Photodynamic Therapy (PDT) is a technique for destroying tumor cells with little harm to surrounding healthy
tissue. However, the light wavelength has limited penetration in the tissue, making the association of a
surgical procedure needed for larger lesions. Electrosurgery (ES) is a recommended excision technique, but
the optical properties of the tissue damaged by ES and its influence on PDT procedure are unknown. Twelve
rats (Wistar) composed the animal model of four groups (ES, PDT, ES+PS+Light, PS+ES+Light), evaluating
different orders of conjugation via fluorescence, imaging and necrosis depth. First histopathological analysis
has shown a highly modified surface of tissue (integral structure loss and dehydration shrinkage), protein
denaturation, accompanied by bleeding and inflammatory damage. Fluorescence imaging showed strong
scattering of light at the surface of modified tissue, which may cause higher losses of light on the surface.
Fluorescence spectra showed different photosensitizer emissions for distinct operation modes. The different
tissue composition can also induce changes on absorption and scattering properties, influencing the light
penetration. The study showed significant necrosis formation beyond the limits of electrosurgery damage,
making possible the conjugate use of ES and PDT.
Spectroscopic properties of ytterbium-doped tellurite glasses with different compositions are reported. Results of linear refractive index, absorption and emission spectra, and fluorescence lifetimes are presented. The studied samples present high refractive index (~2.0) and large transmission window (380-6000nm). Absorption and emission cross-sections are calculated as well as the minimum pump laser intensity. The results are compared with the values of other laser materials, in order to investigate applications as laser media in the infrared region.
Efficient and thermally enhanced frequency upconversion of cw IR radiation at 1.064 micrometers into blue, red and near-IR light in integrated Tm3+/Yb3+-codoped phosphosilicate silica-on-silicon buried waveguides is reported. Thermally induced frequency upconversion enhancement is observed for the first time in a Tm3+/Yb3+-codoped system excited off-resonance at 1.064 micrometers . A sevenfold thermally induced upconversion efficiency enhancement was obtained when the waveguide's temperature was varied in the 20 degrees C-120 degrees C range. The thermal effect is believed to be associated with a temperature dependent effective absorption cross-section for the Yb3+-sensitizer, which depends upon the phonon occupation number in the host matrix.
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