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The cytotoxicity of nanoparticles (NPs) and their properties are important issues in nanotechnology research. Particularly, NPs affect the metabolism of microorganisms due to NP interactions with some biomolecules. In order to assess the mechanisms underlying NPs toxicity, we studied the damage caused by copper oxide nanoparticles (CuO-NPs) on Staphylococcus aureus ATCC 24213 and Pseudomonas aeruginosa ATCC 27833. Spherical CuO-NPs characterized by their diameter (13 ± 3 nm) were synthesized with a maximum of 254 nm. These NPs reduced cell viability, with a minimum inhibitory concentration (MIC) of 500 and 700 ppm for Staphylococcus aureus and Pseudomonas aeruginosa, respectively. Surfactant was added to reduce the NP agglomeration, but it did not present any effect. The mechanism of CuO-NPs as antimicrobial agent was assessed by analyzing solubilized Cu, quantifying DNA release in the culture media, and measuring intracellular reactive oxygen species (ROS). CuO-NPs induced severe damage on cells as revealed by confocal optical microscopy and scanning electron microscopy (SEM). Our results indicated that CuO-NPs interacted with bacteria, triggering an intracellular signaling network which produced oxidative stress, leading to ROS generation. Finally, we concluded that CuO-NPs exhibited higher antibacterial activity on Gram-negative bacteria than on Gram-positive ones.

In this work a 3D flame reconstruction is performed from a 2D projection of the hot gases of a combustion flame. The projection is obtained using an optical schlieren technique. In this technique, a schlieren image is integrated linearly to obtain the hot gases, and then, a temperature field. Each row of the matrix representing the temperature distribution is fitted with a specific function, and its respective error is calculated. In this way, the projected matrix can be represented with the fitted functions. As a result of the procedure used in this research, a slice of the flame is obtained by assuming a cylindrical symmetry of it and multiplying the fitted function by itself. Finally, it was evaluated the mean error in calculations of temperature intensity in the flame under the cylindrical symmetry assumption obtaining an accuracy of 96% which validates the efficiency of our method.

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Topological photonics has attracted remarkable attention in recent years due to its ability to generate robust topological states, especially suitable for the study of cavity quantum electrodynamics. In this work, we present a theoretical study of a topological photonic crystal based on the 2D Su–Schrieffer–Heeger model, with corner states induced by a rotational operation on the axis parallel to the interface of two different topologies of a photonic crystal, forming a bowtie cavity. The studied topological photonic crystal presents inversion symmetry due to the rotation operation allowing the simultaneous existence of two non-degenerated corner states: one located in the weak coupling regime and the other in the strong coupling regime. Therefore, we present the emergence of distinctive effects from both regimes, such as the Purcell effect and Rabi splitting. We also address the study of the origin and evolution of the corner states resulting from the bulk-edge-corner correspondence. The topological bowtie cavity studied in this work combines the virtues of topological systems and the extreme confinement offered by cavities with bowtie architecture, which enriches the study of corner states in sophisticated topological structures.