Ubirajara Agero | Searcharxiv

arXiv2025

Analysis of optical pattern formation on glass: exploring light phenomena in the International Physicists Tournament

Motivated by a problem from the 2023 International Physicists' Tournament, we investigate the formation of particular patterns when light passes through glass. Experimentally, we use various glass plates, registering each reflected and transmitted outcome. Thus, we find the condition to form a common pattern, namely, randomly scratched plates produce the halos. We engineer other optical patterns by means of the specular holography method. Using the Defocusing Microscopy technique, we study the geometric properties of the glass, establishing the physical and mathematical model for a simulation. Our computational results agree well with the experimental ones, leading us to conclude that the pattern formation is governed by specular reflection on various points along the scratches. Our findings give an initial explanation for the pattern formation on glass, in particular for the halo design. We also show that the IPT open questions help students learn physics concepts and develop research skills.

physics.app-ph↗

arXiv2021

Red Blood Cell Sphericity Index Obtained by Defocusing Microscopy and Retinopathy Severity in Sickle Cell Disease

Proliferative sickle cell retinopathy (PSCR) is the most important ocular manifestation of sickle cell disease (SCD), but understanding of its pathophysiology remains incomplete. Red blood cell (RBC) deformability has been identified as a critical factor in SCD and is intrinsically related with cell sphericity index (SI). The aim of this study was to develop an algorithm that automatically analyzes defocusing microscopy (DM) images, providing biomechanical parameters of individual RBCs, including cellular SI. Furthermore, association of RBC SI with severity of PSCR in individuals with HbSC-SCD was also investigated. We determined the SI of 255 RBCs from 17 individuals using DM. Nine individuals (53%) were healthy and eight (47%) had HbSC-SCD. Mean SI was significantly lower in SCD than in control group (0.69 versus 0.73), and also in severe than in mild PSCR (0.67 versus 0.70). Lower SI was also associated with more severe retinopathy (ROC AUC = 0.85) and the proportion of participants with SI <= 0.69 was significantly greater in severe than in mild PSCR (100% versus 25%). In conclusion, lower RBC SI determined by DM was associated not only with the presence of SCD, but also with more severe PSCR, possibly being a surrogate biomarker of disease severity.

physics.app-ph↗