RESUMEN
Surface layer optical turbulence values in the form of the refractive index structure function C n2 are often calculated from surface layer temperature, moisture, and wind characteristics and compared to measurements from sonic anemometers, differential temperature sensors, and imaging systems. A key derived component needed in the surface layer turbulence calculations is the sensible heat value. Typically, the sensible heat is calculated using the bulk aerodynamic method that assumes a certain surface roughness and a friction velocity that approximates the turbulence drag on temperature and moisture mixing from the change in the average surface layer vertical wind velocity. These assumptions/approximations generally only apply in free convection conditions. To obtain the sensible heat, a more robust method, which applies when free convection conditions are not occurring, is via an energy balance method such as the Bowen ratio method. The use of the Bowen ratio--the ratio of sensible heat flux to latent heat flux--allows a more direct assessment of the optical turbulence-driving surface layer sensible heat flux than do more traditional assessments of surface layer sensible heat flux. This study compares surface layer C n2 values using sensible heat values from the bulk aerodynamic and energy balance methods to quantifications from sonic anemometers posted at different heights on a sensor tower. The research shows that the sensible heat obtained via the Bowen ratio method provides a simpler, more reliable, and more accurate way to calculate surface layer C n2 values than what is required to make such calculations from bulk aerodynamic method-obtained sensible heat.
RESUMEN
OBJECTIVES: Epicardial adipose tissue (EAT) thickness, a novel marker of cardiovascular disease (CVD), is increased in children with a healthy weight and type 1 diabetes (T1D). The prevalence of obesity has increased in children with T1D and may confer additional CVD risk. The purpose of this study was to examine EAT thickness in youth with and without T1D in the setting of overweight/obesity. METHODS: Youth with overweight/obesity and T1D (n=38) or without T1D (n=34) between the ages of 6-18 years were included in this study. Echocardiogram using spectral and color flow Doppler was used to measure EAT and cardiac function. Waist circumference, blood pressure, and HbA1c, were used to calculate estimated glucose disposal rate (eGDR) to estimate insulin resistance in children with T1D. RESULTS: EAT thickness was not significantly different in youth with T1D compared to controls (2.10 ± 0.67 mm vs. 1.90 ± 0.59 mm, p=0.19). When groups were combined, EAT significantly correlated with age (r=0.449, p≤0.001), BMI (r=0.538, p≤0.001), waist circumference (r=0.552, p≤0.001), systolic BP (r=0.247, p=0.036), myocardial performance index (r=-0.287, p=0.015), ejection fraction (r=-0.442, p≤0.001), and cardiac output index (r=-0.306, p=0.009). In the group with T1D, diastolic BP (r=0.39, p=0.02) and eGDR (r=-0.48, p=0.002) correlated with EAT. CONCLUSIONS: EAT was associated with measures of adiposity and insulin resistance but does not differ by diabetes status among youth with overweight/obesity. These findings suggest that adiposity rather than glycemia is the main driver of EAT thickness among youth with T1D.