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981.
Proton-coupled electron transfer (PCET) reactions have received much attention over the past 10 years, from an experimental as well as from a theoretical point of view. At the heart of many chemical and biological processes, such reactions are of particular interest in energy conversion and enzymatic processes. Among the numerous examples of PCET reactions, photosynthesis and particularly reactions inside the Photosystem II (PSII) subunit, involving a global four electrons and four protons process to perform water oxidation and respiration, is the most emblematic one. This review focuses on the photochemical approaches of PCET reactions involving phenolic molecules. Indeed, a significant part of photochemical PCET studies were conducted on tyrosine or phenol relevant to PSII and charge transport in enzymes. The mechanisms of these reactions, sequential or concerted, with particular emphasis on the influence of pH, temperature, solvent nature and H-bonding pattern are presented based on photochemical techniques and related theoretical analysis. 相似文献
982.
Julien Jimenez 《Journal of Evolution Equations》2011,11(3):553-576
We deal in this paper with a scalar conservation law, set in a bounded multidimensional domain, and such that the convective
term is discontinuous with respect to the space variable. First, we introduce a weak entropy formulation for the homogeneous
Dirichlet problem associated with the first-order reaction-convection equation that we consider. Then, we establish an existence
and uniqueness property for the weak entropy solution. The method of doubling variables and a pointwise reasoning along the
curve of discontinuity are used to state uniqueness. Finally, the vanishing viscosity method allows us to prove the existence
result. Another method to obtain the existence of a solution, which relies on the regularization of the flux, is also detailled,
at least for a particular case. 相似文献
983.
Olivier Durand de Gevigney Fr��d��ric Meunier Christian Popa Julien Reygner Ayrin Romero 《4OR: A Quarterly Journal of Operations Research》2011,9(2):175-188
Let T = (V, A) be a directed tree. Given a collection P{\mathcal{P}} of dipaths on T, we can look at the arc-intersection graph I(P,T){I(\mathcal{P},T)} whose vertex set is P{\mathcal{P}} and where two vertices are connected by an edge if the corresponding dipaths share a common arc. Monma and Wei, who started
their study in a seminal paper on intersection graphs of paths on a tree, called them DE graphs (for directed edge path graphs)
and proved that they are perfect. DE graphs find one of their applications in the context of optical networks. For instance,
assigning wavelengths to set of dipaths in a directed tree network consists in finding a proper coloring of the arc-intersection
graph. In the present paper, we give
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a simple algorithm finding a minimum proper coloring of the paths. 相似文献
984.
The linear stability of IMEX (IMplicit–EXplicit) methods and exponential integrators for stiff systems of ODEs arising in the discrete solution of PDEs is examined for nonlinear PDEs with both linear dispersion and dissipation, and a clear method of visualization of the linear stability regions is proposed. Predictions are made based on these visualizations and are supported by a series of experiments on five PDEs including quasigeostrophic equations and stratified Boussinesq equations. The experiments, involving 24 IMEX and exponential methods of third and fourth order, confirm the predictions of the linear stability analysis, that the methods are typically limited by small eigenvalues of the linear term and by eigenvalues on or near the imaginary axis rather than by large eigenvalues near the negative real axis. The experiments also demonstrate that IMEX methods achieve comparable stability to exponential methods, and that exponential methods are significantly more accurate only when the problem is nearly linear. Novel IMEX predictor–corrector methods are also derived. 相似文献
985.
Using swelling hydrogels, we study the evolution of a thin circular artificial tumor whose growth is confined at the periphery. When the volume of the outer proliferative ring increases, the tumor loses its initial symmetry and bifurcates towards an oscillatory shape. Depending on the geometrical and elastic parameters, we observe either a smooth large-wavelength undulation of the swelling layer or the formation of sharp creases at the free boundary. Our experimental results as well as previous observations from other studies are in very good agreement with a nonlinear poroelastic model. 相似文献
986.
Bleuse J Claudon J Creasey M Malik NS Gérard JM Maksymov I Hugonin JP Lalanne P 《Physical review letters》2011,106(10):103601
We experimentally investigate the spontaneous emission (SE) rates of single InAs quantum dots embedded in GaAs photonic nanowires. For a diameter leading to the optimal confinement of the fundamental guided mode HE11, the coupling to HE11 dominates the SE process and an increase of the SE rate by a factor of 1.5 is achieved. When the diameter is decreased, the coupling to this mode vanishes rapidly, thus allowing the coupling to the other radiation modes to be probed. In these conditions, a SE inhibition factor of 16, equivalent to the one obtained in state-of-the-art photonic crystals, is measured. These results, which are supported by fully vectorial calculations, confirm the potential of photonic nanowires for a nearly perfect, broadband SE control. 相似文献
987.
A dense granular suspension dripping on an imbibing surface is observed to give rise to slender mechanically stable structures that we call granular towers. Successive drops of grain-liquid mixtures are shown to solidify rapidly upon contact with a liquid absorbing substrate. A balance of excess liquid flux and drainage rate is found to capture the typical growth and height of the towers. The tower width is captured by the Weber number, which gives the relative importance of inertia and capillary forces. Various symmetric, smooth, corrugated, zigzag, and chiral structures are observed by varying the impact velocity and the flux rate from droplet to jetting regime. 相似文献
988.
Wang S Gao J Carlier J Campistron P NDieguene A Guo S Matar OB Dorothee DC Nongaillard B 《Ultrasonics》2011,51(5):532-538
In this paper, we present a feasible microsystem in which the direction of localized ultrahigh frequency (∼1 GHz) bulk acoustic wave can be controlled in a silicon wafer. Deep etching technology on the silicon wafer makes it possible to achieve high aspect ratio etching patterns which can be used to control bulk acoustic wave to transmit in the directions parallel to the surface of the silicon wafer. Passive 45° mirror planes obtained by wet chemical etching were employed to reflect the bulk acoustic wave. Zinc oxide (ZnO) thin film transducers were deposited by radio frequency sputtering with a thickness of about 1 μm on the other side of the wafer, which act as emitter/receptor after aligned with the mirrors. Two opponent vertical mirrors were inserted between the 45° mirrors to guide the transmission of the acoustic waves. The propagation of the bulk acoustic wave was studied with simulations and the characterization of S21 scattering parameters, indicating that the mirrors were efficient to guide bulk acoustic waves in the silicon wafer. 相似文献
989.
A new class of Fabry-Perot filters produced by a multilayer dielectric mirror deposited on top of a reflecting volume Bragg grating is described. The first fabricated prototype for the 852 nm region demonstrates a 30 pm bandwidth, 90+% transmission at resonance, and a good agreement with theoretical simulation. 相似文献
990.
Fluoride glass Raman fiber laser at 2185 nm 总被引:1,自引:0,他引:1
We report on the first Raman laser based on a fluoride glass optical fiber. The Raman fiber laser was pumped by a 9.6?WTm3+:silica CW fiber laser operating at a wavelength of 1940?nm. A maximum output power of 580?mW was measured at 2185.1?nm, corresponding to a frequency shift of 579?cm(-1) (17.37?THz). We observed a threshold power of 3.8?W and a low power slope efficiency of 29% with respect to the launched pump power. Using those results and the known fiber parameters, we estimated a Raman gain peak value of 3.52*10(-14)?m/W, which is lower than the previously reported values. 相似文献
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