排序方式: 共有42条查询结果,搜索用时 15 毫秒
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Multifractality in human heartbeat dynamics. 总被引:35,自引:0,他引:35
P C Ivanov L A Amaral A L Goldberger S Havlin M G Rosenblum Z R Struzik H E Stanley 《Nature》1999,399(6735):461-465
There is evidence that physiological signals under healthy conditions may have a fractal temporal structure. Here we investigate the possibility that time series generated by certain physiological control systems may be members of a special class of complex processes, termed multifractal, which require a large number of exponents to characterize their scaling properties. We report on evidence for multifractality in a biological dynamical system, the healthy human heartbeat, and show that the multifractal character and nonlinear properties of the healthy heart rate are encoded in the Fourier phases. We uncover a loss of multifractality for a life-threatening condition, congestive heart failure. 相似文献
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TGF-beta-induced Foxp3 inhibits T(H)17 cell differentiation by antagonizing RORgammat function 总被引:2,自引:0,他引:2
Zhou L Lopes JE Chong MM Ivanov II Min R Victora GD Shen Y Du J Rubtsov YP Rudensky AY Ziegler SF Littman DR 《Nature》2008,453(7192):236-240
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Niikura H Légaré F Hasbani R Bandrauk AD Ivanov MY Villeneuve DM Corkum PB 《Nature》2002,417(6892):917-922
Experience shows that the ability to make measurements in any new time regime opens new areas of science. Currently, experimental probes for the attosecond time regime (10(-18) 10(-15) s) are being established. The leading approach is the generation of attosecond optical pulses by ionizing atoms with intense laser pulses. This nonlinear process leads to the production of high harmonics during collisions between electrons and the ionized atoms. The underlying mechanism implies control of energetic electrons with attosecond precision. We propose that the electrons themselves can be exploited for ultrafast measurements. We use a 'molecular clock', based on a vibrational wave packet in H(2)(+) to show that distinct bunches of electrons appear during electron ion collisions with high current densities, and durations of about 1 femtosecond (10(-15) s). Furthermore, we use the molecular clock to study the dynamics of non-sequential double ionization. 相似文献
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The use of microring resonators to assist in the evanescent field coupling between dissimilar waveguides is proposed and analyzed. Theoretical analysis based on the coupled mode theory and nu-merical example show that complete cross power transfers can be obtained near the microring resonances. Applications of the device include power dividers, low-power thermo-optic or electro-optic switches, and modulators. 相似文献
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Hinkov V Pailhès S Bourges P Sidis Y Ivanov A Kulakov A Lin CT Chen DP Bernhard C Keimer B 《Nature》2004,430(7000):650-654
The fundamental building block of the copper oxide superconductors is a Cu4O4 square plaquette. The plaquettes in most of these materials are slightly distorted to form a rectangular lattice, for which an influential theory predicts that high-transition-temperature (high-T(c)) superconductivity is nucleated in 'stripes' aligned along one of the axes. This theory received strong support from experiments that indicated a one-dimensional character for the magnetic excitations in the high-T(c) material YBa2Cu3O6.6 (ref. 4). Here we report neutron scattering data on 'untwinned' YBa2Cu3O6+x crystals, in which the orientation of the rectangular lattice is maintained throughout the entire volume. Contrary to the earlier claim, we demonstrate that the geometry of the magnetic fluctuations is two-dimensional. Rigid stripe arrays therefore appear to be ruled out over a wide range of doping levels in YBa2Cu3O6+x, but the data may be consistent with liquid-crystalline stripe order. The debate about stripes has therefore been reopened. 相似文献
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S. L. Todorov Yu. G. Grigoriev N. I. Rizhov B. A. Ivanov T. S. Malyutina M. S. Mileva 《Cellular and molecular life sciences : CMLS》1972,28(8):973-974
Zusammenfassung Zur biologischen Dosimetrie wird eine Analyse für die Dizentiks-Ausbeute in Lymphozyten bei in vitro Bestrahlung aus peripherem Menschenblut mit 50-MeV-Protonen durchgeführt. Zur Approximation der experimentellen Befunde erweist sich eine Regressionskurve, entsprechend der GleichungY=(12,6±1,6)×10–5×D
(1,36±0.027) als vorteilhaft. 相似文献
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