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E. A. Bernardelli T. Belmonte D. Duday G. Frache F. Poncin-Epaillard C. Noël P. Choquet H.-N. Migeon A. Maliska 《Plasma Chemistry and Plasma Processing》2011,31(1):205-215
We study the interaction of thick films (~4 mm) of stearic acid (SA), a C18 alkane skeleton with an acid function, with late Ar–O2 post-discharge. Contrary to what is observed with thin films of SA (~2–3 μm) which are efficiently etched (part I), only functionalization is observed over the first 2 h of treatment with a plasma source operated in the continuous mode, whatever the temperature. The heat released by surface reactions affects non-linearly the temperature of the substrate. Pulsing the source at a frequency ranging from 0.1 to 1 kHz slows down the functionalization process but does not allow any etching of the material. On the contrary, the SA can be etched as thick films by pulsing the oxygen flow rate at a frequency below 50 mHz. By pulsing the reactive gas, the time averaged value of the [O]/[O2] ratio is decreased, limiting the functionalization processes due to oxygen atoms, and the mean temperature is lowered, decreasing the diffusion length of O2 (and/or possibly O2*) species in the SA which are responsible for the scission of C–C bonds of radicals. 相似文献
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Catherine Choquet 《Acta Appl Math》2008,103(3):277-299
We consider a problem of nuclear waste contamination in the basement. We derive a detailed model describing the simultaneous
transport of brine, radionuclides and heat in a compressible flow through a porous medium. It leads to a nonlinear system
of fully coupled partial differential equations. Using a fixed point approach, we prove existence of physically relevant weak
solutions.
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Importance of Outer‐Sphere and Aggregation Phenomena in the Relaxation Properties of Phosphonated Gadolinium Complexes with Potential Applications as MRI Contrast Agents 下载免费PDF全文
Dr. Mourad Elhabiri Dr. Sabah Abada Mohamadou Sy Dr. Aline Nonat Dr. Philippe Choquet Dr. David Esteban‐Gómez Dr. Claudio Cassino Dr. Carlos Platas‐Iglesias Prof. Mauro Botta Dr. Loïc J. Charbonnière 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(17):6535-6546
A series composed of a tetra‐, a tris‐ and a bisphosphonated ligand based on a pyridine scaffold ( L4 , L3 and L2 , respectively) was studied within the frame of lanthanide (Ln) coordination. The stability constants of the complexes formed with lanthanide cations (Ln=La, Nd, Eu, Gd, Tb, Er and Lu) were determined by potentiometry in aqueous solutions (25.0 °C, 0.1 M NaClO4), showing that the tetraphosphonated complexes are among the most stable LnIII complexes reported in the literature. The complexation of L4 was further studied by different titration experiments using mass spectrometry and various spectroscopic techniques including UV/Vis absorption, and steady state and time‐resolved luminescence (Ln=Eu and Tb). Titration experiments confirmed the formation of highly stable [Ln L4 ] complexes. 31P NMR experiments of the Lu L4 complex revealed an intramolecular interconversion process which was studied at different temperatures and was rationalized by DFT modelling. The relaxivity properties of the GdIII complexes were studied by recording their 1H NMRD profiles at various temperatures, by temperature dependent 17O NMR experiments (Gd L4 ) and by pH dependent relaxivity measurements at 0.47 T (Gd L3 and Gd L2 ). In addition to the high relaxivity values observed for all complexes, the results showed an important second‐sphere contribution to relaxivity and pH dependent variations associated with the formation of aggregates for Gd L2 and Gd L3 . Finally, intravenous injection of Gd L4 to a mouse was followed by dynamic MRI imaging at 1.5 T, which showed that the complex can be immediately found in the blood stream and rapidly eliminated through the liver and in large part through the kidneys. 相似文献
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In this paper we study a partially ionized plasma that corresponds to an arc discharge at atmospheric pressure. We derive an inviscid hydrodynamic/diffusion limit, characterized by two temperatures, from a system of Boltzmann type transport equations modelling that plasma problem. The original property of this system is that impact ionization is a leading order collisional process. As a consequence, the density of electrons is given in terms of the density of the other species (and its temperature) via a Saha law. 相似文献
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M. Gueye T. Gries C. Noël S. Migot-Choux S. Bulou E. Lecoq P. Choquet K. Kutasi T. Belmonte 《Plasma Chemistry and Plasma Processing》2016,36(4):1031-1050
The interaction of (3-Aminopropyl)triethoxysilane (APTES) with pulsed late Ar–O2 afterglow is characterized by the synthesis of OH, CO and CO2 in the gas phase as main by-products. Other minor species like CH, CN and C2H are also produced. We suggest that OH radicals are produced in a first step by dehydrogenation of APTES after interaction with oxygen atoms. In a second step, the molecule is oxidized by any O2 state, to form peroxides that transform into by-products, break thus the precursor C–C bonds. If oxidation is limited, i.e. a low duty cycle, fragmentation of the precursor is limited and produced nanoparticles keep the backbone structure of the precursor, but contain amide groups produced from the amine groups initially available in APTES. At high duty cycle, silicon-containing fragments contain some carbon and react together and produce nanoparticles with a non-silica-like structure. 相似文献
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Catherine Choquet 《NoDEA : Nonlinear Differential Equations and Applications》2008,15(6):757-782
We study the asymptotic behavior, with respect to high Peclet numbers, of a model describing a compressible and miscible displacement
in a porous medium. The transport of mass is then described by a nonlinear, fully coupled and degenerate parabolic system.
Using non-classical estimates and renormalization tools, we prove existence of relevant weak solutions for the limit problem.
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Abstract. This paper presents the results obtained by a generalized cut cells strategy on 3-D blast waves problems. The mesh is cartesian
except when it is intersected by the surface of the solids inserted in the computational domain. The improvement, relatively
to a classical cut-cells method, is the treatment of the cut which preserves the real geometry of the surface instead of approximating
it by a plane. This approach avoids a loss of precision of the numerical scheme at the boundaries and allows future extension
to higher order schemes (). Moreover it is useful for any kind of geometry with a high efficiency in computation time. The drawback is the complexity
of the geometrical problems which can rise because of the diversity of situations in the treatment of the cuts. The performance
of the approach is tested on a few examples allowing comparisons with experiments or other techniques and physical discussions.
Received 15 November 1999 / Accepted 11 July 2000 相似文献
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C. Choquet 《Applicable analysis》2013,92(5):477-499
We derive a double porosity model for a displacement of one compressible miscible fluid by another in a naturally fractured reservoir. The microscopic model consists of the usual equations describing Darcy flow in a reservoir except that the porosity and the permeability coefficients are highly discontinuous. The viscosity is assumed to be constant. Over the matrix domain, the coefficients are scaled by a parameter ? representing the size of the matrix blocks. This scaling preserves the physics of the flow in the matrix as ? tends to zero. Using homogenization theory, we derive rigorously the corresponding double porosity model. To this purpose, we mainly use the concept of two-scale convergence. The less permeable part of the rock then contributes as nonlinear memory terms. To specify them in spite of the strong nonlinearities and of the coupling, we then use some appropriate dilation operator. 相似文献