Investigation of external refrigeration systems for long term cryogenic storage Final report

Data on external refrigeration systems for space storage of cryogens for long period

Investigation of external refrigeration systems for long-term cryogenic storage

Evaluation of cryogenic refrigeration systems for space application

SIRTF Telescope Instrument Changeout and Cryogen Replenishment (STICCR) Study

The Space Infrared Telescope Facility (SIRTF) is a long-life cryogenically cooled space-based telescope for infrared astronomy from 2 to 700 micrometers. SIRTF is currently under study by NASA-ARC (Reference AP) and planned for launch in approximately the mid 1990s. SIRTF will operate as a multiuser facility, initially carrying three instruments at the focal plane. It will be cooled to below 2 K by superfluid liquid helium to achieve radiometric sensitivity limited only by the statistical fluctuations in the natural infrared background radiation over most of its spectral range. The lifetime of the mission will be limited by the lifetime of the liquid helium supply, and baseline is currently to be 2 years. The telescope changes required to allow in-space replenishment of the 4,000-L superfluid helium tank was investigated. A preliminary design for the space services equipment was also developed. The impacts of basing the equipment and servicing on the space station were investigated. Space replenishment and changeout of instruments required changes to the telescope design. Preliminary concepts are presented

Mechanically reinforced MgB2 wires and tapes with high transport currents

Monofilamentary MgB2-wires with a 2- or 3-component sheath containing mechanical reinforcing stainless steel (SS) were prepared and characterized. In direct contact to the superconductor Nb, Ta or Fe was used. For a selection of samples with a Fe and Fe/SS sheath, we investigated the transport critical current behaviour in magnetic fields changing systematically the geometrical shape from a round wire to a flat tape. A strong increase of the current densities in flat tapes was observed and possible reasons for this are discussed. Reinforcing the sheath in the outer layer with different amounts of stainless steel leads to a systematic field dependent decrease of the transport critical current density with increasing steel amount. This is an indication for a pre-stress induced degradation of the critical currents in MgB2 wires and first Ic-stress-strain experiments seem to confirm this observation and interpretation.Comment: 12 pages, 5 figures. Submitted to Physica C (Proceedings of EUCAS 2001

Emergence of daptomycin resistance in daptomycin-naïve rabbits with methicillin-resistant Staphylococcus aureus prosthetic joint infection is associated with resistance to host defense cationic peptides and mprF polymorphisms.

BackgroundPrevious studies of both clinically-derived and in vitro passage-derived daptomycin-resistant (DAP-R) Staphylococcus aureus strains demonstrated the coincident emergence of increased DAP MICs and resistance to host defense cationic peptides (HDP-R).MethodsIn the present investigation, we studied a parental DAP-susceptible (DAP-S) methicillin-resistant Staphylococcus aureus (MRSA) strain and three isogenic variants with increased DAP MICs which were isolated from both DAP-treated and DAP-untreated rabbits with prosthetic joint infections. These strains were compared for: in vitro susceptibility to distinct HDPs differing in size, structure, and origin; i.e.; thrombin-induced platelet microbicidal proteins [tPMPs] and human neutrophil peptide-1 [hNP-1]; cell membrane (CM) phospholipid and fatty acid content; CM order; envelope surface charge; cell wall thickness; and mprF single nucleotide polymorphisms (SNPs) and expression profiles.ResultsIn comparison with the parental strain, both DAP-exposed and DAP-naive strains exhibited: (i) significantly reduced susceptibility to each HDP (P<0.05); (ii) thicker cell walls (P<0.05); (iii) increased synthesis of CM lysyl-phosphatidylglycerol (L-PG); (iv) reduced content of CM phosphatidylglycerol (PG); and (v) SNPs within the mprF locus No significant differences were observed between parental or variant strains in outer CM content of L-PG, CM fluidity, CM fatty acid contents, surface charge, mprF expression profiles or MprF protein content. An isolate which underwent identical in vivo passage, but without evolving increased DAP MICs, retained parental phenotypes and genotype.ConclusionsTHESE RESULTS SUGGEST: i) DAP MIC increases may occur in the absence of DAP exposures in vivo and may be triggered by organism exposure to endogenous HDPs: and ii) gain-in-function SNPs in mprF may contribute to such HDP-DAP cross-resistance phenotypes, although the mechanism of this relationship remains to be defined

Handbook of external refrigeration systems for long term cryogenic storage

Handbook of external refrigeration systems for long term cryogenic storag