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Highlights • Propagation model of radially polarized vortex beams in atmospheric turbulence is established. • A radially polarized vortex beam can reduce beam spreading and wander effects in the atmosphere. • Polarization modulation can be an approach to mitigate turbulent effects on OAM-based systems. Abstract Adopting a vortex beam with poor coherence can reduce turbulence-induced beam spreading and wander effects in the atmosphere, but it intensifies the degradation rate of its beam profile from a doughnut shape into a Gaussian shape. Transmission quality of Orbital–angular–momentum (OAM) mode carried by a vortex beam is closely related to its evolution of intensity distribution. After appropriate polarization modulation, a radially polarized vortex beam has a better performance on the reduction of beam spreading and wander effects than its scalar counterpart. A radially polarized vortex beam can also lower the degradation rate of its beam profile and keep "OAM information" a longer distance. Therefore, appropriate polarization modulation can be an effective approach to mitigate the adverse turbulent effects on OAM-based systems operated in the atmosphere. [ABSTRACT FROM AUTHOR]

Analytical expressions of average intensity and long-term beam width for a radially polarized multi-Gaussian Schell-model (MGSM) beam in anisotropic atmospheric turbulence are developed based on the extended Huygens-Fresnel principle. The influences of anisotropic non-Kolmogorov turbulence and source parameters on the average intensity, polarization and long-term beam spreading of radially polarized MGSM beam are examined in detail. The source correlations, free-space diffraction and turbulent effect jointly affect both the intensity and polarization profiles of the beam propagated in the atmosphere. As a radially polarized MGSM beam propagates in the atmosphere, increasing the associated beam order can lower the evolution rate from its flat-topped beam profile into a Gaussian beam profile because of the turbulent effect. Variations in the average intensity and long-term beam width are closely related to the propagation distance, power spectrum index, inner-scale, initial spatial coherence, and beam width. The atmospheric turbulence-induced beam spreading is generally suppressed with the enhanced anisotropy coefficient. [ABSTRACT FROM AUTHOR]

The influences of source parameters, non-Kolmogorov and anisotropic turbulence on the beam spreading and beam wander of electromagnetic Multi-Gaussian Shell-model (EMGSM) beams in the atmosphere with aberration correction were analyzed. Zernike tilt aberration correction method had more effect on beam spreading compared to beam wander. Increasing the anisotropic property of turbulence could degrade both beam spreading and beam wander. EMGSM beams with larger beam order, wavelength could better mitigate the turbulence effects than GSM beams, which could be adopted as a better light source with several adjustable parameters to lower scintillation and beam wander in free-space optical communication. [ABSTRACT FROM AUTHOR]

Abstract: The chiral N,N′-dioxide–Yb(OTf)3 complex-catalyzed enantioselective aza-Diels–Alder reaction of Brassard’s diene with aldimines has been developed, giving the corresponding α,β-unsaturated δ-lactam derivatives in moderate yields with good enantioselectivities (up to 81% ee and up to 99% ee by single recrystallization) under mild conditions. Isolation of the reaction intermediate indicates that this asymmetric aza-Diels–Alder reaction proceeds through a stepwise Mannich-type pathway. [Copyright &y& Elsevier]

• The aging behavior of HSMB and LSMB under heat and UV were investigated. • The microstructure and chemical structure of HSMB and LSMB were analyzed. • The aging reaction rate and activation energy of LSMB and HSMB were studied. In this paper, the aging behavior of high dosage styrene–butadienestyrene (SBS) modified bitumen (HSMB) for waterproof materials and low dosage SBS modified bitumen (LSMB) for pavement were investigated. The effects of heat as well as ultraviolet-heat synergism on properties and chemical structure of HSMB and LSMB were evaluated by physical properties, fluorescence microscope (FM) and Fourier transform infrared spectroscopy (FTIR). The results showed that the change of softening point and low temperature flexibility of HSMB was much less than that of LSMB after heat aging, which indicated that the aging resistance of HSMB was better than that of LSMB. The physical properties changes of HSMB and LSMB after UV-heat synergism aging were much serious than that of HSMB and LSMB after heat aging. FM indicated that HSMB showed the network structure, and its structure was only partially destroyed after heat aging and completely destroyed after UV-heat synergism aging, while LSMB presented the sea-island structure, and the sea-island structure almost disappeared after aging. FTIR also showed that the change of carbonyl index (I C = O ), sulfoxide index (I S = O ) and butadiene double bonds index (I C = C ) of HSMB was smaller than that of LSMB after aging. The aging kinetic models of HSMB and LSMB were established by viscosity, the aging kinetic models showed that HSMB had lower aging reaction rate and larger activation energy than LSMB under the same aging condition, which meant that HSMB had better aging resistance. [ABSTRACT FROM AUTHOR]

• Self-healing capabilities of mortars under different temperatures were investigated. • Self-healing capabilities of mortars with microcapsules increased from 10 °C to 50 °C. • Crack of mortar with nano-SiO 2 /paraffin/PE wax microcapsule self-healed in 3 h at 50 °C. The ambient temperatures have significant effect on self-healing capabilities of concretes with microcapsules. Self-healing capabilities of mortars with different shell composition (paraffin, paraffin/PE wax and nano-SiO 2 /paraffin/PE wax) microcapsules containing toluene-di-isocyanate under the temperature of 10 °C, 30 °C, 50 °C and 60 °C were investigated in this paper. The compressive strength, chloride diffusion coefficient and pore size distribution of mortars containing microcapsules before and after self-healing were characterized by mechanical property test, rapid chloride migration test and nuclear magnetic resonance, respectively. The crack healing ratio of mortars during self-healing period were measured. The self-healing capabilities of mortars containing different microcapsules raised with the increase from 10 °C to 50 °C. Nevertheless, when the temperature reached 60 °C, the self-healing capability of the mortar containing paraffin microcapsules (AM1) decreased obviously, while the self-healing capabilities of the mortars containing paraffin/PE wax microcapsules (AM2) and nano-SiO 2 /paraffin/PE wax microcapsules (AM3) were almost unchanged. The self-healing capability of AM3 was superior to that of AM1 and AM2 at the same temperature. The compressive strength recovery rate, chloride diffusion coefficient recovery rate and harmful pores ratios of AM3 after pre-damaged at 50 °C for 7 d self-healing were 94.1%, 81.2% and 47.3%, respectively. When the ambient temperature reached 50 °C, the surface cracks of the mortar with three kinds of microcapsules could be completely self-healed in 5 h. However, when the temperature raised to 60 °C, the healing ratio of the crack in AM1 with a width of 0.4–0.5 mm decreased to 49.52% after 6 h self-healing. Meanwhile, the surface cracks of AM3 could be completely self-healed less than 3 h. [ABSTRACT FROM AUTHOR]