14,105 research outputs found
Superstatistics
We consider nonequilibrium systems with complex dynamics in stationary states
with large fluctuations of intensive quantities (e.g. the temperature, chemical
potential, or energy dissipation) on long time scales. Depending on the
statistical properties of the fluctuations, we obtain different effective
statistical mechanics descriptions. Tsallis statistics is one, but other
classes of generalized statistics are obtained as well. We show that for small
variance of the fluctuations all these different statistics behave in a
universal way.Comment: 12 pages /a few more references and comments added in revised versio
Generalized statistical mechanics and fully developed turbulence
The statistical properties of fully developed hydrodynamic turbulence can be
successfully described using methods from nonextensive statistical mechanics.
The predicted probability densities and scaling exponents precisely coincide
with what is measured in various turbulence experiments. As a dynamical basis
for nonextensive behaviour we consider nonlinear Langevin equations with
fluctuating friction forces, where Tsallis statistics can be rigorously proved.Comment: 10 pages, 4 figures. To appear in Physica A (Proceedings of Statphys
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The basic analytics of access to financial services
Access to financial services, or rather the lack thereof, is often indiscriminately decried as a problem in many developing countries. The authors argue that the"problem of access"should rather be analyzed by identifying different demand and supply constraints. They use the concept of an access possibilities frontier, drawn for a given set of state variables, to distinguish between cases where a financial system settles below the constrained optimum, cases where this constrained optimum is too low, and-in credit services-cases where the observed outcome is excessively high. They distinguish between payment and savings services and fixed intermediation costs, on the one hand, and lending services and different sources of credit risk, on the other hand. The authors include both supply and demand side frictions that can lead to lower access. The analysis helps identify bankable and banked population, the binding constraint to close the gap between the two, and policies to prudently expand the bankable population. This new conceptual framework can inform the debate on adequate policies to expand access to financial services and can serve as the basis for an informed measurement of access.Banks&Banking Reform,Economic Theory&Research,Markets and Market Access,Access to Markets,Financial Intermediation
Anxiety: An Evolutionary Approach
Anxiety disorders are among the most common mental illnesses, with huge attendant suffering. Current treatments are not universally effective, suggesting that a deeper understanding of the causes of anxiety is needed. To understand anxiety disorders better, it is first necessary to understand the normal anxiety response. This entails considering its evolutionary function as well as the mechanisms underlying it. We argue that the function of the human anxiety response, and homologues in other species, is to prepare the individual to detect and deal with threats. We use a signal detection framework to show that the threshold for expressing the anxiety response ought to vary with the probability of threats occurring, and the individual's vulnerability to them if they do occur. These predictions are consistent with major patterns in the epidemiology of anxiety. Implications for research and treatment are discussed
An observational test for correlations between cosmic rays and magnetic fields
We derive the magnitude of fluctuations in total synchrotron intensity in the
Milky Way and M33, from both observations and theory under various assumption
about the relation between cosmic rays and interstellar magnetic fields. Given
the relative magnitude of the fluctuations in the Galactic magnetic field (the
ratio of the rms fluctuations to the mean magnetic field strength) suggested by
Faraday rotation and synchrotron polarization, the observations are
inconsistent with local energy equipartition between cosmic rays and magnetic
fields. Our analysis of relative synchrotron intensity fluctuations indicates
that the distribution of cosmic rays is nearly uniform at the scales of the
order of and exceeding 100\p, in contrast to strong fluctuations in the
interstellar magnetic field at those scales. A conservative upper limit on the
ratio of the the fluctuation magnitude in the cosmic ray number density to its
mean value is 0.2--0.4 at scales of order 100\,pc. Our results are consistent
with a mild anticorrelation between cosmic-ray and magnetic energy densities at
these scales, in both the Milky Way and M33. Energy equipartition between
cosmic rays and magnetic fields may still hold, but at scales exceeding 1\,kpc.
Therefore, we suggest that equipartition estimates be applied to the observed
synchrotron intensity smoothed to a linear scale of kiloparsec order (in spiral
galaxies) to obtain the cosmic ray distribution and a large-scale magnetic
field. Then the resulting cosmic ray distribution can be used to derive the
fluctuating magnetic field strength from the data at the original resolution.
The resulting random magnetic field is likely to be significantly stronger than
existing estimates.Comment: submitted to MNRA
Experimental Lagrangian Acceleration Probability Density Function Measurement
We report experimental results on the acceleration component probability
distribution function at to probabilities of less than
. This is an improvement of more than an order of magnitude over past
measurements and allows us to conclude that the fourth moment converges and the
flatness is approximately 55. We compare our probability distribution to those
predicted by several models inspired by non-extensive statistical mechanics. We
also look at acceleration component probability distributions conditioned on a
velocity component for conditioning velocities as high as 3 times the standard
deviation and find them to be highly non-Gaussian.Comment: submitted for the special issue of Physica D: "Anomalous
Distributions" 11 pages, 6 figures revised version: light modifications of
the figures and the tex
Regional perturbation of gene transcription is associated with intrachromosomal rearrangements and gene fusion transcripts in high grade ovarian cancer.
Genomic rearrangements are a hallmark of cancer biology and progression, allowing cells to rapidly transform through alterations in regulatory structures, changes in expression patterns, reprogramming of signaling pathways, and creation of novel transcripts via gene fusion events. Though functional gene fusions encoding oncogenic proteins are the most dramatic outcomes of genomic rearrangements, we investigated the relationship between rearrangements evidenced by fusion transcripts and local expression changes in cancer using transcriptome data alone. 9,953 gene fusion predictions from 418 primary serious ovarian cancer tumors were analyzed, identifying depletions of gene fusion breakpoints within coding regions of fused genes as well as an N-terminal enrichment of breakpoints within fused genes. We identified 48 genes with significant fusion-associated upregulation and furthermore demonstrate that significant regional overexpression of intact genes in patient transcriptomes occurs within 1 megabase of 78 novel gene fusions that function as central markers of these regions. We reveal that cancer transcriptomes select for gene fusions that preserve protein and protein domain coding potential. The association of gene fusion transcripts with neighboring gene overexpression supports rearrangements as mechanism through which cancer cells remodel their transcriptomes and identifies a new way to utilize gene fusions as indicators of regional expression changes in diseased cells with only transcriptomic data
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