SPEKTRA Volume 8 issue 2 contains five papers: 1) The Comparison of 2D Dose Patient-Specific Quality Assurance Between Monte Carlo-Convolution and Modified Clarkson Integration Algorithm, 2) Synthesize of TiO₂ Nanoparticles by Planetary Ball Mill for Dye-Sensitized Solar Cells (DSSC) Photoelectrode Application, 3) Experimental and Computational Study of Nitrogen-Doped TiO₂ as A Photoelectrode, 4) Investigation of Subsurface Groundwater Using The Ves Method Around Dendam Lake, Bengkulu City, Indonesia, and 5) Identification of Physical Oceanographic Parameters And Mixing Types at The Transitional Season I in The Estuary of Air Manna Regency South Bengkulu.

The articles in this issue from 4 countries: Indonesia, Gambia, Taiwan and China. We are grateful for all the contributions of the authors. We also appreciate the professional reviewers who are an essential part of this issue.