RESUMO
The reflective properties of randomly rough surfaces at large incidence angles have been reported due to their potential applications in some of the radiative heat transfer research areas. The main purpose of this work is to investigate the formation mechanism of the specular reflection peak of rough surfaces at large incidence angles. The bidirectional reflectance distribution function (BRDF) of rough aluminum surfaces with different roughnesses at different incident angles is measured by a three-axis automated scatterometer. This study used a validated and accurate computational model, the rigorous coupled-wave analysis (RCWA) method, to compare and analyze the measurement BRDF results. It is found that the RCWA results show the same trend of specular peak as the measurement. This paper mainly focuses on the relative roughness at the range of 0.16<σ/λ<5.35. As the relative roughness decreases, the specular peak enhancement dramatically increases and the scattering region significantly reduces, especially under large incidence angles. The RCWA and the Rayleigh criterion results have been compared, showing that the relative error of the total integrated scatter increases as the roughness of the surface increases at large incidence angles. In addition, the zero-order diffractive power calculated by RCWA and the reflectance calculated by Fresnel equations are compared. The comparison shows that the relative error declines sharply when the incident angle is large and the roughness is small.
RESUMO
BACKGROUND AND AIM: Atrial fibrillation (AF) is an important cardiovascular disease in the elderly. The association between hyperuricemia and AF is unclear. Therefore, we aimed to investigate the prospective relationship between uric acid and development of AF in a nationally representative cohort of elderly people. METHODS AND RESULTS: A total of 1485 elderly people (age ≥ 65 yrs) from the Elderly Nutrition and Health Survey in Taiwan (1999-2000) were without AF on "electrocardiography" at baseline. Incident AF events (International Classification of Diseases, Ninth Revision, Clinical Modification, ICD-9-CM: 427.31) were identified using data from the National Health Insurance Dataset. Hyperuricemia was defined as levels of uric acid >7.0 mg/dL in men and 6.0 mg/dL in women. A Cox proportional hazards model was used to evaluate the association between hyperuricemia and incident AF. The follow-up period was from 1999 to 2000 to 2008. During the follow-up period (median: 9.16 yrs), 90 AF events occurred (44 in men and 46 in women). Older age, elevated systolic blood pressure, being an ex-smoker, and high uric acid were positively associated with incident AF. Hyperuricemia was positively associated with incident AF in normotensive (age-adjusted hazard ratio (HR): 2.65 and 95% confidence intervals: 1.05-6.69), but not in (1.20:0.74-1.94) hypertensive individuals (systolic blood pressure ≥130 or diastolic blood pressure ≥85 or using hypertensive medicine). A significant association between hyperuricemia and AF (3.78; 1.24-11.59) remained after adjusting for other potential confounders among normotensive older persons. CONCLUSION: Hyperuricemia is associated with the development of AF in elderly people with normal blood pressure.
