Hydrodynamic behavior in expanding thermal clouds of Rb-87

We study hydrodynamic behavior in expanding thermal clouds of Rb-87 released from an elongated trap. At our highest densities the mean free path is smaller than the radial size of the cloud. After release the clouds expand anisotropically. The cloud temperature drops by as much as 30%. This is attributed to isentropic cooling during the early stages of the expansion. We present an analytical model to describe the expansion and to estimate the cooling. Important consequences for time-of-flight thermometry are discussed.Comment: 7 pages with 2 figure

GOBI and OASIS - A concept and its realization for model-based situation descriptions compliant to ISO 26262

With the introduction of ISO 26262 the awareness for safety in automotive systems has relumed. The first step in safety engineering is the Hazard Analysis and Risk Assessment (HRA). The goal of this step is to define Safety Goals that express the risk reduction necessary. Because all following safety engineering tasks rely on HRA's results it is crucial to ensure completeness and correctness of the Safety Goals. The challenge in HRA is to investigate system failures occurring along with certain environmental conditions. Especially when we talk about the latter, the environmental conditions. It is difficult to decide on completeness of environmental conditions. In practice this becomes evident in the observation that HRAs are mostly based on creativity techniques, which produce an informal representation of the analysis information (usually an Excel sheet). SAHARA, our Systematic Approach for Hazard Analysis and Risk Assessments, addresses the challenge of formalizing HR As in general. In this paper however, we will focus on the completeness challenge of environmental information. In ISO 26262 the parameter concerning the description of operational situations and environmental conditions is called Exposure parameter. The way to more formal and therefore complete situation descriptions is a two step approach. Therefore we describe in this paper GOBI, our conceptual model of necessary HRA information and OASIS, the concrete instantiation and implementation of GOBI

Bose-Einstein condensation into nonequilibrium states studied by condensate focusing

10.1103/PhysRevLett.89.270404PHYSICAL REVIEW LETTERS8927270404