Contribution à l'étude des phénomènes quantiques de transport

Doctorat en Sciencesinfo:eu-repo/semantics/nonPublishe

Specific biomarkers for acute stroke: comparison between human and animal models and development of a new way to improve acute stroke conditions

© 2018 Dr. Marie DagonnierStroke is the third most common cause of death in most Western countries and the major cause of disability. The distinction between stroke subtypes and knowledge of the time of stroke onset is critical in clinical practice. The most specific and biologically powerful treatment for acute ischaemic stroke is thrombolysis with recombinant tissue plasminogen activator (rt-PA) given within the first 4.5 hours of ischaemic stroke onset but this therapy is disappointingly underused. This mainly because of unknown symptoms onset time and uncertainty about stroke diagnostic. Neuroimaging can help decide who and how to treat. Nevertheless, neuroimaging is expensive, has contra-indications and is not always readily available. Cheap and easily measured blood biomarkers serve similar roles for other diseases. The traditional approach to stroke biomarker discovery has been to select candidate markers based on their known involvement in the stroke pathophysiology. This “pick your best candidate” approach inevitably means selection from only a small pool of what is theoretically available. High throughput technologies such as whole genome microarrays and proteomics permit unbiased selection of molecular markers by examining all of genes and proteins expressed in a tissue. In this thesis, these agnostic approaches were used to identify characteristic blood RNA and protein expression profiles occurring after stroke. In the first chapters, we show that most acute stroke patients do not have the indicated imaging done in an appropriate time window, therefore blood biomarkers would have a useful niche. We also show that, to date, most candidate blood biomarkers have not found use in the clinic because they have been selected from experiments that do not address the rapidly changing nature of stroke and have been identified by an ad hoc process that only scratches the surface of the potential candidates available. A pilot gene array experiment performed in rats to specifically look for hyper-acute changes that might be clinically informative in a way not easily realizable in humans, identified gene expression changes of great amplitude which changed markedly with time. This indicated that it should be possible to generate a stroke clock for use in the clinic. A larger follow up confirmation experiment designed also to examine the influence of experimental comorbidities demonstrated that many of the changes could be attributed to the surgical intervention needed to induce stroke in rats. This has important implications for our understanding of stroke inflammatory biology and also suggests the need for a different approach to stroke biomarker discovery. Examination of protein expression in bloods from a clinical trial of hypothermia identified new candidate biomarkers. A clinical trial to examine blood RNA expression, ultimately performed as a pilot because of recruitment difficulties, was designed to examine temporal change. It confirmed that collection of sequential blood samples in a clinically relevant time frame is possible and identified time dependent gene expression with overlap with the rat data. This indicates that generation of a clinically useful stroke clock should indeed be possible

On brownian motion in a fermi fluid

Using the quantum-mechanical Boltzmann equation we study the motion of a heavy ion (mass M) moving through a Fermi fluid of light particles [mass m, γ= (m/M)1/3 T> 1°K) in which a heavy ion experiences what we call quantum-mechanical Brownian motion; the Fokker-Planck equation still holds but the friction coefficient contains quantum-mechanical effects. Using our formula for mobility and the mobility data of Meyer we estimate the effective mass of an ion in liquid 3He to be about 20 times the mass of an 3He atom. This is in agreement with the recent measurements of Dahm and Sanders in liquid 4He. They have found the effective mass to be between 20 to 40 4He atoms. However, since only binary scattering events are accounted for in our mobility formula, its application to liquid 3He should be taken with reservation.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Proton dynamics in H-bonded ferroelectrics. II. Approximated solutions to the kinetic equations

Approximated solutions at T → ∞ and at Tc are proposed for the set of kinetic equations recently obtained to describe the dynamical behaviour of the pseudo-spin correlation functions of the tunnelling model in KDP ferroelectrics. At high temperatures, we predict a width comparable to the protonic-mode frequency, while at Tc the width is finite but much smaller. The existence of the finite width at vanishing protonic-mode frequency at Tc indicates the absence of dynamic scaling. © 1971.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Comments on Brownian motion theory

The validity of the Fokker-Planck equation for a Brownian particle is considered. © 1966.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

On the theory of impurity resistance in quantum systems

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Finite-temperature transport properties of normal fermi systems. III. Dissipative effects in a simple perturbative model

By using the general transport theory of a normal many-fermion system recently developed by Résibois, the collision term is calculated up to fourth order in a coupling parameter. It is shown that the higher order terms can be arranged into the form of the quasiparticle collision term suggested by Landau in the Fermi-liquid theory, except for the transformation operator introduced by Résibois to connect the particle description to the quasiparticle one. We also analyze the three-body collision operator in transport theory from the same quasiparticle point of view to the lowest nontrivial order in the coupling constant. It is shown that the anomalous terms in this operator contain the renormalization effects on the usual two-body collision operator. © 1966 The American Physical Society.SCOPUS: ar.jinfo:eu-repo/semantics/publishe