ABSTRACT
In this work, we propose broadband and switchable terahertz (THz) polarization converters based on either graphene patch metasurface (GPMS) or its complementary structure (graphene hole metasurface, GHMS). The patch and hole are simply cross-shaped, composed of two orthogonal arms, along which plasmonic resonances mediated by Fabry-Perot cavity play a key role in polarization conversion (PC). An incidence of linear polarization will be converted to its cross-polarization (LTL) or circular polarization (LTC), as the reflected wave in the direction of two arms owning the same amplitude and π phase difference (LTL), or ±π/2 phase difference (LTC). Such requirements can be met by optimizing the width and length of two arms, thickness of dielectric layer, and Fermi level EF of graphene. By using GPMS, LTL PC of polarization conversion ratio (PCR) over 90% is achieved in the frequency range of 2.92 THz to 6.26 THz, and by using GHMS, LTC PC of ellipticity χ ≤ -0.9 at the frequencies from 4.45 THz to 6.47 THz. By varying the Fermi level, the operating frequency can be actively tuned, and the functionality can be switched without structural modulation; for instance, GPMS supports LTL PC as EF = 0.6 eV and LTC PC of χ ≥ 0.9 as EF = 1.0 eV, in the frequency range of 2.69 THz to 4.19 THz. Moreover, GHMS can be optimized to sustain LTL PC and LTC PC of |χ| ≥ 0.9, in the frequency range of 4.96 THz to 6.52 THz, which indicates that the handedness of circular polarization can be further specified. The proposed polarization converters of broad bandwidth, active tunability, and switchable functionality will essentially make a significant progress in THz technology and device applications, and can be widely utilized in THz communications, sensing and spectroscopy.
ABSTRACT
BACKGROUND: The relationship between anemia and outcomes after radiotherapy has not been systematically addressed. The study aimed to assess the prevalence and prognostic value of anemia in patients receiving primary radiotherapy for esophageal squamous cell carcinoma (ESCC). METHODS: A total of 103 patients with ESCC were retrospectively reviewed. Anemia was defined as a hemoglobin level <12 g/dl for men and <11 g/dl for women. The 3-year and 5-year overall survival (OS) and disease-free survival (DFS) were analyzed between the anemic and non-anemic groups using the Kaplan-Meier method and the Cox proportional hazards model. RESULTS: No significant differences were observed in patient characteristics between the anemic and non-anemic groups. The prevalence of anemia was 29.1%. The 3-year and the 5-year OS were 43% and 37%, respectively, in the non-anemic group, and 20% and 17%, respectively, in the anemic group. The 3-year and the 5-year DFS were 37% and 26%, respectively, in the non-anemic group, and 13% and 10%, respectively, in the anemic group. Survival analysis using the Kaplan-Meier method showed that there was significant difference between anemia and non-anemia (P < 0.02). In a multivariate analysis, anemia was identified as a highly significant prognostic factor for 3-year OS (hazard ratio 1.916; P = 0.012) and 3-year DFS (hazard ratio 1.973; P = 0.007), independent of T stage and the status of lymph nodes, and 5-year OS (hazard ratio 1.705; P = 0.027) and 5-year DFS (hazard ratio 1.980; P = 0.005), independent of TNM stage and the status of lymph nodes. CONCLUSIONS: Anemia before primary radiotherapy was associated with poor prognosis and an increased risk of relapse, which may serve as a new prognostic factor for ESCC.
