1,230 research outputs found
Relaxation in statistical many-agent economy models
We review some statistical many-agent models of economic and social systems
inspired by microscopic molecular models and discuss their stochastic
interpretation. We apply these models to wealth exchange in economics and study
how the relaxation process depends on the parameters of the system, in
particular on the saving propensities that define and diversify the agent
profiles.Comment: Revised final version. 6 pages, 5 figure
Enteroaggregative Escherichia coli: An Emerging Enteric Food Borne Pathogen
Enteroaggregative Escherichia coli (EAEC) are quite heterogeneous category of an emerging enteric pathogen associated with cases of acute or persistent diarrhea worldwide in children and adults, and over the past decade has received increasing attention as a cause of watery diarrhea, which is often persistent. EAEC infection is an important cause of diarrhea in outbreak and non-outbreak settings in developing and developed countries. Recently, EAEC has been implicated in the development of irritable bowel syndrome, but this remains to be confirmed. EAEC is defined as a diarrheal pathogen based on its characteristic aggregative adherence (AA) to HEp-2 cells in culture and its biofilm formation on the intestinal mucosa with a “stacked-brick” adherence phenotype, which is related to the presence of a 60 MDa plasmid (pAA). At the molecular level, strains demonstrating the aggregative phenotype are quite heterogeneous; several virulence factors are detected by polymerase chain reaction; however, none exhibited 100% specificity. Although several studies have identified specific virulence factor(s) unique to EAEC, the mechanism by which EAEC exerts its pathogenesis is, thus, far unknown. The present review updates the current knowledge on the epidemiology, chronic complications, detection, virulence factors, and treatment of EAEC, an emerging enteric food borne pathogen
Dynamic asset trees and Black Monday
The minimum spanning tree, based on the concept of ultrametricity, is
constructed from the correlation matrix of stock returns. The dynamics of this
asset tree can be characterised by its normalised length and the mean
occupation layer, as measured from an appropriately chosen centre called the
`central node'. We show how the tree length shrinks during a stock market
crisis, Black Monday in this case, and how a strong reconfiguration takes
place, resulting in topological shrinking of the tree.Comment: 6 pages, 3 eps figues. Elsevier style. Will appear in Physica A as
part of the Bali conference proceedings, in pres
Feebly-interacting dark matter
We briefly review scenarios with feebly interacting particles (FIMPs) as dark
matter candidates. The discussion covers issues with dark matter production in
the early universe as well as signatures of FIMPs at the high energy and high
intensity frontier as well as in astroparticle and cosmology.Comment: 6 pages, 2 captioned figures. Review article for EPJ ST Special
Issue: Frontier 23: Elementary particle physics, dark matter and
astroparticle physic
UV completion of an axial, leptophobic,
The -portal is one of most popular and well-explored scenarios of dark
matter (DM). To avoid the strong constraints coming from dilepton resonance
searches at the LHC and direct detection of DM, it is usually required that in
addition to being leptophobic, the is axially coupled to either the
(fermionic) DM or the standard model (SM) quarks. The first possibility has
been extensively studied both in the context of simplified model and UV
complete scenarios. However, the studies on the second possibiliy are largely
confined to simplified models only. Here, we construct the minimal UV
completion of these models satisfying both the criteria of leptophobia and
purely axial quark coupling. The anomaly cancellation conditions demand
highly non-trivial structures, not only in the dark sector, but also in the
Higgs sector.Comment: 15 pages. Improved version with phenomenological implications
addressed and references adde
Study of statistical correlations in intraday and daily financial return time series
The aim of this article is to briefly review and make new studies of
correlations and co-movements of stocks, so as to understand the
"seasonalities" and market evolution. Using the intraday data of the CAC40, we
begin by reasserting the findings of Allez and Bouchaud [New J. Phys. 13,
025010 (2011)]: the average correlation between stocks increases throughout the
day. We then use multidimensional scaling (MDS) in generating maps and
visualizing the dynamic evolution of the stock market during the day. We do not
find any marked difference in the structure of the market during a day. Another
aim is to use daily data for MDS studies, and visualize or detect specific
sectors in a market and periods of crisis. We suggest that this type of
visualization may be used in identifying potential pairs of stocks for "pairs
trade".Comment: 22 pages, 11 figures, Springer-Verlag format. To appear in the
conference proceedings of Econophys-Kolkata VI: "Econophysics of systemic
risk and network dynamics", Eds. F. Abergel, B.K. Chakrabarti, A. Chakraborti
and A. Ghosh, to be published by Springer-Verlag (Italia), Milan (2012
Raman anomalies as signatures of pressure induced electronic topological and structural transitions in black phosphorus: Experiments and Theory
We report high pressure Raman experiments of Black phosphorus up to 24 GPa.
The line widths of first order Raman modes A, B and A of the
orthorhombic phase show a minimum at 1.1 GPa. Our first-principles density
functional analysis reveals that this is associated with the anomalies in
electron-phonon coupling at the semiconductor to topological insulator
transition through inversion of valence and conduction bands marking a change
from trivial to nontrivial electronic topology. The frequencies of B and
A modes become anomalous in the rhombohedral phase at 7.4 GPa, and new
modes appearing in the rhombohedral phase show anomalous softening with
pressure. This is shown to originate from unusual structural evolution of black
phosphorous with pressure, based on first-principles theoretical analysis.Comment: 13pages, 12figure
Relativistic supernovae have shorter-lived central engines or more extended progenitors: the case of SN\,2012ap
Deep late-time X-ray observations of the relativistic, engine-driven, type Ic
SN2012ap allow us to probe the nearby environment of the explosion and reveal
the unique properties of relativistic SNe. We find that on a local scale of
~0.01 pc the environment was shaped directly by the evolution of the progenitor
star with a pre-explosion mass-loss rate <5x10^-6 Msun yr-1 in line with GRBs
and the other relativistic SN2009bb. Like sub-energetic GRBs, SN2012ap is
characterized by a bright radio emission and evidence for mildly relativistic
ejecta. However, its late time (t~20 days) X-ray emission is ~100 times fainter
than the faintest sub-energetic GRB at the same epoch, with no evidence for
late-time central engine activity. These results support theoretical proposals
that link relativistic SNe like 2009bb and 2012ap with the weakest observed
engine-driven explosions, where the jet barely fails to breakout. Furthermore,
our observations demonstrate that the difference between relativistic SNe and
sub-energetic GRBs is intrinsic and not due to line-of-sight effects. This
phenomenology can either be due to an intrinsically shorter-lived engine or to
a more extended progenitor in relativistic SNe.Comment: Version accepted to ApJ. Significantly broadened discussio
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