A detailed investigation of rescaled range (R/S) analysis to search for long-time correlations ͑via the Hurst exponent, H) in plasma turbulence is presented. In order to elucidate important issues related to R/S analysis, structure functions ͑SFs͒, one of several techniques available for calculating H, are also applied, and comparisons between the two methods are made. Time records of both simulated data and fluctuation reflectometry data from the DIII-D tokamak ͓J. L. Luxon and L. G. Davis, Fusion Technol. 8, 441 ͑1985͔͒ are analyzed. It is found that the R/S method can be used to accurately determine H, provided a long enough data record is used, and that H is an indicator of persistence in the data. In addition, subtleties of the correct application of both methods are discussed, and potential advantages of SFs are pointed out.

This population-based study aimed to determine the trend of incidence, prevalence, and mortality of systemic lupus erythematosus (SLE) in a 6-year period in Taiwan. Patients with international classification of diseases ninth revision (ICD-9) code 710.0 were retrieved from the Taiwanese National Health Insurance Research Database (NHIRD), which covered more than 96 % of the entire population, and from the Ministry of Interior between 2003 and 2008 in Taiwan. Patients with SLE registered as catastrophic illness were enrolled for analysis. The incidence rate, prevalence ratio, and mortality rate stratified by sex and age were analyzed. There were a total of 6,675 SLE patients (5,836 females and 839 in males) during the study period. The average annual incidence rate was 4.87 per 100,000 population, and the average female-to-male incidence ratio was 7.15. The ratio increased with age and peaked at the age of 40-49 years, then decreased thereafter. The incidence rate decreased by 4.2 % per year. The highest incidence rate was noted in the 20-29-year-old age group in females and the 70-79-year-old age group in males. The average prevalence and mortality rates were 97.5 and 1.2 per 100,000 population, respectively. Mortality was 3.2 % in patients diagnosed within 1 year and is more prevalent in young patients with average age of 15.6 years. Incidence rate of SLE has been declining in recent years but the prevalence rate has remained steady. The highest mortality rate is among younger patients diagnosed with SLE within 1 year.

Extraction of large-scale coherent structure from plasma turbulence using rake probe and wavelet analysis in a tokamak Rev. Sci. Instrum. 77, 063505 (2006); 10.1063/1.2213217Effect of poloidal sheared flow on the long-range correlation characters of edge plasma turbulent transport Long-range correlations ͑temporal and spatial͒ have been predicted in a number of different turbulence models, both analytical and numerical. These long-range correlations are thought to significantly affect cross-field turbulent transport in magnetically confined plasmas. The Hurst exponent, H-one of a number of methods to identify the existence of long-range correlations in experimental data-can be used to quantify self-similarity scalings and correlations in the mesoscale temporal range. The Hurst exponent can be calculated by several different algorithms, each of which has particular advantages and disadvantages. One method for calculating H is via structure functions ͑SFs͒. The SF method is a robust technique for determining H with several inherent advantages that has not yet been widely used in plasma turbulence research. In this article, the SF method and its advantages are discussed in detail, using both simulated and measured fluctuation data from the DIII-D tokamak ͓J. L. Luxon and L. G. Davis, Fusion Technol. 8, 441 ͑1985͔͒. In addition, it is shown that SFs used in conjunction with rescaled range analysis ͑another method for calculating H͒ can be used to mitigate the effects of coherent modes in some cases.

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