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Teaching/Communication/Extension/Profession,

Stellar structure and compact objects before 1940: Towards relativistic astrophysics

Since the mid-1920s, different strands of research used stars as "physics laboratories" for investigating the nature of matter under extreme densities and pressures, impossible to realize on Earth. To trace this process this paper is following the evolution of the concept of a dense core in stars, which was important both for an understanding of stellar evolution and as a testing ground for the fast-evolving field of nuclear physics. In spite of the divide between physicists and astrophysicists, some key actors working in the cross-fertilized soil of overlapping but different scientific cultures formulated models and tentative theories that gradually evolved into more realistic and structured astrophysical objects. These investigations culminated in the first contact with general relativity in 1939, when J. Robert Oppenheimer and his students George Volkoff and Hartland Snyder systematically applied the theory to the dense core of a collapsing neutron star. This pioneering application of Einstein's theory to an astrophysical compact object can be regarded as a milestone in the path eventually leading to the emergence of relativistic astrophysics in the early 1960s.Comment: 83 pages, 4 figures, submitted to the European Physical Journal

Impact of retrograde shear rate on brachial and superficial femoral artery flow-mediated dilation in older subjects

An inverse, dose-dependent relationship between retrograde shear rate and brachial artery endothelial function exists in young subjects. This relationship has not been investigated in older adults, who have been related to lower endothelial function, higher resting retrograde shear rate and higher risk of cardiovascular disease. Aim To investigate the impact of a step-wise increase in retrograde shear stress on flow-mediated dilation in older males in the upper and lower limbs. Methods Fifteen older (68±9 years) men reported to the laboratory 3 times. We examined brachial artery flow-mediated dilation before and after 30-minutes exposure to cuff inflation around the forearm at 0, 30 and 60 mmHg, to manipulate retrograde shear rate. Subsequently, the 30-minute intervention was repeated in the superficial femoral artery. Order of testing (vessel and intervention) was randomised. Results Increases in cuff pressure resulted in dose-dependent increases in retrograde shear in both the brachial and superficial femoral artery in older subjects. In both the brachial and the superficial femoral artery, no change in endothelial function in response to increased retrograde shear was observed in older males (‘time’ P=0.274, ‘cuff*time P=0.791’, ‘cuff*artery*time P=0.774’). Conclusion In contrast with young subjects, we found that acute elevation in retrograde shear rate does not impair endothelial function in older humans. This may suggest that subjects with a priori endothelial dysfunction are less responsive or requires a larger shear rate stimulus to alter endothelial function

Large-scale phenotyping of patients with long COVID post-hospitalization reveals mechanistic subtypes of disease

One in ten severe acute respiratory syndrome coronavirus 2 infections result in prolonged symptoms termed long coronavirus disease (COVID), yet disease phenotypes and mechanisms are poorly understood1. Here we profiled 368 plasma proteins in 657 participants ≥3 months following hospitalization. Of these, 426 had at least one long COVID symptom and 233 had fully recovered. Elevated markers of myeloid inflammation and complement activation were associated with long COVID. IL-1R2, MATN2 and COLEC12 were associated with cardiorespiratory symptoms, fatigue and anxiety/depression; MATN2, CSF3 and C1QA were elevated in gastrointestinal symptoms and C1QA was elevated in cognitive impairment. Additional markers of alterations in nerve tissue repair (SPON-1 and NFASC) were elevated in those with cognitive impairment and SCG3, suggestive of brain–gut axis disturbance, was elevated in gastrointestinal symptoms. Severe acute respiratory syndrome coronavirus 2-specific immunoglobulin G (IgG) was persistently elevated in some individuals with long COVID, but virus was not detected in sputum. Analysis of inflammatory markers in nasal fluids showed no association with symptoms. Our study aimed to understand inflammatory processes that underlie long COVID and was not designed for biomarker discovery. Our findings suggest that specific inflammatory pathways related to tissue damage are implicated in subtypes of long COVID, which might be targeted in future therapeutic trials