Flux Gate Research Articles

Ice flow of Humboldt, Petermann and Ryder Gletscher, northern Greenland

AbstractRadar interferometry, ice-penetrating radar profiles and an elevation model are used to determine the velocity fields, rates of ice discharge, approximate states of balance and catchment area for three large outlet glaciers in northeast Greenland. Discharge through flux gates is calculated for Humboldt and Petermann Gletscher, which are found to be in balance (at the level that the accumulation is known). A large difference between the measured and estimated fluxes for Ryder Gletscher may be a reflection of unsteady flow behavior for this glacier. The patterns of ice flow for the three glaciers considered are each unique, showing that the nature of ice discharge varies substantially from basin to basin, controlled by bed conditions and the presence of subglacial troughs and obstructions.

Ice flow of Humboldt, Petermann and Ryder Gletscher, northern Greenland

AbstractRadar interferometry, ice-penetrating radar profiles and an elevation model are used to determine the velocity fields, rates of ice discharge, approximate states of balance and catchment area for three large outlet glaciers in northeast Greenland. Discharge through flux gates is calculated for Humboldt and Petermann Gletscher, which are found to be in balance (at the level that the accumulation is known). A large difference between the measured and estimated fluxes for Ryder Gletscher may be a reflection of unsteady flow behavior for this glacier. The patterns of ice flow for the three glaciers considered are each unique, showing that the nature of ice discharge varies substantially from basin to basin, controlled by bed conditions and the presence of subglacial troughs and obstructions.

Ice flow of Humboldt, Petermann and Ryder Gletscher, northern Greenland

AbstractRadar interferometry, ice-penetrating radar profiles and an elevation model are used to determine the velocity fields, rates of ice discharge, approximate states of balance and catchment area for three large outlet glaciers in northeast Greenland. Discharge through flux gates is calculated for Humboldt and Petermann Gletscher, which are found to be in balance (at the level that the accumulation is known). A large difference between the measured and estimated fluxes for Ryder Gletscher may be a reflection of unsteady flow behavior for this glacier. The patterns of ice flow for the three glaciers considered are each unique, showing that the nature of ice discharge varies substantially from basin to basin, controlled by bed conditions and the presence of subglacial troughs and obstructions.

Vision and vestibular adaptation

This article summarizes six recent degree-of-freedom studies of visual-vestibular interaction during natural activities and relates the findings to canal-otolith interactions evaluated during eccentric axis rotations. Magnetic search coils were used to measure angular eye and head movements of young and elderly subjects. A flux gate magnetometer was used to measure three-dimensional head translation. Three activities were studied: standing quietly, walking in place, and running in place. Each activity was evaluated with three viewing conditions: a visible target viewed normally, a remembered target in darkness, and a visible target viewed with ×2 binocular telescopic spectacles. Canal-otolith interaction was assessed with passive, whole-body, transient, and steady-state rotations in pitch and yaw at multiple frequencies about axes that were either oculocentric or eccentric to the eyes. For each rotational axis, subjects regarded visible and remembered targets located at various distances. Horizontal and vertical angular vestibulo-ocular reflexes were demonstrable in all subjects during standing, walking, and running. When only angular gains were considered, gains in both darkness and during normal vision were less than 1.0 and were generally lower in elderly than in young subjects. Magnified vision with ×2 telescopic spectacles produced only small gain increases as compared with normal vision. During walking and running all subjects exhibited significant mediolateral and dorsoventral head translations that were antiphase locked to yaw and pitch head movements, respectively. These head translations and rotations have mutually compensating effects on gaze in a target plane for typical viewing distances and allow angular vestibulo-ocular reflex gains of less than 1.0 to be optimal for gaze stabilization during natural activities. During passive, whole-body eccentric pitch and yaw head rotations, vestibulo-ocular reflex gain was modulated as appropriate to stabilize gaze on targets at the distances used. This modulation was evident within the first 80 msec of onset of head movement, too early to be caused by immediate visual tracking. Modeling suggests a linear interaction between canal signals and otolith signals scaled by the inverse of target distance. Vestibulo-ocular reflex performance appears to be adapted to stabilize gaze during translational and rotational perturbations that occur during natural activities, as is appropriate for relevant target distances. Although immediate visual tracking contributes little to gaze stabilization during natural activities, visual requirements determine the performance of vestibulo-ocular reflexes arising from both canals and otoliths. (Otolaryngol Head Neck Surg 1998;119:78-88.)

New applications of nanocrystalline Fe(Co–Fe)–Hf–O magnetic films to micromagnetic devices

New applications of high resistivity magnetic films, such as Fe–Hf–O and Co–Fe–Hf–O as thin film inductors and flux gate magnetic sensors, were investigated. These soft magnetic films with nanocrystalline structure and high resistivity were deposited on glass substrate by using the oxygen reactive sputtering method. Planar sandwich thin film inductors developed by using Fe–Hf–O or Co–Fe–Hf–O films had a higher quality factor than that of an amorphous Co–Ta–Hf film inductor. The dc–dc converter using the Fe(Co–Fe)–Hf–O film inductor had higher conversion efficiency. These high resistivity magnetic films were also applied to a flux gate magnetic sensor operated at high frequencies over 1 MHz. Both high frequency excitation and high permeability (owing to the low eddy current loss) enabled us to increase the sensitivity, e.g., 39 mV/Oe/turn at 5 MHz when using a 3 μm thick Fe–Hf–O film (12×6 mm2 area).

Nanocrystalline soft magnetic Fe-M-B (M = Zr, Hf, Nb) alloys and their applications

This paper reviews our results on the development of a new type of soft magnetic material with high saturation magnetic flux density (Bs) above 1.5 T as well as excellent soft magnetic properties. A mostly single bcc structure composed of α-Fe grains with about 10–20 nm in size surrounded by a small amount of an intergranular amorphous layer was obtained by crystallization of amorphous alloys prepared by melt-spinning technique. The typical nanocrystalline bcc Fe 90Zr 7B 3, Fe 89Hf 7B 4 and Fe 84Nb 7B 9 ternary alloys subjected to the optimum annealing exhibit high Bs above 1.5 T as well as high effective permeability (μe) at 1 kHz above 20000. Excellent soft magnetic properties of the nanocrystalline Fe-M-B based alloys can be obtained by the decrease in the bcc grain size, magnetostriction (λ) and the increase in Tc of the intergranular amorphous phase by optimizing the crystallization process, chemical composition and adding small amounts of elements. For example, the improved FeZrNbBCu alloy shows the high ue of 160000 combined with the high Bs of 1,57 T. This excellent μe is comparable to those of nanocrystalline Fe 73.5Si 13.5B 9Nb 3Cu 1 and the zero-magnetostrictive Co based amorphous alloys, and the high Bs is comparable to those of the Fe based amorphous alloys with rather good soft magnetic properties. The excellent characteristics of a power transformer, a common mode choke coil, a pulse-transformer and a flux gate magnetic detector made of ‘NANOPERM ™’ were found in agreement with its very low core losses, sufficient thermal stability and low stress-sensibility of magnetic properties. The nanocrystalline Fe-M-B based alloys ‘NANOPERM ™’ is therefore expected to be used for many kinds of magnetic parts and devices.

Applications of nanocrystalline soft magnetic Fe-M-B (M=Zr, Nb) alloys "NANOPERM(R)"

This paper reviews our recent results on some applications of new nanocrystalline soft magnetic Fe-M-B (M=Zr, Hf, Nb) alloy ribbons "NANOPERM(R)". NANOPERM(R) has a structure consisting of nanoscale bcc grains and a small amount of an intergranular amorphous layer. NANOPERM(R) exhibits high saturation magnetic flux density above 1.5 T as well as excellent soft magnetic properties. Furthermore, its remanence ratio can be controlled according to the demands of various applications. Toroidal cores with gap, common mode choke coils, ISDN (integrated service digital network) interface pulse transformers and flux gate magnetic detectors made of "NANOPERM(R) have been developed. The excellent characteristics of the components were confirmed in trial. NANOPERM(R) is therefore expected to be used widely in the magnetic application field.

Visual-Vestibular Interaction During Standing, Walking, and Running

In artificial laboratory situations where subjects undergo repetitive self-generated or externally imposed head rotations, visual-vestibular interaction during the wearing of telescopic spectacles can markedly augment gain of the vestibulo-ocular reflex (VOR). The present study was conducted to determine whether the wearing of these aids for the visually impaired is associated with similar visual-vestibular interaction during more natural activities. Angular eye and head movements of unrestrained normal volunteers were measured using magnetic search coils. In some subjects, head translations and rotations were also monitored by a flux gate magnetometer array. Measurements were performed of the VOR in darkness, and of the visually enhanced VOR (VVOR) in lit conditions, during three natural activities: 1) standing quietly; 2) walking in place; 3) running in place. These data were compared with similar measurements during repetitive voluntary head oscillations at 0.8 Hz in pitch or yaw. During VVOR, subjects viewed a target placed 6 to 10 m away and remembered this target during VOR trials in darkness. To assess the effects of altering visual-vestibular interactions, VVOR testing during normal vision was augmented by wearing of binocular telescopic spectacles of 2X, 4X, and 6X powers. Dorsoventral and mediolateral head translations were consistently phase-locked with pitch and yaw head rotations, respectively, such that head translation at least partially compensated for rotational disturbances of gaze. Angular velocity of the head was greater during walking than during standing, and was greater still during running, with a greater increase in each case for pitch as compared with yaw. Eye movements were phase compensatory for head movements. VOR gain (eye velocity divided by head velocity) was near 1.0 in both pitch and yaw during standing and during actively generated head rotation. During walking and running there was a significant decrease in angular VOR gain in pitch to approximately 0.75 (P < 0.0005). During ambulatory activities, normal and magnified vision were associated with VVOR gain enhancement in pitch and yaw that was statistically significant, but substantially less than was telescope magnification and markedly lower than was the corresponding VVOR gain measured during active head rotation. Measurements of unmagnified VOR and VVOR during walking and running showed that gain was lower than the "ideal" value of 1.0. However, since translational head perturbations during these activities partially offset the visual effects of angular disturbances, lower gains may nevertheless be associated with retinal image stability at typical indoor target distances. In contrast with performance during repetitive, uniplanar motion, vision has very limited influence on VOR gain during natural activities.

An all-terrain intelligent autonomous vehicle with sensor-fusion-based navigation capabilities

This paper reports on preliminary work involving a six-wheeled, all-terrain vehicle being prepared as an autonomous outdoor robotic vehicle, the navigation of which is to be initially supported by flux gate compass, differential global positioning systems (DGPS), range sensing and distance transform based path planning. Extensions involving passive stereopsis ranging and natural-landmark-based localisation will be developed in the longer term.

Atomic magnetic resonance based current source

A current of 1 A has been stabilized by locking the magnetic resonance frequency of Cs atoms placed at the center of a solenoid. Two auxiliary windings are used to obtain at the center of the solenoid a field uniformity better than 0.5 ppm in a 2 cm radius sphere, in agreement with the calculations. The variations of the external field and the effect of temperature changes are compensated for by two auxiliary feedback systems using a flux gate magnetometer and an adjustment of the locking frequency, respectively. The current fluctuation, including the noise of the current measuring system is 0.1 ppm and the current drift for 6 h is less than 0.2 ppm.

An All-Terrain Intelligent Autonomous Vehicle with Sensor Fusion Based Navigation Capabilities

This paper reports on preliminary work involving a six wheeled all-terrain vehicle being prepared as an autonomous outdoor robotic vehicle, the navigation of which is to be initially supported by flux gate compass, differential global positioning systems (DGPS), range sensing and distance transform based path planning. Extensions involving passive stereopsis ranging and natural landmark based localisation will be developed in the longer term.

Fundamental Characteristics of a Large-Scale Cylindrical Magnetic Shield with Shaking

A large-scale cylindrical magnetic shielding case was developed. It was made of permalloy (outer diameter 68 cm, length 180 cm, thickness 1.6 mm, weight approximately 60 kg) with an opening at one end and with Metglas® 2705M amorphous ribbons (width 5 cm, thickness approximately 22 ?m) wound spirally about the permalloy case in 16 layers (total weight 12.1 kg) to cover the surface. A toroidal coil (36 turns) was wound around the amorphous layers to allow the creation of a magnetic shaking field. An external magnetic field was applied to the shielding case by means of a large rectangular Hemholtz coil, to evaluate the shielding factor, which was about 2700 at a frequency of 0.5 Hz when the shaking frequency was 200 Hz. At higher frequencies, it gradually dropped. The shielding factor was almost constant relative to the amplitude of the disturbing field down to 3 mG; beyond that point, a residual field could not be detected because of the limit of resolution of the flux gate magnetometer used. The leakage of the shaking field was about 30 ?G at the center of the shielding case.

Application of amorphous magnetic wires to computer peripherals

The principles and basic properties of a new flux-detection element, called a “magnetoinductive (MI) element”, and a data tablet for inputting hand-written characters and figures into personal computers (PCs) using amorphous magnetic wires are presented. The MI element is as small as a magnetoresistive (MR) element and shows a high sensitivity for flux detection, i.e. as high as that of the flux gate sensor, with a resolution of 10 −5−10 −6 Oe. Also, it is applicable in magnetic heads for computer magnetic discs and disc drive encoders. A quick-response MI element module is constructed using an MI element-FET (field effect transistor) multivibrating oscillator at 200 MHz. A transparent, thin, lightweight and reliable data tablet was constructed using a thin amorphous wire matrrix for a Pen-PC assembly, which has a resolution of 0.3 mm and a processing speed of 150 dots per second.

Experimental study on opening compensation for magnetic shields by current superposition

A new method is studied experimentally by which magnetic fields coming in through an opening of a magnetic shield can be compensated. The horizontal component of the earth’s field is targeted as an external magnetic field to be compensated by the method, in which a single figure-eight coil is used. A cylindrical shielding case is developed for this study using a Permalloy cylindrical case (outer diameter=68 cm, length=180 cm) with an opening at an end and Metglas 2705M amorphous ribbons, which are wound helically on the outer surface of the Permalloy case by 16 layers. A magnetic shaking field of 200 Hz is applied to only the amorphous layers by a toroidal shaking coil of 36 turns. The size of the figure-eight coil used is 74 cm in diameter with 30 turns. Residual magnetic field measured by a flux gate magnetometer in the horizontal center plane of the shielding case shows that the area where the amplitude of the residual magnetic field is within ±0.15 mG is extended by about 30 cm toward the opening.

Isothermal remanent magnetization and anisotropy in iron-terbium thin films

Thin films of composition TbxFe1-x about 150 mu m thick have been studied using the magneto-optical Kerr effect and have also had their acquisition curves of isothermal remanent magnetization measured using a spinner flux gate magnetometer. Both types of measurement show that, for x<0.23, the easy magnetization direction lies in the plane of the film, whereas samples with a higher Tb content are more easily magnetized at high fields perpendicular to the film. At lower fields the remanence measurements show that samples of higher Tb content are almost isotropic. The remanence measurements also indicate that those samples with an easy plane also exhibit a marked anisotropy within the plane so that a preferred axis is present, presumably as a result of some asymmetry in the deposition process.

大型円筒磁気シェイキング付き磁気シールドの基礎特性

A large-scale cylindrical magnetic shielding case was developed. It was made of Permalloy (outer diameter = 68 cm. length = 180 cm. thickness = 1.6 mm, weigt≈60Kg)with an opening at one end and Metglas® 2705M amorphous ribbons (width=5 cm, thickness ≈ 22 μm), which were wound spirally around the Permalloy case in 16 layers (total weight = 12.1 kg) to cover the surface. A toroidal coil (36 turns) was wound around the amorphous layers to allow the creation of a magnetic shaking field. An external magnetic field was applied to the shielding case by means of a large rectangular Helmholtz coil, to evaluate the shielding factor. This was about 2700 at a frequency of 0.5 Hz, when the shaking frequency was 200 Hz. At higher frequencies, it gradually dropped. The shielding factor was almost constant relative to the amplitude of the disturbing field down to 3 mG; beyond that point, a residual field could not be detected because of the limit of resolution of the flux gate magnetometers used. The leakage of the shaking field was about 30,μG at the center of the shielding case.

Calcium gating of H+ fluxes in chloroplasts affects acid-base-driven ATP formation

In previous work, calcium ions, bound at the lumenal side of the CF0H+ channel, were suggested to keep a H+ flux gating site closed, favoring sequestered domain H+ ions flowing directly into the CF0-CF1 and driving ATP formation by a localized delta approximately mu H+ gradient. Treatments expected to displace Ca++ from binding sites had the effect of allowing H+ ions in the sequestered domains to equilibrate with the lumen, and energy coupling showed delocalized characteristics. The existence of such a gating function implies that a closed-gate configuration would block lumenal H+ ions from entering the CF0-CF1 complex. In this work that prediction was tested using as an assay the dark, acid-base jump ATP formation phenomenon driven by H+ ions derived from succinic acid loaded into the lumen. Chlorpromazine, a photoaffinity probe for many proteins having high-affinity Ca(++)-binding sites, covalently binds to the 8-kDa CF0 subunit in the largest amounts when there is sufficient Ca++ to favor the localized energy coupling mode, i.e., the "gate closed" configuration. Photoaffinity-bound chlorpromazine blocked 50% or more of the succinate-dependent acid-base jump ATP formation, provided that the ionic conditions during the UV photoaffinity treatment were those which favor a localized energy coupling pattern and a higher level of chlorpromazine labeling of the 8-kDa CF0 subunit. Thylakoids held under conditions favoring a delocalized energy coupling mode and less chlorpromazine labeling of the CF0 subunit did not show any inhibition of acid-base jump ATP formation. Chlorpromazine and calmidazolium, another Ca(++)-binding site probe, were also shown to block redox-derived H+ initially released into sequestered domains from entering the lumen, at low levels of domain H+ accumulation, but not at higher H+ uptake levels; ie., the closed gate state can be overcome by sufficiently acidic conditions. That is consistent with the observation that the inhibition of lumenal succinate-dependent ATP formation by photoaffinity-attached chlorpromazine can be reversed by lowering the pH of the acid stage from 5.5 to 4.5. The evidence is consistent with the concept that Ca++ bound at the lumenal side of the CF0 H+ channel can block H+ flux from either direction, consistent with the existence of a molecular structure in the CF0 complex having the properties of a gate for H+ flux across the inner boundary of the CF0. Such a gate could control the expression of localized or delocalized delta approximately mu H+ energy coupling gradients.

Sunrise effect on dayside Pc pulsations at the dip equator

A flux gate magnetometer with an amplitude resolution of 6 pT/LSB was installed at Huancayo, Peru (12°S, 750°W in geographic coordinates, 0.8°N, 335.6° in geomagnetic coordinates) in December 1985 and recorded field variations for 1 year with 3‐s sampling intervals. Horizontal field variations of Pc 3‐4 pulsations (periods from 150 to 30 s) were studied and it was found that the oscillations were observed predominantly in the H component (magnetic north‐south), though oscillations in the D component (magnetic east‐west) are superimposed temporarily at local sunrise. The D component signals, which last for ≈2 hours after local sunrise, bring about a large tilt of the polarization azimuth angles in the H‐D plane without a significant change in the ellipticity. The azimuth at sunrise lies in the NW‐SE quadrant during local summer (November to January), while it lies in the NE‐SW quadrant for local winter (March to September). On the basis of the observed seasonal change of the azimuth angles, we present a model of the ionospheric current system setup by the incident Pc 3‐4 pulsations in the dayside region of the dawn terminator at the dip‐equator.

Characterization of small‐scale structures at the magnetopause from ISEE measurements

High‐resolution data (covering up to 8 Hz) from the flux gate magnetometers on the two ISEE spacecraft are used to analyze ultralow‐frequency (ULF) fluctuations observed at the magnetopause and in the adjacent layers. Intersatellite correlations are computed to show that the same structure can be identified in the fluctuations observed on both spacecraft when the interspacecraft distance is small. Then the possibility of deducing the velocity of the structure from two‐point measurements is discussed; it is shown that it can be estimated only in certain cases.

Calcium-dependent interaction of chlorpromazine with the chloroplast 8-kilodalton CF0 protein and calcium gating of H+ fluxes between thylakoid membrane domains and the lumen.

Earlier work suggested that Ca2+ ions in the chloroplast thylakoid lumen interact with thylakoid membrane proteins to produce a proton flux gating structure which functions to regulate the expression of the energy-coupling H+ gradient between localized and delocalized modes [Chiang, G., & Dilley, R. A. (1987) Biochemistry 26, 4911-4916]. In this work, one of the phenothiazine Ca2+ antagonists, chlorpromazine, was used as a photoaffinity probe to test for Ca(2+)-dependent binding of the probe to thylakoid proteins. [3H]Chlorpromazine photoaffinity-labels thylakoid polypeptides of Mr 8K and 6K, with generally much less label occurring in other proteins (some experiments showed labeled proteins at Mr 13K-15K). More label was incorporated in circumstances where it is expected that Ca2+ occupies the putative H+ flux gating site, compared to when the gating site is not occupied by calcium. The photoaffinity labeling of the 8-kDa protein was also influenced by the energization level of the thylakoids (less labeling under H+ uptake energization). The 8-kDa protein was identified by partial amino acid sequence data as subunit III of the thylakoid CF0 H+ channel complex. The partial amino acid sequence of the 6-kDa protein (19 residues were determined with some uncertainties) was compared to data in the GCG sequence analysis data base, and no clear identity to a known sequence was revealed. Neither the exact site of putative Ca2+ binding to the CF0 proteolipid nor the site of covalent attachment of the chlorpromazine to the CF0 component has been identified. Evidence for gating of energy-linked H+ fluxes by the hypothesized Ca(2+)-CF0 gating site came from the correlation between Ca(2+)-dependent binding of chlorpromazine to the CF0 8-kDa protein with inhibition of light-driven H+ uptake into the lumen but no inhibition of H+ uptake into sequestered membrane domains. When conditions favored a delocalized delta mu H+ coupling mode, less chlorpromazine was bound to the CF0 structure, and much larger amounts of H+ ions were accumulated in the lumen. The data support the hypothesis that Ca2+ ions act in concert with the 8-kDa CF0 protein (and perhaps another protein, the 6-kDa polypeptide?) in a gating mechanism for regulating the expression of the energy-coupling H+ gradient between localized or delocalized coupling modes.