Signatures of the self-modulation instability of relativistic proton bunches in the AWAKE experiment

We investigate numerically the detection of the self-modulation instability in a virtual detector located downstream from the plasma in the context of AWAKE. We show that the density structures, appearing in the temporally resolving virtual detector, map the transverse beam phase space distribution at the plasma exit. As a result, the proton bunch radius that appears to grow along the bunch in the detector results from the divergence increase along the bunch, related with the spatial growth of the self-modulated wakefields. In addition, asymmetric bunch structures in the detector are a result of asymmetries of the bunch divergence, and do not necessarily reflect asymmetric beam density distributions in the plasma.Comment: Accepted for publication in NIM-A for the proceedings of the 3rd European Advanced Accelerator Workshop. 5 pages, 2 figure

Exponential Distributions in a Mechanical Model for Earthquakes

We study statistical distributions in a mechanical model for an earthquake fault introduced by Burridge and Knopoff [R. Burridge and L. Knopoff, {\sl Bull. Seismol. Soc. Am.} {\bf 57}, 341 (1967)]. Our investigations on the size (moment), time duration and number of blocks involved in an event show that exponential distributions are found in a given range of the paramenter space. This occurs when the two kinds of springs present in the model have the same, or approximately the same, value for the elastic constants. Exponential distributions have also been seen recently in an experimental system to model earthquake-like dynamics [M. A. Rubio and J. Galeano, {\sl Phys. Rev. E} {\bf 50}, 1000 (1994)].Comment: 11 pages, uuencoded (submitted to Phys. Rev. E

Água e saúde pública: uma perspectiva pós-COVID-19

Paper Position that addresses, in the view of its author, the relationship between Water and Public Health in the current context of the COVID-19 pandemic and the prospects for its after

Chaos and Synchronized Chaos in an Earthquake Model

We show that chaos is present in the symmetric two-block Burridge-Knopoff model for earthquakes. This is in contrast with previous numerical studies, but in agreement with experimental results. In this system, we have found a rich dynamical behavior with an unusual route to chaos. In the three-block system, we see the appearance of synchronized chaos, showing that this concept can have potential applications in the field of seismology.Comment: To appear in Physical Review Letters (13 pages, 6 figures

Qualidade da água em reservatórios prediais. Contributos para o PSA da Póvoa de Varzim

A exploração de sistemas de abastecimento de água para consumo humano é uma atividade de grande complexidade pela necessidade de se garantir uma melhoria contínua de eficácia e eficiência no serviço prestado aos consumidores. De acordo com a Organização Mundial da Saúde, a forma mais eficaz de garantir uma água segura pode concretizar-se através da implementação de planos de segurança da água que contemplam a descrição detalhada do sistema de abastecimento, a identificação de perigos, a avaliação do risco e o estabelecimento de medidas necessárias para os controlar, abarcando todas as etapas do sistema, desde a bacia de captação até à torneira do consumidor. Uma das grandes dificuldades na aplicação deste conceito situa-se nas redes prediais urbanas, uma vez que a propriedade privada limita a responsabilidade das entidades gestoras dos sistemas públicos em assegurar uma responsabilidade direta sobre a qualidade da água nestas redes. O presente trabalho de investigação teve como objetivo avaliar a qualidade da água em reservatórios prediais e em torneiras de consumidores na cidade da Póvoa de Varzim, constituindo-se um contributo para a implantação de um plano de segurança da água nesta cidade portuguesa

Local superconducting density of states of ErNi2B2C

We present local tunnelling microscopy and spectroscopy measurements at low temperatures in single crystalline samples of the magnetic superconductor ErNi2B2C. The electronic local density of states shows a striking departure from s-wave BCS theory with a finite value at the Fermi level, which amounts to half of the normal phase density of states.Comment: 9 pages, 3 figure