[Photoluminescence of silver nanoparticles].

In the present paper, the photoluminescence of silver nanoparticles with different size and surface modifier was studied. The results show that the strong emission peak at 362 nm and the two weak emission peaks at 592 and 725 nm respectively were observed by excitation at different wavelengths. With increasing excitation wavelength, the intensity of emission peak decreased and the emission peak at 362 nm red-shifted. Otherwise, the photoluminescence of silver nanoparticles was sensitive to the excitation light of 210 nm. The emission peak has little relation with the surface modification and particle size of silver nanoparticles, just as the particle size decreased, the intensity of peak decreased. The intensity of emission peak decreased with the slit width decreased. The emission peaks gradually gathered together and merged into single peak at 426 nm, and the intensity first increased and then decreased. The mechanism of photoluminescence of silver nanoparticles was discussed by absorption--reemission of photoelectrons and interface energy hybridization.

Distribution of wall shear stress in carotid plaques using magnetic resonance imaging and computational fluid dynamics analysis: a preliminary study / 中华医学杂志(英文版)

<p><b>BACKGROUND</b>Wall shear stress is an important factor in the destabilization of atherosclerotic plaques. The purpose of this study was to assess the distribution of wall shear stress in advanced carotid plaques using high resolution magnetic resonance imaging and computational fluid dynamics.</p><p><b>METHODS</b>Eight diseased internal carotid arteries in seven patients were evaluated. High resolution magnetic resonance imaging was used to visualize the plaque structures, and the mechanic stress in the plaque was obtained by combining vascular imaging post-processing with computational fluid dynamics.</p><p><b>RESULTS</b>Wall shear stresses in the plaques in all cases were higher than those in control group. Maximal shear stresses in the plaques were observed at the top of plaque hills, as well as the shoulders of the plaques. Among them, the maximal shear stress in the ruptured plaque was observed in the rupture location in three cases and at the shoulder of fibrous cap in two cases. The maximal shear stress was also seen at the region of calcification, in thrombus region and in the thickest region of plaque in the other three cases, respectively.</p><p><b>CONCLUSION</b>Determination of maximal shear stress at the plaque may be useful for predicting the rupture location of the plaque and may play an important role in assessing plaque vulnerability.</p>