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We present a method for synchronization of chaos generators based on transmission of an analog chaotic waveform in a digital form. Experimental comparisons between digital and analog transmission of chaos from a delayed differential feedback system are performed. Synchronization is demonstrated to be between 18 and 39 dB (or equivalently 63 to 7943 times) better for digital transmission than analog. Coherent chaotic modulation and demodulation is demonstrated in a situation where there is no effective synchronization using analog transmission. [ABSTRACT FROM AUTHOR]

We present a methodology for designing wideband, shot noise limited photodetectors using commercially available components and microwave engineering techniques. We use this methodology to design and construct a photodetector using wideband microwave amplifiers and a 3.5 GHz bandwidth photodiode. Consistent with our analytic models, the photodetector exhibits linear behavior up to a level of 6.5 dB clearance between shot noise and dark noise from 2.0 to 3.5 GHz at 10 mA of photocurrent, reducing to 3.5 dB of clearance at 6.4 GHz. [ABSTRACT FROM AUTHOR]

This brief introduces a delayed differential feedback chaos generator with a programmable feedback element. The programmable feedback allows us to implement an arbitrary nonlinearity or modulate the feedback delay time. Delayed differential feedback systems have been suggested for secure communications, and the flexibility of the programmable system is shown to enhance security against published cracking algorithms. [ABSTRACT FROM AUTHOR]

Caries efficacy in clinical trials has been based primarily on visual examinations supplemented by Fiber Optic Transillumination (FOTI) and radiography, with the assessments combined at the surface level to classify each surface as to its caries status. Newer caries diagnostics techniques measure the caries process in a quantitative manner and so thus yield continuous rather than ordinal results. The objective of this study was to examine various methods for the analysis of multiple outcomes in clinical trials and to compare their usefulness for the analysis of caries trials. Four global tests (rank sum, ordinary least squares, general least squares, and generalized estimating equations) and two caries indices (based on average and maximum values of the methods) were evaluated with the use of one-year follow-up data from 1063 children in a recent caries trial. A new hybrid method was also developed and evaluated. All of the methods performed well when the diagnostic measures showed product differences in caries in the same direction. Ease of use, interpretability, and distributional assumptions must be considered before a consensus method for analysis of multiple diagnostic measures in caries trials can be determined. [ABSTRACT FROM AUTHOR]

Conventional caries trials last from 24 to 36 months. This study evaluated whether the previously established difference in efficacy between 1000- and 2500-ppm-fluoride dentifrices could be detected after 12 months. Caries was assessed by clinical visual assessment (CVA-simplified version of Dundee Selectable Threshold Method - DSTM), bitewing radiography, and Fiber Optic Transillumination (FOTI). Changes in status for individual surfaces were classified by means of pre-prepared matrices as 0 (unchanged), +1 (initiation or progression), or -1 (regression) and summed for each subject to yield an event score. Mean group event scores were calculated for each product. DSTM at the D1 [enamel and dentin] threshold showed significant inter-group differences in mean event scores (p < 0.003) and D1MFS increment (< 0.007) at 12 months; these were confirmed at 24 months by traditional increment analysis (CVA & FOTI at the D3 (dentin only) threshold + radiography, p < 0.03). This study confirms the validity of an abbreviated trial protocol. [ABSTRACT FROM AUTHOR]

The aim of this study was to test the feasibility of employing clinical visual examination at the D1 (enamel and dentine caries) diagnostic threshold, fibre-optic transillumination (FOTI), elective temporary tooth separation (ETTS) and electronic caries measurement (ECM) in the environment of an epidemiological study or clinical trial. It also aimed to compare the diagnostic yield of these diagnostic aides and methods. The sample consisted of 182 Latvian children, mean age 13.3 years (range = 10.6-15.7). For 12-year-old subjects the mean D3MFS was 10.58 (SD 6.05) and the mean D1MFS was 19.97 (SD 10.47). The additional diagnostic yield from FOTI examination of approximal sites was 40.0% at the D1 threshold. The additional apparent yield for ETTS was 52.8% at the D1 threshold. ETTS detected 38.3% more carious surfaces than FOTI at the D1 threshold. Conversely 57 surfaces thought to be carious on FOTI examination were judged sound following ETTS. Although the ECM appeared practical to use, it broke early in the trial and the results obtained prior to breappeared inaccurate. In conclusion, all diagnostic methods were feasible under the conditions of an epidemiological study or clinical trial. [ABSTRACT FROM AUTHOR]

The relative efficacy of NaF silica toothpastes containing 1000 ppm fluoride and 1500 ppm fluoride in the control of dental caries is not clear-cut. Also, it has not been established that incorporation of trimetaphosphate (TMP) improves the anticaries activity of NaF toothpastes. A three-year clinical trial was conducted to test the hypotheses that: (i) the anticaries activity of NaF toothpastes containing 1500 ppm F was greater than that of NaF toothpastes containing 1000 ppm F, and (ii) inclusion of TMP improved the efficacy of NaF silica pastes. Subsidiary aims included determination of whether frequency of toothbrushing and method of rinsing after brushing were correlated with caries increments. The study involved 4196 children aged 11 to 12 years at outset. These participants had been selected from a pool of 7374 potential subjects on the basis of caries experience and dental eruption pattern. They were stratified by sex, examiner, and presence of calculus and caries, and were allocated at random to one of the four toothpastes under study. Using mirror and probe and also FOTI, we carried out clinical examinations at baseline and annually thereafter for 3 yrs. Bitewing radiographs of a subset of children were taken at baseline and at the end of the study. The outcome measure for the study, DMFS increment, was defined as the increase in caries over 3 yrs, taking into account changes occurring on individual tooth surfaces. Data for 3467 subjects were available for analyses at both baseline and year 3 examinations. Radiographs were taken for 1942 subjects at both baseline and year 3 examinations. The mean three-year clinical-only DMFS increment for the subjects using 1500-ppm-NaF pastes was 3.93, which was 6% lower than the corresponding mean of 4.19 for the 1000-ppm-NaF pastes. There was no significant difference between the mean DMFS increment for those using paste with or without TMP. Subjects who claimed to brush more frequently or who claimed not to use a tumbler to rinse after toothbrushing had lower three-year DFMS increments. [ABSTRACT FROM AUTHOR]

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