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At the crossroads between astronomy and ecology: exploring links between urban skyglow and nocturnal bird migration
No full textInternational audienceThis study investigates the impact of urban skyglow on nocturnal bird migration by combining night sky brightness measurements and acoustic monitoring in the Grenoble basin. Using photometric sensors and bioacoustic recorders, we tracked the spring migration of the Black-crowned Night Heron (Nycticorax nycticorax) across two urban sites. Preliminary results show no clear effect of night sky brightness on migratory activity, though temporal patterns linked to night progress and seasonality were evident. Methodo- logical limitations and behavioral biases are discussed, with perspectives for integrating radar data in future works
Measurement of the cross-sections as a function of the muon transverse momentum in collisions at 5.02 TeV
No full textInternational audienceThe cross-sections are measured at a proton-proton centre-of-mass energy TeV using a dataset corresponding to an integrated luminosity of 100 pb recorded by the LHCb experiment. Considering muons in the pseudorapidity range , the cross-sections are measured differentially in twelve intervals of muon transverse momentum between GeV. Integrated over , the measured cross-sections are \begin{align*} σ_{W^+ \to μ^+ ν_μ} &= 300.9 \pm 2.4 \pm 3.8 \pm 6.0~\text{pb}, \\ σ_{W^- \to μ^- \barν_μ} &= 236.9 \pm 2.1 \pm 2.7 \pm 4.7~\text{pb}, \end{align*} where the first uncertainties are statistical, the second are systematic, and the third are associated with the luminosity calibration. These integrated results are consistent with theoretical predictions. This analysis introduces a new method to determine the -boson mass using the measured differential cross-sections corrected for detector effects. The measurement is performed on this statistically limited dataset as a proof of principle and yields \begin{align*} m_W = 80369 \pm 130 \pm 33~\text{MeV}, \end{align*} where the first uncertainty is experimental and the second is theoretical
Induced polarization of volcanic rocks. 9. Anatomy of a rising thermal plume
No full textInternational audienceThe dynamic Stern layer petrophysical model can be used to interpret field induced polarization data and can be applied to both magmatic (volcanic and igneous) rocks and sediments. Thanks to it, field-scale tomograms of conductivity and normalized chargeability can be transformed into tomograms of porosity, Cation Exchange Capacity (CEC) and temperature. Fur ther more, kilometer-scale galvanometric induced-polarization surveys are nowadays doable thanks to the recent development of independent stations measuring the primary and secondary electrical fields. This approach reduces capacitive and inductive coupling effects inherent to systems based on long cables and allow for deeper investigations. We apply here this combined methodology (novel equipment and revised petrophysical model) to a geothermal prospect located at Mashyuza, Republic of Rwanda, in Eastern Africa. At this site, the rifting activity led to the occurrence of an extensional regime favouring the occurrence of a rising thermal plume at the intersection between two faults. The existence of this plume is expressed at the ground surface by the presence of a hot spring at a temperature of ∼52 • C (a well nearby provides a temperature of ∼65 • C). A time-domain large-scale induced polarization survey is performed. The current source signal is produced by a VIP-5000 squared signal injector and injection current values range from 1 to 4 A, with stacking of 1 s on-off signals ranging from 100 to 300 stacks to improve the signal-to-noise ratio. The size of the 3-D array is ∼1.5 km and allows a tomography down to a depth of ∼300 m. The data are inverted with the deterministic least-square technique, penalizing the roughness of the resulting tomograms. The conductivity and normalized chargeability tomograms are combined to get the temperature, porosity and CEC distributions. The temperature distribution is consistent with the temperature of the hot spring and well. The results are interpreted in terms of ground water flow pattern and dilution of the mineralized thermal water with the fresher surface meteoric water. The survey images a rising plume of warm water from a depth of at least 300 m along intersecting fracture systems
Interfaces électroniques pour la récupération d'énergie vibratoire par des générateurs piézoélectriques bistables
No full textAs part of an ambitious PSPC project (Structuring Projects for Competitiveness), involving 3 academic and 4 industrial partners, this thesis aims to develop electronics for extracting the electrical energy produced by non-linear vibratory energy harvesting devices. The use of wireless sensors in industrial applications enables gains in productivity, reliability and energy efficiency. Wireless measurement and communication technologies are available, while energy autonomy remains a major barrier to the deployment of sensor networks. The scientific background to this thesis is the development of devices for harvesting ambient vibratory energy, to be used as an energy source to power autonomous wireless sensors, as an alternative to electrochemical batteries, which are polluting and costly to replace. The power delivered must be of the order of a few hundred μW to a few mW. Current devices generally use linear mechanical resonance, which limits the range of ambient vibration frequencies that can be exploited to a few Hz on either side of the resonance frequency. This is a major barrier to the use of such devices in real environments, where ambient vibratory energy is often distributed over a wide frequency band. The approach adopted by the SYMME laboratory is based on the use of bistable (non-linear) mechanical structures combined with piezoelectric transducers. The devices developed in recent years within this framework, notably in collaboration with Cedrat Technologies, a partner in the project, exhibit the special feature of converting energy over a wide frequency band. However, these devices require the development of specific electronics to extract the electrical energy produced. These electronics can also be used to adjust the non-linear dynamics of the harvester to improve its bandwidth. However, due to their non-linear nature, the dynamics of these systems is particularly complex to predict, presenting new challenges in terms of modeling and studying the influence of the energy extraction electronics. This work has led to the development of analytical models to predict the influence of electronics on the non-linear dynamics of the harvester, and to develop a physical interpretation. The models developed have been validated experimentally, and allowed to set up comparison tools to assess the performance of different extraction electronics, and to select the electronics that maximizes the extracted power and the energy conversion frequency band. Finally, an original, self-controlled and self-powered implementation of extraction electronics has been proposed. Its performance were studied experimentally and then compared with standard electronics, highlighting a power gain between 2 and 10 over a wide frequency band, as well as the ability to extract sufficient amount of energy to power wireless sensors.Dans le cadre d'un ambitieux projet PSPC (Projets Structurants pour la Compétitivité), impliquant 3 partenaires académiques et 4 partenaires industriels, cette thèse vise à développer une électronique d'extraction de l'énergie électrique produite par des dispositifs non-linéaires de récupération d'énergie vibratoire. La mise en œuvre de capteurs communicants dans des applications industrielles permet d'obtenir des gains de productivité, de fiabilité et de performance énergétique. Les technologies de mesure et de communication sans fil sont disponibles tandis que l'autonomie énergétique demeure un des verrous majeurs au déploiement de réseaux de capteurs. Le contexte scientifique de cette thèse est le développement de dispositifs de récupération de l'énergie vibratoire ambiante, utilisés comme source d'énergie pour l'alimentation de capteurs autonomes communicants, en alternative aux piles électrochimiques, polluantes et couteuses à remplacer. La puissance délivrée doit être de l'ordre de quelques centaines de μW à quelques mW. Les dispositifs actuels utilisent généralement une résonance mécanique linéaire, ce qui limite la plage de fréquences des vibrations ambiantes pouvant être exploitée à quelques Hz de part et d'autre de la fréquence de résonance. Ceci est un obstacle majeur à l'utilisation de tels dispositifs dans des environnements réels, où l'énergie vibratoire ambiante est souvent répartie sur une large bande de fréquence. L'approche adoptée au laboratoire SYMME repose sur l'utilisation de structures mécaniques bistables (non-linéaires) combinées à des transducteurs piézoélectriques. Les dispositifs réalisés ces dernières années dans ce cadre, notamment en collaboration avec l'entreprise Cedrat Technologies, partenaire du projet, présentent la particularité de convertir de l'énergie sur une large bande de fréquence. Ces dispositifs nécessitent cependant le développement d'une électronique spécifique pour l'extraction de l'énergie électrique produite. Cette électronique peut aussi être utilisée afin d'ajuster la dynamique non-linéaire du récupérateur en vue d'améliorer sa bande passante. Cependant, en raison de leur caractère non-linéaire, la dynamique de ces systèmes est particulièrement complexe à prévoir, faisant ainsi apparaître des nouveaux défis quant à la modélisation et à l'étude de l'influence de l'électronique d'extraction de l'énergie. Ces travaux ont ainsi mené au développement de modèles analytiques permettant de prédire l'influence de l'électronique sur la dynamique non-linéaire du récupérateur et d'en développer une interprétation physique. Les modèles développés ont été validés expérimentalement et ont permis la mise en place d'outils de comparaison permettant d'évaluer les performances de différentes électroniques d'extraction et de sélectionner l'électronique permettant de maximiser la puissance extraite et la bande de fréquence de conversion de l'énergie. Enfin, une implémentation originale, auto-pilotée et auto-alimentée d'une électronique d'extraction a été proposée. Ses performances ont été étudiés expérimentalement puis comparées avec une électronique standard, mettant ainsi en lumière un gain de puissance compris entre 2 et 10 sur une large bande de fréquence, ainsi que la possibilité d'extraire une quantité d'énergie suffisante pour l'alimentation de capteurs communicants
The Longitudinal and Transverse Piezoelectric Effects of the Ferroelectric Polymer P(VDF‐TrFE)
No full textInternational audiencePolyvinylidene fluoride‐trifluoroethylene (P(VDF‐TrFE)) exhibits outstanding electromechanical properties and is a material of choice for non‐volatile memories, energy‐harvesting systems, multifunctional actuators, and sensors. However, this polymer remains one of the least understood materials among ferroelectric materials due to its semi‐crystalline structure with chains folding in elongated grains through the lamellae and amorphous regions. Here, operando high‐resolution X‐ray diffraction is exploited to unravel the P(VDF‐TrFE) structural evolution upon the first electric field application, called poling. This X‐ray technique allows revealing drastic changes in the lamellae with the ordered amorphous (OA) emergence between crystalline nanodomains. The discovery of this OA emergence is critical because it significantly affects the structure, as well as the mechanical, ferroelectric, and piezoelectric properties of the polymer. After poling, even small nanostructural changes lead to measurable effects yielding the piezoelectric coefficients. The longitudinal and transverse piezoelectric effects can be explained by the complex P(VDF‐TrFE) structure. The elongated grains consist of lamellae separated by isotropic amorphous (IA) regions. This study not only sheds light on the fundamental mechanisms occurring in P(VDF‐TrFE), but also offers guidance for new ferroelectric organic materials for flexible, biocompatible sensor and energy applications
Femoral Malpositioning of Anterolateral Ligament Reconstruction Is a Significant Risk Factor for Anterior Cruciate Ligament Graft Failure
No full textInternational audienceBackground: The femoral attachment of the anterolateral ligament (ALL) reported by anatomic studies is posterior and proximal to the lateral femoral epicondyle. Purpose: To assess the femoral positioning of the ALL graft while performing a percutaneous technique and evaluate the correlation between this positioning and the graft rupture rate, as well as clinical and functional outcomes. Study Design: Cohort study; Level of evidence, 3. Methods: A total of 211 patients undergoing combined anterior cruciate ligament (ACL) and ALL reconstruction were included. Radiological measurements, Knee injury and Osteoarthritis Outcome Score (KOOS), International Knee Documentation Committee (IKDC) score, and graft failure rate were collected at 24 months after surgery. Results: The rate of anatomic positioning of ALL femoral anchors was 79.1% (n = 167). The mean proximal and posterior distances relative to the ALL anatomic femoral position were 1.4 ± 2.8 mm and 0.2 ± 0.2 mm, respectively. The rate of outliers, defined as >5 mm from the anatomic position, was 20.85% (n = 44). The mean KOOS and IKDC score were 84 ± 10.9 and 80.1 ± 11.3, respectively. No statistically significant difference in KOOS and IKDC score was observed between the group of patients with anatomic positioning and the group of outliers ( P = .1). The rate of ACL rerupture for all patients was 3.79% (n = 8). Of these, 87.5% (n = 7) were outliers. The correlation between ALL femoral malpositioning and ACL rerupture was statistically significant ( P < .00001). Conclusion: Independent ALL reconstruction while performing a percutaneous technique enabled anatomic positioning of the ALL graft in 79% of cases. The femoral malpositioning was correlated with a higher ACL graft rerupture rate but not with a decrease in the functional outcomes
A weakly-modeled search for compact binary coalescences in Einstein Telescope
No full textInternational audienceEinstein Telescope (ET) is a project of third generation gravitational wave (GW) detector with a planned sensitivity 10 times better than current detectors such as Advanced LIGO and Advanced Virgo. The high rate of GW signals expected in the data will pose several data analysis challenges, like the ability to disentangle overlapping signals or the need to dimension the computational resources required to treat all the candidate events. We explore the behaviour and the performances of a data analysis pipeline designed to search for unmodelled GW signals with duration 1 to 1000 s on a mock dataset that consists of 1 month of data following ET design sensitivity on top of which is added a realistic distribution of compact binary coalescence (CBC) signals. Unmodelled searches are intrinsically less sensitive to CBC signals than template-based searches, but are computationally cheaper and more robust to uncertainties in the waveforms. This search recovers 38% of the total number of injected binary black hole (BBH) signals, including 89% of the systems with a total mass above 100 solar masses, as well as the majority of binary neutron star (BNS) signals closer than 850 Mpc (z = 0.17). It is also able to estimate the chirp mass of the recovered BNS with an average precision of 1.3%. Therefore, we show that this unmodelled search is able to detect a substantial amount of CBC events at a relatively low computational cost, which makes it interesting for low latency analyses and independent validation of detections made by matched filtering pipelines. We also find that the presence of many CBC signals only marginally impacts the sensitivity of the search to other kinds of unmodelled long duration transient signals, by 3% in average
Primordial black hole formation from self-resonant preheating?
No full textInternational audienceWe revisit the question of how generic is the formation of primordial black holes via self-resonant growth of inflaton fluctuations in the post-inflationary, preheating phase. Using analytical and lattice calculations, we find that primordial black hole production is far from being a generic outcome. Also, in most of the parameter space of viable inflationary models, the metric preheating term is subleading to the anharmonic terms and the approximation of a quadratic potential for describing the resonance dynamics is inadequate. Nonetheless, the anharmonicity of the potential cannot be used to rescue the mechanism: The generic outcome of the non-linear evolution of the scalar field in this case is the formation of metastable transients or oscillons, that do not generically collapse into black holes
Dark sector searches with the CMS experiment
No full textInternational audienceAstrophysical observations provide compelling evidence for gravitationally interacting dark matter in the universe that cannot be explained by the standard model of particle physics. The extraordinary amount of data from the CERN LHC presents a unique opportunity to shed light on the nature of dark matter at unprecedented collision energies. This Report comprehensively reviews the most recent searches with the CMS experiment for particles and interactions belonging to a dark sector and for dark-sector mediators. Models with invisible massive particles are probed by searches for signatures of missing transverse momentum recoiling against visible standard model particles. Searches for mediators are also conducted via fully visible final states. The results of these searches are compared with those obtained from direct-detection experiments. Searches for alternative scenarios predicting more complex dark sectors with multiple new particles and new forces are also presented. Many of these models include long-lived particles, which could manifest themselves with striking unconventional signatures with relatively small amounts of background. Searches for such particles are discussed and their impact on dark-sector scenarios is evaluated. Many results and interpretations have been newly obtained for this Report
Overview of high-density QCD studies with the CMS experiment at the LHC
No full textInternational audienceThe heavy ion (HI) physics program has proven to be an essential part of the overall physics program at the Large Hadron Collider at CERN. Its main purpose has been to provide a detailed characterization of the quark-gluon plasma (QGP), a deconfined state of quarks and gluons created in high-energy nucleus-nucleus collisions. From the start of the LHC HI program with lead-lead collisions, the CMS Collaboration has performed measurements using additional data sets in different center-of-mass energies with xenon-xenon, proton-lead, and proton-proton collisions. A broad collection of observables related to high-density quantum chromodynamics (QCD), precision quantum electrodynamics (QED), and even novel searches of phenomena beyond the standard model (BSM) have been studied. Major advances toward understanding the macroscopic and microscopic QGP properties were achieved at the highest temperature reached in the laboratory and for vanishingly small values of the baryon chemical potential. This article summarizes key QCD, QED, as well as BSM physics, results of the CMS HI program for the LHC Runs 1 (2010-2013) and 2 (2015-2018). It reviews findings on the partonic content of nuclei and properties of the QGP and describes the surprising QGP-like effects in collision systems smaller than lead-lead or xenon-xenon. In addition, it outlines the scientific case of using ultrarelativistic HI collisions in the coming decades to characterize the QGP with unparalleled precision and to probe novel fundamental physics phenomena