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In traditional text based medical image retrieval system, it is hard to find visually similar images in large medical image database. Content-based image retrieval is developed to retrieve similar images and it is based on visual attributes describing the content of an image. Developing a method for content based medical image retrieval is a challenging task. This paper proposed a new method for content-based medical image retrieval based on salient regions and deep learning. The proposed method includes two stages: an offline task to extract local object features and an online task for content-based image retrieval in database. In first stage, we extract local object features of medical image depending on shape, texture and intensity, and features extracted by deep learning applied in saliency of decomposition. Secondly, we make online task for content-based image retrieval in database. The user gives query image as an input and the system will retrieve n top most similar images by similarity comparison with bag of code words feature values obtained in the first stage. Evaluation of the proposed method is based on Precision and Recall values. Our dataset includes 5 groups of medical images with their quality varying from low to high. With the best medical image quality group, the accuray can be 91.61% for Precision and 89.61% for Recall. Comparing the average values with others methods, the results of the proposed method are more than 2 to 5% better. [ABSTRACT FROM AUTHOR]

Femtosecond time-resolved pump–probe absorption kinetic spectroscopy was used to show that the presence of plasmonic silver nanoparticles in Ag–CuPc hybrid thin-fi lm nanocomposites leads to a significant reduction in the relaxation time of induced absorption from an excited singlet state of copper phthalocyanine fi lm as compared to the pure fi lm. The observed effect is associated with intersystem crossing acceleration in CuPc molecules located in a nonuniform field near the surface of plasmonic silver nanoparticles in the hybrid nanocomposite. The detected effects were demonstrated to depend on the thickness of the copper phthalocyanine layers in the hybrid (Ag–CuPc)nAg nanocomposites. [ABSTRACT FROM AUTHOR]

We study the electronic excitation dynamics in ensembles of plasmonic gold nanorods (Au NRs), in view of the femtosecond transient absorption spectroscopy, and compare the results with the excitation dynamics of spherical Au nanoparticles (NPs). We use the obtained kinetics of the transient absorption of Au NRs and Au NPs to fit the theoretical profile of the temperature relaxation of the excitation dynamics of electron and lattice nanoparticles, as well as their environment under the excitation by laser pulses with duration of 150 fs. For gold nanorods, the electron–phonon interaction constant reads γNRs = 12 · 1016 W·m−3·K−1, and the heat loss is hNRs = 16 · 108 W·m−2·K−1. In the case of gold nanospheres, the constants are γNPs = 7· 1016 W·m−3·K−1 and hNRs = 8· 108 W·m−2·K−1, respectively. [ABSTRACT FROM AUTHOR]

The mechanism of the nonlinear optical response of colloidal solutions of Ag2S quantum dots passivated with thioglycolic acid molecules is considered. Appearance of nonlinear absorption and nonlinear refraction is shown by the Z-scan method using 10-ns pulses of the second harmonic of a Nd:YAG laser. The absorption coefficient dependence was found to saturate with increasing incident radiation intensity. It is suggested that nonlinear absorption occurs with participation of the localized states of structural defects in Ag2S, including the defect luminescence center, which is confirmed by femtosecond transient absorption spectroscopy. A broad structureless transient absorption band is observed in the range of 500–1000 nm, which decays on a time scale of picoseconds. It is concluded that the transient absorption signal is caused by fast (fractions of picoseconds) capture of charge carriers by localized states, which then induce the nonlinear absorption of 10-ns pulses. [ABSTRACT FROM AUTHOR]