Optimal sensor placement methods and criteria in dynamic testing: comparison and implementation on a pedestrian bridge

Structural health monitoring (SHM) is being widely used for the safety assessment and management of existing bridges and structures. One of the objectives related to SHM is to maximize the information gained from the structural testing, while keeping the number of sensors and consequently the cost of the sensor system to a minimum. The current work investigates four of the most influential optimal sensor placement (OSP) methods: the modal kinetic energy (MKE) method, the effective independence (EFI) method, the information entropy index (IEI) method and the MinMAC method. The methods were developed in MATLAB and used as input data the modal analysis results of a finite element model built in ANSYS of the Streicker Bridge, a pedestrian bridge located on the Princeton University Campus. The resulting sensor positions were estimated for a configuration with 14 sensors, and the four OSP methods were evaluated for different numbers of target sensors in terms of different OSP criteria: the determinant (DET) of the Fisher information matrix, the information entropy index (IEI) and the root mean square (RMS) of the off-diagonal entries of the MAC matrix. The study indicates that the EFI method should be chosen to estimate the optimal sensor positions as it provides the largest amount of information with a relatively low computation time.The authors are indebted to the Spanish Ministry of Economy and Competitiveness for the funding provided through the research project BIA2017-86811-C2-1-R. All these projects are funded with FEDER funds. Authors are also indebted to the Secretaria d’ Universitats i Recerca de la Generalitat de Catalunya for the funding provided through Agaur (2017 SGR 1481).Postprint (author's final draft

Robustness of optimal sensor methods in dynamic testing–comparison and implementation on a footbridge

One of the objectives of structural health monitoring (SHM) is to maximize the information while keeping the number of sensors, and consequently the cost of the sensor system, to a minimum. Besides, the sensor configurations must be robust in the sense that the feasibility of small errors inherent to the process must not lead to large variations in the final results. This paper presents novelties regarding the robustness evaluation to model and measurement errors of four of the most influential optimal sensor placement (OSP) methods: the modal kinetic energy (MKE) method; the effective independence (EFI) method; the information entropy index (IEI) method; and the MinMAC method. The four OSP methods were implemented on the Streicker Bridge, a footbridge located on the Princeton University Campus, to identify five mode shapes of the bridge. The mode shapes, obtained in a FE model’s modal analysis, were used as input data for the OSP analyses. The study indicates that the MKE method seems to be the most suitable method to estimate the optimal sensor positions: it provides a relatively large amount of information with the lowest computational time, and it outperforms the other three methods in terms of robustness in the usual range of number of sensors.Peer ReviewedPostprint (published version

The effects of the invasive mussel mytilus galloprovincialis and human exploitation on the indigenous mussel Perna perna on the South Coast of South Africa

In South Africa, the indigenous mussel Perna perna is threatened by both an invasive species and excessive human exploitation. The Mediterranean mussel Mytilus galloprovincialis is an invasive species that has been introduced to many parts of the world. In South Africa, this species arrived in the 1970s and spread rapidly along the west coast where today it is the dominant mussel species. Along the west coast, M. galloprovincialis is competitively superior in all aspects to the indigenous mussel species, and, as a result, has displaced some of them. On the south coast, M. galloprovincialis found more oligotrophic waters, higher species richness, and a stronger competitor in the indigenous mussel P. perna. The rate of spread of M. galloprovincialis along the south coast has decreased over the last 10 years and the present eastern limit of its distribution in South African is East London. On the south coast, M. galloprovincialis has not yet completely replaced P. perna; instead, the two exhibit spatial segregation, with P. perna dominating the low shore, M. galloprovincialis the high shore and an overlap zone between the two. An experiment on competition was carried out at one site on the south coast. The results showed that, on the low shore, P. perna is a more dominant competitor for space than M. galloprovincialis. Also byssus attachment of the two species differs, P. perna being much stronger than M. galloprovincialis, which suffers high mortality due to wave action on the low shore, especially in monospecific beds. As a result, mortality of M. galloprovincialis through wave action is reduced by the presence of P. perna, which seems to confer protection against dislodgement. However, in the absence of strong wave action, P. perna competitively excludes M. galloprovincialis. Human exploitation along 160 km of coast was examined by sampling mussel populations and using aerial surveys to determine where harvesters were distributed. Collectors did not seem to discriminate between species. The study has shown that higher abundances of mussels were found in protected or inaccessible sites, while in unprotected sites mussels were scarce. Coastal nature reserves are being proven to be effective in protecting mussel populations

Détermination des économies d'émissions de gaz à effet de serre et financières liées à des changements d'habitudes de consommation: choix d'une méthode de calcul, recherche des données de base et quantification

Ce projet de recherche et développement est une étude des économies d’émissions de gaz à effet serre et financières que l’on peut faire avec le changement de certaines habitudes chez nous, dans notre mode de vie quotidienne. Ce projet de recherche est une contribution au projet appelé « Jumelage Carbone » développé par RONGEAD et CEFREPADE, pour la mise en ligne d’un site web ayant comme objectif principal d’obtenir des financements pour pouvoir financer des projets dans des pays en développement. Ces financements proviendraient d’économies faites en modifiant nos propres habitudes de consommation. L’objectif principal de ce projet est de proposer une méthode correcte de calcul et des données pertinentes pour obtenir un résultat le plus proche possible de la réalité pour certains gestes qui apportent des économies d’énergie. Et ainsi, pouvoir avoir le bilan et les épargnes en euros et gaz à effet serre pour chaque geste proposé dans le site web. On trouve dans les chapitres centraux la recherche des données et formules pertinentes puis les analyses et calculs pour avoir des résultats. Comme conclusion on peut voir qu’avec les gestes et actions proposés au cours du projet, il est possible d’avoir une économie en euros et émissions de GES assez importante à l’échelle individuelle et que le site web devrait être un bon outil pour encourager les gens à faire les gestes proposés et aider au financement de projets.Outgoin

A cryopreservation method for bioengineered 3D cell culture models

Technologies to cryogenically preserve (a.k.a. cryopreserve) living tissue, cell lines and primary cells have matured greatly for both clinicians and researchers since their first demonstration in the 1950s and are widely used in storage and transport applications. Currently, however, there remains an absence of viable cryopreservation and thawing methods for bioengineered, three-dimensional (3D) cell models, including patients' samples. As a first step towards addressing this gap, we demonstrate a viable protocol for spheroid cryopreservation and survival based on a 3D carboxymethyl cellulose scaffold and precise conditions for freezing and thawing. The protocol is tested using hepatocytes, for which the scaffold provides both the 3D structure for cells to self-arrange into spheroids and to support cells during freezing for optimal post-thaw viability. Cell viability after thawing is improved compared to conventional pellet models where cells settle under gravity to form a pseudo-tissue before freezing. The technique may advance cryobiology and other applications that demand high-integrity transport of pre-assembled 3D models (from cell lines and in future cells from patients) between facilities, for example between medical practice, research and testing facilities

Designing weights for quartet-based methods when data are heterogeneous across lineages

Homogeneity across lineages is a general assumption in phylogenetics according to which nucleotide substitution rates are common to all lineages. Many phylogenetic methods relax this hypothesis but keep a simple enough model to make the process of sequence evolution more tractable. On the other hand, dealing successfully with the general case (heterogeneity of rates across lineages) is one of the key features of phylogenetic reconstruction methods based on algebraic tools. The goal of this paper is twofold. First, we present a new weighting system for quartets (ASAQ) based on algebraic and semi-algebraic tools, thus especially indicated to deal with data evolving under heterogeneous rates. This method combines the weights of two previous methods by means of a test based on the positivity of the branch lengths estimated with the paralinear distance. ASAQ is statistically consistent when applied to data generated under the general Markov model, considers rate and base composition heterogeneity among lineages and does not assume stationarity nor time-reversibility. Second, we test and compare the performance of several quartet-based methods for phylogenetic tree reconstruction (namely QFM, wQFM, quartet puzzling, weight optimization and Willson’s method) in combination with several systems of weights, including ASAQ weights and other weights based on algebraic and semi-algebraic methods or on the paralinear distance. These tests are applied to both simulated and real data and support weight optimization with ASAQ weights as a reliable and successful reconstruction method that improves upon the accuracy of global methods (such as neighbor-joining or maximum likelihood) in the presence of long branches or on mixtures of distributions on trees.We would like to thank the reviewers of the paper for important contributions that improved the final version of the manuscript. MC, JFS and MGL were partially supported by Spanish State Research Agency grant PID2019-103849GB-I00. MC and JFS were also supported by AEI through the Severo Ochoa and María de Maeztu Program for Centers and Units of Excellence in R &D (project CEX2020-001084-M) and by the AGAUR project 2021 SGR 00603 Geometry of Manifolds and Applications, GEOMVAP.Peer ReviewedPostprint (published version

Experimental Verification of Dielectric Models with a Capacitive Wheatstone Bridge Biosensor for Living Cells: E. coli

Dielectric spectroscopy; E. coli bacteria; Maxwell–Garnet modelEspectroscopia dieléctrica; Bacterias E. coli; Modelo Maxwell-Garnet;Espectroscòpia dielèctrica; Bacteris E. coli; Model Maxwell-GarnetDetection of bioparticles is of great importance in electrophoresis, identification of biomass sources, food and water safety, and other areas. It requires a proper model to describe bioparticles' electromagnetic characteristics. A numerical study of Escherichia coli bacteria during their functional activity was carried out by using two different geometrical models for the cells that considered the bacteria as layered ellipsoids and layered spheres. It was concluded that during cell duplication, the change in the dielectric permittivity of the cell is high enough to be measured at radio frequencies of the order of 50 kHz. An experimental setup based on the capacitive Wheatstone bridge was designed to measure relative changes in permittivity during cell division. In this way, the theoretical model was validated by measuring the dielectric permittivity changes in a cell culture of Escherichia coli ATTC 8739 from WDCM 00012 Vitroids. The spheroidal model was confirmed to be more accurate

Subsidence management and prediction system: a case study in potash mining

Peer ReviewedObjectius de Desenvolupament Sostenible::12 - Producció i Consum ResponsablesObjectius de Desenvolupament Sostenible::9 - Indústria, Innovació i InfraestructuraPostprint (published version

Animals, protists and bacteria share marine biogeographic patterns

Over millennia, ecological and evolutionary mechanisms have shaped macroecological patterns across the tree of life. Research describing these patterns at both regional and global scales has traditionally focused on the study of metazoan species. Consequently, there is a limited understanding of cross-phylum biogeographic structuring and an escalating need to understand the macroecology of both microscopic and macroscopic organisms. Here we used environmental DNA (eDNA) metabarcoding to explore the biodiversity of marine metazoans, protists and bacteria along an extensive and highly heterogeneous coastline. Our results showed remarkably consistent biogeographic structure across the kingdoms of life despite billions of years of evolution. Analyses investigating the drivers of these patterns for each taxonomic kingdom found that environmental conditions (such as temperature) and, to a lesser extent, anthropogenic stressors (such as fishing pressure and pollution) explained some of the observed variation. Additionally, metazoans displayed biogeographic patterns that suggested regional biotic homogenization. Against the backdrop of global pervasive anthropogenic environmental change, our work highlights the importance of considering multiple domains of life to understand the maintenance and drivers of biodiversity patterns across broad taxonomic, ecological and geographical scales

Publisher correction: Detection of introduced and resident marine species using environmental DNA metabarcoding of sediment and water

Correction to: Scientific Reports https://doi.org/10.1038/s41598-019-47899-7, published online 09 August 201