Online teaching modality in a pandemic time: the opinion from a group of undergraduate physics students

The pandemic of SARS-CoV-2 affected educational activities around the world. In this scenario, online teaching was the main strategy adopted by Brazilian universities. The literature presents possibilities and boundaries to physics teaching on distance learning modality. In this context, this article aimed to investigate the opinion from a group of physics undergraduate students to have an overview of challenges for Brazilian universities. This group had the face-to-face classes changed abruptly to online modality. An electronic quiz was conducted to analyse data based on Content Analysis procedures. The group believes in the potential of online teaching during the pandemic time, but agrees that several aspects need to change. The students report that they have faced problems related to technical, pedagogical, and socioeconomic aspects. As consequence of distance learning modality, students have presented symptoms of anxiety, depression, and lack of motivation. The group points out professor training as a focus that might help improve online teaching © Copyright by Sociedade Brasileira de Física. Printed in Brazil

Detection of a SARS-CoV-2 sequence with genosensors using data analysis based on information visualization and machine learning techniques

We report on genosensors to detect an ssDNA sequence from the SARS-CoV-2 genome, which mimics the GU280 gp10 gene (coding the viral nucleocapsid phosphoprotein), using four distinct principles of detection and treating the data with information visualization and machine learning techniques. Genosensors were fabricated on either gold (Au) interdigitated electrodes for electrical and electrochemical measurements or on Au nanoparticles on a glass slide for optical measurements. They contained a matrix of 11-mercaptoundecanoic acid (11-MUA) self-assembled monolayer (SAM) onto which a layer of capture probe (cpDNA) sequence was immobilized. Detection was performed using electrical and electrochemical impedance spectroscopies and localized surface plasmon resonance (LSPR). The highest sensitivity was reached with impedance spectroscopy, including using a low-cost (US$ 100) homemade impedance analyzer. Complementary ssDNA sequences were detected with a detection limit of 0.5 aM (0.3 copy per mu L). This performance may be attributed to the high sensitivity of the electrical impedance technique combined with an appropriate arrangement of the sequences on the electrodes and hybridization between the complementary sequences, as inferred from polarization-modulated infrared reflection absorption spectroscopy (PM-IRRAS). The selectivity of the genosensor was confirmed by plotting the impedance spectroscopy data with a multidimensional projection technique (interactive document mapping, IDMAP), where a clear separation was observed among the samples of the complementary DNA sequence at various concentrations and from buffer samples containing a non-complementary sequence and other DNA biomarkers. The diagnosis of SARS-CoV-2 mimicking sequences was also achieved with machine learning techniques applied to scanning electron microscope images taken from genosensors exposed to distinct concentrations of the complementary ssDNA sequences. In summary, the genosensors proposed here are promising for detecting SARS-CoV-2 genetic material (RNA) in biological fluids in point-of-care settings.