Rubbing effects on the structural and optical properties of poly(3­hexylthiophene) films

International audienc

Thermo-mechanical behavior of surface acoustic waves in ordered arrays of nanodisks studied by near infrared pump-probe diffraction experiments

The ultrafast thermal and mechanical dynamics of a two-dimensional lattice of metallic nano-disks has been studied by near infrared pump-probe diffraction measurements, over a temporal range spanning from 100 fs to several nanoseconds. The experiments demonstrate that, in these systems, a two-dimensional surface acoustic wave (2DSAW), with a wavevector given by the reciprocal periodicity of the array, can be excited by ~120 fs Ti:sapphire laser pulses. In order to clarify the interaction between the nanodisks and the substrate, numerical calculations of the elastic eigenmodes and simulations of the thermodynamics of the system are developed through finite-element analysis. At this light, we unambiguously show that the observed 2DSAW velocity shift originates from the mechanical interaction between the 2DSAWs and the nano-disks, while the correlated 2DSAW damping is due to the energy radiation into the substrate.Comment: 13 pages, 10 figure

The motor cortex of the sheep: laminar organization, projections and diffusion tensor imaging of the intracranial pyramidal and extrapyramidal tracts

The laminar organization of the motor cortex of the sheep and other large domestic herbivores received scarce attention and is generally considered homologous to that of rodents and primates. Thickness of the cortex, subdivision into layers and organization are scarcely known. In the present study, we applied different modern morphological, mathematical and image-analyses techniques to the study of the motor area that controls movements of the forelimb in the sheep. The thickness of the cortex resulted comparable to that of other terrestrial Cetartiodactyls (but thicker than in marine Cetartiodactyls of similar body mass). The laminar organization showed marked development of layer 1, virtual absence of layer 4, and image analysis suggested prevalence of large irregular neural cells in the deeper layers. Diffusion tensor imaging revealed robust projections from the motor cortex to the pyramids in the brainstem, and well evident tracts descending to the tegmentum of the mesencephalon and dorsal pons. Our data contrast the general representation of the motor system of this species, considered to be predominantly based on extra-pyramidal tracts that originate from central pattern generators in the brainstem. © 2019, Springer-Verlag GmbH Germany, part of Springer Nature