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We studied and improved the performance of a terahertz (THz) direct detector based on the superconducting NbN hot electron bolometer (HEB) integrated with microwave readout for imaging arrays and other applications. A 6 nm thick NbN microbridge at the feed point of a twin-slot antenna is embedded into a high-Q quarter-wavelength coplanar waveguide (CPW) resonator made from a 350 nm thick NbN film which is weakly coupled to a CPW feedline. THz direct detection was performed at a signal frequency of 0.66 THz at a bath temperature of 4.2 K. When operating at a low input microwave power level, the device acting as a microwave kinetic inductance detector with a kinetic inductance fraction of 0.45 changes the surface impedance of the resonator in response to incident THz radiation. The estimated optical noise equivalent power (NEP) is ∼0.23 pW · Hz−0.5 which shows about one order of magnitude improvement compared to that of the traditional voltage-biased NbN HEBs. The improved performance of the THz direct detectors with lower NEP and easy readout makes them promising in imaging with a large number of the array pixels. [ABSTRACT FROM AUTHOR]

Objectives: To analyze the relationship between etiology and morphological classification of benign central airway stenosis and its prognosis. Methods: We performed a retrospective study of the medical records of 453 patients initially diagnosed with benign airway stenosis at Department of Respiratory Diseases in Beijing Tiantan Hospital affiliated to Capital Medical University from January 2003 to October 2019. Of 453 patients, 260 were male. The age of the study population was 12-86(44.0±24.5) years. Results: Among the 453 patients diagnosed with benign central airway stenosis, 161 case (35.5%, including 113 post-tracheostomy tracheal stenosis and 48 post-intubation tracheal stenosis) were iatrogenic; 88 cases were from benign tumors (19.4%), 77 cases from tracheal or bronchial tuberculosis (17.0%), 71 case from tracheal foreign bodies (15.7%). Disease causes varied among different gender or age groups. The main type of stenosis was structural stenosis, of which 241 cases (53.2%) were intra-luminal and 183 cases (40.4%) were scar contracture type. The site of stenosis showed a certain relationship with the causes of stenosis. The stenosis degree was mainly from grade 2 to grade 4 (76.4%), and the length was mainly within 3 cm (84.8%). Single factor analysis on the relationship between disease cause, morphological classification and prognosis of benign central airway stenosis showed statistically better prognosis in groups that were caused by benign tumor, intraductal stenosis or stenosis that were 3-4 in degree and 1-2 degree in length. Conclusion: The common causes of central airway stenosis included iatrogenic stenosis, benign tumor, tracheal or bronchial tuberculosis and tracheal foreign bodies. Benign airway stenosis with different disease causes and morphological classification had different prognosis after bronchoscopic interventional treatment. Clinicians should know the disease causes, morphological characterization and risk factors for benign airway stenosis for earlier diagnosis, treatment or prevention.

Objective: To analyze the efficacy and safety of Montgomery T-tube (T-tube) placement for benign complex subglottic tracheal stenosis. Methods: A retrospective analysis of the clinical data of 29 patients with benign complex subglottic tracheal stenosis receiving T-tube placement in Beijing Tiantan Hospital from May 2015 to December 2019. The causes were postintubation tracheal stenosis [27 cases (93.1%), including 21 cases (72.4%) of tracheal stenosis after tracheotomy, 6 cases (20.7%) of tracheal stenosis after tracheal intubation], cervical post-traumatic tracheal stenosis (1 case, 3.4%) and tuberculous tracheal stenosis (1 case, 3.4%), respectively. Three-dimensional reconstruction of tracheal computerized tomography (CT) and bronchoscopy were used to grade the stenosis according to Cotton-Myer classification system before bronchoscopic intervention. The degree of stenosis was Cotton-Myer grade Ⅱ (7 cases, 24.1%), grade Ⅲ (11 cases, 37.9%) and grade Ⅳ (11 cases, 37.9%), respectively. All cases received placement of T-tubes and follow-up. Fisher's exact test was used for comparison between groups. Results: T-tube placement was performed 39 times in 29 patients. T-tubes were successfully placed for 24 cases (82.8%). The main complication during the operation was tracheal mucosal tear (6 cases, 20.7%), which resolved in all cases within 2 weeks. The main postoperative complication was secretion retention (27 cases, 93.1%), which was relieved after home nebulization treatment in 26 cases; and followed by granulation hyperplasia, especially located in T-tube upper margin (12 cases, 41.4%), of which 8 cases were cured after bronchoscopic intervention. None of the patients had T-tube migration. There were no statistically significant differences in the success rate of T-tube placement and the incidence of major complications in patients with benign complex subglottic tracheal stenosis with different degrees of stenosis. After 18 months to 24 months of follow-up, attempt was made to remove the T-tube in 9 patients but failed in 4 patients. The failure was due to collapse of the airway after the T-tube was removed. Conclusion: T-tube placement is a safe and reliable treatment for benign complex subglottic tracheal stenosis with high efficiency and manageable complications.