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131.
The flow in a PEM fuel cell bipolar plate with a diagonal channel structure and across a carbon paper backing layer has been
experimentally studied. To examine the flow inside the plate, a liquid analogue preserving dynamic similarity has been used,
applying laser-induced fluorescence. This analogy, however, cannot be used to study the flow through the carbon paper, because
gas and liquid surface tension are not equivalent and their flow through a porous medium will be different. For this analysis
this paper proposes as a novel application, the use of acetone vapor planar induced fluorescence. With this technique, image
sequences have been obtained to visualize the gas crossing the backing layer while the plate was filled with acetone-seeded
air. It has been demonstrated that the pattern of the flow emerging from the diffusion layer follows that of the pressure
distribution in the plate. Hence, even an apparently non-uniform velocity distribution of the reactant gases in the plate
could result in an acceptable distribution over the catalyzed electrode if the pressure field is sufficiently smooth. 相似文献
132.
The use of sensitized phosphorescence for visualization of gas phase fluid mixing and the requirements for quantitative imaging
measurements are discussed. A model for estimating the molecular-mixing signal's dependence on fluid composition is developed
and candidate molecular reactants are considered within the framework of the model. Experiments based on sensitized phosphorescence
from both an acetonebiacetyl system and a toluene-biacetyl system show good qualitative agreement with modeled results. It
is concluded that quantitative measurements using sensitized phosphorescence are feasible. 相似文献
133.
Theoretical Vibrational Raman and Surface‐Enhanced Raman Scattering Spectra of Water Interacting with Silver Clusters
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Marta Sanchéz‐Lozano Marcos Mandado Ignacio Pérez‐Juste Dr. Jose M. Hermida‐Ramón 《Chemphyschem》2014,15(18):4067-4076
In this study, we analyzed the Raman spectrum of a water molecule adsorbed on a cluster of 20 silver atoms, and the plasmonic electromagnetic effect of the silver surface was also considered to give a theoretical prediction of the surface‐enhanced Raman scattering spectrum. The calculations were performed at the density functional theory (DFT) level by using both frozen and unfrozen silver clusters. Two different models were used to consider the plasmonic enhancement; one of them was a modified classical (dipole) model and the other was the coupled perturbed Hartree–Fock method with excitation frequencies obtained from time‐dependent DFT calculations and with proper detuning of these frequencies. The importance of small geometrical distortions of the silver surface in the orientation of the adsorbed water was shown. Moreover, it was shown how the symmetry of the transition dipole moment and the symmetry of the vibrational modes influence the Raman intensities of the SERS spectrum. 相似文献
134.
Eleonora Casula Maria Manconi Jos Antonio Vzquez Tania Belen Lopez-Mendez Jos Luis Pedraz Esteban Calvo Antonio Lozano Marco Zaru Andreia Ascenso Maria Letizia Manca 《Molecules (Basel, Switzerland)》2021,26(21)
The extract of Cardiospermum halicacabum L. (C. halicacabum) obtained from flower, leaf and vine was loaded into modified phospholipid vesicles aiming at obtaining sprayable, biocompatible and effective nasal spray formulations for the treatment of nasopharyngeal diseases. Penetration enhancer-containing vesicles (PEVs) and hyalurosomes were formulated, and stabilized by adding a commercial gelatin from fish (20 mg/mL) or chondroitin sulfate from catshark cartilages (Scyliorhinus canicula, 20 mg/mL). Cryo-TEM images confirmed the formation of spherical vesicles, while photon correlation spectroscopy analysis disclosed the formation of small and negatively-charged vesicles. PEVs were the smaller vesicles (~100 nm) along with gelatin-hyalurosomes (~120 nm), while chondroitin-PEVs and chondroitin-hyalurosomes were larger (~160 nm). Dispersions prepared with chondroitin sulfate were more homogeneous, as the polydispersity index was ~0.15. The in vitro analysis of the droplet size distribution, average velocity module and spray cone angle suggested a good spray-ability and deposition of formulations in the nasal cavity, as the mean diameter of the droplets was in the range recommended by the Food and Drug Administration for nasal targets. The spray plume analysis confirmed the ability of PEVs, gelatin-PEVs, hyalurosomes and gelatin-hyalurosomes to be atomized in fine droplets homogenously distributed in a full cone plume, with an angle ranging from 25 to 30°. Moreover, vesicles were highly biocompatible and capable of protecting the epithelial cells against oxidative damage, thus preventing the inflammatory state. 相似文献
135.
136.
137.
T. Pérez-Ruiz C. Martínez Lozano V. Tomás J. Carpena 《Fresenius' Journal of Analytical Chemistry》1998,361(5):492-495
The interaction of diflunisal and naproxen with several surfactants was studied. Spectrofluorimetric methods were developed
for the determination of both drugs in sodium dodecylsulfate micellar medium. The mixture of these drugs was resolved by synchronous
fluorescence spectrometry using two scans. At Δλ = 20 nm, only naproxen yields a detectable signal that is unaffected by the
presence of diflunisal. At Δλ = 110 nm the signal of diflunisal is not influenced by the presence of an up to 3-fold excess
of naproxen. Mixtures containing naproxen/ diflunisal in ratios from 50:1 to 1:50 were analyzed with good results. The linear
calibration ranges of both drugs were ca 0.02–2.0 μg mL–1. The method has satisfactorily been applied to a mixture of both drugs in serum.
Received: 7 October 1997 / Revised: 3 December 1997 / Accepted: 7 December 1997 相似文献
138.
Hugh M. Hilden María Teresa Lozano Jos María Montesinos-Amilibia 《Topology and its Applications》2005,150(1-3):267-288
If K is a hyperbolic knot in S3, an algebraic component of its character variety containing one holonomy of the complete hyperbolic structure of finite volume of S3K is an algebraic curve . The traces of the peripheral elements of K define polynomial functions in , which are related in pairs by polynomials (peripheral polynomials). These are determined by just two adjacent peripheral polynomials. The curves defined by the peripheral polynomials are all birationally equivalent to , with only one possible exception. The canonical peripheral polynomial relating the trace of the meridian with the trace of the canonical longitude of K, is a factor of the A-polynomial. 相似文献
139.
Data Envelopment Analysis (DEA) can be used for assessing the relative efficiency of a number of operating units, finding, for each inefficient unit, a target operating point lying on the efficient frontier. Most DEA models project an inefficient unit onto a most distant target, which makes its attainment more difficult. In this paper, we advocate determining a sequence of targets, each one within an appropriate, short distance of the preceding. The proposed Constant Returns to Scale approach has two interesting features: (a) the sequence of targets ends in the efficient frontier and (b) the final, efficient target is generally closer to the original unit than the one-step projection is. 相似文献