Theory of optical spectra of polar quantum wells: Temperature effects

Theoretical and numerical calculations of the optical absorption spectra of excitons interacting with longitudinal-optical phonons in quasi-2D polar semiconductors are presented. In II-VI semiconductor quantum wells, exciton binding energy can be tuned on- and off-resonance with the longitudinal-optical phonon energy by varying the quantum well width. A comprehensive picture of this tunning effect on the temperature-dependent exciton absorption spectrum is derived, using the exciton Green's function formalism at finite temperature. The effective exciton-phonon interaction is included in the Bethe-Salpeter equation. Numerical results are illustrated for ZnSe-based quantum wells. At low temperatures, both a single exciton peak as well as a continuum resonance state are found in the optical absorption spectra. By contrast, at high enough temperatures, a splitting of the exciton line due to the real phonon absorption processes is predicted. Possible previous experimental observations of this splitting are discussed.Comment: 10 pages, 9 figures, to appear in Phys. Rev. B. Permanent address: [email protected]

Unforeseen nodal upstaging in patients undergoing segmentectomy without frozen section: a multicenter retrospective cohort study.

The study aimed to evaluate the risk of unforeseen nodal upstaging (pN+) after pulmonary segmentectomy without intraoperative frozen section. We conducted a retrospective analysis for consecutive patients who underwent segmentectomy for clinical stage IA1-2 non-small cell lung cancer (cIA1-2 NSCLC) in three centers between January 2017 and December 2022. A backward stepwise logistic regression analysis for variables with P < 0.1 in univariable analysis was performed to predict pN+. Kaplan-Meier analysis with log-rank test evaluated the discrepancy for overall (OS) and recurrence-free survivals (RFS). Among 478 patients included in the final analysis, 19 (4.0%) had pN+, including 10 (2.1%) pN1, 6 (1.3%) pN2, and 3 (0.6%) pN1+2. With a median follow-up of 23.5 months (interquartile range 12.6-39.0), patients with pN+ had poorer OS compared to those with pN0 (3-year OS: 70.2% vs. 89.7%, P = 0.002). However, there was no significant difference in RFS and recurrence. The maximum standardized uptake value (SUVmax) of tumor in positron emission tomography scan ≥ 4.5 (versus < 4.5) was the only independent factor for pN + (odds ratio 3.5). Patients with a SUVmax ≥ 4.5 had 7.3% pN+, which was associated with poorer OS and similar RFS and recurrence compared to pN0. In contrast, those with a SUVmax < 4.5 had 2.2% pN+, which had comparable recurrence and survival to pN0. Unforeseen nodal upstaging in segmentectomy for cIA1-2 NSCLC is low. Frozen section of lymph nodes may be necessary for lesions with high metabolic activity