Since its first observational evidence, gravitational lensing - the deflection of light by mass - has become an established astrophysical tool than can be used to study the physical properties and environments of the lens galaxies and to reveal the structure of the lensed quasars. This thesis combines theoretical and observational results of a

Data from the SDSS-IV/Apache Point Observatory Galactic Evolution Experiment (APOGEE-2) have been released as part of SDSS Data Releases 13 (DR13) and 14 (DR14). These include high-resolution H-band spectra, radial velocities, and derived stellar parameters and abundances. DR13, released in 2016 August, contained APOGEE data for roughly 150,000

The data and analysis methodology used for the SDSS/APOGEE Data Releases 13 and 14 are described, highlighting differences from the DR12 analysis presented in Holtzman et al. Some improvement in the handling of telluric absorption and persistence is demonstrated. The derivation and calibration of stellar parameters, chemical abundances, and

Los filamentos y protuberancias solares han sido el foco de muchos estudios desde hace más de 200 años por ser uno de los fenómenos más fascinantes del Sol. Sin embargo, no es hasta ahora, con la instrumentación actual, nuestra potencia de cálculo y una consolidada teoría de generación y transporte de radiación polarizada que podemos estudiar estas