Phonographic detection of mechanical heart valve thrombosis.

The formation of thrombotic deposits affects the functionality of mechanical prosthetic heart valves; as a consequence, mechanical valves thrombosis needs early diagnosis to prevent thromboembolic events. This paper compares the acoustic signals produced by two commercial bileaflet mechanical heart valves in the closing phase to detect the presence of thrombi. The closing sounds were recorded in vitro by means of a phonocardiographic device under different hydrodynamic conditions. Thrombotic deposits of different weight and shape were applied onto the valve leaflet and the annular housing, until the movement of one leaflet was completely blocked. From the acoustic signals, the corresponding spectra were calculated and four diagnostic frequency bands were identified: their comparison allowed detecting malfunctioning valves because of the presence of thrombotic formations.

'We will multiply the fires of resistance': The catalysts of dissent against institutional science and their interplay with refused knowledge communities.

Drawing on a 12-month virtual ethnography on the main online spaces of three refused knowledge communities (RKCs) in Italy, this study aims at contributing to the debate on emerging forms of science-related populism from a two-fold perspective. First, we identify and describe the main features and the role played by an understudied figure who we label the 'catalyst of dissent' - a public influencer who does not belong to the scientific community and contributes to the spread of science-related populist narratives within a grassroots ecosystem of resistance to institutional science. Second, our research highlights how RKCs - communities proposing visions of science and medicine denied acceptance or even consideration by institutional science - can appropriate some key resources produced by the catalysts. The analysis focuses on the interplay between the catalysts and three main RKCs during the pandemic crisis in Italy: The No-5G, the Free-Vax, and the 5 Biological Laws communities.