Roughness characterization of smooth machined surfaces by light scattering.

Characterization of surface roughness has generally been limited to rms deviation from the mean and occasionally the autocorrelation length. By considering the surface to be a superposition of many sinusoidal gratings, the surface spectral density function (SDF) has been calculated from measurements of the light scattered out of a reflected He-Ne laser beam. By rotating the sample, the SDF can be found for anisotropic surfaces (such as machined surfaces). The SDF allows examination of roughness as a function of spatial frequency, which is important for many applications. Interferometric and scattering results are compared for a rough (350-Arms) machined surface, and finally a smooth (50-Arms) diamond machined surface is characterized.

Wavelength and angular dependence of light scattering from beryllium: comparison of theory and experiment.

The purpose of this study was (1) to measure angle-resolved scattering (ARS) and the wavelength dependence of scattering from polished and sputtered beryllium, (2) to measure surface-roughness parameters by profilometry, (3) to calculate the power spectral density (PSD) of the surface roughness and use it with ARS theory to compare with ARS measurements, and (4) to investigate a dual-source scattering theory and compare calculations from the theory with measured ARS. The wavelengths considered here were 0.633, 1.06, and 10.6 µm, the angle of incidence was 60°, and s and p polarization of the incident and scattered radiation were taken into account both in the theory and in the experiments.Two types of theoretical comparison were attempted. First, two-dimensional PSD functions were calculated from one-dimensional, mechanical-stylus-profile data, and these data were used in first-order roughness ARS theory to compare with ARS measurements. The calculated ARS curves were much too low at some wavelengths and showe incorrect wavelength scaling. Second, a dual-source (surfaceroughness and dielectric inhomogeneity) ARS theory was used. In this model the surface-roughness PSD functions calculated from surface-profile data were used, and reasonable values for parameters characterizing the dielectric inhomogeneities were used in an analytic PSD function. This dual-source ARS theory can predict a significantly different angle and wavelength dependence of ARS than that predicted by roughness-only ARS theory. In contrast to ARS predicted by surface roughness alone, it was found that the dual-source theory was able to provide good agreement with measured ARS in angular and wavelength dependence. It is concluded that, for the two beryllium samples studied here, scattering caused by spatial variations in the near-surface dielectric response (variations in reflectance) is a significant and sometimes dominant source of scattering, especially at a 10.6-µim wavelength.

Perceptions of health and their relationship to symptoms in African American women with type 2 diabetes.

Diabetes mellitus is an incurable disease and a major cause of mortality and morbidity. Diabetes disproportionately affects members of minorities who suffer from higher rates of complications and greater disability (Cowie & Eberhardt, 1996). The purpose of this study was to (a) describe the symptoms of African American women with Type 2 diabetes and examine the relationship among diabetes-related symptoms; (b) document complications of diabetes and perceptions of health and functioning; and (c) examine the relationship between duration of diabetes and age at diagnosis and perceived health. A convenience sample of 75 African American women with Type 2 diabetes were interviewed. A 44-item questionnaire measured selected demographic variables, symptoms, documented complications, and their perceived relationship to diabetes. The SF-20 was used to measure perceptions of health status. Data show that African American women with Type 2 diabetes have a wide variety of symptoms and poor perceptions of their general health and physical functioning.