Improved RF Devices for Future Adaptive Wireless Systems Using Two-Sided Contacting and A1N Cooling

This paper reviews special RF/microwave silicon device implementations in a process that allows two-sided contacting of the devices: the back-wafer contacted silicon-on-glass (SOG) substrate-transfer technology (STT) developed at DIMES. In this technology, metal transmission lines can be placed on the low-loss glass substrate, while the resistive/capacitive parasitics of the silicon devices can be minimized by a direct two-sided contacting. Focus is placed here on the improved device performance that can be achieved. In particular, high-quality SOG varactors have been developed and an overview is given of a number of innovative highly-linear circuit configurations that have successfully made use of the special device properties. A high flexibility in device design is achieved by two-sided contacting because it eliminates the need for buried layers. This aspect has enabled the implementation of varactors with special Ndx -2 doping profiles and a straightforward integration of complementary bipolar devices. For the latter, the integration of AlN heatspreaders has been essential for achieving effective circuit cooling. Moreover, the use of Schottky collector contacts is highlighted also with respect to the potential benefits for the speed of SiGe heterojunction bipolar transistors (HBTs).Microelectronics & Computer EngineeringElectrical Engineering, Mathematics and Computer Scienc

Effects of pre‐operative isolation on postoperative pulmonary complications after elective surgery: an international prospective cohort study

We aimed to determine the impact of pre-operative isolation on postoperative pulmonary complications after elective surgery during the global SARS-CoV-2 pandemic. We performed an international prospective cohort study including patients undergoing elective surgery in October 2020. Isolation was defined as the period before surgery during which patients did not leave their house or receive visitors from outside their household. The primary outcome was postoperative pulmonary complications, adjusted in multivariable models for measured confounders. Pre-defined sub-group analyses were performed for the primary outcome. A total of 96,454 patients from 114 countries were included and overall, 26,948 (27.9%) patients isolated before surgery. Postoperative pulmonary complications were recorded in 1947 (2.0%) patients of which 227 (11.7%) were associated with SARS-CoV-2 infection. Patients who isolated pre-operatively were older, had more respiratory comorbidities and were more commonly from areas of high SARS-CoV-2 incidence and high-income countries. Although the overall rates of postoperative pulmonary complications were similar in those that isolated and those that did not (2.1% vs 2.0%, respectively), isolation was associated with higher rates of postoperative pulmonary complications after adjustment (adjusted OR 1.20, 95%CI 1.05-1.36, p = 0.005). Sensitivity analyses revealed no further differences when patients were categorised by: pre-operative testing; use of COVID-19-free pathways; or community SARS-CoV-2 prevalence. The rate of postoperative pulmonary complications increased with periods of isolation longer than 3 days, with an OR (95%CI) at 4-7 days or >= 8 days of 1.25 (1.04-1.48), p = 0.015 and 1.31 (1.11-1.55), p = 0.001, respectively. Isolation before elective surgery might be associated with a small but clinically important increased risk of postoperative pulmonary complications. Longer periods of isolation showed no reduction in the risk of postoperative pulmonary complications. These findings have significant implications for global provision of elective surgical care