A comparative study of calibration methods for low-cost ozone sensors in IoT platforms

© 2019 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes,creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.This paper shows the result of the calibration process of an Internet of Things platform for the measurement of tropospheric ozone (O 3 ). This platform, formed by 60 nodes, deployed in Italy, Spain, and Austria, consisted of 140 metal–oxide O 3 sensors, 25 electro-chemical O 3 sensors, 25 electro-chemical NO 2 sensors, and 60 temperature and relative humidity sensors. As ozone is a seasonal pollutant, which appears in summer in Europe, the biggest challenge is to calibrate the sensors in a short period of time. In this paper, we compare four calibration methods in the presence of a large dataset for model training and we also study the impact of a limited training dataset on the long-range predictions. We show that the difficulty in calibrating these sensor technologies in a real deployment is mainly due to the bias produced by the different environmental conditions found in the prediction with respect to those found in the data training phase.Peer ReviewedPostprint (author's final draft

Nonylphenol, Octyphenol, and Bisphenol A in Groundwaters as a Result of Agronomic Practices

Due to increasing concern about the assessment and protection of the quality of groundwater as a limited natural resource, an extensive monitoring program has been carried out, covering a highly agricultural area of Catalonia where different types of crops have been grown during the last 5–10 years. The paper reports the analytical protocol used (sampling, filtration, preconcentration, and analysis) and the most relevant organic compounds present in groundwaters from agricultural areas as well as the concentration levels found

Del treball d'aula a les competències bàsiques

Aquest article és el resum del treball dut a terme per un grup de professors de l?institut Narcís Xifra de Girona, preocupats per la incorporació de les competències bàsiques, no només en les programacions, sinó en les activitats d?aula i per aconseguir la implicació del màxim nombre de professorat. Si havíem de tirar endavant un projecte com aquest des del primer moment s?havia de tenir clar quan parlàvem de competències: què volíem dir? És a dir, definir què entenia cada un de nosaltres per competència i, a partir d?aquí, analitzar la implicació de les diferents matèries en les diferents competències. També s?estudia com aplicar als grups de diversitat el treball per competències bàsiques (CB) i la part més innovadora era la concreció d?aquestes en activitats d?ensenyament-aprenentatge. Com a resultat es van elaborar quatre graelles, una per cada nivell d?ESO, que recollien activitats o continguts de cada matèria (consensuats per departaments) i que permetien interrelacionar: matèries, competències treballades i lligams amb altres cursos. Això va permetre presentar a l?inici de curs un índex de programació marc que tot el professorat ha utilitzat, crear uns instruments per fer un seguiment i una anàlisi posterior d?aquestes activitats d?aula consensuades. En aquests moments podríem dir que ens hem embarcat en un projecte ambiciós i estem a mitja travessia.From classroom work to key skills. The article summarises a project carried out by a group of school teachers at the Narcís Xifra Secondary School in Girona. Their aim was to include key skills not only in the programming phase but also in classroom activities and to encourage the involvement of a maximum number of teachers. To go ahead with the project, they first had to have a very clear idea about what they considered key skills to involve. Each member defined the skills and their relationship with the different subjects and described how to adapt each one to diversity groups. The group of teachers then took the innovative decision to concretise the skills in teaching-learning activities. This led to the drafting of four grids, one for each level of compulsory secondary education (12-16 yrs, ESO), which included activities or content from each subject (agreed by departments) allowing for overlaps between materials, skills and ESO levels. By the beginning of the school year, they were able to present the index of a framework programme for all teachers to use as well as monitoring instruments to assess the approved classroom activities. The ambitious project is currently at a mid-way stage

Distributed multi-scale calibration of low-cost ozone sensors in wireless sensor networks

New advances in sensor technologies and communications in wireless sensor networks have favored the introduction of low-cost sensors for monitoring air quality applications. In this article, we present the results of the European project H2020 CAPTOR, where three testbeds with sensors were deployed to capture tropospheric ozone concentrations. One of the biggest challenges was the calibration of the sensors, as the manufacturer provides them without calibrating. Throughout the paper, we show how short-term calibration using multiple linear regression produces good calibrated data, but instead produces biases in the calculated long-term concentrations. To mitigate the bias, we propose a linear correction based on Kriging estimation of the mean and standard deviation of the long-term ozone concentrations, thus correcting the bias presented by the sensors.Peer ReviewedPostprint (published version

Multisensor data fusion calibration in IoT air pollution platforms

© 2020 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes,creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.This article investigates the calibration of low-cost sensors for air pollution. The sensors were deployed on three Internet of Things (IoT) platforms in Spain, Austria, and Italy during the summers of 2017, 2018, and 2019. One of the biggest challenges in the operation of an IoT platform, which has a great impact on the quality of the reported pollution values, is the calibration of the sensors in an uncontrolled environment. This calibration is performed using arrays of sensors that measure cross sensitivities and therefore compensate for both interfering contaminants and environmental conditions. This article investigates how the fusion of data taken by sensor arrays can improve the calibration process. In particular, calibration with sensor arrays, multisensor data fusion calibration with weighted averages, and multisensor data fusion calibration with machine learning models are compared. Calibration is evaluated by combining data from various sensors with linear and nonlinear regression models.This work was supported in part by the NationalSpanish funding under Grant TIN2016-78473-C3-1-R, in part by RegionalProject under Grant 2017SGR-990, in part by EU H2020 CAPTOR Project, inpart by AGAUR SGR44, in part by the Agencia Estatal de Investigación underGrant CGL2017-82093-ERC, and in part by the Spanish Ministry of Economy,Industry and Competitiveness under Grant EUIN2017-85799Peer ReviewedPostprint (author's final draft

Cerebral ischaemia and matrix metalloproteinase-9 modulate the angiogenic function of early and late outgrowth endothelial progenitor cells

The enhancement of endogenous angiogenesis after stroke will be critical in neurorepair therapies where endothelial progenitor cells (EPCs) might be key players. Our aim was to determine the influence of cerebral ischaemia and the role of matrix metalloproteinase-9 (MMP-9) on the angiogenic function of EPCs. Permanent focal cerebral ischaemia was induced by middle cerebral artery (MCA) occlusion in MMP-9/knockout (MMP-9/KO) and wild-type (WT) mice. EPCs were obtained for cell counting after ischaemia (6 and 24 hrs) and in control animals. Matrigel™ assays and time-lapse imaging were conducted to monitor angiogenic function of WT and MMP9-deficient EPCs or after treatment with MMP-9 inhibitors. Focal cerebral ischaemia increased the number of early EPCs, while MMP-9 deficiency decreased their number in non-ischaemic mice and delayed their release after ischaemia. Late outgrowth endothelial cells (OECs) from ischaemic mice shaped more vessel structures than controls, while MMP-9 deficiency reduced the angiogenic abilities of OECs to form vascular networks, in vitro. Treatment with the MMP inhibitor GM6001 and the specific MMP-9 inhibitor I also decreased the number of vessel structures shaped by both human and mouse WT OECs, while exogenous MMP-9 could not revert the impaired angiogenic function in MMP-9/KO OECs. Finally, time-lapse imaging showed that the extension of vascular networks was influenced by cerebral ischaemia and MMP-9 deficiency early during the vascular network formation followed by a dynamic vessel remodelling. We conclude that focal cerebral ischaemia triggers the angiogenic responses of EPCs, while MMP-9 plays a key role in the formation of vascular networks by EPCs

Dataclay: A distributed data store for effective inter-player data sharing

In the Big Data era, both the academic community and industry agree that a crucial point to obtain the maximum benefits from the explosive data growth is integrating information from different sources, and also combining methodologies to analyze and process it. For this reason, sharing data so that third parties can build new applications or services based on it is nowadays a trend. Although most data sharing initiatives are based on public data, the ability to reuse data generated by private companies is starting to gain importance as some of them (such as Google, Twitter, BBC or New York Times) are providing access to part of their data. However, current solutions for sharing data with third parties are not fully convenient to either or both data owners and data consumers. Therefore we present dataClay, a distributed data store designed to share data with external players in a secure and flexible way based on the concepts of identity and encapsulation. We also prove that dataClay is comparable in terms of performance with trendy NoSQL technologies while providing extra functionality, and resolves impedance mismatch issues based on the Object Oriented paradigm for data representation.This work has been supported by the Spanish Government (grant SEV2015-0493 of the Severo Ochoa Program), by the Spanish Ministry of Science and Innovation (contract TIN2015-65316) and by Generalitat de Catalunya (contract 2014-SGR-1051). Special thanks go to Dr. Oscar Romero (Universitat Politècnica de Catalunya) for providing helpful feedback on the paper.Peer ReviewedPostprint (published version

A new set of DNA macrochips for the yeast Saccharomyces cerevisiae: features and uses

The yeast Saccharomyces cerevisiae has been widely used for the implementation of DNA chip technologies. For this reason and due to the extensive use of this organism for basic and applied studies, yeast DNA chips are being used by many laboratories for expression or genomic analyses. While membrane arrays (macroarrays) offer several advantages, for many laboratories they are not affordable. Here we report that a cluster of four Spanish molecular-biology yeast laboratories, with relatively small budgets, have developed a complete set of probes for the genome of S. cerevisiae. These have been used to produce a new type of macroarray on a nylon surface. The macroarrays have been evaluated and protocols for their use have been optimized. [Int Microbiol 2004; 7(3):199-206