Light-induced spiral mass transport in azo-polymer films under vortex-beam illumination

When an azobenzene-containing polymer film is exposed to a non-uniform illumination, a light-induced mass migration process may be induced, leading to the formation of relief patterns on the polymer free surface. Despite a research effort of many years and several proposed models many aspects of this phenomenon remain not well understood. Here we report the appearance of spiral-shaped relief patterns on the polymer under the illumination of focused Laguerre-Gauss beams, having helical wavefront and an optical vortex at their axis. The induced spiral reliefs are sensitive to the vortex topological charge and to the wavefront handedness. These findings are unexpected, because the "doughnut"-shaped intensity profile of Laguerre- Gauss beams contains no information about the wavefront handedness. We propose a model that explains the main features of this phenomenon from the surface-mediated interference of the longitudinal and the transverse components of the optical field. These results may find applications in optical micro- and nanolithography and optical-field.Comment: Open Access at Journal Reference homepag

Stimuli Thresholds for Isomerization-Induced Molecular Motions in Azobenzene-Containing Materials.

We use large-scale molecular dynamics simulations of the isomerizations of azobenzene molecules diluted inside a simple molecular material to investigate the effect of a modification of the cis isomer shape on the induced diffusion mechanism. To this end we simulate incomplete isomerizations, modifying the amplitude of the trans-to-cis isomerization. We find thresholds in the evolution of the host molecules mobility with the isomerization amplitude, a result predicted by the cage-breaking mechanism hypothesis (Teboul, V.; Saiddine, M.; Nunzi, J. M.; Accary, J. B. J. Chem. Phys. 2011, 134, 114517) and by the gradient pressure mechanism theory (Barrett, C. J.; Rochon, P. L.; Natansohn, A. L. J. Chem. Phys. 1998, 109, 1505–1516.). Above the threshold the diffusion then increases linearly with the variation of the chromophore size induced by the isomerization

Scanning electron microscopy study of pollen in seedless grape (>Vitis vinifera L.) cultivars

A comparative scanning electron microscopy study and biometric analysis on pollen of 27 Bulgarian and foreign seedless grape cultivars have been performed. Both the degree of similarity and the specific differences in exine ultrastructural organisation and the aperture complex were established. In all investigated cultivars, pollen grains were from elongated elliptical to oval-spheroidal, tricolporate in shape. The exine surface is in low relief, with perforations and crest undulations in the mesocolpiums. It was concluded that the type of exine sculpturing, the length of polar and equatorial axes and colp could be used as additional microstructural parameters in cultivar identification of seedless grapes

Duration of antiplatelet therapy after complex percutaneous coronary intervention in patients at high bleeding risk: a MASTER DAPT trial sub-analysis

Aim To assess the effects of 1- or >= 3-month dual antiplatelet therapy (DAPT) in high bleeding risk (HBR) patients who received biodegradable-polymer sirolimus-eluting stents for complex percutaneous coronary intervention (PCI) and/or acute coronary syndrome (ACS). Methods and results In the MASTER DAPT trial, 3383 patients underwent non-complex (abbreviated DAPT, n = 1707; standard DAPT, n = 1676) and 1196 complex (abbreviated DAPT, n = 588; standard DAPT, n = 608) PCI. Co-primary outcomes at 335 days were net adverse clinical events [NACE; composite of all-cause death, myocardial infarction, stroke, and bleeding academic research consortium (BARC) 3 or 5 bleeding events]; major adverse cardiac or cerebral events (MACCE; all-cause death, myocardial infarction, and stroke); and Types 2, 3, or 5 BARC bleeding. Net adverse clinical events and MACCE did not differ with abbreviated vs. standard DAPT among patients with complex [hazard ratio (HR): 1.03, 95% confidence interval (CI): 0.69-1.52, and HR: 1.24, 95% CI: 0.79-1.92, respectively] and non-complex PCI (HR: 0.90, 95% CI: 0.71-1.15, and HR: 0.91, 95% CI: 0.69-1.21; P-interaction = 0.60 and 0.26, respectively). BARC 2, 3, or 5 was reduced with abbreviated DAPT in patients with and without complex PCI (HR: 0.64; 95% CI: 0.42-0.98, and HR: 0.70; 95% CI: 0.55-0.89; P-interaction = 0.72). Among the 2816 patients with complex PCI and/or ACS, NACE and MACCE did not differ and BARC 2, 3, or 5 was lower with abbreviated DAPT. Conclusion In HBR patients free from recurrent ischaemic events at 1 month, DAPT discontinuation was associated with similar NACE and MACCE and lower bleeding rates compared with standard DAPT, regardless of PCI or patient complexity