Development of a magnetic coagulant based on Moringa oleifera seed extract for water treatment.

PubMed

Santos, Tássia R T; Silva, Marcela F; Nishi, Leticia; Vieira, Angélica M S; Fagundes-Klen, Márcia R; Andrade, Murilo B; Vieira, Marcelo F; Bergamasco, Rosângela

2016-04-01

In this work, to evaluate the effectiveness of the coagulation/flocculation using a natural coagulant, using Moringa oleifera Lam functionalized with magnetic iron oxide nanoparticles, producing flakes that are attracted by an external magnetic field, thereby allowing a fast settling and separation of the clarified liquid, is proposed. The removal efficiency of the parameters, apparent color, turbidity, and compounds with UV254nm absorption, was evaluated. The magnetic functionalized M. oleifera Lam coagulant could effectively remove 90 % of turbidity, 85 % of apparent color, and 50 % for the compounds with absorption at UV254nm, in surface waters under the influence of an external magnetic field within 30 min. It was found that the coagulation/flocculation treatment using magnetic functionalized M. oleifera Lam coagulant was able to reduce the values of the physico-chemical parameters evaluated with reduced settling time.

Green's function integral equation method for propagation of electromagnetic waves in an anisotropic dielectric-magnetic slab

NASA Astrophysics Data System (ADS)

Shu, Weixing; Lv, Xiaofang; Luo, Hailu; Wen, Shuangchun

2010-08-01

We extend the Green's function integral method to investigate the propagation of electromagnetic waves through an anisotropic dielectric-magnetic slab. From a microscopic perspective, we analyze the interaction of wave with the slab and derive the propagation characteristics by self-consistent analyses. Applying the results, we find an alternative explanation to the general mechanism for the photon tunneling. The results are confirmed by numerical simulations and disclose the underlying physics of wave propagation through slab. The method extended is applicable to other problems of propagation in dielectric-magnetic materials, including metamaterials.

Dynamic cross correlation studies of wave particle interactions in ULF phenomena

NASA Technical Reports Server (NTRS)

Mcpherron, R. L.

1979-01-01

Magnetic field observations made by satellites in the earth's magnetic field reveal a wide variety of ULF waves. These waves interact with the ambient particle populations in complex ways, causing modulation of the observed particle fluxes. This modulation is found to be a function of species, pitch angle, energy and time. The characteristics of this modulation provide information concerning the wave mode and interaction process. One important characteristic of wave-particle interactions is the phase of the particle flux modulation relative to the magnetic field variations. To display this phase as a function of time a dynamic cross spectrum program has been developed. The program produces contour maps in the frequency time plane of the cross correlation coefficient between any particle flux time series and the magnetic field vector. This program has been utilized in several studies of ULF wave-particle interactions at synchronous orbit.

Standing Helicon Wave Induced by a Rapidly Bent Magnetic Field in Plasmas.

PubMed

Takahashi, Kazunori; Takayama, Sho; Komuro, Atsushi; Ando, Akira

2016-04-01

An electron energy probability function and a rf magnetic field are measured in a rf hydrogen helicon source, where axial and transverse static magnetic fields are applied to the source by solenoids and to the diffusion chamber by filter magnets, respectively. It is demonstrated that the helicon wave is reflected by the rapidly bent magnetic field and the resultant standing wave heats the electrons between the source and the magnetic filter, while the electron cooling effect by the magnetic filter is maintained. It is interpreted that the standing wave is generated by the presence of a spatially localized change of a refractive index.

Standing Helicon Wave Induced by a Rapidly Bent Magnetic Field in Plasmas

NASA Astrophysics Data System (ADS)

Takahashi, Kazunori; Takayama, Sho; Komuro, Atsushi; Ando, Akira

2016-04-01

An electron energy probability function and a rf magnetic field are measured in a rf hydrogen helicon source, where axial and transverse static magnetic fields are applied to the source by solenoids and to the diffusion chamber by filter magnets, respectively. It is demonstrated that the helicon wave is reflected by the rapidly bent magnetic field and the resultant standing wave heats the electrons between the source and the magnetic filter, while the electron cooling effect by the magnetic filter is maintained. It is interpreted that the standing wave is generated by the presence of a spatially localized change of a refractive index.

Scale-dependent effects on wave propagation in magnetically affected single/double-layered compositionally graded nanosize beams

NASA Astrophysics Data System (ADS)

Ebrahimi, Farzad; Barati, Mohammad Reza

2018-04-01

This article deals with the wave propagation analysis of single/double layered functionally graded (FG) size-dependent nanobeams in elastic medium and subjected to a longitudinal magnetic field employing nonlocal elasticity theory. Material properties of nanobeam change gradually according to the sigmoid function. Applying an analytical solution, the acoustical and optical dispersion relations are explored for various wave number, nonlocality parameter, material composition, elastic foundation constants, and magnetic field intensity. It is found that frequency and phase velocity of waves propagating in S-FGM nanobeam are significantly affected by these parameters. Also, presence of cut-off and escape frequencies in wave propagation analysis of embedded S-FGM nanobeams is investigated.

Nanocomposites of polymer and inorganic nanoparticles for optical and magnetic applications

PubMed Central

Li, Shanghua; Meng Lin, Meng; Toprak, Muhammet S.; Kim, Do Kyung; Muhammed, Mamoun

2010-01-01

This article provides an up-to-date review on nanocomposites composed of inorganic nanoparticles and the polymer matrix for optical and magnetic applications. Optical or magnetic characteristics can change upon the decrease of particle sizes to very small dimensions, which are, in general, of major interest in the area of nanocomposite materials. The use of inorganic nanoparticles into the polymer matrix can provide high-performance novel materials that find applications in many industrial fields. With this respect, frequently considered features are optical properties such as light absorption (UV and color), and the extent of light scattering or, in the case of metal particles, photoluminescence, dichroism, and so on, and magnetic properties such as superparamagnetism, electromagnetic wave absorption, and electromagnetic interference shielding. A general introduction, definition, and historical development of polymer–inorganic nanocomposites as well as a comprehensive review of synthetic techniques for polymer–inorganic nanocomposites will be given. Future possibilities for the development of nanocomposites for optical and magnetic applications are also introduced. It is expected that the use of new functional inorganic nano-fillers will lead to new polymer–inorganic nanocomposites with unique combinations of material properties. By careful selection of synthetic techniques and understanding/exploiting the unique physics of the polymeric nanocomposites in such materials, novel functional polymer–inorganic nanocomposites can be designed and fabricated for new interesting applications such as optoelectronic and magneto-optic applications. PMID:22110855

Control of Spin Wave Dynamics in Spatially Twisted Magnetic Structures

DTIC Science & Technology

2017-06-27

realize high-performance spintronic and magnetic storage devices. 15. SUBJECT TERMS nano- electronics , spin, wave, magnetic, multi-functional, device 16... electronics has required us to develop high-performance and multi-functional electronic devices driven with extremely low power consumption...Spintronics”, simultaneously utilizing the charge and the spin of electrons , provides us with solutions to essential problems for semiconductor-based

CPU--Constructing Physics Understanding[TM]. [CD-ROM].

ERIC Educational Resources Information Center

2000

This CD-ROM consists of simulation software that allows students to conduct countless experiments using 20 Java simulators and curriculum units that explore light and color, forces and motion, sound and waves, static electricity and magnetism, current electricity, the nature of matter, and a unit on underpinnings. Setups can be designed by the…

Localizing high-lying Rydberg wave packets with two-color laser fields

NASA Astrophysics Data System (ADS)

Larimian, Seyedreza; Lemell, Christoph; Stummer, Vinzenz; Geng, Ji-Wei; Roither, Stefan; Kartashov, Daniil; Zhang, Li; Wang, Mu-Xue; Gong, Qihuang; Peng, Liang-You; Yoshida, Shuhei; Burgdörfer, Joachim; Baltuška, Andrius; Kitzler, Markus; Xie, Xinhua

2017-08-01

We demonstrate control over the localization of high-lying Rydberg wave packets in argon atoms with phase-locked orthogonally polarized two-color laser fields. With a reaction microscope, we measure ionization signals of high-lying Rydberg states induced by a weak dc field and blackbody radiation as a function of the relative phase between the two-color fields. We find that the dc-field-ionization yield of high-lying Rydberg argon atoms oscillates with the relative two-color phase with a period of 2 π while the photoionization signal by blackbody radiation shows a period of π . Accompanying simulations show that these observations are a clear signature of the asymmetric localization of electrons recaptured into very elongated (low angular momentum) high-lying Rydberg states after conclusion of the laser pulse. Our findings thus open an effective pathway to control the localization of high-lying Rydberg wave packets.

Shear Wave Wavefront Mapping Using Ultrasound Color Flow Imaging.

PubMed

Yamakoshi, Yoshiki; Kasahara, Toshihiro; Iijima, Tomohiro; Yuminaka, Yasushi

2015-10-01

A wavefront reconstruction method for a continuous shear wave is proposed. The method uses ultrasound color flow imaging (CFI) to detect the shear wave's wavefront. When the shear wave vibration frequency satisfies the required frequency condition and the displacement amplitude satisfies the displacement amplitude condition, zero and maximum flow velocities appear at the shear wave vibration phases of zero and π rad, respectively. These specific flow velocities produce the shear wave's wavefront map in CFI. An important feature of this method is that the shear wave propagation is observed in real time without addition of extra functions to the ultrasound imaging system. The experiments are performed using a 6.5 MHz CFI system. The shear wave is excited by a multilayer piezoelectric actuator. In a phantom experiment, the shear wave velocities estimated using the proposed method and those estimated using a system based on displacement measurement show good agreement. © The Author(s) 2015.

Magnetic Trapping of Atomic Nitrogen (14N) and Cotrapping of NH (X3sigma)

DTIC Science & Technology

2008-11-12

online Diagram of trapping apparatus. The...rb .u ni ts ) Wave number - 48375 (cm-1) In te gr at ed N itr og en F lu or es ce nc e (a rb .u ni ts ) FIG. 2. Color online Integrated nitrogen...nsec) N F lu or es ce nc e (a rb .u ni ts ) (a) (b) N H F lu or es ce nc e (a rb .u ni ts ) FIG. 4. Color online Cotrapping of N and NH, a

An inorganic/organic hybrid magnetic network as a colorimetric fluorescent nanosensor and its recognizing behavior toward Hg2+

NASA Astrophysics Data System (ADS)

Zeng, Xianfei; Xu, Yaohui; Chen, Xiumin; Ma, Wenhui; Zhou, Yang

2017-11-01

An inorganic/organic hybrid magnetic Fe3O4@SiO2 network functionalized with rhodamine derivatives was devised as a nanosensor for selective detection and removal of Hg2+ in this work. The inorganic/organic hybrid composites showed naked-eye color change in water/methanol media. The distinct color change on the surface of functionalized composite network was observed by separating and drying from aqueous solution after adsorbing Hg2+. The fluorescence spectra indicated that the functionalized nanosensor was highly sensitive and selective to Hg2+ in aqueous solution. Density functional theory (DFT) calculation was performed, which revealed a mechanism of fluorescence generated from Hg2+ induced desulfurization of rhodamine derivatives via forming new five-membered ring structure. The as-obtained composites not only had an excellent adsorption capability for Hg2+, but also showed a strong magnetic sensitivity, which allowed one to separate the functionalized magnetic nanocomposites from the solution.

A Miniature Magnetic-Force-Based Three-Axis AC Magnetic Sensor with Piezoelectric/Vibrational Energy-Harvesting Functions.

PubMed

Hung, Chiao-Fang; Yeh, Po-Chen; Chung, Tien-Kan

2017-02-08

In this paper, we demonstrate a miniature magnetic-force-based, three-axis, AC magnetic sensor with piezoelectric/vibrational energy-harvesting functions. For magnetic sensing, the sensor employs a magnetic-mechanical-piezoelectric configuration (which uses magnetic force and torque, a compact, single, mechanical mechanism, and the piezoelectric effect) to convert x -axis and y -axis in-plane and z -axis magnetic fields into piezoelectric voltage outputs. Under the x -axis magnetic field (sine-wave, 100 Hz, 0.2-3.2 gauss) and the z -axis magnetic field (sine-wave, 142 Hz, 0.2-3.2 gauss), the voltage output with the sensitivity of the sensor are 1.13-26.15 mV with 8.79 mV/gauss and 1.31-8.92 mV with 2.63 mV/gauss, respectively. In addition, through this configuration, the sensor can harness ambient vibrational energy, i.e., possessing piezoelectric/vibrational energy-harvesting functions. Under x -axis vibration (sine-wave, 100 Hz, 3.5 g) and z -axis vibration (sine-wave, 142 Hz, 3.8 g), the root-mean-square voltage output with power output of the sensor is 439 mV with 0.333 μW and 138 mV with 0.051 μW, respectively. These results show that the sensor, using this configuration, successfully achieves three-axis magnetic field sensing and three-axis vibration energy-harvesting. Due to these features, the three-axis AC magnetic sensor could be an important design reference in order to develop future three-axis AC magnetic sensors, which possess energy-harvesting functions, for practical industrial applications, such as intelligent vehicle/traffic monitoring, processes monitoring, security systems, and so on.

Neural Signatures of Stimulus Features in Visual Working Memory—A Spatiotemporal Approach

PubMed Central

Jackson, Margaret C.; Klein, Christoph; Mohr, Harald; Shapiro, Kimron L.; Linden, David E. J.

2010-01-01

We examined the neural signatures of stimulus features in visual working memory (WM) by integrating functional magnetic resonance imaging (fMRI) and event-related potential data recorded during mental manipulation of colors, rotation angles, and color–angle conjunctions. The N200, negative slow wave, and P3b were modulated by the information content of WM, and an fMRI-constrained source model revealed a progression in neural activity from posterior visual areas to higher order areas in the ventral and dorsal processing streams. Color processing was associated with activity in inferior frontal gyrus during encoding and retrieval, whereas angle processing involved right parietal regions during the delay interval. WM for color–angle conjunctions did not involve any additional neural processes. The finding that different patterns of brain activity underlie WM for color and spatial information is consistent with ideas that the ventral/dorsal “what/where” segregation of perceptual processing influences WM organization. The absence of characteristic signatures of conjunction-related brain activity, which was generally intermediate between the 2 single conditions, suggests that conjunction judgments are based on the coordinated activity of these 2 streams. PMID:19429863

A Miniature Magnetic-Force-Based Three-Axis AC Magnetic Sensor with Piezoelectric/Vibrational Energy-Harvesting Functions

PubMed Central

Hung, Chiao-Fang; Yeh, Po-Chen; Chung, Tien-Kan

2017-01-01

In this paper, we demonstrate a miniature magnetic-force-based, three-axis, AC magnetic sensor with piezoelectric/vibrational energy-harvesting functions. For magnetic sensing, the sensor employs a magnetic–mechanical–piezoelectric configuration (which uses magnetic force and torque, a compact, single, mechanical mechanism, and the piezoelectric effect) to convert x-axis and y-axis in-plane and z-axis magnetic fields into piezoelectric voltage outputs. Under the x-axis magnetic field (sine-wave, 100 Hz, 0.2–3.2 gauss) and the z-axis magnetic field (sine-wave, 142 Hz, 0.2–3.2 gauss), the voltage output with the sensitivity of the sensor are 1.13–26.15 mV with 8.79 mV/gauss and 1.31–8.92 mV with 2.63 mV/gauss, respectively. In addition, through this configuration, the sensor can harness ambient vibrational energy, i.e., possessing piezoelectric/vibrational energy-harvesting functions. Under x-axis vibration (sine-wave, 100 Hz, 3.5 g) and z-axis vibration (sine-wave, 142 Hz, 3.8 g), the root-mean-square voltage output with power output of the sensor is 439 mV with 0.333 μW and 138 mV with 0.051 μW, respectively. These results show that the sensor, using this configuration, successfully achieves three-axis magnetic field sensing and three-axis vibration energy-harvesting. Due to these features, the three-axis AC magnetic sensor could be an important design reference in order to develop future three-axis AC magnetic sensors, which possess energy-harvesting functions, for practical industrial applications, such as intelligent vehicle/traffic monitoring, processes monitoring, security systems, and so on. PMID:28208693

Real-time measurement of biomagnetic vector fields in functional syncytium using amorphous metal.

PubMed

Nakayama, Shinsuke; Uchiyama, Tusyoshi

2015-03-06

Magnetic field detection of biological electric activities would provide a non-invasive and aseptic estimate of the functional state of cellular organization, namely a syncytium constructed with cell-to-cell electric coupling. In this study, we investigated the properties of biomagnetic waves which occur spontaneously in gut musculature as a typical functional syncytium, by applying an amorphous metal-based gradio-magneto sensor operated at ambient temperature without a magnetic shield. The performance of differentiation was improved by using a single amorphous wire with a pair of transducer coils. Biomagnetic waves of up to several nT were recorded ~1 mm below the sample in a real-time manner. Tetraethyl ammonium (TEA) facilitated magnetic waves reflected electric activity in smooth muscle. The direction of magnetic waves altered depending on the relative angle of the muscle layer and magneto sensor, indicating the existence of propagating intercellular currents. The magnitude of magnetic waves rapidly decreased to ~30% by the initial and subsequent 1 mm separations between sample and sensor. The large distance effect was attributed to the feature of bioelectric circuits constructed by two reverse currents separated by a small distance. This study provides a method for detecting characteristic features of biomagnetic fields arising from a syncytial current.

Real-time Measurement of Biomagnetic Vector Fields in Functional Syncytium Using Amorphous Metal

NASA Astrophysics Data System (ADS)

Nakayama, Shinsuke; Uchiyama, Tusyoshi

2015-03-01

Magnetic field detection of biological electric activities would provide a non-invasive and aseptic estimate of the functional state of cellular organization, namely a syncytium constructed with cell-to-cell electric coupling. In this study, we investigated the properties of biomagnetic waves which occur spontaneously in gut musculature as a typical functional syncytium, by applying an amorphous metal-based gradio-magneto sensor operated at ambient temperature without a magnetic shield. The performance of differentiation was improved by using a single amorphous wire with a pair of transducer coils. Biomagnetic waves of up to several nT were recorded ~1 mm below the sample in a real-time manner. Tetraethyl ammonium (TEA) facilitated magnetic waves reflected electric activity in smooth muscle. The direction of magnetic waves altered depending on the relative angle of the muscle layer and magneto sensor, indicating the existence of propagating intercellular currents. The magnitude of magnetic waves rapidly decreased to ~30% by the initial and subsequent 1 mm separations between sample and sensor. The large distance effect was attributed to the feature of bioelectric circuits constructed by two reverse currents separated by a small distance. This study provides a method for detecting characteristic features of biomagnetic fields arising from a syncytial current.

Rotating magnetic shallow water waves and instabilities in a sphere

NASA Astrophysics Data System (ADS)

Márquez-Artavia, X.; Jones, C. A.; Tobias, S. M.

2017-07-01

Waves in a thin layer on a rotating sphere are studied. The effect of a toroidal magnetic field is considered, using the shallow water ideal MHD equations. The work is motivated by suggestions that there is a stably stratified layer below the Earth's core mantle boundary, and the existence of stable layers in stellar tachoclines. With an azimuthal background field known as the Malkus field, ?, ? being the co-latitude, a non-diffusive instability is found with azimuthal wavenumber ?. A necessary condition for instability is that the Alfvén speed exceeds ? where ? is the rotation rate and ? the sphere radius. Magneto-inertial gravity waves propagating westward and eastward occur, and become equatorially trapped when the field is strong. Magneto-Kelvin waves propagate eastward at low field strength, but a new westward propagating Kelvin wave is found when the field is strong. Fast magnetic Rossby waves travel westward, whilst the slow magnetic Rossby waves generally travel eastward, except for some ? modes at large field strength. An exceptional very slow westward ? magnetic Rossby wave mode occurs at all field strengths. The current-driven instability occurs for ? when the slow and fast magnetic Rossby waves interact. With strong field the magnetic Rossby waves become trapped at the pole. An asymptotic analysis giving the wave speed and wave form in terms of elementary functions is possible both in polar trapped and equatorially trapped cases.

Characteristics of the surface plasma wave in a self-gravitating magnetized dusty plasma slab

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

Lee, Myoung-Jae; Jung, Young-Dae, E-mail: ydjung@hanyang.ac.kr; Department of Applied Physics and Department of Bionanotechnology, Hanyang University, Ansan, Kyunggi-Do 15588

2015-11-15

The dispersion properties of surface dust ion-acoustic waves in a self-gravitating magnetized dusty plasma slab are investigated. The dispersion relation is derived by using the low-frequency magnetized dusty dielectric function and the surface wave dispersion integral for the slab geometry. We find that the self-gravitating effect suppresses the frequency of surface dust ion-acoustic wave for the symmetric mode in the long wavelength regime, whereas it hardly changes the frequency for the anti-symmetric mode. As the slab thickness and the wave number increase, the surface wave frequency slowly decreases for the symmetric mode but increases significantly for the anti-symmetric mode. Themore » influence of external magnetic field is also investigated in the case of symmetric mode. We find that the strength of the magnetic field enhances the frequency of the symmetric-mode of the surface plasma wave. The increase of magnetic field reduces the self-gravitational effect and thus the self-gravitating collapse may be suppressed and the stability of dusty objects in space is enhanced.« less

A Sommerfeld toolbox for colored dark sectors

NASA Astrophysics Data System (ADS)

El Hedri, Sonia; Kaminska, Anna; de Vries, Maikel

2017-09-01

We present analytical formulas for the Sommerfeld corrections to the annihilation of massive colored particles into quarks and gluons through the strong interaction. These corrections are essential to accurately compute the dark matter relic density for coannihilation with colored partners. Our formulas allow us to compute the Sommerfeld effect, not only for the lowest term in the angular momentum expansion of the amplitude, but for all orders in the partial wave expansion. In particular, we carefully account for the effects of the spin of the annihilating particle on the symmetry of the two-particle wave function. This work focuses on strongly interacting particles of arbitrary spin in the triplet, sextet and octet color representations. For typical velocities during freeze-out, we find that including Sommerfeld corrections on the next-to-leading order partial wave leads to modifications of up to 10 to 20 percent on the total annihilation cross section. Complementary to QCD, we generalize our results to particles charged under an arbitrary unbroken SU( N) gauge group, as encountered in dark glueball models. In connection with this paper a Mathematica notebook is provided to compute the Sommerfeld corrections for colored particles up to arbitrary order in the angular momentum expansion.

Human preference for individual colors

NASA Astrophysics Data System (ADS)

Palmer, Stephen E.; Schloss, Karen B.

2010-02-01

Color preference is an important aspect of human behavior, but little is known about why people like some colors more than others. Recent results from the Berkeley Color Project (BCP) provide detailed measurements of preferences among 32 chromatic colors as well as other relevant aspects of color perception. We describe the fit of several color preference models, including ones based on cone outputs, color-emotion associations, and Palmer and Schloss's ecological valence theory. The ecological valence theory postulates that color serves an adaptive "steering' function, analogous to taste preferences, biasing organisms to approach advantageous objects and avoid disadvantageous ones. It predicts that people will tend to like colors to the extent that they like the objects that are characteristically that color, averaged over all such objects. The ecological valence theory predicts 80% of the variance in average color preference ratings from the Weighted Affective Valence Estimates (WAVEs) of correspondingly colored objects, much more variance than any of the other models. We also describe how hue preferences for single colors differ as a function of gender, expertise, culture, social institutions, and perceptual experience.

Three Great Eyes on Kepler Supernova Remnant

NASA Image and Video Library

2004-10-06

NASA's three Great Observatories -- the Hubble Space Telescope, the SpitzerSpace Telescope, and the Chandra X-ray Observatory -- joined forces to probe theexpanding remains of a supernova, called Kepler's supernova remnant, first seen 400 years ago by sky watchers, including astronomer Johannes Kepler. The combined image unveils a bubble-shaped shroud of gas and dust that is 14light-years wide and is expanding at 4 million miles per hour (2,000 kilometersper second). Observations from each telescope highlight distinct features of thesupernova remnant, a fast-moving shell of iron-rich material from the explodedstar, surrounded by an expanding shock wave that is sweeping up interstellar gasand dust. Each color in this image represents a different region of the electromagneticspectrum, from X-rays to infrared light. These diverse colors are shown in thepanel of photographs below the composite image. The X-ray and infrared datacannot be seen with the human eye. By color-coding those data and combining themwith Hubble's visible-light view, astronomers are presenting a more completepicture of the supernova remnant. Visible-light images from the Hubble telescope (colored yellow) reveal where the supernova shock wave is slamming into the densest regions of surrounding gas.The bright glowing knots are dense clumps from instabilities that form behindthe shock wave. The Hubble data also show thin filaments of gas that look likerippled sheets seen edge-on. These filaments reveal where the shock wave isencountering lower-density, more uniform interstellar material. The Spitzer telescope shows microscopic dust particles (colored red) that havebeen heated by the supernova shock wave. The dust re-radiates the shock wave'senergy as infrared light. The Spitzer data are brightest in the regionssurrounding those seen in detail by the Hubble telescope. The Chandra X-ray data show regions of very hot gas, and extremely high-energyparticles. The hottest gas (higher-energy X-rays, colored blue) is locatedprimarily in the regions directly behind the shock front. These regions alsoshow up in the Hubble observations, and also align with the faint rim of glowingmaterial seen in the Spitzer data. The X-rays from the region on the lower left(colored blue) may be dominated by extremely high-energy electrons that wereproduced by the shock wave and are radiating at radio through X-ray wavelengthsas they spiral in the intensified magnetic field behind the shock front. CoolerX-ray gas (lower-energy X-rays, colored green) resides in a thick interior shelland marks the location of heated material expelled from the exploded star. Kepler's supernova, the last such object seen to explode in our Milky Waygalaxy, resides about 13,000 light-years away in the constellation Ophiuchus. The Chandra observations were taken in June 2000, the Hubble in August 2003;and the Spitzer in August 2004. http://photojournal.jpl.nasa.gov/catalog/PIA06907

Propagation of electromagnetic waves parallel to the magnetic field in the nightside Venus ionosphere

NASA Technical Reports Server (NTRS)

Huba, J. D.; Rowland, H. L.

1993-01-01

The propagation of electromagnetic waves parallel to the magnetic field in the nightside Venus ionosphere is presented in a theoretical and numerical analysis. The model assumes a source of electromagnetic radiation in the Venus atmosphere, such as that produced by lightning. Specifically addressed is wave propagation in the altitude range z = 130-160 km at the four frequencies detectable by the Pioneer Venus Orbiter Electric Field Detector: 100 Hz, 730 Hz, 5.4 kHz, and 30 kHz. Parameterizations of the wave intensities, peak electron density, and Poynting flux as a function of magnetic field are presented. The waves are found to propagate most easily in conditions of low electron density and high magnetic field. The results of the model are consistent with observational data.

Tunable ferromagnetic resonance in La-Co substituted barium hexaferrites at millimeter wave frequencies

NASA Astrophysics Data System (ADS)

Korolev, Konstantin A.; Wu, Chuanjian; Yu, Zhong; Sun, Ke; Afsar, Mohammed N.; Harris, Vincent G.

2018-05-01

Transmittance measurements have been performed on La-Co substituted barium hexaferrites in millimeter waves. Broadband millimeter-wave measurements have been carried out using the free space quasi-optical spectrometer, equipped with a set of high power backward wave oscillators covering the frequency range of 30 - 120 GHz. Strong absorption zones have been observed in the millimeter-wave transmittance spectra of all La-Co substituted barium hexaferrites due to the ferromagnetic resonance. Linear shift of ferromagnetic resonance frequency as functions of La-Co substitutions have been found. Real and imaginary parts of dielectric permittivity of La-Co substituted barium hexaferrites have been calculated using the analysis of recorded high precision transmittance spectra. Frequency dependences of magnetic permeability of La-Co substituted barium hexaferrites, as well as saturation magnetization and anisotropy field have been determined based on Schlömann's theory for partially magnetized ferrites. La-Co substituted barium hexaferrites have been further investigated by DC magnetization to assess magnetic behavior and compare with millimeter wave data. Consistency of saturation magnetization determined independently by both millimeter wave absorption and DC magnetization have been found for all La-Co substituted barium hexaferrites. These materials seem to be quite promising as tunable millimeter wave absorbers, filters, circulators, based on the adjusting of their substitution parameters.

Magnetic-graphitic-nanocapsule templated diacetylene assembly and photopolymerization for sensing and multicoded anti-counterfeiting

NASA Astrophysics Data System (ADS)

Nie, Xiang-Kun; Xu, Yi-Ting; Song, Zhi-Ling; Ding, Ding; Gao, Feng; Liang, Hao; Chen, Long; Bian, Xia; Chen, Zhuo; Tan, Weihong

2014-10-01

Molecular self-assembly, a process to design molecular entities to aggregate into desired structures, represents a promising bottom-up route towards precise construction of functional systems. Here we report a multifunctional, self-assembled system based on magnetic-graphitic-nanocapsule (MGN) templated diacetylene assembly and photopolymerization. The as-prepared assembly system maintains the unique color and fluorescence change properties of the polydiacetylene (PDA) polymers, while also pursues the superior Raman, NIR, magnetic and superconducting properties from the MGN template. Based on both fluorescence and magnetic resonance imaging (MRI) T2 relaxivity, the MGN@PDA system could efficiently monitor the pH variations which could be used as a pH sensor. The MGN@PDA system further demonstrates potential as unique ink for anti-counterfeiting applications. Reversible color change, strong and unique Raman scattering and fluorescence emission, sensitive NIR thermal response, and distinctive magnetic properties afford this assembly system with multicoded anti-counterfeiting capabilities.Molecular self-assembly, a process to design molecular entities to aggregate into desired structures, represents a promising bottom-up route towards precise construction of functional systems. Here we report a multifunctional, self-assembled system based on magnetic-graphitic-nanocapsule (MGN) templated diacetylene assembly and photopolymerization. The as-prepared assembly system maintains the unique color and fluorescence change properties of the polydiacetylene (PDA) polymers, while also pursues the superior Raman, NIR, magnetic and superconducting properties from the MGN template. Based on both fluorescence and magnetic resonance imaging (MRI) T2 relaxivity, the MGN@PDA system could efficiently monitor the pH variations which could be used as a pH sensor. The MGN@PDA system further demonstrates potential as unique ink for anti-counterfeiting applications. Reversible color change, strong and unique Raman scattering and fluorescence emission, sensitive NIR thermal response, and distinctive magnetic properties afford this assembly system with multicoded anti-counterfeiting capabilities. Electronic supplementary information (ESI) available. See DOI: 10.1039/c4nr03837a

Karpman-Washimi magnetization with electron-exchange effects in quantum plasmas

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

Hong, Woo-Pyo; Jamil, M.; Rasheed, A.

2015-07-15

The influence of quantum electron-exchange on the Karpman-Washimi ponderomotive magnetization is investigated in quantum plasmas. The ponderomotive magnetization and the total radiation power due to the non-stationary Karpman-Washimi interaction related to the time-varying field intensity are obtained as functions of the de Broglie wave length, Debye length, and electron-exchange parameter. The result shows that the electron-exchange effect enhances the cyclotron frequency due to the ponderomotive interactions in quantum plasmas. It is also shown that the electron-exchange effect on the Karpman-Washimi magnetization increases with increasing wave number. In addition, the Karpman-Washimi magnetization and the total radiation power increase with an increasemore » in the ratio of the Debye length to the de Broglie wave length. In streaming quantum plasmas, it is shown that the electron-exchange effect enhances the ponderomotive magnetization below the resonant wave number and, however, suppresses the ponderomotive magnetization above the resonant wave number. The variation of the Karpman-Washimi magnetization and the radiation power due to the variation of the electron-exchange effect and plasma parameters is also discussed.« less

Ion flux oscillations associated with a radially polarized transverse Pc 5 magnetic pulsation

NASA Technical Reports Server (NTRS)

Takahashi, K.; Mcentire, R. W.; Lui, A. T. Y.; Potemra, T. A.

1990-01-01

The AMPTE CCE spacecraft observed a transverse Pc 5 magnetic pulsation (period of about 200 s) at 2155-2310 UT on November 20, 1985, at a radial distance of 5.7 - 7.0 earth radii, at a magnetic latitude of 1.2 - 19 deg, and near 1300 magnetic local time. The magnetic pulsation exhibits properties consistent with a standing Alfven wave with a second-harmonic standing structure along the ambient magnetic field. The amplitude and the phase of the flux pulsation are found to be a function of the particle detector look direction and the particle energy. The observed energy dependence of the shift is interpreted as the result of a drift-bounce resonance of the ions with the wave. From this interpretation it follows that the wave propagated westward with an azimuthal wave number of approximately 100. Thus the study demonstrates that particle data can be useful for determining the spatial structure of some types of ULF waves.

Achromatic synesthesias - a functional magnetic resonance imaging study.

PubMed

Melero, H; Ríos-Lago, M; Peña-Melián, A; Álvarez-Linera, J

2014-09-01

Grapheme-color synesthetes experience consistent, automatic and idiosyncratic colors associated with specific letters and numbers. Frequently, these specific associations exhibit achromatic synesthetic qualities (e.g. white, black or gray). In this study, we have investigated for the first time the neural basis of achromatic synesthesias, their relationship to chromatic synesthesias and the achromatic congruency effect in order to understand not only synesthetic color but also other components of the synesthetic experience. To achieve this aim, functional magnetic resonance imaging experiments were performed in a group of associator grapheme-color synesthetes and matched controls who were stimulated with real chromatic and achromatic stimuli (Mondrians), and with letters and numbers that elicited different types of grapheme-color synesthesias (i.e. chromatic and achromatic inducers which elicited chromatic but also achromatic synesthesias, as well as congruent and incongruent ones). The information derived from the analysis of Mondrians and chromatic/achromatic synesthesias suggests that real and synesthetic colors/achromaticity do not fully share neural mechanisms. The whole-brain analysis of BOLD signals in response to the complete set of synesthetic inducers revealed that the functional peculiarities of the synesthetic brain are distributed, and reflect different components of the synesthetic experience: a perceptual component, an (attentional) feature binding component, and an emotional component. Additionally, the inclusion of achromatic experiences has provided new evidence in favor of the emotional binding theory, a line of interpretation which constitutes a bridge between grapheme-color synesthesia and other developmental modalities of the phenomenon. Copyright © 2014 Elsevier Inc. All rights reserved.

Quasilinear diffusion operator for wave-particle interactions in inhomogeneous magnetic fields

NASA Astrophysics Data System (ADS)

Catto, P. J.; Lee, J.; Ram, A. K.

2017-10-01

The Kennel-Engelmann quasilinear diffusion operator for wave-particle interactions is for plasmas in a uniform magnetic field. The operator is not suitable for fusion devices with inhomogeneous magnetic fields. Using drift kinetic and high frequency gyrokinetic equations for the particle distribution function, we have derived a quasilinear operator which includes magnetic drifts. The operator applies to RF waves in any frequency range and is particularly relevant for minority ion heating. In order to obtain a physically meaningful operator, the first order correction to the particle's magnetic moment has to be retained. Consequently, the gyrokinetic change of variables has to be retained to a higher order than usual. We then determine the perturbed distribution function from the gyrokinetic equation using a novel technique that solves the kinetic equation explicitly for certain parts of the function. The final form of the diffusion operator is compact and completely expressed in terms of the drift kinetic variables. It is not transit averaged and retains the full poloidal angle variation without any Fourier decomposition. The quasilinear diffusion operator reduces to the Kennel-Engelmann operator for uniform magnetic fields. Supported by DoE Grant DE-FG02-91ER-54109.

Transverse particle acceleration and diffusion in a planetary magnetic field

NASA Technical Reports Server (NTRS)

Barbosa, D. D.

1994-01-01

A general model of particle acceleration by plasma waves coupled with adiabatic radial diffusion in a planetary magnetic field is developed. The model assumes that a spectrum of lower hybird waves is present to resonantly accelerate ions transverse to the magnetic field. The steady state Green's function for the combined radial diffusion and wave acceleration equation is found in terms of a series expansion. The results provide a rigorous demonstration of how a quasi-Maxwellian distribution function is formed in the absence of particle collisons and elucidate the nature of turbulent heating of magnetospheric plasmas. The solution is applied to the magnetosphere of Neptune for which a number of examples are given illustrating how the spectrum of pickup N(+) ions from Triton evolves.

Generation of Electron Whistler Waves at the Mirror Mode Magnetic Holes: MMS Observations and PIC Simulation

NASA Astrophysics Data System (ADS)

Ahmadi, N.; Wilder, F. D.; Usanova, M.; Ergun, R.; Argall, M. R.; Goodrich, K.; Eriksson, S.; Germaschewski, K.; Torbert, R. B.; Lindqvist, P. A.; Le Contel, O.; Khotyaintsev, Y. V.; Strangeway, R. J.; Schwartz, S. J.; Giles, B. L.; Burch, J.

2017-12-01

The Magnetospheric Multiscale (MMS) mission observed electron whistler waves at the center and at the gradients of magnetic holes on the dayside magnetosheath. The magnetic holes are nonlinear mirror structures which are anti-correlated with particle density. We used expanding box Particle-in-cell simulations and produced the mirror instability magnetic holes. We show that the electron whistler waves can be generated at the gradients and the center of magnetic holes in our simulations which is in agreement with MMS observations. At the nonlinear regime of mirror instability, the proton and electron temperature anisotropy are anti-correlated with the magnetic hole. The plasma is unstable to electron whistler waves at the minimum of the magnetic field structures. In the saturation regime of mirror instability, when magnetic holes are dominant, electron temperature anisotropy develops at the edges of the magnetic holes and electrons become isotropic at the magnetic field minimum. We investigate the possible mechanism for enhancing the electron temperature anisotropy and analyze the electron pitch angle distributions and electron distribution functions in our simulations and compare it with MMS observations.

Global Characteristics of Electromagnetic Ion Cyclotron Waves Deduced From Swarm Satellites

NASA Astrophysics Data System (ADS)

Kim, Hyangpyo; Hwang, Junga; Park, Jaeheung; Bortnik, Jacob; Lee, Jaejin

2018-02-01

It is well known that electromagnetic ion cyclotron (EMIC) waves play an important role in controlling particle dynamics inside the Earth's magnetosphere, especially in the outer radiation belt. In order to understand the results of wave-particle interactions due to EMIC waves, it is important to know how the waves are distributed and what features they have. In this paper, we present some statistical analyses on the spatial distribution of EMIC waves in the low Earth orbit by using Swarm satellites from December 2013 to June 2017 ( 3.5 years) as a function of magnetic local time, magnetic latitude, and magnetic longitude. We also study the wave characteristics such as ellipticity, wave normal angle, peak frequency, and wave power using our automatic wave detection algorithm based on the method of Bortnik et al. (2007, https://doi.org/10.1029/2006JA011900). We also investigate the geomagnetic control of the EMIC waves by comparing with geomagnetic activity represented by Kp and Dst indices. We find that EMIC waves are detected with a peak occurrence rate at midlatitude including subauroral region, dawn sector (3-7 magnetic local time), and linear polarization dominated with an oblique propagating direction to the background magnetic field. In addition, our result shows that the waves have some relation with geomagnetic activity; that is, they occur preferably during the geomagnetic storm's late recovery phase at low Earth orbit.

A switchable spin-wave signal splitter for magnonic networks

NASA Astrophysics Data System (ADS)

Heussner, F.; Serga, A. A.; Brächer, T.; Hillebrands, B.; Pirro, P.

2017-09-01

The influence of an inhomogeneous magnetization distribution on the propagation of caustic-like spin-wave beams in unpatterned magnetic films has been investigated by utilizing micromagnetic simulations. Our study reveals a locally controllable and reconfigurable tractability of the beam directions. This feature is used to design a device combining split and switch functionalities for spin-wave signals on the micrometer scale. A coherent transmission of spin-wave signals through the device is verified. This attests the applicability in magnonic networks where the information is encoded in the phase of the spin waves.

Energy density and energy flow of surface waves in a strongly magnetized graphene

NASA Astrophysics Data System (ADS)

Moradi, Afshin

2018-01-01

General expressions for the energy density and energy flow of plasmonic waves in a two-dimensional massless electron gas (as a simple model of graphene) are obtained by means of the linearized magneto-hydrodynamic model and classical electromagnetic theory when a strong external magnetic field perpendicular to the system is present. Also, analytical expressions for the energy velocity, wave polarization, wave impedance, transverse and longitudinal field strength functions, and attenuation length of surface magneto-plasmon-polariton waves are derived, and numerical results are prepared.

Magnetosonic Solitons in Non-Maxwellian Space Plasmas

NASA Astrophysics Data System (ADS)

Pokhotelov, O. A.; Balikhin, M.; Onishchenko, O. G.

2006-12-01

The nonlinear theory of large-amplitude magnetosonic (MS) waves in high-beta space plasmas is developed. It is shown that solitary waves can exist in the form of magnetic humps and holes in which the magnetic field is increased or decreased relative to the background magnetic field. This depends on the shape of the equilibrium ion velocity distribution function. The basic parameter that controls the nonlinear structure is the wave dispersion which can be either positive or negative. A general dispersion relation for MS waves propagating perpendicularly to the external magnetic field in a plasma with an arbitrary velocity distribution function is derived. It takes into account general plasma equilibria such as the Dory-Guest-Harris or Kennel- Ashour-Abdalla loss cone equilibria, as well as distributions with a power law velocity dependence that can be modelled by kappa-distributions. It is shown that in Maxwellian and bi-Maxwellian plasmas the dispersion is negative, i.e. the phase velocity decreases with an increase of the wave number. This means that the solitary solution in this case has the form of a magnetic hump with the magnetic field increased. On the contrary, in some non-Maxwellian plasmas such as those with ring-type ion distributions or DGH plasmas, the solitary solution may have the form of a magnetic hole. The results of similar investigations based on nonlinear Hall-MHD equations are reviewed. The relevance of our theoretical results to experimental observations is outlined

Diffractive ρ and ϕ production at HERA using a holographic AdS/QCD light-front meson wave function

NASA Astrophysics Data System (ADS)

Ahmady, Mohammad; Sandapen, Ruben; Sharma, Neetika

2016-10-01

We use an anti-de Sitter/quantum chromodynamics holographic light-front wave function for the ρ and ϕ mesons, in conjunction with the color glass condensate dipole cross section whose parameters are fitted to the most recent 2015 high precision HERA data on inclusive deep inelastic scattering, in order to predict the cross sections for diffractive ρ and ϕ electroproduction. Our results suggest that the holographic meson light-front wave function is able to give a simultaneous description of ρ and ϕ production data provided we use a set of light quark masses with mu ,d

On the generation of magnetohydrodynamic waves in a stratified and magnetized fluid. II - Magnetohydrodynamic energy fluxes for late-type stars

NASA Technical Reports Server (NTRS)

Musielak, Z. E.; Rosner, R.

1988-01-01

Magnetohydrodynamic (MHD) wave energy fluxes for late-type stars are calculated, using previously obtained formulae for the source functions for the generation of MHD waves in a stratified, but otherwise uniform, turbulent atmosphere; the magnetic fields in the wave generation region are assumed to be homogeneous. In contradiction to previous results, it is shown that in this uniform magnetic field case there is no significant increase in the efficiency of MHD wave generation, at least within the theory's limits of applicability. The major results are that the MHD energy fluxes calculated for late-type stars are less than those obtained for compressible modes in the magnetic field-free case, and that these MHD energy fluxes do not vary enough for a given spectral type to explain the observed range of UV and X-ray fluxes from such stars. It is therefore concluded that MHD waves in stellar atmospheres with homogeneous magnetic fields in the wave generation region cannot explain the observed stellar coronal emissions; if such MHD waves are responsible for a significant component of stellar coronal heating, then nonuniform fields within the generation region must be appealed to.

Impact of the quasi-two-day traveling planetary wave on the ionosphere

NASA Astrophysics Data System (ADS)

Yue, J.; Wang, W.; Richmond, A. D.; Liu, H.; Chang, L. C.

2012-12-01

The Thermosphere Ionosphere Mesosphere Electrodynamics General Circulation Model (TIME-GCM) is used to simulate the quasi-two-day wave (QTDW) modulation of the ionospheric dynamo and electron density. The QTDW can directly penetrate into the lower thermosphere and modulate the neutral winds at a period of two days. On the other hand, the QTDW can change the tidal amplitudes. The QTDW in zonal and meridional winds results in a quasi-two-day oscillation (QTDO) of the dynamo electric fields. The QTDO of the electric fields in the E-region is transmitted along the magnetic field lines to the F-region and leads to the QTDOs of the vertical ion drift and total electron content (TEC) at low and mid latitudes, leading to the 2-day oscillation of the fountain effect. Since the Earth's magnetic field has zonal wavenumber 1 and higher structures in geographic coordinates, the neutral wind dynamo and its associated vertical ion drift can be influenced by the wavenumber interaction between the QTDW and the magnetic field. Thus, longitudinal structures with other wavenumbers in the ionospheric fields, such as electric field, vertical ion drifts, electron densities and TEC, emerge from this interaction. Additionally, because the tides are damped/enhanced during a strong QTDW event, the overall fountain effect and the ionospheric morphology are changed.Amplitude (TECU) and phase (UT hour) of the QTDO of TEC as a function of day and latitude. The contour interval is 0.02 TECU and 4 hr, respectively. The color scale for the amplitude and phase is 0-0.3 TECU and 0 to 48 hr.

Color Composite Image of the Supernova Remnant

NASA Technical Reports Server (NTRS)

2000-01-01

This image is a color composite of the supernova remnant E0102-72: x-ray (blue), optical (green), and radio (red). E0102-72 is the remnant of a star that exploded in a nearby galaxy known as the Small Magellanic Cloud. The star exploded outward at speeds in excess of 20 million kilometers per hour (12 million mph) and collided with surrounding gas. This collision produced two shock waves, or cosmic sonic booms, one traveling outward, and the other rebounding back into the material ejected by the explosion. The radio image, shown in red, was made using the Australia Telescope Compact Array. The radio waves are due to extremely high-energy electrons spiraling around magnetic field lines in the gas and trace the outward moving shock wave. The Chandra X-ray Observatory image, shown in blue, shows gas that has been heated to millions of degrees by the rebounding, or reverse shock wave. The x-ray data show that this gas is rich in oxygen and neon. These elements were created by nuclear reactions inside the star and hurled into space by the supernova. The Hubble Space Telescope optical image, shown in green, shows dense clumps of oxygen gas that have 'cooled' to about 30,000 degrees. Photo Credit: X-ray (NASA/CXC/SAO); optical (NASA/HST): radio: (ACTA)

Electromagnetic plasma wave propagation along a magnetic field. Ph.D. Thesis

NASA Technical Reports Server (NTRS)

Olson, C. L.

1970-01-01

The linearized response of a Vlasov plasma to the steady-state excitation of transverse plasma waves along an external magnetic field is examined. Assuming a delta-function excitation mechanism, and performing a detailed Vlasov-Maxwell equation analysis using Fourier-Laplace transforms, the plasma response is found to consist of three terms: a branch-cut term, a free-streaming term, and a dielectric-pole term. Also considered is the phenomenon of plasma wave echoes. The case of longitudinal electrostatic waves is extended to the case of transverse plasma waves that propagate along an external magnetic field. It is shown that a transverse echo results in lowest order only when one excitation is transverse and the other is longitudinal.

Evolution of ground-state wave function in CeCoIn5 upon Cd or Sn doping

NASA Astrophysics Data System (ADS)

Chen, K.; Strigari, F.; Sundermann, M.; Hu, Z.; Fisk, Z.; Bauer, E. D.; Rosa, P. F. S.; Sarrao, J. L.; Thompson, J. D.; Herrero-Martin, J.; Pellegrin, E.; Betto, D.; Kummer, K.; Tanaka, A.; Wirth, S.; Severing, A.

2018-01-01

We present linear polarization-dependent soft-x-ray absorption spectroscopy data at the Ce M4 ,5 edges of Cd- and Sn-doped CeCoIn5. The 4 f ground-state wave functions have been determined for their superconducting, antiferromagnetic, and paramagnetic ground states. The absence of changes in the wave functions in CeCo (In1-xCdx) 5 suggests that the 4 f -conduction-electron (c f ) hybridization is not affected by global Cd doping, thus supporting the interpretation of magnetic droplets nucleating long-range magnetic order. This is contrasted by changes in the wave function due to Sn substitution. Increasing Sn in CeCo (In1-ySny) 5 compresses the 4 f orbitals into the tetragonal plane of these materials, suggesting enhanced c f hybridization with the in-plane In(1) atoms and a homogeneous altering of the electronic structure. As these experiments show, the 4 f wave functions are a very sensitive probe of small changes in the hybridization of 4 f and conduction electrons, even conveying information about direction dependencies.

The effect of transverse wave vector and magnetic fields on resonant tunneling times in double-barrier structures

NASA Astrophysics Data System (ADS)

Wang, Hongmei; Zhang, Yafei; Xu, Huaizhe

2007-01-01

The effect of transverse wave vector and magnetic fields on resonant tunneling times in double-barrier structures, which is significant but has been frequently omitted in previous theoretical methods, has been reported in this paper. The analytical expressions of the longitudinal energies of quasibound levels (LEQBL) and the lifetimes of quasibound levels (LQBL) in symmetrical double-barrier (SDB) structures have been derived as a function of transverse wave vector and longitudinal magnetic fields perpendicular to interfaces. Based on our derived analytical expressions, the LEQBL and LQBL dependence upon transverse wave vector and longitudinal magnetic fields has been explored numerically for a SDB structure. Model calculations show that the LEQBL decrease monotonically and the LQBL shorten with increasing transverse wave vector, and each original LEQBL splits to a series of sub-LEQBL which shift nearly linearly toward the well bottom and the lifetimes of quasibound level series (LQBLS) shorten with increasing Landau-level indices and magnetic fields.

Precursor Wave Emission Enhanced by Weibel Instability in Relativistic Shocks

NASA Astrophysics Data System (ADS)

Iwamoto, Masanori; Amano, Takanobu; Hoshino, Masahiro; Matsumoto, Yosuke

2018-05-01

We investigated the precursor wave emission efficiency in magnetized purely perpendicular relativistic shocks in pair plasmas. We extended our previous study to include the dependence of upstream magnetic field orientations. We performed two-dimensional particle-in-cell simulations and focused on two magnetic field orientations: the magnetic field in the simulation plane (i.e., in-plane configuration) and that perpendicular to the simulation plane (i.e., out-of-plane configuration). Our simulations in the in-plane configuration demonstrated that not only extraordinary but also ordinary mode waves are excited. We quantified the emission efficiency as a function of the magnetization parameter σ e and found that the large-amplitude precursor waves are emitted for a wide range of σ e . We found that especially at low σ e , the magnetic field generated by Weibel instability amplifies the ordinary mode wave power. The amplitude is large enough to perturb the upstream plasma, and transverse density filaments are generated as in the case of the out-of-plane configuration investigated in the previous study. We confirmed that our previous conclusion holds regardless of upstream magnetic field orientations with respect to the two-dimensional simulation plane. We discuss the precursor wave emission in three dimensions and the feasibility of wakefield acceleration in relativistic shocks based on our results.

Dual-Tasking Alleviated Sleep Deprivation Disruption in Visuomotor Tracking: An fMRI Study

ERIC Educational Resources Information Center

Gazes, Yunglin; Rakitin, Brian C.; Steffener, Jason; Habeck, Christian; Butterfield, Brady; Basner, Robert C.; Ghez, Claude; Stern, Yaakov

2012-01-01

Effects of dual-responding on tracking performance after 49-h of sleep deprivation (SD) were evaluated behaviorally and with functional magnetic resonance imaging (fMRI). Continuous visuomotor tracking was performed simultaneously with an intermittent color-matching visual detection task in which a pair of color-matched stimuli constituted a…

Memory for color reactivates color processing region.

PubMed

Slotnick, Scott D

2009-11-25

Memory is thought to be constructive in nature, where features processed in different cortical regions are synthesized during retrieval. In an effort to support this constructive memory framework, the present functional magnetic resonance imaging study assessed whether memory for color reactivated color processing regions. During encoding, participants were presented with colored and gray abstract shapes. During retrieval, old and new shapes were presented in gray and participants responded 'old-colored', 'old-gray', or 'new'. Within color perception regions, color memory related activity was observed in the left fusiform gyrus, adjacent to the collateral sulcus. A retinotopic mapping analysis indicated this activity occurred within color processing region V8. The present feature specific evidence provides compelling support for a constructive view of memory.

The relationship between color-object associations and color preference: further investigation of ecological valence theory.

PubMed

Taylor, Chloe; Franklin, Anna

2012-04-01

Ecological valence theory (EVT; Palmer & Schloss, Proceedings of the National Academy of Sciences 107:8877-8882, 2010) proposes that color preferences are due to affective responses to color-associated objects: That is, people generally like colors to the degree that they like the objects associated with those colors. Palmer and Schloss found that the average valence of objects associated with a color, when weighted by how well the objects matched the color (weighted affective valence estimates: WAVE) explained 80% of the variation in preference across colors. Here, we replicated and extended Palmer and Schloss's investigation to establish whether color-object associations can account for sex differences in color preference and whether the relationship between associated objects and color preference is equally strong for males and females. We found some degree of sex specificity to the WAVEs, but the relationship between WAVE and color preference was significantly stronger for males than for females (74% shared variance for males, 45% for females). Furthermore, analyses identified a significant inverse relationship between the number of objects associated with a color and preference for the color. Participants generally liked colors associated with few objects and disliked colors associated with many objects. For the sample overall and for females alone, this association was not significantly weaker than the association of the WAVE and preference. The success of the WAVE at capturing color preference was partly due to the relationship between the number of associated objects and color preference. The findings identify constraints of EVT in its current form, but they also provide general support for the link between color preference and color-object associations.

Standing helicon induced by a rapidly bent magnetic field in plasmas

NASA Astrophysics Data System (ADS)

Takahashi, Kazunori; Takayama, Sho; Komuro, Atsushi; Ando, Akira; Plasma physics Team

2016-09-01

An electron energy probability function and an rf magnetic field are measured in an rf hydrogen helicon source, where axial and transverse static magnetic fields are applied to the source by solenoids and to the diffusion chamber by filter magnets, respectively. It is demonstrated that the helicon wave is reflected by the rapidly bent magnetic field and the resultant standing wave heats the electrons between the source and the magnetic filter, while the electron cooling effect by the magnetic filter is maintained. It is interpreted that the standing wave is generated by the presence of spatially localized change of a refractive index. The application to the hydrogen negative ion source used for the neutral beam injection system for fusion plasma heating is discussed. This work is partially supported by grant-in-aid for scientific research (16H04084 and 26247096) from the Japan Society for the Promotion of Science.

Spin flux and magnetic solitons in an interacting two-dimensional electron gas: Topology of two-valued wave functions

NASA Astrophysics Data System (ADS)

John, Sajeev; Golubentsev, Andrey

1995-01-01

It is suggested that an interacting many-electron system in a two-dimensional lattice may condense into a topological magnetic state distinct from any discussed previously. This condensate exhibits local spin-1/2 magnetic moments on the lattice sites but is composed of a Slater determinant of single-electron wave functions which exist in an orthogonal sector of the electronic Hilbert space from the sector describing traditional spin-density-wave or spiral magnetic states. These one-electron spinor wave functions have the distinguishing property that they are antiperiodic along a closed path encircling any elementary plaquette of the lattice. This corresponds to a 2π rotation of the internal coordinate frame of the electron as it encircles the plaquette. The possibility of spinor wave functions with spatial antiperiodicity is a direct consequence of the two-valuedness of the internal electronic wave function defined on the space of Euler angles describing its spin. This internal space is the topologically, doubly-connected, group manifold of SO(3). Formally, these antiperiodic wave functions may be described by passing a flux which couples to spin (rather than charge) through each of the elementary plaquettes of the lattice. When applied to the two-dimensional Hubbard model with one electron per site, this new topological magnetic state exhibits a relativistic spectrum for charged, quasiparticle excitations with a suppressed one-electron density of states at the Fermi level. For a topological antiferromagnet on a square lattice, with the standard Hartree-Fock, spin-density-wave decoupling of the on-site Hubbard interaction, there is an exact mapping of the low-energy one-electron excitation spectrum to a relativistic Dirac continuum field theory. In this field theory, the Dirac mass gap is precisely the Mott-Hubbard charge gap and the continuum field variable is an eight-component Dirac spinor describing the components of physical electron-spin amplitude on each of the four sites of the elementary plaquette in the original Hubbard model. Within this continuum model we derive explicitly the existence of hedgehog Skyrmion textures as local minima of the classical magnetic energy. These magnetic solitons carry a topological winding number μ associated with the vortex rotation of the background magnetic moment field by a phase angle 2πμ along a path encircling the soliton. Such solitons also carry a spin flux of μπ through the plaquette on which they are centered. The μ=1 hedgehog Skyrmion describes a local transition from the topological (antiperiodic) sector of the one-electron Hilbert space to the nontopological sector. We derive from first principles the existence of deep level localized electronic states within the Mott-Hubbard charge gap for the μ=1 and 2 solitons. The spectrum of localized states is symmetric about E=0 and each subgap electronic level can be occupied by a pair of electrons in which one electron resides primarily on one sublattice and the second electron on the other sublattice. It is suggested that flux-carrying solitons and the subgap electronic structure which they induce are important in understanding the physical behavior of doped Mott insulators.

Exploring the Alfven-Wave Acceleration of Auroral Electrons in the Laboratory

NASA Astrophysics Data System (ADS)

Schroeder, James William Ryan

Inertial Alfven waves occur in plasmas where the Alfven speed is greater than the electron thermal speed and the scale of wave field structure across the background magnetic field is comparable to the electron skin depth. Such waves have an electric field aligned with the background magnetic field that can accelerate electrons. It is likely that electrons are accelerated by inertial Alfven waves in the auroral magnetosphere and contribute to the generation of auroras. While rocket and satellite measurements show a high level of coincidence between inertial Alfven waves and auroral activity, definitive measurements of electrons being accelerated by inertial Alfven waves are lacking. Continued uncertainty stems from the difficulty of making a conclusive interpretation of measurements from spacecraft flying through a complex and transient process. A laboratory experiment can avoid some of the ambiguity contained in spacecraft measurements. Experiments have been performed in the Large Plasma Device (LAPD) at UCLA. Inertial Alfven waves were produced while simultaneously measuring the suprathermal tails of the electron distribution function. Measurements of the distribution function use resonant absorption of whistler mode waves. During a burst of inertial Alfven waves, the measured portion of the distribution function oscillates at the Alfven wave frequency. The phase space response of the electrons is well-described by a linear solution to the Boltzmann equation. Experiments have been repeated using electrostatic and inductive Alfven wave antennas. The oscillation of the distribution function is described by a purely Alfvenic model when the Alfven wave is produced by the inductive antenna. However, when the electrostatic antenna is used, measured oscillations of the distribution function are described by a model combining Alfvenic and non-Alfvenic effects. Indications of a nonlinear interaction between electrons and inertial Alfven waves are present in recent data.

Mapping color fluctuations in the photon in ultraperipheral heavy ion collisions at the Large Hadron Collider

DOE PAGES

Alvioli, M.; Frankfurt, L.; Guzey, V.; ...

2017-02-20

Here, we model effects of color fluctuations (CFs) in the light-cone photon wave function and for the first time make predictions for the distribution over the number of wounded nucleons ν in the inelastic photon–nucleus scattering. We show that CFs lead to a dramatic enhancement of this distribution at ν=1 and large ν>10. We also study the implications of different scales and CFs in the photon wave function on the total transverse energy ΣE T and other observables in inelastic γA scattering with different triggers. Our predictions can be tested in proton–nucleus and nucleus–nucleus ultraperipheral collisions at the LHC andmore » will help to map CFs, whose first indications have already been observed at the LHC.« less

Classification and asymptotic scaling of the light-cone wave-function amplitudes of hadrons

DOE PAGES

Ji, Xiangdong; Ma, Jian-Ping; Yuan, Feng

2004-01-29

Here we classify the hadron light-cone wave-function amplitudes in terms of parton helicity, orbital angular momentum, and quark-flavor and color symmetries. We show in detail how this is done for the pion, ρ meson, nucleon, and delta resonance up to and including three partons. For the pion and nucleon, we also consider four-parton amplitudes. Using the scaling law derived previously, we show how these amplitudes scale in the limit that all parton transverse momenta become large.

On the stability of self-gravitating magnetized dusty plasmas

NASA Astrophysics Data System (ADS)

Salimullah, M.; Shukla, P. K.

1999-03-01

The effects of a homogeneous magnetic field and the plasma nonuniformity on the dispersion relations of various electrostatic waves in self-gravitating magnetized dusty plasmas have been investigated. For this purpose, the kinetic dielectric response functions for the electrons and ions distributions have been used and the dielectric response function for the magnetized dust grains has been derived from the hydrodynamic equations that include the self-gravitational potential. Thus, extremely massive charged dust grains are subjected to both the electromagnetic and gravitational forces. Analytical studies of the dispersion relations in various frequency and wave number regimes reveal that both the magnetic fields and plasma inhomogeneities contribute to the stability of a self-gravitating dusty plasma system. The results of this investigation should be useful in understanding the stability of dusty proto-stars and dusty dark molecular clouds, which are held in strong magnetic fields and equilibrium density gradients.

Three-dimensional Hybrid Simulation Study of Anisotropic Turbulence in the Proton Kinetic Regime

NASA Astrophysics Data System (ADS)

Vasquez, Bernard J.; Markovskii, Sergei A.; Chandran, Benjamin D. G.

2014-06-01

Three-dimensional numerical hybrid simulations with particle protons and quasi-neutralizing fluid electrons are conducted for a freely decaying turbulence that is anisotropic with respect to the background magnetic field. The turbulence evolution is determined by both the combined root-mean-square (rms) amplitude for fluctuating proton bulk velocity and magnetic field and by the ratio of perpendicular to parallel wavenumbers. This kind of relationship had been considered in the past with regard to interplanetary turbulence. The fluctuations nonlinearly evolve to a turbulent phase whose net wave vector anisotropy is usually more perpendicular than the initial one, irrespective of the initial ratio of perpendicular to parallel wavenumbers. Self-similar anisotropy evolution is found as a function of the rms amplitude and parallel wavenumber. Proton heating rates in the turbulent phase vary strongly with the rms amplitude but only weakly with the initial wave vector anisotropy. Even in the limit where wave vectors are confined to the plane perpendicular to the background magnetic field, the heating rate remains close to the corresponding case with finite parallel wave vector components. Simulation results obtained as a function of proton plasma to background magnetic pressure ratio β p in the range 0.1-0.5 show that the wave vector anisotropy also weakly depends on β p .

Non-Abelian Yang-Mills analogue of classical electromagnetic duality

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

Chan, Hong-Mo; Faridani, J.; Tsun, T.S.

The classic question of non-Abelian Yang-Mills analogue to electromagnetic duality is examined here in a minimalist fashion at the strictly four-dimensional, classical field, and point charge level. A generalization of the Abelian Hodge star duality is found which, though not yet known to give dual symmetry, reproduces analogues to many dual properties of the Abelian theory. For example, there is a dual potential, but it is a two-indexed tensor {ital T}{sub {mu}{nu}} of the Freedman-Townsend-type. Though not itself functioning as such, {ital T}{sub {mu}{nu}} gives rise to a dual parallel transport {ital {tilde A}}{sub {mu}} for the phase of themore » wave function of the color magnetic charge, this last being a monopole of the Yang-Mills field but a source of the dual field. The standard color (electric) charge itself is found to be a monpole of {ital {tilde A}}{sub {mu}}. At the same time, the gauge symmetry is found doubled from say SU({ital N}) to SU({ital N}){times}SU({ital N}). A novel feature is that all equations of motion, including the standard Yang-Mills and Wong equations, are here derived from a ``universal`` principle, namely, the Wu-Yang criterion for monpoles, where interactions arise purely as a consequence of the topological definition of the monopole charge. The technique used is the loop space formulation of Polyakov.« less

Evolution of ground-state wave function in CeCoIn 5 upon Cd or Sn doping

DOE PAGES

Chen, K.; Strigari, F.; Sundermann, M.; ...

2018-01-17

We present linear polarization-dependent soft-x-ray absorption spectroscopy data at the Ce M 4,5 edges of Cd- and Sn-doped CeCoIn 5. The 4f ground-state wave functions have been determined for their superconducting, antiferromagnetic, and paramagnetic ground states. The absence of changes in the wave functions in CeCo (In 1- xCd x) 5 suggests that the 4f-conduction-electron (c f) hybridization is not affected by global Cd doping, thus supporting the interpretation of magnetic droplets nucleating long-range magnetic order. This is contrasted by changes in the wave function due to Sn substitution. Increasing Sn in CeCo (In 1 - ySn y) 5 compressesmore » the 4f orbitals into the tetragonal plane of these materials, suggesting enhanced c f hybridization with the in-plane In(1) atoms and a homogeneous altering of the electronic structure. As these experiments show, the 4 f wave functions are a very sensitive probe of small changes in the hybridization of 4f and conduction electrons, even conveying information about direction dependencies.« less

Evolution of ground-state wave function in CeCoIn 5 upon Cd or Sn doping

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

Chen, K.; Strigari, F.; Sundermann, M.

We present linear polarization-dependent soft-x-ray absorption spectroscopy data at the Ce M 4,5 edges of Cd- and Sn-doped CeCoIn 5. The 4f ground-state wave functions have been determined for their superconducting, antiferromagnetic, and paramagnetic ground states. The absence of changes in the wave functions in CeCo (In 1- xCd x) 5 suggests that the 4f-conduction-electron (c f) hybridization is not affected by global Cd doping, thus supporting the interpretation of magnetic droplets nucleating long-range magnetic order. This is contrasted by changes in the wave function due to Sn substitution. Increasing Sn in CeCo (In 1 - ySn y) 5 compressesmore » the 4f orbitals into the tetragonal plane of these materials, suggesting enhanced c f hybridization with the in-plane In(1) atoms and a homogeneous altering of the electronic structure. As these experiments show, the 4 f wave functions are a very sensitive probe of small changes in the hybridization of 4f and conduction electrons, even conveying information about direction dependencies.« less

Spiraling Light with Magnetic Metamaterial Quarter-Wave Turbines.

PubMed

Zeng, Jinwei; Luk, Ting S; Gao, Jie; Yang, Xiaodong

2017-09-19

Miniaturized quarter-wave plate devices empower spin to orbital angular momentum conversion and vector polarization formation, which serve as bridges connecting conventional optical beam and structured light. Enabling the manipulability of additional dimensions as the complex polarization and phase of light, quarter-wave plate devices are essential for exploring a plethora of applications based on orbital angular momentum or vector polarization, such as optical sensing, holography, and communication. Here we propose and demonstrate the magnetic metamaterial quarter-wave turbines at visible wavelength to produce radially and azimuthally polarized vector vortices from circularly polarized incident beam. The magnetic metamaterials function excellently as quarter-wave plates at single wavelength and maintain the quarter-wave phase retardation in broadband, while the turbine blades consist of multiple polar sections, each of which contains homogeneously oriented magnetic metamaterial gratings near azimuthal or radial directions to effectively convert circular polarization to linear polarization and induce phase shift under Pancharatnum-Berry's phase principle. The perspective concept of multiple polar sections of magnetic metamaterials can extend to other analogous designs in the strongly coupled nanostructures to accomplish many types of light phase-polarization manipulation and structured light conversion in the desired manner.

Spin waves in rings of classical magnetic dipoles

NASA Astrophysics Data System (ADS)

Schmidt, Heinz-Jürgen; Schröder, Christian; Luban, Marshall

2017-03-01

We theoretically and numerically investigate spin waves that occur in systems of classical magnetic dipoles that are arranged at the vertices of a regular polygon and interact solely via their magnetic fields. There are certain limiting cases that can be analyzed in detail. One case is that of spin waves as infinitesimal excitations from the system’s ground state, where the dispersion relation can be determined analytically. The frequencies of these infinitesimal spin waves are compared with the peaks of the Fourier transform of the thermal expectation value of the autocorrelation function calculated by Monte Carlo simulations. In the special case of vanishing wave number an exact solution of the equations of motion is possible describing synchronized oscillations with finite amplitudes. Finally, the limiting case of a dipole chain with N\\longrightarrow ∞ is investigated and completely solved.

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

Erkaev, N. V.; Semenov, V. S.; Biernat, H. K.

Hall magnetohydrodynamic model is investigated for current sheet flapping oscillations, which implies a gradient of the normal magnetic field component. For the initial undisturbed current sheet structure, the normal magnetic field component is assumed to have a weak linear variation. The profile of the electric current velocity is described by hyperbolic functions with a maximum at the center of the current sheet. In the framework of this model, eigenfrequencies are calculated as functions of the wave number for the ''kink'' and ''sausage'' flapping wave modes. Because of the Hall effects, the flapping eigenfrequency is larger for the waves propagating alongmore » the electric current, and it is smaller for the opposite wave propagation with respect to the current. The asymmetry of the flapping wave propagation, caused by Hall effects, is pronounced stronger for thinner current sheets. This is due to the Doppler effect related to the electric current velocity.« less

Structured light generation by magnetic metamaterial half-wave plates at visible wavelength

NASA Astrophysics Data System (ADS)

Zeng, Jinwei; Luk, Ting S.; Gao, Jie; Yang, Xiaodong

2017-12-01

Metamaterial or metasurface unit cells functioning as half-wave plates play an essential role for realizing ideal Pancharatnam-Berry phase optical elements capable of tailoring light phase and polarization as desired. Complex light beam manipulation through these metamaterials or metasurfaces unveils new dimensions of light-matter interactions for many advances in diffraction engineering, beam shaping, structuring light, and holography. However, the realization of metamaterial or metasurface half-wave plates in visible spectrum range is still challenging mainly due to its specific requirements of strong phase anisotropy with amplitude isotropy in subwavelength scale. Here, we propose magnetic metamaterial structures which can simultaneously exploit the electric field and magnetic field of light for achieving the nanoscale half-wave plates at visible wavelength. We design and demonstrate the magnetic metamaterial half-wave plates in linear grating patterns with high polarization conversion purity in a deep subwavelength thickness. Then, we characterize the equivalent magnetic metamaterial half-wave plates in cylindrical coordinate as concentric-ring grating patterns, which act like an azimuthal half-wave plate and accordingly exhibit spatially inhomogeneous polarization and phase manipulations including spin-to-orbital angular momentum conversion and vector beam generation. Our results show potentials for realizing on-chip beam converters, compact holograms, and many other metamaterial devices for structured light beam generation, polarization control, and wavefront manipulation.

Three Great Eyes on Kepler's Supernova Remnant

NASA Technical Reports Server (NTRS)

2004-01-01

[figure removed for brevity, see original site] Composite

[figure removed for brevity, see original site] [figure removed for brevity, see original site] Chandra X-Ray Data (blue) Chandra X-Ray Data (green)Hubble Telescope (visible-light)Spitzer Telescope (infrared)

NASA's three Great Observatories -- the Hubble Space Telescope, the Spitzer Space Telescope, and the Chandra X-ray Observatory -- joined forces to probe the expanding remains of a supernova, called Kepler's supernova remnant, first seen 400 years ago by sky watchers, including astronomer Johannes Kepler.

The combined image unveils a bubble-shaped shroud of gas and dust that is 14 light-years wide and is expanding at 4 million miles per hour (2,000 kilometers per second). Observations from each telescope highlight distinct features of the supernova remnant, a fast-moving shell of iron-rich material from the exploded star, surrounded by an expanding shock wave that is sweeping up interstellar gas and dust.

Each color in this image represents a different region of the electromagnetic spectrum, from X-rays to infrared light. These diverse colors are shown in the panel of photographs below the composite image. The X-ray and infrared data cannot be seen with the human eye. By color-coding those data and combining them with Hubble's visible-light view, astronomers are presenting a more complete picture of the supernova remnant.

Visible-light images from the Hubble telescope (colored yellow) reveal where the supernova shock wave is slamming into the densest regions of surrounding gas. The bright glowing knots are dense clumps from instabilities that form behind the shock wave. The Hubble data also show thin filaments of gas that look like rippled sheets seen edge-on. These filaments reveal where the shock wave is encountering lower-density, more uniform interstellar material.

The Spitzer telescope shows microscopic dust particles (colored red) that have been heated by the supernova shock wave. The dust re-radiates the shock wave's energy as infrared light. The Spitzer data are brightest in the regions surrounding those seen in detail by the Hubble telescope.

The Chandra X-ray data show regions of very hot gas, and extremely high-energy particles. The hottest gas (higher-energy X-rays, colored blue) is located primarily in the regions directly behind the shock front. These regions also show up in the Hubble observations, and also align with the faint rim of glowing material seen in the Spitzer data. The X-rays from the region on the lower left (colored blue) may be dominated by extremely high-energy electrons that were produced by the shock wave and are radiating at radio through X-ray wavelengths as they spiral in the intensified magnetic field behind the shock front. Cooler X-ray gas (lower-energy X-rays, colored green) resides in a thick interior shell and marks the location of heated material expelled from the exploded star.

Kepler's supernova, the last such object seen to explode in our Milky Way galaxy, resides about 13,000 light-years away in the constellation Ophiuchus.

The Chandra observations were taken in June 2000, the Hubble in August 2003; and the Spitzer in August 2004.

Persistence of Precursor Waves in Two-dimensional Relativistic Shocks

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

Iwamoto, Masanori; Amano, Takanobu; Hoshino, Masahiro

2017-05-01

We investigated the efficiency of coherent upstream large-amplitude electromagnetic wave emission via synchrotron maser instability in relativistic magnetized shocks using two-dimensional particle-in-cell simulations. We considered a purely perpendicular shock in an electron–positron plasma. The coherent wave emission efficiency was measured as a function of the magnetization parameter σ , which is defined as the ratio of the Poynting flux to the kinetic energy flux. The wave amplitude was systematically smaller than that observed in one-dimensional simulations. However, it continued to persist, even at a considerably low magnetization rate, where the Weibel instability dominated the shock transition. The emitted electromagnetic wavesmore » were sufficiently strong to disturb the upstream medium, and transverse filamentary density structures of substantial amplitude were produced. Based on this result, we discuss the possibility of the wakefield acceleration model to produce nonthermal electrons in a relativistic magnetized ion–electron shock.« less

Evanescent Wave Absorption Based Fiber Sensor for Measuring Glucose Solution Concentration

NASA Astrophysics Data System (ADS)

Marzuki, Ahmad; Candra Pratiwi, Arni; Suryanti, Venty

2018-03-01

An optical fiber sensor based on evanescent wave absorption designed for measuring glucose solution consentration was proposed. The sensor was made to detect absorbance of various wavelength in the glucose solution. The sensing element was fabricated by side polishing of multimode polymer optical fiber to form a D-shape. The sensing element was immersed in different concentration of glucoce solution. As light propagated through the optical fiber, the evanescent wave interacted with the glucose solution. Light was absorbed by the glucose solution. The larger concentration the glucose solution has, the more the evanescent wave was absorbed in particular wavelenght. Here in this paper, light absorbtion as function of glucose concentration was measured as function of wavelength (the color of LED). We have shown that the proposed sensor can demonstrated an increase of light absorption as function of glucose concentration.

Experimental investigation of vector static magnetic field detection using an NV center with a single first-shell 13C nuclear spin in diamond

NASA Astrophysics Data System (ADS)

Jiang, Feng-Jian; Ye, Jian-Feng; Jiao, Zheng; Jiang, Jun; Ma, Kun; Yan, Xin-Hu; Lv, Hai-Jiang

2018-05-01

We perform a proof-of-principle experiment that uses a single negatively charged nitrogen–vacancy (NV) color center with a nearest neighbor 13C nuclear spin in diamond to detect the strength and direction (including both polar and azimuth angles) of a static vector magnetic field by optical detection magnetic resonance (ODMR) technique. With the known hyperfine coupling tensor between an NV center and a nearest neighbor 13C nuclear spin, we show that the information of static vector magnetic field could be extracted by observing the pulsed continuous wave (CW) spectrum. Project supported by the National Natural Science Foundation of China (Grant Nos. 11305074, 11135002, and 11275083), the Key Program of the Education Department Outstanding Youth Foundation of Anhui Province, China (Grant No. gxyqZD2017080), and the Education Department Natural Science Foundation of Anhui Province, China (Grant No. KJHS2015B09).

Magnetosonic solitons in space plasmas: dark or bright solitons?

NASA Astrophysics Data System (ADS)

Pokhotelov, O. A.; Onishchenko, O. G.; Balikhin, M. A.; Stenflo, L.; Shukla, P. K.

2007-12-01

The nonlinear theory of large-amplitude magnetosonic (MS) waves in highβ space plasmas is revisited. It is shown that solitary waves can exist in the form of `bright' or `dark' solitons in which the magnetic field is increased or decreased relative to the background magnetic field. This depends on the shape of the equilibrium ion distribution function. The basic parameter that controls the nonlinear structure is the wave dispersion, which can be either positive or negative. A general dispersion relation for MS waves propagating perpendicularly to the external magnetic field in a plasma with an arbitrary velocity distribution function is derived.It takes into account general plasma equilibria, such as the Dory-Guest-Harris (DGH) or Kennel-Ashour-Abdalla (KA) loss-cone equilibria, as well as distributions with a power-law velocity dependence that can be modelled by κdistributions. It is shown that in a bi-Maxwellian plasma the dispersion is negative, i.e. the phase velocity decreases with an increase of the wavenumber. This means that the solitary solution in this case has the form of a `bright' soliton with the magnetic field increased. On the contrary, in some non-Maxwellian plasmas, such as those with ring-type ion distributions or DGH plasmas, the solitary solution may have the form of a magnetic hole. The results of similar investigations based on nonlinear Hall-MHD equations are reviewed. The relevance of our theoretical results to existing satellite wave observations is outlined.

Brain Activation and Deactivation during Location and Color Working Memory Tasks in 11-13-Year-Old Children

ERIC Educational Resources Information Center

Vuontela, Virve; Steenari, Maija-Riikka; Aronen, Eeva T.; Korvenoja, Antti; Aronen, Hannu J.; Carlson, Synnove

2009-01-01

Using functional magnetic resonance imaging (fMRI) and n-back tasks we investigated whether, in 11-13-year-old children, spatial (location) and nonspatial (color) information is differentially processed during visual attention (0-back) and working memory (WM) (2-back) tasks and whether such cognitive task performance, compared to a resting state,…

Theory of Tunneling Spectroscopy in a Mn12 Single-Electron Transistor by Density-Functional Theory Methods

NASA Astrophysics Data System (ADS)

Michalak, Ł.; Canali, C. M.; Pederson, M. R.; Paulsson, M.; Benza, V. G.

2010-01-01

We consider tunneling transport through a Mn12 molecular magnet using spin density functional theory. A tractable methodology for constructing many-body wave functions from Kohn-Sham orbitals allows for the determination of spin-dependent matrix elements for use in transport calculations. The tunneling conductance at finite bias is characterized by peaks representing transitions between spin multiplets, separated by an energy on the order of the magnetic anisotropy. The energy splitting of the spin multiplets and the spatial part of their many-body wave functions, describing the orbital degrees of freedom of the excess charge, strongly affect the electronic transport, and can lead to negative differential conductance.

Theory of tunneling spectroscopy in a Mn12 single-electron transistor by density-functional theory methods.

PubMed

Michalak, Ł; Canali, C M; Pederson, M R; Paulsson, M; Benza, V G

2010-01-08

We consider tunneling transport through a Mn12 molecular magnet using spin density functional theory. A tractable methodology for constructing many-body wave functions from Kohn-Sham orbitals allows for the determination of spin-dependent matrix elements for use in transport calculations. The tunneling conductance at finite bias is characterized by peaks representing transitions between spin multiplets, separated by an energy on the order of the magnetic anisotropy. The energy splitting of the spin multiplets and the spatial part of their many-body wave functions, describing the orbital degrees of freedom of the excess charge, strongly affect the electronic transport, and can lead to negative differential conductance.

A generalized plasma dispersion function for electron damping in tokamak plasmas

DOE PAGES

Berry, L. A.; Jaeger, E. F.; Phillips, C. K.; ...

2016-10-14

Radio frequency wave propagation in finite temperature, magnetized plasmas exhibits a wide range of physics phenomena. The plasma response is nonlocal in space and time, and numerous modes are possible with the potential for mode conversions and transformations. Additionally, diffraction effects are important due to finite wavelength and finite-size wave launchers. Multidimensional simulations are required to describe these phenomena, but even with this complexity, the fundamental plasma response is assumed to be the uniform plasma response with the assumption that the local plasma current for a Fourier mode can be described by the Stix conductivity. But, for plasmas with non-uniformmore » magnetic fields, the wave vector itself is nonlocal. When resolved into components perpendicular (k ) and parallel (k ||) to the magnetic field, locality of the parallel component can easily be violated when the wavelength is large. The impact of this inconsistency is that estimates of the wave damping can be incorrect (typically low) due to unresolved resonances. For the case of ion cyclotron damping, this issue has already been addressed by including the effect of parallel magnetic field gradients. In this case, a modified plasma response (Z function) allows resonance broadening even when k || = 0, and this improves the convergence and accuracy of wave simulations. In our paper, we extend this formalism to include electron damping and find improved convergence and accuracy for parameters where electron damping is dominant, such as high harmonic fast wave heating in the NSTX-U tokamak, and helicon wave launch for off-axis current drive in the DIII-D tokamak.« less

The effects of perceiving color in living environment on QEEG, oxygen saturation, pulse rate, and emotion regulation in humans.

PubMed

Sroykham, Watchara; Wongsathikun, J; Wongsawat, Y

2014-01-01

Light and color have been shown to have substantial physical, psychological and sociological effects on humans. Hence, an investigation on the effect of changes in light and color to the biological signals is a challenging problem. Five participants were measured the oxygen saturation (SpO2), pulse rate, and quantitative electroencephalogram (QEEG) in six colors (white, blue, green, yellow, red and black) of living environment for 5 minutes per color. Then all participants were asked to answer the emotional questionnaire of BRUMS and color performance for each color environment. The results showed brain activity of high beta wave (25-30 Hz) that associated with alertness, agitation, mental activity, and general activation of mind and body functions (at frontal lobes and temporal lobes) in red and yellow colored rooms were higher than blue, green, white and black colored rooms, respectively. It also had the relationship with the psychological effect (BRUMS). The amplitude asymmetry of beta wave (12-25 Hz) was highly attenuated in warm color (red and yellow colored rooms), moderately attenuated in cool color (green and blue colored room) and little attenuated in white and black colored rooms. The BRUMS showed that red and yellow yielded significant effect on anger (F = 4.966, p = 0.002) and confusion (F=3.853, p=0.008). Red and green color yielded high effect on vigor. Green color did not affect the depression. Blue color yielded moderate effect on confusion, tension and fatigue. White and black colors yielded low effect on any mood, but black color had no effect on vigor. In addition, we cannot observe any significant changes of pulse rate and blood oxygen saturation in each color. The results can possibly be used as the recommendation to design the room for either normal people or patients.

Rhenium-phthalocyanine molecular nanojunction with high magnetic anisotropy and high spin filtering efficiency

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

Li, J.; Institute of Nanomaterial and Nanostructure, Changsha University of Science and Technology, Changsha 410114; Hu, J.

2015-07-20

Using the density functional and non-equilibrium Green's function approaches, we studied the magnetic anisotropy and spin-filtering properties of various transition metal-Phthalocyanine molecular junctions across two Au electrodes. Our important finding is that the Au-RePc-Au junction has both large spin filtering efficiency (>80%) and large magnetic anisotropy energy, which makes it suitable for device applications. To provide insights for the further experimental work, we discussed the correlation between the transport property, magnetic anisotropy, and wave function features of the RePc molecule, and we also illustrated the possibility of controlling its magnetic state.

Stochastic analysis of pitch angle scattering of charged particles by transverse magnetic waves

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

Lemons, Don S.; Liu Kaijun; Winske, Dan

2009-11-15

This paper describes a theory of the velocity space scattering of charged particles in a static magnetic field composed of a uniform background field and a sum of transverse, circularly polarized, magnetic waves. When that sum has many terms the autocorrelation time required for particle orbits to become effectively randomized is small compared with the time required for the particle velocity distribution to change significantly. In this regime the deterministic equations of motion can be transformed into stochastic differential equations of motion. The resulting stochastic velocity space scattering is described, in part, by a pitch angle diffusion rate that ismore » a function of initial pitch angle and properties of the wave spectrum. Numerical solutions of the deterministic equations of motion agree with the theory at all pitch angles, for wave energy densities up to and above the energy density of the uniform field, and for different wave spectral shapes.« less

Color quality improvement of reconstructed images in color digital holography using speckle method and spectral estimation

NASA Astrophysics Data System (ADS)

Funamizu, Hideki; Onodera, Yusei; Aizu, Yoshihisa

2018-05-01

In this study, we report color quality improvement of reconstructed images in color digital holography using the speckle method and the spectral estimation. In this technique, an object is illuminated by a speckle field and then an object wave is produced, while a plane wave is used as a reference wave. For three wavelengths, the interference patterns of two coherent waves are recorded as digital holograms on an image sensor. Speckle fields are changed by moving a ground glass plate in an in-plane direction, and a number of holograms are acquired to average the reconstructed images. After the averaging process of images reconstructed from multiple holograms, we use the Wiener estimation method for obtaining spectral transmittance curves in reconstructed images. The color reproducibility in this method is demonstrated and evaluated using a Macbeth color chart film and staining cells of onion.

Process for making diamonds

NASA Technical Reports Server (NTRS)

Rasquin, J. R.; Estes, M. F. (Inventor)

1973-01-01

A description is given of a device and process for making industrial diamonds. The device is composed of an exponential horn tapering from a large end to a small end, with a copper plate against the large end. A magnetic hammer abuts the copper plate. The copper plate and magnetic hammer function together to create a shock wave at the large end of the horn. As the wave propagates to the small end, the extreme pressure and temperature caused by the wave transforms the graphite, present in an anvil pocket at the small end, into diamonds.

Quasi-Phasematched Nonlinear Optics: Materials and Devices

DTIC Science & Technology

2007-04-16

the soliton energy in pump, signal and idler waves as a function of the final wave- vector mismatch in the chirped QPM gratings. We see good agreement...devices including OP-GaAs devices for broadband optical parametric generation (OPG) at mid-infrared wavelengths, bulk PPLN devices for soliton ...Carrasco, and L. Torner,"Engineering of multi-color spatial solitons with chirped-period quasi-phase-matching gratings in optical parametric amplification

Exploring graphene superlattices: Magneto-optical properties

NASA Astrophysics Data System (ADS)

Duque, C. A.; Hernández-Bertrán, M. A.; Morales, A. L.; de Dios-Leyva, M.

2017-02-01

We present a detailed study of magnetic subbands, wave functions, and transition strengths for graphene superlattices (SLs) subject to a perpendicular magnetic field. It is shown that, for a weak magnetic field, the flat subbands of a SL exhibiting extra Dirac points are grouped into subsets, each of which consists of a singlet subband and a nearly degenerate doublet subband, and one nearly degenerate triplet subband. It was found that the wave functions corresponding to a singlet or to a doublet are always located around the image in real space of the central or extra Dirac points in k-space. The latter properties were explained by assuming that the electron motion is quasi-classical. Our study revealed that, for an intermediate field, the general characteristics of the wave functions are very similar to those of the pristine graphene, while for weak field, their behavior is drastically different. The latter is characterized by rapid oscillations which were understood using the solutions provided by the formalism of Luttinger-Kohn. The study on transition strengths allows us to obtain, for SLs with extra Dirac points in a weak magnetic field and different polarizations, the conditions under which transitions between multiplets are approximately allowed. It was shown that these conditions correspond to an unusual selection rule that is broken when the magnetic field intensity increases from weak to an intermediate value.

E-wave generated intraventricular diastolic vortex to L-wave relation: model-based prediction with in vivo validation.

PubMed

Ghosh, Erina; Caruthers, Shelton D; Kovács, Sándor J

2014-08-01

The Doppler echocardiographic E-wave is generated when the left ventricle's suction pump attribute initiates transmitral flow. In some subjects E-waves are accompanied by L-waves, the occurrence of which has been correlated with diastolic dysfunction. The mechanisms for L-wave generation have not been fully elucidated. We propose that the recirculating diastolic intraventricular vortex ring generates L-waves and based on this mechanism, we predict the presence of L-waves in the right ventricle (RV). We imaged intraventricular flow using Doppler echocardiography and phase-contrast magnetic resonance imaging (PC-MRI) in 10 healthy volunteers. L-waves were recorded in all subjects, with highest velocities measured typically 2 cm below the annulus. Fifty-five percent of cardiac cycles (189 of 345) had L-waves. Color M-mode images eliminated mid-diastolic transmitral flow as the cause of the observed L-waves. Three-dimensional intraventricular flow patterns were imaged via PC-MRI and independently validated our hypothesis. Additionally as predicted, L-waves were observed in the RV, by both echocardiography and PC-MRI. The re-entry of the E-wave-generated vortex ring flow through a suitably located echo sample volume can be imaged as the L-wave. These waves are a general feature and a direct consequence of LV and RV diastolic fluid mechanics. Copyright © 2014 the American Physiological Society.

Color of scents: chromatic stimuli modulate odor responses in the human brain.

PubMed

Osterbauer, Robert A; Matthews, Paul M; Jenkinson, Mark; Beckmann, Christian F; Hansen, Peter C; Calvert, Gemma A

2005-06-01

Color has a profound effect on the perception of odors. For example, strawberry-flavored drinks smell more pleasant when colored red than green and descriptions of the "nose" of a wine are dramatically influenced by its color. Using functional magnetic resonance imaging, we demonstrate a neurophysiological correlate of these cross-modal visual influences on olfactory perception. Subjects were scanned while exposed either to odors or colors in isolation or to color-odor combinations that were rated on the basis of how well they were perceived to match. Activity in caudal regions of the orbitofrontal cortex and in the insular cortex increased progressively with the perceived congruency of the odor-color pairs. These findings demonstrate the neuronal correlates of olfactory response modulation by color cues in brain areas previously identified as encoding the hedonic value of smells.

Determination of many-electron basis functions for a quantum Hall ground state using Schur polynomials

NASA Astrophysics Data System (ADS)

Mandal, Sudhansu S.; Mukherjee, Sutirtha; Ray, Koushik

2018-03-01

A method for determining the ground state of a planar interacting many-electron system in a magnetic field perpendicular to the plane is described. The ground state wave-function is expressed as a linear combination of a set of basis functions. Given only the flux and the number of electrons describing an incompressible state, we use the combinatorics of partitioning the flux among the electrons to derive the basis wave-functions as linear combinations of Schur polynomials. The procedure ensures that the basis wave-functions form representations of the angular momentum algebra. We exemplify the method by deriving the basis functions for the 5/2 quantum Hall state with a few particles. We find that one of the basis functions is precisely the Moore-Read Pfaffian wave function.

Intermittent nature of solar wind turbulence near the Earth's bow shock: phase coherence and non-Gaussianity.

PubMed

Koga, D; Chian, A C-L; Miranda, R A; Rempel, E L

2007-04-01

The link between phase coherence and non-Gaussian statistics is investigated using magnetic field data observed in the solar wind turbulence near the Earth's bow shock. The phase coherence index Cphi, which characterizes the degree of phase correlation (i.e., nonlinear wave-wave interactions) among scales, displays a behavior similar to kurtosis and reflects a departure from Gaussianity in the probability density functions of magnetic field fluctuations. This demonstrates that nonlinear interactions among scales are the origin of intermittency in the magnetic field turbulence.

Magnetically Controlled Surface Acoustic Waves on Multiferroic BiFeO3

NASA Astrophysics Data System (ADS)

Ishii, Y.; Sasaki, R.; Nii, Y.; Ito, T.; Onose, Y.

2018-03-01

We fabricate a surface acoustic wave (SAW) device on a multiferroic BiFeO3 crystal while SAW devices are usually fabricated on nonmagnetic piezoelectrics and commercially available as bandpass filters. By using the time-domain technique, we demonstrate the SAW excitation on BiFeO3 . The amplitude and phase of the SAW signal are modulated by the external magnetic field reflecting the multiferroicity of BiFeO3 . The magnetic controllability of the multiferroic SAW device seems useful for the further functionalization of the SAW device.

A study of acoustic halos in active region NOAA 11330 using multi-height SDO observations

NASA Astrophysics Data System (ADS)

Tripathy, S. C.; Jain, K.; Kholikov, S.; Hill, F.; Rajaguru, S. P.; Cally, P. S.

2018-01-01

We analyze data from the Helioseismic Magnetic Imager (HMI) and the Atmospheric Imaging Assembly (AIA) instruments on board the Solar Dynamics Observatory (SDO) to characterize the spatio-temporal acoustic power distribution in active regions as a function of the height in the solar atmosphere. For this, we use Doppler velocity and continuum intensity observed using the magnetically sensitive line at 6173 Å as well as intensity at 1600 Å and 1700 Å. We focus on the power enhancements seen around AR 11330 as a function of wave frequency, magnetic field strength, field inclination and observation height. We find that acoustic halos occur above the acoustic cutoff frequency and extends up to 10 mHz in HMI Doppler and AIA 1700 Å observations. Halos are also found to be strong functions of magnetic field and their inclination angle. We further calculate and examine the spatially averaged relative phases and cross-coherence spectra and find different wave characteristics at different heights.

Correct definition of color singlet P-wave non-perturbative matrix element of heavy quarkonium production

NASA Astrophysics Data System (ADS)

Nayak, Gouranga C.

2017-09-01

Recently we have proved factorization of infrared divergences in NRQCD S-wave heavy quarkonium production at high energy colliders at all orders in coupling constant. One of the problem which still exists in the higher order pQCD calculation of color singlet P-wave heavy quarkonium production/anihillation is the appearance of noncanceling infrared divergences due to real soft gluons exchange, although no such infrared divergences are present in the color singlet S-wave heavy quarkonium. In this paper we find that since the non-perturbative matrix element of the color singlet P-wave heavy quarkonium production contains derivative operators, the gauge links are necessary to make it gauge invariant and be consistent with the factorization of such non-canceling infrared divergences at all orders in coupling constant.

Annular wave packets at Dirac points in graphene and their probability-density oscillation.

PubMed

Luo, Ji; Valencia, Daniel; Lu, Junqiang

2011-12-14

Wave packets in graphene whose central wave vector is at Dirac points are investigated by numerical calculations. Starting from an initial Gaussian function, these wave packets form into annular peaks that propagate to all directions like ripple-rings on water surface. At the beginning, electronic probability alternates between the central peak and the ripple-rings and transient oscillation occurs at the center. As time increases, the ripple-rings propagate at the fixed Fermi speed, and their widths remain unchanged. The axial symmetry of the energy dispersion leads to the circular symmetry of the wave packets. The fixed speed and widths, however, are attributed to the linearity of the energy dispersion. Interference between states that, respectively, belong to two branches of the energy dispersion leads to multiple ripple-rings and the probability-density oscillation. In a magnetic field, annular wave packets become confined and no longer propagate to infinity. If the initial Gaussian width differs greatly from the magnetic length, expanding and shrinking ripple-rings form and disappear alternatively in a limited spread, and the wave packet resumes the Gaussian form frequently. The probability thus oscillates persistently between the central peak and the ripple-rings. If the initial Gaussian width is close to the magnetic length, the wave packet retains the Gaussian form and its height and width oscillate with a period determined by the first Landau energy. The wave-packet evolution is determined jointly by the initial state and the magnetic field, through the electronic structure of graphene in a magnetic field. © 2011 American Institute of Physics

Anomalous skin effects in a weakly magnetized degenerate electron plasma

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

Abbas, G., E-mail: gohar.abbas@gcu.edu.pk; Sarfraz, M.; Shah, H. A.

2014-09-15

Fully relativistic analysis of anomalous skin effects for parallel propagating waves in a weakly magnetized degenerate electron plasma is presented and a graphical comparison is made with the results obtained using relativistic Maxwellian distribution function [G. Abbas, M. F. Bashir, and G. Murtaza, Phys. Plasmas 18, 102115 (2011)]. It is found that the penetration depth for R- and L-waves for degenerate case is qualitatively small in comparison with the Maxwellian plasma case. The quantitative reduction due to weak magnetic field in the skin depth in R-wave for degenerate plasma is large as compared to the non-degenerate one. By ignoring themore » ambient magnetic field, previous results for degenerate field free case are salvaged [A. F. Alexandrov, A. S. Bogdankevich, and A. A. Rukhadze, Principles of Plasma Electrodynamics (Springer-Verlag, Berlin/Heidelberg, 1984), p. 90].« less

Dissipative MHD solutions for resonant Alfven waves in 1-dimensional magnetic flux tubes

NASA Technical Reports Server (NTRS)

Goossens, Marcel; Ruderman, Michail S.; Hollweg, Joseph V.

1995-01-01

The present paper extends the analysis by Sakurai, Goossens, and Hollweg (1991) on resonant Alfven waves in nonuniform magnetic flux tubes. It proves that the fundamental conservation law for resonant Alfven waves found in ideal MHD by Sakurai, Goossens, and Hollweg remains valid in dissipative MHD. This guarantees that the jump conditions of Sakurai, Goossens, and Hollweg, that connect the ideal MHD solutions for xi(sub r), and P' across the dissipative layer, are correct. In addition, the present paper replaces the complicated dissipative MHD solutions obtained by Sakurai, Goossens, and Hollweg for xi(sub r), and P' in terms of double integrals of Hankel functions of complex argument of order 1/3 with compact analytical solutions that allow a straight- forward mathematical and physical interpretation. Finally, it presents an analytical dissipative MHD solution for the component of the Lagrangian displacement in the magnetic surfaces perpen- dicular to the magnetic field lines xi(sub perpendicular) which enables us to determine the dominant dynamics of resonant Alfven waves in dissipative MHD.

Kinetic Alfvén Wave Generation by Large-scale Phase Mixing

NASA Astrophysics Data System (ADS)

Vásconez, C. L.; Pucci, F.; Valentini, F.; Servidio, S.; Matthaeus, W. H.; Malara, F.

2015-12-01

One view of the solar wind turbulence is that the observed highly anisotropic fluctuations at spatial scales near the proton inertial length dp may be considered as kinetic Alfvén waves (KAWs). In the present paper, we show how phase mixing of large-scale parallel-propagating Alfvén waves is an efficient mechanism for the production of KAWs at wavelengths close to dp and at a large propagation angle with respect to the magnetic field. Magnetohydrodynamic (MHD), Hall magnetohydrodynamic (HMHD), and hybrid Vlasov–Maxwell (HVM) simulations modeling the propagation of Alfvén waves in inhomogeneous plasmas are performed. In the linear regime, the role of dispersive effects is singled out by comparing MHD and HMHD results. Fluctuations produced by phase mixing are identified as KAWs through a comparison of polarization of magnetic fluctuations and wave-group velocity with analytical linear predictions. In the nonlinear regime, a comparison of HMHD and HVM simulations allows us to point out the role of kinetic effects in shaping the proton-distribution function. We observe the generation of temperature anisotropy with respect to the local magnetic field and the production of field-aligned beams. The regions where the proton-distribution function highly departs from thermal equilibrium are located inside the shear layers, where the KAWs are excited, this suggesting that the distortions of the proton distribution are driven by a resonant interaction of protons with KAW fluctuations. Our results are relevant in configurations where magnetic-field inhomogeneities are present, as, for example, in the solar corona, where the presence of Alfvén waves has been ascertained.

Radial localization of magnetospheric guided poloidal Pc 4-5 waves

NASA Astrophysics Data System (ADS)

Denton, R. E.; Lessard, M. R.; Kistler, L. M.

2003-03-01

The toroidal Alfvén wave, with magnetic field oscillations in the azimuthal direction, exhibits a singularity in the vicinity of the toroidal resonant frequency (field line resonance), so it is not surprising that this wave often exhibits varying frequency as a function of L shell. It is less clear why the poloidal Alfvén wave, with magnetic field oscillations in the radial direction, often exhibits a relatively constant frequency over a range of L shells. So far, the most promising proposal to explain this phenomenon is the theory of [1994, 1996], who showed that an energetically trapped global poloidal mode can exist in a region where the poloidal Alfvén frequency is lower than the toroidal frequency and where it exhibits a dip (minimum) with respect to L. While this theory is mathematically plausible, it has never been shown that poloidal Alfvén waves actually occur in association with such a dip in poloidal frequency. Here we examine poloidal wave events observed by the AMPTE/IRM spacecraft and calculate the theoretical poloidal frequency as a function of L using the equilibrium parameters obtained from the spacecraft observations. We find that the poloidal Alfvén wave does occur in association with such a dip (or at least a flattening) in poloidal frequency. While Vetoulis and Chen hypothesized that such a dip would occur because of a sharp gradient in plasma pressure, we find that the dip in poloidal frequency may result from the L dependence of the equilibrium density or magnetic field. The observed frequencies are in rough agreement with the theoretical frequencies, though in some cases we must assume that the observed oscillations result from a high harmonic (third or fourth harmonic structure along the magnetic field). We also apply the same analysis to compressional wave events (with oscillations in the direction of the equilibrium magnetic field). Such oscillations may be on the poloidal wave branch or the mirror mode branch. Here also, the observed fluctuations occur in the region of a dip in poloidal frequency. In one case the observed frequency is consistent with the theoretical poloidal frequency, whereas in another case it is not.

BCVEGPY2.0: An upgraded version of the generator BCVEGPY with the addition of hadroproduction of the P-wave B states

NASA Astrophysics Data System (ADS)

Chang, Chao-Hsi; Wang, Jian-Xiong; Wu, Xing-Gang

2006-02-01

The generator BCVEGPY is upgraded by improving some of its features and by adding the hadroproduction of the P-wave excited B states (denoted by BcJ,L=1∗ or by hB_c and χB_c). In order to make the generator more efficient, we manipulate the amplitude as compact as possible with special effort. The correctness of the program is tested by various checks. We denote it as BCVEGPY2.0. As for the added part of the P-wave production, only the dominant gluon-gluon fusion mechanism ( gg→BcJ,L=1∗+c¯+b) is taken into account. Moreover, in the program, not only the ability to compute the contributions from the color-singlet components ( to the P-wave production but also the ability to compute the contributions from the color-octet components ( are available. With BCVEGPY2.0 the contributions from the two 'color components' to the production of each of the P-wave states may be computed separately by an option, furthermore, besides individually the event samples of the S-wave and P-wave ( cb¯)-heavy-quarkonium in various correct (realistic) mixtures can be generated by relevant options too. Program summaryTitle of program: BCVEGPY Version: 2.0 (December, 2004) Catalogue identifier: ADWQ Program summary URL:http://cpc.cs.qub.ac.uk/summaries/ADWQ Program obtained from: CPC Program Library, Queen's University of Belfast, N. Ireland Reference to original program: ADTJ (BCVEGPY1.0) Reference in CPC: Comput. Phys. Comm. 159 (2004) 192 Does the new version supersede the old program: yes Computer: Any computer with FORTRAN 77 or 90 compiler. The program has been tested on HP-SC45 Sigma-X parallel computer, Linux PCs and Windows PCs with Visual Fortran Operating systems: UNIX, Linux and Windows Programming language used: FORTRAN 77/90 Memory required to execute with typical data: About 2.0 MB No. of lines in distributed program, including test data, etc.: 124 297 No. of bytes in distributed program, including test data, etc.: 1 137 177 Distribution format: tar.g2 Nature of physical problem: Hadronic production of B meson itself and its excited states. Method of solution: The code with option can generate weighted and unweighted events. For jet hadronization, an interface to PYTHIA is provided. Reason for the new version: There are two reasons. One is to provide additional codes for the hadronic production of P-wave excited B states: the four via color-singlet P-wave state directly and the two via color-octet S-wave state accordingly. The other one is to decompose the color-flow factor for the amplitude by an approximate way, that is adopted in PYTHIA. Summary of Revisions: (1) The integration efficiency over the momentum fractions of the initial partons x and x are improved; (2) The amplitudes for the hadronic production of the color-singlet components corresponding to the four P-wave states, BcJ,L=1∗ or P1 and P3 ( J=0,1,2), are included; (3) The amplitudes for P-wave production via the two color-octet components |((S1)g> and |((S3)g> are included; (4) For comparison, the S-wave ( S1 and S3) hadronic production via the light quark-antiquark annihilation mechanism is also included; (5) For convenience, 24 data files to record the information of the generated events in one run are added; (6) An additional file, parameter.for, is added to set the initial values of the parameters; (7) Two new parameters 'IMIX' (IMIX = 0 or 1) and 'IMIXTYPE' (IMIXTYPE = 1, = 2 or = 3) are added to meet the needs of generating the events for simulating 'mixing' or 'separate' event samples for various B and its excited states correctly; (8) One switch, 'IVEGGRADE', is added to determine whether to use the existed importance sampling function to generate a more precise importance sampling function or not; (9) Two parameters, 'IOUTPDF' and 'IPDFNUM', are added to determine which type of PDFs to use; (10) The color-flow decomposition for the amplitudes is rewritten by an approximate way, that is adopted in PYTHIA. Restrictions on the complexity of the problem: The hadronic production of (cb¯)-quarkonium in S-wave and P-wave states via the mechanism of gluon-gluon fusion are given by the 'complete calculation' approach of the leading order QCD. The contributions from the other mechanisms for P-wave production which are small comparatively are not included. Typical running time: Generally speaking, it depends on which option is used to drive PYTHIA when generating the B events. Typically, for the hadronic production of the S-wave (cb¯)-quarkonium, if the PYTHIA parameter IDWTUP = 1, then it takes about 20 hours on a 1.8 GHz Intel P4-processor machine to generate 1000 events; however if IDWTUP = 3, to generate 10 6 events, it takes only about 40 minutes. For the hadronic production of the P-wave (cb¯)-quarkonium, the necessary time will be almost two times longer than the S-wave quarkonium production.

Categorical clustering of the neural representation of color.

PubMed

Brouwer, Gijs Joost; Heeger, David J

2013-09-25

Cortical activity was measured with functional magnetic resonance imaging (fMRI) while human subjects viewed 12 stimulus colors and performed either a color-naming or diverted attention task. A forward model was used to extract lower dimensional neural color spaces from the high-dimensional fMRI responses. The neural color spaces in two visual areas, human ventral V4 (V4v) and VO1, exhibited clustering (greater similarity between activity patterns evoked by stimulus colors within a perceptual category, compared to between-category colors) for the color-naming task, but not for the diverted attention task. Response amplitudes and signal-to-noise ratios were higher in most visual cortical areas for color naming compared to diverted attention. But only in V4v and VO1 did the cortical representation of color change to a categorical color space. A model is presented that induces such a categorical representation by changing the response gains of subpopulations of color-selective neurons.

Categorical Clustering of the Neural Representation of Color

PubMed Central

Heeger, David J.

2013-01-01

Cortical activity was measured with functional magnetic resonance imaging (fMRI) while human subjects viewed 12 stimulus colors and performed either a color-naming or diverted attention task. A forward model was used to extract lower dimensional neural color spaces from the high-dimensional fMRI responses. The neural color spaces in two visual areas, human ventral V4 (V4v) and VO1, exhibited clustering (greater similarity between activity patterns evoked by stimulus colors within a perceptual category, compared to between-category colors) for the color-naming task, but not for the diverted attention task. Response amplitudes and signal-to-noise ratios were higher in most visual cortical areas for color naming compared to diverted attention. But only in V4v and VO1 did the cortical representation of color change to a categorical color space. A model is presented that induces such a categorical representation by changing the response gains of subpopulations of color-selective neurons. PMID:24068814

Topologically protected unidirectional edge spin waves

NASA Astrophysics Data System (ADS)

Wang, Xiang Rong; Wang, Xiansi; Su, Ying

Magnetic materials are highly correlated spin systems that do not respect the time-reversal symmetry. The low-energy excitations of magnetic materials are spin waves whose quanta are magnons. Like electronic materials that can be topologically nontrivial, a magnetic material can also be topologically nontrivial with topologically protected unidirectional edge states. These edge states should be superb channels of processing and manipulating spin waves because they are robust against perturbations and geometry changes, unlike the normal spin wave states that are very sensitive to the system changes and geometry. Therefore, the magnetic topological matter is of fundamental interest and technologically useful in magnonics. Here, we show that ferromagnetically interacting spins on a two-dimensional honeycomb lattice with nearest-neighbour interactions and governed by the Landau-Lifshitz-Gilbert equation, can be topologically nontrivial with gapped bulk spin waves and gapless edge spin waves. These edge spin waves are indeed very robust against defects under topological protection. Because of the unidirectional nature of these topologically protected edge spin waves, an interesting functional magnonic device called beam splitter can be made out of a domain wall in a strip. It is shown that an in-coming spin wave beam along one edge splits into two spin wave beams propagating along two opposite directions on the other edge after passing through a domain wall. This work was supported by Hong Kong GRF Grants (Nos. 163011151 and 16301816) and the Grant from NNSF of China (No. 11374249). X.S.W acknowledge support from UESTC.

Numerical simulations of sheared magnetic lines at the solar null line

NASA Astrophysics Data System (ADS)

Kuźma, B.; Murawski, K.; Solov'ev, A.

2015-05-01

Aims: We perform numerical simulations of sheared magnetic lines at the magnetic null line configuration of two magnetic arcades that are settled in a gravitationally stratified and magnetically confined solar corona. Methods: We developed a general analytical model of a 2.5D solar atmospheric structure. As a particular application of this model, we adopted it for the curved magnetic field lines with an inverted Y shape that compose the null line above two magnetic arcades, which are embedded in the solar atmosphere that is specified by the realistic temperature distribution. The physical system is described by 2.5D magnetohydrodynamic equations that are numerically solved by the FLASH code. Results: The magnetic field line shearing, implemented about 200 km below the transition region, results in Alfvén and magnetoacoustic waves that are able to penetrate solar coronal regions above the magnetic null line. As a result of the coupling of these waves, partial reflection from the transition region and scattering from inhomogeneous regions the Alfvén waves experience fast attenuation on time scales comparable to their wave periods, and the physical system relaxes in time. The attenuation time grows with the large amplitude and characteristic growing time of the shearing. Conclusions: By having chosen a different magnetic flux function, the analytical model we devised can be adopted to derive equilibrium conditions for a diversity of 2.5D magnetic structures in the solar atmosphere. Movie associated to Fig. 5 is available in electronic form at http://www.aanda.org

Variational model for one-dimensional quantum magnets

NASA Astrophysics Data System (ADS)

Kudasov, Yu. B.; Kozabaranov, R. V.

2018-04-01

A new variational technique for investigation of the ground state and correlation functions in 1D quantum magnets is proposed. A spin Hamiltonian is reduced to a fermionic representation by the Jordan-Wigner transformation. The ground state is described by a new non-local trial wave function, and the total energy is calculated in an analytic form as a function of two variational parameters. This approach is demonstrated with an example of the XXZ-chain of spin-1/2 under a staggered magnetic field. Generalizations and applications of the variational technique for low-dimensional magnetic systems are discussed.

Designing Image Operators for MRI-PET Image Fusion of the Brain

NASA Astrophysics Data System (ADS)

Márquez, Jorge; Gastélum, Alfonso; Padilla, Miguel A.

2006-09-01

Our goal is to obtain images combining in a useful and precise way the information from 3D volumes of medical imaging sets. We address two modalities combining anatomy (Magnetic Resonance Imaging or MRI) and functional information (Positron Emission Tomography or PET). Commercial imaging software offers image fusion tools based on fixed blending or color-channel combination of two modalities, and color Look-Up Tables (LUTs), without considering the anatomical and functional character of the image features. We used a sensible approach for image fusion taking advantage mainly from the HSL (Hue, Saturation and Luminosity) color space, in order to enhance the fusion results. We further tested operators for gradient and contour extraction to enhance anatomical details, plus other spatial-domain filters for functional features corresponding to wide point-spread-function responses in PET images. A set of image-fusion operators was formulated and tested on PET and MRI acquisitions.

The influence of the magnetic field on running penumbral waves in the solar chromosphere

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

Jess, D. B.; Reznikova, V. E.; Van Doorsselaere, T.

2013-12-20

We use images of high spatial and temporal resolution, obtained using both ground- and space-based instrumentation, to investigate the role magnetic field inclination angles play in the propagation characteristics of running penumbral waves in the solar chromosphere. Analysis of a near-circular sunspot, close to the center of the solar disk, reveals a smooth rise in oscillatory period as a function of distance from the umbral barycenter. However, in one directional quadrant, corresponding to the north direction, a pronounced kink in the period-distance diagram is found. Utilizing a combination of the inversion of magnetic Stokes vectors and force-free field extrapolations, wemore » attribute this behavior to the cut-off frequency imposed by the magnetic field geometry in this location. A rapid, localized inclination of the magnetic field lines in the north direction results in a faster increase in the dominant periodicity due to an accelerated reduction in the cut-off frequency. For the first time, we reveal how the spatial distribution of dominant wave periods, obtained with one of the highest resolution solar instruments currently available, directly reflects the magnetic geometry of the underlying sunspot, thus opening up a wealth of possibilities in future magnetohydrodynamic seismology studies. In addition, the intrinsic relationships we find between the underlying magnetic field geometries connecting the photosphere to the chromosphere, and the characteristics of running penumbral waves observed in the upper chromosphere, directly supports the interpretation that running penumbral wave phenomena are the chromospheric signature of upwardly propagating magneto-acoustic waves generated in the photosphere.« less

Magnetic field effect on photoionization cross-section of hydrogen-like impurity in cylindrical quantum wire

NASA Astrophysics Data System (ADS)

Mughnetsyan, V. N.; Barseghyan, M. G.; Kirakosyan, A. A.

2008-01-01

We consider the photoionization of a hydrogen-like impurity centre in a quantum wire approximated by a cylindrical well of finite depth in a magnetic field directed along the wire axis. The ground state energy and the wave function of the electron localized on on-axis impurity centre are calculated using the variational method. The wave functions and energies of the final states in an one-dimensional conduction subband are also presented. The dependences of photoionization cross-section of a donor centre on magnetic field and frequency of incident radiation both for parallel and perpendicular polarizations and corresponding selection rules for the allowed transitions are found in the dipole approximation. The estimates of photoionization cross-section for various values of wire radius and magnetic field induction for GaAs quantum wire embedded in Ga 1-xAl 1-xAs matrix are given.

J-GEM observations of an electromagnetic counterpart to the neutron star merger GW170817

NASA Astrophysics Data System (ADS)

Utsumi, Yousuke; Tanaka, Masaomi; Tominaga, Nozomu; Yoshida, Michitoshi; Barway, Sudhanshu; Nagayama, Takahiro; Zenko, Tetsuya; Aoki, Kentaro; Fujiyoshi, Takuya; Furusawa, Hisanori; Kawabata, Koji S.; Koshida, Shintaro; Lee, Chien-Hsiu; Morokuma, Tomoki; Motohara, Kentaro; Nakata, Fumiaki; Ohsawa, Ryou; Ohta, Kouji; Okita, Hirofumi; Tajitsu, Akito; Tanaka, Ichi; Terai, Tsuyoshi; Yasuda, Naoki; Abe, Fumio; Asakura, Yuichiro; Bond, Ian A.; Miyazaki, Shota; Sumi, Takahiro; Tristram, Paul J.; Honda, Satoshi; Itoh, Ryosuke; Itoh, Yoichi; Kawabata, Miho; Morihana, Kumiko; Nagashima, Hiroki; Nakaoka, Tatsuya; Ohshima, Tomohito; Takahashi, Jun; Takayama, Masaki; Aoki, Wako; Baar, Stefan; Doi, Mamoru; Finet, Francois; Kanda, Nobuyuki; Kawai, Nobuyuki; Kim, Ji Hoon; Kuroda, Daisuke; Liu, Wei; Matsubayashi, Kazuya; Murata, Katsuhiro L.; Nagai, Hiroshi; Saito, Tomoki; Saito, Yoshihiko; Sako, Shigeyuki; Sekiguchi, Yuichiro; Tamura, Yoichi; Tanaka, Masayuki; Uemura, Makoto; Yamaguchi, Masaki S.

2017-12-01

GW170817 is the first detected gravitational wave source from a neutron star merger. We present the Japanese collaboration for gravitational-wave electro-magnetic (J-GEM) follow-up observations of SSS17a, an electromagnetic counterpart of GW170817. SSS17a shows a 2.5 mag decline in the z band during the period between 1.7 and 7.7 d after the merger. Such a rapid decline is not comparable with supernovae light curves at any epoch. The color of SSS17a also evolves rapidly and becomes redder during later epochs: the z - H color has changed by approximately 2.5 mag during the period between 0.7 and 7.7 d. The rapid evolutions of both the color and the optical brightness are consistent with the expected properties of a kilonova that is powered by the radioactive decay of newly synthesized r-process nuclei. Kilonova models with Lanthanide elements can reproduce the aforementioned observed properties well, which suggests that r-process nucleosynthesis beyond the second peak takes place in SSS17a. However, the absolute magnitude of SSS17a is brighter than the expected brightness of the kilonova models with an ejecta mass of 0.01 M⊙, which suggests a more intense mass ejection (˜0.03 M⊙) or possibly an additional energy source.

Intense laser field effects on a Woods-Saxon potential quantum well

NASA Astrophysics Data System (ADS)

Restrepo, R. L.; Morales, A. L.; Akimov, V.; Tulupenko, V.; Kasapoglu, E.; Ungan, F.; Duque, C. A.

2015-11-01

This paper presents the results of the theoretical study of the effects of non-resonant intense laser field and electric and magnetic fields on the optical properties in an quantum well (QW) make with Woods-Saxon potential profile. The electric field and intense laser field are applied along the growth direction of the Woods-Saxon quantum well and the magnetic field is oriented perpendicularly. To calculate the energy and the wave functions of the electron in the Woods-Saxon quantum well, the effective mass approximation and the method of envelope wave function are used. The confinement in the Woods-Saxon quantum well is changed drastically by the application of intense laser field or either the effect of electric and magnetic fields. The optical properties are calculated using the compact density matrix.

A unique case of "double-orifice aortic valve"-comprehensive assessment by 2-, 3-dimensional, and color Doppler echocardiography.

PubMed

Stirrup, James E; Cowburn, Peter J; Pousios, Dimitrios; Ohri, Sunil K; Shah, Benoy N

2016-09-01

Transesophageal echocardiography (TEE) is a powerful imaging tool for the comprehensive assessment of valvular structure and function. TEE may be of added benefit when anatomy is difficult to delineate accurately by transthoracic echocardiography. In this article, we present 2-, 3-dimensional, and color Doppler TEE images from a male patient with aortic stenosis. A highly unusual and complex pattern of valvular calcification created a functionally "double-orifice" valve. Such an abnormality may have implications for the accuracy of continuous-wave Doppler echocardiography, which assumes a single orifice valve in native aortic valves. © 2016, Wiley Periodicals, Inc.

Enhancement of wave growth for warm plasmas with a high-energy tail distribution

NASA Technical Reports Server (NTRS)

Thorne, Richard M.; Summers, Danny

1991-01-01

The classical linear theory of electromagnetic wave growth in a warm plasma is considered for waves propagating parallel to a uniform ambient magnetic field. Wave-growth rates are calculated for ion-driven right-hand mode waves for Kappa and Maxwellian particle distribution functions and for various values of the spectral index, the temperature anisotropy, and the ratio of plasma pressure to magnetic pressure appropriate to the solar wind. When the anisotropy is low the wave growth is limited to frequencies below the proton gyrofrequency and the growth rate increases dramatically as the spectral index is reduced. The growth rate for any Kappa distribution greatly exceeds that for a Maxwellian with the same bulk properties. For large thermal anisotropy the growth rate from either distribution is greatly enhanced. The growth rates from a Kappa distribution are generally larger than for a Maxwellian distribution, and significant wave growth occurs over a broader range of frequencies.

Excitation of propagating magnetization waves by microstrip antennas

NASA Astrophysics Data System (ADS)

Dmitriev, V. F.; Kalinikos, B. A.

1988-11-01

We discuss the self-consistent theory of excitation of dipole-exchange magnetization waves by microstrip antennas in a metal-dielectric-ferrite-dielectric-metal stratified structure, magnetized under an arbitrary angle to the surface. Spin-wave Green's functions are derived, describing the response of the spin-system to a spatially inhomogeneous varying magnetic field. The radiative resistance of microstrip antenna is calculated. In this case the distribution of surface current density in the antenna is found on the basis of the analytic solution of a singular integral equation. The nature of the effect of metallic screens and redistributed surface current densities in the antenna on the frequency dependence of the resistive radiation is investigated. Approximate relations are obtained, convenient for practical calculations of radiative resistance of microstrip antennas both in a free and in a screened ferromagnetic film. The theoretical calculations are verified by data of experiments carried out on monocrystalline films of iron-yttrium garnet.

Magnetic droplet soliton nucleation in oblique fields

NASA Astrophysics Data System (ADS)

Mohseni, Morteza; Hamdi, M.; Yazdi, H. F.; Banuazizi, S. A. H.; Chung, S.; Sani, S. R.; Åkerman, Johan; Mohseni, Majid

2018-05-01

We study the auto-oscillating magnetodynamics in orthogonal spin-torque nano-oscillators (STNOs) as a function of the out-of-plane (OOP) magnetic-field angle. In perpendicular fields and at OOP field angles down to approximately 50°, we observe the nucleation of a droplet. However, for field angles below 50°, experiments indicate that the droplet gives way to propagating spin waves, in agreement with our micromagnetic simulations. Theoretical calculations show that the physical mechanism behind these observations is the sign changing of spin-wave nonlinearity (SWN) by angle. In addition, we show that the presence of a strong perpendicular magnetic anisotropy free layer in the system reverses the angular dependence of the SWN and dynamics in STNOs with respect to the known behavior determined for the in-plane magnetic anisotropy free layer. Our results are of fundamental interest in understanding the rich dynamics of nanoscale solitons and spin-wave dynamics in STNOs.

Onboard software of Plasma Wave Experiment aboard Arase: instrument management and signal processing of Waveform Capture/Onboard Frequency Analyzer

NASA Astrophysics Data System (ADS)

Matsuda, Shoya; Kasahara, Yoshiya; Kojima, Hirotsugu; Kasaba, Yasumasa; Yagitani, Satoshi; Ozaki, Mitsunori; Imachi, Tomohiko; Ishisaka, Keigo; Kumamoto, Atsushi; Tsuchiya, Fuminori; Ota, Mamoru; Kurita, Satoshi; Miyoshi, Yoshizumi; Hikishima, Mitsuru; Matsuoka, Ayako; Shinohara, Iku

2018-05-01

We developed the onboard processing software for the Plasma Wave Experiment (PWE) onboard the Exploration of energization and Radiation in Geospace, Arase satellite. The PWE instrument has three receivers: Electric Field Detector, Waveform Capture/Onboard Frequency Analyzer (WFC/OFA), and the High-Frequency Analyzer. We designed a pseudo-parallel processing scheme with a time-sharing system and achieved simultaneous signal processing for each receiver. Since electric and magnetic field signals are processed by the different CPUs, we developed a synchronized observation system by using shared packets on the mission network. The OFA continuously measures the power spectra, spectral matrices, and complex spectra. The OFA obtains not only the entire ELF/VLF plasma waves' activity but also the detailed properties (e.g., propagation direction and polarization) of the observed plasma waves. We performed simultaneous observation of electric and magnetic field data and successfully obtained clear wave properties of whistler-mode chorus waves using these data. In order to measure raw waveforms, we developed two modes for the WFC, `chorus burst mode' (65,536 samples/s) and `EMIC burst mode' (1024 samples/s), for the purpose of the measurement of the whistler-mode chorus waves (typically in a frequency range from several hundred Hz to several kHz) and the EMIC waves (typically in a frequency range from a few Hz to several hundred Hz), respectively. We successfully obtained the waveforms of electric and magnetic fields of whistler-mode chorus waves and ion cyclotron mode waves along the Arase's orbit. We also designed the software-type wave-particle interaction analyzer mode. In this mode, we measure electric and magnetic field waveforms continuously and transfer them to the mission data recorder onboard the Arase satellite. We also installed an onboard signal calibration function (onboard SoftWare CALibration; SWCAL). We performed onboard electric circuit diagnostics and antenna impedance measurement of the wire-probe antennas along the orbit. We utilize the results obtained using the SWCAL function when we calibrate the spectra and waveforms obtained by the PWE.[Figure not available: see fulltext.

The normalized magnetic helicity spectrum as a function of the angle between the local mean magnetic field and the flow direction of the solar wind: First results using high resolution magnetic field data from the Wind spacecraft

NASA Astrophysics Data System (ADS)

Podesta, J. J.

2011-12-01

This year, for the first time, the reduced normalized magnetic helicity spectrum has been analyzed as a function of the angle θ between the local mean magnetic field and the flow direction of the solar wind using wavelet techniques. In fast wind, at scales localized near kρp = 1 and kc/ωpp = 1, where ρp is the thermal proton gyro-radius and c/ωpp is the proton inertial length, the analysis reveals two distinct populations of fluctuations. There is a population of fluctuations at oblique angles, centered about an angle of 90 degrees, which are right hand polarized in the spacecraft frame and are believed to be associated with kinetic Alfven waves although the signal covers a wide range of oblique angles and a satisfactory interpretation of their spectrum through comparison with theory has not yet been obtained. A second population of fluctuations is found at angles near zero degrees which are left-hand polarized in the spacecraft frame. The data indicates that these are parallel propagating electromagnetic waves consisting either of left-hand polarized ion cyclotron waves propagating predominantly away from the sun or right-hand polarized whistler waves propagating predominantly toward the sun along the local mean magnetic field. As a consequence of the Doppler shift, both types of waves have the same polarization in the spacecraft frame. Unfortunately, the wave polarization in the plasma frame is difficult to determine using magnetic field data alone. Whether the observed waves are right- or left hand polarized in the plasma frame is a fundamental problem for future investigations. The analyses of spacecraft data performed so far have assumed that the solar wind velocity is directed radially outward from the sun. However, in the ecliptic plane at 1 AU, the flow direction typically deviates from the radial direction by a few degrees, sometimes more, and this adversely affects measurements of the angular helicity spectrum. To correct this, new measurements obtained using data from the Wind spacecraft use the scale dependent local mean solar wind velocity when computing the angle from the data. The first results from this study are presented here.

Quark fragmentation into spin-triplet S -wave quarkonium

DOE PAGES

Bodwin, Geoffrey T.; Chung, Hee Sok; Kim, U-Rae; ...

2015-04-08

We compute fragmentation functions for a quark to fragment to a quarkonium through an S-wave spin-triplet heavy quark-antiquark pair. We consider both color-singlet and color-octet heavy quark-antiquark (Q (Q) over bar) pairs. We give results for the case in which the fragmenting quark and the quark that is a constituent of the quarkonium have different flavors and for the case in which these quarks have the same flavors. Our results for the sum over all spin polarizations of the Q (Q) over bar pairs confirm previous results. Our results for longitudinally polarized Q (Q) over bar pairs agree with previousmore » calculations for the same flavor cases and correct an error in a previous calculation for the different-flavor case.« less

sp-d Exchange Interactions in Wave Function Engineered Colloidal CdSe/Mn:CdS Hetero-Nanoplatelets.

PubMed

Muckel, Franziska; Delikanli, Savas; Hernández-Martínez, Pedro Ludwig; Priesner, Tamara; Lorenz, Severin; Ackermann, Julia; Sharma, Manoj; Demir, Hilmi Volkan; Bacher, Gerd

2018-03-14

In two-dimensional (2D) colloidal semiconductor nanoplatelets, which are atomically flat nanocrystals, the precise control of thickness and composition on the atomic scale allows for the synthesis of heterostructures with well-defined electron and hole wave function distributions. Introducing transition metal dopants with a monolayer precision enables tailored magnetic exchange interactions between dopants and band states. Here, we use the absorption based technique of magnetic circular dichroism (MCD) to directly prove the exchange coupling of magnetic dopants with the band charge carriers in hetero-nanoplatelets with CdSe core and manganese-doped CdS shell (CdSe/Mn:CdS). We show that the strength of both the electron as well as the hole exchange interactions with the dopants can be tuned by varying the nanoplatelets architecture with monolayer accuracy. As MCD is highly sensitive for excitonic resonances, excited level spectroscopy allows us to resolve and identify, in combination with wave function calculations, several excited state transitions including spin-orbit split-off excitonic contributions. Thus, our study not only demonstrates the possibility to expand the extraordinary physical properties of colloidal nanoplatelets toward magneto-optical functionality by transition metal doping but also provides an insight into the excited state electronic structure in this novel two-dimensional material.

Simulation of electromagnetic ion cyclotron triggered emissions in the Earth's inner magnetosphere

NASA Astrophysics Data System (ADS)

Shoji, Masafumi; Omura, Yoshiharu

2011-05-01

In a recent observation by the Cluster spacecraft, emissions triggered by electromagnetic ion cyclotron (EMIC) waves were discovered in the inner magnetosphere. We perform hybrid simulations to reproduce the EMIC triggered emissions. We develop a self-consistent one-dimensional hybrid code with a cylindrical geometry of the background magnetic field. We assume a parabolic magnetic field to model the dipole magnetic field in the equatorial region of the inner magnetosphere. Triggering EMIC waves are driven by a left-handed polarized external current assumed at the magnetic equator in the simulation model. Cold proton, helium, and oxygen ions, which form branches of the dispersion relation of the EMIC waves, are uniformly distributed in the simulation space. Energetic protons with a loss cone distribution function are also assumed as resonant particles. We reproduce rising tone emissions in the simulation space, finding a good agreement with the nonlinear wave growth theory. In the energetic proton velocity distribution we find formation of a proton hole, which is assumed in the nonlinear wave growth theory. A substantial amount of the energetic protons are scattered into the loss cone, while some of the resonant protons are accelerated to higher pitch angles, forming a pancake velocity distribution.

Transesophageal color Doppler evaluation of obstructive lesions using the new "Quasar" technology.

PubMed

Fan, P; Nanda, N C; Gatewood, R P; Cape, E G; Yoganathan, A P

1995-01-01

Due to the unavoidable problem of aliasing, color flow signals from high blood flow velocities cannot be measured directly by conventional color Doppler. A new technology termed Quantitative Un-Aliased Speed Algorithm Recognition (Quasar) has been developed to overcome this limitation. Employing this technology, we used transesophageal color Doppler echocardiography to investigate whether the velocities detected by the Quasar would correlate with those obtained by continuous-wave Doppler both in vitro and in vivo. In the in vitro study, a 5.0 MHz transesophageal transducer of a Kontron Sigma 44 color Doppler flow system was used. Fourteen different peak velocities calculated and recorded by color Doppler-guided continuous-wave Doppler were randomly selected. In the clinical study, intraoperative transesophageal echocardiography was performed using the same transducer 18 adults (13 aortic valve stenosis, 2 aortic and 2 mitral stenosis, 2 hypertrophic obstructive cardiomyopathy and 1 mitral valve stenosis). Following each continuous-wave Doppler measurement, the Quasar was activated, and a small Quasar marker was placed in the brightest area of the color flow jet to obtain the maximum mean velocity readout. The maximum mean velocities measured by Quasar closely correlated with maximum peak velocities obtained by color flow guided continuous-wave Doppler in both in vitro (0.53 to 1.65 m/s, r = 0.99) and in vivo studies (1.50 to 6.01 m/s, r = 0.97). We conclude that the new Quasar technology can accurately measure high blood flow velocities during transesophageal color Doppler echocardiography. This technique has the potential of obviating the need for continuous-wave Doppler.

Ecological Effects in Cross-Cultural Differences Between U.S. and Japanese Color Preferences.

PubMed

Yokosawa, Kazuhiko; Schloss, Karen B; Asano, Michiko; Palmer, Stephen E

2016-09-01

We investigated cultural differences between U.S. and Japanese color preferences and the ecological factors that might influence them. Japanese and U.S. color preferences have both similarities (e.g., peaks around blue, troughs around dark-yellow, and preferences for saturated colors) and differences (Japanese participants like darker colors less than U.S. participants do). Complex gender differences were also evident that did not conform to previously reported effects. Palmer and Schloss's (2010) weighted affective valence estimate (WAVE) procedure was used to test the Ecological Valence Theory's (EVT's) prediction that within-culture WAVE-preference correlations should be higher than between-culture WAVE-preference correlations. The results supported several, but not all, predictions. In the second experiment, we tested color preferences of Japanese-U.S. multicultural participants who could read and speak both Japanese and English. Multicultural color preferences were intermediate between U.S. and Japanese preferences, consistent with the hypothesis that culturally specific personal experiences during one's lifetime influence color preferences. Copyright © 2015 Cognitive Science Society, Inc.

KINETIC ALFVÉN WAVE GENERATION BY LARGE-SCALE PHASE MIXING

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

Vásconez, C. L.; Pucci, F.; Valentini, F.

One view of the solar wind turbulence is that the observed highly anisotropic fluctuations at spatial scales near the proton inertial length d{sub p} may be considered as kinetic Alfvén waves (KAWs). In the present paper, we show how phase mixing of large-scale parallel-propagating Alfvén waves is an efficient mechanism for the production of KAWs at wavelengths close to d{sub p} and at a large propagation angle with respect to the magnetic field. Magnetohydrodynamic (MHD), Hall magnetohydrodynamic (HMHD), and hybrid Vlasov–Maxwell (HVM) simulations modeling the propagation of Alfvén waves in inhomogeneous plasmas are performed. In the linear regime, the rolemore » of dispersive effects is singled out by comparing MHD and HMHD results. Fluctuations produced by phase mixing are identified as KAWs through a comparison of polarization of magnetic fluctuations and wave-group velocity with analytical linear predictions. In the nonlinear regime, a comparison of HMHD and HVM simulations allows us to point out the role of kinetic effects in shaping the proton-distribution function. We observe the generation of temperature anisotropy with respect to the local magnetic field and the production of field-aligned beams. The regions where the proton-distribution function highly departs from thermal equilibrium are located inside the shear layers, where the KAWs are excited, this suggesting that the distortions of the proton distribution are driven by a resonant interaction of protons with KAW fluctuations. Our results are relevant in configurations where magnetic-field inhomogeneities are present, as, for example, in the solar corona, where the presence of Alfvén waves has been ascertained.« less

KSC-07pd0442

NASA Image and Video Library

2007-02-17

KENNEDY SPACE CENTER, FLA. -- At Cape Canaveral Air Force Station, clouds of smoke envelop the Delta II rocket with NASA's THEMIS spacecraft aboard as it blasts off Pad 17-B at 6:01 p.m. EST. THEMIS, an acronym for Time History of Events and Macroscale Interactions during Substorms, consists of five identical probes that will track violent, colorful eruptions near the North Pole. This will be the largest number of scientific satellites NASA has ever launched into orbit aboard a single rocket. The THEMIS mission aims to unravel the mystery behind auroral substorms, an avalanche of magnetic energy powered by the solar wind that intensifies the northern and southern lights. The mission will investigate what causes auroras in the Earth’s atmosphere to dramatically change from slowly shimmering waves of light to wildly shifting streaks of bright color. Photo credit: NASA/Jerry Cannon

Delta II THEMIS Pre-Launch

NASA Image and Video Library

2002-01-01

In this close-up aerial view, the Delta II rocket with the THEMIS spacecraft atop sits ready for launch on Pad 17-B at Cape Canaveral Air Force Station. THEMIS, an acronym for Time History of Events and Macroscale Interactions during Substorms, consists of five identical probes that will track violent, colorful eruptions near the North Pole. This will be the largest number of scientific satellites NASA has ever launched into orbit aboard a single rocket. The THEMIS mission aims to unravel the mystery behind auroral substorms, an avalanche of magnetic energy powered by the solar wind that intensifies the northern and southern lights. The mission will investigate what causes auroras in the Earth’s atmosphere to dramatically change from slowly shimmering waves of light to wildly shifting streaks of bright color. Launch is scheduled for 6:05 p.m.

Delta II Launch with the THEMIS satellite payload from pad 17B C

NASA Image and Video Library

2007-02-17

At Cape Canaveral Air Force Station, clouds of smoke envelop the Delta II rocket with NASA's THEMIS spacecraft aboard as it blasts off Pad 17-B at 6:01 p.m. EST. THEMIS, an acronym for Time History of Events and Macroscale Interactions during Substorms, consists of five identical probes that will track violent, colorful eruptions near the North Pole. This will be the largest number of scientific satellites NASA has ever launched into orbit aboard a single rocket. The THEMIS mission aims to unravel the mystery behind auroral substorms, an avalanche of magnetic energy powered by the solar wind that intensifies the northern and southern lights. The mission will investigate what causes auroras in the Earth’s atmosphere to dramatically change from slowly shimmering waves of light to wildly shifting streaks of bright color.

KSC-07pd0441

NASA Image and Video Library

2007-02-17

KENNEDY SPACE CENTER, FLA. -- At Cape Canaveral Air Force Station, clouds of smoke form around the Delta II rocket with NASA's THEMIS spacecraft aboard as it blasts off Pad 17-B at 6:01 p.m. EST. THEMIS, an acronym for Time History of Events and Macroscale Interactions during Substorms, consists of five identical probes that will track violent, colorful eruptions near the North Pole. This will be the largest number of scientific satellites NASA has ever launched into orbit aboard a single rocket. The THEMIS mission aims to unravel the mystery behind auroral substorms, an avalanche of magnetic energy powered by the solar wind that intensifies the northern and southern lights. The mission will investigate what causes auroras in the Earth’s atmosphere to dramatically change from slowly shimmering waves of light to wildly shifting streaks of bright color. Photo credit: NASA/Jerry Cannon

Delta II Launch with the THEMIS satellite payload from pad 17B C

NASA Image and Video Library

2007-02-17

At Cape Canaveral Air Force Station, the Delta II rocket with NASA's THEMIS spacecraft aboard begins its ascent from Pad 17-B, in sight of the Atlantic Ocean, at 6:01 p.m. EST. THEMIS, an acronym for Time History of Events and Macroscale Interactions during Substorms, consists of five identical probes that will track violent, colorful eruptions near the North Pole. This will be the largest number of scientific satellites NASA has ever launched into orbit aboard a single rocket. The THEMIS mission aims to unravel the mystery behind auroral substorms, an avalanche of magnetic energy powered by the solar wind that intensifies the northern and southern lights. The mission will investigate what causes auroras in the Earth’s atmosphere to dramatically change from slowly shimmering waves of light to wildly shifting streaks of bright color.

KSC-07pd0431

NASA Image and Video Library

2007-02-17

KENNEDY SPACE CENTER, FLA. -- At Cape Canaveral Air Force Station, the Delta II rocket with NASA's THEMIS spacecraft aboard lifts off Pad 17-B on a crisp Florida evening at 6:01 p.m. EST. THEMIS, an acronym for Time History of Events and Macroscale Interactions during Substorms, consists of five identical probes that will track violent, colorful eruptions near the North Pole. This will be the largest number of scientific satellites NASA has ever launched into orbit aboard a single rocket. The THEMIS mission aims to unravel the mystery behind auroral substorms, an avalanche of magnetic energy powered by the solar wind that intensifies the northern and southern lights. The mission will investigate what causes auroras in the Earth’s atmosphere to dramatically change from slowly shimmering waves of light to wildly shifting streaks of bright color. Photo credit: NASA/Kim Shiflett

KSC-07pd0436

NASA Image and Video Library

2007-02-17

KENNEDY SPACE CENTER, FLA. -- Clouds of smoke encompass the Delta II rocket with NASA's THEMIS spacecraft aboard as it blasts off Pad 17-B at Cape Canaveral Air Force Station at 6:01 p.m. EST. THEMIS, an acronym for Time History of Events and Macroscale Interactions during Substorms, consists of five identical probes that will track violent, colorful eruptions near the North Pole. This will be the largest number of scientific satellites NASA has ever launched into orbit aboard a single rocket. The THEMIS mission aims to unravel the mystery behind auroral substorms, an avalanche of magnetic energy powered by the solar wind that intensifies the northern and southern lights. The mission will investigate what causes auroras in the Earth’s atmosphere to dramatically change from slowly shimmering waves of light to wildly shifting streaks of bright color. Photo credit: NASA/Sandra Joseph, Ralph Hernandez

KSC-07pd0435

NASA Image and Video Library

2007-02-17

KENNEDY SPACE CENTER, FLA. -- At Cape Canaveral Air Force Station, the Delta II rocket with NASA's THEMIS spacecraft aboard begins its ascent from Pad 17-B on a crisp Florida evening at 6:01 p.m. EST. THEMIS, an acronym for Time History of Events and Macroscale Interactions during Substorms, consists of five identical probes that will track violent, colorful eruptions near the North Pole. This will be the largest number of scientific satellites NASA has ever launched into orbit aboard a single rocket. The THEMIS mission aims to unravel the mystery behind auroral substorms, an avalanche of magnetic energy powered by the solar wind that intensifies the northern and southern lights. The mission will investigate what causes auroras in the Earth’s atmosphere to dramatically change from slowly shimmering waves of light to wildly shifting streaks of bright color. Photo credit: NASA/Sandra Joseph, Ralph Hernandez

Delta II Launch with the THEMIS satellite payload from pad 17B C

NASA Image and Video Library

2007-02-17

Amid billows of smoke, the Delta II rocket with NASA's THEMIS spacecraft aboard blasts off Pad 17-B at Cape Canaveral Air Force Station at 6:01 p.m. EST. THEMIS, an acronym for Time History of Events and Macroscale Interactions during Substorms, consists of five identical probes that will track violent, colorful eruptions near the North Pole. This will be the largest number of scientific satellites NASA has ever launched into orbit aboard a single rocket. The THEMIS mission aims to unravel the mystery behind auroral substorms, an avalanche of magnetic energy powered by the solar wind that intensifies the northern and southern lights. The mission will investigate what causes auroras in the Earth’s atmosphere to dramatically change from slowly shimmering waves of light to wildly shifting streaks of bright color.

KSC-07pd0409

NASA Image and Video Library

2007-02-16

KENNEDY SPACE CENTER, FLA. -- At Launch Pad 17-B at Cape Canaveral Air Force Station, the mobile service tower surrounds the Delta II rocket with the THEMIS spacecraft atop. THEMIS, an acronym for Time History of Events and Macroscale Interactions during Substorms, consists of five identical probes that will track violent, colorful eruptions near the North Pole. This will be the largest number of scientific satellites NASA has ever launched into orbit aboard a single rocket. The THEMIS mission aims to unravel the mystery behind auroral substorms, an avalanche of magnetic energy powered by the solar wind that intensifies the northern and southern lights. The mission will investigate what causes auroras in the Earth’s atmosphere to dramatically change from slowly shimmering waves of light to wildly shifting streaks of bright color. Launch is scheduled for 6:05 p.m. Photo credit: NASA/Kim Shiflett

Delta II Launch with the THEMIS satellite payload from pad 17B C

NASA Image and Video Library

2007-02-17

At Cape Canaveral Air Force Station, clouds of smoke form around the Delta II rocket with NASA's THEMIS spacecraft aboard as it blasts off Pad 17-B at 6:01 p.m. EST. THEMIS, an acronym for Time History of Events and Macroscale Interactions during Substorms, consists of five identical probes that will track violent, colorful eruptions near the North Pole. This will be the largest number of scientific satellites NASA has ever launched into orbit aboard a single rocket. The THEMIS mission aims to unravel the mystery behind auroral substorms, an avalanche of magnetic energy powered by the solar wind that intensifies the northern and southern lights. The mission will investigate what causes auroras in the Earth’s atmosphere to dramatically change from slowly shimmering waves of light to wildly shifting streaks of bright color.

KSC-07pd0443

NASA Image and Video Library

2007-02-17

KENNEDY SPACE CENTER, FLA. -- The Delta II rocket with NASA's THEMIS spacecraft aboard begins its journey to orbit at 6:01 p.m. EST from Pad 17-B at Cape Canaveral Air Force Station. THEMIS, an acronym for Time History of Events and Macroscale Interactions during Substorms, consists of five identical probes that will track violent, colorful eruptions near the North Pole. This will be the largest number of scientific satellites NASA has ever launched into orbit aboard a single rocket. The THEMIS mission aims to unravel the mystery behind auroral substorms, an avalanche of magnetic energy powered by the solar wind that intensifies the northern and southern lights. The mission will investigate what causes auroras in the Earth’s atmosphere to dramatically change from slowly shimmering waves of light to wildly shifting streaks of bright color. Photo credit: NASA/Ken Thornsley

KSC-07pd0430

NASA Image and Video Library

2007-02-17

KENNEDY SPACE CENTER, FLA. -- Amid billows of smoke, the Delta II rocket with NASA's THEMIS spacecraft aboard lifts off Pad 17-B at Cape Canaveral Air Force Station at 6:01 p.m. EST. THEMIS, an acronym for Time History of Events and Macroscale Interactions during Substorms, consists of five identical probes that will track violent, colorful eruptions near the North Pole. This will be the largest number of scientific satellites NASA has ever launched into orbit aboard a single rocket. The THEMIS mission aims to unravel the mystery behind auroral substorms, an avalanche of magnetic energy powered by the solar wind that intensifies the northern and southern lights. The mission will investigate what causes auroras in the Earth’s atmosphere to dramatically change from slowly shimmering waves of light to wildly shifting streaks of bright color. Photo credit: NASA/Kim Shiflett

KSC-07pd0432

NASA Image and Video Library

2007-02-17

KENNEDY SPACE CENTER, FLA. -- Amid billows of smoke, the Delta II rocket with NASA's THEMIS spacecraft aboard lifts off Pad 17-B at Cape Canaveral Air Force Station at 6:01 p.m. EST. THEMIS, an acronym for Time History of Events and Macroscale Interactions during Substorms, consists of five identical probes that will track violent, colorful eruptions near the North Pole. This will be the largest number of scientific satellites NASA has ever launched into orbit aboard a single rocket. The THEMIS mission aims to unravel the mystery behind auroral substorms, an avalanche of magnetic energy powered by the solar wind that intensifies the northern and southern lights. The mission will investigate what causes auroras in the Earth’s atmosphere to dramatically change from slowly shimmering waves of light to wildly shifting streaks of bright color. Photo credit: NASA/Kim Shiflett

KSC-07pd0433

NASA Image and Video Library

2007-02-17

KENNEDY SPACE CENTER, FLA. -- Amid billows of smoke, the Delta II rocket with NASA's THEMIS spacecraft aboard blasts off Pad 17-B at Cape Canaveral Air Force Station at 6:01 p.m. EST. THEMIS, an acronym for Time History of Events and Macroscale Interactions during Substorms, consists of five identical probes that will track violent, colorful eruptions near the North Pole. This will be the largest number of scientific satellites NASA has ever launched into orbit aboard a single rocket. The THEMIS mission aims to unravel the mystery behind auroral substorms, an avalanche of magnetic energy powered by the solar wind that intensifies the northern and southern lights. The mission will investigate what causes auroras in the Earth’s atmosphere to dramatically change from slowly shimmering waves of light to wildly shifting streaks of bright color. Photo credit: NASA/Sandra Joseph, Ralph Hernandez

KSC-07pd0439

NASA Image and Video Library

2007-02-17

KENNEDY SPACE CENTER, FLA. -- At Cape Canaveral Air Force Station, the Delta II rocket with NASA's THEMIS spacecraft aboard lifts off Pad 17-B on a crisp Florida evening at 6:01 p.m. EST. THEMIS, an acronym for Time History of Events and Macroscale Interactions during Substorms, consists of five identical probes that will track violent, colorful eruptions near the North Pole. This will be the largest number of scientific satellites NASA has ever launched into orbit aboard a single rocket. The THEMIS mission aims to unravel the mystery behind auroral substorms, an avalanche of magnetic energy powered by the solar wind that intensifies the northern and southern lights. The mission will investigate what causes auroras in the Earth’s atmosphere to dramatically change from slowly shimmering waves of light to wildly shifting streaks of bright color. Photo credit: NASA/Jerry Cannon

KSC-07pd0440

NASA Image and Video Library

2007-02-17

KENNEDY SPACE CENTER, FLA. -- Amid billows of smoke, the Delta II rocket with NASA's THEMIS spacecraft aboard blasts off Pad 17-B at Cape Canaveral Air Force Station at 6:01 p.m. EST. THEMIS, an acronym for Time History of Events and Macroscale Interactions during Substorms, consists of five identical probes that will track violent, colorful eruptions near the North Pole. This will be the largest number of scientific satellites NASA has ever launched into orbit aboard a single rocket. The THEMIS mission aims to unravel the mystery behind auroral substorms, an avalanche of magnetic energy powered by the solar wind that intensifies the northern and southern lights. The mission will investigate what causes auroras in the Earth’s atmosphere to dramatically change from slowly shimmering waves of light to wildly shifting streaks of bright color. Photo credit: NASA/Jerry Cannon

KSC-07pd0434

NASA Image and Video Library

2007-02-17

KENNEDY SPACE CENTER, FLA. -- Clouds of smoke encompass the Delta II rocket with NASA's THEMIS spacecraft aboard as it blasts off Pad 17-B at Cape Canaveral Air Force Station at 6:01 p.m. EST. THEMIS, an acronym for Time History of Events and Macroscale Interactions during Substorms, consists of five identical probes that will track violent, colorful eruptions near the North Pole. This will be the largest number of scientific satellites NASA has ever launched into orbit aboard a single rocket. The THEMIS mission aims to unravel the mystery behind auroral substorms, an avalanche of magnetic energy powered by the solar wind that intensifies the northern and southern lights. The mission will investigate what causes auroras in the Earth’s atmosphere to dramatically change from slowly shimmering waves of light to wildly shifting streaks of bright color. Photo credit: NASA/Sandra Joseph, Ralph Hernandez

KSC-07pd0410

NASA Image and Video Library

2007-02-16

KENNEDY SPACE CENTER, FLA. -- At Launch Pad 17-B at Cape Canaveral Air Force Station, the mobile service tower moves away from the Delta II rocket with the THEMIS spacecraft atop. THEMIS, an acronym for Time History of Events and Macroscale Interactions during Substorms, consists of five identical probes that will track violent, colorful eruptions near the North Pole. This will be the largest number of scientific satellites NASA has ever launched into orbit aboard a single rocket. The THEMIS mission aims to unravel the mystery behind auroral substorms, an avalanche of magnetic energy powered by the solar wind that intensifies the northern and southern lights. The mission will investigate what causes auroras in the Earth’s atmosphere to dramatically change from slowly shimmering waves of light to wildly shifting streaks of bright color. Launch is scheduled for 6:05 p.m. Photo credit: NASA/Kim Shiflett

Delta II Launch with the THEMIS satellite payload from pad 17B C

NASA Image and Video Library

2007-02-17

Clouds of smoke encompass the Delta II rocket with NASA's THEMIS spacecraft aboard as it blasts off Pad 17-B at Cape Canaveral Air Force Station at 6:01 p.m. EST. THEMIS, an acronym for Time History of Events and Macroscale Interactions during Substorms, consists of five identical probes that will track violent, colorful eruptions near the North Pole. This will be the largest number of scientific satellites NASA has ever launched into orbit aboard a single rocket. The THEMIS mission aims to unravel the mystery behind auroral substorms, an avalanche of magnetic energy powered by the solar wind that intensifies the northern and southern lights. The mission will investigate what causes auroras in the Earth’s atmosphere to dramatically change from slowly shimmering waves of light to wildly shifting streaks of bright color

Diagnosing the Role of Alfvén Waves in Magnetosphere-Ionosphere Coupling: Swarm Observations of Large Amplitude Nonstationary Magnetic Perturbations During an Interval of Northward IMF

NASA Astrophysics Data System (ADS)

Pakhotin, I. P.; Mann, I. R.; Lysak, R. L.; Knudsen, D. J.; Gjerloev, J. W.; Rae, I. J.; Forsyth, C.; Murphy, K. R.; Miles, D. M.; Ozeke, L. G.; Balasis, G.

2018-01-01

High-resolution multispacecraft Swarm data are used to examine magnetosphere-ionosphere coupling during a period of northward interplanetary magnetic field (IMF) on 31 May 2014. The observations reveal a prevalence of unexpectedly large amplitude (>100 nT) and time-varying magnetic perturbations during the polar passes, with especially large amplitude magnetic perturbations being associated with large-scale downward field-aligned currents. Differences between the magnetic field measurements sampled at 50 Hz from Swarm A and C, approximately 10 s apart along track, and the correspondence between the observed electric and magnetic fields at 16 samples per second, provide significant evidence for an important role for Alfvén waves in magnetosphere-ionosphere coupling even during northward IMF conditions. Spectral comparison between the wave E- and B-fields reveals a frequency-dependent phase difference and amplitude ratio consistent with interference between incident and reflected Alfvén waves. At low frequencies, the E/B ratio is in phase with an amplitude determined by the Pedersen conductance. At higher frequencies, the amplitude and phase change as a function of frequency in good agreement with an ionospheric Alfvén resonator model including Pedersen conductance effects. Indeed, within this Alfvén wave incidence, reflection, and interference paradigm, even quasi-static field-aligned currents might be reasonably interpreted as very low frequency (ω → 0) Alfvén waves. Overall, our results not only indicate the importance of Alfvén waves for magnetosphere-ionosphere coupling but also demonstrate a method for using Swarm data for the innovative experimental diagnosis of Pedersen conductance from low-Earth orbit satellite measurements.

Effect of Local Thermal Equilibrium Misbalance on Long-wavelength Slow Magnetoacoustic Waves

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

Nakariakov, V. M.; Afanasyev, A. N.; Kumar, S.

Evolution of slow magnetoacoustic waves guided by a cylindrical magnetic flux tube that represents a coronal loop or plume, is modeled accounting for the effects of finite gas pressure, weak nonlinearity, dissipation by thermal conduction and viscosity, and the misbalance between the cooling by optically thin radiation and unspecified heating of the plasma. An evolutionary equation of the Burgers–Malthus type is derived. It is shown that the cooling/heating misbalance, determined by the derivatives of the combined radiative cooling and heating function, with respect to the density, temperature, and magnetic field at the thermal equilibrium affect the wave rather strongly. Thismore » effect may either cause additional damping, or counteract it, or lead to the gradual amplification of the wave. In the latter case, the coronal plasma acts as an active medium for the slow magnetoacoustic waves. The effect of the cooling/heating misbalance could be important for coronal slow waves, and could be responsible for certain discrepancies between theoretical results and observations, in particular, the increased or decreased damping lengths and times, detection of the waves at certain heights only, and excitation of compressive oscillations. The results obtained open up a possibility for the diagnostics of the coronal heating function by slow magnetoacoustic waves.« less

Field dependence of nonreciprocal magnons in chiral MnSi

NASA Astrophysics Data System (ADS)

Weber, T.; Waizner, J.; Tucker, G. S.; Georgii, R.; Kugler, M.; Bauer, A.; Pfleiderer, C.; Garst, M.; Böni, P.

2018-06-01

Spin waves in chiral magnetic materials are strongly influenced by the Dzyaloshinskii-Moriya interaction, resulting in intriguing phenomena like nonreciprocal magnon propagation and magnetochiral dichroism. Here, we study the nonreciprocal magnon spectrum of the archetypical chiral magnet MnSi and its evolution as a function of magnetic field covering the field-polarized and conical helix phase. Using inelastic neutron scattering, the magnon energies and their spectral weights are determined quantitatively after deconvolution with the instrumental resolution. In the field-polarized phase the imaginary part of the dynamical susceptibility χ''(ɛ ,q ) is shown to be asymmetric with respect to wave vectors q longitudinal to the applied magnetic field H , which is a hallmark of chiral magnetism. In the helimagnetic phase, χ''(ɛ ,q ) becomes increasingly symmetric with decreasing H due to the formation of helimagnon bands and the activation of additional spin-flip and non-spin-flip scattering channels. The neutron spectra are in excellent quantitative agreement with the low-energy theory of cubic chiral magnets with a single fitting parameter being the damping rate of spin waves.

A single-sided representation for the homogeneous Green's function of a unified scalar wave equation.

PubMed

Wapenaar, Kees

2017-06-01

A unified scalar wave equation is formulated, which covers three-dimensional (3D) acoustic waves, 2D horizontally-polarised shear waves, 2D transverse-electric EM waves, 2D transverse-magnetic EM waves, 3D quantum-mechanical waves and 2D flexural waves. The homogeneous Green's function of this wave equation is a combination of the causal Green's function and its time-reversal, such that their singularities at the source position cancel each other. A classical representation expresses this homogeneous Green's function as a closed boundary integral. This representation finds applications in holographic imaging, time-reversed wave propagation and Green's function retrieval by cross correlation. The main drawback of the classical representation in those applications is that it requires access to a closed boundary around the medium of interest, whereas in many practical situations the medium can be accessed from one side only. Therefore, a single-sided representation is derived for the homogeneous Green's function of the unified scalar wave equation. Like the classical representation, this single-sided representation fully accounts for multiple scattering. The single-sided representation has the same applications as the classical representation, but unlike the classical representation it is applicable in situations where the medium of interest is accessible from one side only.

Shear Wave Imaging of Breast Tissue by Color Doppler Shear Wave Elastography.

PubMed

Yamakoshi, Yoshiki; Nakajima, Takahito; Kasahara, Toshihiro; Yamazaki, Mayuko; Koda, Ren; Sunaguchi, Naoki

2017-02-01

Shear wave elastography is a distinctive method to access the viscoelastic characteristic of the soft tissue that is difficult to obtain by other imaging modalities. This paper proposes a novel shear wave elastography [color Doppler shear wave imaging (CD SWI)] for breast tissue. Continuous shear wave is produced by a small lightweight actuator, which is attached to the tissue surface. Shear wave wavefront that propagates in tissue is reconstructed as a binary pattern that consists of zero and the maximum flow velocities on color flow image (CFI). Neither any modifications of the ultrasound color flow imaging instrument nor a high frame rate ultrasound imaging instrument is required to obtain the shear wave wavefront map. However, two conditions of shear wave displacement amplitude and shear wave frequency are needed to obtain the map. However, these conditions are not severe restrictions in breast imaging. This is because the minimum displacement amplitude is [Formula: see text] for an ultrasonic wave frequency of 12 MHz and the shear wave frequency is available from several frequencies suited for breast imaging. Fourier analysis along time axis suppresses clutter noise in CFI. A directional filter extracts shear wave, which propagates in the forward direction. Several maps, such as shear wave phase, velocity, and propagation maps, are reconstructed by CD SWI. The accuracy of shear wave velocity measurement is evaluated for homogeneous agar gel phantom by comparing with the acoustic radiation force impulse method. The experimental results for breast tissue are shown for a shear wave frequency of 296.6 Hz.

3D radiation belt diffusion model results using new empirical models of whistler chorus and hiss

NASA Astrophysics Data System (ADS)

Cunningham, G.; Chen, Y.; Henderson, M. G.; Reeves, G. D.; Tu, W.

2012-12-01

3D diffusion codes model the energization, radial transport, and pitch angle scattering due to wave-particle interactions. Diffusion codes are powerful but are limited by the lack of knowledge of the spatial & temporal distribution of waves that drive the interactions for a specific event. We present results from the 3D DREAM model using diffusion coefficients driven by new, activity-dependent, statistical models of chorus and hiss waves. Most 3D codes parameterize the diffusion coefficients or wave amplitudes as functions of magnetic activity indices like Kp, AE, or Dst. These functional representations produce the average value of the wave intensities for a given level of magnetic activity; however, the variability of the wave population at a given activity level is lost with such a representation. Our 3D code makes use of the full sample distributions contained in a set of empirical wave databases (one database for each wave type, including plasmaspheric hiss, lower and upper hand chorus) that were recently produced by our team using CRRES and THEMIS observations. The wave databases store the full probability distribution of observed wave intensity binned by AE, MLT, MLAT and L*. In this presentation, we show results that make use of the wave intensity sample probability distributions for lower-band and upper-band chorus by sampling the distributions stochastically during a representative CRRES-era storm. The sampling of the wave intensity probability distributions produces a collection of possible evolutions of the phase space density, which quantifies the uncertainty in the model predictions caused by the uncertainty of the chorus wave amplitudes for a specific event. A significant issue is the determination of an appropriate model for the spatio-temporal correlations of the wave intensities, since the diffusion coefficients are computed as spatio-temporal averages of the waves over MLT, MLAT and L*. The spatiotemporal correlations cannot be inferred from the wave databases. In this study we use a temporal correlation of ~1 hour for the sampled wave intensities that is informed by the observed autocorrelation in the AE index, a spatial correlation length of ~100 km in the two directions perpendicular to the magnetic field, and a spatial correlation length of 5000 km in the direction parallel to the magnetic field, according to the work of Santolik et al (2003), who used multi-spacecraft measurements from Cluster to quantify the correlation length scales for equatorial chorus . We find that, despite the small correlation length scale for chorus, there remains significant variability in the model outcomes driven by variability in the chorus wave intensities.

Quantification of functional mitral regurgitation by real-time 3D echocardiography: comparison with 3D velocity-encoded cardiac magnetic resonance.

PubMed

Marsan, Nina Ajmone; Westenberg, Jos J M; Ypenburg, Claudia; Delgado, Victoria; van Bommel, Rutger J; Roes, Stijntje D; Nucifora, Gaetano; van der Geest, Rob J; de Roos, Albert; Reiber, Johan C; Schalij, Martin J; Bax, Jeroen J

2009-11-01

The aim of this study was to evaluate feasibility and accuracy of real-time 3-dimensional (3D) echocardiography for quantification of mitral regurgitation (MR), in a head-to-head comparison with velocity-encoded cardiac magnetic resonance (VE-CMR). Accurate grading of MR severity is crucial for appropriate patient management but remains challenging. VE-CMR with 3D three-directional acquisition has been recently proposed as the reference method. A total of 64 patients with functional MR were included. A VE-CMR acquisition was applied to quantify mitral regurgitant volume (Rvol). Color Doppler 3D echocardiography was applied for direct measurement, in "en face" view, of mitral effective regurgitant orifice area (EROA); Rvol was subsequently calculated as EROA multiplied by the velocity-time integral of the regurgitant jet on the continuous-wave Doppler. To assess the relative potential error of the conventional approach, color Doppler 2-dimensional (2D) echocardiography was performed: vena contracta width was measured in the 4-chamber view and EROA calculated as circular (EROA-4CH); EROA was also calculated as elliptical (EROA-elliptical), measuring vena contracta also in the 2-chamber view. From these 2D measurements of EROA, the Rvols were also calculated. The EROA measured by 3D echocardiography was significantly higher than EROA-4CH (p < 0.001) and EROA-elliptical (p < 0.001), with a significant bias between these measurements (0.10 cm(2) and 0.06 cm(2), respectively). Rvol measured by 3D echocardiography showed excellent correlation with Rvol measured by CMR (r = 0.94), without a significant difference between these techniques (mean difference = -0.08 ml/beat). Conversely, 2D echocardiographic approach from the 4-chamber view significantly underestimated Rvol (p = 0.006) as compared with CMR (mean difference = 2.9 ml/beat). The 2D elliptical approach demonstrated a better agreement with CMR (mean difference = -1.6 ml/beat, p = 0.04). Quantification of EROA and Rvol of functional MR with 3D echocardiography is feasible and accurate as compared with VE-CMR; the currently recommended 2D echocardiographic approach significantly underestimates both EROA and Rvol.

Some remarks on waves in the solar wind

NASA Technical Reports Server (NTRS)

Kellogg, Paul J.

1995-01-01

Waves are significant to the solar wind in two ways as modifiers of the particle distribution functions, and as diagnostics. In addition, the solar wind serves as an important laboratory for the study of plasma wave processes, as it is possible to make detailed measurements of phenomena which are too small to be easily measured by laboratory sized sensors. There are two areas where waves (we include discontinuities under this heading) must make important modifications of the distribution functions: in accelerating the alpha particles to higher speeds than the protons (Marsch et al.) and in accelerating the solar wind itself. A third area is possibly in maintaining the relative isotropy of the solar wind ion distribution in the solar wind rest frame. As the solar wind is nearly collisionless, the ions should conserve magnetic moment in rushing out from the sun, and therefore Tperp/B should be relatively constant, but it is obviously not. This has not received much attention. The waves, both electromagnetic and electrostatic, which are pan of the solar Type 111 burst phenomenon, have been extensively studied as examples of nonlinear plasma phenomena, and also used as remote sensors to trace the solar magnetic field. The observations made by Ulysses show that the field can be traced in this way out to perhaps a little more than an A.U., but then the electromagnetic pan of the type 111 burst fades out. Nevertheless, sometimes Langmuir waves appear at Ulysses at an appropriate extrapolated time. This seems to support the picture in which the electromagnetic waves at the fundamental plasma frequency are trapped in density fluctuations. Langmuir waves in the solar wind are usually in quasi-thermal equilibrium quasi because the solar wind itself is not isothermal. The Observatory of Paris group (Steinberg. Meyer-Vernet, Hoang) has exploited this with an experiment on WIND which is capable of providing density and temperature on a faster time scale than hitherto. Recently it has been found that Langmuir waves are associated with magnetic holes. This may help to elucidate the nature of magnetic holes. Nonlinear processes are important in the transformation of wave energy to panicle energy. Some recent examples from WIND data will be shown.

Two-color walking Peregrine solitary waves.

PubMed

Baronio, Fabio; Chen, Shihua; Mihalache, Dumitru

2017-09-15

We study the extreme localization of light, evolving upon a non-zero background, in two-color parametric wave interaction in nonlinear quadratic media. We report the existence of quadratic Peregrine solitary waves, in the presence of significant group-velocity mismatch between the waves (or Poynting vector beam walk-off), in the regime of cascading second-harmonic generation. This finding opens a novel path for the experimental demonstration of extreme rogue waves in ultrafast quadratic nonlinear optics.

Physiological Effects of Continuous Colored Light Exposure on Mayer Wave Activity in Cerebral Hemodynamics: A Functional Near-Infrared Spectroscopy (fNIRS) Study.

PubMed

Metz, A J; Klein, S D; Scholkmann, F; Wolf, U

2017-01-01

We are increasingly exposed to colored light, but its impact on human physiology is not yet extensively investigated. In the present study we aimed to determine the effects of colored light on human cerebral Mayer wave activity (MWA). We measured oxy- ([O 2 Hb]), deoxy- ([HHb]), total hemoglobin ([tHb]) concentrations and tissue oxygen saturation (StO 2 ) by functional near-infrared spectroscopy (fNIRS) in the left and right pre-frontal cortex (L-PFC, R-PFC) of 17 subjects (median age: 29 years, 6 women). In a randomized crossover design subjects were exposed to blue, red, green, and yellow LED light for 10 min. Pre-light (8 min, baseline) and post-light (15 min, recovery) conditions were darkness. MWA was calculated from band-pass filtered fNIRS signals (~0.08-0.12 Hz). The medians from the last 3 min of each period (baseline, light exposure, recovery) were statistically analyzed. MWA was increased during red and green light vs. baseline and after blue light exposure in recovery in the L-PFC. MWA differed depending on the chosen frequency range, filter design, and type of signals to analyze (raw intensity, hemoglobin signal from multi-distance method or modified Beer-Lambert law, or within hemoglobin signals).

Switching dynamics of the spin density wave in superconducting CeCoIn 5

DOE PAGES

Kim, Duk Y.; Lin, Shi-Zeng; Bauer, Eric D.; ...

2017-06-21

The ordering wave vector Q of a spin density wave (SDW), stabilized within the superconducting state of CeCoIn 5 in a high magnetic field, has been shown to be hypersensitive to the direction of the field. Q can be switched from a nodal direction of the d-wave superconducting order parameter to a perpendicular node by rotating the in-plane magnetic field through the antinodal direction within a fraction of a degree. In this paper, we address the dynamics of the switching of Q. We use a free-energy functional based on the magnetization density, which describes the condensation of magnetic fluctuations ofmore » nodal quasiparticles, and show that the switching process includes closing of the SDW gap at one Q and then reopening the SDW gap at another Q perpendicular to the first one. The magnetic field couples to Q through the spin-orbit interaction. Our calculations show that the width of the hysteretic region of switching depends linearly on the deviation of magnetic field from the critical field associated with the SDW transition, consistent with our thermal conductivity measurements. Finally, the agreement between theory and experiment supports our scenario of the hypersensitivity of the Q phase on the direction of magnetic field, as well as the magnon condensation as the origin of the SDW phase in CeCoIn 5.« less

Fabrication of magnetic field induced structural colored films with tunable colors and its application on security materials.

PubMed

Shang, Shenglong; Zhang, Qinghong; Wang, Hongzhi; Li, Yaogang

2017-01-01

A flexible, magnetic field induced structurally colored films with brilliant colors and high physical rigidity were reported in this article. Using an external magnetic field, the photocurable colloidal suspensions that containing superparamagnetic Fe 3 O 4 @C colloidal nanocrystal clusters (CNCs) could polymerize under UV light. After polymerization, the films with different colors (red, green, blue) were obtained. Through combination of suspensions which contains Fe 3 O 4 @C CNCs with different sizes, a series of multi-colored films were obtained. Moreover, these structural colors can be patterned easily by photolithography and various structural colored patterns were shown in the article. The structural colored patterns could conceal or display its color according to the changing of background which makes them hold significant potential applications for security materials. Copyright © 2016 Elsevier Inc. All rights reserved.

Wave number determination of Pc 1-2 mantle waves considering He++ ions: A Cluster study

NASA Astrophysics Data System (ADS)

Grison, B.; Escoubet, C. P.; Santolík, O.; Cornilleau-Wehrlin, N.; Khotyaintsev, Y.

2014-09-01

The present case study concerns narrowband electromagnetic emission detected in the distant cusp region simultaneously with upgoing plasma flows. The wave properties match the usual properties of the Pc 1-2 mantle waves: small angle between the wave vector and the magnetic field line, left-hand polarization, and propagation toward the ionosphere. We report here the first direct wave vector measurement of these waves (about 1.2 × 10- 2 rad/km) through multi spacecraft analysis using the three magnetic components and, at the same time, through single spacecraft analysis based on the refractive index analysis using the three magnetic components and two electric components. The refractive index analysis offers a simple way to estimate wave numbers in this frequency range. Numerical calculations are performed under the observed plasma conditions. The obtained results show that the ion distribution functions are unstable to ion cyclotron instability at the observed wave vector value, due to the large ion temperature anisotropy. We thus show that these electromagnetic ion cyclotron (EMIC) waves are amplified in the distant cusp region. The Poynting flux of the waves is counterstreaming with respect to the plasma flow. This sense of propagation is consistent with the time necessary to amplify the emissions to the observed level. We point out the role of the wave damping at the He++ gyrofrequency to explain that such waves cannot be observed from the ground at the cusp foot print location.

Backward propagating branch of surface waves in a semi-bounded streaming plasma system

NASA Astrophysics Data System (ADS)

Lim, Young Kyung; Lee, Myoung-Jae; Seo, Ki Wan; Jung, Young-Dae

2017-06-01

The influence of wake and magnetic field on the surface ion-cyclotron wave is kinetically investigated in a semi-bounded streaming dusty magnetoplasma in the presence of the ion wake-field. The analytic expressions of the frequency and the group velocity are derived by the plasma dielectric function with the spectral reflection condition. The result shows that the ion wake-field enhances the wave frequency and the group velocity of the surface ion-cyclotron wave in a semi-bounded dusty plasma. It is found that the frequency and the group velocity of the surface electrostatic-ion-cyclotron wave increase with an increase of the strength of the magnetic field. It is interesting to find out that the group velocity without the ion flow has the backward propagation mode in a semi-bounded dusty plasma. The variations due to the frequency and the group velocity of the surface ion-cyclotron wave are also discussed.

A Proton-Cyclotron Wave Storm Generated by Unstable Proton Distribution Functions in the Solar Wind

NASA Technical Reports Server (NTRS)

Wicks, R. T.; Alexander, R. L.; Stevens, M.; Wilson, L. B., III; Moya, P. S.; Vinas, A.; Jian, L. K.; Roberts, D. A.; O’Modhrain, S.; Gilbert, J. A.;

ULF/ELF Waves in Near-Moon Space

NASA Astrophysics Data System (ADS)

Nakagawa, Tomoko

2016-02-01

The reflection of the solar wind protons is equivalent to a beam injection against the solar wind flow. It is expected to produce a ring beam with a 3D distribution function in many cases. The reflected protons are responsible for the generation of ultra-low-frequency (ULF) waves at ˜0.01 Hz and narrowband waves at ˜1 Hz in the extremely low frequency (ELF) range through resonant interaction with magnetohydrodynamic waves and whistler mode waves in the solar wind, respectively. This chapter discusses these commonly observed waves in the near-Moon space. The sinusoidal waveforms and sharp spectra of the monochromatic ELF waves are impressive, but commonly observed are non-monochromatic waves in the ELF range ˜0.03-10 Hz. Some of the solar wind protons reflected by the dayside lunar surface or crustal magnetic field gyrate around the solar wind magnetic field and can access the center of the wake owing to the large Larmour radius.

Color tuning in alert macaque V1 assessed with fMRI and single-unit recording shows a bias toward daylight colors.

PubMed

Lafer-Sousa, Rosa; Liu, Yang O; Lafer-Sousa, Luis; Wiest, Michael C; Conway, Bevil R

2012-05-01

Colors defined by the two intermediate directions in color space, "orange-cyan" and "lime-magenta," elicit the same spatiotemporal average response from the two cardinal chromatic channels in the lateral geniculate nucleus (LGN). While we found LGN functional magnetic resonance imaging (fMRI) responses to these pairs of colors were statistically indistinguishable, primary visual cortex (V1) fMRI responses were stronger to orange-cyan. Moreover, linear combinations of single-cell responses to cone-isolating stimuli of V1 cone-opponent cells also yielded stronger predicted responses to orange-cyan over lime-magenta, suggesting these neurons underlie the fMRI result. These observations are consistent with the hypothesis that V1 recombines LGN signals into "higher-order" mechanisms tuned to noncardinal color directions. In light of work showing that natural images and daylight samples are biased toward orange-cyan, our findings further suggest that V1 is adapted to daylight. V1, especially double-opponent cells, may function to extract spatial information from color boundaries correlated with scene-structure cues, such as shadows lit by ambient blue sky juxtaposed with surfaces reflecting sunshine. © 2012 Optical Society of America

Full-wave feasibility study of anti-radar diagnostic of magnetic field based on O-X mode conversion and oblique reflectometry imaging

DOE PAGES

Meneghini, Orso; Volpe, Francesco A.

2016-08-19

An innovative millimeter wave diagnostic is proposed to measure the local magnetic field and edge current as a function of the minor radius in the tokamak pedestal region. The idea is to identify the direction of minimum reflectivity at the O-mode cutoff layer. Correspondingly, the transmissivity due to O-X mode conversion is maximum. That direction, and the angular map of reflectivity around it, contain information on the magnetic field vector B at the cutoff layer. By probing the plasma with different wave frequencies it provides the radial profile of B. Full-wave finite-element simulations are presented here in 2D slab geometry.more » Modeling confirms the existence of a minimum in reflectivity that depends on the magnetic field at the cutoff, as expected from mode conversion physics, giving confidence in the feasibility of the diagnostic. We proposed an reflectometric approach in order to yield superior signal-to-noise ratio and to access wider ranges of density and magnetic field, compared with related radiometric techniques that require the plasma to emit Electron Bernstein Waves. Due to computational limitations, frequencies of 10-20 GHz were considered in this initial study. Furthermore, frequencies above the edge electron-cyclotron frequency (f >28 GHz here) would be preferable for the experiment, because the upper hybrid resonance and right cutoff would lie in the plasma, and would help separate the O-mode of interest from spurious X-waves.« less

Full-wave feasibility study of anti-radar diagnostic of magnetic field based on O-X mode conversion and oblique reflectometry imaging

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

Meneghini, Orso; Volpe, Francesco A., E-mail: fvolpe@columbia.edu

An innovative millimeter wave diagnostic is proposed to measure the local magnetic field and edge current as a function of the minor radius in the tokamak pedestal region. The idea is to identify the direction of minimum reflectivity at the O-mode cutoff layer. Correspondingly, the transmissivity due to O-X mode conversion is maximum. That direction, and the angular map of reflectivity around it, contains information on the magnetic field vector B at the cutoff layer. Probing the plasma with different wave frequencies provides the radial profile of B. Full-wave finite-element simulations are presented here in 2D slab geometry. Modeling confirmsmore » the existence of a minimum in reflectivity that depends on the magnetic field at the cutoff, as expected from mode conversion physics, giving confidence in the feasibility of the diagnostic. The proposed reflectometric approach is expected to yield superior signal-to-noise ratio and to access wider ranges of density and magnetic field, compared with related radiometric techniques that require the plasma to emit electron Bernstein waves. Due to computational limitations, frequencies of 10-20 GHz were considered in this initial study. Frequencies above the edge electron-cyclotron frequency (f > 28 GHz here) would be preferable for the experiment, because the upper hybrid resonance and right cutoff would lie in the plasma, and would help separate the O-mode of interest from spurious X-waves.« less

Contributions to the Fourth Solar Wind Conference. [interplanetary magnetic fields and medium

NASA Technical Reports Server (NTRS)

Acuna, M. H.; Behannon, K. W.; Burlaga, L. F.; Lepping, R.; Ness, N.; Ogilvie, K.; Pizzo, J.

1979-01-01

Recent results in interplanetary physics are examined. These include observations of shock waves and post-shock magnetic fields made by Voyager 1, 2; observations of the electron temperature as a function of distance between 1.36 AU and 2.25 AU; and observations of the structure of sector boundaries observed by Helios 1. A theory of electron energy transport in the collisionless solar wind is presented, and compared with observations. Alfven waves and Alvenic fluctuations in the solar wind are also discussed.

Gravity dual of spin and charge density waves

NASA Astrophysics Data System (ADS)

Jokela, Niko; Järvinen, Matti; Lippert, Matthew

2014-12-01

At high enough charge density, the homogeneous state of the D3-D7' model is unstable to fluctuations at nonzero momentum. We investigate the end point of this instability, finding a spatially modulated ground state, which is a charge and spin density wave. We analyze the phase structure of the model as a function of chemical potential and magnetic field and find the phase transition from the homogeneous state to be first order, with a second-order critical point at zero magnetic field.

PROTON HEATING BY PICK-UP ION DRIVEN CYCLOTRON WAVES IN THE OUTER HELIOSPHERE: HYBRID EXPANDING BOX SIMULATIONS

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

Hellinger, Petr; Trávníček, Pavel M., E-mail: petr.hellinger@asu.cas.cz

Using a one-dimensional hybrid expanding box model, we investigate properties of the solar wind in the outer heliosphere. We assume a proton–electron plasma with a strictly transverse ambient magnetic field and, aside from the expansion, we take into account the influence of a continuous injection of cold pick-up protons through the charge-exchange process between the solar wind protons and hydrogen of interstellar origin. The injected cold pick-up protons form a ring distribution function, which rapidly becomes unstable, and generate Alfvén cyclotron waves. The Alfvén cyclotron waves scatter pick-up protons to a spherical shell distribution function that thickens over that timemore » owing to the expansion-driven cooling. The Alfvén cyclotron waves heat solar wind protons in the perpendicular direction (with respect to the ambient magnetic field) through cyclotron resonance. At later times, the Alfvén cyclotron waves become parametrically unstable and the generated ion-acoustic waves heat protons in the parallel direction through Landau resonance. The resulting heating of the solar wind protons is efficient on the expansion timescale.« less

Low temperature anomaly of light stimulated magnetization and heat capacity of the 1D diluted magnetic semiconductors

NASA Astrophysics Data System (ADS)

Geffe, Chernet Amente

2018-03-01

This article reports magnetization and specific heat capacity anomalies in one dimensional diluted magnetic semiconductors observed at very low temperatures. Based on quantum field theory double time temperature dependent Green function technique is employed to evaluate magnon dispersion and the time correlation function. It is understood that magnon-photon coupling and magnetic impurity concentration controls both, such that near absolute temperature magnetization is nearly zero and abruptly increase to saturation level with decreasing magnon-photon coupling strength. We also found out dropping of magnetic specific heat capacity as a result of increase in magnetic impurity concentration x, perhaps because of inter-band disorder that would suppress the enhancement of density of spin waves.

Controlling of the electromagnetic solitary waves generation in the wake of a two-color laser

NASA Astrophysics Data System (ADS)

Pan, K. Q.; Li, S. W.; Guo, L.; Yang, D.; Li, Z. C.; Zheng, C. Y.; Jiang, S. E.; Zhang, B. H.; He, X. T.

2018-05-01

Electromagnetic solitary waves generated by a two-color laser interaction with an underdense plasma are investigated. It is shown that, when the former wave packet of the two-color laser is intense enough, it will excite nonlinear wakefields and generate electron density cavities. The latter wave packets will beat with the nonlinear wakefield and generate both high-frequency and low-frequency components. When the peak density of the cavities exceeds the critical density of the low-frequency component, this part of the electromagnetic field will be trapped to generate electromagnetic solitary waves. By changing the laser and plasma parameters, we can control the wakefield generation, which will also control the generation of the solitary waves. One-dimensional particle-in-cell simulations are performed to prove the controlling of the solitary waves. The simulation results also show that solitary waves generated by higher laser intensities will become moving solitary waves. The two-dimensional particle-in-cell also shows the generation of the solitary waves. In the two-dimensional case, solitary waves are distributed in the transverse directions because of the filamentation instability.

Jupiter Wave

NASA Image and Video Library

2015-10-13

Scientists spotted a rare wave in Jupiter North Equatorial Belt that had been seen there only once before in this false-color close-up from NASA Hubble Telescope. In Jupiter's North Equatorial Belt, scientists spotted a rare wave that had been seen there only once before. It is similar to a wave that sometimes occurs in Earth's atmosphere when cyclones are forming. This false-color close-up of Jupiter shows cyclones (arrows) and the wave (vertical lines). http://photojournal.jpl.nasa.gov/catalog/PIA19659

Accurate calibration of waveform data measured by the Plasma Wave Experiment on board the ARASE satellite

NASA Astrophysics Data System (ADS)

Kitahara, M.; Katoh, Y.; Hikishima, M.; Kasahara, Y.; Matsuda, S.; Kojima, H.; Ozaki, M.; Yagitani, S.

2017-12-01

The Plasma Wave Experiment (PWE) is installed on board the ARASE satellite to measure the electric field in the frequency range from DC to 10 MHz, and the magnetic field in the frequency range from a few Hz to 100 kHz using two dipole wire-probe antennas (WPT) and three magnetic search coils (MSC), respectively. In particular, the Waveform Capture (WFC), one of the receivers of the PWE, can detect electromagnetic field waveform in the frequency range from a few Hz to 20 kHz. The Software-type Wave Particle Interaction Analyzer (S-WPIA) is installed on the ARASE satellite to measure the energy exchange between plasma waves and particles. Since S-WPIA uses the waveform data measured by WFC to calculate the relative phase angle between the wave magnetic field and velocity of energetic electrons, the high-accuracy is required to calibration of both amplitude and phase of the waveform data. Generally, the calibration procedure of the signal passed through a receiver consists of three steps; the transformation into spectra, the calibration by the transfer function of a receiver, and the inverse transformation of the calibrated spectra into the time domain. Practically, in order to reduce the side robe effect, a raw data is filtered by a window function in the time domain before applying Fourier transform. However, for the case that a first order differential coefficient of the phase transfer function of the system is not negligible, the phase of the window function convoluted into the calibrated spectra is shifted differently at each frequency, resulting in a discontinuity in the time domain of the calibrated waveform data. To eliminate the effect of the phase shift of a window function, we suggest several methods to calibrate a waveform data accurately and carry out simulations assuming simple sinusoidal waves as an input signal and using transfer functions of WPT, MSC, and WFC obtained in pre-flight tests. In consequence, we conclude that the following two methods can reduce an error contaminated through the calibration to less than 0.1 % of amplitude of input waves; (1) a Turkey-type window function with a flat top region of one-third of the window length and (2) modification of the window function for each frequency by referring the estimation of the phase shift due to the first order differential coefficient from the transfer functions.

Micromagnetic computer simulations of spin waves in nanometre-scale patterned magnetic elements

NASA Astrophysics Data System (ADS)

Kim, Sang-Koog

2010-07-01

Current needs for further advances in the nanotechnologies of information-storage and -processing devices have attracted a great deal of interest in spin (magnetization) dynamics in nanometre-scale patterned magnetic elements. For instance, the unique dynamic characteristics of non-uniform magnetic microstructures such as various types of domain walls, magnetic vortices and antivortices, as well as spin wave dynamics in laterally restricted thin-film geometries, have been at the centre of extensive and intensive researches. Understanding the fundamentals of their unique spin structure as well as their robust and novel dynamic properties allows us to implement new functionalities into existing or future devices. Although experimental tools and theoretical approaches are effective means of understanding the fundamentals of spin dynamics and of gaining new insights into them, the limitations of those same tools and approaches have left gaps of unresolved questions in the pertinent physics. As an alternative, however, micromagnetic modelling and numerical simulation has recently emerged as a powerful tool for the study of a variety of phenomena related to spin dynamics of nanometre-scale magnetic elements. In this review paper, I summarize the recent results of simulations of the excitation and propagation and other novel wave characteristics of spin waves, highlighting how the micromagnetic computer simulation approach contributes to an understanding of spin dynamics of nanomagnetism and considering some of the merits of numerical simulation studies. Many examples of micromagnetic modelling for numerical calculations, employing various dimensions and shapes of patterned magnetic elements, are given. The current limitations of continuum micromagnetic modelling and of simulations based on the Landau-Lifshitz-Gilbert equation of motion of magnetization are also discussed, along with further research directions for spin-wave studies.

What Makes the Muscle Twitch: Motor System Connectivity and TMS-Induced Activity.

PubMed

Volz, Lukas J; Hamada, Masashi; Rothwell, John C; Grefkes, Christian

2015-09-01

Transcranial magnetic stimulation (TMS) of the primary motor cortex (M1) evokes several volleys of corticospinal activity. While the earliest wave (D-wave) originates from axonal activation of cortico-spinal neurons (CSN), later waves (I-waves) result from activation of mono- and polysynaptic inputs to CSNs. Different coil orientations preferentially stimulate cortical elements evoking different outputs: latero-medial-induced current (LM) elicits D-waves and short-latency electromyographic responses (MEPs); posterior-anterior current (PA) evokes early I-waves. Anterior-posterior current (AP) is more variable and tends to recruit later I-waves, featuring longer onset latencies compared with PA-TMS. We tested whether the variability in response to AP-TMS was related to functional connectivity of the stimulated M1 in 20 right-handed healthy subjects who underwent functional magnetic resonance imaging while performing an isometric contraction task. The MEP-latency after AP-TMS (relative to LM-TMS) was strongly correlated with functional connectivity between the stimulated M1 and a network involving cortical premotor areas. This indicates that stronger premotor-M1 connectivity increases the probability that AP-TMS recruits shorter latency input to CSNs. In conclusion, our data strongly support the hypothesis that TMS of M1 activates distinct neuronal pathways depending on the orientation of the stimulation coil. Particularly, AP currents seem to recruit short latency cortico-cortical projections from premotor areas. © The Author 2014. Published by Oxford University Press. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.

FAST TRACK COMMUNICATION: Finite-temperature magnetism in bcc Fe under compression

NASA Astrophysics Data System (ADS)

Sha, Xianwei; Cohen, R. E.

2010-09-01

We investigate the contributions of finite-temperature magnetic fluctuations to the thermodynamic properties of bcc Fe as functions of pressure. First, we apply a tight-binding total-energy model parameterized to first-principles linearized augmented plane-wave computations to examine various ferromagnetic, anti-ferromagnetic, and noncollinear spin spiral states at zero temperature. The tight-binding data are fit to a generalized Heisenberg Hamiltonian to describe the magnetic energy functional based on local moments. We then use Monte Carlo simulations to compute the magnetic susceptibility, the Curie temperature, heat capacity, and magnetic free energy. Including the finite-temperature magnetism improves the agreement with experiment for the calculated thermal expansion coefficients.

The magnetic particle in a box: Analytic and micromagnetic analysis of probe-localized spin wave modes

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

Adur, Rohan, E-mail: adur@physics.osu.edu; Du, Chunhui; Manuilov, Sergei A.

2015-05-07

The dipole field from a probe magnet can be used to localize a discrete spectrum of standing spin wave modes in a continuous ferromagnetic thin film without lithographic modification to the film. Obtaining the resonance field for a localized mode is not trivial due to the effect of the confined and inhomogeneous magnetization precession. We compare the results of micromagnetic and analytic methods to find the resonance field of localized modes in a ferromagnetic thin film, and investigate the accuracy of these methods by comparing with a numerical minimization technique that assumes Bessel function modes with pinned boundary conditions. Wemore » find that the micromagnetic technique, while computationally more intensive, reveals that the true magnetization profiles of localized modes are similar to Bessel functions with gradually decaying dynamic magnetization at the mode edges. We also find that an analytic solution, which is simple to implement and computationally much faster than other methods, accurately describes the resonance field of localized modes when exchange fields are negligible, and demonstrating the accessibility of localized mode analysis.« less

Transitional analysis of organic thin color filter layers in displays during baking process using multi-speckle diffusing wave spectroscopy

NASA Astrophysics Data System (ADS)

Park, Baek Sung; Hyung, Kyung Hee; Oh, Gwi Jeong; Jung, Hyun Wook

2018-02-01

The color filter (CF) is one of the key components for improving the performance of TV displays such as liquid crystal display (LCD) and white organic light emitting diodes (WOLED). The profile defects like undercut during the fine fabrication processes for CF layers are inevitably generated through the UV exposure and development processes, however, these can be controlled through the baking process. In order to resolve the profile defects of CF layers, in this study, the real-time dynamic changes of CF layers are monitored during the baking process by changing components such as polymeric binder and acrylate. The motion of pigment particles in CF layers during baking is quantitatively interpreted using multi-speckle diffusing wave spectroscopy (MSDWS), in terms of the autocorrelation function and the characteristic time of α-relaxation.

Chiral Domain Structure in Superfluid 3He-A Studied by Magnetic Resonance Imaging

NASA Astrophysics Data System (ADS)

Kasai, J.; Okamoto, Y.; Nishioka, K.; Takagi, T.; Sasaki, Y.

2018-05-01

The existence of a spatially varying texture in superfluid 3He is a direct manifestation of the complex macroscopic wave function. The real space shape of the texture, namely, a macroscopic wave function, has been studied extensively with the help of theoretical modeling but has never been directly observed experimentally with spatial resolution. We have succeeded in visualizing the texture by a specialized magnetic resonance imaging. With this new technology, we have discovered that the macroscopic chiral domains, of which sizes are as large as 1 mm, and corresponding chiral domain walls exist rather stably in 3He - A film at temperatures far below the transition temperature.

How to use a phase-only spatial light modulator as a color display.

PubMed

Harm, Walter; Jesacher, Alexander; Thalhammer, Gregor; Bernet, Stefan; Ritsch-Marte, Monika

2015-02-15

We demonstrate that a parallel aligned liquid crystal on silicon (PA-LCOS) spatial light modulator (SLM) without any attached color mask can be used as a full color display with white light illumination. The method is based on the wavelength dependence of the (voltage controlled) birefringence of the liquid crystal pixels. Modern SLMs offer a wide range over which the birefringence can be modulated, leading (in combination with a linear polarizer) to several intensity modulation periods of a reflected light wave as a function of the applied voltage. Because of dispersion, the oscillation period strongly depends on the wavelength. Thus each voltage applied to an SLM pixel corresponds to another reflected color spectrum. For SLMs with a sufficiently broad tuning range, one obtains a color palette (i.e., a "color lookup-table"), which allows one to display color images. An advantage over standard liquid crystal displays (LCDs), which use color masks in front of the individual pixels, is that the light efficiency and the display resolution are increased by a factor of three.

Waves in Radial Gravity Using Magnetic Fluid

NASA Technical Reports Server (NTRS)

Ohlsen, D. R.; Hart, J. E.; Weidman, P. D.

1999-01-01

Terrestrial laboratory experiments studying various fluid dynamical processes are constrained, by being in an Earth laboratory, to have a gravitational body force which is uniform and unidirectional. Therefore fluid free-surfaces are horizontal and flat. Such free surfaces must have a vertical solid boundary to keep the fluid from spreading horizontally along a gravitational potential surface. In atmospheric, oceanic, or stellar fluid flows that have a horizontal scale of about one-tenth the body radius or larger, sphericity is important in the dynamics. Further, fluids in spherical geometry can cover an entire domain without any sidewall effects, i.e. have truly periodic boundary conditions. We describe spherical body-force laboratory experiments using ferrofluid. Ferrofluids are dilute suspensions of magnetic dipoles, for example magnetite particles of order 10 nm diameter, suspended in a carrier fluid. Ferrofluids are subject to an additional body force in the presence of an applied magnetic field gradient. We use this body force to conduct laboratory experiments in spherical geometry. The present study is a laboratory technique improvement. The apparatus is cylindrically axisymmetric. A cylindrical ceramic magnet is embedded in a smooth, solid, spherical PVC ball. The geopotential field and its gradient, the body force, were made nearly spherical by careful choice of magnet height-to-diameter ratio and magnet size relative to the PVC ball size. Terrestrial gravity is eliminated from the dynamics by immersing the "planet" and its ferrofluid "ocean" in an immiscible silicone oil/freon mixture of the same density. Thus the earth gravity is removed from the dynamics of the ferrofluid/oil interface and the only dynamically active force there is the radial magnetic gravity. The entire apparatus can rotate, and waves are forced on the ferrofluid surface by exterior magnets. The biggest improvement in technique is in the wave visualization. Fluorescing dye is added to the oil/freon mixture and an argon ion laser generates a horizontal light that can be scanned vertically. Viewed from above, the experiment is a black circle with wave deformations surrounded by a light background. A contour of the image intensity at any light sheet position gives the surface of the ferrofluid "ocean" at that "latitude". Radial displacements of the waves as a function of longitude are obtained by subtracting the contour line positions from a no-motion contour at that laser sheet latitude. The experiments are run by traversing the forcing magnet with the laser sheet height fixed and images are frame grabbed to obtain a time-series at one latitude. The experiment is then re-run with another laser-sheet height to generate a full picture of the three-dimensional wave structure in the upper hemisphere of the ball as a function of time. We concentrate here on results of laboratory studies of waves that are important in Earth's atmosphere and especially the ocean. To get oceanic scaling in the laboratory, the experiment must rotate rapidly (4-second rotation period) so that the wave speed is slow compared to the planetary rotation speed as in the ocean. In the Pacific Ocean, eastward propagating Kelvin waves eventually run into the South American coast. Theory predicts that some of the wave energy should scatter into coastal-trapped Kelvin waves that propagate north and south along the coast. Some of this coastal wave energy might then scatter into mid-latitude Rossby waves that propagate back westward. Satellite observations of the Pacific Ocean sea-surface temperature and height seem to show signatures of westward propagating mid-latitude Rossby waves, 5 to 10 years after the 1982-83 El Nino. The observational data is difficult to interpret unambiguously owing to the large range of motions that fill the ocean at shorter timescales. This series of reflections giving eastward, north- ward, and then westward traveling waves is observed cleanly in the laboratory experiments, confirming the theoretical expectations.

Variations in plasma wave intensity with distance along the electron foreshock boundary at Venus

NASA Technical Reports Server (NTRS)

Crawford, G. K.; Strangeway, R. J.; Russell, C. T.

1991-01-01

Plasma waves are observed in the solar wind upstream of the Venus bow shock by the Pioneer Venus Orbiter. These wave signatures occur during periods when the interplanetary magnetic field through the spacecraft position intersects the bow shock, thereby placing the spacecraft in the foreshock region. Wave intensity is analyzed as a function of distance along the electron foreshock boundary. It is found that the peak wave intensity may increase along the foreshock boundary from the tangent point to a maximum value at several Venus radii, then decrease in intensity with subsequent increase in distance. These observations could be associated with the instability process: the instability of the distribution function increasing with distance from the tangent point to saturation at the peak. Thermalization of the beam for distances beyond this point could reduce the distribution function instability resulting in weaker wave signatures.

Thermal and magnetic properties of electron gas in toroidal quantum dot

NASA Astrophysics Data System (ADS)

Baghdasaryan, D. A.; Hayrapetyan, D. B.; Kazaryan, E. M.; Sarkisyan, H. A.

2018-07-01

One-electron states in a toroidal quantum dot in the presence of an external magnetic field have been considered. The magnetic field operator and the Schrodinger equation have been written in toroidal coordinates. The dependence of one-electron energy spectrum and wave function on the geometrical parameters of a toroidal quantum dot and magnetic field strength have been studied. The energy levels are employed to calculate the canonical partition function, which in its turn is used to obtain mean energy, heat capacity, entropy, magnetization, and susceptibility of noninteracting electron gas. The possibility to control the thermodynamic and magnetic properties of the noninteracting electron gas via changing the geometric parameters of the QD, magnetic field, and temperature, was demonstrated.

Variable dual-frequency electrostatic wave launcher for plasma applications.

PubMed

Jorns, Benjamin; Sorenson, Robert; Choueiri, Edgar

2011-12-01

A variable tuning system is presented for launching two electrostatic waves concurrently in a magnetized plasma. The purpose of this system is to satisfy the wave launching requirements for plasma applications where maximal power must be coupled into two carefully tuned electrostatic waves while minimizing erosion to the launching antenna. Two parallel LC traps with fixed inductors and variable capacitors are used to provide an impedance match between a two-wave source and a loop antenna placed outside the plasma. Equivalent circuit analysis is then employed to derive an analytical expression for the normalized, average magnetic flux density produced by the antenna in this system as a function of capacitance and frequency. It is found with this metric that the wave launcher can couple to electrostatic modes at two variable frequencies concurrently while attenuating noise from the source signal at undesired frequencies. An example based on an experiment for plasma heating with two electrostatic waves is used to demonstrate a procedure for tailoring the wave launcher to accommodate the frequency range and flux densities of a specific two-wave application. This example is also used to illustrate a method based on averaging over wave frequencies for evaluating the overall efficacy of the system. The wave launcher is shown to be particularly effective for the illustrative example--generating magnetic flux densities in excess of 50% of the ideal case at two variable frequencies concurrently--with a high adaptability to a number of plasma dynamics and heating applications.

Simple preparation of magnetic field-responsive structural colored Janus particles.

PubMed

Teshima, Midori; Seki, Takahiro; Takeoka, Yukikazu

2018-03-08

We established a simple method for preparing Janus particles displaying different structural colors using submicron-sized fine silica particles and magnetic nanoparticles composed of Fe 3 O 4 . A w/o emulsion is prepared by vortex-stirring a mixed aqueous solution of suspended fine silica particles and magnetic nanoparticles and of hexadecane containing an emulsifier. Subsequent drying of the emulsion on a hot plate using a magnetic stirrer provides a polydisperse particle aggregate displaying two different structural colors according to the ratio of the amount of fine silica particles to the amount of magnetic nanoparticles. This polydisperse particle aggregate can be converted into monodisperse particles simply by using a sieve made of stainless steel. In the presence of a magnet, the monodisperse Janus particles can change their orientation and can switch between two different structural colors.

Anderson localization of shear waves observed by magnetic resonance imaging

NASA Astrophysics Data System (ADS)

Papazoglou, S.; Klatt, D.; Braun, J.; Sack, I.

2010-07-01

In this letter we present for the first time an experimental investigation of shear wave localization using motion-sensitive magnetic resonance imaging (MRI). Shear wave localization was studied in gel phantoms containing arrays of randomly positioned parallel glass rods. The phantoms were exposed to continuous harmonic vibrations in a frequency range from 25 to 175 Hz, yielding wavelengths on the order of the elastic mean free path, i.e. the Ioffe-Regel criterion of Anderson localization was satisfied. The experimental setup was further chosen such that purely shear horizontal waves were induced to avoid effects due to mode conversion and pressure waves. Analysis of the distribution of shear wave intensity in experiments and simulations revealed a significant deviation from Rayleigh statistics indicating that shear wave energy is localized. This observation is further supported by experiments on weakly scattering samples exhibiting Rayleigh statistics and an analysis of the multifractality of wave functions. Our results suggest that motion-sensitive MRI is a promising tool for studying Anderson localization of time-harmonic shear waves, which are increasingly used in dynamic elastography.

Inhibition of electron thermal conduction by electromagnetic instabilities. [in stellar coronas

NASA Technical Reports Server (NTRS)

Levinson, Amir; Eichler, David

1992-01-01

Heat flux inhibition by electromagnetic instabilities in a hot magnetized plasma is investigated. Low-frequency electromagnetic waves become unstable due to anisotropy of the electron distribution function. The chaotic magnetic field thus generated scatters the electrons with a specific effective mean free path. Saturation of the instability due to wave-wave interaction, nonlinear scattering, wave propagation, and collisional damping is considered. The effective mean free path is found self-consistently, using a simple model to estimate saturation level and scattering, and is shown to decrease with the temperature gradient length. The results, limited to the assumptions of the model, are applied to astrophysical systems. For some interstellar clouds the instability is found to be important. Collisional damping stabilizes the plasma, and the heat conduction can be dominated by superthermal electrons.

KSC-07pd0413

NASA Image and Video Library

2007-02-16

KENNEDY SPACE CENTER, FLA. -- The Delta II rocket with the THEMIS spacecraft atop sits ready for launch on Pad 17-B at Cape Canaveral Air Force Station after the mobile service tower moves away from the pad. THEMIS, an acronym for Time History of Events and Macroscale Interactions during Substorms, consists of five identical probes that will track violent, colorful eruptions near the North Pole. This will be the largest number of scientific satellites NASA has ever launched into orbit aboard a single rocket. The THEMIS mission aims to unravel the mystery behind auroral substorms, an avalanche of magnetic energy powered by the solar wind that intensifies the northern and southern lights. The mission will investigate what causes auroras in the Earth’s atmosphere to dramatically change from slowly shimmering waves of light to wildly shifting streaks of bright color. Launch is scheduled for 6:05 p.m. Photo credit: NASA/Kim Shiflett

Delta II Launch with the THEMIS satellite payload from pad 17B C

NASA Image and Video Library

2007-02-17

At Cape Canaveral Air Force Station, clouds of smoke encompass the Delta II rocket with NASA's THEMIS spacecraft aboard as it blasts off Pad 17-B, in sight of the Atlantic Ocean, at 6:01 p.m. EST. THEMIS, an acronym for Time History of Events and Macroscale Interactions during Substorms, consists of five identical probes that will track violent, colorful eruptions near the North Pole. This will be the largest number of scientific satellites NASA has ever launched into orbit aboard a single rocket. The THEMIS mission aims to unravel the mystery behind auroral substorms, an avalanche of magnetic energy powered by the solar wind that intensifies the northern and southern lights. The mission will investigate what causes auroras in the Earth’s atmosphere to dramatically change from slowly shimmering waves of light to wildly shifting streaks of bright color.

Delta II THEMIS Pre-Launch

NASA Image and Video Library

2002-01-01

In this aerial view, the Delta II rocket with the THEMIS spacecraft sits ready for launch on Pad 17-B at Cape Canaveral Air Force Station, as the mobile service tower moves away from the pad. THEMIS, an acronym for Time History of Events and Macroscale Interactions during Substorms, consists of five identical probes that will track violent, colorful eruptions near the North Pole. This will be the largest number of scientific satellites NASA has ever launched into orbit aboard a single rocket. The THEMIS mission aims to unravel the mystery behind auroral substorms, an avalanche of magnetic energy powered by the solar wind that intensifies the northern and southern lights. The mission will investigate what causes auroras in the Earth’s atmosphere to dramatically change from slowly shimmering waves of light to wildly shifting streaks of bright color. Launch is scheduled for 6:05 p.m.

KSC-07pd0415

NASA Image and Video Library

2007-02-16

KENNEDY SPACE CENTER, FLA. -- The Delta II rocket with the THEMIS spacecraft atop sits ready for launch on Pad 17-B at Cape Canaveral Air Force Station in this aerial view of the launch complex area as the mobile service tower begins to move away. THEMIS, an acronym for Time History of Events and Macroscale Interactions during Substorms, consists of five identical probes that will track violent, colorful eruptions near the North Pole. This will be the largest number of scientific satellites NASA has ever launched into orbit aboard a single rocket. The THEMIS mission aims to unravel the mystery behind auroral substorms, an avalanche of magnetic energy powered by the solar wind that intensifies the northern and southern lights. The mission will investigate what causes auroras in the Earth’s atmosphere to dramatically change from slowly shimmering waves of light to wildly shifting streaks of bright color. Launch is scheduled for 6:05 p.m. Photo credit: NASA/George Shelton

KSC-07pd0420

NASA Image and Video Library

2007-02-16

KENNEDY SPACE CENTER, FLA. -- At Cape Canaveral Air Force Station, the Delta II rocket with the THEMIS spacecraft atop awaits launch on Pad 17-B. Friday's launch attempt was scrubbed due to upper-level wind violation. The launch window is 6:01 p.m. to 6:19 p.m. EST on Saturday. THEMIS, an acronym for Time History of Events and Macroscale Interactions during Substorms, consists of five identical probes that will track violent, colorful eruptions near the North Pole. This will be the largest number of scientific satellites NASA has ever launched into orbit aboard a single rocket. The THEMIS mission aims to unravel the mystery behind auroral substorms, an avalanche of magnetic energy powered by the solar wind that intensifies the northern and southern lights. The mission will investigate what causes auroras in the Earth’s atmosphere to dramatically change from slowly shimmering waves of light to wildly shifting streaks of bright color. Photo credit: NASA/Kim Shiflett

KSC-07pd0416

NASA Image and Video Library

2007-02-16

KENNEDY SPACE CENTER, FLA. -- In this close-up aerial view, the Delta II rocket with the THEMIS spacecraft atop sits ready for launch on Pad 17-B at Cape Canaveral Air Force Station as the mobile service tower begins to move away. THEMIS, an acronym for Time History of Events and Macroscale Interactions during Substorms, consists of five identical probes that will track violent, colorful eruptions near the North Pole. This will be the largest number of scientific satellites NASA has ever launched into orbit aboard a single rocket. The THEMIS mission aims to unravel the mystery behind auroral substorms, an avalanche of magnetic energy powered by the solar wind that intensifies the northern and southern lights. The mission will investigate what causes auroras in the Earth’s atmosphere to dramatically change from slowly shimmering waves of light to wildly shifting streaks of bright color. Launch is scheduled for 6:05 p.m. Photo credit: NASA/George Shelton

KSC-07pd0411

NASA Image and Video Library

2007-02-16

KENNEDY SPACE CENTER, FLA. -- At Launch Pad 17-B at Cape Canaveral Air Force Station, an unusual view of the Delta II rocket with the THEMIS spacecraft atop gives the solid rocket boosters a "larger than life" appearance as the mobile service tower moves away. THEMIS, an acronym for Time History of Events and Macroscale Interactions during Substorms, consists of five identical probes that will track violent, colorful eruptions near the North Pole. This will be the largest number of scientific satellites NASA has ever launched into orbit aboard a single rocket. The THEMIS mission aims to unravel the mystery behind auroral substorms, an avalanche of magnetic energy powered by the solar wind that intensifies the northern and southern lights. The mission will investigate what causes auroras in the Earth’s atmosphere to dramatically change from slowly shimmering waves of light to wildly shifting streaks of bright color. Launch is scheduled for 6:05 p.m. Photo credit: NASA/Kim Shiflett

Delta II THEMIS Pre-Launch

NASA Image and Video Library

2002-01-01

In this close-up aerial view, the Delta II rocket with the THEMIS spacecraft atop sits ready for launch on Pad 17-B at Cape Canaveral Air Force Station as the mobile service tower moves away from the pad. THEMIS, an acronym for Time History of Events and Macroscale Interactions during Substorms, consists of five identical probes that will track violent, colorful eruptions near the North Pole. This will be the largest number of scientific satellites NASA has ever launched into orbit aboard a single rocket. The THEMIS mission aims to unravel the mystery behind auroral substorms, an avalanche of magnetic energy powered by the solar wind that intensifies the northern and southern lights. The mission will investigate what causes auroras in the Earth’s atmosphere to dramatically change from slowly shimmering waves of light to wildly shifting streaks of bright color. Launch is scheduled for 6:05 p.m.

Delta II THEMIS Pre-Launch

NASA Image and Video Library

2002-01-01

The Delta II rocket with the THEMIS spacecraft atop sits ready for launch on Pad 17-B at Cape Canaveral Air Force Station in this aerial view of the launch complex area as the mobile service tower begins to move away. THEMIS, an acronym for Time History of Events and Macroscale Interactions during Substorms, consists of five identical probes that will track violent, colorful eruptions near the North Pole. This will be the largest number of scientific satellites NASA has ever launched into orbit aboard a single rocket. The THEMIS mission aims to unravel the mystery behind auroral substorms, an avalanche of magnetic energy powered by the solar wind that intensifies the northern and southern lights. The mission will investigate what causes auroras in the Earth’s atmosphere to dramatically change from slowly shimmering waves of light to wildly shifting streaks of bright color. Launch is scheduled for 6:05 p.m.

KSC-07pd0414

NASA Image and Video Library

2007-02-16

KENNEDY SPACE CENTER, FLA. -- The Delta II rocket with the THEMIS spacecraft atop sits ready for launch on Pad 17-B at Cape Canaveral Air Force Station after the mobile service tower moves away from the pad. THEMIS, an acronym for Time History of Events and Macroscale Interactions during Substorms, consists of five identical probes that will track violent, colorful eruptions near the North Pole. This will be the largest number of scientific satellites NASA has ever launched into orbit aboard a single rocket. The THEMIS mission aims to unravel the mystery behind auroral substorms, an avalanche of magnetic energy powered by the solar wind that intensifies the northern and southern lights. The mission will investigate what causes auroras in the Earth’s atmosphere to dramatically change from slowly shimmering waves of light to wildly shifting streaks of bright color. Launch is scheduled for 6:05 p.m. Photo credit: NASA/Kim Shiflett

KSC-07pd0412

NASA Image and Video Library

2007-02-16

KENNEDY SPACE CENTER, FLA. -- The Delta II rocket with the THEMIS spacecraft atop sits ready for launch on Pad 17-B at Cape Canaveral Air Force Station after the mobile service tower moves away from the pad. THEMIS, an acronym for Time History of Events and Macroscale Interactions during Substorms, consists of five identical probes that will track violent, colorful eruptions near the North Pole. This will be the largest number of scientific satellites NASA has ever launched into orbit aboard a single rocket. The THEMIS mission aims to unravel the mystery behind auroral substorms, an avalanche of magnetic energy powered by the solar wind that intensifies the northern and southern lights. The mission will investigate what causes auroras in the Earth’s atmosphere to dramatically change from slowly shimmering waves of light to wildly shifting streaks of bright color. Launch is scheduled for 6:05 p.m. Photo credit: NASA/Kim Shiflett

KSC-07pd0437

NASA Image and Video Library

2007-02-17

KENNEDY SPACE CENTER, FLA. -- At Cape Canaveral Air Force Station, the Delta II rocket with NASA's THEMIS spacecraft aboard begins its ascent from Pad 17-B, in sight of the Atlantic Ocean, at 6:01 p.m. EST. THEMIS, an acronym for Time History of Events and Macroscale Interactions during Substorms, consists of five identical probes that will track violent, colorful eruptions near the North Pole. This will be the largest number of scientific satellites NASA has ever launched into orbit aboard a single rocket. The THEMIS mission aims to unravel the mystery behind auroral substorms, an avalanche of magnetic energy powered by the solar wind that intensifies the northern and southern lights. The mission will investigate what causes auroras in the Earth’s atmosphere to dramatically change from slowly shimmering waves of light to wildly shifting streaks of bright color. Photo credit: NASA/Regina MItchell-Ryall, Robert Murray, Tony Gray

KSC-07pd0418

NASA Image and Video Library

2007-02-16

KENNEDY SPACE CENTER, FLA. -- In this close-up aerial view, the Delta II rocket with the THEMIS spacecraft atop sits ready for launch on Pad 17-B at Cape Canaveral Air Force Station. THEMIS, an acronym for Time History of Events and Macroscale Interactions during Substorms, consists of five identical probes that will track violent, colorful eruptions near the North Pole. This will be the largest number of scientific satellites NASA has ever launched into orbit aboard a single rocket. The THEMIS mission aims to unravel the mystery behind auroral substorms, an avalanche of magnetic energy powered by the solar wind that intensifies the northern and southern lights. The mission will investigate what causes auroras in the Earth’s atmosphere to dramatically change from slowly shimmering waves of light to wildly shifting streaks of bright color. Launch is scheduled for 6:05 p.m. Photo credit: NASA/George Shelton

Delta II THEMIS Pre-Launch

NASA Image and Video Library

2002-01-01

In this close-up aerial view, the Delta II rocket with the THEMIS spacecraft atop sits ready for launch on Pad 17-B at Cape Canaveral Air Force Station as the mobile service tower begins to move away. THEMIS, an acronym for Time History of Events and Macroscale Interactions during Substorms, consists of five identical probes that will track violent, colorful eruptions near the North Pole. This will be the largest number of scientific satellites NASA has ever launched into orbit aboard a single rocket. The THEMIS mission aims to unravel the mystery behind auroral substorms, an avalanche of magnetic energy powered by the solar wind that intensifies the northern and southern lights. The mission will investigate what causes auroras in the Earth’s atmosphere to dramatically change from slowly shimmering waves of light to wildly shifting streaks of bright color. Launch is scheduled for 6:05 p.m.

KSC-07pd0417

NASA Image and Video Library

2007-02-16

KENNEDY SPACE CENTER, FLA. -- In this close-up aerial view, the Delta II rocket with the THEMIS spacecraft atop sits ready for launch on Pad 17-B at Cape Canaveral Air Force Station as the mobile service tower moves away from the pad. THEMIS, an acronym for Time History of Events and Macroscale Interactions during Substorms, consists of five identical probes that will track violent, colorful eruptions near the North Pole. This will be the largest number of scientific satellites NASA has ever launched into orbit aboard a single rocket. The THEMIS mission aims to unravel the mystery behind auroral substorms, an avalanche of magnetic energy powered by the solar wind that intensifies the northern and southern lights. The mission will investigate what causes auroras in the Earth’s atmosphere to dramatically change from slowly shimmering waves of light to wildly shifting streaks of bright color. Launch is scheduled for 6:05 p.m. Photo credit: NASA/George Shelton

KSC-07pd0419

NASA Image and Video Library

2007-02-16

KENNEDY SPACE CENTER, FLA. -- In this aerial view, the Delta II rocket with the THEMIS spacecraft sits ready for launch on Pad 17-B at Cape Canaveral Air Force Station, as the mobile service tower moves away from the pad. THEMIS, an acronym for Time History of Events and Macroscale Interactions during Substorms, consists of five identical probes that will track violent, colorful eruptions near the North Pole. This will be the largest number of scientific satellites NASA has ever launched into orbit aboard a single rocket. The THEMIS mission aims to unravel the mystery behind auroral substorms, an avalanche of magnetic energy powered by the solar wind that intensifies the northern and southern lights. The mission will investigate what causes auroras in the Earth’s atmosphere to dramatically change from slowly shimmering waves of light to wildly shifting streaks of bright color. Launch is scheduled for 6:05 p.m. Photo credit: NASA/George Shelton

KSC-07pd0438

NASA Image and Video Library

2007-02-17

KENNEDY SPACE CENTER, FLA. -- At Cape Canaveral Air Force Station, clouds of smoke encompass the Delta II rocket with NASA's THEMIS spacecraft aboard as it blasts off Pad 17-B, in sight of the Atlantic Ocean, at 6:01 p.m. EST. THEMIS, an acronym for Time History of Events and Macroscale Interactions during Substorms, consists of five identical probes that will track violent, colorful eruptions near the North Pole. This will be the largest number of scientific satellites NASA has ever launched into orbit aboard a single rocket. The THEMIS mission aims to unravel the mystery behind auroral substorms, an avalanche of magnetic energy powered by the solar wind that intensifies the northern and southern lights. The mission will investigate what causes auroras in the Earth’s atmosphere to dramatically change from slowly shimmering waves of light to wildly shifting streaks of bright color. Photo credit: NASA/Regina Mitchell-Ryall, Robert Murray, Tony Gray

The effect of cosmic-ray acceleration on supernova blast wave dynamics

NASA Astrophysics Data System (ADS)

Pais, M.; Pfrommer, C.; Ehlert, K.; Pakmor, R.

2018-05-01

Non-relativistic shocks accelerate ions to highly relativistic energies provided that the orientation of the magnetic field is closely aligned with the shock normal (quasi-parallel shock configuration). In contrast, quasi-perpendicular shocks do not efficiently accelerate ions. We model this obliquity-dependent acceleration process in a spherically expanding blast wave setup with the moving-mesh code AREPO for different magnetic field morphologies, ranging from homogeneous to turbulent configurations. A Sedov-Taylor explosion in a homogeneous magnetic field generates an oblate ellipsoidal shock surface due to the slower propagating blast wave in the direction of the magnetic field. This is because of the efficient cosmic ray (CR) production in the quasi-parallel polar cap regions, which softens the equation of state and increases the compressibility of the post-shock gas. We find that the solution remains self-similar because the ellipticity of the propagating blast wave stays constant in time. This enables us to derive an effective ratio of specific heats for a composite of thermal gas and CRs as a function of the maximum acceleration efficiency. We finally discuss the behavior of supernova remnants expanding into a turbulent magnetic field with varying coherence lengths. For a maximum CR acceleration efficiency of about 15 per cent at quasi-parallel shocks (as suggested by kinetic plasma simulations), we find an average efficiency of about 5 per cent, independent of the assumed magnetic coherence length.

Analytic expressions for ULF wave radiation belt radial diffusion coefficients

PubMed Central

Ozeke, Louis G; Mann, Ian R; Murphy, Kyle R; Jonathan Rae, I; Milling, David K

2014-01-01

We present analytic expressions for ULF wave-derived radiation belt radial diffusion coefficients, as a function of L and Kp, which can easily be incorporated into global radiation belt transport models. The diffusion coefficients are derived from statistical representations of ULF wave power, electric field power mapped from ground magnetometer data, and compressional magnetic field power from in situ measurements. We show that the overall electric and magnetic diffusion coefficients are to a good approximation both independent of energy. We present example 1-D radial diffusion results from simulations driven by CRRES-observed time-dependent energy spectra at the outer boundary, under the action of radial diffusion driven by the new ULF wave radial diffusion coefficients and with empirical chorus wave loss terms (as a function of energy, Kp and L). There is excellent agreement between the differential flux produced by the 1-D, Kp-driven, radial diffusion model and CRRES observations of differential electron flux at 0.976 MeV—even though the model does not include the effects of local internal acceleration sources. Our results highlight not only the importance of correct specification of radial diffusion coefficients for developing accurate models but also show significant promise for belt specification based on relatively simple models driven by solar wind parameters such as solar wind speed or geomagnetic indices such as Kp. Key Points Analytic expressions for the radial diffusion coefficients are presented The coefficients do not dependent on energy or wave m value The electric field diffusion coefficient dominates over the magnetic PMID:26167440

Application of Wave Distribution Function Method to the ERG/PWE Data

NASA Astrophysics Data System (ADS)

Ota, M.; Kasahara, Y.; Matsuda, S.; Kojima, H.; Matsuoka, A.; Hikishima, M.; Kasaba, Y.; Ozaki, M.; Yagitani, S.; Tsuchiya, F.; Kumamoto, A.

2017-12-01

The ERG (Arase) satellite was launched on 20 December 2016 to study acceleration and loss mechanisms of relativistic electrons in the Earth's magnetosphere. The Plasma Wave Experiment (PWE), which is one of the science instruments on board the ERG satellite, measures electric field and magnetic field. The PWE consists of three sub-systems; EFD (Electric Field Detector), OFA/WFC (Onboard Frequency Analyzer and Waveform Capture), and HFA (High Frequency Analyzer).The OFA/WFC measures electromagnetic field spectra and raw waveforms in the frequency range from few Hz to 20 kHz. The OFA produces three kind of data; OFA-SPEC (power spectrum), OFA-MATRIX (spectral matrix), and OFA-COMPLEX (complex spectrum). The OFA-MATRIX measures ensemble averaged complex cross-spectra of two electric field components, and of three magnetic field components. The OFA-COMPLEX measures instantaneous complex spectra of electric and magnetic fields. These data are produced every 8 seconds in the nominal mode, and it can be used for polarization analysis and wave propagation direction finding.In general, spectral matrix composed by cross-spectra of observed signals is used for direction finding, and many algorithms have been proposed. For example, Means method and SVD method can be applied on the assumption that the spectral matrix is consists of a single plane wave, while wave distribution function (WDF) method is applicable even to the data in which multiple numbers of plane waves are simultaneously included. In this presentation, we introduce the results when the WDF method is applied to the ERG/PWE data.

SYNTHETIC OBSERVATIONS OF MAGNETIC FIELDS IN PROTOSTELLAR CORES

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

Lee, Joyce W. Y.; Hull, Charles L. H.; Offner, Stella S. R., E-mail: chat.hull@cfa.harvard.edu, E-mail: jwyl1g12@soton.ac.uk

The role of magnetic fields in the early stages of star formation is not well constrained. In order to discriminate between different star formation models, we analyze 3D magnetohydrodynamic simulations of low-mass cores and explore the correlation between magnetic field orientation and outflow orientation over time. We produce synthetic observations of dust polarization at resolutions comparable to millimeter-wave dust polarization maps observed by the Combined Array for Research in Millimeter-wave Astronomy and compare these with 2D visualizations of projected magnetic field and column density. Cumulative distribution functions of the projected angle between the magnetic field and outflow show different degreesmore » of alignment in simulations with differing mass-to-flux ratios. The distribution function for the less magnetized core agrees with observations finding random alignment between outflow and field orientations, while the more magnetized core exhibits stronger alignment. We find that fractional polarization increases when the system is viewed such that the magnetic field is close to the plane of the sky, and the values of fractional polarization are consistent with observational measurements. The simulation outflow, which reflects the underlying angular momentum of the accreted gas, changes direction significantly over over the first ∼0.1 Myr of evolution. This movement could lead to the observed random alignment between outflows and the magnetic fields in protostellar cores.« less

Trial wave functions for a composite Fermi liquid on a torus

NASA Astrophysics Data System (ADS)

Fremling, M.; Moran, N.; Slingerland, J. K.; Simon, S. H.

2018-01-01

We study the two-dimensional electron gas in a magnetic field at filling fraction ν =1/2 . At this filling the system is in a gapless state which can be interpreted as a Fermi liquid of composite fermions. We construct trial wave functions for the system on a torus, based on this idea, and numerically compare these to exact wave functions for small systems found by exact diagonalization. We find that the trial wave functions give an excellent description of the ground state of the system, as well as its charged excitations, in all momentum sectors. We analyze the dispersion of the composite fermions and the Berry phase associated with dragging a single fermion around the Fermi surface and comment on the implications of our results for the current debate on whether composite fermions are Dirac fermions.

Color-coded visualization of magnetic resonance imaging multiparametric maps

NASA Astrophysics Data System (ADS)

Kather, Jakob Nikolas; Weidner, Anja; Attenberger, Ulrike; Bukschat, Yannick; Weis, Cleo-Aron; Weis, Meike; Schad, Lothar R.; Zöllner, Frank Gerrit

2017-01-01

Multiparametric magnetic resonance imaging (mpMRI) data are emergingly used in the clinic e.g. for the diagnosis of prostate cancer. In contrast to conventional MR imaging data, multiparametric data typically include functional measurements such as diffusion and perfusion imaging sequences. Conventionally, these measurements are visualized with a one-dimensional color scale, allowing only for one-dimensional information to be encoded. Yet, human perception places visual information in a three-dimensional color space. In theory, each dimension of this space can be utilized to encode visual information. We addressed this issue and developed a new method for tri-variate color-coded visualization of mpMRI data sets. We showed the usefulness of our method in a preclinical and in a clinical setting: In imaging data of a rat model of acute kidney injury, the method yielded characteristic visual patterns. In a clinical data set of N = 13 prostate cancer mpMRI data, we assessed diagnostic performance in a blinded study with N = 5 observers. Compared to conventional radiological evaluation, color-coded visualization was comparable in terms of positive and negative predictive values. Thus, we showed that human observers can successfully make use of the novel method. This method can be broadly applied to visualize different types of multivariate MRI data.

A "Bit" of Quantum Mechanics

ERIC Educational Resources Information Center

Oss, Stefano; Rosi, Tommaso

2015-01-01

We have developed an app for iOS-based smart-phones/tablets that allows a 3-D, complex phase-based colorful visualization of hydrogen atom wave functions. Several important features of the quantum behavior of atomic orbitals can easily be made evident, thus making this app a useful companion in introductory modern physics classes. There are many…

Ultra-Flexibility and Unusual Electronic, Magnetic and Chemical Properties of Waved Graphenes and Nanoribbons

PubMed Central

Pan, Hui; Chen, Bin

2014-01-01

Two-dimensional materials have attracted increasing attention because of their particular properties and potential applications in next-generation nanodevices. In this work, we investigate the physical and chemical properties of waved graphenes/nanoribbons based on first-principles calculations. We show that waved graphenes are compressible up to a strain of 50% and ultra-flexible because of the vanishing in-plane stiffness. The conductivity of waved graphenes is reduced due to charge decoupling under high compression. Our analysis of pyramidalization angles predicts that the chemistry of waved graphenes can be easily controlled by modulating local curvatures. We further demonstrate that band gaps of armchair waved graphene nanoribbons decrease with the increase of compression if they are asymmetrical in geometry, while increase if symmetrical. For waved zigzag nanoribbons, their anti-ferromagnetic states are strongly enhanced by increasing compression. The versatile functions of waved graphenes enable their applications in multi-functional nanodevices and sensors. PMID:24569444

Quantum Theory of Orbital Magnetization and Its Generalization to Interacting Systems

NASA Astrophysics Data System (ADS)

Shi, Junren; Vignale, G.; Xiao, Di; Niu, Qian

2007-11-01

Based on standard perturbation theory, we present a full quantum derivation of the formula for the orbital magnetization in periodic systems. The derivation is generally valid for insulators with or without a Chern number, for metals at zero or finite temperatures, and at weak as well as strong magnetic fields. The formula is shown to be valid in the presence of electron-electron interaction, provided the one-electron energies and wave functions are calculated self-consistently within the framework of the exact current and spin-density functional theory.

Study of Equatorial Ionospheric irregularities and Mapping of Electron Density Profiles and Ionograms

DTIC Science & Technology

2012-03-09

equation is a product of a complex basis vector in Jackson and a linear combination of plane wave functions. We convert both the amplitudes and the...wave function arguments from complex scalars to complex vectors . This conversion allows us to separate the electric field vector and the imaginary...magnetic field vector , because exponentials of imaginary scalars convert vectors to imaginary vectors and vice versa, while ex- ponentials of imaginary

The Caltech experimental investigation of fast 3D non-equilbrium dynamics: an overview

NASA Astrophysics Data System (ADS)

Bellan, Paul; Shikama, Taiichi; Chai, Kilbyoung; Ha, Bao; Chaplin, Vernon; Kendall, Mark; Moser, Auna; Stenson, Eve; Tobin, Zachary; Zhai, Xiang

2012-10-01

The formation and dynamics of writhing, plasma-filled, twisted open magnetic flux tubes is being investigated using pulsed-power laboratory experiments. This work is relevant to solar corona loops, astrophysical jets, spheromak formation, and open field lines in tokamaks and RFP's. MHD forces have been observed to drive fast axial plasma flows into the flux tube from the boundary it intercepts. These flows fill the flux tube with plasma while simultaneously injecting linked frozen-in azimuthal flux; helicity injection is thus associated with mass injection. Recent results include observation of a secondary instability (Rayleigh-Taylor driven by the effective gravity of an exponentially growing kink mode), color-coded plasmas manifesting bidirectional axial flows in a geometry similar to a solar corona loop, and spectroscopic measurements of the internal vector magnetic field. Experiments underway include investigating how an external magnetic field straps down a solar loop, investigation of the details of the Rayleigh-Taylor instability, development of a fast EUV movie camera, increasing the jet velocity, excitation of Alfven waves, and investigating 3D magnetic reconnection.

Automated detection system of single nucleotide polymorphisms using two kinds of functional magnetic nanoparticles

NASA Astrophysics Data System (ADS)

Liu, Hongna; Li, Song; Wang, Zhifei; Li, Zhiyang; Deng, Yan; Wang, Hua; Shi, Zhiyang; He, Nongyue

2008-11-01

Single nucleotide polymorphisms (SNPs) comprise the most abundant source of genetic variation in the human genome wide codominant SNPs identification. Therefore, large-scale codominant SNPs identification, especially for those associated with complex diseases, has induced the need for completely high-throughput and automated SNP genotyping method. Herein, we present an automated detection system of SNPs based on two kinds of functional magnetic nanoparticles (MNPs) and dual-color hybridization. The amido-modified MNPs (NH 2-MNPs) modified with APTES were used for DNA extraction from whole blood directly by electrostatic reaction, and followed by PCR, was successfully performed. Furthermore, biotinylated PCR products were captured on the streptavidin-coated MNPs (SA-MNPs) and interrogated by hybridization with a pair of dual-color probes to determine SNP, then the genotype of each sample can be simultaneously identified by scanning the microarray printed with the denatured fluorescent probes. This system provided a rapid, sensitive and highly versatile automated procedure that will greatly facilitate the analysis of different known SNPs in human genome.

Physics Notes.

ERIC Educational Resources Information Center

School Science Review, 1983

1983-01-01

Describes computer measurement of capacitor charge decay, change of fringe width with color, computer simulation of color mixing, Doppler effect/carrier waves, gravitational waves, microwave apparatus, computer simulation of Brownian motion, search coils and problems with the teaching of the relationships of velocity, frequency, and wavelength in…

Model of electron lifetimes inside the plasmasphere calculated using a CRRES derived hiss wave amplitude model

NASA Astrophysics Data System (ADS)

Orlova, Ksenia; Spasojevic, Maria; Shprits, Yuri

Particle populations in the inner magnetosphere can change by orders of magnitude on very short time scales. For the last decade observations and theoretical computations showed that resonant interaction of electrons with various plasma waves plays an important role in acceleration and loss mechanisms. Using data from the CRRES plasma wave experiment, we develop quadratic fits to the mean of the wave amplitude squared for plasmaspheric hiss as a function of geomagnetic activity (Kp) and magnetic latitude (lambda) for the dayside (6

Multifocal and full-field electroretinogram changes associated with color-vision loss in mercury vapor exposure.

PubMed

Ventura, Dora F; Costa, Marcelo T V; Costa, Marcelo F; Berezovsky, Adriana; Salomão, Solange R; Simões, Ana Luíza; Lago, Marcos; Pereira, Luiz H M Canto; Faria, Marcília A M; De Souza, John M; Silveira, Luiz Carlos L

2004-01-01

We evaluated the color vision of mercury-contaminated patients and investigated possible retinal origins of losses using electroretinography. Participants were retired workers from a fluorescent lamp industry diagnosed with mercury contamination (n = 43) and age-matched controls (n = 21). Color discrimination was assessed with the Cambridge Colour Test (CCT). Retinal function was evaluated by using the ISCEV protocol for full-field electroretinography (full-field ERG), as well as by means of multifocal electroretinography (mfERG). Color-vision losses assessed by the CCT consisted of higher color-discrimination thresholds along the protan, deutan, and tritan axes and significantly larger discrimination ellipses in mercury-exposed patients compared to controls. Full-field ERG amplitudes from patients were smaller than those of the controls for the scotopic response b-wave, maximum response, sum of oscillatory potentials (OPs), 30-Hz flicker response, and light-adapted cone response. OP amplitudes measured in patients were smaller than those of controls for O2 and O3. Multifocal ERGs recorded from ten randomly selected patients showed smaller N1-P1 amplitudes and longer latencies throughout the 25-deg central field. Full-field ERGs showed that scotopic, photopic, peripheral, and midperipheral retinal functions were affected, and the mfERGs indicated that central retinal function was also significantly depressed. To our knowledge, this is the first demonstration of retinal involvement in visual losses caused by mercury toxicity.

Pitch-angle diffusion of electrons through growing and propagating along a magnetic field electromagnetic wave in Earth's radiation belts

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

Choi, C.-R., E-mail: crchoi@kaist.ac.kr; Dokgo, K.; Min, K.-W.

The diffusion of electrons via a linearly polarized, growing electromagnetic (EM) wave propagating along a uniform magnetic field is investigated. The diffusion of electrons that interact with the growing EM wave is investigated through the autocorrelation function of the parallel electron acceleration in several tens of electron gyration timescales, which is a relatively short time compared with the bounce time of electrons between two mirror points in Earth's radiation belts. Furthermore, the pitch-angle diffusion coefficient is derived for the resonant and non-resonant electrons, and the effect of the wave growth on the electron diffusion is discussed. The results can bemore » applied to other problems related to local acceleration or the heating of electrons in space plasmas, such as in the radiation belts.« less

Facial color processing in the face-selective regions: an fMRI study.

PubMed

Nakajima, Kae; Minami, Tetsuto; Tanabe, Hiroki C; Sadato, Norihiro; Nakauchi, Shigeki

2014-09-01

Facial color is important information for social communication as it provides important clues to recognize a person's emotion and health condition. Our previous EEG study suggested that N170 at the left occipito-temporal site is related to facial color processing (Nakajima et al., [2012]: Neuropsychologia 50:2499-2505). However, because of the low spatial resolution of EEG experiment, the brain region is involved in facial color processing remains controversial. In the present study, we examined the neural substrates of facial color processing using functional magnetic resonance imaging (fMRI). We measured brain activity from 25 subjects during the presentation of natural- and bluish-colored face and their scrambled images. The bilateral fusiform face (FFA) area and occipital face area (OFA) were localized by the contrast of natural-colored faces versus natural-colored scrambled images. Moreover, region of interest (ROI) analysis showed that the left FFA was sensitive to facial color, whereas the right FFA and the right and left OFA were insensitive to facial color. In combination with our previous EEG results, these data suggest that the left FFA may play an important role in facial color processing. Copyright © 2014 Wiley Periodicals, Inc.

Pinning, rotation, and metastability of BiFeO 3 cycloidal domains in a magnetic field

DOE PAGES

Fishman, Randy S.

2018-01-03

Earlier models for the room-temperature multiferroic BiFeO 3 implicitly assumed that a very strong anisotropy restricts the domain wave vectors q to the threefold-symmetric axis normal to the static polarization P. However, recent measurements demonstrate that the domain wave vectors q rotate within the hexagonal plane normal to P away from the magnetic field orientation m. In this paper, we show that the previously neglected threefold anisotropy K 3 restricts the wave vectors to lie along the threefold axis in zero field. Taking m to lie along a threefold axis, the domain with q parallel to m remains metastable belowmore » B c1≈7 T. Due to the pinning of domains by nonmagnetic impurities, the wave vectors of the other two domains start to rotate away from m above 5.6 T, when the component of the torque τ=M×B along P exceeds a threshold value τ pin. Since τ=0 when m⊥q, the wave vectors of those domains never become completely perpendicular to the magnetic field. Our results explain recent measurements of the critical field as a function of field orientation, small-angle neutron scattering measurements of the wave vectors, as well as spectroscopic measurements with m along a threefold axis. Finally, the model developed in this paper also explains how the three multiferroic domains of BiFeO 3 for a fixed P can be manipulated by a magnetic field.« less

Pinning, rotation, and metastability of BiFeO3 cycloidal domains in a magnetic field

NASA Astrophysics Data System (ADS)

Fishman, Randy S.

2018-01-01

Earlier models for the room-temperature multiferroic BiFeO3 implicitly assumed that a very strong anisotropy restricts the domain wave vectors q to the threefold-symmetric axis normal to the static polarization P . However, recent measurements demonstrate that the domain wave vectors q rotate within the hexagonal plane normal to P away from the magnetic field orientation m . We show that the previously neglected threefold anisotropy K3 restricts the wave vectors to lie along the threefold axis in zero field. Taking m to lie along a threefold axis, the domain with q parallel to m remains metastable below Bc 1≈7 T. Due to the pinning of domains by nonmagnetic impurities, the wave vectors of the other two domains start to rotate away from m above 5.6 T, when the component of the torque τ =M ×B along P exceeds a threshold value τpin. Since τ =0 when m ⊥q , the wave vectors of those domains never become completely perpendicular to the magnetic field. Our results explain recent measurements of the critical field as a function of field orientation, small-angle neutron scattering measurements of the wave vectors, as well as spectroscopic measurements with m along a threefold axis. The model developed in this paper also explains how the three multiferroic domains of BiFeO3 for a fixed P can be manipulated by a magnetic field.

Pinning, rotation, and metastability of BiFeO 3 cycloidal domains in a magnetic field

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

Fishman, Randy S.

Earlier models for the room-temperature multiferroic BiFeO 3 implicitly assumed that a very strong anisotropy restricts the domain wave vectors q to the threefold-symmetric axis normal to the static polarization P. However, recent measurements demonstrate that the domain wave vectors q rotate within the hexagonal plane normal to P away from the magnetic field orientation m. In this paper, we show that the previously neglected threefold anisotropy K 3 restricts the wave vectors to lie along the threefold axis in zero field. Taking m to lie along a threefold axis, the domain with q parallel to m remains metastable belowmore » B c1≈7 T. Due to the pinning of domains by nonmagnetic impurities, the wave vectors of the other two domains start to rotate away from m above 5.6 T, when the component of the torque τ=M×B along P exceeds a threshold value τ pin. Since τ=0 when m⊥q, the wave vectors of those domains never become completely perpendicular to the magnetic field. Our results explain recent measurements of the critical field as a function of field orientation, small-angle neutron scattering measurements of the wave vectors, as well as spectroscopic measurements with m along a threefold axis. Finally, the model developed in this paper also explains how the three multiferroic domains of BiFeO 3 for a fixed P can be manipulated by a magnetic field.« less

Significant initial results from the environmental measurements experiment on ATS-6

NASA Technical Reports Server (NTRS)

Fritz, T. A.; Arthur, C. W.; Blake, J. B.; Coleman, P. J., Jr.; Corrigan, J. P.; Cummings, W. D.; Deforest, S. E.; Erickson, K. N.; Konradi, A.; Lennartsson, W.

1977-01-01

The Applications Technology Satellite (ATS-6), launched into synchronous orbit on 30 May 1974, carried a set of six particle detectors and a triaxial fluxgate magnetometer. The particle detectors were able to determine the ion and electron distribution functions from 1 to greater than 10 to the 8th power eV. It was found that the magnetic field is weaker and more tilted than predicted by models which neglect internal plasma and that there is a seasonal dependence to the magnitude and tilt. ATS-6 magnetic field measurements showed the effects of field-aligned currents associated with substorms, and large fluxes of field-aligned particles were observed with the particle detectors. Encounters with the plasmasphere revealed the existence of warm plasma with temperatures up to 30 eV. A variety of correlated waves in both the particles and fields were observed: pulsation continuous oscillations, seen predominantly in the plasmasphere bulge; ultralow frequency (ULF) standing waves; ring current proton ULF waves; and low frequency waves that modulate the energetic electrons. In additon, large scale waves on the energetic-ion-trapping boundary were observed, and the intensity of energetic electrons was modulated in association with the passage of sector boundaries of the interplanetary magnetic field.

Spontaneous long-range calcium waves in developing butterfly wings.

PubMed

Ohno, Yoshikazu; Otaki, Joji M

2015-03-25

Butterfly wing color patterns emerge as the result of a regular arrangement of scales produced by epithelial scale cells at the pupal stage. These color patterns and scale arrangements are coordinated throughout the wing. However, the mechanism by which the development of scale cells is controlled across the entire wing remains elusive. In the present study, we used pupal wings of the blue pansy butterfly, Junonia orithya, which has distinct eyespots, to examine the possible involvement of Ca(2+) waves in wing development. Here, we demonstrate that the developing pupal wing tissue of the blue pansy butterfly displayed spontaneous low-frequency Ca(2+) waves in vivo that propagated slowly over long distances. Some waves appeared to be released from the immediate peripheries of the prospective eyespot and discal spot, though it was often difficult to identify the specific origins of these waves. Physical damage, which is known to induce ectopic eyespots, led to the radiation of Ca(2+) waves from the immediate periphery of the damaged site. Thapsigargin, which is a specific inhibitor of Ca(2+)-ATPases in the endoplasmic reticulum, induced an acute increase in cytoplasmic Ca(2+) levels and halted the spontaneous Ca(2+) waves. Additionally, thapsigargin-treated wings showed incomplete scale development as well as other scale and color pattern abnormalities. We identified a novel form of Ca(2+) waves, spontaneous low-frequency slow waves, which travel over exceptionally long distances. Our results suggest that spontaneous Ca(2+) waves play a critical role in the coordinated development of scale arrangements and possibly in color pattern formation in butterflies.

Novel Imaging Method of Continuous Shear Wave by Ultrasonic Color Flow Mapping

NASA Astrophysics Data System (ADS)

Yamakoshi, Yoshiki; Yamamoto, Atsushi; Yuminaka, Yasushi

Shear wave velocity measurement is a promising method in evaluation of tissue stiffness. Several methods have been developed to measure the shear wave velocity, however, it is difficult to obtain quantitative shear wave image in real-time by low cost system. In this paper, a novel shear wave imaging method for continuous shear wave is proposed. This method uses a color flow imaging which is used in ultrasonic imaging system to obtain shear wave's wavefront map. Two conditions, shear wave frequency condition and shear wave displacement amplitude condition, are required, however, these conditions are not severe restrictions in most applications. Using the proposed method, shear wave velocity of trapezius muscle is measured. The result is consistent with the velocity which is calculated from shear elastic modulus measured by ARFI method.

Many-body calculations of low energy eigenstates in magnetic and periodic systems with self healing diffusion Monte Carlo: steps beyond the fixed-phase

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

Reboredo, Fernando A.

The self-healing diffusion Monte Carlo algorithm (SHDMC) [Reboredo, Hood and Kent, Phys. Rev. B {\\bf 79}, 195117 (2009), Reboredo, {\\it ibid.} {\\bf 80}, 125110 (2009)] is extended to study the ground and excited states of magnetic and periodic systems. A recursive optimization algorithm is derived from the time evolution of the mixed probability density. The mixed probability density is given by an ensemble of electronic configurations (walkers) with complex weight. This complex weigh allows the amplitude of the fix-node wave function to move away from the trial wave function phase. This novel approach is both a generalization of SHDMC andmore » the fixed-phase approximation [Ortiz, Ceperley and Martin Phys Rev. Lett. {\\bf 71}, 2777 (1993)]. When used recursively it improves simultaneously the node and phase. The algorithm is demonstrated to converge to the nearly exact solutions of model systems with periodic boundary conditions or applied magnetic fields. The method is also applied to obtain low energy excitations with magnetic field or periodic boundary conditions. The potential applications of this new method to study periodic, magnetic, and complex Hamiltonians are discussed.« less

Magnetic assembly route to colloidal responsive photonic nanostructures.

PubMed

He, Le; Wang, Mingsheng; Ge, Jianping; Yin, Yadong

2012-09-18

Responsive photonic structures can respond to external stimuli by transmitting optical signals. Because of their important technological applications such as color signage and displays, biological and chemical sensors, security devices, ink and paints, military camouflage, and various optoelectronic devices, researchers have focused on developing these functional materials. Conventionally, self-assembled colloidal crystals containing periodically arranged dielectric materials have served as the predominant starting frameworks. Stimulus-responsive materials are incorporated into the periodic structures either as the initial building blocks or as the surrounding matrix so that the photonic properties can be tuned. Although researchers have proposed various versions of responsive photonic structures, the low efficiency of fabrication through self-assembly, narrow tunability, slow responses to the external stimuli, incomplete reversibility, and the challenge of integrating them into existing photonic devices have limited their practical application. In this Account, we describe how magnetic fields can guide the assembly of superparamagnetic colloidal building blocks into periodically arranged particle arrays and how the photonic properties of the resulting structures can be reversibly tuned by manipulating the external magnetic fields. The application of the external magnetic field instantly induces a strong magnetic dipole-dipole interparticle attraction within the dispersion of superparamagnetic particles, which creates one-dimensional chains that each contains a string of particles. The balance between the magnetic attraction and the interparticle repulsions, such as the electrostatic force, defines the interparticle separation. By employing uniform superparamagnetic particles of appropriate sizes and surface charges, we can create one-dimensional periodicity, which leads to strong optical diffraction. Acting remotely over a large distance, magnetic forces drove the rapid formation of colloidal photonic arrays with a wide range of interparticle spacing. They also allowed instant tuning of the photonic properties because they manipulated the interparticle force balance, which changed the orientation of the colloidal assemblies or their periodicity. This magnetically responsive photonic system provides a new platform for chromatic applications: these colloidal particles assemble instantly into ordered arrays with widely, rapidly, and reversibly tunable structural colors, which can be easily and rapidly fixed in a curable polymer matrix. Based on these unique features, we demonstrated many applications of this system, such as structural color printing, the fabrication of anticounterfeiting devices, switchable signage, and field-responsive color displays. We also extended this idea to rapidly organize uniform nonmagnetic building blocks into photonic structures. Using a stable ferrofluid of highly charged magnetic nanoparticles, we created virtual magnetic moments inside the nonmagnetic particles. This "magnetic hole" strategy greatly broadens the scope of the magnetic assembly approach to the fabrication of tunable photonic structures from various dielectric materials.

Wave Function and Emergent SU(2) Symmetry in the νT=1 Quantum Hall Bilayer

NASA Astrophysics Data System (ADS)

Lian, Biao; Zhang, Shou-Cheng

2018-02-01

We propose a trial wave function for the quantum Hall bilayer system of total filling factor νT=1 at a layer distance d to magnetic length ℓ ratio d /ℓ=κc 1≈1.1 , where the lowest charged excitation is known to have a level crossing. The wave function has two-particle correlations, which fit well with those in previous numerical studies, and can be viewed as a Bose-Einstein condensate of free excitons formed by composite bosons and anticomposite bosons in different layers. We show the free nature of these excitons indicating an emergent SU(2) symmetry for the composite bosons at d /ℓ=κc 1, which leads to the level crossing in low-lying charged excitations. We further show the overlap between the trial wave function, and the ground state of a small size exact diagonalization is peaked near d /ℓ=κc 1, which supports our theory.

GABAa and GABAc receptor-mediated modulation of responses to color stimuli: electroretinographic study in the turtle Emys orbicularis.

PubMed

Kupenova, Petia; Vitanova, Lily; Popova, Elka

2010-04-01

GABAergic transmission is involved in color coding in the retina. The specific contribution of different GABA receptors to spectral sensitivity of the retinal responses is not well characterized. We studied GABAa and GABAc receptor-mediated effects on the intensity-response functions of the electroretinographic ON (b-wave) and OFF (d-wave) responses to color stimuli. For this purpose, we compared the effects of GABAa receptor blockade by bicuculline with the effects of GABAa + GABAc receptor blockade by picrotoxin. The blockade of both GABAa and GABAc receptors caused an amplitude increase of the electroretinographic responses, but the effects of the two blockades depended in a specific manner on stimulus intensity and wavelength. The effects of GABAa receptor blockade showed distinct color ON/OFF asymmetry. The absolute and relative sensitivities of the ON responses to blue stimuli and OFF responses to red stimuli were increased to the greatest degree while the sensitivity of the ON responses to red stimuli and OFF responses to blue stimuli was least increased. In contrast, color ON/OFF asymmetry was not typical of the effects of GABAc receptor blockade. The most prominent GABAc effect was the sensitivity increase of the ON and OFF responses to blue stimuli and, to some lesser extent, to green stimuli. The results of this study indicate a specific role of GABAa and GABAc receptor-mediated influences in processing of chromatic information in the distal retina.

Plasma waves in the magnetic hole

NASA Technical Reports Server (NTRS)

Lin, Naiguo; Kellogg, P. J.; MacDowall, R.; Balogh, A.; Forsyth, R. J.; Phillips, J. L.; Pick, M.

1995-01-01

Magnetic holes in the solar wind, which are characterized by isolated local depressions in the magnetic field magnitude, have been observed previously. The Unified Radio and Plasma Wave (URAP) instrument of Ulysses has found that within such magnetic structures, electrostatic waves at kHz frequency and ultralow frequency electromagnetic waves are often excited and seen as short duration wave bursts. Most of these bursts occur near the ambient electron plasma frequency, which suggests that the waves are Langmuir waves. Such waves are usually excited by electron streams. Some evidence of the streaming of energetic electrons required for exciting Langmuir waves has been observed. These electrons may have originated at sources near the Sun, which would imply that the magnetic structures containing the waves would exist as long channels formed by field and plasma conditions near the Sun. On the other hand, the electrons could be suprathermal 'tails' from wave collapse processes occurring near the spacecraft. In either case, the Langmuir waves excited in the magnetic holes provide a measurement of the plasma density inside the holes. Low frequency electromagnetic waves, having frequencies of a fraction of the local electron cyclotron frequency, sometimes accompany the Langmuir waves observed in magnetic holes. Waves excited in this frequency range are very likely to be whistler-mode waves. They may have been excited by an electron temperature anisotropy which has been observed in the vicinity of the magnetic holes or generated through the decay of Langmuir waves.

Quasiclassical description of a superconductor with a spin density wave

NASA Astrophysics Data System (ADS)

Moor, A.; Volkov, A. F.; Efetov, K. B.

2011-04-01

We derive equations for the quasiclassical Green’s functions ǧ within a simple model of a two-band superconductor with a spin density wave (SDW). The elements of the matrix ǧ are the retarded, advanced, and Keldysh functions, each of which is an 8×8 matrix in the Gor’kov-Nambu, the spin, and the band space. In equilibrium, these equations are a generalization of the Eilenberger equation. On the basis of the derived equations, we analyze the Knight shift, the proximity, and the dc Josephson effects in the superconductors under consideration. The Knight shift is shown to depend on the orientation of the external magnetic field with respect to the direction of the vector of the magnetization of the SDW. The proximity effect is analyzed for an interface between a superconductor with the SDW and a normal metal. The function describing both superconducting and magnetic correlations is shown to penetrate the normal metal or a metal with the SDW due to the proximity effect. The dc Josephson current in an SSDW/N/SSDW junction is also calculated as a function of the phase difference φ. It is shown that in our model, the Josephson current does not depend on the mutual orientation of the magnetic moments in the superconductors SSDW and is proportional to sinφ. The dissipationless spin current jsp depends on the angle α between the magnetization vectors in the same way (jsp~sinα) and is not zero above the superconducting transition temperature.

Nonlinear Dust Acoustic Waves in a Magnetized Dusty Plasma with Trapped and Superthermal Electrons

NASA Astrophysics Data System (ADS)

Ahmadi, Abrishami S.; Nouri, Kadijani M.

2014-06-01

In this work, the effects of superthermal and trapped electrons on the oblique propagation of nonlinear dust-acoustic waves in a magnetized dusty (complex) plasma are investigated. The dynamic of electrons is simulated by the generalized Lorentzian (κ) distribution function (DF). The dust grains are cold and their dynamics are simulated by hydrodynamic equations. Using the standard reductive perturbation technique (RPT) a nonlinear modified Korteweg-de Vries (mKdV) equation is derived. Two types of solitary waves; fast and slow dust acoustic solitons, exist in this plasma. Calculations reveal that compressive solitary structures are likely to propagate in this plasma where dust grains are negatively (or positively) charged. The properties of dust acoustic solitons (DASs) are also investigated numerically.

Oblique ion-acoustic cnoidal waves in two temperature superthermal electrons magnetized plasma

NASA Astrophysics Data System (ADS)

Panwar, A.; Ryu, C. M.; Bains, A. S.

2014-12-01

A study is presented for the oblique propagation of ion acoustic cnoidal waves in a magnetized plasma consisting of cold ions and two temperature superthermal electrons modelled by kappa-type distributions. Using the reductive perturbation method, the nonlinear Korteweg de-Vries equation is derived, which further gives the solutions with a special type of cnoidal elliptical functions. Both compressive and rarefactive structures are found for these cnoidal waves. Nonlinear periodic cnoidal waves are explained in terms of plasma parameters depicting the Sagdeev potential and the phase curves. It is found that the density ratio of hot electrons to ions μ significantly modifies compressive/refractive wave structures. Furthermore, the combined effects of superthermality of cold and hot electrons κ c , κ h , cold to hot electron temperature ratio σ, angle of propagation and ion cyclotron frequency ωci have been studied in detail to analyze the height and width of compressive/refractive cnoidal waves. The findings in the present study could have important implications in understanding the physics of electrostatic wave structures in the Saturn's magnetosphere where two temperature superthermal electrons are present.

Topologically-protected one-way leaky waves in nonreciprocal plasmonic structures

NASA Astrophysics Data System (ADS)

Hassani Gangaraj, S. Ali; Monticone, Francesco

2018-03-01

We investigate topologically-protected unidirectional leaky waves on magnetized plasmonic structures acting as homogeneous photonic topological insulators. Our theoretical analyses and numerical experiments aim at unveiling the general properties of these exotic surface waves, and their nonreciprocal and topological nature. In particular, we study the behavior of topological leaky modes in stratified structures composed of a magnetized plasma at the interface with isotropic conventional media, and we show how to engineer their propagation and radiation properties, leading to topologically-protected backscattering-immune wave propagation, and highly directive and tunable radiation. Taking advantage of the non-trivial topological properties of these leaky modes, we also theoretically demonstrate advanced functionalities, including arbitrary re-routing of leaky waves on the surface of bodies with complex shapes, as well as the realization of topological leaky-wave (nano)antennas with isolated channels of radiation that are completely independent and separately tunable. Our findings help shedding light on the behavior of topologically-protected modes in open wave-guiding structures, and may open intriguing directions for future antenna generations based on topological structures, at microwaves and optical frequencies.

Solar eclipses.

NASA Astrophysics Data System (ADS)

Livingston, W.

The occasion of a total eclipse impacts the human observer with a bewildering rapid sequence of phenomena: mid-day cooling, failing light without accustomed color change, shadow-bands transiting the ground, cessation of bird sounds, possible frantic beating of jungle drums, Baily's beads, appearance of flame-like prominences, and most fantastic of all the solar corona. The author considers that although the corona is known to be 2 - 20(106)K, there is a lack of consensus on the heating mechanism, except the energy must be non-thermal and derived from surface and sub-surface convective motions. Theoreticians invoke the Joule dissipation of magnetic fields by Alfvén waves, electric currents in loop structures, or MHD turbulence. Although eclipse experiments to discriminate between these ideas generally fail, the sighting of 'plasmoids' was reported from the CFHT on Mauna Kea at the 1991 eclipse. Future experiments include: IR mapping of the coronal spectrum, spectroscopic velocity measurements, and the continued search for waves, nanoflares, and plasmoids.

Chromosomal rearrangement segregating with adrenoleukodystrophy: associated changes in color vision.

PubMed Central

Alpern, M; Sack, G H; Krantz, D H; Jenness, J; Zhang, H; Moser, H W

1993-01-01

A patient from a large kindred with adrenoleukodystrophy showed profound disturbance of color ordering, color matching, increment thresholds, and luminosity. Except for color matching, his performance was similar to blue-cone "monochromacy," an X chromosome-linked recessive retinal dystrophy in which color vision is dichromatic, mediated by the visual pigments of rods and short-wave-sensitive cones. Color matching, however, indicated that an abnormal rudimentary visual pigment was also present. This may reflect the presence of a recombinant visual pigment protein or altered regulation of residual pigment genes, due to DNA changes--deletion of the long-wave pigment gene and reorganized sequences 5' to the pigment gene cluster--that segregate with the metabolic defect in this kindred. PMID:8415729

Whistler wave generation by electron temperature anisotropy during asymmetric magnetic reconnection in space

NASA Astrophysics Data System (ADS)

Swerdlow, Josh; Yoo, Jongsoo; Kim, Eun-Hwa; Yamada, Masaaki; Ji, Hantao

2017-10-01

Generation of whistler waves during asymmetric reconnection is studied by analyzing data from a MMS (Magnetospheric Multiscale) event. In particular, the possible role of electron temperature anisotropy in excitation of whistler waves on the magnetosphere side is discussed. The local electron distribution function is fitted into a sum of bi-Maxwellian distribution functions. Then, the dispersion relation solver, WHAMP (waves in homogeneous, anisotropic, multicomponent plasmas), is used to obtain the local dispersion relation and growth rate of the whistler waves. We compare the theoretical calculations with the measured dispersion relation. This work was made possible by funding from the Department of Energy for the Summer Undergraduate Laboratory Internship (SULI) program. This work is supported by the US DOE Contract No. DE-AC02-09CH11466.

Global excitation of wave phenomena in a dissipative multiconstituent medium. I - Transfer function of the earth's thermosphere. II - Impulsive perturbations in the earth's thermosphere

NASA Technical Reports Server (NTRS)

Mayr, H. G.; Harris, I.; Herrero, F. A.; Varosi, F.

1984-01-01

A transfer function approach is taken in constructing a spectral model of the acoustic-gravity wave response in a multiconstituent thermosphere. The model is then applied to describing the thermospheric response to various sources around the globe. Zonal spherical harmonics serve to model the horizontal variations in propagating waves which, when integrated with respect to height, generate a transfer function for a vertical source distribution in the thermosphere. Four wave components are characterized as resonance phenomena and are associated with magnetic activity and ionospheric disturbances. The waves are either trapped or propagate, the latter becoming significant when possessing frequencies above 3 cycles/day. The energy input is distributed by thermospheric winds. The disturbances decay slowly, mainly due to heat conduction and diffusion. Gravity waves appear abruptly and are connected to a sudden switching on or off of a source. Turn off of a source coincides with a reversal of the local atmospheric circulation.

Relating Stellar Cycle Periods to Dynamo Calculations

NASA Technical Reports Server (NTRS)

Tobias, S. M.

1998-01-01

Stellar magnetic activity in slowly rotating stars is often cyclic, with the period of the magnetic cycle depending critically on the rotation rate and the convective turnover time of the star. Here we show that the interpretation of this law from dynamo models is not a simple task. It is demonstrated that the period is (unsurprisingly) sensitive to the precise type of non-linearity employed. Moreover the calculation of the wave-speed of plane-wave solutions does not (as was previously supposed) give an indication of the magnetic period in a more realistic dynamo model, as the changes in length-scale of solutions are not easily captured by this approach. Progress can be made, however, by considering a realistic two-dimensional model, in which the radial length-scale of waves is included. We show that it is possible in this case to derive a more robust relation between cycle period and dynamo number. For all the non-linearities considered in the most realistic model, the magnetic cycle period is a decreasing function of IDI (the amplitude of the dynamo number). However, discriminating between different non-linearities is difficult in this case and care must therefore be taken before advancing explanations for the magnetic periods of stars.

Shear wave mapping of skeletal muscle using shear wave wavefront reconstruction based on ultrasound color flow imaging

NASA Astrophysics Data System (ADS)

Yamakoshi, Yoshiki; Yamamoto, Atsushi; Kasahara, Toshihiro; Iijima, Tomohiro; Yuminaka, Yasushi

2015-07-01

We have proposed a quantitative shear wave imaging technique for continuous shear wave excitation. Shear wave wavefront is observed directly by color flow imaging using a general-purpose ultrasonic imaging system. In this study, the proposed method is applied to experiments in vivo, and shear wave maps, namely, the shear wave phase map, which shows the shear wave propagation inside the medium, and the shear wave velocity map, are observed for the skeletal muscle in the shoulder. To excite the shear wave inside the skeletal muscle of the shoulder, a hybrid ultrasonic wave transducer, which combines a small vibrator with an ultrasonic wave probe, is adopted. The shear wave velocity of supraspinatus muscle, which is measured by the proposed method, is 4.11 ± 0.06 m/s (N = 4). This value is consistent with those obtained by the acoustic radiation force impulse method.

Dynamics in the solar chromosphere as a function of the magnetic field topology

NASA Astrophysics Data System (ADS)

Karlsen, N.; Carlsson, M.

2002-06-01

We have looked at the coupling between the magnetic field and chromospheric dynamics. Observations with the SUMER spectrograph of the continuum radiation at 1319 Å have been correlated with simultaneous MDI magnetograms and dopplergrams in high resolution mode. We have used 7 different observing runs for our analysis, all from 1996. The absolute value of the magnetic field crossing the SUMER slit lies in the range 0-100 gauss. We observe a correlation between continuum intensity and magnetic field strength all the way to the sensitivity limit of MDI (about 2 G as 3σ in the mean value). Relative intensity fluctuations at frequencies corresponding to propagating acoustic waves (>4.5 mHz) have smaller amplitudes with increasing radiation temperature (or magnetic field strength). The absolute intensity fluctuations show an increase with increasing radiation temperature. These findings are consistent with a picture where a basic intensity level is set by a magnetic heating process even in the darkest internetwork areas with superimposed intensity variations caused by acoustic waves.

A highly optimized code for calculating atomic data at neutron star magnetic field strengths using a doubly self-consistent Hartree-Fock-Roothaan method

NASA Astrophysics Data System (ADS)

Schimeczek, C.; Engel, D.; Wunner, G.

2012-07-01

Our previously published code for calculating energies and bound-bound transitions of medium-Z elements at neutron star magnetic field strengths [D. Engel, M. Klews, G. Wunner, Comput. Phys. Comm. 180 (2009) 302-311] was based on the adiabatic approximation. It assumes a complete decoupling of the (fast) gyration of the electrons under the action of the magnetic field and the (slow) bound motion along the field under the action of the Coulomb forces. For the single-particle orbitals this implied that each is a product of a Landau state and an (unknown) longitudinal wave function whose B-spline coefficients were determined self-consistently by solving the Hartree-Fock equations for the many-electron problem on a finite-element grid. In the present code we go beyond the adiabatic approximation, by allowing the transverse part of each orbital to be a superposition of Landau states, while assuming that the longitudinal part can be approximated by the same wave function in each Landau level. Inserting this ansatz into the energy variational principle leads to a system of coupled equations in which the B-spline coefficients depend on the weights of the individual Landau states, and vice versa, and which therefore has to be solved in a doubly self-consistent manner. The extended ansatz takes into account the back-reaction of the Coulomb motion of the electrons along the field direction on their motion in the plane perpendicular to the field, an effect which cannot be captured by the adiabatic approximation. The new code allows for the inclusion of up to 8 Landau levels. This reduces the relative error of energy values as compared to the adiabatic approximation results by typically a factor of three (1/3 of the original error), and yields accurate results also in regions of lower neutron star magnetic field strengths where the adiabatic approximation fails. Further improvements in the code are a more sophisticated choice of the initial wave functions, which takes into account the shielding of the core potential for outer electrons by inner electrons, and an optimal finite-element decomposition of each individual longitudinal wave function. These measures largely enhance the convergence properties compared to the previous code, and lead to speed-ups by factors up to two orders of magnitude compared with the implementation of the Hartree-Fock-Roothaan method used by Engel and Wunner in [D. Engel, G. Wunner, Phys. Rev. A 78 (2008) 032515]. New version program summaryProgram title: HFFER II Catalogue identifier: AECC_v2_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AECC_v2_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.html No. of lines in distributed program, including test data, etc.: v 55 130 No. of bytes in distributed program, including test data, etc.: 293 700 Distribution format: tar.gz Programming language: Fortran 95 Computer: Cluster of 1-13 HP Compaq dc5750 Operating system: Linux Has the code been vectorized or parallelized?: Yes, parallelized using MPI directives. RAM: 1 GByte per node Classification: 2.1 External routines: MPI/GFortran, LAPACK, BLAS, FMlib (included in the package) Catalogue identifier of previous version: AECC_v1_0 Journal reference of previous version: Comput. Phys. Comm. 180 (2009) 302 Does the new version supersede the previous version?: Yes Nature of problem: Quantitative modellings of features observed in the X-ray spectra of isolated magnetic neutron stars are hampered by the lack of sufficiently large and accurate databases for atoms and ions up to the last fusion product, iron, at strong magnetic field strengths. Our code is intended to provide a powerful tool for calculating energies and oscillator strengths of medium-Z atoms and ions at neutron star magnetic field strengths with sufficient accuracy in a routine way to create such databases. Solution method: The Slater determinants of the atomic wave functions are constructed from single-particle orbitals ψi which are products of a wave function in the z direction (the direction of the magnetic field) and an expansion of the wave function perpendicular to the direction of the magnetic field in terms of Landau states, ψi(ρ,φ,z)=Pi(z)∑n=0NLtinϕni(ρ,φ). The tin are expansion coefficients, and the expansion is cut off at some maximum Landau level quantum number n=NL. In the previous version of the code only the lowest Landau level was included (NL=0), in the new version NL can take values of up to 7. As in the previous version of the code, the longitudinal wave functions are expanded in terms of sixth-order B-splines on finite elements on the z axis, with a combination of equidistant and quadratically widening element borders. Both the B-spline expansion coefficients and the Landau weights tin of all orbitals have to be determined in a doubly self-consistent way: For a given set of Landau weights tin, the system of linear equations for the B-spline expansion coefficients, which is equivalent to the Hartree-Fock equations for the longitudinal wave functions, is solved numerically. In the second step, for frozen B-spline coefficients new Landau weights are determined by minimizing the total energy with respect to the Landau expansion coefficients. Both steps require solving non-linear eigenvalue problems of Roothaan type. The procedure is repeated until convergence of both the B-spline coefficients and the Landau weights is achieved. Reasons for new version: The former version of the code was restricted to the adiabatic approximation, which assumes the quantum dynamics of the electrons in the plane perpendicular to the magnetic field to be fixed in the lowest Landau level, n=0. This approximation is valid only if the magnetic field strengths are large compared to the reference magnetic field BZ, for a nuclear charge Z,BZ=Z24.70108×105 T. Summary of revisions: In the new version, the transverse parts of the orbitals are expanded in terms of Landau states up to n=7, and the expansion coefficients are determined, together with the longitudinal wave functions, in a doubly self-consistent way. Thus the back-reaction of the quantum dynamics along the magnetic field direction on the quantum dynamics in the plane perpendicular to it is taken into account. The new ansatz not only increases the accuracy of the results for energy values and transition strengths obtained so far, but also allows their calculation for magnetic field strengths down to B≳BZ, where the adiabatic approximation fails. Restrictions: Intense magnetic field strengths are required, since the expansion of the transverse single-particle wave functions using 8 Landau levels will no longer produce accurate results if the scaled magnetic field strength parameter βZ=B/BZ becomes much smaller than unity. Unusual features: A huge program speed-up is achieved by making use of pre-calculated binary files. These can be calculated with additional programs provided with this package. Running time: 1-30 min.

[Associative Learning between Orientation and Color in Early Visual Areas].

PubMed

Amano, Kaoru; Shibata, Kazuhisa; Kawato, Mitsuo; Sasaki, Yuka; Watanabe, Takeo

2017-08-01

Associative learning is an essential neural phenomenon where the contingency of different items increases after training. Although associative learning has been found to occur in many brain regions, there is no clear evidence that associative learning of visual features occurs in early visual areas. Here, we developed an associative decoded functional magnetic resonance imaging (fMRI) neurofeedback (A-DecNef) to determine whether associative learning of color and orientation can be induced in early visual areas. During the three days' training, A-DecNef induced fMRI signal patterns that corresponded to a specific target color (red) mostly in early visual areas while a vertical achromatic grating was simultaneously, physically presented to participants. Consequently, participants' perception of "red" was significantly more frequently than that of "green" in an achromatic vertical grating. This effect was also observed 3 to 5 months after training. These results suggest that long-term associative learning of two different visual features such as color and orientation, was induced most likely in early visual areas. This newly extended technique that induces associative learning may be used as an important tool for understanding and modifying brain function, since associations are fundamental and ubiquitous with respect to brain function.

Influence of the properties of soft collective spin wave modes on the magnetization reversal in finite arrays of dipolarly coupled magnetic dots

NASA Astrophysics Data System (ADS)

Stebliy, Maxim; Ognev, Alexey; Samardak, Alexander; Chebotkevich, Ludmila; Verba, Roman; Melkov, Gennadiy; Tiberkevich, Vasil; Slavin, Andrei

2015-06-01

Magnetization reversal in finite chains and square arrays of closely packed cylindrical magnetic dots, having vortex ground state in the absence of the external bias field, has been studied experimentally by measuring static hysteresis loops, and also analyzed theoretically. It has been shown that the field Bn of a vortex nucleation in a dot as a function of the finite number N of dots in the array's side may exhibit a monotonic or an oscillatory behavior depending on the array geometry and the direction of the external bias magnetic field. The oscillations in the dependence Bn(N) are shown to be caused by the quantization of the collective soft spin wave mode, which corresponds to the vortex nucleation in a finite array of dots. These oscillations are directly related to the form and symmetry of the dispersion law of the soft SW mode: the oscillation could appear only if the minimum of the soft mode spectrum is not located at any of the symmetric points inside the first Brillouin zone of the array's lattice. Thus, the purely static measurements of the hysteresis loops in finite arrays of coupled magnetic dots can yield important information about the properties of the collective spin wave excitations in these arrays.

Mathematical Development and Computational Analysis of Harmonic Phase-Magnetic Resonance Imaging (HARP-MRI) Based on Bloch Nuclear Magnetic Resonance (NMR) Diffusion Model for Myocardial Motion.

PubMed

Dada, Michael O; Jayeoba, Babatunde; Awojoyogbe, Bamidele O; Uno, Uno E; Awe, Oluseyi E

2017-09-13

Harmonic Phase-Magnetic Resonance Imaging (HARP-MRI) is a tagged image analysis method that can measure myocardial motion and strain in near real-time and is considered a potential candidate to make magnetic resonance tagging clinically viable. However, analytical expressions of radially tagged transverse magnetization in polar coordinates (which is required to appropriately describe the shape of the heart) have not been explored because the physics required to directly connect myocardial deformation of tagged Nuclear Magnetic Resonance (NMR) transverse magnetization in polar geometry and the appropriate harmonic phase parameters are not yet available. The analytical solution of Bloch NMR diffusion equation in spherical geometry with appropriate spherical wave tagging function is important for proper analysis and monitoring of heart systolic and diastolic deformation with relevant boundary conditions. In this study, we applied Harmonic Phase MRI method to compute the difference between tagged and untagged NMR transverse magnetization based on the Bloch NMR diffusion equation and obtained radial wave tagging function for analysis of myocardial motion. The analytical solution of the Bloch NMR equations and the computational simulation of myocardial motion as developed in this study are intended to significantly improve healthcare for accurate diagnosis, prognosis and treatment of cardiovascular related deceases at the lowest cost because MRI scan is still one of the most expensive anywhere. The analysis is fundamental and significant because all Magnetic Resonance Imaging techniques are based on the Bloch NMR flow equations.

Magnetic Snell's law and spin-wave fiber with Dzyaloshinskii-Moriya interaction

NASA Astrophysics Data System (ADS)

Yu, Weichao; Lan, Jin; Wu, Ruqian; Xiao, Jiang

2016-10-01

Spin waves are collective excitations propagating in the magnetic medium with ordered magnetizations. Magnonics, utilizing the spin wave (magnon) as an information carrier, is a promising candidate for low-dissipation computation and communication technologies. We discover that, due to the Dzyaloshinskii-Moriya interaction, the scattering behavior of the spin wave at a magnetic domain wall follows a generalized Snell's law, where two magnetic domains work as two different mediums. Similar to optical total reflection that occurs at water-air interfaces, spin waves may experience total reflection at the magnetic domain walls when their incident angle is larger than a critical value. We design a spin-wave fiber using a magnetic domain structure with two domain walls, and demonstrate that such a spin-wave fiber can transmit spin waves over long distances by total internal reflections, in analogy to an optical fiber.

Color in the Cortex—single- and double-opponent cells

PubMed Central

Shapley, Robert; Hawken, Michael

2011-01-01

This is a review of the research during the past 25 years on cortical processing of color signals. At the beginning of the period the modular view of cortical processing predominated. However, at present an alternative view, that color and form are linked inextricably in visual cortical processing, is more persuasive than it seemed in 1985. Also, the role of the primary visual cortex, V1, in color processing now seems much larger than it did in 1985. The re-evaluation of the important role of V1 in color vision was caused in part by investigations of human V1 responses to color, measured with functional magnetic resonance imaging, fMRI, and in part by the results of numerous studies of single-unit neurophysiology in non-human primates. The neurophysiological results have highlighted the importance of double-opponent cells in V1. Another new concept is population coding of hue, saturation, and brightness in cortical neuronal population activity. PMID:21333672

Early Development of Subcortical Regions Involved in Non-Cued Attention Switching

ERIC Educational Resources Information Center

Casey, B. J.; Davidson, Matthew C.; Hara, Yuko; Thomas, Kathleen M.; Martinez, Antigona; Galvan, Adriana; Halperin, Jeffrey M.; Rodriguez-Aranda, Claudia E.; Tottenham, Nim

2004-01-01

This study examined the cognitive and neural development of attention switching using a simple forced-choice attention task and functional magnetic resonance imaging. Fourteen children and adults made discriminations among stimuli based on either shape or color. Performance on these trials was compared to performance during blocked trials…

Parametric decay of plasma waves near the upper-hybrid resonance

DOE PAGES

Dodin, I. Y.; Arefiev, A. V.

2017-03-28

An intense X wave propagating perpendicularly to dc magnetic field is unstable with respect to a parametric decay into an electron Bernstein wave and a lower-hybrid wave. A modified theory of this effect is proposed that extends to the high-intensity regime, where the instability rate γ ceases to be a linear function of the incident-wave amplitude. An explicit formula for γ is derived and expressed in terms of cold-plasma parameters. Here, theory predictions are in reasonable agreement with the results of the particle-in-cell simulations presented in a separate publication.

Color properties of the motion detectors projecting to the goldfish tectum: I. A color matching study.

PubMed

Maximov, Vadim; Maximova, Elena; Damjanović, Ilija; Maximov, Paul

2014-09-01

Responses of direction-selective and orientation-selective motion detectors were recorded extracellularly from the axon terminals of ganglion cells in the superficial layers of the tectum opticum of immobilized goldfish, Carassius gibelio (Bloch, 1782). Color stripes or edges moving on some color background (presented on the CRT monitor with known emission spectra of its phosphors) served as stimuli. It was shown that stimuli of any color can be more or less matched with the background by varying their intensities what is indicative of color blindness of the motion detectors. Sets of stimuli which matched the background proved to represent planes in the three-dimensional color space of the goldfish. A relative contribution of different types of cones to the spectral sensitivity was estimated according to orientation of the plane of color matches. The spectral sensitivity of any motion detector was shown to be determined mainly by long-wave cones with a weak negative (opponent) contributions of middle-wave and/or short-wave ones. This resulted in reduced sensitivity in the blue-green end of the spectrum, what may be considered as an adaptation to the aquatic environment where, because of the substantial light scattering of a blue-green light, acute vision is possible only in a red region of the spectrum.

FUNDUS AUTOFLUORESCENCE IN RUBELLA RETINOPATHY: Correlation With Photoreceptor Structure and Function.

PubMed

Bukowska, Danuta M; Wan, Sue Ling; Chew, Avenell L; Chelva, Enid; Tang, Ivy; Mackey, David A; Chen, Fred K

2017-01-01

To illustrate altered fundus autofluorescence in rubella retinopathy and to investigate their relationships with photoreceptor structure and function using multimodal imaging. The authors report four cases of rubella retinopathy aged 8, 33, 42, and 50 years. All patients had dilated clinical fundus examination; wide-field color photography; blue, green, and near-infrared autofluorescence imaging and spectral domain optical coherence tomography. Two patients also underwent microperimetry and adaptive optics imaging. En face optical coherence tomography, cone mosaic, and microperimetry were coregistered with autofluorescence images. The authors explored the structure-function correlation. All four patients had a "salt-and-pepper" appearance on dilated fundus examination and wide-field color photography. There were variable-sized patches of hypoautofluorescence on both blue and near-infrared excitation in all four patients. Wave-guiding cones were visible and retinal sensitivity was intact over these regions. There was no correlation between hypoautofluorescence and regions of attenuated ellipsoid and interdigitation zones. Hyperautofluorescent lesions were also noted and some of these were pseudo-vitelliform lesions. Patchy hypoautofluorescence on near-infrared excitation can be a feature of rubella retinopathy. This may be due to abnormal melanin production or loss of melanin within retinal pigment epithelium cells harboring persistent rubella virus infection. Preservation of the ellipsoid zone, wave-guiding cones, and retinal sensitivity within hypoautofluorescent lesions suggest that these retinal pigment epithelium changes have only mild impact on photoreceptor cell function.

Electron-cyclotron damping of helicon waves in low diverging magnetic fields

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

Lafleur, T.; Charles, C.; Boswell, R. W.

2011-04-15

Particle-in-cell simulations are performed to investigate wave propagation and absorption behavior of low-field (B{sub 0}<5 mT) helicon waves in the presence of a diverging magnetic field. The 1D electromagnetic simulations, which include experimental external magnetic field profiles, provide strong evidence for electron-cyclotron damping of helicon waves in the spatially decaying nonuniform magnetic field. For a dipole-type magnetic field configuration, the helicon waves are absence in the downstream (lower field) region of the plasma and are observed to be completely absorbed. As the magnetic field is changed slightly however, wave damping decreases, and waves are able to propagate freely downstream, confirmingmore » previous experimental measurements of this phenomenon.« less

Structure of Kinetic Alfvén Waves of Small Transverse Scale

NASA Astrophysics Data System (ADS)

Morales, G. J.; Maggs, J. E.

1996-11-01

This analytical study illustrates the spatial pattern of kinetic Alfvén waves excited by a current-modulating disk whose dimension R transverse to the confining magnetic field is comparable to cs / Ω_i. The radial structure of the wave azimuthal magnetic field consists of 3 regions: a Bessel function behavior for r < R, a near null at r ~ R, and a driven Airy pattern for r >> R. The pattern spreads at an angle given by tan θ = (ω/Ω_i)(c_s/V_A)/(2 \\cdot 6), where ω is the modulation frequency and VA the Alfvén speed. This arises because there is a maximum value at finite k_⊥ for the ratio of the perpendicular to parallel group velocity, which differs from the cone spreading(G.J. Morales, R.S. Loritsch, and J.E. Maggs, Phys. Plasmas) 1, 3765 (1994) associated with inertial Alfvén waves. Sponsored by ONR

MMS Observations of Ion-Scale Magnetic Island in the Magnetosheath Turbulent Plasma

NASA Technical Reports Server (NTRS)

Huang, S. Y.; Sahraoui, F.; Retino, A.; Contel, O. Le; Yuan, Z. G.; Chasapis, A.; Aunai, N.; Breuillard, H.; Deng, X. H.; Zhou, M.;

Alfven waves in spiral interplanetary field

NASA Technical Reports Server (NTRS)

Whang, Y. C.

1973-01-01

A theoretical study is presented of the Alfven waves in the spiral interplanetary magnetic field. The Alfven waves under consideration are arbitrary, large amplitude, non-monochromatic, microscale waves of any polarization. They superpose on a mesoscale background flow of thermally anisotropic plasma. Using WKB approximation, an analytical solution for the amplitude vectors is obtained as a function of the background flow properties: density, velocity, Alfven speed, thermal anisotropy, and the spiral angel. The necessary condition for the validity of the WKB solution is discussed. The intensity of fluctuations is calculated as a function of heliocentric distance. Relative intensity of fluctuations as compared with the magnitude of the background field has its maximum in the region near l au. Thus outside of this region, the solar wind is less turbulent.

Omnidirectional spin-wave nanograting coupler

PubMed Central

Yu, Haiming; Duerr, G.; Huber, R.; Bahr, M.; Schwarze, T.; Brandl, F.; Grundler, D.

2013-01-01

Magnonics as an emerging nanotechnology offers functionalities beyond current semiconductor technology. Spin waves used in cellular nonlinear networks are expected to speed up technologically, demanding tasks such as image processing and speech recognition at low power consumption. However, efficient coupling to microelectronics poses a vital challenge. Previously developed techniques for spin-wave excitation (for example, by using parametric pumping in a cavity) may not allow for the relevant downscaling or provide only individual point-like sources. Here we demonstrate that a grating coupler of periodically nanostructured magnets provokes multidirectional emission of short-wavelength spin waves with giantly enhanced amplitude compared with a bare microwave antenna. Exploring the dependence on ferromagnetic materials, lattice constants and the applied magnetic field, we find the magnonic grating coupler to be more versatile compared with gratings in photonics and plasmonics. Our results allow one to convert, in particular, straight microwave antennas into omnidirectional emitters for short-wavelength spin waves, which are key to cellular nonlinear networks and integrated magnonics. PMID:24189978

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

Alvioli, M.; Frankfurt, L.; Guzey, V.

Here, we model effects of color fluctuations (CFs) in the light-cone photon wave function and for the first time make predictions for the distribution over the number of wounded nucleons ν in the inelastic photon–nucleus scattering. We show that CFs lead to a dramatic enhancement of this distribution at ν=1 and large ν>10. We also study the implications of different scales and CFs in the photon wave function on the total transverse energy ΣE T and other observables in inelastic γA scattering with different triggers. Our predictions can be tested in proton–nucleus and nucleus–nucleus ultraperipheral collisions at the LHC andmore » will help to map CFs, whose first indications have already been observed at the LHC.« less

Photonic Multitasking Interleaved Si Nanoantenna Phased Array.

PubMed

Lin, Dianmin; Holsteen, Aaron L; Maguid, Elhanan; Wetzstein, Gordon; Kik, Pieter G; Hasman, Erez; Brongersma, Mark L

2016-12-14

Metasurfaces provide unprecedented control over light propagation by imparting local, space-variant phase changes on an incident electromagnetic wave. They can improve the performance of conventional optical elements and facilitate the creation of optical components with new functionalities and form factors. Here, we build on knowledge from shared aperture phased array antennas and Si-based gradient metasurfaces to realize various multifunctional metasurfaces capable of achieving multiple distinct functions within a single surface region. As a key point, we demonstrate that interleaving multiple optical elements can be accomplished without reducing the aperture of each subelement. Multifunctional optical elements constructed from Si-based gradient metasurface are realized, including axial and lateral multifocus geometric phase metasurface lenses. We further demonstrate multiwavelength color imaging with a high spatial resolution. Finally, optical imaging functionality with simultaneous color separation has been obtained by using multifunctional metasurfaces, which opens up new opportunities for the field of advanced imaging and display.

Energy loss of solar p modes due to the excitation of magnetic sausage tube waves: Importance of coupling the upper atmosphere

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

Gascoyne, A.; Jain, R.; Hindman, B. W., E-mail: a.d.gascoyne@sheffield.ac.uk, E-mail: r.jain@sheffield.ac.uk

2014-07-10

We consider damping and absorption of solar p modes due to their energy loss to magnetic tube waves that can freely carry energy out of the acoustic cavity. The coupling of p modes and sausage tube waves is studied in a model atmosphere composed of a polytropic interior above which lies an isothermal upper atmosphere. The sausage tube waves, excited by p modes, propagate along a magnetic fibril which is assumed to be a vertically aligned, stratified, thin magnetic flux tube. The deficit of p-mode energy is quantified through the damping rate, Γ, and absorption coefficient, α. The variation ofmore » Γ and α as a function of frequency and the tube's plasma properties is studied in detail. Previous similar studies have considered only a subphotospheric layer, modeled as a polytrope that has been truncated at the photosphere. Such studies have found that the resulting energy loss by the p modes is very sensitive to the upper boundary condition, which, due to the lack of an upper atmosphere, have been imposed in a somewhat ad hoc manner. The model presented here avoids such problems by using an isothermal layer to model the overlying atmosphere (chromosphere, and, consequently, allows us to analyze the propagation of p-mode-driven sausage waves above the photosphere. In this paper, we restrict our attention to frequencies below the acoustic cut off frequency. We demonstrate the importance of coupling all waves (acoustic, magnetic) in the subsurface solar atmosphere with the overlying atmosphere in order to accurately model the interaction of solar f and p modes with sausage tube waves. In calculating the absorption and damping of p modes, we find that for low frequencies, below ≈3.5 mHz, the isothermal atmosphere, for the two-region model, behaves like a stress-free boundary condition applied at the interface (z = –z{sub 0}).« less

Energy Loss of Solar p Modes due to the Excitation of Magnetic Sausage Tube Waves: Importance of Coupling the Upper Atmosphere

NASA Astrophysics Data System (ADS)

Gascoyne, A.; Jain, R.; Hindman, B. W.

2014-07-01

We consider damping and absorption of solar p modes due to their energy loss to magnetic tube waves that can freely carry energy out of the acoustic cavity. The coupling of p modes and sausage tube waves is studied in a model atmosphere composed of a polytropic interior above which lies an isothermal upper atmosphere. The sausage tube waves, excited by p modes, propagate along a magnetic fibril which is assumed to be a vertically aligned, stratified, thin magnetic flux tube. The deficit of p-mode energy is quantified through the damping rate, Γ, and absorption coefficient, α. The variation of Γ and α as a function of frequency and the tube's plasma properties is studied in detail. Previous similar studies have considered only a subphotospheric layer, modeled as a polytrope that has been truncated at the photosphere. Such studies have found that the resulting energy loss by the p modes is very sensitive to the upper boundary condition, which, due to the lack of an upper atmosphere, have been imposed in a somewhat ad hoc manner. The model presented here avoids such problems by using an isothermal layer to model the overlying atmosphere (chromosphere, and, consequently, allows us to analyze the propagation of p-mode-driven sausage waves above the photosphere. In this paper, we restrict our attention to frequencies below the acoustic cut off frequency. We demonstrate the importance of coupling all waves (acoustic, magnetic) in the subsurface solar atmosphere with the overlying atmosphere in order to accurately model the interaction of solar f and p modes with sausage tube waves. In calculating the absorption and damping of p modes, we find that for low frequencies, below ≈3.5 mHz, the isothermal atmosphere, for the two-region model, behaves like a stress-free boundary condition applied at the interface (z = -z 0).

A consideration on physical tuning for acoustical coloration in recording studio

NASA Astrophysics Data System (ADS)

Shimizu, Yasushi

2003-04-01

Coloration due to particular architectural shapes and dimension or less surface absorption has been mentioned as an acoustical defect in recording studio. Generally interference among early reflected sounds arriving within 10 ms in delay after the direct sound produces coloration by comb filter effect over mid- and high-frequency sounds. In addition, less absorbed room resonance modes also have been well known as a major component for coloration in low-frequency sounds. Small size in dimension with recording studio, however, creates difficulty in characterization associated with wave acoustics behavior, that make acoustical optimization more difficult than that of concert hall acoustics. There still remains difficulty in evaluating amount of coloration as well as predicting its acoustical characteristics in acoustical modeling and in other words acoustical tuning technique during construction is regarded as important to optimize acoustics appropriately to the function of recording studio. This paper presents a example of coloration by comb filtering effect and less damped room modes in typical post-processing recording studio. And acoustical design and measurement technique will be presented for adjusting timbre due to coloration based on psycho-acoustical performance with binaural hearing and room resonance control with line array resonator adjusted to the particular room modes considered.

A quasilinear operator retaining magnetic drift effects in tokamak geometry

NASA Astrophysics Data System (ADS)

Catto, Peter J.; Lee, Jungpyo; Ram, Abhay K.

2017-12-01

The interaction of radio frequency waves with charged particles in a magnetized plasma is usually described by the quasilinear operator that was originally formulated by Kennel & Engelmann (Phys. Fluids, vol. 9, 1966, pp. 2377-2388). In their formulation the plasma is assumed to be homogenous and embedded in a uniform magnetic field. In tokamak plasmas the Kennel-Engelmann operator does not capture the magnetic drifts of the particles that are inherent to the non-uniform magnetic field. To overcome this deficiency a combined drift and gyrokinetic derivation is employed to derive the quasilinear operator for radio frequency heating and current drive in a tokamak with magnetic drifts retained. The derivation requires retaining the magnetic moment to higher order in both the unperturbed and perturbed kinetic equations. The formal prescription for determining the perturbed distribution function then follows a novel procedure in which two non-resonant terms must be evaluated explicitly. The systematic analysis leads to a diffusion equation that is compact and completely expressed in terms of the drift kinetic variables. The equation is not transit averaged, and satisfies the entropy principle, while retaining the full poloidal angle variation without resorting to Fourier decomposition. As the diffusion equation is in physical variables, it can be implemented in any computational code. In the Kennel-Engelmann formalism, the wave-particle resonant delta function is either for the Landau resonance or the Doppler shifted cyclotron resonance. In the combined gyro and drift kinetic approach, a term related to the magnetic drift modifies the resonance condition.

3D MHD Simulations of Waves Excited in an Accretion Disk by a Rotating Magnetized Star

NASA Astrophysics Data System (ADS)

Lovelace, R. V. E.; Romanova, M. M.

2014-01-01

We present results of global 3D MHD simulations of warp and density waves in accretion disks excited by a rotating star with a misaligned dipole magnetic field. A wide range of cases are considered. We find for example that if the star's magnetosphere corotates approximately with the inner disk, then a strong one-arm bending wave or warp forms. The warp corotates with the star and has a maximum amplitude (|zω|/r ~ 0.3) between the corotation radius and the radius of the vertical resonance. If the magnetosphere rotates more slowly than the inner disk, then a bending wave is excited at the disk-magnetosphere boundary, but it does not form a large-scale warp. In this case the angular rotation of the disk [Ω(r,z = 0)] has a maximum as a function of r so that there is an inner region where dΩ/dr > 0. In this region we observe radially trapped density waves in approximate agreement with the theoretical prediction of a Rossby wave instability in this region.

Electromagnetic Ion Cyclotron Waves in the Helium Branch Induced by Multiple Electromagnetic Ion Cyclotron Triggered Emissions

NASA Astrophysics Data System (ADS)

Shoji, M.; Omura, Y.; Grison, B.; Pickett, J. S.; Dandouras, I. S.; Engebretson, M. J.

2011-12-01

Electromagnetic ion cyclotron (EMIC) triggered emissions with rising tones between the H+ and He+ cyclotron frequencies were found in the inner magnetosphere by the recent Cluster observations. Another type of EMIC wave with a constant frequency is occasionally observed below the He+ cyclotron frequency after the multiple EMIC triggered emissions. We performed a self-consistent hybrid simulation with a one-dimensional cylindrical magnetic flux model approximating the dipole magnetic field of the Earth's inner magnetosphere. In the presence of energetic protons with a sufficient density and temperature anisotropy, multiple EMIC triggered emissions are reproduced due to the nonlinear wave growth mechanism of rising-tone chorus emissions, and a constant frequency wave in the He+ EMIC branch is subsequently generated. Through interaction with the multiple EMIC rising-tone emissions, the velocity distribution function of the energetic protons is strongly modified. Because of the pitch angle scattering of the protons, the gradient of the distribution in velocity phase space is enhanced along the diffusion curve of the He+ branch wave, resulting in the linear growth of the EMIC wave in the He+ branch.

Electromagnetic ion cyclotron waves in the helium branch induced by multiple electromagnetic ion cyclotron triggered emissions

NASA Astrophysics Data System (ADS)

Shoji, Masafumi; Omura, Yoshiharu; Grison, Benjamin; Pickett, Jolene; Dandouras, Iannis; Engebretson, Mark

2011-09-01

Electromagnetic ion cyclotron (EMIC) triggered emissions with rising tones between the H+ and He+ cyclotron frequencies were found in the inner magnetosphere by the recent Cluster observations. Another type of EMIC wave with a constant frequency is occasionally observed below the He+ cyclotron frequency after the multiple EMIC triggered emissions. We performed a self-consistent hybrid simulation with a one-dimensional cylindrical magnetic flux model approximating the dipole magnetic field of the Earth's inner magnetosphere. In the presence of energetic protons with a sufficient density and temperature anisotropy, multiple EMIC triggered emissions are reproduced due to the nonlinear wave growth mechanism of rising-tone chorus emissions, and a constant frequency wave in the He+ EMIC branch is subsequently generated. Through interaction with the multiple EMIC rising-tone emissions, the velocity distribution function of the energetic protons is strongly modified. Because of the pitch angle scattering of the protons, the gradient of the distribution in velocity phase space is enhanced along the diffusion curve of the He+ branch wave, resulting in the linear growth of the EMIC wave in the He+ branch.

STATISTICALLY DETERMINED DISPERSION RELATIONS OF MAGNETIC FIELD FLUCTUATIONS IN THE TERRESTRIAL FORESHOCK

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

Hnat, B.; O’Connell, D.; Nakariakov, V. M.

2016-08-20

We obtain dispersion relations of magnetic field fluctuations for two crossings of the terrestrial foreshock by Cluster spacecraft. These crossings cover plasma conditions that differ significantly in their plasma β and in the density of the reflected ion beam, but not in the properties of the encountered ion population, both showing shell-like distribution function. Dispersion relations are reconstructed using two-point instantaneous wave number estimations from pairs of Cluster spacecraft. The accessible range of wave vectors, limited by the available spacecraft separations, extends to ≈2 × 10{sup 4} km. Results show multiple branches of dispersion relations, associated with different powers ofmore » magnetic field fluctuations. We find that sunward propagating fast magnetosonic waves and beam resonant modes are dominant for the high plasma β interval with a dense beam, while the dispersions of the interval with low beam density include Alfvén and fast magnetosonic modes propagating sunward and anti-sunward.« less

A broadband gyrotron backward-wave oscillator with tapered interaction structure and magnetic field

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

Li, G. D.; Chang, P. C.; Chiang, W. Y.

2015-11-15

The gyro-monotron and gyrotron backward-wave oscillator (gyro-BWO) are the two oscillator versions of gyrotrons. While serving different functions, they are also radically different in the RF field formation mechanisms. The gyro-monotron RF field profile is essentially fixed by the resonant interaction structure, while the gyro-BWO possesses an extra degree of freedom in that the axial RF field profile is self-determined by the beam-wave interaction in a waveguide structure. The present study examines ways to utilize the latter feature for bandwidth broadening with a tapered magnetic field, while also employing a tapered waveguide to enhance the interaction efficiency. We begin withmore » a mode competition analysis, which suggests the theoretical feasibility of broadband frequency tuning in single-mode operation. It is then shown in theory that, by controlling the RF field profile with an up- or down-tapered magnetic field, the gyro-BWO is capable of efficient operation with a much improved tunable bandwidth.« less

Influence of Non-Maxwellian Particles on Dust Acoustic Waves in a Dusty Magnetized Plasma

NASA Astrophysics Data System (ADS)

M. Nouri, Kadijani; Zareamoghaddam, H.

2013-11-01

In this paper an investigation into dust acoustic solitary waves (DASWs) in the presence of superthermal electrons and ions in a magnetized plasma with cold dust grains and trapped electrons is discussed. The dynamic of both electrons and ions is simulated by the generalized Lorentzian (κ) distribution function (DF). The dust grains are cold and their dynamics are studied by hydrodynamic equations. The basic set of fluid equations is reduced to modified Korteweg-de Vries (mKdV) equation using Reductive Perturbation Theory (RPT). Two types of solitary waves, fast and slow dust acoustic soliton (DAS) exist in this plasma. Calculations reveal that compressive solitary structures are possibly propagated in the plasma where dust grains are negatively (or positively) charged. The properties of DASs are also investigated numerically.

Directional multimode coupler for planar magnonics: Side-coupled magnetic stripes

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

Sadovnikov, A. V., E-mail: sadovnikovav@gmail.com; Nikitov, S. A.; Kotel'nikov Institute of Radioengineering and Electronics, Russian Academy of Sciences, Moscow 125009

We experimentally demonstrate spin waves coupling in two laterally adjacent magnetic stripes. By the means of Brillouin light scattering spectroscopy, we show that the coupling efficiency depends both on the magnonic waveguides' geometry and the characteristics of spin-wave modes. In particular, the lateral confinement of coupled yttrium-iron-garnet stripes enables the possibility of control over the spin-wave propagation characteristics. Numerical simulations (in time domain and frequency domain) reveal the nature of intermodal coupling between two magnonic stripes. The proposed topology of multimode magnonic coupler can be utilized as a building block for fabrication of integrated parallel functional and logic devices suchmore » as the frequency selective directional coupler or tunable splitter, enabling a number of potential applications for planar magnonics.« less

Magnetic hyperbolic optical metamaterials

DOE PAGES

Kruk, Sergey S.; Wong, Zi Jing; Pshenay-Severin, Ekaterina; ...

2016-04-13

Strongly anisotropic media where the principal components of electric permittivity or magnetic permeability tensors have opposite signs are termed as hyperbolic media. Such media support propagating electromagnetic waves with extremely large wave vectors exhibiting unique optical properties. However, in all artificial and natural optical materials studied to date, the hyperbolic dispersion originates solely from the electric response. This then restricts material functionality to one polarization of light and inhibits free-space impedance matching. Such restrictions can be overcome in media having components of opposite signs for both electric and magnetic tensors. Here we present the experimental demonstration of the magnetic hyperbolicmore » dispersion in three-dimensional metamaterials. We also measure metamaterial isofrequency contours and reveal the topological phase transition between the elliptic and hyperbolic dispersion. In the hyperbolic regime, we demonstrate the strong enhancement of thermal emission, which becomes directional, coherent and polarized. These findings show the possibilities for realizing efficient impedance-matched hyperbolic media for unpolarized light.« less

Magnetoacoustic Tomography with Magnetic Induction: Bioimepedance reconstruction through vector source imaging

PubMed Central

Mariappan, Leo; He, Bin

2013-01-01

Magneto acoustic tomography with magnetic induction (MAT-MI) is a technique proposed to reconstruct the conductivity distribution in biological tissue at ultrasound imaging resolution. A magnetic pulse is used to generate eddy currents in the object, which in the presence of a static magnetic field induces Lorentz force based acoustic waves in the medium. This time resolved acoustic waves are collected with ultrasound transducers and, in the present work, these are used to reconstruct the current source which gives rise to the MAT-MI acoustic signal using vector imaging point spread functions. The reconstructed source is then used to estimate the conductivity distribution of the object. Computer simulations and phantom experiments are performed to demonstrate conductivity reconstruction through vector source imaging in a circular scanning geometry with a limited bandwidth finite size piston transducer. The results demonstrate that the MAT-MI approach is capable of conductivity reconstruction in a physical setting. PMID:23322761

Ferromagnetic quantum critical point avoided by the appearance of another magnetic phase in LaCrGe 3 under pressure

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

Taufour, Valentin; Kaluarachchi, Udhara S.; Khasanov, Rustem

2016-07-13

Here, the temperature-pressure phase diagram of the ferromagnet LaCrGe 3 is determined for the first time from a combination of magnetization, muon-spin-rotation, and electrical resistivity measurements. The ferromagnetic phase is suppressed near 2.1 GPa, but quantum criticality is avoided by the appearance of a magnetic phase, likely modulated, AFMQ. Our density functional theory total energy calculations suggest a near degeneracy of antiferromagnetic states with small magnetic wave vectors Q allowing for the potential of an ordering wave vector evolving from Q=0 to finite Q, as expected from the most recent theories on ferromagnetic quantum criticality. Our findings show that LaCrGemore » 3 is a very simple example to study this scenario of avoided ferromagnetic quantum criticality and will inspire further study on this material and other itinerant ferromagnets.« less

Gluon structure function of a color dipole in the light-cone limit of lattice QCD

NASA Astrophysics Data System (ADS)

Grünewald, D.; Ilgenfritz, E.-M.; Pirner, H. J.

2009-10-01

We calculate the gluon structure function of a color dipole in near-light-cone SU(2) lattice QCD as a function of xB. The quark and antiquark are external nondynamical degrees of freedom which act as sources of the gluon string configuration defining the dipole. We compute the color dipole matrix element of transversal chromo-electric and chromo-magnetic field operators separated along a direction close to the light cone, the Fourier transform of which is the gluon structure function. As vacuum state in the pure glue sector, we use a variational ground state of the near-light-cone Hamiltonian. We derive a recursion relation for the gluon structure function on the lattice similar to the perturbative Dokshitzer-Gribov-Lipatov-Altarelli-Parisi equation. It depends on the number of transversal links assembling the Schwinger string of the dipole. Fixing the mean momentum fraction of the gluons to the “experimental value” in a proton, we compare our gluon structure function for a dipole state with four links with the next-to-leading-order MRST 2002 and the CTEQ AB-0 parametrizations at Q2=1.5GeV2. Within the systematic uncertainty we find rather good agreement. We also discuss the low xB behavior of the gluon structure function in our model calculation.

The Acceleration of Charged Particles at a Spherical Shock Moving through an Irregular Magnetic Field

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

Giacalone, J.

We investigate the physics of charged-particle acceleration at spherical shocks moving into a uniform plasma containing a turbulent magnetic field with a uniform mean. This has applications to particle acceleration at astrophysical shocks, most notably, to supernovae blast waves. We numerically integrate the equations of motion of a large number of test protons moving under the influence of electric and magnetic fields determined from a kinematically defined plasma flow associated with a radially propagating blast wave. Distribution functions are determined from the positions and velocities of the protons. The unshocked plasma contains a magnetic field with a uniform mean andmore » an irregular component having a Kolmogorov-like power spectrum. The field inside the blast wave is determined from Maxwell’s equations. The angle between the average magnetic field and unit normal to the shock varies with position along its surface. It is quasi-perpendicular to the unit normal near the sphere’s equator, and quasi-parallel to it near the poles. We find that the highest intensities of particles, accelerated by the shock, are at the poles of the blast wave. The particles “collect” at the poles as they approximately adhere to magnetic field lines that move poleward from their initial encounter with the shock at the equator, as the shock expands. The field lines at the poles have been connected to the shock the longest. We also find that the highest-energy protons are initially accelerated near the equator or near the quasi-perpendicular portion of the shock, where the acceleration is more rapid.« less

Electromagnetic Ion Cyclotron Wavefields in a Realistic Dipole Field

NASA Astrophysics Data System (ADS)

Denton, R. E.

2018-02-01

The latitudinal distribution and properties of electromagnetic ion cyclotron (EMIC) waves determine the total effect of those waves on relativistic electrons. Here we describe the latitudinal variation of EMIC waves simulated self-consistently in a dipole magnetic field for a plasmasphere or plume-like plasma at geostationary orbit with cold H+, He+, and O+ and hot protons with temperature anisotropy. The waves grow as they propagate away from the magnetic equator to higher latitude, while the wave vector turns outward radially and the polarization becomes linear. We calculate the detailed wave spectrum in four latitudinal ranges varying from magnetic latitude (MLAT) close to 0° (magnetic equator) up to 21°. The strongest waves are propagating away from the magnetic equator, but some wave power propagating toward the magnetic equator is observed due to local generation (especially close to the magnetic equator) or reflection. The He band waves, which are generated relatively high up on their dispersion surface, are able to propagate all the way to MLAT = 21°, but the H band waves experience frequency filtering, with no equatorial waves propagating to MLAT = 21° and only the higher-frequency waves propagating to MLAT = 14°. The result is that the wave power averaged k∥, which determines the relativistic electron minimum resonance energy, scales like the inverse of the local magnetic field for the He mode, whereas it is almost constant for the H mode. While the perpendicular wave vector turns outward, it broadens. These wavefields should be useful for simulations of radiation belt particle dynamics.

Internal Gravity Waves in the Magnetized Solar Atmosphere. I. Magnetic Field Effects

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

Vigeesh, G.; Steiner, O.; Jackiewicz, J., E-mail: vigeesh@leibniz-kis.de

Observations of the solar atmosphere show that internal gravity waves are generated by overshooting convection, but are suppressed at locations of magnetic flux, which is thought to be the result of mode conversion into magnetoacoustic waves. Here, we present a study of the acoustic-gravity wave spectrum emerging from a realistic, self-consistent simulation of solar (magneto)convection. A magnetic field free, hydrodynamic simulation and a magnetohydrodynamic (MHD) simulation with an initial, vertical, homogeneous field of 50 G flux density were carried out and compared with each other to highlight the effect of magnetic fields on the internal gravity wave propagation in themore » Sun’s atmosphere. We find that the internal gravity waves are absent or partially reflected back into the lower layers in the presence of magnetic fields and argue that the suppression is due to the coupling of internal gravity waves to slow magnetoacoustic waves still within the high- β region of the upper photosphere. The conversion to Alfvén waves is highly unlikely in our model because there is no strongly inclined magnetic field present. We argue that the suppression of internal waves observed within magnetic flux concentrations may also be due to nonlinear breaking of internal waves due to vortex flows that are ubiquitously present in the upper photosphere and the chromosphere.« less

Quark correlations in the color glass condensate: Pauli blocking and the ridge

NASA Astrophysics Data System (ADS)

Altinoluk, Tolga; Armesto, Néstor; Beuf, Guillaume; Kovner, Alex; Lublinsky, Michael

2017-02-01

We consider, for the first time, correlations between quarks produced in p-A collisions in the framework of the color glass condensate. We find a quark-quark ridge that shows a dip at Δ η ˜2 relative to the gluon-gluon ridge. The origin of this dip is the short-range (in rapidity) Pauli blocking experienced by quarks in the wave function of the incoming projectile. We observe that these correlations, present in the initial state, survive the scattering process. We suggest that this effect may be observable in open charm-open charm correlations at the Large Hadron Collider.

Wave-Particle Interactions Associated with Nongyrotropic Distribution Functions: A Hybrid Simulation Study

NASA Technical Reports Server (NTRS)

Convery, P. D.; Schriver, D.; Ashour-Abdalla, M.; Richard, R. L.

2002-01-01

Nongyrotropic plasma distribution functions can be formed in regions of space where guiding center motion breaks down as a result of strongly curved and weak ambient magnetic fields. Such are the conditions near the current sheet in the Earth's middle and distant magnetotail, where observations of nongyrotropic ion distributions have been made. Here a systematic parameter study of nongyrotropic proton distributions using electromagnetic hybrid simulations is made. We model the observed nongyrotropic distributions by removing a number of arc length segments from a cold ring distribution and find significant differences with the results of simulations that initially have a gyrotropic ring distribution. Model nongyrotropic distributions with initially small perpendicular thermalization produce growing fluctuations that diffuse the ions into a stable Maxwellian-like distribution within a few proton gyro periods. The growing waves produced by nongyrotropic distributions are similar to the electromagnetic proton cyclotron waves produced by a gyrotropic proton ring distribution in that they propagate parallel to the background magnetic field and occur at frequencies on the order of the proton gyrofrequency, The maximum energy of the fluctuating magnetic field increases as the initial proton distribution is made more nongyrotropic, that is, more highly bunched in perpendicular velocity space. This increase can be as much as twice the energy produced in the gyrotropic case.

Technique for direct measurement of magnetic entropy of solids: Results for dysprosium titanium oxide

NASA Technical Reports Server (NTRS)

Flood, D. J.

1974-01-01

A measurement technique was devised which permits direct observation of the magnetic entropy of solids as a function of applied magnetic field. Measurements were made of the magnetic entropy, in the temperature range 2 to 20 K, of polycrystalline samples of dysprosium titanium oxide (Dy2Ti2O7) to determine its suitability for use as the working substance of a magnetic refrigerator. Magnetization measurements were also made at 4.2 K and below to provide additional information on the nature of the compound. The measurements indicated that crystalline electric fields perturbed the ground state of the dysprosium ions, removed the 16-fold degeneracy predicted by Hund's rules, and left only a twofold degeneracy in its place. A positive, temperature independent contribution to the magnetization was observed in the saturation region, which indicated that the doublet ground-state wave function was perturbed by a nearby unpopulated upper energy level.

Behavioral and neural indices of affective coloring for neutral social stimuli

PubMed Central

Schaefer, Stacey M; Lapate, Regina C; Schoen, Andrew J; Gresham, Lauren K; Mumford, Jeanette A; Davidson, Richard J

2018-01-01

Abstract Emotional processing often continues beyond the presentation of emotionally evocative stimuli, which can result in affective biasing or coloring of subsequently encountered events. Here, we describe neural correlates of affective coloring and examine how individual differences in affective style impact the magnitude of affective coloring. We conducted functional magnetic resonance imaging in 117 adults who passively viewed negative, neutral and positive pictures presented 2 s prior to neutral faces. Brain responses to neutral faces were modulated by the valence of preceding pictures, with greater activation for faces following negative (vs positive) pictures in the amygdala, dorsomedial and lateral prefrontal cortex, ventral visual cortices, posterior superior temporal sulcus, and angular gyrus. Three days after the magnetic resonance imaging scan, participants rated their memory and liking of previously encountered neutral faces. Individuals higher in trait positive affect and emotional reappraisal rated faces as more likable when preceded by emotionally arousing (negative or positive) pictures. In addition, greater amygdala responses to neutral faces preceded by positively valenced pictures were associated with greater memory for these faces 3 days later. Collectively, these results reveal individual differences in how emotions spill over onto the processing of unrelated social stimuli, resulting in persistent and affectively biased evaluations of such stimuli. PMID:29447377

Color discrimination in carriers of color deficiency.

PubMed

Hood, S M; Mollon, J D; Purves, L; Jordan, G

2006-09-01

Carriers of X-linked color vision deficiencies have previously been reported to exhibit mild abnormalities of color matching and discrimination. In a sample of 55 carriers of protan and deutan deficiencies and 55 age-matched normal controls, we measured chromatic discrimination along a red-green axis. We found that discrimination was impaired in the case of carriers of deutan deficiencies (which affect the middle-wave-sensitive cones of the retina), but was normal in the case of carriers of protan deficiencies (which affect the long-wave-sensitive cones). We argue that this result can be explained by the difference in the relative numbers of middle- and long-wave cones in heterozygous retinae: the imbalance of the two cone types is predicted to be much greater in the case of the deutan heterozygote than in the case of the protan heterozygote. In future studies it will be necessary to consider separately the two types of heterozygote.

Confluent Heun functions and the physics of black holes: Resonant frequencies, Hawking radiation and scattering of scalar waves

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

Vieira, H.S., E-mail: horacio.santana.vieira@hotmail.com; Centro de Ciências, Tecnologia e Saúde, Universidade Estadual da Paraíba, CEP 58233-000, Araruna, PB; Bezerra, V.B., E-mail: valdir@fisica.ufpb.br

We apply the confluent Heun functions to study the resonant frequencies (quasispectrum), the Hawking radiation and the scattering process of scalar waves, in a class of spacetimes, namely, the ones generated by a Kerr–Newman–Kasuya spacetime (dyon black hole) and a Reissner–Nordström black hole surrounded by a magnetic field (Ernst spacetime). In both spacetimes, the solutions for the angular and radial parts of the corresponding Klein–Gordon equations are obtained exactly, for massive and massless fields, respectively. The special cases of Kerr and Schwarzschild black holes are analyzed and the solutions obtained, as well as in the case of a Schwarzschild blackmore » hole surrounded by a magnetic field. In all these special situations, the resonant frequencies, Hawking radiation and scattering are studied. - Highlights: • Charged massive scalar field in the dyon black hole and massless scalar field in the Ernst spacetime are analyzed. • The confluent Heun functions are applied to obtain the solution of the Klein–Gordon equation. • The resonant frequencies are obtained. • The Hawking radiation and the scattering process of scalar waves are examined.« less

A magnetic flux leakage and magnetostrictive guided wave hybrid transducer for detecting bridge cables.

PubMed

Xu, Jiang; Wu, Xinjun; Cheng, Cheng; Ben, Anran

2012-01-01

Condition assessment of cables has gained considerable attention for the bridge safety. A magnetic flux leakage and magnetostrictive guided wave hybrid transducer is provided to inspect bridge cables. The similarities and differences between the two methods are investigated. The hybrid transducer for bridge cables consists of an aluminum framework, climbing modules, embedded magnetizers and a ribbon coil. The static axial magnetic field provided by the magnetizers meets the needs of the magnetic flux leakage testing and the magnetostrictive guided wave testing. The magnetizers also provide the attraction for the climbing modules. In the magnetic flux leakage testing for the free length of cable, the coil induces the axial leakage magnetic field. In the magnetostrictive guided wave testing for the anchorage zone, the coil provides a pulse high power variational magnetic field for generating guided waves; the coil induces the magnetic field variation for receiving guided waves. The experimental results show that the transducer with the corresponding inspection system could be applied to detect the broken wires in the free length and in the anchorage zone of bridge cables.

A Magnetic Flux Leakage and Magnetostrictive Guided Wave Hybrid Transducer for Detecting Bridge Cables

PubMed Central

Xu, Jiang; Wu, Xinjun; Cheng, Cheng; Ben, Anran

2012-01-01

Condition assessment of cables has gained considerable attention for the bridge safety. A magnetic flux leakage and magnetostrictive guided wave hybrid transducer is provided to inspect bridge cables. The similarities and differences between the two methods are investigated. The hybrid transducer for bridge cables consists of an aluminum framework, climbing modules, embedded magnetizers and a ribbon coil. The static axial magnetic field provided by the magnetizers meets the needs of the magnetic flux leakage testing and the magnetostrictive guided wave testing. The magnetizers also provide the attraction for the climbing modules. In the magnetic flux leakage testing for the free length of cable, the coil induces the axial leakage magnetic field. In the magnetostrictive guided wave testing for the anchorage zone, the coil provides a pulse high power variational magnetic field for generating guided waves; the coil induces the magnetic field variation for receiving guided waves. The experimental results show that the transducer with the corresponding inspection system could be applied to detect the broken wires in the free length and in the anchorage zone of bridge cables. PMID:22368483

Dynamic studies of small animals with a four-color diffuse optical tomography imager

NASA Astrophysics Data System (ADS)

Schmitz, Christoph H.; Graber, Harry L.; Pei, Yaling; Farber, Mark; Stewart, Mark; Levina, Rita D.; Levin, Mikhail B.; Xu, Yong; Barbour, Randall L.

2005-09-01

We present newly developed instrumentation for full-tomographic four-wavelength, continuous wave, diffuse optical tomography (DOT) imaging on small animals. A small-animal imaging stage was constructed, from materials compatible with in-magnet studies, which offers stereotaxic fixation of the animal and precise, stable probe positioning. Instrument performance, based on calibration and phantom studies, demonstrates excellent long-term signal stability. DOT measurements of the functional rat brain response to electric paw stimulation are presented, and these demonstrate high data quality and excellent sensitivity to hemodynamic changes. A general linear model analysis on individual trials is used to localize and quantify the occurrence of functional behavior associated with the different hemoglobin state responses. Statistical evaluation of outcomes of individual trials is employed to identify significant regional response variations for different stimulation sites. Image results reveal a diffuse cortical response and a strong reaction of the thalamus, both indicative of activation of pain pathways by the stimulation. In addition, a weaker lateralized functional component is observed in the brain response, suggesting presence of motor activation. An important outcome of the experiment is that it shows that reactions to individual provocations can be monitored, without having to resort to signal averaging. Thus the described technology may be useful for studies of long-term trends in hemodynamic response, as would occur, for example, in behavioral studies involving freely moving animals.

Ultrasonic assisted rapid synthesis of high uniform super-paramagnetic microspheres with core-shell structure and robust magneto-chromatic ability

NASA Astrophysics Data System (ADS)

Zhang, Wenyan; Chen, Jiahua; Wang, Wei; Lu, GongXuan; Hao, Lingyun; Ni, Yaru; Lu, Chunhua; Xu, Zhongzi

2017-03-01

Super-paramagnetic core-shell microspheres were synthesized by ultrasonic assisted routine under low ultrasonic irradiation powers. Compared with conventional routine, ultrasonic effect could not only improve the uniformity of the core-shell structure of Fe3O4@SiO2, but shorten the synthesis time in large scale. Owing to their hydrophilicity and high surface charge, the Fe3O4@SiO2 microspheres could be dispersed well in distilled water to form homogeneous colloidal suspension. The suspensions have favorable magneto-chromatic ability that they sensitively exhibit brilliant colorful ribbons by magnetic attraction. The colorful ribbons, which distributed along the magnetic lines, make morphology of the magnetic fields become "visible" to naked eyed. Those colorful ribbons originate from strong magnetic interaction between the microspheres and magnetic fields. Furthermore, the magneto-chromatic performance is reversible as the colorful ribbons vanished rapidly with the removing of magnetic fields. The silica layer effectively enhanced the acid resistance and surface-oxidation resistance of theFe3O4@SiO2 microspheres, so they could exhibit stable magnetic nature and robust magneto-chromatic property in acid environment.

Stimulated Brillouin scatter in a magnetized ionospheric plasma.

PubMed

Bernhardt, P A; Selcher, C A; Lehmberg, R H; Rodriguez, S P; Thomason, J F; Groves, K M; McCarrick, M J; Frazer, G J

2010-04-23

High power electromagnetic waves transmitted from the HAARP facility in Alaska can excite low-frequency electrostatic waves by magnetized stimulated Brillouin scatter. Either an ion-acoustic wave with a frequency less than the ion cyclotron frequency (f(CI)) or an electrostatic ion cyclotron (EIC) wave just above f(CI) can be produced. The coupled equations describing the magnetized stimulated Brillouin scatter instability show that the production of both ion-acoustic and EIC waves is strongly influenced by the wave propagation relative to the background magnetic field. Experimental observations of stimulated electromagnetic emissions using the HAARP transmitter have confirmed that only ion-acoustic waves are excited for propagation along the magnetic zenith and that EIC waves can only be detected with oblique propagation angles. The ion composition can be obtained from the measured EIC frequency.

Topics in Nanophotonic Devices for Nitrogen-Vacancy Color Centers in Diamond

ERIC Educational Resources Information Center

Babinec, Thomas Michael

2012-01-01

Recently, developments in novel and high-purity materials allow for the presence of a single, solitary crystalline defect to define the electronic, magnetic, and optical functionality of a device. The discrete nature of the active dopant, whose properties are defined by a quantum mechanical description of its structure, enables radically new…

Magnetically tunable control of light reflection in an unusual optical protein of squid

NASA Astrophysics Data System (ADS)

Iwasaka, M.; Tagawa, K.; Kikuchi, Y.

2017-05-01

In this study, we focused on the magnetically tunable changes in the reflectivity of the protein reflectin, which is generated by squid and used to control their body surface color for camouflage in seawater. A cellular organelle called an iridosome was separated from the skin of the dorsal part of a squid (cuttlefish; Sepia esculenta), and the light reflection dynamics of iridosomes containing reflectin were measured with and without exposure to a magnetic field of 500 mT. The magnetic field induced both steady and transient increases of reflection by the iridosomes, suggesting that a reversible conformational change occurred inside the iridosomes when the magnetic field was switched on and off. The intensity of light scattering perpendicular to the direction of the magnetic field increased when the magnetic field was applied. This kind of behavior (Type I) occurred in the majority (60%) of the measured samples. Another kind of reflection change (Type II) was a transient increase in light reflection. It is speculated that the wave-shaped structure of the lipid membrane connected to reflectin proteins changed to enhance the light reflection of reflectin by altering the diamagnetic orientation of the lipid layer in the bent part of the membrane under the applied magnetic field. Overall, our results suggest that the mesoscale lipid layers changed their alignment diamagnetically and the length between iridescent layers was modified by the magnetic field, even though no obvious change in alignment occurred at the microscale.

Optimal design and evaluation of a color separation grating using rigorous coupled wave analysis

NASA Astrophysics Data System (ADS)

Nagayoshi, Mayumi; Oka, Keiko; Klaus, Werner; Komai, Yuki; Kodate, Kashiko

2006-02-01

In recent years, the technology which separates white light into the three primary colors of Red (R), Green (G) and Blue (B) and adjusts each optical intensity and composites R, G and B to display various colors is required in the development and spread of color visual equipments. Various color separation devices have been proposed and have been put to practical use in color visual equipments. We have focused on a small and light grating-type device which has the possibility of reduction in cost and large-scale production and generates only the three primary colors of R, G and B so that a high saturation level can be obtained. To perform a rigorous analysis and design of color separation gratings, our group has developed a program that is based on the Rigorous Coupled Wave Analysis (RCWA). We then calculated the parameters to obtain a diffraction efficiency of higher than 70% and the color gamut of about 70%. We will report on the design, fabrication and evaluation of color separation gratings that have been optimized for fabrication by laser drawing.

The locus of color sensation: Cortical color loss and the chromatic visual evoked potential

PubMed Central

Crognale, Michael A.; Duncan, Chad S.; Shoenhard, Hannah; Peterson, Dwight J.; Berryhill, Marian E.

2013-01-01

Color losses of central origin (cerebral achromatopsia and dyschromatopsia) can result from cortical damage and are most commonly associated with stroke. Such cases have the potential to provide useful information regarding the loci of the generation of the percept of color. One available tool to examine this issue is the chromatic visual evoked potential (cVEP). The cVEP has been used successfully to objectively quantify losses in color vision capacity in both congenital and acquired deficiencies of retinal origin but has not yet been applied to cases of color losses of cortical origin. In addition, it is not known with certainty which cortical sites are responsible for the generation of the cVEP waveform components. Here we report psychophysical and electrophysiological examination of a patient with color deficits resulting from a bilateral cerebral infarct in the ventral occipitotemporal region. Although this patient demonstrated pronounced color losses of a general nature, the waveform of the cVEP remains unaffected. Contrast response functions of the cVEP are also normal for this patient. The results suggest that the percept of color arises after the origin of the cVEP and that normal activity in those areas that give rise to the characteristic negative wave of the cVEP are not sufficient to provide for the normal sensation of color. PMID:23986535

Nonlinear equations of motion for Landau resonance interactions with a whistler mode wave

NASA Technical Reports Server (NTRS)

Inan, U. S.; Tkalcevic, S.

1982-01-01

A simple set of equations is presented for the description of the cyclotron averaged motion of Landau resonant particles in a whistler mode wave propagating at an angle to the static magnetic field. A comparison is conducted of the wave magnetic field and electric field effects for the parameters of the magnetosphere, and the parameter ranges for which the wave magnetic field effects would be negligible are determined. It is shown that the effect of the wave magnetic field can be neglected for low pitch angles, high normal wave angles, and/or high normalized wave frequencies.

Magnetic Excitations in Polyoxotungstate-Supported Lanthanoid Single-Molecule Magnets: An Inelastic Neutron Scattering and ab Initio Study.

PubMed

Vonci, Michele; Giansiracusa, Marcus J; Van den Heuvel, Willem; Gable, Robert W; Moubaraki, Boujemaa; Murray, Keith S; Yu, Dehong; Mole, Richard A; Soncini, Alessandro; Boskovic, Colette

2017-01-03

Inelastic neutron scattering (INS) has been used to investigate the crystal field (CF) magnetic excitations of the analogs of the most representative lanthanoid-polyoxometalate single-molecule magnet family: Na 9 [Ln(W 5 O 18 ) 2 ] (Ln = Nd, Tb, Ho, Er). Ab initio complete active space self-consistent field/restricted active space state interaction calculations, extended also to the Dy analog, show good agreement with the experimentally determined low-lying CF levels, with accuracy better in most cases than that reported for approaches based only on simultaneous fitting to CF models of magnetic or spectroscopic data for isostructural Ln families. In this work we demonstrate the power of a combined spectroscopic and computational approach. Inelastic neutron scattering has provided direct access to CF levels, which together with the magnetometry data, were employed to benchmark the ab initio results. The ab initio determined wave functions corresponding to the CF levels were in turn employed to assign the INS transitions allowed by selection rules and interpret the observed relative intensities of the INS peaks. Ultimately, we have been able to establish the relationship between the wave function composition of the CF split Ln III ground multiplets and the experimentally measured magnetic and spectroscopic properties for the various analogs of the Na 9 [Ln(W 5 O 18 ) 2 ] family.

Large-amplitude hydromagnetic waves in collisionless relativistic plasma - Exact solution for the fast-mode magnetoacoustic wave

NASA Technical Reports Server (NTRS)

Barnes, A.

1983-01-01

An exact nonlinear solution is found to the relativistic kinetic and electrodynamic equations (in their hydromagnetic limit) that describes the large-amplitude fast-mode magnetoacoustic wave propagating normal to the magnetic field in a collisionless, previously uniform plasma. It is pointed out that a wave of this kind will be generated by transverse compression of any collisionless plasma. The solution is in essence independent of the detailed form of the particle momentum distribution functions. The solution is obtained, in part, through the method of characteristics; the wave exhibits the familiar properties of steepening and shock formation. A detailed analysis is given of the ultrarelativistic limit of this wave.

Seasonal Variations in Color Preference.

PubMed

Schloss, Karen B; Nelson, Rolf; Parker, Laura; Heck, Isobel A; Palmer, Stephen E

2017-08-01

We investigated how color preferences vary according to season and whether those changes could be explained by the ecological valence theory (EVT). To do so, we assessed the same participants' preferences for the same colors during fall, winter, spring, and summer in the northeastern United States, where there are large seasonal changes in environmental colors. Seasonal differences were most pronounced between fall and the other three seasons. Participants liked fall-associated dark-warm colors-for example, dark-red, dark-orange (brown), dark-yellow (olive), and dark-chartreuse-more during fall than other seasons. The EVT could explain these changes with a modified version of Palmer and Schloss' (2010) weighted affective valence estimate (WAVE) procedure that added an activation term to the WAVE equation. The results indicate that color preferences change according to season, as color-associated objects become more/less activated in the observer. These seasonal changes in color preferences could not be characterized by overall shifts in weights along cone-contrast axes. Copyright © 2016 Cognitive Science Society, Inc.

Drift Wave Chaos and Turbulence in a LAPTAG Plasma Physics experiment

NASA Astrophysics Data System (ADS)

Katz, Cami; Gekelman, Walter; Pribyl, Patrick; Wise, Joe; Birge-Lee, Henry; Baker, Bob; Marmie, Ken; Thomas, Sam; Buckley-Bonnano, Samuel

2015-11-01

Whenever there is a pressure gradient in a magnetized plasma drift waves occur spontaneously. Drift waves have density and electrical potential fluctuations but no self magnetic field. In our experiment the drift waves form spontaneously in a narrow plasma column. (ne = 5 ×1011 cm3 , Te = 5 eV , B = 200 Gauss, dia = 25 cm , L = 1 . 5 m). As the drift waves grow from noise simple averaging techniques cannot be used to map them out in space and time. The ion saturation current Isat n√{Te} is recorded for an ensemble of 50 shots on a fixed probe located on the density gradient and for a movable probe. The probe signals are not sinusoidal and are filtered to calculate the cross-spectral function CSF = ∫ ∑ nshot Ifix, ωr->1 , tImov , ω (r->1 + δr-> , t + τ) dt , which can be used to extract the temporal and spatially varying wave patterns. The dominant wave at 18 kHz is a rotating spiral with m =2. LAPTAG is a university-high school alliance outreach program, which has been in existence for over 20 years. Work done at the BaPSF and supported by NSF/DOE.

Large Amplitude Whistlers in the Magnetosphere Observed with Wind-Waves

NASA Technical Reports Server (NTRS)

Kellogg, P. J.; Cattell, C. A.; Goetz, K.; Monson, S. J.; Wilson, L. B., III

2011-01-01

We describe the results of a statistical survey of Wind-Waves data motivated by the recent STEREO/Waves discovery of large-amplitude whistlers in the inner magnetosphere. Although Wind was primarily intended to monitor the solar wind, the spacecraft spent 47 h inside 5 R(sub E) and 431 h inside 10 R(sub E) during the 8 years (1994-2002) that it orbited the Earth. Five episodes were found when whistlers had amplitudes comparable to those of Cattell et al. (2008), i.e., electric fields of 100 m V/m or greater. The whistlers usually occurred near the plasmapause. The observations are generally consistent with the whistlers observed by STEREO. In contrast with STEREO, Wind-Waves had a search coil, so magnetic measurements are available, enabling determination of the wave vector without a model. Eleven whistler events with useable magnetic measurements were found. The wave vectors of these are distributed around the magnetic field direction with angles from 4 to 48deg. Approximations to observed electron distribution functions show a Kennel-Petschek instability which, however, does not seem to produce the observed whistlers. One Wind episode was sampled at 120,000 samples/s, and these events showed a signature that is interpreted as trapping of electrons in the electrostatic potential of an oblique whistler. Similar waveforms are found in the STEREO data. In addition to the whistler waves, large amplitude, short duration solitary waves (up to 100 mV/m), presumed to be electron holes, occur in these passes, primarily on plasma sheet field lines mapping to the auroral zone.

Segregation of helicity in inertial wave packets

NASA Astrophysics Data System (ADS)

Ranjan, A.

2017-03-01

Inertial waves are known to exist in the Earth's rapidly rotating outer core and could be important for the dynamo generation. It is well known that a monochromatic inertial plane wave traveling parallel to the rotation axis (along positive z ) has negative helicity while the wave traveling antiparallel (negative z ) has positive helicity. Such a helicity segregation, north and south of the equator, is necessary for the α2-dynamo model based on inertial waves [Davidson, Geophys. J. Int. 198, 1832 (2014), 10.1093/gji/ggu220] to work. The core is likely to contain a myriad of inertial waves of different wave numbers and frequencies. In this study, we investigate whether this characteristic of helicity segregation also holds for an inertial wave packet comprising waves with the same sign of Cg ,z, the z component of group velocity. We first derive the polarization relations for inertial waves and subsequently derive the resultant helicity in wave packets forming as a result of superposition of two or more waves. We find that the helicity segregation does hold for an inertial wave packet unless the wave numbers of the constituent waves are widely separated. In the latter case, regions of opposite color helicity do appear, but the mean helicity retains the expected sign. An illustration of this observation is provided by (a) calculating the resultant helicity for a wave packet formed by superposition of four upward-propagating inertial waves with different wave vectors and (b) conducting the direct numerical simulation of a Gaussian eddy under rapid rotation. Last, the possible effects of other forces such as the viscous dissipation, the Lorentz force, buoyancy stratification, and nonlinearity on helicity are investigated and discussed. The helical structure of the wave packet is likely to remain unaffected by dissipation or the magnetic field, but can be modified by the presence of linearly stable stratification and nonlinearity.

Modulated heat pulse propagation and partial transport barriers in chaotic magnetic fields

DOE PAGES

del-Castillo-Negrete, Diego; Blazevski, Daniel

2016-04-01

Direct numerical simulations of the time dependent parallel heat transport equation modeling heat pulses driven by power modulation in 3-dimensional chaotic magnetic fields are presented. The numerical method is based on the Fourier formulation of a Lagrangian-Green's function method that provides an accurate and efficient technique for the solution of the parallel heat transport equation in the presence of harmonic power modulation. The numerical results presented provide conclusive evidence that even in the absence of magnetic flux surfaces, chaotic magnetic field configurations with intermediate levels of stochasticity exhibit transport barriers to modulated heat pulse propagation. In particular, high-order islands and remnants of destroyed flux surfaces (Cantori) act as partial barriers that slow down or even stop the propagation of heat waves at places where the magnetic field connection length exhibits a strong gradient. The key parameter ismore » $$\\gamma=\\sqrt{\\omega/2 \\chi_\\parallel}$$ that determines the length scale, $$1/\\gamma$$, of the heat wave penetration along the magnetic field line. For large perturbation frequencies, $$\\omega \\gg 1$$, or small parallel thermal conductivities, $$\\chi_\\parallel \\ll 1$$, parallel heat transport is strongly damped and the magnetic field partial barriers act as robust barriers where the heat wave amplitude vanishes and its phase speed slows down to a halt. On the other hand, in the limit of small $$\\gamma$$, parallel heat transport is largely unimpeded, global transport is observed and the radial amplitude and phase speed of the heat wave remain finite. Results on modulated heat pulse propagation in fully stochastic fields and across magnetic islands are also presented. In qualitative agreement with recent experiments in LHD and DIII-D, it is shown that the elliptic (O) and hyperbolic (X) points of magnetic islands have a direct impact on the spatio-temporal dependence of the amplitude and the time delay of modulated heat pulses.« less

ISEE observations of low frequency waves and ion distribution function evolution in the plasma sheet boundary layer

NASA Technical Reports Server (NTRS)

Elphic, R. C.; Gary, S. P.

1990-01-01

This paper describes ISEE plasma and magnetic fluctuation observations during two crossings of the plasma sheet boundary layer (PSBL) in the earth's magnetotail. Distribution function observations show that the counterstreaming ion components undergo pitch-angle scattering and evolve into a shell distribution in velocity space. This evolution is correlated with the development of low frequency, low amplitude magnetic fluctuations. However, the measured wave amplitudes are insufficient to accomplish the observed degree of ion pitch-angle scatttering locally; the near-earth distributions may be the result of processes occurring much farther down the magnetotail. Results show a clear correlation between the ion component beta and the relative streaming speed of the two components, suggesting that electromagnetic ion/ion instabilities do play an important role in the scattering of PSBL ions.

Energy levels and radiative rates for Ne-like ions from Cu to Ga

NASA Astrophysics Data System (ADS)

Singh, Narendra; Aggarwal, Sunny

2017-11-01

Energy levels, lifetimes and wave function compositions are computed for 127 fine structural levels in Ne-like ions (Z=29{-}31). Configuration interaction has been included among 51 configurations (generating 1016 levels) and multiconfigurational Dirac-Fock method is used to generate the wave functions. Similar calculations have also been performed using the fully relativistic flexible atomic code (FAC). Transition wavelength, oscillator strength, transition probabilities and line strength are reported for electric dipole (E1), electric quadrupole (E2), magnetic dipole (M1) and magnetic quadrupole (M2) transitions from the ground level. We compared our calculated results with the available data in the literature. The calculated results are found to be in close agreement with the previous results. Further, we predict some new atomic data which may be important for plasma diagnostics.

Modification of wave propagation and wave travel-time by the presence of magnetic fields in the solar network atmosphere

NASA Astrophysics Data System (ADS)

Nutto, C.; Steiner, O.; Schaffenberger, W.; Roth, M.

2012-02-01

Context. Observations of waves at frequencies above the acoustic cut-off frequency have revealed vanishing wave travel-times in the vicinity of strong magnetic fields. This detection of apparently evanescent waves, instead of the expected propagating waves, has remained a riddle. Aims: We investigate the influence of a strong magnetic field on the propagation of magneto-acoustic waves in the atmosphere of the solar network. We test whether mode conversion effects can account for the shortening in wave travel-times between different heights in the solar atmosphere. Methods: We carry out numerical simulations of the complex magneto-atmosphere representing the solar magnetic network. In the simulation domain, we artificially excite high frequency waves whose wave travel-times between different height levels we then analyze. Results: The simulations demonstrate that the wave travel-time in the solar magneto-atmosphere is strongly influenced by mode conversion. In a layer enclosing the surface sheet defined by the set of points where the Alfvén speed and the sound speed are equal, called the equipartition level, energy is partially transferred from the fast acoustic mode to the fast magnetic mode. Above the equipartition level, the fast magnetic mode is refracted due to the large gradient of the Alfvén speed. The refractive wave path and the increasing phase speed of the fast mode inside the magnetic canopy significantly reduce the wave travel-time, provided that both observing levels are above the equipartition level. Conclusions: Mode conversion and the resulting excitation and propagation of fast magneto-acoustic waves is responsible for the observation of vanishing wave travel-times in the vicinity of strong magnetic fields. In particular, the wave propagation behavior of the fast mode above the equipartition level may mimic evanescent behavior. The present wave propagation experiments provide an explanation of vanishing wave travel-times as observed with multi-line high-cadence instruments. Movies are available in electronic form at http://www.aanda.org

Gravitational instability in isotropic MHD plasma waves

NASA Astrophysics Data System (ADS)

Cherkos, Alemayehu Mengesha

2018-04-01

The effect of compressive viscosity, thermal conductivity and radiative heat-loss functions on the gravitational instability of infinitely extended homogeneous MHD plasma has been investigated. By taking in account these parameters we developed the six-order dispersion relation for magnetohydrodynamic (MHD) waves propagating in a homogeneous and isotropic plasma. The general dispersion relation has been developed from set of linearized basic equations and solved analytically to analyse the conditions of instability and instability of self-gravitating plasma embedded in a constant magnetic field. Our result shows that the presence of viscosity and thermal conductivity in a strong magnetic field substantially modifies the fundamental Jeans criterion of gravitational instability.

Spin wave spectra in perpendicularly magnetized permalloy rings

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

Zhou, X.; Ding, J.; Adeyeye, A. O., E-mail: eleaao@nus.edu.sg

2015-03-16

The dynamic behavior of perpendicularly magnetized permalloy circular rings is systematically investigated as a function of film thickness using broadband field modulated ferromagnetic resonance spectroscopy. We observed the splitting of one spin wave mode into a family of dense resonance peaks for the rings, which is markedly different from the single mode observed for continuous films of the same thickness. As the excitation frequency is increased, the mode family observed for the rings gradually converges into one mode. With the increase in the film thickness, a sparser spectrum of modes is observed. Our experimental results are in qualitative agreement withmore » the dynamic micromagnetic simulations.« less

Wave Function and Emergent SU(2) Symmetry in the ν_{T}=1 Quantum Hall Bilayer.

PubMed

Lian, Biao; Zhang, Shou-Cheng

2018-02-16

We propose a trial wave function for the quantum Hall bilayer system of total filling factor ν_{T}=1 at a layer distance d to magnetic length ℓ ratio d/ℓ=κ_{c1}≈1.1, where the lowest charged excitation is known to have a level crossing. The wave function has two-particle correlations, which fit well with those in previous numerical studies, and can be viewed as a Bose-Einstein condensate of free excitons formed by composite bosons and anticomposite bosons in different layers. We show the free nature of these excitons indicating an emergent SU(2) symmetry for the composite bosons at d/ℓ=κ_{c1}, which leads to the level crossing in low-lying charged excitations. We further show the overlap between the trial wave function, and the ground state of a small size exact diagonalization is peaked near d/ℓ=κ_{c1}, which supports our theory.

Relativistic nonlinear plasma waves in a magnetic field

NASA Technical Reports Server (NTRS)

Kennel, C. F.; Pellat, R.

1975-01-01

Five relativistic plane nonlinear waves were investigated: circularly polarized waves and electrostatic plasma oscillations propagating parallel to the magnetic field, relativistic Alfven waves, linearly polarized transverse waves propagating in zero magnetic field, and the relativistic analog of the extraordinary mode propagating at an arbitrary angle to the magnetic field. When the ions are driven relativistic, they behave like electrons, and the assumption of an 'electron-positron' plasma leads to equations which have the form of a one-dimensional potential well. The solutions indicate that a large-amplitude superluminous wave determines the average plasma properties.

Ferromagnetic resonance in a topographically modulated permalloy film

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

Sklenar, J.; Tucciarone, P.; Lee, R. J.

2015-04-01

A major focus within the field of magnonics involves the manipulation and control spin wave modes. This is usually done by patterning continuous soft magnetic films. Here, we report on work in which we use topographic modifications of a continuous magnetic thin film, rather than lithographic patterning techniques, to modify the magnon spectrum. To demonstrate this technique we have performed in-plane, broad-band, ferromagnetic res- onance studies on a 100 nm Permalloy film sputtered unto a colloidal crystal with individual sphere diameters of 200 nm. Effects resulting from the, ideally, six-fold symmetric underlying colloidal crystal were studied as a function ofmore » the in plane field angle through experiment and micromagnetic modeling. Experimentally, we find two primary spin wave modes; the ratio of the amplitude of these two modes exhibits a six-fold dependence. Modeling shows that both modes are fundamental modes that are nodeless in the unit cell but reside in different demagnetized regions of the unit cell. Additionally, modeling suggests the presence of new higher order topographically modified spin wave modes. Our results demonstrate that topographic modification of magnetic thin films opens new directions for manipulating spin wave modes.« less

Dispersion relation for electromagnetic propagation in stochastic dielectric and magnetic helical photonic crystals

NASA Astrophysics Data System (ADS)

Avendaño, Carlos G.; Reyes, Arturo

2017-03-01

We theoretically study the dispersion relation for axially propagating electromagnetic waves throughout a one-dimensional helical structure whose pitch and dielectric and magnetic properties are spatial random functions with specific statistical characteristics. In the system of coordinates rotating with the helix, by using a matrix formalism, we write the set of differential equations that governs the expected value of the electromagnetic field amplitudes and we obtain the corresponding dispersion relation. We show that the dispersion relation depends strongly on the noise intensity introduced in the system and the autocorrelation length. When the autocorrelation length increases at fixed fluctuation and when the fluctuation augments at fixed autocorrelation length, the band gap widens and the attenuation coefficient of electromagnetic waves propagating in the random medium gets larger. By virtue of the degeneracy in the imaginary part of the eigenvalues associated with the propagating modes, the random medium acts as a filter for circularly polarized electromagnetic waves, in which only the propagating backward circularly polarized wave can propagate with no attenuation. Our results are valid for any kind of dielectric and magnetic structures which possess a helical-like symmetry such as cholesteric and chiral smectic-C liquid crystals, structurally chiral materials, and stressed cholesteric elastomers.

Traveling waves in a magnetized Taylor-Couette flow.

PubMed

Liu, Wei; Goodman, Jeremy; Ji, Hantao

2007-07-01

We investigate numerically a traveling wave pattern observed in experimental magnetized Taylor-Couette flow at low magnetic Reynolds number. By accurately modeling viscous and magnetic boundaries in all directions, we reproduce the experimentally measured wave patterns and their amplitudes. Contrary to previous claims, the waves are shown to be transiently amplified disturbances launched by viscous boundary layers, rather than globally unstable magnetorotational modes.

Alertness function of thalamus in conflict adaptation.

PubMed

Wang, Xiangpeng; Zhao, Xiaoyue; Xue, Gui; Chen, Antao

2016-05-15

Conflict adaptation reflects the ability to improve current conflict resolution based on previously experienced conflict, which is crucial for our goal-directed behaviors. In recent years, the roles of alertness are attracting increasing attention when discussing the generation of conflict adaptation. However, due to the difficulty of manipulating alertness, very limited progress has been made in this line. Inspired by that color may affect alertness, we manipulated background color of experimental task and found that conflict adaptation significantly presented in gray and red backgrounds but did not in blue background. Furthermore, behavioral and functional magnetic resonance imaging results revealed that the modulation of color on conflict adaptation was implemented through changing alertness level. In particular, blue background eliminated conflict adaptation by damping the alertness regulating function of thalamus and the functional connectivity between thalamus and inferior frontal gyrus (IFG). In contrast, in gray and red backgrounds where alertness levels are typically high, the thalamus and the right IFG functioned normally and conflict adaptations were significant. Therefore, the alertness function of thalamus is determinant to conflict adaptation, and thalamus and right IFG are crucial nodes of the neural circuit subserving this ability. Present findings provide new insights into the neural mechanisms of conflict adaptation. Copyright © 2016 Elsevier Inc. All rights reserved.

Influence of magnetic field configuration on magnetohydrodynamic waves in Earth's core

NASA Astrophysics Data System (ADS)

Knezek, Nicholas; Buffett, Bruce

2018-04-01

We develop a numerical model to study magnetohydrodynamic waves in a thin layer of stratified fluid near the surface of Earth's core. Past studies have been limited to using simple background magnetic field configurations. However, the choice of field distribution can dramatically affect the structure and frequency of the waves. To permit a more general treatment of background magnetic field and layer stratification, we combine finite volume and Fourier methods to describe the wave motions. We validate our model by comparisons to previous studies and examine the influence of background magnetic field configuration on two types of magnetohydrodynamic waves. We show that the structure of zonal Magnetic-Archimedes-Coriolis (MAC) waves for a dipole background field is unstable to small perturbations of the field strength in the equatorial region. Modifications to the wave structures are computed for a range of field configurations. In addition, we show that non-zonal MAC waves are trapped near the equator for realistic magnetic field distributions, and that their latitudinal extent depends upon the distribution of magnetic field strength at the CMB.

Stimulated Brillouin Scatter in a Magnetized Ionospheric Plasma

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

Bernhardt, P. A.; Selcher, C. A.; Lehmberg, R. H.

2010-04-23

High power electromagnetic waves transmitted from the HAARP facility in Alaska can excite low-frequency electrostatic waves by magnetized stimulated Brillouin scatter. Either an ion-acoustic wave with a frequency less than the ion cyclotron frequency (f{sub CI}) or an electrostatic ion cyclotron (EIC) wave just above f{sub CI} can be produced. The coupled equations describing the magnetized stimulated Brillouin scatter instability show that the production of both ion-acoustic and EIC waves is strongly influenced by the wave propagation relative to the background magnetic field. Experimental observations of stimulated electromagnetic emissions using the HAARP transmitter have confirmed that only ion-acoustic waves aremore » excited for propagation along the magnetic zenith and that EIC waves can only be detected with oblique propagation angles. The ion composition can be obtained from the measured EIC frequency.« less

Homogeneous microwave field emitted propagating spin waves: Direct imaging and modeling

NASA Astrophysics Data System (ADS)

Lohman, Mathis; Mozooni, Babak; McCord, Jeffrey

2018-03-01

We explore the generation of propagating dipolar spin waves by homogeneous magnetic field excitation in the proximity of the boundaries of magnetic microstructures. Domain wall motion, precessional dynamics, and propagating spin waves are directly imaged by time-resolved wide-field magneto-optical Kerr effect microscopy. The aspects of spin wave generation are clarified by micromagnetic calculations matching the experimental results. The region of dipolar spin wave formation is confined to the local resonant excitation due to non-uniform internal demagnetization fields at the edges of the patterned sample. Magnetic domain walls act as a border for the propagation of plane and low damped spin waves, thus restraining the spin waves within the individual magnetic domains. The findings are of significance for the general understanding of structural and configurational magnetic boundaries for the creation, the propagation, and elimination of spin waves.

Reflection and interference of electromagnetic waves in inhomogeneous media

NASA Technical Reports Server (NTRS)

Geiger, F. E.; Kyle, H. L.

1973-01-01

Solutions were obtained of the wave equation for a plane horizontally polarized electro-magnetic wave incident on a semi infinite two dimensional inhomogeneous medium. Two problems were considered: An inhomogeneous half space, and an inhomogeneous layer of arbitrary thickness. Solutions of the wave equation were obtained in terms of Hankel functions with complex arguments. Numerical calculations were made of the reflection coefficient R at the interface of the homogeneous medium. The startling results show that the reflection coefficient for a complex dielectric constant with gradient, can be less than that of the same medium with zero gradient.

Sharp-front wave of strong magnetic field diffusion in solid metal

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

Xiao, Bo; Gu, Zhuo-wei; Kan, Ming-xian

When a strong magnetic field diffuses into a solid metal, if the metal's resistance possesses an abrupt rise at some critical temperature and the magnetic field strength is above some critical value, the magnetic field will diffuse into the metal in the form of a sharp-front wave. Formulas for the critical conditions under which a sharp-front magnetic diffusion wave emerges and a formula for the wave-front velocity are derived in this work.

Multi-Ferroic Polymer Nanoparticle Composites for Next Generation Metamaterials

DTIC Science & Technology

2016-05-23

another application, electromagnetic wave shielding . Electromagnetic wave induces current which results in loss of energy. Thus magnetic nanoparticles...applicable for electromagnetic wave shielding . For better electromagnetic wave shielding capability, i) high dielectric constant, ii) high magnetic ...electromagnetic wave shielding properties7,8. In such point of view, designing a structure, magnetic nanoparticles in two dimensional electric conductive matrix

High performance bias-selectable three-color Short-wave/Mid-wave/Long-wave Infrared Photodetectors based on Type-II InAs/GaSb/AlSb superlattices

PubMed Central

Hoang, Anh Minh; Dehzangi, Arash; Adhikary, Sourav; Razeghi, Manijeh

2016-01-01

We propose a new approach in device architecture to realize bias-selectable three-color shortwave-midwave-longwave infrared photodetectors based on InAs/GaSb/AlSb type-II superlattices. The effect of conduction band off-set and different doping levels between two absorption layers are employed to control the turn-on voltage for individual channels. The optimization of these parameters leads to a successful separation of operation regimes; we demonstrate experimentally three-color photodiodes without using additional terminal contacts. As the applied bias voltage varies, the photodiodes exhibit sequentially the behavior of three different colors, corresponding to the bandgap of three absorbers. Well defined cut-offs and high quantum efficiency in each channel are achieved. Such all-in-one devices also provide the versatility of working as single or dual-band photodetectors at high operating temperature. With this design, by retaining the simplicity in device fabrication, this demonstration opens the prospect for three-color infrared imaging. PMID:27051979

Decoding and reconstructing color from responses in human visual cortex.

PubMed

Brouwer, Gijs Joost; Heeger, David J

2009-11-04

How is color represented by spatially distributed patterns of activity in visual cortex? Functional magnetic resonance imaging responses to several stimulus colors were analyzed with multivariate techniques: conventional pattern classification, a forward model of idealized color tuning, and principal component analysis (PCA). Stimulus color was accurately decoded from activity in V1, V2, V3, V4, and VO1 but not LO1, LO2, V3A/B, or MT+. The conventional classifier and forward model yielded similar accuracies, but the forward model (unlike the classifier) also reliably reconstructed novel stimulus colors not used to train (specify parameters of) the model. The mean responses, averaged across voxels in each visual area, were not reliably distinguishable for the different stimulus colors. Hence, each stimulus color was associated with a unique spatially distributed pattern of activity, presumably reflecting the color selectivity of cortical neurons. Using PCA, a color space was derived from the covariation, across voxels, in the responses to different colors. In V4 and VO1, the first two principal component scores (main source of variation) of the responses revealed a progression through perceptual color space, with perceptually similar colors evoking the most similar responses. This was not the case for any of the other visual cortical areas, including V1, although decoding was most accurate in V1. This dissociation implies a transformation from the color representation in V1 to reflect perceptual color space in V4 and VO1.

Generation and evolution of anisotropic turbulence and related energy transfer in a multi-species solar wind

NASA Astrophysics Data System (ADS)

Maneva, Yana; Poedts, Stefaan

2017-04-01

The electromagnetic fluctuations in the solar wind represent a zoo of plasma waves with different properties, whose wavelengths range from largest fluid scales to the smallest dissipation scales. By nature the power spectrum of the magnetic fluctuations is anisotropic with different spectral slopes in parallel and perpendicular directions with respect to the background magnetic field. Furthermore, the magnetic field power spectra steepen as one moves from the inertial to the dissipation range and we observe multiple spectral breaks with different slopes in parallel and perpendicular direction at the ion scales and beyond. The turbulent dissipation of magnetic field fluctuations at the sub-ion scales is believed to go into local ion heating and acceleration, so that the spectral breaks are typically associated with particle energization. The gained energy can be in the form of anisotropic heating, formation of non-thermal features in the particle velocity distributions functions, and redistribution of the differential acceleration between the different ion populations. To study the relation between the evolution of the anisotropic turbulent spectra and the particle heating at the ion and sub-ion scales we perform a series of 2.5D hybrid simulations in a collisionless drifting proton-alpha plasma. We neglect the fast electron dynamics and treat the electrons as an isothermal fluid electrons, whereas the protons and a minor population of alpha particles are evolved in a fully kinetic manner. We start with a given wave spectrum and study the evolution of the magnetic field spectral slopes as a function of the parallel and perpendicular wave¬numbers. Simultaneously, we track the particle response and the energy exchange between the parallel and perpendicular scales. We observe anisotropic behavior of the turbulent power spectra with steeper slopes along the dominant energy-containing direction. This means that for parallel and quasi-parallel waves we have steeper spectral slope in parallel direction, whereas for highly oblique waves the dissipation occurs predominantly in perpendicular direction and the spectral slopes are steeper across the background magnetic field. The value of the spectral slopes depends on the angle of propagation, the spectral range, as well as the plasma properties. In general the dissipation is stronger at small scales and the corresponding spectral slopes there are steeper. For parallel and quasi-parallel propagation the prevailing energy cascade remains along the magnetic field, whereas for initially isotropic oblique turbulence the cascade develops mainly in perpendicular direction.

Tuning Magnetic Properties of Soft Ferromagnetic Thin Films for High Frequency Applications

NASA Astrophysics Data System (ADS)

Rementer, Colin Richard

This work focuses on the design, synthesis, characterization and integration of soft ferromagnetic multilayer structures for their applications in high frequency applications. Presently, the form factor of current telecommunication devices, i.e., antenna, is fundamentally limited by the wavelength it is designed to transmit or receive. In order to adapt to new technologies, a method for subverting this paradigm has been developed by use of magnetoelectric, strain-coupled multiferroic systems, which requires optimized ferroic materials, especially ferromagnetic thin films. Two approaches were considered to achieve this goal, doping (boron) and multilayer (NiFe) heterostructures, where FeGa was selected as the reference phase for both approaches. Doping magnetic materials with boron has been shown to enhance the magnetic softness while maintaining magnetostriction. Multilayer heterostructures offer the possibility of tuning magnetic responses by taking advantage of materials with complementary magnetic properties. Iron-gallium-boron (FeGaB) was synthesized via co-sputtering of Fe 75Ga25 and boron. The addition of boron to Fe75Ga 25 reduced the magnetocrystalline anisotropy energy, enhancing the high frequency properties. Magnetometry studies showed that the coercivity was reduced by 70% with 15% boron (at. %) while maintaining 90% of the magnetization of FeGa. Fixed frequency FMR studies showed that the addition of boron reduced the linewidth by up to 70% to a value of 210 Oe. Electrically poled hysteresis measurements showed that the film has a saturation magnetostriction of 50 microepsilon. FeGaB's properties were shown to be tunable and can be optimized by controlling the boron concentration within 11-15% but this approach did not yield the desired FMR linewidth. Multilayers of sputtered Fe85Ga15/Ni81Fe 19, or FeGa/NiFe, were examined to tailor their magnetic softness, loss at microwave frequencies, permeability, and magnetoelasticity, leveraging the magnetic softness and low loss of NiFe, and the high saturation magnetostriction (lambdas) and magnetization (MS) of FeGa. A systematic change was observed as the number of bilayers or interfaces increases: a seven-bilayer structure results in an 88% reduction in coercivity and a 55% reduction in FMR linewidth at X-band compared to a single phase FeGa film, while maintaining a high relative permeability of 700. The magnetostriction was slightly reduced by the addition of NiFe but still maintained up to 70% that of single phase FeGa. Analyses of the domain size revealed that this effect is a function of the layer thicknesses: thinner layers have larger in-plane domains, leading to lower coercivity. The depth-dependent composition and magnetization of these heterostructures as a function of magnetic and electric fields were assessed via polarized neutron reflectometry and the rotation of magnetization of the individual layers with applied strain was found to be deterministic. The tunability of these magnetic heterostructures makes them suitable candidates for RF magnetic applications requiring strong magnetoelastic coupling and low loss. Device functionality was assessed by integrating multilayer samples into two different antenna architectures. A surface acoustic wave (SAW) structure was used to determine the magnitude of absorption of acoustic wave energy from piezoelectric LiNbO3. Samples with the optimized 5 BL structure, 5 BL(SAW1) (50 nm) and 5 BL(SAW2) (100 nm), were fabricated and evaluated and absorbed 17 % of the acoustic energy from the strain wave. A bulk acoustic wave (BAW) structure was used to study how the material could convert the energy from an electromagnetic wave into an acoustic wave. A thick 12 BL(BAW) sample was integrated into a device and showed a low FMR linewidth and high permeability. This work provided the proof of concept that both doping and interfacial engineering are viabl approaches for tuning the magnetic properties of FeGa, and could be extended to other magnetoelastic systems. Multilayer magnetic materials are a promising alternative to single phase ferromagnetic materials as well as doped material systems for resonator or sensor applications. The low coercivity, high permeability, and high strain sensitivity of these samples make them promising candidates for high frequency, strain-coupled multiferroic systems.

Wave modeling in a cylindrical non-uniform helicon discharge

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

Chang, L.; Hole, M. J.; Caneses, J. F.

2012-08-15

A radio frequency field solver based on Maxwell's equations and a cold plasma dielectric tensor is employed to describe wave phenomena observed in a cylindrical non-uniform helicon discharge. The experiment is carried out on a recently built linear plasma-material interaction machine: The magnetized plasma interaction experiment [Blackwell et al., Plasma Sources Sci. Technol. (submitted)], in which both plasma density and static magnetic field are functions of axial position. The field strength increases by a factor of 15 from source to target plate, and the plasma density and electron temperature are radially non-uniform. With an enhancement factor of 9.5 to themore » electron-ion Coulomb collision frequency, a 12% reduction in the antenna radius, and the same other conditions as employed in the experiment, the solver produces axial and radial profiles of wave amplitude and phase that are consistent with measurements. A numerical study on the effects of axial gradient in plasma density and static magnetic field on wave propagations is performed, revealing that the helicon wave has weaker attenuation away from the antenna in a focused field compared to a uniform field. This may be consistent with observations of increased ionization efficiency and plasma production in a non-uniform field. We find that the relationship between plasma density, static magnetic field strength, and axial wavelength agrees well with a simple theory developed previously. A numerical scan of the enhancement factor to the electron-ion Coulomb collision frequency from 1 to 15 shows that the wave amplitude is lowered and the power deposited into the core plasma decreases as the enhancement factor increases, possibly due to the stronger edge heating for higher collision frequencies.« less

A Green's function formulation of the k→ ·p→ theory in the presence of spin-orbit interaction and magnetic field: Application to the electronic structure and related properties of w-GaN

NASA Astrophysics Data System (ADS)

Shadangi, Subrat K.; Mishra, Sambit R.; Tripathi, Gouri S.

2018-01-01

We use a Green's function perturbation formalism in the presence of an applied magnetic field and spin-orbit effects in the effective mass representation (EMR). The lack of lattice translational symmetry of the vector potential in the presence of the magnetic field is considered by redefining the Green's function in terms of the Peierls' phase factor. The equation of motion of the Green's function as a function of a magnetic wave vector was solved using perturbation theory, leading to expressions for the effective mass and the g-factor. We study the electronic structure of wurtzite GaN theoretically using the resulting k→ ·π→ method, where k→ is the electronic wave vector and π→ is the relativistic momentum operator by considering the conduction band edge and three valence bands. The k→ ·π→ Hamiltonians for the conduction band edge and the valence bands are diagonalized, considering the conduction band and one valence band at a time. We obtain electron and hole dispersions. Effects of other bands are considered by using perturbation theory. Resulting dispersions agree with the results of other calculations. In order to study the effective mass and the g-factor, we use the eigenvalues and eigenfunctions obtained after the diagonalization. Our results for the effective masses and the g-factors agree fairly well with available theoretical and experimental results, Temperature dependence of both the electronic effective mass and g-factor is studied and trends obtained agree with the existing experimental data.

Magnetic electroanatomical mapping for ablation of focal atrial tachycardias.

PubMed

Marchlinski, F; Callans, D; Gottlieb, C; Rodriguez, E; Coyne, R; Kleinman, D

1998-08-01

Uniform success for ablation of focal atrial tachycardias has been difficult to achieve using standard catheter mapping and ablation techniques. In addition, our understanding of the complex relationship between atrial anatomy, electrophysiology, and surface ECG P wave morphology remains primitive. The magnetic electroanatomical mapping and display system (CARTO) offers an on-line display of electrical activation and/or signal amplitude related to the anatomical location of the recorded sites in the mapped chamber. A window of electrical interest is established based on signals timed from an electrical reference that usually represents a fixed electrogram recording from the coronary sinus or the atrial appendage. This window of electrical interest is established to include atrial activation prior to the onset of the P wave activity associated with the site of origin of a focal atrial tachycardia. Anatomical and electrical landmarks are defined with limited fluoroscopic imaging support and more detailed global chamber and more focal atrial mapping can be performed with minimal fluoroscopic guidance. A three-dimensional color map representing atrial activation or voltage amplitude at the magnetically defined anatomical sites is displayed with on-line data acquisition. This display can be manipulated to facilitate viewing from any angle. Altering the zoom control, triangle fill threshold, clipping plane, or color range can all enhance the display of a more focal area of interest. We documented the feasibility of using this single mapping catheter technique for localizing and ablating focal atrial tachycardias. In a consecutive series of 8 patients with 9 focal atrial tachycardias, the use of the single catheter CARTO mapping system was associated with ablation success in all but one patient who had a left atrial tachycardia localized to the medial aspect of the orifice of the left atrial appendage. Only low power energy delivery was used in this patient because of the unavailability of temperature monitoring in the early version of the Navistar catheter, the location of the arrhythmia, and the history of arrhythmia control with flecainide. No attempt was made to limit fluoroscopy time in our study population. Nevertheless, despite data acquisition from 120-320 anatomically distinct sites during global and more detailed focal atrial mapping, total fluoroscopy exposure was typically < 30 minutes and was as little as 12 minutes. The detailed display capabilities of the CARTO system appear to offer the potential of enhancing our understanding of atrial anatomy, atrial activation, and their relationship to surface ECG P wave morphology during focal atrial tachycardias.

Self-induced quasistationary magnetic fields.

PubMed

Kamenetskii, E O

2006-01-01

The interaction of electromagnetic radiation with temporally dispersive magnetic solids of small dimensions may show very special resonant behaviors. The internal fields of such samples are characterized by magnetostatic-potential scalar wave functions. The oscillating modes have the energy orthogonality properties and unusual pseudoelectric (gauge) fields. Because of a phase factor, that makes the states single valued, a persistent magnetic current exists. This leads to appearance of an eigenelectric moment of a small disk sample. One of the intriguing features of the mode fields is dynamical symmetry breaking.

Tunable short-wavelength spin wave excitation from pinned magnetic domain walls

PubMed Central

Van de Wiele, Ben; Hämäläinen, Sampo J.; Baláž, Pavel; Montoncello, Federico; van Dijken, Sebastiaan

2016-01-01

Miniaturization of magnonic devices for wave-like computing requires emission of short-wavelength spin waves, a key feature that cannot be achieved with microwave antennas. In this paper, we propose a tunable source of short-wavelength spin waves based on highly localized and strongly pinned magnetic domain walls in ferroelectric-ferromagnetic bilayers. When driven into oscillation by a microwave spin-polarized current, the magnetic domain walls emit spin waves with the same frequency as the excitation current. The amplitude of the emitted spin waves and the range of attainable excitation frequencies depend on the availability of domain wall resonance modes. In this respect, pinned domain walls in magnetic nanowires are particularly attractive. In this geometry, spin wave confinement perpendicular to the nanowire axis produces a multitude of domain wall resonances enabling efficient spin wave emission at frequencies up to 100 GHz and wavelengths down to 20 nm. At high frequency, the emission of spin waves in magnetic nanowires becomes monochromatic. Moreover, pinning of magnetic domain wall oscillators onto the same ferroelectric domain boundary in parallel nanowires guarantees good coherency between spin wave sources, which opens perspectives towards the realization of Mach-Zehnder type logic devices and sensors. PMID:26883893

Impact of Gd3+/graphene substitution on the physical properties of magnesium ferrite nanocomposites

NASA Astrophysics Data System (ADS)

Ateia, Ebtesam E.; Mohamed, Amira T.; Elsayed, Kareem

2018-04-01

Magnesium nano ferrite with composition MgFe2O4, MgGd0.05Fe1.95O4 and MgFe2O4 - 5 wt% GO was synthesized using a citrate auto-combustion method. The crystal structure, morphology, and magnetic properties of the investigated samples were studied. High Resolution Transmission Electron Microscopy (HRTEM) images show that the substitution of small amounts of Gd3+/GO causes a considerable reduction of the grain size. Studies on the magnetic properties demonstrate that the coercivity of GO-substituted magnesium nano ferrites is enhanced from 72 Oe to 203 Oe and the magnetocrystalline anisotropy constant increases from 1171 to 3425 emu Oe/gm at 300 K. The direct effects of graphene on morphology, crystal structure as well as the magnetic properties reveal that the studied sample are suitable for turbidity color and removal. The magnetic entropy change is estimated from magnetization data using Maxwell relation. The calculated Curie temperature from the Curie-Weiss law and the maximum entropy change are in good agreement with each other. Based on UV diffuse reflectance spectroscopy studies, the optical band gaps are in the range of 1.4-2.15 eV. In addition, the combination of small particle size and good magnetic properties makes the investigated samples act as a potential candidates for superior catalysts, adsorbents, and electromagnetic wave absorbers.

Filamentation instability of magnetosonic waves in the solar wind environment

NASA Technical Reports Server (NTRS)

Kuo, S. P.; Lee, M. C.

1989-01-01

Intense magnetosonic waves, originally propagating at the right angle with the interplanetary magnetic field, can excite a purely growing mode along the interplanetary magnetic field together with two symmetric magnetosonic sidebands propagating obliquely across the magnetic field. This instability process leads to the filamentation of the magnetosonic pump waves. These two excited magnetosonic sideband modes propagate together perpendicularly across the magnetic field and, meanwhile, form a standing wave pattern along the magnetic field. The thresholds of this filamentation instability can be exceeded in the solar wind environment. It is predicted that the density fluctuations produced by the filamentation instability along the interplanetary magnetic field have wavelengths greater than, at least, a few earth radii. The polarization of the obliquely propagating magnetosonic waves excited by the filamentation instability is determined by the characteristics of the magnetosonic pump waves and the environmental plasmas.

History of Chandra X-Ray Observatory

NASA Image and Video Library

2000-11-01

This image is a color composite of the supernova remnant E0102-72: x-ray (blue), optical (green), and radio (red). E0102-72 is the remnant of a star that exploded in a nearby galaxy known as the Small Magellanic Cloud. The star exploded outward at speeds in excess of 20 million kilometers per hour (12 million mph) and collided with surrounding gas. This collision produced two shock waves, or cosmic sonic booms, one traveling outward, and the other rebounding back into the material ejected by the explosion. The radio image, shown in red, was made using the Australia Telescope Compact Array. The radio waves are due to extremely high-energy electrons spiraling around magnetic field lines in the gas and trace the outward moving shock wave. The Chandra X-ray Observatory image, shown in blue, shows gas that has been heated to millions of degrees by the rebounding, or reverse shock wave. The x-ray data show that this gas is rich in oxygen and neon. These elements were created by nuclear reactions inside the star and hurled into space by the supernova. The Hubble Space Telescope optical image, shown in green, shows dense clumps of oxygen gas that have "cooled" to about 30,000 degrees. Photo Credit: X-ray (NASA/CXC/SAO); optical (NASA/HST): radio: (ACTA)

Sunspot seismology: accounting for magnetohydrodynamic wave processes using imaging spectropolarimetry

NASA Astrophysics Data System (ADS)

Rajaguru, S. P.

Effects of acoustic wave absorption, mode conversion and transmission by a sunspot on the helioseismic inferences are widely discussed, yet accounting for them has proved difficult for lack of a consistent framework within helioseismic modelling. Here, following a discussion of problems and issues that the near-surface magnetohydrodynamics hosts through a complex interplay of radiative transfer, measurement issues, and MHD wave processes, I present some possibilities entirely from observational analyses based on imaging spectropolarimetry. In particular, I present some results on wave evolution as a function of observation height and inclination of magnetic field to the vertical, derived from a high-cadence imaging spectropolarimetric observation of a sunspot and its surroundings using the instrument IBIS (NSO/Sac Peak, USA). These observations were made in magnetically sensitive (Fe I 6173 Å) and insensitive (Fe I 7090 Å) upper photospheric absorption lines. Wave travel time contributions from within the photospheric layers of a sunspot estimated here would then need to be removed from the inversion modelling procedure, that does not have the provision to account for them.

Research Methods

DTIC Science & Technology

1992-01-01

cognitive function. For example. physiological methods allow for visual sensitivity measurements in infants and children with about the same level of...potential (ERP), the event-related magnetic field (ERF), and pupillometry . Where possible, we cite specific experiments that deal with display or stimulus...technical barrier preventing the application of these methods to the analysis of human performance with color displays. Pupillometry . The pupillary

Fundamentals of Plasma Physics

NASA Astrophysics Data System (ADS)

Bellan, Paul M.

2008-07-01

Preface; 1. Basic concepts; 2. The Vlasov, two-fluid, and MHD models of plasma dynamics; 3. Motion of a single plasma particle; 4. Elementary plasma waves; 5. Streaming instabilities and the Landau problem; 6. Cold plasma waves in a magnetized plasma; 7. Waves in inhomogeneous plasmas and wave energy relations; 8. Vlasov theory of warm electrostatic waves in a magnetized plasma; 9. MHD equilibria; 10. Stability of static MHD equilibria; 11. Magnetic helicity interpreted and Woltjer-Taylor relaxation; 12. Magnetic reconnection; 13. Fokker-Planck theory of collisions; 14. Wave-particle nonlinearities; 15. Wave-wave nonlinearities; 16. Non-neutral plasmas; 17. Dusty plasmas; Appendix A. Intuitive method for vector calculus identities; Appendix B. Vector calculus in orthogonal curvilinear coordinates; Appendix C. Frequently used physical constants and formulae; Bibliography; References; Index.

Electrostatic lower hybrid waves excited by electromagnetic whistler mode waves scattering from planar magnetic-field-aligned plasma density irregularities

NASA Technical Reports Server (NTRS)

Bell, T. F.; Ngo, H. D.

1990-01-01

This paper presents a theoretical model for electrostatic lower hybrid waves excited by electromagnetic whistler mode waves propagating in regions of the magnetosphere and the topside ionosphere, where small-scale magnetic-field-aligned plasma density irregularities are thought to exist. In this model, the electrostatic waves are excited by linear mode coupling as the incident electromagnetic whistler mode waves scatter from the magnetic-field-aligned plasma density irregularities. Results indicate that high-amplitude short-wavelength (5 to 100 m) quasi-electrostatic whistler mode waves can be excited when electromagnetic whistler mode waves scatter from small-scale planar magnetic-field-aligned plasma density irregularities in the topside ionosphere and magnetosphere.

Progress on the development of FullWave, a Hot and Cold Plasma Parallel Full Wave Code

NASA Astrophysics Data System (ADS)

Spencer, J. Andrew; Svidzinski, Vladimir; Zhao, Liangji; Kim, Jin-Soo

2017-10-01

FullWave is being developed at FAR-TECH, Inc. to simulate RF waves in hot inhomogeneous magnetized plasmas without making small orbit approximations. FullWave is based on a meshless formulation in configuration space on non-uniform clouds of computational points (CCP) adapted to better resolve plasma resonances, antenna structures and complex boundaries. The linear frequency domain wave equation is formulated using two approaches: for cold plasmas the local cold plasma dielectric tensor is used (resolving resonances by particle collisions), while for hot plasmas the conductivity kernel is calculated. The details of FullWave and some preliminary results will be presented, including: 1) a monitor function based on analytic solutions of the cold-plasma dispersion relation; 2) an adaptive CCP based on the monitor function; 3) construction of the finite differences for approximation of derivatives on adaptive CCP; 4) results of 2-D full wave simulations in the cold plasma model in tokamak geometry using the formulated approach for ECRH, ICRH and Lower Hybrid range of frequencies. Work is supported by the U.S. DOE SBIR program.

Thermodynamic Properties of a Double Ring-Shaped Quantum Dot at Low and High Temperatures

NASA Astrophysics Data System (ADS)

Khordad, R.; Sedehi, H. R. Rastegar

2018-02-01

In this work, we study thermodynamic properties of a GaAs double ring-shaped quantum dot under external magnetic and electric fields. To this end, we first solve the Schrödinger equation and obtain the energy levels and wave functions, analytically. Then, we calculate the entropy, heat capacity, average energy and magnetic susceptibility of the quantum dot in the presence of a magnetic field using the canonical ensemble approach. According to the results, it is found that the entropy is an increasing function of temperature. At low temperatures, the entropy increases monotonically with raising the temperature for all values of the magnetic fields and it is independent of the magnetic field. But, the entropy depends on the magnetic field at high temperatures. The entropy also decreases with increasing the magnetic field. The heat capacity and magnetic susceptibility show a peak structure. The heat capacity reduces with increasing the magnetic field at low temperatures. The magnetic susceptibility shows a transition between diamagnetic and paramagnetic below for T<4 K. The transition temperature depends on the magnetic field.

Electromagnetic Ion Cyclotron Waves in the High Altitude Cusp: Polar Observations

NASA Technical Reports Server (NTRS)

Le, Guan; Blanco-Cano, X.; Russell, C. T.; Zhou, X.-W.; Mozer, F.; Trattner, K. J.; Fuselier, S. A.; Anderson, B. J.; Vondrak, Richard R. (Technical Monitor)

2001-01-01

High-resolution magnetic field data from the Polar Magnetic Field Experiment (MFE) show that narrow band waves at frequencies approximately 0.2 to 3 Hz are a permanent feature in the vicinity of the polar cusp. The waves have been found in the magnetosphere adjacent to the cusp (both poleward and equatorward of the cusp) and in the cusp itself. The occurrence of waves is coincident with depression of magnetic field strength associated with enhanced plasma density, indicating the entry of magnetosheath plasma into the cusp region. The wave frequencies are generally scaled by the local proton cyclotron frequency, and vary between 0.2 and 1.7 times local proton cyclotron frequency. This suggests that the waves are generated in the cusp region by the precipitating magnetosheath plasma. The properties of the waves are highly variable. The waves exhibit both lefthanded and right-handed polarization in the spacecraft frame. The propagation angles vary from nearly parallel to nearly perpendicular to the magnetic field. We find no correlation among wave frequency, propagation angle and polarization. Combined magnetic field and electric field data for the waves indicate that the energy flux of the waves is guided by the background magnetic field and points downward toward the ionosphere.

Double Alfvén waves

NASA Astrophysics Data System (ADS)

Webb, G. M.; Hu, Q.; Dasgupta, B.; Zank, G. P.

2012-02-01

Double Alfvén wave solutions of the magnetohydrodynamic equations in which the physical variables (the gas density ρ, fluid velocity u, gas pressure p, and magnetic field induction B) depend only on two independent wave phases ϕ1(x,t) and ϕ2(x,t) are obtained. The integrals for the double Alfvén wave are the same as for simple waves, namely, the gas pressure, magnetic pressure, and group velocity of the wave are constant. Compatibility conditions on the evolution of the magnetic field B due to changes in ϕ1 and ϕ2, as well as constraints due to Gauss's law ∇ · B = 0 are discussed. The magnetic field lines and hodographs of B in which the tip of the magnetic field B moves on the sphere |B| = B = const. are used to delineate the physical characteristics of the wave. Hamilton's equations for the simple Alfvén wave with wave normal n(ϕ), and with magnetic induction B(ϕ) in which ϕ is the wave phase, are obtained by using the Frenet-Serret equations for curves x=X(ϕ) in differential geometry. The use of differential geometry of 2D surfaces in a 3D Euclidean space to describe double Alfvén waves is briefly discussed.

Electromagnetic Ion Cyclotron Waves in the High-Altitude Cusp: Polar Observations

NASA Technical Reports Server (NTRS)

Le, G.; Blanco-Cano, X.; Russell, C. T.; Zhou, X.-W.; Mozer, F.; Trattner, K. J.; Fuselier, S. A.; Anderson, B. J.

2005-01-01

High-resolution magnetic field data from the Polar Magnetic Field Experiment (MFE) show that narrow-band waves at frequencies approx. 0.2-3 Hz are a permanent feature in the vicinity of the polar cusp. The waves have been found in the magnetosphere adjacent to the cusp (both poleward and equatorward of the cusp) and in the cusp itself. The occurrence of waves is coincident with depression of magnetic field strength associated with enhanced plasma density, indicating the entry of magnetosheath plasma into the cusp region. The wave frequencies are generally scaled by the local proton cyclotron frequency and vary between 0.2 and 1.7 times local proton cyclotron frequency. This suggests that the waves are generated in the cusp region by the precipitating magnetosheath plasma. The properties of the waves are highly variable. The waves exhibit both left-handed and right-handed polarization in the spacecraft frame. The propagation angles vary from nearly parallel to nearly perpendicular to the magnetic field. We find no correlation among wave frequency, propagation angle, and polarization. Combined magnetic field and electric field data for the waves indicate that the energy flux of the waves is guided by the background magnetic field and points downward toward the ionosphere.

Effects of pressure on the magnetic properties of FeO: A diffusion Monte Carlo study

NASA Astrophysics Data System (ADS)

Townsend, Joshua; Shulenburger, Luke; Mattsson, Thomas; Esler, Ken; Cohen, Ronald

While simple in terms of structure and composition, both experimental and computational investigations have demonstrated that FeO has a rich phase diagram of structural phase transformations, electronic spin transitions, insulator-metal transitions, and magnetic ordering transitions, due to the open-shell occupation of the Fe 3d electrons. We investigated the magnetic and electronic structures of FeO under ambient and high pressure conditions using diffusion Quantum Monte Carlo (QMC) within the fixed-node approximation. QMC techniques are especially well suited to the study of strongly correlated systems because they explicitly include correlation into the ground-state wave function. Here we report on the effects of the choice of trial wave function on the ambient pressure lattice distortion due to AFM ordering, as well as the equation of state, spin collapse, and metal-insulator transitions. Sandia National Laboratories is a multi-mission laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE.

Magnetic helicity conservation and inverse energy cascade in electron magnetohydrodynamic wave packets.

PubMed

Cho, Jungyeon

2011-05-13

Electron magnetohydrodynamics (EMHD) provides a fluidlike description of small-scale magnetized plasmas. An EMHD wave propagates along magnetic field lines. The direction of propagation can be either parallel or antiparallel to the magnetic field lines. We numerically study propagation of three-dimensional (3D) EMHD wave packets moving in one direction. We obtain two major results. (1) Unlike its magnetohydrodynamic (MHD) counterpart, an EMHD wave packet is dispersive. Because of this, EMHD wave packets traveling in one direction create opposite-traveling wave packets via self-interaction and cascade energy to smaller scales. (2) EMHD wave packets traveling in one direction clearly exhibit inverse energy cascade. We find that the latter is due to conservation of magnetic helicity. We compare inverse energy cascade in 3D EMHD turbulence and two-dimensional (2D) hydrodynamic turbulence.

Does the Alfvén wave wreck the large-scale magnetic cloud structure?

NASA Astrophysics Data System (ADS)

Raghav, Anil N.; Kule, Ankita

2018-06-01

Alfvén waves are primal and pervasive in space plasmas and significantly contributes to microscale fluctuations in the solar wind and some heliospheric processes. Here, we demonstrate the first observable distinct feature of Alfvén wave while propagating from magnetic cloud to trailing solar wind. The Walén test is used to confirm their presence in selected regions. The amplitude ratio of inward to outward Alfvén waves is employed to establish their flow direction. The dominant inward flow is observed in magnetic cloud whereas trailing solar wind shows the dominant outward flow of Alfvén waves. The observed reduction in Walén slope and correlation coefficient within magnetic cloud suggest (i) the simultaneous presence of an inward & outward Alfvén waves and/or (ii) a possibility of magnetic reconnection and/or (iii) development of thermal anisotropy and/or (iv) dissipation of Alfvénic fluctuations. The study implies that either the Alfvén waves dissipate in the magnetic cloud or its presence can lead to disruption of the magnetic cloud structure.

Analysis of identification of digital images from a map of cosmic microwaves

NASA Astrophysics Data System (ADS)

Skeivalas, J.; Turla, V.; Jurevicius, M.; Viselga, G.

2018-04-01

This paper discusses identification of digital images from the cosmic microwave background radiation map formed according to the data of the European Space Agency "Planck" telescope by applying covariance functions and wavelet theory. The estimates of covariance functions of two digital images or single images are calculated according to the random functions formed of the digital images in the form of pixel vectors. The estimates of pixel vectors are formed on expansion of the pixel arrays of the digital images by a single vector. When the scale of a digital image is varied, the frequencies of single-pixel color waves remain constant and the procedure for calculation of covariance functions is not affected. For identification of the images, the RGB format spectrum has been applied. The impact of RGB spectrum components and the color tensor on the estimates of covariance functions was analyzed. The identity of digital images is assessed according to the changes in the values of the correlation coefficients in a certain range of values by applying the developed computer program.

All electrical propagating spin wave spectroscopy with broadband wavevector capability

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

Ciubotaru, F., E-mail: Florin.Ciubotaru@imec.be; KU Leuven, Departement Electrotechniek; Devolder, T.

2016-07-04

We developed an all electrical experiment to perform the broadband phase-resolved spectroscopy of propagating spin waves in micrometer sized thin magnetic stripes. The magnetostatic surface spin waves are excited and detected by scaled down to 125 nm wide inductive antennas, which award ultra broadband wavevector capability. The wavevector selection can be done by applying an excitation frequency above the ferromagnetic resonance. Wavevector demultiplexing is done at the spin wave detector thanks to the rotation of the spin wave phase upon propagation. A simple model accounts for the main features of the apparatus transfer functions. Our approach opens an avenue for themore » all electrical study of wavevector-dependent spin wave properties including dispersion spectra or non-reciprocal propagation.« less

Studies on the transmission of sub-THz waves in magnetized inhomogeneous plasma sheath

NASA Astrophysics Data System (ADS)

Yuan, Kai; Shen, Linfang; Yao, Ming; Deng, Xiaohua; Chen, Zhou; Hong, Lujun

2018-01-01

There have been many studies on the sub-terahertz (sub-THz) wave transmission in reentry plasma sheaths. However, only some of them have paid attention to the transmission of sub-THz waves in magnetized plasma sheaths. In this paper, the transmission of sub-THz waves in both unmagnetized and magnetized reentry plasma sheaths was investigated. The impacts of temporal evolution of the plasma sheath on the wave transmission were studied. The transmission of "atmospheric window" frequencies in a magnetized plasma sheath was discussed in detail. According to the study, the power transmission rates (Tp) for the left hand circular (LHC) and the right hand circular modes in the magnetized plasma sheath are obviously higher and lower than those in the unmagnetized plasma sheath, respectively. The Tp of LHC mode increases with both wave frequency and external magnetic field strength. Also, the Tp of LHC mode in both magnetized and unmagnetized plasma sheaths varies with time due to the temporal evolution of the plasma sheath. Moreover, the performance of sub-THz waves in magnetized plasma sheath hints at a new approach to the "blackout" problem. The new approach, which is in the capability of modern technology, is to utilize the communication system operating at 140 GHz with an onboard magnet installed near the antenna.

Alfvén wave dynamics at the neighborhood of a 2.5D magnetic null-point

NASA Astrophysics Data System (ADS)

Sabri, S.; Vasheghani Farahani, S.; Ebadi, H.; Hosseinpour, M.; Fazel, Z.

2018-05-01

The aim of the present study is to highlight the energy transfer via the interaction of magnetohydrodynamic waves with a 2.5D magnetic null-point in a finite plasma-β regime of the solar corona. An initially symmetric Alfvén pulse at a specific distance from a magnetic null-point is kicked towards the isothermal null-point. A shock-capturing Godunov-type PLUTO code is used to solve the ideal magnetohydrodynamic set equations in the context of wave-plasma energy transfer. As the Alfvén wave propagates towards the magnetic null-point it experiences speed lowering which ends up in releasing energy along the separatrices. In this line owing to the Alfvén wave, a series of events take place that contribute towards coronal heating. Nonlinear induced waves are by products of the torsional Alfvén interaction with magnetic null-points. The energy of these induced waves which are fast magnetoacoustic (transverse) and slow magnetoacoustic (longitudinal) waves are supplied by the Alfvén wave. The nonlinearly induced density perturbations are proportional to the Alfvén wave energy loss. This supplies energy for the propagation of fast and slow magnetoacoustic waves, where in contrast to the fast wave the slow wave experiences a continuous energy increase. As such, the slow wave may transfer its energy to the medium at later times, maintaining a continuous heating mechanism at the neighborhood of a magnetic null-point.

Heating and Acceleration of Solar Wind Ions by Turbulent Wave Spectrum in Inhomogeneous Expanding Plasma

NASA Technical Reports Server (NTRS)

Ofman, Leon; Ozak, Nataly; Vinas, Adolfo F.

2016-01-01

Near the Sun (< 10Rs) the acceleration, heating, and propagation of the solar wind are likely affected by the background inhomogeneities of the magnetized plasma. The heating and the acceleration of the solar wind ions by turbulent wave spectrum in inhomogeneous plasma is studied using a 2.5D hybrid model. The hybrid model describes the kinetics of the ions, while the electrons are modeled as massless neutralizing fluid in an expanding box approach. Turbulent magnetic fluctuations dominated by power-law frequency spectra, which are evident from in-situ as well as remote sensing measurements, are used in our models. The effects of background density inhomogeneity across the magnetic field on the resonant ion heating are studied. The effect of super- Alfvenic ion drift on the ion heating is investigated. It is found that the turbulent wave spectrum of initially parallel propagating waves cascades to oblique modes, and leads to enhanced resonant ion heating due to the inhomogeneity. The acceleration of the solar wind ions is achieved by the parametric instability of large amplitude waves in the spectrum, and is also affected by the inhomogeneity. The results of the study provide the ion temperature anisotropy and drift velocity temporal evolution due to relaxation of the instability. The non-Maxwellian velocity distribution functions (VDFs) of the ions are modeled in the inhomogeneous solar wind plasma in the acceleration region close to the Sun.

Reversal of radial glow distribution in helicon plasma induced by reversed magnetic field

NASA Astrophysics Data System (ADS)

Wang, Y.; Zhao, G.; Niu, C.; Liu, Z. W.; Ouyang, J. T.; Chen, Q.

2017-02-01

In this work, the reversal of radial glow distribution induced by reversed magnetic field is reported. Based on the Boswell antenna which is symmetric and insensitive to the magnetic field direction, it seems such a phenomenon in theory appears impossible. However, according to the diagnostic of the helicon waves by magnetic probe, it is found that the direction of magnetic field significantly affects the propagation characteristic of helicon waves, i.e., the interchange of the helicon waves at the upper and the lower half of tube was caused by reversing the direction of magnetic field. It is suggested that the variation of helicon wave against the direction of magnetic field causes the reversed radial glow distribution. The appearance of the traveling wave does not only improve the discharge strength, but also determines the transition of the discharge mode.

Wave-function description of conductance mapping for a quantum Hall electron interferometer

NASA Astrophysics Data System (ADS)

Kolasiński, K.; Szafran, B.

2014-04-01

Scanning gate microscopy of quantum point contacts (QPC) in the integer quantum Hall regime is considered in terms of the scattering wave functions with a finite-difference implementation of the quantum transmitting boundary approach. Conductance (G) maps for a clean QPC as well as for a system including an antidot within the QPC constriction are evaluated. The steplike locally flat G maps for clean QPCs turn into circular resonances that are reentrant in an external magnetic field when the antidot is introduced to the constriction. The current circulation around the antidot and the spacing of the resonances at the magnetic field scale react to the probe approaching the QPC. The calculated G maps with a rigid but soft antidot potential reproduce the features detected recently in the electron interferometer [F. Martins et al., Sci. Rep. 3, 1416 (2013), 10.1038/srep01416].

Observation of charge asymmetry dependence of pion elliptic flow and the possible chiral magnetic wave in heavy-ion collisions

DOE PAGES

Adamczyk, L.

2015-06-26

We present measurements of π⁻ and π⁺ elliptic flow, v₂, at midrapidity in Au+Au collisions at √s NN = 200, 62.4, 39, 27, 19.6, 11.5, and 7.7 GeV, as a function of event-by-event charge asymmetry, A ch, based on data from the STAR experiment at RHIC. We find that π⁻ (π⁺) elliptic flow linearly increases (decreases) with charge asymmetry for most centrality bins at √s NN = 27 GeV and higher. At √s NN = 200 GeV, the slope of the difference of v₂ between π⁻ and π⁺ as a function of A ch exhibits a centrality dependence, which ismore » qualitatively similar to calculations that incorporate a chiral magnetic wave effect. In addition, similar centrality dependence is also observed at lower energies.« less

Imaging the dynamics of free-electron Landau states

PubMed Central

Schattschneider, P.; Schachinger, Th.; Stöger-Pollach, M.; Löffler, S.; Steiger-Thirsfeld, A.; Bliokh, K. Y.; Nori, Franco

2014-01-01

Landau levels and states of electrons in a magnetic field are fundamental quantum entities underlying the quantum Hall and related effects in condensed matter physics. However, the real-space properties and observation of Landau wave functions remain elusive. Here we report the real-space observation of Landau states and the internal rotational dynamics of free electrons. States with different quantum numbers are produced using nanometre-sized electron vortex beams, with a radius chosen to match the waist of the Landau states, in a quasi-uniform magnetic field. Scanning the beams along the propagation direction, we reconstruct the rotational dynamics of the Landau wave functions with angular frequency ~100 GHz. We observe that Landau modes with different azimuthal quantum numbers belong to three classes, which are characterized by rotations with zero, Larmor and cyclotron frequencies, respectively. This is in sharp contrast to the uniform cyclotron rotation of classical electrons, and in perfect agreement with recent theoretical predictions. PMID:25105563

Electron Energy Distribution function in a weakly magnetized expanding helicon plasma discharge

NASA Astrophysics Data System (ADS)

Sirse, Nishant; Harvey, Cleo; Gaman, Cezar; Ellingboe, Bert

2016-09-01

Helicon wave heating is well known to produce high-density plasma source for application in plasma thrusters, plasma processing and many more. Our previous study (B Ellingboe et al. APS Gaseous Electronics Conference 2015, abstract #KW2.005) has shown observation of helicon wave in a weakly magnetized inductively coupled plasma source excited by m =0 antenna at 13.56 MHz. In this paper, we investigated the Electron Energy Distribution Function (EEDF) in the same setup by using an RF compensated Langmuir probe. The ac signal superimposition technique (second harmonic technique) is used to determine EEDF. The EEDF is measured for 5-100 mTorr gas pressure, 100 W - 1.5 kW rf power and at different locations in the source chamber, boundary and diffusion chamber. This paper will discuss the change in the shape of EEDF for various heating mode transitions.

High Transparency of Photosphere Plasma for Electromagnetic Waves Polarized Across Strong Magnetic Field on White Dwarfs

NASA Astrophysics Data System (ADS)

Koryagin, S. A.

2015-06-01

We showed that, in the photosphere of a white dwarf with strong magnetic field, the collisional absorption significantly decreases at the frequencies below the electron cyclotron frequency for the electromagnetic waves linearly polarized across the magnetic field lines (for the so-called extraordinary waves in a magnetized plasma). As a result, the extraordinary waves can escape from the deeper and hotter photosphere layers than the ordinary waves and, in this way, can determine the high linear polarization at the infrared and optical continuum.

Wave propagation characteristics of a magnetic granular chain

NASA Astrophysics Data System (ADS)

Leng, Dingxin; Liu, Guijie; Sun, Lingyu; Wang, Xiaojie

2017-10-01

We investigate the wave propagation characteristics of a horizontal alignment of magnetic grains under a non-uniform magnetic field. The magnetic force of each grain is obtained using Maxwell's principle. The contact interaction of grains is based on Hertz potential. The effects of magnetic field strength on the dynamic responses of a granular chain under strong, intermediate, and weak amplitudes of incident impulses in comparison with static precompression force are studied. Different wave propagation modes induced by the magnetic field are observed. The applied field strength demonstrably reinforces the granular-position-dependent behaviors of decreasing amplitude and increasing wave propagation velocity. The magnetic field-induced features of a magnetic granular chain have potential applications in adaptive structures for shock attenuation.

Modeling of Inner Magnetosphere Coupling Processes

NASA Technical Reports Server (NTRS)

Khazanov, George V.

2011-01-01

The Ring Current (RC) is the biggest energy player in the inner magnetosphere. It is the source of free energy for Electromagnetic Ion Cyclotron (EMIC) wave excitation provided by a temperature anisotropy of RC ions, which develops naturally during inward E B convection from the plasmasheet. The cold plasmasphere, which is under the strong influence of the magnetospheric electric field, strongly mediates the RC-EMIC wave-particle-coupling process and ultimately becomes part of the particle and energy interplay. On the other hand, there is a strong influence of the RC on the inner magnetospheric electric and magnetic field configurations and these configurations, in turn, are important to RC dynamics. Therefore, one of the biggest needs for inner magnetospheric research is the continued progression toward a coupled, interconnected system with the inclusion of nonlinear feedback mechanisms between the plasma populations, the electric and magnetic fields, and plasma waves. As we clearly demonstrated in our studies, EMIC waves strongly interact with electrons and ions of energies ranging from approx.1 eV to approx.10 MeV, and that these waves strongly affect the dynamics of resonant RC ions, thermal electrons and ions, and the outer RB relativistic electrons. As we found, the rate of ion and electron scattering/heating in the Earth's magnetosphere is not only controlled by the wave intensity-spatial-temporal distribution but also strongly depends on the spectral distribution of the wave power. The latter is also a function of the plasmaspheric heavy ion content, and the plasma density and temperature distributions along the magnetic field lines. The above discussion places RC-EMIC wave coupling dynamics in context with inner magnetospheric coupling processes and, ultimately, relates RC studies with plasmaspheric and Superthermal Electrons formation processes as well as with outer RB physics.

Blood oxygen-level dependent functional assessment of cerebrovascular reactivity: Feasibility for intraoperative 3 Tesla MRI.

PubMed

Fierstra, Jorn; Burkhardt, Jan-Karl; van Niftrik, Christiaan Hendrik Bas; Piccirelli, Marco; Pangalu, Athina; Kocian, Roman; Neidert, Marian Christoph; Valavanis, Antonios; Regli, Luca; Bozinov, Oliver

2017-02-01

To assess the feasibility of functional blood oxygen-level dependent (BOLD) MRI to evaluate intraoperative cerebrovascular reactivity (CVR) at 3 Tesla field strength. Ten consecutive neurosurgical subjects scheduled for a clinical intraoperative MRI examination were enrolled in this study. In addition to the clinical protocol a BOLD sequence was implemented with three cycles of 44 s apnea to calculate CVR values on a voxel-by-voxel basis throughout the brain. The CVR range was then color-coded and superimposed on an anatomical volume to create high spatial resolution CVR maps. Ten subjects (mean age 34.8 ± 13.4; 2 females) uneventfully underwent the intraoperative BOLD protocol, with no complications occurring. Whole-brain CVR for all subjects was (mean ± SD) 0.69 ± 0.42, whereas CVR was markedly higher for tumor subjects as compared to vascular subjects, 0.81 ± 0.44 versus 0.33 ± 0.10, respectively. Furthermore, color-coded functional maps could be robustly interpreted for a whole-brain assessment of CVR. We demonstrate that intraoperative BOLD MRI is feasible in creating functional maps to assess cerebrovascular reactivity throughout the brain in subjects undergoing a neurosurgical procedure. Magn Reson Med 77:806-813, 2017. © 2016 International Society for Magnetic Resonance in Medicine. © 2016 International Society for Magnetic Resonance in Medicine.

Role of Feshbach resonances in enhancing the production of deeply bound ultracold LiRb molecules with laser pulses

NASA Astrophysics Data System (ADS)

Gacesa, Marko; Ghosal, Subhas; Côté, Robin

2010-03-01

We investigate the possibility of forming deeply bound LiRb molecules in a two-color photoassociation experiment. Ultracold ^6Li and ^87Rb atoms colliding in the vicinity of a magnetic Feshbach resonance are photoassociated into an excited electronic state. A wavepacket is then formed by exciting a few vibrational levels of the excited state and allowed to propagate. We calculate the time-dependent overlaps between the wave packet and the lowest vibrational levels of the ground state. After the optimal overlap is obtained we use the second laser pulse to dump the wave packet and efficiently populate the deeply bound ro-vibrational levels of ^6Li^87Rb in the ground state. The resulting combination of Feshbach-optimized photoassociation (FOPA) with the time-dependent pump-dump approach will produce a large number of stable ultracold molecules in the ground state. This technique is general and applicable to other systems.

Children's Color Perception in Relation to Habitat and Skin Color.

ERIC Educational Resources Information Center

Gaines, Rosslyn; Powell, Gloria J.

1981-01-01

Developmental color perception of 278 four- and eight-year-old Black and White children in three societies was examined in relation to the theories that proximity to the equator and that fundus pigmentation (as measured by skin color) reduce shortwave (blue-green) in comparison to long-wave perception. (Author/MP)

Modeling of vibrations isolation and arrest by shape memory parts and permanent magnets

NASA Astrophysics Data System (ADS)

Belyaev, Fedor S.; Volkov, Aleksandr E.; Evard, Margarita E.; Vikulenkov, Andrey V.; Uspenskiy, Evgeniy S.

2018-05-01

A vibration protection system under consideration consists of a payload connected to a vibrating housing by shape memory alloy (SMA) slotted springs. To provide an arrest function two permanent magnets are inserted into the system. The slotted SMA elements are preliminary deformed in the martensitic state. Activation of one element by heating initiates force and displacement generation, which provide an arrest of the payload by magnets. The magnets also secure the arrest mode after cooling of the SMA element. Activation of the other element results in uncaging of the payload and switching to the vibration isolation mode. Computer simulations of arrest and uncaging when the housing is quiescent or producing sine-wave displacements were carried out. Functional-mechanical behavior of SMA parts was described by means of a microstructural model.

Charge density wave behavior and order-disorder in the antiferromagnetic metallic series Eu (Ga1 -xAlx)4

NASA Astrophysics Data System (ADS)

Stavinoha, Macy; Cooley, Joya A.; Minasian, Stefan G.; McQueen, Tyrel M.; Kauzlarich, Susan M.; Huang, C.-L.; Morosan, E.

2018-05-01

The solid solution Eu (Ga1-xAlx) 4 was grown in single crystal form to reveal a rich variety of crystallographic, magnetic, and electronic properties that differ from the isostructural end compounds EuGa4 and EuAl4, despite the similar covalent radii and electronic configurations of Ga and Al. Here we report the onset of magnetic spin reorientation and metamagnetic transitions for x =0 -1 evidenced by magnetization and temperature-dependent specific heat measurements. TN changes nonmonotonously with x , and it reaches a maximum around 20 K for x =0.50 , where the a lattice parameter also shows an extreme (minimum) value. Anomalies in the temperature-dependent resistivity consistent with charge density wave behavior exist only for x =0.50 and 1. Density functional theory calculations show increased polarization between the Ga-Al covalent bonds in the x =0.50 structure compared to the end compounds, such that crystallographic order and chemical pressure are proposed as the causes of the charge density wave behavior.

Optimised frequency modulation for continuous-wave optical magnetic resonance sensing using nitrogen-vacancy ensembles.

PubMed

El-Ella, Haitham A R; Ahmadi, Sepehr; Wojciechowski, Adam M; Huck, Alexander; Andersen, Ulrik L

2017-06-26

Magnetometers based on ensembles of nitrogen-vacancy centres are a promising platform for continuously sensing static and low-frequency magnetic fields. Their combination with phase-sensitive (lock-in) detection creates a highly versatile sensor with a sensitivity that is proportional to the derivative of the optical magnetic resonance lock-in spectrum, which is in turn dependant on the lock-in modulation parameters. Here we study the dependence of the lock-in spectral slope on the modulation of the spin-driving microwave field. Given the presence of the intrinsic nitrogen hyperfine spin transitions, we experimentally show that when the ratio between the hyperfine linewidth and their separation is ≳ 1/4, square-wave based frequency modulation generates the steepest slope at modulation depths exceeding the separation of the hyperfine lines, compared to sine-wave based modulation. We formulate a model for calculating lock-in spectra which shows excellent agreement with our experiments, and which shows that an optimum slope is achieved when the linewidth/separation ratio is ≲ 1/4 and the modulation depth is less then the resonance linewidth, irrespective of the modulation function used.

Gravitational Wave Signatures of Crystalline Color Superconductors

NASA Astrophysics Data System (ADS)

Lin, Lap-Ming

Deconfined quark matter may exist in a crystalline color-superconducing phase in the interiors of compact stars. One of the special properties of this exotic phase of matter is that it is extremely rigid and the corresponding shear modulus can be up to 1000 times larger than that of the neutron-star crust. In this paper, we review how the extreme rigidity of this crystalline phase of quark matter can lead to unique gravitational-wave signatures that may be detectable by the current or the next-generation gravitational-wave detectors.

Magnetic field and dielectric environment effects on an exciton trapped by an ionized donor in a spherical quantum dot

NASA Astrophysics Data System (ADS)

Aghoutane, N.; Feddi, E.; El-Yadri, M.; Bosch Bailach, J.; Dujardin, F.; Duque, C. A.

2017-11-01

Magnetic field and host dielectric environment effects on the binding energy of an exciton trapped by an ionized donor in spherical quantum dot are investigated. In the framework of the effective mass approximation and by using a variational method, the calculations have been performed by developing a robust ten-terms wave function taking into account the different inter-particles correlations and the distortion of symmetry induced by the orientation of the applied magnetic field. The binding and the localization energies are determined as functions of dot size and magnetic field strength. It appears that the variation of magnetic shift obeys a quadratic law for low magnetic fields regime while, for strong magnetic fields, this shift tends to be linear versus the magnetic field strength. The stability of this complex subjected to a magnetic field is also discussed according to the electron-hole ratio and the dielectric constant of the surrounding medium. A last point to highlight is that the Haynes' rule remains valid even in the presence of an applied magnetic field.

Properties of Langmuir wave bursts associated with magnetic holes

NASA Technical Reports Server (NTRS)

MacDowall, R. J.; Lin, N.; Kellogg, P. J.; Phillips, J. L.; Neugebauer, M.; Balogh, A.; Forsyth, R. J.

1995-01-01

The radio and plasma wave receivers on the Ulysses spacecraft have detected thousands of short-duration bursts of waves at approximately the electron plasma frequency. These wave events believed to be Langmuir waves are usually less than approximately 5 minutes in duration. They occur in or at the boundaries of depletions in the magnetic field amplitude known as magnetic holes. Using the 16 sec time resolution provided by the plasma frequency receiver, it is possible to examine the density structure inside of magnetic holes. Even higher time resolutions are sometimes available from the radio receiver data. The Ulysses observations show that these wave bursts occur more frequently at high heliographic latitudes; the occurrence rates depend on both latitude and distance from the Sun. We review the statistics for the wave events, compare them to magnetic and plasma parameters, and review the reasons for the more frequent occurrence at high heliographic latitudes.

Ponderomotive Force in the Presence of Electric Fields

NASA Technical Reports Server (NTRS)

Khazanov, G. V.; Krivorutsky, E. N.

2013-01-01

This paper presents averaged equations of particle motion in an electromagnetic wave of arbitrary frequency with its wave vector directed along the ambient magnetic field. The particle is also subjected to an E cross B drift and a background electric field slowly changing in space and acting along the magnetic field line. The fields, wave amplitude, and the wave vector depend on the coordinate along the magnetic field line. The derivations of the ponderomotive forces are done by assuming that the drift velocity in the ambient magnetic field is comparable to the particle velocity. Such a scenario leads to new ponderomotive forces, dependent on the wave magnetic field intensity, and, as a result, to the additional energy exchange between the wave and the plasma particles. It is found that the parallel electric field can lead to the change of the particle-wave energy exchange rate comparable to that produced by the previously discussed ponderomotive forces.

Solar energy harvesting by magnetic-semiconductor nanoheterostructure in water treatment technology.

PubMed

Mahmoodi, Vahid; Bastami, Tahereh Rohani; Ahmadpour, Ali

2018-03-01

Photocatalytic degradation of toxic organic pollutants in the wastewater using dispersed semiconductor nanophotocatalysts has a number of advantages such as high activity, cost effectiveness, and utilization of free solar energy. However, it is difficult to recover and recycle nanophotocatalysts since the fine dispersed nanoparticles are easily suspended in waters. Furthermore, a large amount of photocatalysts will lead to color contamination. Thus, it is necessary to prepare photocatalysts with easy separation for the reusable application. To take advantage of high photocatalysis activity and reusability, magnetic photocatalysts with separation function were utilized. In this review, the photocatalytic principle, structure, and application of the magnetic-semiconductor nanoheterostructure photocatalysts under solar light are evaluated. Graphical abstract ᅟ.

Subphotospheric fluctuations in magnetized radiative envelopes: contribution from unstable magnetosonic waves

NASA Astrophysics Data System (ADS)

Sen, Koushik; Fernández, Rodrigo; Socrates, Aristotle

2018-06-01

We examine the excitation of unstable magnetosonic waves in the radiative envelopes of intermediate- and high-mass stars with a magnetic field of ˜kG strength. Wind clumping close to the star and microturbulence can often be accounted for when including small-scale, subphotospheric density or velocity perturbations. Compressional waves - with wavelengths comparable to or shorter than the gas pressure scale height - can be destabilized by the radiative flux in optically thick media when a magnetic field is present, in a process called the radiation-driven magneto-acoustic instability (RMI). The instability does not require radiation or magnetic pressure to dominate over gas pressure, and acts independently of subsurface convection zones. Here we evaluate the conditions for the RMI to operate on a grid of stellar models covering a mass range 3-40 M⊙ at solar metallicity. For a uniform 1 kG magnetic field, fast magnetosonic modes are unstable down to an optical depth of a few tens, while unstable slow modes extend beyond the depth of the iron convection zone. The qualitative behaviour is robust to magnetic field strength variations by a factor of a few. When combining our findings with previous results for the saturation amplitude of the RMI, we predict velocity fluctuations in the range ˜0.1-10 km s-1. These amplitudes are a monotonically increasing function of the ratio of radiation to gas pressure, or alternatively, of the zero-age main sequence mass.

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

Voskoboynikov, O., E-mail: vam@faculty.nctu.edu.tw

We theoretically investigate suppression and recovery of the Aharonov-Bohm oscillations of the diamagnetic response of electrons (holes) confined in self-assembled In{sub c}Ga{sub 1−c}As/GaAs semiconductor reflection asymmetrical quantum rings. Based on the mapping method and gauge-origin-independent definition for the magnetic vector potential we simulate the energies and wave functions of the electron (hole) under external magnetic and electric fields. We examine the transformation of the ground state wave function of the electron (hole) in reflection asymmetrical rings from localized in one of the potential valleys (dotlike shape of the wave function) to distributed over all volume of the ring (ringlike shape)more » under an appropriate lateral electric field. This transformation greatly recovers the electron (hole) diamagnetic coefficient and Aharonov-Bohm oscillations of the diamagnetic response of the ring. However, the recovering electric field for the first Aharonov-Bohm diamagnetic oscillation of the electron is a suppressing one for the hole (and vice versa). This can block the recovery of the optical Aharonow-Bohm effect in In{sub c}Ga{sub 1−c}As/GaAs asymmetrically wobbled rings. However, the recovery of the Aharonov-Bohm oscillations for the independent electron (hole) by the external electric field remains interesting and feasible objective for the asymmetric rings.« less

Study of Wave-Particle Interactions for Whistler Mode Waves at Oblique Angles by Utilizing the Gyroaveraging Method

NASA Astrophysics Data System (ADS)

Hsieh, Yi-Kai; Omura, Yoshiharu

2017-10-01

We investigate the properties of whistler mode wave-particle interactions at oblique wave normal angles to the background magnetic field. We find that electromagnetic energy of waves at frequencies below half the electron cyclotron frequency can flow nearly parallel to the ambient magnetic field. We thereby confirm that the gyroaveraging method, which averages the cyclotron motion to the gyrocenter and reduces the simulation from two-dimensional to one-dimensional, is valid for oblique wave-particle interaction. Multiple resonances appear for oblique propagation but not for parallel propagation. We calculate the possible range of resonances with the first-order resonance condition as a function of electron kinetic energy and equatorial pitch angle. To reveal the physical process and the efficiency of electron acceleration by multiple resonances, we assume a simple uniform wave model with constant amplitude and frequency in space and time. We perform test particle simulations with electrons starting at specific equatorial pitch angles and kinetic energies. The simulation results show that multiple resonances contribute to acceleration and pitch angle scattering of energetic electrons. Especially, we find that electrons with energies of a few hundred keV can be accelerated efficiently to a few MeV through the n = 0 Landau resonance.

Spin torque oscillator neuroanalog of von Neumann's microwave computer.

PubMed

Hoppensteadt, Frank

2015-10-01

Frequency and phase of neural activity play important roles in the behaving brain. The emerging understanding of these roles has been informed by the design of analog devices that have been important to neuroscience, among them the neuroanalog computer developed by O. Schmitt and A. Hodgkin in the 1930s. Later J. von Neumann, in a search for high performance computing using microwaves, invented a logic machine based on crystal diodes that can perform logic functions including binary arithmetic. Described here is an embodiment of his machine using nano-magnetics. Electrical currents through point contacts on a ferromagnetic thin film can create oscillations in the magnetization of the film. Under natural conditions these properties of a ferromagnetic thin film may be described by a nonlinear Schrödinger equation for the film's magnetization. Radiating solutions of this system are referred to as spin waves, and communication within the film may be by spin waves or by directed graphs of electrical connections. It is shown here how to formulate a STO logic machine, and by computer simulation how this machine can perform several computations simultaneously using multiplexing of inputs, that this system can evaluate iterated logic functions, and that spin waves may communicate frequency, phase and binary information. Neural tissue and the Schmitt-Hodgkin, von Neumann and STO devices share a common bifurcation structure, although these systems operate on vastly different space and time scales; namely, all may exhibit Andronov-Hopf bifurcations. This suggests that neural circuits may be capable of the computational functionality as described by von Neumann. Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.

Fully vectorial accelerating diffraction-free Helmholtz beams.

PubMed

Aleahmad, Parinaz; Miri, Mohammad-Ali; Mills, Matthew S; Kaminer, Ido; Segev, Mordechai; Christodoulides, Demetrios N

2012-11-16

We show that new families of diffraction-free nonparaxial accelerating optical beams can be generated by considering the symmetries of the underlying vectorial Helmholtz equation. Both two-dimensional transverse electric and magnetic accelerating wave fronts are possible, capable of moving along elliptic trajectories. Experimental results corroborate these predictions when these waves are launched from either the major or minor axis of the ellipse. In addition, three-dimensional spherical nondiffracting field configurations are presented along with their evolution dynamics. Finally, fully vectorial self-similar accelerating optical wave solutions are obtained via oblate-prolate spheroidal wave functions. In all occasions, these effects are illustrated via pertinent examples.

Exchange interaction effects on waves in magnetized quantum plasmas

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

Trukhanova, Mariya Iv., E-mail: mar-tiv@yandex.ru; Andreev, Pavel A., E-mail: andreevpa@physics.msu.ru

2015-02-15

We have applied the many-particle quantum hydrodynamics that includes the Coulomb exchange interaction to magnetized quantum plasmas. We considered a number of wave phenomena that are affected by the Coulomb exchange interaction. Since the Coulomb exchange interaction affects the longitudinal and transverse-longitudinal waves, we focused our attention on the Langmuir waves, the Trivelpiece-Gould waves, the ion-acoustic waves in non-isothermal magnetized plasmas, the dispersion of the longitudinal low-frequency ion-acoustic waves, and low-frequency electromagnetic waves at T{sub e} ≫ T{sub i}. We have studied the dispersion of these waves and present the numeric simulation of their dispersion properties.

Analytic Wave Functions for the Half-Filled Lowest Landau Level

NASA Astrophysics Data System (ADS)

Ciftja, Orion

We consider a two-dimensional strongly correlated electronic system in a strong perpendicular magnetic field at half-filling of the lowest Landau level (LLL). We seek to build a wave function that, by construction, lies entirely in the Hilbert space of the LLL. Quite generally, a wave function of this nature can be built as a linear combination of all possible Slater determinants formed by using the complete set of single-electron states that belong to the LLL. However, due to the vast number of Slater determinant states required to form such basis functions, the expansion is impractical for any but the smallest systems. Thus, in practice, the expansion must be truncated to a small number of Slater determinants. Among many possible LLL Slater determinant states, we note a particular special class of such wave functions in which electrons occupy either only even, or only odd angular momentum states. We focus on such a class of wave functions and obtain analytic expressions for various quantities of interest. Results seem to suggest that these special wave functions, while interesting and physically appealing, are unlikely to be a very good approximation for the exact ground state at half-filling factor. The overall quality of the description can be improved by including other additional LLL Slater determinant states. It is during this process that we identify another special family of suitable LLL Slater determinant states to be used in an enlarged expansion.

Magnetic Iron Oxide Nanoparticles and a Polydiacetylene Coating to Create a Biocompatible and Stable Molecule for Use in Cancer Diagnostics and Early Detection in Molecular Medicine

NASA Astrophysics Data System (ADS)

Bhatnagar, Shweta

Earlier cancer detection and diagnosis is essential to prevent cancer mortality in nanomedicine and nanotechnology. Fluorescence and magnetic signals provide a way for earlier detection through imaging systems. Magnetic iron oxide nanoparticles have a superparamagnetism feature that allows them to act as contrast agents that can be detected through a magnetic resonance imaging system. These iron oxide cores have a polymer coating around them to provide stability, prevent aggregation, and allow for biocompatibility within the body. In addition, these functional coatings can have ligands and peptides for detection and therapy purposes. One functional coating is a polydiacetylene coating due to its chromatic and optical properties. When polymerized, it has the ability to change color in the visible spectrum to blue (not a fluorescent signal) and when heated, it changes to a red color (fluorescent signal). This way a strong and stable layer is formed around the iron oxide cores. These coatings are placed on the iron cores using a modified dual solvent exchange method, in which DMSO is slowly replaced by water without the use of organic solvents previous used. In addition, these nanoparticles can then be PEGylated, which provides a more stable and water soluble compound in aqueous solutions. Measurements can be taken through dynamic light scattering for size distributions and zeta potential and the Nanodrop for absorbance. Ideal sizes are about 30 nm for MNPs. Moreover, for future directions, there can be more molecules attached to the coated layers to use for molecular detection and analysis.

Spin-waves in thin films with Dzyaloshinskii-Moriya interaction

NASA Astrophysics Data System (ADS)

Diep, H. T.; El Hog, Sahbi; Puszkarski, Henryk

2018-05-01

Using the Green's function method, we calculate the spin-wave (SW) spectrum in a thin film with quantum Heisenberg spins interacting with each other via an exchange interaction J and a Dzyaloshinskii-Moriya interaction of magnitude D. Due to the competition between J and D, the ground state is non collinear. We show that for large D, the first mode in the SW spectrum is proportional to the in plane wave-vector k at the limit k tending to zero. For small D, it is proportional to k2. We show that the surface modes may occur depending on the surface exchange interaction. We calculate the layer magnetizations at temperature T and the transition temperature as a function of the film thickness.

Dynamic current-current susceptibility in three-dimensional Dirac and Weyl semimetals

NASA Astrophysics Data System (ADS)

Thakur, Anmol; Sadhukhan, Krishanu; Agarwal, Amit

2018-01-01

We study the linear response of doped three-dimensional Dirac and Weyl semimetals to vector potentials, by calculating the wave-vector- and frequency-dependent current-current response function analytically. The longitudinal part of the dynamic current-current response function is then used to study the plasmon dispersion and the optical conductivity. The transverse response in the static limit yields the orbital magnetic susceptibility. In a Weyl semimetal, along with the current-current response function, all these quantities are significantly impacted by the presence of parallel electric and magnetic fields (a finite E .B term) and can be used to experimentally explore the chiral anomaly.

Next Generation of Magneto-Dielectric Antennas and Optimum Flux Channels

NASA Astrophysics Data System (ADS)

Yousefi, Tara

There is an ever-growing need for broadband conformal antennas to not only reduce the number of antennas utilized to cover a broad range of frequencies (VHF-UHF) but also to reduce visual and RF signatures associated with communication systems. In many applications antennas needs to be very close to low-impedance mediums or embedded inside low-impedance mediums. However, for conventional metal and dielectric antennas to operate efficiently in such environments either a very narrow bandwidth must be tolerated, or enough loss added to expand the bandwidth, or they must be placed one quarter of a wavelength above the conducting surface. The latter is not always possible since in the HF through low UHF bands, critical to Military and Security functions, this quarter-wavelength requirement would result in impractically large antennas. Despite an error based on a false assumption in the 1950’s, which had severely underestimated the efficiency of magneto-dielectric antennas, recently demonstrated magnetic-antennas have been shown to exhibit extraordinary efficiency in conformal applications. Whereas conventional metal-and-dielectric antennas carrying radiating electric currents suffer a significant disadvantage when placed conformal to the conducting surface of a platform, because they induce opposing image currents in the surface, magnetic-antennas carrying magnetic radiating currents have no such limitation. Their magnetic currents produce co-linear image currents in electrically conducting surfaces. However, the permeable antennas built to date have not yet attained the wide bandwidth expected because the magnetic-flux-channels carrying the wave have not been designed to guide the wave near the speed of light at all frequencies. Instead, they tend to lose the wave by a leaky fast-wave mechanism at low frequencies or they over-bind a slow-wave at high frequencies. In this dissertation, we have studied magnetic antennas in detail and presented the design approach and apparatus required to implement a flux-channel carrying the magnetic current wave near the speed of light over a very broad frequency range which also makes the design of a frequency independent antenna (spiral) possible. We will learn how to construct extremely thin conformal antennas, frequency-independent permeable antennas, and even micron-sized antennas that can be embedded inside the brain without damaging the tissue.

Thermal chiral vortical and magnetic waves: New excitation modes in chiral fluids

DOE PAGES

Kalaydzhyan, Tigran; Murchikova, Elena

2017-03-24

In certain circumstances, chiral (parity-violating) medium can be described hydrodynamically as a chiral fluid with microscopic quantum anomalies. Possible examples of such systems include strongly coupled quark–gluon plasma, liquid helium 3He-A, neutron stars and the Early Universe. Here, we study first-order hy-drodynamics of a chiral fluid on a vortex background and in an external magnetic field. We show that there are two previously undiscovered modes describing heat waves propagating along the vortex and magnetic field. We call them the Thermal Chiral Vortical Wave and Thermal Chiral Magnetic Wave. We also identify known gapless excitations of density (chiral vortical and chiralmore » magnetic waves) and transverse velocity (chiral Alfvén wave). We also demonstrate that the velocity of the chiral vortical wave is zero, when the full hydrodynamic framework is applied, and hence the wave is absent and the excitation reduces to the charge diffusion mode. We also comment on the frame-dependent contributions to the obtained propagation velocities.« less

Spin-wave-driven high-speed domain-wall motions in soft magnetic nanotubes

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

Yang, Jaehak; Yoo, Myoung-Woo; Kim, Sang-Koog, E-mail: sangkoog@snu.ac.kr

We report on a micromagnetic simulation study of interactions between propagating spin waves and a head-to-head domain wall in geometrically confined magnetic nanotubes. We found that incident spin waves of specific frequencies can lead to sufficiently high-speed (on the order of a few hundreds of m/s or higher) domain-wall motions in the same direction as that of the incident spin-waves. The domain-wall motions and their speed vary remarkably with the frequency and the amplitude of the incident spin-waves. High-speed domain-wall motions originate from the transfer torque of spin waves' linear momentum to the domain wall, through the partial or completemore » reflection of the incident spin waves from the domain wall. This work provides a fundamental understanding of the interaction of the spin waves with a domain wall in the magnetic nanotubes as well as a route to all-magnetic control of domain-wall motions in the magnetic nanoelements.« less

Plasma control by modification of helicon wave propagation in low magnetic fields

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

Lafleur, T.; Charles, C.; Boswell, R. W.

2010-07-15

By making use of nonuniform magnetic fields, it is shown experimentally that control of helicon wave propagation can be achieved in a low pressure (0.08 Pa) expanding plasma. The m=1 helicon waves are formed during a direct capacitive to wave mode transition that occurs in a low diverging magnetic field (B{sub 0}<3 mT). In this initial configuration, waves are prevented from reaching the downstream region, but slight modifications to the magnetic field allows the axial distance over which waves can propagate to be controlled. By changing the effective propagation distance in this way, significant modification of the density and plasmamore » potential profiles can be achieved, showing that the rf power deposition can be spatially controlled as well. Critical to the modification of the wave propagation behavior is the magnetic field strength (and geometry) near the exit of the plasma source region, which gives electron cyclotron frequencies close to the wave frequency of 13.56 MHz.« less

Acute and chronic hypothyroidism are associated with similar left ventricular diastolic dysfunction relative to the euthyroid state: results of doppler echocardiographic comparisons.

PubMed

Gauna, A; Messuti, H; Papadopulos, G; Benchuga, G; Viale, F; Marlowe, R J; Silva Croome, M C

2011-10-01

How the duration of hypothyroidism affects left ventricular diastolic function is not well-characterized. We sought to compare left ventricular diastolic function in acutely vs chronically hypothyroid patients vs euthyroid controls, and within individuals while on vs off T4. We prospectively performed such comparisons measuring pulsed-wave and color M-mode Doppler echocardiographic variables: early or late mitral peak velocities (E wave or A wave, respectively), E wave/A wave ratio, E wave deceleration time, isovolumic relaxation time (IVRT), mitral flow propagation velocity (Vp), E wave/Vp ratio. Subjects comprised the acute HYPO group, 10 patients undergoing T4 withdrawal ≥ 6 months post-primary treatment for differentiated thyroid cancer (DTC); the chronic HYPO group, 23 treatment-naïve Hashimoto thyroiditis patients; and 21 healthy euthyroid controls. Subjects were adults aged ≤ 60 yr, predominantly female, with sinus rhythm; exclusion criteria were cardiovascular or thyroid disorder besides DTC (Hashimoto thyroiditis) in acute (chronic) HYPO patients or medication (besides thyroid hormone) affecting cardiac or thyroid function. Mean IVRT was significantly delayed and mean Vp, significantly slowed in both HYPO groups vs controls (p<0.0005), but did not differ between HYPO groups. These variables also were significantly impaired (p<0.05) within individuals when off vs on T4 (no.=8 acute, 10 chronic HYPO patients). Both HYPO groups had elevated mean E wave/Vp ratios vs controls, but the elevation reached significance (p<0.05) only in the larger chronic HYPO group. Left ventricular diastolic dysfunction is largely similar in acutely or chronically hypothyroid patients off T4 vs healthy controls or the same patients on T4.

Color-tuned neurons are spatially clustered according to color preference within alert macaque posterior inferior temporal cortex

PubMed Central

Conway, Bevil R.; Tsao, Doris Y.

2009-01-01

Large islands of extrastriate cortex that are enriched for color-tuned neurons have recently been described in alert macaque using a combination of functional magnetic resonance imaging (fMRI) and single-unit recording. These millimeter-sized islands, dubbed “globs,” are scattered throughout the posterior inferior temporal cortex (PIT), a swath of brain anterior to area V3, including areas V4, PITd, and posterior TEO. We investigated the micro-organization of neurons within the globs. We used fMRI to identify the globs and then used MRI-guided microelectrodes to test the color properties of single glob cells. We used color stimuli that sample the CIELUV perceptual color space at regular intervals to test the color tuning of single units, and make two observations. First, color-tuned neurons of various color preferences were found within single globs. Second, adjacent glob cells tended to have the same color tuning, demonstrating that glob cells are clustered by color preference and suggesting that they are arranged in color columns. Neurons separated by 50 μm, measured parallel to the cortical sheet, had more similar color tuning than neurons separated by 100 μm, suggesting that the scale of the color columns is <100 μm. These results show that color-tuned neurons in PIT are organized by color preference on a finer scale than the scale of single globs. Moreover, the color preferences of neurons recorded sequentially along a given electrode penetration shifted gradually in many penetrations, suggesting that the color columns are arranged according to a chromotopic map reflecting perceptual color space. PMID:19805195

Topological Magnonics: A Paradigm for Spin-Wave Manipulation and Device Design

NASA Astrophysics Data System (ADS)

Wang, X. S.; Zhang, H. W.; Wang, X. R.

2018-02-01

Conventional magnonic devices use magnetostatic waves whose properties are sensitive to device geometry and the details of magnetization structure, so the design and the scalability of the device or circuitry are difficult. We propose topological magnonics, in which topological exchange spin waves are used as information carriers, that do not suffer from conventional problems of magnonic devices with additional nice features of nanoscale wavelength and high frequency. We show that a perpendicularly magnetized ferromagnet on a honeycomb lattice is generically a topological magnetic material in the sense that topologically protected chiral edge spin waves exist in the band gap as long as a spin-orbit-induced nearest-neighbor pseudodipolar interaction (and/or a next-nearest-neighbor Dzyaloshinskii-Moriya interaction) is present. The edge spin waves propagate unidirectionally along sample edges and domain walls regardless of the system geometry and defects. As a proof of concept, spin-wave diodes, spin-wave beam splitters, and spin-wave interferometers are designed by using sample edges and domain walls to manipulate the propagation of topologically protected chiral spin waves. Since magnetic domain walls can be controlled by magnetic fields or electric current or fields, one can essentially draw, erase, and redraw different spin-wave devices and circuitry on the same magnetic plate so that the proposed devices are reconfigurable and tunable. The topological magnonics opens up an alternative direction towards a robust, reconfigurable and scalable spin-wave circuitry.

Optical design of a dual wave band catadioptric endoscope for the Joint European Torus

NASA Astrophysics Data System (ADS)

Greco, Vincenzo; Maddaluno, Giorgio

2004-02-01

In this paper we describe the optical design of a catadioptric endoscope for the Joint European Torus (JET). The JET is the flagship experiment in the European nuclear fusion research programme. It is a large tokamak (Russian acronym for "toroidal magnetic chamber") system located at Culham (UK). At the centre of this machine there is a toroidal (ring - shaped) vacuum vessel where the plasma is confined by magnetic fields. The endoscope explores in two wave bands (4.2 μm - 4.4 μm and 0.6 μm - 0.7 μm) an entire cross section of the vacuum vessel. It then creates for each wave band an image onto a separate area image sensor, located 5500 mm away from the plasma behind a concrete shield. The endoscope performs two different functions namely: infrared thermography on plasma facing components and in vessel inspection.

Rayleigh wave behavior in functionally graded magneto-electro-elastic material

NASA Astrophysics Data System (ADS)

Ezzin, Hamdi; Mkaoir, Mohamed; Amor, Morched Ben

2017-12-01

Piezoelectric-piezomagnetic functionally graded materials, with a gradual change of the mechanical and electromagnetic properties have greatly applying promises. Based on the ordinary differential equation and stiffness matrix methods, a dynamic solution is presented for the propagation of the wave on a semi-infinite piezomagnetic substrate covered with a functionally graded piezoelectric material (FGPM) layer. The materials properties are assumed to vary in the direction of the thickness according to a known variation law. The phase and group velocity of the Rayleigh wave is numerically calculated for the magneto-electrically open and short cases, respectively. The effect of gradient coefficients on the phase velocity, group velocity, coupled magneto-electromechanical factor, on the stress fields, the magnetic potential and the mechanical displacement are discussed, respectively. Illustration is achieved on the hetero-structure PZT-5A/CoFe2O4; the obtained results are especially useful in the design of high-performance acoustic surface devices and accurately prediction of the Rayleigh wave propagation behavior.

Image visualization of hyperspectral spectrum for LWIR

NASA Astrophysics Data System (ADS)

Chong, Eugene; Jeong, Young-Su; Lee, Jai-Hoon; Park, Dong Jo; Kim, Ju Hyun

2015-07-01

The image visualization of a real-time hyperspectral spectrum in the long-wave infrared (LWIR) range of 900-1450 cm-1 by a color-matching function is addressed. It is well known that the absorption spectra of main toxic industrial chemical (TIC) and chemical warfare agent (CWA) clouds are detected in this spectral region. Furthermore, a significant spectral peak due to various background species and unknown targets are also present. However, those are dismissed as noise, resulting in utilization limit. Herein, we applied a color-matching function that uses the information from hyperspectral data, which is emitted from the materials and surfaces of artificial or natural backgrounds in the LWIR region. This information was used to classify and differentiate the background signals from the targeted substances, and the results were visualized as image data without additional visual equipment. The tristimulus value based visualization information can quickly identify the background species and target in real-time detection in LWIR.

Third-generation intelligent IR focal plane arrays

NASA Astrophysics Data System (ADS)

Caulfield, H. John; Jack, Michael D.; Pettijohn, Kevin L.; Schlesselmann, John D.; Norworth, Joe

1998-03-01

SBRC is at the forefront of industry in developing IR focal plane arrays including multi-spectral technology and '3rd generation' functions that mimic the human eye. 3rd generation devices conduct advanced processing on or near the FPA that serve to reduce bandwidth while performing needed functions such as automatic target recognition, uniformity correction and dynamic range enhancement. These devices represent a solution for processing the exorbitantly high bandwidth coming off large area FPAs without sacrificing systems sensitivity. SBRC's two-color approach leverages the company's HgCdTe technology to provide simultaneous multiband coverage, from short through long wave IR, with near theoretical performance. IR systems that are sensitive to different spectral bands achieve enhanced capabilities for target identification and advanced discrimination. This paper will provide a summary of the issues, the technology and the benefits of SBRC's third generation smart and two-color FPAs.

Magneto-optical properties of biogenic photonic crystals in algae

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

Iwasaka, M., E-mail: iwasaka-m@umin.ac.jp; Japan Science and Technology Agency, PRESTO, 4-1-8 Honcho, Kawaguchi 332-0012 Saitama; Mizukawa, Y.

In the present study, the effects of strong static magnetic fields on the structural colors of the cell covering crystals on a microalgae, coccolithophore, were investigated. The coccolithophore, Emiliania huxleyi, generates a precise assembly of calcite crystals called coccoliths by biomineralization. The coccoliths attached to the cells exhibited structural colors under side light illumination, and the colors underwent dynamic transitions when the magnetic fields were changed between 0 T and 5 T, probably due to diamagnetically induced changes of their inclination under the magnetic fields. The specific light-scattering property of individual coccoliths separated from the cells was also observed. Light scattering frommore » a condensed suspension of coccoliths drastically decreased when magnetic fields of more than 4 T were applied parallel to the direction of observation. The magnetically aligned cell-covering crystals of the coccolithophores exhibited the properties of both a photonic crystal and a minimum micromirror.« less

Color Memory: A Yang-Mills Analog of Gravitational Wave Memory.

PubMed

Pate, Monica; Raclariu, Ana-Maria; Strominger, Andrew

2017-12-29

A transient color flux across null infinity in classical Yang-Mills theory is considered. It is shown that a pair of test "quarks" initially in a color singlet generically acquire net color as a result of the flux. A nonlinear formula is derived for the relative color rotation of the quarks. For a weak color flux, the formula linearizes to the Fourier transform of the soft gluon theorem. This color memory effect is the Yang-Mills analog of the gravitational memory effect.

Color Memory: A Yang-Mills Analog of Gravitational Wave Memory

NASA Astrophysics Data System (ADS)

Pate, Monica; Raclariu, Ana-Maria; Strominger, Andrew

2017-12-01

A transient color flux across null infinity in classical Yang-Mills theory is considered. It is shown that a pair of test "quarks" initially in a color singlet generically acquire net color as a result of the flux. A nonlinear formula is derived for the relative color rotation of the quarks. For a weak color flux, the formula linearizes to the Fourier transform of the soft gluon theorem. This color memory effect is the Yang-Mills analog of the gravitational memory effect.

Hearing colors: an example of brain plasticity

PubMed Central

Alfaro, Arantxa; Bernabeu, Ángela; Agulló, Carlos; Parra, Jaime; Fernández, Eduardo

2015-01-01

Sensory substitution devices (SSDs) are providing new ways for improving or replacing sensory abilities that have been lost due to disease or injury, and at the same time offer unprecedented opportunities to address how the nervous system could lead to an augmentation of its capacities. In this work we have evaluated a color-blind subject using a new visual-to-auditory SSD device called “Eyeborg”, that allows colors to be perceived as sounds. We used a combination of neuroimaging techniques including Functional Magnetic Resonance Imaging (fMRI), Diffusion Tensor Imaging (DTI) and proton Magnetic Resonance Spectroscopy (1H-MRS) to study potential brain plasticity in this subject. Our results suggest that after 8 years of continuous use of this device there could be significant adaptive and compensatory changes within the brain. In particular, we found changes in functional neural patterns, structural connectivity and cortical topography at the visual and auditive cortex of the Eyeborg user in comparison with a control population. Although at the moment we cannot claim that the continuous use of the Eyeborg is the only reason for these findings, our results may shed further light on potential brain changes associated with the use of other SSDs. This could help to better understand how the brain adapts to several pathologies and uncover adaptive resources such as cross-modal representations. We expect that the precise understanding of these changes will have clear implications for rehabilitative training, device development and for more efficient programs for people with disabilities. PMID:25926778

Hearing colors: an example of brain plasticity.

PubMed

Alfaro, Arantxa; Bernabeu, Ángela; Agulló, Carlos; Parra, Jaime; Fernández, Eduardo

2015-01-01

Sensory substitution devices (SSDs) are providing new ways for improving or replacing sensory abilities that have been lost due to disease or injury, and at the same time offer unprecedented opportunities to address how the nervous system could lead to an augmentation of its capacities. In this work we have evaluated a color-blind subject using a new visual-to-auditory SSD device called "Eyeborg", that allows colors to be perceived as sounds. We used a combination of neuroimaging techniques including Functional Magnetic Resonance Imaging (fMRI), Diffusion Tensor Imaging (DTI) and proton Magnetic Resonance Spectroscopy ((1)H-MRS) to study potential brain plasticity in this subject. Our results suggest that after 8 years of continuous use of this device there could be significant adaptive and compensatory changes within the brain. In particular, we found changes in functional neural patterns, structural connectivity and cortical topography at the visual and auditive cortex of the Eyeborg user in comparison with a control population. Although at the moment we cannot claim that the continuous use of the Eyeborg is the only reason for these findings, our results may shed further light on potential brain changes associated with the use of other SSDs. This could help to better understand how the brain adapts to several pathologies and uncover adaptive resources such as cross-modal representations. We expect that the precise understanding of these changes will have clear implications for rehabilitative training, device development and for more efficient programs for people with disabilities.

Frequency correlation of probe waves backscattered from small scale ionospheric irregularities generated by high power HF radio waves

NASA Astrophysics Data System (ADS)

Puchkov, V. A.

2016-09-01

Aspect sensitive scattering of multi-frequency probe signals by artificial, magnetic field aligned density irregularities (with transverse size ∼ 1- 10 m) generated in the ionosphere by powerful radio waves is considered. Fluctuations of received signals depending on stochastic properties of the irregularities are calculated. It is shown that in the case of HF probe waves two mechanisms may contribute to the scattered signal fluctuations. The first one is due to the propagation of probe waves in the ionospheric plasma as in a randomly inhomogeneous medium. The second one lies in non-stationary stochastic behavior of irregularities which satisfy the Bragg conditions for the scattering geometry and therefore constitute centers of scattering. In the probe wave frequency band of the order of 10-100 MHz the second mechanism dominates which delivers opportunity to recover some properties of artificial irregularities from received signals. Correlation function of backscattered probe waves with close frequencies is calculated, and it is shown that detailed spatial distribution of irregularities along the scattering vector can be found experimentally from observations of this correlation function.

Solar Wind - Magnetosheath - Magnetopause Interactions in Global Hybrid-Vlasov Simulations

NASA Astrophysics Data System (ADS)

Hoilijoki, S.; Pfau-Kempf, Y.; Ganse, U.; Hietala, H.; Cassak, P.; Walsh, B.; Juusola, L.; Jarvinen, R.; von Alfthan, S.; Palmroth, M.

2017-12-01

We present results of interactions of solar wind and Earth's magnetosphere in global hybrid-Vlasov simulations carried out using the Vlasiator model. Vlasiator propagates ions as velocity distribution functions by solving the Vlasov equation and electrons are treated as charge-neutralizing massless fluid. Vlasiator simulations show a strong coupling between the ion scale and global scale physics. Global scale phenomena affect the local physics and the local phenomena impact the global system. Our results have shown that mirror mode waves growing in the quasi-perpendicular magnetosheath have an impact on the local reconnection rates at the dayside magnetopause. Furthermore, multiple X-line reconnection at the dayside magnetopause leads to the formation of magnetic islands (2D flux transfer events), which launch bow waves upstream propagating through the magnetosheath. These steep bow waves have the ability to accelerate ions in the magnetosheath. When the bow waves reach the bow shock they are able to bulge the shock locally. The bulge in the shock decreases the angle between the interplanetary magnetic field and the shock normal and allows ions to be reflected back to the solar wind along the magnetic field lines. Consequently, Vlasiator simulations show that magnetosheath fluctuations affect magnetopause reconnection and reconnection may influence particle acceleration and reflection in the magnetosheath and solar wind.

Radial Diffusion Coefficients Using E and B Field Data from the Van Allen Probes: Comparison with the CRRES Study

NASA Astrophysics Data System (ADS)

Ali, A.; Elkington, S. R.; Malaspina, D.

2014-12-01

The Van Allen radiation belts contain highly energetic particles which interact with a variety of plasma and MHD waves. Waves with frequencies in the ULF range are understood to play an important role in loss and acceleration of energetic particles. We are investigating the contributions from perturbations in both the magnetic and the electric fields in driving radial diffusion of charged particles and wish to probe two unanswered questions about ULF wave driven radial transport. First, how important are the fluctuations in the magnetic field compared with the fluctuations in the electric field in driving radial diffusion? Second, how does ULF wave power distribution in azimuth affect radial diffusion? Analytic treatments of the diffusion coefficients generally assume uniform distribution of power in azimuth but in situ measurements suggest otherwise. We present results from a study using the electric and magnetic field measurements from the Van Allen Probes to estimate the radial diffusion coefficients as a function of L and Kp. During the lifetime of the RBSP mission to date, there has been a dearth of solar activity. This compels us to consider Kp as the only time and activity dependent parameter instead of solar wind velocity and pressure.

Ultrasonic alignment of bio-functionalized magnetic beads and live cells in PDMS micro-fluidic channel.

PubMed

Islam, Afroja T; Siddique, Ariful H; Ramulu, T S; Reddy, Venu; Eu, Young-Jae; Cho, Seung Hyun; Kim, CheolGi

2012-12-01

In this work, we demonstrated the alignment of polystyrene latex microspheres (diameter of 1 ~45 μm), bio-functionalized superparamagnetic beads (diameter 2.8 μm), and live cells (average diameter 1 ~2 μm) using an ultrasonic standing wave (USW) in a PDMS microfluidic channel (330 μm width) attached on a Si substrate for bio-medical applications. To generate a standing wave inside the channel, ultrasound of 2.25 MHz resonance frequency (for the channel width) was applied by two ultrasound transducers installed at both sides of the channel which caused the radiation force to concentrate the micro-particles at the single pressure nodal plane of USW. By increasing the frequency to the next resonance condition of the channel, the particles were concentrated in dual nodal planes. Migration time of the micro-particles towards the single nodal plane was recorded as 108 s, 17 s, and 115 s for polystyrene particles of 2 μm diameter, bio-functionalized magnetic beads, and live cells, respectively. These successful alignments of the bio-functionalized magnetic beads along the desired part of the channel can enhance the performance of a sensor which is applicable for the bio-hybrid system and the alignment of live cells without any damage can be used for sample pre-treatment for the application of lab-on-a-chip type bioassays.

Hints of hybridizing Majorana fermions in a nanowire coupled to superconducting leads

NASA Astrophysics Data System (ADS)

Finck, A. D. K.; van Harlingen, D. J.; Mohseni, P. K.; Jung, K.; Li, X.

2013-03-01

It has been proposed that a nanowire with strong spin-orbit coupling that is contacted with a conventional superconductor and subjected to a large magnetic field can be driven through a topological phase transition. In this regime, the two ends of the nanowire together host a pair of quasi-particles known as Majorana fermions (MFs). A key feature of MFs is that they are pinned to zero energy when the topological nanowire is long enough such that the wave functions of the two MFs do not overlap significantly, resulting in a zero bias anomaly (ZBA). It has been recently predicted that changes in external parameters can vary the wave function overlap and cause the MFs to hybridize in an oscillatory fashion. This would lead to a non-monotonic splitting or broadening of the ZBA and help distinguish MF transport signatures from a Kondo effect. Here, we present transport studies of an InAs nanowire contacted with niobium nitride leads in high magnetic fields. We observe a number of robust ZBAs that can persist for a wide range of back gate bias and magnetic field strength. Under certain conditions, we find that the height and width of the ZBA can oscillate with back gate bias or magnetic field. This work was supported by Microsoft Project Q.

Magnetism and exchange interaction of small rare-earth clusters; Tb as a representative

PubMed Central

Peters, Lars; Ghosh, Saurabh; Sanyal, Biplab; van Dijk, Chris; Bowlan, John; de Heer, Walt; Delin, Anna; Di Marco, Igor; Eriksson, Olle; Katsnelson, Mikhail I.; Johansson, Börje; Kirilyuk, Andrei

2016-01-01

Here we follow, both experimentally and theoretically, the development of magnetism in Tb clusters from the atomic limit, adding one atom at a time. The exchange interaction is, surprisingly, observed to drastically increase compared to that of bulk, and to exhibit irregular oscillations as a function of the interatomic distance. From electronic structure theory we find that the theoretical magnetic moments oscillate with cluster size in exact agreement with experimental data. Unlike the bulk, the oscillation is not caused by the RKKY mechanism. Instead, the inter-atomic exchange is shown to be driven by a competition between wave-function overlap of the 5d shell and the on-site exchange interaction, which leads to a competition between ferromagnetic double-exchange and antiferromagnetic super-exchange. This understanding opens up new ways to tune the magnetic properties of rare-earth based magnets with nano-sized building blocks. PMID:26795239

A pharmacological functional magnetic resonance imaging study probing the interface of cognitive and emotional brain systems in pediatric bipolar disorder.

PubMed

Pavuluri, Mani N; Passarotti, Alessandra M; Parnes, Stephanie A; Fitzgerald, Jacklynn M; Sweeney, John A

2010-10-01

This functional magnetic resonance imaging (fMRI) study investigated the effects of pharmacotherapy on brain function underlying affect dysregulation and cognitive function in pediatric bipolar disorder (PBD). Healthy controls (HC) (n=14; mean age =14.1 ± 2.4 years) and unmedicated PBD patients with manic or hypomanic episodes (n=17; mean age =14.3 ± 1.1 years) were matched on intelligence quotient (IQ) and demographic factors. The fMRI studies were performed at baseline and after 14 weeks, during which PBD patients were treated initially with second-generation antipsychotics (SGAs) followed by lamotrigine monotherapy. The pediatric affective color-matching task was used where subjects matched the color of a positive, negative, or neutral word with one of the two colored circles below in each of the trials. There were five blocks of each emotional word type, with 10 trials per block. Behavioral data showed that the PBD group was modestly slower and less accurate than the HC, regardless of condition or treatment status. The blood oxygen level-dependent (BOLD) signal activity was reduced with treatment in the PBD group relative to the HC group during the negative versus neutral condition in bilateral dorsolateral prefrontal cortex (DLPFC), right posterior cingulate gyrus, parahippocampal gyrus, and inferior parietal lobule, but increased in left ventromedial prefrontal cortex (VMPFC). Similarly, during the positive versus neutral condition, the PBD group, relative to HC, showed reduced activity in right DLPFC, precuneus, and inferior parietal lobule and increased activity in the right VMPFC. However, within the PBD group, there was treatment related decrease in VMPFC and DLPFC. Improvement on Young Mania Rating Scale (YMRS) score significantly correlated with the decreased activity in VMPFC within the patient group. Pharmacotherapy in PBD patients led to differential effort with persistently increased activity in the affective regions and decreased activity in the cognitive regions relative to HC, demonstrating altered mechanisms of affective and cognitive systems of brain function, regardless of symptom response.

Nonminimal Einstein-Yang-Mills-Higgs theory: Associated, color, and color-acoustic metrics for the Wu-Yang monopole model

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

Balakin, A. B.; Zayats, A. E.; Dehnen, H.

2007-12-15

We discuss a nonminimal Einstein-Yang-Mills-Higgs model with uniaxial anisotropy in the group space associated with the Higgs field. We apply this theory to the problem of propagation of color and color-acoustic waves in the gravitational background related to the nonminimal regular Wu-Yang monopole.

Acoustic holograms of active regions

NASA Astrophysics Data System (ADS)

Chou, Dean-Yi

2008-10-01

We propose a method to study solar magnetic regions in the solar interior with the principle of optical holography. A magnetic region in the solar interior scatters the solar background acoustic waves. The scattered waves and background waves could form an interference pattern on the solar surface. We investigate the feasibility of detecting this interference pattern on the solar surface, and using it to construct the three-dimensional scattered wave from the magnetic region with the principle of optical holography. In solar acoustic holography, the background acoustic waves play the role of reference wave; the magnetic region plays the role of the target object; the interference pattern, acoustic power map, on the solar surface plays the role of the hologram.

Impact of enzyme replacement therapy on cardiac morphology and function and late enhancement in Fabry's cardiomyopathy.

PubMed

Beer, Meinrad; Weidemann, Frank; Breunig, Frank; Knoll, Anita; Koeppe, Sabrina; Machann, Wolfram; Hahn, Dietbert; Wanner, Christoph; Strotmann, Jörg; Sandstede, Jörn

2006-05-15

The present study evaluated the evolution of cardiac morphology, function, and late enhancement as a noninvasive marker of myocardial fibrosis, and their inter-relation during enzyme replacement therapy in patients with Fabry's disease using magnetic resonance imaging and color Doppler myocardial imaging. Late enhancement, which was present in up to 50% of patients, was associated with increased left ventricular mass, the failure of a significant regression of hypertrophy during enzyme replacement therapy, and worse segmental myocardial function. Late enhancement may predict the effect of enzyme replacement therapy on left ventricular mass and cardiac function.

Form factors of the d*(2380 ) resonance

NASA Astrophysics Data System (ADS)

Dong, Yubing; Shen, Pengnian; Zhang, Zongye

2018-06-01

In order to explore the possible physical quantities for judging different structures of the newly observed resonance d*(2380 ), we study its electromagnetic form factors. In addition to the electric charge monopole C 0 , we calculate its electric quadrupole E 2 , magnetic dipole M 1 , and magnetic octupole M 3 form factors on the base of the realistic coupled Δ Δ +C8C8 channel d* wave function with both the S - and D -partial waves. The results show that the magnetic dipole moment and electric quadrupole deformation of d* are 7.602 and 2.53 ×10-2 fm2 , respectively. The calculated magnetic dipole moment in the naive constituent quark model is also compared with the result of D12π picture. By comparing with partial results where the d* state is considered with a single Δ Δ and with a D12π structures, we find that in addition to the charge distribution of d*, the magnetic dipole moment and magnetic radius can be used to discriminate different structures of d*. Moreover, a quite small electric quadrupole deformation indicates that d* is more inclined to a slightly oblate shape due to our compact hexaquark dominated structure of d*.

Spin density waves predicted in zigzag puckered phosphorene, arsenene and antimonene nanoribbons

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

Wu, Xiaohua; Zhang, Xiaoli; Wang, Xianlong

2016-04-15

The pursuit of controlled magnetism in semiconductors has been a persisting goal in condensed matter physics. Recently, Vene (phosphorene, arsenene and antimonene) has been predicted as a new class of 2D-semiconductor with suitable band gap and high carrier mobility. In this work, we investigate the edge magnetism in zigzag puckered Vene nanoribbons (ZVNRs) based on the density functional theory. The band structures of ZVNRs show half-filled bands crossing the Fermi level at the midpoint of reciprocal lattice vectors, indicating a strong Peierls instability. To remove this instability, we consider two different mechanisms, namely, spin density wave (SDW) caused by electron-electronmore » interaction and charge density wave (CDW) caused by electron-phonon coupling. We have found that an antiferromagnetic Mott-insulating state defined by SDW is the ground state of ZVNRs. In particular, SDW in ZVNRs displays several surprising characteristics:1) comparing with other nanoribbon systems, their magnetic moments are antiparallelly arranged at each zigzag edge and almost independent on the width of nanoribbons; 2) comparing with other SDW systems, its magnetic moments and band gap of SDW are unexpectedly large, indicating a higher SDW transition temperature in ZVNRs; 3) SDW can be effectively modified by strains and charge doping, which indicates that ZVNRs have bright prospects in nanoelectronic device.« less

Compressional ULF waves in the outer magnetosphere. 2: A case study of Pc 5 type wave activity

NASA Technical Reports Server (NTRS)

Zhu, Xiaoming; Kivelson, Margaret G.

1994-01-01

In previously published work (Zhu and Kivelson, 1991) the spatial distribution of compressional magnetic pulsations of period 2 - 20 min in the outer magnetosphere was described. In this companion paper, we study some specific compressional events within our data set, seeking to determine the structure of the waves and identifying the wave generation mechanism. We use both the magnetic field and three-dimensional plasma data observed by the International Sun-Earth Explorer (ISEE) 1 and/or 2 spacecraft to characterize eight compressional ultra low frequency (ULF) wave events with frequencies below 8 mHz in the outer magnetosphere. High time resolution plasma data for the event of July 24, 1978, made possible a detailed analysis of the waves. Wave properties specific to the event of July 24, 1978, can be summarized as follows: (1) Partial plasma pressures in the different energy ranges responded to the magnetic field pressure differently. In the low-energy range they oscillated in phase with the magnetic pressure, while oscillations in higher-energy ranges were out-of-phase; (2) Perpendicular wavelengths for the event were determined to be 60,000 and 30,000 km in the radial and azimuthal directions, respectively. Wave properties common to all events can be summarized as follows: (1) Compressional Pc 5 wave activity is correlated with Beta, the ratio of the plasma pressure to the magnetic pressure; the absolute magnitude of the plasma pressure plays a minor role for the wave activity; (2) The magnetic equator is a node of the compressional perturbation of the magnetic field; (3) The criterion for the mirror mode instability is often satisfied near the equator in the outer magnetosphere when the compressional waves are present. We believe these waves are generated by internal magnetohydrodynamic (MHD) instabilities.

All-dielectric reflective half-wave plate metasurface based on the anisotropic excitation of electric and magnetic dipole resonances.

PubMed

Ma, Zhijie; Hanham, Stephen M; Gong, Yandong; Hong, Minghui

2018-02-15

We present an all-dielectric metasurface that simultaneously supports electric and magnetic dipole resonances for orthogonal polarizations. At resonances, the metasurface reflects the incident light with nearly perfect efficiency and provides a phase difference of π in the two axes, making a low-loss half-wave plate in reflection mode. The polarization handedness of the incident circularly polarized light is preserved after reflection; this is different from either a pure electric mirror or magnetic mirror. With the features of high reflection and circular polarization conservation, the metamirror is an ideal platform for the geometric phase-based gradient metasurface functioning in reflection mode. Anomalous reflection with the planar meta-mirror is demonstrated as a proof of concept. The proposed meta-mirror can be a good alternative to plasmonic metasurfaces for future compact and high-efficiency metadevices for polarization and phase manipulation in reflection mode.

Manipulation of propagating spin waves in straight and curved magnetic microstrips

NASA Astrophysics Data System (ADS)

Haldar, Arabinda; Liu, Hau-Jian; Schultheiss, Helmut; Vogt, Katrin; Hoffmann, Axel; Buchanan, Kristen

2012-02-01

The main challenges in realizing magnonics devices are the generation, manipulation and detection of spin waves, especially in metallic magnetic materials where the length scales are of interest for applications. We have studied the propagation of spin waves in transversely magnetized Permalloy (Py) microstrips of different shapes using micro-Brillouin light scattering. The Py stripe was 30-nm thick, several micrometers wide and >50 μm long. Spin waves were excited in the Py strip using a 2-μm wide antenna. We compare the spin wave propagation along a straight wire to the propagation along a magnetic microstrip with a smooth bend. We will also discuss the use of a current through a gold wire under the Permalloy to provide a local magnetic field to maintain a transverse magnetization around the bend.

Contributions of poroelastic-wave potentials to seismoelectromagnetic wavefields and validity of the quasi-static calculation: a view from a borehole model

NASA Astrophysics Data System (ADS)

Guan, Wei; Shi, Peng; Hu, Hengshan

2018-01-01

In this study, we theoretically analyse the contributions of the four poroelastic-wave potentials to seismoelectromagnetic (SEM) wavefields, verify the validity of the quasi-static calculation of the electric field and provide a method to calculate the magnetic field by using the curl-free electric field. Calculations show that both the fast and slow P waves and the SH and SV waves have non-negligible contributions to the SEM fields. The S waves have indirect contribution to the electric field through the EM conversion from the magnetic field, although the direct contribution due to streaming current is negligible if EM wavenumbers are much smaller than those of the S waves. The P waves have indirect contribution to the magnetic field through EM conversion from the electric field, although the direct contribution is absent. The quasi-static calculation of the electric field is practicable since it is normally satisfied in reality that the EM wavenumbers are much smaller than those of poroelastic waves. While the direct contribution of the S waves and the higher-order EM conversions are ignored, the first-order EM conversion from the S-wave-induced magnetic field is reserved through the continuity of the electric-current density. To calculate the magnetic field on this basis, we separate the quasi-static electric field into a rotational and an irrotational part. The magnetic-field solutions are derived through Hertz vectors in which the coefficients of the magnetic Hertz vector are determined from the magnetic-field continuities and those of the electric Hertz vector originate from the irrotational part of the quasi-static electric field.

Use of discrete chromatic space to tune the image tone in a color image mosaic

NASA Astrophysics Data System (ADS)

Zhang, Zuxun; Li, Zhijiang; Zhang, Jianqing; Zheng, Li

2003-09-01

Color image process is a very important problem. However, the main approach presently of them is to transfer RGB colour space into another colour space, such as HIS (Hue, Intensity and Saturation). YIQ, LUV and so on. Virutally, it may not be a valid way to process colour airborne image just in one colour space. Because the electromagnetic wave is physically altered in every wave band, while the color image is perceived based on psychology vision. Therefore, it's necessary to propose an approach accord with physical transformation and psychological perception. Then, an analysis on how to use relative colour spaces to process colour airborne photo is discussed and an application on how to tune the image tone in colour airborne image mosaic is introduced. As a practice, a complete approach to perform the mosaic on color airborne images via taking full advantage of relative color spaces is discussed in the application.

Influence of magnetic fields on the color screening masses

NASA Astrophysics Data System (ADS)

Bonati, Claudio; D'Elia, Massimo; Mesiti, Michele; Negro, Francesco; Rucci, Andrea; Sanfilippo, Francesco

2018-03-01

We present some recent results obtained in the study of the color magnetic and electric screening masses in the QCD plasma. In particular, we discuss how the masses get modified by strong external fields which are expected to be created in physical situations such as heavy-ion collisions.

Observation of Chorus Waves by the Van Allen Probes: Dependence on Solar Wind Parameters and Scale Size

NASA Technical Reports Server (NTRS)

Aryan, Homayon; Sibeck, David; Balikhin, Michael; Agapitov, Oleksiy; Kletzing, Craig

2016-01-01

Highly energetic electrons in the Earths Van Allen radiation belts can cause serious damage to spacecraft electronic systems and affect the atmospheric composition if they precipitate into the upper atmosphere. Whistler mode chorus waves have attracted significant attention in recent decades for their crucial role in the acceleration and loss of energetic electrons that ultimately change the dynamics of the radiation belts. The distribution of these waves in the inner magnetosphere is commonly presented as a function of geomagnetic activity. However, geomagnetic indices are nonspecific parameters that are compiled from imperfectly covered ground based measurements. The present study uses wave data from the two Van Allen Probes to present the distribution of lower band chorus waves not only as functions of single geomagnetic index and solar wind parameters but also as functions of combined parameters. Also the current study takes advantage of the unique equatorial orbit of the Van Allen Probes to estimate the average scale size of chorus wave packets, during close separations between the two spacecraft, as a function of radial distance, magnetic latitude, and geomagnetic activity, respectively. Results show that the average scale size of chorus wave packets is approximately 13002300 km. The results also show that the inclusion of combined parameters can provide better representation of the chorus wave distributions in the inner magnetosphere and therefore can further improve our knowledge of the acceleration and loss of radiation belt electrons.

Evolution of magnetic flux ropes associated with flux transfer events and interplanetary magnetic clouds

NASA Technical Reports Server (NTRS)

Wei, C. Q.; Lee, L. C.; Wang, S.; Akasofu, S.-I.

1991-01-01

Spacecraft observations suggest that flux transfer events and interplanetary magnetic clouds may be associated with magnetic flux ropes which are magnetic flux tubes containing helical magnetic field lines. In the magnetic flux ropes, the azimuthal magnetic field is superposed on the axial field. The time evolution of a localized magnetic flux rope is studied. A two-dimensional compressible MHD simulation code with a cylindrical symmetry is developed to study the wave modes associated with the evolution of flux ropes. It is found that in the initial phase both the fast magnetosonic wave and the Alfven wave are developed in the flux rope. After this initial phase, the Alfven wave becomes the dominant wave mode for the evolution of the magnetic flux rope and the radial expansion velocity of the flux rope is found to be negligible. Numerical results further show that even for a large initial azimuthal component of the magnetic field, the propagation velocity along the axial direction of the flux rope remains the Alfven velocity. It is also found that the localized magnetic flux rope tends to evolve into two separate magnetic ropes propagating in opposite directions. The simulation results are used to study the evolution of magnetic flux ropes associated with flux transfer events observed at the earth's dayside magnetopause and magnetic clouds in the interplanetary space.

Dynamics of magnetization in ferromagnet with spin-transfer torque

NASA Astrophysics Data System (ADS)

Li, Zai-Dong; He, Peng-Bin; Liu, Wu-Ming

2014-11-01

We review our recent works on dynamics of magnetization in ferromagnet with spin-transfer torque. Driven by constant spin-polarized current, the spin-transfer torque counteracts both the precession driven by the effective field and the Gilbert damping term different from the common understanding. When the spin current exceeds the critical value, the conjunctive action of Gilbert damping and spin-transfer torque leads naturally the novel screw-pitch effect characterized by the temporal oscillation of domain wall velocity and width. Driven by space- and time-dependent spin-polarized current and magnetic field, we expatiate the formation of domain wall velocity in ferromagnetic nanowire. We discuss the properties of dynamic magnetic soliton in uniaxial anisotropic ferromagnetic nanowire driven by spin-transfer torque, and analyze the modulation instability and dark soliton on the spin wave background, which shows the characteristic breather behavior of the soliton as it propagates along the ferromagnetic nanowire. With stronger breather character, we get the novel magnetic rogue wave and clarify its formation mechanism. The generation of magnetic rogue wave mainly arises from the accumulation of energy and magnons toward to its central part. We also observe that the spin-polarized current can control the exchange rate of magnons between the envelope soliton and the background, and the critical current condition is obtained analytically. At last, we have theoretically investigated the current-excited and frequency-adjusted ferromagnetic resonance in magnetic trilayers. A particular case of the perpendicular analyzer reveals that the ferromagnetic resonance curves, including the resonant location and the resonant linewidth, can be adjusted by changing the pinned magnetization direction and the direct current. Under the control of the current and external magnetic field, several magnetic states, such as quasi-parallel and quasi-antiparallel stable states, out-of-plane precession, and bistable states can be realized. The precession frequency can be expressed as a function of the current and external magnetic field.

The role of parietal cortex in the formation of color and motion based concepts

PubMed Central

Cheadle, Samuel W.; Zeki, Semir

2014-01-01

Imaging evidence shows that separate subdivisions of parietal cortex, in and around the intraparietal sulcus (IPS), are engaged when stimuli are grouped according to color and to motion (Zeki and Stutters, 2013). Since grouping is an essential step in the formation of concepts, we wanted to learn whether parietal cortex is also engaged in the formation of concepts according to these two attributes. Using functional magnetic resonance imaging (fMRI), and choosing the recognition of concept-based color or motion stimuli as our paradigm, we found that there was strong concept-related activity in and around the IPS, a region whose homolog in the macaque monkey is known to receive direct but segregated anatomical inputs from V4 and V5. Parietal activity related to color concepts was juxtaposed but did not overlap with activity related to motion concepts, thus emphasizing the continuation of the segregation of color and motion into the conceptual system. Concurrent retinotopic mapping experiments showed that within the parietal cortex, concept-related activity increases within later stage IPS areas. PMID:25120447

New Quantum Diffusion Monte Carlo Method for strong field time dependent problems

NASA Astrophysics Data System (ADS)

Kalinski, Matt

2017-04-01

We have recently formulated the Quantum Diffusion Quantum Monte Carlo (QDMC) method for the solution of the time-dependent Schrödinger equation when it is equivalent to the reaction-diffusion system coupled by the highly nonlinear potentials of the type of Shay. Here we formulate a new Time Dependent QDMC method free of the nonlinearities described by the constant stochastic process of the coupled diffusion with transmutation. As before two kinds of diffusing particles (color walkers) are considered but which can further also transmute one into the other. Each of the species undergoes the hypothetical Einstein random walk progression with transmutation. The progressed particles transmute into the particles of the other kind before contributing to or annihilating the other particles density. This fully emulates the Time Dependent Schrödinger equation for any number of quantum particles. The negative sign of the real and the imaginary parts of the wave function is handled by the ``spinor'' densities carrying the sign as the degree of freedom. We apply the method for the exact time-dependent observation of our discovered two-electron Langmuir configurations in the magnetic and circularly polarized fields.

Christian Andreas Doppler--the man and his legacy.

PubMed

Coman, I M

2005-01-01

Reminding the life and legacy of the Austrian Scientist who discovered the famous 'Doppler Effect'. C.A. Doppler was born the 29th of November 1803 in Salzburg. After studies in Linz and Vienna, he graduated in mathematics, became assistant at the University and later worked as a professor in Prague. Back to Vienna, he was appointed as professor at the Polytechnic School and --in 1850--as first director of the new Institute of Physics. C.A. Doppler did publish on magnetism, electricity, optics, and astronomy. He remains in the history of science due to the discovery presented (May 25, 1842) at the Royal Bohemian Society of Science entitled "On the colored light of the double stars and certain other stars of the heavens"; the paper described (applied to light) the shift of frequency which bears nowadays his name. The theory was later experimentally proven and--extended for any electromagnetic and acoustic waves--got myriads if applications in astronomy, physics, aviation, meteorology, and health science. Satomura in Japan (1955) published it's first ultrasound vascular application--with successive achievements in the next decades. Doppler ultrasonagraphy became the main noninvasive instrument for functional assesment of heart and vessels.

Prior Knowledge about Objects Determines Neural Color Representation in Human Visual Cortex.

PubMed

Vandenbroucke, A R E; Fahrenfort, J J; Meuwese, J D I; Scholte, H S; Lamme, V A F

2016-04-01

To create subjective experience, our brain must translate physical stimulus input by incorporating prior knowledge and expectations. For example, we perceive color and not wavelength information, and this in part depends on our past experience with colored objects ( Hansen et al. 2006; Mitterer and de Ruiter 2008). Here, we investigated the influence of object knowledge on the neural substrates underlying subjective color vision. In a functional magnetic resonance imaging experiment, human subjects viewed a color that lay midway between red and green (ambiguous with respect to its distance from red and green) presented on either typical red (e.g., tomato), typical green (e.g., clover), or semantically meaningless (nonsense) objects. Using decoding techniques, we could predict whether subjects viewed the ambiguous color on typical red or typical green objects based on the neural response of veridical red and green. This shift of neural response for the ambiguous color did not occur for nonsense objects. The modulation of neural responses was observed in visual areas (V3, V4, VO1, lateral occipital complex) involved in color and object processing, as well as frontal areas. This demonstrates that object memory influences wavelength information relatively early in the human visual system to produce subjective color vision. © The Author 2014. Published by Oxford University Press. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.

Propagation and dispersion of shock waves in magnetoelastic materials

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

Crum, R. S.; Domann, J. P.; Carman, G. P.

Previous studies examining the response of magnetoelastic materials to shock waves have predominantly focused on applications involving pulsed power generation, with limited attention given to the actual wave propagation characteristics. This study provides detailed magnetic and mechanical measurements of magnetoelastic shock wave propagation and dispersion. Laser generated rarefacted shock waves exceeding 3 GPa with rise times of 10 ns were introduced to samples of the magnetoelastic material Galfenol. The resulting mechanical measurements reveal the evolution of the shock into a compressive acoustic front with lateral release waves. Importantly, the wave continues to disperse even after it has decayed into anmore » acoustic wave, due in large part to magnetoelastic coupling. The magnetic data reveal predominantly shear wave mediated magnetoelastic coupling, and were also used to noninvasively measure the wave speed. The external magnetic field controlled a 30% increase in wave propagation speed, attributed to a 70% increase in average stiffness. Lastly, magnetic signals propagating along the sample over 20× faster than the mechanical wave were measured, indicating these materials can act as passive antennas that transmit information in response to mechanical stimuli.« less

Propagation and dispersion of shock waves in magnetoelastic materials

NASA Astrophysics Data System (ADS)

Crum, R. S.; Domann, J. P.; Carman, G. P.; Gupta, V.

2017-12-01

Previous studies examining the response of magnetoelastic materials to shock waves have predominantly focused on applications involving pulsed power generation, with limited attention given to the actual wave propagation characteristics. This study provides detailed magnetic and mechanical measurements of magnetoelastic shock wave propagation and dispersion. Laser generated rarefacted shock waves exceeding 3 GPa with rise times of 10 ns were introduced to samples of the magnetoelastic material Galfenol. The resulting mechanical measurements reveal the evolution of the shock into a compressive acoustic front with lateral release waves. Importantly, the wave continues to disperse even after it has decayed into an acoustic wave, due in large part to magnetoelastic coupling. The magnetic data reveal predominantly shear wave mediated magnetoelastic coupling, and were also used to noninvasively measure the wave speed. The external magnetic field controlled a 30% increase in wave propagation speed, attributed to a 70% increase in average stiffness. Finally, magnetic signals propagating along the sample over 20× faster than the mechanical wave were measured, indicating these materials can act as passive antennas that transmit information in response to mechanical stimuli.

Propagation and dispersion of shock waves in magnetoelastic materials

DOE PAGES

Crum, R. S.; Domann, J. P.; Carman, G. P.; ...

2017-11-15

Previous studies examining the response of magnetoelastic materials to shock waves have predominantly focused on applications involving pulsed power generation, with limited attention given to the actual wave propagation characteristics. This study provides detailed magnetic and mechanical measurements of magnetoelastic shock wave propagation and dispersion. Laser generated rarefacted shock waves exceeding 3 GPa with rise times of 10 ns were introduced to samples of the magnetoelastic material Galfenol. The resulting mechanical measurements reveal the evolution of the shock into a compressive acoustic front with lateral release waves. Importantly, the wave continues to disperse even after it has decayed into anmore » acoustic wave, due in large part to magnetoelastic coupling. The magnetic data reveal predominantly shear wave mediated magnetoelastic coupling, and were also used to noninvasively measure the wave speed. The external magnetic field controlled a 30% increase in wave propagation speed, attributed to a 70% increase in average stiffness. Lastly, magnetic signals propagating along the sample over 20× faster than the mechanical wave were measured, indicating these materials can act as passive antennas that transmit information in response to mechanical stimuli.« less

Intracompartmental pressure as a predictor of intratesticular blood flow: a rat model.

PubMed

Watson, Matthew J; Bartkowski, Donald P; Nelson, Nathan C

2015-06-01

We identified an intratesticular pressure at which vascular flow would cease in a testicular compartment syndrome model, defining a critical vascular stop flow pressure. A total of 52 male Sprague Dawley® rats were used for the study. The testicle of each rat was delivered from the scrotum and size measurements were taken. An intracompartment pressure monitor needle was inserted into the testis to record basal intratesticular pressure. The monitor needle remained in the testicle for the duration of the procedure. Vascular flow within the testis was measured using a variable frequency linear ultrasound transducer with color flow and pulse wave Doppler modalities. Saline was infused through the compartment monitor in 5 mm Hg increments via a pressure infusion pump. Following each 5 mm Hg increase intratesticular vascular blood flow and velocities were recorded using color flow and pulse wave, respectively. Data collection proceeded until color flow images indicated a complete absence of flow within the testis. Using a paired t-test (p <0.0001), mean color flow stop flow pressure was 52.17 mm Hg (95% CI 49.57-54.77) and pulse wave stop flow pressure was 36.34 mm Hg (95% CI 33.90-38.77). Regression analysis of pulse wave vs color flow showed a slope of 0.6960 ± 0.09112, a y-intercept of 0.02427 ± 4.824 and an x-intercept of -0.03486. This is the first known study to characterize a stop flow pressure within the testicular parenchyma resulting from an increased intracompartmental pressure. Due to probe sensitivity limitations, color flow appears to provide the most precise mean pressure of occlusion of 52.17 mm Hg. Copyright © 2015 American Urological Association Education and Research, Inc. Published by Elsevier Inc. All rights reserved.

Shock Formation and Energy Dissipation of Slow Magnetosonic Waves in Coronal Plumes

NASA Technical Reports Server (NTRS)

Cuntz, M.; Suess, S. T.

2003-01-01

We study the shock formation and energy dissipation of slow magnetosonic waves in coronal plumes. The wave parameters and the spreading function of the plumes as well as the base magnetic field strength are given by empirical constraints mostly from SOHO/UVCS. Our models show that shock formation occurs at low coronal heights, i.e., within 1.3 bun, depending on the model parameters. In addition, following analytical estimates, we show that scale height of energy dissipation by the shocks ranges between 0.15 and 0.45 Rsun. This implies that shock heating by slow magnetosonic waves is relevant at most heights, even though this type of waves is apparently not a solely operating energy supply mechanism.

WASp family verprolin-homologous protein-2 (WAVE2) and Wiskott-Aldrich syndrome protein (WASp) engage in distinct downstream signaling interactions at the T cell antigen receptor site.

PubMed

Pauker, Maor H; Reicher, Barak; Joseph, Noah; Wortzel, Inbal; Jakubowicz, Shlomi; Noy, Elad; Perl, Orly; Barda-Saad, Mira

2014-12-12

T cell antigen receptor (TCR) engagement has been shown to activate pathways leading to actin cytoskeletal polymerization and reorganization, which are essential for lymphocyte activation and function. Several actin regulatory proteins were implicated in regulating the actin machinery, such as members of the Wiskott-Aldrich syndrome protein (WASp) family. These include WASp and the WASp family verprolin-homologous protein-2 (WAVE2). Although WASp and WAVE2 share several structural features, the precise regulatory mechanisms and potential redundancy between them have not been fully characterized. Specifically, unlike WASp, the dynamic molecular interactions that regulate WAVE2 recruitment to the cell membrane and specifically to the TCR signaling complex are largely unknown. Here, we identify the molecular mechanism that controls the recruitment of WAVE2 in comparison with WASp. Using fluorescence resonance energy transfer (FRET) and novel triple-color FRET (3FRET) technology, we demonstrate how WAVE2 signaling complexes are dynamically regulated during lymphocyte activation in vivo. We show that, similar to WASp, WAVE2 recruitment to the TCR site depends on protein-tyrosine kinase, ZAP-70, and the adaptors LAT, SLP-76, and Nck. However, in contrast to WASp, WAVE2 leaves this signaling complex and migrates peripherally together with vinculin to the membrane leading edge. Our experiments demonstrate that WASp and WAVE2 differ in their dynamics and their associated proteins. Thus, this study reveals the differential mechanisms regulating the function of these cytoskeletal proteins. © 2014 by The American Society for Biochemistry and Molecular Biology, Inc.

WASp Family Verprolin-homologous Protein-2 (WAVE2) and Wiskott-Aldrich Syndrome Protein (WASp) Engage in Distinct Downstream Signaling Interactions at the T Cell Antigen Receptor Site*

PubMed Central

Pauker, Maor H.; Reicher, Barak; Joseph, Noah; Wortzel, Inbal; Jakubowicz, Shlomi; Noy, Elad; Perl, Orly; Barda-Saad, Mira

2014-01-01

T cell antigen receptor (TCR) engagement has been shown to activate pathways leading to actin cytoskeletal polymerization and reorganization, which are essential for lymphocyte activation and function. Several actin regulatory proteins were implicated in regulating the actin machinery, such as members of the Wiskott-Aldrich syndrome protein (WASp) family. These include WASp and the WASp family verprolin-homologous protein-2 (WAVE2). Although WASp and WAVE2 share several structural features, the precise regulatory mechanisms and potential redundancy between them have not been fully characterized. Specifically, unlike WASp, the dynamic molecular interactions that regulate WAVE2 recruitment to the cell membrane and specifically to the TCR signaling complex are largely unknown. Here, we identify the molecular mechanism that controls the recruitment of WAVE2 in comparison with WASp. Using fluorescence resonance energy transfer (FRET) and novel triple-color FRET (3FRET) technology, we demonstrate how WAVE2 signaling complexes are dynamically regulated during lymphocyte activation in vivo. We show that, similar to WASp, WAVE2 recruitment to the TCR site depends on protein-tyrosine kinase, ZAP-70, and the adaptors LAT, SLP-76, and Nck. However, in contrast to WASp, WAVE2 leaves this signaling complex and migrates peripherally together with vinculin to the membrane leading edge. Our experiments demonstrate that WASp and WAVE2 differ in their dynamics and their associated proteins. Thus, this study reveals the differential mechanisms regulating the function of these cytoskeletal proteins. PMID:25342748

Magnetic Helicity of Alfven Simple Waves

NASA Technical Reports Server (NTRS)

Webb, Gary M.; Hu, Q.; Dasgupta, B.; Zank, G. P.; Roberts, D.

2010-01-01

The magnetic helicity of fully nonlinear, multi-dimensional Alfven simple waves are investigated, by using relative helicity formulae and also by using an approach involving poloidal and toroidal decomposition of the magnetic field and magnetic vector potential. Different methods to calculate the magnetic vector potential are used, including the homotopy and Biot-Savart formulas. Two basic Alfven modes are identified: (a) the plane 1D Alfven simple wave given in standard texts, in which the Alfven wave propagates along the z-axis, with wave phase varphi=k_0(z-lambda t), where k_0 is the wave number and lambda is the group velocity of the wave, and (b)\\ the generalized Barnes (1976) simple Alfven wave in which the wave normal {bf n} moves in a circle in the xy-plane perpendicular to the mean field, which is directed along the z-axis. The plane Alfven wave (a) is analogous to the slab Alfven mode and the generalized Barnes solution (b) is analogous to the 2D mode in Alfvenic, incompressible turbulence. The helicity characteristics of these two basic Alfven modes are distinct. The helicity characteristics of more general multi-dimensional simple Alfven waves are also investigated. Applications to nonlinear Aifvenic fluctuations and structures observed in the solar wind are discussed.

Fundamental mode of ultra-low frequency electrostatic dust-cyclotron surface waves in a magnetized complex plasma with drifting ions

NASA Astrophysics Data System (ADS)

Lee, Seungjun; Lee, Myoung-Jae

2012-10-01

The electrostatic dust-cyclotron (EDC) waves in a magnetized dusty plasma was reported that they could be excited by gravity in a collisional plasma [1]. Rosenberg suggested that EDC waves could be excited by ions drifting along the magnetic field in a collisional plasma containing dust grains with large thermal speeds [2]. The existing investigations, however, focus on EDC volume waves in which the boundary effects are not considered. In this work, we attempt to obtain some physical results concerning the fundamental mode of EDC surface wave and the stability of wave by utilizing a kinetic method. The EDC surface wave is assumed to propagate along an external magnetic field at the interface between the plasma and the vacuum. The plasma is comprised of drifting ions flowing along an external magnetic field. To derive the growth rate of surface waves, we employ the specular reflection boundary conditions. The EDC surface wave is found to be unstable when the ion drift velocity is larger than the phase velocity of the wave. In addition, the wave becomes to be more unstable if dust particles carry more negative charges.[4pt] [1] N. D'Angelo, Phys. Lett. A 323, 445 (2004).[0pt] [2] M. Rosenberg, Phys. Scr. 82, 035505 (2010).

Relationship between directions of wave and energy propagation for cold plasma waves

NASA Technical Reports Server (NTRS)

Musielak, Zdzislaw E.

1986-01-01

The dispersion relation for plasma waves is considered in the 'cold' plasma approximation. General formulas for the dependence of the phase and group velocities on the direction of wave propagation with respect to the local magnetic field are obtained for a cold magnetized plasma. The principal cold plasma resonances and cut-off frequencies are defined for an arbitrary angle and are used to establish basic regimes of frequency where the cold plasma waves can propagate or can be evanescent. The relationship between direction of wave and energy propagation, for cold plasma waves in hydrogen atmosphere, is presented in the form of angle diagrams (angle between group velocity and magnetic field versus angle between phase velocity and magnetic field) and polar diagrams (also referred to as 'Friedrich's diagrams') for different directions of wave propagation. Morphological features of the diagrams as well as some critical angles of propagation are discussed.

Scanning tunneling spectroscopic (STS) studies of magnetically doped MBE-grown topological insulators (TIs)

NASA Astrophysics Data System (ADS)

Chu, Hao; Teague, Marcus; Chen, Chien-Chang; Woodward, Nicholas; Yeh, Nai-Chang; Kou, Xufeng; He, Liang; Lang, Murong; Wang, Kang; Caltech Collaboration; UCLA Collaboration

2013-03-01

We conduct STS studies on MBE-grown heterostructures of non-magnetic TI (Bi2Se3) with a range of thicknesses (d = 1, 3, 5, 7 quintuple layers, QL) on top of 7-QL magnetically doped TI (Cr-doped Bi2Se3) . For d = 1 and 3-QL, a spatially homogeneous magnetism-induced surface gap (as large as about 150 meV for d = 1-QL) is observed at 77 K, whereas gapless Dirac spectra are found for d = 5 and 7-QL, suggesting that the effective magnetic length for Cr-doped Bi2Se3 is approximately 4 ~ 5-QL. These findings are further corroborated by ARPES and bulk electrical transport measurements. The magnetism-induced surface gap differs from those found in pure Bi2Se3 and (Bi0.5Sb0.5)2 Te3 films of thicknesses smaller than 6-QL, because the latter are due to overlaps of wave functions between the surface and interface layers, which lead to Rashba-like spin-orbit splitting and spin-preserving quasiparticle interference wave-vectors. In contrast, STS studies of TIs with magnetism-induced surface gap do not yield any quasiparticle interferences for energies within the bulk Bi2Se3 gap. Finally, comparative STS studies of pure and magnetically doped TIs in high magnetic fields will be discussed. This work was supported by DARPA.

Hybrid simulations of radial transport driven by the Rayleigh-Taylor instability

NASA Astrophysics Data System (ADS)

Delamere, P. A.; Stauffer, B. H.; Ma, X.

2017-12-01

Plasma transport in the rapidly rotating giant magnetospheres is thought to involve a centrifugally-driven flux tube interchange instability, similar to the Rayleigh-Taylor (RT) instability. In three dimensions, the convective flow patterns associated with the RT instability can produce strong guide field reconnection, allowing plasma mass to move radially outward while conserving magnetic flux (Ma et al., 2016). We present a set of hybrid (kinetic ion / fluid electron) plasma simulations of the RT instability using high plasma beta conditions appropriate for Jupiter's inner and middle magnetosphere. A density gradient, combined with a centrifugal force, provide appropriate RT onset conditions. Pressure balance is achieved by initializing two ion populations: one with fixed temperature, but varying density, and the other with fixed density, but a temperature gradient that offsets the density gradient from the first population and the centrifugal force (effective gravity). We first analyze two-dimensional results for the plane perpendicular to the magnetic field by comparing growth rates as a function of wave vector following Huba et al. (1998). Prescribed perpendicular wave modes are seeded with an initial velocity perturbation. We then extend the model to three dimensions, introducing a stabilizing parallel wave vector. Boundary conditions in the parallel direction prohibit motion of the magnetic field line footprints to model the eigenmodes of the magnetodisc's resonant cavity. We again compare growth rates based on perpendicular wave number, but also on the parallel extent of the resonant cavity, which fixes the size of the largest parallel wavelength. Finally, we search for evidence of strong guide field magnetic reconnection within the domain by identifying areas with large parallel electric fields or changes in magnetic field topology.

Three-wave scattering in magnetized plasmas: From cold fluid to quantized Lagrangian

DOE PAGES

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

2017-08-14

Large amplitude waves in magnetized plasmas, generated either by external pumps or internal instabilities, can scatter via three-wave interactions. While three-wave scattering is well known in collimated geometry, what happens when waves propagate at angles with one another in magnetized plasmas remains largely unknown, mainly due to the analytical difficulty of this problem. In this study, we overcome this analytical difficulty and find a convenient formula for three-wave coupling coefficient in cold, uniform, magnetized, and collisionless plasmas in the most general geometry. This is achieved by systematically solving the fluid-Maxwell model to second order using a multiscale perturbative expansion. Themore » general formula for the coupling coefficient becomes transparent when we reformulate it as the scattering matrix element of a quantized Lagrangian. Using the quantized Lagrangian, it is possible to bypass the perturbative solution and directly obtain the nonlinear coupling coefficient from the linear response of the plasma. To illustrate how to evaluate the cold coupling coefficient, we give a set of examples where the participating waves are either quasitransverse or quasilongitudinal. In these examples, we determine the angular dependence of three-wave scattering, and demonstrate that backscattering is not necessarily the strongest scattering channel in magnetized plasmas, in contrast to what happens in unmagnetized plasmas. Finally, our approach gives a more complete picture, beyond the simple collimated geometry, of how injected waves can decay in magnetic confinement devices, as well as how lasers can be scattered in magnetized plasma targets.« less

Three-wave scattering in magnetized plasmas: From cold fluid to quantized Lagrangian.

PubMed

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

2017-08-01

Large amplitude waves in magnetized plasmas, generated either by external pumps or internal instabilities, can scatter via three-wave interactions. While three-wave scattering is well known in collimated geometry, what happens when waves propagate at angles with one another in magnetized plasmas remains largely unknown, mainly due to the analytical difficulty of this problem. In this paper, we overcome this analytical difficulty and find a convenient formula for three-wave coupling coefficient in cold, uniform, magnetized, and collisionless plasmas in the most general geometry. This is achieved by systematically solving the fluid-Maxwell model to second order using a multiscale perturbative expansion. The general formula for the coupling coefficient becomes transparent when we reformulate it as the scattering matrix element of a quantized Lagrangian. Using the quantized Lagrangian, it is possible to bypass the perturbative solution and directly obtain the nonlinear coupling coefficient from the linear response of the plasma. To illustrate how to evaluate the cold coupling coefficient, we give a set of examples where the participating waves are either quasitransverse or quasilongitudinal. In these examples, we determine the angular dependence of three-wave scattering, and demonstrate that backscattering is not necessarily the strongest scattering channel in magnetized plasmas, in contrast to what happens in unmagnetized plasmas. Our approach gives a more complete picture, beyond the simple collimated geometry, of how injected waves can decay in magnetic confinement devices, as well as how lasers can be scattered in magnetized plasma targets.

Three-wave scattering in magnetized plasmas: From cold fluid to quantized Lagrangian

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

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

Large amplitude waves in magnetized plasmas, generated either by external pumps or internal instabilities, can scatter via three-wave interactions. While three-wave scattering is well known in collimated geometry, what happens when waves propagate at angles with one another in magnetized plasmas remains largely unknown, mainly due to the analytical difficulty of this problem. In this study, we overcome this analytical difficulty and find a convenient formula for three-wave coupling coefficient in cold, uniform, magnetized, and collisionless plasmas in the most general geometry. This is achieved by systematically solving the fluid-Maxwell model to second order using a multiscale perturbative expansion. Themore » general formula for the coupling coefficient becomes transparent when we reformulate it as the scattering matrix element of a quantized Lagrangian. Using the quantized Lagrangian, it is possible to bypass the perturbative solution and directly obtain the nonlinear coupling coefficient from the linear response of the plasma. To illustrate how to evaluate the cold coupling coefficient, we give a set of examples where the participating waves are either quasitransverse or quasilongitudinal. In these examples, we determine the angular dependence of three-wave scattering, and demonstrate that backscattering is not necessarily the strongest scattering channel in magnetized plasmas, in contrast to what happens in unmagnetized plasmas. Finally, our approach gives a more complete picture, beyond the simple collimated geometry, of how injected waves can decay in magnetic confinement devices, as well as how lasers can be scattered in magnetized plasma targets.« less

Coronal ``Wave'': Magnetic Footprint of a Coronal Mass Ejection?

NASA Astrophysics Data System (ADS)

Attrill, Gemma D. R.; Harra, Louise K.; van Driel-Gesztelyi, Lidia; Démoulin, Pascal

2007-02-01

We investigate the properties of two ``classical'' EUV Imaging Telescope (EIT) coronal waves. The two source regions of the associated coronal mass ejections (CMEs) possess opposite helicities, and the coronal waves display rotations in opposite senses. We observe deep core dimmings near the flare site and also widespread diffuse dimming, accompanying the expansion of the EIT wave. We also report a new property of these EIT waves, namely, that they display dual brightenings: persistent ones at the outermost edge of the core dimming regions and simultaneously diffuse brightenings constituting the leading edge of the coronal wave, surrounding the expanding diffuse dimmings. We show that such behavior is consistent with a diffuse EIT wave being the magnetic footprint of a CME. We propose a new mechanism where driven magnetic reconnections between the skirt of the expanding CME magnetic field and quiet-Sun magnetic loops generate the observed bright diffuse front. The dual brightenings and the widespread diffuse dimming are identified as innate characteristics of this process.

Gravitational waves from SU( N) glueball dark matter

DOE PAGES

Soni, Amarjit; Zhang, Yue

2017-05-30

Here, a hidden sector with pure non-abelian gauge symmetry is an elegant and just about the simplest model of dark matter. In this model the dark matter candidate is the lightest bound state made of the confined gauge fields, the dark glueball. In spite of its simplicity, the model has been shown to have several interesting non-standard implications in cosmology. In this work, we explore the gravitational waves from binary boson stars made of self-gravitating dark glueball fields as a natural and important consequence. We derive the dark SU(N) star mass and radius as functions of the only two fundamentalmore » parameters in the model, the glueball mass m and the number of colors N, and identify the regions that could be probed by the LIGO and future gravitational wave observatories.« less

Turbulent Heating and Wave Pressure in Solar Wind Acceleration Modeling: New Insights to Empirical Forecasting of the Solar Wind

NASA Astrophysics Data System (ADS)

Woolsey, L. N.; Cranmer, S. R.

2013-12-01

The study of solar wind acceleration has made several important advances recently due to improvements in modeling techniques. Existing code and simulations test the competing theories for coronal heating, which include reconnection/loop-opening (RLO) models and wave/turbulence-driven (WTD) models. In order to compare and contrast the validity of these theories, we need flexible tools that predict the emergent solar wind properties from a wide range of coronal magnetic field structures such as coronal holes, pseudostreamers, and helmet streamers. ZEPHYR (Cranmer et al. 2007) is a one-dimensional magnetohydrodynamics code that includes Alfven wave generation and reflection and the resulting turbulent heating to accelerate solar wind in open flux tubes. We present the ZEPHYR output for a wide range of magnetic field geometries to show the effect of the magnetic field profiles on wind properties. We also investigate the competing acceleration mechanisms found in ZEPHYR to determine the relative importance of increased gas pressure from turbulent heating and the separate pressure source from the Alfven waves. To do so, we developed a code that will become publicly available for solar wind prediction. This code, TEMPEST, provides an outflow solution based on only one input: the magnetic field strength as a function of height above the photosphere. It uses correlations found in ZEPHYR between the magnetic field strength at the source surface and the temperature profile of the outflow solution to compute the wind speed profile based on the increased gas pressure from turbulent heating. With this initial solution, TEMPEST then adds in the Alfven wave pressure term to the modified Parker equation and iterates to find a stable solution for the wind speed. This code, therefore, can make predictions of the wind speeds that will be observed at 1 AU based on extrapolations from magnetogram data, providing a useful tool for empirical forecasting of the sol! ar wind.

Effect of ion-neutral collisions on the evolution of kinetic Alfvén waves in plasmas

NASA Astrophysics Data System (ADS)

Goyal, R.; Sharma, R. P.

2018-03-01

This paper studies the effect of ion-neutral collisions on the propagation of kinetic Alfvén waves (KAWs) in inhomogeneous magnetized plasma. The inhomogeneity in the plasma imposed by background density in a direction transverse as well as parallel to the ambient magnetic field plays a vital role in the localization process. The mass loading of ions takes place due to their collisions with neutral fluid leading to the damping of the KAWs. Numerical analysis of linear KAWs in inhomogeneous magnetized plasma is done for a fixed finite frequency taking into consideration the ion-neutral collisions. There is a prominent effect of collisional damping on the wave localization, wave magnetic field, and frequency spectrum. A semi-analytical technique has been employed to study the magnetic field amplitude decay process and the effect of wave frequency in the range of ion cyclotron frequency on the propagation of waves leading to damping.

KSC-07pd0425

NASA Image and Video Library

2007-02-17

KENNEDY SPACE CENTER, FLA. -- A weather balloon takes flight from the Cape Canaveral Air Force Station weather station. The balloon is equipped with a radiosonde, an instrument that transmits measurements on atmospheric pressure, humidity, temperature and winds as it ascends. The data will be used to determine if conditions are acceptable for the launch of NASA's THEMIS mission. THEMIS, an acronym for Time History of Events and Macroscale Interactions during Substorms, consists of five identical probes that will track violent, colorful eruptions near the North Pole. This will be the largest number of scientific satellites NASA has ever launched into orbit aboard a single rocket. The THEMIS mission aims to unravel the mystery behind auroral substorms, an avalanche of magnetic energy powered by the solar wind that intensifies the northern and southern lights. The mission will investigate what causes auroras in the Earth’s atmosphere to dramatically change from slowly shimmering waves of light to wildly shifting streaks of bright color. Launch is planned from Pad 17-B in a window that extends from 6:01 to 6:19 p.m. EST. Photo credit: NASA/George Shelton

KSC-07pd0427

NASA Image and Video Library

2007-02-17

KENNEDY SPACE CENTER, FLA. -- A worker prepares a weather balloon for release at the Cape Canaveral Air Force Station weather station. The balloon is equipped with a radiosonde, an instrument that transmits measurements on atmospheric pressure, humidity, temperature and winds as it ascends. The data will be used to determine if conditions are acceptable for the launch of NASA's THEMIS mission. THEMIS, an acronym for Time History of Events and Macroscale Interactions during Substorms, consists of five identical probes that will track violent, colorful eruptions near the North Pole. This will be the largest number of scientific satellites NASA has ever launched into orbit aboard a single rocket. The THEMIS mission aims to unravel the mystery behind auroral substorms, an avalanche of magnetic energy powered by the solar wind that intensifies the northern and southern lights. The mission will investigate what causes auroras in the Earth’s atmosphere to dramatically change from slowly shimmering waves of light to wildly shifting streaks of bright color. Launch is planned from Pad 17-B in a window that extends from 6:01 to 6:19 p.m. EST. Photo credit: NASA/Kim Shiflett

KSC-07pd0426

NASA Image and Video Library

2007-02-17

KENNEDY SPACE CENTER, FLA. -- A worker prepares a weather balloon for release at the Cape Canaveral Air Force Station weather station. The balloon is equipped with a radiosonde, an instrument that transmits measurements on atmospheric pressure, humidity, temperature and winds as it ascends. The data will be used to determine if conditions are acceptable for the launch of NASA's THEMIS mission. THEMIS, an acronym for Time History of Events and Macroscale Interactions during Substorms, consists of five identical probes that will track violent, colorful eruptions near the North Pole. This will be the largest number of scientific satellites NASA has ever launched into orbit aboard a single rocket. The THEMIS mission aims to unravel the mystery behind auroral substorms, an avalanche of magnetic energy powered by the solar wind that intensifies the northern and southern lights. The mission will investigate what causes auroras in the Earth’s atmosphere to dramatically change from slowly shimmering waves of light to wildly shifting streaks of bright color. Launch is planned from Pad 17-B in a window that extends from 6:01 to 6:19 p.m. EST. Photo credit: NASA/Kim Shiflett

KSC-07pd0428

NASA Image and Video Library

2007-02-17

KENNEDY SPACE CENTER, FLA. -- A worker prepares to release a weather balloon outside the Cape Canaveral Air Force Station weather station. The balloon is equipped with a radiosonde, an instrument that transmits measurements on atmospheric pressure, humidity, temperature and winds as it ascends. The data will be used to determine if conditions are acceptable for the launch of NASA's THEMIS mission. THEMIS, an acronym for Time History of Events and Macroscale Interactions during Substorms, consists of five identical probes that will track violent, colorful eruptions near the North Pole. This will be the largest number of scientific satellites NASA has ever launched into orbit aboard a single rocket. The THEMIS mission aims to unravel the mystery behind auroral substorms, an avalanche of magnetic energy powered by the solar wind that intensifies the northern and southern lights. The mission will investigate what causes auroras in the Earth’s atmosphere to dramatically change from slowly shimmering waves of light to wildly shifting streaks of bright color. Launch is planned from Pad 17-B in a window that extends from 6:01 to 6:19 p.m. EST. Photo credit: NASA/Kim Shiflett

KSC-07pd0421

NASA Image and Video Library

2007-02-17

KENNEDY SPACE CENTER, FLA. -- A weather balloon is prepared for release at the Cape Canaveral Air Force Station weather station. The balloon is equipped with a radiosonde, an instrument that transmits measurements on atmospheric pressure, humidity, temperature and winds as it ascends. The data will be used to determine if conditions are acceptable for the launch of NASA's THEMIS mission. THEMIS, an acronym for Time History of Events and Macroscale Interactions during Substorms, consists of five identical probes that will track violent, colorful eruptions near the North Pole. This will be the largest number of scientific satellites NASA has ever launched into orbit aboard a single rocket. The THEMIS mission aims to unravel the mystery behind auroral substorms, an avalanche of magnetic energy powered by the solar wind that intensifies the northern and southern lights. The mission will investigate what causes auroras in the Earth’s atmosphere to dramatically change from slowly shimmering waves of light to wildly shifting streaks of bright color. Launch is planned from Pad 17-B in a window that extends from 6:01 to 6:19 p.m. EST. Photo credit: NASA/George Shelton

KSC-07pd0424

NASA Image and Video Library

2007-02-17

KENNEDY SPACE CENTER, FLA. -- A worker releases a weather balloon at the Cape Canaveral Air Force Station weather station. The balloon is equipped with a radiosonde, an instrument that transmits measurements on atmospheric pressure, humidity, temperature and winds as it ascends. The data will be used to determine if conditions are acceptable for the launch of NASA's THEMIS mission. THEMIS, an acronym for Time History of Events and Macroscale Interactions during Substorms, consists of five identical probes that will track violent, colorful eruptions near the North Pole. This will be the largest number of scientific satellites NASA has ever launched into orbit aboard a single rocket. The THEMIS mission aims to unravel the mystery behind auroral substorms, an avalanche of magnetic energy powered by the solar wind that intensifies the northern and southern lights. The mission will investigate what causes auroras in the Earth’s atmosphere to dramatically change from slowly shimmering waves of light to wildly shifting streaks of bright color. Launch is planned from Pad 17-B in a window that extends from 6:01 to 6:19 p.m. EST. Photo credit: NASA/George Shelton

KSC-07pd0422

NASA Image and Video Library

2007-02-17

KENNEDY SPACE CENTER, FLA. -- A radiosonde, an instrument that transmits measurements on atmospheric pressure, humidity, temperature and winds, is prepared for use on a weather balloon at the Cape Canaveral Air Force Station weather station. The data it returns will be used to determine if conditions are acceptable for the launch of NASA's THEMIS mission. THEMIS, an acronym for Time History of Events and Macroscale Interactions during Substorms, consists of five identical probes that will track violent, colorful eruptions near the North Pole. This will be the largest number of scientific satellites NASA has ever launched into orbit aboard a single rocket. The THEMIS mission aims to unravel the mystery behind auroral substorms, an avalanche of magnetic energy powered by the solar wind that intensifies the northern and southern lights. The mission will investigate what causes auroras in the Earth’s atmosphere to dramatically change from slowly shimmering waves of light to wildly shifting streaks of bright color. Launch is planned from Pad 17-B in a window that extends from 6:01 to 6:19 p.m. EST. Photo credit: NASA/George Shelton

KSC-07pd0429

NASA Image and Video Library

2007-02-17

KENNEDY SPACE CENTER, FLA. -- Two weather balloons take flight from the Cape Canaveral Air Force Station weather station. Each balloon is equipped with a radiosonde, an instrument that transmits measurements on atmospheric pressure, humidity, temperature and winds as it ascends. The data will be used to determine if conditions are acceptable for the launch of NASA's THEMIS mission. THEMIS, an acronym for Time History of Events and Macroscale Interactions during Substorms, consists of five identical probes that will track violent, colorful eruptions near the North Pole. This will be the largest number of scientific satellites NASA has ever launched into orbit aboard a single rocket. The THEMIS mission aims to unravel the mystery behind auroral substorms, an avalanche of magnetic energy powered by the solar wind that intensifies the northern and southern lights. The mission will investigate what causes auroras in the Earth’s atmosphere to dramatically change from slowly shimmering waves of light to wildly shifting streaks of bright color. Launch is planned from Pad 17-B in a window that extends from 6:01 to 6:19 p.m. EST. Photo credit: NASA/Kim Shiflett

Launching a Weather Balloon to check conditions for the THEMIS L

NASA Image and Video Library

2002-01-01

A worker releases a weather balloon at the Cape Canaveral Air Force Station weather station. The balloon is equipped with a radiosonde, an instrument that transmits measurements on atmospheric pressure, humidity, temperature and winds as it ascends. The data will be used to determine if conditions are acceptable for the launch of NASA's THEMIS mission. THEMIS, an acronym for Time History of Events and Macroscale Interactions during Substorms, consists of five identical probes that will track violent, colorful eruptions near the North Pole. This will be the largest number of scientific satellites NASA has ever launched into orbit aboard a single rocket. The THEMIS mission aims to unravel the mystery behind auroral substorms, an avalanche of magnetic energy powered by the solar wind that intensifies the northern and southern lights. The mission will investigate what causes auroras in the Earth’s atmosphere to dramatically change from slowly shimmering waves of light to wildly shifting streaks of bright color. Launch is planned from Pad 17-B in a window that extends from 6:01 to 6:19 p.m. EST.

Launching a Weather Balloon to check conditions for the THEMIS L

NASA Image and Video Library

2002-01-01

A radiosonde, an instrument that transmits measurements on atmospheric pressure, humidity, temperature and winds, is prepared for use on a weather balloon at the Cape Canaveral Air Force Station weather station. The data it returns will be used to determine if conditions are acceptable for the launch of NASA's THEMIS mission. THEMIS, an acronym for Time History of Events and Macroscale Interactions during Substorms, consists of five identical probes that will track violent, colorful eruptions near the North Pole. This will be the largest number of scientific satellites NASA has ever launched into orbit aboard a single rocket. The THEMIS mission aims to unravel the mystery behind auroral substorms, an avalanche of magnetic energy powered by the solar wind that intensifies the northern and southern lights. The mission will investigate what causes auroras in the Earth’s atmosphere to dramatically change from slowly shimmering waves of light to wildly shifting streaks of bright color. Launch is planned from Pad 17-B in a window that extends from 6:01 to 6:19 p.m. EST.

Launching a Weather Balloon to check conditions for the THEMIS L

NASA Image and Video Library

2002-01-01

A weather balloon takes flight from the Cape Canaveral Air Force Station weather station. The balloon is equipped with a radiosonde, an instrument that transmits measurements on atmospheric pressure, humidity, temperature and winds as it ascends. The data will be used to determine if conditions are acceptable for the launch of NASA's THEMIS mission. THEMIS, an acronym for Time History of Events and Macroscale Interactions during Substorms, consists of five identical probes that will track violent, colorful eruptions near the North Pole. This will be the largest number of scientific satellites NASA has ever launched into orbit aboard a single rocket. The THEMIS mission aims to unravel the mystery behind auroral substorms, an avalanche of magnetic energy powered by the solar wind that intensifies the northern and southern lights. The mission will investigate what causes auroras in the Earth’s atmosphere to dramatically change from slowly shimmering waves of light to wildly shifting streaks of bright color. Launch is planned from Pad 17-B in a window that extends from 6:01 to 6:19 p.m. EST.

Launching a Weather Balloon to check conditions for the THEMIS L

NASA Image and Video Library

2002-01-01

A weather balloon is prepared for release at the Cape Canaveral Air Force Station weather station. The balloon is equipped with a radiosonde, an instrument that transmits measurements on atmospheric pressure, humidity, temperature and winds as it ascends. The data will be used to determine if conditions are acceptable for the launch of NASA's THEMIS mission. THEMIS, an acronym for Time History of Events and Macroscale Interactions during Substorms, consists of five identical probes that will track violent, colorful eruptions near the North Pole. This will be the largest number of scientific satellites NASA has ever launched into orbit aboard a single rocket. The THEMIS mission aims to unravel the mystery behind auroral substorms, an avalanche of magnetic energy powered by the solar wind that intensifies the northern and southern lights. The mission will investigate what causes auroras in the Earth’s atmosphere to dramatically change from slowly shimmering waves of light to wildly shifting streaks of bright color. Launch is planned from Pad 17-B in a window that extends from 6:01 to 6:19 p.m. EST.

Spin wave interference in YIG cross junction

DOE PAGES

Balinskiy, M.; Gutierrez, D.; Chiang, H.; ...

2017-01-17

This work is aimed at studying the interference between backward volume magnetostatic spin waves and magnetostatic surface spin waves in a magnetic cross junction. These two types of magnetostatic waves possess different dispersion with zero frequency overlap in infinite magnetic films. However, the interference may be observed in finite structures due to the effect magnetic shape anisotropy. We report experimental data on spin wave interference in a micrometer size Y 3Fe 2(FeO 4) 3 cross junction. There are four micro antennas fabricated at the edges of the cross arms. Two of these antennas located on the orthogonal arms are usedmore » for spin wave generation, and the other two antennas are used for the inductive voltage detection. The phase difference between the input signals is controlled by the phase shifter. Prominent spin wave interference is observed at the selected combination of operational frequency and bias magnetic field. The maximum On/Off ratio exceeds 30dB at room temperature. The obtained results are important for a variety of magnetic devices based on spin wave interference.« less

Halbach array-based design and simulation of disc coreless permanen-magnet integrated starter generator

NASA Astrophysics Data System (ADS)

Li, Y. B.; Yang, Z. X.; Chen, W.; He, Q. Y.

2017-11-01

The functional performance, such as magnetic flux leakage, power density and efficiency, is related to the structural characteristics and design technique for the disc permanent magnet synchronous generators (PMSGs). Halbach array theory-based magnetic circuit structure is developed, and Maxwell3D simulation analysis approach of PMSG is proposed in this paper for integrated starter generator (ISG). The magnetization direction of adjacent permanent magnet is organized in difference of 45 degrees for focusing air gap side, and improving the performance of the generator. The magnetic field distribution and functional performance in load and/or unload conditions are simulated by Maxwell3D module. The proposed approach is verified by simulation analysis, the air gap flux density is 0.66T, and the phase voltage curve has the characteristics of a preferable sinusoidal wave and the voltage amplitude 335V can meet the design requirements while the disc coreless PMSG is operating at rated speed. And the developed magnetic circuit structure can be used for engineering design of the disc coreless PMSG to the integrated starter generator.

Equivalent magnetic vector potential model for low-frequency magnetic exposure assessment

NASA Astrophysics Data System (ADS)

Diao, Y. L.; Sun, W. N.; He, Y. Q.; Leung, S. W.; Siu, Y. M.

2017-10-01

In this paper, a novel source model based on a magnetic vector potential for the assessment of induced electric field strength in a human body exposed to the low-frequency (LF) magnetic field of an electrical appliance is presented. The construction of the vector potential model requires only a single-component magnetic field to be measured close to the appliance under test, hence relieving considerable practical measurement effort—the radial basis functions (RBFs) are adopted for the interpolation of discrete measurements; the magnetic vector potential model can then be directly constructed by summing a set of simple algebraic functions of RBF parameters. The vector potentials are then incorporated into numerical calculations as the equivalent source for evaluations of the induced electric field in the human body model. The accuracy and effectiveness of the proposed model are demonstrated by comparing the induced electric field in a human model to that of the full-wave simulation. This study presents a simple and effective approach for modelling the LF magnetic source. The result of this study could simplify the compliance test procedure for assessing an electrical appliance regarding LF magnetic exposure.

Equivalent magnetic vector potential model for low-frequency magnetic exposure assessment.

PubMed

Diao, Y L; Sun, W N; He, Y Q; Leung, S W; Siu, Y M

2017-09-21

In this paper, a novel source model based on a magnetic vector potential for the assessment of induced electric field strength in a human body exposed to the low-frequency (LF) magnetic field of an electrical appliance is presented. The construction of the vector potential model requires only a single-component magnetic field to be measured close to the appliance under test, hence relieving considerable practical measurement effort-the radial basis functions (RBFs) are adopted for the interpolation of discrete measurements; the magnetic vector potential model can then be directly constructed by summing a set of simple algebraic functions of RBF parameters. The vector potentials are then incorporated into numerical calculations as the equivalent source for evaluations of the induced electric field in the human body model. The accuracy and effectiveness of the proposed model are demonstrated by comparing the induced electric field in a human model to that of the full-wave simulation. This study presents a simple and effective approach for modelling the LF magnetic source. The result of this study could simplify the compliance test procedure for assessing an electrical appliance regarding LF magnetic exposure.

Theory of wave propagation in magnetized near-zero-epsilon metamaterials: evidence for one-way photonic states and magnetically switched transparency and opacity.

PubMed

Davoyan, Arthur R; Engheta, Nader

2013-12-20

We study propagation of transverse-magnetic electromagnetic waves in the bulk and at the surface of a magnetized epsilon-near-zero (ENZ) medium in a Voigt configuration. We reveal that in a certain range of material parameters novel regimes of wave propagation emerge; we show that the transparency of the medium can be altered with the magnetization leading either to magnetically induced Hall opacity or Hall transparency of the ENZ. In our theoretical study, we demonstrate that surface waves at the interface between either a transparent or an opaque Hall medium and a homogeneous medium may, under certain conditions, be predominantly one way. Moreover, we predict that one-way photonic surface states may exist at the interface of an opaque Hall ENZ and a regular metal, giving rise to the possibility for backscattering immune wave propagation and isolation.

Wave propagation downstream of a high power helicon in a dipolelike magnetic field

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

Prager, James; Winglee, Robert; Roberson, B. Race

2010-01-15

The wave propagating downstream of a high power helicon source in a diverging magnetic field was investigated experimentally. The magnetic field of the wave has been measured both axially and radially. The three-dimensional structure of the propagating wave is observed and its wavelength and phase velocity are determined. The measurements are compared to predictions from helicon theory and that of a freely propagating whistler wave. The implications of this work on the helicon as a thruster are also discussed.

All-Dielectric Colored Metasurfaces with Silicon Mie Resonators.

PubMed

Proust, Julien; Bedu, Frédéric; Gallas, Bruno; Ozerov, Igor; Bonod, Nicolas

2016-08-23

The photonic resonances hosted by nanostructures provide vivid colors that can be used as color filters instead of organic colors and pigments in photodetectors and printing technology. Metallic nanostructures have been widely studied due to their ability to sustain surface plasmons that resonantly interact with light. Most of the metallic nanoparticles behave as point-like electric multipoles. However, the needs of an another degree of freedom to tune the color of the photonic nanostructure together with the use of a reliable and cost-effective material are growing. Here, we report a technique to imprint colored images based on silicon nanoparticles that host low-order electric and magnetic Mie resonances. The interplay between the electric and magnetic resonances leads to a large palette of colors. This all-dielectric fabrication technique offers the advantage to use cost-effective, reliable, and sustainable materials to provide vivid color spanning the whole visible spectrum. The interest and potential of this all-dielectric printing technique are highlighted by reproducing at a micrometer scale a Mondrian painting.

Heating and acceleration of solar wind ions by turbulent wave spectrum in inhomogeneous expanding plasma

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

Ofman, Leon, E-mail: Leon.Ofman@nasa.gov; NASA Goddard Space Flight Center, Greenbelt, MD; Visiting, Department of Geosciences, Tel Aviv University, Tel Aviv

Near the Sun (< 10R{sub s}) the acceleration, heating, and propagation of the solar wind are likely affected by the background inhomogeneities of the magnetized plasma. The heating and the acceleration of the solar wind ions by turbulent wave spectrum in inhomogeneous plasma is studied using a 2.5D hybrid model. The hybrid model describes the kinetics of the ions, while the electrons are modeled as massless neutralizing fluid in an expanding box approach. Turbulent magnetic fluctuations dominated by power-law frequency spectra, which are evident from in-situ as well as remote sensing measurements, are used in our models. The effects ofmore » background density inhomogeneity across the magnetic field on the resonant ion heating are studied. The effect of super-Alfvénic ion drift on the ion heating is investigated. It is found that the turbulent wave spectrum of initially parallel propagating waves cascades to oblique modes, and leads to enhanced resonant ion heating due to the inhomogeneity. The acceleration of the solar wind ions is achieved by the parametric instability of large amplitude waves in the spectrum, and is also affected by the inhomogeneity. The results of the study provide the ion temperature anisotropy and drift velocity temporal evolution due to relaxation of the instability. The non-Maxwellian velocity distribution functions (VDFs) of the ions are modeled in the inhomogeneous solar wind plasma in the acceleration region close to the Sun.« less

Invited article: Broadband highly-efficient dielectric metadevices for polarization control

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

Kruk, Sergey; Hopkins, Ben; Kravchenko, Ivan I.

Metadevices based on dielectric nanostructured surfaces with both electric and magnetic Mie-type resonances have resulted in the best efficiency to date for functional flat optics with only one disadvantage: a narrow operational bandwidth. Here we experimentally demonstrate broadband transparent all-dielectric metasurfaces for highly efficient polarization manipulation. We utilize the generalized Huygens principle, with a superposition of the scattering contributions from several electric and magnetic multipolar modes of the constituent meta-atoms, to achieve destructive interference in reflection over a large spectral bandwidth. Furthermore, by employing this novel concept, we demonstrate reflectionless (~90% transmission) half-wave plates, quarter-wave plates, and vector beam q-platesmore » that can operate across multiple telecom bands with ~99% polarization conversion efficiency.« less

Invited article: Broadband highly-efficient dielectric metadevices for polarization control

DOE PAGES

Kruk, Sergey; Hopkins, Ben; Kravchenko, Ivan I.; ...

2016-06-06

Metadevices based on dielectric nanostructured surfaces with both electric and magnetic Mie-type resonances have resulted in the best efficiency to date for functional flat optics with only one disadvantage: a narrow operational bandwidth. Here we experimentally demonstrate broadband transparent all-dielectric metasurfaces for highly efficient polarization manipulation. We utilize the generalized Huygens principle, with a superposition of the scattering contributions from several electric and magnetic multipolar modes of the constituent meta-atoms, to achieve destructive interference in reflection over a large spectral bandwidth. Furthermore, by employing this novel concept, we demonstrate reflectionless (~90% transmission) half-wave plates, quarter-wave plates, and vector beam q-platesmore » that can operate across multiple telecom bands with ~99% polarization conversion efficiency.« less

Stable heavy pentaquarks in constituent models

NASA Astrophysics Data System (ADS)

Richard, J.-M.; Valcarce, A.; Vijande, J.

2017-11-01

It is shown that standard constituent quark models produce (c bar cqqq) hidden-charm pentaquarks, where c denotes the charmed quark and q a light quark, which lie below the lowest threshold for spontaneous dissociation and thus are stable in the limit where the internal c bar c annihilation is neglected. The binding is a cooperative effect of the chromoelectric and chromomagnetic components of the interaction, and it disappears in the static limit with a pure chromoelectric potential. Their wave function contains color sextet and color octet configurations for the subsystems and can hardly be reduced to a molecular state made of two interacting hadrons. These pentaquark states could be searched for in the experiments having discovered or confirmed the hidden-charm meson and baryon resonances.

Metachronal wave of artificial cilia array actuated by applied magnetic field

NASA Astrophysics Data System (ADS)

Tsumori, Fujio; Marume, Ryuma; Saijou, Akinori; Kudo, Kentaro; Osada, Toshiko; Miura, Hideshi

2016-06-01

In this paper, a biomimetic microstructure related to cilia, which are effective fluidic and conveying systems in nature, is described. Authors have already reported that a magnetic elastomer pillar actuated by a rotating magnetic field can work like a natural cilium. In the present work, we show examples of a cilia array with a metachronal wave as the next step. A metachronal wave is a sequential action of a number of cilia. It is theoretically known that a metachronal wave gives a higher fluidic efficiency; however, there has been no report on a metachronal wave by artificial cilia. We prepared magnetic elastomer pillars that contain chainlike clusters of magnetic particles. The orientation of chains was set to be different in each pillar so that each pillar will deform with a different phase.

High-frequency plasma-heating apparatus

DOEpatents

Brambilla, Marco; Lallia, Pascal

1978-01-01

An array of adjacent wave guides feed high-frequency energy into a vacuum chamber in which a toroidal plasma is confined by a magnetic field, the wave guide array being located between two toroidal current windings. Waves are excited in the wave guide at a frequency substantially equal to the lower frequency hybrid wave of the plasma and a substantially equal phase shift is provided from one guide to the next between the waves therein. For plasmas of low peripheral density gradient, the guides are excited in the TE.sub.01 mode and the output electric field is parallel to the direction of the toroidal magnetic field. For exciting waves in plasmas of high peripheral density gradient, the guides are excited in the TM.sub.01 mode and the magnetic field at the wave guide outlets is parallel to the direction of the toroidal magnetic field. The wave excited at the outlet of the wave guide array is a progressive wave propagating in the direction opposite to that of the toroidal current and is, therefore, not absorbed by so-called "runaway" electrons.

Color-suppression of non-planar diagrams in bosonic bound states

NASA Astrophysics Data System (ADS)

Alvarenga Nogueira, J. H.; Ji, Chueng-Ryong; Ydrefors, E.; Frederico, T.

2018-02-01

We study the suppression of non-planar diagrams in a scalar QCD model of a meson system in 3 + 1 space-time dimensions due to the inclusion of the color degrees of freedom. As a prototype of the color-singlet meson, we consider a flavor-nonsinglet system consisting of a scalar-quark and a scalar-antiquark with equal masses exchanging a scalar-gluon of a different mass, which is investigated within the framework of the homogeneous Bethe-Salpeter equation. The equation is solved by using the Nakanishi representation for the manifestly covariant bound-state amplitude and its light-front projection. The resulting non-singular integral equation is solved numerically. The damping of the impact of the cross-ladder kernel on the binding energies are studied in detail. The color-suppression of the cross-ladder effects on the light-front wave function and the elastic electromagnetic form factor are also discussed. As our results show, the suppression appears significantly large for Nc = 3, which supports the use of rainbow-ladder truncations in practical non-perturbative calculations within QCD.

Influence of nitrogen on magnetic properties of indium oxide

NASA Astrophysics Data System (ADS)

Ashok, Vishal Dev; De, S. K.

2013-07-01

Magnetic properties of indium oxide (In2O3) prepared by the decomposition of indium nitrate/indium hydroxide in the presence of ammonium chloride (NH4Cl) has been investigated. Structural and optical characterizations confirm that nitrogen is incorporated into In2O3. Magnetization has been convoluted to individual diamagnetic paramagnetic and ferromagnetic contributions with varying concentration of NH4Cl. Spin wave with diverging thermal exponent dominates in both field cool and zero field cool magnetizations. Uniaxial anisotropy plays an important role in magnetization as a function of magnetic field at higher concentration of NH4Cl. Avrami analysis indicates the absence of pinning effect in the magnetization process. Ferromagnetism has been interpreted in terms of local moments induced by anion dopant and strong hybridization with host cation.

Gigantic transverse x-ray magnetic circular dichroism in ultrathin Co in Au/Co/Au(001)

NASA Astrophysics Data System (ADS)

Koide, T.; Mamiya, K.; Asakura, D.; Osatune, Y.; Fujimori, A.; Suzuki, Y.; Katayama, T.; Yuasa, S.

2014-04-01

Transverse-geometry x-ray magnetic circular dichroism (TXMCD) measurements on Au/Co-staircase/Au(001) reveal the orbital origin of intrinsic in-plane magnetic anisotropy A gigantic TXMCD was successfully observed at the Co L3,2 edges for Co thickness (tC0) in the 2-monolayer regime. A TXMCD-sum-rule analysis shows a remarkable enhancement of an orbital-moment anisotropy (Δmorb) and of an in-plane magnetic dipole moment (m||T). Both Δmorb and m||T exhibit close similarity in tCo dependence, reflecting the in-plane magnetic anisotropy These observations evidence that extremely strong, intrinsic, in-plane magnetic anisotropy originates from the anisotropic orbital part of the wave function, dominating the dipole-dipole-interaction-derived, extrinsic, in-plane magnetic anisotropy.

Kinetic-scale fluctuations resolved with the Fast Plasma Investigation on NASA's Magnetospheric Multiscale mission.

NASA Astrophysics Data System (ADS)

Gershman, D. J.; Figueroa-Vinas, A.; Dorelli, J.; Goldstein, M. L.; Shuster, J. R.; Avanov, L. A.; Boardsen, S. A.; Stawarz, J. E.; Schwartz, S. J.; Schiff, C.; Lavraud, B.; Saito, Y.; Paterson, W. R.; Giles, B. L.; Pollock, C. J.; Strangeway, R. J.; Russell, C. T.; Torbert, R. B.; Moore, T. E.; Burch, J. L.

2017-12-01

Measurements from the Fast Plasma Investigation (FPI) on NASA's Magnetospheric Multiscale (MMS) mission have enabled unprecedented analyses of kinetic-scale plasma physics. FPI regularly provides estimates of current density and pressure gradients of sufficient accuracy to evaluate the relative contribution of terms in plasma equations of motion. In addition, high-resolution three-dimensional velocity distribution functions of both ions and electrons provide new insights into kinetic-scale processes. As an example, for a monochromatic kinetic Alfven wave (KAW) we find non-zero, but out-of-phase parallel current density and electric field fluctuations, providing direct confirmation of the conservative energy exchange between the wave field and particles. In addition, we use fluctuations in current density and magnetic field to calculate the perpendicular and parallel wavelengths of the KAW. Furthermore, examination of the electron velocity distribution inside the KAW reveals a population of electrons non-linearly trapped in the kinetic-scale magnetic mirror formed between successive wave peaks. These electrons not only contribute to the wave's parallel electric field but also account for over half of the density fluctuations within the wave, supplying an unexpected mechanism for maintaining quasi-neutrality in a KAW. Finally, we demonstrate that the employed wave vector determination technique is also applicable to broadband fluctuations found in Earth's turbulent magnetosheath.

Observation of helicon wave with m = 0 antenna in a weakly magnetized inductively coupled plasma source

NASA Astrophysics Data System (ADS)

Ellingboe, Bert; Sirse, Nishant; Moloney, Rachel; McCarthy, John

2015-09-01

Bounded whistler wave, called ``helicon wave,'' is known to produce high-density plasmas and has been exploited as a high density plasma source for many applications, including electric propulsion for spacecraft. In a helicon plasma source, an antenna wrapped around the magnetized plasma column launches a low frequency wave, ωce/2 >ωhelicon >ωce/100, in the plasma which is responsible for maintaining high density plasma. Several antenna designs have been proposed in order to match efficiently the wave modes. In our experiment, helicon wave mode is observed using an m = 0 antenna. A floating B dot probe, compensated to the capacitively coupled E field, is employed to measure axial-wave-field-profiles (z, r, and θ components) in the plasma at multiple radial positions as a function of rf power and pressure. The Bθ component of the rf-field is observed to be unaffected as the wave propagates in the axial direction. Power coupling between the antenna and the plasma column is identified and agrees with the E, H, and wave coupling regimes previously seen in M =1 antenna systems. That is, the Bz component of the rf-field is observed at low plasma density as the Bz component from the antenna penetrates the plasma. The Bz component becomes very small at medium density due to shielding at the centre of the plasma column; however, with increasing density, a sudden ``jump'' occurs in the Bz component above which a standing wave under the antenna with a propagating wave away from the antenna are observed.

Imaging of single magnetic dopants in III-V semiconductor hosts

NASA Astrophysics Data System (ADS)

Koenraad, Paul; Celebi, Cem; Silov, Andrei; Yakunin, Andrei; Tang, Jian-Ming; Flatte, Michael; Kaminska, Maria

2007-03-01

We present room-temperature cross-sectional scanning tunneling microscopy (STM) topographic measurements of the acceptor state wave function for Mn dopants in InP and compare with measurements for the nonmagnetic dopants Zn and Cd as well as with previous results for Mn in GaAs[1]. We find a strongly anisotropic ``bow-tie'' shape for the Mn acceptor state wave function in InP, similar to Mn in GaAs, which has a binding energy of 210 meV (compared to 113 meV for Mn in GaAs). The shape for Mn in InP is more symmetric with respect to the 001 plane than Mn in GaAs, which agrees with a general trend for the magnetic and nonmagnetic acceptor state symmetry as a function of acceptor binding energy. We present a new theoretical model based on the surface strain of GaAs (110) that explains why the 001-plane asymmetry of acceptor states seen in STM measurements is much larger than expected from bulk calculations. [1] A. M. Yakunin, et al., Phys. Rev. Lett. 92, 216806 (2004).

Survey of Coherent Approximately 1 Hz Waves in Mercury's Inner Magnetosphere from MESSENGER Observations

NASA Technical Reports Server (NTRS)

Boardsen, Scott A.; Slavin, James A.; Anderson, Brian J.; Korth, Haje; Schriver, David; Solomon, Sean C.

2012-01-01

We summarize observations by the MESSENGER spacecraft of highly coherent waves at frequencies between 0.4 and 5 Hz in Mercury's inner magnetosphere. This survey covers the time period from 24 March to 25 September 2011, or 2.1 Mercury years. These waves typically exhibit banded harmonic structure that drifts in frequency as the spacecraft traverses the magnetic equator. The waves are seen at all magnetic local times, but their observed rate of occurrence is much less on the dayside, at least in part the result of MESSENGER's orbit. On the nightside, on average, wave power is maximum near the equator and decreases with increasing magnetic latitude, consistent with an equatorial source. When the spacecraft traverses the plasma sheet during its equatorial crossings, wave power is a factor of 2 larger than for equatorial crossings that do not cross the plasma sheet. The waves are highly transverse at large magnetic latitudes but are more compressional near the equator. However, at the equator the transverse component of these waves increases relative to the compressional component as the degree of polarization decreases. Also, there is a substantial minority of events that are transverse at all magnetic latitudes, including the equator. A few of these latter events could be interpreted as ion cyclotron waves. In general, the waves tend to be strongly linear and characterized by values of the ellipticity less than 0.3 and wave-normal angles peaked near 90 deg. Their maxima in wave power at the equator coupled with their narrow-band character suggests that these waves might be generated locally in loss cone plasma characterized by high values of the ratio beta of plasma pressure to magnetic pressure. Presumably both electromagnetic ion cyclotron waves and electromagnetic ion Bernstein waves can be generated by ion loss cone distributions. If proton beta decreases with increasing magnetic latitude along a field line, then electromagnetic ion Bernstein waves are predicted to transition from compressional to transverse, a pattern consistent with our observations. We hypothesize that these local instabilities can lead to enhanced ion precipitation and directly feed field-line resonances.

Diagnostic performance of qualitative shear-wave elastography according to different color map opacities for breast masses.

PubMed

Kim, Hana; Youk, Ji Hyun; Gweon, Hye Mi; Kim, Jeong-Ah; Son, Eun Ju

2013-08-01

To compare the diagnostic performance of qualitative shear-wave elastography (SWE) according to three different color map opacities for breast masses 101 patients aged 21-77 years with 113 breast masses underwent B-mode US and SWE under three different color map opacities (50%, 19% and 100%) before biopsy or surgery. Following SWE features were reviewed: visual pattern classification (pattern 1-4), color homogeneity (Ehomo) and six-point color score of maximum elasticity (Ecol). Combined with B-mode US and SWE, the likelihood of malignancy (LOM) was also scored. The area under the curve (AUC) was obtained by ROC curve analysis to assess the diagnostic performance under each color opacity. A visual color pattern, Ehomo, Ecol and LOM scoring were significantly different between benign and malignant lesions under all color opacities (P<0.001). For 50% opacity, AUCs of visual color pattern, Ecol, Ehomo and LOM scoring were 0.902, 0.951, 0.835 and 0.975. But, for each SWE feature, there was no significant difference in the AUC among three different color opacities. For all color opacities, visual color pattern and Ecol showed significantly higher AUC than Ehomo. In addition, a combined set of B-mode US and SWE showed significantly higher AUC than SWE alone for color patterns, Ehomo, but no significant difference was found in Ecol. Qualitative SWE was useful to differentiate benign from malignant breast lesion under all color opacities. The difference in color map opacity did not significantly influence diagnostic performance of SWE. Copyright © 2013 Elsevier Ireland Ltd. All rights reserved.

APPARENT CROSS-FIELD SUPERSLOW PROPAGATION OF MAGNETOHYDRODYNAMIC WAVES IN SOLAR PLASMAS

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

Kaneko, T.; Yokoyama, T.; Goossens, M.

2015-10-20

In this paper we show that the phase-mixing of continuum Alfvén waves and/or continuum slow waves in the magnetic structures of the solar atmosphere as, e.g., coronal arcades, can create the illusion of wave propagation across the magnetic field. This phenomenon could be erroneously interpreted as fast magnetosonic waves. The cross-field propagation due to the phase-mixing of continuum waves is apparent because there is no real propagation of energy across the magnetic surfaces. We investigate the continuous Alfvén and slow spectra in two-dimensional (2D) Cartesian equilibrium models with a purely poloidal magnetic field. We show that apparent superslow propagation acrossmore » the magnetic surfaces in solar coronal structures is a consequence of the existence of continuum Alfvén waves and continuum slow waves that naturally live on those structures and phase-mix as time evolves. The apparent cross-field phase velocity is related to the spatial variation of the local Alfvén/slow frequency across the magnetic surfaces and is slower than the Alfvén/sound velocities for typical coronal conditions. Understanding the nature of the apparent cross-field propagation is important for the correct analysis of numerical simulations and the correct interpretation of observations.« less

Drift-Alfven wave mediated particle transport in an elongated density depression

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

Vincena, Stephen; Gekelman, Walter

Cross-field particle transport due to drift-Alfven waves is measured in an elongated density depression within an otherwise uniform, magnetized helium plasma column. The depression is formed by drawing an electron current to a biased copper plate with cross-field dimensions of 28x0.24 ion sound-gyroradii {rho}{sub s}=c{sub s}/{omega}{sub ci}. The process of density depletion and replenishment via particle flux repeats in a quasiperiodic fashion for the duration of the current collection. The mode structure of the wave density fluctuations in the plane perpendicular to the background magnetic field is revealed using a two-probe correlation technique. The particle flux as a function ofmore » frequency is measured using a linear array of Langmuir probes and the only significant transport occurs for waves with frequencies between 15%-25% of the ion cyclotron frequency (measured in the laboratory frame) and with perpendicular wavelengths k{sub perpendicular}{rho}{sub s}{approx}0.7. The frequency-integrated particle flux is in rough agreement with observed increases in density in the center of the depletion as a function of time. The experiments are carried out in the Large Plasma Device (LAPD) [Gekelman et al., Rev. Sci. Instrum. 62, 2875 (1991)] at the Basic Plasma Science Facility located at the University of California, Los Angeles.« less

Visualizing Nanocatalysts in Action from Color Change Reaction to Magnetic Recycling and Reuse

ERIC Educational Resources Information Center

Hudson, Reuben; Bishop, Alexandra; Glaisher, Samuel; Katz, Jeffrey L.

2015-01-01

A demonstration to highlight the utility and ease of handling environmentally benign magnetically recoverable nanoparticle catalysts is described. The demonstration offers two powerful visuals. The first is a color change oxidation of tetramethylbenzidine by hydrogen peroxide catalyzed by Fe[subscript 3]O[subscript 4] nanoparticles. The second,…

Structure of kinetic Alfvén waves with small transverse scale length

NASA Astrophysics Data System (ADS)

Morales, G. J.; Maggs, J. E.

1997-11-01

This analytical study illustrates the spatial pattern of kinetic Alfvén waves excited by a current-modulating disk whose dimension a, transverse to the confining magnetic field, is comparable to the ion sound gyroradius cs/Ωi, where cs is the sound speed and Ωi the ion cyclotron frequency. The radial structure of the wave azimuthal magnetic field is found to consist of four regions: a Bessel function behavior for r

Cochlear excitation by the near-field component during stimulation through the partially occluded round window

NASA Astrophysics Data System (ADS)

Weddell, Thomas D.; Yarin, Yury M.; Drexl, Markus; Russell, Ian J.; Elliott, Stephen J.; Lukashkin, Andrei N.

2015-12-01

The round window membrane (RW) provides pressure relief when the cochlea is excited by sound. While normal function of the RW is important for effective stimulation of the cochlea through the conventional oval window route, the cochlea can be stimulated successfully in non-conventional ways (e.g. through bone conduction, through the RW, and through perforations in the cochlea's apical turn). We report measurements of cochlear function from guinea pigs when the cochlea was stimulated at acoustic frequencies by movements of a miniature magnet which partially occluded the RW. Neural response latencies to acoustic and RW stimulation were similar and taken to indicate that both means of stimulation resulted in the generation of conventional travelling waves along the cochlear partition. It was concluded that the relatively high impedance of the ossicles, as seen from the cochlea, enabled the region of the RW not occluded by the magnet, to act as a pressure shunt during RW stimulation. We propose that travelling waves, similar to those due to acoustic far-field pressure changes, are driven by a jet-like, near-field component of a complex fluid-pressure field, which is generated by the magnetically vibrated RW.

Second and third harmonic generation associated to infrared transitions in a Morse quantum well under applied electric and magnetic fields

NASA Astrophysics Data System (ADS)

Restrepo, R. L.; Kasapoglu, E.; Sakiroglu, S.; Ungan, F.; Morales, A. L.; Duque, C. A.

2017-09-01

The effects of electric and magnetic fields on the second and third harmonic generation coefficients in a Morse potential quantum well are theoretically studied. The energy levels and corresponding wave functions are obtained by solving the Schrödinger equation for the electron in the parabolic band scheme and effective mass approximations and the envelope function approach. The results show that both the electric and the magnetic fields have significant influence on the magnitudes and resonant peak energy positions of the second and third harmonic generation responses. In general, the Morse potential profile becomes wider and shallower as γ -parameter increases and so the energies of the bound states will be functions of this parameter. Therefore, we can conclude that the effects of the electric and magnetic fields can be used to tune and control the optical properties of interest in the range of the infrared electromagnetic spectrum.

The comparison of multiple F-wave variable studies and magnetic resonance imaging examinations in the assessment of cervical radiculopathy.

PubMed

Lin, Chu-Hsu; Tsai, Yuan-Hsiung; Chang, Chia-Hao; Chen, Chien-Min; Hsu, Hung-Chih; Wu, Chun-Yen; Hong, Chang-Zern

2013-09-01

The aims of this study were to investigate the correlation of the findings of multiple median and ulnar F-wave variables and magnetic resonance imaging examinations in the prediction of cervical radiculopathy. The data of 68 patients who underwent both nerve conduction studies of the upper extremities and cervical spine magnetic resonance imaging within 3 mos of the nerve conduction studies were retrospectively reviewed and reinterpreted. The associations between multiple median and ulnar F-wave variables (including persistence, chronodispersion, and minimal, maximal, and mean latencies) and magnetic resonance imaging evidence of lower cervical spondylotic radiculopathy (i.e., C7, C8, and T1 radiculopathy) were investigated. Patients with lower cervical radiculopathy exhibited reduced right median F-wave persistence (P = 0.011), increased right ulnar F-wave chronodispersion (P = 0.041), and a trend toward increased left ulnar F-wave chronodispersion (P = 0.059); however, there were no other consistent significant differences in the F-wave variables between patients with and patients without magnetic resonance imaging evidence of lower cervical radiculopathy. In comparison with normal reference values established previously, the sensitivity and positive predictive value of F-wave variable abnormalities for predicting lower cervical radiculopathy were low. There was a low correlation between F-wave studies and magnetic resonance imaging examinations. The diagnostic utility of multiple F-wave variables in the prediction of cervical radiculopathy was not supported by this study.

Observations and modeling of EMIC wave properties in the presence of multiple ion species as function of magnetic local time

NASA Astrophysics Data System (ADS)

Lee, Justin H.; Angelopoulos, Vassilis

2014-11-01

Electromagnetic ion cyclotron (EMIC) wave generation and propagation in Earth's magnetosphere depend on readily measurable hot (a few to tens of keV) plasma sheet ions, elusive plasmaspheric or ionospheric cold (sub-eV to a few eV) ions, and partially heated warm ions (tens to hundreds of eV). Previous work has assumed all low-energy ions are cold and not considered possible effects of warm ions. Using measurements by multiple Time History of Events and Macroscale Interactions during Substorms spacecraft, we analyze four typical EMIC wave events in the four magnetic local time sectors and consider the properties of both cold and warm ions supplied from previous statistical studies to interpret the wave observations using linear theory. As expected, we find that dusk EMIC waves grow due to the presence of drifting hot anisotropic protons and cold plasmaspheric ions with a dominant cold proton component. Near midnight, EMIC waves are less common because warm heavy ions that suppress wave growth are more abundant there. The waves can grow when cold, plume-like density enhancements are present, however. Dawn EMIC waves, known for their peculiar properties, are generated away from the equator and change polarization during propagation through the warm plasma cloak. Noon EMIC waves can also be generated nonlocally and their properties modified during propagation by a plasmaspheric plume combined with low-energy ions from solar and terrestrial sources. Accounting for multiple ion species, measured wave dispersion, and propagation characteristics can explain previously elusive EMIC wave properties and are therefore important for future studies of EMIC wave effects on energetic particle depletion.

A test of the Hall-MHD model: Application to low-frequency upstream waves at Venus

NASA Technical Reports Server (NTRS)

Orlowski, D. S.; Russell, C. T.; Krauss-Varban, D.; Omidi, N.

1994-01-01

Early studies suggested that in the range of parameter space where the wave angular frequency is less than the proton gyrofrequency and the plasma beta, the ratio of the thermal to magnetic pressure, is less than 1 magnetohydrodynamics provides an adequate description of the propagating modes in a plasma. However, recently, Lacombe et al. (1992) have reported significant differences between basic wave characteristics of the specific propagation modes derived from linear Vlasov and Hall-magnetohydrodynamic (MHD) theories even when the waves are only weakly damped. In this paper we compare the magnetic polarization and normalization magnetic compression ratio of ultra low frequency (ULF) upstream waves at Venus with magnetic polarization and normalized magnetic compression ratio derived from both theories. We find that while the 'kinetic' approach gives magnetic polarization and normalized magnetic compression ratio consistent with the data in the analyzed range of beta (0.5 less than beta less than 5) for the fast magnetosonic mode, the same wave characteristics derived from the Hall-MHD model strongly depend on beta and are consistent with the data only at low beta for the fast mode and at high beta for the intermediate mode.

Spin-Hall nano-oscillator with oblique magnetization and Dzyaloshinskii-Moriya interaction as generator of skyrmions and nonreciprocal spin-waves

PubMed Central

Giordano, A.; Verba, R.; Zivieri, R.; Laudani, A.; Puliafito, V.; Gubbiotti, G.; Tomasello, R.; Siracusano, G.; Azzerboni, B.; Carpentieri, M.; Slavin, A.; Finocchio, G.

2016-01-01

Spin-Hall oscillators (SHO) are promising sources of spin-wave signals for magnonics applications, and can serve as building blocks for magnonic logic in ultralow power computation devices. Thin magnetic layers used as “free” layers in SHO are in contact with heavy metals having large spin-orbital interaction, and, therefore, could be subject to the spin-Hall effect (SHE) and the interfacial Dzyaloshinskii-Moriya interaction (i-DMI), which may lead to the nonreciprocity of the excited spin waves and other unusual effects. Here, we analytically and micromagnetically study magnetization dynamics excited in an SHO with oblique magnetization when the SHE and i-DMI act simultaneously. Our key results are: (i) excitation of nonreciprocal spin-waves propagating perpendicularly to the in-plane projection of the static magnetization; (ii) skyrmions generation by pure spin-current; (iii) excitation of a new spin-wave mode with a spiral spatial profile originating from a gyrotropic rotation of a dynamical skyrmion. These results demonstrate that SHOs can be used as generators of magnetic skyrmions and different types of propagating spin-waves for magnetic data storage and signal processing applications. PMID:27786261

First results from the Magnetospheric Multiscale mission

NASA Astrophysics Data System (ADS)

Lavraud, B.

2017-12-01

Since its launch in March 2015, NASA's Magnetospheric Multiscale mission (MMS) provides a wealth of unprecedented high resolution measurements of space plasma properties and dynamics in the near-Earth environment. MMS was designed in the first place to study the fundamental process of collision-less magnetic reconnection. The two first results reviewed here pertain to this topic and highlight how the extremely high resolution MMS data (electrons, in particular, with full three dimensional measurements at 30 ms in burst mode) have permitted to tackle electron dynamics in unprecedented details. The first result demonstrates how electrons become demagnetized and scattered near the magnetic reconnection X line as a result of increased magnetic field curvature, together with a decrease in its magnitude. The second result demonstrates that electrons form crescent-shaped, agyrotropic distribution functions very near the X line, suggestive of the existence of a perpendicular current aligned with the local electric field and consistent with the energy conversion expected in magnetic reconnection (such that J\\cdot E > 0). Aside from magnetic reconnection, we show how MMS contributes to topics such as wave properties and their interaction with particles. Thanks again to extremely high resolution measurements, the lossless and periodical energy exchange between wave electromagnetic fields and particles, as expected in the case of kinetic Alfvén waves, was confirmed. Although not discussed, MMS has the potential to solve many other outstanding issues in collision-less plasma physics, for example regarding shock or turbulence acceleration, with obvious broader impacts in astrophysics in general.

Reflection of Fast Magnetosonic Waves near a Magnetic Reconnection Region

NASA Astrophysics Data System (ADS)

Provornikova, E.; Laming, J. M.; Lukin, V. S.

2018-06-01

Magnetic reconnection in the solar corona is thought to be unstable with the formation of multiple interacting plasmoids, and previous studies have shown that plasmoid dynamics can trigger MHD waves of different modes propagating outward from the reconnection site. However, variations in plasma parameters and magnetic field strength in the vicinity of a coronal reconnection site may lead to wave reflection and mode conversion. In this paper we investigate the reflection and refraction of fast magnetoacoustic waves near a reconnection site. Under a justified assumption of an analytically specified Alfvén speed profile, we derive and solve analytically the full wave equation governing the propagation of fast-mode waves in a non-uniform background plasma without recourse to the small wavelength approximation. We show that the waves undergo reflection near the reconnection current sheet due to the Alfvén speed gradient and that the reflection efficiency depends on the plasma-β parameter, as well as on the wave frequency. In particular, we find that waves are reflected more efficiently near reconnection sites in a low-β plasma, which is typical under solar coronal conditions. Also, the reflection is larger for lower-frequency waves while high-frequency waves propagate outward from the reconnection region almost without the reflection. We discuss the implications of efficient wave reflection near magnetic reconnection sites in strongly magnetized coronal plasma for particle acceleration, and also the effect this might have on first ionization potential (FIP) fractionation by the ponderomotive force of these waves in the chromosphere.

Clinical application of a color map pattern on shear-wave elastography for invasive breast cancer.

PubMed

Lee, Seokwon; Jung, Younglae; Bae, Youngtae

2016-03-01

The aim of this study was to classify the color map pattern on shear-wave elastography (SWE) and to determine its association with clinicopathological factors for clinical application in invasive breast cancer. From June to December 2014, 103 invasive breast cancers were imaged by B-mode ultrasonography (US) and SWE just before surgery. The color map pattern identified on the SWE could be classified into three main categories: type 1 (diffuse pattern), increased stiffness in the surrounding stroma and the interior lesion itself; type 2 (lateral pattern), marked peri-tumoral stiffness at the anterior and lateral portions with no or minor stiffness at the posterior portion; and type 3 (rim-off pattern), marked peri-tumoral stiffness at the anterior and posterior portion with no or minor stiffness at both lateral portions. High-grade density on mammography (grade 3-4) was more frequent in the type 1 pattern than the other pattern types (80.5% in high-grade density vs. 19.5% in low-grade density). For type 1 tumors, the extent of synchronous non-invasive cancers (pT0), ductal carcinoma in situ (DCIS), was 1.8-2.0 times wider than that measured by US or magnetic resonance imaging (MRI). For type 2 tumors, the invasive tumor components (pT size) size was 1.3 times greater than measured by MRI (p = 0.049). On the other hand, the pT size and pT0 extent of type 3 tumors were almost equal to the preoperative US and MRI measurements. In terms of immunohistochemical (IHC) profiles, type 3 tumors showed a high histologic grade (p = 0.021), poor differentiation (p = 0.009), presence of necrosis (p = 0.018), and high Ki-67 (p = 0.002). The percentage of HER2-positive cancers was relatively high within the type 2 group, and the percentage of triple negative breast cancer was relatively high in the type 3 group (p = 0.011). We expect that assessments of the SWE color map pattern will prove useful for surgical or therapeutic plan decisions and to predict prognosis in invasive breast cancer patients. Copyright © 2015 Elsevier Ltd. All rights reserved.

Waves and instabilities in an anisotropic universe

NASA Astrophysics Data System (ADS)

Papadopoulos, D.; Vlahos, L.; Esposito, F. P.

2002-01-01

The excitation of low frequency plasma waves in an expanding anisotropic cosmological model that contains a magnetic field frozen into the matter and pointing in the longitudinal direction is discussed. Using the exact equations governing finite-amplitude wave propagation in hydromagnetic media within the framework of the general theory of relativity, we show that a spectrum of magnetized sound waves will be excited and form large-scale ``damped oscillations'' in the expanding universe. The characteristic frequency of the excited waves is slightly shifted away from the sound frequency and the shift depends on the strength of the primordial magnetic field. This magnetic field dependent shift may have an effect on the acoustic peaks of the CMB.

High-frequency Plasma Waves Associated with Magnetic Reconnection in the Solar Wind

NASA Astrophysics Data System (ADS)

Wang, Y.

2015-12-01

Activities of high-frequency plasma waves associated with magnetic reconnection in the solar wind observed by Time Domain Sampler (TDS) experiments on STEREO/WAVES are preliminarily analyzed. The TDS instrument can provide burst mode electric fields data with as long as 16384 sample points at 250 kHz sampling rate. In all 1120 suspected reconnection events, it is found that the most commonly occurred waves are neither ion acoustic waves, electrostatic solitary waves, nor Langmuir/upper hybrid waves, but Bernstein-like waves with harmonics of the electron cyclotron frequency. In addition, to each type of waves, Langmuir/upper hybrid waves reveal the largest occurrence rate in the reconnection region than in the ambient solar wind. These results indicate that Bernstein-like waves and Langmuir/upper hybrid waves might play important roles in the reconnection associated particle heating processes and they might also influence the dissipation of magnetic reconnection.

Energy partition, scale by scale, in magnetic Archimedes Coriolis weak wave turbulence.

PubMed

Salhi, A; Baklouti, F S; Godeferd, F; Lehner, T; Cambon, C

2017-02-01

Magnetic Archimedes Coriolis (MAC) waves are omnipresent in several geophysical and astrophysical flows such as the solar tachocline. In the present study, we use linear spectral theory (LST) and investigate the energy partition, scale by scale, in MAC weak wave turbulence for a Boussinesq fluid. At the scale k^{-1}, the maximal frequencies of magnetic (Alfvén) waves, gravity (Archimedes) waves, and inertial (Coriolis) waves are, respectively, V_{A}k,N, and f. By using the induction potential scalar, which is a Lagrangian invariant for a diffusionless Boussinesq fluid [Salhi et al., Phys. Rev. E 85, 026301 (2012)PLEEE81539-375510.1103/PhysRevE.85.026301], we derive a dispersion relation for the three-dimensional MAC waves, generalizing previous ones including that of f-plane MHD "shallow water" waves [Schecter et al., Astrophys. J. 551, L185 (2001)AJLEEY0004-637X10.1086/320027]. A solution for the Fourier amplitude of perturbation fields (velocity, magnetic field, and density) is derived analytically considering a diffusive fluid for which both the magnetic and thermal Prandtl numbers are one. The radial spectrum of kinetic, S_{κ}(k,t), magnetic, S_{m}(k,t), and potential, S_{p}(k,t), energies is determined considering initial isotropic conditions. For magnetic Coriolis (MC) weak wave turbulence, it is shown that, at large scales such that V_{A}k/f≪1, the Alfvén ratio S_{κ}(k,t)/S_{m}(k,t) behaves like k^{-2} if the rotation axis is aligned with the magnetic field, in agreement with previous direct numerical simulations [Favier et al., Geophys. Astrophys. Fluid Dyn. (2012)] and like k^{-1} if the rotation axis is perpendicular to the magnetic field. At small scales, such that V_{A}k/f≫1, there is an equipartition of energy between magnetic and kinetic components. For magnetic Archimedes weak wave turbulence, it is demonstrated that, at large scales, such that (V_{A}k/N≪1), there is an equipartition of energy between magnetic and potential components, while at small scales (V_{A}k/N≫1), the ratio S_{p}(k,t)/S_{κ}(k,t) behaves like k^{-1} and S_{κ}(k,t)/S_{m}(k,t)=1. Also, for MAC weak wave turbulence, it is shown that, at small scales (V_{A}k/sqrt[N^{2}+f^{2}]≫1), the ratio S_{p}(k,t)/S_{κ}(t) behaves like k^{-1} and S_{κ}(k,t)/S_{m}(k,t)=1.

Stochastic generation of MAC waves and implications for convection in Earth's core

NASA Astrophysics Data System (ADS)

Buffett, Bruce; Knezek, Nicholas

2018-03-01

Convection in Earth's core can sustain magnetic-Archemedes-Coriolis (MAC) waves through a variety of mechanisms. Buoyancy and Lorentz forces are viable sources for wave motion, together with the effects of magnetic induction. We develop a quantitative description for zonal MAC waves and assess the source mechanisms using a numerical dynamo model. The largest sources at conditions accessible to the dynamo model are due to buoyancy forces and magnetic induction. However, when these sources are extrapolated to conditions expected in Earth's core, the Lorentz force emerges as the dominant generation mechanism. This source is expected to produce wave velocities of roughly 2 km yr-1 when the internal magnetic field is characterized by a dimensionless Elsasser number of roughly Λ ≈ 10 and the root-mean-square convective velocity defines a magnetic Reynolds number of Rm ≈ 103. Our preferred model has a radially varying stratification and a constant (radial) background magnetic field. It predicts a broad power spectrum for the wave velocity with most power distributed across periods from 30 to 100 yr.

Low frequency wave propagation in a cold magnetized dusty plasma

NASA Astrophysics Data System (ADS)

Sarkar, S.; Ghosh, S.; Khan, M.

1998-12-01

In this paper several characteristics of low frequency waves in a cold magnetized dusty plasma propagating parallel and perpendicular to the static background magnetic field have been investigated. In the case of parallel propagation the negatively charged dust particles resonate with the right circularly polarized (RCP) component of em waves when the wave frequency equals the dust cyclotron frequency. It has been shown that an RCP wave in dusty plasma consists of two branches and there exists a region where an RCP wave propagation is not possible. Dispersion relation, phase velocity and group velocity of RCP waves have been obtained and propagation characteristics have been shown graphically. Poynting flux and Faraday rotation angles have been calculated for both lower and upper branches of the RCP wave. It has been observed that sense of rotation of the plane of polarization of the RCP wave corresponding to two distinct branches are opposite. Finally, the effect of dust particles on the induced magnetization from the inverse Faraday effect (IFE) due to the interaction of low frequency propagating and standing em waves with dusty plasmas has been evaluated.

Brain activation and deactivation during location and color working memory tasks in 11-13-year-old children.

PubMed

Vuontela, Virve; Steenari, Maija-Riikka; Aronen, Eeva T; Korvenoja, Antti; Aronen, Hannu J; Carlson, Synnöve

2009-02-01

Using functional magnetic resonance imaging (fMRI) and n-back tasks we investigated whether, in 11-13-year-old children, spatial (location) and nonspatial (color) information is differentially processed during visual attention (0-back) and working memory (WM) (2-back) tasks and whether such cognitive task performance, compared to a resting state, results in regional deactivation. The location 0-back task, compared to the color 0-back task, activated segregated areas in the frontal, parietal and occipital cortices whereas no differentially activated voxels were obtained when location and color 2-back tasks were directly contrasted. Several midline cortical areas were less active during 0- and 2-back task performance than resting state. The task-induced deactivation increased with task difficulty as demonstrated by larger deactivation during 2-back than 0-back tasks. The results suggest that, in 11-13-year-old children, the visual attentional network is differently recruited by spatial and nonspatial information processing, but the functional organization of cortical activation in WM in this age group is not based on the type of information processed. Furthermore, 11-13-year-old children exhibited a similar pattern of cortical deactivation that has been reported in adults during cognitive task performance compared to a resting state.

Evolution of the orbitals Dy-4f in the DyB2 compound using the LDA, PBE approximations, and the PBE0 hybrid functional

NASA Astrophysics Data System (ADS)

Rasero Causil, Diego; Ortega López, César; Espitia Rico, Miguel

2018-04-01

Computational calculations of total energy based on density functional theory were used to investigate the structural, electronic, and magnetic properties of the DyB2 compounds in the hexagonal structure. The calculations were carried out by means of the full-potential linearized augmented plane wave (FP-LAPW) method, employing the computational Wien2k package. The local density approximation (LDA) and the generalized gradient approximation (GGA) were used for the electron-electron interactions. Additionally, we used the functional hybrid PBE0 for a better description the electronic and magnetic properties, because the DyB2 compound is a strongly-correlated system. We found that the calculated lattice constant agrees well with the values reported theoretically and experimentally. The density of states (DOS) calculation shows that the compound exhibits a metallic behavior and has magnetic properties, with a total magnetic moment of 5.47 μ0/cell determined mainly by the 4f states of the rare earth elements. The functional PBE0 shows a strong localization of the Dy-4f orbitals.

Wave heating of the solar atmosphere

NASA Astrophysics Data System (ADS)

Arregui, Iñigo

2015-04-01

Magnetic waves are a relevant component in the dynamics of the solar atmosphere. Their significance has increased because of their potential as a remote diagnostic tool and their presumed contribution to plasma heating processes. We discuss our current understanding of coronal heating by magnetic waves, based on recent observational evidence and theoretical advances. The discussion starts with a selection of observational discoveries that have brought magnetic waves to the forefront of the coronal heating discussion. Then, our theoretical understanding of the nature and properties of the observed waves and the physical processes that have been proposed to explain observations are described. Particular attention is given to the sequence of processes that link observed wave characteristics with concealed energy transport, dissipation and heat conversion. We conclude with a commentary on how the combination of theory and observations should help us to understand and quantify magnetic wave heating of the solar atmosphere.

Wave heating of the solar atmosphere

PubMed Central

Arregui, Iñigo

2015-01-01

Magnetic waves are a relevant component in the dynamics of the solar atmosphere. Their significance has increased because of their potential as a remote diagnostic tool and their presumed contribution to plasma heating processes. We discuss our current understanding of coronal heating by magnetic waves, based on recent observational evidence and theoretical advances. The discussion starts with a selection of observational discoveries that have brought magnetic waves to the forefront of the coronal heating discussion. Then, our theoretical understanding of the nature and properties of the observed waves and the physical processes that have been proposed to explain observations are described. Particular attention is given to the sequence of processes that link observed wave characteristics with concealed energy transport, dissipation and heat conversion. We conclude with a commentary on how the combination of theory and observations should help us to understand and quantify magnetic wave heating of the solar atmosphere. PMID:25897091

Exploring correlations in the CGC wave function: Odd azimuthal anisotropy

DOE PAGES

Kovner, Alex; Lublinsky, Michael; Skokov, Vladimir

2017-07-17

In this paper, we extend the color glass condensate (CGC) approach to a calculation of the double inclusive gluon production by including the high density effect in the CGC wave function of the projectile (proton). Our main result is that these effects lead to the appearance of odd harmonics in the two particle correlation C(k,p). We find that in the high momentum limit, |k|, |p| >> Q s, this results in a positive c 1{2}. Additionally when the magnitudes of the two momenta are approximately equal, |k|/|p| ≈ 1, the density effects also generate a positive third harmonic c 3{2},more » which translates into a nonvanishing v 3 when the momenta of the trigger and an associated particle are in the same momentum bin. Finally, the sign of c 3{2} becomes negative when |k|/|p| > 1.1 suggesting an interesting experimental signature.« less

Apparatus for and method of operating a cylindrical pulsed induction mass launcher

DOEpatents

Cowan, M. Jr.; Duggin, B.W.; Widner, M.M.

1992-06-30

An electromagnetic cylindrical projectile mass launcher and a method of operation is provided which includes a cylindrical projectile having a conducting armature, a cylindrical barrel in which the armature is received, a plurality of electromagnetic drive coil stages, a plurality of pulse energy sources, and a pulsed power arrangement for generating magnetic pulses forming a pulsed magnetic wave along the length of the launcher barrel. The pulsed magnetic wave provides a propelling force on the projectile along the drive coil. The pulsed magnetic wave of the drive coil stages is advanced along the armature faster than the projectile to thereby generate an induced current wave in the armature. The pulsed generation of the magnetic wave minimizes electromagnetic heating of the projectile and provides for smooth acceleration of the projectile through the barrel of the launcher. 2 figs.

Apparatus for and method of operating a cylindrical pulsed induction mass launcher

DOEpatents

Cowan, Jr., Maynard; Duggin, Billy W.; Widner, Melvin M.

1992-01-01

An electromagnetic cylindrical projectile mass launcher and a method of operation is provided which includes a cylindrical projectile having a conducting armature, a cylindrical barrel in which the armature is received, a plurality of electromagnetic drive coil stages, a plurality of pulse energy sources, and a pulsed power arrangement for generating magnetic pulses forming a pulsed magnetic wave along the length of the launcher barrel. The pulsed magnetic wave provides a propelling force on the projectile along the drive coil. The pulsed magnetic wave of the drive coil stages is advanced along the armature faster than the projectile to thereby generate an induced current wave in the armature. The pulsed generation of the magnetic wave minimizes electromagnetic heating of the projectile and provides for smooth acceleration of the projectile through the barrel of the launcher.

Generation of ULF waves by electric or magnetic dipoles. [propagation from earth surface to ionosphere

NASA Technical Reports Server (NTRS)

Harker, K. J.

1975-01-01

The generation of ULF waves by ground-based magnetic and electric dipoles is studied with a simplified model consisting of three adjoining homogeneous regions representing the groud, the vacuum (free space) region, and the ionosphere. The system is assumed to be immersed in a homogeneous magnetic field with an arbitrary tilt angle. By the use of Fourier techniques and the method of stationary phase, analytic expressions are obtained for the field strength of the compressional Alfven waves in the ionosphere. Expressions are also obtained for the strength of the torsional Alfven wave in the ionosphere and the ULF magnetic field at ground level. Numerical results are obtained for the compressional Alfven-wave field strength in the ionosphere with a nonvertical geomagnetic field and for the ULF magnetic field at ground level for a vertical geomagnetic field.