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Companion guide to the marsquake catalog from InSight, Sols 0–478: Data content and non-seismic events
Get PDFThe InSight (Interior Exploration using Seismic Investigations, Geodesy and Heat Transport) mission landed on the surface of Mars on November 26, 2018. One of the scientific instruments in the payload that is essential to
the mission is the SEIS package (Seismic Experiment for Interior Structure) which includes a very broadband and
a short period seismometer. More than one year since the landing, SEIS continues to be fully operational and has
been collecting an exceptional data set which contains not only the signals of seismic origins, but also noise and
artifacts induced by the martian environment, the hardware on the ground that includes the seismic sensors, and
the programmed operational activities of the lander. Many of these non-seismic signals will be unfamiliar to the
scientific community. In addition, many of these signals have signatures that may resemble seismic events either
or both in time and frequency domains. Here, we report our observations of common non-seismic signals as seen
during the first 478 sols of the SEIS data, i.e. from landing until the end of March 2020. This manuscript is
intended to provide a guide to scientists who use the data recorded on SEIS, detailing the general attributes of
the most commonly observed non-seismic features. It will help to clarify the characteristics of the seismic dataset
for future research, and to avoid misinterpretations when searching for marsquakes
How Comparable are Microbial Electrochemical Systems around the Globe? An Electrochemical and Microbiological Cross‐Laboratory Study
Get PDFA cross‐laboratory study on microbial fuel cells (MFC) which involved different institutions around the world is presented. The study aims to assess the development of autochthone microbial pools enriched from domestic wastewater, cultivated in identical single‐chamber MFCs, operated in the same way, thereby approaching the idea of developing common standards for MFCs. The MFCs are inoculated with domestic wastewater in different geographic locations. The acclimation stage and, consequently, the startup time are longer or shorter depending on the inoculum, but all MFCs reach similar maximum power outputs (55±22 μW cm−2) and COD removal efficiencies (87±9 %), despite the diversity of the bacterial communities. It is inferred that the MFC performance starts when the syntrophic interaction of fermentative and electrogenic bacteria stabilizes under anaerobic conditions at the anode. The generated power is mostly limited by electrolytic conductivity, electrode overpotentials, and an unbalanced external resistance. The enriched microbial consortia, although composed of different bacterial groups, share similar functions both on the anode and the cathode of the different MFCs, resulting in similar electrochemical output
On the fluidization/sedimentation velocity of a homogeneous suspension in a low-inertia fluid
Get PDFThe modeling of the fluidization or sedimentation velocity of a suspension of solid particles is revisited by examining experiments conducted in either a liquid or a gas. A general expression is found in the case of negligible fluid inertia, i.e. at low Reynolds or Archimedes number. It is built as the product of the velocity of an isolated particle by three non-dimensional corrections that each takes into account a specific physical mechanism. The first correction reflects the variation of the buoyancy with the particle concentration. The second correction describes how the drag force increases with the concentration in case of negligible particle inertia. The third one accounts for the further increase of the drag when the particle inertia is increased. Remarkably, each correction only relies on a single of the three independent non-dimensional groups that control the problem: (1) the particle volume fraction Φs ; (2) the ratio Φs /Φ pack where Φ pack is the bed packing concentration; (3) the Stokes number St 0 , which characterizes the inertia of the particles and controls their agitation. Moreover, the onset of the instability that separates the homogeneous regime from the heterogeneous one is found to be controlled similarly by the Stokes number. Empirical expressions of the corrections are given, which provide a reliable tool to predict fluidization and sedimentation velocities for all values of the three non-dimensional numbers. The present results emphasize the crucial role of particle inertia, which is often disregarded in previous modeling approaches, such as that of Richardson and Zaki
Bridge expansion after coalescence of two droplets in air: inertial regime
Get PDFWhen two liquid droplets approach at negligible velocity in air, their coalescence spontaneously occurs by jump-to-contact instability and a connecting bridge joining the two facing interfaces at the nanoscale is created. We report experimental investigations of the expansion of this initial bridge by means of high-speed imaging. By considering droplets of water, polydimethylsiloxane or paraffin of a few hundred micrometers, we investigate regimes where inertia takes a major role. Depending on the Ohnesorge number Oh, the dynamics of the bridge differs a lot. For Oh ≈ 1, the initial flow is rapidly attenuated and the connecting bridge between the two droplets adopts a smooth parabolic shape. The maximum interface curvature and the minimum liquid pressure remain at the bridge centre. The expansion is thus caused by the capillary pressure that drives the fluid towards the center. At small Oh, in the inertial regime, the length of the initial bridge grows at constant speed and the bridge expansion can be described by the propagation of non-dispersive capillary wave packets. The central part of the bridge takes a cylindrical shape connected to the droplets by a narrow region of very large curvature. At the resolved scale, the interface exhibits slope discontinuities. By considering dihedral potential flows that result of the presence of the slope discontinuities, we show that the apparent angle made by the interface controls the flow-rate that enters the bridge and thus determines its radial expansion
Vérification d’une bibliothèque mathématique d’un autopilote avec Frama-C
Get PDFLors du développement de système critiques, comme par exemple un autopilote de drone, il est essentiel de s’assurer que le programme est sûr, en utilisant par exemple des méthodes formelles. Pour faciliter la vérification, on se restreint généralement à une abstraction du système ou un sous-ensemble. Cet article présente la vérification d’une bibliothèque mathématique de l’autopilote Paparazzi, à l’aide de l’outil Frama-C, afin de garantir l’absence d’erreur à l’exécution et certaines propriétés fonctionnelles
Carbon nanomaterials-based polymer-matrix nanocomposites for antimicrobial applications: A review
Get PDFCarbon Nanomaterials present many exceptional properties, including antimicrobial ones. The transfer of the latter through their incorporation into materials has generated a growing interest with a significant increase in number of publications since 2011. The use of polymeric matrices presents many advantages, because polymers are efficient nanoparticles holders and also exhibit intrinsic antimicrobial properties in some cases. The state of the art of fabrication methods and presumed antimicrobial mechanism is presented, focusing on antibacterial activity as the latter is, by far, the most discussed in the literature. Even if many examples of such nanocomposites are available, most of them correspond to carbon nanomaterials incorporated in the volume, while only the surface is of interest in terms of intrinsic (and thus expected long-term) activity, and there is still a lack of information concerning the occurring antimicrobial mechanisms. We have identified the good stability of carbon nanomaterials in biological environment as an interesting option in terms of durability of the antimicrobial effect and will discuss this question in detail, as well as the fact that there are currently no clear conclusions concerning toxicity aspects due to the possible release of such nanoparticles in use conditions
Stream Hydrochemical Response to Flood Events in a Multi-Lithological Karstic Catchment from the Pyrenees Mountains (SW France)
Get PDFHydrological variations hold a significant influence over the water chemistry in the karstic critical zone. In this context, the karstic Baget Catchment (BC) has been monitored at a high resolution over two years at the outlet in order to set up a typology of the flood events. The objective was to assess the multiple streamwater physico-chemical patterns in response to hydrological variations, streamflow component (quick-response, subsurface, and baseflow) and lithological contributions, and biogeochemical processes. The karstic catchment exhibited an impulsive response to flood events in relation to the typical structural and morphological characteristics of the karst. In addition, this response was constrained by the magnitude of the rainfall and the preceding hydroclimatic conditions. The variability of the dissolved load in streamflow was closely associated with the characteristics of the weathered rocks and the hydrological conditions throughout the year. Two simple indicators allow to characterize the concentration–discharge relationships with different hysteresis patterns on a set of floods with various intensities and shapes of the hydrograph and under different hydrological conditions before the flood. Almost all elements exhibited either clockwise loops or more complex behaviors, suggesting a higher overall concentration when the major water contribution comes from the quick-response flow (karst and surface runoff fraction). Besides, the epikarst flushing under dry conditions led counterclockwise hysteresis patterns for calcium (Ca2+) and bicarbonate (HCO3−) which revealed an overall chemostatic behavior as a result of carbonate dissolution in the karst. On the contrary, sulfate (SO42−) exhibited the widest relative variation during flooding and showed a significant sensitivity to the dilution process with increasing discharge. For medium flood episodes (Qmax 8.3 m3·s−1) occurring after several rain events, a dilution pattern was noted for all elements originating from rock weathering. Finally, high-frequency sampling during storm events improved the understanding of the factors controlling the hydrochemical dynamic in karstic catchments
Generalized isolation forest for anomaly detection
Get PDFThis letter introduces a generalization of Isolation Forest (IF) based on the existing Extended IF (EIF). EIF has shown some interest compared to IF being for instance more robust to some artefacts. However, some information can be lost when computing the EIF trees since the sampled threshold might lead to empty branches. This letter introduces a generalized isolation forest algorithm called Generalized IF (GIF) to overcome these issues. GIF is faster than EIF with a similar performance, as shown in several simulation results associated with reference databases used for anomaly detection
Outlier detection at the parcel-level in wheat and rapeseed crops using multispectral and SAR time series
Get PDFThis paper studies the detection of anomalous crop development at the parcel-level based on an unsupervised outlier detection technique. The experimental validation is conducted on rapeseed and wheat parcels located in Beauce (France). The proposed methodology consists of four sequential steps: (1) preprocessing of synthetic aperture radar (SAR) and multispectral images acquired using Sentinel-1 and Sentinel-2 satellites, (2) extraction of SAR and multispectral pixel-level features, (3) computation of parcel-level features using zonal statistics and (4) outlier detection. The different types of anomalies that can affect the studied crops are analyzed and described. The different factors that can influence the outlier detection results are investigated with a particular attention devoted to the synergy between Sentinel-1 and Sentinel-2 data. Overall, the best performance is obtained when using jointly a selection of Sentinel-1 and Sentinel-2 features with the isolation forest algorithm. The selected features are co-polarized (VV) and cross-polarized (VH) backscattering coefficients for Sentinel-1 and five Vegetation Indexes for Sentinel-2 (among us, the Normalized Difference Vegetation Index and two variants of the Normalized Difference Water). When using these features with an outlier ratio of 10%, the percentage of detected true positives (i.e., crop anomalies) is equal to 94.1% for rapeseed parcels and 95.5% for wheat parcels
An Artificial Interface for High Cell Voltage Aqueous-Based Electrochemical Capacitors
Get PDFAqueous electrolytes are very effective for supercapacitor applications but their narrow electrochemical potential window (∼1 V) and associated limited energy currently limits their use. Here, we demonstrate a new strategy to enlarge the potential window by designing an artificial interface (ai). An effective ai was achieved via a mixture of siloxanes doped with an ionic liquid, 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (EMI TFSI). Indeed, the as-deposited ai on the carbon-based electrode hinders the electron charge transfer but not the ionic charge transfer, making the ai ionic conductive. As a result, a cell voltage of about 1.8 V was obtained in aqueous electrolyte-EMI HSO4 1 mol l−1 in water. Used as a membrane, the ai was found to be ionically specific to EMI+; the proton transference number being close to zero. These results show the strategy of developing an ai at the electrode/electrolyte interface could represent a new path for aqueous-based carbon-carbon supercapacitors to reach higher cell voltages, providing both higher specific energy and power