Columbus Surpassed: Biophysical Aspects of How Stingless Bees Place an Egg Upright on Their Liquid Food

The highly eusocial stingless bees (reviewed in [1, 2]) constitute a phylogenetically old group [3] within the Apidae. Probably related to this ancient origin is their mass provisioning of brood cells: they deposit all the food on which the larva will develop into the brood cell, prior to oviposition and subsequent closure of the cell. The other social members of the Apidae, the honeybees and the bumblebees, regularly visit the larvae in their cells to administer small amounts of liquid food at a time. This system is called progressive provisioning. Mass provisioning is practiced by almost all the other bees. However, while most of them have a solid type of larval food, the stingless bees produce a liquid food. In relation to this, their cylindrical brood cells are constructed vertically and are often arranged in horizontal combs. The food, regurgitated from the stomach, consists of a mixture of pollen, nectar, and glandular secretions [1, 2, 4]. After the workers have put this liquid food into the cell, the queen oviposits. Her egg, with its elongated shape, stands upright on the fluid

Test beam Characterizations of 3D Silicon Pixel detectors

3D silicon detectors are characterized by cylindrical electrodes perpendicular to the surface and penetrating into the bulk material in contrast to standard Si detectors with planar electrodes on its top and bottom. This geometry renders them particularly interesting to be used in environments where standard silicon detectors have limitations, such as for example the radiation environment expected in an LHC upgrade. For the first time, several 3D sensors were assembled as hybrid pixel detectors using the ATLAS-pixel front-end chip and readout electronics. Devices with different electrode configurations have been characterized in a 100 GeV pion beam at the CERN SPS. Here we report results on unirradiated devices with three 3D electrodes per 50 x 400 um2 pixel area. Full charge collection is obtained already with comparatively low bias voltages around 10 V. Spatial resolution with binary readout is obtained as expected from the cell dimensions. Efficiencies of 95.9% +- 0.1 % for tracks parallel to the electrodes and of 99.9% +- 0.1 % at 15 degrees are measured. The homogeneity of the efficiency over the pixel area and charge sharing are characterized.Comment: 5 pages, 7 figure

Magnetic Structure in Fe/Sm-Co Exchange Spring Bilayers with Intermixed Interfaces

The depth profile of the intrinsic magnetic properties in an Fe/Sm-Co bilayer fabricated under nearly optimal spring-magnet conditions was determined by complementary studies of polarized neutron reflectometry and micromagnetic simulations. We found that at the Fe/Sm-Co interface the magnetic properties change gradually at the length scale of 8 nm. In this intermixed interfacial region, the saturation magnetization and magnetic anisotropy are lower and the exchange stiffness is higher than values estimated from the model based on a mixture of Fe and Sm-Co phases. Therefore, the intermixed interface yields superior exchange coupling between the Fe and Sm-Co layers, but at the cost of average magnetization.Comment: 16 pages, 6 figures and 1 tabl