Study of the mechanical response of the LTP's test masses due to the action of control heaters in LISA Pathfinder

The main aim of the LISA Pathfinder (LPF) mission is to place two Test Masses into a very stable drag free environment and make very precise interferometric measurements of displacements between them. In order to achieve such an objective, it is necessary to characterize and model the disturbances that will appear. Amongst the different physical effects that will appear onboard, temperature fluctuations in the Electrode Housing (EH) generate disturbances on the interferometer (IFO) readouts, therefore they must be known and controlled. Consequently, a simulator of the whole LPF is being developed to provide a validation tool for the mission operations tele-commanding chain, as well as for a deeper understanding of the underlying physical processes happening in the LTP (LISA Technology Package), the instrument hosting the Test Masses. In this study, the whole algorithm required to calculate the forces and torques on the Test Masses due to the activation of the different LTP control heaters is detailed. More specifically, transfer functions relating heat input signals to temperature increments on the Test Masses (TMs) in the LTP frequency band, from 1 mHz to 30 mHz, are determined. Following, the EH environment is studied and discretised to calculate the forces and torques that appear through thermal effects (radiometer effect, radiation pressure effect, etc). Finally, the algorithm is implemented and some experiments from the EMP (Experiment Master Plan) are simulated to evaluate the associated dynamical effects on the Test Masses. A complete thermal model of the entire LPF spacecraft plus payload, elaborated and maintained at European Space Technology Centre (ESTEC), was used to obtain temperature distributions in response to heat inputs at prescribed spots (heaters). As a result of this work, a poster was presented at the 8th LISA Symposium that was held in the SLAC (Stanford Linear Accelerator Center), California (USA) in June 2010. The proceedings of this Symposium allowed the author to submit a paper to be published in a volume of the Journal of Physics: Conference Series, in 2011

¿Aprenden sostenibilidad los alumnos de la FIB?

En este artículo se presenta un estudio realizado para averiguar si los estudiantes de la FIB aprenden sostenibilidad a lo largo de sus estudios en la universidad. Se usa como herramienta el cuestionario de sostenibilidad del proyecto EDINSOST, que se presentó en JENUI 2018. El cuestionario tiene 34 preguntas relativas a las cuatro competencias en sostenibilidad definidas por la Comisión Sectorial de la Competencia Sostenibilidad de la CRUE. El cuestionario se ha pasado durante dos cursos consecutivos a los estudiantes de primer curso y a los estudiantes que realizan el Trabajo de Fin de Grado, con el objetivo de conocer el nivel de sostenibilidad con el que los estudiantes empiezan y acaban sus estudios. Los resultados muestran que los estudiantes presentan mejoras en el aprendizaje de la sostenibilidad en las 34 preguntas analizadas, y que la competencia de la que declaran saber más, y también de la que más aprenden, es “participación en procesos comunitarios que promuevan la sostenibilidad”. Por el contrario, la competencia en la que se declaran peor preparados es la “aplicación de principios éticos relacionados con los valores de la sostenibilidad en los comportamientos personales y profesionales”.This paper presents a study carried out to find out whether or not FIB's students learn sustainability issues throughout their studies at the university. The sustainability questionnaire of the EDINSOST project, which was presented at JENUI 2018, is used as a tool. The questionnaire has 34 questions related to the four sustainability competencies defined by the Sectorial Commission for Sustainability Competency of CRUE. The questionnaire was conducted during two consecutive courses to the first-year students and those who complete the Bachelor Thesis, with the aim of knowing the level of sustainability with which students begin and finish their studies. The results show that students improve in the learning of sustainability in the 34 questions analyzed, and that the competency of which they declare to know more, and also the one they learn the most, is "participation in community processes that promote sustainability". On the contrary, the competency in which they declare themselves less prepared is the "application of ethical principles related to the values of sustainability in personal and professional behaviors".Peer ReviewedPostprint (published version

¿Aprenden sostenibilidad los alumnos de la FIB?

En este artículo se presenta un estudio realizado para averiguar si los estudiantes de la FIB aprenden sostenibilidad a lo largo de sus estudios en la universidad. Se usa como herramienta el cuestionario de sostenibilidad del proyecto EDINSOST, que se presentó en JENUI 2018. El cuestionario tiene 34 preguntas relativas a las cuatro competencias en sostenibilidad definidas por la Comisión Sectorial de la Competencia Sostenibilidad de la CRUE. El cuestionario se ha pasado durante dos cursos consecutivos a los estudiantes de primer curso y a los estudiantes que realizan el Trabajo de Fin de Grado, con el objetivo de conocer el nivel de sostenibilidad con el que los estudiantes empiezan y acaban sus estudios. Los resultados muestran que los estudiantes presentan mejoras en el aprendizaje de la sostenibilidad en las 34 preguntas analizadas, y que la competencia de la que declaran saber más, y también de la que más aprenden, es “participación en procesos comunitarios que promuevan la sostenibilidad”. Por el contrario, la competencia en la que se declaran peor preparados es la “aplicación de principios éticos relacionados con los valores de la sostenibilidad en los comportamientos personales y profesionales”.This paper presents a study carried out to find out whether or not FIB's students learn sustainability issues throughout their studies at the university. The sustainability questionnaire of the EDINSOST project, which was presented at JENUI 2018, is used as a tool. The questionnaire has 34 questions related to the four sustainability competencies defined by the Sectorial Commission for Sustainability Competency of CRUE. The questionnaire was conducted during two consecutive courses to the first-year students and those who complete the Bachelor Thesis, with the aim of knowing the level of sustainability with which students begin and finish their studies. The results show that students improve in the learning of sustainability in the 34 questions analyzed, and that the competency of which they declare to know more, and also the one they learn the most, is "participation in community processes that promote sustainability". On the contrary, the competency in which they declare themselves less prepared is the "application of ethical principles related to the values of sustainability in personal and professional behaviors".Este trabajo ha sido parcialmente financiado por la Facultat d’Informàtica de Barcelona y por los proyectos EDINSOST (EDU2015-65574-R) y EDINSOST2-ODS (RTI2018-094982-BI00)

Optimal Design of Calibration Signals in Space Borne Gravitational Wave Detectors

Future space borne gravitational wave detectors will require a precise definition of calibration signals to ensure the achievement of their design sensitivity. The careful design of the test signals plays a key role in the correct understanding and characterization of these instruments. In that sense, methods achieving optimal experiment designs must be considered as complementary to the parameter estimation methods being used to determine the parameters describing the system. The relevance of experiment design is particularly significant for the LISA Pathfinder mission, which will spend most of its operation time performing experiments to characterize key technologies for future space borne gravitational wave observatories. Here we propose a framework to derive the optimal signals in terms of minimum parameter uncertainty to be injected to these instruments during its calibration phase. We compare our results with an alternative numerical algorithm which achieves an optimal input signal by iteratively improving an initial guess. We show agreement of both approaches when applied to the LISA Pathfinder case

Data series subtraction with unknown and unmodeled background noise

LISA Pathfinder (LPF), ESA's precursor mission to a gravitational wave observatory, will measure the degree to which two test-masses can be put into free-fall, aiming to demonstrate a residual relative acceleration with a power spectral density (PSD) below 30 fm/s$^2$/Hz$^{1/2}$ around 1 mHz. In LPF data analysis, the measured relative acceleration data series must be fit to other various measured time series data. This fitting is required in different experiments, from system identification of the test mass and satellite dynamics to the subtraction of noise contributions from measured known disturbances. In all cases, the background noise, described by the PSD of the fit residuals, is expected to be coloured, requiring that we perform such fits in the frequency domain. This PSD is unknown {\it a priori}, and a high accuracy estimate of this residual acceleration noise is an essential output of our analysis. In this paper we present a fitting method based on Bayesian parameter estimation with an unknown frequency-dependent background noise. The method uses noise marginalisation in connection with averaged Welch's periodograms to achieve unbiased parameter estimation, together with a consistent, non-parametric estimate of the residual PSD. Additionally, we find that the method is equivalent to some implementations of iteratively re-weighted least-squares fitting. We have tested the method both on simulated data of known PSD, and to analyze differential acceleration from several experiments with the LISA Pathfinder end-to-end mission simulator.Comment: To appear Phys. Rev. D90 August 201

Genetic Variants of the DSF Quorum Sensing System in Stenotrophomonas maltophilia Influence Virulence and Resistance Phenotypes Among Genotypically Diverse Clinical Isolates

Altres ajuts: Departament de Salut, Generalitat de Catalunya: SLT002/16/00349The pathogenicity of Stenotrophomonas maltophilia is regulated in part by its quorum sensing (QS) system. The main QS signaling molecule in S. maltophilia is known as diffusible signal factor (DSF), and the rpf gene cluster is responsible for its synthesis and perception. Two cluster variants have been previously described, rpf -1 and rpf -2, which differ basically in the conditions under which DSF is produced. Here, correlations between the rpf variant and antibiotic susceptibility, LPS electrophoretic profiles and virulence-related phenotypes were evaluated for a collection of 78 geographically and genetically diverse clinical strains of S. maltophilia. In general there were associations between previously established genogroups and the genetic variant of the rpf cluster. However, only few genotype-phenotype correlations could be observed. Resistance to the β-lactam antibiotics ceftazidime and ticarcillin was associated with strains carrying the rpf -1 variant, whereas strains of variant rpf -2, particularly those of genogroup C, showed higher resistance levels to colistin. Strains of variant rpf -2 were also significantly more virulent to Galleria mellonella larvae than those of rpf -1, most likely due to an increased ability of rpf -2 strains to form biofilms. A comparative genomic analysis revealed the presence of proteins unique to individual genogroups. In particular, the strains of genogroup C share an operon that encodes for a new virulence determinant in S. maltophilia related to the synthesis of an alternative Flp/Tad pilus. Overall, this study establishes a link between the DSF-based QS system and the virulence and resistance phenotypes in this species, and identifies potential high-risk clones circulating in European hospitals

Genetic variants of the DSF quórum sensing system in Stenotrophomonas maltophilia influence virulence and resistance phenotypes among genotypically diverse clinical isoaltes

The pathogenicity of Stenotrophomonas maltophilia is regulated in part by its quorum sensing (QS) system. The main QS signaling molecule in S. maltophilia is known as diffusible signal factor (DSF), and the rpf gene cluster is responsible for its synthesis and perception. Two cluster variants have been previously described, rpf-1 and rpf-2, which differ basically in the conditions under which DSF is produced. Here, correlations between the rpf variant and antibiotic susceptibility, LPS electrophoretic profiles and virulence-related phenotypes were evaluated for a collection of 78 geographically and genetically diverse clinical strains of S. maltophilia. In general there were associations between previously established genogroups and the genetic variant of the rpf cluster. However, only few genotype-phenotype correlations could be observed. Resistance to the β-lactam antibiotics ceftazidime and ticarcillin was associated with strains carrying the rpf-1 variant, whereas strains of variant rpf-2, particularly those of genogroup C, showed higher resistance levels to colistin. Strains of variant rpf-2 were also significantly more virulent to Galleria mellonella larvae than those of rpf-1, most likely due to an increased ability of rpf-2 strains to form biofilms. A comparative genomic analysis revealed the presence of proteins unique to individual genogroups. In particular, the strains of genogroup C share an operon that encodes for a new virulence determinant in S. maltophilia related to the synthesis of an alternative Flp/Tad pilus. Overall, this study establishes a link between the DSF-based QS system and the virulence and resistance phenotypes in this species, and identifies potential high-risk clones circulating in European hospitals