Higher order liquid crystalline structure in low-polydispersity DEH-PPV

Monodisperse, low molecular weight poly(2,5-di(2'-ethylhexyloxy)-1,4-phenylenevinylene) (DEH-PPV) demonstrates significantly better structural order than polydisperse PPVs. Since optical and electrical properties of polymer electronics are closely related to the structure and morphology of the active layer, morphological control is important for the fabrication of PPV-based devices. Soluble, monodisperse DEH-PPVs with a range of molecular weights showed a sequence of transitions through crystalline, smectic, nematic, and isotropic phases upon heating, and the transition temperatures increased sharply with increasing molecular weight. The layer spacing of the smectic phase is in good agreement with the length of a PPV molecule. The Maier-Saupe parameter for this polymeric system is estimated, and both energetic and entropic contributions are found to be important in describing the liquid crystalline interaction. Thin films revealed that the PPV molecules ordered into thermally stable layers a single molecule thick. The layers arranged into grains that were aligned by shearing. The orientation of molecules within the aligned layers was characterized by polarization-dependent X-ray absorption spectroscopy, and the PPV molecular axis was found to align parallel to the shear direction while the layers aligned perpendicular to the shear direction. Low polydispersity is critical to forming these types of highly ordered structures, and an analogous PPV sample with polydispersity greater than 5 does not form smectic layers

Element-Specific Magnetization Dynamics of Complex Magnetic Systems Probed by Ultrafast Magneto-Optical Spectroscopy

The vision to manipulate and control magnetism with light is driven on the one hand by fundamental questions of direct and indirect photon-spin interactions, and on the other hand by the necessity to cope with ever growing data volumes, requiring radically new approaches on how to write, read and process information. Here, we present two complementary experimental geometries to access the element-specific magnetization dynamics of complex magnetic systems via ultrafast magneto-optical spectroscopy in the extreme ultraviolet spectral range. First, we employ linearly polarized radiation of a free electron laser facility to demonstrate decoupled dynamics of the two sublattices of an FeGd alloy, a prerequisite for all-optical magnetization switching. Second, we use circularly polarized radiation generated in a laboratory-based high harmonic generation setup to show optical inter-site spin transfer in a CoPt alloy, a mechanism which only very recently has been predicted to mediate ultrafast metamagnetic phase transitions

Development and validation of novel clinical endpoints in intermediate age-related macular degeneration in MACUSTAR

Background. Currently, no validated clinical endpoints for treatment studies exist for intermediate age-related macular degeneration (iAMD). Objective. The European MACUSTAR study aims to develop and clinically validate adequate clinical endpoints for future treatment studies in iAMD and to identify early determinants of disease progression to late stage AMD. Material and methods. The MACUSTAR study protocol was developed by an international consortium of researchers from academia, the pharmaceutical industry and medical device companies. The MACUSTAR project is funded by the Innovative Medicines Initiative 2 (IMI2) of the European Union. Results. The MACUSTAR study consists of a cross-sectional and a longitudinal investigation. A total of 750 subjects with early, intermediate and late AMD as well as control subjects with no signs of AMD will be included with a follow-up period of 3 years. Overall, 20 European study centers are involved. Conclusion. The MACUSTAR project will generate large high-quality datasets, which will allow clinical validation of novel endpoints for future interventional trials in iAMD. The aim is that these endpoints will be accepted as suitable for medication approval studies by the regulatory authorities and that understanding of the disease process will be improved

Elemental compositions of comet 81P/Wild 2 samples collected by Stardust

We measured the elemental compositions of material from 23 particles in aerogel and from residue in seven craters in aluminum foil that was collected during passage of the Stardust spacecraft through the coma of comet 81P/Wild 2. These particles are chemically heterogeneous at the largest size scale analyzed (180 ng). The mean elemental composition of this Wild 2 material is consistent with the CI meteorite composition, which is thought to represent the bulk composition of the solar system, for the elements Mg, Si, Mn, Fe, and Ni to 35%, and for Ca and Ti to 60%. The elements Cu, Zn, and Ga appear enriched in this Wild 2 material, which suggests that the CI meteorites may not represent the solar system composition for these moderately volatile minor elements