Reproducibility in the absence of selective reporting : An illustration from large-scale brain asymmetry research

Altres ajuts: Max Planck Society (Germany).The problem of poor reproducibility of scientific findings has received much attention over recent years, in a variety of fields including psychology and neuroscience. The problem has been partly attributed to publication bias and unwanted practices such as p-hacking. Low statistical power in individual studies is also understood to be an important factor. In a recent multisite collaborative study, we mapped brain anatomical left-right asymmetries for regional measures of surface area and cortical thickness, in 99 MRI datasets from around the world, for a total of over 17,000 participants. In the present study, we revisited these hemispheric effects from the perspective of reproducibility. Within each dataset, we considered that an effect had been reproduced when it matched the meta-analytic effect from the 98 other datasets, in terms of effect direction and significance threshold. In this sense, the results within each dataset were viewed as coming from separate studies in an "ideal publishing environment," that is, free from selective reporting and p hacking. We found an average reproducibility rate of 63.2% (SD = 22.9%, min = 22.2%, max = 97.0%). As expected, reproducibility was higher for larger effects and in larger datasets. Reproducibility was not obviously related to the age of participants, scanner field strength, FreeSurfer software version, cortical regional measurement reliability, or regional size. These findings constitute an empirical illustration of reproducibility in the absence of publication bias or p hacking, when assessing realistic biological effects in heterogeneous neuroscience data, and given typically-used sample sizes

Cyclic fatigue and energy-dispersive X-ray spectroscopy examination of the novel ROTATE instrument

To investigate the cyclic fatigue resistance of novel ROTATE instruments and to compare with the same size of One Curve, TF adaptive, and Mtwo instruments using a root canal simulation model. Four-type of 25/0.06 instruments were used: ROTATE, Mtwo, One Curve, TF adaptive. Instruments were divided into two subgroups: Distilled water and 2.5% sodium hypochlorite (n = 20). Instruments were operated at 35°C. The time to fracture and the length of the fractured fragments were compared One-way analysis of variance (ANOVA) followed by Tukey's multiple comparison tests (p <.05). Descriptive analysis was performed for the elemental composition of instruments by Energy-dispersive X-ray spectroscopy. ROTATE demonstrated the lowest Ni content and SD values. ROTATE had significantly higher NCF values than other groups (p <.0001). Sodium hypochlorite was decreased the mean NCF values. This is the first study in the literature on the cyclic fatigue of ROTATE. ROTATE presented higher cyclic fatigue life than One Curve, TF Adaptive, and Mtwo. © 2019 Wiley Periodicals, Inc