5,370 research outputs found
Correlations, Risk and Crisis: From Physiology to Finance
We study the dynamics of correlation and variance in systems under the load
of environmental factors. A universal effect in ensembles of similar systems
under the load of similar factors is described: in crisis, typically, even
before obvious symptoms of crisis appear, correlation increases, and, at the
same time, variance (and volatility) increases too. This effect is supported by
many experiments and observations of groups of humans, mice, trees, grassy
plants, and on financial time series.
A general approach to the explanation of the effect through dynamics of
individual adaptation of similar non-interactive individuals to a similar
system of external factors is developed. Qualitatively, this approach follows
Selye's idea about adaptation energy.Comment: 42 pages, 15 figures, misprints corrections, a proof is added,
improved journal versio
Phase and Intensity Distributions of Individual Pulses of PSR B0950+08
The distribution of the intensities of individual pulses of PSR B0950+08 as a
function of the longitudes at which they appear is analyzed. The flux density
of the pulsar at 111 MHz varies strongly from day to day (by up to a factor of
13) due to the passage of the radiation through the interstellar plasma
(interstellar scintillation). The intensities of individual pulses can exceed
the amplitude of the mean pulse profile, obtained by accumulating 770 pulses,
by more than an order of magnitude. The intensity distribution along the mean
profile is very different for weak and strong pulses. The differential
distribution function for the intensities is a power law with index n = -1.1 +-
0.06 up to peak flux densities for individual pulses of the order of 160 Jy
Evolution of adaptation mechanisms: adaptation energy, stress, and oscillating death
In 1938, H. Selye proposed the notion of adaptation energy and published
"Experimental evidence supporting the conception of adaptation energy".
Adaptation of an animal to different factors appears as the spending of one
resource. Adaptation energy is a hypothetical extensive quantity spent for
adaptation. This term causes much debate when one takes it literally, as a
physical quantity, i.e. a sort of energy. The controversial points of view
impede the systematic use of the notion of adaptation energy despite
experimental evidence. Nevertheless, the response to many harmful factors often
has general non-specific form and we suggest that the mechanisms of
physiological adaptation admit a very general and nonspecific description.
We aim to demonstrate that Selye's adaptation energy is the cornerstone of
the top-down approach to modelling of non-specific adaptation processes. We
analyse Selye's axioms of adaptation energy together with Goldstone's
modifications and propose a series of models for interpretation of these
axioms. {\em Adaptation energy is considered as an internal coordinate on the
`dominant path' in the model of adaptation}. The phenomena of `oscillating
death' and `oscillating remission' are predicted on the base of the dynamical
models of adaptation. Natural selection plays a key role in the evolution of
mechanisms of physiological adaptation. We use the fitness optimization
approach to study of the distribution of resources for neutralization of
harmful factors, during adaptation to a multifactor environment, and analyse
the optimal strategies for different systems of factors
Position-sensitive detector for the 6-meter optical telescope
The Position-Sensitive Detector (PSD) for photometrical and spectral
observation on the 6-meter optical telescope of the Special Astrophysical
Observatory (Russia) is described. The PSD consists of a position-sensitive
tube, amplifiers of output signals, analog-to-digital converters (ADC) and a
digital logic plate, which produces a signal for ADC start and an external
strob pulse for reading information by registration system. If necessary, the
thermoelectric cooler can be used. The position-sensitive tube has the
following main elements: a photocathode, electrodes of inverting optics, a
block of microchannel plates (MCP) and a position-sensitive collector of
quadrant type. The main parameters of the PSD are the diameter of the sensitive
surface is 25 mm, the spatial resolution is better than 100 (\mu)m in the
centre and a little worse on the periphery; the dead time is near 0.5 (\mu)s;
the detection quantum efficiency is defined by the photocathode and it is not
less than 0.1, as a rule; dark current is about hundreds of cps, or less, when
cooling. PSD spectral sensitivity depends on the type of photocathode and input
window material. We use a multialkali photocathode and a fiber or UV-glass,
which gives the short- wave cut of 360 nm or 250 nm, respectively.Comment: 4 pages, 7 figures, to be published in Nuclear Instruments & Methods
in Physics Researc
Formation of the lexemes corpus for the level model development of language
The article deals with the principles of selection of factual material on the problem of fixing language invariants and variant
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