Distribution Of Peak Frequencies Research Articles

Heterogeneity of human serum high density lipoproteins on high performance liquid chromatography.

A combination method consisting of separation by HPLC using gel permeation columns and selective detection of cholesterol or choline-containing phospholipids was applied to the identification and quantitation of subclasses of high density lipoproteins in human serum. The frequency distribution of peaks in the elution patterns on detection of choline-containing phospholipids in a group (n = 71) of normal males and females showed five maxima. Their particle sizes were determined from the relation between Stokes' diameter and elution volume to be as follows: 122.0 +/- 2.8 A, 110.1 +/- 2.1 A, 97.5 +/- 1.8 A, 86.7 +/- 1.3 A, and 76.3 +/- 16 A. The two larger fractions were found to correspond to HDL2 subclasses, i.e., HDL2b and HDL2a. The other three peaks were found to reflect the subclasses of HDL3 and choline-containing phospholipids in the very high density lipoprotein fraction which sedimented at the bottom on ultracentrifugation at the density of 1.21. Moreover, the existence of these five subclasses in the HDL fraction was confirmed by rechromatography using this combination HPLC method. Our results for the particle sizes of HDL subclasses were confirmed by electron microscopy.

Crack propagation due to random thermal fluctuations: Effect of temporal incoherence

Metal components in LMFBR's are subjected to random temperature fluctuations. These are caused by the turbulence in the liquid sodium coolant and the existence of jets at differing inlet temperatures. Here an LEFM approach to crack propagation is used. The metal surface temperature is characterised by the power spectral density of the fluctuations and these fluctuations are assumed to be a Gaussian stochastic process. This enables the frequency distribution of peaks of the stress intensity factor to the determined—and hence the crack propagation rate. The results depend on the thermal and mechanical boundary conditions and on two parameters derived from the thermal fluctuation power spectral density—the microscale and the mean square stress intensity function. Only thin components, such as tubes or plates, are considered explicitly in this paper, but the method is of general application.