A preliminary study of improving the MICP effects via the extractions from seashell nacre

In microbially induced calcium carbonate precipitation (MICP) process, it is the precipitated CaCO3 that cements loose sand particles together to improve their mechanical properties. Seashell nacre composed of CaCO3 is a natural product, which is worth researching for its great hardness, strength, and toughness. However, there is no study connecting this natural nacre mineralization with MICP. Therefore, a precedent herein is established to modify the MICP process via the water-soluble matrix (WSM) extracted from nacre, where WSM contributes to the great mechanical properties of nacre. Correspondingly, this study examines the effects of WSM with different concentrations on urease activity and strength as well as microstructure of bio-cemented sand samples. The experimental results show that a small number of WSM (50mg/L) can improve the average strength of bio-cemented sand samples 1.5 times. This is because 50mg/L WSM can significantly improve the urease activity of bacteria meanwhile increasing the Ca2+ utilization rate. Thus, more CaCO3 crystals are precipitated, and the higher UCS of bio-cemented sand samples is achieved. Moreover, the XRD results indicate that the precipitated CaCO3 is almost calcite, and only a little aragonite is detected when the concentration of WSM increases to 100mg/L. Additionally, the SEM images demonstrate that WSM involvement can affect the shapes and sizes of CaCO3 crystals. Overall, this work is an unprecedented exploration imitating nacre that hopefully paves way for future studies.

Milites Apollinis. Studenti medicíny z českých zemí na basilejské univerzitě v 16. a raném 17. století

This contribution is a preliminary study for a monograph on students from the Czech Lands in Basel, focusing on those who studied medicine. It maps their geographic and social origin, their adherence to religious denominations, the curricula they followed, as well as their careers after a completion of their studies. Separately, attention is paid to their literary activities, which was mostly academic, but also related less formal literary creations.