Excitation power dependent population pathways and absolute quantum yields of upconversion nanoparticles in different solvents.

The rational design of brighter upconversion nanoparticles (UCNPs) requires a better understanding of the radiationless deactivation pathways in these materials. Here, we demonstrate the potential of excitation power density (P)-dependent studies of upconversion (UC) luminescence intensities, slope factors, and absolute quantum yields (ΦUC) of popular ß-NaYF4:20% Yb3+,2% Er3+ UCNPs of different surface chemistries in organic solvents, D2O, and water as a tool to gain deeper insight into the UC mechanism including population and deactivation pathways particularly of the red emission. Our measurements, covering a P regime of three orders of magnitude, reveal a strong difference of the P-dependence of the ratio of the green and red luminescence bands (Ig/r) in water and organic solvents and P-dependent population pathways of the different emissive energy levels of Er3+. In summary, we provide experimental evidence for three photon processes in UCNPs, particularly for the red emission. Moreover, we demonstrate changes in the excited population dynamics via bi- and triphotonic processes dependent on the environment, surface chemistry, and P, and validate our findings theoretically.

[Unusual complications at birth in a stillborn with spinal muscular atrophy]. / Ungewöhnliche Geburtskomplikation bei spinaler progressiver Muskelatrophie.

A report is given on a premature stillborn with severe congenital spinal muscular atrophy, arthrogryposis multiplex congenita and hydrops fetalis. During delivery the head was spontaneously pulled off. The neuromuscular disease was the cause of this unusual complication. No alterations of collagenous fibres were found by light and electron microscopy in dermis, aorta or in the Achilles tendon. The hydrops fetalis was not of immunological nature.

[Effectiveness of clinical action in treatment of premature birth problems (author's transl)]. / Zur Wirksamkeit klinischer Massnahmen bei der Behandlung der Frühgeburtlichkeit.

The effectiveness of clinical action on a general premature birth situation was studied against the background of 21, 244 childbirths (twins and stillbirths included), in the District of Erfurt, between 1974 and 1979. Clinical attention was considerably stepped up in all cases of imminent premature birth. Steps taken included hospitalisation, sedation, medicamentous tocolysis, cerclage, maturity induction, and organisational measures. Many more people than ever before were called in for action. Yet, no significant change was achieved, neither in terms of the absolute premature birth rate nor in restricting such problems to higher age or weight groups. -- Sizable reduction of perinatal mortality in the period under review was in no way related to measures to reduce the premature birth rate, but it was rather attributable to improvement in prenatal and intranatal diagnosis and in postnatal care. -- The conclusion is that action outside hospital should be intensified.

[Dexamethasone for prophylaxis against respiratory distress syndrome - progress report (author's transl)]. / Prophylaxe des Atemnotsyndroms mit dexamethason - ein Erfahrungsbericht.

Reported in this paper is experience obtained from antenatal RDS prophylaxis, using 4 mg of dexamethasone, on three consecutive days. Treatment was applied to 202 premature newborns, and these were compared with 252 untreated controls born on same term. Good success with statistical significance was recordable only from comparison between the two complete groups. - The mother's situations quite often were complicated by outbreak of infections in the wake of obstetric intervention for premature rupture of the amniotic sac. In view of the partial success of dexamethasone prophylaxis and with no alternative to glucocorticoid treatment so far available, continuation of RDS prophylaxis, using dexamethasone, is recommended, however, with strictest observance of contraindications and with higher doses.