420 research outputs found
Wishart and Anti-Wishart random matrices
We provide a compact exact representation for the distribution of the matrix
elements of the Wishart-type random matrices , for any finite
number of rows and columns of , without any large N approximations. In
particular we treat the case when the Wishart-type random matrix contains
redundant, non-random information, which is a new result. This representation
is of interest for a procedure of reconstructing the redundant information
hidden in Wishart matrices, with potential applications to numerous models
based on biological, social and artificial intelligence networks.Comment: 11 pages; v2: references updated + some clarifications added; v3:
version to appear in J. Phys. A, Special Issue on Random Matrix Theor
Surface Hardening and Self-Organized Fractality Through Etching of Random Solids
When a finite volume of etching solution is in contact with a disordered
solid, complex dynamics of the solid-solution interface develop. If the etchant
is consumed in the chemical reaction, the dynamics stop spontaneously on a
self-similar fractal surface. As only the weakest sites are corroded, the solid
surface gets progressively harder and harder. At the same time it becomes
rougher and rougher uncovering the critical spatial correlations typical of
percolation. From this, the chemical process reveals the latent percolation
criticality hidden in any random system. Recently, a simple minimal model has
been introduced by Sapoval et al. to describe this phenomenon. Through analytic
and numerical study, we obtain a detailed description of the process. The time
evolution of the solution corroding power and of the distribution of resistance
of surface sites is studied in detail. This study explains the progressive
hardening of the solid surface. Finally, this dynamical model appears to belong
to the universality class of Gra dient Percolation.Comment: 14 pages, 15 figures (1457 Kb
Low-energy cross section of the 7Be(p,g)8B solar fusion reaction from Coulomb dissociation of 8B
Final results from an exclusive measurement of the Coulomb breakup of 8B into
7Be+p at 254 A MeV are reported. Energy-differential Coulomb-breakup cross
sections are analyzed using a potential model of 8B and first-order
perturbation theory. The deduced astrophysical S_17 factors are in good
agreement with the most recent direct 7Be(p,gamma)8B measurements and follow
closely the energy dependence predicted by the cluster-model description of 8B
by Descouvemont. We extract a zero-energy S_17 factor of 20.6 +- 0.8 (stat) +-
1.2 (syst) eV b.Comment: 14 pages including 16 figures, LaTeX, accepted for publication in
Physical Review C. Minor changes in text and layou
Rising utilization of coronary CT angiography across Europe over the last decade: insights from a large prospective European registry
Abstract
Background/Introduction
The recently updated 2019 ESC guidelines for the diagnosis and management of chronic coronary syndromes endorse the use of coronary computed tomography angiography (CCTA) for exclusion of obstructive coronary artery disease in patients with a low clinical likelihood (Class I, LOE B). Higher demand for CCTA requires broad availability, inevitably involving smaller healthcare providers, such as non-academic hospitals and private practices. Nevertheless, most published data on CCTA image quality and safety rely on exams performed in high-volume academic centers, and little is known about CCTA in non-academic settings.
Purpose
To investigate the utilization of CCTA across Europe over the last decade, focusing on differences between academic and non-academic centers.
Methods
We included patients with stable chest pain and suspected coronary artery disease (CAD) who received CCTA and were included in the European Society of Cardiovascular Radiology MR/CT registry 01/2010–01/2020. We compared CT equipment, image quality, radiation dose, the incidence of periprocedural adverse events, patient characteristics, and CCTA findings between academic (high volume university hospitals) and non-academic centers (non-academic hospitals and private practices).
Results
Overall, 64,317 patients (41.2% women; age 60±13 years) from 212 sites across 19 European countries were included. Academic centers submitted most cases in 2010—2014 (51.6%), whereas non-academic centers accounted for 71.3% of records in 2015–2020. While non-academic centers used less advanced technology, radiation dose remained low (4.54 [interquartile range (IQR) 2.28–6.76] mSv) with a 30% decline of high-dose scans (>7 mSv) over time. Diagnostic image quality was reported in 97.7% of cases, and the rate of acute scan-related events was low (0.4%) (Figure 1). From 2010–2014 to 2015–2020, CCTA nearly doubled in patients with low to intermediate pretest-probability, women >50, and 40–60 years old men (Figure 2). CAD presence and extent decreased slightly over time (prevalence: 2010–2014: 41.5% vs. 2015–2020: 40.6%), (multi-vessel disease in those with CAD: 2010–2014: 61.9% vs. 2015–2020: 55.9%; all p<0.01).
Conclusion
CCTA expands rapidly to non-academic centers across Europe, increasing availability while maintaining relatively low radiation dose, high diagnostic image quality, and safety. Broad availability of high-quality CCTA is essential for a successfully implementation of the recently updated guidelines for the diagnosis and management of chronic coronary syndromes.
Funding Acknowledgement
Type of funding sources: None. Changes in CCTA utilizationChanges in patient characteristic
A novel human ex vivo model for the analysis of molecular events during lung cancer chemotherapy
Feasibility studies of the time-like proton electromagnetic form factor measurements with PANDA at FAIR
The possibility of measuring the proton electromagnetic form factors in the
time-like region at FAIR with the \PANDA detector is discussed. Detailed
simulations on signal efficiency for the annihilation of into a
lepton pair as well as for the most important background channels have been
performed. It is shown that precision measurements of the differential cross
section of the reaction can be obtained in a wide
angular and kinematical range. The individual determination of the moduli of
the electric and magnetic proton form factors will be possible up to a value of
momentum transfer squared of (GeV/c). The total cross section will be measured up to (GeV/c).
The results obtained from simulated events are compared to the existing data.
Sensitivity to the two photons exchange mechanism is also investigated.Comment: 12 pages, 4 tables, 8 figures Revised, added details on simulations,
4 tables, 9 figure
Effects of the TLR2 Agonists MALP-2 and Pam3Cys in Isolated Mouse Lungs
Background: Gram-positive and Gram-negative bacteria are main causes of pneumonia or acute lung injury. They are recognized by the innate immune system via toll-like receptor-2 (TLR2) or TLR4, respectively. Among all organs, the lungs have the highest expression of TLR2 receptors, but little is known about the pulmonary consequences of their activation. Here we studied the effects of the TLR2/6 agonist MALP-2, the TLR2/1 agonist Pam 3Cys and the TLR4 agonist lipopolysaccharide (LPS) on pro-inflammatory responses in isolated lungs. Methodology/Principal Findings: Isolated perfused mouse lungs were perfused for 60 min or 180 min with MALP-2 (25 ng/ mL), Pam3Cys (160 ng/mL) or LPS (1 mg/mL). We studied mediator release by enzyme linked immunosorbent assay (ELISA), the activation of mitogen activated protein kinase (MAPK) and AKT/protein kinase B by immunoblotting, and gene induction by quantitative polymerase chain reaction. All agonists activated the MAPK ERK1/2 and p38, but neither JNK or AKT kinase. The TLR ligands upregulated the inflammation related genes Tnf, Il1b, Il6, Il10, Il12, Ifng, Cxcl2 (MIP-2a) and Ptgs2. MALP-2 was more potent than Pam 3Cys in inducing Slpi, Cxcl10 (IP10) and Parg. Remarkable was the strong induction of Tnc by MALP2, which was not seen with Pam 3Cys or LPS. The growth factor related genes Areg and Hbegf were not affected. In addition, all three TLR agonists stimulated the release of IL-6, TNF, CXCL2 and CXCL10 protein from the lungs
Feasibility studies of time-like proton electromagnetic form factors at PANDA at FAIR
Simulation results for future measurements of electromagnetic proton form
factors at \PANDA (FAIR) within the PandaRoot software framework are reported.
The statistical precision with which the proton form factors can be determined
is estimated. The signal channel is studied on the basis
of two different but consistent procedures. The suppression of the main
background channel, , is studied.
Furthermore, the background versus signal efficiency, statistical and
systematical uncertainties on the extracted proton form factors are evaluated
using two different procedures. The results are consistent with those of a
previous simulation study using an older, simplified framework. However, a
slightly better precision is achieved in the PandaRoot study in a large range
of momentum transfer, assuming the nominal beam conditions and detector
performance
Challenges in QCD matter physics - The Compressed Baryonic Matter experiment at FAIR
Substantial experimental and theoretical efforts worldwide are devoted to
explore the phase diagram of strongly interacting matter. At LHC and top RHIC
energies, QCD matter is studied at very high temperatures and nearly vanishing
net-baryon densities. There is evidence that a Quark-Gluon-Plasma (QGP) was
created at experiments at RHIC and LHC. The transition from the QGP back to the
hadron gas is found to be a smooth cross over. For larger net-baryon densities
and lower temperatures, it is expected that the QCD phase diagram exhibits a
rich structure, such as a first-order phase transition between hadronic and
partonic matter which terminates in a critical point, or exotic phases like
quarkyonic matter. The discovery of these landmarks would be a breakthrough in
our understanding of the strong interaction and is therefore in the focus of
various high-energy heavy-ion research programs. The Compressed Baryonic Matter
(CBM) experiment at FAIR will play a unique role in the exploration of the QCD
phase diagram in the region of high net-baryon densities, because it is
designed to run at unprecedented interaction rates. High-rate operation is the
key prerequisite for high-precision measurements of multi-differential
observables and of rare diagnostic probes which are sensitive to the dense
phase of the nuclear fireball. The goal of the CBM experiment at SIS100
(sqrt(s_NN) = 2.7 - 4.9 GeV) is to discover fundamental properties of QCD
matter: the phase structure at large baryon-chemical potentials (mu_B > 500
MeV), effects of chiral symmetry, and the equation-of-state at high density as
it is expected to occur in the core of neutron stars. In this article, we
review the motivation for and the physics programme of CBM, including
activities before the start of data taking in 2022, in the context of the
worldwide efforts to explore high-density QCD matter.Comment: 15 pages, 11 figures. Published in European Physical Journal
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