27 research outputs found
PM-64QAM Coherent Optical Communications Using a Dark-Pulse Microresonator Frequency Comb
Dark-pulse microresonator combs exhibit efficient pump-to-comb power conversion. Using on-chip pump powers of 21 dBm, we show 20-channel PM-64QAM-based data transmission. These results represent the highest-order modulation format encoded onto any integrated comb
High-Order Coherent Communications Using Modelocked Dark-Pulse Kerr Combs from Microresonators
Microresonator frequency combs harness the nonlinear Kerr effect in an integrated optical cavity to generate a multitude of phase-locked frequency lines. The line spacing can reach values in the order of 100 GHz, making it an attractive multi-wavelength light source for applications in fiber-optic communications. Depending on the dispersion of the microresonator, different physical dynamics have been observed. A recently discovered comb state corresponds to the formation of mode-locked dark pulses in a normal-dispersion microcavity. Such dark-pulse combs are particularly compelling for advanced coherent communications since they display unusually high power-conversion efficiency. Here, we report the first coherent-transmission experiments using 64-quadrature amplitude modulation encoded onto the frequency lines of a dark-pulse comb. The high conversion efficiency of the comb enables transmitted optical signal-to-noise ratios above 33 dB, while maintaining a laser pump power level compatible with state-of-the-art hybrid silicon lasers
Microresonator frequency combs for long-haul coherent communications
Microresonator frequency combs provide a promising platform as multi-wavelength light sources for WDM. The results discussed here show that microresonators can be used in long-haul optical communications systems
Role of chaos for the validity of statistical mechanics laws: diffusion and conduction
Several years after the pioneering work by Fermi Pasta and Ulam, fundamental
questions about the link between dynamical and statistical properties remain
still open in modern statistical mechanics. Particularly controversial is the
role of deterministic chaos for the validity and consistency of statistical
approaches. This contribution reexamines such a debated issue taking
inspiration from the problem of diffusion and heat conduction in deterministic
systems. Is microscopic chaos a necessary ingredient to observe such
macroscopic phenomena?Comment: Latex, 27 pages, 10 eps-figures. Proceedings of the Conference "FPU
50 years since" Rome 7-8 May 200
Reliability, construct and criterion validity of the KIDSCREEN-10 score: a short measure for children and adolescentsâ well-being and health-related quality of life
Background
To assess the criterion and construct validity of the KIDSCREEN-10 well-being and health-related quality of life (HRQoL) score, a short version of the KIDSCREEN-52 and KIDSCREEN-27 instruments.
Methods
The child self-report and parent report versions of the KIDSCREEN-10 were tested in a sample of 22,830 European children and adolescents aged 8â18 and their parents (n = 16,237). Correlation with the KIDSCREEN-52 and associations with other generic HRQoL measures, physical and mental health, and socioeconomic status were examined. Score differences by age, gender, and country were investigated.
Results
Correlations between the 10-item KIDSCREEN score and KIDSCREEN-52 scales ranged from r = 0.24 to 0.72 (r = 0.27â0.72) for the self-report version (proxy-report version). Coefficients below r = 0.5 were observed for the KIDSCREEN-52 dimensions Financial Resources and Being Bullied only. Cronbach alpha was 0.82 (0.78), testâretest reliability was ICC = 0.70 (0.67) for the self- (proxy-)report version. Correlations between other children self-completed HRQoL questionnaires and KIDSCREEN-10 ranged from r = 0.43 to r = 0.63 for the KIDSCREEN children self-report and r = 0.22â0.40 for the KIDSCREEN parent proxy report. Known group differences in HRQoL between physically/mentally healthy and ill children were observed in the KIDSCREEN-10 self and proxy scores. Associations with self-reported psychosomatic complaints were r = â0.52 (â0.36) for the KIDSCREEN-10 self-report (proxy-report). Statistically significant differences in KIDSCREEN-10 self and proxy scores were found by socioeconomic status, age, and gender.
Conclusions
Our results indicate that the KIDSCREEN-10 provides a valid measure of a general HRQoL factor in children and adolescents, but the instrument does not represent well most of the single dimensions of the original KIDSCREEN-52. Testâretest reliability was slightly below a priori defined thresholds
Long-haul coherent communications using microresonator-based frequency combs
Microresonator-based frequency combs are strong contenders as light sources for wavelength-division multiplexing (WDM). Recent experiments have shown the potential of microresonator combs for replacing a multitude of WDM lasers with a single laser-pumped device. Previous demonstrations have however focused on short-distance few-span links reaching an impressive throughput at the expense of transmission distance. Here we report the first long-haul coherent communication demonstration using a microresonator-based comb source. We modulated polarization multiplexed (PM) quadrature phase-shift keying-data onto the comb lines allowing transmission over more than 6300 km in a single-mode fiber. In a second experiment, we reached beyond 700 km with the PM 16 quadrature amplitude modulation format. To the best of our knowledge, these results represent the longest fiber transmission ever achieved using an integrated comb source
Testing the structural and cross-cultural validity of the KIDSCREEN-27 quality of life questionnaire
Objectives: The aim of this study is to assess the structural and cross-cultural validity of the KIDSCREEN-27 questionnaire. Methods: The 27-item version of the KIDSCREEN instrument was derived from a longer 52-item version and was administered to young people aged 8-18 years in 13 European countries in a cross-sectional survey. Structural and cross-cultural validity were tested using multitrait multi-item analysis, exploratory and confirmatory factor analysis, and Rasch analyses. Zumbo's logistic regression method was applied to assess differential item functioning (DIF) across countries. Reliability was assessed using Cronbach's alpha. Results: Responses were obtained from n = 22,827 respondents (response rate 68.9%). For the combined sample from all countries, exploratory factor analysis with procrustean rotations revealed a five-factor structure which explained 56.9% of the variance. Confirmatory factor analysis indicated an acceptable model fit (RMSEA = 0.068, CFI = 0.960). The unidimensionality of all dimensions was confirmed (INFIT: 0.81-1.15). Differential item functioning (DIF) results across the 13 countries showed that 5 items presented uniform DIF whereas 10 displayed non-uniform DIF. Reliability was acceptable (Cronbach's α = 0.78-0.84 for individual dimensions). Conclusions: There was substantial evidence for the cross-cultural equivalence of the KIDSCREEN-27 across the countries studied and the factor structure was highly replicable in individual countries. Further research is needed to correct scores based on DIF results. The KIDSCREEN-27 is a new short and promising tool for use in clinical and epidemiological studies. © 2007 Springer Science+Business Media B.V
The KIDSCREEN-27 quality of life measure for children and adolescents: Psychometric results from a cross-cultural survey in 13 European countries
Objective: To assess the construct and criterion validity of the KIDSCREEN-27 health-related quality of life (HRQoL) questionnaire, a shorter version of the KIDSCREEN-52. Methods: The five-dimensional KIDSCREEN-27 was tested in a sample of 22,827. For criterion validity the correlation with and the percentage explained variance of the scores of the KIDSCREEN-52 instrument were examined. Construct validity was assessed by testing a priori expected associations with other generic HRQoL measures (YQOL-S, PedsQL, CHIP), indicators of physical and mental health, and socioeconomic status. Age and gender differences were investigated. Results: Correlation with corresponding scales of the KIDSCREEN-52 ranged from r = 0.63 to r = 0.96, and r2 ranged from 0.39 to 0.92. Correlations between other HRQoL questionnaires and KIDSCREEN-27 dimensions were moderate to high for those assessing similar constructs (r = 0.36 to 0.63). Statistically significant and sizeable differences between physically and mentally healthy and ill children were found in all KIDSCREEN-27 dimensions together with strong associations with psychosomatic complaints (r = -0.52). Most of the KIDSCREEN-27 dimensions showed a gradient according to socio-economic status, age and gender. Conclusions: The KIDSCREEN-27 seems to be a valid measure of HRQoL in children and adolescents. Further research is needed to assess longitudinal validity and sensitivity to change. © 2007 Springer Science+Business Media B.V