Anion Distribution, Structural Distortion, and Symmetry-Driven Optical Band Gap Bowing in Mixed Halide Cs2SnX6 Vacancy Ordered Double Perovskites.

Mixed anion compounds in the Fm3̅m vacancy ordered perovskite structure were synthesized and characterized experimentally and computationally with a focus on compounds where A = Cs+. Pure anion Cs2SnX6 compounds were formed with X = Cl, Br, and I using a room temperature solution phase method. Mixed anion compounds were formed as solid solutions of Cs2SnCl6 and Cs2SnBr6 and a second series from Cs2SnBr6 and Cs2SnI6. Single phase structures formed across the entirety of both composition series with no evidence of long-range anion ordering observed by diffraction. A distortion of the cubic A2BX6 structure was identified in which the spacing of the BX6 octahedra changes to accommodate the A site cation without reduction of overall symmetry. Optical band gap values varied with anion composition between 4.89 eV in Cs2SnCl6 to 1.35 eV in Cs2SnI6 but proved highly nonlinear with changes in composition. In mixed halide compounds, it was found that lower energy optical transitions appeared that were not present in the pure halide compounds, and this was attributed to lowering of the local symmetry within the tin halide octahedra. The electronic structure was characterized by photoemission spectroscopy, and Raman spectroscopy revealed vibrational modes in the mixed halide compounds that could be assigned to particular mixed halide octahedra. This analysis was used to determine the distribution of octahedra types in mixed anion compounds, which was found to be consistent with a near-random distribution of halide anions throughout the structure, although some deviations from random halide distribution were noted in mixed iodide-bromide compounds, where the larger iodide anions preferentially adopted trans configurations

Der Blick zum Säugling : gestört durch Smartphones?

Bis heute gibt es kaum Studien, die den Einfluss der elterlichen Smartphonenutzung in Bezug auf ihre Säuglinge systematisch untersucht haben. Studien mit älteren Kindern lassen jedoch vermuten, dass die elterliche Nutzung nicht spurlos an den Kindern und der Eltern-Kind-Interaktion vorbeigeht. Hebammen sind hier gefragt, Eltern frühzeitig bzgl. der Nutzung digitaler Medien zu beraten

Sequential Analysis of Livestock Herding Dog and Sheep Interactions

Livestock herding dogs are crucial contributors to Australian agriculture. However, there is a dearth of empirical studies of the behavioural interactions between dog and livestock during herding. A statistical approach that may reveal cause and effect in such interactions is lag sequential analysis. Using 48 video recordings of livestock herding dogs and sheep in a yard trial competition, event-based (time between behaviours is irrelevant) and time-based (time between behaviours is defined) lag sequential analyses identified several significant behavioural interactions (adjusted residuals greater than 2.58; the maximum likelihood-ratio chi-squared statistic for all eight contingency tables identified all sequences as highly significant (p \u3c 0.001)). These sequences were: The dog ceasing all movement followed by the sheep also ceasing movement; the dog chasing the sheep and a group of sheep escaping the main flock; a single sheep escaping the flock and the dog chasing; sheep initiating movement followed by the dog following; foot-stamping followed by the dog ceasing all movement; and, foot-stamping by the sheep and the dog lip-licking in response. Log linear regression identified significant relationships among undesirable behaviours in sheep and both observed trial duration (p = 0.001) and trial score (p = 0.009). No differences in the herding styles of dogs were identified between sex of dog and frequency of sheep escape behaviours (p = 0.355) nor the sex of dog and competition level (p = 0.116). The identification of trial score as a predictor of efficient performance confirms the benefits of incorporating extant objective measures to assess livestock herding dogs

Theory of apparent circular dichroism in a magnetic field

We present a microscopic theory of apparent circular dichroism in chiral thin films, cast explicitly in terms of molecular property tensors. Our theory provides a general foundation for ab initio calculations and reveals that the films should exhibit an interesting magnetochiral apparent circular dichroism and other novel effects when subjected to a static magnetic field