RESUMO
In this paper, we describe the performance of the Los Alamos spallation-driven solid-deuterium ultra-cold neutron (UCN) source. Measurements of the cold neutron flux, the very low energy neutron production rate, and the UCN rates and density at the exit from the biological shield are presented and compared to Monte Carlo predictions. The cold neutron rates compare well with predictions from the Monte Carlo code MCNPX and the UCN rates agree with our custom UCN Monte Carlo code. The source is shown to perform as modeled. The maximum delivered UCN density at the exit from the biological shield is 52(9) UCN/cc with a solid deuterium volume of ~1500 cm(3).
RESUMO
We present the first measurements of the survival time of ultracold neutrons (UCNs) in solid deuterium (SD2). This critical parameter provides a fundamental limitation to the effectiveness of superthermal UCN sources that utilize solid ortho-deuterium as the source material. These measurements are performed utilizing a SD2 source coupled to a spallation source of neutrons, providing a demonstration of UCN production in this geometry and permitting systematic studies of the influence of thermal up-scatter and contamination with para-deuterium on the UCN survival time.
RESUMO
To study the possibility that circulating endogenous inhibitor(s) of prostaglandin synthesis (EIPS) represent a control mechanism for prostaglandin production during human pregnancy and parturition, we have measured maternal plasma EIPS levels serially during pregnancy, labour and the puerperium, and cross-sectionally during the course of labour. No significant trends were detected in relation to pregnancy or parturition. These results do not support a role for maternal plasma EIPS in the control of prostaglandin production during human pregnancy or labour.
