Matching structure and bargaining outcomes in buyer–seller networks

We examine the relationship between the matching structure of a bipartite (buyer-seller) network and the (expected) shares of the unit surplus that each connected pair in this network can create. We show that in different bargaining environments, these shares are closely related to the Gallai-Edmonds Structure Theorem. This theorem characterizes the structure of maximum matchings in an undirected graph. We show that the relationship between the (expected) shares and the tructure Theorem is not an artefact of a particular bargaining mechanism or trade centralization. However, this relationship does not necessarily generalize to non-bipartite networks or to networks with heterogeneous link values

Surveilling the SARS -CoV-2 in sewage: the catalan case

Introduction. Shortly after the outbreak of the COVID-19 pandemic, scientists renewed their interest on the application of wastewater-based epidemiology (WBE) to track the communal circulation of SARS-CoV-2 through the quantification of its genetic traces in sewage. At national scale, such strategy was firstly implemented in The Netherlands in February 2020 and, following the Dutch example, similar sewage surveillance programs were later put into action by other countries at different scales and coverages. At the time of writing, 58 countries are currently monitoring the circulation of SARS-CoV-2 in wastewater as reported at the COVID-Poops19 website. The purpose of this work is to describe the roadmap for the implementation of a wastewater surveillance network at a national scale and to discuss the main challenges faced during its functioning. Material and methods. It should be noted that all data generated are free for scientific use, and it can be downloaded from a public repository at the Zenodo website. The database is weekly updated and contains all molecular data obtained from the samples analyzed. Results. In Catalonia, a Spanish region of 7,5 million inhabitants, the Public Health Agency of the Catalan government and the Catalan Water Agency promoted and funded the implementation of the Catalan Surveillance Network of SARSCoV-2 in Sewage (SARSAIGUA) to provide information on the circulation of SARSCoV-2 at community level that complement epidemiological & clinical data. SARSAIGUA started in 2020 by monitoring 56 WWTPs that assist 193 municipalities, representing 80% of the Catalan population. Within less than 72 hours, weekly samples are collected, analyzed, and results reported to Health authorities and finally published in an on-line dashboard. After 19 months of monitoring, the normalized daily loads of SARS-CoV-2 genes in the 56 WWTPs monitored, fairly matched the sum of COVID-19 cases along the successive pandemic waves. Moreover, a good fit was obtained between the aggregated viral load (gen copies/day/100.000 inhabitants) and the epidemiological evolution of diagnosed cases in the municipalities, served by the monitored WWTPs (rxy=0.59). In 2021, SARSAIGUA started the monitoring of SARS-CoV-2 variants by sequencing sewage samples every two weeks using Oxford nanopore technology and ARCTIC primers targeting the S gene. The deployment of this sequencing approach has allowed to track the introduction and spread of the Omicron variant and the concomitant wane of the Delta variant across the territory. Conclusions. Overall, and despite the difficulties and limitations associated to the inherent complexity of wastewater, the usefulness of WBE to rapidly detect viral transmission at community level is very helpful to Health authorities to better manage the pandemic situation. This is particularly relevant under the current scenario, where new emerging SARS-CoV-2 variants with higher fitness and transmission potential outcompete old ones in a weekly time scale. Acknowledgment. The research was realised in the JPIAMR projects: (PhageLand) – 22.80013.8007.1

The Catalan Surveillance Network of SARS-CoV-2 in Sewage: design, implementation, and performance

Wastewater-based epidemiology has shown to be an efficient tool to track the circulation of SARS-CoV-2 in communities assisted by wastewater treatment plants (WWTPs). The challenge comes when this approach is employed to help Health authorities in their decision-making. Here, we describe the roadmap for the design and deployment of SARSAIGUA, the Catalan Surveillance Network of SARS-CoV-2 in Sewage. The network monitors, weekly or biweekly, 56 WWTPs evenly distributed across the territory and serving 6 M inhabitants (80% of the Catalan population). Each week, samples from 45 WWTPs are collected, analyzed, results reported to Health authorities, and finally published within less than 72 h in an online dashboard ( https://sarsaigua.icra.cat ). After 20 months of monitoring (July 20-March 22), the standardized viral load (gene copies/day) in all the WWTPs monitored fairly matched the cumulative number of COVID-19 cases along the successive pandemic waves, showing a good fit with the diagnosed cases in the served municipalities (Spearman Rho = 0.69). Here we describe the roadmap of the design and deployment of SARSAIGUA while providing several open-access tools for the management and visualization of the surveillance data.The authors wish to thank the staff from all the WWTPs monitored for their help and technical support during the sampling campaigns. The authors acknowledge the funding received from the ACA and the ASPCAT from the Catalan Government (Generalitat de Catalunya). ICRA authors acknowledge the funding provided by the Generalitat de Catalunya through the Consolidated Research Group grants ICRA-ENV 2017 SGR 1124 and ICRA-TiA 2017 SGR 1318. ICRA researchers also thank the funding from the CERCA program of the Catalan Government.Peer reviewe

Price Variation in a Bipartite Exchange Network

We analyze the variation of prices in a model of an exchange market introduced by Kakade et al. [11], in which buyers and sellers are represented by vertices of a bipartite graph and trade is allowed only between neighbors. In this model the graph is generated probabilistically, and each buyer is connected via preferential attachment to v sellers. We show that even though the tail of the degree distribution of the sellers gets heavier as v increases, the prices at equilibrium decrease exponentially with v. This strengthens the intuition that as the number of vendors available to buyers increases, the prices of goods decrease