Development and Assessment of an Inexpensive Smartphone-Based Respiratory Droplet Simulation Model

Background. Droplet simulation often requires expensive and inaccessible equipment. Herein, we develop and assess a low-cost droplet simulation model using easily accessible materials, open-source software, and a smartphone-based cobalt blue light. Methods. The simulation model was developed using commercial-grade materials and fluorescein dye. A clear face shield was assessed ten times following a simulated cough using fluorescein dye. A conventional ultraviolet Woods lamp was compared to a smartphone-based cobalt blue light to detect fluorescein illumination. Results. The simulation platform and smartphone-based cobalt blue light cost $20.18. A Wilcoxon signed rank test revealed that the median droplet area of fluorescence under the UV Wood’s lamp was not significantly different than that of the smartphone-based cobalt blue light (2.89 vs 2.94, P = .386). Conclusions. This simulation model is inexpensive and easily reproducible. The smartphone application may be a convenient alternative to standard ultraviolet lights. This model has great potential for use in financially restricted academic centers during the COVID-19 pandemic and beyond.

Modular MA-XRF Scanner Development in the Multi-Analytical Characterisation of a 17th Century Azulejo from Portugal

A modular X-ray scanning system was developed, to fill in the gap between portable instruments (with a limited analytical area) and mobile instruments (with large analytical areas, and sometimes bulky and difficult to transport). The scanner has been compared to a commercial tabletop instrument, by analysing a Portuguese tile (azulejo) from the 17th century. Complementary techniques were used to achieve a throughout characterisation of the sample in a complete non-destructive approach. The complexity of the acquired X-ray fluorescence (XRF) spectra, due to inherent sample stratigraphy, has been resolved using Monte Carlo simulations, and Raman spectroscopy, as the most suitable technique to complement the analysis of azulejos colours, yielding satisfactory results. The colouring agents were identified as cobalt blue and a Zn-modified Naples-yellow. The stratigraphy of the area under study was partially modelled with Monte Carlo simulations. The scanners performance has been compared by evaluating the images outputs and the global spectrum.

ON COBALT USAGE IN THE OLD RUSSIAN PRODUCTION OF LEAD GLASS

In the Old Russian glassmaking, beginning in XI century and based on the production of lead glass, cobalt was used very rare. Until recently only three assured cases of cobalt usage for blue coloration of bracelets and beads were fixed. In addition, two cases of probable cobalt coloration were published in the middle of the preceding century, but owing to weakness of analytical methods of those times, the presence of cobalt was under detection limit. During the last twenty years another seven samples containing cobalt were analyzed by the author. These bracelets and beads were excavated in Old Russian towns and cities such as Suzdal, Vladimir, Smolensk, Tver, Dmitrov. All artifacts occurred from the strata of pre-Mongolian time dated to XI–XIII centuries and manufactured of potash lead glass. In addition, one blue bracelet of this type comes from Bolgar, the city of medieval Volga Bulgaria, and was analyzed in Kazan University. These analyses together with the two earlier ones are present in the table. The earliest Russian glass article, coming from Kievan St. Sophia Cathedral founded in 1036, only with a high portion of doubt can be determined as a product of Russian workshop. As opposed to all other analyzed artifacts it is a piece of tessera from one of the earliest Russian temples, and demonstrates an extremely high content of cobalt side by side with enhanced content of sodium. This glass, as well as two other artifacts, contains antimony, probably used as opacifier. Another common feature of all samples with antimony is higher content of calcium. One artifact has an enhanced content of manganese, whereas in two others the blue coloration had not been achieved. In spite of some new information for cobalt usage these facts indicate that cobalt blue colorant was imported to Russia occasionally from different sources and tradition of its usage in the pre-Mongolian time had not been developed.