La catalyse, les solvants alternatifs et l'économie d'atome font partie des clés pour le développement de nouvelles stratégies durables de synthèse. Des hétérocycles comme les quinoléines substituées, par réaction de cycloisomérisation catalysée par le cuivre en utilisant les liquides ioniques, et les isoquinoléines carbonylées par réaction de carbonylation oxydante catalysée par le palladium dans le méthanol ont été synthétisées. La formation sélective de 1,3-dihydroisobenzofuranes et/ou 1H-isochromènes a été tentée par réaction de cycloisomérisation catalysée par différent métaux de transition. La synthèse d'hétérocycles à cinq chaînons, par exemple furanes, pyrroles et pyrrolin-4-ones à été mise au point par nouvelle réaction de cycloisomérisation catalysée par de sels de platine ou d'or en utilisant des diols, des amino alcools ou des α-amino-ynones dans le PEG sous activation micro-ondes. Les produits sont récupérés pur après une simple étape de précipitation-filtration. Les α-amino-ynones chiral sont synthétisée à partir de N-protégé carboxyanhydrides des aminoacides (UNCAs). Une réaction de iodocyclisation a été aussi développée pour obtenir de nouvelles structures hétérocycliques. / Catalysis, alternative solvents and atom economy represent key areas for the sustainable development of versatile strategies in organic chemistry. Fused heterocycles, such as substituted quinolines by a cycloisomerization reaction using a recyclable catalytic system copper/ionic liquids and isoquinoline-4-carboxylic esters based on PdI2-catalyzed oxidative carbonylation were prepared. A selective 5-exo-dig or 6-endo-dig cyclization route to obtain 1,3-dihydroisobenzofurans and/or 1H-isochromenes was tested by metal transition cycloisomerization reaction of alkynylbenzyl alcohols in PEG. Five membered ring heterocycles such as furans, pyrroles and pyrrolin-4-ones were successfully obtained by a novel platinum or gold-catalyzed cycloisomerization reaction of diols, aminoalcohols or α-amino-ynones in poly(ethylene glycol) (PEG) under microwave irradiation. The heterocyclic systems were recovered pure after a simple precipitation-filtration work-up. The catalytic systems were studied by using the TEM and XPS techniques. The chiral α-amino-ynone substrates were prepared by an original method starting from N-protected carboxyanhydrides of amino acids (UNCAs). Also unprecedented results are reported in the area of iodocyclization to obtain chiral iodopyrrolin-ones.

Las emulsiones del tipo agua en aceite (w/o) y aceite en agua (o/w) están compuestas por una mezcla de aceite, agua, lodo y otros agentes. Se pueden encontrar en el proceso y/o en los vertidos de diferentes tipos de industrias, tales como refinerías de petróleo, plantas procesadoras de aceite de consumo, industrias farmacéuticas, industrias de alimentos, etc. El calentamiento de un material a una frecuencia de microondas depende de la frecuencia de la onda electromagnética y de las propiedades dieléctricas, así como de la acumulación de energía interna que va ligada a la profundidad de penetración del campo dentro del material. De este modo, el conocimiento preciso de las propiedades dieléctricas de los materiales es fundamental para conocer su comportamiento bajo la influencia de un campo electromagnético. El objetivo general de esta tesis es proponer métodos alternativos basados en la tecnología de microondas para monitorizar, caracterizar y/o separar emulsiones. Para ello, se determinaron los protocolos de preparación de emulsiones prototipo en el laboratorio, empleando dos fases distintas (ácido oleico y aceite mineral SAE 40), de composición similar a las encontradas en la industria. Paralelamente se ha seleccionado, montando y calibrando un sistema de medida de propiedades dieléctricas en un rango de frecuencias de 1 a 4 GHz (rango cercano a la frecuencia estándar de calentamiento f =2.45 GHz) y de esta manera se ha obtenido un amplio espectro de información del comportamiento dieléctrico de las emulsiones, que servirán para diseñar en una fase posterior aplicadores de microondas. En base a este estudio preliminar se planteó una experiencia piloto con emulsiones reales presentes en el proceso de extracción de aceite de palma africana, con el fin de determinar el efecto de las microondas en la separación y en la calidad del aceite recuperado. / Pérez Páez, R. (2009). Aplicación de microondas en el tratamiento de emulsiones del tipo agua en aceite (w/o) y aceite en agua (o/w) [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/4328 / Palancia

<p>Nonlinear transmission lines (NLTLs) are of great interest for high power microwave (HPM) generation because they can sharpen pulses to create an electromagnetic shockwave to produce oscillations from 100 MHz to low GHz. NLTLs provide frequency agility, compactness, durability and reliability, providing a solid-state radiofrequency (RF) source for producing HPM. The essential component of NLTLs is the nonlinear material, typically a dielectric that varies with voltage or a magnetic material whose permeability varies with current, incorporated in the transmission line in various topologies. This thesis presents an alternative approach involving designing composites comprised of nonlinear dielectric inclusions (barium strontium titanate (BST)) and/or nonlinear inductive inclusions (nickel zinc ferrites (NZF)) in a polymer base host material, analogous to electromagnetic interference designs that incorporate stainless steel inclusions of various shapes in a plastic to tune the composite’s electromagnetic properties at GHz. Appropriately designing NLTL composites requires predicting these effective properties both in linear (for a fixed and low voltage and current) and nonlinear regions (permittivity and permeability become voltage dependent and current dependent, respectively) prior to designing HPM systems comprised of them. As a first step, this thesis evaluates and benchmarks composites models in the commercial software CST Microwave Studios (CST MWS) to various effective medium theories (EMTs) to predict the permittivity and permeability of composites of BST and/or NZF inclusions in the linear regime, compared with experimental measurements. The manufacturing and measurement of the nonlinear composites will be briefly discussed with an analysis of the homogeneity of a composite sample using 3D X-ray scan. Long-term application of these approaches to predicting the effective nonlinear composite permittivity and permeability and future work will be discussed.</p>

<p>Nonlinear transmission lines (NLTLs) provide a solid state alternative to conventional vacuum based high power microwave (HPM) sources. The three most common NLTL implementations are the lumped element, split ring resonator (SRR), and the nonlinear bulk material based NLTLs. The nonlinear bulk material implementation provides the highest power output of the three configurations, though they are limited to pulse voltages less than 50 kV; higher voltages are possible when an additional insulator is used, typically SF₆ or dielectric oil, between the nonlinear material and the outer conductor. The additional insulator poses a risk of leaking if structural integrity of the outer conductor is compromised. The desire to provide a fieldable NLTL based HPM system makes the possibility of a leak problematic. The work reported here develops a composite based NLTL system that can withstand voltages higher than 50 kV and not pose a risk of catastrophic failure due to a leak while also decreasing the size and weight of the device and increasing the output power.</p> <p>Composites with barium strontium titanate (BST) or nickel zinc ferrite (NZF) spherical inclusions mixed in a silicone matrix were manufactured at volume fractions ranging from 5% to 25%. The dielectric and magnetic parameters were measured from 1-4 GHz using a coaxial airline. The relative permittivity increased from 2.74±0.01 for the polydimethylsiloxane (PDMS) host material to 7.45±0.33 after combining PDMS with a 25% volume fraction of BST inclusions. The relative permittivity of BST and NZF composites was relatively constant across all measured frequencies. The relative permeability of the composites increased from 1.001±0.001 for PDMS to 1.43±0.04 for a 25% NZF composite at 1 GHz. The relative permeability of the 25% NZF composite decreased from 1.43±0.05 at 1 GHz to 1.17±0.01 at 4 GHz. The NZF samples also exhibited low dielectric and magnetic loss tangents from 0.005±0.01 to 0.091±0.015 and 0.037±0.001 to 0.20±0.038, respectively, for all volume fractions, although the dielectric loss tangent did increase with volume fraction. For BST composites, all volume fraction changes of at least 5% yielded statistically significant changes in permittivity; no changes in BST volume fraction yielded statistically significant changes in permeability. For NZF composites, the change in permittivity was statistically significant when the volume fraction varied by more than 5% and the change in permeability was statistically significant for variations in volume fraction greater than 10%. The DC electrical breakdown strength of NZF composites decreased exponentially with increasing volume fraction of NZF, while BST composites exhibited no statistically significant variation with volume fraction. </p> <p>For composites containing both BST and NZF, increasing the volume fraction of either inclusion increased the permittivity with a stronger dependence on BST volume fraction. Increasing NZF volume fraction increased the magnetic permeability, while changing BST volume fraction had no effect on the composite permeability. The DC dielectric breakdown voltage decreased exponentially with increased NZF volume fraction. Adding as little as 5% BST to an NZF composite more than doubled the breakdown threshold compared to a composite containing NZF alone. For example, adding 10% BST to a 15% NZF composite increased the breakdown strength by over 800%. The combination of tunability of permittivity and permeability by managing BST and NZF volume fractions with the increased dielectric breakdown strength by introducing BST make this a promising approach for designing high power nonlinear transmission lines with input pulses of hundreds of kilovolts.</p> <p>Coaxial nonlinear transmission lines are produced using composites with NZF inclusions and BST inclusions and driven by a Blumlein pulse generator with a 10 ns pulse duration and 1.5 ns risetime. Applying a 30 kV pulse using the Blumlein pulse generator resulted in frequencies ranging from 1.1 to 1.3 GHz with an output power over 20 kW from the nonlinear transmission line. The output frequencies increased with increasing volume fraction of BST, but the high power oscillations characteristic of an NLTL did not occur. Simulations using LT Spice demonstrated that an NLTL driven with a Blumlein modulator did not induce high power oscillations while driving the same NLTL with a pulse forming network did. </p> <p>Finally, a composite-based NLTL could be driven directly by a high voltage power supply without a power modulator to produce oscillations both during and after the formed pulse upon reaching a critical threshold. The output frequency of the NLTLs is 1 GHz after the pulse and ranged from 950 MHz to 2.2 GHz during the pulse. These results demonstrate that the NLTL may be used as both a pulse forming line and high power microwave source, providing a novel way to reduce device size and weight, while the use of composites could provide additional flexibility in pulse output tuning. </p>

Ice particles in the atmosphere affect for example remote sensing measurements made for climate and atmospheric research. When these ice particles melt their single scattering properties alters, which in turn affect the remote sensing measurements. It is therefore of importance to understand how these scattering properties change due to the melting of the particles to be able to interpret the measurements.  The ARTS database contains single scattering data for a large set of ice particles in the microwave region, data which describes how electromagnetic radiation interacts with said particles. The database does not however contain any data for melting ice particles. A software package called RimeCraft has been used to simulate the melting process of ice particles, together with the discrete dipole approximation program ADDA, which simulated their single scattering properties at frequencies between 1 and 247.2 GHz. Neither of the two programs had been extensively tested on melting ice particles. This thesis therefore tests both RimeCraft and ADDA for their suitability and performance on melting ice particles as a preparation for extending the ARTS database with these types of particles.  The simulation results from ADDA showed that the single scattering properties, such as absorption and extinction cross sections, were greatly affected by the melting process, especially during the initial phase of melting (below meltfraction 0.1) where the increase was strong. At higher meltfractions the increase was slower, and sometimes even decreased for certain particles. Some unexpected results were seen, such as spikes and oscillations in the extinction and absorption cross sections.  Both RimeCraft and ADDA are suitable for generating models of melting ice particles, respectively to simulate their single scattering properties, as long as the output from ADDA undergoes quality controls first. / Ispartiklar i atmosfären påverkar fjärranalysmätningar gjorda för bland annat klimat- och atmosfärsforskning. När dessa ispartiklar smälter påverkar det deras spridningsegenskaper, vilket i sin tur påverkar fjärranalysmätningarna. Det är därför viktigt att förstå hur dessa spridningsegenskaper påverkas av att partikeln smälter för att kunna tolka mätningarna.  ARTS databasen innehåller spridningsdata för ett stort antal olika ispartiklar i mikrovågsområdet, data som beskriver hur elektromagnetisk strålning påverkas av dessa partiklar. Databasen innehåller dock inte någon data för smältande ispartiklar.   Ett mjukvarupaket kallat RimeCraft har använts för att simulera smältprocessen av ispartiklar, tillsammans med diskret dipolsapproximationsprogrammet ADDA som användes för att simulera deras spridningsegenskaper för frekvenser mellan 1 och 247.2 GHz. Inget av de två programmen har blivit utförligt testat med smältande ispartiklar. Detta examensarbete testar därför både RimeCrafts och ADDAs lämplighet och prestationsförmåga med smältande ispartiklar som en förberedelse för att utöka ARTS databasen med dessa partiklar.  Simulationsresultaten från ADDA visade att spridningsegenskaperna, så som absorptions- och extinktionstvärsnitt, påverkades starkt av smältprocessen, speciellt under den initiala fasen av smältningen. Vid högre smältgrader var ökningen långsammare och ibland till och med negativ för vissa partiklar. Några oväntade resultat sågs, som t.ex. spikar och oscillationer i extinktions- och absorptionstvärsnitten.  Både RimeCraft och ADDA är lämpade för att generera modeller av smältande ispartiklar, respektive för att simulera deras spridningsegenskaper, så länge utdatan från ADDA genomgår en kvalitetskontroll.

The purpose of this project was to investigate a cylindrical cavity resonator and use microwaves to heat up a material in the cavity. This was done by measuring the Q-factor and the resonance frequency of the cavity, both with and without material inside. The chosen material was graphite, and more accurate measurements were done with that specific material. A program called QZero was used to export the Q-factor and the resonance frequency from the measurement data received from a VNA and the program also gave error estimations. Then electromagnetic simulations were done using Comsol. Both an empty cavity and a cavity where graphite has been inserted were simulated and the results were compared to the actual measurements. To measure temperatures inside the cavity, a pyrometer was to be used. The cavity resonator has small circular holes through the side, and a frame was designed and produced using a 3D-printer in order to lock the pyrometer in place in front of one of the holes. A power supply was also installed to the pyrometer. In order to send microwaves into the cavity, a signal generator was used. It was connected to an amplifier and the amplification as well as the efficiency was noted. The pyrometer could only measure temperatures above 490 $\degree$C. This was not achieved, so a handheld electrical thermometer was used. The temperature of the graphite was measured and then compared to how hot the graphite would be without heat loss. For the empty cavity, a Q-factor of 3200 for the resonance frequency of around 2.4 GHz was measured, which matched the simulated measurements in Comsol. When graphite was inserted to the cavity, the Q-factor lowered to 300 in the real experiment. A discrepancy was found between the actual measurements, and the Comsol simulations in which the graphite only lowered the Q-factor to 2570. The reason for this is believed to be either with an error to how the material was chosen in Comsol, since there were many types of graphite to select with many settings to change. Another reason could be an error with the setup itself due to the sheer complexity of the program. / Syftet med detta projekt är att undersöka en cylindrisk kavitet samt att använda mikrovågor för att värma upp ett material i kaviteten. Detta gjordes genom att mäta kavitetens Q-faktor och resonansfrekvens med och utan material. Sedan valdes grafit ut som det materialet som skulle testas och mer noggranna mätningar gjordes på just det materialet, och programmet QZero användes för att få ut mer noggrann data samt gav en felmarginal på Q-faktorn. Efter det gjordes simuleringar i programmet Comsol av kaviteten med och utan grafit och jämfördes med de faktiska värdena. För att mäta temperatur av materialet i kaviteten designades en hållare som en pyrometer skulle fästas vid och riktas mot materialet i kaviteten. Även en strömförsörjning till pyrometern installerades. För att skicka in mikrovågor i kaviteten användes en signalgenerator som var kopplad till en förstärkare. Förstärkningen mättes och förstärkarens effekt noterades. I slutändan nåddes inte de temperaturer som krävdes för pyrometern, så en elektrisk termometer användes för att mäta temperaturen på grafiten och detta jämfördes sedan mot den energin som absorberades av grafiten, då energin tillförd till grafiten och grafitens specifika värmekapacitet var känt. Prestandan av experimentuppställningen undersöktes också. For den tomma kaviteten mättes en Q-faktor på 3200 och resonansfrekvensen var 2.4 GHz. Detta stämde bra överens med simuleringarna i Comsol. När grafit fördes in i kaviteten sänktes Q-faktorn till 300. En avvikelse upptäcktes mellan de faktiska mätningarna och simuleringarna. I simuleringen sänktes Q-faktorn bara till 2570, en andledning till detta tros vara antingen vara hur materialet valdes, då det fanns olika typer av grafit med olika inställningar att välja mellan i Comsol. En annan felkälla kan vara något fel med uppställningen på grund af hur avancerat Comsol var. I värmeexperimentet hade förstärkaren en låg verkningsgrad vilket ledde till överhettning om för stor effekt användes. Experimentet begränsades därför till att använda upp till två watt. Vid exponerig under 30 sekunder värmdes grafiten upp till 100-150$\degree$C, vilket var avsevärt lägre än den teoretiska uppvärmingen till 1700$\degree$ beräknad från energin tillförd till grafiten. Antagandet är att temperaturen hamnade i ett jämnviktsläge kring 100-200$\degree$C eller att resonansfrekvensen ändrades vilket ledde till en minskning av energi tillförd till grafiten.

Der Betrieb eines Freien Elektronen Lasers (FEL), bei dem die spontan emittierte Undulatorstrahlung ueber Wechselwirkung mit dem Elektronenstrahl selbst verstaerkt wird, setzt eine praezise Ausrichtung des Elektronenstrahls mit dem Photonenstrahl voraus. Um den Ueberlapp von Elektronen-und Photonenstrahl zu gewaehrleisten, wurde ein neuartiger Typ von Wellenleiter-Strahllagemonitor entwickelt, der in eine Vakuumkammer des Undulators des FELs der TESLA Test Facility (TTF) integriert ist. Vier um das Strahlrohr verteilte Wellenleiter koppeln ueber schmale Schlitze einen Bruchteil jenes elektromagnetischen Feldes aus, welches den Strahl begleitet. Die induzierten Signale haengen von der transversalen Strahlposition und der Strahlintensitaet ab. Mit vier Schlitz-Wellenleiter Paaren laesst sich ein lineares Signal ableiten, anhand dessen die Position des Elektronenstrahls bestimmt werden kann. Die induzierten Signale werden mittels eines stegbelasteten Wellenleiters in die erste Stufe eines bei 12 GHz arbeitenden Empfaengers zugefuehrt. Die vorliegende Arbeit beschreibt Design, Tests und Implementierung dieses neuartigen Typs von Strahllagemonitor. / The operation of a free electron laser working in the Self Amplified Spontaneous Emission mode (SASE FEL) requires the electron trajectory to be aligned with very high precision in overlap with the photon beam. In order to ensure this overlap, one module of the SASE FEL undulator at the TESLA Test Facility (TTF) is equipped with a new type of waveguide beam position monitor (BPM). Four waveguides are arranged symmetrically around the beam pipe, each channel couples through a small slot to the electromagnetic beam field. The induced signal depends on the beam intensity and on the transverse beam position in terms of beam--to--slot distance. With four slot--waveguide combinations a linear position sensitive signal can be achieved, which is independent of the beam intensity. The signals transduced by the slots are transferred by ridged waveguides through an impedance matching stage into a narrowband receiver tuned to 12 GHz. The present thesis describes design, tests, and implementation of this new type of BPM.

A description of several experiments carried out to study the existence of evanescent waves behind totally reflecting dielectric surfaces is given in this thesis. Chapter I describes the experimental apparatus used to generate and measure the electromagnetic radiation. A detailed description of the construction of the radiating horns used and the casting of a plastic prism is also given. Chapters II and III give the results of two experiments in the region behind a totally reflecting face of the plastic prism and similar effects noted behind a lucite semicylinder with its plane face towards the source of radiation. Near field diffraction patterns of this cylinder with its plane face towards the source, away from the source, and parallel to the axis of radiation are also given. The above three cases are compared with results obtained by coating the semicylinder with aluminum foil. / Thesis / Master of Science (MSc)

Résumé : L'étude du couvert nival est essentielle afin de mieux comprendre les processus climatiques et hydrologiques. De plus, avec les changements climatiques observés dans l'hémisphère nord, des événements de dégel-regel ou de pluie hivernale sont de plus en plus courants et produisent des croutes de glace dans le couvert nival affectant les moeurs des communautés arctiques en plus de menacer la survie de la faune arctique. La télédétection micro-ondes passives (MOP) démontre un grand potentiel de caractérisation du couvert nival. Toutefois, a fin de bien comprendre les mesures satellitaires, une modélisation adéquate du signal est nécessaire. L'objectif principal de cette thèse est d'analyser le transfert radiatif (TR) MOP des sols, de la neige et de la glace a fin de mieux caractériser les propriétés géophysiques du couvert nival par télédétection. De plus, un indice de détection des croutes de glace par télédétection MOP a été développé. Pour ce faire, le modèle Microwave Emission Model of Layered Snowpacks (MEMLS) a été étudié et calibré afin de minimiser les erreurs des températures de brillance simulées en présences de croutes de glace. La première amélioration faite à la modélisation du TR MOP de la neige a été la caractérisation de la taille des grains de neige. Deux nouveaux instruments, utilisant la réflectance dans le proche infrarouge, ont été développés afin de mesurer la surface spécifique de la neige (SSA). Il a été démontré que la SSA est un paramètre plus précis et plus objectif pour caractériser la taille des grains de neige. Les deux instruments ont démontré une incertitude de 10% sur la mesure de la SSA. De plus, la SSA a été calibré pour la modélisation MOP a n de minimiser l'erreur sur la modélisation de la température de brillance. Il a été démontré qu'un facteur multiplicatif [phi] = 1.3 appliqué au paramètre de taille des grains de neige dans MEMLS, paramètre dérivé de la SSA, est nécessaire afin de minimiser l'erreur des simulations. La deuxième amélioration apportée à la modélisation du TR MOP a été l'estimation de l'émission du sol. Des mesures radiométriques MOP in-situ ainsi que des profils de températures de sols organiques arctiques gelés ont été acquis et caractérisés a fin de simuler l'émission MOP de ces sols. Des constantes diélectriques effectives à 10.7, 19 et 37 GHz ainsi qu'une rugosité de surface effective des sols ont été déterminés pour simuler l'émission des sols. Une erreur quadratique moyenne (RMSE) de 4.65 K entre les simulations et les mesures MOP a été obtenue. Suite à la calibration du TR MOP du sol et de la neige, un module de TR de la glace a été implémenté dans MEMLS. Avec ce nouveau module, il a été possible de démontré que l'approximation de Born améliorée, déjà implémenté dans MEMLS, pouvait être utilisé pour simuler des croutes de glace pure à condition que la couche de glace soit caractérisée par une densité de 917 kg m[indice supérieur _􀀀3] et une taille des grains de neige de 0 mm. Il a aussi été démontré que, pour des sites caractérisés par des croutes de glace, les températures de brillances simulées des couverts de neige avec des croutes de glace ayant les propriétés mesurées in-situ (RMSE=11.3 K), avaient une erreur similaire aux températures de brillances simulées des couverts de neige pour des sites n'ayant pas de croutes de glace (RMSE=11.5 K). Avec le modèle MEMLS validé pour la simulation du TR MOP du sol, de la neige et de la glace, un indice de détection des croutes de glace par télédétection MOP a été développé. Il a été démontré que le ratio de polarisation (PR) était très affecté par la présence de croutes de glace dans le couvert de neige. Avec des simulations des PR à 10.7, 19 et 37 GHz sur des sites mesurés à Churchill (Manitoba, Canada), il a été possible de déterminer des seuils entre la moyenne hivernale des PR et les valeurs des PR mesurés indiquant la présence de croutes de glace. Ces seuils ont été appliqués sur une série temporelle de PR de 33 hivers d'un pixel du Nunavik (Québec, Canada) où les conditions de sols étaient similaires à ceux observés à Churchill. Plusieurs croutes de glace ont été détectées depuis 1995 et les mêmes événements entre 2002 et 2009 que (Roy, 2014) ont été détectés. Avec une validation in-situ, il serait possible de confirmer ces événements de croutes de glace mais (Roy, 2014) a démontré que ces événements ne pouvaient être expliqués que par la présence de croutes de glace dans le couvert de neige. Ces mêmes seuils sur les PR ont été appliqués sur un pixel de l'Île Banks (Territoires du Nord-Ouest, Canada). L'événement répertorié par (Grenfell et Putkonen, 2008) a été détecté. Plusieurs autres événements de croutes de glace ont été détectés dans les années 1990 et 2000 avec ces seuils. Tous ces événements ont suivi une période où les températures de l'air étaient près ou supérieures au point de congélation et sont rapidement retombées sous le point de congélation. Les températures de l'air peuvent être utilisées pour confirmer la possibilité de présence de croutes de glace mais seul la validation in-situ peut définitivement confirmer la présence de ces croutes. / Abstract : Snow cover studies are essential to better understand climatic and hydrologic processes. With recent climate change observed in the northern hemisphere, more frequent rain-on-snow and meltrefreeze events have been reported, which affect the habits of the northern comunities and the survival of arctique wildlife. Passive microwave remote sensing has proven to be a great tool to characterize the state of snow cover. Nonetheless, proper modeling of the microwave signal is needed in order to understand how the parameters of the snowpack affect the measured signal. The main objective of this study is to analyze the soil, snow and ice radiative transfer in order to better characterize snow cover properties and develop an ice lens detection index with satellite passive microwave brightness temperatures. To do so, the passive microwave radiative transfer modeling of the Microwave Emission Model of Layered Snowpacks (MEMLS) was improved in order to minimize the errors on the brightness temperature simulations in the presence of ice lenses. The first improvement to passive microwave radiative transfer modeling of snow made was the snow grain size parameterization. Two new instruments, based on short wave infrared reflectance to measure the snow specific surface area (SSA) were developed. This parameter was shown to be a more accurate and objective to characterize snow grain size. The instruments showed an uncertainty of 10% to measure the SSA of snow. Also, the SSA of snow was calibrated for passive microwave modeling in order to reduce the errors on the simulated brightness temperatures. It was showed that a correction factor of φ = 1.3 needed to be applied to the grain size parameter of MEMLS, obtain through the SSA measurements, to minimize the simulation error. The second improvement to passive microwave radiative transfer modeling was the estimation of passive microwave soil emission. In-situ microwave measurements and physical temperature profiles of frozen organic arctic soils were acquired and characterized to improve the modeling of the soil emission. Effective permittivities at 10.7, 19 and 37 GHz and effective surface roughness were determined for this type of soil and the soil brightness temperature simulations were obtain with a minimal root mean square error (RMSE) of 4.65K. With the snow grain size and soil contributions to the emitted brightness temperature optimized, it was then possible to implement a passive microwave radiative transfer module of ice into MEMLS. With this module, it was possible to demonstrate that the improved Born approximation already implemented in MEMLS was equivalent to simulating a pure ice lens when the density of the layer was set to 917 kg m−3 and the grain size to 0 mm. This study also showed that by simulating ice lenses within the snow with there measured properties, the RMSE of the simulations (RMSE= 11.3 K) was similar to the RMSE for simulations of snowpacks where no ice lenses were measured (only snow, RMSE= 11.5 K). With the validated MEMLS model for snowpacks with ice lenses, an ice index was created. It is shown here that the polarization ratio (PR) was strongly affected by the presence of ice lenses within the snowpack. With simulations of the PR at 10.7, 19 and 37 GHz from measured snowpack properties in Chucrhill (Manitoba, Canada), thresholds between the measured PR and the mean winter PR were determined to detect the presence of ice within the snowpack. These thresholds were applied to a timeseries of nearly 34 years for a pixel in Nunavik (Quebec, Canada) where the soil surface is similar to that of the Churchill site. Many ice lenses are detected since 1995 with these thresholds and the same events as Roy (2014) were detected. With in-situ validation, it would be possible to confirm the precision of these thresholds but Roy (2014) showed that these events can not be explained by anything else than the presence of an ice layer within the snowpack. The same thresholds were applied to a pixel on Banks island (North-West Territories, Canada). The 2003 event that was reported by Grenfell et Putkonen (2008) was detected by the thresholds. Other events in the years 1990 and 2000’s were detected with these thresholds. These events all follow periods where the air temperature were warm and were followed by a quick drop in air temperature which could be used to validate the presence of ice layer within the snowpack. Nonetheless, without in-situ validation, these events can not be confirmed.

Depuis la découverte du Virus de l'Immunodéficience Humaine (VIH) au début des années 80, la recherche de nouvelles molécules anti-VIH demeure un challenge important pour la communauté scientifique. Les effets secondaires liés à l'usage d'inhibiteurs de la réplication virale, la découverte des récepteurs et la compréhension du mécanisme d'entrée du virus dans la cellule hôte ont encouragé la recherche sur de nouveaux inhibiteurs ciblant l'entrée virale. A ce jour, l'Enfuvirtide est le seul inhibiteur d'entrée approuvé en tant qu'inhibiteur de fusion. Bien que ce composé soit un antiviral puissant, il présente néanmoins de sérieuses limitations, son mode d'administration (injection sous cutanée deux fois par jour) et l'émergence de résistances, le classent en agent rétroviral de seconde classe. Une approche alternative est la génération de D-peptides inhibiteurs de fusion, résistants aux protéases et prometteurs pour le développement et l'identification d'une nouvelle classe de médicaments anti-VIH. Basée sur cette dernière approche, cette thèse est consacrée à la synthèse et à l'étude d'analogues peptidiques en tant qu'inhibiteurs de fusion du VIH. Tout d'abord, des études de modélisation associées à la synthèse d'analogues peptidiques ont permis de mettre en évidence et de comprendre les caractéristiques essentielles responsables de l'activité des D-peptides. Ensuite, des études de relations structure-activité, à partir de séquences modifiées, ont conduit à l'obtention de nouveaux analogues peptidiques inhibiteurs de fusion actifs. Enfin, dans le but de réduire la nature peptidique et par conséquent d'améliorer les propriétés pharmaceutiques, des macrocycles peptidiques ont été conçus, et une nouvelle stratégie de synthèse de peptides cycliques a été développée. / Since the discovery of the Human Immunodeficiency Virus (HIV) at the beginning of the 1980's, the search for new anti-HIV molecules remains an important challenge for the scientific community. Secondary effects associated with viral replication inhibitors, the discovery of receptors and the understanding of the mechanism of the viral entry makes HIV viral entry one of the most promising target for HIV drug development. To date, Enfurvitide is the only approved entry inhibitor as HIV fusion inhibitor. Although highly effective, Enfurvirtide has several serious limitations including high dosing requirements, the administration by injection, and the emergence of resistant strains. An alternative approach that has shown considerable potential is the generation of new D-peptides HIV fusion inhibitors expected to be resistant to proteolytic degradation and useful for the development and the identification of a new class of anti-HIV drugs with improv ed bioavailability.Based on this approach, the present work is dedicated to the synthesis and the study of peptide analogs as HIV fusion inhibitors. First, modeling studies and the synthesis of peptide analogs were devoted to point out and to understand the key elements responsible for the activity of the reference D-peptides. Then, structure activity relationship studies based on different modifications sequences led to the discovery of active peptide analogues as HIV fusion inhibitors. In another approach, in order to decrease peptide nature and consequently to improve the pharmaceutical properties, reduced cyclic peptides were designed. Finally, a novel strategy for cyclic peptide synthesis was developed.