Spectroscopie à cavité optique

La spectroscopie à cavité optique (en anglais, cavity ring-down spectroscopy, CRDS) est un type de spectroscopie laser où l'échantillon est placé à l'intérieur d'une cavité hautement réfléchissante au laser et un effet induit par l'absorption de la lumière laser est détecté. Le temps de décroissance de la lumière sortant de la cavité est déterminé en fonction de la longueur d'onde laser pulsée. Présentation Ces méthodes se sont développées pour répondre au besoin dans plusieurs domaines comme la chimie, la physique et même en génie. Les molécules gazeuses qui sont en concentration en partie par milliard dans l’air n’arrivaient pas à être détectées par les autres méthodes spectrométriques telles que la spectrométrie à cellule multipasse. En effet, les bandes d’absorption des molécules en faible concentration étaient trop petites. Une idée fait surface : augmenter la trajectoire optique du faisceau luminaire, afin que les pics des molécules en basses concentrations puissent ê

Rabi oscillation in a quantum cavity: Markovian and non-Markovian dynamics

Pierre-Olivier Guimond, Alexandre Roulet

We investigate the Rabi oscillation of an atom placed inside a quantum cavity where each mirror is formed by a chain of atoms trapped near a one-dimensional waveguide. This proposal was studied previously with the use of Markov approximation, where the delay due to the finite travel time of light between the two cavity mirrors is neglected. We show that Rabi oscillation analogous to that obtained with high-finesse classical cavities is achieved only when this travel time is much larger than the time scale that characterizes the superradiant response of the mirrors. Therefore, the delay must be taken into account and the dynamics of the problem is inherently non-Markovian. Parameters of interest such as the Rabi frequency and the cavity loss rate due to photon leakage through the mirrors are obtained.

Amer Physical Soc2016

Novel Analytical Methods for Allergy-Related Studies

Mikaël Frossard

Managing and treating diseases require a deep understanding of the pathologies coupled with accurate diagnostic procedures. The constant development and improvement of bioanalytical methods reflect the need of diagnosis ameliorations with respect to accuracy, sensitivity and efficiency. The field of allergy diagnosis is a good example. Despite affecting almost a third of the population in western countries, allergies still present complex challenges for the physicians in terms of diagnosis and allergen characterization. This thesis presents novel analytical methods developed for the fast and personalized allergy component-resolved diagnosis (CRD), the allergen identification and quantification in food matrices and the characterization of allergen modifications, notably nitration. Immunomagnetic separation (IMS) was used to perform the allergy diagnosis at the molecular level by extracting the IgE antibodies from allergic patient blood sera and probing them against individual allergens and natural allergenic extracts. The fast and highly selective IMS procedure was coupled to matrix-assisted laser desorption/ionization (MALDI) and electrospray ionization (ESI) mass spectrometry (MS) to identify accurately and with high sensitivity the proteins recognized as sensitizers by the patient antibodies. The developed CRD methods were successful to diagnose cowâs milk, egg, peanut and tree nuts allergies, allowing the resolution of several complex clinical cases. Additionally, precious information was collected for the cross-reactivity and cross-sensitization in peanut and tree nuts allergies using blood sera from the PronNut clinical study. Allergen nitration is one of the potential causes for the increase in allergy prevalence observed recently and requires thorough investigation. Herein, various nitrating agents were tested and compared for in vitro allergen nitration. After modifying allergens using two of the most efficient nitrating procedures, the nitration sites were identified by bottom-up proteomics (BUP) and compared to the known epitopes, bringing useful information and novel insights to the problem of correlation between protein nitration and allergenicity. The presence of a minute amount of allergens in a food product is responsible for potential life-threatening reactions in highly allergic patients and sensitive analytical methods are therefore required in food quality assessments. A proteomic-based method was used for the quality control of several food products suspected of causing severe reactions for peanut and hazelnut-allergic patients. Peptide markers were identified in a first screening of the food extracts by BUP using a high-resolution MS instrument. A standard addition method was then used to quantify peanut and hazelnut proteins by BUP using an untargeted âshotgunâ approach.

EPFL2020

Novel Analytical Methods for Allergy-Related Studies

Mikaël Frossard

EPFL2020

Spectroscopie à cavité optique

Rabi oscillation in a quantum cavity: Markovian and non-Markovian dynamics

Novel Analytical Methods for Allergy-Related Studies

Negative ion characterization in a helicon plasma source for fusion neutral beams by cavity ring-down spectroscopy and Langmuir probe laser photodetachment

Novel Analytical Methods for Allergy-Related Studies

Rabi oscillation in a quantum cavity: Markovian and non-Markovian dynamics

Negative ion characterization in a helicon plasma source for fusion neutral beams by cavity ring-down spectroscopy and Langmuir probe laser photodetachment