National Nuclear Energy Commission

About: National Nuclear Energy Commission is a government organization based out in Rio de Janeiro, Brazil. It is known for research contribution in the topics: Dosimetry & Laser. The organization has 3816 authors who have published 4694 publications receiving 59951 citations.

Random Lasing at Localization Transition in a Colloidal Suspension (TiO2@Silica)

Abstract: Anderson localization of light and random lasing in this critical regime is an open research frontier, which besides being a basic research topic could also lead to important applications This article investigates the random laser action at the localization transition in a strongly disordered scattering medium composed of a colloidal suspension of core–shell nanoparticles (TiO2@Silica) in ethanol solution of Rhodamine 6G The classical superfluorescence band of the random laser was measured separately by collecting the emission at the back of the samples, showing a linear dependence with pumping fluence without gain depletion However, frontal collection showed saturation of the absorption and emission Narrow peaks of approximately equal intensity are observed on top of the classical superfluorescence band, indicating suppression of the interaction between the peaks modes The linewidth of these peaks is lower than that of the passive modes of the scattering medium A method called fraction of absorbed

Effects of ionic strength on the antimicrobial photodynamic efficiency of methylene blue

Abstract: Antimicrobial photodynamic therapy (APDT) may become a useful clinical tool to treat microbial infections, and methylene blue (MB) is a well-known photosensitizer constantly employed in APDT studies, and although MB presents good efficiency in antimicrobial studies, some of the MB photochemical characteristics still have to be evaluated in terms of APDT. This work aimed to evaluate the role of MB solvent's ionic strength regarding dimerization, photochemistry, and photodynamic antimicrobial efficiency. Microbiological survival fraction assays on Escherichia coli were employed to verify the solution's influence on MB antimicrobial activity. MB was evaluated in deionized water and 0.9% saline solution through optical absorption spectroscopy; the solutions were also analysed via dissolved oxygen availability and reactive oxygen species (ROS) production. Our results show that bacterial reduction was increased in deionized water. Also we demonstrated that saline solution presents less oxygen availability than water, the dimer/monomer ratio for MB in saline is smaller than in water and MB presented a higher production of ROS in water than in 0.9% saline. Together, our results indicate the importance of the ionic strength in the photodynamic effectiveness and point out that this variable must be taken into account to design antimicrobial studies and to evaluate similar studies that might present conflicting results.

Estratigrafia do Grupo Bambuí na Serra da Saudade e geologia do depósito fosfático de Cedro do Abaeté, Minas Gerais

Abstract: This work focalizes the Bambui Group in the Serra da Saudade, including lithostratigraphical units description, geological map, and cross sections drawing. The lithofacies of the Serra da Saudade Formation were described: (1) pelitic-psamitic rhythmites; (2) sandstone with hummocky cross estratification; (3) green glauconitic rhythmite; (4) phosphatic rhythmite; (5) reworked carbonates (calcirudites and calcarenites). The pelitic-sandy sediments of Serra da Saudade Formation were deposited on a platform lying at a mean water depth periodically influenced by storm currents. The Serra da Saudade Formation terrigenous rocks show coarsening upward sequence, are immature sediments and were accumulated in a basin under the influence of collisional processes. The phosphatic rhythmite (phosphoarenite) is situated near Cedro do Abaete city. It consists of phosphate intraclasts in a microcrystalline grained matrix (micrite), rich in fluorapatite, and addition to detrital quartz, feldspar, muscovite and other minerals.The phosphatization is a syn-diagenetic phase, but with important development of the wavelite by the supergene alteration.