507 research outputs found
Using Synchronization for Prediction of High-Dimensional Chaotic Dynamics
We experimentally observe the nonlinear dynamics of an optoelectronic
time-delayed feedback loop designed for chaotic communication using commercial
fiber optic links, and we simulate the system using delay differential
equations. We show that synchronization of a numerical model to experimental
measurements provides a new way to assimilate data and forecast the future of
this time-delayed high-dimensional system. For this system, which has a
feedback time delay of 22 ns, we show that one can predict the time series for
up to several delay periods, when the dynamics is about 15 dimensional.Comment: 10 pages, 4 figure
Oscillons: an encounter with dynamical chaos in 1953?
We present evidences that Ben F. Laposky (1914-2000) might have been the
first person who created a family of nonlinear analog circuits that allowed him
to observe chaotic attractors and other trademarks of nonlinear science as
early as 1953.Comment: accepted to Chao
Extracting Lyapunov exponents from the echo dynamics of Bose-Einstein condensates on a lattice
We propose theoretically an experimentally realizable method to demonstrate
the Lyapunov instability and to extract the value of the largest Lyapunov
exponent for a chaotic many-particle interacting system. The proposal focuses
specifically on a lattice of coupled Bose-Einstein condensates in the classical
regime describable by the discrete Gross-Pitaevskii equation. We suggest to use
imperfect time-reversal of system's dynamics known as Loschmidt echo, which can
be realized experimentally by reversing the sign of the Hamiltonian of the
system. The routine involves tracking and then subtracting the noise of
virtually any observable quantity before and after the time-reversal. We
support the theoretical analysis by direct numerical simulations demonstrating
that the largest Lyapunov exponent can indeed be extracted from the Loschmidt
echo routine. We also discuss possible values of experimental parameters
required for implementing this proposal
Analgesic action of acetaminophen in symptomatic osteoarthritis of the knee
Objectives. The study was designed to investigate the analgesic effects and mechanisms of acetaminophen (paracetamol) in symptomatic osteoarthritis (OA) of the knee. Methods. Twenty patients with symptomatic OA were randomly allocated to two groups treated with either acetaminophen or rofecoxib for 3 months. Visits and measurements were scheduled upon entry (T0), at month 1 (T1) and at month 3 (T3). The intensity of joint pain was evaluated with a 100-mm visual analogue scale (VAS). The physical function of the affected knee was evaluated with a questionnaire comparable to the Western Ontario McMaster Universities Osteoarthritis Index (WOMAC). Levels of serotonin, substance P (SP) and β-endorphin (BEND) were determined with commercial enzyme-linked immunoassay kits. The expression of κ opioid receptor (KOR) in peripheral mononuclear blood cells (PBMCs) was quantified by real-time PCR. Results. Both acetaminophen and rofecoxib relieved pain considerably but with different kinetics, and affected different biomarkers. Rofecoxib appeared to be more efficient, reducing pain intensity by 56% at T1 (P<0.01), whereas acetaminophen reduced it by only 29%. Physical function improved in both groups by T3. Correlated with the pain relief, acetaminophen significantly reduced plasma BEND levels, whereas rofecoxib did not do so. In both groups plasma SP levels were elevated compared with T0. A reduction in serum serotonin was detected in the rofecoxib group at T1 (P=0.004) but had recovered at T3. No changes in KOR mRNA in PBMCs were observed in either group. Conclusions. There is a correlation between reduction in circulating BEND and OA pain relief in patients treated with acetaminophe
Analgesic action of acetaminophen in symptomatic osteoarthritis of the knee
Objectives. The study was designed to investigate the analgesic effects and mechanisms of acetaminophen (paracetamol) in symptomatic osteoarthritis (OA) of the knee. Methods. Twenty patients with symptomatic OA were randomly allocated to two groups treated with either acetaminophen or rofecoxib for 3 months. Visits and measurements were scheduled upon entry (T0), at month 1 (T1) and at month 3 (T3). The intensity of joint pain was evaluated with a 100-mm visual analogue scale (VAS). The physical function of the affected knee was evaluated with a questionnaire comparable to the Western Ontario McMaster Universities Osteoarthritis Index (WOMAC). Levels of serotonin, substance P (SP) and β-endorphin (BEND) were determined with commercial enzyme-linked immunoassay kits. The expression of κ opioid receptor (KOR) in peripheral mononuclear blood cells (PBMCs) was quantified by real-time PCR. Results. Both acetaminophen and rofecoxib relieved pain considerably but with different kinetics, and affected different biomarkers. Rofecoxib appeared to be more efficient, reducing pain intensity by 56% at T1 (P<0.01), whereas acetaminophen reduced it by only 29%. Physical function improved in both groups by T3. Correlated with the pain relief, acetaminophen significantly reduced plasma BEND levels, whereas rofecoxib did not do so. In both groups plasma SP levels were elevated compared with T0. A reduction in serum serotonin was detected in the rofecoxib group at T1 (P=0.004) but had recovered at T3. No changes in KOR mRNA in PBMCs were observed in either group. Conclusions. There is a correlation between reduction in circulating BEND and OA pain relief in patients treated with acetaminophe
Falsification Of The Atmospheric CO2 Greenhouse Effects Within The Frame Of Physics
The atmospheric greenhouse effect, an idea that many authors trace back to
the traditional works of Fourier (1824), Tyndall (1861), and Arrhenius (1896),
and which is still supported in global climatology, essentially describes a
fictitious mechanism, in which a planetary atmosphere acts as a heat pump
driven by an environment that is radiatively interacting with but radiatively
equilibrated to the atmospheric system. According to the second law of
thermodynamics such a planetary machine can never exist. Nevertheless, in
almost all texts of global climatology and in a widespread secondary literature
it is taken for granted that such mechanism is real and stands on a firm
scientific foundation. In this paper the popular conjecture is analyzed and the
underlying physical principles are clarified. By showing that (a) there are no
common physical laws between the warming phenomenon in glass houses and the
fictitious atmospheric greenhouse effects, (b) there are no calculations to
determine an average surface temperature of a planet, (c) the frequently
mentioned difference of 33 degrees Celsius is a meaningless number calculated
wrongly, (d) the formulas of cavity radiation are used inappropriately, (e) the
assumption of a radiative balance is unphysical, (f) thermal conductivity and
friction must not be set to zero, the atmospheric greenhouse conjecture is
falsified.Comment: 115 pages, 32 figures, 13 tables (some typos corrected
Probability of local bifurcation type from a fixed point: A random matrix perspective
Results regarding probable bifurcations from fixed points are presented in
the context of general dynamical systems (real, random matrices), time-delay
dynamical systems (companion matrices), and a set of mappings known for their
properties as universal approximators (neural networks). The eigenvalue spectra
is considered both numerically and analytically using previous work of Edelman
et. al. Based upon the numerical evidence, various conjectures are presented.
The conclusion is that in many circumstances, most bifurcations from fixed
points of large dynamical systems will be due to complex eigenvalues.
Nevertheless, surprising situations are presented for which the aforementioned
conclusion is not general, e.g. real random matrices with Gaussian elements
with a large positive mean and finite variance.Comment: 21 pages, 19 figure
The question-behaviour effect: a theoretical and methodological review and meta-analysis
Research has demonstrated that asking people questions about a behaviour can lead to behaviour change. Despite many, varied studies in different domains, it is only recently that this phenomenon has been studied under the umbrella term of the question-behaviour effect (QBE) and moderators of the effect have been investigated. With a particular focus on our own contributions, this article: (1) provides an overview of QBE research; (2) reviews and offers new evidence concerning three theoretical accounts of the QBE (behavioural simulation and processing fluency; attitude accessibility; cognitive dissonance); (3) reports a new meta-analysis of QBE studies (k = 66, reporting 94 tests) focusing on methodological moderators. The findings of this meta-analysis support a small significant effect of the QBE (g = 0.14, 95% CI = 0.11, 0.18, p < .001) with smaller effect sizes observed in more carefully controlled studies that exhibit less risk of bias and (4) also considers directions for future research on the QBE, especially studies that use designs with low risk of bias and consider desirable and undesirable behaviour separately
Why Tenth Graders Fail to Finish High School: A Dropout Typology Latent Class Analysis
A large percentage of the students who drop out of K-12 schools in the United States do so at the end of high school, at some point after grade 10. Yet we know little about the differences between different types of students who drop out of the end of high school. The purpose of this study is to examine a typology of high school dropouts from a large nationally representative dataset (ELS:2002) using latent class analysis (LCA). We found three significantly different types of dropouts; Quiet, Jaded, and Involved. Based on this typology of three subgroups, we discuss implications for future dropout intervention research, policy, and practice
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