The future of wind tunnel technology in Germany

The practical value of a wind tunnel which is not dependent solely on size or achievable Reynolds number was examined. Measurement, interpretative and evaluative procedures developed in small facilities were also studied

Numerical simulations of the magnetorotational instability in protoneutron stars: I. Influence of buoyancy

The magneto-rotational instability (MRI) is considered to be a promising mechanism to amplify the magnetic field in fast rotating protoneutron stars. In contrast to accretion disks, radial buoyancy driven by entropy and lepton fraction gradients is expected to have a dynamical role as important as rotation and shear. We investigate the poorly known impact of buoyancy on the non-linear phase of the MRI, by means of three dimensional numerical simulations of a local model in the equatorial plane of a protoneutron star. The use of the Boussinesq approximation allows us to utilise a shearing box model with clean shearing periodic boundary conditions, while taking into account the buoyancy driven by radial entropy and composition gradients. We find significantly stronger turbulence and magnetic fields in buoyantly unstable flows. On the other hand, buoyancy has only a limited impact on the strength of turbulence and magnetic field amplification for buoyantly stable flows in the presence of a realistic thermal diffusion. The properties of the turbulence are, however, significantly affected in the latter case. In particular, the toroidal components of the magnetic field and of the velocity become even more dominant with respect to the poloidal ones. Furthermore, we observed in the regime of stable buoyancy the formation of long lived coherent structures such as channel flows and zonal flows. Overall, our results support the ability of the MRI to amplify the magnetic field significantly even in stably stratified regions of protoneutron stars.Comment: 22 pages, 15 figures, accepted for publication in MNRA

Uniformly Valid Confidence Sets Based on the Lasso

In a linear regression model of fixed dimension $p \leq n$, we construct confidence regions for the unknown parameter vector based on the Lasso estimator that uniformly and exactly hold the prescribed in finite samples as well as in an asymptotic setup. We thereby quantify estimation uncertainty as well as the "post-model selection error" of this estimator. More concretely, in finite samples with Gaussian errors and asymptotically in the case where the Lasso estimator is tuned to perform conservative model selection, we derive exact formulas for computing the minimal coverage probability over the entire parameter space for a large class of shapes for the confidence sets, thus enabling the construction of valid confidence regions based on the Lasso estimator in these settings. The choice of shape for the confidence sets and comparison with the confidence ellipse based on the least-squares estimator is also discussed. Moreover, in the case where the Lasso estimator is tuned to enable consistent model selection, we give a simple confidence region with minimal coverage probability converging to one. Finally, we also treat the case of unknown error variance and present some ideas for extensions.Comment: Some typos corrected, updated reference

On the effects of changing mortality patterns on investment, labour and consumption under uncertainty

In this paper we extend the consumption-investment life cycle model for an uncertain-lived agent, proposed by Richard (1974), to allow for exible labor supply. We further study the consumption, labor supply and portfolio decisions of an agent facing age-dependent mortality risk, as presented by UK actuarial life tables spanning the time period from 1951-2060 (including mortality forecasts). We find that historical changes in mortality produces significant changes in portfolio investment (more risk taking), labour (decrease of hours) and consumption level (shift to higher level) contributing up to 5% to GDP growth during the period from 1980 until 2010

Tree shading: an efficient method to control alternate bearing?

Conventional and integrated fruit growers, but not organic producers, have the possibility to use thinning agents (e.g. benzyl adenine), which allow crop regulation at a relatively late stage (10-16 mm fruit size). A few surveys have shown that by reducing net photosynthesis after blossom, June fruit drop increases. This could be an interesting new approach for organic apple orchards. Since 2003, different trials have been carried out at the Laimburg Research Station on the variety Golden Delicious rootstock M9 to devise a method for practical use by fruit growers. Unfortunately, there are still several constraints to the practical application of the shading method, not least because it does not sufficiently reduce alternate fruit bearing in the following year

Multichannel pulse height analyzer is inexpensive, features low power requirements

Consumption multichannel pulse height analyzer performs balloon and rocket investigations of solar neutrons with energies greater than 10 MeV. The lightweight unit can operate in a temperature range of minus 30 degrees to plus 70 degrees C and withstand storage temperatures from minus 50 degrees to plus 90 degrees C

Winter treatments against the woolly apple aphid (Eriosoma lanigerum): products and timing of applications

In organic apple growing the woolly apple aphid (Eriosoma lanigerum) is still an unsolved problem. Various approaches to use beneficial insects were not really effective. Only winter treatments with mineral oils showed partial and fluctuating success. In 2006 and 2007 field trials were carried out to evaluate the efficacy of winter treatments to control woolly apple aphids. The efficacy of several products (different mineral oils, lime sulphur, and lime sulphur + mineral oil) was tested in comparison to an untreated control, and possible side effects on the population of predatory mites were investigated. The study furthermore aimed at establishing the best timing of the application against the target pest

Formulated and unformulated carbonates to control apple scab (Venturia inaequalis) on organic apple

In the EC at the moment only copper- and sulphur-based products are allowed to control a variety of diseases on different crops. However, it is well-known that these products also have negative side effects on beneficial organisms and the soil. For many years researchers have been looking for alternatives to reduce their use and /or replace them. Bicarbonates have been brought forward for many years. They are present in nature and were used in the past in organic farming. Up to now, in the EC, carbonates have not been included in the list of active substances, which may be used as plant protection products. A good chance exists that this will change in the future, which would open the possibility to apply for the inclusion of potassium hydrogen carbonate in Annex II B of regulation EEC 2091/92. Field trials carried out in 2006 and 2007 in South Tyrol evidenced an interesting efficacy of potassium hydrogen carbonate-based products against apple scab and other diseases, but also phytotoxic side effects emerged