Stammzellbasierte Ansätze zur Therapie von Innenohrerkrankungen

Zusammenfassung: Das große Potenzial von Stammzellen zur Regeneration verlorener Gewebezellen wird zunehmend in allen Fachbereichen der modernen Medizin erkannt. Abgesehen von Blutstammzellen haben Stammzellen aber noch nicht Einzug in klinische Therapieformen gehalten. Die heutigen Experimente mit Stammzellen für die Therapie von Innenohrerkrankungen sind im Bereich der Grundlagenforschung anzusiedeln. Mehrere vielversprechende Arbeiten haben bewiesen, dass morphologisch und immunologisch differenzierbare Innenohrzellen wie Haarzellen, Stützzellen und auditorische Nervenzellen, in vitro und in vivo aus verschiedenen Stammzelltypen generiert werden können. Bisher haben aber noch keine Studien funktionelle Resultate in Bezug auf das Hörvermögen oder die vestibuläre Funktion geliefer

Overstating the evidence - double counting in meta-analysis and related problems

Background: The problem of missing studies in meta-analysis has received much attention. Less attention has been paid to the more serious problem of double counting of evidence. Methods: Various problems in overstating the precision of results from meta-analyses are described and illustrated with examples, including papers from leading medical journals. These problems include, but are not limited to, simple double-counting of the same studies, double counting of some aspects of the studies, inappropriate imputation of results, and assigning spurious precision to individual studies. Results: Some suggestions are made as to how the quality and reliability of meta-analysis can be improved. It is proposed that the key to quality in meta-analysis lies in the results being transparent and checkable. Conclusions: Existing quality check lists for meta-analysis do little to encourage an appropriate attitude to combining evidence and to statistical analysis. Journals and other relevant organisations should encourage authors to make data available and make methods explicit. They should also act promptly to withdraw meta-analyses when mistakes are found

Harold Jeffreys's Theory of Probability Revisited

Published exactly seventy years ago, Jeffreys's Theory of Probability (1939) has had a unique impact on the Bayesian community and is now considered to be one of the main classics in Bayesian Statistics as well as the initiator of the objective Bayes school. In particular, its advances on the derivation of noninformative priors as well as on the scaling of Bayes factors have had a lasting impact on the field. However, the book reflects the characteristics of the time, especially in terms of mathematical rigor. In this paper we point out the fundamental aspects of this reference work, especially the thorough coverage of testing problems and the construction of both estimation and testing noninformative priors based on functional divergences. Our major aim here is to help modern readers in navigating in this difficult text and in concentrating on passages that are still relevant today.Comment: This paper commented in: [arXiv:1001.2967], [arXiv:1001.2968], [arXiv:1001.2970], [arXiv:1001.2975], [arXiv:1001.2985], [arXiv:1001.3073]. Rejoinder in [arXiv:0909.1008]. Published in at http://dx.doi.org/10.1214/09-STS284 the Statistical Science (http://www.imstat.org/sts/) by the Institute of Mathematical Statistics (http://www.imstat.org

Understanding Variation in Sets of N-of-1 Trials.

A recent paper in this journal by Chen and Chen has used computer simulations to examine a number of approaches to analysing sets of n-of-1 trials. We have examined such designs using a more theoretical approach based on considering the purpose of analysis and the structure as regards randomisation that the design uses. We show that different purposes require different analyses and that these in turn may produce quite different results. Our approach to incorporating the randomisation employed when the purpose is to test a null hypothesis of strict equality of the treatment makes use of Nelder's theory of general balance. However, where the purpose is to make inferences about the effects for individual patients, we show that a mixed model is needed. There are strong parallels to the difference between fixed and random effects meta-analyses and these are discussed

The Principles at Work In High Performing Information Systems Organizations

Although there is a great deal of discussion about high performing information systems (I/S) organizations, little is known about the characteristics and practices they use. A field study was conducted to learn what principles are applied in organizations widely acknowledged to be high performers. The sample of companies for this field study was chosen by a core team of 15 consultants, practitioners, and academic researchers. On-site, structured interviews were conducted with 105 executives and managers in both the functional areas and the I/S groups of the firms. The findings show that a common set of principles are applied in high performing I/S groups. At the same time, there are distinct differences between these leading companies. The results provide useful insights for practice and for future research

Transmission resonances and supercritical states in a one dimensional cusp potential

We solve the two-component Dirac equation in the presence of a spatially one dimensional symmetric cusp potential. We compute the scattering and bound states solutions and we derive the conditions for transmission resonances as well as for supercriticality.Comment: 10 pages. Revtex 4. To appear in Phys Rev.