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11.
M. Meyer M.D. Ph.D. A. Rahmel C. Marconi B. Grassi J. E. Skinner P. Cerretelli 《Integrative psychological & behavioral science》1998,33(1):9-40
The dynamics of heartbeat interval time series over large time scales were studied by a modifed random walk analysis introduced
recently asDetrended Fluctuation Analysis. In this analysis, the intrinsic fractal long-range power-law correlation properties of beat-to-beat fluctuations generated
by the dynamical system (i.e., cardiac rhythm generator), after decomposition from extrinsic uncorrelated sources, can be
quantified by the scaling exponent (α) which, in healthy subjects, for time scales of ∼104 beats is ∼1.0. The effects of chronic hypoxia were determined from serial heartbeat interval time series of digitized twenty-four-hour
ambulatory ECGs recorded in nine healthy subjects (mean age thirty-four years old) at sea level and during a sojourn at 5,050
m for thirty-four days (Ev-K2-CNR Pyramid Laboratory, Sagarmatha National Park, Nepal). The group averaged α exponent (±SD)
was 0.99±0.04 (range 0.93–1.04). Longitudinal assessment of α in individual subjects did not reveal any effect of exposure
to chronic high altitude hypoxia. The finding of α∼1 indicating scale-invariant long-range power-law correlations (1/f noise) of heartbeat fluctuations would reflect a genuinely self-similar fractal process that typically generates fluctuations
on a wide range of time scales. Lack of a characteristic time scale along with the absence of any effect from exposure to
chronic hypoxia on scaling properties suggests that the neuroautonomic cardiac control system is preadapted to hypoxia which
helps prevent excessive mode-locking (error tolerance) that would restrict its functional responsiveness (plasticity) to hypoxic
or other physiological stimuli.
Editorial Note: A philosopher is, by definition, a lover of wisdom. In the following article, Dr. Dimitrov, as a philosopher, examines the
principles that underlie being and thinking as performed by the structures of the brain. He reports his thoughts in a “virtual
context.” Virtual, a word enjoying great popularity today, is derived from the Latin word for man; it describes manliness
and implies apparent, but not actual, power.
In his analysis of how information is dealt with by the human being, the author uses theoretical physics and mathematics that
may seem arcane to some readers. A major aspect of his thesis declares that the effective performance of information systems
relies not on the structures involved, but on the way they interact. 相似文献
12.
Diego Marconi 《Erkenntnis》2006,65(3):301-318
The claim that truth is mind dependent has some initial plausibility only if truth bearers are taken to be mind dependent
entities such as beliefs or statements. Even on that assumption, however, the claim is not uncontroversial. If it is spelled
out as the thesis that “in a world devoid of mind nothing would be true”, then everything depends on how the phrase ‘true
in world w’ is interpreted. If ‘A is true in w’ is interpreted as ‘A is true of
w’ (i.e. ‘w satisfies A’s truth conditions’, the claim need not be true. If on the other hand it is interpreted as ‘A is true of w
and exists in w’ then the claim is trivially true, though devoid of any antirealistic efficacy. Philosophers like Heidegger and Rorty, who
hold that truth is mind dependent but reality is not, must regard such principles as “A if and only if it is true that A”
as only contingently true, which may be a good reason to reject the mind dependence of truth anyway. 相似文献
13.
The design of the present study enabled the authors to distinguish between the possible effects of movement displacement and trajectory length on the pattern of final positions of planar reaching movements. With their eyes closed, 9 subjects performed series of fast and accurate movements from different initial positions to the same target. For some series, the movements were unconstrained and were therefore performed along an approximately straight vertical line. For other series, an obstacle was positioned so that trajectory length was increased because of an increase in movement curvature. Ellipses of variability obtained by means of principal component analysis applied to the scatter of movement final positions enabled the authors to assess the pattern of movement variable errors. The results showed that the orientation of the ellipses was not affected by movement displacement or by trajectory length, whereas variable errors increased with movement displacement. An increase in trajectory length as a consequence of increased curvature caused no change in variable error. From the perspective of current motor control theory, that finding was quite unexpected. Further studies are required so that one can distinguish among the possible effects of various kinematics, kinetics, and other variables that could affect the pattern of variable errors of reaching movements. 相似文献