Geostrophic adjustment in a shallow-water numerical model as it relates to thermospheric dynamics

The theory of geostrophic adjustment and its application to the dynamics of the high latitude thermosphere have been discussed in previous papers based on a linearized treatment of the fluid dynamical equations. However, a linearized treatment is only valid for small Rossby numbers given by Ro = V/fL, where V is the wind speed, f is the local value of the Coriolis parameter, and L is a characteristic horizontal scale for the flow. For typical values in the auroral zone, the approximation is not reasonable for wind speeds greater than 25 m/s or so. A shallow-water (one layer) model was developed that includes the spherical geometry and full nonlinear dynamics in the momentum equations in order to isolate the effects of the nonlinearities on the adjustment process. A belt of accelerated winds between 60 deg and 70 deg latitude was used as the initial condition. The adjustment process was found to proceed as expected from the linear formulation, but that an asymmetry between the response for an eastward and westward flow results from the nonlineawr curvature (centrifugal) terms. In general, the amplitude of an eastward flowing wind will be less after adjustment than a westward wind. For instance, if the initial wind velocity is 300 m/s, the linearized theory predicts a final wind speed of 240 m/s, regardless of the flow direction. However, the nonlinear curvature terms modify the response and produce a final wind speed of only 200 m/s for an initial eastward wind and a final wind speed of almost 300 m/s for an initial westward flow direction. Also, less gravity wave energy is produced by the adjustment of the westward flow than by the adjustment of the eastward flow. The implications are that the response of the thermosphere should be significantly different on the dawn and dusk sides of the auroral oval. Larger flow velocities would be expected on the dusk side since the plasma will accelerate the flow in a westward direction in that sector

EU-Norsewind : Investigation of flow distortion effects on offshore instrumentation

In 2008 the EC programme NORSEWInD kicked off with a mission to deliver high quality offshore wind speed data for the wind industry. The aim of the project is to deliver offshore wind speed data to the wind industry by measuring offshore wind speed data from remote sensing instruments (LiDAR) on off shore platforms. This work reports on the techniques used to assesses the interference effects of the various mounting platforms on the measured wind speed data

Characteristics of Cherenkov Radiation in Naturally Occuring Ice

We revisit the theory of Cherenkov radiation in uniaxial crystals. Historically, a number of flawed attempts have been made at explaining this radiation phenomenon and a consistent error-free description is nowhere available. We apply our calculation to a large modern day telescope - IceCube. Being located at the Antarctica, this detector makes use of the naturally occuring ice as a medium to generate Cherenkov radiation. However, due to the high pressure at the depth of the detector site, large volumes of hexagonal ice crystals are formed. We calculate how this affects the Cherenkov radiation yield and angular dependence. We conclude that the effect is small, at most about a percent, and would only be relevant in future high precision instruments like e.g. Precision IceCube Next Generation Upgrade (PINGU). For radio-Cherenkov experiments which use the presence of a clear Cherenkov cone to determine the arrival direction, any variation in emission angle will directly and linearly translate into a change in apparent neutrino direction. In closing, we also describe a simple experiment to test this formalism, and calculate the impact of anisotropy on light-yields from lead tungstate crystals as used, for example, in the CMS calorimeter at the CERN LHC

Discrete Optimization for Interpretable Study Populations and Randomization Inference in an Observational Study of Severe Sepsis Mortality

Motivated by an observational study of the effect of hospital ward versus intensive care unit admission on severe sepsis mortality, we develop methods to address two common problems in observational studies: (1) when there is a lack of covariate overlap between the treated and control groups, how to define an interpretable study population wherein inference can be conducted without extrapolating with respect to important variables; and (2) how to use randomization inference to form confidence intervals for the average treatment effect with binary outcomes. Our solution to problem (1) incorporates existing suggestions in the literature while yielding a study population that is easily understood in terms of the covariates themselves, and can be solved using an efficient branch-and-bound algorithm. We address problem (2) by solving a linear integer program to utilize the worst case variance of the average treatment effect among values for unobserved potential outcomes that are compatible with the null hypothesis. Our analysis finds no evidence for a difference between the sixty day mortality rates if all individuals were admitted to the ICU and if all patients were admitted to the hospital ward among less severely ill patients and among patients with cryptic septic shock. We implement our methodology in R, providing scripts in the supplementary material

Production of antibiotic-free pigs – tools and results

The present paper describes preliminary results from a Danish project with production of antibiotic-free pigs. The project herd is a traditional Danish 500 sow herd with weaned pigs on the same site. 1/3 of the pigs are kept until slaughter on an adjacent farm and remaining pigs are sold to local finishing producers. Before initiation of the project, the herd had a consumption of antibiotics around 50% of the threshold given by the Danish authorities. However, the farmer took the challenge to produce pigs without any antibiotics at all, with the initial goal to deliver 50% antibiotic-free pigs for slaughter. The measures implemented were a stronger focus on management and vaccination against Lawsonia intracellularis on top of Mycoplasma hyopneumoniae and PCV2 vaccination. The results are promising: In the first 6 months of the project, the herd has not only experienced reduced use of antibiotics, but also an increased productivity. The monthly prescriptions of antibiotics were lowered from 2.15 to 1.86 Animal Daily Doses (ADD) per 100 pigs per day in the sow herd and from 8.30 to 4.19 ADD/100 pigs/day in the weaners. Compared to the previous year, the piglet mortality in the farrowing unit dropped by 2.5 %, the average daily weight gain in weaners increased by 34 g/day and the feed conversion rate dropped by 0.15 FE/kg. Data from finishers are not yet available