3,423 research outputs found
Steering a quantum system over a Schroedinger bridge
A new approach to the steering problem for quantum systems relying on
Nelson's stochastic mechanics and on the theory of Schroedinger bridges is
presented. The method is illustrated by working out a simple Gaussian example.Comment: Proc. Intern. Conf. on the Mathematical Theory of Networks and
Systems, Perpignan, France, June 2000, CD-ROM, paper nr. 268, M. Fliess and
A. El Jai Ed
On the estimation of atmospheric turbulence layers for AO systems
In current and next generation of ground telescopes, Adaptive Optics (AO) are employed to overcome the
detrimental effects induced by the presence of atmospheric
turbulence, that strongly affects the quality of data transmission and therefore limits the actual resolution of the overall system.
The analysis as well as the prediction of the turbulent phase
affecting the light wavefront is therefore of paramount impor-
tance to guarantee the effective performance of the AO solution.
In this work, a layered model of turbulence is proposed, based on the definition of a Markov-Random-Field whose parameters are determined according to the turbulence statistics. The problem of turbulence estimation is formalized within the stochastic framework and conditions for the identifiability of the turbulence structure (numbers of layers, energies and velocities) are stated. Finally, an algorithm to allow the layer detection and characterization from measurements is designed. Numerical simulations are used to assess the proposed procedure and validate the results, confirming the validity of the approach and the accuracy of the detection
Coefficient of thermal expansion of nanostructured tungsten based coatings assessed by thermally induced substrate curvature method
The in plane coefficient of thermal expansion (CTE) and the residual stress
of nanostructured W based coatings are extensively investigated. The CTE and
the residual stresses are derived by means of an optimized ad-hoc developed
experimental setup based on the detection of the substrate curvature by a laser
system. The nanostructured coatings are deposited by Pulsed Laser Deposition.
Thanks to its versatility, nanocrystalline W metallic coatings,
ultra-nano-crystalline pure W and W-Tantalum coatings and amorphous-like W
coatings are obtained. The correlation between the nanostructure, the residual
stress and the CTE of the coatings are thus elucidated. We find that all the
samples show a compressive state of stress that decreases as the structure goes
from columnar nanocrystalline to amorphous-like. The CTE of all the coatings is
higher than the one of the corresponding bulk W form. In particular, as the
grain size shrinks, the CTE increases from 5.1 10 K for
nanocrystalline W to 6.6 10 K in the ultra-nano-crystalline
region. When dealing with amorphous W, the further increase of the CTE is
attributed to a higher porosity degree of the samples. The CTE trend is also
investigated as function of materials stiffness. In this case, as W coatings
become softer, the easier they thermally expand.Comment: The research leading to these results has also received funding from
the European Research Council Consolidator Grant ENSURE (ERC-2014-CoG No.
647554
Thermomechanical properties of amorphous metallic tungsten-oxygen and tungsten-oxide coatings
In this work, we investigate the correlation between morphology, composition,
and the mechanical properties of metallic amorphous tungsten-oxygen and
amorphous tungsten-oxide films deposited by Pulsed Laser Deposition. This
correlation is investigated by the combined use of Brillouin Spectroscopy and
the substrate curvature method. The stiffness of the films is strongly affected
by both the oxygen content and the mass density. The elastic moduli show a
decreasing trend as the mass density decreases and the oxygen-tungsten ratio
increases. A plateaux region is detected in correspondence of the transition
between metallic and oxide films. The compressive residual stresses, moderate
stiffness and high local ductility that characterize compact amorphous
tungsten-oxide films make them promising for applications involving thermal or
mechanical loads. The coefficient of thermal expansion is quite high (i.e. 8.9
10 K), being strictly correlated to the amorphous
structure and stoichiometry of the films. Under thermal treatments they show a
quite low relaxation temperature (i.e. 450 K). They crystallize into the
monoclinic phase of WO starting from 670 K, inducing an increase
by about 70\% of material stiffness.Comment: The research leading to these results has also received funding from
the European Research Council Consolidator Grant ENSURE (ERC-2014-CoG No.
647554). The views and opinions expressed herein do not necessarily reflect
those of the European Commissio
Stroke epidemiology and COVID-19 pandemic
PURPOSE OF REVIEW: The aim of this study was to describe the impact of the COVID-19 outbreak on the epidemiology, cause and clinical characteristics of incident stroke in different settings and populations. RECENT FINDINGS: Several studies have shown that there are three main themes in the epidemiology of stroke during the COVID-19 pandemic: COVID-19 seems to be associated with stroke in a significant number of patients. This association has been reported in several clinical series, mainly from China. There is a consistent trend towards a decreased number of hospital admissions of stroke patients during the pandemic. There are no population-based data available on incident stroke in individuals with COVID-19. SUMMARY: In this review, we report on increased rates and severe prognosis of ischemic stroke among individuals with COVID-19, probably explained by hypercoagulability and inflammation, documented since the early phase of disease.We confirm the presence of falling rates of new ischemic stroke admissions in hospitals, probably due to social consequences of the pandemic: fear to be infected or not adequately treated in the hospital. This phenomenon is restricted to mild stroke and transient ischemic attacks.Short and long-term consequences of this trend of new strokes in the pandemic need to be evaluated
Polymorphism rs7214723 in CAMKK1: a new genetic variant associated with cardiovascular diseases
Cardiovascular diseases (CVDs) are the leading cause of deaths worldwide. CVDs have a
complex etiology due to the several factors underlying its development including environment,
lifestyle, and genetics. Given the role of calcium signal transduction in several CVDs,
we investigated via PCR-restriction fragment length polymorphism (RFLP) the single nucleotide
polymorphism (SNP) rs7214723 within the calcium/calmodulin-dependent kinase
kinase 1 (CAMKK1) gene coding for the Ca2+/calmodulin-dependent protein kinase kinase
I. The variant rs7214723 causes E375G substitution within the kinase domain of CAMKK1.
A cross-sectional study was conducted on 300 cardiac patients. RFLP-PCR technique was
applied, and statistical analysis was performed to evaluate genotypic and allelic frequencies
and to identify an association between SNP and risk of developing specific CVD. Genotype
and allele frequencies for rs7214723 were statistically different between cardiopathic and
several European reference populations. A logistic regression analysis adjusted for gender,
age, diabetes, hypertension, BMI and previous history of malignancy was applied on cardiopathic
genotypic data and no association was found between rs7214723 polymorphism
and risk of developing specific coronary artery disease (CAD) and aortic stenosis (AS). These
results suggest the potential role of rs7214723 in CVD susceptibility as a possible genetic
biomarker
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