共查询到20条相似文献,搜索用时 15 毫秒
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Huang S 《PLoS biology》2012,10(2):e1001274
This study demonstrates that normal yeast cells can be magnetized, and identifies local redox control via carbon metabolism and iron supply as key factors involved in magnetization. 相似文献
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Michael Winklhofer Evelyn Dylda Peter Thalau Wolfgang Wiltschko Roswitha Wiltschko 《Proceedings. Biological sciences / The Royal Society》2013,280(1763)
The avian magnetic compass works in a fairly narrow functional window around the intensity of the local geomagnetic field, but adjusts to intensities outside this range when birds experience these new intensities for a certain time. In the past, the geomagnetic field has often been much weaker than at present. To find out whether birds can obtain directional information from a weak magnetic field, we studied spontaneous orientation preferences of migratory robins in a 4 µT field (i.e. a field of less than 10 per cent of the local intensity of 47 µT). Birds can adjust to this low intensity: they turned out to be disoriented under 4 µT after a pre-exposure time of 8 h to 4 µT, but were able to orient in this field after a total exposure time of 17 h. This demonstrates a considerable plasticity of the avian magnetic compass. Orientation in the 4 µT field was not affected by local anaesthesia of the upper beak, but was disrupted by a radiofrequency magnetic field of 1.315 MHz, 480 nT, suggesting that a radical-pair mechanism still provides the directional information in the low magnetic field. This is in agreement with the idea that the avian magnetic compass may have developed already in the Mesozoic in the common ancestor of modern birds. 相似文献
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Bioferrofluids obtained from carbon coated iron nanoparticles are promising candidates for magnetic drug delivery. The carbon
cages render the particles biocompatible, and provide a good support for drug adsorption. We propose a method in which gold
plated permanent magnets are implanted directly in the affected organ, close to the tumour, by endoscopic techniques. The
bioferrofluid charged with the chemotherapeutic agent is injected and the particles attracted to the magnet, then desorption
of the drug takes place at the tumoral region. This method seems to be more promising, costless and effective than that based
on the application of external magnetic fields. Preliminary results of drug adsorption and a preclinical experimental animal
model are described. 相似文献
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A. B. Mikhailovskii S. V. Konovalov M. S. Shirokov V. S. Tsypin 《Plasma Physics Reports》2004,30(7):549-567
The effect of the magnetic field curvature on magnetic islands in a tokamak is analyzed. It is demonstrated that the original investigation of this effect by Kotschenreuther et al. (1985) is inconsistent: on the one hand, the authors made the correct assumption that this is an ideal effect and, on the other hand, they described it in terms of the parameters characteristic of the “resistive ordering” approach, which is incompatible with the ideal approximation. More recent studies of the magnetic curvature effect have produced further ambiguities; as a result, a branch of the theory of magnetic islands has arisen that is based on the supposition that the effect under discussion can be described in terms of the Glasser-Greene-Johnson parameter DR. This branch is shown to be erroneous, because the parameter DR describes the plasma response to magnetic field perturbations on spatial scales of about the dimension of the linear resistive layer, while the characteristic spatial scale of the magnetic islands is much longer. It is concluded that the correct theory developed here for the magnetic curvature effect makes more optimistic predictions about its stabilizing role. 相似文献
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A. A. Skovoroda 《Plasma Physics Reports》2009,35(4):269-272
The complete set of universal local relationships between geometrical (the curvature and torsion of the force lines of the magnetic field and the field complementary to it) and magnetic (|B|, |?Φ|, b · (? × b), and the local shear s) quantities in currentless magnetic configurations comprising a system of equilibrium nested magnetic surfaces, including those with several magnetic axes, is derived. Possible applications of these relationships are discussed. 相似文献
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I. S. Danilkin 《Plasma Physics Reports》2011,37(7):572-585
A study is made of the boundary regions of magnetic structures formed either near the last closed flux surface of the main
magnetic configuration in a stellarator or near magnetic islands in more general toroidal confinement systems with topologically
equivalent sheared magnetic configurations. With a relatively simple approximate analytic model based on the perturbation
method, it was possible not only to reproduce earlier results on the destruction of hyperbolic magnetic axes in the three-dimensional
toroidal magnetic configurations under consideration but also to obtain some new results, in particular, to analytically estimate
the sizes of the separatrix regions of stochastic magnetic fields that arise in the main stellarator configuration and also
near the inner chains of magnetic islands in any magnetic configuration under consideration. It is notable that the boundary
region of the main stellarator magnetic configuration is a multiply connected structure, the outer part of which is largely
governed by the current distribution in the magnetic system creating this configuration. 相似文献
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Ivo Šafařík Pavel Mucha Jiří Pechoč Jaroslav Stoklasa Mirka Šafaříková 《Biotechnology letters》2001,23(11):851-855
A Davis tube (a matrix-free, flow-through magnetic separator used mainly in mineral processing) has been tested for separation of magnetic affinity biopolymer adsorbents from larger volumes of suspensions. Both magnetic chitosan and magnetic cross-linked erythrocytes could be efficiently separated from litre volumes of suspensions. Up to 90% adsorbent recovery was achieved under optimised separation conditions. 相似文献
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Cytogenetic investigations were performed in human peripheral blood lymphocytes following exposure to 50 Hz magnetic fields alone or in combination with the chemical mutagen mitomycin C or with X-rays. It was found that magnetic fields up to 2500 microT did not significantly influence the chromosome aberration and sister chromatid exchange frequency. Also, the combined treatments failed to indicate the presence of any synergistic, potentiating, or antagonistic effect between the ELF magnetic fields and the mutagens. However, there were two exceptions: Cells exposed to 504 microT magnetic fields before and during cultivation displayed a statistically significant decrease in sister chromatid exchange frequency. Also, when cells were cultivated in the presence of 88.4 microT magnetic fields following X-ray exposures there was a significant increase in chromosome aberration frequency compared to X-ray exposure alone. 相似文献
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The magnetic diver microgasometer 总被引:1,自引:0,他引:1
A magnetic diver microgasometer operated at the constant pressure is described and its application and limitations are evaluated. By the aid of a thin quartz fiber which supports the ampulla the stable equilibrium between bouyancy and magnetic forces is maintained. The control and the sensitivity being independent of the gas volume in the ampulla, reasonably large divers with a low loss of gas can be used. Consequently a sufficient stability is achieved for the measurements of gas changes in the range of 1 × 10−6 μl/hr. 相似文献
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There is public health concern raised by epidemiological studies indicating that extremely low frequency electric and magnetic fields generated by electric power distribution systems in the environment may be hazardous. Possible carcinogenic effects of magnetic field in combination with suggested oncostatic action of melatonin lead to the hypothesis that the primary effects of electric and magnetic fields exposure is a reduction of melatonin synthesis which, in turn, may promote cancer growth. In this review the data on the influence of magnetic fields on melatonin synthesis, both in the animals and humans, are briefly presented and discussed. 相似文献