Minimum thrust levels for spinning drag-free satellites = Niveaux minimums de la force motrice pour des satellites rotatoires sans résistance = Minimum triebkraftniveaus für rotierende wiederstandsfreie satelliten

A drag-free satellite, which contains an internal unsupported proof mass, is shielded from external forces such as solar pressure. Thrustors force the satellite to follow the proof mass and hence the satellite follows an almost purely gravitational orbit. The dominant internal disturbing force is the mass attraction of the satellite on the proof mass. Spinning the satellite reduces this force and it has been investigated what the size of the thrustors must be in this case. This size is much smaller than originally thought. Its impact on some other features is shown

Real-Time Flux Density Measurements of the 2011 Draconid Meteor Outburst

During the 2011 outburst of the Draconid meteor shower, members of the Video Meteor Network of the International Meteor Organization provided, for the first time, fully automated flux density measurements in the optical domain. The data set revealed a primary maximum at 20:09 UT ± 5 min on 8 October 2011 (195.036° solar longitude) with an equivalent meteoroid flux density of (118 ± 10) × 10/km/h at a meteor limiting magnitude of +6.5, which is thought to be caused by the 1900 dust trail. We also find that the outburst had a full width at half maximum of 80 min, a mean radiant position of α = 262.2°, δ = +56.2° (±1.3°) and geocentric velocity of v = 17.4 km/s (±0.5 km/s). Finally, our data set appears to be consistent with a small sub-maximum at 19:34 UT ±7 min (195.036° solar longitude) which has earlier been reported by radio observations and may be attributed to the 1907 dust trail. We plan to implement automated real-time flux density measurements for all known meteor showers on a regular basis soon.Peer reviewedFinal Accepted Versio

Large potential steps at weakly interacting metal-insulator interfaces

Potential steps exceeding 1 eV are regularly formed at metal|insulator interfaces, even when the interaction between the materials at the interface is weak physisorption. From first-principles calculations on metal|h-BN interfaces we show that these potential steps are only indirectly sensitive to the interface bonding through the dependence of the binding energy curves on the van der Waals interaction. Exchange repulsion forms the main contribution to the interface potential step in the weakly interacting regime, which we show with a simple model based upon a symmetrized product of metal and h-BN wave functions. In the strongly interacting regime, the interface potential step is reduced by chemical bonding

Expectations Hypotheses Tests

We investigate the Expectations Hypotheses of the term structure of interest rates and of the foreign exchange market using vector autoregressive methods for the U.S. dollar, Deutsche mark, and British pound interest rates and exchange rates. In addition to standard Wald tests, we formulate Lagrange Multiplier and Distance Metric tests which require estimation under the non-linear constraints of the null hypotheses. Estimation under the null is achieved by iterating on approximate solutions that require only matrix inversions. We use a bias-corrected, constrained vector autoregression as a data generating process and construct extensive Monte Carlo simulations of the various test statistics under the null hypotheses. Wald tests suffer from severe size distortions and use of the asymptotic critical values results in gross over-rejection of the null. The Lagrange Multiplier tests slightly under-reject the null, and the Distance Metric tests over-reject. Use of the small sample distributions of the different tests leads to a common interpretation of the validity of the Expectations Hypotheses. The evidence against the Expectations Hypotheses for these interest rates and exchange rates is much less strong than under asymptotic inference.

NDICEA as a user friendly model tool for crop rotation planning in organic farming

For organic farming systems, the challenge is to become more specific in practices to maintain high standards in sustainability. Soil processes need to be clearly understood if rotations and manure applications are to become more precise. Simulation models like the NDICEA model help in the design and maintenance of these farming systems. These models play a key-role in the design of organic precision farming. The NDICEA model has been calibrated for a number of long-term crop rotation experiments. Recently, the model was validated using research data from more than 35 organic farms all over the country. The model is used to calculate soil-specific mineralization rates in precision applications. In a new easy-to-use application, it was developed to design crop rotations and evaluate performance of crop rotations. This application is used to evaluate the sustainability of farming systems

The inter- and intra-observer reliability of a locomotion scoring scale for sheep

A seven point locomotion scoring scale, ranging from 0 = normal locomotion to 6 = unable to stand or move, has been developed. To test the between and within observer reliability of the scale, 65 movie clips of sheep with normal and varying degrees of abnormal locomotion were made. Three observers familiar with sheep locomotion were trained to read the movie clips. Thirty clips were randomly selected and used to test between and within observer agreement. There was high inter-(intra-class correlation coefficient [ICC] = 0.93, weighted kappa [κw] = 0.93) and intra-(ICC = 0.90, κw = 0.91) observer reliability, with no evidence of observer bias. The main between score differences were for scores 0 (normal) and 1 (uneven posture and shortened stride but no head movement). The results indicate that the locomotion scoring scale using groups of defined observations for each point on the scale was reliable and may be a useful research tool to identify and monitor locomotion in individual sheep when used by trained observers

Band gaps in incommensurable graphene on hexagonal boron nitride

Devising ways of opening a band gap in graphene to make charge-carrier masses finite is essential for many applications. Recent experiments with graphene on hexagonal boron nitride (h-BN) offer tantalizing hints that the weak interaction with the substrate is sufficient to open a gap, in contradiction of earlier findings. Using many-body perturbation theory, we find that the small observed gap is what remains after a much larger underlying quasiparticle gap is suppressed by incommensurability. The sensitivity of this suppression to a small modulation of the distance separating graphene from the substrate suggests ways of exposing the larger underlying gap