Improved nonlinear slot waveguides using dielectric buffer layers: properties of TM waves

International audienceWe propose an improved version of the symmetric metal slot waveguides with a Kerr-type nonlinear di-electric core adding linear dielectric buffer layers between the metal regions and the core. Using a finite element method to compute the stationary nonlinear modes, we provide the full phase diagrams of its main TM modes as a function of total power, buffer layer and core thicknesses, that are more complex than the ones of the simple nonlinear metal slot. We show that these modes can exhibit spatial transitions towards specific modes of the new structure as a function of power. We also demonstrate that, for the main modes, the losses are reduced compared to the previous structures, and that they can now decrease with power. Finally, we describe the stability properties of the main stationary solutions using nonlinear FDTD simulations. Nonlinear plasmonic slot waveguides (NPSWs) have drawn attention in the last decade due to the strong light confinement in the nonlinear dielectric core ensured by the surrounding metal regions, and to their peculiar nonlinear effects [1–6]. Several applications have already been proposed for NPSWs [7, 8]. Nevertheless, the experimental observation of plasmon-soliton waves in these NPSWs is still lacking even if linear slot waveg-uides have already been fabricated [9]. Similarly to the case of the single nonlinear dielectric/metal interface structures [10, 11], the modes already studied in the simple NPSWs suffer from high losses that seriously limit the propagation length of the waves. In the present study, we propose and study an improved structure in which buffer linear dielectric layers are added between the nonlinear dielectric core and the two semi-infinite metal regions. The article is organized as follows. First, we describe the model and numerical method we use to study the stationary nonlinear waves in the improved NPSW we propose. Secondly, we describe the linear solutions of the new structures in order to classify the nonlinear solutions. Thirdly, we give the properties of the nonlinear stationary solutions and show that, for some linear parameter configurations, new modal spatial transitions as a function of power occur compared to the simple NPSW case. We provide full phase diagrams for the improved NPSW as a function of total power, buffer layer and core thicknesses. We also prove that the added buffer dielectric layers are able to reduce losses and allow them to decrease with power in most of the cases. Finally, using the FDTD method we study the stability properties of the main nonlinear solutions

Spatial nonlinearity in anisotropic metamaterial plasmonic slot waveguides

We study the main nonlinear solutions of plasmonic slot waveguides made from an anisotropic metamate-rial core with a positive Kerr-type nonlinearity surrounded by two semi-infinite metal regions. First, we demonstrate that for a highly anisotropic diagonal elliptical core, the bifurcation threshold of the asymmetric mode is reduced from GW/m threshold for the isotropic case to 50 MW/m one indicating a strong enhancement of the spatial nonlinear effects, and that the slope of the dispersion curve of the asymmetric mode stays positive, at least near the bifurcation, suggesting a stable mode. Second, we show that for the hyperbolic case there is no physically meaningful asymmetric mode, and that the sign of the effective nonlinearity can become negative

Impact of Hydroxychloroquine on Fructose-induced Metabolic Syndrome in Rats: Promising Protective Effect

BACKGROUND: Hydroxychloroquine (HCQ) is used in the treatment of malaria and rheumatoid arthritis for a long time. Its effects on inflammation and immune modulation were noted. AIM: This study aims to investigate the effects of HCQ in fructose-induced metabolic syndrome and to explore its possible mechanisms. METHODS AND MATERIALS: Sixty male Sprague-Dawley rats were divided into Group I (negative control), Group II fed on high-fructose diet, and Group III fed on high fructose and subdivided into Group III-a (HCQ 50 mg/kg), Group III-b (HCQ 100 mg/kg), Group III-c (HCQ 200 mg/kg), and Group III-d (metformin 100 mg/kg). Body weight, blood glucose, liver enzymes, and lipid profile were measured. Insulin level, homeostatic model assessment (HOMA), soluble-intercellular adhesion molecule, and vascular cell adhesion molecule were assayed. Tumor necrosis factor (TNF)-α, adipokines (leptin, resistin, and adiponectin), and histological examination of pancreas were assessed. RESULTS: HCQ induces good effects on lipid profile and improves significantly HOMA, endothelial stress markers, and adiponectin, and reduces leptin and TNF-α levels. In addition, significant improvement in structural changes was noted in pancreas with different doses of HCQ. CONCLUSION: Favorable effects of HCQ in fructose-induced metabolic syndrome are promising and can be used early in those at risk of diabetes

Enhancing the Performance of Power System under Abnormal Conditions Using Three Different FACTS Devices

In this paper, a comparison between Flexible Alternating Current Transmission System (FACTS) devices including Static Synchronous Compensator (STATCOM), Static Synchronous Series Compensator (SSSC) and Unified Power Flow Controller (UPFC) for providing a better adaptation to changing operating conditions and improving the usage of current systems. The power system using FACTS devices is presented under different conditions such as single phase fault and three phase fault. A digital simulation using Matlab/Simulink software package is carried out to demonstrate the better performance including the voltage and the current of the presented system using FACTS that located between buses B1 and B2 under different faults types. The results obtained investigate that the presented system gives better response with FACTS as compared to not using them under abnormal conditions besides, the UPFC gives better performance of power system under several faults as compared to STATCOM or SSSC as It can absorb reactive power in a manner which significantly reduced the fault current. It is demonstrated that UPFC can reduce the peak fault current at bus B1 ‎to 63.85% of its value without ‎using FACTS devices under line to ground fault and 79.18% under three line to ‎ground fault whereas STATCOM and SSSC reduce it ‎to (75.21, 94.35%) and (75.40, 94.68%), respectively

Global optimization of metasurface designs using statistical learning methods

International audienceOptimization of the performance of flat optical components, also dubbed metasurfaces, is a crucial step towards their implementation in realistic optical systems. Yet, most of the design techniques, which rely on large parameter search to calculate the optical scattering response of elementary building blocks, do not account for near-field interactions that strongly influence the device performance.In this work, we exploit two advanced optimization techniques based on statistical learning and evolutionary strategies together with a fullwave high order Discontinuous Galerkin Time-Domain (DGTD) solver to optimize phase gradient metasurfaces. We first review the main features of these optimization techniques and then show that they can outperform most of the available designs proposed in the literature. Statistical learning is particularly interesting for optimizing complex problems containing several global minima/maxima. We then demonstrate optimal designs for GaN semiconductor phase gradient metasurfaces operating at visible wavelengths. Our numerical results reveal that rectangular and cylindrical nanopillar arrays can achieve more than respectively 88% and 85% of diffraction efficiency for TM polarization and both TM and TE polarization respectively, using only 150 fullwave simulations. To the best of our knowledge, this is the highest blazed diffraction efficiency reported so far at visible wavelength using such metasurface architectures

Design, synthesis, antitumor activity and molecular docking study of novel 5-deazaalloxazine analogs

open access articleProtein tyrosine kinases (PTKs) are the most potential therapeutic targets for cancer. Herein, we present a sound rationale for synthesis of a series of novel 2-(methylthio), 2-(substituted alkylamino), 2-(heterocyclic substituted), 2-amino, 2,4-dioxo and 2-deoxo-5-deazaalloxazine derivatives by applying structure-based drug design (SBDD) using AutoDock 4.2. Their antitumor activities against human CCRF-HSB-2, KB, MCF-7 and HeLa have been investigated in vitro. Many 5-deazaalloxazine analogs revealed high selective activities against MCF-7 tumor cell lines (IC50: 0.17–2.17 µM) over HeLa tumor cell lines (IC50 > 100 µM). Protein kinase profiling revealed that compound 3h induced multi- targets kinase inhibition including −43% against (FAK), −40% against (CDKI) and −36% against (SCR). Moreover, the Annexin-V/PI apoptotic assay elucidate that compound 3h showed 33% and potentially 140% increase in early and late apoptosis to MCF-7 cells respectively, compared to the control. The structure-activity relationship (SAR) and molecular docking study using PTK as a target enzyme for the synthesized 7-deazaalloaxazine derivatives were investigated as potential antitumor agents. The AutoDock binding affinities of the 5deazaalloxazine analogs into c-kit PTK (PDB code: 1t46) revealed reasonable correlations between their AutoDock binding free energy and IC50

Back-Propagation Optimization and Multi-Valued Artificial Neural Networks for Highly Vivid Structural Color Filter Metasurfaces

We introduce a novel technique for designing color filter metasurfaces using a data-driven approach based on deep learning. Our innovative approach employs inverse design principles to identify highly efficient designs that outperform all the configurations in the dataset, which consists of 585 distinct geometries solely. By combining Multi-Valued Artificial Neural Networks and back-propagation optimization, we overcome the limitations of previous approaches, such as poor performance due to extrapolation and undesired local minima. Consequently, we successfully create reliable and highly efficient configurations for metasurface color filters capable of producing exceptionally vivid colors that go beyond the sRGB gamut. Furthermore, our deep learning technique can be extended to design various pixellated metasurface configurations with different functionalities.Comment: To be published. 25 Pages, 17 Figure

Advanced numerical modeling methods for the characterization and optimization of metasurfaces

International audienceThe last 10 years have witnessed an impressive amount of works aiming at the development of thin metamaterials for controlling the wavefront of light, and thus realize planar photonics also referred as flat optics or metaoptics. The concept of metasurface is at the heart of almost all the discoveries in this domain. Metasurfaces are arrays of subwavelength-spaced and optically thin optical elements, which enable new physics and phenomena that are distinctly different from those observed in three-dimensional bulk metamaterials. We present here our recent activities and achievements in relation with the design of metasurfaces, which are concerned with two topics: on one hand, we study numerical characterization approaches that are well suited to the multiscale nature of metasurfaces; on the other hand, we develop inverse design strategies for discovering non-classical metasurface configurations for a target optical functionality. These two topics are addressed in the context of a multidisciplinary collaborative project, which involve computational scientists and physicists. In particular, we apply the proposed numerical methodologies to the design of phase gradient metasurfaces and light front shaping metalenses. In some cases, the numerically designed metasurfaces have been frabricated and experimentally characterized to confirm their predicted performances