Browsing by Author "Villarroel, Carlos"

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    Avalanche properties at the yielding transition: from externally deformed glasses to active systems
    (2024) Villarroel, Carlos; Duering, Gustavo
    We investigated the yielding phenomenon in the quasistatic limit using numerical simulations of soft particles. Two different deformation scenarios, simple shear (passive) and self-random force (active), and two interaction potentials were used. Our approach reveals that the exponents describing the avalanche distribution are universal within the margin of error, showing consistency between the passive and active systems. This indicates that any differences observed in the flow curves may have resulted from a dynamic effect on the avalanche propagation mechanism. The evolution time required to reach a steady state differs significantly between active and passive scenarios under similar conditions. However, we demonstrated that plastic avalanches under athermal quasistatic simulation dynamics display a similar scaling relationship between avalanche size and relaxation time, which cannot explain the different flow curves.
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    Critical yielding rheology: from externally deformed glasses to active systems
    (2021) Villarroel, Carlos; During, Gustavo
    We use extensive computer simulations to study the yielding transition under two different loading schemes: standard simple shear dynamics and self-propelled dense active systems. In the active systems, a yielding transition toward an out-of-equilibrium flowing state known as the liquid phase is observed when self-propulsion is increased. The range of self-propulsions in which this pure liquid regime exists appears to vanish upon approaching the so-called 'jamming point' at which the solidity of soft-sphere packings is lost. Such an 'active yielding' transition shares similarities with the generic yielding transition for shear flows. A Herschel-Bulkley law is observed along the liquid regime in both loading scenarios, with a clear difference in the critical scaling exponents between the two, suggesting the existence of different universality classes for the yielding transition under different driving conditions. In addition, we present the direct measurements of growing length and time scales for both driving scenarios. A comparison with theoretical predictions from the recent literature reveals poor agreement with our numerical results.
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    Late Pleistocene-dated divergence between South Hemisphere populations of the non-conventional yeast L. cidri
    (2022) Villarreal, Pablo; Villarroel, Carlos; O'Donnell, Samuel; Agier, Nicolas; Quintero-Galvis, Julian; Pena, Tomas; Nespolo, Roberto; Fischer, Gilles; Varela, Cristian; Cubillos, Francisco
    Most organisms belonging to the Saccharomycotina subphylum have high genetic diversity and a vast repertoire of metabolisms and lifestyles. Lachancea cidri is an ideal yeast model for exploring the interplay between genetics, ecological function and evolution. Lachancea cidri diverged from the Saccharomyces lineage before the whole-genome duplication and is distributed across the South Hemisphere, displaying an important ecological success. We applied phylogenomics to investigate the genetic variation of L. cidri isolates obtained from Australia and South America. Our approach revealed the presence of two main lineages according to their geographic distribution (Aus and SoAm). Estimation of the divergence time suggests that SoAm and Aus lineages diverged near the last glacial maximum event during the Pleistocene (64-8 KYA). Interestingly, we found that the French reference strain is closely related to the Australian strains, with a recent divergence (405-51 YA), likely associated to human movements. Additionally, we identified different lineages within the South American population, revealing that Patagonia contains a similar genetic diversity comparable to that of other lineages in S. cerevisiae. These findings support the idea of a Pleistocene-dated divergence between South Hemisphere lineages, where the Nothofagus and Araucaria ecological niches likely favoured the extensive distribution of L. cidri in Patagonia.
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    Micromechanical theory of strain stiffening of biopolymer networks
    (2018) Rens, Robbie; Villarroel, Carlos; Düring, Gustavo; Lerner, Edan