, 1999). The ��multifractal spectrum�� quantifies the relationship between the individual local scaling exponents (h) and their probability distribution D(h). The values of h reflect the degree of ��smoothness�� of components in the data: small values of h correspond to relatively irregular time series http://www.selleckchem.com/ and large values of h represent more regular (smoother) time series (Muzy & Arneodo, 1993; Turiel et?al., 2006). The width of the multifractal spectrum reflects the degree of multifractality (the variety of different structural components) of a time-series. We quantified the multifractal spectrum using a component of the CamBA (Cambridge Brain Activation) software, and the partition function calculation developed for the multifractal.c analysis software available on Physionet (Goldberger et?al., Mdm2 2000). The following parameters were then determined from the singularity spectrum: modal h value, HWHM+ and HWHM? (the half widths at half the maximum amplitude for h values greater than and less than the modal h value, respectively). To assess the cause of any observed multifractality in the time-series, the data were also separately shuffled (order-randomized) as described in previous studies (Ivanov et?al., 1999; Kantelhardt et?al., 2002), and then re-analysed using the same multifractal methods. Following appropriate tests of Normality and Sphericity, the following assessments were performed: (i) Influence of smoking status on cardiac parameters (at baseline, Day 0): (a) two-way ANOVA for each of the linear cardiac parameters, with main factors Smoking Status (Smoker or Non-smoker) and Activity State and (b) two-tailed t-tests (Smoker versus Non-smoker) for each of the non-linear parameters (assessed over the whole recording period) and (ii) Influence of smoking abstinence duration on the cardiac parameters in Previous Smokers (Days 0, 1, 7, 30): repeated measures ANOVA for each of the linear/HRV and multifractal parameters, with main factor Abstinence Duration. During the selleckchem interpretation of ANOVA results, if Mauchly��s test indicated a violation of the Sphericity assumption then multivariate statistics were consulted. When appropriate, post hoc testing using the Bonferroni adjustment identified pair-wise differences in the parameters that had been highlighted by ANOVA. To account for multiple parameter testing, a value of P<0��01 was assumed to represent statistical significance in the results of t-tests. Error bars in the figures represent the SEM (standard error in the mean) for the plotted parameters. Following written informed consent, ten smokers [two male, eight female; age 40?��?16?years (mean?��?SD)] and sixteen healthy non-smokers (Controls: four male, 12 female; age 31?��?8?years) agreed to participate. Subject ages were not significantly different between the groups (P?=?0��14).</p>

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