Passive identification of acoustic propagation media with viscous damping

International audienceThis paper concerns passive identification of an acous- tic propagation medium with viscous damping. We propose a Green correlation approach to retrieve time of arrival be- tween two sensors and to retrieve also times of arrival of first echoes. Green correlation is introduced as the cross- correlation of acoustic field generated by a white noise ex- citing the medium. This approach is experimentally vali- dated and compared to the classical method which consists in retrieving the Green function from the Green correlation through a Ward identity. We show that this latter approach appears to be numerically inaccurate and above all unneces- sary in the acoustic case with viscous damping

A global metagenomic map of urban microbiomes and antimicrobial resistance

International audienc

A global metagenomic map of urban microbiomes and antimicrobial resistance

We present a global atlas of 4,728 metagenomic samples from mass-transit systems in 60 cities over 3 years, representing the first systematic, worldwide catalog of the urban microbial ecosystem. This atlas provides an annotated, geospatial profile of microbial strains, functional characteristics, antimicrobial resistance (AMR) markers, and genetic elements, including 10,928 viruses, 1,302 bacteria, 2 archaea, and 838,532 CRISPR arrays not found in reference databases. We identified 4,246 known species of urban microorganisms and a consistent set of 31 species found in 97% of samples that were distinct from human commensal organisms. Profiles of AMR genes varied widely in type and density across cities. Cities showed distinct microbial taxonomic signatures that were driven by climate and geographic differences. These results constitute a high-resolution global metagenomic atlas that enables discovery of organisms and genes, highlights potential public health and forensic applications, and provides a culture-independent view of AMR burden in cities