Scaling of the Critical Function for the Standard Map: Some Numerical Results

The behavior of the critical function for the breakdown of the homotopically non-trivial invariant (KAM) curves for the standard map, as the rotation number tends to a rational number, is investigated using a version of Greene's residue criterion. The results are compared to the analogous ones for the radius of convergence of the Lindstedt series, in which case rigorous theorems have been proved. The conjectured interpolation of the critical function in terms of the Bryuno function is discussed.Comment: 26 pages, 3 figures, 13 table

Social determinants of content selection in the age of (mis)information

Despite the enthusiastic rhetoric about the so called \emph{collective intelligence}, conspiracy theories -- e.g. global warming induced by chemtrails or the link between vaccines and autism -- find on the Web a natural medium for their dissemination. Users preferentially consume information according to their system of beliefs and the strife within users of opposite narratives may result in heated debates. In this work we provide a genuine example of information consumption from a sample of 1.2 million of Facebook Italian users. We show by means of a thorough quantitative analysis that information supporting different worldviews -- i.e. scientific and conspiracist news -- are consumed in a comparable way by their respective users. Moreover, we measure the effect of the exposure to 4709 evidently false information (satirical version of conspiracy theses) and to 4502 debunking memes (information aiming at contrasting unsubstantiated rumors) of the most polarized users of conspiracy claims. We find that either contrasting or teasing consumers of conspiracy narratives increases their probability to interact again with unsubstantiated rumors.Comment: misinformation, collective narratives, crowd dynamics, information spreadin

Scaling law in the Standard Map critical function. Interpolating hamiltonian and frequency map analysis

We study the behaviour of the Standard map critical function in a neighbourhood of a fixed resonance, that is the scaling law at the fixed resonance. We prove that for the fundamental resonance the scaling law is linear. We show numerical evidence that for the other resonances $p/q$, $q \geq 2$, $p \neq 0$ and $p$ and $q$ relatively prime, the scaling law follows a power--law with exponent $1/q$.Comment: AMS-LaTeX2e, 29 pages with 8 figures, submitted to Nonlinearit

HEALTHCARE-ASSOCIATED INFECTIONS IN PAEDIATRIC AND NEONATAL INTENSIVE CARE UNITS: IMPACT OF UNDERLYING RISK FACTORS AND ANTIMICROBIAL RESISTANCE ON 30-DAY CASE-FATALITY

Objectives. Our aims were (i) to describe trends in the epidemiology of Healthcare-associated Infections (HAIs) in paediatric/neonatal ICUs and (ii) to evaluate risk factors and impact of Multidrug-Resistance (MDR) in children admitted to ICUs. Design. Multicentre, retrospective, cohort study with a nested case-control study conducted between January 2010 and December 2014. Setting. Three tertiary-care paediatric hospitals in Italy and Brazil with a total of 97 ICU beds. Patients. Inclusion criteria were (i) admission to ICU during the study period (ii) age at onset <18 years and (iii) microbiologically-confirmed HAI. Results. 538 HAIs in 454 children were included. 93.3% of patients had comorbidities. Bloodstream infections (BSIs) were the leading pattern (45.4%). The cumulative incidence of HAI was 3.6/100 ICU-admission and the crude 30-day fatality rate was 5.7/1,000-admission. The most frequently isolated pathogens were Enterobacteriaceae, followed by Pseudomonas aeruginosa and Staphylococcus aureus.44% of isolates were MDR. Two multivariate logistic regressions were performed. Factors independently associated with an MDR -HAI were Country, previous antibiotics, transplantation, major surgery, and colonisation by an MDR strain. Factors independently associated with 30-day case-fatality were Country, previous transplantation, fungal infection, BSI, LRTI, and infection caused by MDR strains. Conclusions. Infection control and prevention should be a primary focus to limit the spread of MDR strains and improve the outcome of hospitalised patients. Targeted surveillance programmes collecting neonatal and paediatric HAI/BSI data and outcomes would allow global benchmarking between centres. The next step is to identify simple methods to monitor key HAIs and integrate these into affordable intervention programmes

On RAF Sets and Autocatalytic Cycles in Random Reaction Networks

The emergence of autocatalytic sets of molecules seems to have played an important role in the origin of life context. Although the possibility to reproduce this emergence in laboratory has received considerable attention, this is still far from being achieved. In order to unravel some key properties enabling the emergence of structures potentially able to sustain their own existence and growth, in this work we investigate the probability to observe them in ensembles of random catalytic reaction networks characterized by different structural properties. From the point of view of network topology, an autocatalytic set have been defined either in term of strongly connected components (SCCs) or as reflexively autocatalytic and food-generated sets (RAFs). We observe that the average level of catalysis differently affects the probability to observe a SCC or a RAF, highlighting the existence of a region where the former can be observed, whereas the latter cannot. This parameter also affects the composition of the RAF, which can be further characterized into linear structures, autocatalysis or SCCs. Interestingly, we show that the different network topology (uniform as opposed to power-law catalysis systems) does not have a significantly divergent impact on SCCs and RAFs appearance, whereas the proportion between cleavages and condensations seems instead to play a role. A major factor that limits the probability of RAF appearance and that may explain some of the difficulties encountered in laboratory seems to be the presence of molecules which can accumulate without being substrate or catalyst of any reaction.Comment: pp 113-12

Measurement of the front-end dead-time of the LHCb muon detector and evaluation of its contribution to the muon detection inefficiency

A method is described which allows to deduce the dead-time of the front-end electronics of the LHCb muon detector from a series of measurements performed at different luminosities at a bunch-crossing rate of 20 MHz. The measured values of the dead-time range from 70 ns to 100 ns. These results allow to estimate the performance of the muon detector at the future bunch-crossing rate of 40 MHz and at higher luminosity