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Experimental and numerical study of modulation of ionization front propagation velocity in µs helium plasma gun discharge with nitrogen admixture
No full textInternational audienceThis work reports on experimental and numerical analysis of the effect of nitrogen admixture on the development of helium based atmospheric pressure discharge produced by the Plasma Gun in long dielectric tubes. Besides, the drastic extension of discharge propagation length, reactive species generation can be tailored to specific applications while keeping electric field properties quite constant. This might afford unique opportunities to study specific action of the different plasma components for biomedical applications. Good agreement was found with recently developed model calculations, emphasising the key role of plasma kinetics on the ionization level of the plasma stream connecting the ionization front with the powered electrode of the DBD reactor
Tropical diagonal scaling for asymptotic eigenvalue problems
No full textMinisymposia "Perturbation theory for linear/nonlinear eigenvalue problems in action"International audienceWe study the behaviour of the eigenvalues of a parametric matrix polynomial P in a neighbourhood of zero. If we suppose that the entries of P have Puiseux series expansion, we can build an auxiliary matrix polynomial Q whose entries are the leading exponents of those of P. We show that preconditioning P via a diagonal scaling based on the tropical eigenvalues of Q can improve conditioning and backward error of the eigenvalues
A Bernstein-von Mises theorem for smooth functionals in semiparametric models
No full textInternational audienc
Prediction of Response to Temozolomide in Low-Grade Glioma Patients Based on Tumor Size Dynamics and Genetic Characteristics
No full textInternational audienceBoth molecular profiling of tumors and longitudinal tumor size data modeling are relevant strategies to predict cancer patients' response to treatment. Herein we propose a model of tumor growth inhibition integrating a tumor's genetic characteristics (p53 mutation and 1p/19q codeletion) that successfully describes the time course of tumor size in patients with low-grade gliomas treated with first-line temozolomide chemotherapy. The model captures potential tumor progression under chemotherapy by accounting for the emergence of tissue resistance to treatment following prolonged exposure to temozolomide. Using information on individual tumors' genetic characteristics, in addition to early tumor size measurements, the model was able to predict the duration and magnitude of response, especially in those patients in whom repeated assessment of tumor response was obtained during the first 3 months of treatment. Combining longitudinal tumor size quantitative modeling with a tumor''s genetic characterization appears as a promising strategy to personalize treatments in patients with low-grade gliomas. WHAT IS THE CURRENT KNOWLEDGE ON THE TOPIC? þ First-line temozolomide is frequently used to treat low-grade gliomas (LGG), which are slow-growing brain tumors. The duration of response depends on genetic characteristics such as 1p/19q chromosomal codeletion, p53 mutation, and IDH mutations. However, up to now there are no means of predicting, at the individual level, the duration of the response to TMZ and its potential benefit for a given patient. • WHAT QUESTION DID THIS STUDY ADDRESS? þ The present study assessed whether combining longitudinal tumor size quantitative modeling with a tumor's genetic characterization could be an effective means of predicting the response to temozolomide at the individual level in LGG patients. • WHAT THIS STUDY ADDS TO OUR KNOWLEDGE þ For the first time, we developed a model of tumor growth inhibition integrating a tumor's genetic characteristics which successfully describes the time course of tumor size and captures potential tumor progression under chemotherapy in LGG patients treated with first-line temozolomide. The present study shows that using information on individual tumors' genetic characteristics, in addition to early tumor size measurements, it is possible to predict the duration and magnitude of response to temozolomide. • HOW THIS MIGHT CHANGE CLINICAL PHARMACOLOGY AND THERAPEUTICS þ Our model constitutes a rational tool to identify patients most likely to benefit from temozolomide and to optimize in these patients the duration of temozolomide therapy in order to ensure the longest duration of response to treatment. Response evaluation criteria such as RECIST—or RANO for brain tumors—are commonly used to assess response to anticancer treatments in clinical trials. 1,2 They assign a patient's response to one of four categories, ranging from " complete response " to " disease progression. " Yet, criticisms have been raised regarding the use of such categorical criteria in the drug development process, 3,4 and regulatory agencies have promoted the additional analysis of longitudinal tumor size measurements through the use of quantitative modeling. 5 Several mathematical models of tumor growth and response to treatment have been developed for this purpose. 6,7 These analyses have led to th
A Nonoxidative Passerini Pathway to α-Ketoamides
No full textInternational audienceThe Passerini adducts of cinnamaldehyde derivatives may be efficiently converted into alpha-ketoamides when heated with a base under microwave conditions
Synthèse et réactivité de complexes à ligand iminophosphorane : des métaux de transition aux actinides
No full textFor the past decades, organometallic and coordination chemistry have proven to be fields of major importanceby allowing the preparation of catalysts that are able to perform unpreceded chemical reactions, in addition with the discovery of unusual species with physical and chemical properties that are very interesting. All these studies are underlining the primordial role of the ligand, which allows fine-tuning of the properties of such species. Our laboratory has gained considerable experience in the synthesis and the study of the coordination chemistry of ligands bearing the iminophosphorane moieties (RN=PR’3). These ligands, still poorly studied in the literature, present electronic properties that are strongly deviating from those of their carbon-analogues, i.e. imines. This thesis is focused on the synthesis of a new family of (un)symmetrical, lutidine-based iminophosphorane ligands. Initially, the coordination chemistry of these ligands with transition metals is described with a focus on copper. Hemilabile behaviour is highlighted and shown to be related to the oxidation state of the copper metal centre, furnishing a redox-switchable system. These complexes are then shown to be useful in a number of catalytic reactions. Then, the coordination chemistry of these ligands is explored with lanthanides, more particularly divalent. These metals are strong reductants and are able to activate a variety of substrates like carbon dioxide for example, however such reactivities must be restrained by an appropriate ligand set. In particular, the study of the coordination chemistry of the new ligand family with metallocenes of ytterbium(II) is exhibiting lability phenomena, either of the iminophosphorane ligand or of the phospholyl ligand on the ytterbium centre. Moreover, the coordination chemistry of these ligands with uranium is briefly described. The synthesis and the coordination chemistry of mixed iminophosphorane-phosphine ligands are described subsequently. These ligands exhibit properties of dearomatization of the central pyridine scaffold. This phenomenon is studied with palladium(II) complexes, as the reactivity of these species with boranes. The reactivity of these new mixed ligands is also studied with ruthenium. Particularly, the presence of a hydride leads to the formation of an organometallic bond between the ligand and the ruthenium centre with the loss of hydrogen. In the last part, a new family of ligands bearing phenoxide moieties is studied. The oxidative and reductive chemistry of the copper and uranium complexes are explored and show a large divergence in comparison with the imines analogues of these ligands. Finally, the use of their nickel complexes as catalysts for the dimerization of ethylene is presented. All the results are supported by solid-state analysis, mainly by X-ray diffraction experiments; in solution the behavior of the species are studied by means of multinuclear NMR studies; finally some compounds are also investigated in silico by DFT calculations.La chimie organométallique et de coordination a prouvé dans les dernières décennies son importance enpermettant l’obtention de catalyseurs capables d’effectuer des réactions chimiques sans précèdent mais permettant aussi la découverte d’espèces présentant des propriétés physiques et chimiques très intéressantes. Il ressort de ces études que les ligands jouent un rôle primordial en modulant finement les propriétés de telles espèces. Notre laboratoire a acquis une grande expérience dans la synthèse et l’étude de la chimie de coordination de ligands présentant la fonctionnalité iminophosphorane (RN=PR’3). Ces ligands, encore peu étudiés dans la littérature, présentent des propriétés électroniques divergeant fortement de leurs analogues carbonés, les imines. Ce travail de doctorat est centré sur la synthèse d’une nouvelle famille de ligands iminophosphoranes symétriques ou non, comportant le motif de lutidine. Dans un premier temps, la chimie de coordination de ces espèces avec les métaux de transition et, plus particulièrement, avec le cuivre est décrite. Des phénomènes d’hémilabilité du ligand, liés à l’état d’oxydation du métal, sont mis en évidence , fournissant ainsi un système commutable par un stimulus redox. Ces espèces sont aussi employées dans le cadre de quelques réactions catalytiques. La chimie de ces nouveaux ligands symétriques est ensuite explorée avec les lanthanides, plus particulièrement divalents. Ces métaux fortement réducteurs sont capables d’activer de nombreux substrats comme le dioxyde de carbone, mais leurs réactivités doivent être souvent canalisées par des ligands appropriés. L’étude de la chimie de coordination de la nouvelle famille de ligands iminophosphoranes avec les métallocènes d’ytterbium(II) permet de mettre en évidence des phénomènes de labilité, soit du ligand iminophosphorane, soit des ligands phospholes de l’ytterbium. L’étude de la chimie de coordination de ces espèces avec l’uranium est enfin brièvement abordée. Par la suite, la synthèse et la chimie de coordination de ligands mixtes iminophosphoranes-phosphines sont abordées. Ces ligands présentent des propriétés de déaromatisation de la pyridine centrale. La chimie de coordination et l’étude du phénomène de déaromatisation avec le palladium(II) sont présentés, ainsi que la réactivité de ces espèces vis-à-vis des boranes. La réactivité de ces nouveaux ligands vis-à-vis du ruthénium est aussi explorée. En particulier la présence d’un hydrure conduit à la formation d’une liaison organométallique entre le ligand et le ruthénium et le départ de dihydrogène. Dans une dernière partie, des ligands iminophosphoranes présentant une fonctionnalité phénolate sont étudiés. La chimie d’oxydation et de réduction des complexes de cuivre et d’uranium est explorée et met en évidence une forte divergence par rapport aux analogues imines de ces ligands. Enfin, l’utilisation de complexes de nickel(II) pour catalyse de dimérisation de l’éthylène est décrite. L’ensemble des résultats est soutenu par des analyses à l’état solide, principalement par diffraction des rayons X ; en solution, par des études RMN multinoyaux mais aussi in silico par des calculs DFT
Solving Shift Register Problems over Skew Polynomial Rings using Module Minimisation
No full textInternational audienceFor many algebraic codes the main part of decoding can be reduced to a shift register synthesis problem. In this paper we present an approach for solving generalised shift register problems over skew polynomial rings which occur in error and erasure decoding of L-interleaved Gabidulin codes. The algorithm is based on module minimisation and has time complexity O(L*mu^2) where mu measures the size of the input problem
Towards Deciding Second-order Unification Problems Using Regular Tree Automata
No full textInternational audienceThe second-order unification problem is undecidable [5]. While unification procedures, like Huet's pre-unification, terminate with success on unifiable problems, they might not terminate on non-unifiable ones. There are several decidability results for unification problems with infinitely-many pre-unifiers, such as for monadic second-order problems [3]. These results are based on the regular structure of the solutions of these problems and by computing minimal unifiers. Beyond the importance of the knowledge that searching for unifiers of decidable problems always terminates, one can also use this information in order to optimize unification algorithms, such as in the case for pattern unification [10]. Nevertheless, being able to prove that the unification problem of a certain class of unification constraints is decidable is far from easy. Some results were obtained for certain syntactic restrictions on the problems (see Levy [8] for some results and references) or on the unifiers (see Schmidt-Schauß [11], Schmidt-Schauß and Schulz [12, 13] and Je˙ z [7] for some results). Infinitary unification problems, like the ones we are considering, might suggest that known tools for dealing with the infinite might be useful. One such tool is the regular tree automaton. The drawback of using regular automata for unification is, of course, their inability to deal with variables. In this paper we try to overcome this obstacle and describe an ongoing work about using regular tree automata [1] in order to decide more general second-order unification problems. The second-order unification problems we will consider are of the form λz n .x 0 t. = λz n .C(x 0 s) where C is a non-empty context [2] and x 0 does not occur in t or s. We will call such problems cyclic problems. An important result in second-order unification was obtained by Ganzinger et al. [4] and stated that second-order unification is undecidable already when there is only one second-order variable occurring twice. The unification problem they used for proving the undecidability result was an instance of the following cyclic problem. Note that we chose to use in the definition only unary second-order variables but that this restriction should not be essential. x 0 (w 1 , g(y 1 , a)) = g(y 2 , x 0 (w 2 , a)) (1) Our decidability result is obtained by posing one further restriction over cyclic problems which is based on the existence and location of variables other than the cyclic one. A sufficient condition for the decidability of second-order unification problems was given by Levy [8]. This condition states that if we can never encounter, when applying Huet's pre-unification procedure [6] to a problem, a cyclic equation, then the procedure terminates. It follows from this result that deciding second-order unification problems depends on the ability to decide cyclic problems. The rules of Huet's procedure (PUA) are given in Fig. 1. Imitation partial bindings and projection partial bindings are defined in [14] and are denoted, respectively, by PB(f, α) and PB(i, α) where α is a type, Σ a signature f ∈ Σ and i > 0
