1,259 research outputs found
A model based framework for air quality indices and population risk evaluation, with an application to the analysis of Scottish air quality data
The paper is devoted to the development of a statistical framework for air quality assessment at the country level and for the evaluation of the ambient population exposure and risk with respect to airborne pollutants. The framework is based on a multivariate space–time model and on aggregated indices defined at different levels of aggregation in space and time. The indices are evaluated, uncertainty included, by considering both the model outputs and the information on the population spatial distribution. The framework is applied to the analysis of air quality data for Scotland for 2009 referring to European and Scottish air quality legislation
On the robustness of acoustic black hole spectra
We study the robustness of the spectrum emitted by an acoustic black hole by
considering series of stationary flows that become either subsonic or
supersonic, i.e. when the horizon disappears. We work with the superluminal
Bogoliubov dispersion of Bose--Einstein condensates. We find that the spectrum
remains remarkably Planckian until the horizon disappears. When the flow is
everywhere supersonic, new pair creation channels open. This will be the
subject of a forthcoming work.Comment: 4 pages, 2 figure, jpconf.cls; to appear in the proceedings of the
Spanish Relativity Meeting ERE201
Instability of the superfluid flow as black-hole lasing effect
We show that the instability leading to the decay of the one-dimensional
superfluid flow through a penetrable barrier are due to the black-hole lasing
effect. This dynamical instability is triggered by modes resonating in an
effective cavity formed by two horizons enclosing the barrier. The location of
the horizons is set by , with being the local fluid
velocity and sound speed, respectively. We compute the critical velocity
analytically and show that it is univocally determined by the horizons
configuration. In the limit of broad barriers, the continuous spectrum at the
origin of the Hawking-like radiation and of the Landau energetic instability is
recovered.Comment: 18 pages, 3 figure
Neurodegeneration with brain iron accumulation: update on pathogenic mechanisms.
Perturbation of iron distribution is observed in many neurodegenerative disorders, including Alzheimer's and Parkinson's disease, but the comprehension of the metal role in the development and progression of such disorders is still very limited. The combination of more powerful brain imaging techniques and faster genomic DNA sequencing procedures has allowed the description of a set of genetic disorders characterized by a constant and often early accumulation of iron in specific brain regions and the identification of the associated genes; these disorders are now collectively included in the category of neurodegeneration with brain iron accumulation (NBIA). So far 10 different genetic forms have been described but this number is likely to increase in short time. Two forms are linked to mutations in genes directly involved in iron metabolism: neuroferritinopathy, associated to mutations in the FTL gene and aceruloplasminemia, where the ceruloplasmin gene product is defective. In the other forms the connection with iron metabolism is not evident at all and the genetic data let infer the involvement of other pathways: Pank2, Pla2G6, C19orf12, COASY, and FA2H genes seem to be related to lipid metabolism and to mitochondria functioning, WDR45 and ATP13A2 genes are implicated in lysosomal and autophagosome activity, while the C2orf37 gene encodes a nucleolar protein of unknown function. There is much hope in the scientific community that the study of the NBIA forms may provide important insight as to the link between brain iron metabolism and neurodegenerative mechanisms and eventually pave the way for new therapeutic avenues also for the more common neurodegenerative disorders. In this work, we will review the most recent findings in the molecular mechanisms underlining the most common forms of NBIA and analyze their possible link with brain iron metabolism
Black hole lasers in Bose-Einstein condensates
We consider elongated condensates that cross twice the speed of sound. In the
absence of periodic boundary conditions, the phonon spectrum possesses a
discrete and finite set of complex frequency modes that induce a laser effect.
This effect constitutes a dynamical instability and is due to the fact that the
supersonic region acts as a resonant cavity. We numerically compute the complex
frequencies and density-density correlation function. We obtain patterns with
very specific signatures. In terms of the gravitational analogy, the flows we
consider correspond to a pair of black hole and white hole horizons, and the
laser effect can be conceived as a self-amplified Hawking radiation. This is
verified by comparing the outgoing flux at early time with the standard black
hole radiation.Comment: iopams, 37 pages, 14 figures, 1 table; for associated gif animations,
see http://people.sissa.it/~finazzi/bec_bhlasers/movies/ or
http://iopscience.iop.org/1367-2630/12/9/095015/media. Published on New. J.
Phys. (http://iopscience.iop.org/1367-2630/12/9/095015/). V2: few new
comments, modified figure
Recent finding and new technologies in nephrolithiasis: a review of the recent literature
This review summarizes recent literature on advances regarding renal and ureteral
calculi, with particular focus in areas of recent advances in the overall field
of urolithiasis. Clinical management in everyday practice requires a complete
understanding of the issues regarding metabolic evaluation and subgrouping of
stone-forming patients, diagnostic procedures, effective treatment regime in
acute stone colic, medical expulsive therapy, and active stone removal. In this
review we focus on new perspectives in managing nephrolitihiasis and discuss
recentadvances, including medical expulsive therapy, new technologies, and
refinements of classical therapy such as shock wave lithotripsy, give a
fundamental modification of nephrolithiasis management. Overall, this field
appears to be the most promising, capable of new developments in ureterorenoscopy
and percutaneous approaches. Further improvements are expected from
robotic-assisted procedures, such as flexible robotics in ureterorenoscopy
Modification of magnetic and transport properties of manganite layers in Au/La_0.67Sr_0.33MnO_3/SrTiO_3 interfaces
The effect of gold capping on magnetic and transport properties of optimally
doped manganite thin films is studied. An extraordinary suppression of
conductivity and magnetic properties occurs in epitaxial (001)
La_0.67Sr_0.33MnO_3 (LSMO) films grown on SrTiO_3 upon deposition of 2 nm of
Au: in the case of ultrathin films of LSMO (4 nm thick) the resistivity
increases by four orders of magnitude while the Curie temperature decreases by
180 K. Zero-field 55Mn nuclear magnetic resonance reveals a significant
reduction of ferromagnetic double-exchange mechanism in manganite films upon
the gold capping. We find evidence for the formation of a 1.9-nm thick magnetic
"dead-layer" at the Au/LSMO interface, associated with the creation of
interfacial non double-exchange insulating phases.Comment: 4 figure
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