Airlines jet fuel hedging strategies, ou, Les stratégies de couverture des compagnies aériennes pour faire face au risque de fluctuations du prix du kérosène

Si nous regardons l’évolution du prix du pétrole depuis 1995, nous remarquons qu’il a beaucoup fluctué. En effet, le prix du baril a progressé jusqu’en 2008 pour finalement retomber brutalement en l’espace de quelques mois. Cette instabilité peut avoir un impact sérieux sur les compagnies qui dépendent de cette matière première. Les compagnies aériennes ont vu leurs coûts sur le carburant augmenter dramatiquement. Malgré les progrès technologiques pour diminuer la consommation de carburant, ces coûts peuvent atteindre jusqu’à 40% des charges d’exploitation. La concurrence sur le marché pousse ces compagnies à baisser leurs marges. En effet, la marge avant imposition en 2013 était en moyenne de 3%. Face à la forte volatilité du prix du pétrole, les compagnies aériennes sont exposées au risque de subir des pertes liées à ces coûts. Pour contrer ce risque, certaines compagnies adoptent des stratégies de hedging afin de stabiliser leurs coûts de carburant. Ces stratégies impliquent l’utilisation d’instruments financiers tels que les swaps et les options. Ces derniers sont les plus utilisés puisqu’ils peuvent être adaptés aux besoins des compagnies aériennes. Cependant, plusieurs compagnies ont renoncé à opter pour une stratégie de hedging. En effet, certaines compagnies aériennes ont subi d’énormes pertes à cause de leurs stratégies de hedging. Depuis 2011, le pétrole brut n’a pas subi d’énormes fluctuations comme celles de 2008. Les compagnies non-couvertes ont pu bénéficier d’un avantage sur leurs concurrents couverts qui ont payé le carburant plus cher à cause du coût de la stratégie de hedging. En revanche, ces compagnies sont exposées au risque d’une augmentation du prix du carburant qui peut leur être fatale. Est-ce que cet avantage en vaut la peine ? La compagnie aérienne américaine Delta a opté pour une tout autre stratégie. En effet, cette dernière a acheté une raffinerie afin de produire partiellement ses besoins en carburant. La société souhaite grâce à cette intégration verticale réduire ses coûts. Ces différentes stratégies ont toutes des avantages et des inconvénients. Est-ce que les compagnies doivent se couvrir, ne pas se couvrir ou bien acheter une raffinerie ? Ce travail tâchera d’explorer ces options en les évaluant

Merging microfluidics and micro-array concepts: from molecular to nematode-based bioassays

Essential in biomedical research is the necessity of gathering statistically relevant data about large populations of specific biological entities, e.g. organisms, cells or molecules, while preserving detailed information about each single entity under investigation. This thesis deals with this need and proposes the combination of microfluidics and micro-arraying techniques in developing technological tools to conceive bio-assays at single molecule/cell/organism resolution. First, we propose an on-chip immunoassay technique, through which we demonstrated detection of the biomarker tumor necrosis factor alpha in serum down to concentrations in the attomolar range (10-18 M). In particular, we provide a comprehensive predictive model of the assay, which employs micro-arrays of superparamagnetic beads. We introduce the concept of magnetic particle-scanning, as a method for building immunoassays with extremely low limit of detection, down to the single-molecule level. Afterwards, we modified our bead micro-arraying technique, to make it suitable for the immobilization of particles and cells of various sizes and properties. Specifically, we present a method for the electrostatic self-assembly of dielectric microspheres in well templates, as a technique for fast and versatile fabrication of microlens arrays. By combining these arrays with microfluidics, we created a new tool for single-nanoparticle detection in flowing media, able to detect moving objects of sub-diffraction size through conventional low-magnification microscopes. An analogous micro-arraying method was then developed to seed large populations of non-adherent cells in isolated micro-compartments. In combination with an electrowetting-on-dielectric microfluidic platform, this technique allows implementing high-throughput cytotoxicity assays on yeast cells, at single-cell resolution. Subsequently, we conceived technological solutions for the automated analysis of Caenorhabditis elegans, one of the most employed model organisms in biomedical research. First, we developed a microfluidic platform for on-chip nematode culture and creation of synchronized C. elegans embryo micro-arrays. Long-term multi-dimensional imaging in our device allows systematic phenotyping studies at single-embryo resolution. We could discriminate embryonic development variations with unprecedented accuracy and we successfully analyzed the impact of perturbations of the mitochondrial functions on the embryogenesis. A second generation prototype of the device is then presented, enabling long-term automated studies on C. elegans at single-nematode resolution and over the whole organism development, from early embryogenesis to adulthood. Finally, we introduce a third generation prototype, which features: (i) a new microfluidic design tailored for the isolation of larvae at a desired developmental stage and for their successive culture and treatment; (ii) a method for reversible immobilization of nematodes, enabling long-term high-resolution imaging. We successfully employed this platform to analyze protein aggregation in a C. elegans model for human amyotrophic lateral sclerosis (ALS). The device allows precisely localizing protein aggregates within the nematode tissues, as well as monitoring the evolution of single aggregates over consecutive days at sub-cellular level

Lens array by electrostatic patterning of dielectric microspheres in a Parylene-C well template

We present the fabrication of a microlens array which can be integrated into a microfluidic device. In the demonstrated technique, a microwell array is firstly fabricated in a Parylene-C layer by a standard cleanroom process. Afterwards, the optically transparent dielectric microspheres with high refractive index are patterned inside the well template by utilizing an electrostatic technique. The mechanism of microsphere patterning is studied, and the lens effect of the microsphere is experimentally verified in a water-based medium. We also present a detailed two-dimensional numerical optical simulation study on the patterned microspheres using the Finite Element Method (FEM)

Fast detection of single nanoparticles in a microfluidic channel by a microlens array in combination with a conventional optical microscope

We present the use of a microlens array in combination with a conventional optical microscope set-up for the detection of single nanoparticles (NPs) in fluid medium. Optically transparent dielectric microspheres are patterned in a microfabricated well array template and used as microlenses focusing the light originating from a microscope objective into so-called photonic nanojets that expose the medium within the microfluidic channel. When the NPs pass the nanojets, the detection signal is highly enhanced, Au NPs with size down to 50 nm, fluorescent NPs down to 20 nm in size, as well as biomolecule-linked NPs are clearly observed

Photonic Nanojet Array for Fast Detection of Single Nanoparticles in a Flow

We detect by optical microscopy Au and fluorescent nanopartides (NPs) during their motion in water based medium, using an array of dielectric microspheres that are patterned in a microwell array template. The Microspheres act as lenses focusing the light originating from a microscope objective into so-called photonic nanojets that expose the medium Within a microfluidic channel When a NP is randomly transported through a nanojet, its backscattered light (for a bare Au NP) or its fluorescent emission is instantaneously detected by video microscopy. Au NPs down to 50 nit in size, as well as fluorescent NPs down to 20 rim in size, are observed by using a low magnification/low numerical aperture microscope objective in bright field or fluorescence mode, respectively. Compared to the NPs present outside of the photonic nanojets, the light scattering or fluorescence intensity of the NPs in the nanojets is typically enhanced by tip to a factor of The experimental intensity is found to be proportional to the area Occupied by the NP in the nanojet. The technique is also used for immunodectection of biomolecules immobilized on At NPs in buffer and; in future, it may develop into a versatile tool to detect nanometric objects of environmental or biological importance, such as NPs, viruses, or other biological agents

Automated longitudinal monitoring of in vivo protein aggregation in neurodegenerative disease C. elegans models

Background: While many biological studies can be performed on cell-based systems, the investigation of molecular pathways related to complex human dysfunctions - e.g. neurodegenerative diseases - often requires long-term studies in animal models. The nematode Caenorhabditis elegans represents one of the best model organisms for many of these tests and, therefore, versatile and automated systems for accurate time-resolved analyses on C. elegans are becoming highly desirable tools in the field. Results: We describe a new multi-functional platform for C. elegans analytical research, enabling automated worm isolation and culture, reversible worm immobilization and long-term high-resolution imaging, and this under active control of the main culture parameters, including temperature. We employ our platform for in vivo observation of biomolecules and automated analysis of protein aggregation in a C. elegans model for amyotrophic lateral sclerosis (ALS). Our device allows monitoring the growth rate and development of each worm, at single animal resolution, within a matrix of microfluidic chambers. We demonstrate the progression of individual protein aggregates, i.e. mutated human superoxide dismutase 1 - Yellow Fluorescent Protein (SOD1-YFP) fusion proteins in the body wall muscles, for each worm and over several days. Moreover, by combining reversible worm immobilization and on-chip high-resolution imaging, our method allows precisely localizing the expression of biomolecules within the worms' tissues, as well as monitoring the evolution of single aggregates over consecutive days at the sub-cellular level. We also show the suitability of our system for protein aggregation monitoring in a C. elegans Huntington disease (HD) model, and demonstrate the system's ability to study long-term doxycycline treatment-linked modification of protein aggregation profiles in the ALS model. Conclusion: Our microfluidic-based method allows analyzing in vivo the long-term dynamics of protein aggregation phenomena in C. elegans at unprecedented resolution. Pharmacological screenings on neurodegenerative disease C. elegans models may strongly benefit from this method in the near future, because of its full automation and high-throughput potential

Study of constrained Brownian motion of nanoparticles near an interface using optical tweezers

We demonstrate a method to determine the Brownian motion and the diffusion coefficient of a nanoparticle in water in a plane that is parallel to a solid boundary and as function of the distance normal to that boundary by using an optical tweezers instrument. A solution of 190 nm-diameter fluorescent polystyrene nanoparticles in de-ionized (DI) water is introduced in a micro-chamber built from two thin glass substrates. A single particle is trapped by the tweezers and optically moved in the z-direction normal to a substrate. By analyzing a scatter plot of the time-dependent positions of the nanoparticle in the x-y plane in a histogram, the diffusion coefficient parallel to the substrate of the Brownian particle constrained by the substrate is determined as a function of the distance between the substrate and the nanoparticle. The experimental results indicate the increased drag effect on the nanoparticle when it is close to the substrate, as evidenced by an experimental diffusion coefficient nearby the substrate that is about half of that of the particle in the bulk fluid

Dose-response curve of a microfluidic magnetic bead-based surface coverage sandwich assay

Magnetic micro-and nanoparticles ('magnetic beads') have been used to advantage in many microfluidic devices for sensitive antigen (Ag) detection. Today, assays that use as read-out of the signal the number count of immobilized beads on a surface for quantification of a sample's analyte concentration have been among the most sensitive and have allowed protein detection lower than the fg mL(-1) concentration range. Recently, we have proposed in this category a magnetic bead surface coverage assay (Tekin et al., 2013 [1]), in which 'large' (2.8 mm) antibody (Ab)-functionalized magnetic beads captured their Ag from a serum and these Ag-carrying beads were subsequently exposed to a surface pattern of fixed 'small' (1.0 mm) Ab-coated magnetic beads. When the system was exposed to a magnetic induction field, the magnet dipole attractive interactions between the two bead types were used as a handle to approach both bead surfaces and assist with Ag-Ab immunocomplex formation, while unspecific binding (in absence of an Ag) of a large bead was reduced by exploiting viscous drag flow. The dose-response curve of this type of assay had two remarkable features: (i) its ability to detect an output signal (i.e. bead number count) for very low Ag concentrations, and (ii) an output signal of the assay that was non-linear with respect to Ag concentration. We explain here the observed dose-response curves and show that the type of interactions and the concept of our assay are in favour of detecting the lowest analyte concentrations (where typically either zero or one Ag is carried per large bead), while higher concentrations are less efficiently detected. We propose a random walk process for the Ag-carrying bead over the magnetic landscape of small beads and this model description explains the enhanced overall capture probability of this assay and its particular non-linear dose response curves. Research Pape

A microfluidic device for longitudinal studies of C.elegans neurodegenerative disease models

We describe a microfluidic device for automated culture and long-term high resolution imaging of Caenorhabditis elegans nematodes, which we specifically employed as model organisms for the analysis of neurodegenerative disease progression. In this platform, we integrated: (i) a microfluidic design tailored for the confinement of worms at the L2 larval stage in separate culture chambers by means of passive hydrodynamics; (ii) an optimized protocol for worm feeding and progeny removal at desired rate, allowing follow-up of the same worms over long-term studies; (iii) a technique for reversible C.elegans immobilization, based on the thermoreversible gelation of Pluronic F127 (PF127) inside the microfluidic chip; (iv) active control of the device temperature; (v) a compact device assembly, suitable for automated multi-dimensional imaging on any upright or inverted microscope