No abstract

Globally elevated temperatures during the Cretaceous extreme greenhouse climate interval were punctuated by the Valanginian Weissert event, which was characterised by a positive carbon isotope excursion, global cooling, and a glacial event approximately at 135 Ma. The inability to disentangle ocean temperature and continental ice volume trends hinders our understanding of these climate fluctuations in deep-time. We investigated the ocean temperature–ice sheet dynamics of glaciation events that occurred in the Cretaceous greenhouse world. New clumped isotope and δ18O data from sits in the Tethyan Ocean show that seawater temperatures decreased by 5°C–6°C, consistent with the development of glacial periods, and maximum ice volumes about half the size of present-day Antarctica. This cooling event provides a counter-example to other Mesozoic climate transitions driven by changes in atmospheric greenhouse gas contents. Our results suggest a robust coupling between mid-latitude seawater temperatures and polar ice volume as atmospheric CO2 contents decline.

Varicose veins in the lower limb are a common and progressive venous disorder that can significantly reduce patients’ quality of life and pose a threat to their overall health if left untreated. However, current treatment approaches often involve invasive intervention. High-intensity focused ultrasound (HIFU) technology has the potential to treat varicose veins non-invasively, but most systems are bulky and expensive. This study proposes an innovative, integrated system that uses a 4.5 MHz therapeutic probe guided by a 12 MHz ultrasound imaging probe to treat varicose veins in the lower limb. The system aims to achieve high accuracy in repeated treatments by using a high-speed scanning positioning structure, increasing the imaging framerate, and reducing the system’s overall volume. The system’s accuracy is evaluated through reset error tests on an acrylic board, and its effectiveness is tested through in vivo experiments on rabbit marginal ear veins. Tests on porcine arteries are conducted to identify suitable focal points for vascular treatment. The experimental results demonstrate the system’s high accuracy, with a reset error of less than 0.07 mm, and an obvious shrinkage of the predetermined treatment area of the marginal ear veins after therapy. The study identifies that setting the focus on the vascular wall can improve the efficiency of vascular treatment, resulting in significant vasoconstriction changes. These experimental findings provide sufficient evidence for the system’s potential for clinical application in vascular treatment.