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BACKGROUND: A model of thyroxine and metamorphosis of highland amphibians is frequently mentioned as an example of experiments on extremely diluted substances in discussions around 'homeopathy'. METHODS: The model was scrutinized by reanalysing the results of the initial researcher A and a second researcher B as well as of 5 external researchers C between 1990 and 2013. Rana temporaria larvae were taken from an alpine highland biotope. The test solution was thyroxine 10(-30) (T30x), tetra-iodo-thyronine sodium pentahydrate diluted with pure water in 26 steps of 1:10, being agitated after each step. Analogously prepared water (W30x) was used for control. Tadpoles were observed from the 2-legged to the 4-legged stage. Experiments were performed in different years, at different times of season, and their duration could vary. Frequencies of 4-legged animals, effect sizes and areas under the curves (AUCs) were calculated and regression analyses were performed to investigate possible correlations between year, season, duration etc. Experiments were in line with animal protection guidelines. RESULTS: The total set of data A + B + C as well as subsets A (initial researcher, N=286+293), B (second centre, 965 + 965) and C (5 external researchers, 690 + 690) showed an effect of extremely diluted agitated thyroxine reverse to that known of molecular thyroxin, i.e. test values were below control by 11.4% for A, 9.5% for B and 7.0% for C (p<0.001 for each of the subsets). The effect size (Cohen's d) was >0.8 (large) for both A and B and 0.74 (medium) for C. CONCLUSION: Although a perfect reproducibility was not obtained, this paradoxical phenomenon was generally consistent in different observations. Correlations were found between details of laboratory handling, as well as environment temperature, and the size of the results.

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INTRODUCTION: The purpose of this study was to reproduce an experiment with diluted thyroxine and amphibians. A detailed account of the difficulties of this line of research has been published by the initial team (Endler and Scherer-Pongratz). One experiment which has been reported reproducible by the initial team and independent researchers is the effect of extremely diluted agitated thyroxine (T30x) versus analogously prepared water (W30x) in amphibians from biotopes above the tree line (highland amphibians). METHODS: (A) The author replicated the experiment. Rana temporaria were taken from an alpine biotope and the methods given in the original protocols were followed. Animals were treated from the 2-legged stage on. (B), the author reanalyzed the results reported by the initial team and by independent researchers (van Wijk, Lassnig, Zausner-Lukitsch, Bach, Harrer). RESULTS: (A) In the author's own experiment, there was a clear trend of T30x animals developing more slowly (i.e. up to 6 h within 3 days) than W30x animals. This is in line with the previous experiments. Due to small numbers of animals, the differences in the frequency of larvae reaching the 4-legged stage and the stage with reduced tail were not statistically significant (p > 0.05). The effect size was large (d > 0.08). (B) In the analysis of all available data with regard to the 4-legged stage, pooled T30x values from the initial team were 10.1% smaller than W30x values (100%) and pooled T30x values from the 5 independent researchers were 12.4% smaller (p < 0.01 and d > 0.08). Analogously, the number of animals entering the juvenile stage with reduced tail was smaller for T30x than for W30x.

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X-ray computed tomography (XCT) has become a very important method for non-destructive 3D-characterization and evaluation of materials. Due to measurement speed and quality, XCT systems with cone beam geometry and matrix detectors have gained general acceptance. Continuous improvements in the quality and performance of X-ray tubes and XCT devices have led to cone beam CT systems that can now achieve spatial resolutions down to 1 µm and even below. However, the polychromatic nature of the source, limited photon flux and cone beam artefacts mean that there are limits to the quality of the CT-data achievable; these limits are particularly pronounced with materials of higher density like metals. Synchrotron radiation offers significant advantages by its monochromatic and parallel beam of high brilliance. These advantages usually cause fewer artefacts, improved contrast and resolution.Tomography data of a steel sample and of two multi-phase Al-samples (AlSi12Ni1, AlMg5Si7) are recorded by advanced cone beam XCT-systems with a µ-focus (µXCT) and a sub-µm (nano-focus, sub-µXCT) X-ray source with voxel dimensions between 0.4 and 3.5 µm and are compared with synchrotron computed tomography (sXCT) with 0.3 µm/voxel. CT data features like beam hardening and ring artefacts, detection of details, sharpness, contrast, signal-to-noise ratio and the grey value histogram are systematically compared. In all cases µXCT displayed the lowest performance. Sub-µXCT gives excellent results in the detection of details, spatial and contrast resolution, which are comparable to synchrotron-XCT recordings. The signal-to-noise ratio is usually significantly lower for sub-µXCT compared with the two other methods. With regard to measurement costs "for industrial users", scanning volume, accessibility and user-friendliness sub-µXCT has significant advantages in comparison to synchrotron-XCT.