3,437 research outputs found
Spatial heterogeneity of air pollution statistics in Europe
Air pollution is one of the leading causes of death globally, and continues to have a detrimental effect on our health. In light of these impacts, an extensive range of statistical modelling approaches has been devised in order to better understand air pollution statistics. However, the time-varying statistics of different types of air pollutants are far from being fully understood. The observed probability density functions (PDFs) of concentrations depend very much on the spatial location and on the pollutant substance. In this paper, we analyse a large variety of data from 3544 different European monitoring sites and show that the PDFs of nitric oxide (NO), nitrogen dioxide ([Formula: see text] ) and particulate matter ([Formula: see text] and [Formula: see text] ) concentrations generically exhibit heavy tails and are asymptotically well approximated by q-exponential distributions with a given width parameter [Formula: see text] . We observe that the power-law parameter q and the width parameter [Formula: see text] vary widely for the different spatial locations. For each substance, we find different patterns of parameter clouds in the [Formula: see text] plane. These depend on the type of pollutants and on the environmental characteristics (urban/suburban/rural/traffic/industrial/background). This means the effective statistical physics description of air pollution exhibits a strong degree of spatial heterogeneity
Calibration of GRB Luminosity Relations with Cosmography
For the use of Gamma-Ray Bursts (GRBs) to probe cosmology in a
cosmology-independent way, a new method has been proposed to obtain luminosity
distances of GRBs by interpolating directly from the Hubble diagram of SNe Ia,
and then calibrating GRB relations at high redshift. In this paper, following
the basic assumption in the interpolation method that objects at the same
redshift should have the same luminosity distance, we propose another approach
to calibrate GRB luminosity relations with cosmographic fitting directly from
SN Ia data. In cosmography, there is a well-known fitting formula which can
reflect the Hubble relation between luminosity distance and redshift with
cosmographic parameters which can be fitted from observation data. Using the
Cosmographic fitting results from the Union set of SNe Ia, we calibrate five
GRB relations using GRB sample at and deduce distance moduli of GRBs
at by generalizing above calibrated relations at high
redshift. Finally, we constrain the dark energy parameterization models of the
Chevallier-Polarski-Linder (CPL) model, the Jassal-Bagla-Padmanabhan (JBP)
model and the Alam model with GRB data at high redshift, as well as with the
Cosmic Microwave Background radiation (CMB) and the baryonic acoustic
oscillation (BAO) observations, and we find the CDM model is
consistent with the current data in 1- confidence region.Comment: 15 pages, 4 figures, 2 tables; accepted for publication in IJMP
Fluctuations in the quark-meson model for QCD with isospin chemical potential
We study the two-flavor quark-meson (QM) model with the functional
renormalization group (FRG) to describe the effects of collective mesonic
fluctuations on the phase diagram of QCD at finite baryon and isospin chemical
potentials, and . With only isospin chemical potential there is
a precise equivalence between the competing dynamics of chiral versus pion
condensation and that of collective mesonic and baryonic fluctuations in the
quark-meson-diquark model for two-color QCD at finite baryon chemical
potential. Here, finite introduces an additional dimension to the
phase diagram as compared to two-color QCD, however. At zero temperature, the
()-plane of this phase diagram is strongly constrained by the
"Silver Blaze problem." In particular, the onset of pion condensation must
occur at , independent of as long as
stays below the constituent quark mass of the QM model or the liquid-gas
transition line of nuclear matter in QCD. In order to maintain this relation
beyond mean field it is crucial to compute the pion mass from its timelike
correlator with the FRG in a consistent way.Comment: 10 pages, 11 figures; matches published versio
Stability of the curvature perturbation in dark sectors' mutual interacting models
We consider perturbations in a cosmological model with a small coupling
between dark energy and dark matter. We prove that the stability of the
curvature perturbation depends on the type of coupling between dark sectors.
When the dark energy is of quintessence type, if the coupling is proportional
to the dark matter energy density, it will drive the instability in the
curvature perturbations; however if the coupling is proportional to the energy
density of dark energy, there is room for the stability in the curvature
perturbations. When the dark energy is of phantom type, the perturbations are
always stable, no matter whether the coupling is proportional to the one or the
other energy density.Comment: 9 page, 4 figures, revised version, accepted for publication in PL
Relation Between Chiral Susceptibility and Solutions of Gap Equation in Nambu--Jona-Lasinio Model
We study the solutions of the gap equation, the thermodynamic potential and
the chiral susceptibility in and beyond the chiral limit at finite chemical
potential in the Nambu--Jona-Lasinio (NJL) model. We give an explicit relation
between the chiral susceptibility and the thermodynamic potential in the NJL
model. We find that the chiral susceptibility is a quantity being able to
represent the furcation of the solutions of the gap equation and the
concavo-convexity of the thermodynamic potential in NJL model. It indicates
that the chiral susceptibility can identify the stable state and the
possibility of the chiral phase transition in NJL model.Comment: 21 pages, 6 figures, misprints are correcte
Cosmological Constraints on the Modified Entropic Force Model
Very recently, Verlinde considered a theory in which space is emergent
through a holographic scenario, and proposed that gravity can be explained as
an entropic force caused by changes in the information associated with the
positions of material bodies. Then, motivated by the Debye model in
thermodynamics which is very successful in very low temperatures, Gao modified
the entropic force scenario. The modified entropic force (MEF) model is in fact
a modified gravity model, and the universe can be accelerated without dark
energy. In the present work, we consider the cosmological constraints on the
MEF model, and successfully constrain the model parameters to a narrow range.
We also discuss many other issues of the MEF model. In particular, we clearly
reveal the implicit root to accelerate the universe in the MEF model.Comment: 16 pages, 7 figures, revtex4; v2: discussions added, Phys. Lett. B in
press; v3: published versio
EphA2 is a functional receptor for the growth factor progranulin.
Although the growth factor progranulin was discovered more than two decades ago, the functional receptor remains elusive. Here, we discovered that EphA2, a member of the large family of Ephrin receptor tyrosine kinases, is a functional signaling receptor for progranulin. Recombinant progranulin bound with high affinity to EphA2 in both solid phase and solution. Interaction of progranulin with EphA2 caused prolonged activation of the receptor, downstream stimulation of mitogen-activated protein kinase and Akt, and promotion of capillary morphogenesis. Furthermore, we found an autoregulatory mechanism of progranulin whereby a feed-forward loop occurred in an EphA2-dependent manner that was independent of the endocytic receptor sortilin. The discovery of a functional signaling receptor for progranulin offers a new avenue for understanding the underlying mode of action of progranulin in cancer progression, tumor angiogenesis, and perhaps neurodegenerative diseases
Identification of a novel heterozygous guanosine monophosphate reductase (GMPR) variant in a patient with a late-onset disorder of mitochondrial DNA maintenance
Autosomal dominant progressive external ophthalmoplegia (adPEO) is a late-onset, Mendelian mitochondrial disorder characterised by paresis of the extraocular muscles, ptosis and skeletal-muscle restricted multiple mitochondrial DNA (mtDNA) deletions. While dominantly-inherited, pathogenic variants in POLG, TWNK and RRM2B are among the most common genetic defects of adPEO, identification of novel candidate genes and the underlying pathomechanisms remain challenging. We report the clinical, genetic and molecular investigations of a patient who presented in the seventh decade of life with PEO. Oxidative histochemistry revealed cytochrome c oxidase deficient fibres and occasional ragged red fibres showing subsarcolemmal mitochondrial accumulation in skeletal muscle, while molecular studies identified the presence of multiple mtDNA deletions. Negative candidate screening of known nuclear genes associated with PEO prompted diagnostic exome sequencing, leading to the prioritisation of a novel heterozygous c.547G > C variant in GMPR (NM_006877.3) encoding guanosine monophosphate reductase, a cytosolic enzyme required for maintaining the cellular balance of adenine and guanine nucleotides. We show that the novel c.547G > C variant causes aberrant splicing, decreased GMPR protein levels in patient skeletal muscle, proliferating and quiescent cells and is associated with subtle changes in nucleotide homeostasis protein levels and evidence of disturbed mtDNA maintenance in skeletal muscle. Despite confirmation of GMPR deficiency, demonstrating marked defects of mtDNA replication or nucleotide homeostasis in patient cells proved challenging. Our study proposes that GMPR is the nineteenth (19th) locus for PEO and highlights the complexities of uncovering disease mechanisms in late-onset PEO phenotypes
- …