Active solids{,} more specifically elastic lattices embedded with polar active units{,} exhibit collective actuation when the elasto-active feedback{,} generically present in such systems{,} exceeds some critical value. The dynamics then condensates on a small fraction of the vibrational modes{,} the selection of which obeys non trivial rules rooted in the nonlinear part of the dynamics. So far{,} the complexity of the selection mechanism has limited the design of specific actuation. Here{,} we investigate numerically how localizing activity to a fraction of modes enables the selection of non-trivial collective actuation. We perform numerical simulations of an agent-based model on triangular and disordered lattices and vary the concentration and the localization of the active agents on the lattice nodes. Both contribute to the distribution of the elastic energy across the modes. We then introduce an algorithm{,} which{,} for a given fraction of active nodes{,} evolves the localization of the activity in such a way that the energy distribution on a few targeted modes is maximized – or minimized. We illustrate on a specific targeted actuation{,} how the algorithm performs as compared to manually chosen localization of the activity. While{,} in the case of the ordered lattice{,} a well-educated guess performs better than the algorithm{,} and the latter outperform the manual trials in the case of the disordered lattice. Finally{,} the analysis of the results in the case of the ordered lattice leads us to introduce a design principle based on a measure of the susceptibility of the modes to be activated along certain activation paths.

Neste Editorial são apresentadas algumas reflexões sobre o processo de institucionalização e busca pela autonomia da área de pesquisa em Ensino de Física do Brasil. Sob uma perspectiva sociológica e com base empírica se discute o atual cenário das lutas concorrenciais internas e externas, indicando caminhos futuros a serem percorridos para construção de uma identidade e fortalecimento da autonomia da área.

n/a

n/a

It is known that diversity matters to improve scientific excellence and that scientific events are important occasions to discuss new ideas and create networks, beyond the fact that it helps to put the work of the scientists in evidence. Hence, increasing diversity in scientific events is crucial to improve their scientific quality and help to promote minorities. In Brazil, important physics scientific events are organized by the Brazilian Physical Society (SBF, in Portuguese), and in this work, some aspects related to the participation of women in these physics events are analyzed from 2005 to 2021. The analysis shows that women’s participation has increased over the years, reaching in some areas of Physics the same percentage as the one observed in the SBF community (always below 25%). However, female participation as members of organizing committees and as keynote speakers is always lower. Some proposals are listed to change the current picture of inequality.

The relation between wetting properties and geometric parameters of fractal surfaces are widely discussed on the literature and, however, there are still divergences on this topic. Here we propose a simple theoretical model to describe the wetting properties of a droplet of water placed on a hierarchical structured surface and test the predictions of the model and the dependence of the droplet wetting state on the initial conditions using simulation of the 3-spin Potts model. We show that increasing the auto-similarity level of the hierarchy – called n – does not affect considerably the stable wetting state of the droplet but increases its contact angle. Simulations also explicit the existence of metastable states on this type of surfaces and shows that, when n increases, the metastability becomes more pronounced. Finally we show that the fractal dimension of the surface is not a good predictor of the contact angle of the droplet.

{Surficial shell accumulations from shallow marine settings are typically averaged over centennial-to-millennial time scales and dominated by specimens that died in the most recent centuries, resulting in strongly right-skewed age-frequency distributions (AFDs). However, AFDs from modern offshore settings (outer shelf and uppermost continental slope) still need to be explored. Using individually dated shells (14C-calibrated amino acid racemization), we compared AFDs along an onshore-offshore gradient across the southern Brazilian shelf, with sites ranging from the inner shelf, shallow-water (\< 40 m) to offshore, deep-water (ġt; 100 m) settings. The duration of time averaging is slightly higher in deeper water environments, and the AFD shapes change along the depositional profile. The inner shelf AFDs are strongly right-skewed due to the dominance of shells from the most recent millennia (median age range: 0–3 ka). In contrast, on the outer shelf and the uppermost continental slope, AFDs are symmetrical to left-skewed and dominated by specimens that died following the Last Glacial Maximum (median age range: 15–18 ka). The onshore-offshore changes in the observed properties of AFDs—increased median age and decreased skewness, but only slightly increased temporal mixing—likely reflect changes in sea level and concurrent water depth-related changes in biological productivity. These results suggest that on a passive continental margin subject to post-glacial sea-level changes, the magnitude of time-averaging of shell assemblages is less variable along the depositional profile than shell assemblage ages and the shapes of AFDs.}

Abstract We design and implement an effective fully discrete Lagrangian–Eulerian scheme for a class of scalar, local and nonlocal models, and systems of hyperbolic problems in 1D. We propose statements, via a weak asymptotic analysis, which include existence, uniqueness, regularity, and numerical approximations of entropy-weak solutions computed with the scheme for the corresponding nonlinear initial value problem for the local scalar case. We study both convergence and weak bounded variation (BV) properties of the scheme to the entropy solution (for the local and scalar case) in the sense of Kruzhkov. The approach is based on the improved concept of no-flow curves, as introduced by the authors, and we highlight the strengths of the method: (i) the scheme for systems of hyperbolic problems does not require computation of the eigenvalues (exact or approximate) either to the numerical flux function or the weak CFL stability condition (wCFL) and (ii) we prove the properties: positivity-preserving, total variation nonincreasing, and maximum principle subject to the wCFL. We present numerical experiments to evaluate the shock capturing capabilities of the scheme in resolving the main features for hyperbolic problems: shock waves, rarefaction waves, contact discontinuities, positivity-preserving properties, and nonlinear wave formations and interactions.