We compare two recently developed methods to determine crystal nucleation rates in stirred solutions by using isonicotinamide (INA) in ethanol as an example. The two developed methods make use of the stochastic nature of crystal nucleation, which is reflected in induction time and metastable zone width variations measured in sufficiently small volumes. These methods give easy experimental access to the nucleation rate parameters in solution under industrially realistic crystallization conditions. While the metastable zone width method is less labor intensive, the induction time method has higher accuracy and is easier to analyze.

COVID-19 has affected millions of people and put an unparalleled burden on healthcare systems as well as economies throughout the world. Currently, there is no decisive therapy for COVID-19 or related complications. The only hope to mitigate this pandemic is through vaccines. The COVID-19 vaccines are being developed rapidly, compared to traditional vaccines, and are being approved via Emergency Use Authorization (EUA) worldwide. So far, there are 232 vaccine candidates. One hundred and seventy-two are in preclinical development and 60 in clinical development, of which 9 are approved under EUA by different countries. This includes the United Kingdom (UK), United States of America (USA), Canada, Russia, China, and India. Distributing vaccination to all, with a safe and efficacious vaccine is the leading priority for all nations to combat this COVID-19 pandemic. However, the current accelerated process of COVID-19 vaccine development and EUA has many unanswered questions. In addition, the change in strain of SARS-CoV-2 in UK and South Africa, and its increasing spread across the world have raised more challenges, both for the vaccine developers as well as the governments across the world. In this review, we have discussed the different type of vaccines with examples of COVID-19 vaccines, their rapid development compared to the traditional vaccine, associated challenges, and future prospects.

Thermally activated, untethered μ-grippers can reach narrow conduits in the body and be used to excise tissue for diagnostic analyses. As depicted in the figure, we show the feasibility of an in vivo biopsy of the porcine bile duct using untethered μ-grippers.

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