, Shiono; Shimizu, Keiko

2018-05-01

Electrical injury is damage caused by an electrical current passing through the body. We have previously reported that irregular stripes crossing skeletal muscle fibers (python pattern) and multiple small nuclei arranged in the longitudinal direction of the muscle fibers (chained nuclear change) are uniquely observed by histopathological analysis in the skeletal muscle tissues of patients with electrical injury. However, it remains unclear whether these phenomena are caused by the electrical current itself or by the joule heat generated by the electric current passing through the body. To clarify the causes underlying these changes, we applied electric and heat injury to the exteriorized rat soleus muscle in situ. Although both the python pattern and chained nuclear change were induced by electric injury, only the python pattern was induced by heat injury. Furthermore, a chained nuclear change was induced in the soleus muscle cells by electric current flow in physiological saline at 40 °C ex vivo, but a python pattern was not observed. When the skeletal muscle was exposed to electrical injury in cardiac-arrested rats, a python pattern was induced within 5 h after cardiac arrest, but no chained nuclear change was observed. Therefore, a chained nuclear change is induced by an electrical current alone in tissues in vital condition, whereas a python pattern is caused by joule heat, which may occur shortly after death. The degree and distribution of these skeletal muscle changes may be useful histological markers for analyzing cases of electrical injury in forensic medicine. Copyright © 2017 Elsevier B.V. All rights reserved.

Magnetophoretic circuits for digital control of single particles and cells

NASA Astrophysics Data System (ADS)

Lim, Byeonghwa; Reddy, Venu; Hu, Xinghao; Kim, Kunwoo; Jadhav, Mital; Abedini-Nassab, Roozbeh; Noh, Young-Woock; Lim, Yong Taik; Yellen, Benjamin B.; Kim, Cheolgi

2014-05-01

The ability to manipulate small fluid droplets, colloidal particles and single cells with the precision and parallelization of modern-day computer hardware has profound applications for biochemical detection, gene sequencing, chemical synthesis and highly parallel analysis of single cells. Drawing inspiration from general circuit theory and magnetic bubble technology, here we demonstrate a class of integrated circuits for executing sequential and parallel, timed operations on an ensemble of single particles and cells. The integrated circuits are constructed from lithographically defined, overlaid patterns of magnetic film and current lines. The magnetic patterns passively control particles similar to electrical conductors, diodes and capacitors. The current lines actively switch particles between different tracks similar to gated electrical transistors. When combined into arrays and driven by a rotating magnetic field clock, these integrated circuits have general multiplexing properties and enable the precise control of magnetizable objects.

Ballistic interference in ultraclean suspended monolayer graphene

NASA Astrophysics Data System (ADS)

Schonenberger, Christian; Rickhaus, Peter; Maurand, Romain; Makk, Peter; Hess, Samuel; Tovari, Endre; Weiss, Markus; Liu, Ming-Hao; Richter, Klaus

2014-03-01

We have developed a versatile technology that allows to suspend graphene and complement it with arbitrary bottom and top-gate structures. Using current annealing we demonstrate exceptional high mobililties in monolayer graphene approaching 100 m2/Vs. These suspended devices are ballistic over micrometer length scales and display intriguing interference patterns in the electrical con-ductance when different gate potentials are applied. Specifically we will discuss different types of Fabry-Perot resonances that appear in different gate voltage regimes of ballistic pn devices. We will go beyond our recent publication and also show electric transport measurements in magnetic field, where intriguing features appear in the intermediate field range in between the low-field Klein-tunneling regime and the quantum Hall regime. We observe a large number of non-dispersing states which might be due to so-called snake states confined to the pn interface. We will also discuss first results on electron guiding in ultraclean monolayer graphene. We acknowledge funding from the Swiss NFS and the EC.

Kerr electro-optic field mapping study of the effect of charge injection on the impulse breakdown strength of transformer oil

NASA Astrophysics Data System (ADS)

Zhang, X.; Zahn, M.

2013-10-01

The smart use of charge injection to improve breakdown strength in transformer oil is demonstrated in this paper. Hypothetically, bipolar homo-charge injection with reduced electric field at both electrodes may allow higher voltage operation without insulation failure, since electrical breakdown usually initiates at the electrode-dielectric interfaces. To find experimental evidence, the applicability and limitation of the hypothesis is first analyzed. Impulse breakdown tests and Kerr electro-optic field mapping measurements are then conducted with different combinations of parallel-plate aluminum and brass electrodes stressed by millisecond duration impulse. It is found that the breakdown voltage of brass anode and aluminum cathode is ˜50% higher than that of aluminum anode and brass cathode. This can be explained by charge injection patterns from Kerr measurements under a lower voltage, where aluminum and brass electrodes inject negative and positive charges, respectively. This work provides a feasible approach to investigating the effect of electrode material on breakdown strength.

Electromagnetic Measurements in an Active Oilfield Environment

NASA Astrophysics Data System (ADS)

Weiss, C. J.; Aur, K. A.; Schramm, K. A.; Aldridge, D. F.; O'rourke, W. T.

2016-12-01

An important issue in oilfield development is mapping fracture distributions (either natural or man-made) controlling subsurface fluid flow. Although microseismic monitoring has been successful in constraining fracture system geometry and dynamics, accurate interpretation of microseismic data can be confounded by factors such as complex or poorly-understood velocity distributions, reactivation of previously unknown faults and fractures, and the problem of relating flow patterns to the cloud of hypocenter locations. For the particular problem of hydrocarbon production, the question of which fractures remain sufficiently "open" to allow economical fluid extraction is critical. As a supplement to microseismic analysis, we are investigating a novel electromagnetic (EM) technique for detecting and mapping hydraulic fractures in a hydrocarbon or geothermal reservoir by introducing an electrically conductive contrast agent into the fracturing fluid. In the field experiment presented here, a proppant-filled fracture zone is illuminated by a large engineered antenna consisting of an insulated current-carrying cable, grounded to `Earth' near the wellhead, and grounded at the other end to the steel-cased borehole near the target. Time-lapse measurements of horizontal electric field are subsequently made on Earth's surface to map the change in subsurface conductivity due to proppant emplacement. As predicted by 3D numerical modelling, observed differences in electric field values are very small. While these numbers are above the noise floor of electric field sensors, pervasive anthropogenic EM noise and regional-scale magnetotelluric signals make extraction of the differences from the observed time series especially difficult. We present field-acquired data on ambient EM noise in an active oilfield environment and demonstrate techniques for extracting the difference signal due to proppant emplacement. These techniques include classical spectral methods along with estimation of time-domain Green's function by regularized, linear least squares methods.

Polarity-sensitive transient patterned state in a twisted nematic liquid crystal driven by very low frequency fields.

PubMed

Krishnamurthy, K S; Kumar, Pramoda; Kumar, M Vijay

2013-02-01

We report, for a rodlike nematic liquid crystal with small positive dielectric and conductivity anisotropies, and in the 90°-twisted configuration, low frequency (<2 Hz) square wave electric field generated Carr-Helfrich director modulation appearing transiently over a few seconds at each polarity reversal and vanishing almost completely under steady field conditions. Significantly, the instability is polarity sensitive, with the maximum distortion localized in the vicinity of the negative electrode, rather than in the midplane of the layer. This is revealed by the wave vector alternating in the two halves of the driving cycle between the alignment directions at the two substrates. Besides the Carr-Helfrich mechanism, quadrupolar flexoelectric polarization arising under electric field gradient is strongly indicated as being involved in the development of the transient periodic order. Similar transient instability is also observed in other nematic compounds with varying combinations of dielectric and conductivity anisotropies, showing its general nature. The study also deals with various characteristics of the electro-optic effect that emerge from the temporal variation of optical response for different driving voltages, frequencies, and temperatures.

Stabilization of green bodies via sacrificial gelling agent during electrophoretic deposition

DOEpatents

Worsley, Marcus A.; Kuntz, Joshua D.; Rose, Klint A.

2016-03-22

In one embodiment, a method for electrophoretic deposition of a three-dimensionally patterned green body includes suspending a first material in a gelling agent above a patterned electrode of an electrophoretic deposition (EPD) chamber, and gelling the suspension while applying a first electric field to the suspension to cause desired patterning of the first material in a resulting gelation. In another embodiment, a ceramic, metal, or cermet includes a plurality of layers, wherein each layer includes a gradient in composition, microstructure, and/or density in an x-y plane oriented parallel to a plane of deposition of the plurality of layers along a predetermined distance in a z-direction perpendicular to the plane of deposition.

Anatomical and morphogenetic analysis of seismoelectric conversion patterns at geological units

NASA Astrophysics Data System (ADS)

Kröger, B.; Kemna, A.

2012-04-01

Characterisation of the hydraulic properties of a reservoir, such as porosity and permeability, and their spatial distribution plays an important role in many subsurface geophysical investigations. A fully developed seismoelectric exploration method is very appealing since it would offer the potential to directly determine these parameters in field-scale applications. In fluid-saturated rocks, seismic waves can generate electromagnetic fields, due to electrokinetic coupling mechanisms at the fluid-mineral interface. Using numerical modelling, we investigated the spatio-temporal occurrence and evolution of the seismoelectric effects that occur in spatially confined lithological units. Such geometries may represent clay lenses embedded in an aquifer or petroleum deposits in a host rock. For the modelling, we use a simplified time-domain formulation of the coupled physical problem and its efficient implementation in a 2D finite-element framework. Two occurring seismoelectric phenomena are investigated: (1) the co-seismic field associated with the seismic displacement at each point and (2) the interface response generated at layer boundaries. To gain insight into the morphogenetic field behaviour of the seismoelectric effects, we run numerical simulations using several material parameter set-ups for various target geometries. Accordingly, we varied both the thickness of the confined units and the value of the electrical bulk conductivity in the considered media. The analysis of the seismoelectric effects revealed an important difference in the generation of the interface response at either electrically conductive or resistive units. We find that the contrast in the electrical bulk conductivity between the host rock and the target geological unit controls the shape and structure of the seismoelectric conversion patterns. Our results show that the seismoelectric interface response captures both the petrophysical and geometrical characteristics of the converting geological unit. The considered models indicate the general potential of using the seismoelectric interface response for reservoir characterisation in hydrogeological or hydrocarbon exploration studies.

An Advanced Electrospinning Method of Fabricating Nanofibrous Patterned Architectures with Controlled Deposition and Desired Alignment

NASA Astrophysics Data System (ADS)

Rasel, Sheikh Md

We introduce a versatile advanced method of electrospinning for fabricating various kinds of nanofibrous patterns along with desired alignment, controlled amount of deposition and locally variable density into the architectures. In this method, we employed multiple electrodes whose potentials have been altered in milliseconds with the help of microprocessor based control system. Therefore, key success of this method was that the electrical field as well as charge carrying fibers could be switched shortly from one electrode's location to another, as a result, electrospun fibers could be deposited on the designated areas with desired alignment. A wide range of nanofibrous patterned architectures were constructed using proper arrangement of multiple electrodes. By controlling the concurrent activation time of two adjacent electrodes, we demonstrated that amount of fibers going into the pattern can be adjusted and desired alignment in electrospun fibers can be obtained. We also revealed that the deposition density of electrospun fibers in different areas of patterned architectures can be varied. We showed that by controlling the deposition time between two adjacent electrodes, a number of functionally graded patterns can be generated with uniaxial alignment. We also demonstrated that this handy method was capable of producing random, aligned, and multidirectional nanofibrous mats by engaging a number of electrodes and switching them in desired patterns. A comprehensive study using finite element method was carried out to understand the effects of electrical field. Simulation results revealed that electrical field strength alters shortly based on electrode control switch patterns. Nanofibrous polyvinyl alcohol (PVA) scaffolds and its composite reinforced with wollastonite and wood flour were fabricated using rotating drum electrospinning technique. Morphological, mechanical, and thermal, properties were characterized on PVA/wollastonite and PVA/wood flour nanocomposites containing 0, 5, 10, and 20 wt % of fillers. Morphological analyses carried out by digital optical microscope, scanning electron microscopy, x-ray computed tomography, and Fourier transform infrared spectroscopy, confirmed the presence and well dispersion of fillers in the composites. In addition, improvement of mechanical properties with increased filler content further emphasized the adhesion between matrix and reinforcement. PVA with 20 wt % wollastonite composite exhibited the highest tensile strength (11.99 MPa) and tensile module (198 MPa) as compared to pure PVA (3.92 MPa and 83 MPa, respectively). Moreover, the thermal tests demonstrated that there is no major deviation in the thermal stability due to the addition of wollastonite in PVA scaffolds. Almost similar trend was observed in PVA/wood flour nanocomposites where tensile strength improved by 228 % for 20 wt % of reinforcement. The PVA/wollastonite and PVA/wood flour fibrous nanocomposite which poses higher mechanical properties might be potentially suitable for many advanced applications such as filtration, tissue engineering, and food processing. We believe this study will contribute to further scientific understanding of the patterning mechanism of electrospun nanofibers and to allow for variety of design of specific patterned nanofibrous architectures with desired functional properties. Therefore, this improved scheme of electrospinning can have significant impact in a broad range of applications including tissue engineering scaffolds, filtrations, and nanoelectronics.

A Comparison of Inductive Sensors in the Characterization of Partial Discharges and Electrical Noise Using the Chromatic Technique.

PubMed

Ardila-Rey, Jorge Alfredo; Montaña, Johny; de Castro, Bruno Albuquerque; Schurch, Roger; Covolan Ulson, José Alfredo; Muhammad-Sukki, Firdaus; Bani, Nurul Aini

2018-03-29

Partial discharges (PDs) are one of the most important classes of ageing processes that occur within electrical insulation. PD detection is a standardized technique to qualify the state of the insulation in electric assets such as machines and power cables. Generally, the classical phase-resolved partial discharge (PRPD) patterns are used to perform the identification of the type of PD source when they are related to a specific degradation process and when the electrical noise level is low compared to the magnitudes of the PD signals. However, in practical applications such as measurements carried out in the field or in industrial environments, several PD sources and large noise signals are usually present simultaneously. In this study, three different inductive sensors have been used to evaluate and compare their performance in the detection and separation of multiple PD sources by applying the chromatic technique to each of the measured signals.

Social interactions between live and artificial weakly electric fish: Electrocommunication and locomotor behavior of Mormyrus rume proboscirostris towards a mobile dummy fish

PubMed Central

Kirschbaum, Frank; von der Emde, Gerhard

2017-01-01

Mormyrid weakly electric fish produce short, pulse-type electric organ discharges for actively probing their environment and to communicate with conspecifics. Animals emit sequences of pulse-trains that vary in overall frequency and temporal patterning and can lead to time-locked interactions with the discharge activity of other individuals. Both active electrolocation and electrocommunication are additionally accompanied by stereotypical locomotor patterns. However, the concrete roles of electrical and locomotor patterns during social interactions in mormyrids are not well understood. Here we used a mobile fish dummy that was emitting different types of electrical playback sequences to study following behavior and interaction patterns (electrical and locomotor) between individuals of weakly electric fish. We confronted single individuals of Mormyrus rume proboscirostris with a mobile dummy fish designed to attract fish from a shelter and recruit them into an open area by emitting electrical playbacks of natural discharge sequences. We found that fish were reliably recruited by the mobile dummy if it emitted electrical signals and followed it largely independently of the presented playback patterns. While following the dummy, fish interacted with it spatially by displaying stereotypical motor patterns, as well as electrically, e.g. through discharge regularizations and by synchronizing their own discharge activity to the playback. However, the overall emission frequencies of the dummy were not adopted by the following fish. Instead, social signals based on different temporal patterns were emitted depending on the type of playback. In particular, double pulses were displayed in response to electrical signaling of the dummy and their expression was positively correlated with an animals' rank in the dominance hierarchy. Based on additional analysis of swimming trajectories and stereotypical locomotor behavior patterns, we conclude that the reception and emission of electrical communication signals play a crucial role in mediating social interactions in mormyrid weakly electric fish. PMID:28902915

Wireless Electrical Device Using Open-Circuit Elements Having No Electrical Connections

NASA Technical Reports Server (NTRS)

Taylor, Bryant Douglas (Inventor); Woodard, Stanley E. (Inventor)

2012-01-01

A wireless electrical device includes an electrically unconnected electrical conductor and at least one electrically unconnected electrode spaced apart from the electrical conductor. The electrical conductor is shaped for storage of an electric field and a magnetic field. In the presence of a time-varying magnetic field, the electrical conductor so-shaped resonates to generate harmonic electric and magnetic field responses. Each electrode is at a location lying within the magnetic field response so-generated and is constructed such that a linear movement of electric charges is generated in each electrode due to the magnetic field response so-generated.

Static electric fields modify the locomotory behaviour of cockroaches.

PubMed

Jackson, Christopher W; Hunt, Edmund; Sharkh, Suleiman; Newland, Philip L

2011-06-15

Static electric fields are found throughout the environment and there is growing interest in how electric fields influence insect behaviour. Here we have analysed the locomotory behaviour of cockroaches (Periplaneta americana) in response to static electric fields at levels equal to and above those found in the natural environment. Walking behaviour (including velocity, distance moved, turn angle and time spent walking) were analysed as cockroaches approached an electric field boundary in an open arena, and also when continuously exposed to an electric field. On approaching an electric field boundary, the greater the electric field strength the more likely a cockroach would be to turn away from, or be repulsed by, the electric field. Cockroaches completely exposed to electric fields showed significant changes in locomotion by covering less distance, walking slowly and turning more often. This study highlights the importance of electric fields on the normal locomotory behaviour of insects.

Study on electrical current variations in electromembrane extraction process: Relation between extraction recovery and magnitude of electrical current.

PubMed

Rahmani, Turaj; Rahimi, Atyeh; Nojavan, Saeed

2016-01-15

This contribution presents an experimental approach to improve analytical performance of electromembrane extraction (EME) procedure, which is based on the scrutiny of current pattern under different extraction conditions such as using different organic solvents as supported liquid membrane, electrical potentials, pH values of donor and acceptor phases, variable extraction times, temperatures, stirring rates, different hollow fiber lengths and the addition of salts or organic solvents to the sample matrix. In this study, four basic drugs with different polarities were extracted under different conditions with the corresponding electrical current patterns compared against extraction recoveries. The extraction process was demonstrated in terms of EME-HPLC analyses of selected basic drugs. Comparing the obtained extraction recoveries with the electrical current patterns, most cases exhibited minimum recovery and repeatability at the highest investigated magnitude of electrical current. . It was further found that identical current patterns are associated with repeated extraction efficiencies. In other words, the pattern should be repeated for a successful extraction. The results showed completely different electrical currents under different extraction conditions, so that all variable parameters have contributions into the electrical current pattern. Finally, the current patterns of extractions from wastewater, plasma and urine samples were demonstrated. The results indicated an increase in the electrical current when extracting from complex matrices; this was seen to decrease the extraction efficiency. Copyright © 2015 Elsevier B.V. All rights reserved.

Characterization of a Honeycomb-Like Scaffold With Dielectrophoresis-Based Patterning for Tissue Engineering.

PubMed

Huan, Zhijie; Chu, Henry K; Yang, Jie; Sun, Dong

2017-04-01

Seeding and patterning of cells with an engineered scaffold is a critical process in artificial tissue construction and regeneration. To date, many engineered scaffolds exhibit simple intrinsic designs, which fail to mimic the geometrical complexity of native tissues. In this study, a novel scaffold that can automatically seed cells into multilayer honeycomb patterns for bone tissue engineering application was designed and examined. The scaffold incorporated dielectrophoresis for noncontact manipulation of cells and intrinsic honeycomb architectures were integrated in each scaffold layer. When a voltage was supplied to the stacked scaffold layers, three-dimensional electric fields were generated, thereby manipulating cells to form into honeycomb-like cellular patterns for subsequent culture. The biocompatibility of the scaffold material was confirmed through the cell viability test. Experiments were conducted to evaluate the cell viability during DEP patterning at different voltage amplitudes, frequencies, and manipulating time. Three different mammalian cells were examined and the effects of the cell size and the cell concentration on the resultant cellular patterns were evaluated. Results showed that the proposed scaffold structure was able to construct multilayer honeycomb cellular patterns in a manner similar to the natural tissue. This honeycomb-like scaffold and the dielectrophoresis-based patterning technique examined in this study could provide the field with a promising tool to enhance seeding and patterning of a wide range of cells for the development of high-quality artificial tissues.

Upward gaze and head deviation with frontal eye field stimulation.

PubMed

Kaiboriboon, Kitti; Lüders, Hans O; Miller, Jonathan P; Leigh, R John

2012-03-01

Using electrical stimulation to the deep, most caudal part of the right frontal eye field (FEF), we demonstrate a novel pattern of vertical (upward) eye movement that was previously only thought possible by stimulating both frontal eye fields simultaneously. If stimulation was started when the subject looked laterally, the initial eye movement was back to the midline, followed by upward deviation. Our finding challenges current view of topological organisation in the human FEF and may have general implications for concepts of topological organisation of the motor cortex, since sustained stimulation also induced upward head movements as a component of the vertical gaze shift. [Published with video sequences].

A portable and integrated instrument for cell manipulation by dielectrophoresis.

PubMed

Burgarella, Sarah; Di Bari, Marco

2015-07-01

The physical manipulation of biological cells is a key point in the development of miniaturized systems for point-of-care analyses. Dielectrophoresis (DEP) has been reported by several laboratories as a promising method in biomedical research for label-free cell manipulation without physical contact, by exploiting the dielectric properties of cells suspended in a microfluidic sample, under the action of high-gradient electric fields. In view of a more extended use of DEP phenomena in lab-on-chip devices for point-of-care settings, we have developed a portable instrument, integrating on the same device the microfluidic biochip for cell manipulation and all the laboratory functions (i.e., DEP electric signal generation, microscopic observation of the biological sample under test and image acquisition) that are normally obtained by combining different nonportable standard laboratory instruments. The nonuniform electric field for cell manipulation on the biochip is generated by microelectrodes, patterned on the silicon substrate of microfluidic channels, using standard microfabrication techniques. Numerical modeling was performed to simulate the electric field distribution, quantify the DEP force, and optimize the geometry of the microelectrodes. The developed instrument includes an electronic board, which allows the control of the electric signal applied to electrodes necessary for DEP, and a miniaturized optical microscope system that allows visual inspection and eventually cell counting, as well as image and video recording. The system also includes the control software. The portable and integrated platform described in this work therefore represents a complete and innovative solution of applied research, suitable for many biological applications. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Wet etch methods for InAs nanowire patterning and self-aligned electrical contacts

NASA Astrophysics Data System (ADS)

Fülöp, G.; d'Hollosy, S.; Hofstetter, L.; Baumgartner, A.; Nygård, J.; Schönenberger, C.; Csonka, S.

2016-05-01

Advanced synthesis of semiconductor nanowires (NWs) enables their application in diverse fields, notably in chemical and electrical sensing, photovoltaics, or quantum electronic devices. In particular, indium arsenide (InAs) NWs are an ideal platform for quantum devices, e.g. they may host topological Majorana states. While the synthesis has been continously perfected, only a few techniques have been developed to tailor individual NWs after growth. Here we present three wet chemical etch methods for the post-growth morphological engineering of InAs NWs on the sub-100 nm scale. The first two methods allow the formation of self-aligned electrical contacts to etched NWs, while the third method results in conical shaped NW profiles ideal for creating smooth electrical potential gradients and shallow barriers. Low temperature experiments show that NWs with etched segments have stable transport characteristics and can serve as building blocks of quantum electronic devices. As an example we report the formation of a single electrically stable quantum dot between two etched NW segments.

Efficient band structure modulations in two-dimensional MnPSe3/CrSiTe3 van der Waals heterostructures

NASA Astrophysics Data System (ADS)

Pei, Qi; Wang, Xiaocha; Zou, Jijun; Mi, Wenbo

2018-05-01

As a research upsurge, van der Waals (vdW) heterostructures give rise to numerous combined merits and novel applications in nanoelectronics fields. Here, we systematically investigate the electronic structure of MnPSe3/CrSiTe3 vdW heterostructures with various stacking patterns. Then, particular attention of this work is paid on the band structure modulations in MnPSe3/CrSiTe3 vdW heterostructures via biaxial strain or electric field. Under a tensile strain, the relative band edge positions of heterostructures transform from type-I (nested) to type-II (staggered). The relocation of conduction band minimum also brings about a transition from indirect to direct band gap. Under a compressive strain, the electronic properties change from semiconducting to metallic. The physical mechanism of strain-dependent band structure may be ascribed to the shifts of the energy bands impelled by different superposition of atomic orbitals. Meanwhile, our calculations manifest that band gap values of MnPSe3/CrSiTe3 heterostructures are insensitive to the electric field. Even so, by applying a suitable intensity of negative electric field, the band alignment transition from type-I to type-II can also be realized. The efficient band structure modulations via external factors endow MnPSe3/CrSiTe3 heterostructures with great potential in novel applications, such as strain sensors, photocatalysis, spintronic and photoelectronic devices.

Efficient band structure modulations in two-dimensional MnPSe3/CrSiTe3 van der Waals heterostructures.

PubMed

Pei, Qi; Wang, Xiaocha; Zou, Jijun; Mi, Wenbo

2018-05-25

As a research upsurge, van der Waals (vdW) heterostructures give rise to numerous combined merits and novel applications in nanoelectronics fields. Here, we systematically investigate the electronic structure of MnPSe 3 /CrSiTe 3 vdW heterostructures with various stacking patterns. Then, particular attention of this work is paid on the band structure modulations in MnPSe 3 /CrSiTe 3 vdW heterostructures via biaxial strain or electric field. Under a tensile strain, the relative band edge positions of heterostructures transform from type-I (nested) to type-II (staggered). The relocation of conduction band minimum also brings about a transition from indirect to direct band gap. Under a compressive strain, the electronic properties change from semiconducting to metallic. The physical mechanism of strain-dependent band structure may be ascribed to the shifts of the energy bands impelled by different superposition of atomic orbitals. Meanwhile, our calculations manifest that band gap values of MnPSe 3 /CrSiTe 3 heterostructures are insensitive to the electric field. Even so, by applying a suitable intensity of negative electric field, the band alignment transition from type-I to type-II can also be realized. The efficient band structure modulations via external factors endow MnPSe 3 /CrSiTe 3 heterostructures with great potential in novel applications, such as strain sensors, photocatalysis, spintronic and photoelectronic devices.

Sensor array for toxic gas detection

DOEpatents

Stetter, Joseph R.; Zaromb, Solomon; Penrose, William R.

1987-01-01

A portable instrument for use in the field in detecting and identifying a hazardous component in air or other gas including an array of small sensors which upon exposure to the gas from a pattern of electrical responses, a source of standard response patterns characteristic of various components, and microprocessor means for comparing the sensor-formed response pattern with one or more standard patterns to thereby identify the component on a display. The number of responses may be increased beyond the number of sensors by changing the operating voltage, temperature or other condition associated with one or more sensors to provide a plurality of responses from each of one or more of the sensors. In one embodiment, the instrument is capable of identifying anyone of over 50-100 hazardous components.

Consideration of the effects of intense tissue heating on the RF electromagnetic fields during MRI: simulations for MRgFUS in the hip

NASA Astrophysics Data System (ADS)

Xuegang Xin, Sherman; Gu, Shiyong; Carluccio, Giuseppe; Collins, Christopher M.

2015-01-01

Due to the strong dependence of tissue electrical properties on temperature, it is important to consider the potential effects of intense tissue heating on the RF electromagnetic fields during MRI, as can occur in MR-guided focused ultrasound surgery. In principle, changes of the RF electromagnetic fields could affect both efficacy of RF pulses, and the MRI-induced RF heating (SAR) pattern. In this study, the equilibrium temperature distribution in a whole-body model with 2 mm resolution before and during intense tissue heating up to 60 °C at the target region was calculated. Temperature-dependent electric properties of tissues were assigned to the model to establish a temperature-dependent electromagnetic whole-body model in a 3T MRI system. The results showed maximum changes in conductivity, permittivity, ≤ft|\\mathbf{B}1+\\right|, and SAR of about 25%, 6%, 2%, and 20%, respectively. Though the B1 field and SAR distributions are both temperature-dependent, the potential harm to patients due to higher SARs is expected to be minimal and the effects on the B1 field distribution should have minimal effect on images from basic MRI sequences.

Tailored Fano resonance and localized electromagnetic field enhancement in Ag gratings

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

Li, Zhaozhu; Klopf, J. Michael; Wang, Lei

Metallic gratings can support Fano resonances when illuminated with EM radiation, and their characteristic reflectivity versus incident angle lineshape can be greatly affected by the surrounding dielectric environment and the grating geometry. By using conformal oblique incidence thin film deposition onto an optical grating substrate, it is possible to increase the grating amplitude due to shadowing effects, thereby enabling tailoring of the damping processes and electromagnetic field couplings of the Fano resonances, hence optimizing the associated localized electric field intensity. To investigate these effects we compare the optical reflectivity under resonance excitation in samples prepared by oblique angle deposition (OAD)more » and under normal deposition (ND) onto the same patterned surfaces. We observe that by applying OAD method, the sample exhibits a deeper and narrower reflectivity dip at resonance than that obtained under ND. This can be explained in terms of a lower damping of Fano resonance on obliquely deposited sample and leads to a stronger localized electric field. This approach opens a fabrication path for applications where tailoring the electromagnetic field induced by Fano resonance can improve the figure of merit of specific device characteristics, e.g. quantum efficiency (QE) in grating-based metallic photocathodes.« less

Tailored Fano resonance and localized electromagnetic field enhancement in Ag gratings

DOE PAGES

Li, Zhaozhu; Klopf, J. Michael; Wang, Lei; ...

2017-03-14

Metallic gratings can support Fano resonances when illuminated with EM radiation, and their characteristic reflectivity versus incident angle lineshape can be greatly affected by the surrounding dielectric environment and the grating geometry. By using conformal oblique incidence thin film deposition onto an optical grating substrate, it is possible to increase the grating amplitude due to shadowing effects, thereby enabling tailoring of the damping processes and electromagnetic field couplings of the Fano resonances, hence optimizing the associated localized electric field intensity. To investigate these effects we compare the optical reflectivity under resonance excitation in samples prepared by oblique angle deposition (OAD)more » and under normal deposition (ND) onto the same patterned surfaces. We observe that by applying OAD method, the sample exhibits a deeper and narrower reflectivity dip at resonance than that obtained under ND. This can be explained in terms of a lower damping of Fano resonance on obliquely deposited sample and leads to a stronger localized electric field. This approach opens a fabrication path for applications where tailoring the electromagnetic field induced by Fano resonance can improve the figure of merit of specific device characteristics, e.g. quantum efficiency (QE) in grating-based metallic photocathodes.« less

Analysis of Acoustic Emission Parameters from Corrosion of AST Bottom Plate in Field Testing

NASA Astrophysics Data System (ADS)

Jomdecha, C.; Jirarungsatian, C.; Suwansin, W.

Field testing of aboveground storage tank (AST) to monitor corrosion of the bottom plate is presented in this chapter. AE testing data of the ten AST with different sizes, materials, and products were employed to monitor the bottom plate condition. AE sensors of 30 and 150 kHz were used to monitor the corrosion activity of up to 24 channels including guard sensors. Acoustic emission (AE) parameters were analyzed to explore the AE parameter patterns of occurring corrosion compared to the laboratory results. Amplitude, count, duration, and energy were main parameters of analysis. Pattern recognition technique with statistical was implemented to eliminate the electrical and environmental noises. The results showed the specific AE patterns of corrosion activities related to the empirical results. In addition, plane algorithm was utilized to locate the significant AE events from corrosion. Both results of parameter patterns and AE event locations can be used to interpret and locate the corrosion activities. Finally, basic statistical grading technique was used to evaluate the bottom plate condition of the AST.

Electrical engram: how deep brain stimulation affects memory.

PubMed

Lee, Hweeling; Fell, Jürgen; Axmacher, Nikolai

2013-11-01

Deep brain stimulation (DBS) is a surgical procedure involving implantation of a pacemaker that sends electric impulses to specific brain regions. DBS has been applied in patients with Parkinson's disease, depression, and obsessive-compulsive disorder (among others), and more recently in patients with Alzheimer's disease to improve memory functions. Current DBS approaches are based on the concept that high-frequency stimulation inhibits or excites specific brain regions. However, because DBS entails the application of repetitive electrical stimuli, it primarily exerts an effect on extracellular field-potential oscillations similar to those recorded with electroencephalography. Here, we suggest a new perspective on how DBS may ameliorate memory dysfunction: it may enhance normal electrophysiological patterns underlying long-term memory processes within the medial temporal lobe. Copyright © 2013 Elsevier Ltd. All rights reserved.

Magnetoelectricity in Multi-Scale Composites and Application in Nanorobotics for Live Cell Manipulation

NASA Astrophysics Data System (ADS)

Betal, Soutik

In this research biomedical and sensor applications of magnetoelectric effect have been broadly explored using magnetoelectric composites. Firstly NiFe2O4/Pb(Zr0.52Ti0.48)O 3/NiFe2O4 layered bulk composite have been studied to achieve high magnetoelectric coefficient for their applications in brain magnetic field detection at room temperature. Magnetic sensors like SQUID (superconducting quantum interference device) nowadays are able to detect pico-Tesla magnetic fields produced outside the brain by the neuronal currents which can be used for diagnostic application, but due to heavy liquid helium cooling and insulation requirements, the technique become quite inefficient in gaining high resolution measurement. At room temperature layered ME samples exhibit high magnetoelectric response in mV/cm.Oe range and hence can transform very low magnetic field into electric signal which can be measured even in femtovolts. Moreover temperature and a.c. frequency dependent studies were done to extensively characterize the layered ME sample for sensor application. Secondly core-shell magnetoelectric nanoparticles (CSMEN) have been fabricated, characterized and their interaction with biological cell in presence of a.c. and d.c. field have been thoroughly analyzed. A magnetically controlled elastically driven electroporation phenomenon, or Magneto-Elasto- Electroporation (MEEP), is discovered while studying interactions between core-shell magneto-electric nanoparticles (CSMEN) and biological cells in the presence of an AC magnetic field. In this research MEEP effect was observed via a series of in-vitro experiments using core (CoFe2O4)-shell (BaTiO3 ) structured magnetoelectric nanoparticles and human epithelial cells (HEP2). Cell electroporation phenomenon and its correlation with the magnetic field modulated CSMEN have been elaborately studied. Potential of CSMEN for application in targeted single cell electroporation have been confirmed by analysing crystallographic phases, multiferroic properties of the fabricated CSMEN , influences of DC and AC magnetic field on the CSMEN and cytotoxicity tests. We also report the mathematical formalism to quantitatively describe the phenomena. The reported findings provide the basis of the underlying MEEP mechanism and demonstrate the utility of CSMEN as electric pulse generating nano-probe in cell electroporation experiments for the potential application towards accurate and efficient targeted cell permeation as well as drug delivery. Thirdly, experiments of fabricated magnetoelectric nanocomposites with biological cells in controlled boundary condition under fluctuating and biased magnetic field excitation revealed the smart nanorobotics characteristics of the nanostructure to achieve remote controlled dynamically targeted live cell manipulation. A remotely controlled dynamic process of manipulating targeted biological live cells using fabricated core-shell magnetoelectric nanocomposites have been fabricated, which comprises of single crystalline ferromagnetic cores (CoFe2O4) coated with crystalline ferroelectric thin film shells (BaTiO3). These nanocomposites are demonstrated as a unique family of inorganic magnetoelectric nanorobots (MENRs), controlled remotely by applied a.c. or d.c. magnetic fields, to perform cell targeting, permeation, patterning and transport. MENRs performs these functions via localized electric periodic pulse generation, local electric-field sensing, or thrust generation and acts as a unique tool for remotely controlled dynamically targeted cellular manipulation. Under a.c. magnetic field excitation (50 Oe, 60 Hz), the MENR acts as a localized periodic electric pulse generator and can permeate a series of misaligned cells, while aligning/patterning them to an equipotential mono-array. Under a.c. magnetic field (40 Oe, 30 Hz) excitation, MENRs can be dynamically driven to a targeted cell, avoiding untargeted cells in the path, irrespective of cell density. D.C. magnetic field (-50 Oe) excitation causes the MENRs to act as thrust generator and exerts motion in a group of cells. Visualization of magnetoelectricity at nanoscale and its application in dynamically targeted live cell manipulation have been presented in this research.

External-Field-Induced Gradient Wetting for Controllable Liquid Transport: From Movement on the Surface to Penetration into the Surface.

PubMed

Li, Yan; He, Linlin; Zhang, Xiaofang; Zhang, Na; Tian, Dongliang

2017-12-01

External-field-responsive liquid transport has received extensive research interest owing to its important applications in microfluidic devices, biological medical, liquid printing, separation, and so forth. To realize different levels of liquid transport on surfaces, the balance of the dynamic competing processes of gradient wetting and dewetting should be controlled to achieve good directionality, confined range, and selectivity of liquid wetting. Here, the recent progress in external-field-induced gradient wetting is summarized for controllable liquid transport from movement on the surface to penetration into the surface, particularly for liquid motion on, patterned wetting into, and permeation through films on superwetting surfaces with external field cooperation (e.g., light, electric fields, magnetic fields, temperature, pH, gas, solvent, and their combinations). The selected topics of external-field-induced liquid transport on the different levels of surfaces include directional liquid motion on the surface based on the wettability gradient under an external field, partial entry of a liquid into the surface to achieve patterned surface wettability for printing, and liquid-selective permeation of the film for separation. The future prospects of external-field-responsive liquid transport are also discussed. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Proton beam shaped by “particle lens” formed by laser-driven hot electrons

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

Zhai, S. H.; Shen, B. F., E-mail: bfshen@mail.shcnc.ac.cn, E-mail: wwpvin@hotmail.com, E-mail: yqgu@caep.cn; Wang, W. P., E-mail: bfshen@mail.shcnc.ac.cn, E-mail: wwpvin@hotmail.com, E-mail: yqgu@caep.cn

2016-05-23

Two-dimensional tailoring of a proton beam is realized by a “particle lens” in our experiment. A large quantity of electrons, generated by an intense femtosecond laser irradiating a polymer target, produces an electric field strong enough to change the trajectory and distribution of energetic protons flying through the electron area. The experiment shows that a strip pattern of the proton beam appears when hot electrons initially converge inside the plastic plate. Then the shape of the proton beam changes to a “fountain-like” pattern when these hot electrons diffuse after propagating a distance.

Particle Line Assembly/Patterning by Microfluidic AC Electroosmosis

NASA Astrophysics Data System (ADS)

Lian, Meng; Islam, Nazmul; Wu, Jie

2006-04-01

Recently AC electroosmosis has attracted research interests worldwide. This paper is the first to investigate particle line assembly/patterning by AC electroosmosis. Since AC electroosmotic force has no dependence on particle sizes, this technique is particularly useful for manipulating nanoscale substance, and hopefully constructs functional nanoscale devices. Two types of ACEO devices, in the configurations of planar interdigitated electrodes and parallel plate electrodes, and a biased ACEO technique are studied, which provides added flexibility in particle manipulation and line assembly. The paper also investigates the effects of electrical field distributions on generating microflows for particle assembly. The results are corroborated experimentally.

Calligraphic Poling of Ferroelectric Material

NASA Technical Reports Server (NTRS)

Mohageg, Makan; Strekalov, Dmitry; Savchenkov, Anatoliy; Matsko, Adrey; Maleki, Lute; Iltchenko, Vladimir

2007-01-01

Calligraphic poling is a technique for generating an arbitrary, possibly complex pattern of localized reversal in the direction of permanent polarization in a wafer of LiNbO3 or other ferroelectric material. The technique is so named because it involves a writing process in which a sharp electrode tip is moved across a surface of the wafer to expose the wafer to a polarizing electric field in the desired pattern. The technique is implemented by use of an apparatus, denoted a calligraphic poling machine (CPM), that includes the electrode and other components as described in more detail below.

Simulating and discussion on surface plasmon typical optical properties of patterned periodic metallic nanostructures

NASA Astrophysics Data System (ADS)

Liu, Runhan; Yuan, Ying; Long, Huabao; Peng, Sha; Wei, Dong; Zhang, Xinyu; Wang, Haiwei; Xie, Changsheng

2018-02-01

The intense surface plasmons (SPs) can be generated by patterned metal nano-structure arrays, through coupling incident light onto the functioned metal surface, so as to construct highly constrained surface electromagnetic modes. Therefore, a localized micro-nano-field array with a highly compressed surface electron distribution, can also be shaped and even nano-focused over the surface, which will lead to a lot of special physical effects such as anti-reflection effect, and thus indicate many new potential applications in the field of nano-photonics and -optoelectronics. In this paper, several typical patterned sub-wavelength metal nano-structure arrays were designed according to the process, in which common silicon wafer was employed as the substrate material and aluminum as the metal film with different structural size and arrangement circle. In addition, by adjusting the dielectric constant of metal material appropriately, the power control effect on metallic nanostructure was simulated. The key properties such as the excitation intensity of the surface plasmons were studied by simulating the reflectivity characteristic curves and the electric field distribution of the nanostructure excited by incident infrared beams. It is found that the angle of corners, the arrangement cycle and the metal material properties of the patterned nano-structures can be utilized as key factors to control the excitation intensity of surface plasmons.

Electric Field Sensor for Lightning Early Warning System

NASA Astrophysics Data System (ADS)

Premlet, B.; Mohammed, R.; Sabu, S.; Joby, N. E.

2017-12-01

Electric field mills are used popularly for atmospheric electric field measurements. Atmospheric Electric Field variation is the primary signature for Lightning Early Warning systems. There is a characteristic change in the atmospheric electric field before lightning during a thundercloud formation.A voltage controlled variable capacitance is being proposed as a method for non-contacting measurement of electric fields. A varactor based mini electric field measurement system is developed, to detect any change in the atmospheric electric field and to issue lightning early warning system. Since this is a low-cost device, this can be used for developing countries which are facing adversities. A network of these devices can help in forming a spatial map of electric field variations over a region, and this can be used for more improved atmospheric electricity studies in developing countries.

Apparatuses and methods for generating electric fields

DOEpatents

Scott, Jill R; McJunkin, Timothy R; Tremblay, Paul L

2013-08-06

Apparatuses and methods relating to generating an electric field are disclosed. An electric field generator may include a semiconductive material configured in a physical shape substantially different from a shape of an electric field to be generated thereby. The electric field is generated when a voltage drop exists across the semiconductive material. A method for generating an electric field may include applying a voltage to a shaped semiconductive material to generate a complex, substantially nonlinear electric field. The shape of the complex, substantially nonlinear electric field may be configured for directing charged particles to a desired location. Other apparatuses and methods are disclosed.

Aircraft measurements of the atmospheric electrical global circuit during the period 1971-1984

NASA Technical Reports Server (NTRS)

Markson, R.

1985-01-01

This report will update an investigation of the global circuit conducted over the last 14 years through aircraft measurements of the variation of ionospheric potential and associated parameters. The data base included electric field, conductivity, and air-earth current density profiles from the tropics (25 deg N) to the Arctic (79 deg N). Almost all of the data have been obtained over the ocean to reduce noise associated with local generators, aerosols, and convection. Recently, two aircraft have been utilized to obtain, for the first time, quasi-periodic sets of simultaneous ionospheric potential (VI) soundings at remote locations and extending over time spans sufficiently long so that the universal time diurnal variation (Carnegie curve) could be observed. In additon, these measurements provided the first detection of the modulation of electric fields in the troposphere caused by the double vortex ionospheric convection pattern. Besides summarizing these measurements and comparing them to similar data obtained by other groups, this report discusses meteorological sources of error and criteria for determining if the global circuit is being measured rather than variations caused by local meteorological processes.

Magnetically Responsive Optical Nanoprobes (MagRONs) and Systems

DTIC Science & Technology

2004-02-28

5f. WORK UNIT NUMBER 7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) 8. PERFORMING ORGANIZATION REPORT NUMBER The regents of the University of...research. MagMOON Architechtures I Controlled deposition of magnetic materials onto any nanosensor Prism coated nanoparticles Electric field sensors...into a predefined pattern has been the focus of many investigations.[7-11] For example, strawberry-like composite materials using organic -inorganic

Time-to-space mapping of femtosecond pulses.

PubMed

Nuss, M C; Li, M; Chiu, T H; Weiner, A M; Partovi, A

1994-05-01

We report time-to-space mapping of femtosecond light pulses in a temporal holography setup. By reading out a temporal hologram of a short optical pulse with a continuous-wave diode laser, we accurately convert temporal pulse-shape information into a spatial pattern that can be viewed with a camera. We demonstrate real-time acquisition of electric-field autocorrelation and cross correlation of femtosecond pulses with this technique.

Exploring Instructive Physiological Signaling with the Bioelectric Tissue Simulation Engine

PubMed Central

Pietak, Alexis; Levin, Michael

2016-01-01

Bioelectric cell properties have been revealed as powerful targets for modulating stem cell function, regenerative response, developmental patterning, and tumor reprograming. Spatio-temporal distributions of endogenous resting potential, ion flows, and electric fields are influenced not only by the genome and external signals but also by their own intrinsic dynamics. Ion channels and electrical synapses (gap junctions) both determine, and are themselves gated by, cellular resting potential. Thus, the origin and progression of bioelectric patterns in multicellular tissues is complex, which hampers the rational control of voltage distributions for biomedical interventions. To improve understanding of these dynamics and facilitate the development of bioelectric pattern control strategies, we developed the BioElectric Tissue Simulation Engine (BETSE), a finite volume method multiphysics simulator, which predicts bioelectric patterns and their spatio-temporal dynamics by modeling ion channel and gap junction activity and tracking changes to the fundamental property of ion concentration. We validate performance of the simulator by matching experimentally obtained data on membrane permeability, ion concentration and resting potential to simulated values, and by demonstrating the expected outcomes for a range of well-known cases, such as predicting the correct transmembrane voltage changes for perturbation of single cell membrane states and environmental ion concentrations, in addition to the development of realistic transepithelial potentials and bioelectric wounding signals. In silico experiments reveal factors influencing transmembrane potential are significantly different in gap junction-networked cell clusters with tight junctions, and identify non-linear feedback mechanisms capable of generating strong, emergent, cluster-wide resting potential gradients. The BETSE platform will enable a deep understanding of local and long-range bioelectrical dynamics in tissues, and assist the development of specific interventions to achieve greater control of pattern during morphogenesis and remodeling. PMID:27458581

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

Combining sprinkling experiments and superconducting gravimetry in the field: a qualitative approach to identify dominant infiltration patterns

NASA Astrophysics Data System (ADS)

Reich, Marvin; Mikolaj, Michal; Blume, Theresa; Güntner, Andreas

2017-04-01

Hydrological process research at the plot to catchment scale commonly involves invasive field methods, leading to a large amount of point data. A promising alternative, which gained increasing interest in the hydrological community over the last years, is gravimetry. The combination of its non-invasive and integrative nature opens up new possibilities to approach hydrological process research. In this study we combine a field-scale sprinkling experiment with continuous superconducting gravity (SG) measurements. The experimental design consists of 8 sprinkler units, arranged symmetrically within a radius of about ten meters around an iGrav (SG) in a field enclosure. The gravity signal of the infiltrating sprinkling water is analyzed using a simple 3D water mass distribution model. We first conducted a number of virtual sprinkling experiments resulting in different idealized infiltration patterns and determined the pattern specific gravity response. In a next step we determined which combination of idealized infiltration patterns was able to reproduce the gravity response of our real-world experiment at the Wettzell Observatory (Germany). This process hypothesis is then evaluated with measured point-scale soil moisture responses and the results of the time-lapse electric resistivity survey which was carried out during the sprinkling experiment. This study demonstrates that a controlled sprinkling experiment around a gravimeter in combination with a simple infiltration model is sufficient to identify subsurface flow patterns and thus the dominant infiltration processes. As gravimeters become more portable and can actually be deployed in the field, their combination with sprinkling experiments as shown here constitutes a promising possibility to investigate hydrological processes in a non-invasive way.

Distribution of electric currents in sunspots from photosphere to corona

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

Gosain, Sanjay; Démoulin, Pascal; López Fuentes, Marcelo

2014-09-20

We present a study of two regular sunspots that exhibit nearly uniform twist from the photosphere to the corona. We derive the twist parameter in the corona and in the chromosphere by minimizing the difference between the extrapolated linear force-free field model field lines and the observed intensity structures in the extreme-ultraviolet images of the Sun. The chromospheric structures appear more twisted than the coronal structures by a factor of two. Further, we derive the vertical component of electric current density, j{sub z} , using vector magnetograms from the Hinode Solar Optical Telescope (SOT). The spatial distribution of j{sub z}more » has a zebra pattern of strong positive and negative values owing to the penumbral fibril structure resolved by Hinode/SOT. This zebra pattern is due to the derivative of the horizontal magnetic field across the thin fibrils; therefore, it is strong and masks weaker currents that might be present, for example, as a result of the twist of the sunspot. We decompose j{sub z} into the contribution due to the derivatives along and across the direction of the horizontal field, which follows the fibril orientation closely. The map of the tangential component has more distributed currents that are coherent with the chromospheric and coronal twisted structures. Moreover, it allows us to map and identify the direct and return currents in the sunspots. Finally, this decomposition of j{sub z} is general and can be applied to any vector magnetogram in order to better identify the weaker large-scale currents that are associated with coronal twisted/sheared structures.« less

Silicon-Based Chemical Motors: An Efficient Pump for Triggering and Guiding Fluid Motion Using Visible Light.

PubMed

Esplandiu, Maria J; Farniya, Ali Afshar; Bachtold, Adrian

2015-11-24

We report a simple yet highly efficient chemical motor that can be controlled with visible light. The motor made from a noble metal and doped silicon acts as a pump, which is driven through a light-activated catalytic reaction process. We show that the actuation is based on electro-osmosis with the electric field generated by chemical reactions at the metal and silicon surfaces, whereas the contribution of diffusio-osmosis to the actuation is negligible. Surprisingly, the pump can be operated using water as fuel. This is possible because of the large ζ-potential of silicon, which makes the electro-osmotic fluid motion sizable even though the electric field generated by the reaction is weak. The electro-hydrodynamic process is greatly amplified with the addition of reactive species, such as hydrogen peroxide, which generates higher electric fields. Another remarkable finding is the tunability of silicon-based pumps. That is, it is possible to control the speed of the fluid with light. We take advantage of this property to manipulate the spatial distribution of colloidal microparticles in the liquid and to pattern colloidal microparticle structures at specific locations on a wafer surface. Silicon-based pumps hold great promise for controlled mass transport in fluids.

Global scale equatorial ionization anomaly (EIA) response to magnetospheric disturbances based on the May-June 1987 SUNDIAL-coordinated observations

NASA Astrophysics Data System (ADS)

Abdu, M. A.; Walker, G. O.; Reddy, B. M.; de Paula, E. R.; Sobral, J. H. A.; Fejer, B. G.

1993-07-01

Equatorial ionization anomaly (EIA) responses to magnetospheric disturbances have been investigated using ionosonde and geomagnetic data sets obtained for different longitude sectors during the 9-day (28 May-7 June) globally-coordinated SUNDIAL 87 campaign. Attention is focused on the EIA response features of the two magnetically most-disturbed days of the campaign window, 29 May and 6 June. Anomalous EIA inhibition and development were simultaneously observed at widely separated (American and Asian) longitude sectors, accompanied respectively by events of morning electrojet reversal and evening partial ring current development. A numerical model of the low-latitude ionosphere has been used to quantify the role that a disturbance electric field could play in the observed EIA response features. The implications of the results on the global low-latitude disturbance electric field pattern is discussed.

Theory of Charged Quantum Dot Molecules

NASA Astrophysics Data System (ADS)

Ponomarev, I. V.; Scheibner, M.; Stinaff, E. A.; Bracker, A. S.; Doty, M. F.; Ware, M. E.; Gammon, D.; Reinecke, T. L.; Korenev, V. L.

2006-03-01

Recent optical spectroscopy of excitonic molecules in coupled quantum dots (CQDs) tuned by electric field reveal a richer diversity in spectral line patterns than in their single quantum dot counterparts. We developed a theoretical model that allows us to classify energies and intensities of various PL transitions. In this approach the electric field induced resonance tunneling of the electron and hole states occurs at different biases due to the inherent asymmetry of CQDs. The truncated many-body basis configurations for each molecule are constructed from antisymmetrized products of single-particle states, where the electron occupies only one ground state level in single QD and the hole can occupy two lowest levels of CQD system. The Coulomb interaction between particles is treated with perturbation theory. As a result the observed PL spectral lines can be described with a small number of parameters. The theoretical predictions account well for recent experiments.

Spectroscopy of Charged Quantum Dot Molecules

NASA Astrophysics Data System (ADS)

Stinaff, E. A.; Scheibner, M.; Bracker, A. S.; Ponomarev, I. V.; Ware, M. E.; Doty, M. F.; Reinecke, T. L.; Gammon, D.; Korenev, V. L.

2006-03-01

Spins of single charges in quantum dots are attractive for many quantum information and spintronic proposals. Scalable quantum information applications require the ability to entangle and operate on multiple spins in coupled quantum dots (CQDs). To further the understanding of these systems, we present detailed spectroscopic studies of InAs CQDs with control of the discrete electron or hole charging of the system. The optical spectrum reveals a pattern of energy anticrossings and crossings in the photoluminescence as a function of applied electric field. These features can be understood as a superposition of charge and spin configurations of the two dots and represent clear signatures of quantum mechanical coupling. The molecular resonance leading to these anticrossings is achieved at different electric fields for the optically excited (trion) states and the ground (hole) states allowing for the possibility of using the excited states for optically induced coupling of the qubits.

Effect of the electric field pattern on the generation of fast electrons in front of lower hybrid launchers

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

Valade, Laurent, E-mail: laurent.valade@cea.fr; Ekedahl, Annika; Colas, Laurent

2015-12-10

The effect of the detailed waveguide spectrum on the electron acceleration has been studied for the 3.7 GHz LHCD launchers in Tore Supra, i.e. the ITER-like passive-active multijunction (PAM) launcher and the fully-active-multijunction (FAM) launcher, using test electron modelling technique. The detailed launched antenna wave spectrum is used as input to the code that computes the dynamics of the electrons in the electric field. Comparison with the LHCD launchers in EAST, operating at 2.45 GHz and 4.6 GHz, has also been made. The simulations show that the PAM-design generates lower flux of fast electrons than FAM-launchers, this could be themore » consequence of the wider waveguide of PAM-launcher (14.65 mm for Tore-Supra) than FAM-launcher (8 mm for Tore-Supra)« less

Modeling and simulations of the double-probe electric field instrument in tenuous and cold streaming plasmas

NASA Astrophysics Data System (ADS)

Miyake, Y.; Cully, C. M.; Usui, H.; Nakashima, H.

2013-12-01

In order to increase accuracy and reliability of in-situ measurements made by scientific spacecraft, it is imperative to develop comprehensive understanding of spacecraft-plasma interactions. In space environments, not only the spacecraft charging but also surrounding plasma disturbances such as caused by the wake formation may interfere directly with in-situ measurements. The self-consistent solutions of such phenomena are necessary to assess their effects on scientific spacecraft systems. As our recent activity, we work on the modeling and simulations of Cluster double-probe instrument in tenuous and cold streaming plasmas [1]. Double-probe electric field sensors are often deployed using wire booms with radii much less than typical Debye lengths of magnetospheric plasmas (millimeters compared to tens of meters). However, in tenuous and cold streaming plasmas seen in the polar cap and lobe regions, the wire booms have a high positive potential due to photoelectron emission and can strongly scatter approaching ions. Consequently, an electrostatic wake formed behind the spacecraft is further enhanced by the presence of the wire booms. We reproduce this process for the case of the Cluster satellite by performing plasma particle-in-cell (PIC) simulations [2], which include the effects of both the spacecraft body and the wire booms in a simultaneous manner, on modern supercomputers. The simulations reveal that the effective thickness of the booms for the Cluster Electric Field and Wave (EFW) instrument is magnified from its real thickness (2.2 millimeters) to several meters, when the spacecraft potential is at 30-40 volts. Such booms enhance the wake electric field magnitude by a factor of about 2 depending on the spacecraft potential, and play a principal role in explaining the in situ Cluster EFW data showing sinusoidal spurious electric fields of about 10 mV/m amplitudes. The boom effects are quantified by comparing PIC simulations with and without wire booms. The paper also reports some recent progress of ongoing PIC simulation research that focuses on spurious electric field generation in subsonic ion flows. Our preliminary simulation results revealed that; (1) there is no apparent wake signature behind the spacecraft in such a condition, but (2) spurious electric field over 1 mV/m amplitude is observed in the direction of the flow vector. The observed field amplitude is sometimes comparable to the convection electric field (a few mV/m) associated with the flow. Our analysis also confirmed that the spurious field is caused by a weakly-asymmetric potential pattern created by the ion flow. We will present the parametric study of such spurious fields for various conditions of plasma flows. [References] [1] Miyake, Y., C. M. Cully, H. Usui, and H. Nakashima (2013), Plasma particle simulations of wake formation behind a spacecraft with thin wire booms, submitted to J. Geophys. Res. [2] Miyake, Y., and H. Usui (2009), New electromagnetic particle simulation code for the analysis of spacecraft-plasma interactions, Phys. Plasmas, 16, 062904, doi:10.1063/1.3147922.

Electro-osmosis of nematic liquid crystals under weak anchoring and second-order surface effects

NASA Astrophysics Data System (ADS)

Poddar, Antarip; Dhar, Jayabrata; Chakraborty, Suman

2017-07-01

Advent of nematic liquid crystal flows has attracted renewed attention in view of microfluidic transport phenomena. Among various transport processes, electro-osmosis stands as one of the efficient flow actuation mechanisms through narrow confinements. In the present study, we explore the electrically actuated flow of an ordered nematic fluid with ionic inclusions, taking into account the influences from surface-induced elasticity and electrical double layer (EDL) phenomena. Toward this, we devise the coupled flow governing equations from fundamental free-energy analysis, considering the contributions from first- and second-order elastic, dielectric, flexoelectric, charged surface polarization, ionic and entropic energies. The present study focuses on the influence of surface charge and elasticity effects in the resulting linear electro-osmosis through a slit-type microchannel whose surfaces are chemically treated to display a homeotropic-type weak anchoring state. An optical periodic stripe configuration of the nematic director has been observed, especially for higher electric fields, wherein the Ericksen number for the dynamic study is restricted to the order of unity. Contrary to the isotropic electrolytes, the EDL potential in this case was found to be dependent on the external field strength. Through a systematic investigation, we brought out the fact that the wavelength of the oscillating patterns is dictated mainly by the external field, while the amplitude depends on most of the physical variables ranging from the anchoring strength and the flexoelectric coefficients to the surface charge density and electrical double layer thickness.

Saturation of the Electric Field Transmitted to the Magnetosphere

NASA Technical Reports Server (NTRS)

Lyatsky, Wladislaw; Khazanov, George V.; Slavin, James A.

2010-01-01

We reexamined the processes leading to saturation of the electric field, transmitted into the Earth's ionosphere from the solar wind, incorporating features of the coupled system previously ignored. We took into account that the electric field is transmitted into the ionosphere through a region of open field lines, and that the ionospheric conductivity in the polar cap and auroral zone may be different. Penetration of the electric field into the magnetosphere is linked with the generation of the Alfven wave, going out from the ionosphere into the solar wind and being coupled with the field-aligned currents at the boundary of the open field limes. The electric field of the outgoing Alfven wave reduces the original electric field and provides the saturation effect in the electric field and currents during strong geomagnetic disturbances, associated with increasing ionospheric conductivity. The electric field and field-aligned currents of this Alfven wave are dependent on the ionospheric and solar wind parameters and may significantly affect the electric field and field-aligned currents, generated in the polar ionosphere. Estimating the magnitude of the saturation effect in the electric field and field-aligned currents allows us to improve the correlation between solar wind parameters and resulting disturbances in the Earth's magnetosphere.

Application of the aberration ring test (ARTEMIS) to determine lens quality and predict its lithographic performance

NASA Astrophysics Data System (ADS)

Moers, Marco H. P.; van der Laan, Hans; Zellenrath, Mark; de Boeij, Wim; Beaudry, Neil A.; Cummings, Kevin D.; van Zwol, Adriaan; Brecht, Arthur; Willekers, Rob

2001-09-01

ARTEMISTM (Aberration Ring Test Exposed at Multiple Illumination Settings) is a technique to determine in-situ, full-field, low and high order lens aberrations. In this paper we are analyzing the ARTEMISTM data of PAS5500/750TM DUV Step & Scan systems and its use as a lithographic prediction tool. ARTEMISTM is capable of determining Zernike coefficients up to Z25 with a 3(sigma) reproducibility range from 1.5 to 4.5 nm depending on the aberration type. 3D electric field simulations, that take the extended geometry of the phase shift feature into account, have been used for an improved treatment of the extraction of the spherical Zernike coefficients. Knowledge of the extracted Zernike coefficients allows an accurate prediction of the lithographic performance of the scanner system. This ability is demonstrated for a two bar pattern and an isolation pattern. The RMS difference between the ARTEMISTM-based lithographic prediction and the lithographic measurement is 2.5 nm for the two bar pattern and 3 nm for the isolation pattern. The 3(sigma) reproducibility of the prediction for the two bar pattern is 2.5 nm and 1 nm for the isolation pattern. This is better than the reproducibility of the lithographic measurements themselves.

Field induced transient current in one-dimensional nanostructure

NASA Astrophysics Data System (ADS)

Sako, Tokuei; Ishida, Hiroshi

2018-07-01

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

Bioelectrical Signals and Ion Channels in the Modeling of Multicellular Patterns and Cancer Biophysics.

PubMed

Cervera, Javier; Alcaraz, Antonio; Mafe, Salvador

2016-02-04

Bioelectrical signals and ion channels are central to spatial patterns in cell ensembles, a problem of fundamental interest in positional information and cancer processes. We propose a model for electrically connected cells based on simple biological concepts: i) the membrane potential of a single cell characterizes its electrical state; ii) the long-range electrical coupling of the multicellular ensemble is realized by a network of gap junction channels between neighboring cells; and iii) the spatial distribution of an external biochemical agent can modify the conductances of the ion channels in a cell membrane and the multicellular electrical state. We focus on electrical effects in small multicellular ensembles, ignoring slow diffusional processes. The spatio-temporal patterns obtained for the local map of cell electric potentials illustrate the normalization of regions with abnormal cell electrical states. The effects of intercellular coupling and blocking of specific channels on the electrical patterns are described. These patterns can regulate the electrically-induced redistribution of charged nanoparticles over small regions of a model tissue. The inclusion of bioelectrical signals provides new insights for the modeling of cancer biophysics because collective multicellular states show electrical coupling mechanisms that are not readily deduced from biochemical descriptions at the individual cell level.

Bioelectrical Signals and Ion Channels in the Modeling of Multicellular Patterns and Cancer Biophysics

PubMed Central

Cervera, Javier; Alcaraz, Antonio; Mafe, Salvador

2016-01-01

Bioelectrical signals and ion channels are central to spatial patterns in cell ensembles, a problem of fundamental interest in positional information and cancer processes. We propose a model for electrically connected cells based on simple biological concepts: i) the membrane potential of a single cell characterizes its electrical state; ii) the long-range electrical coupling of the multicellular ensemble is realized by a network of gap junction channels between neighboring cells; and iii) the spatial distribution of an external biochemical agent can modify the conductances of the ion channels in a cell membrane and the multicellular electrical state. We focus on electrical effects in small multicellular ensembles, ignoring slow diffusional processes. The spatio-temporal patterns obtained for the local map of cell electric potentials illustrate the normalization of regions with abnormal cell electrical states. The effects of intercellular coupling and blocking of specific channels on the electrical patterns are described. These patterns can regulate the electrically-induced redistribution of charged nanoparticles over small regions of a model tissue. The inclusion of bioelectrical signals provides new insights for the modeling of cancer biophysics because collective multicellular states show electrical coupling mechanisms that are not readily deduced from biochemical descriptions at the individual cell level. PMID:26841954

Bioelectrical Signals and Ion Channels in the Modeling of Multicellular Patterns and Cancer Biophysics

NASA Astrophysics Data System (ADS)

Cervera, Javier; Alcaraz, Antonio; Mafe, Salvador

2016-02-01

Bioelectrical signals and ion channels are central to spatial patterns in cell ensembles, a problem of fundamental interest in positional information and cancer processes. We propose a model for electrically connected cells based on simple biological concepts: i) the membrane potential of a single cell characterizes its electrical state; ii) the long-range electrical coupling of the multicellular ensemble is realized by a network of gap junction channels between neighboring cells; and iii) the spatial distribution of an external biochemical agent can modify the conductances of the ion channels in a cell membrane and the multicellular electrical state. We focus on electrical effects in small multicellular ensembles, ignoring slow diffusional processes. The spatio-temporal patterns obtained for the local map of cell electric potentials illustrate the normalization of regions with abnormal cell electrical states. The effects of intercellular coupling and blocking of specific channels on the electrical patterns are described. These patterns can regulate the electrically-induced redistribution of charged nanoparticles over small regions of a model tissue. The inclusion of bioelectrical signals provides new insights for the modeling of cancer biophysics because collective multicellular states show electrical coupling mechanisms that are not readily deduced from biochemical descriptions at the individual cell level.

Electromagnetic holographic sensitivity field of two-phase flow in horizontal wells

NASA Astrophysics Data System (ADS)

Zhang, Kuo; Wu, Xi-Ling; Yan, Jing-Fu; Cai, Jia-Tie

2017-03-01

Electromagnetic holographic data are characterized by two modes, suggesting that image reconstruction requires a dual-mode sensitivity field as well. We analyze an electromagnetic holographic field based on tomography theory and Radon inverse transform to derive the expression of the electromagnetic holographic sensitivity field (EMHSF). Then, we apply the EMHSF calculated by using finite-element methods to flow simulations and holographic imaging. The results suggest that the EMHSF based on the partial derivative of radius of the complex electric potential φ is closely linked to the Radon inverse transform and encompasses the sensitivities of the amplitude and phase data. The flow images obtained with inversion using EMHSF better agree with the actual flow patterns. The EMHSF overcomes the limitations of traditional single-mode sensitivity fields.

Electrically induced contraction levels of the quadriceps femoris muscles in healthy men: the effects of three patterns of burst-modulated alternating current and volitional muscle fatigue.

PubMed

Parker, Michael G; Broughton, Alex J; Larsen, Ben R; Dinius, Josh W; Cimbura, Mac J; Davis, Matthew

2011-12-01

The purpose of this study was to compare electrically induced contraction levels produced by three patterns of alternating current in fatigued and nonfatigued skeletal muscles. Eighteen male volunteers without health conditions, with a mean (SD) age of 24.9 (3.4) yrs were randomly exposed to a fatiguing volitional isometric quadriceps contraction and one of three patterns of 2.5-KHz alternating current; two were modulated at 50 bursts per second (10% burst duty cycle with five cycles per burst and 90% burst duty cycle with 45 cycles per burst), and one pattern was modulated at 100 bursts per second (10% burst duty cycle with 2.5 cycles per burst). The electrically induced contraction levels produced by the three patterns of electrical stimulation were compared before and after the fatiguing contraction. The 10% burst duty cycles produced 42.9% (95% confidence interval, 29.1%-56.7%) and 32.1% (95% confidence interval, 18.2%-45.9%) more muscle force (P < 0.001) than did the 90% burst duty cycle pattern. There was no significant interaction effect (P = 0.392) of electrical stimulation patterns and fatigue on the electrically induced contraction levels. The lower burst duty cycle (10%) patterns of electrical stimulation produced stronger muscle contractions. Furthermore, the stimulation patterns had no influence on the difference in muscle force before and after the fatiguing quadriceps contraction. Consequently, for clinical applications in which high forces are desired, the patterns using the 10% burst duty cycle may be helpful.

Laser-driven electron acceleration in a plasma channel with an additional electric field

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

Cheng, Li-Hong; Xue, Ju-Kui, E-mail: xuejk@nwnu.edu.cn; Liu, Jie, E-mail: liu-jie@iapcm.ac.cn

2016-05-15

We examine the electron acceleration in a two-dimensional plasma channel under the action of a laser field and an additional static electric field. We propose to design an appropriate additional electric field (its direction and location), in order to launch the electron onto an energetic trajectory. We find that the electron acceleration strongly depends on the coupled effects of the laser polarization, the direction, and location of the additional electric field. The additional electric field affects the electron dynamics by changing the dephasing rate. Particularly, a suitably designed additional electric field leads to a considerable energy gain from the lasermore » pulse after the interaction with the additional electric field. The electron energy gain from the laser with the additional electric field can be much higher than that without the additional electric field. This engineering provides a possible means for producing high energetic electrons.« less

SansEC Sensing Technology - A New Tool for Designing Space Systems and Components

NASA Technical Reports Server (NTRS)

Woodard, Stanley E.

2011-01-01

This paper presents concepts for using the NASA developed SansEC sensing technology for reconfiguring/modifying many space subsystems to add to their original function the ability to be sensors/sensor arrays without the addition of the electrical circuitry typically used for sensors. Each sensor is a self-resonating planar pattern of electrically conductive material that is an open-circuit single component without electrical connections. The sensors are wirelessly powered using external oscillating magnetic fields and when electrically excited respond with their own magnetic fields whose frequency, amplitude and bandwidth can be correlated with the magnitude of multiple unrelated physical quantities. These sensors have been demonstrated for numerous measurements required for spacecraft and inflatable/expandable structures. SansEC sensors are damage resilient and simple to fabricate. Thin films of conductive material can be used to create sensor arrays that function as sensing skins. Each sensor on the skin can be tailored for a science or engineering measurement. Additionally, each sensor has an inherent damage detection capability. These sensing skins can be used to redesign inflatable habitat multi-layer insulation to provide additional functions of environmental measurement and micrometeorite/orbital debris damage detections. The sensing skins can be deposited on planetary exploratory vehicles to increase the number of measurements with negligible weight increase.

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

Auroral zone electric fields from DE 1 and 2 at magnetic conjunctions

NASA Technical Reports Server (NTRS)

Weimer, D. R.; Goertz, C. K.; Gurnett, D. A.; Maynard, N. C.; Burch, J. L.

1985-01-01

Nearly simultaneous measurements of auroral zone electric fields are obtained by the Dynamics Explorer spacecraft at altitudes below 900 km and above 4,500 km during magnetic conjunctions. The measured electric fields are usually perpendicular to the magnetic field lines. The north-south meridional electric fields are projected to a common altitude by a mapping function which accounts for the convergence of the magnetic field lines. When plotted as a function of invariant latitude, graphs of the projected electric fields measured by both DE-1 and DE-2 show that the large-scale electric field is the same at both altitudes, as expected. Superimposed on the large-scale fields, however, are small-scale features with wavelengths less than 100 km which are larger in magnitude at the higher altitude. Fourier transforms of the electric fields show that the magnitudes depend on wavelength. Outside of the auroral zone the electric field spectrums are nearly identical. But within the auroral zone the high and low altitude electric fields have a ratio which increases with the reciprocal of the wavelength. The small-scale electric field variations are associated with field-aligned currents. These currents are measured with both a plasma instrument and magnetometer on DE-1.

Patterning via optical saturable transitions

NASA Astrophysics Data System (ADS)

Cantu, Precious

For the past 40 years, optical lithography has been the patterning workhorse for the semiconductor industry. However, as integrated circuits have become more and more complex, and as device geometries shrink, more innovative methods are required to meet these needs. In the far-field, the smallest feature that can be generated with light is limited to approximately half the wavelength. This, so called far-field diffraction limit or the Abbe limit (after Prof. Ernst Abbe who first recognized this), effectively prevents the use of long-wavelength photons >300nm from patterning nanostructures <100nm. Even with a 193nm laser source and extremely complicated processing, patterns below ˜20nm are incredibly challenging to create. Sources with even shorter wavelengths can potentially be used. However, these tend be much more expensive and of much lower brightness, which in turn limits their patterning speed. Multi-photon reactions have been proposed to overcome the diffraction limit. However, these require very large intensities for modest gain in resolution. Moreover, the large intensities make it difficult to parallelize, thus limiting the patterning speed. In this dissertation, a novel nanopatterning technique using wavelength-selective small molecules that undergo single-photon reactions, enabling rapid top-down nanopatterning over large areas at low-light intensities, thereby allowing for the circumvention of the far-field diffraction barrier is developed and experimentally verified. This approach, which I refer to as Patterning via Optical Saturable Transitions (POST) has the potential for massive parallelism, enabling the creation of nanostructures and devices at a speed far surpassing what is currently possible with conventional optical lithographic techniques. The fundamental understanding of this technique goes beyond optical lithography in the semiconductor industry and is applicable to any area that requires the rapid patterning of large-area two or three-dimensional complex geometries. At a basic level, this research intertwines the fields of electrochemistry, material science, electrical engineering, optics, physics, and mechanical engineering with the goal of developing a novel super-resolution lithographic technique.

Analysis of Surface Electric Field Measurements from an Array of Electric Field Mills

NASA Astrophysics Data System (ADS)

Lucas, G.; Thayer, J. P.; Deierling, W.

2016-12-01

Kennedy Space Center (KSC) has operated an distributed array of over 30 electric field mills over the past 18 years, providing a unique data set of surface electric field measurements over a very long timespan. In addition to the electric field instruments there are many meteorological towers around KSC that monitor the local meteorological conditions. Utilizing these datasets we have investigated and found unique spatial and temporal signatures in the electric field data that are attributed to local meteorological effects and the global electric circuit. The local and global scale influences on the atmospheric electric field will be discussed including the generation of space charge from the ocean surf, local cloud cover, and a local enhancement in the electric field that is seen at sunrise.

Preliminary Findings from the One-Year Electric Field Study in the North Slope of Alaska (OYES-NSA), Atmospheric Radiation Measurement (ARM) Field Campaign

NASA Astrophysics Data System (ADS)

Lavigne, T.; Liu, C.

2017-12-01

Previous studies focusing on the comparison of the measured electric field to the physical properties of global electrified clouds have been conducted almost exclusively in the Southern Hemisphere. The One-Year Electric Field Study-North Slope of Alaska (OYES-NSA) aims to establish a long-running collection of this valuable electric field data in the Northern Hemisphere. Presented here is the six-month preliminary data and results of the OYES-NSA Atmospheric Radiation Mission (ARM) field campaign. The local electric field measured in Barrow, Alaska using two CS110 reciprocating shutter field meters, has been compared to simultaneous measurements from the ARM Ka-Band zenith radar, to better understand the influence and contribution of different types of clouds on the local electric field. The fair-weather electric field measured in Barrow has also been analyzed and compared to the climatology of electric field at Vostok Station, Antarctica. The combination of the electric field dataset in the Northern Hemisphere, alongside the local Ka cloud radar, global Precipitation Feature (PF) database, and quasi-global lightning activity (55oN-55oS), allows for advances in the physical understanding of the local electric field, as well as the Global Electric Circuit (GEC).

Fully synthetic taped insulation cables

DOEpatents

Forsyth, Eric B.; Muller, Albert C.

1984-01-01

A high voltage oil-impregnated electrical cable with fully polymer taped insulation operable to 765 kV. Biaxially oriented, specially processed, polyethylene, polybutene or polypropylene tape with an embossed pattern is wound in multiple layers over a conductive core with a permeable screen around the insulation. Conventional oil which closely matches the dielectric constant of the tape is used, and the cable can be impregnated after field installation because of its excellent impregnation characteristics.

Fabrication of an a-IGZO thin film transistor using selective deposition of cobalt by the self-assembly monolayer (SAM) process.

PubMed

Cho, Young-Je; Kim, HyunHo; Park, Kyoung-Yun; Lee, Jaegab; Bobade, Santosh M; Wu, Fu-Chung; Choi, Duck-Kyun

2011-01-01

Interest in transparent oxide thin film transistors utilizing ZnO material has been on the rise for many years. Recently, however, IGZO has begun to draw more attention due to its higher stability and superior electric field mobility when compared to ZnO. In this work, we address an improved method for patterning an a-IGZO film using the SAM process, which employs a cost-efficient micro-contact printing method instead of the conventional lithography process. After a-IGZO film deposition on the surface of a SiO2-layered Si wafer, the wafer was illuminated with UV light; sources and drains were then patterned using n-octadecyltrichlorosilane (OTS) molecules by a printing method. Due to the low surface energy of OTS, cobalt was selectively deposited on the OTS-free a-IGZO surface. The selective deposition of cobalt electrodes was successful, as confirmed by an optical microscope. The a-IZGO TFT fabricated using the SAM process exhibited good transistor performance: electric field mobility (micro(FE)), threshold voltage (V(th)), subthreshold slope (SS) and on/off ratio were 2.1 cm2/Vs, 2.4 V, 0.35 V/dec and 2.9 x 10(6), respectively.

Ionospheric convection driven by NBZ currents

NASA Technical Reports Server (NTRS)

Rasmussen, C. E.; Schunk, R. W.

1987-01-01

Computer simulations of Birkeland currents and electric fields in the polar ionosphere during periods of northward IMF were conducted. When the IMF z component is northward, an additional current system, called the NBZ current system, is present in the polar cap. These simulations show the effect of the addition of NBZ currents on ionospheric convection, particularly in the polar cap. When the total current in the NBZ system is roughly 25 to 50 percent of the net region 1 and 2 currents, convection in the central portion of the polar cap reverses direction and turns sunward. This creates a pattern of four-cell convection with two small cells located in the polar cap, rotating in an opposite direction from the larger cells. When the Birkeland currents are fixed (constant current source), the electric field is reduced in regions of relatively high conductivity, which affects the pattern of ionospheric convection. Day-night asymmetries in conductivity change convection in such a way that the two polar-cap cells are located within the large dusk cell. When ionospheric convection is fixed (constant voltage source), Birkeland currents are increased in regions of relatively high conductivity. Ionospheric currents, which flow horizontally to close the Birkeland currents, are changed appreciably by the NBZ current system. The principal effect is an increase in ionospheric current in the polar cap.

Electrical and Optical Characterization of Nanowire based Semiconductor Devices

NASA Astrophysics Data System (ADS)

Ayvazian, Talin

This research project is focused on a new strategy for the creation of nanowire based semiconductor devices. The main goal is to understand and optimize the electrical and optical properties of two types of nanoscale devices; in first type lithographically patterned nanowire electrodeposition (LPNE) method has been utilized to fabricate nanowire field effect transistors (NWFET) and second type involved the development of light emitting semiconductor nanowire arrays (NWLED). Field effect transistors (NWFETs) have been prepared from arrays of polycrystalline cadmium selenide (pc-CdSe) nanowires using a back gate configuration. pc-CdSe nanowires were fabricated using the lithographically patterned nanowire electrode- position (LPNE) process on SiO2 /Si substrates. After electrodeposition, pc-CdSe nanowires were thermally annealed at 300 °C x 4 h either with or without exposure to CdCl 2 in methanol a grain growth promoter. The influence of CdCl2 treatment was to increase the mean grain diameter as determined by X-ray diffraction pattern and to convert the crystal structure from cubic to wurtzite. Transfer characteristics showed an increase of the field effect mobility (mu eff) by an order of magnitude and increase of the Ion/I off ratio by a factor of 3-4. Light emitting devices (NW-LED) based on lithographically patterned pc-CdSe nanowire arrays have been investigated. Electroluminescence (EL) spectra of CdSe nanowires under various biases exhibited broad emission spectra centered at 750 nm close to the band gap of CdSe (1.7eV). To enhance the intensity of the emitted light and the external quantum efficiency (EQE), the distance between the contacts were reduced from 5 mum to less than 1 mum which increased the efficiency by an order of magnitude. Also, increasing the annealing temperature of nanowires from 300 °C x4 h to 450 This research project is focused on a new strategy for the creation of nanowire based semiconductor devices. The main goal is to understand and optimize the electrical and optical properties of two types of nanoscale devices; in first type lithographically patterned nanowire electrodeposition (LPNE) method has been utilized to fabricate nanowire field effect transistors (NWFET) and second type involved the development of light emitting semiconductor nanowire arrays (NWLED). Field effect transistors (NWFETs) have been prepared from arrays of polycrystalline cadmium selenide (pc-CdSe) nanowires using a back gate configuration. pc-CdSe nanowires were fabricated using the lithographically patterned nanowire electrode- position (LPNE) process on SiO2 /Si substrates. After electrodeposition, pc-CdSe nanowires were thermally annealed at 300 °C x 4 h either with or without exposure to CdCl2 in methanol- a grain growth promoter. The influence of CdCl2 treatment was to increase the mean grain diameter as determined by X-ray diffraction pattern and to convert the crystal structure from cubic to wurtzite. Transfer characteristics showed an increase of the field effect mobility (mueff<) by an order of magnitude and increase of the Ion/Ioff ratio by a factor of 3-4. Light emitting devices (NW-LED) based on lithographically patterned pc-CdSe nanowire arrays have been investigated. Electroluminescence (EL) spectra of CdSe nanowires under various biases exhibited broad emission spectra centered at 750 nm close to the band gap of CdSe (1.7eV). To enhance the intensity of the emitted light and the external quantum efficiency (EQE), the distance between the contacts were reduced from 5 mum to less than 1 mum which increased the efficiency by an order of magnitude. Also, increasing the annealing temperature of nanowires from 300 °C x4 h to 450 °C x 1h enhanced grain growth confirmed by structural characterization including X-ray diffraction (XRD), Scanning electron microscopy (SEM) and Raman Spectroscopy. Correspondingly the light emission intensity and EQE improved due to this grain growth. Kelvin probe force microscopy (KPFM) was utilized to understand mechanism of light emission in CdSe nanowires. Arrays of CdTe nanowires were electrodeposited using LPNE process where the elec- trodeposition of pc-CdTe was carried out at two temperatures: 20 °C (cold) and 55 °C (hot). Transmission electron microscopy (TEM) and X-ray diffraction (XRD) re- sults revealed higher crystallinity, larger grain size and presence of Te for nanowires prepared at 55°C compared to nanowires deposited at 20°C. Nanowires prepared at 55°C showed higher electrical conductivity and enhanced electroluminescence proper- ties, including higher light emission intensity and improved External Quantum Efficiency (EQE). Electrical conduction mechanism also investigated for CdTe nanowires. Thermionic emission over schottky barrier height was identified as the dominant charge transport mechanism in pc-CdTe nanowires.°C x 1h enhanced grain growth confirmed by structural characterization including X-ray diffraction (XRD), Scanning electron microscopy (SEM) and Raman Spectroscopy. Correspondingly the light emission intensity and EQE improved due to this grain growth. Kelvin probe force microscopy (KPFM) was utilized to understand mechanism of light emission in CdSe nanowires. Arrays of CdTe nanowires were electrodeposited using LPNE process where the electrodeposition of pc-CdTe was carried out at two temperatures: 20 °C (cold) and 55 °C (hot). Transmission electron microscopy (TEM) and X-ray diffraction (XRD) re- sults revealed higher crystallinity, larger grain size and presence of Te for nanowires prepared at 55°C compared to nanowires deposited at 20°C. Nanowires prepared at 55°C showed higher electrical conductivity and enhanced electroluminescence properties, including higher light emission intensity and improved External Quantum Efficiency (EQE). Electrical conduction mechanism also investigated for CdTe nanowires. Thermionic emission over schottky barrier height was identified as the dominant charge transport mechanism in pc-CdTe nanowires.

Seizure entrainment with polarizing low-frequency electric fields in a chronic animal epilepsy model

NASA Astrophysics Data System (ADS)

Sunderam, Sridhar; Chernyy, Nick; Peixoto, Nathalia; Mason, Jonathan P.; Weinstein, Steven L.; Schiff, Steven J.; Gluckman, Bruce J.

2009-08-01

Neural activity can be modulated by applying a polarizing low-frequency (Lt100 Hz) electric field (PLEF). Unlike conventional pulsed stimulation, PLEF stimulation has a graded, modulatory effect on neuronal excitability, and permits the simultaneous recording of neuronal activity during stimulation suitable for continuous feedback control. We tested a prototype system that allows for simultaneous PLEF stimulation with minimal recording artifact in a chronic tetanus toxin animal model (rat) of hippocampal epilepsy with spontaneous seizures. Depth electrode local field potentials recorded during seizures revealed a characteristic pattern of field postsynaptic potentials (fPSPs). Sinusoidal voltage-controlled PLEF stimulation (0.5-25 Hz) was applied in open-loop cycles radially across the CA3 of ventral hippocampus. For stimulated seizures, fPSPs were transiently entrained with the PLEF waveform. Statistical significance of entrainment was assessed with Thomson's harmonic F-test, with 45/132 stimulated seizures in four animals individually demonstrating significant entrainment (p < 0.04). Significant entrainment for multiple presentations at the same frequency (p < 0.01) was observed in three of four animals in 42/64 stimulated seizures. This is the first demonstration in chronically implanted freely behaving animals of PLEF modulation of neural activity with simultaneous recording.

On the Effect of IMF Turning on Ion Dynamics at Mercury

NASA Technical Reports Server (NTRS)

Delcourt, D. C.; Moore, T. E.; Fok, M.-C. H.

2011-01-01

We investigate the effect of a rotation of the Interplanetary Magnetic Field (IMF) on the transport of magnetospheric ion populations at Mercury. We focus on ions of planetary origin and investigate their large-scale circulation using three-dimensional single-particle simulations. We show that a nonzero Bx component of the IMF leads to a pronounced asymmetry in the overall circulation pattern . In particular, we demonstrate that the centrifugal acceleration due to curvature of the E x B drift paths is more pronounced in one hemisphere than the other, leading to filling of the magnetospheric lobes and plasma sheet with more or less energetic material depending upon the hemisphere of origin. Using a time-varying electric and magnetic field model, we investigate the response of ions to rapid (a few tens of seconds) re-orientation of the IMF. We show that, for ions with gyroperiods comparable to the field variation time scale, the inductive electric field should lead to significant nonadiabatic energization, up to several hundreds of eVs or a few keVs. It thus appears that IMP turning at Mercury should lead to localized loading of the magnetosphere with energetic material of planetary origin (e.g., Na+).

Biofield Physiology: A Framework for an Emerging Discipline

PubMed Central

Levin, Michael; McCraty, Rollin; Bat, Namuun; Ives, John A.; Lutgendorf, Susan K.; Oschman, James L.

2015-01-01

Biofield physiology is proposed as an overarching descriptor for the electromagnetic, biophotonic, and other types of spatially-distributed fields that living systems generate and respond to as integral aspects of cellular, tissue, and whole organism self-regulation and organization. Medical physiology, cell biology, and biophysics provide the framework within which evidence for biofields, their proposed receptors, and functions is presented. As such, biofields can be viewed as affecting physiological regulatory systems in a manner that complements the more familiar molecular-based mechanisms. Examples of clinically relevant biofields are the electrical and magnetic fields generated by arrays of heart cells and neurons that are detected, respectively, as electrocardiograms (ECGs) or magnetocardiograms (MCGs) and electroencephalograms (EEGs) or magnetoencephalograms (MEGs). At a basic physiology level, electromagnetic activity of neural assemblies appears to modulate neuronal synchronization and circadian rhythmicity. Numerous nonneural electrical fields have been detected and analyzed, including those arising from patterns of resting membrane potentials that guide development and regeneration, and from slowly-varying transepithelial direct current fields that initiate cellular responses to tissue damage. Another biofield phenomenon is the coherent, ultraweak photon emissions (UPE), detected from cell cultures and from the body surface. A physiological role for biophotons is consistent with observations that fluctuations in UPE correlate with cerebral blood flow, cerebral energy metabolism, and EEG activity. Biofield receptors are reviewed in 3 categories: molecular-level receptors, charge flux sites, and endogenously generated electric or electromagnetic fields. In summary, sufficient evidence has accrued to consider biofield physiology as a viable scientific discipline. Directions for future research are proposed. PMID:26665040

Biofield Physiology: A Framework for an Emerging Discipline.

PubMed

Hammerschlag, Richard; Levin, Michael; McCraty, Rollin; Bat, Namuun; Ives, John A; Lutgendorf, Susan K; Oschman, James L

2015-11-01

Biofield physiology is proposed as an overarching descriptor for the electromagnetic, biophotonic, and other types of spatially-distributed fields that living systems generate and respond to as integral aspects of cellular, tissue, and whole organism self-regulation and organization. Medical physiology, cell biology, and biophysics provide the framework within which evidence for biofields, their proposed receptors, and functions is presented. As such, biofields can be viewed as affecting physiological regulatory systems in a manner that complements the more familiar molecular-based mechanisms. Examples of clinically relevant biofields are the electrical and magnetic fields generated by arrays of heart cells and neurons that are detected, respectively, as electrocardiograms (ECGs) or magnetocardiograms (MCGs) and electroencephalograms (EEGs) or magnetoencephalograms (MEGs). At a basic physiology level, electromagnetic activity of neural assemblies appears to modulate neuronal synchronization and circadian rhythmicity. Numerous nonneural electrical fields have been detected and analyzed, including those arising from patterns of resting membrane potentials that guide development and regeneration, and from slowly-varying transepithelial direct current fields that initiate cellular responses to tissue damage. Another biofield phenomenon is the coherent, ultraweak photon emissions (UPE), detected from cell cultures and from the body surface. A physiological role for biophotons is consistent with observations that fluctuations in UPE correlate with cerebral blood flow, cerebral energy metabolism, and EEG activity. Biofield receptors are reviewed in 3 categories: molecular-level receptors, charge flux sites, and endogenously generated electric or electromagnetic fields. In summary, sufficient evidence has accrued to consider biofield physiology as a viable scientific discipline. Directions for future research are proposed.

Simple estimation of induced electric fields in nervous system tissues for human exposure to non-uniform electric fields at power frequency

NASA Astrophysics Data System (ADS)

Tarao, Hiroo; Miyamoto, Hironobu; Korpinen, Leena; Hayashi, Noriyuki; Isaka, Katsuo

2016-06-01

Most results regarding induced current in the human body related to electric field dosimetry have been calculated under uniform field conditions. We have found in previous work that a contact current is a more suitable way to evaluate induced electric fields, even in the case of exposure to non-uniform fields. If the relationship between induced currents and external non-uniform fields can be understood, induced electric fields in nervous system tissues may be able to be estimated from measurements of ambient non-uniform fields. In the present paper, we numerically calculated the induced electric fields and currents in a human model by considering non-uniform fields based on distortion by a cubic conductor under an unperturbed electric field of 1 kV m-1 at 60 Hz. We investigated the relationship between a non-uniform external electric field with no human present and the induced current through the neck, and the relationship between the current through the neck and the induced electric fields in nervous system tissues such as the brain, heart, and spinal cord. The results showed that the current through the neck can be formulated by means of an external electric field at the central position of the human head, and the distance between the conductor and the human model. As expected, there is a strong correlation between the current through the neck and the induced electric fields in the nervous system tissues. The combination of these relationships indicates that induced electric fields in these tissues can be estimated solely by measurements of the external field at a point and the distance from the conductor.

Spherical Ethylene/Air Diffusion Flames Subject to Concentric DC Electric Field in Microgravity

NASA Technical Reports Server (NTRS)

Yuan, Z. -G.; Hegde, U.; Faeth, G. M.

2001-01-01

It is well known that microgravity conditions, by eliminating buoyant flow, enable many combustion phenomena to be observed that are not possible to observe at normal gravity. One example is the spherical diffusion flame surrounding a porous spherical burner. The present paper demonstrates that by superimposing a spherical electrical field on such a flame, the flame remains spherical so that we can study the interaction between the electric field and flame in a one-dimensional fashion. Flames are susceptible to electric fields that are much weaker than the breakdown field of the flame gases owing to the presence of ions generated in the high temperature flame reaction zone. These ions and the electric current of the moving ions, in turn, significantly change the distribution of the electric field. Thus, to understand the interplay between the electric field and the flame is challenging. Numerous experimental studies of the effect of electric fields on flames have been reported. Unfortunately, they were all involved in complex geometries of both the flow field and the electric field, which hinders detailed study of the phenomena. In a one-dimensional domain, however, the electric field, the flow field, the thermal field and the chemical species field are all co-linear. Thus the problem is greatly simplified and becomes more tractable.

Coherent manipulation of photons and electrons

NASA Astrophysics Data System (ADS)

Zhao, Lu

In modern physics, coherent manipulation of photons and electrons has been intensively studied, and may have important applications in classical and quantum information processing. In this dissertation, we consider some interesting schemes to realize photonic and electronic coherent manipulation. In order to coherently manipulate photons, electromagnetically induced transparency (EIT) systems have been widely adopted because the optical response of EIT systems can be controlled by the laser-induced atomic coherence. In the second chapter, we theoretically investigate image storage in hot-vapor EIT media. A so-called 4f system is adopted for imaging, and an atomic vapor cell is placed over the transform plane. The Fraunhofer diffraction pattern of an object in the object plane can thus be transformed into atomic Raman coherence according to the idea of "light storage". We investigate how the stored diffraction pattern evolves under diffusion and discuss the essence of the stability of its dark spots. Our result indicates under appropriate conditions that an image can be reconstructed with high fidelity. The main reason for this procedure is the fact that diffusion of opposite-phase components of the diffraction pattern interfere destructively. In the third chapter, we show theoretical evidence that EIT systems can function as optically addressed spatial light modulators with megahertz modulation rates. The transverse spatial properties of continuous-wave probe fields can be modulated rapidly using two-dimensional optical patterns. To exemplify our proposal, we study real-time generation and manipulation of Laguerre-Gaussian beams by means of phase or amplitude modulation using flat-top image-bearing pulse trains as coupling fields in low-cost hot-vapor EIT systems. In order to coherently manipulate electrons, we consider graphene systems, including single-layer graphene and bilayer graphene, which have recently attracted considerable attention. Due to the long coherence length and electrically tunable Fermi levels, electrons in graphene systems have some photon-like behaviors, and could be coherently manipulated. Therefore, in the fourth chapter, we theorize that at a sharp electrostatic step potential in graphene massless Dirac fermions can obtain Goos-Hanchen-like shifts under total internal reflection. Also, we study coherent propagation of the quasiparticles along a sharp graphene p-n-p waveguide, and derive novel dispersion relations for the guided modes. Consequently, coherent graphene-based devices, e.g., movable mirrors, buffers and memories, induced only by the electric field effects may be proposed. Finally, we theoretically investigate the coherent propagation of massive chiral fermions along a sharp bilayer graphene p-n-p waveguide, and indicate that the guided quasiparticles can be coherently slowed, stored and retrieved based on tunable electric field effects. Controlling group velocity in the bilayer graphene p-n-p waveguide is accomplished via interband tunneling through the p-n interfaces, and does not depend on the bandgap opening.

Study of electric field distorted by space charges under positive lightning impulse voltage

NASA Astrophysics Data System (ADS)

Wang, Zezhong; Geng, Yinan

2018-03-01

Actually, many insulation problems are related to electric fields. And measuring electric fields is an important research topic of high-voltage engineering. In particular, the electric field distortion caused by space charge is the basis of streamer theory, and thus quantitatively measuring the Poisson electric field caused by space charge is significant to researching the mechanism of air gap discharge. In this paper, we used our photoelectric integrated sensor to measure the electric field distribution in a 1-m rod-plane gap under positive lightning impulse voltage. To verify the reliability of this quantitative measurement, we compared the measured results with calculated results from a numerical simulation. The electric-field time domain waveforms on the axis of the 1-m rod-plane out of the space charge zone were measured with various electrodes. The Poisson electric fields generated by space charge were separated from the Laplace electric field generated by applied voltages, and the amplitudes and variations were measured for various applied voltages and at various locations. This work also supplies the feasible basis for directly measuring strong electric field under high voltage.

LiNbO{sub 3}: A photovoltaic substrate for massive parallel manipulation and patterning of nano-objects

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

Carrascosa, M.; García-Cabañes, A.; Jubera, M.

The application of evanescent photovoltaic (PV) fields, generated by visible illumination of Fe:LiNbO{sub 3} substrates, for parallel massive trapping and manipulation of micro- and nano-objects is critically reviewed. The technique has been often referred to as photovoltaic or photorefractive tweezers. The main advantage of the new method is that the involved electrophoretic and/or dielectrophoretic forces do not require any electrodes and large scale manipulation of nano-objects can be easily achieved using the patterning capabilities of light. The paper describes the experimental techniques for particle trapping and the main reported experimental results obtained with a variety of micro- and nano-particles (dielectricmore » and conductive) and different illumination configurations (single beam, holographic geometry, and spatial light modulator projection). The report also pays attention to the physical basis of the method, namely, the coupling of the evanescent photorefractive fields to the dielectric response of the nano-particles. The role of a number of physical parameters such as the contrast and spatial periodicities of the illumination pattern or the particle deposition method is discussed. Moreover, the main properties of the obtained particle patterns in relation to potential applications are summarized, and first demonstrations reviewed. Finally, the PV method is discussed in comparison to other patterning strategies, such as those based on the pyroelectric response and the electric fields associated to domain poling of ferroelectric materials.« less

Wireless Chemical Sensor and Sensing Method for Use Therewith

NASA Technical Reports Server (NTRS)

Oglesby, Donald M. (Inventor); Taylor, Bryant D. (Inventor); Woodard, Stanley E. (Inventor)

2016-01-01

A wireless chemical sensor includes an electrical conductor and a material separated therefrom by an electric insulator. The electrical conductor is an unconnected open-circuit shaped for storage of an electric field and a magnetic field. In the presence of a time-varying magnetic field, the first electrical conductor resonates to generate harmonic electric and magnetic field responses. The material is positioned at a location lying within at least one of the electric and magnetic field responses so-generated. The material changes in electrical conductivity in the presence of a chemical-of-interest.

Wireless Chemical Sensor and Sensing Method for Use Therewith

NASA Technical Reports Server (NTRS)

Woodard, Stanley E. (Inventor); Oglesby, Donald M. (Inventor); Taylor, Bryant Douglas (Inventor)

2014-01-01

A wireless chemical sensor includes an electrical conductor and a material separated therefrom by an electric insulator. The electrical conductor is an unconnected open-circuit shaped for storage of an electric field and a magnetic field. In the presence of a time-varying magnetic field, the first electrical conductor resonates to generate harmonic electric and magnetic field responses. The material is positioned at a location lying within at least one of the electric and magnetic field responses so-generated. The material changes in electrical conductivity in the presence of a chemical-of-interest.

Wireless Chemical Sensing Method

NASA Technical Reports Server (NTRS)

Taylor, Bryant D. (Inventor); Woodard, Stanley E. (Inventor); Oglesby, Donald M. (Inventor)

2017-01-01

A wireless chemical sensor includes an electrical conductor and a material separated therefrom by an electric insulator. The electrical conductor is an unconnected open-circuit shaped for storage of an electric field and a magnetic field. In the presence of a time-varying magnetic field, the first electrical conductor resonates to generate harmonic electric and magnetic field responses. The material is positioned at a location lying within at least one of the electric and magnetic field responses so-generated. The material changes in electrical conductivity in the presence of a chemical-of-interest.

Investigating EMIC Wave Dynamics with RAM-SCB-E

NASA Astrophysics Data System (ADS)

Jordanova, V. K.; Fu, X.; Henderson, M. G.; Morley, S.; Welling, D. T.; Yu, Y.

2017-12-01

The distribution of ring current ions and electrons in the inner magnetosphere depends strongly on their transport in realistic electric (E) and magnetic (B) fields and concurrent energization or loss. To investigate the high variability of energetic particle (H+, He+, O+, and electron) fluxes during storms selected by the GEM Surface Charging Challenge, we use our kinetic ring current model (RAM) two-way coupled with a 3-D magnetic field code (SCB). This model was just extended to include electric field calculations, making it a unique, fully self-consistent, anisotropic ring current-atmosphere interactions model, RAM-SCB-E. Recently we investigated electromagnetic ion cyclotron (EMIC) instability in a local plasma using both linear theory and nonlinear hybrid simulations and derived a scaling formula that relates the saturation EMIC wave amplitude to initial plasma conditions. Global dynamic EMIC wave maps obtained with our RAM-SCB-E model using this scaling will be presented and compared with statistical models. These plasma waves can affect significantly both ion and electron precipitation into the atmosphere and the subsequent patterns of ionospheric conductance, as well as the global ring current dynamics.

Numerical modeling of Joule heating effects in insulator-based dielectrophoresis microdevices.

PubMed

Kale, Akshay; Patel, Saurin; Hu, Guoqing; Xuan, Xiangchun

2013-03-01

Insulator-based DEP (iDEP) has been established as a powerful tool for manipulating particles in microfluidic devices. However, Joule heating may become an issue in iDEP microdevices due to the local amplification of electric field around the insulators. This results in an electrothermal force that can manifest itself in the flow field in the form of circulations, thus affecting the particle motion. We develop herein a transient, 3D, full-scale numerical model to study Joule heating and its effects on the coupled transport of charge, heat, and fluid in an iDEP device with a rectangular constriction microchannel. This model is validated by comparing the simulation results with the experimentally obtained fluid flow patterns and particle images that were reported in our recent works. It identifies a significant difference in the time scales of the electric, temperature, and flow fields in iDEP microdevices. It also predicts the locations of electrothermal flow circulations in different halves of the channel at the upstream and downstream of the constriction. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

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.

Biological and Agricultural Studies on Application of Discharge Plasma and Electromagnetic Fields 5. Effects of High Electric Fields on Animals

NASA Astrophysics Data System (ADS)

Isaka, Katsuo

The biological effects of extremely low frequency electric fields on animals are reviewed with emphasis on studies of the nervous system, behavior, endocrinology, and blood chemistry. First, this paper provides a histrical overview of studies on the electric field effects initiated in Russia and the United States mainly regarding electric utility workers in high voltage substations and transmission lines. Then, the possible mechanisms of electric field effects are explained using the functions of surface electric fields and induced currents in biological objects. The real mechanisms have not yet been identified. The thresholds of electric field perception levels for rats, baboons, and humans are introduced and compared. The experimental results concerning the depression of melatonin secretion in rats exposed to electric fields are described.

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.

Application of digital soil mapping in Argentina: An example using apparent soil electrical conductivity

NASA Astrophysics Data System (ADS)

Domenech, Marisa; Castro Franco, Mauricio; Costa, Jose Luis; Aparicio, Virginia

2017-04-01

Apparent soil electrical conductivity (ECa) has been used to capture soil data in several Argentinean Pampas locations. The aim of this study was to generate digital soil mapping on the basis of understanding the relation among ECa and soil properties in three farming fields of the southeast Buenos Aires province. We carried out a geostatistical analysis using ECa data obtained at two depths 0-30cm (ECa_30cm) and 0-90cm (ECa_90cm). Then, two zones derived from ECa measurements were delimited in each field. A soil-sampling scheme was applied in each zone using two depths: 0-30cm and 30-90cm. Texture, Organic Matter Content (OMC), cation-exchange capacity (CEC), pH, saturated paste electrical conductivity (ECe) and effective depth were analyzed. The relation between zones and soil properties were studied using nested factor ANOVA. Our results indicated that clay content and effective depth showed significant differences among ECa_30 zones in all fields. In Argentine Pampas, the presence of petrocalcic horizons limits the effective soil depth at field scale. These horizons vary in depth, structure, hardness and carbonates content. In addition, they influence the spatial pattern of clay content. The relation among other physical and chemical soil properties was not consistent. Two soil unit maps were delimited in each field. These results might support irrigation management due to clay content and effective depth would be controlling soil water storage. Our findings highlight the high accuracy use of soil sensors in developing digital soil mapping at field scale, irrigation management zones, precision agriculture and hydrological modeling in Pampas region conditions.

How much detail is needed in modeling a transcranial magnetic stimulation figure-8 coil: Measurements and brain simulations

PubMed Central

Mandija, Stefano; Sommer, Iris E. C.; van den Berg, Cornelis A. T.; Neggers, Sebastiaan F. W.

2017-01-01

Background Despite TMS wide adoption, its spatial and temporal patterns of neuronal effects are not well understood. Although progress has been made in predicting induced currents in the brain using realistic finite element models (FEM), there is little consensus on how a magnetic field of a typical TMS coil should be modeled. Empirical validation of such models is limited and subject to several limitations. Methods We evaluate and empirically validate models of a figure-of-eight TMS coil that are commonly used in published modeling studies, of increasing complexity: simple circular coil model; coil with in-plane spiral winding turns; and finally one with stacked spiral winding turns. We will assess the electric fields induced by all 3 coil models in the motor cortex using a computer FEM model. Biot-Savart models of discretized wires were used to approximate the 3 coil models of increasing complexity. We use a tailored MR based phase mapping technique to get a full 3D validation of the incident magnetic field induced in a cylindrical phantom by our TMS coil. FEM based simulations on a meshed 3D brain model consisting of five tissues types were performed, using two orthogonal coil orientations. Results Substantial differences in the induced currents are observed, both theoretically and empirically, between highly idealized coils and coils with correctly modeled spiral winding turns. Thickness of the coil winding turns affect minimally the induced electric field, and it does not influence the predicted activation. Conclusion TMS coil models used in FEM simulations should include in-plane coil geometry in order to make reliable predictions of the incident field. Modeling the in-plane coil geometry is important to correctly simulate the induced electric field and to correctly make reliable predictions of neuronal activation PMID:28640923

Atmospheric electrical detection of organized convection.

PubMed

Markson, R

1975-06-20

Relatively simple atmospheric electrical instrumentation carried on a small aircraft constitutes a flexible and sensitive system for detecting organized convection. Data can be obtained close to the sea surface, and low-velocity flight enhances the spatial resolution. With a slow-flying airplane or powered glider, it may be possible to trace the circulation of individual convection cells and to investigate the trajectory of air which forms cumulus clouds, one of the major unsolved problems in tropical meteorology. Since space charge near the ocean surface was found on some days to be organized on a horizontal scale equivalent to the cumulus cloud scale, this suggests that some of the air which forms maritime cumulus clouds may come from within a few meters of the ocean and that atmospheric electrical instrumentation may have the potential for tracing air from the sea surface to the clouds. Although the atmospheric electrical instrumentation technique described here cannot be used for direct measurement of air velocity, it may be possible to develop model that can be used to calculate air velocities from electric field data. Even though with the technique described here it is not possible to make direct measurements of wind velocity, airborne electric field records can provide useful information about convection by delineating patterns in the wind field and structural features of thermals (rising bodies of relatively warm air) and by making possible the remote detection of thermals (29). Future plans include attempting to trace interfaces between adjacent roll vortices from the sea surface through the depth of the mixed layer (i) by flying the aircraft parallel to the wind so as to nullify the horizontal electric field (measured between wing-tip probes) while ascending and descending along the interface between adjacent roll vortices and (ii) by measuring vertical and horizontal potential gradient variations at different flight levels (30). The sensitivity of atmospheric electrical instrumentation to the top of the mixed layer and structure within it can be used to explore another important problem in boundary layer convection-why convective cloud cover and oceanic rainfall are greater at night than during the day(31). Workers in atmospheric electricity have long recognized that their domain is strongly controlled by turbulence in the lower atmosphere, and many have believed that the most effective use of atmospheric electrical techniques to assist meteorological research would be in studying exchange processes. Reiter [see (8)] effectively extended atmospheric electrical studies of boundary layer phenomena through a height range by mounting instruments on cable cars traveling between the valley floor and mountain tops in the Alps. The airborne measurements described here extend this approach. Relating the electrical structure of the atmosphere to its dynamic structure poses an interesting problem which may contribute to our understanding of the atmosphere.

Novel localized heating technique on centrifugal microfluidic disc with wireless temperature monitoring system.

PubMed

Joseph, Karunan; Ibrahim, Fatimah; Cho, Jongman

2015-01-01

Recent advances in the field of centrifugal microfluidic disc suggest the need for electrical interface in the disc to perform active biomedical assays. In this paper, we have demonstrated an active application powered by the energy harvested from the rotation of the centrifugal microfluidic disc. A novel integration of power harvester disc onto centrifugal microfluidic disc to perform localized heating technique is the main idea of our paper. The power harvester disc utilizing electromagnetic induction mechanism generates electrical energy from the rotation of the disc. This contributes to the heat generation by the embedded heater on the localized heating disc. The main characteristic observed in our experiment is the heating pattern in relative to the rotation of the disc. The heating pattern is monitored wirelessly with a digital temperature sensing system also embedded on the disc. Maximum temperature achieved is 82 °C at rotational speed of 2000 RPM. The technique proves to be effective for continuous heating without the need to stop the centrifugal motion of the disc.

Babinet's principle and the band structure of surface waves on patterned metal arrays

NASA Astrophysics Data System (ADS)

Edmunds, J. D.; Taylor, M. C.; Hibbins, A. P.; Sambles, J. R.; Youngs, I. J.

2010-05-01

The microwave response of an array of square metal patches and its complementary structure, an array of square holes, has been experimentally studied. The resonant phenomena, which yield either enhanced transmission or reflection, are attributed to the excitation of diffractively coupled surface waves. The band structure of these surface modes has been quantified for both p-(transverse magnetic) and s-(transverse electric) polarized radiation and is found to be dependent on the periodicity of the electric and magnetic fields on resonance. The results are in excellent accord with predictions from finite element method modeling and the electromagnetic form of Babinet's principle [Babinet, C. R. Acad. Sci. 4, 638 (1837)].

Implications of driving patterns on well-to-wheel performance of plug-in hybrid electric vehicles.

PubMed

Raykin, Leon; MacLean, Heather L; Roorda, Matthew J

2012-06-05

This study examines how driving patterns (distance and conditions) and the electricity generation supply interact to impact well-to-wheel (WTW) energy use and greenhouse gas (GHG) emissions of plug-in hybrid electric vehicles (PHEVs). The WTW performance of a PHEV is compared with that of a similar (nonplug-in) gasoline hybrid electric vehicle and internal combustion engine vehicle (ICEV). Driving PHEVs for short distances between recharging generally results in lower WTW total and fossil energy use and GHG emissions per kilometer compared to driving long distances, but the extent of the reductions depends on the electricity supply. For example, the shortest driving pattern in this study with hydroelectricity uses 81% less fossil energy than the longest driving pattern. However, the shortest driving pattern with coal-based electricity uses only 28% less fossil energy. Similar trends are observed in reductions relative to the nonplug-in vehicles. Irrespective of the electricity supply, PHEVs result in greater reductions in WTW energy use and GHG emissions relative to ICEVs for city than highway driving conditions. PHEVs charging from coal facilities only reduce WTW energy use and GHG emissions relative to ICEVs for certain favorable driving conditions. The study results have implications for environmentally beneficial PHEV adoption and usage patterns.

Patterned, highly stretchable and conductive nanofibrous PANI/PVDF strain sensors based on electrospinning and in situ polymerization.

PubMed

Yu, Gui-Feng; Yan, Xu; Yu, Miao; Jia, Meng-Yang; Pan, Wei; He, Xiao-Xiao; Han, Wen-Peng; Zhang, Zhi-Ming; Yu, Liang-Min; Long, Yun-Ze

2016-02-07

A facile fabrication strategy via electrospinning and followed by in situ polymerization to fabricate a patterned, highly stretchable, and conductive polyaniline/poly(vinylidene fluoride) (PANI/PVDF) nanofibrous membrane is reported. Owing to the patterned structure, the nanofibrous PANI/PVDF strain sensor can detect a strain up to 110%, for comparison, which is 2.6 times higher than the common nonwoven PANI/PVDF mat and much larger than the previously reported values (usually less than 15%). Meanwhile, the conductivity of the patterned strain sensor shows a linear response to the applied strain in a wide range from 0% to about 85%. Additionally, the patterned PANI/PVDF strain sensor can completely recover to its original electrical and mechanical values within a strain range of more than 22%, and exhibits good durability over 10,000 folding-unfolding tests. Furthermore, the strain sensor also can be used to detect finger motion. The results demonstrate promising application of the patterned nanofibrous membrane in flexible electronic fields.

Polarization-Dependent Quasi-Far-Field Superfocusing Strategy of Nanoring-Based Plasmonic Lenses.

PubMed

Sun, Hao; Zhu, Yechuan; Gao, Bo; Wang, Ping; Yu, Yiting

2017-12-01

The two-dimensional superfocusing of nanoring-based plasmonic lenses (NRPLs) beyond the diffraction limit in the far-field region remains a great challenge at optical wavelengths. In this paper, in addition to the modulation of structural parameters, we investigated the polarization-dependent focusing performance of a NRPL employing the finite-difference time-domain (FDTD) method. By utilizing the state of polarization (SOP) of incident light, we successfully realize the elliptical-, donut-, and circular-shape foci. The minimum full widths at half maximum (FWHMs) of these foci are ~0.32, ~0.34, and ~0.42 λ 0 in the total electric field, respectively, and the depth of focus (DOF) lies in 1.41~1.77 λ 0 . These sub-diffraction-limit foci are well controlled in the quasi-far-field region. The underlying physical mechanism on the focal shift and an effective way to control the focusing position are proposed. Furthermore, in the case of a high numerical aperture, the longitudinal component, which occupies over 80% of the electric-field energy, decides the focusing patterns of the foci. The achieved sub-diffraction-limit focusing can be widely used for many engineering applications, including the super-resolution imaging, particle acceleration, quantum optical information processing, and optical data storage.

Mixing enhancement of low-Reynolds electro-osmotic flows in microchannels with temperature-patterned walls.

PubMed

Alizadeh, A; Zhang, L; Wang, M

2014-10-01

Mixing becomes challenging in microchannels because of the low Reynolds number. This study aims to present a mixing enhancement method for electro-osmotic flows in microchannels using vortices caused by temperature-patterned walls. Since the fluid is non-isothermal, the conventional form of Nernst-Planck equation is modified by adding a new migration term which is dependent on both temperature and internal electric potential gradient. This term results in the so-called thermo-electrochemical migration phenomenon. The coupled Navier-Stokes, Poisson, modified Nernst-Planck, energy and advection-diffusion equations are iteratively solved by multiple lattice Boltzmann methods to obtain the velocity, internal electric potential, ion distribution, temperature and species concentration fields, respectively. To enhance the mixing, three schemes of temperature-patterned walls have been considered with symmetrical or asymmetrical arrangements of blocks with surface charge and temperature. Modeling results show that the asymmetric arrangement scheme is the most efficient scheme and enhances the mixing of species by 39% when the Reynolds number is on the order of 10(-3). Current results may help improve the design of micro-mixers at low Reynolds number. Copyright © 2014 Elsevier Inc. All rights reserved.

Patterns of motor activity in the isolated nerve cord of the octopus arm.

PubMed

Gutfreund, Yoram; Matzner, Henry; Flash, Tamar; Hochner, Binyamin

2006-12-01

The extremely flexible octopus arm provides a unique opportunity for studying movement control in a highly redundant motor system. We describe a novel preparation that allows analysis of the peripheral nervous system of the octopus arm and its interaction with the muscular and mechanosensory elements of the arm's intrinsic muscular system. First we examined the synaptic responses in muscle fibers to identify the motor pathways from the axial nerve cord of the arm to the surrounding musculature. We show that the motor axons project to the muscles via nerve roots originating laterally from the arm nerve cord. The motor field of each nerve is limited to the region where the nerve enters the arm musculature. The same roots also carry afferent mechanosensory information from the intrinsic muscle to the axial nerve cord. Next, we characterized the pattern of activity generated in the dorsal roots by electrically stimulating the axial nerve cord. The evoked activity, although far reaching and long lasting, cannot alone account for the arm extension movements generated by similar electrical stimulation. The mismatch between patterns of activity in the isolated cord and in an intact arm may stem from the involvement of mechanosensory feedback in natural arm extension.

Towards an ankle neuroprosthesis for hybrid robotics: Concepts and current sources for functional electrical stimulation.

PubMed

Casco, S; Fuster, I; Galeano, R; Moreno, J C; Pons, J L; Brunetti, F

2017-07-01

Hybrid rehabilitation robotics combine neuro-prosthetic devices (close-loop functional electrical stimulation systems) and traditional robotic structures and actuators to explore better therapies and promote a more efficient motor function recovery or compensation. Although hybrid robotics and ankle neuroprostheses (NPs) have been widely developed over the last years, there are just few studies on the use of NPs to electrically control both ankle flexion and extension to promote ankle recovery and improved gait patterns in paretic limbs. The aim of this work is to develop an ankle NP specifically designed to work in the field of hybrid robotics. This article presents early steps towards this goal and makes a brief review about motor NPs and Functional Electrical Stimulation (FES) principles and most common devices used to aid the ankle functioning during the gait cycle. It also shows a current sources analysis done in this framework, in order to choose the best one for this intended application.

A Comparison of Inductive Sensors in the Characterization of Partial Discharges and Electrical Noise Using the Chromatic Technique

PubMed Central

Ardila-Rey, Jorge Alfredo; Montaña, Johny; Schurch, Roger; Covolan Ulson, José Alfredo; Bani, Nurul Aini

2018-01-01

Partial discharges (PDs) are one of the most important classes of ageing processes that occur within electrical insulation. PD detection is a standardized technique to qualify the state of the insulation in electric assets such as machines and power cables. Generally, the classical phase-resolved partial discharge (PRPD) patterns are used to perform the identification of the type of PD source when they are related to a specific degradation process and when the electrical noise level is low compared to the magnitudes of the PD signals. However, in practical applications such as measurements carried out in the field or in industrial environments, several PD sources and large noise signals are usually present simultaneously. In this study, three different inductive sensors have been used to evaluate and compare their performance in the detection and separation of multiple PD sources by applying the chromatic technique to each of the measured signals. PMID:29596337

From static electric images to electric flow: towards dynamic perceptual cues in active electroreception.

PubMed

Hofmann, Volker; Sanguinetti-Scheck, Juan I; Gómez-Sena, Leonel; Engelmann, Jacob

2013-01-01

Active electroreception is an ancestral trait found in many aquatic vertebrates and has evolved independently in two teleost lineages, the Gymnotiformes and the Mormyriformes. Unique to these so-called weakly electric fish is their ability to actively generate electrical currents in the water and sense the electrical properties of the environment. How natural behavior contributes to this sensory system has been of interest to neuroethologists since the pioneering works of Lissmann. Here we report on a mutual modeling and experimental study of the stimuli available during active electrolocation of Gnathonemus petersii (Mormyridae). We show the validity of the model (I) by demonstrating that localized spatial patterns of object induced modulations in the electric field (electric images) are comparable to experimentally mapped 2-dimensional electric images and (II) by replicating earlier key findings showing that a normalized metric of electric image width provides an unambiguous cue for distance estimation. We then show that electric images and the distance metric vary systematically when an object is moved along the trunk. These potential ambiguities with regard to localization lead us to a spatiotemporal analysis of electric images. We introduce a new temporal metric for distance estimation that is based on the normalized spatial properties of electrical images. Finally, based on a survey of exploratory behavior, we show how objects situated at the tail, a region previously neglected, cast global electric images that extend over the whole sensory epithelium of the animals. Copyright © 2012 Elsevier Ltd. All rights reserved.

Micropatterning of poly(dimethylsiloxane) using a photoresist lift-off technique for selective electrical insulation of microelectrode arrays

PubMed Central

Park, Jaewon; Kim, Hyun Soo; Han, Arum

2009-01-01

A poly(dimethylsiloxane) (PDMS) patterning method based on a photoresist lift-off technique to make an electrical insulation layer with selective openings is presented. The method enables creating PDMS patterns with small features and various thicknesses without any limitation in the designs and without the need for complicated processes or expensive equipments. Patterned PDMS layers were created by spin-coating liquid phase PDMS on top of a substrate having sacrificial photoresist patterns, followed by a photoresist lift-off process. The thickness of the patterned PDMS layers could be accurately controlled (6.5–24 µm) by adjusting processing parameters such as PDMS spin-coating speeds, PDMS dilution ratios, and sacrificial photoresist thicknesses. PDMS features as small as 15 µm were successfully patterned and the effects of each processing parameter on the final patterns were investigated. Electrical resistance tests between adjacent electrodes with and without the insulation layer showed that the patterned PDMS layer functions properly as an electrical insulation layer. Biocompatibility of the patterned PDMS layer was confirmed by culturing primary neuron cells on top of the layer for up to two weeks. An extensive neuronal network was successfully formed, showing that this PDMS patterning method can be applied to various biosensing microdevices. The utility of this fabrication method was further demonstrated by successfully creating a patterned electrical insulation layer on flexible substrates containing multi-electrode arrays. PMID:19946385

Molecules with an induced dipole moment in a stochastic electric field.

PubMed

Band, Y B; Ben-Shimol, Y

2013-10-01

The mean-field dynamics of a molecule with an induced dipole moment (e.g., a homonuclear diatomic molecule) in a deterministic and a stochastic (fluctuating) electric field is solved to obtain the decoherence properties of the system. The average (over fluctuations) electric dipole moment and average angular momentum as a function of time for a Gaussian white noise electric field are determined via perturbative and nonperturbative solutions in the fluctuating field. In the perturbative solution, the components of the average electric dipole moment and the average angular momentum along the deterministic electric field direction do not decay to zero, despite fluctuations in all three components of the electric field. This is in contrast to the decay of the average over fluctuations of a magnetic moment in a Gaussian white noise magnetic field. In the nonperturbative solution, the component of the average electric dipole moment and the average angular momentum in the deterministic electric field direction also decay to zero.

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.

Massive ordering and alignment of cylindrical micro-objects by photovoltaic optoelectronic tweezers.

PubMed

Elvira, Iris; Muñoz-Martínez, Juan F; Barroso, Álvaro; Denz, Cornelia; Ramiro, José B; García-Cabañes, Angel; Agulló-López, Fernando; Carrascosa, Mercedes

2018-01-01

Optical tools for manipulation and trapping of micro- and nano-objects are a fundamental issue for many applications in nano- and biotechnology. This work reports on the use of one such method, known as photovoltaic optoelectronics tweezers, to orientate and organize cylindrical microcrystals, specifically elongated zeolite L, on the surface of Fe-doped LiNbO 3 crystal plates. Patterns of aligned zeolites have been achieved through the forces and torques generated by the bulk photovoltaic effect. The alignment patterns with zeolites parallel or perpendicular to the substrate surface are highly dependent on the features of light distribution and crystal configuration. Moreover, dielectrophoretic chains of zeolites with lengths up to 100 μm have often been observed. The experimental results of zeolite trapping and alignment have been discussed and compared together with theoretical simulations of the evanescent photovoltaic electric field and the dielectrophoretic potential. They demonstrate the remarkable capabilities of the optoelectronic photovoltaic method to orientate and pattern anisotropic microcrystals. The combined action of patterning and alignment offers a unique tool to prepare functional nanostructures with potential applications in a variety of fields such as nonlinear optics or plasmonics.

Cloaking magnetic field and generating electric field with topological insulator and superconductor bi-layer sphere

NASA Astrophysics Data System (ADS)

Xu, Jin

2017-12-01

When an electric field is applied on a topological insulator, not only the electric field is generated, but also the magnetic field is generated, vice versa. I designed topological insulator and superconductor bi-layer magnetic cloak, derived the electric field and magnetic field inside and outside the topological insulator and superconductor sphere. Simulation and calculation results show that the applied magnetic field is screened by the topological insulator and superconductor bi-layer, and the electric field is generated in the cloaked region.

Electric Field Feature of Moving Magnetic Field

NASA Astrophysics Data System (ADS)

Chen, You Jun

2001-05-01

A new fundamental relationship of electric field with magnetic field has been inferred from the fundamental experimental laws and theories of classical electromagnetics. It can be described as moving magnetic field has or gives electric feature. When a field with magnetic induction of B moves in the velocity of V, it will show electric field character, the electric field intensity E is E = B x V and the direction of E is in the direction of the vector B x V. It is improper to use the time-varying electromagnetics theories as the fundamental theory of the electromagnetics and group the electromagnetic field into static kind and time-varying kind for the static is relative to motional not only time-varying. The relationship of time variation of magnetic field induction or magnetic flux with electric field caused by magnetic field is fellowship not causality. Thus time-varying magnetic field can cause electric field is not a nature principle. Sometime the time variation of magnetic flux is equal to the negative electromotive force or the time variation of magnetic field induction is equal to the negative curl of electric field caused by magnetic field motion, but not always. And not all motion of magnetic field can cause time variation of magnetic field. Therefore Faraday-Lenz`s law can only be used as mathematics tool to calculate the quantity relation of the electricity with the magnetism in some case like the magnetic field moving in uniform medium. Faraday-Lenz`s law is unsuitable to be used in moving uniform magnetic field or there is magnetic shield. Key word: Motional magnetic field, Magnetic induction, Electric field intensity, Velocity, Faraday-Lenz’s law

Landau-Zener-Stückelberg-Majorana Interferometry of a Single Hole

NASA Astrophysics Data System (ADS)

Bogan, Alex; Studenikin, Sergei; Korkusinski, Marek; Gaudreau, Louis; Zawadzki, Piotr; Sachrajda, Andy S.; Tracy, Lisa; Reno, John; Hargett, Terry

2018-05-01

We perform Landau-Zener-Stückelberg-Majorana (LZSM) spectroscopy on a system with strong spin-orbit interaction (SOI), realized as a single hole confined in a gated double quantum dot. Analogous to electron systems, at a magnetic field B =0 and high modulation frequencies, we observe photon-assisted tunneling between dots, which smoothly evolves into the typical LZSM funnel-shaped interference pattern as the frequency is decreased. In contrast to electrons, the SOI enables an additional, efficient spin-flip interdot tunneling channel, introducing a distinct interference pattern at finite B . Magnetotransport spectra at low-frequency LZSM driving show the two channels to be equally coherent. High-frequency LZSM driving reveals complex photon-assisted tunneling pathways, both spin conserving and spin flip, which form closed loops at critical magnetic fields. In one such loop, an arbitrary hole spin state is inverted, opening the way toward its all-electrical manipulation.

Processes in suspensions of nanocomposite microcapsules exposed to external electric fields

NASA Astrophysics Data System (ADS)

Ermakov, A. V.; Lomova, M. V.; Kim, V. P.; Chumakov, A. S.; Gorbachev, I. A.; Gorin, D. A.; Glukhovskoy, E. G.

2016-04-01

Microcapsules with and without magnetite nanoparticles incorporated in the polyelectrolyte shell were prepared. The effect of external electric field on the nanocomposite polyelectrolyte microcapsules containing magnetite nanoparticles in the shell was studied in this work as a function of the electric field strength. Effect of electric fields on polyelectrolyte microcapsules and the control over integrity of polyelectrolyte microcapsules with and without inorganic nanoparticles by constant electric field has been investigated. Beads effect, aggregation and deformations of nanocomposite microcapsule shell in response to electric field were observed by confocal laser scanning microscopy (CLSM). Thus, a new approach for effect on the nanocomposite microcapsule, including opening microcapsule shell by an electric field, was demonstrated. These results can be used for creation of new systems for drug delivery systems with controllable release by external electric field.

On high-latitude convection field inhomogeneities, parallel electric fields and inverted-V precipitation events

NASA Technical Reports Server (NTRS)

Lennartsson, W.

1977-01-01

A simple model of a static electric field with a component parallel to the magnetic field is proposed for calculating the electric field and current distributions at various altitudes when the horizontal distribution of the convection electric field is given at a certain altitude above the auroral ionosphere. The model is shown to be compatible with satellite observations of inverted-V electron precipitation structures and associated irregularities in the convection electric field.

Permanent magnetic field, direct electric field, and infrared to reduce blood glucose level and hepatic function in mus musculus with diabetic mellitus

NASA Astrophysics Data System (ADS)

Suhariningsih; Basuki Notobroto, Hari; Winarni, Dwi; Achmad Hussein, Saikhu; Anggono Prijo, Tri

2017-05-01

Blood contains several electrolytes with positive (cation) and negative (anion) ion load. Both electrolytes deliver impulse synergistically adjusting body needs. Those electrolytes give specific effect to external disturbance such as electric, magnetic, even infrared field. A study has been conducted to reduce blood glucose level and liver function, in type 2 Diabetes Mellitus patients, using Biophysics concept which uses combination therapy of permanent magnetic field, electric field, and infrared. This study used 48 healthy mice (mus musculus), male, age 3-4 weeks, with approximately 25-30 g in weight. Mice was fed with lard as high fat diet orally, before Streptozotocin (STZ) induction become diabetic mice. Therapy was conducted by putting mice in a chamber that emits the combination of permanent magnetic field, electric field, and infrared, every day for 1 hour for 28 days. There were 4 combinations of therapy/treatment, namely: (1) permanent magnetic field, direct electric field, and infrared; (2) permanent magnetic field, direct electric field, without infrared; (3) permanent magnetic field, alternating electric field, and infrared; and (4) permanent magnetic field, alternating electric field, without infrared. The results of therapy show that every combination is able to reduce blood glucose level, AST, and ALT. However, the best result is by using combination of permanent magnetic field, direct electric field, and infrared.

Complex Electric-Field Induced Phenomena in Ferroelectric/Antiferroelectric Nanowires

NASA Astrophysics Data System (ADS)

Herchig, Ryan Christopher

Perovskite ferroelectrics and antiferroelectrics have attracted a lot of attention owing to their potential for device applications including THz sensors, solid state cooling, ultra high density computer memory, and electromechanical actuators to name a few. The discovery of ferroelectricity at the nanoscale provides not only new and exciting possibilities for device miniaturization, but also a way to study the fundamental physics of nanoscale phenomena in these materials. Ferroelectric nanowires show a rich variety of physical characteristics which are advantageous to the design of nanoscale ferroelectric devices such as exotic dipole patterns, a strong dependence of the polarization and phonon frequencies on the electrical and mechanical boundary conditions, as well as a dependence of the transition temperatures on the diameter of the nanowire. Antiferroelectricity also exists at the nanoscale and, due to the proximity in energy of the ferroelectric and antiferroelectric phases, a phase transition from the ferroelectric to the antiferroelectric phase can be facilitated through the application of the appropriate mechanical and electrical boundary conditions. While much progress has been made over the past several decades to understand the nature of ferroelectricity/antiferroelectricity in nanowires, many questions remain unanswered. In particular, little is known about how the truncated dimensions affect the soft mode frequency dynamics or how various electrical and mechanical boundary conditions might change the nature of the phase transitions in these ferroelectric nanowires. Could nanowires offer a distinct advantage for solid state cooling applications? Few studies have been done to elucidate the fundamental physics of antiferroelectric nanowires. How the polarization in ferroelectric nanowires responds to a THz electric field remains relatively underexplored as well. In this work, the aim is to to develop and use computational tools that allow first-principles-based modeling of electric-field-induced phenomena in ferroelectric/antiferroelectric nanowires in order to address the aforementioned questions. (Abstract shortened by ProQuest.).

Enhancement of convective heat transfer in internal flows using an electrically-induced corona jet

NASA Astrophysics Data System (ADS)

Baghaei Lakeh, Reza

The enhancement of heat transfer by active and passive methods has been the subject of many academic and industrial research studies. Internal flows play a major role in many applications and different methods have been utilized to augment the heat transfer to internal flows. Secondary flows consume part of the kinetic energy of the flow and disturb the boundary layer. Inducing secondary flows is known as mechanism for heat transfer enhancement. Secondary flows may be generated by corona discharge and ion-driven flows. When a high electric potential is applied to a conductor, a high electric field will be generated. The high electric field may exceed the partial break-down of the neutral molecules of surrounding gas (air) and generate a low-temperature plasma in the vicinity of the conductor. The generated plasma acts as a source of ions that accelerate under the influence of the electric field and escape beyond the plasma region and move toward the grounded electrode. The accelerating ions collide with neutral particles of the surrounding gas and impose a dragging effect which is interpreted as a body-force to the air particles. The shape and configuration of the emitting and receiving electrodes has a significant impact on the distribution of the electric body-force and the resulting electrically-induced flow field. It turned out that the certain configurations of longitudinal electrodes may cause a jet-like secondary flow field on the cross section of the flow passage in internal flows. The impingement effect of the corona jet on the walls of the channel disturbs the boundary layer, enhances the convective heat transfer, and generates targeted cooling along the centerline of the jet. The results of the current study show that the concentric configuration of a suspended wire-electrode in a circular tube leads to a hydrostatic condition and do not develop any electrically-induced secondary flow; however, the eccentric wire-electrode configuration generates a corona jet along the eccentricity direction. The generated corona jet exhibits interesting specifications similar to conventional inertia-driven air jets which are among common techniques for cooling and heat transfer enhancement. On the other hand, wall-mounted flat electrode pairs along the parallel walls of a rectangular mini-channel develop a similar jet-like flow pattern. The impingement of the corona jet to the receiving wall causes excessive heat transfer enhancement and cooling effect. The flat electrode pairs were also utilized to study the effect of corona discharge on the heat transfer specifications of the internal flow between parallel plates in fully-developed condition. It turned out that the electrically-induced secondary flow along with a pressure-driven main flow generates a swirling effect which can enhance the heat transfer significantly in fully-developed condition.

Investigating nitrate dynamics in a fine-textured soil affected by feedlot effluents.

PubMed

Veizaga, E A; Rodríguez, L; Ocampo, C J

2016-10-01

Feedlots concentrate large volumes of manure and effluents that contain high concentrations of nitrate, among other constituents. If not managed properly, pen surfaces run-off and lagoons overflows may spread those effluents to surrounding land, infiltrating into the soil. Soil nitrate mobilization and distribution are of great concern due to its potential migration towards groundwater resources. This work aimed at evaluating the migration of nitrate originated on feedlots effluents in a fine-textured soil under field conditions. Soil water constituents were measured during a three-year period at three distinct locations adjacent to feedlot retention lagoons representing different degrees of exposure to water flow and manure accumulation. A simple statistical analysis was undertaken to identify patterns of observed nitrate and chloride concentrations and electrical conductivity and their differences with depth. HYDRUS-1D was used to simulate water flow and solute transport of Cl - , NO 4 + N, NO 3 - N and electrical conductivity to complement field data interpretation. Results indicated that patterns of NO 3 - N concentrations were not only notoriously different from electrical conductivity and Cl - but also ranges and distribution with depth differed among locations. A combination of dilution, transport, reactions such as nitrification/denitrification and vegetation water and solute uptake took place at each plots denoting the complexity of soil-solution behavior under extreme polluting conditions. Simulations using the concept of single porosity-mobile/immobile water (SP-MIM) managed structural controls and correctly simulated - all species concentrations under field data constrains. The opposite was true for the other two locations experiencing near-saturation conditions, absence of vegetation and frequent manure accumulation and runoff from feedlot lagoons. Although the results are site specific, findings are relevant to advance the understanding of NO 3 - N dynamics resulting from FL operations under heavy soils. Copyright © 2016 Elsevier B.V. All rights reserved.

High sensitive space electric field sensing based on micro fiber interferometer with field force driven gold nanofilm.

PubMed

Zhu, Tao; Zhou, Liming; Liu, Min; Zhang, Jingdong; Shi, Leilei

2015-10-28

The traditional electrical field sensing can be realized by utilizing electro-optic materials or liquid crystals, and has limitations of easy breakdown, free assembly and difficult measurement of low-frequency. Here, we propose a new method to realize safe measurement of spatial dynamic electric field by using a micro fiber interferometer integrated with gold nanofilm. The energy of the electric charge received through antenna forms the intrinsic electric field with two micro electrodes, one of which is the 120 nm gold film vibration beam micromachined by femtosecond lasers and integrated with the micro fiber. The change of the intrinsic electric field force due to the spatial electric field will cause the vibration of the film beam. By demodulating the output signal of the micro fiber interferometer, the electric field can be measured. We demonstrate the detectable frequency ranges from tens of Hz to tens of KHz, and the minimum electric field intensity is ~200 V/m at 1 KHz. Our electric field measurement technology combining optical fiber interference with gold nanostructures shows the advantages of security, high sensitivity, compact size, and multiplexed multi-point and remote detection.

High sensitive space electric field sensing based on micro fiber interferometer with field force driven gold nanofilm

PubMed Central

Zhu, Tao; Zhou, Liming; Liu, Min; Zhang, Jingdong; Shi, Leilei

2015-01-01

The traditional electrical field sensing can be realized by utilizing electro-optic materials or liquid crystals, and has limitations of easy breakdown, free assembly and difficult measurement of low-frequency. Here, we propose a new method to realize safe measurement of spatial dynamic electric field by using a micro fiber interferometer integrated with gold nanofilm. The energy of the electric charge received through antenna forms the intrinsic electric field with two micro electrodes, one of which is the 120 nm gold film vibration beam micromachined by femtosecond lasers and integrated with the micro fiber. The change of the intrinsic electric field force due to the spatial electric field will cause the vibration of the film beam. By demodulating the output signal of the micro fiber interferometer, the electric field can be measured. We demonstrate the detectable frequency ranges from tens of Hz to tens of KHz, and the minimum electric field intensity is ~200 V/m at 1 KHz. Our electric field measurement technology combining optical fiber interference with gold nanostructures shows the advantages of security, high sensitivity, compact size, and multiplexed multi-point and remote detection. PMID:26507680