115 research outputs found
Tuning spreading and avalanche-size exponents in directed percolation with modified activation probabilities
We consider the directed percolation process as a prototype of systems
displaying a nonequilibrium phase transition into an absorbing state. The model
is in a critical state when the activation probability is adjusted at some
precise value p_c. Criticality is lost as soon as the probability to activate
sites at the first attempt, p1, is changed. We show here that criticality can
be restored by "compensating" the change in p1 by an appropriate change of the
second time activation probability p2 in the opposite direction. At
compensation, we observe that the bulk exponents of the process coincide with
those of the normal directed percolation process. However, the spreading
exponents are changed, and take values that depend continuously on the pair
(p1, p2). We interpret this situation by acknowledging that the model with
modified initial probabilities has an infinite number of absorbing states.Comment: 9 pages, 11 figure
SE(3)-equivariant Graph Neural Networks for Learning Glassy Liquids Representations
Within the glassy liquids community, the use of Machine Learning (ML) to
model particles' static structure in order to predict their future dynamics is
currently a hot topic. The actual state of the art consists in Graph Neural
Networks (GNNs) (Bapst 2020) which, beside having a great expressive power, are
heavy models with numerous parameters and lack interpretability. Inspired by
recent advances (Thomas 2018), we build a GNN that learns a robust
representation of the glass' static structure by constraining it to preserve
the roto-translation (SE(3)) equivariance. We show that this constraint not
only significantly improves the predictive power but also allows to reduce the
number of parameters while improving the interpretability. Furthermore, we
relate our learned equivariant features to well-known invariant expert
features, which are easily expressible with a single layer of our network.Comment: 8 pages, 7 figures plus appendi
Les mĂ©tiers de la territorialisation du street art : de lâintermĂ©diation Ă la valorisation
Introduction Le street art sâinscrit dans des configurations territoriales multiples, impliquant un grand nombre dâacteurs, au-delĂ des seuls artistes, faisant le lien avec les collectivitĂ©s commanditaires et prescriptives, et/ou les publics du street art, des habitants aux visiteurs et touristes. Ces acteurs proviennent dâinstitutions, dâassociations variĂ©es, ancrĂ©es localement ou intervenant en intermĂ©diaires sur des territoires multiples. Comment ces diffĂ©rentes provenances jouent sur les ..
Roadmap on machine learning glassy liquids
Unraveling the connections between microscopic structure, emergent physical
properties, and slow dynamics has long been a challenge in the field of the
glass transition. The absence of clear visible structural order in amorphous
configurations complicates the identification of the key features related to
structural relaxation and transport properties. The difficulty in sampling
equilibrated configurations at low temperatures hampers thorough numerical and
theoretical investigations. This roadmap article explores the potential of
machine learning (ML) techniques to face these challenges, building on the
algorithms that have revolutionized computer vision and image recognition. We
present successful ML applications, as well as many open problems for the
future, such as transferability and interpretability of ML approaches. We
highlight new ideas and directions in which ML could provide breakthroughs to
better understand glassy liquids. To foster a collaborative community effort,
the article introduces the "GlassBench" dataset, providing simulation data and
benchmarks for both two-dimensional and three-dimensional glass-formers.
Emphasizing the importance of benchmarks, we identify critical metrics for
comparing the performance of emerging ML methodologies, in line with
benchmarking practices in image and text recognition. The goal of this roadmap
is to provide guidelines for the development of ML techniques in systems
displaying slow dynamics, while inspiring new directions to improve our
understanding of glassy liquids
Do pĂșblico e do privado: uma perspectiva de gĂ©nero sobre uma dicotomia moderna
Neste texto propomos uma interpretação crĂtica da dicotomia histĂłrica entre pĂșblico e privado como dinĂąmica fundamental da modernidade. A partir de uma perspectiva de gĂ©nero, discutimos as fronteiras construĂdas entre espaço coletivo de cidadania e de sociabilidade e espaço individual de intimidade e desigualdade. Argumentamos a favor de uma relação de cumplicidade, ainda que tensa, entre as duas esferas, observando que a vida privada foi, em grande medida, moldada pelas mudanças operadas na vida pĂșblica. Recorrendo a diferentes definiçÔes de "pĂșblico", notamos que, Ă medida que as sociabilidades tradicionais, essencialmente masculinas, estudadas entre outros por AriĂšs ou Sennett, sofriam uma erosĂŁo, crescia o sentimento de intimidade, aumentando igualmente a inclusĂŁo do privado no pĂșblico atravĂ©s do alargamento da cidadania, em consequĂȘncia das lutas travadas na esfera pĂșblica por vĂĄrios movimentos de emancipação, como o operĂĄrio ou o feminista. Ă medida que a pessoa era retirada da comunidade, do clĂŁ, do grupo de parentesco, em que eram "naturais" as desigualdades, no sentido aristotĂ©lico do termo, ia-se reencontrando progressivamente como indivĂduo portador de cidadania. Se o espaço privado se tornou central na definição de uma identidade, ele Ă© tambĂ©m crescentemente atravessado por mecanismos pĂșblicos de regulação. Nesse sentido, o movimento de ascensĂŁo do privado, que nas Ășltimas dĂ©cadas tem ocupado espaço de debate, deve ser cuidadosamente reinterpretado
Contribution of Maternal Antiretroviral Therapy and Breastfeeding to 24-Month Survival in Human Immunodeficiency Virus-Exposed Uninfected Children: An Individual Pooled Analysis of African and Asian Studies
Background:
Increasing numbers of HIV-infected pregnant women receive antiretroviral therapy (ART) to prevent mother-to-child transmission (PMTCT). Studies suggested that HIV-exposed uninfected (HEU) children face higher mortality than HIV-unexposed children, but evidence mostly relates to the pre-ART era, breastfeeding of limited duration and considerable maternal mortality. Maternal ART and prolonged breastfeeding under cover of ART may improve survival, although this has not been reliably quantified.
Methods:
Individual data on 19,219 HEU children from 21 PMTCT trials/cohorts undertaken 1995-2015 in Africa and Asia were pooled and the association between 24-month mortality and maternal/infant factors quantified using random-effects Cox proportional hazards models accounting for between-study heterogeneity. Adjusted attributable fractions of risks computed using the predict function in the R package "frailtypack" estimate the relative contribution of risk factors to overall mortality in HEU children.
Results:
Cumulative incidence of death was 5.5% (95%CI: 5.1-5.9) by age 24 months. Low birth weight (LBW<2500g, adjusted Hazard Ratio (aHR: 2.9), no breastfeeding (aHR: 2.5) and maternal death (aHR: 11.1) were significantly associated with increased mortality. Maternal ART (aHR: 0.5) was significantly associated with lower mortality. At population level, LBW accounted for 16.2% of child deaths by 24 months, never breastfeeding for 10.8%, mother not receiving ART for 45.6%, and maternal death for 4.3%; these factors combined explained 63.6% of deaths by age 24 months.
Conclusion:
Survival of HEU children could be substantially improved if public health strategies provided all mothers living with HIV with ART and supported optimal infant feeding and care for LBW neonates
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