Hemodynamic effects of a dielectric elastomer augmented aorta on aortic wave intensity: An in-vivo study

Dielectric elastomer actuator augmented aorta (DEA) represents a novel approach with high potential for assisting a failing heart. The soft tubular device replaces a section of the aorta and increases its diameter when activated. The hemodynamic interaction between the DEA and the left ventricle (LV) has not been investigated with wave intensity (WI) analysis before. The objective of this study is to investigate the hemodynamic effects of the DEA on the aortic WI pattern. WI was calculated from aortic pressure and flow measured in-vivo in the descending aorta of two pigs implanted with DEAs. The DEAs were tested for different actuation phase shifts (PS). The DEA generated two decompression waves (traveling upstream and downstream of the device) at activation followed by two compression waves at deactivation. Depending on the PS, the end-diastolic pressure (EDP) decreased by 7% (or increased by 5–6%). The average early diastolic pressure augmentation (P_dia) increased by 2% (or decreased by 2–3%). The hydraulic work (W_H) measured in the aorta decreased by 2% (or increased by 5%). The DEA-generated waves interfered with the LV-generated waves, and the timing of the waves affected the hemodynamic effect of the device. For the best actuation timing the upstream decompression wave arrived just before aortic valve opening and the upstream compression wave arrived just before aortic valve closure leading to a decreased EDP, an increased P_dia and a reduced W_H

A novel soft cardiac assist device based on a dielectric elastomer augmented aorta: an in vivo study

Although heart transplant is the preferred solution for patients suffering from heart failures, cardiac assist devices remain key substitute therapies. Among them, aortic augmentation using dielectric elastomer actuators (DEAs) might be an alternative technological application for the future. The electrically driven actuator does not require bulky pneumatic elements (such as conventional intra-aortic balloon pumps) and conforms tightly to the aorta thanks to the manufacturing method presented here. In this study, the proposed DEA-based device replaces a section of the aorta and acts as a counterpulsation device. The feasibility and validation of in vivo implantation of the device into the descending aorta in a porcine model, and the level of support provided to the heart are investigated. Additionally, the influence of the activation profile and delay compared to the start of systole is studied. We demonstrate that an activation of the DEA just before the start of systole (30 ms at 100 bpm) and deactivation just after the start of diastole (0-30 ms) leads to an optimal assistance of the heart with a maximum energy provided by the DEA. The end-diastolic and left ventricular pressures were lowered by up to 5% and 1%, respectively, compared to baseline. The early diastolic pressure was augmented in average by up to 2%

Assay harmonization and use of biological standards to improve the reproducibility of the hemagglutination inhibition assay: A FLUCOP collaborative study

The hemagglutination inhibition (HAI) assay is an established technique for assessing influenza immunity, through measurement of antihemagglutinin antibodies. Improved reproducibility of this assay is required to provide meaningful data across different testing laboratories. This study assessed the impact of harmonizing the HAI assay protocol/reagents and using standards on interlaboratory variability. Human pre- and postvaccination sera from individuals (n = 30) vaccinated against influenza were tested across six laboratories. We used a design of experiment (DOE) method to evaluate the impact of assay parameters on interlaboratory HAI assay variability. Statistical and mathematical approaches were used for data analysis. We developed a consensus protocol and assessed its performance against in-house HAI testing. We additionally tested the performance of several potential biological standards. In-house testing with four reassortant viruses showed considerable interlaboratory variation (geometric coefficient of variation [GCV] range of 50% to 117%). The age, concentration of turkey red blood cells, incubation duration, and temperature were key assay parameters affecting variability. Use of a consensus protocol with common reagents, including viruses, significantly reduced GCV between laboratories to 22% to 54%. Pooled postvaccination human sera from different vaccination campaigns were effective as biological standards. Our results demonstrate that the harmonization of protocols and critical reagents is effective in reducing interlaboratory variability in HAI assay results and that pools of postvaccination human sera have potential as biological standards that can be used over multiple vaccination campaigns. Moreover, the use of standards together with in-house protocols is as potent as the use of common protocols and reagents in reducing interlaboratory variability.publishedVersio

Joint inversion of satellite-detected tidal and magnetospheric signals constrains electrical conductivity and water content of the upper mantle and transition zone

We present a new global electrical conductivity model of Earths mantle. The model was derived by using a novel methodology, which is based on inverting satellite magnetic field measurements from different sources simultaneously. Specifically, we estimated responses of magnetospheric origin and ocean tidal magnetic signals from the most recent Swarm and CHAMP data. The challenging task of properly accounting for the ocean effect in the data was addressed through full three-dimensional solution of Maxwell's equations. We show that simultaneous inversion of magnetospheric and tidal magnetic signals results in a model with much improved resolution. Comparison with laboratory-based conductivity profiles shows that obtained models are compatible with a pyrolytic composition and a water content of 0.01 wt and 0.1 wt in the upper mantle and transition zone, respectively

Influences of various magnetospheric and ionospheric current systems on geomagnetically induced currents around the world

Ground-based observations of geomagnetic field (B field) are usually a superposition of signatures from different source current systems in the magnetosphere and ionosphere. Fluctuating B fields generate geoelectric fields (E fields), which drive geomagnetically induced currents (GIC) in technological conducting media at the Earth's surface. We introduce a new Fourier integral B field model of east/west directed line current systems over a one-dimensional multilayered Earth in plane geometry. Derived layered-Earth profiles, given in the literature, are needed to calculate the surface impedance, and therefore reflection coefficient in the integral. The 2003 Halloween storm measurements were Fourier transformed for B field spectrum Levenberg-Marquardt least squares inversion over latitude. The inversion modeled strengths of the equatorial electrojets, auroral electrojets, and ring currents were compared to the forward problem computed strength. It is found the optimized and direct results match each other closely and supplement previous established studies about these source currents. Using this model, a data set of current system magnitudes may be used to develop empirical models linking solar wind activity to magnetospheric current systems. In addition, the ground E fields are also calculated directly, which serves as a proxy for computing GIC in conductor-based networks

International Geomagnetic Reference Field: the 12th generation

The 12th generation of the International Geomagnetic Reference Field (IGRF) was adopted in December 2014 by the Working Group V-MOD appointed by the International Association of Geomagnetism and Aeronomy (IAGA). It updates the previous IGRF generation with a definitive main field model for epoch 2010.0, a main field model for epoch 2015.0, and a linear annual predictive secular variation model for 2015.0-2020.0. Here, we present the equations defining the IGRF model, provide the spherical harmonic coefficients, and provide maps of the magnetic declination, inclination, and total intensity for epoch 2015.0 and their predicted rates of change for 2015.0-2020.0. We also update the magnetic pole positions and discuss briefly the latest changes and possible future trends of the Earth’s magnetic fiel

Characterization of the electrical internal structure of Mars from electromagnetic induction method using Mars Global Surveyor satellite magnetic data

Les méthodes d'induction électromagnétique permettent de caractériser la conductivité électrique des matériaux, dont les corps planétaires telluriques, depuis les couches superficielles de la croûte jusqu'aux zones les plus internes, dans le manteau inférieur. Pour une source de champ électromagnétique donnée, des courants sont induits dans les matériaux qui y sont soumis. Avec l'essor des données magnétiques satellitaires, de nouvelles méthodes d'analyse des données magnétiques permettent d'obtenir des images unidimensionnelles de la structure électrique de ces corps car la structure spatio-temporelle de la source électromagnétique en est bien connue. Les travaux de mon doctorat ont eu pour but de mettre en place une nouvelle méthode d'analyse permettant de déterminer des modèles de structure interne globaux pour n'importe quel corps du système solaire pour lequel on dispose de longues séries temporelles magnétiques satellitaires. Après avoir testé cette méthode sur des modèles synthétiques et l'avoir appliqué au cas de données réelles terrestre pour lesquelles des études d'induction électromagnétiques antérieurs permettent d'avoir un a priori sur le modèle de conductivité électrique attendu, nous avons obtenu les premiers modèles de conductivité électrique martien en utilisant les données magnétiques du satellite Mars Global Surveyor. Ces résultats nous ont permis de valider des modèles de structure interne antérieurs établis à partir d'analyses géochimiques et minéralogiques des météorites martiennes. Cette méthode innovante est aujourd'hui la seule capable d'obtenir une image électrique des manteaux telluriques à partir de données magnétiques satellitaires pour des corps autres que la Terre ou la Lune et pour lesquels aucun a priori sur la structure spatio-temporelle du champ électromagnétique inducteur externe n'est nécessaire.My Ph.D. work consists in the investigation of satellite magnetic data to infer the deep internal conductivity distribution. I developed a new global electromagnetic induction method applied to planetary magnetic datasets without strong a priori hypothesis on the external inducing source field. My method is based on a spectral correction of gapped data magnetic time series to restore the time spectral content of the source field. This external source depends on the planetary environment and is therefore different for each planetary bodies. The method aims at recovering with a maximum accuracy internal and external spherical harmonic coefficients of transients fields, whose ratio is used as a transfer function to retrieve the internal distribution of electrical conductivity. While for the Earth, a good proxy of the source field activity is the Dst index, no such proxy exists for other planets. Hence, for our study of Mars transient magnetic field from MGS, one of the major part of my work is the determination of an appropriate continuous proxy for the external variability. On Earth the external electromagnetic source is well known, and may be described by a spherical harmonic geometry dominated by the dipole term. This source field may be characterized using a magnetic activity index named the Dst index. The method has been tested on synthetic data generated within the framework of SWARM mission. This mission consists of a 3 satellites constellation. One of the main objectives is to infer the 3D electrical distribution in the deep Earth. SWARM synthetic data consist in a time series of spherical harmonic (SH) coefficients, external and internal, generated from a simple non-realistic 3D model. In this model, several regional and local conductors, in a radially symmetric 3 layers model have been embedded. Using this dataset, our method give satisfactory results. We have been able to obtain the external and internal SH coefficients - for the first SH degree, which is known to be the most energetic degree of the external source - using only one of the 3 synthetic time series. Then, the method has been used on real data from Ørsted. In this case, we had to pre-process the data to correct from ionospheric and aligned currents contributions. We developed a statistical analysis to remove the ionospheric field using 2 geomagnetic indices : AL and Kp. Hence, we have enlarged data toward higher and lower latitudinal zones than what has been done in previous works. Finally, we have been able to obtain 1D conductivity models, which fits reasonably with existing conductivity data in the deep Earth. Finally, we worked on Mars Global Surveyor (MGS) data. One of the most time consuming parts of this work was the determination of an appropriate continuous proxy for the external variability in the vicinity of Mars. Without any measurements of the IMF (Interplanetary Magnetic Field) during MGS sciences acquisition, we have used ACE (Advanced Composition Explorer) data. This satellite orbits around the L1 point of the Sun-Earth system, measuring solar wind magnetic characteristics. We have time-shifted ACE data to Mars position for 4 temporal windows where Mars and Earth were closed to the same Parker's spiral's arm, and finally determined a proxy explaining the major part of the variability observed in Mars data. Despite numerous gaps in MGS data, we have been able to establish the 1D conductivity distribution, fitting reasonably existing geochemical models. Although the method may be unstable for some cases, we obtained satisfactory results for in depth conductivity of the planet

Control of the frequency of the electromechanical resonators MEMS

A l’heure actuelle, les Micro-Electro-Mechanical-Systems (MEMS) sont devenusincontournables dans les produits technologiques quotidiens. De par leur taille,leurs performances et leur intégration, les microsystèmes résonants se sontinscrits dans la diversification de la fameuse Loi de Moore. Cependant les applications detype base de temps demeurent le segment de marché où les MEMS ne parviennent pas às’imposer durablement. En effet, grâce à une stabilité en fréquence de quelques parties parmillions, l’oscillateur à base de résonateur en Quartz reste le produit numéro 1 d’unmarché estimé à dix-sept milliards de dollars.Etant donné le lien entre la fréquence d’un résonateur silicium MEMS et ses dimensionsintrinsèques, les différentes étapes de fabrication induisent un décalage de cette fréquencepar rapport à la valeur visée. C’est donc cet écart que nous tenterons d’adresser. Dans cecontexte, nous avons proposé une nouvelle méthode de correction à l’échelle du substrat.Cette méthode consiste en une ultime étape technologique, après une première mesureélectrique des dispositifs qui permet de quantifier l’erreur, à ramener la fréquence à lavaleur souhaitée par un ajout localisé de matière. Nous montrerons qu’il est possible, enune seule étape, de réduire la Gaussienne représentative de la variation de la fréquence ausein du substrat à quelques parties par million. Pour cela, nous avons développé deuxmodèles physiques qui permettent de quantifier la correction pour atteindre les objectifs.En parallèle, nous avons mis en place un processus de fabrication compatible avec la filièreCMOS avec seulement dix-sept étapes et deux masques photolithographiques dont le pointde départ est un substrat de type SOI. Ce procédé a permis la fabrication de résonateur àmodes de flexion et ondes de volume, dont les performances intrinsèques (f et Q)permettent de concurrencer les résonateurs Quartz. Enfin, nous avons validé notre conceptet nos modèles physiques par des caractérisations électriques de nos dispositifs.L’analyse des résultats nous a permis de dresser une liste des pistes d’amélioration pourétablir une voie vers l’industrialisation durable des résonateurs MEMS. Dans un premiertemps, une attention toute particulière se portera sur le choix du substrat et la technologieutilisée pour garantir des performances optimales. La méthode de correction nécessite unemesure électrique intermédiaire, cette étape doit être précisée et il faudra s’assurer qu’ellen’augmente pas le coût global de la fonction. Bien que discutés, le packaging du MEMS etl’intégration seront des points à étudier, tout particulièrement pour conserver lesspécifications du résonateur lui-même.Present, Micro-Electro-Mechanical-Systems (MEMS) have become essential ineveryday technology products. Thanks to their size, performances andintegration, resonant microsystems have been enrolled in the diversification ofthe famous Moore's Law. However, the time based applications remain the market segmentwhere MEMS are unable to settle permanently. Indeed, the oscillator-based Quartz is thenumber one product on the market, a market estimated at 17 billions dollars, thanks to afrequency stability of a few parts per million over its lifetime.Given the link between the frequency of a MEMS resonator and its intrinsic dimensions,the various manufacturing steps induce a shift of this frequency from the target value. Wewill try to address this difference.In this context, we proposed a new method of correction across the wafer. This methodconsists of a final technological step after a first electrical measurement to quantify theshift. We will show that it is possible in one step, to reduce the Gaussian representing thefrequency variation within the wafer to a few parts per million. From this perspective, wehave developed two physical models that quantify the correction to achieve the objectives.Moreover, we set up a manufacturing process CMOS compatible with only 17 steps and2 photolithographic masks starting with a SOI wafer. This process has enabled theproduction of flexural mode resonators and bulk mode resonators, whose intrinsicperformances (f, Q) can compete with Quartz. Finally, we validated our concept and ourphysical models thanks to electrical characterization of our devices.Analysis of the results allowed us to develop a list of possible improvements to establish aroute to the industrialization of MEMS resonators. First, special attention will be focusedon the choice of substrate and the technology used to ensure perfect performances.Correction method requires a preliminary electrical measurement, this step must bedetailed and one have to ensure that it does not increase the overall cost. Although partiallystudied, the packaging of MEMS and integration are the points to consider in particularkeeping the specifications of the resonator itself

Compensation de la fréquence des résonateurs MEMS pour des applications de référence temps

Present, Micro-Electro-Mechanical-Systems (MEMS) have become essential ineveryday technology products. Thanks to their size, performances andintegration, resonant microsystems have been enrolled in the diversification ofthe famous Moore's Law. However, the time based applications remain the market segmentwhere MEMS are unable to settle permanently. Indeed, the oscillator-based Quartz is thenumber one product on the market, a market estimated at 17 billions dollars, thanks to afrequency stability of a few parts per million over its lifetime.Given the link between the frequency of a MEMS resonator and its intrinsic dimensions,the various manufacturing steps induce a shift of this frequency from the target value. Wewill try to address this difference.In this context, we proposed a new method of correction across the wafer. This methodconsists of a final technological step after a first electrical measurement to quantify theshift. We will show that it is possible in one step, to reduce the Gaussian representing thefrequency variation within the wafer to a few parts per million. From this perspective, wehave developed two physical models that quantify the correction to achieve the objectives.Moreover, we set up a manufacturing process CMOS compatible with only 17 steps and2 photolithographic masks starting with a SOI wafer. This process has enabled theproduction of flexural mode resonators and bulk mode resonators, whose intrinsicperformances (f, Q) can compete with Quartz. Finally, we validated our concept and ourphysical models thanks to electrical characterization of our devices.Analysis of the results allowed us to develop a list of possible improvements to establish aroute to the industrialization of MEMS resonators. First, special attention will be focusedon the choice of substrate and the technology used to ensure perfect performances.Correction method requires a preliminary electrical measurement, this step must bedetailed and one have to ensure that it does not increase the overall cost. Although partiallystudied, the packaging of MEMS and integration are the points to consider in particularkeeping the specifications of the resonator itself.A l’heure actuelle, les Micro-Electro-Mechanical-Systems (MEMS) sont devenusincontournables dans les produits technologiques quotidiens. De par leur taille,leurs performances et leur intégration, les microsystèmes résonants se sontinscrits dans la diversification de la fameuse Loi de Moore. Cependant les applications detype base de temps demeurent le segment de marché où les MEMS ne parviennent pas às’imposer durablement. En effet, grâce à une stabilité en fréquence de quelques parties parmillions, l’oscillateur à base de résonateur en Quartz reste le produit numéro 1 d’unmarché estimé à dix-sept milliards de dollars.Etant donné le lien entre la fréquence d’un résonateur silicium MEMS et ses dimensionsintrinsèques, les différentes étapes de fabrication induisent un décalage de cette fréquencepar rapport à la valeur visée. C’est donc cet écart que nous tenterons d’adresser. Dans cecontexte, nous avons proposé une nouvelle méthode de correction à l’échelle du substrat.Cette méthode consiste en une ultime étape technologique, après une première mesureélectrique des dispositifs qui permet de quantifier l’erreur, à ramener la fréquence à lavaleur souhaitée par un ajout localisé de matière. Nous montrerons qu’il est possible, enune seule étape, de réduire la Gaussienne représentative de la variation de la fréquence ausein du substrat à quelques parties par million. Pour cela, nous avons développé deuxmodèles physiques qui permettent de quantifier la correction pour atteindre les objectifs.En parallèle, nous avons mis en place un processus de fabrication compatible avec la filièreCMOS avec seulement dix-sept étapes et deux masques photolithographiques dont le pointde départ est un substrat de type SOI. Ce procédé a permis la fabrication de résonateur àmodes de flexion et ondes de volume, dont les performances intrinsèques (f et Q)permettent de concurrencer les résonateurs Quartz. Enfin, nous avons validé notre conceptet nos modèles physiques par des caractérisations électriques de nos dispositifs.L’analyse des résultats nous a permis de dresser une liste des pistes d’amélioration pourétablir une voie vers l’industrialisation durable des résonateurs MEMS. Dans un premiertemps, une attention toute particulière se portera sur le choix du substrat et la technologieutilisée pour garantir des performances optimales. La méthode de correction nécessite unemesure électrique intermédiaire, cette étape doit être précisée et il faudra s’assurer qu’ellen’augmente pas le coût global de la fonction. Bien que discutés, le packaging du MEMS etl’intégration seront des points à étudier, tout particulièrement pour conserver lesspécifications du résonateur lui-même

Caractérisation de la structure électrique de Mars par méthode d'induction électromagnétique globale à partir des données magnétiques satellitaires de Mars Global Surveyor

My Ph.D. work consists in the investigation of satellite magnetic data to infer the deep internal conductivity distribution. I developed a new global electromagnetic induction method applied to planetary magnetic datasets without strong a priori hypothesis on the external inducing source field. My method is based on a spectral correction of gapped data magnetic time series to restore the time spectral content of the source field. This external source depends on the planetary environment and is therefore different for each planetary bodies. The method aims at recovering with a maximum accuracy internal and external spherical harmonic coefficients of transients fields, whose ratio is used as a transfer function to retrieve the internal distribution of electrical conductivity. While for the Earth, a good proxy of the source field activity is the Dst index, no such proxy exists for other planets. Hence, for our study of Mars transient magnetic field from MGS, one of the major part of my work is the determination of an appropriate continuous proxy for the external variability. On Earth the external electromagnetic source is well known, and may be described by a spherical harmonic geometry dominated by the dipole term. This source field may be characterized using a magnetic activity index named the Dst index. The method has been tested on synthetic data generated within the framework of SWARM mission. This mission consists of a 3 satellites constellation. One of the main objectives is to infer the 3D electrical distribution in the deep Earth. SWARM synthetic data consist in a time series of spherical harmonic (SH) coefficients, external and internal, generated from a simple non-realistic 3D model. In this model, several regional and local conductors, in a radially symmetric 3 layers model have been embedded. Using this dataset, our method give satisfactory results. We have been able to obtain the external and internal SH coefficients - for the first SH degree, which is known to be the most energetic degree of the external source - using only one of the 3 synthetic time series. Then, the method has been used on real data from Ørsted. In this case, we had to pre-process the data to correct from ionospheric and aligned currents contributions. We developed a statistical analysis to remove the ionospheric field using 2 geomagnetic indices : AL and Kp. Hence, we have enlarged data toward higher and lower latitudinal zones than what has been done in previous works. Finally, we have been able to obtain 1D conductivity models, which fits reasonably with existing conductivity data in the deep Earth. Finally, we worked on Mars Global Surveyor (MGS) data. One of the most time consuming parts of this work was the determination of an appropriate continuous proxy for the external variability in the vicinity of Mars. Without any measurements of the IMF (Interplanetary Magnetic Field) during MGS sciences acquisition, we have used ACE (Advanced Composition Explorer) data. This satellite orbits around the L1 point of the Sun-Earth system, measuring solar wind magnetic characteristics. We have time-shifted ACE data to Mars position for 4 temporal windows where Mars and Earth were closed to the same Parker's spiral's arm, and finally determined a proxy explaining the major part of the variability observed in Mars data. Despite numerous gaps in MGS data, we have been able to establish the 1D conductivity distribution, fitting reasonably existing geochemical models. Although the method may be unstable for some cases, we obtained satisfactory results for in depth conductivity of the planet.Les méthodes d'induction électromagnétique permettent de caractériser la conductivité électrique des matériaux, dont les corps planétaires telluriques, depuis les couches superficielles de la croûte jusqu'aux zones les plus internes, dans le manteau inférieur. Pour une source de champ électromagnétique donnée, des courants sont induits dans les matériaux qui y sont soumis. Avec l'essor des données magnétiques satellitaires, de nouvelles méthodes d'analyse des données magnétiques permettent d'obtenir des images unidimensionnelles de la structure électrique de ces corps car la structure spatio-temporelle de la source électromagnétique en est bien connue. Les travaux de mon doctorat ont eu pour but de mettre en place une nouvelle méthode d'analyse permettant de déterminer des modèles de structure interne globaux pour n'importe quel corps du système solaire pour lequel on dispose de longues séries temporelles magnétiques satellitaires. Après avoir testé cette méthode sur des modèles synthétiques et l'avoir appliqué au cas de données réelles terrestre pour lesquelles des études d'induction électromagnétiques antérieurs permettent d'avoir un a priori sur le modèle de conductivité électrique attendu, nous avons obtenu les premiers modèles de conductivité électrique martien en utilisant les données magnétiques du satellite Mars Global Surveyor. Ces résultats nous ont permis de valider des modèles de structure interne antérieurs établis à partir d'analyses géochimiques et minéralogiques des météorites martiennes. Cette méthode innovante est aujourd'hui la seule capable d'obtenir une image électrique des manteaux telluriques à partir de données magnétiques satellitaires pour des corps autres que la Terre ou la Lune et pour lesquels aucun a priori sur la structure spatio-temporelle du champ électromagnétique inducteur externe n'est nécessaire