The high frequency dielectric constant of poly-adenine (poly-A) was measured between 1 MHz and 1 GHz. The purpose of these experiments was to investigate the state of water molecules that are bound to the charged groups of the poly-A molecule. Analysis of the data using the Maxwell's mixture equation revealed the dielectric constant of bound water higher than we expected. Using Onsager's internal field in Debye's equation, we calculated the dielectric constant of water in the vicinity of a charged ion. The result of this computation demonstrates that the dielectric constant of bound water is much smaller than the normal value only in the immediate proximity of charged ions (within 2 A). The dielectric constant increases rapidly to the normal value as the distance increases from 2 to 4 A. This observation indicates that charged sites of polyions have only short range interactions with the surrounding water molecules. However, this conclusion pertains only to rotary diffusion of bound water since dielectric measurement is unable to detect translational diffusion.

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The Correlation Dimension (Dz) is an algorithm which allows the estimation of a non linear system degrees of freedom.It can be applied to a real time series (such as an ECG signal), but the Dz determination is difficult, probably because of the presence of noise affecting the signal itself.In this paper we study how the Dz determination can be affected by the presence of noise, and we will show that the poor accuracy often reached computing Dz can be related to the noise fraction of the signal measurement. We propose a very simple and empirical way to adjust the Dz value, and some preliminary results on a rough way for the noise fraction estimation. This study has been done mainly on Henon attractor, and Dz adjustment have been tried on ECG signals obtained from MIT-BIH Library, yielding to Dz values ranging between 1 and 2, in the case of healthy subjects. IntroductionDuring the last years, non linear system analysis has been widely studied, and it has been found to be possible to investigate on some characteristics of unknown systems analyzing their outputs. A growing deal of theoretical and experimental evidences suggested that many Merent biomedical activity measurements can be investigated in order to get insight on the corresponding systems. Proposed examples can be in human brain activity 111 and in cardiac activity [2,3].Different characteristics can be considered we used the Correlation Dimension (Dz) proposed by Grassberger & Procaccia [4,5] which is thought to be a good approximation of the effective number of the system degrees of freedom.In the literature the Dz of ECG signals have been computed and values ranging between 3 and 5 have been obtained [2,3]. Nevertheless authors claimed that ECG signal seemed not to be so complicated to need a so great number of equations to be described. Some work has been also done, using this technique, analyzing fibrillatory ECG signals, but results seemed not to be completely satisfactory.Often, researchers found a drift which were making more complicated the Dz determination. In our last work to Computers in Cardiology we proposed that a noisy environment can be responsible of misunderstandings in the Dz evaluation.In this paper we are investigating further how the estimation of this parameter can be modified by the presence of noise affecting the signal.We exploit this point by considering a well known attractor (the Henon attractor) generating a clean time series, then adding to each point of the time series different fraction of noise using FORTRAN VAX Ran function.In this way we formed noisy time series with different noise fraction, we computed the Dz for all of them, and we analysed the relationship between the obtained Dz and the noise fraction added to the signal. Fwthermore we looked for a relationship between the poor accuracy in the Dz determination (the drift obtained increasing the embedding dimension) and the noise fraction in order to try a very rough estimation of the noise fraction. Our analysis lead to the following results: on the Henon ...