Charging of a conducting sphere in a weakly ionized collisional plasma: Temporal dynamics and stationary state

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

Grach, V. S., E-mail: vsgrach@app.sci-nnov.ru; Garasev, M. A.

2015-07-15

We consider the interaction of a isolated conducting sphere with a collisional weakly ionized plasma in an external field. We assume that the plasma consists of two species of ions neglecting of electrons. We take into account charging of the sphere due to sedimentation of plasma ions on it, the field of the sphere charge and the space charge, as well as recombination and molecular diffusion. The nonstationary problem of interaction of the sphere with the surrounding plasma is solved numerically. The temporal dynamics of the sphere charge and plasma perturbations is analyzed, as well as the properties of themore » stationary state. It is shown that the duration of transient period is determined by the recombination time and by the reverse conductivity of ions. The temporal dynamics of the sphere charge and plasma perturbations is determined by the intensity of recombination processes relative to the influence of the space charge field and diffusion. The stationary absolute value of the sphere charge increases linearly with the external electric field, decreases with the relative intensity of recombination processes and increases in the presence of substantial diffusion. The scales of the perturbed region in the plasma are determined by the radius of the sphere, the external field, the effect of diffusion, and the relative intensity of recombination processes. In the limiting case of the absence of molecular diffusion and a strong external field, the properties of the stationary state coincide with those obtained earlier as a result of approximate solution.« less

Studying internal and external magnetic fields in Japan using MAGSAT data

NASA Technical Reports Server (NTRS)

Fukushima, N. (Principal Investigator); Maeda, H.; Yukutake, T.; Tanaka, M.; Oshima, S.; Ogawa, K.; Kawamura, M.; Miyazaki, Y.; Uyeda, S.; Kobayashi, K.

1980-01-01

Examination of the total intensity data of CHRONIT on a few paths over Japan and its neighboring sea shows MAGSAT is extremely useful for studying the local magnetic anomaly. In high latitudes, the signatures of field aligned currents are clearly recognized. These include (1) the persistent basic pattern of current flow; (2) the more intense currents in the summer hemisphere than in the winter hemisphere; (3) more fluctuations in current intensities in summer dawn hours; and (4) apparent dawn-dusk asymmetry in the field-aligned current intensity between the north and south polar regions.

Influence of external magnetic field on laser-induced gold nanoparticles fragmentation

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

Serkov, A. A.; The Federal State Educational Institution of Higher Professional Education, “Moscow Institute of Physics and Technology; Rakov, I. I.

Laser-assisted fragmentation is an efficient method of the nanoparticles size and morphology control. However, its exact mechanisms are still under consideration. One of the remaining problems is the plasma formation, inevitably occurring upon the high intensity laser irradiation. In this Letter, the role of the laser-induced plasma is studied via introduction of high-intensity external magnetic field (up to 7.5 T). Its presence is found to cause the plasma emission to start earlier regarding to a laser pulse, also increasing the plume luminosity. Under these conditions, the acceleration of nanoparticles fragmentation down to a few nanometers is observed. Laser-induced plasma interaction withmore » magnetic field and consequent energy transfer from plasma to nanoparticles are discussed.« less

A study of occurrence rates of Electromagnetic Interference (EMI) to aircraft with a focus on HIRF (external) High Intensity Radiated Fields

NASA Technical Reports Server (NTRS)

Shooman, Martin L.

1994-01-01

This report presents the methodology and results of a subjective study done by Polytechnic University to investigate Electromagnetic Interference (EMI) events on aircraft. The results cover various types of EMI from on-board aircraft systems, passenger carry-on devices, and externally generated disturbances. The focus of the study, however, was on externally generated EMI, termed High Intensity Radiated Fields (HIRF), from radars, radio and television transmitters, and other man-made emitters of electromagnetic energy. The study methodology used an anonymous questionnaire distributed to experts to gather the data. This method is known as the Delphi or Consensus Estimation technique. The questionnaire was sent to an expert population of 230 and there were 57 respondents. Details of the questionnaire, a few anecdotes, and the statistical results of the study are presented.

Effect of strong electric field on the conformational integrity of insulin.

PubMed

Wang, Xianwei; Li, Yongxiu; He, Xiao; Chen, Shude; Zhang, John Z H

2014-10-02

A series of molecular dynamics (MD) simulations up to 1 μs for bovine insulin monomer in different external electric fields were carried out to study the effect of external electric field on conformational integrity of insulin. Our results show that the secondary structure of insulin is kept intact under the external electric field strength below 0.15 V/nm, but disruption of secondary structure is observed at 0.25 V/nm or higher electric field strength. Although the starting time of secondary structure disruption of insulin is not clearly correlated with the strength of the external electric field ranging between 0.15 and 0.60 V/nm, long time MD simulations demonstrate that the cumulative effect of exposure time under the electric field is a major cause for the damage of insulin's secondary structure. In addition, the strength of the external electric field has a significant impact on the lifetime of hydrogen bonds when it is higher than 0.60 V/nm. The fast evolution of some hydrogen bonds of bovine insulin in the presence of the 1.0 V/nm electric field shows that different microwaves could either speed up protein folding or destroy the secondary structure of globular proteins deponding on the intensity of the external electric field.

Controlling dynamic SERS hot spots on a monolayer film of Fe3O4@Au nanoparticles by a magnetic field.

PubMed

Guo, Qing-Hua; Zhang, Chen-Jie; Wei, Chao; Xu, Min-Min; Yuan, Ya-Xian; Gu, Ren-Ao; Yao, Jian-Lin

2016-01-05

A large surface-enhanced Raman scattering (SERS) effect is critically dependent on the gap distance of adjacent nanostructures, i.e., "hot spots". However, the fabrication of dynamically controllable hot spots still remains a remarkable challenge. In the present study, we employed an external magnetic field to dynamically control the interparticle spacing of a two-dimensional monolayer film of Fe3O4@Au nanoparticles at a hexane/water interface. SERS measurements were performed to monitor the expansion and shrinkage of the nanoparticles gaps, which produced an obvious effect on SERS activities. The balance between the electrostatic repulsive force, surface tension, and magnetic attractive force allowed observation of the magnetic-field-responsive SERS effect. Upon introduction of an external magnetic field, a very weak SERS signal appeared initially, indicating weak enhancement due to a monolayer film with large interparticle spacing. The SERS intensity reached maximum after 5s and thereafter remained almost unchanged. The results indicated that the observed variations in SERS intensities were fully reversible after removal of the external magnetic field. The reduction of interparticle spacing in response to a magnetic field resulted in about one order of magnitude of SERS enhancement. The combined use of the monolayer film and external magnetic field could be developed as a strategy to construct hot spots both for practical application of SERS and theoretical simulation of enhancement mechanisms. Copyright © 2015 Elsevier B.V. All rights reserved.

Effect of electric field on adsorption of formaldehyde by β-cellobiose in micro-scale

NASA Astrophysics Data System (ADS)

Xu, Bo; Chen, Zhenqian

2018-05-01

To provide a microcosmic theoretical support for the reduction of formaldehyde in building material by the effect of electric fields, the adsorption between formaldehyde molecule and β-cellobiose was studied by density function theory (DFT). Details of geometric structures, molecule bonds and adsorption energy were discussed respectively. The obtained results indicated the energy of formaldehyde molecule decreased while the energy of β-cellobiose increased with greater electric intensity. In addition, the adsorption energy between formaldehyde molecule and β-cellobiose was greatly influenced by external electric field. The adsorption energy reduced gradually with greater electric intensity, and the changing curve of adsorption energy could be fitted as an exponential function, verified by the experiment. The results of this study confirmed the external electric field would be a good strategy for decreasing formaldehyde within building materials in the microcosmic view.

MD simulation study of direct permeation of a nanoparticle across the cell membrane under an external electric field.

PubMed

Shimizu, Kenta; Nakamura, Hideya; Watano, Satoru

2016-06-09

Nanoparticles (NPs) have been attracting much attention for biomedical and pharmaceutical applications. In most of the applications, NPs are required to translocate across the cell membrane and to reach the cell cytosol. Experimental studies have reported that by applying an electric field NPs can directly permeate across the cell membrane without the confinement of NPs by endocytic vesicles. However, damage to the cell can often be a concern. Understanding of the mechanism underlying the direct permeation of NPs under an external electric field can greatly contribute to the realization of a technology for the direct delivery of NPs. Here we investigated the permeation of a cationic gold NP across a phospholipid bilayer under an external electric field using a coarse-grained molecular dynamics simulation. When an external electric field that is equal to the membrane breakdown intensity was applied, a typical NP delivery by electroporation was shown: the cationic gold NP directly permeated across a lipid bilayer without membrane wrapping of the NP, while a persistent transmembrane pore was formed. However, when a specific range of the electric field that is lower than the membrane breakdown intensity was applied, a unique permeation pathway was exhibited: the generated transmembrane pore immediately resealed after the direct permeation of NP. Furthermore, we found that the affinity of the NP for the membrane surface is a key for the self-resealing of the pore. Our finding suggests that by applying an electric field in a suitable range NPs can be directly delivered into the cell with less cellular damage.

External-Stimuli-Assisted Control over Assemblies of Plasmonic Metals.

PubMed

Watanabe, Kanako; Kuroda, Kotaro; Nagao, Daisuke

2018-05-15

Assembly of plasmonic nanoparticles (NPs) in suspensions is a promising approach for the control of optical and sensing properties that depend on the assembled states of plasmonic NPs. This review focuses on the controlling methods to assemble the NP via external stimuli such as pH, temperature, light, magnetic field, and electric field. External stimuli are introduced as powerful tools to assemble the NPs because of various operational factors, such as the intensity, application time, and frequency, which can be employed. In addition to a summary of recent studies on the controlling methods, a future study on the reversible control over assembled states of the plasmonic NPs via external stimuli is proposed.

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

PubMed

Sebestikova, Lenka; Slamova, Elena; Sevcikova, Hana

2005-03-01

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

Plasma expansion into a vacuum with an arbitrarily oriented external magnetic field

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

García-Rubio, F., E-mail: fernando.garcia.rubio@upm.es; Sanz, J.; Ruocco, A.

2016-01-15

Plasma expansion into a vacuum with an external magnetic field is studied under the ideal magnetohydrodynamic hypothesis. The inclination of the magnetic field with respect to the expansion direction is arbitrary, and both the perpendicular and the oblique cases are separately analyzed. A self-similar solution satisfying the boundary conditions is obtained. The interface with the vacuum is treated as a fluid surface, and jump conditions concerning the momentum conservation are imposed. The effect of the intensity of the magnetic field and its inclination is thoroughly studied, and the consistency of the solution for small and large inclinations is investigated.

Effect of the external electric field on the kinetics of recombination of photoexcited carriers in a ZnSe/BeTe type II heterostructure

NASA Astrophysics Data System (ADS)

Filatov, E. V.; Maksimov, A. A.; Tartakovskii, I. I.; Yakovlev, D. R.; Waag, A.

2011-12-01

The kinetics of the radiative recombination of photoexcited electrons and holes for a spatially direct transition in a ZnSe/BeTe type II heterostructure in an external electric field has been analyzed. A strong decrease (more than two orders of magnitude) in the photoluminescence intensity, as well as a decrease in the duration of the relaxation of the direct transition, is observed when the electric field is applied. The energy levels and wavefunctions of electrons and holes in the ZnSe/BeTe heterostructure subjected to the electric field have been numerically calculated. It has been shown that the observed decrease in the photoluminescence intensity and duration of the relaxation of the direct transition is due to both an increase in the radiative recombination time and an increase in the rate of escape of photoexcited holes from the above-barrier level in the ZnSe layer to the BeTe layer.

Effect of the external electric field on the kinetics of recombination of photoexcited carriers in a ZnSe/BeTe type II heterostructure

NASA Astrophysics Data System (ADS)

Filatov, E. V.; Maksimov, A. A.; Tartakovskii, I. I.; Yakovlev, D. R.; Waag, A.

2012-02-01

The kinetics of the radiative recombination of photoexcited electrons and holes for a spatially direct transition in a ZnSe/BeTe type II heterostructure in an external electric field has been analyzed. A strong decrease (more than two orders of magnitude) in the photoluminescence intensity, as well as a decrease in the duration of the relaxation of the direct transition, is observed when the electric field is applied. The energy levels and wavefunctions of electrons and holes in the ZnSe/BeTe heterostructure subjected to the electric field have been numerically calculated. It has been shown that the observed decrease in the photoluminescence intensity and duration of the relaxation of the direct transition is due to both an increase in the radiative recombination time and an increase in the rate of escape of photoexcited holes from the above-barrier level in the ZnSe layer to the BeTe layer.

Near-microsecond human aquaporin 4 gating dynamics in static and alternating external electric fields: Non-equilibrium molecular dynamics

NASA Astrophysics Data System (ADS)

English, Niall J.; Garate, José-A.

2016-08-01

An extensive suite of non-equilibrium molecular-dynamics simulation has been performed for ˜0.85-0.9 μs of human aquaporin 4 in the absence and presence of externally applied static and alternating electric fields applied along the channels (in both axial directions in the static case, taken as the laboratory z-axis). These external fields were of 0.0065 V/Å (r.m.s.) intensity (of the same order as physiological electrical potentials); alternating fields ranged in frequency from 2.45 to 500 GHz. In-pore gating dynamics was studied, particularly of the relative propensities for "open" and "closed" states of the conserved arginines in the arginine/aromatic area (itself governed in no small part by external-field response of the dipolar alignment of the histidine-201 residue in the selectivity filter). In such a manner, the intimate connection of field-response governing "two-state" histidine states was established statistically and mechanistically. Given the appreciable size of the energy barriers for histidine-201 alignment, we have also performed non-equilibrium metadynamics/local-elevation of static fields applied along both directions to construct the free-energy landscape thereof in terms of external-field direction, elucidating the importance of field direction on energetics. We conclude from direct measurement of deterministic molecular dynamics in conjunction with applied-field metadynamics that the intrinsic electric field within the channel points along the +z-axis, such that externally applied static fields in this direction serve to "open" the channel in the selectivity-filter and the asparagine-proline-alanine region.

Near-microsecond human aquaporin 4 gating dynamics in static and alternating external electric fields: Non-equilibrium molecular dynamics.

PubMed

English, Niall J; Garate, José-A

2016-08-28

An extensive suite of non-equilibrium molecular-dynamics simulation has been performed for ∼0.85-0.9 μs of human aquaporin 4 in the absence and presence of externally applied static and alternating electric fields applied along the channels (in both axial directions in the static case, taken as the laboratory z-axis). These external fields were of 0.0065 V/Å (r.m.s.) intensity (of the same order as physiological electrical potentials); alternating fields ranged in frequency from 2.45 to 500 GHz. In-pore gating dynamics was studied, particularly of the relative propensities for "open" and "closed" states of the conserved arginines in the arginine/aromatic area (itself governed in no small part by external-field response of the dipolar alignment of the histidine-201 residue in the selectivity filter). In such a manner, the intimate connection of field-response governing "two-state" histidine states was established statistically and mechanistically. Given the appreciable size of the energy barriers for histidine-201 alignment, we have also performed non-equilibrium metadynamics/local-elevation of static fields applied along both directions to construct the free-energy landscape thereof in terms of external-field direction, elucidating the importance of field direction on energetics. We conclude from direct measurement of deterministic molecular dynamics in conjunction with applied-field metadynamics that the intrinsic electric field within the channel points along the +z-axis, such that externally applied static fields in this direction serve to "open" the channel in the selectivity-filter and the asparagine-proline-alanine region.

Laser pulse propagation in inhomogeneous magnetoplasma channels and wakefield acceleration

NASA Astrophysics Data System (ADS)

Sharma, B. S.; Jain, Archana; Jaiman, N. K.; Gupta, D. N.; Jang, D. G.; Suk, H.; Kulagin, V. V.

2014-02-01

Wakefield excitation in a preformed inhomogeneous parabolic plasma channel by an intense relativistic (≃1019 W/cm2) circularly polarized Gaussian laser pulse is investigated analytically and numerically in the presence of an external longitudinal magnetic field. A three dimensional envelope equation for the evolution of the laser pulse is derived, which includes the effect of the nonparaxial and applied external magnetic field. A relation for the channel radius with the laser spot size is derived and examines numerically to see the external magnetic field effect. It is observed that the channel radius depends on the applied external magnetic field. An analytical expression for the wakefield is derived and validated with the help of a two dimensional particle in cell (2D PIC) simulation code. It is shown that the electromagnetic nature of the wakes in an inhomogeneous plasma channel makes their excitation nonlocal, which results in change of fields with time and external magnetic field due to phase mixing of the plasma oscillations with spatially varying frequencies. The magnetic field effect on perturbation of the plasma density and decreasing length is also analyzed numerically. In addition, it has been shown that the electron energy gain in the inhomogeneous parabolic magnetoplasma channel can be increased significantly compared with the homogeneous plasma channel.

Electron transport estimated from electron spectra using electron spectrometer in LFEX laser target experiments

NASA Astrophysics Data System (ADS)

Ozaki, T.; Hata, M.; Matsuo, K.; Kojima, S.; Arikawa, Y.; Fujioka, S.; Sakagami, H.; Sunahara, A.; Nagatomo, H.; Johzaki, T.; Yogo, A.; Morace, A.; Zhang, Z.; Shiraga, H.; Sakata, S.; Nagai, T.; Abe, Y.; Lee, S.; Nakai, M.; Nishimura, H.; Azechi, H.; FIREX Group; GXII-LFEX Group

2016-05-01

Hot electrons which are generated from targets irradiated by a high-intense laser are measured by two electron spectrometers (ESMs). However, total electron energy observed by the ESM is only less than 1%. Hot electrons are confined by self-fields due to the huge current. When an external magnetic field of several hundred Tesla is applied during the laser irradiation on targets, the ESM signals always increase. In the simulation, the same result can be obtained. The reason is that the Alfvén limit can be mitigated due to the external longitudinal magnetic field.

Dynamics of Deformable Active Particles under External Flow Field

NASA Astrophysics Data System (ADS)

Tarama, Mitsusuke

2017-10-01

In most practical situations, active particles are affected by their environment, for example, by a chemical concentration gradient, light intensity, gravity, or confinement. In particular, the effect of an external flow field is important for particles swimming in a solvent fluid. For deformable active particles such as self-propelled liquid droplets and active vesicles, as well as microorganisms such as euglenas and neutrophils, a general description has been developed by focusing on shape deformation. In this review, we present our recent studies concerning the dynamics of a single active deformable particle under an external flow field. First, a set of model equations of active deformable particles including the effect of a general external flow is introduced. Then, the dynamics under two specific flow profiles is discussed: a linear shear flow, as the simplest example, and a swirl flow. In the latter case, the scattering dynamics of the active deformable particles by the swirl flow is also considered.

Infrared non-destructive evaluation method and apparatus

DOEpatents

Baleine, Erwan; Erwan, James F; Lee, Ching-Pang; Stinelli, Stephanie

2014-10-21

A method of nondestructive evaluation and related system. The method includes arranging a test piece (14) having an internal passage (18) and an external surface (15) and a thermal calibrator (12) within a field of view (42) of an infrared sensor (44); generating a flow (16) of fluid characterized by a fluid temperature; exposing the test piece internal passage (18) and the thermal calibrator (12) to fluid from the flow (16); capturing infrared emission information of the test piece external surface (15) and of the thermal calibrator (12) simultaneously using the infrared sensor (44), wherein the test piece infrared emission information includes emission intensity information, and wherein the thermal calibrator infrared emission information includes a reference emission intensity associated with the fluid temperature; and normalizing the test piece emission intensity information against the reference emission intensity.

Change of magnetic properties of nanocrystalline alloys under influence of external factors

NASA Astrophysics Data System (ADS)

Sitek, Jozef; Holková, Dominika; Dekan, Julius; Novák, Patrik

2016-10-01

Nanocrystalline (Fe3Ni1)81Nb7B12 alloys were irradiated using different types of radiation and subsequently studied by Mössbauer spectroscopy. External magnetic field of 0.5 T, electron-beam irradiation up to 4 MGy, neutron irradiation up to 1017 neutrons/cm2 and irradiation with Cu ions were applied on the samples. All types of external factors had an influence on the magnetic microstructure manifested as a change in the direction of the net magnetic moment, intensity of the internal magnetic field and volumetric fraction of the constituent phases. The direction of the net magnetic moment was the most sensitive parameter. Changes of the microscopic magnetic parameters were compared after different external influence and results of nanocrystalline samples were compared with their amorphous precursors.

Ultrafast optical pulse convertor caused by oscillations of the energy level structure in the conjugated polymer poly(p-phenylenevinylene).

PubMed

Zhang, Yusong; Chen, Weikang; Lin, Zhe; Li, Sheng; George, Thomas F

2017-08-21

For a conjugated polymer irradiated by two optical pulses, the whole process of excitation, involving lattice oscillations, oscillations of the energy level structure, and evolution of the electron cloud, is investigated. Localization of the electron cloud appears in the first 100 fs of irradiation, which in turn induces vibrations of lattice of the polymer chain as well as oscillations of the band gap. These oscillations filter the absorption of the external optical field inversely and convert the original optical field to an ultrafast light field whose intensity varies with a certain period. Based on the mechanism, oscillations of the energy level structure, induced by the external excitation, can be designed as an ultrafast response optical convertor that is able to change the external optical pulse into a new effective light field with a certain oscillation period. This helps provide new insight into designing nanostructures for polymeric optoelectronics.

Method of Modeling and Simulation of Shaped External Occulters

NASA Technical Reports Server (NTRS)

Lyon, Richard G. (Inventor); Clampin, Mark (Inventor); Petrone, Peter, III (Inventor)

2016-01-01

The present invention relates to modeling an external occulter including: providing at least one processor executing program code to implement a simulation system, the program code including: providing an external occulter having a plurality of petals, the occulter being coupled to a telescope; and propagating light from the occulter to a telescope aperture of the telescope by scalar Fresnel propagation, by: obtaining an incident field strength at a predetermined wavelength at an occulter surface; obtaining a field propagation from the occulter to the telescope aperture using a Fresnel integral; modeling a celestial object at differing field angles by shifting a location of a shadow cast by the occulter on the telescope aperture; calculating an intensity of the occulter shadow on the telescope aperture; and applying a telescope aperture mask to a field of the occulter shadow, and propagating the light to a focal plane of the telescope via FFT techniques.

The controllable electron-heating by external magnetic fields at relativistic laser-solid interactions in the presence of large scale pre-plasmas

NASA Astrophysics Data System (ADS)

Wu, D.; Luan, S. X.; Wang, J. W.; Yu, W.; Gong, J. X.; Cao, L. H.; Zheng, C. Y.; He, X. T.

2017-06-01

The two-stage electron acceleration/heating model (Wu et al 2017 Nucl. Fusion 57 016007 and Wu et al 2016 Phys. Plasmas 23 123116) is extended to the study of laser magnetized-plasmas interactions at relativistic intensities and in the presence of large-scale preformed plasmas. It is shown that the electron-heating efficiency is a controllable value by the external magnetic fields. Detailed studies indicate that for a right-hand circularly polarized laser, the electron heating efficiency depends on both strength and directions of external magnetic fields. The electron-heating is dramatically enhanced when the external magnetic field is of B\\equiv {ω }c/{ω }0> 1. When magnetic field is of negative direction, i.e. B< 0, it trends to suppress the electron heating. The underlining physics—the dependences of electron-heating on both the strength and directions of the external magnetic fields—is uncovered. With -∞ < B< 1, the electron-heating is explained by the synergetic effects by longitudinal charge separation electric field and the reflected ‘envelop-modulated’ CP laser. It is indicated that the ‘modulation depth’ of reflected CP laser is significantly determined by the external magnetic fields, which will in turn influence the efficiency of the electron-heating. While with B> 1, a laser front sharpening mechanism is identified at relativistic laser magnetized-plasmas interactions, which is responsible for the dramatical enhancement of electron-heating.

Magnetic field in expanding quark-gluon plasma

NASA Astrophysics Data System (ADS)

Stewart, Evan; Tuchin, Kirill

2018-04-01

Intense electromagnetic fields are created in the quark-gluon plasma by the external ultrarelativistic valence charges. The time evolution and the strength of this field are strongly affected by the electrical conductivity of the plasma. Yet, it has recently been observed that the effect of the magnetic field on the plasma flow is small. We compute the effect of plasma flow on magnetic field and demonstrate that it is less than 10%. These observations indicate that the plasma hydrodynamics and the dynamics of electromagnetic field decouple. Thus, it is a very good approximation, on the one hand, to study QGP in the background electromagnetic field generated by external sources and, on the other hand, to investigate the dynamics of magnetic field in the background plasma. We also argue that the wake induced by the magnetic field in plasma is negligible.

In situ observation of atomic movement in a ferroelectric film under an external electric field and stress

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

Lee, Hyeon Jun; Guo, Er-Jia; Min, Taewon

Atomic movement under application of external stimuli (i.e., electric field or mechanical stress) in oxide materials has not been observed due to a lack of experimental methods but has been well known to determine the electric polarization. Here, we investigated atomic movement arising from the ferroelectric response of BiFeO 3 thin films under the effect of an electric field and stress in real time using a combination of switching spectroscopy, time-resolved X-ray microdiffraction, and in situ stress engineering. Under an electric field applied to a BiFeO 3 film, the hysteresis loop of the reflected X-ray intensity was found to resultmore » from the opposing directions of displaced atoms between the up and down polarization states. An additional shift of atoms arising from the linearly increased dielectric component of the polarization in BiFeO 3 was confirmed through gradual reduction of the diffracted X-ray intensity. The electric-fieldinduced displacement of oxygen atoms was found to be larger than that of Fe atom for both ferroelectric switching and increase of the polarization. In conclusion, the effect of external stress on the BiFeO 3 thin film, which was controlled by applying an electric field to the highly piezoelectric substrate, showed smaller atomic shifts than for the case of applying an electric field to the film, despite the similar tetragonality.« less

In situ observation of atomic movement in a ferroelectric film under an external electric field and stress

DOE PAGES

Lee, Hyeon Jun; Guo, Er-Jia; Min, Taewon; ...

2017-12-28

Atomic movement under application of external stimuli (i.e., electric field or mechanical stress) in oxide materials has not been observed due to a lack of experimental methods but has been well known to determine the electric polarization. Here, we investigated atomic movement arising from the ferroelectric response of BiFeO 3 thin films under the effect of an electric field and stress in real time using a combination of switching spectroscopy, time-resolved X-ray microdiffraction, and in situ stress engineering. Under an electric field applied to a BiFeO 3 film, the hysteresis loop of the reflected X-ray intensity was found to resultmore » from the opposing directions of displaced atoms between the up and down polarization states. An additional shift of atoms arising from the linearly increased dielectric component of the polarization in BiFeO 3 was confirmed through gradual reduction of the diffracted X-ray intensity. The electric-fieldinduced displacement of oxygen atoms was found to be larger than that of Fe atom for both ferroelectric switching and increase of the polarization. In conclusion, the effect of external stress on the BiFeO 3 thin film, which was controlled by applying an electric field to the highly piezoelectric substrate, showed smaller atomic shifts than for the case of applying an electric field to the film, despite the similar tetragonality.« less

Effects of magnetic fields on improving mass transfer in flue gas desulfurization using a fluidized bed

NASA Astrophysics Data System (ADS)

Zhang, Qi; Gui, Keting; Wang, Xiaobo

2016-02-01

The effects of magnetic fields on improving the mass transfer in flue gas desulfurization using a fluidized bed are investigated in the paper. In this research, the magnetically fluidized bed (MFB) is used as the reactor in which ferromagnetic particles are fluidized with simulated flue gas under the influence of an external magnetic field. Lime slurry is continuously sprayed into the reactor. As a consequence, the desulfurization reaction and the slurry drying process take place simultaneously in the MFB. In this paper, the effects of ferromagnetic particles and external magnetic fields on the desulphurization efficiency are studied and compared with that of quartz particles as the fluidized particles. Experimental results show that the ferromagnetic particles not only act as a platform for lime slurry to precipitate on like quartz particles, but also take part in the desulfurization reaction. The results also show that the specific surface area of ferromagnetic particles after reaction is enlarged as the magnetic intensity increases, and the external magnetic field promotes the oxidation of S(IV), improving the mass transfer between sulphur and its sorbent. Hence, the efficiency of desulphurization under the effects of external magnetic fields is higher than that in general fluidized beds.

Dramatic impact of the giant local magnetic fields on spin-dependent recombination processes in gadolinium based garnets

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

Romanov, N. G., E-mail: nikolai.romanov@mail.ioffe.ru; Tolmachev, D. O.; Gurin, A. S.

2015-06-29

A giant magnetic field effect on spin-dependent recombination of the radiation-induced defects has been found in cerium doped gadolinium based garnet crystals and ceramics, promising materials for scintillator applications. A sharp and strong increase in the afterglow intensity stimulated by external magnetic field and an evidence of the magnetic field memory have been discovered. The effect was ascribed to huge Gd-induced internal magnetic fields, which suppress the recombination, and cross-relaxation with Gd{sup 3+} ions leading to reorientation of the spins of the electron and hole centers. Thus, the spin system of radiation-induced defects in gadolinium garnet based scintillator materials wasmore » shown to accumulate significant energy which can be released in external magnetic fields.« less

Propagation of a Toroidal Magnetic Cloud through the Inner Heliosphere

NASA Astrophysics Data System (ADS)

Romashets, Eugene; Vandas, Marek

2003-09-01

An analytical solution for a potential magnetic field with arbitrary intensity around a toroidal magnetic cloud has been found. The background external field may have a gradient. The solution is used for calculation of magnetic cloud propagation. Obtained velocity profiles show a good agreement with in situ observations near the Earth's orbit.

Combined effects of an intense laser field, electric field and hydrostatic pressure on donor impurity states in zinc-blende InGaN/GaN quantum dots

NASA Astrophysics Data System (ADS)

Wang, Guangxin; Zhou, Rui; Duan, Xiuzhi

2016-07-01

The shallow-donor impurity states in cylindrical zinc-blende (ZB) In x Ga1- x N/GaN quantum dots (QDs) have been theoretically investigated, considering the combined effects of an intense laser field (ILF), an external electric field, and hydrostatic pressure. The numerical results show that for an on-center impurity in ZB In x Ga1- x N/GaN QD, (1) the ground-state binding energy of the donor impurity is a decreasing function of the laser-dressing parameter and/or the QD's height; (2) as the QD's radius decreases, the binding energy of the donor impurity increases at first, reaches a maximum value, and then drops rapidly; (3) the binding energy of the donor impurity is a decreasing function of the external electric field due to the Stark effect; (4) the binding energy of the donor impurity increases as the applied hydrostatic pressure becomes large. In addition, the position of the impurity ion was also found to have an important influence on the binding energy of the donor impurity. The physical reasons have been analyzed in detail.

Quantum dynamics of charge state in silicon field evaporation

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

Silaeva, Elena P.; Uchida, Kazuki; Watanabe, Kazuyuki, E-mail: kazuyuki@rs.kagu.tus.ac.jp

2016-08-15

The charge state of an ion field-evaporating from a silicon-atom cluster is analyzed using time-dependent density functional theory coupled to molecular dynamics. The final charge state of the ion is shown to increase gradually with increasing external electrostatic field in agreement with the average charge state of silicon ions detected experimentally. When field evaporation is triggered by laser-induced electronic excitations the charge state also increases with increasing intensity of the laser pulse. At the evaporation threshold, the charge state of the evaporating ion does not depend on the electrostatic field due to the strong contribution of laser excitations to themore » ionization process both at low and high laser energies. A neutral silicon atom escaping the cluster due to its high initial kinetic energy is shown to be eventually ionized by external electrostatic field.« less

LINEAR ACCELERATOR

DOEpatents

Christofilos, N.C.; Polk, I.J.

1959-02-17

Improvements in linear particle accelerators are described. A drift tube system for a linear ion accelerator reduces gap capacity between adjacent drift tube ends. This is accomplished by reducing the ratio of the diameter of the drift tube to the diameter of the resonant cavity. Concentration of magnetic field intensity at the longitudinal midpoint of the external sunface of each drift tube is reduced by increasing the external drift tube diameter at the longitudinal center region.

The effect of external magnetic field on the Raman peaks in manganites

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

Sahu, A. K., E-mail: ajitsahu@seemantaengg.ac.in; Rout, G. C.

2014-04-24

We report here a microscopic theoretical model study exhibiting the effect of external magnetic field on the Raman excitation peaks in the CMR manganite system. The Hamiltonian consists of Jahn-Teller (J-T) distortion in e{sub g} band, the double exchange interaction and the Heisenberg spin-spin interaction. Further the phonons are coupled to e{sub g} band electrons, J-T distorted e{sub g} band and the double exchange interaction. The Raman spectral intensity is calculated from the imaginary part of the phonon Green function. The spectra exhibits three peaks besides a very weak high energy peak. The magnetic field effect on these peaks aremore » reported.« less

Optical response in a laser-driven quantum pseudodot system

NASA Astrophysics Data System (ADS)

Kilic, D. Gul; Sakiroglu, S.; Ungan, F.; Yesilgul, U.; Kasapoglu, E.; Sari, H.; Sokmen, I.

2017-03-01

We investigate theoretically the intense laser-induced optical absorption coefficients and refractive index changes in a two-dimensional quantum pseudodot system under an uniform magnetic field. The effects of non-resonant, monochromatic intense laser field upon the system are treated within the framework of high-frequency Floquet approach in which the system is supposed to be governed by a laser-dressed potential. Linear and nonlinear absorption coefficients and relative changes in the refractive index are obtained by means of the compact-density matrix approach and iterative method. The results of numerical calculations for a typical GaAs quantum dot reveal that the optical response depends strongly on the magnitude of external magnetic field and characteristic parameters of the confinement potential. Moreover, we have demonstrated that the intense laser field modifies the confinement and thereby causes remarkable changes in the linear and nonlinear optical properties of the system.

Evolution of a Gaussian laser beam in warm collisional magnetoplasma

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

Jafari, M. J.; Jafari Milani, M. R., E-mail: mrj.milani@gmail.com; Niknam, A. R.

2016-07-15

In this paper, the spatial evolution of an intense circularly polarized Gaussian laser beam propagated through a warm plasma is investigated, taking into account the ponderomotive force, Ohmic heating, external magnetic field, and collisional effects. Using the momentum transfer and energy equations, both modified electron temperature and electron density in plasma are obtained. By introducing the complex dielectric permittivity of warm magnetized plasma and using the complex eikonal function, coupled differential equations for beam width parameter are established and solved numerically. The effects of polarization state of laser and magnetic field on the laser spot size evolution are studied. Itmore » is observed that in case of the right-handed polarization, an increase in the value of external magnetic field causes an increase in the strength of the self-focusing, especially in the higher values, and consequently, the self-focusing occurs in shorter distance of propagation. Moreover, the results demonstrate the existence of laser intensity and electron temperature ranges where self-focusing can occur, while the beam diverges outside of these regions; meanwhile, in these intervals, there exists a turning point for each of intensity and temperature in which the self-focusing process has its strongest strength. Finally, it is found that the self-focusing effect can be enhanced by increasing the plasma frequency (plasma density).« less

MAGNETOMETER

DOEpatents

Leavitt, M.A.

1958-11-18

A magnetometer ls described, partlcularly to a device which accurately indicates the polarity and intensity of a magnetlc field. The main feature of the invention is a unique probe construction in combinatlon wlth a magnetic fleld detector system. The probe comprises two coils connected in series opposition for energization with an a-c voltage. The voltage lnduced in a third coll on the probe, a pick-up coil, is distorted by the presence of an external field to produce even harmonic voltages. A controlled d-c current is passed through the energized coils to counter the dlstortlon and reduce tbe even harmonic content to a null. When the null point is reached, the d-c current is a measure of the external magnetic field strength, and the phase of the pickup coil voltage indicates tbe field polarlty.

The Geomagnetic Field as a Transient: Constraints From Paleomagnetic Intensity Data

NASA Astrophysics Data System (ADS)

Aldridge, K. D.; Baker, R.; McMillan, D. G.

2009-12-01

Measurement of Earth’s magnetic field intensity from sedimentary rocks confirms that the field is a transient on millennial time scales. In accounting for this observation, parameters from dynamo models need to be compared with those obtained from observations. Here we model temporal changes in intensity of the geomagnetic field as either growths or decays, sometimes separated by stationary states. In order to obtain temporal properties of the geomagnetic field, our model, developed as a Matlab algorithm, searches records of relative paleointensity to measure objectively the rates of growth and decay of the field. Here we report on the application of our algorithm to six records of relative paleointensity obtained from oceanic cores. Our model for the fluid velocity field in Earth’s core is based on parametric instability produced externally through gradients of the gravitational field. It is well known that these gradients can lead to instability of the core fluid through both elliptical and shear straining of fluid streamlines. Such an instability will exist as long as the externally produced strain rate exceeds the dissipation rate in Earth’s fluid core. As known from both theoretical models and experimental observations that a sequence of alternately growing and decaying velocities will develop in the fluid, our algorithm has searched the records of relative paleointensity for exponential growths and decays. Since a balance may exist between strain and decay rates described above, our algorithm includes the possibility for a segment of relative paleointensity that is stationary. Such segments do indeed occur in the relative paleointensity record and are expected by the model of parametric instability. Results of the application of our algorithm spanning two Ma with broad geographical coverage will be presented.

The Action of a Magnetic Field on Water,

DTIC Science & Technology

The effect of a low intensity magnetic field on water as a flotation medium with the enrichment of coal and dressing of copper sulfied ore is studied...magnetic field with flotation is expressed. The imposition of an external magnetic field disturbs the energy state of water, which leads to a change in...intermolecular interaction, stability of hydrogen bonds, deterioration in the wettability of rigid surfaces, and a change in the technological indices of flotation enrichment. (Author)

Guiding-center equations for electrons in ultraintense laser fields

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

Moore, J.E.; Fisch, N.J.

1994-01-01

The guiding-center equations are derived for electrons in arbitrarily intense laser fields also subject to external fields and ponderomotive forces. Exhibiting the relativistic mass increase of the oscillating electrons, a simple frame-invariant equation is shown to govern the behavior of the electrons for sufficiently weak background fields and ponderomotive forces. The parameter regime for which such a formulation is valid is made precise, and some predictions of the equation are checked by numerical simulation.

Dielectric-spectroscopy approach to ferrofluid nanoparticle clustering induced by an external electric field.

PubMed

Rajnak, Michal; Kurimsky, Juraj; Dolnik, Bystrik; Kopcansky, Peter; Tomasovicova, Natalia; Taculescu-Moaca, Elena Alina; Timko, Milan

2014-09-01

An experimental study of magnetic colloidal particles cluster formation induced by an external electric field in a ferrofluid based on transformer oil is presented. Using frequency domain isothermal dielectric spectroscopy, we study the influence of a test cell electrode separation distance on a low-frequency relaxation process. We consider the relaxation process to be associated with an electric double layer polarization taking place on the particle surface. It has been found that the relaxation maximum considerably shifts towards lower frequencies when conducting the measurements in the test cells with greater electrode separation distances. As the electric field intensity was always kept at a constant value, we propose that the particle cluster formation induced by the external ac electric field accounts for that phenomenon. The increase in the relaxation time is in accordance with the Schwarz theory of electric double layer polarization. In addition, we analyze the influence of a static electric field generated by dc bias voltage on a similar shift in the relaxation maximum position. The variation of the dc electric field for the hysteresis measurements purpose provides understanding of the development of the particle clusters and their decay. Following our results, we emphasize the utility of dielectric spectroscopy as a simple, complementary method for detection and study of clusters of colloidal particles induced by external electric field.

Strong field QED in lepton colliders and electron/laser interactions

NASA Astrophysics Data System (ADS)

Hartin, Anthony

2018-05-01

The studies of strong field particle physics processes in electron/laser interactions and lepton collider interaction points (IPs) are reviewed. These processes are defined by the high intensity of the electromagnetic fields involved and the need to take them into account as fully as possible. Thus, the main theoretical framework considered is the Furry interaction picture within intense field quantum field theory. In this framework, the influence of a background electromagnetic field in the Lagrangian is calculated nonperturbatively, involving exact solutions for quantized charged particles in the background field. These “dressed” particles go on to interact perturbatively with other particles, enabling the background field to play both macroscopic and microscopic roles. Macroscopically, the background field starts to polarize the vacuum, in effect rendering it a dispersive medium. Particles encountering this dispersive vacuum obtain a lifetime, either radiating or decaying into pair particles at a rate dependent on the intensity of the background field. In fact, the intensity of the background field enters into the coupling constant of the strong field quantum electrodynamic Lagrangian, influencing all particle processes. A number of new phenomena occur. Particles gain an intensity-dependent rest mass shift that accounts for their presence in the dispersive vacuum. Multi-photon events involving more than one external field photon occur at each vertex. Higher order processes which exchange a virtual strong field particle resonate via the lifetimes of the unstable strong field states. Two main arenas of strong field physics are reviewed; those occurring in relativistic electron interactions with intense laser beams, and those occurring in the beam-beam physics at the interaction point of colliders. This review outlines the theory, describes its significant novel phenomenology and details the experimental schema required to detect strong field effects and the simulation programs required to model them.

F-centers mechanism of long-term relaxation in lead zirconate-titanate based piezoelectric ceramics. 2. After-field relaxation

NASA Astrophysics Data System (ADS)

Ishchuk, V. M.; Kuzenko, D. V.

2016-08-01

The paper presents results of experimental study of the dielectric constant relaxation during aging process in Pb(Zr,Ti)O3 based solid solutions (PZT) after action of external DC electric field. The said process is a long-term one and is described by the logarithmic function of time. Reversible and nonreversible relaxation process takes place depending on the field intensity. The relaxation rate depends on the field strength also, and the said dependence has nonlinear and nonmonotonic form, if external field leads to domain disordering. The oxygen vacancies-based model for description of the long-term relaxation processes is suggested. The model takes into account the oxygen vacancies on the sample's surface ends, their conversion into F+- and F0-centers under external effects and subsequent relaxation of these centers into the simple oxygen vacancies after the action termination. F-centers formation leads to the violation of the original sample's electroneutrality, and generate intrinsic DC electric field into the sample. Relaxation of F-centers is accompanied by the reduction of the electric field, induced by them, and relaxation of the dielectric constant, as consequent effect.

How do protozoa respond to intense magnetic fields?

NASA Astrophysics Data System (ADS)

Guevorkian, Karine

2005-03-01

Most microorganisms such as Paramecium Caudatum, swim in helical paths in nature. In the absence of any external stimuli (e.g. obstacles, electric field, heat, etc.) the axes of these helical paths, which define the trajectories, are straight lines and are distributed in random directions. Our experiments reveal that these trajectories can be manipulated by applying intense DC magnetic fields of the order of several Tesla. Swimming paramecia, for example, align their trajectories with magnetic fields in excess of about 7 Tesla in fraction of a second. We will describe this phenomenon in fields up to 25 T. We will address whether this effect is an active or passive response to the magnetic torque exerted on the diamagnetically anisotropic structures in Paramecium. In addition we will present results for other species as they are obtained.

Free-Free Transitions of the e-H System Inside a Dense Plasma Irradiated by a Laser Field at Very Low Incident-Electron Energies

NASA Technical Reports Server (NTRS)

Bhatia, A. K.; Sinha, C.

2012-01-01

The free-free transition is studied for an electron-hydrogen atom in ground state when a low-energy electron (external) is injected into hydrogenic plasma in the presence of an external homogenous, monochromatic, and linearly polarized laser field. The effect of plasma screening is considered in the Debye-Huckel approximation. The calculations are performed in the soft photon limit. The incident electron is considered to be dressed by the laser field in a nonperturbative manner by choosing the Volkov solutions in both the initial and final channels. The space part of the scattering wave function for the electron is solved numerically by taking into account the electron exchange. The laser-assisted differential and total cross sections are calculated for single-photon absorption or emission and no-photon exchange in the soft photon limit, the laser intensity being much less than the atomic field intensity. The calculations have been carried out for various values of Debye parameter, ranging from 0.005 to 0.12. A strong suppression is noted in the laser-assisted cross sections as compared to the field-free situation. A significant difference is noted for the singlet and triplet cross sections. The suppression is much more in the triplet states.

The lunar dynamo

NASA Astrophysics Data System (ADS)

Weiss, Benjamin P.; Tikoo, Sonia M.

2014-12-01

The inductive generation of magnetic fields in fluid planetary interiors is known as the dynamo process. Although the Moon today has no global magnetic field, it has been known since the Apollo era that the lunar rocks and crust are magnetized. Until recently, it was unclear whether this magnetization was the product of a core dynamo or fields generated externally to the Moon. New laboratory and spacecraft measurements strongly indicate that much of this magnetization is the product of an ancient core dynamo. The dynamo field persisted from at least 4.25 to 3.56 billion years ago (Ga), with an intensity reaching that of the present Earth. The field then declined by at least an order of magnitude by ∼3.3 Ga. The mechanisms for sustaining such an intense and long-lived dynamo are uncertain but may include mechanical stirring by the mantle and core crystallization.

A global analysis of the 1991 geomagnetic jerk

NASA Astrophysics Data System (ADS)

De Michelis, Paola; Cafarella, Lili; Meloni, Antonio

2000-12-01

A recent examination of the geomagnetic annual mean values for the European magnetic observatories has shown the existence of a sudden change in the secular acceleration in about 1991 (Cafarella & Meloni 1995; Macmillan 1996). Using first differences of the Y (east geomagnetic field component) mean values from 74 observatories, the worldwide character of the 1991 impulse has been determined (De Michelis et al. 1998). Using data from 109 observatories widely distributed all over the world, the structure of the secular variation for the X (north) and Z (vertical) magnetic field intensities around 1990 was investigated, and evidence of this most recent jerk was found. External effects were removed from the annual mean data by comparing the long-term variations of the geomagnetic field components at individual observatories with the long-term variations of two geomagnetic indices, aa and Dst, and of a solar index, the Wolf number R. A careful analysis has been carried out on the amplitude of the external disturbance, on its dependence on latitude, and on the weights of the geomagnetic indices in the evaluation of the resulting external field. The secular variation has been evaluated from the corrected annual means. Around 1990, the secular variation can be fitted at many observatories by two straight lines with a sudden and marked change in slope. In this manner the jerk occurrence time and the intensity of the step in the second time derivative (ΔX'', ΔY'' and ΔZ'') were computed. Maps of ΔX'', ΔY'' and ΔZ'' provide information on the worldwide intensity distribution of the examined event. Maps of the jerk occurrence-time distributions are also given. The mean jerk occurrence time is 1990.1+/-0.6. Finally, a spherical harmonic analysis was used to complete the quantitative description of this phenomenon in order to study the trend of the energy density spectrum as a function of the harmonic degree n.

Simulating Chiral Magnetic and Separation Effects with Spin-Orbit Coupled Atomic Gases

PubMed Central

Huang, Xu-Guang

2016-01-01

The chiral magnetic and chiral separation effects—quantum-anomaly-induced electric current and chiral current along an external magnetic field in parity-odd quark-gluon plasma—have received intense studies in the community of heavy-ion collision physics. We show that analogous effects occur in rotating trapped Fermi gases with Weyl-Zeeman spin-orbit coupling where the rotation plays the role of an external magnetic field. These effects can induce a mass quadrupole in the atomic cloud along the rotation axis which may be tested in future experiments. Our results suggest that the spin-orbit coupled atomic gases are potential simulators of the chiral magnetic and separation effects. PMID:26868084

Main field and secular variation candidate models for the 12th IGRF generation after 10 months of Swarm measurements

NASA Astrophysics Data System (ADS)

Saturnino, Diana; Langlais, Benoit; Civet, François; Thébault, Erwan; Mandea, Mioara

2015-06-01

We describe the main field and secular variation candidate models for the 12th generation of the International Geomagnetic Reference Field model. These two models are derived from the same parent model, in which the main field is extrapolated to epoch 2015.0 using its associated secular variation. The parent model is exclusively based on measurements acquired by the European Space Agency Swarm mission between its launch on 11/22/2013 and 09/18/2014. It is computed up to spherical harmonic degree and order 25 for the main field, 13 for the secular variation, and 2 for the external field. A selection on local time rather than on true illumination of the spacecraft was chosen in order to keep more measurements. Data selection based on geomagnetic indices was used to minimize the external field contributions. Measurements were screened and outliers were carefully removed. The model uses magnetic field intensity measurements at all latitudes and magnetic field vector measurements equatorward of 50° absolute quasi-dipole magnetic latitude. A second model using only the vertical component of the measured magnetic field and the total intensity was computed. This companion model offers a slightly better fit to the measurements. These two models are compared and discussed.We discuss in particular the quality of the model which does not use the full vector measurements and underline that this approach may be used when only partial directional information is known. The candidate models and their associated companion models are retrospectively compared to the adopted IGRF which allows us to criticize our own choices.

Abnormal characteristics of binary molecular clusters in DMSO–ethanol mixtures under external electric fields

NASA Astrophysics Data System (ADS)

Wu, Zhiyan; Huang, Kama

2018-05-01

For the nonlinearly phenomena on the dielectric properties of dimethyl sulfoxide (DMSO)-ethanol mixtures under a low intensity microwave field, we propose a conjecture that there exist some abnormal molecular clusters. To interpret the mechanism of abnormal phenomena and confirm our conjecture about the existence of abnormal molecular clusters, an in-depth investigation about the structure evolutions of (DMSO)m(C2H5OH)n (m = 0-4; n = 0-4; m + n ≤ 4) molecular clusters induced by external electric fields has been given by using density functional theory. The results show that there exist some binary molecular clusters with large cluster radii in mixtures, and some of them are unstable under exposure of electric fields. It implies that the existence of certain abnormal molecular clusters in DMSO-ethanol mixtures results in their abnormality of dielectric properties.

Research on external flow field of a car based on reverse engineering

NASA Astrophysics Data System (ADS)

Hu, Shushan; Liu, Ronge

2018-05-01

In this paper, the point cloud data of FAW-VOLKSWAGEN car body shape is obtained by three coordinate measuring instrument and laser scanning method. The accurate three dimensional model of the car is obtained using CATIA software reverse modelling technology. The car body is gridded, the calculation field and boundary condition type of the car flow field are determined, and the numerical simulation is carried out in Hyper Mesh software. The pressure cloud diagram, velocity vector diagram, air resistance coefficient and lift coefficient of the car are obtained. The calculation results reflect the aerodynamic characteristics of the car's external flow field. The motion of the separation flow on the surface of the vehicle body is well simulated, and the area where the vortex motion is relatively intense has been determined. The results provide a theoretical basis for improving and optimizing the body shape.

Electric Field Induce Blue Shift and Intensity Enhancement in 2D Exciplex Organic Light Emitting Diodes; Controlling Electron-Hole Separation.

PubMed

Al Attar, Hameed A; Monkman, Andy P

2016-09-01

A simple but novel method is designed to study the characteristics of the exciplex state pinned at a donor-acceptor abrupt interface and the effect an external electric field has on these excited states. The reverse Onsager process, where the field induces blue-shifted emission and increases the efficiency of the exciplex emission as the e-h separation reduces, is discussed. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

A Dynamic Model of Mercury's Magnetospheric Magnetic Field

PubMed Central

Johnson, Catherine L.; Philpott, Lydia; Tsyganenko, Nikolai A.; Anderson, Brian J.

2017-01-01

Abstract Mercury's solar wind and interplanetary magnetic field environment is highly dynamic, and variations in these external conditions directly control the current systems and magnetic fields inside the planetary magnetosphere. We update our previous static model of Mercury's magnetic field by incorporating variations in the magnetospheric current systems, parameterized as functions of Mercury's heliocentric distance and magnetic activity. The new, dynamic model reproduces the location of the magnetopause current system as a function of systematic pressure variations encountered during Mercury's eccentric orbit, as well as the increase in the cross‐tail current intensity with increasing magnetic activity. Despite the enhancements in the external field parameterization, the residuals between the observed and modeled magnetic field inside the magnetosphere indicate that the dynamic model achieves only a modest overall improvement over the previous static model. The spatial distribution of the residuals in the magnetic field components shows substantial improvement of the model accuracy near the dayside magnetopause. Elsewhere, the large‐scale distribution of the residuals is similar to those of the static model. This result implies either that magnetic activity varies much faster than can be determined from the spacecraft's passage through the magnetosphere or that the residual fields are due to additional external current systems not represented in the model or both. Birkeland currents flowing along magnetic field lines between the magnetosphere and planetary high‐latitude regions have been identified as one such contribution. PMID:29263560

Influence of thermodynamic mechanism of inter- facial adsorption on purifying air-conditioning engineering under intensification of electric field

NASA Astrophysics Data System (ADS)

Chen, Yun-Yu

2016-12-01

As a kind of mass transfer process as well as the basis of separating and purifying mixtures, interfacial adsorption has been widely applied to fields like chemical industry, medical industry and purification engineering in recent years. Influencing factors of interfacial adsorption, in addition to the traditional temperature, intensity of pressure, amount of substance and concentration, also include external fields, such as magnetic field, electric field and electromagnetic field, etc. Starting from the point of thermodynamics and taking the Gibbs adsorption as the model, the combination of energy axiom and the first law of thermodynamics was applied to boundary phase, and thus the theoretical expression for the volume of interface absorption under electric field as well as the mathematical relationship between surface tension and electric field intensity was obtained. In addition, according to the obtained theoretical expression, the volume of interface absorption of ethanol solution under different electric field intensities and concentrations was calculated. Moreover, the mechanism of interfacial adsorption was described from the perspective of thermodynamics and the influence of electric field on interfacial adsorption was explained reasonably, aiming to further discuss the influence of thermodynamic mechanism of interfacial adsorption on purifying air-conditioning engineering under intensification of electric field.

Magneto-optical visualization of three spatial components of inhomogeneous stray fields

NASA Astrophysics Data System (ADS)

Ivanov, V. E.

2012-08-01

The article deals with the physical principles of magneto-optical visualization (MO) of three spatial components of inhomogeneous stray fields with the help of FeCo metal indicator films in the longitudinal Kerr effect geometry. The inhomogeneous field is created by permanent magnets. Both p- and s-polarization light is used for obtaining MO images with their subsequent summing, subtracting and digitizing. As a result, the MO images and corresponding intensity coordinate dependences reflecting the distributions of the horizontal and vertical magnetization components in pure form have been obtained. Modeling of both the magnetization distribution in the indicator film and the corresponding MO images shows that corresponding to polar sensitivity the intensity is proportional to the normal field component, which permits normal field component mapping. Corresponding to longitudinal sensitivity, the intensity of the MO images reflects the angular distribution of the planar field component. MO images have singular points in which the planar component is zero and their movement under an externally homogeneous planar field permits obtaining of additional information on the two planar components of the field under study. The intensity distribution character in the vicinity of sources and sinks (singular points) remains the same under different orientations of the light incidence plane. The change of incident plane orientation by π/2 alters the distribution pattern in the vicinity of the saddle points.

The lunar dynamo.

PubMed

Weiss, Benjamin P; Tikoo, Sonia M

2014-12-05

The inductive generation of magnetic fields in fluid planetary interiors is known as the dynamo process. Although the Moon today has no global magnetic field, it has been known since the Apollo era that the lunar rocks and crust are magnetized. Until recently, it was unclear whether this magnetization was the product of a core dynamo or fields generated externally to the Moon. New laboratory and spacecraft measurements strongly indicate that much of this magnetization is the product of an ancient core dynamo. The dynamo field persisted from at least 4.25 to 3.56 billion years ago (Ga), with an intensity reaching that of the present Earth. The field then declined by at least an order of magnitude by ∼3.3 Ga. The mechanisms for sustaining such an intense and long-lived dynamo are uncertain but may include mechanical stirring by the mantle and core crystallization. Copyright © 2014, American Association for the Advancement of Science.

Magnetically Diffused Radial Electric-Arc Air Heater Employing Water-Cooled Copper Electrodes

NASA Technical Reports Server (NTRS)

Mayo, R. F.; Davis, D. D., Jr.

1962-01-01

A magnetically rotated electric-arc air heater has been developed that is novel in that an intense magnetic field of the order of 10,000 to 25,000 gauss is employed. This field is supplied by a coil that is connected in series with the arc. Experimentation with this heater has shown that the presence of an intense magnetic field transverse to the arc results in diffusion of the arc and that the arc has a positive effective resistance. With the field coil in series with the arc, highly stable arc operation is obtained from a battery power supply. External ballast is not required to stabilize the arc when it is operating at maximum power level. The electrode erosion rate is so low that the airstream contamination is no more than 0.07 percent and may be substantially less.

Ultrafast proton radiography of the magnetic fields generated by a laser-driven coil current

DOE PAGES

Gao, Lan; Ji, Hantao; Fiksel, Gennady; ...

2016-04-15

Magnetic fields generated by a current flowing through a U-shaped coil connecting two copper foils were measured using ultrafast proton radiography. Two ~ 1.25 kJ, 1-ns laser pulses propagated through laser entrance holes in the front foil and were focused to the back foil with an intensity of ~ 3 x 10 16 W/cm 2. The intense laser-solid interaction induced a high voltage between the copper foils and generated a large current in the connecting coil. The proton data show ~ 40-50 T magnetic fields at the center of the coil ~ 3-4 ns after laser irradiation. In conclusion, themore » experiments provide significant insight for future target designs that aim to develop a powerful source of external magnetic fields for various applications in high-energy-density science.« less

Coupling behaviors of graphene/SiO2/Si structure with external electric field

NASA Astrophysics Data System (ADS)

Onishi, Koichi; Kirimoto, Kenta; Sun, Yong

2017-02-01

A traveling electric field in surface acoustic wave was introduced into the graphene/SiO2/Si sample in the temperature range of 15 K to 300 K. The coupling behaviors between the sample and the electric field were analyzed using two parameters, the intensity attenuation and time delay of the traveling-wave. The attenuation originates from Joule heat of the moving carriers, and the delay of the traveling-wave was due to electrical resistances of the fixed charge and the moving carriers with low mobility in the sample. The attenuation of the external electric field was observed in both Si crystal and graphene films in the temperature range. A large attenuation around 190 K, which depends on the strength of external electric field, was confirmed for the Si crystal. But, no significant temperature and field dependences of the attenuation in the graphene films were detected. On the other hand, the delay of the traveling-wave due to ionic scattering at low temperature side was observed in the Si crystal, but cannot be detected in the films of the mono-, bi- and penta-layer graphene with high conductivities. Also, it was indicated in this study that skin depth of the graphene film was less than thickness of two graphene atomic layers in the temperature range.

Pulsed dynamical decoupling for fast and robust two-qubit gates on trapped ions

NASA Astrophysics Data System (ADS)

Arrazola, I.; Casanova, J.; Pedernales, J. S.; Wang, Z.-Y.; Solano, E.; Plenio, M. B.

2018-05-01

We propose a pulsed dynamical decoupling protocol as the generator of tunable, fast, and robust quantum phase gates between two microwave-driven trapped-ion hyperfine qubits. The protocol consists of sequences of π pulses acting on ions that are oriented along an externally applied magnetic-field gradient. In contrast to existing approaches, in our design the two vibrational modes of the ion chain cooperate under the influence of the external microwave driving to achieve significantly increased gate speeds. Our scheme is robust against the dominant noise sources, which are errors on the magnetic-field and microwave pulse intensities, as well as motional heating, predicting two-qubit gates with fidelities above 99.9% in tens of microseconds.

Characterization of Three-Stream Jet Flow Fields

NASA Technical Reports Server (NTRS)

Henderson, Brenda S.; Wernet, Mark P.

2016-01-01

Flow-field measurements were conducted on single-, dual- and three-stream jets using two-component and stereo Particle Image Velocimetry (PIV). The flow-field measurements complimented previous acoustic measurements. The exhaust system consisted of externally-plugged, externally-mixed, convergent nozzles. The study used bypass-to-core area ratios equal to 1.0 and 2.5 and tertiary-to-core area ratios equal to 0.6 and 1.0. Axisymmetric and offset tertiary nozzles were investigated for heated and unheated high-subsonic conditions. Centerline velocity decay rates for the single-, dual- and three-stream axisymmetric jets compared well when axial distance was normalized by an equivalent diameter based on the nozzle system total exit area. The tertiary stream had a greater impact on the mean axial velocity for the small bypass-to-core area ratio nozzles than for large bypass-to-core area ratio nozzles. Normalized turbulence intensities were similar for the single-, dual-, and three-stream unheated jets due to the small difference (10 percent) in the core and bypass velocities for the dual-stream jets and the low tertiary velocity (50 percent of the core stream) for the three-stream jets. For heated jet conditions where the bypass velocity was 65 percent of the core velocity, additional regions of high turbulence intensity occurred near the plug tip which were not present for the unheated jets. Offsetting the tertiary stream moved the peak turbulence intensity levels upstream relative to those for all axisymmetric jets investigated.

Characterization of Three-Stream Jet Flow Fields

NASA Technical Reports Server (NTRS)

Henderson, Brenda S.; Wernet, Mark P.

2016-01-01

Flow-field measurements were conducted on single-, dual- and three-stream jets using two-component and stereo Particle Image Velocimetry (PIV). The flow-field measurements complimented previous acoustic measurements. The exhaust system consisted of externally-plugged, externally-mixed, convergent nozzles. The study used bypass-to-core area ratios equal to 1.0 and 2.5 and tertiary-to-core area ratios equal to 0.6 and 1.0. Axisymmetric and offset tertiary nozzles were investigated for heated and unheated high-subsonic conditions. Centerline velocity decay rates for the single-, dual- and three-stream axisymmetric jets compared well when axial distance was normalized by an equivalent diameter based on the nozzle system total exit area. The tertiary stream had a greater impact on the mean axial velocity for the small bypass-to-core area ratio nozzles than for large bypass-to-core area ratio nozzles. Normalized turbulence intensities were similar for the single-, dual-, and three-stream unheated jets due to the small difference (10%) in the core and bypass velocities for the dual-stream jets and the low tertiary velocity (50% of the core stream) for the three-stream jets. For heated jet conditions where the bypass velocity was 65% of the core velocity, additional regions of high turbulence intensity occurred near the plug tip which were not present for the unheated jets. Offsetting the tertiary stream moved the peak turbulence intensity levels upstream relative to those for all axisymmetric jets investigated.

Time-dependent scattering of incident light of various wavelengths in ferrofluids under external magnetic field

NASA Astrophysics Data System (ADS)

Jin, Jingyu; Song, Dongxing; Geng, Jiafeng; Jing, Dengwei

2018-02-01

Ferrofluids can exhibit the anisotropic thermodynamic properties under magnetic fields. The dynamic optical properties of ferrofluids in the presence of magnetic fields are of particular interest due to their potential application as various optical devices. Although time-dependent light scattering by ferrofluids have been extensively studied, the effect of wavelength of incident light have been rarely considered. Here, for the first time, we investigated both the time- and wavelength-dependent light scattering in water based ferrofluids containing Fe3O4 nanoparticles under an external magnetic field. The field-induced response behavior of the prepared ferrofluid samples was determined and verified first by thermal conductivity measurement and numerical simulation. Double-beam UV-Vis spectrophotometer was employed to record the temporal evolution of transmitted intensity of incident light of various wavelengths passing through the ferrofluid sample and propagating parallel to the applied field. As expected, the light intensity decreases to a certain value right after the field is turned on due to the thermal fluctuation induced disorder inside the flexible particle chains. Then the light intensity further decreases with time until the appearance of a minimum at time τ0 followed by an inversed increase before finally reaches equilibrium at a particular time. More importantly, the characteristic inversion time τ0 was found to follow a power law increase with the wavelength of incident light (τ0 ∼ λα, where α = 2.07). A quantitative explanation for the wavelength dependence of characteristic time was proposed based on the finite-difference time-domain (FDTD) method. The simulation results are in good agreement with our experimental observations. The time-dependent light scattering in ferrofluids under different incident wavelengths was rationalized by considering both the coarsening process of the particle chains and the occurrence of resonance within the magnetic scatterers. Our finding should be of value for the development of various light-tunable optical devices.

Laser-pulse compression using magnetized plasmas

DOE PAGES

Shi, Yuan; Qin, Hong; Fisch, Nathaniel J.

2017-02-28

Proposals to reach the next generation of laser intensities through Raman or Brillouin backscattering have centered on optical frequencies. Higher frequencies are beyond the range of such methods mainly due to the wave damping that accompanies the higher-density plasmas necessary for compressing higher frequency lasers. However, we find that an external magnetic field transverse to the direction of laser propagation can reduce the required plasma density. Using parametric interactions in magnetized plasmas to mediate pulse compression, both reduces the wave damping and alleviates instabilities, thereby enabling higher frequency or lower intensity pumps to produce pulses at higher intensities and longermore » durations. Finally, in addition to these theoretical advantages, our method in which strong uniform magnetic fields lessen the need for high-density uniform plasmas also lessens key engineering challenges or at least exchanges them for different challenges.« less

Adsorption and diffusion of lithium in a graphene/blue-phosphorus heterostructure and the effect of an external electric field.

PubMed

Fan, Kaimin; Tang, Jing; Wu, Shiyun; Yang, Chengfu; Hao, Jiabo

2016-12-21

The adsorption and diffusion behaviors of lithium (Li) in a graphene/blue-phosphorus (G/BP) heterostructure have been investigated using a first principles method based on density functional theory (DFT). The effect of an external electric field on the adsorption and diffusion behaviors has also been investigated. The results show that the adsorption energy of Li on the graphene side of the G/BP heterostructure is higher than that on monolayer graphene, and Li adsorption on the BP side of the G/BP/Li system is slightly stronger than that on monolayer BP (BP/Li). The adsorption energy of Li reaches 2.47 eV, however, the energy barriers of Li diffusion decrease in the interlayer of the G/BP heterostructure. The results mentioned above suggest that the rate performance of the G/BP heterostructure is better than that of monolayer graphene. Furthermore, the adsorption energies of Li atoms in the three different most stable sites, i.e., H G , T P and H 1 sites, increase by about 0.49 eV, 0.26 eV, and 0.13 eV, respectively, as the electric field intensity reaches 0.6 V Å -1 . The diffusion energy barrier is significantly decreased by an external electric field. It is demonstrated that the external electric field can not only enhance the adsorption but can also modulate the diffusion barriers of Li atoms in the G/BP heterostructure.

Theoretical study of the photodissociation of Li(2)+ in one-color intense laser fields.

PubMed

Li, Yuanjun; Jiang, Wanyi; Khait, Yuriy G; Hoffmann, Mark R

2011-05-07

A theoretical treatment of the photodissociation of the molecular ion Li(2) (+) in one-color intense laser fields, using the time-dependent wave packet approach in a Floquet Born-Oppenheimer representation, is presented. Six electronic states 1,2 (2)Σ(g)(+), 1,2 (2)Σ(u)(+), 1 (2)Π(g), and 1 (2)Π(u) are of relevance in this simulation and have been included. The dependences of the fragmental dissociation probabilities and kinetic energy release (KER) spectra on pulse width, peak intensity, polarization angle, wavelength, and initial vibrational level are analyzed to interpret the influence of control parameters of the external field. Three main dissociation channels, 1 (2)Σ(g)(+) (m = -1), 2 (2)Σ(g)(+) (m = -2), and 2 (2)Σ(u)(+) (m = -3), are seen to dominate the dissociation processes under a wide variety of laser conditions and give rise to well separated groups of KER features. Different dissociation mechanisms for the involved Floquet channels are discussed.

Ultrafast proton radiography of the magnetic fields generated by a laser-driven coil current

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

Gao, Lan; Ji, Hantao; Princeton Plasma Physics Laboratory, Princeton University, Princeton, New Jersey 08543

2016-04-15

Magnetic fields generated by a current flowing through a U-shaped coil connecting two copper foils were measured using ultrafast proton radiography. Two ∼1.25 kJ, 1-ns laser pulses propagated through laser entrance holes in the front foil and were focused to the back foil with an intensity of ∼3 × 10{sup 16 }W/cm{sup 2}. The intense laser-solid interaction induced a high voltage between the copper foils and generated a large current in the connecting coil. The proton data show ∼40–50 T magnetic fields at the center of the coil ∼3–4 ns after laser irradiation. The experiments provide significant insight for future target designs that aim tomore » develop a powerful source of external magnetic fields for various applications in high-energy-density science.« less

Generation of disc-like plasma from laser-matter interaction in the presence of a strong external magnetic field

NASA Astrophysics Data System (ADS)

Ivanov, V. V.; Maximov, A. V.; Betti, R.; Wiewior, P. P.; Hakel, P.; Sherrill, M. E.

2017-08-01

Dynamics of laser produced plasma in a strong magnetic field was studied using a 1 MA pulsed power generator coupled to an intense, high-energy laser. A 2-2.5 MG magnetic field was generated on the surface of a rod load 0.8-1.2 mm in diameter. A sub-nanosecond laser pulse with intensity of 3 × 1015 W cm-2 was focused on the rod load surface. Side-on laser diagnostics showed the generation of two collimated jets 1-3 mm long on the front and rear sides of the load. End-on laser diagnostics reveal that the laser produced plasma in the MG magnetic field takes the form of a thin disc as the plasma propagates along the magnetic field lines. The disc-like plasma expands radially across the magnetic field with a velocity of 250 km s-1. An electron temperature of 400 eV was measured in the laser-produced plasma on the rod load.

Influence of intrinsic decoherence on tripartite entanglement and bipartite fidelity of polar molecules in pendular states

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

Han, Jia-Xing; Hu, Yuan; Jin, Yu

An array of ultracold polar molecules trapped in an external electric field is regarded as a promising carrier of quantum information. Under the action of this field, molecules are compelled to undergo pendular oscillations by the Stark effect. Particular attention has been paid to the influence of intrinsic decoherence on the model of linear polar molecular pendular states, thereby we evaluate the tripartite entanglement with negativity, as well as fidelity of bipartite quantum systems for input and output signals using electric dipole moments of polar molecules as qubits. According to this study, we consider three typical initial states for bothmore » systems, respectively, and investigate the temporal evolution with variable values of the external field intensity, the intrinsic decoherence factor, and the dipole-dipole interaction. Thus, we demonstrate the sound selection of these three main parameters to obtain the best entanglement degree and fidelity.« less

Influence of intrinsic decoherence on tripartite entanglement and bipartite fidelity of polar molecules in pendular states.

PubMed

Han, Jia-Xing; Hu, Yuan; Jin, Yu; Zhang, Guo-Feng

2016-04-07

An array of ultracold polar molecules trapped in an external electric field is regarded as a promising carrier of quantum information. Under the action of this field, molecules are compelled to undergo pendular oscillations by the Stark effect. Particular attention has been paid to the influence of intrinsic decoherence on the model of linear polar molecular pendular states, thereby we evaluate the tripartite entanglement with negativity, as well as fidelity of bipartite quantum systems for input and output signals using electric dipole moments of polar molecules as qubits. According to this study, we consider three typical initial states for both systems, respectively, and investigate the temporal evolution with variable values of the external field intensity, the intrinsic decoherence factor, and the dipole-dipole interaction. Thus, we demonstrate the sound selection of these three main parameters to obtain the best entanglement degree and fidelity.

X-ray plane-wave diffraction effects in a crystal with third-order nonlinearity

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

Balyan, M. K., E-mail: mbalyan@ysu.am

The two-wave dynamical diffraction in the Laue geometry has been theoretically considered for a plane X-ray wave in a crystal with a third-order nonlinear response to the external field. An analytical solution to the problem stated is found for certain diffraction conditions. A nonlinear pendulum effect is analyzed. The nonlinear extinction length is found to depend on the incident-wave intensity. A pendulum effect of a new type is revealed: the intensities of the transmitted and diffracted waves periodically depend on the incidentwave intensity at a fixed crystal thickness. The rocking curves and Borrmann nonlinear effect are numerically calculated.

Theory of diatomic molecules in an external electromagnetic field from first quantum mechanical principles.

PubMed

Sindelka, Milan; Moiseyev, Nimrod

2006-04-27

We study a general problem of the translational/rotational/vibrational/electronic dynamics of a diatomic molecule exposed to an interaction with an arbitrary external electromagnetic field. The theory developed in this paper is relevant to a variety of specific applications, such as alignment or orientation of molecules by lasers, trapping of ultracold molecules in optical traps, molecular optics and interferometry, rovibrational spectroscopy of molecules in the presence of intense laser light, or generation of high order harmonics from molecules. Starting from the first quantum mechanical principles, we derive an appropriate molecular Hamiltonian suitable for description of the center of mass, rotational, vibrational, and electronic molecular motions driven by the field within the electric dipole approximation. Consequently, the concept of the Born-Oppenheimer separation between the electronic and the nuclear degrees of freedom in the presence of an electromagnetic field is introduced. Special cases of the dc/ac-field limits are then discussed separately. Finally, we consider a perturbative regime of a weak dc/ac field, and obtain simple analytic formulas for the associated Born-Oppenheimer translational/rotational/vibrational molecular Hamiltonian.

Magnetooptics of the luminescent transitions in Tb3+:Gd3Ga5O12

NASA Astrophysics Data System (ADS)

Valiev, Uygun V.; Gruber, John B.; Ivanov, Igor'A.; Burdick, Gary W.; Liang, Hongbin; Zhou, Lei; Fu, Dejun; Pelenovich, Oleg V.; Pelenovich, Vasiliy O.; Lin, Zhou

2015-08-01

The spectra of the luminescence and magnetic circular polarization of luminescence in terbium-gadolinium gallium garnet Tb3+:Gd3Ga5O12 (Tb3+:GGG) were studied within the visible spectral range at temperatures T = 90 and 300 K in an external magnetic field of 0.45 T. The Zeeman effect in the luminescence "green" band associated with 4f → 4f transition 5D4 → 7F5 of Tb3+:GGG was also studied at T = 90 K in an external field of 0.55 T. Measurement of the Zeeman effect in Tb3+:GGG carried out for some doublet lines of the luminescence band 5D4 → 7F5 at T = 90 K shows that a magnetooptical effect of the intensity change of the emitted light is observed on these lines, in contrast to pure Zeeman splitting of the emission lines measured in the luminescence band 5D4 → 7F6. For the systems we have studied, the maximal value of the magnetooptical effect of the intensity change of the luminescence line at low temperatures has been achieved in paramagnetic garnet Tb0.2Y2.8Al5O12 at comparatively low magnetic fields.

Study on elimination of screening-current-induced field in pancake-type non-insulated HTS coil

NASA Astrophysics Data System (ADS)

Kim, K. L.; Song, J. B.; Yang, D. G.; Kim, Y. G.; Kim, T. H.; Kim, S. K.; Park, M. W.; Lee, H. G.

2016-03-01

This paper presents the details of a recent study on the removal of the screening-current-induced field (SCIF) in a pancake-type non-insulated high-temperature superconductor coil (NI coil). To determine the SCIF in the NI coil, the magnetic flux density (B z ) was calculated using the equivalent circuit model of the coil and compared to the B z obtained empirically. The experimental results indicate that the SCIF elimination in the NI coil was enhanced upon increasing the amplitude and frequency of the AC current being supplied to the background coil. Moreover, the SCIF in the NI coil was successfully removed by applying the appropriate external AC magnetic field intensity. This is because the magnetization direction of the SCIF changed completely from radial to spiral, a phenomenon termed the ‘vortex shaking effect.’ Overall, this study confirmed that the SCIF in a pancake-type NI coil can be effectively removed by exposing the coil to an external AC magnetic field.

Modelling in conventional electroporation for model cell with organelles using COMSOL Multiphysics

NASA Astrophysics Data System (ADS)

Sulaeman, M. Y.; Widita, R.

2016-03-01

Conventional electroporation is a formation of pores in the membrane cell due to the external electric field applied to the cell. The purpose of creating pores in the cell using conventional electroporation are to increase the effectiveness of chemotherapy (electrochemotherapy) and to kill cancer tissue using irreversible electroporation. Modeling of electroporation phenomenon on a model cell had been done by using software COMSOL Multiphysics 4.3b with the applied external electric field with intensity at 1.1 kV/cm to find transmembrane voltage and pore density. It can be concluded from the results of potential distribution and transmembrane voltage, it show that pores formation only occurs in the membrane cells and it could not penetrate into inside the model cell so there is not pores formation in its organells.

Experimental Evidence for LENR in a Polarized Pd/D Lattice

NASA Astrophysics Data System (ADS)

Szpak, S.

2005-03-01

Experimental evidence in support of claims that excess enthalpy production in a polarized Pd/D lattice is of a nuclear origin is questioned on various grounds, eg marginal intensity and difficulty in reproducing. Here, evidence is presented that is 100% reproducible and of sufficient intensity to be well outside of experimental errors. In addition to the thermal behavior, the nuclear manifestations include: X-ray emission; tritium production; and, when an operating cell is placed in an external electric field, fusion to create heavier metals such as Ca, Al, Mg, and Zn.

Modeling of the charge-state separation at ITEP experimental facility for material science based on a Bernas ion source.

PubMed

Barminova, H Y; Saratovskyh, M S

2016-02-01

The experiment automation system is supposed to be developed for experimental facility for material science at ITEP, based on a Bernas ion source. The program CAMFT is assumed to be involved into the program of the experiment automation. CAMFT is developed to simulate the intense charged particle bunch motion in the external magnetic fields with arbitrary geometry by means of the accurate solution of the particle motion equation. Program allows the consideration of the bunch intensity up to 10(10) ppb. Preliminary calculations are performed at ITEP supercomputer. The results of the simulation of the beam pre-acceleration and following turn in magnetic field are presented for different initial conditions.

Modeling of the charge-state separation at ITEP experimental facility for material science based on a Bernas ion source

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

Barminova, H. Y., E-mail: barminova@bk.ru; Saratovskyh, M. S.

2016-02-15

The experiment automation system is supposed to be developed for experimental facility for material science at ITEP, based on a Bernas ion source. The program CAMFT is assumed to be involved into the program of the experiment automation. CAMFT is developed to simulate the intense charged particle bunch motion in the external magnetic fields with arbitrary geometry by means of the accurate solution of the particle motion equation. Program allows the consideration of the bunch intensity up to 10{sup 10} ppb. Preliminary calculations are performed at ITEP supercomputer. The results of the simulation of the beam pre-acceleration and following turnmore » in magnetic field are presented for different initial conditions.« less

Human aquaporin 4 gating dynamics under and after nanosecond-scale static and alternating electric-field impulses: a molecular dynamics study of field effects and relaxation.

PubMed

Reale, Riccardo; English, Niall J; Garate, José-Antonio; Marracino, Paolo; Liberti, Micaela; Apollonio, Francesca

2013-11-28

Water self-diffusion and the dipolar response of the selectivity filter within human aquaporin 4 have been studied using molecular dynamics (MD) simulations in the absence and presence of pulses of external static and alternating electric fields. The pulses were approximately 50 and 100 ns in duration and 0.0065 V/Å in (r.m.s.) intensity and were either static or else 2.45 or 100 GHz in frequency and applied both along and perpendicular to the channels. In addition, the relaxation of the aquaporin, water self-diffusion and gating dynamics following cessation of the impulses was studied. In previous work it was determined that switches in the dihedral angle of the selectivity filter led to boosting of water permeation events within the channels, in the presence of identical external static and alternating electric fields, although applied continuously. Here the application of field impulses (and subsequently, upon removal) has shown that it is the dipolar orientation of the histidine-201 residue in the selectivity filter which governs the dihedral angle, and hence influences water self-diffusion; this constitutes an appropriate order parameter. The dipolar response of this residue to the applied field leads to the adoption of four distinct states, which we modelled as time-homogeneous Markov jump processes, and may be distinguished in the potential of mean force (PMF) as a function of the dipolar orientation of histidine-201. The observations of enhanced "dipolar flipping" of H201 serve to explain increased levels of water self-diffusion within aquaporin channels during, and immediately following, field impulses, although the level of statistical certainty here is lower. Given the appreciable size of the energy barriers evident in PMFs computed directly from deterministic MD (whether in the absence or presence of external fields), metadynamics calculations were undertaken to explore the free-energy landscape of histidine-201 orientation with greater accuracy and precision. These indicate that electric fields do alter the free-energy profile of the H201 side-chain orientation, wherein a perturbation of the symmetric bimodal state evident in the zero-field case is observed. These effects are dependent on the field intensities.

Effect of interdiffusion and external magnetic field on electronic states and light absorption in Gaussian-shaped double quantum ring

NASA Astrophysics Data System (ADS)

Aziz-Aghchegala, V. L.; Mughnetsyan, V. N.; Kirakosyan, A. A.

2018-02-01

The effect of interdiffusion and magnetic field on confined states of electron and heavy hole as well as on interband absorption spectrum in a Ga1-xAlxAs/GaAs Gaussian-shaped double quantum ring are investigated. It is shown that both interdiffusion and magnetic field lead to the change of the charge carriers' quantum states arrangement by their energies. The oscillating behavior of the electron ground state energy as a function of magnetic field induction gradually disappears with the increase of diffusion parameter due to the enhanced tunneling of electron to the central region of the ring. For the heavy hole the ground state energy oscillations are not observable in the region of the values of magnetic field induction B = 0 - 10 T . For considered transitions both the magnetic field and the interdiffusion lead to a blue-shift of the absorption spectrum and to decreasing of the absorption intensity. The obtained results indicate on the opportunity of purposeful manipulation of energy states and absorption spectrum of a Gaussian-shaped double quantum ring by means of the post growth annealing and the external magnetic field.

Breit-Rabi Zeeman states of atomic hydrogen

NASA Astrophysics Data System (ADS)

Dickson, R. S.; Weil, J. A.

1991-02-01

The magnetic field dependence of the isotropic nonrelativistic one-electron atom with nuclear spin-1/2, in its electronic ground state, is reviewed. Attention is called to the little-known fact that a level crossing exists (at field B˜17 T for 1H) between the two members of the upper spin (MS=1/2) doublet. Anisotropy of such a hydrogenic atom, due to the presence of a suitable external electric field (for instance, 1H trapped in crystalline SiO2) causes anticrossing of these levels and causes previously forbidden magnetic-dipole transitions to attain appreciable intensity in that B region.

Laterally coupled circular quantum dots under applied electric field

NASA Astrophysics Data System (ADS)

Duque, C. M.; Correa, J. D.; Morales, A. L.; Mora-Ramos, M. E.; Duque, C. A.

2016-03-01

The optical response of a system of two laterally coupled quantum dots with circular cross-sectional shape is investigated within the effective mass approximation, taking into account the effects of the change in the geometrical configuration, the application of an external static electric field, and the presence of a donor impurity center. The first-order dielectric susceptibility is calculated in order to derive the corresponding light absorption and relative refractive index coefficients. The possibility of tuning these optical properties by means of changes in the quantum dot symmetry and the electric field intensity is particularly discussed.

Photoelastic Analysis of Cracked Thick Walled Cylinders

NASA Astrophysics Data System (ADS)

Pastramă, Ştefan Dan

2017-12-01

In this paper, the experimental determination of the stress intensity factor in thick walled cylinders subject to uniform internal pressure and having longitudinal non-penetrating cracks is presented. Photoelastic measurements were used together with the expressions of the stress field near the crack tip for Mode I crack extension and a specific methodology for stress intensity factor determination. Two types of longitudinal cracks - internal and external - were considered. Four plane models were manufactured and analyzed in a plane polariscope at different values of the applied internal pressure. The values of the normalized stress intensity factor were calculated and the results were compared to those reported by other authors. A good accuracy was noticed, showing the reliability of the experimental procedure.

Laser Assisted Free-Free Transition in Electron - Atom Collision

NASA Technical Reports Server (NTRS)

Sinha, C.; Bhatia, A. K.

2011-01-01

Free-free transition is studied for electron-Hydrogen atom system in ground state at very low incident energies in presence of an external homogeneous, monochromatic and linearly polarized laser field. The incident electron is considered to be dressed by the laser in a non perturbative manner by choosing the Volkov solutions in both the channels. The space part of the scattering wave function for the electron is solved numerically by taking into account the effect of electron exchange, short range as well as of the long range interactions. Laser assisted differential as well as elastic total cross sections are calculated for single photon absorption/emission in the soft photon limit, the laser intensity being much less than the atomic field intensity. A strong suppression is noted in the laser assisted cross sections as compared to the field free situations. Significant difference is noted in the singlet and the triplet cross sections.

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

Generation of disc-like plasma from laser-matter interaction in the presence of a strong external magnetic field

DOE PAGES

Ivanov, V. V.; Maximov, A. V.; Betti, R.; ...

2017-05-16

Dynamics of laser produced plasma in a strong magnetic field was studied here using a 1 MA pulsed power generator coupled to an intense, high-energy laser. A 2–2.5 MG magnetic field was generated on the surface of a rod load 0.8–1.2 mm in diameter. A sub-nanosecond laser pulse with intensity of 3 × 10 15 W cm -2 was focused on the rod load surface. Side-on laser diagnostics showed the generation of two collimated jets 1–3 mm long on the front and rear sides of the load. End-on laser diagnostics reveal that the laser produced plasma in the MG magneticmore » field takes the form of a thin disc as the plasma propagates along the magnetic field lines. The disc-like plasma expands radially across the magnetic field with a velocity of 250 km s -1. An electron temperature of 400 eV was measured in the laser-produced plasma on the rod load.« less

Efficient two-step photocarrier generation in bias-controlled InAs/GaAs quantum dot superlattice intermediate-band solar cells.

PubMed

Kada, T; Asahi, S; Kaizu, T; Harada, Y; Tamaki, R; Okada, Y; Kita, T

2017-07-19

We studied the effects of the internal electric field on two-step photocarrier generation in InAs/GaAs quantum dot superlattice (QDSL) intermediate-band solar cells (IBSCs). The external quantum efficiency of QDSL-IBSCs was measured as a function of the internal electric field intensity, and compared with theoretical calculations accounting for interband and intersubband photoexcitations. The extra photocurrent caused by the two-step photoexcitation was maximal for a reversely biased electric field, while the current generated by the interband photoexcitation increased monotonically with increasing electric field intensity. The internal electric field in solar cells separated photogenerated electrons and holes in the superlattice (SL) miniband that played the role of an intermediate band, and the electron lifetime was extended to the microsecond scale, which improved the intersubband transition strength, therefore increasing the two-step photocurrent. There was a trade-off relation between the carrier separation enhancing the two-step photoexcitation and the electric-field-induced carrier escape from QDSLs. These results validate that long-lifetime electrons are key to maximising the two-step photocarrier generation in QDSL-IBSCs.

Generation of disc-like plasma from laser-matter interaction in the presence of a strong external magnetic field

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

Ivanov, V. V.; Maximov, A. V.; Betti, R.

Dynamics of laser produced plasma in a strong magnetic field was studied here using a 1 MA pulsed power generator coupled to an intense, high-energy laser. A 2–2.5 MG magnetic field was generated on the surface of a rod load 0.8–1.2 mm in diameter. A sub-nanosecond laser pulse with intensity of 3 × 10 15 W cm -2 was focused on the rod load surface. Side-on laser diagnostics showed the generation of two collimated jets 1–3 mm long on the front and rear sides of the load. End-on laser diagnostics reveal that the laser produced plasma in the MG magneticmore » field takes the form of a thin disc as the plasma propagates along the magnetic field lines. The disc-like plasma expands radially across the magnetic field with a velocity of 250 km s -1. An electron temperature of 400 eV was measured in the laser-produced plasma on the rod load.« less

Effect of low frequency magnetic fields on the growth of MNP-treated HT29 colon cancer cells

NASA Astrophysics Data System (ADS)

Spyridopoulou, K.; Makridis, A.; Maniotis, N.; Karypidou, N.; Myrovali, E.; Samaras, T.; Angelakeris, M.; Chlichlia, K.; Kalogirou, O.

2018-04-01

Recent investigations have attempted to understand and exploit the impact of magnetic field-actuated internalized magnetic nanoparticles (MNPs) on the proliferation rate of cancer cells. Due to the complexity of the parameters governing magnetic field-exposure though, individual studies to date have raised contradictory results. In our approach we performed a comparative analysis of key parameters related to the cell exposure of cancer cells to magnetic field-actuated MNPs, and to the magnetic field, in order to better understand the factors affecting cellular responses to magnetic field-stimulated MNPs. We used magnetite MNPs with a hydrodynamic diameter of 100 nm and studied the proliferation rate of MNPs-treated versus untreated HT29 human colon cancer cells, exposed to either static or alternating low frequency magnetic fields with varying intensity (40-200 mT), frequency (0-8 Hz) and field gradient. All three parameters, field intensity, frequency, and field gradient affected the growth rate of cells, with or without internalized MNPs, as compared to control MNPs-untreated and magnetic field-untreated cells. We observed that the growth inhibitory effects induced by static and rotating magnetic fields were enhanced by pre-treating the cells with MNPs, while the growth promoting effects observed in alternating field-treated cells were weakened by MNPs. Compared to static, rotating magnetic fields of the same intensity induced a similar extend of cell growth inhibition, while alternating fields of varying intensity (70 or 100 mT) and frequency (0, 4 or 8 Hz) induced cell proliferation in a frequency-dependent manner. These results, highlighting the diverse effects of mode, intensity, and frequency of the magnetic field on cell growth, indicate that consistent and reproducible results can be achieved by controlling the complexity of the exposure of biological samples to MNPs and external magnetic fields, through monitoring crucial experimental parameters. We demonstrate that further research focusing on the accurate manipulation of the aforementioned magnetic field exposure parameters could lead to the development of successful non-invasive therapeutic anticancer approaches.

Application of turbulence modeling to predict surface heat transfer in stagnation flow region of circular cylinder

NASA Technical Reports Server (NTRS)

Wang, Chi R.; Yeh, Frederick C.

1987-01-01

A theoretical analysis and numerical calculations for the turbulent flow field and for the effect of free-stream turbulence on the surface heat transfer rate of a stagnation flow are presented. The emphasis is on the modeling of turbulence and its augmentation of surface heat transfer rate. The flow field considered is the region near the forward stagnation point of a circular cylinder in a uniform turbulent mean flow. The free stream is steady and incompressible with a Reynolds number of the order of 10 to the 5th power and turbulence intensity of less than 5 percent. For this analysis, the flow field is divided into three regions: (1) a uniform free-stream region where the turbulence is homogeneous and isotropic; (2) an external viscid flow region where the turbulence is distorted by the variation of the mean flow velocity; and, (3) an anisotropic turbulent boundary layer region over the cylinder surface. The turbulence modeling techniques used are the kappa-epsilon two-equation model in the external flow region and the time-averaged turbulence transport equation in the boundary layer region. The turbulence double correlations, the mean velocity, and the mean temperature within the boundary layer are solved numerically from the transport equations. The surface heat transfer rate is calculated as functions of the free-stream turbulence longitudinal microlength scale, the turbulence intensity, and the Reynolds number.

Practicing Reiki does not appear to routinely produce high-intensity electromagnetic fields from the heart or hands of Reiki practitioners.

PubMed

Baldwin, Ann Linda; Rand, William Lee; Schwartz, Gary E

2013-06-01

The study objective was to determine whether Reiki practice increases the electromagnetic field strength from the heart and hands of Reiki practitioners. This study repeated experiments performed 20 years ago that detected exceptionally high-strength electromagnetic fields (100 nT) from the hands of several energy healers. The equipment used was far more sensitive than in the original studies. Using a Magnes 2500 WH SQUID, the electromagnetic field from the hands and heart of each of 3 Reiki masters was measured when they were (1) not practicing Reiki, (2) sending Reiki to a distant person, and (3) sending Reiki to a person in the room. Similar measurements were made on 4 Reiki-naïve volunteers before and after they received a Reiki training/attunement enabling them to self-administer Reiki. The study setting was the Scripps Institute, San Diego, CA. Magnetic field intensity of hands and heart recorded over 5-minute sessions with corresponding frequency spectra. For all subjects, under all conditions, sensors closest to the heart and the hands produced spikes of 2 pT corresponding to the heartbeat. Recordings from 2 Masters and 1 volunteer showed a low-intensity sine wave oscillation of 0.25-0.3 Hz (intensity 0.1-0.5 pT) whether or not they were practicing Reiki. This oscillation probably reflected respiratory sinus arrhythmia, judged by comparison with recent previous studies. These signals were not detected in the original studies. In the current study, no electromagnetic field intensities greater than 3 pT were observed in any of the recordings. Practicing Reiki does not appear to routinely produce high-intensity electromagnetic fields from the heart or hands. Alternatively, it is possible that energy healing is stimulated by tuning into an external environmental radiation, such as the Schumann resonance, which was blocked in the present study by the strong magnetic shielding surrounding the SQUID.

Functionalization of group-14 two-dimensional materials

NASA Astrophysics Data System (ADS)

Krawiec, Mariusz

2018-06-01

The great success of graphene has boosted intensive search for other single-layer thick materials, mainly composed of group-14 atoms arranged in a honeycomb lattice. This new class of two-dimensional (2D) crystals, known as 2D-Xenes, has become an emerging field of intensive research due to their remarkable electronic properties and the promise for a future generation of nanoelectronics. In contrast to graphene, Xenes are not completely planar, and feature a low buckled geometry with two sublattices displaced vertically as a result of the interplay between sp2 and sp3 orbital hybridization. In spite of the buckling, the outstanding electronic properties of graphene governed by Dirac physics are preserved in Xenes too. The buckled structure also has several advantages over graphene. Together with the spin–orbit (SO) interaction it may lead to the emergence of various experimentally accessible topological phases, like the quantum spin Hall effect. This in turn would lead to designing and building new electronic and spintronic devices, like topological field effect transistors. In this regard an important issue concerns the electron energy gap, which for Xenes naturally exists owing to the buckling and SO interaction. The electronic properties, including the magnitude of the energy gap, can further be tuned and controlled by external means. Xenes can easily be functionalized by substrate, chemical adsorption, defects, charge doping, external electric field, periodic potential, in-plane uniaxial and biaxial stress, and out-of-plane long-range structural deformation, to name a few. This topical review explores structural, electronic and magnetic properties of Xenes and addresses the question of their functionalization in various ways, including external factors acting simultaneously. It also points to future directions to be explored in functionalization of Xenes. The results of experimental and theoretical studies obtained so far have many promising features making the 2D-Xene materials important players in the field of future nanoelectronics and spintronics.

NONLINEAR OPTICAL EFFECTS AND FIBER OPTICS: Modulation of radiation in a fiber Sagnac interferometer induced by an external field

NASA Astrophysics Data System (ADS)

Zakhidov, É. A.; Kasymdzhanov, M. A.; Mirtadzhiev, F. M.; Tartakovskiĭ, G. Kh; Khabibullaev, P. K.

1988-12-01

A study was made of the influence of the Kerr nonlinearity of a fiber waveguide on fluctuations of the output signal from a fiber-optic interferometer. The intensity fluctuations were modeled using the radiation from a pulsed high-power laser with a controlled intensity and pulse profile. Interferograms of the output radiation were obtained for different interferometer configurations. A comparison of the experiment and theory made it possible to explain the observed changes in the signal and to estimate the phase noise due to the Kerr nonlinearity in the investigated fiber waveguide.

A novel coaxial Ku-band transit radiation oscillator without external guiding magnetic field

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

Ling, Junpu, E-mail: lingjunpu@163.com; Zhang, Jiande; He, Juntao

2014-02-15

A novel coaxial transit radiation oscillator without external guiding magnetic field is designed to generate high power microwave at Ku-band. By using a coaxial structure, the space-charge potential energy is suppressed significantly, that is good for enhancing efficient beam-wave interaction. In order to improve the transmission stability of the unmagnetized intense relativistic electron beam, a Pierce-like cathode is employed in the novel device. By contrast with conventional relativistic microwave generators, this kind of device has the advantages of high stability, non-guiding magnetic field, and high efficiency. Moreover, with the coaxial design, it is possible to improve the power-handing capacity bymore » increasing the radial dimension of the Ku-band device. With a 550 keV and 7.5 kA electron beam, a 1.25 GW microwave pulse at 12.08 GHz has been obtained in the simulation. The power conversion efficiency is about 30%.« less

Effects of laser-polarization and wiggler magnetic fields on electron acceleration in laser-cluster interaction

NASA Astrophysics Data System (ADS)

Singh Ghotra, Harjit; Kant, Niti

2018-06-01

We examine the electron dynamics during laser-cluster interaction. In addition to the electrostatic field of an individual cluster and laser field, we consider an external transverse wiggler magnetic field, which plays a pivotal role in enhancing the electron acceleration. Single-particle simulation has been presented with a short pulse linearly polarized as well as circularly polarized laser pulses for electron acceleration in a cluster. The persisting Coulomb field allows the electron to absorb energy from the laser field. The stochastically heated electron finds a weak electric field at the edge of the cluster from where it is ejected. The wiggler magnetic field connects the regions of the stochastically heated, ejected electron from the cluster and high energy gain by the electron from the laser field outside the cluster. This increases the field strength and hence supports the electron to meet the phase of the laser field for enhanced acceleration. A long duration resonance appears with an optimized magnetic wiggler field of about 3.4 kG. Hence, the relativistic energy gain by the electron is enhanced up to a few 100 MeV with an intense short pulse laser with an intensity of about 1019 W cm‑2 in the presence of a wiggler magnetic field.

DIRBE External Calibrator (DEC)

NASA Technical Reports Server (NTRS)

Wyatt, Clair L.; Thurgood, V. Alan; Allred, Glenn D.

1987-01-01

Under NASA Contract No. NAS5-28185, the Center for Space Engineering at Utah State University has produced a calibration instrument for the Diffuse Infrared Background Experiment (DIRBE). DIRBE is one of the instruments aboard the Cosmic Background Experiment Observatory (COBE). The calibration instrument is referred to as the DEC (Dirbe External Calibrator). DEC produces a steerable, infrared beam of controlled spectral content and intensity and with selectable point source or diffuse source characteristics, that can be directed into the DIRBE to map fields and determine response characteristics. This report discusses the design of the DEC instrument, its operation and characteristics, and provides an analysis of the systems capabilities and performance.

Pressure sensor for sealed containers

DOEpatents

Hodges, Franklin R.

2001-01-01

A magnetic pressure sensor for sensing a pressure change inside a sealed container. The sensor includes a sealed deformable vessel having a first end attachable to an interior surface of the sealed container, and a second end. A magnet mounted to the vessel second end defining a distance away from the container surface provides an externally detectable magnetic field. A pressure change inside the sealed container causes deformation of the vessel changing the distance of the magnet away from the container surface, and thus the detectable intensity of the magnetic field.

Magnetically controlled terahertz modulator based on Fe3O4 nanoparticle ferrofluids

NASA Astrophysics Data System (ADS)

Liu, Xin; Xiong, Luyao; Yu, Xiang; He, Shuli; Zhang, Bo; Shen, Jingling

2018-03-01

A multifunctional terahertz (THz) wave modulator fabricated from Fe3O4 nanoparticle ferrofluids and metamaterials was characterized in externally applied magnetic fields. Specifically, modulation depths and frequency shifts by the wave modulators were examined. A 34% THz amplitude modulation depth was demonstrated and the absorption peak of the metamaterial induced a frequency shift of 33 GHz at low magnetic field intensities. It is anticipated that this device structure and its tunable properties will have many potential applications in THz filtering, modulation, and sensing.

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

He, W.; Zhao, H.W.; Liu, Zh.W.

To study the injection of additional electrons from an external electron gun into the plasma of a Penning ionization gauge (PIG) ion source, a test bench for the external electron-beam enhancement of the PIG (E-PIG) ion source was set up. A source magnet assembly was built to satisfy the request for magnetic field configuration of the E-PIG ion source. Numerical calculations have been done to optimize the magnetic field configuration so as to fit the primary electrons to be fed into the PIG discharge chamber along the spreading magnetic field lines. Many possible methods for improving the performance and stabilitymore » of the PIG ion source have been used in the E-PIG ion source, including the use of multicrystal LaB{sub 6} cathode and optimized axial magnetic field. This article presents a detailed design of the E-PIG ion source. Substantial enhancement of ion charge state is expected to be observed which demonstrates that the E-PIG is a viable alternative to other much more costly and difficult to operate devices for the production of intense ion beams of higher charge state.« less

The Martian crustal magnetic field as seen from MGS and MAVEN

NASA Astrophysics Data System (ADS)

Langlais, B.; Thebault, E.

2017-12-01

We present a new model of the Martian crustal magnetic field. This model combines constraints from all available measurements made by Mars Global Surveyor (1997-2006) and MAVEN (2014-). This is the first time a planet (besides the Earth) is flown twice with spacecraft providing high quality vector magnetic field measurements over its entire surface. Both missions have pros and cons which are fully taken into account and exploited. The constant altitude and local time of MGS during its (high altitude) mapping orbit phases allows to separate static, internal fields from transient, external fields. Low altitude measurements (below 250 km) by MAVEN allow to a posteriori validate MGS magnetic field measurements both on the day and night sides. The indirect estimates of the field intensity by the Electron Reflectometer experiment completes the dataset. The new model in constructed with carefully selected measurements, using local and extrapolated proxies to estimate the level of the external field activity. Tracks are individually checked to remove spurious or noisy measurements. The final model has a horizontal resolution close to 100 km. At a local scale, anomalies are better defined, which should ease their interpretation in terms of magnetization properties and processes. During this presentation we will compare this model to previous ones and discuss its new findings.

High magnetic field behavior of NbFe2

NASA Astrophysics Data System (ADS)

Rauch, D.; Steinki, N.; Knafo, W.; Pfleiderer, C.; Duncan, W. J.; Grosche, F. M.; Süllow, S.

2018-05-01

We have carried out a high magnetic field study on single crystalline stoichiometric NbFe2, a material discussed in terms quantum criticality in itinerant ferromagnets, by means of high field resistivity experiments. Our experiments have been performed at the Laboratoire National des Champs Magnétiques Intenses in Toulouse, France. The resistivity of single crystalline NbFe2, has been investigated in external fields up to 15.5 T aligned along the c-axis in the temperature range of 1.4-55 K. The main focus of our study lies on the method to extract TN from the magnetoresistivity measurements, because TN could not be easily observed in temperature dependent resistivity for stoichiometric NbFe2.

Dynamical regimes and intracavity propagation delay in external cavity semiconductor diode lasers

NASA Astrophysics Data System (ADS)

Jayaprasath, E.; Sivaprakasam, S.

2017-11-01

Intracavity propagation delay, a delay introduced by a semiconductor diode laser, is found to significantly influence synchronization of multiple semiconductor diode lasers, operated either in stable or in chaotic regime. Two diode lasers coupled in unidirectional scheme is considered in this numerical study. A diode laser subjected to an optical feedback, also called an external cavity diode laser, acts as the transmitter laser (TL). A solitary diode laser acts as the receiver laser (RL). The optical output of the TL is coupled to the RL and laser operating parameters are optimized to achieve synchronization in their output intensities. The time-of-flight between the TL and RL introduces an intercavity time delay in the dynamics of RL. In addition to this, an intracavity propagation delay arises as the TL's field propagated within the RL. This intracavity propagation delay is evaluated by cross-correlation analysis between the output intensities of the lasers. The intracavity propagation delay is found to increase as the external cavity feedback rate of TL is increased, while an increment in the injection rate between the two lasers resulted in a reduction of intracavity propagation delay.

Sleep of 1- and 2-year-old children in intensive care.

PubMed

Corser, N C

1996-01-01

Physiologic and psychologic changes associated with sleep disturbance decrease the ability of a critically ill child to adapt to hospitalization and thus hamper recovery. Research demonstrates that intensive care settings interfere with sleep of adults, but little is known about the impact of these settings on children's sleep. An exploratory field study was conducted to describe the sleep-wake patterns of 1- and 2-year-old children in intensive care, identify intensive care environmental stimuli associated with sleep and waking states, compare the intensive care sleep-wake pattern to the pre-illness sleep-wake pattern, and determine the time required for children to return to their pre-illness sleep-wake pattern. Twelve children aged 13 to 35 months composed the sample for the study. Pre-illness and postdischarge sleep patterns, sleep patterns during a 12-hour night in the pediatric intensive care unit (PICU), and external and internal environmental stimuli were measured. Prior to hospitalization, subjects demonstrated sleep similar to that documented in healthy children. Children in the PICU experienced a significant loss of sleep, frequent awakenings, and a virtual rapid eye movement (REM) sleep deprivation. External environmental stimuli of light, noise, and caregiver activity were negatively correlated with sleep state. Pain and treatment with benzodiazepines were associated with sleep acquisition. Sleep changes persisted after discharge from the PICU and the hospital. Total sleep time recovered more rapidly than nighttime awakening. Parents perceived that their child's sleep remained different longer than total sleep time and night awakening values demonstrated.

Thermoelectric magnetohydrodynamic effects on the crystal growth rate of undercooled Ni dendrites

NASA Astrophysics Data System (ADS)

Kao, A.; Gao, J.; Pericleous, K.

2018-01-01

In the undercooled solidification of pure metals, the dendrite tip velocity has been shown experimentally to have a strong dependence on the intensity of an external magnetic field, exhibiting several maxima and minima. In the experiments conducted in China, the undercooled solidification dynamics of pure Ni was studied using the glass fluxing method. Visual recordings of the progress of solidification are compared at different static fields up to 6 T. The introduction of microscopic convective transport through thermoelectric magnetohydrodynamics is a promising explanation for the observed changes of tip velocities. To address this problem, a purpose-built numerical code was used to solve the coupled equations representing the magnetohydrodynamic, thermal and solidification mechanisms. The underlying phenomena can be attributed to two competing flow fields, which were generated by orthogonal components of the magnetic field, parallel and transverse to the direction of growth. Their effects are either intensified or damped out with increasing magnetic field intensity, leading to the observed behaviour of the tip velocity. The results obtained reflect well the experimental findings. This article is part of the theme issue `From atomistic interfaces to dendritic patterns'.

Tls Field Data Based Intensity Correction for Forest Environments

NASA Astrophysics Data System (ADS)

Heinzel, J.; Huber, M. O.

2016-06-01

Terrestrial laser scanning (TLS) is increasingly used for forestry applications. Besides the three dimensional point coordinates, the 'intensity' of the reflected signal plays an important role in forestry and vegetation studies. The benefit of the signal intensity is caused by the wavelength of the laser that is within the near infrared (NIR) for most scanners. The NIR is highly indicative for various vegetation characteristics. However, the intensity as recorded by most terrestrial scanners is distorted by both external and scanner specific factors. Since details about system internal alteration of the signal are often unknown to the user, model driven approaches are impractical. On the other hand, existing data driven calibration procedures require laborious acquisition of separate reference datasets or areas of homogenous reflection characteristics from the field data. In order to fill this gap, the present study introduces an approach to correct unwanted intensity variations directly from the point cloud of the field data. The focus is on the variation over range and sensor specific distortions. Instead of an absolute calibration of the values, a relative correction within the dataset is sufficient for most forestry applications. Finally, a method similar to time series detrending is presented with the only pre-condition of a relative equal distribution of forest objects and materials over range. Our test data covers 50 terrestrial scans captured with a FARO Focus 3D S120 scanner using a laser wavelength of 905 nm. Practical tests demonstrate that our correction method removes range and scanner based alterations of the intensity.

Influence of continuous magnetic field on the separation of ephedrine enantiomers by molecularly imprinted polymers.

PubMed

Guerreiro, António R; Korkhov, Vadim; Mijangos, Irene; Piletska, Elena V; Rodins, Juris; Turner, Anthony P F; Piletsky, Sergey A

2008-02-28

A set of polymers was imprinted with (-)-ephedrine using UV initiation, under the influence of a constant external magnetic field with intensities ranging from 0 to 1.55 T. Synthesised materials were characterised by X-ray crystallography, infrared spectroscopy, swelling and surface area. Recognition properties were assessed by the ability to discriminate between (+) and (-)-ephedrine and by Scatchard analyses on chromatographic mode. It was shown that polymer morphology and recognition properties are affected by the magnetic field. This resulted in considerable improvements in the chromatographic resolution of ephedrine enantiomers by materials synthesised under the influence of magnetic field. Apparently the magnetic field improved the ordering of the polymer structure and facilitated the formation of more uniform imprinting sites.

Response of Cultured Neuronal Network Activity After High-Intensity Power Frequency Magnetic Field Exposure

PubMed Central

Saito, Atsushi; Takahashi, Masayuki; Makino, Kei; Suzuki, Yukihisa; Jimbo, Yasuhiko; Nakasono, Satoshi

2018-01-01

High-intensity and low frequency (1–100 kHz) time-varying electromagnetic fields stimulate the human body through excitation of the nervous system. In power frequency range (50/60 Hz), a frequency-dependent threshold of the external electric field-induced neuronal modulation in cultured neuronal networks was used as one of the biological indicator in international guidelines; however, the threshold of the magnetic field-induced neuronal modulation has not been elucidated. In this study, we exposed rat brain-derived neuronal networks to a high-intensity power frequency magnetic field (hPF-MF), and evaluated the modulation of synchronized bursting activity using a multi-electrode array (MEA)-based extracellular recording technique. As a result of short-term hPF-MF exposure (50–400 mT root-mean-square (rms), 50 Hz, sinusoidal wave, 6 s), the synchronized bursting activity was increased in the 400 mT-exposed group. On the other hand, no change was observed in the 50–200 mT-exposed groups. In order to clarify the mechanisms of the 400 mT hPF-MF exposure-induced neuronal response, we evaluated it after blocking inhibitory synapses using bicuculline methiodide (BMI); subsequently, increase in bursting activity was observed with BMI application, and the response of 400 mT hPF-MF exposure disappeared. Therefore, it was suggested that the response of hPF-MF exposure was involved in the inhibitory input. Next, we screened the inhibitory pacemaker-like neuronal activity which showed autonomous 4–10 Hz firing with CNQX and D-AP5 application, and it was confirmed that the activity was reduced after 400 mT hPF-MF exposure. Comparison of these experimental results with estimated values of the induced electric field (E-field) in the culture medium revealed that the change in synchronized bursting activity occurred over 0.3 V/m, which was equivalent to the findings of a previous study that used the external electric fields. In addition, the results suggested that the potentiation of neuronal activity after 400 mT hPF-MF exposure was related to the depression of autonomous activity of pacemaker-like neurons. Our results indicated that the synchronized bursting activity was increased by hPF-MF exposure (E-field: >0.3 V/m), and the response was due to reduced inhibitory pacemaker-like neuronal activity. PMID:29662453

Calculation and manipulation of the chirp rates of high-order harmonics

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

Murakami, M.; Mauritsson, J.; Schafer, K.J.

2005-01-01

We calculate the linear chirp rates of high-order harmonics in argon, generated by intense, 810 nm laser pulses, and explore the dependence of the chirp rate on harmonic order, driving laser intensity, and pulse duration. By using a time-frequency representation of the harmonic fields we can identify several different linear chirp contributions to the plateau harmonics. Our results, which are based on numerical integration of the time-dependent Schroedinger equation, are in good agreement with the adiabatic predictions of the strong field approximation for the chirp rates. Extending the theoretical analysis in the recent paper by Mauritsson et al. [Phys. Rev.more » A 70, 021801(R) (2004)], we also manipulate the chirp rates of the harmonics by adding a chirp to the driving pulse. We show that the chirp rate for harmonic q is given by the sum of the intrinsic chirp rate, which is determined by the new duration and peak intensity of the chirped driving pulse, and q times the external chirp rate.« less

Fundamental and future prospects of printed ambipolar fluorene-type polymer light-emitting transistors for improved external quantum efficiency, mobility, and emission pattern

NASA Astrophysics Data System (ADS)

Kajii, Hirotake

2018-05-01

In this review, we focus on the improved external quantum efficiency, field-effect mobility, and emission pattern of top-gate-type polymer light-emitting transistors (PLETs) based on ambipolar fluorene-type polymers. A low-temperature, high-efficiency, printable red phosphorescent PLET based on poly(alkylfluorene) with modified alkyl side chains fabricated by a film transfer process is demonstrated. Device fabrication based on oriented films leads to an improved EL intensity owing to the increase in field-effect mobility. There are three factors that affect the transport of carriers, i.e., the energy level, threshold voltage, and mobility of each layer for heterostructure PLETs, which result in various emission patterns such as the line-shaped, multicolor and in-plane emission pattern in the full-channel area between source and drain electrodes. Fundamentals and future prospects in heterostructure devices are discussed and reviewed.

Consistent approach to describing aircraft HIRF protection

NASA Technical Reports Server (NTRS)

Rimbey, P. R.; Walen, D. B.

1995-01-01

The high intensity radiated fields (HIRF) certification process as currently implemented is comprised of an inconsistent combination of factors that tend to emphasize worst case scenarios in assessing commercial airplane certification requirements. By examining these factors which include the process definition, the external HIRF environment, the aircraft coupling and corresponding internal fields, and methods of measuring equipment susceptibilities, activities leading to an approach to appraising airplane vulnerability to HIRF are proposed. This approach utilizes technically based criteria to evaluate the nature of the threat, including the probability of encountering the external HIRF environment. No single test or analytic method comprehensively addresses the full HIRF threat frequency spectrum. Additional tools such as statistical methods must be adopted to arrive at more realistic requirements to reflect commercial aircraft vulnerability to the HIRF threat. Test and analytic data are provided to support the conclusions of this report. This work was performed under NASA contract NAS1-19360, Task 52.

Numerical simulation of magnetic nano drug targeting in patient-specific lower respiratory tract

NASA Astrophysics Data System (ADS)

Russo, Flavia; Boghi, Andrea; Gori, Fabio

2018-04-01

Magnetic nano drug targeting, with an external magnetic field, can potentially improve the drug absorption in specific locations of the body. However, the effectiveness of the procedure can be reduced due to the limitations of the magnetic field intensity. This work investigates this technique with the Computational Fluid Dynamics (CFD) approach. A single rectangular coil generates the external magnetic field. A patient-specific geometry of the Trachea, with its primary and secondary bronchi, is reconstructed from Digital Imaging and Communications in Medicine (DICOM) formatted images, throughout the Vascular Modelling Tool Kit (VMTK) software. A solver, coupling the Lagrangian dynamics of the magnetic nanoparticles with the Eulerian dynamics of the air, is used to perform the simulations. The resistive pressure, the pulsatile inlet velocity and the rectangular coil magnetic field are the boundary conditions. The dynamics of the injected particles is investigated without and with the magnetic probe. The flow field promotes particles adhesion to the tracheal wall. The particles volumetric flow rate in both cases has been calculated. The magnetic probe is shown to increase the particles flow in the target region, but at a limited extent. This behavior has been attributed to the small particle size and the probe configuration.

Study of the intensity noise and intensity modulation in a of hybrid soliton pulsed source

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

Dogru, Nuran; Oziazisi, M Sadetin

2005-10-31

The relative intensity noise (RIN) and small-signal intensity modulation (IM) of a hybrid soliton pulsed source (HSPS) with a linearly chirped Gaussian apodised fibre Bragg grating (FBG) are considered in the electric-field approximation. The HSPS is described by solving the dynamic coupled-mode equations. It is shown that consideration of the carrier density noise in the HSPS in addition to the spontaneous noise is necessary to analyse accurately noise in the mode-locked HSPS. It is also shown that the resonance peak spectral splitting (RPSS) of the IM near the frequency inverse to the round-trip time of light in the external cavitymore » can be eliminated by selecting an appropriate linear chirp rate in the Gaussian apodised FBG. (laser applications and other topics in quantum electronics)« less

Voltage- and Light-Controlled Spin Properties of a Two-Dimensional Hole Gas in p-Type GaAs/AlAs Resonant Tunneling Diodes

NASA Astrophysics Data System (ADS)

Galeti, H. V. A.; Galvão Gobato, Y.; Brasil, M. J. S. P.; Taylor, D.; Henini, M.

2018-03-01

We have investigated the spin properties of a two-dimensional hole gas (2DHG) formed at the contact layer of a p-type GaAs/AlAs resonant tunneling diode (RTD). We have measured the polarized-resolved photoluminescence of the RTD as a function of bias voltage, laser intensity and external magnetic field up to 15T. By tuning the voltage and the laser intensity, we are able to change the spin-splitting from the 2DHG from almost 0 meV to 5 meV and its polarization degree from - 40% to + 50% at 15T. These results are attributed to changes of the local electric field applied to the two-dimensional gas which affects the valence band and the hole Rashba spin-orbit effect.

Internal additive noise effects in stochastic resonance using organic field effect transistor

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

Suzuki, Yoshiharu; Asakawa, Naoki; Matsubara, Kiyohiko

Stochastic resonance phenomenon was observed in organic field effect transistor using poly(3-hexylthiophene), which enhances performance of signal transmission with application of noise. The enhancement of correlation coefficient between the input and output signals was low, and the variation of correlation coefficient was not remarkable with respect to the intensity of external noise, which was due to the existence of internal additive noise following the nonlinear threshold response. In other words, internal additive noise plays a positive role on the capability of approximately constant signal transmission regardless of noise intensity, which can be said “homeostatic” behavior or “noise robustness” against externalmore » noise. Furthermore, internal additive noise causes emergence of the stochastic resonance effect even on the threshold unit without internal additive noise on which the correlation coefficient usually decreases monotonically.« less

Investigation of High-Intensity Ion Beam Generation in the Diode with External Magnetic Insulation and Explosive Plasma Emission Source

NASA Astrophysics Data System (ADS)

Shamanin, V. I.; Stepanov, A. V.; Rysbaev, K. Zh.

2018-04-01

The ion Br-diode in which plasma is generated under the action of a negative pre-pulse voltage is presented. Preliminary plasma formation allows the energy released in the diode during a positive voltage pulse to be increased. The high-energy ion beam parameters are investigated for the magnetic field induction changing from 0.8Bcr to 1.7Bcr.

FDTD simulation of radar cross section reduction by a collisional inhomogeneous magnetized plasma

NASA Astrophysics Data System (ADS)

Foroutan, V.; Azarmanesh, M. N.; Foroutan, G.

2018-02-01

The recursive convolution finite difference time domain method is addressed in the scattered field formulation and employed to investigate the bistatic radar cross-section (RCS) of a square conductive plate covered by a collisional inhomogeneous magnetized plasma. The RCS is calculated for two different configurations of the magnetic field, i.e., parallel and perpendicular to the plate. The results of numerical simulations show that, for a perpendicularly applied magnetic field, the backscattered RCS is significantly reduced when the magnetic field intensity coincides with the value corresponding to the electron cyclotron resonance. By increasing the collision frequency, the resonant absorption is suppressed, but due to enhanced wave penetration and bending, the reduction in the bistatic RCS is improved. At very high collision frequencies, the external magnetic field has no significant impact on the bistatic RCS reduction. Application of a parallel magnetic field has an adverse effect near the electron cyclotron resonance and results in a large and asymmetric RCS profile. But, the problem is resolved by increasing the magnetic field and/or the collision frequency. By choosing proper values of the collision frequency and the magnetic field intensity, a perpendicular magnetic field can be effectively used to reduce the bistatic RCS of a conductive plate.

Magneto-therapy of human joint cartilage.

PubMed

Wierzcholski, Krzysztof; Miszczak, Andrzej

2017-01-01

The topic of the present paper concerns the human joint cartilage therapy performed by the magnetic induction field. There is proved the thesis that the applied magnetic field for concrete cartilage illness should depend on the proper relative and concrete values of applied magnetic induction, intensity as well the time of treatment duration. Additionally, very important are frequencies and amplitudes of magnetic field as well as magnetic permeability of the synovial fluid. The research methods used in this paper include: magnetic induction field produced by a new Polish and German magneto electronic devices for the therapy of human joint cartilage diseases, stationary and movable magnetic applicators, magnetic bandage, ferrofluid injections, author's experience gained in Germany research institutes and practical results after measurements and information from patients. The results of this paper concern concrete parameters of time dependent electro-magnetic field administration during the joint cartilage therapy duration and additionally concern the corollaries which are implied from reading values gained on the magnetic induction devices. The main conclusions obtained in this paper are as follows: Time dependent magnetic induction field increases the dynamic viscosity of movable synovial fluid and decreases symptoms of cartilage illness for concrete intensity of magnetic field and concrete field line architecture. The ferrofluid therapy and phospholipids bilayer simultaneously with the administrated external electromagnetic field, increases the dynamic viscosity of movable synovial fluid.

The growth of the central region by acquisition of counterrotating gas in star-forming galaxies

PubMed Central

Chen, Yan-Mei; Shi, Yong; Tremonti, Christy A.; Bershady, Matt; Merrifield, Michael; Emsellem, Eric; Jin, Yi-Fei; Huang, Song; Fu, Hai; Wake, David A.; Bundy, Kevin; Stark, David; Lin, Lihwai; Argudo-Fernandez, Maria; Bergmann, Thaisa Storchi; Bizyaev, Dmitry; Brownstein, Joel; Bureau, Martin; Chisholm, John; Drory, Niv; Guo, Qi; Hao, Lei; Hu, Jian; Li, Cheng; Li, Ran; Lopes, Alexandre Roman; Pan, Kai-Ke; Riffel, Rogemar A.; Thomas, Daniel; Wang, Lan; Westfall, Kyle; Yan, Ren-Bin

2016-01-01

Galaxies grow through both internal and external processes. In about 10% of nearby red galaxies with little star formation, gas and stars are counter-rotating, demonstrating the importance of external gas acquisition in these galaxies. However, systematic studies of such phenomena in blue, star-forming galaxies are rare, leaving uncertain the role of external gas acquisition in driving evolution of blue galaxies. Here, based on new measurements with integral field spectroscopy of a large representative galaxy sample, we find an appreciable fraction of counter-rotators among blue galaxies (9 out of 489 galaxies). The central regions of blue counter-rotators show younger stellar populations and more intense, ongoing star formation than their outer parts, indicating ongoing growth of the central regions. The result offers observational evidence that the acquisition of external gas in blue galaxies is possible; the interaction with pre-existing gas funnels the gas into nuclear regions (<1 kpc) to form new stars. PMID:27759033

The growth of the central region by acquisition of counterrotating gas in star-forming galaxies.

PubMed

Chen, Yan-Mei; Shi, Yong; Tremonti, Christy A; Bershady, Matt; Merrifield, Michael; Emsellem, Eric; Jin, Yi-Fei; Huang, Song; Fu, Hai; Wake, David A; Bundy, Kevin; Stark, David; Lin, Lihwai; Argudo-Fernandez, Maria; Bergmann, Thaisa Storchi; Bizyaev, Dmitry; Brownstein, Joel; Bureau, Martin; Chisholm, John; Drory, Niv; Guo, Qi; Hao, Lei; Hu, Jian; Li, Cheng; Li, Ran; Lopes, Alexandre Roman; Pan, Kai-Ke; Riffel, Rogemar A; Thomas, Daniel; Wang, Lan; Westfall, Kyle; Yan, Ren-Bin

2016-10-19

Galaxies grow through both internal and external processes. In about 10% of nearby red galaxies with little star formation, gas and stars are counter-rotating, demonstrating the importance of external gas acquisition in these galaxies. However, systematic studies of such phenomena in blue, star-forming galaxies are rare, leaving uncertain the role of external gas acquisition in driving evolution of blue galaxies. Here, based on new measurements with integral field spectroscopy of a large representative galaxy sample, we find an appreciable fraction of counter-rotators among blue galaxies (9 out of 489 galaxies). The central regions of blue counter-rotators show younger stellar populations and more intense, ongoing star formation than their outer parts, indicating ongoing growth of the central regions. The result offers observational evidence that the acquisition of external gas in blue galaxies is possible; the interaction with pre-existing gas funnels the gas into nuclear regions (<1 kpc) to form new stars.

Field induced anomalous spreading, oscillation, ejection, spinning, and breaking of oil droplets on a strongly slipping water surface.

PubMed

Kumar, Sunny; Sarma, Bhaskarjyoti; Dasmahapatra, Ahsok Kumar; Dalal, Amaresh; Basu, Dipankar Narayan; Bandyopadhyay, Dipankar

2017-07-01

Application of an electric field on an oil droplet floating on the surface of a deionized water bath showed interesting motions such as spreading, oscillation, and ejection. The electric field was generated by connecting a pointed platinum cathode at the top of the oil droplet and a copper anode coated with polymer at the bottom of the water layer. The experimental setup mimicked a conventional electrowetting setup with the exception that the oil was spread on a soft and deformable water isolator. While at relatively lower field intensities we observed spreading of the droplet, at intermediate field intensities the droplet oscillated around the platinum cathode, before ejecting out at a speed as high as ∼5 body lengths per second at even stronger field intensities. The experiments suggested that when the electric field was ramped up abruptly to a particular voltage, any of the spreading, oscillation, or ejection motions of the droplet could be engendered at lower, intermediate and higher field intensities, respectively. However, when the field was ramped up progressively by increasing by a definite amount of voltage per unit time, all three aforementioned motions could be generated simultaneously with the increase in the field intensity. Interestingly, when the aforementioned setup was placed on a magnet, the droplet showed a rotational motion under the influence of the Lorentz force, which was generated because of the coupling of the weak leakage current with the externally applied magnetic field. The spreading, oscillation, ejection, and rotation of the droplet were found to be functions of the oil-water interfacial tension, viscosity, and size of the oil droplet. We developed simple theoretical models to explain the experimental results obtained. Importantly, rotating at a higher speed broke the droplet into a number of smaller ones, owing to the combined influence of the spreading due to the centripetal force and the shear at the oil-water interface. While the oscillatory and rotational motions of the incompressible droplet could be employed as stirrers or impellers inside microfluidic devices for mixing applications, the droplet ejection could be employed for futuristic applications such as payload transport or drug delivery.

A vacuum-sealed miniature X-ray tube based on carbon nanotube field emitters

NASA Astrophysics Data System (ADS)

Heo, Sung Hwan; Kim, Hyun Jin; Ha, Jun Mok; Cho, Sung Oh

2012-05-01

A vacuum-sealed miniature X-ray tube based on a carbon nanotube field-emission electron source has been demonstrated. The diameter of the X-ray tube is 10 mm; the total length of the tube is 50 mm, and no external vacuum pump is required for the operation. The maximum tube voltage reaches up to 70 kV, and the X-ray tube generates intense X-rays with the air kerma strength of 108 Gy·cm2 min-1. In addition, X-rays produced from the miniature X-ray tube have a comparatively uniform spatial dose distribution.

An empirical model of the quiet daily geomagnetic field variation

USGS Publications Warehouse

Yamazaki, Y.; Yumoto, K.; Cardinal, M.G.; Fraser, B.J.; Hattori, P.; Kakinami, Y.; Liu, J.Y.; Lynn, K.J.W.; Marshall, R.; McNamara, D.; Nagatsuma, T.; Nikiforov, V.M.; Otadoy, R.E.; Ruhimat, M.; Shevtsov, B.M.; Shiokawa, K.; Abe, S.; Uozumi, T.; Yoshikawa, A.

2011-01-01

An empirical model of the quiet daily geomagnetic field variation has been constructed based on geomagnetic data obtained from 21 stations along the 210 Magnetic Meridian of the Circum-pan Pacific Magnetometer Network (CPMN) from 1996 to 2007. Using the least squares fitting method for geomagnetically quiet days (Kp ??? 2+), the quiet daily geomagnetic field variation at each station was described as a function of solar activity SA, day of year DOY, lunar age LA, and local time LT. After interpolation in latitude, the model can describe solar-activity dependence and seasonal dependence of solar quiet daily variations (S) and lunar quiet daily variations (L). We performed a spherical harmonic analysis (SHA) on these S and L variations to examine average characteristics of the equivalent external current systems. We found three particularly noteworthy results. First, the total current intensity of the S current system is largely controlled by solar activity while its focus position is not significantly affected by solar activity. Second, we found that seasonal variations of the S current intensity exhibit north-south asymmetry; the current intensity of the northern vortex shows a prominent annual variation while the southern vortex shows a clear semi-annual variation as well as annual variation. Thirdly, we found that the total intensity of the L current system changes depending on solar activity and season; seasonal variations of the L current intensity show an enhancement during the December solstice, independent of the level of solar activity. Copyright 2011 by the American Geophysical Union.

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.

Investigation of scrubbing and impingement noise

NASA Technical Reports Server (NTRS)

Fink, M. R.

1975-01-01

Tests were conducted in an acoustic wind tunnel to determine surface pressure spectra and far field noise caused by turbulence impinging on an airfoil and turbulence convected past a sharp trailing edge. Measured effects of flow velocity and turbulence intensity were compared with predictions from several theories. Also, tests were conducted in an anechoic chamber to determine surface pressure spectra and far field noise caused by a deflected airfoil scrubbed by a subsonic jet. This installation simulated both an under-the-wing and an upper-surface-blowing externally blown flap, depending on the deflection angle. Surface and far field spectra, and cross correlation coherence and delay time, were utilized to infer the major noise-producing mechanisms.

Damping factor estimation using spin wave attenuation in permalloy film

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

Manago, Takashi, E-mail: manago@fukuoka-u.ac.jp; Yamanoi, Kazuto; Kasai, Shinya

2015-05-07

Damping factor of a Permalloy (Py) thin film is estimated by using the magnetostatic spin wave propagation. The attenuation lengths are obtained by the dependence of the transmission intensity on the antenna distance, and decrease with increasing magnetic fields. The relationship between the attenuation length, damping factor, and external magnetic field is derived theoretically, and the damping factor was determined to be 0.0063 by fitting the magnetic field dependence of the attenuation length, using the derived equation. The obtained value is in good agreement with the general value of Py. Thus, this estimation method of the damping factor using spinmore » waves attenuation can be useful tool for ferromagnetic thin films.« less

Operating Point Self-Regulator for Giant Magneto-Impedance Magnetic Sensor.

PubMed

Zhou, Han; Pan, Zhongming; Zhang, Dasha

2017-05-11

The giant magneto-impedance (GMI) magnetic sensor based on the amorphous wire has been believed to be tiny dimensions, high sensitivity, quick response, and small power consumption. This kind of sensor is usually working under a bias magnetic field that is called the sensor's operating point. However, the changes in direction and intensity of the external magnetic field, or the changes in sensing direction and position of the sensor, will lead to fluctuations in operating point when the sensor is working without any magnetic shield. In this work, a GMI sensor based on the operating point self-regulator is designed to overcome the problem. The regulator is based on the compensated feedback control that can maintain the operating point of a GMI sensor in a uniform position. With the regulator, the GMI sensor exhibits a stable sensitivity regardless of the external magnetic field. In comparison with the former work, the developed operating point regulator can improve the accuracy and stability of the operating point and therefore decrease the noise and disturbances that are introduced into the GMI sensor by the previous self-regulation system.

Operating Point Self-Regulator for Giant Magneto-Impedance Magnetic Sensor

PubMed Central

Zhou, Han; Pan, Zhongming; Zhang, Dasha

2017-01-01

The giant magneto-impedance (GMI) magnetic sensor based on the amorphous wire has been believed to be tiny dimensions, high sensitivity, quick response, and small power consumption. This kind of sensor is usually working under a bias magnetic field that is called the sensor’s operating point. However, the changes in direction and intensity of the external magnetic field, or the changes in sensing direction and position of the sensor, will lead to fluctuations in operating point when the sensor is working without any magnetic shield. In this work, a GMI sensor based on the operating point self-regulator is designed to overcome the problem. The regulator is based on the compensated feedback control that can maintain the operating point of a GMI sensor in a uniform position. With the regulator, the GMI sensor exhibits a stable sensitivity regardless of the external magnetic field. In comparison with the former work, the developed operating point regulator can improve the accuracy and stability of the operating point and therefore decrease the noise and disturbances that are introduced into the GMI sensor by the previous self-regulation system. PMID:28492514

Feedback-controlled radiation pressure cooling

NASA Astrophysics Data System (ADS)

Prior, Yehiam; Vilensky, Mark; Averbukh, Ilya Sh.

2008-03-01

We propose a new approach to laser cooling of micromechanical devices, which is based on the phenomenon of optical bistability. These devices are modeled as a Fabry-Perot resonator with one fixed and one oscillating mirror. The bistability may be induced by an external feedback loop. When excited by an external laser, the cavity field has two co-existing stable steady-states depending on the position of the moving mirror. If the latter moves slow enough, the field in the cavity adjusts itself adiabatically to the mirror's instantaneous position. The mirror experiences radiation pressure corresponding to the intensity value. A sharp transition between two values of the radiation pressure force happens twice per every period of the mirror oscillation at non-equivalent positions (hysteresis effect), which leads to a non-zero net energy loss. The cooling mechanism resembles Sisyphus cooling in which the cavity mode performs sudden transitions between two stable states. We provide a dynamical stability analysis of the coupled moving mirror -- cavity field system, and find the parameters for efficient cooling. Direct numerical simulations show that a bistable cavity provides much more efficient cooling compared to the regular one.

Numerical simulation of magnetic nano drug targeting in a patient-specific coeliac trunk

NASA Astrophysics Data System (ADS)

Boghi, Andrea; Russo, Flavia; Gori, Fabio

2017-09-01

Magnetic nano drug targeting, through the use of an external magnetic field, is a new technique for the treatment of several diseases, which can potentially avoid the dispersion of drugs in undesired locations of the body. Nevertheless, due to the limitations on the intensity of the magnetic field applied, the hydrodynamic forces can reduce the effectiveness of the procedure. This technique is studied in this paper with the Computational Fluid Dynamics (CFD), focusing on the influence of the magnetic probe position, and the direction of the circulating electric current. A single rectangular coil is used to generate the external magnetic field. A patient-specific geometry of the coeliac trunk is reconstructed from DICOM images, with the use of VMTK. A new solver, coupling the Lagrangian dynamics of the nanoparticles with the Eulerian dynamics of the blood, is implemented in OpenFOAM to perform the simulations. The resistive pressure, the Womersley's profile for the inlet velocity and the magnetic field of a rectangular coil are implemented in the software as boundary conditions. The results show the influence of the position of the probe, as well as the limitations associated with the rectangular coil configuration.

[Quality management in intensive care medicine].

PubMed

Martin, J; Braun, J-P

2014-02-01

Treatment of critical ill patients in the intensive care unit is tantamount to well-designed risk or quality management. Several tools of quality management and quality assurance have been developed in intensive care medicine. In addition to external quality assurance by benchmarking with regard to the intensive care medicine, peer review procedures have been established for external quality assurance in recent years. In the process of peer review of an intensive care unit (ICU), external physicians and nurses visit the ICU, evaluate on-site proceedings, and discuss with the managing team of the ICU possibilities for optimization. Furthermore, internal quality management in the ICU is possible based on the 10 quality indicators of the German Interdisciplinary Society for Intensive Care Medicine (DIVI, "Deutschen Interdisziplinären Vereinigung für Intensiv- und Notfallmedizin"). Thereby every ICU has numerous possibilities to improve their quality management system.

[Quality management in intensive care medicine].

PubMed

Martin, J; Braun, J-P

2013-09-01

Treatment of critical ill patients in the intensive care unit is tantamount to well-designed risk or quality management. Several tools of quality management and quality assurance have been developed in intensive care medicine. In addition to extern quality assurance by benchmarking with regard to the intensive care medicine, peer review procedures have been established for external quality assurance in recent years. In the process of peer review of an intensive care unit (ICU), external physicians and nurses visit the ICU, evaluate on-site proceedings, and discuss with the managing team of the ICU possibilities for optimization. Furthermore, internal quality management in the ICU is possible based on the 10 quality indicators of the German Interdisciplinary Society for Intensive Care Medicine (DIVI, "Deutschen Interdisziplinären Vereinigung für Intensiv- und Notfallmedizin"). Thereby every ICU has numerous possibilities to improve their quality management system.

Self-shielded electron linear accelerators designed for radiation technologies

NASA Astrophysics Data System (ADS)

Belugin, V. M.; Rozanov, N. E.; Pirozhenko, V. M.

2009-09-01

This paper describes self-shielded high-intensity electron linear accelerators designed for radiation technologies. The specific property of the accelerators is that they do not apply an external magnetic field; acceleration and focusing of electron beams are performed by radio-frequency fields in the accelerating structures. The main characteristics of the accelerators are high current and beam power, but also reliable operation and a long service life. To obtain these characteristics, a number of problems have been solved, including a particular optimization of the accelerator components and the application of a variety of specific means. The paper describes features of the electron beam dynamics, accelerating structure, and radio-frequency power supply. Several compact self-shielded accelerators for radiation sterilization and x-ray cargo inspection have been created. The introduced methods made it possible to obtain a high intensity of the electron beam and good performance of the accelerators.

Low intensity magnetic field influences short-term memory: A study in a group of healthy students.

PubMed

Navarro, Enrique A; Gomez-Perretta, Claudio; Montes, Francisco

2016-01-01

This study analyzes if an external magnetic stimulus (2 kHz and approximately 0.1 μT applied near frontal cortex) influences working memory, perception, binary decision, motor execution, and sustained attention in humans. A magnetic stimulus and a sham stimulus were applied to both sides of the head (frontal cortex close to temporal-parietal area) in young and healthy male test subjects (n = 65) while performing Sternberg's memory scanning task. There was a significant change in reaction time. Times recorded for perception, sustained attention, and motor execution were lower in exposed subjects (P < 0.01). However, time employed in binary decision increased for subjects exposed to magnetic fields. From results, it seems that a low intensity 2 kHz exposure modifies short-term working memory, as well as perception, binary decision, motor execution, and sustained attention. © 2015 Wiley Periodicals, Inc.

Nonlinear optical modulation in a plasmonic Bi:YIG Mach-Zehnder interferometer

NASA Astrophysics Data System (ADS)

Firby, C. J.; Elezzabi, A. Y.

2017-02-01

In this work, we propose a magnetoplasmonic modulator for nonlinear radio-frequency (RF) modulation of an integrated optical signal. The modulator consists of a plasmonic Mach-Zehnder interferometer (MZI), constructed of the ferrimagnetic garnet, bismuth-substituted yttrium iron garnet (Bi:YIG). The transverse component of the Bi:YIG magnetization induces a nonreciprocal phase shift (NRPS) onto the guided optical mode, which can be actively modulated through external magnetic fields. In an MZI, the modulated phase shift in turn modulates the output optical intensity. Due to the highly nonlinear evolution of the Bi:YIG magnetization, we show that the spectrum of the output modulated intensity signal can contain harmonics of the driving RF field, frequency splitting around the driving frequency, down-conversion, or mixing of multiple RF signals. This device provides a unique mechanism of simultaneously generating a number of modulation frequencies within a single device.

Electric polarization and the viability of living systems: ion cyclotron resonance-like interactions.

PubMed

Liboff, A R

2009-01-01

Wellness can be described in physical terms as a state that is a function of the organism's electric polarization vector P(r, t). One can alter P by invasive application of electric fields or by non invasive external pulsed magnetic fields (PMF) or ion cyclotron resonance (ICR)-like combinations of static and sinusoidal magnetic fields. Changes in human (total) body bioimpedance are significantly altered during exposure to ICR magnetic field combinations. The conductivities of polar amino acids in solution exhibit sharp discontinuities at ICR magnetic fields tuned to the specific charge to mass ratio of the amino acid. It has been reported that protein peptide bonds are broken by such amino acid ICR fields. Remarkably, some of these effects are only found at ultra-low AC magnetic intensities, on the order of .05 muT. This is approximately 10(3) below accepted levels determined by engineering estimates. Such strikingly low magnetic intensities imply the existence of physically equivalent endogenous weak electric field oscillations. These observations not only make claims related to electromagnetic pollution more credible but also provide a basis for future electromagnetic applications in medicine. They also reinforce the notion that physical factors acting to influence the electric polarization in living organisms play a key role in biology.

On charged particle equilibrium violation in external photon fields.

PubMed

Bouchard, Hugo; Seuntjens, Jan; Palmans, Hugo

2012-03-01

In a recent paper by Bouchard et al. [Med. Phys. 36(10), 4654-4663 (2009)], a theoretical model of quality correction factors for idealistic so-called plan-class specific reference (PCSR) fields was proposed. The reasoning was founded on the definition of PCSR fields made earlier by Alfonso et al. [Med. Phys. 35(11), 5179-5186 (2008)], requiring the beam to achieve charged particle equilibrium (CPE), in a time-averaged sense, in the reference medium. The relation obtained by Bouchard et al. was derived using Fano's theorem (1954) which states that if CPE is established in a given medium, the dose is independent of point-to-point density variations. A potential misconception on the achievability of the condition required by Fano (1954) might be responsible for false practical conclusions, both in the definition of PCSR fields as well as the theoretical model of quality correction factor. In this paper, the practical achievability of CPE in external beams is treated in detail. The fact that this condition is not achievable in single or composite deliveries is illustrated by an intuitive method and is also formally demonstrated. Fano's theorem is not applicable in external beam radiation dosimetry without (virtually) removing attenuation effects, and therefore, the relation conditionally defined by Bouchard et al. (2009) cannot be valid in practice. A definition of PCSR fields in the recent formalism for nonstandard beams proposed by Alfonso et al. (2008) should be modified, revising the criterion of CPE condition. The authors propose reconsidering the terminology used to describe standard and nonstandard beams. The authors argue that quality correction factors of intensity modulated radiation therapy PCSR fields (i.e., k(Q(pcsr),Q) (f(pcsr),f(ref) )) could be unity under ideal conditions, but it is concluded that further investigation is necessary to confirm that hypothesis.

A Brownian dynamics study on ferrofluid colloidal dispersions using an iterative constraint method to satisfy Maxwell’s equations

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

Dubina, Sean Hyun, E-mail: sdubin2@uic.edu; Wedgewood, Lewis Edward, E-mail: wedge@uic.edu

2016-07-15

Ferrofluids are often favored for their ability to be remotely positioned via external magnetic fields. The behavior of particles in ferromagnetic clusters under uniformly applied magnetic fields has been computationally simulated using the Brownian dynamics, Stokesian dynamics, and Monte Carlo methods. However, few methods have been established that effectively handle the basic principles of magnetic materials, namely, Maxwell’s equations. An iterative constraint method was developed to satisfy Maxwell’s equations when a uniform magnetic field is imposed on ferrofluids in a heterogeneous Brownian dynamics simulation that examines the impact of ferromagnetic clusters in a mesoscale particle collection. This was accomplished bymore » allowing a particulate system in a simple shear flow to advance by a time step under a uniformly applied magnetic field, then adjusting the ferroparticles via an iterative constraint method applied over sub-volume length scales until Maxwell’s equations were satisfied. The resultant ferrofluid model with constraints demonstrates that the magnetoviscosity contribution is not as substantial when compared to homogeneous simulations that assume the material’s magnetism is a direct response to the external magnetic field. This was detected across varying intensities of particle-particle interaction, Brownian motion, and shear flow. Ferroparticle aggregation was still extensively present but less so than typically observed.« less

[Investigation of non-ionizing radiation hazards from physiotherapy equipment in 16 medical institutions].

PubMed

He, Jia-xi; Zhou, Wei; Qiu, Hai-li; Yang, Guang-tao

2013-12-01

To investigate the non-ionizing radiation hazards from physiotherapy equipment in medical institutions and to explore feasible control measures for occupational diseases. On-site measurement and assessment of ultra-high-frequency radiation, high-frequency electromagnetic field, microwave radiation, and laser radiation were carried out in 16 medical institutions using the methods in the Measurement of Physical Agents in Workplace (GBZ/T189-2007). All the investigated medical institutions failed to take effective protective measures against non-ionizing radiation. Of the 17 ultra-short wave therapy apparatus, 70.6%, 47.1%, and 17.64% had a safe intensity of ultra-high-frequency radiation on the head, chest, and abdomen, respectively. Of the 4 external high-frequency thermotherapy apparatus, 100%, 75%, and 75%had a safe intensity of high-frequency electromagnetic field on the head, chest, and abdomen, respectively. In addition, the intensities of microwave radiation and laser radiation produced by the 18 microwave therapy apparatus and 12 laser therapeutic apparatus met national health standards. There are non-ionizing radiation hazards from physiotherapy equipment in medical institutions, and effective prevention and control measures are necessary.

The feasibility and safety of high-intensity focused ultrasound combined with low-dose external beam radiotherapy as supplemental therapy for advanced prostate cancer following hormonal therapy.

PubMed

Wu, Rui-Yi; Wang, Guo-Min; Xu, Lei; Zhang, Bo-Heng; Xu, Ye-Qing; Zeng, Zhao-Chong; Chen, Bing

2011-05-01

The aim of this study was to investigate the feasibility and safety of high-intensity focused ultrasound (HIFU) combined with (+) low-dose external beam radiotherapy (LRT) as supplemental therapy for advanced prostate cancer (PCa) following hormonal therapy (HT). Our definition of HIFU+LRT refers to treating primary tumour lesions with HIFU in place of reduced field boost irradiation to the prostate, while retaining four-field box irradiation to the pelvis in conventional-dose external beam radiotherapy (CRT). We performed a prospective, controlled and non-randomized study on 120 patients with advanced PCa after HT who received HIFU, CRT, HIFU+LRT and HT alone, respectively. CT/MR imaging showed the primary tumours and pelvic lymph node metastases visibly shrank or even disappeared after HIFU+LRT treatment. There were significant differences among four groups with regard to overall survival (OS) and disease-specific survival (DSS) curves (P = 0.018 and 0.015). Further comparison between each pair of groups suggested that the long-term DSS of the HIFU+LRT group was higher than those of the other three groups, but there was no significant difference between the HIFU+LRT group and the CRT group. Multivariable Cox's proportional hazard model showed that both HIFU+LRT and CRT were independently associated with DSS (P = 0.001 and 0.035) and had protective effects with regard to the risk of death. Compared with CRT, HIFU+LRT significantly decreased incidences of radiation-related late gastrointestinal (GI) and genitourinary (GU) toxicity grade ≥ II. In conclusion, long-term survival of patients with advanced PCa benefited from strengthening local control of primary tumour and regional lymph node metastases after HT. As an alternative to CRT, HIFU+LRT showed good efficacy and better safety.

Ultralong time response of magnetic fluid based on fiber-optic evanescent field.

PubMed

Du, Bobo; Yang, Dexing; Bai, Yang; Yuan, Yuan; Xu, Jian; Jiang, Yajun; Wang, Meirong

2016-07-20

The ultralong time (a few hours) response properties of magnetic fluid using etched optical fiber are visualized and investigated experimentally. The operating structure is made by injecting magnetic fluid into a capillary tube that contains etched single-mode fiber. An interesting extreme asymmetry is observed, in which the transmitted light intensity after the etched optical fiber cannot reach the final steady value when the external magnetic field is turned on (referred to as the falling process), while it can reach the stable state quickly once the magnetic field is turned off (referred to as the rising process). The relationship between the response times/loss rates of the transmitted light and the strength of the applied magnetic field is obtained. The physical mechanisms of two different processes are discussed qualitatively.

Boundary-value problem for a counterrotating electrical discharge in an axial magnetic field. [plasma centrifuge for isotope separation

NASA Technical Reports Server (NTRS)

Hong, S. H.; Wilhelm, H. E.

1978-01-01

An electrical discharge between two ring electrodes embedded in the mantle of a cylindrical chamber is considered, in which the plasma in the anode and cathode regions rotates in opposite directions under the influence of an external axial magnetic field. The associated boundary-value problem for the coupled partial differential equations describing the azimuthal velocity and radial current-density fields is solved in closed form. The velocity, current density, induced magnetic induction, and electric fields are presented for typical Hartmann numbers, magnetic Reynolds numbers, and geometry parameters. The discharge is shown to produce anodic and cathodic plasma sections rotating at speeds of the order 1,000,000 cm/sec for conventional magnetic field intensities. Possible application of the magnetoactive discharge as a plasma centrifuge for isotope separation is discussed.

EFFECTS OF LASER RADIATION ON MATTER: Role of the external photoelectric effect in surface microprocessing

NASA Astrophysics Data System (ADS)

Ageev, Vladimir P.; Konov, Vitalii I.; Krechetov, A. I.

1990-08-01

An analysis is made of the photoemission of electrons in gases when the surface of a solid is subjected to high-intensity ultraviolet laser radiation which does not cause surface heating. Various situations are considered in which generation of high local electric fields and of a dense cloud of charged particles near the surface may alter and even determine the mechanism of laser-stimulated processes on surfaces of solids.

Free-Free Transitions in the Presence of Laser Fields at Very Low Incident Electron Energy

NASA Technical Reports Server (NTRS)

Bhatia, A. K.; Sinha, Chandana

2010-01-01

We study the free-free transition in electron-hydrogenic systems in ground state in presence of an external laser field at very loud incident energies. The laser field is treated classically while the collision dynamics is treated quantum mechanically. The laser field is chosen to be monochromatic, linearly polarized and homogeneous. The incident electron is considered to be dressed by the laser in a nonperturbative manner by choosing a Volkov wave function for it. The scattering weave function for the electron is solved numerically by taking into account the effect of the electron exchange, short-range as well as of the long-range interactions to get the S and P wave phase shifts while for the higher angular momentum phase shifts the exchange approximation has only been considered. We calculate the laser assisted differential cross sections (LADCS) for the aforesaid free-free transition process for single photon absorption/emission. The laser intensity is chosen to be much less than the atomic field intensity. A strong suppression is noted in the LADCS as compared to the field free (FF) cross sections. Unlike the FF ones, the LADCS exhibit some oscillations having a distinct maximum at a low value of the scattering angle depending on the laser parameters as well as on the incident energies.

Free-Free Transitions in the Presence of Laser Fields at Very Low Incident Electron Energy

NASA Technical Reports Server (NTRS)

Bhatia, Anand K.; Sinha, Chandana

2009-01-01

We study the free-free transition in electron-hydrogenic systems in ground state in presence of an external laser field at very low incident energies. The laser field is treated classically while the collision dynamics is treated quantum mechanically. The laser field is chosen to be monochromatic, linearly polarized and homogeneous. The incident electron is considered to be dressed by the laser in a nonperturbative manner by choosing a Volkov wave function for it The scattering wave function for the electron is solved numerically by taking into account the effect of the electron exchange, short-range as well as of the long-range interactions to get the S and P wave phase shifts while for the higher angular momentum phase shifts, the exchange approximation has only been considered. We calculate the laser-assisted differential cross sections (LADCS) for the aforesaid free-free transition process for single photon absorption/emission. The laser intensity is chosen to be much less than the atomic field intensity. A strong suppression is noted in the LADCS as compared to the field free (FF) cross sections. Unlike the FF ones, the LADCS exhibit some oscillations having a distinct maximum at a low value of the scattering angle depending on the laser parameters as well as on the incident energies.

Electron-related linear and nonlinear optical responses in vertically coupled triangular quantum dots

NASA Astrophysics Data System (ADS)

Martínez-Orozco, J. C.; Mora-Ramos, M. E.; Duque, C. A.

2014-11-01

The conduction band states of GaAs-based vertically coupled double triangular quantum dots in two dimensions are investigated within the effective mass and parabolic approximation, using a diagonalization procedure to solve the corresponding Schrödinger-like equation. The effect of an externally applied static electric field is included in the calculation, and the variation of the lowest confined energy levels as a result of the change of the field strength is reported for different geometrical setups. The linear and nonlinear optical absorptions and the relative change of the refractive index, associated with the energy transition between the ground and the first excited state in the system, are studied as a function of the incident light frequency for distinct configurations of inter-dot distance and electric field intensities. The blueshift of the resonant absorption peaks is detected as a consequence of the increment in the field intensity, whereas the opposite effect is obtained from the increase of inter-dot vertical distance. It is also shown that for large enough values of the electric field there is a quenching of the optical absorption due to field-induced change of symmetry of the first excited state wavefunction, in the case of triangular dots of equal shape and size.

Boosted Hyperthermia Therapy by Combined AC Magnetic and Photothermal Exposures in Ag/Fe3O4 Nanoflowers.

PubMed

Das, R; Rinaldi-Montes, N; Alonso, J; Amghouz, Z; Garaio, E; García, J A; Gorria, P; Blanco, J A; Phan, M H; Srikanth, H

2016-09-28

Over the past two decades, magnetic hyperthermia and photothermal therapy are becoming very promising supplementary techniques to well-established cancer treatments such as radiotherapy and chemotherapy. These techniques have dramatically improved their ability to perform controlled treatments, relying on the procedure of delivering nanoscale objects into targeted tumor tissues, which can release therapeutic killing doses of heat either upon AC magnetic field exposure or laser irradiation. Although an intense research effort has been made in recent years to study, separately, magnetic hyperthermia using iron oxide nanoparticles and photothermal therapy based on gold or silver plasmonic nanostructures, the full potential of combining both techniques has not yet been systematically explored. Here we present a proof-of-principle experiment showing that designing multifunctional silver/magnetite (Ag/Fe3O4) nanoflowers acting as dual hyperthermia agents is an efficient route for enhancing their heating ability or specific absorption rate (SAR). Interestingly, the SAR of the nanoflowers is increased by at least 1 order of magnitude under the application of both an external magnetic field of 200 Oe and simultaneous laser irradiation. Furthermore, our results show that the synergistic exploitation of the magnetic and photothermal properties of the nanoflowers reduces the magnetic field and laser intensities that would be required in the case that both external stimuli were applied separately. This constitutes a key step toward optimizing the hyperthermia therapy through a combined multifunctional magnetic and photothermal treatment and improving our understanding of the therapeutic process to specific applications that will entail coordinated efforts in physics, engineering, biology, and medicine.

Effects of electric field and light polarization on the electromagnetically induced transparency in an impurity doped quantum ring

NASA Astrophysics Data System (ADS)

Bejan, D.; Stan, C.; Niculescu, E. C.

2018-01-01

We theoretically investigated the effects of the impurity position, in-plane electric field, intensity and polarization of the probe and control lasers on the electromagnetically induced transparency (EIT) in GaAs/GaAlAs disc shaped quantum ring. Our study reveals that, depending on the impurity position, the quantum system presents two specific configurations for the EIT occurrence even in the absence of the external electric field, i.e. ladder-configuration or V-configuration, and changes the configuration from ladder to V for specific electric field values. The polarization of the probe and control lasers plays a crucial role in obtaining a good transparency. The electric field controls the red-shift (blue-shift) of the transparency window and modifies its width. The system exhibits birefringence for the probe light in a limited interval of electric field values.

Dynamics of magnetic-field-induced clustering in ionic ferrofluids from Raman scattering

NASA Astrophysics Data System (ADS)

Heinrich, D.; Goñi, A. R.; Thomsen, C.

2007-03-01

Using Raman spectroscopy, the authors have investigated the aggregation/disgregation of magnetic nanoparticles in dense ionic ferrofluids (IFF) into clusters due to the action of an inhomogeneous external magnetic field. Evidence for changes in particle density and/or effective cluster size were obtained from the variation of the Raman intensity in a time window from 10sto10min for magnetic fields up to 350mT and at a temperature of 28°C. Clustering sets in already at very low fields (>15mT) and the IFF samples exhibit a clear hysteresis in the Raman spectra after releasing the magnetic field, which lasts for many hours at room temperature. The authors determined the characteristic times of the two competing processes, that of field-induced cluster formation and, at room temperature, that of thermal-activated dissociation, to range from 100to150s.

Dynamic colloidal sorting on a magnetic bubble lattice

NASA Astrophysics Data System (ADS)

Tierno, Pietro; Soba, Alejandro; Johansen, Tom H.; Sagués, Francesc

2008-11-01

We use a uniaxial garnet film with a magnetic bubble lattice to sort paramagnetic colloidal particles with different diameters, i.e., 1.0 and 2.8μm. We apply an external magnetic field which precesses around an axis normal to the film with a frequency Ω =62.8s-1 and intensity 3120A/m

Suppression and spectral splitting of the amplitude noise due to mode beatings in a single-frequency injection laser

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

Bogatov, A.P.; Eliseev, P.G.; Kobildzhanov, O.A.

1987-06-01

Investigations of intensity fluctuations in a single-frequency injection laser showed that they are due to beatings between coherent field and superluminescent spontaneous emission. It has been experimentally found that in the region of developed laser emission, the level of fluctuations is decreased with an increase of the output power, and so the relative spectral shift of external cavity superluminescent mode frequencies is dependent on the laser output power. The explanation of this phenomenon was made on the basis of the mechanism of a nonlinear interaction of a field in the active region of a laser diode.

Multi-mode of Four and Six Wave Parametric Amplified Process

NASA Astrophysics Data System (ADS)

Zhu, Dayu; Yang, Yiheng; Zhang, Da; Liu, Ruizhou; Ma, Danmeng; Li, Changbiao; Zhang, Yanpeng

2017-03-01

Multiple quantum modes in correlated fields are essential for future quantum information processing and quantum computing. Here we report the generation of multi-mode phenomenon through parametric amplified four- and six-wave mixing processes in a rubidium atomic ensemble. The multi-mode properties in both frequency and spatial domains are studied. On one hand, the multi-mode behavior is dominantly controlled by the intensity of external dressing effect, or nonlinear phase shift through internal dressing effect, in frequency domain; on the other hand, the multi-mode behavior is visually demonstrated from the images of the biphoton fields directly, in spatial domain. Besides, the correlation of the two output fields is also demonstrated in both domains. Our approach supports efficient applications for scalable quantum correlated imaging.

Multi-mode of Four and Six Wave Parametric Amplified Process.

PubMed

Zhu, Dayu; Yang, Yiheng; Zhang, Da; Liu, Ruizhou; Ma, Danmeng; Li, Changbiao; Zhang, Yanpeng

2017-03-03

Multiple quantum modes in correlated fields are essential for future quantum information processing and quantum computing. Here we report the generation of multi-mode phenomenon through parametric amplified four- and six-wave mixing processes in a rubidium atomic ensemble. The multi-mode properties in both frequency and spatial domains are studied. On one hand, the multi-mode behavior is dominantly controlled by the intensity of external dressing effect, or nonlinear phase shift through internal dressing effect, in frequency domain; on the other hand, the multi-mode behavior is visually demonstrated from the images of the biphoton fields directly, in spatial domain. Besides, the correlation of the two output fields is also demonstrated in both domains. Our approach supports efficient applications for scalable quantum correlated imaging.

Uniform magnetic fields and double-wrapped coil systems: improved techniques for the design of bioelectromagnetic experiments.

PubMed

Kirschvink, J L

1992-01-01

A common mistake in biomagnetic experimentation is the assumption that Helmholtz coils provide uniform magnetic fields; this is true only for a limited volume at their center. Substantial improvements on this design have been made during the past 140 years with systems of three, four, and five coils. Numerical comparisons of the field uniformity generated by these designs are made here, along with a table of construction details and recommendations for their use in experiments in which large volumes of uniform intensity magnetic exposures are needed. Double-wrapping, or systems of bifilar windings, can also help control for the non-magnetic effects of the electric coils used in many experiments. In this design, each coil is wrapped in parallel with two separate, adjacent strands of copper wire, rather than the single strand used normally. If currents are flowing in antiparallel directions, the magnetic fields generated by each strand will cancel and yield virtually no external magnetic field, whereas parallel currents will yield an external field. Both cases will produce similar non-magnetic effects of ohmic heating, and simple measures can reduce the small vibration and electric field differences. Control experiments can then be designed such that the only major difference between treated and untreated groups is the presence or absence of the magnetic field. Double-wrapped coils also facilitate the use of truly double-blind protocol, as the same apparatus can be used either for experimental or control groups.

Qubit-qubit entanglement dynamics control via external classical pumping and Kerr nonlinearity mediated by a single detuned cavity field powered by two-photon processes

NASA Astrophysics Data System (ADS)

Ateto, M. S.

2017-11-01

The nonlinear time-dependent two-photon Hamiltonian of a couple of classically pumped independent qubits is analytically solved, and the corresponding time evolution unitary operator, in an exact form, is derived. Using the concurrence, entanglement dynamics between the qubits under the influence of a wide range of effective parameters are examined and, in detail, analyzed. Observations analysis is documented with aid of the field phase-space distribution Wigner function. A couple of initial qubit states is considered, namely similar excited states and a Bell-like pure state. It is demonstrated that an initial Bell-like pure state is as well typical initial qubits setting for robust, regular and a high degree of entanglement. Moreover, it is established that high-constant Kerr media represent an effective tool for generating periodical entanglement at fixed time cycles of maxima reach unity forever when qubits are initially in a Bell-like pure state. Further, it is showed that the medium strength of the classical pumping stimulates efficiently qubits entanglement, specially, when the interaction occurs off resonantly. However, the high-intensity pumping thermalizes the coherent distribution of photons, thus, the least photons number is used and, hence, the least minimum degree of qubits entanglement could be created. Furthermore, when the cavity field and external pumping are detuned, the external pumping acts like an auxiliary effective frequency for the cavity, as a result, the field Gaussian distribution acquires linear chirps, and consequently, more entanglement revivals appear in the same cycle during timescale.

[INVITED] Magnetic field vector sensor by a nonadiabatic tapered Hi-Bi fiber and ferrofluid nanoparticles

NASA Astrophysics Data System (ADS)

Layeghi, Azam; Latifi, Hamid

2018-06-01

A magnetic field vector sensor based on super-paramagnetic fluid and tapered Hi-Bi fiber (THB) in fiber loop mirror (FLM) is proposed. A two-dimensional detection of external magnetic field (EMF) is experimentally demonstrated and theoretically simulated by Jones matrix to analyze the physical operation in detail. A birefringence is obtained due to magnetic fluid (MF) in applied EMF. By surrounding the THB with MF, a tunable birefringence of MF affect the transmission of the sensor. Slow and fast axes of this obtained birefringence are determined by the direction of applied EMF. In this way, the transmission response of the sensor is depended on the angle between the EMF orientation and the main axes of polarization maintaining fiber (PMF) in FLM. The wavelength shift and intensity shift versus EMF orientation show a sinusoidal behavior, while the applied EMF is constant. Also, the changes in the intensity of EMF in a certain direction results in wavelength shift in the sensor spectrum. The maximum wavelength sensitivity of 214 pm/mT is observed.

Optical response of hybrid semiconductor quantum dot-metal nanoparticle system: Beyond the dipole approximation

NASA Astrophysics Data System (ADS)

Mohammadzadeh, Atefeh; Miri, MirFaez

2018-01-01

We study the response of a semiconductor quantum dot-metal nanoparticle system to an external field E 0 cos ( ω t ) . The borders between Fano, double peaks, weak transition, strong transition, and bistability regions of the phase diagram move considerably as one regards the multipole effects. The exciton-induced transparency is an artifact of the dipole approximation. The absorption of the nanoparticle, the population inversion of the quantum dot, the upper and lower limits of intensity where bistability occurs, the characteristic time to reach the steady state, and other features of the hybrid system change due to the multipole effects. The phase diagrams corresponding to the fields parallel and perpendicular to the axis of system are quite distinguishable. Thus, both the intensity and the polarization of the incident field can be used to control the system. In particular, the incident polarization can be used to switch on and switch off the bistable behavior. For applications such as miniaturized bistable devices and nanosensors sensitive to variations of the dielectric constant of the surrounding medium, multipole effects must be considered.

Central venous catheter-associated bloodstream infections in a pediatric intensive care unit: effect of the location of catheter insertion.

PubMed

Krishnaiah, Anil; Soothill, James; Wade, Angie; Mok, Quen Q; Ramnarayan, Padmanabhan

2012-05-01

To compare the rate of central venous catheter-associated bloodstream infections between pediatric intensive care unit admissions where central venous catheters were inserted within the same hospital (internal central venous catheters) and those where central venous catheters were inserted before transfer from other hospitals (external central venous catheters). Retrospective analysis of prospectively collected data. A tertiary care pediatric intensive care unit in London, UK. Consecutive pediatric intensive care unit admissions between May 2007 and March 2009. None. Catheter-associated bloodstream infections were identified using a widely accepted surveillance definition. The rate and time to occurrence of catheter-associated bloodstream infection were compared between internal and external nontunneled central venous catheters. A multilevel Cox-regression model was used to study the association between location of central venous catheter insertion and time to catheter-associated bloodstream infection. In total, 382 central venous catheters were studied (245 internal; 137 external) accounting for a total of 1,737 central venous catheter days. There was a higher catheter-associated bloodstream infection incidence density among external central venous catheters (23.1 [95% confidence interval 11.0-35.2] vs. 9.7 [95% confidence interval 3.9-15.5] per 1,000 catheter-days). Multivariable analyses demonstrated higher infection risk with external central venous catheters (hazard ratio 2.65 [95% confidence interval 1.18-5.96]) despite adjustment for confounding variables. The rate of catheter-associated bloodstream infections in the pediatric intensive care unit is significantly affected by external insertion of the central venous catheter. Future interventions to reduce nosocomial infections on pediatric intensive care units will need to be specifically targeted at this high-risk patient group.

A theoretical study of molecular structure, optical properties and bond activation of energetic compound FOX-7 under intense electric fields

NASA Astrophysics Data System (ADS)

Tao, Zhiqiang; Wang, Xin; Wei, Yuan; Lv, Li; Wu, Deyin; Yang, Mingli

2017-02-01

Molecular structure, vibrational and electronic absorption spectra, chemical reactivity of energetic compound FOX-7, one of the most widely used explosives, were studied computationally in presence of an electrostatic field of 0.01-0.05 a.u. The Csbnd N bond, which usually triggers the decomposition of FOX-7, is shortened/elongated under a parallel/antiparallel field. The Csbnd N bond activation energy varies with the external electric field, decreasing remarkably with the field strength in regardless of the field direction. This is attributed to two aspects: the bond weakening by the field parallel to the Csbnd N bond and the stabilization effect on the transition-state structure by the field antiparallel to the bond. The variations in the structure and property of FOX-7 under the electric fields were further analyzed with its distributional polarizability, which is dependent on the charge transfer characteristics through the Csbnd N bond.

Electron acceleration in quantum plasma with spin-up and spin-down exchange interaction

NASA Astrophysics Data System (ADS)

Kumar, Punit; Singh, Shiv; Ahmad, Nafees

2018-05-01

Electron acceleration by ponderomotive force of an intense circularly polarized laser pulse in high density magnetized quantum plasma with two different spin states embedded in external static magnetic field. The basic mechanism involves electron acceleration by axial gradient in the ponderomotive potential of laser. The effects of Bohm potential, fermi pressure and intrinsic spin of electron have been taken into account. A simple solution for ponderomotive electron acceleration has been established and effect of spin polarization is analyzed.

Magneto-optic dynamics in a ferromagnetic nematic liquid crystal

NASA Astrophysics Data System (ADS)

Potisk, Tilen; Mertelj, Alenka; Sebastián, Nerea; Osterman, Natan; Lisjak, Darja; Brand, Helmut R.; Pleiner, Harald; Svenšek, Daniel

2018-01-01

We investigate dynamic magneto-optic effects in a ferromagnetic nematic liquid crystal experimentally and theoretically. Experimentally we measure the magnetization and the phase difference of the transmitted light when an external magnetic field is applied. As a model we study the coupled dynamics of the magnetization, M , and the director field, n , associated with the liquid crystalline orientational order. We demonstrate that the experimentally studied macroscopic dynamic behavior reveals the importance of a dynamic cross-coupling between M and n . The experimental data are used to extract the value of the dissipative cross-coupling coefficient. We also make concrete predictions about how reversible cross-coupling terms between the magnetization and the director could be detected experimentally by measurements of the transmitted light intensity as well as by analyzing the azimuthal angle of the magnetization and the director out of the plane spanned by the anchoring axis and the external magnetic field. We derive the eigenmodes of the coupled system and study their relaxation rates. We show that in the usual experimental setup used for measuring the relaxation rates of the splay-bend or twist-bend eigenmodes of a nematic liquid crystal one expects for a ferromagnetic nematic liquid crystal a mixture of at least two eigenmodes.

Inside-out: comparing internally generated and externally generated basic emotions.

PubMed

Salas, Christian E; Radovic, Darinka; Turnbull, Oliver H

2012-06-01

A considerable number of mood induction (MI) procedures have been developed to elicit emotion in normal and clinical populations. Although external procedures (e.g., film clips, pictures) are widely used, a number of experiments elicit emotion by using self-generated procedures (e.g., recalling an emotional personal episode). However, no study has directly compared the effectiveness of two types of internal versus external MI across multiple discrete emotions. In the present experiment, 40 undergraduate students watched film clips (external procedure) and recalled personal events (internal procedure) inducing 4 basic emotions (fear, anger, joy, sadness) and later completed a self-report questionnaire. Remarkably, both internal and external procedures elicited target emotions selectively, compared with nontarget emotions. When contrasting the intensity of target emotions, both techniques showed no significant differences, with the exception of Joy, which was more intensely elicited by the internal procedure. Importantly, when considering the overall level of intensity, it was always greater in the internal procedure, for each stimulus. A more detailed investigation of the data suggest that recalling personal events (a type of internal procedure) generates more negative and mixed blends of emotions, which might account for the overall higher intensity of the internal mood induction.

Loop-locked coherent population trapping magnetometer based on a fiber electro-optic modulator.

PubMed

Hu, Yong; Feng, Y Y; Xu, Chi; Xue, H B; Sun, Li

2014-04-01

We have set up a coherent population trapping (CPT)-based magnetometer prototype with the D1 line of ⁸⁷Rb atoms. The dichromatic light field is derived from a fiber electro-optic modulator (FEOM) connected to an external cavity laser diode. A CPT resonance signal with a 516 Hz linewidth is observed. By feeding back the derivative of the resonance curve to the FEOM with a proportional integral controller, of which the voltage output is directly converted to the measured magnetic field intensity, the resonance peak is locked to the environmental magnetic field. The measurement data we have achieved are well matched with the data measured by a commercial fluxgate magnetometer within 2 nT, and the sensitivity is better than 8 pT/√Hz in a parallel B field.

Observed emotion frequency versus intensity as predictors of socioemotional maladjustment.

PubMed

Hernández, Maciel M; Eisenberg, Nancy; Valiente, Carlos; Spinrad, Tracy L; VanSchyndel, Sarah K; Diaz, Anjolii; Berger, Rebecca H; Silva, Kassondra M; Southworth, Jody; Piña, Armando A

2015-12-01

The purpose of this study was to assess whether observed emotional frequency (the proportion of instances an emotion was observed) and intensity (the strength of an emotion when it was observed) uniquely predicted kindergartners' (N = 301) internalizing and externalizing problems. Analyses were tested in a structural equation modeling (SEM) framework with data from multireporters (reports of problem behaviors from teachers and parents) and naturalistic observations of emotion in the fall semester. For observed positive emotion, both frequency and intensity negatively predicted parent- or teacher-reported internalizing symptoms. Anger frequency positively predicted parent- and teacher-reported externalizing symptoms, whereas anger intensity positively predicted parent- and teacher-reported externalizing and parent-reported internalizing symptoms. The findings support the importance of examining both aspects of emotion when predicting maladjustment. (c) 2015 APA, all rights reserved).

Using an intense laser beam in interaction with muon/electron beam to probe the noncommutative QED

NASA Astrophysics Data System (ADS)

Tizchang, S.; Batebi, S.; Haghighat, M.; Mohammadi, R.

2017-02-01

It is known that the linearly polarized photons can partly transform to circularly polarized ones via forward Compton scattering in a background such as the external magnetic field or noncommutative space time. Based on this fact we explore the effects of the NC-background on the scattering of a linearly polarized laser beam from an intense beam of charged leptons. We show that for a muon/electron beam flux {overline{ɛ}}_{μ, e}˜ 1{0}^{12}/{10}^{10} TeV cm-2 sec-1 and a linearly polarized laser beam with energy k 0 ˜1 eV and average power {overline{P}}_{laser}˜eq 1{0}^3 KW, the generation rate of circularly polarized photons is about R V ˜ 104 /sec for noncommutative energy scale ΛNC ˜ 10 TeV. This is fairly large and can grow for more intense beams in near future.

High-intensity polarized H- ion source for the RHIC SPIN physics

NASA Astrophysics Data System (ADS)

Zelenski, A.; Atoian, G.; Raparia, D.; Ritter, J.; Kolmogorov, A.; Davydenko, V.

2017-08-01

A novel polarization technique had been successfully implemented for the RHIC polarized H- ion source upgrade to higher intensity and polarization. In this technique a proton beam inside the high magnetic field solenoid is produced by ionization of the atomic hydrogen beam (from external source) in the He-gas ionizer cell. Further proton polarization is produced in the process of polarized electron capture from the optically-pumped Rb vapour. The use of high-brightness primary beam and large cross-sections of charge-exchange cross-sections resulted in production of high intensity H- ion beam of 85% polarization. High beam brightness and polarization resulted in 75% polarization at 23 GeV out of AGS and 60-65% beam polarization at 100-250 GeV colliding beams in RHIC. The status of un-polarized magnetron type (Cs-vapour loaded) BNL source is also discussed.

Nonequilibrium transition induced by mass media in a model for social influence

NASA Astrophysics Data System (ADS)

González-Avella, J. C.; Cosenza, M. G.; Tucci, K.

2005-12-01

We study the effect of mass media, modeled as an applied external field, on a social system based on Axelrod’s model for the dissemination of culture. The numerical simulations show that the system undergoes a nonequilibrium phase transition between an ordered phase (homogeneous culture) specified by the mass media and a disordered (culturally fragmented) one. The critical boundary separating these phases is calculated on the parameter space of the system, given by the intensity of the mass media influence and the number of options per cultural attribute. Counterintuitively, mass media can induce cultural diversity when its intensity is above some threshold value. The nature of the phase transition changes from continuous to discontinuous at some critical value of the number of options.

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

NASA Astrophysics Data System (ADS)

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

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

When the research is not reproducible: The importance of author-initiated and institution-driven responses and investigations.

PubMed

Tang, Bor Luen

2018-05-20

Important and potentially useful findings in the sciences are under more intense public scrutiny now more than ever. Other researchers in the field dive into replicating and expanding the findings while the media swamps the community and the public with peripheral reporting and analyses. How should authors and the hosting/funding institutions respond when other workers in the field could not reproduce or replicate their published results? To illustrate the importance of author-initiated and institution-driven investigations in response to outcries of research irreproducibility, I draw on comparisons between three recent and well-publicized cases in the life sciences: betatrophin, STAP cells, and NgAgo. Swift, transparent responses and investigations facilitate activation of the self-correcting mechanism of science and are likely also critical in preserving the community's resources, public trust, and the reputation of the institutions and individuals concerned. Operational guidelines for "author and institutional responses" towards external reports of irreproducibility should therefore be in place for all research intensive institutions.

Near-field polarization distribution of Si nanoparticles near substrate

NASA Astrophysics Data System (ADS)

Reshetov, S. A.; Vladimirova, Yu. V.; Gevorkian, L. P.; Zadkov, V. N.

2017-01-01

Structure of the near-field intensity and polarization distributions, the latter is described with the generalized 3D Stokes parameters, of a spherical Si subwavelength nanoparticle in a non-magnetic and non-absorbing media near a dielectric substrate has been studied in detail with the help of the Mie theory and an extension of the Weyl's method for the calculation of the reflection of dipole radiation by a flat surface. It is shown that for the nanoparticle near the substrate the interference effects due to the scattering by the nanoparticle and interaction with the substrate play an essential role. We also demonstrate how these effects depend on the dielectric properties of the nanoparticle, its size, distance to the substrate as well as on the polarization, wavelength and incident angle of the external light field.

Extension of Gibbs-Duhem equation including influences of external fields

NASA Astrophysics Data System (ADS)

Guangze, Han; Jianjia, Meng

2018-03-01

Gibbs-Duhem equation is one of the fundamental equations in thermodynamics, which describes the relation among changes in temperature, pressure and chemical potential. Thermodynamic system can be affected by external field, and this effect should be revealed by thermodynamic equations. Based on energy postulate and the first law of thermodynamics, the differential equation of internal energy is extended to include the properties of external fields. Then, with homogeneous function theorem and a redefinition of Gibbs energy, a generalized Gibbs-Duhem equation with influences of external fields is derived. As a demonstration of the application of this generalized equation, the influences of temperature and external electric field on surface tension, surface adsorption controlled by external electric field, and the derivation of a generalized chemical potential expression are discussed, which show that the extended Gibbs-Duhem equation developed in this paper is capable to capture the influences of external fields on a thermodynamic system.

Low and Midlatitude Ionospheric Plasma Density Irregularities and Their Effects on Geomagnetic Field

NASA Astrophysics Data System (ADS)

Yokoyama, Tatsuhiro; Stolle, Claudia

2017-03-01

Earth's magnetic field results from various internal and external sources. The electric currents in the ionosphere are major external sources of the magnetic field in the daytime. High-resolution magnetometers onboard low-Earth-orbit satellites such as CHAMP and Swarm can detect small-scale currents in the nighttime ionosphere, where plasma density gradients often become unstable and form irregular density structures. The magnetic field variations caused by the ionospheric irregularities are comparable to that of the lithospheric contribution. Two phenomena in the nighttime ionosphere that contribute to the magnetic field variation are presented: equatorial plasma bubble (EPB) and medium-scale traveling ionospheric disturbance (MSTID). EPB is formed by the generalized Rayleigh-Taylor instability over the dip equator and grows nonlinearly to as high as 2000 km apex altitude. It is characterized by deep plasma density depletions along magnetic flux tubes, where the diamagnetic effect produced by a pressure-gradient-driven current enhances the main field intensity. MSTID is a few hundred kilometer-scale disturbance in the midlatitude ionosphere generated by the coupled electrodynamics between the ionospheric E and F regions. The field-aligned currents associated with EPBs and MSTIDs also have significant signatures in the magnetic field perpendicular to the main field direction. The empirical discovery of the variations in the magnetic field due to plasma irregularities has motivated the inclusion of electrodynamics in the physical modeling of these irregularities. Through an effective comparison between the model results and observations, the physical process involved has been largely understood. The prediction of magnetic signatures due to plasma irregularities has been advanced by modeling studies, and will be helpful in interpreting magnetic field observations from satellites.

Interaction of laser radiation with plasma under the MG external magnetic field

NASA Astrophysics Data System (ADS)

Ivanov, V. V.; Maximov, A. V.; Betti, R.; Sawada, H.; Sentoku, Y.

2016-10-01

Strong magnetic fields play an important role in many physical processes relevant to astrophysical events and fusion research. Laser produced plasma in the MG external magnetic field was studied at the 1 MA pulsed power generator coupled with the laser operated in ns and ps regimes. Rod loads and coils under 1 MA current were used to produce a magnetic field of 2-3 MG. In one type of experiments, a 0.8 ns laser pulse was focused on the load surface with intensity of 3x1015 W/cm2. Laser diagnostics showed that the laser produced plasma expands in the transversal magnetic field and forms a thin plasma disc with a typical diameter of 3-7 mm and thickness of 0.2-0.4 mm. A magnetosonic-type wave was observed in the plasma disc and on the surface of the rod load. The plasma disc expands radially across the magnetic field with a velocity of the order of the magnetosonic velocity. Physical mechanisms involved in the formation of the plasma disc may be relevant to the generation of plasma loops in sun flares. Other experiments, with a 0.4 ps laser pulse were carried for investigation of the isochoric heating of plasma with fast electrons confined by the strong magnetic field. The laser beam was focused by the parabola mirror on a solid target in the magnetic field of the coil. Work was supported by the DOE Grant DE-SC0008824 and DOE/NNSA UNR Grant DE-FC52-06NA27616.

Review of inductively coupled plasmas: Nano-applications and bistable hysteresis physics

NASA Astrophysics Data System (ADS)

Lee, Hyo-Chang

2018-03-01

Many different gas discharges and plasmas exhibit bistable states under a given set of conditions, and the history-dependent hysteresis that is manifested by intensive quantities of the system upon variation of an external parameter has been observed in inductively coupled plasmas (ICPs). When the external parameters (such as discharge powers) increase, the plasma density increases suddenly from a low- to high-density mode, whereas decreasing the power maintains the plasma in a relatively high-density mode, resulting in significant hysteresis. To date, a comprehensive description of plasma hysteresis and a physical understanding of the main mechanism underlying their bistability remain elusive, despite many experimental observations of plasma bistability conducted under radio-frequency ICP excitation. This fundamental understanding of mode transitions and hysteresis is essential and highly important in various applied fields owing to the widespread use of ICPs, such as semiconductor/display/solar-cell processing (etching, deposition, and ashing), wireless light lamp, nanostructure fabrication, nuclear-fusion operation, spacecraft propulsion, gas reformation, and the removal of hazardous gases and materials. If, in such applications, plasma undergoes a mode transition and hysteresis occurs in response to external perturbations, the process result will be strongly affected. Due to these reasons, this paper comprehensively reviews both the current knowledge in the context of the various applied fields and the global understanding of the bistability and hysteresis physics in the ICPs. At first, the basic understanding of the ICP is given. After that, applications of ICPs to various applied fields of nano/environmental/energy-science are introduced. Finally, the mode transition and hysteresis in ICPs are studied in detail. This study will show the fundamental understanding of hysteresis physics in plasmas and give open possibilities for applications to various applied fields to find novel control knob and optimizing processing conditions.

Determination of the external mass transfer coefficient and influence of mixing intensity in moving bed biofilm reactors for wastewater treatment.

PubMed

Nogueira, Bruno L; Pérez, Julio; van Loosdrecht, Mark C M; Secchi, Argimiro R; Dezotti, Márcia; Biscaia, Evaristo C

2015-09-01

In moving bed biofilm reactors (MBBR), the removal of pollutants from wastewater is due to the substrate consumption by bacteria attached on suspended carriers. As a biofilm process, the substrates are transported from the bulk phase to the biofilm passing through a mass transfer resistance layer. This study proposes a methodology to determine the external mass transfer coefficient and identify the influence of the mixing intensity on the conversion process in-situ in MBBR systems. The method allows the determination of the external mass transfer coefficient in the reactor, which is a major advantage when compared to the previous methods that require mimicking hydrodynamics of the reactor in a flow chamber or in a separate vessel. The proposed methodology was evaluated in an aerobic lab-scale system operating with COD removal and nitrification. The impact of the mixing intensity on the conversion rates for ammonium and COD was tested individually. When comparing the effect of mixing intensity on the removal rates of COD and ammonium, a higher apparent external mass transfer resistance was found for ammonium. For the used aeration intensities, the external mass transfer coefficient for ammonium oxidation was ranging from 0.68 to 13.50 m d(-1) and for COD removal 2.9 to 22.4 m d(-1). The lower coefficient range for ammonium oxidation is likely related to the location of nitrifiers deeper in the biofilm. The measurement of external mass transfer rates in MBBR will help in better design and evaluation of MBBR system-based technologies. Copyright © 2015 Elsevier Ltd. All rights reserved.

Magnetization dynamics of weak stripe domains in Fe-N thin films: a multi-technique complementary approach.

PubMed

Camara, Ibrahima; Tacchi, Silvia; Garnier, Louis-Charles; Eddrief, Mahmoud; Fortuna, Franck; Carlotti, Giovanni; Marangolo, Massimiliano

2017-09-26

The resonant eigenmodes of a nitrogen-implanted iron α'-FeN characterized by weak stripe domains are investigated by Brillouin light scattering and broadband ferromagnetic resonance experiments, assisted by micromagnetic simulations. The spectrum of the dynamic eigenmodes in the presence of the weak stripes is very rich and two different families of modes can be selectively detected using different techniques or different experimental configurations. Attention is paid to the evolution of the mode frequencies and spatial profiles under the application of an external magnetic field, of variable intensity, in the direction parallel or transverse to the stripes. The different evolution of the modes with the external magnetic field is accompanied by a distinctive spatial localization in specific regions, such as the closure domains at the surface of the stripes and the bulk domains localized in the inner part of the stripes. The complementarity of BLS and FMR techniques, based on different selection rules, is found to be a fruitful tool for the study of the wealth of localized mag-netic excitations generally found in nanostructures. © 2017 IOP Publishing Ltd.

Magnetization dynamics of weak stripe domains in Fe-N thin films: a multi-technique complementary approach

NASA Astrophysics Data System (ADS)

Camara, I. S.; Tacchi, S.; Garnier, L.-C.; Eddrief, M.; Fortuna, F.; Carlotti, G.; Marangolo, M.

2017-11-01

The resonant eigenmodes of an α‧-FeN thin film characterized by weak stripe domains are investigated by Brillouin light scattering and broadband ferromagnetic resonance experiments, assisted by micromagnetic simulations. The spectrum of the dynamic eigenmodes in the presence of the weak stripes is very rich and two different families of modes can be selectively detected using different techniques or different experimental configurations. Attention is paid to the evolution of the mode frequencies and spatial profiles under the application of an external magnetic field, of variable intensity, in the direction parallel or transverse to the stripes. The different evolution of the modes with the external magnetic field is accompanied by a distinctive spatial localization in specific regions, such as the closure domains at the surface of the stripes and the bulk domains localized in the inner part of the stripes. The complementarity of BLS and FMR techniques, based on different selection rules, is found to be a fruitful tool for the study of the wealth of localized magnetic excitations generally found in nanostructures.

Reactive molecular dynamics of the initial oxidation stages of Ni111 in pure water: effect of an applied electric field.

PubMed

Assowe, O; Politano, O; Vignal, V; Arnoux, P; Diawara, B; Verners, O; van Duin, A C T

2012-12-06

Corrosion processes occurring in aqueous solutions are critically dependent upon the interaction between the metal electrode and the solvent. In this work, the interaction of a nickel substrate with water molecules has been investigated using reactive force field (ReaxFF) molecular dynamics simulations. This approach was originally developed by van Duin and co-workers to study hydrocarbon chemistry and the catalytic properties of organic compounds. To our knowledge, this method has not previously been used to study the corrosion of nickel. In this work, we studied the interaction of 480 molecules of water (ρ = 0.99 g·cm(-3)) with Ni(111) surfaces at 300 K. The results showed that a water "bilayer" was adsorbed on the nickel surface. In the absence of an applied electric field, no dissociation of water was observed. However, the nickel atoms at the surface were charged positively, whereas the first water layer was charged negatively, indicating the formation of an electric double layer. To study the corrosion of nickel in pure water, we introduced an external electric field between the metal and the solution. The electric field intensity varied between 10 and 20 MeV/cm. The presence of this electric field led to oxidation of the metal surface. The structural and morphological differences associated with the growth of this oxide film in the presence of the electric field were evaluated. The simulated atomic trajectories were used to analyze the atomic displacement during the reactive process. The growth of the oxide scale on the nickel surface was primarily due to the movement of anions toward the interior of the metal substrate and the migration of nickel toward the free surface. We found that increasing the electric field intensity sped up the corrosion of nickel. The results also showed that the oxide film thickness increased linearly with increasing electric field intensity.

Influence of magnetic field on chemically reactive blood flow through stenosed bifurcated arteries

NASA Astrophysics Data System (ADS)

Hossain, Khan Enaet; Haque, Md. Mohidul

2017-06-01

Dynamic response of mass transfer in chemically reactive blood flow through bifurcated arteries under the stenotic condition is numerically studied in the present of a uniform magnetic field. The blood flowing through the artery is assumed an incompressible, fully developed and Newtonian. The nonlinear unsteady flow phenomena are governed by the Navier-Stokes and concentration equations. All these equations together with the appropriate boundary conditions describing the present biomechanical problem are transformed by using a radial transformation and the numerical results are obtained using a finite difference technique. Effects of stenosed bifurcation and externally applied magnetic field on the blood flow with chemical reaction are discussed with the help of graph. All the flow characteristics are found to be affected by the presence of chemical reaction and exposure of magnetic field of different intensities. Finally some important findings of the problem are concluded in this work.

Photovoltaic spatial solitons affected by a resistor in the external circuit

NASA Astrophysics Data System (ADS)

Wang, Xiao Sheng; She, Wei Long

2002-09-01

We have found that the FWHM of one-dimensional photovoltaic spatial soliton is modified by the space-charge field in the crystal, which can be controlled by a resistor in the external circuit. In this case, the photovoltaic contribution of a background beam is taken into account. In a crystal with a positive perturbation of refractive index, the FWHM of dark soliton decreases with the resistance of the resistor, while the FWHM of bright soliton increases with the resistance. Furthermore, when R (the ratio of the effective Glass constant of a signal beam over a background beam) is higher than 1, we can switch a dark soliton to a bright soliton by decreasing the resistance or vice versa. During such process, both the wavelengths and the intensities of the signal beam and the background beam are kept unchanged.

Possible signature of the magnetic fields related to quasi-periodic oscillations observed in microquasars

NASA Astrophysics Data System (ADS)

Kološ, Martin; Tursunov, Arman; Stuchlík, Zdeněk

2017-12-01

The study of quasi-periodic oscillations (QPOs) of X-ray flux observed in the stellar-mass black hole binaries can provide a powerful tool for testing of the phenomena occurring in the strong gravity regime. Magnetized versions of the standard geodesic models of QPOs can explain the observationally fixed data from the three microquasars. We perform a successful fitting of the HF QPOs observed for three microquasars, GRS 1915+105, XTE 1550-564 and GRO 1655-40, containing black holes, for magnetized versions of both epicyclic resonance and relativistic precession models and discuss the corresponding constraints of parameters of the model, which are the mass and spin of the black hole and the parameter related to the external magnetic field. The estimated magnetic field intensity strongly depends on the type of objects giving the observed HF QPOs. It can be as small as 10^{-5} G if electron oscillatory motion is relevant, but it can be by many orders higher for protons or ions (0.02-1 G), or even higher for charged dust or such exotic objects as lighting balls, etc. On the other hand, if we know by any means the magnetic field intensity, our model implies strong limit on the character of the oscillating matter, namely its specific charge.

Giant lipid vesicles under electric field pulses assessed by non invasive imaging.

PubMed

Mauroy, Chloé; Portet, Thomas; Winterhalder, Martin; Bellard, Elisabeth; Blache, Marie-Claire; Teissié, Justin; Zumbusch, Andreas; Rols, Marie-Pierre

2012-10-01

We present experimental results regarding the effects of electric pulses on giant unilamellar vesicles (GUVs). We have used phase contrast and coherent anti-Stokes Raman scattering (CARS) microscopy as relevant optical approaches to gain insight into membrane changes under electropermeabilization. No addition of exogenous molecules (lipid analogue, fluorescent dye) was needed. Therefore, experiments were performed on pure lipid systems avoiding possible artefacts linked to their use. Structural membrane changes were assessed by loss of contrast inside the GUVs due to sucrose and glucose mixing. Our observations, performed at the single vesicle level, indicate these changes are under the control of the number of pulses and field intensity. Larger number of pulses enhances membrane alterations. A threshold value of the field intensity must be applied to allow exchange of molecules between GUVs and the external medium. This threshold depends on the size of the vesicles, the larger GUVs being affected at lower electric field strengths than the smaller ones. Our experimental data are well described by a simple model in which molecule entry is driven by direct exchange. The CARS microscopic study of the effect of pulse duration confirms that pulses, in the ms time range, induce loss of lipids and membrane deformations facing the electrodes. Copyright © 2012 Elsevier B.V. All rights reserved.

Gigantic terahertz magnetochromism via electromagnons in the hexaferrite magnet Ba2Mg2Fe12O22

NASA Astrophysics Data System (ADS)

Kida, N.; Kumakura, S.; Ishiwata, S.; Taguchi, Y.; Tokura, Y.

2011-02-01

Effects of temperature (6-225 K) and magnetic field (0-7 T) on the low-energy (1.2-5 meV) electrodynamics of the electromagnon, the magnetic resonance driven by the light electric field, have been investigated for a hexaferrite magnet Ba2Mg2Fe12O22 by using terahertz time-domain spectroscopy. We find the gigantic terahertz magnetochromism via electromagnons; the magnetochromic change, as defined by the difference of the absorption intensity with and without magnetic field, exceeds 500% even at 0.6 T. The results arise from the fact that the spectral intensity of the electromagnon critically depends on the magnetic structure. With changing the conical spin structures in terms of the conical angle θ from the proper screw (θ=0°) to the ferrimagnetic (θ=90°) through the conical spin-ordered phases (0°<θ<90°) by external magnetic fields, we identify the maximal magnetochromism around θ≈45°. On the contrary, there is no remarkable signature of the electromagnon in the proper screw and spin-collinear (ferrimagnetic) phases, clearly indicating the important role of the conical spin order to produce the magnetically controllable electromagnons. The possible origin of this electromagnon is argued in terms of the exchange-striction mechanism.

Core Problem: Does the CV Parent Body Magnetization require differentiation?

NASA Astrophysics Data System (ADS)

O'Brien, T.; Tarduno, J. A.; Smirnov, A. V.

2016-12-01

Evidence for the presence of past dynamos from magnetic studies of meteorites can provide key information on the nature and evolution of parent bodies. However, the suggestion of a past core dynamo for the CV parent body based on the study of the Allende meteorite has led to a paradox: a core dynamo requires differentiation, evidence for which is missing in the meteorite record. The key parameter used to distinguish core dynamo versus external field mechanisms is absolute field paleointensity, with high values (>>1 μT) favoring the former. Here we explore the fundamental requirements for absolute field intensity measurement in the Allende meteorite: single domain grains that are non-interacting. Magnetic hysteresis and directional data define strong magnetic interactions, negating a standard interpretation of paleointensity measurements in terms of absolute paleofield values. The Allende low field magnetic susceptibility is dominated by magnetite and FeNi grains, whereas the magnetic remanence is carried by an iron sulfide whose remanence-carrying capacity increases with laboratory cycling at constant field values, indicating reordering. The iron sulfide and FeNi grains are in close proximity, providing mineralogical context for interactions. We interpret the magnetization of Allende to record the intense early solar wind with metal-sulfide interactions amplifying the field, giving the false impression of a higher field value in some prior studies. An undifferentiated CV parent body is thus compatible with Allende's magnetization. Early solar wind magnetization should be the null hypothesis for evaluating the source of magnetization for chondrites and other meteorites.

Differentiating submarine channel-related thin-bedded turbidite facies: Outcrop examples from the Rosario Formation, Mexico

NASA Astrophysics Data System (ADS)

Hansen, Larissa; Callow, Richard; Kane, Ian; Kneller, Ben

2017-08-01

Thin-bedded turbidites deposited by sediment gravity flows that spill from submarine channels often contain significant volumes of sand in laterally continuous beds. These can make up over 50% of the channel-belt fill volume, and can thus form commercially important hydrocarbon reservoirs. Thin-bedded turbidites can be deposited in environments that include levees and depositional terraces, which are distinguished on the basis of their external morphology and internal architecture. Levees have a distinctive wedge shaped morphology, thinning away from the channel, and confine both channels (internal levees) and channel-belts (external levees). Terraces are flat-lying features that are elevated above the active channel within a broad channel-belt. Despite the ubiquity of terraces and levees in modern submarine channel systems, the recognition of these environments in outcrop and in the subsurface is challenging. In this outcrop study of the Upper Cretaceous Rosario Formation (Baja California, Mexico), lateral transects based on multiple logged sections of thin-bedded turbidites reveal systematic differences in sandstone layer thicknesses, sandstone proportion, palaeocurrents, sedimentary structures and ichnology between channel-belt and external levee thin-bedded turbidites. Depositional terrace deposits have a larger standard deviation in sandstone layer thicknesses than external levees because they are topographically lower, and experience a wider range of turbidity current sizes overspilling from different parts of the channel-belt. The thickness of sandstone layers within external levees decreases away from the channel-belt while those in depositional terraces are less laterally variable. Depositional terrace environments of the channel-belt are characterized by high bioturbation intensities, and contain distinctive trace fossil assemblages, often dominated by ichnofabrics of the echinoid trace fossil Scolicia. These assemblages contrast with the lower bioturbation intensities that are recorded from external levee environments where Scolicia is typically absent. Multiple blocks of external levee material are observed in the depositional terrace area where the proximal part of the external levee has collapsed into the channel-belt; their presence characterizes the channel-belt boundary zone. The development of recognition criteria for different types of channel-related thin-bedded turbidites is critical for the interpretation of sedimentary environments both at outcrop and in the subsurface, which can reduce uncertainty during hydrocarbon field appraisal and development.

Analysis of Influence of Heat Insulation on the Thermal Regime of Storage Tanks with Liquefied Natural Gas

NASA Astrophysics Data System (ADS)

Maksimov, Vyacheslav I.; Nagornova, Tatiana A.; Glazyrin, Viktor P.; Shestakov, Igor A.

2016-02-01

Is numerically investigated the process of convective heat transfer in the reservoirs of liquefied natural gas (LNG). The regimes of natural convection in a closed rectangular region with different intensity of heat exchange at the external borders are investigated. Is solved the time-dependent system of energy and Navier-Stokes equations in the dimensionless variables "vorticity - the stream function". Are obtained distributions of the hydrodynamic parameters and temperatures, that characterize basic regularities of the processes. The special features of the formation of circulation flows are isolated and the analysis of the temperature distribution in the solution region is carried out. Is shown the influence of geometric characteristics and intensity of heat exchange on the outer boundaries of reservoir on the temperature field in the LNG storage.

Scattering on hyperbolic microspheres: From photonic nanojets to Poisson-Arago bright spots

NASA Astrophysics Data System (ADS)

Hodges, Reed; Dean, Cleon; Durach, Maxim

We investigate optical properties of metal-dielectric metamaterial microspheres composed of subwavelength spherical shells of two different materials alternating in an onion-layer fashion. Recently such metamaterial spheres were considered as cavities and their whispering gallery modes were investigated. We focus on the scattering of external radiation by the meta-micropheres in this work. We show that different scenarios are produced by altering the metal fraction in the spheres: as the microsphere transitions from all-dielectric to hyperbolic to all-metal, the photonic nanojets transform into Poisson-Arago bright spots. A new phenomenon also emerges as the percentage of metal in the microsphere increases. ``Hot spots'' of optical fields intensity appear at the center of the sphere. Their intensity is much higher than that of the incident plane wave.

Synchronization behaviors of coupled neurons under electromagnetic radiation

NASA Astrophysics Data System (ADS)

Ma, Jun; Wu, Fuqiang; Wang, Chunni

2017-01-01

Based on an improved neuronal model, in which the effect of magnetic flux is considered during the fluctuation and change of ion concentration in cells, the transition of synchronization is investigated by imposing external electromagnetic radiation on the coupled neurons, and networks, respectively. It is found that the synchronization degree depends on the coupling intensity and the intensity of external electromagnetic radiation. Indeed, appropriate intensity of electromagnetic radiation could be effective to realize intermittent synchronization, while stronger intensity of electromagnetic radiation can induce disorder of coupled neurons and network. Neurons show rhythm synchronization in the electrical activities by increasing the coupling intensity under electromagnetic radiation, and spatial patterns can be formed in the network under smaller factor of synchronization.

Interaction between pancreatic β cell and electromagnetic fields: A systematic study toward finding the natural frequency spectrum of β cell system.

PubMed

Farashi, Sajjad

2017-01-01

Interaction between biological systems and environmental electric or magnetic fields has gained attention during the past few decades. Although there are a lot of studies that have been conducted for investigating such interaction, the reported results are considerably inconsistent. Besides the complexity of biological systems, the important reason for such inconsistent results may arise due to different excitation protocols that have been applied in different experiments. In order to investigate carefully the way that external electric or magnetic fields interact with a biological system, the parameters of excitation, such as intensity or frequency, should be selected purposefully due to the influence of these parameters on the system response. In this study, pancreatic β cell, the main player of blood glucose regulating system, is considered and the study is focused on finding the natural frequency spectrum of the system using modeling approach. Natural frequencies of a system are important characteristics of the system when external excitation is applied. The result of this study can help researchers to select proper frequency parameter for electrical excitation of β cell system. The results show that there are two distinct frequency ranges for natural frequency of β cell system, which consist of extremely low (or near zero) and 100-750 kHz frequency ranges. There are experimental works on β cell exposure to electromagnetic fields that support such finding.

Free-space QKD system hacking by wavelength control using an external laser.

PubMed

Lee, Min Soo; Woo, Min Ki; Jung, Jisung; Kim, Yong-Su; Han, Sang-Wook; Moon, Sung

2017-05-15

We develop a way to hack free-space quantum key distribution (QKD) systems by changing the wavelength of the quantum signal laser using an external laser. Most free-space QKD systems use four distinct lasers for each polarization, thereby making the characteristics of each laser indistinguishable. We also discover a side-channel that can distinguish the lasers by using an external laser. Our hacking scheme identifies the lasers by automatically applying the external laser to each signal laser at different intensities and detecting the wavelength variation according to the amount of incident external laser power. We conduct a proof-of-principle experiment to verify the proposed hacking structure and confirm that the wavelength varies by several gigahertzes to several nanometers, depending on the intensity of the external laser. The risk of hacking is successfully proven through the experimental results. Methods for prevention are also suggested.

Free-Free Transitions of e-H System Inside a Dense Plasma Irradiated by a Laser Field at Very Low Incident Electron Energies

NASA Technical Reports Server (NTRS)

Bhatia, A. K.; Sinha, C.

2012-01-01

The free-free transition is studied for an electron-hydrogen in the ground state at low incident energies in the presence of an external homogenous, monochromatic, and linearly polarized laser-field inside a hot dense plasma.The effect of plasma screening is considered in the Debye-Huckel approximation. The calculations are performed in the soft photon limit, assuming that the plasma frequency is much higher than the laser frequency. The incident electron is considered to be dressed by the laser field in a nonperturbative manner by choosing the Volkov solutions in both the initial and final channels. The space part of the scattering wave function for the electron is solved numerically by taking into account the electron exchange. The laser-assisted differential and total cross sections are calculated for single-photon absorption /emission and no photon exchange in the soft photon limit, the laser intensity being much less than the atomic field intensity. The calculations have been carried out for various values of Debye parameter, ranging from 0.005 to 0.12. A strong suppression is noted in the laser-assisted cross sections as compared to the field-free situation. A significant difference is noted for the singlet and triplet cross sections. The suppression is much more in the triplet states.

Magnetic field induced quantum dot brightening in liquid crystal synergized magnetic and semiconducting nanoparticle composite assemblies

DOE PAGES

Amaral, Jose Jussi; Wan, Jacky; Rodarte, Andrea L.; ...

2014-10-22

The design and development of multifunctional composite materials from artificial nano-constituents is one of the most compelling current research areas. This drive to improve over nature and produce ‘meta-materials’ has met with some success, but results have proven limited with regards to both the demonstration of synergistic functionalities and in the ability to manipulate the material properties post-fabrication and in situ. Here, magnetic nanoparticles (MNPs) and semiconducting quantum dots (QDs) are co-assembled in a nematic liquid crystalline (LC) matrix, forming composite structures in which the emission intensity of the quantum dots is systematically and reversibly controlled with a small appliedmore » magnetic field (<100 mT). This magnetic field-driven brightening, ranging between a two- to three-fold peak intensity increase, is a truly cooperative effect: the LC phase transition creates the co-assemblies, the clustering of the MNPs produces LC re-orientation at atypical low external field, and this re-arrangement produces compaction of the clusters, resulting in the detection of increased QD emission. These results demonstrate a synergistic, reversible, and an all-optical process to detect magnetic fields and additionally, as the clusters are self-assembled in a fluid medium, they offer the possibility for these sensors to be used in broad ranging fluid-based applications.« less

Broadband radio spectro-polarimetric observations of high-Faraday-rotation-measure AGN

NASA Astrophysics Data System (ADS)

Pasetto, Alice; Carrasco-González, Carlos; O'Sullivan, Shane; Basu, Aritra; Bruni, Gabriele; Kraus, Alex; Curiel, Salvador; Mack, Karl-Heinz

2018-06-01

We present broadband polarimetric observations of a sample of high-Faraday-rotation-measure (high-RM) active galactic nuclei (AGN) using the Karl. G. Jansky Very Large Array (JVLA) telescope from 1 to 2 GHz, and 4 to 12 GHz. The sample (14 sources) consists of very compact sources (linear resolution smaller than ≈5 kpc) that are unpolarized at 1.4 GHz in the NRAO VLA Sky Survey (NVSS). Total intensity data have been modeled using a combination of synchrotron components, revealing complex structure in their radio spectra. Depolarization modeling, through the so-called qu-fitting (the modeling of the fractional quantities of the Stokes Q and U parameters), has been performed on the polarized data using an equation that attempts to simplify the process of fitting many different depolarization models. These models can be divided into two major categories: external depolarization (ED) and internal depolarization (ID) models. Understanding which of the two mechanisms is the most representative would help the qualitative understanding of the AGN jet environment and whether it is embedded in a dense external magneto-ionic medium or if it is the jet-wind that causes the high RM and strong depolarization. This could help to probe the jet magnetic field geometry (e.g., helical or otherwise). This new high-sensitivity data shows a complicated behavior in the total intensity and polarization radio spectrum of individual sources. We observed the presence of several synchrotron components and Faraday components in their total intensity and polarized spectra. For the majority of our targets (12 sources), the depolarization seems to be caused by a turbulent magnetic field. Thus, our main selection criteria (lack of polarization at 1.4 GHz in the NVSS) result in a sample of sources with very large RMs and depolarization due to turbulent magnetic fields local to the source. These broadband JVLA data reveal the complexity of the polarization properties of this class of radio sources. We show how the new qu-fitting technique can be used to probe the magnetized radio source environment and to spectrally resolve the polarized components of unresolved radio sources.

Intensive Language Teaching in Schools. Teaching Languages 1.

ERIC Educational Resources Information Center

Hawkins, Eric, Ed.; Perren, G. E., Ed.

The papers in this volume concerning intensive language teaching are grouped into three sections: "Sections bilingues,""Intensive courses within schools," and "Intensive courses at external centres." A preliminary chapter by Eric Hawkins introduces the historical context of intensive language teaching and a concluding…

Single laser beam of spatial coherence from an array of GaAs lasers - Free-running mode

NASA Technical Reports Server (NTRS)

Philipp-Rutz, E. M.

1975-01-01

Spatially coherent radiation from a monolithic array of three GaAs lasers in a free-running mode is reported. The lasers, with their mirror faces antireflection coated, are operated in an external optical cavity built of spherical lenses and plane mirrors. The spatially coherent-beam formation makes use of the Fourier-transformation property of the internal lenses. Transverse mode control is accomplished by a spatial filter. The optical cavity is similar to that used for the phase-controlled mode of spatially coherent-beam formation; only the spatial filters are different. In the far field (when restored by an external lens), the intensities of the lasers in the array are concentrated in a single laser beam of spatial coherence, without any grating lobes. The far-field distribution of the laser array in the free-running mode differs significantly from the interference pattern of the phase-controlled mode. The modulation characteristics of the optical waveforms of the two modes are also quite different because modulation is related to the interaction of the spatial filter with the longitudinal modes of the laser array within the optical cavity. The modulation of the optical waveform of the free-running mode is nonperiodic, confirming that the fluctuations of the optical fields of the lasers are random.

Investigation of magneto-optical properties of ferrofluids by laser light scattering techniques

NASA Astrophysics Data System (ADS)

Nepomnyashchaya, E. K.; Prokofiev, A. V.; Velichko, E. N.; Pleshakov, I. V.; Kuzmin, Yu I.

2017-06-01

Investigation of magnetooptical characteristics of ferrofluids is an important task aimed at the development of novel optoelectronic systems. This article reports on the results obtained in the experimental studies of the factors that affect the intensity and spatial distribution of the laser radiation scattered by magnetic particles and their agglomerates in a magnetic field. Laser correlation spectroscopy and direct measurements of laser radiation scattering for studies of the interactions and magnetooptical properties of magnetic particles in solutions were employed. The objects were samples of nanodispersed magnetite (Fe3O4) suspended in kerosene and in water. Our studies revealed some new behavior of magnetic particles in external magnetic and light fields, which make ferrofluids promising candidates for optical devices.

NEUTRON SOURCE USING MAGNETIC COMPRESSION OF PLASMA

DOEpatents

Quinn, W.E.; Elmore, W.C.; Little, E.M.; Boyer, K.; Tuck, J.L.

1961-10-31

A fusion reactor is described that utilizes compression and heating of an ionized thermonuclear fuel by an externally applied magnetic field, thus avoiding reliance on the pinch effect and its associated instability problems. The device consists of a gas-confining ceramic container surrounded by a single circumferential coil having a shape such as to produce a magnetic mirror geometry. A sinusoidally-oscillating, exponentially-damped current is passed circumferentially around the container, through the coil, inducing a circumferential current in the gas. Maximum compression and plasma temperature are obtained at the peak of the current oscillations, coinciding with maximum magnetic field intensity. Enhanced temperatures are obtained in the second and succeeding half cycles because the thermal energy accumulates from one half cycle to the next. (AEC)

Wearable Wireless Telemetry System for Implantable Bio-MEMS Sensors

NASA Technical Reports Server (NTRS)

Simons, Rainee N.; Miranda, Felix A.; Wilson, Jeffrey D.; Simons, Renita E.

2006-01-01

In this paper, a telemetry and contact-less powering system consisting of an implantable bio-MEMS sensor with a miniature printed square spiral chip antenna and an external wearable garment with printed loop antenna is investigated. The wearable garment pick-up antenna and the implantable chip antenna are in close proximity to each other and hence couple inductively through their near-fields and behave as the primary and the secondary circuits of a transformer, respectively. The numerical and experimental results are graphically presented, and include the design parameter values as a function of the geometry, the relative RF magnetic near-field intensity as a function of the distance and angle, and the current density on the strip conductors, for the implantable chip antenna.

Generalized Kapchinskij-Vladimirskij Distribution and Beam Matrix for Phase-Space Manipulations of High-Intensity Beams

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

Chung, Moses; Qin, Hong; Davidson, Ronald C.

In an uncoupled linear lattice system, the Kapchinskij-Vladimirskij (KV) distribution formulated on the basis of the single-particle Courant-Snyder invariants has served as a fundamental theoretical basis for the analyses of the equilibrium, stability, and transport properties of high-intensity beams for the past several decades. Recent applications of high-intensity beams, however, require beam phase-space manipulations by intentionally introducing strong coupling. Here in this Letter, we report the full generalization of the KV model by including all of the linear (both external and space-charge) coupling forces, beam energy variations, and arbitrary emittance partition, which all form essential elements for phase-space manipulations. Themore » new generalized KV model yields spatially uniform density profiles and corresponding linear self-field forces as desired. Finally, the corresponding matrix envelope equations and beam matrix for the generalized KV model provide important new theoretical tools for the detailed design and analysis of high-intensity beam manipulations, for which previous theoretical models are not easily applicable.« less

Generalized Kapchinskij-Vladimirskij Distribution and Beam Matrix for Phase-Space Manipulations of High-Intensity Beams

DOE PAGES

Chung, Moses; Qin, Hong; Davidson, Ronald C.; ...

2016-11-23

In an uncoupled linear lattice system, the Kapchinskij-Vladimirskij (KV) distribution formulated on the basis of the single-particle Courant-Snyder invariants has served as a fundamental theoretical basis for the analyses of the equilibrium, stability, and transport properties of high-intensity beams for the past several decades. Recent applications of high-intensity beams, however, require beam phase-space manipulations by intentionally introducing strong coupling. Here in this Letter, we report the full generalization of the KV model by including all of the linear (both external and space-charge) coupling forces, beam energy variations, and arbitrary emittance partition, which all form essential elements for phase-space manipulations. Themore » new generalized KV model yields spatially uniform density profiles and corresponding linear self-field forces as desired. Finally, the corresponding matrix envelope equations and beam matrix for the generalized KV model provide important new theoretical tools for the detailed design and analysis of high-intensity beam manipulations, for which previous theoretical models are not easily applicable.« less

Preparation research of Nano-SiC/Ni-P composite coating under a compound field

NASA Astrophysics Data System (ADS)

Zhou, H. Z.; Wang, W. H.; Gu, Y. Q.; Liu, R.; Zhao, M. L.

2016-07-01

In this paper, the preparation process of Ni-P-SiC composite coatings on 45 steel surfaces with the assistance of magnetic and ultrasound fields was researched. The influence of external field on the surface morphology and performance of the composite layer is also discussed. Experimental results showed that when prepared under magnetic and ultrasonic fields, composite layers are significantly more dense and uniform than coatings made without external fields. Nano-SiC particles, dispersed uniformly in the layer, significantly improve the hardness of the composite layer, and the composite layer under the external field had the highest hardness at 680 HV The external fields can also accelerate deposition and increase the thickness of the layer. Compared to layers processed without the assistance of external fields, the thickness of the layers increased by nearly ten µm.

Externalities and the Coase Theorem: A Diagrammatic Presentation

ERIC Educational Resources Information Center

Halteman, James

2005-01-01

In intermediate microeconomic textbooks the reciprocal nature of externalities is presented using numerical examples of costs and benefits. This treatment of the Coase theorem obscures the fact that externality costs and benefits are best understood as being on a continuum where costs vary with the degree of intensity of the externality. When…

Exciton Absorption in Semiconductor Quantum Wells Driven by a Strong Intersubband Pump Field

NASA Technical Reports Server (NTRS)

Liu, Ansheng; Ning, Cun-Zheng

1999-01-01

Optical interband excitonic absorption of semiconductor quantum wells (QW's) driven by a coherent pump field is investigated based on semiconductor Bloch equations. The pump field has a photon energy close to the intersubband spacing between the first two conduction subbands in the QW's. An external weak optical field probes the interband transition. The excitonic effects and pump-induced population redistribution within the conduction subbands in the QW system are included. When the density of the electron-hole pairs in the QW structure is low, the pump field induces an Autler-Townes splitting of the exciton absorption spectrum. The split size and the peak positions of the absorption doublet depend not only on the pump frequency and intensity but also on the carrier density. As the density of the electron-hole pairs is increased, the split contrast (the ratio between the maximum and minimum values) is decreased because the exciton effect is suppressed at higher densities due to the many-body screening.

InGaN/GaN quantum dots as optical probes for the electric field at the GaN/electrolyte interface

NASA Astrophysics Data System (ADS)

Teubert, J.; Koslowski, S.; Lippert, S.; Schäfer, M.; Wallys, J.; Dimitrakopulos, G.; Kehagias, Th.; Komninou, Ph.; Das, A.; Monroy, E.; Eickhoff, M.

2013-08-01

We investigated the electric-field dependence of the photoluminescence-emission properties of InGaN/GaN quantum dot multilayers in contact with an electrolyte. Controlled variations of the surface potential were achieved by the application of external electric fields using the electrolytic Schottky contact and by variation of the solution's pH value. Prior to characterization, a selective electrochemical passivation process was required to suppress leakage currents. The quantum dot luminescence is strongly affected by surface potential variations, i.e., it increases exponentially with cathodic bias and acidic pH values. The results cannot be explained by a modification of intra-dot polarization induced electric fields via the quantum confined Stark effect but are attributed to the suppression/enhancement of non-radiative recombination processes, i.e., mainly hole transfer into the electrolyte. The results establish a link between the photoluminescence intensity and the magnitude of electric fields at the semiconductor/electrolyte interface.

Antipodal Magnetic Anomalies on the Moon, Contributions from Impact Induced Currents Due to Positive Holes and Flexoelectric Phenomina and Dynamo

NASA Technical Reports Server (NTRS)

Kletetschka, G.; Freund, F.; Wasilewski, P. J.; Mikula, V.; Kohout, Tomas

2005-01-01

Large impacts on the Moon generate large pressure pulses that penetrate the whole body. Several of these large impacts may have generated antipodal structure with anomalous magnetic intensity.These regions can be more than a thousand km across, with fields of the order of tens to hundreds of nT. This is the case of Orientale, Imbrium, Serenitatis, Crisium, and Nectaris impact basins. The production of large-scale magnetic fields and associated crustal magnetization due to lunar basin-forming impacts was hypothesized to have an origin in fields external to the impact plasma cloud that are produced by the magnetohydrodynamic interaction of the cloud with ambient magnetic fields and plasmas. During the period of compressed antipodal field amplification, seismic compressional waves from the impact converge at the antipode resulting in transient shock pressures that reach 2 GPa (20 kbar). This can produce conditions for shock magnetic acquisition of the crust antipodal to impact basins.

Measurement technology based on laser internal/external cavity tuning

NASA Astrophysics Data System (ADS)

Zhang, Shulian

2011-08-01

For an ordinary laser with two cavity mirrors, if the length of laser cavity changes half wavelength the laser frequency changes one longitudinal mode separation. For a laser with three cavity mirrors, in which a feedback mirror is used to feed part of the laser output beam back into the laser cavity, the external cavity length changes half wavelength the laser intensity fluctuates one period. This presentation gives some research results in measurement field based on changing (tuning) the length of laser internal/external cavity, including 1) HeNe laser cavity-tuning nanometer displacement measurement instruments (laser nanometer rulers), 2) HeNe laser feedback displacement measurement, 3) Nd:YAG laser feedback nanometer displacement measurement, 4) benchmark of waveplate phase retardation measurement based on laser frequency splitting, 5) in-site waveplate phase retardation measurement instruments based on laser feedback and polarization hopping, 6) quasi-common-path microchip Nd:YAG laser feedback interferometer, 7) non-contact Nd:YAG laser feedback surface profile measurement. Some of these instruments have been put into application and display some irreplaceable advantages.

Investigation of shock-acoustic-wave interaction in transonic flow

NASA Astrophysics Data System (ADS)

Feldhusen-Hoffmann, Antje; Statnikov, Vladimir; Klaas, Michael; Schröder, Wolfgang

2018-01-01

The buffet flow field around supercritical airfoils is dominated by self-sustained shock wave oscillations on the suction side of the wing. Theories assume that this unsteadiness is driven by an acoustic feedback loop of disturbances in the flow field downstream of the shock wave whose upstream propagating part is generated by acoustic waves. Therefore, in this study, first variations in the sound pressure level of the airfoil's trailing-edge noise during a buffet cycle, which force the shock wave to move upstream and downstream, are detected, and then, the sensitivity of the shock wave oscillation during buffet to external acoustic forcing is analyzed. Time-resolved standard and tomographic particle-image velocimetry (PIV) measurements are applied to investigate the transonic buffet flow field over a supercritical DRA 2303 airfoil. The freestream Mach number is M_{∞} = 0.73, the angle of attack is α = {3.5}°, and the chord-based Reynolds number is Re_c = 1.9× 10^6. The perturbed Lamb vector field, which describes the major acoustic source term of trailing-edge noise, is determined from the tomographic PIV data. Subsequently, the buffet flow field is disturbed by an artificially generated acoustic field, the acoustic intensity of which is comparable to the Lamb vector that is determined from the PIV data. The results confirm the hypothesis that buffet is driven by an acoustic feedback loop and show the shock wave oscillation to directly respond to external acoustic forcing. That is, the amplitude modulation frequency of the artificial acoustic perturbation determines the shock oscillation.

Direct Detection of Singlet-Triplet Interconversion in OLED Magnetoelectroluminescence with a Metal-Free Fluorescence-Phosphorescence Dual Emitter

NASA Astrophysics Data System (ADS)

Ratzke, Wolfram; Bange, Sebastian; Lupton, John M.

2018-05-01

We demonstrate that a simple phenazine derivative can serve as a dual emitter for organic light-emitting diodes, showing simultaneous luminescence from the singlet and triplet excited states at room temperature without the need of heavy-atom substituents. Although devices made with this emitter achieve only low quantum efficiencies of <0.2 % , changes in fluorescence and phosphorescence intensity on the subpercent scale caused by an external magnetic field of up to 30 mT are clearly resolved with an ultra-low-noise optical imaging technique. The results demonstrate the concept of using simple reporter molecules, available commercially, to optically detect the spin of excited states formed in an organic light-emitting diode and thereby probe the underlying spin statistics of recombining electron-hole pairs. A clear anticorrelation of the magnetic-field dependence of singlet and triplet emission shows that it is the spin interconversion between singlet and triplet which dominates the magnetoluminescence response: the phosphorescence intensity decreases by the same amount as the fluorescence intensity increases. The concurrent detection of singlet and triplet emission as well as device resistance at cryogenic and room temperature constitute a useful tool to disentangle the effects of spin-dependent recombination from spin-dependent transport mechanisms.

Simple method for the characterization of intense Laguerre-Gauss vector vortex beams

NASA Astrophysics Data System (ADS)

Allahyari, E.; JJ Nivas, J.; Cardano, F.; Bruzzese, R.; Fittipaldi, R.; Marrucci, L.; Paparo, D.; Rubano, A.; Vecchione, A.; Amoruso, S.

2018-05-01

We report on a method for the characterization of intense, structured optical fields through the analysis of the size and surface structures formed inside the annular ablation crater created on the target surface. In particular, we apply the technique to laser ablation of crystalline silicon induced by femtosecond vector vortex beams. We show that a rapid direct estimate of the beam waist parameter is obtained through a measure of the crater radii. The variation of the internal and external radii of the annular crater as a function of the laser pulse energy, at fixed number of pulses, provides another way to evaluate the beam spot size through numerical fitting of the obtained experimental data points. A reliable estimate of the spot size is of paramount importance to investigate pulsed laser-induced effects on the target material. Our experimental findings offer a facile way to characterize focused, high intensity complex optical vector beams which are more and more applied in laser-matter interaction experiments.

Gyrokinetic simulations with external resonant magnetic perturbations: Island torque and nonambipolar transport with plasma rotation

NASA Astrophysics Data System (ADS)

Waltz, R. E.; Waelbroeck, F. L.

2012-03-01

Static external resonant magnetic field perturbations (RMPs) have been added to the gyrokinetic code GYRO [J. Candy and R. E. Waltz, J. Comp. Phys. 186, 545 (2003)]. This allows nonlinear gyrokinetic simulations of the nonambipolar radial current flow jr, and the corresponding j→×B→ plasma torque (density) R[jrBp/c], induced by magnetic islands that break the toroidal symmetry of a tokamak. This extends the previous GYRO formulation for the transport of toroidal angular momentum (TAM) [R. E. Waltz, G. M. Staebler, J. Candy, and F. L. Hinton, Phys. Plasmas 14, 122507 (2007); errata 16, 079902 (2009)]. The focus is on electrostatic full torus radial slice simulations of externally induced q =m/n=6/3 islands with widths 5% of the minor radius or about 20 ion gyroradii. Up to moderately strong E ×B rotation, the island torque scales with the radial electric field at the resonant surface Er, the island width w, and the intensity I of the high-n micro-turbulence, as Erw√I . The radial current inside the island is carried (entirely in the n =3 component) and almost entirely by the ion E ×B flux, since the electron E ×B and magnetic flutter particle fluxes are cancelled. The net island torque is null at zero Er rather than at zero toroidal rotation. This means that while the expected magnetic braking of the toroidal plasma rotation occurs at strong co- and counter-current rotation, at null toroidal rotation, there is a small co-directed magnetic acceleration up to the small diamagnetic (ion pressure gradient driven) co-rotation corresponding to the zero Er and null torque. This could be called the residual stress from an externally induced island. At zero Er, the only effect is the expected partial flattening of the electron temperature gradient within the island. Finite-beta GYRO simulations demonstrate almost complete RMP field screening and n =3 mode unlocking at strong Er.

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.

Electron-proton spectrometer: Summary for critical design review

NASA Technical Reports Server (NTRS)

1972-01-01

The electron-proton spectrometer (EPS) is mounted external to the Skylab module complex on the command service module. It is designed to make a 2 pi omni-directional measurement of electrons and protons which result from solar flares or enhancement of the radiation belts. The EPS data will provide accurate radiation dose information so that uncertain Relative biological effectiveness factors are eliminated by measuring the external particle spectra. Astronaut radiation safety, therefore, can be ensured, as the EPS data can be used to correct or qualify radiation dose measurements recorded by other radiation measuring instrumentation within the Skylab module complex. The EPS has the capability of measuring and extremely wide dynamic radiation dose rate range, approaching 10 to the 7th power. Simultaneously the EPS has the capability to process data from extremely high radiation fields such as might be encountered in the wake of an intense solar flare.

Influence of damping on the frequency-dependent polarizabilities of doped quantum dot

NASA Astrophysics Data System (ADS)

Pal, Suvajit; Ghosh, Manas

2014-09-01

We investigate the profiles of diagonal components of frequency-dependent linear (αxx and αyy), and first nonlinear (βxxx and βyyy) optical response of repulsive impurity doped quantum dots. The dopant impurity potential chosen assumes Gaussian form. The study principally focuses on investigating the role of damping on the polarizability components. In view of this the dopant is considered to be propagating under damped condition which is otherwise linear inherently. The frequency-dependent polarizabilities are then analyzed by placing the doped dot to a periodically oscillating external electric field of given intensity. The damping strength, in conjunction with external oscillation frequency and confinement potentials, fabricate the polarizability components in a fascinating manner which is adorned with emergence of maximization, minimization, and saturation. The discrimination in the values of the polarizability components in x and y-directions has also been addressed in the present context.

Regulatory aspects of low intensity photon emission.

PubMed

Van Wijk, R; Schamhart, D H

1988-07-15

Photon emission from unicellular and multicellular organisms has been a subject of study for many decennia. In contrast to the well-known phenomenon of bioluminescence originating in luciferin-luciferase reactions, low intensity emission in the visible region of the electromagnetic spectrum has been found in almost every species studied so far. At present, the nomenclature of this phenomenon has not crystallized and it is referred to by a variety of names, such as mitogenetic radiation 29, dark luminescence 7, low-level chemiluminescence 20,36, and biophotons 57. Particular attention has been focussed on the relationship between photon emission and the regulation of various aspects of cellular metabolism, although in many cases quantitative data are still lacking. Throughout the history of this field of research the question of a functional biological role of the low intensity emission has been repeatedly raised; this is reflected, for instance, in the heterogeneity of the terms used to describe it. The discussion concerns the possible participation of photons of low intensity in intra- and intercellular communication. This paper reviews literature on the metabolic regulation of low intensity emission, as well as the regulation of photon emission initiated by external light. Furthermore, recent data are discussed with respect to a possible biocommunicative function of low intensity photon emission.

Pressurized rf cavities in ionizing beams

DOE PAGES

Freemire, B.; Tollestrup, A.  V.; Yonehara, K.; ...

2016-06-20

A muon collider or Higgs factory requires significant reduction of the six dimensional emittance of the beam prior to acceleration. One method to accomplish this involves building a cooling channel using high pressure gas filled radio frequency cavities. The performance of such a cavity when subjected to an intense particle beam must be investigated before this technology can be validated. To this end, a high pressure gas filled radio frequency (rf) test cell was built and placed in a 400 MeV beam line from the Fermilab linac to study the plasma evolution and its effect on the cavity. Hydrogen, deuterium, helium and nitrogen gases were studied. Additionally, sulfur hexafluoride and dry air were used as dopants to aid in the removal of plasma electrons. Measurements were made using a variety of beam intensities, gas pressures, dopant concentrations, and cavity rf electric fields, both with and without a 3 T external solenoidal magnetic field. In conclusion, energy dissipation per electron-ion pair, electron-ion recombination rates, ion-ion recombination rates, and electron attachment times to SFmore » $$_6$$ and O$$_2$$ were measured.« less

Exploring the ring current of carbon nanotubes by first-principles calculations.

PubMed

Ren, Pengju; Zheng, Anmin; Xiao, Jianping; Pan, Xiulian; Bao, Xinhe

2015-02-01

Ring current is a fundamental concept to understand the nuclear magnetic resonance (NMR) properties and aromaticity for conjugated systems, such as carbon nanotubes (CNTs). Employing the recently developed gauge including projector augmented wave (GIPAW) method, we studied the ring currents of CNTs systematically and visualized their distribution. The ring current patterns are determined by the semiconducting or metallic properties of CNTs. The discrepancy is mainly caused by the axial component of external magnetic fields, whereas the radial component induced ring currents are almost independent of the electronic structures of CNTs, where the intensities of the ring currents are linearly related to the diameters of the CNTs. Although the ring currents induced by the radial component are more intense than those by the axial component, only the latter determines the overall NMR responses and aromaticity of the CNTs as well. Furthermore, the semiconducting CNTs are more aromatic than their metallic counterparts due to the existence of delocalized ring currents on the semiconducting CNTs. These fundamental features are of vital importance for the development of CNT-based nanoelectronics and applications in magnetic fields.

Exploring the ring current of carbon nanotubes by first-principles calculations

PubMed Central

Ren, Pengju; Zheng, Anmin; Xiao, Jianping; Pan, Xiulian

2015-01-01

Ring current is a fundamental concept to understand the nuclear magnetic resonance (NMR) properties and aromaticity for conjugated systems, such as carbon nanotubes (CNTs). Employing the recently developed gauge including projector augmented wave (GIPAW) method, we studied the ring currents of CNTs systematically and visualized their distribution. The ring current patterns are determined by the semiconducting or metallic properties of CNTs. The discrepancy is mainly caused by the axial component of external magnetic fields, whereas the radial component induced ring currents are almost independent of the electronic structures of CNTs, where the intensities of the ring currents are linearly related to the diameters of the CNTs. Although the ring currents induced by the radial component are more intense than those by the axial component, only the latter determines the overall NMR responses and aromaticity of the CNTs as well. Furthermore, the semiconducting CNTs are more aromatic than their metallic counterparts due to the existence of delocalized ring currents on the semiconducting CNTs. These fundamental features are of vital importance for the development of CNT-based nanoelectronics and applications in magnetic fields. PMID:29560175

Analysis of regional crustal magnetization in Vector Cartesian Harmonics

NASA Astrophysics Data System (ADS)

Gubbins, D.; Ivers, D. J.; Williams, S.

2017-12-01

We introduce a set of basis functions for analysing magnetization in a plane layer, called Vector Cartesian Harmonics, that separate the part of the magnetization responsible for generating the external potential field from the part that generates no observable field. They are counterparts of similar functions defined on a sphere, Vector Spherical Harmonics, which we introduced earlier for magnetization in a spherical shell. We expand four example magnetizations in these functions and determine which parts are responsible for the observed magnetic field above the layer. For a point dipole, the component of magnetization responsible for the external potential field is the sum of a point dipole of half strength and a distributed magnetization that gives the same field. The dipping prism has no magnetic field if magnetized along strike; otherwise it, like the point dipole, has the correct dipping structure but of half the correct intensity accompanied by a distributed magnetization producing the same magnetic field. Interestingly, the distributed magnetization has singularities at the edges of the dipping slab. The buried cube is done numerically and again only a fraction of the true magnetization appears along with distributed magnetizations, strongest at the edges of the cube, making up the rest of the field. The Bishop model, a model of magnetization often used to test analysis methods, behaves similarly. In cases where the magnetization is induced by a known, non-horizontal field it is always possible to recover the vertically averaged susceptibility except for its horizontal average. Simple damped inversion of magnetic data will return only the harmonics responsible for the external field, so the analysis gives a clear indication of how any combination of induced and remanent magnetization would be returned. In practice, most interpretations of magnetic surveys are done in combination with other geological data and insights. We propose using this prior information to construct a quantitative magnetization that can be expanded in Vector Cartesian Harmonics to determine the part that generates the observed magnetic anomalies; this part can be refined to fit the data while the remaining part can only be improved using different information. The separation is simple and fast to implement using standard software because it involves only elementary manipulations of 2-dimensional Fourier transforms.

Suppression of multipactor discharge on a dielectric surface by an external magnetic field

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

Cai Libing; Zhu Xiangqin; Wang Yue

2011-07-15

The multipactor discharge on a dielectric surface in an external magnetic field is simulated by using the particle-in-cell method, and the electron number, energy, the velocity of the yield of secondary electrons, and the power deposited on dielectric surface in the process of multipactor discharge are investigated. The effects of the strength of the external magnetic field on multipactor are studied. The results show that when the external magnetic field reaches a certain value, the multipactor is weaker than that in the case of no external magnetic field and becomes much lighter versus the strength of the external magnetic fieldmore » in the half microwave period in which the ExB drift pulls the electrons back to dielectric surface. And in the other half microwave period in which the ExB drift pushes the electrons away from the dielectric surface, the multipactor is cut off. So the power capability can be increased to the fourfold by the suppression of multipactor by applying an external magnetic field.« less

Engineering Topological Surface State of Cr-doped Bi2Se3 under external electric field

NASA Astrophysics Data System (ADS)

Zhang, Jian-Min; Lian, Ruqian; Yang, Yanmin; Xu, Guigui; Zhong, Kehua; Huang, Zhigao

2017-03-01

External electric field control of topological surface states (SSs) is significant for the next generation of condensed matter research and topological quantum devices. Here, we present a first-principles study of the SSs in the magnetic topological insulator (MTI) Cr-doped Bi2Se3 under external electric field. The charge transfer, electric potential, band structure and magnetism of the pure and Cr doped Bi2Se3 film have been investigated. It is found that the competition between charge transfer and spin-orbit coupling (SOC) will lead to an electrically tunable band gap in Bi2Se3 film under external electric field. As Cr atom doped, the charge transfer of Bi2Se3 film under external electric field obviously decreases. Remarkably, the band gap of Cr doped Bi2Se3 film can be greatly engineered by the external electric field due to its special band structure. Furthermore, magnetic coupling of Cr-doped Bi2Se3 could be even mediated via the control of electric field. It is demonstrated that external electric field plays an important role on the electronic and magnetic properties of Cr-doped Bi2Se3 film. Our results may promote the development of electronic and spintronic applications of magnetic topological insulator.

Potential of Multitemporal Tandem-X Derived Crop Surface Models for Maize Growth Monitoring

NASA Astrophysics Data System (ADS)

Hütt, C.; Tilly, N.; Schiedung, H.; Bareth, G.

2016-06-01

In this study, first results of retrieving plant heights of maize fields from multitemporal TanDEM-X images are shown. Three TanDEM-X dual polarization spotlight acquisitions were taken over a rural area in Germany in the growing season 2014. By interferometric processing, digital terrain models (DTM) were derived for each date with 5m resolution. From the data of the first acquisition (June 1st) taken before planting, a DTM of the bare ground is generated. The data of the following acquisition dates (July 15th, July 26th) are used to establish crop surface models (CSM). A CSM represents the crop surface of a whole field in a high resolution. By subtracting the DTM of the ground from each CSM, the actual plant height is calculated. Within these data sets 30 maize fields in the area of interest could be detected and verified by external land use data. Besides the spaceborne measurements, one of the maize fields was intensively investigated using terrestrial laser scanning (TLS), which was carried out at the same dates as the predicted TanDEM-X acquisitions. Visual inspection of the derived plant heights, and accordance of the individually processed polarisations over the maize fields, demonstrate the feasibility of the proposed method. Unfortunately, the infield variability of the intensively monitored field could not be successfully captured in the TanDEM-X derived plant heights and merely the general trend is visible. Nevertheless, the study shows the potential of the TanDEM-X constellation for maize height monitoring on field level.

Evolution of the axial electron cyclotron maser instability, with applications to solar microwave spikes

NASA Technical Reports Server (NTRS)

Vlahos, Loukas; Sprangle, Phillip

1987-01-01

The nonlinear evolution of cyclotron radiation from streaming and gyrating electrons in an external magnetic field is analyzed. The nonlinear dynamics of both the fields and the particles are treated fully relativistically and self-consistently. The model includes a background plasma and electrostatic effects. The analytical and numerical results show that a substantial portion of the beam particle energy can be converted to electromagnetic wave energy at frequencies far above the electron cyclotron frequency. In general, the excited radiation can propagate parallel to the magnetic field and, hence, escape gyrothermal absorption at higher cyclotron harmonics. The high-frequency Doppler-shifted cyclotron instability can have saturation efficiencies far higher than those associated with well-known instabilities of the electron cyclotron maser type. Although the analysis is general, the possibility of using this model to explain the intense radio emission observed from the sun is explored in detail.

Observation of spin-polarized photoconductivity in (Ga,Mn)As/GaAs heterojunction without magnetic field

PubMed Central

Wu, Qing; Liu, Yu; Wang, Hailong; Li, Yuan; Huang, Wei; Zhao, Jianhua; Chen, Yonghai

2017-01-01

In the absent of magnetic field, we have observed the anisotropic spin polarization degree of photoconduction (SPD-PC) in (Ga,Mn)As/GaAs heterojunction. We think three kinds of mechanisms contribute to the magnetic related signal, (i) (Ga,Mn)As self-producing due to the valence band polarization, (ii) unequal intensity of left and right circularly polarized light reaching to GaAs layer to excite unequal spin polarized carriers in GaAs layer, and (iii) (Ga,Mn)As as the spin filter layer for spin transport from GaAs to (Ga,Mn)As. Different from the previous experiments, the influence coming from the Zeeman splitting induced by an external magnetic field can be avoided here. While temperature dependence experiment indicates that the SPD-PC is mixed with the magnetic uncorrelated signals, which may come from current induced spin polarization. PMID:28084437

Real-time detection of fast and thermal neutrons in radiotherapy with CMOS sensors.

PubMed

Arbor, Nicolas; Higueret, Stephane; Elazhar, Halima; Combe, Rodolphe; Meyer, Philippe; Dehaynin, Nicolas; Taupin, Florence; Husson, Daniel

2017-03-07

The peripheral dose distribution is a growing concern for the improvement of new external radiation modalities. Secondary particles, especially photo-neutrons produced by the accelerator, irradiate the patient more than tens of centimeters away from the tumor volume. However the out-of-field dose is still not estimated accurately by the treatment planning softwares. This study demonstrates the possibility of using a specially designed CMOS sensor for fast and thermal neutron monitoring in radiotherapy. The 14 microns-thick sensitive layer and the integrated electronic chain of the CMOS are particularly suitable for real-time measurements in γ/n mixed fields. An experimental field size dependency of the fast neutron production rate, supported by Monte Carlo simulations and CR-39 data, has been observed. This dependency points out the potential benefits of a real-time monitoring of fast and thermal neutron during beam intensity modulated radiation therapies.

Characterization of magnetic material in the mound-building termite Macrotermes gilvus in Southeast Asia

NASA Astrophysics Data System (ADS)

Esa, Mohammad Faris Mohammad; Rahim, Faszly; Hassan, Ibrahim Haji; Hanifah, Sharina Abu

2015-09-01

Magnetic material such as magnetite are known as particles that respond to external magnetic field with their ferromagnetic properties as they are believed contribute to in responding to the geomagnetic field. These particles are used by terrestrial animals such as termites for navigation and orientation. Since our earth react as giant magnetic bar, the magnitude of this magnetic field present by intensity and direction (inclination and direction). The magnetic properties and presence of magnetite in termites Macrotermes gilvus, common mound-building termite were tested. M. gilvus termites was tested with a Vibrating Sample Magnetometer VSM to determine the magnetic properties of specimen. The crushed body sample was characterized with X-Ray Diffraction XRD to show the existent of magnetic material (magnetite) in the specimens. Results from VSM indicate that M. gilvus has diamagnetism properties. The characterization by XRD shows the existent of magnetic material in our specimen in low concentration.

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

Esa, Mohammad Faris Mohammad; Hassan, Ibrahim Haji; Rahim, Faszly

Magnetic material such as magnetite are known as particles that respond to external magnetic field with their ferromagnetic properties as they are believed contribute to in responding to the geomagnetic field. These particles are used by terrestrial animals such as termites for navigation and orientation. Since our earth react as giant magnetic bar, the magnitude of this magnetic field present by intensity and direction (inclination and direction). The magnetic properties and presence of magnetite in termites Macrotermes gilvus, common mound-building termite were tested. M. gilvus termites was tested with a Vibrating Sample Magnetometer VSM to determine the magnetic properties ofmore » specimen. The crushed body sample was characterized with X-Ray Diffraction XRD to show the existent of magnetic material (magnetite) in the specimens. Results from VSM indicate that M. gilvus has diamagnetism properties. The characterization by XRD shows the existent of magnetic material in our specimen in low concentration.« less

Residual tumour volumes and grey zones after external beam radiotherapy (with or without chemotherapy) in cervical cancer patients. A low-field MRI study.

PubMed

Schmid, M P; Mansmann, B; Federico, M; Dimopoulous, J C A; Georg, P; Fidarova, E; Dörr, W; Pötter, R

2013-03-01

Grey zones, which are defined as tissue with intermediate signal intensity in the area of primary hyperintense tumour extension, can be seen during radiation with or without chemotherapy on the T2-weighted MRI in patients with cervical cancer. The purpose of this study was to systematically measure the tumour volume at the time of diagnosis and the residual tumour volume at the time of brachytherapy without and with consideration of the grey zones and to estimate tumour regression during external beam radiotherapy (EBRT). T2-weighted MRI datasets of 175 patients with locally advanced cervical cancer (FIGO stage IB-IVA), who underwent combined external beam radiotherapy and brachytherapy with or without concomitant chemotherapy were available for this study. The gross tumour volume at the time of diagnosis (GTV(init)) and at the time of first brachytherapy without (GTV(res)) and with (GTV(res)+ GZ) consideration of grey zones were measured for each patient. A descriptive statistical analysis was performed and tumour regression rates without (R) and with consideration of grey zones (R(GZ)) were calculated. Further, the role of prognostic factors on GTV(init), GTV(res), GTV(res)+ GZ and tumour regression rates was investigated. The median GTV(init), GTV(res), GTV(res)+ GZ in all patients were 44.4 cm(3), 8.2 cm(3), 20.3 cm(3), respectively. The median R was 78.5% and the median R(GZ) was 50.1%. The histology and FIGO staging showed a significant impact on GTV(init), GTV(res) and GTV(res)+ GZ. Grey zones represent a substantial proportion of the residual tumour volume at the time of brachytherapy. Differentiation of high signal intensity mass and surrounding intermediate signal intensity grey zones may be reasonable.

Determination of the space-charge field amplitude in polymeric photorefractive polymers.

PubMed

Hwang, Ui-Jung; Choi, Chil-Sung; Vuong, Nguyen Quoc; Kim, Nakjoong

2005-12-22

The space-charge field built in a polymeric photorefractive polymer was calculated by a simple method based on the oriented gas model. When anisotropic chromophores in a photorefractive polymer were exposed to an external field, they oriented preferentially to exhibit a birefringence. Then, under illumination of two coherent beams and an external field, they reoriented to form a photorefractive grating. During the formation of the grating, the chromophores were reoriented by the space-charge field as well as by the external applied field. The birefringence induced in the material by an external electric field was determined by measuring the transmittance of the sample which is placed between crossed polarizers, where birefringence depicts the orientation of the chromophores. By measuring the diffraction efficiency with a modified degenerate four-wave mixing setup, the index amplitude of the grating was determined. Finally, the space-charge field was determined by comparing the diffraction efficiency with the birefringence with respect to the applied electric field. In our study, the space-charge field was about 20% of the external applied field, which coincided with previous results obtained from our laboratory.

Electric field measurements in a near atmospheric pressure nanosecond pulse discharge with picosecond electric field induced second harmonic generation

NASA Astrophysics Data System (ADS)

Goldberg, Benjamin M.; Chng, Tat Loon; Dogariu, Arthur; Miles, Richard B.

2018-02-01

We present an optical electric field measurement method for use in high pressure plasma discharges. The method is based upon the field induced second harmonic generation technique and can be used for localized electric field measurements with sub-nanosecond resolution in any gaseous species. When an external electric field is present, a dipole is induced in the typically centrosymmetric medium, allowing for second harmonic generation with signal intensities which scale by the square of the electric field. Calibrations have been carried out in 100 Torr room air, and a minimum sensitivity of 450 V/cm is demonstrated. Measurements were performed with nanosecond or faster temporal resolution in a 100 Torr room air environment both with and without a plasma present. It was shown that with no plasma present, the field follows the applied voltage to gap ratio, as measured using the back current shunt method. When the electric field is strong enough to exceed the breakdown threshold, the measured field was shown to exceed the anticipated voltage to gap ratio which is taken as an indication of the ionization wave front as it sweeps through the plasma volume.

Evaluation of surface and shallow depth dose reductions using a Superflab bolus during conventional and advanced external beam radiotherapy.

PubMed

Yoon, Jihyung; Xie, Yibo; Zhang, Rui

2018-03-01

The purpose of this study was to evaluate a methodology to reduce scatter and leakage radiations to patients' surface and shallow depths during conventional and advanced external beam radiotherapy. Superflab boluses of different thicknesses were placed on top of a stack of solid water phantoms, and the bolus effect on surface and shallow depth doses for both open and intensity-modulated radiotherapy (IMRT) beams was evaluated using thermoluminescent dosimeters and ion chamber measurements. Contralateral breast dose reduction caused by the bolus was evaluated by delivering clinical postmastectomy radiotherapy (PMRT) plans to an anthropomorphic phantom. For the solid water phantom measurements, surface dose reduction caused by the Superflab bolus was achieved only in out-of-field area and on the incident side of the beam, and the dose reduction increased with bolus thickness. The dose reduction caused by the bolus was more significant at closer distances from the beam. Most of the dose reductions occurred in the first 2-cm depth and stopped at 4-cm depth. For clinical PMRT treatment plans, surface dose reductions using a 1-cm Superflab bolus were up to 31% and 62% for volumetric-modulated arc therapy and 4-field IMRT, respectively, but there was no dose reduction for Tomotherapy. A Superflab bolus can be used to reduce surface and shallow depth doses during external beam radiotherapy when it is placed out of the beam and on the incident side of the beam. Although we only validated this dose reduction strategy for PMRT treatments, it is applicable to any external beam radiotherapy and can potentially reduce patients' risk of developing radiation-induced side effects. © 2018 The Authors. Journal of Applied Clinical Medical Physics published by Wiley Periodicals, Inc. on behalf of American Association of Physicists in Medicine.

Nanosecond pulsed electric fields have differential effects on cells in the S-phase.

PubMed

Hall, Emily H; Schoenbach, Karl H; Beebe, Stephen J

2007-03-01

Nanosecond pulsed electric fields (nsPEFs) are a type of nonthermal, nonionizing radiation that exhibit intense electric fields with high power, but low energy. NsPEFs extend conventional electroporation (EP) to affect intracellular structures and functions and depending on the intensity, can induce lethal and nonlethal cell signaling. In this study, HCT116 human colon carcinoma cells were synchronized to the S-phase or remained unsynchronized, exposed to electric fields of 60 kV/cm with either 60-ns or 300-ns durations, and analyzed for apoptosis and proliferative markers. Several nsPEF structural and functional targets were identified. Unlike unsynchronized cells, S-phase cells under limiting conditions exhibited greater membrane integrity and caspase activation and maintained cytoskeletal structure. Regardless of synchronization, cells exposed to nsPEFs under these conditions primarily survived, but exhibited some turnover and delayed proliferation in cell populations, as well as reversible increases in phosphatidylserine externalization, membrane integrity, and nuclei size. These results show that nsPEFs can act as a nonligand agonist to modulate plasma membrane (PM) and intracellular structures and functions, as well as differentially affect cells in the S-phase, but without effect on cell survival. Furthermore, nsPEF effects on the nucleus and cytoskeleton may provide synergistic therapeutic actions with other agents, such as ionizing radiation or chemotherapeutics that affect these same structures.

Effects of space weather on GOCE electrostatic gravity gradiometer measurements

NASA Astrophysics Data System (ADS)

Ince, E. Sinem; Pagiatakis, Spiros D.

2016-12-01

We examine the presence of residual nongravitational signatures in gravitational gradients measured by GOCE electrostatic gravity gradiometer. These signatures are observed over the magnetic poles during geomagnetically active days and can contaminate the trace of the gravitational gradient tensor by up to three to five times the expected noise level of the instrument (˜ 11 mE). We investigate these anomalies in the gradiometer measurements along many satellite tracks and examine possible causes using external datasets, such as interplanetary electric field measurements from the ACE (advanced composition explorer) and WIND spacecraft, and Poynting vector (flux) estimated from equivalent ionospheric currents derived from spherical elementary current systems over North America and Greenland. We show that the variations in the east-west and vertical electrical currents and Poynting vector components at the satellite position are highly correlated with the disturbances observed in the gradiometer measurements. The results presented in this paper reveal that the disturbances are due to intense ionospheric current variations that are enhanced by increased solar activity that causes a very dynamic drag environment. Moreover, successful modelling and removal of a high percentage of these disturbances are possible using external geomagnetic field observations.

Nonlinear optical response in a zincblende GaN cylindrical quantum dot with donor impurity center

NASA Astrophysics Data System (ADS)

Hoyos, Jaime H.; Correa, J. D.; Mora-Ramos, M. E.; Duque, C. A.

2016-03-01

We calculate the nonlinear optical absorption coefficient of a cylindrical zincblende GaN-based quantum dot. For this purpose, we consider Coulomb interactions between electrons and an impurity ionized donor atom. The electron-donor-impurity spectrum and the associated quantum states are calculated using the effective mass approximation with a parabolic potential energy model describing both the radial and axial electron confinement. We also include the effects of the hydrostatic pressure and external electrostatic fields. The energy spectrum is obtained through an expansion of the eigenstates as a linear combination of Gaussian-type functions which reduces the computational effort since all the matrix elements are obtained analytically. Therefore, the numerical problem is reduced to the direct diagonalization of the Hamiltonian. The obtained energies are used in the evaluation of the dielectric susceptibility and the nonlinear optical absorption coefficient within a modified two-level approach in a rotating wave approximation. This quantity is investigated as a function of the quantum dot dimensions, the impurity position, the external electric field intensity and the hydrostatic pressure. The results of this research could be important in the design and fabrication of zincblende GaN-quantum-dot-based electro-optical devices.

Resolution-of-identity stochastic time-dependent configuration interaction for dissipative electron dynamics in strong fields.

PubMed

Klinkusch, Stefan; Tremblay, Jean Christophe

2016-05-14

In this contribution, we introduce a method for simulating dissipative, ultrafast many-electron dynamics in intense laser fields. The method is based on the norm-conserving stochastic unraveling of the dissipative Liouville-von Neumann equation in its Lindblad form. The N-electron wave functions sampling the density matrix are represented in the basis of singly excited configuration state functions. The interaction with an external laser field is treated variationally and the response of the electronic density is included to all orders in this basis. The coupling to an external environment is included via relaxation operators inducing transition between the configuration state functions. Single electron ionization is represented by irreversible transition operators from the ionizing states to an auxiliary continuum state. The method finds its efficiency in the representation of the operators in the interaction picture, where the resolution-of-identity is used to reduce the size of the Hamiltonian eigenstate basis. The zeroth-order eigenstates can be obtained either at the configuration interaction singles level or from a time-dependent density functional theory reference calculation. The latter offers an alternative to explicitly time-dependent density functional theory which has the advantage of remaining strictly valid for strong field excitations while improving the description of the correlation as compared to configuration interaction singles. The method is tested on a well-characterized toy system, the excitation of the low-lying charge transfer state in LiCN.

Resolution-of-identity stochastic time-dependent configuration interaction for dissipative electron dynamics in strong fields

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

Klinkusch, Stefan; Tremblay, Jean Christophe

In this contribution, we introduce a method for simulating dissipative, ultrafast many-electron dynamics in intense laser fields. The method is based on the norm-conserving stochastic unraveling of the dissipative Liouville-von Neumann equation in its Lindblad form. The N-electron wave functions sampling the density matrix are represented in the basis of singly excited configuration state functions. The interaction with an external laser field is treated variationally and the response of the electronic density is included to all orders in this basis. The coupling to an external environment is included via relaxation operators inducing transition between the configuration state functions. Single electronmore » ionization is represented by irreversible transition operators from the ionizing states to an auxiliary continuum state. The method finds its efficiency in the representation of the operators in the interaction picture, where the resolution-of-identity is used to reduce the size of the Hamiltonian eigenstate basis. The zeroth-order eigenstates can be obtained either at the configuration interaction singles level or from a time-dependent density functional theory reference calculation. The latter offers an alternative to explicitly time-dependent density functional theory which has the advantage of remaining strictly valid for strong field excitations while improving the description of the correlation as compared to configuration interaction singles. The method is tested on a well-characterized toy system, the excitation of the low-lying charge transfer state in LiCN.« less

Strain engineering of graphene nanoribbons: pseudomagnetic versus external magnetic fields

NASA Astrophysics Data System (ADS)

Prabhakar, Sanjay; Melnik, Roderick; Bonilla, Luis

2017-05-01

Bandgap opening due to strain engineering is a key architect for making graphene's optoelectronic, straintronic, and spintronic devices. We study the bandgap opening due to strain induced ripple waves and investigate the interplay between pseudomagnetic fields and externally applied magnetic fields on the band structures and spin relaxation in graphene nanoribbons (GNRs). We show that electron-hole bands of GNRs are highly influenced (i.e. level crossing of the bands are possible) by coupling two combined effects: pseudomagnetic fields (PMF) originating from strain tensor and external magnetic fields. In particular, we show that the tuning of the spin-splitting band extends to large externally applied magnetic fields with increasing values of pseudomagnetic fields. Level crossings of the bands in strained GNRs can also be observed due to the interplay between pseudomagnetic fields and externally applied magnetic fields. We also investigate the influence of this interplay on the electromagnetic field mediated spin relaxation mechanism in GNRs. In particular, we show that the spin hot spot can be observed at approximately B = 65 T (the externally applied magnetic field) and B0 = 53 T (the magnitude of induced pseudomagnetic field due to ripple waves) which may not be considered as an ideal location for the design of straintronic devices. Our analysis might be used for tuning the bandgaps in strained GNRs and utilized to design the optoelectronic devices for straintronic applications.

Origin of Polar Order in Dense Suspensions of Phototactic Micro-Swimmers

PubMed Central

Furlan, Silvano; Comparini, Diego; Ciszak, Marzena; Beccai, Lucia; Mancuso, Stefano; Mazzolai, Barbara

2012-01-01

A main question for the study of collective motion in living organisms is the origin of orientational polar order, i.e., how organisms align and what are the benefits of such collective behaviour. In the case of micro-organisms swimming at a low Reynolds number, steric repulsion and long-range hydrodynamic interactions are not sufficient to explain a homogeneous polar order state in which the direction of motion is aligned. An external symmetry-breaking guiding field such as a mechanism of taxis appears necessary to understand this phonemonon. We have investigated the onset of polar order in the velocity field induced by phototaxis in a suspension of a motile micro-organism, the algae Chlamydomonas reinhardtii, for density values above the limit provided by the hydrodynamic approximation of a force dipole model. We show that polar order originates from a combination of both the external guiding field intensity and the population density. In particular, we show evidence for a linear dependence of a phototactic guiding field on cell density to determine the polar order for dense suspensions and demonstrate the existence of a density threshold for the origin of polar order. This threshold represents the density value below which cells undergoing phototaxis are not able to maintain a homogeneous polar order state and marks the transition to ordered collective motion. Such a transition is driven by a noise dominated phototactic reorientation where the noise is modelled as a normal distribution with a variance that is inversely proportional to the guiding field strength. Finally, we discuss the role of density in dense suspensions of phototactic micro-swimmers. PMID:22723904

Interaction of a penny-shaped crack and an external circular crack in a transversely isotropic composite

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

Tsai, Y.M.

1998-12-31

The interaction of a penny-shaped crack and an external circular crack in a transversely isotropic composite is investigated using the techniques of Hankel transform and multiplying factors. The boundary conditions of the problem have three different parts. The stress intensity factors at the inner and the outer crack tips are obtained in exact expressions as the products of a dimensional quantity and nondimensional functions. The presence of a penny-shaped crack is shown to have a strong effect on the magnitude of the stress intensity of the external circular crack. The crack surface displacement is also obtained and evaluated numerically formore » different values of the ratio of the inner crack radius to the external crack radius.« less

Liquid phase electroepitaxial bulk growth of binary and ternary alloy semiconductors under external magnetic field

NASA Astrophysics Data System (ADS)

Sheibani, Hamdi

2002-01-01

Liquid Phase Electroepitaxy (LPEE) and is a relatively new, promising technique for producing high quality, thick compound semiconductors and their alloys. The main objectives are to reduce the adverse effect of natural convection and to determine the optimum growth conditions for reproducible desired crystals for the optoelectronic and electronic device industry. Among the available techniques for suppressing the adverse effect of natural convection, the application of an external magnetic field seems the most feasible one. The research work in this dissertation consists of two parts. The first part is focused on the design and development of a state of the art LPEE facility with a novel crucible design, that can produce bulk crystals of quality higher than those achieved by the existing LPEE system. A growth procedure was developed to take advantage of this novel crucible design. The research of the growth of InGaAs single crystals presented in this thesis will be a basis for the future LPEE growth of other important material and is an ideal vehicle for the development of a ternary crystal growth process. The second part of the research program is the experimental study of the LPEE growth process of high quality bulk single crystals of binary/ternary semiconductors under applied magnetic field. The compositional uniformity of grown crystals was measured by Electron Probe Micro-analysis (EPMA) and X-ray microanalysis. The state-of-the-art LPEE system developed at University of Victoria, because of its novel design features, has achieved a growth rate of about 4.5 mm/day (with the application of an external fixed magnetic field of 4.5 KGauss and 3 A/cm2 electric current density), and a growth rate of about 11 mm/day (with 4.5 KGauss magnetic field and 7 A/cm2 electric current density). This achievement is simply a breakthrough in LPEE, making this growth technique absolutely a bulk growth technique and putting it in competition with other bulk growth techniques. The growth rates achieved can even be higher for higher electric current and magnetic field intensities. (Abstract shortened by UMI.)

Applications of a micro-pixel chamber (μPIC) based, time-resolved neutron imaging detector at pulsed neutron beams

NASA Astrophysics Data System (ADS)

Parker, J. D.; Harada, M.; Hattori, K.; Iwaki, S.; Kabuki, S.; Kishimoto, Y.; Kubo, H.; Kurosawa, S.; Matsuoka, Y.; Miuchi, K.; Mizumoto, T.; Nishimura, H.; Oku, T.; Sawano, T.; Shinohara, T.; Suzuki, J.-I.; Takada, A.; Tanimori, T.; Ueno, K.; Ikeno, M.; Tanaka, M.; Uchida, T.

2014-04-01

The realization of high-intensity, pulsed spallation neutron sources such as J-PARC in Japan and SNS in the US has brought time-of-flight (TOF) based neutron techniques to the fore and spurred the development of new detector technologies. When combined with high-resolution imaging, TOF-based methods become powerful tools for direct imaging of material properties, including crystal structure/internal strain, isotopic/temperature distributions, and internal and external magnetic fields. To carry out such measurements in the high-intensities and high gamma backgrounds found at spallation sources, we have developed a new time-resolved neutron imaging detector employing a micro-pattern gaseous detector known as the micro-pixel chamber (μPIC) coupled with a field-programmable-gate-array-based data acquisition system. The detector combines 100μm-level (σ) spatial and sub-μs time resolutions with low gamma sensitivity of less than 10-12 and a rate capability on the order of Mcps (mega-counts-per-second). Here, we demonstrate the application of our detector to TOF-based techniques with examples of Bragg-edge transmission and neutron resonance transmission imaging (with computed tomography) carried out at J-PARC. We also consider the direct imaging of magnetic fields with our detector using polarized neutrons.

Scaling, clustering and avalanches for steel beads in an external magnetic field

NASA Astrophysics Data System (ADS)

Marquinez, Alyse; Thvedt, Ingrid; Lehman, S. Y.; Jacobs, D. T.

2011-03-01

We investigated avalanches using uniform 3mm steel spheres (``beads'') dropped onto a conical bead pile within a uniform magnetic field. The bead pile is built by pouring beads onto a circular base where the bottom layer of beads had been glued randomly. Beads are then individually dropped from a fixed height after which the pile is massed. This process is repeated for thousands of bead drops. By measuring the number of avalanches of a given size that occurred during the experiment, the resulting avalanche size distribution was compared to a power law description as predicted by self-organized criticality. As the magnetic field intensity increased, the beads clustered to give a larger angle of repose and we measured the change in the avalanche size distribution. The moments of the distribution give a sensitive test of mean-field theory as the universality class for these bead piles. We acknowledge support from Research Corporation and NSF-REU grant DMR 0649112.

Determination of domain wall chirality using in situ Lorentz transmission electron microscopy

DOE PAGES

Chess, Jordan J.; Montoya, Sergio A.; Fullerton, Eric E.; ...

2017-02-23

Controlling domain wall chirality is increasingly seen in non-centrosymmetric materials. Mapping chiral magnetic domains requires knowledge about all the vector components of the magnetization, which poses a problem for conventional Lorentz transmission electron microscopy (LTEM) that is only sensitive to magnetic fields perpendicular to the electron beams direction of travel. The standard approach in LTEM for determining the third component of the magnetization is to tilt the sample to some angle and record a second image. Furthermore, this presents a problem for any domain structures that are stabilized by an applied external magnetic field (e.g. skyrmions), because the standard LTEMmore » setup does not allow independent control of the angle of an applied magnetic field, and sample tilt angle. Here we show that applying a modified transport of intensity equation analysis to LTEM images collected during an applied field sweep, we can determine the domain wall chirality of labyrinth domains in a perpendicularly magnetized material, avoiding the need to tilt the sample.« less

Determination of domain wall chirality using in situ Lorentz transmission electron microscopy

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

Chess, Jordan J.; Montoya, Sergio A.; Fullerton, Eric E.

Controlling domain wall chirality is increasingly seen in non-centrosymmetric materials. Mapping chiral magnetic domains requires knowledge about all the vector components of the magnetization, which poses a problem for conventional Lorentz transmission electron microscopy (LTEM) that is only sensitive to magnetic fields perpendicular to the electron beams direction of travel. The standard approach in LTEM for determining the third component of the magnetization is to tilt the sample to some angle and record a second image. Furthermore, this presents a problem for any domain structures that are stabilized by an applied external magnetic field (e.g. skyrmions), because the standard LTEMmore » setup does not allow independent control of the angle of an applied magnetic field, and sample tilt angle. Here we show that applying a modified transport of intensity equation analysis to LTEM images collected during an applied field sweep, we can determine the domain wall chirality of labyrinth domains in a perpendicularly magnetized material, avoiding the need to tilt the sample.« less

Spontaneous reorientations of meta-atoms and electromagnetic spatial solitons in a liquid metacrystal.

PubMed

Zharov, Alexander A; Zharov, Alexander A; Zharova, Nina A

2014-08-01

We show that transverse electromagnetic waves propagating along an external static electric field in liquid metacrystal (LMC) can provoke spontaneous rearrangement of elongated meta-atoms that changes the direction of the anisotropy axis of the LMC. This kind of instability may reorient the meta-atoms from the equilibrium state parallel to a static field to the state along a high-frequency field and back at the different threshold intensities of electromagnetic waves in such a way that bistability in the system takes place. Reorientation of meta-atoms causes a change in the effective refraction index of LMC that creates, in turn, the conditions for the formation of bright spatial solitons. Such spatial solitons are the self-consistent domains of redirected meta-atoms with trapped photons. We find that the instability thresholds as well as energy flux captured by the spatial soliton can be easily managed by variation of the static electric field applied to the LMC. We study the effects of soliton excitation and collisions via numerical simulations.

Step-wise potential development across the lipid bilayer under external electric fields

NASA Astrophysics Data System (ADS)

Majhi, Amit Kumar

2018-04-01

Pore formation across the bilayers under external electric field is an important phenomenon, which has numerous applications in biology and bio-engineering fields. However, it is not a ubiquitous event under all field applications. To initiate a pore in the bilayer a particular threshold electric field is required. The electric field alters the intrinsic potential distribution across the bilayer as we as it enhances total potential drop across the bilayer, which causes the pore formation. The intrinsic potential profile has a maximum peak value, which is 0.8 V and it gets enhanced under application of external field, 0.43 V/nm. The peak value becomes 1.4 V when a pore appears in the bilayer and it continues to evolve as along as the external electric field remains switched on.

Calcium and initial surface binding phase of pinocytosis in Amoeba proteus.

PubMed

Prusch, R D

1986-08-01

The uptake of membrane-bound solute and external medium by bulk-phase pinocytosis in Amoeba proteus is influenced by the level of Ca2+ in the external medium. Increasing external Ca2+ to approximately 10(-4) M increases pinocytotic intensity, while increases in Ca2+ above this level decrease the intensity of pinocytosis. The initial interaction of pinocytotic inducers and Ca2+ at the surface of Amoeba proteus was therefore examined. Alcian blue and Na+, both inducers of pinocytosis, differ in the manner with which they associate with the amoeba surface, suggesting the possibility of different pinocytosis-inducing sites on the amoeba surface. Low levels of external Ca2+ in the range of 3 X 10(-5) to 1.5 X 10(-4) M increase the amount of cationic inducer associated with the cell surface while, at the same time, decreasing anion association with the cell surface. It is suggested that Ca2+ influences ion association with the cell surface by controlling the availability of negative surface sites, which in turn influences pinocytotic intensity.

Rationale for a GRAVSAT-MAGSAT mission: A perspective on the problem of external/internal transient field effects

NASA Technical Reports Server (NTRS)

Hermance, J. F.

1985-01-01

The Earth's magnetic field at MAGSAT altitudes not only has contributions from the Earth's core and static magnetization in the lithosphere, but also from external electric current systems in the ionosphere and magnetosphere, along with induced electric currents flowing in the conducting earth. Hermance assessed these last two contributions; the external time-varying fields and their associated internal counter-parts which are electromagnetically induced. It is readily recognized that during periods of magnetic disturbance, external currents often contribute from 10's to 100's of nanoteslas (gammas) to observations of the Earth's field. Since static anomalies from lithospheric magnetization are of this same magnitude or less, these external source fields must be taken into account when attempting to delineate gross structural features in the crust.

Targeting to carcinoma cells with chitosan- and starch-coated magnetic nanoparticles for magnetic hyperthermia.

PubMed

Kim, Dong-Hyun; Kim, Kyoung-Nam; Kim, Kwang-Mahn; Lee, Yong-Keun

2009-01-01

The delivery of hyperthermic thermoseeds to a specific target site with minimal side effects is an important challenge in targeted hyperthermia, which employs magnetic method and functional polymers. An external magnetic field is used to control the site-specific targeting of the magnetic nanoparticles. Polymer-coated magnetic nanoparticles can confer a higher affinity to the biological cell membranes. In this study, uncoated, chitosan-coated, and starch-coated magnetic nanoparticles were synthesized for use as a hyperthermic thermoseed. Each sample was examined with respect to their applications to hyperthermia using XRD, VSM, and FTIR. In addition, the temperature changes under an alternating magnetic field were observed. As in vitro tests, the magnetic responsiveness of chitosan- and starch-coated magnetite was determined by a simple blood vessel model under various intensities of magnetic field. L929 normal cells and KB carcinoma cells were used to examine the cytotoxicity and affinity of each sample using the MTT method. The chitosan-coated magnetic nanoparticles generated a higher DeltaT of 23 degrees C under an AC magnetic field than the starch-coated magnetite, and the capturing rate of the particles was 96% under an external magnetic field of 0.4 T. The highest viability of L929 cells was 93.7%. Comparing the rate of KB cells capture with the rate of L929 cells capture, the rate of KB cells capture relatively increased with 10.8% in chitosan-coated magnetic nanoparticles. Hence, chitosan-coated magnetic nanoparticles are biocompatible and have a selective affinity to KB cells. The targeting of magnetic nanoparticles in hyperthermia was improved using a controlled magnetic field and a chitosan-coating. Therefore, chitosan-coated magnetic nanoparticles are expected to be promising materials for use in magnetic targeted hyperthermia. 2008 Wiley Periodicals, Inc.

The Triggering Mechanism of Quiet-Region Coronal Jet Eruptions: Flux Cancelation

NASA Technical Reports Server (NTRS)

Panesar, Navdeep K.; Sterling, Alphonse C.; Moore, Ronald L.

2017-01-01

Coronal jets are frequent transient features on the Sun, observed in EUV and X-ray emissions. They occur in active regions, quiet Sun and coronal holes, and appear as a bright spire with base brightenings. Recent studies show that many coronal jets are driven by the eruption of a minifilament. Here we investigate the magnetic cause of jet-driving minifilament eruptions. We study ten randomly-found on-disk quiet-region coronal jets using SDO/AIA intensity images and SDO/HMI magnetograms. For all ten events, we track the evolution of photospheric magnetic flux in the jet-base region in EUV images and find that (a) a cool (transition-region temperature) minifilament is present prior to each jet eruption; (b) the pre-eruption minifilament resides above the polarity-inversion line between majority-polarity and minority-polarity magnetic flux patches; (c) the opposite-polarity flux patches converge and cancel with each other; (d) the cancelation between the majority-polarity and minority-polarity flux patches eventually destabilizes the field holding the minifilament to erupt outwards; (e) the envelope of the erupting field barges into ambient oppositely-directed far-reaching field and undergoes external reconnection (interchange reconnection); (f) the external reconnection opens the envelope field and the minifilament field inside, allowing reconnected-heated hot material and cool minifilament material to escape along the far-reaching field, producing the jet spire. In summary, we found that each of our ten jets resulted from a minifilament eruption following flux cancelation at the magnetic neutral line under the pre-eruption minifilament. These observations show that flux cancelation is usually the trigger of quiet-region coronal jet eruptions.

Lévy noise improves the electrical activity in a neuron under electromagnetic radiation.

PubMed

Wu, Juan; Xu, Yong; Ma, Jun

2017-01-01

As the fluctuations of the internal bioelectricity of nervous system is various and complex, the external electromagnetic radiation induced by magnet flux on membrane can be described by the non-Gaussian type distribution of Lévy noise. Thus, the electrical activities in an improved Hindmarsh-Rose model excited by the external electromagnetic radiation of Lévy noise are investigated and some interesting modes of the electrical activities are exhibited. The external electromagnetic radiation of Lévy noise leads to the mode transition of the electrical activities and spatial phase, such as from the rest state to the firing state, from the spiking state to the spiking state with more spikes, and from the spiking state to the bursting state. Then the time points of the firing state versus Lévy noise intensity are depicted. The increasing of Lévy noise intensity heightens the neuron firing. Also the stationary probability distribution functions of the membrane potential of the neuron induced by the external electromagnetic radiation of Lévy noise with different intensity, stability index and skewness papremeters are analyzed. Moreover, through the positive largest Lyapunov exponent, the parameter regions of chaotic electrical mode of the neuron induced by the external electromagnetic radiation of Lévy noise distribution are detected.

Lévy noise improves the electrical activity in a neuron under electromagnetic radiation

PubMed Central

Wu, Juan; Ma, Jun

2017-01-01

As the fluctuations of the internal bioelectricity of nervous system is various and complex, the external electromagnetic radiation induced by magnet flux on membrane can be described by the non-Gaussian type distribution of Lévy noise. Thus, the electrical activities in an improved Hindmarsh-Rose model excited by the external electromagnetic radiation of Lévy noise are investigated and some interesting modes of the electrical activities are exhibited. The external electromagnetic radiation of Lévy noise leads to the mode transition of the electrical activities and spatial phase, such as from the rest state to the firing state, from the spiking state to the spiking state with more spikes, and from the spiking state to the bursting state. Then the time points of the firing state versus Lévy noise intensity are depicted. The increasing of Lévy noise intensity heightens the neuron firing. Also the stationary probability distribution functions of the membrane potential of the neuron induced by the external electromagnetic radiation of Lévy noise with different intensity, stability index and skewness papremeters are analyzed. Moreover, through the positive largest Lyapunov exponent, the parameter regions of chaotic electrical mode of the neuron induced by the external electromagnetic radiation of Lévy noise distribution are detected. PMID:28358824

Phenobarbital in intensive care unit pediatric population: predictive performances of population pharmacokinetic model.

PubMed

Marsot, Amélie; Michel, Fabrice; Chasseloup, Estelle; Paut, Olivier; Guilhaumou, Romain; Blin, Olivier

2017-10-01

An external evaluation of phenobarbital population pharmacokinetic model described by Marsot et al. was performed in pediatric intensive care unit. Model evaluation is an important issue for dose adjustment. This external evaluation should allow confirming the proposed dosage adaptation and extending these recommendations to the entire intensive care pediatric population. External evaluation of phenobarbital published population pharmacokinetic model of Marsot et al. was realized in a new retrospective dataset of 35 patients hospitalized in a pediatric intensive care unit. The published population pharmacokinetic model was implemented in nonmem 7.3. Predictive performance was assessed by quantifying bias and inaccuracy of model prediction. Normalized prediction distribution errors (NPDE) and visual predictive check (VPC) were also evaluated. A total of 35 infants were studied with a mean age of 33.5 weeks (range: 12 days-16 years) and a mean weight of 12.6 kg (range: 2.7-70.0 kg). The model predicted the observed phenobarbital concentrations with a reasonable bias and inaccuracy. The median prediction error was 3.03% (95% CI: -8.52 to 58.12%), and the median absolute prediction error was 26.20% (95% CI: 13.07-75.59%). No trends in NPDE and VPC were observed. The model previously proposed by Marsot et al. in neonates hospitalized in intensive care unit was externally validated for IV infusion administration. The model-based dosing regimen was extended in all pediatric intensive care unit to optimize treatment. Due to inter- and intravariability in pharmacokinetic model, this dosing regimen should be combined with therapeutic drug monitoring. © 2017 Société Française de Pharmacologie et de Thérapeutique.

Lopsidedness of Self-consistent Galaxies Caused by the External Field Effect of Clusters

NASA Astrophysics Data System (ADS)

Wu, Xufen; Wang, Yougang; Feix, Martin; Zhao, HongSheng

2017-08-01

Adopting Schwarzschild’s orbit-superposition technique, we construct a series of self-consistent galaxy models, embedded in the external field of galaxy clusters in the framework of Milgrom’s MOdified Newtonian Dynamics (MOND). These models represent relatively massive ellipticals with a Hernquist radial profile at various distances from the cluster center. Using N-body simulations, we perform a first analysis of these models and their evolution. We find that self-gravitating axisymmetric density models, even under a weak external field, lose their symmetry by instability and generally evolve to triaxial configurations. A kinematic analysis suggests that the instability originates from both box and nonclassified orbits with low angular momentum. We also consider a self-consistent isolated system that is then placed in a strong external field and allowed to evolve freely. This model, just like the corresponding equilibrium model in the same external field, eventually settles to a triaxial equilibrium as well, but has a higher velocity radial anisotropy and is rounder. The presence of an external field in the MOND universe generically predicts some lopsidedness of galaxy shapes.

Lopsidedness of Self-consistent Galaxies Caused by the External Field Effect of Clusters

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

Wu, Xufen; Wang, Yougang; Feix, Martin

2017-08-01

Adopting Schwarzschild’s orbit-superposition technique, we construct a series of self-consistent galaxy models, embedded in the external field of galaxy clusters in the framework of Milgrom’s MOdified Newtonian Dynamics (MOND). These models represent relatively massive ellipticals with a Hernquist radial profile at various distances from the cluster center. Using N -body simulations, we perform a first analysis of these models and their evolution. We find that self-gravitating axisymmetric density models, even under a weak external field, lose their symmetry by instability and generally evolve to triaxial configurations. A kinematic analysis suggests that the instability originates from both box and nonclassified orbitsmore » with low angular momentum. We also consider a self-consistent isolated system that is then placed in a strong external field and allowed to evolve freely. This model, just like the corresponding equilibrium model in the same external field, eventually settles to a triaxial equilibrium as well, but has a higher velocity radial anisotropy and is rounder. The presence of an external field in the MOND universe generically predicts some lopsidedness of galaxy shapes.« less

Transient development of Zeeman electromagnetically induced transparency during propagation of Raman-Ramsey pulses through Rb buffer gas cell

NASA Astrophysics Data System (ADS)

Nikolić, S. N.; Radonjić, M.; Lučić, N. M.; Krmpot, A. J.; Jelenković, B. M.

2015-02-01

We investigate, experimentally and theoretically, time development of Zeeman electromagnetically induced transparency (EIT) during propagation of two time separated polarization laser pulses, preparatory and probe, through Rb vapour. The pulses were produced by modifying laser intensity and degree of elliptical polarization. The frequency of the single laser beam is locked to the hyperfine {{F}g}=2\\to {{F}e}=1 transition of the D1 line in 87Rb. Transients in the intensity of {{σ }-} component of the transmitted light are measured or calculated at different values of the external magnetic field, during both preparatory and probe pulse. Zeeman EIT resonances at particular time instants of the pulse propagation are reconstructed by appropriate sampling of the transients. We observe how laser intensity, Ramsey sequence and the Rb cell temperature affect the time dependence of EIT line shapes, amplitudes and linewidths. We show that at early times of the probe pulse propagation, several Ramsey fringes are present in EIT resonances, while at later moments a single narrow peak prevails. Time development of EIT amplitudes are determined by the transmitted intensity of the {{σ }-} component during the pulse propagation.

The suppression effect of external magnetic field on the high-power microwave window multipactor phenomenon

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

Zhang, Xue, E-mail: zhangxue.iecas@yahoo.com; Wang, Yong; Fan, Junjie

2015-02-15

To suppress the surface multipactor phenomenon and improve the transmitting power of the high-power microwave window, the application of external magnetic fields is theoretically analyzed and simulated. A Monte Carlo algorithm is used to track the secondary electron trajectories and study the multipactor scenario on the surface of a cylinder window. It is confirmed that over-resonant magnetic fields (an external magnetic field whose magnitude is slightly greater than that of a resonant magnetic field) will generate a compensating trajectory and collision, which can suppress the secondary electron avalanche. The optimal value of this external magnetic field that will avoid themore » multipactor phenomenon on cylinder windows is discussed.« less

Magnetization-induced enhancement of photoluminescence in core-shell CoFe{sub 2}O{sub 4}@YVO{sub 4}:Eu{sup 3+} composite

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

Jia, Yanmin, E-mail: ymjia@zjnu.edu.cn, E-mail: wuzheng@zjnu.cn; Zhou, Zhihua; Wei, Yongbin

2013-12-07

After the core-shell CoFe{sub 2}O{sub 4}@YVO{sub 4}:Eu{sup 3+} composite synthesized through a facile sol-gel method was magnetized under an external magnetic field of 0.25 T for 4 h, an enhancement of ∼56% in photoluminescence intensity was observed. The remanent magnetization of the CoFe{sub 2}O{sub 4} core increases the intensity of the excited charge transfer transition of VO{sub 4}{sup 3−} group in YVO{sub 4}:Eu{sup 3+} shell, which may enhance the probability related to the Eu{sup 3+} radiative transition {sup 5}D{sub 0}-{sup 7}F{sub 2}, yielding to a high photoluminescence. The obvious remanent-magnetization-induced enhancement in photoluminescence is helpful in developing excellent magnetic/luminescent material for themore » practical display devices.« less

Mapping Farming Practices in Belgian Intensive Cropping Systems from Sentinel-1 SAR Time Series

NASA Astrophysics Data System (ADS)

Chome, G.; Baret, P. V.; Defourny, P.

2016-08-01

The environmental impact of the so-called conventional farming system calls for new farming practices reducing negative externalities. Emerging farming practices such as no-till and new inter-cropping management are promising tracks. The development of methods to characterize crop management across an entire region and to understand their spatial dimension offers opportunities to accompany the transition towards a more sustainable agriculture.This research takes advantage of the unmatched polarimetric and temporal resolutions of Sentinel-1 SAR C- band to develop a method to identify farming practices at the parcel level. To this end, the detection of changes in backscattering due to surface roughness modification (tillage, inter-crop cover destruction ...) is used to detect the farming management. The final results are compared to a reference dataset collected through an intensive field campaign. Finally, the performances are discussed in the perspective of practices monitoring of cropping systems through remote sensing.

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

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

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

2015-09-30

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

Fast neutron detection at near-core location of a research reactor with a SiC detector

NASA Astrophysics Data System (ADS)

Wang, Lei; Jarrell, Josh; Xue, Sha; Tan, Chuting; Blue, Thomas; Cao, Lei R.

2018-04-01

The measurable charged-particle produced from the fast neutron interactions with the Si and C nucleuses can make a wide bandgap silicon carbide (SiC) sensor intrinsically sensitive to neutrons. The 4H-SiC Schottky detectors have been fabricated and tested at up to 500 °C, presenting only a slightly degraded energy resolution. The response spectrum of the SiC detectors were also obtained by exposing the detectors to external neutron beam irradiation and at a near-core location where gamma-ray field is intense. The fast neutron flux of these two locations are ∼ 4 . 8 × 104cm-2 ṡs-1 and ∼ 2 . 2 × 107cm-2 ṡs-1, respectively. At the external beam location, a Si detector was irradiated side-by-side with SiC detector to disjoin the neutron response from Si atoms. The contribution of gamma ray, neutron scattering, and charged-particles producing reactions in the SiC was discussed. The fast neutron detection efficiencies were determined to be 6 . 43 × 10-4 for the external fast neutron beam irradiation and 6 . 13 × 10-6 for the near-core fast neutron irradiation.

Quantum correlations and violation of the Bell inequality induced by an external field in a two-photon radiative cascade

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

Yuan Luqi; Das, Sumanta

2011-06-15

We study the polarization-dependent second-order correlation of a pair of photons emitted in a four-level radiative cascade driven by an external field. It is found that the quantum correlations of the emitted photons, degraded by the energy splitting of the intermediate levels in the radiative cascade, can be efficiently revived by a far-detuned external field. The physics of this revival is linked to an induced Stark shift and the formation of dressed states in the system by the nonresonant external field. Furthermore, we investigated the competition between the effect of the coherent external field and incoherent dephasing of the intermediatemore » levels. We find that the degradation of quantum correlations due to the incoherent dephasing can be contained for small dephasing with the external field. We also studied the nonlocality of the correlations by evaluating the Bell inequality in the linear polarization basis for the radiative cascade. We find that the Bell parameter decreases rapidly with increase in the intermediate-level energy splitting or incoherent dephasing rate to the extent that there is no violation. However, the presence of an external field leads to control over the degrading mechanisms and preservation of nonlocal correlation among the photons. This in turn can induce a violation of Bell's inequality in the radiative cascade for arbitrary intermediate-level splitting and small incoherent dephasing.« less

Field coupling-induced pattern formation in two-layer neuronal network

NASA Astrophysics Data System (ADS)

Qin, Huixin; Wang, Chunni; Cai, Ning; An, Xinlei; Alzahrani, Faris

2018-07-01

The exchange of charged ions across membrane can generate fluctuation of membrane potential and also complex effect of electromagnetic induction. Diversity in excitability of neurons induces different modes selection and dynamical responses to external stimuli. Based on a neuron model with electromagnetic induction, which is described by magnetic flux and memristor, a two-layer network is proposed to discuss the pattern control and wave propagation in the network. In each layer, gap junction coupling is applied to connect the neurons, while field coupling is considered between two layers of the network. The field coupling is approached by using coupling of magnetic flux, which is associated with distribution of electromagnetic field. It is found that appropriate intensity of field coupling can enhance wave propagation from one layer to another one, and beautiful spatial patterns are formed. The developed target wave in the second layer shows some difference from target wave triggered in the first layer of the network when two layers are considered by different excitabilities. The potential mechanism could be pacemaker-like driving from the first layer will be encoded by the second layer.

Convective hydromagnetic instabilities of a power-law liquid saturating a porous medium: Flux conditions

NASA Astrophysics Data System (ADS)

Chahtour, C.; Ben Hamed, H.; Beji, H.; Guizani, A.; Alimi, W.

2018-01-01

We investigate how an external imposed magnetic field affects thermal instability in a horizontal shallow porous cavity saturated by a non-Newtonian power-law liquid. The magnetic field is assumed to be constant and parallel to the gravity. A uniform heat flux is applied to the horizontal walls of the layer while the vertical walls are adiabatic. We use linear stability analysis to find expressions for the critical Rayleigh number as a function of the power-law index and the intensity of the magnetic field. We use nonlinear parallel flow theory to find some explicit solutions of the problem, and we use finite difference numerical simulations to solve the full nonlinear equations. We show how the presence of magnetic field alters the known hydrodynamical result of Newtonian flows and power-law flows and how it causes the presence of subcritical finite amplitude convection for both pseudoplastic and dilatant fluids. We also show that in the limit of very strong magnetic field, the dissipation of energy by Joule effect dominates the dissipation of energy by shear stress and gives to the liquid an inviscid character.

Exactly solvable relativistic model with the anomalous interaction

NASA Astrophysics Data System (ADS)

Ferraro, Elena; Messina, Antonino; Nikitin, A. G.

2010-04-01

A special class of Dirac-Pauli equations with time-like vector potentials of an external field is investigated. An exactly solvable relativistic model describing the anomalous interaction of a neutral Dirac fermion with a cylindrically symmetric external electromagnetic field is presented. The related external field is a superposition of the electric field generated by a charged infinite filament and the magnetic field generated by a straight line current. In the nonrelativistic approximation the considered model is reduced to the integrable Pron’ko-Stroganov model.

Decreasing Temporal Lobe Dose With Five-Field Intensity-Modulated Radiotherapy for Treatment of Pituitary Macroadenomas

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

Parhar, Preeti K.; Duckworth, Tamara; Shah, Parinda

2010-10-01

Purpose: To compare temporal lobe dose delivered by three pituitary macroadenoma irradiation techniques: three-field three-dimensional conformal radiotherapy (3D-CRT), three-field intensity-modulated radiotherapy (3F IMRT), and a proposed novel alternative of five-field IMRT (5F IMRT). Methods and Materials: Computed tomography-based external beam radiotherapy planning was performed for 15 pituitary macroadenoma patients treated at New York University between 2002 and 2007 using: 3D-CRT (two lateral, one midline superior anterior oblique [SAO] beams), 3F IMRT (same beam angles), and 5F IMRT (same beam angles with additional right SAO and left SAO beams). Prescription dose was 45 Gy. Target volumes were: gross tumor volume (GTV)more » = macroadenoma, clinical target volume (CTV) = GTV, and planning target volume = CTV + 0.5 cm. Structure contouring was performed by two radiation oncologists guided by an expert neuroradiologist. Results: Five-field IMRT yielded significantly decreased temporal lobe dose delivery compared with 3D-CRT and 3F IMRT. Temporal lobe sparing with 5F IMRT was most pronounced at intermediate doses: mean V25Gy (% of total temporal lobe volume receiving {>=}25 Gy) of 13% vs. 28% vs. 29% for right temporal lobe and 14% vs. 29% vs. 30% for left temporal lobe for 5F IMRT, 3D-CRT, and 3F IMRT, respectively (p < 10{sup -7} for 5F IMRT vs. 3D-CRT and 5F IMRT vs. 3F IMRT). Five-field IMRT plans did not compromise target coverage, exceed normal tissue dose constraints, or increase estimated brain integral dose. Conclusions: Five-field IMRT irradiation technique results in a statistically significant decrease in the dose to the temporal lobes and may thus help prevent neurocognitive sequelae in irradiated pituitary macroadenoma patients.« less

Magnetic Torque in Single Crystal Ni-Mn-Ga

NASA Astrophysics Data System (ADS)

Hobza, Anthony; Müllner, Peter

2017-06-01

Magnetic shape memory alloys deform in an external magnetic field in two distinct ways: by axial straining—known as magnetic-field-induced strain—and by bending when exposed to torque. Here, we examine the magnetic torque that a magnetic field exerts on a long Ni-Mn-Ga rod. A single crystal specimen of Ni-Mn-Ga was constrained with respect to bending and subjected to an external magnetic field. The torque required to rotate the specimen in the field was measured as a function of the orientation of the sample with the external magnetic field, strain, and the magnitude of the external magnetic field. The torque was analyzed based on the changes in the free energy with the angle between the field and the sample. The contributions of magnetocrystalline anisotropy and shape anisotropy to the Zeeman energy determine the net torque. The torque is large when magneotcrystalline and shape anisotropies act synergistically and small when these anisotropies act antagonistically.

Fluctuations of the partition function in the generalized random energy model with external field

NASA Astrophysics Data System (ADS)

Bovier, Anton; Klimovsky, Anton

2008-12-01

We study Derrida's generalized random energy model (GREM) in the presence of uniform external field. We compute the fluctuations of the ground state and of the partition function in the thermodynamic limit for all admissible values of parameters. We find that the fluctuations are described by a hierarchical structure which is obtained by a certain coarse graining of the initial hierarchical structure of the GREM with external field. We provide an explicit formula for the free energy of the model. We also derive some large deviation results providing an expression for the free energy in a class of models with Gaussian Hamiltonians and external field. Finally, we prove that the coarse-grained parts of the system emerging in the thermodynamic limit tend to have a certain optimal magnetization, as prescribed by the strength of the external field and by parameters of the GREM.

Instabilities of Current Carrying Torus

NASA Astrophysics Data System (ADS)

Liu, Wenjuan; Qiu, J.

2010-05-01

We investigate the initial equilibrium and stability conditions for an uniform current-carrying plasma ring with a non-trivial toroidal magnetic field Bt. Realistic parameters comparable to observations are used to describe the magnetic field inside and outside the torus. The external poloidal magnetic field is assumed to fall off as a power function with decay index n (n = - d log (Bex) /d log(h)). The parameter space is explored to find all initial equilibrium solutions, at which perturbation is introduced. It is shown that with non-trivial toroidal field, the current ring attains equilibrium with a weaker external field. It is also shown that the torus attains equilibrium at higher altitude when the external field decays more rapidly (greater n) or the ratio of the toroidal flux in the torus to the external field increases. We further study stabilities of the torus at equilibrium by defining a critical decay index ncr (Kliem and Török 2006). A sufficiently strong toroidal field can completely suppress the torus instability due to the current hoop force. With a weak toroidal field, similar to the case of Bt=0, the instability occurs when the external magnetic field declines rapidly with height when the field decay index n>ncr. For realistic sets of parameters, the equilibrium height is within 10 solar radii, and the effective ncr is in the range of 1.0-1.6. The critical decay index increases when the ratio of the toroidal flux to the external field decreases. This work is supported by NSF CAREER grant ATM-0748428.

High sensitivity optical measurement of skin gloss

PubMed Central

Ezerskaia, Anna; Ras, Arno; Bloemen, Pascal; Pereira, Silvania F.; Urbach, H. Paul; Varghese, Babu

2017-01-01

We demonstrate a low-cost optical method for measuring the gloss properties with improved sensitivity in the low gloss regime, relevant for skin gloss properties. The gloss estimation method is based on, on the one hand, the slope of the intensity gradient in the transition regime between specular and diffuse reflection and on the other on the sum over the intensities of pixels above threshold, derived from a camera image obtained using unpolarized white light illumination. We demonstrate the improved sensitivity of the two proposed methods using Monte Carlo simulations and experiments performed on ISO gloss calibration standards with an optical prototype. The performance and linearity of the method was compared with different professional gloss measurement devices based on the ratio of specular to diffuse intensity. We demonstrate the feasibility for in-vivo skin gloss measurements by quantifying the temporal evolution of skin gloss after application of standard paraffin cream bases on skin. The presented method opens new possibilities in the fields of cosmetology and dermatopharmacology for measuring the skin gloss and resorption kinetics and the pharmacodynamics of various external agents. PMID:29026683

High sensitivity optical measurement of skin gloss.

PubMed

Ezerskaia, Anna; Ras, Arno; Bloemen, Pascal; Pereira, Silvania F; Urbach, H Paul; Varghese, Babu

2017-09-01

We demonstrate a low-cost optical method for measuring the gloss properties with improved sensitivity in the low gloss regime, relevant for skin gloss properties. The gloss estimation method is based on, on the one hand, the slope of the intensity gradient in the transition regime between specular and diffuse reflection and on the other on the sum over the intensities of pixels above threshold, derived from a camera image obtained using unpolarized white light illumination. We demonstrate the improved sensitivity of the two proposed methods using Monte Carlo simulations and experiments performed on ISO gloss calibration standards with an optical prototype. The performance and linearity of the method was compared with different professional gloss measurement devices based on the ratio of specular to diffuse intensity. We demonstrate the feasibility for in-vivo skin gloss measurements by quantifying the temporal evolution of skin gloss after application of standard paraffin cream bases on skin. The presented method opens new possibilities in the fields of cosmetology and dermatopharmacology for measuring the skin gloss and resorption kinetics and the pharmacodynamics of various external agents.

Electromyographic activity of selected scapular stabilizers during glenohumeral internal and external rotation contractions.

PubMed

Schachter, Aaron K; McHugh, Malachy P; Tyler, Timothy F; Kreminic, Ian J; Orishimo, Karl F; Johnson, Christopher; Ben-Avi, Simon; Nicholas, Stephen J

2010-09-01

An important synergistic relationship exists between the scapular stabilizers and the glenohumeral rotators. Information on the relative contribution of the scapular stabilizers to glenohumeral rotation would be useful for exercise prescription for overhead athletes and for patients with shoulder pathology. We hypothesized that the scapular stabilizers would be highly active during both maximal and submaximal internal and external rotation. Eight healthy male volunteers (16 shoulders) performed internal and external glenohumeral rotation testing at maximal and submaximal intensities. They also performed a scapular retraction rowing exercise at maximal and submaximal levels. Electromyographic (EMG) signals were recorded from the infraspinatus, pectoralis major, serratus anterior, and middle trapezius. Values were compared among muscle groups, among individual muscles at different intensity levels, and among individual muscles at different points in the arc of motion. For submaximal glenohumeral internal rotation, activity in the scapular stabilizers was not different (P = .1-.83) from activity in the internal rotator throughout the range of motion. For the initial two-thirds of maximal internal rotation, middle trapezius activity and pectoralis major activity were higher (P < .05) than serratus anterior activity. For submaximal external rotation, activity in the scapular stabilizers during the middle phase of the motion was higher (P < .05) than activity in the external rotators. For maximal external rotation these differences were present throughout the motion with middle trapezius activity exceeding 100% maximal voluntary contraction. The scapular stabilizers functioned at a similar or higher intensity than the glenohumeral rotators during internal and external rotation. This highlights the importance of training the scapular stabilizers in upper extremity athletes and in patients with shoulder pathology. (c) 2010 Journal of Shoulder and Elbow Surgery Board of Trustees. Published by Mosby, Inc. All rights reserved.

The MFA ground states for the extended Bose-Hubbard model with a three-body constraint

NASA Astrophysics Data System (ADS)

Panov, Yu. D.; Moskvin, A. S.; Vasinovich, E. V.; Konev, V. V.

2018-05-01

We address the intensively studied extended bosonic Hubbard model (EBHM) with truncation of the on-site Hilbert space to the three lowest occupation states n = 0 , 1 , 2 in frames of the S = 1 pseudospin formalism. Similar model was recently proposed to describe the charge degree of freedom in a model high-T c cuprate with the on-site Hilbert space reduced to the three effective valence centers, nominally Cu1+;2+;3+. With small corrections the model becomes equivalent to a strongly anisotropic S = 1 quantum magnet in an external magnetic field. We have applied a generalized mean-field approach and quantum Monte-Carlo technique for the model 2D S = 1 system with a two-particle transport to find the ground state phase with its evolution under deviation from half-filling.

The IRAS radiation environment

NASA Technical Reports Server (NTRS)

Stassinopoulos, E. G.

1978-01-01

Orbital flux integration for three selected mission altitudes and geographic instantaneous flux-mapping for nominal flight-path altitude were used to determine the external charged particle radiation predicted for the Infrared Astronomy Satellite. A current field model was used for magnetic field definitions for three nominal circular trajectories and for the geographic mapping positions. Innovative analysis features introduced include (1) positional fluxes as a function of time and energy for the most severe pass through the South Atlantic Anomaly; (2) total positional doses as a function of time and shield thickness; (3) comparison mapping fluxes for ratios of positional intensities to orbit integrated averages; and (4) statistical exposure-time history of a trajectory as a function of energy indicating, in percent of total mission duration, the time intervals over which the instantaneous fluxes would exceed the orbit integrated averages. Results are presented in tables and graphs.

Effect of external magnetic field on locking range of spintronic feedback nano oscillator

NASA Astrophysics Data System (ADS)

Singh, Hanuman; Konishi, K.; Bose, A.; Bhuktare, S.; Miwa, S.; Fukushima, A.; Yakushiji, K.; Yuasa, S.; Kubota, H.; Suzuki, Y.; Tulapurkar, A. A.

2018-05-01

In this work we have studied the effect of external applied magnetic field on the locking range of spintronic feedback nano oscillator. Injection locking of spintronic feedback nano oscillator at integer and fractional multiple of its auto oscillation frequency was demonstrated recently. Here we show that the locking range increases with increasing external magnetic field. We also show synchronization of spintronic feedback nano oscillator at integer (n=1,2,3) multiples of auto oscillation frequency and side band peaks at higher external magnetic field values. We have verified experimental results with macro-spin simulation using similar conditions as used for the experimental study.

An initial physical mechanism in the treatment of neurologic disorders with externally applied pico Tesla magnetic fields.

PubMed

Jacobson, J I; Yamanashi, W S

1995-04-01

The recent clinical studies describing the treatment of some neurological disorders with an externally applied pico Tesla (10(-12) Tesla, or 10(-8) gauss) magnetic field are considered from a physical view point. An equation relating the intrinsic (or rest) energy of a charged particle of mass m with its energy of interaction in an externally applied magnetic field B is presented. The equation represents an initial basic physical interaction as a part of a more complex biological mechanism to explain the therapeutic effects of externally applied magnetic fields in these and other neurologic disorders.

A physical mechanism in the treatment of neurologic disorders with externally applied pico Tesla magnetic fields.

PubMed

Jacobson, J I; Yamanashi, W S

1995-06-01

The clinical studies describing the treatment of some neurological disorders with an externally applied pico Tesla (10R Tesla, or 10(-8) gauss) magnetic field are considered from a physical view point. An equation relating the intrinsic or "rest" energy of a charged particle of mass with its energy of interaction in an externally applied magnetic field B is presented. The equation is proposed to represent an initial basic physical interaction as a part of a more complex biological mechanism to explain the therapeutic effects of externally applied magnetic fields in these and other neurologic disorders.

Dipole interaction of the Quincke rotating particles.

PubMed

Dolinsky, Yu; Elperin, T

2012-02-01

We study the behavior of particles having a finite electric permittivity and conductivity in a weakly conducting fluid under the action of the external electric field. We consider the case when the strength of the external electric field is above the threshold, and particles rotate due to the Quincke effect. We determine the magnitude of the dipole interaction of the Quincke rotating particles and the shift of frequency of the Quincke rotation caused by the dipole interaction between the particles. It is demonstrated that depending on the mutual orientation of the vectors of angular velocities of particles, vector-directed along the straight line between the centers of the particles and the external electric field strength vector, particles can attract or repel each other. In contrast to the case of nonrotating particles when the magnitude of the dipole interaction increases with the increase of the strength of the external electric field, the magnitude of the dipole interaction of the Quincke rotating particles either does not change or decreases with the increase of the strength of the external electric field depending on the strength of the external electric field and electrodynamic parameters of the particles.

Dipole interaction of the Quincke rotating particles

NASA Astrophysics Data System (ADS)

Dolinsky, Yu.; Elperin, T.

2012-02-01

We study the behavior of particles having a finite electric permittivity and conductivity in a weakly conducting fluid under the action of the external electric field. We consider the case when the strength of the external electric field is above the threshold, and particles rotate due to the Quincke effect. We determine the magnitude of the dipole interaction of the Quincke rotating particles and the shift of frequency of the Quincke rotation caused by the dipole interaction between the particles. It is demonstrated that depending on the mutual orientation of the vectors of angular velocities of particles, vector-directed along the straight line between the centers of the particles and the external electric field strength vector, particles can attract or repel each other. In contrast to the case of nonrotating particles when the magnitude of the dipole interaction increases with the increase of the strength of the external electric field, the magnitude of the dipole interaction of the Quincke rotating particles either does not change or decreases with the increase of the strength of the external electric field depending on the strength of the external electric field and electrodynamic parameters of the particles.

Hubbard pair cluster in the external fields. Studies of the magnetic properties

NASA Astrophysics Data System (ADS)

Balcerzak, T.; Szałowski, K.

2018-06-01

The magnetic properties of the two-site Hubbard cluster (dimer or pair), embedded in the external electric and magnetic fields and treated as the open system, are studied by means of the exact diagonalization of the Hamiltonian. The formalism of the grand canonical ensemble is adopted. The phase diagrams, on-site magnetizations, spin-spin correlations, mean occupation numbers and hopping energy are investigated and illustrated in figures. An influence of temperature, mean electron concentration, Coulomb U parameter and external fields on the quantities of interest is presented and discussed. In particular, the anomalous behaviour of the magnetization and correlation function vs. temperature near the critical magnetic field is found. Also, the effect of magnetization switching by the external fields is demonstrated.

Tunable Holstein model with cold polar molecules

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

Herrera, Felipe; Krems, Roman V.

2011-11-15

We show that an ensemble of polar molecules trapped in an optical lattice can be considered as a controllable open quantum system. The coupling between collective rotational excitations and the motion of the molecules in the lattice potential can be controlled by varying the strength and orientation of an external dc electric field as well as the intensity of the trapping laser. The system can be described by a generalized Holstein Hamiltonian with tunable parameters and can be used as a quantum simulator of excitation energy transfer and polaron phenomena. We show that the character of excitation energy transfer canmore » be modified by tuning experimental parameters.« less

Optical memory based on quantized atomic center-of-mass motion.

PubMed

Lopez, J P; de Almeida, A J F; Felinto, D; Tabosa, J W R

2017-11-01

We report a new type of optical memory using a pure two-level system of cesium atoms cooled by the magnetically assisted Sisyphus effect. The optical information of a probe field is stored in the coherence between quantized vibrational levels of the atoms in the potential wells of a 1-D optical lattice. The retrieved pulse shows Rabi oscillations with a frequency determined by the reading beam intensity and are qualitatively understood in terms of a simple theoretical model. The exploration of the external degrees of freedom of an atom may add another capability in the design of quantum-information protocols using light.

Stochastic memory: Memory enhancement due to noise

NASA Astrophysics Data System (ADS)

Stotland, Alexander; di Ventra, Massimiliano

2012-01-01

There are certain classes of resistors, capacitors, and inductors that, when subject to a periodic input of appropriate frequency, develop hysteresis loops in their characteristic response. Here we show that the hysteresis of such memory elements can also be induced by white noise of appropriate intensity even at very low frequencies of the external driving field. We illustrate this phenomenon using a physical model of memory resistor realized by TiO2 thin films sandwiched between metallic electrodes and discuss under which conditions this effect can be observed experimentally. We also discuss its implications on existing memory systems described in the literature and the role of colored noise.

Field Effect Transistor Behavior in Electrospun Polyaniline/Polyethylene Oxide Nanofibers

NASA Technical Reports Server (NTRS)

Miranda, Felix A.; Theofylaktos, Noulle; Robinson, Daryl C.; Mueller, Carl H.; Pinto, Nicholas J.

2004-01-01

Novel translators and logic devices based on nanotechnology concepts are under intense development. The potential for ultra-low power circuitry makes nanotechnology attractive for applications such as digital electronics and sensors. Furthermore, the ability to form devices on flexible substrates expands the range of applications where electronic circuitry can be introduced. For NASA, nonotechndogy offers opportunities for increased onboard data processing and thus autonomous decision-making ability, ad novel sensors that detect and respond to external stimuli with few oversight requirements. The goat of this work is to demonstrate transistor behavior in polyaniline/ polyethylene oxide nanofibers, thus creating a foundation for future logic devices.

Confirmatory Factor Analysis and Test-Retest Reliability of the Alcohol and Drug Confrontation Scale (ADCS)

PubMed Central

Polcin, Douglas L.; Galloway, Gantt P.; Bond, Jason; Korcha, Rachael; Greenfield, Thomas K.

2008-01-01

The addiction field lacks an accepted definition and reliable measure of confrontation. The Alcohol and Drug Confrontation Scale (ADCS) defines confrontation as warnings about the potential consequences of substance use. To assess psychometric properties, 323 individual entering recovery houses in U.S. urban and suburban areas were interviewed between 2003 and 2005 (20% women, 68% white). Analyses included test-retest reliability, confirmatory factor analysis, and measures of internal consistency. Findings support the ADCS as a reliable way of assessing two factors: Internal Support and External intensity. Confrontation was experienced as supportive, accurate and helpful. Additional studies should assess confrontation in different contexts. PMID:20686635

Theoretical analysis of flux amplification by soft magnetic material in a putative biological magnetic-field receptor.

PubMed

Shcherbakov, Valera P; Winklhofer, Michael

2010-03-01

Birds are endowed with a magnetic sense that allows them to detect Earth's magnetic field and to use it for orientation. Physiological and behavioral experiments have shown the upper beak to host a magnetoreceptor. Putative magnetoreceptive structures in the beak are nerve terminals that each contain a dozen or so of micrometer-sized clusters of superparamagnetic nanocrystals made of magnetite/maghemite and numerous electron-opaque platelets filled with a so far unidentified, amorphous ferric iron compound. The platelets typically form chainlike structures, which have been proposed to function as magnetic flux focusers for detecting the intensity of the geomagnetic field. Here, we test that proposition from first principles and develop an unconstrained model to determine the equilibrium distribution of magnetization along a linear chain of platelets which we assume to behave magnetically soft and to have no magnetic remanence. Our analysis, which is valid for arbitrary values of the intrinsic magnetic susceptibility chi , shows that chi needs to be much greater than unity to amplify the external field by two orders of magnitude in a chain of platelets. However, the high amplification is confined to the central region of the chain and subsides quadratically toward the ends of the chain. For large values of chi , the possibility opens up of realizing magnetoreceptor mechanisms on the basis of attraction forces between adjacent platelets in a linear chain. The force in the central region of the chain may amount to several pN, which would be sufficient to convert magnetic input energy into mechanical output energy. The striking feature of an ensemble of platelets is its ability to organize into tightly spaced chains under the action of an external field of given strength. We discuss how this property can be exploited for a magnetoreception mechanism.

Communication: Influence of external static and alternating electric fields on water from long-time non-equilibrium ab initio molecular dynamics

NASA Astrophysics Data System (ADS)

Futera, Zdenek; English, Niall J.

2017-07-01

The response of water to externally applied electric fields is of central relevance in the modern world, where many extraneous electric fields are ubiquitous. Historically, the application of external fields in non-equilibrium molecular dynamics has been restricted, by and large, to relatively inexpensive, more or less sophisticated, empirical models. Here, we report long-time non-equilibrium ab initio molecular dynamics in both static and oscillating (time-dependent) external electric fields, therefore opening up a new vista in rigorous studies of electric-field effects on dynamical systems with the full arsenal of electronic-structure methods. In so doing, we apply this to liquid water with state-of-the-art non-local treatment of dispersion, and we compute a range of field effects on structural and dynamical properties, such as diffusivities and hydrogen-bond kinetics.

Strong Magnetic Field Fluctuations within Filamentary Auroral Density Cavities Interpreted as VLF Saucer Sources

NASA Technical Reports Server (NTRS)

Knudsen, D. L.; Kabirzadeh, R.; Burchill, J. K.; Pfaff, Robert F.; Wallis, D. D.; Bounds, S. R.; Clemmons, J. H.; Pincon, J.-L.

2012-01-01

The Geoelectrodynamics and Electro-Optical Detection of Electron and SuprathermalIon Currents (GEODESIC) sounding rocket encountered more than 100 filamentary densitycavities associated with enhanced plasma waves at ELF (3 kHz) and VLF (310 kHz)frequencies and at altitudes of 800990 km during an auroral substorm. These cavities weresimilar in size (20 m diameter in most cases) to so-called lower-hybrid cavities (LHCs)observed by previous sounding rockets and satellites; however, in contrast, many of theGEODESIC cavities exhibited up to tenfold enhancements in magnetic wave powerthroughout the VLF band. GEODESIC also observed enhancements of ELF and VLFelectric fields both parallel and perpendicular to the geomagnetic field B0 within cavities,though the VLF E field increases were often not as large proportionally as seen in themagnetic fields. This behavior is opposite to that predicted by previously published theoriesof LHCs based on passive scattering of externally incident auroral hiss. We argue thatthe GEODESIC cavities are active wave generation sites capable of radiating VLF wavesinto the surrounding plasma and producing VLF saucers, with energy supplied by cold,upward flowing electron beams composing the auroral return current. This interpretation issupported by the observation that the most intense waves, both inside and outside cavities,occurred in regions where energetic electron precipitation was largely inhibited orabsent altogether. We suggest that the wave-enhanced cavities encountered by GEODESICwere qualitatively different from those observed by earlier spacecraft because of thefortuitous timing of the GEODESIC launch, which placed the payload at apogee within asubstorm-related return current during its most intense phase, lasting only a few minutes.

Effect of external magnetic field on the crystal growth of nano-structured Zn xMn 1- x+ yZr yFe 2-2 yO 4 thin films

NASA Astrophysics Data System (ADS)

Anjum, Safia; Rafique, M. S.; Khaleeq-ur-Rahaman, M.; Siraj, K.; Usman, Arslan; Ahsan, A.; Naseem, S.; Khan, K.

2011-06-01

Zn 0.2Mn 0.81Zr 0.01Fe 1.98O 4 and Zn 0.2Mn 0.83Zr 0.03Fe 1.94O 4 thin films with different concentrations of Mn and Zr have been deposited on single crystal n-Si (400) at room temperature (RT) by pulse laser deposition technique (PLD). The films have been deposited under two conditions: (i) with the applied external magnetic field across the propagation of the plume (ii) without applied external magnetic field ( B=0). XRD results show the films have spinel cubic structure when deposited in the presence of magnetic field. SEM and AFM observations clearly show the effect of external applied magnetic field on the growth of films in terms of small particle size, improved uniformity and lower r.m.s. roughness. Thin films deposited under the influence of external magnetic field exhibit higher magnetization as measured by the VSM. The optical band gap energy Eg, refractive index n, reflection, absorption and the thickness of the thin films were measured by spectroscopy ellipsometer. The reflection of Zn 0.2Mn 0.83Zr 0.03Fe 1.94O 4 thin films is higher than Zn 0.2Mn 0.81Zr 0.01Fe 1.98O 4 thin films due to the greater concentration of Zr. The thicknesses of the thin films under the influence of external magnetic field are larger than the films grown without field for both samples. The optical band gap energy Eg decreases with increasing film thickness. The films with external magnetic field are found highly absorbing in nature due to the larger film thickness.

Method and apparatus for the formation of a spheromak plasma

DOEpatents

Jardin, Stephen C.; Yamada, Masaaki; Furth, Harold P.; Okabayashi, Mitcheo

1984-01-01

An inductive method and apparatus for forming detached spheromak plasma using a thin-walled metal toroidal ring, with external current leads and internal poloidal and toroidal field coils located inside a vacuum chamber filled with low density hydrogen gas and an external axial field generating coil. The presence of a current in the poloidal field coils, and an externally generated axial field sets up the initial poloidal field configuration in which the field is strongest toward the major axis of the toroid. The internal toroidal-field-generating coil is then pulsed on, ionizing the gas and inducing poloidal current and toroidal magnetic field into the plasma region in the sleeve exterior to and adjacent to the ring and causing the plasma to expand away from the ring and toward the major axis. Next the current in the poloidal field coils in the ring is reversed. This induces toroidal current into the plasma and causes the poloidal magnetic field lines to reconnect. The reconnection continues until substantially all of the plasma is formed in a separated spheromak configuration held in equilibrium by the initial external field.

Real-time in vivo Cherenkoscopy imaging during external beam radiation therapy.

PubMed

Zhang, Rongxiao; Gladstone, David J; Jarvis, Lesley A; Strawbridge, Rendall R; Jack Hoopes, P; Friedman, Oscar D; Glaser, Adam K; Pogue, Brian W

2013-11-01

Cherenkov radiation is induced when charged particles travel through dielectric media (such as biological tissue) faster than the speed of light through that medium. Detection of this radiation or excited luminescence during megavoltage external beam radiotherapy (EBRT) can allow emergence of a new approach to superficial dose estimation, functional imaging, and quality assurance for radiation therapy dosimetry. In this letter, the first in vivo Cherenkov images of a real-time Cherenkoscopy during EBRT are presented. The imaging system consisted of a time-gated intensified charge coupled device (ICCD) coupled with a commercial lens. The ICCD was synchronized to the linear accelerator to detect Cherenkov photons only during the 3.25-μs radiation bursts. Images of a tissue phantom under irradiation show that the intensity of Cherenkov emission is directly proportional to radiation dose, and images can be acquired at 4.7 frames/s with SNR>30. Cherenkoscopy was obtained from the superficial regions of a canine oral tumor during planned, Institutional Animal Care and Use Committee approved, conventional (therapeutically appropriate) EBRT irradiation. Coregistration between photography and Cherenkoscopy validated that Cherenkov photons were detected from the planned treatment region. Real-time images correctly monitored the beam field changes corresponding to the planned dynamic wedge movement, with accurate extent of overall beam field, and expected cold and hot regions.

Characterization of magnetic force microscopy probe tip remagnetization for measurements in external in-plane magnetic fields

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

Weis, Tanja; Engel, Dieter; Ehresmann, Arno

2008-12-15

A quantitative analysis of magnetic force microscopy (MFM) images taken in external in-plane magnetic fields is difficult because of the influence of the magnetic field on the magnetization state of the magnetic probe tip. We prepared calibration samples by ion bombardment induced magnetic patterning with a topographically flat magnetic pattern magnetically stable in a certain external magnetic field range for a quantitative characterization of the MFM probe tip magnetization in point-dipole approximation.

Stable solitary waves in super dense plasmas at external magnetic fields

NASA Astrophysics Data System (ADS)

Ghaani, Azam; Javidan, Kurosh; Sarbishaei, Mohsen

2015-07-01

Propagation of localized waves in a Fermi-Dirac distributed super dense matter at the presence of strong external magnetic fields is studied using the reductive perturbation method. We have shown that stable solitons can be created in such non-relativistic fluids in the presence of an external magnetic field. Such solitary waves are governed by the Zakharov-Kuznetsov (ZK) equation. Properties of solitonic solutions are studied in media with different values of background mass density and strength of magnetic field.

Magnetization-induced second-harmonic generation in electrochemically synthesized magnetic films of ternary metal Prussian blue analogs

NASA Astrophysics Data System (ADS)

Ikeda, Katsuyoshi; Ohkoshi, Shin-ichi; Hashimoto, Kazuhito

2003-02-01

We observed magnetic field effects on transmitted second-harmonic generation (SHG) in electrochemically synthesized (FexIICr1-xII)1.5[CrIII(CN)6]ṡ7.5H2O magnetic films. These films showed a variety of temperature dependences for SH intensities below magnetic phase transition temperatures (TC). The SH intensity for x=0.25 increased monotonically with decreasing temperature and that for x=0.13 exhibited a minimum value around the magnetic compensation temperature under a zero magnetic field. These temperature dependences resembled those of the absolute value of magnetization, indicating that the magnetic strain of the films is responsible for the increase in SH below TC. In addition, the polarization of SH light was rotated by an applied external magnetic field. The observed SH rotation angle of 1.3° was much larger than the Faraday rotation angle of 0.079° at 388 nm. This SH rotation can be understood by the mechanism of magnetization-induced SHG caused by interaction between the electric polarization along the out-of-plane of film and spontaneous magnetization. The magnetic linear term [χijkLmagn(1)] contributed particularly to the SH rotation. The value of the magnetic linear tensor component relative to the crystallographic tensor component [|χyyyXmagn(1)|/|χzyycr], which induced the SH rotation, was 0.023 at 50 K under 10 kOe.

Contacts in the Office of Pesticide Programs, Field and External Affairs Division

EPA Pesticide Factsheets

Contact the Field and External Affairs Division (FEAD) about program policies and regulations; legislation and congressional interaction; regional, state, and tribal coordination and assistance; international and field programs; and communication activity.

Nonlinear ultrasonic imaging method for closed cracks using subtraction of responses at different external loads.

PubMed

Ohara, Yoshikazu; Horinouchi, Satoshi; Hashimoto, Makoto; Shintaku, Yohei; Yamanaka, Kazushi

2011-08-01

To improve the selectivity of closed cracks for objects other than cracks in ultrasonic imaging, we propose an extension of a novel imaging method, namely, subharmonic phased array for crack evaluation (SPACE) as well as another approach using the subtraction of responses at different external loads. By applying external static or dynamic loads to closed cracks, the contact state in the cracks varies, resulting in an intensity change of responses at cracks. In contrast, objects other than cracks are independent of external load. Therefore, only cracks can be extracted by subtracting responses at different loads. In this study, we performed fundamental experiments on a closed fatigue crack formed in an aluminum alloy compact tension (CT) specimen using the proposed method. We examined the static load dependence of SPACE images and the dynamic load dependence of linear phased array (PA) images by simulating the external loads with a servohydraulic fatigue testing machine. By subtracting the images at different external loads, we show that this method is useful in extracting only the intensity change of responses related to closed cracks, while canceling the responses of objects other than cracks. Copyright © 2010 Elsevier B.V. All rights reserved.

Magnetic ground state and magnon-phonon interaction in multiferroic h -YMnO3

NASA Astrophysics Data System (ADS)

Holm, S. L.; Kreisel, A.; Schäffer, T. K.; Bakke, A.; Bertelsen, M.; Hansen, U. B.; Retuerto, M.; Larsen, J.; Prabhakaran, D.; Deen, P. P.; Yamani, Z.; Birk, J. O.; Stuhr, U.; Niedermayer, Ch.; Fennell, A. L.; Andersen, B. M.; Lefmann, K.

2018-04-01

Inelastic neutron scattering has been used to study the magnetoelastic excitations in the multiferroic manganite hexagonal YMnO3. An avoided crossing is found between magnon and phonon modes close to the Brillouin zone boundary in the (a ,b ) plane. Neutron polarization analysis reveals that this mode has mixed magnon-phonon character. An external magnetic field along the c axis is observed to cause a linear field-induced splitting of one of the spin-wave branches. A theoretical description is performed, using a Heisenberg model of localized spins, acoustic phonon modes, and a magnetoelastic coupling via the single-ion magnetostriction. The model quantitatively reproduces the dispersion and intensities of all modes in the full Brillouin zone, describes the observed magnon-phonon hybridized modes, and quantifies the magnetoelastic coupling. The combined information, including the field-induced magnon splitting, allows us to exclude several of the earlier proposed models and point to the correct magnetic ground state symmetry, and provides an effective dynamic model relevant for the multiferroic hexagonal manganites.

Enhancement of lateral flow assay performance by electromagnetic relocation of reporter particles

PubMed Central

Jacinto, Maria João; Trabuco, João R. C.; Vu, Binh V.; Garvey, Gavin; Khodadady, Mohammad; Azevedo, Ana M.; Aires-Barros, Maria Raquel; Chang, Long; Kourentzi, Katerina; Litvinov, Dmitri

2018-01-01

Lateral flow assays (LFAs) are a widely-used point-of care diagnostic format, but suffer from limited analytical sensitivity, especially when read by eye. It has recently been reported that LFA performance can be improved by using magnetic reporter particles and an external magnetic field applied at the test line. The mechanism of sensitivity/performance enhancement was suggested to be concentration/retardation of reporter particles at the test line. Here we demonstrate an additional mechanism of particle relocation where reporter particles from the lower depths of the translucent LFA strip relocate to more-visible locations nearer to the top surface, producing a more visible signal. With a magnetic field we observed an improvement in sensitivity of human chorionic gonadotropin (hCG) detection from 1.25 ng/mL to 0.31 ng/mL. We also observed an increase of the color intensity per particle in test lines when the magnetic field was present. PMID:29309424

Human Aquaporin 4 Gating Dynamics under Perpendicularly-Oriented Electric-Field Impulses: A Molecular Dynamics Study

PubMed Central

Marracino, Paolo; Liberti, Micaela; Trapani, Erika; Burnham, Christian J.; Avena, Massimiliano; Garate, José-Antonio; Apollonio, Francesca; English, Niall J.

2016-01-01

Human aquaporin 4 has been studied using molecular dynamics (MD) simulations in the absence and presence of pulses of external static electric fields. The pulses were 10 ns in duration and 0.012–0.065 V/Å in intensity acting along both directions perpendicular to the pores. Water permeability and the dipolar response of all residues of interest (including the selectivity filter) within the pores have been studied. Results showed decreased levels of water osmotic permeability within aquaporin channels during orthogonally-oriented field impulses, although care must be taken with regard to statistical certainty. This can be explained observing enhanced “dipolar flipping” of certain key residues, especially serine 211, histidine 201, arginine 216, histidine 95 and cysteine 178. These residues are placed at the extracellular end of the pore (serine 211, histidine 201, and arginine 216) and at the cytoplasm end (histidine 95 and cysteine 178), with the key role in gating mechanism, hence influencing water permeability. PMID:27428954

Time-resolved imaging of domain pattern destruction and recovery via nonequilibrium magnetization states

NASA Astrophysics Data System (ADS)

Wessels, Philipp; Ewald, Johannes; Wieland, Marek; Nisius, Thomas; Vogel, Andreas; Viefhaus, Jens; Meier, Guido; Wilhein, Thomas; Drescher, Markus

2014-11-01

The destruction and formation of equilibrium multidomain patterns in permalloy (Ni80Fe20 ) microsquares has been captured using pump-probe x-ray magnetic circular dichroism (XMCD) spectromicroscopy at a new full-field magnetic transmission soft x-ray microscopy endstation with subnanosecond time resolution. The movie sequences show the dynamic magnetization response to intense Oersted field pulses of approximately 200-ps root mean square (rms) duration and the magnetization reorganization to the ground-state domain configuration. The measurements display how a vortex flux-closure magnetization distribution emerges out of a nonequilibrium uniform single-domain state. During the destruction of the initial vortex pattern, we have traced the motion of the central vortex core that is ejected out of the microsquare at high velocities exceeding 1 km/s. A reproducible recovery into a defined final vortex state with stable chirality and polarity could be achieved. Using an additional external bias field, the transient reversal of the square magnetization direction could be monitored and consistently reproduced by micromagnetic simulations.

Superconducting magnetoresistance in ferromagnet/superconductor/ferromagnet trilayers

PubMed Central

Stamopoulos, D.; Aristomenopoulou, E.

2015-01-01

Magnetoresistance is a multifaceted effect reflecting the diverse transport mechanisms exhibited by different kinds of plain materials and hybrid nanostructures; among other, giant, colossal, and extraordinary magnetoresistance versions exist, with the notation indicative of the intensity. Here we report on the superconducting magnetoresistance observed in ferromagnet/superconductor/ferromagnet trilayers, namely Co/Nb/Co trilayers, subjected to a parallel external magnetic field equal to the coercive field. By manipulating the transverse stray dipolar fields that originate from the out-of-plane magnetic domains of the outer layers that develop at coercivity, we can suppress the supercurrent of the interlayer. We experimentally demonstrate a scaling of the magnetoresistance magnitude that we reproduce with a closed-form phenomenological formula that incorporates relevant macroscopic parameters and microscopic length scales of the superconducting and ferromagnetic structural units. The generic approach introduced here can be used to design novel cryogenic devices that completely switch the supercurrent ‘on’ and ‘off’, thus exhibiting the ultimate magnetoresistance magnitude 100% on a regular basis. PMID:26306543

Communication: Polarizable polymer chain under external electric field in a dilute polymer solution.

PubMed

Budkov, Yu A; Kolesnikov, A L; Kiselev, M G

2015-11-28

We study the conformational behavior of polarizable polymer chain under an external homogeneous electric field within the Flory type self-consistent field theory. We consider the influence of electric field on the polymer coil as well as on the polymer globule. We show that when the polymer chain conformation is a coil, application of external electric field leads to its additional swelling. However, when the polymer conformation is a globule, a sufficiently strong field can induce a globule-coil transition. We show that such "field-induced" globule-coil transition at the sufficiently small monomer polarizabilities goes quite smoothly. On the contrary, when the monomer polarizability exceeds a certain threshold value, the globule-coil transition occurs as a dramatic expansion in the regime of first-order phase transition. The developed theoretical model can be applied to predicting polymer globule density change under external electric field in order to provide more efficient processes of polymer functionalization, such as sorption, dyeing, and chemical modification.

Diffusion of external magnetic fields into the cone-in-shell target in the fast ignition

NASA Astrophysics Data System (ADS)

Sunahara, Atsushi; Morita, Hiroki; Johzaki, Tomoyuki; Nagatomo, Hideo; Fujioka, Shinsuke; Hassanein, Ahmed; Firex Project Team

2017-10-01

We simulated the diffusion of externally applied magnetic fields into cone-in-shell target in the fast ignition. Recently, in the fast ignition scheme, the externally magnetic fields up to kilo-Tesla is used to guide fast electrons to the high-dense imploded core. In order to study the profile of the magnetic field, we have developed 2D cylindrical Maxwell equation solver with Ohm's law, and carried out simulations of diffusion of externally applied magnetic fields into a cone-in-shell target. We estimated the conductivity of the cone and shell target based on the assumption of Saha-ionization equilibrium. Also, we calculated the temporal evolution of the target temperature heated by the eddy current driven by temporal variation of magnetic fields, based on the accurate equation of state. Both, the diffusion of magnetic field and the increase of target temperature interact with each other. We present our results of temporal evolution of the magnetic field and its diffusion into the cone and shell target.

Nonlinear modeling of forced magnetic reconnection in slab geometry with NIMROD

NASA Astrophysics Data System (ADS)

Beidler, M. T.; Callen, J. D.; Hegna, C. C.; Sovinec, C. R.

2017-05-01

The nonlinear, extended-magnetohydrodynamic (MHD) code NIMROD is benchmarked with the theory of time-dependent forced magnetic reconnection induced by small resonant fields in slab geometry in the context of visco-resistive MHD modeling. Linear computations agree with time-asymptotic, linear theory of flow screening of externally applied fields. The inclusion of flow in nonlinear computations can result in mode penetration due to the balance between electromagnetic and viscous forces in the time-asymptotic state, which produces bifurcations from a high-slip state to a low-slip state as the external field is slowly increased. We reproduce mode penetration and unlocking transitions by employing time-dependent externally applied magnetic fields. Mode penetration and unlocking exhibit hysteresis and occur at different magnitudes of applied field. We also establish how nonlinearly determined flow screening of the resonant field is affected by the square of the magnitude of the externally applied field. These results emphasize that the inclusion of nonlinear physics is essential for accurate prediction of the reconnected field in a flowing plasma.

Light-intensity modulator withstands high heat fluxes

NASA Technical Reports Server (NTRS)

Maples, H. G.; Strass, H. K.

1966-01-01

Mechanism modulates and controls the intensity of luminous radiation in light beams associated with high-intensity heat flux. This modulator incorporates two fluid-cooled, externally grooved, contracting metal cylinders which when rotated about their longitudinal axes present a circular aperture of varying size depending on the degree of rotation.

A New Approach to Isolating External Magnetic Field Components in Spacecraft Measurements of the Earth's Magnetic Field Using Global Positioning System observables

NASA Technical Reports Server (NTRS)

Raymond, C.; Hajj, G.

1994-01-01

We review the problem of separating components of the magnetic field arising from sources in the Earth's core and lithosphere, from those contributions arising external to the Earth, namely ionospheric and magnetospheric fields, in spacecraft measurements of the Earth's magnetic field.

On noninvasive assessment of acoustic fields acting on the fetus

NASA Astrophysics Data System (ADS)

Antonets, V. A.; Kazakov, V. V.

2014-05-01

The aim of this study is to verify a noninvasive technique for assessing the characteristics of acoustic fields in the audible range arising in the uterus under the action of maternal voice, external sounds, and vibrations. This problem is very important in view of actively developed methods for delivery of external sounds to the uterus: music, maternal voice recordings, sounds from outside the mother's body, etc., that supposedly support development of the fetus at the prenatal stage psychologically and cognitively. However, the parameters of acoustic signals have been neither measured nor normalized, which may be dangerous for the fetus and hinder actual assessment of their impact on fetal development. The authors show that at frequencies below 1 kHz, acoustic pressure in the uterus may be measured noninvasively using a hydrophone placed in a soft capsule filled with liquid. It was found that the acoustic field at frequencies up to 1 kHz arising in the uterus under the action of an external sound field has amplitude-frequency parameters close to those of the external field; i.e., the external field penetrates the uterus with hardly any difficulty.

Parity Deformed Jaynes-Cummings Model: “Robust Maximally Entangled States”

PubMed Central

Dehghani, A.; Mojaveri, B.; Shirin, S.; Faseghandis, S. Amiri

2016-01-01

The parity-deformations of the quantum harmonic oscillator are used to describe the generalized Jaynes-Cummings model based on the λ-analog of the Heisenberg algebra. The behavior is interestingly that of a coupled system comprising a two-level atom and a cavity field assisted by a continuous external classical field. The dynamical characters of the system is explored under the influence of the external field. In particular, we analytically study the generation of robust and maximally entangled states formed by a two-level atom trapped in a lossy cavity interacting with an external centrifugal field. We investigate the influence of deformation and detuning parameters on the degree of the quantum entanglement and the atomic population inversion. Under the condition of a linear interaction controlled by an external field, the maximally entangled states may emerge periodically along with time evolution. In the dissipation regime, the entanglement of the parity deformed JCM are preserved more with the increase of the deformation parameter, i.e. the stronger external field induces better degree of entanglement. PMID:27917882

Numerical simulation of a helical shape electric arc in the external axial magnetic field

NASA Astrophysics Data System (ADS)

Urusov, R. M.; Urusova, I. R.

2016-10-01

Within the frameworks of non-stationary three-dimensional mathematical model, in approximation of a partial local thermodynamic equilibrium, a numerical calculation was made of characteristics of DC electric arc burning in a cylindrical channel in the uniform external axial magnetic field. The method of numerical simulation of the arc of helical shape in a uniform external axial magnetic field was proposed. This method consists in that that in the computational algorithm, a "scheme" analog of fluctuations for electrons temperature is supplemented. The "scheme" analogue of fluctuations increases a weak numerical asymmetry of electrons temperature distribution, which occurs randomly in the course of computing. This asymmetry can be "picked up" by the external magnetic field that continues to increase up to a certain value, which is sufficient for the formation of helical structure of the arc column. In the absence of fluctuations in the computational algorithm, the arc column in the external axial magnetic field maintains cylindrical axial symmetry, and a helical form of the arc is not observed.

Thermoelectric efficiency enhanced in a quantum dot with polarization leads, spin-flip and external magnetic field

NASA Astrophysics Data System (ADS)

Yao, Hui; Niu, Peng-Bin; Zhang, Chao; Xu, Wei-Ping; Li, Zhi-Jian; Nie, Yi-Hang

2018-03-01

We theoretically study the thermoelectric transport properties in a quantum dot system with two ferromagnetic leads, the spin-flip scattering and the external magnetic field. The results show that the spin polarization of the leads strongly influences thermoelectric coefficients of the device. For the parallel configuration the peak of figure of merit increases with the increase of polarization strength and non-collinear configuration trends to destroy the improvement of figure of merit induced by lead polarization. While the modulation of the spin-flip scattering on the figure of merit is effective only in the absence of external magnetic field or small magnetic field. In terms of improving the thermoelectric efficiency, the external magnetic field plays a more important role than spin-flip scattering. The thermoelectric efficiency can be significantly enhanced by the magnetic field for a given spin-flip scattering strength.

Particles with nonlinear electric response: Suppressing van der Waals forces by an external field.

PubMed

Soo, Heino; Dean, David S; Krüger, Matthias

2017-01-01

We study the classical thermal component of Casimir, or van der Waals, forces between point particles with highly anharmonic dipole Hamiltonians when they are subjected to an external electric field. Using a model for which the individual dipole moments saturate in a strong field (a model that mimics the charges in a neutral, perfectly conducting sphere), we find that the resulting Casimir force depends strongly on the strength of the field, as demonstrated by analytical results. For a certain angle between the external field and center-to-center axis, the fluctuation force can be tuned and suppressed to arbitrarily small values. We compare the forces between these particles with those between particles with harmonic Hamiltonians and also provide a simple formula for asymptotically large external fields, which we expect to be generally valid for the case of saturating dipole moments.

Anomalous transport from holography. Part I

NASA Astrophysics Data System (ADS)

Bu, Yanyan; Lublinsky, Michael; Sharon, Amir

2016-11-01

We revisit the transport properties induced by the chiral anomaly in a charged plasma holographically dual to anomalous U(1) V ×U(1) A Maxwell theory in Schwarzschild-AdS5. Off-shell constitutive relations for vector and axial currents are derived using various approximations generalising most of known in the literature anomaly-induced phenomena and revealing some new ones. In a weak external field approximation, the constitutive relations have all-order derivatives resummed into six momenta-dependent transport co-efficient functions: the diffusion, the electric/magnetic conductivity, and three anomaly induced functions. The latter generalise the chiral magnetic and chiral separation effects. Nonlinear transport is studied assuming presence of constant background external fields. The chiral magnetic effect, including all order nonlinearity in magnetic field, is proven to be exact when the magnetic field is the only external field that is turned on. Non-linear corrections to the constitutive relations due to electric and axial external fields are computed.

Decadal period external magnetic field variations determined via eigenanalysis

NASA Astrophysics Data System (ADS)

Shore, R. M.; Whaler, K. A.; Macmillan, S.; Beggan, C.; Velímský, J.; Olsen, N.

2016-06-01

We perform a reanalysis of hourly mean magnetic data from ground-based observatories spanning 1997-2009 inclusive, in order to isolate (after removal of core and crustal field estimates) the spatiotemporal morphology of the external fields important to mantle induction, on (long) periods of months to a full solar cycle. Our analysis focuses on geomagnetically quiet days and middle to low latitudes. We use the climatological eigenanalysis technique called empirical orthogonal functions (EOFs), which allows us to identify discrete spatiotemporal patterns with no a priori specification of their geometry -- the form of the decomposition is controlled by the data. We apply a spherical harmonic analysis to the EOF outputs in a joint inversion for internal and external coefficients. The results justify our assumption that the EOF procedure responds primarily to the long-period external inducing field contributions. Though we cannot determine uniquely the contributory source regions of these inducing fields, we find that they have distinct temporal characteristics which enable some inference of sources. An identified annual-period pattern appears to stem from a north-south seasonal motion of the background mean external field distribution. Separate patterns of semiannual and solar-cycle-length periods appear to stem from the amplitude modulations of spatially fixed background fields.

Thermophysical properties and rheological behavior of electro-rheological fluids at different temperatures

NASA Astrophysics Data System (ADS)

Korobko, Evguenia V.; Korobko, Yulia O.

2000-04-01

Fluid disperse systems, sensitive to the external electric field-electrorheological fluids, are finding increasing use in various areas of industry and technology. Their physicomechanical, electrophysical characteristics determine the valuable specific properties of the materials with assigned structure, obtainable with everwide use of electric fields, which makes it possible to substantially enhance efficiency and productiveness of technological processes and to improve the control of operational regimes of the equipment which employ fluid disperse media. The present investigations has been undertaken with the aim of studying thermophysical properties and rheophysical behavior of low-concentration ER- fluid (diatomite in transformer oil) at different temperatures. It was shown that the electric field, which changes considerably the structure of electrorheological fluid, influences effective thermal conductivity and diffusivity coefficients. Their increase with electric field intensity and the increase of the effective viscosity with temperature are connected with the increase of the conductive component of the overall heat transfer through the contact spots between the solid particles, and with intensification of electric convection in the spaces between the dispersed particles.

GCaMP expression in retinal ganglion cells characterized using a low-cost fundus imaging system

NASA Astrophysics Data System (ADS)

Chang, Yao-Chuan; Walston, Steven T.; Chow, Robert H.; Weiland, James D.

2017-10-01

Objective. Virus-transduced, intracellular-calcium indicators are effective reporters of neural activity, offering the advantage of cell-specific labeling. Due to the existence of an optimal time window for the expression of calcium indicators, a suitable tool for tracking GECI expression in vivo following transduction is highly desirable. Approach. We developed a noninvasive imaging approach based on a custom-modified, low-cost fundus viewing system that allowed us to monitor and characterize in vivo bright-field and fluorescence images of the mouse retina. AAV2-CAG-GCaMP6f was injected into a mouse eye. The fundus imaging system was used to measure fluorescence at several time points post injection. At defined time points, we prepared wholemount retina mounted on a transparent multielectrode array and used calcium imaging to evaluate the responsiveness of retinal ganglion cells (RGCs) to external electrical stimulation. Main results. The noninvasive fundus imaging system clearly resolves individual (RGCs and axons. RGC fluorescence intensity and the number of observable fluorescent cells show a similar rising trend from week 1 to week 3 after viral injection, indicating a consistent increase of GCaMP6f expression. Analysis of the in vivo fluorescence intensity trend and in vitro neurophysiological responsiveness shows that the slope of intensity versus days post injection can be used to estimate the optimal time for calcium imaging of RGCs in response to external electrical stimulation. Significance. The proposed fundus imaging system enables high-resolution digital fundus imaging in the mouse eye, based on off-the-shelf components. The long-term tracking experiment with in vitro calcium imaging validation demonstrates the system can serve as a powerful tool monitoring the level of genetically-encoded calcium indicator expression, further determining the optimal time window for following experiment.

Flowing Active Liquids in a Pipe: Hysteretic Response of Polar Flocks to External Fields

NASA Astrophysics Data System (ADS)

Morin, Alexandre; Bartolo, Denis

2018-04-01

We investigate the response of colloidal flocks to external fields. We first show that individual colloidal rollers align with external flows, as would a classical spin with magnetic fields. Assembling polar active liquids from colloidal rollers, we experimentally demonstrate their hysteretic response: Confined colloidal flocks can proceed against external flows. We theoretically explain this collective robustness, using an active hydrodynamic description, and show how orientational elasticity and confinement protect the direction of collective motion. Finally, we exploit the intrinsic bistability of confined active flows to devise self-sustained microfluidic oscillators.

Using induced electroosmotic micromixer to enhance the reproducibility of chemiluminescence intensity.

PubMed

Chen, Hsiao-Ping; Yeh, Chun-Yi; Hung, Pei-Chin; Wang, Shau-Chun

2014-02-01

In this study, induced electroosmotic vortex flows were generated using an AC electric field by one pair of external electrodes to rapidly mix luminescence reagents in a 30 μL micromixer and enhance the reproducibility of chemiluminescence (CL) assays. A solution containing the catalyst reagent ferricyanide ions (4 μL) was pipetted into a reservoir containing luminol to produce CL in the presence of hydrogen peroxide. When the added ferricyanide aliquot contacted the reservoir solution, the CL began flashing, but rapidly diminished as the ferricyanide was consumed. In such a short illumination period, the solutes could not mix homogeneously. Therefore, the reproducibility of CL intensities collected using a CCD and multiple aliquot additions was determined to be inadequate. By contrast, when the solutes were efficiently mixed after adding a ferricyanide aliquot to a micromixer, the intensity reproducibility was significantly improved. When the CL temporal profile was analyzed using a PMT, a consistent improvement in reproducibility was observed between the CL intensity and estimated CL reaction rate. Replicating the proposed device would create a multiple well plate that contains a micromixer in each reservoir; this system is compatible with conventional CL instrumentation and requires no CL enhancer to slow a reaction. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Inductively-Charged High-Temperature Superconductors And Methods Of Use

DOEpatents

Bromberg, Leslie

2003-09-16

The invention provides methods of charging superconducting materials and, in particular, methods of charging high-temperature superconducting materials. The methods generally involve cooling a superconducting material to a temperature below its critical temperature. Then, an external magnetic field is applied to charge the material at a nearly constant temperature. The external magnetic field first drives the superconducting material to a critical state and then penetrates into the material. When in the critical state, the superconducting material loses all the pinning ability and therefore is in the flux-flow regime. In some embodiments, a first magnetic field may be used to drive the superconducting material to the critical state and then a second magnetic field may be used to penetrate the superconducting material. When the external field or combination of external fields are removed, the magnetic field that has penetrated into the material remains trapped. The charged superconducting material may be used as solenoidal magnets, dipole magnets, or other higher order multipole magnets in many applications.

Improving Keyhole Stability by External Magnetic Field in Full Penetration Laser Welding

NASA Astrophysics Data System (ADS)

Li, Min; Xu, Jiajun; Huang, Yu; Rong, Youmin

2018-05-01

An external magnetic field was used to improve the keyhole stability in full penetration laser welding 316L steel. The increase of magnetic field strength gave rise to a shorter flying time of the spatter, a weaker size and brightness of the spatter, and a larger spreading area of vapor plume. This suggested that the dynamic behavior of the keyhole was stabilized by the external magnetic field. In addition, a stronger magnetic field could result in a more homogeneous distribution of laser energy, which increased the width of the weld zone, and the height of the bottom weld zone from 381 μm (0 mT) to 605 μm (50 mT). Dendrite and cellular crystal near the weld center disappeared, and grain size was refined. The external magnetic field was beneficial to the keyhole stability and improved the joint quality, because the weld pool was stirred by a Lorentz force resulting from the coupling effect of the magnetic field and inner thermocurrent.

Social Intelligence and Top Management Team: An Exploratory Study of External Knowledge Acquisition for Strategic Change in Global IT Service Providers in India

ERIC Educational Resources Information Center

Kong, Eric; Chadee, Doren; Raman, Revti

2012-01-01

This paper focuses on the processes by which firms, particularly knowledge intensive firms, can augment their overall knowledge stock by tapping into external sources of knowledge. It is argued that Top Management Teams' (TMTs') social intelligence is a critical learning capability in acquiring external knowledge that leads to strategic change.…

RichMol: A general variational approach for rovibrational molecular dynamics in external electric fields

NASA Astrophysics Data System (ADS)

Owens, Alec; Yachmenev, Andrey

2018-03-01

In this paper, a general variational approach for computing the rovibrational dynamics of polyatomic molecules in the presence of external electric fields is presented. Highly accurate, full-dimensional variational calculations provide a basis of field-free rovibrational states for evaluating the rovibrational matrix elements of high-rank Cartesian tensor operators and for solving the time-dependent Schrödinger equation. The effect of the external electric field is treated as a multipole moment expansion truncated at the second hyperpolarizability interaction term. Our fully numerical and computationally efficient method has been implemented in a new program, RichMol, which can simulate the effects of multiple external fields of arbitrary strength, polarization, pulse shape, and duration. Illustrative calculations of two-color orientation and rotational excitation with an optical centrifuge of NH3 are discussed.

Salience of Somatosensory Stimulus Modulating External-to-Internal Orienting Attention.

PubMed

Peng, Jiaxin; Chan, Sam C C; Chau, Bolton K H; Yu, Qiuhua; Chan, Chetwyn C H

2017-01-01

Shifting between one's external and internal environments involves orienting attention. Studies on differentiating subprocesses associated with external-to-internal orienting attention are limited. This study aimed to reveal the characteristics of the disengagement, shifting and reengagement subprocesses by using somatosensory external stimuli and internally generated images. Study participants were to perceive nociceptive external stimuli (External Low (E L ) or External High (E H )) induced by electrical stimulations (50 ms) followed by mentally rehearsing learned subnociceptive images (Internal Low (I L ) and Internal High (I H )). Behavioral responses and EEG signals of the participants were recorded. The three significant components elicited were: fronto-central negativity (FCN; 128-180 ms), fronto-central P2 (200-260 ms), and central P3 (320-380 ms), which reflected the three subprocesses, respectively. Differences in the FCN and P2 amplitudes during the orienting to the subnociceptive images revealed only in the E H but not E L stimulus condition that are new findings. The results indicated that modulations of the disengagement and shifting processes only happened if the external nociceptive stimuli were of high salience and the external-to-internal incongruence was large. The reengaging process reflected from the amplitude of P3 correlated significantly with attenuation of the pain intensity felt from the external nociceptive stimuli. These findings suggested that the subprocesses underlying external-to-internal orienting attention serve different roles. Disengagement subprocess tends to be stimulus dependent, which is bottom-up in nature. Shifting and reengagement tend to be top-down subprocesses, which taps on cognitive control. This subprocess may account for the attenuation effects on perceived pain intensity after orienting attention.

Salience of Somatosensory Stimulus Modulating External-to-Internal Orienting Attention

PubMed Central

Peng, Jiaxin; Chan, Sam C. C.; Chau, Bolton K. H.; Yu, Qiuhua; Chan, Chetwyn C. H.

2017-01-01

Shifting between one’s external and internal environments involves orienting attention. Studies on differentiating subprocesses associated with external-to-internal orienting attention are limited. This study aimed to reveal the characteristics of the disengagement, shifting and reengagement subprocesses by using somatosensory external stimuli and internally generated images. Study participants were to perceive nociceptive external stimuli (External Low (EL) or External High (EH)) induced by electrical stimulations (50 ms) followed by mentally rehearsing learned subnociceptive images (Internal Low (IL) and Internal High (IH)). Behavioral responses and EEG signals of the participants were recorded. The three significant components elicited were: fronto-central negativity (FCN; 128–180 ms), fronto-central P2 (200–260 ms), and central P3 (320–380 ms), which reflected the three subprocesses, respectively. Differences in the FCN and P2 amplitudes during the orienting to the subnociceptive images revealed only in the EH but not EL stimulus condition that are new findings. The results indicated that modulations of the disengagement and shifting processes only happened if the external nociceptive stimuli were of high salience and the external-to-internal incongruence was large. The reengaging process reflected from the amplitude of P3 correlated significantly with attenuation of the pain intensity felt from the external nociceptive stimuli. These findings suggested that the subprocesses underlying external-to-internal orienting attention serve different roles. Disengagement subprocess tends to be stimulus dependent, which is bottom-up in nature. Shifting and reengagement tend to be top-down subprocesses, which taps on cognitive control. This subprocess may account for the attenuation effects on perceived pain intensity after orienting attention. PMID:28970787

Plasma coating of nanoparticles in the presence of an external electric field

NASA Astrophysics Data System (ADS)

Ebadi, Zahra; Pourali, Nima; Mohammadzadeh, Hosein

2018-04-01

Film deposition onto nanoparticles by low-pressure plasma in the presence of an external electric field is studied numerically. The plasma discharge fluid model along with surface deposition and heating models for nanoparticles, as well as a dynamics model considering the motion of nanoparticles, are employed for this study. The results of the simulation show that applying external field during the process increases the uniformity of the film deposited onto nanoparticles and leads to that nanoparticles grow in a spherical shape. Increase in film uniformity and particles sphericity is related to particle dynamics that is controlled by parameters of the external field like frequency and amplitude. The results of this work can be helpful to produce spherical core-shell nanoparticles in nanomaterial industry.

Self-Powered Nanocomposites under an External Rotating Magnetic Field for Noninvasive External Power Supply Electrical Stimulation.

PubMed

Wu, Fengluan; Jin, Long; Zheng, Xiaotong; Yan, Bingyun; Tang, Pandeng; Yang, Huikai; Deng, Weili; Yang, Weiqing

2017-11-08

Electrical stimulation in biology and gene expression has attracted considerable attention in recent years. However, it is inconvenient that the electric stimulation needs to be supplied an implanted power-transported wire connecting the external power supply. Here, we fabricated a self-powered composite nanofiber (CNF) and developed an electric generating system to realize electrical stimulation based on the electromagnetic induction effect under an external rotating magnetic field. The self-powered CNFs generating an electric signal consist of modified MWNTs (m-MWNTs) coated Fe 3 O 4 /PCL fibers. Moreover, the output current of the nanocomposites can be increased due to the presence of the magnetic nanoparticles during an external magnetic field is applied. In this paper, these CNFs were employed to replace a bullfrog's sciatic nerve and to realize the effective functional electrical stimulation. The cytotoxicity assays and animal tests of the nanocomposites were also used to evaluate the biocompatibility and tissue integration. These results demonstrated that this self-powered CNF not only plays a role as power source but also can act as an external power supply under an external rotating magnetic field for noninvasive the replacement of injured nerve.

Calcium and initial surface binding phase of pinocytosis in Amoeba proteus

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

Prusch, R.D.

1986-08-01

The uptake of membrane-bound solute and external medium by bulk-phase pinocytosis in Amoeba proteus is influenced by the level of Ca/sup 2 +/ in the external medium. Increasing external Ca/sup 2 +/ to approx.10/sup -4/ M increases pinocytotic intensity, while increases in Ca/sup 2 +/ above this level decrease the intensity of pinocytosis. The initial interaction of pinocytotic inducers and Ca/sup +2/ at the surface of A moeba proteus was therefore examined. Alcain blue and Na/sup +/, both inducers of pinocytosis, differ in the manner with which they associate with the amoeba surface, suggesting the possibility of different pinocytosis-inducing sitesmore » on the amoeba surface. Low levels of external Ca/sup 2 +/ in the range of 3 x 10/sup -5/ to 4.5 x 10/sup -4/ M increase the amount of cationic inducer associated with the cell surface while, at the same time, decreasing anion association with the cell surface. It is suggested that Ca/sup 2 +/ influences ion association with the cell surface by controlling the availability of negative surface sites, which in turn influences pinocytotic intensity. Surface binding of Na/sup +/, Ca/sup 2 +/ and Cl/sup -/ was determined by adding /sup 22/Na, /sup 45/Ca or /sup 36/Cl.« less

Hydrodynamic Capture and Release of Passively Driven Particles by Active Particles Under Hele-Shaw Flows

NASA Astrophysics Data System (ADS)

Mishler, Grant; Tsang, Alan Cheng Hou; Pak, On Shun

2018-03-01

The transport of active and passive particles plays central roles in diverse biological phenomena and engineering applications. In this paper, we present a theoretical investigation of a system consisting of an active particle and a passive particle in a confined micro-fluidic flow. The introduction of an external flow is found to induce the capture of the passive particle by the active particle via long-range hydrodynamic interactions among the particles. This hydrodynamic capture mechanism relies on an attracting stable equilibrium configuration formed by the particles, which occurs when the external flow intensity exceeds a certain threshold. We evaluate this threshold by studying the stability of the equilibrium configurations analytically and numerically. Furthermore, we study the dynamics of typical capture and non-capture events and characterize the basins of attraction of the equilibrium configurations. Our findings reveal a critical dependence of the hydrodynamic capture mechanism on the external flow intensity. Through adjusting the external flow intensity across the stability threshold, we demonstrate that the active particle can capture and release the passive particle in a controllable manner. Such a capture-and-release mechanism is desirable for biomedical applications such as the capture and release of therapeutic payloads by synthetic micro-swimmers in targeted drug delivery.

Field gradients can control the alignment of nanorods.

PubMed

Ooi, Chinchun; Yellen, Benjamin B

2008-08-19

This work is motivated by the unexpected experimental observation that field gradients can control the alignment of nonmagnetic nanorods immersed inside magnetic fluids. In the presence of local field gradients, nanorods were observed to align perpendicular to the external field at low field strengths, but parallel to the external field at high field strengths. The switching behavior results from the competition between a preference to align with the external field (orientational potential energy) and preference to move into regions of minimum magnetic field (positional potential energy). A theoretical model is developed to explain this experimental behavior by investigating the statistics of nanorod alignment as a function of both the external uniform magnetic field strength and the local magnetic field variation above a periodic array of micromagnets. Computational phase diagrams are developed which indicate that the relative population of nanorods in parallel and perpendicular states can be adjusted through several control parameters. However, an energy barrier to rotation was discovered to influence the rate kinetics and restrict the utility of this assembly technique to nanorods which are slightly shorter than the micromagnet length. Experimental results concerning the orientation of nanorods inside magnetic fluid are also presented and shown to be in strong agreement with the theoretical work.

Can even-order laser harmonics exhibited by Bohmian trajectories in symmetric potentials be observed?

PubMed

Peatross, J; Johansen, J

2014-01-13

Strong-field laser-atom interactions provide extreme conditions that may be useful for investigating the de Broglie-Bohm quantum interpretation. Bohmian trajectories representing bound electrons in individual atoms exhibit both even and odd harmonic motion when subjected to a strong external laser field. The phases of the even harmonics depend on the random initial positions of the trajectories within the wave function, making the even harmonics incoherent. In contrast, the phases of odd harmonics remain for the most part coherent regardless of initial position. Under the conjecture that a Bohmian point particle plays the role of emitter, this suggests an experiment to determine whether both even and odd harmonics are produced at the atomic level. Estimates suggest that incoherent emission of even harmonics may be detectable out the side of an intense laser focus interacting with a large number of atoms.

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

Paranin, V. D.

In work we investigated yttrium iron garnet epitaxial films with a thickness of 10 µm and 55 µm which were grown on the surface of garnet substrate. Using the polarizing microscopy method the branching domain structure of films was shown with the period of domains 21.5 µm and 42.5 µm. Disappearance of domains at presence of an external magnetic field up to 100 Oe was noted. The optical transmission of films for the polarized beam of HeNe laser is investigated and zero diffraction order and odd diffraction rings orders were shown. Interconnection of the period of chaotically oriented domains with angles of axially symmetricmore » diffraction rings orders was shown. Diffraction patterns at various longitudinal magnetic fields are investigated. Disappearance of odd diffraction orders and increasing in intensity of zero diffraction order were fixed. Optical transmission of epitaxial films was measured in range of 500 - 900 nm.« less

Validation of non-local electron heat conduction model for radiation MHD simulation in magnetized laser plasma

NASA Astrophysics Data System (ADS)

Nagatomo, Hideo; Matsuo, Kazuki; Nicolai, Pilippe; Asahina, Takashi; Fujioka, Shinsuke

2017-10-01

In laser plasma physics, application of an external magnetic field is an attractive method for various research of high energy density physics including fast ignition. Meanwhile, in the high intense laser plasma the behavior of hot electron cannot be ignored. In the radiation hydrodynamic simulation, a classical electron conduction model, Spitzer-Harm model has been used in general. However the model has its limit, and modification of the model is necessary if it is used beyond the application limit. Modified SNB model, which considering the influence of magnetic field is applied to 2-D radiation magnetohydrodynamic code PINOCO. Some experiments related the non-local model are carried out at GXII, Osaka University. In this presentation, these experimental results are shown briefly. And comparison between simulation results considering the non-local electron heat conduction mode are discussed. This study was supported JSPS KAKENHI Grant No. 17K05728.

Design of magneto-rheological mount for a cabin of heavy equipment vehicles

NASA Astrophysics Data System (ADS)

Yang, Soon-Yong; Do, Xuan Phu; Choi, Seung-Bok

2016-04-01

In this paper, magneto-rheological (MR) mount for a cabin of heavy equipment vehicles is designed for improving vibration isolation in both low and high frequency domains. The proposed mount consists of two principal parts of mount, rubber part and MR fluid path. The rubber part of existed mount and spring are used to change the stiffness and frequency characteristics for low vibration frequency range. The MR fluid path is a valve type structure using flow mode. In order to control the external magnetic field, a solenoid coil is placed in MR mount. Magnetic intensity analysis is then conducted to optimize dimensions using computer simulation. Experimental results show that magnetic field can reduce low frequency vibration. The results presented in this work indicate that proper application of MR fluid and rubber characteristic to devise MR mount can lead to the improvement of vibration control performance in both low and high frequency ranges.

The influence of an external electric field on the propagation of light waves in cholesteric liquid crystal cells

NASA Astrophysics Data System (ADS)

Aksenova, E. V.; Karetnikov, A. A.; Kovshik, A. P.; Krainyukov, E. S.; Svanidze, A. V.

2017-05-01

The specific features of light transmission in a cholesteric liquid crystal (LC) cell with a director rotated by 90° have been investigated. In this structure, where a light wave is incident at a large angle with respect to the LC surface, the light is reflected (refracted) in the LC layer near the opposite boundary. It is shown that the application of an electric field changes the character of extraordinary wave refraction, as a result of which light starts passing through a cell. The transmission threshold voltage is determined, and its dependence on the angle of incidence of light is obtained. The dependence of the transmitted-light intensity on the voltage across the cell is obtained as well. The same dependences are also derived by numerical calculations with allowance for the turning points and extinction.

PEG-PLGA electrospun nanofibrous membranes loaded with Au@Fe2O3 nanoparticles for drug delivery applications

NASA Astrophysics Data System (ADS)

Spadaro, Salvatore; Santoro, Marco; Barreca, Francesco; Scala, Angela; Grimato, Simona; Neri, Fortunato; Fazio, Enza

2018-02-01

A PEGylated-PLGA random nanofibrous membrane loaded with gold and iron oxide nanoparticles and with silibinin was prepared by electrospinning deposition. The nanofibrous membrane can be remotely controlled and activated by a laser light or magnetic field to release biological agents on demand. The nanosystems were characterized using scanning electron microscopy, Fourier transform infrared spectroscopy, nuclear magnetic resonance spectroscopy, and thermogravimetric analyses. The drug loading efficiency and drug content percentages were determined by UV-vis optical absorption spectroscopy. The nanofibrous membrane irradiated by a relatively low-intensity laser or stimulated by a magnetic field showed sustained silibinin release for at least 60 h, without the burst effect. The proposed low-cost electrospinning procedure is capable of assembling, via a one-step procedure, a stimuli-responsive drug-loaded nanosystem with metallic nanoparticles to be externally activated for controlled drug delivery.

Multimodal chemo-magnetic control of self-propelling microbots

NASA Astrophysics Data System (ADS)

Singh, Amit Kumar; Dey, Krishna Kanti; Chattopadhyay, Arun; Mandal, Tapas Kumar; Bandyopadhyay, Dipankar

2014-01-01

We report a controlled migration of an iron nanoparticle (FeNP) coated polymer micromotor. The otherwise diffusive motion of the motor was meticulously directed through an in situ pH-gradient and an external magnetic field. The self-propulsion owing to the asymmetric catalytic decomposition of peroxide fuel was directed through a pH gradient imposed across the motor-surface, while the magnetic field induced an external control on the movement and the speed of the motor. Interestingly, the sole influence of the pH gradient could move the motor as high as ~25 body lengths per second, which was further magnified by the external assistance from the magnetic field. Applying a magnetic field against the pH directed motion helped in the quantitative experimental estimation of the force-field required to arrest the chemotactic migration. The influence of the coupled internal and external fields could halt, steer or reverse the direction the motor inside a microchannel, rotate the motor around a target, and deliver the motor to a cluster of cells. This study showcases a multimodal chemical-magnetic field regulated migration of micro-machines for sensing, transport, and delivery inside a fluidic environment.We report a controlled migration of an iron nanoparticle (FeNP) coated polymer micromotor. The otherwise diffusive motion of the motor was meticulously directed through an in situ pH-gradient and an external magnetic field. The self-propulsion owing to the asymmetric catalytic decomposition of peroxide fuel was directed through a pH gradient imposed across the motor-surface, while the magnetic field induced an external control on the movement and the speed of the motor. Interestingly, the sole influence of the pH gradient could move the motor as high as ~25 body lengths per second, which was further magnified by the external assistance from the magnetic field. Applying a magnetic field against the pH directed motion helped in the quantitative experimental estimation of the force-field required to arrest the chemotactic migration. The influence of the coupled internal and external fields could halt, steer or reverse the direction the motor inside a microchannel, rotate the motor around a target, and deliver the motor to a cluster of cells. This study showcases a multimodal chemical-magnetic field regulated migration of micro-machines for sensing, transport, and delivery inside a fluidic environment. Electronic supplementary information (ESI) available: Scanning electron microscopy, transmission electron microscopy, X-ray diffraction pattern, vibrating sample magnetometry (VSM) hysteresis loop of freshly prepared FeNP coated micromotor and movies of micromotor motion. See DOI: 10.1039/c3nr05294j

Gyrokinetic Simulations with External Resonant Magnetic Perturbations: Island Torque and Nonambipolar Transport with Rotation

NASA Astrophysics Data System (ADS)

Waltz, R. E.; Waelbroeck, F. L.

2012-03-01

Static external resonant magnetic perturbations (RMPs) have been added to the δf gyrokinetic code GYRO. This allows nonlinear gyrokinetic simulations of the nonambipolar radial current flow jr and the corresponding plasma torque (density) R[jrBθ/c], induced by islands that break the toroidal symmetry of a tokamak. This extends previous GYRO simulations for the transport of toroidal angular momentum (TAM) [1,2]. The focus is on full torus radial slice electrostatic simulations of induced q=m/n=6/3 islands with widths 5% of the minor radius. The island torque scales with the radial electric field Er the island width w, and the intensity I of the high-n micro-turbulence, as wErI^1/2. The net island torque is null at zero Er rather than at zero toroidal rotation. This means that there is a small co-directed magnetic acceleration to the small diamagnetic co-rotation corresponding to the zero Er which can be called the residual stress [2] from an externally induced island. Finite-beta GYRO simulations of a core radial slice demonstrate island unlocking and the RMP screening. 6pt[1] R.E. Waltz, et al., Phys. Plasmas 14, 122507 (2007). [2] R.E. Waltz, et al., Phys. Plasmas 18, 042504 (2011).

Superconducting Sphere in an External Magnetic Field Revisited

ERIC Educational Resources Information Center

Sazonov, Sergey N.

2013-01-01

The purpose of this article is to give the intelligible procedure for undergraduate students to grasp proof of the fact that the magnetic field outside the hollow superconducting sphere (superconducting shell) coincides with the field of a point magnetic dipole both when an uniform external magnetic field is applied as when a ferromagnetic sphere…

Design and application of permanent magnet flux sources for mechanical testing of magnetoactive elastomers at variable field directions.

PubMed

Hiptmair, F; Major, Z; Haßlacher, R; Hild, S

2015-08-01

Magnetoactive elastomers (MAEs) are a class of smart materials whose mechanical properties can be rapidly and reversibly changed by an external magnetic field. Due to this tunability, they are useable for actuators or in active vibration control applications. An extensive magnetomechanical characterization is necessary for MAE material development and requires experiments under cyclic loading in uniform but variable magnetic fields. MAE testing apparatus typically rely on fields of adjustable strength, but fixed (transverse) direction, often provided by electromagnets. In this work, two permanent magnet flux sources were developed as an add-on for a modular test stand, to allow for mechanical testing in uniform fields of variable direction. MAE specimens, based on a silicone matrix with isotropic and anisotropic carbonyl iron particle distributions, were subjected to dynamic mechanical analysis under different field and loading configurations. The magneto-induced increase of stiffness and energy dissipation was determined by the change of the hysteresis loop area and dynamic modulus values. A distinct influence of the composite microstructure and the loading state was observed. Due to the very soft and flexible matrix used for preparing the MAE samples, the material stiffness and damping behavior could be varied over a wide range via the applied field direction and intensity.

[INVITED] Coupling of polarisation of high frequency electric field and electronic heat conduction in laser created plasma

NASA Astrophysics Data System (ADS)

Gamaly, Eugene G.; Rode, Andrei V.

2016-08-01

Powerful short laser pulse focused on a surface swiftly transforms the solid into the thermally and electrically inhomogeneous conductive plasma with the large temperature and dielectric permeability gradients across the focal spot. The laser-affected spot becomes thermally inhomogeneous with where temperature has maximum in the centre and gradually decreasing to the boundaries of the spot in accord to the spatial intensity distribution of the Gaussian pulse. Here we study the influence of laser polarisation on ionization and absorption of laser radiation in the focal spot. In this paper we would like to discuss new effect in thermally inhomogeneous plasma under the action of imposed high frequency electric field. We demonstrate that high-frequency (HF) electric field is coupled with the temperature gradient generating the additional contribution to the conventional electronic heat flow. The additional heat flow strongly depends on the polarisation of the external field. It appears that effect has maximum when the imposed electric field is collinear to the thermal gradient directed along the radius of a circular focal spot. Therefore, the linear polarised field converts the circular laser affected spot into an oval with the larger oval's axis parallel to the field direction. We compare the developed theory to the available experiments, discuss the results and future directions.

Photorefractive InGaAs/GaAs multiple quantum wells in the Franz{endash}Keldysh geometry

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

Iwamoto, S.; Kageshima, H.; Yuasa, T.

2001-06-01

We fabricate semi-insulating InGaAs/GaAs multiple quantum wells and observe the excitonic enhancement of the photorefractivity in the Franz{endash}Keldysh geometry at wavelengths of 0.92{endash}0.94 {mu}m. A maximum two-wave mixing gain of 138 cm{sup {minus}1} and a maximum diffraction efficiency of 1.5{times}10{sup {minus}4} are obtained. The saturation intensity and the spatial resolution are also measured by four-wave mixing. The diffraction efficiency is saturated at a high external electric field. The dominant cause of this saturation is the deviation of the excitonic electroabsorption from its quadratic law. {copyright} 2001 American Institute of Physics.

Dielectric behavior of CaCu3Ti4O12 ceramics in the terahertz range.

PubMed

Wu, Liang; Ling, Furi; Liu, Ting; Liu, Jinsong; Xu, Yebin; Yao, Jianquan

2011-03-14

The dielectric properties of 1050 °C/12h sintered CaCu3Ti4O12 (CCTO) ceramics have been investigated by using terahertz time domain spectroscopy in the frequency range of 0.2-1.6 THz at room temperature. When applying an external optical field, an obvious variation of dielectric constant was observed and reached up to 7%. However, the dielectric loss does not change appreciably. From the results, we found the change of refractive index has a linear relationship on scale with the applied light intensity. These findings were attributed to the change of spontaneous polarization in the ceramic caused by the excited free carriers.

Influence of damped propagation of dopant on the static and frequency-dependent third nonlinear polarizability of quantum dot

NASA Astrophysics Data System (ADS)

Pal, Suvajit; Ghosh, Manas

2014-07-01

We investigate the profiles of diagonal components of static and frequency-dependent third nonlinear (γxxxx and γyyyy) polarizability of repulsive impurity doped quantum dots. The dopant impurity potential takes a GAUSSIAN form. We have considered propagation of the dopant within an environment that damps the motion. The study focuses on role of damping strength on the diagonal components of both static and frequency-dependent third nonlinear polarizability of the doped system. The doped system is further exposed to an external electric field of given intensity. Damping subtly modulates the dot-impurity interaction and fabricates the polarizability components in a noticeable manner.

Painting with light-powered bacteria.

PubMed

Arlt, Jochen; Martinez, Vincent A; Dawson, Angela; Pilizota, Teuta; Poon, Wilson C K

2018-02-22

Self-assembly is a promising route for micro- and nano-fabrication with potential to revolutionise many areas of technology, including personalised medicine. Here we demonstrate that external control of the swimming speed of microswimmers can be used to self assemble reconfigurable designer structures in situ. We implement such 'smart templated active self assembly' in a fluid environment by using spatially patterned light fields to control photon-powered strains of motile Escherichia coli bacteria. The physics and biology governing the sharpness and formation speed of patterns is investigated using a bespoke strain designed to respond quickly to changes in light intensity. Our protocol provides a distinct paradigm for self-assembly of structures on the 10 μm to mm scale.

Ensemble of single quadrupolar nuclei in rotating solids: sidebands in NMR spectrum.

PubMed

Kundla, Enn

2006-07-01

A novel way is proposed to describe the evolution of nuclear magnetic polarization and the induced NMR spectrum. In this method, the effect of a high-intensity external static magnetic field and the effects of proper Hamiltonian left over interaction components, which commute with the first, are taken into account simultaneously and equivalently. The method suits any concrete NMR problem. This brings forth the really existing details in the registered spectra, evoked by Hamiltonian secular terms, which may be otherwise smoothed due to approximate treatment of the effects of the secular terms. Complete analytical expressions are obtained describing the NMR spectra including the rotational sideband sets of single quadrupolar nuclei in rotating solids.

An Investigation of EME as a Potential Cause of Fuel Tank Ignition

NASA Technical Reports Server (NTRS)

Ely, Jay J.; Nguyen, Truong X.; Dudley, Kenneth L.; Scearce, Stephen A.; Beck, Fred B.; Deshpande, Manohar D.; Cockrell, C. R.

2000-01-01

NASA researchers were tasked to study the potential for radio signals to excite an aircraft fuel quantity indication system (FQIS) enough to cause arcing, sparking or excessive heating within a fuel tank. Computational techniques were used to determine the threat from external high intensity radiated field (HIRF) transmitters nearby, like shipboard and airborne RADAR systems. Experimental methods were used to determine the threat from Portable Electronic Devices (PEDs) carried aboard by passengers. To support this work, unique electromagnetic coupling measurements were performed on a retired Boeing 747 aircraft, and new test and analysis methods were developed that may be applied to other FQIS designs as well as other aircraft electronic systems.

Internal and External Match Loads of University-Level Soccer Players: A Comparison Between Methods.

PubMed

Sparks, Martinique; Coetzee, Ben; Gabbett, Tim J

2017-04-01

Sparks, M, Coetzee, B, and Gabbett, TJ. Internal and external match loads of university-level soccer players: a comparison between methods. J Strength Cond Res 31(4): 1072-7077, 2017-The aim of this study was to use individualized intensity zones to compare the external (velocity and player load, PL) and internal loads (heart rate, HR) of a cohort of university-level soccer players. Thirteen soccer players completed a 40-m maximum speed test and the Yo-Yo intermittent recovery test 1 (Yo-Yo IR1) to determine individualized velocity and HR thresholds. Heart rate values and global positioning system (GPS) data of each player were recorded during 5 league matches. A large (r = 0.46; p ≤ 0.01) correlation was found between time spent in the low-intensity (LI) velocity zone (LIVZ) and the LI HR zone. Similarly, there were moderate (r = 0.25; p ≤ 0.01) to large (r = 0.57; p ≤ 0.01) correlations between the relative and absolute time spent in the moderate-intensity (MI) velocity zone (MIVZ) and the MI HR zone. No significant correlations (p ≤ 0.01) existed between the high-intensity (HI) velocity zones (HIVZ) and the HI HR zone. On the other hand, PL showed significant correlations with all velocity and HR (absolute and relative) variables, with the exception of a nonsignificant correlation between the HI HR variables and PL. To conclude, PL showed good correlations with both velocity and HR zones and therefore may have the potential to serve as a good indicator of both external and internal soccer match loads.

Observation of Landau levels on nitrogen-doped flat graphite surfaces without external magnetic fields

PubMed Central

Kondo, Takahiro; Guo, Donghui; Shikano, Taishi; Suzuki, Tetsuya; Sakurai, Masataka; Okada, Susumu; Nakamura, Junji

2015-01-01

Under perpendicular external magnetic fields, two-dimensional carriers exhibit Landau levels (LLs). However, it has recently been reported that LLs have been observed on graphene and graphite surfaces without external magnetic fields being applied. These anomalous LLs have been ascribed primarily to a strain of graphene sheets, leading to in-plane hopping modulation of electrons. Here, we report the observation of the LLs of massive Dirac fermions on atomically flat areas of a nitrogen-doped graphite surface in the absence of external magnetic fields. The corresponding magnetic fields were estimated to be as much as approximately 100 T. The generation of the LLs at the area with negligible strain can be explained by inequivalent hopping of π electrons that takes place at the perimeter of high-potential domains surrounded by positively charged substituted graphitic-nitrogen atoms. PMID:26549618

Influence of external magnetic field on the microwave absorption properties of carbonyl iron and polychloroprene composites film

NASA Astrophysics Data System (ADS)

Wang, Haiyan; Li, Mingjie; Li, Xueai

2016-12-01

The carbonyl iron particles were dispersed in a polychloroprene rubber (CR) matrix under a magnetic field for a practical application as microwave absorption composites film. In comparison with the carbonyl iron particles (CIP)/CR composites film prepared by general route, such films made with external magnetic field exhibit excellent microwave absorption properties, strongly depending on the increment of anisotropy and rearrangement of magnetic particles. The film made under external magnetic field with a thickness of only 0.54 mm shows least reflection loss of -15.98 dB and the reflection loss value less than -10.0 dB over the frequency range of 11.4˜14.8 GHz. The results indicated the composite film made under external magnetic field have excellent microwave absorption properties, which suggest that the composites thin film could be used as a thinner and lighter microwave absorber.

Electronic structure and bonding properties of potassium (K) on graphite under external electric field.

NASA Astrophysics Data System (ADS)

Tapia, Alejandro; Canto, Gabriel

2005-03-01

The effect of an external electric field on the potassium (K) adsorption on the graphite surface, are studied by means of first-principles total-energy calculations. The results were obtained with the pseudopotentials LCAO method (SIESTA code) and the Generalized Gradient Approximation (GGA) for the exchange-correlation potential. The structural parameters, bonding properties, and electronic structure of the K-graphite system are studied in the triangular (2x2) overlayer phase as a function of the external electric field magnitude. We find an important change in the K-graphite bonding as a consequence of the charge transfer from the adatom towards the substrate induced by the electric field. The results are discussed in the light of the experimental observed difussion of K into graphite induced by external electric fields. This work was supported by Consejo Nacional de Ciencia y Tecnolog'ia (CONACYT, M'exico) under Grants No. 43830-F and No. 44831-F.

SU-E-T-447: Growth of Metal Whiskers Under External Beam Irradiation: Experimental Evidence and Implications in Medical Electronic Devices for Radiation Therapy Treatments

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

Shvydka, D; Warrell, G; Parsai, E

2015-06-15

Purpose: Thin metallic protrusions, termed “whiskers,” have been identified as a cause of failure in devices ranging from satellites to pacemakers. For decades, lead was used in tin-based soldering alloys to suppress whisker formation. With the adoption of the Restriction of Hazardous Substances act and the expiration of its exemption on medical devices, including implanted medical devices (IMDs), electronic circuits are required to be lead-free as of July 2014. The effect of radiation on such soldering components remains unknown. Methods: We have irradiated a thin (150 nm) tin metal layer, deposited on a 3 mm thick glass substrate, with amore » 6 MeV medical linac (Varian TrueBeam) electron beam in five 2-hour long sessions. After receiving ∼10 kGy, whisker growth on the sample was assessed with scanning electron microscopy and compared to a reference sample not exposed to radiation. Results: After 10 hours of irradiation, the sample was found to develop intense whisker infestation, while the reference sample remained in its pristine as-deposited condition. Repeating the same irradiation schedule generated more and longer whiskers. The observed phenomenon can be explained through charge accumulation in the glass substrate, generating an electric field that promotes whisker growth. The observed substrate glass darkening under irradiation points towards development of color centers related to charge trapping. Experiments on the same type of samples with direct application of the external field in a capacitor-like setting also resulted in intense whisker growth. Conclusion: Extreme care should be taken in dealing with all electronic devices, especially IMDs, produced with lead-free solder and components, subject to radiation exposure. While in our experiments strong electric fields were intentionally generated to accelerate whisker growth over hours, in everyday use the circuit soldering may cause problems in a matter of days or months. Designated reliability testing under radiation must be conducted. This work is partially supported by NRC grant No. NRC-HQ-12-G-38-0042.« less

A road damage and life-cycle greenhouse gas comparison of trucking and pipeline water delivery systems for hydraulically fractured oil and gas field development in Colorado

PubMed Central

Duthu, Ray C.

2017-01-01

The process of hydraulic fracturing for recovery of oil and natural gas uses large amounts of fresh water and produces a comparable amount of wastewater, much of which is typically transported by truck. Truck transport of water is an expensive and energy-intensive process with significant external costs including roads damages, and pollution. The integrated development plan (IDP) is the industry nomenclature for an integrated oil and gas infrastructure system incorporating pipeline-based transport of water and wastewater, centralized water treatment, and high rates of wastewater recycling. These IDP have been proposed as an alternative to truck transport systems so as to mitigate many of the economic and environmental problems associated with natural gas production, but the economic and environmental performance of these systems have not been analyzed to date. This study presents a quantification of lifecycle greenhouse gas (GHG) emissions and road damages of a generic oil and gas field, and of an oil and gas development sited in the Denver-Julesburg basin in the northern Colorado region of the US. Results demonstrate that a reduction in economic and environmental externalities can be derived from the development of these IDP-based pipeline water transportation systems. IDPs have marginal utility in reducing GHG emissions and road damage when they are used to replace in-field water transport, but can reduce GHG emissions and road damage by factors of as much as 6 and 7 respectively, when used to replace fresh water transport and waste-disposal routes for exemplar Northern Colorado oil and gas fields. PMID:28686682

A road damage and life-cycle greenhouse gas comparison of trucking and pipeline water delivery systems for hydraulically fractured oil and gas field development in Colorado.

PubMed

Duthu, Ray C; Bradley, Thomas H

2017-01-01

The process of hydraulic fracturing for recovery of oil and natural gas uses large amounts of fresh water and produces a comparable amount of wastewater, much of which is typically transported by truck. Truck transport of water is an expensive and energy-intensive process with significant external costs including roads damages, and pollution. The integrated development plan (IDP) is the industry nomenclature for an integrated oil and gas infrastructure system incorporating pipeline-based transport of water and wastewater, centralized water treatment, and high rates of wastewater recycling. These IDP have been proposed as an alternative to truck transport systems so as to mitigate many of the economic and environmental problems associated with natural gas production, but the economic and environmental performance of these systems have not been analyzed to date. This study presents a quantification of lifecycle greenhouse gas (GHG) emissions and road damages of a generic oil and gas field, and of an oil and gas development sited in the Denver-Julesburg basin in the northern Colorado region of the US. Results demonstrate that a reduction in economic and environmental externalities can be derived from the development of these IDP-based pipeline water transportation systems. IDPs have marginal utility in reducing GHG emissions and road damage when they are used to replace in-field water transport, but can reduce GHG emissions and road damage by factors of as much as 6 and 7 respectively, when used to replace fresh water transport and waste-disposal routes for exemplar Northern Colorado oil and gas fields.

The Quality of the Embedding Potential Is Decisive for Minimal Quantum Region Size in Embedding Calculations: The Case of the Green Fluorescent Protein.

PubMed

Nåbo, Lina J; Olsen, Jógvan Magnus Haugaard; Martínez, Todd J; Kongsted, Jacob

2017-12-12

The calculation of spectral properties for photoactive proteins is challenging because of the large cost of electronic structure calculations on large systems. Mixed quantum mechanical (QM) and molecular mechanical (MM) methods are typically employed to make such calculations computationally tractable. This study addresses the connection between the minimal QM region size and the method used to model the MM region in the calculation of absorption properties-here exemplified for calculations on the green fluorescent protein. We find that polarizable embedding is necessary for a qualitatively correct description of the MM region, and that this enables the use of much smaller QM regions compared to fixed charge electrostatic embedding. Furthermore, absorption intensities converge very slowly with system size and inclusion of effective external field effects in the MM region through polarizabilities is therefore very important. Thus, this embedding scheme enables accurate prediction of intensities for systems that are too large to be treated fully quantum mechanically.

Comparison of the far-infrared and carbon monoxide emission in Heiles' Cloud 2 and B18

NASA Technical Reports Server (NTRS)

Snell, Ronald L.; Schloerb, F. Peter; Heyer, Mark H.

1989-01-01

A comparison is made of the far-IR emission detected by IRAS at 60 and 100 microns and the emission from C(-13)O in B18 and Heiles' Cloud 2. The results show that both these clouds have extended emission at the studied wavelengths and that this emission is correlated with the integrated intensity of (C-13)O emission. The dust temperature and optical depth, the gas column density, the mass of gas and dust, and the far-IR luminosity are derived and presented. The analysis shows that the dust optical depth is much better correlated with the gas column density than with the far-IR intensity. The dust temperature is found to be anticorrelated with the gas column density, suggesting that these clouds are externally heated by the interstellar radiation field. The far-IR luminosity-to-mass ratios for the clouds are substantially less than the average for the inner Galaxy.

Grape Berry Acclimation to Excessive Solar Irradiance Leads to Repartitioning between Major Flavonoid Groups.

PubMed

Reshef, N; Agam, N; Fait, A

2018-04-11

Warm viticulture regions are associated with inferior wines, resulting from the interaction between microclimate and fruit biochemistry. Solar irradiance triggers biosynthetic processes in the fruit and dominates its thermal balance. Therefore, deciphering its impact on fruit metabolism is pivotal to develop strategies for fruit protection and ameliorate its quality traits. Here, we modified light quality and intensity in the fruit-zone and integrated micrometeorology with grape and wine metabolomics, allowing a complete assessment, from field to bottle. We analyzed the dynamics of fruit's adaptation to altered conditions during ripening and constructed temporal-based metabolic networks. Micrometeorological modifications shifted the balance between the major flavonoids, associating increased solar exposure with lower levels of anthocyanins and flavan-3-ols, and higher flavonols. Differences were fixed from 2 weeks postveraison until harvest, suggesting a controlled acclimation response rather than external modulation. Differences in grape composition manifested in the wine and resulted in higher color intensity and improved wine hue under partial shading.

Enhanced response of non-Hermitian photonic systems near exceptional points

NASA Astrophysics Data System (ADS)

Sunada, Satoshi

2018-04-01

This paper theoretically and numerically studies the response characteristics of non-Hermitian resonant photonic systems operating near an exceptional point (EP), where two resonant eigenmodes coalesce. It is shown that a system near an EP can exhibit a non-Lorentzian frequency response, whose line shape and intensity strongly depend on the modal decay rate and coupling parameters for the input waves, unlike a normal Lorentzian response around a single resonance. In particular, it is shown that the peak intensity of the frequency response is inversely proportional to the fourth power of the modal decay rate and can be significantly enhanced with the aid of optical gain. The theoretical results are numerically verified by a full wave simulation of a microring cavity with gain. In addition, the effects of the nonlinear gain saturation and spontaneous emission are discussed. The response enhancement and its parametric dependence may be useful for designing and controlling the excitation of eigenmodes by external fields.

Forced magnetohydrodynamic turbulence in a uniform external magnetic field

NASA Technical Reports Server (NTRS)

Hossain, M.; Vahala, G.; Montgomery, D.

1985-01-01

Two-dimensional dissipative MHD turbulence is randomly driven at small spatial scales and is studied by numerical simulation in the presence of a strong uniform external magnetic field. A behavior is observed which is apparently distinct from the inverse cascade which prevails in the absence of an external magnetic field. The magnetic spectrum becomes dominated by the three longest wavelength Alfven waves in the system allowed by the boundary conditions: those which, in a box size of edge 2 pi, have wave numbers (kx, ky) = (1, 1), and (1, -1), where the external magnetic field is in the x direction. At any given instant, one of these three modes dominates the vector potential spectrum, but they do not constitute a resonantly coupled triad. Rather, they are apparently coupled by the smaller-scale turbulence.

Forced MHD turbulence in a uniform external magnetic field

NASA Technical Reports Server (NTRS)

Hossain, M.; Vahala, G.; Montgomery, D.

1985-01-01

Two-dimensional dissipative MHD turbulence is randomly driven at small spatial scales and is studied by numerical simulation in the presence of a strong uniform external magnetic field. A behavior is observed which is apparently distinct from the inverse cascade which prevails in the absence of an external magnetic field. The magnetic spectrum becomes dominated by the three longest wavelength Alfven waves in the system allowed by the boundary conditions: those which, in a box size of edge 2 pi, have wave numbers (kx' ky) = (1, 1), and (1, -1), where the external magnetic field is in the x direction. At any given instant, one of these three modes dominates the vector potential spectrum, but they do not constitute a resonantly coupled triad. Rather, they are apparently coupled by the smaller-scale turbulence.

HOx radical chemistry in oxidation flow reactors with low-pressure mercury lamps systematically examined by modeling

NASA Astrophysics Data System (ADS)

Peng, Z.; Day, D. A.; Stark, H.; Li, R.; Palm, B. B.; Brune, W. H.; Jimenez, J. L.

2015-04-01

Oxidation flow reactors (OFRs) using OH produced from low-pressure Hg lamps at 254 nm (OFR254) or both 185 and 254 nm (OFR185) are commonly used in atmospheric chemistry and other fields. OFR254 requires the addition of externally formed O3 since OH is formed from O3 photolysis, while OFR185 does not since O2 can be photolyzed to produce O3 and OH can also be formed from H2O photolysis. In this study, we use a plug-flow kinetic model to investigate OFR properties under a very wide range of conditions applicable to both field and laboratory studies. We show that the radical chemistry in OFRs can be characterized as a function of UV light intensity, H2O concentration, and total external OH reactivity (OHRext, e.g., from VOCs, NOx, and SO2). OH exposure is decreased by added external OH reactivity. OFR185 is especially sensitive to this effect at low UV intensity due to low primary OH production. OFR254 can be more resilient against OH suppression at high injected O3 (e.g., 70 ppm), as a larger primary OH source from O3, as well as enhanced recycling of HO2 to OH, make external perturbations to the radical chemistry less significant. However if the external OH reactivity in OFR254 is much larger than OH reactivity from injected O3, OH suppression can reach two orders of magnitude. For a typical input of 7 ppm O3 (OHRO3 = 10 s-1) ten-fold OH suppression is observed at OHRext ∼ 100 s-1, which is similar or lower than used in many laboratory studies. This finding may have important implications for the interpretation of past laboratory studies, as applying OHexp measurements acquired under different conditions could lead to over an order-of-magnitude error in the estimated OHexp. The uncertainties of key model outputs due to uncertainty in all rate constants and absorption cross-sections in the model are within ± 25% for OH exposure and within ± 60% for other parameters. These uncertainties are small relative to the dynamic range of outputs. Uncertainty analysis shows that most of the uncertainty is contributed by photolysis rates of O3, O2, and H2O and reactions of OH and HO2 with themselves or with some abundant species, i.e., O3 and H2O2. Using HOx-recycling vs. destructive external OH reactivity only leads to small changes in OHexp under most conditions. Changing the identity (rate constant) of external OH reactants can result in substantial changes in OHexp due to different reductions in OH suppression as the reactant is consumed. We also report two equations for estimating OH exposure in OFR254. We find that the equation estimating OHexp from measured O3 consumption performs better than an alternative equation that does not use it, and thus recommend measuring both input and output O3 concentrations in OFR254 experiments. This study contributes to establishing a firm and systematic understanding of the gas-phase HOx and Ox chemistry in these reactors, and enables better experiment planning and interpretation as well as improved design of future reactors.

The Relationships Between Internal and External Measures of Training Load and Intensity in Team Sports: A Meta-Analysis.

PubMed

McLaren, Shaun J; Macpherson, Tom W; Coutts, Aaron J; Hurst, Christopher; Spears, Iain R; Weston, Matthew

2018-03-01

The associations between internal and external measures of training load and intensity are important in understanding the training process and the validity of specific internal measures. We aimed to provide meta-analytic estimates of the relationships, as determined by a correlation coefficient, between internal and external measures of load and intensity during team-sport training and competition. A further aim was to examine the moderating effects of training mode on these relationships. We searched six electronic databases (Scopus, Web of Science, PubMed, MEDLINE, SPORTDiscus, CINAHL) for original research articles published up to September 2017. A Boolean search phrase was created to include search terms relevant to team-sport athletes (population; 37 keywords), internal load (dependent variable; 35 keywords), and external load (independent variable; 81 keywords). Articles were considered for meta-analysis when a correlation coefficient describing the association between at least one internal and one external measure of session load or intensity, measured in the time or frequency domain, was obtained from team-sport athletes during normal training or match-play (i.e., unstructured observational study). The final data sample included 122 estimates from 13 independent studies describing 15 unique relationships between three internal and nine external measures of load and intensity. This sample included 295 athletes and 10,418 individual session observations. Internal measures were session ratings of perceived exertion (sRPE), sRPE training load (sRPE-TL), and heart-rate-derived training impulse (TRIMP). External measures were total distance (TD), the distance covered at high and very high speeds (HSRD ≥ 13.1-15.0 km h -1 and VHSRD ≥ 16.9-19.8 km h -1 , respectively), accelerometer load (AL), and the number of sustained impacts (Impacts > 2-5 G). Distinct training modes were identified as either mixed (reference condition), skills, metabolic, or neuromuscular. Separate random effects meta-analyses were conducted for each dataset (n = 15) to determine the pooled relationships between internal and external measures of load and intensity. The moderating effects of training mode were examined using random-effects meta-regression for datasets with at least ten estimates (n = 4). Magnitude-based inferences were used to interpret analyses outcomes. During all training modes combined, the external load relationships for sRPE-TL were possibly very large with TD [r = 0.79; 90% confidence interval (CI) 0.74 to 0.83], possibly large with AL (r = 0.63; 90% CI 0.54 to 0.70) and Impacts (r = 0.57; 90% CI 0.47 to 0.64), and likely moderate with HSRD (r = 0.47; 90% CI 0.32 to 0.59). The relationship between TRIMP and AL was possibly large (r = 0.54; 90% CI 0.40 to 0.66). All other relationships were unclear or not possible to infer (r range 0.17-0.74, n = 10 datasets). Between-estimate heterogeneity [standard deviations (SDs) representing unexplained variation; τ] in the pooled internal-external relationships were trivial to extremely large for sRPE (τ range = 0.00-0.47), small to large for sRPE-TL (τ range = 0.07-0.31), and trivial to moderate for TRIMP (τ range= 0.00-0.17). The internal-external load relationships during mixed training were possibly very large for sRPE-TL with TD (r = 0.82; 90% CI 0.75 to 0.87) and AL (r = 0.81; 90% CI 0.74 to 0.86), and TRIMP with AL (r = 0.72; 90% CI 0.55 to 0.84), and possibly large for sRPE-TL with HSRD (r = 0.65; 90% CI 0.44 to 0.80). A reduction in these correlation magnitudes was evident for all other training modes (range of the change in r when compared with mixed training - 0.08 to - 0.58), with these differences being unclear to possibly large. Training mode explained 24-100% of the between-estimate variance in the internal-external load relationships. Measures of internal load derived from perceived exertion and heart rate show consistently positive associations with running- and accelerometer-derived external loads and intensity during team-sport training and competition, but the magnitude and uncertainty of these relationships are measure and training mode dependent.

Self-focusing and defocusing of Gaussian laser beams in collisional underdense magnetized plasmas with considering the nonlinear ohmic heating and ponderomotive force effects

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

Ettehadi Abari, Mehdi; Sedaghat, Mahsa; Shokri, Babak, E-mail: b-shokri@sbu.ac.ir

2015-10-15

The propagation characteristics of a Gaussian laser beam in collisional magnetized plasma are investigated by considering the ponderomotive and ohmic heating nonlinearities. Here, by taking into account the effect of the external magnetic field, the second order differential equation of the dimensionless beam width parameter is solved numerically. Furthermore, the nonlinear dielectric permittivity of the mentioned plasma medium in the paraxial approximation and its dependence on the propagation characteristics of the Gaussian laser pulse is obtained, and its variation in terms of the dimensionless plasma length is analyzed at different initial normalized plasma and cyclotron frequencies. The results show thatmore » the dimensionless beam width parameter is strongly affected by the initial plasma frequency, magnetic strength, and laser pulse intensity. Furthermore, it is found that there exists a certain intensity value below which the laser pulse tends to self focus, while the beam diverges above of this value. In addition, the results confirm that, by increasing the plasma and cyclotron frequencies (plasma density and magnetic strength), the self-focusing effect can occur intensively.« less

Separation of the Magnetic Field into Parts Produced by Internal and External Sources

NASA Astrophysics Data System (ADS)

Lazanja, David

2005-10-01

Given the total magnetic field on a toroidal plasma surface, a method for decomposing the field into a part due to internal currents (often the plasma) and a part due to external currents is presented. The decomposition exploits Laplace theory which is valid in the vacuum region between the plasma surface and the chamber walls. The method does not assume toroidal symmetry, and it is partly based on Merkel's 1986 work on vacuum field computations. A change in the plasma shape is produced by the total normal field perturbation on the plasma surface. This method allows a separation of the total normal field perturbation into a part produced by external currents and a part produced by the plasma response.

Effects of Complex System Structure and External Field in Opinion Formation

NASA Astrophysics Data System (ADS)

Guo, Long; Cai, Xu

Around us, the society structure and external field, such as government policy, the newspaper, the internet and other mass media, play a special role in shaping the attitudes, beliefs and public opinion. For studying the role of the society structure and the external field, we propose a new opinion model based on the former models. With computer simulations of opinion dynamics, we find that the smaller the clustering coefficient and the society size, the easier the consensus phase is reached and other interesting results.

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.

Mechanical improvement of metal reinforcement rings for a finite ring-shaped superconducting bulk

NASA Astrophysics Data System (ADS)

Huang, Chen-Guang; Zhou, You-He

2018-03-01

As a key technique, reinforcement of type-II superconducting bulks with metal rings can efficiently improve their mechanical properties to enhance the maximum trapped field. In this paper, we study the magnetostrictive and fracture behaviors of a finite superconducting ring bulk reinforced by three typical reinforcing structures composed of metal rings during the magnetizing process by means of the minimization of magnetic energy and the finite element method. After a field-dependent critical current density is adopted, the magnetostriction, pinning-induced stress, and crack tip stress intensity factor are calculated considering the demagnetization effects. The results show that the mechanical properties of the ring bulk are strongly dependent on the reinforcing structure and the material and geometrical parameters of the metal rings. Introducing the metal ring can significantly reduce the hoop stress, and the reduction effect by internal reinforcement is much improved relative to external reinforcement. By comparison, bilateral reinforcement seems to be the best candidate structure. Only when the metal rings have particular Young's modulus and radial thickness will they contribute to improve the mechanical properties the most. In addition, if an edge crack is pre-existing in the ring bulk, the presence of metal rings can effectively avoid crack propagation since it reduces the crack tip stress intensity factor by nearly one order of magnitude.

The Effect of External Magnetic Fields on the MRT Instability in MagLIF

NASA Astrophysics Data System (ADS)

Hess, Mark; Peterson, Kyle; Weis, Matthew; Lau, Yue Ying

2014-10-01

Recent experiments on MagLIF which incorporate an external B-field suggest that the MRT instability within the liner has a different behavior than without the B-field. Previous work by Chandrasekhar and Harris have illustrated how the MRT growth rate, assuming fixed liner density and fixed acceleration, can change due to the presence of an external B-field. In this work, we show how the growth rate of the MRT instability is dynamically affected by the rapidly varying acceleration, liner density, and surface magnetic field, which is composed of the external B-field and the drive B-field of the liner in the MagLIF experiments. In addition, we also examine the effects of finite liner resistivity on MRT growth, which gives rise to an additional time scale corresponding to magnetic diffusion. We discuss the implications of this result for future MagLIF designs. Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy under Contract DE-AC04-94AL85000.

Nonequilibrium electrophoresis of an ion-selective microgranule for weak and moderate external electric fields

NASA Astrophysics Data System (ADS)

Frants, E. A.; Ganchenko, G. S.; Shelistov, V. S.; Amiroudine, S.; Demekhin, E. A.

2018-02-01

Electrokinetics and the movement of charge-selective micro-granules in an electrolyte solution under the influence of an external electric field are investigated theoretically. Straightforward perturbation analysis is applied to a thin electric double layer and a weak external field, while a numerical solution is used for moderate electric fields. The asymptotic solution enables the determination of the salt concentration, electric charge distribution, and electro-osmotic velocity fields. It may also be used to obtain a simple analytical formula for the electrophoretic velocity in the case of quasi-equilibrium electrophoresis (electrophoresis of the first kind). This formula differs from the famous Helmholtz-Smoluchowski relation, which applies to dielectric microparticles, but not to ion-selective granules. Numerical calculations are used to validate the derived formula for weak external electric fields, but for moderate fields, nonlinear effects lead to a significant increase in electrophoretic mobility and to a transition from quasi-equilibrium electrophoresis of the first kind to nonequilibrium electrophoresis of the second kind. Theoretical results are successfully compared with experimental data.

Brushed permanent magnet DC MLC motor operation in an external magnetic field.

PubMed

Yun, J; St Aubin, J; Rathee, S; Fallone, B G

2010-05-01

Linac-MR systems for real-time image-guided radiotherapy will utilize the multileaf collimators (MLCs) to perform conformal radiotherapy and tumor tracking. The MLCs would be exposed to the external fringe magnetic fields of the linac-MR hybrid systems. Therefore, an experimental investigation of the effect of an external magnetic field on the brushed permanent magnet DC motors used in some MLC systems was performed. The changes in motor speed and current were measured for varying external magnetic field strengths up to 2000 G generated by an EEV electromagnet. These changes in motor characteristics were measured for three orientations of the motor in the external magnetic field, mimicking changes in motor orientations due to installation and/or collimator rotations. In addition, the functionality of the associated magnetic motor encoder was tested. The tested motors are used with the Varian 120 leaf Millennium MLC (Maxon Motor half leaf and full leaf motors) and the Varian 52 leaf MKII MLC (MicroMo Electronics leaf motor) including a carriage motor (MicroMo Electronics). In most cases, the magnetic encoder of the motors failed prior to any damage to the gearbox or the permanent magnet motor itself. This sets an upper limit of the external magnetic field strength on the motor function. The measured limits of the external magnetic fields were found to vary by the motor type. The leaf motor used with a Varian 52 leaf MKII MLC system tolerated up to 450 +/- 10 G. The carriage motor tolerated up to 2000 +/- 10 G field. The motors used with the Varian 120 leaf Millennium MLC system were found to tolerate a maximum of 600 +/- 10 G. The current Varian MLC system motors can be used for real-time image-guided radiotherapy coupled to a linac-MR system, provided the fringe magnetic fields at their locations are below the determined tolerance levels. With the fringe magnetic fields of linac-MR systems expected to be larger than the tolerance levels determined, some form of magnetic shielding would be required.

Spherical Particle in Nematic Liquid Crystal Under an External Field: The Saturn Ring Regime

NASA Astrophysics Data System (ADS)

Alama, Stan; Bronsard, Lia; Lamy, Xavier

2018-03-01

We consider a nematic liquid crystal occupying the exterior region in R^3 outside of a spherical particle, with radial strong anchoring. Within the context of the Landau-de Gennes theory, we study minimizers subject to an external field, modeled by an additional term which favors nematic alignment parallel to the field. When the external field is high enough, we obtain a scaling law for the energy. The energy scale corresponds to minimizers concentrating their energy in a boundary layer around the particle, with quadrupolar symmetry. This suggests the presence of a Saturn ring defect around the particle, rather than a dipolar director field typical of a point defect.

Crisis route to chaos in semiconductor lasers subjected to external optical feedback

NASA Astrophysics Data System (ADS)

Wishon, Michael J.; Locquet, Alexandre; Chang, C. Y.; Choi, D.; Citrin, D. S.

2018-03-01

Semiconductor lasers subjected to optical feedback have been intensively used as archetypical testbeds for high-speed (sub-ns) and high-dimensional nonlinear dynamics. By simultaneously extracting all the dynamical variables, we demonstrate that for larger current, the commonly named "quasiperiodic" route is in fact based on mixed external-cavity solutions that lock the oscillation frequency of the intensity, voltage, and separation in optical frequency through a mechanism involving successive rejections along the unstable manifold of an antimode. We show that chaos emerges from a crisis resulting from the inability to maintain locking as the unstable manifold becomes inaccessible.

Frequency analysis for modulation-enhanced powder diffraction.

PubMed

Chernyshov, Dmitry; Dyadkin, Vadim; van Beek, Wouter; Urakawa, Atsushi

2016-07-01

Periodic modulation of external conditions on a crystalline sample with a consequent analysis of periodic diffraction response has been recently proposed as a tool to enhance experimental sensitivity for minor structural changes. Here the intensity distributions for both a linear and nonlinear structural response induced by a symmetric and periodic stimulus are analysed. The analysis is further extended for powder diffraction when an external perturbation changes not only the intensity of Bragg lines but also their positions. The derived results should serve as a basis for a quantitative modelling of modulation-enhanced diffraction data measured in real conditions.

Neural network evaluation of tokamak current profiles for real time control

NASA Astrophysics Data System (ADS)

Wróblewski, Dariusz

1997-02-01

Active feedback control of the current profile, requiring real-time determination of the current profile parameters, is envisioned for tokamaks operating in enhanced confinement regimes. The distribution of toroidal current in a tokamak is now routinely evaluated based on external (magnetic probes, flux loops) and internal (motional Stark effect) measurements of the poloidal magnetic field. However, the analysis involves reconstruction of magnetohydrodynamic equilibrium and is too intensive computationally to be performed in real time. In the present study, a neural network is used to provide a mapping from the magnetic measurements (internal and external) to selected parameters of the safety factor profile. The single-pass, feedforward calculation of output of a trained neural network is very fast, making this approach particularly suitable for real-time applications. The network was trained on a large set of simulated equilibrium data for the DIII-D tokamak. The database encompasses a large variety of current profiles including the hollow current profiles important for reversed central shear operation. The parameters of safety factor profile (a quantity related to the current profile through the magnetic field tilt angle) estimated by the neural network include central safety factor, q0, minimum value of q, qmin, and the location of qmin. Very good performance of the trained neural network both for simulated test data and for experimental datais demonstrated.

Neural network evaluation of tokamak current profiles for real time control (abstract)

NASA Astrophysics Data System (ADS)

Wróblewski, Dariusz

1997-01-01

Active feedback control of the current profile, requiring real-time determination of the current profile parameters, is envisioned for tokamaks operating in enhanced confinement regimes. The distribution of toroidal current in a tokamak is now routinely evaluated based on external (magnetic probes, flux loops) and internal (motional Stark effect) measurements of the poloidal magnetic field. However, the analysis involves reconstruction of magnetohydrodynamic equilibrium and is too intensive computationally to be performed in real time. In the present study, a neural network is used to provide a mapping from the magnetic measurements (internal and external) to selected parameters of the safety factor profile. The single-pass, feedforward calculation of output of a trained neural network is very fast, making this approach particularly suitable for real-time applications. The network was trained on a large set of simulated equilibrium data for the DIII-D tokamak. The database encompasses a large variety of current profiles including the hollow current profiles important for reversed central shear operation. The parameters of safety factor profile (a quantity related to the current profile through the magnetic field tilt angle) estimated by the neural network include central safety factor, q0, minimum value of q, qmin, and the location of qmin. Very good performance of the trained neural network both for simulated test data and for experimental data is demonstrated.

Magnetically Responsive Superhydrophobic Surface: In Situ Reversible Switching of Water Droplet Wettability and Adhesion for Droplet Manipulation.

PubMed

Yang, Chao; Wu, Lei; Li, Gang

2018-06-13

A smart, magnetically responsive superhydrophobic surface was facilely prepared by combining spray coating and magnetic-field-directed self-assembly. The surface comprised a dense array of magnetorheological elastomer micropillars (MREMPs). Benefitting from the magnetic field-stiffening effect of the MREMPs, the surface exhibited reversible switching of the wettability and adhesion that was responsive to an on/off magnetic field. The wettability and adhesion properties of the surfaces with MREMPs were investigated under different magnetic fields. The results revealed that the adhesion force and sliding behaviors of these surfaces were strongly dependent on the intensity of the applied magnetic field and the mixing ratio of poly(dimethylsiloxane) (PDMS), iron particles, and solvent (in solution) used for preparation of the magnetically responsive superhydrophobic surfaces. The adhesion transition was attributed to the tunable mechanical properties of the MREMPs, which was easily controlled by an external magnetic field. It was also demonstrated that the magnetically responsive superhydrophobic surface can be used as a "mechanical hand" for no-loss liquid droplet transportation. This magnetically responsive superhydrophobic surface not only provides a novel interface for microfluidic control and droplet transportation, but also opens up new avenues for achieving smart liquid-repellent skin, programmable fluid collection and transport, and smart microfluidic devices.

Direct ion heating in overdense plasmas through the Brillouin instability driven by relativistic whistler waves

NASA Astrophysics Data System (ADS)

Sano, Takayoshi; Hata, Masayasu; Iwata, Natsumi; Mima, Kunioki; Sentoku, Yasuhiko

2017-10-01

Strong magnetic fields over kilo-Tesla have been available in the laboratory by the use of ultra-intense lasers. It would be interesting to apply those strong fields to other laser experiments such as the inertial confinement fusion and laboratory astrophysics. The characteristics of laser-plasma interactions could be modified significantly by the presence of such strong magnetic fields. We investigate electromagnetic wave propagation in overdense plasmas along the magnetic field for a right-hand circularly polarized wave by PIC simulations. Since the whistler mode has no cutoff density, it can penetrate into overdense plasmas and interact directly with charged particles there. When the external field strength is near a critical value defined by that the cyclotron frequency is equal to the laser one, it is reported that electrons are accelerated efficiently by the cyclotron resonance. However, if the field strength is far beyond the critical value, the cyclotron resonance is inefficient, while the ions gain a large amount of energy directly from the laser light owning to the Brillouin scattering. As the result, only ions are heated up selectively. We will discuss about the application of this ion heating in dense plasmas. This work was supported by JSPS KAKENHI Grant Number JP15K21767.

Modulating the band gap of a boron nitride bilayer with an external electric field for photocatalyst

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

Tang, Y. R.; Cao, J. X., E-mail: jxcao@xtu.edu.cn; Zhang, Y.

2016-05-21

By virtue of first principle calculations, we propose an approach to reduce the band gap of layered semiconductors through the application of external electric fields for photocatalysis. As a typical example, the band gap of a boron nitride (BN) bilayer was reduced in the range from 4.45 eV to 0.3 eV by varying the external electric field strength. More interestingly, it is found that the uppermost valence band and the lowest conduction band are dominated by the N-p{sub z} and B-p{sub z} from different layers of the BN sheet, which suggests a wonderful photoexcited electron and hole separation system for photocatalysis. Ourmore » results imply that the strong external electric field can present an abrupt polarized surface.« less

Condition for a Bounded System of Klein-Gordon Particles in Electric and Magnetic Fields

NASA Astrophysics Data System (ADS)

Kisoglu, Hasan Fatih; Sogut, Kenan

2018-07-01

We investigate the motion of relativistic spinless particles in an external electromagnetic field that is considered to has a constant magnetic field and a time-dependent electric field. For such a system, we obtain analytical eigenfunctions through Asymptotic Iteration Method. We also obtain a condition of choosing the external magnetic field for which the system is bounded with usage of the method in perturbation theory.

Sports Management Faculty External Grant-Writing Activities in the United States

ERIC Educational Resources Information Center

DeVinney, Timothy P.

2012-01-01

This study was conducted to fill a void in information, provide relevant, current data for faculty members related to external grant-writing activities related to the academic field of sport management and serve as a tool that may aid in the advancement of external grant-writing efforts within the field of sport management. All data is specific to…

Magnetism and high magnetic-field-induced stability of alloy carbides in Fe-based materials.

PubMed

Hou, T P; Wu, K M; Liu, W M; Peet, M J; Hulme-Smith, C N; Guo, L; Zhuang, L

2018-02-14

Understanding the nature of the magnetic-field-induced precipitation behaviors represents a major step forward towards unravelling the real nature of interesting phenomena in Fe-based alloys and especially towards solving the key materials problem for the development of fusion energy. Experimental results indicate that the applied high magnetic field effectively promotes the precipitation of M 23 C 6 carbides. We build an integrated method, which breaks through the limitations of zero temperature and zero external field, to concentrate on the dependence of the stability induced by the magnetic effect, excluding the thermal effect. We investigate the intimate relationship between the external field and the origins of various magnetics structural characteristics, which are derived from the interactions among the various Wyckoff sites of iron atoms, antiparallel spin of chromium and Fe-C bond distances. The high-magnetic-field-induced exchange coupling increases with the strength of the external field, which then causes an increase in the parallel magnetic moment. The stability of the alloy carbide M 23 C 6 is more dependent on external field effects than thermal effects, whereas that of M 2 C, M 3 C and M 7 C 3 is mainly determined by thermal effects.

Swim stress, motion, and deformation of active matter: effect of an external field.

PubMed

Takatori, Sho C; Brady, John F

2014-12-21

We analyze the stress, dispersion, and average swimming speed of self-propelled particles subjected to an external field that affects their orientation and speed. The swimming trajectory is governed by a competition between the orienting influence (i.e., taxis) associated with the external (e.g., magnetic, gravitational, thermal, nutrient concentration) field versus the effects that randomize the particle orientations (e.g., rotary Brownian motion and/or an intrinsic tumbling mechanism like the flagella of bacteria). The swimmers' motion is characterized by a mean drift velocity and an effective translational diffusivity that becomes anisotropic in the presence of the orienting field. Since the diffusivity yields information about the micromechanical stress, the anisotropy generated by the external field creates a normal stress difference in the recently developed "swim stress" tensor [Takatori, Yan, and Brady, Phys. Rev. Lett., 2014]. This property can be exploited in the design of soft, compressible materials in which their size, shape, and motion can be manipulated and tuned by loading the material with active swimmers. Since the swimmers exert different normal stresses in different directions, the material can compress/expand, elongate, and translate depending on the external field strength. Such an active system can be used as nano/micromechanical devices and motors. Analytical solutions are corroborated by Brownian dynamics simulations.

Simulation of the formation of nonequilibrium structures in magnetorheological fluids subject to an external magnetic field

NASA Astrophysics Data System (ADS)

Mohebi, M.; Jamasbi, N.; Liu, Jing

1996-11-01

We developed a computer model to understand the nonequilibrium structures induced in a magnetorheological (MR) fluid by rapidly applying an external magnetic field. MR fluids consist of particles suspended in a liquid where particles interact through dipole moments induced by the external magnetic field. We have simulated these induced structures in both directions, parallel and perpendicular to the field, in the limit of fastest response, by neglecting thermal motion and applying the field instantaneously. Our results show that the process of structure formation starts with particles forming chains aligned with the external field. The chains then coalesce to form columns and wall-like structures (``worms'' as viewed from the top). The complexity of this pattern is found to depend on the concentration of particles and the confinement of the cell in the direction of the external field. These results are consistent with experimental observations [G.A. Flores et al., in Proceedings of the Fifth International Conference on ER Fluids, MR Suspensions, and Associate Technology, University of Sheffield, Sheffield, 1995, edited by W. Bullough (World Scientific, Singapore, 1996), p. 140]. We have also used this model to study the interaction of two chains. The results of this study help in the understanding of the connection between the thickness of the sample and the increased complexity of the observed lateral pattern.

Visco-Resistive MHD Modeling Benchmark of Forced Magnetic Reconnection

NASA Astrophysics Data System (ADS)

Beidler, M. T.; Hegna, C. C.; Sovinec, C. R.; Callen, J. D.; Ferraro, N. M.

2016-10-01

The presence of externally-applied 3D magnetic fields can affect important phenomena in tokamaks, including mode locking, disruptions, and edge localized modes. External fields penetrate into the plasma and can lead to forced magnetic reconnection (FMR), and hence magnetic islands, on resonant surfaces if the local plasma rotation relative to the external field is slow. Preliminary visco-resistive MHD simulations of FMR in a slab geometry are consistent with theory. Specifically, linear simulations exhibit proper scaling of the penetrated field with resistivity, viscosity, and flow, and nonlinear simulations exhibit a bifurcation from a flow-screened to a field-penetrated, magnetic island state as the external field is increased, due to the 3D electromagnetic force. These results will be compared to simulations of FMR in a circular cross-section, cylindrical geometry by way of a benchmark between the NIMROD and M3D-C1 extended-MHD codes. Because neither this geometry nor the MHD model has the physics of poloidal flow damping, the theory of will be expanded to include poloidal flow effects. The resulting theory will be tested with linear and nonlinear simulations that vary the resistivity, viscosity, flow, and external field. Supported by OFES DoE Grants DE-FG02-92ER54139, DE-FG02-86ER53218, DE-AC02-09CH11466, and the SciDAC Center for Extended MHD Modeling.

Large-scale, near-field magnetic fields from external sources and the corresponding induced internal field

NASA Technical Reports Server (NTRS)

Langel, R. A.; Estes, R. H.

1985-01-01

Data from Magsat analyzed as a function of the Dst index to determine the first degree/order spherical harmonic description of the near-earth external field and its corresponding induced field. The analysis was done separately for data from dawn and dusk. The Magsat data was compared with POGO data. A local time variation of the external field persists even during very quiet magnetic conditions; both a diurnal and 8-hour period are present. A crude estimate of Sq current in the 45 deg geomagnetic latitude range is obtained for 1966 to 1970. The current strength, located in the ionosphere and induced in the earth, is typical of earlier determinations from surface data, although its maximum is displaced in local time from previous results.

The mond external field effect on the dynamics of the globular clusters: general considerations and application to NGC 2419

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

Derakhshani, Kamran, E-mail: kderakhshani@iasbs.ac.ir

2014-03-01

In this paper, we investigate the external field effect in the context of the MOdified Newtonian Dynamics (MOND) on the surface brightness and velocity dispersion profiles of globular clusters (GCs). Using N-MODY, which is an N-body simulation code with a MOND potential solver, we show that the general effect of the external field for diffuse clusters, which obey MOND in most of their parts, is that it pushes the dynamics toward the Newtonian regime. On the other hand, for more compact clusters, which are essentially Newtonian in their inner parts, the external field is effective mainly in the outer partsmore » of compact clusters. As a case study, we then choose the remote Galactic GC NGC 2419. By varying the cluster mass, half-light radius, and mass-to-light ratio, we aim to find a model that will reproduce the observational data most effectively, using N-MODY. We find that even if we take the Galactic external field into account, a Newtonian Plummer sphere represents the observational data better than MOND to an order of magnitude in terms of the total χ{sup 2} of surface brightness and velocity dispersion.« less

The MOND External Field Effect on the Dynamics of the Globular Clusters: General Considerations and Application to NGC 2419

NASA Astrophysics Data System (ADS)

Derakhshani, Kamran

2014-03-01

In this paper, we investigate the external field effect in the context of the MOdified Newtonian Dynamics (MOND) on the surface brightness and velocity dispersion profiles of globular clusters (GCs). Using N-MODY, which is an N-body simulation code with a MOND potential solver, we show that the general effect of the external field for diffuse clusters, which obey MOND in most of their parts, is that it pushes the dynamics toward the Newtonian regime. On the other hand, for more compact clusters, which are essentially Newtonian in their inner parts, the external field is effective mainly in the outer parts of compact clusters. As a case study, we then choose the remote Galactic GC NGC 2419. By varying the cluster mass, half-light radius, and mass-to-light ratio, we aim to find a model that will reproduce the observational data most effectively, using N-MODY. We find that even if we take the Galactic external field into account, a Newtonian Plummer sphere represents the observational data better than MOND to an order of magnitude in terms of the total χ2 of surface brightness and velocity dispersion.

Memory effects for a stochastic fractional oscillator in a magnetic field

NASA Astrophysics Data System (ADS)

Mankin, Romi; Laas, Katrin; Laas, Tõnu; Paekivi, Sander

2018-01-01

The problem of random motion of harmonically trapped charged particles in a constant external magnetic field is studied. A generalized three-dimensional Langevin equation with a power-law memory kernel is used to model the interaction of Brownian particles with the complex structure of viscoelastic media (e.g., dusty plasmas). The influence of a fluctuating environment is modeled by an additive fractional Gaussian noise. In the long-time limit the exact expressions of the first-order and second-order moments of the fluctuating position for the Brownian particle subjected to an external periodic force in the plane perpendicular to the magnetic field have been calculated. Also, the particle's angular momentum is found. It is shown that an interplay of external periodic forcing, memory, and colored noise can generate a variety of cooperation effects, such as memory-induced sign reversals of the angular momentum, multiresonance versus Larmor frequency, and memory-induced particle confinement in the absence of an external trapping field. Particularly in the case without external trapping, if the memory exponent is lower than a critical value, we find a resonancelike behavior of the anisotropy in the particle position distribution versus the driving frequency, implying that it can be efficiently excited by an oscillating electric field. Similarities and differences between the behaviors of the models with internal and external noises are also discussed.

Pseudoclassical Foldy-Wouthuysen transformation and canonical quantization of (D-2n)-dimensional relativistic particle with spin in an external electromagnetic field

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

Grigoryan, G.V.; Grigoryan, R.P.

1995-09-01

The canonical quantization of a (D=2n)-dimensional Dirac particle with spin in an arbitrary external electromagnetic field is performed in a gauge that makes it possible to describe simultaneously particles and antiparticles (both massive and massless) already at the classical level. A pseudoclassical Foldy-Wouthuysen transformation is used to find the canonical (Newton-Wigner) coordinates. The connection between this quantization scheme and Blount`s picture describing the behavior of a Dirac particle in an external electromagnetic field is discussed.

Momentum dependence in pair production by an external field

NASA Astrophysics Data System (ADS)

Asakawa, M.

1992-08-01

The transverse and the longitudinal momentum dependences of the pair production under an adiabatically exerted uniform abelian external field are calculated with their importance in models for the production of quark-gluon plasma in ultrarelativistic heavy ion collisions in mind. The importance of the initial condition is revealed. We show that superposition of acceleration by the external field and barrier penetration is reflected in the longitudinal momentum dependence. The peculiar nature of the boost invariant system which is expected to be approximately realized in ultrarelativistic nuclear collisions is pointed out.

Effects of external magnetic fields and Rashba spin-orbit coupling on spin conductance in graphene

NASA Astrophysics Data System (ADS)

Shirkani, H.; Amiri, F.; Golshan, M. M.

2013-12-01

The present article is concerned with spin conductance in graphene (SCG) when both the application of an external magnetic field and Rashba spin-orbit coupling (RSOC) are taken into account. Introducing a Casimir operator, we analyze the structure of total Hamiltonian and demonstrate how the matrix elements along with the summations involved in the suitably adopted Kubo’s formula, may be analytically calculated. From the results so-obtained one finds that, in addition to discrete and symmetric behavior of SCG against the external field, it exhibits large peaks as high as six times that in ordinary two dimensional electron gases. Moreover, it is shown that for any Fermi energy the SCG asymptotically approaches a value three times larger than the standard unit of (e/4π), for large magnetic fields. Effects of the magnetic field, RSOC and Fermi energy on the characteristics of SCG are also discussed. The material presented in this article thus provides novel means of controlling the SCG by external agents.

Neutral meson properties under an external magnetic field in nonlocal chiral quark models

NASA Astrophysics Data System (ADS)

Gómez Dumm, D.; Izzo Villafañe, M. F.; Scoccola, N. N.

2018-02-01

We study the behavior of neutral meson properties in the presence of a static uniform external magnetic field in the context of nonlocal chiral quark models. The formalism is worked out introducing Ritus transforms of Dirac fields, which allow to obtain closed analytical expressions for π0 and σ meson masses and for the π0 decay constant. Numerical results for these observables are quoted for various parametrizations. In particular, the behavior of the π0 meson mass with the magnetic field is found to be in good agreement with lattice QCD results. It is also seen that the Goldberger-Treiman and Gell-Mann-Oakes-Renner chiral relations remain valid within these models in the presence of the external magnetic field.

Electrically tunable negative refraction in core/shell-structured nanorod fluids.

PubMed

Su, Zhaoxian; Yin, Jianbo; Guan, Yanqing; Zhao, Xiaopeng

2014-10-21

We theoretically investigate optical refraction behavior in a fluid system which contains silica-coated gold nanorods dispersed in silicone oil under an external electric field. Because of the formation of a chain-like or lattice-like structure of dispersed nanorods along the electric field, the fluid shows a hyperbolic equifrequency contour characteristic and, as a result, all-angle broadband optical negative refraction for transverse magnetic wave propagation can be realized. We calculate the effective permittivity tensor of the fluid and verify the analysis using finite element simulations. We also find that the negative refractive index can vary with the electric field strength and external field distribution. Under a non-uniform external field, the gradient refraction behavior can be realized.

Bubble Dynamics, Two-Phase Flow, and Boiling Heat Transfer in Microgravity

NASA Technical Reports Server (NTRS)

Chung, Jacob N.

1996-01-01

The objective of the research is to study the feasibility of employing an external force to replace the buoyancy force in order to maintain nucleate boiling in microgravity. We have found that a bulk velocity field, an electric field and an acoustic field could each play the role of the gravity field in microgravity. Nucleate boiling could be maintained by any one of the three external force fields in space.

Small-size controlled vacuum spark-gap in an external magnetic field

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

Asyunin, V. I., E-mail: asvi@mail.ru; Davydov, S. G.; Dolgov, A. N., E-mail: alnikdolgov@mail.ru

2015-02-15

It is demonstrated that the operation of a small-size controlled spark-gap can be controlled by applying a uniform external magnetic field. It is shown that the magnetic field of such a simple configuration efficiently suppresses the effect of localization of the discharge current after multiple actuations of the spark-gap.

Electric Field-Dependent Photoluminescence in Multilayer Transition Metal Dichalcogenides

NASA Astrophysics Data System (ADS)

Stanev, T. K.; Henning, A.; Sangwan, V. K.; Speiser, N.; Stern, N. P.; Lauhon, L. J.; Hersam, M. C.; Wang, K.; Valencia, D.; Charles, J.; Kubis, T. C.

Owing to interlayer coupling, transition metal dichalcogenides (TMDCs) such as MoS2 exhibit strong layer dependence of optical and electronic phenomena such as the band gap and trion and neutral exciton population dynamics. Here, we systematically measure the effect of layer number on the optical response of multilayer MoS2 in an external electric field, observing field and layer number dependent emission energy and photoluminescence intensity. These effects are studied in few (2-6) and bulk (11 +) layered structures at low temperatures. In MoS2\\ the observed layer dependence arises from several mechanisms, including interlayer charge transfer, band structure, Stark Effect, Fermi level changes, screening, and surface effects, so it can be challenging to isolate how these mechanisms impact the observables. Because it behaves like a stack of weakly interacting monolayers rather than multilayer or bulk, ReS2 provides a comparison to traditional TMDCs to help isolate the underlying physical mechanisms dictating the response of multilayers. This work is supported by the National Science Foundation MRSEC program (DMR-1121262), and the 2-DARE Grant (EFRI-1433510). N.P.S. is an Alfred P. Sloan Research Fellow.

Photodetectors Based on Organic–Inorganic Hybrid Lead Halide Perovskites

PubMed Central

Zhou, Jiachen

2017-01-01

Abstract Recent years have witnessed skyrocketing research achievements in organic–inorganic hybrid lead halide perovskites (OIHPs) in the photovoltaic field. In addition to photovoltaics, more and more studies have focused on OIHPs‐based photodetectors in the past two years, due to the remarkable optoelectronic properties of OIHPs. This article summarizes the latest progress in this research field. To begin with, the factors influencing the performance of photodetectors are discussed, including both internal and external factors. In particular, the channel width and the incident power intensities should be taken into account to precisely and objectively evaluate and compare the output performance of different photodetectors. Next, photodetectors fabricated on single‐component perovskites in terms of different micromorphologies are discussed, namely, 3D thin‐film and single crystalline, 2D nanoplates, 1D nanowires, and 0D nanocrystals, respectively. Then, bilayer structured perovskite‐based photodetectors incorporating inorganic and organic semiconductors are discussed to improve the optoelectronic performance of their pristine counterparts. Additionally, flexible OIHPs‐based photodetectors are highlighted. Finally, a brief conclusion and outlook is given on the progress and challenges in the field of perovskites‐based photodetectors. PMID:29375959

External magnetic field-induced selective biodistribution of magnetoliposomes in mice

NASA Astrophysics Data System (ADS)

García-Jimeno, Sonia; Escribano, Elvira; Queralt, Josep; Estelrich, Joan

2012-08-01

This study looked at the effect of an external magnet on the biodistribution of magnetoliposomes intravenously administrated in mice (8 mg iron/kg) with and without induced acute inflammation. Our results showed that due to enhanced vascular permeability, magnetoliposomes accumulated at the site of inflammation in the absence of an external magnetic field, but the amount of iron present increased under the effect of a magnet located at the inflammation zone. This increase was dependent on the time (20 or 60 min) of exposure of the external magnetic field. It was also observed that the presence of the magnet was associated with lower amounts of iron in the liver, spleen, and plasma than was found in mice in which a magnet had not been applied. The results of this study confirm that it is possible to target drugs encapsulated in magnetic particles by means of an external magnet.

Static magnetic field (SMF) sensing of the P(723)/P(689) photosynthetic complex.

PubMed

Bhattacharya, Abhishek; Chakraborty, Madhurima; Raja, Sufi O; Ghosh, Avijit; Dasgupta, Maitrayee; Dasgupta, Anjan Kr

2014-12-01

Moderate intensity SMF have been shown to act as a controller of the protic potential in the coherent milieu of the thylakoid membranes. SMF of the order of 60-500 mT induces memory-like effect in photosystem I (PSI, P723) emission with a correlated oscillation of photosystem II (PSII, P689) fluorescence emission at a temperature of 77 K. The observed magnetic perturbation that affects the thylakoid photon capture circuitry was also found to be associated with the bio-energetic machinery of the thylakoid membranes. At normal pH, SMF causes an enhancement of PSI fluorescence emission intensity (P723/P689 > 1), followed by a slow relaxation on the removal of SMF. The enhancement of the PSI fluorescence intensity also occurs under no-field condition, if either the pH of the medium is lowered, or protonophores, such as carbonyl cyanide chlorophenylhydrazine or nigericin are added (P723/P689≥ 2). If SMF was applied under such a low pH condition or in the presence of protonophore, a reverse effect, particularly, a reduction of the enhanced PSI emission was observed. Because SMF is essentially equivalent to a spin perturbation, the observed effects can be explained in terms of spin re-organization, illustrating a memory effect via membrane re-alignment and assembly. The mimicry of conventional uncouplers by SMF is also notable; the essential difference being the reversibility and manoeuvrability of the latter (SMF). Finally, the effect implies numerous possibilities of externally regulating the photon capture and proton circulation in the thylakoid membranes using controlled SMF.

Investigating the effects of external fields polarization on the coupling of pure magnetic waves in the human body in very low frequencies

PubMed Central

2007-01-01

In this paper we studied the effects of external fields' polarization on the coupling of pure magnetic fields into human body. Finite Difference Time Domain (FDTD) method is used to calculate the current densities induced in a 1 cm resolution anatomically based model with proper tissue conductivities. Twenty different tissues have been considered in this investigation and scaled FDTD technique is used to convert the results of computer code run in 15 MHz to low frequencies which are encountered in the vicinity of industrial induction heating and melting devices. It has been found that external magnetic field's orientation due to human body has a pronounced impact on the level of induced currents in different body tissues. This may potentially help developing protecting strategies to mitigate the situations in which workers are exposed to high levels of external magnetic radiation. PMID:17504520

The energy associated with MHD waves generation in the solar wind plasma

NASA Technical Reports Server (NTRS)

delaTorre, A.

1995-01-01

Gyrotropic symmetry is usually assumed in measurements of electron distribution functions in the heliosphere. This prevents the calculation of a net current perpendicular to the magnetic field lines. Previous theoretical results derived by one of the authors for a collisionless plasma with isotropic electrons in a strong magnetic field have shown that the excitation of MHD modes becomes possible when the external perpendicular current is non-zero. We consider then that any anisotropic electron population can be thought of as 'external', interacting with the remaining plasma through the self-consistent electromagnetic field. From this point of view any perpendicular current may be due to the anisotropic electrons, or to an external source like a stream, or to both. As perpendicular currents cannot be derived from the measured distribution functions, we resort to Ampere's law and experimental data of magnetic field fluctuations. The transfer of energy between MHD modes and external currents is then discussed.

Research on the effect of the external magnetic field in the joule balance at NIM

NASA Astrophysics Data System (ADS)

Xu, Jinxin; You, Qiang; Li, Zhengkun; Bai, Yang; Lu, Yunfeng; Zhang, Zhonghua; He, Qing

2018-06-01

The first determination of the Planck constant with the second generation of the joule balance, NIM-2, was completed in 2017 with an uncertainty of 2.4  ×  10‑7. Due to the movement of the magnet during the measurement process, the effect of the external field is a critical problem in NIM-2. At present, the electromagnet system is used in NIM-2. By taking the average of the results with positive and negative exciting currents, the uncertainty from the external field is reduced to 1.7  ×  10‑7, which is still the largest source in the uncertainty budget as all the other items are less than 1  ×  10‑7. In the near future, a permanent magnet system will be applied in NIM-2 and the main field cannot be reversed. Although the coupling of the external magnetic field in the permanent magnet system is about 40 times less than that in the electromagnet system, further reduction of this effect is still required in the permanent magnet system. In this paper, the effect of the external field is analyzed in both an electromagnet system and a permanent magnet system based on simulations and experiments. Then, the methods of magnetic shielding and compensation coils are proposed and simulated in the permanent magnet system. The results show that it may be possible to reduce the uncertainty of the external field to less than 2  ×  10‑8 in the permanent magnet system by employing the two methods.

Enhanced magnetic field probe array for improved excluded flux calculations on the C-2U advanced beam-driven field-reversed configuration plasma experiment

NASA Astrophysics Data System (ADS)

Roche, T.; Thompson, M. C.; Mendoza, R.; Allfrey, I.; Garate, E.; Romero, J.; Douglass, J.

2016-11-01

External flux conserving coils were installed onto the exterior of the C-2U [M. W. Binderbauer et al., Phys. Plasmas 22, 056110 (2015)] confinement vessel to increase the flux confinement time of the system. The 0.5 in. stainless steel vessel wall has a skin time of ˜5 ms. The addition of the external copper coils effectively increases this time to ˜7 ms. This led to better-confined/longer-lived field-reversed configuration (FRC) plasmas. The fringing fields generated by the external coils have the side effect of rendering external field measurements invalid. Such measurements were key to the previous method of excluded flux calculation [M. C. Thompson et al., Rev. Sci. Instrum. 83, 10D709 (2012)]. A new array of B-dot probes and Rogowski coils were installed to better determine the amount of flux leaked out of the system and ultimately provide a more robust measurement of plasma parameters related to pressure balance including the excluded flux radius. The B-dot probes are surface mountable chip inductors with inductance of 33 μH capable of measuring the DC magnetic field and transient field, due to resistive current decay in the wall/coils, when coupled with active integrators. The Rogowski coils measure the total change in current in each external coil (150 A/2 ms). Currents were also actively driven in the external coils. This renders the assumption of total flux conservation invalid which further complicates the analysis process. The ultimate solution to these issues and the record breaking resultant FRC lifetimes will be presented.

Enhanced magnetic field probe array for improved excluded flux calculations on the C-2U advanced beam-driven field-reversed configuration plasma experiment.

PubMed

Roche, T; Thompson, M C; Mendoza, R; Allfrey, I; Garate, E; Romero, J; Douglass, J

2016-11-01

External flux conserving coils were installed onto the exterior of the C-2U [M. W. Binderbauer et al., Phys. Plasmas 22, 056110 (2015)] confinement vessel to increase the flux confinement time of the system. The 0.5 in. stainless steel vessel wall has a skin time of ∼5 ms. The addition of the external copper coils effectively increases this time to ∼7 ms. This led to better-confined/longer-lived field-reversed configuration (FRC) plasmas. The fringing fields generated by the external coils have the side effect of rendering external field measurements invalid. Such measurements were key to the previous method of excluded flux calculation [M. C. Thompson et al., Rev. Sci. Instrum. 83, 10D709 (2012)]. A new array of B-dot probes and Rogowski coils were installed to better determine the amount of flux leaked out of the system and ultimately provide a more robust measurement of plasma parameters related to pressure balance including the excluded flux radius. The B-dot probes are surface mountable chip inductors with inductance of 33 μH capable of measuring the DC magnetic field and transient field, due to resistive current decay in the wall/coils, when coupled with active integrators. The Rogowski coils measure the total change in current in each external coil (150 A/2 ms). Currents were also actively driven in the external coils. This renders the assumption of total flux conservation invalid which further complicates the analysis process. The ultimate solution to these issues and the record breaking resultant FRC lifetimes will be presented.

Enhanced magnetic field probe array for improved excluded flux calculations on the C-2U advanced beam-driven field-reversed configuration plasma experiment

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

Roche, T., E-mail: troche@trialphaenergy.com; Thompson, M. C.; Mendoza, R.

2016-11-15

External flux conserving coils were installed onto the exterior of the C-2U [M. W. Binderbauer et al., Phys. Plasmas 22, 056110 (2015)] confinement vessel to increase the flux confinement time of the system. The 0.5 in. stainless steel vessel wall has a skin time of ∼5 ms. The addition of the external copper coils effectively increases this time to ∼7 ms. This led to better-confined/longer-lived field-reversed configuration (FRC) plasmas. The fringing fields generated by the external coils have the side effect of rendering external field measurements invalid. Such measurements were key to the previous method of excluded flux calculation [M.more » C. Thompson et al., Rev. Sci. Instrum. 83, 10D709 (2012)]. A new array of B-dot probes and Rogowski coils were installed to better determine the amount of flux leaked out of the system and ultimately provide a more robust measurement of plasma parameters related to pressure balance including the excluded flux radius. The B-dot probes are surface mountable chip inductors with inductance of 33 μH capable of measuring the DC magnetic field and transient field, due to resistive current decay in the wall/coils, when coupled with active integrators. The Rogowski coils measure the total change in current in each external coil (150 A/2 ms). Currents were also actively driven in the external coils. This renders the assumption of total flux conservation invalid which further complicates the analysis process. The ultimate solution to these issues and the record breaking resultant FRC lifetimes will be presented.« less

Shaping Social Activity by Incentivizing Users

PubMed Central

Farajtabar, Mehrdad; Du, Nan; Rodriguez, Manuel Gomez; Valera, Isabel; Zha, Hongyuan; Song, Le

2015-01-01

Events in an online social network can be categorized roughly into endogenous events, where users just respond to the actions of their neighbors within the network, or exogenous events, where users take actions due to drives external to the network. How much external drive should be provided to each user, such that the network activity can be steered towards a target state? In this paper, we model social events using multivariate Hawkes processes, which can capture both endogenous and exogenous event intensities, and derive a time dependent linear relation between the intensity of exogenous events and the overall network activity. Exploiting this connection, we develop a convex optimization framework for determining the required level of external drive in order for the network to reach a desired activity level. We experimented with event data gathered from Twitter, and show that our method can steer the activity of the network more accurately than alternatives. PMID:26005312

General Matrix Inversion Technique for the Calibration of Electric Field Sensor Arrays on Aircraft Platforms

NASA Technical Reports Server (NTRS)

Mach, D. M.; Koshak, W. J.

2007-01-01

A matrix calibration procedure has been developed that uniquely relates the electric fields measured at the aircraft with the external vector electric field and net aircraft charge. The calibration method can be generalized to any reasonable combination of electric field measurements and aircraft. A calibration matrix is determined for each aircraft that represents the individual instrument responses to the external electric field. The aircraft geometry and configuration of field mills (FMs) uniquely define the matrix. The matrix can then be inverted to determine the external electric field and net aircraft charge from the FM outputs. A distinct advantage of the method is that if one or more FMs need to be eliminated or deemphasized [e.g., due to a malfunction), it is a simple matter to reinvert the matrix without the malfunctioning FMs. To demonstrate the calibration technique, data are presented from several aircraft programs (ER-2, DC-8, Altus, and Citation).

Development of data communication system with ultra high frequency radio wave for implantable artificial hearts.

PubMed

Tsujimura, Shinichi; Yamagishi, Hiroto; Sankai, Yoshiyuki

2009-01-01

In order to minimize infection risks of patients with artificial hearts, wireless data transmission methods with electromagnetic induction or light have been developed. However, these methods tend to become difficult to transmit data if the external data transmission unit moves from its proper position. To resolve this serious problem, the purpose of this study is to develop a prototype wireless data communication system with ultra high frequency radio wave and confirm its performance. Due to its high-speed communication rate, low power consumption, high tolerance to electromagnetic disturbances, and secure wireless communication, we adopted Bluetooth radio wave technology for our system. The system consists of an internal data transmission unit and an external data transmission unit (53 by 64 by 16 mm, each), and each has a Bluetooth module (radio field intensity: 4 dBm, receiver sensitivity: -80 dBm). The internal unit also has a micro controller with an 8-channel 10-bit A/D converter, and the external unit also has a RS-232C converter. We experimented with the internal unit implanted into pig meat, and carried out data transmission tests to evaluate the performance of this system in tissue thickness of up to 3 mm. As a result, data transfer speeds of about 20 kbps were achieved within the communication distance of 10 m. In conclusion, we confirmed that the system can wirelessly transmit the data from the inside of the body to the outside, and it promises to resolve unstable data transmission due to accidental movements of an external data transmission unit.

External split field generator

DOEpatents

Thundat, Thomas George [Knoxville, TN; Van Neste, Charles W [Kingston, TN; Vass, Arpad Alexander [Oak Ridge, TN

2012-02-21

A generator includes a coil disposed about a core. A first stationary magnetic field source may be disposed on a first end portion of the core and a second stationary magnetic field source may be disposed on a second end portion of core. The first and second stationary magnetic field sources apply a stationary magnetic field to the coil. An external magnetic field source may be disposed outside the coil to apply a moving magnetic field to the coil. Electrical energy is generated in response to an interaction between the coil, the moving magnetic field, and the stationary magnetic field.

BEST medical radioisotope production cyclotrons

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

Sabaiduc, Vasile; Milton, Bruce; Suthanthiran, Krishnan

2013-04-19

Best Cyclotron Systems Inc (BCSI) is currently developing 14 MeV, 25 MeV, 35MeV and 70MeV cyclotrons for radioisotope production and research applications as well as the entire spectrum of targets and nuclear synthesis modules for the production of Positron Emission Tomography (PET), Single Photon Emission Computed Tomography (SPECT) and radiation therapy isotopes. The company is a subsidiary of Best Medical International, renowned in the field of medical instrumentation and radiation therapy. All cyclotrons have external negative hydrogen ion sources, four radial sectors with two dees in opposite valleys, cryogenic vacuum system and simultaneous beam extraction on opposite lines. The beammore » intensity ranges from 400 {mu}A to 1000 {mu}A, depending on the cyclotron energy and application.« less

Nuclear resonance reflectivity from a [57Fe/Cr]30 multilayer with the Synchrotron Mössbauer Source.

PubMed

Andreeva, Marina A; Baulin, Roman A; Chumakov, Aleksandr I; Rüffer, Rudolf; Smirnov, Gennadii V; Babanov, Yurii A; Devyaterikov, Denis I; Milyaev, Mikhail A; Ponomarev, Dmitrii A; Romashev, Lazar N; Ustinov, Vladimir V

2018-03-01

Mössbauer reflectivity spectra and nuclear resonance reflectivity (NRR) curves have been measured using the Synchrotron Mössbauer Source (SMS) for a [ 57 Fe/Cr] 30 periodic multilayer, characterized by the antiferromagnetic interlayer coupling between adjacent 57 Fe layers. Specific features of the Mössbauer reflectivity spectra measured with π-polarized radiation of the SMS near the critical angle and at the `magnetic' maximum on the NRR curve are analyzed. The variation of the ratio of lines in the Mössbauer reflectivity spectra and the change of the intensity of the `magnetic' maximum under an applied external field has been used to reveal the transformation of the magnetic alignment in the investigated multilayer.

The influence of the Earth's magnetosphere on the high-energy solar protons

NASA Technical Reports Server (NTRS)

Bazilevskaya, G. A.; Makhmutov, V. S.; Charakhchyan, T. N.

1985-01-01

In the Earth's polar regions the intensity of the solar protons with the energy above the critical energy of geomagnetic cutoff is the same as in the interplanetary space. The penumbra in the polar regions is small and the East-West effect is also small. However the geomagnetic cutoff rigidity R sub c in polar regions is difficult to calculate because it is not sufficient to include only the internal sources of the geomagnetic field. During the magneto-quiescent periods the real value of R sub c can be less by 0.1 GV than the calculated value because of the external sources. During the geomagnetic storms the real value of R sub c is still lower.

Analysis of plasmas generated by fission fragments. [nuclear pumped lasers and helium plasma

NASA Technical Reports Server (NTRS)

Deese, J. E.; Hassan, H. A.

1977-01-01

A kinetic model is developed for a plasma generated by fission fragments and the results are employed to study helium plasma generated in a tube coated with fissionable material. Because both the heavy particles and electrons play important roles in creating the plasma, their effects are considered simultaneously. The calculations are carried out for a range of neutron fluxes and pressures. In general, the predictions of the theory are in good agreement with available intensity measurements. Moreover, the theory predicts the experimentally measured inversions. However, the calculated gain coefficients are such that lasing is not expected to take place in a helium plasma generated by fission fragments. The effects of an externally applied electric field are also considered.

Electric control of magnon frequencies and magnetic moment of bismuth ferrite thin films at room temperature.

PubMed

Kumar, Ashok; Scott, J F; Katiyar, R S

2011-08-08

Here, we report the tuning of room-temperature magnon frequencies from 473 GHz to 402 GHz (14%) and magnetic moment from 4 to 18 emu∕cm(3) at 100 Oe under the application of external electric fields (E) across interdigital electrodes in BiFeO(3) (BFO) thin films. A decrease in magnon frequencies and increase in phonon frequencies were observed with Magnon and phonon Raman intensities are asymmetric with polarity, decreasing with positive E (+E) and increasing with negative E (-E) where polarity is with respect to in-plane polarization P. The magnetoelectric coupling (α) is proved to be linear and a rather isotropic α = 8.5 × 10(-12) sm(-1).

Numerical study of MHD supersonic flow control

NASA Astrophysics Data System (ADS)

Ryakhovskiy, A. I.; Schmidt, A. A.

2017-11-01

Supersonic MHD flow around a blunted body with a constant external magnetic field has been simulated for a number of geometries as well as a range of the flow parameters. Solvers based on Balbas-Tadmor MHD schemes and HLLC-Roe Godunov-type method have been developed within the OpenFOAM framework. The stability of the solution varies depending on the intensity of magnetic interaction The obtained solutions show the potential of MHD flow control and provide insights into for the development of the flow control system. The analysis of the results proves the applicability of numerical schemes, that are being used in the solvers. A number of ways to improve both the mathematical model of the process and the developed solvers are proposed.

Design of experiments for microencapsulation applications: A review.

PubMed

Paulo, Filipa; Santos, Lúcia

2017-08-01

Microencapsulation techniques have been intensively explored by many research sectors such as pharmaceutical and food industries. Microencapsulation allows to protect the active ingredient from the external environment, mask undesired flavours, a possible controlled release of compounds among others. The purpose of this review is to provide a background of design of experiments in microencapsulation research context. Optimization processes are required for an accurate research in these fields and therefore, the right implementation of micro-sized techniques at industrial scale. This article critically reviews the use of the response surface methodologies in pharmaceutical and food microencapsulation research areas. A survey of optimization procedures in the literature, in the last few years is also presented. Copyright © 2017 Elsevier B.V. All rights reserved.

Brachytherapy next generation: robotic systems

PubMed Central

Popescu, Tiberiu; Kacsó, Alex Cristian; Pisla, Doina

2015-01-01

In a field dominated by external beam radiation therapy (EBRT), both the therapeutic and technical possibilities of brachytherapy (BT) are underrated, shadowed by protons and intensity modulated radiotherapy. Decreasing expertise and indications, as well as increasing lack of specific BT training for radiation therapy (RT) residents led to the real need of shortening its learning curve and making it more popular. Developing robotic BT devices can be a way to mitigate the above issues. There are many teams working at custom-made robotic BT platforms to perfect and overcome the limitations of the existing systems. This paper provides a picture of the current state-of-the-art in robotic assisted BT, as it also conveys the author's solution to the problem, a parallel robot that uses CT-guidance. PMID:26816510

BEST medical radioisotope production cyclotrons

NASA Astrophysics Data System (ADS)

Sabaiduc, Vasile; Milton, Bruce; Suthanthiran, Krishnan; Gelbart, W. Z.; Johnson, Richard R.

2013-04-01

Best Cyclotron Systems Inc (BCSI) is currently developing 14 MeV, 25 MeV, 35MeV and 70MeV cyclotrons for radioisotope production and research applications as well as the entire spectrum of targets and nuclear synthesis modules for the production of Positron Emission Tomography (PET), Single Photon Emission Computed Tomography (SPECT) and radiation therapy isotopes. The company is a subsidiary of Best Medical International, renowned in the field of medical instrumentation and radiation therapy. All cyclotrons have external negative hydrogen ion sources, four radial sectors with two dees in opposite valleys, cryogenic vacuum system and simultaneous beam extraction on opposite lines. The beam intensity ranges from 400 μA to 1000 μA, depending on the cyclotron energy and application [1].

Strong-Field Driven Dynamics of Metal and Dielectric Nanoparticles

NASA Astrophysics Data System (ADS)

Powell, Jeffrey

The motion of electrons in atoms, molecules, and solids in the presence of intense electromagnetic radiation is an important research topic in physics and physical chemistry because of its fundamental nature and numerous practical applications, ranging from precise machining of materials to optical control of chemical reactions and light-driven electronic devices. Mechanisms of light-matter interactions critically depend on the dimensions of the irradiated system and evolve significantly from single atoms or molecules to the macroscopic bulk. Nanoparticles provide the link between these two extremes. In this thesis, I take advantage of this bridge to study light-matter interactions as a function of nanoparticle size, shape, and composition. I present here three discrete, but interconnected, experiments contributing to our knowledge of nanoparticle properties and their response to intense, short-pulsed light fields. First, I investigate how individual nanoparticles interact with each other in solution, studying their temperature-dependent solubility. The interaction potential between 5.5nm gold nanoparticles, ligated by an alkanethiol was found to be -0.165eV, in reasonable agreement with a phenomenological model. The other two experiments explore ultrafast dynamics driven by intense femtosecond lasers in isolated, gas-phase metallic and dielectric nanoparticles. Photoelectron momentum imaging is applied to study the response of gold, silica, and gold-shell/silica-core nanoparticles (ranging from single to several hundred nanometers in size) with near-infrared (NIR), 25 fs laser pulses in the intensity range of 1011 - 1014 W/cm2. These measurements, which constitute the bulk of my graduate work, reveal the complex interplay between the external optical field and the induced near-field of the nanoparticle, resulting in the emission of very energetic electrons that are much faster than those emitted from isolated atoms or molecules exposed to the same light pulses. The highest photoelectron energies ("cutoffs") were measured as a function of laser intensity, nanoparticle material and size. We found that the energy cutoffs increase monotonically with laser intensity and nanoparticle size, except for the gold/silica hybrid where the plasmon resonance response modifies this behavior at low intensities. The measured photoelectron spectra for metallic nanoparticles display a large energy enhancement over silica. Finally, the last part of this thesis explores the possibility to apply time-resolved x-ray scattering as a probe of the ultrafast dynamics in isolated nanoparticles driven by very intense ( 1015 W/cm2) NIR laser radiation. To do this, I developed and built a nanoparticle source capable of injecting single, gas-phase nanoparticles with a narrow size distribution into the laser focus. We used femtosecond x-ray pulses from an x-ray free electron laser (XFEL) to map the evolution of the laser-irradiated nanoparticle. The ultrafast dynamics were observed in the single-shot x-ray diffraction patterns measured as a function of delay between the NIR and x-ray pulses, which allows for femtosecond temporal and nanometer spatial resolution. We found that the intense IR laser pulse rapidly ionizes the nanoparticle, effectively turning it into a nanoplasma within less than a picosecond, and observed signatures of the nanoparticle surface softening on a few hundred-femtosecond time scale.

Influence of electromagnetic field on soliton-mediated charge transport in biological systems.

PubMed

Brizhik, Larissa

2015-01-01

It is shown that electromagnetic fields affect dynamics of Davydov's solitons which provide charge transport processes in macromolecules during metabolism of the system. There is a resonant frequency of the field at which it can cause the transition of electrons from bound soliton states into delocalised states. Such decay of solitons reduces the effectiveness of charge transport, and, therefore, inhibits redox processes. Solitons radiate their own electromagnetic field of characteristic frequency determined by their average velocity. This self-radiated field leads to synchronization of soliton dynamics and charge transport processes, and is the source of the coherence in the system. Exposition of the system to the oscillating electromagnetic field of the frequency, which coincides with the eigen-frequency of solitons can enhance eigen-radiation of solitons, and, therefore, will enhance synchronization of charge transpor, stimulate the redox processes and increase coherence in the system. Electromagnetic oscillating field causes also ratchet phenomenon of solitons, i.e., drift of solitons in macromolecules in the presence of unbiased periodic field. Such additional drift enhances the charge transport processes. It is shown that temperature facilitates the ratchet drift. In particular, temperature fluctuations lead to the lowering of the critical value of the intensity and period of the field, above which the drift of solitons takes place. Moreover, there is a stochastic resonance in the soliton dynamics in external electromagnetic fields. This means, that there is some optimal temperature at which the drift of solitons is maximal.

Electron beam therapy with coil-generated magnetic fields.

PubMed

Nardi, Eran; Barnea, Gideon; Ma, Chang-Ming

2004-06-01

This paper presents an initial study on the issues involved in the practical implementation of the use of transverse magnetic fields in electron beam therapy. By using such magnetic fields the dose delivered to the tumor region can increase significantly relative to that deposited to the healthy tissue. Initially we calculated the magnetic fields produced by the Helmholtz coil and modified Helmholtz coil configurations. These configurations, which can readily be used to generate high intensity magnetic fields, approximate the idealized magnetic fields studied in our previous publications. It was therefore of interest to perform a detailed study of the fields produced by these configurations. Electron beam dose distributions for 15 MeV electrons were calculated using the ACCEPTM code for a 3T transverse magnetic field produced by the modified Helmholtz configuration. The dose distribution was compared to those obtained with no magnetic field. The results were similar to those obtained in our previous work, where an idealized step function magnetic field was used and a 3T field was shown to be the optimal field strength. A simpler configuration was also studied in which a single external coil was used to generate the field. Electron dose distributions are also presented for a given geometry and given magnetic field strength using this configuration. The results indicate that this method is more difficult to apply to radiotherapy due to its lack of symmetry and its irregularity. For the various configurations dealt with here, a major problem is the need to shield the magnetic field in the beam propagation volume, a topic that must be studied in detail.

Controlling three-dimensional vortices using multiple and moving external fields

NASA Astrophysics Data System (ADS)

Das, Nirmali Prabha; Dutta, Sumana

2017-08-01

Spirals or scroll wave activities in cardiac tissues are the cause of lethal arrhythmias. The external control of these waves is thus of prime interest to scientists and physicians. In this article, we demonstrate the spatial control of scroll waves by using external electric fields and thermal gradients in experiments with the Belousov-Zhabotinsky reaction. We show that a scroll ring can be made to trace cyclic trajectories under a rotating electric field. Application of a thermal gradient in addition to the electric field deflects the motion and changes the nature of the trajectory. Our experimental results are analyzed and corroborated by numerical simulations based on an excitable reaction diffusion model.

Influence of periodic external fields in multiagent models with language dynamics

NASA Astrophysics Data System (ADS)

Palombi, Filippo; Ferriani, Stefano; Toti, Simona

2017-12-01

We investigate large-scale effects induced by external fields, phenomenologically interpreted as mass media, in multiagent models evolving with the microscopic dynamics of the binary naming game. In particular, we show that a single external field, broadcasting information at regular time intervals, can reverse the majority opinion of the population, provided the frequency and the effectiveness of the sent messages lie above well-defined thresholds. We study the phase structure of the model in the mean field approximation and in numerical simulations with several network topologies. We also investigate the influence on the agent dynamics of two competing external fields, periodically broadcasting different messages. In finite regions of the parameter space we observe periodic equilibrium states in which the average opinion densities are reversed with respect to naive expectations. Such equilibria occur in two cases: (i) when the frequencies of the competing messages are different but close to each other; (ii) when the frequencies are equal and the relative time shift of the messages does not exceed half a period. We interpret the observed phenomena as a result of the interplay between the external fields and the internal dynamics of the agents and conclude that, depending on the model parameters, the naming game is consistent with scenarios of first- or second-mover advantage (to borrow an expression from the jargon of business strategy).

Equilibrium and initial linear stability analysis of liquid metal falling film flows in a varying spanwise magnetic field

NASA Astrophysics Data System (ADS)

Gao, D.; Morley, N. B.

2002-12-01

A 2D model for MHD free surface flow in a spanwise field is developed. The model, designed to simulate film flows of liquid metals in future thermo­nuclear fusion reactors, considers an applied spanwise magnetic field with spatial and temporal variation and an applied streamwise external current. A special case - a thin falling film flow in spanwise magnetic field with constant gradient and constant applied external streamwise current, is here investigated in depth to gain insight into the behavior of the MHD film flow. The fully developed flow solution is derived and initial linear stability analysis is performed for this special case. It is seen that the velocity profile is significantly changed due to the presence of the MHD effect, resulting in the free surface analog of the classic M-shape velocity profile seen in developing pipe flows in a field gradient. The field gradient is also seen to destabilize the film flow under most conditions. The effect of external current depends on the relative direction of the field gradient to the current direction. By controlling the magnitude of an external current, it is possible to obtain a linearly stable falling film under these magnetic field conditions. Tables 1, Figs 12, Refs 20.

Field-testing of a cost-effective mobile-phone based microscope for screening of Schistosoma haematobium infection (Conference Presentation)

NASA Astrophysics Data System (ADS)

Ceylan Koydemir, Hatice; Bogoch, Isaac I.; Tseng, Derek; Ephraim, Richard K. D.; Duah, Evans; Tee, Joseph; Andrews, Jason R.; Ozcan, Aydogan

2016-03-01

Schistosomiasis is a parasitic and neglected tropical disease, and affects <200-million people across the world, with school-aged children disproportionately affected. Here we present field-testing results of a handheld and cost effective smartphone-based microscope in rural Ghana, Africa, for point-of-care diagnosis of S. haematobium infection. In this mobile-phone microscope, a custom-designed 3D printed opto-mechanical attachment (~150g) is placed in contact with the smartphone camera-lens, creating an imaging-system with a half-pitch resolution of ~0.87µm. This unit includes an external lens (also taken from a mobile-phone camera), a sample tray, a z-stage to adjust the focus, two light-emitting-diodes (LEDs) and two diffusers for uniform illumination of the sample. In our field-testing, 60 urine samples, collected from children, were used, where the prevalence of the infection was 72.9%. After concentration of the sample with centrifugation, the sediment was placed on a glass-slide and S. haematobium eggs were first identified/quantified using conventional benchtop microscopy by an expert diagnostician, and then a second expert, blinded to these results, determined the presence/absence of eggs using our mobile-phone microscope. Compared to conventional microscopy, our mobile-phone microscope had a diagnostic sensitivity of 72.1%, specificity of 100%, positive-predictive-value of 100%, and a negative-predictive-value of 57.1%. Furthermore, our mobile-phone platform demonstrated a sensitivity of 65.7% and 100% for low-intensity infections (≤50 eggs/10 mL urine) and high-intensity infections (<50 eggs/10 mL urine), respectively. We believe that this cost-effective and field-portable mobile-phone microscope may play an important role in the diagnosis of schistosomiasis and various other global health challenges.

Control of thermal therapies with moving power deposition field.

PubMed

Arora, Dhiraj; Minor, Mark A; Skliar, Mikhail; Roemer, Robert B

2006-03-07

A thermal therapy feedback control approach to control thermal dose using a moving power deposition field is developed and evaluated using simulations. A normal tissue safety objective is incorporated in the controller design by imposing constraints on temperature elevations at selected normal tissue locations. The proposed control technique consists of two stages. The first stage uses a model-based sliding mode controller that dynamically generates an 'ideal' power deposition profile which is generally unrealizable with available heating modalities. Subsequently, in order to approximately realize this spatially distributed idealized power deposition, a constrained quadratic optimizer is implemented to compute intensities and dwell times for a set of pre-selected power deposition fields created by a scanned focused transducer. The dwell times for various power deposition profiles are dynamically generated online as opposed to the commonly employed a priori-decided heating strategies. Dynamic intensity and trajectory generation safeguards the treatment outcome against modelling uncertainties and unknown disturbances. The controller is designed to enforce simultaneous activation of multiple normal tissue temperature constraints by rapidly switching between various power deposition profiles. The hypothesis behind the controller design is that the simultaneous activation of multiple constraints substantially reduces treatment time without compromising normal tissue safety. The controller performance and robustness with respect to parameter uncertainties is evaluated using simulations. The results demonstrate that the proposed controller can successfully deliver the desired thermal dose to the target while maintaining the temperatures at the user-specified normal tissue locations at or below the maximum allowable values. Although demonstrated for the case of a scanned focused ultrasound transducer, the developed approach can be extended to other heating modalities with moving deposition fields, such as external and interstitial ultrasound phased arrays, multiple radiofrequency needle applicators and microwave antennae.

Ion beam enhancement in magnetically insulated ion diodes for high-intensity pulsed ion beam generation in non-relativistic mode

NASA Astrophysics Data System (ADS)

Zhu, X. P.; Zhang, Z. C.; Pushkarev, A. I.; Lei, M. K.

2016-01-01

High-intensity pulsed ion beam (HIPIB) with ion current density above Child-Langmuir limit is achieved by extracting ion beam from anode plasma of ion diodes with suppressing electron flow under magnetic field insulation. It was theoretically estimated that with increasing the magnetic field, a maximal value of ion current density may reach nearly 3 times that of Child-Langmuir limit in a non-relativistic mode and close to 6 times in a highly relativistic mode. In this study, the behavior of ion beam enhancement by magnetic insulation is systematically investigated in three types of magnetically insulated ion diodes (MIDs) with passive anode, taking into account the anode plasma generation process on the anode surface. A maximal enhancement factor higher than 6 over the Child-Langmuir limit can be obtained in the non-relativistic mode with accelerating voltage of 200-300 kV. The MIDs differ in two anode plasma formation mechanisms, i.e., surface flashover of a dielectric coating on the anode and explosive emission of electrons from the anode, as well as in two insulation modes of external-magnetic field and self-magnetic field with either non-closed or closed drift of electrons in the anode-cathode (A-K) gap, respectively. Combined with ion current density measurement, energy density characterization is employed to resolve the spatial distribution of energy density before focusing for exploring the ion beam generation process. Consistent results are obtained on three types of MIDs concerning control of neutralizing electron flows for the space charge of ions where the high ion beam enhancement is determined by effective electron neutralization in the A-K gap, while the HIPIB composition of different ion species downstream from the diode may be considerably affected by the ion beam neutralization during propagation.

Intensity noise limit in a phase-sensitive optical time-domain reflectometer with a semiconductor laser source

NASA Astrophysics Data System (ADS)

E Alekseev, A.; Tezadov, Ya A.; Potapov, V. T.

2017-05-01

In the present paper we perform, for the first time, the analysis of the average intensity noise power level at the output of a coherent phase-sensitive optical time-domain reflectometer (phase-OTDR) with a semiconductor laser source. The origin of the considered intensity noise lies in random phase fluctuations of a semiconductor laser source field. These phase fluctuations are converted to intensity noise in the process of interference of backscattered light. This intensity noise inevitably emerges in every phase-OTDR spatial channel and limits its sensitivity to external phase actions. The analysis of intensity noise in a phase-OTDR was based on the study of a fiber scattered-light interferometer (FSLI) which is treated as the constituent part of OTDR. When considered independently, FSLI has a broad intensity noise spectrum at its output; when FSLI is treated as a part of a phase-OTDR, due to aliasing effect, the wide FSLI noise spectrum is folded within the spectral band, determined by the probe pulse repetition frequency. In the analysis one of the conventional phase-OTDR schemes with rectangular dual-pulse probe signal was considered, the FSLI, which corresponds to this OTDR scheme, has two scattering fiber segments with additional time delay introduced between backscattered fields. The average intensity noise power and resulting noise spectrum at the output of this FSLI are determined by the degree of coherence of the semiconductor laser source, the length of the scattering fiber segments and by the additional time delay between the scattering segments. The average intensity noise characteristics at the output of the corresponding phase-OTDR are determined by the analogous parameters: the source coherence, the lengths of the parts constituting the dual-pulse and the time interval which separates the parts of the dual-pulse. In the paper the expression for the average noise power spectral density (NPSD) at the output of FSLI was theoretically derived and experimentally verified. Based on the found average NPSD of FSLI, a simple relation connecting the phase-OTDR parameters and the limiting level of full average intensity noise power at its output was derived. This relation was verified by experimental measurement of the average noise power at the output of phase-OTDR. The limiting noise level, considered in the paper, determines the fundamental noise floor for the phase-OTDR with given parameters of the source coherence, probe pulse length and time delay between two pulses constituting the dual-pulse.

Experimental studies of protozoan response to intense magnetic fields and forces

NASA Astrophysics Data System (ADS)

Guevorkian, Karine

Intense static magnetic fields of up to 31 Tesla were used as a novel tool to manipulate the swimming mechanics of unicellular organisms. It is shown that homogenous magnetic fields alter the swimming trajectories of the single cell protozoan Paramecium caudatum, by aligning them parallel to the applied field. Immobile neutrally buoyant paramecia also oriented in magnetic fields with similar rates as the motile ones. It was established that the magneto-orientation is mostly due to the magnetic torques acting on rigid structures in the cell body and therefore the response is a non-biological, passive response. From the orientation rate of paramecia in various magnetic field strengths, the average anisotropy of the diamagnetic susceptibility of the cell was estimated. It has also been demonstrated that magnetic forces can be used to create increased, decreased and even inverted simulated gravity environments for the investigation of the gravi-responses of single cells. Since the mechanisms by which Earth's gravity affects cell functioning are still not fully understood, a number of methods to simulate different strength gravity environments, such as centrifugation, have been employed. Exploiting the ability to exert magnetic forces on weakly diamagnetic constituents of the cells, we were able to vary the gravity from -8 g to 10 g, where g is Earth's gravity. Investigations of the swimming response of paramecia in these simulated gravities revealed that they actively regulate their swimming speed to oppose the external force. This result is in agreement with centrifugation experiments, confirming the credibility of the technique. Moreover, the Paramecium's swimming ceased in simulated gravity of 10 g, indicating a maximum possible propulsion force of 0.7 nN. The magnetic force technique to simulate gravity is the only earthbound technique that can create increased and decreased simulated gravities in the same experimental setup. These findings establish a general technique for applying continuously variable forces to cells or cell populations suitable for exploring their force transduction mechanisms.

Photoelectron transport tuning of self-assembled subbands

NASA Astrophysics Data System (ADS)

Xiong, Zhengwei; Wang, Xinmin; Wu, Weidong; Wang, Xuemin; Peng, Liping; Zhao, Yan; Yan, Dawei; Jiang, Tao; Shen, Changle; Zhan, Zhiqiang; Cao, Linhong; Li, Weihua

2016-02-01

Conventionally, electrical transport of quantum subbands occurs at very high electric fields, indicating that the medium is easy to break down. In the experiments and practical applications, the extreme condition is difficult to satisfy. For quantum information transmission, low power consumption and convenient implementation are what we expect. In this paper, we engineered a special quantum dot array (QDA) embedded in a single crystal matrix. By external optical field excitation, we found a series of subbands made of the self-assembled QDA discretely located in the matrix. Changing the spacing between the quantum dots leads to the variation of subband spacing. Artificially manipulating the microcosmic QDA system can bring interesting macroscopic effects, such as an enhanced absorption intensity in the ultraviolet range, a blue-shift of the surface plasmon resonance peak and nonlinear absorption changed from two-photon absorption to saturated absorption. The intrinsic mechanism of the subband optical response was revealed due to the strong quantum confinement effect and dominant intraband transitions. The weak surface plasmon resonance absorption of Ni QDA gave an excellent figure of merit of the order of 10-10. The composite films are expectation enough to become a prime candidate for nonlinear applications near 532 nm. Therefore with interplay of the weak optical field and subbands, we achieved a tunable photoelectron transport process.Conventionally, electrical transport of quantum subbands occurs at very high electric fields, indicating that the medium is easy to break down. In the experiments and practical applications, the extreme condition is difficult to satisfy. For quantum information transmission, low power consumption and convenient implementation are what we expect. In this paper, we engineered a special quantum dot array (QDA) embedded in a single crystal matrix. By external optical field excitation, we found a series of subbands made of the self-assembled QDA discretely located in the matrix. Changing the spacing between the quantum dots leads to the variation of subband spacing. Artificially manipulating the microcosmic QDA system can bring interesting macroscopic effects, such as an enhanced absorption intensity in the ultraviolet range, a blue-shift of the surface plasmon resonance peak and nonlinear absorption changed from two-photon absorption to saturated absorption. The intrinsic mechanism of the subband optical response was revealed due to the strong quantum confinement effect and dominant intraband transitions. The weak surface plasmon resonance absorption of Ni QDA gave an excellent figure of merit of the order of 10-10. The composite films are expectation enough to become a prime candidate for nonlinear applications near 532 nm. Therefore with interplay of the weak optical field and subbands, we achieved a tunable photoelectron transport process. Electronic supplementary information (ESI) available: Tables 1 and 2. See DOI: 10.1039/c5nr07861j

Study of light-absorbing crystal birefringence and electrical modulation mechanisms for coupled thermal-optical effects.

PubMed

Zhou, Ji; He, Zhihong; Ma, Yu; Dong, Shikui

2014-09-20

This paper discusses Gaussian laser transmission in double-refraction crystal whose incident light wavelength is within its absorption wave band. Two scenarios for coupled radiation and heat conduction are considered: one is provided with an applied external electric field, the other is not. A circular heat source with a Gaussian energy distribution is introduced to present the crystal's light-absorption process. The electromagnetic field frequency domain analysis equation and energy equation are solved to simulate the phenomenon by using the finite element method. It focuses on the influence of different values such as wavelength, incident light intensity, heat transfer coefficient, ambient temperature, crystal thickness, and applied electric field strength. The results show that the refraction index of polarized light increases with the increase of crystal temperature. It decreases as the strength of the applied electric field increases if it is positive. The mechanism of electrical modulation for the thermo-optical effect is used to keep the polarized light's index of refraction constant in our simulation. The quantitative relation between thermal boundary condition and strength of applied electric field during electrical modulation is determined. Numerical results indicate a possible approach to removing adverse thermal effects such as depolarization and wavefront distortion, which are caused by thermal deposition during linear laser absorption.

TEMHD Effects on Solidification Under Microgravity Conditions

NASA Technical Reports Server (NTRS)

Kao, Andrew; Pericleous, Koulis

2012-01-01

An unexplored potential exists to control microstructure evolution through the use of external DC magnetic fields. Thermoelectric currents form during solidification and interact with this external field to drive microscopic fluid dynamics within the inter-dendritic region. The convective heat and mass transport can lead to profound changes on the dendritic structure. In this paper the effect of high magnetic fields is demonstrated through the use of both 3-dimensional and 2-dimensional numerical models. The results show that the application of a magnetic field causes significant disruption to the dendritic morphology. Investigation into the underlying mechanism gives initial indicators of how external magnetic fields can either lead to unexpected growth behaviour, or alternatively can be used to control the evolution of microstructure in undercooled melts as encountered in levitated droplet solidification.

Large-scale, near-Earth, magnetic fields from external sources and the corresponding induced internal field

NASA Technical Reports Server (NTRS)

Langel, R. A.; Estes, R. H.

1983-01-01

Data from MAGSAT analyzed as a function of the Dst index to determine the first degree/order spherical harmonic description of the near-Earth external field and its corresponding induced field. The analysis was done separately for data from dawn and dusk. The MAGSAT data was compared with POGO data. A local time variation of the external field persists even during very quiet magnetic conditions; both a diurnal and 8-hour period are present. A crude estimate of Sq current in the 45 deg geomagnetic latitude range is obtained for 1966 to 1970. The current strength, located in the ionosphere and induced in the Earth, is typical of earlier determinations from surface data, although its maximum is displaced in local time from previous results.

Antiferromagnetic nano-oscillator in external magnetic fields

NASA Astrophysics Data System (ADS)

Checiński, Jakub; Frankowski, Marek; Stobiecki, Tomasz

2017-11-01

We describe the dynamics of an antiferromagnetic nano-oscillator in an external magnetic field of any given time distribution. The oscillator is powered by a spin current originating from spin-orbit effects in a neighboring heavy metal layer and is capable of emitting a THz signal in the presence of an additional easy-plane anisotropy. We derive an analytical formula describing the interaction between such a system and an external field, which can affect the output signal character. Interactions with magnetic pulses of different shapes, with a sinusoidal magnetic field and with a sequence of rapidly changing magnetic fields are discussed. We also perform numerical simulations based on the Landau-Lifshitz-Gilbert equation with spin-transfer torque effects to verify the obtained results and find a very good quantitative agreement between analytical and numerical predictions.

On the characteristics of a residual external signal seen in coefficients of main geomagnetic field models

NASA Astrophysics Data System (ADS)

Stefan, Cristiana; Demetrescu, Crisan; Dobrica, Venera

2014-05-01

Several recently developed main geomagnetic field models, based on both observatory and satellite data (e.g. IGRF, CHAOS, GRIMM, COV-OBS), as well as the historical model gufm1, have been designed to describe only the internal part of the field, except for the COV-OBS that also accounts for the external dipole. In this paper we analyze data and coefficients from two main field models, namely gufm1 (Jackson et al., 2000) and COV-OBS (Gillet et al., 2013), by means of low pass filters with a cutoff period of 11-year, to evidence a residual signal with seemingly external sources, superimposed on the internal part of the field. The characteristics of the residual signal in the dipole and non-dipole coefficients are discussed.

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.

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.

Internalizing and externalizing problems in adolescence: general and dimension-specific effects of familial loadings and preadolescent temperament traits.

PubMed

Ormel, J; Oldehinkel, A J; Ferdinand, R F; Hartman, C A; De Winter, A F; Veenstra, R; Vollebergh, W; Minderaa, R B; Buitelaar, J K; Verhulst, F C

2005-12-01

We investigated the links between familial loading, preadolescent temperament, and internalizing and externalizing problems in adolescence, hereby distinguishing effects on maladjustment in general versus dimension-specific effects on either internalizing or externalizing problems. In a population-based sample of 2230 preadolescents (10-11 years) familial loading (parental lifetime psychopathology) and offspring temperament were assessed at baseline by parent report, and offspring psychopathology at 2.5-years follow-up by self-report, teacher report and parent report. We used purified measures of temperament and psychopathology and partialled out shared variance between internalizing and externalizing problems. Familial loading of internalizing psychopathology predicted offspring internalizing but not externalizing problems, whereas familial loading of externalizing psychopathology predicted offspring externalizing but not internalizing problems. Both familial loadings were associated with Frustration, low Effortful Control, and Fear. Frustration acted as a general risk factor predicting severity of maladjustment; low Effortful Control and Fear acted as dimension-specific risk factors that predicted a particular type of psychopathology; whereas Shyness, High-Intensity Pleasure, and Affiliation acted as direction markers that steered the conditional probability of internalizing versus externalizing problems, in the event of maladjustment. Temperament traits mediated one-third of the association between familial loading and psychopathology. Findings were robust across different composite measures of psychopathology, and applied to girls as well as boys. With regard to familial loading and temperament, it is important to distinguish general risk factors (Frustration) from dimension-specific risk factors (familial loadings, Effortful Control, Fear), and direction markers that act as pathoplastic factors (Shyness, High-Intensity Pleasure, Affiliation) from both types of risk factors. About one-third of familial loading effects on psychopathology in early adolescence are mediated by temperament.

Quantum phase transition in dimerised spin-1/2 chains

NASA Astrophysics Data System (ADS)

Das, Aparajita; Bhadra, Sreeparna; Saha, Sonali

2015-11-01

Quantum phase transition in dimerised antiferromagnetic Heisenberg spin chain has been studied. A staircase structure in the variation of concurrence within strongly coupled pairs with that of external magnetic field has been observed indicating multiple critical (or critical like) points. Emergence of entanglement due to external magnetic field or magnetic entanglement is observed for weakly coupled spin pairs too in the same dimer chain. Though closed dimerised isotropic XXX Heisenberg chains with different dimer strengths were mainly explored, analogous studies on open chains as well as closed anisotropic (XX interaction) chains with tilted external magnetic field have also been studied.

Magnetoresistors as a tool for investigating the mechanical properties of ferromagnetic materials

NASA Astrophysics Data System (ADS)

Kaleta, Jerzy; Tumański, Slawomir; Żebracki, Jacek

1996-07-01

We have investigated the possibility of applying the Villari effect for measurements of the dependence of deformation on the external loading. The magnetic field arising due to the deformation has been measured with a Permalloy magnetoresistive sensor. The plot of the dependence of the external field H on the strain ɛ agrees almost perfectly with the classical dependence σ = f( ɛ) in tensile tests. In steel and nickel samples stress changes in the range 0-500 MPa were accompanied by changes in the external magnetic field in the range 0-300 A/m.

Cooling Stability Test of MgB2 Wire Immersed in Liquid Hydrogen under External Magnetic Field

NASA Astrophysics Data System (ADS)

Shirai, Yasuyuki; Hikawa, Kyosuke; Shiotsu, Masahiro; Tatsumoto, Hideki; Naruo, Yoshihiro; Kobayashi, Hiroaki; Inagaki, Yoshifumi

2014-05-01

Liquid hydrogen (LH2), which has large latent heat, low viscosity coefficient, is expected to be a candidate for a cryogen for superconducting wires, not only MgB2 but also other HTC superconductors. LH2 cooled superconducting wires are expected to have excellent electro-magnetic characteristics, which is necessary to be clear for cooling stability design of LH2 cooled superconducting device, however, due to handling difficulties of LH2, there are only few papers on the properties of LH2 cooled superconductors, especially under external magnetic field. We designed and made an experimental setup which can energize superconducting wires immersed in LH2 with the current of up to 500A under the condition of external magnetic field up to 7 T and pressure up to 1.5 MPa. In order to confirm experimental method and safety operation of the setup, over current tests were carried out using MgB2 superconducting wires under various external magnetic field conditions. Critical current of the test wire at the temperature 21, 24, 27, 29 K under external magnetic fields up to 1.2 T was successfully measured. The resistance of the wire also was measured, while the transport current exceeded the critical current of the wire.

Evaluation of the Match External Load in Soccer: Methods Comparison.

PubMed

Castagna, Carlo; Varley, Matthew; Póvoas, Susana C A; D'Ottavio, Stefano

2017-04-01

To test the interchangeability of 2 match-analysis approaches for external-load detection considering arbitrary selected speeds and metabolic power (MP) thresholds in male top-level soccer. Data analyses were performed considering match physical performance of 60 matches (1200 player cases) of randomly selected Spanish, German, and English first-division championship matches (2013-14 season). Match analysis was performed with a validated semiautomated multicamera system operating at 25 Hz. During a match, players covered 10,673 ± 348 m, of which 1778 ± 208 m and 2759 ± 241 m were performed at high intensity, as measured using speed (≥16 km/h, HI) and metabolic power (≥20 W/kg, MPHI) notations. High-intensity notations were nearly perfectly associated (r = .93, P < .0001). A huge method bias (980.63 ± 87.82 m, d = 11.67) was found when considering MPHI and HI. Very large correlations were found between match total distance covered and MPHI (r = .84, P < .0001) and HI (r = .74, P < .0001). Player high-intensity decelerations (≥-2 m/s 2 ) were very largely associated with MPHI (r = .73, P < .0001). The speed and MP methods are highly interchangeable at relative level (magnitude rank) but not absolute level (measure magnitude). The 2 physical match-analysis methods can be independently used to track match external load in elite-level players. However, match-analyst decisions must be based on use of a single method to avoid bias in external-load determination.

Quantitative determination of mineral composition by powder x-ray diffraction

DOEpatents

Pawloski, G.A.

1984-08-10

An external standard intensity ratio method is used for quantitatively determining mineralogic compositions of samples by x-ray diffraction. The method uses ratios of x-ray intensity peaks from a single run. Constants are previously determined for each mineral which is to be quantitatively measured. Ratios of the highest intensity peak of each mineral to be quantified in the sample and the highest intensity peak of a reference mineral contained in the sample are used to calculate sample composition.

Quantitative determination of mineral composition by powder X-ray diffraction

DOEpatents

Pawloski, Gayle A.

1986-01-01

An external standard intensity ratio method is used for quantitatively determining mineralogic compositions of samples by x-ray diffraction. The method uses ratios of x-ray intensity peaks from a single run. Constants are previously determined for each mineral which is to be quantitatively measured. Ratios of the highest intensity peak of each mineral to be quantified in the sample and the highest intensity peak of a reference mineral contained in the sample are used to calculate sample composition.

Defect dynamics and coarsening dynamics in smectic-C films

NASA Astrophysics Data System (ADS)

Pargellis, A. N.; Finn, P.; Goodby, J. W.; Panizza, P.; Yurke, B.; Cladis, P. E.

1992-12-01

We study the dynamics of defects generated in free-standing films of liquid crystals following a thermal quench from the smectic-A phase to the smectic-C phase. The defects are type-1 disclinations, and the strain field between defect pairs is confined to 2π walls. We compare our observations with a phenomenological model that includes dipole coupling of the director field to an external ordering field. This model is able to account for both the observed coalescence dynamics and the observed ordering dynamics. In the absence of an ordering field, our model predicts the defect density ρ to scale with time t as ρ lnρ~t-1. When the dipole coupling of the director field to an external ordering field is included, both the model and experiments show the defect coarsening proceeds as ρ~e-αt with the strain field confined to 2π walls. The external ordering field most likely arises from the director's tendency to align with edge dislocations within the liquid-crystal film.

Molecular dynamics study of response of liquid N,N-dimethylformamide to externally applied electric field using a polarizable force field

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

Gao, Weimin; Niu, Haitao; Lin, Tong

2014-01-28

The behavior of Liquid N,N-dimethylformamide subjected to a wide range of externally applied electric fields (from 0.001 V/nm to 1 V/nm) has been investigated through molecular dynamics simulation. To approach the objective the AMOEBA polarizable force field was extended to include the interaction of the external electric field with atomic partial charges and the contribution to the atomic polarization. The simulation results were evaluated with quantum mechanical calculations. The results from the present force field for the liquid at normal conditions were compared with the experimental and molecular dynamics results with non-polarizable and other polarizable force fields. The uniform externalmore » electric fields of higher than 0.01 V/nm have a significant effect on the structure of the liquid, which exhibits a variation in numerous properties, including molecular polarization, local cluster structure, rotation, alignment, energetics, and bulk thermodynamic and structural properties.« less

General Matrix Inversion for the Calibration of Electric Field Sensor Arrays on Aircraft Platforms

NASA Technical Reports Server (NTRS)

Mach, D. M.; Koshak, W. J.

2006-01-01

We have developed a matrix calibration procedure that uniquely relates the electric fields measured at the aircraft with the external vector electric field and net aircraft charge. Our calibration method is being used with all of our aircraft/electric field sensing combinations and can be generalized to any reasonable combination of electric field measurements and aircraft. We determine a calibration matrix that represents the individual instrument responses to the external electric field. The aircraft geometry and configuration of field mills (FMs) uniquely define the matrix. The matrix can then be inverted to determine the external electric field and net aircraft charge from the FM outputs. A distinct advantage of the method is that if one or more FMs need to be eliminated or de-emphasized (for example, due to a malfunction), it is a simple matter to reinvert the matrix without the malfunctioning FMs. To demonstrate our calibration technique, we present data from several of our aircraft programs (ER-2, DC-8, Altus, Citation).

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

Takahashi, Masato; Maeda, Hideaki; Graduate School of Yokohama City University, Yokohama, Kanagawa 230-0045

Achieving a higher magnetic field is important for solid-state nuclear magnetic resonance (NMR). But a conventional low temperature superconducting (LTS) magnet cannot exceed 1 GHz (23.5 T) due to the critical magnetic field. Thus, we started a project to replace the Nb{sub 3}Sn innermost coil of an existing 920 MHz NMR (21.6 T) with a Bi-2223 high temperature superconducting (HTS) innermost coil. Unfortunately, the HTS magnet cannot be operated in persistent current mode; an external dc power supply is required to operate the NMR magnet, causing magnetic field fluctuations. These fluctuations can be stabilized by a field-frequency lock system basedmore » on an external NMR detection coil. We demonstrate here such a field-frequency lock system in a 500 MHz LTS NMR magnet operated in an external current mode. The system uses a {sup 7}Li sample in a microcoil as external NMR detection system. The required field compensation is calculated from the frequency of the FID as measured with a frequency counter. The system detects the FID signal, determining the FID frequency, and calculates the required compensation coil current to stabilize the sample magnetic field. The magnetic field was stabilized at 0.05 ppm/3 h for magnetic field fluctuations of around 10 ppm. This method is especially effective for a magnet with large magnetic field fluctuations. The magnetic field of the compensation coil is relatively inhomogeneous in these cases and the inhomogeneity of the compensation coil can be taken into account.« less

Coherent inductive communications link for biomedical applications

NASA Technical Reports Server (NTRS)

Hogrefe, Arthur F. (Inventor); Radford, Wade E. (Inventor)

1985-01-01

A two-way coherent inductive communications link between an external transceiver and an internal transceiver located in a biologically implanted programmable medical device. Digitally formatted command data and programming data is transmitted to the implanted medical device by frequency shift keying the inductive communications link. Internal transceiver is powered by the inductive field between internal and external transceivers. Digitally formatted data is transmitted to external transceiver by internal transceiver amplitude modulating inductive field. Immediate verification of the establishment of a reliable communications link is provided by determining existence of frequency lock and bit phase lock between internal and external transceivers.

Oscillating dynamo in the presence of a fossil magnetic field - The solar cycle

NASA Technical Reports Server (NTRS)

Levy, E. H.; Boyer, D.

1982-01-01

Hydromagnetic dynamo generation of oscillating magnetic fields in the presence of an external, ambient magnetic field introduces a marked polarity asymmetry between the two halves of the magnetic cycle. The principle of oscillating dynamo interaction with external fields is developed, and a tentative application to the sun is described. In the sun a dipole moment associated with the stable fluid beneath the convection zone would produce an asymmetrical solar cycle.

Magnetoelectric effects in the spin-1/2 XXZ model with Dzyaloshinskii-Moriya interaction

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

Thakur, Pradeep; Durganandini, P., E-mail: pdn@physics.unipune.ac.in

2015-06-24

We study the 1D spin-1/2 XXZ chain in the presence of the Dzyaloshinskii-Moriya (D-M) interaction and with longitudinal and transverse magnetic fields. We assume the spin-current mechanism of Katsura-Nagaosa-Balatsky at play and interpret the D-M interaction as a coupling between the local electric polarization and an external electric field. We study the interplay of electric and magnetic order in the ground state using the numerical density matrix renormalization group(DMRG) method. Specifically, we investigate the dependences of the magnetization and electric polarization on the external electric and magnetic fields. We find that for transverse magnetic fields, there are two different regimesmore » of polarization while for longitudinal magnetic fields, there are three different regimes of polarization. The different regimes can be tuned by the external magnetic fields.« less

Electroconvection in one-dimensional liquid crystal cells

NASA Astrophysics Data System (ADS)

Huh, Jong-Hoon

2018-04-01

We investigate the alternating current (ac) -driven electroconvection (EC) in one-dimensional cells (1DCs) under the in-plane switching mode. In 1DCs, defect-free EC can be realized. In the presence and absence of external multiplicative noise, the features of traveling waves (TWs), such as their Hopf frequency fH and velocity, are examined in comparison with those of conventional two-dimensional cells (2DCs) accompanying defects of EC rolls. In particular, we show that the defects significantly contribute to the features of the TWs. Additionally, owing to the defect-free EC in the 1DCs, the effects of the ac and noise fields on the TW are clarified. The ac field linearly increases fH, independent of the ac frequency f . The noise increases fH monotonically, but fH does not vary below a characteristic noise intensity VN*. In addition, soliton-like waves and unfamiliar oscillation of EC vortices in 1DCs are observed, in contrast to the localized EC (called worms) and the oscillation of EC rolls in 2DCs.

Detection of the ODMR signal of a nitrogen vacancy centre in nanodiamond in propagating surface plasmons

NASA Astrophysics Data System (ADS)

Al-Baiaty, Zahraa; Cumming, Benjamin P.; Gan, Xiaosong; Gu, Min

2018-02-01

We demonstrate that the optically detected magnetic resonance (ODMR) signal of a nitrogen vacancy (NV) centre can be coupled to propagating surface plasmons for the detection of the NV centre spin states, and of external magnetic fields. By coupling the spin dependent luminescence signal of a NV centre in a nanodiamond (ND) to a chemically synthesized silver nanowire, we demonstrate the readout of the ODMR signal as a reduction in the surface plasmon polariton intensity, with improved contrast in comparison to the emission from the NV centre. Furthermore, on the application of a permanent magnetic field from zero to 13 G, we demonstrate that the Zeeman splitting of the magnetic spin states of the nitrogen vacancy centre ground states can also be detected in the coupled surface plasmons. This is an important step in the development of a compact on-chip information processing system utilizing the nitrogen vacancy in nanodiamond as an on-chip source with efficient magnetometry sensing properties.

Reduced body condition and enzymatic alterations in frogs inhabiting intensive crop production areas.

PubMed

Brodeur, Julie C; Suarez, Romina P; Natale, Guillermo S; Ronco, Alicia E; Elena Zaccagnini, Maria

2011-07-01

Parameters indicative of general condition and health were compared amongst adult frogs inhabiting uncultivated lands and fields subjected to agricultural practices typical of the humid pampas of Argentina. Whereas no significant differences existed in the parasite load and external malformations prevalence rate of adult frogs from either environments, a reduced condition factor was clearly demonstrated in frogs from agricultural lands. This conclusion was reached for four frog species of different life habits: the terrestrial fossorial Rhinella fernandezae, the terrestrial Leptodactylus latinasus, the semi-aquatic Leptodactylus ocellatus, and the arborescent Hypsiboas pulchellus. A distinct pattern of enzymatic modifications was furthermore observed in L. ocellatus and H. pulchellus from agricultural lands, including elevated hepatic activities of catalase and cholinesterase, and an inhibition of liver GST activity. Further studies should investigate the causes and consequences of the systematically low condition factor observed in frogs from agricultural fields of the humid pampas of Argentina. Copyright © 2011 Elsevier Inc. All rights reserved.

Bioinspired sensory systems for local flow characterization

NASA Astrophysics Data System (ADS)

Colvert, Brendan; Chen, Kevin; Kanso, Eva

2016-11-01

Empirical evidence suggests that many aquatic organisms sense differential hydrodynamic signals.This sensory information is decoded to extract relevant flow properties. This task is challenging because it relies on local and partial measurements, whereas classical flow characterization methods depend on an external observer to reconstruct global flow fields. Here, we introduce a mathematical model in which a bioinspired sensory array measuring differences in local flow velocities characterizes the flow type and intensity. We linearize the flow field around the sensory array and express the velocity gradient tensor in terms of frame-independent parameters. We develop decoding algorithms that allow the sensory system to characterize the local flow and discuss the conditions under which this is possible. We apply this framework to the canonical problem of a circular cylinder in uniform flow, finding excellent agreement between sensed and actual properties. Our results imply that combining suitable velocity sensors with physics-based methods for decoding sensory measurements leads to a powerful approach for understanding and developing underwater sensory systems.

Application of an Externally Applied Rotating Magnetic Field for Control of MHD Relaxation Phenomena in the HIST Spherical Torus Device

NASA Astrophysics Data System (ADS)

Kikuchi, Yusuke; Yoshikawa, Tatsuya; Nishioka, Tsutomu; Hashimoto, Shotaro; Fukumoto, Naoyuki; Nagata, Masayoshi

Application of an externally applied rotating magnetic field (RMF) for control of MHD relaxation phenomena driven by a coaxial helicity injection has been proposed in the HIST spherical torus device. In this letter, the plasma responses to the RMF evaluated by magnetic fields inside the plasma in HIST are shown.

Study of transport phenomena in laser-driven, non- equilibrium plasmas in the presence of external magnetic fields

NASA Astrophysics Data System (ADS)

Kemp, G. Elijah; Mariscal, D. A.; Williams, G. J.; Blue, B. E.; Colvin, J. D.; Fears, T. M.; Kerr, S. M.; May, M. J.; Moody, J. D.; Strozzi, D. J.; Lefevre, H. J.; Klein, S. R.; Kuranz, C. C.; Manuel, M. J.-E.; Gautier, D. C.; Montgomery, D. S.

2017-10-01

We present experimental and simulation results from a study of thermal transport inhibition in laser-driven, mid-Z, non-equilibrium plasmas in the presence external magnetic fields. The experiments were performed at the Jupiter Laser Facility at LLNL, where x-ray spectroscopy, proton radiography, and Brillouin backscatter data were simultaneously acquired from sub-critical-density, Ti-doped silica aerogel foams driven by a 2 ω laser at 5 ×1014 W /cm2 . External B-field strengths up to 20 T (aligned antiparallel to the laser propagation axis) were provided by a capacitor-bank-driven Helmholtz coil. Pre-shot simulations with Hydra, a radiation-magnetohydrodyanmics code, showed increasing electron plasma temperature with increasing B-field strength - the result of thermal transport inhibition perpendicular to the B-field. The influence of this thermal transport inhibition on the experimental observables as a function of external field strength and target density will be shown and compared with simulations. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract No. DE-AC52-07NA27344 and funded by LDRD project 17-ERD-027.

Conformation and structural changes of diblock copolymers with octopus-like micelle formation in the presence of external stimuli

NASA Astrophysics Data System (ADS)

Dammertz, K.; Saier, A. M.; Marti, O.; Amirkhani, M.

2014-04-01

External stimuli such as vapours and electric fields can be used to manipulate the formation of AB-diblock copolymers on surfaces. We study the conformational variation of PS-b-PMMA (polystyrene-block-poly(methyl methacrylate)), PS and PMMA adsorbed on mica and their response to saturated water or chloroform atmospheres. Using specimens with only partial polymer coverage, new unanticipated effects were observed. Water vapour, a non-solvent for all three polymers, was found to cause high surface mobility. In contrast, chloroform vapour (a solvent for all three polymers) proved to be less efficient. Furthermore, the influence of an additional applied electric field was investigated. A dc field oriented parallel to the sample surface induces the formation of polymer islands which assemble into wormlike chains. Moreover, PS-b-PMMA forms octopus-like micelles (OLMs) on mica. Under the external stimuli mentioned above, the wormlike formations of OLMs are able to align in the direction of the external electric field. In the absence of an electric field, the OLMs disaggregate and exhibit phase separated structures under chloroform vapour.

Effects of external stress field on the charge stability of nitrogen vacancy centers in diamond

NASA Astrophysics Data System (ADS)

Yao, Miao-Miao; Zhu, Tian-Yuan; Shu, Da-Jun

2017-07-01

The interaction of the atom-like defects in semiconductors with external fields provides an avenue to quantum information processing and nanoscale sensors. Meanwhile, external fields may induce instability of the desired charge state of the defects. It is essential to understand how the charge state of a defect is affected by external fields that introduced in diverse applications. In this letter, we explore the stability of the negatively charged state (NV-) and the neutral state (NV0) of the nitrogen vacancy (NV) center in diamond under stress by first-principles calculations. We find that the relative stability of NV- to NV0 is always reduced by the stress if the NV center is free to relax its orientation. Once the NV center has formed and retains its orientation, however, the relative stability of NV- can be always enhanced by compressive stress along its trigonal symmetry axis. We believe that the results are not only significant for control of the charge stability of NV center but also enlightening for applications based on specific charge states of other kinds of defects in the stress field.

PREFACE: Joint IPPP Durham/Cockcroft Institute/ICFA Workshop on Advanced QED methods for Future Accelerators

NASA Astrophysics Data System (ADS)

Bailey, I. R.; Barber, D. P.; Chattopadhyay, S.; Hartin, A.; Heinzl, T.; Hesselbach, S.; Moortgat-Pick, G. A.

2009-11-01

The joint IPPP Durham/Cockcroft Institute/ICFA workshop on advanced QED methods for future accelerators took place at the Cockcroft Institute in early March 2009. The motivation for the workshop was the need for a detailed consideration of the physics processes associated with beam-beam effects at the interaction points of future high-energy electron-positron colliders. There is a broad consensus within the particle physics community that the next international facility for experimental high-energy physics research beyond the Large Hadron Collider at CERN should be a high-luminosity electron-positron collider working at the TeV energy scale. One important feature of such a collider will be its ability to deliver polarised beams to the interaction point and to provide accurate measurements of the polarisation state during physics collisions. The physics collisions take place in very dense charge bunches in the presence of extremely strong electromagnetic fields of field strength of order of the Schwinger critical field strength of 4.4×1013 Gauss. These intense fields lead to depolarisation processes which need to be thoroughly understood in order to reduce uncertainty in the polarisation state at collision. To that end, this workshop reviewed the formalisms for describing radiative processes and the methods of calculation in the future strong-field environments. These calculations are based on the Furry picture of organising the interaction term of the Lagrangian. The means of deriving the transition probability of the most important of the beam-beam processes - Beamsstrahlung - was reviewed. The workshop was honoured by the presentations of one of the founders, V N Baier, of the 'Operator method' - one means for performing these calculations. Other theoretical methods of performing calculations in the Furry picture, namely those due to A I Nikishov, V I Ritus et al, were reviewed and intense field quantum processes in fields of different form - namely those present in intense lasers - were also presented. Within the Furry picture the lowest order physics processes are represented by one vertex Feynman diagrams. Additionally, higher order processes in the Furry picture are thought to be important and are still not fully studied. The Advanced QED methods workshop also benefited greatly from reports on ongoing and planned experimental work on quantum processes in intense external fields. Some of the experiments reviewed were the NA43 and NA63 experiments using the inter atomic fields in aligned crystals at CERN. In the past, evidence has been obtained from successful experiments using an intense laser at the SLAC experiment E144. The possibility now exists for new experiments with intense laser light with the planned XFEL at DESY and the European Extreme Light Infrastructure. For upcoming accelerator projects, computer simulations of the first order processes in the Furry Picture during the bunch-bunch collision are being performed using the programs CAIN and Guinea-Pig++. The implementation of spin dynamics in these simulation programs was reported on at the workshop. This relatively small workshop generated a very productive intermix of theoretical, experimental and computational developments covering this important field of physics. Fruitful discussions took place covering improvements to the models, estimations of the remaining theoretical uncertainties and future updates to the existing simulations. It was felt that ongoing workshops in the same field would be of benefit to all those involved. The organisers would like to express their sincere thanks to all of the attendees for their contributions, to the staff of the Cockcroft Institute for hosting the workshop, to the IPPP at Durham for providing substantial funding and administrative support, and to ICFA for their sponsorship. We would also like to thank IOP Publishing for their assistance in publishing our proceedings in the Journal of Physics: Conference Series.

Formation of a high intensity low energy positron string

NASA Astrophysics Data System (ADS)

Donets, E. D.; Donets, E. E.; Syresin, E. M.; Itahashi, T.; Dubinov, A. E.

2004-05-01

The possibility of a high intensity low energy positron beam production is discussed. The proposed Positron String Trap (PST) is based on the principles and technology of the Electron String Ion Source (ESIS) developed in JINR during the last decade. A linear version of ESIS has been used successfully for the production of intense highly charged ion beams of various elements. Now the Tubular Electron String Ion Source (TESIS) concept is under study and this opens really new promising possibilities in physics and technology. In this report, we discuss the application of the tubular-type trap for the storage of positrons cooled to the cryogenic temperatures of 0.05 meV. It is intended that the positron flux at the energy of 1-5 eV, produced by the external source, is injected into the Tubular Positron Trap which has a similar construction as the TESIS. Then the low energy positrons are captured in the PST Penning trap and are cooled down because of their synchrotron radiation in the strong (5-10 T) applied magnetic field. It is expected that the proposed PST should permit storing and cooling to cryogenic temperature of up to 5×109 positrons. The accumulated cooled positrons can be used further for various physics applications, for example, antihydrogen production.

Non-perturbative measurement of low-intensity charged particle beams

NASA Astrophysics Data System (ADS)

Fernandes, M.; Geithner, R.; Golm, J.; Neubert, R.; Schwickert, M.; Stöhlker, T.; Tan, J.; Welsch, C. P.

2017-01-01

Non-perturbative measurements of low-intensity charged particle beams are particularly challenging to beam diagnostics due to the low amplitude of the induced electromagnetic fields. In the low-energy antiproton decelerator (AD) and the future extra low energy antiproton rings at CERN, an absolute measurement of the beam intensity is essential to monitor the operation efficiency. Superconducting quantum interference device (SQUID) based cryogenic current comparators (CCC) have been used for measuring slow charged beams in the nA range, showing a very good current resolution. But these were unable to measure fast bunched beams, due to the slew-rate limitation of SQUID devices and presented a strong susceptibility to external perturbations. Here, we present a CCC system developed for the AD machine, which was optimised in terms of its current resolution, system stability, ability to cope with short bunched beams, and immunity to mechanical vibrations. This paper presents the monitor design and the first results from measurements with a low energy antiproton beam obtained in the AD in 2015. These are the first CCC beam current measurements ever performed in a synchrotron machine with both coasting and short bunched beams. It is shown that the system is able to stably measure the AD beam throughout the entire cycle, with a current resolution of 30 {nA}.

Dynamic effects and applications for nanosecond pulsed electric fields in cells and tissues

NASA Astrophysics Data System (ADS)

Beebe, Stephen J.; Blackmore, Peter F.; Hall, Emily; White, Jody A.; Willis, Lauren K.; Fauntleroy, Laura; Kolb, Juergen F.; Schoenbach, Karl H.

2005-04-01

Nanosecond, high intensity pulsed electric fields [nsPEFs] that are below the plasma membrane [PM] charging time constant have decreasing effects on the PM and increasing effects on intracellular structures and functions as the pulse duration decreases. When human cell suspensions were exposed to nsPEFs where the electric fields were sufficiently intense [10-300ns, <=300 kV/cm.], apoptosis signaling pathways could be activated in several cell models. Multiple apoptosis markers were observed in Jurkat, HL-60, 3T3L1-preadipocytes, and isolated rat adipocytes including decreased cell size and number, caspase activation, DNA fragmentation, and/or cytochrome c release into the cytoplasm. Phosphatidylserine externalization was observed as a biological response to nsPEFs in 3T3-L1 preadipocytes and p53-wildtype and -null human colon carcinoma cells. B10.2 mouse fibrosarcoma tumors that were exposed to nsPEFs ex vivo and in vivo exhibited DNA fragmentation, elevated caspase activity, and reduced size and weight compared to contralateral sham-treated control tumors. When nsPEF conditions were below thresholds for apoptosis and classical PM electroporation, non-apoptotic responses were observed similar to those initiated through PM purinergic receptors in HL-60 cells and thrombin in human platelets. These included Ca2+ mobilization from intracellular stores [endoplasmic reticulum] and subsequently through store-operated Ca2+ channels in the PM. In addition, platelet activation measured as aggregation responses were observed in human platelets. Finally, when nsPEF conditions followed classical electroporation-mediated transfection, the expression intensity and number of GFP-expressing cells were enhanced above cells exposed to electroporation conditions alone. These studies demonstrate that application of nsPEFs to cells or tissues can modulate cell-signaling mechanisms with possible applications as a new basic science tool, cancer treatment, wound healing, and gene therapy.

Multifractal evaluation of simulated precipitation intensities from the COSMO NWP model

NASA Astrophysics Data System (ADS)

Wolfensberger, Daniel; Gires, Auguste; Tchiguirinskaia, Ioulia; Schertzer, Daniel; Berne, Alexis

2017-12-01

The framework of universal multifractals (UM) characterizes the spatio-temporal variability in geophysical data over a wide range of scales with only a limited number of scale-invariant parameters. This work aims to clarify the link between multifractals (MFs) and more conventional weather descriptors and to show how they can be used to perform a multi-scale evaluation of model data. The first part of this work focuses on a MF analysis of the climatology of precipitation intensities simulated by the COSMO numerical weather prediction model. Analysis of the spatial structure of the MF parameters, and their correlations with external meteorological and topographical descriptors, reveals that simulated precipitation tends to be smoother at higher altitudes, and that the mean intermittency is mostly influenced by the latitude. A hierarchical clustering was performed on the external descriptors, yielding three different clusters, which correspond roughly to Alpine/continental, Mediterranean and temperate regions. Distributions of MF parameters within these three clusters are shown to be statistically significantly different, indicating that the MF signature of rain is indeed geographically dependent. The second part of this work is event-based and focuses on the smaller scales. The MF parameters of precipitation intensities at the ground are compared with those obtained from the Swiss radar composite during three events corresponding to typical synoptic conditions over Switzerland. The results of this analysis show that the COSMO simulations exhibit spatial scaling breaks that are not present in the radar data, indicating that the model is not able to simulate the observed variability at all scales. A comparison of the operational one-moment microphysical parameterization scheme of COSMO with a more advanced two-moment scheme reveals that, while no scheme systematically outperforms the other, the two-moment scheme tends to produce larger extreme values and more discontinuous precipitation fields, which agree better with the radar composite.

Interaction of Low Frequency External Electric Fields and Pancreatic β-Cell: A Mathematical Modeling Approach to Identify the Influence of Excitation Parameters.

PubMed

Farashi, Sajjad; Sasanpour, Pezhman; Rafii-Tabar, Hashem

2018-05-24

Purpose-Although the effect of electromagnetic fields on biological systems has attracted attraction in recent years, there has not been any conclusive result concerning the effects of interaction and the underlying mechanisms involved. Besides the complexity of biological systems, the parameters of the applied electromagnetic field have not been estimated in most of the experiments. Material and Method-In this study, we have used computational approach in order to find the excitation parameters of an external electric field which produces sensible effects in the function of insulin secretory machinery, whose failure triggers the diabetes disease. A mathematical model of the human β-cell has been used and the effects of external electric fields with different amplitudes, frequencies and wave shapes have been studied. Results-The results from our simulations show that the external electric field can influence the membrane electrical activity and perhaps the insulin secretion when its amplitude exceeds a threshold value. Furthermore, our simulations reveal that different waveforms have distinct effects on the β-cell membrane electrical activity and the characteristic features of the excitation like frequency would change the interaction mechanism. Conclusion-The results could help the researchers to investigate the possible role of the environmental electromagnetic fields on the promotion of diabetes disease.

Matter-induced magnetic moment and neutrino helicity rotation in external fields

NASA Astrophysics Data System (ADS)

Ternov, Alexei I.

2016-11-01

The induced magnetic moment that arises due to the propagation of neutrinos in a dispersive medium can affect the dynamics of the neutrino spin in an external electromagnetic field. In particular, it can cause a helicity flip of a massive neutrino in a magnetic field. In some astrophysical media, this helicity transition mechanism could be more effective than a similar process caused by the anomalous magnetic moment of the neutrino. If the neutrino energy is sufficiently high, the two helicity transition mechanisms mentioned above can compensate each other. Then a helicity flip in an external field will not occur. Calculations are carried out using both the methods of relativistic quantum mechanics and the quasiclassical Bargmann-Michel-Telegdi equation.

Markov model of the loan portfolio dynamics considering influence of management and external economic factors

NASA Astrophysics Data System (ADS)

Bozhalkina, Yana; Timofeeva, Galina

2016-12-01

Mathematical model of loan portfolio in the form of a controlled Markov chain with discrete time is considered. It is assumed that coefficients of migration matrix depend on corrective actions and external factors. Corrective actions include process of receiving applications, interaction with existing solvent and insolvent clients. External factors are macroeconomic indicators, such as inflation and unemployment rates, exchange rates, consumer price indices, etc. Changes in corrective actions adjust the intensity of transitions in the migration matrix. The mathematical model for forecasting the credit portfolio structure taking into account a cumulative impact of internal and external changes is obtained.

Electronic confinement in graphene quantum rings due to substrate-induced mass radial kink.

PubMed

Xavier, L J P; da Costa, D R; Chaves, A; Pereira, J M; Farias, G A

2016-12-21

We investigate localized states of a quantum ring confinement in monolayer graphene defined by a circular mass-related potential, which can be induced e.g. by interaction with a substrate that breaks the sublattice symmetry, where a circular line defect provides a change in the sign of the induced mass term along the radial direction. Electronic properties are calculated analytically within the Dirac-Weyl approximation in the presence of an external magnetic field. Analytical results are also compared with those obtained by the tight-binding approach. Regardless of its sign, a mass term [Formula: see text] is expected to open a gap for low-energy electrons in Dirac cones in graphene. Both approaches confirm the existence of confined states with energies inside the gap, even when the width of the kink modelling the mass sign transition is infinitely thin. We observe that such energy levels are inversely proportional to the defect line ring radius and independent on the mass kink height. An external magnetic field is demonstrated to lift the valley degeneracy in this system and easily tune the valley index of the ground state in this system, which can be polarized on either K or [Formula: see text] valleys of the Brillouin zone, depending on the magnetic field intensity. Geometrical changes in the defect line shape are considered by assuming an elliptic line with different eccentricities. Our results suggest that any defect line that is closed in a loop, with any geometry, would produce the same qualitative results as the circular ones, as a manifestation of the topologically protected nature of the ring-like states investigated here.

Impact of Cattaneo-Christov heat flux on electroosmotic transport of third-order fluids in a magnetic environment

NASA Astrophysics Data System (ADS)

Misra, J. C.; Mallick, B.; Sinha, A.; Roy Chowdhury, A.

2018-05-01

In the case of steady flow of a fluid under the combined influence of external electric and magnetic fields, the fluid moves forward by forming an axial momentum boundary layer. With this end in view a study has been performed here to investigate the problem of entropy generation during electroosmotically modulated flow of a third-order electrically conducting fluid flowing on a microchannel bounded by silicon-made parallel plates under the influence of a magnetic field, by paying due consideration to the steric effect. The associated mechanism of heat transfer has also been duly taken care of, by considering Cattaneo-Christov heat flux. A suitable finite difference scheme has been developed for the numerical procedure. A detailed study of the velocity and temperature distributions has been made by considering their variations with respect to different physical parameters involved in the problem. The results of numerical computation have been displayed graphically. The computational work has been carried out by considering blood as the working fluid, with the motivation of exploring some interesting phenomena in the context of hemodynamical flow in micro-vessels. Among other variables, parametric variations of the important physical variables, viz. i) skin friction and ii) Nusselt number have been investigated. The study confirms that the random motion of the fluid particles can be controlled by a suitable adjustment of the intensity of an externally applied magnetic field in the transverse direction. It is further revealed that the Nusselt number diminishes, as the Prandtl number gradually increases; however, a steady increase in the Nusselt number occurs with increase in thermal relaxation. Entropy generation is also found to be enhanced with increase in Joule heating. The results of the present study have also been validated in a proper manner.

Diffusion of hydrogen interstitials in the near-surface region of Pd(111) under the influence of surface coverage and external static electric fields

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

Blanco-Rey, M.; Donostia International Physics Center; Tremblay, J. C.

2015-04-21

Past scanning tunneling microscopy (STM) experiments of H manipulation on Pd(111), at low temperature, have shown that it is possible to induce diffusion of surface species as well as of those deeply buried under the surface. Several questions remain open regarding the role of subsurface site occupancies. In the present work, the interaction potential of H atoms with Pd(111) under various H coverage conditions is determined by means of density functional theory calculations in order to provide an answer to two of these questions: (i) whether subsurface sites are the final locations for the H impurities that attempt to emergemore » from bulk regions, and (ii) whether penetration of the surface is a competing route of on-surface diffusion during depletion of surface H on densely covered Pd(111). We find that a high H coverage has the effect of blocking resurfacing of H atoms travelling from below, which would otherwise reach the surface fcc sites, but it hardly alters deeper diffusion energy barriers. Penetration is unlikely and restricted to high occupancies of hcp hollows. In agreement with experiments, the Pd lattice expands vertically as a consequence of H atoms being blocked at subsurface sites, and surface H enhances this expansion. STM tip effects are included in the calculations self-consistently as an external static electric field. The main contribution to the induced surface electric dipoles originates from the Pd substrate polarisability. We find that the electric field has a non-negligible effect on the H-Pd potential in the vicinity of the topmost Pd atomic layer, yet typical STM intensities of 1-2 VÅ{sup −1} are insufficient to invert the stabilities of the surface and subsurface equilibrium sites.« less

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.

Effect of multilayer structure, stacking order and external electric field on the electrical properties of few-layer boron-phosphide.

PubMed

Chen, Xianping; Tan, Chunjian; Yang, Qun; Meng, Ruishen; Liang, Qiuhua; Jiang, Junke; Sun, Xiang; Yang, D Q; Ren, Tianling

2016-06-28

Development of nanoelectronics requires two-dimensional (2D) systems with both direct-bandgap and tunable electronic properties as they act in response to the external electric field (E-field). Here, we present a detailed theoretical investigation to predict the effect of atomic structure, stacking order and external electric field on the electrical properties of few-layer boron-phosphide (BP). We demonstrate that the splitting of bands and bandgap of BP depends on the number of layers and the stacking order. The values for the bandgap show a monotonically decreasing relationship with increasing layer number. We also show that AB-stacking BP has a direct-bandgap, while ABA-stacking BP has an indirect-bandgap when the number of layers n > 2. In addition, for a bilayer and a trilayer, the bandgap increases (decreases) as the electric field increases along the positive direction of the external electric field (E-field) (negative direction). In the case of four-layer BP, the bandgap exhibits a nonlinearly decreasing behavior as the increase in the electric field is independent of the electric field direction. The tunable mechanism of the bandgap can be attributed to a giant Stark effect. Interestingly, the investigation also shows that a semiconductor-to-metal transition may occur for the four-layer case or more layers beyond the critical electric field. Our findings may inspire more efforts in fabricating new nanoelectronics devices based on few-layer BP.

External control of photonic bands in a magnetized cold plasma

NASA Astrophysics Data System (ADS)

Kumar, N.; Singh, P. P.; Suthar, B.; Kumar, A.; Thapa, K. B.

2018-05-01

In this analysis, the effect of external rectangle-wave-like periodic magnetic field, on photonic bandgaps (PBGs) exhibited by bulk cold plasma, has been illustrated. It is found that the forbidden gap for normal incidence decreases with a decrease in the thickness ratio for a constant magnetic field. A new gap appears for TM polarization at oblique incidence that is attributed to the Bragg's interference of plasma layers and this new gap width depends on the incident angle as well as the magnitude of the magnetic field. There is also a shifting in gap locations depending on the magnitude of the magnetic field. It is demonstrated that external parameters like magnetic field strength and the ratio of two parts of spatial period along with incident angle can tune the PBGs in a magnetized cold plasma.

Chiral magnetic effect in the presence of electroweak interactions as a quasiclassical phenomenon

NASA Astrophysics Data System (ADS)

Dvornikov, Maxim; Semikoz, Victor B.

2018-03-01

We elaborate the quasiclassical approach to obtain the modified chiral magnetic effect (CME) in the case when the massless charged fermions interact with electromagnetic fields and the background matter by the electroweak forces. The derivation of the anomalous current along the external magnetic field involves the study of the energy density evolution of chiral particles in parallel electric and magnetic fields. We consider both the particle acceleration by the external electric field and the contribution of the Adler anomaly. The condition of the validity of this method for the derivation of the CME is formulated. We obtain the expression for the electric current along the external magnetic field, which appears to coincide with our previous results based on the purely quantum approach. Our results are compared with the findings of other authors.

Ising game: Nonequilibrium steady states of resource-allocation systems

NASA Astrophysics Data System (ADS)

Xin, C.; Yang, G.; Huang, J. P.

2017-04-01

Resource-allocation systems are ubiquitous in the human society. But how external fields affect the state of such systems remains poorly explored due to the lack of a suitable model. Because the behavior of spins pursuing energy minimization required by physical laws is similar to that of humans chasing payoff maximization studied in game theory, here we combine the Ising model with the market-directed resource-allocation game, yielding an Ising game. Based on the Ising game, we show theoretical, simulative and experimental evidences for a formula, which offers a clear expression of nonequilibrium steady states (NESSs). Interestingly, the formula also reveals a convertible relationship between the external field (exogenous factor) and resource ratio (endogenous factor), and a class of saturation as the external field exceeds certain limits. This work suggests that the Ising game could be a suitable model for studying external-field effects on resource-allocation systems, and it could provide guidance both for seeking more relations between NESSs and equilibrium states and for regulating human systems by choosing NESSs appropriately.

Ionization of Rydberg atoms colliding with a metal surface

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

Sjakste, J.; Borisov, A. G.; Gauyacq, J. P.

2006-04-15

We report on a theoretical study of the ionization process of Xe* Rydberg atoms colliding with a metal surface, in the presence of an external electric field. The evolution of the Xe* outer electron is studied by a wave packet propagation approach, allowing to include all dynamical aspects of the collision, in particular nonadiabatic inter-Rydberg transitions. We investigate how the different Xe* Stark states formed in the external field couple together and ionize on the surface and how the different polarizations of the electronic cloud in the Xe* states are reflected in their ionization properties. We show that the presencemore » of the external electric field can significantly perturb the dynamics of the ionization process. Our results account for recent results from Dunning et al. [Nucl. Inst. Meth. B 203, 69 (2003)]. In particular, it is explained how the external electric field present in the experimental procedure of Dunning et al. leads to the apparent absence of a polarization effect in the ionization process.« less

Guiding of High Laser Intensities in Long Plasma Channels

NASA Astrophysics Data System (ADS)

Levin, M.; Eisenmann, S.; Palchan, T.; Zigler, A.; Sugiyama, K.; Nakajima, K.; Kaganovich, D.; Hubbard, R. F.; Ting, A.; Gordon, D. F.; Sprangle, P.; Fraenkel, M.; Maman, S.; Henis, Z.

Plasma channels have been widely used to guide intense laser pulses over many Rayleigh lengths. Using optimized segmented capillary discharges, we demonstrated guided propagation of ultra short (100 fs) high intensity (1016 W/cm-2, limited by the laser system) pulses over distances up to 12.6 cm and intensities above 1018W/cm2 for 1.5cm boron nitride capillary. Both radial and longitudinal density profiles of plasma channels were studied under various discharge conditions. A new diagnostic technique is presented in which the transport of a guided laser pulse at different delay times from the initiation of the discharge is sampled on a single discharge shot. Using external, 10 nsec Nd YAG laser of several tenths of milijoules to ignite polyethylene capillaries we have demonstrated channels of various length in density range of 1017 - 1019 cm-3 and up to 25% deep. The longitudinal profiles were found to be remarkably uniform in both short and long capillaries. The Boron Nitride capillary has provided a guiding medium that can withstand more than 1000 shots. Using these capillaries we have guided laser intensities above 1018W/cm2. The laser ignition of capillary discharge provided reliable almost jitter free approach. The concerns related to influence of relatively high current density flow through capillary on the injected electrons were studied extensively by us both theoretically and experimentally using a simple injection method. The method is based on the interaction of a high intensity laser pulse with a thin wire placed near capillary entrance. The influence of magnetic fields was found to be insignificant. Using this method we have studied transport of electrons though capillary discharge.

Chaotic He-Ne laser

NASA Astrophysics Data System (ADS)

Kuusela, Tom A.

2017-09-01

A He-Ne laser is an example of a class A laser, which can be described by a single nonlinear differential equation of the complex electric field. This laser system has only one degree of freedom and is thus inherently stable. A He-Ne laser can be driven to the chaotic condition when a large fraction of the output beam is injected back to the laser. In practice, this can be done simply by adding an external mirror. In this situation, the laser system has infinite degrees of freedom and therefore it can have a chaotic attractor. We show the fundamental laser equations and perform elementary stability analysis. In experiments, the laser intensity variations are measured by a simple photodiode circuit. The laser output intensity time series is studied using nonlinear analysis tools which can be found freely on the internet. The results show that the laser system with feedback has an attractor of a reasonably high dimension and that the maximal Lyapunov exponent is positive, which is clear evidence of chaotic behaviour. The experimental setup and analysis steps are so simple that the studies can even be implemented in the undergraduate physics laboratory.

Relative Intensity of a Cross-Over Resonance to Lamb Dips Observed in Stark Spectroscopy of Methane

NASA Astrophysics Data System (ADS)

Okuda, Shoko; Sasada, Hiroyuki

2017-06-01

Last ISMS, we reported on Stark effects of the νb{3} band of methane observed with a sub-Doppler resolution spectrometer. We determined the rotation-induced permanent dipole moment (PEDM) in the vibrational ground state and the vibration-, rotation-, and Coriolis-type-interaction-induced PEDMs in the v_{3}=1 state. Figure illustrates Stark modulation spectrum of the Q(6)E with the external electric field of 31.0 kV/cm and the selection rule of Δ M=±1, where M is the magnetic quantum number. The Δ M=1 and -1 components of the Lamb dips labeled by A and B are resolved, and the central component C is identified with the cross-over resonance. The Lamb dips are assigned to the magnetic quantum numbers of the lower and upper states, (M'',M') according to the Clebsch-Gordan coefficients. We found that the relative intensity of the cross-over resonance to the associated Lamb dips depends on the P, Q, and R branches. We ascribe the dependence to the collisional relaxation processes.

Uncondensed atoms in the regime of velocity-selective coherent population trapping

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

Il’ichov, L. V.; Tomilin, V. A., E-mail: 8342tomilin@mail.ru

2016-01-15

We consider the model of a Bose condensate in the regime of velocity-selective coherent population trapping. As a result of interaction between particles, some fraction of atoms is outside the condensate, remaining in the coherent trapping state. These atoms are involved in brief events of intense interaction with external resonant electromagnetic fields. Intense induced and spontaneous transitions are accompanied by the exchange of momenta between atoms and radiation, which is manifested as migration of atoms in the velocity space. The rate of such migration is calculated. A nonlinear kinetic equation for the many-particle statistical operator for uncondensed atoms is derivedmore » under the assumption that correlations of atoms with different momenta are insignificant. The structure of its steady-state solution leads to certain conclusions about the above-mentioned migration pattern taking the Bose statistics into consideration. With allowance for statistical effects, we derive nonlinear integral equations for frequencies controlling the migration. The results of numerical solution of these equations are represented in the weak interatomic interaction approximation.« less

A cylindrical shell with a stress-free end which contains an axial part-through or through crack

NASA Technical Reports Server (NTRS)

Erdogan, F.; Yahsi, O. S.

1985-01-01

The interaction problem of a through or a part through crack with a stress free boundary in a semi-infinite cylindrical shell is considered. It is assumed that the crack lies in a meridional plane which is a plane of symmetry with respect to the external loads as well as the geometry. The circular boundary of the semi-infinite cylinder is assumed to be stress free. By using a transverse shear theory the problem is formulated in terms of a system of singular integral equations. The line spring model is used to treat the part through crack problem. In the case of a through crack the interaction between the perturbed stress fields due to the crack and the free boundary is quite strong and there is a considerable increase in the stress intensity factors caused by the interaction. On the other hand in the problem of a surface crack the interaction appears to be much weaker and consequently the magnification in the stress intensity factors is much less significant.

A cylindrical shell with a stress-free end which contains an axial part-through or through crack

NASA Technical Reports Server (NTRS)

Erdogan, F.; Yahsi, O. S.

1983-01-01

The interaction problem of a through or a part through crack with a stress free boundary in a semi-infinite cylindrical shell is considered. It is assumed that the crack lies in a meridional plane which is a plane of symmetry with respect to the external loads as well as the geometry. The circular boundary of the semi-infinite cylinder is assumed to be stress free. By using a transverse shear theory the problem is formulated in terms of a system of singular integral equations. The line spring model is used to treat the part through crack problem. In the case of a through crack the interaction between the perturbed stress fields due to the crack and the free boundary is quite strong and there is a considerable increase in the stress intensity factors caused by the interaction. On the other hand in the problem of a surface crack the interaction appears to be much weaker and consequently the magnification in the stress intensity factors is much less significant.

The study of the dynamics of erythrocytes under the influence of an external electric field

NASA Astrophysics Data System (ADS)

Mamaeva, Sargylana N.; Maksimov, Georgy V.; Antonov, Stepan R.

2017-11-01

A mathematical model is considered for the determination of the surface charge of an erythrocyte with its shape approximated by a surface of revolution of the second order, and the investigation of the dynamics of erythrocytes under the influence of an external electric field. In the first part of this work, the electrical surface charge of the erythrocyte of the patient was calculated with the assumption that the change in the shape and size of the red blood cells leads to stabilization of the electric field, providing a normal electrostatic repulsion. In the second part of the work, the research results of dynamics of changes in the morphology of erythrocytes under the influence of an external electric field depending on the values of their surface charge and resistance of blood plasma is presented. In the course of the work, the dependence of the surface charge of red blood cells from their shape and size is presented. The determination of the relationship between the value of the charge field and the surface of erythrocytes in norm and in pathology is shown. The dependence of the velocity of the erythrocytes on the characteristics of the external electric field, surface charge of the erythrocyte and properties of the medium is obtained. The results of this study can be applied indirectly to diagnose diseases and to develop recommendations for experimental studies of hemodynamics under the influence of various external physical factors.

DC conductivity with external magnetic field in hyperscaling violating geometry

NASA Astrophysics Data System (ADS)

Bhatnagar, Neha; Siwach, Sanjay

2018-02-01

We investigate the holographic DC conductivity of (2+1)-dimensional systems while considering hyperscaling violating geometry in bulk. We consider Einstein-Maxwell-dilaton system with two gauge fields and Liouville-type potential for dilaton. We also consider axionic fields in bulk to introduce momentum relaxation in the system. We apply an external magnetic field to study the response of the system and obtain analytic expressions for DC conductivity, Hall angle and (thermo)electric conductivity.

Electrical characterization of gold-DNA-gold structures in presence of an external magnetic field by means of I-V curve analysis.

PubMed

Khatir, Nadia Mahmoudi; Banihashemian, Seyedeh Maryam; Periasamy, Vengadesh; Ritikos, Richard; Abd Majid, Wan Haliza; Abdul Rahman, Saadah

2012-01-01

This work presents an experimental study of gold-DNA-gold structures in the presence and absence of external magnetic fields with strengths less than 1,200.00 mT. The DNA strands, extracted by standard method were used to fabricate a Metal-DNA-Metal (MDM) structure. Its electric behavior when subjected to a magnetic field was studied through its current-voltage (I-V) curve. Acquisition of the I-V curve demonstrated that DNA as a semiconductor exhibits diode behavior in the MDM structure. The current versus magnetic field strength followed a decreasing trend because of a diminished mobility in the presence of a low magnetic field. This made clear that an externally imposed magnetic field would boost resistance of the MDM structure up to 1,000.00 mT and for higher magnetic field strengths we can observe an increase in potential barrier in MDM junction. The magnetic sensitivity indicates the promise of using MDM structures as potential magnetic sensors.