Deferred and deterred: a review of literature on the impact of deferrals on blood donors

Background: Potential blood donors can be deferred due to concerns about the impact of the donation on their health or the safety of the blood supply. To date, we lack a comprehensive review of the impact of deferrals on donors and how to mitigate adverse effects. Aims: The aim of this review was to describe the available literature on deferrals, with a focus on the impact of deferrals on donors’ subsequent behaviour, potential reasons for impact and the effectiveness of strategies to improve deferral processes and facilitate donor return. Method: A narrative review of the literature on blood donation deferrals was undertaken. Results: Deferral rates vary widely across different contexts, with female, younger, first time and minority donors more likely to be ineligible to donate. There is clear evidence that deferrals impact on future donation behaviour, particularly for those deferred at their first donation attempt. Deferral has a negative emotional impact if the deferral is permanent or related to positive test results, while emotions experienced at the time of a temporary deferral are related to donors’ willingness to return. Conclusion: An understanding of the impact of deferrals from the donor perspective provides key information to improve the blood centre practices. There is preliminary evidence of the effectiveness of strategies to retain donors, including enabling the ineligible donor to make an alternative contribution, providing clear information about the deferral, notifying the donor when they can return to donate and addressing practical barriers to return

Direct quartz-coesite transformation in shocked porous sandstone from Kamil Crater (Egypt)

Coesite, a high-pressure silica polymorph (pressure 3–10 GPa, temperature <3000 K), is a diagnostic feature of shock metamorphism associated with impact cratering on quartz-bearing target rocks. It is preserved as a metastable phase in sedimentary target rocks that experienced peak pressures in excess of ~10 GPa, where it typically occurs as intergranular polycrystalline aggregates of microcrystals embedded in silica glass known as “symplectic regions.” The presence of coesite in the symplectic regions of rocks experiencing shock conditions beyond the limits of the coesite stability field is a controversial issue. Through a combined scanning and transmission electron microscopy and Raman spectroscopy study of shocked quartzarenites from the 45-m-diameter Kamil Crater (southwest Egypt), we show that coesite in symplectic regions forms through direct subsolidus transformation from quartz, in contrast with the prevailing hypothesis for crystalline targets. The quartz-to-coesite transformation takes place during localized shock-wave reverberation at the beginning of the pore collapse process. Complete pore collapse generates the high temperature regimes responsible for the subsequent production of the embedding silica melts, in part at the expense of the previously formed coesite. This work documents the role of pore collapse in producing localized pressure-temperature-time gradients in shocked porous targets, as predicted by numerical models in the literature