Beifütterung von Ferkeln in freien Haltungssystemen

The digestive capacity of a piglet and the enzyme activity in the first weeks are aimed corresponding to the piglets requirements. Early provision of creep feed is necessary. The aim of the project was to study the feeding behaviour of piglets and sows during lactation in three different housing systems. In total data of 93 litters and 917 piglets were evaluated. The sows farrowed in either the Welser pen or the WelCon pen. They either remained in these systems until the end of lactation, or changed after 14 days to a multi-suckling system. The sows were fed ad libitum. Feed consumption was recorded weekly. The creep feeding started when piglet´s age reached 17 days on average. The feed supply for the piglets was dry and on the ground. Weight gain and feed consumption of piglets and sows were examined. In order to determine the length of stay of piglets and sows at the feeding place, video observation were performed. Only in the last suckling week the feed consumption of the piglets increased. Significant differences between the Welser pen, WelCon pen and multi-suckling system were found

Magnetically Driven Warping, Precession and Resonances in Accretion Disks

The inner region of the accretion disk onto a rotating magnetized central star (neutron star, white dwarf or T Tauri star) is subjected to magnetic torques which induce warping and precession of the disk. The origin of these torques lies in the interaction between the (induced) surface current on the disk and the horizontal magnetic field (parallel to the disk) produced by the inclined magnetic dipole. Under quite general conditions, there exists a magnetic warping instability in which the magnetic torque drives the disk plane away from the equatorial plane of the star toward a state where the disk normal vector is perpendicular to the spin axis. Viscous stress tends to suppress the warping instability at large radii, but the magnetic torque always dominates as the disk approaches the magnetosphere boundary. The magnetic torque also drives the tilted inner disk into retrograde precession around the stellar spin axis. Moreover, resonant magnetic forcing on the disk can occur which may affect the dynamics of the disk. The magnetically driven warping instability and precession may be related to a number observational puzzles, including: (1) Spin evolution (torque reversal) of accreting X-ray pulsars; (2) Quasi-periodic oscillations in low-mass X-ray binaries; (3) Super-orbital periods in X-ray binaries; (4) Photometric period variations of T Tauri stars.Comment: 39 pages including 1 ps figure; Published version; ApJ, 524, 1030-1047 (1999

Modeling of non-stationary accretion disks in X-ray novae A 0620-00 and GRS 1124-68 during outburst

We address the task of modeling soft X-ray and optical light curves of X-ray novae in the high/soft state. The analytic model of viscous evolution of an externally truncated accretion \alpha-disk is used. Relativistic effects near a Kerr black hole and self-irradiation of an accretion disk are taken into account. The model is applied to the outbursts of X-ray nova Monocerotis 1975 (A 0620-00) and X-ray nova Muscae 1991 (GRS 1124-68). Comparison of observational data with the model yields constraints on the angular momentum (the Kerr parameter) of the black holes in A 0620-00 and GRS 1124-68: 0.3-0.6 and \leq 0.4, and on the viscosity parameter \alpha of the disks: 0.7-0.95 and 0.55-0.75. We also conclude that the accretion disks should have an effective geometrical thickness 1.5-2 times greater than the theoretical value of the distance between the photometric layers.Comment: 12 pages, 11 figures, 1 table, accepted for publication in A&A (minor changens following the referee's comments, five references added

Foundations of Black Hole Accretion Disk Theory

This review covers the main aspects of black hole accretion disk theory. We begin with the view that one of the main goals of the theory is to better understand the nature of black holes themselves. In this light we discuss how accretion disks might reveal some of the unique signatures of strong gravity: the event horizon, the innermost stable circular orbit, and the ergosphere. We then review, from a first-principles perspective, the physical processes at play in accretion disks. This leads us to the four primary accretion disk models that we review: Polish doughnuts (thick disks), Shakura-Sunyaev (thin) disks, slim disks, and advection-dominated accretion flows (ADAFs). After presenting the models we discuss issues of stability, oscillations, and jets. Following our review of the analytic work, we take a parallel approach in reviewing numerical studies of black hole accretion disks. We finish with a few select applications that highlight particular astrophysical applications: measurements of black hole mass and spin, black hole vs. neutron star accretion disks, black hole accretion disk spectral states, and quasi-periodic oscillations (QPOs).Comment: 91 pages, 23 figures, final published version available at http://www.livingreviews.org/lrr-2013-

Auswirkungen des Abliegeverhaltens von Zuchtsauen auf die Höhe der Erdrückungsverluste auf biologisch geführten Betrieben

In this study the lying down behaviour of sows was analyzed to find out whether there are differences in the amount of crushed piglets per litter when sows show varying lying down behaviour. The lying down behaviour of the sows, litter size, number of stillborn piglets and number of dead piglets and cause of death during the weaning period were recorded. The data was collected on seven organic farms in Austria and on two agricultural research stations. It was shown that animals that lie down slowly crush fewer piglets than sows that let their hind quarter drop quickly to the floor