11 research outputs found
Strongly Enhanced Thermal Stability of Crystalline Organic Thin Films Induced by Aluminum Oxide Capping Layers
We show that the thermal stability of thin films of the organic semiconductor
diindenoperylene (DIP) can be strongly enhanced by aluminum oxide capping
layers. By thermal desorption spectroscopy and in-situ X-ray diffraction we
demonstrate that organic films do not only stay on the substrate, but even
remain crystalline up to 460C, i.e. 270 deg. above their desorption point for
uncapped films (190C). We argue that this strong enhancement of the thermal
stability compared to uncapped and also metal-capped organic layers is related
to the very weak diffusion of aluminum oxide and the structurally well-defined
as-grown interfaces. We discuss possible mechanisms for the eventual breakdown
at high temperatures.Comment: 5 pages, 4 figures, submitted to Adv. Mat., for further information
see http://www.physchem.ox.ac.uk/~f
Electron-Beam-Induced Antiphase Boundary Reconstructions in a ZrO<sub>2</sub>‑LSMO Pillar-Matrix System
The availability
of aberration correctors for the probe-forming lenses makes simultaneous
modification and characterization of materials down to atomic scale
inside a transmission electron microscopy (TEM) realizable. In this
work, we report on the electron-beam-induced reconstructions of three
types of antiphase boundaries (APBs) in a probe-aberration-corrected
TEM. With the utilization of high-angle annular dark-field scanning
transmission electron microscopy (STEM), annular bright-field STEM,
and electron energy-loss spectroscopy, the motion of both heavy element
Mn and light element O atomic columns under moderate electron beam
irradiation are revealed at atomic resolution. Besides, Mn segregated
in the APBs was observed to have reduced valence states which can
be directly correlated with oxygen loss. Charge states of the APBs
are finally discussed on the basis of these experimental results.
This study provides support for the design of radiation-engineering
solid-oxide fuel cell materials
Titanium–silicon oxide film structures for polarization-modulated infrared reflection absorption spectroscopy
miR-7a regulation of Pax6 controls spatial origin of forebrain dopaminergic neurons.
International audienceIn the postnatal and adult mouse forebrain, a mosaic of spatially separated neural stem cells along the lateral wall of the ventricles generates defined types of olfactory bulb neurons. To understand the mechanisms underlying the regionalization of the stem cell pool, we focused on the transcription factor Pax6, a determinant of the dopaminergic phenotype in this system. We found that, although Pax6 mRNA was transcribed widely along the ventricular walls, Pax6 protein was restricted to the dorsal aspect. This dorsal restriction was a result of inhibition of protein expression by miR-7a, a microRNA (miRNA) that was expressed in a gradient opposing Pax6. In vivo inhibition of miR-7a in Pax6-negative regions of the lateral wall induced Pax6 protein expression and increased dopaminergic neurons in the olfactory bulb. These findings establish miRNA-mediated fine-tuning of protein expression as a mechanism for controlling neuronal stem cell diversity and, consequently, neuronal phenotype