Study of star-forming galaxies in SDSS up to redshift 0.4: I. Metallicity evolution

The chemical composition of the gas in galaxies versus cosmic time provides a very important tool for understanding galaxy evolution. Although there are many studies at high redshift, they are rather scarce at lower redshifts. However, low redshift studies can provide important clues about the evolution of galaxies, furnishing the required link between local and high redshift universe. In this work we focus on the metallicity of the gas of star-forming galaxies at low redshift, looking for signs of chemical evolution. To analyze the metallicity contents star-forming galaxies of similar luminosities and masses at different redshifts. With this purpose, we present a study of the metallicity of relatively massive (log(M_star/M_sun)>10.5) star forming galaxies from SDSS--DR5 (Sloan Digital Sky Survey--Data Release 5), using different redshift intervals from 0.04 to 0.4. We used data processed with the STARLIGHT spectral synthesis code, correcting the fluxes for dust extinction, estimating metallicities using the R_23 method, and segregating the samples with respect to the value of the [NII]6583/[OII]3727 line ratio in order to break the R_23 degeneracy selecting the upper branch. We analyze the luminosity and mass-metallicity relations, and the effect of the Sloan fiber diameter looking for possible biases. By dividing our redshift samples in intervals of similar magnitude and comparing them, significant signs of metallicity evolution are found. Metallicity correlates inversely with redshift: from redshift 0 to 0.4 a decrement of ~0.1 dex in 12+log(O/H) is found.Comment: 11 pages, 9 figures, Accepted for publication in A&

Uprolides N, O and P from the Panamanian Octocoral Eunicea succinea.

Three new diterpenes, uprolide N (1), uprolide O (2), uprolide P (3) and a known one, dolabellane (4), were isolated from the CH₂Cl₂-MeOH extract of the gorgonian octocoral Eunicea succinea, collected from Bocas del Toro, on the Caribbean coast of Panama. Their structures were determined using spectroscopic analyses, including 1D and 2D NMR and high-resolution mass spectrometry (HRMS) together with molecular modeling studies. Compounds 1-3 displayed anti-inflammatory properties by inhibiting production of Tumor Necrosis Factor (TNF) and Interleukin (IL)-6 induced by lipopolysaccharide (LPS) in murine macrophages

Design of arbitrary optical filters in silicon-on-insulator using evanescently-coupled Bragg gratings

Spectral filters are experiencing an increasing demand in several applications of the silicon- on-insulator (SOI) platform. Many works have demonstrated that arbitrary frequency responses can be synthesized by apodizing the coupling coefficient profile of an integrated Bragg grating. However, the high index contrast of the SOI platform hinders their practical implementation, due to the difficulty of achieving the precise control required in the Bragg strength. In this paper, we propose the implementation of spectral filters using an architecture based on placing loading segments within the evanescent field region of a photonic wire waveguide. The Bragg coupling coefficient can be accurately controlled by simply moving the segments away from, or closer to, the waveguide core. The layerpeeling algorithm, in conjunction with a Floquet-Bloch modal analysis, allows to determine the spatial distribution of the segments that synthesizes the desired spectrum. The proposed topology is verified by designing a filter with five arbitrary passbands.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Ultra-broadband polarization beam splitter with a gradual anisotropy engineered subwavelength metamaterial

In this work we propose a polarization beam splitter based on an advanced SWG metamaterial topology which controls the propagation of multiple TE and TM modes at the same time. The proposed device achieves a simulated insertion loss 20 dB over a 400 nm bandwidth.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech.; Ministerio de Educación, Cultura y Deporte (MECD) (FPU16/06762), Ministerio de Ciencia, Innovación y Universidades (MCIU) (PID2019-106747RB-I00), Consejería de Economía, Conocimiento, Empresas y Universidad (CECEU) (UMA18-FEDERJA-219, P18-RT-1453, P18-RT-793

Diseño de grating couplers de orden cero de banda ancha y alta eficiencia para el infrarrojo medio

The mode fields of optical fibers and high-index contrast photonic waveguides have different dimensions, making difficult the coupling of light from one to the other. To solve this problem, surface grating couplers are one of the most used alternatives. However, in conventional grating couplers the bandwidth is limited. To overcome this drawback, we have recently proposed zero-order grating couplers, which, making use of a high-index prism and subwavelength grating structures, substantially mitigate the wavelength dependency of conventional grating couplers. In the near-infrared (λ = 1.55 μm) it is not possible to take full benefit from the potential bandwidth enhancement of zero-order grating couplers. Thus, in this work we migrate our zero-order grating coupler design from the near-infrared wavelength range to the mid-infrared one, which is attaining increasing attention because of its sensing applications. Subdecibel coupling efficiencies and broad bandwidths up to ~680 nm are achieved at λ = 3.8 μm for silicon-on-insulator and germanium-on-silicon nitride platforms.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Metamaterial engineered C+L band 90º hybrid with 150 nm feature size

90º hybrids are important components for coherent optical communications. Conventional implementations only cover the C band, while broadband, metamaterial-based devices require sub-100nm feature sizes. We propose a design based on dual-etch silicon subwavelength structures that achieves a 170 nm bandwidth with deep-UV compatible feature sizes.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech. Ministerio de Universidades (FPU-16/03401) Ministerio de Economía y Competitividad FEDER (TEC2016-80718-R) Programa Operativo FEDER Andalucía 2014-2020 (UMA18-FEDERJA-219

Enhanced sensitivity subwavelength grating waveguides for silicon photonics sensing applications

OSA (Optical Society of America)In this work we will review the enormous potential of subwavelength grating waveguides for sensing applications in the near and mid-infrared bands, demonstrating the capability to engineer the mode profile to maximize the light-matter interaction.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech