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We treat here of the question of absorbing boundary conditionsfor nonlinear diffusion equations. We use the conditions designedfor the linear equation, we prove them to be well posed forthe nonlinear problem, and through numerical experiments thatthey are well suited for reactiondiffusion equations. 相似文献
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Monitoring the Transition from Spherical to Polymer‐like Surfactant Micelles Using Small‐Angle X‐Ray Scattering 下载免费PDF全文
Dr. Grethe Vestergaard Jensen Dr. Reidar Lund Dr. Jérémie Gummel Dr. Theyencheri Narayanan Prof. Jan Skov Pedersen 《Angewandte Chemie (International ed. in English)》2014,53(43):11524-11528
Despite over a century of modern surfactant science, the kinetic pathways of morphological transitions in micellar systems are still not well understood. This is mainly as a result of the lack of sufficiently fast methods that can capture the structural changes of such transitions. Herein, a simple surfactant system consisting of sodium dodecyl sulfate (SDS) in aqueous NaCl solutions is investigated. Combining synchrotron radiation small‐angle X‐ray scattering (SAXS) with fast stopped‐flow mixing schemes allows monitoring the process where polymer‐like micelles are formed from globular micelles when the salt concentration is suddenly increased. The results show that “worm‐like” micelles are formed by fusion of globular micelles and short cylinders in a fashion that bears similarities to a step‐like polymerization process. 相似文献
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J. Gummel Y. Corvis J. Jestin J. M’Hamdi L. Barré 《The European physical journal. Special topics》2009,167(1):171-176
Presence of suspended particles such as asphaltene in crude oils
could significantly affect the production by means of deposition in porous
media especially near the well bore. We investigate this phenomenon using
the ability of Small Angle Neutron Scattering technique to probe directly
the asphaltene adsorption process in a porous medium at the nanometer length
scale under flow conditions. A device based on a quartz tube filled with SiC
particles constitute the porous medium in which an asphaltene solution in a
mixture of good (toluene)/bad (heptane) solvent is injected under
controlled flow. The contrast matching technique enables to match the porous
medium scattering contributions and to measure the signal of the deposit.
Such a device can be used for curves surface measurements on a setup
originally designed for bulk studies and permit thus the direct comparison
with measurements on flat surfaces (neutron reflectivity) and indirect
adsorption measurements (adsorption isotherm). We show here that asphaltene
in good solvent leads to a monolayer whereas addition of bad solvent results
in a multilayer growth which is consistent with the deposition behaviour
described in the literature. 相似文献
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C. A. Peridier J. L. Matthews M. J. Leitch H. Jeremie M. Irshad B. L. Roberts 《Zeitschrift für Physik A Hadrons and Nuclei》1983,310(4):317-328
The cross section for the3He(γ, 2p) reaction has been measured in a complete kinematics experiment in the energy rangeE γ=80–170 MeV, forθ P1=θ P2=90°. This configuration was selected in order to investigate the role of proton-proton final state interactions in the three-body breakup process. The measured proton spectra are seen to be consistent with a prediction using the Watson-Migdal formalism. The magnitude of the observed cross section clearly indicates an enhancement over phase space, presumably due to the strong proton-proton interaction in the final state. The experimental results agree, within their limited statistical accuracy, with a theoretical calculation which includes this effect. 相似文献
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L. A. Hamel L. Lessard H. Jeremie J. Chauvin 《Zeitschrift für Physik A Hadrons and Nuclei》1985,321(3):439-441
The beta decay rate of the16N(0?; 120keV) →16O(0+, G.S.) transition has been remeasured. Our result (Λ β =0.48±0.024 s?1) is in excellent agreement with a previous measurement but strongly disagrees with another experimental value. The two agreeing results provide an experimental verification of the importance of meson exchange currents in 0+-0? weak transitions. A value ofg p/g A~11–12 can be inferred from the correspondingΛ μ rate. 相似文献
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A. Champagne G. Beaudoin L. A. Hamel H. Jeremie L. Lessard 《Zeitschrift für Physik A Hadrons and Nuclei》1988,330(4):377-385
We have measured the beta spectrum of the 0?(120 keV,t 1/2=5.25 μs) state of16N. The response function of our detector has been measured, parameterized and then fitted to known spectral shapes taken under conditions close to those in the actual experiment. Using this response function and subtracting a 56 μs half-life background due to neutron capture in the detector, the measured 0? spectrum compares well with the allowed shape for the 0?→0+ spectrum plus a small contribution from the allowed 0?→1? transition. 相似文献
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Flavonols are naturally occurring dyes that can be extracted from plants. Because of their antioxidant properties, they are thought to have health benefits. In this study, the photochemical degradation properties of selected flavonols were investigated. Dilute solutions of dyes were exposed to light from a broadband visible light source, and the rate of photodegradation was determined by measuring the decrease in fluorescence of the dyes with respect to time. At pH 9.24, the first-order rate constants for 10?µg?mL?1 solutions of myricetin, quercetin, kaempferol, and morin were 0.468, 0.162, 0.108, and 0.126?s?1, respectively. Interestingly, the stability of these historical dyes was also found to be greatly affected by pH. Awareness of the photochemical properties and stability of flavonol dyes is very important for capillary electrophoresis (CE) separations. Photodegradation of the flavonol dyes under the alkaline conditions (pH 9.2) used in CE can have a profound effect on the reproducibility of repeated separations. Even a modest decrease in pH (pH 8.5) greatly improved the stability of these dyes and enabled the successful separation of these flavonol dyes with minimal degradation over time. 相似文献