Unintended conceptions leading to wanted pregnancies - an integral perspective on pregnancy acceptance from a mixed-methods study in Germany.

OBJECTIVE: The study examines the differences within unintended first pregnancies in the life course of 20-44 year old women. Special attention is paid to response and pregnancy acceptance. Exploring determinants and dynamics, this study will contribute to a better understanding of 'happiness with an unintended pregnancy', as this is assumed to be indicative of fewer social problems and health risks. METHODS: Retrospective survey data on first unintended pregnancies carried to term (n = 2,306) were analysed using bivariate analysis. Qualitative analysis of the narrations of such pregnancies (n = 59) used the technique of comparing cases. Standardised and qualitative data are available for first intended or aborted pregnancies as comparison groups. All data were collected from the cross-sectional mixed-methods study of 'Women's Lives: Family Planning in the Life Course' (2012-2018, Federal Centre of Health Education, Germany). RESULTS: Two-fifth of the unintended pregnancies carried to term were '(very) welcome'. Pregnancy intention, contraceptive use, living conditions, and attitudes had a significant impact. Five pathways of acceptance - sooner or later, more easy or hard to achieve - were identified in the qualitative data. CONCLUSION: Unintended pregnancies form a continuum ranging from readily accepted 'happy' pregnancies to pregnancies hard to accept. A new measure should also include postconception acceptance, besides preconception desire.

Decoupling the Contributions of ZnO and Silica in the Characterization of Industrially-Mixed Filled Rubbers by Combining Small Angle Neutron and X-Ray Scattering.

Scattering techniques with neutrons and X-rays are powerful methods for the investigation of the hierarchical structure of reinforcing fillers in rubber matrices. However, when using only X-ray scattering, the independent determination of the filler response itself sometimes remains an issue because of a strong parasitic contribution of the ZnO catalyst and activator in the vulcanization process. Microscopic characterization of filler-rubber mixtures even with only catalytic amounts of ZnO is, therefore, inevitably complex. Here, we present a study of silica aggregates dispersed in an SBR rubber in the presence of the catalyst and show that accurate partial structure factors of both components can be determined separately from the combination of the two scattering probes, neutrons, and X-rays. A unique separation of the silica filler scattering function devoid of parasitic catalyst scattering becomes possible. From the combined analysis, the catalyst contribution is determined as well and results to be prominent in the correction scheme. The experimental nano-structure of the ZnO after the mixing process as the by-product of the scattering decomposition was found also to be affected by the presence or absence of silica in the rubber mixture, correlated with the shear forces in the mixing and milling processes during sample preparation. The presented method is well suited for studies of novel dual filler systems.

Rapid nanoparticle self-assembly at elevated temperatures.

We demonstrate that rapid nanoparticle self-assembly is possible in organic solvents if the temperature is above the melting point of the particles' ligand shell. Flow experiments coupled to small-angle X-ray scattering reveal the agglomeration kinetics and agglomerate structures of alkylthiol-coated gold nanoparticles at different temperatures, interparticle potentials, and times. Our experiments allow to discriminate between the effects of long-range and short-range interactions on self-assembly: crystalline agglomerates formed for a wide range of potentials, but only at temperatures where the short-ranged mobility was sufficient. Rapid superlattice formation in less than 3 s was observed for strongly attractive potentials at high temperatures, implying an assembly rate that is sufficient for large-scale material synthesis. Strong attraction between the particles did not impede high-quality self-assembly when short-ranged mobility was provided by ligands above a specific temperature.

Spinning Hierarchical Gold Nanowire Microfibers by Shear Alignment and Intermolecular Self-Assembly.

Hierarchical structures lend strength to natural fibers made of soft nanoscale building blocks. Intermolecular interactions connect the components at different levels of hierarchy, distribute stresses, and guarantee structural integrity under load. Here, we show that synthetic ultrathin gold nanowires with interacting ligand shells can be spun into biomimetic, free-standing microfibers. A solution spinning process first aligns the wires, then lets their ligand shells interact, and finally converts them into a hierarchical superstructure. The resulting fiber contained 80 vol % organic ligand but was strong enough to be removed from the solution, dried, and mechanically tested. Fiber strength depended on the wire monomer alignment. Shear in the extrusion nozzle was systematically changed to obtain process-structure-property relations. The degree of nanowire alignment changed breaking stresses by a factor of 1.25 and the elongation at break by a factor of 2.75. Plasma annealing of the fiber to form a solid metal shell decreased the breaking stress by 65%.

Self-assembly of gold nanoparticles at the oil-vapor interface: from mono- to multilayers.

Alkylthiol-coated gold nanoparticles spontaneously segregate from dispersion in toluene to the toluene-vapor interface. We show that surface tension drops during segregation with a rate that depends on particle concentration. Mono- and multilayers of particles form depending on particle concentration, time, and temperature. X-ray reflectometry indicates fast monolayer formation and slow multilayer formation. A model that combines diffusion-limited segregation driven by surface energy and heterogeneous agglomeration driven by dispersive van der Waals particle interactions is proposed to describe film formation.