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Planktonic processes playing a key role in the fate of matter and global biogeochemical cycles, gross primary production (GPP), net community production (NCP) respiration (R), growth (µ) and loss (l) rates of phytoplankton were quantified using high-frequency (HF) data acquired by sensors immersed in in situ mesocosms during experiments simulating warming (Thau Lagoon) and brownification (Hopavågen Bay, Norway). A new method for estimating GPP, R and NCP was established using sensor data measuring dissolved O2 concentration from experiments in Thau lagoon. It was compared with an existing method using HF data and with the classical incubation technique (Winkler). It has the advantage of considering the variability in the coupling between day-night and dissolved O2 cycles and allowed to estimate a daytime respiration on average 41% higher than the nighttime one, in agreement with the positive theoretical effect of light on respiration. Application of this new method in an experiment testing the effects of brownification on planktonic community functioning in Hopavågen Bay revealed a negative effect of brownification of about 30% on GPP and R, associated with significant changes in phytoplankton pigment concentration related to physiological acclimation to low light conditions.The warming scenario for 2100 in the Mediterranean was tested in two in situ mesocosm experiments in spring and autumn 2018 in Thau lagoon. Warming increased phytoplankton’s µ and l, estimated with HF fluorescence data. The estimates of µ and l were compared to the growth and grazing rates obtained via the dilution technique, highlighting a good agreement between the two methods, confirming the robustness of the estimates obtained with the HF data, despite some differences between results due to the fact that l, estimated with the HF data, considers sedimentation, mesozooplankton grazing mortality and viral lysis while the dilutions only allow the estimation of microzooplankton grazing. An experiment simulating a heatwave was also carried out in Thau in spring 2019. The HF data showed a positive effect of the heat wave on GPP, R, µ and l that lasted for several days after the end of the heatwave, except for µ. The heatwave shifted the trophic state of the system towards heterotrophy and favored cyanobacteria at the expense of dinoflagellates, however most of the studied processes showed good resistance and recovery from the heatwave. Warming induced contrasting responses in Thau lagoon planktonic community, shifting the system towards autotrophy or heterotrophy depending on the investigated season. The community from Thau lagoon was more resilient and recovered better from a punctual climate change event than the community from Hopavågen, potentially because the planktonic community from Thau evolved in an environment naturally subject to strong temperature variations and/or because warming is a less drastic disturbance than brownification. The methods established in the thesis represent a novel approach to obtain reliable estimates of planktonic processes highlighting the effects of climate change on the functioning of coastal ecosystems. There are many perspectives to continue this work, using these new methods to study other disturbances in other ecosystems; Les processus planctoniques jouant un rôle primordial dans le devenir de la matière et les cycles biogéochimiques globaux, la production primaire brute (PPB), la production communautaire nette (PCN), la respiration (R) et les taux de croissance (µ) et de pertes (l) du phytoplancton ont été quantifiés via l’utilisation de données à haute-fréquence (HF) acquises par des capteurs immergés dans des mésocosmes in situ lors d’expériences simulant le réchauffement (lagune de Thau) et le brunissement (baie d’Hopavågen, Norvège). Une nouvelle méthode pour estimer la PPB, la R et la PCN a été établie à partir des données de capteurs mesurant la concentration en O2 dissout issues d’expériences dans la lagune de Thau. Elle a été comparée avec une méthode utilisant des données HF déjà existante ainsi qu’avec la technique classique des incubations (Winkler). Elle présente l’avantage de prendre en compte la variabilité dans le couplage entre cycles jour-nuit et de l’O2 dissout et a permis d’estimer une respiration la journée en moyenne 41% plus élevée que celle de la nuit, en accord avec l’effet théorique positif de la lumière sur la respiration. L’application de cette nouvelle méthode lors d’une expérience testant les effets du brunissement sur le fonctionnement des communautés planctoniques de la baie d’Hopavågen a révélé un effet négatif du brunissement d’environ 30% sur la PPB et la R, associé à d’importants changements dans la concentration des pigments phytoplanctoniques liés à une acclimatation physiologique aux faibles conditions de lumières. Le réchauffement simulant les scénarios pour 2100 en Méditerranée a été testée lors de deux expériences de mésocosmes in situ au printemps et à l’automne 2018 à Thau. Ainsi, le réchauffement a augmenté µ et l du phytoplancton, estimés avec les données de fluorescence HF. Les estimations de µ et de l ont été comparées aux taux de croissance et de prédation obtenus via la technique des dilutions, mettant en évidence une bonne concordance entre les résultats obtenus, confirmant la robustesse des estimations obtenues avec les données HF, ceci malgré certaines différences entre les résultats de deux méthodes employées du fait que l, estimé avec les données HF, prend en compte la sédimentation, la mortalité par le broutage du mésozooplancton et par la lyse virale alors que les dilutions ne permettent d’estimer que le broutage du microzooplancton. Une expérience simulant une vague de chaleur a également été réalisée à Thau au printemps 2019. Les données HF ont mis en lumière un effet positif de la vague de chaleur sur la PPB, la R, µ et l qui s’est prolongé plusieurs jours après l’arrêt de la vague de chaleur, sauf pour µ. La vague de chaleur a basculé l’état trophique du système vers l’hétérotrophie et a favorisé les cyanobactéries au détriment des dinoflagellés, cependant la majorité des processus étudiés ont montré de bonnes résistance et récupération face à la vague de chaleur. Le réchauffement a induit des réponses contrastées du plancton de la lagune de Thau, basculant le système vers l’autotrophie ou l’hétérotrophie en fonction de la saison investiguée. La communauté de Thau a été plus résistante et a mieux récupéré face à un événement ponctuel du changement climatique que la communauté d’Hopavågen, potentiellement parce que la communauté planctonique de Thau a évolué au sein d’un environnement naturellement soumis aux fortes variations de température et/ou parce que le réchauffement est une perturbation moins drastique que le brunissement. Les méthodes établies dans la thèse représentent une approche novatrice afin d’obtenir des estimations fiables de processus planctoniques mettant en évidence sur les effets du changement climatique sur le fonctionnement des écosystèmes côtiers. De nombreuses perspectives s’ouvrent quant à la poursuite de ces travaux, en utilisant ces nouvelles méthodes pour étudier d’autres perturbations dans d’autres écosystèmes

We present a physics-based circuit-compatible model for double-gated two-dimensional semiconductor-based field-effect transistors, which provides explicit expressions for the drain current, terminal charges, and intrinsic capacitances. The drain current model is based on the drift-diffusion mechanism for the carrier transport and considers Fermi–Dirac statistics coupled with an appropriate field-effect approach. The terminal charge and intrinsic capacitance models are calculated adopting a Ward–Dutton linear charge partition scheme that guarantees charge conservation. It has been implemented in Verilog-A to make it compatible with standard circuit simulators. In order to benchmark the proposed modeling framework we also present experimental DC and high-frequency measurements of a purposely fabricated monolayer MoS2-FET showing excellent agreement between the model and the experiment and thus demonstrating the capabilities of the combined approach to predict the performance of 2DFETs., The authors would like to thank the financial support of Spanish Government under projects TEC2017-89955-P (MINECO/AEI/FEDER, UE), TEC2015-67462-C2-1-R (MINECO), and RTI2018-097876-B-C21 (MCIU/AEI/FEDER, UE). F.P. and D.J. also acknowledge the support from the European Union’s Horizon 2020 Research and Innovation Program under Grant Agreement No. 785219 GrapheneCore2. A.G. acknowledges the funding by the Consejería de Economía, Conocimiento, Empresas y Universidad de la Junta de Andalucía and European Regional Development Fund (ERDF), ref. SOMM17/6109/UGR. E.G.M. gratefully acknowledges Juan de la Cierva Incorporación IJCI-2017-32297 (MINECO/AEI). A.T.-L. acknowledges the FPU program (FPU16/04043). D.A. acknowledges the Army Research Office for partial support of this work, and the NSF NASCENT ERC and NNCI programs.

Mg substituted X–type hexagonal ferrites with the chemical composition Ba2Zn2-xMgxFe28O46 (x = 0.0, 0.4, 0.8, 1.2, 1.6 and 2.0) were successfully synthesised by a sol–gel auto–combustion technique, in order to investigate the effect of Mg substitution on structural, magnetic and dielectric properties. XRD analysis of prepared samples revealed the formation of pure X–type phase. The variations (decreasing trend) in lattice parameters with Mg substitution indicate the incorporation of Mg substitution into the crystal structure. The average crystallite size of heated powders was found to be in the range of 16–22 nm. For the first time, the RT hysteresis loops of Ba2Zn2Fe28O46 (Zn2X), Ba2Mg2Fe28O46 (Mg2X) and Ba2Zn2-xMgxFe28O46 (x = 0.0, 0.4, 0.8, 1.2, 1.6 and 2.0) were measured. The saturation magnetisation showed an initial decrease with x = 0.4 − 1.2, and then an increase with x > 1.2, to the largest final values of 63.29 A m2 kg−1 for the fully Mg–substituted x = 2.0. The value of coercivity lies in the range of 89.9–209.3 kA m−1 (1130–2630 Oe), and the magnetic results suggest that the compositions x = 0.0, 0.4 and 1.2 possess multi-domain microstructures, while x = 0.8, 1.6 and 2.0 possess single domain microstructures. The room temperature Mӧssbauer spectra were analysed with six sextets of five magnetic sublattices, and the results are presented as a function of Mg substitution. It was found that initial levels of Mg substitution reduce the Fe populations at a and b (spin up) sublattices, but that with x > 1.2 these become repopulated at fIV (spin down) site, resulting in an increase in magnetisation. Dielectric parameters such as dielectric constant and loss factor were studied as a function of frequency, and results show normal behaviour for ferrimagnetic materials. At low frequencies (100 Hz–2 MHz), relative permittivity was constant between 0.3 and 1.5 above 20 kHz, with the higher values belonging to the more dense samples. All Mg substituted samples had lower losses above 20 kHz than the pure Zn2X. In complex measurements at microwave frequencies (500 MHz–13.5 GHz), all samples had a real permittivity of around 7.5, except for the fully Mg–substituted sample (x = 2.0), which had a lower e′ of 5.5. For two samples (x = 0.4 and 1.6) we observed dielectric resonances between 12.85 and 13.25 GHz. All showed a steady real permeability of around 1.2–1.5 over the whole 1–13 GHz range, and ferromagnetic resonance (FMR) between 1 and 5 GHz, and ∼12.5 GHz.

International audience; Urban lakes provide many ecosystem services, e.g., flood control, nature protection, coolness island, recreation. Hydrodynamic models will increasingly be used to enhance these benefits. We present the first validation of a three-dimensional (3D) hydrodynamic model on a small shallow lake with high resolution and high frequency measurements. Lake Créteil, France (area 0.4 km2, mean depth 4.5 m, and catchment area 1 km2) is a former gravel pit and now part of a regional park. The model Delft3D-FLOW was calibrated on a one-month period, with continuous measurements of temperature at five depths at the center of the lake and at three depths at two other stations, and with current speed profiles at the centre of the lake. The model was then verified on 18 1-month periods with similar temperature measurements. The model reproduced very well the temperature dynamics, including the alternation between mixing and stratification periods and internal wave patterns. The mean absolute errors over the five depths at the central point remained below 0.55∘C in spring and summer, the most favorable seasons for phytoplankton growth. Horizontal temperature differences, which rose up to 3∘C at the beginning of stratification periods, were also well reproduced, as well as current speeds. These results are very promising for assessing nutrient and pollutant diffusion, settling and resuspension, as well as for understanding how phytoplankton blooms start in small shallow lakes.

The fate of pollutants in the boundary layer is strongly affected by turbulence which is extremely complicated in the complex terrain and over heterogeneous landscapes. The stable boundary layer (SBL) is generally favorable for establishment of air pollution episodes. Therefore, investigations of its characteristics are of the great importance. In this work we investigate turbulence characteristics in the stable, wintertime nocturnal boundary layer over inhomogeneous surface. We analyze data measured at five levels of 62 m high mast located near the industrial town of Kutina. Kutina is located at the southern slopes of the afforested Moslavacka Mountain in the hilly region of Moslavina, Croatia. The mast is located in the vicinity of a petrochemical plant, which is the main source of the pollution in the area. The measurement tower is placed over the heterogeneous surface, surrounded by approximately 20 m high trees. The closest trees are 20 to 30 m away from the tower. Wind data were collected by five WindMaster ultrasonic anemometers (Gill Instruments), which were installed at heights of 20, 32, 40, 55 and 62 m. Each of the sonic anemometers measured three wind components and sonic temperature at a sampling frequency of 20 Hz. Since our intention was to capture highly stable situations, we analyze the wintertime, nighttime data collected during December 2008 – February 2009 period. Here we address the issue of selecting the averaging time scale used for separation of turbulent perturbation from the mean flow, which is appropriate for the nocturnal, stable conditions. This scale is determined by applying several methods widely used in the literature. Preliminary results based on the case study analysis, which were obtained previously for the same location, suggest turbulence averaging time scales between 7 and 11.5 minutes and local maximums of vertical momentum flux and kinematic heat flux at the height of 55 m. Compared to the previous study, here we inspect the larger dataset. In addition, apart from the vertical profiles of vertical momentum flux and kinematic heat flux, here we also investigate vertical profiles of some other turbulence variables.

Evaluation of turbulent fluxes in the surface layer is important for characterization of the atmospheric boundary layer (ABL). The turbulent heat flux in the surface layer is significant for the surface energy balance, while momentum turbulent flux is responsible for production of turbulence in stably stratified boundary layer. Additionally, turbulence, and specifically, turbulent fluxes strongly affect the fate of pollutants in the boundary layer. In order to investigate turbulent characteristics, it is necessary to separate turbulent perturbations from the mean flow. Turbulent and synoptic scales are typically separated by the spectral energy gap, which is often found at the mesoscale. Here we focus on nighttime conditions, which are generally favorable for the establishment of pollution episodes. In order to determine turbulent quantities from fine-resolution wind measurements, it is necessary to assess averaging time appropriate for the turbulent timescales. Therefore, here we also address to the problem of proper selection of averaging time interval.Wind data were measured by five ultrasonic anemometers with a sampling frequency of 20 Hz. Anemometers were placed at five heights, namely, 20, 32, 40, 55 and 62 m above the ground. The meteorological mast is located in a suburban, industrial area of Kutina, Croatia. The mast is above the grassy surface, and it is surrounded by approximately 20 m high trees, where the closest trees are about 20 – 30 meters distant.Lengths of averaging interval are determined by two methods based on Fourier analysis. The first method takes the length of interval as an inverse of frequency at which a minimum in the velocity spectrum is found. The second method (ogive) uses cumulative integral of cospectrum of perturbances of any two turbulent quantities. Here we employ perturbations of wind components and/or sonic temperatures. Afterwards, the averaging interval is taken as a value at which ogive converges to a constant. The time series of 5-min vertical momentum flux shows decreasing values with height up to 55 m where it starts to increase. At two uppermost levels in the nighttime period between 20 and 2 LST upward directed momentum flux exists. Kinematic heat flux has large values which decrease with height up to 55 m where it has a local maximal value.

International audience; In order to better understand the cyanobacteria dynamics in fresh water bodies, a continuous in situ monitoring system was developed by PROLIPHYC project (funded by the French National Agency for Research ANR). It consists in a measurement buoy equipped with meteorological sensors and immersed probes to measure Chl-a, DO at 15-min time step and send them as a daily email to a database through GPRS protocol. This new monitoring approach offers several advantages over historical monitoring techniques: survey of remote sites, reduction of qualified personnel to perform sampling, reduction of overall cost of data collection and significant increase of quantity and quality of data set. In 2009, such a monitoring system was implemented in Lake Enghien (France), an urban lake (mean depth 1.3 m, 41 ha) frequently affected by blooms of the cyanobacterium Planktothrix agardhii. Collected data were used to input the coupled model DYRESM-CAEDYM in order to simulate the water temperature and the cyanobacteria biomass. Model calibration was performed with data collected during 15 days (1-16 June) and model validation was performed during a 5-month period (17 June -29 November). DYCD showed to be an appropriate model for simulating cyanobacteria dynamics in short and medium-term. The next step of our research consists in investigating the link between watershed changes and cyanobacteria dynamics. The study site is a tropical urban lake located in Brazil. Lake Pampulha (mean depth 5.0 m, 197 ha) inlet and outlet will be equipped with sensors to measure water temperature, turbidity and conductivity, flow and rainfall. Automatic samplers will collect water for analysis of quality parameters. Phytoplankton biomass and water temperature into the lake will be monitored by a measurement buoy fit out with a fluoroprobe and a CTD probe. This monitoring system is expected to provide lake response to new management strategies of the watershed.

9 p.; International audience; Urban lakes performed several essential functions for the cities such as storing rainwater and providing recreation spaces. Blooms of cyanobacteria frequently occur in these lakes, disrupting water uses and decreasing ecosystem biodiversity. In order to study the impacts of watershed changes on cyanobacteria dynamics in urban lakes, a modelling approach in which an ecological lake model is connected to a hydrologic watershed model is proposed. To validate this approach, two study sites were selected: Lake Enghien (France) and Lake Pampulha (Brazil). In the first part of the paper, we assess the performance of a lake ecological model fed with high-frequency data collected in Lake Enghien. In the second part, we propose a methodology to connect the lake ecological model to a watershed hydrological model using data set from Lake Pampulha. Our results on cyanobacteria modelling in Lake Enghien (correlation coefficient = 0.71-0.97; RMSE = 15.8 - 25.7 μg chl-a L-1) show the reliability of the lake model. In Lake Pampulha, the high-frequency data are expected to provide understanding about poorly known processes in lake functioning. Finally, as future steps of this research, the integrated modelling approach will be used to estimate lake response to different scenarios of the watershed evolution.

En la presente tesis se muestra una nueva metodología de extracción "inteligente" de modelos circuitales lineales y no lineales para dispositivos MESFET y HEMT, además de efectuar numerosas aportaciones en el campo de las medidas radioeléctricas de dichos dispositivos mediante diseño del hardware y del software necesario para la automatización de las mismas. Por otro lado se presenta un novedoso modelo de Gran Señal para dispositivos HEMT de potencia que da cuenta del fenómeno de la compresión de la transconductancia y es fácilmente implementable en simuladores no lineales comerciales del tipo de MDS, LIBRA, HARMONICA, etc. Además se ha aumentado el rango de validez frecuencial de los modelos de pequeña señal mediante la obtención de las expresiones "exactas" de los modelos usuales de pequeña señal Vendelin-Dambrine, Vickes, Berroth & Bosch, etc. Otra novedad aportada por este trabajo de tesis ha sido aplicar estos modelos lineales a los transistores HEMT, evitando la obtención valores carentes de significado físico como ocurría hasta ahora. Como validación del modelo no lineal de HEMT se han llevado a cabo numerosas simulaciones del mismo en MDS que han sido comparadas con las medidas experimentales realizadas en nuestro laboratorio (Scattering, DC, Pulsadas y Pin/Pout) poniendo de manifiesto la exactitud del modelo. Para validar los modelos de pequeña señal se han efectuado simulaciones con el simulador lineal MMICAD utilizando transistores de diferentes tamaños procedentes de distintas foundries con objeto de visualizar el comportamiento del dispositivo independientemente del origen del mismo., In this thesis a new methodology for the "intelligent" parameter extraction of linear and non-linear model for GaAs MESFET and HEMT devices is shown, besides numerous contributions in the field of Scattering and DC measurements of this kind of devices by means of hardware design and necessary software for the automation of the same have been done. On the other hand a novel Great Signal model for HEMT devices is presented. This model is capable to model the transconductance compression phenomenon and it is easily to built in commercial non-linear simulators like MDS, LIBRA, Microwave HARMONICA, etc. This work has also increased the frequency range for the usual small-signal models by means of calculate "exact" expressions of them. Another novelty contribution of this thesis is to apply for first time these linear models to HEMT transistors, avoiding the lacking of physical meaning values like it occurred up to now. To make possible the validation of non-linear HEMT model, simulations with MDS software and comparisons with experimental measurements made in our laboratory (Scattering, DC, Pulsed and Pin/ Pout) have been carried out and there was very good agreement between measured and simulated data. To validate small-signal models referred before, simulations with MMICAD software and comparisons between simulated and experimental scattering measurements using transistors of different sizes from several foundries and technological processes have been made.

Scanning probe microscopy is opening new applications in microelectronic engineering due to easy and reliable instrumentation in combination with superior resolution limits without any sample preparation under ambient conditions. Beside the standard topography imaging possible application are static and dynamic surface potential measurements, doping profiling, and scanning thermal applications. In this paper, we report dynamic voltage contrast measurements of analog and digital gigahertz signals on 200 nm wave guides within integrated microelectronic devices and components. The results are obtained by using a time resolved device internal test technique based on a scanning force microscope using the electrostatic force interaction. This technique enables voltage contrast even within passivated integrated circuits with nanometer spatial resolution and gigahertz measurement bandwidth and additionally millivolt sensitivity.

Partial discharges are a transient phenomena whose measurement is remarkably important for electrical equipment diagnosis and maintenance. These discharges appear in the measurement circuit as very narrow current pulses of some nanoseconds. Therefore, discharge pulse detection is a particularly difficult problem, especially because they are superposed on the high voltage waveforms that cause them. In this paper, we present an inductively coupled probe able to measure this physical phenomenon by means of a very simple and inexpensive device that can be installed. in the equipment under test. After modeling the probe, its response will be compared to that of commercial devices using both calibrated discharges and partial discharges occurring at real power This research has been supported by the Spanish Science and Technology Ministry DPI 2006-15625-C03-02.