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  • 1
    Electronic Resource
    Electronic Resource
    Source analysis of MEG activities during sleep (abstract) : 35th annual conference on magnetism and magnetic materials (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 6023-6023 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The present study focuses on magnetic fields of the brain activities during sleep, in particular on K-complexes, vertex waves, and sleep spindles in human subjects. We analyzed these waveforms based on both topographic EEG (electroencephalographic) maps and magnetic fields measurements, called MEGs (magnetoencephalograms). The components of magnetic fields perpendicular to the surface of the head were measured using a dc SQUID magnetometer with a second derivative gradiometer. In our computer simulation, the head is assumed to be a homogeneous spherical volume conductor, with electric sources of brain activity modeled as current dipoles. Comparison of computer simulations with the measured data, particularly the MEG, suggests that the source of K-complexes can be modeled by two current dipoles. A source for the vertex wave is modeled by a single current dipole which orients along the body axis out of the head. By again measuring the simultaneous MEG and EEG signals, it is possible to uniquely determine the orientation of this dipole, particularly when it is tilted slightly off-axis. In sleep stage 2, fast waves of magnetic fields consistently appeared, but EEG spindles appeared intermittently. The results suggest that there exist sources which are undetectable by electrical measurement but are detectable by magnetic-field measurement. Such source can be described by a pair of opposing dipoles of which directions are oppositely oriented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.347802
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  • 2
    Electronic Resource
    Electronic Resource
    Mechanism of orientation of stimulating currents in magnetic brain stimulation (abstract) : 35th annual conference on magnetism and magnetic materials (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 6023-6023 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We made a functional map of the human motor cortex related to the hand and foot areas by stimulating the human brain with a focused magnetic pulse. We observed that each functional area in the cortex has an optimum direction for which stimulating currents can produce neural excitation. The present report focuses on the mechanism which is responsible for producing this anisotropic response to brain stimulation. We first obtained a functional map of the brain related to the left ADM (abductor digiti minimi muscles). When the stimulating currents were aligned in the direction from the left to the right hemisphere, clear EMG (electromyographic) responses were obtained only from the left ADM to magnetic stimulation of both hemisphere. When the stimulating currents were aligned in the direction from the right to the left hemisphere, clear EMG signals were obtained only from the right ADM to magnetic stimulation of both hemisphere. The functional maps of the brain were sensitive to changes in the direction of the stimulating currents. To explain the phenomena obtained in the experiments, we developed a model of neural excitation elicited by magnetic stimulation. When eddy currents which are induced by pulsed magnetic fields flow in the direction from soma to the distal part of neural fiber, depolarized area in the distal part are excited, and the membrane excitation propagates along the nerve fiber. In contrast, when the induced currents flow in the direction from the distal part to soma, hyperpolarized parts block or inhibit neural excitation even if the depolarized parts near the soma can be excited. The model explains our observation that the orientation of the induced current vectors reflect both the functional and anatomical organization of the neural fibers in the brain.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.347801
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  • 3
    Electronic Resource
    Electronic Resource
    Control of heat transport in heat pipes by magnetic fields : 35th annual conference on magnetism and magnetic materials (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 4925-4927 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have observed that gas flow can be blocked or disturbed by magnetic fields. To explain this phenomenon, we developed a model called a "magnetic curtain'' based on the paramagnetic properties of the oxygen molecule. In this paper, we applied this phenomenon to the control of heat transport in heat pipes. We used a heat pipe 20 mm in diameter and 500 mm in length packed with oxygen as a working fluid. We positioned this device vertically in an airgap 70-mm wide between the poles of electromagnet with 240 mm in diameter, in the direction perpendicular to the axis of the magnetic poles. The top side of the heat pipe was chilled with liquid nitrogen (77 K), and the lower side of the heat pipe was exposed to the room temperature (290 K). The efficiency of heat transport was measured by monitoring the change of the temperature at seven points inside and outside of the heat pipe in response to the step change of the top temperature from 290 to 77 K. When the middle part of the heat pipe was exposed to magnetic fields of 1.0 T with the gradient of 5–50 T/m, the heat transport was apparently blocked.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.348202
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  • 4
    Electronic Resource
    Electronic Resource
    Spinal reflex evoked by a pair of opposing pulsed magnetic fields : 35th annual conference on magnetism and magnetic materials (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 6019-6021 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A noninvasive method of magnetic stimulation of the spinal roots was designed. The basic idea is to concentrate induced eddy currents in a target by a pair of opposing pulsed magnetic fields. A figure-eight coil was positioned outside the median of the back so that time varying magnetic fields pass through the body in opposite directions around the target. Magnetic stimulation of the spinal roots of human and a rabbit was carried out. It was found that each spine level can be stimulated selectively, producing electromyographic waves related to both the H-reflex and M-wave. The results indicate that the M-wave can be produced by currents flowing either in the rostral or caudal direction, whereas the H-reflex is only generated by currents flowing in the caudal direction. The H-reflex elicited by magnetic stimulation of nerves in the vicinity of the spine becomes a new tool in diagnosis of neuromuscular system diseases.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.347798
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  • 5
    Electronic Resource
    Electronic Resource
    Effects of magnetic fields on combustion (abstract) (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 67 (1990), S. 5477-5477 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have observed a phenomenon that candle flames are pressed down by magnetic fields. We have also observed that flows of gases such as carbon dioxide and oxygen are blocked by magnetic fields. A model, called a "magnetic curtain,'' has been introduced to explain these phenomena. The magnetic curtain is a wall of air which is produced by magnetic fields. We have demonstrated an experiment to show that candle flames are quenched by the magnetic curtain. The present study focuses on the mechanism of the phenomena involving quenching of flames using magnetic fields. An electromagnet with a pair of columnar magnetic poles in which inner sidepieces were hollowed out was used first. Magnetic fields of 1.5 T at the brim gave a gradient of 50–300 T/m in the direction perpendicular to the pole axis. Alcohol was burned in the hollowed space between magnetic poles. Gases around flames in the hollowed space were sampled into gas sensors through an inhalation nozzle. Oxygen, carbon dioxide, and carbon monoxide were simultaneously measured during the combustion of methanol and ethanol. During magnetic field exposures, oxygen concentration decreased, whereas concentrations of carbon dioxide and carbon monoxide increased. However, when flames were quenced in a few seconds, oxygen concentration in the hallowed space was not changed, and very little of carbon dioxide and carbon monoxide were produced. The interception of a small amount of oxygen near the surface of the flames may quench flames. Emission spectra of flames of methanol and ethanol were measured before, during, and after magnetic field exposures, using both uniform and gradient magnetic fields. Intensity of the OH radical was not changed by magnetic fields up to 1.6 T, whereas the emission intensity was increased when the product of magnetic fields and the gradient increased.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.345855
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  • 6
    Electronic Resource
    Electronic Resource
    The Simian Virus 40 Large T Antigen Does Not Inhibit Translation of the 14-kDa Myelin Basic Protein mRNA in Reticulocyte Lysates or in Transfected Cells (1995)
    Oxford, UK : Blackwell Science Ltd
    Journal of neurochemistry 64 (1995), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: Viral T antigens are transcription factors that have been suspected of inhibiting expression of the myelin basic protein (MBP) mRNA at the translational level in vitro and in vivo. The effect of simian virus 40 (SV40) large T antigen (T-ag) was examined on the translation of the 14-kDa MBP mRNA in reticulocyte lysates and on MBP expression after transfection into cells that express SV40 T-ag. SV40 T-ag did not inhibit translation of 14-kDa MBP cRNAs in cell-free translations even at 30 µM (∼600 µg/ml) T-ag. Permanent transfection of COS-1 cells (which endogenously express SV40 T-ag) with the 14-kDa MBP cDNA resulted in the expression of the 14-kDa MBP as determined by western blot analysis. Permanent transfection of N20.1 cells, an oligodendrocyte line immortalized with a temperature-sensitive SV40 T-ag, with the 14-kDa MBP cDNA construct also resulted in the expression of the 14-kDa MBP under conditions in which the cells expressed functional SV40 T-ag. These results indicate that SV40 T-ag does not prevent expression of the MBP gene at the translational level and that in those immortalized oligodendrocyte lines that express MBP mRNA, but not MBP protein, some factor other than the SV40 large T-ag is responsible for the posttranscriptional regulation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1471-4159.1995.64020928.x
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  • 7
    Electronic Resource
    Electronic Resource
    Measurement of clottability of fibrin polymers using magnetic orientation : The 40th annual conference on magnetism and magnetic materials (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 4708-4710 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Fibrin polymers, as a kind of diamagnetic material, are oriented parallel to the direction of magnetic fields. We investigated the polymerization of partially digested fibrinogens in an 8 T magnetic field in order to observe the clotting ability of various sizes of fibrinogen fractions using a magnetic orientation technique. We purified high-molecular weight fraction (F1) and low-molecular weight fraction from human fibrinogen (F2). Fibrin gels were formed in an 8 T magnetic field for 9 h, and transmittancies were measured to evaluate the degree of magnetic orientation. The results show that a lack at the C-terminal half of one Aα chain did not affect the magnetic orientation of fibrin. We also investigated the effect of the digestion of fibrinogen by plasmin on the magnetic orientation of fibrin. The result shows that partially digested fibrin molecules also orient in an 8 T magnetic field. However, the degree of magnetic orientation significantly decreases when fragment X and fragment Y appear. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.361647
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  • 8
    Electronic Resource
    Electronic Resource
    Catalytic activity of catalase under strong magnetic fields of up to 8 T : The 40th annual conference on magnetism and magnetic materials (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 4705-4707 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The question of whether or not magnetic fields affect enzymatic activity is of considerable interest in biomagnetics and biochemistry. This study focuses on whether magnetically related enzymatic activities can be affected by magnetic fields. We examined the effect of magnetic fields of up to 8 T on catalytic decomposition of hydrogen peroxide (H2O2). We observed changes in absorbance of reaction mixture of hydrogen peroxide and catalase at 240 nm, during and after magnetic field exposures. When the reaction mixture was not treated with nitrogen-gas bubbling, it was observed that the initial reaction rate of the reaction which was exposed to magnetic fields of up to 8 T was 50%–85% lower than the control data. This magnetic field effect was not observed, however, when the reaction mixture was bubbled with nitrogen gas to remove the dissolved oxygen molecules which were produced in the solution. We also measured concentration of dissolved oxygen which was produced by the decomposition of hydrogen peroxide. Dissolved oxygen concentration in the reaction mixture which was exposed to magnetic fields increased 20%–25% compared to the control solution. The results of the present study indicate that magnetic fields affect dynamic movement of oxygen bubbles which are produced in the reaction mixture by the decomposition of hydrogen peroxide, but not the catalytic activity of catalase itself. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.361646
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  • 9
    Electronic Resource
    Electronic Resource
    Bioluminescence under static magnetic fields : The 7th joint MMM-intermag conference on magnetism and magnetic materials (1998)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 83 (1998), S. 6456-6458 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In the present study, the effect of magnetic fields on the emission of light by a living system was studied. The fireflies Hotaria parvula and Luciola cruciata were used as the bioluminescence systems. The firefly light organ was fixed at the edge of an optical fiber. The emitted light was introduced into a single-channel photon-counting system using an optical fiber. We measured both the spectrum of a constant light emission and, the time course of bioluminescence pulses. Two horizontal-type superconducting magnets, which produced 8 and 14 T magnetic fields at their center, were used as the magnetic-field generators. We also carried out an in vitro study of bioluminescence. The enzymatic activity of luciferase was measured under a 14 T magnetic field. We measured emission spectra of bioluminescence over the interval 500–600 nm at 25 °C in a stable emission state. It was observed that the peak wavelength around 550 nm shifted to 560 nm under a 14 T magnetic field. However, the effects of magnetic fields were not significant. Also, we measured the time course of emissions at 550 nm in a transient emission state. The rate in the light intensity under a 14 T magnetic field increased compared to the control. There is a possibility that the change in the emission intensities under a magnetic field is related to a change in the biochemical systems of the firefly, such as the enzymatic process of luciferase and the excited singlet state with subsequent light emission. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.367736
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  • 10
    Electronic Resource
    Electronic Resource
    Measurements of biomagnetic fields using a high-resolution dc superconducting quantum interference device magnetometer : The 7th joint MMM-intermag conference on magnetism and magnetic materials (1998)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 83 (1998), S. 6465-6467 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have developed a multichannel high-resolution superconducting quantum interference device magnetometer for measuring biomagnetic fields produced by small animals. We measured the magnetocardiogram produced by a rat. Topographies of the P wave, QRS wave, and T wave of the rat magnetocardiogram were obtained. We also measured the magnetoretinogram, visually evoked magnetic fields, and auditory evoked magnetic fields of the rat. The signals of the magnetoretinogram appeared at 60 ms latency and the field intensities were about 0.6 pT. It was not possible to obtain the clear visually evoked fields because those signals were hidden behind the magnetoretinogram. It was possible to obtain auditory evoked magnetic fields of the rat. The significant differences of the wave forms were observed in both sides of the right ear, which are separated by 15 mm. Our system has adequate spatial resolution for measurement of the magnetocardiogram and auditory evoked magnetic fields produced by small animals. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.367739
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