More about discrete symmetries in compactified string theories

We discuss discrete symmetries in several string compactification schemes. The same constraints on the light spectra as for Gepner models \cite{rosss} are found in various cases for non-$R$ symmetries. The analogous constraints for $R$ symmetries are also established.Therefore it seems natural to conjecture that they always apply.Comment: 10 pages, OUTP-93-15

The Vector Valued Quartile Operator

Certain vector-valued inequalities are shown to hold for a Walsh analog of the bilinear Hilbert transform. These extensions are phrased in terms of a recent notion of quartile type of a UMD (Unconditional Martingale Differences) Banach space X. Every known UMD Banach space has finite quartile type, and it was recently shown that the Walsh analog of Carleson's Theorem holds under a closely related assumption of finite tile type. For a Walsh model of the bilinear Hilbert transform however, the quartile type should be sufficiently close to that of a Hilbert space for our results to hold. A full set of inequalities is quantified in terms of quartile type.Comment: 32 pages, 5 figures, incorporates referee's report, to appear in Collect. Mat

Paying for Safety: Preferences for Mortality Risk Reductions on Alpine Roads

This paper presents a choice experiment, which values reductions in mortality risk on Alpine roads. These roads are on one hand threatened by common road hazards, on the other hand they are also endangered by natural hazards such as avalanches and rockfalls. Drawing on choice data from frequently exposed and barely exposed respondents, we are not only able to estimate the VSL but to explore how the respondents differ in their individual willingness-to-pay depending on personal characteristics. To address heterogeneity in preferences for risk reduction, we use a non-linear conditional logit model with interaction effects. The best estimate of the VSL in the context of fatal accidents on Alpine roads is in the range of €4.9–5.4 million with distinct differences between the urban and the mountain sample groups. We find the VSL to be significantly altered by socio-economic factors but only marginally altered by the type of hazard.Value of Statistical Life, Choice Experiment, Natural Hazard Mitigation, Traffic Safety

Policy Evaluation and Economic Policy Advice

Arguably, one of the most important developments in the field of applied economics during the last decades has been the emergence of systematic policy evaluation, with its distinct focus on the establishment of causality.By contrast to the natural sciences, the objects of our scientific interest typically exert some influence on their treatment status under the policy to be evaluated and on their economic outcomes. Thus, economic policy advice can only be successful, if it is based on an appropriate study design, experimental or observational. It will strive in societies that provide liberal access to data, accept the merits of randomized assignment and guard the independence of research institutions.Policy evaluation, applied economics, causality, policy advice

The Role of Family-Based Designs in Genome-Wide Association Studies

Genome-Wide Association Studies (GWAS) offer an exciting and promising new research avenue for finding genes for complex diseases. Traditional case-control and cohort studies offer many advantages for such designs. Family-based association designs have long been attractive for their robustness properties, but robustness can mean a loss of power. In this paper we discuss some of the special features of family designs and their relevance in the era of GWAS.Comment: Published in at http://dx.doi.org/10.1214/08-STS280 the Statistical Science (http://www.imstat.org/sts/) by the Institute of Mathematical Statistics (http://www.imstat.org

Tropospheric water vapour observations by ground-based lidar

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Ownership and Financial Performance in the German Hospital Sector

This paper considers the role of ownership form for the financial performance of German acute care hospitals and its development over time.We measure financial performance by a hospital-specific yearly probability of default (PD). Using a panel of hospital data, our models allow for state dependence in the PD as well as unobserved individual heterogeneity. We find that private ownership is more likely to be associated with sound levels in financial performance than public ownership. Moreover, state dependence in the PD is substantial, albeit not ownership-specific.Finally, our evidence suggests that overall efficiency may be enhanced most by closing down some loss-making public hospitals rather than by their restructuring, especially because the German hospital market has substantial excess capacities.Hospitals ownership, financial performance, state dependence