Violation of the sphericity assumption and its effect on Type-I error rates in repeated measures ANOVA and multi-level linear models (MLM)

This study aims to investigate the effects of violations of the sphericity assumption on Type I error rates for different methodical approaches of repeated measures analysis using a simulation approach. In contrast to previous simulation studies on this topic, up to nine measurement occasions were considered. Therefore, two populations representing the conditions of a violation vs. a non-violation of the sphericity assumption without any between-group effect or within-subject effect were created and 5,000 random samples of each population were drawn. Finally, the mean Type I error rates for Multilevel linear models (MLM) with an unstructured covariance matrix (MLM-UN), MLM with compound-symmetry (MLM-CS) and for repeated measures analysis of variance (rANOVA) models (without correction, with Greenhouse-Geisser-correction, and Huynh-Feldt-correction) were computed. To examine the effect of both the sample size and the number of measurement occasions, sample sizes of n = 20, 40, 60, 80, and 100 were considered as well as measurement occasions of m = 3, 6 and 9. For MLM-UN, the results illustrate a massive progressive bias for small sample sizes (n =20) and m = 6 or more measurement occasions. This effect could not be found in previous simulation studies with a smaller number of measurement occasions. The mean Type I error rates for rANOVA with Greenhouse-Geisser-correction demonstrate a small conservative bias if sphericity was not violated, sample sizes were small (n = 20), and m = 6 or more measurement occasions were conducted. The results plead for a use of rANOVA with Huynh-Feldt-correction, especially when the sphericity assumption is violated, the sample size is rather small and the number of measurement occasions is large. MLM-UN may be used when the sphericity assumption is violated and when sample sizes are large.Comment: 14 pages, 6 figure

The EU and the Governance of Globalisation. Bruegel Working Papers, 2006/02, September 2006

Bruegel Scholars Alan Ahearne, Jean Pisani-Ferry, André Sapir and Nicolas Véron contributed this paper to the project Globalisation Challenges for Europe and Finland organised for the secretariat of the Economic Council of Finland. The project is part of Finland's EU presidency programme and its objective is to add momentum to the discussion in the European Union on golbalisation, Europe's competitiveness policy and the Lisbon Strategy

2015 updated position statement of the management of hyperglycaemia in type 2 diabetes

peer reviewedThe strategy for the management ot type 2 diabetes, summarized by a group of European and American experts, has been updated early 2015. A patient-centered approach is recommended and the first drug choice is metformin combined with lifestyle improvement. After failure of metformin monotherapy, the selection of a second drug should be based on the efficacy, safety and cost of each pharmacological class. When compared to the position statement of 2012, the most important changes are the possible addition of a gliptin to a dual oral therapy or even to insulin, the commercialization of sodium-glucose cotransporters type 2 (SGLT2) inhibitors (gliflozins, to be used in dual or triple therapy, even in combination with insulin) and the possible combination of a glucagon-like peptide-I receptor agonist together with a basal insulin

Centre de développement durable d'Ayent: concept NER pour le site A

Proposer un scénario d’approvisionnement en énergies renouvelables et de gestion de l’énergie pour le centre de développement durable d’Ayent, avec l’ambition d’être coupé du réseau électrique et d’un impact environnemental nul

On the origin of variable structures in the winds of hot luminous stars

Examination of the temporal variability properties of several strong optical recombination lines in a large sample of Galactic Wolf-Rayet (WR) stars reveals possible trends, especially in the more homogeneous WC than the diverse WN subtypes, of increasing wind variability with cooler subtypes. This could imply that a serious contender for the driver of the variations is stochastic, magnetic subsurface convection associated with the 170 kK partial-ionization zone of iron, which should occupy a deeper and larger zone of greater mass in cooler WR subtypes. This empirical evidence suggests that the heretofore proposed ubiquitous driver of wind variability, radiative instabilities, may not be the only mechanism playing a role in the stochastic multiple small-scaled structures seen in the winds of hot luminous stars. In addition to small-scale stochastic behaviour, subsurface convection guided by a global magnetic field with localized emerging loops may also be at the origin of the large-scale corotating interaction regions as seen frequently in O stars and occasionally in the winds of their descendant WR stars.Comment: 8 pages, 2 figures and 2 tables. Monthly Notices of the Royal Astronomical Society 201

Lab-on-a-chip Raman sensors outperforming Raman microscopes

We demonstrate that the signal-to-noise ratio and signal collection efficiency in evanescent waveguide-based Raman spectroscopy exceeds that in Raman microscopes. We investigate the effect of silicon-nitride waveguide geometry to further improve the performance

Diagnostic of the unstable envelopes of Wolf-Rayet stars

The envelopes of stars near the Eddington limit are prone to various instabilities. A high Eddington factor in connection with the Fe opacity peak leads to convective instability, and a corresponding envelope inflation may induce pulsational instability. Here, we investigate the occurrence and consequences of both instabilities in models of Wolf-Rayet stars. We determine the convective velocities in the sub-surface convective zones to estimate the amplitude of the turbulent velocity at the base of the wind that potentially leads to the formation of small-scale wind structures, as observed in several WR stars. We also investigate the effect of mass loss on the pulsations of our models. We approximated solar metallicity WR stars by models of mass-losing helium stars, and we characterized the properties of convection in the envelope adopting the standard MLT. Our results show the occurrence of sub-surface convective regions in all studied models. Small surface velocity amplitudes are predicted for models with masses below 10Msun. For models with M>10Msun, the surface velocity amplitudes are of the order of 10km/s. Moreover we find the occurrence of pulsations for stars in the mass range 9-14Msun, while mass loss appears to stabilize the more massive WR stars. We confront our results with observationally derived line variabilities of 17 WN stars. The data suggest variability to occur for stars above 10Msun, which is increasing linearly with mass above this value, in agreement with our results. We further find some of our models to be unstable to radial pulsations, and predict local magnetic fields of the order of hundreds of Gauss in WR stars more massive than 10Msun. Our study relates the surface velocity fluctuations induced by sub-surface convection to the formation of clumping in the inner part of the wind. From this mechanism, we expect a stronger variability in more massive WR stars.Comment: A&A, accepte