97 research outputs found
Stability of a neural network model with small-world connections
Small-world networks are highly clustered networks with small distances among
the nodes. There are many biological neural networks that present this kind of
connections. There are no special weightings in the connections of most
existing small-world network models. However, this kind of simply-connected
models cannot characterize biological neural networks, in which there are
different weights in synaptic connections. In this paper, we present a neural
network model with weighted small-world connections, and further investigate
the stability of this model.Comment: 4 pages, 3 figure
Ising model in small-world networks
The Ising model in small-world networks generated from two- and
three-dimensional regular lattices has been studied. Monte Carlo simulations
were carried out to characterize the ferromagnetic transition appearing in
these systems. In the thermodynamic limit, the phase transition has a
mean-field character for any finite value of the rewiring probability p, which
measures the disorder strength of a given network. For small values of p, both
the transition temperature and critical energy change with p as a power law. In
the limit p -> 0, the heat capacity at the transition temperature diverges
logarithmically in two-dimensional (2D) networks and as a power law in 3D.Comment: 6 pages, 7 figure
Phase ordering on small-world networks with nearest-neighbor edges
We investigate global phase coherence in a system of coupled oscillators on a
small-world networks constructed from a ring with nearest-neighbor edges. The
effects of both thermal noise and quenched randomness on phase ordering are
examined and compared with the global coherence in the corresponding \xy model
without quenched randomness. It is found that in the appropriate regime phase
ordering emerges at finite temperatures, even for a tiny fraction of shortcuts.
Nature of the phase transition is also discussed.Comment: 5 pages, 4 figures, Phys. Rev. E (in press
Chikungunya virus infections among travellers returning to Spain, 2008 to 2014
Since the first documented autochthonous transmission of
chikungunya virus in the Caribbean island of Saint Martin in
2013, the infection has been reported within the Caribbean
region as well as North, Central and South America. The risk of
autochthonous transmission of chikungunya virus becoming
established in Spain may be elevated due to the large numbers of
travellers returning to Spain from countries affected by the
2013 epidemic in the Caribbean and South America, as well as the
existence of the Aedes albopictus vector in certain parts of
Spain. We retrospectively analysed the laboratory diagnostic
database of the National Centre for Microbiology, Institute of
Health Carlos III (CNM-ISCIII) from 2008 to 2014. During the
study period, 264 confirmed cases, of 1,371 suspected cases,
were diagnosed at the CNM-ISCIII. In 2014 alone, there were 234
confirmed cases. The highest number of confirmed cases were
reported from the Dominican Republic (n = 136), Venezuela (n =
30) and Haiti (n = 11). Six cases were viraemic in areas of
Spain where the vector is present. This report highlights the
need for integrated active case and vector surveillance in Spain
and other parts of Europe where chikungunya virus may be
introduced by returning travellers
Characterizing global evolutions of complex systems via intermediate network representations
Recent developments in measurement techniques have enabled us to observe the time series of many components simultaneously. Thus, it is important to understand not only the dynamics of individual time series but also their interactions. Although there are many methods for analysing the interaction between two or more time series, there are very few methods that describe global changes of the interactions over time. Here, we propose an approach to visualise time evolution for the global changes of the interactions in complex systems. This approach consists of two steps. In the first step, we construct a meta-time series of networks. In the second step, we analyse and visualise this meta-time series by using distance and recurrence plots. Our two-step approach involving intermediate network representations elucidates the half-a-day periodicity of foreign exchange markets and a singular functional network in the brain related to perceptual alternations
Statistical mechanics of complex networks
Complex networks describe a wide range of systems in nature and society, much
quoted examples including the cell, a network of chemicals linked by chemical
reactions, or the Internet, a network of routers and computers connected by
physical links. While traditionally these systems were modeled as random
graphs, it is increasingly recognized that the topology and evolution of real
networks is governed by robust organizing principles. Here we review the recent
advances in the field of complex networks, focusing on the statistical
mechanics of network topology and dynamics. After reviewing the empirical data
that motivated the recent interest in networks, we discuss the main models and
analytical tools, covering random graphs, small-world and scale-free networks,
as well as the interplay between topology and the network's robustness against
failures and attacks.Comment: 54 pages, submitted to Reviews of Modern Physic
Anisotropy studies around the galactic centre at EeV energies with the Auger Observatory
Data from the Pierre Auger Observatory are analyzed to search for
anisotropies near the direction of the Galactic Centre at EeV energies. The
exposure of the surface array in this part of the sky is already significantly
larger than that of the fore-runner experiments. Our results do not support
previous findings of localized excesses in the AGASA and SUGAR data. We set an
upper bound on a point-like flux of cosmic rays arriving from the Galactic
Centre which excludes several scenarios predicting sources of EeV neutrons from
Sagittarius . Also the events detected simultaneously by the surface and
fluorescence detectors (the `hybrid' data set), which have better pointing
accuracy but are less numerous than those of the surface array alone, do not
show any significant localized excess from this direction.Comment: Matches published versio
Varespladib and cardiovascular events in patients with an acute coronary syndrome: the VISTA-16 randomized clinical trial
IMPORTANCE: Secretory phospholipase A2(sPLA2) generates bioactive phospholipid products implicated in atherosclerosis. The sPLA2inhibitor varespladib has favorable effects on lipid and inflammatory markers; however, its effect on cardiovascular outcomes is unknown. OBJECTIVE: To determine the effects of sPLA2inhibition with varespladib on cardiovascular outcomes. DESIGN, SETTING, AND PARTICIPANTS: A double-blind, randomized, multicenter trial at 362 academic and community hospitals in Europe, Australia, New Zealand, India, and North America of 5145 patients randomized within 96 hours of presentation of an acute coronary syndrome (ACS) to either varespladib (n = 2572) or placebo (n = 2573) with enrollment between June 1, 2010, and March 7, 2012 (study termination on March 9, 2012). INTERVENTIONS: Participants were randomized to receive varespladib (500 mg) or placebo daily for 16 weeks, in addition to atorvastatin and other established therapies. MAIN OUTCOMES AND MEASURES: The primary efficacy measurewas a composite of cardiovascular mortality, nonfatal myocardial infarction (MI), nonfatal stroke, or unstable angina with evidence of ischemia requiring hospitalization at 16 weeks. Six-month survival status was also evaluated. RESULTS: At a prespecified interim analysis, including 212 primary end point events, the independent data and safety monitoring board recommended termination of the trial for futility and possible harm. The primary end point occurred in 136 patients (6.1%) treated with varespladib compared with 109 patients (5.1%) treated with placebo (hazard ratio [HR], 1.25; 95%CI, 0.97-1.61; log-rank P = .08). Varespladib was associated with a greater risk of MI (78 [3.4%] vs 47 [2.2%]; HR, 1.66; 95%CI, 1.16-2.39; log-rank P = .005). The composite secondary end point of cardiovascular mortality, MI, and stroke was observed in 107 patients (4.6%) in the varespladib group and 79 patients (3.8%) in the placebo group (HR, 1.36; 95% CI, 1.02-1.82; P = .04). CONCLUSIONS AND RELEVANCE: In patients with recent ACS, varespladib did not reduce the risk of recurrent cardiovascular events and significantly increased the risk of MI. The sPLA2inhibition with varespladib may be harmful and is not a useful strategy to reduce adverse cardiovascular outcomes after ACS. TRIAL REGISTRATION: clinicaltrials.gov Identifier: NCT01130246. Copyright 2014 American Medical Association. All rights reserved
Effectiveness and Safety of the Sequential Use of a Second and Third Anti-TNF Agent in Patients with Inflammatory Bowel Disease: Results from the Eneida Registry
Background: The effectiveness of the switch to another anti-tumor necrosis factor (anti-TNF) agent is not known. The aim of this study was to analyze the effectiveness and safety of treatment with a second and third anti-TNF drug after intolerance to or failure of a previous anti-TNF agent in inflammatory bowel disease (IBD) patients. Methods: We included patients diagnosed with IBD from the ENEIDA registry who received another anti-TNF after intolerance to or failure of a prior anti-TNF agent. Results: A total of 1122 patients were included. In the short term, remission was achieved in 55% of the patients with the second anti-TNF. The incidence of loss of response was 19% per patient-year with the second anti-TNF. Combination therapy (hazard ratio [HR], 2.4; 95% confidence interval [CI], 1.8-3; P < 0.0001) and ulcerative colitis vs Crohn''s disease (HR, 1.6; 95% CI, 1.1-2.1; P = 0.005) were associated with a higher probability of loss of response. Fifteen percent of the patients had adverse events, and 10% had to discontinue the second anti-TNF. Of the 71 patients who received a third anti-TNF, 55% achieved remission. The incidence of loss of response was 22% per patient-year with a third anti-TNF. Adverse events occurred in 7 patients (11%), but only 1 stopped the drug. Conclusions: Approximately half of the patients who received a second anti-TNF achieved remission; nevertheless, a significant proportion of them subsequently lost response. Combination therapy and type of IBD were associated with loss of response. Remission was achieved in almost 50% of patients who received a third anti-TNF; nevertheless, a significant proportion of them subsequently lost response
A window to the sea: environmental indicators for coastal risk management under the RAIA observatory (NW-Iberian Peninsula)
ECSA 59 Using the best scientific knowledge for the sustainable management of estuaries and coastal seas, San Sebastian (Spain), 5thâ8th September 2022The international RAIA Observatory (www.marnaraia.org) resulted from the effort of 12 research and academic institutions and public agencies (Spanish and Portuguese) working in the field of meteorology and oceanography. The RAIA Observatory serves the main maritime activities of the Galicia-Northern Portugal Euroregion and contributes to collaborative observational networks.
Under the framework of coastal risk management, environmental indicators are fundamental tools for the evaluation and mitigation of environmental risks, showing the current state and helping to predict future changes on ecosystem health regarding environmental risks. In last years, the different partners of the RAIA Observatory have identified 38 environmental indicators, in which 12 key risks affecting the ecosystem services of the Galicia-Northern Portugal Euroregion are being evaluated. Data was analyzed and compiled by the various partners of the RAIA Observatory and the development and optimization of the environmental indicators has been done according to the specifications provided by the European Environmental Agency (EEA) and the International Panel for Climate Change (IPCC).
The resulting environmental indicators are included and shared on a publicly-accessible Web service, georeferenced and accompanied by plots (https://marrisk.inesctec.pt/public/#!/indicators). So far, the current status of the indicators has allowed us to establish risk assessment protocols for the Euroregion, and identify critical gaps in a temporal and spatial coverage. The inclusion of the environmental indicators in the RAIA Observatory is of great relevance for national and international data exchange and promotes future collaborationsN
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