Stationary dark energy: the present universe as a global attractor

We propose a cosmological model that makes a significant step toward solving the coincidence problem of the near similarity at the present of the dark energy and dark matter components. Our cosmology has the following properties: a) among flat and homogeneous spaces, the present universe is a global attractor: all the possible initial conditions lead to the observed proportion of dark energy and dark matter; once reached, it remains fixed forever; b) the expansion is accelerated at the present, as requested by the supernovae observations; c) the model is consistent with the large-scale structure and microwave background data; d) the dark energy and the dark matter densities always scale similarly after equivalence and are close to within two orders of magnitude. The model makes use of a non-linear coupling of the dark energy to the dark matter that switches on after structure formation.Comment: 5 pages, 4 figures, submitted to Phys. Rev. Lett. Minor revision (added some refs, shortened to match PRL requirements

Diffraction and reflection of irregular waves in a harbor employing a spectral model

The SWAN wave model is widely used in coastal waters and the main focus of this work is on its application in a harbor. Its last released version - SWAN 40.51 - includes an approximation to compute diffraction, however, so far there are few published works that discuss this matter. The performance of the model is therefore investigated in a harbor where reflection and diffraction play a relevant role. To assess its estimates, a phase-resolving Boussinesq wave model is employed as well, together with measurements carried out at a small-scale model of the area behind the breakwater. For irregular, short-crested waves with broad directional spreading, the importance of diffraction is relatively small. On the other hand, reflection of the incident waves is significant, increasing the energy inside the harbor. Nevertheless, the SWAN model does not achieve convergence when it is set to compute diffraction and reflection simultaneously. It is concluded that, for situations typically encountered in harbors, with irregular waves near reflective obstacles, the model should be set without the diffraction option.O modelo de ondas SWAN é amplamente empregado em simulações na região costeira e o presente trabalho investiga sua aplicação dentro de um porto. A última versão disponibilizada para a comunidade - SWAN 40.51 - inclui uma aproximação para computar a difração, embora, até o momento, poucos trabalhos abordando este tema foram publicados. O desempenho do modelo é estudado em um porto onde os fenômenos de reflexão e difração são importantes. Para avaliar suas estimativas, um modelo do tipo Boussinesq também é empregado, juntamente com medições realizadas em um modelo em escala reduzida da área atrás do quebramar. Para ondas irregulares, com cristas curtas e espalhamento direcional mais amplo, a importância da difração é relativamente menor. Contudo, o modelo SWAN não alcança convergência quando programado para estimar difração e reflexão simultaneamente. Conclui-se que, para situações normalmente encontradas em portos, com ondas irregulares próximas a obstáculos refletivos, o modelo deve ser empregado sem a opção de difração

Quality indicators in acute stroke care: a prospective observational survey in 13 Italian regions

BACKGROUND AND AIMS: Quality monitoring has great relevance in stroke care. The Project "How to guarantee adherence to effective interventions in stroke care" aimed to estimate adherence to acute-phase guidelines in stroke care in Italy. METHODS: A prospective observational study was performed in 27 hospitals of 13 Italian Regions. Adherence to 15 process indicators was evaluated, comparing also stroke units (SU) with conventional wards. An overall score of care, defined as the sum of achieved indicators, was calculated. A multilevel hierarchical model described performance at patient, hospital and regional level. RESULTS: Overall, 484 consecutive stroke patients (mean age, 73.4 years; 52.7 % males) were included. Total score ranged from 2 to 15 (mean 8.5 ± 2.4). SU patients were more often evaluated with the National Institutes of Health Stroke Scale (NIHSS) within 24 h, had more frequently an assessment of pre- and post-stroke disability, and a CT scan the same or the day after admission. Regional-hospital- and patient-level variability explained, respectively, 25, 34, and 41 % of total score variance. In multivariate models, patients >80 years vs. younger showed a change in total score of -0.45 (95 % CI -0.79 to -0.12), and those with NIHSS ≥14 vs. ≤5 of -0.92 (95 % CI -1.53 to -0.30). A negative change means a worse adjusted average adherence to process indicators. SU admission increased total score of 1.55 (95 % CI 0.52-2.58). CONCLUSIONS: Our data confirm the need of quality monitoring in stroke care. Although SU patients showed a better adherence to quality indicators, overall compliance was unsatisfactory