596 research outputs found
Laue Lens Development for Hard X-rays (>60 keV)
Results of reflectivity measurements of mosaic crystal samples of Cu (111)
are reported. These tests were performed in the context of a feasibility study
of a hard X-ray focusing telescope for space astronomy with energy passband
from 60 to 600 keV. The technique envisaged is that of using mosaic crystals in
transmission configuration that diffract X-rays for Bragg diffraction (Laue
lens). The Laue lens assumed has a spherical shape with focal length . It is
made of flat mosaic crystal tiles suitably positioned in the lens. The samples
were grown and worked for this project at the Institute Laue-Langevin (ILL) in
Grenoble (France), while the reflectivity tests were performed at the X-ray
facility of the Physics Department of the University of Ferrara.Comment: 6 pages, 12 figures, accepted for publication in IEEE Transactions on
Nuclear Scienc
Heterogeneous-k-core versus Bootstrap Percolation on Complex Networks
We introduce the heterogeneous--core, which generalizes the -core, and
contrast it with bootstrap percolation. Vertices have a threshold which
may be different at each vertex. If a vertex has less than neighbors it
is pruned from the network. The heterogeneous--core is the sub-graph
remaining after no further vertices can be pruned. If the thresholds are
with probability or with probability , the process
forms one branch of an activation-pruning process which demonstrates
hysteresis. The other branch is formed by ordinary bootstrap percolation. We
show that there are two types of transitions in this heterogeneous--core
process: the giant heterogeneous--core may appear with a continuous
transition and there may be a second, discontinuous, hybrid transition. We
compare critical phenomena, critical clusters and avalanches at the
heterogeneous--core and bootstrap percolation transitions. We also show that
network structure has a crucial effect on these processes, with the giant
heterogeneous--core appearing immediately at a finite value for any
when the degree distribution tends to a power law with
.Comment: 10 pages, 4 figure
Introduction en bourse et croissance externe des PME françaises
L'introduction en bourse est une étape majeure du développement des entreprises. Cependant peu de travaux explorent l'articulation entre politique d'acquisition et introduction en bourse. Nos résultats soulignent que les PME françaises sont nombreuses à mener des acquisitions après l'introduction, même lorsqu'elles n'ont pas d'expérience préalable en la matière, adoptant une stratégie de croissance externe en deux étapes. Ainsi, nous montrons qu'il existe une imbrication étroite entre décisions financières et stratégiques dans le cadre de l'introduction en bourse
Understanding edge-connectivity in the Internet through core-decomposition
Internet is a complex network composed by several networks: the Autonomous
Systems, each one designed to transport information efficiently. Routing
protocols aim to find paths between nodes whenever it is possible (i.e., the
network is not partitioned), or to find paths verifying specific constraints
(e.g., a certain QoS is required). As connectivity is a measure related to both
of them (partitions and selected paths) this work provides a formal lower bound
to it based on core-decomposition, under certain conditions, and low complexity
algorithms to find it. We apply them to analyze maps obtained from the
prominent Internet mapping projects, using the LaNet-vi open-source software
for its visualization
Exploring the Hard X-/soft gamma-ray Continuum Spectra with Laue Lenses
The history of X-ray astronomy has shown that any advancement in our
knowledge of the X-ray sky is strictly related to an increase in instrument
sensitivity. At energies above 60 keV, there are interesting prospects for
greatly improving the limiting sensitivity of the current generation of direct
viewing telescopes (with or without coded masks), offered by the use of Laue
lenses. We will discuss below the development status of a Hard X-Ray focusing
Telescope (HAXTEL) based on Laue lenses with a broad bandpass (from 60 to 600
keV) for the study of the X-ray continuum of celestial sources. We show two
examplesof multi-lens configurations with expected sensitivity orders of
magnitude better ( photons cm s keV
at 200 keV) than that achieved so far. With this unprecedented sensitivity,
very exciting astrophysical prospects are opened.Comment: 4 pages, 10 figures, to be published in the Proc. of the 39th ESLAB
Symosium, 19-21 April 200
The influence of constitutive material models on accumulated plastic strain in finite element weld analyses
Recent studies in computational weld mechanics have revealed the importance of the material plasticity model when predicting weld residual stresses. The present work seeks to extend this level of understanding to include the effects of the assumed material annealing behaviour, particularly when modelling multi-pass welds that comprise several thermo-mechanical loading cycles. A series of numerical analyses are performed to examine the variability in predicted residual stress profiles for different material models, using a validated finite element model for a three-pass slot weld in AISI 316LN austenitic steel. The material models consider both the work hardening and annealing assumptions for the chosen material. Model sensitivity is established not only from a weld residual stress perspective, but also from an assessment of the post-weld plastic strain accumulated in the weldment. Predictions are compared with indirect measurements acquired using cross-weld micro-hardness maps taken from benchmark specimens. Sensitivity studies reveal that the choice of annealing behaviour will have a significant impact on plastic flow predictions, which is dependent on the annealing temperature specified. Annealing assumptions will have a varying impact on the weld residual stress predictions, such that the extent of sensitivity is dependent on the plasticity model chosen. In contrast, the choice of plasticity model will have a significant effect on the predicted weld residual stresses, but relatively little effect on predictions of equivalent plastic strain
GPR, a ground‐penetrating radar for the Netlander mission
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/95485/1/jgre1563.pd
CSRP3 mediates polyphenols-induced cardioprotection in hypertension
Berries contain bioactive polyphenols, whose capacity to prevent cardiovascular diseases has been established recently in animal models as well in human clinical trials. However, cellular processes and molecular targets of berries polyphenols remain to be identified. The capacity of a polyphenol-enriched diet (i.e., blueberries, blackberries, raspberries, strawberry tree fruits and Portuguese crowberries berries mixture) to promote animal survival and protect cardiovascular function from salt-induced hypertension was evaluated in a chronic salt-sensitive Dahl rat model. The daily consumption of berries improved survival of Dahl/salt-sensitive rats submitted to high-salt diet and normalized their body weight, renal function and blood pressure. In addition, a prophylactic effect was observed at the level of cardiac hypertrophy and dysfunction, tissue cohesion and cardiomyocyte hypertrophy. Berries also protected the aorta from fibrosis and modulated the expression of aquaporin-1, a channel involved in endothelial water and nitric oxide permeability. Left ventricle proteomics analysis led to the identification of berries and salt metabolites targets, including cystein and glycin-rich protein 3 (CSRP3), a protein involved in myocyte cytoarchitecture. In neonatal rat ventricular cardiomyocytes, CSRP3 was validated as a target of a berries-derived polyphenol metabolite, 4-methylcatechol sulfate, at micromolar concentrations, mimicking physiological conditions of human plasma circulation. Accordingly, siRNA silencing of CSRP3 and 4-methylcatechol sulfate pretreatment reversed cardiomyocyte hypertrophy and CSRP3 overexpression induced by phenylephrine. Our systemic study clearly supports the modulation of CSRP3 by a polyphenol-rich berries diet as an efficient cardioprotective strategy in hypertension-induced heart failure
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