We investigated the hypothesis that beat-to-beat variability in hemodynamic parameters reflects the dynamic interplay between ongoing perturbations to circulatory function and the compensatory response of short-term cardiovascular control systems. Spontaneous fluctuations in heart rate (HR), arterial blood pressure, and respiration were analyzed by spectral analysis in the 0.02- to 1-Hz frequen...

Observations from basal water-pressure sensors along the length of Bench Glacier, Alaska, USA, show that diurnal fluctuations of water pressure are seasonal and restricted to summer. Most notable about these fluctuations is their disappearance in the late summer and early autumn, long before the seasonal end of diurnal meltwater input. Here we present data documenting the end of diurnal water-p...

The goal of this research is to determine how spectral analysis of pressure fluctuations can be used as a diagnostic and design tool for both bubbling fluidized beds (BFB) and circulating fluidized beds (CFB). Static pressure fluctuations are measured from two BFB models, two CFB models, and two Pyropower CFB boilers located at the ISU power plant/cogeneration facility. Analyzing the fluctuatio...

Direct numerical simulations of a turbulent boundary layer over a bump were performed to examine the effects of surface longitudinal curvature on wall pressure fluctuations (pw) and flow induced noise. Turbulence statistics and frequency spectra were obtained to elucidate the response of wall pressure fluctuations to the longitudinal curvature and to the corresponding pressure gradient. Wall pr...

Interacting ocean surface waves force water column pressure fluctuations with spectral peaks at the same frequencies of primary microseisms (PM), double-frequency microseisms (DF), and seismic hum. Prior treatment of nonlinear ocean wave interactions has focused on the DF pressure fluctuations which, in the presence of opposing waves, do not decay with depth and hence are dominant in deep water...

Though many consider the magnitude of respiratory sinus arrhythmia as an index of cardiac vagal control, its physiological origins remain unclear. One influential model postulates that the systolic pressure rise within a given beat stimulates the baroreflex arc to adjust the following heart period such that diastolic pressure is "stabilized" and hence displays lesser fluctuation. Accordingly, t...

Energy equation for turbulent flow in a rotating system was derived in terms of second order correlation tensors, where the correlation tensors were functions of space coordinates, distance between two points and time. To reveal the relationship of turbulent energy between two points, one point was taken as origin of the coordinate system. Due to rotation, the Coriolis force played an important...