No abstract

In this paper, the affine connection approach [D. Baalss and S. Hess, Phys. Rev. Lett. 57, 86 (1986)] will be defined in terms of a local transformation. Accordingly, the macroscopic anisotropy of the nematic medium will be conceived as resulting from a local transformation where, at each point of the sample, the spherical molecules of an idealized hypothetic isotropic liquid have their shape changed to the ellipsoidal form of the nematic liquid crystals molecules. When such local character is imposed to this transformation, the patterns determined by the director configuration of the nematic medium acquire an intrinsic curvature whose correct treatment requires the replacement of the techniques and methods of the usual calculus by those of the differential geometry of nonflat surfaces. Such an approach will be used in the calculus of the nematic elastic constants. As a result, the dependence of the elastic constants on the scalar order parameter, on the eccentricity of the nematic molecules, and on the interaction between them will be determined and compared with the experimental data of the 4-methoxybenzylidene-4-n-butylaniline.

The alkali-aggregate reaction and the internal sulfate attack are two chemical reactions that lead to expansions in concrete structures. The former is one of the main causes of expansions in concrete dams and has been extensively reported in the literature, whereas the latter is less common and, thus, less studied. The confluence of both reactions in one structure is highly unlikely but still possible as shown by the case of the dam studied in this paper. This gravity dam exhibits significantly high non-recoverable displacements that may only be justified by the 17 superposition of both phenomena. This paper focuses on the study of a concrete dam whose 18 diagnosis hypotheses have changed throughout the years according to evolution of the behavior 19 observed. The hypotheses proposed in the study are validated by conducting numerical analyses 20 through 3D and 2D finite element models. The results confirmed the diagnosis proposed and the 21 capability of the model to reproduce the behavior of the dam.

2D materials are currently very promising candidates for various photonic applications. Optimizing their optical nonlinearities requires a thorough adjustment of several properties including the film thickness. In this work thin Sb2Te3 layers with different thicknesses (ranging from 2.5 to 50 nm) are prepared by the electron beam deposition technique, and then they are properly annealed in order to achieve significant third order nonlinearities. The film structure and morphology are extensively studied by means of X-ray diffraction, scanning electron microscopy, transmission electron microscopy and energy-dispersive X-ray spectroscopy. The presence of nanocrystals with sizes highly depending on the film thickness has been observed. Optical studies are carried out by Vis–NIR spectrophotometric studies. Finally, a thickness dependent study of the ultrafast third order nonlinear optical properties of the Sb2Te3 thin films is performed. This study is carried out by means of the Z-scan technique, employing 400 fs laser pulses at 1030 nm. The observed optical nonlinearities are very high, compared with those of state-of-the-art nonlinear optical materials. Moreover they are highly dependent on the thickness of the layers. The findings demonstrate the importance of a fine adjustment of the Sb2Te3 thickness in order to enhance its nonlinear optical efficiency. They are expected to be of significant importance for mode-locking of laser systems and super-resolved direct laser writing.

Expansions in concrete dams may be caused by chemical or physical sources; however in certain occasions the evidences observed in the dam may not be attributed to a single cause. Mequinenza is an example of a concrete dam affected by expansions and high non-recoverable displacements that cannot be explained by the most frequent pathologies. This paper presents new hypotheses that could justify such behavior by assuming the superposition of a global phenomenon of water induced expansion in concrete in the entire dam and a localized effect consisting in the opening of cracks in the construction joints located in one of the blocks. This is validated by conducting numerical analyses through 2D finite element models that consider the nonlinear behavior of the construction joints and use zero-thickness interface elements to simulate the potential cracking planes in the dam. The results confirmed the diagnosis proposed and the capability of the model to reproduce the behavior of the dam, revealing the significant contribution of the opening of the cracks to the non-recoverable displacements in the dam.