Bayesian Learning for a Class of Priors with Prescribed Marginals

We present Bayesian updating of an imprecise probability measure, represented by a class of precise multidimensional probability measures. Choice and analysis of our class are motivated by expert interviews that we conducted with modelers in the context of climatic change. From the interviews we deduce that generically, experts hold a much more informed opinion on the marginals of uncertain parameters rather than on their correlations. Accordingly, we specify the class by prescribing precise measures for the marginals while letting the correlation structure subject to complete ignorance. For sake of transparency, our discussion focuses on the tutorial example of a linear two-dimensional Gaussian model. We operationalize Bayesian learning for that class by various updating rules, starting with (a modified version of) the generalized Bayes' rule and the maximum likelihood update rule (after Gilboa and Schmeidler). Over a large range of potential observations, the generalized Bayes' rule would provide non-informative results. We restrict this counter-intuitive and unnecessary growth of uncertainty by two means, the discussion of which refers to any kind of imprecise model, not only to our class. First, we find our class of priors too inclusive and, hence, require certain additional properties of prior measures in terms of smoothness of probability density functions. Second, we argue that both updating rules are dissatisfying, the generalized Bayes' rule being too conservative, i.e., too inclusive, the maximum likelihood rule being too exclusive. Instead, we introduce two new ways of Bayesian updating of imprecise probabilities: a ``weighted maximum likelihood method'' and a ``semi-classical method.'' The former bases Bayesian updating on the whole set of priors, however, with weighted influence of its members. By referring to the whole set, the weighted maximum likelihood method allows for more robust inferences than the standard maximum likelihood method and, hence, is better to justify than the latter.Furthermore, the semi-classical method is more objective than the weighted maximum likelihood method as it does not require the subjective definition of a weighting function. Both new methods reveal much more informative results than the generalized Bayes' rule, what we demonstrate for the example of a stylized insurance model

A model for the study of ligand binding to the ribosomal RNA helix h44.

Oligonucleotide models of ribosomal RNA domains are powerful tools to study the binding and molecular recognition of antibiotics that interfere with bacterial translation. Techniques such as selective chemical modification, fluorescence labeling and mutations are cumbersome for the whole ribosome but readily applicable to model RNAs, which are readily crystallized and often give rise to higher resolution crystal structures suitable for detailed analysis of ligand-RNA interactions. Here, we have investigated the HX RNA construct which contains two adjacent ligand binding regions of helix h44 in 16S ribosomal RNA. High-resolution crystal structure analysis confirmed that the HX RNA is a faithful structural model of the ribosomal target. Solution studies showed that HX RNA carrying a fluorescent 2-aminopurine modification provides a model system that can be used to monitor ligand binding to both the ribosomal decoding site and, through an indirect effect, the hygromycin B interaction region

They are even larger! More (on) puzzling labor market volatilities

"This paper shows that the German labor market is more volatile than the US labor market at the business cycle frequency. Specifically, the volatility of the cyclical component of several labor market variables (e.g., the job-finding rate, the labor market tightness and vacancies) divided by the volatility of labor productivity is roughly twice as large as in the United States. We derive and simulate a simple model to explain this seemingly puzzling result. This new model provides explanations for this phenomenon, in particular the longer job tenure in Germany." (Author's abstract, IAB-Doku) ((en))Arbeitsmarktindikatoren - internationaler Vergleich, Beschäftigungsschwankung, offene Stellen, Arbeitsproduktivität, Konjunkturabhängigkeit, Betriebszugehörigkeit, Beschäftigungsdauer, Arbeitslosenquote, labour turnover, Kündigung - Quote, Lohnhöhe, institutionelle Faktoren, Lohnfindung, matching - Quote, Produktivitätsentwicklung, USA, Bundesrepublik Deutschland

Principles for Shape Sonification

Hermann T. Principles for Shape Sonification. Empirical Musicology Review. 2013;8(2):88-91.This commentary starts with a critical reflection on Jensenius and Godøy’s sonomotiongrams as a sonification technique to represent movement shapes. Based on this we propose alternative mappings that require less information reduction. Furthermore, design criteria such as invariance, convergence, and stability are presented and applied to sonomotiongrams. Finally, we formulate necessary conditions for sonifications of movement shapes to support the perception and categorization of shapes, and we propose an experimental procedure to assess and compare movement shapes from auditory representations

Laboratory studies on cometary crust formation: The importance of sintering

It is demonstrated by experiments and theoretical considerations that sintering processes, so far used to describe the densification of metal and ceramic powders, are relevant for icy materials and therefore probably also for comets. A theoretical model is presented which describes the evolution of so called sinter necks, the contact zone between ice particles. With this model the strength increase of a porous, loosley packed icy body is calculated in which the sinter necks grow by evaporation and condensation of water vapor at a constant temperature. Experiments with ice powders validate the model qualitatively. An increase in strength up to a factor of four is observed during isothermal sintering. In order to check the relevance of the experimental results and the basic theoretical ideas with respect to real comets, more exact theories and improved experiments taking into account additional mass transport mechanisms are needed

Evaluation of (non-sink) AIJ projects in developing countries (Ensadec)

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