Absolute Differential Positronium-Formation Cross Sections.

The first absolute experimental determinations of the differential cross sections for the formation of ground-state positronium are presented for He, Ar, H2, and CO2 near 0°. Results are compared with available theories. The ratio of the differential and integrated cross sections for the targets exposes the higher propensity for forward emission of positronium formed from He and H2.

PP021 Outcomes for adolescent women and their pregnancies in greater Western Sydney.

INTRODUCTION: Hypertensive disorders in pregnancy (HDP) are a common complication of pregnancy. It is widely believed that this is a more common complication of adolescent pregnancies. Adolescent pregnancies are generally primiparous and result in earlier delivery, and these factors put them at a greater risk of preeclampsia. However, the generally lower blood pressure of the group should act as a protective measure against this. OBJECTIVES: The aim of this investigation was to compare the adolescent age group (maternal age <20years at time of recruitment) to those in the 20-34years age group in terms of their change in blood pressure and diagnosis of HDP and preeclampsia. Immediate obstetric outcomes (gestation at delivery, birthweight and mode of delivery) were also compared. METHODS: Questionnaires were administered to pregnant women at Campbelltown and Liverpool hospitals as part of a much broader study looking at sleep disordered breathing in pregnancy. Data collected included demographic information, pregnancy blood pressure readings, pregnancy complications, delivery type and neonatal outcomes. Adolescents (Group 1 age <20years) were compared to older women (Group 2 aged 20-34years) utilizing Student's t-tests analysed with IBM SPSS v.19™. RESULTS: Results were available on 2306 women, 108 in Group 1 and 2198 in Group 2. Adolescents had a lower booking systolic blood pressure (105mmHg and 109mmHg, p<0.005) and diastolic blood pressure (63mmHg and 65mmHG, p<0.002) than older women respectively. There was no statistical difference in the highest recorded systolic blood pressure antenatally (119mmHg and 121mmHg, p<0.06) nor the highest recorded diastolic blood pressure readings between Groups 1 and 2 respectively (74mmHg and 75mmHg, p=0.6). There was no difference in the rates of HDP between the groups (8.3% and 8.2%, p=0.8) nor the rates of preeclampsia (2.8% and 2.9%, p=1.0). CONCLUSION: Although adolescents have lower booking blood pressures than their older peers, their highest antenatal blood pressure readings are similar and they have the same incidence of HDP and preeclampsia.

Fragmentation of positronium in collision with He atoms.

The absolute cross section for the fragmentation of positronium in collision with He atoms has been measured. The results are compared with available theories. The longitudinal energy distributions of positrons resulting from fragmentation have also been determined and are found to display a peak situated just below half the residual energy. This is suggestive of the occurrence of "electron loss to the continuum" in which the two residual charged particles lie in a low relative-velocity Coulomb-continuum state.