Measurement of heat flux in multi-layer insulated helium cryostats after loss of insulating vacuum

The dimensioning of pressure relief devices (PRD) for cryogenic pressure equipment requires knowledge on the heat input at the maximum credible incident. In helium cryostats, this situation is typically defined by the loss of insulating vacuum (LIV), where the heat load is induced by desublimation and condensation of atmospheric air on the cryogenic surface. This surface is often covered with multi-layer insulation (MLI) in order to reduce the thermal radiation heat load in standard operation. During loss of insulating vacuum, the MLI represents a diffusive barrier for the air to reach the cryogenic surface, reducing the heat flux as well. Experimental reference data for the heat flux in case of LIV exist mainly for blank surfaces; only few data are published for MLI-covered helium surfaces. Therefore, the effect has been investigated in the cryogenic safety test facility PICARD at KIT. This paper presents the results of venting experiments carried out with different numbers of layers and different types of MLI

A novel family of highly conserved antigens that induce protective immunity against Staphylococcus aureus

ABSTRACT In the human pathogen Staphylococcus aureus there exists an enormous diversity of proteins containing domains of unknown function (DUF). Here, we characterized the family of conserved staphylococcal antigens (Csa) classified as DUF576 and taxonomically restricted to S. aureus. The 18 Csa paralogs in S. aureus Newman are highly similar at the sequence level yet were found to be expressed in multiple cellular localizations. Extracellular Csa1A was shown to be post-translationally processed and released. Molecular interaction studies revealed a dynamic complex formation of Csa1A with several Csa paralogs regulated by metal ions. Interestingly, the paralogs presented various modes of interaction with Csa1A, suggesting that the proteins are involved in the same cellular process in which each paralog might contribute with a particular role. The structures of Csa1A and Csa1B were determined by X-ray crystallography, unveiling a peculiar structure with limited structural similarity to other known proteins, confirming the uniqueness of this family. Since immunization with Csa proteins protected mice from lethal challenge with S. aureus, we propose these antigens as potential vaccine candidates