NON-CONCAVE MULTIFRACTAL SPECTRA WITH WAVELET LEADERS PROJECTION OF SIGNALS WITH AND WITHOUT CHIRPS

The multifractal spectrum has been revealed recently as a very useful tool for the analysis of signals, especially in those coming from the measurement of physical variables in chaotic or critical systems with multifractal structure, and in which many phenomena interact in multiple scales. In addition, in this context, the presence of singularities of rapid oscillation, chirps, is frequently difficult to handle. In this work we propose a way for using "wavelet leaders", avoiding the Legendre transform, for developing a new method capable of recognizing if a non-concave multifractal spectrum arises in a given signal, and is also capable of obtaining it in the case in which oscillating singularities appear, and so it succeeds where any other method fails.

Rapid oscillation of insulin release by the rat pancreatic islets under stringent Ca2+-free conditions

Oscillation of insulin release by the pancreatic islets was evaluated under stringent Ca(2+)-free conditions for the first time. Isolated single rat islets were exposed to 16.7 mM glucose in the presence of 1.9 mM Ca(2+), or under the stringent Ca(2+)-free conditions (Ca(2+) omission with 1 mM EGTA, 6 microM forskolin and 100 nM phorbol 12-myristate 13-acetate). Fifteen minutes after the initiation of glucose stimulation, effluent was collected at a 6-s interval, insulin was determined in duplicate by a highly sensitive insulin radioimmunoassay, and oscillation and pulsatility of release statistically analyzed. Significant oscillation of insulin release was observed in all islets irrespective of presence and absence of Ca(2+). Significant pulsatility of release was detected in 7 of 11 islets in the presence of Ca(2+) and three of six isl! ets in the absence of Ca(2+). In conclusion, high glucose elicits oscillatory insulin release both in the presence and absence of extracellular Ca(2+).